Label-free quantitative data dependent (DDA) nano-LC-MS/MS analysis of proteomic changes in the mesenteric lymph harvested from healthy (control) and DSS-fed mice models of colitis

The gastrointestinal mucosa constitutes a critical barrier where millions of microbes and environmental antigens can interact with the host immune system. Intestinal barrier defects have been linked to a broad range of pathological states, including autoimmune, cancer and neurodegenerative diseases. Accordingly, it has been proposed as a leading therapeutic target. This research aimed to investigate the qualitative and quantitative changes in the proteomes of pre- and post-nodal mesenteric lymph at steady state and following inflammatory disruption of the intestinal barrier which could lead to the identification the antigenic and inflammatory load draining to the mesenteric lymph nodes, in both healthy and DSS-feed mice models of colitis and inflammatory bowel disease (IBD). To achieve this goal, we employed label-free quantitative (LFQ) bottom-up proteomics analysis of pre- and post-nodal mesenteric lymph. To map changes in the lymph composition following inflammatory damage, mice were fed dextran sulfate sodium (DSS), a sulfated polysaccharide which causes ulcerative colitis-like pathologies and as an additional inflammatory effect on the ileum mucosa. DSS-mediated inflammation in mice mediated significant qualitative and quantitative proteomic changes mapped to the release of damage-associated molecular pattern (DAMPS) in the afferent lymph, mostly generated from the damaged epithelia. In addition, molecular signatures of colitis/enteritis, organ injury and gastrointestinal inflammation were further found by the proteomics analysis. Importantly, enzymes normally confined to the gut, such as chymotrypsin, peptidases, phospholipases, elastases were mapped in the afferent lymph, consistent with the proteolysis and lipolysis observed following breaking down of the gut barrier.