Endothelial semaphorin 7A promotes seawater aspiration-induced acute lung injury through plexin C1 and β1 integrin.

Inflammation and edema are two main characteristics in seawater aspiration‑induced acute lung injury (ALI). In a previous study of the authors, it was demonstrated that endothelial semaphorin 7A (SEMA7A) serves an important role in the development of seawater‑induced inflammation and edema. However, the mechanism of endothelial SEMA7A‑mediated ALI remains unclear. Therefore, the authors explored the effect of SEMA7A in rat pulmonary microvascular endothelial cells (RPMVECs) and the interaction between endothelial SEMA7A and alveolar macrophages during seawater aspiration‑induced ALI. The role of SEMA7A in endothelial permeability was detected using plexin C1 blocking antibody or SEMA7A small interfering (si)RNA. In addition, RPMVECs were co‑cultured with rat alveolar macrophage cell line‑NR8383 cells and pro‑inflammatory cytokine production was detected. Interaction between the β1 integrin and SEMA7A was detected using the β1 integrin blocking antibody or SEMA7A siRNA. Seawater stimulation induced endothelial cytoskeleton remodeling, endothelial permeability, phosphorylation of cofilin, and increased the vascular endothelial growth factor (VEGF) expression in RPMVECs. Moreover, seawater stimulation led to expression of proinflammatory cytokines and activated the nuclear factor‑κB pathway in co‑cultured cells. However, blockage with the plexin C1 antibody inhibited endothelial cytoskeleton remodeling, endothelial permeability, phosphorylation of cofilin, and treatment with SEMA7A siRNA inhibited expression of VEGF in RPMVECs. In addition, blockage with β1 integrin antibody reduced expression of proinflammatory cytokines and inhibited activation of NF‑κB in co‑culture cells. These results suggest that SEMA7A promotes seawater induced lung edema via plexin C1 and stimulates seawater induced lung inflammation via β1 integrin.