Elucidating the Role of Cytokines in Enteric Neuron Responses

Abstract

Emerging studies have established the role of neuroimmune interactions in regulating intestinal immunity. Our lab has shown that neuropeptides- neuromedin (NMU) and calcitonin gene-related peptide (CGRP) are potent modulators of type-2 innate lymphoid cells (ILC2s) which orchestrate type-2 immune responses essential for maintaining intestinal homeostasis. However, the effects of these cytokines on enteric neuron functions remain unexplored. Reanalysis of published data on single-cell RNA sequencing of enteric neurons indicates that enteric neurons form distinct transcriptional clusters with unique neuropeptide profiles. Interestingly, a single subset of neurons expressing CGRP and NMU co-expresses the genes required to form the IL-13Ra/IL-4Ra heteroreceptor that interacts with both IL-13 and IL-4. In order to explore the effects of activation of IL-13Ra/IL4Ra heteroreceptor on the enteric nervous system (ENS) functions, we used primary neuron cultures derived from ENS stem cell progenitors. We validated the expression of IL-13Ra on enteric neurons in cultures using immunocytochemistry and studied the transcriptional changes induced upon IL-13/IL-4 stimulation by qPCR. Preliminary data shows a significant increase in the expression of Calcb and Nmu, which modulate ILC2 responses. These results demonstrate that a bidirectional communication exists between the enteric neurons and ILC2s which modulate intestinal homeostasis. We also studied the effects of abrogation of IL-33/ST2 signaling in ENS and IL-27 production by enteric neurons on intestinal immune responses using DSS-induced colitis model. However, our findings suggest that neither IL-33/ST2 pathway nor IL-27 production by enteric neurons is directly involved in regulating DSS mediated colitis. Through this study, we have tried to advance our understanding of the complex neuroimmune interactions involved in maintaining intestinal immunity in health and disease.