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Abstract or Project Description

The bacteria in the human colon can influence gastrointestinal lining cells [intestinal epithelial cells (IECs)] and immune cells within the intestines and throughout the body. One way that bacteria do this is through their metabolites, the chemicals they produce. By influencing IECs and immune cells, gut bacterial metabolites affect resistance and susceptibility to Inflammatory Bowel Disease (IBD), as bacterial metabolites can positively or negatively affect intestinal inflammation and IEC function. Using the methods employed in most human IBD metabolite stool studies, 99% of bacterial metabolites remain unidentified. We have developed a workflow to determine which of these molecules are potentially important for IBD, which are bacterially derived, and which are active or act on immune cells and IECs. In this proposal, we will focus on determining the activity of a class of bacterial molecules called fatty acid amides. We will investigate if they change the activity of IECs and an important immune cell type called dendritic cells. A subset of the fatty acid amide compounds that we find act on IECs and/or dendritic cells will be tested in two models of colonic injury and inflammation.

Abstract or Project Description

Inflammatory Bowel Disease (IBD) is caused by multiple genetic and environmental factors but the molecular mechanisms leading to chronic inflammation in the gut are largely not understood. Much of the heritable human risk for IBD, particularly in Crohn’s disease, can be mapped to defects in lysosomes, a cellular organelle responsible for bacterial degradation. Previous studies implicate defective lysosome in Paneth and dendritic cells as major liabilities for IBD, but understanding the lysosomes in these cell-types have been challenging due to studying rare organelles (<3% cell mass) within rare cell types (<5% cells).

To address this challenge, we propose to adopt a recently developed rapid lysosomal purification method called LysoIP, a technique that enables robust profiling of lysosomal proteins that are often below the detection threshold at the whole-cell level. Our hypothesis is that molecular defects in intestinal lysosomes underlie IBD pathology and that molecular identification of lysosomal contents will reveal mechanisms leading to chronic inflammation. To this end, we will use genetic mouse models that share similarities to human gut and purify lysosomes from multiple epithelial and immune subsets in the intestine. We anticipate that our dataset will be useful in providing a comprehensive understanding of lysosomes mediating gut health.