BBA - Molecular Basis of Disease (v.1852, #1)
Editorial Board (i).
Pathologic function and therapeutic potential of exosomes in cardiovascular disease by Shaina Ailawadi; Xiaohong Wang; Haitao Gu; Guo-Chang Fan (1-11).
The heart is a very complex conglomeration of organized interactions between various different cell types that all aid in facilitating myocardial function through contractility, sufficient perfusion, and cell-to-cell reception. In order to make sure that all features of the heart work effectively, it is imperative to have a well-controlled communication system among the different types of cells. One of the most important ways that the heart regulates itself is by the use of extracellular vesicles, more specifically, exosomes. Exosomes are types of nano-vesicles, naturally released from living cells. They are believed to play a critical role in intercellular communication through the means of certain mechanisms including direct cell-to-cell contact, long-range signals as well as electrical and extracellular chemical molecules. Exosomes contain many unique features like surface proteins/receptors, lipids, mRNAs, microRNAs, transcription factors and other proteins. Recent studies indicate that the exosomal contents are highly regulated by various stress and disease conditions, in turn reflective of the parent cell status. At present, exosomes are well appreciated to be involved in the process of tumor and infection disease. However, the research on cardiac exosomes is just emerging. In this review, we summarize recent findings on the pathologic effects of exosomes on cardiac remodeling under stress and disease conditions, including cardiac hypertrophy, peripartum cardiomyopathy, diabetic cardiomyopathy and sepsis-induced cardiovascular dysfunction. In addition, the cardio-protective effects of stress-preconditioned exosomes and stem cell-derived exosomes are also summarized. Finally, we discuss how to epigenetically reprogram exosome contents in host cells which makes them beneficial for the heart.
Keywords: Exosomes; Cardiomyopathy; Cardiac remodeling; Stem cells; miRNAs;
Threonine 56 phosphorylation of Bcl-2 is required for LRRK2 G2019S-induced mitochondrial depolarization and autophagy by Yu-Chin Su; Xing Guo; Xin Qi (12-21).
The G2019S leucine-rich repeat kinase 2 (LRRK2) mutation is the most common cause of genetic Parkinson's disease (PD). However, the molecular mechanism underlying LRRK2 G2019S-induced cellular pathology is poorly understood. Here, we demonstrated that LRRK2 G2019S bound to and phosphorylated Bcl-2, a mitochondrial anti-apoptotic protein, at Threonine 56. Either stable expression of Bcl-2 or transient expression of a Bcl-2 phosphor mutant (Bcl-2T56A) abolished LRRK2 G2019S-induced mitochondrial depolarization and autophagy. Together, our findings reveal a previously unidentified target of LRRK2 G2019S, showing that Bcl-2 serves as a point of crosstalk between LRRK2 G2019S-mediated mitochondrial disorder and dysregulation of autophagy.
Keywords: LRRK2 G2019S; Bcl-2; Phosphorylation; Mitochondrial depolarization; Mitophagy;
Protein phosphatase-1 is involved in the maintenance of normal homeostasis and in UVA irradiation-induced pathological alterations in HaCaT cells and in mouse skin by Dóra Dedinszki; Adrienn Sipos; Andrea Kiss; Róbert Bátori; Zoltán Kónya; László Virág; Ferenc Erdődi; Beáta Lontay (22-33).
The number of ultraviolet (UV) radiation-induced skin diseases such as melanomas is on the rise. The altered behavior of keratinocytes is often coupled with signaling events in which Ser/Thr specific protein kinases and phosphatases regulate various cellular functions. In the present study the role of protein phosphatase-1 (PP1) was investigated in the response of human keratinocyte (HaCaT) cells and mouse skin to UV radiation. PP1 catalytic subunit (PP1c) isoforms, PP1cα/γ and PP1cδ, are all localized to the cytoskeleton and cytosol of keratinocytes, but PP1cδ was found to be dominant over PP1α/γ in the nucleus. PP1c-silencing in HaCaT cells decreased the phosphatase activity and suppressed the viability of the cells. Exposure to a 10 J/cm2 UVA dose induced HaCaT cell death and resulted in a 30% decrease of phosphatase activity. PP1c-silencing and UVA irradiation altered the gene expression profile of HaCaT cells and suggested that the expression of 19 genes was regulated by the combined treatments with many of these genes being involved in malignant transformation. Microarray analysis detected altered expression levels of genes coding for melanoma-associated proteins such as keratin 1/10, calcium binding protein S100A8 and histone 1b. Treatment of Balb/c mice with the PP1-specific inhibitor tautomycin (TM) exhibited increased levels of keratin 1/10 and S100A8, and a decreased level of histone 1b proteins following UVA irradiation. Moreover, TM treatment increased pigmentation of the skin which was even more apparent when TM was followed by UVA irradiation. Our data identify PP1 as a regulator of the normal homeostasis of keratinocytes and the UV-response.
Keywords: Keratinocyte; Protein phosphatase-1; UV irradiation; Gene expression; Keratin 1/10; Histone 1b;
Novel curcumin analog C66 prevents diabetic nephropathy via JNK pathway with the involvement of p300/CBP-mediated histone acetylation by Yangwei Wang; Yonggang Wang; Manyu Luo; Hao Wu; Lili Kong; Ying Xin; Wenpeng Cui; Yunjie Zhao; Jingying Wang; Guang Liang; Lining Miao; Lu Cai (34-46).
Glomerulosclerosis and interstitial fibrosis represent the key events in development of diabetic nephropathy (DN), with connective tissue growth factor (CTGF), plasminogen activator inhibitor-1 (PAI-1) and fibronectin 1 (FN-1) playing important roles in these pathogenic processes. To investigate whether the plant metabolite curcumin, which exerts epigenetic modulatory properties when applied as a pharmacological agent, may prevent DN via inhibition of the JNK pathway and epigenetic histone acetylation, diabetic and age-matched non-diabetic control mice were administered a 3-month course of curcumin analogue (C66), c-Jun N-terminal kinase inhibitor (JNKi, sp600125), or vehicle alone. At treatment end, half of the mice were sacrificed for analysis and the other half were maintained without treatment for an additional 3 months. Renal JNK phosphorylation was found to be significantly increased in the vehicle-treated diabetic mice, but not the C66- and JNKi-treated diabetic mice, at both the 3-month and 6-month time points. C66 and JNKi treatment also significantly prevented diabetes-induced renal fibrosis and dysfunction. Diabetes-related increases in histone acetylation, histone acetyl transferases' (HATs) activity, and the p300/CBP HAT expression were also significantly attenuated by C66 or JNKi treatment. Chromatin immunoprecipitation assays showed that C66 and JNKi treatments decreased H3-lysine9/14-acetylation (H3K9/14Ac) level and p300/CBP occupancy at the CTGF, PAI-1 and FN-1 gene promoters. Thus, C66 may significantly and persistently prevent renal injury and dysfunction in diabetic mice via down-regulation of diabetes-related JNK activation and consequent suppression of the diabetes-related increases in HAT activity, p300/CBP expression, and histone acetylation.Display Omitted
Keywords: Diabetic nephropathy; Fibrosis; JNK; p300/CBP; Histone acetylation; Curcumin;
Sarcomeric protein isoform transitions in cardiac muscle: A journey to heart failure by Zhiyong Yin; Jun Ren; Wei Guo (47-52).
Sarcomeric protein isoforms are mainly governed by alternative promoter-driven expression, distinct gene expression, gene mutation and alternative mRNA splicing. The transitions of sarcomeric proteins have been implicated to play a role in the onset and development of human heart failure. In this mini-review, we summarized isoform transitions of several most widely examined sarcomeric proteins including myosin, actin, troponin, tropomyosin, titin and myosin binding protein-C, and the consequence of these abnormal isoform transitions. Even though the isoform transitions of sarcomeric proteins have been described in individual sarcomeric protein reviews, no concise summary of these results has been presented previously. This review is intended to fill this gap and discuss possible future perspectives.
Keywords: Protein isoform transition; Sarcomere proteins; Alternative splicing; Heart failure;
Reductive potential — A savior turns stressor in protein aggregation cardiomyopathy by Madhusudhanan Narasimhan; Namakkal S. Rajasekaran (53-60).
Redox homeostasis is essential for basal signaling of several physiological processes, but a unilateral shift towards an ‘oxidative’ or ‘reductive’ trait will alter intracellular redox milieu. Typically, such an event influences the structure and the native function of a cell or an organelle. Numerous experimental research and clinical trials over the last 6 decades have demonstrated that enhanced oxygen-derived free radicals constitute a major stimulus to trigger damage in several human diseases, including cardiovascular complications supporting the theory of oxidative stress (OS). However, until our key discovery, the dynamic interrelationship between “Reductive Stress (RS)” and cardiac health has been obscured by overwhelming OS studies (Rajasekaran et al., 2007). Notably, this seminal finding spurred considerable interest in investigations of other mechanistic insights, and thus far the results indicate a similar or stronger role for RS, as that of OS. In addition, from our own findings we strongly believe that constitutive activation of pathways that enable sustained generation of reducing equivalents of glutathione (GSH), reduced nicotinamide adenine dinucleotide phosphate (NADPH) will cause RS and impair the basal cellular signaling mechanisms operating through harmless pro-oxidative events, in turn, disrupting single and/or a combination of key cellular processes such as growth, maturation, differentiation, survival, death etc., that govern healthy cell physiology. Here, we have discussed the role of RS as a causal or contributing factor in relevant pathophysiology of a major cardiac disease of human origin.
Keywords: Cardiomyopathy; Reductive stress; Protein aggregation; hR120GCryAB; Nrf2; GSH;
Triosephosphate isomerase I170V alters catalytic site, enhances stability and induces pathology in a Drosophila model of TPI deficiency by Bartholomew P. Roland; Christopher G. Amrich; Charles J. Kammerer; Kimberly A. Stuchul; Samantha B. Larsen; Sascha Rode; Anoshé A. Aslam; Annie Heroux; Ronald Wetzel; Andrew P. VanDemark; Michael J. Palladino (61-69).
Triosephosphate isomerase (TPI) is a glycolytic enzyme which homodimerizes for full catalytic activity. Mutations of the TPI gene elicit a disease known as TPI Deficiency, a glycolytic enzymopathy noted for its unique severity of neurological symptoms. Evidence suggests that TPI Deficiency pathogenesis may be due to conformational changes of the protein, likely affecting dimerization and protein stability. In this report, we genetically and physically characterize a human disease-associated TPI mutation caused by an I170V substitution. Human TPII170V elicits behavioral abnormalities in Drosophila. An examination of hTPII170V enzyme kinetics revealed this substitution reduced catalytic turnover, while assessments of thermal stability demonstrated an increase in enzyme stability. The crystal structure of the homodimeric I170V mutant reveals changes in the geometry of critical residues within the catalytic pocket. Collectively these data reveal new observations of the structural and kinetic determinants of TPI Deficiency pathology, providing new insights into disease pathogenesis.
Keywords: Triosephosphate isomerase; Drosophila; Structure; Triosephosphate isomerase deficiency;
Curcumin ameliorates testicular damage in diabetic rats by suppressing cellular stress-mediated mitochondria and endoplasmic reticulum-dependent apoptotic death by Kahkashan Rashid; Parames C. Sil (70-82).
In the present study, we sought to explore whether curcumin plays any beneficial role against STZ induced testicular abnormalities in diabetic rats, and if so, what possible mechanism it utilizes to provide protection. Exposure to STZ (50 mg/kg body weight, i.p., once) reduced testis-to-body weight ratio, enhanced blood glucose level and intracellular ROS, altered testicular markers, diminished serum testosterone and impaired cellular redox balance. Administration of curcumin at a dose of 100 mg/kg body weight for 8 weeks effectively normalized all the alterations. Curcumin also showed inhibitory effect on the elevation of pro-inflammatory cytokines and translocation of NFκB into the nucleus and promoted the activation of the transcription factor Nrf-2 to provide protection against oxidants. To protect cells from STZ-induced stress-mediated damage, curcumin acted on the key mediators of the apoptotic cell death such as JNK and p38. In addition, this active molecule upregulated Bcl-2 expression, blocked the expression of pro-apoptotic proteins (Bax, Bad and Bid), decreased intracellular Ca2 + level, inhibited active caspase cascade and attenuated PARP cleavage. These results suggest that curcumin provides protection against cellular stress-mediated mitochondrial and endoplasmic reticulum-dependent apoptotic death of the testicular cells under diabetic condition and suggests the possibility of using this molecule as a potential therapeutic in the treatment of stress-mediated diabetic testicular dysfunction.Display Omitted
Keywords: Oxidative and ER stress; Diabetes; Testicular damage; Endoplasmic reticulum and mitochondrial-dependent apoptosis; Antioxidant; Curcumin;
Zinc-induced structural changes of the disordered tppp/p25 inhibits its degradation by the proteasome by Attila Lehotzky; Judit Oláh; Sándor Szunyogh; Adél Szabó; Tímea Berki; Judit Ovádi (83-91).
Tubulin Polymerization Promoting Protein/p25 (TPPP/p25), a neomorphic moonlighting protein displaying both physiological and pathological functions, plays a crucial role in the differentiation of the zinc-rich oligodendrocytes, the major constituent of myelin sheath; and it is enriched and co-localizes with α-synuclein in brain inclusions hallmarking Parkinson's disease and other synucleinopathies. In this work we showed that the binding of Zn2 + to TPPP/p25 promotes its dimerization resulting in increased tubulin polymerization promoting activity. We also demonstrated that the Zn2 + increases the intracellular TPPP/p25 level resulting in a more decorated microtubule network in CHO10 and CG-4 cells expressing TPPP/p25 ectopically and endogenously, respectively. This stabilization effect is crucial for the differentiation and aggresome formation under physiological and pathological conditions, respectively. The Zn2 +-mediated effect was similar to that produced by treatment of the cells with MG132, a proteasome inhibitor or Zn2 + plus MG132 as quantified by cellular ELISA. The enhancing effect of zinc ion on the level of TPPP/p25 was independent of the expression level of the protein produced by doxycycline induction at different levels or inhibition of the protein synthesis by cycloheximide. Thus, we suggest that the zinc as a specific divalent cation could be involved in the fine-tuning of the physiological TPPP/p25 level counteracting both the enrichment and the lack of this protein leading to distinct central nervous system diseases.
Keywords: Tubulin Polymerization Promoting Protein/p25; Zinc; Oligodendrocyte;
In vitro study of the direct effect of extracellular hemoglobin on myelin components by Vladimir V. Bamm; Danielle K. Lanthier; Erin L. Stephenson; Graham S.T. Smith; George Harauz (92-103).
There is a relationship between cerebral vasculature and multiple sclerosis (MS) lesions: abnormal accumulations of iron have been found in the walls of dilated veins in MS plaques. The sources of this iron can be varied, but capillary and venous hemorrhages leading to blood extravasation have been recorded, and could result in the release of hemoglobin extracellularly. Extracellular hemoglobin oxidizes quickly and is known to become a reactive molecule that triggers low-density lipoprotein oxidation and plays a pivotal role in atherogenesis. In MS, it could lead to local oxidative stress, inflammation, and tissue damage. Here, we investigated whether extracellular hemoglobin and its breakdown products can cause direct oxidative damage to myelin components in a peroxidative environment such as occurs in inflamed tissue. Oxidation of lipids was assessed by the formation of fluorescent peroxidized lipid–protein covalent adducts, by the increase in conjugated diene and malondialdehyde. Oxidation of proteins was analyzed by the change in protein mass. The results suggest that the globin radical could be a trigger of myelin basic protein oxidative cross-linking, and that heme transferred to the lipids is involved in lipid peroxidation. This study provides new insight into the mechanism by which hemoglobin exerts its pathological oxidative activity towards myelin components. This work supports further research into the vascular pathology in MS, to gain insight into the origin and role of iron deposits in disease pathogenesis, or in stimulation of different comorbidities such as cardiovascular disease.Display Omitted
Keywords: Multiple sclerosis; Myelin; Myelin basic protein; Oxidative stress; Hemoglobin; Globin radical;
Role of microtubules in attenuation of PepG-induced vascular endothelial dysfunction by atrial natriuretic peptide by Yufeng Tian; Isa Mambetsariev; Nicolene Sarich; Fanyong Meng; Anna A. Birukova (104-119).
Apart from control of circulating fluid, atrial natriuretic peptide (ANP) exhibits anti-inflammatory effects in the lung. However, molecular mechanisms of ANP anti-inflammatory effects are not well-understood. Peripheral microtubule (MT) dynamics is essential for agonist-induced regulation of vascular endothelial permeability. Here we studied the role of MT-dependent signaling in ANP protective effects against endothelial cell (EC) barrier dysfunction and acute lung injury induced by Staphylococcus aureus-derived peptidoglican-G (PepG). PepG-induced vascular endothelial dysfunction was accompanied by MT destabilization and disruption of MT network. ANP attenuated PepG-induced MT disassembly, NFκB signaling and activity of MT-associated Rho activator GEF-H1 leading to attenuation of EC inflammatory activation reflected by expression of adhesion molecules ICAM1 and VCAM1. ANP-induced EC barrier preservation and MT stabilization were linked to phosphorylation and inactivation of MT-depolymerizing protein stathmin. Expression of stathmin phosphorylation-deficient mutant abolished ANP protective effects against PepG-induced inflammation and EC permeability. In contrast, siRNA-mediated stathmin knockdown prevented PepG-induced peripheral MT disassembly and endothelial barrier dysfunction. ANP protective effects in a murine model of PepG-induced lung injury were associated with increased phosphorylation of stathmin, while exacerbated lung injury in the ANP knockout mice was accompanied by decreased pool of stable MT. Stathmin knockdown in vivo reversed exacerbation of lung injury in the ANP knockout mice. These results show a novel MT-mediated mechanism of endothelial barrier protection by ANP in pulmonary EC and animal model of PepG-induced lung injury via stathmin-dependent control of MT assembly.
Keywords: Endothelium; Permeability; Cytoskeleton; Vascular leak; Lung injury;
Nucleotide receptors control IL-8/CXCL8 and MCP-1/CCL2 secretions as well as proliferation in human glioma cells by Elizandra Braganhol; Filip Kukulski; Sébastien A. Lévesque; Michel Fausther; Elise G. Lavoie; Alfeu Zanotto-Filho; Leticia S. Bergamin; Julie Pelletier; Fariborz Bahrami; Fethia Ben Yebdri; José Claudio Fonseca Moreira; Ana Maria O. Battastini; Jean Sévigny (120-130).
Glioma cells release cytokines to stimulate inflammation that facilitates cell proliferation. Here, we show that Lipopolysaccharide (LPS) treatment could induce glioma cells to proliferate and this process was dependent on nucleotide receptor activation as well as interleukin-8 (IL-8/CXCL8) secretion. We observed that extracellular nucleotides controlled IL-8/CXCL8 and monocyte chemoattractant protein 1 (MCP-1/CCL2) release by U251MG and U87MG human glioma cell lines via P2X7 and P2Y6 receptor activation. The LPS-induced release of these cytokines was also modulated by purinergic receptor activation since IL-8 and MCP-1 release was decreased by the nucleotide scavenger apyrase as well as by the pharmacological P2Y6 receptor antagonists suramin and MRS2578. In agreement with these observations, the knockdown of P2Y6 expression decreased LPS-induced IL-8 release as well as the spontaneous release of IL-8 and MCP-1, suggesting an endogenous basal release of nucleotides. Moreover, high millimolar concentrations of ATP increased IL-8 and MCP-1 release by the glioma cells stimulated with suboptimal LPS concentration which were blocked by P2X7 and P2Y6 antagonists. Altogether, these data suggest that extracellular nucleotides control glioma growth via P2 receptor-dependent IL-8 and MCP-1 secretions.
Keywords: Glioma; ATP; P2 receptor; IL-8/CXCL8; MCP-1/CCL2;
Total bile acids in the maternal and fetal compartment in relation to placental ABCG2 expression in preeclamptic pregnancies complicated by HELLP syndrome by Jiska Jebbink; Geertruda Veenboer; Souad Boussata; Remco Keijser; Andreas E. Kremer; Ronald Oude Elferink; Joris van der Post; Gijs Afink; Carrie Ris-Stalpers (131-136).
To investigate total bile acid (TBA) levels in maternal (MB) and umbilical cord blood (UCB) in normotensive, preeclamptic (PE), and PE pregnancies complicated by hemolysis elevated liver enzymes and low platelets (HELLP) syndrome in the context of ABCG2 placental gene expression levels, a recently reported placental bile acid transporter.TBA levels were determined in 83 paired MB and UCB samples of normotensive, PE and PE/HELLP pregnancies and in 22 paired arterial and venous UCB samples from uncomplicated term pregnancies. ABCG2 gene expression was measured in 104 human placentas by reverse transcriptase quantitative polymerase chain reaction.Overall, TBA levels in MB are higher compared to levels in UCB (p < 0.0001), but this comparison looses statistical significance for the 11 PE/HELLP cases. TBA levels in maternal blood are increased in PE/HELLP compared to PE pregnancies (p = 0.016). TBA levels in arterial and venous UCB from 22 normotensive pregnancies are not statistically different. ABCG2 expression is reduced in pregnancies where preeclampsia is further complicated by HELLP syndrome. ABCG2 expression in human placenta is not correlated with TBA levels in either the maternal or fetal compartment.Increased maternal TBA levels in PE/HELLP pregnancies indicate a relation between bile acids in the maternal circulation and HELLP syndrome. As overall TBA levels in maternal blood are increased compared to UCB, we conclude that the placenta partly protects the fetus from increased maternal TBA levels. This consistent difference in TBA levels between the maternal and fetal compartment is unrelated to the placental expression of ABCG2.
Keywords: Bile acids; Preeclampsia; HELLP;
Bone marrow-derived c-jun N-terminal kinase-1 (JNK1) mediates liver regeneration by Frederik M. Schaefer; Jin Peng; Wei Hu; Oliver Drvarov; Yulia A. Nevzorova; Gang Zhao; Malika Al Masaoudi; Roger J. Davis; Christian Trautwein; Francisco Javier Cubero (137-145).
Liver regeneration is controlled by a complex network of signaling molecules, and a prominent role for c-jun N-terminal kinase has been suggested during this process. In the present study, we aimed to characterize and define the cell-type-specific contribution of JNK1 activation during liver regeneration. We used hepatocyte-specific JNK1 knockout mice (JNK1Δhepa) using the cre/lox-P system. We performed partial hepatectomy (PH) in WT, JNK1Δhepa and JNK1−/− animals and investigated time-points up to 72 h after PH. Additionally, bone marrow transplantation experiments were conducted in order to identify the contribution of hematopoietic cell-derived JNK1 activation for liver regeneration. Our results show that liver regeneration was significantly impaired in JNK1−/− compared to JNK1Δhepa and WT animals. These data were evidenced by lower BrdU incorporation and decreased cell cycle markers such as Cyclin A, Cyclin D, E2F1 and PCNA 48 h after PH in JNK1−/− compared with JNK1Δhepa and WT livers. In JNK1−/− mice, our findings were associated with a reduced acute phase response as evidenced by a lower activation of the IL-6/STAT3/SAA-1 cascade. Additionally, CD11b+Ly6G+-cells were decreased in JNK1−/− compared with JNK1Δhepa and WT animals after PH. The transplantation of bone marrow-derived JNK1−/− into WT recipients caused significant reduction in liver regeneration. Interestingly, the transplantation of JNK1−/− into mice lacking JNK1 in hepatocytes only partially delayed liver regeneration. In summary, we provide evidence that (1) JNK1 in hematopoietic cells is crucial for liver regeneration, and (2) a synergistic function between JNK1 in hepatocytes and hematopoietic-derived cells is involved in the hepatic regenerative response.Display Omitted
Keywords: Partial hepatectomy; JNK1; STAT3; Hepatocyte; Immune cells;
Identification of thyrotropin-releasing hormone as hippocampal glutaminyl cyclase substrate in neurons and reactive astrocytes by Alexander Waniek; Maike Hartlage-Rübsamen; Corinna Höfling; Astrid Kehlen; Stephan Schilling; Hans-Ulrich Demuth; Steffen Roßner (146-155).
Recently, Aβ peptide variants with an N-terminal truncation and pyroglutamate modification were identified and shown to be highly neurotoxic and prone to aggregation. This modification of Aβ is catalyzed by glutaminyl cyclase (QC) and pharmacological inhibition of QC diminishes Aβ deposition and accompanying gliosis and ameliorates memory impairment in transgenic mouse models of Alzheimer's disease (AD). QC expression was initially described in the hypothalamus, where thyrotropin-releasing hormone (TRH) is one of its physiological substrates. In addition to its hormonal role, a novel neuroprotective function of TRH following excitotoxicity and Aβ-mediated neurotoxicity has been reported in the hippocampus. Functionally matching this finding, we recently demonstrated QC expression by hippocampal interneurons in mouse brain.Here, we detected neuronal co-expression of QC and TRH in the hippocampus of young adult wild type mice using double immunofluorescence labeling. This provides evidence for TRH being a physiological QC substrate in hippocampus. Additionally, in neocortex of aged but not of young mice transgenic for amyloid precursor protein an increase of QC mRNA levels was found compared to wild type littermates. This phenomenon was not observed in hippocampus, which is later affected by Aβ pathology. However, in hippocampus of transgenic — but not of wild type mice — a correlation between QC and TRH mRNA levels was revealed. This co-regulation of the enzyme QC and its substrate TRH was reflected by a co-induction of both proteins in reactive astrocytes in proximity of Aβ deposits. Also, in primary mouse astrocytes a co-induction of QC and TRH was demonstrated upon Aβ stimulation.Display Omitted
Keywords: Glutaminyl cyclase; Hippocampus; Thyrotropin-releasing hormone; Amyloid pathology;
IRE1 impairs insulin signaling transduction of fructose-fed mice via JNK independent of excess lipid by Ruo-Qiong Sun; Hao Wang; Xiao-Yi Zeng; Stanley M.H. Chan; Song-Pei Li; Eunjung Jo; Sit-Lam Leung; Juan C. Molero; Ji-Ming Ye (156-165).
The unfolded protein response (UPR) pathways have been implicated in the development of hepatic insulin resistance during high fructose (HFru) feeding. The present study investigated their roles in initiating impaired insulin signaling transduction in the liver induced by HFru feeding in mice. HFru feeding resulted in hepatic steatosis, increased de novo lipogenesis and activation of two arms of the UPR pathways (IRE1/XBP1 and PERK/eIF2α) in similar patterns from 3 days to 8 weeks. In order to identify the earliest trigger of impaired insulin signaling in the liver, we fed mice a HFru diet for one day and revealed that only the IRE1 branch was activated (by 2-fold) and insulin-mediated Akt phosphorylation was blunted (~ 25%) in the liver. There were significant increases in phosphorylation of JNK (~ 50%) and IRS at serine site (~ 50%), protein content of ACC and FAS (up to 2.5-fold) and triglyceride level (2-fold) in liver (but not in muscle or fat). Blocking IRE1 activity abolished increases in JNK activity, IRS serine phosphorylation and protected insulin-stimulated Akt phosphorylation without altering hepatic steatosis or PKCε activity, a key link between lipids and insulin resistance. Our findings together suggest that activation of IRE1–JNK pathway is a key linker of impaired hepatic insulin signaling transduction induced by HFru feeding.
Keywords: High carbohydrate diet; Hepatic steatosis; Insulin signaling; UPR signaling pathways;
MALAT1 promotes colorectal cancer cell proliferation/migration/invasion via PRKA kinase anchor protein 9 by Min-Hui Yang; Zhi-Yan Hu; Chuan Xu; Lin-Ying Xie; Xiao-Yan Wang; Shi-You Chen; Zu-Guo Li (166-174).
Our previous studies have shown that the 3′ end of metastasis associated lung adenocarcinoma transcript 1 (MALAT1) is involved in colorectal cancer (CRC) cell proliferation and migration/invasion in vitro. The role and mechanism of MALAT1 in CRC metastasis in vivo, however, remain largely unknown. In the present study, we found that MALAT1 was up-regulated in human primary CRC tissues with lymph node metastasis. Overexpression of MALAT1 via RNA activation promoted CRC cell proliferation, invasion and migration in vitro, and stimulated tumor growth and metastasis in mice in vivo. Conversely, knockdown of MALAT1 inhibited CRC tumor growth and metastasis. MALAT1 regulated at least 243 genes in CRC cells in a genome-wide expression profiling. Among these genes, PRKA kinase anchor protein 9 (AKAP-9) was significantly up-regulated at both mRNA and protein levels. AKAP-9 was highly expressed in CRC cells with metastatic potential and human primary CRC tissues with lymph node metastasis, but not in normal cells or tissues. Importantly, knockdown of AKAP-9 blocked MALAT1-mediated CRC cell proliferation, migration and invasion. These data indicate that MALAT1 may promote CRC tumor development via its target protein AKAP-9.
Keywords: Metastasis associated lung adenocarcinoma transcript 1; PRKA kinase anchor protein 9; Colorectal cancer; Metastasis; Long non-coding RNA;
Hepatic nerve growth factor induced by iron overload triggers defenestration in liver sinusoidal endothelial cells by Lynda Addo; Hiroki Tanaka; Masayo Yamamoto; Yasumichi Toki; Satoshi Ito; Katsuya Ikuta; Katsunori Sasaki; Takaaki Ohtake; Yoshihiro Torimoto; Mikihiro Fujiya; Yutaka Kohgo (175-183).
The fenestrations of liver sinusoidal endothelial cells (LSECs) play important roles in the exchange of macromolecules, solutes, and fluid between blood and surrounding liver tissues in response to hepatotoxic drugs, toxins, and oxidative stress. As excess iron is a hepatotoxin, LSECs may be affected by excess iron. In this study, we found a novel link between LSEC defenestration and hepatic nerve growth factor (NGF) in iron-overloaded mice. By Western blotting, NGF was highly expressed, whereas VEGF and HGF were not, and hepatic NGF mRNA levels were increased according to digital PCR. Immunohistochemically, NGF staining was localized in hepatocytes, while TrkA, an NGF receptor, was localized in LSECs. Scanning electron microscopy revealed LSEC defenestration in mice overloaded with iron as well as mice treated with recombinant NGF. Treatment with conditioned medium from iron-overloaded primary hepatocytes reduced primary LSEC fenestrations, while treatment with an anti-NGF neutralizing antibody or TrkA inhibitor, K252a, reversed this effect. However, iron-loaded medium itself did not reduce fenestration. In conclusion, iron accumulation induces NGF expression in hepatocytes, which in turn leads to LSEC defenestration via TrkA. This novel link between iron and NGF may aid our understanding of the development of chronic liver disease.
Keywords: NGF; Iron; Liver sinusoidal endothelial cells; Defenestration;