Serum Renalase Levels Correlate with Disease Activity in Lupus Nephritis

Association of renalase with clinical outcomes in hospitalized patients with COVID-19

Renalase is a secreted flavoprotein with anti-inflammatory and pro-cell survival properties. COVID-19 is associated with disordered inflammation and apoptosis. We hypothesized that blood renalase levels would correspond to severe COVID-19 and survival. In this retrospective cohort study, clinicopathologic data and blood samples were collected from hospitalized COVID-19 subjects (March—June 2020) at a single institution tertiary hospital. Plasma renalase and cytokine levels were measured and clinical data abstracted from health records. Of 3,450 COVID-19 patients, 458 patients were enrolled. Patients were excluded if <18 years, or opted out of research. The primary composite outcome was intubation or death within 180 days. Secondary outcomes included mortality alone, intensive care unit admission, use of vasopressors, and CPR. Enrolled patients had mean age 64 years (SD±17), were 53% males, and 48% non-whites. Mean renalase levels was 14,108·4 ng/ml (SD±8,137 ng/ml). Compared to patients with high renalase, those with low renalase (< 8,922 ng/ml) were more likely to present with hypoxia, increased ICU admission (54% vs. 33%, p < 0.001), and cardiopulmonary resuscitation (10% vs. 4%, p = 0·023). In Cox proportional hazard model, every 1000 ng/ml increase in renalase decreased the risk of death or intubation by 5% (HR 0·95; 95% CI 0·91–0·98) and increased survival alone by 6% (HR 0·95; CI 0·90–0·98), after adjusting for socio-demographics, initial disease severity, comorbidities and inflammation. Patients with high renalase-low IL-6 levels had the best survival compared to other groups (p = 0·04). Renalase was independently associated with reduced intubation and mortality in hospitalized COVID-19 patients. Future studies should assess the pathophysiological relevance of renalase in COVID-19 disease.

Lupus nephritis pathology prediction with clinical indices

Effective treatment of lupus nephritis and assessment of patient prognosis depend on accurate pathological classification and careful use of acute and chronic pathological indices. Renal biopsy can provide most reliable predicting power. However, clinicians still need auxiliary tools under certain circumstances. Comprehensive statistical analysis of clinical indices may be an effective support and supplementation for biopsy. In this study, 173 patients with lupus nephritis were classified based on histology and scored on acute and chronic indices. These results were compared against machine learning predictions involving multilinear regression and random forest analysis. For three class random forest analysis, total classification accuracy was 51.3% (class II 53.7%, class III&IV 56.2%, class V 40.1%). For two class random forest analysis, class II accuracy reached 56.2%; class III&IV 63.7%; class V 61%. Additionally, machine learning selected out corresponding important variables for each class prediction. Multiple linear regression predicted the index of chronic pathology (CI) (Q² = 0.746, R² = 0.771) and the acute index (AI) (Q² = 0.516, R² = 0.576), and each variable’s importance was calculated in AI and CI models. Evaluation of lupus nephritis by machine learning showed potential for assessment of lupus nephritis.

Rapid detection of urinary soluble intercellular adhesion molecule-1 for determination of lupus nephritis activity

The current methods of monitoring the activity of lupus nephritis (LN) may cause unnecessary hospital visits or delayed immunosuppressive therapy. We aimed to find a urinary biomarker that could be developed as a home-based test for monitoring the activity of LN.Urine samples were collected immediately before a renal biopsy from patients of suspected active LN, and also from patients with inactive LN, systemic lupus erythematous without LN or healthy controls. Biomarker search was conducted on a cytokine antibody array and confirmation was done by quantitative evaluation with enzyme-linked immunosorbent assay. The Mann-Whiney test or Student t test was used to compare the levels of 9 cytokines between different groups. The sensitivity and specificity of each cytokine for diagnosis of LN was evaluated by receiver operating characteristic curve. A rapid test based on colloidal gold immunochromatography was then developed for bedside or home use. Furthermore, an experimental e-healthcare system was constructed for recording and sharing the results of the rapid test a cloud-assisted internet of things (IoT) consisting of a sensing device, an IoT device and a cloud server.Adiponectin (Acrp30), soluble intercellular cell adhesion molecule-1 (sICAM-1), neural cell adhesion molecule 1 (NCAM-1), and CD26 were significantly higher in urine samples of active LN patients. sICAM-1 appeared more sensitive and specific among these candidates. When the cut-off value of sICAM-1 was set at 1.44 ng/mL, the sensitivity reached 98.33% with a specificity at 85.71%. The sICAM-1 strip test showed comparable sensitivity of 95% and a specificity of 83.3% for assessing the LN activity. Meanwhile, the e-healthcare system was able to conveniently digitize and share the sICAM-1 rapid test results.sICAM-1 appeared to be an excellent biomarker for monitoring LN activity. The e-healthcare system with cloud-assisted IoT could assist the digitalization and sharing of the bedside or home-based sICAM-1 test results.

Synergistic effect of renalase and chronic kidney disease on endothelin-1 in patients with coronary artery disease ‒ a cross-sectional study

Endothelin-1 (ET-1) is associated with endothelial dysfunction and vasoconstriction. Increased circulating ET-1 levels are associated with long-term cardiovascular mortality. Renalase, released from kidney, metabolizes catecholamines and regulates blood pressure. An increase in circulating renalase levels has been reported in patients with chronic kidney disease (CKD) and is associated with coronary artery disease (CAD). We hypothesized the existence of a synergistic effect of serum renalase levels and CKD on ET-1 levels in patients with CAD. We evaluated 342 non-diabetic patients with established CAD. ET-1 and renalase levels were measured in all patients after an overnight fast. Patients with CKD had higher ET-1 (1.95 ± 0.77 vs. 1.62 ± 0.76 pg/ml, P < 0.001) and renalase levels (46.8 ± 17.1 vs. 33.9 ± 9.9 ng/ml, P < 0.001) than patients without CKD. Patients with both CKD and high renalase levels (>the median of 36.2 ng/ml) exhibited the highest serum ET-1 (P value for the trend <0.001). According to multivariate linear regression analysis, the combination of high serum renalase levels with CKD was a significant risk factor for increased serum ET-1 levels (regression coefficient = 0.297, 95% confidence interval = 0.063‒0.531, P = 0.013). In conclusion, our data suggest a synergistic effect of high serum renalase levels and CKD on increases in ET-1 levels in patients with established CAD.

Coagulation cascade and complement system in systemic lupus erythematosus

This study was conducted to (1) characterize coagulation cascade and complement system in systemic lupus erythematosus (SLE); (2) evaluate the associations between coagulation cascade, complement system, inflammatory response and SLE disease severity; (3) test the diagnostic value of a combination of D-dimer and C4 for lupus activity. Transcriptomics, proteomics and metabolomics were performed in 24 SLE patients and 24 healthy controls. The levels of ten coagulations, seven complements and three cytokines were measured in 112 SLE patients. Clinical data were collected from 2025 SLE patients. The analysis of multi-omics data revealed the common links for the components of coagulation cascade and complement system. The results of ELISA showed coagulation cascade and complement system had an interaction effect on SLE disease severity, this effect was pronounced among patients with excess inflammation. The analysis of clinical data revealed a combination of D-dimer and C4 provided good diagnostic performance for lupus activity. This study suggested that coagulation cascade and complement system become 'partners in crime', contributing to SLE disease severity and identified the diagnostic value of D-dimer combined with C4for lupus activity.

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.

Increased serum renalase in peritoneal dialysis patients: Is it related to cardiovascular disease risk?

BACKGROUND

Renalase, with possible monoamine oxidase activity, is implicated in degradation of catecholamines; which suggests novel mechanisms of cardiovascular complications in patients with chronic kidney diseases. Epicardial adipose tissue (EAT) has been found to correlate with cardiovascular diseases (CVD) in dialysis patients. The present study aimed to evaluate the association of serum renalase levels with EAT thickness and other CVD risk factors in peritoneal dialysis (PD) patients.

METHODS

The study included 40 PD patients and 40 healthy controls. All subjects underwent blood pressure and anthropometric measurements. Serum renalase was assessed by using a commercially available assay. Transthoracic echocardiography was used to measure EAT thickness and left ventricular mass index (LVMI) in all subjects.

RESULTS

The median serum renalase level was significantly higher in the PD patients than in the control group [176.5 (100-278.3) vs 122 (53.3-170.0)ng/ml] (p=0.001). Renalase was positively correlated with C-reactive protein (r=0.705, p<0.001) and negatively correlated with RRF (r=-0.511, p=0.021). No correlation was observed between renalase and EAT thickness or LVMI. There was a strong correlation between EAT thickness and LVMI in both the PD patients and the controls (r=0.848, p<0.001 and r=0.640, p<0.001 respectively).

CONCLUSIONS

This study indicates that renalase is associated with CRP and residual renal function but not with EAT thickness as CVD risk factors in PD patients.