Suppression of N-methyl-N '-nitro-N-nitrosoguanidine- and S-nitrosoglutathione-induced apoptosis by Bcl-2 through inhibiting glutathione-S-transferase pi in NIH3T3 cells

In this study, both NIH3T3 and Bcl-2 transfected NIH3T3 cells were examined for their propensity to undergo nitroso compound-induced apoptosis. Bcl-2- expressing NIH3T3 prevented N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)- an d S-nitrosoglutathione (GSNO)-induced apoptosis as compared with the contro l NIH3T3 cells. Flow cytometry revealed that NIH3T3 cells treated with MNNG undergo apoptotic death, which occurred after G(2)-M arrest in the second cycle of cell proliferation. The mechanism of MNNG-induced NIH3T3 cells apo ptosis was observed throughout the activation of caspase-3 protease, PARP d egradation and cytochrome c release; it was independent of p53 activation. Glutathione-S-transferanse pi (GST pi) is activated through the transcripti on activation of antioxidant response element (ARE) during MNNG- and GSNO-i nduced cell apoptosis. Moreover, overexpression of Bcl-2 in NIH3T3 cells ca n prevent these features of cell death. Furthermore, both MNNG- and GSNO-in duced apoptosis of NIH3T3 cells were accompanied with a decrease in the lev el of glutathione (GSH); whereas Bcl-2 overexpression led to an increase in total cellular glutathione. MNNG was metabolized rapidly to nitric oxide t hat reacted with glutathione under the catalysis of GSH transferase in NIH3 T3 cell to form GSNO. In short, the production of GSNO in cells was found c apable of apoptosis initiation while the overexpression of Bcl-2 can preven t MNNG-mediated cell apoptosis through the elevation of glutathione levels. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.