Effect of cross-fostering on renal anti-oxidant/oxidant status and development of hypertension in spontaneously hypertensive rats

Exercise during pregnancy enhances vascular function via epigenetic repression of CaV1.2 channel in offspring of hypertensive rats

AIMS

Studies suggest that cardiovascular function in offspring can be epigenetically programmed by environmental changes during pregnancy. Ca_V1.2 channel plays a major role in the regulation of the vascular tone. This study investigated the effects and underlying mechanisms of exercise during pregnancy on Ca_V1.2 channel functional remodeling in hypertensive offspring.

MAIN METHODS

Exercise groups were subjected to swimming at the first day of pregnancy and on a regular schedule thereafter for 3 weeks. Their offspring (6-month-old, male) were tested for baseline blood pressure, cardiovascular response, and vascular tone of the mesenteric artery. Mesenteric artery smooth muscle cells were taken to study the whole-cell current of the Ca_V1.2 channel. Western blotting, RT-PCR and DNA bisulfite sequencing PCR were performed to study the protein, mRNA expression and DNA methylation of the Ca_V1.2 channel α1C subunit.

KEY FINDINGS

Exercise during pregnancy reduced the pressor response to norepinephrine and Bay K8644, and the depressor response to nifedipine in offspring of hypertensive rats. The level of the Ca_V1.2 channel in norepinephrine-induced vasoconstrictions decreased, and the whole-cell current of the Ca_V1.2 channel declined in the SHR-EX group. Further studies found that exercise during pregnancy reduced the protein and mRNA expression of the Ca_V1.2 channel α1C subunit and upregulated DNA methylation of the Cacna1c gene promoter region in the hypertensive offspring.

SIGNIFICANCE

These data suggest that exercise during pregnancy improves vascular functional remodeling in offspring of hypertensive rats, downregulating the Ca_V1.2 channel function and protein expression, a change that is most likely caused by DNA methylation.

Cross-fostering: Elucidating the effects of gene×environment interactions on phenotypic development

Cross-fostering of litters from soon after birth until weaning is a valuable tool to study the ways in which gene×environment interactions program the development of neural, physiological and behavioral characteristics of mammalian species. In laboratory mice and rats, the primary focus of this review, cross-fostering of litters between mothers of different strains or treatment groups (intraspecific) or between mothers of different species (interspecific) has been conducted over the past 9 decades. Areas of particular interest have included maternal effects on emotionality, social preferences, responses to stressful stimulation, nutrition and growth, blood pressure regulation, and epigenetic effects on brain development and behavior. Results from these areas of research highlight the critical role of the postnatal maternal environment in programming the development of offspring phenotypic characteristics. In addition, experimental paradigms that have included cross-fostering have permitted investigators to tease apart prenatal versus postnatal effects of various treatments on offspring development and behavior.

Maternal Treatment of Spontaneously Hypertensive Rats With Pentaerythritol Tetranitrate Reduces Blood Pressure in Female Offspring

Pentaerythritol tetranitrate is devoid of nitrate tolerance and shows no reproductive or developmental toxicity in animal studies. Recently, pentaerythritol tetranitrate has been demonstrated to reduce the risk of intrauterine growth restriction and the risk of preterm birth in women with abnormal placental perfusion. This study was conducted to test the perinatal programming effect of pentaerythritol tetranitrate in spontaneously hypertensive rats, a rat model of genetic hypertension. Parental spontaneously hypertensive rats were treated with pentaerythritol tetranitrate (50 mg/kg per day) during pregnancy and lactation periods; the offspring received standard chow without pentaerythritol tetranitrate after weaning. Maternal treatment with pentaerythritol tetranitrate had no effect on blood pressure in male offspring. In the female offspring, however, a persistent reduction in blood pressure was observed at 6 and 8 months. This long-lasting effect was accompanied by an upregulation of endothelial nitric oxide synthase, mitochondrial superoxide dismutase, glutathione peroxidase 1, and heme oxygenase 1 in the aorta of 8-month-old female offspring, which was likely to result from epigenetic changes (enhanced histone 3 lysine 27 acetylation and histone 3 lysine 4 trimethylation) and transcriptional activation (enhanced binding of DNA-directed RNA polymerase II to the transcription start site of the genes). In organ chamber experiments, the endothelium-dependent, nitric oxide–mediated vasodilation to acetylcholine was enhanced in aorta from female offspring of the pentaerythritol tetranitrate–treated parental spontaneously hypertensive rats. In conclusion, maternal pentaerythritol tetranitrate treatment leads to epigenetic modifications, gene expression changes, an improvement of endothelial function and a persistent blood pressure reduction in the female offspring.