Transcriptomic profiling reveals a pronociceptive role for angiotensin II in inflammatory bowel disease.

Abstract

Visceral pain is a leading cause of morbidity in inflammatory bowel disease (IBD), contributing significantly to reduced quality of life. Currently available analgesics often lack efficacy or have intolerable side effects, driving the need for a more complete understanding of the mechanisms causing pain. Whole transcriptome gene expression analysis was performed by bulk RNA sequencing of colonic biopsies from patients with ulcerative colitis (UC) and Crohn disease (CD) reporting abdominal pain and compared with noninflamed control biopsies. Putative pronociceptive mediators were identified based on analysis of differentially expressed genes in IBD biopsy tissue and single-cell gene expression in murine colonic sensory neurons. Pronociceptive activity of identified mediators was assessed in assays of sensory neuron and colonic afferent activity. RNA sequencing analysis highlighted a 7.6-fold increase in the expression of angiotensinogen transcripts, Agt, which encode the precursor to angiotensin II (Ang II), in samples from UC patients (P = 3.2 × 10-8). Consistent with the marked expression of the angiotensin AT1 receptor in colonic sensory neurons, Ang II elicited an increase in intracellular Ca2+ in capsaicin-sensitive, voltage-gated sodium channel subtype NaV1.8-positive sensory neurons. Ang II also evoked action potential discharge in high-threshold colonic nociceptors. These effects were inhibited by the AT1 receptor antagonist valsartan. Findings from our study identify AT1 receptor-mediated colonic nociceptor activation as a novel pathway of visceral nociception in patients with UC. This work highlights the potential utility of angiotensin receptor blockers, such as valsartan, as treatments for pain in IBD.