Biology subjects

Nagarkatti, M.

Publications and source records attributed to Nagarkatti, M..

4 recordsLinked to original sources

bioRxiv2024

Studying the cellular basis of small bowel enteropathy using high-parameter flow cytometry in mouse models of primary antibody deficiency

BackgroundPrimary immunodeficiencies are heritable defects in immune system function. Antibody deficiency is the most common form of primary immunodeficiency in humans, can be caused by abnormalities in both the development and activation of B cells, and may result from B-cell-intrinsic defects or defective responses by other cells relevant to humoral immunity. Inflammatory gastrointestinal complications are commonly observed in antibody-deficient patients, but the underlying immune mechanisms driving this are largely undefined. MethodsIn this study, several mouse strains reflecting a spectrum of primary antibody deficiency (IgA-/-, Aicda-/-, CD19-/- and JH-/-) were used to generate a functional small-bowel-specific cellular atlas using a novel high-parameter flow cytometry approach that allows for the enumeration of 59 unique cell subsets. Using this cellular atlas, we generated a direct and quantifiable estimate of immune dysregulation. This estimate was then used to identify specific immune factors most predictive of the severity of inflammatory disease of the small bowel (small bowel enteropathy). ResultsResults from our experiments indicate that the severity of primary antibody deficiency positively correlates with the degree of immune dysregulation that can be expected to develop in an individual. In the SI of mice, immune dysregulation is primarily explained by defective homeostatic responses in T cell and invariant natural killer-like T (iNKT) cell subsets. These defects are strongly correlated with abnormalities in the balance between protein (MHCII-mediated) versus lipid (CD1d-mediated) antigen presentation by intestinal epithelial cells (IECs) and intestinal stem cells (ISCs), respectively. ConclusionsMultivariate statistical approaches can be used to obtain quantifiable estimates of immune dysregulation based on high-parameter flow cytometry readouts of immune function. Using one such estimate, we reveal a previously unrecognized tradeoff between iNKT cell activation and type 1 immunity that underlies disease in the small bowel. The balance between protein/lipid antigen presentation by ISCs may play a crucial role in regulating this balance and thereby suppressing inflammatory disease in the small bowel.

immunology↗

bioRxiv2023

Human Gut Microbial Sulfonolipids are linked to Inflammatory Bowel Diseases through Toll-Like Receptor 4 Signaling

The trillions of microorganisms inhabiting the human gut are intricately linked to human health. At the species abundance level, correlational studies have connected specific bacterial taxa to various diseases. While the abundances of these bacteria in the gut serve as good indicators for disease progression, understanding the functional metabolites they produce is critical to decipher how these microbes influence human health. Here, we report a unique biosynthetic enzyme-guided disease correlation approach to uncover microbial functional metabolites as potential molecular mechanisms in human health. We directly connect the expression of gut microbial sulfonolipid (SoL) biosynthetic enzymes to inflammatory bowel disease (IBD) in patients, revealing a negative correlation. This correlation is then corroborated by targeted metabolomics, identifying that SoLs abundance is significantly decreased in IBD patient samples. We experimentally validate our analysis in a mouse model of IBD, showing that SoLs production is indeed decreased while inflammatory markers are increased in diseased mice. In support of this connection, we apply bioactive molecular networking to show that SoLs consistently contribute to the immunoregulatory activity of SoL-producing human microbes. We further reveal that sulfobacins A and B, two representative SoLs, primarily target Toll-like receptor 4 (TLR4) to mediate immunomodulatory activity through blocking TLR4s natural ligand lipopolysaccharide (LPS) binding to myeloid differentiation factor 2, leading to significant suppression of LPS-induced inflammation and macrophage M1 polarization. Together, these results suggest that SoLs mediate a protective effect against IBD through TLR4 signaling and showcase a widely applicable biosynthetic enzyme-guided disease correlation approach to directly link the biosynthesis of gut microbial functional metabolites to human health.

biochemistry↗

bioRxiv2022

Inactivation of Vascular Stem Cells Suppresses Intimal Hyperplasia in Vein Grafts

Chronic vein graft (VG) failure (VGF) is associated with VG intimal hyperplasia characterized by abnormal proliferation and accumulation of vascular smooth muscle cells (SMCs), which are derived predominantly from pre-existing vascular SMCs via a process of vascular SMC dedifferentiation.1 Therapeutic approaches focused on vascular SMCs, however, have not changed chronic VGF rates,2 indicating additional and yet unrecognized causes of chronic VGF. Herein, we uncover a novel diagram in which after transplantation, recipient vascular stem cells (VSCs) expressing Sca1 are activated and accumulated in the adventitia of VGs, and they do not differentiate into SMCs but promote intimal hyperplasia via paracrine enforcement of medial SMC dedifferentiation into synthetic SMCs in VGs, suggesting that VSCs may be a novel target for the treatment of chronic VGF.

cell biology↗

bioRxiv2021

Correlational networking guides the discovery of cryptic proteases for lanthipeptide maturation

Bacterial natural product biosynthetic genes, canonically clustered, have been increasingly found to rely on cryptic enzymes encoded elsewhere in the genome for completion of biosynthesis. The study and application of lanthipeptides are frequently hindered by cryptic proteases required for final maturation. Here, we establish a global correlation network bridging the gap between lanthipeptide precursors and cryptic proteases. Applying our analysis to 161,954 bacterial genomes, we establish 5,209 correlations between precursors and cryptic proteases, with 91 prioritized. We use network predictions and co-expression analysis to reveal a previously missing protease for the maturation of class I lanthipeptide paenilan. We further discover widely distributed bacterial M16B metallopeptidases of previously unclear biological function as a new family of lanthipeptide proteases. We show the involvement of a pair of bifunctional M16B proteases in the production of novel class III lanthipeptides with high substrate specificity. Together, these results demonstrate the strength of our correlational networking approach to the discovery of cryptic lanthipeptide proteases and potentially other missing enzymes for natural products biosynthesis. Graphical abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

biochemistry↗