BBA - Molecular Basis of Disease (v.1852, #5)
Editorial Board (i).
Phosphorylation of caveolin-1 on tyrosine-14 induced by ROS enhances palmitate-induced death of beta-pancreatic cells by Sergio Wehinger; Rina Ortiz; María Inés Díaz; Adam Aguirre; Manuel Valenzuela; Paola Llanos; Christopher Mc Master; Lisette Leyton; Andrew F.G. Quest (693-708).
A considerable body of evidence exists implicating high levels of free saturated fatty acids in beta pancreatic cell death, although the molecular mechanisms and the signaling pathways involved have not been clearly defined. The membrane protein caveolin-1 has long been implicated in cell death, either by sensitizing to or directly inducing apoptosis and it is normally expressed in beta cells. Here, we tested whether the presence of caveolin-1 modulates free fatty acid-induced beta cell death by reexpressing this protein in MIN6 murine beta cells lacking caveolin-1. Incubation of MIN6 with palmitate, but not oleate, induced apoptotic cell death that was enhanced by the presence of caveolin-1. Moreover, palmitate induced de novo ceramide synthesis, loss of mitochondrial transmembrane potential and reactive oxygen species (ROS) formation in MIN6 cells. ROS generation promoted caveolin-1 phosphorylation on tyrosine-14 that was abrogated by the anti-oxidant N-acetylcysteine or the incubation with the Src-family kinase inhibitor, PP2 (4-amino-5-(4-chlorophenyl)-7(dimethylethyl)pyrazolo[3,4-d]pyrimidine). The expression of a non-phosphorylatable caveolin-1 tyrosine-14 to phenylalanine mutant failed to enhance palmitate-induced apoptosis while for MIN6 cells expressing the phospho-mimetic tyrosine-14 to glutamic acid mutant caveolin-1 palmitate sensitivity was comparable to that observed for MIN6 cells expressing wild type caveolin-1. Thus, caveolin-1 expression promotes palmitate-induced ROS-dependent apoptosis in MIN6 cells in a manner requiring Src family kinase mediated tyrosine-14 phosphorylation.
Keywords: Caveolin-1; Palmitate; Reactive oxygen species; Tyrosine-14; Apoptosis; Beta cell;
Mild hypoxia in vivo regulates cardioprotective SUR2A: A role for Akt and LDH by Khaja Shameem Mohammed Abdul; Sofija Jovanović; Qingyou Du; Andriy Sukhodub; Aleksandar Jovanović (709-719).
High-altitude residents have lower mortality rates for ischaemic heart disease and this is ascribed to cardiac gene remodelling by chronic hypoxia. SUR2A is a cardioprotective ABC protein serving as a subunit of sarcolemmal ATP-sensitive K+ channels. The purpose of this study was to determine whether SUR2A is regulated by mild hypoxia in vivo and to elucidate the underlying mechanism. Mice were exposed to either 21% (control) or 18% (mild hypoxia) oxygen for 24 h. Exposure to 18% oxygen did not affect partial pressure of O2 (PO2) and CO2 (PCO2) in the blood, haematocrit or level of ATP in the heart. However, hypoxia increased myocardial lactate dehydrogenase (LDH) and lactate as well as NAD+ without affecting total NAD. SUR2A levels were significantly increased as well as myocardial resistance to ischaemia–reperfusion. Exposure to 18% oxygen did not phosphorylate extracellular signal regulated kinases (ERK1/2) or AMP activated protein kinase (AMPK), but it phosphorylated protein kinase B (Akt). An inhibitor of phosphoinositide 3-kinases (PI3K), LY294002 (0.2 mg/mouse), abolished all observed effects of hypoxia. LDH inhibitors, galloflavin (50 μM) and sodium oxamate (80 mM) significantly decreased levels of SUR2A in heart embryonic H9c2 cells, while inactive mutant LDH form, gly193-M-LDH increased cellular sensitivity towards stress induced by 2,4-dinitrophenol (10 mM). Treatment of H9c2 cells with sodium lactate (30 mM) increased intracellular lactate, but did not affect LDH activity or SUR2A levels. We conclude that PI3K/Akt signalling pathway and LDH play a crucial role in increase of cardiac SUR2A induced by in vivo exposure to 18% oxygen.
Keywords: Hypoxia; LDH; Oxygen; SUR2A; Heart; Akt;
The neuroprotective role of metformin in advanced glycation end product treated human neural stem cells is AMPK-dependent by Ming-Min Chung; Yen-Lin Chen; Dee Pei; Yi-Chuan Cheng; Binggui Sun; Christopher J. Nicol; Chia-Hui Yen; Han-Min Chen; Yao-Jen Liang; Ming-Chang Chiang (720-731).
Diabetic neuronal damage results from hyperglycemia followed by increased formation of advanced glycosylation end products (AGEs), which leads to neurodegeneration, although the molecular mechanisms are still not well understood. Metformin, one of the most widely used anti-diabetic drugs, exerts its effects in part by activation of AMP-activated protein kinase (AMPK). AMPK is a critical evolutionarily conserved enzyme expressed in the liver, skeletal muscle and brain, and promotes cellular energy homeostasis and biogenesis by regulating several metabolic processes. While the mechanisms of AMPK as a metabolic regulator are well established, the neuronal role for AMPK is still unknown. In the present study, human neural stem cells (hNSCs) exposed to AGEs had significantly reduced cell viability, which correlated with decreased AMPK and mitochondria associated gene/protein (PGC1α, NRF-1 and Tfam) expressions, as well as increased activation of caspase 3 and 9 activities. Metformin prevented AGEs induced cytochrome c release from mitochondria into cytosol in the hNSCs. Co-treatment with metformin significantly abrogated the AGE-mediated effects in hNSCs. Metformin also significantly rescued hNSCs from AGE-mediated mitochondrial deficiency (lower ATP, D-loop level, mitochondrial mass, maximal respiratory function, COX activity, and mitochondrial membrane potential). Furthermore, co-treatment of hNSCs with metformin significantly blocked AGE-mediated reductions in the expression levels of several neuroprotective genes (PPARγ, Bcl-2 and CREB). These findings extend our understanding of the molecular mechanisms of both AGE-induced neuronal toxicity, and AMPK-dependent neuroprotection by metformin. This study further suggests that AMPK may be a potential therapeutic target for treating diabetic neurodegeneration.
Keywords: AMPK; Metformin; AGEs; hNSCs;
Hyperhomocysteinemia associated skeletal muscle weakness involves mitochondrial dysfunction and epigenetic modifications by Sudhakar Veeranki; Lee J. Winchester; Suresh C. Tyagi (732-741).
HHcy has been implicated in elderly frailty, but the underlying mechanisms are poorly understood. Using C57 and CBS +/− mice and C2C12 cell line, we investigated mechanisms behind HHcy induced skeletal muscle weakness and fatigability. Possible alterations in metabolic capacity (levels of LDH, CS, MM-CK and COX-IV), in structural proteins (levels of dystrophin) and in mitochondrial function (ATP production) were examined. An exercise regimen was employed to reverse HHcy induced changes. CBS +/− mice exhibited more fatigability, and generated less contraction force. No significant changes in muscle morphology were observed. However, there is a corresponding reduction in large muscle fiber number in CBS +/− mice. Excess fatigability was not due to changes in key enzymes involved in metabolism, but was due to reduced ATP levels. A marginal reduction in dystrophin levels along with a decrease in mitochondrial transcription factor A (mtTFA) were observed. There was also an increase in the mir-31, and mir-494 quantities that were implicated in dystrophin and mtTFA regulation respectively. The molecular changes elevated during HHcy, with the exception of dystrophin levels, were reversed after exercise. In addition, the amount of NRF-1, one of the transcriptional regulators of mtTFA, was significantly decreased. Furthermore, there was enhancement in mir-494 levels and a concomitant decline in mtTFA protein quantity in homocysteine treated cells. These changes in C2C12 cells were also accompanied by an increase in DNMT3a and DNMT3b proteins and global DNA methylation levels. Together, these results suggest that HHcy plays a causal role in enhanced fatigability through mitochondrial dysfunction which involves epigenetic changes.
Keywords: MicroRNA; mtTFA; Dystrophin; Exercise; Epigenetics; NRF-1;
The ITM2B (BRI2) gene is a target of BCL6 repression: Implications for lymphomas and neurodegenerative diseases by Beverly W. Baron; Rebecca M. Baron; Joseph M. Baron (742-748).
The human BCL6 gene encodes a transcriptional repressor that is crucial for germinal center B cell development and T follicular helper cell differentiation. It is involved in the pathogenesis of certain human lymphomas. In an effort to identify targets of BCL6 repression, we used a previously described cell system in which BCL6 repressive effects are inhibited, followed by subtractive hybridization, and identified the integral membrane 2B gene (ITM2B, formerly BRI2) as a potential target. Here we show that BCL6 can bind to its preferential consensus binding site within the first intron of ITM2B and represses its transcription. Knockdown of endogenous BCL6 in a human B cell lymphoma line increases ITM2B expression. Further, there is an inverse relationship between the expression levels of BCL6 and ITM2B proteins in 16 human B- and T-cell lymphomas studied by immunohistochemistry. Both the BCL6 and ITM2B proteins are expressed ubiquitously. Similar to some other targets of BCL6, a short form of the ITM2B protein generated by alternative splicing induces apoptosis in hematopoietic cell lines. Molecular alterations in the ITM2B gene are associated with two neurodegenerative diseases, Familial British and Familial Danish dementia. ITM2B dysfunction also may be relevant for the development of Alzheimer's disease. Our data confirm ITM2B as a target of BCL6 repression in lymphoma. A further understanding of the genes that function as regulators of the ITM2B protein may provide insights for the development of new molecular tools not only for targeted lymphoma therapy but also for the treatment of these dementias.
Keywords: ITM2B gene; BCL6 target; Familial British dementia; Familial Danish dementia; Alzheimer's disease;
Palmitoyl-carnitine increases RyR2 oxidation and sarcoplasmic reticulum Ca2 + leak in cardiomyocytes: Role of adenine nucleotide translocase by J. Roussel; J. Thireau; C. Brenner; N. Saint; V. Scheuermann; A. Lacampagne; J.-Y. Le Guennec; J. Fauconnier (749-758).
Long chain fatty acids bind to carnitine and form long chain acyl carnitine (LCAC), to enter into the mitochondria. They are oxidized in the mitochondrial matrix. LCAC accumulates rapidly under metabolic disorders, such as acute cardiac ischemia, chronic heart failure or diabetic cardiomyopathy. LCAC accumulation is associated with severe cardiac arrhythmia including ventricular tachycardia or fibrillation. We thus hypothesized that palmitoyl-carnitine (PC), alters mitochondrial function leading to Ca2 + dependent-arrhythmia. In isolated cardiac mitochondria from C57Bl/6 mice, application of 10 μM PC decreased adenine nucleotide translocase (ANT) activity without affecting mitochondrial permeability transition pore (mPTP) opening. Mitochondrial reactive oxygen species (ROS) production, measured with MitoSOX Red dye in isolated ventricular cardiomyocytes, increased significantly under PC application. Inhibition of ANT by bongkrekic acid (20 μM) prevented PC-induced mitochondrial ROS production. In addition, PC increased type 2 ryanodine receptor (RyR2) oxidation, S-nitrosylation and dissociation of FKBP12.6 from RyR2, and therefore increased sarcoplasmic reticulum (SR) Ca2 + leak. ANT inhibition or anti-oxidant strategy (N-acetylcysteine) prevented SR Ca2 + leak, FKBP12.6 depletion and RyR2 oxidation/S-nitrosylation induced by PC. Finally, both bongkrekic acid and NAC significantly reduced spontaneous Ca2 + wave occurrences under PC. Altogether, these results suggest that an elevation of PC disturbs ANT activity and alters Ca2 + handling in a ROS-dependent pathway, demonstrating a new pathway whereby altered FA metabolism may contribute to the development of ventricular arrhythmia in pathophysiological conditions.
Keywords: Long chain acyl carnitine; Reactive oxygen species; ANT; RyR2;
Disturbance of energy and redox homeostasis and reduction of Na+,K+-ATPase activity provoked by in vivo intracerebral administration of ethylmalonic acid to young rats by Luciana Ritter; Daniele Kleemann; Fernanda Hermes Hickmann; Alexandre Umpierrez Amaral; Ângela Sitta; Moacir Wajner; César Augusto João Ribeiro (759-767).
Ethylmalonic acid (EMA) accumulation occurs in various metabolic diseases with neurological manifestation, including short acyl-CoA dehydrogenase deficiency (SCADD) and ethylmalonic encephalopathy (EE). Since pathophysiological mechanisms responsible for brain damage in these disorders are still poorly understood, we investigated the ex vivo effects of acute intrastriatal administration of EMA on important parameters of energy and redox homeostasis in striatum from young rats. We evaluated CO2 production from glucose, glucose utilization and lactate production, as well as the activities of the citric acid cycle (CAC) enzymes, the electron transfer chain (ETC) complexes II–IV (oxidative phosphorylation, OXPHOS) and synaptic Na+,K+-ATPase. We also tested the effect of EMA on malondialdehyde (MDA) levels (marker of lipid oxidation) and reduced glutathione (GSH) levels. EMA significantly reduced CO2 production, increased glucose utilization and lactate production, and reduced the activities of citrate synthase and of complexes II and II–III of the ETC, suggesting an impairment of CAC and OXPHOS. EMA injection also reduced Na+,K+-ATPase activity and GSH concentrations, whereas MDA levels were increased. Furthermore, EMA-induced diminution of Na+,K+-ATPase activity and reduction of GSH levels were prevented, respectively, by the antioxidants melatonin and N-acetylcysteine, indicating that reactive species were involved in these effects. Considering the importance of CAC and ETC for energy production and Na+,K+-ATPase for the maintenance of the cell membrane potential, the present data indicate that EMA compromises mitochondrial homeostasis and neurotransmission in striatum. We presume that these pathomechanisms may be involved to a certain extent in the neurological damage found in patients affected by SCADD and EE.
Keywords: Ethylmalonic acid; Energy metabolism; Redox homeostasis; Synaptic Na+,K+-ATPase; Striatum;
Multifactorial modulation of susceptibility to l-lysine in an animal model of glutaric aciduria type I by Sven W. Sauer; Silvana Opp; Shoko Komatsuzaki; Anna-Eva Blank; Michel Mittelbronn; Peter Burgard; D.M. Koeller; Jürgen G. Okun; Stefan Kölker (768-777).
Glutaric aciduria type I is an inherited defect in l-lysine, l-hydroxylysine and l-tryptophan degradation caused by deficiency of glutaryl-CoA dehydrogenase (GCDH). The majority of untreated patients presents with accumulation of neurotoxic metabolites – glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA) – and striatal injury. Gcdh−/− mice display elevated levels of GA and 3-OH-GA but do not spontaneously develop striatal lesions. l-lysine-enriched diets (appr. 235 mg/d) were suggested to induce a neurological phenotype similar to affected patients. In our hands 93% of mice stressed according to the published protocol remained asymptomatic. To understand the underlying mechanism, we modified their genetic background (F1 C57BL6/Jx129/SvCrl) and increased the daily oral l-lysine supply (235–433 mg). We identified three modulating factors, (1) gender, (2) genetic background, and (3) amount of l-lysine. Male mice displayed higher vulnerability and inbreeding for more than two generations as well as elevating l-lysine supply increased the diet-induced mortality rate (up to 89%). Onset of first symptoms leads to strongly reduced intake of food and, thus, l-lysine suggesting a threshold for toxic metabolite production to induce neurological disease. GA and 3-OH-GA tissue concentrations did not correlate with dietary l-lysine supply but differed between symptomatic and asymptomatic mice. Cerebral activities of glyceraldehyde 3-phosphate dehydrogenase, 2-oxoglutarate dehydrogenase complex, and aconitase were decreased. Symptomatic mice did not develop striatal lesions or intracerebral hemorrhages. We found severe spongiosis in the hippocampus of Gcdh−/− mice which was independent of dietary l-lysine supply. In conclusion, the l-lysine-induced pathology in Gcdh−/− mice depends on genetic and dietary parameters.
Keywords: Inborn errors of metabolism; Neurodegenerative disease; Amino acid; Animal model; Neural metabolism;
Prostacyclin post-treatment improves LPS-induced acute lung injury and endothelial barrier recovery via Rap1 by Anna A. Birukova; Fanyong Meng; Yufeng Tian; Angelo Meliton; Nicolene Sarich; Lawrence A. Quilliam; Konstantin G. Birukov (778-791).
Protective effects of prostacyclin (PC) or its stable analog beraprost against agonist-induced lung vascular inflammation have been associated with elevation of intracellular cAMP and Rac GTPase signaling which inhibited the RhoA GTPase-dependent pathway of endothelial barrier dysfunction. This study investigated a distinct mechanism of PC-stimulated lung vascular endothelial (EC) barrier recovery and resolution of LPS-induced inflammation mediated by small GTPase Rap1. Efficient barrier recovery was observed in LPS-challenged pulmonary EC after prostacyclin administration even after 15 h of initial inflammatory insult and was accompanied by the significant attenuation of p38 MAP kinase and NFκB signaling and decreased production of IL-8 and soluble ICAM1. These effects were reproduced in cells post-treated with 8CPT, a small molecule activator of Rap1-specific nucleotide exchange factor Epac. By contrast, pharmacologic Epac inhibitor, Rap1 knockdown, or knockdown of cell junction-associated Rap1 effector afadin attenuated EC recovery caused by PC or 8CPT post-treatment. The key role of Rap1 in lung barrier restoration was further confirmed in the murine model of LPS-induced acute lung injury. Lung injury was monitored by measurements of bronchoalveolar lavage protein content, cell count, and Evans blue extravasation and live imaging of vascular leak over 6 days using a fluorescent tracer. The data showed significant acceleration of lung recovery by PC and 8CPT post-treatment, which was abrogated in Rap1a−/− mice. These results suggest that post-treatment with PC triggers the Epac/Rap1/afadin-dependent mechanism of endothelial barrier restoration and downregulation of p38MAPK and NFκB inflammatory cascades, altogether leading to accelerated lung recovery.
Keywords: Cytoskeleton; Endothelium; Permeability; Lung; Inflammation;
γ-Glutamyl cysteine and γ-glutamyl valine inhibit TNF-α signaling in intestinal epithelial cells and reduce inflammation in a mouse model of colitis via allosteric activation of the calcium-sensing receptor by Hua Zhang; Jennifer Kovacs-Nolan; Tomohiro Kodera; Yuzuru Eto; Yoshinori Mine (792-804).
The extracellular calcium-sensing receptor (CaSR) is distributed throughout the gastrointestinal tract, and its activation has been shown to promote intestinal homeostasis, suggesting that CaSR may be a promising target for novel therapies to prevent chronic intestinal inflammation such as inflammatory bowel disease (IBD). The γ-glutamyl dipeptides γ-glutamyl cysteine (γ-EC) and γ-glutamyl valine (γ-EV) are dietary flavor enhancing compounds, and have been shown to activate CaSR via allosteric ligand binding. The aim of this study was to examine the anti-inflammatory effects of γ-EC and γ-EV in vitro in intestinal epithelial cells and in a mouse model of intestinal inflammation. In vitro, treatment of Caco-2 cells with γ-EC and γ-EV resulted in the CaSR-mediated reduction of TNF-α-stimulated pro-inflammatory cytokines and chemokines including IL-8, IL-6, and IL-1β, and inhibited phosphorylation of JNK and IκBα, while increasing expression of IL-10. In vivo, using a mouse model of dextran sodium sulfate (DSS)-induced colitis, γ-EC and γ-EV treatment ameliorated DSS-induced clinical signs, weight loss, colon shortening and histological damage. Moreover, γ-EC and γ-EV reduced the expression of TNF-α, IL-6, INF-γ, IL-1β, and IL-17, and increased the expression of IL-10 in the colon, in a CaSR-dependent manner. The CaSR-mediated anti-inflammatory effects of γ-EC were abrogated in β-arrestin2 knock-down Caco-2 cells, and involvement of β-arrestin2 was found to inhibit TNF-α-dependent signaling via cross-talk with the TNF-α receptor (TNFR).Thus CaSR activation by γ-EC and γ-EV can aid in maintaining intestinal homeostasis and reducing inflammation in chronic inflammatory conditions such as IBD.Display Omitted
Keywords: Inflammatory bowel disease (IBD); Tumor necrosis factor (TNF); Intestinal epithelium; Dextran sodium sulfate (DSS) colitis; γ-Glutamyl dipeptides; Calcium-sensing receptor (CaSR);
Activation of NADPH oxidase mediates increased endoplasmic reticulum stress and left ventricular remodeling after myocardial infarction in rabbits by Bao Li; Jing Tian; Yi Sun; Tao-Rui Xu; Rui-Fang Chi; Xiao-Li Zhang; Xin-Ling Hu; Yue-an Zhang; Fu-Zhong Qin; Wei-Fang Zhang (805-815).
Nicotinamide adenine dinucleotide 3-phosphate (NADPH) oxidase activity and endoplasmic reticulum (ER) stress are increased after myocardial infarction (MI). In this study, we proposed to test whether activation of the NADPH oxidase in the remote non-infarcted myocardium mediates ER stress and left ventricular (LV) remodeling after MI. Rabbits with MI or sham operation were randomly assigned to orally receive an NADPH oxidase inhibitor apocynin or placebo for 30 days. The agents were administered beginning at 1 week after surgery. MI rabbits exhibited decreases in LV fractional shortening, LV ejection fraction and the first derivative of the LV pressure rise, which were abolished by apocynin treatment. NADPH oxidase Nox2 protein and mRNA expressions were increased in the remote non-infarcted myocardium after MI. Immunolabeling further revealed that Nox2 was increased in cardiac myocytes in the remote myocardium. The apocynin treatment prevented increases in the Nox2 expression, NADPH oxidase activity, oxidative stress, myocyte apoptosis and GRP78, CHOP and cleaved caspase 12 protein expression in the remote myocardium. The apocynin treatment also attenuated increases in myocyte diameter and cardiac fibrosis. In cultured H9C2 cardiomyocytes exposed to angiotensin II, an important stimulus for post-MI remodeling, Nox2 knockdown with siRNA significantly inhibited angiotensin II-induced NADPH oxidase activation, reactive oxygen species and GRP78 and CHOP protein expression. We conclude that NADPH oxidase inhibition attenuates increased ER stress in the remote non-infarcted myocardium and LV remodeling late after MI in rabbits. These findings suggest that the activation of NADPH oxidase in the remote non-infarcted myocardium mediates increased ER stress, contributing to myocyte apoptosis and LV remodeling after MI.
Keywords: NADPH oxidase; Endoplasmic reticulum stress; Myocyte apoptosis; Left ventricular remodeling; Myocardial infarction;
Sex differences in the relationship of IL-6 signaling to cancer cachexia progression by Kimbell L. Hetzler; Justin P. Hardee; Melissa J. Puppa; Aditi A. Narsale; Shuichi Sato; J. Mark Davis; James A. Carson (816-825).
A devastating aspect of cancer cachexia is severe loss of muscle and fat mass. Though cachexia occurs in both sexes, it is not well-defined in the female. The ApcMin/+ mouse is genetically predisposed to develop intestinal tumors; circulating IL-6 is a critical regulator of cancer cachexia in the male ApcMin/+ mouse. The purpose of this study was to examine the relationship between IL-6 signaling and cachexia progression in the female ApcMin/+ mouse. Male and female ApcMin/+ mice were examined during the initiation and progression of cachexia. Another group of females had IL-6 overexpressed between 12 and 14 weeks or 15–18 weeks of age to determine whether IL-6 could induce cachexia. Cachectic female ApcMin/+ mice lost body weight, muscle mass, and fat mass; increased muscle IL-6 mRNA expression was associated with these changes, but circulating IL-6 levels were not. Circulating IL-6 levels did not correlate with downstream signaling in muscle in the female. Muscle IL-6r mRNA expression and SOCS3 mRNA expression as well as muscle IL-6r protein and STAT3 phosphorylation increased with severe cachexia in both sexes. Muscle SOCS3 protein increased in cachectic females but decreased in cachectic males. IL-6 overexpression did not affect cachexia progression in female ApcMin/+ mice. Our results indicate that female ApcMin/+ mice undergo cachexia progression that is at least initially IL-6-independent. Future studies in the female will need to determine mechanisms underlying regulation of IL-6 response and cachexia induction.
Keywords: IL-6r; STAT3; SOCS3; Skeletal muscle; ApcMin/+ ;
On the role of 4-hydroxynonenal in health and disease by Miklós Csala; Tamás Kardon; Balázs Legeza; Beáta Lizák; József Mandl; Éva Margittai; Ferenc Puskás; Péter Száraz; Péter Szelényi; Gábor Bánhegyi (826-838).
Polyunsaturated fatty acids are susceptible to peroxidation and they yield various degradation products, including the main α,β-unsaturated hydroxyalkenal, 4-hydroxy-2,3-trans-nonenal (HNE) in oxidative stress. Due to its high reactivity, HNE interacts with various macromolecules of the cell, and this general toxicity clearly contributes to a wide variety of pathological conditions. In addition, growing evidence suggests a more specific function of HNE in electrophilic signaling as a second messenger of oxidative/electrophilic stress. It can induce antioxidant defense mechanisms to restrain its own production and to enhance the cellular protection against oxidative stress. Moreover, HNE-mediated signaling can largely influence the fate of the cell through modulating major cellular processes, such as autophagy, proliferation and apoptosis. This review focuses on the molecular mechanisms underlying the signaling and regulatory functions of HNE. The role of HNE in the pathophysiology of cancer, cardiovascular and neurodegenerative diseases is also discussed.
Keywords: 4-Hydroxynonenal; Lipid peroxidation; Nrf2; Electrophilic stress; Proteostasis;
Fibroblast growth factor and canonical WNT/β-catenin signaling cooperate in suppression of chondrocyte differentiation in experimental models of FGFR signaling in cartilage by Marcela Buchtova; Veronika Oralova; Anie Aklian; Jan Masek; Iva Vesela; Zhufeng Ouyang; Tereza Obadalova; Zaneta Konecna; Tereza Spoustova; Tereza Pospisilova; Petr Matula; Miroslav Varecha; Lukas Balek; Iva Gudernova; Iva Jelinkova; Ivan Duran; Iveta Cervenkova; Shunichi Murakami; Alois Kozubik; Petr Dvorak; Vitezslav Bryja; Pavel Krejci (839-850).
Aberrant fibroblast growth factor (FGF) signaling disturbs chondrocyte differentiation in skeletal dysplasia, but the mechanisms underlying this process remain unclear. Recently, FGF was found to activate canonical WNT/β-catenin pathway in chondrocytes via Erk MAP kinase-mediated phosphorylation of WNT co-receptor Lrp6. Here, we explore the cellular consequences of such a signaling interaction. WNT enhanced the FGF-mediated suppression of chondrocyte differentiation in mouse limb bud micromass and limb organ cultures, leading to inhibition of cartilage nodule formation in micromass cultures, and suppression of growth in cultured limbs. Simultaneous activation of the FGF and WNT/β-catenin pathways resulted in loss of chondrocyte extracellular matrix, expression of genes typical for mineralized tissues and alteration of cellular shape. WNT enhanced the FGF-mediated downregulation of chondrocyte proteoglycan and collagen extracellular matrix via inhibition of matrix synthesis and induction of proteinases involved in matrix degradation. Expression of genes regulating RhoA GTPase pathway was induced by FGF in cooperation with WNT, and inhibition of the RhoA signaling rescued the FGF/WNT-mediated changes in chondrocyte cellular shape. Our results suggest that aberrant FGF signaling cooperates with WNT/β-catenin in suppression of chondrocyte differentiation.
Keywords: Fibroblast growth factor receptor; FGFR3; WNT; Chondrocyte; Differentiation; Cartilage;
Over-expression of cofilin-1 suppressed growth and invasion of cancer cells is associated with up-regulation of let-7 microRNA by Cheng-Han Tsai; Liang-Ting Lin; Chung-Yih Wang; Yu-Wen Chiu; Yen-Ting Chou; Shu-Jun Chiu; Hsin-Ell Wang; Ren-Shyan Liu; Chun-Yi Wu; Pei-Chia Chan; Muh-Hwa Yang; Shih-Hwa Chiou; Man-Jyun Liao; Yi-Jang Lee (851-861).
Cofilin-1, a non-muscle isoform of actin regulatory protein that belongs to the actin-depolymerizing factor (ADF)/cofilin family is known to affect cancer development. Previously, we found that over-expression of cofilin-1 suppressed the growth and invasion of human non-small cell lung cancer (NSCLC) cells in vitro. In this study, we further investigated whether over-expression of cofilin-1 can suppress tumor growth in vivo, and performed a microRNA array analysis to better understand whether specific microRNA would be involved in this event. The results showed that over-expression of cofilin-1 suppressed NSCLC tumor growth using the xenograft tumor model with the non-invasive reporter gene imaging modalities. Additionally, cell motility and invasion were significantly suppressed by over-expressed cofilin-1, and down-regulation of matrix metalloproteinase (MMPs) -1 and -3 was concomitantly detected. According to the microRNA array analysis, the let-7 family, particularly let-7b and let-7e, were apparently up-regulated among 248 microRNAs that were affected after over-expression of cofilin-1 up to 7 days. Knockdown of let-7b or let-7e using chemical locked nucleic acid (LNA) could recover the growth rate and the invasion of cofilin-1 over-expressing cells. Next, the expression of c-myc, LIN28 and Twist-1 proteins known to regulate let-7 were analyzed in cofilin-1 over-expressing cells, and Twist-1 was significantly suppressed under this condition. Up-regulation of let-7 microRNA by over-expressed cofilin-1 could be eliminated by co-transfected Twist-1 cDNA. Taken together, current data suggest that let-7 microRNA would be involved in over-expression of cofilin-1 mediated tumor suppression in vitro and in vivo.
Keywords: NSCLC; Cofilin-1; Xenograft tumor model; Reporter gene imaging; Let-7 microRNA;
Flavonoid derivative 7,8-DHF attenuates TBI pathology via TrkB activation by Rahul Agrawal; Emily Noble; Ethika Tyagi; Yumei Zhuang; Zhe Ying; Fernando Gomez-Pinilla (862-872).
Traumatic brain injury (TBI) is followed by a state of metabolic dysfunction, affecting the ability of neurons to use energy and support brain plasticity; there is no effective therapy to counteract the TBI pathology. Brain-derived neurotrophic factor (BDNF) has an exceptional capacity to support metabolism and plasticity, which highly contrasts with its poor pharmacological profile. We evaluated the action of a flavonoid derivative 7,8-dihydroxyflavone (7,8-DHF), a BDNF receptor (TrkB) agonist with the pharmacological profile congruent for potential human therapies. Treatment with 7,8-DHF (5 mg/kg, ip, daily for 7 days) was effective to ameliorate the effects of TBI on plasticity markers (CREB phosphorylation, GAP-43 and syntaxin-3 levels) and memory function in Barnes maze test. Treatment with 7,8-DHF restored the decrease in protein and phenotypic expression of TrkB phosphorylation after TBI. In turn, intrahippocampal injections of K252a, a TrkB antagonist, counteracted the 7,8-DHF induced TrkB signaling activation and memory improvement in TBI, suggesting the pivotal role of TrkB signaling in cognitive performance after brain injury. A potential action of 7,8-DHF on cell energy homeostasis was corroborated by the normalization in levels of PGC-1α, TFAM, COII, AMPK and SIRT1 in animals subjected to TBI. Results suggest a potential mechanism by which 7,8-DHF counteracts TBI pathology via activation of the TrkB receptor and engaging the interplay between cell energy management and synaptic plasticity. Since metabolic dysfunction is an important risk factor for the development of neurological and psychiatric disorders, these results set a precedent for the therapeutic use of 7,8-DHF in a larger context.
Keywords: Cognition; 7,8-Dihydroxyflavone; Metabolism; Plasticity; Traumatic brain injury;
Sarcoplasmic reticulum Ca2 + ATPase pump is a major regulator of glucose transport in the healthy and diabetic heart by Amanda P. Waller; Anuradha Kalyanasundaram; Summer Hayes; Muthu Periasamy; Véronique A. Lacombe (873-881).
Despite intensive research, the pathways that mediate calcium (Ca2 +)-stimulated glucose transport in striated muscle remain elusive. Since the sarcoplasmic reticulum calcium ATPase (SERCA) pump tightly regulates cytosolic [Ca2 +], we investigated whether the SERCA pump is a major regulator of cardiac glucose transport. We used healthy and insulin-deficient diabetic transgenic (TG) mice expressing SERCA1a in the heart. Active cell surface glucose transporter (GLUT)-4 was measured by a biotinylated photolabeled assay in the intact perfused myocardium and isolated myocytes. In healthy TG mice, cardiac-specific SERCA1a expression increased active cell-surface GLUT4 and glucose uptake in the myocardium, as well as whole body glucose tolerance. Diabetes reduced active cell-surface GLUT4 content and glucose uptake in the heart of wild type mice, all of which were preserved in diabetic TG mice. Decreased basal AS160 and increased proportion of calmodulin-bound AS160 paralleled the increase in cell surface GLUT4 content in the heart of TG mice, suggesting that AS160 regulates GLUT trafficking by a Ca2 +/calmodulin dependent pathway. In addition, cardiac-specific SERCA1a expression partially rescues hyperglycemia during diabetes. Collectively, these data suggested that the SERCA pump is a major regulator of cardiac glucose transport by an AS160 dependent mechanism during healthy and insulin-deficient state. Our data further indicated that cardiac-specific SERCA overexpression rescues diabetes induced-alterations in cardiac glucose transport and improves whole body glucose homeostasis. Therefore, findings from this study provide novel mechanistic insights linking upregulation of the SERCA pump in the heart as a potential therapeutic target to improve glucose metabolism during diabetes.
Keywords: GLUT4; SERCA pump; AS160; Biotinylated photolabeled assay; Micropositron emission tomography;
Calpain-1 induces endoplasmic reticulum stress in promoting cardiomyocyte apoptosis following hypoxia/reoxygenation by Dong Zheng; Grace Wang; Shuai Li; Guo-Chang Fan; Tianqing Peng (882-892).
Both calpain activation and endoplasmic reticulum (ER) stress are implicated in ischemic heart injury. However, the role of calpain in ER stress remains largely elusive. This study investigated whether calpain activation causes ER stress, thereby mediating cardiomyocyte apoptosis in an in vitro model of hypoxia/re-oxygenation (H/R). In neonatal mouse cardiomyocytes and rat cardiomyocyte-like H9c2 cells, up-regulation of calpain-1 sufficiently induced ER stress, c-Jun N-terminal protein kinase1/2 (JNK1/2) activation and apoptosis. Inhibition of ER stress or JNK1/2 prevented apoptosis induced by calpain-1. In an in vitro model of H/R-induced injury in cardiomyocytes, H/R was induced by a 24-hour hypoxia followed by a 24-hour re-oxygenation. H/R activated calpain-1, induced ER stress and JNK1/2 activation, and triggered apoptosis. Inhibition of calpain and ER stress blocked JNK1/2 activation and prevented H/R-induced apoptosis. Furthermore, blockade of JNK1/2 signaling inhibited apoptosis following H/R. The role of calpain in ER stress was also demonstrated in an in vivo model of ischemia/reperfusion using transgenic mice over-expressing calpastatin. In summary, calpain-1 induces ER stress and JNK1/2 activation, thereby mediating apoptosis in cardiomyocytes. Accordingly, inhibition of calpain prevents ER stress, JNK1/2 activation and apoptosis in H/R-induced cardiomyocytes. Thus, ER stress/JNK1/2 activation may represent an important mechanism linking calpain-1 to ischemic injury.
Keywords: Calpain; ER stress; JNK1/2; Apoptosis; Hypoxia/reoxygenation;
Treatment in vitro with PPARα and PPARγ ligands drives M1-to-M2 polarization of macrophages from T. cruzi-infected mice by Federico Penas; Gerardo A. Mirkin; Marcela Vera; Ágata Cevey; Cintia D. González; Marisa I. Gómez; María Elena Sales; Nora B. Goren (893-904).
Trypanosoma cruzi, the etiological agent of Chagas' disease, induces a persistent inflammatory response. Macrophages are a first line cell phenotype involved in the clearance of infection. Upon parasite uptake, these cells increase inflammatory mediators like NO, TNF-α, IL-1β and IL-6, leading to parasite killing. Although desired, inflammatory response perpetuation and exacerbation may lead to tissue damage. Peroxisome proliferator-activated receptors (PPARs) are ligand-dependent nuclear transcription factors that, besides regulating lipid and carbohydrate metabolism, have a significant anti-inflammatory effect. This is mediated through the interaction of the receptors with their ligands. PPARγ, one of the PPAR isoforms, has been implicated in macrophage polarization from M1, the classically activated phenotype, to M2, the alternatively activated phenotype, in different models of metabolic disorders and infection. In this study, we show for the first time that, besides PPARγ, PPARα is also involved in the in vitro polarization of macrophages isolated from T. cruzi-infected mice. Polarization was evidenced by a decrease in the expression of NOS2 and proinflammatory cytokines and the increase in M2 markers like Arginase I, Ym1, mannose receptor and TGF-β. Besides, macrophage phagocytic activity was significantly enhanced, leading to increased parasite load. We suggest that modulation of the inflammatory response by both PPARs might be due, at least in part, to a change in the profile of inflammatory macrophages. The potential use of PPAR agonists as modulators of overt inflammatory response during the course of Chagas' disease deserves further investigation.
Keywords: Trypanosoma cruzi; Macrophage polarization; PPAR; Inflammatory mediators;
Peroxide-mediated oxidation and inhibition of the peptidyl-prolyl isomerase Pin1 by Brendan T. Innes; Modupeola A. Sowole; Laszlo Gyenis; Michelle Dubinsky; Lars Konermann; David W. Litchfield; Christopher J. Brandl; Brian H. Shilton (905-912).
Pin1 is a phosphorylation-dependent peptidyl-prolyl isomerase that plays a critical role in mediating protein conformational changes involved in signaling processes related to cell cycle control. Pin1 has also been implicated as being neuroprotective in aging-related neurodegenerative disorders including Alzheimer's disease where Pin1 activity is diminished. Notably, recent proteomic analysis of brain samples from patients with mild cognitive impairment revealed that Pin1 is oxidized and also displays reduced activity. Since the Pin1 active site contains a functionally critical cysteine residue (Cys113) with a low predicted pK a, we hypothesized that Cys113 is sensitive to oxidation. Consistent with this hypothesis, we observed that treatment of Pin1 with hydrogen peroxide results in a 32 Da mass increase, likely resulting from the oxidation of Cys113 to sulfinic acid (Cys-SO2H). This modification results in loss of peptidyl-prolyl isomerase activity. Notably, Pin1 with Cys113 substituted by aspartic acid retains activity and is no longer sensitive to oxidation. Structural studies by X-ray crystallography revealed increased electron density surrounding Cys113 following hydrogen peroxide treatment. At lower concentrations of hydrogen peroxide, oxidative inhibition of Pin1 can be partially reversed by treatment with dithiothreitol, suggesting that oxidation could be a reversible modification with a regulatory role. We conclude that the loss of Pin1 activity upon oxidation results from oxidative modification of the Cys113 sulfhydryl to sulfenic (Cys-SOH) or sulfinic acid (Cys-SO2H). Given the involvement of Pin1 in pathological processes related to neurodegenerative diseases and to cancer, these findings could have implications for the prevention or treatment of disease.
Keywords: Peptidyl-prolyl cis–trans isomerase; Oxidation; Cysteine sulfenic and sulfinic acid; Alzheimer's disease; Kinase signaling; Cancer biology;
Pseudophosphorylation of Tau at distinct epitopes or the presence of the P301L mutation targets the microtubule-associated protein Tau to dendritic spines by Di Xia; Chuanzhou Li; Jürgen Götz (913-924).
Alzheimer's disease is characterized by the accumulation of amyloid-β (Aβ) and Tau in the brain. In mature neurons, Tau is concentrated in the axon and found at lower levels in the dendrite where it is required for targeting Fyn to the spines. Here Fyn mediates Aβ toxicity, which is vastly abrogated when Tau is either deleted or a truncated form of Tau (Tau1-255) is co-expressed. Interestingly, MAP2, a microtubule-binding protein with mainly dendritic localization that shares Fyn-binding motifs with Tau, does not mediate Aβ's synaptic toxicity in the absence of Tau. Here we show in hippocampal neurons that endogenous Tau enters the entire spine, albeit at low levels, whereas MAP2 only enters its neck or is restricted to the dendritic shaft. Based on an extensive mutagenesis study, we also reveal that the spine localization of Tau is facilitated by deletion of the microtubule-binding repeat domain. When distinct phosphorylation sites (AT180–T231/S235, 12E8–S262/S356, PHF1–S396/S404) were pseudophosphorylated (with glutamic acid, using alanine replacements as controls), Tau targeting to spines was markedly increased, whereas the pseudophosphorylation of the late phospho-epitope S422 had no effect. In determining the role physiological Fyn has in the spine localization of Tau, we found that neither were endogenous Tau levels reduced in Fyn knockout compared with wild-type synaptosomal brain fractions nor was the spine localization of over-expressed pseudophosphorylated or P301L Tau. This demonstrates that although Fyn targeting to the spine is Tau dependent, elevated levels of phosphorylated Tau or P301L Tau can enter the spine in a Fyn-independent manner.
Keywords: Alzheimer's disease; Frontotemporal dementia; Fyn; Phosphorylation; PSD95; Tau;
Astrocytes and mitochondria from adrenoleukodystrophy protein (ABCD1)-deficient mice reveal that the adrenoleukodystrophy-associated very long-chain fatty acids target several cellular energy-dependent functions by Nicol Kruska; Peter Schönfeld; Aurora Pujol; Georg Reiser (925-936).
X-linked adrenoleukodystrophy (X-ALD) is a severe neurodegenerative disorder resulting from defective ABCD1 transport protein. ABCD1 mediates peroxisomal uptake of free very-long-chain fatty acids (VLCFA) as well as their CoA-esters. Consequently, VLCFA accumulate in patients' plasma and tissues, which is considered as pathogenic X-ALD triggering factor. Clinical symptoms are mostly manifested in neural tissues and adrenal gland. Here, we investigate astrocytes from wild-type control and a genetic X-ALD mouse model (Abcd1-knockout), exposed to supraphysiological VLCFA (C22:0, C24:0 and C26:0) concentrations. They exhibit multiple impairments of energy metabolism. Furthermore, brain mitochondria from Abcd1 −/− mice and wild-type control respond similarly to VLCFA with increased ROS generation, impaired oxidative ATP synthesis and diminished Ca2 + uptake capacity, suggesting that a defective ABCD1 exerts no adaptive pressure on mitochondria. In contrast, astrocytes from Abcd1 −/− mice respond more sensitively to VLCFA than wild-type control astrocytes. Moreover, long-term application of VLCFA induces high ROS generation, and strong in situ depolarization of mitochondria, and, in Abcd1 −/− astrocytes, severely diminishes the capability to revert oxidized pyridine nucleotides to NAD(P)H. In addition, observed differences in responses of mitochondria and astrocytes to the hydrocarbon chain length of VLCFA suggest that detrimental VLCFA activities in astrocytes involve defective cellular functions other than mitochondria. In summary, we clearly demonstrate that VLCFA increase the vulnerability of Abcd1 −/− astrocytes.Display Omitted
Keywords: Adrenoleukodystrophy (X-ALD); Astrocyte; Mitochondrion; Peroxisomal disorder; Reactive oxygen species; Very long chain fatty acids (VLCFA);
Inflaming the diseased brain: a role for tainted melanins by T.M. Jeitner; M. Kalogiannis; P.A. Patrick; I. Gomolin; T. Palaia; L. Ragolia; D. Brand; E.J. Delikatny (937-950).
Inflammation plays a crucial role in neurodegenerative diseases, but the irritants responsible for this response remain largely unknown. This report addressed the hypothesis that hypochlorous acid reacts with dopamine to produce melanic precipitates that promote cerebral inflammation. Spectrophotometric studies demonstrated that nM amounts of HOCl and dopamine react within seconds. A second-order rate constant for the reaction of HOCl and dopamine of 2.5 × 104 M− 1 s− 1 was obtained by measuring loss of dopaminergic fluorescence due to HOCl. Gravimetric measurements, electron microscopy, elemental analysis, and a novel use of flow cytometry confirmed that the major product of this reaction is a precipitate with an average diameter of 1.5 μm. Flow cytometry was also used to demonstrate the preferential reaction of HOCl with dopamine rather than albumin. Engulfment of the chlorodopamine particulates by phagocytes in vitro caused these cells to release TNFα and die. Intrastriatal administration of 106 particles also increased the content of TNFα in the brain and led to a 50% loss of the dopaminergic neurons in the nigra. These studies indicate that HOCl and dopamine react quickly and preferentially with each other to produce particles that promote inflammation and neuronal death in the brain.
Keywords: Inflammation; Brain; Parkinson disease; Dopamine; Hypochlorous acid;
Curcumin boosts DHA in the brain: Implications for the prevention of anxiety disorders by Aiguo Wu; Emily E. Noble; Ethika Tyagi; Zhe Ying; Yumei Zhuang; Fernando Gomez-Pinilla (951-961).
Dietary deficiency of docosahexaenoic acid (C22:6 n-3; DHA) is linked to the neuropathology of several cognitive disorders, including anxiety. DHA, which is essential for brain development and protection, is primarily obtained through the diet or synthesized from dietary precursors, however the conversion efficiency is low. Curcumin (diferuloylmethane), which is a principal component of the spice turmeric, complements the action of DHA in the brain, and this study was performed to determine molecular mechanisms involved. We report that curcumin enhances the synthesis of DHA from its precursor, α-linolenic acid (C18:3 n-3; ALA) and elevates levels of enzymes involved in the synthesis of DHA such as FADS2 and elongase 2 in both liver and brain tissues. Furthermore, in vivo treatment with curcumin and ALA reduced anxiety-like behavior in rodents. Taken together, these data suggest that curcumin enhances DHA synthesis, resulting in elevated brain DHA content. These findings have important implications for human health and the prevention of cognitive disease, particularly for populations eating a plant-based diet or who do not consume fish, a primary source of DHA, since DHA is essential for brain function and its deficiency is implicated in many types of neurological disorders.
Keywords: DHA synthesis; Curcumin; ALA; DPA; Omega 3 fatty acid; Docosahexaenoic acid;
Reduced nuclear protein 1 expression improves insulin sensitivity and protects against diet-induced glucose intolerance through up-regulation of heat shock protein 70 by H.C. Barbosa-Sampaio; R. Drynda; B. Liu; A.M. Rodriguez De Ledesma; C. Malicet; J.L. Iovanna; P.M. Jones; D.S. Muller; S.J. Persaud (962-969).
We recently reported that deletion of the stress-regulated nuclear protein 1 (Nupr1) protected against obesity-associated metabolic alterations due to increased beta cell mass, but complete Nupr1 ablation was not advantageous since it led to insulin resistance on a normal diet. The current study used Nupr1 haplodeficient mice to investigate whether a partial reduction in Nupr1 expression conferred beneficial effects on glucose homeostasis. Islet number, morphology and area, assessed by immunofluorescence and morphometric analyses, were not altered in Nupr1 haplodeficient mice under normal diet conditions and nor was beta cell BrdU incorporation. Glucose and insulin tolerance tests indicated that there were no significant changes in in vivo insulin secretion and glucose clearance in Nupr1 haplodeficient mice, and beta cell function in vitro was normal. However, reduced Nupr1 expression decreased visceral fat deposition and significantly increased insulin sensitivity in vivo. In contrast to wild type animals, high fat diet-fed Nupr1 haplodeficient mice were not hyperinsulinaemic or glucose intolerant, and their sustained insulin sensitivity was demonstrated by appropriate insulin-induced Akt phosphorylation, as determined by Western blotting. At the molecular level, measurements of gene expression levels and promoter activities identified Nupr1-dependent inhibition of heat shock factor-1-induced heat shock protein 70 (Hsp70) expression as a mechanism through which Nupr1 regulates insulin sensitivity. We have shown for the first time that Nupr1 plays a central role in inhibiting Hsp70 expression in tissues regulating glucose homeostasis, and reductions in Nupr1 expression could be used to protect against the metabolic defects associated with obesity-induced insulin resistance.
Keywords: Islets of Langerhans; Glucose homeostasis; High fat diet; Insulin resistance; Heat shock protein;
miR218-5p regulates the proliferation of gastric cancer cells by targeting TFF1 in an Erk1/2-dependent manner by Ying Shi; Guo-Bin Chen; Qing-Wen Huang; Xu Chen; Jing-Jing Liu; Wei Xu; Xiao-Xiao Huang; Yun-Peng Liu; Chuan-Xing Xiao; Deng-Chyang Wu; Bayasi Guleng; Jian-Lin Ren (970-979).
Trefoil factor 1 (TFF1), a member of the trefoil peptide family, is not only associated with mucosal protection and restoration but is also correlated with tumorigenesis of the gastrointestinal tract. In an early study, we performed sequence analysis and identified one potential miR423-5p binding site within the 3′-untranslated region of TFF1 using microRNA target prediction tools. In the current study, we demonstrated that the coding DNA region within TFF1 is also a candidate for miR218-5p targeting. We used real-time PCR and in situ hybridization to analyze the correlation between miR218-5p and TFF1 expression in tumor lesions and paracancerous tissue in gastric cancer (GC) samples. Additionally, endogenous and exogenous TFF1 were suppressed by miR218-5p in gastric cancer cells and influenced the progression of GC in an Erk1/2-dependent manner. Targeting miR218-5p may provide a novel strategy for the treatment of GC.
Keywords: TFF1; Coding region; miR218-5p; Gastric cancer; Erk1/2;
Expression of the kynurenine pathway enzymes in the pancreatic islet cells. Activation by cytokines and glucolipotoxicity by J.J. Liu; S. Raynal; D. Bailbé; B. Gausseres; C. Carbonne; V. Autier; J. Movassat; M. Kergoat; B. Portha (980-991).
The tryptophan/kynurenine pathway (TKP) is the main route of tryptophan degradation and generates several neuroactive and immunomodulatory metabolites. Experimental and clinical data have clearly established that besides fat, muscle and liver, pancreatic islet tissue itself is a site of inflammation during obesity and type 2 diabetes. Therefore it is conceivable that pancreatic islet exposure to increased levels of cytokines may induce upregulation of islet kynurenine metabolism in a way resembling that seen in the brain in many neurodegenerative disorders. Using normal rat islets and the INS-1 β-cell line, we have demonstrated for the first time that: 1/only some TKP genes are constitutively expressed, both in β-cells as well as non β-cells; 2/ the regulatory enzyme indoleamine 2,3-dioxygenase (IDO1) is not constitutively expressed; 3/ IDO1 and kynurenine 3-monoxygenase (KMO) expression are potently activated by proinflammatory cytokines (IFN-γ, IL-1β) and glucolipotoxicity respectively, rather in β-cells than in non β-cells; 4/ Islet kynurenine/kynurenic acid production ratio is enhanced following IFN-γ and glucolipotoxicity; 5/ acute exposure to KYN potentiates glucose-induced insulin secretion by normal islets; and 6/ oxidative stress or glucocorticoid modulates TKP genes only marginally. Pancreatic islets may represent a new target tissue for inflammation and glucolipotoxicity to activate the TKP. Since inflammation is now recognized as a crucial mechanism in the development of the metabolic syndrome and more specifically at the islet level, it is needed to evaluate the potential induction of the TKP in the endocrine pancreas during obesity and/or diabetes and its relationship to the islet cell functional alterations.Display Omitted
Keywords: Kynurenine pathway; IFN-γ; IL-1β; Glucolipotoxicity; β-cells; Non β-cells;
Effect of chronic hypoxia on RAGE and its soluble forms in lungs and plasma of mice by P. Gopal; H.R. Gosker; C.C. de Theije; I.M. Eurlings; D.R. Sell; V.M. Monnier; N.L. Reynaert (992-1000).
The receptor for advanced glycation end products (RAGE) is a multi-ligand receptor. Alternative splicing and enzymatic shedding produce soluble forms that protect against damage by ligands including Advanced Glycation End products (AGEs). A link between RAGE and oxygen levels is evident from studies showing RAGE-mediated injury following hyperoxia. The effect of hypoxia on pulmonary RAGE expression and circulating sRAGE levels is however unknown. Therefore mice were exposed to chronic hypoxia for 21 d and expression of RAGE, sheddases in lungs and circulating sRAGE were determined. In addition, accumulation of AGEs in lungs and expression of the AGE detoxifying enzyme GLO1 and receptors were evaluated.In lung tissue gene expression of total RAGE, variants 1 and 3 were elevated in mice exposed to hypoxia, whereas mRAGE and sRAGE protein levels were decreased. In the hypoxic group plasma sRAGE levels were enhanced. Although the levels of pro-ADAM10 were elevated in lungs of hypoxia exposed mice, the relative amount of the active form was decreased and gelatinase activity unaffected. In the lungs, the RAGE ligand HMGB1 was decreased and of the AGEs, only LW-1 was increased by chronic hypoxia. Gene expression of AGE receptors 2 and 3 was significantly upregulated.Chronic hypoxia is associated with downregulation of pulmonary RAGE protein levels, but a relative increase in sRAGE. These alterations might be part of the adaptive and protective response mechanism to chronic hypoxia and are not associated with AGE formation except for the fluorophore LW-1 which emerges as a novel marker of tissue hypoxia.
Keywords: Hypoxia; RAGE expression; Shedding; AGEs; Detoxification;
Interleukin-6 gene transfer reverses body weight gain and fatty liver in obese mice by Yongjie Ma; Mingming Gao; Hao Sun; Dexi Liu (1001-1011).
Interleukin-6 (IL-6) is a multifunctional protein and has a major influence on energy metabolism. The current study was designed to assess the therapeutic effect of overexpression of Il-6 gene through gene transfer on high fat diet-induced obese mice. Hydrodynamic delivery of 1 μg pLIVE-IL6 plasmid per mouse into C57BL/6 obese mice resulted in peak level at 10 ng/ml of circulating IL-6 1 day after gene transfer and above 1 ng/ml thereafter for a period of 6 weeks. Persistent Il-6 gene expression did not affect food intake but induced a significant reduction in body weight and improved obesity-associated hepatic steatosis. Il-6 gene delivery enhanced thermogenic gene expression and elevated protein levels of phosphorylated STAT3, PGC1α and UCP1 in brown adipose tissue. Il-6 overexpression elevated mRNA levels of lipolysis genes, triggered phosphorylation of STAT3, AMPK, and ACC, and increased expression of genes involved in fatty acid oxidation in skeletal muscle. IL-6 did not affect macrophage infiltration but maintained the M2 macrophage population in adipose tissue. Collectively, these results suggest that overexpression of the Il-6 gene by hydrodynamic gene delivery induces weight loss and alleviates obesity-induced fatty liver and insulin resistance, supporting the notion that gene transfer is a valid approach in managing obesity epidemics.
Keywords: IL-6; Obesity; Weight loss; Insulin resistance; Energy expenditure;
Oxidative stress and inflammation in mucopolysaccharidosis type IVA patients treated with enzyme replacement therapy by Bruna Donida; Desirèe P. Marchetti; Giovana B. Biancini; Marion Deon; Paula R. Manini; Helen T. da Rosa; Dinara J. Moura; Jenifer Saffi; Fernanda Bender; Maira G. Burin; Adriana S. Coitinho; Roberto Giugliani; Carmen Regla Vargas (1012-1019).
Mucopolysaccharidosis type IVA (MPS IVA) is an inborn error of glycosaminoglycan (GAG) catabolism due to the deficient activity of N-acetylgalactosamine-6-sulfate sulfatase that leads to accumulation of the keratan sulfate and chondroitin 6-sulfate in body fluids and in lysosomes. The pathophysiology of this lysosomal storage disorder is not completely understood. The aim of this study was to investigate oxidative stress parameters, pro-inflammatory cytokine and GAG levels in MPS IVA patients. We analyzed urine and blood samples from patients under ERT (n = 17) and healthy age-matched controls (n = 10–15). Patients presented a reduction of antioxidant defense levels, assessed by a decrease in glutathione content and by an increase in superoxide dismutase activity in erythrocytes. Concerning lipid and protein damage, it was verified increased urine isoprostanes and di-tyrosine levels and decreased plasma sulfhydryl groups in MPS IVA patients compared to controls. MPS IVA patients showed higher DNA damage than control group and this damage had an oxidative origin in both pyrimidine and purine bases. Interleukin 6 was increased in patients and presented an inverse correlation with GSH levels, showing a possible link between inflammation and oxidative stress in MPS IVA disease. The data presented suggest that pro-inflammatory and pro-oxidant states occur in MPS IVA patients even under ERT. Taking these results into account, supplementation of antioxidants in combination with ERT can be a tentative therapeutic approach with the purpose of improving the patient's quality of life. To the best of our knowledge, this is the first study relating MPS IVA patients with oxidative stress.
Keywords: Mucopolysaccharidosis type IVA; Morquio A Syndrome; Oxidative stress; Glycosaminoglycan; Inflammation;
CEACAM6 promotes tumor angiogenesis and vasculogenic mimicry in gastric cancer via FAK signaling by Mingde Zang; Yunqiang Zhang; Baogui Zhang; Lei Hu; Jianfang Li; Zhiyuan Fan; Hexiao Wang; Liping Su; Zhenggang Zhu; Chen Li; Chao Yan; Qinlong Gu; Bingya Liu; Min Yan (1020-1028).
CEACAM6 is a member of glycosylphosphatidylinositol-linked immunoglobulin superfamily that is implicated in a variety of human cancers. In our previous study, we reported that CEACAM6 was overexpressed in gastric cancer tissues and promoted cancer metastasis. The purpose of this study is to determine the role of CEACAM6 in tumor angiogenesis and mimicry formation. We found that overexpressed CEACAM6 promoted tubule formation dependent on HUVEC cells and vasculogenic mimicry formation of gastric cancer cells; opposing results were achieved in CEACAM6-silenced groups. Moreover, we found that mosaic vessels formed by HUVEC cells and gastric cancer cells were observed in vitro by 3D-culture assay. Overexpressed CEACAM6 in gastric cancer cells promoted tumor growth, VEGF expression and vasculogenic mimicry structures formation in vivo. In accordance with these observations, we found that phosphorylation of FAK and phosphorylation of paxillin were up-regulated in CEACAM6-overexpressing gastric cancer cells, and FAK inhibitor Y15 could reduce tubule and vasculogenic mimicry formation. These findings suggest that CEACAM6 promotes tumor angiogenesis and vasculogenic mimicry formation via FAK signaling in gastric cancer and CEACAM6 may be a new target for cancer anti-vascular treatment.
Keywords: CEACAM6; Gastric cancer; Angiogenesis; VM; FAK;
Growth arrest in the ribosomopathy, Bowen–Conradi syndrome, is due to dramatically reduced cell proliferation and a defect in mitotic progression by Joy Armistead; Nehal Patel; Xiaoli Wu; Richard Hemming; Biswajit Chowdhury; Gagandeep Singh Basra; Marc R. Del Bigio; Hao Ding; Barbara Triggs-Raine (1029-1037).
Bowen–Conradi syndrome (BCS) is a ribosomopathy characterized by severe developmental delay and growth failure that typically leads to death by one year of age. It is caused by a c.257A>G, p.D86G substitution in the ribosomal biogenesis protein, Essential for Mitotic Growth 1 (EMG1). We generated a knock-in of the D86G substitution in mice to characterize the effects of EMG1 deficiency, particularly in the brain, where EMG1 expression is high. Embryos homozygous for the mutation in Emg1 were small for gestational age with neural tube defects, and died between embryonic days 8.5 and 12.5. These embryos exhibited dramatically reduced cell proliferation, which we also detected in autopsy brain tissue and bone marrow of BCS patients, consistent with a requirement for high levels of EMG1 in tissues with rapid cell proliferation. In fibroblasts derived from the BCS mouse embryos, we detected a high proportion of binucleated cells, indicating that a mitotic defect underlies the growth arrest in BCS. These studies add to growing evidence of a link between ribosome biogenesis, mitotic progression, and brain development that is currently unexplored.
Keywords: Ribosomopathy; Bowen–Conradi syndrome; Intrauterine growth retardation; Proliferation; Mitotic progression; Ribosome biogenesis;
Tamoxifen induces the development of hernia in mice by activating MMP-2 and MMP-13 expression by Xingzhe Ma; Ying Liu; Qixue Wang; Yuanli Chen; Mengyang Liu; Xiaoju Li; Rong Xiang; Yuquan Wei; Yajun Duan; Jihong Han (1038-1048).
Hernia is a disease with defects in collagen synthesis/metabolism. However, the underlying mechanisms for hernia formation have not been fully defined. Tamoxifen is a selective estrogen receptor modulator and used for patients with breast cancer. Tamoxifen also has pleiotropic and side effects. Herein, we report that tamoxifen treatment resulted in an appearance of a large bulge in the low abdomen between the hind legs in male but not in female mice. The autopsy demonstrated that the low abdominal wall was broken and a large amount of intestine herniated out of the abdominal cavity. Histological analysis indicated that tamoxifen caused structural abnormalities in the low abdominal wall which were associated with decreased type II collagen content. Furthermore, we determined increased matrix metalloproteinase-2 (MMP-2) and MMP-13 expression in the tissue. In vitro, tamoxifen induced MMP-2 and MMP-13 expression in fibroblasts. The promoter activity analysis and ChIP assay demonstrate that induction of MMP-13 expression was associated with activation of JNK–AP-1 and ERK1/2 signaling pathways while induction of MMP-2 expression was related to activation of the ERK1/2 signaling pathway. Taken together, our study establishes a novel murine hernia model, defines a severe side effect of tamoxifen, and suggests a caution to male patients receiving tamoxifen treatment.
Keywords: Collagen; Fibroblast; Hernia; MMP-13; Tamoxifen; AP-1;
PPARβ/δ ameliorates fructose-induced insulin resistance in adipocytes by preventing Nrf2 activation by Emma Barroso; Rosalía Rodríguez-Rodríguez; Matilde R. Chacón; Elsa Maymó-Masip; Laura Ferrer; Laia Salvadó; Emilio Salmerón; Martin Wabistch; Xavier Palomer; Joan Vendrell; Walter Wahli; Manuel Vázquez-Carrera (1049-1058).
We studied whether PPARβ/δ deficiency modifies the effects of high fructose intake (30% fructose in drinking water) on glucose tolerance and adipose tissue dysfunction, focusing on the CD36-dependent pathway that enhances adipose tissue inflammation and impairs insulin signaling. Fructose intake for 8 weeks significantly increased body and liver weight, and hepatic triglyceride accumulation in PPARβ/δ-deficient mice but not in wild-type mice. Feeding PPARβ/δ-deficient mice with fructose exacerbated glucose intolerance and led to macrophage infiltration, inflammation, enhanced mRNA and protein levels of CD36, and activation of the JNK pathway in white adipose tissue compared to those of water-fed PPARβ/δ-deficient mice. Cultured adipocytes exposed to fructose also exhibited increased CD36 protein levels and this increase was prevented by the PPARβ/δ activator GW501516. Interestingly, the levels of the nuclear factor E2-related factor 2 (Nrf2), a transcription factor reported to up-regulate Cd36 expression and to impair insulin signaling, were increased in fructose-exposed adipocytes whereas co-incubation with GW501516 abolished this increase. In agreement with Nrf2 playing a role in the fructose-induced CD36 protein level increases, the Nrf2 inhibitor trigonelline prevented the increase and the reduction in insulin-stimulated AKT phosphorylation caused by fructose in adipocytes. Protein levels of the well-known Nrf2 target gene NAD(P)H:quinone oxidoreductase 1 (Nqo1) were increased in water-fed PPARβ/δ-null mice, suggesting that PPARβ/δ deficiency increases Nrf2 activity; and this increase was exacerbated in fructose-fed PPARβ/δ-deficient mice. These findings indicate that the combination of high fructose intake and PPARβ/δ deficiency increases CD36 protein levels via Nrf2, a process that promotes chronic inflammation and insulin resistance in adipose tissue.
Keywords: PPARβ/δ; Adipocyte; Fructose; CD36; JNK; Oxidized LDL;
SNP rs1049430 in the 3′-UTR of SH3GL2 regulates its expression: Clinical and prognostic implications in head and neck squamous cell carcinoma by Guru Prasad Maiti; Amlan Ghosh; Pinaki Mondal; Aradhita Baral; Sayantan Datta; Sudip Samadder; Sandeep P. Nayak; Jayanta Chakrabarti; Jaydeep Biswas; Nilabja Sikdar; Shantanu Chowdhury; Bidyut Roy; Susanta Roychowdhury; Chinmay Kumar Panda (1059-1067).
Single nucleotide polymorphisms (SNPs) in the 3′-UTR region are emerging cis-regulatory factors associated with the occurrences of several human diseases. SH3GL2, which is located at chromosome 9p21-22, is associated with hyperplastic/mildly dysplastic lesions of the head and neck and has a long 3′-UTR with multiple SNPs. The aim of the present study was to determine the susceptible allele(s) in the 3′-UTR SNPs of SH3GL2 in head and neck squamous cell carcinoma (HNSCC). First, we screened the genotypes of all SNPs located in the 3′-UTR of SH3GL2 in 110 controls and 147 cases in Indian populations by sequencing. A SNP (rs1049430:> G/T) that showed only heterozygosity was further confirmed by genotyping with an Illumina GoldenGate platform in 530 controls and 764 cases. Genotype-specific survival analysis of the HNSCC patients was performed. In addition, genotype-specific mRNA stability, isoform expression and protein expression were analyzed. SNP rs1049430 was not associated with disease occurrence, but it was associated with poor patient outcome. The G allele was associated with decreased SH3GL2 mRNA stability, differential splicing and low protein expression. Thus, our data demonstrate that the presence of the susceptible G allele in SNP rs1049430 is associated with the inactivation of SH3GL2 and could be used as a prognostic marker of HNSCC.
Keywords: 3′-UTR; Allele-specific isoform; HNSCC; rs1049430; SH3GL2;