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Regional differences in the small intestinal proteome of control mice and of mice lacking lysosomal acid lipase

ABSTRACT: Background: Despite recent studies investigating the involvement of single cells in regional differences of the small intestine (SI), the metabolic contribution of the duodenum, jejunum, and ileum to the overall intestinal metabolism is still unclear. Basic procedures and main findings: Using an untargeted proteomics approach, we identified similarities and differences between the three intestinal tracts of C57BL/6J mice and found that proteins highly abundant in the mouse ileum correlated with high ileal expression of the corresponding genes in humans. Consistent with human data, we detected increasing abundance of lysosomal acid lipase (LAL) in C57BL/6J mice from the duodenum to ileum. LAL is the only enzyme known to degrade triacylglycerols and cholesteryl esters within the lysosome. Lipid accumulation in various organs along with gastrointestinal disturbances and malabsorption are typical features of patients and mice with LAL deficiency. We previously demonstrated that macrophages massively infiltrate the SI of Lal-deficient (KO) mice, especially the duodenum. To identify potential mechanisms behind the intestinal lipid accumulation and infiltration of immune cells, we used untargeted proteomics. Our results revealed a general inflammatory response and a common lipid-associated macrophage phenotype in all three intestinal segments of Lal KO mice, accompanied by higher expression of GPNMB and increased concentrations of circulating sTREM2. However, only duodenal macrophages activated a metabolic switch from lipids to other pathways such as glycolysis, TCA cycle, and oxidative phosphorylation to meet their high energy demand. Unexpectedly, these pathways were downregulated in the jejunum and ileum of Lal KO mice. Conclusion: Our results provide new insights into the process of absorption in control mice and the basis for novel markers of LAL-D and/or systemic inflammation in LAL-D.

INSTRUMENT(S): Orbitrap Fusion

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Jejunum, Duodenum, Ileum

SUBMITTER: Monika Svecla

LAB HEAD: Giuseppe Danilo Norata

PROVIDER: PXD048378 | Pride | 2024-02-20

REPOSITORIES: Pride

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Project description:Background: Tissue-resident gd intraepithelial lymphocytes (IELs) orchestrate innate and adaptive immune responses to maintain intestinal epithelial barrier integrity. Epithelia-specific butyrophilin-like (Btnl) molecules induce perinatal development of distinct Vg TCR+ IELs, however, the mechanisms that control gd IEL maintenance within discrete intestinal segments are unclear. Btnl2, a member of Btnl family, has been shown to induce Treg differentiation and suppress T cell activation and proliferation in vitro. Btnl2 is highly enriched in villous IECs across different intestinal compartments and its expression is reported to be altered by inflammatory cues such as epithelial injury and tumor burden. We sought to understand the role of Btnl2 in regulating intestinal immune responses during homeostasis and inflammation and, particularly, in the induction and maintenance of intestinal gd IELs. Methods: We surveyed the gut immune system of in-house generated Btnl2-KO and WT mice within discrete intestinal segments (duodenum, jejunum, ileum, colon) during homeostasis and DSS-induced epithelial injury using flow cytometry, primary cell assays, immunoassays, and gene expression profiling. In addition, we performed high throughput transcriptomic (bulk RNAseq and scRNAseq) and TCR repertoire (scTCRseq) characterization of segment-specific Btnl2-KO and WT gd IELs at steady-state. Results: We characterized newly generated Btnl2 knockout mice and identify a role for Btnl2 in regulating the frequencies and phenotype of gd IELs preferentially in the ileum at steady state. We found that gd IELs derived from the ileum, but not duodenum, of Btnl2-KO mice possess a dysregulated antibacterial response module. By integrating RNA and single-cell TCR expression data we identified distinct transcriptional signatures and greater TCR repertoire diversity in ileal Btnl2-KO gd IELs. Upon DSS challenge, Btnl2-KO mice displayed enhanced colonic, but not ileal, intestinal inflammation and delayed mucosal repair. Conclusions: Collectively, our findings suggest that context-dependent Btnl2 expression fine-tunes intestinal immune responses to protect against epithelial injury. Overall, Btnl-mediated targeting of γδ IEL development and maintenance may help dissect their immunological functions in intestinal diseases with segment-specific manifestations.

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Regional differences in the small intestinal proteome of control mice and of mice lacking lysosomal acid lipase

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