Decrease of Intracellular Chloride Concentration Promotes Endothelial Cell Inflammation by Activating Nuclear Factor-κB Pathway

Recent evidence suggested that ClC-3 channel/antiporter is involved in regulation of nuclear factor (NF)-κB activation. However, the mechanism explaining how ClC-3 modulates NF-κB signaling is not well understood. We hypothesized that ClC-3-dependent alteration of intracellular chloride concentration ([Cl − ] i ) underlies the effect of ClC-3 on NF-κB activity in endothelial cells. Here, we found that reduction of [Cl − ] i increased tumor necrosis factor-α (TNFα)-induced expression of intercellular adhesion molecule 1 and vascular cell adhesion molecule 1 and adhesion of monocytes to endothelial cells ( P 0.05; n=6). In Cl − reduced solutions, TNFα-evoked IκB kinase complex β and inhibitors of κBα phosphorylation, inhibitors of κBα degradation, and NF-κB nuclear translocation were enhanced. In addition, TNFα and interleukin 1β could activate an outward rectifying Cl − current in human umbilical vein endothelial cells and mouse aortic endothelial cells. Knockdown or genetic deletion of ClC-3 inhibited or abolished this Cl − conductance. Moreover, Cl − channel blockers, ClC-3 knockdown or knockout remarkably reduced TNFα-induced intercellular adhesion molecule 1 and vascular cell adhesion molecule 1expression, monocytes to endothelial cell adhesion, and NF-κB activation ( P 0.01; n=6). Furthermore, TNFα-induced vascular inflammation and neutrophil infiltration into the lung and liver were obviously attenuated in ClC-3 knockout mice ( P 0.01; n=7). Our results demonstrated that decrease of [Cl − ] i induced by ClC-3-dependent Cl − efflux promotes NF-κB activation and thus potentiates TNFα-induced vascular inflammation, suggesting that inhibition of ClC-3-dependent Cl − current or modification of intracellular Cl − content may be a novel therapeutic approach for inflammatory diseases.