Nephrology
Abstract
Acute kidney injury (AKI) can lead to chronic kidney disease (CKD) if injury is severe and/or repair is incomplete. However, the pathogenesis of CKD following renal ischemic injury is not fully understood. Capillary rarefaction and tubular hypoxia are common findings during the AKI to CKD transition. We investigated the tubular stress response to hypoxia and demonstrated that a stress responsive transcription factor, FoxO3, was regulated by prolyl hydroxylase. Hypoxia inhibited FoxO3 prolyl hydroxylation and FoxO3 degradation, thus leading to FoxO3 accumulation and activation in tubular cells. Hypoxia-activated Hif-1α contributed to FoxO3 activation and functioned to protect kidneys, as tubular deletion of Hif-1α decreased hypoxia-induced FoxO3 activation, and resulted in more severe tubular injury and interstitial fibrosis following ischemic injury. Strikingly, tubular deletion of FoxO3 during the AKI to CKD transition aggravated renal structural and functional damage leading to a more profound CKD phenotype. We showed that tubular deletion of FoxO3 resulted in decreased autophagic response and increased oxidative injury, which may explain renal protection by FoxO3. Our study indicates that in the hypoxic kidney, stress responsive transcription factors can be activated for adaptions to counteract hypoxic insults, thus attenuating CKD development.
Authors
Ling Li, Huimin Kang, Qing Zhang, Vivette D. D'Agati, Qais Al-Awqati, Fangming Lin
Abstract
We identified 2 genes, histone deacetylase 1 (HDAC1) and HDAC2, contributing to the pathogenesis of proteinuric kidney diseases, the leading cause of end-stage kidney disease. mRNA expression profiling from proteinuric mouse glomeruli was linked to Connectivity Map databases, identifying HDAC1 and HDAC2 with the differentially expressed gene set reversible by HDAC inhibitors. In numerous progressive glomerular disease models, treatment with valproic acid (a class I HDAC inhibitor) or SAHA (a pan-HDAC inhibitor) mitigated the degree of proteinuria and glomerulosclerosis, leading to a striking increase in survival. Podocyte HDAC1 and HDAC2 activities were increased in mice podocytopathy models, and podocyte-associated Hdac1 and Hdac2 genetic ablation improved proteinuria and glomerulosclerosis. Podocyte early growth response 1 (EGR1) was increased in proteinuric patients and mice in an HDAC1- and HDAC2-dependent manner. Loss of EGR1 in mice reduced proteinuria and glomerulosclerosis. Longitudinal analysis of the multicenter Veterans Aging Cohort Study demonstrated a 30% reduction in mean annual loss of estimated glomerular filtration rate, and this effect was more pronounced in proteinuric patients receiving valproic acid. These results strongly suggest that inhibition of HDAC1 and HDAC2 activities may suppress the progression of human proteinuric kidney diseases through the regulation of EGR1.
Authors
Kazunori Inoue, Geliang Gan, Maria Ciarleglio, Yan Zhang, Xuefei Tian, Christopher E. Pedigo, Corey Cavanaugh, Janet Tate, Ying Wang, Elizabeth Cross, Marwin Groener, Nathan Chai, Zhen Wang, Amy Justice, Zhenhai Zhang, Chirag R. Parikh, Francis P. Wilson, Shuta Ishibe
Non-immune cell-derived ICOS ligand functions as a renoprotective αvβ3 integrin-selective antagonist
Abstract
Soluble urokinase receptor (suPAR) is a circulatory molecule that activates αvβ3 integrin on podocytes, causes foot process effacement, and contributes to proteinuric kidney disease. While active integrin can be targeted by antibodies and small molecules, endogenous inhibitors haven’t been discovered yet. Here we report a novel, renoprotective role for inducible costimulator (ICOS) ligand (ICOSL) in early kidney disease through its selective binding to podocyte αvβ3 integrin. Contrary to ICOSL’s immune-regulatory role, ICOSL in non-hematopoietic cells limited the activation of αvβ3 integrin. Specifically, ICOSL contains arginine-glycine-aspartate (RGD) motif, which allowed for a high affinity and selective binding to αvβ3 and modulation of podocyte adhesion. This binding was largely inhibited either by a synthetic RGD peptide or by a disrupted RGD sequence in ICOSL. ICOSL binding favored the active αvβ3 rather than the inactive form and showed little affinity for other integrins. Consistent with the rapid induction of podocyte ICOSL by inflammatory stimuli, glomerular ICOSL expression was increased in biopsies of early stage human proteinuric kidney diseases. Icosl deficiency in mice resulted in an increased susceptibility to proteinuria that was rescued by recombinant ICOSL. Our work identified a novel role for ICOSL, which serves as an endogenous αvβ3-selective antagonist to maintain glomerular filtration.
Authors
Kwi Hye Koh, Yanxia Cao, Steve Mangos, Nicholas J. Tardi, Ranadheer R. Dande, Ha Won Lee, Beata Samelko, Mehmet M. Altintas, Vincent P. Schmitz, Hyun Lee, Kamalika Mukherjee, Vasil Peev, David J. Cimbaluk, Jochen Reiser, Eunsil Hahm
Abstract
Epithelial-mesenchymal transition (EMT) contributes significantly to interstitial matrix deposition in diabetic kidney disease (DKD). However, detection of EMT in kidney tissue is impracticable, and anti-EMT therapies have long been hindered. We reported that phosphatase and tensin homolog (PTEN) promoted transforming growth factor beta 1 (TGF-β), sonic hedgehog (SHH), connective tissue growth factor (CTGF), interleukin 6 (IL-6), and hyperglycemia-induced EMT when PTEN was modified by a MEX3C-catalyzed K27-linked polyubiquitination at lysine 80 (referred to as PTENK27-polyUb). Genetic inhibition of PTENK27-polyUb alleviated Col4a3 knockout–, folic acid–, and streptozotocin-induced (STZ-induced) kidney injury. Serum and urine PTENK27-polyUb concentrations were negatively correlated with glomerular filtration rate (GFR) for diabetic patients. Mechanistically, PTENK27-polyUb facilitated dephosphorylation and protein stabilization of TWIST, SNAI1, and YAP in renal epithelial cells, leading to enhanced EMT. We identified that a small molecule, triptolide, inhibited MEX3C-catalyzed PTENK27-polyUb and EMT of renal epithelial cells. Treatment with triptolide reduced TWIST, SNAI1, and YAP concurrently and improved kidney health in Col4a3 knockout–, folic acid–injured disease models and STZ-induced, BTBR ob/ob diabetic nephropathy models. Hence, we demonstrated the important role of PTENK27-polyUb in DKD and a promising therapeutic strategy that inhibited the progression of DKD.
Authors
Yajuan Li, Qingsong Hu, Chunlai Li, Ke Liang, Yu Xiang, Heidi Hsiao, Tina K. Nguyen, Peter K. Park, Sergey D. Egranov, Chandrashekar R. Ambati, Nagireddy Putluri, David H. Hawke, Leng Han, Mien-Chie Hung, Farhad R. Danesh, Liuqing Yang, Chunru Lin
Abstract
Soluble urokinase plasminogen activator receptor (suPAR) is an immune-derived circulating signaling molecule that has been implicated in chronic kidney disease such as focal segmental glomerulosclerosis (FSGS). Typically, native uPAR (isoform 1) translates to a three-domain protein capable of binding and activating integrins, yet the function of additional isoforms generated by alternative splicing is unknown. Here, we characterized mouse uPAR isoform 2 (msuPAR2), encoding domain I and nearly one-half of domain II, as a dimer in solution, as revealed by 3D electron microscopy structural analysis. In vivo, msuPAR2 transgenic mice exhibited signs of severe renal disease characteristic of FSGS with proteinuria, loss of kidney function and glomerulosclerosis. Sequencing of the glomerular RNAs from msuPAR2-Tg mice revealed differentially expressed gene signature that includes upregulation of the suPAR receptor Itgb3, encoding β3 integrin. Crossing msuPAR2-transgenic mice with three different integrin β3 deficiency models rescued msuPAR2-mediated kidney function. Further analyses indicated a central role for β3 integrin and c-Src in msuPAR2 signaling and in human FSGS kidney biopsies. Administration of Src inhibitors reduced proteinuria in msuPAR2-transgenic mice. In conclusion, mouse uPAR isoform 2 may play an important role in certain forms of scarring kidney disease.
Authors
Changli Wei, Jing Li, Brian D. Adair, Ke Zhu, Jian Cai, Michael Merchant, Beata Samelko, Zhongji Liao, Kwi Hye Koh, Nicholas J. Tardi, Ranadheer R. Dande, Shuangxin Liu, Jianchao Ma, Salvatore DiBartolo, Stefan Hägele, Vasil Peev, Salim S. Hayek, David J. Cimbaluk, Melissa Tracy, Jon B. Klein, Sanja Sever, Sanford J. Shattil, M. Amin Arnaout, Jochen Reiser
Abstract
Atypical hemolytic uremic syndrome (aHUS) is frequently associated in humans with loss-of-function mutations in complement-regulating proteins or gain-of-function mutations in complement-activating proteins. Thus, aHUS provides an archetypal complement-mediated disease with which to model new therapeutic strategies and treatments. Herein, we show that, when transferred to mice, an aHUS-associated gain-of-function change (D1115N) to the complement-activation protein C3 results in aHUS. Homozygous C3 p.D1115N (C3KI) mice developed spontaneous chronic thrombotic microangiopathy together with hematuria, thrombocytopenia, elevated creatinine, and evidence of hemolysis. Mice with active disease had reduced plasma C3 with C3 fragment and C9 deposition within the kidney. Therapeutic blockade or genetic deletion of C5, a protein downstream of C3 in the complement cascade, protected homozygous C3KI mice from thrombotic microangiopathy and aHUS. Thus, our data provide in vivo modeling evidence that gain-of-function changes in complement C3 drive aHUS. They also show that long-term C5 deficiency is not accompanied by development of other renal complications (such as C3 glomerulopathy) despite sustained dysregulation of C3. Our results suggest that this preclinical model will allow testing of novel complement inhibitors with the aim of developing precisely targeted therapeutics that could have application in many complement-mediated diseases.
Authors
Kate Smith-Jackson, Yi Yang, Harriet Denton, Isabel Y. Pappworth, Katie Cooke, Paul N. Barlow, John P. Atkinson, M. Kathryn Liszewski, Matthew C. Pickering, David Kavanagh, H. Terence Cook, Kevin J. Marchbank
Abstract
In response to viral pathogens, the host upregulates antiviral genes that suppress translation of viral mRNAs. However, induction of such antiviral responses may not be exclusive to viruses, as the pathways lie at the intersection of broad inflammatory networks that can also be induced by bacterial pathogens. Using a model of Gram-negative sepsis, we show that propagation of kidney damage initiated by a bacterial origin ultimately involves antiviral responses that result in host translation shutdown. We determined that activation of the eukaryotic translation initiation factor 2-α kinase 2/eukaryotic translation initiation factor 2α (Eif2ak2/Eif2α) axis is the key mediator of translation initiation block in late-phase sepsis. Reversal of this axis mitigated kidney injury. Furthermore, temporal profiling of the kidney translatome revealed that multiple genes involved in formation of the initiation complex were translationally altered during bacterial sepsis. Collectively, our findings imply that translation shutdown is indifferent to the specific initiating pathogen and is an important determinant of tissue injury in sepsis.
Authors
Takashi Hato, Bernhard Maier, Farooq Syed, Jered Myslinski, Amy Zollman, Zoya Plotkin, Michael T. Eadon, Pierre C. Dagher
Abstract
People with diabetes mellitus have increased infection risk. With diabetes, urinary tract infection (UTI) is more common and has worse outcomes. Here, we investigate how diabetes and insulin resistance impact the kidney’s innate defenses and urine sterility. We report that type 2 diabetic mice have increased UTI risk. Moreover, insulin-resistant prediabetic mice have increased UTI susceptibility, independent of hyperglycemia or glucosuria. To identify how insulin resistance affects renal antimicrobial defenses, we genetically deleted the insulin receptor in the kidney’s collecting tubules and intercalated cells. Intercalated cells, located within collecting tubules, contribute to epithelial defenses by acidifying the urine and secreting antimicrobial peptides (AMPs) into the urinary stream. Collecting duct and intercalated cell–specific insulin receptor deletion did not impact urine acidification, suppressed downstream insulin-mediated targets and AMP expression, and increased UTI susceptibility. Specifically, insulin receptor–mediated signaling regulates AMPs, including lipocalin 2 and ribonuclease 4, via phosphatidylinositol-3-kinase signaling. These data suggest that insulin signaling plays a critical role in renal antibacterial defenses.
Authors
Matthew J. Murtha, Tad Eichler, Kristin Bender, Jackie Metheny, Birong Li, Andrew L. Schwaderer, Claudia Mosquera, Cindy James, Laura Schwartz, Brian Becknell, John David Spencer
Abstract
The pathogenesis of ischemic diseases remains unclear. Here we demonstrate the induction of microRNA-668 (mir-668) in ischemic acute kidney injury (AKI) in human patients, mice, and renal tubular cells. The induction was HIF-1dependant as HIF-1-deficiency in cells and kidney proximal tubules attenuated mir-668 expression. We further identified a functional HIF-1 binding site in mir-668 gene promoter. Anti-mir-668 increased apoptosis in renal tubular cells and enhanced ischemic AKI in mice, whereas mir-668 mimic was protective. Mechanistically, anti-mir-668 induced mitochondrial fragmentation, whereas mir-668 blocked mitochondrial fragmentation during hypoxia. We analyzed mir-668 target genes through immunoprecipitation of microRNA-induced silencing complexes followed by RNA deep sequencing and identified 124 protein-coding genes as likely targets of mir-668. Among these genes, only Mitochondrial Protein 18 KDa (MTP18) has been implicated in mitochondrial dynamics. In renal cells and mouse kidneys, mir-668 mimic suppressed MTP18, whereas anti-mir-668 increased MTP18 expression. Luciferase microRNA target reporter assay further verified MTP18 as a direct target of mir-668. In renal tubular cells, knockdown of MTP18 suppressed mitochondrial fragmentation and apoptosis. Together, the results suggest that mir-668 is induced via HIF-1 in ischemic AKI and, upon induction, mir-668 represses MTP18 to preserve mitochondrial dynamics for renal tubular cell survival and kidney protection.
Authors
Qingqing Wei, Haipeng Sun, Shuwei Song, Yong Liu, Pengyuan Liu, Man J. Livingston, Jianwen Wang, Mingyu Liang, Qing-Sheng Mi, Yuqing Huo, N. Stanley Nahman, Changlin Mei, Zheng Dong
Abstract
Steroid-resistant nephrotic syndrome (SRNS) almost invariably progresses to end-stage renal disease. Although more than 50 monogenic causes of SRNS have been described, a large proportion of SRNS remains unexplained. Recently, it was discovered that mutations of NUP93 and NUP205, encoding 2 proteins of the inner ring subunit of the nuclear pore complex (NPC), cause SRNS. Here, we describe mutations in genes encoding 4 components of the outer rings of the NPC, namely NUP107, NUP85, NUP133, and NUP160, in 13 families with SRNS. Using coimmunoprecipitation experiments, we showed that certain pathogenic alleles weakened the interaction between neighboring NPC subunits. We demonstrated that morpholino knockdown of nup107, nup85, or nup133 in Xenopus disrupted glomerulogenesis. Re-expression of WT mRNA, but not of mRNA reflecting mutations from SRNS patients, mitigated this phenotype. We furthermore found that CRISPR/Cas9 knockout of NUP107, NUP85, or NUP133 in podocytes activated Cdc42, an important effector of SRNS pathogenesis. CRISPR/Cas9 knockout of nup107 or nup85 in zebrafish caused developmental anomalies and early lethality. In contrast, an in-frame mutation of nup107 did not affect survival, thus mimicking the allelic effects seen in humans. In conclusion, we discovered here that mutations in 4 genes encoding components of the outer ring subunits of the NPC cause SRNS and thereby provide further evidence that specific hypomorphic mutations in these essential genes cause a distinct, organ-specific phenotype.
Authors
Daniela A. Braun, Svjetlana Lovric, David Schapiro, Ronen Schneider, Jonathan Marquez, Maria Asif, Muhammad Sajid Hussain, Ankana Daga, Eugen Widmeier, Jia Rao, Shazia Ashraf, Weizhen Tan, C. Patrick Lusk, Amy Kolb, Tilman Jobst-Schwan, Johanna Magdalena Schmidt, Charlotte A. Hoogstraten, Kaitlyn Eddy, Thomas M. Kitzler, Shirlee Shril, Abubakar Moawia, Kathrin Schrage, Arwa Ishaq A. Khayyat, Jennifer A. Lawson, Heon Yung Gee, Jillian K. Warejko, Tobias Hermle, Amar J. Majmundar, Hannah Hugo, Birgit Budde, Susanne Motameny, Janine Altmüller, Angelika Anna Noegel, Hanan M. Fathy, Daniel P. Gale, Syeda Seema Waseem, Ayaz Khan, Larissa Kerecuk, Seema Hashmi, Nilufar Mohebbi, Robert Ettenger, Erkin Serdaroğlu, Khalid A. Alhasan, Mais Hashem, Sara Goncalves, Gema Ariceta, Mercedes Ubetagoyena, Wolfram Antonin, Shahid Mahmood Baig, Fowzan S. Alkuraya, Qian Shen, Hong Xu, Corinne Antignac, Richard P. Lifton, Shrikant Mane, Peter Nürnberg, Mustafa K. Khokha, Friedhelm Hildebrandt
Copyright © 2020 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)