RESUMO
AIM:To study whether cordycepin (Cordy) plays a role in myocardial protection by regulating the expression of microRNA-455 ( miR-455) and reducing apoptosis induced by endoplasmic reticulum stress in the ischemia -reperfusion (IR) rats.METHODS: SD rats (250 ~300 g) were randomly divided into 3 groups: control group, the chests of the rats were only opened;IR group, the rats were given myocardial ischemia for 30 min, and then reperfusion for 120 min;IR+Cordy group:before IR, the rats were given Cordy (10 mg/kg) through femoral vein injection once a day for one week, and the last injection was given 30 min before ischemia.Automated biochemical analysis was used to detect rat serum activity of LDH and CK-MB.The myocardial endothelial cell ( EC) apoptotic rate was measured by TUNEL , and the ultrastructural changes of the myocardial EC were observed under transmission electron microscope .RT-qPCR was used to detect the expression of miR-455 and the mRNA levels of glucose-regulated protein 78 ( Grp78) and caspase-12 in the myo-cardium.RESULTS:Compared with control group, EC apoptosis in IR group was significantly increased (P<0.05). Compared with IR group , EC apoptosis in IR +Cordy group decreased significantly ( P<0.05 ) .Compared with control group, swelling of mitochondria , irregular membrane , loose wrinkles with vacuoles , disappeared matrix granules , irregular nuclear membrane , chromatin condensation , disappeared nucleoli and even small apoptosis body in the EC were found in IR group.Compared with IR group , the symptoms in IR +Cordy group were greatly improved .Compared with control group, the mRNA expression of Grp78 and caspase-12 as well as the miR-455 level in IR group was increased (P<0.05). Compared with IR group , the mRNA expression of Grp78 and caspase-12, as well as the miR-455 level in IR+Cordy group was decreased (P<0.05).CONCLUSION:Cordycepin attenuates myocardial EC apoptosis , down-regulates the expres-sion of miR-455, and inhibits endoplasmic reticulum stress in the myocardium .
RESUMO
Objective The protective effect of hydrogen sulfide (H2 S) against myocardial ischemia/reperfusion ( IR) injury via anti-apoptotic signaling is well established , but the underlying mechanism remains unclear .This study was to investigate whether H 2 S could protect cardiomyocytes from endoplasmic reticulum stress ( ERS)-mediated apoptosis in hypoxia/reoxygenation ( HR) injury by regulating the expression of microRNA-455 ( miR-455 ) . Methods Cardiomyocytes from neonatal SD rats were primarily cultured and the model of HR injury was established .The cardiomyocytes were divided into a control group (normally cultured for 27 hours), an HR group (subjected to HR injury), and an H2S protection group (pretreated with the precursor of H2S NaHS at 40 μmol/L at 30 min before HR treatment followed by the same procedure as in the HR group ) .The cell viability was monitored by MTT , the release of lactate de-hydrogenase ( LDH) in the culture supernatant measured by full-automatic chemical analysis , and the apoptosis rate of the cardiomyo-cytes detected by flow cytometry .The mRNA and protein expressions of Grp 78 and caspase-12 were determined by real-time RT-PCR and Western bot .To verify whether miR-455 was involved in the ERS-mediated apoptosis of the cardiomyocytes , the cells were subjec-ted to HR after transfected with miR-455 mimic or anti-miR-455 oligonucleotide (AMO) for 24 hours, followed by detection of the ex-pressions of Grp78 and caspase-12. Results After HR injury, the H2 S protection group showed an enhanced viability of the cardio-myocytes in comparison with the control group ([67.02 ±6.90] vs [29.27 ±5.66] %), an decreased LDH release ([91.33 ± 10.63] vs [168.17 ±15.38] U/L), and a reduced rate of cell apoptosis ([13.98 ±1.90] vs [24.31 ±2.79] %).H2 S pretreat-ment significantly downregulated the mRNA and protein expressions of Grp 78 and caspase-12 (1.66 ±0.39 vs 2.56 ±0.34;1.75 ± 0.32 vs 2.54 ±0.48;2.01 ±0.45 vs 3.26 ±0.34;1.85 ±0.52 vs 3.21 ±0.84, P<0.05).The mRNA and protein expressions of Grp78 and caspase-12 were evidently increased after transfection with miR-455 mimic (3.56 ±0.37 vs 1.00 ±0.00;3.61 ±0.41 vs 1.00 ±0.00;2.87 ±0.38 vs 1.00 ±0.00;2.98 ±0.49 vs 1.00 ±0.00), but remarkably decreased after transfection with miR-455 AMO (0.62 ±0.16 vs 1.00 ±0.00;0.65 ±0.13 vs 1.00 ±0.00;0.54 ±0.13 vs 1.00 ±0.00;0.62 ±0.16 vs 1.00 ±0.00, P<0.05). Conclusion H2S could protect cardiomyocytes from HR injury by regulating the expression of miR-455 and reducing ERS-mediated cell apoptosis .