Proximal tubular FHL2, a novel downstream target of hypoxia inducible factor 1, is a protector against ischemic acute kidney injury.

Four-and-a-half LIM domains protein 2 (FHL2) is an adaptor protein that may interact with hypoxia inducible factor 1α (HIF-1α) or ß-catenin, two pivotal protective signaling in acute kidney injury (AKI). However, little is known about the regulation and function of FHL2 during AKI. We found that FHL2 was induced in renal tubular cells in patients with acute tubular necrosis and mice model of ischemia-reperfusion injury (IRI). In cultured renal proximal tubular cells (PTCs), hypoxia induced FHL2 expression and promoted the binding of HIF-1 to FHL2 promoter. Compared with control littermates, mice with PTC-specific deletion of FHL2 gene displayed worse renal function, more severe morphologic lesion, more tubular cell death and less cell proliferation, accompanying by downregulation of AQP1 and Na, K-ATPase after IRI. Consistently, loss of FHL2 in PTCs restricted activation of HIF-1 and ß-catenin signaling simultaneously, leading to attenuation of glycolysis, upregulation of apoptosis-related proteins and downregulation of proliferation-related proteins during IRI. In vitro, knockdown of FHL2 suppressed hypoxia-induced activation of HIF-1α and ß-catenin signaling pathways. Overexpression of FHL2 induced physical interactions between FHL2 and HIF-1α, ß-catenin, GSK-3ß or p300, and the combination of these interactions favored the stabilization and nuclear translocation of HIF-1α and ß-catenin, enhancing their mediated gene transcription. Collectively, these findings identify FHL2 as a direct downstream target gene of HIF-1 signaling and demonstrate that FHL2 could play a critical role in protecting against ischemic AKI by promoting the activation of HIF-1 and ß-catenin signaling through the interactions with its multiple protein partners.

External Validation of the International Prognosis Prediction Model of IgA Nephropathy.

BACKGROUND: The International IgA Nephropathy (IgAN) Network developed and validated two prognostic prediction models for IgAN, one incorporating a race parameter. These models could anticipate the risk of a 50% reduction in estimated glomerular filtration rate (eGFR) or progression to end-stage renal disease (ESRD) subsequent to an IgAN diagnosis via renal biopsy. This investigation aimed to validate the International IgA Nephropathy Prediction Tool (IIgANPT) within a contemporary Chinese cohort. METHODS: Within this study,185 patients diagnosed with IgAN via renal biopsy at the Center for Kidney Disease, Second Affiliated Hospital of Nanjing Medical University, between January 2012 and December 2021, were encompassed. Each patient's risk of progression was assessed utilizing the IIgANPT formula. The primary outcome, a 50% decline in eGFR or progression to ESRD, was examined. Two predictive models, one inclusive and the other exclusive of a race parameter, underwent evaluation via receiver-operating characteristic (ROC) curves, subgroup survival analyses, calibration plots, and decision curve analyses. RESULTS: The median follow-up duration within our cohort spanned 5.1 years, during which 18 patients encountered the primary outcome. The subgroup survival curves exhibited distinct separations, and the comparison of clinical and histological characteristics among the risk subgroups revealed significant differences. Both models demonstrated outstanding discrimination, evidenced by the areas under the ROC curve at five years: 0.882 and 0.878. Whether incorporating the race parameter or not, both prediction models exhibited acceptable calibration. Decision curve analysis affirmed the favorable clinical utility of both models. CONCLUSIONS: Both prognostic risk evaluation models for IgAN exhibited remarkable discrimination, sound calibration, and acceptable clinical utility.

Increased thoracic fluid content is associated with higher risk for pneumonia in patients undergoing maintenance hemodialysis.

BACKGROUND: Pneumonia is the most common infectious disease in patients undergoing maintenance hemodialysis (MHD). The aim of this study is to determine the possible predictive value of thoracic fluid content (TFC) for pneumonia in this population. METHOD: Clinical data were recorded for 1412 MHD patients who were hospitalized for certain comorbidities or complications. Each patient underwent an impedance cardiography (ICG) examination before next dialysis session after admission. Patients were divided into Having-, Will-have-, and Non-pneumonia groups based on whether they had pneumonia at the time of ICG examination after the admission and within five months after the examination. Hemodynamic parameters and other clinical data were compared and analyzed. RESULTS: Patients who were going to develop pneumonia were older, and had a higher proportion of diabetes, poorer nutritional status, a higher level of inflammatory, poorer cardiac function, and more fluid volume load than those who did not develop pneumonia. Multivariate binary logistic analysis revealed that for each 1/KΩ increase in TFC and 1 increase in neutrophil-to-lymphocyte ratio (NLR), the risk of the development of pneumonia increased by 3.1% (p ˂ 0.01) and 7.2% (p = 0.035), respectively, whereas for each 1 g/L increase in hemoglobin and 1 g/L increase in serum albumin, the risk of the development of pneumonia decreased by 1.3% (p = 0.034) and 5% (p = 0.048), respectively. CONCLUSIONS: TFC, NLR, hemoglobin, and serum albumin were independent risk factors for the development of pneumonia in MHD patients. Given the advantages of ICG, TFC can be used clinically as a helpful predictor of pneumonia in MHD patients.

Tuberous sclerosis 1 (Tsc1) mediated mTORC1 activation promotes glycolysis in tubular epithelial cells in kidney fibrosis.

Energy reprogramming to glycolysis is closely associated with the development of chronic kidney disease. As an important negative regulatory factor of the mammalian target of rapamycin complex 1 (mTORC1) signal, tuberous sclerosis complex 1 (Tsc1) is also a key regulatory point of glycolysis. Here, we investigated whether Tsc1 could mediate the progression of kidney interstitial fibrosis by regulating glycolysis in proximal tubular epithelial cells. We induced mTORC1 signal activation in tubular epithelial cells in kidneys with fibrosis via unilateral ureteral occlusion. This resulted in increased tubular epithelial cell proliferation and glycolytic enzyme upregulation. Prior incubation with rapamycin inhibited mTORC1 activation and abolished the enhanced glycolysis and tubular epithelial cell proliferation. Furthermore, knockdown of Tsc1 expression promoted glycolysis in the rat kidney epithelial cell line NRK-52E. Specific deletion of Tsc1 in the proximal tubules of mice resulted in enlarged kidneys characterized by a high proportion of proliferative tubular epithelial cells, dilated tubules with cyst formation, and a large area of interstitial fibrosis in conjunction with elevated glycolysis. Treatment of the mice with the glycolysis inhibitor 2-deoxyglucose notably ameliorated tubular epithelial cell proliferation, cystogenesis, and kidney fibrosis. Thus, our findings suggest that Tsc1-associated mTORC1 signaling mediates the progression of kidney interstitial fibrosis by regulating glycolysis in proximal tubular epithelial cells.

Yap/Taz mediates mTORC2-stimulated fibroblast activation and kidney fibrosis.

Our previously published study demonstrated that mammalian target of rapamycin complex 2 (mTORC2) signaling mediates TGFß1-induced fibroblast activation. However, the underlying mechanisms for mTORC2 in stimulating fibroblast activation remain poorly understood. Here, we found that TGFß1 could stimulate mTORC2 and Yap/Taz activation in NRK-49F cells. Blocking either mTORC2 or Yap/Taz signaling diminished TGFß1-induced fibroblast activation. In addition, blockade of mTORC2 could down-regulate the expression of Yap/Taz, connective tissue growth factor (CTGF), and ankyrin repeat domain 1 (ANKRD1). Overexpression of constitutively active Taz (Taz-S89A) could restore fibroblast activation suppressed by PP242, an mTOR kinase inhibitor in NRK-49F cells. In mouse kidneys with unilateral ureter obstructive (UUO) nephropathy, both mTORC2 and Yap/Taz were activated in the interstitial myofibroblasts. Ablation of Rictor in fibroblasts/pericytes or blockade of mTOR signaling with PP242 attenuated Yap/Taz activation and UUO nephropathy in mice. Together, this study uncovers that targeting mTORC2 retards fibroblast activation and kidney fibrosis through suppressing Yap/Taz activation.

Protein kinase Cα drives fibroblast activation and kidney fibrosis by stimulating autophagic flux.

Kidney fibrosis is a histological hallmark of chronic kidney disease and arises in large part through extracellular matrix deposition by activated fibroblasts. The signaling protein complex mTOR complex 2 (mTORC2) plays a critical role in fibroblast activation and kidney fibrosis. Protein kinase Cα (PKCα) is one of the major sub-pathways of mTORC2, but its role in fibroblast activation and kidney fibrosis remains to be determined. Here, we found that transforming growth factor ß1 (TGFß1) activates PKCα signaling in cultured NRK-49F cells in a time-dependent manner. Blocking PKCα signaling with the chemical inhibitor Go6976 or by transfection with PKCα siRNA largely reduced expression of the autophagy-associated protein lysosomal-associated membrane protein 2 (LAMP2) and also inhibited autophagosome-lysosome fusion and autophagic flux in the cells. Similarly to chloroquine, Go6976 treatment and PKCα siRNA transfection also markedly inhibited TGFß1-induced fibroblast activation. In murine fibrotic kidneys with unilateral ureteral obstruction (UUO) nephropathy, PKCα signaling is activated in the interstitial myofibroblasts. Go6976 administration largely blocked autophagic flux in fibroblasts in the fibrotic kidneys and attenuated the UUO nephropathy. Together, our findings suggest that blocking PKCα activity may retard autophagic flux and thereby prevent fibroblast activation and kidney fibrosis.

The signaling protein Wnt5a promotes TGFß1-mediated macrophage polarization and kidney fibrosis by inducing the transcriptional regulators Yap/Taz.

M2 macrophage polarization is known to underlie kidney fibrosis. We previously reported that most of the members of the Wnt family of signaling proteins are induced in fibrotic kidneys. Dysregulation of the signaling protein Wnt5a is associated with fibrosis, but little is known about the role of Wnt5a in regulating M2 macrophage activation that results in kidney fibrosis. Here, using murine Raw 264.7 cells and bone marrow-derived macrophages, we found that Wnt5a enhanced transforming growth factor ß1 (TGFß1)-induced macrophage M2 polarization as well as expression of the transcriptional regulators Yes-associated protein (Yap)/transcriptional coactivator with PDZ-binding motif (Taz). Verteporfin blockade of Yap/Taz inhibited both Wnt5a- and TGFß1-induced macrophage M2 polarization. In mouse models of kidney fibrosis, shRNA-mediated knockdown of Wnt5a expression diminished kidney fibrosis, macrophage Yap/Taz expression, and M2 polarization. Moreover, genetic ablation of Taz in macrophages attenuated kidney fibrosis and macrophage M2 polarization in mice. Collectively, these results indicate that Wnt5a promotes kidney fibrosis by stimulating Yap/Taz-mediated macrophage M2 polarization.

Digital microvascular reactivity does not decline with impaired renal function in chronic kidney disease.

BACKGROUND: The reactive hyperemia index (RHI), measured by peripheral arterial tonometry (PAT), is a novel measurement of endothelial function and has been proven to be valuable in cardiovascular risk stratification in several populations. The current study aims to explore its relation to renal function and its association with traditional cardiovascular risk factors in patients with chronic kidney disease (CKD). METHODS: Subjects with non-dialysis dependent CKD were recruited and 252 of them had a successful PAT test. In addition to general demographic and medical information, carotid-femoral pulse wave velocity (cfPWV), carotid-radial pulse wave velocity (crPWV) and augmentation index (AIx) were recorded. RESULTS: The mean age of the study population was 57.7 (±14.7) years and 155 (61.5%) were males. The average RHI was 1.92 (±14.7) with no difference noted between males and females. There was no statistically significant correlation between RHI and eGFR (r = - 0.107, p = 0.089) or urine protein-to-creatinine ratio (r = 0.036, p = 0.570). With adjustment for age and sex, RHI was associated with systolic blood pressure (BP) (ß = 0.006, p = 0.001), diastolic BP (ß = 0.008, p = 0.010), heart rate (ß = - 0.007, p = 0.015) crPWV (ß = 0.037, p = 0.022) and AIx (ß = 0.006, p = 0.001), but not with cfPWV or any other conventional risk factors analyzed. Systolic BP remained the only predictor for RHI in the stepwise regression analysis. CONCLUSIONS: RHI did not decline with reduced renal function in CKD patients and had a modest association with traditional cardiovascular risk factors. Further studies are warranted to determine if RHI could predict cardiovascular outcome in CKD patients.

Wnt/ß-Catenin-Promoted Macrophage Alternative Activation Contributes to Kidney Fibrosis.

The Wnt/ß-catenin pathway is crucial in normal development and throughout life, but aberrant activation of this pathway has been linked to kidney fibrosis, although the mechanisms involved remain incompletely determined. Here, we investigated the role of Wnt/ß-catenin in regulating macrophage activation and the contribution thereof to kidney fibrosis. Treatment of macrophages with Wnt3a exacerbated IL-4- or TGFß1-induced macrophage alternative (M2) polarization and the phosphorylation and nuclear translocation of STAT3 in vitro Conversely, inhibition of Wnt/ß-catenin signaling prevented these IL-4- or TGFß1-induced processes. In a mouse model, induced deletion of ß-catenin in macrophages attenuated the fibrosis, macrophage accumulation, and M2 polarization observed in the kidneys of wild-type littermates after unilateral ureter obstruction. This study shows that activation of Wnt/ß-catenin signaling promotes kidney fibrosis by stimulating macrophage M2 polarization.

FHL2 promotes tubular epithelial-to-mesenchymal transition through modulating ß-catenin signalling.

ß-Catenin signalling plays an important role in regulating tubular epithelial-to-mesenchymal transition (EMT), an indispensable programme for driving renal fibrosis. As an adapter protein, four and a half LIM domain protein 2 (FHL2) acts as a coregulator of ß-catenin in several other cell types. To determine whether FHL2 affects ß-catenin signalling and thus is involved in tubular EMT, we examined its expression and function in the process of TGF-ß1-induced EMT. FHL2 mRNA and protein were induced by TGF-ß1 in rat tubular epithelial cells (NRK-52E), an effect that intracellular Smad signalling was required. Ectopic expression of FHL2 inhibited E-cadherin and enhanced α-smooth muscle actin (α-SMA) and fibronectin expression, whereas knockdown of FHL2 partially restored E-cadherin and reduced α-SMA and fibronectin induction stimulated by TGF-ß1. Overexpression of FHL2 increased ß-catenin dephosphorylation (Ser37/Thr41), nuclear translocation and ß-catenin-mediated transcription and up-regulated expression of ß-catenin target, EMT-related genes, such as Snail, Twist, vimentin, plasminogen activator inhibitor-1 and matrix metalloproteinase-7. Conversely, knockdown of FHL2 increased ß-catenin phosphorylation (Ser33/37/Thr41), decreased its nuclear translocation and inhibited ß-catenin-mediated transcription and target genes expression. TGF-ß1 induced a FHL2/ß-catenin interaction in NRK-52E cells, especially in the nuclei. In a mouse model of obstructive nephropathy, FHL2 mRNA and protein were induced in a time-dependent fashion, and the extent and pattern of renal ß-catenin activation were positively correlated with FHL2 induction. Collectively, this study suggests that FHL2, via modulating ß-catenin signalling, may implicate in regulation of TGF-ß1-mediated tubular EMT and could be a potential therapeutic target for fibrotic kidney disease.

Rictor/mammalian target of rapamycin complex 2 promotes macrophage activation and kidney fibrosis.

Mammalian target of rapamycin (mTOR) signalling controls many essential cellular functions. However, the role of Rictor/mTOR complex 2 (mTORC2) in regulating macrophage activation and kidney fibrosis remains largely unknown. We report here that Rictor/mTORC2 was activated in macrophages from the fibrotic kidneys of mice. Ablation of Rictor in macrophages reduced kidney fibrosis, inflammatory cell accumulation, macrophage proliferation and polarization after unilateral ureter obstruction or ischaemia/reperfusion injury. In bone marrow-derived macrophages (BMMs), deletion of Rictor or blockade of protein kinase Cα inhibited cell migration. Additionally, deletion of Rictor or blockade of Akt abolished interleukin-4-stimulated or transforming growth factor (TGF)-ß1-stimulated macrophage M2 polarization. Furthermore, deletion of Rictor downregulated TGF-ß1-stimulated upregulation of multiple profibrotic cytokines, including platelet-derived growth factor, vascular endothelial growth factor and connective tissue growth factor, in BMMs. Conditioned medium from TGF-ß1-pretreated Rictor-/- macrophages stimulated fibroblast activation less efficiently than that from TGF-ß1-pretreated Rictor+/+ macrophages. These results demonstrate that Rictor/mTORC2 signalling can promote macrophage activation and kidney fibrosis. Targeting this signalling pathway in macrophages may shine light on ways to protect against kidney fibrosis in patients with chronic kidney diseases. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

WNT/ß-catenin signaling promotes VSMCs to osteogenic transdifferentiation and calcification through directly modulating Runx2 gene expression.

Arterial medial calcification (AMC) is prevalent in patients with chronic kidney disease (CKD) and contributes to elevated risk of cardiovascular events and mortality. Vascular smooth muscle cells (VSMCs) to osteogenic transdifferentiation (VOT) in a high-phosphate environment is involved in the pathogenesis of AMC in CKD. WNT/ß-catenin signaling is indicated to play a crucial role in osteogenesis via promoting Runx2 expression in osteoprogenitor cells, however, its role in Runx2 regulation and VOT remains incompletely clarified. In this study, Runx2 was induced and ß-catenin was activated by high-phosphate in VSMCs. Two forms of active ß-catenin, dephosphorylated on Ser37/Thr41 and phosphorylated on Ser675 sites, were upregulated by high-phosphate. Activation of ß-catenin, through ectopic expression of stabilized ß-catenin, inhibition of GSK-3ß, or WNT-3A protein, induced Runx2 expression, whereas blockade of WNT/ß-catenin signaling with Porcupine (PORCN) inhibitor or Dickkopf-1 (DKK1) protein inhibited Runx2 induction by high-phosphate. WNT-3A promoted osteocalcin expression and calcium deposition in VSMCs, whereas DKK1 ameliorated calcification of VSMCs induced by high-phosphate. Two functional T cell factor (TCF)/lymphoid enhancer-binding factor binding sites were identified in the promoter region of Runx2 gene in VSMCs, which interacted with TCF upon ß-catenin activation. Site-directed mutation of each of them attenuated Runx2 response to ß-catenin, and deletion or destruction of both of them completely abolished this responsiveness. In the aortic tunica media of rats with chronic renal failure, followed by AMC, Runx2 and ß-catenin was induced, and the Runx2 mRNA level was positively associated with the abundance of phosphorylated ß-catenin (Ser675). Collectively, our study suggested that high-phosphate may activate WNT/ß-catenin signaling through different pathways, and the activated WNT/ß-catenin signaling, through direct downstream target Runx2, could play an important role in promoting VOT and AMC.

Rehabilitation Treatment and Progress of Traumatic Brain Injury Dysfunction.

Traumatic brain injury (TBI) is a major cause of chronic disability. Worldwide, it is the leading cause of disability in the under 40s. Behavioral problems, mood, cognition, particularly memory, attention, and executive function are commonly impaired by TBI. Spending to assist, TBI survivors with disabilities are estimated to be costly per year. Such impaired functional outcomes following TBI can be improved via various rehabilitative approaches. The objective of the present paper is to review the current rehabilitation treatment of traumatic brain injury in adults.

Mutual antagonism of Wilms' tumor 1 and ß-catenin dictates podocyte health and disease.

Activation of ß-catenin, the intracellular mediator of canonical Wnt signaling, has a critical role in mediating podocyte injury and proteinuria. However, the underlying mechanisms remain poorly understood. Here, we show that ß-catenin triggers ubiquitin-mediated protein degradation of Wilms' tumor 1 (WT1) and functionally antagonizes its action. In mice injected with adriamycin, WT1 protein was progressively lost in glomerular podocytes at 1, 3, and 5 weeks after injection. Notably, loss of WT1 apparently did not result from podocyte depletion but was closely associated with upregulation of ß-catenin. This change in WT1/ß-catenin ratio was accompanied by loss of podocyte-specific nephrin, podocalyxin, and synaptopodin and acquisition of mesenchymal markers Snail1, α-smooth muscle actin, and fibroblast-specific protein 1. In vitro, overexpression of ß-catenin induced WT1 protein degradation through the ubiquitin proteasomal pathway, which was blocked by MG-132. WT1 and ß-catenin also competed for binding to common transcriptional coactivator CREB-binding protein and mutually repressed the expression of their respective target genes. In glomerular miniorgan culture, activation of ß-catenin by Wnt3a repressed WT1 and its target gene expression. In vivo, blockade of Wnt/ß-catenin signaling by endogenous antagonist Klotho induced WT1 and restored podocyte integrity in adriamycin nephropathy. These results show that ß-catenin specifically targets WT1 for ubiquitin-mediated degradation, leading to podocyte dedifferentiation and mesenchymal transition. Our data also suggest that WT1 and ß-catenin have opposing roles in podocyte biology, and that the ratio of their expression levels dictates the state of podocyte health and disease in vivo.

Rictor/mTORC2 signaling mediates TGFß1-induced fibroblast activation and kidney fibrosis.

The mammalian target of rapamycin (mTOR) was recently identified in two structurally distinct multiprotein complexes: mTORC1 and mTORC2. Previously, we found that Rictor/mTORC2 protects against cisplatin-induced acute kidney injury, but the role and mechanisms for Rictor/mTORC2 in TGFß1-induced fibroblast activation and kidney fibrosis remains unknown. To study this, we initially treated NRK-49F cells with TGFß1 and found that TGFß1 could activate Rictor/mTORC2 signaling in cultured cells. Blocking Rictor/mTORC2 signaling with Rictor or Akt1 small interfering RNAs markedly inhibited TGFß1-induced fibronection and α-smooth muscle actin expression. Ensuing western blotting or immunostaining results showed that Rictor/mTORC2 signaling was activated in kidney interstitial myofibroblasts from mice with unilateral ureteral obstruction. Next, a mouse model with fibroblast-specific deletion of Rictor was generated. These knockout mice were normal at birth and had no obvious kidney dysfunction or kidney morphological abnormality within 2 months of birth. Compared with control littermates, the kidneys of Rictor knockout mice developed less interstitial extracellular matrix deposition and inflammatory cell infiltration at 1 or 2 weeks after ureteral obstruction. Thus our study suggests that Rictor/mTORC2 signaling activation mediates TGFß1-induced fibroblast activation and contributes to the development of kidney fibrosis. This may provide a therapeutic target for chronic kidney diseases.

Cyclophilin A/Cluster of Differentiation 147 Interactions Participate in Early Brain Injury After Subarachnoid Hemorrhage in Rats.

OBJECTIVES: Cyclophilin A has been found to be involved in many inflammatory diseases via its receptor, cluster of differentiation 147 (CD147). This study was designed to estimate the potential role of cyclophilin A/CD147 in subarachnoid hemorrhage-induced early brain injury. DESIGN: Controlled in vivo laboratory study. SETTING: Animal research laboratory. SUBJECTS: Two hundred ninety adult male Sprague-Dawley rats weighing 300-350 g. INTERVENTIONS: A prechiasmatic cistern single-injection model was used to produce experimental subarachnoid hemorrhage in Sprague-Dawley rats. The expressions of cyclophilin A and CD147, the interaction between cyclophilin A and CD147, and the secretion of cyclophilin A were assessed using immunofluorescence staining, Western blot analysis, and coimmunoprecipitation analysis. Down-regulation of cyclophilin A expression by small interfering RNA was performed, and recombinant human cyclophilin A and monoclonal antibody of CD147 were exploited to study the role of cyclophilin A/CD147 in subarachnoid hemorrhage-induced early brain injury. MEASUREMENTS AND MAIN RESULTS: The expressions of cyclophilin A and CD147 in neurons were higher than that of the sham group and peaked at 24 hours after subarachnoid hemorrhage. Compared with sham group, subarachnoid hemorrhage was found to increase the secretion of cyclophilin A and the interaction between cyclophilin A and CD147. Cyclophilin A small interfering RNA and anti-CD147 treatments were found to ameliorate subarachnoid hemorrhage-induced early brain injury, including cortical apoptosis and necrosis, brain edema, blood-brain barrier damage, and neurobehavioral deficits. Cyclophilin A small interfering RNA and anti-CD147 treatments also decreased the phosphorylation of extracellular signal-regulated protein kinase 1/2, the protein levels of p53 and caspase-3, and the level of active nuclear factor-κB. Finally, recombinant human cyclophilin A treatment resulted in an opposite effect, which was inhibited by anti-CD147 treatment. CONCLUSIONS: Cyclophilin A/CD147 interactions may participate in subarachnoid hemorrhage-induced early brain injury via increasing neuronal apoptosis pathway, at least partly through the ERK1/2-nuclear factor-κB pathway. Cyclophilin A/CD147 may be a suitable therapeutic target for subarachnoid hemorrhage.

Autophagy inhibition induces podocyte apoptosis by activating the pro-apoptotic pathway of endoplasmic reticulum stress.

Podocyte apoptosis is a major factor inducing podocyte depletion that predicts the progressive course of glomerulosclerosis. However, the molecular mechanisms underlying podocyte apoptosis are still not well understood. Autophagy is a lysosomal degradation system involving the degradation and recycling of obsolete, damaged, or harmful cytoplasmic materials and organelles. Recent advances in the understanding of the molecular processes contributing to autophagy have provided insight into the relationship between autophagy and apoptosis. However, their cross-talk remains largely obscure until now. Here, we found that podocytes both in vivo and in vitro always exhibited high basal levels of autophagy, whereas autophagy inhibition could induce podocyte apoptosis, suggesting the pro-survival role of autophagy in podocytes. Besides, we found that autophagy inhibition by 3-methyladenine (3-MA) could induce the activation of endoplasmic reticulum stress even without any external stimulations, whereas knockdown of CHOP could effectively improve podocyte apoptosis and down-regulated expression of slit-diaphragm proteins induced by autophagy inhibition. Collectively, this study demonstrated that autophagy might act as a crucial regulatory mechanism of apoptotic cell death by modulating the balance between the pro-survival pathway and the pro-apoptotic pathway of endoplasmic reticulum stress, which might provide a novel mechanistic insight into the interface between autophagy and apoptosis in the progression of podocyte injury.

miR-125b/Ets1 axis regulates transdifferentiation and calcification of vascular smooth muscle cells in a high-phosphate environment.

OBJECTIVES: Vascular calcification is highly prevalent in patients with chronic kidney disease (CKD) and contributes to increased risk of cardiovascular disease and mortality. Accumulated evidences suggested that vascular smooth muscle cells (VSMCs) to osteoblast-like cells transdifferentiation (VOT) plays a crucial role in promoting vascular calcification. MicroRNAs (miRNAs) are a novel class of small RNAs that negatively regulate gene expression via repression of the target mRNAs. In the present work, we sought to determine the role of miRNAs in VSMCs phenotypic transition and calcification induced by ß-glycerophosphoric acid. APPROACH AND RESULTS: Primary cultured rat aortic VSMCs were treated with ß-glycerophosphoric acid for different periods of time. In VSMCs, after ß-glycerophosphoric acid treatment, the expressions of cbf ß1, osteocalcin and osteopontin were significantly increased and SM-22ß expression was decreased. ALP activity was induced by ß-glycerophosphoric acid in a time or dose dependent manner. Calcium deposition was detected in VSMCs incubated with calcification media; then, miR-125b expression was detected by real-time RT PCR. miR-125b expression was significantly decreased in VSMCs after incubated with ß-glycerophosphoric acid. Overexpression of miR-125b could inhibit ß-glycerophosphoric acid-induced osteogenic markers expression and calcification of VSMCs whereas knockdown of miR-125b promoted the phenotypic transition of VSMCs and calcification. Moreover, miR-125b targeted Ets1 and regulated its protein expression in VSMCs. Downregulating Ets1 expression by its siRNA inhibited ß-glycerophosphoric acid-induced the VSMCs phenotypic transition and calcification. CONCLUSION: Our study suggests that down-regulation of miR-125b after ß-glycerophosphoric acid treatment facilitates VSMCs transdifferentiation and calcification through targeting Ets1.

Calmodulin-dependent protein kinase II/cAMP response element-binding protein/Wnt/ß-catenin signaling cascade regulates angiotensin II-induced podocyte injury and albuminuria.

Angiotensin II (Ang II) plays a pivotal role in promoting podocyte dysfunction and albuminuria, however, the underlying mechanisms have not been fully delineated. In this study, we found that Ang II induced Wnt1 expression and ß-catenin nuclear translocation in cultured mouse podocytes. Blocking Wnt signaling with Dickkopf-1 (Dkk1) or ß-catenin siRNA attenuated Ang II-induced podocyte injury. Ang II could also induce the phosphorylation of calmodulin-dependent protein kinase (CaMK) II and cAMP response element-binding protein (CREB) in cultured podocytes. Blockade of this pathway with CK59 or CREB siRNA could significantly inhibit Ang II-induced Wnt/ß-catenin signaling and podocyte injury. In in vivo studies, administration of Ang II promoted Wnt/ß-catenin signaling, aggregated podocyte damage, and albuminuria in mice. CK59 could remarkably ameliorate Ang II-induced podocyte injury and albuminuria. Furthermore, ectopic expression of exogenous Dkk1 also attenuated Ang II-induced podocytopathy in mice. Taken together, this study demonstrates that the CaMK II/CREB/Wnt/ß-catenin signaling cascade plays an important role in regulating Ang II-induced podocytopathy. Targeting this signaling pathway may offer renal protection against the development of proteinuric kidney diseases.

Mammalian target of rapamycin complex 1 activation in podocytes promotes cellular crescent formation.

Podocytes play a key role in the formation of cellular crescents in experimental and human diseases. However, the underlying mechanisms for podocytes in promoting crescent formation need further investigation. Here, we demonstrated that mammalian target of rapamycin complex 1 (mTORC1) signaling was remarkably activated and hypoxia-inducible factor (HIF) 1α expression was largely induced in cellular crescents from patients with crescentic glomerular diseases. Specific deletion of Tsc1 in podocytes led to mTORC1 activation in podocytes and kidney dysfunction in mice. Interestingly, 33 of 36 knockouts developed cellular or mixed cellular and fibrous crescents at 7 wk of age (14.19±3.86% of total glomeruli in knockouts vs. 0% in control littermates, n=12-36, P=0.04). All of the seven knockouts developed crescents at 12 wk of age (30.92±11.961% of total glomeruli in knockouts vs. 0% in control littermates, n=4-7, P=0.002). Most notably, bridging cells between the glomerular tuft and the parietal basement membrane as well as the cellular crescents were immunostaining positive for WT1, p-S6, HIF1α, and Cxcr4. Furthermore, continuously administrating rapamycin starting at 7 wk of age for 5 wk abolished crescents as well as the induction of p-S6, HIF1α, and Cxcr4 in the glomeruli from the knockouts. Together, it is concluded that mTORC1 activation in podocytes promotes cellular crescent formation, and targeting this signaling may shed new light on the treatment of patients with crescentic glomerular diseases.