Anti-inflammatory and ultrastructural effects of Turkish propolis in a rat model of endotoxin-induced uveitis

Abstract

Introduction. Experimental animal models of acute uveitis, an inflammatory eye disease, can be established via endotoxin-induced inflammation. Propolis, a natural substance collected by honeybees from buds and tree exudates, has antioxidant, antibacterial, antiviral, and anti-inflammatory effects. We investigated the effects of propolis, obtained from the Sakarya province of Turkey, on endotoxin-induced uveitis using immunohistochemical, ultrastructural, and biochemical approaches. Material and methods. Male Wistar albino rats (n = 6/group) received intraperitoneal (ip) lipopolysaccharide (LPS) endotoxin (150 mu g/kg) followed by aqueous extract of propolis (50 mg/kg ip) or vehicle; two additional groups received either saline (control) or propolis only. After 24 h, aqueous humor (AH) was collected from both eyes of each animal for analysis of tumor necrosis factor-alpha (TNF-alpha) and hypoxia-inducible factor-1 alpha (HIF-1 alpha). Right eyeballs were paraffin-embedded for immunohistochemical staining of nuclear factor kappa B (NF-kappa B)/p65 and left eyeballs were araldite-embedded for ultrastructural analysis. Results. Treatment of LPS-induced uveitis with propolis significantly reduced ciliary body NF-kappa B/p65 immunoreactivity and AH levels of HIF-1 alpha and TNF-alpha. Ultrastructural analysis showed fewer vacuoles and reduced mitochondrial degeneration in the retinal pigment epithelium, as compared to the uveitis group. The intercellular spaces of the inner nuclear layer and outer limiting membrane were comparable with those of the control group; no polymorphonuclear cells or stasis was observed in intravascular or extravascular spaces. Conclusions. This is the first report demonstrating an anti-inflammatory effect of Turkish propolis in a rat model of LPS-induced acute uveitis, suggesting a therapeutic potential of propolis for the treatment of inflammatory ophthalmic diseases.