Prostasin: An Epithelial Sodium Channel Regulator

Human Plasma Proteomics Links Modifiable Lifestyle Exposome to Disease Risk

Environmental exposures influence disease risk, yet their underlying biological mechanisms remain poorly understood. We present the Human Exposomic Architecture of the Proteome (HEAP), a framework and resource integrating genetic, exposomic, and proteomic data to uncover how lifestyle influences disease through plasma proteins. Applying HEAP to 2,686 proteins in 53,014 UK Biobank participants, we identified over 11,000 exposure-protein associations across 135 lifestyle exposures. Exposures explained a substantial portion of proteomic variation, with 9% of proteins more influenced by lifestyle than genetics. Mediation analyses across 270 diseases revealed proteins linking exposures to disease risk; for instance, IGFBP1 and IGFBP2 mediated the effects of exercise and diet on type 2 diabetes. These findings were supported by concordant proteomic shifts in interventional studies of exercise and GLP1 agonists, underscoring therapeutic relevance. HEAP provides a resource for advancing disease prevention and precision medicine by revealing mechanisms through which lifestyle shapes human health.

Proteolytic Activation of the Epithelial Sodium Channel (ENaC): Its Mechanisms and Implications

Epithelial sodium channel (ENaC) are integral to maintaining salt and water homeostasis in various biological tissues, including the kidney, lung, and colon. They enable the selective reabsorption of sodium ions, which is a process critical for controlling blood pressure, electrolyte balance, and overall fluid volume. ENaC activity is finely controlled through proteolytic activation, a process wherein specific enzymes, or proteases, cleave ENaC subunits, resulting in channel activation and increased sodium reabsorption. This regulatory mechanism plays a pivotal role in adapting sodium transport to different physiological conditions. In this review article, we provide an in-depth exploration of the role of proteolytic activation in regulating ENaC activity. We elucidate the involvement of various proteases, including furin-like convertases, cysteine, and serine proteases, and detail the precise cleavage sites and regulatory mechanisms underlying ENaC activation by these proteases. We also discuss the physiological implications of proteolytic ENaC activation, focusing on its involvement in blood pressure regulation, pulmonary function, and intestinal sodium absorption. Understanding the mechanisms and consequences of ENaC proteolytic activation provides valuable insights into the pathophysiology of various diseases, including hypertension, pulmonary disorders, and various gastrointestinal conditions. Moreover, we discuss the potential therapeutic avenues that emerge from understanding these mechanisms, offering new possibilities for managing diseases associated with ENaC dysfunction. In summary, this review provides a comprehensive discussion of the intricate interplay between proteases and ENaC, emphasizing the significance of proteolytic activation in maintaining sodium and fluid balance in both health and disease.

A Serine Protease Inhibitor, Camostat Mesilate, Suppresses Urinary Plasmin Activity and Alleviates Hypertension and Podocyte Injury in Dahl Salt-Sensitive Rats

In proteinuric renal diseases, the serine protease (SP) plasmin activates the epithelial sodium channel (ENaC) by cleaving its γ subunit. We previously demonstrated that a high-salt (HS) diet provoked hypertension and proteinuria in Dahl salt-sensitive (DS) rats, accompanied by γENaC activation, which were attenuated by camostat mesilate (CM), an SP inhibitor. However, the effects of CM on plasmin activity in DS rats remain unclear. In this study, we investigated the effects of CM on plasmin activity, ENaC activation, and podocyte injury in DS rats. The DS rats were divided into the control diet, HS diet (8.0% NaCl), and HS+CM diet (0.1% CM) groups. After weekly blood pressure measurement and 24-h urine collection, the rats were sacrificed at 5 weeks. The HS group exhibited hypertension, massive proteinuria, increased urinary plasmin, and γENaC activation; CM treatment suppressed these changes. CM prevented plasmin(ogen) attachment to podocytes and mitigated podocyte injury by reducing the number of apoptotic glomerular cells, inhibiting protease-activated receptor-1 activation, and suppressing inflammatory and fibrotic cytokine expression. Our findings highlight the detrimental role of urinary plasmin in the pathogenesis of salt-sensitive hypertension and glomerular injury. Targeting plasmin with SP inhibitors, such as CM, may be a promising therapeutic approach for these conditions.

Early Mid-pregnancy Blood-Based Proteins as Possible Biomarkers of Increased Infant Birth Size in Sex-Stratified Analyses

The objective of this study was to evaluate the associations of 92 maternal blood-based proteins with increased infant birth size. The study was performed at the Uppsala University Hospital, Sweden, and included 857 mother and child dyads. The mean age of the women was 30.3 years, and 53.2% were nulliparous. Blood samples were collected at mean 18 + 2 weeks' gestation, and the Olink cardiovascular II panel was used to measure 92 proteins, either known to be or suspected to be markers of cardiovascular and inflammatory disease in humans. Multiple linear regression models adjusted for maternal age, parity, pre-conception BMI, height, and smoking were performed to evaluate the association of each individual protein with infant birth size. We also performed sex-stratified analyses. Eight proteins (Matrix metalloproteinase-12 (MMP-12), Prostasin (PRSS8), Adrenomedullin (ADM), Pappalysin-1 (PAPP-A), Angiotensin-converting enzyme 2 (ACE2), Sortilin (SORT1), Lectin-like oxidized LDL receptor 1 (LOX-1), and Thrombomodulin (TM)) were associated with infant birth size after false discovery rate adjustment. In the analyses including only female infants, ten proteins (MMP-12, Growth/differentiation factor 2 (GDF-2), PRSS8, SORT1, ADM, Interleukin-1 receptor antagonist protein (IL-1ra), Leptin (LEP), ACE2, TM, and Tumor necrosis factor receptor superfamily member 11A (TNFRSF11A)) were associated with infant birth size. Two proteins (PAPP-A and PRSS8) were associated with infant birth size among male infants. Our study suggests several proteins as potential biomarkers for increased birth weight, and our findings could act as a base for future research to identify new potential markers that could be added to improve screening for large infants.

Current and emerging biomarkers in ovarian cancer diagnosis; CA125 and beyond

Ovarian cancer (OC) is one of the most common causes of cancer-related death in women worldwide. Its five-year survival rates are worse than the two most common gynecological cancers, cervical and endometrial. This is because it is asymptomatic in the early stages and usually detected in the advanced metastasized stage. Thus, survival is increasingly dependent on timely diagnosis. The delay in detection is contributed partly by the occurrence of non-specific clinical symptoms in the early stages and the lack of effective biomarkers and detection approaches. This underlines the need for biomarker identification and clinical validation, enabling earlier diagnosis, effective prognosis, and response to therapy. Apart from the traditional diagnostic biomarkers for OC, several new biomarkers have been delineated using advanced high-throughput molecular approaches in recent years. They are currently being clinically evaluated for their true diagnostic potential. In this chapter, we document the commonly utilized traditional screening markers and recently identified emerging biomarkers in OC diagnosis, focusing on secretory and protein biomarkers. We also briefly reviewed the recent advances and prospects in OC diagnosis.

Plasma prostasin: a novel risk marker for incidence of diabetes and cancer mortality

AIMS/HYPOTHESIS

Diabetes is associated with an increased risk of cancer. Prostasin is an epithelial sodium channel stimulator that has been associated with suppression of tumours, glucose metabolism and hyperglycaemia-associated tumour pathology. However, the association between prostasin, diabetes and cancer mortality has not been well investigated in humans. We aim to investigate the associations between plasma prostasin and diabetes, and to explore whether prostasin has an effect on cancer mortality risk in individuals with hyperglycaemia.

METHODS

Plasma prostasin was measured using samples from the Malmö Diet and Cancer Study Cardiovascular Cohort, and statistical analysis was performed from both sex-specific quartiles and per 1 SD. The cross-sectional association between plasma prostasin and diabetes was first studied in 4658 participants (age 57.5 ± 5.9 years, 39.9% men). After excluding 361 with prevalent diabetes, the associations of prostasin with incident diabetes and cancer mortality risk were assessed using Cox regression analysis. The interactions between prostasin and blood glucose levels as well as other covariates were tested.

RESULTS

The adjusted OR for prevalent diabetes in the 4th vs 1st quartile of prostasin concentrations was 1.95 (95% CI 1.39, 2.76) (p for trend <0.0001). During mean follow-up periods of 21.9 ± 7.0 and 23.5 ± 6.1 years, respectively, 702 participants developed diabetes and 651 died from cancer. Prostasin was significantly associated with the incidence of diabetes. The adjusted HR for diabetes in the 4th vs 1st quartile of prostasin concentrations was 1.76 (95% CI 1.41, 2.19) (p for trend <0.0001). Prostasin was also associated with cancer mortality There was a significant interaction between prostasin and fasting blood glucose for cancer mortality risk (p for interaction =0.022), with a stronger association observed in individuals with impaired fasting blood glucose levels at baseline (HR per 1 SD change 1.52; 95% CI 1.07, 2.16; p=0.019).

CONCLUSIONS/INTERPRETATION

Plasma prostasin levels are positively associated with diabetes risk and with cancer mortality risk, especially in individuals with high blood glucose levels, which may shed new light on the relationship between diabetes and cancer.

Biomarkers for Early Diagnosis of Ovarian Carcinoma

The leading cause of gynecological cancer-related morbidity and mortality is ovarian cancer (OC), which is dubbed a silent killer. Currently, OC is a target of intense biomarker research, because it is often not discovered until the disease is advanced. The goal of OC research is to develop effective tests using biomarkers that can detect the disease at the earliest stages, which would eventually decrease the mortality, thereby preventing recurrence. Therefore, there is a pressing need to revisit the existing biomarkers to recognize the potential biomarkers that can lead to efficient predictors for the OC diagnosis. This Perspective covers an update on the currently available biomarkers used in the triaging of OC to gain certain insights into the potential role of these biomarkers and their estimation that are crucial to the understanding of neoplasm progression, diagnostics, and therapy.

Mapping the proteo-genomic convergence of human diseases

Characterization of the genetic regulation of proteins is essential for understanding disease etiology and developing therapies. We identified 10,674 genetic associations for 3892 plasma proteins to create a cis-anchored gene-protein-disease map of 1859 connections that highlights strong cross-disease biological convergence. This proteo-genomic map provides a framework to connect etiologically related diseases, to provide biological context for new or emerging disorders, and to integrate different biological domains to establish mechanisms for known gene-disease links. Our results identify proteo-genomic connections within and between diseases and establish the value of cis-protein variants for annotation of likely causal disease genes at loci identified in genome-wide association studies, thereby addressing a major barrier to experimental validation and clinical translation of genetic discoveries.

Prevalence, risk factors and proteomic bioprofiles associated with heart failure in rheumatoid arthritis: The RA-HF study

BACKGROUND

Rheumatoid arthritis (RA) patients have high risk of heart failure (HF).

AIMS

Identifying the risk factors and mechanistic pathways associated with HF in patients with RA.

METHODS

Cohort study enrolling 355 RA patients. HF was defined according to the ESC criteria. 93 circulating protein-biomarkers (91CVDIIOlink®+troponin-T+c-reactive protein) were measured. Regression modeling (multivariate and multivariable) were built and network analyses were performed - based on the identified relevant protein biomarkers.

RESULTS

115 (32.4%) patients fulfilled the ESC criteria for HF, but only 24 (6.8%) had a prior HF diagnosis. Patients with HF were older (67 vs. 55yr), had a longer RA duration (10 vs. 14yr), had more frequently diabetes, hypertension, obesity, dyslipidemia, atrial fibrillation, and ischemic arterial disease. Several protein-biomarkers remained independently associated with HF, the top (FDR1%) were adrenomedullin, placenta-growth-factor, TNF-receptor-11A, and angiotensin-converting-enzyme-2. The networks underlying the expression of these biomarkers pointed towards congestion, apoptosis, inflammation, immune system signaling and RAAS activation as central determinants of HF in RA. Similar HF-associated biomarker-pathways were externally found in patients without RA. Having RA plus HF increased the risk of cardiovascular events compared to RA patients without RF; adjusted-HR (95%CI)=2.37 (1.07-5.30), p=0.034 CONCLUSION: Age, cardiovascular risk factors, and RA duration increase the HF odds in patients with RA. Few RA patients had a correct prior HF diagnosis, but the presence of HF increased the patients` risk. RA patients with HF largely share the mechanistic pathways of HF patients without RA. Randomized HF trials should include patients with RA. CLINICALTRIALS.

GOV ID

NCT03960515.

Genetic polymorphism of the prostasin gene in hypertensive pregnant Pakistani females

Objective

The study was performed to investigate the association of hypertension in pregnancy with prostasin gene polymorphism in Pakistani females.

Methods

This case-control study was performed at University of Karachi, Pakistan from April 2018 to May 2019. A total of 160 females, including 90 hypertensives and 70 healthy pregnant females, were recruited by purposive sampling after obtaining informed written consent. Genotyping was performed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP).

Results

The frequencies of the TC and CC genotypes were higher in hypertensive pregnant females compared to healthy controls. A significant difference was evident for CC (P=0.012) genotype; however, no significant difference was observed for TC (P=0.49) and TT genotypes (P=0.06) between control and hypertensive groups. The adjusted odds ratio for CC genotype was 6.2 (P=0.025) and 1.48 (P=0.44) for TC genotype compared to the TT genotype. There was a significantly higher prevalence of the C allele of the prostasin gene at rs12597511 in the hypertensive group, suggesting that this allele is a risk factor for hypertension and cardiovascular diseases.

Conclusion

C allele at rs12597511 of prostasin gene demonstrate as a risk factor for having hypertension in pregnancy.

Prostasin and hepatocyte growth factor B in factor VIIa generation: Serine protease knockdowns in zebrafish

BACKGROUND

Blood clotting in humans is initiated by the binding of tissue factor to activated coagulation factor VII (FVIIa) in the plasma. Previous studies have reported that hepsin and factor VII (FVII)-activating protease are responsible for generating FVIIa.

OBJECTIVES

We aimed to identify other proteases that may activate FVII using zebrafish as a model.

METHODS

We screened 179 genes encoding serine protease domains using the piggyback knockdown method to identify genes involved in the activation of zebrafish Fvii. A prolonged kinetic prothrombin time (kPT) assay was used to detect gene knockdown effects.

RESULTS

In the primary screen, 21 genes showed prolonged kPT. In the secondary screen, 14 of 21 genes showed positive results. In the tertiary screen, all 14 genes showed prolonged kPT. These 14 genes were knocked down again to estimate relative levels of zebrafish Fviia. Six genes, including known genes, such as f10 and novel prostasin and hepatocyte growth factor B (hgfb), showed lower Fviia levels. Fvii levels were affected only by the knockdown of f7 and not by the knockdown of the other five genes.

CONCLUSIONS

Prostasin and hgfb are involved in generating Fviia. We hypothesize that prostasin exerts serine protease activity directly or indirectly to activate Fvii. As Hgfb has a mutated serine protease domain, it may not cleave Fvii but may bind to Fvii to induce autoactivation. The approach developed here may be extended to design other large-scale knockdown screens.

Sodium absorption stimulator prostasin (PRSS8) has an anti-inflammatory effect via downregulation of TLR4 signaling in inflammatory bowel disease

BACKGROUND

Prostasin (PRSS8) is a stimulator of epithelial sodium transport. In this study, we evaluated alteration of prostasin expression in the inflamed mucosa of patients with inflammatory bowel disease (IBD) and investigated the role of prostasin in the gut inflammation.

METHODS

Prostasin expression was evaluated by immunohistochemical staining. Dextran sodium sulfate (DSS)-colitis was induced in mice lacking prostasin specifically in intestinal epithelial cells (PRSS8^ΔIEC mice).

RESULTS

In colonic mucosa of healthy individuals, prostasin was strongly expressed at the apical surfaces of epithelial cells, and this was markedly decreased in active mucosa of both ulcerative colitis and Crohn's disease. DSS-colitis was exacerbated in PRSS8^ΔIEC mice compared to control PRSS8^lox/lox mice. Toll-like receptor4 (TLR4) expression in colonic epithelial cells was stronger in DSS-treated PRSS8^ΔIEC mice than in DSS-treated PRSS8 ^lox/lox mice. NF-κB activation in colonic epithelial cells was more pronounced in DSS-treated PRSS8^ΔIEC mice than in DSS-treated PRSS8^lox/lox mice, and the mRNA expression of inflammatory cytokines was significantly higher in DSS-treated PRSS8^ΔIEC mice. Broad-spectrum antibiotic treatment completely suppressed the exacerbation of DSS-colitis in PRSS8^ΔIEC mice. The mRNA expression of tight junction proteins and mucosal permeability assessed using FITC-dextran were comparable between DSS-treated PRSS8^lox/lox and DSS-treated PRSS8^ΔIEC mice.

CONCLUSION

Prostasin has an anti-inflammatory effect via downregulation of TLR4 expression in colonic epithelial cells. Reduced prostasin expression in IBD mucosa is linked to the deterioration of local anti-inflammatory activity and may contribute to the persistence of mucosal inflammation.

Cytokine-Ion Channel Interactions in Pulmonary Inflammation

The lungs conceptually represent a sponge that is interposed in series in the bodies’ systemic circulation to take up oxygen and eliminate carbon dioxide. As such, it matches the huge surface areas of the alveolar epithelium to the pulmonary blood capillaries. The lung’s constant exposure to the exterior necessitates a competent immune system, as evidenced by the association of clinical immunodeficiencies with pulmonary infections. From the in utero to the postnatal and adult situation, there is an inherent vital need to manage alveolar fluid reabsorption, be it postnatally, or in case of hydrostatic or permeability edema. Whereas a wealth of literature exists on the physiological basis of fluid and solute reabsorption by ion channels and water pores, only sparse knowledge is available so far on pathological situations, such as in microbial infection, acute lung injury or acute respiratory distress syndrome, and in the pulmonary reimplantation response in transplanted lungs. The aim of this review is to discuss alveolar liquid clearance in a selection of lung injury models, thereby especially focusing on cytokines and mediators that modulate ion channels. Inflammation is characterized by complex and probably time-dependent co-signaling, interactions between the involved cell types, as well as by cell demise and barrier dysfunction, which may not uniquely determine a clinical picture. This review, therefore, aims to give integrative thoughts and wants to foster the unraveling of unmet needs in future research.