NEURONAL PANNEXIN-1 SHAPES INTESTINAL IMMUNE PROFILES AND FUNCTIONS

Integration between neural and immune systems is critical for gastrointestinal functions, and disruptions of this communication contribute to inflammatory bowel disease (IBD). Pannexin-1 (Panx1) is a membrane channel expressed by enteric neurons and immune cells that contributes to intercellular communication and regulation of intestinal inflammatory responses. Although Panx1 expression is reduced in IBD and its activation promotes neurodegeneration in colitis, the specific contribution of neuronal Panx1 in immune regulation and intestinal function remains unknown. Here, we tested the hypothesis that neuronal Panx1 signaling regulates intestinal function and immune recruitment through direct neuro-immune and neuro-glial communication.

Panx1 expression was evaluated by RT-qPCR in submucosa and muscularis from healthy controls and IBD patients. Panx1 expression in the murine enteric nervous system was assessed by immunolabeling. Intestinal motility and barrier permeability were measured by standard assays in wild-type and mice with a targeted deletion of neuronal Panx1 (Wnt1^Cre;Panx1^f/f). Immune cell populations in the lamina propria were assessed by flow cytometry in wild-type and knock-out animals. Neuronal and glial activity was measured by calcium imaging following focal application of ADP or ATP in the colon from knock-out (Wnt1^Cre;GCaMPTdt^f/f;Panx1^f/f) and wild-type (Wnt1^Cre;GCaMPTdt^f/f) animals.

Panx1 expression is significantly reduced in the submucosa from IBD patients (p=0.017) to a similar extent in Crohn’s disease and ulcerative colitis. Immunolabeling in mice showed that Panx1 is mainly expressed by intrinsic primary afferent neurons. Neuronal Panx1 deletion does not affect total gastrointestinal transit time in either sex but doubled colonic transit time in males (p=0.01) and reduced intestinal paracellular permeability (p=0.04), suggesting a role in primary intestinal functions. These changes in intestinal functions are associated with abnormal purinergic neuro-glia communication in the myenteric plexus, where neurons and glia exhibited greater responsiveness to both ADP (p< 0.01) and ATP (p< 0.01). Importantly, neuronal Panx1 deletion increased immune cell infiltration in the lamina propria of the distal colon, with an increase in T lymphocyte proportion and a decrease in neutrophils. This shift in the immune profile is associated with reduced physical interaction between neuronal fibers and immune cells, suggesting a role of Panx1 in the regulation of neuro-immune communication.

These findings demonstrate that neuronal Panx1 is essential in regulating primary intestinal functions. Dysregulations of Panx1 signaling may contribute to intestinal motility and permeability disorders and immune alterations observed in IBD. Panx1 could, therefore, be a promising therapeutic target for the management of IBD-related intestinal dysfunction.