Beta-glucogallin Suppresses Lipopolysaccharide-induced Inflammatory Markers by Aldose Reductase Inhibition in Murine Macrophages and Ocular Tissues

Abstract

Purpose: Uveitis is a chronic inflammatory disease of the eye and can be induced in experimental mice by exposure to endotoxins such as lipopolysaccharide (LPS). Among other effectors, aldose reductase (AR) has been linked to ocular inflammation in the endotoxin-induced uveitis (EIU) model. We recently discovered β-glucogallin (BGG) as a novel AR inhibitor from extracts of the Indian gooseberry (Emblica officinalis). The purpose of this study is to investigate whether BGG is effective against various inflammatory markers in the EIU model.

Methods: Cytotoxicity of BGG was determined by cell viability assay. AR activity in cells was estimated by measuring sorbitol accumulation with an enzyme-linked assay. The detection of inflammatory markers was investigated by ELISA assay and western blotting. The presence and severity of uveitis was estimated by counting inflammatory cells in histological sections. The morphology of macrophage cells was observed by fluorescence microscopy. Cell migration was measured using a transwell assay. Active MMP-9 was detected by gelatin zymography.

Results: BGG showed low cytotoxicity in Raw264.7 murine macrophages (5% cell growth inhibition in the presence of 50 µM) and effectively inhibited AR activity as measured by suppression of sorbitol accumulation by approximately 50% compared to control. In addition, BGG prevented LPS-induced release of TNF-α and IL-1β, activation of JNK, p38 and lowered ROS levels. We also demonstrated that BGG suppresses the infiltration of inflammatory cells into the ocular media of mice with experimental uveitis. In Raw267.4 macrophages, BGG attenuated LPS-induced morphological changes and migration, and inhibited activation of MMP-9.

Conclusions: These results suggest that BGG may be useful as a therapeutic agent against inflammatory diseases in the eye.

Keywords: 746 uveitis-clinical/animal model • 514 enzymes/enzyme inhibitors • 503 drug toxicity/drug effects