Endothelial-cell permeability and protein kinase C in pre-eclampsia

Ca2+-Activated K+ Channels and the Regulation of the Uteroplacental Circulation

Adequate uteroplacental blood supply is essential for the development and growth of the placenta and fetus during pregnancy. Aberrant uteroplacental perfusion is associated with pregnancy complications such as preeclampsia, fetal growth restriction (FGR), and gestational diabetes. The regulation of uteroplacental blood flow is thus vital to the well-being of the mother and fetus. Ca²⁺-activated K⁺ (K_Ca) channels of small, intermediate, and large conductance participate in setting and regulating the resting membrane potential of vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) and play a critical role in controlling vascular tone and blood pressure. K_Ca channels are important mediators of estrogen/pregnancy-induced adaptive changes in the uteroplacental circulation. Activation of the channels hyperpolarizes uteroplacental VSMCs/ECs, leading to attenuated vascular tone, blunted vasopressor responses, and increased uteroplacental blood flow. However, the regulation of uteroplacental vascular function by K_Ca channels is compromised in pregnancy complications. This review intends to provide a comprehensive overview of roles of K_Ca channels in the regulation of the uteroplacental circulation under physiological and pathophysiological conditions.

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.

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

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

Protein Kinase C Epsilon Contributes to NADPH Oxidase Activation in a Pre-Eclampsia Lymphoblast Cell Model

Pre-eclampsia is a pregnancy-specific disorder characterised by hypertension and proteinuria, which in severe cases results in multi-system disturbances. The maternal syndrome is associated with a pro-inflammatory state, consisting of leukocyte activation, which is thought to contribute to the widespread endothelial dysfunction. We previously showed increased activation of NADPH oxidase in pre-eclampsia, in both neutrophils and B-lymphoblast cell lines (B-LCLs). In this study, the mechanism by which NADPH oxidase activity is increased in pre-eclampsia was further investigated. NADPH oxidase activity was found to be increased in phorbol-12-myristate-13-acetate (PMA) stimulated B-LCLs isolated from women with pre-eclampsia. This correlated with an increase in protein kinase C (PKC) substrate phosphorylation, p47-phox phosphorylation (a regulatory component of NADPH oxidase) and p47-phox directed-kinase activity. Using ion exchange and hydroxyapatite chromatography we identified a major peak of PMA regulated p47-phox kinase activity. Chromatography fractions were probed for PKC isoforms. We found the major peak of p47-phox kinase activity could not be separated from the elution profile of PKC epsilon. Using a peptide inhibitor of PKC epsilon, PMA-induced reactive oxygen species (ROS) production could be reduced to that of a normal B-LCL. These data suggest a pro-inflammatory role for PKC epsilon in the pathogenesis of pre-eclampsia.

The obstetric syndromes: clinical relevance of placental hormones

Preterm delivery, preeclampsia and intrauterine growth restriction are the major diseases of pregnancy. A key role in their pathogenesis is played by the placenta, which is the source of hormones and other important regulatory molecules providing the metabolic and endocrine homeostasis of the fetal-placental unit. Since obstetric syndromes are characterized by important maternal and neonatal morbidity and mortality worldwide, numerous efforts have been made over the years to prevent and treat them. Due to their complex pathogenesis, however, the therapy is poor and not very effective. Therefore, great emphasis is currently given to the prevention of these diseases through the identification of biochemical and biophysical markers, among which placental factors play a crucial role. The increasing knowledge of the role of placental molecules can indeed lead to the development of new therapeutic and diagnostic tools.

Clinical significance of proteinuria determined with dipstick test, edema, and weekly weight gain ⩾500g at antenatal visit

OBJECTIVE

To determine how urine dipstick test, edema, and/or excessive weight gain (EWG, defined as ⩾500g/week) at antenatal visits predict significant proteinuria (defined as a protein-to-creatinine ratio [P/Cr, mg/mg] ⩾0.27) and preeclampsia.

METHODS

Data from 3279 antenatal visits between 30 and 36weeks of gestation were studied in 783 women with singleton pregnancies. In 24 preeclamptic pregnancies, data from 89 antenatal visits at and before diagnosis of preeclampsia were used. Spot P/Cr was determined in women with repeated positive dipstick test results in two successive antenatal visits or in those with a positive dipstick test result tested in the presence of hypertension.

RESULTS

Proteinuria on dipstick test, edema, and EWG appeared often in both women with and without preeclampsia; 66.7% vs. 27.7%, 83.3% vs. 44.1%, and 91.7% vs. 81.6%, respectively. However, repeated positive dipstick test results in two successive antenatal visits yielded sensitivity of 45.5%, specificity of 95.2%, and positive and negative predictive values of 30.0% and 97.4%, respectively, for detection of significant proteinuria and corresponding figures of 33.3%, 94.1%, 14.0%, and 98.0% for prediction of preeclampsia.

CONCLUSION

Repeated positive dipstick test results in two successive antenatal visits warrant a need for a confirmation test of significant proteinuria.

Vitamin D improves the angiogenic properties of endothelial progenitor cells

The main pathogenic feature of preeclampsia is maternal endothelial dysfunction that results from impaired angiogenesis and reduced endothelial repair capacity. In addition, preeclampsia risk is associated with vitamin D deficiency. We hypothesized that vitamin D(3) stimulates proangiogenic properties of endothelial colony-forming cells (ECFCs). ECFCs were obtained and cultured from cord blood and characterized by immunocytochemistry and flow cytometry. Proliferation, total length of tubule formation on Matrigel, expression of VEGF mRNA, and pro-matrix metalloproteinases (MMP)-2 activity were assessed after treatment of ECFCs with vitamin D(3). Specificity of the observed effects was tested by blocking the vitamin D receptor (VDR) or the VEGF signaling pathway. ECFCs treated with 10 nM vitamin D(3) showed a 1.27 times higher tubule formation compared with vehicle-treated controls (1.27 ± 0.19) as well as a 1.36 times higher proliferation rate (1.36 ± 0.06). Vitamin D(3) induced pro-MMP-2 activity (1.29 ± 0.17) and VEGF mRNA levels (1.74 ± 0.73) in ECFCs. VDR blocking by pyridoxal-5-phosphate (0.73 ± 0.19) or small interfering RNA (0.75 ± 0.17) and VEGF inhibition by Su5416 (0.56 ± 0.16) or soluble fms-like tyrosine kinase-1 (0.7 ± 0.14) reduced tubule formation and pro-MMP-2 activity (pyridoxal-5-phosphate: 0.84 ± 0.09; Su5416: 0.79 ± 0.11; or sFlt: 0.88 ± 0.13). This effect was neutralized by vitamin D(3). Consequently, vitamin D(3) significantly promoted angiogenesis in ECFCs in vitro possibly due to an increase in VEGF expression and pro-MMP-2 activity. Since angiogenesis is a crucial feature in the pathophysiology of preeclampsia these findings could explain the positive influence of vitamin D(3) in reducing preeclampsia risk.

Risk factors of eclampsia other than hypertension: pregnancy-induced antithrombin deficiency and extraordinary weight gain

OBJECTIVE

Recent findings suggest that cerebral edema is a characteristic finding on magnetic resonance imaging in women with eclampsia and that pregnancy-induced antithrombin deficiency (PIATD) may reflect enhanced vascular permeability and may allow the retention of excess water in the interstitial space. Whether PIATD and extraordinary weight gain (EOWG) are risk factors for eclampsia remains to be studied.

METHODS

The medical records of 11 women with eclampsia among 17,522 deliveries were reviewed retrospectively with respect to changes in the laboratory data and the maternal body weight. PIATD was defined as a perinatal antithrombin activity of ≤65% of the normal activity levels with an antenatal decline and/or a prompt postnatal increase. A large net weight gain during the last two antenatal weeks >97.5th percentile value (>4.01 kg) obtained from 272 control women with neither hypertension nor PIATD was defined as EOWG. Relative risk was obtained on the assumption that the prevalences of PIATD and EOWG were 2.0 and 2.5%, respectively, among 17,511 women who did not develop eclampsia.

RESULTS

The duration of hypertension until an eclamptic fit was within 7 days in all 11 cases. PIATD and EOWG were observed in 6 (54.5%) and 2 (18.2%) cases, yielding a relative risk (95% confidential interval) of 57.9 (17.7-188.7) and 8.65 (1.87-39.91) for eclampsia among women with PIATD and EOWG, respectively.

CONCLUSIONS

PIATD and EOWG may be risk factors for eclampsia.

Evidence of the escape of antithrombin from the blood into the interstitial space in pregnant women

OBJECTIVE

we investigated whether ascites samples obtained from pregnant women during cesarean sections contained antithrombin because it is unknown whether antithrombin escapes from the blood and passes into the interstitial space during pregnancy.

METHODS

the concentration and activity levels of antithrombin were determined in six ascites samples obtained from six consecutive women who exhibited generalized edema, ascites, and a gradual decline in antithrombin activity.

RESULTS

all six ascites samples contained antithrombin (mean ± SD, 4.9 ± 2.2 mg/dL; range, 2.7-8.8 mg/dL) and exhibited an antithrombin activity level of 15.5 ± 6.0% (range, 10-24%).

CONCLUSIONS

antithrombin escapes from the blood into the interstitial space in pregnant women. This phenomenon partially explains the gradual decline in antithrombin activity observed in these six pregnant women with generalized edema and large volumes of ascites.

Pregnancy-induced antithrombin deficiency

OBJECTIVE

This retrospective study was performed to characterize the laboratory features and water metabolism of women with pregnancy-induced antithrombin deficiency (PIATD).

METHODS

Among 1493 women who gave birth to a singleton infant at our institution, 114 women who developed PIATD and/or pregnancy-induced hypertension (PIH) were reviewed with respect to perinatal changes in laboratory variables (hematocrit value, fibrinogen, fibrinogen degradation product, D-dimer, uric acid, aspartate aminotransferase, lactate dehydrogenase) and body weight. PIATD was defined as a gradual decline in antithrombin (AT) activity to <or=65% of normal activity levels. One hundred and fourteen women with neither PIATD nor PIH and matched for the cesarean delivery rate were selected as a control group.

RESULTS

Of the 81 women who developed PIH, 19 (23.4%) also developed PIATD. Thirty-three women developed PIATD in the absence of PIH. Coagulation-fibrinolysis was significantly more enhanced and the postpartum reduction in the hematocrit value was significantly larger in women with PIATD, irrespective of the presence or absence of hypertension, than in women without PIATD. The postpartum decrease in body weight was significantly smaller in women with PIATD, irrespective of the presence or absence of hypertension.

CONCLUSIONS

A decrease in AT activity may occur in the absence of hypertension. Even in the absence of hypertension, a decreased plasma volume and enhanced coagulation-fibrinolysis seem to characterize women with PIATD. The monitoring of AT activity may help in distinguishing pregnant women with these insidious risks.

Vascular and cellular calcium in normal and hypertensive pregnancy

Normal pregnancy is associated with significant hemodynamic changes in the cardiovascular system in order to meet the metabolic demands of mother and fetus. These changes include increased cardiac output, decreased vascular resistance, and vascular remodeling in the uterine and systemic circulation. Preeclampsia (PE) is a major complication of pregnancy characterized by proteinuria and hypertension. Several risk factors have been implicated in the pathogenesis of PE including genetic and dietary factors. Ca2+ is an essential dietary element and an important regulator of many cellular processes including vascular function. The importance of adequate dietary Ca2+ intake during pregnancy is supported by many studies. Pregnancy-associated changes in Ca2+ metabolism and plasma Ca2+ have been observed. During pregnancy, changes in intracellular free Ca2+ concentration ([Ca2+](i)) have been described in red blood cells, platelets and immune cells. Also, during pregnancy, an increase in [Ca2+](i) in endothelial cells (EC) stimulates the production of vasodilator substances such as nitric oxide and prostacyclin. Normal pregnancy is also associated with decreased vascular smooth muscle (VSM) [Ca2+](i) and possibly the Ca2+-sensitization pathways of VSM contraction including protein kinase C, Rho-kinase, and mitogen-activated protein kinase. Ca2+-dependent matrix metalloproteinases could also promote extracellular matrix degradation and vascular remodeling during pregnancy. Disruption in the balance between dietary, plasma and vascular cell Ca2+ may be responsible for some of the manifestation of PE including procoagulation, decreased vasodilation, and increased vasoconstriction and vascular resistance. The potential benefits of Ca2+ supplements during pregnancy, and the use of modulators of vascular Ca2+ to reduce the manifestations of PE in susceptible women remain an important area for experimental and clinical research.

Placenta-derived chymotrypsin-like protease (CLP) disturbs endothelial junctional structure in preeclampsia

Placenta-derived chymotrypsin-like protease may contribute to endothelial activation in preeclampsia. In this study, we determined if placenta-derived chymotrypsin-like protease could disturb endothelial junctional integrity to promote endothelial permeability in preeclampsia. Confluent endothelial cells were cocultured with placental trophoblasts or treated with preeclampsia placenta-conditioned medium. Endothelial junction protein vascular endothelial cadherin expression and distribution were examined by fluorescent staining of endothelial cells with or without depletion of chymotrypsin. The association of endothelial cell junction protein complex VE-cadherin/beta-catenin/p120 was examined by a combined immuno-precipitation and immuno-blotting assay. Our results showed that endothelial cells cocultured with preeclampsia trophoblasts or exposed to preeclampsia placental conditioned medium exhibited a discontinuous distribution and reduced expression of vascular endothelial cadherin at cell contact regions. Vascular endothelial cadherin and p120 were expressed in control endothelial cells, but reduced or lost in endothelial cells exposed to preeclampsia placental conditioned medium, suggesting that the junctional protein complex of VE-cadherin/beta-catenin/p120 was disrupted in endothelial cells exposed to preeclampsia placental conditioned medium. We also observed that removal of trophoblasts from the coculture system and depletion of the protease from the preeclampsia placental conditioned medium could restore the dysregulated endothelial junction protein expression and distribution. Chymotrypsin also induced a dose dependent increase in endothelial monolayer permeability. We conclude that chymotrypsin-like protease released by the placenta is at least one important mediator responsible for disrupting endothelial cell integrity and inducing endothelial permeability in preeclampsia.

AKAP12 in astrocytes induces barrier functions in human endothelial cells through protein kinase Czeta

Interactions between astrocytes and blood vessels are essential for the formation and maintenance of the blood-neural barrier (BNB). Astrocyte-derived A-kinase anchor protein 12 (AKAP12) influences BNB formation, but the mechanism of regulation of BNB functions by AKAP12 is not fully understood. We have defined a new pathway of barriergenesis in human retina microvascular endothelial cells (HRMECs) involving astrocytic AKAP12. Treatment of HRMECs with conditioned media from AKAP12-overexpressing astrocytes reduced phosphorylation of protein kinase Czeta (PKCzeta), decreased the levels of vascular endothelial growth factor (VEGF) mRNA and protein, and increased thrombospondin-1 (TSP-1) levels, which led to antiangiogenesis and barriergenesis. Transfection of a small interference RNA targeting PKCzeta decreased VEGF levels and increased TSP-1 levels in HRMECs. Rho is a putative downstream signal of PKCzeta, and inhibition of Rho kinase with a specific inhibitor, Y27632, decreased VEGF levels and increased TSP-1 levels. We therefore suggest that AKAP12 in astrocytes differentially regulates the expression of VEGF and TSP-1 via the inhibition of PKCzeta phosphorylation and Rho kinase activity in HRMECs.

Circulating endothelial cells: a marker of vascular damage in patients with preeclampsia

OBJECTIVE

Preeclampsia is a disorder of endothelial cells, and novel markers of the disease are eagerly awaited. We tested the hypothesis that circulating endothelial cells (CECs) are elevated in preeclampsia and that cell numbers correlate with disease activity.

STUDY DESIGN

CECs were measured in 10 patients with preeclampsia as well as pregnant and nonpregnant controls. Cells were enumerated prior to delivery, 1 and 3-5 days thereafter. Enumeration of CECs was performed with anti-CD 146-driven immunomagnetic isolation and subsequent Ulex lectin staining.

RESULTS

Markedly elevated CEC numbers were detected in women with preeclampsia (median 88 cells/mL; P < .001) when compared with normal pregnancies (median 16 cells/mL) and healthy nonpregnant women (12 cells/mL). There was a significant correlation of CEC numbers and systolic blood pressure (P < .02). A rapid decline of cell numbers after delivery paralleled the clinical recovery.

CONCLUSION

Circulating endothelial cells are a novel marker of vascular damage in preeclampsia.

A profound decrease in maternal arginine uptake provokes endothelial nitration in the pregnant rat

While a specific role for nitric oxide (NO) in inducing the hemodynamic alterations of pregnancy is somewhat controversial, it is widely accepted that excess NO is generated during pregnancy. l-Arginine is the sole precursor for NO biosynthesis. Among several transporters that mediate l-arginine uptake, cationic amino acid transporter-1 (CAT-1) acts as the specific arginine transporter for endothelial NO synthase. The present study was designed to test the hypothesis that, during pregnancy, when arginine consumption by the fetus is significantly increased, compensatory changes in maternal arginine uptake affect the endothelium. Uptake of radiolabeled arginine (l-[3H]arginine) by freshly harvested maternal aortic rings from pregnant rats decreased by 65 and 30% in mid- and late pregnancy, respectively, compared with those obtained from virgin animals. This decrease was associated with a significant increase in endothelial protein nitration (the footprint of peroxynitrite generation), as shown by both Western blotting and immunohistochemistry utilizing anti-nitrotyrosine antibodies, reflecting endothelial damage. Northern blot analysis revealed that steady-state aortic CAT-1 mRNA levels did not change throughout pregnancy, whereas CAT-1 protein abundance was significantly increased, peaking at mid-pregnancy. Protein content of protein kinase C (PKC)-α, which was previously shown to decrease CAT-1 activity, increased significantly in the pregnant animals and was associated with a significant increase in CAT-1 phosphorylation. Intraperitoneal injection of α-tocopherol, a PKC-α inhibitor, prevented the decrease in arginine transport and attenuated protein nitration. In conclusion, aortic arginine uptake is reduced during pregnancy, through posttranslational modulation of CAT-1 protein, presumably via upregulation of PKC-α. The aforementioned findings are associated with an increase in protein nitration and, therefore, in selected individuals, may lead to the development of certain forms of endothelial dysfunction, like preeclampsia.

Rottlerin causes pulmonary edema in vivo: a possible role for PKCδ

In the present study, we assessed the effects of chemical inhibitors shown to be selective for protein kinase C (PKC) isoforms on lung barrier function both in vitro and in vivo. Rottlerin, a purported inhibitor of PKCδ, but not other chemical inhibitors, dose dependently promoted barrier dysfunction in lung endothelial cells in vitro. This barrier dysfunction correlated with structural changes in focal adhesions and stress fibers, which were consistent with functional changes in cell stiffness. To determine whether the effects noted in vitro correlated with changes in intact lungs, we tested the effects of rottlerin in the formation of pulmonary edema in rats using both ex vivo and in vivo models. Isolated, perfused lungs demonstrated a significant increase in filtration coefficients on exposure to rottlerin, compared with vehicle-treated lungs, an effect that correlated with increased extravasation of Evan's blue dye (EBD)-conjugated albumin. Additionally, compared with vehicle, the ratio of the wet lung weights to dry lung weights was significantly greater on exposure of animals to rottlerin; rottlerin also produced a dose-dependent increase in EBD extravasation into the lungs. These effects on lung edema occurred without any increase in right ventricular pressures. Microscopic assessment of edema in the ex vivo lungs demonstrated perivascular cuffing, with no evidence of septal capillary leak, in rottlerin-exposed lungs. Taken together, rottlerin increases barrier dysfunction in pulmonary endothelial cell monolayers and causes pulmonary edema in rats; results suggestive of an important role for PKCδ in maintaining lung endothelial barrier function.

Increased leukocyte adhesion to vascular endothelium in preeclampsia is inhibited by antioxidants

OBJECTIVE

To test the hypothesis that plasma from women with preeclampsia increases leukocyte adhesion to vascular endothelial cells and that antioxidants inhibit this effect.

STUDY DESIGN

Plasma from 12 women with severe preeclampsia and 12 with normal pregnancy was tested in an in vitro leukocyte-endothelium adhesion assay in the presence or absence of vitamin E, vitamin C, or N-acetylcysteine.

RESULTS

Preeclamptic plasma significantly increased monocyte (U937 cells) and T-cell (Jurkat) adhesion to human umbilical vein (HUVEC) and microvascular endothelial cells, compared with normal pregnant plasma. The antioxidants vitamin E, vitamin C, and N-acetylcysteine significantly inhibited monocyte adhesion to HUVEC in the presence of preeclamptic but not normal pregnant plasma. Increased adhesion in response to preeclamptic plasma was not mediated through a protein kinase C (PKC) mechanism, because the PKC inhibitor bisindolylmaleimide I had no effect on adhesion in the presence of preeclamptic plasma.

CONCLUSION

Severe preeclampsia is associated with increased leukocyte-endothelium adhesion and clinically useful antioxidants can inhibit this effect.

Immunoregulation in normal pregnancy and pre-eclampsia: an overview

Pre-eclampsia is a major disorder of human pregnancy, which may have an immunological basis. It is a disease of two stages. The first stage concerns the relative failure of early trophoblast invasion and remodelling of the spiral arteries, leading to a poor blood supply to the placenta, exposing it to oxidative stress. The inadequate trophoblast invasion may result from decreased expression of human leukocyte antigen-G (HLA-G) leading to an abnormal interaction with decidual natural killer (NK) cells, which are believed to play a major role in these processes through the production of immunoregulatory cytokines and angiogenic factors. Recent evidence suggests that the interaction between trophoblast human leukocyte antigen-C (HLA-C) molecules and decidual NK cell receptors may be the point at which the apparent partner specificity of the disease originates. The second stage is the maternal syndrome, which is characterized by a generalized systemic inflammatory response involving both leukocytes and endothelium. The inflammatory stimulus is believed to come from the placenta. In pre-eclampsia, placental oxidative stress may lead to increased shedding of apoptotic and/or necrotic syncytiotrophoblast debris into the maternal circulation. There is evidence that such trophoblast debris interacts with maternal leukocytes and endothelial cells to stimulate the release of proinflammatory cytokines, which could then trigger the maternal disease.

Pregnancy outcome of patients with pruritic urticarial papules and plaques of pregnancy

OBJECTIVE

The study was designed to investigate obstetric risk factors and pregnancy outcome of patients with pruritic urticarial papules and plaques of pregnancy (PUPPP).

METHODS

A population-based study comparing all pregnancies of women with and without PUPPP was conducted. Deliveries occurred during the years 1988-2002 at the Soroka University Medical Center. A multivariable logistic regression model was constructed in order to find independent risk factors associated with PUPPP.

RESULTS

During a 15-year period, 159 197 deliveries took place. PUPPP complicated 42 (0.03%) of all pregnancies. Using a multivariable analysis, the following conditions were significantly associated with PUPPP: multiple pregnancies (odds ratio (OR) = 4.9, 95% confidence interval (CI) 1.7-14.1), hypertensive disorders (OR = 2.2, 95% CI 1.1-4.7), and induction of labor (OR = 7.6, 95% CI 4.0-14.5). Higher rates of 5-minute Apgar scores lower than 7 (OR = 8.0, 95% CI 4.4-14.9) and of cesarean deliveries (OR = 2.9, 95% CI 1.5-5.6) were noted in the PUPPP as compared to the comparison group. While investigating other perinatal outcome parameters such as oligohydramnios, intrauterine growth restriction, meconium-stained amniotic fluid and perinatal mortality, no significant differences were observed between the groups.

CONCLUSION

Pruritic urticarial papules and plaques of pregnancy is a condition significantly associated with multiple pregnancies, hypertensive disorders, and induction of labor. Perinatal outcome is comparable to pregnancies without PUPPP.

Cellular and molecular mechanisms of tissue protection by lipophilic calcium channel blockers

Long-acting third-generation dihydropyridine calcium channel blockers (CCBs) improve endothelial dysfunction and prevent cardiovascular events in humans, but their cellular and molecular mechanisms of tissue protection are not elucidated in detail. We assessed organ (renal) protection by the highly lipophilic CCB lercanidipine in a double-transgenic rat (dTGR) model with overexpression of human renin and angiotensinogen genes. We randomly treated dTGR with lercanidipine (2.5 mg/kg/day; n=20) or vehicle (n=20) for 3 wk. Furthermore, we explored the influence of lercanidipine on protein kinase C (PKC) signaling in vivo and in vitro using endothelial and vascular smooth muscle cell cultures. Cumulative mortality was 60% in untreated dTGR, whereas none of the lercanidipine-treated animals died (P<0.001). We found significantly less albuminuria and improved renal function in lercanidipine-treated dTGR (both P<0.05). Lercanidipine treatment also significantly (P<0.05) reduced blood levels of the endogenous NOS inhibitor asymmetric dimethylarginine. On histological examination, we observed significantly less tissue inflammation and fibrosis in lercanidipine-treated animals (both P<0.05). Lercanidipine significantly inhibited angiotensin (ANG) I-mediated PKC-alpha and -delta activation in vivo and in vitro, partly due to reduced intracellular calcium flux. As a result, lercanidipine improved endothelial cell permeability in vitro. Lercanidipine prevents tissue injury and improves survival in a model of progressive organ damage. These effects may result, at least in part, from inhibition of tissue inflammation as well as improved NO bioavailability. Modulation of PKC activity may be an important underlying intracellular mechanism.

Role of protein kinase Cζ in thrombin-induced endothelial permeability changes: inhibition by angiopoietin-1

Endothelial cell leakiness is regulated by mediators such as thrombin, which promotes endothelial permeability, and anti-inflammatory agents, such as angiopoietin-1. Here we define a new pathway involved in thrombin-induced permeability that involves the atypical protein kinase C isoform, PKCζ. Chemical inhibitor studies implicated the involvement of an atypical PKC isoform in thrombin-induced permeability changes in human umbilical vein endothelial cells. Thrombin stimulation resulted in PKCζ, but not the other atypical PKC isoform, PKCλ, translocating to the membrane, an event known to be critical to enzyme activation. The involvement of PKCζ was confirmed by overexpression of constitutively active PKCζ, resulting in enhanced basal permeability. Dominant-negative PKCζ prevented the thrombin-mediated effects on endothelial cell permeability and inhibited thrombin-induced activation of PKCζ. Rho activation does not appear to play a role, either upstream or downstream of PKCζ, as C3 transferase does not block thrombin-induced PKCζ activation and dominant-negative PKCζ does not block thrombin-induced Rho activation. Finally, we show that angiopoietin-1 inhibits thrombin-induced PKCζ activation, Rho activation, and Ca++ flux, thus demonstrating that the powerful antipermeability action of angiopoietin-1 is mediated by its action on a number of signaling pathways induced by thrombin and implicated in permeability changes. (Blood. 2004; 104:1716-1724)

Proliferation of human melanoma cells is under tight control of protein kinase C alpha

Exponential proliferation of human melanoma cells has been associated with low levels of protein kinase C (PKC)-alpha. The aim of the present study was to investigate the functional relationship between PKC-alpha and melanoma cell proliferation. Treatment of human melanoma cells with the selective PKC inhibitor Ro-31-8220 resulted in a significant increase of cell proliferation as measured by (3)H-thymidine incorporation and a fluorometric microassay. In addition, phosphorothioate antisense-oligodeoxynucleotides (ODNs) to PKC-alpha enhanced DNA-synthesis of human melanoma cells. Furthermore, microinjection and transient transfection of melanoma cells with PKC-alpha decreased their proliferation, as shown by the reduction of nuclear staining with the proliferation marker Ki-67. The presented data demonstrate a cause-effect relationship between PKC-alpha and melanoma cell growth, whereby PKC-alpha reversely influences the rate of cell proliferation.

Avancées dans la physiopathologie de la pré-éclampsie : place de la réponse inflammatoire

Inflammatory response is a major component in physiopathology of preeclampsia and intra-uterine growth retardation. Endothelium is a main connection between placental ischemia and clinical manifestations during vascular pregnancy complications. In this review recent findings concerning inflammatory response and its links with endothelium are reported. Studies concerning isolated intra-uterine growth retardation confirm the hypothesis of a similar pathophysiology with an activation confined to utero-placental bed or at a lower level. Current information on oxidative stress, atherosclerosis, and apoptosis in vascular pregnancy complications are available in this review. These concepts offer innovative possibilities of treatment.

L-Arginine erythrocyte transport in normal pregnant and preeclamptic women

OBJECTIVE

Uptake of L-arginine by the cell via amino acid transporter systems is the first step for nitric oxide (NO) production. The current study aimed to assess the total L-arginine uptake in erythrocytes of normal pregnant and preeclamptic women.

STUDY DESIGN

Twenty-one normal pregnant and 21 preeclamptic women were studied. To measure total L-arginine uptake in erythrocytes, carbon 14 was used as a marker and Michaelis-Menten kinetic parameters (V(max) and K(m)) were evaluated.

RESULTS

In preeclamptic women, there was a significant increase (P<.004) in the mean maximal capacity of transport in erythrocytes (V(max)=982.69 micromol/L cells/h+/-433.51) in comparison with normal pregnant women (V(max)=584.73 micromol/L cells/h+/-422.33). No significant difference was detected in the half-saturation constant (P=0.978).

CONCLUSION

The transport kinetics of the NO precursor, L-arginine, is altered in erythrocytes of preeclamptic women. It is possible that abnormal L-arginine uptake may contribute to the pathophysiologic mechanisms of preeclampsia syndrome.

AT1 receptor agonistic antibodies from preeclamptic patients stimulate NADPH oxidase

BACKGROUND

We recently identified agonistic autoantibodies directed against the angiotensin AT1 receptor (AT1-AA) in the plasma of preeclamptic women. To elucidate their role further, we studied the effects of AT1-AA on reactive oxygen species (ROS), NADPH oxidase expression, and nuclear factor-kappaB (NF-kappaB) activation.

METHODS AND RESULTS

We investigated human vascular smooth muscle cells (VSMC) and trophoblasts, as well as placentas. AT1-AA were isolated from sera of preeclamptic women. Angiotensin II (Ang II) and AT1-AA increased ROS production and the NADPH oxidase components, p22, p47, and p67 phox in Western blotting. We next tested if AT1-AA lead to NF-kappaB activation in VSMC and trophoblasts. AT1-AA activated NF-kappaB. Inhibitor-kappaBalpha (I-kappaBalpha) expression was reduced in response to AT1-AA. AT1 receptor blockade with losartan, diphenylene iodonium, tiron, and antisense against p22 phox all reduced ROS production and NF-kappaB activation. VSMC from p47phox-/- mice showed markedly reduced ROS generation and NF-kappaB activation in response to Ang II and AT1-AA. The p22, p47, and p67 phox expression in placentas from preeclamptic patients was increased, compared with normal placentas. Furthermore, NF-kappaB was activated and I-kappaBalpha reduced in placentas from preeclamptic women.

CONCLUSIONS

NADPH oxidase is potentially an important source of ROS that may upregulate NF-kappaB in preeclampsia. We suggest that AT1-AA through activation of NADPH oxidase could contribute to ROS production and inflammatory responses in preeclampsia.

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

We showed that sera from patients with preeclampsia contain autoantibodies directed against the angiotensin II AT1 receptor. The antibodies recognize an epitope on the second extracellular loop of the receptor and are immunoglobulins of the IgG3 subclass. The antibodies accelerate the beating rate of neonatal rat cardiomyocytes. The agonistic effect can be blocked with the AT1 receptor blocker losartan and can be neutralized by a peptide corresponding to the AT1 receptor's second extracellular loop. In further studies we shown that the autoantibodies recognize a specific conformation of the AT1 receptor. Cleavage of the external disulfide bond with dithiothreitol caused an inactivation of the receptor when stimulated either with Ang II or the autoantibodies in a system of cultured neonatal rat cardiomyocytes. Long-term stimulation of the AT1 receptor with either agonists down-regulated the AT1 receptor-mediated response to a second Ang II stimulation. These observations show that the agonistic autoantibodies behave pharmacologically in a similar fashion to Ang II. We have found the autoantibodies in all women meeting the clinical criteria of preeclampsia and suggest that they may be important to the pathogenesis of the disease.

The endothelium: a gynecological and obstetric point of view

The endothelium, long considered merely an inert, semipermeable membrane between blood and the vessel wall, is now viewed as an important, large and highly active endocrine organ which is responsible for a number of vital physiological functions. In this editorial we will discuss the important role of the endothelium and endothelial (dys)function in health and disease, with particular focus on postmenopausal cardiovascular disease and preeclampsia.

AT(1) receptor agonistic antibodies from preeclamptic patients cause vascular cells to express tissue factor

BACKGROUND

We recently described autoantibodies (angiotensin-1 receptor autoantibodies, AT(1)-AA) directed at the AT(1) receptor in the serum of preeclamptic patients, whose placentas are commonly infarcted and express tissue factor (TF). Mechanisms of how AT(1)-AA might contribute to preeclampsia are unknown. We tested the hypothesis that AT(1)-AA cause vascular smooth muscle cells (VSMC) to express TF.

METHODS AND RESULTS

IgG from preeclamptic patients containing AT(1)-AA was purified with anti-human IgG columns. AT(1)-AA were separated from the IgG by ammonium sulfate precipitation. We transfected Chinese hamster ovary cells overexpressing the AT(1) receptor with TF promoter constructs coupled to a luciferase reporter gene. VSMC were obtained from human coronary arteries. Extracellular signal-related kinase activation was detected by an in-gel kinase assay. AP-1 activation was determined by electromobility shift assay. TF was measured by ELISA and detected by immunohistochemistry. Placentas from preeclamptic women stained strongly for TF, whereas control placentas showed far less staining. We proved AT(1)-AA specificity by coimmunoprecipitating the AT(1) receptor with AT(1)-AA but not with nonspecific IgG. Angiotensin (Ang) II and AT(1)-AA both activated extracellular signal-related kinase, AP-1, and the TF promoter transfected VSMC and Chinese hamster ovary cells, but only when the AP-1 binding site was present. We then demonstrated TF expression in VSMC exposed to either Ang II or AT(1)-AA. All these effects were blocked by losartan. Nonspecific IgG or IgG from nonpreeclamptic pregnant women had a negligible effect.

CONCLUSIONS

We conclude that AT(1)-AA and Ang II both stimulate the AT(1) receptor and initiate a signaling cascade resulting in TF expression. These results show an action of AT(1)-AA on human cells that could contribute to the pathogenesis of preeclampsia.

The effects of vascular endothelial growth factor on endothelial cells: a potential role in preeclampsia

OBJECTIVES

Preeclampsia is primarily a disorder of the maternal endothelium. An as yet unidentified circulating factor causes widespread alteration in endothelial function, and levels of vascular endothelial growth factor are elevated in preeclampsia. We hypothesized that vascular endothelial growth factor is involved in the alteration of endothelial function and set out to find further evidence for this contention.

STUDY DESIGN

Bovine microvascular endothelial cells (B-88) were cultured in vitro. These cultured cells were then stimulated with vascular endothelial growth factor and with plasma from women with preeclampsia in the presence and absence of anti-vascular endothelial growth factor antibody. Prostacyclin, nitric oxide, and lactate dehydrogenase levels were measured.

RESULTS

Vascular endothelial growth factor induced a significant concentration-dependent increase in prostacyclin production but not nitric oxide production. Cells stimulated with plasma from women with preeclampsia showed increases in production of both prostacyclin and nitric oxide. Vascular endothelial growth factor concentration in plasma was correlated with prostacyclin production by stimulated cells. The increase in prostacyclin production that usually followed the addition of plasma did not occur when anti-vascular endothelial growth factor antibody was present.

CONCLUSIONS

Vascular endothelial growth factor has the ability to alter endothelial cell function in a manner analogous to that of plasma from women with preeclampsia.

Fluid management in pre-eclampsia

We review the evidence base for fluid management in pre-eclampsia. Current understanding of the relevant pathophysiology and the possible impact of styles of fluid management on maternal and fetal outcome are presented. There is little evidence upon which to base the management of fluid balance in pre-eclampsia. Reports are conflicting and no large prospective outcome studies of fluid management have been performed. Volume expansion does not appear to reduce the incidence of fetal distress. Pulmonary oedema and oliguria receive particular attention. There is no evidence of long-term renal damage in pre-eclampsia, but there are strong suggestions that pulmonary oedema is linked to fluid administration. Monitoring is discussed and some principles of management are suggested

Calcium antagonists ameliorate ischemia-induced endothelial cell permeability by inhibiting protein kinase C

BACKGROUND

Dihydropyridines block calcium channels; however, they also influence endothelial cells, which do not express calcium channels. We tested the hypothesis that nifedipine can prevent ischemia-induced endothelial permeability increases by inhibiting protein kinase C (PKC) in cultured porcine endothelial cells.

METHODS AND RESULTS

Ischemia was induced by potassium cyanide/deoxyglucose, and permeability was measured by albumin flux. Ion channels were characterized by patch clamp. [Ca2+]i was measured by fura 2. PKC activity was measured by substrate phosphorylation after cell fractionation. PKC isoforms were assessed by Western blot and confocal microscopy. Nifedipine prevented the ischemia-induced increase in permeability in a dose-dependent manner. Ischemia increased [Ca2+]i, which was not affected by nifedipine. Instead, ischemia-induced PKC translocation was prevented by nifedipine. Phorbol ester also increased endothelial cell permeability, which was dose dependently inhibited by nifedipine. The effects of non-calcium-channel-binding dihydropyridine derivatives were similar. Analysis of the PKC isoforms showed that nifedipine prevented ischemia-induced translocation of PKC-alpha and PKC-zeta. Specific inhibition of PKC isoforms with antisense oligodeoxynucleotides demonstrated a major role for PKC-alpha.

CONCLUSIONS

Nifedipine exerts a direct effect on endothelial cell permeability that is independent of calcium channels. The inhibition of ischemia-induced permeability by nifedipine seems to be mediated primarily by PKC-alpha inhibition. Anti-ischemic effects of dihydropyridine calcium antagonists could be due in part to their effects on endothelial cell permeability.

Patients with preeclampsia develop agonistic autoantibodies against the angiotensin AT1 receptor

Immune mechanisms and the renin-angiotensin system are implicated in preeclampsia. We investigated 25 preeclamptic patients and compared them with 12 normotensive pregnant women and 10 pregnant patients with essential hypertension. Antibodies were detected by the chronotropic responses to AT1 receptor-mediated stimulation of cultured neonatal rat cardiomyocytes coupled with receptor-specific antagonists. Immunoglobulin from all preeclamptic patients stimulated the AT1 receptor, whereas immunoglobulin from controls had no effect. The increased autoimmune activity decreased after delivery. Affinity-column purification and anti-human IgG and IgM antibody exposure implicated an IgG antibody directed at the AT1 receptor. Peptides corresponding to sites on the AT1 receptor's second extracellular loop abolished the stimulatory effect. Western blotting with purified patient IgG and a commercially obtained AT1 receptor antibody produced bands of identical molecular weight. Furthermore, confocal microscopy of vascular smooth muscle cells showed colocalization of purified patient IgG and AT1 receptor antibody. The protein kinase C (PKC) inhibitor calphostin C prevented the stimulatory effect. Our results suggest that preeclamptic patients develop stimulatory autoantibodies against the second extracellular AT1 receptor loop. The effect appears to be PKC-mediated. These novel autoantibodies may participate in the angiotensin II-induced vascular lesions in these patients.