Lysophosphatidic acid receptor 1 is important for intestinal epithelial barrier function and susceptibility to colitis.

Intestinal epithelial cells form a barrier that is critical in protecting the host from the hostile luminal environment. Previously, we showed that lysophosphatidic acid receptor 1 (LPAR1) regulates proliferation of intestinal epithelial cells such that the absence of LPA1 mitigates epithelial wound healing process. This study provides evidence that LPA1 is important for the maintenance of epithelial barrier integrity. The epithelial permeability, determined by fluorescently labeled dextran flux and transepithelial resistance, is increased in Lpar1(-/-) (Lpa1(-/-)) mouse intestine. Serum liposaccharide level and bacteria loads in the intestinal mucosa and peripheral organs were elevated in Lpa1(-/-) mice. Decreased claudin-4, caudin-7, and E-cadherin expression in Lpa1(-/-) mice further suggested defective apical junction integrity in these mice. Regulation of LPA1 expression in Caco-2 cells modulated epithelial permeability and the expression levels of junctional proteins. The increased epithelial permeability in Lpa1(-/-) mice correlated with increased susceptibility to an experimental model of colitis that resulted in more severe inflammation and increased mortality compared to control mice. Treatment of Caco-2 cells with tumor necrosis factor-α and interferon-γ significantly increased paracellular permeability, which was blocked by co-treatment with LPA, but not in LPA1 knockdown cells. Similarly, orally given LPA blocked tumor necrosis factor-mediated intestinal barrier defect in mice. LPA1 plays a significant role in maintenance of epithelial barrier in the intestine via regulation of apical junction integrity.