AUTHOR=Xie Alison Xiaoqiao , Pan Xiao-Qing , Meacham Randall B. , Malykhina Anna P. 

TITLE=The Expression of Transcription Factors Mecp2 and CREB Is Modulated in Inflammatory Pelvic Pain

JOURNAL=Frontiers in Systems Neuroscience

VOLUME=Volume 12 - 2018

YEAR=2019

URL=https://www.frontiersin.org/journals/systems-neuroscience/articles/10.3389/fnsys.2018.00069

DOI=10.3389/fnsys.2018.00069

ISSN=1662-5137

ABSTRACT=Early activation of transcription factors is one of the epigenetic mechanisms contributing to the induction and maintenance of chronic pain states. Previous studies identified the changes in a number of nociception-related genes, such as calcitonin gene-related peptide (CGRP), substance P (SP), and brain-derived neurotropic factor (BDNF) in the pelvic organs after transient colonic inflammation. The gene and protein expression of these neuropeptides could be modulated by transcription factors Methyl-CpG-binding protein 2 (Mecp2) and cAMP response element-binding protein (CREB). In this study, we aimed to evaluate time-dependent changes in the expression levels of Mecp2 and CREB in the lumbosacral (LS) spinal cord and sensory ganglia after inflammation-induced pelvic pain in rat. Adult Sprague Dawley rats were treated with 2,4,6-trinitrobenzenesulfonic acid (TNBS) to induce transient colonic inflammation. Lumbosacral (L6-S2) spinal cord segments and respective dorsal root ganglia (DRGs) were isolated from control and experimental animals at 1, 2, 6, 24 hours and 3 days post-TNBS treatment. Immunohistochemical (IHC) labeling and Western blotting experiments were performed to assess the expression of Mecp2, CREB and their phosphorylated forms. Total Mecp2 expression, but not phosphorylated p- Mecp2 (pS421Mecp2) expression was detected in the cells of the spinal dorsal horn under control conditions. Colonic inflammation triggered a significant decrease in the number of Mecp2-expressing neurons in parallel with elevated numbers of pS421Mecp2-expressing cells at 2 hours and 6 hour post-TNBS. The majority of Mecp2-positive cells (80±6%) co-expressed CREB. TNBS treatment caused a transient up-regulation of CREB-expressing cells at 1h post-TNBS only. The number of cells expressing phosphorylated CREB (pS133CREB) did not change at 1 hour and 2 hours post-TNBS, but was down-regulated by 3 folds at 6 hours post-TNBS. Analysis of DRG sections revealed that the number of Mecp2-positive neurons was up-regulated by TNBS treatment, reaching 3-fold increase at 2 hours post-TNBS, and 8-fold increase at 6 hours post-TNBS (p≤0.05 to control). These data showed early changes in Mecp2 and CREB expression in the dorsal horn of the spinal cord and sensory ganglia after colonic inflammation, suggesting a possible contribution Mecp2 and CREB signaling in the development of visceral hyperalgesia and pelvic pain following peripheral inflammation.