Figure 5.

GSH, but not GSSG or other antioxidants, inhibits ceramide generation induced by H₂O₂ in lung epithelial cells. A549 cells were preincubated for 1 h in medium supplemented with 1% serum in the presence or absence of 10 mM of GSH, GSSG, DTT, or 2-mercaptoethanol, followed by incubations with 250 μM H₂O₂ for an additional 30 min. The cells were rinsed with ice-cold PBS to terminate the treatments and harvested by trypsinization. GSH (A) and ceramide (B) levels were determined as described in Materials and Methods. Values represent mean ± SEM. *Mean of the group that was significantly different from the mean of the H₂O₂-treated group (P < 0.05). All other comparisons were statistically not significant (P > 0.05). Statistical analysis was performed using the Mann-Whitney, nonparametric, two-tailed test.