Luteolin attenuates endotoxin-induced uveitis in Lewis rats

Abstract

The aim of the present study was to investigate the efficacy of luteolin on endotoxin-induced uveitis (EIU) in rats. EIU was induced in Lewis rats by subcutaneous injections of lipopolysaccharide (LPS). One hr before the LPS injection, 0.1, 1 or 10 mg/kg luteolin or 1 mg/kg prednisolone was intraperitoneally injected. We investigated its effect upon clinical scores, cellular infiltration and protein leakage, as well as on the level of tumor necrosis factor (TNF)-α, nitric oxide (NO) and prostaglandin (PG) E2 in the aqueous humor (AqH). Histologic examination and immunohistochemical analysis in the iris-ciliary body (ICB) were performed to determine the expressions of cyclooxygenase (COX)-2 and inducible NO synthase (iNOS), and then the activated nuclear factor (NF)-κB p65, I kappa B (IκB)-α degradation, phosphorylated (p)-IκB kinase (IKK) α/β and activator protein (AP)-1 c-Jun. Luteolin suppressed, in a dose-dependent manner, the clinical scores, number of inflammatory cells, the protein concentration, and the TNF-α, NO and PGE2 levels in the AqH and improved the histiologic status of the ocular tissue. Luteolin suppressed the expression of iNOS and COX-2 and the activated NF-κB p65, IκB-α degradation, p-IKKα/β and AP-1 p-c-Jun in the ICB. The anti-inflammatory potency of 10 mg/kg luteolin was as strong as that observed with 1 mg/kg prednisolone. These results demonstrate that luteolin attenuates ocular inflammation by inhibiting expression and release of inflammatory markers, along with the inhibition of the activated NF-κB pathway and at least partly AP-1 activity in the ICB.