Figure 4.

Modulation of cellular thiol level regulates SIRT1 protein level. A) BEAS-2B cells were treated with BSO (100 μM) to deplete GSH levels. BSO was pretreated 18 h before a 24-h treatment with CSE (0.5 or 1%) or H₂O₂ (150 μM). B) BEAS-2B cells were treated with NAC (2 mM) for 2 h prior to a 24-h treatment with CSE (0.5 or 1%) or H₂O₂ (150 μM). C, D) BEAS-2B cells (C) and SAECs (D) were treated with glutathione monoethyl ester (GSHmee; 2 mM) for 2 h, washed off with sterile PBS, and treated with CSE (1%) for 6 h. E) PEG-conjugated SOD (200 U/ml) and catalase (200 U/ml) were given to BEAS-2B cells alone or in combination for 30 min prior to being washed off with PBS, followed by a 6-h treatment with CSE (1%). Whole-cell extracts were analyzed by immunoblot. Gels are representative of 3 separate experiments (n=3). β-Actin was used as a loading control.