MiR-199a-5p aggravates against renal ischemia-reperfusion and transplant injury by targeting AKAP1 to disrupt mitochondrial dynamics.

Renal ischemia-reperfusion injury (IRI) is a major cause of delayed graft function (DGF) after transplantation. Currently, a targeted therapy for this important clinical disorder is still lacking. MicroRNA (miRNA) has important roles in the pathogenesis of IRI and may therapeutic approaches to mitigate renal IRI. METHODS: Small RNA sequencing was performed to profile microRNA expression in mouse kidneys after transplantation. Lentivirus incorporating a miR-199a-5p modulator was injected into mouse kidney in situ before unilateral IRI and syngenetic transplantation, to determine the effect of miR-199a-5p in vivo. miR-199a-5p mimic or inhibitor was transfected cultured tubular cells before renal tubular ATP depletion recovery treatment to the examine the role of miR-199a-5p in vitro. RESULTS: Sequencing showed upregulation of miR-199a-5p in post-transplantation mouse kidney following renal IRI was localized to renal tubular epithelial cells. Lentivirus incorporating a miR-199a-5p mimic aggravated renal IRI and opposing effects were obtained with a miR-199a-5p inhibitor. Treatment with the miR-199a-5p inhibitor ameliorated graft function loss, tubular injury and immune response after cold storage transplantation. In vitro experiments demonstrated aggravation of cell death caused by ATP depletion and repletion when the miR-199a-5p mimic was present while the miR-199a-5p inhibitor reduced cell death. miR-199a-5p was shown to target a-kinase anchoring protein 1(AKAP1) by double luciferase assay and miR-199a-5p activation reduced dynamin related protein 1 (Drp1)-s637 phosphorylation and mitochondrial length. Overexpression of AKAP1 preserved Drp1-s637 phosphorylation and reduced mitochondrial fission. CONCLUSION: MiR-199a-5p activation reduced AKAP1 expression, promoted Drp1-s637 dephosphorylation, aggravated the disruption of mitochondrial dynamics and contributed to ischemic kidney injury.

A novel role of ADAMTS16 in renal fibrosis through activating TGF-ß/Smad signaling.

Chronic Kidney Disease (CKD) has emerged as a global public health concern, with its primary pathological basis being Renal Fibrosis (RF), crucial to halt its progression to End-Stage Renal Disease (ESRD). However, effective treatment options are currently lacking. Therefore, exploring the mechanisms of RF, identifying drug targets and diagnostic biomarkers are important. In this study, we identified ADAMTS16 as a newly expressed regulatory factor highly expressed in renal fibrosis tissue. ADAMTS16 interacts with latency-associated peptide (LAP)-transforming growth factor (TGF)-ß, leading to the activation of TGF-ß. Loss of ADAMTS16 expression effectively reduces TGF-ß-dependent transcription activity. Furthermore, the use of RRFR tetrapeptide derived from ADAMTS16 can activate the TGF-ß/Smad signaling axis, promoting RF. In summary, ADAMTS16 is induced in the progression of CKD, interacting with LAP-TGF-ß and potentially activating SMAD2/3. Therefore, targeting ADAMTS16 may serve as a crucial new strategy to alleviate RF and treat CKD patients.

Dapagliflozin attenuates AKI to CKD transition in diabetes by activating SIRT3/PGC1-α signaling and alleviating aberrant metabolic reprogramming.

BACKGROUND: Patients with diabetes are prone to acute kidney injury (AKI) with a high mortality rate, poor prognosis, and a higher risk of progression to chronic kidney disease than non-diabetic patients. METHODS: Streptozotocin (STZ)-treated type 1 and db/db type 2 diabetes model were established, AKI model was induced in mice by ischemia-reperfusion injury(IRI). Mouse proximal tubular cell cells were subjected to high glucose and hypoxia-reoxygenation in vitro. Transcriptional RNA sequencing was performed for clustering analysis and target gene screening. Renal structural damage was determined by histological staining, whereas creatinine and urea nitrogen levels were used to measure renal function. RESULTS: Deteriorated renal function and renal tissue damage were observed in AKI mice with diabetic background. RNA sequencing showed a decrease in fatty acid oxidation (FAO) pathway and an increase in abnormal glycolysis. Treatment with Dapa, Sitagliptin(a DPP-4 inhibitor)and insulin reduced blood glucose levels in mice, and improved renal function. However, Dapa had a superior therapeutic effect and alleviated aberrant FAO and glycosis. Dapa reduced cellular death in cultured cells under high glucose hypoxia-reoxygenation conditions, alleviated FAO dysfunction, and reduced abnormal glycolysis. RNA sequencing showed that SIRT3 expression was reduced in diabetic IRI, which was largely restored by Dapa intervention. 3-TYP, a SIRT3 inhibitor, reversed the renal protective effects of Dapa and mediated abnormal FAO and glycolysis in mice and tubular cells. CONCLUSION: Our study provides experimental evidence for the use of Dapa as a means to reduce diabetic AKI by ameliorating metabolic reprogramming in renal tubular cells.

Inhibition of Drp1- Fis1 interaction alleviates aberrant mitochondrial fragmentation and acute kidney injury.

BACKGROUND: Acute kidney injury (AKI) is a common clinical disorder with complex etiology and poor prognosis, and currently lacks specific and effective treatment options. Mitochondrial dynamics dysfunction is a prominent feature in AKI, and modulation of mitochondrial morphology may serve as a potential therapeutic approach for AKI. METHODS: We induced ischemia-reperfusion injury (IRI) in mice (bilateral) and Bama pigs (unilateral) by occluding the renal arteries. ATP depletion and recovery (ATP-DR) was performed on proximal renal tubular cells to simulate in vitro IRI. Renal function was evaluated using creatinine and urea nitrogen levels, while renal structural damage was assessed through histopathological staining. The role of Drp1 was investigated using immunoblotting, immunohistochemistry, immunofluorescence, and immunoprecipitation techniques. Mitochondrial morphology was evaluated using confocal microscopy. RESULTS: Renal IRI induced significant mitochondrial fragmentation, accompanied by Dynamin-related protein 1 (Drp1) translocation to the mitochondria and Drp1 phosphorylation at Ser616 in the early stages (30 min after reperfusion), when there was no apparent structural damage to the kidney. The use of the Drp1 inhibitor P110 significantly improved kidney function and structural damage. P110 reduced Drp1 mitochondrial translocation, disrupted the interaction between Drp1 and Fis1, without affecting the binding of Drp1 to other mitochondrial receptors such as MFF and Mid51. High-dose administration had no apparent toxic side effects. Furthermore, ATP-DR induced mitochondrial fission in renal tubular cells, accompanied by a decrease in mitochondrial membrane potential and an increase in the translocation of the pro-apoptotic protein Bax. This process facilitated the release of dsDNA, triggering the activation of the cGAS-STING pathway and promoting inflammation. P110 attenuated mitochondrial fission, suppressed Bax mitochondrial translocation, prevented dsDNA release, and reduced the activation of the cGAS-STING pathway. Furthermore, these protective effects of P110 were also observed renal IRI model in the Bama pig and folic acid-induced nephropathy in mice. CONCLUSIONS: Dysfunction of mitochondrial dynamics mediated by Drp1 contributes to renal IRI. The specific inhibitor of Drp1, P110, demonstrated protective effects in both in vivo and in vitro models of AKI.

DUSP1 protects against ischemic acute kidney injury through stabilizing mtDNA via interaction with JNK.

The mechanism underlying acute kidney injury (AKI) and AKI-to-Chronic kidney disease (CKD) transition remains unclear, but mitochondrial dysfunction may be a key driving factor. Literature reports suggest that dual-specificity phosphatase 1 (DUSP1) plays a critical role in maintaining mitochondrial function and structural integrity. In this study, ischemic Acute Kidney Injury (AKI) and post-ischemic fibrosis models were established by clamping the renal pedicle with different reperfusion times. To investigate the role of DUSP1, constitutional Dusp1 knockout mice and tubular-specific Sting knockout mice were used. Mitochondrial damage was assessed through electron microscopy observation, measurements of mitochondrial membrane potential, mtDNA release, and BAX translocation. We found that Dusp1 expression was significantly upregulated in human transplant kidney tissue and mouse AKI tissue. Dusp1 gene deletion exacerbated acute ischemic injury, post-ischemic renal fibrosis, and tubular mitochondrial dysfunction in mice. Mechanistically, DUSP1 could directly bind to JNK, and DUSP1 deficiency could lead to aberrant phosphorylation of JNK and BAX mitochondria translocation. BAX translocation promoted mitochondrial DNA (mtDNA) leakage and activated the cGAS-STING pathway. Inhibition of JNK or BAX could inhibit mtDNA leakage. Furthermore, STING knockout or JNK inhibition could significantly mitigate the adverse effects of DUSP1 deficiency in ischemic AKI model. Collectively, our findings suggest that DUSP1 is a regulator for the protective response during AKI. DUSP1 protects against AKI by preventing BAX-induced mtDNA leakage and blocking excessive activation of the cGAS-STING signaling axis through JNK dephosphorylation.

Flavin containing monooxygenase 2 regulates renal tubular cell fibrosis and paracrine secretion via SMURF2 in AKI­CKD transformation.

In the follow­up of hospitalized patients with acute kidney injury (AKI), it has been observed that 15­30% of these patients progress to develop chronic kidney disease (CKD). Impaired adaptive repair of the kidneys following AKI is a fundamental pathophysiological mechanism underlying renal fibrosis and the progression to CKD. Deficient repair of proximal tubular epithelial cells is a key factor in the progression from AKI to CKD. However, the molecular mechanisms involved in the regulation of fibrotic factor paracrine secretion by injured tubular cells remain incompletely understood. Transcriptome analysis and an ischemia­reperfusion injury (IRI) model were used to identify the contribution of flavin­containing monooxygenase 2 (FMO2) in AKI­CKD. Lentivirus­mediated overexpression of FMO2 was performed in mice. Functional experiments were conducted using TGF­ß­induced tubular cell fibrogenesis and paracrine pro­fibrotic factor secretion. Expression of FMO2 attenuated kidney injury induced by renal IRI, renal fibrosis, and immune cell infiltration into the kidneys. Overexpression of FMO2 not only effectively blocked TGF secretion in tubular cell fibrogenesis but also inhibited aberrant paracrine activation of pro­fibrotic factors present in fibroblasts. FMO2 negatively regulated TGF­ß­mediated SMAD2/3 activation by promoting the expression of SMAD ubiquitination regulatory factor 2 (SMURF2) and its nuclear translocation. During the transition from AKI to CKD, FMO2 modulated tubular cell fibrogenesis and paracrine secretion through SMURF2, thereby affecting the outcome of the disease.

S100-A8/A9 activated TLR4 in renal tubular cells to promote ischemia-reperfusion injury and fibrosis.

Renal ischemia/reperfusion injury (IRI) is a significant clinical problem without effective therapy. Unbiased omics approaches may reveal key renal mediators to initiate IRI. S100-A8/A9 was identified as the most significantly upregulated gene and protein base on proteomic analysis and RNA sequencing during the early reperfusion stage. S100-A8/A9 levels were significantly increased 1 day after transplantation in patients with donation after brain death (DBD). S100-A8/A9 production was associated with CD11b+Ly6G+ CXCR2+ immunocytes infiltration. Administration of S100-A8/A9 blocker ABR238901 significantly alleviates renal tubular injury, inflammatory cell infiltration, and renal fibrosis after renal IRI. Mechanistically, S100-A8/A9 could promote renal tubular cell injury and profibrotic cytokine production via TLR4. In conclusion, our findings found that early activation of S100-A8/A9 in renal IRI and targeting S100-A8/A9 signaling alleviates tubular injury and inhibits inflammatory response and renal fibrosis, which may provide a novel target for the prevention and treatment of acute kidney injury.

RP105 protects against ischemic and septic acute kidney injury via suppressing TLR4/NF-κB signaling pathways.

Acute kidney injury (AKI) is a critical and severe clinical disease caused by a variety of factors. Toll-like receptors (TLRs) play a crucial role in pathogenesis of AKI. Radioprotective 105 kDa protein (RP105) is a member of the TLR family, but the role of RP105 in AKI is unknown. In this study, we overexpressed RP105 in renal tissue and cultured proximal tubular cells in which we then induced ischemic and septic AKI. Renal structure injuries were examined by hematoxylin eosin staining, while renal function was assessed by measuring serum blood urea nitrogen (BUN) and creatinine (SCr) levels. The TUNEL assay was used to detect apoptosis induced changes in the expression of RP105, and nuclear factor κB (NF-κB) in renal tissue detected by Western blot. Inflammatory cytokines including iNOS, IL-1ß, IL-6, and TNF-α were detected by quantitative real-time PCR. The inflammatory indicators, F4/80 and MPO, were identified by IHC staining. The results showed that expression of the TLR4/NF-kB signaling pathway was enhanced in renal ischemia-reperfusion injury and septic renal injury, and that overexpression of RP105 in renal tissue alleviated ischemic and septic AKI. Moreover, RP105 gene delivery was associated with reduced renal inflammatory cells infiltration and inflammatory cytokines after AKI. RP105 overexpression also inhibited nuclear translocation of NF-κB after AKI in both in vitro and in vivo, and blunted the interaction between Myeloid Differentiation factor 2 (MD2) and TLR4. These results indicated that RP105 protected against renal ischemic and septic AKI injury by suppressing inflammatory responses mediated by TLR4 signaling pathways. This study suggests that the anti-inflammatory roles of RP105 have potential for preventing and treating renal ischemic and septic AKI.

Vitamin D/vitamin D receptor/Atg16L1 axis maintains podocyte autophagy and survival in diabetic kidney disease.

OBJECTIVE: To investigate the effect of vitamin D/vitamin D receptor (VDR)/Atg16L1 signaling on podocyte autophagy and survival in diabetic nephropathy. METHODS: Diabetic rat models were induced by intraperitoneal injection of streptozotocin (STZ) (60 mg/kg) and treated with and without gavage of 0.1 µg/kg/d active vitamin D3 (aVitD3; 1,25- OH vitamin D3) and kidney tissues assessed by histopathology and immunohistochemistry. The murine podocyte cell line MPC-5 was cultured under hyperglycemic conditions in the absence or presence of 100 nmol/L calcitriol to investigate podocyte injury and autophagy. Cell survival rates were analyzed using Cell Counting Kit-8 (CCK-8) assays and the numbers of autophagosomes were determined after transduction with the mRFP-GFP-LC3 autophagy reporter construct. The expression of autophagy-related proteins (LC3-II, beclin-1, Atg16L1) and podocyte-related proteins (nephrin, podocin, synaptopodin, and desmin) was determined by Western blotting. RESULTS: VDR expression and autophagy were decreased in diabetic nephropathy. Calcitriol treatment repressed renal injury in rat diabetic kidneys and reduced high glucose-induced damage to cultured podocytes. Mechanistically, Atg16L1 was identified as a functional target of VDR, and siRNA-mediated knockdown of VDR and Atg16L1 blocked the protective effects of aVitD3 against podocyte damage. CONCLUSION: Autophagy protects podocytes from damage in DN and is modulated by VitD3/VDR signaling and downstream regulation of Atg16L1 expression.