Enhanced growth and improved vascular function in offspring from successive pregnancies in endothelial nitric oxide synthase knockout mice

In Utero Origins of Hypertension: Mechanisms and Targets for Therapy

The developmental origins of health and disease theory is based on evidence that a suboptimal environment during fetal and neonatal development can significantly impact the evolution of adult-onset disease. Abundant evidence exists that a compromised prenatal (and early postnatal) environment leads to an increased risk of hypertension later in life. Hypertension is a silent, chronic, and progressive disease defined by elevated blood pressure (>140/90 mmHg) and is strongly correlated with cardiovascular morbidity/mortality. The pathophysiological mechanisms, however, are complex and poorly understood, and hypertension continues to be one of the most resilient health problems in modern society. Research into the programming of hypertension has proposed pharmacological treatment strategies to reverse and/or prevent disease. In addition, modifications to the lifestyle of pregnant women might impart far-reaching benefits to the health of their children. As more information is discovered, more successful management of hypertension can be expected to follow; however, while pregnancy complications such as fetal growth restriction, preeclampsia, preterm birth, etc., continue to occur, their offspring will be at increased risk for hypertension. This article reviews the current knowledge surrounding the developmental origins of hypertension, with a focus on mechanistic pathways and targets for therapeutic and pharmacologic interventions.

Sex-specific effects of nicotine exposure on developmental programming of blood pressure and vascular reactivity in the C57Bl/6J mouse

OBJECTIVE

The objective of the study was to determine whether perinatal nicotine exposure adversely affects cardiovascular health in adulthood.

STUDY DESIGN

C57Bl/6J female mice were randomized to 200 μg/mL nicotine in 2% saccharin or 2% saccharin alone from 2 weeks before breeding until weaning. Offspring weight, vital signs, and carotid artery vascular reactivity were studied. A second cohort was subjected to shaker stress on day 4 of 7 days. Selected mediators of vascular tone were evaluated by molecular studies. Student t or Mann-Whitney U test was performed for statistical analysis (significance: P < .05).

RESULTS

Nicotine-exposed compared with control female offspring had significantly elevated mean blood pressure under normal and stress conditions. Nicotine females lacked heart rate elevation after stress. Nicotine males had higher mean heart rate and a blunted contractile response to phenylephrine compared with controls, without an increase in blood pressure.

CONCLUSION

Perinatal nicotine exposure has an impact on the developmental programming of future cardiovascular health, with adverse effects more evident in female offspring.

Pre-eclampsia and offspring cardiovascular health: mechanistic insights from experimental studies

Pre-eclampsia is increasingly recognized as more than an isolated disease of pregnancy. Women who have had a pregnancy complicated by pre-eclampsia have a 4-fold increased risk of later cardiovascular disease. Intriguingly, the offspring of affected pregnancies also have an increased risk of higher blood pressure and almost double the risk of stroke in later life. Experimental approaches to identify the key features of pre-eclampsia responsible for this programming of offspring cardiovascular health, or the key biological pathways modified in the offspring, have the potential to highlight novel targets for early primary prevention strategies. As pre-eclampsia occurs in 2–5% of all pregnancies, the findings are relevant to the current healthcare of up to 3 million people in the U.K. and 15 million people in the U.S.A. In the present paper, we review the current literature that concerns potential mechanisms for adverse cardiovascular programming in offspring exposed to pre-eclampsia, considering two major areas of investigation: first, experimental models that mimic features of the in utero environment characteristic of pre-eclampsia, and secondly, how, in humans, offspring cardiovascular phenotype is altered after exposure to pre-eclampsia. We compare and contrast the findings from these two bodies of work to develop insights into the likely key pathways of relevance. The present review and analysis highlights the pivotal role of long-term changes in vascular function and identifies areas of growing interest, specifically, response to hypoxia, immune modification, epigenetics and the anti-angiogenic in utero milieu.

Effect of a previous pregnancy on vascular function in endothelial nitric oxide synthase 3 knockout mice

OBJECTIVE

Nitric oxide deficiency has been implicated in adverse pregnancy outcomes. Mice that lack endothelial nitric oxide synthase (NOS3) have abnormal in vitro vascular reactivity. Our objective was to assess the effect of a previous pregnancy on the abnormal vascular function of NOS3 knockout mice.

STUDY DESIGN

Carotid arteries from pregnant NOS3 knockout (NOS3(-/-KO)) and wild-type control mice (NOS3(+/+WT)) from first and second pregnancy were obtained for in vitro vascular reactivity studies. Vascular responses to cumulative concentrations of the vasoconstrictors phenylephrine, serotonin, and thromboxane and the vasorelaxants acetylcholine, sodium nitroprusside, and isoproterenol were determined.

RESULTS

In the first pregnancy, contractile responses were exaggerated in the knockout animals, compared with the wild-type animals. However, the second pregnancy in knockout animals was associated with normalization of responses to phenylephrine and serotonin and increased responses to the endothelium-independent relaxants.

CONCLUSION

The vascular function of NOS3 knockout mice improves with subsequent pregnancy becoming comparable to wild-type animals.

Inhibitory effect of erythropoietin on contractility of human chorionic plate vessels

OBJECTIVE

Placenta is a major source of erythropoietin production in the fetus; hypoxia is associated with elevated erythropoietin levels in the fetal circulation. We investigated fetoplacental vascular reactivity after exposure to erythropoietin in vitro.

STUDY DESIGN

Third-order chorionic plate arteries from human term placentae were incubated in culture medium with or without erythropoietin (3 U/mL) for 24 hours. Vessels were mounted in a myograph for isometric tension recording, and their responses to vasopressors and vasorelaxants were studied.

RESULTS

Contractile responses to endothelin-1 and the thromboxane analogue U46619 were decreased in erythropoietin-exposed vessels compared with controls. Relaxant responses to the nitric oxide donor sodium nitroprusside and the phosphodiesterase inhibitor papaverine were not influenced by erythropoietin.

CONCLUSION

Exposure to elevated levels of erythropoietin has an inhibitory effect on contractile responses in human placental chorionic plate arteries. We speculate that this may improve fetoplacental perfusion in hypoxic fetuses with elevated erythropoietin production.