Phosphorylation of proteins and apoptosis induced by c-Jun N-terminal kinase1 activation in rat cardiomyocytes by H2O2 stimulation

Cytokines and various cellular stresses are known to activate c-Jun N-termi nal kinase-1 (JNK1), which is involved in physiological function. Here, we investigate the activation of JNK1 by oxidative stress in H9c2 cells derive d from rat cardiomyocytes. H2O2 (100 muM) significantly induces the tyrosin e phosphorylation of JNK1 with a peak 25 min after the stimulation. The amo unt of JNK1 protein remains almost constant during stimulation. Immunocytoc hemical observation shows that JNK1 staining in the nucleus is enhanced aft er H2O2 stimulation. To clarify the physiological role of JNK1 activation u nder these conditions, we transfected antisense JNK1 DNA into H9c2 cells. T he antisense DNA (2 muM) inhibits JNK1 expression by 80% as compared with e xpression in the presence of the sense DNA, and significantly blocks H2O2-i nduced cell death. Consistent with the decrease in cell number, we detected condensation of the nuclei, a hallmark of apoptosis, 3 h after H2O2 stimul ation in the presence of the sense DNA for JNK1. The antisense DNA of JNK1 inhibits the condensation of nuclei by H2O2. Under these conditions, the H2 O2-induced phosphorylation of proteins with molecular masses of 55, 72, and 78 kDa is blocked by treatment with the antisense DNA for JNK1 as compared with the sense DNA for JNK1. These findings suggest that JNK1 induces apop totic cell death in response to H2O2, and that the cell death may be involv ed in the phosphorylations of 55, 72, and 78 kDa proteins induced by JNK1 a ctivation. (C) 2001 Elsevier Science B.V. All rights reserved.