HIF-1 contributes to autophagy activation via BNIP3 to facilitate renal fibrosis in hypoxia in vitro and UUO in vivo.

The molecular basis of renal interstitial fibrosis, a major pathological feature of progressive kidney diseases, remains poorly understood. Autophagy has been implicated in renal fibrosis, but whether it promotes or inhibits fibrosis remains controversial. Moreover, it is unclear how autophagy is activated and sustained in renal fibrosis. The present study was designed to address these questions using the in vivo mouse model of unilateral ureteral obstruction and the in vitro model of hypoxia in renal tubular cells. Both models showed the activation of hypoxia-inducible factor-1 (HIF-1) and autophagy along with fibrotic changes. Inhibition of autophagy with chloroquine reduced renal fibrosis in unilateral ureteral obstruction model, whereas chloroquine and autophagy-related gene 7 knockdown decreased fibrotic changes in cultured renal proximal tubular cells, supporting a profibrotic role of autophagy. Notably, pharmacological and genetic inhibition of HIF-1 led to the suppression of autophagy and renal fibrosis in these models. Mechanistically, knock down of BCL2 and adenovirus E1B 19-kDa-interacting protein 3 (BNIP3), a downstream target gene of HIF, decreased autophagy and fibrotic changes during hypoxia in BUMPT cells. Together, these results suggest that HIF-1 may activate autophagy via BNIP3 in renal tubular cells to facilitate the development of renal interstitial fibrosis.NEW & NOTEWORTHY Autophagy has been reported to participate in renal fibrosis, but its role and underlying activation mechanism is unclear. In this study, we report the role of HIF-1 in autophagy activation in models of renal fibrosis and further investigate the underlying mechanism.

Male-pronuclei-specific granulin facilitates somatic cells reprogramming via mitigating excessive cell proliferation and enhancing lysosomal function.

Critical reprogramming factors resided predominantly in the oocyte or male pronucleus can enhance the efficiency or the quality of induced pluripotent stem cells (iPSCs) induction. However, few reprogramming factors exist in the male pronucleus had been verified. Here, we demonstrated that granulin (Grn), a factor enriched specifically in male pronucleus, can significantly improve the generation of iPSCs from mouse fibroblasts. Grn is highly expressed on Day 1, Day 3, Day 14 of reprogramming induced by four Yamanaka factors and functions at the initial stage of reprogramming. Transcriptome analysis indicates that Grn can promote the expression of lysosome-related genes, while inhibit the expression of genes involved in DNA replication and cell cycle at the early reprogramming stage. Further verification determined that Grn suppressed cell proliferation due to the arrest of cell cycle at G2/M phase. Moreover, ectopic Grn can enhance the lysosomes abundance and rescue the efficiency reduction of reprogramming resulted from lysosomal protease inhibition. Taken together, we conclude that Grn serves as an activator for somatic cell reprogramming through mitigating cell hyperproliferation and promoting the function of lysosomes.

Rodent models of AKI and AKI-CKD transition: an update in 2024.

Despite known drawbacks, rodent models are essential tools in the research of renal development, physiology, and pathogenesis. In the past decade, rodent models have been developed and used to mimic different etiologies of acute kidney injury (AKI), AKI to chronic kidney disease (CKD) transition or progression, and AKI with comorbidities. These models have been applied for both mechanistic research and preclinical drug development. However, current rodent models have their limitations, especially since they often do not fully recapitulate the pathophysiology of AKI in human patients, and thus need further refinement. Here, we discuss the present status of these rodent models, including the pathophysiologic compatibility, clinical translational significance, key factors affecting model consistency, and their main limitations. Future efforts should focus on establishing robust models that simulate the major clinical and molecular phenotypes of human AKI and its progression.

Genetic Deletion of LRP5 and LRP6 in Macrophages Exacerbates Colitis-Associated Systemic Inflammation and Kidney Injury in Response to Intestinal Commensal Microbiota.

Extraintestinal manifestations are common in inflammatory bowel disease and involve several organs, including the kidney. However, the mechanisms responsible for renal manifestation in inflammatory bowel disease are not known. In this study, we show that the Wnt-lipoprotein receptor-related proteins 5 and 6 (LRP5/6) signaling pathway in macrophages plays a critical role in regulating colitis-associated systemic inflammation and renal injury in a murine dextran sodium sulfate-induced colitis model. Conditional deletion of the Wnt coreceptors LRP5/6 in macrophages in mice results in enhanced susceptibility to dextran sodium sulfate colitis-induced systemic inflammation and acute kidney injury (AKI). Furthermore, our studies show that aggravated colitis-associated systemic inflammation and AKI observed in LRP5/6LysM mice are due to increased bacterial translocation to extraintestinal sites and microbiota-dependent increased proinflammatory cytokine levels in the kidney. Conversely, depletion of the gut microbiota mitigated colitis-associated systemic inflammation and AKI in LRP5/6LysM mice. Mechanistically, LRP5/6-deficient macrophages were hyperresponsive to TLR ligands and produced higher levels of proinflammatory cytokines, which are associated with increased activation of MAPKs. These results reveal how the Wnt-LRP5/6 signaling in macrophages controls colitis-induced systemic inflammation and AKI.

WD repeat domain 82 (Wdr82) facilitates mouse iPSCs generation by interfering mitochondrial oxidative phosphorylation and glycolysis.

BACKGROUND: Abundantly expressed factors in the oocyte cytoplasm can remarkably reprogram terminally differentiated germ cells or somatic cells into totipotent state within a short time. However, the mechanism of the different factors underlying the reprogramming process remains uncertain. METHODS: On the basis of Yamanaka factors OSKM induction method, MEF cells were induced and reprogrammed into iPSCs under conditions of the oocyte-derived factor Wdr82 overexpression and/or knockdown, so as to assess the reprogramming efficiency. Meanwhile, the cellular metabolism was monitored and evaluated during the reprogramming process. The plurpotency of the generated iPSCs was confirmed via pluripotent gene expression detection, embryoid body differentiation and chimeric mouse experiment. RESULTS: Here, we show that the oocyte-derived factor Wdr82 promotes the efficiency of MEF reprogramming into iPSCs to a greater degree than the Yamanaka factors OSKM. The Wdr82-expressing iPSC line showed pluripotency to differentiate and transmit genetic material to chimeric offsprings. In contrast, the knocking down of Wdr82 can significantly reduce the efficiency of somatic cell reprogramming. We further demonstrate that the significant suppression of oxidative phosphorylation in mitochondria underlies the molecular mechanism by which Wdr82 promotes the efficiency of somatic cell reprogramming. Our study suggests a link between mitochondrial energy metabolism remodeling and cell fate transition or stem cell function maintenance, which might shed light on the embryonic development and stem cell biology.

Susceptibility of renal fibrosis in diabetes: Role of hypoxia inducible factor-1.

Diabetes may prevent kidney repair and sensitize the kidney to fibrosis or scar formation. To test this possibility, we examined renal fibrosis induced by unilateral ureteral obstruction (UUO) in diabetic mouse models. Indeed, UUO induced significantly more renal fibrosis in both Akita and STZ-induced diabetic mice than in nondiabetic mice. The diabetic mice also had more apoptosis and interstitial macrophage infiltration during UUO. In vitro, hypoxia induced higher expression of the fibrosis marker protein fibronectin in high glucose-conditioned renal tubular cells than in normal glucose cells. Mechanistically, hypoxia induced significantly more hypoxia-inducible factor-1 α (HIF-1 α) in high glucose cells than in normal glucose cells. Inhibition of HIF-1 attenuated the expression of fibronectin induced by hypoxia in high-glucose cells. Consistently, UUO induced significantly higher HIF-1α expression along with fibrosis in diabetic mice kidneys than in nondiabetic kidneys. The increased expression of fibrosis induced by UUO in diabetic mice was diminished in proximal tubule-HIF-1α-knockout mice. Together, these results indicate that diabetes sensitizes kidney tissues and cells to fibrogenesis probably by enhancing HIF-1 activation.

Lipopolysaccharide Pretreatment Prevents Medullary Vascular Congestion following Renal Ischemia by Limiting Early Reperfusion of the Medullary Circulation.

BACKGROUND: Vascular congestion of the renal medulla-trapped red blood cells in the medullary microvasculature-is a hallmark finding at autopsy in patients with ischemic acute tubular necrosis. Despite this, the pathogenesis of vascular congestion is not well defined. METHODS: In this study, to investigate the pathogenesis of vascular congestion and its role in promoting renal injury, we assessed renal vascular congestion and tubular injury after ischemia reperfusion in rats pretreated with low-dose LPS or saline (control). We used laser Doppler flowmetry to determine whether pretreatment with low-dose LPS prevented vascular congestion by altering renal hemodynamics during reperfusion. RESULTS: We found that vascular congestion originated during the ischemic period in the renal venous circulation. In control animals, the return of blood flow was followed by the development of congestion in the capillary plexus of the outer medulla and severe tubular injury early in reperfusion. Laser Doppler flowmetry indicated that blood flow returned rapidly to the medulla, several minutes before recovery of full cortical perfusion. In contrast, LPS pretreatment prevented both the formation of medullary congestion and its associated tubular injury. Laser Doppler flowmetry in LPS-pretreated rats suggested that limiting early reperfusion of the medulla facilitated this protective effect, because it allowed cortical perfusion to recover and clear congestion from the large cortical veins, which also drain the medulla. CONCLUSIONS: Blockage of the renal venous vessels and a mismatch in the timing of cortical and medullary reperfusion results in congestion of the outer medulla's capillary plexus and promotes early tubular injury after renal ischemia. These findings indicate that hemodynamics during reperfusion contribute to the renal medulla's susceptibility to ischemic injury.

TeCVP: A Time-Efficient Control Method for a Hexapod Wheel-Legged Robot Based on Velocity Planning.

Addressing the problem that control methods of wheel-legged robots for future Mars exploration missions are too complex, a time-efficient control method based on velocity planning for a hexapod wheel-legged robot is proposed in this paper, which is named time-efficient control based on velocity planning (TeCVP). When the foot end or wheel at knee comes into contact with the ground, the desired velocity of the foot end or knee is transformed according to the velocity transformation of the rigid body from the desired velocity of the torso which is obtained by the deviation of torso position and posture. Furthermore, the torques of joints can be obtained by impedance control. When suspended, the leg is regarded as a system consisting of a virtual spring and a virtual damper to realize control of legs in the swing phase. In addition, leg sequences of switching motion between wheeled configuration and legged configuration are planned. According to a complexity analysis, velocity planning control has lower time complexity and less times of multiplication and addition compared with virtual model control. In addition, simulations show that velocity planning control can realize stable periodic gait motion, wheel-leg switching motion and wheeled motion and the operation time of velocity planning control is about 33.89% less than that of virtual model control, which promises a great prospect for velocity planning control in future planetary exploration missions.

Theoretical and Experimental Investigations on High-Precision Micro-Low-Gravity Simulation Technology for Lunar Mobile Vehicle.

With the development of space technology, the functions of lunar vehicles are constantly enriched, and the structure is constantly complicated, which puts forward more stringent requirements for its ground micro-low-gravity simulation test technology. This paper puts forward a high-precision and high-dynamic landing buffer test method based on the principle of magnetic quasi-zero stiffness. Firstly, the micro-low-gravity simulation system for the lunar vehicle was designed. The dynamic model of the system and a position control method based on fuzzy PID parameter tuning were established. Then, the dynamic characteristics of the system were analyzed through joint simulation. At last, a prototype of the lunar vehicle's vertical constant force support system was built, and a micro-low-gravity landing buffer test was carried out. The results show that the simulation results were in good agreement with the test results. The sensitivity of the system was better than 0.1%, and the constant force deviation was 0.1% under landing impact conditions. The new method and idea are put forward to improve the micro-low-gravity simulation technology of lunar vehicles.

PHB3 Is Required for the Assembly and Activity of Mitochondrial ATP Synthase in Arabidopsis.

Mitochondrial ATP synthase is a multiprotein complex, which consists of a matrix-localized F1 domain (F1-ATPase) and an inner membrane-embedded Fo domain (Fo-ATPase). The assembly process of mitochondrial ATP synthase is complex and requires the function of many assembly factors. Although extensive studies on mitochondrial ATP synthase assembly have been conducted on yeast, much less study has been performed on plants. Here, we revealed the function of Arabidopsis prohibitin 3 (PHB3) in mitochondrial ATP synthase assembly by characterizing the phb3 mutant. The blue native PAGE (BN-PAGE) and in-gel activity staining assays showed that the activities of ATP synthase and F1-ATPase were significantly decreased in the phb3 mutant. The absence of PHB3 resulted in the accumulation of the Fo-ATPase and F1-ATPase intermediates, whereas the abundance of the Fo-ATPase subunit a was decreased in the ATP synthase monomer. Furthermore, we showed that PHB3 could interact with the F1-ATPase subunits ß and δ in the yeast two-hybrid system (Y2H) and luciferase complementation imaging (LCI) assay and with Fo-ATPase subunit c in the LCI assay. These results indicate that PHB3 acts as an assembly factor required for the assembly and activity of mitochondrial ATP synthase.

Persistent vascular congestion in male spontaneously hypertensive rats contributes to delayed recovery of renal function following renal ischemia perfusion compared with females.

Acute kidney injury (AKI) due to ischemia is a serious and frequent clinical complication with mortality rates as high as 80%. Vascular congestion in the renal outer medulla occurs early after ischemia reperfusion (IR) injury, and congestion has been linked to worsened outcomes following IR. There is evidence implicating both male sex and preexisting hypertension as risk factors for poor outcomes following IR. The present study tested the hypothesis that male spontaneously hypertensive rats (SHR) have greater vascular congestion and impaired renal recovery following renal IR vs. female SHR and normotensive male Sprague-Dawley rats (SD). Thirteen-week-old male and female SHR and SD were subjected to sham surgery or 30 min of warm bilateral ischemia followed by reperfusion. Rats were euthanized 24 h or 7 days post-IR. IR increased renal injury in all groups vs. sham controls at 24 h. At 7 days post-IR, injury remained elevated only in male SHR. Histological examination of SD and SHR kidneys 24 h post-IR showed vascular congestion in males and females. Vascular congestion was sustained only in male SHR 7 days post-IR. To assess the role of vascular congestion on impaired recovery following IR, additional male and female SHR were pretreated with heparin (200 U/kg) prior to IR. Heparin pretreatment reduced IR-induced vascular congestion and improved renal function in male SHR 7 days post-IR. Interestingly, preventing increases in blood pressure (BP) in male SHR did not alter sustained vascular congestion. Our data demonstrate that IR-induced vascular congestion is a major driving factor for impaired renal recovery in male SHR.

Protein Kinase C-δ Mediates Kidney Tubular Injury in Cold Storage-Associated Kidney Transplantation.

BACKGROUND: Kidney injury associated with cold storage is a determinant of delayed graft function and the long-term outcome of transplanted kidneys, but the underlying mechanism remains elusive. We previously reported a role of protein kinase C-δ (PKCδ) in renal tubular injury during cisplatin nephrotoxicity and albumin-associated kidney injury, but whether PKCδ is involved in ischemic or transplantation-associated kidney injury is unknown. METHODS: To investigate PKCδ's potential role in injury during cold storage-associated transplantation, we incubated rat kidney proximal tubule cells in University of Wisconsin (UW) solution at 4°C for cold storage, returning them to normal culture medium at 37°C for rewarming. We also stored kidneys from donor mice in cold UW solution for various durations, followed by transplantation into syngeneic recipient mice. RESULTS: We observed PKCδ activation in both in vitro and in vivo models of cold-storage rewarming or transplantation. In the mouse model, PKCδ was activated and accumulated in mitochondria, where it mediated phosphorylation of a mitochondrial fission protein, dynamin-related protein 1 (Drp1), at serine 616. Drp1 activation resulted in mitochondrial fission or fragmentation, accompanied by mitochondrial damage and tubular cell death. Deficiency of PKCδ in donor kidney ameliorated Drp1 phosphorylation, mitochondrial damage, tubular cell death, and kidney injury during cold storage-associated transplantation. PKCδ deficiency also improved the repair and function of the renal graft as a life-supporting kidney. An inhibitor of PKCδ, δV1-1, protected kidneys against cold storage-associated transplantation injury. CONCLUSIONS: These results indicate that PKCδ is a key mediator of mitochondrial damage and renal tubular injury in cold storage-associated transplantation and may be an effective therapeutic target for improving renal transplant outcomes.

Canagliflozin reduces cisplatin uptake and activates Akt to protect against cisplatin-induced nephrotoxicity.

Cisplatin is a widely used chemotherapy drug with notorious nephrotoxicity. Na+-glucose cotransporter 2 inhibitors are a class of novel antidiabetic agents that may have other effects in the kidneys besides blood glucose control. In the present study, we demonstrated that canagliflozin significantly attenuates cisplatin-induced nephropathy in C57BL/6 mice and suppresses cisplatin induced renal proximal tubular cell apoptosis in vitro. The protective effect of canagliflozin was associated with inhibition of p53, p38 and JNK activation. Mechanistically, canagliflozin partially reduced cisplatin uptake by kidney tissues in mice and renal tubular cells in culture. In addition, canagliflozin enhanced the activation of Akt and inhibited the mitochondrial pathway of apoptosis during cisplatin treatment. The protective effect of canagliflozin was diminished by the phosphatidylinositol 3-kinase/Akt inhibitor LY294002. Notably, canagliflozin did not affect the chemotherapeutic efficacy of cisplatin in A549 and HCT116 cancer cell lines. These results suggest a new application of canagliflozin for renoprotection in cisplatin chemotherapy. Canagliflozin may protect kidneys by reducing cisplatin uptake and activating cell survival pathways.

Ultrasound measurement of change in kidney volume is a sensitive indicator of severity of renal parenchymal injury.

Noninvasive determination of the severity of parenchymal injury in acute kidney injury remains challenging. Edema is an early pathological process following injury, which may correlate with changes in kidney volume. The goal of the present study was to test the hypothesis that "increases in kidney volume measured in vivo using ultrasound correlate with the degree of renal parenchymal injury." Ischemia-reperfusion (IR) of varying length was used to produce graded tissue injury. We first determined 1) whether regional kidney volume in rats varied with the severity (0, 15, 30, and 45 min) of warm bilateral IR and 2) whether this correlated with tubular injury score. We then determined whether these changes could be measured in vivo using three-dimensional ultrasound. Finally, we evaluated cumulative changes in kidney volume up to 14 days post-IR in rats to determine whether changes in renal volume were predictive of latent tubular injury following recovery of filtration. Experiments concluded that noninvasive ultrasound measurements of change in kidney volume over 2 wk are predictive of tubular injury following IR even in animals in which plasma creatinine was not elevated. We conclude that ultrasound measurements of volume are a sensitive, noninvasive marker of tissue injury in rats and that the use of three-dimensional ultrasound measurements may provide useful information regarding the timing, severity, and recovery from renal tissue injury in experimental studies.

Novel strategy for septic acute kidney injury rescue: maintenance of the tubular integrity.

Fluid resuscitation for oliguria rescue in septic acute kidney injury (AKI) has limited success. By examination of the proximal tubular integrity, Nakano et al. identified paracellular renal filtrate leakage in proximal tubules after lipopolysaccharide induced tight junction disruption to contribute to oliguria. Suppression of lipopolysaccharide injury to proximal tubules by Toll-like receptor 4 knockout significantly ameliorated the oliguria and renal function loss in septic AKI. This commentary discusses the new therapeutic strategy for septic AKI rescue by proximal tubular integrity protection and the potential impact of tight junction injury in all AKI conditions.

Glycolysis inhibitors suppress renal interstitial fibrosis via divergent effects on fibroblasts and tubular cells.

Renal interstitial fibrosis is a common pathological feature of chronic kidney disease that may involve changes of metabolism in kidney cells. In the present study, we first showed that blockade of glycolysis with either dichloroacetate (DCA) or shikonin to target different glycolytic enzymes reduced renal fibrosis in a mouse model of unilateral ureteral obstruction (UUO). Both inhibitors evidently suppressed the induction of fibronectin and collagen type I in obstructed kidneys, with DCA also showing inhibitory effects on collagen type IV and α-smooth muscle actin (α-SMA). Histological examination also confirmed less collagen deposition in DCA-treated kidneys. Both DCA and shikonin significantly inhibited renal tubular apoptosis but not interstitial apoptosis in UUO. Macrophage infiltration after UUO injury was also suppressed. Shikonin, but not DCA, caused obvious animal weight loss during UUO. To determine whether shikonin and DCA worked on tubular cells and/or fibroblasts, we tested their effects on cultured renal proximal tubular BUMPT cells and renal NRK-49F fibroblasts during hypoxia or transforming growth factor-ß1 treatment. Although both inhibitors reduced fibronectin and α-SMA production in NRK-49F cells during hypoxia or transforming growth factor-ß1 treatment, they did not suppress fibronectin and α-SMA expression in BUMPT cells. Altogether, these results demonstrate the inhibitory effect of glycolysis inhibitors on renal interstitial fibrosis. In this regard, DCA is more potent for fibrosis inhibition and less toxic to animals than shikonin.

Establishment of an HPLC-based method to identify key proteases of proteins in vitro.

Given that the biological functions of proteins may decrease or even be lost due to degradation by proteases, it is of great significance to identify potential proteases that degrade protein drugs during systemic circulation. In this work, we describe a method based on high-performance liquid chromatography (HPLC) to identify key proteases that degrade therapeutic proteins in blood, including endopeptidases and exopeptidases. Here, the degradation of proteins was detected by competition with standard substrates of proteases and is shown as the relative residue rate. Four protein drugs were subjected to this method, and the results suggested that growth hormone was degraded by aminopeptidase N and kallikrein-related peptidase 5, pertuzumab was hardly degraded by the proteases, factor VII was degraded by carboxypeptidase B, neprilysin, dipeptidyl peptidase-4 and peptidyl dipeptidase A, and fibrinogen was degraded by carboxypeptidase B and kallikrein-related peptidase 5, findings consistent with the literature. The results were confirmed by microscale thermophoresis; additionally, activity detection in vitro substantiated that the degradation of factor VII decreased its activity. We demonstrate that this method can be used to identify key proteases of proteins with high accuracy, precision and durability.

The Arabidopsis nucleoporin NUP1 is essential for megasporogenesis and early stages of pollen development.

KEY MESSAGE: Loss-of-function of nucleoporin NUP1 in Arabidopsis causes defect in both male and female gametogenesis. Its ovules are arrested during meiosis, and its pollen grains are aborted at mitosis I. Nuclear pore complex (NPC) plays crucial roles in nucleocytoplasmic trafficking of proteins and RNAs. The NPC contains approximately 30 different proteins termed nucleoporins (NUPs). So far, only a few of plant NUPs have been characterized. The Arabidopsis NUP1 was identified as an ortholog of the yeast NUP1 and animal NUP153. Loss-of-function of NUP1 in Arabidopsis caused fertility defect; however, the molecular mechanism of this defect remains unknown. Here, we found that both male and female gametogenesis of the nup1 mutants were defective. nup1 ovules were arrested from the meiosis stage onward; only approximately 6.7% and 3% ovules of the nup1-1 and nup1-4 mutants developed up to the FG7 stage, respectively. Pollen development of the nup1 mutants was arrested during the first mitotic division. In addition, enlarged pollen grains with increased DNA content were observed in the nup1 mutant. RNA-sequencing showed that expression levels of genes involved in pollen development or regulation of cell size were reduced dramatically in nup1 compared with wild type. These results suggest that NUP1 plays an important role in gametogenesis.

MicroRNA-375 Is Induced in Cisplatin Nephrotoxicity to Repress Hepatocyte Nuclear Factor 1-ß.

Nephrotoxicity is a major adverse effect of cisplatin-mediated chemotherapy in cancer patients. The pathogenesis of cisplatin-induced nephrotoxicity remains largely unclear, making it difficult to design effective renoprotective approaches. Here, we have examined the role of microRNAs (miRNAs) in cisplatin-induced nephrotoxicity. We show that cisplatin nephrotoxicity was not affected by overall depletion of both beneficial and detrimental miRNAs from kidney proximal tubular cells in mice in which the miRNA-generating enzyme Dicer had been conditionally knocked out. To identify miRNAs involved in cisplatin nephrotoxicity, we used microarray analysis to profile miRNA expression and identified 47 up-regulated microRNAs and 20 down-regulated microRNAs in kidney cortical tissues. One up-regulated miRNA was miR-375, whose expression was also induced in cisplatin-treated renal tubular cells. Interestingly, inhibition of miR-375 decreased cisplatin-induced apoptosis, suggesting that miR-375 is a cell-damaging or pro-apoptotic agent. Blockade of P53 or NF-κB attenuated cisplatin-induced miR-375 expression, supporting a role of P53 and NF-κB in miR-375 induction. We also identified hepatocyte nuclear factor 1 homeobox B (HNF-1ß) as a key downstream target of miR-375. Of note, we further demonstrated that HNF-1ß protected renal cells against cisplatin-induced apoptosis. Together, these results suggest that upon cisplatin exposure, P53 and NF-κB collaboratively induce miR-375 expression, which, in turn, represses HNF-1ß activity, resulting in renal tubular cell apoptosis and nephrotoxicity.

Dicer deficiency in proximal tubules exacerbates renal injury and tubulointerstitial fibrosis and upregulates Smad2/3.

Renal fibrosis is a common pathological feature in chronic kidney disease (CKD), including diabetic kidney disease (DKD) and obstructive nephropathy. Multiple microRNAs have been implicated in the pathogenesis of both DKD and obstructive nephropathy, although the overall role of microRNAs in tubular injury and renal fibrosis in CKD is unclear. Dicer (a key RNase III enzyme for microRNA biogenesis) was specifically ablated from kidney proximal tubules in mice via the Cre-lox system to deplete micoRNAs. Proximal tubular Dicer knockout (PT- Dicer KO) mice and wild-type (WT) littermates were subjected to streptozotocin (STZ) treatment to induce DKD or unilateral ureteral obstruction (UUO) to induce obstructive nephropathy. Renal hypertrophy, renal tubular apoptosis, kidney inflammation, and tubulointerstitial fibrosis were examined. Compared with WT mice, PT- Dicer KO mice showed more severe tubular injury and renal inflammation following STZ treatment. These mice also developed higher levels of tubolointerstitial fibrosis. Meanwhile, PT- Dicer KO mice had a significantly higher Smad2/3 expression in kidneys than WT mice (at 6 mo of age) in both control and STZ-treated mice. Similarly, UUO induced more severe renal injury, inflammation, and interstitial fibrosis in PT- Dicer KO mice than WT. Although we did not detect obvious Smad2/3 expression in sham-operated mice (2-3 mo old), significantly more Smad2/3 was induced in obstructed PT- Dicer KO kidneys. These results supported a protective role of Dicer-dependent microRNA synthesis in renal injury and fibrosis development in CKD, specifically in DKD and obstructive nephropathy. Depletion of Dicer and microRNAs may upregulate Smad2/3-related signaling pathway to enhance the progression of CKD.