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)- and S-nitrosoglutathione (GSNO)-induced apoptosis as compared with the control NIH3T3 cells. Flow cytometry revealed that NIH3T3 cells treated with MNNG undergo apoptotic death, which occurred after G2-M arrest in the second cycle of cell proliferation. The mechanism of MNNG-induced NIH3T3 cells apoptosis was observed throughout the activation of caspase-3 protease, PARP degradation and cytochrome c release; it was independent of p53 activation. Glutathione-S-transferanse pi (GST pi) is activated through the transcription activation of antioxidant response element (ARE) during MNNG- and GSNO-induced cell apoptosis. Moreover, overexpression of Bcl-2 in NIH3T3 cells can prevent these features of cell death. Furthermore, both MNNG- and GSNO-induced apoptosis of NIH3T3 cells were accompanied with a decrease in the level of glutathione (GSH); whereas Bcl-2 overexpression led to an increase in total cellular glutathione. MNNG was metabolized rapidly to nitric oxide that reacted with glutathione under the catalysis of GSH transferase in NIH3T3 cell to form GSNO. In short, the production of GSNO in cells was found capable of apoptosis initiation while the overexpression of Bcl-2 can prevent MNNG-mediated cell apoptosis through the elevation of glutathione levels.