Agonistic antibodies directed at the angiotensin II, AT1 receptor in preeclampsia

Prepregnancy physiology and subsequent preterm preeclampsia

BACKGROUND

Preeclampsia is a common pregnancy complication with debated etiology.

OBJECTIVE

To evaluate the contribution of prepregnancy physiology, biochemistry, and anthropometrics to the subsequent development of preterm preeclampsia.

STUDY DESIGN

One hundred twenty-four participants were recruited through open recruitment and targeted mailings. Participants included 81 nulliparous women and 43 with a history of preterm preeclampsia. We characterized cardiovascular function, metabolic profile, and body composition in 100 nonpregnant women who went on to subsequent pregnancy. Measures included plasma volume, baseline cardiovascular function and cardiovascular response to volume challenge, body composition, and circulating biochemical measures. Pregnancy outcome was obtained through chart review. Prepregnancy metrics for women who developed preterm preeclampsia were compared with measurements for those who did not, with adjustment for a history of prior preterm preeclampsia. Logistic regression modeling was used to identify the strongest prepregnancy factors associated with preterm preeclampsia.

RESULTS

Pregnancy outcomes included 11 women with preterm preeclampsia, 7 women with term preeclampsia, 20 women with other hypertension affecting their pregnancy, and 62 with uncomplicated pregnancies. We observed no difference in maternal age, study cycle day, lean body mass, uterine hemodynamics, or flow-mediated dilation across groups. Women with preterm preeclampsia had greater android fat content 3215±1143 vs 1918±1510 g (P=.002), faster supine pulse, 77±7 vs 67±10 beats per minute (P=.001), higher supine diastolic blood pressure 82±6 vs 68±6 mmHg (P<.001), increased cardiac output 5.6±1.1 vs 4.6±1 L/min (P=.002), faster aortic-popliteal pulse wave velocity 4.5±0.7 vs 3.8±0.5 m/sec (P<.001), and exaggerated cardiac output response to volume challenge 20±9 vs 9±12 L/min (P=.002) compared to those with other pregnancy outcomes. Women who developed preterm preeclampsia also had reduced renal vascular resistance index 0.86±0.08 vs 0.97±0.12 (P=.005) compared with other pregnancy outcomes when assessed prior to pregnancy. Women with subsequent preterm preeclampsia had higher serum c-reactive protein 10.7±12.5 vs 4.1±5.8 mg/mL (P=.003) and greater insulin resistance, as assessed by Homeostatic Model Assessment for Insulin Resistance calculation 2.2±1.1 vs 1.2±0.9 (P<.001).

CONCLUSION

Prepregnancy physiology is linked to subsequent preterm preeclampsia. The same factors associated with metabolic syndrome are more prominent in patients who develop preterm preeclampsia than those who do not, including increased vessel stiffness, low vascular compliance, high cardiac output, reduced renal vascular resistance index, insulin resistance, and increased android fat, all consistent with subclinical features of the metabolic syndrome.

Neurodevelopmental Disruptions in Children of Preeclamptic Mothers: Pathophysiological Mechanisms and Consequences

Preeclampsia (PE) is a multisystem disorder characterized by elevated blood pressure in the mother, typically occurring after 20 weeks of gestation and posing risks to both maternal and fetal health. PE causes placental changes that can affect the fetus, particularly neurodevelopment. Its key pathophysiological mechanisms encompass hypoxia, vascular and angiogenic dysregulation, inflammation, neuronal and glial alterations, and disruptions in neuronal signaling. Animal models indicate that PE is correlated with neurodevelopmental alterations and cognitive dysfunctions in offspring and in humans, an association between PE and conditions such as cerebral palsy, autism spectrum disorder, attention deficit hyperactivity disorder, and sexual dimorphism has been observed. Considering the relevance for mothers and children, we conducted a narrative literature review to describe the relationships between the pathophysiological mechanisms behind neurodevelopmental alterations in the offspring of PE mothers, along with their potential consequences. Furthermore, we emphasize aspects pertinent to the prevention/treatment of PE in pregnant mothers and alterations observed in their offspring. The present narrative review offers a current, complete, and exhaustive analysis of (i) the pathophysiological mechanisms that can affect neurodevelopment in the children of PE mothers, (ii) the relationship between PE and neurological alterations in offspring, and (iii) the prevention/treatment of PE.

Regulation of vascular angiotensin II type 1 and type 2 receptor and angiotensin-(1-7)/MasR signaling in normal and hypertensive pregnancy

Normal pregnancy (Norm-Preg) is associated with a slight reduction in blood pressure (BP) and decreased BP response to vasoconstrictor stimuli such as angiotensin II (Ang II), although the renin-angiotensin-aldosterone system (RAAS) is upregulated. Preeclampsia (PE) is a complication of pregnancy manifested as hypertension-in-pregnancy (HTN-Preg), and dysregulation of angiotensin biosynthesis and signaling have been implicated. Ang II activates vascular Ang II type-1 receptor (AT1R) and Ang II type-2 receptor (AT2R), while angiotensin-(1-7) promotes Ang-(1-7)/MasR signaling. The role of AT1R in vasoconstriction and the activated cellular mechanisms are well-characterized. The sensitivity of vascular AT1R to Ang II and consequent activation of vasoconstrictor mechanisms decrease during Norm-Preg, but dramatically increase in HTN-Preg. Placental ischemia in late pregnancy could also initiate the release of AT1R agonistic autoantibodies (AT1AA) with significant impact on endothelial dysfunction and activation of contraction pathways in vascular smooth muscle including [Ca2+]c and protein kinase C. On the other hand, the role of AT2R and Ang-(1-7)/MasR in vascular relaxation, particularly during Norm-Preg and PE, is less clear. During Norm-Preg, increases in the expression/activity of vascular AT2R and Ang-(1-7)/MasR promote the production of endothelium-derived relaxing factors such as nitric oxide (NO), prostacyclin and endothelium-derived hyperpolarizing factor leading to generalized vasodilation. Aortic segments of Preg rats show prominent endothelial AT2R staining and increased relaxation and NO production in response to AT2R agonist CGP42112A, and treatment with AT2R antagonist PD123319 enhances phenylephrine-induced contraction. Decreased vascular AT2R and Ang-(1-7)/MasR expression and receptor-mediated mechanisms of vascular relaxation have been suggested in HTN-Preg animal models, but their role in human PE needs further testing. Changes in angiotensin-converting enzyme-2 (ACE2) have been observed in COVID-19 patients, and whether ACE2 influences the course of COVID-19 viral infection/immunity in Norm-Preg and PE is an intriguing area for research.

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.

Abnormal development of cerebral arteries and veins in offspring of experimentally preeclamptic rats: Potential role in perinatal stroke

Preeclampsia, a hypertensive disorder of pregnancy, complicates up to 10 % of all pregnancies and increases the risk for perinatal stroke in offspring. The mechanism of this increase is unknown, but may involve vascular dysfunction. The goal of this study was to evaluate the effect of experimental preeclampsia (ePE) on cerebrovascular function in offspring to eludciate a possible mechanism for this association. Dams were fed a high cholesterol diet beginning on day 7 of gestation to induce experimental preeclampsia. Middle cerebral arteries (MCA) and the Vein of Galen (VoG) were isolated from pups from ePE dams and compared to pups from normal pregnant (NP) dams at postnatal days 16, 23, and 30 and studied pressurized in an arteriograph chamber. Markers of inflammation and oxidative stress were measured in serum. Our results suggest altered structure and function in both MCA and VoG of ePE pups. We also found evidence of systemic inflammation and oxidative stress in ePE pups. These findings provide a potential link between preeclampsia and the occurrence or severity of perinatal stroke.

CD4+ T cells cause renal and placental mitochondrial oxidative stress as mechanisms of hypertension in response to placental ischemia

The reduced uterine perfusion pressure (RUPP) rat model and normal pregnant (NP) rat recipients of RUPP CD4+ T cells recapitulate many characteristics of preeclampsia such as hypertension and oxidative stress. We have shown an important hypertensive role for natural killer (NK) cells to cause mitochondrial dysfunction in RUPP rats; however, the role for RUPP CD4+ T cells to stimulate NK cells is unknown. Therefore, we hypothesized that RUPP-induced CD4+ T cells activate NK cells to cause mitochondrial dysfunction/reactive oxygen species (ROS) as mechanisms of hypertension during pregnancy. We tested our hypothesis by adoptive transfer of RUPP CD4+ T cells into NP rats or by inhibiting the activation of RUPP CD4+ T cells with Orencia (abatacept) and examining hypertension, NK cells, and mitochondrial function. RUPP was performed on gestation day (GD) 14, and splenic CD4+ T cells were isolated on GD 19 and injected into NP rats on GD 13. In a separate group of rats, Orencia was infused and the RUPP procedure was performed. Mean arterial pressure and placental and renal mitochondrial ROS increased in RUPP (n = 7, P < 0.05) and NP + RUPP CD4+ T-cell recipients (n = 13, P < 0.05) compared with control NP (n = 7) and NP + NP CD4+ T-cell recipients (n = 5) but was reduced with Orencia (n = 13, P < 0.05). Placental and renal respiration was reduced in RUPP (n = 6, P < 0.05) and NP + RUPP CD4+ T-cell recipients (n = 6, state 3 P < 0.05) compared with NP (n = 5) and NP + NP CD4+ T-cell recipients (n = 5) but improved with Orencia (n = 9, n = 8 P < 0.05). These data indicate that CD4+ T cells, independent of NK cells, cause mitochondrial dysfunction/ROS contributing to hypertension in response to placental ischemia during pregnancy.

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.

Preeclampsia: Pathophysiology and management

Preeclampsia is a pregnancy-related multisystem disorder, frequently encountered pregnancy-related medical complications next to gestational diabetes mellitus. It is the onset of hypertension during pregnancy. The preeclampsia can be of two types, placental or maternal preeclampsia. Among these two types former, i.e., placental preeclampsia is more severe than the latter. According to the recent survey by National Health Portal of India, the incidence of preeclampsia is about 8-10 % among pregnant women. Though our understanding of preeclampsia has improved in recent years, the development and interpretation of the clinical tests remain difficult for preeclampsia. Hence, we have made an attempt to understand the pathophysiology, associated conditions/consequences, treatment and management/prevention of the condition in this review.

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 magnesium in different inflammatory diseases

Magnesium deficiency (MgD) can cause inflammation in human body. The known mechanisms of inflammation caused by MgD include activation of phagocytic cells, opening of calcium channels, activation of the N-methyl-D-aspartate (NMDA) receptor, and activation of nuclear factor (NF)-κB. In addition, MgD causes systemic stress response through neuroendocrinological pathways. The inflammation caused by MgD can result in pro-atherogenic changes in the metabolism of lipoproteins, endothelial dysfunction, and high blood pressure. Studies suggest that magnesium may play an important role in the pathophysiology of some inflammatory diseases. Several clinical trials and laboratory studies have been done on the functional role of magnesium. In this study, we review some inflammatory diseases, in which the magnesium has a role in their pathophysiology. Among these diseases, diabetes, asthma, preeclampsia, atherosclerosis, heart damage, and rheumatoid arthritis have been highlighted.

Doxazosin attenuates renal matrix remodeling mediated by anti-α1-adrenergic receptor antibody in a rat model of diabetes mellitus

Diabetic nephropathy is a major complication of diabetes mellitus (DM). Recent studies suggest that immunological mechanisms have a key role in the pathogenesis of DM, therefore these mechanisms may be important targets for diabetes therapy. The present study evaluated the effects of anti-α₁-adrenergic receptor antibody (α₁-R Ab) mediation and doxazosin treatment in a rat model of DM. It was observed that levels of 24-h urinary protein, serum creatinine and transforming growth factor-β₁ in DM were significantly increased after α₁-R Ab mediation (all P<0.05). In addition, electron microscopy identified severe damage in the renal tissue microstructures of DM rats following α₁-R Ab mediation, while only mild abnormalities were observed in that of healthy rats mediated with α₁-R Ab and of untreated DM rats. No marked abnormalities were observed in the renal tissue of healthy blank controls. Furthermore, in DM rats treated with α₁-R Ab mediation + doxazosin intervention, the expression of TGF-β₁ significantly decreased, and renal functions and renal matrix remodeling were significantly improved, relative to untreated DM controls (P<0.01). These results suggest that α₁-R Ab may be involved in renal matrix remodeling during DM, and that kidney protection during DM may be achieved through treatment with corresponding receptor antagonists.

Proliferation of endogenous regulatory T cells improve the pathophysiology associated with placental ischaemia of pregnancy

PROBLEM

Preeclampsia (PE) is associated with inflammation and decreased Treg cells and IL-10. The reduced uterine perfusion pressure (RUPP) rat model of PE exhibits these characteristics, and we hypothesized that induction of endogenous Tregs by a specific stimulus (CD28 superagonistic monoclonal antibody) would reduce inflammation, vasoactive factors, and hypertension in RUPP rats.

METHOD OF STUDY

RUPP was performed at gestation day (GD) 14; CD28 superagonist was administered intraperitoneally GD15; GD18 carotid catheters were inserted, and GD19 MAP and pup weight, blood, and tissues were collected.

RESULTS

MAP (mmHg) in NP rats was 99±5 and 122±2 in RUPPs and was 111±1 mmHg in RUPP+SA. Circulating Tregs were 6±2% in NP rats and 0.77±0.49% in RUPP rats but increased to 11± 3% in RUPP+SA rats. Circulating IL-6 and IL-2 were decreased while IL-10 and TGF-B were significantly increased in RUPP+SA compared to RUPP controls. Vasoactive pathways such as ET-1, AT1-AA, and ROS were all reduced in RUPP+SA compared to RUPP. Pup weight was 2.4±0.05 mg in NP and 1.94±0.062 mg in RUPP and increased to 2.1± 0.05 mg in RUPP+SA.

CONCLUSION

These data suggest that stimulating endogenous Tregs lower factors causing hypertension and can improve fetal weight in response to PE.

Reduced uterine perfusion pressure T-helper 17 cells cause pathophysiology associated with preeclampsia during pregnancy

Preeclampsia is associated with chronic inflammation and an imbalance among T-helper cell subtypes with an increase in T-helper 17 (T_H17) cells. The objective of this study was to determine a role for T_H17s, from the reduced uterine perfusion pressure (RUPP) rat model of preeclampsia, in the etiology of hypertension and chronic inflammation during pregnancy. CD4⁺/CD25^- T cells were isolated from rat spleens, cultured in T_H17 media, and were verified as T_H17s via flow cytometry. On day 12 of gestation, 1×10⁶ T_H17 cells from RUPP rats were adoptively transferred into NP rats, carotid catheters were inserted on day 18, and on day 19, mean arterial pressure (MAP) was recorded, serum and plasma were collected, and oxidative stress and production of agonistic autoantibodies to the ANG II type I receptor (AT₁-AA) were analyzed. MAP increased from 100.3 ± 1.7 mmHg in normal pregnant (NP; n = 17) to 124.8 ± 2.1 mmHg in RUPP (n = 22; P < 0.0001) and to 110.8 ± 2.8 mmHg in NP+RUPP T_H17 (n = 11). Pup weights in NP+RUPP T_H17s were decreased to 1.92 ± 0.09 g from 2.39 ± 0.14 in NP rats (P < 0.01). AT₁-AA significantly increased from 0.1 ± 0.2 beats/min in NP to 15.6 ± 0.7 beats/min in NP+RUPP T_H17s. IL-6 was 22.3 ± 5.7 pg/ml in NP and increased to 60.45 ± 13.8 pg/ml in RUPP (P < 0.05) and 75.9 ± 6.8 pg/ml in NP+RUPP T_H17 rats (P < 0.01). Placental and renal oxidative stress were 238 ± 27.5 and 411 ± 129.9 relative light units·min^-1·mg^-1 in NP and 339 ± 104.6 and 833 ± 331.1 relative light units·min^-1·mg^-1 in NP+RUPP T_H17, respectively. In conclusion, RUPP T_H17 cells induced intrauterine growth restriction and increased blood pressure, AT₁-AA, IL-6, and tissue oxidative stress when transferred to NP rats, indicating a role for autoimmune associated T_H17 cells, to cause much of the pathophysiology associated with preeclampsia.

Agonistic Autoantibodies to the Angiotensin II Type 1 Receptor Enhance Angiotensin II-Induced Renal Vascular Sensitivity and Reduce Renal Function During Pregnancy

Preeclamptic women produce agonistic autoantibodies to the angiotensin II type 1 receptor (AT1-AA) and exhibit increased blood pressure (mean arterial pressure), vascular sensitivity to angiotensin II (ANG II), and display a decrease in renal function. The objective of this study was to examine the renal hemodynamic changes during pregnancy in the presence of AT1-AAs with or without a slow pressor dose of ANG II. In this study, mean arterial pressure was elevated in all pregnant rats treated with ANG II with or without AT1-AA. Glomerular filtration rate was reduced from 1.90±0.16 mL/min in normal pregnant (NP) to 1.20±0.08 in ANG II+AT1-AA rats. Renal blood flow was decreased in ANG II+AT1-AA versus NP rats to 7.4±1.09 versus 15.4±1.75 mL/min. Renal vascular resistance was drastically increased between ANG II+AT1-AA versus NP rats (18.4±2.91 versus 6.4±0.77 mm Hg/mL per minute). Isoprostane excretion was increased by 3.5-fold in ANG II+AT1-AA versus NP (1160±321 versus 323±52 pg/mL). In conclusion, ANG II and AT1-AA together significantly decrease glomerular filtration rate by 37% and renal blood flow by 50% and caused a 3-fold increase in renal vascular resistance and isoprostane levels versus NP rats. These data indicate the importance of AT1-AAs to enhance ANG II-induced renal vasoconstriction and reduce renal function as mechanisms to cause hypertension as observed during preeclampsia.

Identifying immune mechanisms mediating the hypertension during preeclampsia

Preeclampsia (PE) is a pregnancy-associated disorder that affects 5-8% of pregnancies and is a major cause of maternal, fetal, and neonatal morbidity and mortality. Hallmark characteristics of PE are new onset hypertension after 20 wk gestation with or without proteinuria, chronic immune activation, fetal growth restriction, and maternal endothelial dysfunction. However, the pathophysiological mechanisms that lead to the development of PE are poorly understood. Recent data from studies of both clinical and animal models demonstrate an imbalance in the subpopulations of CD4+ T cells and a role for these cells as mediators of inflammation and hypertension during pregnancy. Specifically, it has been proposed that the imbalance between two CD4+ T cell subtypes, regulatory T cells (Tregs) and T-helper 17 cells (Th17s), is involved in the pathophysiology of PE. Studies from our laboratory highlighting how this imbalance contributes to vasoactive factors, endothelial dysfunction, and hypertension during pregnancy will be discussed in this review. Therefore, the purpose of this review is to highlight hypertensive mechanisms stimulated by inflammatory factors in response to placental ischemia, thereby elucidating a role.

The role of inflammation in the pathology of preeclampsia

Preeclampsia (PE) affects 5-7% of all pregnancies in the United States and is the leading cause of maternal and prenatal morbidity. PE is associated with hypertension after week 20 of gestation, decreased renal function and small-for-gestational-age babies. Women with PE exhibit chronic inflammation and production of autoantibodies. It is hypothesized that during PE, placental ischaemia occurs as a result of shallow trophoblast invasion which is associated with an immune imbalance where pro-inflammatory CD4(+) T-cells are increased and T regulatory cells (Tregs) are decreased. This imbalance leads to chronic inflammation characterized by oxidative stress, pro-inflammatory cytokines and autoantibodies. Studies conducted in our laboratory have demonstrated the importance of this immune imbalance in causing hypertension in response to placental ischaemia in pregnant rats. These studies confirm that increased CD4(+) T-cells and decreased Tregs during pregnancy leads to elevated inflammatory cytokines, endothelin (ET-1), reactive oxygen species (ROS) and agonistic autoantibodies to the angiotensin II (Ang II), type 1 receptor (AT1-AA). All of these factors taken together play an important role in increasing the blood pressure during pregnancy. Specifically, this review focuses on the decrease in Tregs, and their associated regulatory cytokine interleukin (IL)-10, which is seen in response to placental ischaemia during pregnancy. This study will also examine the effect of regulatory immune cell repopulation on the pathophysiology of PE. These studies show that restoring the balance of the immune system through increasing Tregs, either by adoptive transfer or by infusing IL-10, reduces the blood pressure and pathophysiology associated with placental ischaemia in pregnant rats.

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.

An increased population of regulatory T cells improves the pathophysiology of placental ischemia in a rat model of preeclampsia

The reduced uterine perfusion pressure (RUPP) rat model of preeclampsia exhibits much of the pathology characterizing this disease, such as hypertension, inflammation, suppressed regulatory T cells (TRegs), reactive oxygen species (ROS), and autoantibodies to the ANG II type I receptor (AT1-AA) during pregnancy. The objective of this study was to determine whether supplementation of normal pregnant (NP) TRegs into RUPP rats would attenuate the pathophysiology associated with preeclampsia during pregnancy. CD4(+)/CD25(+) T cells were isolated from spleens of NP and RUPP rats, cultured, and injected into gestation day (GD) 12 normal pregnant rats that underwent the RUPP procedure on GD 14. On GD 1, mean arterial pressure (MAP) was recorded, and blood and tissues were collected for analysis. One-way ANOVA was used for statistical analysis. MAP increased from 99 ± 2 mmHg in NP (n = 12) to 127 ± 2 mmHg in RUPP (n = 21) but decreased to 118 ± 2 mmHg in RUPP+NP TRegs (n = 17). Circulating IL-6 and IL-10 were not significantly changed, while circulating TNF-α and IL-17 were significantly decreased after supplementation of TRegs. Placental and renal ROS were 339 ± 58.7 and 603 ± 88.1 RLU·min(-1)·mg(-1) in RUPP and significantly decreased to 178 ± 27.8 and 171 ± 55.6 RLU·min(-1)·mg(-1), respectively, in RUPP+NP TRegs; AT1-AA was 17.81 ± 1.1 beats per minute (bpm) in RUPP but was attenuated to 0.50 ± 0.3 bpm with NP TRegs. This study demonstrates that NP TRegs can significantly improve inflammatory mediators, such as IL-17, TNF-α, and AT1-AA, which have been shown to increase blood pressure during pregnancy.

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.

Hypertension, inflammation and T lymphocytes are increased in a rat model of HELLP syndrome

OBJECTIVE

An animal model of hemolysis, elevated liver enzymes, low platelet count (HELLP) was used to determine if T lymphocytes accompany hypertension and increased inflammatory cytokines.

METHODS

sFlt-1 (4.7 µg/kg/day) and sEndoglin (7 µg/kg/day) were infused into normal pregnant rats (HELLP rats) for 8 days.

RESULTS

HELLP was associated with increased mean arterial pressure (p = 0.0001), hemolysis (p = 0.044), elevated liver enzymes (p = 0.027), and reduced platelets (p = 0.035). HELLP rats had increased plasma levels of TNFα (p = 0.039), IL-6 (p = 0.038) and IL-17 (p = 0.04). CD4(+) and CD8(+) T lymphocytes were increased.

CONCLUSION

These data support the hypothesis that T cells are associated with hypertension and inflammation.

Regulation of soluble fms-like tyrosine kinase-1 production in response to placental ischemia/hypoxia: role of angiotensin II

While soluble fms-like tyrosine-1 (sFlt-1) is implicated in the pathogenesis of hypertension during preeclampsia, the mechanisms leading to the enhanced sFlt-1 production remain unclear. A recent report suggests exogenous angiotensin II (ANGII) stimulates sFlt-1 production in pregnant rats, however, the role of endogenous ANGII in mediating the placental production of sFlt-1 in response to placental ischemia remains unknown. Therefore, the purpose of this study was to determine the role of endogenous ANGII in mediating the placental production of sFlt-1 in response to placental ischemia in pregnant Sprague–Dawley rats. To this end we compared sFlt-1 and ANGII levels from placental explants collected from normal pregnant (NP) and Reduced Uterine Perfusion Pressure (RUPP) rats. sFlt-1 (3271 ± 264 vs. 2228 ± 324 pg/mL, P < 0.05) and ANGII levels (43.2 ± 2.8 vs. 26.7 ± 1.9 pg/mL, P < 0.05) were higher in placental explants from RUPP rats versus NP rats. Administration of Losartan, an angiotensin type 1 (AT₁) receptor antagonist, (10 mg/day for 5 days) to RUPP rats significantly reduced plasma levels of sFlt-1 (1432 ± 255 pg/mL, P < 0.05) when compared with untreated control rats (3431 ± 454 pg/mL). In addition, RUPP-induced hypertension was significantly reduced (113 ± 2 mmHg vs. 139 ± 2 mmHg, P < 0.05). In conclusion, placental sFlt-1 and ANGII production are significantly elevated in response to placental ischemia in pregnant rats. In addition, AT₁ receptor activation, by endogenous ANGII, appears to play an important role in mediating the placental production of sFlt-1 in response to placental ischemia in pregnant rats.

B cells: the old new players in reproductive immunology

Reproductive immunology research has long focused on T cell responses to paternal antigens and tolerance mechanisms supporting fetal well-being. The participation of B cells herein was not widely studied. Because of the fascinating immunological uniqueness of pregnancy, it is however to be expected that such pleiotropic cells play a considerable role. In fact, on the one hand B cells contribute toward pregnancy tolerance by secreting the immunomodulatory cytokine IL-10 but on the other hand can seriously harm pregnancy because of their capacity of producing autoantibodies. As for protective B cells, new evidences in mouse models arise suggesting that IL-10 producing B cells, the so-called B10 cells, help in maintaining tolerance toward semi-allogenic fetal antigens. They may be also important to fight danger signals at the fetal-maternal interface as, e.g., in the case of infections with the aim to restore the disrupted fetal tolerance. In human pregnancies, IL-10 producing B cells increase with pregnancy onset but not in the case of spontaneous abortions. In vitro, they are able to suppress TNF-α production by T cells from pregnant individuals. Their generation and functionality will be discussed throughout this review article. B cells can be deleterious to pregnancy as well. Aberrant B cell compartment is associated with obstetric pathologies. In particular, the capacity of B2 cells to produce specific autoantibodies or of B-1a B cells to secrete natural autoantibodies that can turn autoreactive will be discussed herein.

Administration of interleukin-17 soluble receptor C suppresses TH17 cells, oxidative stress, and hypertension in response to placental ischemia during pregnancy

Preeclampsia, new onset hypertension with proteinuria during pregnancy, is associated with chronic inflammation and placental oxidative stress (ROS). Chronic interleukin-17 (IL-17) increases blood pressure, autoantibodies (angiotensin II type I receptor [AT1-AA]), and ROS during pregnancy. The objective of this study was to determine whether T-helper 17 (TH17) suppression via IL-17 recombinant receptor C (IL-17RC) decreases pathophysiology associated with placental ischemia (reduced uterine perfusion pressure [RUPP]). On gestation day 14, miniosmotic pumps infusing 100 pg of IL-17RC per day were implanted into pregnant rats undergoing RUPP. On gestation day 18, carotid catheters were inserted. On gestation day 19, mean arterial pressure was recorded and TH17 cells, oxidative stress, and AT1-AA were measured and analyzed via 1-way ANOVA. Mean arterial pressure increased from 101 ± 2 mm Hg in normal pregnant rats (n = 19) to 120 ± 1 mm Hg in RUPP rats (n = 17) but decreased to 110 ± 2 mm Hg in RUPP+IL-17RC rats (n = 22). Pup weight decreased from 2.28 ± 0.2 g in normal pregnant rats to 1.96 ± 0.3 g in RUPP rats but was significantly increased to 2.01 ± 0.1 in RUPP+IL-17RC rats. TH17 cells were 1.77% in RUPP rats but decreased to 0.65% in RUPP+IL-17RC rats. Urinary isoprostanes were normalized in RUPP+IL-17RC rats (52 pg/µg) compared with 89 pg/µg in RUPP controls. Placental ROS was 652 relative light units in RUPP rats but decreased to 337 relative light units in RUPP+IL-17RC rats. AT1-AA was 17.27 ± 0.7 bpm in RUPP rats but decreased to 5.00 ± 0.5 bpm in RUPP+IL-17RC rats. With this study, we show that infusion of IL-17RC blunts TH17s, oxidative stress, AT1-AA, and hypertension in the RUPP model of preeclampsia, indicating that TH17 cells may play an important role in disease pathophysiology.

Seeking the mechanism(s) of action for corticosteroids in HELLP syndrome: SMASH study

INTRODUCTION

Administration of dexamethasone to the hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome patients (10 mg intravenously [IV] every 12 hours) shortens the disease course and reduces maternal morbidity in patients treated at the University of Mississippi Medical Center (UMMC), associated with this severe form of preeclampsia. However, the pathophysiological mechanisms involved with this intervention remain unclear.

OBJECTIVE

We sought to investigate the potential role of IV dexamethasone to restore the imbalance among antiangiogenic and inflammatory factors known to be significantly elevated in women with HELLP syndrome.

STUDY DESIGN

This was a single-center prospective study of women diagnosed with HELLP syndrome who were treated for IV dexamethasone at UMMC. Blood was drawn prior to dexamethasone administration and again 12 and 24 hours after the initial dexamethasone administration. Enzyme-linked immune assays were used to measure circulating inflammatory cytokines and antiangiogenic factors. A repeated-measures analysis of variance was used to analyze the data collected before, after, and during dexamethasone administration.

RESULTS

Seventeen women with HELLP syndrome were enrolled in this study. Dexamethasone significantly decreased evidence of hemolysis (P = .002) and liver enzymes (P = .003), and significantly increased platelets (P = .0001) within 24 hours of administration. Circulating interleukin-6 levels after 24 hours were decreased (P < .001); soluble fms-like tyrosine kinase-1 and soluble endoglin were also significantly decreased by 24 hours after dexamethasone administration (P < .002 and P < .004, respectively). There were no significant differences in circulating levels of placental growth factor (P = .886) due to dexamethasone administration. Angiotensin II receptor autoantibody levels were unchanged by dexamethasone administration.

CONCLUSION

We conclude that 1 important mechanism of dexamethasone administration is to blunt the release of both antiangiogenic and inflammatory factors suggested to play role in the pathophysiology of HELLP syndrome.

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.

Hypertension in pregnancy

Hypertension complicates 5% to 7% of all pregnancies. A subset of preeclampsia, characterized by new-onset hypertension, proteinuria, and multisystem involvement, is responsible for substantial maternal and fetal morbidity and is a marker for future cardiac and metabolic disease. This American Society of Hypertension (ASH) position paper summarizes the clinical spectrum of hypertension in pregnancy, focusing on preeclampsia. Recent research breakthroughs relating to etiology are briefly reviewed. Topics include classification of the different forms of hypertension during pregnancy, and status of the tests available to predict preeclampsia, and strategies to prevent preeclampsia and to manage this serious disease. The use of antihypertensive drugs in pregnancy, and the prevention and treatment of the convulsive phase of preeclampsia, eclampsia, with intravenous MgSO(4) is also highlighted. Of special note, this guideline article, specifically requested, reviewed, and accepted by ASH, includes solicited review advice from the American College of Obstetricians and Gynecologists.

IL-17-mediated oxidative stress is an important stimulator of AT1-AA and hypertension during pregnancy

Preeclampsia is associated with autoimmune cells T(H)17, secreting interleukin-17, autoantibodies activating the angiotensin II type I receptor (AT1-AA), and placental oxidative stress (ROS). The objective of our study was to determine whether chronic IL-17 increases blood pressure by stimulating ROS and AT1-AAs during pregnancy. To answer this question four groups of rats were examined: normal pregnant (NP, n = 20), NP+IL-17 (n = 12), NP+tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) (n = 7) (a superoxide dismutase mimetic that scavenges ROS), and NP+IL-17+tempol (n = 11). IL-17 (150 pg/day) was infused into NP rats while tempol was administered via the drinking water ad libitum. On day 19 blood pressure (MAP) was recorded, and plasma, urine, and tissue were collected for isolation of ROS detected by chemilluminescent technique. Urinary isoprostane was measured by ELISA. AT1-AAs were determined via cardiomyocyte assay and expressed as beats per minute. MAP increased from 98 ± 3 mmHg in NP to 123 ± 3 mmHg in IL-17-infused NP rats. Urinary isoprostane increased from 1,029 ± 1 in NP to 3,526 ± 2 pg·mg(-1)·day(-1) in IL-17-infused rats (P < 0.05). Placental ROS was 436 ± 4 RLU·ml(-1)·min(-1) (n = 4) in NP and 702 ± 5 (n = 5) RLU·ml(-1)·min(-1) in IL-17-treated rats. Importantly, AT1-AA increased from 0.41 ± 0.05 beats/min in NP rats (n = 8) to 18.4 ± 1 beats/min in IL-17 rats (n = 12). Administration of tempol attenuated the hypertension (101 ± 3 mmHg) ROS (459 ± 5 RLU·ml(-1)·min(-1)) and blunted AT1-AAs (7.3 ± 0.6 beats/min) in NP+IL-17+tempol-treated rats. Additionally, AT1 receptor blockade inhibited IL-17-induced hypertension and placental oxidative stress. MAP was 105 ± 5 mmHg and ROS was 418 ± 5 RLU·ml(-1)·min(-1) in NP+IL 17-treated with losartan. These data indicate that IL-17 causes placental oxidative stress, which serves as stimulus modulating AT1-AAs that may play an important role in mediating IL-17-induced hypertension during pregnancy.

Agonistic autoantibodies to the angiotensin II type I receptor cause pathophysiologic characteristics of preeclampsia

BACKGROUND

Preeclampsia (PE), new-onset hypertension with proteinuria during pregnancy, is associated with increased reactive oxygen species, the vasoactive peptide endothelin-1 (ET-1), T and B lymphocytes, soluble antiangiogenic factors sFlt-1 and sEndoglin (sFlt-1 and sEng), and agonistic autoantibodies to the angiotensin II type I receptor (AT1-AA).

OBJECTIVES

One important area of investigation for our laboratory was to determine what role AT1-AA plays in the pathophysiology associated with PE.

METHODS

To achieve this goal, we examined the effect of AT1-AA suppression on hypertension in response to placental ischemia as well as the effect of AT1-AA on increased blood pressure, ET-1, reactive oxygen species, and sFlt-1 in normal pregnant rats (NP).

RESULTS

We demonstrated reductions in uterine perfusion pressure (RUPP) to be a stimulus for AT1-AA during pregnancy. We utilized the technique of B-cell depletion to suppress circulating AT1-AA in RUPP rats and found that AT1-AA suppression in RUPP rats was associated with lower blood pressure and ET-1 activation. To determine a role for AT1-AA to mediate hypertension during pregnancy, we infused purified rat AT1-AA (1:50) into NP rats, and analyzed blood pressure and soluble factors. We consistently found that AT1-AA infused rats had significantly increased AT1-AA and blood pressure above NP rats. This hypertension was associated with significantly increased ET-1 in renal cortices (11-fold) and placenta (4-fold), and there was an approximately 2- to 3-fold increase in placental oxidative stress. Furthermore, antiangiogenic factors sFlt-1 and sEng were significantly increased in the AT1-AA induced hypertensive group compared with the NP controls.

CONCLUSIONS

Collectively, these data indicated an important role for AT1-AA stimulated in response to placental ischemia that caused hypertension during pregnancy.

Activating autoantibodies to the angiotensin II type I receptor play an important role in mediating hypertension in response to adoptive transfer of CD4+ T lymphocytes from placental ischemic rats

Hypertension in rats with chronic placental ischemia (reduced uterine perfusion pressure, RUPP) is associated with elevated inflammatory cytokines, agonistic autoantibodies to the angiotensin II type I receptor (AT1-AA) and CD4(+) T cells; all of which are elevated in preclamptic women. Additionally, we have shown that adoptive transfer of RUPP CD4(+) T cells increases blood pressure, inflammatory cytokines, and sFlt-1. The objective of this study was to determine the long-term effects of RUPP CD4(+) T cells on AT1-AA, renal and systemic hemodynamics in pregnant rats. To answer this question CD4(+) T splenocytes were magnetically isolated on day 19 of gestation from control RUPP and normal pregnant (NP) rats and injected into a new group of NP rats at day 13 of gestation. On day 19 of gestation mean arterial pressure (MAP) and renal function (glomerular filtration rates, GFR) were analyzed and serum collected for AT1-AA analysis. To determine a role for AT1-AA to mediate RUPP CD4(+) T cell-induced blood pressure increases, MAP was analyzed in a second group of rats treated with AT1 receptor blockade losartan (10 mg·kg(-1)·day(-1)) and in a third group of rats treated with rituximab, a B cell-depleting agent (250 mg/kg) we have shown previously to decrease AT1-AA production in RUPP rats. MAP increased from 101 ± 2 mmHg NP to 126 ± 2 mmHg in RUPP rats (P < 0.001) and to 123 ± 1 mmHg in NP rats injected with RUPP CD4(+) T cells (NP+RUPP CD4(+)T cells) (P < 0.001). Furthermore, GFR decreased from 2.2 ml/min (n = 7) in NP rats to 1.0 ml/min (n = 5) NP+RUPP CD4(+)T cell. Circulating AT1-AA increased from 0.22 ± 0.1 units in NP rats to 13 ± 0.7 (P < 0.001) units in NP+RUPP CD4(+)T cell-treated rats but decreased to 8.34 ± 1 beats/min in NP+RUPP CD4(+) T cells chronically treated with rituximab. Hypertension in NP+RUPP CD4(+)T cell group was attenuated by losartan (102 ± 4 mmHg) and with B cell depletion (101 ± 5 mmHg). Therefore, we conclude that one mechanism of hypertension in response to CD4(+) T lymphocytes activated during placental ischemia is via AT1 receptor activation, potentially via AT1-AA during pregnancy.

Hypertension in response to IL-6 during pregnancy: role of AT1-receptor activation

BACKGROUND: Increases in interleukin 6 (IL-6) and agonistic autoantibodies to the angiotensin II type 1 receptor (AT1-AA) are proposed to be important links between placental ischemia and hypertension in preeclampsia. METHODS: The purpose of this study was to determine whether IL-6 (5 ng/day), infused into normal pregnant (NP) rats, increased mean arterial pressure (MAP) and AT1-AA. MAP was analyzed in the presence and absence of an angiotensin type 1 receptor (AT1R) antagonist, losartan, L. RESULTS: MAP and AT1-AA increased from 102 ± 2 to 118 ± 4 mmHg and 0.7 ± 0.3 NP to 14.1 ± 1.4 chronotropic units with chronic IL-6 infusion. MAP responses to IL-6 were abolished in losartan pretreated rats (85 ± 4 in NP + L vs 85 ± 3 mmHg in IL-6 + L). CONCLUSION: These data indicate that IL-6 stimulates AT1-AA and that activation of the AT1R mediates IL-6 induced hypertension during pregnancy.

Correlation between HLA-DRB1, HLA-DQB1 polymorphism and autoantibodies against angiotensin AT(1) receptors in Chinese patients with essential hypertension

BACKGROUND

The autoantibodies (AAs) against angiotensin AT(1) receptors (AT(1) -AAs) have been discovered in patients with preeclampsia, malignant hypertension, and essential hypertension (EH); however, the mechanism of AA production remains to be investigated.

HYPOTHESIS

Polymorphisms of HLA-DRB1 or HLA-DQB1 are related to production of AAs in autoimmune diseases. We hypothesis that the polymorphisms of the HLA molecules are also associated with production of AT(1) -AAs in patients with EH.

METHODS

We enrolled 394 patients with EH and 224 normotensive subjects in this study. Autoantibodies in sera of donors were detected by enzyme-linked immunosorbent assay. The subjects' clinical data were collected, including gender, age, body mass index, blood pressure, smoking status, and diabetes. The patients and the normotensive subjects were classified respectively into AA-positive and AA-negative groups. Typing of DNA for HLA-DRB1 and HLA-DQB1 alleles was done by polymerase chain reaction amplification with sequence-specific primers.

RESULTS

Thirteen HLA-DRB1 and 7 HLA-DQB1 alleles were found in this population. The frequencies of AT(1) -AAs were related to blood pressure level. The frequency of AT(1) -AAs in the EH group was higher than that in the normotensive group (P = 0.0001). The levels of AAs in different groups of EH show a significant difference (P = 0.027). In addition, HLA-DRB1(*) 04 and HLA-DRB1(*) 14 (odds ratio [OR]: 3.06, 95% confidence interval [CI]: 1.56-5.97, P = 0.001; and OR: 2.53, 95% CI: 1.080-5.91, P = 0.033, respectively) were related to AT(1) -AA production in normotensive subjects after adjusting for covariants. The HLA-DRB1(*) 04 allele might be related to AT(1) -AA production in hypertensive subjects, and the P value was of baseline statistical significance after adjusting for blood pressure and other covariants (OR: 1.63, 95% CI: 0.95-2.78, P = 0.070).

CONCLUSIONS

These results suggest a difference in the immunogenetic background between the positive and negative AAs with hypertension or normotension. The HLA-DRB1(*) 04 allele increases the risk for AT(1) -AA production.

Role of angiotensin II type I receptor agonistic autoantibodies (AT1-AA) in preeclampsia

Despite being one of the leading causes of maternal death and a major contributor of maternal and perinatal morbidity, the mechanisms responsible for the pathogenesis of preeclampsia are unclear. One important initiating event in preeclampsia is thought to be reduced placental perfusion leading to the production of a variety of factors that cause widespread dysfunction of the maternal vasculature. The major objective of this review is to discuss the potential role of a novel agonistic autoantibody to the angiotensin II type I receptor (AT1-AA) in mediating hypertension during pregnancy. Although animal studies suggest that increasing plasma AT1-AA concentration in pregnant rats to levels observed in preeclamptic women or placental ischemic rats result in significant increases in arterial pressure, the quantitative importance of AT1-AA in the pathophysiology of preeclampsia in humans has yet to be fully elucidated.

Hypertension in response to AT1-AA: role of reactive oxygen species in pregnancy-induced hypertension

BACKGROUND

Agonistic autoantibodies to the angiotensin II type I receptor (AT1-AA) and reactive oxygen species (ROS) are implicated in the pathophysiology of preeclampsia. The objective of this study was to determine the role of AT1-AA to stimulate placental oxidative stress in vivo and role ROS in mediating hypertension in response to AT1-AA during pregnancy.

METHODS

To achieve these goals, blood pressure (mean arterial pressure (MAP)) and ROS were analyzed in AT1-AA-induced hypertensive pregnant rats in the presence and absence of a superoxide dismutase mimetic, tempol. Rat AT1-AA (1:50) and tempol (30 mg/kg/day) were administered to pregnant rats beginning on day 12 of gestation. On day 19, MAP was analyzed and tissues collected for ROS analysis via lucigenin chemiluminescence.

RESULTS

MAP increased from 101 ± 2 normal pregnant (NP) rats to 116 ± 2 mm Hg in chronic AT1-AA infused rats (P = 0.002). Placental basal and NADPH oxidase stimulated ROS was 29 ± 6 and 92 ± 10 relative light units (RLUs) in NP rats. These levels increased to 159 ± 29 (P < 0.0001) and 287 ± 60 RLUs (P < 0.006) in AT1-AA infused rats. MAP in AT1-AA + tempol rats was 109 ± 2 mm Hg, no difference than tempol-treated controls (109 ± 3 mm Hg). Administration of tempol decreased basal and NADPH-stimulated placental ROS in AT1-AA-treated rats (121 ± 13; 262 ± 21 RLUs). Basal and NADPH-stimulated ROS in tempol-treated controls were 69 ± 24; 141 ± 33 RLUs.

CONCLUSION

This study indicates that AT1-AA's contribute to placental oxidative stress; one mechanism whereby the AT1-AA mediates hypertension during pregnancy.

Angiotensin II type 1 autoantibody induced hypertension during pregnancy is associated with renal endothelial dysfunction

BACKGROUND

Previous investigations suggested that agonistic autoantibodies to the angiotensin II type I receptor (AT1-AA) might mediate a hypertensive response through dysregulation of the endothelin-1 system. AT1-AA induced hypertension was attenuated by the AT1 receptor and/or endothelin-1 type A receptor antagonists.

OBJECTIVES

This study was undertaken to determine if AT1-AA induced hypertension was associated with renal endothelial dysfunction.

METHODS

We compared the vascular reactivity of renal interlobar arteries from normal pregnant control rats and AT1-AA long-term infused pregnant rats in the presence and absence of endothelin type A (ET(A)) receptor antagonism. Renal endothelial function was tested using isolated renal interlobar arteries in a pressure myograph, which were exposed to acetylcholine or sodium nitroprusside.

RESULTS

Vasodilatory responses to the endothelial-dependent agonist acetylcholine were impaired in AT1-AA rats (74 [10]%) compared with normal pregnant controls (95 [5]%, P < 0.05). In the presence of ET(A) receptor antagonism, no differences were observed between controls or the AT1-AA treated group with regard to endothelial-dependent (acetylcholine) relaxation.

CONCLUSION

AT1-AA induced hypertension during pregnancy was associated with disparate renal endothelial responses to acetylcholine. The difference in renal vascular responses between AT1-AA and normal pregnant rats was abolished by ET(A) receptor blockade.

Hypertension in response to placental ischemia during pregnancy: role of B lymphocytes

Preeclampsia is associated with innate inflammatory response resulting in elevated tumor necrosis factor-α, agonistic autoantibodies to the angiotensin II type I receptor, and activation of endothelin 1 (ET-1). This study was designed to determine the role of B-cell depletion, resulting in agonistic autoantibodies to the angiotensin II type I receptor suppression to mediate hypertension via activation of ET-1 in the placental ischemic reduced uterine perfusion pressure (RUPP) rat model of preeclampsia. To achieve this goal we examined the effect of RUPP on mean arterial pressure and ET-1 in the presence and absence of chronically infused rituximab (R; 250 mg/kg), a B-lymphocyte-suppressive agent used clinically to treat autoimmune diseases. Mean arterial pressure was 103±1 mm Hg in normal pregnant (NP) rats; 103±3 mm Hg in NP+R versus 133±2 mm Hg in RUPP rats, and 118±2 mm Hg in RUPP+R rats (P<0.001 vs RUPP controls). B lymphocytes decreased from 6.0±0.5% gated cells in RUPP to 3.7±0.8% gated cells in RUPP+R rats. Importantly, agonistic autoantibodies to the angiotensin II type I receptor decreased from 18±1 bpm in RUPP rats to 10±1 bpm in RUPP+R rats. ET-1 decreased 1.5-fold in kidneys and 4-fold in the placenta (P<0.01) of RUPP+R versus RUPP rats. Media ET-1 excretion from endothelial cells exposed to serum from NP, RUPP, NP+R, or RUPP+R rats was determined. ET-1 from endothelial cells treated with NP serum was 53+13 pg/mg and increased to 75+10 pg/mg with RUPP serum. In contrast, ET-1 secretion decreased in response to B-cell-depleted RUPP serum to 50±8 pg/mg and was unchanged in response to NP+R sera (46±12 pg/mg). These data demonstrate the important roles that B-lymphocyte activation and agonistic autoantibodies to the angiotensin II type I receptors play in the pathophysiology of hypertension in response to placental ischemia.

Protein microarrays discover angiotensinogen and PRKRIP1 as novel targets for autoantibodies in chronic renal disease

Biomarkers for early detection of chronic kidney disease are needed, as millions of patients suffer from chronic diseases predisposing them to kidney failure. Protein microarrays may also hold utility in the discovery of auto-antibodies in other conditions not commonly considered auto-immune diseases. We hypothesized that proteins are released as a consequence of damage at a cellular level during end-organ damage from renal injury, not otherwise recognized as self-antigens, and an adaptive humoral immune response to these proteins might be detected in the blood, as a noninvasive tracker of this injury. The resultant antibodies (Ab) detected in the blood would serve as effective biomarkers for occult renal injury, enabling earlier clinical detection of chronic kidney disease than currently possible, because of the redundancy of the serum creatinine as a biomarker for early kidney injury. To screen for novel autoantibodies in chronic kidney disease, 24 protein microarrays were used to compare serum Ab from patients with chronic kidney disease against matched controls. From a panel of 38 antigens with increased Ab binding, four were validated in 71 individuals, with (n=50) and without (n=21) renal insufficiency. Significant elevations in the titer of novel auto-Ab were noted against angiotensinogen and PRKRIP1 in renal insufficiency. Current validation is underway to evaluate if these auto-Ab can provide means to follow the evolution of chronic kidney disease in patients with early stages of renal insufficiency, and if these rising titers of these auto-Ab correlate with the rate of progression of chronic kidney disease.

Expression of the vasoactive proteins AT1, AT2, and ANP by pregnancy-induced mouse uterine natural killer cells

Angiotensin II receptor type 1 (AT1) activation leads to vasoconstriction and type 2 receptor (AT2) leads to vasodilation. Atrial natriuretic peptide (ANP) antagonizes the effects of AT1. In human and murine pregnancies, uterine natural killer (uNK) cells closely associate with decidual blood vessels. Protein localization of AT1, AT2, and ANP to mouse uNK cells was examined between gestation days (gds) 6 and 12, the interval of uNK cell expansion. Percentages of uNK cells expressing AT1 or AT2 changed between gd6 and gd10. Atrial natriuretic peptide did not localize to uNK cells at gd6 or 8, but did colocalize to uNK cells at gd10 and 12, times immediately after spiral arterial modification. This is the first report of AT1, AT2, and ANP expression in uterine immune cells. Expression of these molecules suggests that uNK cells have the potential to contribute to the changes in blood pressure that occur between days 5 and 12 of pregnancy in mice.

The effect of immune factors, tumor necrosis factor-alpha, and agonistic autoantibodies to the angiotensin II type I receptor on soluble fms-like tyrosine-1 and soluble endoglin production in response to hypertension during pregnancy

BACKGROUND

Preeclampsia is considered a disease of immunological origin associated with abnormalities in inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha), and activated lymphocytes secreting autoantibodies to the angiotensin II receptor (AT1-AA). Recent studies have also demonstrated that an imbalance of angiogenic factors, soluble fms-like tyrosine kinase (sFlt-1), and sEndoglin, exists in preeclampsia; however, the mechanisms that initiate their overproduction are unclear.

METHODS

To determine the role of immune regulation of these factors, circulating and placental sFlt-1 and/or sEndoglin was examined from pregnant rats chronically treated with TNF-alpha or AT1-AA. On day 19 of gestation blood pressure was analyzed and serum and tissues were collected. Placental villous explants were excised and cultured on matrigel coated inserts for 24 h and sFlt-1 and sEndoglin was measured from media.

RESULTS

In response to TNF-alpha-induced hypertension, sFlt-1 increased from 180 +/- 5 to 2,907 +/- 412 pg/ml. sFlt-1 was also increased from cultured placental explants of TNF-alpha induced hypertensive pregnant rats (n = 12) (2,544 +/- 1,132 pg/ml) vs. explants from normal pregnant (NP) rats (n = 12) (2,189 +/- 586 pg/ml) where as sEng was undetectable. Circulating sFlt-1 increased from 245 +/- 38 to 3,920 +/- 798 pg/ml in response to AT1-AA induced hypertension. sFlt-1 levels were higher (3,400 +/- 350 vs. 2,480 +/- 900 pg/ml) in placental explants from AT1-AA infused rats (n = 12) than NP rats (n = 7). In addition, sEndoglin increased from 30 +/- 2.7 to 44 +/- 3.3 pg/ml (P < 0.047) in AT1-AA infused rats but was undetectable in the media of the placental explants.

CONCLUSIONS

These data suggest that immune factors may serve as an important stimulus for both sFlt-1 and sEndoglin production in response to placental ischemia.

Hypertension in pregnancy

Hypertension complicates 5% to 7% of all pregnancies. A subset of preeclampsia, characterized by new-onset hypertension, proteinuria, and multisystem involvement, is responsible for substantial maternal and fetal morbidity and is a marker for future cardiac and metabolic disease. This American Society of Hypertension (ASH) position paper summarizes the clinical spectrum of hypertension in pregnancy, focusing on preeclampsia. Recent research breakthroughs relating to etiology are briefly reviewed. Topics include classification of the different forms of hypertension during pregnancy, and status of the tests available to predict preeclampsia, and strategies to prevent preeclampsia and to manage this serious disease. The use of antihypertensive drugs in pregnancy, and the prevention and treatment of the convulsive phase of preeclampsia, eclampsia, with intravenous MgSO(4) is also highlighted. Of special note, this guideline article, specifically requested, reviewed, and accepted by ASH, includes solicited review advice from the American College of Obstetricians and Gynecologists.

Chronic maternal hypertension characterized by renal dysfunction is associated with reduced placental blood flow during late gestation in rabbits

Maternal hypertension associated with renal disease is a common pregnancy complication. Previously, we have shown in a rabbit model of mild hypertension that offspring from hypertensive mothers have increased blood pressure as adults. In human pregnancy, hypertension has been associated with decreased utero-placental blood flow. The aim of this study was to determine placental blood flow (PBF) in mild (2-kidney-1-wrapped; 2K-1W) and moderate (2-kidney-2-wrapped; 2K-2W) rabbit models of maternal hypertension. We hypothesized that PBF would be inversely related to the severity of the hypertension. PBF and renal blood flow (RBF) were measured using microspheres on day 28 of a 32-day gestation, in normotensive (sham), 2K-1W, and 2K-2W hypertensive groups. Mean arterial pressure (MAP, ∼7 mmHg, P < 0.05) was increased, and RBF (∼35%, P < 0.05) was reduced in the 2K-1W and 2K-2W (MAP ∼20 mmHg, P < 0.01; RBF ∼53%, P < 0.05) groups compared with the sham group. In the 2K-1W group, PBF fell by ∼12% ( P = 0.08) and fetal-to-placental weight ratio increased by ∼12% ( P < 0.01) compared with the sham group, reflecting an increase in the functional capacity of the placenta to deliver nutrients to the fetus. In the 2K-2W group, PBF decreased ∼51% ( P < 0.05) compared with the sham group, without changes in placental efficiency. Thus, in late gestation, placental blood flow was significantly reduced in the moderate hypertension group, without accompanying changes in fetal or placental weight or placental efficiency. In contrast, mild hypertension resulted in an increase in placental efficiency, without significant changes in placental blood flow. These findings suggest that mild and moderate hypertension may alter placental delivery of nutrients via differing mechanisms dependent upon the severity of the hypertension.