ClC-2 regulates mucosal barrier function associated with structural changes to the villus and epithelial tight junction. Am J Physiol Gastrointest Liver Physiol - We have previously shown an important role of the chloride channel ClC-2 in orchestrating repair of tight junctions in ischemic-injured mucosa. In this study, we examined the role of ClC-2 in regulating barrier function of normal murine intestinal mucosa. Ex vivo, ClC-2-/- ileal mucosa mounted in Ussing chambers had significantly higher transepithelial electrical resistance (TER) and reduced 3H-mannitol mucosal-to-serosal flux compared to wild type (WT) mouse mucosa. We also noted that ileum from ClC-2-/- mice had a significantly reduced in vivo 3H-mannitol blood-to-lumen clearance as compared to WT animals. Using scanning electron microscopy, flat leaf-like villi were found to have tapering, rounded apical tips in ClC-2-/- mucosa. In transmission electron microscopy, the apical inter-cellular tight junctions in ClC-2-/- intestine revealed lateral membranes that were less well defined but closely aligned as compared to electron dense and closely apposed tight junctions in WT mucosa. The width of apical tight junctions was significantly reduced in ClC-2-/- intestine. Such an alteration in tight junction ultrastructure was also noted in the testicular tissue from ClC-2-/- mice. The ClC-2-/- intestinal mucosa had reduced expression of phospho-MLC, and inhibition of MLCK in WT mucosa partially increased TER toward the TER in ClC-2-/- intestine. Contrary to our prior work on the reparative role of ClC-2 in injured mucosa, this study indicates that ClC-2 reduces barrier function in normal mucosa. The mechanisms underlying these differing roles are not entirely clear, although ultrastructural morphology of tight junctions and MLCK appear to be important to the function of ClC-2 in normal mucosa.
- tight junction
- barrier function
- myosin light chain kinase
- Copyright © 2009, American Journal of Physiology- Gastrointestinal and Liver Physiology