Aliskiren and captopril improve cognitive deficits in poorly controlled STZ-induced diabetic rats via amelioration of the hippocampal P-ERK, GSK3β, P-GSK3β pathway

Learning and memory deficits are obvious symptoms that develop over time in patients with poorly controlled diabetes. Hyperactivity of the renin-angiotensin system (RAS) is directly associated with β-cell dysfunction and diabetic complications, including cognitive impairment. Here, we investigated the protective and molecular effects of two RAS modifiers, aliskiren; renin inhibitor and captopril; angiotensin converting enzyme inhibitor, on cognitive deficits in the rat hippocampus. Injection of low dose streptozotocin for 4 days resulted in type 1 diabetes. Then, poorly controlled diabetes was mimicked with ineffective daily doses of insulin for 4 weeks. The hyperglycaemia and pancreatic atrophy caused memory disturbance that were identifiable in behavioural tests, hippocampal neurodegeneration, and the following significant changes in the hippocampus, increases in the inflammatory marker interleukin 1β, cholinesterase, the oxidative stress marker malondialdehyde and protein expression of phosphorylated extracellular-signal-regulated kinase and glycogen synthase kinase-3 beta versus decrease in the antioxidant reduced glutathione and protein expression of phosphorylated glycogen synthase kinase-3 beta. Blocking RAS with either drugs along with insulin amended all previously mentioned parameters. Aliskiren stabilized the blood glucose level and restored normal pancreatic integrity and hippocampal malondialdehyde level. Aliskiren showed superior protection against the hippocampal degeneration displayed in the earlier behavioural modification in the passive avoidance test, and the aliskiren group outperformed the control group in the novel object recognition test. We therefore conclude that aliskiren and captopril reversed the diabetic state and cognitive deficits in rats with poorly controlled STZ-induced diabetes through reducing oxidative stress and inflammation and modulating protein expression.

[Expressions of Renin, angiotensin converting enzyme, angiotensin receptor 1, and angiotensin receptor 2 in synovial tissue of osteoarthritis at different stages]

OBJECTIVE

To study the expressions of Renin, angiotensin converting enzyme (ACE), angiotensin receptor 1 (AT1R), and AT2R in synovial tissue of osteoarthritis (OA) at different stages.

METHODS

The patients who were treated with upper knee amputation because of trauma or total knee arthroplasty for OA between January 2018 and December 2018 were enrolled. Among them, 32 patients who met the selection criteria were included in the study. According to the Kellgren-Lawrence (K-L) X-ray classification, they were allocated to normal synovial group (group A, n=9), moderate OA synovial group (group B, n=11, K-L level 3), and advanced OA synovial group (group C, n=12, K-L level 4). The relative expressions of Renin, ACE, AT1R, and AT2R mRNAs and proteins were detected by real-time fluorescence quantitative PCR (qRT-PCR) and Western blot.

RESULTS

The relative expressions of Renin, ACE, and AT1R mRNAs and proteins were significantly higher in group B and group C than in group A ( P<0.05). The relative expressions of ACE and AT1R mRNAs and proteins and Renin protein were significantly higher in group C than in group B ( P<0.05). However, the relative expressions of AT2R mRNA and protein were lower in group B and group C than in group A ( P<0.05), and in group C than in group B ( P<0.05).

CONCLUSION

The expressions of Renin, ACE, and AT1R in synovial tissue of osteoarthritis significantly increase as the K-L level increased, and the expression of AT2R decreases. Renin, ACE, AT1R, and AT2R have a certain degree of correlation with the development of OA.

Megalin: a Novel Determinant of Renin-Angiotensin System Activity in the Kidney?

PURPOSE OF REVIEW

Megalin is well known for its role in the reabsorption of proteins from the ultrafiltrate. Recent studies suggest that megalin also reabsorbs renin and angiotensinogen. Indeed, without megalin urinary renin and angiotensinogen levels massively increase, and even prorenin becomes detectable in urine.

RECENT FINDINGS

Intriguingly, megalin might also contribute to renal angiotensin production, as evidenced from studies in megalin knockout mice. This review discusses these topics critically, concluding that urinary renin-angiotensin system components reflect diminished reabsorption rather than release from renal tissue sites and that alterations in renal renin levels or megalin-dependent signaling need to be ruled out before concluding that angiotensin production at renal tissue sites is truly megalin dependent. Future studies should evaluate megalin-mediated renin/angiotensinogen transcytosis (allowing interstitial angiotensin generation), and determine whether megalin prefers prorenin over renin, thus explaining why urine normally contains no prorenin.

Clinical determinants and prognostic implications of renin and aldosterone in patients with symptomatic heart failure

Aims

Activation of the renin–angiotensin–aldosterone system plays an important role in the pathophysiology of heart failure (HF) and has been associated with poor prognosis. There are limited data on the associations of renin and aldosterone levels with clinical profiles, treatment response, and study outcomes in patients with HF.

Methods and results

We analysed 2,039 patients with available baseline renin and aldosterone levels in BIOSTAT‐CHF (a systems BIOlogy study to Tailored Treatment in Chronic Heart Failure). The primary outcome was the composite of all‐cause mortality or HF hospitalization. We also investigated changes in renin and aldosterone levels after administration of mineralocorticoid receptor antagonists (MRAs) in a subset of the EPHESUS trial and in an acute HF cohort (PORTO). In BIOSTAT‐CHF study, median renin and aldosterone levels were 85.3 (percentile_25–75 = 28–247) μIU/mL and 9.4 (percentile_25–75 = 4.4–19.8) ng/dL, respectively. Prior HF admission, lower blood pressure, sodium, poorer renal function, and MRA treatment were associated with higher renin and aldosterone. Higher renin was associated with an increased rate of the primary outcome [highest vs. lowest renin tertile: adjusted‐HR (95% CI) = 1.47 (1.16–1.86), P = 0.002], whereas higher aldosterone was not [highest vs. lowest aldosterone tertile: adjusted‐HR (95% CI) = 1.16 (0.93–1.44), P = 0.19]. Renin and/or aldosterone did not improve the BIOSTAT‐CHF prognostic models. The rise in aldosterone with the use of MRAs was observed in EPHESUS and PORTO studies.

Conclusions

Circulating levels of renin and aldosterone were associated with both the disease severity and use of MRAs. By reflecting both the disease and its treatments, the prognostic discrimination of these biomarkers was poor. Our data suggest that the “point” measurement of renin and aldosterone in HF is of limited clinical utility.

The Renin-Angiotensin System in the Central Nervous System and Its Role in Blood Pressure Regulation

Purpose of the Review

The main goal of this article is to discuss how the development of state-of-the-art technology has made it possible to address fundamental questions related to how the renin-angiotensin system (RAS) operates within the brain from the neurophysiological and molecular perspective.

Recent Findings

The existence of the brain RAS remains surprisingly controversial. New sensitive in situ hybridization techniques and novel transgenic animals expressing reporter genes have provided pivotal information of the expression of RAS genes within the brain. We discuss studies using genetically engineered animals combined with targeted viral microinjections to study molecular mechanisms implicated in the regulation of the brain RAS. We also discuss novel drugs targeting the brain RAS that have shown promising results in clinical studies and trials.

Summary

Over the last 50 years, several new physiological roles of the brain RAS have been identified. In the coming years, efforts to incorporate cutting-edge technologies such as optogenetics, chemogenetics, and single-cell RNA sequencing will lead to dramatic advances in our full understanding of how the brain RAS operates at molecular and neurophysiological levels.

Statins in COVID-19: is there any foundation?

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causal agent of coronavirus disease 2019 (COVID-19). Acute respiratory distress syndrome is the main cause of death from COVID-19 and occurs due to an exaggerated inflammatory response that causes the release of pro-inflammatory cytokines such as interleukins and tumor necrosis factor-alpha (TNF-α). Statins are lipid lowering drugs with pleiotropic effects. They have shown benefit in the management of inflammatory and autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis and multiple sclerosis. Furthermore, due to their immunomodulatory properties, they have been used in the treatment of various infectious diseases such as community-acquired pneumonia and influenza. In this review we analyze the pathophysiological foundations that support the use of statins as an adjunctive treatment in patients with COVID-19.

Modeling Human Diabetic Kidney Disease by Combining Hyperglycemia and Hypertension in a Transgenic Rodent Model

Traditional animal models mimic only the earliest stages of human diabetic nephropathy (DN), which limits their utility to dissect the pathogenesis of progressive disease or test novel therapeutics. In this chapter we describe in detail the experimental procedures required to conduct the Cyp1a1mRen2 rodent model, in which hyperglycemia and renin-dependent hypertension synergize to promote moderate proteinuria, renal fibrosis, and induction of many of the transcriptomic changes observed in the kidney of patients with progressive DN.

Lactation Leads to Modifications in Maternal Renin-Angiotensin System in Later Life

The objective of this study was to evaluate whether the renin-angiotensin system (RAS) is associated with maternal cardioprotective phenotype observed in post-lactated mice later in life. Following the delivery, CD-1 female mice were randomized to one of the following groups: lactated (nursed pups for 3 weeks, n = 10) or non-lactated (pups were removed after birth, n = 10). The mice were sacrificed 6 months after the delivery, and tissues were collected. Protein levels of angiotensinogen, angiotensin type 1 and 2 receptors (AT1R, AT2R), angiotensin converting enzymes (ACE, ACE2), and MAS receptor were determined using Western blot. Results were analyzed using Student's t-test and Mann-Whitney test as appropriate (significance: P < 0.05). Angiotensinogen levels were significantly lower in the liver (P = 0.0002), and ACE was significantly decreased in the lungs (P = 0.04) and kidney (P = 0.001) from lactated mice as compared to non-lactated. The levels of AT2R in the kidney (P = 0.02) and visceral adipose tissue (VAT, P = 0.04), the ACE 2 in the VAT (P = 0.03) and heart (P = 0.04), and MAS receptor in VAT (P = 0.02) were significantly elevated in tissues from lactated mice. No other differences were found. Lactation led to the upregulation and downregulation of selected RAS components in lactated mice as compared to non-lactated group and may be a contributing factor to maternal cardioprotective phenotype later in life. Further studies are needed to dissect the mechanisms between lactation and the long-term maternal cardiometabolic benefits, which could lead to the therapies to prevent cardiovascular disease in women.

Short- and long-term effects of lipoprotein apheresis on plasma hormones in patients with therapy-resistant dyslipidemia

BACKGROUND AND AIMS

Lipoprotein apheresis (LA) is a highly effective method to improve the clinical and metabolic situation in patients with therapy-resistant disorders of lipid metabolism. Cholesterol is the substrate for the synthesis of all steroid hormones. If repeated massive reduction of LDL-cholesterol may interfere with human adrenal steroidogenesis, and could become clinically relevant is unknown, so far. Thus, the aim of this study was to determine possible short- and long-term effects of LA on blood plasma levels of ACTH, cortisol, aldosterone, DHEAS, renin and testosterone.

METHODS

In total, 39 patients, treated with one of four LA techniques were studied: 1. Lipid Filtration (LF; n = 7), 2. Dextran Sulfate Adsorption (DSA; n = 7), 3. Membrane Filtration Optimised Novel Extracorporeal Treatment (MONET; n = 8), and 4. Direct Absorption of Lipoproteins (DALI; n = 15). Hormone levels were analyzed before and after five LA sessions with an interval of 20 weeks covering a total observation time of two years. In addition patients were comprehensively characterized by clinical and laboratory data.

RESULTS

Patients treated with LA revealed an acute reduction of steroid hormones and ACTH, independent of apheresis technology but no long-term insufficiency in steroidogenesis was observed. Plasma renin levels were stable in LF patients and were highly elevated in patients under DSA, MONET and DALI apheresis throughout the observation period.

CONCLUSIONS

In summary, these data suggest that although different LA techniques considerably differ in their acute effects on hormone levels during LA, they did not alter long-term hormone levels sustainably.

Kidney therapeutic potential of peptides derived from the bromelain hydrolysis of green peas protein

Objectives

Kidney disease is a global health problem that needs a solution to its therapy. In the previous study, we found that protein hydrolysate of green peas origin of Indonesia hydrolysed by bromelain (PHGPB) showed improve kidney function in cisplatin-induced nephropathy rats. In this study, we investigated the effect of PHGPB to obtain effective dose that exerts a therapeutic effect on chronic kidney disease (CKD) based on reducing urea and creatinine levels and to elucidate its mechanism of action.

Materials and Methods

Two sets of experiments were conducted: (1) characteristics and proteomic profile of PHGPB, (2) in vivo test of PHGPB in gentamycin-induced Wistar rats, including urea and creatinine measurements, activities of antioxidant and kidney-related peptides (ANP, COX-1, and renin).

Results

PHGPB showed three bands under 10 kDa using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and contained 10 identified proteins using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Significant differences in urea and creatinine levels were found between all PHGPB treatments and positive controls (P<0.01). The lowest levels of urea and creatinine that were validated by high super oxide dismutase (SOD) activity and atrial natriuretic peptide (ANP) level were obtained in the 200 mg/day PHGPB treatment. However, the mean renin level was high and cyclooxygenase-1 (COX-1) level did not exceed positive and negative control levels.

Conclusion

PHGPB at dose 200 mg/kgBW shows a potential CKD therapeutic effect that is dose-dependent. Higher PHGPB dose corresponds to better effect on kidney function by increasing antioxidant activity and ANP levels in gentamycin-induced Wistar rats.

Understanding the dual mechanism of bioactive peptides targeting the enzymes involved in Renin Angiotensin System (RAS): An in-silico approach

Understanding the dual inhibition mechanism of food derivative peptides targeting the enzymes (Renin and Angiotensin Converting enzyme) in the Renin Angiotensin System. Two peptides RALP and WYT were reported to possess antihypertensive activity targeting both renin and ACE, and we have used molecular docking and molecular dynamics simulation, in order to understand the underlying mechanism. The selected peptides (RALP and WYT) from the series of peptides reported were docked to renin and ACE and two binding modes were selected based on the binding energy, interaction pattern and clusters of docking simulation. The enzyme-peptide complexes for renin and ACE (Renin/RALP_1,2; ACE/RALP_1,2; Renin/WYT_1,2 and ACE/WYT_1,2) were subjected to molecular dynamics simulation. Our results identified that the peptides inhibiting renin, tends to move out of the binding pockets (S1' S2') which is critical for potent binding and occupies the less important pockets (S4 and S3). This could possibly be the reason for its low potency. Whereas, the same peptides targeting ACE, tends to be intact in the pocket because of the metal ion coordination and there is an ample room to improve on its efficacy. Our results further pave way for the biochemist, medicinal chemist to design dual peptides targeting the RAS effectively. Communicated by Ramaswamy H. Sarma.

Resistant Hypertension: A Clinical Perspective

Resistant hypertension is a common clinical entity, defined as suboptimal blood pressure response to multiple therapies after excluding medication nonadherence and secondary forms of hypertension. Patients with resistant hypertension generally share several comorbidities. Resistant hypertension is more common in individuals of African descent. Blood pressure should be optimized using multiple strategies, including lifestyle changes and single-pill combination therapies, with the aim of reducing cardiovascular events while reducing side effects from using antihypertensive therapy. A renin/aldosterone-based diagnostic and treatment approach will help tailor therapy. The use of mineralocorticoid receptor antagonists or amiloride as appropriate is favored.

Vasopressin actions in the kidney renin angiotensin system and its role in hypertension and renal disease

Vasopressin, also named antidiuretic hormone (ADH), arginine vasopressin (AVP) is the main hormone responsible for water maintenance in the body through the antidiuretic actions in the kidney. The posterior pituitary into the blood releases vasopressin formed in the hypothalamus. Hypothalamic osmotic neurons are responsible to initiate the cascade for AVP actions. The effects of AVP peptide includes activation of V2 receptors which stimulate the formation of cyclic AMP (cAMP) and phosphorylation of water channels aquaporin 2 (AQP2) in the collecting duct. AVP also has vasoconstrictor effects through V1a receptors in the vasculature, while V1b is found in the nervous system. V1a and b receptors increases intracellular Ca²⁺ while activation of V2 receptors of signaling pathways are related to cAMP-dependent phosphorylation in kidney collecting ducts acting in coordination to stimulate water and electrolyte homeostasis. AVP potentiate formation of intratubular angiotensin II (Ang II) through V2 receptors-dependent distal tubular renin formation, contributing to Na+ reabsorption. On the same way, Ang II receptors are able to potentiate the effects of V2-dependent stimulation of AQP2 abundance in the plasma membrane. The role of AVP in hypertension and renal disease has been demonstrated in pathological states with the involvement of V2 receptors in the progression of kidney damage in diabetes and also on the stimulation of intracellular pathways linked to the development of polycystic kidney.

The association between maternal and foetal REN gene polymorphisms and preeclampsia/eclampsia: A hybrid design study

OBJECTIVES

Preeclampsia (PE)/eclampsia (E) is an important cause of foetal and maternal morbidity and mortality, and its aetiology is poorly understood. Good evidence suggests that renin (REN) might be associated with PE/E. The risk of PE/E is determined by both maternal and foetal genes, but most previous studies have focused on maternal contributions. This study aimed to explore the association of maternal and foetal REN polymorphisms with PE/E in pregnant Han Chinese women.

METHODS

A case-parents/mother-control study including 347 PE/E patients with their partners and offspring and 700 control mothers with their offspring was conducted. A log-linear model was used to investigate the association between maternal and foetal REN SNPs and PE/E simultaneously, as well as the interaction of REN SNPs and environmental factors on PE/E.

RESULTS

The foetal REN rs5707 AC genotype in combination with a pre-pregnancy BMI ≥ 24 kg/m² was significantly associated with an increased risk of PE/E, with an OR of 2.75 (95%CI = 1.50-5.06). Maternal and foetal rs5707 were significantly associated with an increased risk of PE/E under the recessive model (AA + AC/CC). In haplotype analyses, foetal CCT (in the order of rs2368564, rs5707, rs5705) and TAT genotypes were positively associated with the risk of PE/E. There was no significant association between maternal and foetal REN SNP genotypes and PE/E in the transmission disequilibrium test (TDT) and log-linear model analysis.

CONCLUSIONS

Findings from this study indicate that foetal rs5707 polymorphisms may play a significant role in PE/E development, especially among overweight or obese pregnant women in China.

Systemic ß adrenergic stimulation/ sympathetic nerve system stimulation influences intraocular RAS through cAMP in the RPE

Several lines of evidence support the existence of a renin-angiotensin system (RAS) in the retina that is separated from the blood stream by the retinal pigment epithelium (RPE). Under physiological conditions, increased activity of intraretinal RAS regulates neuronal activity of the retina but patho-physiologically participates in retinal degeneration such as hypertensive or diabetic retinopathy. Interestingly, the RPE appears to be a modulator of intraretinal RAS in response to changes in systemic RAS. As increased systemic RAS activity is associated with increased sympathetic tonus, we investigated whether systemic β-adrenergic stimulation of the RPE also modulates renin expression in the RPE. In vivo, the mouse RPE expresses the β-adrenergic receptor subtypes 1 and 2. Staining of retina sagittal sections showed tyrosine hydroxylase positive nerve endings in the choroid indicating adrenaline/noradrenaline production sites in close proximity to the RPE. Systemic infusion of isoproterenol increased renin expression in the RPE but not in the retina. This increase was sensitive to concomitant systemic application of the angiotensin-2 receptor-type-1 blocker losartan. In vitro analysis of renin gene expression using polarized porcine RPE showed that the activity of the renin promoter can be increased by cAMP stimulation (IBMX/forskolin) but was not influenced by angiotensin-2. Thus, with the identification of the β-adrenergic system we added a new regulator of the retinal RAS with relevance for retinal function and pathology. Furthermore, it appears that the RPE is not only a close interaction partner of the photoreceptors but also a regulator or retinal activity in general.

Juxtaglomerular Cell Tumor: Reviewing a Cryptic Cause of Surgically Correctable Hypertension

Juxtaglomerular cell tumor (JGCT), or reninoma, is a typically benign neoplasm generally affecting adolescents and young adults due to modified smooth muscle cells from the afferent arteriole of the juxtaglomerular apparatus. Patients experience symptoms related to hypertension and hypoka-lemia due to renin-secretion by the tumor. MRI, PET, CT, and renal vein catheterizations can be used to capture JGCTs, with laparoscopic ultrasonography being most cost-efective. Surgical removal is the best option for management; electrolyte imbalances are a potential complication which may be assuaged via pre-surgical administration of aliskiren, a renin inhibitor. Considering the vast etiology for hypertension and rarity of JGCT, the diagnosing physician must have a high index of suspicion for JGCT. Early recognition and management can help prevent cardiovascular or pregnancy complications and fatalities, vascular invasion and metastasis, improve quality of life, and limit socioeconomic liabilities. Herein we review the epidemiology, genetics, histopathol-ogy, clinical presentation, and management of this rare condition. The impact of genetics on prognosis warrant further research.

Differential activation of the renin-angiotensin-aldosterone-system in response to childhood and adulthood trauma

OBJECTIVE

Previous evidence suggested lasting and cumulative effects of traumatization on the renin-angiotensin-aldosterone-system (RAAS). However, it is unclear whether traumas during childhood and those experienced in adulthood differentially impact the RAAS. In this study, we sought to investigate main and putative interactive effects of childhood and adulthood trauma on RAAS functioning.

METHODS

Plasma concentrations of renin and aldosterone were measured in a general population sample (n = 2016). Childhood trauma was assessed using the Childhood Trauma Questionnaire (CTQ), adulthood trauma was measured using the PTSD module of the Structured Clinical Interview of the DSM-IV. Linear regression models were calculated to assess the relations between childhood or adulthood traumatization with renin and aldosterone concentrations.

RESULTS

Exposure to (ß = 0.094; p = 0.01), severity of childhood trauma (ß = 0.004; p = 0.01) were associated with increased aldosterone, but not renin levels. Results were carried by all dimensions of abuse, while childhood neglect was not associated with altered RAAS activity. In contrast, adulthood traumas (ß = 0.113; p < 0.01) were significantly associated with increased renin concentrations. Subjects with PTSD (renin: ß = 0.345; p = 0.01; aldosterone: ß = 0.232; p = 0.04) and those who had been exposed to both childhood and adulthood trauma showed increases in renin (ß = 0.180; p < 0.01) and aldosterone (ß = 0.340; p < 0.01) levels.

DISCUSSION

These findings indicate that trauma is associated with differential alterations of the RAAS depending on the time of traumatization. Moreover, exposure to childhood or adulthood trauma may act synergistically on the RAAS, resulting in severe dysregulation of the RAAS. The results contribute to explain associations between trauma and enhanced risk for physical disease.

Immunohistochemical expression of renin is a prognostic factor for recurrence in nonmetastatic renal cell carcinoma

PURPOSE

To analyze the intratumoral immunohistochemical expression of renin and its value as a prognostic factor for recurrence in nonmetastatic clear cell renal cell carcinoma (ccRCC).

METHODS

A total of 498 patients with nonmetastatic ccRCC from the Latin American Renal Cancer Group database who underwent partial or radical nephrectomy between 1990 and 2016 were selected. All cases were revised, and 2 distinct samples were obtained for tissue microarray construction. Ten years of follow-up was assessed, and disease-free survival rates (DFS) were analyzed. Renin expression was classified qualitatively as negative or positive. For the quantitative analysis, a cutoff was estimated using the maximum of the standardized log-rank statistic.

RESULTS

Nuclear renin was qualitatively positive in 360 cases (72%) and negative in 138 (28%), whereas quantitatively, an equal number of cases had ≤35% or >35% renin-positive nuclei. The absence of renin expression was associated with high-grade tumors (by ISUP and Fuhrman classification, both P < 0.001), greater microscopic venous invasion (P = 0.046), and renal vein invasion (P = 0.026). In the multivariate analyses, qualitatively negative renin expression was an unfavorable prognostic factor for DFS (RR = 2.923, P < 0.001). With regard to quantitative renin expression, a cutoff of ≤35 was associated with worse DFS (RR = 4.085, P < 0.001).

CONCLUSIONS

The intratumoral immunohistochemical expression of renin in patients with ccRCC provides valuable prognostic data regarding the likelihood of recurrence.

Angiotensin II and aldosterone in retinal vasculopathy and inflammation

Angiotensin II and aldosterone are the main effectors of the renin-angiotensin aldosterone system (RAAS) and have a central role in hypertension as well as cardiovascular and renal disease. The localization of RAAS components within the retina has led to studies investigating the roles of angiotensin II, aldosterone and the counter regulatory arm of the pathway in vision-threatening retinopathies. This review will provide a brief overview of RAAS components as well as the vascular pathology that develops in the retinal diseases, retinopathy of prematurity, diabetic retinopathy and neovascular age-related macular degeneration. The review will discuss pre-clinical and clinical evidence that modulation of the RAAS alters the development of vasculopathy and inflammation in the aforementioned retinopathies, as well as the emerging role of aldosterone and the mineralocorticoid receptor in central serous chorioretinopathy.

Impact of renin-angiotensin-aldosterone system polymorphisms on myocardial perfusion: Correlations with myocardial single photon emission computed tomography-derived parameters

BACKGROUND

Renin-angiotensin-aldosterone system (RAAS) has an important role in atherosclerosis. We investigated the effects of six RAAS gene polymorphisms on myocardial perfusion.

METHODS AND RESULTS

We examined 810 patients with known or suspected coronary artery disease (CAD) using stress-rest myocardial single-photon emission computed tomography. Summed stress score (SSS), summed rest score (SRS), summed difference score (SDS), transient ischemic dilation (TID), and lung/heart ratio (LHR) were recorded. The following gene polymorphisms were investigated: angiotensin-converting enzyme (ACE) insertion/deletion (I/D), angiotensinogen (AGT) M235T and T174M, angiotensin II type 1 receptor (AT1R) A1166C, renin (REN) C5312T, and angiotensin II type 2 receptor (AT2R) C3123A. The heterozygotes or homozygotes on ACE D allele were 7.54 times more likely to have abnormal SSS, while the AGT (T174M) heterozygotes were 5.19 times more likely to have abnormal SSS. The homozygotes of ACE D had significantly higher values on TID and LHR, while the AGT (T174M) heterozygotes had higher values on TID. The AT1R heterozygotes had greater odds for having SSS ≥ 3. The patients carried AT1R homozygosity of C allele had significantly higher values on TID, while heterozygotes of AT1R had significantly higher values on LHR.

CONCLUSIONS

Among the polymorphisms investigated, ACE D allele had the strongest association with abnormal myocardial perfusion.

IgA Nephropathy in Elderly Patients

BACKGROUND AND OBJECTIVES

Some studies suggest that the incidence of IgA nephropathy is increasing in older adults, but there is a lack of information about the epidemiology and behavior of the disease in that age group.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this retrospective multicentric study, we analyzed the incidence, forms of presentation, clinical and histologic characteristics, treatments received, and outcomes in a cohort of 151 patients ≥65 years old with biopsy-proven IgA nephropathy diagnosed between 1990 and 2015. The main outcome was a composite end point of kidney replacement therapy or death before kidney replacement therapy.

RESULTS

We found a significant increase in the diagnosis of IgA nephropathy over time from six patients in 1990-1995 to 62 in 2011-2015 (P value for trend =0.03). After asymptomatic urinary abnormalities (84 patients; 55%), AKI was the most common form of presentation (61 patients; 40%). Within the latter, 53 (86%) patients presented with hematuria-related AKI (gross hematuria and tubular necrosis associated with erythrocyte casts as the most important lesions in kidney biopsy), and eight patients presented with crescentic IgA nephropathy. Six (4%) patients presented with nephrotic syndrome. Among hematuria-related AKI, 18 (34%) patients were receiving oral anticoagulants, and this proportion rose to 42% among the 34 patients older than 72 years old who presented with hematuria-related AKI. For the whole cohort, survival rates without the composite end point were 74%, 48%, and 26% at 1, 2, and 5 years, respectively. Age, serum creatinine at presentation, and the degree of interstitial fibrosis in kidney biopsy were risk factors significantly associated with the outcome, whereas treatment with renin-angiotensin-aldosterone blockers was associated with a lower risk. Immunosuppressive treatments were not significantly associated with the outcome.

CONCLUSIONS

The diagnosis of IgA nephropathy among older adults in Spain has progressively increased in recent years, and anticoagulant therapy may be partially responsible for this trend. Prognosis was poor.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2019_07_16_CJASNPodcast_19_08_.mp3.

Short-term exposure to 12‰ brackish water has significant effects on the endocrine physiology of juvenile American alligator (Alligator mississippiensis)

American alligators (Alligator mississippiensis) mainly inhabit freshwater habitats but can be exposed to a wide range of salinities during storm surges, droughts or from alterations in freshwater flows. Although some salinization events last weeks, others only last a few days. This study assessed changes in the endocrine function of the renin-angiotensin-aldosterone system (RAAS) and steroid hormone production (steroidogenesis) in juvenile alligators exposed to brackish water (12‰) for 7 days. We quantified plasma levels of angiotensin II and the corticosteroids (aldosterone, corticosterone and 11-deoxycortisol). Various progestogens, androgens, and estrogens were further assessed. The protein expression for the RAAS enzymes, renin and angiotensin converting enzyme (ACE), was quantified immunohistochemically in kidney and lung tissue, respectively, and histology was performed on kidney, lung and gonad tissues. Finally, blood biochemistry parameters such as electrolyte levels and diagnostic indicators for dehydration, renal, and hepatic function were measured. Corticosterone, 11-deoxycortisol, Na⁺, Cl^-, total protein, albumin, uric acid, and cholesterol levels were all significantly elevated in alligators exposed to brackish water compared with alligators in freshwater. The levels of 17β-estradiol and estrone were significantly lowered while histology showed alterations in gonad tissue in the brackish water exposed group. In contrast, while there were no effects of exposure on aldosterone levels, angiotensin II was significantly reduced in brackish water exposed alligators. These results correlated with significantly decreased expressions for both renin and ACE in kidney and lung tissue. Overall, this study showed that short-term exposure of alligators to 12‰ brackish water has significant endocrine effects on juvenile alligators.

Renin-angiotensin system research: from molecules to the whole body

Hypertension is one of the most important risk factors and a leading cause of death from cardiovascular and cerebrovascular diseases. Based on numerous previous studies, hypertension is thought to be caused by the complex mutual interactions of genetic factors and environmental factors, such as excessive salt intake and stress. However, its detailed mechanisms are not yet clearly understood. The renin-angiotensin system (RAS) is a key hormonal system in the pathogenesis of hypertension. New knowledge is still accruing on this cascade, even after more than 120 years since the discovery of renin. To clarify the molecular mechanisms of RAS in vivo, we created transgenic mice with chronic hypertension. These mice carry the human genes encoding renin, a hypertensive enzyme, and its substrate angiotensinogen. Hypotensive mice homozygous for a targeted disruption of the angiotensinogen gene were also created. This review presents our 47-year history of RAS research.

Systematic review: Renin-angiotensin system inhibitors in chemoprevention of hepatocellular carcinoma

BACKGROUND

Neoangiogenesis is one of the key pathogenetic mechanisms in hepatocellular carcinoma (HCC). Modulation of the renin-angiotensin system (RAS) by angiotensin-converting enzyme inhibitors (ACE-Is) and angiotensin receptor blockers (ARBs) seems to be a possible adjuvant therapy for HCC, due to the anti-angiogenic and anti-fibrogenic activity of these drugs.

AIM

To elucidate the role of ARBs and ACE-Is in HCC.

METHODS

We performed an electronic search of the literature using the most accessed online databases (PubMed, Cochrane library, Scopus and Web of Science), entering the query terms "angiotensin-converting enzyme inhibitors" OR "ACE inhibitors" OR "ACE-I" AND "hepatocarcinoma*" OR "hepatocellular carcinoma; moreover "angiotensin II type 1 receptor blockers" OR "ARBs" AND "hepatocarcinoma*" OR "hepatocellular carcinoma". Eligibility criteria were: (1) prospective or retrospective clinical studies; (2) epidemiological studies; and (3) experimental studies conducted in vivo or in vitro. Abstracts, conference papers, and reviews were excluded a priori. We limited our literature search to articles published in English, in peer-reviewed journals.

RESULTS

Thirty-one studies were selected. Three interventional studies showed that ACE-Is had a significant protective effect on HCC recurrence only when used in combination with vitamin K or branched chain aminoacids, without a significant increase in overall survival. Of six retrospective observational studies, mainly focused on overall survival, only one demonstrated a prolonged survival in the ACE-Is group, whereas the two that also evaluated tumor recurrence showed conflicting results. All experimental studies displayed beneficial effects of RAS inhibitors on hepatocarcinogenesis. Numerous experimental studies, conducted either on animals and cell cultures, demonstrated the anti-angiogenetic and antifibrotic effect of ACE-Is and ARBs, thanks to the suppression of some cytokines such as vascular endothelial growth factor, hypoxia-inducible factor-1a, transforming growth factor-beta and tumor necrosis factor alpha. All or parts of these mechanisms were demonstrated in rodents developing fewer HCC and preneoplastic lesions after receiving such drugs.

CONCLUSION

In humans, RAS inhibitors - alone or in combination - significantly suppressed the cumulative HCC recurrence, without prolonging patient survival, but some limitations intrinsic to these studies prompt further investigations.

[Reninoma: A Rare Cause of Endocrine Hypertension]

Juxtaglomerular tumours are rare causes of secondary hypertension. They typically present with difficult-to-manage hypertension, hypokalemia, hyperreninemia and secondary hyperaldosteronism. The authors describe a clinical case of a 45 years old female patient, with personal history of difficult-to-manage hypertension and hypokalemia since age 35, medicated with four types of anti-hypertensive agents. An analytical study was performed, which revealed secondary hyperaldosteronism [aldosterone 44.3 ng/dL (4 - 28 ng/dL), renin > 1000 mIU/mL (4.4 - 46.2 mIU/mL)]. Abdominal computed tomography scan identified a heterogeneous nodule located in the middle third of the right kidney, with 3.7 cm. Partial nephrectomy was performed and histological analysis confirmed the diagnosis of reninoma. After surgery, the patient had normal levels of aldosterone (9.2 ng/dL) and renin (1.20 mIU/mL), as well as normal blood pressure. The authors want to highlight this potentially curable cause of endocrine hypertension. Surgical resection is the treatment of choice and leads to normalization of blood pressure.

Classic and Nonclassic Renin-Angiotensin Systems in the Critically Ill

Classic and nonclassic renin-angiotensin systems (RAS) are 2 sides of an ubiquitous endocrine/paracrine cascade regulating blood pressure and homeostasis. Angiotensin II and angiotensin-converting enzyme (ACE) levels are associated with severity of disease in the critically ill, and are central to the physiology and the pathogenesis of circulatory shock. Angiotensin (1-7) and ACE2 act as an endogenous counterregulatory arm to the angiotensin II/ACE axis. The tissue-based RAS has paracrine effects dissociated from those of the circulating RAS. Exogenous angiotensin II or ACE2 may improve the outcome of septic shock and acute respiratory distress syndrome, respectively.

Efficacy and Safety of Imarikiren in Patients with Type 2 Diabetes and Microalbuminuria: A Randomized, Controlled Trial

BACKGROUND AND OBJECTIVES

Imarikiren is a novel, potent, and selective direct renin inhibitor that has shown high oral availability during clinical development for the treatment of diabetic nephropathy. We evaluated the efficacy and safety of imarikiren in patients with type 2 diabetes mellitus and microalbuminuria.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a randomized, multicenter, placebo-controlled, double-blind, phase 2, dose-finding trial. A total of 415 patients were randomized to imarikiren 5, 20, 40, or 80 mg; placebo; or candesartan cilexetil 8 mg treatment for 12 weeks. The primary end point was change in log-transformed urine albumin-to-creatinine ratio from baseline to the end of treatment analyzed using analysis of covariance and a fixed sequence testing procedure. Secondary efficacy end points included urine albumin-to-creatinine ratio at each assessment point and remission and progression rates. Exploratory efficacy end points included eGFR and sitting BP before dosing.

RESULTS

Changes in the urine albumin-to-creatinine ratio from baseline to the end of treatment were 16% (placebo), -16% (imarikiren 5 mg), -27% (imarikiren 20 mg), -38% (imarikiren 40 mg), -39% (imarikiren 80 mg), and -31% (candesartan cilexetil 8 mg). Urine albumin-to-creatinine ratio reductions from baseline were statistically significant in all imarikiren groups versus placebo (P<0.001 each) as well as for candesartan cilexetil 8 mg versus placebo (P<0.001). Remission rates (urine albumin-to-creatinine ratio <30 mg/g creatinine and decreased ≥30% from baseline) were higher in all imarikiren groups versus the placebo group. Incidence of adverse events was higher in the imarikiren 80-mg group (52%) versus placebo (42%) and candesartan cilexetil (43%) groups. Incidence of adverse events for the other imarikiren groups ranged from 33% to 42%. Adverse events were mild or moderate in severity. All imarikiren doses were well tolerated.

CONCLUSIONS

Imarikiren resulted in a dose-dependent improvement in albuminuria compared with placebo, and it was well tolerated in patients with type 2 diabetes mellitus and microalbuminuria.

Endocrine responses after a single bout of moderate aerobic exercise in healthy adult humans

Exercise is a stress stimulus for the human organism affecting the homeostatic mechanisms of the body, depending on the type, duration, intensity and frequency of exercise. The aim of this study was to determine the effects of a moderate aerobic exercise bout on the Hypothalamo-Pituitary-Adrenal (HPA) axis acute hormonal responses in healthy adult humans. Twelve healthy male and female volunteers (age: 30.6 ± 4.4 years), performed a single bout of a 30-minute aerobic exercise at 70% of VO2max on a treadmill, following standard diet. Blood samples were collected before (t0), at the end of the exercise bout (t30), and 30 min after the completion of exercise (t60). Serum adrenocorticotropic hormone (ACTH), cortisol (COR), aldosterone (ALDO) and renin (REN) were measured. One-way ANOVA was used for statistics. ACTH and COR decreased after exercise, reaching significance (p < 0.01) 30 min after the completion of the exercise bout. ALDO increased at the end of exercise and remained elevated 30 min after its completion. REN significantly increased at the end of exercise (p < 0.05) and remained elevated. The exercise regimen used in this study had beneficial effects on the stress axis, suggesting that specific exercise protocols can be characterised by mild physiological stress-inducing effects hence be prescribed for special diseased populations.

[Two case reports on resistant hypertension]

Primary aldosteronism (PA) is a frequent cause of resistant hypertension. The clinical presentation is heterogeneous, but a suppressed or low normal renin (especially with ACE inhibitors or sartans) should raise suspicion for primary aldosteronism, even when aldosterone levels are in the normal range. Diagnosis of unilateral hormone production from an adrenal adenoma (Conn syndrome), which is curable by surgery, requires adrenal vein sampling, which should be performed in experienced centers.

Nicousamide attenuates renal dysfunction and glomerular injury in remnant kidneys by inhibiting TGF-β1 internalisation and renin activity

Nicousamide has been shown to exert renal protective effects against diabetic nephropathy and has moved to a phase II clinical trial in China for diabetic nephropathy indication. To expand its clinical indications, 5/6-nephrectomised rats were used to mimic glomerular and vascular sclerosis and tubulointerstitial scarring, with subsequent progression towards end-stage renal disease. Adult Wistar rats underwent 5/6 nephrectomy to induce the development of chronic kidney disease, with a sham operation performed as a control. The nephrectomised animals were treated orally with either saline, nicousamide (7.5,15, or 45 mg/kg), benazepril (4 mg/kg), or losartan (10 mg/kg) daily for 20 weeks. At 8, 16, and 20 weeks of treatment, blood pressure was measured in each animal, and blood and urine samples were collected for biochemical analysis, while kidney remnants were collected for histological examination. Levels of fibronectin and transforming growth factor beta 1 (TGF-β1) were measured in kidneys by immunohistochemistry. Renin activity in the plasma was measured by an enzyme-linked immunosorbent assay. The results showed that nicousamide treatment significantly reduced systemic hypertension, proteinuria, and blood urea nitrogen (P < 0.05), effectively alleviated glomerular sclerosis scores and tubulointerstitial injuries in a dose-dependent manner (P < 0.01), and markedly decreased fibronectin and TGF-β1 levels in kidney tissues of the 5/6-nephrectomised animals. In vitro studies suggested that nicousamide could moderately inhibit the renin activity and strongly block the TGF-β1 internalisation into fibroblast cells. In summary, nicousamide may protect from renal failure through dual targeting, which involves a TGF-β1-dependent mechanism and inhibition of renin activity.

Leukemia development initiated by deletion of RBP-J: mouse strain, deletion efficiency and cell of origin

Conditional deletion of RBP-J, the major transcriptional effector of Notch signaling, specifically within renin-expressing cells leads to the development of B-cell leukemia. However, the influence of contributing factors such as mouse strain, cell of origin and Cre recombinase copy number are unknown. In this study, we compared RBP-J deletion efficiency using one versus two copies of Cre recombinase. Further, we compared the incidence and timing of leukemia development in two unique strains of mice, C57BL/6 and 129/SV, as well as at different B-cell developmental stages. We found that animals expressing two copies of Cre recombinase developed B-cell leukemia at an earlier age and with more fulminant disease, compared with control animals and animals expressing one copy of Cre recombinase. In addition, we found a difference in leukemia incidence between C57BL/6 and 129/SV mouse strains. Whereas deletion of RBP-J in renin-expressing cells of C57BL/6 mice leads to the development of B-cell leukemia, 129/SV mice develop dermatitis with a reactive, myeloproliferative phenotype. The difference in phenotypes is explained, in part, by the differential expression of extra-renal renin; C57BL/6 mice have more renin-expressing cells within hematopoietic tissues. Finally, we found that deletion of RBP-J in Mb1- or CD19-expressing B lymphocytes does not result in leukemia development. Together, these studies establish that renin progenitors are vulnerable cells for neoplastic transformation and emphasize the importance of genetic background on the development of inflammatory and malignant conditions.This article has an associated First Person interview with the first author of the paper.

Investigating the RAS can be a fishy business: interdisciplinary opportunities using Zebrafish

The renin-angiotensin system (RAS) is highly conserved, and components of the RAS are present in all vertebrates to some degree. Although the RAS has been studied since the discovery of renin, its biological role continues to broaden with the identification and characterization of new peptides. The evolutionarily distant zebrafish is a remarkable model for studying the kidney due to its genetic tractability and accessibility for in vivo imaging. The zebrafish pronephros is an especially useful kidney model due to its structural simplicity yet complex functionality, including capacity for glomerular and tubular filtration. Both the pronephros and mesonephros contain renin-expressing perivascular cells, which respond to RAS inhibition, making the zebrafish an excellent model for studying the RAS. This review summarizes the physiological and genetic tools currently available for studying the zebrafish kidney with regards to functionality of the RAS, using novel imaging techniques such as SPIM microscopy coupled with targeted single cell ablation and synthesis of vasoactive RAS peptides.

The SHRIMP study

It remains unknown which surrogate markers can predict diagnostic test results for primary hyperaldosteronism (PA). The Secondary Hypertension Registry Investigation in Mie Prefecture (SHRIMP) study has sequentially and prospectively recruited 128 patients with hypertension with an aldosterone-to-renin ratio (ARR) greater than 20, evaluated the differences among essential hypertension (EHT), idiopathic hyperaldosteronism (IHA), and aldosterone-producing adenoma (APA), and analyzed the predictors for the confirmatory tests. The patients underwent saline-loading, captopril-challenge, and upright furosemide-loading tests. Carotid, renovascular, and cardiac echography, brachial ankle pulse wave velocity (baPWV), endothelial function, nocturnal blood pressure decline, and the apnea hypopnea index were evaluated. Multivariate regression analyses showed that the plasma aldosterone concentration (PAC) at screening was a strong predictor of the saline and captopril test results. The plasma renin activity (PRA) at screening, urine β2-microglobulin, and left ventricular mass index (LVMI) were independent predictors for the captopril test. The estimated saline PAC and captopril 60 and 90 min ARRs predicted by the equations were highly correlated with the real values. The ROC curve analysis showed PAC at screening among each of predictors for the diagnostic tests and PAC after the saline-loading test had the highest diagnostic abilities of APA. Patients with IHA were older and had glucose intolerance and increased U-Alb/gCre and resistive indices. In patients with APA, the levels of U-Alb/gCre and urine β2-microglobulin were increased, and levels of insulin and the HOMA-IR were decreased. In conclusion, our proposed equations may be useful for estimating saline PAC and captopril ARR. Diagnostic predictors may differ for each confirmatory test.

Reninoma: a rare cause of curable hypertension

The most common type of refractory hypertension found in children is secondary hypertension, which is a potentially curable disease. Reninoma, a renin-secreting juxtaglomerular cell tumor, is a rare cause of severe hypertension that is usually diagnosed in adolescents and young adults. Surgical resection of the tumor completely cures the hypertension of patients with reninoma. The typical clinical presentation of reninoma includes hypokalemia, metabolic alkalosis, and features secondary to the increased activation of the renin-angiotensin system without renal artery stenosis. We report a case of reninoma in a female adolescent with a typical clinical presentation, in which surgical removal of the tumor completely cured hypertension. We discuss here the clinical features, imaging studies, and immunohistochemical examination of the tumor used to establish the diagnosis of reninoma and for the management of the condition.

Riligustilide Attenuated Renal Injury by the Blockade of Renin

BACKGROUND/AIMS

Nephropathy related with renin can be alleviated with ACE-inhibitors or AT1R blockers, whereas they might be ineffective after long-term administration because of a feedback production of enhanced renin. Therefore, it is urgent to develop a new category of anti-nephropathy medicine directly targeting renin. Riligustilide (C20), originally isolated from the Chinese herb Ligusticumporteri, a rhizome, was confirmed effective against many diseases.

METHODS

The therapeutic effect of C20 on renal injury and its underlying mechanism were investigated in three different nephrotic models, which were spontaneously hypertension rats (SHR) model, diabetic nephropathy in BTBR ob/ob mice model and 5/6-nephrectomized (5/6NX) rats model.

RESULTS

The intensity of kidney fibrosis was extensively decreased in the C20-treated rats compared to the vehicle animals. C20 significantly alleviated renal injury much more in 5/6 NX rats than in vehicle group. The rats in 5/6 NX without administrated C20 developed albuminuria earlier with more severe symptoms. Additionally, our findings showed that C20 down-regulated the renin expression and relocation of CREB-CBP complex in vivo and in vitro.

CONCLUSION

C20 plays importantly reno-protective roles most likely through the relocation of CREB-CBP complex.

Low plasma renin activity is an independent predictor of near-term incidence of hypertension in Asian populations

BACKGROUND

Plasma renin activity is involved in the regulation of body salt content and blood pressure. However, there is a paucity of data regarding the association between low or high plasma renin activity and the development of hypertension.

METHOD

We investigated the relation of baseline plasma renin activity to increases in blood pressure and the incidence of hypertension after four years in 2,146 non-hypertensive individuals from a community-based Korean population (mean age, 50 years), 58% of whom were women. We defined an "increase in blood pressure" as an increment of systolic blood-pressure ≥ 10 mmHg or initiation of antihypertensive drugs and defined "hypertension" as a systolic blood pressure of 140 mm Hg or higher, a diastolic blood pressure of 90 mm Hg or higher, or the use of antihypertensive medications.

RESULTS

After 4 years, the increase in blood pressure had increased in 27.9% of the participants, and hypertension had developed in 17.9%. After adjustment, the lowest sex-specific tertile of plasma renin activity was an independent risk factor of an elevation in blood pressure (Adjusted Odds Ratio 1.37, 95% confidence interval 1.07-1.74, p = 0.011) and hypertension (Adjusted Odds Ratio 1.84, 95% confidence interval 1.36-2.50, p < 0.001) compared to the highest sex-specific tertile. The associations between the plasma renin activity and blood-pressure outcomes were evident in adults with especially high urine sodium excretion.

CONCLUSION

Low plasma renin activity was associated with the development of hypertension in the middle-aged Asian population, especially in peoples with high sodium intake.

Lack of connexin 40 decreases the calcium sensitivity of renin-secreting juxtaglomerular cells

The so-called calcium paradoxon of renin describes the phenomenon that exocytosis of renin from juxtaglomerular cells of the kidney is stimulated by lowering of the extracellular calcium concentration. The yet poorly understood effect of extracellular calcium on renin secretion appears to depend on the function of the gap junction protein connexin 40 (Cx40) in renin-producing cells. This study aimed to elucidate the role of Cx40 for the calcium dependency of renin secretion in more detail by investigating if Cx40 function is really essential for the influence of extracellular calcium on renin secretion, if and how Cx40 affects intracellular calcium dynamics in renin-secreting cells and if Cx40-mediated gap junctional coupling of renin-secreting cells with the mesangial cell area is relevant for the influence of extracellular calcium on renin secretion. Renin secretion was studied in isolated perfused mouse kidneys. Calcium measurements were performed in renin-producing cells of microdissected glomeruli. The ultrastructure of renin-secreting cells was examined by electron microscopy. We found that Cx40 was not essential for stimulation of renin secretion by lowering of the extracellular calcium concentration. Instead, Cx40 increased the sensitivity of renin secretion response towards lowering of the extracellular calcium concentration. In line, the sensitivity and dynamics of intracellular calcium in response to lowering of extracellular calcium were dampened when renin-secreting cells lacked Cx40. Disruption of gap junctional coupling of renin-secreting cells by selective deletion of Cx40 from mesangial cells, however, did not change the stimulation of renin secretion by lowering of the extracellular calcium concentration. Deletion of Cx40 from renin cells but not from mesangial cells was associated with a shift of renin expression from perivascular cells of afferent arterioles to extraglomerular mesangial cells. Our findings suggest that Cx40 is not directly involved in the regulation of renin secretion by extracellular calcium. Instead, it appears that in renin-secreting cells of the kidney lacking Cx40, intracellular calcium dynamics and therefore also renin secretion are desensitized towards changes of extracellular calcium. Whether the dampened calcium response of renin-secreting cells lacking Cx40 function results from a direct involvement of Cx40 in intracellular calcium regulation or from the cell type shift of renin expression from perivascular to mesangial cells remains to be clarified. In any case, Cx40-mediated gap junctional coupling between renin and mesangial cells is not relevant for the calcium paradoxon of renin secretion.

A review on autosomal dominant tubulointerstitial kidney disease

In recent years there has been a reclassification of hereditary tubulointerstitial renal diseases. The old concepts of nephronoptisis or medullary cystic disease have been reordered based on the discovery of new genes. The 2015 KDIGO guidelines proposed a unification of terminology, diagnostic criteria and monitoring. So far 4genes causing autosomal dominant tubulointerstitial kidney disease have been described: MUC1, UMOD, HNF1B and REN. Although the mutation in each of them causes distinctive features in how they present, all have in common the progressive tubulointerstitial damage and renal fibrosis. In this article, we present a review of the guidelines and the literature, and some practical recommendations for dealing with this disease.

Aliskiren: Preclinical evidence for the treatment of hyperproliferative skin disorders

Psoriasis is a complex inflammatory and hyperproliferative skin disease. The pathogenesis and mechanisms involved are not completely understood, which makes treatment a difficult issue. Angiotensin II, the most active peptide of the renin-angiotensin system, seems to be involved in processes related to psoriasis pathogenesis, such as inflammation and cell proliferation. The aim of this study was to investigate the influence of renin inhibition on inflammation parameters and keratinocyte proliferation in a mouse model of chronic skin inflammation induced by croton oil. Aliskiren had anti-inflammatory effects by reducing levels of tumor necrosis factor-α and interleukin -6, and by inhibiting myeloperoxidase activity. Aliskiren also showed antiproliferative activity by reducing epidermal hyperplasia and proliferating cell nuclear antigen levels. Aliskiren treatment did not induce alterations in the cardiovascular system, normal skin thickness, and organ weight. These results suggest that aliskiren could be a valuable tool to be incorporated in the treatment of hyperproliferative and inflammatory skin disorders such as psoriasis.

Essential role of ATP6AP2 enrichment in caveolae/lipid raft microdomains for the induction of neuronal differentiation of stem cells

Background

The subcellular distribution of prorenin receptor and adaptor protein ATP6AP2 may affect neurogenesis. In this study, we hypothesized that ATP6AP2 expression and subcellular relocalization from caveolae/lipid raft microdomains (CLR-Ms) to intracellular sites may correlate with neuronal differentiation (Neu-Dif) of adipose-derived mesenchymal stem cells (ADSCs).

Methods

Human ADSCs isolated from 24 healthy donors and 24 patients with neurological disorders (ND) were cultured and induced for Neu-Dif. The mechanism of action of ATP6AP2 and the impact of its localization within the plasma membrane (particularly CLR-Ms) and intracellular sites on several pathways (mitogen-activated protein kinase, Wnt(s) signaling and others) and intracellular calcium and exosome release were evaluated. The impact of CLR-Ms on ATP6AP2 or vice versa was determined by pharmacological disruption of CLR-Ms or siATP6AP2 assays.

Results

In patients with ND, loss of ATP6AP2 from CLR-Ms correlated with an inhibition of Neu-Dif and signaling. However, its relocalization in CLR-Ms was positively correlated to induction of Neu-Dif in healthy subjects. An apparent switch from canonical to noncanonical Wnt signaling as well as from caveolin to flotillin occurs concurrently with the increases of ATP6AP2 expression during neurogenesis. Stimulation by renin activates ERK/JNK/CREB/c-Jun but failed to induce β-catenin. Wnt5a enhanced the renin-induced JNK responsiveness. Gα proteins crosslink ATP6AP2 to caveolin where a switch from Gαi to Gαq is necessary for Neu-Dif. In ATP6AP2-enriched CLR-Ms, the release of exosomes was induced dependently from the intracellular Ca²⁺ and Gαq. Pharmacological disruption of CLR-M formation/stability impairs both ATP6AP2 localization and Neu-Dif in addition to reducing exosome release, indicating an essential role of ATP6AP2 enrichment in CLR-Ms for the induction of Neu-Dif. The mechanism is dependent on CLR-M dynamics, particularly the membrane fluidity. Knockdown of ATP6AP2 inhibited Neu-Dif but increased astrocytic-Dif, depleted ATP6AP2/flotillin/Gαq but accumulated caveolin/Gαi in CLR-Ms, and blocked the activation of JNK/ERK/c-Jun/CREB/exosome release. siATP6AP2 cells treated with sphingomyelinase/methyl-β-cyclodextrin reversed the levels of caveolin/flotillin in CLR-Ms but did not induce Neu-Dif, indicating the crucial relocalization of ATP6AP2 in CLR-Ms for neurogenesis. Treatment of ND-derived cells with nSMase showed reversibility in ATP6AP2 abundance in CLR-Ms and enhanced Neu-Dif.

Conclusions

This study gives evidence of the determinant role of CLR-M ATP6AP2 localization for neuronal and oligodendrocyte differentiation involving mechanisms of switches from Gαi/caveolin/canonical to Gαq/flotillin/PCP, the ERK/JNK pathway and Ca²⁺-dependent release of exosomes and as a potential target of drug therapy for neurodegenerative disorders.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0862-9) contains supplementary material, which is available to authorized users.

The relationship between the central serous chorioretinopathy, choroidal thickness, and serum hormone levels

PURPOSE

The purpose of this study were to compare the levels of serum cortisol, aldosterone, testosterone, dehydroepiandrosterone (DHEA), and renin hormone between patients with central serous chorioretinopathy (CSC) and a control group, and to investigate whether there was a difference regarding serum hormone levels in patients with acute/chronic CSC.

METHODS

This prospective study included 30 CSC eyes, 30 fellow eyes, and 32 normal eyes of 32 healthy volunteers who were age and sex matched. The patients were classified as acute or chronic depending on the clinical, fluorescein angiography (FFA), and optical coherence tomography (OCT) findings. Serum cortisol, aldosterone, renin, total testosterone, and DHEA levels were measured. The levels of hormones were compared with the values of the control group. Choroidal thickness and central macular thickness were measured with spectral domain OCT.

RESULTS

Fifteen patients had acute CSC, and 15 patients had chronic CSC. Serum testosterone levels were 357 ± 10.4 ng/ml in the CSC group, and 255.94 ± 7.43 ng/ml in the control group. The difference between them was statistically significant (p < 0.001). The difference between the levels of cortisol, renin, aldosterone, and DHEA was not statistically significant. Serum hormone levels were within the normal range for all patients and were not statistically different between the acute and chronic CSC groups.

CONCLUSION

According to our results, CSC is related to elevated total testosterone levels. Testosterone may play a role in predisposing males to CSC.

[Bradykinin and cardiovascular protection. Role of perindopril, an inhibitor of angiotensin conversion enzyme]

The endothelium plays a vital role as part of the cardiovascular continuum. Risk factors such as hypertension and dyslipidemia unbalance angiotensin II - bradykinin homeostasis, leading to endothelial dysfunction and changes in vascular structure that promote atherosclerosis and thrombosis. When dealing with risk factors, treatment should focus on the prevention and restoration of endothelial function. Not all cardiovascular drugs are able to reverse vascular and structural endothelial dysfunction. Increasing levels of bradykinin is an effect of the use of angiotensin-converting enzyme inhibitors (ACE-Is), and also a fundamental part of their mode of action. The cardiovascular protection observed with ACE-I, and not with sartans, can be explained rationally by the specific effects of bradykinin on the endothelium. In the pharmacological class of ACE-Is, perindopril likely produces the strongest effects on bradykinin, which may explain, at least in part, the documented superiority of this drug in the prevention and treatment of cardiovascular disease.

Integrative Physiological Aspects of Brain RAS in Hypertension

PURPOSE OF REVIEW

The renin-angiotensin system (RAS) plays an important role in modulating cardiovascular function and fluid homeostasis. While the systemic actions of the RAS are widely accepted, the role of the RAS in the brain, its regulation of cardiovascular function, and sympathetic outflow remain controversial. In this report, we discuss the current understanding of central RAS on blood pressure (BP) regulation, in light of recent literature and new experimental techniques.

RECENT FINDINGS

Studies using neuronal or glial-specifc mouse models have allowed for greater understanding into the site-specific expression and role centrally expressed RAS proteins have on BP regulation. While all components of the RAS have been identified in cardiovascular regulatory regions of the brain, their actions may be site specific. In a number of animal models of hypertension, reduction in Ang II-mediated signaling, or upregulation of the central ACE2/Ang 1-7 pathway, has been shown to reduce BP, via a reduction in sympathetic signaling and increase parasympathetic tone, respectively. Emerging evidence also suggests that, in part, the female protective phenotype against hypertension may be due to inceased ACE2 activity within cardiovascular regulatory regions of the brain, potentially mediated by estrogen. Increasing evidence suggests the importance of a central renin-angiotensin pathway, although its localization and the mechanisms involved in its expression and regulation still need to be clarified and more precisely defined. All reported studies/experiments with human or animal subjects performed by the authors have been previously published and complied with all applicable ethical standards (including the Helsinki declaration and its amendments, institutional/national research committee standards, and international/national/institutional guidelines).

Efficacy of aliskiren supplementation for heart failure : A meta-analysis of randomized controlled trials

BACKGROUND

Aliskiren might be beneficial for heart failure. However, the results of various studies are controversial. We conducted a systematic review and meta-analysis to explore the efficacy of aliskiren supplementation for heart failure.

METHODS

PubMed, Embase, Web of Science, EBSCO, and the Cochrane Library databases were systematically searched. Randomized controlled trials (RCTs) assessing the efficacy of aliskiren for heart failure were included. Two investigators independently searched for articles, extracted data, and assessed the quality of included studies. The meta-analysis was performed using the random-effect model.

RESULTS

Five RCTs comprising 1973 patients were included in the meta-analysis. Compared with control interventions in heart failure, aliskiren supplementation was found to significantly reduce NT-proBNP levels (standardized mean difference [SMD] = -0.12; 95% CI = -0.21 to -0.03 pg/ml; p = 0.008) and plasma renin activity (SMD = -0.66; 95% CI = -0.89 to -0.44 ng/ml.h; p < 0.00001) while increasing plasma renin concentration (SMD = 0.52; 95% CI = 0.30-0.75 ng/l; p < 0.00001); however, it demonstrated no significant influence on BNP levels (SMD = -0.08; 95% CI = -0.31-0.15 pg/ml; p = 0.49), mortality (RR = 0.97; 95% CI = 0.79-1.20; p = 0.79), aldosterone levels (SMD = -0.09; 95% CI = -0.32-0.14 pmol/l; p = 0.44), adverse events (RR = 3.03; 95% CI = 0.18-49.51; p = 0.44), and serious adverse events (RR = 1.34; 95% CI = 0.54-3.33; p = 0.53).

CONCLUSION

Aliskiren supplementation was found to significantly decrease NT-proBNP levels and plasma renin activity and to improve plasma renin concentration in the setting of heart failure.

COX-2-derived PGE2 triggers hyperplastic renin expression and hyperreninemia in aldosterone synthase-deficient mice

Pharmacological inhibition or genetic loss of function defects of the renin angiotensin aldosterone system (RAAS) causes compensatory renin cell hyperplasia and hyperreninemia. The triggers for the compensatory stimulation of renin synthesis and secretion in this situation may be multimodal. Since cyclooxygenase-2 (COX-2) expression in the macula densa is frequently increased in states of a defective RAAS, we have investigated a potential role of COX-2 and its derived prostaglandins for renin expression and secretion in aldosterone synthase-deficient mice (AS^−/−) as a model for a genetic defect of the RAAS. In comparison with wild-type mice (WT), AS^−/− mice had 9-fold and 30-fold increases of renin mRNA and of plasma renin concentrations (PRC), respectively. Renin immunoreactivity in the kidney cortex of AS^−/− mice was 10-fold higher than in WT. Macula densa COX-2 expression was 5-fold increased in AS^−/− kidneys relative to WT kidneys. Treatment of AS^−/− mice with the COX-2 inhibitor SC-236 for 1 week lowered both renal renin mRNA and PRC by 70%. Hyperplastic renin cells in AS^−/− kidneys were found to express the prostaglandin E₂ receptors EP2 and EP4. Global deletion of EP2 receptors did not alter renin mRNA nor PRC values in AS^−/− mice. Renin cell-specific inducible deletion of the EP4 receptor lowered renin mRNA and PRC by 25% in AS^−/− mice. Renin cell-specific inducible deletion of the EP4 receptor in combination with global deletion of the EP2 receptor lowered renin mRNA and PRC by 70–75% in AS^−/− mice. Lineage tracing of renin-expressing cells revealed that deletion of EP2 and EP4 leads to a preferential downregulation of perivascular renin expression. Our findings suggest that increased macula densa COX-2 activity in AS^−/− mice triggers perivascular renin expression and secretion via prostaglandin E₂.

Complete remission of hypertension in a hemodialysis patient after adrenalectomy for primary aldosteronism and renal transplantation

A 64-year-old man was admitted to our hospital for the hormonal evaluation of a right adrenal adenoma. He had been diagnosed with severe proteinuria and hypertension, and antihypertensive treatment was started at the age of 60. His renal function gradually declined, and hemodialysis was begun at the age of 64. Since his blood pressure was uncontrollable and resistant to antihypertensive treatment, an endocrinological examination was performed for an incidental right adrenal mass detected by computed tomography. The results of screening, including captopril challenge and an adrenocorticotropin stimulation test for primary aldosteronism, and adrenal venous sampling suggested excessive aldosterone secretion from the right adrenal gland. Adrenalectomy was performed; his blood pressure decreased and became well-controlled with a reduced antihypertensive regimen. Furthermore, he received renal transplantation which resulted in normalization of his serum potassium level, improvement of renal function and hormonal levels such as plasma renin activity and aldosterone concentration, and satisfactory blood pressure without any antihypertensive medications. This case is extremely important to demonstrate the effects of adrenalectomy for primary aldosteronism in a hemodialysis patient. It is possible that adrenalectomy may be a useful treatment for primary aldosteronism even in patients undergoing hemodialysis. Careful long-term follow-up of our case and investigations of the efficacy of adrenalectomy in similar cases are needed to address this issue.

The Renin-Angiotensin-Aldosterone System in Smokers and Non-Smokers of the Ludwigshafen Risk and Cardiovascular Health (LURIC) Study

High concentrations of renin and aldosterone are risk factors for cardiovascular diseases (CVD) which are the leading cause of morbidity and mortality worldwide. Enhanced activation of the renin-angiotensin-aldosterone system (RAAS) by cigarette smoking has been reported. The aim of our study was to analyze the effect of cigarette smoking on parameters of the RAAS in active smokers (AS) and life-time non-smokers (NS) of the Ludwigshafen Risk and Cardiovascular Health (LURIC) Study as well as the utility of RAAS parameter for risk prediction. We determined the concentration of aldosterone, renin, angiotensin-I and angiotensin-II in participants of the LURIC study. Smoking status was assessed by a questionnaire and the measurement of plasma cotinine concentration. Parameters were log transformed before entering analyses, where appropriate. We used a multivariate Cox regression analysis to assess the effect of parameters on mortality. From the 3316 LURIC participants 777 were AS and 1178 NS. Within a median observation period of 10 years 221 (28.4 %) AS and 302 (25.6 %) NS died. After adjustment for age, gender, and the use of anti-hypertensive medication, only angiotensin-I was significantly different in AS compared to NS with an estimated marginal mean (95 % CI) of 1607 (1541-1673) ng/L and 1719 (1667-1772) ng/L, respectively. For both NS and AS renin and angiotensin-II were directly associated with mortality in the multivariate Cox regression analysis. Angiotensin-I was only associated with increased risk for mortality in NS (HR (95 % CI) of 0.69 (0.53-0.89)). We conclude that increased renin and angiotensin-II are independent predictors of mortality in AS and NS, while angiotensin-I was associated with reduced risk of death in NS only.

Plasma renin activity, response to aliskiren, and clinical outcomes in patients hospitalized for heart failure: the ASTRONAUT trial

AIMS

The direct renin inhibitor, aliskiren, is known to reduce plasma renin activity (PRA), but whether the efficacy of aliskiren varies based on an individual's baseline PRA in patients hospitalized for heart failure (HF) is presently unknown. We characterized the prognostic value of PRA and determined if this risk is modifiable with use of aliskiren.

METHODS AND RESULTS

This pre-specified neurohormonal substudy of ASTRONAUT analysed all patients hospitalized for HF with ejection fraction (EF) ≤40% with available baseline PRA data (n = 1306, 80.9%). Risk associated with baseline PRA and short-term changes in PRA from baseline to 1 month was modelled with respect to 12-month clinical events. Median baseline PRA was 3.0 (interquartile range 0.6-16.4) ng/mL/h. Aliskiren significantly reduced PRA early after treatment initiation through 12-month follow-up compared with placebo (P < 0.001). The lowest baseline PRA quartile (<0.6 ng/mL/h) was independently predictive of lower all-cause mortality [adjusted hazard ratio (HR) 0.50, 95% confidence interval (CI) 0.31-0.81] and the composite of cardiovascular mortality and HF hospitalization (adjusted HR 0.57, 95% CI 0.40-0.79). Delta log-normalized PRA (from baseline to 1 month) was not predictive of either primary endpoint at 12 months (P ≥ 0.43). The prognostic value of baseline PRA and short-term changes in PRA did not vary by randomization to aliskiren or placebo (interaction P ≥ 0.13).

CONCLUSIONS

Plasma renin activity is reduced early and durably by aliskiren, but this did not translate into improved clinical outcomes in ASTRONAUT. Baseline PRA or short-term reduction in PRA do not identify a subgroup who may preferentially benefit from direct renin inhibition. Clinical Trial Registration ClinicalTrials.gov Unique Identifier: NCT00894387.

Ovariectomy modify local renin-angiotensin-aldosterone system gene expressions in the heart of ApoE (-/-) mice

AIMS

The evaluation of the local Renin-Angiotensin-Aldosterone system (RAAS) gene expressions in the heart of ovariectomized (OVX) apolipoprotein E deficient mice (ApoE).

METHODS

Four-months old C57BL/6 female mice (wild-type, wt, n=20), and ApoE female mice (n=20), were submitted to OVX or a surgical procedure without ovary removal (SHAM) and formed four groups (n=10/group): SHAM/wt, SHAM/ApoE, OVX/wt, and OVX/ApoE.

KEY FINDINGS

OVX led to greater body mass, plasma triglycerides (TG) and total cholesterol, and resulted in insulin resistance and altered RAAS gene expressions in the heart tissue. The gene expression of angiotensin-converting enzyme (ACE)-2 was lower in OVX/wt than in SHAM/wt (P=0.0004), Mas receptor (MASr) was lower in OVX/wt compared to SHAM/wt (P<0.0001). Also, angiotensin II receptor type 1 (AT1r) was higher in OVX/wt than in SHAM/wt (P=0.0229), and AT2r was lower in OVX/wt than in SHAM/wt (P=0.0121). OVX and ApoE deficiency showed interaction potentializing the insulin resistance, increasing TG levels and altering ACE and MASr gene expressions. ACE gene expression was higher in OVX/ApoE than in OVX/wt (P<0.0001), and MASr gene expression was lower in OVX/ApoE than in OVX/wt (P<0.0001).

SIGNIFICANCE

The impact of OVX on local RAAS cascade in the heart of ApoE deficient animals, besides the metabolic changes culminating with insulin resistance, involves an upregulation of renin, ACE, and AT1r gene expressions. The findings may contribute to clarify the mechanisms of development of postmenopausal hypertension and the link between RAAS and apolipoprotein E.