Reduced flow-mediated vasodilation is not due to a decrease in production of nitric oxide in preeclampsia

Neurovascular dysfunctions in hypertensive disorders of pregnancy

Hypertensive disorders in pregnancy pose a huge challenge to the socioeconomic stability of a community; being a major cause of maternal and neonatal morbidity and mortality during delivery. Although there have been recent improvements in management strategies, still, the diversified nature of the underlying pathogenesis undermines their effectiveness. Generally, these disorders are categorized into two; hypertensive disorders of pregnancy with proteinuria (pre-eclampsia and eclampsia) and hypertensive disorders of pregnancy without proteinuria (gestational and chronic hypertension). Each of these conditions may present with unique characteristics that have interwoven symptoms. However, the tendency of occurrence heightens in the presence of any pre-existing life-threatening condition(s), environmental, and/or other genetic factors. Investigations into the cerebrovascular system demonstrate changes in the histoarchitectural organization of neurons, the proliferation of glial cells with an associated increase in inflammatory cytokines. These are oxidative stress indicators which impose a deteriorating impact on the structures that form the neurovascular unit and the blood-brain barrier (BBB). Such a pathologic state distorts the homeostatic supply of blood into the brain, and enhances the permeability of toxins/pathogens through a process called hyperperfusion at the BBB. Furthermore, a notable aspect of the pathogenesis of hypertensive disorders of pregnancy is endothelial dysfunction aggravated when signaling of the vasoprotective molecule, nitric oxide, amongst other neurotransmitter regulatory activities are impaired. This review aims to discuss the alterations in cerebrovascular regulation that determine the incidence of hypertension in pregnancy.

Preeclampsia biomarkers: An assessment of maternal cardiometabolic health

Preeclampsia is a serious pregnancy condition defined as new-onset hypertension and proteinuria, commonly characterized as either early, 'placental', or late onset, 'maternal', using a cut-off of 34 weeks gestation. However, it may be more useful to differentiate between the vascular remodelling and placental invasion vs. inflammation and metabolic pathophysiology that underlie these forms of preeclampsia. Due to rising rates of obesity, the late-onset, maternal form is increasingly occurring earlier in pregnancy. Predictive tests for preeclampsia typically include biophysical markers such as maternal body mass index and mean arterial pressure, indicating the importance of cardiovascular and metabolic health in its pathophysiology. In contrast, the placental, inflammatory, endothelial and/or metabolic biomarkers used in these tests are generally thought to indicate an abnormal response to placentation and predict the disease. However, many of these non-placental biomarkers are known to predict impaired metabolic health in non-pregnant subjects with obesity (metabolically unhealthy obesity) and coronary artery disease or stroke in people at risk for cardiovascular events. Similarities between the performance of these markers in the prediction of cardiovascular and metabolic health outside of pregnancy suggests that they may be more indicative of maternal health than predictive for preeclampsia. This paper reviews the biophysical and biochemical markers in preeclampsia prediction and compares their performance to tests assessing metabolic health and risk of cardiovascular disease, particularly in the obese population.

Pre-eclampsia: the Potential of GSNO Reductase Inhibitors

PURPOSE OF REVIEW

Pre-eclampsia remains a leading worldwide cause of maternal death and of perinatal morbidity. There remains no definitive treatment except delivery of the fetus.

RECENT FINDINGS

Recent insights into the cardiovascular changes that are evident prior to, during, and persist after pre-eclampsia have improved understanding of the underlying pathophysiology-disruption of normal endothelial function and decreased nitric oxide bioavailability. S-nitrosoglutathione (GSNO) is an endogenous S-nitrosothiol that acts as a NO pool and, by replenishing or preventing the breakdown of GSNO, endothelial dysfunction can be ameliorated. GSNO reductase inhibitors are a novel class of drug that can increase NO bioavailability. GSNO reductase inhibitors have demonstrated improvement of endothelial dysfunction in animal models, and in vivo human studies have shown them to be well tolerated. GSNOR inhibitors offer a potentially promising option for the management of pre-eclampsia.

Flow-mediated dilation: can new approaches provide greater mechanistic insight into vascular dysfunction in preeclampsia and other diseases?

Endothelial dysfunction is a key feature of preeclampsia and may contribute to increased cardiovascular disease risk years after pregnancy. Flow-mediated dilation (FMD) is a non-invasive endothelial function test that predicts cardiovascular event risk. New protocols allow researchers to measure three components of the FMD response: FMD, low flow-mediated constriction, and shear stimulus. This review encourages researchers to think beyond "low FMD" by examining how these three components may provide additional insights into the mechanisms and location of vascular dysfunction. The review then examines what FMD studies reveal about vascular dysfunction in preeclampsia while highlighting opportunities to gain greater mechanistic insight from new protocols. Studies using traditional protocols show that FMD is low in mid-pregnancy prior to preeclampsia, at diagnosis, and for 3 years post-partum. However, FMD returns to normal by 10 years post-partum. Studies using new protocols are needed to gain more mechanistic insight.

Assessment of endothelial function by flow-mediated dilation of the brachial artery in adolescents with a history of preeclampsia or a normotensive pregnancy

Objectives: to determine the prevalence of endothelial dysfunction and its association with a history of mild and severe preeclampsia in adolescents. Methods: a cross-sectional study was carried out at the MEAC-UFC with 103 primiparous adolescents postpartum. The assessment of endothelial function was performed by way of flow-mediated dilatation of the brachial artery. Variables (age, body mass index, gestational age at delivery, systolic and diastolic blood pressure and flow-mediated dilation) were compared between groups. p<0.05 was considered to be statistically significant. Results: twenty-four (23.3%) patients had preeclampsia (PE): 11 mild and 13 severe. The overall prevalence of endothelial dysfunction was 23.3% (21.5% of patients with normotensive pregnancies and 29.2% of the PE patients: 18.2% of those with mild PE and 38.5% of those with severe PE). The figures were statistically significant for systolic blood pressure, p=0.007. Conclusions: patients with a history of PE have higher systolic blood pressure than patients with a history of normotensive pregnancy, but did not have more endothelial dysfunction.

[Endothelial dysfunction: role in the maternal syndrome of preeclampsia and long-term consequences for the cardiovascular system]

Preeclampsia is a pregnancy disorder being a leading cause of maternal and fetal mortality and morbidity. It is a complex multisystem disease characterized by hypertension and proteinuria. In preeclampsia the placenta releases factors into the maternal circulation which cause a systemic endothelial dysfunction. Here, we review data demonstrating the central role played by the endothelium in the development of the maternal syndrome of preeclampsia. We present also original data showing how circulating factors present in the plasma of preeclamptic women can alter the transcriptome of endothelial cells. The expression of genes involved in essential functions such as vasoregulation, oxidative stress, apoptosis and cell proliferation show differential expression when endothelial cells are exposed to preeclamptic or normal pregnancy plasma. We conclude by discussing the growing evidences that the alterations of the endothelium during preeclampsia are linked to an increased risk of cardiovascular diseases latter on life. Therefore, a better understanding of the modifications undergone by the endothelial cells during preeclampsia is essential to develop new therapeutic approaches to both, manage preeclampsia and to prevent the long-term sequelae of the disease on women cardiovascular system.

Investigation of the role of the NO-cGMP pathway on YC-1 and DEA/NO effects on thoracic aorta smooth muscle responses in a rat preeclampsia model

The present study was designed to investigate the effects of YC-1, a nitric oxide (NO)-independent soluble guanylate cyclase (sGC) activator, and DEA/NO, a NO donor, on smooth muscle responses in the preeclampsia model with suramin-treated rats and on the levels of cyclic guanosine monophosphate (cGMP) of thoracic aorta rings isolated from term-pregnant rats. Rats of 2 groups, control group and suramin group, were given intraperitoneal injection of saline or suramin, respectively. Suramin injection caused increased blood pressure, protein in urine, and fetal growth retardation. Thoracic aorta rings were exposed to contractile and relaxant agents. KCl contraction and papaverine relaxation responses were similar. Relaxation responses of YC-1 and DEA/NO decreased in suramin group. In both groups in the presence of ODQ, a sGC inhibitor, the relaxation responses of YC-1 and DEA/NO decreased. The cGMP content was determined by radioimmunoassay technique. The content of cGMP in the suramin group decreased. In the presence of YC-1 and DEA/NO in both groups, cGMP content increased, but in ODQ-added groups, there was a significant decrease. We conclude that in preeclampsia, the decrease of relaxation responses and the decrease of cGMP content could be due to the reduction in stimulation of sGC and the decrease in cGMP levels.

Prepregnancy Vascular Dysfunction in Women who Subsequently Develop Hypertension During Pregnancy

OBJECTIVE

To evaluate vascular dysfunction using both physiologic measures and biochemical markers, longitudinally, prior to and during pregnancy, in nulliparous women who had uncomplicated pregnancies compared to those who developed complicated hypertension during pregnancy.

METHODS

Twenty healthy nulliparous women were studied during the follicular phase and in early (EP) and late (LP) pregnancy. All had singleton conceptions and delivered at term, seventeen with uncomplicated pregnancies (NP) and three who developed complicated hypertension (HP) after the LP evaluation. We compared prepregnancy, EP and LP pulse wave velocity (PWV) and soluble vascular cell adhesion molecule (sVCAM-1) between the NP and HP groups. PWV was measured using ultrasound and simultaneous echocardiogram tracing then calculated as the estimated distance divided by interval between EKG r-wave peak and peak brachial artery flow. SVCAM-1 was measured using a commercially available kit. Data are means ± SE, significance accepted as p < 0.05.

RESULTS

The NP group had significantly lower prepregnant PWV (NP: 2.66 ± 0.06 m/s, HP: 3.00 ± 0.04, p=.02), but PWV was not different at the EP or LP time points. SVCAM-1 was significantly lower prior to pregnancy and during EP and LP in the NP group (Prepregnancy: NP: 712 ± 32 ng/mL, HP: 1058 ± 107, p < .001; EP: NP: 695 ± 31 ng/mL, HP: 924 ± 52, p = .004; LP: NP: 663 ± 25 ng/mL, HP: 946 ± 36, p < .001).

CONCLUSIONS

PWV and sVCAM-1 may be important prepregnancy discriminators useful in assessing risk for preeclampsia prior to pregnancy.

The association between preeclampsia and arterial stiffness

A systematic review and meta-analysis was conducted using MEDLINE, EMBASE, and the Cochrane Library to investigate the association between preeclampsia and arterial stiffness. Twenty-three relevant studies were included. A significant increase in all arterial stiffness indices combined was observed in women with preeclampsia vs. women with normotensive pregnancies [standardized mean difference 1.62, 95% confidence interval (CI) 0.73-2.50]; carotid-femoral pulse wave velocity (cfPWV) and augmentation index (AIx) were also significantly increased (weighted mean difference, WMDcfPWV 1.04, 95% CI 0.34-1.74; WMDAIx 15.10, 95% CI 5.08-25.11), whereas carotid-radial PWV (crPWV) increase did not reach significance (WMDcrPWV 0.99, 95% CI -0.07 to 2.05). Significant increases in arterial stiffness measurements were noted in women with preeclampsia compared with those with gestational hypertension. Arterial stiffness measurements may also be useful in predicting preeclampsia and may play a role in the increased risk of future cardiovascular complications seen in women with a history of preeclampsia.

Prevention of vascular dysfunction after preeclampsia: a potential long-term outcome measure and an emerging goal for treatment

Preeclampsia is increasingly being recognised as more than an isolated disease of pregnancy. In particular, preeclampsia has emerged as an independent risk factor for maternal cardiovascular disease and has recently been recognised as a risk factor for cardiovascular disease in children exposed in utero. Preeclampsia and cardiovascular disease may share important pathophysiological and molecular mechanisms and further investigation into these is likely to offer insight into the origins of both conditions. This paper considers the links between cardiovascular disease and preeclampsia and the implication of these findings for refinement of the management of patients whose care is complicated by preeclampsia.

The relationship between brachial artery flow-mediated dilatation, high sensitivity C-reactive protein, and uterine artery doppler velocimetry in women with pre-eclampsia

PURPOSE

To investigate serum high sensitivity C-reactive protein (hs-CRP) levels and endothelial function in pregnancies complicated by pre-eclampsia and to clarify their relationship with uterine artery Doppler velocimetry.

METHODS

A cross-sectional study was carried out in 70 pregnant women (35 patients with pre-eclampsia and 35 age-matched normotensive healthy pregnant women) during the third trimester of pregnancy. The maternal levels of serum hs-CRP were determined in all cases by immunonephelometry. Uterine artery Doppler velocimetry was performed. Flow-mediated dilatation was measured by sonography of the brachial artery for the assessment of endothelial function.

RESULTS

Serum hs-CRP levels were higher in the pre-eclamptic group than in the normotensive group. hs-CRP levels were positively correlated with mean arterial pressure. Eleven patients with pre-eclampsia had abnormal uterine artery Doppler velocimetry. hs-CRP levels were significantly higher in pre-eclamptic patients with than without abnormal uterine artery Doppler velocimetry. Endothelial function was inversely correlated with hs-CRP levels and mean arterial pressure.

CONCLUSIONS

These findings suggest that maternal serum hs-CRP levels increase with the severity of pre-eclampsia, reflecting endothelial dysfunction and constituting a potential marker of pathological utero-placental perfusion, with a high risk for fetal growth restriction.

The biological investigation of prostacyclin in preeclamptic women seen reduced endothelial function

OBJECTIVE

Our aim was to determine the biological investigation of prostacyclin in preeclamptic women seen reduced endothelial vasodilatation by non-invasive technique in vivo.

METHODS

Using a high resolution ultrasound transducer, diameters of brachial arteries were determined after reactive hyperemia in 15 non-pregnant, 20 normotensive pregnant and 20 preeclamptic women. The concentrations of 6-keto-prostaglandin F 1alpha (6keto-PGF 1alpha) in plasma and the concentrations of adenosine-3', 5'-cyclic monophosphate (cyclic AMP) in platelets and serum were measured among the groups.

RESULTS

Flow-mediated vasodilatation at 1 min after reactive hyperemia was higher in normotensive pregnant than in the non-pregnant or preeclamptic women. The plasma concentration of 6 keto-PGF 1alpha as well as the serum concentration of cyclic AMP were lower in preeclamptic than those in normotensive pregnant women. The increase in cyclic AMP in the presence of a prostacyclin analogue in platelets was seen at similar levels in all three groups.

CONCLUSION

From these results, the concentrations of prostacyclin in plasma and cyclic AMP in serum might be low possibly due to reduced production of prostacyclin in preeclamptic women seen reduced endothelial function.

The role of the L-arginine-nitric oxide pathway in preeclampsia

Preeclampsia (PE) is a major cause of maternal and perinatal mortality, especially in developing countries. Its etiology involves multiple factors, but no specific cause has been identified. Evidence suggests that clinical manifestations are caused by endothelial dysfunction. Nitric oxide (NO), which is synthesized from L-arginine in endothelial cells by the endothelial nitric oxide synthase (eNOS), provides a tonic dilator tone and regulates the adhesion of white blood cells and platelet aggregation. Alterations in the L-arginine-NO pathway have been associated with the development of PE. Various studies, reporting decreased, elevated or unchanged levels of nitrite (NO(2)) and nitrate (NO(3)), two end products of NO metabolism, have been published. Our group contributed to those contradictory reports describing cases of PE with both elevated and decreased levels of NO(2) and NO(3). Apparently, diminished levels of NO could be related to deficiencies in the ingestion of dietary calcium associated to low levels of plasma ionic calcium, which is crucial to the eNOS' activity. Also, low levels of NO could be associated with the presence of eNOS polymorphisms or the presence of increased levels of ADMA, the endogenous inhibitor of NO. High levels of NO associated to low levels of cGMP suggest a decreased bioactivity of NO, which is probably related to an increased degradation of NO caused by a high production of superoxide in states of infection and inflammation. The present article analyses and reviews the reported paradoxical roles of the L-arginine-NO pathway in PE and gives a possible explanation for these results.

Aspects of nitric oxide in health and disease: a focus on hypertension and cardiovascular disease

Nitric oxide (nitrogen monoxide) (NO) plays an important role in a wide range of physiologic processes. A major mediator of endothelial function, NO regulates vasodilatory and antithrombotic actions in the vasculature and plays a role in reproductive functions, bronchodilation, bone formation, memory, insulin sensitivity, and gastrointestinal relaxation. NO is formed from NO synthase. Impaired NO bioactivity is strongly associated with endothelial dysfunction and cardiovascular disease, but is also implicated in a broad range of other disorders, including pulmonary hypertension, insulin resistance, erectile dysfunction, and preeclampsia. Numerous therapies designed to target NO are being investigated and developed, including NO donors and stimulants. The recent African-American Heart Failure Trial (A-HeFT) showed that the NO donor isosorbide dinitrate, combined with the vasodilator hydralazine, significantly reduced morbidity and mortality in black patients with moderate-to-severe heart failure. Antihypertensive drugs, including angiotensin-converting enzyme inhibitors, calcium channel blockers, and third-generation beta-blockers, are NO stimulants that have demonstrated significant improvement of endothelial function and NO bioactivity. Other cardiovascular therapies that may improve NO bioactivity include statins, l-arginine, and nonpharmacologic approaches such as exercise and dietary changes.

Organ systems dependent on nitric oxide and the potential for nitric oxide-targeted therapies in related diseases

Nitric oxide (NO) is a universal messenger molecule that plays diverse and essential physiologic roles in multiple organ systems, including the vasculature, bone, muscle, heart, kidney, liver, and central nervous system. NO is produced by 3 known isoforms-endothelial, neuronal, and inducible NO synthase-each of which perform distinct functions. Impairment of NO bioactivity may be an important factor in the pathogenesis of a wide range of conditions, including preeclampsia, osteoporosis, nephropathy, liver disease, and neurodegenerative diseases. Although increased levels of NO synthase or NO bioactivity have been associated with some of these disease states, research increasingly suggests that preservation or promotion of normal NO bioactivity may be beneficial in reducing the risks and perhaps reversing the underlying pathophysiology. Based on this rationale, studies investigating the use of NO-donating or NO-promoting agents in some of these diseases have produced positive results, at least to some degree, in either animal or human studies. Further investigation of NO-targeted therapies in these diverse diseases is clearly mandated.

Pregnancy as the prodrome to vascular dysfunction and cardiovascular risk

In previously apparently healthy women, glucose intolerance and high blood pressure during pregnancy are common and frequently occur together. This article reviews the role of these gestational disorders as markers of vascular dysfunction and its pathophysiology. Mechanisms include alterations to function of large arteries and resistance vessels and to capillary blood flow. Much of the vessel pathology is seen in both gestational diabetes and hypertension. In women who have had transient diabetes during pregnancy and later redeveloped overt diabetes, cardiovascular risk is already elevated nearly fourfold before diagnosis, which is almost as high as the average risk after a clinical diagnosis of diabetes is made. This key finding suggests that vascular risk in such women is at least partly independent of overt hyperglycemia.

Maternal medicine: Increased serum phosphodiesterase activity in women with pre-eclampsia

OBJECTIVE

To measure the activity of serum phosphodiesterase (PDE) in pre-eclampsia.

DESIGN

Case-control study.

SETTING

Nephrology Laboratory and Obstetrics Unit at São Lucas Hospital from Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre, Brazil.

SAMPLE

Twenty-nine normal and 28 pregnant women with pre-eclampsia.

METHODS

Serum was collected from women with pre-eclampsia, at the time of diagnosis, and from gestation-matched controls. Circulating PDE activity was assessed by measuring consumption of the substrate thymidine 5'-monophosphate p-nitrophenyl ester and expressed as PDE units/l.

MAIN OUTCOME MEASURES

Serum PDE Activity.

RESULTS

Mean substrate consumption was higher in pre-eclamptic condition (V(max)= 15.8 +/- 1.4 versus 12.7 +/- 0.9 U/L, P= 3.7 x 10(-14)).

CONCLUSION

These data suggest that altered PDE activity may play a role in pre-eclampsia endothelial dysfunction.

Increase in serum concentrations of inhibin in early onset pre-eclampsia with intrauterine growth restriction

AIM

Recently, it has been hypothesized that reduced placental blood flow in early pregnancy causes changes in endothelial function, leading to pre-eclampsia. To clarify this clinically, we assessed serum concentrations of inhibin and uric acid in pre-eclamptic women compared with those of normotensive pregnant women.

METHODS

One hundred and forty normotensive pregnant women (at 20-41 weeks' gestation) and 50 women with pre-eclampsia (at 24-41 weeks' gestation) were the study subjects. Pre-eclamptic women were classified according to the new criteria for pregnancy-induced hypertension produced by the Japanese Society of Obstetrics and Gynecology (JSOG). Serum concentrations of uric acid and inhibin were measured enzymatically and by radioimmunoassay, respectively.

RESULTS

Serum concentrations of inhibin and uric acid in the pre-eclamptic women were significantly higher than in gestational age-matched normotensive pregnant women. There were significant correlations among inhibin and uric acid, blood pressure and birth weight. According to JSOG criteria, of the 50 pre-eclamptic women, 18 were early onset (EO), including 16 cases complicated by intrauterine growth restriction (IUGR), and 32 cases were late onset, including 12 cases complicated by IUGR. In the patients with EO and IUGR, serum concentrations of inhibin, but not uric acid, were significantly elevated as compared with those of the other pre-eclamptic women.

CONCLUSION

The results suggest that an increase in the serum concentration of inhibin seen in EO pre-eclampsia, together with IUGR, might be a cause of reduced placental blood flow.

Reduced Nitric Oxide in Amniotic Fluid of Patients with Chorioamnionitis

OBJECTIVE

Levels of nitric oxide (NO) and cytokines were assessed in amniotic fluid obtained from patients with severe chorioamnionitis (CAM) and appropriate controls.

METHODS

Amniotic fluid was obtained from 12 patients with CAM (17-24 weeks of gestation) and 89 patients undergoing diagnostic amniocentesis (16-18 weeks of gestation). The concentrations of NO, interleukin-6 (IL-6), and leukocyte elastase (LE) in amniotic fluid were then measured and compared.

RESULTS

The concentrations of NO, IL-6, and LE were all higher in CAM cases than in normal pregnant women. Furthermore, an inverse correlation between NO and LE was suggested in the CAM group.

CONCLUSIONS

These results indicate that in severe CAM, the action of NO might be reduced, not only due to blockage of action but also by degradation, despite increased production.