Dipeptidase 1 promotes ferroptosis in renal tubular epithelial cells in diabetic nephropathy via inhibition of the GSH/GPX4 axis.

Renal tubular injury is an important pathological change associated with diabetic nephropathy (DN), in which ferroptosis of renal tubular epithelial cells is critical to its pathogenesis. Inhibition of the glutathione/glutathione peroxidase 4 (GSH/GPX4) axis is the most important mechanism in DN tubular epithelial cell ferroptosis, but the underlying reason for this is unclear. Our biogenic analysis showed that a zinc-dependent metalloproteinase, dipeptidase 1 (DPEP1), is associated with DN ferroptosis. Here, we investigated the role and mechanism of DPEP1 in DN tubular epithelial cell ferroptosis. DPEP1 upregulation was observed in the renal tubular epithelial cells of DN patients and model mice, as well as in HK-2 cells stimulated with high glucose. Furthermore, the level of DPEP1 upregulation was associated with the degree of tubular injury in DN patients and HK-2 cell ferroptosis. Mechanistically, knocking down DPEP1 expression could alleviate the inhibition of GSH/GPX4 axis and reduce HK-2 cell ferroptosis levels in a high glucose environment. HK-2 cells with stable DPEP1 overexpression also showed GSH/GPX4 axis inhibition and ferroptosis, but blocking the GSH/GPX4 axis could mitigate these effects. Additionally, treatment with cilastatin, a DPEP1 inhibitor, could ameliorate GSH/GPX4 axis inhibition and relieve ferroptosis and DN progression in DN mice. These results revealed that DPEP1 can promote ferroptosis in DN renal tubular epithelial cells via inhibition of the GSH/GPX4 axis.

Secreted frizzled-related protein 5 protects against renal fibrosis by inhibiting Wnt/ß-catenin pathway.

Renal fibrosis (RF) is an important pathogenesis for renal function deterioration in chronic kidney disease. Secreted frizzled-related protein 5 (SFRP5) is an anti-fibrotic adipokine but its direct role on RF remains unknown. It was aimed to study the protective effect of SFRP5 against RF and interference with Wnt/ß-catenin signaling pathway for the first time. First, the therapeutic efficacy of SFRP5 was evaluated by adenovirus overexpression in rats with unilateral ureteral obstruction (UUO) in vivo. Thirty-six rats were randomly divided into the sham, UUO, and SFRP5 (UUO + Ad-SFRP5) groups. Half rats in each group were selected at random for euthanasia at 7 days and the others until 14 days. Then, the transforming growth factor (TGF)-ß1-induced epithelial-mesenchymal transition (EMT) was established in HK-2 cells in vitro. The cells were divided into four groups: the control group, the TGF-ß1 group, the TGF-ß1 + SFRP5 group, and the TGF-ß1 + SFRP5 + anti-SFRP5 group. The makers of EMT and Wnt/ß-catenin pathway proteins were investigated. In the UUO model, expression of SFRP5 showed compensatory upregulation, and adenoviral-mediated SFRP5 over-expression remarkably attenuated RF, as demonstrated by maintenance of E-cadherin and suppression of α-smooth muscle actin (SMA). In vitro, SFRP5 was shown to inhibit TGF-ß1-mediated positive regulation of α-SMA, fibronectin, collagen I but negative regulation of E-cadherin. Furthermore, SFRP5 abrogated activation of Wnt/ß-catenin, which was the essential pathway in EMT and RF pathogenesis. The changes after a neutralizing antibody to SFRP5 confirmed the specificity of SFRP5 for inhibition. These findings suggest that SFRP5 can directly ameliorate EMT and protect against RF by inhibiting Wnt/ß-catenin pathway.

Pericyte activation accompanied by peritubular capillaries dysfunction and pericyte-to-myofibroblast transition is associated with renal fibrosis in diabetic nephropathy.

Background: Tubulointerstitial renal fibrosis is an essential feature of diabetic nephropathy (DN). Pericytes play a critical role in microvascular diseases and renal fibrogenesis. However, the role of pericytes in DN remains unclear. Herein, we aimed to explore the properties and possible mechanisms of pericytes in renal fibrosis in DN. Methods: We used multiplex immunofluorescence staining to evaluate the location and expression of activated pericytes and to assess capillary dilation and interstitial fibrosis in the kidneys of db/db mice. Pericytes were co-stained for alpha-smooth muscle actin (α-SMA) to determine which ones differentiate into myofibroblasts in db/db mice. Expression of CD34 and platelet-derived growth factor receptor beta (PDGFR-ß) was assessed in kidney tissue from patients with DN by immunohistochemical staining. Results: We found that cell staining for nerve/glial antigen 2 (NG2)+ and PDGFR-ß+ was greater in the kidneys of db/db mice than in those of db/m mice. There was impaired pericyte coverage of blood vessels and capillary dilation in the renal interstitium. These changes were accompanied by increased collagen I staining and an increase in the number of pericytes with profibrotic phenotypes, as identified by increased NG2+/PDGFR-ß+/α-SMA+ and decreased NG2+/PDGFR-ß+/α-SMA- staining. In DN patients, expression of PDGFR-ß was stronger and there was loss of CD34 compared with the findings in control patients with minor glomerular lesions. Conclusion: In this study, we demonstrated that pericyte activation accompanied by peritubular capillary dysfunction and pericytemyofibroblast transition is associated with renal fibrosis in DN.

Nirmatrelvir/ritonavir use in patients with COVID-19 on hemodialysis: a case series.

Patients undergoing hemodialysis (HD) are particularly vulnerable to coronavirus disease 2019 (COVID-19) and are at increased risk of developing severe infection. However, given the exclusion of such patients from clinical trials, there are limited data regarding the effectiveness of the antiviral drug nirmatrelvir/ritonavir (N/R) in patients on HD. We prescribed N/R to 4 patients on HD with COVID-19 after obtaining informed consent. Their clinical symptoms were improved at approximately 3 days after N/R administration. The viral load was reduced after approximately 10 days. The main adverse effects were nausea and vomiting. Rational dosage adjustment obtained good tolerance but did not influence the efficacy. These results suggest that N/R may be a promising agent for patients on HD with COVID-19.

Adrenomedullin induces cisplatin chemoresistance in ovarian cancer through reprogramming of glucose metabolism.

Background and Objectives: The metabolic network of cancer cells has been reprogrammed - relying more on aerobic glycolysis to gain energy, which is an important reason for drug resistance. Expression of adrenomedullin (ADM) in ovarian cancer tissues is related to resistance to platinum-based drugs. In view of this, we intended to investigate the correlation between ADM and glucose metabolism reprogramming of tumor cells to clarify the possible mechanism of ADM-induced ovarian cancer cisplatin resistance through glucose metabolism reprogramming. Methods: Epithelial ovarian cancer (EOC) cell viability and apoptosis were determined. Different gene expression and protein levels were detected by real-time revere transcription polymerase chain reaction and western blotting. Oxygen consumption rate (OCR) and extracellular acidification rates (ECARs) were measured. Results: ADM expression was upregulated in cisplatin-resistant EOC cells. ADM attenuated cisplatin-inhibited cell survival and cisplatin-induced apoptosis in sensitive EOC cells; knockdown of ADM enhanced cisplatin chemosensitivity of cisplatin-resistant EOC cells. ADM enhanced glycolysis in cisplatin-sensitive EOC cells; knockdown of ADM significantly inhibited glycolysis in cisplatin-resistant EOC cells. ADM significantly upregulated pyruvate kinase isozyme type M2 (PKM2) protein level, the key enzyme during glycolysis; PKM2 inhibitor significantly abolished the ADM-improved cell survival and ADM-inhibited apoptosis. Conclusion: ADM promoted proliferation and inhibited apoptosis of ovarian cancer cells through reprogramming of glucose metabolism, so as to promote cisplatin resistance. The study is expected to identify multidrug resistance markers of ovarian cancer and provide a target for the prevention and treatment of ovarian cancer, which is important for clinical translational research.

Title: Bioinformatic Identification of Genes Involved in Diabetic Nephropathy Fibrosis and their Clinical Relevance.

Tubulointerstitial fibrosis is an important pathological feature of diabetic nephropathy that is associated with impaired renal function. However, the mechanism by which fibrosis occurs in diabetic nephropathy is unclear. Differentially expressed genes were identified from transcriptome profiles of renal tissue from diabetic patients and unilateral ureteral obstruction mice and intersected to obtain genes that may be involved in diabetic fibrosis. Biological function analysis and protein-protein interaction network analysis were performed. ROC curve and Pearson correlation analysis between hub genes were performed and glomerular filtration rate estimated. Finally, the RNA levels of hub genes were measured using real-time PCR. A total of 283 genes were identified as potentially involved in diabetic nephropathy fibrosis. TYROBP, CTSS, LCP2, LUM and TLR7 were identified as aberrantly expressed hub genes. Immune cell infiltration analysis demonstrated higher numbers of cytotoxic lymphocytes, B lineage cells, monocyte lineage cells, myeloid dendritic cells, neutrophils, and fibroblasts in the diabetic nephropathy group. The areas under ROC curves for TYROBP, CTSS, LCP2, LUM and TLR7 were 0.9167, 0.9583, 0.9917, 0.93333, and 0.9583, respectively (P < 0.001), and their correlation coefficients with estimated glomerular filtration rate were - 0.8332, - 0.752, - 0.7875, - 0.7567, and - 0.7136, respectively (P < 0.001). The RNA levels of TYROBP, CTSS, LUM and TLR7 were upregulated in high-glucose-treated human renal tubular epithelial cells (P < 0.005). Our study identified TYROBP, CTSS, LCP2, LUM and TLR7 as potentially involved in diabetic nephropathy fibrosis. Furthermore, TYROBP, CTSS, LUM and TLR7 may be associated with epithelial-mesenchymal transition of tubular epithelial cells.

Adenosine A1 Receptor Deficiency Aggravates Extracellular Matrix Accumulation in Diabetic Nephropathy through Disturbance of Peritubular Microenvironment.

BACKGROUND: We previously observed that adenosine A1 receptor (A1AR) had a protective role in proximal tubular megalin loss associated with albuminuria in diabetic nephropathy (DN). In this study, we aimed to explore the role of A1AR in the fibrosis progression of DN. METHODS: We collected DN patients' samples and established a streptozotocin-induced diabetes model in wild-type (WT) and A1AR-deficient (A1AR-/-) mice. The location and expression of CD34, PDGFRß, and A1AR were detected in kidney tissue samples from DN patients by immunofluorescent and immunohistochemical staining. We also analyzed the expression of TGFß, collagen (I, III, and IV), α-SMA, and PDGFRß using immunohistochemistry in WT and A1AR-/- mice. CD34 and podoplanin expression were analyzed by Western blotting and immunohistochemical staining in mice, respectively. Human renal proximal tubular epithelial cells (HK2) were cultured in medium containing high glucose and A1AR agonist as well as antagonist. RESULTS: In DN patients, the expression of PDGFRß was higher with the loss of CD34. The location of PDGFRß and TGFß was near to each other. The A1AR, which was colocalized with CD34 partly, was also upregulated in DN patients. In WT-DN mice, obvious albuminuria and renal pathological leisure were observed. In A1AR-/- DN mice, more severe renal tubular interstitial fibrosis and more extracellular matrix deposition were observed, with lower CD34 expression and pronounced increase of PDGFRß. In HK2 cells, high glucose stimulated the epithelial-mesenchymal transition (EMT) process, which was inhibited by A1AR agonist. CONCLUSION: A1AR played a critical role in protecting the tubulointerstitial fibrosis process in DN by regulation of the peritubular microenvironment.

Clinical and laboratory features of female Gitelman syndrome and the pregnancy outcomes in a Chinese cohort.

AIM: Gitelman syndrome (GS) is a rare inherited salt-losing renal tubulopathy. Data on clinical features and the pregnancy outcome for female GS patients in a large cohort are lacking. The study was aimed to explore the phenotype and pregnant issue for female GS patients. METHODS: GS cases from the National Rare Diseases Registry System of China (NRSC) were collected, and detailed clinical, laboratory and genetic data were analysed. Articles on pregnancy in GS were also systemically reviewed. RESULTS: A total of 101 GS patients were included; among them, 42.6% were female and 79.2% showed hypomagnesaemia. A lower proportion of female patients presented before 18 years of age, with less frequently reported polyuria, higher serum potassium and less urine sodium and chloride excretions. There was no gender difference in the sodium-chloride cotransporter (NCC) dysfunction evaluated by hydrochlorothiazide test. Twelve of the 43 female GS patients delivered after disease symptom onset, and their pregnancies were generally uneventful. As a group, pregnant GS patients had lower potassium levels in the first-trimester (P = .002) requiring higher potassium supplementation. After delivery, serum potassium (P = .02) and magnesium (P = .03) increased significantly. Both caesarean section and vaginal delivery were safe. CONCLUSION: Female GS patients may have a less severe phenotype with generally favourable outcomes of pregnancy. Intensive monitoring and increased potassium supplementation are necessary during pregnancy, especially in the first-trimester.

Early-start and conventional-start peritoneal dialysis: a Chinese cohort study on outcome.

Background: Early-start peritoneal dialysis (PD) is an effective option for patients need unplanned dialysis. However, there are few studies on the long-term prognosis of early-start PD patients.Methods: In this retrospective study, 635 eligible patients from 1 March 1996 to 30 September 2016 were included, and divided into three groups according to the duration of break-in period: 3 days or less, 4-13 days and more than 14 days. Patients started PD within 2 weeks and after 2 weeks were defined as early-start and conventional-start, respectively. The primary outcome was all-cause mortality, and the secondary outcome measures were peritonitis free survival and technical survival. Mechanical and infectious complications in the first 180 days were also analyzed.Results: Early-start PD patients were more likely to have higher serum total carbon dioxide and creatinine levels and lower serum albumin, Kt/v, creatinine clearance (Ccr) and residual glomerular filtration rate (rGFR) levels at the start of PD. The median follow-up period was 30 months (interquartile range, 13-53 months). A worse survival was observed in the early-start group than that in the conventional-start group (p < 0.001), even adjustment for the covariates (HR 1.549, 95%CI 1.104-2.173, p = 0.011). In the subgroup analysis, in patients commencing PD after 2006 early-start and conventional-start PD patients had comparable survival. No differences were observed in the rate of infectious and mechanical complications, peritonitis-free survival and technique survival between early-start and conventional-start PD patients.Conclusions: Early-start PD could be a safe and effective strategy for patients needing unplanned dialysis initiation with the progress of technology on PD.

The effect of A1 adenosine receptor in diabetic megalin loss with caspase-1/IL18 signaling.

PURPOSE: In our previous study, exacerbation of albuminuria was observed in A1 adenosine receptor knockout (A1AR-/-) mice with diabetic nephropathy (DN), but the mechanism was unclear. Here, we investigated the relationship of megalin loss and albuminuria, to identify the protective effect of A1AR in megalin loss associated albuminuria by inhibiting pyroptosis-related caspase-1/IL-18 signaling of DN. METHODS: We successfully collected DN patients' samples and built diabetes mice models induced by streptozotocin. Megalin, cubilin, and A1AR expression were detected in kidney tissue samples from DN patients and mice through immunohistochemical and immunofluorescent staining. A1AR, caspase-1, interleukin-18 (IL-18) expression were analyzed using Western blotting in wild-type and A1AR -/- mice. Human renal proximal tubular epithelial cells (PTC) were cultured with high glucose to observe the effect of A1AR agonist and antagonist on caspase-1/IL-18 and megalin injury. RESULTS: The loss of megalin, co-localized with A1AR at PTC, was associated with the level of albuminuria in diabetic patients and mice. The injury of megalin-cubilin was accompanied with the A1AR upregulation (1.30±0.1 vs 0.98±0.2, P=0.042), the caspase-1 (1.33±0.1 vs 1.0±0.2, P=0.036), and IL-18 (1.26±0.2 vs 0.96±0.2, P=0.026) signaling activation in mice with DN. More severe pathological injury, 24 hrs urine albumin excretion (170.8±4.1 µg/d vs 132.0±2.9 µg/d vs 17.9±2.8 µg/d, P<0.001) and megalin-cubilin loss were observed in A1AR -/- DN mice with more pronounced caspase-1 (1.52±0.03 vs 1.20±0.01, P=0.017) and IL-18 (1.42±0.02 vs 1.21±0.02, P=0.018) secretion. High glucose could stimulate the secretion of caspase-1 (1.72 times, P≤0.01) and IL-18 (1.64 times, P≤0.01), which was abolished by A1AR agonist and aggravated by A1AR antagonist. CONCLUSION: A1AR played a protective role in proximal tubular megalin loss associated albuminuria by inhibiting the pyroptosis-related caspase-1/IL-18 signaling in DN.

Effects of sodium-glucose co-transporter 2 (SGLT2) inhibitors on serum uric acid level: A meta-analysis of randomized controlled trials.

The aim of this study was to describe the effects of sodium-glucose co-transporter 2 (SGLT2) inhibitors on serum uric acid (SUA) in patients with type 2 diabetes mellitus (T2DM). PubMed, CENTRAL, EMBASE and ClinicalTrials.gov were searched for randomized controlled trials of SGLT2 inhibitors in patients with T2DM up to May 20, 2017. A total of 62 studies, comprising 34 941 patients, were included. Any of the SGLT2 inhibitors (empagliflozin, canagliflozin, dapagliflozin, tofogliflozin, luseogliflozin or ipragliflozin) significantly decreased SUA levels compared with control (total weighted mean difference [WMD] -37.73 µmol/L, 95% CI [-40.51, -34.95]). Treatment with empagliflozin resulted in a superior reduction in SUA (WMD -45.83 µmol/L, 95% CI [-53.03, -38.63]). The effect persisted during long-term treatment. Dapagliflozin decreased SUA in a dose-dependent manner (from 5 to 50 mg, P = .014). In subgroup analyses, greater reductions could be observed during the course of early diabetes and the SUA-lowering effect was abolished in patients with chronic kidney disease (estimated glomerular filtration rate <60 mL/min per 1.73 m2 ). The effect of SGLT2 inhibitors on SUA reduction suggests that this class of drugs might be beneficial for diabetic patients with hyperuricaemia.