N-Acetyl-L-Cysteine Counteracts Oxidative Stress and Prevents H2O2 Induced Germ Cell Apoptosis Through Down-Regulation of Caspase-9 and JNK/c-Jun

The mechanism of H2O2 induced oxidative stress leading to male germ cell apoptosis was earlier reported from our laboratory. In the present study, we investigated the mechanisms by which N-acetyl-L-cysteine (NAC, which is highly cell specific with strong antioxidant and anti-genotoxic properties), stimulated cell survival under such conditions. Co-incubation with 5mM NAC significantly (P < 0.001) reduced the germ cell apoptosis induced by 10 mu M H2O2. Lipid peroxidation was brought down with significant restoration of activities of antioxidant enzymes, SOD, GST, and catalase. Expression of pro-apoptotic marker, Bax up-regulated following H2O2 exposure, was reversed back to control levels. In contrast, expression of anti-apoptotic Bcl-2 and phospho-Akt revealed a completely opposite trend. While caspase-8 activity remained unaffected, NAC successfully attenuated the increased activities of caspase-3 and -9 in the H2O2 treated cells. Simultaneously, the increased expression of caspase-9, phospho-JNK, and phospho-c-Jun after H2O2 treatment was down-regulated by NAC. The above findings indicate that the mechanism of inhibition of H2O2 induced male germ cell apoptosis by NAC is mediated through regulation of caspase-9 and JNK. Mol. Reprod. Dev. 78: 69-79, 2011. (c) 2010 Wiley-Liss, Inc.