Yue Zhang

Introduction: Obstructive nephropathy is frequently associated with downregulation of key renal water and sodium transporters, resulting in impaired urinary concentration and disrupted fluid balance. The present study aimed to investigate the role of Polo-like kinase 1 (Plk1), a kinase traditionally recognized for its function in cell-cycle regulation, in modulating renal water and sodium transporters in a unilateral ureteral obstruction (UUO) model, and to elucidate the underlying molecular mechanisms. Methods: Plk1 function was inhibited pharmacologically using BI6727 or genetically using heterozygous Plk1 knockout mice. In vitro, renal collecting duct M1 cells were stimulated with TGF-β to examine mechanistic pathways. Results: Inhibition of Plk1 with BI6727 preserved the expression of aquaporin 2 (AQP2) and sodium-potassium-chloride cotransporter 2 (NKCC2) in UUO kidneys. Similarly, heterozygous Plk1 knockout mice exhibited higher AQP2 and NKCC2 levels than wild-type controls. Mechanistically, Plk1 regulated cytosolic phospholipase A2 (cPLA2) activity, leading to elevated prostaglandin E2 (PGE2) production. PGE2 subsequently upregulated the E3 ubiquitin ligases NEDD4 and NEDD4L, promoting ubiquitin-proteasome-mediated degradation of AQP2 and NKCC2. Conclusion: These findings indicate that Plk1 contributes to the maladaptive downregulation of renal water and sodium transporters during obstruction. Pharmacological inhibition or genetic reduction of Plk1 preserves transporter expression, highlighting the Plk1-cPLA2-PGE2-NEDD4/NEDD4L axis as a potential therapeutic target for correcting water and sodium imbalance in obstructive nephropathy.

The mode of electron transport in mitochondrial respiratory chain determines whether it generates energy or more reactive oxygen species (ROS), a key for cellular adaptation to diverse oxygen environments. However, the understanding of the mechanisms remains incomplete. Here, we find that NIMA-related kinase 7 (NEK7), targeted to mitochondria by its signal peptides, binds to succinate dehydrogenase complex iron sulfur subunit B (SDHB), stabilizing the spatial conformation of complex II and promoting forward electron transport. Deficiency of NEK7 in hepatocytes induces reverse electron transport (RET) and inhibits mitochondrial respiration, thereby promoting ROS generation, triggering spontaneous liver fibrosis and aggravating CCl ₄ -induced liver fibrosis, which can be attenuated by RET inhibitors. More importantly, NEK7 overexpression effectively alleviates CCl ₄ - and choline-deficient, high-fat diet-induced liver fibrosis. Overall, these findings highlight the pivotal role of NEK7 in orchestrating complex II and electron transport, providing new insights into the regulation of mitochondrial homeostasis and potential fibrosis treatments.

Chronic Kidney Disease (CKD) is a global health challenge, with acute kidney injury (AKI) from ischemia‐reperfusion injury (IRI) as a common cause. This study explored the role of Hepatocyte Nuclear Factor 3 alpha (HNF3α/FOXA1) in renal fibrosis and CKD after IRI. Kidney biopsy specimens from CKD patients and mouse models (IRI or unilateral ureteral obstruction) showed HNF3α upregulation in fibrotic kidneys, linked to renal function decline. Additional experiments demonstrated that deletion of HNF3α mitigated IRI‐induced renal fibrosis, and that overexpression of HNF3α led to increased fibrosis. Examination of the potential mechanism by transcriptome sequencing and CUT&Tag sequencing suggested that HNF3α promoted renal fibrosis by increasing the expression of the NCK associated protein 1 like (Nckap1l, formerly known as hematopoietic protein 1 [Hem1]), a vital component of the WAVE complex which plays a significant role in cytoskeletal regulation and cell migration. These results underscore the critical function of HNF3α in renal fibrosis following IRI, and also identify Nckap1l as a potential therapeutic target, thus opening new avenues for research and potential therapeutic interventions for CKD and renal fibrosis.

Introduction: Purinergic signaling has been recognized as important extracellular regulator in multiple physiological and pathophysiological conditions. Adenosine triphosphate–purinergic receptor P2Y2 signaling pathway is associated with glomerular nephritis (GN), diabetic nephropathy (DN), and chronic kidney disease. Recently, there has been evidence that global knockout of P2Y2 exacerbated bilateral ischemic reperfusion-induced acute kidney injury (AKI). However, its role in cisplatin-induced AKI (CIA) remains unknown. Cisplatin is a platinum-containing antineoplastic drug widely used in variety of solid malignant tumors. Nephrotoxicity is one of the major serious side effect that limit its clinical use. In the present study, we investigated whether inhibition of P2Y2 has an effect on CIA. Methods: We used AR-C118925 (AR-C), a selective antagonist of P2Y2, and gene transfection for interruption of the P2Y2 pathway. Mice were pretreated with AR-C (10 mg/kg/day) and then challenged with cisplatin at a dose of 20 mg/kg. Seventy-two hours after cisplatin administration, all mice developed kidney failure. Knockdown and overexpression of P2Y2 in mice and mouse proximal tubular cells (mPTCs) were employed to validate that ARC acts through P2Y2 receptor. Results: AR-C markedly ameliorated cisplatin-induced nephrotoxicity evidenced by improved renal function, renal morphology, and tubular injury marker expression. Further analysis of the mechanism revealed that AR-C significantly reduced kidney oxidative stress, inflammation, apoptosis, and necroptosis. Consistently, AR-C protects mPTCs from injury caused by cisplatin. To verify that AR-C acts through the P2Y2 receptor, we knocked down P2Y2 in mice or in mPTC cells. Both showed beneficial effects, while overexpression of P2Y2 promotes cisplatin-induced cell death. Conclusion: Taken together, our study, for the first time revealed that P2Y2 plays an important role in CIA by regulating oxidative stress, inflammation, apoptosis, and necroptosis and its inhibitor, AR-C, is a potential drug for treating CIA.

Acute kidney injury (AKI) is a significant global health issue, which is often caused by cisplatin therapy and characterized by mitochondrial dysfunction. Restoring mitochondrial homeostasis in tubular cells could exert therapeutic effects. Here, we investigated Slc25a21, a mitochondrial carrier, as a potential target for AKI intervention. Renal Slc25a21 expression is negatively associated with kidney function in both AKI patients and cisplatin-induced murine models. Sustaining renal expression of Slc25a21 slowed down AKI progression by reducing cellular apoptosis, necroptosis, and the inflammatory response, likely through its regulation of 2-oxoadipate conversion. Slc25a21 is highly expressed in proximal tubular epithelial cells, and its down-regulation contributes to compromised mitochondrial biogenesis and integrity, as well as impaired oxidative phosphorylation. Mechanistically, reduced Slc25a21 in AKI disrupts mitochondrial 2-oxoadipate transport, affecting related metabolites influx and the tricarboxylic acid cycle. These findings demonstrate a previously unappreciated metabolic function of Slc25a21 in tubular cells, and suggest that targeting mitochondrial metabolic homeostasis by sustaining Slc25a21 expression could be a potential novel therapeutic strategy for AKI.

The prevalence of chronic kidney disease (CKD) has been increasing over the past decades. However, no effective therapies are available for delaying or curing CKD. Progressive fibrosis is the major pathological feature of CKD, which leads to end-stage renal disease (ESRD). The present study showed that Polo-like kinase 1 (Plk1) was upregulated in the kidneys of CKD patients and mice subjected to unilateral ureteral obstruction (UUO) with location in proximal tubules and tubulointerstitial fibroblasts. Pharmacological inhibition, genetic silencing or knockout of Plk1 attenuated obstructive nephropathy due to suppressed fibroblast activation mediated by reduced autophagic flux. We found Plk1 plays a critical role in maintaining intralysosomal pH by regulating ATP6V1A phosphorylation, and inhibition of Plk1 impaired lysosomal function leading to blockade of autophagic flux. In addition, Plk1 also prevented partial epithelial-mesenchymal transition (pEMT) of tubular epithelial cells via autophagy pathway. In conclusion, this study demonstrated that Plk1 plays a pathogenic role in renal tubulointerstitial fibrosis by regulating autophagy/lysosome axis. Thus, targeting Plk1 could be a promising strategy for CKD treatment.