Vasoactive intestinal peptide protects alveolar epithelial cells against hyperoxia via promoting the activation of STAT3.

Oxidative stress injury and death in alveolar epithelial cells plays an important role in the pathogenesis of prolonged hyperoxia-induced lung impairment. A reduced survival of type II alveolar epithelial cells (AECIIs) may lead to abnormal repair, resulting in acute and chronic pulmonary diseases. Hyperoxia lung injury is associated with the secretion of various bioactive substances and the activation of multiple transcription factors. Vasoactive intestinal peptide (VIP), as a pulmonary sensory neuropeptide, performs a vital function in regulating cell proliferation and cell death through signal transducers and activators of transcription 3 (STAT3). In the present study, we investigated the effects of VIP and STAT3 on AECIIs upon the exposure of hyperoxia. MLE-12 cells were random to air (21% oxygen), hyperoxia (95% oxygen) and VIP treatment with or without STAT3 siRNA transfection. The proliferation of AECIIs was detected by MTT cell proliferation assay. The apoptosis rate was measured by flow cytometry. Mitochondrial membrane potential was evaluated by fluorescent dye JC-1 to understand mitochondrial and cell damage. The activation of STAT3 was assessed by western blot detection of phosphorylated STAT3. Compared with hyperoxia exposure alone, additional VIP treatment promoted cell proliferation, maintained the mitochondrial membrane potential and reduced the apoptosis and necrosis of AECIIs. The protective effects aforesaid were weakened after STAT3 expression was down regulated by siRNA. Cells with STAT3 siRNA transfection had a higher mortality and a sharper decline in the mitochondrial membrane potential as well as a lower proliferation compared with wild-type cells after hyperoxia exposure with VIP administration. VIP interference, a protective management, could decrease hyperoxia-induced cell injury and death and improve the survival of AECIIs exposed to hyperoxia, which might be associated with the activation of STAT3.