Renalase's expression and distribution in renal tissue and cells

Renalase mediates macrophage-to-fibroblast crosstalk to attenuate pressure overload-induced pathological myocardial fibrosis

A potential antifibrotic mechanism in pathological myocardial remodeling is the recruitment of beneficial functional subpopulations of macrophages or the transformation of their phenotype. Macrophages are required to activate molecular cascades that regulate fibroblast behavior. Identifying mediators that activate the antifibrotic macrophage phenotype is tantamount to identifying the button that retards pathological remodeling of the myocardium; however, relevant studies are inadequate. Circulating renalase (RNLS) is mainly of renal origin, and cardiac myocytes also secrete it autonomously. Our previous studies revealed that RNLS delivers cell signaling to exert multiple cardiovascular protective effects, including the improvement of myocardial ischemia, and heart failure. Here, we further investigated the potential mechanism by which macrophage phenotypic transformation is targeted by RNLS to mediate stress load-induced myocardial fibrosis. Mice subjected to transverse aortic constriction (TAC) were used as a model of myocardial fibrosis. The co-incubation of macrophages and cardiac fibroblasts was used to study intercellular signaling. The results showed that RNLS co-localized with macrophages and reduced protein expression after cardiac pressure overload. TAC mice exhibited improved cardiac function and alleviated left ventricular fibrosis when exogenous RNLS was administered. Flow sorting showed that RNLS is essential for macrophage polarization towards a restorative phenotype (M2-like), thereby inhibiting myofibroblast activation, as proven by both mouse RAW264.7 and bone marrow-derived macrophage models. Mechanistically, we found that activated protein kinase B is a major pathway by which RNLS promotes M2 polarization in macrophages. RNLS may serve as a prognostic biomarker and a potential clinical candidate for the treatment of myocardial fibrosis.

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.

Levels of Serum and Urine Catecholaminergic and Apelinergic System Members in Acute Ischemic Stroke Patients

Objective: To compare levels of catecholaminergic system members, renalase, cerebellin, and their substrates, epinephrine, norepinephrine, and dopamine, and apelinergic system members, apelin, elabela, and nitric oxide in the blood and urine of patients with acute ischemic stroke and healthy controls. Materials and Methods: 42 patients with acute ischemic stroke and 42 age and sex-matched healthy controls were included in the study. Blood and urine samples were collected simultaneously and within the first 24 hours after the onset of acute stroke clinical manifestations and were measured using an ELISA method. Results: The levels of serum and urine cerebellin, renalase, epinephrine, norepinephrine, dopamine, apelin, elebela, and nitric oxide were similar in ischemic stroke and in control groups (P>0.05). Strong correlations were found between renalase, cerebellin, and catecholamine levels in serum and urine (p

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.

Associations of Renalase With Blood Pressure and Hypertension in Chinese Adults

Objective

Renalase, a novel secretory flavoprotein with amine oxidase activity, is secreted into the blood by the kidneys and is hypothesized to participate in blood pressure (BP) regulation. We investigated the associations of renalase with BP and the risk of hypertension by examining renalase single nucleopeptide polymorphism (SNPs), serum renalase levels, and renal expression of renalase in humans.

Methods

① Subjects (n = 514) from the original Baoji Salt-Sensitive Study cohort were genotyped to investigate the association of renalase SNPs with longitudinal BP changes and the risk of hypertension during 14 years of follow-up. ② Two thousand three hundred and ninety two participants from the Hanzhong Adolescent Hypertension Study cohort were used to examine the association of serum renalase levels with hypertension. Renalase expression in renal biopsy specimens from 193 patients were measured by immunohistochemistry. ③ Renalase expression was compared in hypertensive vs. normotensive patients.

Results

① SNP rs7922058 was associated with 14-year change in systolic BP, and rs10887800, rs796945, rs1935582, rs2296545, and rs2576178 were significantly associated with 14-year change in diastolic BP while rs1935582 and rs2576178 were associated with mean arterial pressure change over 14 years. In addition, SNPs rs796945, rs1935582, and rs2576178 were significantly associated with hypertension incidence. Gene-based analysis found that renalase gene was significantly associated with hypertension incidence over 14-year follow-up after adjustment for multiple measurements. ② Hypertensive subjects had higher serum renalase levels than normotensive subjects (27.2 ± 0.4 vs. 25.1 ± 0.2 μg/mL). Serum renalase levels and BPs showed a linear correlation. In addition, serum renalase was significantly associated with the risk of hypertension [OR = 1.018 (1.006–1.030)]. ③ The expression of renalase in human renal biopsy specimens significantly decreased in hypertensive patients compared to non-hypertensive patients (0.030 ± 0.001 vs. 0.038 ± 0.004).

Conclusions

These findings indicate that renalase may play an important role in BP progression and development of hypertension.

A new biomarker (RENALASE) for the diagnosis of blunt renal trauma in an experimental study

INTRODUCTION

Kidneys are the most frequently injured organ in the genitourinary system, but there is no specific biological marker for this trauma. Renalase may be a descriptive biomarker of the pathology that causes renal ischemia, nephrotoxicity, and acute renal failure.

OBJECTIVE

This study investigated the role of serum and urine levels of renalase for the diagnosis of renal injury in rats with experimentally induced blunt renal trauma.

STUDY DESIGN

Thirty 3-month-old Sprague-Dawley adult male rats were divided into five groups (n = 6) as follows: control (Group 1), sham (Group 2), right nephrectomy (Group 3), left renal trauma (Group 4), and right nephrectomy plus left renal trauma (Group 5). Serum samples were acquired 3, 24 and 48 h post-trauma, and urine samples were acquired between 0-24 and 24-48 h post-trauma. Changes in serum and urine levels of renalase, dopamine, epinephrine, metanephrine, normetanephrine, urea, and creatinine were assessed after blunt renal trauma.

RESULTS

No significant changes in serum levels of these compounds were observed at 3 h post-trauma in Groups 1 and 2 or in urine collected sequentially at 0-24 and 24-48 h. By contrast, levels of renalase, dopamine, metanephrine, and normetanephrine in serum increased during hour 3 in Groups 4 and 5. Moreover, increases in urine levels of renalase, dopamine, epinephrine, metanephrine, and normetanephrine were observed at hours 0-24 in Groups 4 and 5.

DISCUSSION

A definitive diagnosis of traumatic renal injury in children is made with contrast-enhanced computed tomography. However, the scan results in high doses of radiation exposure to children. Here, we report for the first time that renalase levels may be useful as a biomarker for the diagnosis of renal injury due to blunt renal trauma.

CONCLUSION

Renalase may be a simple, effective, and noninvasive biomarker that indicates traumatic renal injury. It could be used as an adjunct for evaluation, particularly for isolated traumatic renal injury in cases where access to computed tomography is not straightforward.

The Effect of Renalase rs2576178 and rs10887800 Polymorphisms on Ischemic Stroke Susceptibility in Young Patients (<50 Years): A Case-Control Study and In Silico Analysis

Background

Ischemic stroke (IS) is the most common form of cerebrovascular accident which its precise etiology remains mysterious. Renalase is a catecholamine-degrading enzyme playing a major role in blood pressure control. Recent studies show the effect of renalase activity on various diseases like IS. In the current study, we examined the possible effects of renalase gene (RNLS) rs2576178 and rs10887800 variants at the 5′-flanking and intron 6 regions on IS, respectively.

Methods

One hundred and fifty-four IS patients younger than 50 years and 165 age- and sex-matched controls were recruited in the study. For genotyping of rs2576178 and rs10887800 variants, the PCR-RFLP method was used.

Results

The RNLS rs10887800 AG genotype was more repeated in IS patients, but the difference was marginally nonsignificant (P = 0.054). This variant was associated with IS in the overdominant model, and the AG genotype is associated with a1.6-fold increased risk of IS compared to AA+ GG genotypes (OR = 1.6, 95% CI: 1-2.5, P = 0.033). No relationship was observed between RNLS rs2576178 polymorphism and IS in all genetic models. The findings of the haplotype and combination effects of rs10887800 and rs2576178 variants on IS showed no significant association. The in silico analysis showed no effect of rs2576178 and rs10887800 polymorphisms in the RNA structure, but the alteration of RNA sequence in rs2576178 results in the lack of a MBNL1 protein binding site.

Conclusions

RNLS rs10887800 but not rs2576178 polymorphism was associated with IS susceptibility in the overdominant model (AG vs AA+ GG genotypes).

Differences in Noradrenaline Receptor Expression Across Different Neuronal Subtypes in Macaque Frontal Eye Field

Cognitive functions such as attention and working memory are modulated by noradrenaline receptors in the prefrontal cortex (PFC). The frontal eye field (FEF) has been shown to play an important role in visual spatial attention. However, little is known about the underlying circuitry. The aim of this study was to characterize the expression of noradrenaline receptors on different pyramidal neuron and inhibitory interneuron subtypes in macaque FEF. Using immunofluorescence, we found broad expression of noradrenaline receptors across all layers of the FEF. Differences in the expression of different noradrenaline receptors were observed across different inhibitory interneuron subtypes. No significant differences were observed in the expression of noradrenaline receptors across different pyramidal neuron subtypes. However, we found that putative long-range projecting pyramidal neurons expressed all noradrenaline receptor subtypes at a much higher proportion than any of the other neuronal subtypes. Nearly all long-range projecting pyramidal neurons expressed all types of noradrenaline receptor, suggesting that there is no receptor-specific machinery acting on these long-range projecting pyramidal neurons. This pattern of expression among long-range projecting pyramidal neurons suggests a mechanism by which noradrenergic modulation of FEF activity influences attention and working memory.

Can renalase be a novel candidate biomarker for distinguishing renal tumors?

Renalase (RNLS) is synthesized mainly in renal tissues. The function of RNLS in cancerous renal tissues has not been investigated. We investigated the synthesis of RNLS in chromophobe renal cell carcinoma, papillary renal cell carcinoma and clear cell renal cell carcinoma with Fuhrman grades (FG): FG1, nucleoli are absent or inconspicuous and basophilic; FG2, nucleoli are conspicuous and eosinophilic and visible but not prominent; FG3, nucleoli are conspicuous and eosinophilic; FG4, extreme nuclear pleomorphism, multinucleate giant cells, and/or rhabdoid and/or sarcomatoid differentiation. We used 90 tissue samples including 15 healthy controls, 15 chromophobe renal cell carcinoma tissues and 10 papillary renal cell carcinoma renal tissues: 12 FG1, 14 FG 2, 14 FG 3 and 10 FG4. RNLS in the tissue samples was measured using enzyme linked immunosorbent assay and immunostaining of RNLS in these tissues. RNLS was significantly greater in the chromophobe renal cell carcinoma and papillary renal cell carcinoma tissues than the control. The least amount of RNLS was found in the renal tissues of clear cell renal cell carcinoma FG1; the amount of RNLS increased as the FG grades increased. Because RNLS increased significantly in renal tissues due to cancer, except for clear cell renal cell carcinoma FG1, RNLS may be useful biomarker for distinguishing grades of renal cancer. Because RNLS increases cell survival, anti-RNLS preparations may be useful for treating cancer in the future.

Serum-to-urine renalase ratio and renalase fractional excretion in healthy adults and chronic kidney disease patients

Background

Renalase is a flavoprotein that plays a protective role in chronic kidney disease (CKD) and cardiovascular diseases. The secretion and way of action of this protein are still discussed. The aim of our study was to estimate the balance between serum and urine renalase in healthy individuals and CKD patients, using two parameters: fractional excretion (FE) and serum-to-urine renalase ratio (StURR).

Methods

Our study involved 28 healthy volunteers and 62 patients with CKD in stages I to IV. The concentration of renalase in serum and urine was measured using an enzyme-linked immunosorbent assay (ELISA) kit (EIAab, Wuhan, China). We analyzed associations between renalase levels in urine and serum, and other parameters: sex, age, GFR, presence of hypertension, diabetes, and proteinuria, and determined the serum-to-urine renalase ratio and fractional excretion of renalase.

Results

Renalase and serum-to-urine ratio were significantly higher in CKD patients in comparison with the control group. Fractional excretion was lower in CKD patients but this difference did not reach the statistical significance (p = 0.092). Multivariate analysis performed in the CKD group showed, that from mentioned parameters, serum renalase was the only significant independent factor strongly positively associated with urinary renalase concentration.

Conclusions

The serum-to-urine ratio is significantly and about 6.5-fold higher in CKD patients, and the fractional excretion of renalase is 3-fold, but not significantly lower in CKD patients. Renalase levels in both serum and urine are not related to the glomerular filtration rate and not associated with blood pressure.

The role of urinary renalase on early-stage renal damage in Chinese adults with primary hypertension

It would be of great clinical value to find an indicator that can accurately evaluate the early-stage renal injury in primary hypertension. Previous findings have shown renalase not only plays an important role in hypertension but also closely correlates with kidney function. The purpose of this study is to investigate whether urinary renalase could be used as a predictive index of early-stage renal damage in patients with primary hypertension. Urinary albumin to creatinine ratio (UACR) was used to divide subjects with primary hypertension into two groups: a no renal damage (NRD) group (UACR <30 mg/g) and an early-stage renal damage (RD) group (UACR >30 mg/g). Subjects with normal examination results were randomly included in a healthy control (HC) group. Urinary renalase was determined through an enzyme-linked immunosorbent assay (ELISA). Urinary renalase continued to reduce among the HC (n = 81), NRD (n = 84) and RD group (n = 80), while systolic blood pressure (SBP) increased. Urinary renalase was negatively correlated with SBP in all the groups. Among the subjects with stage 1 primary hypertension, urinary renalase in the RD group was lower than the NRD group, while the UACR was higher, and urinary renalase was negatively correlated with the UACR. A multiple linear stepwise regression analysis showed that there was a linear regression relationship between the increase of the UACR and urinary renalase, heart rate (HR), SBP and serum creatinine. In addition, the standardized partial regression coefficient of urinary renalase was the highest. The performance of urinary renalase as a marker for the diagnosis of early-stage renal damage in patients with primary hypertension was 0.968 with a cut off value of 2.01 µg/ml. Taken together, urinary renalase was further decreased in patients with early-stage renal damage and primary hypertension, and consequently, it could be used as a predictive index.

Atorvastatin and losartan may upregulate renalase activity in hypertension but not coronary artery diseases: The role of gene polymorphism

The aim is to explore the treatment effect of coronary artery disease (CAD) and hypertension on plasma levels of renalase activity and also the possible association of renalase rs10887800 gene polymorphism with CAD and hypertension. A total of 286 patients who received coronary angiography were included in the study. Subjects were divided into four groups including (1) hypertensive with no CAD (H-Tens, n = 60); (2) CAD with hypertension (CAD + H-Tens, n = 71); (3) CAD with no hypertension (CAD, n = 61); and (4) nonhypertensive with no CAD as a control group (Con, n = 69). The plasma renalase activity was measured using the Amplex Red Monoamine Oxidase Assay Kit. Renalase rs10887800 single-nucleotide polymorphisms (SNPs) were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Atorvastatin (P = 0.005), losartan (P < 0.001), and captopril (P = 0.001) were administered significantly more in case groups compared with the Con group. Significant higher and lower levels of renalase activity were observed in H-Tens and CAD patients compared with control subjects (P < 0.001 for both comparisons). Furthermore, no significant differences were obtained in the risk or protective effects of renalase rs10887800 SNP against hypertension and/or CAD in both recessive and dominant genetic models (P > 0.05). According to the findings of the present study, atorvastatin and losartan therapy assumes considerable significance in alleviating hypertension, but not CAD, by increasing the renalase activity. Furthermore, it was found that renalase rs10887800 is less likely a predisposing factor for susceptibility to hypertension and/or CAD in an Iranian southeast population.

Tanshinone IIA attenuates renal damage in STZ-induced diabetic rats via inhibiting oxidative stress and inflammation

Oxidative stress and inflammation have been demonstrated to be involved in the onset and promotion of diabetic nephropathy (DN).Tanshinone IIA (Tan) possesses both antioxidant and anti-inflammatory properties. Here, the aim of the present study was to explore whether Tan could attenuate renal damage in the rats with streptozotocin (STZ)-induced diabetes and its potential mechanisms. Tan was gavaged to STZ-induced diabetic rats at the dose of 10mg/kg once a day for 12 weeks. Tan treatment significantly attenuated albuminuria and renal histopathology in diabetic rats. Besides, Tan treatment also effectively inhibited oxidative stress and inflammatory reaction in the kidneys of diabetic rats. Our study provided evidence that the protective effect of Tan on diabetes-induced renal injury is associated with inhibition of oxidative stress and inflammation. Tan may be a potential candidate for the treatment of DN.

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.

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.

Rs10887800 renalase gene polymorphism is associated with an increased risk of coronary artery disease in hemodialyzed patients

Purpose

Coronary artery disease (CAD) is common in patients with end-stage renal disease (ESRD). Recent studies have suggested that renalase, a novel FAD-dependent amine oxidase, may play an important role in the pathogenesis of cardiovascular complications in ESRD patients. The aim of the study was to investigate the association between renalase gene polymorphisms and a risk of CAD in patients on hemodialysis.

Methods

In a case–control study, a total of 309 hemodialyzed patients (107 with and 202 without CAD) were genotyped for two SNPs in the renalase gene (rs10887800 and rs2576178) using the PCR–RFLP method.

Results

By multivariate logistic regression analysis, we found that rs10887800GG genotype was associated with an increased risk of CAD under the codominant model [GG vs AA; adjusted OR 2.66 (95 % CI, 1.19–5.94), p = .017] and under the recessive model [GG vs AG + AA; adjusted OR 2.10 (95 % CI, 1.10–4.02), p = .025]. The rs2576178 polymorphism did not influence the risk of CAD.

Conclusion

The study suggested for the first time that the rs10887800 renalase gene polymorphism may be involved in the pathogenesis of CAD in hemodialyzed patients and thus could be considered a new genetic risk factor for CAD in this population.

The association study on renalase polymorphism and hypertension: a meta-analysis

Hypertension is considered a multi-factorial disease since its development is affected by both genetic and environmental factors. Intensive efforts have been focused on identifying gene(s) related to hypertension. Renalase is a recently discovered protein that expressed in kidney, heart, liver, and brain that metabolizes catecholamines, regulation of blood pressure in humans and animals. A common missense polymorphism in the flavin-adenine dinucleotide-binding domain of human renalase (Glu37Asp) has recently been described. But the reported results are not always consistent. In this meta-analysis, we examined the association between (Glu37Asp) polymorphism (rs2296545) in renalase gene and risk of hypertension. Through a systematic literature search for publications between 2007 and 2014, we summarized the data from 4 studies on polymorphism (rs2296545) in renalase gene and risk of hypertension. We did not find any association of rs2296545 with risk of hypertension in dominant model (OR=0.64; 95% CI: 0.41-1.00), recessive model (OR=1.29, 95% CI: 0.95-1.75), co-dominant model (OR=1.38, 95% CI: 0.92-2.08), and allelic model (OR=1.19; 95% CI: 0.96-1.47). The results of the present study indicated that the renalase genetic polymorphism was not associated with risk of hypertension.

Effect of Salt Intake and Potassium Supplementation on Urinary Renalase and Serum Dopamine Levels in Chinese Adults

Objective: The aim of our study was to assess the effects of altered salt and potassium intake on urinary renalase and serum dopamine levels in humans. Methods: Forty-two subjects (28-65 years of age) were selected from a rural community of northern China. All subjects were sequentially maintained on a low-salt diet for 7 days (3.0 g/day of NaCl), a high-salt diet for an additional 7 days (18.0 g/day of NaCl), and a high-salt diet with potassium supplementation for a final 7 days (18.0 g/day of NaCl + 4.5 g/day of KCl). Results: Urinary renalase excretions were significantly higher during the high-salt diet intervention than during the low-salt diet. During high-potassium intake, urinary renalase excretions were not significantly different from the high-salt diet, whereas they were significantly higher than the low-salt levels. Serum dopamine levels exhibited similar trends across the interventions. Additionally, a significant positive relationship was observed between the urine renalase and serum dopamine among the different dietary interventions. Also, 24-hour urinary sodium excretion positively correlated with urine renalase and serum dopamine in the whole population. Conclusions: The present study indicates that dietary salt intake and potassium supplementation increase urinary renalase and serum dopamine levels in Chinese subjects.

Renalase contributes to the renal protection of delayed ischaemic preconditioning via the regulation of hypoxia-inducible factor-1α

Ischaemic preconditioning (IPC) attenuates acute kidney injury (AKI) from renal ischaemia reperfusion. Renalase, an amine oxidase secreted by the proximal tubule, not only degrades circulating catecholamines but also protects against renal ischaemia reperfusion injury. Here, it has been suggested that the renoprotective effect of renal IPC is partly mediated by renalase. In a model of brief intermittent renal IPC, the increased cortex renalase expression was found to last for 48 hrs. IPC significantly reduced renal tubular inflammation, necrosis and oxidative stress following renal ischaemia reperfusion injury. Such effects were attenuated by blocking renalase with an anti-renalase monoclonal antibody. We further demonstrated that renalase expression was up-regulated by hypoxia in vitro via an hypoxia-inducible factor (HIF)-1α mechanism. The IPC-induced up-regulation of renalase in vivo was also reduced by pre-treatment with an HIF-1α inhibitor, 3-(5′-Hydroxymethyl-2′-furyl)-1-benzyl indazole. In summary, the renoprotective effect of IPC is partly dependent on the renalase expression, which may be triggered by hypoxia via an HIF-1α mechanism. Endogenous renalase shows potential as a therapeutic agent for the prevention and treatment of AKI.

Renalase, kidney and cardiovascular disease: are they related or just coincidentally associated?

Cardiovascular diseases, including hypertension are the leading cause of death in the developed countries. Diabetes and chronic kidney disease became also more prevalent reaching almost the level of epidemy. Researchers are looking eagerly for the new risk and/or pathogenetic factors, as well as therapeutic option in these disease. It has been suggested that human kidney releases a protein named renalase into the bloodstream. It is supposed to be an enzyme which breaks down catecholamines in the blood circulation and regulate blood pressure. However, there were several doubts whether renalase exerts monoaminooxidase activity, or if it is monoaminooxidase at all. Recently, a hypothesis that it is also a cytokine was postulated. Studies on renalase polymorphisms in hypertension, cardiovascular disease or diabetes are inconsistent. Similarly, there are several discrepancies in the animal on the possible role of renalase in hypertension and cardiovascular diseases. Some studies report a protective role of renalase in acute kidney injury, whereas others showed that renalase levels were mainly dependent on kidney function, indicating rather a role of kidney in excretion of this substance. Moreover, validated assays are needed to evaluate renalase levels and activity. On one hand a deeper and more accurate link between renalase and cardiovascular diseases require further profound research, on the other hand whether or not renalase protein could be a new therapeutic target in these pathologies should also be considered. Whether renalase, discovered in 2005, might be a Holy Grail of hypertension, linking kidney and cardiovascular diseases, remains to be proven.

Renalase protects against contrast-induced nephropathy in Sprague-Dawley rats

Background

Contrast-induced nephropathy (CIN) is the third leading cause of hospital-acquired acute renal failure. Oxidative stress, apoptosis and inflammation play crucial roles in CIN. Renalase is a newly discovered monoamine oxidase from the kidney. We hypothesize that renalase could protect against CIN through anti-oxidation, anti-inflammation and anti-apoptosis pathways.

Methods

We tested our hypothesis in vivo with a rat model of Ioversol-induced CIN and in vitro. Sprague-Dawley rats were divided into 4 groups (n = 6 per group): control group, Ioversol group (rats subjected to Ioversol-induced CIN), Ioversol plus vehicle group (CIN rats pretreated with vehicle) and Ioversol plus renalase group (CIN rats pretreated with 2 mg/kg recombinant renalase). HK2 cells were treated with Ioversol or H₂O₂.

Results

The results showed that pretreatment with renalase attenuated the deterioration of renal function, tubular necrosis, oxidative stress, apoptosis and inflammation (P<0.05). Furthermore, renalase protected HK2 cells against the cytotoxicity of Ioversol and suppressed Caspase-3 activity, oxidative stress and apoptosis induced by H₂O₂.

Conclusion

Recombinant renalase protected CIN in rats through anti-oxidation, anti-apoptosis and anti-inflammation mechanisms.

Magnolin protects against contrast-induced nephropathy in rats via antioxidation and antiapoptosis

Background. Magnolin is the major active ingredient of the herb Magnolia fargesii which has anti-inflammatory and antioxidative effects. Oxidative stress and apoptosis are involved in the pathogenesis of contrast-induced nephropathy (CIN). We hypothesize that Magnolin could protect against CIN through antioxidative and antiapoptotic properties. Methods. To test whether Magnolin could attenuate CIN, oxidative stress and apoptosis, in vivo and in vitro, we utilized a rat model of ioversol-induced CIN and a cell model of oxidative stress in which HK2 cells were treated with H₂O₂. Rats were assigned to 4 groups (n = 6 per group): control group, ioversol group (ioversol-induced CIN), vehicle group (CIN rats pretreated with vehicle), and Magnolin group (CIN rats pretreated with 1 mg/kg Magnolin). Results. The results showed that magnolin ameliorated the renal tubular necrosis, apoptosis, and the deterioration of renal function (P < 0.05). Furthermore, Magnolin reduced the renal oxidative stress, suppressed caspase-3 activity, and increased Bcl-2 expression in vivo and in vitro. Conclusion. Magnolin might protect CIN in rats through antioxidation and antiapoptosis.

Effect of salt intake and potassium supplementation on serum renalase levels in Chinese adults: a randomized trial

Renalase, a recently discovered enzyme released by the kidneys, breaks down blood-borne catecholamines and may thus regulate blood pressure (BP). Animal studies have suggested that high levels of dietary salt might reduce blood and kidney renalase levels. We conducted a randomized trial to assess the effects of altered salt and potassium intake on serum renalase levels and the relationship between serum renalase levels and BP in humans.Forty-two subjects (28-65 years of age) were selected from a rural community of northern China. All subjects were sequentially maintained on a low-salt diet for 7 days (3.0 g/day of NaCl), a high-salt diet for additional 7 days (18.0 g/day of NaCl), and a high-salt diet with potassium supplementation for final 7 days (18.0 g/day of NaCl + 4.5 g/day of KCl).Serum renalase levels were significantly higher than baseline levels during the low-salt diet intervention period. Renalase levels decreased with the change from the low-salt to high-salt diet, whereas dietary potassium prevented the decrease in serum renalase induced by the high-salt diet. There was a significant inverse correlation between the serum renalase level and 24-h urinary sodium excretion. No significant correlation was found between the renalase level and BP among the different dietary interventions.The present study indicates that variations in dietary salt intake and potassium supplementation affect the serum renalase concentration in Chinese subjects.

Renalase, a new secretory enzyme: Its role in hypertensive-ischemic cardiovascular diseases

Abstract Renalase, a novel amine oxidase, is mainly expressed in the kidney, heart, and skeletal muscle. It has been known to degrade circulating catecholamines and plays a crucial role in human diseases. Recent studies have demonstrated its structure, unique bioactivities, function, and the gene polymorphisms in human diseases. In this review, we summarize the effects of renalase on hypertension, myocardial ischemia, acute kidney injury (AKI), ischemic stroke, cardiac dysfunction, organ transplantation, and diabetes mellitus reported in numerous studies.

Plasma and urine renalase levels and activity during the recovery of renal function in kidney transplant recipients

Renalase is a recently described enzyme secreted by the kidney into both plasma and urine, where it was suggested to degrade catecholamines contributing to blood pressure control. While there is a controversy regarding the relationship between renal function and plasma renalase levels, there is virtually no data in humans on plasma renalase activity as well as on both urine renalase levels and activity. We prospectively examined the time course of plasma and urine renalase levels and activity in 26 end-stage renal disease (ESRD) patients receiving a cadaver kidney transplant (cadaver kidney recipients [CKR]) before surgery and during the recovery of renal function up to day 90 post transplant. The relationship with sympathetic and renal dopaminergic activities was also evaluated. The recovery of renal function in CKR closely predicted decreases in plasma renalase levels ( r = 0.88; P < 0.0001), urine renalase levels ( r = 0.75; P < 0.0001) and urine renalase activity ( r = 0.56; P < 0.03), but did not predict changes in plasma renalase activity ( r = −0.02; NS). Plasma norepinephrine levels positively correlated with plasma renalase levels ( r = 0.64, P < 0.002) as well as with urine renalase levels and activity ( r = 0.47 P < 0.02; r = 0.71, P < 0.0005, respectively) and negatively correlated with plasma renalase activity ( r = −0.57, P < 0.002). By contrast, plasma epinephrine levels positively correlated with plasma renalase activity ( r = 0.67, P < 0.0001) and negatively correlated with plasma renalase levels ( r = −0.62, P < 0.003). A significant negative relationship was observed between urine dopamine output and urine renalase levels ( r = −0.48; P < 0.03) but not with urine renalase activity ( r = −0.33, NS). We conclude that plasma and urine renalase levels closely depend on renal function and sympathetic nervous system activity. It is suggested that epinephrine-mediated activation of circulating renalase may occur in renal transplant recipients with good recovery of renal function. The increase in plasma renalase activity observed in ESRD patients and renal transplant recipients can be explained on the basis of reduced inhibition of the circulating enzyme.

Normal values for urine renalase excretion in children

BACKGROUND

The objective of this study was to establish age-dependent values for urinary renalase/creatinine (renalase/Cr) ratio in healthy children and adolescents.

METHODS

The study was conducted on a random sample of 157 healthy children and adolescents (0.1-17.9 years) divided into six age groups in 3-year intervals. Urine renalase concentration was measured using an enzyme-linked immunosorbent assay (ELISA) kit (Uscn Life Science, Wuhan, China).

RESULTS

We analyzed median urine renalase/Cr ratio in particular age groups with the use of analysis of variance (ANOVA). Renalase/Cr levels were significantly higher in the youngest children < 3 years in comparison with other age groups (4.07 ng/mg Cr, p < 0.05). There was a statistically significant negative correlation between urine renalase/Cr and body mass index (BMI) Z-score (r = -0.22, p < 0.05) and both systolic (r = -0.22, p < 0.05) and diastolic (r = -0.21, p < 0.05) blood pressure. We constructed the reference renalase/Cr percentiles according to age in 3-year intervals.

CONCLUSIONS

To the best of our knowledge, this study is the first to present reference values of urine renalase excretion in a healthy pediatric population. Further studies should concentrate on the influence of increased blood pressure or obesity on urine renalase excretion in children and teenagers.

Construction of the coding sequence of the transcription variant 2 of the human Renalase gene and its expression in the prokaryotic system

Renalase is a recently discovered protein, involved in regulation of blood pressure in humans and animals. Although several splice variants of human renalase mRNA transcripts have been recognized, only one protein product, hRenalase1, has been found so far. In this study, we have used polymerase chain reaction (PCR)-based amplification of individual exons of the renalase gene and their joining for construction of full-length hRenalase2 coding sequence followed by expression of hRenalase2 as a polyHis recombinant protein in Escherichia coli cells. To date this is the first report on synthesis and purification of hRenalase2. Applicability of this approach was verified by constructing hRenalase1 coding sequence, its sequencing and expression in E. coli cells. hRenalase1 was used for generation of polyclonal antiserum in sheep. Western blot analysis has shown that polyclonal anti-renalase1 antibodies effectively interact with the hRenalase2 protein. The latter suggests that some functions and expression patterns of hRenalase1 documented by antibody-based data may be attributed to the presence of hRenalase2. The realized approach may be also used for construction of coding sequences of various (especially weakly expressible) genes, their transcript variants, etc.