Clinical significance of urinary inflammatory biomarkers in patients with IgA nephropathy.

BACKGROUND: IgA nephropathy (IgAN) is the most common type of primary glomerulonephritis, although the definitive markers are unknown. We aimed to investigate the clinical significance of urinary cytokines in patients with IgAN. METHODS: From 2009 to 2018, the patients were divided into three groups: IgAN (n = 191), disease control (n = 53), and normal control (n = 76). We used a multiplex enzyme-linked immunosorbent assay to measure 16 selected urinary inflammatory cytokines, evaluated the correlation between clinical and pathological features following regression analysis on progression. RESULTS: The IgAN group exhibited significantly different levels of urinary cytokines compared to the normal control and disease control groups. Urinary levels of B-cell-activating factor, vascular endothelial growth factor receptor-2, monocyte chemoattractant protein-1, C-X-C motif chemokine 10, C-X-C motif ligand 16, epidermal growth factor (EGF), endocan, endostatin, growth/differentiation factor-15 (GDF-15), interleukin-6 (IL-6), mannose-binding lectin, transferrin receptor, and kidney injury molecule-1 were significantly correlated with both the estimated glomerular filtration rate and urine protein-creatinine ratio. In a multivariate Cox regression analysis, urinary EGF (hazard ratio [HR] 0.40, 95% confidence interval [CI] 0.17-0.95, P = 0.04), GDF-15 (HR 2.45, 95% CI 1.01-5.94, P = 0.048), and IL-6 (HR 3.02, 95% CI 1.05-8.64, P = 0.04) were associated with progression in IgAN. CONCLUSIONS: Urinary inflammatory biomarkers may serve as alternative predictive biomarkers in patients with IgAN. Further studies are needed to elucidate the physiological mechanisms and confirm the results.

Association of the Intensive Blood Pressure Target and Cardiovascular Outcomes in the Population With Chronic Kidney Disease: A Retrospective Study in Korea.

BACKGROUND: Recently, the target systolic blood pressure (BP) <120 mm Hg was suggested in the population with chronic kidney disease. We aimed to determine the applicability of intensified BP and to assess the incidence of cardiovascular disease (CVD) in the population with chronic kidney disease. METHODS AND RESULTS: Participants who were >20 years old and had estimated glomerular filtration rate 15 to 60 mL/min per 1.73 m2 during 2009 to 2011 were included from the database of Korean National Health Insurance Service and were followed up to 2018. Participants were categorized by BP as <120/80 mm Hg; 120 to 129/<80 mm Hg; 130 to 139/80 to 89 mm Hg; ≥140/90 mm Hg. The primary outcome was CVD risk and the secondary outcomes were all-cause mortality and progression to end-stage renal disease followed by subgroup analysis. Among the 45 263 adults with chronic kidney disease, 5196 CVD events were noted. In Cox regression analysis, higher BP was associated with a higher risk for CVD (hazard ratio [HR], 1.15 [95% CI, 1.12-1.19]; P for trend <0.001), end-stage renal disease (HR, 1.29 [95% CI, 1.22-1.37]; P for trend <0.001), and all-cause mortality (HR, 1.09 [95% CI, 1.06-1.13]; P for trend <0.001) than BP <120/80 mm Hg. In subgroup analysis, the association between BP and CVD showed a different trend in participants taking antihypertensives compared with those not using antihypertensive drugs. When comparing BP-treated individuals to untreated individuals, a significant interaction in the association between BP categories and end-stage renal disease was observed. CONCLUSIONS: The new intensive BP target proposed by 2021 Kidney Disease: Improving Global Outcomes should be applied to patients with chronic kidney disease in a personalized and advisory manner.

Fasting blood glucose and the risk of all-cause mortality in patients with diabetes mellitus undergoing hemodialysis.

Background: Glycemic control is particularly important in hemodialysis (HD) patients with diabetes mellitus (DM). Although fasting blood glucose (FBG) level is an important indicator of glycemic control, a clear target for reducing mortality in HD patients with DM is lacking. Methods: A total of 26,162 maintenance HD patients with DM were recruited from the National Health Insurance Database of Korea between 2002 and 2018. We analyzed the association of FBG levels at the baseline health examination with the risk of all-cause and cause-specific mortality. Results: Patients with FBG 80100 mg/dL showed a higher survival rate compared with that of other FBG categories (p < 0.001). The risk of all-cause mortality increased with the increase in FBG levels, and adjusted hazard ratios (HRs) were 1.10 (95% confidence interval [CI], 1.04-1.17), 1.21 (95% CI, 1.13-1.29), 1.36 (95% CI, 1.26-1.46), and 1.61 (95% CI, 1.51-1.72) for patients with FBG 100-125, 125-150, 150-180, and ≥180 mg/dL, respectively. The HR for mortality was also significantly increased in patients with FBG < 80 mg/dL (adjusted HR, 1.14; 95% CI, 1.05-1.23). The analysis of cause-specific mortality also revealed a J-shaped curve between FBG levels and the risk of cardiovascular deaths. However, the risk of infection or malignancy-related deaths was not linearly increased as FBG levels increased. Conclusion: A J-shaped association was observed between FBG levels and the risk of all-cause mortality, with the lowest risk at FBG 80100 mg/dL in HD patients with DM.

Clinical significance of urinary exosomal microRNAs in patients with IgA nephropathy.

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. The clinical relevance of 11 urinary exosomal microRNAs (miRNAs) was evaluated in patients with IgAN. From January 2009 to November 2018, IgAN (n = 93), disease control (n = 11), and normal control (n = 19) groups were enrolled. We evaluated the expression levels of urinary exosomal miRNAs at the baseline and their relationship with clinical and pathologic features. This study aimed to discriminate statistically powerful urinary exosomal miRNAs for the prognosis of IgAN. Urinary miRNA levels of miR-16-5p, miR-29a-3p, miR-124-3p, miR-126-3p, miR-199a-3p, miR-199b-5p, and miR-335-3p showed significant correlation with both estimated glomerular filtration rate (eGFR) and urine protein-to-creatinine ratio (uPCR). In univariate regression analysis, age, body mass index, hypertension, eGFR, uPCR, Oxford classification E, and three miRNAs (miR-16-5p, miR-199a-3p, and miR-335-3p) were associated with disease progression in patients with IgAN. The area under the curve (AUC) of miR-199a-3p was high enough (0.749) without any other clinical or pathologic factors, considering that the AUC of the International IgAN Risk Prediction Tool was 0.853. Urinary exosomal miRNAs may serve as alternative prognostic biomarkers of IgAN with further research.

Korean guidelines for the management of gout.

Gout is the most common form of arthritis, with the prevalence increasing worldwide. The present treatment guidelines provide recommendations for the appropriate treatment of acute gout, management during the inter-critical period, and prevention of chronic complications. The guidelines were developed based on evidence-based medicine and draft recommendations finalized after expert consensus. These guidelines are designed to provide clinicians with clinical evidence to enable efficient treatment of gout.

Korean guidelines for the management of gout.

Gout is the most common form of arthritis, with the prevalence increasing worldwide. The present treatment guidelines provide recommendations for the appropriate treatment of acute gout, management during the inter-critical period, and prevention of chronic complications. The guidelines were developed based on evidence-based medicine and draft recommendations finalized after expert consensus. These guidelines are designed to provide clinicians with clinical evidence to enable efficient treatment of gout.

Corrigendum: Development and validation of urinary exosomal microRNA biomarkers for the diagnosis of acute rejection in kidney transplant recipients.

[This corrects the article DOI: 10.3389/fimmu.2023.1190576.].

Development and validation of urinary exosomal microRNA biomarkers for the diagnosis of acute rejection in kidney transplant recipients.

Introduction: Acute rejection (AR) continues to be a significant obstacle for short- and long-term graft survival in kidney transplant recipients. Herein, we aimed to examine urinary exosomal microRNAs with the objective of identifying novel biomarkers of AR. Materials and methods: Candidate microRNAs were selected using NanoString-based urinary exosomal microRNA profiling, meta-analysis of web-based, public microRNA database, and literature review. The expression levels of these selected microRNAs were measured in the urinary exosomes of 108 recipients of the discovery cohort using quantitative real-time polymerase chain reaction (qPCR). Based on the differential microRNA expressions, AR signatures were generated, and their diagnostic powers were determined by assessing the urinary exosomes of 260 recipients in an independent validation cohort. Results: We identified 29 urinary exosomal microRNAs as candidate biomarkers of AR, of which 7 microRNAs were differentially expressed in recipients with AR, as confirmed by qPCR analysis. A three-microRNA AR signature, composed of hsa-miR-21-5p, hsa-miR-31-5p, and hsa-miR-4532, could discriminate recipients with AR from those maintaining stable graft function (area under the curve [AUC] = 0.85). This signature exhibited a fair discriminative power in the identification of AR in the validation cohort (AUC = 0.77). Conclusion: We have successfully demonstrated that urinary exosomal microRNA signatures may form potential biomarkers for the diagnosis of AR in kidney transplantation recipients.

National trends in the prevalence of chronic kidney disease among Korean adults, 2007-2020.

Little is known about the prevalence of chronic kidney disease (CKD) during the coronavirus disease 2019 (COVID-19) pandemic. We aimed to investigate the long-term trends in CKD prevalence from South Korea including the early pandemic. We used data from 108,152 Korean adults from 2007 to 2020 obtained from a representative longitudinal serial study. We defined CKD as a condition when the participant's estimated glomerular filtration rate was < 60 mL/min/1.73 m2, or one-time spot proteinuria was ≥ 1 +, and then examined the overall trends in the prevalence of CKD. Among the included adults (n = 80,010), the overall national prevalence of CKD was 6.2%. The trend slope gradually increased from 2007 to 2019, however, there was a sudden decrease in 2020 (2007-2010, 5.1% [95% confidence interval (CI) 4.7-5.5]; 2017-2019, 7.1% [95% CI 6.6-7.6]; pandemic period, 6.5% [95% CI 5.7-7.3]; and ßdiff, - 0.19; 95% CI - 0.24 to - 0.13). The prevalence of CKD among younger adults and those with poor medical utilization significantly decreased during the early pandemic. This study was the first large-scale study to investigate the longitudinal prevalence of CKD from 2007 to 2020. Further research is needed to fully understand the exact causes for this decline and to identify healthcare policy strategies for preventing and managing CKD.

Acute Kidney Injury: Biomarker-Guided Diagnosis and Management.

Acute kidney injury (AKI) is a common clinical syndrome that is characterized by abnormal renal function and structure. The Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference in 2019 reviewed the stages of AKI and the definitions of AKI-related terminologies, and discussed the advances in the last decade. Along with serum creatinine level and urine output, more accurate novel biomarkers for predicting AKI are being applied for the early detection of renal dysfunction. A literature search was conducted in PubMed, Scopus, Medline, and ClinicalTrials.gov using the terms AKI and biomarker, combined with diagnosis, management, or prognosis. Because of the large volume of data (160 articles) published between 2005 and 2022, representative literature was chosen. A number of studies have demonstrated that new biomarkers are more sensitive in detecting AKI in certain populations than serum creatinine and urine output according to the recommendations from the Acute Disease Quality Initiative Consensus Conference. To be specific, there is a persistently unresolved need for earlier detection of patients with AKI before AKI progresses to a need for renal replacement therapy. Biomarker-guided management may help to identify a high-risk group of patients in progression to severe AKI, and decide the initiation time to renal replacement therapy and optimal follow-up period. However, limitations such as biased data to certain studied populations and absence of cutoff values need to be solved for worldwide clinical use of biomarkers in the future. Here, we provide a comprehensive review of biomarker-based AKI diagnosis and management and highlight recent developments.

Urinary mRNA Signatures as Predictors of Renal Function Decline in Patients With Biopsy-Proven Diabetic Kidney Disease.

The clinical manifestations of diabetic kidney disease (DKD) are more heterogeneous than those previously reported, and these observations mandate the need for the recruitment of patients with biopsy-proven DKD in biomarker research. In this study, using the public gene expression omnibus (GEO) repository, we aimed to identify urinary mRNA biomarkers that can predict histological severity and disease progression in patients with DKD in whom the diagnosis and histologic grade has been confirmed by kidney biopsy. We identified 30 DKD-specific mRNA candidates based on the analysis of the GEO datasets. Among these, there were significant alterations in the urinary levels of 17 mRNAs in patients with DKD, compared with healthy controls. Four urinary mRNAs-LYZ, C3, FKBP5, and G6PC-reflected tubulointerstitial inflammation and fibrosis in kidney biopsy and could predict rapid progression to end-stage kidney disease independently of the baseline eGFR (tertile 1 vs. tertile 3; adjusted hazard ratio of 9.68 and 95% confidence interval of 2.85-32.87, p < 0.001). In conclusion, we demonstrated that urinary mRNA signatures have a potential to indicate the pathologic status and predict adverse renal outcomes in patients with DKD.

Urinary chemokine C-X-C motif ligand 16 and endostatin as predictors of tubulointerstitial fibrosis in patients with advanced diabetic kidney disease.

BACKGROUND: Interstitial fibrosis and tubular atrophy (IFTA) is a well-recognized risk factor for poor renal outcome in patients with diabetic kidney disease (DKD). However, a noninvasive biomarker for IFTA is currently lacking. The purpose of this study was to identify urinary markers of IFTA and to determine their clinical relevance as predictors of renal prognosis. METHODS: Seventy patients with biopsy-proven isolated DKD were enrolled in this study. We measured multiple urinary inflammatory cytokines and chemokines by multiplex enzyme-linked immunosorbent assay in these patients and evaluated their association with various pathologic features and renal outcomes. RESULTS: Patients enrolled in this study exhibited advanced DKD at the time of renal biopsy, characterized by moderate to severe renal dysfunction [mean estimated glomerular filtration rate (eGFR) 36.1 mL/min/1.73 m2] and heavy proteinuria (mean urinary protein:creatinine ratio 7.8 g/g creatinine). Clinicopathologic analysis revealed that higher IFTA scores were associated with worse baseline eGFR (P < 0.001) and poor renal outcome (P = 0.002), whereas glomerular injury scores were not. Among measured urinary inflammatory markers, C-X-C motif ligand 16 (CXCL16) and endostatin showed strong correlations with IFTA scores (P = 0.001 and P < 0.001, respectively), and patients with higher levels of urinary CXCL16 and/or endostatin experienced significantly rapid renal progression compared with other patients (P < 0.001). Finally, increased urinary CXCL16 and endostatin were independent risk factors for poor renal outcome after multivariate adjustments (95% confidence interval 1.070-3.455, P = 0.029). CONCLUSIONS: Urinary CXCL16 and endostatin could reflect the degree of IFTA and serve as biomarkers of renal outcome in patients with advanced DKD.

Gait speed and handgrip strength as predictors of all-cause mortality and cardiovascular events in hemodialysis patients.

BACKGROUND: Low physical performance in patients undergoing maintenance hemodialysis is associated with a high mortality rate. We investigated the clinical relevance of gait speed and handgrip strength, the two most commonly used methods of assessing physical performance. METHODS: We obtained data regarding gait speed and handgrip strength from 277 hemodialysis patients and evaluated their relationships with baseline parameters, mental health, plasma inflammatory markers, and major adverse clinical outcomes. Low physical performance was defined by the recommendations suggested by the Asian Working Group on Sarcopenia. RESULTS: The prevalence of low gait speed and handgrip strength was 28.2 and 44.8%, respectively. Old age, low serum albumin levels, high comorbidity index score, and impaired cognitive functions were associated with low physical performance. Patients with isolated low gait speed exhibited a general trend for worse quality of life than those with isolated low handgrip strength. Gait speed and handgrip strength showed very weak correlations with different determining factors (older age, the presence of diabetes, and lower serum albumin level for low gait speed, and lower body mass index and the presence of previous cardiovascular events for low handgrip strength). Patients with low gait speed and handgrip strength had elevated levels of plasma endocan and matrix metalloproteinase-7 and the highest risks for all-cause mortality and cardiovascular events among the groups (adjusted hazard ratio of 2.72, p = 0.024). Elderly patients with low gait speed and handgrip strength were at the highest risk for poor clinical outcomes. CONCLUSION: Gait speed and handgrip strength reflected distinctive aspects of patient characteristics and the use of both factors improved the prediction of adverse clinical outcomes in hemodialysis patients. Gait speed seems to be a better indicator of poor patient outcomes than is handgrip strength.

High dose haemodialysis and haemodiafiltration parameters and the relationship with advanced vascular calcification.

BACKGROUND: Vascular calcification (VC) is a risk factor for cardiovascular disease in end-stage renal disease (ESRD) patients undergoing maintenance haemodialysis (MHD). However, evidence is still insufficient about the association between dialysis parameters and VC. Thus, this study was to evaluate association of dialysis parameters with VC. METHODS: We enrolled 297 ESRD patients undergoing MHD at six distinct centers in Korea. Study participants were categorized into 3 groups by the scoring system of abdominal aortic calcification based on lateral lumbar radiography (no VC group: 0, mild VC group: 1-7 and advanced VC group: 8-24). We compared the features of dialysis parameters according to the severity of VC. Multivariate logistic regression analysis was used to calculate adjusted odd ratios (ORs) and 95% confidence interval (CI) for mild and advanced VC in each haemodialysis parameter (adjusted OR [95% CI]). RESULTS: Pooled Kt/V (spKt/V), equilibrated Kt/V (eKt/V), standard Kt/V (stdKt/V) and the proportion of haemodiafiltration were increased along with the severity of VC. Multivariate regression analysis indicated that advanced VC was positively associated with spKt/V (5.27 [1.51-18.41]), eKt/V (6.16 [1.45-26.10]), stdKt/V (10.67 [1.74-65.52]) and haemodiafiltration (3.27 [1.74 to 6.16]). CONCLUSION: High dose dialysis and haemodiafiltration were significantly associated with advanced VC.

Clinical relevance of cell-free mitochondrial DNA during the early postoperative period in kidney transplant recipients.

Recent studies indicate that urinary mitochondrial DNA (mtDNA) is predictive of ischemic AKI and is related to delayed graft function (DGF) in renal transplantation. Nevertheless, the clinical implications and prognostic value of urinary mtDNA in kidney transplantation remain undetermined. Here, we aimed to evaluate the associations between cell-free mtDNA and clinical parameters, including pathological findings in allograft biopsy and post-transplant renal function. A total of 85 renal transplant recipients were enrolled, and blood and urine samples were collected at a median of 17 days after transplantation. Cell-free nuclear and mtDNA levels were measured by quantitative polymerase chain reaction for LPL and ND1 genes. Urinary cell-free mtDNA levels were significantly higher in patients with DGF (P < 0.001) and cases of deceased donor transplantation (P < 0.001). The subjects with acute rejection showed higher urinary mtDNA levels than those without abnormalities (P = 0.043). In addition, allograft functions at 9- and 12-month post-transplantation were significantly different between tertile groups of mtDNA independent of the presence of DGF or acute rejection, showing significantly better graft outcome in the lowest tertile group. Urinary cell-free mtDNA levels during the early post-transplant period are significantly associated with DGF, acute rejection in graft biopsy, and short-term post-transplant renal function.

Long-term Trends in the Clinicopathologic Features of Kidney Transplant Recipients With Graft Dysfunction.

BACKGROUND: Graft biopsy is the gold standard for the differential diagnosis of graft dysfunction. The time interval between transplant surgery and biopsy often provides clinicians with diagnostic clues. However, the clinicopathologic features of late graft biopsy, especially those obtained at more than 5 years after kidney transplant, are not well understood. MATERIALS AND METHODS: We retrospectively collected graft biopsy tissues obtained from kidney transplant recipients who underwent indication biopsy between February 2012 and March 2017. Patients were divided according to their post-transplant period, and their clinical characteristics, pathologic diagnosis, and Banff scores were compared across groups. RESULTS: A total of 410 indication biopsy specimens obtained from 321 kidney transplant recipients were analyzed in this study. Overall, the incidence of T cell-mediated rejection, borderline rejection, and BK virus-associated nephropathy decreased while that of antibody-mediated rejection, nonspecific interstitial fibrosis and tubular atrophy, and glomerulonephritis increased over time. Most samples obtained over 5 years after kidney transplant exhibited chronic glomerular and tubulointerstitial injuries irrespective of their pathologic diagnosis. In patients whose post-transplant period was less than 5 years, urine protein-to-creatinine ratio was significantly elevated in the glomerulonephritis and chronic active antibody-mediated rejection groups only. In contrast, patients who underwent graft biopsy more than 5 years after kidney transplant showed significantly high levels of proteinuria irrespective of the pathologic diagnosis, and there was no statistical difference between groups. CONCLUSION: We demonstrated that the etiology of graft dysfunction is largely influenced by the biopsy time point.

Combination therapy of low-dose cyclosporine and steroid in adults with IgA nephropathy
.

BACKGROUND: A few clinical trials in IgA nephropathy (IgAN) have shown that cyclosporine A (CyA) had therapeutic efficacy in reducing proteinuria. MATERIALS AND METHODS: This is a retrospective study, and all cases were selected based on kidney biopsy-proven IgAN. We reviewed the data of IgAN patients in the glomerulonephritis registry at Kyung Hee University Medical center and collected data on 86 patients with urinary protein/Cr ratio (PCR; g/g) > 0.5 and estimated GFR (eGFR) of > 50 mL/min/1.73m2 who were treated with combination therapy of low-dose CyA plus low-dose steroid (C+P; n = 37) and high-dose steroid single therapy (P; n = 49). RESULTS: In the C+P group, the mean duration of therapy was 14.5 ± 13.1 months, and the mean duration of follow-up 66.2 ± 36.3 months. In the C+P group, the urine PCR levels significantly declined after treatment (< 0.05). After 6 months of treatment, 12 (32%) patients were in complete remission and 7 (19%) in partial remission in the C+P group, compared with 21 (42%) and 11 (22%) in the P group, respectively. Urine PCR levels were also significantly reduced in 12 patients in the C+P group who had initial urine PCR between 0.5 and 1.0. The degree of hematuria was significantly reduced after treatment in the C+P group. These effects of C+P therapy on proteinuria and hematuria were very comparable to high-dose P therapy. After 2 years, a decline in renal function, > 25% decrease in eGFR from baseline levels, developed in 3 (8.1%) in the C+P group, compared with 4 (8.2%) in the P group. The rate of decline in renal function during follow-up was -0.14 ± 0.40 mL/min/1.73m2/month in the C+P group compared with -0.12 ± 0.22 mL/min/1.73m2/month in the P group. There were no changes of mean eGFR during the first 24 months, but the eGFR significantly decreased at last follow-up in both groups. When patients in the C+P group were divided into progressive (n = 9) and nonprogressive (n = 28) groups, a significant reduction in the amount of proteinuria after treatment was observed in the nonprogressive group, in contrast to the progressive group. In the C+P group, there were no severe adverse effects, especially no acute renal impairment, requiring discontinuation of CyA in this study. The incidence of infection was much lower in the C+P group than that in the P group. The limitation is that CyA acts to nonspecifically reduce proteinuria, so it requires long-term follow-up off CyA therapy for more than 2 years to determine. CONCLUSION: Our retrospective uncontrolled study provides only weak evidence that combination therapy of low-dose C+P could be an alternative to high-dose P therapy and be safe in adult IgAN patients with relatively normal renal function and proteinuria of > 0.5 g/g. Development of safe and effective therapy is still a major challenge requiring well-controlled prospective studies with this or other combination therapies.

Endocan as a marker of microvascular inflammation in kidney transplant recipients.

Endocan is a water-soluble proteoglycan exclusively secreted by vascular endothelium. Endocan levels may be elevated in kidney transplant recipients experiencing antibody-mediated rejection (ABMR), which is characterized by vascular inflammation in transplanted kidney. We evaluated the clinical relevance of endocan as markers of microvascular inflammation in patients who underwent kidney transplantation. Plasma and urinary endocan levels were measured in 203 kidney transplant recipients and were compared across different etiologies of allograft dysfunction and various pathologic scores. Both plasma and urinary endocan levels were significantly higher in patients with acute ABMR than those in patients with normal pathology, acute tubular necrosis (ATN), acute pyelonephritis, BK virus associated nephropathy (BKVN), and T-cell mediated rejection (TCMR). Patients with chronic active ABMR also exhibited significantly higher plasma and urinary endocan levels than patients with long-term graft survival. Scores of glomerulitis and peritubular capillaritis, which are typical features of microvascular inflammation, were significantly elevated in patients with higher plasma and/or urinary endocan levels. Furthermore, plasma and urinary endocan levels could effectively discriminate ABMR from ATN, BKVN, and TCMR. Finally, patients exhibiting high urinary and plasma endocan levels in acute ABMR group showed significantly worse renal survival. Altogether, plasma and urinary endocan levels may serve as potential markers of microvascular inflammation in kidney transplant recipients.

Inflammasome-Independent Role of NLRP3 Mediates Mitochondrial Regulation in Renal Injury.

The NOD-like receptor family, pyrin domain containing-3 (NLRP3) inflammasome has been implicated in renal inflammation and fibrosis. However, the biological function of inflammasome-independent NLRP3 in non-immune cells is still unclear. We evaluated the role of inflammasome-independent NLRP3 in renal tubular cells and assessed the value of NLRP3 as a therapeutic target for acute kidney injury (AKI). Various renal tubular cell lines and primary cultured tubular cells from NLRP3 knockout (KO) mice were used for in vitro studies. We also tested the role of tubular NLRP3 in AKI with a unilateral ureter obstruction model (UUO). Hypoxia induced significant increase of NLRP3 independent of ASC, caspase-1, and IL-1ß. NLRP3 in renal tubular cells relocalized from the cytosol to the mitochondria during hypoxia and bound to mitochondrial antiviral signal protein (MAVS). The deletion of NLRP3 or MAVS in renal tubular cells attenuated mitochondrial reactive oxygen species (ROS) production and depolarization of the mitochondrial membrane potentials under hypoxia. In response to UUO, NLRP3 KO mice showed less fibrosis, apoptosis, and ROS injury than wild type (WT) mice. Compared with WT kidney, mitophagy was up-regulated in NLRP3 KO kidney relative to the baseline and it was protective against AKI. Our results indicate that inflammasome-independent NLRP3 in renal tubular cells plays important role in mitochondrial ROS production and injury by binding to MAVS after hypoxic injury. This mitochondrial regulation in the absence of NLRP3 increases autophagy and attenuates apoptosis after UUO. We suggest that inflammasome-independent NLRP3 could be a therapeutic target of AKI to prevent the progression of chronic kidney disease.