The different response of cardiomyocytes and cardiac fibroblasts to mitochondria inhibition and the underlying role of STAT3

Nitazoxanide protects against heart failure with preserved ejection and metabolic syndrome induced by high-fat diet (HFD) plus L-NAME "two-hit" in mice

The clinical antiprotozoal drug nitazoxanide has been demonstrated to improve the experimental diabetes mellitus, lipid metabolism disorders, atherosclerosis and inhibit inflammation. Since the pathogenesis of heart failure with preserved ejection (HFpEF) is multifactorial and closely associated with the aforementioned diseases, we aim to study the effect of nitazoxanide on high-fat diet (HFD) plus L-NAME (N ω-nitro-l-arginine methyl ester)-induced HFpEF and metabolic syndrome in mice. We found that oral nitazoxanide improved cardiac hypertrophy, cardiac fibrosis, cardiac diastolic dysfunction, increased blood pressure, impaired exercise tolerance, impaired glucose handling, serum lipid disorders, hepatic steatosis, increased weight of white adipose tissues and kidney fibrosis in HFD + L-NAME-treated mice. In the established HFD + L-NAME-induced HFpEF and metabolic syndrome mouse model, therapeutic treatment with nitazoxanide rescued HFD + L-NAME-induced pathological phenotypes as mentioned above. The in vitro experiments revealed that tizoxanide, the active metabolite of nitazoxanide, increased the basal mitochondria metabolism of cardiomyocytes, inhibited cardiomyocyte hypertrophy and collagen secretion from cardiac fibroblasts, and relaxed phenylephrine- and U46619-induced constriction of rat mesenteric arteries, indicating that the direct effect of tizoxanide might partly contribute to the protective effect of nitazoxanide against HFpEF in vivo. The present study suggests that nitazoxanide might be a potential drug for HFpEF and metabolic syndrome therapy.

ECSIT-X4 is Required for Preventing Pressure Overload-Induced Cardiac Hypertrophy via Regulating Mitochondrial STAT3

Mitochondrial dysfunction is a key factor in exacerbating pressure overload-induced cardiac hypertrophy and is linked to increased morbidity and mortality. ECSIT, a crucial adaptor for inflammation and mitochondrial function, has been reported to express multiple transcripts in various species and tissues, leading to distinct protein isoforms with diverse subcellular localizations and functions. However, whether an unknown ECSIT isoform exists in cardiac cells and its potential role in regulating mitochondrial function and pathological cardiac hypertrophy has remained unclear. This study identified a 42-kDa ECSIT isoform encoded by the transcript variant Ecsit-X4, which is highly expressed in the mitochondria of adult cardiomyocytes but down-regulated in hypertrophic human heart samples and TAC-treated mouse hearts. AAV9-mediated Ecsit-X4 gene therapy, administered either before or after TAC surgery, significantly attenuated cardiac hypertrophy. Cardiomyocyte-specific Ecsit deficiency worsened TAC-induced cardiac hypertrophy, while Ecsit-X4 compensation independently rescued hypertrophic phenotypes in EcsitcKO mice. Mechanistically, ECSIT-X4 localized to the mitochondria and interacted with STAT3, leading to increased STAT3 levels and enhanced serine 727 phosphorylation in cardiomyocyte mitochondria, thereby promoting strong mitochondrial bioenergetics. This study identified a novel transcript variant of ECSIT localized in the mitochondria of adult cardiomyocytes and highlights its potential as a therapeutic target for heart failure.

Vascular endothelial cell injury: causes, molecular mechanisms, and treatments

Vascular endothelial cells form a single layer of flat cells that line the inner surface of blood vessels, extending from large vessels to the microvasculature of various organs. These cells are crucial metabolic and endocrine components of the body, playing vital roles in maintaining circulatory stability, regulating vascular tone, and preventing coagulation and thrombosis. Endothelial cell injury is regarded as a pivotal initiating factor in the pathogenesis of various diseases, triggered by multiple factors, including infection, inflammation, and hemodynamic changes, which significantly compromise vascular integrity and function. This review examines the causes, underlying molecular mechanisms, and potential therapeutic approaches for endothelial cell injury, focusing specifically on endothelial damage in cardiac ischemia/reperfusion (I/R) injury, sepsis, and diabetes. It delves into the intricate signaling pathways involved in endothelial cell injury, emphasizing the roles of oxidative stress, mitochondrial dysfunction, inflammatory mediators, and barrier damage. Current treatment strategies-ranging from pharmacological interventions to regenerative approaches and lifestyle modifications-face ongoing challenges and limitations. Overall, this review highlights the importance of understanding endothelial cell injury within the context of various diseases and the necessity for innovative therapeutic methods to improve patient outcomes.

Comprehensive analysis of scRNA-seq and bulk RNA-seq reveals the non-cardiomyocytes heterogeneity and novel cell populations in dilated cardiomyopathy

BACKGROUND

Dilated cardiomyopathy (DCM) is one of the most common causes of heart failure. Infiltration and alterations in non-cardiomyocytes of the human heart involve crucially in the occurrence of DCM and associated immunotherapeutic approaches.

METHODS

We constructed a single-cell transcriptional atlas of DCM and normal patients. Then, the xCell algorithm, EPIC algorithm, MCP counter algorithm, and CIBERSORT method were applied to identify DCM-related cell types with a high degree of precision and specificity using RNA-seq datasets. We further analyzed the heterogeneity among cell types, performed trajectory analysis, examined transcription factor regulatory networks, investigated metabolic heterogeneity, and conducted intercellular communication analysis. Finally, we used bulk RNA-seq data to confirm the roles of M2-like2 subpopulations and GAS6 in DCM.

RESULTS

We integrated and analyzed Single-cell sequencing (scRNA-seq) data from 7 DCM samples and 3 normal heart tissue samples, totaling 70,958 single-cell data points. Based on gene-specific expression and prior marker genes, we identified 9 distinct subtypes, including fibroblasts, endothelial cells, myeloid cells, pericytes, T/NK cells, smooth muscle cells, neuronal cells, B cells, and cardiomyocytes. Using machine learning methods to quantify bulk RNA-seq data, we found significant differences in fibroblasts, T cells, and macrophages between DCM and normal samples. Further analysis revealed high heterogeneity in tissue preference, gene expression, functional enrichment, immunodynamics, transcriptional regulatory factors, metabolic changes, and communication patterns in fibroblasts and myeloid cells. Among fibroblast subpopulations, proliferative F3 cells were implicated in the fibroblast transition process in DCM, while myofibroblast F6 cells promoted the fibroblast transition to a late cell state in DCM. Additionally, two subpopulations of M2 macrophages, M2-like1 and M2-like2, were identified with distinct features. The M2-like2 cell subpopulation, which was enriched in glycolysis and fatty acid metabolism, involved in inflammation inhibition and fibrosis promotion. Cell‒cell communication analysis indicated the GAS6-MERTK axis might exhibit interaction between M2 macrophage and M2-like1 macrophage. Furthermore, deconvolution analysis for bulk RNA-seq data revealed a significant increase in M2-like2 subpopulations in DCM, suggesting a more important role for this cell population in DCM.

CONCLUSIONS

We revealed the heterogeneity of non-cardiomyocytes in DCM and identified subpopulations of myofibroblast and macrophages engaged in DCM, which suggested a potential significance of non-cardiomyocytes in treatment of DCM.

Label-Free Raman Spectroscopy for Assessing Purity and Maturation of hiPSC-Derived Cardiac Tissue

I.

BACKGROUND

Human induced pluripotent stem cell (hiPSC) derived cardiomyocytes (CMs) have been utilized in drug toxicity evaluation, drug discovery, and treating heart failure patients, showing substantial effects. Ensuring the quality, purity, and maturation of hiPSC-CMs during large-scale production is crucial. There is a growing demand for a novel method to characterize cell molecular profiles without labels and without causing damage. II.

METHODS

In this study, we employed label-free Raman microscopy to evaluate hiPSC-derived CMs. The study involved the characterization of cell molecular profiles without labels and without causing damage. The correlation between Raman spectroscopy of specific components, such as cytochrome c and myoglobin, and CM purity and maturation following hiPSC differentiation was investigated. Additionally, the validation of this correlation was performed by assessing mixtures of commercially available CMs (iCell cardiomyocytes2) and fibroblasts at various ratios as well as hiPSC-derived CMs with different efficiencies. Furthermore, CMs were matured using rapid pacing of traveling waves, and the Raman profiles of matured CMs were compared to those of immature ones. III.

RESULTS

Raman spectroscopy indicated that the cytochrome c and myoglobin showed correlation with the purity and maturation of CMs following differentiation of hiPSCs. This correlation was validated through experiments involving different CM-fibroblast mixtures and hiPSC-derived CMs with varying efficiencies. Moreover, matured CMs exhibited markedly different Raman profiles compared to immature ones, indicating the potential of Raman imaging as a tool for assessing CM maturation. IV.

CONCLUSIONS

We discovered that Raman spectroscopy of certain components, such as cytochrome c and myoglobin, correlates with the CM purity and maturation following hiPSC differentiation. The findings of this study highlight the potential of label-free Raman microscopy as a nondestructive, high-content, and time-efficient method for quality control of hiPSC-derived CMs. This approach could significantly contribute to ensuring the quality and maturity of hiPSC-CMs for various applications in drug discovery and regenerative medicine.

BDNF mimetics recover palmitic acid-induced injury in cardiomyocytes by ameliorating Akt-dependent mitochondrial impairments

Cardiac lipotoxicity is a prevalent consequence of lipid metabolism disorders occurring in cardiomyocytes, which in turn precipitates the onset of heart failure. Mimetics of brain-derived neurotrophic factor (BDNF), such as 7,8-dihydroxyflavone (DHF) and 7,8,3'-trihydroxyflavone (THF), have demonstrated significant cardioprotective effects. However, it remains unclear whether these mimetics can protect cardiomyocytes against lipotoxicity. The aim of this study was to examine the impact of DHF and THF on the lipotoxic effects induced by palmitic acid (PA), as well as the concurrent mitochondrial dysfunction. H9c2 cells were subjected to treatment with PA alone or in conjunction with DHF or THF. Various factors such as cell viability, lactate dehydrogenase (LDH) release, death ratio, and mitochondrial function including mitochondrial membrane potential (MMP), mitochondrial-derived reactive oxygen species (mito-SOX) production, and mitochondrial respiration were assessed. PA dose-dependently reduced cell viability, which was restored by DHF or THF. Additionally, both DHF and THF decreased LDH content, death ratio, and mito-SOX production, while increasing MMP and regulating mitochondrial oxidative phosphorylation in cardiomyocytes. Moreover, DHF and THF specifically activated Akt signaling. The protective effects of DHF and THF were abolished when an Akt inhibitor was used. In conclusion, BDNF mimetics attenuate PA-induced injury in cardiomyocytes by alleviating mitochondrial impairments through the activation of Akt signaling.

ROS-Suppression Nanoplatform Combined Activation of STAT3/Bcl-2 Pathway for Preventing Myocardial Infarction in Mice

Myocardial infarction (MI) is the leading cause of death worldwide. The most effective way to treat myocardial infarction is to rescue ischemic cardiomyocytes. After an ischemic event, the overproduction of reactive oxygen species (ROS) is a key driver of myocardial injury. The produced ROS affects mitochondrial function and induces apoptosis in cardiomyocytes. This was accomplished by constructing platelet-membrane-encapsulated ROS-responsive drug-releasing nanoparticles (PMN@NIC-MalNPs) to deliver malonate and niclosamide (NIC). The results revealed that PMN@NIC-MalNPs degraded and released malonate and niclosamide in a high-level ROS microenvironment, effectively reducing the oxidative stress and apoptosis rate. By enhancing basal mitochondrial oxygen consumption rate (OCR), adenosine triphosphate (ATP) production, and spare respiratory capacity (SRC) in vitro, reduced the oxidative stress levels and restored mitochondrial function. In vivo studies revealed that the PMN@NIC-MalNPs improved cardiac dysfunction, inhibited succinate dehydrogenase (SDH) activity, increased ATP production, and reduced the myocardial infarct size in myocardial infarction model mice. Further, transcriptome analysis and Western blot revealed that PMN@NIC-MalNPs prevented apoptosis by activating the expressions of the signal transducer and activator of transcription 3 (STAT3) and Bcl-2, and inhibiting the expression of Bax. Thus, this study provides a novel therapeutic solution for treating myocardial infarction and predicting the viability of an antioxidant and antiapoptotic therapeutic solution in the treatment of myocardial injury.

5-Hydroxytryptophan acts as a gap junction inhibitor to limit the spread of chemotherapy-induced cardiomyocyte injury and mitochondrial dysfunction

Anthracycline chemotherapeutics like doxorubicin (DOX) are widely used against various cancers but are accompanied by severe cardiotoxic effects that can lead to heart failure. Through whole transcriptome sequencing and pathological tissue analysis in a murine model, our study has revealed that DOX impairs collagen expression in the early phase, causing extracellular matrix anomalies that weaken the mechanical integrity of the heart. This results in ventricular wall thinning and dilation, exacerbating cardiac dysfunction. In this work, we have identified 5-hydroxytryptophan (5-HTP) as a potent inhibitor of gap junction communication. This inhibition is key to limiting the spread of DOX-induced cardiotoxicity. Treatment with 5-HTP effectively countered the adverse effects of DOX on the heart, preserving ventricular structure and ejection fraction. Moreover, 5-HTP enhanced mitochondrial respiratory function, as shown by the O2k mitochondrial function assay, by improving mitochondrial complex activity and ATP production. Importantly, the cardioprotective benefits of 5-HTP did not interfere with DOX's ability to combat cancer. These findings shed light on the cardiotoxic mechanisms of DOX and suggest that 5-HTP could be a viable strategy to prevent heart damage during chemotherapy, offering a foundation for future clinical development. This research opens the door for 5-HTP to be considered a dual-purpose agent that can protect the heart without compromising the oncological efficacy of anthracycline chemotherapy.

Anthelmintic nitazoxanide protects against experimental pulmonary fibrosis

BACKGROUND AND PURPOSE

Nitazoxanide is a therapeutic anthelmintic drug. Our previous studies found that nitazoxanide and its metabolite tizoxanide activated adenosine 5'-monophosphate-activated protein kinase (AMPK) and inhibited signal transducer and activator of transcription 3 (STAT3) signals. As AMPK activation and/or STAT3 inhibition are targets for treating pulmonary fibrosis, we hypothesized that nitazoxanide would be effective in experimental pulmonary fibrosis.

EXPERIMENTAL APPROACH

The mitochondrial oxygen consumption rate of cells was measured by using the high-resolution respirometry system Oxygraph-2K. The mitochondrial membrane potential of cells was evaluated by tetramethyl rhodamine methyl ester (TMRM) staining. The target protein levels were measured by using western blotting. The mice pulmonary fibrosis model was established through intratracheal instillation of bleomycin. The examination of the lung tissues changes were carried out using haematoxylin and eosin (H&E), and Masson staining.

KEY RESULTS

Nitazoxanide and tizoxanide activated AMPK and inhibited STAT3 signalling in human lung fibroblast cells (MRC-5 cells). Nitazoxanide and tizoxanide inhibited transforming growth factor-β1 (TGF-β1)-induced proliferation and migration of MRC-5 cells, collagen-I and α-smooth muscle cell actin (α-SMA) expression, and collagen-I secretion from MRC-5 cells. Nitazoxanide and tizoxanide inhibited epithelial-mesenchymal transition (EMT) and inhibited TGF-β1-induced Smad2/3 activation in mouse lung epithelial cells (MLE-12 cells). Oral administration of nitazoxanide reduced the bleomycin-induced mice pulmonary fibrosis and, in the established bleomycin-induced mice, pulmonary fibrosis. Delayed nitazoxanide treatment attenuated the fibrosis progression.

CONCLUSIONS AND IMPLICATIONS

Nitazoxanide improves the bleomycin-induced pulmonary fibrosis in mice, suggesting a potential application of nitazoxanide for pulmonary fibrosis treatment in the clinic.

7,8,3'-Trihydroxyflavone prevents doxorubicin-induced cardiotoxicity and mitochondrial dysfunction via activating Akt signaling pathway in H9c2 cells

Clinical application of the widely used chemotherapeutic agent, doxorubicin (DOX), is limited by its cardiotoxicity. Mitochondrial dysfunction has been revealed as a crucial factor in DOX-induced cardiotoxicity. 7,8,3'-Trihydroxyflavone (THF) is a mimetic brain-derived neurotrophic factor with neuroprotective effects. However, the potential effects of THF on DOX-induced cardiomyocyte damage and mitochondrial disorders remain unclear. H9c2 cardiomyoblasts were exposed to DOX and/or THF at different concentrations. Cardiomyocyte injury was evaluated using lactate dehydrogenase (LDH) assay and Live/Dead cytotoxicity kit. Meanwhile, mitochondrial membrane potential (MMP), morphology, mitochondrial reactive oxygen species (mito-ROS) production, and the oxygen consumption rate of cardiomyocytes were measured. The protein levels of key mitochondria-related factors such as adenosine monophosphate-activated protein kinase (AMPK), mitofusin 2 (Mfn2), dynamin-related protein 1 (Drp1), and optic atrophy protein 1 (OPA1) were examined. We found that THF reduced LDH content and death ratio of DOX-treated cardiomyocytes in a concentration-dependent manner, while increasing MMP without significantly affecting the routine and maximum capacity of mitochondrial respiration. Mechanistically, THF increased the activity of Akt and protein levels of Mfn2 and heme oxygenase 1 (HO-1). Moreover, inhibition of Akt reversed the protective role of THF, increased mito-ROS levels, and repressed Mfn2 and HO-1 expression. Therefore, we conclude, THF relieves DOX-induced cardiotoxicity and improves mitochondrial function by activating Akt-mediated Mfn2 and HO-1 pathways. This finding provides promising therapeutic insights for DOX-induced cardiac dysfunction.

Puerarin Inhibits NLRP3-Caspase-1-GSDMD-Mediated Pyroptosis via P2X7 Receptor in Cardiomyocytes and Macrophages

Diabetic cardiomyopathy (DCM) is a critical complication of long-term chronic diabetes mellitus, and it is characterized by myocardial fibrosis and myocardial hypertrophy. Previous studies have shown that the pyroptosis pathway was significantly activated in DCM and may be related to the P2X7 receptor. However, the role of the P2X7 receptor in the development of DCM with pyroptosis is still unclear. In this study, we aimed to explore the mechanism of puerarin and whether the P2X7 receptor can be used as a new target for puerarin in the treatment of DCM. We adopted systematic pharmacology and bioinformatic approaches to identify the potential targets of puerarin for treating DCM. Additionally, we employed D-glucose-induced H9C2 rat cardiomyocytes and lipopolysaccharide-treated RAW264.7 mouse mononuclear macrophages as the in vitro model on DCM research, which is close to the pathological conditions. The mRNA expression of cytokines in H9C2 cells and RAW264.7 macrophages was detected. The protein expressions of NLRP3, N-GSDMD, cleaved-caspase-1, and the P2X7 receptor were investigated with Western blot analysis. Furthermore, molecular docking of puerarin and the P2X7 receptor was conducted based on CDOCKER. A total of 348 puerarin targets and 4556 diabetic cardiomyopathy targets were detected, of which 218 were cross targets. We demonstrated that puerarin is effective in enhancing cardiomyocyte viability and improving mitochondrial function. In addition, puerarin is efficacious in blocking NLRP3-Caspase-1-GSDMD-mediated pyroptosis in H9C2 cells and RAW264.7 cells, alleviating cellular inflammation. On the other hand, similar experimental results were obtained by intervention with the P2X7 receptor antagonist A740003, suggesting that the protective effects of puerarin are related to the P2X7 receptor. The molecular docking results indicated key binding activity between the P2X7 receptor and puerarin. These findings indicate that puerarin effectively regulated the pyroptosis signaling pathway during DCM, and this regulation was associated with the P2X7 receptor.

Piezo1 channel activation stimulates ATP production through enhancing mitochondrial respiration and glycolysis in vascular endothelial cells

BACKGROUND AND PURPOSE

Piezo1 channels are mechanosensitive cationic channels that are activated by mechanical stretch or shear stress. Endothelial Piezo1 activation by shear stress caused by blood flow induces ATP release from endothelial cells; however, the link between shear stress and endothelial ATP production is unclear.

EXPERIMENTAL APPROACH

The mitochondrial respiratory function of cells was measured by using high-resolution respirometry system Oxygraph-2k. The intracellular Ca2+ concentration was evaluated by using Fluo-4/AM and mitochondrial Ca2+ concentration by Rhod-2/AM.

KEY RESULTS

The specific Piezo1 channel activator Yoda1 or its analogue Dooku1 increased [Ca2+ ]i in human umbilical vein endothelial cells (HUVECs), and both Yoda1 and Dooku1 increased mitochondrial oxygen consumption rates (OCRs) and mitochondrial ATP production in HUVECs and primary cultured rat aortic endothelial cells (RAECs). Knockdown of Piezo1 inhibited Yoda1- and Dooku1-induced increases of mitochondrial OCRs and mitochondrial ATP production in HUVECs. The shear stress mimetics, Yoda1 and Dooku1, and the Piezo1 knock-down technique also demonstrated that Piezo1 activation increased glycolysis in HUVECs. Chelating extracellular Ca2+ with EGTA or chelating cytosolic Ca2+ with BAPTA-AM did not affect Yoda1- and Dooku1-induced increases of mitochondrial OCRs and ATP production, but chelating cytosolic Ca2+ inhibited Yoda1- and Dooku1-induced increase of glycolysis. Confocal microscopy showed that Piezo1 channels are present in mitochondria of endothelial cells, and Yoda1 and Dooku1 increased mitochondrial Ca2+ in endothelial cells.

CONCLUSION AND IMPLICATIONS

Piezo1 channel activation stimulates ATP production through enhancing mitochondrial respiration and glycolysis in vascular endothelial cells, suggesting a novel role of Piezo1 channel in endothelial ATP production.

BDNF mimetic 7,8-dihydroxyflavone rescues rotenone-induced cytotoxicity in cardiomyocytes by ameliorating mitochondrial dysfunction

The relationship between mitochondrial dysfunction and cardiovascular disease pathogenesis is well recognized. 7,8-Dihydroxyflavone (7,8-DHF), a mimetic of brain-derived neurotrophic factor, inhibits mitochondrial impairments and improves cardiac function. However, the regulatory role of 7,8-DHF in the mitochondrial function of cardiomyocytes is not fully understood. To investigate the potential mito-protective effects of 7,8-DHF in cardiomyocytes, we treated H9c2 or HL-1 cells with the mitochondrial respiratory complex I inhibitor rotenone (Rot) as an in vitro model of mitochondrial dysfunction. We found that 7,8-DHF effectively eliminated various concentrations of Rot-induced cell death and reduced lactate dehydrogenase release. 7,8-DHF significantly improved mitochondrial membrane potential and inhibited mitochondrial reactive oxygen species. Moreover, 7,8-DHF decreased routine and leak respiration, restored protein levels of mitochondrial complex I-IV, and increased ATP production in Rot-treated H9c2 cells. The protective role of 7,8-DHF in Rot-induced damage was validated in HL-1 cells. Nuclear phosphorylation protein expression of signal transducer and activator of transcription 3 (STAT3) was significantly increased by 7,8-DHF. The present study suggests that 7,8-DHF rescues Rot-induced cytotoxicity by inhibiting mitochondrial dysfunction and promoting nuclear translocation of p-STAT3 in cardiomyocytes, thus nominating 7,8-DHF as a new pharmacological candidate agent against mitochondrial dysfunction in cardiac diseases.

S100a8/a9 contributes to sepsis-induced cardiomyopathy by activating ERK1/2-Drp1-mediated mitochondrial fission and respiratory dysfunction

Sepsis-induced cardiomyopathy (SIC) is the main complication and a leading cause of death in intensive care units. S100a8/a9 is a calcium-binding protein that participates in various inflammatory diseases; however, its role in sepsis-induced cardiomyopathy and the underlying mechanism remains to be explored. Here, septic cardiomyopathy was induced with cecal ligation and puncture (CLP) in S100a9-knockout (KO) mice lacking the heterodimer S100a8/a9 or wild-type (WT) mice administered with an S100a9-specific inhibitor Paquinimod (Paq), which prevents the binding of S100a9 toTLR4. Our results showed that S100a8/a9 expression in the heart peaked 24 h following the CLP operation, declined at 48 h and returned to baseline at 72 h. Loss of S100a9 by knockout in mice protected against CLP-induced mortality, cardiac dysfunction, myocyte apoptosis, recruitment of Mac-2⁺ macrophages, superoxide production, and the expression of pro-inflammatory cytokines genes compared with WT mice. Moreover, S100a9-KO significantly attenuated CLP-induced activation of the ERK1/2-Drp1 (S616) pathway, excessive mitochondrial fission, and mitochondrial respiration dysfunction. In contrast, activation of ERK1/2 with its agonist tBHQ reversed the inhibitory effects of S100a9-knockout on CLP-induced cardiomyopathy and mitochondrial dysfunction. Finally, administration of Paq to WT mice markedly prevented the CLP-induced cardiomyopathy mitochondrial fission and dysfunction compared with vehicle control. In summary, our data reveal, for the first time, that S100a8/a9 plays a critical role in mediating SIC, presumably by activating TLR4-ERK1/2-Drp1-dependent mitochondrial fission and dysfunction and highlight that blockage of S100a8/a9 may be a promising therapeutic strategy to prevent SIC in patients with sepsis.

Role of Mitophagy in Myocardial Ischemia/Reperfusion Injury and Chinese Medicine Treatment

Mitophagy is one of the important targets for the prevention and treatment of myocardial ischemia/reperfusion injury (MIRI). Moderate mitophagy can remove damaged mitochondria, inhibit excessive reactive oxygen species accumulation, and protect mitochondria from damage. However, excessive enhancement of mitophagy greatly reduces adenosine triphosphate production and energy supply for cell survival, and aggravates cell death. How dysfunctional mitochondria are selectively recognized and engulfed is related to the interaction of adaptors on the mitochondrial membrane, which mainly include phosphatase and tensin homolog deleted on chromosome ten (PTEN)-induced kinase 1/Parkin, hypoxia-inducible factor-1 α/Bcl-2 and adenovirus e1b19k Da interacting protein 3, FUN-14 domain containing protein 1 receptor-mediated mitophagy pathway and so on. In this review, the authors briefly summarize the main pathways currently studied on mitophagy and the relationship between mitophagy and MIRI, and incorporate and analyze research data on prevention and treatment of MIRI with Chinese medicine, thereby provide relevant theoretical basis and treatment ideas for clinical prevention of MIRI.

Repurposing nitazoxanide as a novel anti-atherosclerotic drug based on mitochondrial uncoupling mechanisms

BACKGROUND AND PURPOSE

The anthelmintic drug nitazoxanide has a mitochondrial uncoupling effect. Mitochondrial uncouplers have been proven to inhibit smooth muscle cell proliferation and migration, inhibit NLRP3 inflammasome activation of macrophages and improve dyslipidaemia. Therefore, we aimed to demonstrate that nitazoxanide would protect against atherosclerosis.

EXPERIMENTAL APPROACH

The mitochondrial oxygen consumption of cells was measured by using the high-resolution respirometry system, Oxygraph-2K. The proliferation and migration of A10 cells were measured by using Edu immunofluorescence staining, wound-induced migration and the Boyden chamber assay. Protein levels were measured by using the western blot technique. ApoE (-/-) mice were fed with a Western diet to establish an atherosclerotic model in vivo.

KEY RESULTS

The in vitro experiments showed that nitazoxanide and tizoxanide had a mitochondrial uncoupling effect and activated cellular AMPK. Nitazoxanide and tizoxanide inhibited serum- and PDGF-induced proliferation and migration of A10 cells. Nitazoxanide and tizoxanide inhibited NLRP3 inflammasome activation in RAW264.7 macrophages, the mechanism by which involved the AMPK/IκBα/NF-κB pathway. Nitazoxanide and tizoxanide also induced autophagy in A10 cells and RAW264.7 macrophages. The in vivo experiments demonstrated that oral administration of nitazoxanide reduced the increase in serum IL-1β and IL-6 levels and suppressed atherosclerosis in Western diet-fed ApoE (-/-) mice.

CONCLUSION AND IMPLICATIONS

Nitazoxanide inhibits the formation of atherosclerotic plaques in ApoE (-/-) mice fed on a Western diet. In view of nitazoxanide being an antiprotozoal drug already approved by the FDA, we propose it as a novel anti-atherosclerotic drug with clinical translational potential.

Class I HDAC modulates angiotensin II-induced fibroblast migration and mitochondrial overactivity

BACKGROUND

Inhibition of histone deacetylases (HDACs) attenuates cardiac fibrosis. In this study, we evaluated whether the inhibition of class I HDACs can attenuate angiotensin II (ANG II)-induced fibrogenesis and mitochondrial malfunction through its effects on reactive oxygen species (ROS) and calcium dysregulation in human cardiac fibroblasts (CFs).

METHODS

Seahorse XF24 extracellular flux analyser, fluorescence staining, Western blotting, HDAC activity assays and Transwell migration assay were used to study mitochondrial respiration, adenosine triphosphate (ATP) production, mitochondrial calcium uptake and ROS, HDAC expression and activity and fibroblast activity in CFs without (control) or with ANG II (100 nM) and/or MS-275 (HDAC class 1 inhibitor, 10 μM) for 24 h.

RESULTS

ANG II increased HDAC activity without changing protein expression in CFs. Compared with controls, ANG II-treated CFs had greater migration activity, higher ATP production, maximal respiration and spare capacity with higher mitochondrial Ca²⁺ uptake and ROS generation, which was attenuated by the administration of MS-275. ANG II activated CFs by increasing mitochondrial calcium content and ATP production, which may be caused by increased HDAC activity. Inhibition of HDAC1 attenuated the effects of ANG II by reducing mitochondrial ROS generation and calcium overload.

CONCLUSIONS

Modulating mitochondrial function by regulation of HDAC may be a novel strategy for controlling CF activity.

Anthelmintics nitazoxanide protects against experimental hyperlipidemia and hepatic steatosis in hamsters and mice

Lipid metabolism disorders contribute to hyperlipidemia and hepatic steatosis. It is ideal to develop drugs simultaneous improving both hyperlipidemia and hepatic steatosis. Nitazoxanide is an FDA-approved oral antiprotozoal drug with excellent pharmacokinetic and safety profile. We found that nitazoxanide and its metabolite tizoxanide induced mild mitochondrial uncoupling and subsequently activated AMPK in HepG2 cells. Gavage administration of nitazoxanide inhibited high-fat diet (HFD)-induced increases of liver weight, blood and liver lipids, and ameliorated HFD-induced renal lipid accumulation in hamsters. Nitazoxanide significantly improved HFD-induced histopathologic changes of hamster livers. In the hamsters with pre-existing hyperlipidemia and hepatic steatosis, nitazoxanide also showed therapeutic effect. Gavage administration of nitazoxanide improved HFD-induced hepatic steatosis in C57BL/6J mice and western diet (WD)-induced hepatic steatosis in Apoe -/- mice. The present study suggests that repurposing nitazoxanide as a drug for hyperlipidemia and hepatic steatosis treatment is promising.

Intrinsic cardiac adrenergic cells contribute to LPS-induced myocardial dysfunction

Intrinsic cardiac adrenergic (ICA) cells regulate both developing and adult cardiac physiological and pathological processes. However, the role of ICA cells in septic cardiomyopathy is unknown. Here we show that norepinephrine (NE) secretion from ICA cells is increased through activation of Toll-like receptor 4 (TLR4) to aggravate myocardial TNF-α production and dysfunction by lipopolysaccharide (LPS). In ICA cells, LPS activated TLR4-MyD88/TRIF-AP-1 signaling that promoted NE biosynthesis through expression of tyrosine hydroxylase, but did not trigger TNF-α production due to impairment of p65 translocation. In a co-culture consisting of LPS-treated ICA cells and cardiomyocytes, the upregulation and secretion of NE from ICA cells activated cardiomyocyte β₁-adrenergic receptor driving Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) to crosstalk with NF-κB and mitogen-activated protein kinase pathways. Importantly, blockade of ICA cell-derived NE prevented LPS-induced myocardial dysfunction. Our findings suggest that ICA cells may be a potential therapeutic target for septic cardiomyopathy.

Anthelmintic niclosamide attenuates pressure-overload induced heart failure in mice

The heart is a high energy demand organ and enhancing mitochondrial function is proposed as the next-generation therapeutics for heart failure. Our previous study found that anthelmintic drug niclosamide enhanced mitochondrial respiration and increased adenosine triphosphate (ATP) production in cardiomyocytes, therefore, this study aimed to determine the effect of niclosamide on heart failure in mice and the potential molecular mechanisms. The heart failure model was induced by transverse aortic constriction (TAC) in mice. Oral administration of niclosamide improved TAC-induced cardiac hypertrophy, cardiac fibrosis, and cardiac dysfunction in mice. Oral administration of niclosamide reduced TAC-induced increase of serum IL-6 in heart failure mice. In vitro, niclosamide within 0.1 μM increased mitochondrial respiration and ATP production in mice heart tissues. At the concentrations more than 0.1 μM, niclosamide reduced the increased interleukin- 6 (IL-6) mRNA expression in lipopolysaccharide (LPS)-stimulated RAW264.7 and THP-1 derived macrophages. In cultured primary cardiomyocytes and cardiac fibroblasts, niclosamide (more than 0.1 μM) suppressed IL-6- and phenylephrine-induced cardiomyocyte hypertrophy, and inhibited collagen secretion from cardiac fibroblasts. In conclusion, niclosamide attenuates heart failure in mice and the underlying mechanisms include enhancing mitochondrial respiration of cardiomyocytes, inhibiting collagen secretion from cardiac fibroblasts, and reducing the elevated serum inflammatory mediator IL-6. The present study suggests that niclosamide might be therapeutic for heart failure.

Punicalagin Protects Against Diabetic Cardiomyopathy by Promoting Opa1-Mediated Mitochondrial Fusion via Regulating PTP1B-Stat3 Pathway

Aims: This study aims to explore the efficacy of punicalagin (PG) on diabetic cardiomyopathy (DCM), with a specific focus on the mechanisms underlying the effects of PG on mitochondrial fusion/fission dynamics. Results: Cardiac structural and functional abnormalities were ameliorated in diabetic rats receiving PG administration as evidenced by increased ejection fraction, and attenuated myocardial fibrosis and hypertrophy. PG enhanced mitochondrial function and inhibited mitochondria-derived oxidative stress by promoting Opa1-mediated mitochondrial fusion. The benefits of PG could be abrogated by knockdown of Opa1 in vivo and in vitro. Inhibitor screening and chromatin immunoprecipitation analysis showed that Stat3 directly regulated the transcriptional expression of Opa1 by binding to its promoter and was responsible for PG-induced Opa1-mediated mitochondrial fusion. Moreover, pharmmapper screening and molecular docking studies revealed that PG embedded into the activity pocket of PTP1B and inhibited the activity of PTP1B. Overexpression of PTP1B blocked the promoting effect of PG on Stat3 phosphorylation and Opa1-mediated mitochondrial fusion, whereas knockdown of PTP1B mimicked the benefits of PG in high-glucose-treated cardiomyocytes. Innovation: Our study is the first to identify PG as a novel mitochondrial fusion promoter against hyperglycemia-induced mitochondrial oxidative injury and cardiomyopathy by upregulating Opa1 via regulating PTP1B-Stat3 pathway. Conclusion: PG protects against DCM by promoting Opa1-mediated mitochondrial fusion, a process in which PG interacts with PTP1B and inhibits its activity, which in turn increases Stat3 phosphorylation and then enhances the transcriptional expression of Opa1. These results suggest that PG might be a promising new therapeutic approach against diabetic cardiac complication. Antioxid. Redox Signal. 35, 618-641.

Oxidative stress pathogenically remodels the cardiac myocyte cytoskeleton via structural alterations to the microtubule lattice

In the failing heart, the cardiac myocyte microtubule network is remodeled, which contributes to cellular contractile failure and patient death. However, the origins of this deleterious cytoskeletal reorganization are unknown. We now find that oxidative stress, a condition characteristic of heart failure, leads to cysteine oxidation of microtubules. Our electron and fluorescence microscopy experiments revealed regions of structural damage within the microtubule lattice that occurred at locations of oxidized tubulin. The incorporation of GTP-tubulin into these damaged, oxidized regions led to stabilized "hot spots" within the microtubule lattice, which suppressed the shortening of dynamic microtubules. Thus, oxidative stress may act inside of cardiac myocytes to facilitate a pathogenic shift from a sparse microtubule network into a dense, aligned network. Our results demonstrate how a disease condition characterized by oxidative stress can trigger a molecular oxidation event, which likely contributes to a toxic cellular-scale transformation of the cardiac myocyte microtubule network.

Novel Insights and Current Evidence for Mechanisms of Atherosclerosis: Mitochondrial Dynamics as a Potential Therapeutic Target

Cardiovascular disease (CVD) is the main cause of death worldwide. Atherosclerosis is the underlying pathological basis of CVD. Mitochondrial homeostasis is maintained through the dynamic processes of fusion and fission. Mitochondria are involved in many cellular processes, such as steroid biosynthesis, calcium homeostasis, immune cell activation, redox signaling, apoptosis, and inflammation, among others. Under stress conditions, mitochondrial dynamics, mitochondrial cristae remodeling, and mitochondrial ROS (mitoROS) production increase, mitochondrial membrane potential (MMP) decreases, calcium homeostasis is imbalanced, and mitochondrial permeability transition pore open (mPTP) and release of mitochondrial DNA (mtDNA) are activated. mtDNA recognized by TLR9 can lead to NF-κB pathway activation and pro-inflammatory factor expression. At the same time, TLR9 can also activate NLRP3 inflammasomes and release interleukin, an event that eventually leads to tissue damage and inflammatory responses. In addition, mitochondrial dysfunction may amplify the activation of NLRP3 through the production of mitochondrial ROS, which together aggravate accumulating mitochondrial damage. In addition, mtDNA defects or gene mutation can lead to mitochondrial oxidative stress. Finally, obesity, diabetes, hypertension and aging are risk factors for the progression of CVD, which are closely related to mitochondrial dynamics. Mitochondrial dynamics may represent a new target in the treatment of atherosclerosis. Antioxidants, mitochondrial inhibitors, and various new therapies to correct mitochondrial dysfunction represent a few directions for future research on therapeutic intervention and amelioration of atherosclerosis.

CoenzymeQ in cellular redox regulation and clinical heart failure

Coenzyme Q (CoQ) is ubiquitously embedded in lipid bilayers of various cellular organelles. As a redox cycler, CoQ shuttles electrons between mitochondrial complexes and extramitochondrial reductases and oxidases. In this way, CoQ is crucial for maintaining the mitochondrial function, ATP synthesis, and redox homeostasis. Cardiomyocytes have a high metabolic rate and rely heavily on mitochondria to provide energy. CoQ levels, in both plasma and the heart, correlate with heart failure in patients, indicating that CoQ is critical for cardiac function. Moreover, CoQ supplementation in clinics showed promising results for treating heart failure. This review provides a comprehensive view of CoQ metabolism and its interaction with redox enzymes and reactive species. We summarize the clinical trials and applications of CoQ in heart failure and discuss the caveats and future directions to improve CoQ therapeutics.

Constitutive activation of ERK1/2 signaling protects against myocardial ischemia via inhibition of mitochondrial fragmentation in the aging heart

Background

Studies have shown that the ability of the myocardium to tolerate ischemia becomes significantly compromised with age. During ischemia, several endogenous protective signals are activated to protect the heart from injury, among which extracellular-signal regulated kinase (ERK) 1/2 signaling has been established as playing a pivotal role. However, in aging hearts, the activation of ERK1/2 is compromised. Mitogen-activated protein kinase/ERK kinase (MEK) is a major regulator of ERK1/2 signaling. In the present study, we investigated whether transduction of CaMEK, a constitutively activated MEK, using adeno-associated virus serotype 9 (AAV9) could protect the aging heart against ischemia.

Methods

Myocardial ischemia models were established in aging mice and senescent cardiomyocytes, and AAV9-mediated delivery of CaMEK was applied. Echocardiography, fluorescent staining, transmission electron microscopy, flow cytometry, and immunoblotting were used to explore the effects of CaMEK and their underlying mechanism.

Results

AAV9-CaMEK activated ERK1/2 signaling and exerted cardioprotective effects against ischemia in aging hearts. Specifically, CaMEK transduction decreased dynamin-related protein-1 (Drp1) expression and phosphorylation at serine 616, resulting in improved mitochondrial morphology and function in aging ischemic hearts. Furthermore, CaMEK transduction exerted similar protective effects in senescent cardiomyocytes under hypoxia. Meanwhile, with the inhibition of ERK1/2 signaling in senescent cardiomyocytes under hypoxia, the opposite effects were observed, including an increase in mitochondrial fragmentation and aggravation of mitochondrial dysfunction and cell apoptosis.

Conclusions

Our results suggested that AAV9-CaMEK alleviated ischemia-induced myocardium injury in the aging heart, at least in part, through inhibition of mitochondrial fragmentation. Therefore, AAV9-CaMEK is a potential intervention for prevention of ischemia-induced injury of the aging myocardium.

Ketogenic diets inhibit mitochondrial biogenesis and induce cardiac fibrosis

In addition to their use in relieving the symptoms of various diseases, ketogenic diets (KDs) have also been adopted by healthy individuals to prevent being overweight. Herein, we reported that prolonged KD exposure induced cardiac fibrosis. In rats, KD or frequent deep fasting decreased mitochondrial biogenesis, reduced cell respiration, and increased cardiomyocyte apoptosis and cardiac fibrosis. Mechanistically, increased levels of the ketone body β-hydroxybutyrate (β-OHB), an HDAC2 inhibitor, promoted histone acetylation of the Sirt7 promoter and activated Sirt7 transcription. This in turn inhibited the transcription of mitochondrial ribosome-encoding genes and mitochondrial biogenesis, leading to cardiomyocyte apoptosis and cardiac fibrosis. Exogenous β-OHB administration mimicked the effects of a KD in rats. Notably, increased β-OHB levels and SIRT7 expression, decreased mitochondrial biogenesis, and increased cardiac fibrosis were detected in human atrial fibrillation heart tissues. Our results highlighted the unknown detrimental effects of KDs and provided insights into strategies for preventing cardiac fibrosis in patients for whom KDs are medically necessary.

RAS inhibition in resident fibroblast biology

Angiotensin II (Ang II) is a primary mediator of profibrotic signaling in the heart and more specifically, the cardiac fibroblast. Ang II-mediated cardiomyocyte hypertrophy in combination with cardiac fibroblast proliferation, activation, and extracellular matrix production compromise cardiac function and increase mortality in humans. Profibrotic actions of Ang II are mediated by increasing production of fibrogenic mediators (e.g. transforming growth factor beta, scleraxis, osteopontin, and periostin), recruitment of immune cells, and via increased reactive oxygen species generation. Drugs that inhibit Ang II production or action, collectively referred to as renin angiotensin system (RAS) inhibitors, are first line therapeutics for heart failure. Moreover, transient RAS inhibition has been found to persistently alter hypertensive cardiac fibroblast responses to injury providing a useful tool to identify novel therapeutic targets. This review summarizes the profibrotic actions of Ang II and the known impact of RAS inhibition on cardiac fibroblast phenotype and cardiac remodeling.

Mitochondrial quality control mechanisms as molecular targets in cardiac ischemiareperfusion injury

Mitochondrial damage is a critical contributor to cardiac ischemia/reperfusion (I/R) injury. Mitochondrial quality control (MQC) mechanisms, a series of adaptive responses that preserve mitochondrial structure and function, ensure cardiomyocyte survival and cardiac function after I/R injury. MQC includes mitochondrial fission, mitochondrial fusion, mitophagy and mitochondria-dependent cell death. The interplay among these responses is linked to pathological changes such as redox imbalance, calcium overload, energy metabolism disorder, signal transduction arrest, the mitochondrial unfolded protein response and endoplasmic reticulum stress. Excessive mitochondrial fission is an early marker of mitochondrial damage and cardiomyocyte death. Reduced mitochondrial fusion has been observed in stressed cardiomyocytes and correlates with mitochondrial dysfunction and cardiac depression. Mitophagy allows autophagosomes to selectively degrade poorly structured mitochondria, thus maintaining mitochondrial network fitness. Nevertheless, abnormal mitophagy is maladaptive and has been linked to cell death. Although mitochondria serve as the fuel source of the heart by continuously producing adenosine triphosphate, they also stimulate cardiomyocyte death by inducing apoptosis or necroptosis in the reperfused myocardium. Therefore, defects in MQC may determine the fate of cardiomyocytes. In this review, we summarize the regulatory mechanisms and pathological effects of MQC in myocardial I/R injury, highlighting potential targets for the clinical management of reperfusion.

Effects of Standardized Green Tea Extract and Its Main Component, EGCG, on Mitochondrial Function and Contractile Performance of Healthy Rat Cardiomyocytes

We recently showed that the long-term in vivo administration of green tea catechin extract (GTE) resulted in hyperdynamic cardiomyocyte contractility. The present study investigates the mechanisms underlying GTE action in comparison to its major component, epigallocatechin-3-gallate (EGCG), given at the equivalent amount that would be in the entirety of GTE. Twenty-six male Wistar rats were given 40 mL/day of a tap water solution with either standardized GTE or pure EGCG for 4 weeks. Cardiomyocytes were then isolated for the study. Cellular bioenergetics was found to be significantly improved in both GTE- and EGCG-fed rats compared to that in controls as shown by measuring the maximal mitochondrial respiration rate and the cellular ATP level. Notably, the improvement of mitochondrial function was associated with increased levels of oxidative phosphorylation complexes, whereas the cellular mitochondrial mass was unchanged. However, only the GTE supplement improved cardiomyocyte mechanics and intracellular calcium dynamics, by lowering the expression of total phospholamban (PLB), which led to an increase of both the phosphorylated-PLB/PLB and the sarco-endoplasmic reticulum calcium ATPase/PLB ratios. Our findings suggest that GTE might be a valuable adjuvant tool for counteracting the occurrence and/or the progression of cardiomyopathies in which mitochondrial dysfunction and alteration of intracellular calcium dynamics constitute early pathogenic factors.

Resveratrol Improves Bnip3-Related Mitophagy and Attenuates High-Fat-Induced Endothelial Dysfunction

Statin treatment reduces cardiovascular risk. However, individuals with well-controlled low-density lipoprotein (LDL) levels may remain at increased risk owing to persistent high triglycerides and low high-density lipoprotein cholesterol. Because resveratrol promotes glucose metabolism and mitigates cardiovascular disorders, we explored its mechanism of protective action on high-fat-induced endothelial dysfunction. Human umbilical venous endothelial cells were treated with oxidized LDL (ox-LDL) in vitro. Endothelial function, cell survival, proliferation, migration, and oxidative stress were analyzed through western blots, quantitative polymerase chain reaction, ELISA, and immunofluorescence. ox-LDL induced endothelial cell apoptosis, proliferation arrest, and mobilization inhibition, all of which resveratrol reduced. ox-LDL suppressed the activities of mitochondrial respiration complex I and III and reduced levels of intracellular antioxidative enzymes, resulting in reactive oxygen species overproduction and mitochondrial dysfunction. Resveratrol treatment upregulated Bnip3-related mitophagy and prevented ox-LDL-mediated mitochondrial respiration complexes inactivation, sustaining mitochondrial membrane potential and favoring endothelial cell survival. We found that resveratrol enhanced Bnip3 transcription through hypoxia-inducible factor 1 (HIF1) and 5' AMP-activated protein kinase (AMPK). Inhibition of AMPK and HIF1 abolished resveratrol-mediated protection of mitochondrial redox balance and endothelial viability. Together, these data demonstrate resveratrol reduces hyperlipemia-related endothelial damage by preserving mitochondrial homeostasis.

ROCK1 knockdown inhibits non-small-cell lung cancer progression by activating the LATS2-JNK signaling pathway

Rho-associated kinase 1 (ROCK1) regulates tumor metastasis by maintaining cellular cytoskeleton homeostasis. However, the precise role of ROCK1 in non-small-cell lung cancer (NSCLC) apoptosis remains largely unknown. In this study, we examined the function of ROCK1 in NSCLS survival using RNA interference-mediated knockdown. Our results showed that ROCK1 knockdown reduced A549 lung cancer cell viability in vitro. It also inhibited A549 cell migration and proliferation. Transfection of ROCK1 siRNA was associated with increased expression of large tumor suppressor kinase 2 (LATS2) and c-Jun N-terminal kinase (JNK). Moreover, ROCK1 knockdown-induced A549 cell apoptosis and inhibition of proliferation were suppressed by LATS2 knockdown or JNK inactivation, suggesting that ROCK1 deficiency triggers NSCLC apoptosis in a LATS2-JNK pathway-dependent manner. Functional analysis further demonstrated that ROCK1 knockdown dysregulated mitochondrial dynamics and inhibited mitochondrial biogenesis. This effect too was reversed by LATS2 knockdown or JNK inactivation. We have thus identified a potential pathway by which ROCK1 downregulation triggers apoptosis in NSCLC by inducing LATS2-JNK-dependent mitochondrial damage.

Exenatide inhibits NF-κB and attenuates ER stress in diabetic cardiomyocyte models

Exenatide is used to treat patients with type-2 diabetes and it also exerts cardioprotective effects. Here, we tested whether Exenatide attenuates hyperglycemia-related cardiomyocyte damage by inhibiting endoplasmic reticulum (ER) stress and the NF-κB signaling pathway. Our results demonstrated that hyperglycemia activates the NF-κB signaling pathway, eliciting ER stress. We also observed cardiomyocyte contractile dysfunction, inflammation, and cell apoptosis induced by hyperglycemia. Exenatide treatment inhibited inflammation, improved cardiomyocyte contractile function, and rescued cardiomyocyte viability. Notably, re-activation of the NF-κB signaling pathway abolished Exenatide's protective effects on hyperglycemic cardiomyocytes. Taken together, our results demonstrate that Exenatide directly reduces hyperglycemia-induced cardiomyocyte damage by inhibiting ER stress and inactivating the NF-κB signaling pathway.

Cardioprotective Role of Melatonin in Acute Myocardial Infarction

Melatonin is a pleiotropic, indole secreted, and synthesized by the human pineal gland. Melatonin has biological effects including anti-apoptosis, protecting mitochondria, anti-oxidation, anti-inflammation, and stimulating target cells to secrete cytokines. Its protective effect on cardiomyocytes in acute myocardial infarction (AMI) has caused widespread interest in the actions of this molecule. The effects of melatonin against oxidative stress, promoting autophagic repair of cells, regulating immune and inflammatory responses, enhancing mitochondrial function, and relieving endoplasmic reticulum stress, play crucial roles in protecting cardiomyocytes from infarction. Mitochondrial apoptosis and dysfunction are common occurrence in cardiomyocyte injury after myocardial infarction. This review focuses on the targets of melatonin in protecting cardiomyocytes in AMI, the main molecular signaling pathways that melatonin influences in its endogenous protective role in myocardial infarction, and the developmental prospect of melatonin in myocardial infarction treatment.

Exendin-4 attenuates inflammation-mediated endothelial cell apoptosis in varicose veins through inhibiting the MAPK-JNK signaling pathway

Context: Inflammation response has been found to be associated with endothelial cell death in the progression of varicose veins. Exendin-4 is able to reduce inflammation and thus attenuate cell apoptosis.Aim: The aim of our study is to explore the influence of Exendin-4 on LPS-treated endothelial cells.Methods: Cells were treated with LPS. Exendin-4 was added into the medium of cells. Western blots, qPCR, and ELISA were used to analyze the role of Exendin-4 in LPS-mediated cell death.Results: We found that LPS treatment caused significantly cell death. Whereas this trend could be attenuated by Exendin-4. After treatment with Exendin-4, inflammation factors upregulation and oxidative stress activation were significantly repressed, an effect that was followed by a drop in the levels of glucose production and lactic acid generation. At the molecular levels, Exendin-4 treatment inhibited the activity of MAPK-JNK signaling pathway in the presence of LPS treatment.Conclusions: LPS causes cell apoptosis through inducing inflammation response, oxidative stress and energy stress. Exendin-4 treatment enhances cell survival, reduces inflammation, and improves energy stress through inhibiting the MAPK-JNK signaling pathway.

MST1-Hippo pathway regulates inflammation response following myocardial infarction through inhibiting HO-1 signaling pathway

Context: Mammalian STE20-like protein kinases 1 (MST1) has been found to be associated with cardiomyocyte damage following acute myocardial infarction.Aim: The aim of our study is to explore the influence of MST1 in inflammation response following myocardial infarction.Methods: Cardiomyocyte cell line was used in vitro with hypoxia treatment to establish myocardial infarction model. ELISA, qPCR, Western blots, and siRNA technology were used to analyze the role of MST1 in inflammation response following myocardial infarction.Results: The transcription and expression of MST1 was significantly elevated following myocardial infarction. Loss of MST1 attenuated the levels of inflammation response and thus contributed to the survival of cardiomyocyte in vitro. Mechanistically, MST1 deletion reversed the activity of heme oxygenase-1 (HO-1) and thus reduced hypoxia-mediated cardiomyocyte death.Conclusions: Altogether, in this study, we found that MST1-Hippo pathway is activated in myocardial infarction and contributes to the inflammation response in cardiomyocytes through inhibiting the HO-1 signaling pathway. This finding would provide a potential target to reverse cardiomyocyte viability and reduce inflammation response in myocardial infarction.

Cerebral ischemia-reperfusion is modulated by macrophage-stimulating 1 through the MAPK-ERK signaling pathway

Cerebral ischemia-reperfusion (IR) injury is associated with mitochondrial damage. Macrophage-stimulating 1 (MST1) reportedly stimulates mitochondrial apoptosis by suppressing BCL-2. We investigated whether MST1 promotes the progression of cerebral IR injury by inducing mitochondrial dysfunction in vivo and in vitro. Western blot analysis, quantitative polymerase chain reaction, immunofluorescence, and mitochondrial function assays were conducted in cells from wild-type and Mst1-knockout mice subjected to cerebral IR injury. MST1 expression in wild-type glial cells increased following cerebral IR injury. Cerebral IR injury reduced the mitochondrial membrane potential and mitochondrial metabolism in glial cells, while it enhanced mitochondrial reactive oxygen species generation and mitochondrial calcium levels in these cells. The deletion of Mst1 attenuated cerebral IR injury by improving mitochondrial function and reducing mitochondrial damage. The mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathway was suppressed in wild-type glial cell upon cerebral IR injury but was reactivated in Mst1-knockout glial cell. Accordingly, blocking the MAPK/ERK pathway abolished the beneficial effects of Mst1 deletion during cerebral IR injury by inducing mitochondrial damage in glial cells. Our results suggest that cerebral IR injury is associated with MST1 upregulation in the brain, while the genetic ablation of Mst1 can attenuate mitochondrial damage and sustain brain function following cerebral IR injury.

Sphingosine kinase 1 promotes cerebral ischemia-reperfusion injury through inducing ER stress and activating the NF-κB signaling pathway

Endoplasm reticulum stress and inflammation response have been found to be linked to cerebral ischemia-reperfusion (IR) injury. Sphingosine kinase 1 (SPHK1) has been reported to be a novel endoplasm reticulum regulator. The aim of our study is to figure out the role of SPHK1 in cerebral IR injury and verify whether it has an ability to regulate inflammation and endoplasm reticulum stress. Hydrogen peroxide was used to induce cerebral IR injury. Enzyme-linked immunosorbent assay, quantitative polymerase chain reaction, western blots, and immunofluorescence were used to measure the alterations of cell viability, inflammation response, and endoplasm reticulum stress. The results demonstrated that after exposure to hydrogen peroxide, cell viability was reduced whereas SPHK1 expression was significantly elevated. Knockdown of SPHK1 attenuated hydrogen peroxide-mediated cell death and reversed cell viability. Our data also demonstrated that SPHK1 deletion reduced endoplasm reticulum stress and alleviated inflammation response in hydrogen peroxide-treated cells. In addition, we also found that SHPK1 modulated endoplasm reticulum stress and inflammation response to through the NF-κB signaling pathway. Inhibition of NF-κB signaling pathway has similar results when compared with the cells with SPHK1 deletion. Altogether, our results demonstrated that SPHK1 upregulation, induced by hydrogen peroxide, is responsible for cerebral IR injury through inducing endoplasm reticulum stress and inflammation response in a manner working through the NF-κB signaling pathway. This finding provides new insight into the molecular mechanism to explain the neuron death induced by cerebral IR injury.

Combination of melatonin and irisin ameliorates lipopolysaccharide-induced cardiac dysfunction through suppressing the Mst1-JNK pathways

Despite significant advances in therapies in past decades, the mortality rate of septic cardiomyopathy remains high. The aim of this study is to explore the therapeutic effects of combined treatment using melatonin and irisin in a mouse model of lipopolysaccharide (LPS)-mediated septic cardiomyopathy. Our data found that melatonin and irisin could further attenuate LPS-induced myocardial depression. Molecular investigation illustrated that melatonin and irisin cotreatment sustained cardiomyocyte viability and improved mitochondrial function under LPS stress. Pathway analysis demonstrated that macrophage-stimulating 1 (Mst1), which was significantly activated by LPS, was drastically inhibited by melatonin/irisin cotreatment. Mechanically, Mst1 activated c-Jun N-terminal kinase (JNK) pathway and the latter induced oxidative stress, adenosine triphosphate metabolism disorder, mitochondrial membrane potential reduction, and cardiomyocyte death activation. Melatonin and irisin cotreatment effectively inhibited the Mst1-JNK pathway and, thus, promoted cardiomyocyte survival and mitochondrial homeostasis. Interestingly, Mst1 overexpression abolished the beneficial effects of melatonin and irisin in vivo and in vitro. Altogether, our results confirmed that melatonin and irisin combination treatment could protect heart against sepsis-induced myocardial depression via modulating the Mst1-JNK pathways.

Brain-derived neurotrophic factor mimetic, 7,8-dihydroxyflavone, protects against myocardial ischemia by rebalancing optic atrophy 1 processing

Brain-derived neurotrophic factor (BDNF)/tropomyosin-related kinase B (TrkB) pathway is associated with ischemic heart diseases (IHD). 7,8-dihydroxyflavone (7,8-DHF), BDNF mimetic, is a potent agonist of TrkB. We aimed to investigate the effects and the underlying mechanisms of 7,8-DHF on cardiac ischemia. Myocardial ischemic mouse model was induced by ligation of left anterior descending coronary artery. 7,8-DHF (5 mg/kg) was administered intraperitoneally two days after ischemia for four weeks. Echocardiography, HE staining and transmission electron microscope were used to examine the function, histology and ultrastructure of the heart. H9c2 cells were treated with hydrogen peroxide (H₂O₂), 7,8-DHF or TrkB inhibitor ANA-12. The effects of 7,8-DHF on cell viability, mitochondrial membrane potential (MMP) and mitochondrial superoxide generation were examined. Furthermore, mitochondrial fission and protein expression of mitochondrial dynamics (Mfn2 [mitofusin 2], OPA1 [optic atrophy 1], Drp1 [dynamin-related protein 1] and Fis-1 [fission 1]) was detected by mitotracker green staining and western blot, respectively. 7,8-DHF attenuated cardiac dysfunction and cardiomyocyte abnormality of myocardial ischemic mice. Moreover, 7,8-DHF increased cell viability and reduced cell death accompanied by improving MMP, inhibiting mitochondrial superoxide and preventing excessive mitochondrial fission of H₂O₂-treated H9c2 cells. The cytoprotective effects of 7,8-DHF were antagonized by ANA-12. Mechanistically, 7,8-DHF repressed OMA1-dependent conversion of L-OPA1 into S-OPA1, which was abolished by Akt inhibitor. In conclusion, 7,8-DHF protects against cardiac ischemic injury by inhibiting the proteolytic cleavage of OPA1. These findings provide a novel pharmacological effect of 7,8-DHF on mitochondrial dynamics and a new potential target for IHD.

Considerations for an In Vitro, Cell-Based Testing Platform for Detection of Adverse Drug-Induced Inotropic Effects in Early Drug Development. Part 1: General Considerations for Development of Novel Testing Platforms

Drug-induced effects on cardiac contractility can be assessed through the measurement of the maximal rate of pressure increase in the left ventricle (LVdP/dt_max) in conscious animals, and such studies are often conducted at the late stage of preclinical drug development. Detection of such effects earlier in drug research using simpler, in vitro test systems would be a valuable addition to our strategies for identifying the best possible drug development candidates. Thus, testing platforms with reasonably high throughput, and affordable costs would be helpful for early screening purposes. There may also be utility for testing platforms that provide mechanistic information about how a given drug affects cardiac contractility. Finally, there could be in vitro testing platforms that could ultimately contribute to the regulatory safety package of a new drug. The characteristics needed for a successful cell or tissue-based testing platform for cardiac contractility will be dictated by its intended use. In this article, general considerations are presented with the intent of guiding the development of new testing platforms that will find utility in drug research and development. In the following article (part 2), specific aspects of using human-induced stem cell-derived cardiomyocytes for this purpose are addressed.