NF-κB RNAi decreases the Bax/Bcl-2 ratio and inhibits TNF-α-induced apoptosis in human alveolar epithelial cells

Apoptosis of alveolar epithelial cells (AECs) plays a key role in acute lung injury (ALI). Understanding the underlying mechanism is conducive to the treatment of ALI. The goal of this study was to determine the possible involvement of nuclear factor-kappa B (NF-kappa B)/p65 and Bax/Bcl-2 in tumor necrosis factor-alpha (TNF-alpha)-induced apoptosis in AECs. Type II AECs, A549, with or without NF-kappa B/p65 expression silenced by small interfering RNA (siRNA) were challenged with TNF-alpha. The levels of NF-kappa B/p65, Bcl-2 and Bax were detected by reverse transcription-polymerase chain reaction, Western blotting, and immunocytochemical staining. The apoptosis rate was measured by flow cytometry. TNF-alpha challenge significantly increased the transcription and translation of NF-kappa B/p65 and Bax genes, but significantly decreased the Bcl-2 gene level. siRNA silencing of NF-kappa B/p65 reversed the effect of TNF-alpha on NF-kappa B/p65, Bcl-2 and Bax, and significantly decreased the TNF-alpha-induced apoptosis rate of AECs, as compared to the non-silenced cells. This study indicates that NF-kappa B plays an important role in the process of TNF-alpha-induced apoptosis in AECs, via regulation of the expression of Bcl-2 and Bax.