Protective role of oligomycin against intestinal epithelial barrier dysfunction caused by IFN-γ and TNF-α

Although the precise mechanisms involved in intestinal barrier dysfunction induced by proinflammatory cytokines are incompletely understood, pharmacological restoration of barrier function is very important to the management of intestinal disease. This study was aimed to investigate the protective role of HIF-1α inhibitor oligomycin against intestinal epithelial barrier dysfunction induced by proinflammatory cytokines IFN-γ and TNF-α, and the underlying mechanisms. To induce barrier dysfunction, Caco-2 monolayers were treated with IFN-γ and TNF-α simultaneously. The cytokines-treated Caco-2 monolayers in the absence and in the presence of oligomycin were used for physiological, morphological, and biochemical analyses. The results showed that at the concentration of blocking HIF-1α activation, oligomycin significantly ameliorated TER reduction and paracellular permeability increase in Caco-2 monolayers challenged with IFN-γ and TNF-α. Oligomycin also largely attenuated the IFN-γ and TNF-α-related relocalization of tight junction proteins ZO-1 and occludin. Western blot analysis revealed that oligomycin abolished the increases of both MLC phosphorylation and MLCK protein expression induced by IFN-γ and TNF-α challenge. Quantitative RT-PCR analysis showed that oligomycin inhibited the IFN-γ and TNF-α-induced up-regulation of MLCK mRNA. It is concluded that oligomycin is able to attenuate intestinal epithelial barrier dysfunction induced by proinflammatory cytokines IFN-γ and TNF-α. The mechanism by which oligomycin protects intestinal barrier function may, at least in part, be attributed to block the up-regulated MLCK transcription and protein expression induced by IFN-γ and TNF-α.