Cardiomyocyte Death Research Articles

Glycogen Synthase Kinase 3 beta confers refractoriness to the microRNA-210-elicited exacerbation of hypoxia-reoxygenation stress-induced apoptotic cell death

Abstract Introduction Apoptotic cell death is a detrimental signatory molecular hallmark of Ischemia / Reperfusion (I/R) injury. Despite the exhaustive findings and significant advancements in the realm of I/R research, there is a paucity of viable molecular strategies that could be targeted to combat the underlying deleterious biochemical pathways that precipitate Hypoxia-Reoxygenation (H-R) stress, the cellular manifestation of I/R injury. The master hypoxamiR, microRNA-210 (miR-210), is an indispensable molecular component of the protective cellular adaptive response to hypoxia stress that paradoxically exacerbates apoptotic cell death during the cellular reoxygenation phase. While the entire repertoire of molecular entities mediating this paradoxical deleterious impact of miR-210 on H-R stress induced apoptotic cell death are largely unknown, recent studies have unveiled and posited, the evolutionary conserved serine/threonine kinase, Glycogen Synthase Kinase 3 beta (GSK3β) as a pivotal molecular focal point of the convergent and divergent signaling cascades that modulate the miR-210-regulated apoptotic cell death during the cellular reoxygenation phase. Purpose In this study, we elucidated and delineated the role of GSK3β (in)activation in the miR-210-induced exacerbation of the H-R stress-induced apoptotic cell death in AC-16 cardiomyocytes. Methods Using transient overexpression vectors and decoy / inhibition vectors to modulate miR-210 expression concomitant with the ectopic expression of the constitutive active GSK3β S9A (ca-GSK3β S9A) and the catalytically-dead dominant negative GSK3β K85A (dn-GSK3β K85A) mutants, we performed exhaustive biochemical and molecular assays determining apoptotic cell death in AC-16 cardiomyocytes subjected H-R stress. Results Caspase-3 activity analysis coupled with DNA fragmentation assays demonstrated that the H-R driven augmented GSK3β kinase activity significantly attenuates the miR-210-induced exacerbation of H-R evoked apoptotic cell death during the cellular reoxygenation phase. Resolution of the multimodal components of the apoptotic signaling pathway, unveiled that the H-R driven augmented GSK3β kinase activity modestly increases the miR-210-driven exacerbation of the intrinsic apoptotic pathway during the cellular reoxygenation phase, as molecularly inferred by the levels of the release of Cytochrome C from the mitochondria into the cytosol. However, in a stark contrast, H-R driven augmented GSK3β kinase activity concomitantly overwhelmingly attenuated the flux through the extrinsic apoptotic pathway during the cellular reoxygenation phase, as molecularly inferred by caspase-8 activity analysis. Conclusion Our study is the first to unveil that the H-R driven augmented GSK3β kinase activity during the cellular reoxygenation phase, is an inherent protective cellular adaptive response that mitigates the miR-210-orchestrated exacerbation of the cellular reoxygenation-elicited apoptotic cell death.

Single-nucleus RNA sequencing of TMEM43 induced arrhythmogenic cardiomyopathy reveals altered cell compositions and transcriptional states in mice

Abstract Introduction and purpose TMEM43 induced Arrhythmogenic cardiomyopathy, also referred to as arrhythmogenic cardiomyopathy type 5 or ACM5, is caused by a point mutation in TMEM43 (p.S358L). The disease is characterised by chamber dilation and a progressive dystrophy of the ventricular myocardium causing life-threatening ventricular arrhythmias and sudden cardiac death. Loss of cardiomyocytes and fibrofatty replacement of the myocardium is clearly observed in our transgenic mouse model of ACM5 overexpressing TMEM43-S358L in postnatal cardiomyocytes. However, the mechanisms underlying cardiomyocyte death and fibroblast activation remain elusive, precluding the development of effective therapeutic options. Here we applied the state-of-the-art analysis on single-nucleus RNA sequencing (snRNA-seq) to characterise the cellular compositions and molecular states in ACM5 mouse hearts. Methods Left ventricular heart tissues of severely affected ACM5 mice and their corresponding transgenic controls overexpressing wild-type TMEM43 were used for snRNA-seq analysis. We identified 10 major cell types, which aggregated into 23 distinct clusters on the basis of transcriptional similarity. Results ACM5 nuclei showed significant depletion of cardiomyocytes and expanded populations of fibroblasts and myeloid cells. Fibroblasts from mutant mice acquired an activated phenotype related to remodelling of the extracellular matrix with a large number of genes like LOX, POSTN, NOX4 or COL1A1 significantly upregulated. In addition, the mutant cardiomyocytes showed altered transcriptional states characterized by cardiac stress and heart failure markers such as NPPB or MYH7. Interestingly, we were able to identify a cluster of mutant cardiomyocytes with a highly apoptotic profile. This cluster is also enriched in genes related to the unfolding protein response (UPR) stress sensors and the DNA damage response (DDR), elucidating a new potential mechanism of myocyte death in ACM5. Furthermore, heterogeneity of the myeloid populations is also observed. The number of tissue resident macrophages is increased in mutant samples and myeloid cells show additional disease-associated transcriptional states that are almost entirely absent in control samples. Conclusion Together these data illuminated shared and distinct cell and molecular architectures of ACM5 in mouse hearts. Further confirmation on diverse gene expression profiles like the UPR and DDR pathways related to cardiomyocyte death will establish a valuable resource to explore novel therapeutic targets and personalized therapies for ACM5.

Transcriptome and methylome analyses of stromal cells from ACM patients reveal the additional role of alterations in mitochondrial homeostasis and chromatin organization in disease pathogenesis

Abstract Background Arrhythmogenic cardiomyopathy (ACM) is a rare genetic disorder of the heart, characterized by ventricular arrhythmias and contractile dysfunctions, which can cause sudden cardiac death and heart failure. Typically, the hallmarks of ACM ventricular myocardium are cardiomyocyte death, inflammation and fibro-adipose replacement, resulting in electrical and mechanical abnormalities of the tissue. Cardiac mesenchymal stromal cells (CMSC) participate to disease pathogenesis by differentiating towards adipocytes and myofibroblasts. Some altered pathways in ACM are known, but many pathogenetic molecular mechanisms are yet to be discovered. Purpose Our work aims to contribute to a comprehensive understanding of the pathogenic mechanism occurring in ACM, focusing on the molecular pathways underlying stromal cell involvement, through the functional validation of gene expression and epigenetic profile of ACM-CMSC. Methods We conducted total RNA transcriptome and DNA methylome analyses in ACM- and healthy control (HC)- CMSC to identify pathways differentially regulated in the two groups. We performed category enrichment and gene network analyses and we built transcript functional networks. To validate our findings, we measured the protein levels coded by selected genes differentially expressed by Western Blot analysis and we evaluated the relative pathways, such as mitochondria homeostasis, proliferation rate and epithelial-to-mesenchymal transition (EMT) through cytofluorimetric analyses. Results By transcriptomic analysis we found 529 genes differentially expressed; in particular, 327 genes were more expressed and 202 less expressed in ACM- vs HC-CMSC. Among those with the highest logFC and the lowest p value, we identified COX7C (implicated in mitochondrial respiration), S100A11 (involved in EMT) and CCND2 (one of the promoters of the cell cycle), whose protein expression was validated. Through the enrichment and gene network analysis we identified some pathways differentially regulated in ACM vs. HC. Some of these are known to be altered in ACM hearts, as matrix homeostasis and cell junction arrangement. Other pathways have never been associated to ACM, such as mitochondrial functioning and chromatin organization. By the DNA-methylation investigation, we identified 74 differentially methylated nucleotides and most of them were located on the mitochondrial genome. We also found that ACM-CMSC exhibited a greater number of mitochondria and a greater amount of mitochondrial reactive oxygen species than HC. Furthermore, ACM-CMSC showed a higher proliferation rate and a more pronounced EMT, compared to controls. Conclusions ACM-CMSC -omics revealed some new altered molecular pathways, not yet explored, which are relevant in the pathogenesis of the disease and may constitute novel targets for specific therapeutic approaches.

Modeling cardiac injury using human cardiac slices to test therapeutic approaches for cardiac regeneration and repair

Abstract Background Due to limited regenerative capacity of the adult human heart, myocardial infarction causes irreversible damage by inducing the death of cardiomyocytes and the formation of a fibrotic scar. These remodeling mechanisms cause loss of contractility and eventually heart failure ensues in a significant proportion of patients. Purpose There is a need for a reliable model that can replicate the adult cardiac pathophysiology in order to test treatments against cardiac remodeling. Here, we developed a cardiac tissue culture model that can simulate in vitro the molecular changes occurring after cardiac injury using human cultured cardiac slices. Methods We obtained cardiac slices by sectioning ventricular myocardium from the surgical waste material of adult patients undergoing valve surgery or Morrow myectomy. Cardiac slices were cultured at a liquid-air interface and were viable up to 7 days of culture, even in the absence of stimulation. During this time cardiac slices underwent mechanical and chemical treatments to induce ischemia and/or local injury. Results We found that following these treatments we were able to simulate cardiac remodeling in terms of cardiomyocyte death, activation of cardiac fibroblasts and induction of inflammation and oxidative stress. Following small molecule screening, we discovered that addition of compounds with anti-inflammatory properties (e.g. dexamethasone) or targeting the TGF-β pathway (e.g. SB-431542) into our culture medium helped in preserving the microscopic structure of the slices. Additionally, we found that treatment with these compounds protected cardiac slices against remodeling following ischemic injury. Conclusions In conclusion, our model can emulate cardiac pathophysiology in culture, providing us a reliable platform to test therapies for cardiac regeneration and repair in an adult, multicellular, 3-D environment.

Role of long non-coding RNA Zeb2os in protection of the injured heart

Abstract Heart failure due to ischemic heart disease is one of the leading causes of death worldwide. Terminated vasculature and cardiomyocyte apoptosis due to myocardial infarction are critical events in infarct healing. Therefore, identifying factors that can enhance cardiac repair by restoring the capillary network and inhibiting cardiomyocyte death is of great significance. Accumulating evidence implies that long non-coding RNAs (lncRNAs) are potent regulators of cardiac development and disease. Our preliminary data show the potential cardioprotective function of the long non-coding RNA Zeb2 opposite strand (Zeb2os). This lncRNA overlaps and is antisense to ZEB2 at the 5' splice site of an intron within the 5' UTR. Zeb2os was shown to prevent splicing of the intron containing an internal ribosome entry site (IRES) that increases translation of the ZEB2 transcript. In line with the known function of ZEB2, Zeb2os has pro-angiogenic and anti-apoptotic functions in different organs. However, its role in the heart still has to be determined. Our results show that Zeb2os expression is decreased in cultured cardiomyocytes subjected to H2O2-mediated oxidative stress, which correlates with increased apoptosis and reduced antioxidant defence of cardiac muscle cells. AAV6-mediated overexpression of Zeb2os in hiPSC-derived cardiomyocytes protects from H2O2-induced apoptosis, suggesting it may have cardioprotective activity, possibly through regulating Zeb2 translation. Additionally, systemic AAV9-mediated delivery of Zeb2os to the mouse heart enhanced angiogenesis by increasing the number of proliferating endothelial cells. Moreover, RNA-sequencing of Zeb2os overexpressing hearts at baseline implicated Zeb2os in the regulation of numerous genes related to response to hypoxia. In conclusion, we uncovered/identified Zeb2os as a new potential cardioprotective factor with pro-angiogenic and anti-apoptotic properties. We are currently investigating the effect of AAV9-mediated delivery of Zeb2os in a mouse model of cardiac ischemia to understand further its protective role in the injured heart, which is an essential step towards the development of improved therapies for ischemic heart disease.

Long-term spermidine therapy potentially protects the heart against estrogen deprivation in female rats via suppressing cardiac mitochondrial dysfunction, inflammation, oxidative stress, and apoptosis

Abstract Background Postmenopausal women have been associated with a higher risk of cardiovascular diseases (CVDs). Several pathophysiological mechanisms, including cardiac mitochondrial dysfunction, oxidative stress, inflammation, and cardiomyocyte apoptosis, played a key role in the development of postmenopausal CVDs. Long-term estrogen supplementation is widely used to treat postmenopausal symptoms, but it has been linked to an increased risk of breast cancer and cardiac complications. Spermidine is a natural organic compound which has been shown to exert cardioprotection under several pathological conditions. However, the benefits of spermidine against impaired cardiac function due to estrogen-deprivation are unknown. Purpose To investigate the effects of therapeutic intervention with spermidine on cardiac mitochondrial function, oxidative stress, inflammation, and programmed cardiomyocyte death in rats with estrogen deprivation. Methods Fifteen female Wistar rats underwent ovariectomy (OVX) to induce estrogen deprivation. After 12 weeks, all OVX-operated rats were randomly divided into three interventional groups as follows: 1) vehicle or OV (n = 5), 2) spermidine or OS (20 mg/kg/day, p.o., n = 5), and 3) estradiol or OE (50 µg/kg/day, s.c., n = 5) for an additional 8 weeks. At the end of the experiment, echocardiography for the heart’s function was performed. Then, all the rats were sacrificed, and their hearts were dissected for mitochondrial and molecular analysis, including the protein expressions of inflammation, oxidative stress, and apoptosis. Results Treatment with either spermidine or estrogen provided a similar cardioprotective efficacy against OVX-induced estrogen deprivation in reducing mitochondrial membrane potential depolarization and cardiac inflammation, as shown by increased red to green fluorescence and lowered p-NFkB to NFkB ratios, respectively (Fig. 1A, B). Spermidine and estrogen also exerted anti-oxidative stress via increasing glutathione peroxidase (GPX4) and anti-apoptosis via decreasing the cleaved caspase-3 to procaspase-3 ratio following OVX-induced estrogen deficiency (Fig. 1C, D). All of the beneficial effects of spermidine and estrogen led to an improved left ventricular ejection fraction (89% for OS and OE vs. 76% for OV). Conclusion Long-term treatment with spermidine rescued cardiac mitochondrial dysfunction, inflammation, oxidative stress, and apoptosis, resulting in the restoration of left ventricular function with the same efficacy as estrogen treatment. These findings suggest that spermidine could be a novel therapeutic strategy to alleviate the adverse cardiac complications associated with postmenopausal women.

Mitochondrial succinate transport as a novel therapeutic target for cardiac ischemia/reperfusion injury

Abstract Background The accumulation of the mitochondrial metabolite succinate during ischemia and its rapid oxidation by succinate dehydrogenase (SDH) upon reperfusion drives ischemia/reperfusion injury (IRI) in myocardial infarction. Succinate oxidation leads to the production of reactive oxygen species (ROS) by reverse electron transport (RET) at mitochondrial complex I, orchestrating a cascade of events leading to cardiomyocyte death. Modulating succinate metabolism, such as SDH inhibition, is a promising therapeutic strategy. During ischemia, the mitochondria produced succinate is transported into the cytosol, enabling the accumulation of a large succinate pool. On reperfusion, the succinate is transported back into mitochondria and oxidised by SDH, thus we hypothesised that targeting succinate mitochondrial transport could be a novel therapeutic target to prevent cardiac IRI. Purpose To assess the role of succinate mitochondrial transport as a novel therapeutic target to prevent cardiac IRI. Methods Isolated heart mitochondria were used to assess mitochondrial respiration by Oroboros, RET-ROS production by Amplex Red and butylmalonate delivery. Cultured H9C2 myoblasts and isolated primary adult cardiomyocytes from C57BL/6J mice were used to assess butylmalonate uptake and delivery from esters, as well as their impact on succinate accumulation and oxidation in vitro. LAD ligation and reperfusion in C57BL/6J mice was used as an in vivo MI model. Metabolite levels were measured by LC-MS/MS. Results Butylmalonate, an inhibitor of the mitochondrial dicarboxylate carrier (DIC), blocks succinate-dependent respiration and RET-ROS production in isolated mitochondria. However, butylmalonate entry into cells was inefficient and does not impact infarct size after IRI in vivo. We developed novel butylmalonate esters to improve butylmalonate delivery to cardiomyocytes in vivo. We found that diacetoxymethyl butylmalonate (DAB) effectively delivered butylmalonate and could prevent succinate accumulation and oxidation in vitro. DAB could also prevent succinate-mediated respiration and RET-ROS at lower concentrations than butylmalonate alone. Finally, DAB reduced acute infarct size in vivo when administered at reperfusion. Conclusions Blocking succinate transport back into mitochondria at reperfusion prevents the damage in IRI by preventing the oxidation of succinate by SDH and downstream RET-ROS production. Therefore, targeting the mitochondrial transport of succinate may be a promising novel strategy in preventing cardiac IRI.

Abstract 14250: ND-13, a Small DJ-1 Derived Peptide, Confers Cardioprotection by Targeting Mitochondrial Homeostasis

Objectives: DJ-1 protein is a multifunctional protein with cardioprotective effects against acute myocardial ischemia-reperfusion injury (IRI). This study aims to elucidate whether ND-13, a small peptide derived from DJ-1, can confer acute cardioprotection after IRI by preserving mitochondrial homeostasis through improvements in mitochondrial respiratory capacity and regulating the balance between mitochondrial fusion/fission. By enhancing mitochondrial respiration and maintaining the integrity of the mitochondrial network, ND-13 may provide a novel therapeutic strategy for cardioprotection in cardiomyocytes following IRI. Methods: In vitro , ex vivo and in vivo murine models of IRI were used to elucidate the cardioprotective effects of ND-13. Infarct size, cardiac function and mitochondrial function were assessed. Results: ND-13 was shown to confer cardioprotection in three distinct models of IRI: (i) in vitro , cardiomyocyte (CM) death was reduced by 42% (64±1% untreated vs 37±2% treated; p≤0.01); (ii) ex vivo Langendorrf, with 43% decrease in infarct size (51±6.4% untreated vs 29±8.8% treated; p≤0.05); (iii) in vivo , with 35% reduction in infarct size (49±6.4% untreated vs 32±5.0% treated; p≤0.0001). CMs treated with ND-13 in the in vitro model of IRI demonstrated a significant increase in mitochondrial respiration rates, (basal: untreated 37±3 vs treated 63±10 pmol/min/cells, p≤0.05; maximal: untreated 286±20 vs treated 494±53 pmol/min/cells, p≤0.001; and spare respiratory capacity: untreated 251±18 vs treated 421±43 pmol/min/cells, p≤0.001) and a significant increase in levels of cytosolic ATP (untreated 4.0 ± 0.3 vs treated 5.6 ± 0.5 μM, p≤0.05). Conclusion: We demonstrate for the first time, cardioprotection with the DJ-1-derived peptide, ND-13, and this beneficial effect appears to be mediated by its mitoprotective actions with enhanced mitochondrial respiratory efficiency and increased ATP production. Upcoming research aims to explore if ND-13 promotes oxidative phosphorylation by directly binding to complexes of the electron transport chain to maximize respiratory function or by enhancing pyruvate dehydrogenase activity, thereby potentially influencing the regulation of the fission/fusion process.

Abstract 18503: Endogenously Released Factors From Doxorubicin-Treated Breast Cancer Spheroids Contribute to Toxicity in Human Cardiomyocytes: Protective Effect of Combination Therapy With PDE5-mTOR Inhibitors

Background: We previously demonstrated that a novel combination therapy with the phosphodiesterase 5 (PDE5) inhibitor (sildenafil, Sild) and mTOR inhibitor (rapamycin, Rapa) potentiates doxorubicin (DOX)-induced breast cancer cell killing, but attenuates cardiotoxicities. However, it remains unclear whether there are any factors released from cancer cells treated with DOX that contribute to the injury in cardiomyocytes, which can be modified by Sild and Rapa in combination. Therefore, we designed experiments using spheroid cultures of breast cancer and human AC-16 cardiomyocytes to determine the role of endogenously released factors following treatment with DOX. Methods & Results: Spheroid cultures of breast cancer MDA-MB-231 cells were treated with DOX (1 μμ), and/or Sild (10 μμ) and Rapa (100 nμ) for 48 hours. The medium was replaced and spheroids were further incubated for 48 hours in the fresh medium. Thereafter, the AC-16 cardiomyocytes were treated with the medium from drugs-treated spheroids for 48 hours. Our results showed that treatment with DOX and/or Sild and Rapa was highly effective in reducing the size of spheroids as compared to the control ( Fig. A ). Moreover, Western blots showed that p-mTOR/mTOR and p-S6/S6 were induced and p-AKT/AKT was suppressed after DOX treatment in cancer cells, which were normalized following treatment with Sild and Rapa ( Fig. B ). The medium from DOX-treated spheroids caused increase of cardiomyocytes death as assessed by trypan blue exclusion assay, which was attenuated by co-treatment with the medium from Sild and Rapa treated spheroids ( Fig. C ). Conclusion: These results suggest that cardiotoxicity of chemotherapeutic agents could be partly contributed by the endogenously released unknown factors from tumors, which can be modulated by a novel combination treatment with Sild and Rapa via regulating mTOR-signaling pathways.

Water Extract of Capsella bursa-pastoris Mitigates Doxorubicin-Induced Cardiotoxicity by Upregulating Antioxidant Enzymes

Doxorubicin (DOX), an effective chemotherapeutic drug, causes cardiotoxicity in a cumulative and dose-dependent manner. The aim of this study is to investigate the effects of hot-water extract of Capsella bursa-pastoris (CBW) on DOX-induced cardiotoxicity (DICT). We utilized H9c2 rat cardiomyocytes and MDA-MB-231 human breast cancer cells to evaluate the effects of CBW on DOX-induced cell death. Superoxide dismutase (SOD) levels, reactive oxygen species (ROS) production, and oxygen consumption rate were measured in H9c2 cells. C57BL/6 mice were treated with DOX and CBW to assess their impact on various cardiac parameters. Human-induced pluripotent stem-cell-derived cardiomyocytes were also used to investigate DOX-induced electrophysiological changes and the potential ameliorative effects of CBW. UPLC-TQ/MS analysis identified seven flavonoids in CBW, with luteolin-7-O-glucoside and isoorientin as the major compounds. CBW inhibited DOX-induced death of H9c2 rat cardiomyocytes but did not affect DOX-induced death of MDA-MB-231 human breast cancer cells. CBW increased SOD levels in a dose-dependent manner, reducing ROS production and increasing the oxygen consumption rate in H9c2 cells. The heart rate, RR interval, QT, and ST prolongation remarkably recovered in C57BL/6 mice treated with the combination of DOX and CBW compared to those in mice treated with DOX alone. Administration of CBW with DOX effectively alleviated collagen accumulation, cell death in mouse heart tissues, and reduced the levels of creatinine kinase (CK) and lactate dehydrogenase (LDH) in serum. Furthermore, DOX-induced pathological electrophysiological features in human-induced pluripotent stem-cell-derived cardiomyocytes were ameliorated by CBW. CBW may prevent DICT by stabilizing SOD and scavenging ROS. The presence of flavonoids, particularly luteolin-7-O-glucoside and isoorientin, in CBW may contribute to its protective effects. These results suggest the potential of CBW as a traditional therapeutic option to mitigate DOX-induced cardiotoxicity.

Taxifolin protects against doxorubicin-induced cardiotoxicity and ferroptosis by adjusting microRNA-200a-mediated Nrf2 signaling pathway

The chemotherapeutic agent doxorubicin (Dox) is commonly used to treat various types of cancer, even though it can cause life-threatening cardiotoxicity. Clinically, there is no particularly effective way to treat Dox-induced cardiotoxicity. Therefore, it is imperative to identify compounds that can effectively alleviate Dox-induced cardiotoxicity. Ferroptosis and oxidative stress play a key role in Dox-induced cardiotoxicity, and the inhibition of ferroptosis and oxidative stress could effectively protect against doxorubicin-induced cardiotoxicity. Taxifolin (TAX) is a flavonoid commonly found in onions and citrus fruits. In the present study, we evaluated the effects of TAX on Dox-induced cardiac injury and dysfunction and aimed to explore the mechanisms underlying these effects. Using a mouse model of Dox-induced cardiotoxicity, we administered 20 mg/kg/day of TAX by gavage for 2 weeks. A week after the first use of TAX, each mouse was administered a 10 mg/kg dose of Dox. TAX was first evaluated for its cardioprotective properties, and the outcomes showed that TAX significantly reduced the damage caused by Dox to the myocardium in terms of structural and functional damage by effectively inhibiting ferroptosis and oxidative stress. In vivo, echocardiography, histopathologic assay, serum biochemical analysis and western blotting was used to find the results that Dox promoted ferroptosis-induced cardiomyocyte death, while TAX reversed these effects. In vitro, we also found that TAX alleviated Dox-induced cardiotoxicity by using ROS/DHE staining assay, Cellular immunofluorescence and western blotting. TAX increasing expression of microRNA-200a (miR-200a) which affects ferroptosis by activating Nrf2 signaling pathway. We believe that TAX inhibits ferroptosis and is a potential phytochemical that prevents Dox-induced cardiotoxicity.

Implications of Activating the ANT2/mTOR/PGC-1α Feedback Loop: Insights into Mitochondria-Mediated Injury in Hypoxic Myocardial Cells.

Mitochondrial dysfunction is known to play a critical role in the development of cardiomyocyte death during acute myocardial infarction (AMI). However, the exact mechanisms underlying this dysfunction are still under investigation. Adenine nucleotide translocase 2 (ANT2) is a key functional protein in mitochondria. We aimed at exploring the potential benefits of ANT2 inhibition against AMI. We utilized an oxygen-glucose deprivation (OGD) cell model and an AMI mice model to detect cardiomyocyte injury. We observed elevated levels of reactive oxygen species (ROS), disrupted mitochondrial membrane potential (MMP), and increased apoptosis due to the overexpression of ANT2. Additionally, we discovered that ANT2 is involved in myocardial apoptosis by activating the mTOR (mechanistic target of rapamycin kinase)-dependent PGC-1α (PPARG coactivator 1 alpha) pathway, establishing a novel feedback loop during AMI. In our experiments with AC16 cells under OGD conditions, we observed protective effects when transfected with ANT2 siRNA and miR-1203. Importantly, the overexpression of ANT2 counteracted the protective effect resulting from miR-1203 upregulation in OGD-induced AC16 cells. All these results supported that the inhibition of ANT2 could alleviate myocardial cell injury under OGD conditions. Based on these findings, we propose that RNA interference (RNAi) technology, specifically miRNA and siRNA, holds therapeutic potential by activating the ANT2/mTOR/PGC-1α feedback loop. This activation could help mitigate mitochondria-mediated injury in the context of AMI. These insights may contribute to the development of future clinical strategies for AMI.

HNEAP Regulates Necroptosis of Cardiomyocytes by Suppressing the m5 C Methylation of Atf7 mRNA.

PIWI-interacting RNAs (piRNAs) are highly expressed in various cardiovascular diseases. However, their role in cardiomyocyte death caused by ischemia/reperfusion (I/R) injury, especially necroptosis, remains elusive. In this study, a heart necroptosis-associated piRNA (HNEAP) is found that regulates cardiomyocyte necroptosis by targeting DNA methyltransferase 1 (DNMT1)-mediated 5-methylcytosine (m5 C) methylation of the activating transcription factor 7 (Atf7) mRNA transcript. HNEAP expression level is significantly elevated in hypoxia/reoxygenation (H/R)-exposed cardiomyocytes and I/R-injured mouse hearts. Loss of HNEAP inhibited cardiomyocyte necroptosis and ameliorated cardiac function in mice. Mechanistically, HNEAP directly interacts with DNMT1 and attenuates m5 C methylation of the Atf7 mRNA transcript, which increases Atf7 expression level. ATF7 can further downregulate the transcription of Chmp2a, an inhibitor of necroptosis, resulting in the reduction of Chmp2a level and the progression of cardiomyocyte necroptosis. The findings reveal that piRNA-mediated m5 C methylation is involved in the regulation of cardiomyocyte necroptosis. Thus, the HNEAP-DNMT1-ATF7-CHMP2A axis may be a potential target for attenuating cardiac injury caused by necroptosis in ischemic heart disease.

Role of cAMP in Cardiomyocyte Viability: Beneficial or Detrimental?

3', 5'-cyclic AMP (cAMP) regulates numerous cardiac functions. Various hormones and neurotransmitters elevate intracellular cAMP (i[cAMP]) in cardiomyocytes through activating GsPCRs (stimulatory-G-protein-coupled-receptors) and membrane-bound ACs (adenylyl cyclases). Increasing evidence has indicated that stimulating different GsPCRs and ACs exhibits distinct, even opposite effects, on cardiomyocyte viability. However, the underlying mechanisms are not fully understood. We used molecular and pharmacological approaches to investigate how different GsPCR/cAMP signaling differentially regulate cardiomyocyte viability with in vitro, ex vivo, and in vivo models. For prodeath GsPCRs, we explored β1AR (beta1-adrenergic receptor) and H2R (histamine-H2-receptor). We found that their prodeath effects were similarly dependent on AC5 activation, ATP release to the extracellular space via PANX1 (pannexin-1) channel, and extracellular ATP (e[ATP])-mediated signaling involving in P2X7R (P2X purinoceptor 7) and CaMKII (Ca2+/calmodulin-dependent protein kinase II). PANX1 phosphorylation at Serine 206 by cAMP-dependent-PKA (protein-kinase-A) promoted PANX1 activation, which was critical in β1AR- or H2R-induced cardiomyocyte death in vitro and in vivo. β1AR or H2R was localized proximately to PANX1, which permits ATP release. For prosurvival GsPCRs, we explored adenosine-A2-receptor (A2R), CGRPR (calcitonin-gene-related-peptide-receptor), and RXFP1 (relaxin-family peptide-receptor 1). Their prosurvival effects were dependent on AC6 activation, cAMP efflux via MRP4 (multidrug resistance protein 4), extracellular cAMP metabolism to adenosine (e[cAMP]-to-e[ADO]), and e[ADO]-mediated signaling. A2R, CGRPR, or RXFP1 was localized proximately to MRP4, which enables cAMP efflux. Interestingly, exogenously increasing e[cAMP] levels by membrane-impermeable cAMP protected against cardiomyocyte death in vitro and in ex vivo and in vivo mouse hearts with ischemia-reperfusion injuries. Our findings indicate that the functional diversity of different GsPCRs in cardiomyocyte viability could be achieved by their ability to form unique signaling complexes (signalosomes) that determine the fate of cAMP: either stimulate ATP release by activating PKA or directly efflux to be e[cAMP].

Ferroptosis inhibitor improves cardiac function more effectively than inhibitors of apoptosis and necroptosis through cardiac mitochondrial protection in rats with iron-overloaded cardiomyopathy

Iron overload cardiomyopathy (IOC) is the leading cause of death in cases of iron overload in patients. Previous studies demonstrated that iron overload led to cardiomyocyte dysfunction and death through multiple pathways including apoptosis, necroptosis and ferroptosis. However, the dominant cell death pathway in the iron-overloaded heart needs clarification. We tested the hypothesis that ferroptosis, an iron-dependent cell death, plays a dominant role in IOC, and ferroptosis inhibitor exerts greater efficacy than inhibitors of apoptosis and necroptosis on improving cardiac function in iron-overloaded rats. Iron dextran was injected intraperitoneally into male Wistar rats for four weeks to induce iron overload. Then, the rats were divided into 5 groups: treated with vehicle, apoptosis inhibitor (z-VAD-FMK), necroptosis inhibitor (Necrostatin-1), ferroptosis inhibitor (Ferrostatin-1) or iron chelator (deferoxamine) for 2 weeks. Cardiac function, mitochondrial function, apoptosis, necroptosis and ferroptosis were determined. The increased expression of apoptosis-, necroptosis- and ferroptosis-related proteins, were associated with impaired cardiac and mitochondrial function in iron-overloaded rats. All cell death inhibitors attenuated cardiac apoptosis, necroptosis and ferroptosis in iron-overloaded rats. Ferrostatin-1 was more effective than the other drugs in diminishing mitochondrial dysfunction and Bax/Bcl-2 ratio. Moreover, both Ferrostatin-1 and deferoxamine reversed iron overload-induced cardiac dysfunction as indicated by restored left ventricular ejection fraction and E/A ratio, whereas z-VAD-FMK and Necrostatin-1 only partially improved this parameter. These results indicated that ferroptosis could be the predominant form of cardiomyocyte death in IOC, and that inhibiting ferroptosis might be a potential novel treatment for IOC.

Cinnamaldehyde alleviates doxorubicin-induced cardiotoxicity by decreasing oxidative stress and ferroptosis in cardiomyocytes.

Although doxorubicin (DOX) is an efficient chemotherapeutic drug for human tumors, severe cardiotoxicity restricts its clinical use. Cinnamaldehyde (CA), a bioactive component isolated from Cinnamonum cassia, possesses potent anti-oxidative and anti-apoptotic potentials. The major aim of this study was to evaluate the protective role of CA against DOX-induced cardiotoxicity. To this end, cardiomyocyte injury models were developed using DOX-treated H9c2 cells and DOX-treated rats, respectively. Herein, we found that CA treatment increased cardiomyocyte viability and attenuated DOX-induced cardiomyocyte death in vitro. CA further protected rats against DOX-induced cardiotoxicity, as indicated by elevated creatine kinase (CK) and lactate dehydrogenase (LDH) levels, myocardium injury, and myocardial fibrosis. CA alleviated DOX-induced myocardial oxidative stress by regulating reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione (GSH) levels. Mechanistically, CA markedly accelerated nuclear translocation of nuclear erythroid factor 2-related factor 2 (Nrf2) and increased heme oxygenase-1 (HO-1) expression. Consequently, CA decreased DOX-induced cardiomyocyte ferroptosis, while Erastin (a ferroptosis agonist) treatment destroyed the effect of CA on increasing cardiomyocyte viability. Taken together, the current results demonstrate that CA alleviates DOX-induced cardiotoxicity, providing a promising opportunity to increase the clinical application of DOX.

Vagus nerve stimulation and acetylcholinesterase inhibitor donepezil provide cardioprotection against trastuzumab-induced cardiotoxicity in rats by attenuating mitochondrial dysfunction

Trastuzumab (Trz) is a targeted anticancer drug for human epidermal growth factor receptor 2 (HER2)-positive tumors, as Trz-induced cardiotoxicity (TIC) is commonly observed in Trz-treated patients. Since cardiac autonomic modulation with electrical vagus nerve stimulation (VNS) and acetylcholinesterase (AChE) inhibitors exerts cardioprotection against various heart diseases, the comparative effects of electrical VNS and an AChE inhibitor (donepezil) on cardiac and mitochondrial functions and programmed cell death pathways in TIC are not known. VNS devices were implanted in thirty-two male Wistar rats and were divided into 4 groups: (i) Control-Sham (CSham), (ii) Trz-Sham (TSham), (iii) Trz-VNS (TVNS), and (iv) Trz-donepezil (TDPZ). Rats in the Trz-treated groups were intraperitoneally injected with Trz (4 mg/kg/day) for 7 days, while CSham rats were injected with NSS. VNS devices were activated in the TVNS rats during the 7-day Trz treatment, but not in the sham rats. Rats in the TDPZ group received donepezil orally (5 mg/kg/day) for 7 days. At the end, left ventricular (LV) function and heart rate variability were evaluated, and heart tissue was collected for biochemical and histological analysis. Trz rats showed LV dysfunction and cardiac sympathovagal imbalance. In addition, mitochondrial function and dynamics were impaired in TIC rats. Trz also increased cardiomyocyte death by inducing apoptosis, pyroptosis, and ferroptosis. Electrical VNS and donepezil had similar efficacy in alleviating cardiac mitochondrial dysfunction, dynamic imbalances, and cardiomyocyte death, leading to improved LV function. These findings suggested that parasympathetic activation via either VNS or an AChE inhibitor could be a promising therapeutic intervention against TIC.

Delivery of SAV-siRNA via Exosomes from Adipose-Derived Stem Cells for the Treatment of Myocardial Infarction.

Myocardial infarction (MI) leads to cardiomyocyte death, poor cardiac remodeling, and heart failure, making it a major cause of mortality and morbidity. To restore cardiac pumping function, induction of cardiomyocyte regeneration has become a focus of academic interest. The Hippo pathway is known to regulate cardiomyocyte proliferation and heart size, and its inactivation allows adult cardiomyocytes to re-enter the cell cycle. In this study, we investigated whether exosomes from adipose-derived stem cells (ADSCs) could effectively transfer siRNA for the Hippo pathway regulator Salvador (SAV) into cardiomyocytes to induce cardiomyocyte regeneration in a mouse model of MI. Our results showed that exosomes loaded with SAV-siRNA effectively transferred siRNA into cardiomyocytes and induced cardiomyocyte re-entry into the cell cycle, while retaining the previously demonstrated therapeutic efficacy of ADSC-derived exosomes to improve post-infarction cardiac function through anti-fibrotic, pro-angiogenic, and other effects. Our findings suggest that siRNA delivery via ADSC-derived exosomes may be a promising approach for the treatment of MI.

P58 WITHDRAWN Cardiomyocyte death after AAV gene transfer can be related to proteotoxicity or to transgene abnormal function or localization

P58 WITHDRAWN Cardiomyocyte death after AAV gene transfer can be related to proteotoxicity or to transgene abnormal function or localization

The role of heat shock proteins in thepathogenesis of heart failure (Review).

The influence of heat shock proteins (HSPs) on protein quality control systems in cardiomyocytes is currently under investigation. The effect of HSPs on the regulated cell death of cardiomyocytes (CMCs) is of great importance, since they play a major role in the implementation of compensatory and adaptive mechanisms in the event of cardiac damage. HSPs mediate a number of mechanisms that activate the apoptotic cascade, playing both pro‑ and anti‑apoptotic roles depending on their location in the cell. Another type of cell death, autophagy, can in some cases lead to cell death, while in other situations it acts as a cell survival mechanism. The present review considered the characteristics of the expression of HSPs of different molecular weights in CMCs in myocardial damage caused by heart failure, as well as their role in the realization of certain types of regulated cell death.