Abstract
BACKGROUND: Acute inflammation and its timely resolution play important roles in the body's responses to the environmental stimulation. Although IFN-γ is well known for the induction of inflammation, its role in the inflammation resolution is still poorly understood. METHODOLOGY AND PRINCIPAL FINDINGS: In this study, we investigated the function of interferon gamma (IFN-γ) during the resolution of PMA-induced skin inflammation in vivo. The results revealed that the expression levels of IL-6, TNF-α, and monocyte chemoattractant protein 1 (MCP-1) in skin decreased during the resolution stage of PMA-induced inflammation, while IFN-γ is still maintained at a relatively high level. Neutralization of endogenous IFN-γ led to accelerated reduction of epidermal thickness and decreased epithelial cell proliferation. Similarly, decreased infiltration of inflammatory cells (Gr1(+) or CD11b(+) cells) and a significant reduction of proinflammatory cytokines were also observed upon the blockade of IFN-γ. Furthermore, neutralization of IFN-γ boosted ALOX15 expression of the skin during inflammation resolution. In accordance, application of lipoxin A4 (LXA4, a product of ALOX15) obtained a proresolution effect similar to neutralization of IFN-γ. These results demonstrated that through upregulating ALOX15-LXA4 pathway, blockage of IFN-γ can promote the resolution of PMA-induced skin inflammation.