Activation Of Estrogen Signaling Contributes To P2X Receptor Sensitization In Chronic Visceral Hyperalgesia In Adult Female Rats Induced By Neonatal Colonic Inflammation

AimsChronic abdominal pain and cramping in patients with irritable bowel syndrome （IBS）remains a big challenge for clinicians. IBS is2³times more prevalent in women than inmen. However, the precise mechanism remains unknown. The aim of this study wasdesigned to investigate whether estrogen signaling is involved in visceral hypersensitivityand whether estrogen enhances expression ofP₂X₃and CBS receptors in colon-specificdorsal root ganglion （DRG） in a rat model of neonatal colonic inflammation （NCI）.Methods1, Visceral hyperalgesia was induced by colonic injection of0.5%acetic acid （AA） in10-day-old female rats and ovariectomized （OVX） experiments were conducted whenrats grown to adult.2, Behavioral response to colorectal distension （CRD） was measured by visualobservation of abdominal withdrawal reflex （AWR）.3, Colon specific DRGs(T₁₃-L₂)were analyzed forP₂X₃and CBS receptor expression bywestern blotting.4, Estrogen was incubated with colon specific DRGs (T₁₃-L₂) then the expression ofP2X3and CBS receptor was measured.Results1, NCI significantly increased the visceromoter response to CRD at20,40,60and80mmHg. The increased response lasted from7weeks to11weeks （*p<0.05）anddisappeared at12weeks（p>0.05） within our observation time period. 2, OVX significantly decreased AWR scores when compared with these rats with neonatalAA infusion before surgery. OVX produced no obvious effect on rats received normalsaline injection when they were10-day-old. After OVX, some rats were treated with17β-estradiol injection（20ug/kg）（OVX+E2）. AWR scores were significantly increasedtwo weeks after E2treatment.3, CBS andP₂X₃expression was markedly increased when NCI was compared with CON.The expression of CBS andP₂X₃reduced in OVX rats compared with age-matched NCIrats. Estrogen significantly increased CBS andP₂X₃expression compared with that in ovariectomizedrats.4, Expression ofP₂X₃in (T₁₃-L₂) DRGs of rats was significantly decreased after AOAAadministration. Incubation of (T₁₃-L₂) DRGs with freshly prepared NaHS cansignificantly increased the expression ofP₂X₃. Incubation of these neurons with estrogensignificantly increased the expression ofP₂X₃and CBS. However, the upregulation ofP₂X₃expression can be reversed when incubate these neurons with CBS Inhibitor（AOAA）for3hours before drop in estrogen.5, Systemic administration（i. p.）of AOAA（CBS Inhibitor）can prevented AA-inducedvisceral hyperalgesia in a dose dependent manner. This antagonist did not produce anyeffect on AWR scores in healthy rats.ConclusionsEstrogen induced upregulation ofP₂X₃expression, which is mediated by upregulation ofCBS, thus contributing to NCI-induced CVH. This pathway might be a potential target forrelieving CVH in patients with IBS.