Gestational intermittent hypoxia induces endothelial dysfunction and hypertension in pregnant rats: role of endothelin type B receptor†.

Obstructive sleep apnea is a recognized risk factor for gestational hypertension, yet the exact mechanism behind this association remains unclear. Here, we tested the hypothesis that intermittent hypoxia, a hallmark of obstructive sleep apnea, induces gestational hypertension through perturbed endothelin-1 signaling. Pregnant Sprague-Dawley rats were subjected to normoxia (control), mild intermittent hypoxia (10.5% O2), or severe intermittent hypoxia (6.5% O2) from gestational days 10-21. Blood pressure was monitored. Plasma was collected and mesenteric arteries were isolated for myograph and protein analyses. The mild and severe intermittent hypoxia groups demonstrated elevated blood pressure, reduced plasma nitrate/nitrite, and unchanged endothelin-1 levels compared to the control group. Western blot analysis revealed decreased expression of endothelin type B receptor and phosphorylated endothelial nitric oxide synthase, while the levels of endothelin type A receptor and total endothelial nitric oxide synthase remained unchanged following intermittent hypoxia exposure. The contractile responses to potassium chloride, phenylephrine, and endothelin-1 were unaffected in endothelium-denuded arteries from mild and severe intermittent hypoxia rats. However, mild and severe intermittent hypoxia rats exhibited impaired endothelium-dependent vasorelaxation responses to endothelin type B receptor agonist IRL-1620 and acetylcholine compared to controls. Endothelium denudation abolished IRL-1620-induced vasorelaxation, supporting the involvement of endothelium in endothelin type B receptor-mediated relaxation. Treatment with IRL-1620 during intermittent hypoxia exposure significantly attenuated intermittent hypoxia-induced hypertension in pregnant rats. This was associated with elevated circulating nitrate/nitrite levels, enhanced endothelin type B receptor expression, increased endothelial nitric oxide synthase activation, and improved vasodilation responses. Our data suggested that intermittent hypoxia exposure during gestation increases blood pressure in pregnant rats by suppressing endothelin type B receptor-mediated signaling, providing a molecular mechanism linking intermittent hypoxia and gestational hypertension.

PFOS Impairs Mitochondrial Biogenesis and Dynamics and Reduces Oxygen Consumption in Human Trophoblasts.

Perfluorooctane sulfonate (PFOS), a synthetic chemical used in various commercial applications and industrial settings, has led to contamination of drinking water and has been detected in the bloodstream of pregnant women with gestational complications. Recent investigations have indicated that PFOS disrupts placental function; however, the mechanism remains elusive. Given the significant abundance of mitochondria in the placenta, which play a pivotal role in fulfilling the heightened energy requirements of pregnancy, our research aimed to examine the repercussions of PFOS exposure on mitochondrial dynamics within placental trophoblasts. Specifically, human trophoblasts (HTR-8/SVneo) were exposed to environmentally relevant concentrations of PFOS ranging from 0.1 to 50 µM for 48 hours. Findings revealed that PFOS exposure elicited a concentration-dependent decrease in basal, maximal, and ATP-linked respiration. PFOS inhibited the activity of electron transport complexes I, II, and III, resulting in diminished ATP production. Furthermore, PFOS reduced mitochondrial DNA copy number, indicating less mitochondrial content. Concurrently, there was a downregulation in the expression of mitochondrial biogenesis-related genes, including PGC-1α, NRF1, and NRF2. Notably, PFOS perturbed mitochondrial dynamics by suppressing the expression of fission-related genes (FIS1 and DRP1) and fusion-related genes (MFN1 and MFN2). In summary, our findings suggest that PFOS exposure leads to a decline in mitochondrial content and compromises the bioenergetic capacity of trophoblasts by impairing cellular respiration. This reduction in mitochondrial biogenesis and alterations in fission/fusion dynamics induced by PFOS may contribute to mitochondrial dysfunction in trophoblasts. Consequently, strategies that preserve mitochondrial function in trophoblasts may mitigate PFOS-induced impairment of placental energy metabolism.

Restoring Angiotensin Type 2 Receptor Function Reverses PFOS-Induced Vascular Hyper-Reactivity and Hypertension in Pregnancy.

Perfluorooctane sulfonic acid (PFOS) exposure during pregnancy induces hypertension with decreased vasodilatory angiotensin type-2 receptor (AT2R) expression and impaired vascular reactivity and fetal weights. We hypothesized that AT2R activation restores the AT1R/AT2R balance and reverses gestational hypertension by improving vascular mechanisms. Pregnant Sprague-Dawley rats were exposed to PFOS through drinking water (50 µg/mL) from gestation day (GD) 4-20. Controls received drinking water with no detectable PFOS. Control and PFOS-exposed rats were treated with AT2R agonist Compound 21 (C21; 0.3 mg/kg/day, SC) from GD 15-20. In PFOS dams, blood pressure was higher, blood flow in the uterine artery was reduced, and C21 reversed these to control levels. C21 mitigated the heightened contraction response to Ang II and enhanced endothelium-dependent vasorelaxation in uterine arteries of PFOS dams. The observed vascular effects of C21 were correlated with reduced AT1R levels and increased AT2R and eNOS protein levels. C21 also increased plasma bradykinin production in PFOS dams and attenuated the fetoplacental growth restriction. These data suggest that C21 improves the PFOS-induced maternal vascular dysfunction and blood flow to the fetoplacental unit, providing preclinical evidence to support that AT2R activation may be an important target for preventing or treating PFOS-induced adverse maternal and fetal outcomes.

Perfluorooctane sulfonic acid modulates expression of placental steroidogenesis-associated genes and hormone levels in pregnant rats.

Perfluorooctane sulfonate (PFOS) is a widespread and persistent chemical in the environment. Reports show that PFOS is a potential endocrine disruptor; however, the possible effects of PFOS on placental endocrine function are unclear. This study aimed to investigate the endocrine-disrupting effects of PFOS on the placenta in pregnant rats and its potential mechanism. Pregnant rats from gestational days 4-20 were exposed to 0, 10, and 50 µg/mL PFOS through drinking water followed by analysis of various biochemical parameters. PFOS dose-dependently decreased fetal and placental weight in both sexes, with a specific decrease in weight of labyrinth but not junctional layer. Plasma progesterone (↑166%), aldosterone (↑201%), corticosterone (↑205%), testosterone (↑45%), luteinizing hormone (↑49%) levels were significantly increased, while estradiol (↓27%), prolactin (↓28%) and hCG (↓62%) levels were reduced in groups exposed to higher doses of PFOS. Real-time quantitative reverse transcriptase-polymerase chain reaction analysis revealed a significant increase in mRNA levels of placental steroid biosynthesis enzymes, including Cyp11A1 and 3ß-HSD1 in male placenta and StAR, Cyp11A1, 17ß-HSD1 and 17ß-HSD3 in female placenta of PFOS dams. Cyp19A1 expression in ovaries was significantly decreased in PFOS dams. mRNA levels for placental steroid metabolism enzyme UGT1A1 increased in male but not in female placenta of PFOS dams. These results suggest that the placenta is a target tissue of PFOS and PFOS-induced dysregulation in steroid hormone production might be related to the altered expression of hormone biosynthesis and metabolism enzyme genes in the placenta. This hormone disruption might affect maternal health and fetal growth.

Gestational Intermittent Hypoxia Programs Hypertensive Response in Female Rat Offspring: Impact of Ovaries.

Obstructive sleep apnea (OSA) is a chronic condition frequently observed in pregnant women. We have shown that gestational intermittent hypoxia (GIH), a hallmark of OSA, leads to sex-specific impairment in the endothelium-dependent relaxation response and an increase in blood pressure in adult male but not female rat offspring. The present study tested the hypothesis that functional ovaries normalize GIH-induced hypertensive response in female offspring. Experiments were done in female offspring of pregnant rats exposed to normoxia or GIH (FIO2 21-10.5% from gestational days 10 to 21). Ovariectomy and sham surgery were performed at 5 weeks of age. Pups born to GIH dams were significantly smaller than the controls, but they exhibited catch-up growth and were similar to controls by 5 weeks of age. Ovariectomy significantly exacerbated bodyweight gain to a similar extent in both control and GIH offspring. Marked increases in blood pressure were observed in pre-pubertal GIH offspring compared to controls; however, after puberty, blood pressure in GIH offspring progressively decreased and became normotensive at adulthood. Ovariectomy led to the maintenance of higher blood pressure in post-pubertal GIH offspring with no significant effect in controls. Vascular contractile and relaxation responses were not affected in the GIH and control offspring; however, ovariectomy selectively decreased endothelium-dependent relaxation response along with a decrease in endothelial nitric oxide synthase expression in the GIH offspring. These findings suggest that functional ovaries are crucial in protecting females against GIH-mediated endothelial dysfunction and hypertension in adulthood.

Maternal perfluorooctane sulfonic acid exposure during rat pregnancy causes hypersensitivity to angiotensin II and attenuation of endothelium-dependent vasodilation in the uterine arteries †.

Epidemiological studies show a strong association between environmental exposure to perfluorooctane sulfonic acid (PFOS) and preeclampsia and fetal growth restriction; however, the underlying mechanisms are unclear. We tested the hypothesis that gestational PFOS exposure leads to pregnancy complications via alterations in uterine vascular endothelium-independent angiotensin II-related mechanisms and endothelium-derived factors such as nitric oxide. Pregnant Sprague-Dawley rats were exposed to PFOS 0.005, 0.05, 0.5, 5, 10, and 50 µg/mL through drinking water from gestational day 4 to 20, and dams with PFOS 50 µg/mL were used to assess mechanisms. PFOS exposure dose dependently increased maternal blood pressure but decreased fetal weights. Uterine artery blood flow was lower and resistance index was higher in the PFOS dams. In PFOS dams, uterine artery contractile responses to angiotensin II were significantly greater, whereas contractile responses to K+ depolarization and phenylephrine were unaffected. Plasma angiotensin II levels were not significantly different between control and PFOS dams; however, PFOS exposure significantly increased Angiotensin II type 1 receptor (AGTR1) and decreased AGTR2 protein levels in uterine arteries. Endothelium-dependent relaxation response to acetylcholine was significantly reduced with decreased endothelial nitric oxide synthase expression in the uterine arteries of PFOS dams. Left ventricular hypertrophy and fibrosis were observed, along with increased ejection fraction and fractional shortening in PFOS dams. These results suggest that elevated maternal PFOS levels decrease uterine blood flow and increase vascular resistance via heightened angiotensin II-mediated vasoconstriction and impaired endothelium-dependent vasodilation, which provides a molecular mechanism linking elevated maternal PFOS levels with gestational hypertension and fetal growth restriction.

Gestational Intermittent Hypoxia Induces Sex-Specific Impairment in Endothelial Mechanisms and Sex Steroid Hormone Levels in Male Rat Offspring.

Obstructive sleep apnea (OSA) is highly prevalent during gestation and is linked with adverse fetal outcomes. We examined whether gestational intermittent hypoxia (GIH), the main feature of OSA, leads to sex-specific alterations in cardiovascular function and vascular mechanisms in the offspring. Pregnant rats exposed to intermittent hypoxia or ambient air from gestation days 10 to 21 and their offspring were used for the study. GIH exposure did not affect water and food intake in dams. Compared to controls, the male and female offspring born to GIH dams were smaller in weight by 14% and 12%, respectively, and exhibited catch-up growth. Cardiac function was not affected in either GIH males or females. At 12 weeks of age, blood pressure was increased in GIH males, but not GIH females, compared to their control counterparts. While mesenteric arterial contractile responses to phenylephrine and endothelin were unaffected in GIH males and females, relaxation response to acetylcholine was reduced in GIH males but not GIH females. Relaxation to sodium nitroprusside was unaffected in both GIH males and females. Total eNOS expression was not affected, but phospho(Ser1177)-eNOS levels were decreased in GIH males. eNOS expression and its phosphorylation status were unaffected in GIH females. Serum testosterone and estradiol levels were higher in GIH males but were unaltered in GIH females. Together, these findings suggest that GIH leads to a sex-specific increase in blood pressure in adult male offspring with blunted endothelium-mediated relaxation, decreased eNOS activity, and elevated sex steroid hormone levels.

Perfluorooctane sulfonic acid (PFOS) exposure during pregnancy increases blood pressure and impairs vascular relaxation mechanisms in the adult offspring.

Perfluorooctanesulfonate (PFOS) is a persistent environmental agent. We examined whether PFOS exposure during pregnancy alters blood pressure in male and female offspring, and if this is related to sex-specific changes in vascular mechanisms. PFOS was administered through drinking water (50 µg/mL) to pregnant Sprague-Dawley rats from gestational day 4 until delivery. PFOS-exposure decreased maternal weight gain but did not significantly alter feed and water intake in dams. The male and female pups born to PFOS mothers were smaller in weight by 29 % and 27 %, respectively. The male PFOS offspring remained smaller through adulthood, but the female PFOS offspring exhibited catch-up growth. The blood pressure at 12 and 16 weeks of age was elevated at similar magnitude in PFOS males and females than controls. Mesenteric arterial relaxation to acetylcholine was reduced in both PFOS males and females, but the extent of decrease was greater in females. Relaxation to sodium-nitroprusside was reduced in PFOS females but unaffected in PFOS males. Vascular eNOS expression was not changed, but phospho(Ser1177)-eNOS was decreased in PFOS males. In PFOS females, both total eNOS and phospho(Ser1177)-eNOS expression were reduced. In conclusion, PFOS exposure during prenatal life (1) caused low birth weight followed by catch-up growth only in females (2) lead to hypertension of similar magnitude in both males and females; (2) decreased endothelium-dependent vascular relaxation in males but suppressed both endothelium-dependent and -independent relaxation in females. The endothelial dysfunction is associated with reduced activity of eNOS in males and decreased expression and activity of eNOS in females.

Relationship between more follicles in right than left ovary in recently born calves and right ovary propensity for ovulation in cattle.

The mechanism for more frequent ovulation from right ovary (RO) than left ovary (LO) was considered by determining if RO of recently born calves had a propensity for more follicles. Rationale was from reports that RO in heifers has more 6-mm follicles before selection of the future ovulatory follicle as well as greater frequency of RO ovulation. Dimensions, weight, and number of follicles per ovary were compared between LO and RO in 10 Holstein calves (age, 1 to 7 days). Weight of an ovary was greater (P < 0.05) for RO (0.393 ±â€¯0.04 g) than LO (0.355 ±â€¯0.05 g). Follicles were delineated by translucency of follicular fluid from transmitted light. Follicles from 0.3 mm diameter (smallest identified) to 4.8 mm (largest present) were counted. Mean number of translucent antral follicles (8.1 ±â€¯1.8 vs 5.3 ±â€¯1.2 follicles) and means for follicle diameter, fluid volume, and surface area were each greater (P < 0.01) for RO than LO. Combined for all diameters (0.3-4.8 mm), the hypothesis was supported that more follicles are present in RO than LO in calves 1 to 7 days of age. Although follicle activity in the fetus has not been compared between LO and RO, more follicles in RO than LO in recently born calves is consistent with the concept that the propensity for RO ovulation is congenital.