Isorhamnetin protects against hypoxia/reoxygenation-induced injure by attenuating apoptosis and oxidative stress in H9c2 cardiomyocytes.

To unveil the possible protective role of isorhamnetin, an immediate 3'-O-methylated metabolite of quercetin, in cardiomyocyte under hypoxia/reoxygenation (H/R) condition and the underlying mechanisms involved, H9c2 cardiomyocytes were exposed to the vehicle or H/R for 6 h (2 h of hypoxia following by 4 h of reoxygenation) with isorhamnetin (0, 3, 6, 12, 25, 50 μM for 4 h prior to H/R exposure). Apoptosis was evaluated by TUNEL staining, flow cytometry analysis and western blot assay for cleaved caspase-3. Myocardial injure in vivo was determined by infarct size using TTC staining, histological damage using H&E staining and myocardial apoptosis. Here, we found that isorhamnetin dose-dependently protected H9c2 cardiomyocytes against H/R-induced injure, as evidenced by the reduction in lactate dehydrogenase (LDH) levels, increases in cell viability, superoxide dismutase (SOD) and catalase (CAT) activity, with the maximal effects at 25 μΜ. In addition, isorhamnetin treatment significantly inhibited apoptosis in H/R-induced H9c2 cardiomyocytes and ameliorated H/R-induced myocardial injure in vivo, concomitant with the upregulation of sirtuin 1 (SIRT1) expression. Mechanism studies demonstrated that isorhamnetin pretreatment remarkably abolished H/R-induced downregulation of Nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) expressions and upregulation of NADPH oxidase-2/4 (NOX-2/4) expressions in cardiomyocytes. However, SIRT1 inhibition (Sirtinol) not only inhibited isorhamnetin-induced Nrf2/HO-1 upregulation and NOX-2/4 downregulation, but also alleviated its anti-apoptotic effects. Taken together, these data indicate that isorhamnetin can exhibit positive effect on H/R-induced injure by attenuating apoptosis and oxidative stress in H9c2 cardiomyocytes, which is partly attributable to the upregulation of SIRT1 and Nrf2/HO-1-mediated antioxidant signaling pathway.

Zhao TT ，Yang TL ，Gong L ，Wu P ... -  《-》

Stachydrine ameliorates hypoxia reoxygenation injury of cardiomyocyte via enhancing SIRT1-Nrf2 pathway.

Hypoxia/reoxygenation (H/R)-induced cardiomyocyte cell apoptosis is critical in developing myocardial infarction. Stachydrine (STA), an active constituent of Leonurus heterophyllus sweet, could have a protective effect on myocardial H/R injury, which remains unexplored. Therefore, the study aimed to investigate the protective effects and mechanisms of STA on H/R injury of cardiomyocytes. Rat cardiomyocyte H9c2 cells underwent H/R (hypoxia for 4 h and reoxygenation for 12 h). Cells were pretreated with STA (50 µM) 2 h before H/R. Cardiomyocyte injury was evaluated by CCK-8 assay and lactate dehydrogenase (LDH) release. Apoptosis was assessed by TUNEL staining and caspase-3 activity. Oxidative stress was assessed by lipid oxidation product MDA and a ROS-scavenging enzyme SOD in culture media. Western blot was performed to measure the protein expressions of SIRT1, Nrf2, and heme oxygenase-1 (HO-1). STA reversed the decrease in cell viability and increased LDH release in H9c2 cells with the H/R insult. STA significantly suppressed oxidative stress, reduced MDA content, and increased SOD activity in H9c2 cells exposed to H/R. STA reduced apoptosis in H9c2 cells exposed to H/R, as evidenced by the reduced TUNEL positive cells and caspase-3 activity. In addition, STA enhanced SIRT1, Nrf2, and HO-1 protein expression in H/R-stimulated H9c2 cells. SIRT1 and Nrf2 involved the protective effect of STA in H/R-exposed H9c2 cells, as the changes in cell viability and caspase-3 activity by STA can be reversed by SIRT1 inhibitor EX-527 or Nrf2 siRNA. Our data speculated that STA protects H/R injury and inhibits oxidative stress and apoptosis in cardiomyocytes by activation of the SIRT1-Nrf2 pathway.

Zhu X ，Wu Y ，Zhang X ，Gu W ，Ning Z ... -  《Journal of Cardiothoracic Surgery》

Rutin alleviates hypoxia/reoxygenation-induced injury in myocardial cells by up-regulating SIRT1 expression.

Rutin possesses multiple pharmacological activities, including the cardioprotective effect. The present study aimed to evaluate the protective effects of rutin on hypoxia/reoxygenation (H/R)-induced myocardial injury and its underlying mechanism involved. H9c2 cells were pretreated with 50 μM rutin or combined with 1 μM silent information regulator 1 (SIRT1) inhibitor (EX-527) for 1 h, and subjected to hypoxia for 6 h, followed by reoxygenation for 24 h. SIRT1 expression was detected by qRT-PCR and western blot. The effects of rutin or combined with EX-527 on cell viability, myocardial injury, apoptotic rate, and oxidative stress in H/R-stimulated H9c2 cells were assayed. The results showed that rutin elevated SIRT1 expression in H9c2 cells, as well as H/R-stimulated H9c2 cells. Rutin increased cell viability in H9c2 cells exposed to H/R. H/R stimulation induced myocardial injury, as evidenced by the increased levels of lactate dehydrogenase (LDH), creatine kinase-MB (CK-MB) and aspartate transaminase (AST), which were abolished in the presence of rutin. Rutin attenuated H/R-induced increase of apoptotic rate and caspase-3 activity in H/R-treated cells. Moreover, H/R-induced decrease in the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT), and increase in malondialdehyde (MDA) content were reversed by rutin treatment. The presence of EX-527 abolished these protective effects of rutin. In conclusion, rutin protected H9c2 cells against H/R injury through increasing SIRT1 expression. Our findings suggested that rutin might be a potential therapeutic agent for the treatment of myocardial H/R injury.

Yang H ，Wang C ，Zhang L ，Lv J ，Ni H ... -  《-》

Platycodin D inhibits oxidative stress and apoptosis in H9c2 cardiomyocytes following hypoxia/reoxygenation injury.

Myocardial ischemia/reperfusion (I/R) injury is a complex pathophysiological process related to the occurrence of myocardial infarction (MI). Oxidative stress is known to play a crucial role in the pathogenesis of I/R injury. Platycodin D (PD) is an active natural saponin that possesses strong anti-oxidant activity. The aim of the present study was to investigate the effect of PD on myocardial I/R injury. An in vitro hypoxia/reoxygenation (H/R) model was established in cardiomyocyte H9c2 cells. The results showed that PD improved the cell viability in H/R-stimulated H9c2 cells. The H/R-induced increase in the production of reactive oxygen species (ROS) and malondialdehyde (MDA), and decrease in the activities of superoxide dismutase (SOD) and catalase (CAT) were reversed by PD pretreatment. The histone-associated DNA fragment was increased by H/R stimulation, while decreased after PD treatment. Besides, PD pretreatment reduced the expressions of Bax and cleaved caspase-3, while induced Bcl-2 expression in H/R-induced H9c2 cells. Furthermore, PD was found to induce the activation of Akt/Nrf2/HO-1 pathway. The inhibitor of Akt, LY294002, attenuated the effects of PD on H/R-induced H9c2 cells. These findings indicated that PD exerted its protective effect via inducing the activation of Akt/Nrf2/HO-1 pathway. Our work provided new insights into the potential therapeutic role of PD in myocardial I/R injury.

Wang Y ，Che J ，Zhao H ，Tang J ，Shi G ... -  《-》

Baicalin protects H9c2 cardiomyocytes against hypoxia/reoxygenation-induced apoptosis and oxidative stress through activation of mitochondrial aldehyde dehydrogenase 2.

Baicalin, a flavonoid glycoside separated from Scutellaria baicalensis, has cardioprotection against ischaemia/reperfusion (I/R) injury. Mitochondrial aldehyde dehydrogenase 2 (ALDH2) is considered as an endogenous protective mechanism against I/R injury depending on its anti-oxidant and anti-apoptotic characteristics. The present study demonstrates whether ALDH2 contributes to the cardioprotection of baicalin against hypoxia/reoxygenation (H/R)-inudced H9c2 cardiomyocytes injury. Our results observed that H/R treatment resulted in a significant decrease in cells viability and obvious increases in caspase-3 activity and apoptosis rate in H9c2 cells, while these alterations were evidently reversed by baicalin pretreatment. Simultaneously, baicalin mitigated H/R-induced the decreases in the levels of ALDH2 mRNA and protein as well as the activity of ALDH2 in H9c2 cells. However, we found that daidzin, an ALDH2 antagonist, remarkably attenuated baicalin-elicited inhibitory action on H/R-induced the downregulation of cells viability and Bcl-2 protein expression, and the upregulations of caspase-3 activity, apoptosis rate, cytochrome c and Bax proteins expressions in H9c2 cells. In addition, baicalin reversed H/R-induced oxidative stress as evidenced by the downregulation of malondialdehyde (MAD) and 4-hydroxy aldehydes (4-HNE) levels, the inhibition of endogenous reactive oxygen species (ROS) generation, and the downregulation of superoxide dismutase (SOD) activity induced by H/R treatment, while these effects were also blocked by daidzin. Furthermore, we found that Alda-1, an ALDH2 agonist, also abolished H/R-induced cytotoxicity, apoptosis, and oxidative stress, indicating that ALDH2 mediated H/R-induced H9c2 cell injury. Overall, these results suggested that baicalin prevents H/R-induced apoptosis and oxidative stress through enhancing ALDH activity and expression in H9c2 cardiomyocytes.

Jiang WB ，Zhao W ，Chen H ，Wu YY ，Wang Y ，Fu GS ，Yang XJ ... -  《-》