Activator protein-2alpha inhibits activation of Caspase 3 and cell apoptosis induced by cigarette smoke extract in vascular endothelial cells.

Objective: To investigate the effect of activator protein-2alpha (AP-2alpha) on activation of cysteine proteases with aspartate specificity 3 (Caspase 3) and the apoptosis of vascular endothelial cells (ECV304) induced by cigarette smoke extract (CSE).

Methods: ECV304 were cultured in vitro, and those at the exponential growth phase were studied in experiments. The cells were cultured with 0.0%, 2.5%, 5.0%, 10.0%, 15.0%, and 20.0%CSE respectively for 24 h, and in another experiment, the cells were exposed to 5.0%CSE for 0, 6, 12, 18, 24, 36, and 48 h respectively. Then the cells were infected with different virus vectors or treated by 5%CSE alone for 24 h. Cell apoptosis, and proliferation were tested by Hoechst staining and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) respectively, while the expression of cleaved Caspase 3 and AP-2alpha induced by CSE were tested by Western blot. The effects of over-expression of AP-2alpha on ECV304 apoptosis and the expression of cleaved Caspase 3 were investigated by transfection, Hoechst staining and Western blot.

Results: Compared with the blank control group (0.630 +/- 0.086), the proliferation was significantly increased in 2.5% CSE group (0.754 +/- 0.109), while that was decreased in the 5.0%, 10.0%, 15.0% and 20.0% CSE groups in a concentration-dependent manner. The cell apoptosis rate induced by 5.0%CSE was increased in a time-dependent manner [from (5.0 +/- 1.0)% to (72.6 +/- 12.1)%], and the differences among the groups was significant (chi(2) = 1773.0, P < 0.01). The expressions of AP-2alpha (0.882 +/- 0.014) in 24 h CSE-treatment group was higher than that of the control group (0.635 +/- 0.005, t = 5.21, P < 0.01). Over-expression of AP-2alpha inhibited the cell apoptosis [the apoptosis rate was (0.9 +/- 0.4)%, (7.5 +/- 0.9)% respectively] and the expression of cleaved Caspase 3 (the ratio were 0.300 +/- 0.020, 0.484 +/- 0.025) induced by CSE (t = 6.96, 8.75, all P < 0.01).

Conclusions: AP-2alpha was shown to inhibit the activation of Caspase 3 and the apoptosis of ECV304 induced by CSE.