Hypertension in mice lacking the proatrial natriuretic peptide convertase corin

The endocrine basis of the cardio-renal axis: New perspectives regarding corin

The central role of natriuretic peptides (NPs) in the complex cardio-renal integrated physiology and organ failure has been revealed over the last four decades. Atrial natriuretic peptide (ANP), the oldest representative of the NPs family, is produced through conversion of proANP to the mature peptide by corin, a trans-membrane protease localized to the cardiac myocyte membrane. Similarly, brain natriuretic peptide (BNP) is generated by furin, which cleaves proBNP to BNP in myocytes. Though the components of NPs system, their synthesis and target organs are well established, understanding their role in the interplay between the heart and the kidney is steadily evolving. In this context, Feldman et al. (New England Journal of Medicine, 389, 1685) recently described patients with hypertension, cardiomyopathy, atrial arrhythmia and left atrial fibrosis, associated with a homozygous loss-of-function variant of the gene encoding corin (Cor-/-). Notably, reduced baseline urinary electrolyte and creatinine excretion have been observed in one of the studied patients. This renal excretory functional impairment could be attributed to the lack of cardiac-derived ANP in these patients, as implied by Feldman et al. Yet, in this mini-review we suggest that this aberrant renal manifestation may principally stem from lack of local ANP production at renal tissue, as corin is normally expressed in proximal tubules, Henle's loop and collecting ducts, with locally produced ANP provoking Na+ and water exertion. Collectively, it seems that beside the classic well-established cardio-renal axis, the renal NPs system functions as local endocrine machinery in the regulation of sodium excretion.

Early-pregnancy N-terminal pro-brain natriuretic peptide level is inversely associated with hypertensive disorders of pregnancy diagnosed after 35 weeks of gestation

Hypertensive disorders of pregnancy (HDP) are among the major causes of high maternal and fetal/neonatal morbidity and mortality rates. Patients with HDP have significantly elevated N-terminal pro-brain natriuretic peptide (NT-proBNP) levels at diagnosis; however, the NT-proBNP levels during early pregnancy are largely unknown. This study aimed to validate the association between HDP and NT-proBNP levels. This retrospective study evaluated 103 pregnant women who developed HDP diagnosed after 35 weeks of gestation and 667 who did not. The HDP group had significantly lower early-pregnancy NT-proBNP levels than the without HDP group. However, the two groups did not significantly differ in terms of the late-pregnancy NT-proBNP levels. After adjusting for confounding factors such as age, body mass index, parity, and blood pressure levels, high early-pregnancy NT-proBNP levels were associated with a lower HDP risk. Early-pregnancy NT-proBNP levels ≥ 60.5 pg/mL had a negative predictive value of 97.0% for ruling out HDP, with a sensitivity of 87.4% and specificity of 62.5%. In conclusion, elevated early-pregnancy NT-proBNP levels were associated with a lower HDP risk. Moreover, a cutoff point of ≥ 60.5 pg/mL for early-pregnancy NT-proBNP levels had a high negative predictive value and sensitivity for ruling out HDP. These findings can provide new clinical implications.

The molecular mechanism of obesity: The science behind natural exercise yoga and healthy diets in the treatment of obesity

The review centers on the scientific evidence underlying obesity, providing a detailed examination of the role of perilipin in this condition. It explores potential causes of obesity and delves into therapeutic approaches involving exercise, yoga, and herbal treatments. The paper discusses natural sources that can contribute to combating obesity and underscores the importance of exercise in a scientific context for overcoming obesity. Additionally, it includes information on herbal ingredients that aid in reducing obesity. The review also examines the impact of exercise type and intensity at various time intervals on muscle development. It elucidates triglyceride hydrolysis through different enzymes and the deposition of fatty acids in adipose tissue. The mechanisms by which alpha/beta hydrolase domain-containing protein 5 (ABHD5) and hormone-sensitive lipase (HSL) target and activate their functions are detailed. The inflammatory response in obesity is explored, encompassing inflammatory markers, lipid storage diseases, and their classification with molecular mechanisms. Furthermore, the hormonal regulation of lipolysis is elaborated upon in the review.

Corin protects against acute kidney injury in mice through anti-inflammatory effects

Corin is a type II transmembrane serine protease mainly expressed in the heart. Recently, corin was detected in the kidney and was reported to be associated with multiple kidney diseases. To date, its effect on acute kidney injury (AKI) has not been clarified. Here, we found that corin was constitutively expressed in renal tubules, especially in proximal and distal tubular epithelial cells. The expression of corin was dramatically reduced in ischemia/reperfusion injury (IRI)-induced AKI mouse model and oxygen-glucose deprivation (OGD)-induced human proximal tubular epithelial (HK-2) cells injury model, suggesting a potential role of corin in AKI. Corin deficient mice exhibited aggravated renal injury in AKI, as indicated by higher elevation of serum creatinine (SCr) and blood urea nitrogen (BUN), more severe tubular damage, and increased cell death versus wild type mice, demonstrating a protective effect of corin on AKI. In vitro overexpression of corin didn't directly alleviate hypoxia-induced HK-2 cells death, revealing that the protective effect of corin against AKI is not due to direct protection of tubular epithelial cells but may be through indirect protection. Microarray analysis showed enhanced inflammatory chemokines signaling and leukocyte chemotaxis in corin-/- mice after AKI, identifying an important role of corin in halting leukocyte chemotaxis and inflammatory response. Consistently, corin-/- mice after AKI displayed increased tubulointerstitial neutrophils and macrophages infiltration, as well as higher inflammatory mediators in kidneys. Taken together, our study indicates that tubular corin exerts a protective effect against AKI through negative regulation of chemotaxis signaling and inflammation in the kidney.

Cardiac Localized Polycystin-2 plays a Functional Role in Natriuretic Peptide Production and its Absence Contributes to Hypertension

Cardiovascular complications are the most common cause of mortality in patients with autosomal dominant polycystic kidney disease (ADPKD). Hypertension is seen in 70% of patients by the age of 30 prior to decline in kidney function. The natriuretic peptides (NPs), atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), are released by cardiomyocytes in response to membrane stretch, increasing urinary excretion of sodium and water. Mice heterozygous for Pkd2 have attenuated NP responses and we hypothesized that cardiomyocyte-localized polycystin proteins contribute to production of NPs. Cardiomyocyte-specific knock-out models of polycystin-2 (PC2), one of the causative genes of ADPKD, demonstrate diurnal hypertension. These mice have decreased ANP and BNP expression in the left ventricle. Analysis of the pathways involved in production, maturation, and activity of NPs identified decreased transcription of CgB, PCSK6, and NFAT genes in cPC2-KOs. Engineered heart tissue with human iPSCs driven into cardiomyocytes with CRISPR/Cas9 KO of PKD2 failed to produce ANP. These results suggest that PC2 in cardiomyocytes are involved in NP production and lack of cardiac PC2 predisposes to a hypertensive volume expanded phenotype, which may contribute to the development of hypertension in ADPKD.

Corin and Left Atrial Cardiomyopathy, Hypertension, Arrhythmia, and Fibrosis

Two siblings presented with cardiomyopathy, hypertension, arrhythmia, and fibrosis of the left atrium. Each had a homozygous null variant in CORIN, the gene encoding atrial natriuretic peptide (ANP)-converting enzyme. A plasma sample obtained from one of the siblings had no detectable levels of corin or N-terminal pro-ANP but had elevated levels of B-type natriuretic peptide (BNP) and one of the two protein markers of fibrosis that we tested. These and other findings support the hypothesis that BNP cannot fully compensate for a lack of activation of the ANP pathway and that corin is critical to normal ANP activity, left atrial function, and cardiovascular homeostasis.

Golgi α-mannosidases regulate cell surface N-glycan type and ectodomain shedding of the transmembrane protease corin

Corin is a transmembrane protease that activates natriuretic peptides on the cell membrane. Reduced cell surface targeting or increased ectodomain shedding disrupts cell membrane homeostasis of corin, thereby impairing its cell surface expression and enzyme activity. N-glycans are essential in corin ectodomain shedding. Lack of N-glycans promotes corin ectodomain shedding in the juxtamembrane and frizzled-1 domains. The nascent N-glycans, transferred onto the polypeptide of corin, undergo multistep N-glycan processing in the endoplasmic reticulum and Golgi. It remains unclear how trimming by Golgi α-mannosidases, the critical N-glycan processing steps in N-glycan maturation, may regulate corin biosynthesis. In this study, we examined the effects of kifunensine and swainsonine, the inhibitors for α-mannosidases I and II, on corin expression and function. Western analysis of corin proteins in cell lysates and conditioned media from the inhibitor-treated corin-stable HEK293 cells and AC16 cells showed that both α-mannosidases I and II were required to maintain complex N-glycans on cell surface corin and protect corin from ectodomain shedding in the juxtamembrane and frizzled-1 domains. Cell viability analysis revealed that inhibition of α-mannosidase I or II sensitized cardiomyocytes to hydrogen peroxide-induced injury via regulating corin. Moreover, either one of the two coding genes was sufficient to perform Golgi α-mannosidase I trimming of N-glycans on corin. Similarly, this sufficiency was observed in Golgi α-mannosidase II-coding genes. Inhibition of ectodomain shedding restored corin zymogen activation from kifunensine- or swainsonine-induced reduction. Together, our results show the important roles of Golgi α-mannosidases in maintaining cell membrane homeostasis and biological activities of corin.

Corin deficiency impairs cardiac function in mouse models of heart failure

Introduction

Corin is a protease in the natriuretic peptide system. Deleterious CORIN variants are associated with hypertension and heart disease. It remains unclear if and to what extent corin deficiency may contribute to heart failure (HF).

Methods

Corin knockout (KO) mice were used as a model. Cardiac function was assessed by echocardiography and tissue analysis in Corin KO mice at different ages or subjected to transverse aortic constriction (TAC), which increased pressure overload. Heart and lung tissues were analyzed for cardiac hypertrophy and lung edema using wheat germ agglutinin, Sirius red, Masson's trichrome, and Prussian blue staining. Recombinant corin was tested for its effect on cardiac function in the TAC-operated Corin KO mice. Selected gene expression in the heart was examined by RT-PCR. ELISA was used to analyze factors in plasma.

Results

Corin KO mice had progressive cardiac dysfunction with cardiac hypertrophy and fibrosis after 9 months of age, likely due to chronic hypertension. When Corin KO mice were subjected to TAC at 10-12 weeks of age, cardiac function decreased more rapidly than in similarly treated wild-type mice. When the TAC-operated Corin KO mice were treated with recombinant corin protein, cardiac dysfunction, hypertrophy, and fibrosis were ameliorated. The corin treatment also decreased the gene expression associated with cardiac hypertrophy and fibrosis, increased plasma cGMP levels, lowered plasma levels of N-terminal pro-atrial natriuretic peptide, angiotensin II, and aldosterone, and lessened lung edema in the Corin KO mice subjected to TAC.

Conclusion

Corin deficiency impairs cardiac function and exacerbates HF development in mice. Corin protein may be used to reduce cardiac hypertrophy and fibrosis, suppress the renin-angiotensin-aldosterone system, and improve cardiac function in HF.

Natriuretic Peptide Signaling in Uterine Biology and Preeclampsia

Endometrial decidualization is a uterine process essential for spiral artery remodeling, embryo implantation, and trophoblast invasion. Defects in endometrial decidualization and spiral artery remodeling are important contributing factors in preeclampsia, a major disorder in pregnancy. Atrial natriuretic peptide (ANP) is a cardiac hormone that regulates blood volume and pressure. ANP is also generated in non-cardiac tissues, such as the uterus and placenta. In recent human genome-wide association studies, multiple loci with genes involved in natriuretic peptide signaling are associated with gestational hypertension and preeclampsia. In cellular experiments and mouse models, uterine ANP has been shown to stimulate endometrial decidualization, increase TNF-related apoptosis-inducing ligand expression and secretion, and enhance apoptosis in arterial smooth muscle cells and endothelial cells. In placental trophoblasts, ANP stimulates adenosine 5'-monophosphate-activated protein kinase and the mammalian target of rapamycin complex 1 signaling, leading to autophagy inhibition and protein kinase N3 upregulation, thereby increasing trophoblast invasiveness. ANP deficiency impairs endometrial decidualization and spiral artery remodeling, causing a preeclampsia-like phenotype in mice. These findings indicate the importance of natriuretic peptide signaling in pregnancy. This review discusses the role of ANP in uterine biology and potential implications of impaired ANP signaling in preeclampsia.

Corin Deficiency Diminishes Intestinal Sodium Excretion in Mice

Sodium excretion, a critical process in sodium homeostasis, occurs in many tissues, including the kidney and intestine. Unlike in the kidney, the hormonal regulation of intestinal sodium excretion remains unclear. Atrial natriuretic peptide (ANP) is a crucial hormone in renal natriuresis. Corin is a protease critical for ANP activation. Corin and ANP are expressed mainly in the heart. In this study, we investigated corin, ANP, and natriuretic peptide receptor A (Npra) expression in mouse intestines. Corin and ANP expression was co-localized in enteroendocrine cells, whereas Npra expression was on the luminal epithelial cells. In Corin knockout (KO) mice, fecal Na⁺ and Cl^- excretion decreased compared with that in wild-type (WT) mice. Such a decrease was not found in conditional Corin KO mice lacking cardiac corin selectively. In kidney conditional Corin KO mice lacking renal corin, fecal Na⁺ and Cl^- excretion increased, compared to that in WT mice. When WT, Corin KO, and the kidney conditional KO mice were treated with aldosterone, the differences in fecal Na⁺ and Cl^- levels disappeared. These results suggest that intestinal corin may promote fecal sodium excretion in a paracrine mechanism independent of the cardiac corin function. The increased fecal sodium excretion in the kidney conditional Corin KO mice likely reflected an intestinal compensatory response to renal corin deficiency. Our results also suggest that intestinal corin activity may antagonize aldosterone action in the promotion of fecal sodium excretion. These findings help us understand the hormonal mechanism controlling sodium excretion the intestinal tract.

Association between CORIN methylation and hypertension in Chinese adults

Background

Corin, a physical activator of atrial natriuretic peptide, has been associated with hypertension with unclear mechanisms. Here, we aimed to examine whether CORIN gene methylation was involved in the underlying molecular mechanisms.

Methods

DNA methylation levels of CORIN were measured by target bisulfite sequencing using genomic DNA isolated from peripheral blood mononuclear cells in 2498 participants in the Gusu cohort (discovery sample) and 1771 independent participants (replication sample). We constructed a mediation model with DNA methylation as the predictor, serum corin as the mediator, and hypertension as the outcome, adjusting for covariates. Multiple testing was controlled by false discovery rate (FDR) approach.

Results

Of the 9 CpGs assayed, hypermethylation at all CpGs were significantly associated with a lower level of blood pressure in the discovery sample and eight associations were also significant in the replication sample (all FDR-adjusted p<0.05). Serum corin mediated approximately 3.07% (p=0.004), 6.25% (p=0.002) and 10.11% (p=0.034) of the associations of hypermethylation at one CpG (Chr4:47840096) with systolic and diastolic blood pressure, and hypertension, respectively. All these mediations passed the causal inference test.

Conclusions

These results suggest that hypermethylation in the CORIN gene is associated with a lower odds of prevalent hypertension and may be involved in the role of corin in blood pressure regulation.

The recent progress of peptide regulators for the Wnt/β-catenin signaling pathway

Wnt signaling plays an important role in many biological processes such as stem cell self-renewal, cell proliferation, migration, and differentiation. The β-catenin-dependent signaling pathway mainly regulates cell proliferation, differentiation, and migration. In the Wnt/β-catenin signaling pathway, the Wnt family ligands transduce signals through LRP5/6 and Frizzled receptors to the Wnt/β-catenin signaling cascades. Wnt-targeted therapy has garnered extensive attention. The most commonly used approach in targeted therapy is small-molecule regulators. However, it is difficult for small-molecule regulators to make great progress due to their inherent defects. Therapeutic peptide regulators targeting the Wnt signaling pathway have become an alternative therapy, promising to fill the gaps in the clinical application of small-molecule regulators. In this review, we describe recent advances in peptide regulators for Wnt/β-catenin signaling.

Natriuretic peptides potentiate cardiac hypertrophic response to noradrenaline in rats

Excessive activation of the sympathetic nervous system is involved in cardiovascular damage including cardiac hypertrophy. Natriuretic peptides are assumed to exert protective actions for the heart, alleviating hypertrophy and/or fibrosis of the myocardium. In contrast to this assumption, we show in the present study that both atrial and C-type natriuretic peptides (ANP and CNP) potentiate cardiac hypertrophic response to noradrenaline (NA) in rats. Nine-week-old male Wistar rats were continuously infused with subcutaneous 30 micro-g/h NA without or with persistent intravenous administration of either 1.0 micro-g/h ANP or CNP for 14 days. Blood pressure (BP) was recorded under an unrestrained condition by a radiotelemetry system. Cardiac hypertrophic response to NA was evaluated by heart weight/body weight (HW/BW) ratio and microscopic measurement of myocyte size of the left ventricle. Mean BP levels at the light and dark cycles rose by about 20mmHg following NA infusion for 14 days, with slight increases in HW/BW ratio and ventricular myocyte size. Infusions of ANP and CNP had no significant effects on mean BP in NA-infused rats, while two natriuretic peptides potentiated cardiac hypertrophic response to NA. Cardiac hypertrophy induced by co-administration of NA and ANP was attenuated by treatment with prazosin or atenolol. In summary, both ANP and CNP potentiated cardiac hypertrophic effect of continuously infused NA in rats, suggesting a possible pro-hypertrophic action of natriuretic peptides on the heart.

Identification of a new Corin atrial natriuretic peptide-converting enzyme substrate: Agouti-signaling protein (ASIP)

Corin is a transmembrane tethered enzyme best known for processing the hormone atrial natriuretic peptide (ANP) in cardiomyocytes to control electrolyte balance and blood pressure. Loss of function mutations in Corin prevent ANP processing and lead to hypertension. Curiously, Corin loss of function variants also result in lighter coat color pigmentation in multiple species. Corin pigmentation effects are dependent on a functional Agouti locus encoding the agouti-signaling protein (ASIP) based on a genetic interaction. However, the nature of this conserved role of Corin has not been defined. Here we report that ASIP is a direct proteolytic substrate of the Corin enzyme.

Impact of Adverse Gestational Milieu on Maternal Cardiovascular Health

Cardiovascular disease affects 1% to 4% of the nearly 4 million pregnancies in the United States each year and is the primary cause of pregnancy-related mortality. Adverse pregnancy outcomes are associated with cardiovascular complications during pregnancy persisting into the postpartum period. Recently, investigations have identified an altered sex hormone milieu, such as in the case of hyperandrogenism, as a causative factor in the development of gestational cardiovascular dysfunction. The mechanisms involved in the development of cardiovascular disease in postpartum women are largely unknown. Animal studies have attempted to recapitulate adverse pregnancy outcomes to investigate causal relationships and molecular underpinnings of adverse gestational cardiac events and progression to the development of cardiovascular disease postpartum. This review will focus on summarizing clinical and animal studies detailing the impact of adverse pregnancy outcomes, including preeclampsia, gestational diabetes mellitus, and maternal obesity, on gestational cardiometabolic dysfunction and postpartum cardiovascular disease. Specifically, we will highlight the adverse impact of gestational hyperandrogenism and its potential to serve as a biomarker for maternal gestational and postpartum cardiovascular dysfunctions.

Association between CORIN promoter methylation and stroke: Results from two independent samples of Chinese adults

Objective

As the physical activator of natriuretic peptides, corin has been associated with stroke, but the underlying mechanism is not very clear. Here, we examined whether the CORIN promoter’s methylation, an epigenetic DNA modification, was associated with the risk of stroke in two independent samples.

Methods

A total of 1771 participants including 853 stroke cases and 918 healthy controls were included as a discovery sample and 2,498 community members with 10 years of follow-up were included as a replication sample. DNA methylation of the CORIN promoter was quantified by target bisulfite sequencing in both samples. We first examined the single CpG association, followed by a gene-based analysis of the joint association between multiple CpG methylation and stroke, adjusting for conventional risk factors.

Results

The single CpG association analysis found that hypermethylation at all of the 9 CpG sites assayed was significantly associated with lower odds of prevalent stroke in the discovery sample (all p < 0.05), and three of them located at Chr4:47840038 (HR = 0.74, p = 0.015), Chr4:47839941 (HR = 0.80, p = 0.047), and Chr4:47839933 (HR = 0.82, p = 0.050) were also significantly associated with incident stroke in the replication sample. The gene-based association analysis found that DNA methylation of the 9 CpG sites at the CORIN promoter was jointly associated with stroke in both samples (all p < 0.05).

Conclusion

DNA methylation levels of the CORIN gene promoter were lower in stroke patients and predicted a higher risk of incident stroke in Chinese adults. The underlying causality warranted further investigation.

Attenuated Relationships Between Indexes of Volume Overload and Atrial Natriuretic Peptide in Uncontrolled, Sustained Volume-Dependent Primary Hypertension

BACKGROUND

Whether systolic blood pressure (SBP) control in sustained volume-dependent primary hypertension is associated with blunted ANP (atrial natriuretic peptide) relationships with indexes of volume load is unknown.

METHODS

Systemic hemodynamics (central pressure, echocardiographic aortic velocity and diameter measurements in the outflow tract), circulating ANP concentrations (ELISA assays) and glomerular and tubular function (24-hour urine collections [n=519]) were determined in a community of African ancestry (n=772).

RESULTS

As compared with those with a controlled SBP, those with an uncontrolled SBP (n=198) showed lower ANP concentrations (P<0.005) despite higher stroke volume and cardiac output (P<0.0001) and renal differences consistent with enhanced fluid retention. In those with a controlled SBP, fractional Na⁺ excretion (FeNa⁺; P<0.0005) and creatinine clearance (glomerular filtration rate; P<0.005) were inversely associated with ANP concentrations independent of confounders. Moreover, in those with a controlled SBP, stroke volume and cardiac output (P<0.0001) were independently and positively associated with ANP concentrations. In addition, in those with a controlled SBP, ANP concentrations were independently and inversely associated with systemic vascular resistance (SVR; P<0.0001) and aortic characteristic impedance (Zc; P<0.005). By contrast, in those with uncontrolled SBP, no relationships between either stroke volume (P>0.25), cardiac output (P>0.29), FeNa⁺ (P>0.77), or glomerular filtration rate (P>0.47) and ANP concentrations were noted. Furthermore, in those with an uncontrolled SBP, no relationships between ANP concentrations and SVR or Zc were observed (P>0.34).

CONCLUSIONS

In a population where primary hypertension is strongly volume-dependent, those with an uncontrolled SBP have an attenuated relationship between ANP and both renal and hemodynamic indexes of volume overload and the vascular effects of ANP.

Corin-The Early Marker of Preeclampsia in Pregestational Diabetes Mellitus

Preeclampsia (PE) is one of the leading causes of mortality and morbidity in pregnant women. Pregestational diabetes (PGDM) patients are prone to vascular complications and preeclampsia, whereas vascular exposure to hyperglycemia induces inflammation, vascular remodeling, and arterial stiffness. Corin is a serine protease, converting inactive pro-atrial natriuretic peptide (pro-ANP) into an active form. It also promotes salt and water excretion by activating atrial natriuretic peptide (ANP), and significantly increases trophoblast invasion. The study aimed to determine whether corin may be a predictor of PE in a high-risk group-women with long-term PGDM. The nested case-control prospective study involved 63 patients with long-term pregestational type 1 diabetes (PGDM). In total, 17 patients developed preeclampsia (the study group), whereas 43 patients without PE constituted the control group. To assess corin concentration, blood samples were collected at two time points: between 18th-22nd week of gestation and 28th-32nd week of gestation. PE patients presented significantly higher mid-gestation corin levels, urine protein loss in each trimester, serum creatinine in the third trimester, and lower creatinine clearance in the third trimester. The results of our study indicate that serum corin assessment may play a role in predicting preeclampsia. Thus, it may be included in the PE risk calculator, initially in high-risk groups, such as patients with PGDM.

Proprotein Convertase Subtilisin/Kexin 6 in Cardiovascular Biology and Disease

Proprotein convertase subtilisin/kexin 6 (PCSK6) is a secreted serine protease expressed in most major organs, where it cleaves a wide range of growth factors, signaling molecules, peptide hormones, proteolytic enzymes, and adhesion proteins. Studies in Pcsk6-deficient mice have demonstrated the importance of Pcsk6 in embryonic development, body axis specification, ovarian function, and extracellular matrix remodeling in articular cartilage. In the cardiovascular system, PCSK6 acts as a key modulator in heart formation, lipoprotein metabolism, body fluid homeostasis, cardiac repair, and vascular remodeling. To date, dysregulated PCSK6 expression or function has been implicated in major cardiovascular diseases, including atrial septal defects, hypertension, atherosclerosis, myocardial infarction, and cardiac aging. In this review, we describe biochemical characteristics and posttranslational modifications of PCSK6. Moreover, we discuss the role of PCSK6 and related molecular mechanisms in cardiovascular biology and disease.

Mechanism and modeling of human disease-associated near-exon intronic variants that perturb RNA splicing

It is estimated that 10%-30% of disease-associated genetic variants affect splicing. Splicing variants may generate deleteriously altered gene product and are potential therapeutic targets. However, systematic diagnosis or prediction of splicing variants is yet to be established, especially for the near-exon intronic splice region. The major challenge lies in the redundant and ill-defined branch sites and other splicing motifs therein. Here, we carried out unbiased massively parallel splicing assays on 5,307 disease-associated variants that overlapped with branch sites and collected 5,884 variants across the 5' splice region. We found that strong splice sites and exonic features preserve splicing from intronic sequence variation. Whereas the splice-altering mechanism of the 3' intronic variants is complex, that of the 5' is mainly splice-site destruction. Statistical learning combined with these molecular features allows precise prediction of altered splicing from an intronic variant. This statistical model provides the identity and ranking of biological features that determine splicing, which serves as transferable knowledge and out-performs the benchmarking predictive tool. Moreover, we demonstrated that intronic splicing variants may associate with disease risks in the human population. Our study elucidates the mechanism of splicing response of intronic variants, which classify disease-associated splicing variants for the promise of precision medicine.

Edema formation in congestive heart failure and the underlying mechanisms

Congestive heart failure (HF) is a complex disease state characterized by impaired ventricular function and insufficient peripheral blood supply. The resultant reduced blood flow characterizing HF promotes activation of neurohormonal systems which leads to fluid retention, often exhibited as pulmonary congestion, peripheral edema, dyspnea, and fatigue. Despite intensive research, the exact mechanisms underlying edema formation in HF are poorly characterized. However, the unique relationship between the heart and the kidneys plays a central role in this phenomenon. Specifically, the interplay between the heart and the kidneys in HF involves multiple interdependent mechanisms, including hemodynamic alterations resulting in insufficient peripheral and renal perfusion which can lead to renal tubule hypoxia. Furthermore, HF is characterized by activation of neurohormonal factors including renin-angiotensin-aldosterone system (RAAS), sympathetic nervous system (SNS), endothelin-1 (ET-1), and anti-diuretic hormone (ADH) due to reduced cardiac output (CO) and renal perfusion. Persistent activation of these systems results in deleterious effects on both the kidneys and the heart, including sodium and water retention, vasoconstriction, increased central venous pressure (CVP), which is associated with renal venous hypertension/congestion along with increased intra-abdominal pressure (IAP). The latter was shown to reduce renal blood flow (RBF), leading to a decline in the glomerular filtration rate (GFR). Besides the activation of the above-mentioned vasoconstrictor/anti-natriuretic neurohormonal systems, HF is associated with exceptionally elevated levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP). However, the supremacy of the deleterious neurohormonal systems over the beneficial natriuretic peptides (NP) in HF is evident by persistent sodium and water retention and cardiac remodeling. Many mechanisms have been suggested to explain this phenomenon which seems to be multifactorial and play a major role in the development of renal hyporesponsiveness to NPs and cardiac remodeling. This review focuses on the mechanisms underlying the development of edema in HF with reduced ejection fraction and refers to the therapeutic maneuvers applied today to overcome abnormal salt/water balance characterizing HF.

Renal Corin Is Essential for Normal Blood Pressure and Sodium Homeostasis

Atrial natriuretic peptide (ANP)-mediated natriuresis is known as a cardiac endocrine function in sodium and body fluid homeostasis. Corin is a protease essential for ANP activation. Here, we studied the role of renal corin in regulating salt excretion and blood pressure. We created corin conditional knockout (cKO), in which the Corin gene was selectively disrupted in the kidney (kcKO) or heart (hcKO). We examined the blood pressure, urinary Na⁺ and Cl⁻ excretion, and cardiac hypertrophy in wild-type, corin global KO, kcKO, and hcKO mice fed normal- and high-salt diets. We found that on a normal-salt diet (0.3% NaCl), corin kcKO and hcKO mice had increased blood pressure, indicating that both renal and cardiac corin is necessary for normal blood pressure in mice. On a high-salt diet (4% NaCl), reduced urinary Na⁺ and Cl⁻ excretion, increased body weight, salt-exacerbated hypertension, and cardiac hypertrophy were observed in corin kcKO mice. In contrast, impaired urinary Na⁺ and Cl⁻ excretion and salt-exacerbated hypertension were not observed in corin hcKO mice. These results indicated that renal corin function is important in enhancing natriuresis upon high salt intakes and that this function cannot be compensated by the cardiac corin function in mice.

Soluble Corin Predicts the Risk of Cardiovascular Disease

Background

As a key enzyme of the natriuretic peptides system, corin may participate in the development of cardiovascular disease (CVD). Its level in circulation predicted CVD recurrence in patients with myocardial infarction and heart failure, but no study examined this prediction in general populations.

Objectives

This study sought to examine the prospective association between corin and CVD in a community-based population of Chinese adults.

Methods

The Gusu cohort included 2,498 participants (mean age 53 years, 39% men) who were free of CVD at baseline. Serum corin was measured by enzyme-linked immunosorbent assay kits at baseline and CVD events were followed every 2 years for all participants. A competing-risks survival regression model was used to examine the association between serum corin and CVD.

Results

During 10 years of follow-up, 210 participants developed CVD including 88 stroke events. A higher serum corin (after log-transformation) at baseline was significantly associated with an increased risk of CVD (HR: 1.88; P = 0.019) and stroke (HR: 3.19; P = 0.014). Analysis using categorical serum corin (in quartiles) showed that participants in the highest quartile had a 62% and 179% increased risk for CVD (HR: 1.62; P = 0.024) and stroke (HR: 2.79; P = 0.004), respectively, compared with those in the lowest quartile. We did not find a significant association between serum corin and coronary heart disease.

Conclusions

A higher serum corin at baseline predicted a higher risk of CVD events and stroke, but not coronary heart disease, in Chinese adults, independent of conventional risk factors. Serum corin may be a predictor for stroke but the underlying mechanism needs further investigation.

Association between CORIN methylation and hypertension in Chinese adults

BACKGROUND

Corin, a physical activator of atrial natriuretic peptide, has been associated with hypertension with unclear mechanisms. Here, we aimed to examine whether CORIN gene methylation was involved in the underlying molecular mechanisms.

METHODS

DNA methylation levels of CORIN were measured by target bisulfite sequencing using genomic DNA isolated from peripheral blood mononuclear cells in 2498 participants in the Gusu cohort (discovery sample) and 1771 independent participants (replication sample). We constructed a mediation model with DNA methylation as the predictor, serum corin as the mediator, and hypertension as the outcome, adjusting for covariates. Multiple testing was controlled by false discovery rate (FDR) approach.

RESULTS

Of the 9 CpGs assayed, hypermethylation at all CpGs were significantly associated with a lower level of blood pressure in the discovery sample and eight associations were also significant in the replication sample (all FDR-adjusted p<0.05). Serum corin mediated approximately 3.07% (p=0.004), 6.25% (p=0.002) and 10.11% (p=0.034) of the associations of hypermethylation at one CpG (Chr4:47840096) with systolic and diastolic blood pressure, and hypertension, respectively. All these mediations passed the causal inference test.

CONCLUSIONS

These results suggest that hypermethylation in the CORIN gene is associated with a lower odds of prevalent hypertension and may be involved in the role of corin in blood pressure regulation.

Salt-Sensitive Ileal Microbiota Plays a Role in Atrial Natriuretic Peptide Deficiency-Induced Cardiac Injury

Atrial natriuretic peptide (ANP) activity deficiency contributes to salt-sensitive hypertension in humans and mice. However, the role of ileal microbiota in salt sensitivity in ANP deficiency-related cardiac injury has not been investigated yet. This study used ANP^−/− mice to analyze the role of the salt-sensitive ileal microbiome on cardiac injury. ANP^−/− mice showed an increase in blood pressure (BP), the heart weight/body weight (HW/BW) ratio, and cardiac hypertrophy compared with wild-type (WT) mice. ANP deficiency did not impact the histological structure but reduced occludin expression in the ileum. Antibiotics significantly relieved BP and cardiac hypertrophy in ANP^−/− mice. A high-salt diet (HSD) increased BP, the HW/BW ratio, and cardiac hypertrophy/fibrosis in WT and ANP^−/− mice, and an HSD treatment in ANP^−/− mice exacerbated these cardiac parameters. The HSD markedly decreased muscularis layer thickening, villus length, and numbers of Paneth and goblet cells in the ileum of WT and ANP^−/− mice. Furthermore, the HSD increased the level of TLR4 and IL-1β in ANP^−/− mice ileum compared with WT mice. Antibiotics reduced the HW/BW ratio, cardiac hypertrophy/fibrosis, and the level of TLR4 and IL-1β in the ileum, and rescued the muscularis layer thickening, villus length, and numbers of Paneth and goblet cells in the ileum of HSD-ANP^−/− mice. Importantly, ANP deficiency induced the colonization of Burkholderiales bacterium YL45, Lactobacillus johnsonii, and Lactobacillus reuteri in the ileum on the NSD diet, which was only observed in HSD-induced WT mice but not in WT mice on the NSD. Besides, the HSD significantly enhanced the sum of the percentage of the colonization of Burkholderiales bacterium YL45, Lactobacillus johnsonii, and Lactobacillus reuteri in the ileum of ANP^−/− mice. Ileal microbiota transfer (IMT) from ANP^−/− mice to healthy C57BL/6J mice drove Lactobacillus johnsonii and Lactobacillus reuteri colonization in the ileum, which manifested an increase in BP, the HW/BW ratio, cardiac hypertrophy, and ileal pathology compared with IMT from WT mice. The HSD in C57BL/6J mice with IMT from ANP^−/− mice drove the colonization of Burkholderiales bacterium YL45, Lactobacillus johnsonii, and Lactobacillus reuteri in the ileum and further exacerbated the cardiac and ileal pathology. Our results suggest that salt-sensitive ileal microbiota is probably related to ANP deficiency-induced cardiac injury.

Corin Deficiency Alters Adipose Tissue Phenotype and Impairs Thermogenesis in Mice

Atrial natriuretic peptide (ANP) is a key regulator in body fluid balance and cardiovascular biology. In addition to its role in enhancing natriuresis and vasodilation, ANP increases lipolysis and thermogenesis in adipose tissue. Corin is a protease responsible for ANP activation. It remains unknown if corin has a role in regulating adipose tissue function. Here, we examined adipose tissue morphology and function in corin knockout (KO) mice. We observed increased weights and cell sizes in white adipose tissue (WAT), decreased levels of uncoupling protein 1 (Ucp1), a brown adipocyte marker in WAT and brown adipose tissue (BAT), and suppressed thermogenic gene expression in BAT from corin KO mice. At regular room temperature, corin KO and wild-type mice had similar metabolic rates. Upon cold exposure at 4 °C, corin KO mice exhibited impaired thermogenic responses and developed hypothermia. In BAT from corin KO mice, the signaling pathway of p38 mitogen-activated protein kinase, peroxisome proliferator-activated receptor c coactivator 1a, and Ucp1 was impaired. In cell culture, ANP treatment increased Ucp1 expression in BAT-derived adipocytes from corin KO mice. These data indicate that corin mediated-ANP activation is an important hormonal mechanism in regulating adipose tissue function and body temperature upon cold exposure in mice.

B-Type Natriuretic Peptide (BNP) Revisited—Is BNP Still a Biomarker for Heart Failure in the Angiotensin Receptor/Neprilysin Inhibitor Era?

Simple Summary

Active BNP-32, less active proBNP-108, and inactive N-terminal proBNP-76 all circulate in the blood. The circulating protease neprilysin has lower substrate specificity for BNP than ANP, while proBNP and N-terminal proBNP are not degraded by neprilysin. Currently available BNP immunoassays react with both mature BNP and proBNP; therefore, measured plasma BNP is mature BNP + proBNP. Because ARNI administration increases mature BNP, measured plasma BNP initially increases with ARNI administration by the amount of the increase in mature BNP. Later, ARNI administration reduces myocardial wall stress, and the resultant reduction in BNP production more than offsets the increase of mature BNP due to inhibition of degradation by neprilysin, resulting in lower plasma BNP levels. In the ARNI era, BNP remains a useful biomarker for heart failure, though mild increases early during ARNI administration should be taken into consideration.

Abstract

Myocardial wall stress, cytokines, hormones, and ischemia all stimulate B-type (or brain) natriuretic peptide (BNP) gene expression. Within the myocardium, ProBNP-108, a BNP precursor, undergoes glycosylation, after which a portion is cleaved by furin into mature BNP-32 and N-terminal proBNP-76, depending on the glycosylation status. As a result, active BNP, less active proBNP, and inactive N-terminal proBNP all circulate in the blood. There are three major pathways for BNP clearance: (1) cellular internalization via natriuretic peptide receptor (NPR)-A and NPR-C; (2) degradation by proteases in the blood, including neprilysin, dipeptidyl-peptidase-IV, insulin degrading enzyme, etc.; and (3) excretion in the urine. Because neprilysin has lower substrate specificity for BNP than atrial natriuretic peptide (ANP), the increase in plasma BNP after angiotensin receptor neprilysin inhibitor (ARNI) administration is much smaller than the increase in plasma ANP. Currently available BNP immunoassays react with both mature BNP and proBNP. Therefore, BNP measured with an immunoassay is mature BNP + proBNP. ARNI administration increases mature BNP but not proBNP, as the latter is not degraded by neprilysin. Consequently, measured plasma BNP initially increases with ARNI administration by the amount of the increase in mature BNP. Later, ARNI reduces myocardial wall stress, and the resultant reduction in BNP production more than offsets the increase in mature BNP mediated by inhibiting degradation by neprilysin, which lowers plasma BNP levels. These results suggest that even in the ARNI era, BNP can be used for diagnosis and assessment of the pathophysiology and prognosis of heart failure, though the mild increases early during ARNI administration should be taken into consideration.

Corin: A Key Mediator in Sodium Homeostasis, Vascular Remodeling, and Heart Failure

Simple Summary

Atrial natriuretic peptide (ANP) is an important hormone that regulates many physiological and pathological processes, including electrolyte and body fluid balance, blood volume and pressure, cardiac channel activity and function, inflammatory response, lipid metabolism, and vascular remodeling. Corin is a transmembrane serine protease that activates ANP. Variants in the CORIN gene are associated with cardiovascular disease, including hypertension, cardiac hypertrophy, atrial fibrillation, heart failure, and preeclampsia. The current data indicate a key role of corin-mediated ANP production and signaling in the maintenance of cardiovascular homeostasis. In this review, we discuss the latest findings regarding the molecular and cellular mechanisms underlying the role of corin in sodium homeostasis, uterine spiral artery remodeling, and heart failure.

Abstract

Atrial natriuretic peptide (ANP) is a crucial element of the cardiac endocrine function that promotes natriuresis, diuresis, and vasodilation, thereby protecting normal blood pressure and cardiac function. Corin is a type II transmembrane serine protease that is highly expressed in the heart, where it converts the ANP precursor to mature ANP. Corin deficiency prevents ANP activation and causes hypertension and heart disease. In addition to the heart, corin is expressed in other tissues, including those of the kidney, skin, and uterus, where corin-mediated ANP production and signaling act locally to promote sodium excretion and vascular remodeling. These results indicate that corin and ANP function in many tissues via endocrine and autocrine mechanisms. In heart failure patients, impaired natriuretic peptide processing is a common pathological mechanism that contributes to sodium and body fluid retention. In this review, we discuss most recent findings regarding the role of corin in non-cardiac tissues, including the kidney and skin, in regulating sodium homeostasis and body fluid excretion. Moreover, we describe the molecular mechanisms underlying corin and ANP function in supporting orderly cellular events in uterine spiral artery remodeling. Finally, we assess the potential of corin-based approaches to enhance natriuretic peptide production and activity as a treatment of heart failure.

Correlation between N-terminal pro-atrial natriuretic peptide, corin, and target organ damage in hypertensive disorders of pregnancy

The objective was to evaluate the correlation between N‐terminal pro‐atrial natriuretic peptide (NT‐proANP), corin and the severity of target organ injury in hypertensive disorders of pregnancy. A total of 78 women with hypertensive disorders of pregnancy and 49 normotensive pregnancies were enrolled. The clinical characteristics, laboratory index and echocardiogram results were collected. NT‐proANP, corin, sFlt‐1 and PlGF levels were measured. A receiver's operating characteristics (ROC) curve was performed to evaluate the efficacy of predicting target organ injury in the HDP group. The NT‐proANP, corin, and sFlt‐1/PlGF ratio were increased in the HDP group (p < .05). The area under the curve (AUC) predicted by NT‐proANP and corin were larger than sFlt‐1/PlGF ratio (0.779, 0.867, and 0.766, respectively). The creatinine and urine protein were significantly increased, while the estimated glomerular filtration rate (eGFR) was dramatically decreased in the HDP group (p < .05 each). The left atrial diameter (LAD), left atrial volume index (LAVI), left ventricular posterior wall thickness (LVPWT), and left ventricular septal thickness (LVST) were larger in the HDP group (p < .001 each). The NT‐proANP/corin levels were positively correlated with LAD, creatinine, and urine protein, and negatively correlated with eGFR in HDP group (p < .05 each). Multiple regressions demonstrated that NT‐proANP was an independent risk factor of LAD and urine protein, and corin was an independent risk factor of creatinine and eGFR in HDP group. NT‐proANP and corin may be reliable biomarkers for evaluating the severity of target organ damage in the hypertensive disorders of pregnant patients.

Evolutionary history of type II transmembrane serine proteases involved in viral priming

Type II transmembrane serine proteases (TTSPs) are a family of trypsin-like membrane-anchored serine proteases that play key roles in the regulation of some crucial processes in physiological conditions, including cardiac function, digestion, cellular iron homeostasis, epidermal differentiation, and immune responses. However, some of them, in particular TTSPs expressed in the human airways, were identified as host factors that promote the proteolytic activation and spread of respiratory viruses such as influenza virus, human metapneumovirus, and coronaviruses, including SARS-CoV-2. Given their involvement in viral priming, we hypothesized that members of the TTSP family may represent targets of positive selection, possibly as the result of virus-driven pressure. Thus, we investigated the evolutionary history of sixteen TTSP genes in mammals. Evolutionary analyses indicate that most of the TTSP genes that have a verified role in viral proteolytic activation present signals of pervasive positive selection, suggesting that viral infections represent a selective pressure driving the evolution of these proteases. We also evaluated genetic diversity in human populations and we identified targets of balancing selection in TMPRSS2 and TMPRSS4. This scenario may be the result of an ancestral and still ongoing host–pathogen arms race. Overall, our results provide evolutionary information about candidate functional sites and polymorphic positions in TTSP genes.

Atrial Natriuretic Peptide: Structure, Function, and Physiological Effects: A Narrative Review

Atrial natriuretic peptide (ANP) is a cardiac peptide with multiple physiological effects, including natriuresis, blood pressure regulation, and renin-angiotensin-aldosterone system (RAAS) antagonism. Pre-proANP is synthesized in the atria and must be extensively cleaved by the protease corin to produce the mature 28 amino acid ANP. The downstream signaling pathway of ANP acts through the guanylyl cyclase receptor and the second messenger cGMP. Studies on ANP's physiological effects have demonstrated its activity on channels present in the apical membrane in the renal nephron, potentially inhibiting or decreasing sodium reabsorption. Recent research has also identified several clinical conditions, such as dilated cardiomyopathy, renal failure, and aging, associated with increased and decreased ANP levels. ANP levels could serve as a potential biomarker for the diagnosis of acute stages of heart failure, and ANP infusion could have a role in the management of acute or chronic heart failure.

Associations of corin genetic polymorphisms with salt sensitivity, blood pressure changes, and hypertension incidence in Chinese adults

Corin, a transmembrane serine protease that can cleave pro‐atrial natriuretic peptide (Pro‐ANP) into smaller bioactive molecule atrial natriuretic peptide, has been shown to be involved in the pathophysiology of hypertension, cardiac hypertrophy. We sought to examine the associations of corin genetic variations with salt sensitivity, blood pressure (BP) changes and hypertension incidence. We studied participants of the original Baoji Salt‐Sensitive cohort, recruited from 124 families from seven Chinese villages in 2004 who sequentially received a usual baseline salt diet, a 7‐day low salt diet (3 g/day) and a 7‐day high salt diet (18 g/day), respectively. They were followed up for 8 years (in 2009, 2012) to evaluate the development of hypertension. Corin SNP rs3749584 was significantly associated with diastolic BP (DBP) and mean arterial pressure (MAP) response to low‐salt diet, while rs4695253, rs17654278 were associated with pulse pressure (PP) response to low‐salt diet. SNPs rs4695253, rs12509275, rs2351783, rs2271036, rs2271037 were significantly associated with systolic BP (SBP), DBP, and MAP responses to high‐salt diet. In addition, SNPs rs12641823, rs6834933, rs2271036, and rs22710367 were significantly associated with the longitudinal changes in SBP, DBP, MAP, or PP over 8 years of follow‐up. SNP rs73814824 was significantly associated with the incidence of hypertension over 8 years. Gene‐based analysis showed that corin gene was significantly associated with longitudinal BP changes and hypertension incidence after 8‐year follow‐up. This study suggests that corin may play a role in salt sensitivity, BP progression, and development of hypertension.

Distribution of Cardiac and Renal Corin and Proprotein Convertase Subtilisin/Kexin-6 in the Experimental Model of Cardio-Renal Syndrome of Various Severities

Congestive heart failure (CHF) often leads to progressive cardiac hypertrophy and salt/water retention. However, its pathogenesis remains largely unclarified. Corin, a cardiac serine protease, is responsible for converting proANP and proBNP to biologically active peptides. Although the involvement of corin in cardiac hypertrophy and heart failure was extensively studied, the alterations in corin and proprotein convertase subtilisin/kexin-6 (PCSK6), a key enzyme in the conversion of procorin to corin, has not been studied simultaneously in the cardiac and renal tissues in cardiorenal syndrome. Thus, this study aims to examine the status of PCSK6/corin in the cardiac and renal tissues of rats with CHF induced by the creation of aorto-caval fistula (ACF). We divided rats with ACF into two subgroups based on the pattern of their urinary sodium excretion, namely, compensated and decompensated. Placement of ACF led to cardiac hypertrophy, pulmonary congestion, and renal dysfunction, which were more profound in the decompensated subgroup. Corin immunoreactive peptides were detected in all heart chambers at the myocyte membranal and cytosolic localization and in the renal tissue, especially in the apical membrane of the proximal tubule, mTAL, and the collecting duct. Interestingly, the expression and abundance of corin in both the cardiac ventricles and renal tissues were significantly increased in compensated animals as compared with the decompensated state. Noteworthy, the abundance of PCSK6 in these tissues followed a similar pattern as corin. In contrast, furin expression was upregulated in the cardiac and renal tissues in correlation with CHF severity. We hypothesize that the obtained upregulation of cardiac and renal PCSK6/corin in rats with compensated CHF may represent a compensatory response aiming at maintaining normal Na⁺ balance, whereas the decline in these two enzymes may contribute to the pathogenesis of avid sodium retention, cardiac hypertrophy, and blunted atrial natriuretic peptide/brain natriuretic peptide actions in decompensated CHF.

Atrial natriuretic peptide promotes uterine decidualization and a TRAIL-dependent mechanism in spiral artery remodeling

Atrial natriuretic peptide (ANP) is an important hormone in cardiovascular biology. It is activated by the protease corin. In pregnancy, ANP and corin promote uterine spiral artery remodeling, but the underlying mechanism remains unknown. Here we report an ANP function in uterine decidualization and TNF-related apoptosis-inducing ligand-dependent (TRAIL-dependent) death in spiral arterial smooth muscle cells (SMCs) and endothelial cells (ECs). In ANP- or corin-deficient mice, uterine decidualization markers and TRAIL expression were decreased, whereas in cultured human endometrial stromal cells (HESCs), ANP increased decidualization and TRAIL expression. In uterine spiral arteries from pregnant wild-type mice, SMC and EC loss occurred sequentially before trophoblast invasion. In culture, TRAIL from decidualized HESCs induced apoptosis in uterine SMCs, but not in ECs with low TRAIL receptor expression. Subsequently, cyclophilin B was identified from apoptotic SMCs that upregulated endothelial TRAIL receptor and caused apoptosis in ECs. These results indicate that ANP promotes decidualization and TRAIL expression in endometrial stromal cells, contributing to sequential events in remodeling of spiral arteries, including SMC death and cyclophilin B release, which in turn induces TRAIL receptor expression and apoptosis in ECs.

Single-Nucleotide Polymorphisms in the 3' Untranslated Region of CORIN Associated With Cardiovascular Diseases in a Chinese Han Population: A Case-Control Study

Background: Corin is a transmembrane serine protease that activates pro-forms of atrial and brain natriuretic peptides. Numerous studies have indicated that corin played an important role in cardiovascular diseases (CVDs). However, there have been few studies about the correlation between single-nucleotide polymorphisms (SNPs) in the 3' untranslated region (3'UTR) of CORIN and CVDs. The aims of this study were to investigate the associations of three SNPs (rs3749585, rs4695253, and rs12641823) in the 3'UTR of CORIN with CVDs and to find the seed regions of microRNAs (miRNAs) that bind to SNPs of CORIN.

Methods and Results: A case–control study (n = 3,537) was performed in a Han population of northeastern China. CVDs included essential hypertension (EH), atrial fibrillation (AF), heart failure (HF), and coronary artery disease (CAD). Genotyping was performed using high-resolution melt analysis. In the EH-control study, rs3749585^T was significantly associated with the risk of EH after adjusting for sex and age in allelic (p_adj = 0.049; OR: 1.113) and dominant (p_adj = 0.015, OR: 1.233) models. Rs4695253^T was significantly associated with the risk of EH in the recessive model after adjusting for sex and age (p_adj = 0.005, OR: 2.084). Rs3749585^T was significantly and negatively associated with AF in the dominant and additive models after adjusting for sex, age, EH, HF, T2DM, and CAD (dominant: p_adj = 0.009, OR: 0.762; additive: p_adj = 0.048, OR: 0.873). In the HF-control study and CAD-control study, none of the three SNPs was associated with HF and CAD after adjusting for covariates in any models (p_adj > 0.05). The levels of high-density lipoprotein (HDL) in rs4695253^CC+CT were lower than the levels of HDL in rs4695253^TT (42.47 ± 10.30 vs. 48.0 ± 10.24 mg/dl, p_adj = 0.008). The levels of total cholesterol (TC) in rs4695253^CC+CT were lower than the levels of TC in rs4695253^TT (164.01 ± 49.15 vs. 180.81 ± 43.92 mg/dl, p_adj = 0.036). Luciferase assay revealed that the relative luciferase activity of rs3749585^CC-transfected cells was significantly decreased by miR-494-3p, in comparison to cells transfected with rs3749585^TT (p < 0.001). A significant decrease in the relative luciferase activity of rs3749585^TT reporter was observed as compared with rs3749585^CC reporter in the presence of miR-1323 or miR-548o-3p (p = 0.017 and 0.012, respectively).

Conclusions: We found significant associations between rs3749585^T and rs4695253^T and EH, between rs4695253^T and the levels of TC and HDL, and between rs3749585^T and AF. Hsa-miR-494-3p may serve as a potential therapeutic target for EH and AF patients in the future.

Function and regulation of corin in physiology and disease

Atrial natriuretic peptide (ANP) is of major importance in the maintenance of electrolyte balance and normal blood pressure. Reduced plasma ANP levels are associated with the increased risk of cardiovascular disease. Corin is a type II transmembrane serine protease that converts the ANP precursor to mature ANP. Corin deficiency prevents ANP generation and alters electrolyte and body fluid homeostasis. Corin is synthesized as a zymogen that is proteolytically activated on the cell surface. Factors that disrupt corin folding, intracellular trafficking, cell surface expression, and zymogen activation are expected to impair corin function. To date, CORIN variants that reduce corin activity have been identified in hypertensive patients. In addition to the heart, corin expression has been detected in non-cardiac tissues, where corin and ANP participate in diverse physiological processes. In this review, we summarize the current knowledge in corin biosynthesis and post-translational modifications. We also discuss tissue-specific corin expression and function in physiology and disease.

Low serum corin levels predict end-organ damage in patients with hypertensive crisis

OBJECTIVE

The study aimed to investigate the predictive power of serum corin levels for distinguishing between hypertensive urgency (HU) and hypertensive emergency (HE) in patients with hypertensive crisis (HC) admitted to the emergency department.

METHODS

A total of 120 consecutive consenting adult patients diagnosed with HC and 55 age- and sex-matched healthy controls were enrolled. Blood pressure measurements [(systolic, diastolic, and mean arterial pressure (MAP)] and the evidence of end-organ damage at the first admission were recorded. Patients with HC were classified as patients with HE or HU according to the presence or absence of acute end-organ damage. Serum corin levels were compared between the 2 groups.

RESULTS

The mean serum corin level was significantly lower in the HC group than in the control group; it was also lower in the HE group than in the HU group (p<0.001 for all). In the HE group, clinical features associated with end-organ damage included ST-elevation myocardial infarction (n=28, 46.7%), hemorrhagic stroke (n=11, 18.3%), ischemic stroke (n=11, 18.3%), and non-ST-elevation myocardial infarction (n=10, 16.7%). The receiving operator characteristic (ROC) analysis identified a serum corin cutoff value of 45 pg/mL for distinguishing patients with HE from patients with HU with 98.3% sensitivity and 95% specificity.

CONCLUSION

Our findings suggest that serum corin levels play an important role in regulating blood pressure and are involved in the pathogenesis of HC. Low serum corin levels may predict end-organ damage and serve as a guide for diagnostic decision making in patients with HC.

Integrative genomic analysis of blood pressure and related phenotypes in rats

Despite remarkable progress made in human genome-wide association studies, there remains a substantial gap between statistical evidence for genetic associations and functional comprehension of the underlying mechanisms governing these associations. As a means of bridging this gap, we performed genomic analysis of blood pressure (BP) and related phenotypes in spontaneously hypertensive rats (SHR) and their substrain, stroke-prone SHR (SHRSP), both of which are unique genetic models of severe hypertension and cardiovascular complications. By integrating whole-genome sequencing, transcriptome profiling, genome-wide linkage scans (maximum n=1415), fine congenic mapping (maximum n=8704), pharmacological intervention and comparative analysis with transcriptome-wide association study (TWAS) datasets, we searched causal genes and causal pathways for the tested traits. The overall results validated the polygenic architecture of elevated BP compared with a non-hypertensive control strain, Wistar Kyoto rats (WKY); e.g. inter-strain BP differences between SHRSP and WKY could be largely explained by an aggregate of BP changes in seven SHRSP-derived consomic strains. We identified 26 potential target genes, including rat homologs of human TWAS loci, for the tested traits. In this study, we re-discovered 18 genes that had previously been determined to contribute to hypertension or cardiovascular phenotypes. Notably, five of these genes belong to the kallikrein-kinin/renin-angiotensin systems (KKS/RAS), in which the most prominent differential expression between hypertensive and non-hypertensive alleles could be detected in rat Klk1 paralogs. In combination with a pharmacological intervention, we provide in vivo experimental evidence supporting the presence of key disease pathways, such as KKS/RAS, in a rat polygenic hypertension model.

Cell surface markers for immunophenotyping human pluripotent stem cell-derived cardiomyocytes

Human pluripotent stem cells (hPSC) self-renew and represent a potentially unlimited source for the production of cardiomyocytes (CMs) suitable for studies of human cardiac development, drug discovery, cardiotoxicity testing, and disease modelling and for cell-based therapies. However, most cardiac differentiation protocols yield mixed cultures of atrial-, ventricular-, and pacemaker-like cells at various stages of development, as well as non-CMs. The proportions and maturation states of these cell types result from disparities among differentiation protocols and time of cultivation, as well as hPSC reprogramming inconsistencies and genetic background variations. The reproducible use of hPSC-CMs for research and therapy is therefore limited by issues of cell population heterogeneity and functional states of maturation. A validated method that overcomes issues of cell heterogeneity is immunophenotyping coupled with live cell sorting, an approach that relies on accessible surface markers restricted to the desired cell type(s). Here we review current progress in unravelling heterogeneity in hPSC-cardiac cultures and in the identification of surface markers suitable for defining cardiac identity, subtype specificity, and maturation states.

Recombinant Soluble Corin Improves Cardiac Function in Mouse Models of Heart Failure

Background

Corin is a transmembrane protease that activates ANP and BNP (atrial and B‐type natriuretic peptides). Impaired corin expression and function are associated with heart failure. In this study, we characterized a soluble form of corin (sCorin) and examined its effects on cardiac morphology and function in mouse heart failure models.

Methods and Results

sCorin, consisting of the full‐length extracellular fragment of human corin with an engineered activation site, was expressed in Chinese hamster ovary cells, purified from the conditioned medium with affinity chromatography, and characterized in pro‐ANP processing assays in vitro and pharmacokinetic studies in mice. Effects of sCorin on mouse models of heart failure induced by left coronary artery ligation and transverse aortic constriction were assessed by ELISA analysis of plasma markers, histologic examination, and echocardiography. We showed that purified and activated sCorin converted pro‐ANP to ANP that stimulated cGMP production in cultured cells. In mice, intravenously and intraperitoneally administered sCorin had plasma half‐lives of 3.5±0.1 and 8.3±0.3 hour, respectively. In the mouse heart failure models, intraperitoneal injection of sCorin increased plasma ANP, BNP, and cGMP levels; lowered plasma levels of NT‐proANP (N‐terminal‐pro‐ANP), angiotensin II, and aldosterone; reduced cardiac hypertrophy and fibrosis; and improved cardiac function.

Conclusions

We show that sCorin treatment enhanced natriuretic peptide processing and activity, suppressed the renin‐angiotensin‐aldosterone system, and improved cardiac morphology and function in mice with failing hearts.

Correlation between corin, N-terminal pro-atrial natriuretic peptide and neonatal adverse prognostic in hypertensive disorders of pregnancy

INTRODUCTION

Atrial natriuretic peptide (ANP) regulates water-salt balance and blood pressure by promoting renal sodium and water excretion.

OBJECTIVE

Our study was to investigate plasma N-terminal pro-atrial natriuretic peptide (NT-proANP) and corin in hypertensive disorders of pregnancy (HDP) patients. Furthermore, the relationship between corin/NT-proANP and neonatal adverse prognosis were evaluated.

METHODS

Seventy-seven HDP patients and forty-eight normotensive women as control group were recruited. Clinical characteristic and plasma were collected. Plasma NT-proANP and corin were determined by ELISA. Gestational age, neonatal weight and APGAR scores were recorded. Statistical analysis was conducted.

RESULTS

NT-proANP and corin were significantly increased in HDP group compared with that of control (P < 0.05). NT-proANP and corin were significantly elevated in HDP patients who suffered from premature delivery (P < 0.05). Both NT-proANP and corin were negatively associated with delivery time, neonatal weight and APGAR scores in HDP group. Multiple regressions demonstrated that NT-proANP and corin were independent risk factor of delivery time, neonatal weight and APGAR scores.

CONCLUSIONS

Plasma NT-proANP and corin were significantly increased in HDP. NT-proANP and corin were associated with neonatal adverse events in HDP patients. Thus, NT-proANP and corin may become new biomarkers for evaluating severity of pregnancy and neonatal adverse events in HDP patients.

Soluble Neprilysin and Corin Concentrations in Relation to Clinical Outcome in Chronic Heart Failure

OBJECTIVES

This study investigated whether patients with chronic heart failure (HF) can be stratified according to the combination of soluble neprilysin and corin concentrations and whether this is related to clinical outcome.

BACKGROUND

Natriuretic peptide processing by the enzymes corin and neprilysin plays a pivotal role in conversion of pro-natriuretic peptides to active natriuretic peptides, as well as their degradation, respectively.

METHODS

A prospective cohort of patients with chronic HF (n = 1,009) was stratified into 4 equal groups based on high or low neprilysin/corin concentration relative to the median: 1) low neprilysin/low corin; 2) low neprilysin/high corin; 3) high neprilysin/low corin; and 4) high neprilysin/high corin. Cox regression survival analysis was performed for the composite primary endpoint of cardiovascular death and HF hospitalization.

RESULTS

Median neprilysin and corin concentrations were not correlated (rho: -0.04; p = 0.21). Although in univariate analysis there was no association with outcome, after correction for baseline differences in age and sex, a significant association with survival was demonstrated: with highest survival in group 1 (low neprilysin/low corin) and lowest in group 4 (high neprilysin/high corin) (adjusted hazard ratio: 1.56; p = 0.003), which remained statistically significant after comprehensive multivariable analysis (adjusted hazard ratio: 1.41; p = 0.03).

CONCLUSIONS

Stratification of patients with chronic HF based on circulating neprilysin and corin concentrations is associated with clinical outcomes. These results suggest that regulation of these enzymes is of importance in chronic HF and may offer an interesting approach for classification of patients with HF in a step toward individualized HF patient management.

Intensified hemodialysis for complicated pregnancy in a primigravida with advanced maternal age: a case report with literature review focusing on appropriate hemodialysis management during pregnancy

Background

Pregnancy in dialysis patients is rare but challenging both for nephrologists and obstetricians. Although intensified hemodialysis is effective to achieve favorable clinical outcomes in this clinical setting, the evidence concerning reliable parameters for the optimal dialysis prescription is scarce. Herein, we report a case of a primigravida with advanced maternal age who underwent a normal spontaneous vaginal delivery at full term managed by intensified hemodialysis, and discuss reliable indicators of the appropriate dialysis prescription.

Case presentation

A 39-year-old primigravida with end-stage renal disease was referred to our department for hemodialysis management during pregnancy. She had a history of multiple gynecologic disorders, including cervical dysplasia, right tubal ectopic pregnancy and spontaneous abortion; consequently, she conceived through in vitro fertilization and embryo transfer. After pregnancy was confirmed, an intensified hemodialysis schedule with weekly duration of 36 hours was employed to prevent volume overload and the accumulation of hyperosmotic substances. Utilizing maternal blood pressure, plasma atrial natriuretic peptide levels and fetal development as indicators of volume status, we incremented her dry weight by 300–400 g per week in the first and second trimester and 100–200 g per week in the third trimester, respectively. Serum urea nitrogen levels were persistently maintained below 50 mg/dL. Throughout pregnancy, fetal growth and development were within normal limits. At 38 weeks and 3 days of gestation, she delivered a healthy child vaginally without complications. To date, the child’s development has been normal, both physically and mentally.

Conclusions

Pregnancy in dialysis patients with advanced age that leads to a normal childbirth is exceptionally rare. Our case is the hemodialysis patient with the most advanced age who achieves a normal spontaneous vaginal delivery at full term. Considering that cardiovascular system and endogenous metabolism dynamically alter during pregnancy, various clinical parameters should be closely monitored to modify dialysis settings accordingly. Of note, our case suggests that plasma atrial natriuretic peptide level is a useful parameter for the appropriate dry weight. Intensified hemodialysis is an effective and reliable measure that can achieve normal pregnancy in dialysis patients, even in a primigravida with advanced maternal age.

Natriuretic peptides and neprilysin inhibition in hypertension and hypertensive organ damage

The family of natriuretic peptides (NPs) discovered in mammalian tissues including cardiac atrium and brain consists of three members, namely, atrial, B- and C-type natriuretic peptides (ANP, BNP, CNP). Since the discovery, basic and clinical studies have been vigorously performed to explore the biological functions and pathophysiological roles of NPs in a wide range of diseases including hypertension and heart failure. These studies revealed that ANP and BNP are hormones secreted from the heart into the blood stream in response to pre- or after-load, counteracting blood pressure (BP) elevation and fluid retention through specific receptors. Meanwhile, CNP was found to be produced by the vascular endothelium, acting as a local mediator potentially serving protective functions for the blood vessels. Because NPs not only exert blood pressure lowering actions but also alleviate hypertensive organ damage, attempts have been made to develop therapeutic agents for hypertension by utilizing this family of NPs. One strategy is to inhibit neprilysin, an enzyme degrading NPs, thereby enhancing the actions of endogenous peptides. Recently, a dual inhibitor of angiotensin receptor-neprilysin was approved for heart failure, and neprilysin inhibition has also been shown to be beneficial in treating patients with hypertension. This review summarizes the roles of NPs in regulating BP, with special references to hypertension and hypertensive organ damage, and discusses the therapeutic implications of neprilysin inhibition.

Differential effects of low-dose sacubitril and/or valsartan on renal disease in salt-sensitive hypertension

Diuretics and renin-angiotensin system blockers are often insufficient to control the blood pressure (BP) in salt-sensitive (SS) subjects. Abundant data support the proposal that the level of atrial natriuretic peptide may correlate with the pathogenesis of SS hypertension. We hypothesized here that increasing atrial natriuretic peptide levels with sacubitril, combined with renin-angiotensin system blockage by valsartan, can be beneficial for alleviation of renal damage in a model of SS hypertension, the Dahl SS rat. To induce a BP increase, rats were challenged with a high-salt 4% NaCl diet for 21 days, and chronic administration of vehicle or low-dose sacubitril and/or valsartan (75 μg/day each) was performed. Urine flow, Na+ excretion, and water consumption were increased on the high-salt diet compared with the starting point (0.4% NaCl) in all groups but remained similar among the groups at the end of the protocol. Upon salt challenge, we observed a mild decrease in systolic BP and urinary neutrophil gelatinase-associated lipocalin levels (indicative of alleviated tubular damage) in the valsartan-treated groups. Sacubitril, as well as sacubitril/valsartan, attenuated the glomerular filtration rate decline induced by salt. Alleviation of protein cast formation and lower renal medullary fibrosis were observed in the sacubitril/valsartan- and valsartan-treated groups, but not when sacubitril alone was administered. Interestingly, proteinuria was mildly mitigated only in rats that received sacubitril/valsartan. Further studies of the effects of sacubitril/valsartan in the setting of SS hypertension, perhaps involving a higher dose of the drug, are warranted to determine if it can interfere with the progression of the disease.

Aberrant corin and PCSK6 in placentas of the maternal hyperinsulinemia IUGR rat model

OBJECTIVES

Corin is a protease that converts pro-atrial natriuretic peptide (pro-ANP) to ANP. While the involvement of ANP in the cardiovascular regulation is well established, there is increasing evidence that the pregnant uterus produces ANP, which promotes spiral artery remodeling. The present study examines the alterations in corin and PCSK6, a key enzyme in the conversion of pro-corin to corin, in the placenta of hyperinsulinemic dams (HD) featuring pregnancy-induced hypertension (PIH).

MATERIALS AND METHODS

The study was conducted on female Wistar rats. Rats were rendered hyperinsulinemic by subcutaneous insulin pellet, mated and followed to the twenty-first day of pregnancy. Normal pregnant dams (NPD) served as controls. Both groups were sacrificed on day 21 of gestation and their placentas were dissected along with the mesometrial triangle (MT). The tissue was then sectioned from the maternal surface to the base of the MT, and processed for histological and molecular biology analysis of Corin, PCSK6 and ANP expression/immunoreactivity.

RESULTS

Hyperinsulinemic dams developed PIH, along lower placental and fetal weights. Corin expression and immunoreactivity were significantly decreased in the placenta by ~40-50%, but not in the MT. Similarly, placental but not MT PCSK6 immunoreactivity was lower in HD. Concomitantly with the downregulation of corin/PCSK6, proANP levels increased in the placenta of HD.

CONCLUSIONS

Corin and PCSK6 are expressed in the placenta and MT. The decline in these two enzymes in the placenta of HD suggests a role of corin/PCSK6 machinery in the development of PIH and intrauterine growth restriction characterizing hyperinsulinemia.

Membrane-anchored serine proteases as regulators of epithelial function

Cleavage of proteins in the extracellular milieu, including hormones, growth factors and their receptors, ion channels, and various cell adhesion and extracellular matrix molecules, plays a key role in the regulation of cell behavior. Among more than 500 proteolytic enzymes encoded by mammalian genomes, membrane-anchored serine proteases (MASPs), which are expressed on the surface of epithelial cells of all major organs, are excellently suited to mediate signal transduction across the epithelia and are increasingly being recognized as important regulators of epithelial development, function, and disease [ 1-3]. In this minireview, we summarize current knowledge of the in vivo roles of MASPs in acquisition and maintenance of some of the defining functions of epithelial tissues, such as barrier formation, ion transport, and sensory perception.

Placental Overexpression of Soluble CORIN in Preeclampsia

Preeclampsia (PE) is a hypertensive disease of pregnancy associated with substantial maternal and fetal morbidity and mortality. CORIN is a transmembrane type II serine protease expressed in cardiomyocytes that converts pro-atrial natriuretic peptide into atrial natriuretic peptide, a cardiac hormone that regulates blood pressure. High levels of soluble CORIN have been reported in PE and are supposed to be cardiac in origin. We hypothesized that during pregnancy soluble CORIN is released by the syncytiotrophoblast and that increased levels of soluble CORIN in preeclampsia originate from placenta. A total of 375 patients (181 PE patients and 194 controls) were analyzed. High levels of soluble CORIN were confirmed in maternal blood from preeclamptic pregnancies compared with controls. Differentiated primary villous cytotrophoblasts showed that CORIN was expressed (mRNA and protein levels) and secreted by trophoblastic cells, mostly by the syncytiotrophoblast. Finally, placental explants showed a significant increase in CORIN production and secretion in PE cases compared with controls. This study showed that CORIN is secreted by trophoblastic cells and that high levels of soluble CORIN in preeclampsia have a placental origin.

Associations between potentially functional CORIN SNPs and serum corin levels in the Chinese Han population

Background

Corin is an important convertase involved in the natriuretic peptide system and may indirectly regulate blood pressure. Genetic factors relate to corin remain unclear. The purpose of the current study was to comprehensively examine the associations among CORIN SNPs, methylations, serum corin levels and hypertension.

Results

We genotyped 9 tag-SNPs in the CORIN gene and measured serum corin levels in 731 new-onset hypertensive cases and 731 age- and sex-matched controls. DNA methylations were tested in 43 individuals. Mendelian randomization was used to investigate the causal associations. Under additive models, we observed associations of rs2289433 (p.Cys13Tyr), rs6823184, rs10517195, rs2271037 and rs12509275 with serum corin levels after adjustment for covariates (P = 0.0399, 0.0238, 0.0016, 0.0148 and 0.0038, respectively). The tag-SNP rs6823184 and SNPs that are in strong linkage disequilibrium with it, i.e., rs10049713, rs6823698 and rs1866689, were associated with CORIN gene expression (P = 2.38 × 10^− 24, 5.94 × 10^− 27, 6.31 × 10^− 27 and 6.30 × 10^− 27, respectively). Neither SNPs nor corin levels was found to be associated with hypertension. SNP rs6823184, which is located in a DNase hypersensitivity cluster, a CpG island and transcription factor binding sites, was significantly associated with cg02955940 methylation levels (P = 1.54 × 10^− 7). A putative causal association between cg02955940 methylation and corin levels was detected (P = 0.0011).

Conclusion

This study identified potentially functional CORIN SNPs that were associated with serum corin level in the Chinese Han population. The effect of CORIN SNPs on corin level may be mediated by DNA methylation.