Evidence for compromised aldosterone synthase enzyme activity in preeclampsia

The dilemma of sodium intake in preeclampsia: beneficial or detrimental?

Preeclampsia (PE) is a disorder involving de novo development of hypertension plus end organ damage after 20 weeks of gestation. PE is considered to be a heterogeneous disease. There are 2 main types of PE: early-onset (<34 weeks of gestation), which is considered to be a placental disorder and is associated with vasoconstriction, low cardiac output, and placental hypoperfusion and organ damage due to decreased microcirculation to maternal organs; and late-onset PE, which is primarily a disorder of pregnant women with obesity, diabetes, and/or cardiovascular abnormalities. In late-onset PE, there is avid sodium reabsorption by the maternal kidneys, causing hypervolemia and increased cardiac output, along with vasodilatation causing venous congestion of organs. Although PE has been a well-known disease for a long time, it is interesting to note that there is no specific sodium (salt) intake recommendation for these patients. This may be due to the fact that studies since as far back as the 1900s have shown conflicting results, and the reasons for the inconsistent findings have not been fully explained; furthermore, the type of PE in these studies was not specifically defined. Some studies suggest that sodium restriction may be detrimental in early-onset PE, but may be feasible in late-onset PE. To explore this paradox, the current review explains the hemodynamic factors involved in these 2 types of PE, summarizes the findings of the current studies, and highlights the knowledge gaps and the research needed to determine whether increase or restriction of salt or sodium intake is beneficial in different types of PE.

Pertinence between risk of preeclampsia and the renin-angiotensin-aldosterone system (RAAS) gene polymorphisms: an updated meta-analysis based on 73 studies

The aetiological mechanism of preeclampsia (PE) is unclear exactly, so we attempted to investigate the association between susceptibility to preeclampsia and renin-angiotensin-aldosterone system (RAAS) gene polymorphisms to explore the aetiology in terms of genetics. A systematic search was performed in electronic databases to identify relevant studies. Eventually 73 studies were enrolled, odds ratios were generated by 5 genetic models. In overall analysis, significant associations were detected for AGT M235T, AT1R A1166C and CYP11B2 C344T whereas negative correlation was shown for AGT T174M. As stratified by race and geography, AGT 235T allele and AT1R 1166C allele increased preeclampsia risk and AGT T174M was justified uncorrelated with preeclampsia. Our meta-analysis illustrated that AGT 235T allele and AT1R 1166C allele increased and CYP11B2 344T allele decreased preeclampsia risk while AGT T174M polymorphism did not change preeclampsia risk. Hence, pregnant women carrying high-risk genotypes need strengthened management to prevent and early identification of preeclampsia.

Galectin-7 dysregulates renin-angiotensin-aldosterone and NADPH oxide synthase pathways in preeclampsia

OBJECTIVES

Preeclampsia is a life-threatening disorder of pregnancy unique to humans. Poor placentation in the first trimester of pregnancy is widely accepted to be an underlying cause of preeclampsia. Galectin-7 is abnormally elevated in chorionic villous samples and serum from women that subsequently develop pre-term preeclampsia. Administration of exogenous galectin-7 to pregnant mice causes preeclampsia-like features (hypertension, proteinuria), associated with dysregulation of the renin-angiotensin system (RAS). In this study investigated the mechanism by which galectin-7 induces alterations to tissue RAS homeostasis and ROS production. We hypothesized that galectin-7 induces alterations in the production of either placental RAS or NADPH oxidases (or both) to drive the dysregulated RAS and ROS production seen in preeclampsia.

STUDY DESIGN

Mated female mice (n = 5-6/group) received single (embryonic day [E]12/13) or multiple (E8-12) subcutaneous injections of 400 μg/kg/day galectin-7 or vehicle control and killed on E13 or E18. Human first trimester placental villous and decidual tissue (n = 11) was cultured under 8 % oxygen with 1 µg/mL galectin-7 or vehicle control for 16 h.

RESULTS

Galectin-7 administration to pregnant mice impaired placental labyrinth formation, suppressed circulating aldosterone and altered placental RAS (Agt, Renin) and NADPH oxidase (Cyba, Cybb and Icam1) mRNA expression. In vitro, galectin-7 regulated human placental villous RAS (AGT) and NADPH oxidase (CYBA, ICAM1 and VCAM1) mRNA expression.

CONCLUSIONS

Overall, galectin-7 likely drives hypertension in preeclampsia via its direct regulation of multiple pathways associated with preeclampsia in the placenta. Galectin-7 may therefore be a therapeutic target to improve placental function and prevent preeclampsia.

Increased glucocorticoid metabolism in diabetic kidney disease

Aims

Glomerular damage indicated by proteinuria is a main symptom in diabetic nephropathy. Mineralocorticoid receptor (MR) antagonists (MRAs) are beneficial irrespective of aldosterone availability. Thus, we hypothesized an alternatively activated MR to promote glomerular damage in proteinuric diabetic nephropathy. Specifically, we aimed first to demonstrate the presence of steroid hormones serving as alternative MR targets in type II diabetic patients with proteinuric kidney disease, second whether MR selectivity was modified, third to characterize MR and glucocorticoid receptor (GR) expression and activity in glomerular cell types exposed to eu- and hyperglycemic conditions, fourth to characterize the pro-fibrotic potential of primary human renal mesangial cells (HRMC) upon stimulation with aldosterone and cortisol, and fifth to specify the involvement of the MR and/or GR in pro-fibrotic signaling.

Materials and methods

Urinary steroid hormone profiles of patients with diabetic kidney disease were analyzed by gas chromatography–mass spectrometry and compared to an age and gender matched healthy control group taken out of a population study. In both cohorts, the activity of the MR pre-receptor enzyme 11β-hydroxysteroid dehydrogenase type 2 (HSD11B2), which inactivates cortisol to prevent it from binding to the MR, was assessed to define a change in MR selectivity. Expression of HSD11B2, MR and GR was quantified in HRMC and primary human renal glomerular endothelial cells (HRGEC). Activity of MR and GR was explored in HRMC by measuring the MR/GR down-stream signal SGK1 and the pro-fibrotic genes TGFB1, FN1 and COL1A1 in normal and high glucose conditions with the MR/GR agonists aldosterone/cortisol and the MR/GR antagonists spironolactone/RU486.

Results

Patients with diabetic kidney disease excreted more tetrahydroaldosterone than the control group reaching significance in men. The excretion of MR-agonistic steroid hormones was only increased for 18-hydroxytetrahydrocorticosterone in diabetic women. The excretion of most glucocorticoids was higher in the diabetic cohort. Higher apparent systemic HSD11B2 activity suggested less activation of the MR by cortisol in diabetic patients. Both cell types, HRMC and HRGEC, lacked expression of HSD11B2. Hyperglycemic conditions did not change MR and GR expression and activity. Stimulation with both aldosterone and cortisol promoted upregulation of pro-fibrotic genes in HRMC. This effect of MR and/or GR activation was more pronounced in high glucose conditions and partially inhibited by MRAs and GR antagonists.

Conclusions

In patients with diabetic kidney disease alternative MR activation is conceivable as cortisol and cortisone metabolites are increased. Systemic availability of active metabolites is counteracted via an increased HSD11B2 activity. As this cortisol deactivation is absent in HRMC and HRGEC, cortisol binding to the MR is enabled. Both, cortisol and aldosterone stimulation led to an increased expression of pro-fibrotic genes in HRMC. This mechanism was related to the MR as well as the GR and more marked in high glucose conditions linking the benefit of MRAs in diabetic kidney disease to these findings.

Developmental Vitamin D Deficiency in Pregnant Rats Does Not Induce Preeclampsia

Preeclampsia is a pregnancy disorder characterized by hypertension. Epidemiological studies have associated preeclampsia with an increased risk of neurodevelopmental disorders in offspring, such as autism and schizophrenia. Preeclampsia has also been linked with maternal vitamin D deficiency, another candidate risk factor also associated with autism. Our laboratory has established a gestational vitamin-D-deficient rat model that shows consistent and robust behavioural phenotypes associated with autism- and schizophrenia-related animal models. Therefore, we explored here whether this model also produces preeclampsia as a possible mediator of behavioural phenotypes in offspring. We showed that gestational vitamin D deficiency was not associated with maternal blood pressure or proteinuria during late gestation. Maternal and placental angiogenic and vasculogenic factors were also not affected by a vitamin-D-deficient diet. We further showed that exposure to low vitamin D levels did not expose the placenta to oxidative stress. Overall, gestational vitamin D deficiency in our rat model was not associated with preeclampsia-related features, suggesting that well-described behavioural phenotypes in offspring born to vitamin-D-deficient rat dams are unlikely to be mediated via a preeclampsia-related mechanism.

Fecal stress, nutrition and reproductive hormones for monitoring environmental impacts on tigers (Panthera tigris)

Non-invasive stress and nutritional hormone analysis in relation to ecological and other biological indices have tremendous potential to address environmental disturbance impacts on wildlife health. To this end, we examined the relation between glucocorticoid (GC) and thyroid (T3) hormone indices of disturbance and nutritional stress in response to ACTH and TSH challenges in captive tigers, as well as how reproductive hormones vary by sex and reproductive condition. Glucocorticoid, thyroid, progesterone and androgen assays conducted on high-performance liquid chromatography separated fractions of biologically relevant fecal extracts revealed high cross-reactivity of these assays for their respective biologically relevant fecal hormone metabolites. Both adrenal and thyroid hormone metabolites were elevated in response to ACTH and TSH challenges. However, the adrenal and thyroid hormone responses to ACTH challenge were concurrent, whereas the adrenal response to TSH challenge was delayed relative to thyroid hormone elevation in both males and females. The concurrently elevated T3 in response to ACTH may serve to raise metabolic rate to maximize use of GC-mobilized glucose, whereas the relatively delayed GC rise following TSH challenge may be a response to glucose depletion due to increased metabolic rate associated with elevated T3. Progesterone, testosterone and androstenedione hormone metabolites were significantly elevated during gestation compared to lactation in a female monitored from conception through early lactation. Results suggest that the glucocorticoid, thyroid and reproductive hormone assays we tested can accurately measure the stress, nutrition and reproductive response from tiger feces, providing useful non-invasive tools to assess physiological responses to environmental stressors and their reproductive consequences in the wild.

Association of CYP11B2 gene polymorphism with preeclampsia in north east of Iran (Khorasan province)

PURPOSE

Identification the genetic factors in preeclampsia (PE) are useful to increase the current knowledge of the pathophysiology of the disorder. The genetic factors implicated for all cases of PE remain to be determined. This study was aimed to investigate association between ADD1 1378G > T, AGTR2 1675G > A, AGTR1 1166A > C, NOS3 894 G > T and CYP11B2 -344C > T gene polymorphisms in Iranian women with PE.

MATERIAL AND METHODS

117 pregnant women with PE and 103 healthy women without affected previous pregnancy by PE were selected. Genomic DNA was extracted from peripheral blood and real-time PCR was performed to investigate the polymorphisms using a commercial kit.

RESULTS

There was a significant difference in CYP11B2 -344C > T gene polymorphism between case and control groups (P = 0.025). The odds ratio was 0.71 (CI 95% = 0.28-1.79). There were no statistical significant differences between other genetic polymorphisms.

CONCLUSION

Our results showed a significant association between CYP11B2 -344C > T gene polymorphism with PE. This finding suggests that mentioned polymorphism may be associated with susceptibility to PE at least in IRAN.

Aldosterone, Salt, and Potassium Intakes as Predictors of Pregnancy Outcome, Including Preeclampsia

The mineralocorticoid aldosterone increases in plasma in healthy pregnancy along with renin and angiotensin II and plays a key role in the physiological plasma volume expansion. In mice, aldosterone contributes to an optimal fetal development by enhancing PlGF (placental growth factor) expression and trophoblast cell proliferation. In preeclampsia, there is coincident suppression of aldosterone and impaired placental development. We hypothesized that aldosterone independently contributes to placental and birth weight in humans, and high dietary sodium and low potassium intakes affect this relationship adversely. We analyzed 24-hour urine collections and plasma samples from gestational week 29 in a subsample of 569 pregnant women from the Odense Child Cohort-a Danish population-based longitudinal cohort study. Plasma and urinary aldosterone were measured by ELISA, sodium and potassium excretions by flame photometer. Predictive values of aldosterone levels and sodium and potassium intakes were assessed by multiple and Cox regression analyses. Primary outcomes were placental weight and birth weight. Secondary outcome was preeclampsia. Urinary aldosterone excretion at gestational week 29 independently contributed to placental and birth weights (adjusted β-coefficients [95% CI], 24.50 [9.66-39.35] and 9.59 [4.57-14.61], respectively). Aldosterone levels were not associated to preeclampsia incidence. Salt intake >6 g/d was associated with development of preeclampsia (hazard ratio [95% CI], 5.68 [1.51-21.36]). At gestational week 29, urinary aldosterone excretion is an independent predictor of placental and birth weights. High salt intake is a risk factor for preeclampsia. In perspective, suppression of aldosterone in pregnancy has adverse trophic effects.

Responses of the renin-angiotensin-aldosterone system in pregnant chronic kidney disease patients with and without superimposed pre-eclampsia

Background

Women with chronic kidney disease (CKD) are at increased risk of superimposed pre-eclampsia (SPE). Accurate identification of SPE is challenging. We hypothesized that specific components of the renin-angiotensin-aldosterone system (RAAS) would discriminate between CKD and SPE. The aim of the study was to establish differences in circulating and intrarenal RAAS in women with CKD with and without SPE and compare these to normotensive controls (NCs) and women with pre-eclampsia (PE).

Methods

White European NC women (n = 20), women with PE (n = 9), normotensive CKD without SPE (n = 8) and with SPE (n = 11) were recruited in the third trimester. Plasma renin, plasma and urine total angiotensinogen (AGT) concentrations were quantified by enzyme-linked immunosorbent assay, urinary tetrahydroaldosterone (TH-aldo) concentration by gas chromatography-mass spectrometry and placental growth factor (PlGF) by immunoassay.

Results

Urinary TH-aldo:creatinine ratios were lower in women with PE or SPE compared with NC or women with CKD (P < 0.05 for all). The same group differences were observed for plasma active renin and PlGF concentrations (P < 0.05 for all). Urine total AGT was higher in women with PE compared with NC (P < 0.05) and urine TH-aldo:urine AGT was lower (P < 0.05). However, women with SPE had lower urinary AGT concentrations compared with women with PE (P < 0.05). No differences in plasma total AGT were observed between groups.

Conclusions

Women with SPE have a lower urinary TH-aldo:creatinine ratio, lower plasma active renin and lower PlGF concentrations than women with CKD, comparable to women with PE without pre-existing disease, suggestive of similar pathophysiology. These data suggest disruption of the RAAS pathway in SPE similar to PE. Exploration of the predictive value of RAAS components for adverse pregnancy events in women with CKD is required.

Association of gene polymorphisms of aldosterone synthase and angiotensin converting enzyme in pre-eclamptic South African Black women

INTRODUCTION

The exact cause of preeclampsia (PE) remains elusive. Recently, many researchers have focused on the role of genetic variations in pathogenesis of PE. The renin-angiotensin-aldosterone system is affected in the pathogenesis of PE.

OBJECTIVES

To determine association of gene polymorphisms of aldosterone synthase (CYP11B2) and angiotensin converting enzyme (ACE) in PE and normotensive South African Black women.

METHODS

A group of 603 South African Black pregnant women, 246 normotensive and 357 with PE, was recruited. Purified DNA was extracted from venous blood. The distribution and frequencies of gene polymorphisms of CYP11B2 (C-344T) and ACE deletion/insertion (D/I) were determined by real time polymerase chain reaction.

RESULTS

As the main outcome measure, the risk of C allele for PE was 1.28 (95%CI: 0.94-1.74; p = .1) for all allele comparisons. Thus no significant association with development of PE was observed for the CYP11B2 variants. However, post analysis of the distribution of TT genotypes of CYP11B2 were higher in the HIV uninfected normotensive than in the HIV uninfected PE group (OR: 0.47, 95%CI: 0.27-0.79, p = .0027). The C alleles of late-onset PE and HIV uninfected PE were higher than all normotensive and HIV uninfected normotensive (OR: 1.47, 95%CI: 1.02-2.10, p = .03 and OR: 1.77, 95%CI: 1.13-2.81, p = .0094 respectively). The CT genotype of CYP11B2 was statistically significant between normotensive and PE in HIV uninfected groups (OR: 2.24, 95%CI: 1.28-3.98, p = .0026). There was no significant difference in frequencies of D/I for ACE gene in PE.

Salt, aldosterone and extrarenal Na+ - sensitive responses in pregnancy

Outside of pregnancy excessive salt consumption is known to be harmful being linked to increased blood pressure and cardiovascular disease. However, pregnancy represents a major change to a woman's physiology resulting in an intimate adaptation to environmental conditions. It is now becoming apparent that salt is essential for a number of these changes during pregnancy including haematological, cardiac adaptations as well as directly influencing placental development and the uteroplacental immune environment. The present review discusses the important role that salt has during normal pregnancy and evidence will also be presented to show how the placenta may act as a salt sensing organ temporarily, yet substantially regulating maternal blood pressure.

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The placenta may function as an extrarenal regulator of maternal blood pressure.

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Na⁺handling in pregnancy is completely different to the non-pregnant situation.

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Na⁺may actually lower blood pressure in pregnancy affected with pre-eclampsia.

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Aldosterone is an important regulator of placental and fetal development.

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Na⁺ may compensate for aldosterone deficiency in pregnancy.

Placental expression of the angiogenic placental growth factor is stimulated by both aldosterone and simulated starvation

Aldosterone is an important factor supporting placental growth and fetal development. Recently, expression of placental growth factor (PlGF) has been observed in response to aldosterone exposure in different models of atherosclerosis. Thus, we hypothesized that aldosterone up-regulates growth-adaptive angiogenesis in pregnancy, via increased placental PlGF expression. We followed normotensive pregnant women (n = 24) throughout pregnancy and confirmed these results in a second independent first trimester cohort (n = 36). Urinary tetrahydroaldosterone was measured by gas chromatography-mass spectrometry and corrected for creatinine. Circulating PlGF concentrations were determined by ELISA. Additionally, cultured cell lines, adrenocortical H295R and choriocarcinoma BeWo cells, as well as primary human third trimester trophoblasts were tested in vitro. PlGF serum concentrations positively correlated with urinary tetrahydroaldosterone corrected for creatinine in these two independent cohorts. This observation was not due to PlGF, which did not induce aldosterone production in cultured H295R cells. On the other hand, PlGF expression was specifically enhanced by aldosterone in the presence of forskolin (p < 0.01) in trophoblasts. A pronounced stimulation of PlGF expression was observed with reduced glucose concentrations simulating starvation (p < 0.001). In conclusion, aldosterone stimulates placental PlGF production, enhancing its availability during human pregnancy, a response amplified by reduced glucose supply. Given the crucial role of PlGF in maintaining a healthy pregnancy, these data support a key role of aldosterone for a healthy pregnancy outcome.

Gestation-specific reference intervals for comprehensive spot urinary steroid hormone metabolite analysis in normal singleton pregnancy and 6 weeks postpartum

BACKGROUND

Normal pregnancy depends on pronounced adaptations in steroid hormone concentrations. Although in recent years, the understanding of these hormones in pregnancy has improved, the interpretation is hampered by insufficient reference values. Our aim was to establish gestation-specific reference intervals for spot urinary steroid hormone levels in normal singleton pregnancies and 6 weeks postpartum.

METHODS

Cross-sectional multicentre observational study. Women recruited between 2008 and 2013 at 3 University Hospitals in Switzerland (Bern), Scotland (Glasgow) and Austria (Graz). Spot urine was collected from healthy women undergoing a normal pregnancy (age, 16-45 years; mean, 31 years) attending routine antenatal clinics at gestation weeks 11, 20, and 28 and approximately 6 weeks postpartum. Urine steroid hormone levels were analysed using gas-chromatography mass spectrometry. Creatinine was also measured by routine analysis and used for normalisation.

RESULTS

From the results, a reference interval was calculated for each hormone metabolite at each trimester and 6 weeks postpartum. Changes in these concentrations between trimesters and postpartum were also observed for several steroid hormones and followed changes proposed for index steroid hormones.

CONCLUSIONS

Normal gestation-specific reference values for spot urinary steroid hormones throughout pregnancy and early postpartum are now available to facilitate clinical management and research approaches to steroid hormone metabolism in pregnancy and the early postpartum period.

Cytokines, angiogenic, and antiangiogenic factors and bioactive lipids in preeclampsia

Preeclampsia is a low-grade systemic inflammatory condition in which oxidative stress and endothelial dysfunction occurs. Plasma levels of soluble receptor for vascular endothelial growth factor (VEGFR)-1, also known as sFlt1 (soluble fms-like tyrosine kinase 1), an antiangiogenic factor have been reported to be elevated in preeclampsia. It was reported that pregnant mice deficient in catechol-O-methyltransferase (COMT) activity show a preeclampsia-like phenotype due to a deficiency or absence of 2-methoxyoestradiol (2-ME), a natural metabolite of estradiol that is elevated during the third trimester of normal human pregnancy. Additionally, autoantibodies (AT1-AAs) that bind and activate the angiotensin II receptor type 1 a (AT1 receptor) also have a role in preeclampsia. None of these abnormalities are consistently seen in all the patients with preeclampsia and some of them are not specific to pregnancy. Preeclampsia could occur due to an imbalance between pro- and antiangiogenic factors. VEGF, an angiogenic factor, is necessary for the transport of polyunsaturated fatty acids (PUFAs) to endothelial cells. Hence reduced VEGF levels decrease the availability of PUFAs to endothelial cells. This leads to a decrease in the formation of anti-inflammatory and angiogenic factors: lipoxins, resolvins, protectins, and maresins from PUFAs. Lipoxins, resolvins, protectins, maresins, and PUFAs suppress insulin resistance; activation of leukocytes, platelets, and macrophages; production of interleukin-6 and tumor necrosis factor-α; and oxidative stress and endothelial dysfunction; and enhance production of prostacyclin and nitric oxide (NO). Estrogen enhances the formation of lipoxin A4 and NO. PUFAs also augment the production of NO and inhibit the activity of angiotensin-converting enzyme and antagonize the actions of angiotensin II. Thus, PUFAs can prevent activation of angiotensin II receptor type 1 a (AT1 receptor). Patients with preeclampsia have decreased plasma phospholipid concentrations of arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), the precursors of lipoxins (from AA), resolvins (from EPA and DHA), and protectins (from DHA) and prostaglandin E1 (PGE1 from DGLA: dihomo-γ-linolenic acid) and prostacyclin (PGI2 derived from AA). Based on these evidences, it is proposed that preeclampsia may occur due to deficiency of PUFAs and their anti-inflammatory products: lipoxins, resolvins, protectins, and maresins.

Urinary serine proteases and activation of ENaC in kidney--implications for physiological renal salt handling and hypertensive disorders with albuminuria

Serine proteases, both soluble and cell-attached, can activate the epithelial sodium channel (ENaC) proteolytically through release of a putative 43-mer inhibitory tract from the ectodomain of the γ-subunit. ENaC controls renal Na(+) excretion and loss-of-function mutations lead to low blood pressure, while gain-of-function mutations lead to impaired Na(+) excretion, hypertension, and hypokalemia. We review an emerging pathophysiological concept that aberrant glomerular filtration of plasma proteases, e.g., plasmin, prostasin, and kallikrein, contributes to proteolytic activation of ENaC, both in acute conditions with proteinuria, like nephrotic syndrome and preeclampsia, and in chronic diseases, such as diabetes with microalbuminuria. A vast literature on renin-angiotensin-aldosterone system and volume homeostasis from the last four decades show a number of common characteristics for conditions with albuminuria compatible with impaired renal Na(+) excretion: hypertension and volume retention is secondary to proteinuria in, e.g., preeclampsia and nephrotic syndrome; plasma concentrations of renin, angiotensin II, and aldosterone are frequently suppressed in proteinuric conditions, e.g., preeclampsia and diabetic nephropathy; blood pressure is salt-sensitive in conditions with microalbuminuria/proteinuria; and extracellular volume is expanded, plasma atrial natriuretic peptide (ANP) concentration is increased, and diuretics, like amiloride and spironolactone, are effective blood pressure-reducing add-ons. Active plasmin in urine has been demonstrated in diabetes, preeclampsia, and nephrosis. Urine from these patients activates, plasmin-dependently, amiloride-sensitive inward current in vitro. The concept predicts that patients with albuminuria may benefit particularly from reduced salt intake with RAS blockers; that distally acting diuretics, in particular amiloride, are warranted in low-renin/albuminuric conditions; and that urine serine proteases and their activators may be pharmacological targets.

Suppression of aldosterone and progesterone in preeclampsia

OBJECTIVE

Preeclampsia (preE) is a hypertensive disorder seen in 3-10% of human pregnancies and is diagnosed by de novo onset of hypertension and proteinuria. Several research groups provided evidence for reduced aldosterone (Aldo) and progesterone (Prog) availability in preE. The aim of this study was to determine the levels of Aldo and Prog in preE.

METHODS

Normal pregnant (NP; n = 39) and preE (n = 30) patients were recruited to have their blood drawn between 21 and 40 weeks of pregnancy. Two groups of rats were used in this study: NP rats (n = 10) and preE rats (n = 10), which were given weekly injections of desoxycorticosterone acetate and 0.9% saline to drink. Aldo and Prog levels were assayed in plasma and urine samples by ELISA kits.

RESULTS

In preE patients, the mean Aldo and Prog levels were suppressed (p < 0.05) compared to NP patients. NP patients exhibited a trend of increased levels of Aldo with an increase in gestational age; however, preE patients had the opposite trend. Both normal and preE patients exhibited a trend of increased levels of Prog with an increase in gestational age. The plasma and urinary Aldo and Prog levels were lower (p < 0.05) in preE rats compared to NP rats.

CONCLUSIONS

We have demonstrated using a rat model and patients that both Aldo and Prog are suppressed in preE and thus may be used as biomarkers for preE.

Primary male osteoporosis is associated with enhanced glucocorticoid availability

OBJECTIVE

While systemic glucocorticoids compromise bone metabolism, altered intracellular cortisol availability may also contribute to the pathogenesis of primary male osteoporosis (MO). The objective of this study was to assess whether intracellular cortisol availability is increased in MO due to a distorted local cortisol metabolism.

METHODS

Forty-one patients with MO were compared with age- and BMI-matched non-osteoporotic subjects after excluding overt systemic hypercortisolism (N = 41). Cortisol, cortisone and the respective tetrahydro-, 5α-tetrahydro- and total cortisol metabolites were analysed by GC-MS in 24 h urine. Apparent 11β-hydroxysteroid dehydrogenase (11β-HSD) enzyme activities, excretion of cortisol metabolites and calcium, and fractional urinary calcium excretion were assessed and related to BMD.

RESULTS

Fractional and total urinary calcium excretion negatively correlated with BMD at all (P < 0.05) and at three of five (P < 0.05) measurement sites, respectively. While systemic cortisol was unchanged, apparent 11β-HSD enzyme activity in MO patients (P < 0.01) suggested increased intracellular cortisol availability. Total and fractional urinary calcium excretion was higher, with apparent 11β-HSD enzyme activities consistent with an enhanced intracellular cortisol availability (P < 0.05).

CONCLUSION

Apparent 11β-HSD enzyme activities consistent with increased intracellular cortisol availability correlated with urinary calcium loss and reduced bone mineral density in MO. The changes in 11β-HSD activity were associated with both the fractional calcium excretion, suggesting altered renal calcium handling, and the absolute urinary calcium excretion. Both mechanisms could result in a marked bone calcium deficiency if insufficiently compensated for by intestinal calcium uptake.

Novel ideas about salt, blood pressure, and pregnancy

The molecular mechanisms leading to preeclampsia are poorly understood. It has been related to certain immune mechanisms, as well as the pathological regulation of the renin-angiotensin system together with perturbed salt and plasma volume regulation. Finally, a non-specific, vascular, inflammatory response is generated, which leads to the clinical syndrome. Here, we present novel findings in salt (NaCl) metabolism implying that salt is not only important in blood pressure control and volume homeostasis, but also in immune regulation. Sodium and chloride can be stored without accumulation of water in the interstitium at hypertonic concentrations through interactions with proteoglycans. Macrophages in the interstitium act as osmosensors for salt, producing increased amounts of vascular endothelial factor C, which increases the density of the lymph-capillary network and the production of nitric oxide in vessels. An increased interstitial salt concentration activates the innate immune system, especially Th17 cells, and may be an important trigger for autoimmune diseases. The novel findings with the idea of sodium storage and local mechanisms of volume and immune regulation are appealing for preeclampsia and may unify the "immune" and "vascular" hypotheses of preeclampsia.

Vascular Endothelial Growth Factor-A and Aldosterone

Aldosterone levels are markedly elevated during normal pregnancy but fall even though volume contracts when preeclampsia occurs. The level of aldosterone in either condition cannot be explained solely by the activity of the renin–angiotensin II system. In normal gestation, vascular endothelial growth factor (VEGF) is thought to maintain vascular health, but its role in adrenal hormone production is unknown. We hypothesized that the role of VEGF in the adrenal gland is to maintain vascular health and regulate aldosterone production. Here, we demonstrate that supernatant of endothelial cells grown in the presence of VEGF enhanced aldosterone synthase activity in human adrenocortical cells. VEGF either alone or combined with angiotensin II increased aldosterone production in adrenal cells. These data suggest that endothelial cell–dependent and independent activation of aldosterone is regulated by VEGF. In contrast to angiotensin II, VEGF did not upregulate the steroidogenic acute regulatory protein. Consistent with this observation, angiotensin II stimulated both aldosterone and cortisol synthesis from progesterone, whereas VEGF stimulated selectively aldosterone production. In rats, overexpression of soluble fms-like tyrosine kinase-1, an endogenous VEGF inhibitor, led to adrenocortical capillary rarefaction and fall in aldosterone concentrations that correlated inversely with soluble fms-like tyrosine kinase-1 levels. These findings may explain why aldosterone increases so markedly during normal gestation and why preeclampsia, a condition characterized by high soluble fms-like tyrosine kinase-1, is associated with inappropriately low aldosterone levels in spite of relatively lower plasma volumes.

The role of the renin-angiotensin-aldosterone system in preeclampsia: genetic polymorphisms and microRNA

The compensatory alterations in the rennin-angiotensin-aldosterone system (RAAS) contribute to the salt-water balance and sufficient placental perfusion for the subsequent well-being of the mother and fetus during normal pregnancy and is characterized by an increase in almost all the components of RAAS. Preeclampsia, however, breaks homeostasis and leads to a disturbance of this delicate equilibrium in RAAS both for circulation and the uteroplacental unit. Despite being a major cause for maternal and neonatal morbidity and mortality, the pathogenesis of preeclampsia remains elusive, where RAAS has been long considered to be involved. Epidemiological studies have indicated that preeclampsia is a multifactorial disease with a strong familial predisposition regardless of variations in ethnic, socioeconomic, and geographic features. The heritable allelic variations, especially the genetic polymorphisms in RAAS, could be the foundation for the genetics of preeclampsia and hence are related to the development of preeclampsia. Furthermore, at a posttranscriptional level, miRNA can interact with the targeted site within the 3'-UTR of the RAAS gene and thereby might participate in the regulation of RAAS and the pathology of preeclampsia. In this review, we discuss the recent achievements of genetic polymorphisms, as well as the interactions between maternal and fetal genotypes, and miRNA posttranscriptional regulation associated with RAAS in preeclampsia. The results are controversial but utterly inspiring and attractive in terms of potential prognostic significance. Although many studies suggest positive associations with genetic mutations and increased risk for preeclampsia, more meticulously designed large-scale investigations are needed to avoid the interference from different variations.

The migratory capacity of human trophoblastic BeWo cells: effects of aldosterone and the epithelial sodium channel

Aldosterone is a key regulator of the epithelial sodium channel (ENaC) and stimulates protein methylation on the β-subunit of the ENaC. We found that aldosterone (100 nM) promotes cellular migration in a wound-healing model in trophoblastic BeWo cells. Here, we tested if the positive influence of aldosterone on wound healing is related to methylation reactions. Cell migration and proliferation were measured in BeWo cells at 6 h, when mitosis is still scarce. Cell migration covered 12.4, 25.3, 19.6 and 45.1 % of the wound when cultivated under control, aldosterone (12 h), 8Br-cAMP and aldosterone plus 8Br-cAMP, respectively. Amiloride blocked the effects of aldosterone alone or in the presence of 8Br-cAMP on wound healing. Wound healing decreased in aldosterone (plus 8Br-cAMP) coexposed with the methylation inhibitor 3-deaza-adenosine (3-DZA, 12.9 % reinvasion of the wound). There was an increase in wound healing in aldosterone-, 8Br-cAMP- and 3-DZA-treated cells in the presence of AdoMet, a methyl donor, compared to cells in the absence of AdoMet (27.3 and 12.9 % reinvasion of the wound, respectively). Cell proliferation assessed with the reagent MTT was not changed in any of these treatments, suggesting that cellular migration is the main factor for reinvasion of wound healing. Electrophysiological studies showed an increase in ENaC current in the presence of aldosterone. This effect was higher with 8Br-cAMP, and there was a decrease when 3-DZA was present. AdoMet treatment partially reversed this phenomenon. We suggest that aldosterone positively influences wound healing in BeWo cells, at least in part through methylation of the ENaC.

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

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

Epigenetics and microRNAs in preeclampsia

Strong evidence suggests a potential link among epigenetics, microRNAs (miRNAs), and pregnancy complications. Much research still needs to be carried out to determine whether epigenetic factors are predictive in the pathogenesis of preeclampsia (PE), a life-threatening disease during pregnancy. Recently, the importance of maternal epigenetic features, including DNA methylation, histone modifications, epigenetically regulated miRNA, and the effect of imprinted or non-imprinted genes on trophoblast growth, invasion, as well as fetal development and hypertension in pregnancy, has been demonstrated in a series of articles. This article discusses the current evidence of this complicated network of miRNA and epigenetic factors as potential mechanisms that may underlie the theories of disease for PE. Translating these basic epigenetic findings to clinical practice could potentially serve as prognostic biomarkers for diagnosis in its early stages and could help in the development of prophylactic strategies.

Regulation of placental growth by aldosterone and cortisol

During pregnancy, trophoblasts grow to adapt the feto-maternal unit to fetal requirements. Aldosterone and cortisol levels increase, the latter being inactivated by a healthy placenta. By contrast, preeclamptic placental growth is reduced while aldosterone levels are low and placental cortisol tissue levels are high due to improper deactivation. Aldosterone acts as a growth factor in many tissues, whereas cortisol inhibits growth. We hypothesized that in preeclampsia low aldosterone and enhanced cortisol availability might mutually affect placental growth and function. Proliferation of cultured human trophoblasts was time- and dose-dependently increased with aldosterone (P < 0.04 to P < 0.0001) and inhibited by spironolactone and glucocorticoids (P < 0.01). Mineralo- and glucocorticoid receptor expression and activation upon agonist stimulation was verified by visualization of nuclear translocation of the receptors. Functional aldosterone deficiency simulated in pregnant mice by spironolactone treatment (15 μg/g body weight/day) led to a reduced fetal umbilical blood flow (P < 0.05). In rat (P < 0.05; R(2) = 0.2055) and human (X(2) = 3.85; P = 0.0249) pregnancy, placental size was positively related to plasma aldosterone. Autocrine production of these steroid hormones was excluded functionally and via the absence of specific enzymatic transcripts for CYP11B2 and CYP11B1. In conclusion, activation of mineralocorticoid receptors by maternal aldosterone appears to be required for trophoblast growth and a normal feto-placental function. Thus, low aldosterone levels and enhanced cortisol availability may be one explanation for the reduced placental size in preeclampsia and related disorders.

Relationship of aldosterone synthase gene (C-344T) and mineralocorticoid receptor (S810L) polymorphisms with gestational hypertension

The extent of genetic influence in the aetiology of gestational hypertension has not been completely determined. The aim of this study was to analyse the relationship between aldosterone levels and the -344T/C polymorphism of the aldosterone synthase gene (CYP11B2) and to investigate the frequency of the S810L mutation of mineralocorticoid receptor (MR) in gestational hypertension. One hundred women with pregnancy-induced hypertension and 100 with normal pregnancy were studied to measure serum aldosterone and progesterone levels and for the genotypification of the -344T/C polymorphism of CYP11B2 gene and the S810L mutation of MR by RFLP-PCR and SSP, respectively. Serum aldosterone levels were reduced (<0.000001) and serum progesterone levels increased (<0.000001) in gestational hypertensive women as compared with normal pregnant women. The -344T/C of CYP11B2 genotypic frequencies were similar in the hypertensive and normotensive pregnant women. The 810L-mutated allele of MR was found in 12% of the hypertensive and 9.4% of the normotensive pregnant women. In contrast to the observations made in preeclampsia, the genotype of -344T/C of CYP11B2 was neither related with gestational hypertension nor with aldosterone levels at delivery. The frequency of the S810L mutation was similar in the hypertensive and normotensive women but higher than observed in other reports.

Cell migration in BeWo cells and the role of epithelial sodium channels

Cell migration/proliferation processes associated with wound healing were measured in BeWo cells at 6 h, when mitosis is still scarce. Cells were cultured in medium with 1% fetal bovine serum to minimize proliferation. BeWo cell migration covered 20.6 +/- 7.0%, 38.0 +/- 5.4%, 16.6 +/- 4.8% and 13.7 +/- 3.6% of the wound when cultivated under control, aldosterone (100 nM, 12 h), aldosterone plus amiloride (10 muM) and amiloride treatments, respectively. When BeWo cells were treated with aldosterone, there was an increase in wound healing (P < 0.05), which was prevented by adding the ENaC blocker amiloride (P < 0.05, n = 16). Immunocytochemistry studies showed that the three ENaC subunits showed greater expression at the leading edge of the wound 3 h after injury, supporting the notion that these proteins participate in a postinjury signal. Antisense oligonucleotides directed against the alpha-ENaC subunit decreased the migratory response of the cells compared to the sense treated cells or the cells without oligonucleotides (P < 0.001, n = 16): 30.2 +/- 3.7%, 17.6 +/- 1.3%, 27.5 +/- 1.5% and 20.2 +/- 1.5% reinvasion of the wound with aldosterone, aldosterone plus antisense, aldosterone plus sense treatments and control conditions, respectively. Aldosterone and amiloride influence wound healing in BeWo cells, probably by their effects upon ENaCs, transmitting a signal to the cell cytoplasm for the release of several agents that promote cell migration.

Hyperaldosteronism in pregnancy

Aldosterone is a key regulator of electrolyte and water homeostasis and plays a central role in blood pressure regulation. Hormonal changes during pregnancy, among them increased progesterone and aldosterone production, lead to the required plasma volume expansion of the maternal body as an accommodation mechanism for fetus growth. This review discusses the regulation of aldosterone production by aldosterone synthase (CYP11B2); the impact on aldosterone secretion due to the presence of a chimeric gene originating from a crossover between CYP11B1 and CYP11B2 in glucocorticoid remediable aldosteronism (GRA) — the inherited form of hypertension; enhanced aldosterone production in aldosterone-producing adenoma (APA); and idiopathic hyperaldosteronism (IHA). Features of hyperaldosteronism are also found in patients with apparent mineralocorticoid excess (AME), in which glucocorticoids exacerbate activation of the mineralocorticoid receptor (MR) because of a defect in the 11β-hydroxysteroid dehydrogenase type 2 enzyme. Regulation of aldosterone production and tissue-specific activation of the mineralocorticoid receptor are prerequisites for optimal control of body fluids and blood pressure during pregnancy and contribute largely to the wellbeing of the mother-to-be.

High aldosterone-to-renin variants of CYP11B2 and pregnancy outcome

BACKGROUND

Increased aldosterone concentrations and volume expansion of normal pregnancies are hallmarks of normal pregnancies and blunted in pre-eclampsia. Accordingly, we hypothesized an active mineralocorticoid system to protect from pre-eclampsia.

METHODS

In pregnant women (normotensive n = 44; pre-eclamptic n = 48), blood pressure, urinary tetrahydro-aldosterone excretion and activating polymorphisms (SF-1 site and intron 2) of the aldosterone synthase gene (CYP11B2) were determined; 185 non-pregnant normotensive individuals served as control. Amino acid-changing polymorphisms of the DNA- and agonist-binding regions of the mineralocorticoid receptor were evaluated by RT-PCR, SSCP and sequencing.

RESULTS

Urinary tetrahydro-aldosterone excretion was reduced in pre-eclampsia as compared to normal pregnancy (P < 0.05). It inversely correlated with blood pressure (r = 0.99, P < 0.04). Homozygosity for activating CYP11B2 polymorphisms was preferably present in normotensive as compared to pre-eclamptic pregnancies, identified (intron 2, P = 0.005; SF-1 site, P = 0.016). Two mutant haplotypes decreased the risk of developing pre-eclampsia (RR 0.16; CI 0.05-0.54; P < 0.001). In contrast, intron 2 wild type predisposed to pre-eclampsia (P < 0.0015). No functional mineralocorticoid receptor mutant has been observed.

CONCLUSIONS

High aldosterone availability is associated with lower maternal blood pressure. In line with this observation, gain-of-function variants of the CYP11B2 reduce the risk of developing pre-eclampsia. Mutants of the mineralocorticoid receptor cannot explain the frequent syndrome of pre-eclampsia.

Age-dependent decrease in 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) activity in hypertensive patients

BACKGROUND

The prevalence of arterial hypertension lacking a defined underlying cause increases with age. Age-related arterial hypertension is insufficiently understood, yet known characteristics suggest an aldosterone-independent activation of the mineralocorticoid receptor. Therefore, we hypothesized that 11beta-HSD2 activity is age-dependently impaired, resulting in a compromised intracellular inactivation of cortisol (F) with F-mediated mineralocorticoid hypertension.

METHODS

Steroid hormone metabolites in 24-h urine samples of 165 consecutive hypertensive patients were analyzed for F and cortisone (E), and their TH-metabolites tetrahydro-F (THF), 5alphaTHF, TH-deoxycortisol (THS), and THE by gas chromatography-mass spectroscopy. Apparent 11beta-HSD2 and 11beta-hydroxylase activity and excretion of F metabolites were assessed.

RESULTS

In 72 female and 93 male patients aged 18-84 years, age correlated positively with the ratios of (THF + 5alphaTHF)/THE (P = 0.065) and F/E (P < 0.002) suggesting an age-dependent reduction in the apparent 11beta-HSD2 activity, which persisted (F/E; P = 0.020) after excluding impaired renal function. Excretion of F metabolites remained age-independent most likely as a consequence of an age-dependent diminished apparent 11beta-hydroxylase activity (P = 0.038).

CONCLUSION

Reduced 11beta-HSD2 activity emerges as a previously unrecognized risk factor contributing to the rising prevalence of arterial hypertension in elderly. This opens new perspectives for targeted treatment of age-related hypertension.