DY131 activates ERRγ/TFAM axis to protect against metabolic disorders and acute kidney injury.

Renal tubular injury is considered as the main pathological feature of acute kidney injury (AKI), and mitochondrial dysfunction in renal tubular cells is implicated in the pathogenesis of AKI. The estrogen-related receptor γ (ERRγ) is a member of orphan nuclear receptors which plays a regulatory role in mitochondrial biosynthesis, energy metabolism and many metabolic pathways. Online datasets showed a dominant expression of ERRγ in renal tubules, but the role of ERRγ in AKI is still unknown. In the present study, we investigated the role of ERRγ in the pathogenesis of AKI and the therapeutic efficacy of ERRγ agonist DY131 in several murine models of AKI. ERRγ expression was reduced in kidneys of AKI patients and AKI murine models along with a negative correlation to the severity of AKI. Consistently, silencing ERRγ in vitro enhanced cisplatin-induced tubular cells apoptosis, while ERRγ overexpression in vivo utilizing hydrodynamic-based tail vein plasmid delivery approach alleviated cisplatin-induced AKI. ERRγ agonist DY131 could enhance the transcriptional activity of ERRγ and ameliorate AKI in various murine models. Moreover, DY131 attenuated the mitochondrial dysfunction of renal tubular cells and metabolic disorders of kidneys in AKI, and promoted the expression of the mitochondrial transcriptional factor A (TFAM). Further investigation showed that TFAM could be a target gene of ERRγ and DY131 might ameliorate AKI by enhancing ERRγ-mediated TFAM expression protecting mitochondria. These findings highlighted the protective effect of DY131 on AKI, thus providing a promising therapeutic strategy for AKI.

CDC20 inhibition alleviates fibrotic response of renal tubular epithelial cells and fibroblasts by regulating nuclear translocation of ß-catenin.

Fibrosis is a common pathological phenomenon in progressive kidney disease leading to eventual loss of kidney function. Previous studies demonstrated that CDC20 plays a role in cancers by regulating epithelial-mesenchymal transition (EMT) and the infiltration of fibroblasts, suggesting the potential of CDC20 in regulating fibrotic response. However, the role of CDC20 in renal fibrosis is yet unclear. Herein, we reported that renal CDC20 was remarkably upregulated in renal tubular epithelial cells and fibroblasts in chronic kidney disease (CKD) patients, which was in line with a positive correlation with the severity of kidney fibrosis. In mice with unilateral urinary obstruction, CDC20 was also strikingly enhanced, and treatment with Apcin, an inhibitor of CDC20, ameliorated kidney fibrosis. Consistently, the pharmacological inhibition of CDC20 in mouse proximal tubular epithelial cells and rat fibroblasts attenuated TGF-ß1-induced fibrotic responses, while overexpression of CDC20 aggravated such responses. Additional studies revealed that CDC20 induces nuclear translocation of ß-catenin, which in turn initiates and promotes the pathological process of fibrosis in CKD. Thus, enhanced CDC20 in renal tubular cells and fibroblasts promotes renal fibrosis by activating ß-catenin, and CDC20 inhibition may serve as a promising strategy for the prevention and treatment of renal fibrosis.

LONP1 targets HMGCS2 to protect mitochondrial function and attenuate chronic kidney disease.

Mitochondria comprise the central metabolic hub of cells and their imbalance plays a pathogenic role in chronic kidney disease (CKD). Here, we studied Lon protease 1 (LONP1), a major mitochondrial protease, as its role in CKD pathogenesis is unclear. LONP1 expression was decreased in human patients and mice with CKD, and tubular-specific Lonp1 overexpression mitigated renal injury and mitochondrial dysfunction in two different models of CKD, but these outcomes were aggravated by Lonp1 deletion. These results were confirmed in renal tubular epithelial cells in vitro. Mechanistically, LONP1 downregulation caused mitochondrial accumulation of the LONP1 substrate, 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), which disrupted mitochondrial function and further accelerated CKD progression. Finally, computer-aided virtual screening was performed, which identified a novel LONP1 activator. Pharmacologically, the LONP1 activator attenuated renal fibrosis and mitochondrial dysfunction. Collectively, these results imply that LONP1 is a promising therapeutic target for treating CKD.

Anti-anemia drug FG4592 retards the AKI-to-CKD transition by improving vascular regeneration and antioxidative capability.

Acute kidney injury (AKI) is a known risk factor for the development of chronic kidney disease (CKD), with no satisfactory strategy to prevent the progression of AKI to CKD. Damage to the renal vascular system and subsequent hypoxia are common contributors to both AKI and CKD. Hypoxia-inducible factor (HIF) is reported to protect the kidney from acute ischemic damage and a novel HIF stabilizer, FG4592 (Roxadustat), has become available in the clinic as an anti-anemia drug. However, the role of FG4592 in the AKI-to-CKD transition remains elusive. In the present study, we investigated the role of FG4592 in the AKI-to-CKD transition induced by unilateral kidney ischemia-reperfusion (UIR). The results showed that FG4592, given to mice 3 days after UIR, markedly alleviated kidney fibrosis and enhanced renal vascular regeneration, possibly via activating the HIF-1α/vascular endothelial growth factor A (VEGFA)/VEGF receptor 1 (VEGFR1) signaling pathway and driving the expression of the endogenous antioxidant superoxide dismutase 2 (SOD2). In accordance with the improved renal vascular regeneration and redox balance, the metabolic disorders of the UIR mice kidneys were also attenuated by treatment with FG4592. However, the inflammatory response in the UIR kidneys was not affected significantly by FG4592. Importantly, in the kidneys of CKD patients, we also observed enhanced HIF-1α expression which was positively correlated with the renal levels of VEGFA and SOD2. Together, these findings demonstrated the therapeutic effect of the anti-anemia drug FG4592 in preventing the AKI-to-CKD transition related to ischemia and the redox imbalance.

Blocking AURKA with MK-5108 attenuates renal fibrosis in chronic kidney disease.

Renal fibrosis, a common feature of chronic kidney disease (CKD), is characterized by excessive deposition of extracellular matrix (ECM) leading to scar formation in the renal parenchyma. Active epithelial-mesenchymal communication (EMC), and the proliferation and activation of fibroblasts are implicated in the causation of renal fibrosis. Aurora-A kinase (AURKA) is a serine/threonine kinase required for the process of mitosis. Dysregulation of AURKA has been demonstrated in the context of various cancers. However, the role of AURKA in CKD-associated fibrosis has not been elucidated. MK-5108, a potent and highly selective AURKA inhibitor, was shown to exhibit anti-cancer activity in recent preclinical and clinical studies. In the present study, we investigated the role of MK-5108 in renal fibrosis employing animal and cell models. In vivo, AURKA was highly expressed in fibrotic kidneys of CKD patients and in mouse kidneys with unilateral ureteral obstruction (UUO). Post treatment with MK-5108 at the 3rd day after UUO remarkably alleviated renal fibrosis, possibly by inhibiting the proliferation and activation of fibroblasts and suppressing the phenotypic transition of renal cells. Moreover, the enhanced inflammatory factors in obstructive kidneys were also repressed. In vitro, MK-5108 treatment inhibited the pro-fibrotic response in renal cells induced by transforming growth factor-ß1. Finally, overexpression of AURKA in renal fibroblasts promoted fibrotic response, while silencing AURKA showed anti-fibrotic effect, further confirming the pro-fibrotic role of AURKA. In this study, inhibition of AURKA by MK-5108 markedly attenuated renal fibrosis. MK-5108 is a potential therapeutic agent for treatment of renal fibrosis in CKD.

The emerging role of MEIS1 in cell proliferation and differentiation.

Cell proliferation and differentiation are the foundation of reproduction and growth. Mistakes in these processes may affect cell survival, or cause cell cycle dysregulation, such as tumorigenesis, birth defects and degenerative diseases, or cell death. Myeloid ecotropic viral integration site 1 (MEIS1) was initially discovered in leukemic mice. Recent research identified MEIS1 as an important transcription factor that regulates cell proliferation and differentiation during cell fate commitment. MEIS1 has a pro-proliferative effect in leukemia cells; however, its overexpression in cardiomyocytes restrains neonatal and adult cardiomyocyte proliferation. In addition, MEIS1 has carcinogenic or tumor suppressive effects in different neoplasms. Thus, this uncertainty suggests that MEIS1 has a unique function in cell proliferation and differentiation. In this review, we summarize the primary findings of MEIS1 in regulating cell proliferation and differentiation. Correlations between MEIS1 and cell fate specification might suggest MEIS1 as a therapeutic target for diseases.

MicroRNA-214 promotes chronic kidney disease by disrupting mitochondrial oxidative phosphorylation.

Mitochondria are critical in determining a cell's energy homeostasis and fate, and mitochondrial dysfunction has been implicated in the pathogenesis of chronic kidney disease (CKD). We sought to identify causative mitochondrial microRNAs. A microarray screen of kidney tissue from healthy mice identified 97 microRNAs that were enriched in the mitochondrial fraction. We focused on microRNA-214-3p (miR-214) because of a very high ratio of mitochondrial to cytoplasmic expression in the kidney compared to other organs. Tubular expression of miR-214 was more abundant in kidney tissue from patients with CKD than from healthy controls, and was positively correlated with the degree of proteinuria and kidney fibrosis. Expression of miR-214 was also increased in the kidney of mouse models of CKD induced by obstruction, ischemia/reperfusion, and albumin overload. Proximal tubule-specific deletion of miR-214 attenuated apoptosis, inflammation, fibrosis, and mitochondrial damage in these CKD models. Pharmacologic inhibition of miR-214 had a similar effect in the albumin overload model of CKD. In vitro, overexpressing miR-214 in proximal tubular cell lines induced apoptosis and disrupted mitochondrial oxidative phosphorylation, while miR-214 expression was upregulated in response to a variety of insults. The mitochondrial genes mt-Nd6 and mt-Nd4l were identified as the specific targets of miR-214 in the kidney. Together, these results demonstrate a pathogenic role of miR-214 in CKD through the disruption of mitochondrial oxidative phosphorylation, and suggest the potential for miR-214 to serve as a therapeutic target and diagnostic biomarker for CKD.

MicroRNA-709 Mediates Acute Tubular Injury through Effects on Mitochondrial Function.

Mitochondrial dysfunction has important roles in the pathogenesis of AKI, yet therapeutic approaches to improve mitochondrial function remain limited. In this study, we investigated the pathogenic role of microRNA-709 (miR-709) in mediating mitochondrial impairment and tubular cell death in AKI. In a cisplatin-induced AKI mouse model and in biopsy samples of human AKI kidney tissue, miR-709 was significantly upregulated in the proximal tubular cells (PTCs). The expression of miR-709 in the renal PTCs of patients with AKI correlated with the severity of kidney injury. In cultured mouse PTCs, overexpression of miR-709 markedly induced mitochondrial dysfunction and cell apoptosis, and inhibition of miR-709 ameliorated cisplatin-induced mitochondrial dysfunction and cell injury. Further analyses showed that mitochondrial transcriptional factor A (TFAM) is a target gene of miR-709, and genetic restoration of TFAM attenuated mitochondrial dysfunction and cell injury induced by cisplatin or miR-709 overexpression in vitro Moreover, antagonizing miR-709 with an miR-709 antagomir dramatically attenuated cisplatin-induced kidney injury and mitochondrial dysfunction in mice. Collectively, our results suggest that miR-709 has an important role in mediating cisplatin-induced AKI via negative regulation of TFAM and subsequent mitochondrial dysfunction. These findings reveal a pathogenic role of miR-709 in acute tubular injury and suggest a novel target for the treatment of AKI.

MicroRNA-30e targets BNIP3L to protect against aldosterone-induced podocyte apoptosis and mitochondrial dysfunction.

MicroRNAs are essential for the maintenance of podocyte homeostasis. Emerging evidence has demonstrated a protective role of microRNA-30a (miR-30a), a member of the miR-30 family, in podocyte injury. However, the roles of other miR-30 family members in podocyte injury are unclear. The present study was undertaken to investigate the contribution of miR-30e to the pathogenesis of podocyte injury induced by aldosterone (Aldo), as well as the underlying mechanism. After Aldo treatment, miR-30e was reduced in a dose-and time-dependent manner. Notably, overexpression of miR-30e markedly attenuated Aldo-induced apoptosis in podocytes. In agreement with this finding, miR-30e silencing led to significant podocyte apoptosis. Mitochondrial dysfunction (MtD) has been shown to be an early event in Aldo-induced podocyte injury. Here we found that overexpression of miR-30e improved Aldo-induced MtD while miR-30e silencing resulted in MtD. Next, we found that miR-30e could directly target the BCL2/adenovirus E1B-interacting protein 3-like (BNIP3L) gene. Aldo markedly enhanced BNIP3L expression in podocytes, and silencing of BNIP3L largely abolished Aldo-induced MtD and cell apoptosis. On the contrary, overexpression of BNIP3L induced MtD and apoptosis in podocytes. Together, these findings demonstrate that miR-30e protects mitochondria and podocytes from Aldo challenge by targeting BNIP3L.

A vital role for myosin-9 in puromycin aminonucleoside-induced podocyte injury by affecting actin cytoskeleton.

Podocyte injury is an early pathological change of many kidney diseases. In particular, the actin cytoskeleton plays an important role in maintaining the normal function of podocytes. Disruption of the actin cytoskeleton is a feature of podocyte injury in proteinuric nephropathies. Recent studies showed that myosin-9 was localized in the podocyte foot processes and was necessary in maintaining podocyte structural homeostasis. However, it is unclear whether myosin-9 maintains podocyte structure by affecting actin cytoskleton. Here, the role of myosin-9 in puromycin aminonucleoside (PAN)-induced podocyte injury was explored both in vitro and in vivo. In cultured mouse podocytes (MPC5), it was determined that PAN downregulated myosin-9 expression, disrupted the actin cytoskeleton and reduced the adhesion ability. Reduced myosin-9 expression by siRNA precipitated podocyte cytoskeletal damage and accelerated PAN-induced podocyte detachment. Overexpression of myosin-9 protected against PAN-induced podocyte detachment. Furthermore, administration of an antioxidant Mn(III)tetrakis (4-benzoic acid) porphyrin (MnTBAP) inhibited PAN-induced podocyte cytoskeletal damage and podocyte detachment by restoring the expression of myosin-9. In the rat PAN nephropathy model, MnTBAP could also attenuate PAN-induced reduction of myosin-9 and podocyte loss. Taken together, these findings pinpointed that oxidative stress contributed to PAN-induced podocyte injury through the repression of a cytoskeletal protein myosin-9, which provided novel insights into a potential target for the treatment of podocyte injury-associated glomerulopathies.

Reactive oxygen species-initiated autophagy opposes aldosterone-induced podocyte injury.

Evidence has demonstrated that aldosterone (Aldo) is involved in the development and progression of chronic kidney diseases. The purpose of the present study was to investigate the role of autophagy in Aldo-induced podocyte damage and the underlying mechanism. Mouse podocytes were treated with Aldo in the presence or absence of 3-methyladenine and N-acetylcysteine. Cell apoptosis was investigated by detecting annexin V conjugates, apoptotic bodies, caspase-3 activity, and alterations of the podocyte protein nephrin. Autophagy was evaluated by measuring the expressions of light chain 3, p62, beclin-1, and autophagy-related gene 5. Aldo (10-7 mol/l) induced podocyte apoptosis, autophagy, and downregulation of nephrin protein in a time-dependent manner. Aldo-induced apoptosis was further promoted by the inhibition of autophagy via 3-methyladenine and autophagy-related gene 5 small interfering RNA pretreatment. Moreover, Aldo time dependently increased ROS generation, and H2O2 (10-4 mol/l) application remarkably elevated podocyte autophagy. After treatment with N-acetylcysteine, the autophagy induced by Aldo or H2O2 was markedly attenuated, suggesting a key role of ROS in mediating autophagy formation in podocytes. Inhibition of ROS could also lessen Aldo-induced podocyte injury. Taken together, our findings suggest that ROS-triggered autophagy played a protective role against Aldo-induced podocyte injury, and targeting autophagy in podocytes may represent a new therapeutic strategy for the treatment of podocytopathy.

Mitochondrial dysfunction confers albumin-induced NLRP3 inflammasome activation and renal tubular injury.

Proteinuria is involved in the development of tubular lesions and in the progressive loss of renal function in chronic kidney diseases via uncertain mechanisms. Growing evidence suggests a pathogenic role of mitochondrial dysfunction in chronic kidney diseases. Therefore, the present study aimed to define the roles of mitochondria in proteinuria-induced renal tubular injury and their underlying mechanisms. Using the albumin-overload mouse model, we observed severe tubular structure damage and striking tubular cell apoptosis. Furthermore, tubular epithelial cells displayed a loss of E-cadherin expression and gained expression of α-smooth muscle actin and vimentin, indicating a cellular phenotypic alteration. Strikingly, these albumin overload-induced abnormalities were robustly blocked by a mitochondrial SOD2 mimic, Mn(III) tetrakis (4-benzoic acid)porphyrin chloride (MnTBAP). In agreement with these results, we observed a marked change in mitochondrial morphology accompanied by mitochondrial cytochrome c release and a copy number reduction of mitochondrial DNA. These alterations were largely reversed by MnTBAP, suggesting a key role for mitochondria-derived oxidative stress in mediating the albumin effect on mitochondrial dysfunction and subsequent tubular injury. Moreover, the NOD-like receptor family, pyrin domain-containing 3 (NLRP3)/caspase-1/cytokine cascade was activated in the kidney by albumin overload and was entirely abolished by MnTBAP. In albumin-treated mouse proximal tubular cells, albumin directly induced ROS production, mitochondrial dysfunction, NLRP3/caspase-1/cytokine cascade activation, cell apoptosis, and cellular phenotypic transition. Similar to our in vivo results, treatment with either MnTBAP or cyclosporin A, a mitochondrial permeability transition pore inhibitor, remarkably attenuated these abnormalities in cells. Taken together, these novel findings demonstrate a potential role for the mitochondrial dysfunction/NLRP3 inflammasome axis in the pathogenesis of proteinuria-induced renal tubular injury.

Activation of ERK1/2 by NADPH oxidase-originated reactive oxygen species mediates uric acid-induced mesangial cell proliferation.

Hyperuricemia is associated with kidney complications including glomerulosclerosis and mesangial cell (MC) proliferation by poorly understood mechanisms. The present study investigated the underlying mechanisms that mediate uric acid (UA)-induced MC proliferation. A rat MC line, HBZY-1, was treated with various concentrations of UA in the presence or absence of a specific extracellular-regulated protein kinase 1/2 (ERK1/2) inhibitor (U0126), apocynin. UA dose dependently stimulated MC proliferation as shown by increased DNA synthesis and number of cells in the S and G2 phases in parallel with the upregulation of cyclin A2 and cyclin D1. In addition, UA time dependently promoted MC proliferation and significantly increased phosphorylation of ERK1/2 but not c-Jun NH2-terminal kinase and p38 MAPK in MCs as assessed by immunoblotting. Inhibition of ERK1/2 signaling via U0126 markedly blocked UA-induced MC proliferation. More importantly, UA induced intracellular reactive oxygen species (ROS) production of MCs dose dependently, which was completely blocked by apocynin, a specific NADPH oxidase inhibitor. Toll-like receptor (TLR)2 and TLR4 signaling had no effect on NADPH-derived ROS and UA-induced MC proliferation. Interestingly, pretreatment with apocynin inhibited ERK1/2 activation, the upregulation of cyclin A2 and cyclin D1, and MC proliferation. In conclusion, UA-induced MC proliferation was mediated by NADPH/ROS/ERK1/2 signaling pathway. This novel finding not only reveals the mechanism of UA-induced MC cell proliferation but also provides some potential targets for future treatment of UA-related glomerular injury.