Probiotic Yeast Inhibits VEGFR Signaling and Angiogenesis in Colonic Inflammation

Abstract

Saccharomyces boulardii (Sb), a probiotic yeast, has been used for decades to protect against intestinal injury and inflammation. We previously reported Sb protects against Clostridium difficile colitis and intestinal tumor formation in animal models through modulation of host signaling pathways including EGFR/Erk signaling. There is increasing evidence that angiogenesis is an important component of intestinal inflammation clinically and in experimental IBD models. The aim of this study was to determine whether Sb alters VEGFR (vascular endothelial growth factor receptor) signaling, a central regulator of angiogenesis. HUVEC cells were used to examine the effects of Sb on cell signaling and on capillary tube formation (using the ECMatrixTM system). The effects of Sb on VEGF-mediated angiogenesis were examined in vivo using an adenovirus expressing VEGF-A(164) in the ears of adult nude mice (NuNu). The effects of Sb on neo-vascularization in acute DSS-induced colitis was quantified by three dimensional analyses of blood vessel volume and density in mouse colon. 1) In HUVEC, Sb reduced basal VEGFR-2 phosphorylation, VEGFR-2 phosphorylation in response to VEGF as well as activation of the downstream kinases PLCγ and Erk1/2. 2) Sb significantly inhibited angiogenesis in vitro in the capillary tube assay in a dose-dependent manner (p<0.01) 3) Sb also inhibited VEGF-induced angiogensis in vivo in the mouse ear model. 4) Sb treatment attenuated weightloss (p<0.01) in DSS colitis. Quantitative colonic vascular network imaging showed significantly increased blood vessel density and volume in DSS-treated mice compared to control. Sb treatment significantly reduced the neo-vascularization associated with DSS colitis and restored the vascular network to a normal morphology. Sb inhibits VEGFR signaling in vitro and reduces neo-vascularization in vitro and in two separate in vivo models. Our findings indicate that the probiotic yeast S boulardii can modulate angiogenesis in intestinal injury and repair, which provides a novel mechanism for its beneficial effects.