P2X3 Receptors Mediate Visceral Hypersensitivity during Acute Chemically-Induced Colitis and in the Post-Inflammatory Phase via Different Mechanisms of Sensitization

Abstract

ObjectivesExperiments using P2X3 knock-out mice or more general P2X receptor antagonists suggest that P2X3 receptors contribute to visceral hypersensitivity. We aimed to investigate the effect of the selective P2X3 antagonist A-317491 on visceral sensitivity under physiological conditions, during acute colitis and in the post-inflammatory phase of colitis.MethodsTrinitrobenzene sulphonic-acid colitis was monitored by colonoscopy: on day 3 to confirm the presence of colitis and then every 4 days, starting from day 10, to monitor convalescence and determine the exact timepoint of endoscopic healing in each rat. Visceral sensitivity was assessed by quantifying visceromotor responses to colorectal distension in controls, rats with acute colitis and post-colitis rats. A-317491 was administered 30 min prior to visceral sensitivity testing. Expression of P2X3 receptors (RT-PCR and immunohistochemistry) and the intracellular signalling molecules cdk5, csk and CASK (RT-PCR) were quantified in colonic tissue and dorsal root ganglia. ATP release in response to colorectal distension was measured by luminiscence.ResultsRats with acute TNBS-colitis displayed significant visceral hypersensitivity that was dose-dependently, but not fully, reversed by A-317491. Hypersenstivity was accompanied by an increased colonic release of ATP. Post-colitis rats also displayed visceral hypersensitivity that was dose-dependently reduced and fully normalized by A-317491 without increased release of ATP. A-317491 did not modify visceral sensitivity in controls. P2X3 mRNA and protein expression in the colon and dorsal root ganglia were similar in control, acute colitis and post-colitis groups, while colonic mRNA expression of cdk5, csk and CASK was increased in the post-colitis group only.ConclusionsThese findings indicate that P2X3 receptors are not involved in sensory signaling under physiological conditions whereas they modulate visceral hypersensitivity during acute TNBS-colitis and even more so in the post-inflammatory phase, albeit via different mechanisms of sensitization, validating P2X3 receptors as potential new targets in the treatment of abdominal pain syndromes.

Purinergic receptors in the carotid body as a new drug target for controlling hypertension

“…The association of P2X3 receptor up-regulation and aberrant afferent signalling is not new 28 but consistent with sensitisation of visceral sensing mechanisms from, for example, the bladder 44,45 , urinary tract 46 , larynx 29 , lungs 47 , gastro-intestinal-tract 48,49 and skeletal muscle 50 in numerous diseased states including chronic pain 51 . Elucidation of the mechanisms controlling P2x3 receptor expression at both transcriptional and cytosolic trafficking levels within the carotid body and other organs now becomes an important issue to allow translation into the clinical arena.…”

The role of P2X3 receptors in bilateral masseter muscle allodynia in rats

“…The expression levels of P2X 3 -specific mRNA were measured using Applied Biosystems 7500 Fast Real-Time PCR and Taqman Gene Expression Assays (Applied Biosystems) for P2X 3 (Rn00579301_m1) as the target and beta-actin (Rn00667869_m1) and GAPDH (Rn01775763_g1) as housekeeping genes (27,28). The evaluation of two different housekeeping genes was used to normalize the values of the cDNA libraries used in the real-time quantification and minimize the RNA isolation and transcription errors.…”

Purinergic drug targets for gastrointestinal disorders

“…P2X3R mediate visceral hypersensitivity during 2,4,6-trinitrobenzene sulphonic-acid-induced colitis, identifying it as a potential new target for abdominal pain syndrome treatment (Deiteren et al, 2015). …”

“…P2X3R antagonists and anti-P2X3R antibodies are being explored as therapeutic agents against colic and colitis pain (Deiteren et al, 2015; Shcherbatko et al, 2016). …”