Signaling Pathway In Cardiomyocytes Research Articles

Tert promotes cardiac regenerative repair after MI through alleviating ROS-induced DNA damage response in cardiomyocyte

Telomerase reverse transcriptase (Tert) has been found to have a protective effect on telomeric DNA, but whether it could improve the repair of reactive oxygen species (ROS)-induced DNA damage and promote myocardial regenerative repair after myocardial infarction (MI) by protecting telomeric DNA is unclear. The immunofluorescence staining with TEL-CY3 and the TeloTAGGG Telomerase PCR ELISA kit were used to show the telomere length and telomerase activity. The heart-specific Tert-deletion homozygotes were generated by using commercial Cre tool mice and flox heterozygous mice for mating. We measured the telomere length and telomerase activity of mouse cardiomyocytes (CMs) at different days of age, and the results showed that they were negatively correlated with age. Overexpressed Tert could enhance telomerase activity and lengthen telomeres, thereby repairing the DNA damage induced by ROS and promoting CM proliferation in vitro. The in vivo results indicated that enhanced Tert could significantly improve cardiac function and prognosis by alleviating CM DNA damage and promoting angiogenesis post-MI. In terms of mechanism, DNA pulldown assay was used to identify that nuclear ribonucleoprotein A2B1 (hnRNPA2B1) could be an upstream regulator of Tert in CMs. Overexpressed Tert could activate the NF-κB signaling pathway in CMs and bind to the VEGF promoter in the endothelium to increase the VEGF level. Further immunoblotting showed that Tert protected DNA from ROS-induced damage by inhibiting ATM phosphorylation and blocking the Chk1/p53/p21 pathway activation. HnRNPA2B1-activated Tert could repair the ROS-induced telomeric DNA damage to induce the cell cycle re-entry in CMs and enhance the interaction between CMs and endothelium, thus achieving cardiac regenerative repair after MI.

Loss of Cavin-2 destabilizes PTEN and enhances Akt signaling pathway in cardiomyocytes.

Specific cavins and caveolins, known as caveolae-related proteins, have been implicated in cardiac hypertrophy and myocardial injury. Cavin-2 forms complexes with other caveolae-related proteins, but the role of Cavin-2 in cardiomyocytes (CMs) is poorly understood. Here, we investigated an unknown function of Cavin-2 in CMs. Under cardiac stress-free conditions, systemic Cavin-2 knockout (KO) induced mild and significant CM hypertrophy. Cavin-2 KO suppressed phosphatase and tensin homolog (PTEN) associated with Akt signaling, whereas there was no difference in Akt activity between the hearts of the wild-type and the Cavin-2 KO mice under cardiac stress-free conditions. However, after swim training, CM hypertrophy was more facilitated with enhanced PI3K-Akt activity in the hearts of Cavin-2 KO mice. Cavin-2 knockdown neonatal rat CMs (NRCMs) using adenovirus expressing Cavin-2 shRNA were hypertrophied and resistant to hypoxia and H2O2-induced apoptosis. Cavin-2 knockdown increased Akt phosphorylation in NRCMs, and an Akt inhibitor inhibited Cavin-2 knockdown-induced anti-apoptotic responses in a dose-dependent manner. Cavin-2 knockdown increased PIP3 production and attenuated PTEN at the membrane fraction of NRCMs. Immunostaining and immunoprecipitation showed that Cavin-2 was associated with PTEN at the plasma membrane of NRCMs. A protein stability assay showed that Cavin-2 knockdown promoted PTEN destabilization in NRCMs. In an Angiotensin II (2-week continuous infusion)-induced pathological cardiac hypertrophy model, CM hypertrophy and CM apoptosis were suppressed in cardiomyocyte-specific Cavin-2 conditional KO (Cavin-2 cKO) mice. Because Cavin-2 cKO mouse hearts showed increased Akt activity but not decreased extracellular signal-regulated kinase activity, suppression of pathological hypertrophy by Cavin-2 loss may be due to increased survival of healthy CMs. Cavin-2 plays a negative regulator in the PI3K-Akt signaling in CMs through interaction with PTEN. Loss of Cavin-2 enhances Akt activity by promoting PTEN destabilization, which promotes physiological CM hypertrophy and may enhance Akt-mediated cardioprotective effects against pathological CM hypertrophy.

Abstract 18443: Early Inflammation in βII-Spectrin Deficient Hearts Promote Cardiac Remodeling and Heart Failure

Background: Dysregulation of cardiac cytoskeletal proteins such as βII-spectrin has been recognized to promote accelerated heart failure (HF) and arrhythmias in human and mouse models. However, the mechanism by which βII-spectrin dysregulation underlies HF is poorly understood. Hypothesis: We hypothesized that cardiomyocyte loss of βII-spectrin leads to recruitment of inflammatory macrophages that augment cardiac remodeling by promoting arrhythmogenesis and increased susceptibility to HF. Methods: Cardiomyocyte-specific βII-spectrin knockout (βII-cKO) and control mice (βII-flox) were generated and harvested for RNA-sequencing (RNA-seq), qRT-PCR (to validate candidate inflammatory genes), immunohistochemistry, immunoblotting, and flow cytometry. siRNA was also used to knockdown βII-spectrin in cultured cells to validate that direct loss of βII-spectrin contributes to immune cell recruitment. Transaortic constriction (TAC) was used to induce pressure overload. Results: RNA-seq demonstrated an early significant increase of inflammatory macrophages and T cell markers following βII-spectrin loss. Consistent with RNA-seq and qRT-PCR results, immunohistochemistry demonstrated an increase in CD45 positive cells in juvenile βII-cKO mouse hearts compared to control. siRNA targeted depletion of βII-spectrin in cultured cardiomyocyte led to increased expression and secretion of TGFβ-1 protein, which can promote infiltrating of immune cells. Notably, accelerated HF at two weeks was observed in βII-cKO mice compared to controls after TAC. Conclusions: These data suggest that βII-spectrin loss may mediate inflammation via the TGFβ-1 pathway, which in part contributes to βII-spectrin-mediated accelerated HF. Furthermore, these are the first data implicating βII-spectrin in the TGFβ1-immune signaling pathway in cardiomyocytes.

GSK-3α aggravates inflammation, metabolic derangement, and cardiac injury post-ischemia/reperfusion.

Reperfusion after acute myocardial infarction further exaggerates cardiac injury and adverse remodeling. Irrespective of cardiac cell types, loss of specifically the α isoform of the protein kinase GSK-3 is protective in chronic cardiac diseases. However, the role of GSK-3α in clinically relevant ischemia/reperfusion (I/R)-induced cardiac injury is unknown. Here, we challenged cardiomyocyte-specific conditional GSK-3α knockout (cKO) and littermate control mice with I/R injury and investigated the underlying molecular mechanism using an in vitro GSK-3α gain-of-function model in AC16 cardiomyocytes post-hypoxia/reoxygenation (H/R). Analysis revealed a significantly lower percentage of infarct area in the cKO vs. control hearts post-I/R. Consistent with in vivo findings, GSK-3α overexpression promoted AC16 cardiomyocyte death post-H/R which was accompanied by an induction of reactive oxygen species (ROS) generation. Consistently, GSK-3α gain-of-function caused mitochondrial dysfunction by significantly suppressing mitochondrial membrane potential. Transcriptomic analysis of GSK-3α overexpressing cardiomyocytes challenged with hypoxia or H/R revealed that NOD-like receptor (NLR), TNF, NF-κB, IL-17, and mitogen-activated protein kinase (MAPK) signaling pathways were among the most upregulated pathways. Glutathione and fatty acid metabolism were among the top downregulated pathways post-H/R. Together, these observations suggest that loss of cardiomyocyte-GSK-3α attenuates cardiac injury post-I/R potentially through limiting the myocardial inflammation, mitochondrial dysfunction, and metabolic derangement. Therefore, selective inhibition of GSK-3α may provide beneficial effects in I/R-induced cardiac injury and remodeling. KEY MESSAGES: GSK-3α promotes cardiac injury post-ischemia/reperfusion (I/R). GSK-3α regulates inflammatory and metabolic pathways post-hypoxia/reoxygenation (H/R). GSK-3α overexpression upregulates NOD-like receptor (NLR), TNF, NF-kB, IL-17, and MAPK signaling pathways in cardiomyocytes post-H/R. GSK-3α downregulates glutathione and fatty acid metabolic pathways in cardiomyocytes post-H/R.

MiR-130b-3p alleviates palmitate-induced lipotoxicity via the PPARυ signaling pathway in cardiomyocytes

miR-130b-3p alleviates palmitate-induced lipotoxicity via the PPARυ signaling pathway in cardiomyocytes

A Kaposi’s sarcoma-associated herpes virus-encoded microRNA contributes to dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is the leading cause of heart transplantation. By microRNA (miRNA) array, a Kaposi’s sarcoma-associated herpes virus (KSHV)-encoded miRNA, kshv-miR-K12-1-5p, was detected in patients with DCM. The KSHV DNA load and kshv-miR-K12-1-5p level in plasma from 696 patients with DCM were measured and these patients were followed-up. Increased KSHV seropositivity and quantitative titers were found in the patients with DCM compared with the non-DCM group (22.0% versus 9.1%, p < 0.05; 168 versus 14 copies/mL plasma, p < 0.05). The risk of the individual end point of death from cardiovascular causes or heart transplantation was increased among DCM patients with the KSHV DNA seropositivity during follow-up (adjusted hazard ratio 1.38, 95% confidence interval 1.01–1.90; p < 0.05). In heart tissues, the KSHV DNA load was also increased in the heart from patients with DCM in comparison with healthy donors (1016 versus 29 copies/105 cells, p < 0.05). The KSHV and kshv-miR-K12-1-5p in DCM hearts were detected using immunofluorescence and fluorescence staining in situ hybridization. KSHV itself was exclusively detectable in CD31-positive endothelium, while kshv-miR-K12-1-5p could be detected in both endothelium and cardiomyocytes. Moreover, kshv-miR-K12-1-5p released by KSHV-infected cardiac endothelium could disrupt the type I interferon signaling pathway in cardiomyocytes. Two models of kshv-miR-K12-1-5p overexpression (agomiR and recombinant adeno-associated virus) were used to explore the roles of KSHV-encoded miRNA in vivo. The kshv-miR-K12-1-5p aggravated known cardiotropic viruses-induced cardiac dysfunction and inflammatory infiltration. In conclusion, KSHV infection was a risk factor for DCM, providing developmental insights of DCM involving virus and its miRNA (https://clinicaltrials.gov. Unique identifier: NCT03461107).

PO-01-147 ACTIVATION OF AUTOPHAGY ATTENUATES PROGRESSION OF ARRHYTHMOGENIC RIGHT VENTRICULAR CARDIOMYOPATHY

Studies of autophagy in ARVC are quite rare. Even autophagy had the opposite effects in desmin-related cardiomyopathy and dilated cardiomyopathy. This study aimed to explore the regulatory role of autophagy in the progression of ARVC. The ARVC cardiomyocytes (HL-1/shJup) were treated with autophagy activator (rapamycin) and inhibitor (chloroquine) to manipulate autophagy activity. Western blotting and immunofluorescence determined the changes of disease progression and signaling pathways. Then, autophagy was manipulated in cardiac tissue-specific Jup knockout mice to confirm the cell-derived findings. The autophagy activity of HL-1/shJup cell line was higher than that of control cells. In HL-1/shJup cells, the upstream signaling pathway of autophagy was active. During rapamycin treatment, the proteins related to lipogenesis and fibrogenesis in HL-1/shJup cells were reduced. In contrast, chloroquine treatment had the opposite effect. Moreover, rapamycin decreased and chloroquine increased intracellular oil droplet accumulation in HL-1/shJup cells. In addition, there was no significant change in Wnt/Hippo signaling pathways in cardiomyocytes after rapamycin treatment. Instead, the protein expression of the transcription factor SREBP1 that regulates lipogenesis and lysyl oxidase (LOX) that promotes fibrosis were related to the regulatory mechanism of autophagy. In ARVC mice, activated/inhibited autophagy also reduced/increased RV distance, arrhythmia, and lipogenesis through SREBP1, but not in wild-type mice. Autophagy plays a protective role in ARVC by regulating lipogenesis to attenuate disease progression. Based on this study, autophagy activators may be used in combination with existing drugs in patients with ARVC disease in the future to provide additional protection for early heart failure or heart transplantation.

Exogenous spermidine alleviates diabetic cardiomyopathy via suppressing reactive oxygen species, endoplasmic reticulum stress, and Pannexin-1-mediated ferroptosis.

Diabetic cardiomyopathy (DCM) is a serious complication and death cause of diabetes mellitus (DM). Recent cardiology studies suggest that spermidine (SPD) has cardioprotective effects. Here, we verified the hypothesis of SPD's protective effects on DCM. Therefore, db/db mice and primary neonatal mouse cardiomyocytes were used to observe the effects of SPD. Immunoblotting showed that ornithine decarboxylase (ODC) and SPD/spermine N1-acetyltransferase (SSAT) were downregulated and upregulated in the myocardium of db/db mice, respectively. We found that diabetic mice showed cardiac dysfunction in 12 weeks. Conversely, exogenous SPD could improve cardiac functions and reduce the deposition of collagens, myocardial damage, reactive oxygen species (ROS) levels, and endoplasmic reticulum stress (ERS) in diabetic mouse hearts. Our results also demonstrated that cardiomyocytes displayed ferroptosis and then activated Pannexin-1 expression, which resulted in the increase of the extracellular adenosine triphosphate (ATP). Subsequently, increased ATP as a paracrine molecule combined to purinergic receptor P2X7 to activate ERK1/2 signaling pathway in cardiomyocytes and activated NCOA4-mediated ferroptinophagy to promote lipid peroxidation and ferroptosis. Interestingly, SPD could reverse these molecular processes. Our findings indicate an important new mechanism for DCM and suggest that SPD has potential applicability to protect against deterioration of cardiac function with DCM.

Profoundal Effects of Microcystin-LR Induced Cardiotoxicity in Mammals

Eutrophication and climate change have raised obnoxious cyanobacterial blooms, which have become a global public health problem. The most dangerous cyanotoxin found in water bodies is microcystin (MC), a byproduct of cyanobacterial metabolism. Several studies suggest that in addition to the liver, the heart may be another target organ for MCs poisoning. Recent research indicates a clear link between MC exposure and cardiotoxicity, posing a risk to human cardiovascular health. The cardiovascular system, which includes all tissues, cells, blood, and vascular tissues of the heart, can be unswervingly affected by MCs, resulting in abnormal cardiovascular system structure and/or function. This review concludes that MC cardiotoxicity may be linked to protein phosphatase suppression and the contractile unit, generation of contractile force, the role of intercellular junction proteins, and the role of the angiotensin signaling pathway in cardiomyocytes.

Tingli Dazao Decoction pretreatment ameliorates mitochondrial damage induced by oxidative stress in cardiomyocytes

Ethnopharmacological relevanceTingli Dazao Decoction (TLDZD) recorded in “Synopsis of Prescriptions of the Golden Chamber” is a classical prescription used for the treatment of heart failure nowadays. The studies of TLDZD were mainly focused on clinical practice where the formula was usually combined with other medicinal herbs. Chemical composition and cardiovascular pharmacological research of TLDZD were still insufficient. Aim of the studyThis study aimed to investigate the chemical constituents of TLDZD, evaluate the effects of TLDZD on mitochondria of myocardial cells under oxidative stress, and identify its potential cardioprotective components. Materials and methodsChemical composition analysis of TLDZD was performed by ultra-performance liquid chromatography-quadrupole-time of flight-mass spectrometry. An in vitro oxidative stress model of cardiomyocytes was established by treating H9c2 cells with tert-butyl hydroperoxide (tBHP). The impact of TLDZD and its components on the production of cellular reactive oxygen species (ROS) and mitochondrial ROS (mROS), the level of malonaldehyde as well as the structure and function of mitochondria were evaluated. The effect of TLDZD on AKT/Nrf2/HO-1 signaling pathway in cardiomyocytes under oxidative stress were observed. ResultsSeventy-eight compounds were characterized from TLDZD, among which flavonoids, glucosinolates and phenylpropanoids were abundant, and a small number of cardiac glycosides and alkaloids also existed in TLDZD. Pretreatment with TLDZD significantly attenuated cell death, accompanied by decreased ROS and mROS production, reduced malonaldehyde level, lower mitochondrial membrane potential and adenosine triphosphate content in H9c2 cells stimulated with tBHP. The active components were mainly flavonoids of TLZ represented by quercetin-3-O-β-D-glucose-7-O-β-D-gentiobioside. In mechanism, the cardioprotective effect of TLDZD was proved to be associated with the activation of the AKT/Nrf2/HO-1 signaling pathway. ConclusionsThe chemical profile of TLDZD was comprehensively investigated. Flavonoids with quercetin-3-O-β-D-glucose-7-O-β-D-gentiobioside as the representative, were the main component in TLDZD responsible for attenuating mitochondrial oxidative damage in cardiomyocytes.

Abstract P2116: Hyperglycemia Mediated Changes In A Human Cardiomyocyte Cell Model

Introduction: Hyperglycemia-mediated cardiac dysfunction is a critical initiator in the development of vascular complications, which, in turn, leads to cardiac fibrosis. In this study, we investigated the role of the Hippo signaling pathway in cardiomyocytes to study the complex signaling network of YAP1/TAZ on fibrotic and vascular inflammatory mediators in hyperglycemic condition. This in-vitro study demonstrated that YAP1/TAZ signaling is highly activated in the hyperglycemic cardiomyocytes. To further investigate the differentially expressed genes that are related to inflammation and fibrosis, RNA-sequencing studies were employed. Methods: To investigate the effects of hyperglycemia-mediated changes in cardiomyocytes, we used human AC16 cells cultured in-vitro under normoglycemic (5 mM D-Glucose) and hyperglycemic (50 mM D-glucose) conditions. After 24-hours of hyperglycemic insult, cells were collected and processed for RNA-seq studies. Furthermore, we also performed Western Blot analysis to evaluate the protein expression of YAP1/TAZ under hyperglycemia induced stress conditions. Results: Our study showed a significant upregulation of the protein expression of the YAP1/TAZ pathway in hyperglycemic cardiomyocytes. RNA-seq studies revealed differentially expressed genes (DEG) in the hyperglycemic condition in comparison with the normoglycemic condition. Among the extracellular matrix proteins, the following ECM and related markers were significantly upregulated including MMP3, TNC, TGF-beta1 and 2, COL4A1, FN1 and FGF-2. Altered expression of inflammatory mediators included the following markers, IL-6, CXCL10, CXCL12, CCL2 and VEGF-C. In addition, the following transcriptional co-activators were also significantly upregulated, including EPHA2 and MYOCD. Conclusions: This study suggests that changes in YAP1/TAZ signaling increases vascular inflammation in response to hyperglycemia. This also leads to increased expression of inflammatory mediators as shown by our results. Thus, the inhibition of the YAP1/TAZ pathway may prevent and improve hyperglycemia associated vascular damage and inflammation.

Chaperone-mediated autophagy attenuates H2 O2 -induced cardiomyocyte apoptosis by targeting poly (ADP-ribose) polymerase 1 (PARP1) for lysosomal degradation.

Poly (ADP-ribose) polymerase 1 (PARP1)is a typical representative of the PARP enzyme family and is mainly related to DNA repair, gene transcription regulation, inflammation, and oxidative stress. Studies have found that PARP1 is involved in the pathophysiological processes of a variety of cardiovascular diseases. Chaperone-mediated autophagy (CMA)is involved in the molecular regulation of various diseases, including cardiovascular diseases, and plays a critical role in maintaining intracellular metabolism balance. However, the link between PARP1 and CMA in cardiomyocytes remains unclear. Therefore, the aims of this study were to investigate whether CMA is involved in PARP1 regulation and to further clarify the specific molecular mechanisms. Earle's balanced salt solution(EBSS)-induced activation of autophagy reduced PARP1 expression, whereas the autophagy lysosomal inhibitor CQ had the opposite effect. Correspondingly, treatment with the autophagy inhibitor 3-methyladeninedid not abolish the autophagy-inducing effects of EBSS. Additionally, PARP1 binds to heat shock cognate protein 70and lysosome-associated membrane protein 2A(LAMP2A). Moreover, adenovirus-mediated LAMP2A overexpression to activate the CMA signaling pathway in cardiomyocytes reduces PARP1 (cleaved) expression and further decreases cardiomyocyte apoptosis caused by oxidative stress. In contrast, downregulation of LAMP2A increased PARP1 (cleaved) expression and the degree of apoptosis. More importantly, we report that appropriate concentrations of H2 O2 triggered the nuclear translocation of PARP1, which subsequently promoted the degradation of PARP1 through the CMA pathway. In summary, our data are the first to reveal that CMA targeted PARP1 for lysosomal degradation in cardiomyocytes, which ultimately inhibited apoptosis by promoting the degradation of the PARP1 protein.

In vivo imaging of heart failure with preserved ejection fraction by simultaneous monitoring of cardiac nitric oxide and glutathione using a three-channel fluorescent probe

The pathophysiology of heart failure with preserved ejection fraction (HFpEF) remains unclear, making the diagnosis and treatment challenging. Cardiac oxidative and nitrative stress are strongly implicated in the pathogenesis of HFpEF. Herein, we present a unique three-channel fluorescent probe for evaluating cardiac oxidative and nitrative stress in HFpEF by simultaneous detection of NO and GSH. The probe exhibits a native green fluorescence (probe channel), while the presence of GSH and NO can sensitively turn the native green fluorescence into red fluorescence (GSH channel) and near-infrared fluorescence (NO channel), respectively. The probe clearly reveals that both GSH and NO levels are upregulated in cardiomyocytes and heart tissue with HFpEF. Moreover, it uncovers that the enhancement in NO and GSH levels are closely associated with increased level of iNOS (inducible nitric oxide synthase) and activation of the Keap1 (Kelch-like ECH-associated protein 1)/Nrf2 (nuclear factor erythroid 2–related factor 2)/ARE (antioxidant response element) signaling pathway in cardiomyocytes, respectively. This work proposes a promising approach for distinguishing normal heart and HFpEF heart by in vivo noninvasive imaging of both GSH and NO, and greatly contributing to the improvement of the diagnosis and treatment of HFpEF.

TRPC1 contributes to endotoxemia-induced myocardial dysfunction via mediating myocardial apoptosis and autophagy

Cardiac dysfunction is a vital complication of endotoxemia (ETM) with limited therapeutic options. Transient receptor potential canonical channel (TRPC)1 was involved in various heart diseases. While, the role of TRPC1 in ETM-induced cardiac dysfunction remains to be defined. In this study, we found that TRPC1 protein expression was significantly upregulated in hearts of lipopolysaccharide (LPS)-challenged mice. What’s more, TRPC1 knockdown significantly alleviated LPS-induced cardiac dysfunction and injury. Further myocardial mRNA-sequencing analysis revealed that TRPC1 might participate in pathogenesis of ETM-induced cardiac dysfunction via mediating myocardial apoptosis and autophagy. Data showed that knockdown of TRPC1 significantly ameliorated LPS-induced myocardial apoptotic injury, cardiomyocytes autophagosome accumulation, and myocardial autophagic flux. Simultaneously, deletion of TRPC1 reversed LPS-induced molecular changes of apoptosis/autophagy signaling pathway in cardiomyocytes. Moreover, TRPC1 could promote LPS-triggered intracellular Ca2+ release, subsequent calpain activation and caveolin-1 degradation. Either blocking calpain by PD150606 or enhancing the amount of caveolin-1 scaffolding domain that interacts with TRPC1 by cell-permeable peptide cavtratin significantly alleviated the LPS-induced cardiac dysfunction and cardiomyocytes apoptosis/autophagy. Furthermore, cavtratin could inhibit LPS-induced calpain activation in cardiomyocytes. caveolin-1 could directly interact with calpain 2 both in vivo and in vitro. Importantly, cecal ligation and puncture-stimulated cardiac dysfunction and mortality were significantly alleviated in Trpc1-/- and cavtratin-treated mice, which further validated the contribution of TRPC1-caveolin-1 signaling axis in sepsis-induced pathological process. Overall, this study indicated that TRPC1 could promote LPS-triggered intracellular Ca2+ release, mediate caveolin-1 reduction, and in turn activates calpain to regulate myocardial apoptosis and autophagy, contributing to ETM-induced cardiac dysfunction of mice.

Mitofilin Mitigates Myocardial Damage in Acute Myocardial Infarction by Regulating Pyroptosis of Cardiomyocytes.

BackgroundAcute myocardial infarction (AMI) can lead to sudden cardiac death after prolonged ischemia or heart failure (HF) and impaired left ventricular pump function. However, the underlying mechanism remains largely unknown. The purpose of this study was to investigate the role of mitofilin in alleviating AMI.MethodsRecombinant adenoviral vectors for mitofilin overexpression or mitofilin knockdown were constructed, respectively. A mouse AMI model was established and the effect of mitofilin on myocardial pyroptosis was examined by detecting the lactate dehydrogenase (LDH) level and inflammatory factors. Moreover, a cellular model of AMI was established by treating cardiomyocytes with hypoxia/reoxygenation (H/R). An enzyme-linked immunosorbent assay (ELISA) and a western blot analysis were used to detect the effect of mitofilin knockdown on the expression of pyroptosis-related factors. Furthermore, the regulatory role of mitofilin in PI3K/AKT pathway was evaluated by the western blot and PI3K inhibitor.ResultsMitofilin was downregulated in the heart tissue of the AMI mice and H/R induced cardiomyocytes. The overexpression of mitofilin significantly alleviated AMI and reduced pyroptosis-related factors. Meanwhile, in cardiomyocytes, mitofilin knockdown aggravated cellular damages by promoting pyroptosis. Further analysis showed that the anti-pyroptotic effect of mitofilin was dependent on the activation of the PI3K/AKT signaling pathway.ConclusionsOur study suggests that mitofilin regulates pyroptosis through the PI3K/AKT signaling pathway in cardiomyocytes to ameliorate AMI, which may serve as a therapeutic strategy for the management of AMI.

SARS‐CoV‐2 and Hippo Signaling Pathway: A Potential Therapeutic Target

SARS‐CoV‐2 is responsible for the ongoing COVID‐19 pandemic, which causes respiratory failure and damage to multiple organ systems. Emergence of new variants of concern (VOCs), including Omicron can potentially render the current vaccines ineffective. However, our understanding of COVID‐19 pathophysiology and molecular basis of SARS‐CoV‐2 infection is very limited. The role of the Hippo signaling pathway, an evolutionarily conserved organogenesis circuitry, in tissue inflammation and innate immune response is beginning to be understood. Given the complexity of COVID‐19 associated cell injury and immunopathogenesis processes, we investigated this Hippo pathway dynamic in SARS‐CoV‐2 infection by utilizing COVID‐19 lung samples, transcriptome and human cell models based on pluripotent stem cell‐derived cardiomyocytes (PSC‐CMs) and human primary lung air‐liquid interface (ALI) culture. The SARS‐CoV‐2 infection resulted in stoppage of cardiomyocyte beating and extensive apoptotic cell death. Especially the infection caused activation of Hippo signaling pathway in cardiomyocytes, as shown by increased level of phosphorylated form of YAP, a downstream transcriptional co‐factor involved in tissue growth, mitochondrial biogenesis and innate immunity. Similar activation was noted in SARS‐CoV‐2 infected lung ALI epithelial cells and COVID‐19 lung autopsy samples. The shRNA‐mediated partial knockdown and pharmacological inhibitor of YAP/TAZ resulted in significantly reduced SARS‐CoV‐2 replication, whereas inhibition of Hippo pathway upstream LATS1 and MST1 kinases led to enhanced virus replication. These results indicate a direct role of Hippo signaling in SARS‐CoV‐2 mediated disease pathogenesis and this pathway can be pharmacologically targeted to treat COVID‐19.

Silica nanoparticles induce pyroptosis and cardiac hypertrophy via ROS/NLRP3/Caspase-1 pathway

Growing literatures suggest that silica nanoparticles (SiNPs) exposure is correlated with adverse cardiovascular effects. Cardiac hypertrophy is one of the most common risk factors for heart failure. However, whether SiNPs involved in cardiac hypertrophy and the underlying mechanisms was remained unexploited. Our study aimed to investigate the molecular mechanisms of SiNPs on pyroptosis and cardiac hypertrophy. The in vivo results found that SiNPs induced ultrastructural change and histopathological damage, accompanied by oxidative damage occurred and increased levels of inflammatory factors (IL-18 and IL-1β) in heart tissue. In addition, SiNPs could upregulate the expressions of cardiac hypertrophy-related special marker including ANP, BNP, β-MHC, it also elevated the pyroptosis-related protein, such as NLRP3, Cleaved-Caspase-1, GSDMD, IL-18 and Cleaved-IL-1β in vivo. For in vitro study, SiNPs increased the intracellular ROS generation and activated the NLRP3/Caspase-1/GSDMD signaling pathway in cardiomyocytes. Whereas, the NADPH oxidase (NOX) inhibitor VAS2870 had effectively inhibited the ROS level and suppressed the expression of NLRP3, ASC, Pro-Caspase-1, Cleaved-Caspase-1, N-GSDMD, IL-18, Cleaved-IL-1β, ANP, BNP and β-MHC. Moreover, transfected with si-NLRP3 or adopted with Caspase-1 inhibitor VX-765 in cardiomyocytes showed an inhibitory effect on SiNPs-induced pyroptosis and cardiac hypertrophy. In summary, our results demonstrated that SiNPs could trigger pyroptosis and cardiac hypertrophy via ROS/NLRP3/Caspase-1 signaling pathway.

Maltol mitigates cisplatin‐evoked cardiotoxicity via inhibiting the PI3K/Akt signaling pathway in rodents in vivo and in vitro

Our current research aims to evaluate the efficiency of a flavor enhancer, maltol (produced by heating ginseng) against cisplatin-evoked cardiotoxicity by establishing cisplatin-induced heart injury in vivo and H9C2 rat cardiomyocyte model. The cisplatin-treated mice at 3mg/kg for four times on the 7th, 9th, 11th and 13th day, and in them appeared a serious cardiac damage accompanied with the increase in indicators of heart damage. Multiple exposure of 3mg/kg for four times of cisplatin increased cardiac cells apoptosis with increased expression of Bax and cleaved-caspase 3, and decreased expression of Bcl-2. Interestingly, supplement of maltol at doses of 50 and 100 mg/kg for 15 days significantly suppressed the cardiac disturbance. In cultured H9C2 cells, maltol enhanced PI3K/Akt expression level during cisplatin treatment, and reduced cisplatin-induced apoptosis. Notably, inhibition of PI3K/Akt by LY294002 and HY-10249A lessened the efficacy of maltol. In mice, maltol apparently induced PI3K/Akt in heart tissues and protected against cisplatin-induced cardiotoxicity. In conclusion, maltol exerted the protective effects against cisplatin-induced cardiotoxicity, at least partially by inhibiting the activation of PI3K/Akt signaling pathways in cardiomyocytes, to ease oxidative stress, and alleviate reactive oxygen species-mediated apoptosis.

Protective Mechanism of Trimetazidine in Myocardial Cells in Myocardial Infarction Rats through ERK Signaling Pathway.

Objective To study the protective effect of trimetazidine on myocardial cells in rats with myocardial infarction and explore its effect on ERK signaling pathway. Methods 40 SD rats were randomly divided into the sham operation group, model group, low-dose group, and high-dose group (intra-abdominal injection of trimetazidine 5 mg/kg and 10 mg/kg, respectively), construction of rat myocardial infarction model by coronary artery left anterior descending artery ligation. 7 days after surgery, the survival rate and cardiac function of each group of rats were recorded. The myocardial infarct size was detected by TTC staining. The apoptosis level of rat cardiomyocytes was detected by TUNEL staining. The content of ROS in rat cardiomyocytes was detected by DCFH-DA. Western-blot was used to detection of Caspase-3, Bcl-2/Bax, and ERK signaling pathway-related proteins in myocardial tissue. Results Compared with the model group, the survival rate of the rats in the low-dose group and the high-dose group was significantly increased (P < 0.01), the cardiac function was significantly improved (P < 0.01), the myocardial infarct size was significantly decreased (P < 0.01), the level of apoptosis was significantly decreased (P < 0.01), the content of ROS in cardiomyocytes was significantly decreased (P < 0.01), the protein expression of Caspase-3 and NF-κB in cardiomyocytes was significantly decreased (P < 0.01), and the expression of Bcl-2/Bax and p-ERK were significantly increased (P < 0.01). Conclusion Trimetazidine can activate ERK signaling pathway in cardiomyocytes of rats with myocardial infarction, increase the expression of p-ERK, decrease the content of ROS in cardiomyocytes, decrease the expression of apoptotic proteins, reduce myocardial infarct size, improve cardiac function, and increase myocardial function.

S-Propargyl-Cysteine Attenuates Diabetic Cardiomyopathy in db/db Mice Through Activation of Cardiac Insulin Receptor Signaling.

Background: Endogenous hydrogen sulfide (H2S) is emerging as a key signal molecule in the development of diabetic cardiomyopathy. The aim of this study was to explore the effect and underlying mechanism of S-propargyl-cysteine (SPRC), a novel modulator of endogenous H2S, on diabetic cardiomyopathy in db/db diabetic mice.Methods and Results: Vehicle or SPRC were orally administered to 8-month-old male db/db mice and their wild type littermate for 12 weeks. SPRC treatment ameliorated myocardial hypertrophy, fibrosis, and cardiac systolic dysfunction assessed by histopathological examinations and echocardiography. The functional improvement by SPRC was accompanied by a reduction in myocardial lipid accumulation and ameliorated plasma lipid profiles. SPRC treatment improved glucose tolerance in db/db mice, with fasting blood glucose and peripheral insulin resistance remaining unchanged. Furthermore, insulin receptor signaling involving the phosphorylation of protein kinase B (Akt/PKB) and glycogen synthase kinase 3β (GSK3β) were elevated and activated by SPRC treatment. Primary neonatal mice cardiomyocytes were cultured to explore the mechanisms of SPRC on diabetic cardiomyopathy in vitro. Consistent with the results in vivo, SPRC not only up-regulated insulin receptor signaling pathway in cardiomyocytes in dose-dependent manner in the basal state, but also relieved the suppression of insulin receptor signaling induced by high concentrations of glucose and insulin. Furthermore, SPRC also enhanced the expression of glucose transporter 4 (GLUT4) and 3H glucose uptake in cardiomyocytes.Conclusions: In this study, we found a novel beneficial effect of SPRC on diabetic cardiomyopathy, which was associated with activation of insulin receptor signaling. SPRC may be a promising medication for diabetic cardiomyopathy in type 2 diabetes mellitus patients.