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 ... -  《-》

Alda-1, an ALDH2 activator, protects against hepatic ischemia/reperfusion injury in rats via inhibition of oxidative stress.

Zhang T ，Zhao Q ，Ye F ，Huang CY ，Chen WM ，Huang WQ ... -  《-》

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 ... -  《-》

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 ... -  《-》

Aqueous extract of Cortex Dictamni protects H9c2 cardiomyocytes from hypoxia/reoxygenation-induced oxidative stress and apoptosis by PI3K/Akt signaling pathway.

Ischemia-reperfusion injury is the major manifestation of ischemic heart disease, which facilitates cardiac arrhythmias, heart failure and death. Oxidative stress and apoptosis have been involved in the pathogenesis of myocardial ischemia-reperfusion injury. Modern pharmacological studies have indicated that the extracts and active compounds of Cortex Dictamni exhibit antioxidative and cardiovascular protective activities. This study was designed to investigate the protective effect of aqueous extract of Cortex Dictamni (CDAE) on regulating hypoxia/reoxygenation (H/R)-induced cardiomyocytes oxidative stress and apoptosis. H9c2 cardiomyocytes pretreatmented with CDAE for 24h were exposed to hypoxia/reoxygenation. Cell survival was measured by methyl thiazolyl tetrazolium (MTT) assay, and by the detections of lactate dehydrogenase (LDH) activity and cardiac troponin I (cTn-I) content in cultured supernatant. Cell apoptosis was measured by Hoechst 33342/propidium iodide (PI) staining, Annexin-V/PI staining, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) assay. Intracellular reactive oxygen species (ROS) production, superoxide dismutase (SOD) activity and malondialdehyde (MDA) level were measured to examine antioxidant activity. Mitochondrial membrane potential and release of cytochrome c were measured to examine mitochondrial changes. The expressions of anti-oxidant, pro-apoptosis and anti-apoptosis proteins were measured by performing western blotting assay. Inhibitor LY294002 was used to confirm the regulation effect of CDAE on PI3K/Akt signaling pathway. CDAE pretreatment prevents H/R-induced cardiomyocytes oxidative stress and apoptosis through activation of PI3K/Akt signaling pathway.

Li L ，Zhou Y ，Li Y ，Wang L ，Sun L ，Zhou L ，Arai H ，Qi Y ，Xu Y ... -  《-》