P123 LACTOBACILLUS ACIDOPHILUS MODULATION OF MOUSE INTESTINAL TIGHT JUNCTION BARRIER: ROLE OF TOLL-LIKE RECEPTOR-2 (TLR-2)

Abstract

Lactobacillus acidophilus (LA) is one of the most commonly used probiotics that has been shown to improve the mucosal immune response and protect against pathogens permeation. Few studies suggested that LA may have beneficial effect on intestinal tight junction (TJ) barrier function by direct interaction with intestinal epithelial cells. Although probiotic enhancement of intestinal TJ barrier has been postulated as an important therapeutic mechanism, the effects of LA on intestinal epithelial TJ barrier function and the intracellular mechanisms involved in TJ barrier modulation remain unclear. The major aim of this study was to elucidate the intracellular mechanisms involved in LA modulation of intestinal epithelial TJ barrier function using an in-vivo model consisting of mouse small intestinal perfusion system; in wild type, TLR-2 deficient (TLR -/-) mice and in animal model of DSS-colitis. 1) Oral gavage of LA (1 x 109cfu/ml) caused enhancement of intestinal TJ barrier as measured by the decrease in mouse small intestinal permeability to dextran-10 kDa by day 1 of LA administration, and the LA effect on intestinal barrier continued up to day 5. 2) LA caused an increase in mouse intestinal tissue TLR-2 expression in wild type mice, which correlated with the decrease in mouse intestinal permeability. On the other hand, LA did not cause a decrease in mouse intestinal permeability in TLR-2 deficient mice (TLR-2-/-). 3) We examined the barrier protective effects of LA on the development of DSS-induced colitis. Oral DSS administration caused an increase in mouse intestinal permeability by day 2, prior to the development of colitis which occurs between 5-7 days. 4) LA administration by oral gavage daily starting 2 days prior to DSS treatment and continuing throughout the 7 days of DSS treatment inhibited the DSS-induced increase in colonic permeability. 5) The DSS-induced weight loss and disease activity index were also significantly attenuated in LA-treated mice. 6) Lastly, the involvement of TLR-2 in mediating the LA inhibition of DSS-induced increase in intestinal permeability was examined. LA did not inhibit the DSS-induced increase in mouse colonic permeability or inhibit the DSS-induced colitis in TLR-2-/- mice In conclusion, our data show that LA enhancement of mouse intestinal epithelial TJ barrier function was regulated via upregulation of TLR-2. Our findings also show that administration of probiotic LA is capable to preserve the disruption of tight junctions proteins associated with DSS-induced colitis, an animal model of IBD. Therefore, LA plays an important role as regulator of the integrity of the intestinal barrier in a TLR-2 dependent mechanism, which might have important implications for understanding of probiotic mechanisms in preventing/treating inflammatory conditions of the gut.