Metagenome-wide analysis uncovers gut microbial signatures and implicates taxon-specific functions in end-stage renal disease.

BACKGROUND: The gut microbiota plays a crucial role in regulating host metabolism and producing uremic toxins in patients with end-stage renal disease (ESRD). Our objective is to advance toward a holistic understanding of the gut ecosystem and its functional capacity in such patients, which is still lacking. RESULTS: Herein, we explore the gut microbiome of 378 hemodialytic ESRD patients and 290 healthy volunteers from two independent cohorts via deep metagenomic sequencing and metagenome-assembled-genome-based characterization of their feces. Our findings reveal fundamental alterations in the ESRD microbiome, characterized by a panel of 348 differentially abundant species, including ESRD-elevated representatives of Blautia spp., Dorea spp., and Eggerthellaceae, and ESRD-depleted Prevotella and Roseburia species. Through functional annotation of the ESRD-associated species, we uncover various taxon-specific functions linked to the disease, such as antimicrobial resistance, aromatic compound degradation, and biosynthesis of small bioactive molecules. Additionally, we show that the gut microbial composition can be utilized to predict serum uremic toxin concentrations, and based on this, we identify the key toxin-contributing species. Furthermore, our investigation extended to 47 additional non-dialyzed chronic kidney disease (CKD) patients, revealing a significant correlation between the abundance of ESRD-associated microbial signatures and CKD progression. CONCLUSION: This study delineates the taxonomic and functional landscapes and biomarkers of the ESRD microbiome. Understanding the role of gut microbiota in ESRD could open new avenues for therapeutic interventions and personalized treatment approaches in patients with this condition.

14-3-3ζ targets ß-catenin nuclear translocation to maintain mitochondrial homeostasis and promote the balance between proliferation and apoptosis in cisplatin-induced acute kidney injury.

Cisplatin is a chemotherapeutic agent that is used extensively to treat solid tumors; however, its clinical application is limited by side effects, especially nephrotoxicity. Cisplatin-induced acute kidney injury (AKI) is characterized by DNA damage, cell-cycle arrest, and mitochondrial oxidative stress. Recent research demonstrated that 14-3-3ζ plays an important role in cancers, nerve disease, and kidney disease, although the regulatory mechanisms underlying cisplatin-induced AKI have yet to be fully elucidated. In the present study, we found that 14-3-3ζ mRNA was upregulated in human kidney organoids (GSE145085) when treated with cisplatin; subsequently, this was confirmed in experimental mice. The application of a protein interaction inhibitor for 14-3-3 (BV02) resulted in a decline in renal function, along with apoptosis, mitochondrial dysfunction, and oxidative stress in cisplatin-induced AKI. Accordingly, the knockdown of 14-3-3ζ in cisplatin-treated NRK-52E cells led to increased apoptosis, cell-cycle arrest, the production of reactive oxygen species (ROS), and lipid dysbolism. Furthermore, the blockade of 14-3-3ζ, both in vivo and in vitro, suppressed ß-catenin and its nuclear translocation, thus downregulating expression of the downstream gene cyclin D1 in cisplatin-induced damage. In contrast, the overexpression of 14-3-3ζ alleviated the injury caused by cisplatin both in vivo and in vitro. Furthermore, a non-specific agonist of ß-catenin, BIO, reversed the effects of 14-3-3ζ knockdown in terms of cisplatin-induced damage in NRK-52E cells by activating ß-catenin. Next, we verified the direct interaction between 14 - 3-3ζ and ß-catenin by CO-IP and immunofluorescence. Collectively, these findings indicate that 14-3-3ζ protects against cisplatin-induced AKI by improving mitochondrial function and the balance between proliferation and apoptosis by facilitating the nuclear translocation of ß-catenin.

Risk factor mining and prediction of urine protein progression in chronic kidney disease: a machine learning- based study.

BACKGROUND: Chronic kidney disease (CKD) is a global public health concern. Therefore, to provide timely intervention for non-hospitalized high-risk patients and rationally allocate limited clinical resources is important to mine the key factors when designing a CKD prediction model. METHODS: This study included data from 1,358 patients with CKD pathologically confirmed during the period from December 2017 to September 2020 at Zhongshan Hospital. A CKD prediction interpretation framework based on machine learning was proposed. From among 100 variables, 17 were selected for the model construction through a recursive feature elimination with logistic regression feature screening. Several machine learning classifiers, including extreme gradient boosting, gaussian-based naive bayes, a neural network, ridge regression, and linear model logistic regression (LR), were trained, and an ensemble model was developed to predict 24-hour urine protein. The detailed relationship between the risk of CKD progression and these predictors was determined using a global interpretation. A patient-specific analysis was conducted using a local interpretation. RESULTS: The results showed that LR achieved the best performance, with an area under the curve (AUC) of 0.850 in a single machine learning model. The ensemble model constructed using the voting integration method further improved the AUC to 0.856. The major predictors of moderate-to-severe severity included lower levels of 25-OH-vitamin, albumin, transferrin in males, and higher levels of cystatin C. CONCLUSIONS: Compared with the clinical single kidney function evaluation indicators (eGFR, Scr), the machine learning model proposed in this study improved the prediction accuracy of CKD progression by 17.6% and 24.6%, respectively, and the AUC was improved by 0.250 and 0.236, respectively. Our framework can achieve a good predictive interpretation and provide effective clinical decision support.

Urinary N-Acetyl-Beta-D-Glucosaminidase levels predict immunoglobulin a nephropathy remission status.

BACKGROUND: Tubulointerstitial lesions play a pivotal role in the progression of IgA nephropathy (IgAN). Elevated N-acetyl-beta-D-glucosaminidase (NAG) in urine is released from damaged proximal tubular epithelial cells (PTEC) and may serve as a biomarker of renal progression in diseases with tubulointerstitial involvement. METHODS: We evaluated the predictive value of urinary NAG (uNAG) for disease progression in 213 biopsy-proven primary IgAN patients from January 2018 to December 2019 at Zhongshan Hospital, Fudan University. We compared the results with those of serum cystatin C (sCysC). RESULTS: Increased uNAG and sCysC levels were associated with worse clinical and histological manifestations. Only uNAG level was independently associated with remission status after adjustment. Patients with high uNAG levels (> 22.32 U/g Cr) had a 4.32-fold greater risk of disease progression. The combination of baseline uNAG and clinical data may achieve satisfactory risk prediction in IgAN patients with relatively preserved renal function (eGFR ≥ 60 ml/min/1.73 m2, area under the curve [AUC] 0.760). CONCLUSION: Our results suggest that uNAG is a promising biomarker for predicting IgAN remission status.

Acid-sensing ion channel 1a exacerbates renal ischemia-reperfusion injury through the NF-κB/NLRP3 inflammasome pathway.

Ischemia-reperfusion injury (IRI) is the main cause of acute kidney injury (AKI), and there is no effective therapy. Microenvironmental acidification is generally observed in ischemic tissues. Acid-sensing ion channel 1a (ASIC1a) can be activated by a decrease in extracellular pH which mediates neuronal IRI. Our previous study demonstrated that, ASIC1a inhibition alleviates renal IRI. However, the underlying mechanisms have not been fully elucidated. In this study, we determined that renal tubule-specific deletion of ASIC1a in mice (ASIC1afl/fl/CDH16cre) attenuated renal IRI, and reduced the expression of NLRP3, ASC, cleaved-caspase-1, GSDMD-N, and IL-1ß. Consistent with these in vivo results, inhibition of ASIC1a by the specific inhibitor PcTx-1 protected HK-2 cells from hypoxia/reoxygenation (H/R) injury, and suppressed H/R-induced NLRP3 inflammasome activation. Mechanistically, the activation of ASIC1a by either IRI or H/R induced the phosphorylation of NF-κB p65, which translocates to the nucleus and promotes the transcription of NLRP3 and pro-IL-1ß. Blocking NF-κB by treatment with BAY 11-7082 validated the roles of H/R and acidosis in NLRP3 inflammasome activation. This further confirmed that ASIC1a promotes NLRP3 inflammasome activation, which requires the NF-κB pathway. In conclusion, our study suggests that ASIC1a contributes to renal IRI by affecting the NF-κB/NLRP3 inflammasome pathway. Therefore, ASIC1a may be a potential therapeutic target for AKI. KEY MESSAGES: Knockout of ASIC1a attenuated renal ischemia-reperfusion injury. ASIC1a promoted the NF-κB pathway and NLRP3 inflammasome activation. Inhibition of the NF-κB mitigated the NLRP3 inflammasome activation induced by ASIC1a.

A NOVEL RAT MODEL OF CONTRAST-INDUCED ACUTE KIDNEY INJURY BASED ON RENAL CONGESTION AND THE RENO-PROTECTION OF MITOCHONDRIAL FISSION INHIBITION.

ABSTRACT: Contrast-induced acute kidney injury (CI-AKI) is a serious and common complication in patients receiving intravenous iodinated contrast medium (CM). Clinically, congestive heart failure is the most critical risk factor for CI-AKI and always leads to renal congestion for increased central venous pressure and fluid overload. Here, we aimed to investigate a novel CI-AKI rat model based on renal congestion. After the exploratory testing phase, we successfully constructed a CI-AKI rat model by inducing renal congestion by clamping the unilateral renal vein, removing the contralateral kidney, and a single tail vein injection of iohexol. This novel CI-AKI rat model showed elevated serum creatinine, urea nitrogen, and released tubular injury biomarkers (KIM-1 and NGAL), reduced glomerular filtration rate, and typical pathologic features of CM-induced tubular injury with extensive foamy degeneration, tubular edema, and necrosis. Electron microscopy and confocal laser scanning revealed excessive mitochondrial fission and increased translocation of Drp1 from the cytoplasm to the mitochondrial surface in tubular epithelial cells. As a Drp1 inhibitor, Mdivi-1 attenuated excessive mitochondrial fission and exerted reno-protection against CM injury. Simultaneously, Mdivi-1 alleviated oxidative stress, apoptosis, and inflammatory responses induced by CM toxicity. We concluded that renal congestion exacerbated CM toxicity and presented a novel CI-AKI rat model. Excessive mitochondrial fission plays a crucial role in CM reno-toxicity and is a promising target for preventing and treating CI-AKI.

Temporal trends in prevalence and mortality for chronic kidney disease in China from 1990 to 2019: an analysis of the Global Burden of Disease Study 2019.

Background: This study aimed to characterize the temporal trends of chronic kidney disease (CKD) burden in China during 1990-2019, evaluate their age, period and cohort effects, and predict the disease burden for the next 10 years. Methods: Data were obtained from the Global Burden of Disease (GBD) 2019 study. Join-point regression model was used to estimate the average annual percentage change (AAPC) of CKD prevalence and mortality, and the age-period-cohort analysis was used to estimate the age, period and cohort effects. We extended the autoregressive integrated moving average (ARIMA) model to predict the disease burden of CKD in 2020-2029. Results: In 2019, there were 150.5 million cases of (10.6%) and 196 726 deaths from (13.8 per 100 000 general population) CKD in China. Between 1990 and 2019, the prevalence and mortality rate of CKD increased significantly from 6.7% to 10.6%, and from 8.3/100 000 to 13.8/100 000. The AAPC was estimated as 1.6% and 1.8%, respectively. Females had a higher CKD prevalence of CKD but a lower mortality rate. Setting the mean level of age, period and cohort as reference groups, the risk of developing CKD increased with age [RRage(15-19) = 0.18 to RRage(85-89) = 2.45]. The cohort risk was significantly higher in the early birth cohort [RRcohort(1905-1909) = 1.56]. In contrast, the increase in age-specific CKD mortality rate after 60-64 years was exponential [RRage(60-64) = 1.24]. The cohort-based mortality risk remained high prior to the 1945-1949 birth cohorts (RRcohort ranging from 1.69 to 1.89) and then declined in the 2000-2004 birth cohort [RRcohort(2000-2004) = 0.22]. The CKD prevalence and mortality are projected to rise to 11.7% and 17.1 per 100 000, respectively, by 2029. Conclusions: To reduce the disease burden of CKD, a comprehensive strategy that includes risk factors prevention at the primary care level, CKD screening among the elderly and high-risk population, and access to high-quality medical services is required.

TWIK-related acid-sensitive K+ channel 2 promotes renal fibrosis by inducing cell-cycle arrest.

TWIK-related acid-sensitive K+ channel-2 (TASK-2, encoded by Kcnk5) is essential in cell biological processes, by regulating transmembrane K+ balance. In the present study, we aimed to clarify the role of TASK-2 in renal fibrosis and explore the underlying mechanism. We found that TASK-2 level was elevated in the renal tubular UUO- and UIR-induced renal fibrosis as well as in patients with renal tubulointerstitial fibrosis. Knockout of Kcnk5 or inhibition of TASK-2 in renal tubules attenuated G2/M cell-cycle arrest and alleviated renal fibrosis. Mechanistically, demethylase fat mass and obesity-associated protein (FTO) reduced N6-adenosine methylation (m6A) of Kcnk5 mRNA following renal fibrosis. FTO deficiency attenuated the upregulation of TASK-2 and renal fibrosis. The results demonstrated the crucial role of TASK-2 in renal fibrosis, which is conducive to a better understanding of the pathogenesis of renal fibrosis. TASK-2 may be a potential treatment strategy to alleviate the development of renal fibrosis.

Social Isolation Is Associated With Rapid Kidney Function Decline and the Development of Chronic Kidney Diseases in Middle-Aged and Elderly Adults: Findings From the China Health and Retirement Longitudinal Study (CHARLS).

Background: There is limited evidence on the relationship between social isolation and renal outcomes. To address this gap, this study estimated the prospective relationship of social isolation with rapid kidney function decline and the development of chronic kidney disease (CKD) in middle-aged and elderly Chinese with normal kidney function. Methods: We analyzed data from 3,031 participants aged ≥ 45 years with baseline estimated glomerular filtration rates (eGFR) ≥ 60 ml/min/1.73 m2. All data were obtained from the 2011 and 2015 waves of the Chinese Longitudinal Study of Health and Retirement (CHARLS). eGFR was estimated based on a combination of serum creatinine and cystatin C. The primary outcome was rapid decline in renal function, as defined by an eGFR decrease of > 5 ml/min/1.73 m2 per year, while the secondary outcome was the development of CKD, as defined by an eGFR decrease to a level < 60 ml/min/1.73 m2. Results: During the follow-up of 4 years, 258 (8.5%) participants experienced a rapid decline in renal function, while 87 (2.9%) developed CKD. In the fully adjusted model, high social isolation was significantly related to an increased risk of experiencing a rapid decline in renal function (OR 1.805, 95% CI 1.310-2.487) and CKD onset (OR 1.842, 95% CI 1.084-3.129). Among the five components of social isolation, being unmarried, not participating in social activities, and living alone independently predicted declined renal function. Conclusions: Social isolation is significantly associated with the risk of rapid eGFR decline and CKD onset in middle-aged and older adults with normal kidney function in China.

METTL14 aggravates podocyte injury and glomerulopathy progression through N6-methyladenosine-dependent downregulating of Sirt1.

Podocytes are known to play a determining role in the progression of proteinuric kidney disease. N6-methyladenosine (m6A), as the most abundant chemical modification in eukaryotic mRNA, has been reported to participate in various pathological processes. However, its role in podocyte injury remains unclear. In this study, we observed the elevated m6A RNA levels and the most upregulated METTL14 expression in kidneys of mice with adriamycin (ADR) and diabetic nephropathy. METTL14 was also evidently increased in renal biopsy samples from patients with focal segmental glomerulosclerosis (FSGS) and diabetic nephropathy and in cultured human podocytes with ADR or advanced glycation end product (AGE) treatment in vitro. Functionally, we generated mice with podocyte-specific METTL14 deletion, and identified METTL14 knockout in podocytes improved glomerular function and alleviated podocyte injury, characterized by activation of autophagy and inhibition of apoptosis and inflammation, in mice with ADR nephropathy. Similar to the results in vivo, knockdown of METTL14 facilitated autophagy and alleviated apoptosis and inflammation in podocytes under ADR or AGE condition in vitro. Mechanically, we identified METTL14 knockdown upregulated the level of Sirt1, a well-known protective deacetylase in proteinuric kidney diseases, in podocytes with ADR or AGE treatment. The results of MeRIP-qPCR and dual-luciferase reporter assay indicated METTL14 promoted Sirt1 mRNA m6A modification and degradation in injured podocytes. Our findings suggest METTL14-dependent RNA m6A modification contributes to podocyte injury through posttranscriptional regulation of Sirt1 mRNA, which provide a potential approach for the diagnosis and treatment of podocytopathies.

Dynamics in perioperative neutrophil-to-lymphocyte*platelet ratio as a predictor of early acute kidney injury following cardiovascular surgery.

BACKGROUND: In this study, we applied a composite index of neutrophil-lymphocyte * platelet ratio (NLPR), and explore the significance of the dynamics of perioperative NLPR in predicting cardiac surgery-associated acute kidney injury (CSA-AKI). METHODS: During July 1st and December 31th 2019, participants were prospectively derived from the 'Zhongshan Cardiovascular Surgery Cohort'. NLPR was determined using neutrophil counts, lymphocyte and platelet count at the two-time points. Dose-response relationship analyses were applied to delineate the non-linear odds ratio (OR) of CSA-AKI in different NLPR levels. Then NLPRs were integrated into the generalized estimating equation (GEE) to predict the risk of AKI. RESULTS: Of 2449 patients receiving cardiovascular surgery, 838 (34.2%) cases developed CSA-AKI with stage 1 (n = 658, 26.9%), stage 2-3 (n = 180, 7.3%). Compared with non-AKI patients, both preoperative and postoperative NLPR were higher in AKI patients (1.1[0.8, 1.8] vs. 0.9[0.7,1.4], p < 0.001; 12.4[7.5, 20.0] vs. 10.1[6.4,16.7], p < 0.001). Such an effect was a 'J'-shaped relationship: CSA-AKI's risk was relatively flat until 1.0 of preoperative NLPR and increased rapidly afterward, with an odds ratio of 1.13 (1.06-1.19) per 1 unit. Similarly, patients whose postoperative NLPR value >11.0 were more likely to develop AKI with an OR of 1.02. Integrating the dynamic NLPRs into the GEE model, we found that the AUC was 0.806(95% CI 0.793-0.819), which was significantly higher than the AUC without NLPR (0.799, p < 0.001). CONCLUSION: Dynamics of perioperative NPLR is a promising marker for predicting acute kidney injury. It will facilitate AKI risk management and allow clinicians to intervene early so as to reverse renal damage.

Genistein Ameliorates Renal Fibrosis Through Regulation Snail via m6A RNA Demethylase ALKBH5.

Renal tubule-interstitial fibrosis is related to chronic kidney disease progression and a typical feature of the aging kidney. Epigenetic modifications of fibrosis-prone genes regulate the development of renal fibrosis. As a kind of "epigenetic diet", soy isoflavone genistein was reported to have renal protective action and epigenetic-modulating effects. However, its renal protection role and underlying mechanisms are yet to be fully clarified. Herein, we showed that genistein exhibits a demonstrable anti-fibrotic effect on kidney in vivo UUO (unilateral ureteral occlusion) model and renal epithelial cells in vitro model. The mechanism is strongly associated with epithelial-to-mesenchymal transition and m6A RNA demethylase ALKBH5. Mouse fibrotic kidneys induced by UUO exhibited adverse expression of renal fibrosis-related proteins and significant increases in the total m6A level. As an eraser, ALKBH5 showed severer suppression in the renal fibrosis process. However, genistein pretreatment restored ALKBH5 loss remarkably and reduced renal fibrosis, abnormal protein, and inflammatory markers. The examination of possible mechanisms revealed that genistein promoted ALKBH5 and maybe induced the level of mRNA m6A methylation in some epithelial-to-mesenchymal transition-related transcription factors. We found snail was the critical regulator and critical for the protective role of genistein. To verify the relationship between ALKBH5 and snail, we generated knockdown and overexpression of ALKBH5 cells in vitro. ALKBH5 knockdown enhanced the mesenchymal phenotype marker α-smooth muscle actin and snail expression. In agreement, overexpression ALKBH5 increased epithelial adhesion molecule E-cadherin and reduced snail expression. In conclusion, genistein increased renal ALKBH5 expression in UUO-induced renal fibrosis and reduced RNA m6A levels and ameliorates renal damages.

Caloric restriction alleviates aging-related fibrosis of kidney through downregulation of miR-21 in extracellular vesicles.

Glomerulosclerosis and renal interstitial fibrosis occur with the aging kidney. In this study, we examined the expression of miR-21, peroxisome proliferator-activated receptor(PPARα), hypoxia-inducible factor(HIF-1α) in the kidney of 3-month-old rats fed ad libitum (YAL), 24-month-old rats fed ad libitum (OAL) and 24-month-old rats subjected to a 70% calorie-restricted diet for 8 months (OCR). We found long-term caloric restriction (CR) ameliorated aging and aging-related fibrosis. CR ameliorated the increment of miR-21 and HIF-1α, as well as the decrement of PPARα in old ad libitum group. Human proximal tubular cells (HPTCs) presented phenotypes of senescence and epithelial to mesenchymal transition (EMT) under high-glucose conditions, in which senescence occurred earlier than EMT. Senescent cells secreted extracellular vesicles (EVs) which contained miR-21 into the recipient cells. Inhibiting miR-21 of donor cells prevented the occurrence of EMT in recipient cells. In addition, miR-21 induced EMT through targeting PPARα protein and consequently enhancing HIF-1α expression, although other pathways cannot be ruled out. These findings demonstrated that miR-21-containing EVs derived from the senescent cells could facilitate EMT of HPTCs via PPARα-HIF-1α signaling pathway. Long-term caloric restriction and caloric restriction mimetics alleviated aging-related-fibrosis of kidney through downregulation of miR-21.

METTL14-dependent m6A regulates vascular calcification induced by indoxyl sulfate.

AIMS: Although the functional importance of N6-methyladenosine (m6A) in various fundamental bioprocesses are well known, its effect on vascular calcification is not well studied. We investigated the role of methyltransferase-like 14 (METTL14), an m6A methylase, in vascular calcification. MAIN METHODS: We used clinical human samples as well as rat models and primary human artery smooth muscle cell (HASMC) cultures to study the functional role of m6A and METTL14 in vascular calcification and in HASMCs. We modulated the expression of METTL14 using siRNAs (in vitro) to study its function in regulating HASMCs m6A, osteoblasts induced by indoxyl sulfate. We performed the MeRIP-qPCR assays to map and validate m6A in individual transcripts, controls, and calcific HASMCs. KEY FINDINGS: We discovered that the METTL14 expression increases in calcific arteries and in HASMCs induced by indoxyl sulfate, thereby increasing the m6A level in RNA and decreasing the vascular repair function. Decreasing the expression of METTL14 in calcified arteries attenuated the indoxyl sulfate-induced increase in m6A and decrease in HASMCs calcification. We performed the methylation activity of METTL14, which selectively methylates vascular osteogenic transcripts, thereby promoting their degradation and improving their protein expression induced by indoxyl sulfate. Moreover, we demonstrated that the METTL14 de-expression in HASMCs models of calcification decreased the calcification and enhanced the vascular repair function. SIGNIFICANCE: Collectively, our results demonstrated the functional importance of METTL14-dependent vascular m6A methylome in vascular functions during calcification and provided a novel mechanistic insight to the therapeutic mechanisms of METTL14.

Exogenous biological renal support ameliorates renal pathology after ischemia reperfusion injury in elderly mice.

We established an exogenous biological renal support model through the generation of parabiotic mice. At 72 hours after ischemia reperfusion injury (IRI), the aged mice that received exogenous biological renal support showed significantly higher levels of renal cell proliferation and dedifferentiation, lower levels of renal tubular injury, improved renal function, and a lower mortality than those that did not receive exogenous biological renal support. Using the Quantibody Mouse Cytokine Antibody Array, we found that aged IRI mice that received exogenous biological renal support had an up-regulation of multiple inflammatory related cytokines compared to the group that did not receive exogenous biological renal support. We suggest that the exogenous biological renal support might promote renal tubular epithelial cell proliferation and dedifferentiation and improve the prognosis of aged IRI mice. Exogenous biological renal support may play an important role in the amelioration of renal IRI by regulating the expression of multiple cytokines.

Acid-sensing ion channel 1a is involved in ischaemia/reperfusion induced kidney injury by increasing renal epithelia cell apoptosis.

Acidic microenvironment is commonly observed in ischaemic tissue. In the kidney, extracellular pH dropped from 7.4 to 6.5 within 10 minutes initiation of ischaemia. Acid-sensing ion channels (ASICs) can be activated by pH drops from 7.4 to 7.0 or lower and permeates to Ca2+ entrance. Thus, activation of ASIC1a can mediate the intracellular Ca2+ accumulation and play crucial roles in apoptosis of cells. However, the role of ASICs in renal ischaemic injury is unclear. The aim of the present study was to test the hypothesis that ischaemia increases renal epithelia cell apoptosis through ASIC1a-mediated calcium entry. The results show that ASIC1a distributed in the proximal tubule with higher level in the renal tubule ischaemic injury both in vivo and in vitro. In vivo, Injection of ASIC1a inhibitor PcTx-1 previous to ischaemia/reperfusion (I/R) operation attenuated renal ischaemic injury. In vitro, HK-2 cells were pre-treated with PcTx-1 before hypoxia, the intracellular concentration of Ca2+ , mitochondrial transmembrane potential (∆ψm) and apoptosis was measured. Blocking ASIC1a attenuated I/R induced Ca2+ overflow, loss of ∆ψm and apoptosis in HK-2 cells. The results revealed that ASIC1a localized in the proximal tubular and contributed to I/R induced kidney injury. Consequently, targeting the ASIC1a may prove to be a novel strategy for AKI patients.

Amelioration of Uremic Toxin Indoxyl Sulfate-Induced Osteoblastic Calcification by SET Domain Containing Lysine Methyltransferase 7/9 Protein.

BACKGROUND: Vascular calcification (VC) is a very common phenomenon in patients with chronic kidney disease (CKD). It has been reported that some histone methylation play a role in VC as an epigenetic regulator. Indoxyl sulfate (IS) is a protein-bound uremic toxin that has been proven as one of the major risk factors of cardiovascular disease in CKD. SET domain containing lysine methyltransferase 7/9 (SET7/9) is one of the important histone methyltransferases. OBJECTIVES: This study aimed to determine the effect of IS on the expression of SET7/9 and the role of SET7/9 in IS-induced osteoblastic differentiation and calcification of vascular smooth muscle cells (VSMCs). METHODS: VSMCs were incubated with various concentrations of IS for different durations to assess osteoblastic differentiation and expression of SET7/9. Western blot analysis and quantitative real-time polymerase chain reaction were performed to assess the protein and mRNA levels of SET7/9 respectively. The calcium content was measured to evaluate calcification. RESULTS: Osteoblastic differentiation and calcification of VSMCs and downregulation of the expression of SET7/9 were observed after IS treatment. The autophagy was activated after treatment with IS, whereas the inhibition of the autophagy partially attenuated the effect of IS on both the stimulation of the expression of runt-related transcription factor 2 and calcium deposition. CONCLUSIONS: Our data demonstrated that SET7/9 downregulation and autophagy activation may be the key mechanism of IS-induced VC in CKD.

Transforming growth factor-ß1-overexpressing mesenchymal stromal cells induced local tolerance in rat renal ischemia/reperfusion injury.

BACKGROUND: Regulatory T cells (Tregs) suppress excessive immune responses and play a crucial protective role in acute kidney injury (AKI). The aim of this study was to examine the therapeutic potential of transforming growth factor (TGF)-ß1-overexpressing mesenchymal stromal cells (MSCs) in inducing local generation of Tregs in the kidney after ischemia/reperfusion (I/R) injury. METHODS: MSCs were transduced with a lentiviral vector expressing the TGF-ß1 gene; TGF-ß1-overexpressing MSCs (designated TGF-ß1/MSCs) were then transfused into the I/R-injured kidney via the renal artery. RESULTS: MSCs genetically modified with TGF-ß1 achieved overexpression of TGF-ß1. Compared with green fluorescent protein (GFP)/MSCs, TGF-ß1/MSCs markedly improved renal function after I/R injury and reduced epithelial apoptosis and subsequent inflammation. The enhanced immunosuppressive and therapeutic abilities of TGF-ß1/MSCs were associated with increased generation of induced Tregs and improved intrarenal migration of the injected cells. Futhermore, the mechanism of TGF-ß1/MSCs in attenuating renal I/R injury was not through a direct canonical TGF-ß1/Smad pathway. CONCLUSION: TGF-ß1/MSCs can induce a local immunosuppressive effect in the I/R-injured kidney. The immunomodulatory activity of TGF-ß1-modified MSCs appears to be a gateway to new therapeutic approaches to prevent renal I/R injury.

Youthful systemic milieu alleviates renal ischemia-reperfusion injury in elderly mice.

The incidence of acute kidney injury (AKI) is high in elderly people, and is difficult to prevent and treat. One of its major causes is renal ischemia-reperfusion injury (IRI). A young systemic environment may prevent the senescence of old organs. However, it is unknown whether a young milieu may reduce renal IRI in the elderly. To examine this question, bilateral renal IRI was induced in old (24 months) mice three weeks after parabiosis model establishment. At 24 hours after IRI, compared to old wild-type mice, the old mice with IRI had significantly damaged renal histology, decreased renal function, increased oxidative stress, inflammation, and apoptosis. However, there was no increase in autophagy. Compared to old mice with IRI, old-old parabiosis mice with IRI did not show differences in renal histological damage, oxidative stress, inflammation, apoptosis, or autophagy, but did exhibit improved renal function. Compared to the old-old parabiosis mice with IRI, the old mice with IRI in the young (12 week)-old parabiosis showed less renal histological injury and better renal function. Renal oxidative stress, inflammation, and apoptosis were significantly decreased, and autophagy was significantly increased. Thus, a youthful systemic milieu may decrease oxidative stress, inflammation, and apoptosis, and increase autophagy in old mice with IRI. These effects ameliorated IRI injuries in old mice. Our study provides new ideas for effectively preventing and treating AKI in the elderly.

Necrostatin-1 Attenuates Cisplatin-Induced Nephrotoxicity Through Suppression of Apoptosis and Oxidative Stress and Retains Klotho Expression.

Aim: Cisplatin is an effective chemotherapeutic drug, but the application in clinical is greatly limited by its nephrotoxicity. Necrostatin-1 (Nec-1), an inhibitor of RIP1 kinase, has been reported to inhibit RIP-mediated necroptosis. The aim of this study is to detect the protective effects of Nec-1 on the nephrotoxicity of cisplatin and to investigate its renoprotection mechanism. Methods: 8-week-old male C57BL/6 mice were randomly assigned into four groups: Control, Nec-1, Cisplatin, and Cisplatin+Nec-1. Mice were treated with cisplatin with or without Nec-1 pre-treatment. Renal function, histological changes, necroptosis, and apoptotic markers were investigated. NFκB pathway related proteins, proinflammatory cytokines, oxidative stress markers, renal Klotho, and autophagy-related proteins levels were also examined. Results: Renal function and histological data displayed that the treatment with Nec-1 significantly attenuates cisplatin-induced renal damage. The expression of RIPK1/RIPK3/MLKL were significantly enhanced in cisplatin group as compared to the control group (p < 0.05) and was significantly reduced by pre-treatment of Nec-1 (p < 0.05). The level of stress and apoptosis-related protein, including p-JNK, p-c-Jun, p-p38, Bax/Bcl-2 ratio, and caspase-3 showed the similar trend. Pre-treatment with Nec-1 inhibit NFκB signaling, reduced proinflammatory cytokines and oxidative stress, up-regulated renal Klotho, and autophagy-related proteins levels. Conclusion: Our results suggest that Nec-1 could be a potential therapeutic drug against the cisplatin-induced nephrotoxicity through its anti-necroptosis, anti-apoptotic, anti-inflammatory anti-oxidant and retain Klotho expression and activate autophagy effects in the kidney.