Mechanisms Underlying Role of Intestinal P-glycoprotein in Inflammatory Bowel Disease

Jesse Brown Va Medical Center, Chicago IL

Investigators

Linked publications & trials

Abstract

Project Summary/Abstract Background and Innovation: P-glycoprotein (Pgp/MDR1), encoded by the ABCB1 gene protects intestinal epithelium by mediating the efflux of xenobiotics and bacterial toxins from the mucosa into the lumen. Polymorphisms in the human MDR1 gene have been associated with ulcerative colitis (UC) and Crohn's disease. A decrease in function and expression of Pgp has been shown in mouse models of inflammation and patients with Inflammatory Bowel Disease (IBD). Additionally, Pgp deficient mice spontaneously develop severe colitis resembling human UC. However, the mechanisms underlying Pgp dysfunction in intestinal inflammation and IBD pathogenesis remain elusive. Our exciting preliminary data provide strong evidence that Pgp deficiency induces abnormal Paneth cell function (PC) with a significant decrease in lysozyme 1 and other PC-secreted antimicrobial peptides (AMPs). PC dysfunction in Pgp knockout (KO) mice was associated with gut microbial dysbiosis exhibiting an expansion of species linked to gut inflammation such as Turicibacter sanguinis, Alistipes sp., and a decline in Bacteroides thetaiotamicron and short chain fatty acid (SCFA)-producing bacteria critical in limiting the colonization of enteric pathogens. Indeed, previous studies have shown that Pgp KO mice are more susceptible and vulnerable to enteric pathogen infection. Since Paneth cell AMPs play an essential role in host defense against enteric pathogens and influence gut microbiome composition, our novel findings in Pgp KO mice suggest that Paneth cell antimicrobial defect leads to gut dysbiosis that precedes inflammation in Pgp KO mice and is likely to contribute to increased susceptibility to infection and or inflammation. Based upon these findings, we hypothesize that “Pgp deficiency results in impaired Paneth cell function which triggers microbial dysbiosis resulting in i) increased susceptibility to infection by enteric pathogens; ii) compromised colonic barrier integrity contributing to the development of spontaneous colitis in Pgp KO mice”. We further hypothesize that “restoration of AMP levels in Pgp KO mice maintains a healthy microbiome that can prevent susceptibility to infection and development of spontaneous colitis”. To test this hypothesis, Specific Aim 1 will investigate mechanisms underlying Pgp deficiency-induced Paneth cell defects in triggering gut dysbiosis, increased susceptibility to infection by enteric pathogen (Citrobacter rodentium), compromised epithelial barrier function and development of spontaneous inflammation in Pgp KO mice. We will also examine the role of oral supplementation of AMP in preventing infection and inflammation in Pgp KO mice. Specific Aim 2 will examine mechanisms underlying Pgp deficiency-associated gut dysbiosis in compromised epithelial barrier function and susceptibility to colitis by determining the impact of microbiota transfer from Pgp KO mice to recipient germ-free (GF) mice with or without DSS-induced and IL-10 receptor antibody-induced colitis as well as examining the effects of colonization of both Turicibacter sanguinis and Alistipes sp., together in eliciting similar effects of Pgp deficiency on epithelial barrier function and inflammation in GF mice. Significance and Impact to Veterans Healthcare: Despite advances in current therapies, many VA patients with IBD fail to respond to treatment or lose their initial response over time and lack of treatment outcomes can further impart a substantial financial burden on VA patients. Also, extended use of corticosteroids by elderly VA patients can lead to adverse health conditions. Therefore, a better understanding of the molecular events contributing to the pathophysiology of IBD is warranted. Our proposal investigates the novel role of Pgp deficiency-induced abnormal Paneth cell function in gut microbial dysbiosis contributing to IBD. These studies are relevant to the VA mission and are among the key VHA/ORD research priorities. Path to translation/implementation: The proposed studies at the preclinical stage are crucial for identifying and developing novel and effective therapeutic interventions for IBD that is prevalent among Veterans.