Lipoxin A4 attenuates hyperoxia­induced lung epithelial cell injury via the upregulation of heme oxygenase­1 and inhibition of proinflammatory cytokines.

ABSTRACT

The present study examined whether lipoxin A4 (LXA4) increases the expression of HO­1, and inhibits the production of interleukin 6 (IL­6) and monocyte chemotactic protein 1 (MCP­1) in LXA4­induced protection during hyperoxia­induced injury in murine lung epithelial cells (MLE­12) and what signal pathway may participate in the actions of LXA4 inhibiting IL­6 and MCP­1. MLE­12 cells were exposed to air or hyperoxia with or without pretreatment with LXA4, Zinc protoporphyrin IX (ZnPP­IX), IL­6, anti­IL­6, MCP­1, anti­MCP­1, inhibitors of p38 mitogen­activated protein kinase (p38 MAPK), protein kinase B (Akt) and extracellular signal­regulated kinase 1/2 (ERK1/2) signaling pathways. The cell survival rates, cell viability, apoptosis rates, expression of superoxide dismutase (SOD), heme oxygenase­1 (HO­1), IL­6 and MCP­1, and the activations of p38 MAPK, ERK1/2 and Akt were measured. LXA4 significantly increased the cell survival rates, cell viability, SOD levels and HO­1 expression, reduced the apoptosis rates, and inhibited the MCP­1 and IL­6 levels induced by hyperoxia in cells. ZnPP­IX, an inhibitor of HO­1, blocked LXA4­induced protection on cell viability in cells exposed to hyperoxia. Anti­IL­6 and anti­MCP­1 improved the cell viability of cells exposed to hyperoxia. Inhibition of p38 MAPK and ERK1/2 blocked the expression of MCP­1 and IL­6 induced by hyperoxia. LXA4 inhibited the activation of p38 MAPK and ERK1/2 induced by hyperoxia, and increased the activation of the Akt signaling pathway, which was inhibited by hyperoxia. Therefore, LXA4 attenuated hyperoxia­induced injury in MLE­12 cells via the upregulation of HO­1 expression. The protection of LXA4 in hyperoxia­induced cell injury may be associated with the downregulation IL­6 and MCP­1 levels via the inhibition of the p38 MAPK and ERK1/2 signaling pathways.