Mitochondria in Ischemic Heart Disease

Er-xian ameliorates myocardial ischemia-reperfusion injury in rats through RISK pathway involving estrogen receptors

Curculigo orchioides (CUR) and Epimedium (EPI) are traditional Chinese medicines with estrogen-like biological activity, called Xianmao and Xianlingpi (Er-xian) in Chinese. However, whether Er-xian exerts protective effects on myocardial ischemia-reperfusion injury (MIRI) is unknown. This study aimed to investigate the cardioprotective effects of Er-xian preconditioning against MIRI and the underlying mechanisms. CUR or EPI was administered intragastrically to aged female rats as a monotherapy or combination therapy. 2 weeks later, a rat MIRI model was established. Myocardial infarction size, myocardial morphology, cTnT, cell apoptosis rate, intracellular calcium concentration, mitochondrial permeability transition pore (MPTP) opening and reperfusion injury salvage kinase (RISK) signaling pathway molecules were observed after the surgery. To evaluate the mechanisms of Er-xian, estrogen receptors antagonists ICI 182780 and G15 were used. In this study, Er-xian notably alleviated myocardial tissue damage, maintained mitochondrial morphology, reduced infarct size and cardiac markers, and increased sera levels of E2. Moreover, Er-xian inhibited calcium overload and mPTP opening, and decreased cardiomyocyte apoptosis. We found that the dual therapy of CUR and EPI elicited more noticeable results than CUR or EPI monotherapy. The significant protective effects of Er-xian on ischemia-reperfusion myocardium were attributed to the up-regulation of AKT, ERK1/2 and GSK-3β phosphorylation levels. The cardioprotective effects of Er-xian were significantly reduced after estrogen receptor blockade, especially GPER30. These results indicate that Er-xian attenuates MIRI through RISK signaling pathway and estrogen receptors are the critical mediators.

[Role of PNPT1 in cardiomyocyte apoptosis induced by oxygen-glucose deprivation]

OBJECTIVE

To explore the effect of inhibiting polyribonucleotide nucleotidyl-transferase 1 (PNPT1) on oxygen-glucose deprivation (OGD)-induced apoptosis of mouse atrial myocytes.

METHODS

Cultured mouse atrial myocytes (HL-1 cells) with or without OGD were transfected with PNPT1-siRNA or a negative control siRNA (NC-siRNA group), and the cell survival rate was detected using CCK-8 assay. The expression levels of ACTB and TUBA mRNA were detected with qPCR, and the protein expression of PNPT1 was detected with Western blotting. The apoptosis rate of the treated cells was determined with flow cytometry, the mitochondrial membrane potential was detected using JC-1 kit, and the mitochondrial morphology was observed using transmission electron microscope.

RESULTS

With the extension of OGD time, the protein expression levels of PNPT1 increased progressively in the cytoplasm of HL-1 cells (P < 0.05). Transfection with PNPT1-siRNA significantly reduced PNPT1 expression in HL-1 cells (P < 0.05). Exposure to OGD significantly enhanced degradation of ACTB and TUBA mRNA (P < 0.05) and markedly increased the apoptosis rate of HL-1 cells (P < 0.05), and these changes were significantly inhibited by transfection with PNPT1-siRNA (P < 0.05), which obviously increased mitochondrial membrane potential and improved mitochondrial morphology of HL-1 cells exposed to OGD.

CONCLUSION

Inhibition of PNPT1 improves mitochondrial damage and reduces degradation of apoptotic-associated mRNAs to alleviate OGD-induced apoptosis of mouse atrial myocyte.

Ferroptosis-Specific Inhibitor Ferrostatin-1 Relieves H2O2-Induced Redox Imbalance in Primary Cardiomyocytes through the Nrf2/ARE Pathway

Objective

Ischemic heart disease (IHD) has always been the focus of attention of many researchers in cardiovascular disease, and its pathogenesis is also very complicated. Ferroptosis may be involved in the occurrence and development of IHD.

Methods

First, primary cardiomyocytes were treated with H₂O₂ to simulate the IHD in vitro model. After pretreatment with different concentrations of ferrostatin-1, cell survival rate was detected by MTT method, cell apoptosis was detected by TUNEL staining and flow cytometry, and the expression of oxidative stress, ferroptosis, and related molecules of Nrf2/ARE pathway was detected by Western blotting (WB) and quantitative real-time polymerase chain reaction (qRT-PCR).

Results

The mortality of primary cardiomyocytes in the H₂O₂ group was obviously increased. Ferrostatin-1 treatment can effectively inhibit cell death, improve antioxidant enzyme activity, inhibit the expression of ferroptosis-related molecules, and activate Nrf2/ARE pathway expression.

Conclusion

Ferroptosis-specific inhibitor ferrostatin-1 relieves H₂O₂-induced redox imbalance in primary cardiomyocytes through the Nrf2/ARE pathway, inhibits ferroptosis, and thereby slows cardiomyocyte death.

Raman Spectroscopic Assessment of Myocardial Viability in Langendorff-Perfused Ischemic Rat Hearts

Spontaneous Raman spectroscopy, which senses changes in cellular contents of reduced cytochrome c, could be a powerful tool for label-free evaluation of ischemic hearts. However, undetermined is whether it is applicable to evaluation of myocardial viability in ischemic hearts. To address this issue, we investigated sequential changes in Raman spectra of the subepicardial myocardium in the Langendorff-perfused rat heart before and during ligation of the left coronary artery and its subsequent release and re-ligation. Under 532-nm wavelength excitation, the Raman peak intensity of reduced cytochrome c at 747 cm^-1 increased quickly after the coronary ligation, and reached a quasi-steady state within 30 min. Subsequent reperfusion of the heart after a short-term (30-min) ligation that simulates reversible conditions resulted in quick recovery of the peak intensity to the baseline. Further re-ligation resulted in resurgence of the peak intensity to nearly the identical value to the first ischemia value. In contrast, reperfusion after prolonged (120-min) ligation that assumes irreversible states resulted in incomplete recovery of the peak intensity, and re-ligation resulted in inadequate resurgence. Electron microscopic observations confirmed the spectral findings. Together, the Raman spectroscopic measurement for cytochrome c could be applicable to evaluation of viability of the ischemic myocardium without labeling.

Hesperetin modulates the Sirt1/Nrf2 signaling pathway in counteracting myocardial ischemia through suppression of oxidative stress, inflammation, and apoptosis

Hesperetin (HSP) is a natural flavonoid that offers useful curative effects for cardiovascular diseases, but its effect on myocardial ischemia and its precise mechanism remains unclear. The aim of this study is to explore the potential cardioprotective mechanism of HSP on myocardial ischemia caused by isoproterenol (ISO). Adult male Kunming mice were randomly divided into five groups: control, ISO, low-dose HSP (L-HSP, 25 mg/kg/d), high-dose HSP (H-HSP, 50 mg/kg/d), and verapamil (VER) group. Treatment groups of mice received HSP or VER for seven days, and the groups other than the control group were injected with ISO (100 mg/kg/d) subcutaneously for two consecutive days to establish a model of myocardial ischemia. Electrocardiogram and heart-histology changes were used to assess changes in myocardial architecture. The activities and the content of oxidative stress markers and inflammatory cytokines were determined and assayed using kits respectively. The expressions of proteins associated with apoptosis and the Sirt1/Nrf2 pathway were evaluated by Western blotting. The results demonstrate that VER, L-HSP and H-HSP significantly reduced the J-point displacement, heart rate, cardiac pathomorphological changes, and the levels of creatine kinase, lactated dehydrogenase, malonaldehyde, interleukin-6, and tumor necrosis factor-α in serum while promoting the activation of superoxide dismutase, catalase, glutathione in serum in the ISO-treated animals. Furthermore, L-HSP and H-HSP also reversed the ISO-induced apoptosis and the changes in the Sirt1/Nrf2 signaling pathway, as evident from the levels of proteins Bax, Bcl-2, caspase-3, Sirt1, Nrf2, NQO-1, and HO-1. In conclusion, HSP plays a protective role in ISO-induced myocardial ischemia by modulating oxidative stress, inflammation, and apoptosis via Sirt1/Nrf2 pathway activation.

Fas-Activated Serine/Threonine Kinase Governs Cardiac Mitochondrial Complex I Functional Integrity in Ischemia/Reperfusion Heart

Cardiac energy homeostasis is strictly controlled by the mitochondrial complex-mediated respiration. In the heart, mitochondrial complex I is highly susceptible to functional and structural destroy after ischemia/reperfusion (I/R), thereby contributing to myocardial energy insufficiency and cardiomyocyte death. Fas-activated serine/threonine kinase (FASTK) is recently recognized as a key modulator of mitochondrial gene expression and respiration. However, the role of FASTK in cardiac I/R process is undetermined. Here, we show that FASTK expression was down-regulated in the post-I/R heart. The reactive oxygen species scavenger N-acetyl-L-cysteine reversed I/R-induced FASTK down-regulation. Genetic deletion of FASTK exacerbated I/R-induced cardiac dysfunction, enlarged myocardial infarct size, and increased cardiomyocyte apoptosis. Compared with the wild type control, the FASTK deficient heart exhibited a lower mRNA expression of NADH dehydrogenase subunit-6 (MTND6, a mitochondrial gene encoding a subunit of complex I) and was more vulnerable to I/R-associated complex I inactivation. Replenishment of FASTK expression via adenovirus-mediated gene delivery restored mitochondrial complex I activity and ameliorated cardiomyocyte death induced by I/R, whereas these beneficial effects were blocked by the co-treatment with rotenone, a specific complex I inhibitor. in vivo experiments further confirmed that cardiac overexpression of FASTK ameliorated I/R-related MTND6 down-regulation and mitochondrial complex I inactivation, thereby protecting the heart against I/R injury. Collectively, these data for the first time identify that the down-regulation of FASTK is a direct culprit behind the loss of mitochondrial complex I functional integrity and cardiac injury induced by I/R process. Targeting FASTK might be a promising and effective strategy for MI/R intervention.

Effects of cyclosporine A on proliferation, invasion and migration of HTR-8/SVneo human extravillous trophoblasts

As shown in our previous study, cyclosporine A (CsA) promotes the proliferation, invasion and migration of villous trophoblasts, thus improving embryo implantation. In addition, the incidence of preeclampsia (PE) is decreased in patients with recurrent spontaneous abortion (RSA) and repeated implantation failure (RIF) treated with CsA during the first trimester. Abnormal function of extravillous trophoblasts (EVTs) in early pregnancy is recognized as the pathogenetic mechanism of PE. EVTs share homology and function with pre-villous trophoblasts and villous trophoblasts; thus, we hypothesized that CsA may have the same regulatory effect on EVTs. In this study, we investigated the effects of CsA on HTR-8/SVneo trophoblasts in the extravillous layer and explored the underlying mechanisms. QPCR and Western blot (WB) analyses were performed to detect expression alterations in relevant proliferation and invasion proteins in response to different concentrations of CsA. We used an Affymetrix IVT expression microarray to examine the target genes of CsA in preeclamptic placentas versus normal placentas. Our results showed that certain concentrations of CsA could promote the proliferation, invasion and migration of HTR8/SVneo cells. CsA was also found to promote the expression of titin, MMP9, EGFR, and PRR15. TRAIL may be a target gene for CsA-mediated regulation of EVTs. CONCLUSIONS: By promoting the expression of related proteins and regulating the functions of HTR8/SVneo cells, CsA can promote vascular recasting and placental function, which may affect the pathogenesis of PE.

Natural Drugs as a Treatment Strategy for Cardiovascular Disease through the Regulation of Oxidative Stress

Oxidative stress (OS) refers to the physiological imbalance between oxidative and antioxidative processes leading to increased oxidation, which then results in the inflammatory infiltration of neutrophils, increased protease secretion, and the production of a large number of oxidative intermediates. Oxidative stress is considered an important factor in the pathogenesis of cardiovascular disease (CVD). At present, active components of Chinese herbal medicines (CHMs) have been widely used for the treatment of CVD, including coronary heart disease and hypertension. Since the discovery of artemisinin for the treatment of malaria by Nobel laureate Youyou Tu, the therapeutic effects of active components of CHM on various diseases have been widely investigated by the medical community. It has been found that various active CHM components can regulate oxidative stress and the circulatory system, including ginsenoside, astragaloside, and resveratrol. This paper reviews advances in the use of active CHM components that modulate oxidative stress, suggesting potential drugs for the treatment of various CVDs.

κ-opioid receptor activation promotes mitochondrial fusion and enhances myocardial resistance to ischemia and reperfusion injury via STAT3-OPA1 pathway

Mitochondrial dynamics, determining mitochondrial morphology, quality and abundance, have recently been implicated in myocardial ischemia and reperfusion (MI/R) injury. The roles of κ-opioid receptor activation in cardioprotection have been confirmed in our previous studies, while the underlying mechanism associated with mitochondrial dynamics remains unclear. This study aims to investigate the effect of κ-opioid receptor activation on the pathogenesis of MI/R and its underlying mechanisms. MI/R mouse model and hypoxia-reoxygenation cardiomyocyte model were established in this study. Mitochondrial dynamics were analyzed with transmission electron microscopy in vivo and confocal microscopy in vitro. STAT3 phosphorylation and OPA1 expression were detected by Western blotting. We show here that κ-opioid receptor activation with its selective receptor agonist U50,488H promoted mitochondrial fusion and enhanced myocardial resistance to MI/R injury, while these protective effects were blockaded by nor-BNI, a selective κ-opioid receptor antagonist. In addition, κ-opioid receptor activation increased STAT3 phosphorylation and OPA1 expression, which were blockaded by nor-BNI. Furthermore, inhibition of STAT3 phosphorylation by stattic, a specific STAT3 inhibitor, repressed the effects of κ-opioid receptor activation on promoting OPA1 expression and mitochondrial fusion, as well as inhibiting cell apoptosis and oxidative stress both in vivo and in vitro during MI/R injury. Overall, our data for the first time provide evidence that κ-opioid receptor activation promotes mitochondrial fusion and enhances myocardial resistance to MI/R injury via STAT3-OPA1 pathway. Targeting the pathway regulated by κ-opioid receptor activation may be a potential therapeutic strategy for MI/R injury.

Regulation of mitochondria function by natriuretic peptides

Natriuretic peptides (NPs) are well known to promote renal Na⁺ excretion, counteracting the effects of the renin-angiotensin-aldosterone system. Thus, NPs serve as a key component in the maintenance of blood pressure, influencing fluid retention capabilities via osmoregulation. Recently, NPs have been shown to affect lipolysis and enhance lipid oxidation and mitochondrial respiration. Here, we provide an overview of current knowledge about the relationship between NPs and mitochondria-mediated processes such as reactive oxygen species production, Ca²⁺ signaling, and apoptosis. Establishing a clear physiological and mechanistic connection between NPs and mitochondria in the cardiovascular system will open new avenues of research aimed at understanding and potentially using it as a therapeutic target from a completely new angle.

Activation of mitochondrial KATP channels mediates neuroprotection induced by chronic morphine preconditioning in hippocampal CA-1 neurons following cerebral ischemia

PURPOSE

Pharmacologic preconditioning, through activating several mechanisms and mediators, can increase the tolerance of different tissues against ischemia/reperfusion (I/R) injury. Recent studies have shown that morphine preconditioning has protective effects in different organs, especially in the heart. Nevertheless, its mechanisms are not well elucidated in the brain. The present study aimed to clarify whether the activation of mitochondrial KATP (mKATP) channels in chronic morphine (CM) preconditioning could decrease hippocampus damage following I/R injury.

MATERIALS AND METHODS

CM preconditioning was performed by the administration of additive doses of morphine for 5days before I/R injury induction. I/R injury was induced by the occlusion of bilateral common carotid arteries. The possible role of mKATP channels was evaluated by the injection of 5-hydroxydecanoate (5-HD) before I/R injury. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) was performed to detect apoptosis in hippocampal neurons. The expressions of B-cell lymphoma-2 (Bcl-2) and Bcl-2-associated X protein (BAX) and levels of malondialdehyde (MDA) and catalase (CAT) enzymes were assessed.

RESULTS

CM attenuated apoptosis in the hippocampal CA1 neurons (P<0.001 vs I/R), and mKATP channel blocking with 5-HD significantly increased apoptosis (P<0.001 vs CM+I/R). CM increased CAT activity (P<0.05 vs I/R) and Bcl-2 protein expression (P<0.01 vs I/R), while it decreased MDA level (P<0.05 vs I/R) and BAX protein expression (P<0.05 vs I/R). Pretreatment with 5-HD abolished all the above-mentioned effects of CM.

CONCLUSIONS

These findings describe novel evidence whereby CM preconditioning in hippocampal CA1 neurons can improve oxidative stress and apoptosis through the activation of mKATP channels and eventually protect the hippocampal tissue against I/R injury.

Fmr1 protects cardiomyocytes against lipopolysaccharide-induced myocardial injury

The present study explored the mechanisms by which fragile X mental retardation 1 (fmr1) overexpression inhibits lipopolysaccharide (LPS)-induced cardiomyocyte injury. Factors including oxidative stress reaction, mitochondrial membrane potential variation and cell apoptosis were evaluated. The viability of H9c2 cells was evaluated with a Cell Counting Kit-8 assay after cells were treated with LPS at different concentrations (0, 1, 3, 6 and 9 µg/ml) for various durations (4, 12 and 24 h). Flow cytometry was used to determine variations in reactive oxygen species (ROS), mitochondrial membrane potential and cell apoptosis. Reverse transcription-quantitative polymerase chain reaction and western blot analysis were performed to detect the levels of apoptosis-associated factors, and western blot analysis was used to determine the phosphorylation levels of phosphoinositide-3 kinase (PI3K), Akt and forkhead box (Fox)O3a. The results indicated that LPS decreased the viability of H9c2 cells in a dose- and time-dependent manner. Overexpression of fmr1 inhibited the LPS-induced decrease in the mitochondrial membrane potential and the production of ROS as well as apoptosis in H9c2 cells. Fmr1 also inhibited LPS-induced reductions in antioxidant enzyme activities, including those of superoxide dismutase and reduced/oxidized glutathione ratio, and decreased LPS-associated increases in the lipid peroxidation product malondialdehyde. Apoptosis-associated factors were identified to be involved in the effects of Fmr1. Overexpression of Fmr1 attenuated LPS-associated increases in the apoptosis-activating factors B-cell lymphoma 2 (Bcl-2)-associated X protein and caspase-3 and decreases in apoptosis inhibitors, including Bcl-2 and X-linked inhibitor of apoptosis protein. Fmr1 overexpression also reduced LPS-induced increases in the phosphorylation levels of PI3K, Akt and FoxO3a. In conclusion, fmr1 overexpression alleviated oxidative stress and apoptosis in H9c2 cardiomyocytes injured by LPS via regulating oxidative stress and apoptosis-associated factors, as well as the PI3K/Akt pathway. This information may provide a novel and effective therapeutic strategy for heart diseases.

Fisetin Confers Cardioprotection against Myocardial Ischemia Reperfusion Injury by Suppressing Mitochondrial Oxidative Stress and Mitochondrial Dysfunction and Inhibiting Glycogen Synthase Kinase 3β Activity

Acute myocardial infarction (AMI) is the leading cause of morbidity and mortality worldwide. Timely reperfusion is considered an optimal treatment for AMI. Paradoxically, the procedure of reperfusion can itself cause myocardial tissue injury. Therefore, a strategy to minimize the reperfusion-induced myocardial tissue injury is vital for salvaging the healthy myocardium. Herein, we investigated the cardioprotective effects of fisetin, a natural flavonoid, against ischemia/reperfusion (I/R) injury (IRI) using a Langendorff isolated heart perfusion system. I/R produced significant myocardial tissue injury, which was characterized by elevated levels of lactate dehydrogenase and creatine kinase in the perfusate and decreased indices of hemodynamic parameters. Furthermore, I/R resulted in elevated oxidative stress, uncoupling of the mitochondrial electron transport chain, increased mitochondrial swelling, a decrease of the mitochondrial membrane potential, and induction of apoptosis. Moreover, IRI was associated with a loss of the mitochondrial structure and decreased mitochondrial biogenesis. However, when the animals were pretreated with fisetin, it significantly attenuated the I/R-induced myocardial tissue injury, blunted the oxidative stress, and restored the structure and function of mitochondria. Mechanistically, the fisetin effects were found to be mediated via inhibition of glycogen synthase kinase 3β (GSK3β), which was confirmed by a biochemical assay and molecular docking studies.