TNBS colitis induces architectural changes and alpha-synuclein overexpression in mouse distal colon: A morphological study

Alpha-synuclein (α-syn) is widely expressed in presynaptic neuron terminals, and its structural alterations play an important role in the pathogenesis of Parkinson's disease (PD). Aggregated α-syn has been found in brain, in the peripheral nerves of the enteric nervous system (ENS) and in the intestinal neuroendocrine cells during synucleinopathies and inflammatory bowel disorders. In the present study, we evaluated the histomorphological features of murine colon with 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis, a common model of colitis. Thereafter, we investigated the expression of α-syn, Toll-like receptor 4 (TLR4), choline acetyltransferase (ChAT), vasoactive intestinal peptide (VIP), tyrosine hydroxylase (TH), calcitonin gene-related peptide (CGRP), and calcitonin-like receptor (CALCR). Finally, we investigated the presence of phosphorylated α-syn (pS129 α-syn) aggregates and their relationship with inflammatory cells. Colon from TNBS mice showed an increase in inflammatory cells infiltrate and significative changes in the architecture of the intestinal mucosa. α-Syn expression was significantly higher in inflamed colon. VIP was increased in both the mucosa and muscularis externa of TNBS mice, while TH, CGRP, and CALCR were significantly reduced in TNBS mice. Amyloid aggregates of pS129 α-syn were detectable in the ENS, as in the macrophages around the glands of the mucosa correlating with the markers of inflammation. This study describes - for the first time - the altered expression of α-syn and the occurrence of amyloid α-syn aggregates in the inflammatory cells under colitis, supporting the critical role of bowel inflammation in synucleinopathies and the involvement of α-syn in IBD.