Antenatal Hypoxia and Programming of Glucocorticoid Receptor Expression in the Adult Rat Heart.

Juanxiu Lv,Lubo Zhang,Chiranjib Dasgupta,Zhice Xu,Qingyi Ma

doi:10.3389/fphys.2019.00323

Abstract

Glucocorticoid receptor (GR) signaling is critical for development and function of the heart. Our previous study demonstrated that gestational hypoxia induced epigenetic repression of the GR gene in the developing heart. The present study aims to determine that the alterations of promoter methylation level and epigenetic repression of the GR gene in the developing heart in response to maternal hypoxia is sustained in adult offspring and potential gender differences in the programming of GR gene. Pregnant rats were treated with 10.5% O2 from gestational day 15 (E15) to 21 (E21). Hearts were isolated from 5-month-old male and female offspring with the developing stage being equivalent to 18-year-old human. GR mRNA and protein abundance was determined with real time qRT-PCR and Western blot. GR gene promoter methylation and binding of transcription factors were measured with methylated DNA immunoprecipitation (MeDIP) and Chromatin immunoprecipitation (ChIP). The results showed that antenatal hypoxia significantly decreased the expression of GR mRNA and protein in the hearts of adult male offspring, but not in females, which is ascribed to the differential changes of alternative exon1 mRNA variants of GR gene in male and female hearts in response to prenatal hypoxia. In addition, the downregulation of GR expression in the male heart was correlated with increased methylation levels of CpG dinucleotides in promoters of exon 14, 15, 16, 17, and 110, which resulted in a decrease in the binding of their transcription factors. Thus, the study reveals that antenatal hypoxia results in a reprogramming and long-term change in GR gene expression in the heart by hypermethylation of GR promoter in a sex-differential pattern, which provides a novel mechanism regarding the increased vulnerability of heart later in life with exposure of prenatal hypoxia.

Highlights

Numerous human and animal studies have shown that prenatal and early neonatal environments change developmental trajectories of the heart and contribute to the individual life-long health problems such as cardiology disorders (Barker, 2004; Gluckman and Hanson, 2004; Dasinger and Alexander, 2016; Morton et al, 2016)
Our previous study has determined that prenatal hypoxia results in downregulation of Glucocorticoid receptor (GR) expression mainly via promoter hypermethylation in the developing heart
We found that the expression of GR was significantly reduced in the heart of adult offspring exposed to prenatal hypoxia and the downregulation of GR gene showed a sex-differential pattern

Summary

Introduction

Numerous human and animal studies have shown that prenatal and early neonatal environments change developmental trajectories of the heart and contribute to the individual life-long health problems such as cardiology disorders (Barker, 2004; Gluckman and Hanson, 2004; Dasinger and Alexander, 2016; Morton et al, 2016). Hypoxia and Developmental Programming of GR in the Heart include insufficient uterine blood flow, increased placental vascular resistance, reduced umbilical cord blood flow and decreased oxygen level. The fetus is able to make a series of adaption to hypoxia challenge, which helps to ensure its survival. This “developmental plasticity” may cause health problems in adulthood (Nathanielsz, 2006). A study from Camm et al (2011) using rodents suggested that prenatal hypoxia was linked to the insulin resistance in adult offspring. We determined that prenatal hypoxia increased the susceptibility of adult offspring to cardiac ischemia/reperfusion injury in rats, which was associated with a decreased expression of PKCε, a cardiac protective gene. Further study revealed that promoter hypermethylation of PKC gene was the primary mechanism responsible for the downregulation PKC gene in rat heart after prenatal hypoxia, which was reversed by DNA methylation inhibitors (Patterson and Zhang, 2010)

Methods

Results

Conclusion