Basic Study
Copyright ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Aug 14, 2021; 27(30): 5060-5075
Published online Aug 14, 2021. doi: 10.3748/wjg.v27.i30.5060
Estrogen augmented visceral pain and colonic neuron modulation in a double-hit model of prenatal and adult stress
Jing-Hong Chen, Ying Sun, Pei-Jun Ju, Jin-Bao Wei, Qing-Jie Li, John H Winston
Jing-Hong Chen, Ying Sun, Pei-Jun Ju, Jin-Bao Wei, Shanghai Key Laboratory of Psychotic Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai 200030, China
Jing-Hong Chen, Qing-Jie Li, John H Winston, Department of Internal Medicine, University of Texas Medical Branch, Galveston, TX 77555, United States
Author contributions: Chen JH and Winston JH contributed to the concept and design of the experiments; Chen JH performed the experiments; Chen JH, Sun Y, Ju PJ, Wei JB, Li QJ and Winston JH analyzed the data and prepared the paper.
Supported by NIDDK, No. 5R01DK111819-03 and No. 5R01DK032346-28; National Natural Science Foundation of China, No. 81571326.
Institutional review board statement: The study was undertaken with the approval of the Institutional Animal Care and Use Committee of the University of Texas Medical Branch at Galveston, TX, United States.
Institutional animal care and use committee statement: The study was undertaken with the approval of the Institutional Animal Care and Use Committee of the University of Texas Medical Branch at Galveston, TX.
Conflict-of-interest statement: The authors declare that they have no conflicting interests.
Data sharing statement: No additional data are available.
ARRIVE guidelines statement: The authors have read the ARRIVE guidelines, and the manuscript was prepared and revised according to the ARRIVE guidelines.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: John H Winston, PhD, Professor, Department of Internal Medicine, University of Texas Medical Branch, 8-104 Med Res Bldg, Galveston, TX 77555, United States. jhwinsto@utmb.edu
Received: March 4, 2021
Peer-review started: March 4, 2021
First decision: May 5, 2021
Revised: May 19, 2021
Accepted: July 5, 2021
Article in press: July 5, 2021
Published online: August 14, 2021
ARTICLE HIGHLIGHTS
Research background

Chronic stress during pregnancy may increase visceral hyperalgesia in the offspring. Combining adult stress in offspring will increase this sensitivity. Therefore, based on the evidence implicating estrogen exacerbates visceral hypersensitivity in female rodents in preclinical models, we predicted that chronic prenatal stress (CPS) + chronic adult stress (CAS) would maximize visceral hyperalgesia and that estrogen has an important role in colonic hyperalgesia.

Research motivation

The mechanisms of visceral hypersensitivity are not well defined. Understanding the neurophysiological mechanisms driving visceral hypersensitivity will spur the development of female pain-specific therapies.

Research objectives

The objective was to identify the enhancement of visceral hypersensitivity in a CPS + CAS model and explain the role of estrogen in that process.

Research methods

A CPS + CAS rodent model was established. Single fiber recording in vivo and patch clamp experiments in vitro were used to monitor the activity of colonic neurons. Reverse transcription-polymerase chain reaction (RT-PCR), western blots, and immunofluorescence were used to study the effects of CPS and CAS on colon primary afferent sensitivity. We used ovariectomy (OVX) and letrozole to reduce estrogen levels in female rats in order to assess the role of estrogen in female-specific enhanced primary afferent sensitization.

A CPS + CAS rodent model was established. Single fiber recording in vivo and patch clamp experiments were used to monitor the colonic neuron activity in vitro. RT-PCR, western blots, and immunofluorescence were used to study the effects of CPS and CAS on colon primary afferent sensitivity. We used OVX and letrozole to reduce estrogen levels of female rats in order to assess the role of estrogen in female-specific enhanced primary afferent sensitization.

Research results

Spontaneous activity and single fiber activity were significantly greater in females than in males. The enhanced sensitization in female rats mainly came from the low-threshold neurons. CPS significantly increased single-unit afferent fiber activity in the L6-S2 dorsal roots in response. Activity was further enhanced by CAS. In addition, the increased excitability of colon-projecting DRG neurons in CPS + CAS rats was associated with a decrease in transient A-type K+ currents. Compared with OVX, letrozole treatment further reduced the estrogen levels of female rats, which confirmed the gender difference. Moreover, rats treated with letrozole had decreased colonic DRG neuron excitability. The intrathecal infusion of estrogen increased BDNF protein levels and contributed to the response to visceral pain. Western blots showed that nerve growth factor protein was upregulated in CPS + CAS rats.

Research conclusions

This study adds to the evidence of the development of chronic stress-induced visceral hypersensitivity in females, and that it involves estrogen-dependent sensitization of primary afferent colon neurons.

Research perspectives

This study demonstrated that CAS + CPS induced visceral hypersensitivity and that estrogen played a role in the process. Understanding the molecular and neurophysiological mechanisms driving this response will spur the development of female pain-specific therapies.