Intestinal origins of Parkinson's Disease pathologies

Accumulating evidence suggests that Parkinson’s disease (PD) pathology may arise in the gut. This likely occurs through the enteric nervous system (ENS), which facilitates bidirectional communication between the brain and intestines. A hallmark of PD is neuronal accumulation of misfolded α-synuclein (aSyn) proteins which have been shown to travel from the ENS to the brain via the vagus nerve. The goal of this study was to connect related neural and immune phenotypes in ex vivo and in vivo mouse models of PD.Recent data suggests that enteric neuronal fibers containing calcitonin gene related peptide (CGRP) act as chemo-sensors that can be stimulated to release CGRP in response to bacterial and chemical signals. CGRP can activate receptors that influence goblet cells (GCs) and immune cells. GCs are responsible for secreting mucus to maintain mucosal barrier integrity. Deterioration of gut barrier integrity is hallmark of PD patients. We hypothesize that alterations in luminal contents modifies and disturbs GCs disrupting the gut barrier in PD. This may result in increased release of CGRP leading to alterations in mucus production, immune responses, and aSyn aggregation in enteric neurons. In this study, the pesticide rotenone was given to C57BL/6 mice to facilitate aggregation of misfolded aSyn. Lectin and immuno-histochemistry were performed on sections of ileum and colon. GC mucopolysaccharides were fluorescently labeled with the lectin Ulex Europaeus Agglutinin I (UEA) conjugated to rhodamine. UEA-1+ cells in crypts were 25% more prevalent (68.5 +/- 0.5 vs. 52.5 +/-2.5) with rotenone treatment but 53% less prevalent in the luminal portion of crypts (22.5 +/- 2.5 vs. 47.5 +/-2.5). Fewer GCs in luminal positions is consistent with decreased mucus seen in PD patients. T cells were identified by immunoreactive (ir) CD3. Approximately 50% fewer CD3+ cells were in rotenone treated lamina propria (17 +/- 1.4) compared to control (36.2 +/- 3.5) consistent with previous reports. The area of CGRP-ir fibers in the lamina propria was 114% higher in control (6.4%+/-1.3) compared to rotenone treated tissue (5.6%+/-0.6). Rotenone treatment resulted in a 217% increase in the area average of CGRP-ir fibers in the region just below the epithelial monolayer (12.8%+/-1.3) compared to control (5.8%+/-0.7). While we did not observe CGRP fibers beyond the epithelial cell layer, GC cell disruption that could allow luminal contents to access CGRP fibers was suggested by the potential failure of GCs to migrate toward luminal surfaces from crypts. Future studies are needed to test the hypothesis that rotenone disturbance of mitochondrial function in GCs causes intestinal wall failure that leads to altered neuroimmune function. Aggregation of aSyn in enteric neurons may thereby be mediated by altered immune to neural actions as exacerbated by alterations in CGRP containing fibers and T cell populations in the gut. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.