Protease-Activated Receptor 1 is Implicated in Irritable Bowel Syndrome Mediators-Induced Signalling to Thoracic Human Sensory Neurons

Abstract

Proteases and Protease-Activated Receptors (PARs) are major mediators involved in irritable bowel syndrome (IBS). Our objectives were to decipher the expression and functionality (calcium signaling) of PARs in human dorsal root ganglia (DRG) neurons, and to define mechanisms involved in human sensory neuron signaling by IBS patient mediators.

Human thoracic DRG were obtained from the national disease resource interchange. Expression of PAR1, PAR2 and PAR4 was assessed by immunohistochemistry and RT-qPCR in whole DRG or in primary cultures of isolated neurons. Calcium signaling in response to PAR agonist peptides (PAR-AP), their inactive peptides (PAR-IP), thrombin (10u/ml), supernatants from colonic biopsies of IBS patients or healthy controls (HC), with or without PAR1 or PAR4 antagonist were studied in cultured human DRG neurons.

PAR1, PAR2 and PAR4 were all expressed in human DRG, respectively in 20%, 40% and 40% of the sensory neurons. PAR1-AP increased intracellular calcium concentration in a dose-dependent manner. This increase was inhibited by PAR1 antagonism. In contrast, PAR2-AP, PAR4-AP and PAR-IP did not cause calcium mobilization. PAR1-AP-induced calcium flux was significantly reduced by pre-incubation with PAR4-AP, but not with PAR2-AP. Thrombin increased calcium flux, which was inhibited by a PAR1 antagonist and increased by a PAR4 antagonist. Supernatants from colonic biopsies of IBS patients induced calcium flux in human sensory neurons compared to HC, this induction was reversed by a PAR1 antagonist.

Taken together, our results highlight that PAR1 antagonism should be investigated as a new therapeutic target for IBS symptoms.