SIGNAL TRANSDUCTION OF NITRIC OXIDE DONOR-INDUCED PROTECTION IN HYDROGEN PEROXIDE-MEDIATED APOPTOSIS IN H9C2 CARDIOMYOBLASTS

Abstract

Nitric oxide (NO) attenuates hydrogen peroxide (H₂O₂)-mediated injury to H9C2 cardiomyoblasts. To examine the role of nitric oxide, cultured H9C2 cardiomyoblasts were treated with H₂O₂ for 2 h in the presence or absence of the NO donor, diethylamine nitric oxide (DEANO). DEANO (30 μM) attenuated H₂O₂-induced apoptosis in H9C2 cells. H₂O₂-exposed H9C2 cells resulted in apoptosis in a time-dependent manner estimated by DNA fragmentation assay, nuclear morphology stained with fluorescent dye, Hoechst 33258 and Annexin V staining. Pretreatment with z-VAD-FMK, a pancaspase inhibitor, or z-DEVD-CHO, a specific caspase-3 inhibitor, completely suppressed the DNA ladder in response to H₂O₂. An increase in caspase-3-like protease (DEVDase) activity was observed during apoptosis, but no caspase-1 activity (YVADase) was detected. Treatment of H9C2 cells with 100 μM H₂O₂, resulted in a strong activation of JNK/SAPK. However, the activation of JNK/SAPK was clearly attenuated by 30 μM DEANO. Furthermore, the dominant negative JNK and SEK1-expressing cells displayed a marked decrease in a number of apoptotic cells. This inhibition of JNK1 in the system is involved in the protection of H₂O₂-induced apoptosis in H9C2 cardiomyoblasts.