Renalase does not catalyze the oxidation of catecholamines

Cardiovascular Risk in Pediatric Renal Transplant Recipients

BACKGROUND

The survival of pediatric chronic kidney disease (CKD) patients has improved in recent decades due to advances in dialysis and transplantation. However, cardiovascular disease (CVD) emerges as the main cause of mortality in patients with CKD.

OBJECTIVES

To estimate cardiovascular risk in children with CKD at least 1 year after kidney transplantation. In addition, the possible association of cardiovascular risk with classic biochemical markers and potential new markers of this outcome was investigated.

METHODS

An observational ambidirectional (retrospective capture of risk factors and prospective study of outcomes) research including 75 patients who underwent renal transplant between 2003 and 2013 with postoperative follow-up of at least 1 year was conducted. The outcome variables adopted were the LV mass Z-score and the presence of coronary calcification on computed tomography using calcium Agatston score.

RESULT

Only one patient had an elevated calcium score, and three children (4%) had an LV mass Z-score ≥ 2.0. After multivariable analysis, only gender, serum triglyceride, and serum renalase concentration remained significantly associated with LV mass.

CONCLUSION

The low incidence of cardiovascular changes in the population studied confirms the benefit of transplantation for the cardiovascular health of children. Nevertheless, long-term follow-up of these patients is recommended, given the limited duration of kidney function provided by transplantation and the high likelihood of further dialysis and kidney transplants being required in these children.

Relation Between Exposure to Tobacco Smoke Assessed by Serum Cotinine Concentration and Questionnaire Method, and Serum Renalase Concentration-the Importance of the Coexistence of Arterial Hypertension and Other Cardiovascular Diseases

Exposure to tobacco smoke (ETS) is one of the main risk factors for cardiovascular disease (CVD). Renalase is a protein that may play a role in the pathogenesis of CVD. The aim of the study was to assess the relationship between ETS and serum renalase concentration. A group of 109 patients was recruited for this study (49.7 ± 14.7 years). In accordance with the questionnaire, patients were divided into the following subgroups: subgroup A- declaring themselves active smokers (n = 36), subgroup B- declaring themselves non-smokers and exposed to environmental tobacco smoke (n = 35), subgroup C- declaring themselves non-smokers and not exposed to environmental tobacco smoke (n = 38). The same patients were divided based on cotinine concentration into the following subgroups: subgroup D- active smokers (n = 42), subgroup E- non-smokers exposed to environmental tobacco smoke (n = 66), and subgroup F- non-smokers not exposed to environmental tobacco smoke (n = 1). Serum cotinine concentration and serum renalase concentration were measured using ELISA tests. Serum renalase concentration was statistically significantly higher in subgroup C than in subgroups A and B and in subgroup E and F than in D. There was a negative correlation between serum cotinine concentration and serum renalase concentration (r = -0.41, p < 0.05). Regression analysis showed that higher BMI, higher diastolic blood pressure, coronary artery disease and higher serum cotinine concentration are independent risk factors of lower serum renalase concentration. The questionnaire method of assessing exposure to tobacco smoke was characterized by high sensitivity, but only moderate specificity, especially in terms of assessing environmental exposure to tobacco smoke. In summary, the study showed an independent relationship between exposure to tobacco smoke and lower serum renalase concentration.

Renalase Potential as a Marker and Therapeutic Target in Chronic Kidney Disease

Hypertension and cardiovascular disease are prominent features of chronic kidney disease, and they are associated with premature mortality and progression toward end-stage kidney disease. Renalase, an enzyme secreted predominantly by the kidney and identified in 2005, seems to be one of the missing pieces in the puzzle of heart and kidney interaction in chronic kidney disease by lowering blood pressure and reducing the overactivity of sympathetic tone. This review aims to summarize evidence from clinical studies performed on subjects with CKD in order to explore the value of renalase as a marker and/or a therapeutic target in this disease.

Renalase inhibition regulates β cell metabolism to defend against acute and chronic stress

Renalase (Rnls), annotated as an oxidase enzyme, is a GWAS gene associated with Type 1 Diabetes (T1D) risk. We previously discovered that Rnls inhibition delays diabetes onset in mouse models of T1D in vivo , and protects pancreatic β cells against autoimmune killing, ER and oxidative stress in vitro . The molecular biochemistry and functions of Rnls are entirely uncharted. Here we find that Rnls inhibition defends against loss of β cell mass and islet dysfunction in chronically stressed Akita mice in vivo . We used RNA sequencing, untargeted and targeted metabolomics and metabolic function experiments in mouse and human β cells and discovered a robust and conserved metabolic shift towards glycolysis, amino acid abundance and GSH synthesis to counter protein misfolding stress, in vitro . Our work illustrates a function for Rnls in mammalian cells, and suggests an axis by which manipulating intrinsic properties of β cells can rewire metabolism to protect against diabetogenic stress.

Selenoprotein P, peroxiredoxin-5, renalase, and total antioxidant status in patients with suspected obstructive sleep apnea

PURPOSE

The aim of this study was to investigate the relationship between selenoprotein P, peroxiredoxin-5, renalase, total antioxidant status (TAS), mean blood pressure (mBP), and apnea-hypopnea index (AHI).

METHODS

The study group consisted of 112 patients hospitalized to verify the diagnosis of obstructive sleep apnea (OSA). The inclusion criteria were consent to participate in the study and age ≥ 18 years. Patients with active proliferative disease, severe systemic diseases, or mental diseases were excluded from the study. Each patient underwent full polysomnography and had blood pressure measured. Blood samples were collected and laboratory test was performed.

RESULTS

Among 112 patients enrolled, there was a statistically significant negative linear correlation between blood pressure values (sBP, dBP, mBP) and selenoprotein P, renalase, and TAS levels. Similarly, there was a negative linear correlation between AHI and selenoprotein P, renalase, and TAS levels, but none between AHI and peroxiredoxin-5. Based on the obtained regression models, higher selenoprotein P, peroxiredoxin-5, and renalase levels were independently associated with higher TAS. Lower mBP values were independently associated with the use of antihypertensive drugs, higher TAS, and younger age. Male gender, higher BMI, and higher mBP were independently associated with higher AHI.

CONCLUSIONS

Higher concentrations of selenoprotein P, peroxiredoxin-5, and renalase were associated with higher TAS, which confirms their antioxidant properties. There was an indirect connection between tested antioxidants and blood pressure values.

Cardiac-specific renalase overexpression alleviates CKD-induced pathological cardiac remodeling in mice

Introduction

CKD-induced pathological cardiac remodeling is characterized by myocardial hypertrophy and cardiac fibrosis. The available therapeutic options are limited, it is thus urgently needed to identify novel therapeutic targets. Renalase (RNLS) is a newly discovered protein secreted by the kidney and was found beneficial in many renal diseases. But whether it exerts protective effects on cardiac remodeling in CKD remains unclear.

Methods

RNLS knockout (KO) and wild-type (WT) mice were both used to build CKD models and the adeno-associated virus (AAV9) system was used to overexpress RNLS cardiac specifically. Echocardiography was performed to detect cardiac structural changes every 6 weeks until 18 weeks post-surgery. High throughput sequencing was performed to understand the underlying mechanisms and the effects of RNLS on cardiac fibroblasts were validated in vitro.

Results

Knockout of RNLS aggravated cardiac remodeling in CKD, while RNLS cardiac-specific overexpression significantly reduced left ventricular hypertrophy and cardiac fibrosis induced by CKD. The following RNA-sequencing analysis revealed that RNLS significantly downregulated the extracellular matrix (ECM) receptor interaction pathway, ECM organization, and several ECM-related proteins. GSEA results showed RNLS significantly downregulated several profibrotic biological processes of cardiac fibroblasts which were upregulated by CKD, including fibroblast proliferation, leukocyte migration, antigen presentation, cytokine production, and epithelial-mesenchymal transition (EMT). In vitro, we validated that RNLS reduced the primary cardiac fibroblast proliferation and α-SMA expression stimulated by TGF-β.

Conclusion

In this study, we examined the cardioprotective role of RNLS in CKD-induced cardiac remodeling. RNLS may be a potential therapeutic factor that exerts an anti-fibrotic effect in pathological cardiac remodeling.

Renalase: a novel regulator of cardiometabolic and renal diseases

Renalase is a ~38 kDa flavin-adenine dinucleotide (FAD) domain-containing protein that can function as a cytokine and an anomerase. It is emerging as a novel regulator of cardiometabolic diseases. Expressed mainly in the kidneys, renalase has been reported to have a hypotensive effect and may control blood pressure through regulation of sympathetic tone. Furthermore, genetic variations in the renalase gene, such as a functional missense polymorphism (Glu37Asp), have implications in the cardiovascular and renal systems and can potentially increase the risk of cardiometabolic disorders. Research on the physiological functions and biochemical actions of renalase over the years has indicated a role for renalase as one of the key proteins involved in various disease states, such as diabetes, impaired lipid metabolism, and cancer. Recent studies have identified three transcription factors (viz., Sp1, STAT3, and ZBP89) as key positive regulators in modulating the expression of the human renalase gene. Moreover, renalase is under the post-transcriptional regulation of two microRNAs (viz., miR-29b, and miR-146a), which downregulate renalase expression. While renalase supplementation may be useful for treating hypertension, inhibition of renalase signaling may be beneficial to patients with cancerous tumors. However, more incisive investigations are required to unravel the potential therapeutic applications of renalase. Based on the literature pertaining to the function and physiology of renalase, this review attempts to consolidate and comprehend the role of renalase in regulating cardiometabolic and renal disorders.

Elevated Levels of Renalase, the β-NAD(P)H Isomerase, Can Be Used as Risk Factors of Major Adverse Cardiovascular Events and All-Cause Death in Patients with Chronic Kidney Disease

BACKGROUND

Renalase is an enzyme and a cytokine involved in cell survival. Since its discovery, associations between it and both cardiovascular and kidney disease have been noted. Recognizing this, we conducted a study in which we followed patients with chronic kidney disease.

MATERIAL AND METHODS

The study involved 90 CKD patients with varying stages of the disease and 30 healthy controls. Renalase was measured with an ELISA kit, and patients were followed-up after a median of 18 months. During the follow-up, we asked about the occurrence of MACE, all-cause mortality and the need for dialysis initiation.

RESULTS

In CKD subgroups, RNSL correlated with all-cause death only in the HD group (Rs = 0.49, p < 0.01). In the whole CKD population, we found a positive correlation of RNSL concentration and both MACE occurrence (Rs = 0.38, p < 0.001) and all-cause death (Rs = 0.34, p < 0.005). There was a significant increase in MACE occurrence probability in patients with elevated renalase levels (>25 μg/mL).

CONCLUSIONS

Elevated renalase levels can be used as a risk factor of MACE in patients with CKD, but its long-term utility needs further research. High renalase levels are a risk factor of death among CKD patients. In HD patients, all deaths were observed among patients with >30 μg/mL; this level could be used as a "red flag" marker in future studies.

Renalase: A Multi-Functional Signaling Molecule with Roles in Gastrointestinal Disease

The survival factor renalase (RNLS) is a recently discovered secretory protein with potent prosurvival and anti-inflammatory effects. Several evolutionarily conserved RNLS domains are critical to its function. These include a 20 aa site that encodes for its prosurvival effects. Its prosurvival effects are shown in GI disease models including acute cerulein pancreatitis. In rodent models of pancreatic cancer and human cancer tissues, increased RNLS expression promotes cancer cell survival but shortens life expectancy. This 37 kD protein can regulate cell signaling as an extracellular molecule and probably also at intracellular sites. Extracellular RNLS signals through a specific plasma membrane calcium export transporter; this interaction appears most relevant to acute injury and cancer. Preliminary studies using RNLS agonists and antagonists, as well as various preclinical disease models, suggest that the immunologic and prosurvival effects of RNLS will be relevant to diverse pathologies that include acute organ injuries and select cancers. Future studies should define the roles of RNLS in intestinal diseases, characterizing the RNLS-activated pathways linked to cell survival and developing therapeutic agents that can increase or decrease RNLS in relevant clinical settings.

Roles and mechanisms of renalase in cardiovascular disease: A promising therapeutic target

Cardiovascular disease (CVD) is prevalent worldwide and remains a leading cause of death. Although substantial progress has been made in the diagnosis and treatment of CVD, the prognosis remains unsatisfactory. Renalase is a newly discovered cytokine that is synthesized by the kidney and then secreted into blood. Numerous studies have suggested the efficacy of renalase in treating CVD by metabolizing catecholamines in the circulatory system. As a new biomarker of heart disease, renalase is normally recognized as a signalling molecule that activates cytoprotective intracellular signals to lower blood pressure, protect ischaemic heart muscle and promote atherosclerotic plaque stability in CVD, which subsequently improves cardiac function. Due to its important regulatory role in the circulatory system, renalase has gradually become a potential target in the treatment of CVD. This review summarizes the structure, mechanism and function of renalase in CVD, thereby providing preclinical evidence for alternative approaches and new prospects in the development of renalase-related drugs against CVD.

Direct laboratory evidence that pregnancy-induced hypertension might be associated with increased catecholamines and decreased renalase concentrations in the umbilical cord and mother’s blood

Background

Renalase (RNL) is a controversial enzyme as to whether it oxidizes catecholamines (CAs) (as is generally accepted) in the blood or not. CAs (dopamine [DPMN], epinephrine [EPI] and norepinephrine [NEPI]) are associated with hypertension, including pregnancy-induced hypertension, which occurs in 8–10% of all pregnancies. Therefore, the aim of the study was to compare CAs and renalase concentration in (i) normotensive controls (C), (ii) patients with preeclampsia (PE) and (iii) patients with severe preeclampsia (SPE), which is one of the well-known symptoms of hypertension.

Methods

This case-control study involved 90 women divided into three groups – 30 C, 30 PE and 30 SPE – whose age and body mass indexes (BMIs) were similar. A total of 270 blood samples (90 maternal samples, 90 umbilical cord artery samples and 90 umbilical cord vein samples) were obtained. CAs and RNL concentrations of the biological samples were measured by enzyme-linked immunosorbent assay (ELISA).

Results

Comparing the amounts of CAs, RNL and systolic blood pressure (SBP)/diastolic blood pressure (DBP) between healthy control pregnant women and pregnant women with PE and SPE (SBP/DBP was 120/80 mm Hg for C, above 140/90 mm Hg for PE and above 160/110 mm Hg for SPE), the levels of CAs were significantly increased whereas RNL was reduced. The correlation between SBP/DBP and the amount of RNL in pregnant women with PE and SPE was negative.

Conclusions

These novel results are evidence that hypertension seen in PE and SPE is directly related to increased levels of CAs and reduced RNL concentrations. The use of RNL preparations may be preferred in future to prevent maternal and perinatal morbidity and mortality due to pregnancy-induced hypertension.

Urinary renalase concentration in patients with preserved kidney function undergoing coronary angiography

AIM

The purpose of the study was to evaluate urinary renalase concentration before and after coronary angiography/percutaneous coronary interventions (CA/PCI) in patients with coronary artery disease (CAD) and preserved kidney function and verify its potential application as contrast-induced acute kidney injury (CI-AKI) diagnostic marker.

METHODS

This prospective study comprised 95 consecutive patients (69.5% men; median age 65 years) with CAD submitted to elective or urgent CA/PCI. Data regarding 128 clinical variables were obtained. Urine samples were collected on admission and 6 h after CA/PCI and tested for urinary renalase using ELISA method, which was expressed as renalase-to-creatinine ratio. The CI-AKI diagnosis was based on ≥50% relative or ≥0.3 mg/dl absolute increase of serum creatinine concentration 48 h following the procedure.

RESULTS

Nine patients developed CI-AKI (9.5%). In comparison to baseline values, urinary renalase-to-creatinine ratio significantly decreased 6 h following CA/PCI, (2843.6 vs.1540.7 ng/mg, P < 0.0001). Nine patients developed CI-AKI (9.5%).The reduction of renalase level was profound both in CI-AKI (2709.7 vs. 1585.7 ng/mg, P = 0.007) and non-CI-AKI group (2814.9 vs.1561.8 ng/mg, P < 0.0001). There was a trend towards a greater relative decrease of urinary renalase in CI-AKI group (-57.3 vs.-41.8%, P = 0.10). Univariate analysis revealed that both pre- and post-procedural urinary renalase did not predict CI-AKI onset; however, absolute decrease of renalase below 25 percentile was a predictor of CI-AKI (OR = 5.4, 95% CI:1.3-21.9, P = 0.027).

CONCLUSION

Urinary renalase concentration is reduced in the aftermath of CA/PCI, which may be related to CI-AKI development. Further studies are warranted to elucidate the role of urinary renalase as a CI-AKI diagnostic marker.

Endocan Concentration in Patients With Primary Hypertension

Inflammation and endothelial dysfunction may play an important role in the multifactorial pathogenesis of hypertension. Endocan is also thought to play a role in cell adhesion and inflammatory disorders. The aim of the study was to compare endocan concentrations in patients with primary hypertension and healthy volunteers. There were 104 patients with hypertension (study group) and 21 healthy volunteers (control group). The correlation between endocan, catecholamines, and blood pressure control in patients with primary hypertension and the control group was analyzed. The median endocan concentration in the study group (2.03 ng/mL) was significantly higher than in the control group (1.09 ng/mL, P = .0001). Endocan concentration was correlated positively with renalase ( r = .2, P = .047) and norepinephrine ( r = .25, P = .02). Negative correlation was observed between endocan and body mass index ( r = −.25, P = .016) and leukocyte count ( r = −.36, P = .0004). The present study reports higher plasma endocan concentration in patients with treated, well-controlled primary hypertension compared with healthy volunteers. The higher endocan concentration in the study group may reflect endothelial dysfunction in this population.

Functional polymorphism of the renalase gene is associated with cardiac hypertrophy in female patients with aortic stenosis

Renalase decreases circulating catecholamines concentration and is important in maintaining primary cellular metabolism. Renalase acts through the plasma membrane calcium ATPase 4b in the heart, which affects pressure overload but not exercise induced heart hypertrophy. The aim of this study was to test the association between a functional polymorphism Glu37Asp (rs2296545) of the renalase gene and left ventricular hypertrophy in a large cohort of patients with aortic stenosis. The study group consisted of 657 patients with aortic stenosis referred for aortic valve replacement. Preoperative echocardiographic assessment was performed to obtain cardiac phenotypes. Generalized-linear models were implemented to analyze data using crude or full model adjusted for selected clinical factors. In females, the Asp37 variant of the Glu37Asp polymorphism was associated with higher left ventricular mass (p = 0.0021 and p = 0.055 crude and full model respectively), intraventricular septal thickness (p = 0.0003 and p = 0.0143) and posterior wall thickness (p = 0.0005 and p = 0.0219) all indexed to body surface area, as well as relative wall thickness (p = 0.001 and p = 0.0097). No significant associations were found among the male patients. In conclusion, we have found the association of the renalase Glu37Asp polymorphism with left ventricle hypertrophy in large group of females with aortic stenosis. The Glu37Asp polymorphism causes not only amino-acid substitution in FAD binding domain but may also change binding affinity of the hypoxia- and hypertrophy-related transcription factors and influence renalase gene expression. Our data suggest that renalase might play a role in hypertrophic response to pressure overload, but the exact mechanism requires further investigation.

Relationship between microRNA-146a expression and plasma renalase levels in hemodialyzed patients

BACKGROUND

microRNA (miRNA) belongs to the non-coding RNAs family responsible for the regulation of gene expression. Renalase is a protein composed of 342 amino acids, secreted by the kidneys and possibly plays an important role in the regulation of sympathetic tone and blood pressure. The aim of the present study was to investigate plasma renalase concentration, and explore the relationship between miRNA-146a-5p expression and plasma renalase levels in hemodialyzed patients.

METHODS

The study population comprised 55 subjects who succumbed to various cardiac events, 27 women and 28 men, aged 65-70 years. The total RNA including miRNA fraction was isolated using QiagenmiRNEasy Serum/Plasma kit according to the manufacturer's protocol. The isolated miRNAs were analyzed using a quantitative polymerase chain reaction (qRT-PCR) technique. The plasma renalase levels were measured using a commercial ELISA kit.

RESULTS

In the group of patients with high levels of renalase, higher miRNA-146a expression was found, compared with those with low concentration of renalase. Patients with simultaneous low miRNA-146a expression and high level of renalase were confirmed to deliver a significantly longer survival time compared with other patients.

CONCLUSIONS

miRNA-146a and plasma renalase levels were estimated as independent prognostic factors of hemodialyzed patients' survival time. Patients with low miRNA-146a expression demonstrated a significantly longer survival time in contrast to the patients with a high expression level of miRNA-146a. Moreover, a significantly longer survival time was found in patients with high renalase activity compared with patients with low activity of the enzyme.

The enzyme: Renalase

Within the last two years catalytic substrates for renalase have been identified, some 10 years after its initial discovery. 2- and 6-dihydronicotinamide (2- and 6-DHNAD) isomers of β-NAD(P)H (4-dihydroNAD(P)) are rapidly oxidized by renalase to form β-NAD(P)⁺. The two electrons liberated are then passed to molecular oxygen by the renalase FAD cofactor forming hydrogen peroxide. This activity would appear to serve an intracellular detoxification/metabolite repair function that alleviates inhibition of primary metabolism dehydrogenases by 2- and 6-DHNAD molecules. This activity is supported by the complete structural assignment of the substrates, comprehensive kinetic analyses, defined species specific substrate specificity profiles and X-ray crystal structures that reveal ligand complexation consistent with this activity. This apparently intracellular function for the renalase enzyme is not allied with the majority of the renalase research that holds renalase to be a secreted mammalian protein that functions in blood to elicit a broad array of profound physiological changes. In this review a description of renalase as an enzyme is presented and an argument is offered that its enzymatic function can now reasonably be assumed to be uncoupled from whole organism physiological influences.

Renalase Protects against Renal Fibrosis by Inhibiting the Activation of the ERK Signaling Pathways

Renal interstitial fibrosis is a common pathway for the progression of chronic kidney disease (CKD) to end-stage renal disease. Renalase, acting as a signaling molecule, has been reported to have cardiovascular and renal protective effects. However, its role in renal fibrosis remains unknown. In this study, we evaluated the therapeutic efficacy of renalase in rats with complete unilateral ureteral obstruction (UUO) and examined the inhibitory effects of renalase on transforming growth factor-β1 (TGF-β1)-induced epithelial-mesenchymal transition (EMT) in human proximal renal tubular epithelial (HK-2) cells. We found that in the UUO model, the expression of renalase was markedly downregulated and adenoviral-mediated expression of renalase significantly attenuated renal interstitial fibrosis, as evidenced by the maintenance of E-cadherin expression and suppressed expression of α-smooth muscle actin (α-SMA), fibronectin and collagen-I. In vitro, renalase inhibited TGF-β1-mediated upregulation of α-SMA and downregulation of E-cadherin. Increased levels of Phospho-extracellular regulated protein kinases (p-ERK1/2) in TGF-β1-stimulated cells were reversed by renalase cotreatment. When ERK1 was overexpressed, the inhibition of TGF-β1-induced EMT and fibrosis mediated by renalase was attenuated. Our study provides the first evidence that renalase can ameliorate renal interstitial fibrosis by suppression of tubular EMT through inhibition of the ERK pathway. These results suggest that renalase has potential renoprotective effects in renal interstitial fibrosis and may be an effective agent for slowing CKD progression.

Extracellular renalase protects cells and organs by outside-in signalling

Renalase was discovered as a protein synthesized by the kidney and secreted in blood where it circulates at a concentration of approximately 3-5 μg/ml. Initial reports suggested that it functioned as an NAD(P)H oxidase and could oxidize catecholamines. Administration of renalase lowers blood pressure and heart rate and also protects cells and organs against ischaemic and toxic injury. Although renalase's protective effect was initially ascribed to its oxidase properties, a paradigm shift in our understanding of the cellular actions of renalase is underway. We now understand that, independent of its enzymatic properties, renalase functions as a cytokine that provides protection to cells, tissues and organs by interacting with its receptor to activate protein kinase B, JAK/STAT, and the mitogen-activated protein kinase pathways. In addition, recent studies suggest that dysregulated renalase signalling may promote survival of several tumour cells due to its capacity to augment expression of growth-related genes. In this review, we focus on the cytoprotective actions of renalase and its capacity to sustain cancer cell growth and also the translational opportunities these findings represent for the development of novel therapeutic strategies for organ injury and cancer.

Association of Renalase SNPs rs2296545 and rs2576178 with the Risk of Hypertension: A Meta-Analysis

Background/Aims

Two renalase single nucleotide polymorphisms (SNPs) rs2296545 and rs2576178 have been reported to be associated with the susceptibility to hypertension (HT). Given the inconsistent results, we conducted a meta-analysis to assess the association between these two SNPs and the risk of HT.

Methods

Electronic databases were systematically searched to find relevant studies. Subgroup analysis was conducted according to the different concomitant diseases and ethnicities in the study population. Pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated using fixed-effect or random-effect models.

Results

A total of six case–control studies on rs2296545 and six studies on rs2576178 were included. In the combined analysis, results showed a significant association between SNP rs2296545 and risk of HT in all genetic models (dominant model CG+CC/GG: OR = 1.43, 95% CI = 1.24–1.65; recessive model CC/CG+GG: OR = 1.36, 95% CI = 1.09–1.69; codominant model CC/GG: OR = 1.63, 95% CI = 1.20–2.20, CG/GG: OR = 1.30, 95% CI = 1.12–1.52; allelic model C/G: OR = 1.29, 95% CI = 1.10–1.51). In subgroup analysis, we observed a significant association between rs2296545 and risk of essential HT. Although we did not observe an association between rs2576178 polymorphism and HT in the combined analysis, an increased risk was observed in the essential HT patients versus healthy controls (subgroup 1) analysis under the dominant, recessive, and codominant genetic models.

Conclusions

Renalase gene rs2296545 polymorphism is significantly associated with increased risk of HT, whereas rs2576178 polymorphism may not be associated with the susceptibility to HT.

Renalase attenuates hypertension, renal injury and cardiac remodelling in rats with subtotal nephrectomy

Chronic kidney disease is associated with higher risk of cardiovascular complication and this interaction can lead to accelerated dysfunction in both organs. Renalase, a kidney-derived cytokine, not only protects against various renal diseases but also exerts cardio-protective effects. Here, we investigated the role of renalase in the progression of cardiorenal syndrome (CRS) after subtotal nephrectomy. Sprague-Dawley rats were randomly subjected to sham operation or subtotal (5/6) nephrectomy (STNx). Two weeks after surgery, sham rats were intravenously injected with Hanks' balanced salt solution (sham), and STNx rats were randomly intravenously injected with adenovirus-β-gal (STNx+Ad-β-gal) or adenovirus-renalase (STNx+Ad-renalase) respectively. After 4 weeks of therapy, Ad-renalase administration significantly restored plasma, kidney and heart renalase expression levels in STNx rats. We noticed that STNx rats receiving Ad-renalase exhibited reduced proteinuria, glomerular hypertrophy and interstitial fibrosis after renal ablation compared with STNx rats receiving Ad-β-gal; these changes were associated with significant decreased expression of genes for fibrosis markers, proinflammatory cytokines and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase components. At the same time, systemic delivery of renalase attenuated hypertension, cardiomyocytes hypertrophy and cardiac interstitial fibrosis; prevented cardiac remodelling through inhibition of pro-fibrotic genes expression and phosphorylation of extracellular signal-regulated kinase (ERK)-1/2. In summary, these results indicate that renalase protects against renal injury and cardiac remodelling after subtotal nephrectomy via inhibiting inflammation, oxidative stress and phosphorylation of ERK-1/2. Renalase shows potential as a therapeutic target for the prevention and treatment of CRS in patients with chronic kidney disease.

[The history of renalase from amine oxidase to a a-NAD(P)H-oxidase/anomerase]

Renalase is a recently discovered secretory protein, which plays a certain (still poorly understood) role in regulation of blood pressure. The review summarizes own and literature data accumulated since the first publication on relanase (2005). Initial reports on FAD-dependent amine oxidase activity of this protein were not confirmed in independent experiments performed in different laboratories. In addition, proposed amine oxidase activity of circulating extracellular renalase requires the presence of FAD, which has not been detected either in blood or urinary renalase. Moreover, renalase excreted into urine lacks its N-terminal peptide, which is ultimately needed for accommodation of the FAD cofactor. Results of the Aliverti's group on NAD(P)H binding by renalase and weak diaphorase activity of this protein stimulated further studies of renalase as NAD(P)H oxidase catalyzing reaction of catecholamine co-oxidation. However, physiological importance of such extracellular catecholamine-metabolizing activity (demonstrated in one laboratory and not detected in another laboratory) remains unclear due to existence of much more active enzymatic systems (e.g. neutrophil NAD(P)H oxidase, xanthine oxidase/xanthine) in circulation, which can perform such co-oxidation reactions. Recently a-NAD(P)H oxidase/anomerase activity of renalase, which also pomotes oxidative conversion of b-NADH isomers inhibiting activity of NAD-dependent dehydrogenases, has been described. However, its possible contribution to the antihypertensive effect of renalase remains unclear. Thus, the antihypertensive effect of renalase still remains a phenomenon with unclear biochemical mechanim(s) and functions of intracellular and extracellular (circulating) renalases obviously differ.