New insights into the importance of aminopeptidase A in hypertension

Shared genetic etiology and antagonistic relationship of plasma renin activity and systolic blood pressure in a Korean cohorts

Despite extensive studies on blood pressure, its genetic risk factors remain uncertain. Even one of the most researched blood pressure-related traits - renin - is not fully understood genetically. Here, we determine the genetic relationship and associated predisposition between blood pressure and baseline renin. In 8840 Korean individuals, we observed a strong negative genome-wide genetic correlation (r_g = -0.484) between systolic blood pressure (SBP) and plasma renin activity (PRA), suggesting that antagonistic genetic signals explain the variance in the two traits. We found 51 significant pleiotropic SNPs affecting the two traits, which could contribute to the Renin-Angiotensin-Aldosterone System (RAAS). Our findings provide insight into studies on RAAS by identifying the genome-wide relationship and susceptibility loci of SBP and PRA.

Functional genomics and epigenomics of atrial fibrillation

Atrial fibrillation is a progressive cardiac arrhythmia that increases the risk of hospitalization and adverse cardiovascular events. Despite years of study, we still do not have a full comprehension of the molecular mechanism responsible for the disease. The recent implementation of large-scale approaches in both patient samples, population studies and animal models has helped us to broaden our knowledge on the molecular drivers responsible for AF and on the mechanisms behind disease progression. Understanding genomic and epigenomic changes that take place during chronification of AF will prove essential to design novel treatments leading to improved patient care.

The SARS-CoV-2 receptor and other key components of the Renin-Angiotensin-Aldosterone System related to COVID-19 are expressed in enterocytes in larval zebrafish

People with underlying conditions, including hypertension, obesity, and diabetes, are especially susceptible to negative outcomes after infection with coronavirus SARS-CoV-2, which causes COVID-19. Hypertension and respiratory inflammation are exacerbated by the Renin-Angiotensin-Aldosterone System (RAAS), which normally protects from rapidly dropping blood pressure via Angiotensin II (Ang II) produced by the enzyme Ace. The Ace paralog Ace2 degrades Ang II, counteracting its chronic effects, and serves as the SARS-CoV-2 receptor. Ace, the coronavirus, and COVID-19 comorbidities all regulate Ace2, but we do not yet understand how. To exploit zebrafish (Danio rerio) to help understand the relationship of the RAAS to COVID-19, we must identify zebrafish orthologs and co-orthologs of human RAAS genes and understand their expression patterns. To achieve these goals, we conducted genomic and phylogenetic analyses and investigated single cell transcriptomes. Results showed that most human RAAS genes have one or more zebrafish orthologs or co-orthologs. Results identified a specific type of enterocyte as the specific site of expression of zebrafish orthologs of key RAAS components, including Ace, Ace2, Slc6a19 (SARS-CoV-2 co-receptor), and the Angiotensin-related peptide cleaving enzymes Anpep (receptor for the common cold coronavirus HCoV-229E), and Dpp4 (receptor for the Middle East Respiratory Syndrome virus, MERS-CoV). Results identified specific vascular cell subtypes expressing Ang II receptors, apelin, and apelin receptor genes. These results identify genes and cell types to exploit zebrafish as a disease model for understanding mechanisms of COVID-19.

Aminopeptidase A (ENPEP) gene polymorphisms and preeclampsia: Descriptive analysis

OBJECTIVE

The etiology of preeclampsia (PE) remains elusive. Recent genome-wide association studies have identified a number of genetic variants associated with blood pressure variations in east Asians. One of the genetic variants is the aminopeptidase A (ENPEP) gene, which converts angiotensin II to angiotensin III. The C allele of rs6825911 is a risk for hypertension. The current study investigated whether genetic variants of ENPEP play a role in the pathogenesis of preeclampsia.

STUDY DESIGN

The study was a descriptive analysis of gene polymorphisms of ENPEP; 602 pregnant women of African ancestry [normotensive (n = 245) and PE (n = 357)] were recruited. The two groups were divided according to their HIV status. The PE group consisted of early- and late-onset sub-categories. A single nucleotide polymorphism of rs6825911 was analyzed using the TaqMan® Probe mix and by means of real time polymerase chain reaction.

RESULTS

The risk of C allele for PE was 1.07 (95 % CI 0.83-1.38, P = 0.589) for allele comparison and the risk for preeclampsia CC to CT/TT was 1.33 (95 % CI 0.96-1.85, P = 0.086). The sub analysis for the PE group without HIV infection the risk of C allele was 1.25 (95 % CI 0.838-1.78, P = 0.199) and the risk of PE of CC to CT/TT was 1.51 (95 %CI: 0.96-2.35, P = 0.071).

CONCLUSION

This is the first study in a homogenous South African population of African ancestry to show that the variant of ENPEP gene does not play a role in pathogenesis of preeclampsia.

Chromosome 2 Fragment Substitutions in Dahl Salt-Sensitive Rats and RNA Sequencing Identified Enpep and Hs2st1 as Vascular Inflammatory Modulators

Chromosome 2 introgression from normotensive Brown Norway (BN) rats into hypertensive Dahl salt-sensitive (SS) background (SS-chromosome 2^BN/Mcwi; consomic S2^B) reduced blood pressure and vascular inflammation under a normal-salt diet (NSD). We hypothesized that BN chromosome 2 contains anti-inflammatory genes that could reduce blood pressure and vascular inflammation in rats fed NSD or high-salt diet (HSD). Four- to 6-week old male SS and congenic rats containing the BN chromosome 2 distal portion (SS.BN-[rs13453786-rs66377062]/Aek; S2^Ba) and middle segment (SS.BN-[rs106982173-rs65057186]/Aek; S2^Bb) were fed NSD or HSD (4% NaCl) up to age 12 to 13 weeks. Systolic blood pressure determined by telemetry was higher in SS rats fed HSD versus NSD. Systolic blood pressure was lower in both congenic rats than in SS under NSD, but similar under HSD versus SS. Reactive oxygen species generation using dihydroethidium staining, expression of vascular cell adhesion molecule-1 and monocyte chemoattractant protein-1, and immune cell infiltration by immunofluorescence demonstrated that S2^Ba rats present less inflammation under NSD and more under HSD versus SS rats. RNA sequencing and reverse transcription-quantitative PCR identified 2 differentially expressed genes encoded within BN chromosome 2 distal portion that could act as regulators of vascular inflammation. These were downregulated glutamyl aminopeptidase (Enpep) that was anti-inflammatory under NSD and upregulated heparan sulfate 2-O-sulfotransferase 1 (Hs2st1) that was proinflammatory under HSD. In conclusion, 2 differentially expressed genes encoded within introgressed BN chromosome 2 distal fragment were identified: Enpep associated with reduced vascular inflammation under NSD, and Hs2st1, associated with increased vascular inflammation under HSD.

An intestinal cell type in zebrafish is the nexus for the SARS-CoV-2 receptor and the Renin-Angiotensin-Aldosterone System that contributes to COVID-19 comorbidities

People with underlying conditions, including hypertension, obesity, and diabetes, are especially susceptible to negative outcomes after infection with the coronavirus SARS-CoV-2. These COVID-19 comorbidities are exacerbated by the Renin-Angiotensin-Aldosterone System (RAAS), which normally protects from rapidly dropping blood pressure or dehydration via the peptide Angiotensin II (Ang II) produced by the enzyme Ace. The Ace paralog Ace2 degrades Ang II, thus counteracting its chronic effects. Ace2 is also the SARS-CoV-2 receptor. Ace , the coronavirus, and COVID-19 comorbidities all regulate Ace2 , but we don't yet understand how. To exploit zebrafish ( Danio rerio ) as a disease model to understand mechanisms regulating the RAAS and its relationship to COVID-19 comorbidities, we must first identify zebrafish orthologs and co-orthologs of human RAAS genes, and second, understand where and when these genes are expressed in specific cells in zebrafish development. To achieve these goals, we conducted genomic analyses and investigated single cell transcriptomes. Results showed that most human RAAS genes have an ortholog in zebrafish and some have two or more co-orthologs. Results further identified a specific intestinal cell type in zebrafish larvae as the site of expression for key RAAS components, including Ace, Ace2, the coronavirus co-receptor Slc6a19, and the Angiotensin-related peptide cleaving enzymes Anpep and Enpep. Results also identified specific vascular cell subtypes as expressing Ang II receptors, apelin , and apelin receptor genes. These results identify specific genes and cell types to exploit zebrafish as a disease model for understanding the mechanisms leading to COVID-19 comorbidities.

SUMMARY STATEMENT

Genomic analyses identify zebrafish orthologs of the Renin-Angiotensin-Aldosterone System that contribute to COVID-19 comorbidities and single-cell transcriptomics show that they act in a specialized intestinal cell type.

Gene Expression Profiles Induced by a Novel Selective Peroxisome Proliferator-Activated Receptor α Modulator (SPPARMα) Pemafibrate

Pemafibrate is the first clinically-available selective peroxisome proliferator-activated receptor α modulator (SPPARMα) that has been shown to effectively improve hypertriglyceridemia and low high-density lipoprotein cholesterol (HDL-C) levels. Global gene expression analysis reveals that the activation of PPARα by pemafibrate induces fatty acid (FA) uptake, binding, and mitochondrial or peroxisomal oxidation as well as ketogenesis in mouse liver. Pemafibrate most profoundly induces HMGCS2 and PDK4, which regulate the rate-limiting step of ketogenesis and glucose oxidation, respectively, compared to other fatty acid metabolic genes in human hepatocytes. This suggests that PPARα plays a crucial role in nutrient flux in the human liver. Additionally, pemafibrate induces clinically favorable genes, such as ABCA1, FGF21, and VLDLR. Furthermore, pemafibrate shows anti-inflammatory effects in vascular endothelial cells. Pemafibrate is predicted to exhibit beneficial effects in patients with atherogenic dyslipidemia and diabetic microvascular complications.

Imbalance in Renal Vasoactive Enzymes Induced by Mild Hypoxia: Angiotensin-Converting Enzyme Increases While Neutral Endopeptidase Decreases

Chronic hypoxia has been postulated as one of the mechanisms involved in salt-sensitive hypertension and chronic kidney disease (CKD). Kidneys have a critical role in the regulation of arterial blood pressure through vasoactive systems, such as the renin-angiotensin and the kallikrein-kinin systems, with the angiotensin-converting enzyme (ACE) and kallikrein being two of the main enzymes that produce angiotensin II and bradykinin, respectively. Neutral endopeptidase 24.11 or neprilysin is another enzyme that among its functions degrade vasoactive peptides including angiotensin II and bradykinin, and generate angiotensin 1-7. On the other hand, the kidneys are vulnerable to hypoxic injury due to the active electrolyte transportation that requires a high oxygen consumption; however, the oxygen supply is limited in the medullary regions for anatomical reasons. With the hypothesis that the chronic reduction of oxygen under normobaric conditions would impact renal vasoactive enzyme components and, therefore; alter the normal balance of the vasoactive systems, we exposed male Sprague-Dawley rats to normobaric hypoxia (10% O₂) for 2 weeks. We then processed renal tissue to identify the expression and distribution of kallikrein, ACE and neutral endopeptidase 24.11 as well as markers of kidney damage. We found that chronic hypoxia produced focal damage in the kidney, mainly in the cortico-medullary region, and increased the expression of osteopontin. Moreover, we observed an increase of ACE protein in the brush border of proximal tubules at the outer medullary region, with increased mRNA levels. Kallikrein abundance did not change significantly with hypoxia, but a tendency toward reduction was observed at protein and mRNA levels. Neutral endopeptidase 24.11 was localized in proximal tubules, and was abundantly expressed under normoxic conditions, which markedly decreased both at protein and mRNA levels with chronic hypoxia. Taken together, our results suggest that chronic hypoxia produces focal kidney damage along with an imbalance of key components of the renal vasoactive system, which could be the initial steps for a long-term contribution to salt-sensitive hypertension and CKD.

Mammalian Glutamyl Aminopeptidase Genes (ENPEP) and Proteins: Comparative Studies of a Major Contributor to Arterial Hypertension

Glutamyl aminopeptidase (ENPEP) is a member of the M1 family of endopeptidases which are mammalian type II integral membrane zinc-containing endopeptidases. ENPEP is involved in the catabolic pathway of the renin-angiotensin system forming angiotensin III, which participates in blood pressure regulation and blood vessel formation. Comparative ENPEP amino acid sequences and structures and ENPEP gene locations were examined using data from several mammalian genome projects. Mammalian ENPEP sequences shared 71-98% identities. Five N-glycosylation sites were conserved for all mammalian ENPEP proteins examined although 9-18 sites were observed, in each case. Sequence alignments, key amino acid residues and predicted secondary and tertiary structures were also studied, including transmembrane and cytoplasmic sequences and active site residues. Highest levels of human ENPEP expression were observed in the terminal ileum of the small intestine and in the kidney cortex. Mammalian ENPEP genes contained 20 coding exons. The human ENPEP gene promoter and first coding exon contained a CpG island (CpG27) and at least 6 transcription factor binding sites, whereas the 3'-UTR region contained 7 miRNA target sites, which may contribute to the regulation of ENPEP gene expression in tissues of the body. Phylogenetic analyses examined the relationships of mammalian ENPEP genes and proteins, including primate, other eutherian, marsupial and monotreme sources, using chicken ENPEP as a primordial sequence for comparative purposes.

Transcriptome Analysis of K-877 (a Novel Selective PPARα Modulator (SPPARMα))-Regulated Genes in Primary Human Hepatocytes and the Mouse Liver

AIM

Selective PPARα modulators (SPPARMα) are under development for use as next-generation lipid lowering drugs. In the current study, to predict the pharmacological and toxicological effects of a novel SPPARMα K-877, comprehensive transcriptome analyses of K-877-treated primary human hepatocytes and mouse liver tissue were carried out.

METHODS

Total RNA was extracted from the K-877 treated primary human hepatocytes and mouse liver and adopted to the transcriptome analysis. Using a cluster analysis, commonly and species specifically regulated genes were identified. Also, the profile of genes regulated by K-877 and fenofibrate were compared to examine the influence of different SPPARMα on the liver gene expression.

RESULTS

Consequently, a cell-based transactivation assay showed that K-877 activates PPARα with much greater potency and selectivity than fenofibric acid, the active metabolite of clinically used fenofibrate. K-877 upregulates the expression of several fatty acid β-oxidative genes in human hepatocytes and the mouse liver. Almost all genes up- or downregulated by K-877 treatment in the mouse liver were also regulated by fenofibrate treatment. In contrast, the K-877-regulated genes in the mouse liver were not affected by K-877 treatment in the Ppara-null mouse liver. Depending on the species, the peroxisomal biogenesis-related gene expression was robustly induced in the K-877-treated mouse liver, but not human hepatocytes, thus suggesting that the clinical dose of K-877 may not induce peroxisome proliferation or liver toxicity in humans. Notably, K-877 significantly induces the expression of clinically beneficial target genes (VLDLR, FGF21, ABCA1, MBL2, ENPEP) in human hepatocytes.

CONCLUSION

These results indicate that changes in the gene expression induced by K-877 treatment are mainly mediated through PPARα activation. K-877 regulates the hepatic gene expression as a SPPARMα and thus may improve dyslipidemia as well as metabolic disorders, such as metabolic syndrome and type 2 diabetes, without untoward side effects.

Long-range regulatory interactions at the 4q25 atrial fibrillation risk locus involve PITX2c and ENPEP

BACKGROUND

Recent genome-wide association studies have uncovered genomic loci that underlie an increased risk for atrial fibrillation, the major cardiac arrhythmia in humans. The most significant locus is located in a gene desert at 4q25, approximately 170 kilobases upstream of PITX2, which codes for a transcription factor involved in embryonic left-right asymmetry and cardiac development. However, how this genomic region functionally and structurally relates to PITX2 and atrial fibrillation is unknown.

RESULTS

To characterise its function, we tested genomic fragments from 4q25 for transcriptional activity in a mouse atrial cardiomyocyte cell line and in transgenic mouse embryos, identifying a non-tissue-specific potentiator regulatory element. Chromosome conformation capture revealed that this region physically interacts with the promoter of the cardiac specific isoform of Pitx2. Surprisingly, this regulatory region also interacts with the promoter of the next neighbouring gene, Enpep, which we show to be expressed in regions of the developing mouse heart essential for cardiac electrical activity.

CONCLUSIONS

Our data suggest that de-regulation of both PITX2 and ENPEP could contribute to an increased risk of atrial fibrillation in carriers of disease-associated variants, and show the challenges that we face in the functional analysis of genome-wide disease associations.

Serum uric acid concentrations and SLC2A9 genetic variation in Hispanic children: the Viva La Familia Study

BACKGROUND

Elevated concentrations of serum uric acid are associated with increased risk of gout and renal and cardiovascular diseases. Genetic studies in adults have consistently identified associations of solute carrier family 2, member 9 (SLC2A9), polymorphisms with variation in serum uric acid. However, it is not known whether the association of serum uric acid with SLC2A9 polymorphisms manifests in children.

OBJECTIVE

The aim was to investigate whether variation in serum uric acid is under genetic influence and whether the association with SLC2A9 polymorphisms generalizes to Hispanic children of the Viva La Familia Study.

DESIGN

We conducted a genomewide association study with 1.1 million genetic markers in 815 children.

RESULTS

We found serum uric acid to be significantly heritable [h(2) ± SD = 0.45 ± 0.08, P = 5.8 × 10(-11)] and associated with SLC2A9 variants (P values between 10(-16) and 10(-7)). Several of the significantly associated polymorphisms were previously identified in studies in adults. We also found positive genetic correlations between serum uric acid and BMI z score (ρG = 0.45, P = 0.002), percentage of body fat (ρG = 0.28, P = 0.04), fat mass (ρG = 0.34, P = 0.02), waist circumference (ρG = 0.42, P = 0.003), and waist-to-height ratio (ρG = 0.46, P = 0.001).

CONCLUSIONS

Our results show that variation in serum uric acid in Hispanic children is under considerable genetic influence and is associated with obesity-related phenotypes. As in adults, genetic variation in SLC2A9 is associated with serum uric acid concentrations, an important biomarker of renal and cardiovascular disease risk, in Hispanic children.

Resveratrol prevents pathological but not physiological cardiac hypertrophy

The mechanisms responsible for how resveratrol inhibits pathological left ventricular hypertrophy (LVH) but not physiological LVH have not been elucidated. Herein, we show that in rat cardiomyocytes, lower concentrations of resveratrol (0.1 and 1 μM) are efficient at selectively inhibiting important regulators involved in pathological LVH (such as nuclear factor of activated T cells (NFAT)) while not affecting pathways involved in physiological LVH (Akt and p70S6 kinase (p70S6K)). These differential responses are also observed in both mouse and rat models of in vivo physiological and pathological LVH. Interestingly, in all of the experiments involving a low concentration of resveratrol (1 μM), the observed effects on Akt, p70S6K, and NFAT were independent from AMP-activated protein kinase (AMPK) activation while these effects at higher concentrations of resveratrol (50 μM) were potentiated by AMPK activation. In summary, we show that resveratrol can concentration/dose selectively inhibit various pro-hypertrophic signaling pathways and that resveratrol has differential effects on the modification of these signaling cascades in response to pathological stimuli versus physiological stimuli. This has important clinical implications as our findings support the concept that resveratrol may be useful in the selective treatment of pathological LVH.

KEY MESSAGE

Resveratrol differentially regulates pathological and physiological cardiac hypertrophy. Resveratrol dose selectively inhibits pathological cardiac signaling pathways. Resveratrol inhibits NFAT-dependent transcription. At low concentrations, effects of resveratrol are AMPK-independent. Resveratrol may be used to selectively treat pathological cardiac hypertrophy.

Role of estrogen in diastolic dysfunction

The prevalence of left ventricular diastolic dysfunction (LVDD) sharply increases in women after menopause and may lead to heart failure. While evidence suggests that estrogens protect the premenopausal heart from hypertension and ventricular remodeling, the specific mechanisms involved remain elusive. Moreover, whether there is a protective role of estrogens against cardiovascular disease, and specifically LVDD, continues to be controversial. Clinical and basic science have implicated activation of the renin-angiotensin-aldosterone system (RAAS), linked to the loss of ovarian estrogens, in the pathogenesis of postmenopausal diastolic dysfunction. As a consequence of increased tissue ANG II and low estrogen, a maladaptive nitric oxide synthase (NOS) system produces ROS that contribute to female sex-specific hypertensive heart disease. Recent insights from rodent models that mimic the cardiac phenotype of an estrogen-insufficient or -deficient woman (e.g., premature ovarian failure or postmenopausal), including the ovariectomized congenic mRen2.Lewis female rat, provide evidence showing that estrogen modulates the tissue RAAS and NOS system and related intracellular signaling pathways, in part via the membrane G protein-coupled receptor 30 (GPR30; also called G protein-coupled estrogen receptor 1). Complementing the cardiovascular research in this field, the echocardiographic correlates of LVDD as well as inherent limitations to its use in preclinical rodent studies will be briefly presented. Understanding the roles of estrogen and GPR30, their interactions with the local RAAS and NOS system, and the relationship of each of these to LVDD is necessary to identify new therapeutic targets and alternative treatments for diastolic heart failure that achieve the cardiovascular benefits of estrogen replacement without its side effects and contraindications.

New insights into the role of aminopeptidases in the treatment for both preeclampsia and preterm labor

INTRODUCTION

Evidence elucidating the pathophysiology and pharmacology of conventional drugs, β-2 stimulants and magnesium sulfate, on safety and effectiveness for preeclampsia and preterm labor are rarely found. Both compounds pass through the placental barrier and could exert their adverse effects on the fetus. Exposure to these agents could be problematic long after the birth, and possibly result in diseases such as autism and cardiomyopathy. Since 1970 the possible roles of placental aminopeptidases, which degrade peptide hormones, in preeclampsia and preterm labor have been studied.

AREAS COVERED

Many studies reveal that the fetus secretes peptide hormones, such as angiotensin II, vasopressin, and oxytocin, under hypoxia (stress) during the course of its growth, suggesting the critical effects these hormones have during pregnancy. The roles of placental aminopeptidases, the enzymes which degrade fetal hormones without passing through the placental barrier, were clarified. A first-step production system for recombinant aminopeptidases was established, by which engineered recombinant aminopeptidases were used for further experiments testing expected efficacy on controlling the level of hormones.

EXPERT OPINION

The authors conclude that both aminopeptidase A and placental leucine aminopeptidase could be potentially safe and effective drugs for patients and their babies in the treatment of preeclampsia and preterm labor.

Structural insights into central hypertension regulation by human aminopeptidase A

Hypertension is regulated through both the central and systemic renin-angiotensin systems. In the central renin-angiotensin system, zinc-dependent aminopeptidase A (APA) up-regulates blood pressure by specifically cleaving the N-terminal aspartate, but not the adjacent arginine, from angiotensin II, a process facilitated by calcium. Here, we determined the crystal structures of human APA and its complexes with different ligands and identified a calcium-binding site in the S1 pocket of APA. Without calcium, the S1 pocket can bind both acidic and basic residues through formation of salt bridges with the charged side chains. In the presence of calcium, the binding of acidic residues is enhanced as they ligate the cation, whereas the binding of basic residues is no longer favorable due to charge repulsion. Of the peptidomimetic inhibitors of APA, amastatin has higher potency than bestatin by fitting better in the S1 pocket and interacting additionally with the S3' subsite. These results explain the calcium-modulated substrate specificity of APA in central hypertension regulation and can guide the design and development of brain-targeting antihypertensive APA inhibitors.

Qiliqiangxin improves cardiac function in spontaneously hypertensive rats through the inhibition of cardiac chymase

BACKGROUND

This study was designed to investigate the effects and mechanism of action of the traditional Chinese drug formula, qiliqiangxin (QLQX), on cardiac function in spontaneously hypertensive rats (SHRs).

METHODS

We evaluated the effects of oral high-dose (4 g/kg/day, n = 7) and low-dose (1 g/kg/day, n = 7) QLQX on cardiac function in SHRs aged between 8 compared to control, the 8-week-old Wistar-Kyoto (WKY) rats. Echocardiography was performed to evaluate cardiac function and hemodynamic parameters. Hematoxylin and eosin (HE) and Masson's trichrome staining were performed, and the expression of myocardial angiotensin (Ang)-converting enzyme, chymase, transforming growth factor (TGF)-β, and collagen-type I and III were evaluated with real-time reverse transcription-PCR. Myocardial chymase, Ang-converting enzyme (ACE), and Ang II activities were measured with radioimmunoassay (RIA) techniques. Cardiac mast cells were detected with toluidine blue staining.

RESULTS

In SHRs, the number of chymase enzyme-positive mast cells increased in the left ventricle (LV) compared with WKY rats. QLQX significantly decreased mast cell density and cardiac chymase levels, and it improved ejection fraction values and cardiac systolic function compared with vehicle. Moreover, QLQX decreased left atrial diameters and improved the E/A ratio. QLQX suppressed collagen-type I and III and TGF-β mRNA levels, and Ang II activity, in a dose-dependent manner. Whereas no difference in ACE activity was found between SHRs, chymase expression and activity were significantly decreased with QLQX.

CONCLUSIONS

These data suggest that QLQX improves both systolic and diastolic cardiac function in SHRs through downregulating the cardiac chymase signaling pathway and chymase-mediated Ang II production.

Activity of soluble aminopeptidase A and dipeptidyl peptidase IV and membrane-bound aminopeptidase B and pyroglutamyl peptidase I in adenoid hyperplasia, tonsillar hyperplasia and chronic tonsillitis

OBJECTIVE

To analyze soluble and membrane-bound peptidase activities in the tonsils and adenoids removed from patients with adenoid hyperplasia, tonsillar hyperplasia and chronic tonsillitis.

METHODS

A total of 48 tissue samples from patients undergoing adenoidectomy and tonsillectomy for adenoid hyperplasia, tonsillar hyperplasia or chronic tonsillitis were analyzed. The catalytic activity of a pool of peptidases in the soluble (dipeptidyl peptidase IV, aminopeptidase A, aminopeptidase N and cystinyl aminopeptidase) and membrane-bound (prolyl endopeptidase, aspartyl aminopeptidase, aminopeptidase B and pyroglutamyl peptidase I) fractions was measured fluorometrically.

RESULTS

The activity of membrane-bound aminopeptidase B was higher in cases of chronic tonsillitis and adenoid hyperplasia than in tonsillar hyperplasia, p=0.004. Soluble dipeptidyl peptidase IV and membrane-bound pyroglutamyl peptidase I were found to be more active in tissues from male chronic tonsillitis tissues, p<0.05, while membrane-bound aminopeptidase B activity was higher in tissues of females with tonsillar hyperplasia, p<0.001. In the case of chronic tonsillitis, soluble aminopeptidase A was found to have a higher level of activity in tissues from children than those from adults, p=0.005.

CONCLUSIONS

Our results suggest a potential role of soluble aminopeptidase A, soluble dipeptidyl peptidase IV, membrane-bound aminopeptidase B and membrane-bound pyroglutamyl peptidase I in the pathobiology of adenoid hyperplasia, tonsillar hyperplasia and chronic tonsillitis that is differently regulated as a function of gender. These finfings may modify in the future the clinical approach to these diseases.

Meta-analysis of genome-wide association studies identifies common variants associated with blood pressure variation in east Asians

We conducted a meta-analysis of genome-wide association studies of systolic (SBP) and diastolic (DBP) blood pressure in 19,608 subjects of east Asian ancestry from the AGEN-BP consortium followed up with de novo genotyping (n = 10,518) and further replication (n = 20,247) in east Asian samples. We identified genome-wide significant (P < 5 × 10(-8)) associations with SBP or DBP, which included variants at four new loci (ST7L-CAPZA1, FIGN-GRB14, ENPEP and NPR3) and a newly discovered variant near TBX3. Among the five newly discovered variants, we obtained significant replication in the independent samples for all of these loci except NPR3. We also confirmed seven loci previously identified in populations of European descent. Moreover, at 12q24.13 near ALDH2, we observed strong association signals (P = 7.9 × 10(-31) and P = 1.3 × 10(-35) for SBP and DBP, respectively) with ethnic specificity. These findings provide new insights into blood pressure regulation and potential targets for intervention.

Placental leucine aminopeptidase- and aminopeptidase A- deficient mice offer insight concerning the mechanisms underlying preterm labor and preeclampsia

Preeclampsia and preterm delivery are important potential complications in pregnancy and represent the leading causes for maternal and perinatal morbidity and mortality. The mechanisms underlying both diseases remain unknown, thus available treatments (beta2-stimulants and magnesium sulfate) are essentially symptomatic. Both molecules have molecular weights less than 5–8 kDa, cross the placental barrier, and thus exert their effects on the fetus. The fetus produces peptides that are highly vasoactive and uterotonic and increase in response to maternal stress and with continued development. Fetal peptides are also small molecules that inevitably leak across into the maternal circulation. Aminopeptidases such as placental leucine aminopeptidase (P-LAP) and aminopeptidase A (APA) are large molecules that do not cross the placental barrier. We have shown that APA acts as an antihypertensive agent in the pregnant spontaneously hypertensive rat by degrading vasoactive peptides and as a result returns the animal to a normotensive state. P-LAP also acts as an antiuterotonic agent by degrading uterotonic peptides and thus prolongs gestation in the pregnant mouse. Given the ever increasing worldwide incidences of preeclampsia and preterm labor, it is imperative that new agents be developed to safely prolong gestation. We believe that the use of aminopeptidases hold promise in this regard.

Ischemia-induced angiogenesis is impaired in aminopeptidase A deficient mice via down-regulation of HIF-1α

Aminopeptidase A (APA; EC 3.4.11.7) is a transmembrane metalloprotease with several functions in tumor angiogenesis. To investigate the role of APA in the process of ischemia-induced angiogenesis, we evaluated the cellular angiogenic responses under hypoxic conditions and the process of perfusion recovery in the hindlimb ischemia model of APA-deficient (APA-KO; C57Bl6/J strain) mice. Western blotting of endothelial cells (ECs) isolated from the aorta of APA-KO mice revealed that the accumulation of hypoxia-inducible factor-1α (HIF-1α) protein in response to hypoxic challenge was blunted. Regarding the proteasomal ubiquitination, a proteasome inhibitor MG-132 restored the reduced accumulation of HIF-1α in ECs from APA-KO mice similar to control mice under hypoxic conditions. These were associated with decreased growth factor secretion and capillary formation in APA-KO mice. In the hindlimb ischemia model, perfusion recovery in APA-KO mice was decreased in accordance with a significantly lower capillary density at 2weeks. Regarding vasculogenesis, no differences were observed in cell populations and distribution patterns between wild type and APA-KO mice in relation to endothelial progenitor cells. Our results suggested that Ischemia-induced angiogenesis is impaired in APA-KO mice partly through decreased HIF-1α stability by proteasomal degradation and subsequent suppression of HIF-1α-driven target protein expression such as growth factors. APA is a functional target for ischemia-induced angiogenesis.

The Renin-Angiotensin System in the Development of Salt-Sensitive Hypertension in Animal Models and Humans

Hypertension is still one of the major causes of death from cardiovascular failure. Increased salt intake may aggravate the rise in blood pressure and the development of consequential damage of the heart, the vessels and other organs. The general necessity of restricted salt intake regardless of blood pressure or salt sensitivity has been a matter of debate over the past decades. This review summarizes the main pathogenic mechanisms of hypertension and salt sensitivity in rat models, particularly in the spontaneously hypertensive rat (SHR), and in patients with essential hypertension (EH). Although SHRs are commonly considered to be salt-resistant, there is much evidence that salt loading may deteriorate blood pressure and cardiovascular function even in these animals. Similarly, EH is not a homogenous disorder - some patients, but not all, exhibit pronounced salt sensitivity. The renin-angiotensin system (RAS) plays a key role in the regulation of blood pressure and salt and fluid homeostasis and thus is one of the main targets of antihypertensive therapy. This review focuses on the contribution of the RAS to the pathogenesis of salt-sensitive hypertension in SHRs and patients with EH.

Histidine 379 of human laeverin/aminopeptidase Q, a nonconserved residue within the exopeptidase motif, defines its distinctive enzymatic properties

Human laeverin/aminopeptidase Q (LVRN/APQ) is a novel member of the M1 family of zinc aminopeptidases and is specifically expressed on the cell surface of human extravillous trophoblasts. Multiple sequence alignment of human M1 aminopeptidase revealed that the first Gly residue within the conserved exopeptidase motif of the M1 family, GXMEN motif, is uniquely substituted for His in human LVRN/APQ. In this study, we evaluated the roles of nonconserved His(379), comprising the exopeptidase motif in the enzymatic properties of human LVRN/APQ. We revealed that the substitution of His(379) with Gly caused significant changes in substrate specificity both toward fluorogenic substrates and natural peptide hormones. In addition, the susceptibilities of bestatin, a sensitive inhibitor for human LVRN/APQ, and natural inhibitory peptides were decreased in the H379G mutant. A molecular model suggested a conformational difference between wild-type and H379G human LVRN/APQs. These results indicate that His(379) of the enzyme plays essential roles in its distinctive enzymatic properties and contributes to maintaining the appropriate structure of the catalytic cavity of the enzyme. Our data may bring new insight into the biological significance of the unique exopeptidase motif of LVRN/APQ obtained during the evolution of primates.

The effect of recombinant aminopeptidase A (APA) on hypertension in pregnant spontaneously hypertensive rats (SHRs)

BACKGROUND

We have tested the effects of aminopeptidase A (APA), MgSO(4) and various conventional antihypertensive drugs on hypertension in pregnant spontaneously hypertensive rats (SHRs) and examined the effects on both fetal heart and kidney.

METHODS

We used recombinant human APA, which has been recently shown to work as an antihypertensive agent in SHRs (n=5). Each drug was administered from gestational day 10 to day 20 and each dose was increased daily up to 10 fold until the end of treatment except for MgSO(4) (n=5 per each group). Blood pressure (BP) was monitored and fetal kidneys and heart were histologically examined.

RESULTS

The antihypertensive effects of the drugs were in the following order: hydralazine>aminopeptidase A and angiotensin receptor blockers (ARBs), candesartan>MgSO(4) and methyldopa. Microscopic examination showed that fetal exposure to candesartan is associated with poor proximal tubular differentiation in the kidney and that to MgSO(4) is associated with poor blood vessel formation in the heart, respectively.

CONCLUSIONS

Our present study showed that APA is one of the candidates for antihypertensive agents in hypertension during pregnancy.

Physiological and pathophysiological roles of placental aminopeptidase in maternal sera: possible relation to preeclampsia and preterm delivery

BACKGROUND

Both preeclampsia and preterm delivery are important complications in pregnancy and are still diseases of unknown causes, despite considerable research in recent times. These complications constitute obstetric emergencies that require expert knowledge and management skills.

OBJECTIVES

This article reviews the emerging role of aminopeptidases in the monitoring and development of improved therapeutic strategies that provide better patient selection for therapeutic personalization.

METHODS

A literature review (PubMed, Medline) to the present.

RESULTS/CONCLUSION

The fetus produces angiotensin II, vasopressin and oxytocin, which are highly vasoactive and uterotonic, and these peptides increase in parallel with fetal growth and in response to stressors such as hypoxia. Because these hormones are small molecules, it is probable that there occurs the leak out of these hormones from the feto-placental unit. Oxytocinase and angiotensinase in human placenta are identical to placental leucine aminopeptidase and aminopeptidase A, respectively. They work as barriers of peptide hormones between fetus and mother and their activities in pregnancy sera increase with advancing gestation. Aminopeptidase activities in maternal sera might be useful for monitoring of preeclampsia and predicting the prognosis of preterm delivery.