Vital imaging of H9c2 myoblasts exposed to tert-butylhydroperoxide--characterization of morphological features of cell death

Heterogeneous redox responses in NHDF cells primed to enhance mitochondrial bioenergetics

Aging and lifestyle-related diseases, such as cardiovascular diseases, diabetes, cancer, and neurodegenerative disorders, are major global health challenges. These conditions are often linked to redox imbalances, where cells fail to regulate reactive redox species (RRS), leading to oxidative stress and cellular damage. Although antioxidants are known to neutralize harmful RRS, their clinical efficacy remains inconsistent. One reason for this inconsistency is the inadequacy of current in vitro models to accurately mimic in vivo redox conditions. This study addresses the gap in understanding the heterogeneity of redox responses in cells by using metabolically primed human dermal fibroblasts (NHDF), a model relevant for precision mitochondrial medicine. We investigated how metabolic priming, which enhances mitochondrial bioenergetics, influences redox responses to oxidative stress induced by hydrogen peroxide (H2O2) and tert-butyl hydroperoxide (tBHP). Specifically, we explored the impact of cell population density and cell cycle distribution on redox dynamics. Our findings indicate that NHDF cells cultured in oxidative phosphorylation-promoting medium (OXm) exhibit significantly larger variability in oxidative stress responses. This variability suggests that enhanced mitochondrial bioenergetics necessitates a constant regulation of the cellular redox machinery, potentially leading to heterogeneous responses. Additionally, cells grown in OXm showed increased mitochondrial polarization and a lower percentage of cells in the G2/M phase, contributing to the observed heterogeneity. Key factors influencing this variability included cell population density at the time of oxidant exposure and fluctuations in cell cycle distribution. Our results highlight the necessity of employing multiple oxidants in metabolic priming models to achieve a comprehensive understanding of oxidative stress responses and redox regulation mechanisms. Furthermore, the study emphasizes the need to refine in vitro models to better reflect in vivo conditions, which is crucial for the development of effective redox-based therapeutic strategies.

A novel combinatory treatment against a CDDP-resistant non-small cell lung cancer based on a Ruthenium(II)-cyclopentadienyl compound

The therapeutic approach to many solid tumors, including non-small cell lung cancer (NSCLC), is mainly based on the use of platinum-containing anticancer agents and is often characterized by acquired or intrinsic resistance to the drug. Therefore, the search for safer and more effective drugs is still an open challenge. Two organometallic ruthenium(II)-cyclopentadienyl compounds [Ru(η5-C5H4CHO)(Me2bipy)(PPh3)]+ (RT150) and [Ru(η5-C5H4CH2OH)(Me2bipy)(PPh3)][CF3SO3] (RT151) were tested against a panel of cisplatin-resistant NSCLC cell lines and xenografts. They were more effective than cisplatin in inducing oxidative stress and DNA damage, affecting the cell cycle and causing apoptosis. Importantly, they were found to be inhibitors of drug efflux transporters. Due to this property, the compounds significantly increased the retention and cytotoxicity of cisplatin within NSCLC cells. Notably, they did not display high toxicity in vitro against non-transformed cells (red blood cells, fibroblasts, bronchial epithelial cells, cardiomyocytes, and endothelial cells). Both compounds induced vasorelaxation and reduced endothelial cell migration, suggesting potential anti-angiogenic properties. RT151 confirmed its efficacy against NSCLC xenografts resistant to cisplatin. Either alone or combined with low doses of cisplatin, RT151 showed a good biodistribution profile in the liver, kidney, spleen, lung, and tumor. Hematochemical analysis and post-mortem organ pathology confirmed the safety of the compound in vivo, also when combined with cisplatin. To sum up, we have confirmed the effectiveness of a novel class of drugs against cisplatin-resistant NSCLC. Additionally, the compounds have a good biocompatibility and safety profile.

In vitro characterization of Trypanosoma cruzi infection dynamics in skeletal and cardiac myotubes models suggests a potential cell-to-cell transmission in mediating cardiac pathology

Chagas disease predominantly affects the heart, esophagus, and colon in its chronic phase. However, the precise infection mechanisms of the causal agent Trypanosoma cruzi in these tissue types remain incompletely understood. This study investigated T. cruzi infection dynamics in skeletal (SM) and cardiac myotubes (CM) differentiated from H9c2(2-1) myoblasts (control). SM and CM were generated using 1% fetal bovine serum (FBS) without or with retinoic acid, respectively. Initial invasion efficiencies and numbers of released parasites were equivalent between undifferentiated and differentiated cells (~0.3-0.6%). Concomitantly, parasite motility patterns were similar across cell lines. However, CM demonstrated significantly higher infection kinetics over time, reaching 13.26% infected cells versus 3.12% for SM and 3.70% for myoblasts at later stages. Cellular automata modeling suggested an enhanced role for cell-to-cell transmission in driving the heightened parasitism observed in CM. The increased late-stage susceptibility of CM, potentially mediated by cell-to-cell transfer mechanisms of the parasite, aligns with reported clinical tropism patterns. The myotube infection models provide novel insights into Chagas disease pathogenesis that are not fully attainable through in vivo examination alone. Expanding knowledge in this area could aid therapeutic development for this neglected illness.

A tipping point in dihydroxyacetone exposure: mitochondrial stress and metabolic reprogramming alter survival in rat cardiomyocytes H9c2 cells

Exogenous exposures to the triose sugar dihydroxyacetone (DHA) occur from sunless tanning products and electronic cigarette aerosol. Once inhaled or absorbed, DHA enters cells, is converted to dihydroxyacetone phosphate (DHAP), and incorporated into several metabolic pathways. Cytotoxic effects of DHA vary across the cell types depending on the metabolic needs of the cells, and differences in the generation of reactive oxygen species (ROS), cell cycle arrest, and mitochondrial dysfunction have been reported. We have shown that cytotoxic doses of DHA induced metabolic imbalances in glycolysis and oxidative phosphorylation in liver and kidney cell models. Here, we examine the dose-dependent effects of DHA on the rat cardiomyocyte cell line, H9c2. Cells begin to experience cytotoxic effects at low millimolar doses, but an increase in cell survival was observed at 2 mM DHA. We confirmed that 2 mM DHA increased cell survival compared to the low cytotoxic 1 mM dose and investigated the metabolic differences between these two low DHA doses. Exposure to 1 mM DHA showed changes in the cell's fuel utilization, mitochondrial reactive oxygen species (ROS), and transient changes in the glycolysis and mitochondrial energetics, which normalized 24 h after exposure. The 2 mM dose induced robust changes in mitochondrial flux through acetyl CoA and elevated expression of fatty acid synthase. Distinct from the 1 mM dose, the 2 mM exposure increased mitochondrial ROS and NAD(P)H levels, and sustained changes in LDHA/LDHB and acetyl CoA-associated enzymes were observed. Although the cells were exposed to low cytotoxic (1 mM) and non-cytotoxic (2 mM) acute doses of DHA, significant changes in mitochondrial metabolic pathways occurred. Further, the proliferation increase at the acute 2 mM DHA dose suggests a metabolic adaption occurred with sustained consequences in survival and proliferation. With increased exogenous exposure to DHA through e-cigarette aerosol, this work suggests cell metabolic changes induced by acute or potentially chronic exposures could impact cell function and survival.

Oxidative stress induces mitochondrial iron overload and ferroptotic cell death

Oxidative stress has been shown to induce cell death in a wide range of human diseases including cardiac ischemia/reperfusion injury, drug induced cardiotoxicity, and heart failure. However, the mechanism of cell death induced by oxidative stress remains incompletely understood. Here we provide new evidence that oxidative stress primarily induces ferroptosis, but not apoptosis, necroptosis, or mitochondria-mediated necrosis, in cardiomyocytes. Intriguingly, oxidative stress induced by organic oxidants such as tert-butyl hydroperoxide (tBHP) and cumene hydroperoxide (CHP), but not hydrogen peroxide (H2O2), promoted glutathione depletion and glutathione peroxidase 4 (GPX4) degradation in cardiomyocytes, leading to increased lipid peroxidation. Moreover, elevated oxidative stress is also linked to labile iron overload through downregulation of the transcription suppressor BTB and CNC homology 1 (Bach1), upregulation of heme oxygenase 1 (HO-1) expression, and enhanced iron release via heme degradation. Strikingly, oxidative stress also promoted HO-1 translocation to mitochondria, leading to mitochondrial iron overload and lipid reactive oxygen species (ROS) accumulation. Targeted inhibition of mitochondrial iron overload or ROS accumulation, by overexpressing mitochondrial ferritin (FTMT) or mitochondrial catalase (mCAT), respectively, markedly inhibited oxidative stress-induced ferroptosis. The levels of mitochondrial iron and lipid peroxides were also markedly increased in cardiomyocytes subjected to simulated ischemia and reperfusion (sI/R) or the chemotherapeutic agent doxorubicin (DOX). Overexpressing FTMT or mCAT effectively prevented cardiomyocyte death induced by sI/R or DOX. Taken together, oxidative stress induced by organic oxidants but not H2O2 primarily triggers ferroptotic cell death in cardiomyocyte through GPX4 and Bach1/HO-1 dependent mechanisms. Our results also reveal mitochondrial iron overload via HO-1 mitochondrial translocation as a key mechanism as well as a potential molecular target for oxidative stress-induced ferroptosis in cardiomyocytes.

Dimethylarginine Dimethylaminohydrolase - 1 expression is increased under tBHP-induced oxidative stress regulates nitric oxide production in PCa cells attenuates mitochondrial ROS-mediated apoptosis

Dimethylarginine dimethylaminohydrolase-1 (DDAH1) expression is frequently elevated in different cancers including prostate cancer (PCa) and enhances nitric oxide (NO) production in tumor cells by metabolising endogenous nitric oxide synthase (NOS) inhibitors. DDAH1 protects the PCa cells from cell death and promotes survival. In this study, we have investigated the cytoprotective role of DDAH1 and determined the mechanism of DDAH1 in protecting the cells in tumor microenvironment. Proteomic analysis of PCa cells with stable overexpression of DDAH1 has identified that oxidative stress-related activity is altered. Oxidative stress promotes cancer cell proliferation, survival and causes chemoresistance. A known inducer of oxidative stress, tert-Butyl Hydroperoxide (tBHP) treatment to PCa cells led to elevated DDAH1 level that is actively involved in protecting the PCa cells from oxidative stress induced cell damage. In PC3-DDAH1- cells, tBHP treatment led to higher mROS levels indicating that the loss of DDAH1 increases the oxidative stress and eventually leads to cell death. Under oxidative stress, nuclear Nrf2 controlled by SIRT1 positively regulates DDAH1 expression in PC3 cells. In PC3-DDAH1+ cells, tBHP induced DNA damage is well tolerated compared to wild-type cells while PC3-DDAH1- became sensitive to tBHP. In PC3 cells, tBHPexposure has increased the production of NO and GSH which may be acting as an antioxidant defence to overcome oxidative stress. Furthermore, in tBHP treated PCa cells, DDAH1 is controlling the expression of Bcl2, active PARP and caspase 3. Taken together, these results confirm that DDAH1 is involved in the antioxidant defence system and promotes cell survival.

The retinoic acid response is a minor component of the cardiac phenotype in H9c2 myoblast differentiation

The H9c2 myoblast cell line, isolated from the left ventricular tissue of rat, is currently used in vitro as a mimetic for skeletal and cardiac muscle due to its biochemical, morphological, and electrical/hormonal signaling properties. During culture, H9c2 cells acquire a myotube phenotype, where a critical component is the inclusion of retinoic acid (RA). The results from some authors on H9c2 suggested that thousands of genes respond to RA stimuli, while others report hundreds of genes responding to RA over different cell types. In this article, using a more appropriate experimental design, we first confirm the H9c2 cardiac phenotype with and without RA and report transcriptomic and physiological changes regarding calcium handling, bioenergetics, and other biological concepts. Interestingly, of the 2360 genes showing a transcriptional change, 622 genes were statistically associated with the RA response. Of these genes, only 305 were RA-specific, and the rest also showed a culture-time component. Thus, the major expression changes (from 74 to 87%) were indeed due to culture conditions over time. Unexpectedly, only a few components of the retinol pathway in KEGG responded to RA. Our results show the role of RA in the H9c2 cultures impacting the interpretation using H9c2 as an in vitro model.

The anti-cancer drug doxorubicin induces substantial epigenetic changes in cultured cardiomyocytes

The anthracycline doxorubicin (DOX) is widely used in cancer therapy with the limitation of cardiotoxicity leading to the development of congestive heart failure. DOX-induced oxidative stress and changes of the phosphoproteome as well as epigenome were described but the exact mechanisms of the adverse long-term effects are still elusive. Here, we tested the impact of DOX treatment on cell death, oxidative stress parameters and expression profiles of proteins involved in epigenetic pathways in a cardiomyocyte cell culture model. Markers of oxidative stress, apoptosis and expression of proteins involved in epigenetic processes were assessed by immunoblotting in cultured rat myoblasts (H9c2) upon treatment with DOX (1 or 5 μM for 24 or 48 h) in adherent viable and detached apoptotic cells. The apoptosis markers cleaved caspase-3 and fractin as well as oxidative stress markers 3-nitrotyrosine and malondialdehyde were dose-dependently increased by DOX treatment. Histone deacetylases (SIRT1 and HDAC2), histone lysine demethylases (KDM3A and LSD1) and histone lysine methyltransferases (SET7 and SMYD1) were significantly regulated by DOX treatment with generation of cleaved protein fragments and posttranslational modifications. Overall, we found significant decrease in histone 3 acetylation in DOX-treated cells. DOX treatment of cultured cardiomyocyte precursor cells causes severe cell death by apoptosis associated with cellular oxidative stress. In addition, significant regulation of proteins involved in epigenetic processes and changes in global histone 3 acetylation were observed. However, the significance and clinical impact of these changes remain elusive.

Sulodexide attenuates endoplasmic reticulum stress induced by myocardial ischaemia/reperfusion by activating the PI3K/Akt pathway

Acute myocardial ischaemia/reperfusion (MI/R) injury causes severe arrhythmias with a high rate of lethality. Extensive research focus on endoplasmic reticulum (ER) stress and its dysfunction which leads to cardiac injury in MI/R Our study evaluated the effects of sulodexide (SDX) on MI/R by establishing MI/R mice models and in vitro oxidative stress models in H9C2 cells. We found that SDX decreases cardiac injury during ischaemia reperfusion and decreased myocardial apoptosis and infarct area, which was paralleled by increased superoxide dismutase and reduced malondialdehyde in mice plasm, increased Bcl‐2 expression, decreased BAX expression in a mouse model of MI/R. In vitro, SDX exerted a protective effect by the suppression of the ER stress which induced by tert‐butyl hydroperoxide (TBHP) treatment. Both of the in vivo and in vitro effects were involved in the phosphatidylinositol 3‐kinase (PI3K)/Akt signalling pathway. Inhibition of PI3K/Akt pathway by specific inhibitor, LY294002, partially reduced the protective effect of SDX. In short, our results suggested that the cardioprotective role of SDX was related to the suppression of ER stress in mice MI/R models and TBHP‐induced H9C2 cell injury which was through the PI3K/Akt signalling pathway.

Protective Effect of Morphine Against the Oxidant-Induced Injury in H9c2 Cells

There are some indications that morphine may exert myocardial protective effects under certain conditions. The aim of the present study was to investigate the effect of morphine on viability and oxidative state of H9c2 cells (rat cardiomyoblasts) influenced by oxidative stress that was elicited by exposure to tert-butyl hydroperoxide (t-BHP). Our experiments showed that pretreatment with morphine before the addition of t-BHP markedly improved cell viability. Morphine was able to increase total antioxidant capacity of H9c2 cells and to reduce the production of reactive oxygen species, protein carbonylation, and lipid peroxidation. Cellular damage caused by t-BHP was associated with low levels of p38 MAPK and GSK-3β phosphorylation. Pretreatment with morphine augmented p38 phosphorylation, and the increased phospho-p38/p38 ratio was preserved even in the presence of t-BHP. Morphine did not change the level of GSK-3β phosphorylation, but interestingly, the phospho-GSK-3β/GSK-3β ratio significantly increased after subsequent incubation with t-BHP. Furthermore, morphine exposure resulted in upregulation of the antioxidant enzyme catalase. The protective effect of morphine was abrogated by the addition of the PI3K inhibitor wortmannin and/or p38 MAPK inhibitor SB203580. It can be concluded that morphine may protect H9c2 cells against oxidative stress and that this protection is at least partially mediated through activation of the p38 MAPK and PI3K/GSK-3β pathways.

The role of ginsenoside Rb1, a potential natural glutathione reductase agonist, in preventing oxidative stress-induced apoptosis of H9C2 cells

Background

Oxidative stress-induced cardiomyocytes apoptosis is a key pathological process in ischemic heart disease. Glutathione reductase (GR) reduces glutathione disulfide to glutathione (GSH) to alleviate oxidative stress. Ginsenoside Rb1 (GRb1) prevents the apoptosis of cardiomyocytes; however, the role of GR in this process is unclear. Therefore, the effects of GRb1 on GR were investigated in this study.

Methods

The antiapoptotic effects of GRb1 were evaluated in H9C2 cells by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, annexin V/propidium iodide staining, and Western blotting. The antioxidative effects were measured by a reactive oxygen species assay, and GSH levels and GR activity were examined in the presence and absence of the GR inhibitor 1,3-bis-(2-chloroethyl)-1-nitrosourea. Molecular docking and molecular dynamics simulations were used to investigate the binding of GRb1 to GR. The direct influence of GRb1 on GR was confirmed by recombinant human GR protein.

Results

GRb1 pretreatment caused dose-dependent inhibition of tert-butyl hydroperoxide-induced cell apoptosis, at a level comparable to that of the positive control N-acetyl-L-cysteine. The binding energy between GRb1 and GR was positive (−6.426 kcal/mol), and the binding was stable. GRb1 significantly reduced reactive oxygen species production and increased GSH level and GR activity without altering GR protein expression in H9C2 cells. Moreover, GRb1 enhanced the recombinant human GR protein activity in vitro, with a half-maximal effective concentration of ≈2.317 μM. Conversely, 1,3-bis-(2-chloroethyl)-1-nitrosourea co-treatment significantly abolished the GRb1's apoptotic and antioxidative effects of GRb1 in H9C2 cells.

Conclusion

GRb1 is a potential natural GR agonist that protects against oxidative stress–induced apoptosis of H9C2 cells.

DHA and 19,20-EDP induce lysosomal-proteolytic-dependent cytotoxicity through de novo ceramide production in H9c2 cells with a glycolytic profile

Docosahexaenoic acid (DHA) and their CYP-derived metabolites, epoxydocosapentaenoic acids (EDPs), are important fatty acids obtained from dietary sources. While it is known that they have significant biological effects, which can differ between cell type and disease state, our understanding of how they work remains limited. Previously, we demonstrated that DHA and 19,20-EDP triggered pronounced cytotoxicity in H9c2 cells correlating with increased ceramide production. In this study, we examine whether DHA- and 19,20-EDP-induced cell death depends on the type of metabolism (glycolysis or OXPHOS). We cultivated H9c2 cells in distinct conditions that result in either glycolytic or oxidative metabolism. Our major findings suggest that DHA and its epoxy metabolite, 19,20-EDP, trigger cytotoxic effects toward H9c2 cells with a glycolytic metabolic profile. Cell death occurred through a mechanism involving activation of a lysosomal-proteolytic degradation pathway. Importantly, accumulation of ceramide played a critical role in the susceptibility of glycolytic H9c2 cells to cytotoxicity. Furthermore, our data suggest that an alteration in the cellular metabolic profile is a major factor determining the type and magnitude of cellular toxic response. Together, the novelty of this study demonstrates that DHA and 19,20-EDP induce cell death in H9c2 cells with a glycolytic metabolicwct 2 profile through a lysosomal-proteolytic mechanism.

Indolylmaleimide Derivative IM-17 Shows Cardioprotective Effects in Ischemia-Reperfusion Injury

We previously developed IM-54 as a novel type of inhibitor of hydrogen-peroxide-induced necrotic cell death. Here, we examined its cell death inhibition profile. IM-54 was found to selectively inhibit oxidative stress-induced necrosis, but it did not inhibit apoptosis induced by various anticancer drugs or Fas ligand, or necroptosis. IM-17, an IM derivative having improved water-solubility and metabolic stability, was developed and confirmed to retain necrosis-inhibitory activity. IM-17 showed cardioprotective effects in an isolated rat heart model and an in vivo arrhythmia model, suggesting that IM derivatives may have therapeutic potential.

Cardiac tissue regeneration: A preliminary study on carbon-based nanotubes gelatin scaffold

The aim of this study was set-up and test of gelatin and carbon nanotubes scaffolds. Gelatin-based (5%) genipin cross-linked (0.2%) scaffolds embedding single-walled carbon nanotubes (SWCNTs, 0.3, 0.5, 0.7, 0.9, and 1.3% w/w) were prepared and mechanically/electrically characterized. For biological evaluation, H9c2 cell line was cultured for 10 days. Cytotoxicity, cell growth and differentiation, immunohistochemistry, and real-time PCR analysis were performed. Myoblast and cardiac differentiation were obtained by serum reduction to 1% (C_1% ) and stimulation with 50 nM all trans-retinoic acid (C_RA ), respectively. Immunohistochemistry showed elongated myotubes in C_1% while round and multinucleated cells in C_RA with also a significantly increased expression of natriuretic peptides (NP) and ET-1 receptors in parallel with a decreased ET-1. On scaffolds, cell viability was similar for Gel-SWCNT_0.3%/0.9% ; NP and ET systems expression decreased in both concentrations with respect to control and CX-43, mainly due to a lacking of complete differentiation in cardiac phenotype during that time. Although further analyses on novel biomaterials are necessary, these results represent a useful starting point to develop new biomaterial-based scaffolds. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2750-2762, 2018.

Esculetin Neutralises Cytotoxicity of t-BHP but Not of H2O2 on Human Leukaemia NB4 Cells

The coumarin esculetin shows antioxidant action on some cell types, both by scavenging ROS and by decreasing ROS production. We have previously demonstrated the induction of apoptosis by esculetin on NB4 human leukaemia cells by an ill-defined mechanism related to ROS levels. In this work, we analyze the effect of the simultaneous treatment with esculetin and two oxidants to observe the early events in the mechanism of esculetin-induced apoptosis. Our results show that, from the early time of 15 min, esculetin acts synergistically with H₂O₂ to decrease cell viability and metabolic activity and to increase apoptosis in NB4 cells. In contrast, the early oxidative effects of t-BHP are neutralised by esculetin, protecting human leukaemia NB4 cells from apoptosis. Esculetin seems to restrict the increase in peroxides caused by H₂O₂ or t-BHP in the time interval analyzed. These results contribute to a better understanding of the cytotoxic effect caused by esculetin on NB4 cells. At the same time, the early neutralisation of exogenous oxidants could be of interest to prevent diseases related to oxidative stress imbalance.

LEDGF/p75 Overexpression Attenuates Oxidative Stress-Induced Necrosis and Upregulates the Oxidoreductase ERP57/PDIA3/GRP58 in Prostate Cancer

Prostate cancer (PCa) mortality is driven by highly aggressive tumors characterized by metastasis and resistance to therapy, and this aggressiveness is mediated by numerous factors, including activation of stress survival pathways in the pro-inflammatory tumor microenvironment. LEDGF/p75, also known as the DFS70 autoantigen, is a stress transcription co-activator implicated in cancer, HIV-AIDS, and autoimmunity. This protein is targeted by autoantibodies in certain subsets of patients with PCa and inflammatory conditions, as well as in some apparently healthy individuals. LEDGF/p75 is overexpressed in PCa and other cancers, and promotes resistance to chemotherapy-induced cell death via the transactivation of survival proteins. We report in this study that overexpression of LEDGF/p75 in PCa cells attenuates oxidative stress-induced necrosis but not staurosporine-induced apoptosis. This finding was consistent with the observation that while LEDGF/p75 was robustly cleaved in apoptotic cells into a p65 fragment that lacks stress survival activity, it remained relatively intact in necrotic cells. Overexpression of LEDGF/p75 in PCa cells led to the upregulation of transcript and protein levels of the thiol-oxidoreductase ERp57 (also known as GRP58 and PDIA3), whereas its depletion led to ERp57 transcript downregulation. Chromatin immunoprecipitation and transcription reporter assays showed LEDGF/p75 binding to and transactivating the ERp57 promoter, respectively. Immunohistochemical analysis revealed significantly elevated co-expression of these two proteins in clinical prostate tumor tissues. Our results suggest that LEDGF/p75 is not an inhibitor of apoptosis but rather an antagonist of oxidative stress-induced necrosis, and that its overexpression in PCa leads to ERp57 upregulation. These findings are of significance in clarifying the role of the LEDGF/p75 stress survival pathway in PCa.

Irisin Controls Growth, Intracellular Ca2+ Signals, and Mitochondrial Thermogenesis in Cardiomyoblasts

Exercise offers short-term and long-term health benefits, including an increased metabolic rate and energy expenditure in myocardium. The newly-discovered exercise-induced myokine, irisin, stimulates conversion of white into brown adipocytes as well as increased mitochondrial biogenesis and energy expenditure. Remarkably, irisin is highly expressed in myocardium, but its physiological effects in the heart are unknown. The objective of this work is to investigate irisin’s potential multifaceted effects on cardiomyoblasts and myocardium. For this purpose, H9C2 cells were treated with recombinant irisin produced in yeast cells (r-irisin) and in HEK293 cells (hr-irisin) for examining its effects on cell proliferation by MTT [3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and on gene transcription profiles by qRT-PCR. R-irisin and hr-irisin both inhibited cell proliferation and activated genes related to cardiomyocyte metabolic function and differentiation, including myocardin, follistatin, smooth muscle actin, and nuclear respiratory factor-1. Signal transduction pathways affected by r-irisin in H9C2 cells and C57BL/6 mice were examined by detecting phosphorylation of PI3K-AKT, p38, ERK or STAT3. We also measured intracellular Ca²⁺ signaling and mitochondrial thermogenesis and energy expenditure in r-irisin-treated H9C2 cells. The results showed that r-irisin, in a certain concentration rage, could activate PI3K-AKT and intracellular Ca²⁺ signaling and increase cellular oxygen consumption in H9C2 cells. Our study also suggests the existence of irisin-specific receptor on the membrane of H9C2 cells. In conclusion, irisin in a certain concentration rage increased myocardial cell metabolism, inhibited cell proliferation and promoted cell differentiation. These effects might be mediated through PI3K-AKT and Ca²⁺ signaling, which are known to activate expression of exercise-related genes such as follistatin and myocardin. This work supports the value of exercise, which promotes irisin release.

Gene Expression Profiling of H9c2 Myoblast Differentiation towards a Cardiac-Like Phenotype

H9c2 myoblasts are a cell model used as an alternative for cardiomyocytes. H9c2 cells have the ability to differentiate towards a cardiac phenotype when the media serum is reduced in the presence of all-trans-retinoic acid (RA), creating multinucleated cells with low proliferative capacity. In the present study, we performed for the first time a transcriptional analysis of the H9c2 cell line in two differentiation states, i.e. embryonic cells and differentiated cardiac-like cells. The results show that RA-induced H9c2 differentiation increased the expression of genes encoding for cardiac sarcomeric proteins such as troponin T, or calcium transporters and associated machinery, including SERCA2, ryanodine receptor and phospholamban as well as genes associated with mitochondrial energy production including respiratory chain complexes subunits, mitochondrial creatine kinase, carnitine palmitoyltransferase I and uncoupling proteins. Undifferentiated myoblasts showed increased gene expression of pro-survival proteins such as Bcl-2 as well as cell cycle-regulating proteins. The results indicate that the differentiation of H9c2 cells lead to an increase of transcripts and protein levels involved in calcium handling, glycolytic and mitochondrial metabolism, confirming that H9c2 cell differentiation induced by RA towards a more cardiac-like phenotype involves remodeled mitochondrial function. PI3K, PDK1 and p-CREB also appear to be involved on H9c2 differentiation. Furthermore, complex analysis of differently expressed transcripts revealed significant up-regulation of gene expression related to cardiac muscle contraction, dilated cardiomyopathy and other pathways specific for the cardiac tissue. Metabolic and gene expression remodeling impacts cell responses to different stimuli and determine how these cells are used for biochemical assays.

Cardiomyocyte culture - an update on the in vitro cardiovascular model and future challenges

The success of any work with isolated cardiomyocytes depends on the reproducibility of cell isolation, because the cells do not divide. To date, there is no suitable in vitro model to study human adult cardiac cell biology. Although embryonic stem cells and induced pluripotent stem cells are able to differentiate into cardiomyocytes in vitro, the efficiency of this process is low. Isolation and expansion of human cardiomyocyte progenitor cells from cardiac surgical waste or, alternatively, from fetal heart tissue is another option. However, to overcome various issues related to human tissue usage, especially ethical concerns, researchers use large- and small-animal models to study cardiac pathophysiology. A simple model to study the changes at the cellular level is cultures of cardiomyocytes. Although primary murine cardiomyocyte cultures have their own advantages and drawbacks, alternative strategies have been developed in the last two decades to minimise animal usage and interspecies differences. This review discusses the use of freshly isolated murine cardiomyocytes and cardiomyocyte alternatives for use in cardiac disease models and other related studies.

Mitochondrial accumulation under oxidative stress is due to defects in autophagy

Mitochondrial dynamics maintains normal mitochondrial function by degrading damaged mitochondria and generating newborn mitochondria. The accumulation of damaged mitochondria influences the intracellular environment by promoting mitochondrial dysfunction, and thus initiating a vicious cycle. Oxidative stress induces mitochondrial malfunction, which is involved in many cardiovascular diseases. However, the mechanism of mitochondrial accumulation in cardiac myoblasts remains unclear. We observed mitochondrial dysfunction and an increase in mitochondrial mass under the oxidative conditions produced by tert-butyl hydroperoxide (tBHP) in cardiac myoblast H9c2 cells. However, in contrast to the increase in mitochondrial mass, mitochondrial DNA (mtDNA) decreased, suggesting that enhanced mitochondrial biogenesis may be not the primary cause of the mitochondrial accumulation. Therefore, we investigated changes in a number of proteins involved in autophagy. Beclin1, Atg12-Atg5 conjugate, Atg7 contents decreased but LC3-II accumulated in tBHP-treated H9c2 cells. Moreover, the capacity for acid hydrolysis decreased in H9c2 cells. We also demonstrated a decrease in DJ-1 protein under the oxidative conditions that deregulate mitochondrial dynamics. These results reveal that autophagy became defective under oxidative stress. We therefore suggest that defects in autophagy mediate mitochondrial accumulation under these conditions.

Pretreatment of therapeutic cells with poly(ADP-ribose) polymerase inhibitor enhances their efficacy in an in vitro model of cell-based therapy in myocardial infarct

The potential of cell-based therapies in diseases involving ischemia-reperfusion is greatly hampered by the excessive loss of administered cells in the harsh and oxidative environment where these cells are supposed to act. Therefore, we investigated if inhibition of poly(ADP-ribose) polymerase (PARP) in the therapeutically added cells would lead to their increased viability and, subsequently, to an enhanced effect in an in vitro simulated ischemia-reperfusion (I-R) setting. Ischemic conditions were simulated by oxygen and glucose deprivation for 160 min using H9c2 rat cardiomyoblast cells. After 30 min of reperfusion, these cells received 4 types of treatments: no added cells (I-R model), fluorescently labeled (Vybrant DiD) therapeutic H9c2 cells with vehicle (H9c2) or PARP inhibitor (10 μM or 100 μM PJ34) pretreatment. We assessed viability (live, apoptotic and necrotic) of both ‘postischemic’ and therapeutic cells with flow cytometric analysis using calcein-AM/ethidium homodimer-2 fluorescent staining after 24 h of co-culture. Further measurements on necrosis and metabolic activity were performed using lactate dehydrogenase (LDH) release and resazurin based assays. The percentage of surviving therapeutic cells increased significantly with PARP inhibition (untreated, 52.02±5.01%; 10 μM PJ34, 63.38±4.50%; 100 μM PJ34, 64.99±3.47%). The percentage of necrotic cells decreased in a similar manner (untreated, 37.23±4.40%; 10 μM PJ34, 26.83±3.49%; 100 μM PJ34, 24.96±2.43%). Notably, the survival of the cells that suffered I-R injury was also significantly higher when treated with PARP-inhibited therapeutic cells (I-R model, 36.44±5.05%; H9c2, 42.81±5.11%; 10 μM PJ34, 52.07±5.80%; 100 μM PJ34, 54.95±5.55%), while necrosis was inhibited (I-R model, 43.64±4.00%; H9c2, 37.29±4.55%; 10 μM PJ34, 30.18±4.60%; 100 μM PJ34, 25.52±3.47%). In subsequent experiments, PARP inhibition decreased LDH-release of the observed combined cell population and enhanced the metabolic activity. Thus, our results suggest that pretreating the therapeutically added cells with a PARP inhibitor could be beneficial in the setting of cell-based therapies.

Carotenoid compositions of coloured tomato cultivars and contribution to antioxidant activities and protection against H(2)O(2)-induced cell death in H9c2

The carotenoid compositions, antioxidant activities and the potential cardio-protective role of 13 tomato cultivars with distinct colour were studied. Colour coordinates were evaluated by colorimeter and the carotenoid compositions were analysed by UPLC. Red tomatoes had the highest total carotenoid contents (TCC) and antioxidant activities, followed by purple, orange, pink and yellow ones. The TCC were 120.5-278.0 μg/gDW, and the antioxidant activities were 21.32-40.07 μmolTE/gDW (PCL), 64.42-89.98% (DPPH) and 10.47-13.76 μmolTE/g DW (ORAC), respectively. The lipophilic extracts were also found to prevent cell death in a cell-based model system using cardiac H9c2 cells and H(2)O(2), via attenuation of the caspase-3 and matrix metalloproteinase-2 activities. The extracts of different tomatoes showed strong but different antioxidant activities. Roles of total and individual carotenoids in the antioxidant activities were studied and lycopene showed the highest correlation. Results of this study can be used to guide the development of new tomato cultivars and functional foods, and benefit the consumers.

Disrupted ATP synthase activity and mitochondrial hyperpolarisation-dependent oxidative stress is associated with p66Shc phosphorylation in fibroblasts of NARP patients

p66Shc is an adaptor protein involved in cell proliferation and differentiation that undergoes phosphorylation at Ser36 in response to oxidative stimuli, consequently inducing a burst of reactive oxygen species (ROS), mitochondrial disruption and apoptosis. Its role during several pathologies suggests that p66Shc mitochondrial signalling can perpetuate a primary mitochondrial defect, thus contributing to the pathophysiology of that condition. Here, we show that in the fibroblasts of neuropathy, ataxia and retinitis pigmentosa (NARP) patients, the p66Shc phosphorylation pathway is significantly induced in response to intracellular oxidative stress related to disrupted ATP synthase activity and mitochondrial membrane hyperpolarisation. We postulate that the increased phosphorylation of p66Shc at Ser36 is partially responsible for further increasing ROS production, resulting in oxidative damage of proteins. Oxidative stress and p66Shc phosphorylation at Ser36 may be mitigated by antioxidant administration or the use of a p66Shc phosphorylation inhibitor. This article is part of a Directed Issue entitled: Bioenergetic dysfunction, adaptation and therapy.

Biomechanical characterization of a desminopathy in primary human myoblasts

Heterozygous mutations of the human desmin gene on chromosome 2q35 cause hereditary and sporadic myopathies and cardiomyopathies. The expression of mutant desmin brings about partial disruption of the extra sarcomeric desmin cytoskeleton and abnormal protein aggregation in the sarcoplasm of striated muscle cells. The precise molecular pathways and sequential steps that lead from a desmin gene defect to progressive muscle damage are still unclear. We tested whether mutant desmin changes the biomechanical properties and the intrinsic mechanical stress response of primary cultured myoblasts derived from a patient carrying a heterozygous R350P desmin mutation. Compared to wildtype controls, undifferentiated mutant desmin myoblasts revealed increased cell death and substrate detachment in response to cyclic stretch on flexible membranes. Moreover, magnetic tweezer microrheometry of myoblasts using fibronectin-coated beads showed increased stiffness of diseased cells. Our findings provide the first evidence that altered mechanical properties may contribute to the progressive striated muscle pathology in desminopathies. We postulate that the expression of mutant desmin leads to increased mechanical stiffness, which results in excessive mechanical stress in response to strain and consecutively to increased mechanical vulnerability and damage of muscle cells.

Cytoprotective effect of Coreopsis tinctoria extracts and flavonoids on tBHP and cytokine-induced cell injury in pancreatic MIN6 cells

ETHNOPHARMACOLOGICAL RELEVANCE

[corrected] Coreopsis tinctoria flowering tops infusion is traditionally used in Portugal for treating the symptoms of diabetes. Recent studies have revealed its antihyperglycemic activity when administered for 3 weeks to a STZ-induced glucose intolerance model in the rat and glucose tolerance regain was even clearer and pancreatic function recovery was achieved when administering Coreopsis tinctoria flavonoid-rich AcOEt fraction. In this study we aimed to evaluate the protective effect of Coreopsis tinctoria flowering tops aqueous extract, AcOEt fraction and the pure compounds marein and flavanomarein, against beta-cell injury, in a mouse insulinoma cell line (MIN6) challenged with pro-oxidant tert-butyl-hydroperoxide (tBHP) or cytokines.

MATERIALS AND METHODS

The protective effects of Coreopsis tinctoria flowering tops extracts and pure compounds were evaluated through pre-incubating MIN6 cells with samples followed by treatment with tBHP (400 μM for 2 h) after which viability was determined through ATP measurements. In order to assess whether plant extracts were involved in decreasing reactive oxygen species, superoxide anion production was determined through a lucigenin-enhanced chemiluminescent method. Lastly, the direct influence of Coreopsis tinctoria extracts and main compounds on cell survival/apoptosis was determined measuring caspase 3 and 7 cleavage induced by cytokines.

RESULTS

Coreopsis tinctoria flowering tops extracts (25-100 μg/mL) and pure compounds (200-400 μM), when pre-incubated with MIN6 cells did not present any cytotoxicity, instead they increased cell viability in a dose dependent manner when challenged with tBHP. Treatment with this pro-oxidant also showed a rise in superoxide radical anion formation in MIN6 cells. This increase was significantly reduced by treatment with superoxide dismutase enzyme (SOD) but not by pre-treatment with Coreopsis tinctoria flowering tops extracts. Caspase 3/7 activation measurements show that Coreopsis tinctoria flowering tops extracts, as well as marein and flavanomarein, significantly inhibit apoptosis.

CONCLUSIONS

Coreopsis tinctoria extracts and pure compounds show cytoprotection that seems to be due to inhibition of the apoptotic pathway, and not through a decrease on superoxide radical production.

Proteome changes in the myocardium of experimental chronic diabetes and hypertension: role of PPARα in the associated hypertrophy

Diabetes with or without the presence of hypertension damages the heart. However, there is currently a lack of information about these associated pathologies and the alteration of linked proteins. For these reasons, we were interested in the potential synergistic interaction of diabetes and hypertension in the heart, focusing on the proteome characterization of the pathological phenotypes and the associated hypertrophic response. We treated normotensive and spontaneously hypertensive (SHR) rats with either streptozotocin or vehicle. After 22weeks, type-I diabetic (DM1), SHR, SHR/DM1 and control left-ventricles were studied using proteomic approaches. Proteomics revealed that long-term DM1, SHR and SHR/DM1 rats exhibited 24, 53 and 53 altered proteins in the myocardia, respectively. DM1 myocardium showed over-expression of apoptotic and cytoskeleton proteins, and down-regulation of anti-apoptotic and mitochondrial metabolic enzymes. In both SHR and SHR/DM1 these changes were exacerbated and free fatty-acid (FFA) ß-oxidation enzymes were additionally decreased. Furthermore, SHR/DM1 hearts exhibited a misbalance of specific pro-hypertrophic, anti-apoptotic and mitochondrial ATP-carrier factors, which could cause additional damage. Differential proteins were validated and then clustered into different biological pathways using bioinformatics. These studies suggested the implication of FFA-nuclear receptors and hypertrophic factors in these pathologies. Although key ß-oxidation enzymes were not stimulated in DM1 and hypertensive hearts, peroxisome proliferator-activated receptors-α (PPARα) were potentially activated for other responses. In this regard, PPARα stimulation reduced hypertrophy and pro-hypertrophic factors such as annexin-V in high-glucose and angiotensin-II induced cardiomyocytes. Thus, activation of PPARα could reflect a compensatory response to the metabolic-shifted, apoptotic and hypertrophic status of the hypertensive-diabetic cardiomyopathy.

Isoproterenol cytotoxicity is dependent on the differentiation state of the cardiomyoblast H9c2 cell line

H9c2 cells are used as a surrogate for cardiac cells in several toxicological studies, which are usually performed with cells in their undifferentiated state, raising questions on the applicability of the results to adult cardiomyocytes. Since H9c2 myoblasts have the capacity to differentiate into skeletal and cardiac muscle cells under different conditions, the hypothesis of the present work was that cells in different differentiation states differ in their susceptibility to toxicants. In order to test the hypothesis, the effects of the cardiotoxicant isoproterenol (ISO) were investigated. The present work demonstrates that differentiated H9c2 cells are more susceptible to ISO toxicity. Cellular content of beta(1)-adrenergic receptors (AR), beta(3)-AR, and calcineurin is decreased as cells differentiate, as opposed to the content on the mitochondrial voltage-dependent anion channel (VDAC) and phosphorylated p38-MAPK, which increase. After ISO treatment, the pro-apoptotic protein Bax increases in all experimental groups, although only undifferentiated myoblasts up-regulate the anti-apoptotic Bcl-2. Calcineurin is decreased in differentiated H9c2 cells, which suggests an important role against ISO-induced cell death. The results indicate that the differentiation state of H9c2 myoblasts influence ISO toxicity, which may involve calcineurin, p38-MAPK, and Bax/Bcl-2 alterations. The data also provide new insights into cardiovascular toxicology during early development.

Stem cell transplantation in an in vitro simulated ischemia/reperfusion model

Stem cell transplantation protocols are finding their way into clinical practice. Getting better results, making the protocols more robust, and finding new sources for implantable cells are the focus of recent research. Investigating the effectiveness of cell therapies is not an easy task and new tools are needed to investigate the mechanisms involved in the treatment process. We designed an experimental protocol of ischemia/reperfusion in order to allow the observation of cellular connections and even subcellular mechanisms during ischemia/reperfusion injury and after stem cell transplantation and to evaluate the efficacy of cell therapy. H9c2 cardiomyoblast cells were placed onto cell culture plates. Ischemia was simulated with 150 minutes in a glucose free medium with oxygen level below 0.5%. Then, normal media and oxygen levels were reintroduced to simulate reperfusion. After oxygen glucose deprivation, the damaged cells were treated with transplantation of labeled human bone marrow derived mesenchymal stem cells by adding them to the culture. Mesenchymal stem cells are preferred in clinical trials because they are easily accessible with minimal invasive surgery, easily expandable and autologous. After 24 hours of co-cultivation, cells were stained with calcein and ethidium-homodimer to differentiate between live and dead cells. This setup allowed us to investigate the intercellular connections using confocal fluorescent microscopy and to quantify the survival rate of postischemic cells by flow cytometry. Confocal microscopy showed the interactions of the two cell populations such as cell fusion and formation of intercellular nanotubes. Flow cytometry analysis revealed 3 clusters of damaged cells which can be plotted on a graph and analyzed statistically. These populations can be investigated separately and conclusions can be drawn on these data on the effectiveness of the simulated therapeutical approach.

Synthesis and initial in vitro evaluations of novel antioxidant aroylhydrazone iron chelators with increased stability against plasma hydrolysis

Oxidative stress is known to contribute to a number of cardiovascular pathologies. Free intracellular iron ions participate in the Fenton reaction and therefore substantially contribute to the formation of highly toxic hydroxyl radicals and cellular injury. Earlier work on the intracellular iron chelator salicylaldehyde isonicotinoyl hydrazone (SIH) has demonstrated its considerable promise as an agent to protect the heart against oxidative injury both in vitro and in vivo. However, the major limitation of SIH is represented by its labile hydrazone bond that makes it prone to plasma hydrolysis. Hence, in order to improve the hydrazone bond stability, nine compounds were prepared by a substitution of salicylaldehyde by the respective methyl- and ethylketone with various electron donors or acceptors in the phenyl ring. All the synthesized aroylhydrazones displayed significant iron-chelating activities and eight chelators showed significantly higher stability in rabbit plasma than SIH. Furthermore, some of these chelators were observed to possess higher cytoprotective activities against oxidative injury and/or lower toxicity as compared to SIH. The results of the present study therefore indicate the possible applicability of several of these novel agents in the prevention and/or treatment of cardiovascular disorders with a known (or presumed) role of oxidative stress. In particular, the methylketone HAPI and nitro group-containing NHAPI merit further in vivo investigations.

NecroX as a novel class of mitochondrial reactive oxygen species and ONOO⁻ scavenger

Mitochondrial reactive oxygen species and reactive nitrogen species are proven to be major sources of oxidative stress in the cell; they play a prominent role in a wide range of human disorders resulting from nonapoptotic cell death. The aim of this study is to examine the cytoprotective effect of the NecroX series against harmful stresses, including pro-oxidant (tertiarybutylhydroperoxide), doxorubicin, CCl₄, and hypoxic injury. In this study, these novel chemical molecules inhibited caspase-independent cell death with necrotic morphology, which is distinctly different from apoptosis, autophagy, and necroptosis. In addition, they displayed strong mitochondrial reactive oxygen species and ONOO⁻ scavenging activity. Further, oral administration of these molecules in C57BL/6 mice attenuated streptozotocin-induced pancreatic islet β-cell destruction as well as CCl₄-induced hepatotoxicity in vivo. Taken together, these results demonstrate that the NecroX series are involved in the blockade of nonapoptotic cell death against mitochondrial oxidative stresses. Thus, these chemical molecules are potential therapeutic agents in mitochondria-related human diseases involving necrotic tissue injury.

Hydrogen sulfide attenuates hyperhomocysteinemia-induced cardiomyocytic endoplasmic reticulum stress in rats

The mechanisms responsible for the cardioprotective effect of hydrogen sulfide (H(2)S) are unclear. The present study was designed to examine whether H(2)S could regulate hyperhomocysteinemia (HHcy)-induced cardiomyocytic endoplasmic reticulum (ER) stress. A rat model of HHcy was produced, and H9c2 cells (rat embryonic heart-derived cell line) were cultured. The plasma homocysteine was measured by using HPLC. Plasma H(2)S concentration and myocardial H(2)S production were measured with a sulfide-sensitive electrode. Confocal immunofluorescent analysis for cardiomyocytic C/EBP homologous protein (CHOP) was performed. Glucose-regulated protein 78 (GRP78), CHOP, and caspase 12 expressions by myocardial tissues and cleaved caspase 12 and p-eIF2alpha expressions by H9c2 cells were detected with Western blotting. The results showed that methionine overload induced HHcy, resulting in a marked cardiomyocytic ER stress, whereas endogenous production of H(2)S was reduced in rats with HHcy. H(2)S supplementation, however, decreased expressions of ER stress-associated proteins, including GRP78, CHOP, and caspase 12, by myocardial tissues in vivo. The inhibition of endogenous H(2)S production further enhanced cardiomyocytic ER stress, but H(2)S supplementation effectively antagonized the H9c2 cell CHOP, cleaved caspase 12 and p-eIF2alpha expressions induced by Hcy, thapsigargin, or tunicamycin in vitro. The results suggest that H(2)S can attenuate cardiomyocytic ER stress in HHcy-induced cardiomyocytic injury.

Myocardial fibrosis and apoptosis, but not inflammation, are present in long-term experimental diabetes

The aim of this paper is to study the myocardial damage secondary to long-term streptozotocin-induced type 1 diabetes mellitus (DM1). Normotensive and spontaneously hypertensive rats (SHR) received either streptozotocin injections or vehicle. After 22 or 6 wk, DM1, SHR, DM1/SHR, and control rats were killed, and the left ventricles studied by histology, quantitative PCR, Western blot, ELISA, and electromobility shift assay. Cardiomyocyte cultures were also performed. The expression of profibrotic factors, transforming growth factor-β (TGF-β1), connective tissue growth factor, and matrix proteins was increased, and the TGF-β1-linked transcription factors phospho-Smad3/4 and activator protein-1 were activated in the DM1 myocardium. Proapoptotic molecules FasL, Fas, Bax, and cleaved caspase-3 were also augmented. Myocardial injury in long-term hypertension shared these features. In addition, hypertension was associated with activation of NF-κB, increased inflammatory cell infiltrate, and expression of the mediators [interleukin-1β (IL-1β), tumor necrosis factor-α, monocyte chemoattractant protein 1, vascular cell adhesion molecule 1, angiotensinogen, and oxidants], which were absent in long-term DM1. At this stage, the combination of DM1 and hypertension resulted in nonsignificant additive effects. Moreover, the coexistence of DM1 blunted the inflammatory response to hypertension. Anti-inflammatory IL-10 and antioxidants were induced in long-term DM1 and DM1/SHR hearts. Myocardial inflammation was, however, observed in the short-term model. In cultured cardiomyocytes, IL-10, TGF-β1, and catalase blocked the glucose-stimulated expression of proinflammatory genes. Fibrosis and apoptosis are features of long-term myocardial damage in experimental DM1. Associated hypertension does not induce additional changes. Myocardial inflammation is present in hypertension and short-term DM1, but is not a key feature in long-term DM1. Local reduction of proinflammatory factors and expression of anti-inflammatory and antioxidant molecules may underlie this effect.

Melatonin prevents oxidative stress-mediated mitochondrial permeability transition and death in skeletal muscle cells

Oxidative stress-induced mitochondrial dysfunction plays a crucial role in the pathogenesis of a wide range of diseases including muscle disorders. In this study, we demonstrate that melatonin readily rescued mitochondria from oxidative stress-induced dysfunction and effectively prevented subsequent apoptosis of primary muscle cultures prepared from C57BL/6J mice. In particular, melatonin (10(-4)-10(-6) m) fully prevented myotube death induced by tert-butylhydroperoxide (t-BHP; 10 microm-24 hr) as assessed by acid phosphatase, caspase-3 activities and cellular morphological changes. Using fluorescence imaging, we showed that the mitochondrial protection provided by melatonin was associated with an inhibition of t-BHP-induced reactive oxygen species generation. In line with this observation, melatonin prevented t-BHP-induced mitochondrial depolarization and mitochondrial permeability transition pore (PTP) opening. This was associated with a highly reduced environment as reflected by an increased glutathione content and an increased ability to maintain mitochondrial pyridine nucleotides and glutathione in a reduced state. Using isolated mitochondria, in a similar manner as cyclosporin A, melatonin (10(-8)-10(-6) m) desensitized the PTP to Ca(2+) and prevented t-BHP-induced mitochondrial swelling, pyridine nucleotide and glutathione oxidation. In conclusion, our findings suggest that inhibition of the PTP essentially contributes to the protective effect of melatonin against oxidative stress in myotubes.

Acute hyperoxia increases lipid peroxidation and induces plasma membrane blebbing in human U87 glioblastoma cells

Atomic force microscopy (AFM), malondialdehyde (MDA) assays, and amperometric measurements of extracellular hydrogen peroxide (H(2)O(2)) were used to test the hypothesis that graded hyperoxia induces measurable nanoscopic changes in membrane ultrastructure and membrane lipid peroxidation (MLP) in cultured U87 human glioma cells. U87 cells were exposed to 0.20 atmospheres absolute (ATA) O(2), normobaric hyperoxia (0.95 ATA O(2)) or hyperbaric hyperoxia (HBO(2), 3.25 ATA O(2)) for 60 min. H(2)O(2) (0.2 or 2 mM; 60 min) was used as a positive control for MLP. Cells were fixed with 2% glutaraldehyde immediately after treatment and scanned with AFM in air or fluid. Surface topography revealed ultrastructural changes such as membrane blebbing in cells treated with hyperoxia and H(2)O(2). Average membrane roughness (R(a)) of individual cells from each group (n=35 to 45 cells/group) was quantified to assess ultrastructural changes from oxidative stress. The R(a) of the plasma membrane was 34+/-3, 57+/-3 and 63+/-5 nm in 0.20 ATA O(2), 0.95 ATA O(2) and HBO(2), respectively. R(a) was 56+/-7 and 138+/-14 nm in 0.2 and 2 mM H(2)O(2). Similarly, levels of MDA were significantly elevated in cultures treated with hyperoxia and H(2)O(2) and correlated with O(2)-induced membrane blebbing (r(2)=0.93). Coapplication of antioxidant, Trolox-C (150 microM), significantly reduced membrane R(a) and MDA levels during hyperoxia. Hyperoxia-induced H(2)O(2) production increased 189%+/-5% (0.95 ATA O(2)) and 236%+/-5% (4 ATA O(2)) above control (0.20 ATA O(2)). We conclude that MLP and membrane blebbing increase with increasing O(2) concentration. We hypothesize that membrane blebbing is an ultrastructural correlate of MLP resulting from hyperoxia. Furthermore, AFM is a powerful technique for resolving nanoscopic changes in the plasma membrane that result from oxidative damage.

The Isopeptidase Inhibitor G5 Triggers a Caspase-independent Necrotic Death in Cells Resistant to Apoptosis: A COMPARATIVE STUDY WITH THE PROTEASOME INHIBITOR BORTEZOMIB

Inhibitors of the ubiquitin-proteasome system (UPSIs) promote apoptosis of cancer cells and show encouraging anti-tumor activities in vivo. In this study, we evaluated the death activities of two different UPSIs: bortezomib and the isopeptidase inhibitor G5. To unveil whether these compounds elicit different types of death, we compared their effect both on apoptosis-proficient wild type mouse embryo fibroblasts and on cells defective for apoptosis (double-deficient Bax/Bak mouse embryo fibroblasts) (double knockout; DKO). We have discovered that (i) both inhibitors induce apoptosis in a Bax and Bak-dependent manner, (ii) both inhibitors elicit autophagy in WT and DKO cells, and (iii) only G5 can kill apoptosis-resistant DKO cells by activating a necrotic response. The induction of necrosis was confirmed by different experimental approaches, including time lapse analysis, HMGB1 release, and electron microscopy studies. Neither treatment with antinecrotic agents, such as antioxidants, poly(ADP-ribose) polymerase and JNK inhibitors, necrostatin, and the intracellular Ca(2+) chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester, nor overexpression of Bcl-2 and Bcl-xL prevented necrosis induced by G5. This necrotic death is characterized by the absence of protein oxidation and by the rapid cyclosporin A-independent dissipation of the mitochondrial membrane potential. Notably, a peculiar feature of the G5-induced necrosis is an early and dramatic reorganization of the actin cytoskeleton, coupled to an alteration of cell adhesion. The importance of cell adhesion impairment in the G5-induced necrotic death of DKO cells was confirmed by the antagonist effect of the extracellular matrix-adhesive components, collagen and fibronectin.

Sanguinarine cytotoxicity on mouse melanoma K1735-M2 cells--nuclear vs. mitochondrial effects

Sanguinarine (SANG) is an alkaloid recognized to have anti-proliferative activity against various human tumour cell lines. No data is available on the susceptibility of advanced malignant melanoma to SANG, although this disease has a very poor prognosis if not detected in time due to the resistance to conventional chemotherapy. The present work was designed to study the nuclear and mitochondrial involvement in the pro-apoptotic effect of SANG in an invasive mouse melanoma cell line. The results obtained show that SANG is primarily accumulated by the cell nuclei, causing inhibition of cell proliferation and inducing cell death, as confirmed by an increase in sub-G1 peaks. At low concentrations, SANG induces mitochondrial depolarization in a sub-population of melanoma cells, which also generally displayed strong nuclear labelling of phosphorylated histone H2AX. Western blotting revealed an increase in p53, but not Bax protein, in both whole-cell extracts and in mitochondrial fractions. Isolated hepatic mitochondrial fractions revealed that SANG affects the mitochondrial respiratory chain, and has dual effects on mitochondrial calcium loading capacity. We suggest that SANG is able to induce apoptosis in metastatic melanoma cells. The knowledge of mitochondrial vs. nuclear effects of SANG is important in the development of this promising compound for clinical use against aggressive melanoma.

Implication of caspases and subcellular compartments in tert-butylhydroperoxide induced apoptosis

Oxidative stress has been implicated in many physiopathologies including neurodegenerative diseases, cancer, cardiovascular and respiratory diseases, and in mechanisms of action of environmental toxicants. tert-butylhydroperoxide (t-BHP) is an organic lipid hydroperoxide analogue, which is commonly used as a pro-oxidant for evaluating mechanisms involving oxidative stress in cells and tissues. This study investigates mechanisms of apoptosis induced by oxidative stress in hepatocytes, in particular, the involvement of caspases and subcellular compartments. Freshly isolated hepatocytes were exposed to 0.4 mM t-BHP during 1 h. A general caspase inhibitor, Boc-D-FMK, reduced t-BHP-induced apoptosis (chromatin condensation), confirming the involvement of caspases in apoptosis. A caspase-9 inhibitor, Z-LEHD-FMK, also reduced t-BHP-induced apoptosis, suggesting that caspase-9 plays a critical role in this process. Procaspase-9 underwent cleavage in mitochondria and translocation to the nucleus, where increased caspase-9 activity was detected. The caspase-9 substrates, caspase-3 and caspase-7, were not activated. Caspase-7 was translocated from the cytosol to the endoplasmic reticulum (ER), where it underwent processing; however, enzymatic activity of caspase-7 was inhibited by t-BHP. t-BHP caused cleavage of procaspase-12 at the ER and its subsequent translocation to the nucleus, where increased caspase-12 activity was found. t-BHP caused translocation of calpain from the cytosol to the ER. Calpain inhibition reduced chromatin condensation and caspase-12 activity in the nucleus, suggesting that calpain is involved in caspase-12 activation and apoptosis. This study demonstrates that caspase-9 and caspase-12 are activated in t-BHP-induced apoptosis in hepatocytes. We highlight the importance of subcellular compartments such as mitochondria, ER and nuclei in the apoptotic process.