miR-147 Represses NDUFA4, Inducing Mitochondrial Dysfunction and Tubular Damage in Cold Storage Kidney Transplantation

Mitochondrial dysfunction in acute kidney injury

Acute kidney injury (AKI) is a systemic clinical syndrome increasing morbidity and mortality worldwide in recent years. Renal tubular epithelial cells (TECs) death caused by mitochondrial dysfunction is one of the pathogeneses. The imbalance of mitochondrial quality control is the main cause of mitochondrial dysfunction. Mitochondrial quality control plays a crucial role in AKI. Mitochondrial quality control mechanisms are involved in regulating mitochondrial integrity and function, including antioxidant defense, mitochondrial quality control, mitochondrial DNA (mtDNA) repair, mitochondrial dynamics, mitophagy, and mitochondrial biogenesis. Currently, many studies have used mitochondrial dysfunction as a targeted therapeutic strategy for AKI. Therefore, this review aims to present the latest research advancements on mitochondrial dysfunction in AKI, providing a valuable reference and theoretical foundation for clinical prevention and treatment of this condition, ultimately enhancing patient prognosis.

microRNAs in kidney diseases: Regulation, therapeutics, and biomarker potential

MicroRNAs (miRNAs) are small, non-coding RNA molecules that play a crucial role in regulating gene expression by inhibiting the translation of their specific target messenger RNAs. To date, numerous studies have demonstrated changes in the expression of miRNAs in the kidneys throughout the progression of both acute kidney injury (AKI) and chronic kidney disease (CKD) in both human patients and experimental models. The role of specific microRNAs in the pathogenesis of kidney diseases has also been demonstrated. Further studies have elucidated the regulation of these microRNAs in diseased kidneys. Besides, certain miRNAs are detected in plasma and/or urine in kidney diseases and are potential diagnostic biomarkers. In this review, we provide an overview of recent developments in our understanding of how miRNAs contribute to kidney diseases. We also explore the potential of miRNAs as both biomarkers and therapeutic targets for these conditions, and highlight future research directions.

Identification of Differentially Expressed Genes in Cold Storage-associated Kidney Transplantation

BACKGROUND

Although it is acknowledged that ischemia-reperfusion injury is the primary pathology of cold storage-associated kidney transplantation, its underlying mechanism is not well elucidated.

METHODS

To extend the understanding of molecular events and mine hub genes posttransplantation, we performed bulk RNA sequencing at different time points (24 h, day 7, and day 14) on a murine kidney transplantation model with prolonged cold storage (10 h).

RESULTS

In the present study, we showed that genes related to the regulation of apoptotic process, DNA damage response, cell cycle/proliferation, and inflammatory response were steadily elevated at 24 h and day 7. The upregulated gene profiling delicately transformed to extracellular matrix organization and fibrosis at day 14. It is prominent that metabolism-associated genes persistently took the first place among downregulated genes. The gene ontology terms of particular note to enrich are fatty acid oxidation and mitochondria energy metabolism. Correspondingly, the key enzymes of the above processes were the products of hub genes as recognized. Moreover, we highlighted the proximal tubular cell-specific increased genes at 24 h by combining the data with public RNA-Seq performed on proximal tubules. We also focused on ferroptosis-related genes and fatty acid oxidation genes to show profound gene dysregulation in kidney transplantation.

CONCLUSIONS

The comprehensive characterization of transcriptomic analysis may help provide diagnostic biomarkers and therapeutic targets in kidney transplantation.

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.

Mouse kidney transplantation model: Three novel methods

OBJECTIVES

The mouse kidney transplantation model presents challenges in terms of surgical difficulty and low success rate, making it difficult to master. This study aims to provide a crucial model for transplantation immunology research by modifying and developing novel techniques for mouse kidney transplantation.

METHODS

A total of 57 pairs of mice were used to establish and compare the modified and innovative surgical techniques for mouse kidney transplantation. Three different surgical models were established, including the abdominal suture technique for orthotopic kidney transplantation, the abdominal cuff technique for orthotopic kidney transplantation, and the cervical cuff technique for ectopic kidney transplantation. BALB/c or C57BL/6 male mice, aged 8 to 12 weeks and weighed 20 to 25 g with specified pathogen free-grade were served as the donor mice or the recipient mice. The surgical technique characteristics, key surgical times, complications, and pathological examination in the early postoperative period were summarized and compared.

RESULTS

Three different surgical models of mouse kidney transplantation were successfully established. The comparison of warm ischemic time for the 3 groups of mice showed no statistical significance (P=0.510 4). The abdominal suture group had the shortest total operation time of the donor compared with the abdominal cuff group and the cervical cuff group [(18.3±3.6) min vs (26.2±4.7) min and (22.8±2.5) min; both P<0.000 1]. There was a significant difference in cold ischemia time among the 3 groups (all P<0.000 1), with (60.8±4.1) min in the cervical cuff group, (43.3±5.0) min in the abdominal suture group, and (88.8±6.7) min in the abdominal cuff group. Due to different anastomosis methods, the cervical cuff group had the shortest time [(17.6±2.7) min], whereas the abdominal cuff group had the longest time [(38.8±5.4) min]. The total operation time for the recipients showed significant differences (P<0.000 1), with the abdominal suture group having the shortest time [(44.0±6.9) min], followed by the cervical cuff group [(64.1±5.2) min], and the abdominal cuff group [(80.0±6.0) min] being the longest. In the 32 mice of the abdominal suture group, there were 6 with intraoperative bleeding, including 1 arterial intimal injury bleeding and 5 with bleeding after vessel opening. Six mice had ureteral complications, including ureteral bladder anastomotic stenosis, necrosis, and renal pelvis dilation. Two mice had postoperative abdominal infections. In the abdominal cuff group, there was no intraoperative bleeding, but 6 mice showed mild arterial stenosis and 5 showed venous stenosis, 4 arterial injury, 4 arterial thrombosis, and 2 ureteral complications. No postoperative infections occurred in the mice. In the cervical cuff group, no intraoperative bleeding, arterial intimal injury, arterial/venous stenosis, or thrombosis were found in 13 mice. Five mice had ureteral complications, including ureteral necrosis and infection, which were the main complications in the cervical cuff group. The renal function in mice of the 3 groups remained stable 7 days after surgery. Hematoxylin and eosin staining and periodic acid-Schiff staining showed no significant differences in terms of acute rejection among the 3 surgical methods (all P>0.05).

CONCLUSIONS

All 3 surgical methods are able to successfully establish mouse kidney transplantation models, with no significant differences observed in the short-term graft survival and acute rejection. The modified abdominal suture technique and abdominal cuff technique have their respective advantages in research applications. The novel cervical cuff technique for ectopic kidney transplantation model is relatively simple to be prepared and causes less trauma to the mice, providing more options for studies involving xenotransplantation, secondary transplantation, and local lymphatic drainage. However, the difficulty in harvesting the donor kidney and the high incidence of ureteral infections need further validation in long-term survival. This study holds important reference value for choosing the type of mouse kidney transplantation model for different research needs.

Integrative analysis identifies oxidative stress biomarkers in non-alcoholic fatty liver disease via machine learning and weighted gene co-expression network analysis

Background

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease globally, with the potential to progress to non-alcoholic steatohepatitis (NASH), cirrhosis, and even hepatocellular carcinoma. Given the absence of effective treatments to halt its progression, novel molecular approaches to the NAFLD diagnosis and treatment are of paramount importance.

Methods

Firstly, we downloaded oxidative stress-related genes from the GeneCards database and retrieved NAFLD-related datasets from the GEO database. Using the Limma R package and WGCNA, we identified differentially expressed genes closely associated with NAFLD. In our study, we identified 31 intersection genes by analyzing the intersection among oxidative stress-related genes, NAFLD-related genes, and genes closely associated with NAFLD as identified through Weighted Gene Co-expression Network Analysis (WGCNA). In a study of 31 intersection genes between NAFLD and Oxidative Stress (OS), we identified three hub genes using three machine learning algorithms: Least Absolute Shrinkage and Selection Operator (LASSO) regression, Support Vector Machine - Recursive Feature Elimination (SVM-RFE), and RandomForest. Subsequently, a nomogram was utilized to predict the incidence of NAFLD. The CIBERSORT algorithm was employed for immune infiltration analysis, single sample Gene Set Enrichment Analysis (ssGSEA) for functional enrichment analysis, and Protein-Protein Interaction (PPI) networks to explore the relationships between the three hub genes and other intersecting genes of NAFLD and OS. The distribution of these three hub genes across six cell clusters was determined using single-cell RNA sequencing. Finally, utilizing relevant data from the Attie Lab Diabetes Database, and liver tissues from NASH mouse model, Western Blot (WB) and Reverse Transcription Quantitative Polymerase Chain Reaction (RT-qPCR) assays were conducted, this further validated the significant roles of CDKN1B and TFAM in NAFLD.

Results

In the course of this research, we identified 31 genes with a strong association with oxidative stress in NAFLD. Subsequent machine learning analysis and external validation pinpointed two genes: CDKN1B and TFAM, as demonstrating the closest correlation to oxidative stress in NAFLD.

Conclusion

This investigation found two hub genes that hold potential as novel targets for the diagnosis and treatment of NAFLD, thereby offering innovative perspectives for its clinical management.

PIM1 attenuates cisplatin-induced AKI by inhibiting Drp1 activation

Cisplatin, an effective anti-cancer drug, always causes acute kidney injury (AKI) by inducing mitochondrial damage. PIM1 is a serine/threonine kinase, which has been shown to regulate mitochondrial function. However, the role and mechanisms of PIM1 in cisplatin-induced AKI remain unexplored. This study aimed to investigate the effects of PIM1 in cisplatin-induced AKI and its underlying mechanisms. To established Cisplatin-induced AKI model, mice were given a single intraperitoneal injection(20 mg/kg) and BUMPT cells were treated with cisplatin(20 μM). PIM1 inhibitor AZD1208 was used to inhibit PIM1 and PIM1-experssing adenovirus was used to overexpress PIM1. Drp1 inhibitor P110 and pcDNA3-Drp1K38A were used to inhibit the activation of Drp1 and mitochondrial fission. The indicators of renal function, renal morphology, apoptosis and mitochondrial dysfunction were assessed to evaluate cisplatin-induced nephrotoxicity. We observed that PIM1 was activated in cisplatin-induced AKI in vivo and cisplatin-induced tubular cells injury in vitro. PIM1 inhibition aggravated cisplatin-induced AKI in vivo, while PIM1 overexpression attenuated cisplatin-induced kidney injury in vivo and in vitro. Moreover, inhibiting PIM1 exacerbated mitochondrial damage in mice, but overexpressing PIM1 relieved mitochondrial damage in mice and BUMPT cells. In mice and BUMPT cells, inhibiting PIM1 deregulated the expression of p-Drp1S637, overexpressing PIM1 upregulated the ex-pression of p-Drp1S637. And inhibiting Drp1 activity alleviated cell damage in BUMPT cells with PIM1 knockdown or inhibition. This study demonstrated the protective effect of PIM1 in cisplatin-induced AKI, and regulation of Drp1 activation might be the underlying mechanism. Altogether, PIM1 may be a potential therapeutic target for cisplatin-induced AKI.

MicroRNA-192-5p downregulates Fat Mass and Obesity-associated Protein to aggravate renal ischemia/reperfusion injury

Acute kidney injury (AKI) is a common disorder without effective therapy yet. Renal ischemia/reperfusion (I/R) injury is a common cause of AKI. MicroRNA miR-192-5p has been previously reported to be upregulated in AKI models. However, its functional role in renal I/R injury is not fully understood. This study aimed to investigate the effects and the underlying mechanism of miR-192-5p in renal I/R progression. Hypoxia/reoxygenation (H/R)-induced cell injury model in HK-2 cells and I/R-induced renal injury model in mice were established in this study. Cell counting kit-8 assay was performed to determine cell viability. Quantitative real-time PCR and western blot analysis were performed to detect gene expressions. Hematoxylin-eosin and periodic acid-Schiff staining were performed to observe the histopathological changes. Enzyme-linked immunosorbent assay was performed to detect the kidney markers' expression. In vivo and in vitro results showed that miR-192-5p was up-regulated in the I/R-induced mice model and H/R-induced cell model, and miR-192-5p overexpression exacerbated I/R-induced renal damage. Then, the downstream target of miR-192-5p was analyzed by combining the differentially expressed mRNAs and the predicted genes and confirmed using a dual-luciferase reporter assay. It was found that miR-192-5p was found to regulate fat mass and obesity-associated (FTO) protein expression by directly targeting the 3' untranslated region of FTO mRNA. Moreover, in vivo and in vitro studies unveiled that FTO overexpression alleviated renal I/R injury and promoted HK-2 cell viability via stimulating autophagy flux. In conclusion, miR-192-5p aggravated I/R-induced renal injury by blocking autophagy flux via down-regulating FTO.

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.

Mitochondrial iron regulation as an emerging target in ischemia/reperfusion injury during kidney transplantation

The injury caused by ischemia and subsequent reperfusion (I/R) is inevitable during kidney transplantation and its current management remains unsatisfactory. Iron is considered to play a remarkable pathologic role in the initiation or progression of tissue damage induced by I/R, whereas the effects of iron-related therapy remain controversial owing to the complicated nature of iron's involvement in multiple biological processes. A significant portion of the cellular iron is located in the mitochondria, which exerts a central role in the development and progression of I/R injury. Recent studies of iron regulation associated with mitochondrial function represents a unique opportunity to improve our knowledge on the pathophysiology of I/R injury. However, the molecular mechanisms linking mitochondria to the iron homeostasis remain unclear. In this review, we provide a comprehensive analysis of the alterations to iron metabolism in I/R injury during kidney transplantation, analyze the current understanding of mitochondrial regulation of iron homeostasis and discussed its potential application in I/R injury. The elucidation of regulatory mechanisms regulating mitochondrial iron homeostasis will offer valuable insights into potential therapeutic targets for alleviating I/R injury with the ultimate aim of improving kidney graft outcomes, with potential implications that could also extend to acute kidney injury or other I/R injuries.

microRNA Expression of Renal Proximal Tubular Epithelial Cells and Their Extracellular Vesicles in an Inflammatory Microenvironment In Vitro

Renal proximal tubular epithelial cells (PTCs) are central players during renal inflammation. In response to inflammatory signals, PTCs not only self-express altered mRNAs, microRNAs (miRNAs), proteins, and lipids, but also release altered extracellular vesicles (EVs). These EVs also carry inflammation-specific cargo molecules and are key players in cell-cell-communication. Understanding the precise molecular and cellular mechanisms that lead to inflammation in the kidney is the most important way to identify early targets for the prevention or treatment of acute kidney injury. Therefore, highly purified human PTCs were used as an in vitro model to study the cellular response to an inflammatory microenvironment. A cytokine-induced inflammatory system was established to analyze different miRNA expression in cells and their EVs. In detail, we characterized the altered miR expression of PTCs and their released EVs during induced inflammation and showed that 12 miRNAs were significantly regulated in PTCs (6 upregulated and 6 downregulated) and 9 miRNAs in EVs (8 upregulated and 1 downregulated). We also showed that only three of the miRNAs were found to overlap between cells and EVs. As shown by the KEGG pathway analysis, these three miRNAs (miR-146a-5p, miR-147b, and miR-155-5p) are functionally involved in the regulation of the Toll-like receptor signaling pathway and significantly correlated with the inflammatory mediators IL6 and ICAM1 released by stimulated PTCs. Especially with regard to a possible clinical use of miRs as new biomarkers, an accurate characterization of the miR expression altered during inflammatory processes is of enormous importance.