Suppression of nitric oxide–induced apoptosis by N‐acetyl‐l‐cysteine through modulation of glutathione, bcl‐2, and bax protein levels

Abstract

It has been demonstrated that nitric oxide (NO) can promote apoptosis in human cancer cells. To test the protective effects of antioxidants (N-acetyl-L-cysteine (LNAC) and free-radical spin traps (5,5-dimethyl-1-pyrroline N-oxide and 2,2,6,6,-tetramethyl-1-piperidinyloxy) against NO-induced apoptosis, a human colon cancer cell line (COLO 205) was treated with NO, and its survival rate was evaluated both with and without antioxidant therapy. LNAC arrested the development of progression of apoptosis in COLO 205 cells in a dose-dependent manner, promoted long-term survival, and prevented the internucleosomal DNA cleavage induced by NO. The intracellular level of glutathione (GSH) was found to be elevated in cells after exposure to LNAC. The bax protein levels were elevated by NO treatment, and this effect was blocked by LNAC. On the other hand, the bcl-2 oncoprotein level in the LNAC-pretreated cells was significantly elevated in a time-dependent manner compared to cells that received NO pretreatment. In summary, our results suggest that the protective effect of LNAC may be linked to its inducement of increases in cellular GSH and bcl-2 protein levels and to its suppression of cellular bax protein in treated cells.

Induction of apoptosis by S-Nitrosoglutathione and Cu2+ or Ni2+ ion through modulation of bax, bad, and bcl-2 proteins in human colon adenocarcinoma cells

“…In this study, we con®rmed and extended our earlier ®ndings on the apoptotic effects of NO. The p53 and bax proteins were stimulated in NO-induced apoptosis, and, in contrast, expression of the bcl-2 gene was inhibited by NO [5,39]. Similar results were observed in previous studies that demonstrated that bcl-2 expression attenuates NO-induced apoptosis, caspase activation, and PARP cleavage in human cells [46±48].…”

“…Our previous report showed that the intracellular level of GSH was elevated in cells after exposure to LNAC [39]. We found that elevation of the intracellular GSH level could attenuate NO-induced apoptosis in human cancer cells.…”

“…In our previous studies [5,39], we demonstrated that bcl-2 protein expression was downregulated and bax protein expression was induced in NOtreated human cancer cells. Figure 5 shows that the expression of bcl-2 was downregulated in a timedependent manner when cells were treated with GSNO (2 mM).…”

Ketoconazole potentiates terfenadine‐induced apoptosis in human Hep G2 cells through inhibition of cytochrome p450 3A4 activity

“…However, none of the stimuli altered the expression levels of the bcl‐2 and bax protein. On the other hand, others' and ours studies demonstrated that agents which cause DNA damage (such as NO and γ‐radiation) might elevate p53 and bax levels, inhibit bcl‐2 expression and eventually cause apoptosis [Ho et al, 1996, 1997, Ho et al, 1999a,b,; Kitada et al, 1996]. Such results implied that the p53 ‐regulated bax and bcl‐2 protein expression was not changed by all of the apoptotic inducing agents.…”

Polyphenol interaction with the T47D human breast cancer cell line

“…Polyphenols can interact with the production (Visioli et al 1998;Kampa et al 2000) or with some biological effects of NO (Ahmad et al 1997;Ho et al 1997). Our results indicate that all four polyphenols inhibit cell growth by modifying NOS expression and NOS activity.…”