Stretch-induced Expression of CYR61 Increases the Secretion of IL-8 in A549 Cells via the NF-κβ/lκβ Pathway.

Mechanical ventilation (MV) with large tidal volumes can increase lung alveolar permeability and initiate inflammatory responses, resulting in ventilator-induced lung injury (VILI). The mechanisms of the injurious effects of MV and the genetic susceptibility remain unclear. VILI-related genes such as cysteine-rich angiogenic inducer 61 (Cyr61) have been demonstrated to play a detrimental role in the aggressive ventilation strategies. In the present study, we investigated the involvement of Cyr61 in the VILI and the underlying mechanism. A549 cells were exposed to cyclic stretch of varying durations and then the mRNA and protein levels of Cyr61 were measured by real-time PCR and Western blotting, respectively. Additionally, after exposure of A549 cells to cyclic stretch for 5 min to 1 h,the expression levels of nuclear factor kappaB (NF-κB) and IL-8 were detected by E L I S A and Western blotting. Thereafter, Cyr61 expression was depressed in A549 cells with the siRNA pGenesil1.1-Cyr61-3 before the cyclic stretch, and IL-8 secretion and the activation of NF-κB pathways were probed by ELISA and Western blotting, respectively. Moreover, A NF-κB inhibitor (PDTC) and an activator (TNF) were used before mechanical stretch. Realtime PCR and ELISA were performed to detect the mRNA and protein of IL-8, respectively. The results showed that the mechanical cyclic stretch led to increased Cyr61 expression at mRNA and protein levels in A549 cells. Additionally, cyclic stretch also mobilized NF-κB from the cytoplasm to the nucleus and increased IL-8 secretion in A549 cells. The inhibition of Cyr61 blocked the NF-κB activation and IL-8 secretion in response to cyclic stretch. Inhibition of NF-κB attenuated the mRNA and protein expression of IL-8 in A549 cells transfected with Cyr61 siRNA. It was suggested that Cyr61/NF-κB signaling pathway mediates the upregulation of IL-8 in response to cyclic stretch in A594 cells. These findings support the hypothesis that Cyr61 plays a critical role in acute lung inflammation triggered by mechanical strain.