Agonistic autoantibodies directed against the angiotensin II AT1 receptor in patients with preeclampsia

Long COVID: Association of Functional Autoantibodies against G-Protein-Coupled Receptors with an Impaired Retinal Microcirculation

Long COVID (LC) describes the clinical phenotype of symptoms after infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Diagnostic and therapeutic options are limited, as the pathomechanism of LC is elusive. As the number of acute SARS-CoV-2 infections was and is large, LC will be a challenge for the healthcare system. Previous studies revealed an impaired blood flow, the formation of microclots, and autoimmune mechanisms as potential factors in this complex interplay. Since functionally active autoantibodies against G-protein-coupled receptors (GPCR-AAbs) were observed in patients after SARS-CoV-2 infection, this study aimed to correlate the appearance of GPCR-AAbs with capillary microcirculation. The seropositivity of GPCR-AAbs was measured by an established cardiomyocyte bioassay in 42 patients with LC and 6 controls. Retinal microcirculation was measured by OCT–angiography and quantified as macula and peripapillary vessel density (VD) by the Erlangen-Angio Tool. A statistical analysis yielded impaired VD in patients with LC compared to the controls, which was accentuated in female persons. A significant decrease in macula and peripapillary VD for AAbs targeting adrenergic β2-receptor, MAS-receptor angiotensin-II-type-1 receptor, and adrenergic α1-receptor were observed. The present study might suggest that a seropositivity of GPCR-AAbs can be linked to an impaired retinal capillary microcirculation, potentially mirroring the systemic microcirculation with consecutive clinical symptoms.

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.

Case Report: Neutralization of Autoantibodies Targeting G-Protein-Coupled Receptors Improves Capillary Impairment and Fatigue Symptoms After COVID-19 Infection

Clinical features of Coronavirus disease 2019 (COVID-19) are caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Acute infection management is a substantial healthcare issue, and the development of long-Covid syndrome (LCS) is extremely challenging for patients and physicians. It is associated with a variety of characteristics as impaired capillary microcirculation, chronic fatigue syndrome (CFS), proinflammatory cytokines, and functional autoantibodies targeting G-protein-coupled receptors (GPCR-AAbs). Here, we present a case report of successful healing of LCS with BC 007 (Berlin Cures, Berlin, Germany), a DNA aptamer drug with a high affinity to GPCR-AAbs that neutralizes these AAbs. A patient with a documented history of glaucoma, recovered from mild COVID-19, but still suffered from CFS, loss of taste, and impaired capillary microcirculation in the macula and peripapillary region. He was positively tested for various targeting GPCR-AAbs. Within 48 h after a single BC 007 treatment, GPCR-AAbs were functionally inactivated and remained inactive during the observation period of 4 weeks. This observation was accompanied by constant improvement of the fatigue symptoms of the patient, taste, and retinal capillary microcirculation. Therefore, the removal of GPCR-AAb might ameliorate the characteristics of the LCD, such as capillary impairment, loss of taste, and CFS.

Angiotensin II type 1 receptor agonistic autoantibody blockade improves postpartum hypertension and cardiac mitochondrial function in rat model of preeclampsia

Women with preeclampsia (PE) have a greater risk of developing hypertension, cardiovascular disease (CVD), and renal disease later in life. Angiotensin II type I receptor agonistic autoantibodies (AT1-AAs) are elevated in women with PE during pregnancy and up to 2-year postpartum (PP), and in the reduced uterine perfusion pressure (RUPP) rat model of PE. Blockade of AT1-AA with a specific 7 amino acid peptide binding sequence (‘n7AAc’) improves pathophysiology observed in RUPP rats; however, the long-term effects of AT1-AA inhibition in PP is unknown. Pregnant Sprague Dawley rats were divided into three groups: normal pregnant (NP) (n = 16), RUPP (n = 15), and RUPP + ‘n7AAc’ (n = 16). Gestational day 14, RUPP surgery was performed and ‘n7AAc’ (144 μg/day) administered via osmotic minipump. At 10-week PP, mean arterial pressure (MAP), renal glomerular filtration rate (GFR) and cardiac functions, and cardiac mitochondria function were assessed. MAP was elevated PP in RUPP vs. NP (126 ± 4 vs. 116 ± 3 mmHg, p < 0.05), but was normalized in in RUPP + ‘n7AAc’ (109 ± 3 mmHg) vs. RUPP (p < 0.05). PP heart size was reduced by RUPP + ’n7AAc’ vs. RUPP rats (p < 0.05). Complex IV protein abundance and enzymatic activity, along with glutamate/malate-driven respiration (complexes I, III, and IV), were reduced in the heart of RUPP vs. NP rats which was prevented with ‘n7AAc’. AT1-AA inhibition during pregnancy not only improves blood pressure and pathophysiology of PE in rats during pregnancy, but also long-term changes in blood pressure, cardiac hypertrophy, and cardiac mitochondrial function PP.

Epigenetic processes during preeclampsia and effects on fetal development and chronic health

Preeclampsia (PE), the leading cause of maternal and fetal morbidity and mortality, is associated with poor fetal growth, intrauterine growth restriction (IUGR) and low birth weight (LBW). Offspring of women who had PE are at increased risk for cardiovascular (CV) disease later in life. However, the exact etiology of PE is unknown. Moreover, there are no effective interventions to treat PE or alleviate IUGR and the developmental origins of chronic disease in the offspring. The placenta is critical to fetal growth and development. Epigenetic regulatory processes such as histone modifications, microRNAs and DNA methylation play an important role in placental development including contributions to the regulation of trophoblast invasion and remodeling of the spiral arteries. Epigenetic processes that lead to changes in placental gene expression in PE mediate downstream effects that contribute to the development of placenta dysfunction, a critical mediator in the onset of PE, impaired fetal growth and IUGR. Therefore, this review will focus on epigenetic processes that contribute to the pathogenesis of PE and IUGR. Understanding the epigenetic mechanisms that contribute to normal placental development and the initiating events in PE may lead to novel therapeutic targets in PE that improve fetal growth and mitigate increased CV risk in the offspring.

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.

Functional autoantibodies against G-protein coupled receptors in patients with persistent Long-COVID-19 symptoms

Impairment of health after overcoming the acute phase of COVID-19 is being observed more and more frequently. Here different symptoms of neurological and/or cardiological origin have been reported. With symptoms, which are very similar to the ones reported but are not caused by SARS-CoV-2, the occurrence of functionally active autoantibodies (fAABs) targeting G-protein coupled receptors (GPCR-fAABs) has been discussed to be involved. We, therefore investigated, whether GPCR-fAABs are detectable in 31 patients suffering from different Long-COVID-19 symptoms after recovery from the acute phase of the disease. The spectrum of symptoms was mostly of neurological origin (29/31 patients), including post-COVID-19 fatigue, alopecia, attention deficit, tremor and others. Combined neurological and cardiovascular disorders were reported in 17 of the 31 patients. Two recovered COVID-19 patients were free of follow-up symptoms. All 31 former COVID-19 patients had between 2 and 7 different GPCR-fAABs that acted as receptor agonists. Some of those GPCR-fAABs activate their target receptors which cause a positive chronotropic effect in neonatal rat cardiomyocytes, the read-out in the test system for their detection (bioassay for GPCR-fAAB detection). Other GPCR-fAABs, in opposite, cause a negative chronotropic effect on those cells. The positive chronotropic GPCR-fAABs identified in the blood of Long-COVID patients targeted the β2-adrenoceptor (β2-fAAB), the α1-adrenoceptor (α1-fAAB), the angiotensin II AT1-receptor (AT1-fAAB), and the nociceptin-like opioid receptor (NOC-fAAB). The negative chronotropic GPCR-fAABs identified targeted the muscarinic M2-receptor (M2-fAAB), the MAS-receptor (MAS-fAAB), and the ETA-receptor (ETA-fAAB). It was analysed which of the extracellular receptor loops was targeted by the autoantibodies.

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.

Angiotensin II type 1 receptor autoantibody blockade improves cerebral blood flow autoregulation and hypertension in a preclinical model of preeclampsia

Introduction:Women with preeclampsia (PE) and reduced uterine perfusion pressure (RUPP) pre-clinical rat model of PE have elevated angiotensin II type 1 receptor agonistic autoantibodies (AT1-AA) and cerebrovascular dysfunction. Methods:Sprague Dawley rats had RUPP surgery with/without AT1-AA inhibitor ('n7AAc'144 μg/day) osmotic minipumps. Mean arterial pressure (MAP), CBF autoregulation, blood brain barrier (BBB) permeability, cerebral edema, oxidative stress, and eNOS were assessed. Results:'n7AAc' improved MAP, restored CBF autoregulation, prevented cerebral edema, elevated oxidative stress, and increased phosphorylated eNOS protein in RUPP rats. Conclusion:Inhibiting the AT1-AA in placental ischemic rats prevents hypertension, cerebrovascular dysfunction, and improves cerebral metabolic function.

Prevalence of Angiotensin II Type 1 Receptor Antibodies in Persons With Hypertension and Relation to Blood Pressure and Medication

BACKGROUND

We aimed to determine the prevalence of antibodies against angiotensin II type 1 receptor (AT1RAb) in hypertensive adults and elucidate the relation of antihypertensive medication type to blood pressure (BP) among persons with and without AT1RAb.

METHODS

Sera from participants in the Healthy Aging in Neighborhoods of Diversity across the Life Span (HANDLS) study with hypertension were tested for AT1RAb using a commercial Enzyme-linked immunosorbent assay (ELISA) (One Lambda; positive ≥17 units/ml). BP measurements, uncontrolled BP (systolic BP ≥140 and/or diastolic BP ≥90 mm Hg), and effect of BP medication type were compared for AT1RAb positive (+) vs. negative (-) participants using descriptive statistics and multivariable regression.

RESULTS

One hundred and thirty-two (13.1%) participants were AT1RAb+. Compared with AT1RAb-, AT1RAb+ persons were more likely to be white (47% vs. 36.7%; P = 0.03) but had similar comorbid disease burden. In models adjusting for age, sex, and race, AT1RAb+ persons had higher diastolic BP (β = 2.61 mm Hg; SE = 1.03; P = 0.01) compared with AT1RAb- participants. Rates of uncontrolled BP were similar between the groups. AT1RAb+ persons on an angiotensin receptor blocker (ARB; n = 21) had a mean of 10.5 mm Hg higher systolic BP (SE = 4.56; P = 0.02) compared with AT1RAb+ persons using other BP medications. The odds of uncontrolled BP among AT1RAb+ participants on an ARB was 2.05 times that of those on other medications. AT1RAb- persons prescribed an angiotensin-converting enzyme inhibitor (ACEi) had 1.8 mm Hg lower diastolic BP (SE = 0.81; P = 0.03) than AT1RAb- persons not prescribed an ACEi.

CONCLUSIONS

AT1RAb was prevalent among hypertensive adults and was associated with higher BP among persons on an ARB.

Adaptations in autonomic nervous system regulation in normal and hypertensive pregnancy

There is an increase in basal sympathetic nerve activity (SNA) during normal pregnancy; this counteracts profound primary vasodilation. However, pregnancy also impairs baroreflex control of heart rate and SNA, contributing to increased mortality secondary to peripartum hemorrhage. Pregnancy-induced hypertensive disorders evoke even greater elevations in SNA, which likely contribute to the hypertension. Information concerning mechanisms is limited. In normal pregnancy, increased angiotensin II acts centrally to support elevated SNA. Hypothalamic sites, including the subfornical organ, paraventricular nucleus, and arcuate nucleus, are likely (but unproven) targets. Moreover, no definitive mechanisms for exaggerated sympathoexcitation in hypertensive pregnancy have been identified. In addition, normal pregnancy increases gamma aminobutyric acid inhibition of the rostral ventrolateral medulla (RVLM), a key brainstem site that transmits excitatory inputs to spinal sympathetic preganglionic neurons. Accumulated evidence supports a major role for locally increased production and actions of the neurosteroid allopregnanolone as one mechanism. A consequence is suppression of baroreflex function, but increased basal SNA indicates that excitatory influences predominate in the RVLM. However, many questions remain regarding other sites and factors that support increased SNA during normal pregnancy and, more importantly, the mechanisms underlying excessive sympathoexcitation in life-threatening hypertensive pregnancy disorders such as preeclampsia.

The Role of Agonistic Autoantibodies to the Angiotensin II Type 1 Receptor (AT1-AA) in Pathophysiology of Preeclampsia

Preeclampsia is the leading cause of death and morbidity worldwide for the mother and fetus during pregnancy. Preeclampsia does not only affect the mother and the baby during pregnancy, but can also have long-term effects, such as the increased risk of hypertension and cardiovascular disease on the offspring and the postpartum mother later in life. The exact cause of preeclampsia is unknown, but women with preeclampsia have elevated concentrations of agonistic autoantibodies against the angiotensin II type 1 receptor (AT1-AA). These AT1-AA's through multiple studies have shown to play a significant role in the pathology and possible genesis of preeclampsia. This review will discuss the discovery of AT1-AAs and the role of AT1-AAs in the pathophysiology of preeclampsia. This review will also discuss future therapeutic approaches towards the AT1-AA to prevent adverse pregnancy outcomes. Furthermore, we will examine the relationship between AT1-AA induced hypertension associated with increased oxidative stress, antiangiogenic factors (such as soluble fms-related tyrosine kinase-1 (sFlt-1), endothelin-1 (ET-1), inflammation, endothelial dysfunction, and reduced renal function. Understanding the pathological role of AT1-AAs in hypertensive pregnancies is important as we search for novel therapies to manage preeclampsia.

Autoantibodies against AT1 and α1-adrenergic receptors predict arterial stiffness progression in normotensive subjects over a 5-year period

Arterial stiffness is an independent indicator of cardiovascular risk. Autoantibodies (AAs) against angiotensin AT1 receptor (AT1-AAs) and α1-adrenergic receptor (α1-AAs) are important in the pathogenesis of hypertension. We identified the types of AT1-AAs and α1-AAs in normotensive subjects, with the aim of determining whether these antibodies predict aortic stiffness progression. Carotid–femoral pulse wave velocity (cf-PWV) was used to measure aortic stiffness. Overall, 816 subjects (71% of those invited) underwent a medical examination and evaluation of aortic stiffness. The types of AT1-AAs and α1-AAs were measured at baseline. Meanwhile, plasma renin, angiotensin II (Ang II), and norepinephrine (NE) concentrations were measured at baseline and follow-up. Baseline mean cf-PWV was 9.90 ± 0.84 m/s and follow-up was 10.51 ± 1.12 m/s. The annualized ΔPWV was 0.12 ± 0.08 m/s/year. At the end of follow-up, 129 normotensive subjects developed hypertension and 144 subjects had PWV progression. After adjustment for covariates, AA type was independently associated with ΔPWV, annualized ΔPWV, and abnormal PWV. In our study, the risk of developing hypertension (RR =2.028, 95% CI: 1.227–3.351, P=0.006) and PWV progression (RR =2.910, 95% CI: 1.612–5.253, P<0.001) in AA-positive subjects was significantly higher than that in AA-negative subjects. Receiver operating characteristic (ROC) curve showed AA had an identify power to discriminate subjects with or without PWV and hypertension progression. We have shown for the first time that the types of A1-AAs and α1-AAs are independent predictors for aortic stiffness progression in normotensive subjects. Our data collectively support the utility of these AAs as potential markers of aortic stiffness.

Preeclampsia and the brain: neural control of cardiovascular changes during pregnancy and neurological outcomes of preeclampsia

Preeclampsia (PE) is a form of gestational hypertension that complicates ∼5% of pregnancies worldwide. Over 70% of the fatal cases of PE are attributed to cerebral oedema, intracranial haemorrhage and eclampsia. The aetiology of PE originates from abnormal remodelling of the maternal spiral arteries, creating an ischaemic placenta that releases factors that drive the pathophysiology. An initial neurological outcome of PE is the absence of the autonomically regulated cardiovascular adaptations to pregnancy. PE patients exhibit sympathetic overactivation, in comparison with both normotensive pregnant and hypertensive non-pregnant females. Moreover, PE diminishes baroreceptor reflex sensitivity (BRS) beyond that observed in healthy pregnancy. The absence of the cardiovascular adaptations to pregnancy, combined with sympathovagal imbalance and a blunted BRS leads to life-threatening neurological outcomes. Behaviourally, the increased incidences of maternal depression, anxiety and post-traumatic stress disorder (PTSD) in PE are correlated to low fetal birth weight, intrauterine growth restriction (IUGR) and premature birth. This review addresses these neurological consequences of PE that present in the gravid female both during and after the index pregnancy.

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.

Discovery and Validation of Agonistic Angiotensin Receptor Autoantibodies as Biomarkers of Adverse Outcomes

BACKGROUND

Agonistic angiotensin II type 1 receptor autoantibodies (AT1RaAbs) have not been associated with functional measures or risk for adverse health outcomes. AT1RaAbs could be used to stratify patient risk and to identify patients who can benefit from angiotensin receptor blocker treatment.

METHODS

Demographic and physiological covariates were measured in a discovery set of community-dwelling adults from Baltimore (N=255) and AT1RaAb associations with physical function tests and outcomes assessed. A group from Chicago (N=60) was used for validation of associations and to explore the impact of angiotensin receptor blocker treatment.

RESULTS

The Baltimore group had 28 subjects with falls, 32 frail subjects, and 5 deaths. Higher AT1RaAbs correlated significantly with interleukin-6 (Spearman r=0.33, P<0.0001), systolic blood pressure (Spearman r=0.28, P<0.0001), body mass index (Spearman r=0.28, P<0.0001), weaker grip strength (Spearman r=-0.34, P<0.01), and slower walking speed (Spearman r=-0.30, P<0.05). Individuals with high AT1RaAbs were 3.9 (95% confidence interval, 1.38-11.0) times more likely to be at high risk after adjusting for age (P<0.05). Every 1 µg/mL increase in AT1RaAbs increased the odds of falling 30% after adjusting for age, sex, body mass index, and blood pressure. The Chicago group had 46 subjects with falls and 60 deaths. Serum AT1RaAb levels were significantly correlated with grip strength (Spearman r=-0.57, P<0.005), walking speed (Spearman r=-0.47, P<0.005), and falls (Spearman r=0.30, P<0.05). Every 1 µg/mL increase in AT1RaAbs, decreased time to death by 9% after adjusting for age, sex, body mass index, and blood pressure. Chronic treatment with angiotensin receptor blockers was associated with better control of systolic blood pressure and attenuation of decline in both grip strength and time to death.

CONCLUSIONS

In older individuals, higher AT1RaAb levels were associated with inflammation, hypertension, and adverse outcomes. Angiotensin receptor blocker treatment may blunt the harm associated with high levels of AT1RaAb.

Aptamer BC 007 - A broad spectrum neutralizer of pathogenic autoantibodies against G-protein-coupled receptors

The effect of autoantibodies on G-protein coupled receptors in the pathogenesis of diseases, especially of the heart and vascular system, is an increasingly accepted fact today. Dilated cardiomyopathy (DCM) is the most intensively investigated pathological situation of these. With DCM, autoantibodies against the β1-adrenoceptor and the muscarinic M2-receptor have been found in high percentage of investigated patients. Immunoadsorption for autoantibody removal has already shown a long-term beneficial therapeutic effect, but has remained limited in its application because of the complexity of this method. A new easy applicable treatment strategy has, therefore, been discovered. Because of intra- and inter-loop epitope variability of the β1-adrenoceptor specific autoantibodies and also the occurrence of further autoantibodies of this class such as the ones against the β2- and α1-adrenoceptor, the ETA-, proteinase activated-, and the AT1-receptors in different pathological situations, this newly discovered broad-spectrum neutralizer of all these autoantibodies - aptamer BC 007 - is under development. The binding and neutralizing effect was investigated applying a bioassay of spontaneously beating neonatal rat cardiomyocytes and enzyme-linked immunosorbent assay (ELISA) - technology. The usefulness of aptamer BC 007 to specify column technology for the removal of serum autoantibodies was also demonstrated. The presented data suggest that aptamer BC 007 might be an appropriate molecule candidate to support future research about the meaning of G-protein-coupled receptor autoantibodies.

A Dormant Microbial Component in the Development of Preeclampsia

Preeclampsia (PE) is a complex, multisystem disorder that remains a leading cause of morbidity and mortality in pregnancy. Four main classes of dysregulation accompany PE and are widely considered to contribute to its severity. These are abnormal trophoblast invasion of the placenta, anti-angiogenic responses, oxidative stress, and inflammation. What is lacking, however, is an explanation of how these themselves are caused. We here develop the unifying idea, and the considerable evidence for it, that the originating cause of PE (and of the four classes of dysregulation) is, in fact, microbial infection, that most such microbes are dormant and hence resist detection by conventional (replication-dependent) microbiology, and that by occasional resuscitation and growth it is they that are responsible for all the observable sequelae, including the continuing, chronic inflammation. In particular, bacterial products such as lipopolysaccharide (LPS), also known as endotoxin, are well known as highly inflammagenic and stimulate an innate (and possibly trained) immune response that exacerbates the inflammation further. The known need of microbes for free iron can explain the iron dysregulation that accompanies PE. We describe the main routes of infection (gut, oral, and urinary tract infection) and the regularly observed presence of microbes in placental and other tissues in PE. Every known proteomic biomarker of "preeclampsia" that we assessed has, in fact, also been shown to be raised in response to infection. An infectious component to PE fulfills the Bradford Hill criteria for ascribing a disease to an environmental cause and suggests a number of treatments, some of which have, in fact, been shown to be successful. PE was classically referred to as endotoxemia or toxemia of pregnancy, and it is ironic that it seems that LPS and other microbial endotoxins really are involved. Overall, the recognition of an infectious component in the etiology of PE mirrors that for ulcers and other diseases that were previously considered to lack one.

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.

IL-10 supplementation increases Tregs and decreases hypertension in the RUPP rat model of preeclampsia

OBJECTIVE

The reduced uterine perfusion pressure (RUPP) rat model of preeclampsia was used to determine the effects of added interleukin-10 (IL-10) on Tregs and hypertension in response to placental ischemia and how the decrease in these anti-inflammatory factors mediates the pathophysiology of preeclampsia.

METHODS

IL-10 (2.5 ng/kg/d) was infused via osmotic mini-pump implanted intraperitoneally on day 14 of gestation and, at the same time, the RUPP procedure was performed.

RESULTS

IL-10 reduced mean arterial pressure (p < 0.001), decreased CD4(+) T cells (p = 0.044), while increasing Tregs (p = 0.043) which led to lower IL-6 and TNF-α (p = 0.008 and p = 0.003), reduced AT1-AA production (p < 0.001), and decreased oxidative stress (p = 0.029) in RUPP rats.

CONCLUSION

These data indicate that IL-10 supplementation increases Tregs and helps to balance the altered immune system seen during preeclampsia.

Autoantibodies targeting AT1 receptor from patients with acute coronary syndrome upregulate proinflammatory cytokines expression in endothelial cells involving NF-κB pathway

Our study intended to prove whether agonistic autoantibodies to angiotensin II type 1 receptor (AT1-AAs) exist in patients with coronary heart disease (CHD) and affect the human endothelial cell (HEC) by upregulating proinflammatory cytokines expression involved in NF-κB pathway. Antibodies were determined by chronotropic responses of cultured neonatal rat cardiomyocytes coupled with receptor-specific antagonists (valsartan and AT1-EC2) as described previously. Interleukin-6 (IL-6), vascular cell adhesion molecule-1 (VCAM-1), and monocyte chemotactic protein-1 (MCP-1) expression were improved at both mRNA and protein levels in HEC, while NF-κB in the DNA level was improved detected by electrophoretic mobility shift assays (EMSA). These improvements could be inhibited by specific AT1 receptor blocker valsartan, NF-κB blocker pyrrolidine dithiocarbamate (PDTC), and specific short peptides from the second extracellular loop of AT1 receptor. These results suggested that AT1-AAs, via the AT1 receptor, induce expression of proinflammatory cytokines involved in the activation of NF-κB. AT1-AAs may play a great role in the pathogenesis of the acute coronary syndrome by mediating vascular inflammatory effects involved in the NF-κB pathway.

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.

Maternal plasma fetuin-A concentration is lower in patients who subsequently developed preterm preeclampsia than in uncomplicated pregnancy: a longitudinal study

Objective: Fetuin-A is a negative acute phase protein reactant that acts as a mediator for lipotoxicity, leading to insulin resistance. Intravascular inflammation and insulin resistance have been implicated in the mechanisms of disease responsible for preeclampsia (PE). Maternal plasma concentrations of fetuin-A at the time of diagnosis of preterm PE are lower than in control patients with a normal pregnancy outcome. However, it is unknown if the changes in maternal plasma fetuin-A concentrations precede the clinical diagnosis of the disease. We conducted a longitudinal study to determine whether patients who subsequently developed PE had a different profile of maternal plasma concentrations of fetuin-A as a function of gestational age (GA) than those with uncomplicated pregnancies. Methods: A longitudinal case-control study was performed and included 200 singleton pregnancies in the following groups: (1) patients with uncomplicated pregnancies who delivered appropriate for gestational age (AGA) neonates (n = 160); and (2) patients who subsequently developed PE (n = 40). Longitudinal samples were collected at each prenatal visit and scheduled at 4-week intervals from the first or early second trimester until delivery. Plasma fetuin-A concentrations were determined by ELISA. Analysis was performed using mixed-effects models. Results: The profiles of maternal plasma concentrations of fetuin-A differ between PE and uncomplicated pregnancies. Forward analysis indicated that the rate of increase of plasma fetuin-A concentration in patients who subsequently developed PE was lower at the beginning of pregnancy (p = 0.001), yet increased faster mid-pregnancy (p = 0.0017) and reached the same concentration level as controls by 26 weeks. The rate of decrease was higher towards the end of pregnancy in patients with PE than in uncomplicated pregnancies (p = 0.002). The mean maternal plasma fetuin-A concentration was significantly lower in patients with preterm PE at the time of clinical diagnosis than in women with uncomplicated pregnancies (p < 0.05). In contrast, there were no significant differences in maternal plasma fetuin-A concentration in patients who developed PE at term. Conclusions: (1) The profile of maternal plasma concentrations of fetuin-A over time (GA) in patients who develop PE is different from that of normal pregnant women; (2) the rate of change of maternal plasma concentrations of fetuin-A is positive (increases over time) in the midtrimester of normal pregnancy, and negative (decreases over time) in patients who subsequently develop PE; (3) at the time of diagnosis, the maternal plasma fetuin-A concentration is lower in patients with preterm PE than in those with a normal pregnancy outcome; however, such differences were not demonstrable in patients with term PE.

Placental ischemia induces changes in gene expression in chorionic tissue

Preeclampsia is a serious and common hypertensive complication of pregnancy, affecting ~5 to 8 % of pregnancies. The underlying cause of preeclampsia is believed to be placental ischemia, which causes secretion of pathogenic factors into the maternal circulation. While a number of these factors have been identified, it is likely that others remain to be elucidated. Here, we have utilized a relevant preclinical rodent model of placental ischemia-induced hypertension, the reduced uterine perfusion pressure (RUPP) model, to determine the effect of chronic placental ischemia on the underlying chorionic tissue and placental villi. Tissue from control and RUPP rats were isolated on gestational day 19 and mRNA from these tissues was subjected to microarray analysis to determine differential gene expression. At a statistical cutoff of p < 0.05, some 2,557 genes were differentially regulated between the two groups. Interestingly, only a small subset (22) of these genes exhibited changes of greater than 50 % versus control, a large proportion of which were subsequently confirmed using qRT-PCR analysis. Network analysis indicated a strong effect on inflammatory pathways, including those involving NF-κB and inflammatory cytokines. Of the most differentially expressed genes, the predominant gene classes were extracellular remodeling proteins, pro-inflammatory proteins, and a coordinated upregulation of the prolactin genes. The functional implications of these novel factors are discussed.

Perindopril treatment promote left ventricle remodeling in patients with heart failure screened positive for autoantibodies against angiotensin II type 1 receptor

Background

Autoantibodies specific to the angiotensin II type I receptor (anti-AT₁-AR) have been implicated in the pathology of congestive heart failure (CHF). Anti-AT₁-AR may be associated with left ventricular function in CHF patients treated with perindopril.

Methods

Synthetic angiotensin II type 1 receptor (AT₁-R) peptides served as the target antigen. ELISA was used to screen the sera of 156 CHF patients, which were divided into positive and negative groups based on their anti-AT₁-AR reactivity. Echocardiography and a 6-minute walk test were performed at baseline and after one year of perindopril therapy. The end-point events were compared over a 5-year follow-up.

Results

Final analysis covered 138 patients, including 82 positive and 56 negative. The frequency and geometric mean titre of anti-AT₁-AR were significantly lower in the positive group after one year of treatment (all P < 0.01, from 100% to 73.2% and from 1:125.3 ± 1.0 to 1:69.2 ± 1.1). Of these, 22 patients showed no antibodies. Both groups showed improvement in left ventricular end-diastole, end-systolic dimensions, ejection fraction, and a 6-minute walk test by perindopril in combination with standard treatment regime for one year (all P < 0.01). However, the 82 patients positive for anti-AT₁-AR showed more pronounced improvement than the 56 negative patients (all P < 0.05). However, after 5 years of follow-up, the rate of all causes and cardiovascular mortality attributable to any cause and the re-hospitalisation rate showed no significant differences between the two groups (all P > 0.05).

Conclusions

Perindopril treatment significantly decreased the frequency and geometric mean titre in patients positive for anti-AT₁-AR, even to complete ablation. These patients showed greater improvement in left ventricular remodeling and heart function than negative that in patients after one year of perindopril treatment in combination with standard treatment, but no significant differences in endpoint events were observed in the following 5 years. Anti-AT₁-AR might be a useful biomarker of over-activation of the renin-angiotensin-aldosterone system for clinical medication.

A complicated role for the renin-angiotensin system during pregnancy: highlighting the importance of drug discovery

INTRODUCTION

Blood pressure management is recommended to avoid maternal cerebrovascular or cardiovascular compromise during pregnancy. Current antihypertensive treatment during pregnancy with positive safety profiles includes labetalol, hydralazine, methyldopa and nifedipine.

AREAS COVERED

Many earlier animal and human studies indicate that angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs) are associated with fetopathy; therefore, these drugs are contraindicated during pregnancy, especially if these medications were taken during the second and third trimesters. The role of the RAS is quite complex, with fetal development heavily dependent on its appropriate expression and function. New findings indicate that the placental unit expresses its own RAS in order to regulate angiogenesis. Multiple studies have shown that women with abnormal uterine doppler sonography produce an agonistic autoantibody to the angiotensin I receptor, implicating a role for RAS function and regulation in abnormal pregnancies. Importantly, interruption of a normal RAS compromises fetal development.

EXPERT OPINION

Traditional medications that inhibit components of RAS for long-term hypertension control are not appropriate for use before or during pregnancy. Further study and drug discovery are needed to find alternative pathways for treatment of hypertensive disorders when pregnancy is present or a possibility.

High viral load and elevated angiogenic markers associated with increased risk of preeclampsia among women initiating highly active antiretroviral therapy in pregnancy in the Mma Bana study, Botswana

BACKGROUND

Risk factors associated with preeclampsia in HIV-infected women remain largely unknown. Systemic angiogenic imbalance contributes to preeclampsia in HIV-uninfected women, but changes in angiogenic markers after highly active antiretroviral therapy (HAART) initiation have not been studied.

METHODS

The Mma Bana study randomized 560 HIV-infected, HAART-naive pregnant women with CD4 counts ≥ 200 cells per cubic millimeter between 26 and 34 weeks gestation to lopinavir/ritonavir/zidovudine/lamivudine or abacavir/zidovudine/lamivudine. Another 170 participants with CD4 counts less than 200 cells per cubic millimeter initiated nevirapine/zidovudine/lamivudine between 18 and 34 weeks gestation. Characteristics of 11 women who developed preeclampsia were compared with the remaining 722 Mma Bana participants who delivered using logistic regression. Plasma samples drawn at HAART initiation and 1 month later from 60 women without preeclampsia and at HAART initiation for all 11 preeclamptic women were assayed for placental growth factor (PlGF) and soluble FMS toll-like tyrosine kinase-1 (sFlt-1).

RESULTS

Pre-HAART viral load greater than 100,000 copies per milliliter was associated with preeclampsia (odds ratio: 5.8, 95% confidence interval: 1.8 to 19.4, P = 0.004). Median pre-HAART PlGF level was lower and sFlt-1 was higher in women who developed preeclampsia vs those who did not (130 vs 992 pg/mL, P = 0.001; 17.5 vs 9.4 pg/mL, P = 0.03, respectively). In multivariate analysis, PlGF and viral load remained significantly associated with preeclampsia. No significant changes in angiogenic factors were noted after 1 month of HAART treatment among non-preeclamptic women.

CONCLUSIONS

Pre-HAART viral load greater than 100,000 copies per milliliter and PlGF predicted preeclampsia among women starting HAART in pregnancy. Among non-preeclamptic women, HAART treatment did not significantly alter levels of PlGF or sFlt-1 after 1 month of treatment.

Angiotensin II type I receptor agonistic autoantibody-induced apoptosis in neonatal rat cardiomyocytes is dependent on the generation of tumor necrosis factor-α

Angiotensin II type I receptor agonistic autoantibodies (AT1-AA) are related to pre-eclampsia and hypertension and have a direct effect of stimulating the production of tumor necrosis factor-alpha (TNF-α) in the placenta. TNF-α is a known mediator of apoptosis. However, few studies have reported the role of TNF-α and its relationship within AT1-AA-induced apoptosis of cardiomyocytes. In this study, neonatal rat cardiomyocytes were treated with various concentrations of AT1-AA. The apoptosis of neonatal rat cardiomyocytes was determined using TUNEL assay and flow cytometry. The level of secreted TNF-α was measured by enzyme-linked immunosorbent assay, and caspase-3 activity was measured by a fluorogenic protease assay kit. AT1 receptor blockade and TNF inhibitor were added to determine whether they could inhibit the apoptotic effect of AT1-AA. Results showed that AT1-AA induced the apoptosis of neonatal rat cardiomyocytes in a dose-dependent and time-dependent manner. AT1-AA increased TNF secretion and caspase-3 activities. AT1 receptor blockade completely abrogated AT1-AA-induced TNF-α secretion, caspase-3 activation, and cardiomyocyte apoptosis. TNF-α receptor inhibitor significantly attenuated AT1-AA-induced neonatal rat cardiomyocyte apoptosis. AT1-AA in the plasma of pre-eclamptic patients promoted neonatal rat cardiomyocyte apoptosis through a TNF-caspase signaling pathway.

Cytochrome P450 subfamily 2J polypeptide 2 expression and circulating epoxyeicosatrienoic metabolites in preeclampsia

BACKGROUND

Preeclampsia is a multisystem disorder of pregnancy, originating in the placenta. Cytochrome P450 (CYP)-dependent eicosanoids regulate vascular function, inflammation, and angiogenesis, which are mechanistically important in preeclampsia.

METHODS AND RESULTS

We performed microarray screening of placenta and decidua (maternal placenta) from 25 preeclamptic women and 23 control subjects. The CYP subfamily 2J polypeptide 2 (CYP2J2) was upregulated in preeclamptic placenta and decidua. Reverse-transcription polymerase chain reaction confirmed the upregulation, and immunohistochemistry localized CYP2J2 in trophoblastic villi and deciduas at 12 weeks and term. The CYP2J2 metabolites, 5,6-epoxyeicosatrienoic acid (EET), 14,15-EET, and the corresponding dihydroxyeicosatrienoic acids, were elevated in preeclamptic women compared with controls in the latter two thirds of pregnancy and after delivery. Stimulating a trophoblast-derived cell line with the preeclampsia-associated cytokine tumor necrosis factor-α enhanced CYP2J2 gene and protein expression. In 2 independent rat models of preeclampsia, reduced uterine-perfusion rat and the transgenic angiotensin II rat, we observed elevated EET, dihydroxyeicosatrienoic acid, and preeclamptic features that were ameliorated by the CYP epoxygenase inhibitor N-(methylsulfonyl)-2-(2-propynyloxy)-benzenehexanamide (MsPPOH). Uterine arterial rings of these rats also dilated in response to MsPPOH. Furthermore, 5,6-EET could be metabolized to a thromboxane analog. In a bioassay, 5,6-EET increased the beating rate of neonatal cardiomyocytes. Blocking thromboxane synthesis reversed that finding and also normalized large-conductance calcium-activated potassium channel activity.

CONCLUSIONS

Our data implicate CYP2J2 in the pathogenesis of preeclampsia and as a potential candidate for the disturbed uteroplacental remodeling, leading to hypertension and endothelial dysfunction.

CD19 + CD5 + Cells as Indicators of Preeclampsia

Preeclampsia is a devastating pregnancy-associated disorder affecting 5% to 8% of pregnant women worldwide. It emerges as an autoimmune-driven disease, and, among others, the autoantibodies against angiotensin type 1 receptor II have been proposed to account for preeclampsia symptoms. Despite much attention focused on describing autoantibodies associated with preeclampsia, there is no clue concerning the cell population producing them. CD19 + CD5 + B-1a B cells constitute the main source of natural and polyreactive antibodies, which can be directed against own structures. Here, we aimed to identify the B-cell subpopulation responsible for autoantibody production during preeclampsia and to study their regulation, as well as their possible use as markers for the disease. The frequency of CD19 + CD5 + cells in peripheral blood of preeclamptic patients is dramatically increased compared with normal pregnant women as analyzed by flow cytometry. This seems to be driven by the high human chorionic gonadotropin levels present in the serum and placenta supernatant of preeclamptic patients versus normal pregnant women. Not only ≈95% of CD19 + CD5 + cells express the human chorionic gonadotropin receptor, but these cells also expand on human chorionic gonadotropin stimulation in a lymphocyte culture. Most importantly, isolated CD19 + CD5 + cells produce autoantibodies against angiotensin type 1 receptor II, and CD19 + CD5 + cells were further detected in the placenta of preeclamptic but not of normal pregnancies where barely B cells are present. Our results identify a B-cell population able to produce pregnancy-pathological autoantibodies as possible markers for preeclampsia, which opens vast diagnostic and therapeutic applications.

Changes in cardiac structure and function in rats immunized by angiotensin type 1 receptor peptides

Angiotensin II (Ang II) is known to induce cardiomyocyte hypertrophy by activating the Ang II type 1 (AT1) receptor. Some studies have demonstrated that the autoantibodies against angiotensin AT1 receptor (AT1-AAs) cause functional effects, which is similar to those observed for the natural agonist Ang II. In this study, we investigated the effects of AT1-AAs on cardiomyocytes' structure and function. Male Wistar rats were immunized with synthetic peptides corresponding to the second extracellular loop of AT1 receptor and Freund's adjuvant. The titers of AT1-AAs in rat serum were detected by enzyme-linked immunosorbent assay every week. Hemodynamic analysis and heart weight (HW) indices were measured on the 4th and 8th months after initial immunization, respectively. Cultured neonatal rat cardiomyocytes were used to observe the hypertrophic effects of AT1-AAs. Results showed that systolic blood pressure and heart rate were significantly increased, the titers of AT1-AAs were also increased after 4 weeks of initial immunization. Compared with control group, the HW/body weight (BW) and left ventricular weight/BW of immunized rats were increased significantly and cardiac function was enhanced compensatively. The cultured neonatal rat cardiomyocytes respond to AT1-AAs stimulation with increased (3)H-leucine incorporation and cell surface area in a dose-dependent manner. These results suggest that the AT1-AAs have an agonist effect similar to Ang II in hypertrophy of cardiomyocytes in vivo and in vitro. AT1-AAs are involved in the pathogenesis of cardiovascular diseases and hypertension.

The kidney in normal pregnancy and preeclampsia

Complicating up to 8% of pregnancies, preeclampsia is, in fact, the most common glomerular disease worldwide. In this article, we review the effect of normal pregnancy on the kidney as well as the role of the kidney in preeclampsia. We discuss blood pressure in pregnancy and preeclampsia, followed by the physiology of hyperfiltration in normal pregnancy as well as the pathophysiology of hypofiltration and proteinuria in preeclampsia. Recent studies have suggested that the clinical syndrome of preeclampsia, which recovers rapidly after delivery of the placenta, is caused by impaired vascular endothelial growth factor signaling that disturbs the status of vascular dilatation as well as the symbiosis between the glomerular endothelium and the podocytes. Finally, we discuss the intriguing association between chronic kidney disease (CKD) and preeclampsia. We hypothesize that the imbalance between angiogenic and anti-angiogenic factors, which may be common to both preeclampsia and CKD, might explain why CKD predisposes pregnant women to develop preeclampsia.

Stimulating autoantibodies against the angiotensin II type 1 receptor are not associated with preeclampsia in Mexican-Mestizo women

OBJECTIVE

Recent studies have demonstrated that stimulating autoantibodies against the angiotensin II type 1 receptor (AT1R-AA) are frequently detected in the sera from women with preeclampsia, suggesting that they may play an important role in the pathogenesis of this disease. Nevertheless, the real clinical significance of AT1R-AA in preeclampsia is still controversial due to the paucity of appropriate large comparative studies that require cumbersome, time-consuming, and expensive bioassays to detect AT1R-AA. At present, the prevalence of AT1R-AA in large populations of preeclamptic women is unknown. In an attempt to clarify this issue, we assessed the presence and potential clinical significance of AT1R-AA in a large population of Mexican-Mestizo women with preeclampsia.

METHODS

Using a cross-sectional design, we determined the presence of AT1R-AA in 525 pregnant women (99 healthy pregnant, 96 with mild preeclampsia, and 330 with severe preeclampsia) by a new bioassay that employs human embryonic kidney-293 cells stably expressing the recombinant rat AT1R and a 4x nuclear factor of activated T cells responsive luciferase construct as well as by the reference assay in Chinese hamster ovary (CHO) cells.

RESULTS

We found that IgG obtained from sera of healthy pregnant women and patients with preeclampsia were unable to induce luciferase activity in both HEK-293 and Chinese hamster ovary cells expressing functional angiotensin II receptor type 1. Therefore, the frequency of patients with AT1R-AA was zero.

CONCLUSION

We concluded that in Mexican-Mestizo women agonistic AT1R-AA cannot be invoked as a factor involved in the pathogenesis of preeclampsia. Whether these findings can be attributed to genetic or environmental factors remains unknown.

Aetiology and physiopathology of preeclampsia and related forms

Preeclampsia, a pregnancy-specific syndrome characterized by hypertension, proteinuria and oedema, resolves on placental delivery. Its pathogenesis is thought to be associated to a hypoxic placenta. Placental hypoxia is responsible for the maternal vascular dysfunction via the increased placental release of anti-angiogenic factors such as soluble flt1 and endoglin. These soluble receptors bind VEGF, PLGF and TGFbeta1 and 3 in the maternal circulation, causing endothelial dysfunction in many maternal tissues. Despite these recent and important new molecular findings, it is important to consider that normal pregnancy is also characterized by systemic inflammation, oxidative stress and alterations in levels of angiogenic factors and vascular reactivity. Both the placenta and maternal vasculatures are major sources of reactive oxygen and nitrogen species which can produce powerful pro-oxidants that covalently modify proteins and alter vascular function in preeclampsia. Finally, the recent demonstration of activating auto-antibodies to the Angiotensin 1 receptor that experimentally play a major pathogenic role in preeclampsia further indicates the pleiotropism of aetiologies of this condition.

Placental ischemia and cardiovascular dysfunction in preeclampsia and beyond: making the connections

Hypertensive disorders of pregnancy continue to be a significant source of maternal and fetal morbidity and mortality, and recent evidence suggests that the incidence of preeclampsia (PE) is increasing. Recent epidemiological studies indicate that the effects of PE may persist long after pregnancy, in both the mother and the offspring, as increased incidence of cardiovascular disease. The last decade has produced new insights into the pathogenesis of PE. The initiating event in PE appears to be impaired placental perfusion and subsequent placental ischemia, which results in the elaboration of numerous factors. Factors such as soluble fms-like tyrosine kinase-1, soluble endoglin and the angiotensin II type-1 receptor autoantibodies contribute to maternal endothelial and cardiovascular dysfunction, marked by increased reactive oxygen species and decreased bioavailable VEGF, nitric oxide and prostacyclin. However, the importance of the various endothelial and humoral factors that mediate these changes during PE remain to be elucidated.

Angiotensin receptor agonistic autoantibodies induce pre-eclampsia in pregnant mice

Pre-eclampsia affects approximately 5% of pregnancies and remains a leading cause of maternal and neonatal mortality and morbidity in the United States and the world. The clinical hallmarks of this maternal disorder include hypertension, proteinuria, endothelial dysfunction and placental defects. Advanced-stage clinical symptoms include cerebral hemorrhage, renal failure and the HELLP (hemolysis, elevated liver enzymes and low platelets) syndrome. An effective treatment of pre-eclampsia is unavailable owing to the poor understanding of the pathogenesis of the disease. Numerous recent studies have shown that women with pre-eclampsia possess autoantibodies, termed AT(1)-AAs, that bind and activate the angiotensin II receptor type 1a (AT(1) receptor). We show here that key features of pre-eclampsia, including hypertension, proteinuria, glomerular endotheliosis (a classical renal lesion of pre-eclampsia), placental abnormalities and small fetus size appeared in pregnant mice after injection with either total IgG or affinity-purified AT(1)-AAs from women with pre-eclampsia. These features were prevented by co-injection with losartan, an AT(1) receptor antagonist, or by an antibody neutralizing seven-amino-acid epitope peptide. Thus, our studies indicate that pre-eclampsia may be a pregnancy-induced autoimmune disease in which key features of the disease result from autoantibody-induced angiotensin receptor activation. This hypothesis has obvious implications regarding pre-eclampsia screening, diagnosis and therapy.

Pathophysiology of hypertension during preeclampsia: linking placental ischemia with endothelial dysfunction

Studies over the last decade have provided exciting new insights into potential mechanisms underlying the pathogenesis of preeclampsia. The initiating event in preeclampsia is generally regarded to be placental ischemia/hypoxia, which in turn results in the elaboration of a variety of factors from the placenta that generates profound effects on the cardiovascular system. This host of molecules includes factors such as soluble fms-like tyrosine kinase-1, the angiotensin II type 1 receptor autoantibody, and cytokines such as tumor necrosis factor-alpha, which generate widespread dysfunction of the maternal vascular endothelium. This dysfunction manifests as enhanced formation of factors such as endothelin, reactive oxygen species, and augmented vascular sensitivity to angiotensin II. Alternatively, the preeclampsia syndrome may also be evidenced as decreased formation of vasodilators such as nitric oxide and prostacyclin. Taken together, these alterations cause hypertension by impairing renal pressure natriuresis and increasing total peripheral resistance. Moreover, the quantitative importance of the various endothelial and humoral factors that mediate vasoconstriction and elevation of arterial pressure during preeclampsia remains to be elucidated. Thus identifying the connection between placental ischemia/hypoxia and maternal cardiovascular abnormalities in hopes of revealing potential therapeutic regimens remains an important area of investigation and will be the focus of this review.

Oxidant stress, immune dysregulation, and vascular function in type I diabetes

Although high glucose is an important contributor to diabetic vasculopathies, complications still occur in spite of tight glycemic control, suggesting that some critical event prior to or concurrent with hyperglycemia may contribute to early vascular changes. Utilizing previously published and new experimental evidence, this review will discuss how prior to the hyperglycemic state, an imbalance between oxidants and antioxidants may contribute to early vascular dysfunction and set in motion proinflammatory insults that are further amplified as the diabetes develops. This imbalance results from the resetting of the equilibrium between vessel superoxide/H(2)O(2) production and/or decreased antioxidant defenses. Such an imbalance may cause endothelial dysfunction, characterized by abnormal endothelium-dependent vasoreactivity, as the first sign of blood vessel damage, followed by morphological changes of the vessel wall and inflammation. As such, increased oxidant stress in preglycemic states may be a critically central initiating event that underlies the pathogenesis of life-threatening vascular diseases in autoimmune diabetes. This review focuses on the relationship between oxidative stress, immune dysregulation, and vascular injury in type 1 diabetes, and how the discovery of novel pathways of vascular disease in nonobese diabetic mice may direct future studies in patients with type 1 diabetes.

Effects of autoantibodies removed by immunoadsorption from patients with dilated cardiomyopathy on neonatal rat cardiomyocytes

INTRODUCTION

Immunoadsorption has been shown to improve cardiac performance and reduce mortality in patients with dilated cardiomyopathy. In this study, the underlying mechanism for these beneficial effects was investigated in cultured rat cardiomyocytes.

METHODS AND RESULTS

Immunoadsorption was performed in patients with dilated cardiomyopathy (n=7). Antibody-induced complement-dependent cytotoxicity was investigated by colorimetric MTT. Autoantibodies against the beta(1)-adrenoceptor were detected by ELISA and purified. Column eluent from six patients exhibited a cytotoxic effect, three patients were positive for the beta(1)-adrenoceptor autoantibodies. The purified autoantibodies were able to visualize the beta(1)-adrenoceptors by immunocytofluorescence on rat cardiomyocytes, and also displayed partial agonist properties and induced a positive chronotropic effect, which were blocked by the beta(1)-selective antagonist bisoprolol and the peptide corresponding to the beta(1)-adrenoceptor. Column eluent from one patient induced apoptosis in nick end labelling test (8.1+/-1.7% vs. 2.9+/-1.2% in control, p<0.05).

CONCLUSION

Autoantibodies removed by immunoadsorption from patients with dilated cardiomyopathy have a pathophysiological role, as shown by the complement-dependent cytotoxicity and chronotropic action on rat cardiomyocytes. This implies that removal of circulating autoantibodies might be part of the underlying mechanism for improved cardiac function.

RETRACTED: Transcriptional regulation of the AT1 receptor gene in immortalized human trophoblast cells

Studies investigating the mechanisms that govern the expression of the human angiotensin II (Ang II) type 1 receptor (hAT1R) gene have progressed slowly due to the lack of human cell lines that express the AT1R. Recently, however, an immortalized human trophoblast cell line (HTR-8/SVNeo) was demonstrated to respond to Ang II. Therefore, we utilized this cell line to characterize the AT1R expressed on the cell surface and to investigate the mechanisms by which the hAT1R gene is regulated in these cells. HTR-8/SVNeo cells were shown to express functional high affinity AT1Rs having a Bmax value of 114+/-11 fmol/mg protein and a Kd value of 0.14+/-0.1 nM. Additionally, Ang II-induced IP3 production was mediated via the AT1R. Deletional analysis of the hAT1R promoter localized a major basal regulatory sequence within the -105 to -79 bp region, relative to the transcription start site, in HTR-8/SVNeo cells. Electrophoretic mobility shift assay (EMSA) and Chromatin Immunoprecipitation (ChIP) assay demonstrated that the transcription factors, Sp1 and Sp3, interact with this region of the hAT1R promoter in vitro and in vivo. Taken together, our data demonstrate that HTR-8/SVNeo cells express functional AT1Rs and that basal level expression of this gene is regulated, in part, by Sp1 and Sp3 in this cell line.

Animal models of preeclampsia

There have been many attempts to produce animal models that mimic the hypertensive disorders of pregnancy, especially preeclampsia, but most are incomplete when compared to the full spectrum of the human disease. This review assesses a number of these models, organized according to the investigators attempt to focus on a specific pathogenic mechanism believed to play a role in the human disease. These mechanisms include uterine ischemia, impairments in the nitric oxide system, insulin resistance, overactivity of the autonomic nervous and/or renin-angiotensin systems, activation of a systemic inflammatory response, and most recently, activation of circulating proteins that interfere with angiogenesis. In addition a model of renal disease that mimics superimposed preeclampsia is discussed. Defining these animal models should help in our quest to understand the cause, as well as to test preventative and therapeutic strategies in the management of these hypertensive disorders of pregnancy.