Fetal programming of adrenal PNMT and hypertension by glucocorticoids in WKY rats is dose and sex-dependent

Abstract

Biochemical changes in utero may alter normal fetal development, resulting in disease later in life, a phenomenon known as fetal programming. Recent epidemiological studies link fetal programming to negative health outcomes, such as low birth weight and hypertension in adulthood. Here, we used a WKY rat model and studied the molecular changes triggered by prenatal glucocorticoid (GC) exposure on the development of hypertension, and on the regulation of phenylethanolamine N-methyl transferase (PNMT), the enzyme responsible for biosynthesis of epinephrine, and a candidate gene linked to hypertension. Clinically, high doses of the synthetic GC dexamethasone (DEX) are used to treat infant respiratory distress syndrome. Elevated maternal GCs have been correlated with fetal programming of hypertension. The aim of this study was to determine if lower doses of DEX would not lead to detrimental fetal programming effects such as hypertension. Our data suggests that prenatal stress programs for increased expression of PNMT and altered regulation of PNMT in males and females. Importantly, we identified that DEX mediated programming was more apparent in the male rats, and the lower dose 10μg/kg/day of DEX did not lead to changes in blood pressure (BP) in female rats suggesting that this dose is below the threshold for programming of hypertension. Furthermore, sex-specific differences were observed in regards to programming mechanisms that may account for hypertension in males.

Fig 1. Body weight of DEX exposed offspring.

Body weight (grams; g) of male (left) and female (right) offspring at 5 weeks (A, B), and 19 weeks of age (C, D), of naive, saline, 10-DEX, 50-DEX, and 100-DEX groups. Data are displayed as a box plot with average, minimal, and maximal weights ± SEM. ANOVA: Statistical significance between naive and DEX-treated groups is shown by: * p < 0.05, ** p < 0.01, and *** p < 0.001.

Fig 2. Blood pressure of 19-week-old DEX exposed offspring.

Systolic (A, B) and mean arterial blood pressure (C, D) of male (left) and female (right) naive, saline, 10-DEX, 50-DEX, and 100-DEX offspring are expressed in mmHg. Data are expressed in mean ± SEM. ANOVA: Statistical significance between naive and DEX-treated groups is shown by: * p < 0.05, ** p < 0.01, *** p < 0.001, and **** p < 0.0001.

Fig 3. Gene expression of catecholamine biosynthetic enzymes in adrenal glands of 19-week-old prenatally DEX-exposed offspring.

mRNA levels of TH (A, B), DBH (C, D), and PNMT (E, F) in male (left) and female (right) offspring of saline, 10-DEX, 50-DEX, and 100-DEX treatment groups. Data is expressed as mean fold change ± SEM. ANOVA: Statistical significance between saline and DEX-treated groups is shown by: * p < 0.05, ** p < 0.01, and *** p < 0.001.

Fig 4. mRNA levels of PNMT transcriptional regulators in adrenal glands of 19-week-old prenatally DEX-exposed offspring.

mRNA levels of Egr-1 (A,B), GR (C,D), Sp1 (E, F), and AP-2 (G, H) in male (left) and female (right) offspring of saline, 10-DEX, 50-DEX, and 100-DEX treatment groups. Data is expressed as mean fold change ± SD. ANOVA: Statistical significance between saline and DEX-treated groups is shown by *, p < 0.05, ** p < 0.01, and *** p < 0.001.

Fig 5. Effect of prenatal DEX exposure on plasma corticosterone and epinephrine levels.

Plasma corticosterone (A, B), and epinephrine levels (C, D), in male and female offspring from saline or DEX-exposed animals. Fold changes between saline controls versus DEX-treated animals are presented as mean ± SEM. Significant difference between groups designated as *, p ≤ 0.05.

Fig 6. mRNA levels of stress related genes in adrenal glands of 19 week old prenatally DEX-exposed offspring.

mRNA levels of PAH (A,B), SLC9A3 (C,D), and CYP2E1 (E, F) in male (left) and female (right) offspring of saline and 100-DEX treatment groups. Data is expressed as mean fold change ± SEM. ANOVA: Statistical significance between saline and DEX-treated groups is shown by: * p < 0.05, ** p < 0.01, and *** p < 0.001, and **** p < 0.001.