R01AI164772

Nuclear Receptor Control of T Cell Function in Discrete Intestinal Microenvironments - Project Summary

The gut is a central immunological organ, where host-microbe interactions shape immune tolerance and inflammation, both locally and systemically. Yet prevailing immunological views conflate the two distinct organs that comprise the gut—small and large intestine (or SI and LI)—which impedes more robust understanding of mucosal immune regulation, and misses opportunities to develop safer, more targeted therapies for human inflammatory bowel diseases (IBDs).

The premise of this application, founded on recent discoveries from, and synergy between, the two PIs (Sundrud, Weaver), is that mucosal CD4+ T cells use distinct sets of nuclear receptors (NRs) in the SI and LI to interface with divergent classes of host- and microbe-derived metabolites, respectively. Recent work from the Sundrud lab establishes that FOXP3- T effector (Teff) subsets—TH1, TH17 cells—use a NR with no previously known immunological function, the constitutive androstane receptor (CAR/NR1I3), to direct a 'hepatocyte-like' transcriptional response to contend with potentially cytotoxic bile acid (BA) concentrations in the SI.

A large gradient of BAs exists between the SI (millimolar) and LI (micromolar) due to 'enterohepatic' circulation—primary BAs synthesized in the liver, stored in the gallbladder, and secreted post-prandially into the duodenum are actively reabsorbed by specialized enterocytes in the ileum for portal recirculation to the liver. Because BAs are lipophilic, they can be toxic and pro-inflammatory in enterohepatic tissues; a host of nuclear receptors—including CAR—have evolved to suppress BA toxicity in hepatocytes and enterocytes. Our data suggest that enterohepatic circulation creates a uniquely harsh SI microenvironment to which infiltrating T cells must adapt to maintain tolerance and tissue homeostasis.

The LI, by contrast, harbors 10^3-10^7 times more bacteria than the SI, and ~1000-fold less BAs. Accordingly, microbes and their metabolites—short chain fatty acids (SCFAs; e.g., butyrate), secondary BAs (produced via microbial metabolism of residual primary BAs)—become central to immune regulation in the LI. SCFAs inhibit histone deacetylase enzymes (HDACs) and stabilize FOXP3 gene expression in peripherally-induced T regulatory cells (iTregs), whereas secondary BAs promote LI Treg maintenance through another NR, vitamin D receptor (VDR).

Thus, while antigens from the enteric flora are required for priming both pro- and anti-inflammatory T cell responses throughout the intestinal tract, we hypothesize that marked differences in the abundance of bugs and bile in the SI vs. LI establish consequential metabolite gradients that are sensed by different NRs to instruct compartmentalized T cell regulatory functions.

We test this hypothesis through complementary, but not inter-dependent, aims, leveraging new mouse models, as well as a library of recombinant protein-based NR activity assays, to define the mechanisms governing the transcriptional regulation, biochemical activation, and downstream cellular functions of CAR (in SI Teff cells) and VDR (in LI iTreg cells).

Successful completion of these aims will establish new biological paradigms and inform more precise approaches to treat human IBDs.

Dartmouth-Hitchcock Clinic

TO ASSIST PUBLIC AND PRIVATE NONPROFIT INSTITUTIONS AND INDIVIDUALS TO ESTABLISH, EXPAND AND IMPROVE BIOMEDICAL RESEARCH AND RESEARCH TRAINING IN INFECTIOUS DISEASES AND RELATED AREAS, TO CONDUCT DEVELOPMENTAL RESEARCH, TO PRODUCE AND TEST RESEARCH MATERIALS. TO ASSIST PUBLIC, PRIVATE AND COMMERCIAL INSTITUTIONS TO CONDUCT DEVELOPMENTAL RESEARCH, TO PRODUCE AND TEST RESEARCH MATERIALS, TO PROVIDE RESEARCH SERVICES AS REQUIRED BY THE AGENCY FOR PROGRAMS IN INFECTIOUS DISEASES, AND CONTROLLING DISEASE CAUSED BY INFECTIOUS OR PARASITIC AGENTS, ALLERGIC AND IMMUNOLOGIC DISEASES AND RELATED AREAS. PROJECTS RANGE FROM STUDIES OF MICROBIAL PHYSIOLOGY AND ANTIGENIC STRUCTURE TO COLLABORATIVE TRIALS OF EXPERIMENTAL DRUGS AND VACCINES, MECHANISMS OF RESISTANCE TO ANTIBIOTICS AS WELL AS RESEARCH DEALING WITH EPIDEMIOLOGICAL OBSERVATIONS IN HOSPITALIZED PATIENTS OR COMMUNITY POPULATIONS AND PROGRESS IN ALLERGIC AND IMMUNOLOGIC DISEASES. BECAUSE OF THIS DUAL FOCUS, THE PROGRAM ENCOMPASSES BOTH BASIC RESEARCH AND CLINICAL RESEARCH. SMALL BUSINESS INNOVATION RESEARCH (SBIR) PROGRAM EXPANDS AND IMPROVES PRIVATE SECTOR PARTICIPATION IN BIOMEDICAL RESEARCH. THE SBIR PROGRAM INTENDS TO INCREASE AND FACILITATE PRIVATE SECTOR COMMERCIALIZATION OF INNOVATIONS DERIVED FROM FEDERAL RESEARCH AND DEVELOPMENT, TO INCREASE SMALL BUSINESS PARTICIPATION IN FEDERAL RESEARCH AND DEVELOPMENT, AND TO FOSTER AND ENCOURAGE PARTICIPATION OF SOCIALLY AND ECONOMICALLY DISADVANTAGED SMALL BUSINESS CONCERNS AND WOMEN-OWNED SMALL BUSINESS CONCERNS IN TECHNOLOGICAL INNOVATION. THE SMALL BUSINESS TECHNOLOGY TRANSFER (STTR) PROGRAM STIMULATES AND FOSTERS SCIENTIFIC AND TECHNOLOGICAL INNOVATION THROUGH COOPERATIVE RESEARCH AND DEVELOPMENT CARRIED OUT BETWEEN SMALL BUSINESS CONCERNS AND RESEARCH INSTITUTIONS, TO FOSTER TECHNOLOGY TRANSFER BETWEEN SMALL BUSINESS CONCERNS AND RESEARCH INSTITUTIONS, TO INCREASE PRIVATE SECTOR COMMERCIALIZATION OF INNOVATIONS DERIVED FROM FEDERAL RESEARCH AND DEVELOPMENT, AND TO FOSTER AND ENCOURAGE PARTICIPATION OF SOCIALLY AND ECONOMICALLY DISADVANTAGED SMALL BUSINESS CONCERNS AND WOMEN-OWNED SMALL BUSINESS CONCERNS IN TECHNOLOGICAL INNOVATION. RESEARCH CAREER DEVELOPMENT AWARDS SUPPORT THE DEVELOPMENT OF SCIENTISTS DURING THE FORMATIVE STAGES OF THEIR CAREERS. INDIVIDUAL NATIONAL RESEARCH SERVICE AWARDS (NRSAS) ARE MADE DIRECTLY TO APPROVE APPLICANTS FOR RESEARCH TRAINING IN SPECIFIED BIOMEDICAL SHORTAGE AREAS. IN ADDITION, INSTITUTIONAL NATIONAL RESEARCH SERVICE AWARDS ARE MADE TO ENABLE INSTITUTIONS TO SELECT AND MAKE AWARDS TO INDIVIDUALS TO RECEIVE TRAINING UNDER THE AEGIS OF THEIR INSTITUTIONAL PROGRAM.

93.855 - Allergy and Infectious Diseases Research

National Institute of Allergy and Infectious Diseases (NIAID) [HHS - NIH]

Lebanon, New Hampshire 03756 United States

Single Zip Code

NIH Research Project Grant (Parent R01 Clinical Trial Not Allowed) (PA-20-185)

Amendment Since initial award the total obligations have increased 381% from $938,621 to $4,511,823.