Tubulointerstitial Injury Research Articles

Triptolide attenuates renal damage by limiting inflammatory responses in DOCA-salt hypertension

BackgroundTriptolide (TP), a principal bioactive component of traditional Chinese medicine Tripterygium wilfordii Hook. F., has been shown to have immunosuppressive/anti-inflammatory actions in vitro. Moreover, it is well established that inflammatory mechanisms contribute to the progression of hypertension-induced renal injury. Therefore, this study was performed to determine the protective effects of TP on renal injury in salt-sensitive hypertension and to identify the possible mechanisms for TP-induced protection. MethodsTen-week-old male C57BL/6 mice were subjected to uninephrectomy and deoxycorticosterone acetate (DOCA)-salt treatment with or without intraperitoneal administration of various concentrations of TP. ResultsFive weeks after the treatment, systolic blood pressure measured by tail-cuff plethysmography increased in DOCA-salt-treated mice, but no difference was found between DOCA-salt-treated mice with or without TP treatment. Treatment with TP dose-dependently attenuated increments in urinary albumin and 8-isoprostane excretion, and glomerulosclerosis and tubulointerstitial injury and fibrosis in DOCA-salt-treated mice. Moreover, our data showed that treatment with TP dose-dependently inhibited DOCA-salt-induced interstitial monocyte/macrophage infiltration associated with decreases in renal levels of proinflammatory cytokine/chemokine and adhesion molecule, as well as renal activated NF-κB concentrations. Our results also demonstrated that suppression of inflammatory responses with dexamethasone, an immunosuppressive agent, alleviated DOCA-salt hypertension-induced renal injury. ConclusionsTP treatment induced renal protection associated with inhibition of monocyte/macrophage-mediated inflammatory responses without lowering blood pressure. Thus, our data for the first time indicate that TP treatment ameliorates renal injury possibly via attenuating inflammatory responses in salt-sensitive hypertension.

Urine Biomarkers of Tubulointerstitial Injury in Diabetic Kidney Disease

Urine Biomarkers of Tubulointerstitial Injury in Diabetic Kidney Disease

Resistant starch slows the progression of CKD in the 5/6 nephrectomy mouse model.

BackgroundResistant Starch (RS) improves CKD outcomes. In this report, we study how RS modulates host‐microbiome interactions in CKD by measuring changes in the abundance of proteins and bacteria in the gut. In addition, we demonstrate RS‐mediated reduction in CKD‐induced kidney damage.MethodsEight mice underwent 5/6 nephrectomy to induce CKD and eight served as healthy controls. CKD and Healthy (H) groups were further split into those receiving RS (CKDRS, n = 4; HRS, n = 4) and those on normal diet (CKD, n = 4, H, n = 4). Kidney injury was evaluated by measuring BUN/creatinine and by histopathological evaluation. Cecal contents were analyzed using mass spectrometry‐based metaproteomics and de novo sequencing using PEAKS. All the data were analyzed using R/Bioconductor packages.ResultsThe 5/6 nephrectomy compromised kidney function as seen by an increase in BUN/creatinine compared to healthy groups. Histopathology of kidney sections showed reduced tubulointerstitial injury in the CKDRS versus CKD group; while no significant difference in BUN/creatinine was observed between the two CKD groups. Identified proteins point toward a higher population of butyrate‐producing bacteria, reduced abundance of mucin‐degrading bacteria in the RS fed groups, and to the downregulation of indole metabolism in CKD groups.ConclusionRS slows the progression of chronic kidney disease. Resistant starch supplementation leads to active bacterial proliferation and the reduction of harmful bacterial metabolites.

Quantitative Magnetization Transfer Detects Renal Fibrosis in Murine Kidneys With Renal Artery Stenosis.

Renal fibrosis is a common pathway in tubulointerstitial injury and a major determinant of renal insufficiency. Collagen deposition, a key feature of renal fibrosis, may serve as an imaging biomarker to differentiate scarred from healthy kidneys. To test the feasibility of using quantitative magnetization transfer (qMT), which assesses tissue macromolecule content, to measure renal fibrosis. Prospective. Fifteen 129S1 mice were studied 4 weeks after either sham (n = 7) or unilateral renal artery stenosis (RAS, n = 8) surgeries. Magnetization transfer (MT)-weighted images were acquired at 16.4T using an MT-prepared fast-low-angle-shot sequence. Renal B0, B1, and T1 maps were also acquired, using a dual-echo gradient echo, an actual flip angle, and inversion recovery method, respectively. A two-pool model was used to estimate the bound water fraction (f) and other tissue imaging biomarkers. Masson's trichrome staining was subsequently performed ex vivo to evaluate renal fibrosis. Comparisons of renal parameters between sham and RAS were performed using independent samples t-tests. Pearson's correlation was conducted to investigate the relationship between renal fibrosis by histology and the qMT-derived bound pool fraction f. The two-pool model provided accurate fittings of measured MT signal. The qMT-derived f of RAS kidneys was significantly increased compared to sham in all kidney zones (renal cortex [CO], 7.6 ± 2.4% vs. 4.6 ± 0.6%; outer medulla [OM], 8.2 ± 4.2% vs. 4.2 ± 0.9%; inner medulla [IM] + P, 5.8 ± 1.6% vs. 2.9 ± 0.6%, all P < 0.05). Measured f correlated well with histological fibrosis in all kidney zones (CO, Pearson's correlation coefficient r = 0.95; OM, r = 0.93; IM + P, r = 0.94, all P < 0.05). The bound pool fraction f can be quantified using qMT at 16.4T in murine kidneys, increases significantly in fibrotic RAS kidneys, and correlates well with fibrosis by histology. Therefore, qMT may constitute a valuable tool for measuring renal fibrosis in RAS. 1 TECHNICAL EFFICACY STAGE: 3.

Histological diagnosis of immune checkpoint inhibitor induced acute renal injury in patients with metastatic melanoma: a retrospective case series report

BackgroundImmune checkpoint inhibitors (ICI) have become the standard of care in many oncological conditions but are associated with a spectrum of renal immune-related adverse events (IrAEs). We aimed to describe the spectrum, histology, management and outcomes of renal IrAE in patients with metastatic melanoma undergoing ICI therapy.MethodsWe conducted a retrospective review of 23 patients with a diagnosis of metastatic melanoma treated with ICI between January 2017 and April 2019 who developed a renal IrAE. Baseline demographic data, biochemical and histopathological results, management and outcomes were analyzed.ResultsThe majority of patients who developed renal irAE were male and received combination immunotherapy. The median time of onset from initiation of ICI therapy to renal IrAE was 4 months. 52% of the treated renal IrAE had histopathologically confirmed renal IrAE. The most common histological pattern of injury was acute tubulo-interstitial nephritis (92%). One patient developed anti-GBM disease with non-dialysis dependent stage 5 CKD. In tubulointerstitial injury, there was no association between peak creatinine, renal recovery and histologically reported inflammation or fibrosis. Patients with renal IrAE demonstrated persisting renal dysfunction at 3, 6 and 12 months with a mean baseline, 3 and 12 month creatinine of 90.0 μmol/L, 127.0 μmol/L and 107.5 μmol/L respectively.ConclusionRenal IrAE is most commonly attributable to steroid responsive acute tubulointerstitial nephritis. The outcome of rarer pathologies such as anti-GBM disease may be adversely affected by a delayed diagnosis. There is persisting renal dysfunction following an episode of renal IrAE that may have impact on future renal and overall survival outcomes.

Abstract P033: PRESSOR, NATRIURETIC, AND RENAL RESPONSES IN ANGIOTENSIN II-INDUCED HYPERTENSION IN MALE AND FEMALE WILD-TYPE AND PROXIMAL TUBULE-SPECIFIC AT 1A RECEPTOR KNOCKOUT MICE

Dysregulation of intrarenal renin-angiotensin system is one of the key factors of human hypertension, but the mechanisms involved remain incompletely understood. To determine the roles of AT 1a receptors in the proximal tubules of the kidney, we infused angiotensin II (Ang II) for 2 weeks (40 ng / min, i.p.) in adult male and female wild-type C57BL/6J and mutant mice with deletion of AT 1a receptors in the proximal tubules (PT- Agtr1a -/- ), and treated with or without the AT 1 receptor blocker losartan (20 mg/kg/day, p.o.) (n=8 per group). The pressor response, 24 h urinary Na + excretion, glomerular and tubulointerstitial injury were compared between male and female wild-type and PT- Agtr1a -/- mice. Basal systolic, diastolic, and mean arterial blood pressure were about 13 ± 3 mmHg lower in male and female PT- Agtr1a -/- mice ( P &lt;0.01), but no differences were observed between male and female wild-type or PT- Agtr1a -/- mice. In response to Ang II, both male and female wild-type and PT- Agtr1a -/- mice developed hypertension ( P &lt;0.01), and the net pressor response were similar in male and female wild-type and PT- Agtr1a -/- mice (n.s.). However, absolute blood pressure was about 12 ± 3 mmHg lower in male and female PT- Agtr1a -/- mice ( P &lt;0.01 vs. wild-type). Ang II-induced hypertension increased the natriuretic response in both male and female wild-type and PT- Agtr1a -/- mice ( P &lt;0.01), but there were no significant differences between male and female wild-type and PT- Agtr1a -/- mice (n.s). Losartan did not increase the natriuretic responses further in all animals. Furthermore, Ang II-induced hypertension was associated with significant increases in glomerular and tubulointerstitial injury in male and female wild-type mice ( P &lt;0.01), which were attenuated in male and female PT- Agtr1a -/- mice ( P &lt;0.01). LOS treatment attenuated Ang II-induced hypertension and decreased Ang II-induced glomerular and tubulointerstitial injury in male and female wild-type and PT- Agtr1a -/- mice ( P &lt;0.01). Taken together, we demonstrated that intratubular AT 1 (AT 1a ) receptors in the proximal tubules of the kidney plays a key role in maintaining basal blood pressure homeostasis and overall body salt and fluid balance, and the development of Ang II-induced hypertension and kidney injury.

Severity of Intrarenal Arterial Lesions Can Predict the Clinical Prognosis of Hepatitis B Virus-Associated Glomerulonephritis: A Retrospective Study

Background: Intrarenal arterial lesions (IALs) have been studied in immunoglobulin A nephropathy and lupus nephritis, but this has not been reported in hepatitis B virus-associated glomerulonephritis (HBV-GN). This study aims to investigate the prevalence and the role of IALs in HBV-GN. Methods: IALs were examined in kidney biopsy specimens from 205 patients with HBV-GN retrospectively. The severity of IALs and tubular interstitial lesions was scored semi-quantitatively. The severity of IALs was divided into 4 groups on the basis of ILA score, which were no IALs (Score 0), mild IALs (Score 1–2), moderate IALs (Score 3–4), and severe IALs (Score 5–10) groups. Survival analysis was performed using the Kaplan-Meier method between the severity of IALs and clinical events (doubling of serum creatinine [SCr], ESRD, and death due to the kidney disease). Results: Among 205 patients with HBV-GN, 143 (69.8%) had IALs in their kidney biopsy specimens. IALs were mild in 28 (19.6%) patients, moderate in 101 (70.6%) patients, and severe in 14 (9.8%) patients. The severity of IALs was associated with high blood pressure (BP), high SCr, and severe tubulointerstitial injuries. The average follow-up time of these 205 HBV-GN patients was 94.2 ± 47.1 months, in which 46 cases had clinical event. The proportions of clinical events in no IAL, mild IAL, moderate IAL, and severe IAL groups were 9.7, 14.3, 25.7, and 71.4%, respectively. Event-free survival of patient in IAL group was significantly lower than that in the no IAL group (p = 0.000). Multivariate cox regression analysis indicated SCr (1.011, 1.007–1.016), hypertension (1.767, 1.004–3.108), and IAL (2.194, 1.062–4.530) were independent risk factors for clinical events after adjustment for age and gender. Event-free clinical survival in moderate and severe IAL groups was significantly lower than that in the no IAL group (p = 0.0111 and p = 0.0001, respectively). Besides, event-free renal survival in severe IAL group was significantly lower than that in moderate IAL group (p = 0.009). Multivariate cox regression analysis showed that the more severe the IALs, the higher the risk of the clinical event, with a hazard ratio of 2.284 for moderate IALs (1.085–4.907) and 3.315 for severe IALs (1.296–8.482). Conclusions: Severity of IALs is associated with high BP, reduced renal function, and poor clinical prognosis in HBV-GN patients.

Sodium Oxalate-Induced Acute Kidney Injury Associated With Glomerular and Tubulointerstitial Damage in Rats.

Acute crystalline nephropathy is closely related to tubulointerstitial injury, but few studies have investigated glomerular changes in this condition. Thus, in the current study, we investigated the factors involved in glomerular and tubulointerstitial injury in an experimental model of crystalline-induced acute kidney injury (AKI). We treated male Wistar rats with a single injection of sodium oxalate (NaOx, 7 mg⋅100 g–1⋅day–1, resuspended in 0.9% NaCl solution, i.p.) or vehicle (control). After 24 h of treatment, food and water intake, urine output, body weight gain, and renal function were evaluated. Renal tissue was used for the morphological studies, quantitative PCR and protein expression studies. Our results revealed that NaOx treatment did not change metabolic or electrolyte and water intake parameters or urine output. However, the treated group exhibited tubular calcium oxalate (CaOx) crystals excretion, followed by a decline in kidney function demonstrated along with glomerular injury, which was confirmed by increased plasma creatinine and urea concentrations, increased glomerular desmin immunostaining, nephrin mRNA expression and decreased WT1 immunofluorescence. Furthermore, NaOx treatment resulted in tubulointerstitial injury, which was confirmed by tubular dilation, albuminuria, increased Kim-1 and Ki67 mRNA expression, decreased megalin and Tamm–Horsfall protein (THP) expression. Finally, the treatment induced increases in CD68 protein staining, MCP-1, IL-1β, NFkappaB, and α-SMA mRNA expression, which are consistent with proinflammatory and profibrotic signaling, respectively. In conclusion, our findings provide relevant information regarding crystalline-induced AKI, showing strong tubulointerstitial and glomerular injury with a possible loss of podocyte viability.

Complete remission of nephrotic syndrome in a young woman with anti-LRP2 nephropathy after immunosuppressive therapy

BackgroundAnti-low density lipoprotein receptor-related protein 2 (LRP2) nephropathy/anti-brush border antibody (ABBA) disease is a disorder characterized by acute tubulointerstitial injury associated with circulating antibodies to kidney proximal tubular brush border protein LRP2/megalin. Patients are typically elderly and present with acute kidney injury and subnephrotic proteinuria. They progress to end-stage renal disease with poor response to immunosuppressive therapies.Case presentationWe report a case of a 29-year-old Chinese woman, who presented with nephrotic syndrome with normal kidney function. Kidney biopsy showed no obvious tubular injury or interstitial inflammation. Positive immunoglobulin G (IgG) staining was revealed along the brush border of proximal tubular cells. Anti-LRP2 antibody was identified in serum, consistent with a diagnosis of anti-LRP2 nephropathy. The patient achieved complete remission after receiving prednisone and cyclophosphamide.ConclusionsAnti-LRP2 nephropathy can also present as nephrotic syndrome in young patients and complete remission from nephrotic syndrome may be achieved after immunosuppressive therapy.

Renoprotective effects of paramylon, a β-1,3-D-Glucan isolated from Euglena gracilis Z in a rodent model of chronic kidney disease

Paramylon is a novel β-glucan that is stored by Euglena gracilis Z, which is a unicellular photosynthesizing green alga with characteristics of both animals and plants. Recent studies have indicated that paramylon functions as an immunomodulator or a dietary fiber. Currently, chronic kidney disease (CKD) is a global health problem, and there is no effective preventive treatment for CKD progression. However, paramylon may suppress the progression of CKD via the elimination of uremic toxins or modulation of gut microbiota, leading to the alleviation of inflammation. The aim of this study was to evaluate the effect of paramylon in CKD rat model. Eight-week-old male Wistar rats with a 5/6 nephrectomy were given either a normal diet or a diet containing 5% paramylon for 8 weeks. Proteinuria was measured intermittently. Serum and kidney tissues were harvested after sacrifice. We performed a renal molecular and histopathological investigation, serum metabolome analysis, and gut microbiome analysis. The results showed that paramylon attenuated renal function, glomerulosclerosis, tubulointerstitial injury, and podocyte injury in the CKD rat model. Renal fibrosis, tubulointerstitial inflammatory cell infiltration, and proinflammatory cytokine gene expression levels tended to be suppressed with paramylon treatment. Further, paramylon inhibited the accumulation of uremic toxins, including tricarboxylic acid (TCA) cycle-related metabolites and modulated a part of CKD-related gut microbiota in the CKD rat model. In conclusion, we suggest that paramylon mainly inhibited the absorption of non-microbiota-derived uremic solutes, leading to protect renal injury via anti-inflammatory and anti-fibrotic effects. Paramylon may be a novel compound that can act against CKD progression.

Electrophoretic analysis (sds-page) of canine urinary proteins according to the stage of chronic kidney disease

ABSTRACT Glomerular proteinuria is characterized by the loss of high-molecular-weight proteins (HMWPs), while tubulointerstitial proteinuria is characterized by the loss of low-molecular-weight proteins (LMWPs). The objective was to assess the molecular weight of urinary proteins (MWUP) in dogs with naturally acquired CKD and determine the proportion of HMWPs and LMWPs according to CKD stage. Twenty-eight dogs with CKD were recruited and divided into 4 groups based on serum creatinine (Cr) levels (group1: Cr&lt;1,4, n=8; group2: 1,4&lt;Cr&lt;2,0, n=6; group3: 2,1&lt;Cr&lt;5, n=9; group4: Cr&gt;5,0, n=5). The control group consisted of 5 healthy dogs. The MWUP was determined by SDS-PAGE. The urinary protein-to-creatinine ratio (UP/C) was used to quantitatively assess proteinuria. The electrophoresis pattern revealed a proportionally greater loss of HMWPthan of LMWP in all groups with CKD and an increased loss of LMWP in group 4 (P&lt;0.05). These results suggest a predominance of glomerular injuries throughout all stages of CKD in these dogs and an increase in tubulointerstitial injury towards the end-stage of the disease. The results of the present study support the recommendation of SDS-PAGE as an effective technique for the qualitative assessment of proteinuria, as well as a method for assessing the severity and location of renal injury.

A nomogram for the prediction of renal outcomes among patients with idiopathic membranous nephropathy

The early prediction of renal outcomes in patients with idiopathic membranous nephropathy (iMN) remains challenging. The present retrospective study evaluated patients with iMN confirmed by renal biopsy. An optimized Cox regression model and a nomogram were constructed for the early prediction of renal outcomes. A total of 141 patients who met the inclusion criteria were evaluated in the present study. In total 18 (12.8%) patients eventually progressed to the endpoint, 6 of whom developed end-stage renal disease, and one patient died during follow-up. The optimized model demonstrated that 24-h proteinuria [hazard ratio (HR) 1.24; 95% CI, 1.10-1.40; P-value <0.001] and chronic tubulointerstitial injury [referred to as grade 0, grade 1 (HR), 5.12; 95% CI, 1.33-19.75; P-value=0.02] or grade 2 (HR, 6.43; 95% CI, 1.35-30.59; P-value=0.02) were independent risk factors for a poor renal outcome. Patients with an estimated three-year renal survival rate (ETR) less than 0.87 had a high risk of a poor renal outcome. In addition, patients with an ETR of 0.87 to 0.98 more quickly developed a decreased estimated glomerular filtration rate after two years of follow-up. In the present study a nomogram for the early prediction of renal outcomes in patients with iMN was developed. This nonogram suggested that patients with an ETR of 0.87-0.98 should receive greater attention during follow-up.

Cholesterol crystals tubulointerstitial injury during nephrotic syndrome; can be classified as tubular crystallopathy?

Introduction: Cholesterol crystals and granulomas in tubular lumen and interstitium of the kidney are infrequent findings during nephrotic syndrome (NS) and are poorly described. We attempt to discuss cholesterol crystals in NS as a form of crystallopathy. Case Presentation: Three cases of 207 (1.5%) performed kidney biopsies, between 2001 and 2019, in patients with NS, showed cholesterol crystals deposition in tubules, interstitium and even cholesterol granulomas with some degree of interstitial mononuclear inflammation with giant cells, interstitial fibrosis and variable tubular atrophy. Oil Red O staining revealed lipid laden macrophages in interstitium and lipid droplets in tubular epithelium. Two patients had membranous glomerulonephritis (MGN) and one membranoproliferative glomerulonephritis (MPGN). The proteinuria ranged from 6.08 to 12.57 g/24 hours, lasting from 1 to 22 months. All had hypertension, high values of serum cholesterol and triglycerides. Conclusion: Clinically significant deposition of cholesterol crystals in kidney is mainly in atheroembolic renal disease, however deposition of cholesterol crystals during NS is rare and it is not considered a form of crystallopathy. Cholesterol crystals do not seem to be correlated with degree of proteinuria, persistence of NS or type of glomerulonephritis, but it is correlated with amount of serum cholesterol which is strongly associated with the severity of NS. Therefore we propose it as tubular crystallopathy, in the setting of NS associated hypercholesterolemia which may cause chronic kidney disease (CKD).

Huangkui Capsule Ameliorates Renal Fibrosis in a Unilateral Ureteral Obstruction Mouse Model Through TRPC6 Dependent Signaling Pathways.

Renal fibrosis is the final common pathological manifestation of almost all progressive chronic kidney diseases (CKD). Transient receptor potential canonical (TRPC) channels, especially TRPC3/6, were proposed to be essential therapeutic targets for kidney injury. Huangkui capsule (HKC), an important adjuvant therapy for CKD, showed superior efficacy for CKD at stages 1–2 in clinical practice. However, its anti-fibrotic effect and the underlying mechanisms remain to be investigated. In the present study, we evaluated the efficacy of HKC on renal fibrosis in a mouse model of unilateral ureteral obstruction (UUO) and explored the potential underlying mechanism. Administration of HKC by intragastric gavage dose-dependently suppressed UUO-induced kidney injury and tubulointerstitial fibrosis. Similarly, HKC suppressed the expression level of α-smooth muscle actin (α-SMA), increased the expression of E-cadherin, and suppressed the mRNA expression of a plethora of proinflammatory mediators that are necessary for the progression of renal fibrosis. Mechanistically, HKC suppressed both canonical and non-canonical TGF-β signaling pathways in UUO mice as well as the TRPC6/calcineurin A (CnA)/nuclear factor of activated T cells (NFAT) signaling axis. In addition, TRPC6 knockout mice and HKC treated wild type mice displayed comparable protection on UUO-triggered kidney tubulointerstitial injury, interstitial fibrosis, and α-SMA expression. More importantly, HKC had no additional protective effect on UUO-triggered kidney tubulointerstitial injury and interstitial fibrosis in TRPC6 knockout mouse. Further investigation demonstrated that HKC could directly suppress TRPC3/6 channel activities. Considered together, these data demonstrated that the protective effect of HKC on renal injury and interstitial fibrosis is dependent on TRPC6, possibly through direct inhibition of TRPC6 channel activity and indirect suppression of TRPC6 expression.

Cardio-renal protective effect of the xanthine oxidase inhibitor febuxostat in the 5/6 nephrectomy model with hyperuricemia

Although hyperuricemia has been shown to be associated with the progression of cardiovascular disorder and chronic kidney disease (CKD), there is conflicting evidence as to whether xanthine oxidase (XO) inhibitors confer organ protection besides lowering serum urate levels. In this study, we addressed the cardio-renal effects of XO inhibition in rodent CKD model with hyperuricemia. Sprague-Dawley rats underwent 5/6 nephrectomy and received a uricase inhibitor oxonic acid for 8 weeks (RK + HUA rats). In some rats, a XO inhibitor febuxostat was administered orally. Compared with control group, RK + HUA group showed a significant increase in albuminuria and renal injury. Febuxostat reduced serum uric acid as well as urinary albumin levels. Histological and immunohistochemical analysis of the kidney revealed that febuxostat alleviated glomerular, tubulointerstitial, and arteriolar injury in RK + HUA rats. Moreover, in the heart, RK + HUA showed individual myofiber hypertrophy and cardiac fibrosis, which was significantly attenuated by febuxostat. We found that renal injury and the indices of cardiac changes were well correlated, confirming the cardio-renal interaction in this model. Finally, NF-E2-related factor 2 (Nrf2) and the downstream target heme oxygenase-1 (HO-1) protein levels were increased both in the heart and in the kidney in RK + HUA rats, and these changes were alleviated by febuxostat, suggesting that tissue oxidative stress burden was attenuated by the treatment. These data demonstrate that febuxostat protects against cardiac and renal injury in RK + HUA rats, and underscore the pathological importance of XO in the cardio-renal interaction.

Characterization of acute kidney injury in critically ill patients with severe coronavirus disease 2019.

BackgroundCoronavirus disease 2019 (COVID-19)-associated acute kidney injury (AKI) frequency, severity and characterization in critically ill patients has not been reported.MethodsSingle-centre cohort performed from 3 March 2020 to 14 April 2020 in four intensive care units in Bordeaux University Hospital, France. All patients with COVID-19 and pulmonary severity criteria were included. AKI was defined using Kidney Disease: Improving Global Outcomes (KDIGO) criteria. A systematic urinary analysis was performed. The incidence, severity, clinical presentation, biological characterization (transient versus persistent AKI; proteinuria, haematuria and glycosuria) and short-term outcomes were evaluated.ResultsSeventy-one patients were included, with basal serum creatinine (SCr) of 69 ± 21 µmol/L. At admission, AKI was present in 8/71 (11%) patients. Median [interquartile range (IQR)] follow-up was 17 (12–23) days. AKI developed in a total of 57/71 (80%) patients, with 35% Stage 1, 35% Stage 2 and 30% Stage 3 AKI; 10/57 (18%) required renal replacement therapy (RRT). Transient AKI was present in only 4/55 (7%) patients and persistent AKI was observed in 51/55 (93%). Patients with persistent AKI developed a median (IQR) urine protein/creatinine of 82 (54–140) (mg/mmol) with an albuminuria/proteinuria ratio of 0.23 ± 20, indicating predominant tubulointerstitial injury. Only two (4%) patients had glycosuria. At Day 7 after onset of AKI, six (11%) patients remained dependent on RRT, nine (16%) had SCr >200 µmol/L and four (7%) had died. Day 7 and Day 14 renal recovery occurred in 28% and 52%, respectively.ConclusionSevere COVID-19-associated AKI is frequent, persistent, severe and characterized by an almost exclusive tubulointerstitial injury without glycosuria.

Induction of Autophagy by Pterostilbene Contributes to the Prevention of Renal Fibrosis via Attenuating NLRP3 Inflammasome Activation and Epithelial-Mesenchymal Transition.

Chronic kidney disease (CKD) is recognized as a global public health problem. NLRP3 inflammasome activation has been characterized to mediate diverse aspect mechanisms of CKD through regulation of proinflammatory cytokines, tubulointerstitial injury, glomerular diseases, renal inflammation, and fibrosis pathways. Autophagy is a characterized negative regulation mechanism in the regulation of the NLRP3 inflammasome, which is now recognized as the key regulator in the pathogenesis of inflammation and fibrosis in CKD. Thus, autophagy is undoubtedly an attractive target for developing new renal protective treatments of kidney disease via its potential effects in regulation of inflammasome. However, there is no clinical useful agent targeting the autophagy pathway for patients with renal diseases. Pterostilbene (PT, trans-3,5-dimethoxy-4-hydroxystilbene) is a natural analog of resveratrol that has various health benefits including autophagy inducing effects. Accordingly, we aim to investigate underlying mechanisms of preventive and therapeutic effects of PT by reducing NLRP3 inflammasome activation and fibrosis through autophagy-inducing effects. The renal protective effects of PT were evaluated by potassium oxonate (PO)-induced hyperuricemia and high adenine diet-induced CKD models. The autophagy induction mechanisms and anti-fibrosis effects of PT by down-regulation of NLRP3 inflammasome are investigated by using immortalized rat kidney proximal tubular epithelial NRK-52E cells. To determine the role of autophagy induction in the alleviating of NLRP3 inflammasome activation and epithelial-mesenchymal transition (EMT), NRK-52E with Atg5 knockdown [NRK-Atg5-(2)] cells were applied in the study. The results indicated that PT significantly reduces serum uric acid levels, liver xanthine oxidase activity, collagen accumulation, macrophage recruitment, and renal fibrosis in CKD models. At the molecular levels, pretreatment with PT downregulating TGF-β-triggered NLRP3 inflammasome activation, and subsequent EMT in NRK-52E cells. After blockage of autophagy by treatment of Atg5 shRNA, PT loss of its ability to prevent NLRP3 inflammasome activation and EMT. Taken together, we suggested the renal protective effects of PT in urate nephropathy and proved that PT induces autophagy leading to restraining TGF-β-mediated NLRP3 inflammasome activation and EMT. This study is also the first one to provide a clinical potential application of PT for a better management of CKD through its autophagy inducing effects.

P0739PANEL OF SENSITIVE BIOMARKERS OF THE PRIMARY RESPONSE TO RENAL INJURY FOR AN EARLY DIAGNOSIS OF CHRONIC KIDNEY DISEASE

Abstract Background and Aims The identification of early kidney injury biomarkers is of utmost importance, since most widely used markers of kidney function vary only after several biological changes. Biomarkers allowing an earlier diagnosis of chronic kidney disease (CKD) would avoid delays in the treatment of patients. It is unlikely that a single marker is sufficient to detect the onset of CKD considering the multiple pathophysiological changes underlying primary renal response to renal injury. Several markers of inflammation, endothelial (dys)function, glomerular and tubulointerstitial injuries have been proposed and could be used combined as a panel of markers with different specificities, allowing an early detection of renal injury. Our aim was to study a panel of biomarkers proposed as early markers of renal injury, with different specificities, to evaluate and compare their sensitivities at different CKD stages. Method In this preliminary study, we enrolled 22 healthy individuals and 27 CKD patients separated into 3 groups, according to the CKD stage: 9 in stages 1 and 2; 9 in stage 3, and 9 in stages 4 and 5. None of the patients presented inflammatory, infectious or neoplastic diseases. Diagnosis and CKD stage assignment were performed according to KDIGO guidelines. We evaluated circulating levels of cystatin C (CystC), creatinine (Cr), beta trace protein (BTP) as markers of renal function; tissue inhibitor metalloproteinase 1 (TIMP-1), neutrophil gelatinase-associated lipocalin (NGAL) and transforming growth factor-β (TGF-β) as markers of interstitial tubulointerstitial injury; asymmetric dimethylarginine (ADMA) and tissue plasminogen activator (t-PA), as markers of endothelial (dys)function; pentraxin 3 (PTX3), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), as markers of inflammation; and, pro B-type natriuretic peptides (proBNP), as a marker of cardiac (dys)function. Results In early stages of CKD (1 and 2), we found significant changes in markers of renal function (BTP, but not Cr and CystC), of tubular interstitial injury (TIMP-1 and TGF-β), of inflammation (TNF-α), of endothelial (ADMA) and cardiac (proBNP) dysfunction (vs. controls). In stage 3, we found significant changes (vs. stages 1-2) in markers of renal function (Cr and CystC), inflammation (TNF-α, IL-6), endothelial dysfunction (t-PA) and tubulointerstitial injury (TIMP-1); in stages 4-5 (vs. stage 3), we found significant changes only in the classic marker, Cr, and a trend towards increased CystC. Moreover, we found that at stages 1-2 all patients showed higher levels of BTP and proBNP when compared to the median value in the control group; TIMP-1 and ADMA were increased in 7/9 patients; TNF-α was increased in 7/9 patients; and 7/9 patients had lower values of TGF-β compared to the median value of controls. For the classical markers, Cr and CystC, we found that 5/9 and 4/9 patients, respectively, had lower values than the median value of controls; however, only 2/9 patients showed abnormal creatinine values (vs. reference values). Conclusion Our data suggest that a panel including classic (Cr and CystC) and more sensitive blood markers of the primary response to renal injury (BTP, TIMP-1 or TGF-β, ADMA, TNF-α and proBNP) would allow an earlier diagnosis of CKD, avoiding a delay in diagnosis and management of CKD patients.

AB0412 URINARY SOLUBLE VCAM-1 IS A USEFUL BIOMARKER OF DISEASE ACTIVITY AND TREATMENT RESPONSE IN LUPUS NEPHRITIS

Background:The traditional lupus nephritis (LN) biomarkers are not sensitive nor specific enough for detecting ongoing disease activity and early relapse of nephritis and they do not reflect kidney damage nor have prognostic value1. Urinary biomarkers are directly excreted by the kidney and are easily obtained. They can also differentiate the renal activity of the disease from other organic manifestations more accurately than the serum biomarkers2. Vascular cell adhesion molecule-1 (VCAM-1) is involved in the progression of glomerular and tubulointerstitial injury in LN and its soluble form can be easily assessed in urine (uVCAM-1)3. Several studies correlated the uVCAM-1 levels with urine protein-creatinine ratio (UPC), with general disease activity and with active LN3.Objectives:To assess uVCAM-1 as a biomarker of disease activity and treatment response in LN.Methods:This prospective study enrolled patients with class III, IV or V LN diagnosed within the last three years and divided them in two groups: with and without active nephritis at the inclusion. The patients with active nephritis were included before they started a new immunosuppressive treatment. Active LN was defined as proteinuria (UPC≥0.5) plus active urinary sediment (hematuria, leukocyturia or cellular hematic/granular casts). At each visit, a urine sample was collected for uVCAM-1 evaluation and the nephritis status was accessed.Results:Median uVCAM-1 level was elevated in patients with active compared to inactive LN (p&lt;0.001). The ROC curve of uVCAM-1 demonstrated an AUC of 0.84 and a cutoff of 47.2 ng/mgCr yielded a good sensitivity (74.2%) and specificity (74.2%) for the diagnosis of active LN. A significant correlation was found between uVCAM-1 level and renal activity scores and traditional biomarkers of LN (table 1). The level of uVCAM-1 dropped in patients with active LN who went into remission (p&lt;0.001), increased in patients who went into activity (p=0.002) and did not change in patients who remained inactive (p=0.797) (figure 1). The level of uVCAM-1 peaked during the flare of LN (p&lt;0.05) (figure 2).Table 1.Correlations between urinary soluble VCAM-1 and other LN biomarkers/disease scoresLN biomarkers/disease scoresVCAM-1SLEDAI-2k0.597***Renal SLEDAI0.569***Renal SLAM-R0.470***Renal SLICC0.620***Anti-dsDNA0.342**C3-0.344**C4-0.382**UPC0.654***Spearman’s correlation coefficients*pvalue &lt;0.05; **pvalue &lt;0.01; ***pvalue &lt;0.001C, complement; LN, lupus nephritis; SLEDAI, Systemic Lupus Erythematosus Disease Activity Index; renal SLAM-R, The renal Systemic Lupus Activity Measure revised; renal SLICC, The Systemic Lupus International Collaborating Clinics renal activity/response exercise; UPC, urine protein-creatinine ratio.Conclusion:The uVCAM-1 is a reliable biomarker that reflects renal disease activity and is useful for monitoring individual patients with lupus nephritis over time.

P0061LOSS OF UBIQUITIN SPECIFIC PROTEASE-40 CAUSES PODOCYTE DETACHMENT AND CONTRIBUTES TO THE DISEASE PROGRESSION OF GLOMERULOSCLEROSIS

Abstract Background and Aims We reported that the ubiquitin specific protease-40 (USP40) is expressed in podocytes beyond the species and plays a crucial role in glomerulogenesis in zebrafish (Takagi H, Am J Physiol Renal Physiol 2017). However, the role of USP40 in podocytes and its functional downstream after birth is largely unknown. Recent report indicated that other USP family: USP10 regulates integrin beta1 and fibrotic wound healing in myofibroblasts (Gillespie SR, J Cell Sci 2017). The present study aimed to explore the biological role of USP40 in the acquired podocyte injury and to determine the interacting partner by focusing on podocyte detachment. Method We generated USP40-knockout mice (USP40KO); however, they showed no apparent kidney abnormality. Therefore, to explore the biological role of USP40 in acquired podocyte injury, we crossed USP40KO with NEP25 mice, in which selective podocyte injury can be induced by injection with an immunotoxin, LMB2. Urinary protein was analyzed until day 9 after LMB2 injection, and then kidney tissues were subjected to light microscopy, immunohistochemistry of p57, and immunofluorescence microscopy of integrin beta1. The glomeruli were isolated and subjected to immunoblot analysis of integrin beta1. The effect of USP40 knockdown on integrin beta1 expression was studied in cultured mouse podocytes. Finally, the protein binding of integrin beta1 with USP40 was determined by immunoprecipitation using cultured mouse podocytes. Results NEP-USP40KO mice developed earlier and higher levels of proteinuria compared with NEP mice. Light microscopy and immunohistochemistry showed higher levels of kidney injury in NEP-USP40KO mice compared with NEP mice in terms of hyalinosis (p&amp;lt;0.01), crescent formation (p&amp;lt;0.01), and cell proliferation (p&amp;lt;0.01) in the glomeruli, podocyte loss (p&amp;lt;0.05), and tubulointerstitial injury (p&amp;lt;0.01). Immunoblot analysis and immunofluorescence revealed decreased expression of integrin beta1 in podocytes of NEP-USP40KO mice compared with NEP mice. Gene knockdown of USP40 in cultured podocytes decreased the protein expression of integrin beta1. Finally, apparent protein binding of USP40 with integrin beta1 was observed. Conclusion Integrin beta1 is known to play a crucial role as the adhesion molecule that connects the podocytes with the extracellular matrix of the glomerular basement membrane. It is also known that the lack of integrin beta1 causes podocyte detachment, which is involved in the disease progression of glomerulosclerosis. Therefore, the present study suggests that USP40 may be involved in a self-defense mechanism in podocyte injury probably through interacting with the regulatory machinery of integrin beta1 in podocytes.