BBA - Molecular Basis of Disease (v.1842, #7)
Editorial Board (i).
Receptors, cells and circuits involved in pruritus of systemic disorders by Andreas E. Kremer; Jamison Feramisco; Peter W. Reeh; Ulrich Beuers; Ronald P.J. Oude Elferink (869-892).
Pruritus is a sensory phenomenon accompanying a broad range of systemic disorders including hematologic and lymphoproliferative disorders, metabolic and endocrine diseases, solid tumours, and infectious diseases. The molecular mechanisms involved in itch sensation remain enigmatic in most of these diseases. However, from studies in patients and animal models a large number of mediators and receptors responsible for scratching behaviour have been identified in recent years. New insights into the interplay between neuronal and non-neuronal cells in the initiation, modulation and sensitization of itch sensation have been acquired. This review highlights the current knowledge of the molecular mechanism involved in pruritus of systemic disorders and summarizes the signalling pathways of biogenic amines, neuropeptides, proteases, eicosanoids, cytokines, opioids, endocannabinoids, neurotrophins, phospholipids and other signalling molecules participating in pruritus.
Keywords: Itch; Sensory neuron; TRPV1; Haematological disorder; Cholestasis; Uraemia;
Ubiquinol-10 ameliorates mitochondrial encephalopathy associated with CoQ deficiency by Laura García-Corzo; Marta Luna-Sánchez; Carolina Doerrier; Francisco Ortiz; Germaine Escames; Darío Acuña-Castroviejo; Luis C. López (893-901).
Keywords: Ubiquinol-10; CoQ10 deficiency; Mitochondrial encephalopathy; Mouse model;
Effect of resveratrol on mitochondrial function: Implications in parkin-associated familiar Parkinson's disease by Anna Ferretta; Antonio Gaballo; Paola Tanzarella; Claudia Piccoli; Nazzareno Capitanio; Beatrice Nico; Tiziana Annese; Marco Di Paola; Claudia Dell'Aquila; Michele De Mari; Ermanno Ferranini; Vincenzo Bonifati; Consiglia Pacelli; Tiziana Cocco (902-915).
Mitochondrial dysfunction and oxidative stress occur in Parkinson's disease (PD), but the molecular mechanisms controlling these events are not completely understood. Peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) is a transcriptional coactivator known as master regulator of mitochondrial functions and oxidative metabolism. Recent studies, including one from our group, have highlighted altered PGC-1α activity and transcriptional deregulation of its target genes in PD pathogenesis suggesting it as a new potential therapeutic target. Resveratrol, a natural polyphenolic compound proved to improve mitochondrial activity through the activation of several metabolic sensors resulting in PGC-1α activation. Here we have tested in vitro the effect of resveratrol treatment on primary fibroblast cultures from two patients with early-onset PD linked to different Park2 mutations. We show that resveratrol regulates energy homeostasis through activation of AMP-activated protein kinase (AMPK) and sirtuin 1 (SIRT1) and raise of mRNA expression of a number of PGC-1α's target genes resulting in enhanced mitochondrial oxidative function, likely related to a decrease of oxidative stress and to an increase of mitochondrial biogenesis. The functional impact of resveratrol treatment encompassed an increase of complex I and citrate synthase activities, basal oxygen consumption, and mitochondrial ATP production and a decrease in lactate content, thus supporting a switch from glycolytic to oxidative metabolism. Moreover, resveratrol treatment caused an enhanced macro-autophagic flux through activation of an LC3-independent pathway. Our results, obtained in early-onset PD fibroblasts, suggest that resveratrol may have potential clinical application in selected cases of PD-affected patients.
Keywords: Parkinson's disease; Parkin; Mitochondria; Resveratrol; PGC-1α; Sirtuin 1;
Cyclic GMP catabolism up-regulation in MRL/lpr lupus-prone mice is associated with organ remodeling by Issaka Yougbaré; Thérèse Keravis; Abdurazzag Abusnina; Marion Decossas; Nicolas Schall; Sylviane Muller; Claire Lugnier (916-926).
Production of high titer of antibodies against nuclear components is a hallmark of systemic lupus erythematosus, an autoimmune disease characterized by the progressive chronic inflammation of multiple joints and organs. Organ damage and dysfunction such as renal failure are typical clinical features in lupus. Cell hypermetabolism and hypertrophy can accelerate organ dysfunction. In this study we focus on a specific murine model of lupus, the MRL/lpr strain, and investigated the role of cyclic guanosine monophosphate (cGMP) catabolism in organ remodeling of main target tissues (kidney, spleen and liver) in comparison with age-matched control mice. In MRL/lpr-prone mice, the cGMP-phosphodiesterase (PDE) activities were significantly increased in the kidney (3-fold, P < 0.001), spleen (2-fold, P < 0.001) and liver (1.6-fold, P < 0.05). These raised activity levels were paralleled by both an increased activity of PDE1 in the kidney (associated with nephromegaly) and in the liver, and PDE2 in the spleen of lupus-prone mice. The up-regulation of PDE1 and PDE2 activities were associated with a decrease in intracellular cGMP levels. This underlines an alteration of cGMP-PDE signaling in the kidney, spleen and liver targeting different PDEs according to organs. In good agreement with these findings, a single intravenous administration to MRL/lpr mice of nimodipine (PDE1 inhibitor) but not of EHNA (PDE2 inhibitor) was able to significantly lower peripheral hypercellularity (P = 0.0401), a characteristic feature of this strain of lupus-prone mice. Collectively, our findings are important for generating personalized strategies to prevent certain forms of the lupus disease as well as for understanding the role of PDEs and cGMP in the pathophysiology of lupus.
Keywords: Systemic lupus erythematosus (SLE); PDE1; PDE2; cGMP; Kidney organomegaly; PDE inhibitor;
H2O2- or l-DOPA-injured dopaminergic neurons trigger the release of soluble mediators that up-regulate striatal GDNF through different signalling pathways by Carla Pais Fonseca; Susana Gama; Ana Saavedra; Graça Baltazar (927-934).
Glial cell line-derived neurotrophic factor (GDNF) is a potent neuroprotective molecule for dopaminergic neurons of the nigrostriatal pathway that degenerate in Parkinson's disease. We have previously shown that H2O2- or l-3,4-dihydroxyphenylalanine (l-DOPA)-challenged dopaminergic neurons trigger the release of soluble factors that signal ventral midbrain astrocytes to increase GDNF expression. In the present work, we evaluated whether the factors released by ventral midbrain-challenged cells were able to alter GDNF expression in striatal cells, the targets of dopaminergic neurons projecting from the substantia nigra, and investigated the signalling pathways involved. Our data showed that soluble mediators released upon H2O2- or l-DOPA-induced dopaminergic injury up-regulated GDNF in striatal cells, with different temporal patterns depending on the oxidative agent used. Conditioned media from H2O2- or l-DOPA-challenged midbrain astrocyte cultures failed to up-regulate GDNF in striatal cultures. Likewise, there was no direct effect of H2O2 or l-DOPA on striatal GDNF levels suggesting that GDNF up-regulation was mediated by soluble factors released in the presence of failing dopaminergic neurons. Both phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways were involved in striatal GDNF up-regulation triggered by H2O2-induced dopaminergic injury, while diffusible factors released in the presence of l-DOPA-challenged dopaminergic neurons induced GDNF expression in striatal cells through the activation of the MAPK pathway. These soluble mediators may constitute, in the future, important targets for the control of endogenous GDNF expression enabling the development of new and, hopefully, more efficient neuroprotective/neurorestorative strategies for the treatment of Parkinson's disease.
Keywords: Dopaminergic neuron; GDNF; Neuroprotection; Parkinson's disease; Signalling pathway; Striatum;
A quinazoline-derivative compound with PARP inhibitory effect suppresses hypertension-induced vascular alterations in spontaneously hypertensive rats by Klara Magyar; Laszlo Deres; Krisztian Eros; Kitti Bruszt; Laszlo Seress; Janos Hamar; Kalman Hideg; Andras Balogh; Ferenc Gallyas; Balazs Sumegi; Kalman Toth; Robert Halmosi (935-944).
Oxidative stress and neurohumoral factors play important role in the development of hypertension-induced vascular remodeling, likely by disregulating kinase cascades and transcription factors. Oxidative stress activates poly(ADP-ribose)-polymerase (PARP-1), which promotes inflammation and cell death. We assumed that inhibition of PARP-1 reduces the hypertension-induced adverse vascular changes. This hypothesis was tested in spontaneously hypertensive rats (SHR).Ten-week-old male SHRs and wild-type rats received or not 5 mg/kg/day L-2286 (a water-soluble PARP-inhibitor) for 32 weeks, then morphological and functional parameters were determined in their aortas. L-2286 did not affect the blood pressure in any of the animal groups measured with tail-cuff method. Arterial stiffness index increased in untreated SHRs compared to untreated Wistar rats, which was attenuated by L-2286 treatment. Electron and light microscopy of aortas showed prominent collagen deposition, elevation of oxidative stress markers and increased PARP activity in SHR, which were attenuated by PARP-inhibition. L-2286 treatment decreased also the hypertension-activated mitochondrial cell death pathway, characterized by the nuclear translocation of AIF. Hypertension activated all three branches of MAP-kinases. L-2286 attenuated these changes by inducing the expression of MAPK phosphatase-1 and by activating the cytoprotective PI-3-kinase/Akt pathway. Hypertension activated nuclear factor-kappaB, which was prevented by PARP-inhibition via activating its nuclear export.PARP-inhibition has significant vasoprotective effects against hypertension-induced vascular remodeling. Therefore, PARP-1 can be a novel therapeutic drug target for preventing hypertension-induced vascular remodeling in a group of patients, in whom lowering the blood pressure to optimal range is harmful or causes intolerable side effects.
Keywords: PARP-inhibition; Spontaneously hypertensive rat; Vascular remodeling;
UCH-L1 induces podocyte hypertrophy in membranous nephropathy by protein accumulation by Frithjof Lohmann; Marlies Sachs; Tobias N. Meyer; Henning Sievert; Maja T. Lindenmeyer; Thorsten Wiech; Clemens D. Cohen; Stefan Balabanov; R.A.K. Stahl; Catherine Meyer-Schwesinger (945-958).
Podocytes are terminally differentiated cells of the glomerular filtration barrier that react with hypertrophy in the course of injury such as in membranous nephropathy (MGN). The neuronal deubiquitinase ubiquitin C-terminal hydrolase L1 (UCH-L1) is expressed and activated in podocytes of human and rodent MGN. UCH-L1 regulates the mono-ubiquitin pool and induces accumulation of poly-ubiquitinated proteins in affected podocytes. Here, we investigated the role of UCH-L1 in podocyte hypertrophy and in the homeostasis of the hypertrophy associated “model protein” p27Kip1. A better understanding of the basic mechanisms leading to podocyte hypertrophy is crucial for the development of specific therapies in MGN. In human and rat MGN, hypertrophic podocytes exhibited a simultaneous up-regulation of UCH-L1 and of cytoplasmic p27Kip1 content. Functionally, inhibition of UCH-L1 activity and knockdown or inhibition of UCH-L1 attenuated podocyte hypertrophy by decreasing the total protein content in isolated glomeruli and in cultured podocytes. In contrast, UCH-L1 levels and activity increased podocyte hypertrophy and total protein content in culture, specifically of cytoplasmic p27Kip1. UCH-L1 enhanced cytoplasmic p27Kip1 levels by nuclear export and decreased poly-ubiquitination and proteasomal degradation of p27Kip1. In parallel, UCH-L1 increased podocyte turnover, migration and cytoskeletal rearrangement, which are associated with known oncogenic functions of cytoplasmic p27Kip1 in cancer. We propose that UCH-L1 induces podocyte hypertrophy in MGN by increasing the total protein content through altered degradation and accumulation of proteins such as p27Kip1 in the cytoplasm of podocytes. Modification of both UCH-L1 activity and levels could be a new therapeutic avenue to podocyte hypertrophy in MGN.
Keywords: Membranous nephropathy; Passive Heymann nephritis; Ubiquitin C-terminal hydrolase-L1; Proteasomal degradation; Hypertrophy; p27Kip1;
Role of adipose tissue in methionine–choline-deficient model of non-alcoholic steatohepatitis (NASH) by Pooja Jha; Astrid Knopf; Harald Koefeler; Michaela Mueller; Carolin Lackner; Gerald Hoefler; Thierry Claudel; Michael Trauner (959-970).
Methionine–choline-deficient (MCD) diet is a widely used dietary model of non-alcoholic steatohepatitis (NASH) in rodents. However, the contribution of adipose tissue to MCD-induced steatosis, and inflammation as features of NASH are not fully understood. The goal of this study was to elucidate the role of adipose tissue fatty acid (FA) metabolism, adipogenesis, lipolysis, inflammation and subsequent changes in FA profiles in serum and liver in the pathogenesis of steatohepatitis. We therefore fed ob/ob mice with control or MCD diet for 5 weeks. MCD-feeding increased adipose triglyceride lipase and hormone sensitive lipase activities in all adipose depots which may be attributed to increased systemic FGF21 levels. The highest lipase enzyme activity was exhibited by visceral WAT. Non-esterified fatty acid (NEFA)-18:2n6 was the predominantly elevated FA species in serum and liver of MCD-fed ob/ob mice, while overall serum total fatty acid (TFA) composition was reduced. In contrast, an overall increase of all FA species from TFA pool was found in liver, reflecting the combined effects of increased FA flux to liver, decreased FA oxidation and decrease in lipase activity in liver. NAFLD activity score was increased in liver, while WAT showed no changes and BAT showed even reduced inflammation. Conclusion: This study demonstrates a key role for adipose tissue lipases in the pathogenesis of NASH and provides a comprehensive lipidomic profiling of NEFA and TFA homeostasis in serum and liver. Our findings provide novel mechanistic insights for the role of WAT in progression of MCD-induced liver injury.
Keywords: NAFLD; Lipolysis; Liver; ATGL; HSL; FGF21;
Epigenetic modifications in colorectal cancer: Molecular insights and therapeutic challenges by Aristeidis G. Vaiopoulos; Kalliopi Ch. Athanasoula; Athanasios G. Papavassiliou (971-980).
Colorectal cancer, a leading cause of mortality worldwide, is a multistep disorder that results from the alteration of genetic and epigenetic mechanisms under contextual influence. Epigenetic aberrations, including DNA methylation, histone modifications, chromatin remodeling and non-coding RNAs, affect every aspect of tumor development from initiation to metastasis. Cancer stem cell promotion is also included in the wide spectrum of epigenetic dysregulations. Elucidation of this complex crosstalk network may offer new insights in the molecular interactions involved in the pathogenesis of colorectal carcinogenesis. In the era of translational medicine new horizons are opened for the pursuit of personalized therapeutic approaches and the development of novel and accurate diagnostic, prognostic and therapy-assessment markers. This review discusses the implications of epigenetic mechanisms in tumor biology and their applications “from bench to bedside”.
Keywords: Colorectal cancer; Epigenetics; Histone modification; DNA methylation; Therapy; Prognosis;
Live-cell FRET imaging reveals clustering of the prion protein at the cell surface induced by infectious prions by Evandro Tavares; Joana A. Macedo; Pedro M.R. Paulo; Catarina Tavares; Carlos Lopes; Eduardo P. Melo (981-991).
Prion diseases are associated to the conversion of the prion protein into a misfolded pathological isoform. The mechanism of propagation of protein misfolding by protein templating remains largely unknown. Neuroblastoma cells were transfected with constructs of the prion protein fused to both CFP-GPI-anchored and to YFP-GPI-anchored and directed to its cell membrane location. Live-cell FRET imaging between the prion protein fused to CFP or YFP was measured giving consistent values of 10 ± 2%. This result was confirmed by fluorescence lifetime imaging microscopy and indicates intermolecular interactions between neighbor prion proteins. In particular, considering that a maximum FRET efficiency of 17 ± 2% was determined from a positive control consisting of a fusion CFP-YFP-GPI-anchored. A stable cell clone expressing the two fusions containing the prion protein was also selected to minimize cell-to-cell variability. In both, stable and transiently transfected cells, the FRET efficiency consistently increased in the presence of infectious prions — from 4 ± 1% to 7 ± 1% in the stable clone and from 10 ± 2% to 16 ± 1% in transiently transfected cells. These results clearly reflect an increased clustering of the prion protein on the membrane in the presence of infectious prions, which was not observed in negative control using constructs without the prion protein and upon addition of non-infected brain. Our data corroborates the recent view that the primary site for prion conversion is the cell membrane. Since our fluorescent cell clone is not susceptible to propagate infectivity, we hypothesize that the initial event of prion infectivity might be the clustering of the GPI-anchored prion protein.Display Omitted
Keywords: Prion protein; Live-cell FRET imaging; CFP-YFP; m-turquoise2; FLIM; Prion propagation;
Paget disease of bone-associated UBA domain mutations of SQSTM1 exert distinct effects on protein structure and function by Alice Goode; Jed E. Long; Barry Shaw; Stuart H. Ralston; Micaela Rios Visconti; Fernando Gianfrancesco; Teresa Esposito; Luigi Gennari; Daniela Merlotti; Domenico Rendina; Sarah L. Rea; Melanie Sultana; Mark S. Searle; Robert Layfield (992-1000).
SQSTM1 mutations are common in patients with Paget disease of bone (PDB), with most affecting the C-terminal ubiquitin-associated (UBA) domain of the SQSTM1 protein. We performed structural and functional analyses of two UBA domain mutations, an I424S mutation relatively common in UK PDB patients, and an A427D mutation associated with a severe phenotype in Southern Italian patients. Both impaired SQSTM1's ubiquitin-binding function in pull-down assays and resulted in activation of basal NF-κB signalling, compared to wild-type, in reporter assays. We found evidence for a relationship between the ability of different UBA domain mutants to activate NF-κB signalling in vitro and number of affected sites in vivo in 1152 PDB patients from the UK and Italy, with A427D-SQSTM1 producing the greatest level of activation (relative to wild-type) of all PDB mutants tested to date. NMR and isothermal titration calorimetry studies were able to demonstrate that I424S is associated with global structural changes in the UBA domain, resulting in 10-fold weaker UBA dimer stability than wild-type and reduced ubiquitin-binding affinity of the UBA monomer. Our observations provide insights into the role of SQSTM1-mediated NF-κB signalling in PDB aetiology, and demonstrate that different mutations in close proximity within loop 2/helix 3 of the SQSTM1 UBA domain exert distinct effects on protein structure and stability, including indirect effects at the UBA/ubiquitin-binding interface.
Keywords: Sequestosome 1; SQSTM1; p62; Paget disease of bone; NF-κB; Ubiquitin;
miR-223: An inflammatory oncomiR enters the cardiovascular field by Fatiha Taïbi; Valérie Metzinger-Le Meuth; Ziad A. Massy; Laurent Metzinger (1001-1009).
MicroRNAs (miRNAs) are small, noncoding RNAs of 18–22 nucleotides in length that regulate post-transcriptional expression by base-pairing with target mRNAs. It is now clearly established that miRNAs are involved in most of the cell's physiopathological processes (including carcinogenesis and metabolic disorders). This review focuses on miR-223, which was first described as a modulator of hematopoietic lineage differentiation. We outline the role of miR-223 deregulation in several types of cancers and highlight its inclusion in a newly identified and fast-growing family of miRNAs called oncomiRs. We then look at miR-223's emerging role in inflammatory and metabolic disorders, with a particular focus on muscle diseases, type II diabetes, atherosclerosis and vascular calcification. miR-223 is one of the growing number of RNA biomarkers of various human metabolic diseases and is thus of special interest to both researchers and clinicians in the cardiovascular field.
Keywords: miR-223; MicroRNA; Cancer; Vascular disease; Muscle; Hematopoiesis;
Alternating Hemiplegia of Childhood mutations have a differential effect on Na+,K+-ATPase activity and ouabain binding by Karl M. Weigand; Muriël Messchaert; Herman G.P. Swarts; Frans G.M. Russel; Jan B. Koenderink (1010-1016).
De novo mutations in ATP1A3, the gene encoding the α3-subunit of Na+,K+-ATPase, are associated with the neurodevelopmental disorder Alternating Hemiplegia of Childhood (AHC). The aim of this study was to determine the functional consequences of six ATP1A3 mutations (S137Y, D220N, I274N, D801N, E815K, and G947R) associated with AHC. Wild type and mutant Na+,K+-ATPases were expressed in Sf9 insect cells using the baculovirus expression system. Ouabain binding, ATPase activity, and phosphorylation were absent in mutants I274N, E815K and G947R. Mutants S137Y and D801N were able to bind ouabain, although these mutants lacked ATPase activity, phosphorylation, and the K+/ouabain antagonism indicative of modifications in the cation binding site. Mutant D220N showed similar ouabain binding, ATPase activity, and phosphorylation to wild type Na+,K+-ATPase. Functional impairment of Na+,K+-ATPase in mutants S137Y, I274N, D801N, E815K, and G947R might explain why patients having these mutations suffer from AHC. Moreover, mutant D801N is able to bind ouabain, whereas mutant E815K shows a complete loss of function, possibly explaining the different phenotypes for these mutations.
Keywords: AHC; Alpha 3; Alternating Hemiplegia of Childhood; ATP1A3; Na+,K+-ATPase;
RAGE overexpression confers a metastatic phenotype to the WM115 human primary melanoma cell line by Varsha Meghnani; Stefan W. Vetter; Estelle Leclerc (1017-1027).
The formation of melanoma metastases from primary tumor cells is a complex phenomenon that involves the regulation of multiple genes. We have previously shown that the receptor for advanced glycation end products (RAGE) was up-regulated in late metastatic stages of melanoma patient samples and we hypothesized that up-regulation of RAGE in cells forming a primary melanoma tumor could contribute to the metastatic switch of these cells. To test our hypothesis, we overexpressed RAGE in the WM115 human melanoma cell line that was established from a primary melanoma tumor of a patient. We show here that overexpression of RAGE in these cells is associated with mesenchymal-like morphologies of the cells. These cells demonstrate higher migration abilities and reduced proliferation properties, suggesting that the cells have switched to a metastatic phenotype. At the molecular level, we show that RAGE overexpression is associated with the up-regulation of the RAGE ligand S100B and the down-regulation of p53, ERK1/2, cyclin E and NF-kB. Our study supports a role of RAGE in the metastatic switch of melanoma cells.
Keywords: RAGE; S100B; Melanoma; p53 cancer; Metastatic switch;
Ubiquitin C-terminal hydrolase L1 deletion ameliorates glomerular injury in mice with ACTN4-associated focal segmental glomerulosclerosis by Naomi C. Read; Alex Gutsol; Chet E. Holterman; Anthony Carter; Josée Coulombe; Douglas A. Gray; Chris R.J. Kennedy (1028-1040).
Renal ubiquitin C-terminal hydrolase L1 (UCHL1) is upregulated in a subset of human glomerulopathies, including focal segmental glomerulosclerosis (FSGS), where it may serve to promote ubiquitin pools for degradation of cytotoxic proteins. In the present study, we tested whether UCHL1 is expressed in podocytes of a mouse model of ACTN4-associated FSGS. Podocyte UCHL1 protein was detected in glomeruli of K256E-ACTN4 pod +/UCHL1+/+ mice. UCHL1+/− mice were intercrossed with K256E-ACTN4 pod + mice and monitored for features of glomerular disease. 10-week-old K256E-ACTN4 pod +/UCHL1−/− mice exhibited significantly ameliorated albuminuria, glomerulosclerosis, tubular pathology and blood pressure. Interestingly, while UCHL1 deletion diminished both tubular and glomerular apoptosis, WT1-positive nuclei were unchanged. Finally, UCHL1 levels correlated positively with poly-ubiquitinated proteins but negatively with K256E-α-actinin-4 levels, implying reduced K256E-α-actinin-4 proteolysis in the absence of UCHL1. Our data suggest that UCHL1 upregulation in ACTN4-associated FSGS fuels the proteasome and that UCHL1 deletion may impair proteolysis and thereby preserve K256E/wt-α-actinin-4 heterodimers, maintaining podocyte cytoskeletal integrity and protecting the glomerular filtration barrier.
Keywords: UCHL1; α-Actinin-4; K256E; Ubiquitin; Glomerular disease; Podocyte;
Involvement of IGF-II receptors in the antioxidant and neuroprotective effects of IGF-II on adult cortical neuronal cultures by Elisa Martin-Montañez; José Pavia; Luis J. Santin; Federica Boraldi; Guillermo Estivill-Torrus; José A. Aguirre; Maria Garcia-Fernandez (1041-1051).
Insulin-like growth factor-II (IGF-II) is a naturally occurring peptide that exerts known pleiotropic effects ranging from metabolic modulation to cellular development, growth and survival. IGF-II triggers its actions by binding to and activating IGF (IGF-I and IGF-II) receptors. In this study, we assessed the neuroprotective effect of IGF-II on corticosterone-induced oxidative damage in adult cortical neuronal cultures and the role of IGF-II receptors in this effect. We provide evidence that treatment with IGF-II alleviates the glucocorticoid-induced toxicity to neuronal cultures, and this neuroprotective effect occurred due to a decrease in reactive oxygen species (ROS) production and a return of the antioxidant status to normal levels. IGF-II acts via not only the regulation of synthesis and/or activity of antioxidant enzymes, especially manganese superoxide dismutase, but also the restoration of mitochondrial cytochrome c oxidase activity and mitochondrial membrane potential. Although the antioxidant effect of IGF-I receptor activation has been widely reported, the involvement of the IGF-II receptor in these processes has not been clearly defined. The present report is the first evidence describing the involvement of IGF-II receptors in redox homeostasis. IGF-II may therefore contribute to the mechanisms of neuroprotection by acting as an antioxidant, reducing the neurodegeneration induced by oxidative insults. These results open the field to new pharmacological approaches to the treatment of diseases involving imbalanced redox homeostasis. In this study, we demonstrated that the antioxidant effect of IGF-II is at least partially mediated by IGF-II receptors.
Keywords: Insulin like growth factor-II; Insulin like growth factor-II receptor; Antioxidant; Mitochondria; Neuroprotective; Neurodegeneration;
Unusual splice site mutations disrupt FANCA exon 8 definition by Chiara Mattioli; Giulia Pianigiani; Daniela De Rocco; Anna Monica Rosaria Bianco; Enrico Cappelli; Anna Savoia; Franco Pagani (1052-1058).
The pathological role of mutations that affect not conserved splicing regulatory sequences can be difficult to determine. In a patient with Fanconi anemia, we identified two unpredictable splicing mutations that act on either sides of FANCA exon 8. In patients-derived cells and in minigene splicing assay, we showed that both an apparently benign intronic c.710-5T>C transition and the nonsense c.790C>T substitution induce almost complete exon 8 skipping. Site-directed mutagenesis experiments indicated that the c.710-5T>C transition affects a polypyrimidine tract where most of the thymidines cannot be compensated by cytidines. The c.790C>T mutation located in position − 3 relative to the donor site induce exon 8 skipping in an NMD-independent manner and complementation experiments with modified U1 snRNAs showed that U1 snRNP is only partially involved in the splicing defect. Our results highlight the importance of performing splicing functional assay for correct identification of disease-causing mechanism of genomic variants and provide mechanistic insights on how these two FANCA mutations affect exon 8 definition.
Keywords: Nonsense codon; Fanconi anemia; Nonsense mediated mRNA decay; U1 small nuclear ribonucleoprotein; RNA splice sites; RNA splicing;
Bulk autophagy, but not mitophagy, is increased in cellular model of mitochondrial disease by María Morán; Aitor Delmiro; Alberto Blázquez; Cristina Ugalde; Joaquín Arenas; Miguel A. Martín (1059-1070).
Oxidative phosphorylation system (OXPHOS) deficiencies are rare diseases but constitute the most frequent inborn errors of metabolism. We analyzed the autophagy route in 11 skin fibroblast cultures derived from patients with well characterized and distinct OXPHOS defects. Mitochondrial membrane potential determination revealed a tendency to decrease in 5 patients' cells but reached statistical significance only in 2 of them. The remaining cells showed either no change or a slight increase in this parameter. Colocalization analysis of mitochondria and autophagosomes failed to show evidence of increased selective elimination of mitochondria but revealed more intense autophagosome staining in patients' fibroblasts compared with controls. Despite the absence of increased mitophagy, Parkin recruitment to mitochondria was detected in both controls' and patients' cells and was slightly higher in cells harboring complex I defects. Western blot analysis of the autophagosome marker LC3B, confirmed significantly higher levels of the protein bound to autophagosomes, LC3B-II, in patients' cells, suggesting an increased bulk autophagy in OXPHOS defective fibroblasts. Inhibition of lysosomal proteases caused significant accumulation of LC3B-II in control cells, whereas in patients' cells this phenomenon was less pronounced. Electron microscopy studies showed higher content of late autophagic vacuoles and lysosomes in OXPHOS defective cells, accompanied by higher levels of the lysosomal marker LAMP-1. Our findings suggest that in OXPHOS deficient fibroblasts autophagic flux could be partially hampered leading to an accumulation of autophagic vacuoles and lysosomes.Display Omitted
Keywords: Autophagy; OXPHOS deficiency; Parkin; Autophagosome; Mitophagy; Lysosome;
Induction of ATM/ATR pathway combined with Vγ2Vδ2 T cells enhances cytotoxicity of ovarian cancer cells by Jingwei Lu; Manjusri Das; Suman Kanji; Reeva Aggarwal; Matthew Joseph; Alo Ray; Charles L. Shapiro; Vincent J. Pompili; Hiranmoy Das (1071-1079).
Many ovarian cancer cells express stress-related molecule MICA/B on their surface that is recognized by Vγ2Vδ2 T cells through their NKG2D receptor, which is transmitted to downstream stress-signaling pathway. However, it is yet to be established how Vγ2Vδ2 T cell-mediated recognition of MICA/B signal is transmitted to downstream stress-related molecules. Identifying targeted molecules would be critical to develop a better therapy for ovarian cancer cells. It is well established that ATM/ATR signal transduction pathways, which is modulated by DNA damage, replication stress, and oxidative stress play central role in stress signaling pathway regulating cell cycle checkpoint and apoptosis. We investigated whether ATM/ATR and its down stream molecules affect Vγ2Vδ2 T cell-mediated cytotoxicity. Herein, we show that ATM/ATR pathway is modulated in ovarian cancer cells in the presence of Vγ2Vδ2 T cells. Furthermore, downregulation of ATM pathway resulted downregulation of MICA, and reduced Vγ2Vδ2 T cell-mediated cytotoxicity. Alternately, stimulating ATM pathway enhanced expression of MICA, and sensitized ovarian cancer cells for cytotoxic lysis by Vγ2Vδ2 T cells. We further show that combining currently approved chemotherapeutic drugs, which induced ATM signal transduction, along with Vγ2Vδ2 T cells enhanced cytotoxicity of resistant ovarian cancer cells. These findings indicate that ATM/ATR pathway plays an important role in tumor recognition, and drugs promoting ATM signaling pathway might be considered as a combination therapy together with Vγ2Vδ2 T cells for effectively treating resistant ovarian cancer cells.
Keywords: Vγ2Vδ2 T cells; Ovarian cancer; Cytotoxicity; ATM/ATR pathway; MICA; Combination therapy;
Dysregulation of the TGFBI gene is involved in the oncogenic activity of the nonsense mutation of hepatitis B virus surface gene sW182* by Shih Sheng Jiang; Shiu-Feng Huang; Min-Syuan Huang; Yng-Tay Chen; Hsiang-Ju Jhong; Il-Chi Chang; Ya-Ting Chen; Jer-Wei Chang; Wen-Ling Chen; Wei-Chen Lee; Miin-Fu Chen; Chau-Ting Yeh; Isao Matsuura (1080-1087).
The nonsense mutations of the hepatitis B virus (HBV) surface (S) gene have been reported to have oncogenic potential. We have previously identified several transforming nonsense mutations of the HBV S gene from hepatocarcinoma (HCC) patients. Among them, the sW182* mutant (the stop codon for tryptophan 182) showed the most potent oncogenicity in a mouse xenograft model using stably transfected mouse fibroblast cells. This study is aimed at understanding the molecular mechanisms leading to the oncogenic activity of the sW182* mutant.A gene expression microarray in combination with gene set enrichment analysis (GSEA) revealed differentially expressed gene sets in the sW182* cells, including those related to cell-cycle regulation, deoxyribonucleic acid repair, and genome instability. Of the differentially expressed genes, the transforming growth factor-β-induced (TGFBI) gene was further validated to be dysregulated in the sW182* cells. This dysregulation was accompanied by hypermethylation of the TGFBI promoter.The level of cyclin D1, a negatively regulated TGFBI target, was highly elevated in the sW182* mutant cells, which is consistent with the potent oncogenicity. Furthermore, frequent abnormal mitosis and multinucleation were observed in the mutant cells. Exogenous expression of TGFBI alleviated the oncogenic activity of the sW182* cells. In human HBV-related HCC cancerous tissue, expression of TGFBI was downregulated in 25 of the 55 (45%) patients examined, suggesting that TGFBI dysregulation could occur in HBV-related HCC development in some cases.These results suggest that dysregulation of TGFBI is involved in the oncogenic activity of the sW182* mutant of the hepatitis B virus S gene.
Keywords: Nonsense mutation; HBV PreS/S gene; HCC; TGFBI; Cyclin D1; Hepatocarcinogenesis;
DNA damage response in renal ischemia–reperfusion and ATP-depletion injury of renal tubular cells by Zhengwei Ma; Qingqing Wei; Guie Dong; Yuqing Huo; Zheng Dong (1088-1096).
Renal ischemia–reperfusion leads to acute kidney injury (AKI) that is characterized pathologically by tubular damage and cell death, followed by tubular repair, atrophy and interstitial fibrosis. Recent work suggested the possible presence of DNA damage response (DDR) in AKI. However, the evidence is sketchy and the role and regulation of DDR in ischemic AKI remain elusive. In this study, we demonstrated the induction of phosphorylation of ATM, H2AX, Chk2 and p53 during renal ischemia–reperfusion in mice, suggesting DDR in kidney tissues. DDR was also induced in vitro during the recovery or “reperfusion” of renal proximal tubular cells (RPTCs) after ATP depletion. DDR in RPTCs was abrogated by supplying glucose to maintain ATP via glycolysis, indicating that the DDR depends on ATP depletion. The DDR was also suppressed by the general caspase inhibitor z-VAD and the overexpression of Bcl-2, supporting a role of apoptosis-associated DNA damage in the DDR. N-acetylcysteine (NAC), an antioxidant, suppressed the phosphorylation of ATM and p53 and, to a less extent, Chk2, but NAC increased the phosphorylation and nuclear foci formation of H2AX. Interestingly, NAC increased apoptosis, which may account for the observed H2AX activation. Ku55933, an ATM inhibitor, blocked ATM phosphorylation and ameliorated the phosphorylation of Chk2 and p53, but it increased H2AX phosphorylation and nuclear foci formation. Ku55933 also increased apoptosis in RPTCs following ATP depletion. The results suggest that DDR occurs during renal ischemia–reperfusion in vivo and ATP-depletion injury in vitro. The DDR is partially induced by apoptosis and oxidative stress-related DNA damage. ATM, as a sensor in the DDR, may play a cytoprotective role against tubular cell injury and death.
Keywords: Renal ischemia–reperfusion; Acute kidney injury; ATP depletion; DNA damage response; Apoptosis;
Fatty acids are novel nutrient factors to regulate mTORC1 lysosomal localization and apoptosis in podocytes by Mako Yasuda; Yuki Tanaka; Shinji Kume; Yoshikata Morita; Masami Chin-Kanasaki; Hisazumi Araki; Keiji Isshiki; Shin-ichi Araki; Daisuke Koya; Masakazu Haneda; Atsunori Kashiwagi; Hiroshi Maegawa; Takashi Uzu (1097-1108).
Podocyte apoptosis is a potent mechanism of proteinuria in diabetic nephropathy. More detailed mechanistic insight into podocyte apoptosis is needed to better understand the pathogenesis of diabetic nephropathy. An elevated level of serum free fatty acid (FFA), as well as hyperglycemia, is a clinical characteristic in diabetes, although its causal role in podocyte apoptosis remains unclear. This study examined the effect of three types of FFAs, saturated, monounsaturated and polyunsaturated FFAs, on podocyte apoptosis. Palmitate, a saturated FFA, induced endoplasmic reticulum (ER) stress-dependent apoptosis in podocytes. Oleate, a monounsaturated FFA, and eicosapentaenoic acid (EPA), an ω − 3 polyunsaturated FFA did not induce apoptosis; rather, they antagonized palmitate-induced apoptosis. Palmitate activated mammalian target of rapamycin (mTOR) complex 1 (mTORC1), a nutrient-sensing kinase regulating a wide range of cell biology. Furthermore, inhibition of mTORC1 activity by rapamycin or siRNA for Raptor, a component of mTORC1, ameliorated palmitate-induced ER stress and apoptosis in podocytes. Activity of mTORC1 is regulated by upstream kinases and Rag/Ragulator-dependent recruitment of mTOR onto lysosomal membranes. Palmitate activated mTORC1 by enhancing recruitment of mTOR onto lysosomal membranes, which was inhibited by co-incubation with oleate or EPA. Inhibition of mTOR translocation onto lysosomes by transfection with dominant-negative forms of Rag ameliorated palmitate-induced apoptosis. This study suggests that saturated and unsaturated FFAs have opposite effects on podocyte apoptosis by regulating mTORC1 activity via its translocation onto lysosomal membranes, and the results provide a better understanding of the pathogenesis in diabetic nephropathy and a novel role of mTORC1 in cell apoptosis.
Keywords: Podocyte apoptosis; Free fatty acid; mTORC1; Diabetic nephropathy; Lysosome;
Negatively regulating TLR4/NF-κB signaling via PPARα in endotoxin-induced uveitis by Wei Shen; Yang Gao; Boyu Lu; Qingjiong Zhang; Yang Hu; Ying Chen (1109-1120).
Toll-like receptor (TLR) signaling plays a fundamental role in the induction and progression of autoimmune disease. In the present study, we showed that lipopolysaccharide (LPS), a TLR4 ligand, functions as an antagonist of peroxisome proliferator-activated receptor alpha (PPARα), a nuclear transcription factor. Using endotoxin induced uveitis (EIU) as a model, we found that TLR was negatively regulated by PPARα. Our data revealed that treatment with the PPARα agonist fenofibrate dramatically prevented LPS-induced uveitis and inhibited TLR/ Nuclear factor-kappaB (NF-κB) signaling during inflammation. Evaluation of the severity of anterior uveitis further showed that PPARα agonist treatment significantly decreased inflammatory cell infiltration, total protein concentration, vessel density, inflammatory cytokine production, and clinical scores in the anterior section of the eye during EIU. Moreover, fenofibrate administration recovered retinal function and decreased the production of inflammatory cytokines, retinal vascular leukostasis, and inflammatory cell infiltration into the posterior section of the eyes during EIU. In vitro studies further showed that down-regulation or deletion of PPARα led to increased TLR4 levels and the activation of NF-κB signaling in RPE cells and also blocked the anti-inflammatory effects of fenofibrate. Furthermore, activation or up-regulation of PPARα decreased TLR4 levels and inhibited the NF-κB signaling pathway induced by LPS in RPE cells. In TLR4-expressing reporter cells, activation or up-regulation of PPARα partially inhibited the activation of NF-κB and also decreased TLR4 transcriptional activity. In conclusion, the activation of PPARα represents a novel therapeutic strategy for human uveitis, as PPARα negatively regulates TLR4 activity and therefore exerts anti-inflammatory actions.
Keywords: Endotoxin induced uveitis; LPS; TLR4; PPARα;
CERKL interacts with mitochondrial TRX2 and protects retinal cells from oxidative stress-induced apoptosis by Chang Li; Lei Wang; Jing Zhang; Mi Huang; Fulton Wong; Xuexue Liu; Fei Liu; Xiukun Cui; Guohua Yang; Jiaxiang Chen; Ying Liu; Jiuxiang Wang; Shengjie Liao; Meng Gao; Xuebin Hu; Xinhua Shu; Qing Wang; Zhan Yin; Zhaohui Tang; Mugen Liu (1121-1129).
Mutations in the ceramide kinase-like gene (CERKL) are associated with severe retinal degeneration. However, the exact function of the encoded protein (CERKL) remains unknown. Here we show that CERKL interacts with mitochondrial thioredoxin 2 (TRX2) and maintains TRX2 in the reduced redox state. Overexpression of CERKL protects cells from apoptosis under oxidative stress, whereas suppressing CERKL renders cells more sensitive to oxidative stress. In zebrafish, CERKL protein prominently locates in the outer segment and inner segment of the photoreceptor of the retina. Knockdown of CERKL in the zebrafish leads to an increase of retinal cell death, including cone and rod photoreceptor degeneration. Signs of oxidative damage to macromolecules were also detected in CERKL deficient zebrafish retina. Our results show that CERKL interacts with TRX2 and plays a novel key role in the regulation of the TRX2 antioxidant pathway and, for the first time, provides an explanation of how mutations in CERKL may lead to retinal cell death.
Keywords: CERKL; TRX2; Oxidative stress; Retina; Apoptosis;
TET2 gene expression and 5-hydroxymethylcytosine level in multiple sclerosis peripheral blood cells by R. Calabrese; E. Valentini; F. Ciccarone; T. Guastafierro; M.G. Bacalini; V.A.G. Ricigliano; M. Zampieri; V. Annibali; R. Mechelli; C. Franceschi; M. Salvetti; P. Caiafa (1130-1136).
Aberrant DNA methylation can lead to genome destabilization and to deregulated gene expression. Recently, 5-hydroxymethylcytosine (5hmC), derived from oxidation of 5-methylcytosine (5mC) by the Ten-Eleven Translocation (TET) enzymes, has been detected. 5hmC is now considered as a new epigenetic DNA modification with relevant roles in cell homeostasis regulating DNA demethylation and transcription. Our aim was to investigate possible changes in the DNA methylation/demethylation machinery in MS. We assessed the expression of enzymes involved in DNA methylation/demethylation in peripheral blood mononuclear cells (PBMCs) from 40 subjects with MS and 40 matched healthy controls. We performed also, DNA methylation analysis of specific promoters and analysis of global levels of 5mC and 5hmC. We show that TET2 and DNMT1 expression is significantly down-regulated in MS PBMCs and it is associated with aberrant methylation of their promoters. Furthermore, 5hmC is decreased in MS PBMCs, probably as a result of the diminished TET2 level.
Keywords: Epigenetics; Multiple sclerosis; Ten-Eleven Translocation 2; 5-Hydroxymethylcytosine; DNA methylation; Peripheral blood mononuclear cells;
Serum lactate as a novel potential biomarker in multiple sclerosis by Angela M. Amorini; Viviana Nociti; Axel Petzold; Claudio Gasperini; Esmeralda Quartuccio; Giacomo Lazzarino; Valentina Di Pietro; Antonio Belli; Stefano Signoretti; Roberto Vagnozzi; Giuseppe Lazzarino; Barbara Tavazzi (1137-1143).
Multiple sclerosis (MS) is a primary inflammatory demyelinating disease associated with a probably secondary progressive neurodegenerative component. Impaired mitochondrial functioning has been hypothesized to drive neurodegeneration and to cause increased anaerobic metabolism in MS. The aim of our multicentre study was to determine whether MS patients had values of circulating lactate different from those of controls. Patients (n = 613) were recruited, assessed for disability and clinically classified (relapsing–remitting, secondary progressive, primary progressive) at the Catholic University of Rome, Italy (n = 281), at the MS Centre Amsterdam, The Netherlands (n = 158) and at the S. Camillo Forlanini Hospital, Rome, Italy (n = 174). Serum lactate levels were quantified spectrophotometrically with the analyst being blinded to all clinical information. In patients with MS serum lactate was three times higher (3.04 ± 1.26 mmol/l) than that of healthy controls (1.09 ± 0.25 mmol/l, p < 0.0001) and increased across clinical groups, with higher levels in cases with a progressive than with a relapsing–remitting disease course. In addition, there was a linear correlation between serum lactate levels and the expanded disability scale (EDSS) (R2 = 0.419; p < 0.001). These data support the hypothesis that mitochondrial dysfunction is an important feature in MS and of particular relevance to the neurodegenerative phase of the disease. Measurement of serum lactate in MS might be a relative inexpensive test for longitudinal monitoring of “virtual hypoxia” in MS and also a secondary outcome for treatment trials aimed to improve mitochondrial function in patients with MS.
Keywords: Clinical disability; Energy penalty; Mitochondrial dysfunction; Multiple sclerosis; Serum lactate;
Neuropathological role of PI3K/Akt/mTOR axis in Down syndrome brain by Marzia Perluigi; Gilda Pupo; Antonella Tramutola; Chiara Cini; Raffaella Coccia; Eugenio Barone; Elizabeth Head; D. Allan Butterfield; Fabio Di Domenico (1144-1153).
Down syndrome (DS) is the most frequent genetic cause of intellectual disability characterized by the presence of three copies of chromosome 21 (Chr21). Individuals with DS have sufficient neuropathology for a diagnosis of Alzheimer's disease (AD) after the age of 40 years. The aim of our study is to gain new insights in the molecular mechanisms impaired in DS subjects that eventually lead to the development of dementia. We evaluate the PI3K/Akt/mTOR axis in the frontal cortex from DS cases (under the age of 40 years) and DS with AD neuropathology compared with age-matched controls (Young and Old). The PI3K/Akt/mTOR axis may control several key pathways involved in AD that, if aberrantly regulated, affect amyloid beta (Aβ) deposition and tau phosphorylation. Our results show a hyperactivation of PI3K/Akt/mTOR axis in individuals with DS, with and without AD pathology, in comparison with respective controls. The PI3K/Akt/mTOR deregulation results in decreased autophagy, inhibition of IRS1 and GSK3β activity. Moreover, our data suggest that aberrant activation of the PI3K/Akt/mTOR axis acts in parallel to RCAN1 in phosphorylating tau, in DS and DS/AD. In conclusion, this study provides insights into the neuropathological mechanisms that may be engaged during the development of AD in DS. We suggest that deregulation of this signaling cascade is already evident in young DS cases and persist in the presence of AD pathology. The impairment of the PI3K/Akt/mTOR axis in DS population might represent a key-contributing factor to the neurodegenerative process that culminates in Alzheimer-like dementia.Display Omitted
Keywords: mTOR; Akt; PI3K; Autophagy; Insulin signaling; Trisomy 21;
Insulin therapy modulates mitochondrial dynamics and biogenesis, autophagy and tau protein phosphorylation in the brain of type 1 diabetic rats by R.X. Santos; S.C. Correia; M.G. Alves; P.F. Oliveira; S. Cardoso; C. Carvalho; A.I. Duarte; M.S. Santos; P.I. Moreira (1154-1166).
The main purpose of this study was to examine whether streptozotocin (STZ)-induced type 1 diabetes (T1D) and insulin (INS) treatment affect mitochondrial function, fission/fusion and biogenesis, autophagy and tau protein phosphorylation in cerebral cortex from diabetic rats treated or not with INS. No significant alterations were observed in mitochondrial function as well as pyruvate levels, despite the significant increase in glucose levels observed in INS-treated diabetic rats. A significant increase in DRP1 protein phosphorylated at Ser616 residue was observed in the brain cortex of STZ rats. Also an increase in NRF2 protein levels and in the number of copies of mtDNA were observed in STZ diabetic rats, these alterations being normalized by INS. A slight decrease in LC3-II levels was observed in INS-treated rats when compared to STZ diabetic animals. An increase in tau protein phosphorylation at Ser396 residue was observed in STZ diabetic rats while INS treatment partially reversed that effect. Accordingly, a modest reduction in the activation of GSK3β and a significant increase in the activity of phosphatase 2A were found in INS-treated rats when compared to STZ diabetic animals. No significant alterations were observed in caspases 9 and 3 activity and synaptophysin and PSD95 levels. Altogether our results show that mitochondrial alterations induced by T1D seem to involve compensation mechanisms since no significant changes in mitochondrial function and synaptic integrity were observed in diabetic animals. In addition, INS treatment is able to normalize the alterations induced by T1D supporting the importance of INS signaling in the brain.
Keywords: Autophagy; Cerebral cortex; Insulin treatment; Tau protein phosphorylation; Type 1 diabetes; Mitochondrial fission, fusion and biogenesis;