[Injurious effect of zinc deficiency on cardiomyocytes].

The aim of the present study was to investigate the effect of zinc deficiency on cardiomyocyte survival and the underlying mechanisms. Simulated zinc deficiency model was developed in H9c2 cardiac cells with zinc chelator N, N, N', N'-tetrakis (2-pyridylmethyl) ethylenediamine (TPEN). MTT assay was used to evaluate cell viability. Morphological changes of the cells were observed by optical microscope. Lacate dehydrogenase (LDH) levels of the cells were determined with LDH assay kit. Mitochondrial membrane potential (ΔΨ) was measured with confocal microscope using JC-1 dye. Intracellular reactive oxygen species (ROS) levels were determined by DCFH-DA staining. PD98059 (an inhibitor of ERK), SNAP, which can activate ERK, and the ROS scavenger, MPG, were respectively used to investigate mechanism of signal transduction. The phosphorylation of ERK was detected by Western blot. The results showed that TPEN significantly induced the cell morphological damage and the loss of ΔΨ, increased LDH leakage, and promoted ROS generation. In the H9c2 cells, TPEN significantly inhibited ERK phosphorylation and decreased cell viability, which was potentiated by PD98059, whereas both SNAP and MPG reversed the inhibitory effects of TPEN. These data suggest that zinc deficiency leads to the injury in H9c2 cardiac cells through down-regulating ERK pathway. Increased intracellular ROS may account for the effect of zinc deficiency.

[Resveratrol attenuates oxidant-induced mitochondrial damage in embryonic rat cardiomyocytes via inactivating GSK-3ß].

OBJECTIVE: To investigate the underlying mechanism of the protective effects of resveratrol on oxidant-induced mitochondrial damage in embryonic rat cardiomyocytes. METHODS: H9c2 cells, a permanent cell line derived from embryonic rat cardiac tissue, and then randomly divided into control group [PBS, cells exposed to H2O2 (600 µmol/L) for 20 min to induce mitochondrial oxidant damage], resveratrol group (0.01, 0.1, 1, 5, 10 and 20 µmol/L for 20 min at 20 min before exposing to H2O2), resveratrol plus inhibitor group (1 µmol/L KT5823 for 10 min at 10 min before 5 µmol/L resveratrol treatment) and inhibitor group (1 µmol/L KT5823 for 10 min). Mitochondrial membrane potential (ΔΨm) was measured by staining cells with tetramethylrhodamine ethyl ester (TMRE) and the mitochondrial permeability transition pore (mPTP) opening was evaluated by measuring the decrease of TMRE fluorescence intensity. Immunofluorescence assay was used to observe GSK-3ß phosphorylation. The phosphorylation of GSK-3ß and VASP were determined by Western blot. To detect intracellular NO, cells were loaded with DAF-FM DA (specific fluorescent dye of NO) and imaged with confocal microscopy. RESULTS: Compared to the control group, resveratrol (0.01-5 µmol/L) attenuated H2O2-induced mitochondrial damage reflected by attenuating the H2O2-induced TMRE fluorescence intensity decrease in a dose-dependent manner and the efficacy of 10 and 20 µmol/L resveratrol was significantly lower than that of 5 µmol/L resveratrol. Resveratrol also significantly upregulated the protein expression of VASP and increased GSK-3ß Ser(9) phosphorylation, which could lead the inactivation of GSK-3ß. These effects of resveratrol could be significantly abolished by protein kinase G inhibitor KT5823, while KT5823 alone did not affect GSK-3ß and VASP phosphorylation. Confocal microscopy showed that DAF-FM (specific NO indicator) was similar between resveratrol and control group, suggesting that resveratrol did not produce NO. CONCLUSIONS: Resveratrol could attenuate oxidant-induced mitochondrial damage in embryonic rat cardiomyocytes by inactivating GSK-3ß via cGMP/PKG signaling pathway independent of NO-related mechanism.

Cardioprotection against reperfusion injury: updated mechanisms and strategies.

Early restoration of blood flow to the ischemic myocardium not only saves myocardium but also induces reperfusion injury. While no specific therapy to reduce reperfusion injury has yet been established, recent laboratory studies have shown that G protein-coupled receptor (GPCR) agonists, insulin, and postconditioning can effectively prevent reperfusion injury in various experimental settings and animal species. The potential mechanisms underlying the cardioprotection initiated by these interventions may include activation of the reperfusion injury salvage kinase (RISK) pathway, inactivation of glycogen synthase kinase 3beta (GSK-3beta), and modulation of mitochondrial permeability transition pore (mPTP) opening. These encouraging laboratory findings may help us develop successful clinical strategies to salvage reperfused myocardium in patients with acute myocardial infarction.