Attivazione di differenti vie di segnalazione redox nella risposta cellulare allo stress ossidativo: ruolo del glutatione e dello status tiolico

Previously we demonstrated that human adenocarcinoma gastric cells AGS are able to counteract the detrimental effects of the ROS-inducer diallyl-disulfide. Here we report that such resistance can be extended to other pro-oxidant molecules. Conversely, AGS cells were induced to apoptosis via the mitochondrial pathway upon treatment with thiols-oxidizing agents, such as diamide. Apoptosis is associated with persistent oxidative damages, as evidenced by the increase of carbonylated proteins and the expression/activation of DNA damage-sensitive proteins histone H2A.X and DNA-PK. Resistance to H2O2, as well as sensitivity to diamide are correlated with GSH redox state, with H2O2 transiently increasing protein-GSH mixed disulfides, and diamide dramatically elevating GSSG. Moreover, the inhibition of GSH neo-synthesis, by buthionine sulfoximine, or the enrichment of intracellular sulphydryl pool, by N-acetylcysteine, was able to protect cells. Nrf2 rapidly translocates to the nuclei when AGS cells are treated with H2O2; whereas p53 is activated in response to diamide treatment by the oxidative induction of Trx1/p38MAPK signaling pathway. Finally, experiments carried out with p53 siRNA or dominant-negative Nrf2, indicate that these transcription factors play an important role in cell death and resistance to it. Our results are of particular importance for inducing apoptosis in tumor histotypes resistant to ROS-producing chemotherapeutics.