P2Y1, P2Y2, and TRPV1 Receptors Are Increased in Diarrhea-Predominant Irritable Bowel Syndrome and P2Y2 Correlates with Abdominal Pain

Previous studies indicated that P2Y(1) and P2Y(2) receptors, which are widely distributed in the enteric nervous system, are related to pain, while TRPV1 may contribute to visceral pain and hypersensitivity states in irritable bowel syndrome (IBS). Other studies showed that ATP activates the capsaicin-sensitive TRPV1 channel via P2Y receptors. To detect the expression of P2Y(1), P2Y(2), and TRPV1 receptors in diarrhea-predominant IBS (IBS-D) patients and analyze any correlations with abdominal pain and to investigate interactions between P2Y receptors and the TRPV1 receptor in IBS-D patients. Rectosigmoid biopsies were collected from patients with IBS-D (n = 36) and healthy controls (n = 15). Abdominal pain was scored using a 10-cm visual analogue scale. Expression levels of P2Y(1), P2Y(2), and TRPV1 receptors in rectosigmoid biopsies were determined by real-time PCR and double-labeling immunofluorescence with specific antibodies. Both mRNA and protein expression levels of P2Y(1), P2Y(2), and TRPV1 receptors were increased in IBS-D compared with controls. Of these receptors, P2Y(2) expression correlated with the maximum pain scores (p = 0.02, r = 0.63, Spearman correlation) in IBS-D patients. However, no relationships were detected between P2Y receptors and the TRPV1 receptor. In the present study, we identified an increased expression of P2Y(1) and P2Y(2) receptors in the rectosigmoid mucosa of IBS-D patients, and P2Y(2) correlated with abdominal pain. Furthermore, we identified an increase in TRPV1 expression; however, there were no correlations found between P2Y receptors and the TRPV1 receptor.