Mechanisms of Fetal and Neonatal Renal Impairment by Pharmacologic Inhibition of Angiotensin

Hypertension and renal disease programming: focus on the early postnatal period

The developmental origin of hypertension and renal disease is a concept highly supported by strong evidence coming from both human and animal studies. During development there are periods in which the organs are more vulnerable to stressors. Such periods of susceptibility are also called 'sensitive windows of exposure'. It was shown that as earlier an adverse event occurs; the greater are the consequences for health impairment. However, evidence show that the postnatal period is also quite important for hypertension and renal disease programming, especially in rodents because they complete nephrogenesis postnatally, and it is also important during preterm human birth. Considering that the developing kidney is vulnerable to early-life stressors, renal programming is a key element in the developmental programming of hypertension and renal disease. The purpose of this review is to highlight the great number of studies, most of them performed in animal models, showing the broad range of stressors involved in hypertension and renal disease programming, with a particular focus on the stressors that occur during the early postnatal period. These stressors mainly include undernutrition or specific nutritional deficits, chronic behavioral stress, exposure to environmental chemicals, and pharmacological treatments that affect some important factors involved in renal physiology. We also discuss the common molecular mechanisms that are activated by the mentioned stressors and that promote the appearance of these adult diseases, with a brief description on some reprogramming strategies, which is a relatively new and promising field to treat or to prevent these diseases.

Adverse pregnancy outcomes associated with first-trimester exposure to angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers: A systematic review and meta-analysis

This study aimed to determine the effects of prenatal exposure to angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs), particularly when exposure is limited to the first trimester of pregnancy, on adverse maternal and neonatal outcomes. A systematic search was performed on four databases, that is, PubMed, Scopus, Web of Science, and Cochrane Library, to identify relevant articles published up to December 31, 2019. Included studies were limited to original investigations assessing the association between prenatal exposure to ACEIs/ARBs and adverse pregnancy outcomes. Odds ratios were used as a summary effect measure. Pooled-effect estimates of each outcome were calculated by the random-effects meta-analysis. The main outcomes included overall and specific congenital malformations, low birth weight, miscarriage, elective termination of pregnancy, stillbirth, and preterm delivery. Of 19 included articles involving a total of 4 163 753 pregnant women, 13 studies reported an increased risk of, at least, one adverse pregnancy outcome in pregnant women who were exposed to ACEIs/ARBs. Meta-analysis revealed a significant association between overall congenital malformations and first trimester-only exposure to ACEIs/ARBs (OR = 1.94, 95% CI = 1.71-2.21, P < .0001). Cardiovascular malformations, miscarriage, and stillbirth also provided a significant relation with ACEI/ARB exposure. In conclusion, prenatal exposure to ACEIs/ARBs in the first trimester of pregnancy was found to be associated with an increased risk of adverse pregnancy outcomes. Women of reproductive age should be aware of the potential teratogenic risks of these drugs if they become pregnant.

Current evidence on the use of anti-RAAS agents in congenital or acquired solitary kidney

RATIONAL

The inhibition of renin-angiotensin-aldosterone system (RAAS) is a major strategy for slowing the progression of chronic kidney disease (CKD). The utility of anti-RAAS agents in patients with congenital or acquired solitary kidney is still controversial.

OBJECTIVE

A systematic literature review was conducted.

MAIN FINDINGS

The conclusions of the few available studies on the topic are homogeneously in agreement with a long-term reno-protective activity of anti-RAAS drugs in patients with solitary kidney, especially if patients are hypertensive or proteinuric. However, angiotensin 2 (ANG2) levels permit a functional adaptation to a reduced renal mass in adults and is crucial for sustaining complete kidney development and maturation in children. A hormonal interference on ANG2 levels has been supposed in women. Consequently, at least in children and women, the use of ARBs appears more appropriate. Principle conclusions: Available data on this topic are limited; however, by their overall assessment, it would appear that anti-RAAS drugs might also be reno-protective in patients with solitary kidney. The use of ARBs, especially in children and in women, seems to be more appropriate. However, more experimental data would be strictly necessary to confirm this hypothesis.

Pregnancy, Proteinuria, Plant-Based Supplemented Diets and Focal Segmental Glomerulosclerosis: A Report on Three Cases and Critical Appraisal of the Literature

Chronic kidney disease (CKD) is increasingly recognized in pregnant patients. Three characteristics are associated with a risk of preterm delivery or small for gestational age babies; kidney function reduction, hypertension, and proteinuria. In pregnancy, the anti-proteinuric agents (ACE-angiotensin converting enzyme-inhibitors or ARBS -angiotensin receptor blockers) have to be discontinued for their potential teratogenicity, and there is no validated approach to control proteinuria. Furthermore, proteinuria usually increases as an effect of therapeutic changes and pregnancy-induced hyperfiltration. Based on a favourable effect of low-protein diets on proteinuria and advanced CKD, our group developed a moderately protein-restricted vegan-vegetarian diet tsupplemented with ketoacids and aminoacids for pregnant patients. This report describes the results obtained in three pregnant patients with normal renal function, nephrotic or sub-nephrotic proteinuria, and biopsy proven diagnosis of focal segmental glomerulosclerosis, a renal lesion in which hyperfiltration is considered of pivotal importance (case 1: GFR (glomerular filtration rate): 103 mL/min; proteinuria 2.1 g/day; albumin 3.2 g/dL; case 2: GFR 86 mL/min, proteinuria 3.03 g/day, albumin 3.4 g/dL; case 3: GFR 142 mL/min, proteinuria 6.3 g/day, albumin 3.23 g/dL). The moderately restricted diet allowed a stabilisation of proteinuria in two cases and a decrease in one. No significant changes in serum creatinine and serum albumin were observed. The three babies were born at term (38 weeks + 3 days, female, weight 3180 g-62th centile; 38 weeks + 2 days, female, weight 3300 g-75th centile; male, 38 weeks + 1 day; 2770 g-8th centile), thus reassuring us of the safety of the diet. In summary, based on these three cases studies and a review of the literature, we suggest that a moderately protein-restricted, supplemented, plant-based diet might contribute to controlling proteinuria in pregnant CKD women with focal segmental glomerulosclerosis. However further studies are warranted to confirm the potential value of such a treatment strategy.

Angiotensin-Converting Enzyme Inhibitor Initiation and Dose Uptitration in Children With Cardiovascular Disease: A Retrospective Review of Standard Clinical Practice and a Prospective Randomized Clinical Trial

Background

Angiotensin‐converting enzyme inhibitors (ACEIs) are a mainstay of medical management in pediatric cardiology. However, there are no data defining how best to initiate and uptitrate the dose of these medications in children.

Methods and Results

Retrospective chart review revealed only 24% of our pediatric cardiology inpatients were discharged on predefined optimal doses of ACEIs and few underwent further dose uptitration in the 8 weeks after hospital discharge. Therefore, 2 alternative protocols for initiation of captopril were compared in a prospective randomized clinical trial. A “rapid uptitration” protocol reached an optimal dose on day 3, whereas the alternative, “prolonged uptitration” protocol, reached an optimal dose on day 9. Forty‐6 patients (54% male) were recruited to the trial, with a median age of 0.7 year (IQR 0.5–2.3 years). Captopril was initiated while in intensive care in 39% of patients and on the cardiology ward in 61%. There were no differences between the protocols in episodes of hypotension, symptomatic hypotension, or indices of renal function. Patients following the rapid protocol reached higher doses of captopril (0.93±0.24 versus 0.57±0.38 mg/kg per dose, P<0.0001) and were more likely to have achieved the predefined target (88% versus 43%, P=0.002) and optimal ACEI doses (80% versus 29%, P=0.001) before discharge.

Conclusions

A protocol of rapid ACEI dose uptitration for infants and children with cardiovascular disease can be introduced safely, even in patients receiving intensive care therapy. Compared with standard clinical practice or with a more prolonged protocol, rapid ACEI dose uptitration achieves a higher dosage in this population with no evident disadvantages.

Clinical Trial Registration

URL: https://www.clinicaltrials.gov/. Unique identifier: NCT00742040.

Reduced sensitivity of the renal vasculature to angiotensin II in young rats: the role of the angiotensin type 2 receptor

BACKGROUND

The angiotensin type-2 receptor (AT2R) opposes the vasoconstrictor actions of angiotensin II (AngII) mediated through the angiotensin type-1 receptor (AT1R). Renal AT2R levels are high during fetal life, but decrease significantly during postnatal maturation. To provide insight into the functional role of the AT2R in the kidney during postnatal development, we investigated the effects of AT2R antagonism on cardiovascular responses to AngII in young and adult male rats.

METHODS

In anesthetized 3- and 6-wk-old male Sprague-Dawley rats, mean arterial pressure (MAP) and renal blood flow (RBF) were measured in response to AngII in the presence of vehicle treatment or AT2R blockade with PD123319.

RESULTS

The pressor effect of AngII and associated reduction in RBF were significantly less in 3-wk- than 6-wk-old rats. AT2R blockade potentiated the reduction in RBF in response to AngII in 3-wk-old rats only.

CONCLUSION

In young rats, the AT2R modulates the response to AngII, blunting renal vasoconstriction. This effect is attenuated with age in association with a developmental reduction in renal AT2R expression. These findings may have implications for the development of novel therapies that target the renin-angiotensin system for the improvement of renal function in term and, in particular, preterm infants.

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

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

Transforming growth factor-β1 receptor inhibition preserves glomerulotubular integrity during ureteral obstruction in adults but worsens injury in neonatal mice

Unilateral ureteral obstruction (UUO), a widely used model of chronic kidney disease and congenital obstructive uropathy, causes proximal tubular injury and formation of atubular glomeruli. Because transforming growth factor-β1 (TGF-β1) is a central regulator of renal injury, neonatal and adult mice were subjected to complete UUO while under general anesthesia and treated with vehicle or ALK5 TGF-β1 receptor inhibitor (IN-1130, 30 mg·kg(-1)·day(-1)). After 14 days, glomerulotubular integrity and proximal tubular mass were determined by morphometry of Lotus tetragonolobus lectin distribution, and the fraction of atubular glomeruli was determined by serial section analysis of randomly selected individual glomeruli. Glomerular area, macrophage infiltration, fibronectin distribution, and interstitial collagen were measured by morphometry. Compared with placebo, inhibition of TGF-β1 by IN-1130 decreased apoptosis and formation of atubular glomeruli, prevented parenchymal loss, increased glomerular area and glomerulotubular integrity, and increased proximal tubule fraction of the adult obstructed kidney parenchyma from 17 to 30% (P < 0.05, respectively). IN-1130 decreased macrophage infiltration and fibronectin and collagen deposition in the adult obstructed kidney by ∼50% (P < 0.05, respectively). In contrast to these salutary effects in the adult, IN-1130 caused widespread necrosis in obstructed neonatal kidneys. We conclude that whereas IN-1130 reduces obstructive injury in adult kidneys through preservation of glomerulotubular integrity and proximal tubular mass, TGF-β1 inhibition aggravates obstructive injury in neonates. These results indicate that while caution is necessary in treating congenital uropathies, ALK5 inhibitors may prevent nephron loss due to adult kidney disease.