Prenatal Hypoxia Induced Dysfunction in Cerebral Arteries of Offspring Rats

Sex-specific differences in the mechanisms for enhanced thromboxane A2-mediated vasoconstriction in adult offspring exposed to prenatal hypoxia

BACKGROUND

Prenatal hypoxia, a common pregnancy complication, leads to impaired cardiovascular outcomes in the adult offspring. It results in impaired vasodilation in coronary and mesenteric arteries of the adult offspring, due to reduced nitric oxide (NO). Thromboxane A2 (TxA2) is a potent vasoconstrictor increased in cardiovascular diseases, but its role in the impact of prenatal hypoxia is unknown. To prevent the risk of cardiovascular disease by prenatal hypoxia, we have tested a maternal treatment using a nanoparticle-encapsulated mitochondrial antioxidant (nMitoQ). We hypothesized that prenatal hypoxia enhances vascular TxA2 responses in the adult offspring, due to decreased NO modulation, and that this might be prevented by maternal nMitoQ treatment.

METHODS

Pregnant Sprague-Dawley rats received a single intravenous injection (100 µL) of vehicle (saline) or nMitoQ (125 µmol/L) on gestational day (GD)15 and were exposed to normoxia (21% O2) or hypoxia (11% O2) from GD15 to GD21 (term = 22 days). Coronary and mesenteric arteries were isolated from the 4-month-old female and male offspring, and vasoconstriction responses to U46619 (TxA2 analog) were evaluated using wire myography. In mesenteric arteries, L-NAME (pan-NO synthase (NOS) inhibitor) was used to assess NO modulation. Mesenteric artery endothelial (e)NOS, and TxA2 receptor expression, superoxide, and 3-nitrotyrosine levels were assessed by immunofluorescence.

RESULTS

Prenatal hypoxia resulted in increased U46619 responsiveness in coronary and mesenteric arteries of the female offspring, and to a lesser extent in the male offspring, which was prevented by nMitoQ. In females, there was a reduced impact of L-NAME in mesenteric arteries of the prenatal hypoxia saline-treated females, and reduced 3-nitrotyrosine levels. In males, L-NAME increased U46619 responses in mesenteric artery to a similar extent, but TxA2 receptor expression was increased by prenatal hypoxia. There were no changes in eNOS or superoxide levels.

CONCLUSIONS

Prenatal hypoxia increased TxA2 vasoconstrictor capacity in the adult offspring in a sex-specific manner, via reduced NO modulation in females and increased TP expression in males. Maternal placental antioxidant treatment prevented the impact of prenatal hypoxia. These findings increase our understanding of how complicated pregnancies can lead to a sex difference in the programming of cardiovascular disease in the adult offspring.

Paternal preconception alcohol consumption increased Angiotensin II-mediated vasoconstriction in male offspring cerebral arteries via oxidative stress-AT1R pathway

Alcohol consumption is popular worldwidely and closely associated with cardiovascular diseases. Influences of paternal preconception alcohol consumption on offspring cerebral arteries are largely unknown. Male rats were randomly given alcohol or water before being mated with alcohol-naive females to produce alcohol- and control-sired offspring. Middle cerebral artery (MCA) was tested with a Danish Myo Technology wire myograph, patch-clamp, IONOPTIX, immunofluorescence and quantitative PCR. Alcohol consumption enhanced angiotensin II (AngII)-mediated constriction in male offspring MCA mainly via AT1R. PD123,319 only augmented AngII-induced constriction in control offspring. AngII and Bay K8644 induced stronger intracellular calcium transient in vascular smooth muscle cells (VSMCs) from MCA of alcohol offspring. L-type voltage-dependent calcium channel (L-Ca2+ ) current at baseline and after AngII-stimulation was higher in VSMCs. Influence of large-conductance calcium-activated potassium channel (BKC a ) was lower. Caffeine induced stronger constriction and intracellular calcium release in alcohol offspring. Superoxide anion was higher in alcohol MCA than control. Tempol and thenoyltrifluoroacetone alleviated AngII-mediated contractions, while inhibition was significantly higher in alcohol group. The mitochondria were swollen in alcohol MCA. Despite lower Kcnma1 and Prkce expression, many genes expressions were higher in alcohol group. Hypoxia induced reactive oxygen species production and increased AT1R expression in control MCA and rat aorta smooth muscle cell line. In conclusion, this study firstly demonstrated paternal preconception alcohol potentiated AngII-mediated vasoconstriction in offspring MCA via ROS-AT1R. Alcohol consumption increased intracellular calcium via L-Ca2+ channel and endoplasmic reticulum and decreased BKCa function. The present study provided new information for male reproductive health and developmental origin of cerebrovascular diseases.

The renin-angiotensin system modulates endotoxic postconditioning of exacerbated renal vasoconstriction in preeclamptic offspring

We recently reported exacerbated endotoxic signs of neuroinflammation and autonomic defects in offspring of preeclamptic (PE) dams. Here, we investigated whether PE programming similarly modifies hemodynamic and renal vasoconstrictor responsiveness to endotoxemia in PE offspring and whether this interaction is modulated by gestational angiotensin 1-7 (Ang1-7). Preeclampsia was induced by gestational treatment with L-NAME. Adult offspring was challenged with lipopolysaccharides (LPS, 5 mg/kg) and systolic blood pressure (SBP) and renal vasoconstrictions were assessed 4 h later. Male, but not female, offspring of PE rats exhibited SBP elevations that were blunted by LPS. Renal vasoconstrictions induced by angiotensin II (Ang II), but not phenylephrine, were intensified in perfused kidneys of either sex. LPS blunted the heightened Ang II responses in male, but not female, kidneys. While renal expressions of AT1-receptors and angiotensin converting enzyme (ACE) were increased in PE offspring of both sexes, ACE2 was upregulated in female offspring only. These molecular effects were diminished by LPS in male offspring. Gestational Ang1-7 caused sex-unrelated attenuation of phenylephrine vasoconstrictions and preferentially downregulated Ang II responses and AT1-receptor and nuclear factor-kB (NFkB) expressions in females. Together, endotoxemia and Ang1-7 offset in sexually-related manners imbalances in renal vasoconstriction and AT1/ACE/ACE2 signaling in PE offspring.

Perinatal Fat-Diets Increased Angiotensin II-Mediated Ca2+ through PKC-L-Type Calcium Channel Axis in Resistance Arteries via Agtr1a-Prkcb Gene Methylation

Perinatal malnutrition affects vascular functions, and calcium is important in vascular regulations. It is unknown whether and how perinatal maternal high-fat diets (MHF)-mediated vascular dysfunction occurs via the angiotensin-PKC-L-type-calcium-channels (LTCC) axis. This study determined angiotensin II (AII) roles in the PKC-LTCC axis in controlling calcium influx in the arteries of offspring after perinatal MHF. Mesenteric arteries (MA) and smooth muscle cells (SMCs) from 5-month-old offspring rats were studied using physiological, ion channel, molecular, and epigenetic analysis. Pressor responses to AII were significantly increased in the free-moving MHF offspring rats. In cell experiments, MA-SMC proliferation was enhanced, and associated with thicker vascular wall in the obese offspring. Imaging analysis showed increase of fluorescence Ca²⁺ intensity in the SMCs of the MHF group. Angiotensin II receptor (AT1R)-mediated PKC-LTCC axis in vasoconstrictions was altered by perinatal MHF via reduced DNA methylation at specific CpG sites of Agtr1a and Prkcb gene promoters at the transcription level. Accordingly, mRNA and protein expression of AT1R and PKCβ in the offspring MA were increased, contributing to enhanced Ca²⁺ currents and vascular tone. The results showed that DNA methylation resulted in perinatal MHF-induced vascular disorders via altered AT1-PKC-LTCC pathway in resistance arteries of the offspring, providing new insights into the pathogenesis and early prevention/treatments for hypertension in developmental origins.

Prenatal Hypoxia Affects Foetal Cardiovascular Regulatory Mechanisms in a Sex- and Circadian-Dependent Manner: A Review

Prenatal hypoxia during the prenatal period can interfere with the developmental trajectory and lead to developing hypertension in adulthood. Prenatal hypoxia is often associated with intrauterine growth restriction that interferes with metabolism and can lead to multilevel changes. Therefore, we analysed the effects of prenatal hypoxia predominantly not associated with intrauterine growth restriction using publications up to September 2021. We focused on: (1) The response of cardiovascular regulatory mechanisms, such as the chemoreflex, adenosine, nitric oxide, and angiotensin II on prenatal hypoxia. (2) The role of the placenta in causing and attenuating the effects of hypoxia. (3) Environmental conditions and the mother's health contribution to the development of prenatal hypoxia. (4) The sex-dependent effects of prenatal hypoxia on cardiovascular regulatory mechanisms and the connection between hypoxia-inducible factors and circadian variability. We identified that the possible relationship between the effects of prenatal hypoxia on the cardiovascular regulatory mechanism may vary depending on circadian variability and phase of the days. In summary, even short-term prenatal hypoxia significantly affects cardiovascular regulatory mechanisms and programs hypertension in adulthood, while prenatal programming effects are not only dependent on the critical period, and sensitivity can change within circadian oscillations.

Prenatal hypoxia induced ETBR activation and abnormal ROS signalling in pulmonary artery cells of rat offspring

Pulmonary arterial hypertension is a progressive disorder characterized by remodeling and increased small pulmonary arteries resistance. Endothelin-1 (ET-1) was related to PAH and ET-1 receptors were up-regulated selectively in the lung when exposed to toxic factor hypoxia. However, the role of ET-1 signaling in the pathogenesis of prenatal hypoxia-induced pulmonary abnormalities remains to be elucidated. Pregnant rats were divided into prenatal hypoxia (10.5 % O2 from gestational day 4-21) and control group. Their three-month-old offspring male rats were tested for vascular functions and molecular analysis, DNA methylation was assessed for cellular hypoxia. Functional testing showed that ET-1-mediated vasoconstriction was enhanced, and the expressions of endothelin A receptor/B receptor (ETAR/ETBR), inositol 1,4,5-trisphosphate receptor, type 1, and the sensitivity of calcium channels were increased in the small pulmonary arteries following prenatal hypoxia. q-PCR and DHE staining showed that the expressions of NADPH oxidase 1/4 (Nox1/4) were up-regulated, along with the increased production of superoxide anion. Furthermore, superoxide anion promoted ET-1-mediated pulmonary artery contraction. In the pulmonary artery smooth muscle cell experiments, q-PCR, Western Blot, CCK8 and DHE staining showed that the expressions of ETBR, Nox1/4, and superoxide anion were increased by hypoxia, along with promoted cell proliferation. 2,2,6,6-Tetramethyl-1-piperidinyloxy reversed hypoxia-induced cell proliferation. ETBR antagonist BQ788 inhibited hypoxia-increased expressions of Nox1/4, superoxide anion production, and proliferation of cells. Moreover, methylation analysis indicated that hypoxia decreased the methylation levels of the ETBR promoter in the pulmonary artery smooth muscle cells. The results indicated that prenatal toxic factor hypoxia resulted in abnormal ETBR activation, which enhanced ET-1-mediated vasoconstriction of pulmonary arteries and pulmonary artery smooth muscle cell proliferation through ETBR/Nox1/4-derived ROS pathway.

Antenatal Hypoxia Affects Pulmonary Artery Contractile Functions via Downregulating L-type Ca2+ Channels Subunit Alpha1 C in Adult Male Offspring

Background

Antenatal intrauterine fetal hypoxia is a common pregnancy complication that has profound adverse effects on an individual's vascular health later in life. Pulmonary arteries are sensitive to hypoxia, but adverse effects of antenatal hypoxia on pulmonary vasoreactivities in the offspring remain unknown. This study aimed to determine the effects and related mechanisms of antenatal hypoxia on pulmonary artery functions in adult male offspring.

Methods and Results

Pregnant Sprague‐Dawley rats were housed in a normoxic or hypoxic (10.5% O₂) chamber from gestation days 10 to 20. Male offspring were euthanized at 16 weeks old (adult offspring). Pulmonary arteries were collected for vascular function, electrophysiology, target gene expression, and promoter methylation studies. In pulmonary artery rings, contractions to serotonin hydrochloride, angiotensin II, or phenylephrine were reduced in the antenatal hypoxic offspring, which resulted from inactivated L‐type Ca²⁺ channels. In pulmonary artery smooth muscle cells, the basal whole‐cell Ca²⁺ currents, as well as vasoconstrictor‐induced Ca²⁺ transients were significantly reduced in antenatal hypoxic offspring. In addition, increased promoter methylations within L‐type Ca²⁺ channel subunit alpha1 C were compatible with its reduced expressions.

Conclusions

This study indicated that antenatal hypoxia programmed long‐lasting vascular hypocontractility in the male offspring that is linked to decreases of L‐type Ca²⁺ channel subunit alpha1 C in the pulmonary arteries. Antenatal hypoxia resulted in pulmonary artery adverse outcomes in postnatal offspring, was strongly associated with reprogrammed L‐type Ca²⁺ channel subunit alpha1 C expression via a DNA methylation‐mediated epigenetic mechanism, advancing understanding toward the effect of antenatal hypoxia in early life on long‐term vascular health.

DNA Methylation-Reprogrammed Ang II (Angiotensin II) Type 1 Receptor-Early Growth Response Gene 1-Protein Kinase C ε Axis Underlies Vascular Hypercontractility in Antenatal Hypoxic Offspring

As the most common clinical stress during mid and late pregnancy, antenatal hypoxia has profound adverse effects on individual's vascular health later in life, but the underlying mechanisms are still not understood. The purpose of this study was to reveal the mechanisms of the acquired vascular dysfunction in offspring imposed by antenatal hypoxia. Pregnant rats were housed in a normoxic or hypoxic (10.5% oxygen) chamber from gestation day 10 to 21. Male offspring were euthanized at gestational day 21 (fetus) or postnatal 16 weeks old (adult offspring). Mesenteric arteries were collected for examining Ang II (angiotensin II)-mediated vascular contractility, gene expression, and promoter methylation. Antenatal hypoxia increased vascular sensitivity to Ang II, which was resulted by an upregulated AT1R (angiotensin II type 1 receptor). The increased AT1R was correlated with a hypomethylation-mediated activated transcription of Agtr1a (alpha subtype of AT1R). In addition, we presented evidences that there was an AT1R-Egr1 (early growth response gene 1)-PKCε (ε isoform of protein kinase C) axis in vasculature; AT1R could modulate PKCε expression via upregulating Egr1; Egr1 mediated transcription activation of PKCε via Egr1 binding sites in PKCε gene promoter. Overall, antenatal hypoxia activated AT1R-Egr1-PKCε axis in vasculature, eventually predisposed offspring to vascular hypercontractility. This is the first description that antenatal hypoxia resulted in vascular adverse outcomes in postnatal offspring, was strongly associated with reprogrammed gene expression via a DNA methylation-mediated epigenetic mechanism, advancing understanding toward the influence of adverse antenatal factors in early life on long-term vascular health.

Comparison of Vascular Responses to Vasoconstrictors in Human Placenta in Preeclampsia between Preterm and Later Term

BACKGROUND

Placental blood vessels play important roles in maternal-fetal circulation. Although pathologic mechanisms of preeclampsia are unclear, it is known that placental vascular dysfunction could contribute to pregnant hypertension. However, placental micro-vessel function or dysfunction at preterm has not been investigated.

METHODS

Human placentas from normal and preeclamptic pregnancies at preterm and term were obtained. Placental micro-vessels were used for determining vascular tension and responses to various vasoconstrictors as well as intracellular calcium store capability. It was the first time to show vascular responses in placental arteries to angiotensin II, endothelin-1, and other vascular drugs at preterm.

RESULTS

Compared to the control, placental vascular contractile responses to angiotensin II and caffeine were significantly decreased, while placental vascular responses to KCl, endothelin-1, and bradykinin were not significantly altered in the later term group in preeclampsia. In comparison of placental micro-vessel tension between the preterm and later term, caffeine- and serotonin-induced vascular contractions were significantly weaker in the preterm than that in the later term. On the contrary, vascular response to angiotensin II was increased in the preterm preeclampsia, while KCl-, endothelin-1, and bradykinin-mediated placental vessel responses in the preterm preeclampsia were similar to that in later term preeclampsia.

CONCLUSION

New data showed that micro-vessel responses to angiotensin II and serotonin, not endothelin- 1 or bradykinin, were significantly reduced in the human placentas at preterm, and intracellular Ca2+ store capacity was damaged too, providing important information on possible contributions of placental vascular dysfunction to pregnant hypertension.

MARCKS mediates vascular contractility through regulating interactions between voltage-gated Ca2+ channels and PIP2

Phosphatidylinositol 4,5-bisphosphate (PIP₂) acts as substrate and unmodified ligand for Gq-protein-coupled receptor signalling in vascular smooth muscle cells (VSMCs) that is central for initiating contractility. The present work investigated how PIP₂ might perform these two potentially conflicting roles by studying the effect of myristoylated alanine-rich C kinase substrate (MARCKS), a PIP₂-binding protein, on vascular contractility in rat and mouse mesenteric arteries. Using wire myography, MANS peptide (MANS), a MARCKS inhibitor, produced robust contractions with a pharmacological profile suggesting a predominantly role for L-type (CaV1.2) voltage-gated Ca²⁺ channels (VGCC). Knockdown of MARCKS using morpholino oligonucleotides reduced contractions induced by MANS and stimulation of α₁-adrenoceptors and thromboxane receptors with methoxamine (MO) and U46619 respectively. Immunocytochemistry and proximity ligation assays demonstrated that MARCKS and CaV1.2 proteins co-localise at the plasma membrane in unstimulated tissue, and that MANS and MO reduced these interactions and induced translocation of MARCKS from the plasma membrane to the cytosol. Dot-blots revealed greater PIP₂ binding to MARCKS than CaV1.2 in unstimulated tissue, with this binding profile reversed following stimulation by MANS and MO. MANS evoked an increase in peak amplitude and shifted the activation curve to more negative membrane potentials of whole-cell voltage-gated Ca²⁺ currents, which were prevented by depleting PIP₂ levels with wortmannin. This present study indicates for the first time that MARCKS is important regulating vascular contractility and suggests that disinhibition of MARCKS by MANS or vasoconstrictors may induce contraction through releasing PIP₂ into the local environment where it increases voltage-gated Ca²⁺ channel activity.

Animal Models of Preeclampsia: Causes, Consequences, and Interventions

Preeclampsia is a common pregnancy complication, affecting 2% to 8% of pregnancies worldwide, and is an important cause of both maternal and fetal morbidity and mortality. Importantly, although aspirin and calcium are able to prevent preeclampsia in some women, there is no cure apart from delivery of the placenta and fetus, often necessitating iatrogenic preterm birth. Preclinical models of preeclampsia are widely used to investigate the causes and consequences of preeclampsia and to evaluate safety and efficacy of potential preventative and therapeutic interventions. In this review, we provide a summary of the published preclinical models of preeclampsia that meet human diagnostic criteria, including the development of maternal hypertension, together with new-onset proteinuria, maternal organ dysfunction, and uteroplacental dysfunction. We then discuss evidence from preclinical models for multiple causal factors of preeclampsia, including those implicated in early-onset and late-onset preeclampsia. Next, we discuss the impact of exposure to a preeclampsia-like environment for later maternal and progeny health. The presence of long-term impairment, particularly cardiovascular outcomes, in mothers and progeny after an experimentally induced preeclampsia-like pregnancy, implies that later onset or reduced severity of preeclampsia will improve later maternal and progeny health. Finally, we summarize published intervention studies in preclinical models and identify gaps in knowledge that we consider should be targets for future research.

Mechanisms linking exposure to preeclampsia in utero and the risk for cardiovascular disease

Preeclampsia (PE) is now recognised as a cardiovascular risk factor for women. Emerging evidence suggests that children exposed to PE in utero may also be at increased risk of cardiovascular disease (CVD) in later life. Individuals exposed to PE in utero have higher systolic and diastolic blood pressure and higher body mass index (BMI) compared to those not exposed to PE in utero. The aim of this review is to discuss the potential mechanisms driving the relationship between PE and offspring CVD. Exposure to an adverse intrauterine environment as a consequence of the pathophysiological changes that occur during a pregnancy complicated by PE is proposed as one mechanism that programs the fetus for future CVD risk. Consistent with this hypothesis, animal models of PE where progeny have been studied demonstrate causality for programming of offspring cardiovascular health by the preeclamptic environment. Shared alleles between mother and offspring, and shared lifestyle factors between mother and offspring provide alternate pathways explaining associations between PE and offspring CVD risk. In addition, adverse lifestyle habits can also act as second hits for those programmed for increased CVD risk. PE and CVD are both multifactorial diseases and, hence, identifying the relative contribution of PE to offspring risk for CVD is a very complex task. However, considering the emerging strong association between PE and CVD, those exposed to PE in utero may benefit from targeted primary CVD preventive strategies.

Prenatal hypoxia inhibited propionate-evoked BK channels of mesenteric artery smooth muscle cells in offspring

As a common complication of pregnancy, gestational hypoxia has been shown to predispose offspring to vascular dysfunction. Propionate, one of short‐chain fatty acids, exerts cardioprotective effects via reducing blood pressure. This study examined whether prenatal hypoxia impaired propionate‐stimulated large‐conductance Ca²⁺‐activated K⁺ (BK) channel activities in vascular smooth muscle cells (VSMCs) of offspring. Pregnant rats were exposed to hypoxia (10.5% oxygen) and normoxia (21% oxygen) from gestational day 7‐21. At 6 weeks of age, VSMCs in mesenteric arteries of offspring were analysed for BK channel functions and gene expressions. It was shown firstly that propionate could open significantly BK single channel in VSMCs in a concentration‐dependent manner. Antagonists of G protein βγ subunits and inositol trisphosphate receptor could completely suppress the activation of BK by propionate, respectively. Gα_i/o and ryanodine receptor were found to participate in the stimulation on BK. Compared to the control, vasodilation and increments of BK NPo (the open probability) evoked by propionate were weakened in the offspring by prenatal hypoxia with down‐regulated Gβγ and PLCβ. It was indicated that prenatal hypoxia inhibited propionate‐stimulated BK activities in mesenteric VSMCs of offspring via reducing expressions of Gβγ and PLCβ, in which endoplasmic reticulum calcium release might be involved.

Prenatal metyrapone treatment modulates neonatal cerebrovascular structure, function, and vulnerability to mild hypoxic-ischemic injury

This study explored the hypothesis that late gestational reduction of corticosteroids transforms the cerebrovasculature and modulates postnatal vulnerability to mild hypoxic-ischemic (HI) injury. Four groups of Sprague-Dawley neonates were studied: 1) Sham-Control, 2) Sham-MET, 3) HI-Control, and 4) HI-MET. Metyrapone (MET), a corticosteroid synthesis inhibitor, was administered via drinking water from gestational day 11 to term. In Shams, MET administration 1) decreased reactivity of the hypothalamic-pituitary-adrenal (HPA) axis to surgical trauma in postnatal day 9 (P9) pups by 37%, 2) promoted cerebrovascular contractile differentiation in middle cerebral arteries (MCAs), 3) decreased compliance ≤46% and increased depolarization-induced calcium mobilization in MCAs by 28%, 4) mildly increased hemispheric cerebral edema by 5%, decreased neuronal degeneration by 66%, and increased astroglial and microglial activation by 10- and 4-fold, respectively, and 5) increased righting reflex times by 29%. Regarding HI, metyrapone-induced fetal transformation 1) diminished reactivity of the HPA axis to HI-induced stress in P9/P10 pups, 2) enhanced HI-induced contractile dedifferentiation in MCAs, 3) lessened the effects of HI on MCA compliance and calcium mobilization, 4) decreased HI-induced neuronal injury but unmasked regional HI-induced depression of microglial activation, and 5) attenuated the negative effects of HI on open-field exploration but enhanced the detrimental effects of HI on negative geotaxis responses by 79%. Overall, corticosteroids during gestation appear essential for normal cerebrovascular development and glial quiescence but induce persistent changes that in neonates manifest beneficially as preservation of postischemic contractile differentiation but detrimentally as worsened ischemic cerebrovascular compliance, increased ischemic neuronal injury, and compromised neurobehavior.

Inherited risk plus prenatal insult caused malignant dysfunction in mesenteric arteries in adolescent SHR offspring

Prenatal hypoxia can induce cardiovascular diseases in the offspring. This study determined whether and how prenatal hypoxia may cause malignant hypertension and impaired vascular functions in spontaneous hypertension rat (SHR) offspring at adolescent stage. Pregnant SHR were placed in a hypoxic chamber (11% O2) or normal environment (21% O2) from gestational day 6 until birth. Body weight and blood pressure (BP) of SHR offspring were measured every week from 5 weeks old. Mesenteric arteries were tested. Gestational hypoxia resulted in growth restriction during 6-12 weeks and a significant elevation in systolic pressure in adolescent offspring at 12 weeks old. Notably, endothelial vasodilatation of mesenteric arteries was impaired in SHR adolescent offspring exposed to prenatal hypoxia, vascular responses to acetylcholine (ACh) and sodium nitroprusside (SNP) were reduced, as well as plasma nitric oxide levels and expression of endothelial nitric oxide synthase (eNOS) in vessels were decreased. Moreover, mesenteric arteries in SHR offspring following prenatal hypoxia showed enhanced constriction responses to phenylephrine (PE), associated with up-regulated activities of L-type calcium channel (Ca2+-dependent), RhoA/Rock pathway signaling (Ca2+-sensitization), and intracellular Ca2+ flow. Pressurized myograph demonstrated altered mechanical properties with aggravated stiffness in vessels, while histological analysis revealed vascular structural disorganization in prenatal hypoxia offspring. The results demonstrated that blood pressure and vascular function in young SHR offspring were affected by prenatal hypoxia, providing new information on development of hypertension in adolescent offspring with inherited hypertensive backgrounds.

Magnesium Sulfate-Mediated Vascular Relaxation and Calcium Channel Activity in Placental Vessels Different From Nonplacental Vessels

Background

Magnesium sulfate (MgSO₄) has been used as a common therapy for preeclampsia and eclampsia for many years. MgSO₄ decreases peripheral vascular resistance so as to reduce maternal blood pressure. Whether placental blood vessels react to MgSO₄ in the same patterns as that in maternal vessels is largely unknown.

Methods and Results

This study compared placental vessels (PV) versus nonplacental vessels (non‐PV) in human and animal models. MgSO₄‐caused vascular dilation was significantly weaker in PV than that in non‐PV. Prostaglandin I₂ synthetase affected MgSO₄‐mediated vasodilatation in PV, not in umbilical vessels, while cyclooxygenase did not influence MgSO₄‐induced relaxation in both PV and non‐PV. Mg²⁺‐caused vasodilatation was mainly through calcium channels. In PV, calcium channel activities were significantly weaker in PV than that in non‐PV. Relative mRNA expression of CACNA1D,CACNB2, and CACNB3 was significantly higher in PV than those in umbilical vessels, despite the fact that the expression of CACNA1F was less in PV. The contractile phenotype of smooth muscle cell marker (CALD1) was less and the synthetic phenotype (MYH10) was more in PV than that in UV.

Conclusions

These results demonstrated that PV were characterized by much weaker responses to MgSO₄ compared with nonplacental vessels. The difference was related to weaker calcium channel activity and minor contractile phenotype smooth muscle cells in PV, providing important information for further understanding treatments with MgSO₄ in preeclampsia.