Autoantibody against AT1 receptor from preeclamptic patients induces vasoconstriction through angiotensin receptor activation

Association of Perinatal Cardiovascular Features with Angiotensin System Expressions in Maternal Preeclampsia

We hypothesized and investigated whether prenatal exposure to preeclampsia (PE) would simultaneously affect perinatal cardiovascular features and angiotensin system expressions. This prospective study was composed of mother-neonate dyads with (n = 49) and without maternal preeclampsia (n = 48) in a single tertiary medical center. The neonates exposed to PE had significantly larger relative sizes for the left and right coronary arteries and a higher cord plasma level of aminopeptidase-N, which positively correlated with the maternal diastolic blood pressures and determined the relative sizes of the left and right coronary arteries, whereas the encoding aminopeptidase-N (ANPEP) mRNA level in the PE cord blood leukocytes was significantly decreased, positively correlated with the neonatal systolic blood pressures (SBPs), and negatively correlated with the cord plasma-induced endothelial vascular cell adhesion molecule-1 mRNA levels. The PE cord plasma significantly induced higher endothelial mRNA levels of angiotensin II type 1 receptor (AT1R) and AT4R, whereas in the umbilical arteries, the protein expressions of AT2R and AT4R were significantly decreased in the PE group. The endothelial AT1R mRNA level positively determined the maternal SBPs, and the AT4R mRNA level positively determined the neonatal chamber size and cardiac output. In conclusion, PE may influence perinatal angiotensin system and cardiovascular manifestations of neonates across placentae. Intriguing correlations between these two warrant further mechanistic investigation.

Pre-Eclampsia: From Etiology and Molecular Mechanisms to Clinical Tools-A Review of the Literature

Pre-eclampsia is a severe pregnancy-related complication that manifests as a syndrome with multisystem involvement and damage. It has significantly grown in frequency during the past 30 years and could be considered as one of the major causes of maternal and fetal morbidity and mortality. However, the specific etiology and molecular mechanisms of pre-eclampsia are still poorly known and could have a variety of causes, such as altered angiogenesis, inflammations, maternal infections, obesity, metabolic disorders, gestational diabetes, and autoimmune diseases. Perhaps the most promising area under investigation is the imbalance of maternal angiogenic factors and its effects on vascular function, though studies in placental oxidative stress and maternal immune response have demonstrated intriguing findings. However, to determine the relative importance of each cause and the impact of actions aiming to significantly reduce the incidence of this illness, more research is needed. Moreover, it is necessary to better understand the etiologies of each subtype of pre-eclampsia as well as the pathophysiology of other major obstetrical syndromes to identify a clinical tool able to recognize patients at risk of pre-eclampsia early.

Primary aldosteronism in pregnancy

Primary aldosteronism (PA) is the most common form of secondary hypertension. Although hypertensive disorders seem to affect around 5-10% of pregnancies worldwide, literature counts less than 80 cases of PA diagnosed during the peri-partum period. In this review we discuss about current knowledge on pathophysiology, natural history, diagnosis and treatment of PA in pregnancy. Because of the physiologic changes in the renin-angiotensin-aldosterone system (RAAS) and the contraindication to both confirmatory test and subtype differentiation, diagnosis of PA during pregnancy is challenging and relies mostly on detection of low/suppressed renin and high aldosterone levels. The course of pregnancy in patients with PA is highly variable, ranging from progesterone-induced amelioration of blood pressure (BP) control to severe and resistant hypertension with potential maternal and fetal complications. Mineralcorticoid receptor antagonists (MRA) are the recommended and most effective drugs for treatment of PA. As the anti-androgenic effect of spironolactone can potentially interfere with sexual development, their prescription is not recommended during pregnancy. On the other side, eplerenone, has proven to be safe and effective in 6 pregnant women and may be added to conventional first line drug regimen in presence of resistant hypertension or persistent hypokalemia. Ideally, patients with unilateral forms of PA should undergo adrenalectomy prior to conception, however, when PA is diagnosed during pregnancy and medical therapy fails to adequately control hypertension or its complications, adrenalectomy can be considered during the second trimester in case of unilateral adrenal mass at MRI-scan.

Preeclampsia and the Kidney: Pathophysiology and Clinical Implications

Preeclampsia and other hypertensive disorders of pregnancy are major contributors to maternal morbidity and mortality worldwide. This group of disorders includes chronic hypertension, gestational hypertension, preeclampsia, preeclampsia superimposed on chronic hypertension, and eclampsia. The body undergoes important physiological changes during pregnancy to allow for normal placental and fetal development. Several mechanisms have been proposed that may lead to preeclampsia, including abnormal placentation and placental hypoxia, impaired angiogenesis, excessive pro-inflammatory response, immune system imbalance, abnormalities of cellular senescence, alterations in regulation and activity of angiotensin II, and oxidative stress, ultimately resulting in upregulation of multiple mediators of endothelial cell dysfunction leading to maternal disease. The clinical implications of preeclampsia are significant as there are important short-term and long-term health consequences for those affected. Preeclampsia leads to increased risk of preterm delivery and increased morbidity and mortality of both the developing fetus and mother. Preeclampsia also commonly leads to acute kidney injury, and women who experience preeclampsia or another hypertensive disorder of pregnancy are at increased lifetime risk of chronic kidney disease and cardiovascular disease. An understanding of normal pregnancy physiology and the pathophysiology of preeclampsia is essential to develop novel treatment approaches and manage patients with preeclampsia and hypertensive disorders of pregnancy. © 2023 American Physiological Society. Compr Physiol 13:4231-4267, 2023.

[Immunogenetics of primary hyperaldosteronism: fundamental studies and their clinical prospects]

Primary hyperaldosteronism (PHA) is the most common form of endocrine hypertension. Until recently, the reason for the development of this condition was believed to be the presence of genetic mutations, however, many studies declare that the disease can be polyetiologic, be the result of genetic mutations and autoimmune triggers or cell clusters of aldosterone-producing cells diffusely located in the adrenal gland at the zona glonerulosa, zona fasculata, zona reticularis, as well as directly under the adrenal capsule. Recently, the actions of autoantibodies to type 1 angiotensin II receptors have been described in patients with renal transplant rejection, with preeclampsia, and with primary hyperaldosteronism. The diagnostic role of antibodies in both forms of PHA (aldosterone-producing adenoma and bilateral hyperaldosteronism) requires clarification. Diagnosis and confirmation of the focus of aldosterone hypersecretion is a multi-stage procedure that requires a long time and economic costs. The relevance of timely diagnosis of primary hyperaldosteronism is to reduce medical and social losses. This work summarizes the knowledge about genetic mutations and presents all the original studies devoted to autoantibodies in PHA, as well as discusses the diagnostic capabilities and limitations of the available methods of primary and differential diagnosis of the disease and the prospects for therapy.

Large‐Conductance Calcium‐Activated Potassium Channel Opener, NS1619, Protects Against Mesenteric Artery Remodeling Induced by Agonistic Autoantibodies Against the Angiotensin II Type 1 Receptor

Background

Agonistic autoantibodies against the angiotensin II type 1 receptor (AT1‐AAs) extensively exist in patients with hypertensive diseases and have been demonstrated to play crucial roles in the pathophysiological process of vascular remodeling. However, the treatment options are limited. The large‐conductance calcium‐activated potassium (BK) channel is a critical regulator and potential therapeutic target of vascular tone and architecture. We have previously observed that AT1‐AAs have an inhibitory effect on BK channels. However, whether BK channel dysfunction is involved in AT1‐AAs‐induced vascular remodeling and the therapeutic effect of BK channel opener is unclear.

Methods and Results

In our study, mesenteric arteries from AT1‐AAs‐positive rats exhibited increased wall thickness, narrowing of the arteriolar lumen, and increased collagen accumulation. Patch clamp test results showed that the voltage sensitivity of BK channel declined in mesenteric arteriolar smooth muscle cells from AT1‐AAs‐positive rats. Experiments with freshly isolated mesenteric arteriolar smooth muscle cells showed that AT1‐AAs reduced the opening probability, open levels, open dwell time, and calcium sensitivity of BK channel. Experiments with HEK293T cells transfected with GFP‐ZERO‐BK α‐subunit plasmids suggested a BK channel α‐subunit‐dependent mechanism. BK channel α‐subunit deficient, namely KCNMA1^−/− rats showed a phenotype of mesenteric artery remodeling. The administration of NS1619, a specific BK channel opener targeting the α‐subunit, reversed the phenotypic transition and migration induced by AT1‐AAs in cultured mesenteric arteriolar smooth muscle cells. Finally, perfusion of NS1619 significantly relieved the pathological effects induced by AT1‐AAs in vivo.

Conclusions

In summary, we provide compelling evidence that BK channel α‐subunit dysfunction mediates AT1‐AAs‐induced mesenteric artery remodeling. Preservation of BK channel activity may serve as a potential strategy for the treatment of AT1‐AAs‐induced maladaptive resistance artery remodeling.

The etiology of preeclampsia

Preeclampsia is one of the "great obstetrical syndromes" in which multiple and sometimes overlapping pathologic processes activate a common pathway consisting of endothelial cell activation, intravascular inflammation, and syncytiotrophoblast stress. This article reviews the potential etiologies of preeclampsia. The role of uteroplacental ischemia is well-established on the basis of a solid body of clinical and experimental evidence. A causal role for microorganisms has gained recognition through the realization that periodontal disease and maternal gut dysbiosis are linked to atherosclerosis, thus possibly to a subset of patients with preeclampsia. The recent reports indicating that SARS-CoV-2 infection might be causally linked to preeclampsia are reviewed along with the potential mechanisms involved. Particular etiologic factors, such as the breakdown of maternal-fetal immune tolerance (thought to account for the excess of preeclampsia in primipaternity and egg donation), may operate, in part, through uteroplacental ischemia, whereas other factors such as placental aging may operate largely through syncytiotrophoblast stress. This article also examines the association between gestational diabetes mellitus and maternal obesity with preeclampsia. The role of autoimmunity, fetal diseases, and endocrine disorders is discussed. A greater understanding of the etiologic factors of preeclampsia is essential to improve treatment and prevention.

Recent Advances in the Endogenous Brain Renin-Angiotensin System and Drugs Acting on It

The RAS (renin-angiotensin system) is the part of the endocrine system that plays a prime role in the control of essential hypertension. Since the discovery of brain RAS in the seventies, continuous efforts have been put by the scientific committee to explore it more. The brain has shown the presence of various components of brain RAS such as angiotensinogen (AGT), converting enzymes, angiotensin (Ang), and specific receptors (ATR). AGT acts as the precursor molecule for Ang peptides—I, II, III, and IV—while the enzymes such as prorenin, ACE, and aminopeptidases A and N synthesize it. AT1, AT2, AT4, and mitochondrial assembly receptor (MasR) are found to be plentiful in the brain. The brain RAS system exhibits pleiotropic properties such as neuroprotection and cognition along with regulation of blood pressure, CVS homeostasis, thirst and salt appetite, stress, depression, alcohol addiction, and pain modulation. The molecules acting through RAS predominantly ARBs and ACEI are found to be effective in various ongoing and completed clinical trials related to cognition, memory, Alzheimer's disease (AD), and pain. The review summarizes the recent advances in the brain RAS system highlighting its significance in pathophysiology and treatment of the central nervous system-related disorders.

Uteroplacental Circulation in Normal Pregnancy and Preeclampsia: Functional Adaptation and Maladaptation

Uteroplacental blood flow increases as pregnancy advances. Adequate supply of nutrients and oxygen carried by uteroplacental blood flow is essential for the well-being of the mother and growth/development of the fetus. The uteroplacental hemodynamic change is accomplished primarily through uterine vascular adaptation, involving hormonal regulation of myogenic tone, vasoreactivity, release of vasoactive factors and others, in addition to the remodeling of spiral arteries. In preeclampsia, hormonal and angiogenic imbalance, proinflammatory cytokines and autoantibodies cause dysfunction of both endothelium and vascular smooth muscle cells of the uteroplacental vasculature. Consequently, the vascular dysfunction leads to increased vascular resistance and reduced blood flow in the uteroplacental circulation. In this article, the (mal)adaptation of uteroplacental vascular function in normal pregnancy and preeclampsia and underlying mechanisms are reviewed.

Deletion of BK channels decreased skeletal and cardiac muscle function but increased smooth muscle contraction in rats

Large conductance calcium-activated potassium channel (BK channel) is widely expressed in skeletal muscle, myocardium, smooth muscle and other muscle tissues. Mutation, abnormal expression and altered activity of BK channel are linked to muscle-related diseases such as dyskinesia, epilepsy and erectile dysfunction. In order to compare the effects of BK channel on different muscle tissues, we constructed BK channel gene knockout rats‌‌‌‌‍‍‍ (BK^-/- rats). HE staining, open field and grip strength tests, ultrasound, blood pressure measurement and vascular tension test were utilized to explore the effects of BK channel deletion on the structure and function changes in skeletal muscle, myocardium, and vascular smooth muscle (VSM). It was found that compared with wild-type rats, the BK^-/- rats showed decreased skeletal muscle fiber area, grip, movement distance and speed at 2 and 12 months of ages. At heart, the muscle fiber area, cardiac systolic/diastolic function and heart rate decreased in BK^-/- rats. The wall of the left ventricle became thin. However, the vascular wall of BK^-/- rats thickened, the pulse wave velocity was increased, and the VSM contraction was enhanced. Unexpectedly, both systolic and diastolic blood pressure were reduced in BK^-/- rats, while pulse pressure difference was increased. These results suggest that BK channel may have different effects on different types of muscle tissue, and it should be noted that different parts of muscle tissue may have different effects when BK channel-related drugs are used.

A Narrative Review of the Renin-Angiotensin-Aldosterone System in the Placenta and Placental Bed of HIV Infected Women of African Ancestry with Preeclampsia

PURPOSE OF REVIEW

Both HIV infection and preeclampsia (PE), a pregnancy-specific disorder of hypertension and multi-system organ involvement, have high prevalence rates especially in low-to-middle-income countries. The immunoexpression of specific renin-angiotensin-aldosterone system (RAAS) receptors in the placenta and placental bed interface may forecast the risk of PE.

RECENT FINDINGS

Preeclampsia is a leading risk factor for mortality worldwide and remains a challenge in HIV-infected individuals especially those on antiretroviral therapy (ART). Irregular RAAS stimulation may be linked to the pathophysiology of hypertension in HIV infection and in PE. The AT1 receptor is expressed across all trimesters of pregnancy, within placental tissue, eliciting vasoconstriction. This increased expression is associated with the severity of PE, implying that the increased expression may be involved in the pathogenesis of this pregnancy disorder. The AT2 receptor expression in normotensive pregnancies was shown to be lower as compared to non-pregnant individuals. Furthermore, in the PE placental bed, the AT2 receptor is the predominant receptor subtype and is found in extravillous trophoblast cells where they facilitate vasodilation. However, AT4R in placentae of PE pregnancies are found to be significantly reduced compared to normotensives pregnancies. The data on the role played by the RAAS pathway in pregnancy is conflicting. Investigation into a tissue-based RAAS with emphasis on immune-expression within the placenta and placental bed may help resolve this conundrum.

AT1-receptor autoantibody exposure in utero contributes to cardiac dysfunction and increased glycolysis in fetal mice

Exposure to adverse factors in utero may lead to adaptive changes in cardiac structure and metabolism, which increases the risk of chronic cardiovascular disease later in life. Studies showed that the angiotensin II type 1 receptor autoantibodies (AT1-AAs) are able to cross the placenta into the circulation of pregnant rodents' embryo, which adversely affects embryogenesis. However, the effects of AT1-AA exposure on the fetal heart in utero are still unknown. In this study, we investigated whether intrauterine AT1-AA exposure has adverse effects on fetal heart structure, function and metabolism. AT1-AA-positive pregnant mouse models were successfully established by passive immunity, evidenced by increased AT1-AA content. Morphological and ultrasonic results showed that the fetal mice on embryonic day 18 (E18) of AT1-AA group have loose and disordered myocardial structure, and decreased left ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS), compared with control groups. The myocardium of AT1-AA group fetal mice on E18 exhibited increased expression of the key molecules in the glycolytic pathway, pyruvate and lactic acid content and ATP production, suggesting that the glycolysis rate was enhanced. Furthermore, the enhanced effect of glycolysis caused by AT1-AA is mainly through the PPARβ/δ pathway. These data confirmed that fetus exposure to AT1-AA in utero developed left ventricular dysfunction, myocardial structural arrangement disorders, and enhanced glycolysis on E18. Our results support AT1-AA being a potentially harmful factor for cardiovascular disease in fetal mice.

Current understanding of autoantibody against angiotensin II type 1 receptor in preeclampsia

Preeclampsia (PE) remains a leading cause of fetal and maternal mortality. Angiotensin II type 1 receptor autoantibody (AT1-AA) is implicated in the dysregulation of the renin-angiotensin-aldosterone system. A strong relationship between AT1-AA and the occurrence and severity of PE has been confirmed in previous literature. Recent evidences suggested that AT1-AA was responsible for blood pressure elevation, reactive oxygen species synthesis, and inflammatory factors release and engaged in multiple signaling cascades. The inhibition of AT1-AA might be a potential therapeutic target in future days. Here we reviewed the current understanding of AT1-AA, aiming to provide clarity surrounding the role of AT1-AA in PE.

The Role of the Renin-Angiotensin-Aldosterone System in Preeclampsia: a Review

PURPOSE OF REVIEW

Preeclampsia (PE) is a complex human pregnancy-specific condition and is clinically characterized by new onset hypertension and proteinuria in the second half of pregnancy. The precise etiology of PE is unknown, but much of the pathophysiology has been elucidated, and it is accepted that the disorder is multifactorial in nature. Historically, because of the presence of proteinuria, the role of the renin-angiotensin-aldosterone system (RAAS) has been considered in the etiology of PE. However, the results of studies (including maternal circulatory angiotensin II, urinary angiotensinogen, plasma renin and prorenin, AT1 receptor antibodies, and gene polymorphisms) on the role of the RAAS in the etiology of PE have proved controversial. The purpose of this narrative review was to evaluate the contemporary literature on the RAAS and its role in the pathophysiology of pregnancy.

RECENT FINDINGS

The current review shows that although the RAAS has a role in the development of normal pregnancy, it does not have a significant role in the pathophysiology of PE except for the AT1-AA components. Despite many researchers having measured increases in s[P}RR and [P]RR, this may be independent of the RAAS. Our view is in keeping with contemporary thinking that the placenta rather than the RAAS plays a central role in elaborating pro-inflammatory factors (antiangiogenic and angiogenic) into the maternal circulation resulting in widespread endothelial dysfunction in all organ systems including the renal system.

Limited AT1 Receptor Internalization Is a Novel Mechanism Underlying Sustained Vasoconstriction Induced by AT1 Receptor Autoantibody From Preeclampsia

Background

Angiotensin II type 1 receptor (AT₁R) autoantibody (AT1‐AA) was first identified as a causative factor in preeclampsia. Unlike physiological ligand angiotensin II (Ang II), AT1‐AA can induce vasoconstriction in a sustained manner, causing a series of adverse effects, such as vascular injury and poor placental perfusion. However, its underlying mechanisms remain unclear. Here, from the perspective of AT₁R internalization, the present study investigated the molecular mechanism of sustained vasoconstriction induced by AT₁R autoantibody.

Methods and Results

In the current study, we used the vascular‐ring technique to determine that AT1‐AA‐positive IgG, which was obtained from the sera of preeclamptic patients, induced long‐term vasoconstriction in endothelium‐intact or endothelium‐denuded rat thoracic arteries. The effect was caused by prolonged activation of AT₁R downstream signals in vascular smooth muscle cells, including Ca²⁺, protein kinase C, and extracellular signal‐regulated kinase 1 and 2. Then, using subcellular protein fractionation, cell surface protein biotinylation, and total internal reflection fluorescence, we found that AT1‐AA‐positive IgG resulted in significantly less AT₁R internalization than in the Ang II treatment group. Moreover, through use of fluorescent tracing and bioluminescence resonance energy transfer, we found that AT1‐AA‐positive IgG cannot induce the recruitment of β‐arrestin1/2, which mediated receptor internalization. Then, the effect of sustained AT₁R activation induced by AT1‐AA‐positive IgG was rescued by overexpression of β‐arrestin2.

Conclusions

These data suggested that limited AT₁R internalization resulting from the inhibition of β‐arrestin1/2 recruitment played an important role in sustained vasoconstriction induced by AT1‐AA‐positive IgG, which may set the stage for avoiding AT₁R overactivation in the management of preeclampsia.

Angiotensin II Type 1 Receptor Autoantibodies in Primary Aldosteronism

Primary aldosteronism (PA) is the most common form of endocrine hypertension. Agonistic autoantibodies against the angiotensin II type 1 receptor (AT₁R-Abs) have been described in transplantation medicine and women with pre-eclampsia and more recently in patients with PA. Any functional role of AT₁R-Abs in either of the two main subtypes of PA (aldosterone-producing adenoma or bilateral adrenal hyperplasia) requires clarification. In this review, we discuss the studies performed to date on AT₁R-Abs in PA.

Angiotensin II receptor agonist antibodies are associated with microvascular damage in lupus nephritis

Angiotensin II type 1 receptor agonist antibodies (AT1R-AAs) have been associated with hypertension, atherosclerosis and vascular inflammation in human diseases. The aim of the study was to evaluate the prevalence of AT1R-AAs in active lupus nephritis (LN) patients and their association with vascular damage. One hundred and seven active LN patients underwent a complete clinical examination, measurement of AT1R-AAs, ambulatory blood pressure monitoring, carotid intima-media thickness measurement and morphometric analysis of subintimal fibrosis and medial hyperplasia of the vessels in the kidney tissue. Plasma AT1R-AAs were positive in 58 (54.2%) patients. The Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) score, complement C3 and C4 levels and titers of anti-dsDNA antibodies were higher in the group with positive AT1R-AAs compared with those with negative AT1R-AAs. The AT1R-AA titers correlated with anti-dsDNA antibody titers and with complement C3 and C4 serum levels. In the kidney biopsy, the percentage of subintimal fibrosis and the area of medial hyperplasia were greater in the AT1R-AA-positive patients. No differences in arterial pressure, carotid intima-media thickness and response to therapy were detected. In conclusion, AT1R-AAs are prevalent in active LN patients and are associated with histologic features of microvascular damage.

Evaluation of maternal renal cortical elasticity in pregnancies with early- and late-onset preeclampsia

Objective: The current study aimed to investigate renal cortical elasticity (RCE) in early- and late-onset preeclampsia patients and compare the results with healthy controls.Materials and methods: The study consisted of 136 pregnant women. Three groups were identified as; the late-onset preeclampsia (LOP) group (n = 40), the early-onset preeclampsia (EOP) group (n = 32) and the control group (n = 64). RCE values were measured by point shear wave elastography (pSWE). Nine measurements were taken for each kidney and the mean of nine measurements was accepted as the mean RCE value for each kidney. The arithmetic mean of left and right RCE values was accepted as the overall RCE value of a subject. Groups were compared in terms of clinical and biochemical parameters, ultrasonography findings and pSWE values.Results: There was a statistically significant difference between groups in terms of overall RCE values (F[2,133] = 17.96, p < .001). Post hoc comparisons indicated that both preeclampsia groups exhibited significantly higher RCE values than the control group. However, overall RCE values were not significantly different between the EOP and LOP groups. Overall RCE values were significantly and positively correlated with systolic blood pressure (r = 0.363, p < .001), diastolic blood pressure (r = 0.347, p < .001), proteinuria (r = 0.343, p < .001), serum creatinine level (r = 0.181, p = .035), serum uric acid level (r = 0.243, p = .004) and blood urea nitrogen (r = 0.27, p = .001).Conclusion: Our study demonstrated that maternal renal cortical stiffness increased in women with preeclampsia. The increased RCE values may be indicative for the severity of preeclampsia due to positive correlations between renal cortical stiffness and systolic - diastolic blood pressure and serum creatinine level.

Targeting the vascular dysfunction: Potential treatments for preeclampsia

Preeclampsia is a pregnancy-specific disorder, primarily characterized by new-onset hypertension in combination with a variety of other maternal or fetal signs. The pathophysiological mechanisms underlying the disease are still not entirely clear. Systemic maternal vascular dysfunction underlies the clinical features of preeclampsia. It is a result of oxidative stress and the actions of excessive anti-angiogenic factors, such as soluble fms-like tyrosine kinase, soluble endoglin, and activin A, released by a dysfunctional placenta. The vascular dysfunction then leads to impaired regulation and secretion of relaxation factors and an increase in sensitivity/production of constrictors. This results in a more constricted vasculature rather than the relaxed vasodilated state associated with normal pregnancy. Currently, the only effective "treatment" for preeclampsia is delivery of the placenta and therefore the baby. Often, this means a preterm delivery to save the life of the mother, with all the attendant risks and burdens associated with fetal prematurity. To lessen this burden, there is a pressing need for more effective treatments that target the maternal vascular dysfunction that underlies the hypertension. This review details the vascular effects of key drugs undergoing clinical assessment as potential treatments for women with preeclampsia.

The inhibitory effect of BKCa channels induced by autoantibodies against angiotensin II type 1 receptor is independent of AT1R

Autoantibodies against angiotensin II Type 1 receptor (AT1-AA) are routinely detected in the serum of preeclampsia patients, which results in an increase in vascular tone and an elevation in intracellular calcium concentration of rat vascular smooth muscle (VSM). The big conductance calcium-activated potassium channels (BKCa channels) account for the dominant outward currents in VSMCs, contributing to membrane hyperpolarization and vasodilation. In the present study, we investigated the effect of AT1-AA on BKCa channels. A preeclampsia model was established by passively immunizing healthy pregnant BALB/c mice with AT1-AA extracted from hybridoma culture supernatant. Blood pressure, serum AT1-AA levels, and urinary protein were measured in the immunized mice. BKCa channel expression was detected using qRT-PCR and immunohistochemical technique. The patch-clamp technique was used to record the single currents of BKCa channels in the HEK293T cells that had been transfected. AT1-AA immunized mice exhibited elevated AT1-AA and urinary protein levels compared with mice of the vehicle group. Systolic blood pressure was also increased in the immunized group. BKCa channel β1-subunit expression was reduced in the mesenteric arteries of immunized mice. AT1-AA could inhibit the BKCa currents and the inhibitory effects were not completely reversed following the application of valsartan, an inhibitor of AT1 receptor. In conclusion, AT1-AA could decrease BKCa expression and inhibit BKCa activity independent of AT1R. These inhibitory effects are likely to be contributory factors in the promotion of increased vascular tone caused by AT1-AA in preeclampsia.

Increased Angiotensin II Sensitivity Contributes to Microvascular Dysfunction in Women Who Have Had Preeclampsia

Women who have had preeclampsia have increased cardiovascular disease risk; however, the mechanism(s) responsible for this association remain unclear. Microvascular damage sustained during a preeclamptic pregnancy may persist postpartum. The putative mechanisms mediating this dysfunction include a reduction in NO-dependent dilation and an increased sensitivity to angiotensin II. In this study, we evaluated endothelium-dependent dilation, angiotensin II sensitivity, and the therapeutic effect of angiotensin II receptor blockade (losartan) on endothelium-dependent dilation in vivo in the microvasculature of women with a history of preeclampsia (n=12) and control women who had a healthy pregnancy (n=12). We hypothesized that preeclampsia would have (1) reduced endothelium-dependent dilation, (2) reduced NO-mediated dilation, and (3) increased sensitivity to angiotensin II. We further hypothesized that localized losartan would increase endothelium-dependent vasodilation in preeclampsia. We assessed microvascular endothelium-dependent vasodilator function by measurement of cutaneous vascular conductance responses to graded infusion of acetylcholine (acetylcholine; 10^-7-102 mmol/L) and a standardized local heating protocol in control sites and sites treated with 15 mmol/L L-NAME (N^G-nitro-l-arginine methyl ester; NO-synthase inhibitor) or 43 µmol/L losartan. Further, we assessed microvascular vasoconstrictor sensitivity to angiotensin II (10^-20-10^-4 mol/L). Preeclampsia had significantly reduced endothelium-dependent dilation (-0.3±0.5 versus -1.0±0.4 log_EC50; P<0.001) and NO-dependent dilation (16±3% versus 39±6%; P=0.006). Preeclampsia also had augmented vasoconstrictor sensitivity to angiotensin II (-10.2±1.3 versus -8.3±0.5; P=0.006). Angiotensin II type I receptor inhibition augmented endothelium-dependent vasodilation and NO-dependent dilation in preeclampsia but had no effect in healthy pregnancy. These data suggest that women who have had preeclampsia have persistent microvascular dysfunction postpartum, mediated, in part, by increased sensitivity to angiotensin II.

The Prognostic Role of Angiotensin II Type 1 Receptor Autoantibody in Non-Gravid Hypertension and Pre-eclampsia: A Meta-analysis and Our Studies

Angiotensin II type 1 receptor autoantibody (AT1-AA) is found in patients with non-gravid hypertension or pre-eclampsia, but the relationship is uncertain.The aim of the present study was to assess the association between AT1-AA and high blood pressure using meta-analysis, and to evaluate the prognosis value of AT1-AA for hypertensive diseases.Literature search from PubMed, Embase, and Cochrane databases were conducted using keywords "hypertension" or "pre-eclampsia," "angiotensin II receptor type 1 autoantibody," and its aliases from April 1999 to December 2015.Studies evaluating the association between AT1-AA and non-gravid hypertension or pre-eclampsia were included in this analysis. The quality of the eligible studies was assessed based on the Newcastle-Ottawa Scale with some modifications.Two researchers then independently reviewed all included studies and extracted all relevant data. Association between AT1-AA and hypertension was tested with pooled odds ratios (ORs) and 95% confidence intervals (CIs). Finally, we evaluated whether AT1-AA predicted the prognosis of hypertension by using a summary receiver-operating characteristic (ROC) curve and sensitivity analysis.Ten studies were finally included in this meta-analysis. AT1-AA showed more significant association with pre-eclampsia than that with non-gravid hypertension (pooled OR 32.84, 95% CI 17.19-62.74; and pooled OR 4.18, 95% CI 2.20-7.98, respectively). Heterogeneity among studies was also detected probably due to different hypertensive subtypes and AT1-AA measuring methods. Area under summary ROC curve (AUC) of pre-eclampsia was 0.92 (sensitivity 0.76; specificity 0.86). Area under the ROC curve of overall hypertensive diseases or non-gravid hypertension was lower than that of pre-eclampsia (0.86 and 0.72, respectively) with lower sensitivities (0.46 and 0.26, respectively).The major limitation of this analysis was the publication bias due to lack of unpublished data and the language limitation during literature search. Prospective study with large simple size and specific measuring data collection are needed to enhance our findings in the future.Our analysis confirms that elevated AT1-AA in serum is significantly associated with hypertensive disorder, especially pre-eclampsia. AT1-AA may be a valuable indicator for poorer prognosis of patients with pre-eclampsia, and could be used in patients with hypertensive disease for risk evaluation and making individual treatment decision.

Mechanism of agonistic angiotensin II type I receptor autoantibody-amplified contractile response to Ang II in the isolated rat thoracic aorta

Agonistic autoantibody to the angiotensin II type I receptor (AT1-AA) is highly associated with preeclampsia by increasing the sensitivity of Ang II during pregnancy in rats, thus leading to a preeclampsia-like syndrome. However, the mechanism underlying this phenomenon remains unclear. The purpose of this study was to observe AT1-AA amplification of Ang II-induced vasoconstriction in rat thoracic aortic rings. It was found that exposure to low concentrations of AT1-AA (0.4 nM) caused a contraction of <5% of the maximal response to 60 mM KCl. In addition, the Ang II-induced contractile response was amplified in the presence of a threshold contraction to AT1-AA, as manifested by a leftward shift of the midpoint of the concentration-response curve with no change in the maximal response. These results showed that preincubation with low AT1-AA could amplify the Ang II dose-response curve, and this amplification could be attenuated markedly by 0.1 µM heptapeptide AFHYESQ. In calcium-free Krebs solution, 10 µM of 2-aminoethoxydiphenyl borate (an IP3 receptor inhibitor) both blocked the AT1-AA base contraction and completely abolished the amplification. Both 5 µM of U-73122 (a phospholipase C inhibitor) and 10 µM of εV1-2 (an εPKC inhibitor) could partially inhibit the Ang II-induced contractile response. εV1-2, but not U-73122, could completely inhibit the amplification response of AT1-AA to Ang II. These results suggest that AT1-AA is able to cause amplification response to Ang II probably via the calcium-independent protein kinase C pathway, which may provide a new therapy strategy for preeclampsia.

Linking the old and new -- do angiotensin II type 1 receptor antibodies provide the missing link in the pathophysiology of preeclampsia?

Preeclampsia remains a leading cause of maternal and neonatal morbidity and mortality. The pathophysiology of preeclampsia remains poorly understood with various pathological mechanisms being implicated including the renin angiotensin system (RAAS), angiogenic pathways and various components of the immune system. Recently a pathogenic autoimmune factor has been identified in the form of auto-agonistic angiotensin II type 1 receptor antibodies (AT1-AA). AT1-AA have been studied in vitro and in vivo in various human and animal models and these data have provided compelling evidence for their role in preeclampsia. This review summarises the current literature surrounding the role of AT1-AA in preeclampsia and draws links between this relatively novel antibody to well-established pathological mechanisms including the immune system, the RAAS, angiogenic pathways and placental ischaemia.

Angiotensin II receptor type 1 autoantibodies promote endothelial microparticles formation through activating p38 MAPK pathway

BACKGROUND

Endothelial microparticles (EMPs) are small vesicular structures that serve as a marker of endothelial function. Angiotensin II receptor type 1 autoantibody (AT1-AA) can cause endothelial dysfunction. However, whether AT1-AA promotes EMPs formation and the mechanism remains obscure.

METHODS

The titres of sera AT1-AA of 126 hypertensive patients and 30 normotensive individuals were evaluated by ELISA. EMPs in the sera and the supernatants of human umbilical vein endothelial cells (HUVECs) were measured by flow cytometry. The phosphorylation levels of mitogen-activated protein kinase (MAPK) pathways in HUVECs treated by AT1-AA were assessed and their correlation with microparticle formation was also analysed. Furthermore, the production of intracellular reactive oxygen species (ROS) and nitric oxide in HUVECs was examined after incubation with 'injured' endothelial microparticle (iEMPs) (EMPs derived from AT1-AA treated HUVECs).

RESULTS

The positive rate of AT1-AA in 126 hypertensive patients was 21.4% (27/126), and higher than that in normotensive individuals [3.3% (1/30), P < 0.01]. Circulating EMP (CD31+/CD42b-) levels were corresponding to the AT1-AA titres in hypertensive group (r(2) = 0.3661, P < 0.01). AT1-AA promoted EMPs generation from HUVECs in a time and dose-dependent manner than the vehicle or nonspecific IgG. Meanwhile, AT1-AA significantly elevated phosphorylation level of P38 and ERK in HUVECs. Lorsartan and P38 inhibitor could suppress the AT1-AA's stimulation effect on EMPs generation. Moreover, the iEMP greatly increased ROS production and reduced nitric oxide synthesis in HUVECs.

CONCLUSION

Our findings showed that circulating EMPs levels positively correlate to the serum AT1-AA titres in essential hypertension patients. The AT1-AA could promote EMPs generation in HUVECs through activation of P38 MAPK signalling pathway, and this effect could be effectively inhibited by losartan or p38 inhibitor. Angiotensin receptor blockers (ARBs) may be more suitable for AT1-AA(+) hypertensive patients on account of suppressing the AT1-AA's stimulation effect on EMPs generation.

Autoantibodies isolated from preeclamptic patients induce endothelial dysfunction via interaction with the angiotensin II AT1 receptor

Complete understanding of the etiology underlying endothelial damage in preeclampsia (PE) remains deficient. Recent studies suggest that autoantibodies against angiotensin II AT1 receptors (AT1-AA) may affect vascular endothelial integrity. However, direct evidence demonstrating association between AT1-AA from preeclamptic patients and vascular endothelial injury is lacking. The current study determined the effects of AT1-AA isolated from preeclamptic patients (Pre-IgG) upon the endothelium and attempted to elucidate the underlying mechanisms of injury. Pre-IgG markedly induced dose-dependent vasoconstriction in aortic vascular rings, an effect blocked by AT1 receptor antagonist losartan. Pre-IgG-induced vasoconstriction was increased in the absence of intact endothelium (1.59 ± 0.04 g vs. 1.63 ± 0.08 g, P < 0.05). Additionally, Pre-IgG incubation with human umbilical vein endothelial cells significantly increased lactate dehydrogenase release in a time-dependent manner (0.84 ± 0.07 vs. 3.50 ± 0.09, 24 vs. 72-h exposure group, P < 0.01) and increased caspase-3 and -8 activities (peaking at 48 h), but did not affect caspase-9 activity. Taken together, these results support the contribution of AT1-AA to endothelial cell injury and dysfunction in PE.

Vascular dysfunction in preeclampsia

Preeclampsia is a complex disorder which affects an estimated 5% of all pregnancies worldwide. It is diagnosed by hypertension in the presence of proteinuria after the 20th week of pregnancy and is a prominent cause of maternal morbidity and mortality. As delivery is currently the only known treatment, preeclampsia is also a leading cause of preterm delivery. Preeclampsia is associated with maternal vascular dysfunction, leading to serious cardiovascular risk both during and following pregnancy. Endothelial dysfunction, resulting in increased peripheral resistance, is an integral part of the maternal syndrome. While the cause of preeclampsia remains unknown, placental ischemia resulting from aberrant placentation is a fundamental characteristic of the disorder. Poor placentation is believed to stimulate the release of a number of factors including pro- and antiangiogenic factors and inflammatory activators into the maternal systemic circulation. These factors are critical mediators of vascular function and impact the endothelium in distinctive ways, including enhanced endothelial oxidative stress. The mechanisms of action and the consequences on the maternal vasculature will be discussed in this review.

Increased angiotensin II contraction of the uterine artery at early gestation in a transgenic model of hypertensive pregnancy is reduced by inhibition of endocannabinoid hydrolysis

Increased vascular sensitivity to angiotensin II (Ang II) is a marker of a hypertensive human pregnancy. Recent evidence of interactions between the renin-angiotensin system and the endocannabinoid system suggests that anandamide and 2-arachidonoylglycerol may modulate Ang II contraction. We hypothesized that these interactions may contribute to the enhanced vascular responses in hypertensive pregnancy. We studied Ang II contraction in isolated uterine artery (UA) at early gestation in a rat model that mimics many features of preeclampsia, the transgenic human angiotensinogen×human renin (TgA), and control Sprague-Dawley rats. We determined the role of the cannabinoid receptor 1 by blockade with SR171416A, and the contribution of anandamide and 2-arachidonoylglycerol degradation to Ang II contraction by inhibiting their hydrolyzing enzyme fatty acid amide hydrolase (with URB597) or monoacylglycerol lipase (with JZL184), respectively. TgA UA showed increased maximal contraction and sensitivity to Ang II that was inhibited by indomethacin. Fatty acid amide hydrolase blockade decreased Ang IIMAX in Sprague-Dawley UA, and decreased both Ang IIMAX and sensitivity in TgA UA. Monoacylglycerol lipase blockade had no effect on Sprague-Dawley UA and decreased Ang IIMAX and sensitivity in TgA UA. Blockade of the cannabinoid receptor 1 in TgA UA had no effect. Immunolocalization of fatty acid amide hydrolase and monoacylglycerol lipase showed a similar pattern between groups; fatty acid amide hydrolase predominantly localized in endothelium and monoacylglycerol lipase in smooth muscle cells. We demonstrated an increased Ang II contraction in TgA UA before initiation of the hypertensive phenotype. Anandamide and 2-arachidonoylglycerol reduced Ang II contraction in a cannabinoid receptor 1-independent manner. These renin-angiotensin system-endocannabinoid system interactions may contribute to the enhanced vascular reactivity in early stages of hypertensive pregnancy.

Examination of intrarenal resistance indices indicate the involvement of renal pathology as a significant diagnostic classifier of preeclampsia

BACKGROUND

Preeclampsia (PE) is a hypertensive disorder during pregnancy with endotheliosis leading to occlusion of renal perfusion with an impact on the glomerular filtration barrier. We therefore analyzed the role of intrarenal resistance indices in the renal interlobular arteries measured by Doppler ultrasound as a diagnosis of PE.

METHODS

Women with preeclampsia (n = 24; mean blood pressure/24 h = 145 ± 11/ 93 ± 7 mm Hg; mean proteinuria = 5.63 ± 1.0 g/24 h) were compared against a group of healthy pregnant women (n = 24). All patients underwent a Doppler ultrasound of the intrarenal arteries between the 24th week of gestation and the 5th week postpartum. Several risk factors for PE, as well as the arterial resistive indices of the Arteriae uterinae and the Arteria umbilicalis, were monitored in parallel.

RESULTS

The intrarenal resistive index (mean ± SD = 0.63 ± 0.05 in women with preeclampsia vs. 0.59 ± 0.056 in healthy pregnant women; P < 0.003), the pulsatile index (mean ± SD = 1.15 ± 0.19 in women with preeclampsia vs. 0.92 ± 0.13 in healthy pregnant women; P < 0.0001), and the end diastolic flow velocity (mean ± SD = 14.16 ± 4.75 cm/s in women with preeclampsia vs. 10.67 ± 2.68 cm/s in healthy pregnant women, P < 0.006) were elevated in patients with PE, as were the arterial resistive indices of the Aa. uterinae and A. umbilicalis. The intrarenal resistive indices correctly classified 84.2% of the women as having PE.

CONCLUSIONS

Intrarenal resistive indices are a significant classifier of PE, providing the possibility to predict nephropathy. They could be a prognostic tool for cardiovascular comorbidity in PE patients even after delivery.

The correlation between peripartum cardiomyopathy and autoantibodies against cardiovascular receptors

Background

Peripartum cardiomyopathy (PPCM) is characterized by left ventricular systolic dysfunction and heart failure. However, its pathogenesis is not clear. Our preliminary study revealed that autoantibodies against β₁-adrenergic receptors (β₁R-AABs) and M₂-muscarinic receptors (M₂R-AABs) participated in heart failure regardless of primary heart disease. Whether β₁R-AABs and M₂R-AABs participate in the pathogenesis of PPCM is still unknown.

Methods

Totally 37 diagnosed PPCM patients and 36 normal pregnant women were enrolled in this study. Clinical assessment and 2-dimensional echocardiographic studies as well as the measurement of β₁R-AABs or M₂R-AABs by enzyme linked immunosorbent assay (ELISA) were performed.

Results

The positive rates for β₁R-AABs and M₂R-AABs were 59.5% (22/37) and 45.9% (17/37) in PPCM patients, and 19.4% (7/36) (P<0.001) and 16.67% (6/36) (P<0.001) in normal pregnant women, respectively. Both β₁R-AABs and M₂R-AABs had a positive correlation with serum expression level of NT-proBNP, left ventricular dimension and NYHA FC (rs: 0.496–0.892, P<0.01). In addition, a negative correlation between the activity of β₁R-AABs and M₂R-AABs and LVEF, LVFS was observed (rs: −0.488–0.568, P<0.01). Moreover, autoantibodies against cardiovascular receptors increased the risk of the onset of PPCM (OR = 18.786, 95% confidence interval 1.926–183.262, P = 0.012).

Conclusions

The β₁R-AABs and M₂R-AABs reveal a significant elevation and are correlated with the increased left ventricular dimension and worse cardiac contraction function. The autoantibodies of cardiovascular receptors are independent risk factors for the onset of PPCM.

Autoantibodies against the β3-adrenoceptor protect from cardiac dysfunction in a rat model of pressure overload

β₃-adrenoceptors (β₃-ARs) mediate a negative inotropic effect in human ventricular cardiomyocytes, which is opposite to that of β₁- and β₂-ARs. It has been previously demonstrated that autoantibodies against the β_1/β₂-AR exist in the sera of some patients with heart failure (HF) and these autoantibodies display agonist-like effects. Our aim in this study was to observe whether autoantibodies against the β₃-AR (β₃-AR Abs) exist in the sera of patients with HF and to assess the effects of β₃-AR Abs on rat model of pressure overload cardiomyopthy. In the present study, the level of β₃-AR Abs in the sera of HF patients was screened by ELISA. β₃-AR Abs from HF patients were administrated to male adult rats with abdominal aortic banding (AAB), and the cardiac function was measured by echocardiographic examination and hemodynamic studies. The biological effects of this autoantibody on cardiomyocytes were evaluated using a motion-edge detection system, intracellular calcium transient assay, and patch clamp techniques. Compared to healthy subjects, the frequency of occurrence and titer of β₃-AR Abs in the sera of HF patients were greatly increased, and β₃-AR Abs could prevent LV dilation and improve the cardiac function of rats with AAB. β₃-AR Abs exhibited negative chronotropic and inotropic effects and were accompanied by a decreased intracellular Ca²⁺ transient and membrane L-type Ca²⁺ current in cardiomyocytes. Our results demonstrated the existence of β₃-AR Abs in the sera of patients with HF and found that this autoantibody could alleviate the cardiac dysfunction induced by pressure-overload in AAB rats.

Autoantibody against angiotensin AT1 receptor from preeclamptic patients enhances collagen-induced human platelet aggregation

Hypercoagulability, platelet activation, and thrombocytopenia are the chief characteristics of preeclampsia, but their responsible underlying molecular mechanisms remain obscure. Recent studies have demonstrated that the autoantibody against angiotensin II type 1 receptor (AT1-AA) constitutes a novel risk factor for preeclampsia. However, the role of AT1-AA in platelet activation and hypercoagulability in preeclampsia has never been investigated. In the present study, we determined whether AT1-AA promotes platelet aggregation in vitro, and dissected the potential underlying mechanisms. AT1-AA was detected by enzyme-linked immunosorbent assay. After immunoglobulin G fractions purified from the preeclamptic patient positive sera were added to platelets isolated from healthy volunteers, platelet aggregation and intracellular Ca(2+) levels were detected. AT1-AA significantly enhanced in vitro collagen-induced platelet aggregation, an effect blocked by the AT1 receptor antagonist losartan. Additionally, AT1-AA increased and maintained collagen-induced cytosolic calcium concentration throughout the experiment. We demonstrated for the first time that AT1-AA significantly promotes collagen-induced platelet aggregation through angiotensin type 1 receptor activation in vitro, potentially via increased intracellular Ca(2+) concentration, supporting AT1-AA as a potential contributor to the hypercoagulable state of preeclampsia.

RAS in Pregnancy and Preeclampsia and Eclampsia

Preeclampsia is a common disease of pregnancy characterized by the presence of hypertension and commitment of many organs, including the brain, secondary to generalized endothelial dysfunction. Its etiology is not known precisely, but it involved several factors, highlighting the renin angiotensin system (RAS), which would have an important role in the origin of multisystem involvement. This paper reviews the evidence supporting the involvement of RAS in triggering the disease, in addition to the components of this system that would be involved and how it eventually produces brain engagement.

Renin-angiotensin system in pre-eclampsia: everything old is new again

This review presents an update of the role of the renin-angiotensin system in normal pregnancy and pre-eclampsia. We have known for years that the circulatory renin-angiotensin system in pre-eclampsia is suppressed. We now know that the circulating renin-angiotensin system does not only have a vasoconstrictor arm, but also a vasodilator arm, which is upregulated in normal pregnancy; this balance is probably disturbed in pre-eclampsia. Recent studies show the importance of the local renin-angiotensin system in the uteroplacental unit for early placentation and regulation of placental blood flow. We discuss the possible role of autoantibodies against the AT1-receptor in pre-eclampsia and the suggestion that activation of the AT1-receptor in the placenta may lead to placental dysfunction and the clinical syndrome of pre-eclampsia.

Increased susceptibility to metabolic syndrome in adult offspring of angiotensin type 1 receptor autoantibody-positive rats

AIMS

Abnormal fetal and early postnatal growth is closely associated with adult-onset metabolic syndrome (MetS). However, the underlying etiological factors remain complex. The presence of the autoantibody against the angiotensin II type 1 receptor (AT1-Ab), a known risk factor for pre-eclampsia, may create a suboptimal intrauterine fetal environment. The current study investigated whether middle-aged offspring of AT1-Ab-positive mothers were prone to metabolic disorder development.

RESULTS

The AT1-Abs was detected in placental trophoblastic cells, capillary endothelium, and milk of pregnant rats actively immunized with the second extracellular loop of the AT1 receptor. AT1-Abs in newborn rats induced vasoconstriction, increased intracellular-free Ca(2+) in vitro, and was undetectable 7 weeks later. Immunized group offspring exhibited increased weight variability and insulin resistance at 40 weeks of age under a normal diet, evidenced by elevated fasting serum insulin and homeostasis model assessment score compared with the vehicle control. To further observe metabolic alterations, the offspring were given a high-sugar diet (containing 20% sucrose) 40-48 weeks postnatally. The fasting plasma glucose in immunized group offspring was markedly increased. Concomitantly, these offspring manifested increased visceral adipose tissue, increased fatty liver, increased triglycerides, decreased high-density lipoprotein cholesterol, and decreased adiponectin levels, indicative of MetS.

INNOVATION

AT1-Abs could be transferred from mother to offspring via the placenta and milk. Moreover, offspring of an AT1-Ab-positive mother were more vulnerable to MetS development in middle age.

CONCLUSION

AT1-Ab-positivity of mothers during pregnancy is a previously unrecognized "silent" risk factor for MetS development in their offspring.

Receptor-activating autoantibodies and disease: preeclampsia and beyond

The research reviewed in this article provides examples of autoantibody-mediated receptor activation that likely contributes to disease. The classic example is Graves' hyperthyroidism, in which autoantibodies activate the thyroid-stimulating hormone receptor resulting in overproduction of thyroid hormones. Other compelling examples come from the cardiovascular literature and include agonistic autoantibodies targeting the cardiac β(1)-adrenergic receptor, which are associated with dilated cardiomyopathy. Autoantibodies capable of activating α(1)-adrenergic receptors are associated with refractory hypertension and cardiomyopathy. A prominent example is preeclampsia, a hypertensive disease of pregnancy, characterized by the presence of autoantibodies that activate the major angiotensin receptor, AT(1). AT(1) receptor-activating autoantibodies are also observed in kidney transplant recipients suffering from severe vascular rejection and malignant hypertension. AT(1) receptor-activating autoantibodies and antibodies that activate the endothelin-1 receptor, ET(A), are prevalent in individuals diagnosed with systemic sclerosis. Thus, the presence of agonistic autoantibodies directed to G protein-coupled receptors has been observed in numerous cardiovascular disease states. Rapidly emerging evidence indicates that receptor-activating autoantibodies contribute to disease, and that efforts to detect and remove these pathogenic autoantibodies or block their actions will provide promising therapeutic possibilities.

Angiotensin II type 1 receptor antibodies and increased angiotensin II sensitivity in pregnant rats

Pregnant women who subsequently develop preeclampsia are highly sensitive to infused angiotensin (Ang) II; the sensitivity persists postpartum. Activating autoantibodies against the Ang II type 1 (AT(1)) receptor are present in preeclampsia. In vitro and in vivo data suggest that they could be involved in the disease process. We generated and purified activating antibodies against the AT(1) receptor (AT(1)-AB) by immunizing rabbits against the AFHYESQ epitope of the second extracellular loop, which is the binding epitope of endogenous activating autoantibodies against AT(1) from patients with preeclampsia. We then purified AT(1)-AB using affinity chromatography with the AFHYESQ peptide. We were able to detect AT(1)-AB both by ELISA and a functional bioassay. We then passively transferred AT(1)-AB into pregnant rats, alone or combined with Ang II. AT(1)-AB activated protein kinase C-α and extracellular-related kinase 1/2. Passive transfer of AT(1)-AB alone or Ang II (435 ng/kg per minute) infused alone did not induce a preeclampsia-like syndrome in pregnant rats. However, the combination (AT(1)-AB plus Ang II) induced hypertension, proteinuria, intrauterine growth retardation, and arteriolosclerosis in the uteroplacental unit. We next performed gene-array profiling of the uteroplacental unit and found that hypoxia-inducible factor 1α was upregulated by Ang II plus AT(1)-AB, which we then confirmed by Western blotting in villous explants. Furthermore, endothelin 1 was upregulated in endothelial cells by Ang II plus AT(1)-AB. We show that AT(1)-AB induces Ang II sensitivity. Our mechanistic study supports the existence of an "autoimmune-activating receptor" that could contribute to Ang II sensitivity and possible to preeclampsia.

Protecting against vascular disease in brain

Endothelial cells exert an enormous influence on blood vessels throughout the circulation, but their impact is particularly pronounced in the brain. New concepts have emerged recently regarding the role of this cell type and mechanisms that contribute to endothelial dysfunction and vascular disease. Activation of the renin-angiotensin system plays a prominent role in producing these abnormalities. Both oxidative stress and local inflammation are key mechanisms that underlie vascular disease of diverse etiology. Endogenous mechanisms of vascular protection are also present, including antioxidants, anti-inflammatory molecules, and peroxisome proliferator-activated receptor-γ. Despite their clear importance, studies of mechanisms that underlie cerebrovascular disease continue to lag behind studies of vascular biology in general. Identification of endogenous molecules and pathways that protect the vasculature may result in targeted approaches to prevent or slow the progression of vascular disease that causes stroke and contributes to the vascular component of dementia and Alzheimer's disease.