Molecular mechanisms of topical anti-inflammatory effects of lipoxin A(4) in endotoxin-induced uveitis.

Lipoxin A(4) (LXA(4)) is a lipid mediator that plays an important role in inflammation resolution. We assessed the anti-inflammatory effect of LXA(4) on endotoxin-induced uveitis (EIU) in rats. The inflammatory cell number and levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), prostaglandin E(2) (PGE(2)), and protein, as well as expression of cyclooxygenase-2 (COX-2) and vascular endothelial growth factor (VEGF), in the anterior chamber of the eye were determined 24 h after lipopolysaccharide (LPS; 200 mug/paw) intradermal injection. The immunohistochemical reactivities of nuclear factor-kappaB (NF-kappaB) and c-Jun were also examined. Topical LXA(4) (1-10 ng/eye) pretreatment decreased the number of inflammatory cells and the protein leakage into the aqueous humor (AqH). In addition, topical LXA(4) (10 ng/eye) inhibited the LPS-induced production of IL-1beta, TNF-alpha, and PGE(2), and expression of COX-2 and VEGF. A decreased activation of NF-kappaB and c-Jun was also found in LXA(4)-treated eyes. It is very interesting that an anti-inflammatory effect was achieved even when LXA(4) (10 ng/eye) was applied topically after LPS challenge, as indicated by the reduction in the cellular and protein extravasations into the AqH. Moreover, topical treatment of corticosteroid prednisolone (200 mug/eye) beginning before or after LPS injection reduced all of the molecular and biochemical alterations promoted on EIU rats in an efficacy similar to that of LXA(4). Together, the present results provide clear evidence that pharmacological activation of LXA(4) signaling pathway potently reduces the EIU in rats. Therefore, LXA(4) stable analogs could represent promising agents for the management of ocular inflammatory diseases.