Inhibition of renalase expression and signaling has antitumor activity in pancreatic cancer

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.

APOBEC-1 deletion enhances cisplatin-induced acute kidney injury

Cisplatin (CP) induces acute kidney injury (AKI) whereby proximal tubules undergo regulated necrosis. Repair is almost complete after a single dose. We now demonstrate a role for Apolipoprotein B mRNA editing enzyme, catalytic polypeptide 1 (Apobec-1) that is prominently expressed at the interface between acute and chronic kidney injury (CKD), in the recovery from AKI. Apobec-1 knockout (KO) mice exhibited greater mortality than in wild type (WT) and more severe AKI in both CP- and unilateral ischemia reperfusion (IR) with nephrectomy. Specifically, plasma creatinine (pCr) 2.6 ± 0.70 mg/dL for KO, n = 10 and 0.16 ± 0.02 for WT, n = 6, p < 0.0001 in CP model and 1.34 ± 0.22 mg/dL vs 0.75 ± 0.06, n = 5, p < 0.05 in IR model. The kidneys of Apobec-1 KO mice showed increased necrosis, increased expression of KIM-1, NGAL, RIPK1, ASCL4 and increased lipid accumulation compared to WT kidneys (p < 0.01). Neutrophils and activated T cells were both increased, while macrophages were reduced in kidneys of Apobec-1 KO animals. Overexpression of Apobec-1 in mouse proximal tubule cells protected against CP-induced cytotoxicity. These findings suggest that Apobec-1 mediates critical pro-survival responses to renal injury and increasing Apobec-1 expression could be an effective strategy to mitigate AKI.

The Multi-Faceted Nature of Renalase for Mitochondrial Dysfunction Improvement in Cardiac Disease

The cellular mechanisms and signaling network that guide the cardiac disease pathophysiology are inextricably intertwined, which explains the current scarcity of effective therapy and to date remains the greatest challenge in state-of-the-art cardiovascular medicine. Accordingly, a novel concept has emerged in which cardiomyocytes are the centerpiece of therapeutic targeting, with dysregulated mitochondria as a critical point of intervention. Mitochondrial dysfunction pluralism seeks a multi-faceted molecule, such as renalase, to simultaneously combat the pathophysiologic heterogeneity of mitochondria-induced cardiomyocyte injury. This review provides some original perspectives and, for the first time, discusses the functionality spectrum of renalase for mitochondrial dysfunction improvement within cardiac disease, including its ability to preserve mitochondrial integrity and dynamics by suppressing mitochondrial ΔΨm collapse; overall ATP content amelioration; a rise of mtDNA copy numbers; upregulation of mitochondrial genes involved in oxidative phosphorylation and cellular vitality promotion; mitochondrial fission inhibition; NAD⁺ supplementation; sirtuin upregulation; and anti-oxidant, anti-apoptotic, and anti-inflammatory traits. If verified that renalase, due to its multi-faceted nature, behaves like the "guardian of mitochondria" by thwarting pernicious mitochondrial dysfunction effects and exerting therapeutic potential to target mitochondrial abnormalities in failing hearts, it may provide large-scale benefits for cardiac disease patients, regardless of the underlying causes.

Cyclic-AMP response element binding protein (CREB) and microRNA miR-29b regulate renalase gene expression under catecholamine excess conditions

AIMS

Renalase, a key mediator of cross-talk between kidneys and sympathetic nervous system, exerts protective roles in various cardiovascular/renal disease states. However, molecular mechanisms underpinning renalase gene expression remain incompletely understood. Here, we sought to identify the key molecular regulators of renalase under basal/catecholamine-excess conditions.

MATERIALS AND METHODS

Identification of the core promoter domain of renalase was carried out by promoter-reporter assays in N2a/HEK-293/H9c2 cells. Computational analysis of the renalase core promoter domain, over-expression of cyclic-AMP-response-element-binding-protein (CREB)/dominant negative mutant of CREB, ChIP assays were performed to determine the role of CREB in transcription regulation. Role of the miR-29b-mediated-suppression of renalase was validated in-vivo by using locked-nucleic-acid-inhibitors of miR-29. qRT-PCR and Western-blot analyses measured the expression of renalase, CREB, miR-29b and normalization controls in cell lysates/ tissue samples under basal/epinephrine-treated conditions.

KEY FINDINGS

CREB, a downstream effector in epinephrine signaling, activated renalase expression via its binding to the renalase-promoter. Physiological doses of epinephrine and isoproteronol enhanced renalase-promoter activity and endogenous renalase protein level while propranolol diminished the promoter activity and endogenous renalase protein level indicating a potential role of beta-adrenergic receptor in renalase gene regulation. Multiple animal models (acute exercise, genetically hypertensive/stroke-prone mice/rat) displayed directionally-concordant expression of CREB and renalase. Administration of miR-29b inhibitor in mice upregulated endogenous renalase expression. Moreover, epinephrine treatment down-regulated miR-29b promoter-activity/transcript levels.

SIGNIFICANCE

This study provides evidence for renalase gene regulation by concomitant transcriptional activation via CREB and post-transcriptional attenuation via miR-29b under excess epinephrine conditions. These findings have implications for disease states with dysregulated catecholamines.

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.

Value of serological markers for early diagnosis and prognosis prediction of pancreatic cancer

Pancreatic cancer (PC) is a kind of malignant tumor with a poor prognosis. Its incidence rate is almost equal to the mortality rate, which shows an increasing trend, especially in recent years. At present, the radical cure of pancreatic cancer is mainly achieved by surgery, but the complex pathophysiology, the lack of early diagnosis and prognostic markers, and low surgical survival rate are the main obstacles to surgical treatment of pancreatic cancer. Serological markers are sensitive biological markers, and they have been used in recent years for the diagnosis and prediction of the prognosis of patients with postoperative pancreatic cancer. Therefore, serum markers are of vital importance in pancreatic cancer. This article summarizes various serological markers for early diagnosis and prognosis prediction of pancreatic cancer to provide a theoretical reference for clinical workers.

Renalase Challenges the Oxidative Stress and Fibroproliferative Response in COVID-19

The hallmark of the coronavirus disease 2019 (COVID-19) pathophysiology was reported to be an inappropriate and uncontrolled immune response, evidenced by activated macrophages, and a robust surge of proinflammatory cytokines, followed by the release of reactive oxygen species, that synergistically result in acute respiratory distress syndrome, fibroproliferative lung response, and possibly even death. For these reasons, all identified risk factors and pathophysiological processes of COVID-19, which are feasible for the prevention and treatment, should be addressed in a timely manner. Accordingly, the evolving anti-inflammatory and antifibrotic therapy for severe COVID-19 and hindering post-COVID-19 fibrosis development should be comprehensively investigated. Experimental evidence indicates that renalase, a novel amino-oxidase, derived from the kidneys, exhibits remarkable organ protection, robustly addressing the most powerful pathways of cell trauma: inflammation and oxidative stress, necrosis, and apoptosis. As demonstrated, systemic renalase administration also significantly alleviates experimentally induced organ fibrosis and prevents adverse remodeling. The recognition that renalase exerts cytoprotection via sirtuins activation, by raising their NAD⁺ levels, provides a “proof of principle” for renalase being a biologically impressive molecule that favors cell protection and survival and maybe involved in the pathogenesis of COVID-19. This premise supports the rationale that renalase's timely supplementation may prove valuable for pathologic conditions, such as cytokine storm and related acute respiratory distress syndrome. Therefore, the aim for this review is to acknowledge the scientific rationale for renalase employment in the experimental model of COVID-19, targeting the acute phase mechanisms and halting fibrosis progression, based on its proposed molecular pathways. Novel therapies for COVID-19 seek to exploit renalase's multiple and distinctive cytoprotective mechanisms; therefore, this review should be acknowledged as the thorough groundwork for subsequent research of renalase's employment in the experimental models of COVID-19.

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.

The Scientific Rationale for the Introduction of Renalase in the Concept of Cardiac Fibrosis

Cardiac fibrosis represents a redundant accumulation of extracellular matrix proteins, resulting from a cascade of pathophysiological events involved in an ineffective healing response, that eventually leads to heart failure. The pathophysiology of cardiac fibrosis involves various cellular effectors (neutrophils, macrophages, cardiomyocytes, fibroblasts), up-regulation of profibrotic mediators (cytokines, chemokines, and growth factors), and processes where epithelial and endothelial cells undergo mesenchymal transition. Activated fibroblasts and myofibroblasts are the central cellular effectors in cardiac fibrosis, serving as the main source of matrix proteins. The most effective anti-fibrotic strategy will have to incorporate the specific targeting of the diverse cells, pathways, and their cross-talk in the pathogenesis of cardiac fibroproliferation. Additionally, renalase, a novel protein secreted by the kidneys, is identified. Evidence demonstrates its cytoprotective properties, establishing it as a survival element in various organ injuries (heart, kidney, liver, intestines), and as a significant anti-fibrotic factor, owing to its, in vitro and in vivo demonstrated pleiotropy to alleviate inflammation, oxidative stress, apoptosis, necrosis, and fibrotic responses. Effective anti-fibrotic therapy may seek to exploit renalase’s compound effects such as: lessening of the inflammatory cell infiltrate (neutrophils and macrophages), and macrophage polarization (M1 to M2), a decrease in the proinflammatory cytokines/chemokines/reactive species/growth factor release (TNF-α, IL-6, MCP-1, MIP-2, ROS, TGF-β1), an increase in anti-apoptotic factors (Bcl2), and prevention of caspase activation, inflammasome silencing, sirtuins (1 and 3) activation, and mitochondrial protection, suppression of epithelial to mesenchymal transition, a decrease in the pro-fibrotic markers expression (’α-SMA, collagen I, and III, TIMP-1, and fibronectin), and interference with MAPKs signaling network, most likely as a coordinator of pro-fibrotic signals. This review provides the scientific rationale for renalase’s scrutiny regarding cardiac fibrosis, and there is great anticipation that these newly identified pathways are set to progress one step further. Although substantial progress has been made, indicating renalase’s therapeutic promise, more profound experimental work is required to resolve the accurate underlying mechanisms of renalase, concerning cardiac fibrosis, before any potential translation to clinical investigation.

Inhibition of renalase drives tumour rejection by promoting T cell activation

BACKGROUND

Although programmed cell death protein 1 (PD-1) inhibitors have revolutionised treatment for advanced melanoma, not all patients respond. We previously showed that inhibition of the flavoprotein renalase (RNLS) in preclinical melanoma models decreases tumour growth. We hypothesised that RNLS inhibition promotes tumour rejection by effects on the tumour microenvironment (TME).

METHODS

We used two distinct murine melanoma models, studied in RNLS knockout (KO) or wild-type (WT) mice. WT mice were treated with the anti-RNLS antibody, m28, with or without anti-PD-1. 10X single-cell RNA-sequencing was used to identify transcriptional differences between treatment groups, and tumour cell content was interrogated by flow cytometry. Samples from patients treated with immunotherapy were examined for RNLS expression by quantitative immunofluorescence.

RESULTS

RNLS KO mice injected with wild-type melanoma cells reject their tumours, supporting the importance of RNLS in cells in the TME. This effect was blunted by anti-cluster of differentiation 3. However, MØ-specific RNLS ablation was insufficient to abrogate tumour formation. Anti-RNLS antibody treatment of melanoma-bearing mice resulted in enhanced T cell infiltration and activation and resulted in immune memory on rechallenging mice with injection of melanoma cells. At the single-cell level, treatment with anti-RNLS antibodies resulted in increased tumour density of MØ, neutrophils and lymphocytes and increased expression of IFNγ and granzyme B in natural killer cells and T cells. Intratumoural Forkhead Box P3 + CD4 cells were decreased. In two distinct murine melanoma models, we showed that melanoma-bearing mice treated with anti-RNLS antibodies plus anti-PD-1 had superior tumour shrinkage and survival than with either treatment alone. Importantly, in pretreatment samples from patients treated with PD-1 inhibitors, high RNLS expression was associated with decreased survival (log-rank P = 0.006), independent of other prognostic variables.

CONCLUSIONS

RNLS KO results in melanoma tumour regression in a T-cell-dependent fashion. Anti-RNLS antibodies enhance anti-PD-1 activity in two distinct aggressive murine melanoma models resistant to PD-1 inhibitors, supporting the development of anti-RNLS antibodies with PD-1 inhibitors as a novel approach for melanomas poorly responsive to anti-PD-1.

Renalase and its receptor, PMCA4b, are expressed in the placenta throughout the human gestation

Placental function requires organized growth, transmission of nutrients, and an anti-inflammatory milieu between the maternal and fetal interface, but placental factors important for its function remain unclear. Renalase is a pro-survival, anti-inflammatory flavoprotein found to be critical in other tissues. We examined the potential role of renalase in placental development. PCR, bulk RNA sequencing, immunohistochemistry, and immunofluorescence for renalase and its binding partners, PMCA4b and PZP, were performed on human placental tissue from second-trimester and full-term placentas separated into decidua, placental villi and chorionic plates. Quantification of immunohistochemistry was used to localize renalase across time course from 17 weeks to term. Endogenous production of renalase was examined in placental tissue and organoids. Renalase and its receptor PMCA4b transcripts and proteins were present in all layers of the placenta. Estimated RNLS protein levels did not change with gestation in the decidual samples. However, placental villi contained more renalase immunoreactive cells in fetal than full-term placental samples. RNLS co-labeled with markers for Hofbauer cells and trophoblasts within the placental villi. Endogenous production of RNLS, PMCA4b, and PZP by trophoblasts was validated in placental organoids. Renalase is endogenously expressed throughout placental tissue and specifically within Hofbauer cells and trophoblasts, suggesting a potential role for renalase in placental development and function. Future studies should assess renalase's role in normal and diseased human placenta.

Kidney-Targeted Renalase Agonist Prevents Cisplatin-Induced Chronic Kidney Disease by Inhibiting Regulated Necrosis and Inflammation

BACKGROUND

Repeated administration of cisplatin causes CKD. In previous studies, we reported that the kidney-secreted survival protein renalase (RNLS) and an agonist peptide protected mice from cisplatin-induced AKI.

METHODS

To investigate whether kidney-targeted delivery of RNLS might prevent cisplatin-induced CKD in a mouse model, we achieved specific delivery of a RNLS agonist peptide (RP81) to the renal proximal tubule by encapsulating the peptide in mesoscale nanoparticles (MNPs). We used genetic deletion of RNLS, single-cell RNA sequencing analysis, and Western blotting to determine efficacy and to explore underlying mechanisms. We also measured plasma RNLS in patients with advanced head and neck squamous cell carcinoma receiving their first dose of cisplatin chemotherapy.

RESULTS

In mice with CKD induced by cisplatin, we observed an approximate 60% reduction of kidney RNLS; genetic deletion of RNLS was associated with significantly more severe cisplatin-induced CKD. In this severe model of cisplatin-induced CKD, systemic administration of MNP-encapsulated RP81 (RP81-MNP) significantly reduced CKD as assessed by plasma creatinine and histology. It also decreased inflammatory cytokines in plasma and inhibited regulated necrosis in kidney. Single-cell RNA sequencing analyses revealed that RP81-MNP preserved epithelial components of the nephron and the vasculature and suppressed inflammatory macrophages and myofibroblasts. In patients receiving their first dose of cisplatin chemotherapy, plasma RNLS levels trended lower at day 14 post-treatment.

CONCLUSIONS

Kidney-targeted delivery of RNLS agonist RP81-MNP protects against cisplatin-induced CKD by decreasing cell death and improving the viability of the renal proximal tubule. These findings suggest that such an approach might mitigate the development of CKD in patients receiving cisplatin cancer chemotherapy.

RENALASE: DISCOVERY, BIOLOGY, AND THERAPEUTIC APPLICATIONS

While investigating the mechanisms that could mediate the significant burden of cardiovascular complications observed in persons with chronic kidney disease (CKD) and end stage renal disease (ESRD), we identified a previously unknown protein, which we named renalase (RNLS). Over the past 15 years, our understanding of the biology, physiology, and pathophysiology of RNLS has matured. Here we aim to highlight that RNLS is a bifunctional protein. It metabolizes intracellular nicotinamide adenine dinucleotide (NADH), modulates mitochondrial function, and protects energy metabolism. When secreted outside the cell, independent of its enzymatic properties, it functions as a signaling molecule that mediates resistance to stressful stimuli and promotes cell and organ survival. RNLS has been shown to modulate the severity of acute injury to the pancreas, liver, kidney, and heart. It also protects against the development of chronic injury, and here we highlight the potential use of exogenous RNLS peptide agonists to prevent cisplatin-mediated CKD (CP-CKD).

Renalase is a novel tissue and serological biomarker in pancreatic ductal adenocarcinoma

Dysregulated expression of the secretory protein renalase can promote pancreatic ductal adenocarcinoma (PDAC) growth in animal models. We characterized renalase expression in premalignant and malignant PDAC tissue and investigated whether plasma renalase levels corresponded to clinical PDAC characteristics. Renalase immunohistochemistry was used to determine the presence and distribution of renalase in normal pancreas, chronic pancreatitis, PDAC precursor lesions, and PDAC tissues. Associations between pretreatment plasma renalase and PDAC clinical status were assessed in patients with varied clinical stages of PDAC and included tumor characteristics, surgical resection in locally advanced/borderline resectable PDAC, and overall survival. Data were retrospectively obtained and correlated using non-parametric analysis. Little to no renalase was detected by histochemistry in the normal pancreatic head in the absence of abdominal trauma. In chronic pancreatitis, renalase immunoreactivity localized to peri-acinar spindle-shaped cells in some samples. It was also widely present in PDAC precursor lesions and PDAC tissue. Among 240 patients with PDAC, elevated plasma renalase levels were associated with worse tumor characteristics, including greater angiolymphatic invasion (80.0% vs. 58.1%, p = 0.012) and greater node positive disease (76.5% vs. 56.5%, p = 0.024). Overall survival was worse in patients with high plasma renalase levels with median follow-up of 27.70 months vs. 65.03 months (p < 0.001). Renalase levels also predicted whether patients with locally advanced/borderline resectable PDAC underwent resection (AUC 0.674; 95%CI 0.42-0.82, p = 0.04). Overall tissue renalase was increased in both premalignant and malignant PDAC tissues compared to normal pancreas. Elevated plasma renalase levels were associated with advanced tumor characteristics, decreased overall survival, and reduced resectability in patients with locally advanced/borderline resectable PDAC. These studies show that renalase levels are increased in premalignant pancreatic tissues and that its levels in plasma correspond to the clinical behavior of PDAC.

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.

Renalase improves pressure overload-induced heart failure in rats by regulating extracellular signal-regulated protein kinase 1/2 signaling

Renalase, a novel flavoprotein that is mainly expressed in the kidney and heart, plays a crucial role in hypertension. Recent studies have shown that renalase is expressed at low levels in the serum of patients with heart failure, while the role of renalase and its mechanism in cardiac failure is unclear. Adult Sprague-Dawley (SD) rats were used to investigate the role and function of renalase in the pathological process of transverse aortic constriction (TAC)-induced heart failure. Renalase-human protein chip analysis showed that renalase was directly associated with P38 and extracellular signal-regulated protein kinase 1/2 (ERK1/2) signaling. We further used lentivirus-mediated RNA interference to study the role of renalase in the progression of pathological ventricular hypertrophy and found that renalase inhibition attenuated the noradrenaline-induced hypertrophic response in vitro or the pressure overload-induced hypertrophic response in vivo. Recombinant renalase protein significantly alleviated pressure overload-induced cardiac failure and was associated with P38 and ERK1/2 signaling. These findings demonstrate that renalase is a potential biomarker of hypertrophy and that exogenous recombinant renalase is a potential and novel drug for heart failure.

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.

A protective role of renalase in diabetic nephropathy

Renalase, a recently discovered secreted flavoprotein, exerts anti-apoptotic and anti-inflammatory effects against renal injury in acute and chronic animal models. However, whether Renalase elicits similar effects in the development of diabetic nephropathy (DN) remains unclear. The studies presented here tested the hypothesis that Renalase may play a key role in the development of DN and may have therapeutic potential for DN. Renalase expression was measured in human kidney biopsies with DN and in kidneys of db/db mice. The role of Renalase in the development of DN was examined using a genetically engineered mouse model: Renalase knockout mice with db/db background. The renoprotective effects of Renalase in DN was evaluated in db/db mice with Renalase overexpression. In addition, the effects of Renalase on high glucose-induced mesangial cells were investigated. Renalase was down-regulated in human diabetic kidneys and in kidneys of db/db mice compared with healthy controls or db/m mice. Renalase homozygous knockout increased arterial blood pressure significantly in db/db mice while heterozygous knockout did not. Renalase heterozygous knockout resulted in elevated albuminuria and increased renal mesangial expansion in db/db mice. Mesangial hypertrophy, renal inflammation, and pathological injury in diabetic Renalase heterozygous knockout mice were significantly exacerbated compared with wild-type littermates. Moreover, Renalase overexpression significantly ameliorated renal injury in db/db mice. Mechanistically, Renalase attenuated high glucose-induced profibrotic gene expression and p21 expression through inhibiting extracellular regulated protein kinases (ERK1/2). The present study suggested that Renalase protected against the progression of DN and might be a novel therapeutic target for the treatment of DN.

Engineering Genetic Predisposition in Human Neuroepithelial Stem Cells Recapitulates Medulloblastoma Tumorigenesis

Human neural stem cell cultures provide progenitor cells that are potential cells of origin for brain cancers. However, the extent to which genetic predisposition to tumor formation can be faithfully captured in stem cell lines is uncertain. Here, we evaluated neuroepithelial stem (NES) cells, representative of cerebellar progenitors. We transduced NES cells with MYCN, observing medulloblastoma upon orthotopic implantation in mice. Significantly, transcriptomes and patterns of DNA methylation from xenograft tumors were globally more representative of human medulloblastoma compared to a MYCN-driven genetically engineered mouse model. Orthotopic transplantation of NES cells generated from Gorlin syndrome patients, who are predisposed to medulloblastoma due to germline-mutated PTCH1, also generated medulloblastoma. We engineered candidate cooperating mutations in Gorlin NES cells, with mutation of DDX3X or loss of GSE1 both accelerating tumorigenesis. These findings demonstrate that human NES cells provide a potent experimental resource for dissecting genetic causation in medulloblastoma.

Where Is Dopamine and how do Immune Cells See it?: Dopamine-Mediated Immune Cell Function in Health and Disease

Dopamine is well recognized as a neurotransmitter in the brain, and regulates critical functions in a variety of peripheral systems. Growing research has also shown that dopamine acts as an important regulator of immune function. Many immune cells express dopamine receptors and other dopamine related proteins, enabling them to actively respond to dopamine and suggesting that dopaminergic immunoregulation is an important part of proper immune function. A detailed understanding of the physiological concentrations of dopamine in specific regions of the human body, particularly in peripheral systems, is critical to the development of hypotheses and experiments examining the effects of physiologically relevant dopamine concentrations on immune cells. Unfortunately, the dopamine concentrations to which these immune cells would be exposed in different anatomical regions are not clear. To address this issue, this comprehensive review details the current information regarding concentrations of dopamine found in both the central nervous system and in many regions of the periphery. In addition, we discuss the immune cells present in each region, and how these could interact with dopamine in each compartment described. Finally, the review briefly addresses how changes in these dopamine concentrations could influence immune cell dysfunction in several disease states including Parkinson's disease, multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease, as well as the collection of pathologies, cognitive and motor symptoms associated with HIV infection in the central nervous system, known as NeuroHIV. These data will improve our understanding of the interactions between the dopaminergic and immune systems during both homeostatic function and in disease, clarify the effects of existing dopaminergic drugs and promote the creation of new therapeutic strategies based on manipulating immune function through dopaminergic signaling. Graphical Abstract.

Elevated renalase levels in patients with acute coronary microvascular dysfunction - A possible biomarker for ischemia

AIMS

We explored the relationship between inflammation, renalase an anti-inflammatory protein, and acute chest pain with coronary microvascular dysfunction (CMD).

METHODS AND RESULTS

We used cardiac Rb-82 PET/CT imaging to diagnose coronary artery disease (CAD/CALC) (defect or coronary calcification) and CMD (depressed coronary flow reserve without CAD) in patients with chest pain in an emergency department (ED). Blood samples were collected pre-imaging within 24 h of ED presentation and were analyzed for renalase and inflammatory markers including C-reactive protein, interleukins, interferon gamma, tumor necrosis factor, vascular endothelial growth factor, and metalloproteinases. Exclusions were age ≤30 years, myocardial infarction, hemodynamic instability, hypertensive crisis, heart failure or dialysis. Between 6/2014 and 11/2015, 80 patients undergoing PET/CT provided blood and were categorized as normal (18%), CAD/CALC (27%) and CMD (55%). Median renalase values were highest in patients with CMD (5503 ng/ml; IQR 3070) compared to patients with normal flows (4266 ng/ml; IQR 1503; p = 0.02) or CAD/CALC (4069 ng/ml IQR 1850; p = 0.004). CMD patients had similar median values for inflammatory markers as normal patients (p > 0.05). Renalase remained an independent predictor of CMD (OR 1.34; 95% CI = 1.1-1.7, per 1000 ng/ml) after adjustment for smoking, family history, obesity and Framingham risk score. In a model for CMD diagnosis with Framingham risk score, typical angina history and CRP, renalase improved discrimination from C-statistic = 0.60 (95% CI 0.47, 0.73) to 0.70 (95% CI, 0.59-0.82).

CONCLUSION

We found elevated renalase in response to ischemia from acute CMD. Its role as a biomarker needs validation in larger trials.

Influence of acute exercise on renalase and its regulatory mechanism

AIMS

Renalase expression in the kidneys and liver is regulated by nuclear factor (NF)-κB, Sp1, and hypoxia-inducible factor (HIF)-1α. The dynamics of renalase expression in acute exercise, and its mechanism and physiological effects are unclear. We evaluated the effect of different exercise intensities on renalase expression and examined its mechanism and physiological effects.

MAIN METHODS

21 male Wistar rats ran for 30 min on a treadmill after resting for 15 min. The sedentary group rested on the treadmill while the exercise group ran for 30 min at 10 or 30 m/min. Skeletal muscles, the kidney, heart, liver, and blood samples were collected after exercise. The expression of renalase and phosphate IkB-α and Akt was measured by western blotting, while HIF-1α, Sp1, MuRF-1, and MAFbx were measured in the skeletal muscle by real-time RT-PCR.

KEY FINDINGS

Renalase expression in skeletal muscles increased after acute exercise, while its expression in the kidneys, heart, and liver decreased. NF-κB regulated renalase expression in the plantaris muscle and that of HIF-1α in the soleus muscle. Phosphate Akt in the plantaris muscle significantly increased in the 30 m/min group compared with that in the sedentary group. MuRF-1 in the plantaris did not change between these groups.

SIGNIFICANCE

Renalase expression in skeletal muscles increased after acute exercise but decreased in other tissues. This increase may be a response to exercise-induced oxidative stress. Furthermore, NF-κB in the plantaris muscle may mainly regulate renalase expression, and support a relationship with the cell protective effects of renalase.

Renalase overexpression in ER-positive breast cancer

OBJECTIVES

To explore the expression and pathologic significance of renalase in tumor tissues of different molecular subtypes of breast cancer.

DESIGN

Immunofluorescence methods and laser confocal scanning microscope observations were used to detect expression of renalase, estrogen receptor (ER), phospho-extracellular signal-regulated kinase 1 and 2 (p-ERK1/2), and phospho-signal transducer and activator of transcription (p-STAT3) in 58 cases of breast cancer tissue, 11 normal tissues, and 14 benign fibroadenomas. Statistical analysis of its expression in different molecular subtypes of breast cancer was employed.

RESULTS

Compared with control tissue (benign lesions and normal breast tissue), renalase was highly expressed in invasive breast cancer and the difference was significant (P<0.0001). Renalase was also expressed significantly higher in ER-positive breast cancer, compared with control tissue (P<0.0001). There was a positive correlation between renalase and ER expression in breast cancer tissues (R=0.7246, P<0.0001) and a positive correlation between renalase and p-ERK 1/2 expression (R=0.6599, P<0.0001). Renalase had no significant correlation with p-STAT3 protein expression.

CONCLUSION

Renalase is a new molecular marker for ER-positive breast cancer and may become a potential therapeutic target for the ER-positive/HER2-negative subtype breast cancer. Renalase may promote high ER expression and breast cancer cell proliferation and growth through the p-ERK1/2 pathway.

The serum protein renalase reduces injury in experimental pancreatitis

Acute pancreatitis is a disease associated with inflammation and tissue damage. One protein that protects against acute injury, including ischemic injury to both the kidney and heart, is renalase, which is secreted into the blood by the kidney and other tissues. However, whether renalase reduces acute injury associated with pancreatitis is unknown. Here, we used both in vitro and in vivo murine models of acute pancreatitis to study renalase's effects on this condition. In isolated pancreatic lobules, pretreatment with recombinant human renalase (rRNLS) blocked zymogen activation caused by cerulein, carbachol, and a bile acid. Renalase also blocked cerulein-induced cell injury and histological changes. In the in vivo cerulein model of pancreatitis, genetic deletion of renalase resulted in more severe disease, and administering rRNLS to cerulein-exposed WT mice after pancreatitis onset was protective. Because pathological increases in acinar cell cytosolic calcium levels are central to the initiation of acute pancreatitis, we also investigated whether rRNLS could function through its binding protein, plasma membrane calcium ATPase 4b (PMCA4b), which excretes calcium from cells. We found that PMCA4b is expressed in both murine and human acinar cells and that a PMCA4b-selective inhibitor worsens pancreatitis-induced injury and blocks the protective effects of rRNLS. These findings suggest that renalase is a protective plasma protein that reduces acinar cell injury through a plasma membrane calcium ATPase. Because exogenous rRNLS reduces the severity of acute pancreatitis, it has potential as a therapeutic agent.

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.

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.

Polymorphism of the renalase gene in gestational diabetes mellitus

Renalase is considered as a novel candidate gene for type 2 diabetes. In this study, we aimed to investigate the relationship of serum renalase and two single nucleotide polymorphisms with gestational diabetes mellitus. One hundred and ninety-eight normotensive pregnant females (n = 99 gestational diabetes mellitus; n = 99 euglycemic pregnant controls) were classified according to the International Association of the Diabetes and Pregnancy Study criteria. Fasting and 2-h post glucose load blood levels and anthropometric assessment was performed. Serum renalase was measured using enzyme-linked immunosorbent assay, whereas DNA samples were genotyped for renalase single nucleotide polymorphisms rs2576178 and rs10887800 using Polymerase chain reaction-Restriction fragment length polymorphism method. In an age-matched case control study, no difference was observed in the serum levels of renalase (p > 0.05). The variant rs10887800 showed an association with gestational diabetes mellitus and remained significant after multiple adjustments (p < 0.05), whereas rs2576178 showed weak association (p = 0.030) that was lost after multiple adjustments (p = 0.09). We inferred a modest association of the rs10887800 polymorphism with gestational diabetes. Although gestational diabetes mellitus is self-reversible, yet presence of this minor G allele might predispose to metabolic syndrome phenotypes in near the future.

Ligand binding phenomena that pertain to the metabolic function of renalase

Renalase catalyzes the oxidation of isomers of β-NAD(P)H that carry the hydride in the 2 or 6 positions of the nicotinamide base to form β-NAD(P)⁺. This activity is thought to alleviate inhibition of multiple β-NAD(P)-dependent enzymes of primary and secondary metabolism by these isomers. Here we present evidence for a variety of ligand binding phenomena relevant to the function of renalase. We offer evidence of the potential for primary metabolism inhibition with structures of malate dehydrogenase and lactate dehydrogenase bound to the 6-dihydroNAD isomer. The previously observed preference of renalase from Pseudomonas for NAD-derived substrates over those derived from NADP is accounted for by the structure of the enzyme in complex with NADPH. We also show that nicotinamide nucleosides and mononucleotides reduced in the 2- and 6-positions are renalase substrates, but bind weakly. A seven-fold enhancement of acquisition (k_red/K_d) for 6-dihydronicotinamide riboside was observed for human renalase in the presence of ADP. However, generally the addition of complement ligands, AMP for mononucleotide or ADP for nucleoside substrates, did not enhance the reductive half-reaction. Non-substrate nicotinamide nucleosides or nucleotides bind weakly suggesting that only β-NADH and β-NADPH compete with dinucleotide substrates for access to the active site.

Limb ischemic preconditioning protects against contrast-induced nephropathy via renalase

Clinical trials shows that remote ischemic preconditioning (IPC) can protect against contrast induced nephropathy (CIN) in risky patients, however, the exact mechanism is unclear. In this study, we explored whether renalase, an amine oxidase that has been previously shown to mediate reno-protection by local IPC, would also mediate the same effect elicited by remote IPC in animal model. Limb IPC was performed for 24 h followed by induction of CIN. Our results indicated that limb IPC prevented renal function decline, attenuated tubular damage and reduced oxidative stress and inflammation in the kidney. All those beneficial effects were abolished by silencing of renalase with siRNA. This suggests that similar to local IPC, renalase is also critically involved in limb IPC-elicited reno-protection. Mechanistic studies showed that limb IPC increased TNFα levels in the muscle and blood, and up-regulated renalase and phosphorylated IκBα expression in the kidney. Pretreatment with TNFα antagonist or NF-κB inhibitor, largely blocked renalase expression. Besides, TNFα preconditioning increased expression of renal renalase in vivo and in vitro, and attenuated H₂O₂ induced apoptosis in renal tubular cells. Collectively, our results suggest that limb IPC-induced reno-protection in CIN is dependent on increased renalase expression via activation of the TNFα/NF-κB pathway.

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Limb ischemic preconditioning (IPC) leads to renalase upregulation in kidney tissue.

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Renalase is critically involved in limb IPC-elicited renal protection in contrast induced nephropathy.

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Limb IPC induces renalase upregulation via activation of the tumor necrosis factor α (TNFα)/ nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway.

Renalase, a kidney-secreted protein, serves as extracellular pro-survival signals and has been reported to participate in the local ischemic preconditioning (IPC) induced renal protection against ischemia-reperfusion injury. Whether renalase contributes to the beneficial effects of limb IPC on contrast induced nephropathy (CIN) remains unknown. This study revealed that limb IPC induced reno-protection in CIN was at least in part dependent on increased renalase expression, which is evidenced by our observations that knockdown of renalase abolished reno-protective effects conferred by limb IPC. The upregulation of renalase elicited by limb IPC may be mediated by activation of TNFα/NF-κB pathway.

Renalase Expression by Melanoma and Tumor-Associated Macrophages Promotes Tumor Growth through a STAT3-Mediated Mechanism

To sustain their proliferation, cancer cells overcome negative-acting signals that restrain their growth and promote senescence and cell death. Renalase (RNLS) is a secreted flavoprotein that functions as a survival factor after ischemic and toxic injury, signaling through the plasma calcium channel PMCA4b to activate the PI3K/AKT and MAPK pathways. We show that RNLS expression is increased markedly in primary melanomas and CD163(+) tumor-associated macrophages (TAM). In clinical specimens, RNLS expression in the tumor correlated inversely with disease-specific survival, suggesting a pathogenic role for RNLS. Attenuation of RNLS by RNAi, blocking antibodies, or an RNLS-derived inhibitory peptide decreased melanoma cell survival, and anti-RNLS therapy blocked tumor growth in vivo in murine xenograft assays. Mechanistic investigations showed that increased apoptosis in tumor cells was temporally related to p38 MAPK-mediated Bax activation and that increased cell growth arrest was associated with elevated expression of the cell-cycle inhibitor p21. Overall, our results established a role for the secreted flavoprotein RNLS in promoting melanoma cell growth and CD163(+) TAM in the tumor microenvironment, with potential therapeutic implications for the management of melanoma. Cancer Res; 76(13); 3884-94. ©2016 AACR.