Nephrology
Abstract
The role and mechanisms for upregulating complement factor B (CFB) expression in podocyte dysfunction in diabetic kidney disease (DKD) are not fully understood. Here, analyzing Gene Expression Omnibus GSE30528 data, we identified genes enriched in mTORC1 signaling, CFB, and complement alternative pathways in podocytes from patients with DKD. In mouse models, podocyte mTOR complex 1 (mTORC1) signaling activation was induced, while blockade of mTORC1 signaling reduced CFB upregulation, alternative complement pathway activation, and podocyte injury in the glomeruli. Knocking down CFB remarkably alleviated alternative complement pathway activation and DKD in diabetic mice. In cultured podocytes, high glucose treatment activated mTORC1 signaling, stimulated STAT1 phosphorylation, and upregulated CFB expression, while blockade of mTORC1 or STAT1 signaling abolished high glucose–upregulated CFB expression. Additionally, high glucose levels downregulated protein phosphatase 2Acα (PP2Acα) expression, while PP2Acα deficiency enhanced high glucose–induced mTORC1/STAT1 activation, CFB induction, and podocyte injury. Taken together, these findings uncover a mechanism by which CFB mediates podocyte injury in DKD.
Authors
Qingmiao Lu, Qing Hou, Kai Cao, Xiaoli Sun, Yan Liang, Mengru Gu, Xian Xue, Allan Zijian Zhao, Chunsun Dai
Abstract
Proline rich 11 (PRR11), a novel tumor-related gene, has been identified in different tumors. However, the relevant biological functions of PRR11 in human clear cell renal cell carcinoma (ccRCC) have not been studied. In this study, we first identified PRR11 as a biomarker of ccRCC and predictor of poor prognosis by bioinformatics. Then, we confirmed that PRR11 silencing significantly reduced ccRCC cell proliferation and migration in vitro and in vivo. Importantly, we found that PRR11 could induce the degradation of the E2F1 protein through its interaction with E2F1, and PRR11 reduced the stability of the E2F1 protein in ccRCC cells, thereby affecting cell cycle progression. Further results indicated that the downregulation of E2F1 expression could partially reverse the changes in ccRCC cell biology caused by PRR11 deletion. In addition, we proved for the first time that PRR11 is a target gene of c-Myc. The transcription factor c-Myc may promote the expression of PRR11 in ccRCC cells by binding to the PRR11 promoter region, thereby accelerating the progression of ccRCC. In summary, we found that PRR11 could serve as a novel oncogene in ccRCC, and PRR11 could reduce the protein stability of E2F1 and could be activated by c-Myc.
Authors
Siming Chen, Zhiwen He, Tiancheng Peng, Fenfang Zhou, Gang Wang, Kaiyu Qian, Lingao Ju, Yu Xiao, Xinghuan Wang
Abstract
The prevailing view is that ClC-Ka chloride channel (mouse Clc-k1) functions in thin ascending limb for urine concentration, whereas ClC-Kb (mouse Clc-k2) in thick ascending limb (TAL) for salt reabsorption, respectively. Mutations of ClC-Kb cause classic Bartter syndrome with renal salt wasting with onset from perinatal to adolescent. We study the roles of Clc-k channels in perinatal mouse kidneys using constitutive or inducible kidney-specific gene ablation and 2-D and advanced 3-D imaging of optically cleared kidneys. We show that Clc-k1 and -k2 are broadly expressed and colocalized in perinatal kidneys. Deletion of Clc-k1 and -k2 reveals that both participate in NKCC2- and NCC-mediated NaCl reabsorption in neonatal kidneys. Embryonic deletion of Clc-k2 causes tubular injury and impairs renal medulla and TAL development. Inducible deletion of Clc-k2 begins after medulla maturation produces mild salt wasting resulting from reduced NCC activity. Thus, both Clc-k1 and -k2 contribute to salt reabsorption in TAL and DCT in neonates, potentially explaining less severe phenotypes in classic Bartter. As opposed to the current understanding that salt wasting in adult Bartter patients is due to Clc-k2 deficiency in adult TAL, our results suggest that it is mainly originated from medulla and TAL defects during development.
Authors
Meng-Hsuan Lin, Jen-Chi Chen, Xuejiao Tian, Chia-Ming Lee, I-Shing Yu, Yi-Fen Lo, Shinichi Uchida, Chou-Long Huang, Bi-Chang Chen, Chih-Jen Cheng
Abstract
We reported that Shroom3 knockdown, via Fyn inhibition, induced albuminuria with foot process effacement (FPE) without glomerulosclerosis (FSGS) or podocytopenia. Interestingly, knockdown mice had reduced podocyte volumes. Human minimal change disease, where podocyte Fyn inactivation was reported, also showed lower glomerular volumes than FSGS. We hypothesized that lower glomerular volume prevented the progression to podocytopenia. To test this hypothesis, we utilized unilateral- and 5/6th nephrectomy models in Shroom3 knockdown mice. Knockdown mice exhibited less glomerular and podocyte hypertrophy after nephrectomy. FYN-knockdown podocytes had similar reductions in podocyte volume, implying Fyn was downstream of Shroom3. Using SHROOM3- or FYN-knockdown, we confirmed reduced podocyte protein content, along with significantly increased phosphorylated AMP-kinase, a negative regulator of anabolism. AMP-Kinase activation resulted from increased cytoplasmic redistribution of LKB1 in podocytes. Inhibition of AMP-Kinase abolished the reduction in glomerular volume and induced podocytopenia in mice with FPE, suggesting a protective role for AMP-Kinase activation. In agreement with this, treatment of glomerular injury models with AMP-Kinase activators restricted glomerular volume, podocytopenia and progression to FSGS. Glomerular transcriptomes from MCD biopsies also showed significant enrichment of Fyn-inactivation and Ampk-activation vs FSGS glomeruli. In summary, we demonstrate the important role of AMP-Kinase in glomerular volume regulation and podocyte survival. Our data suggest that AMP-Kinase activation adaptively regulates glomerular volume to prevent podocytopenia in the context of podocyte injury.
Authors
Khadija Banu, Qisheng Lin, John M. Basgen, Marina Planoutene, Chengguo Wei, Anand C. Reghuvaran, Xuefei Tian, Hongmei Shi, Felipe Garzon, Aitor Garzia, Nicholas Chun, Arun Cumpelik, Andrew D. Santeusanio, Weijia Zhang, Bhaskar Das, Fadi Salem, LI LI, Shuta Ishibe, Lloyd G. Cantley, Lewis Kaufman, Kevin V. Lemley, Zhaohui Ni, John Cijiang He, Barbara Murphy, Madhav C. Menon
Abstract
The prevalence of hypertension is increasing globally, while strategies for prevention and treatment of hypertension remain limited. FG-4592 (Roxadustat) is a novel, orally active small-molecule HIF stabilizer, and is being used clinically to treat CKD anemia. In the present study, we evaluate the effects of FG-4592 on hypertension. In an Ang II hypertension model, FG-4592 abolished hypertensive responses, prevented vascular thickening, cardiac hypertrophy, and kidney injury, downregulated AGTR1 expression, and enhanced AGTR2, eNOS, and HIF1α protein levels in the aortas of mice. Additionally, the levels of thiobarbituric acid reactive substances (TBARs) in blood and urine were diminished by FG-4592 treatment. In vascular smooth muscle cells, FG-4592 treatment reduced AGTR1 and increased AGTR2 levels, while preventing Ang II-induced oxidative stress. In vascular endothelial cells, FG-4592 upregulated total and phosphorylated eNOS. Moreover, FG-4592 treatment was hypotensive in L-NAME-induced hypertension. In summary, FG-4592 treatment remarkably ameliorated hypertension and organ injury, possibly through stabilizing HIF1α and subsequently targeting eNOS, AGTR1, AGTR2, and oxidative stress. Therefore, in addition to its role in treating CKD anemia, FG-4592 could be explored as a treatment for hypertension associated with high RAS activity or eNOS defects.
Authors
Jing Yu, Shuqin Wang, Wei Shi, Wei Zhou, Yujia Niu, Songming Huang, Yue Zhang, Aihua Zhang, Zhanjun Jia
Abstract
The transcription factor Twist1 regulates several processes that could impact kidney disease progression, including epithelial cell differentiation and inflammatory cytokine induction. Podocytes are specialized epithelia that exhibit features of immune cells and could therefore mediate unique effects of Twist1 on glomerular disease. To study Twist1 functions in podocytes during proteinuric kidney disease, we employed a conditional mutant mouse in which Twist1 was selectively ablated in podocytes (Twist1-PKO). Deletion of Twist1 in podocytes augmented proteinuria, podocyte injury, and foot process effacement in glomerular injury models. Twist1 in podocytes constrained renal accumulation of monocytes/macrophages and glomerular expression of CCL2 and the macrophage cytokine TNF-α after injury. Deletion of TNF-α selectively from podocytes had no impact on the progression of proteinuric nephropathy. By contrast, the inhibition of CCL2 abrogated the exaggeration in proteinuria and podocyte injury accruing from podocyte Twist1 deletion. Collectively, Twist1 in podocytes mitigated urine albumin excretion and podocyte injury in proteinuric kidney diseases by limiting CCL2 induction that drove monocyte/macrophage infiltration into injured glomeruli. Myeloid cells, rather than podocytes, further promoted podocyte injury and glomerular disease by secreting TNF-α. These data highlight the capacity of Twist1 in the podocyte to mitigate glomerular injury by curtailing the local myeloid immune response.
Authors
Jiafa Ren, Yuemei Xu, Xiaohan Lu, Liming Wang, Shintaro Ide, Gentzon Hall, Tomokazu Souma, Jamie R. Privratsky, Robert F. Spurney, Steven D. Crowley
Abstract
The mitochondrial enzyme acetaldehyde dehydrogenase 2 (ALDH2) catalyzes the detoxification of acetaldehyde and endogenous lipid aldehydes. Approximately 40% of East Asians, accounting for 8% of the human population, carry the E504K mutation in ALDH2 that leads to accumulation of toxic reactive aldehydes and increases the risk for cardiovascular disease (CVD), cancer and Alzheimer’s, among other diseases. However, the role of ALDH2 in acute kidney injury (AKI) remains poorly defined and is therefore the subject of the present study using various cellular and organismal sources. In murine models in which AKI was induced by either the contrast agent Iohexol or renal ischemia/reperfusion, knockout and activation/overexpression of ALDH2 was associated with increased and decreased renal injury, respectively. In murine renal tubular epithelial cells (RTECs), ALDH2 upregulated Beclin-1 expression, promoted autophagy activation and eliminated reactive oxygen species (ROS). In vivo and in vitro, both 3-MA and Beclin-1 siRNAs inhibited autophagy and abolished ALDH2 mediated renoprotection. In mice with Iohexol induced AKI, ALDH2 knockdown in RTECs using AAV-shRNA impaired autophagy activation and aggravated renal injury. In human renal proximal tubular epithelial HK-2 cells exposed to Iohexol, ALDH2 activation potentiated autophagy and attenuated apoptosis. In mice with AKI induced by renal ischemia ischemia/reperfusion, ALDH2 overexpression or pretreatment regulated autophagy mitigating apoptosis of RTECs and renal injury. Our data collectively substantiate a critical role of ALDH2 in AKI via autophagy activation involving the Beclin-1 pathway.
Authors
Tonghui Xu, Jialin Guo, Maozeng Wei, Jiali Wang, Kehui Yang, Chang Pan, Jiaojiao Pang, Li Xue, Qiu-huan Yuan, Mengyang Xue, Jian Zhang, Wentao Sang, Tangxing Jiang, Yuguo Chen, Feng Xu
Abstract
Idiopathic nephrotic syndrome (INS) is characterized by proteinuria and renal Na retention leading to oedema. This Na retention is usually attributed to epithelial sodium channel (ENaC) activation following plasma aldosterone increase. However, most nephrotic patients show normal aldosterone levels. Using a corticosteroid-clamped rat model of INS (CC-PAN), we showed that the observed electrogenic and amiloride-sensitive Na retention could not be attributed to ENaC. We, then, identified a truncated variant of acid sensing ion channel 2b (ASIC2b) that induced sustained acid-stimulated sodium currents when co-expressed with ASIC2a. Interestingly, CC-PAN nephrotic ASIC2b-null rats did not develop sodium retention. We finally showed that expression of the truncated ASIC2b in kidney was dependent on the presence of albumin in the tubule lumen and activation of ERK in renal cells. Finally, the presence of ASIC2 mRNA was also detected in kidney biopsies from patients with INS but not in any of the patients with other renal diseases. We have, therefore, identified a novel variant of ASIC2b responsible for the renal Na retention in the pathological context of INS.
Authors
Marc Fila, Ali Sassi, Gaelle Brideau, Lydie Cheval, Luciana Morla, Pascal Houillier, Christine Walter, Michel Gennaoui, Laure Collignon, Mathilde Keck, Gabrielle Planelles, Naziha Bakouh, Michel Peuchmaur, Georges Deschenes, Ignacio Anegon, Séverine Remy, Bruno Vogt, Gilles Crambert, Alain Doucet
Abstract
PDCD10, also known as CCM3, is a gene found to be associated with the human disease cerebral cavernous malformations (CCMs). PDCD10 forms a complex with GCKIII kinases including STK24, STK25, and MST4. Studies in C. elegans and Drosophila have shown a pivotal role of the PDCD10-GCKIII complex in maintaining epithelial integrity. Here, we found that mice deficient of Pdcd10 or Stk24/25 in the kidney tubules developed polyuria and displayed increased water consumption. Although the expression levels of aquaporin genes were not decreased, the levels of total and phosphorylated aquaporin 2 (Aqp2) protein in the apical membrane of tubular epithelial cells were decreased in Pdcd10- and Stk24/25-deficient mice. This loss of Aqp2 was associated with increased expression and membrane targeting of Ezrin and phosphorylated Ezrin, Radixin, Moesin (p-ERM) proteins and impaired intracellular vesicle trafficking. Treatment with Erlotinib, a tyrosine kinase inhibitor promoting exocytosis and inhibiting endocytosis, normalized the expression level and membrane abundance of Aqp2 protein, and partially rescued the water reabsorption defect observed in the Pdcd10-deficient mice. Our current study identified the PDCD10-STK-ERM signaling pathway as a potentially novel pathway required for water balance control by regulating vesicle trafficking and protein abundance of AQP2 in the kidneys.
Authors
Rui Wang, Shi-Ting Wu, Xi Yang, Yude Qian, Jaesung P. Choi, Rui Gao, Siliang Song, Yixuan Wang, Tao Zhuang, Justin J.L. Wong, Yuzhen Zhang, Zhiming Han, Hua A. Lu, Stephen I. Alexander, Renjing Liu, Yin Xia, Xiangjian Zheng
Abstract
Single cell sequencing studies have characterized the transcriptomic signature of cell types within the kidney. However, the spatial distribution of acute kidney injury (AKI) is regional and affects cells heterogeneously. We first optimized coordination of spatial transcriptomics and single nuclear sequencing datasets, mapping 30 dominant cell types to a human nephrectomy. The predicted cell type spots corresponded with the underlying histopathology. To study the implications of AKI on transcript expression, we then characterized the spatial transcriptomic signature of two murine AKI models: ischemia reperfusion injury (IRI) and cecal ligation puncture (CLP). Localized regions of reduced overall expression were associated with injury pathways. Using single cell sequencing, we deconvoluted the signature of each spatial transcriptomic spot, identifying patterns of colocalization between immune and epithelial cells. Neutrophils infiltrated the renal medulla in the ischemia model. Atf3 was identified as a chemotactic factor in S3 proximal tubules. In the CLP model, infiltrating macrophages dominated the outer cortical signature and Mdk was identified as a corresponding chemotactic factor. The regional distribution of these immune cells was validated with multiplexed CO-Detection by inDEXing (CODEX) immunofluorescence. Spatial transcriptomic sequencing complements single cell sequencing by uncovering mechanisms driving immune cell infiltration and detection of relevant cell subpopulations.
Authors
Ricardo Melo Ferreira, Angela R. Sabo, Seth Winfree, Kimberly S. Collins, Danielle Janosevic, Connor J. Gulbronson, Ying-Hua Cheng, Lauren Casbon, Daria Barwinska, Michael J. Ferkowicz, Xiaoling Xuei, Chi Zhang, Kenneth W. Dunn, Katherine J. Kelly, Timothy A. Sutton, Takashi Hato, Pierre C. Dagher, Tarek M. El-Achkar, Michael T. Eadon
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