UC San Diego

In Inflammatory Bowel Disease (IBD), the colon and small intestine are chronically inflamed due, at least in part, to increased epithelial permeability and an inappropriate immune response to luminal antigens. IFN-gamma is a prominent pro-inflammatory cytokine that increases permeability of the intestinal epithelium and T-Cell Protein Tyrosine Phosphatase (TCPTP) is a negative regulator of IFN-gamma signaling. This research explores the effects of a probiotic preparation on TCPTP abundance, resolution of inflammatory signaling, and intestinal epithelial permeability by studying a probiotic blend called VSL#3. Research showed that in T84 colonic epithelial cells, VSL#3 was able to increase TCPTP protein levels by 150 ± 3% and enzymatic activity by 100 ± 5% (106 CFU/mL for 9 hours). Moreover, VSL#3 was able to decrease epithelial monolayer permeability by 25 ± 2% over 9 hours (106 CFU/mL). When IFN-gamma and VSL#3 were co-incubated, VSL#3 attenuated the increase in permeability that resulted from 24 hours pre-treatment of T84 cells with IFN-gamma by 120 ± 2%. Moreover, levels of phosphorylated STAT-1 (a downstream effect of IFN-gamma signaling) decreased when VSL#3 and IFN-gamma were co- incubated and TCPTP levels showed an increase as VSL#3 doses were increased. Results were inconclusive as to whether VSL#3's effects on transepithelial resistance in IFN-gamma pre-treated cells were TCPTP-mediated because the TCPTP inhibitor failed to display its expected action. Overall, the findings of this thesis indicate that VSL#3 can repair epithelial permeability defects caused by IFN- gamma and this may be due in part to upregulation of a negative regulator of IFN-gamma signaling, TCPTP