Nephrology
Abstract
BACKGROUND. Active vitamin D metabolites, including 25-hydroxyvitamin D (25D) and 1,25-dihydroxyvitamin D (1,25D), have potent immunomodulatory effects that attenuate acute kidney injury (AKI) in animal models. METHODS. We conducted a phase 2, randomized, double-blind, multiple-dose, 3-arm clinical trial comparing oral calcifediol (25D), calcitriol (1,25D), and placebo among 150 critically ill adult patients at high-risk of moderate-to-severe AKI. The primary endpoint was a hierarchical composite of death, kidney replacement therapy (KRT), and kidney injury (baseline-adjusted mean change in serum creatinine), each assessed within 7 days following enrollment using a rank-based procedure. Secondary endpoints included new or progressive AKI and a composite of KRT or death. Hypercalcemia was the key safety endpoint. We also performed RNA sequencing on circulating CD14+ monocytes collected immediately prior to randomization and two days later. RESULTS. The global rank score for the primary endpoint was similar among calcifediol (n = 51) vs. placebo (n = 49) treated patients (P = 0.85) and for calcitriol (n = 50) versus placebo-treated patients (P = 0.58). Secondary endpoints also occurred at similar rates across groups. Hypercalcemia occurred in one patient in the calcifediol group (1.7%), one patient in the calcitriol group (2.0%), and none of the patients in the placebo group. Compared to placebo, calcitriol upregulated more individual genes and pathways in circulating monocytes than did calcifediol, including pathways involving interferon (IFN)-α, IFN-γ, oxidative phosphorylation, DNA repair, and heme metabolism. CONCLUSION. Treatment with calcifediol or calcitriol in critically ill adults upregulated multiple genes and pathways involving immunomodulation, DNA repair, and heme metabolism, but did not attenuate AKI. TRIAL REGISTRATION. ClinicalTrials.gov (NCT02962102). FUNDING. NIH/NIDDK grant K23DK106448 (Leaf) and NIH/NHLBI grant R01HL16687 (Kim)
Authors
David E. Leaf, Tushar Shenoy, Kevin Zinchuk, Shruti Gupta, Julie-Alexia Dias, Daniel Sanchez-Almanzar, Adit A. Ginde, Humra Athar, Changde Cheng, Tomoyoshi Tamura, Edy Y. Kim, Sushrut S. Waikar
Abstract
Mutations on genes encoding polycystin-1 (PC1) and -2 (PC2) cause autosomal-dominant polycystic kidney disease. How these two proteins work together to exert anti-cystogenesis remains elusive. PC1 resembles adhesion G-protein coupled receptors and undergoes autocleavage in the extracellular N-terminus to expose a hidden “stalk” region, which is hypothesized to act as a “tethered agonist”. Here, we showed that wildtype PC1 and PC2 formed functional heteromeric channel complexes in Xenopus oocytes with different biophysical properties from PC2 homomeric channels. Deletion of PC1 N-terminus, which exposed the stalk, increased calcium permeability in PC1/PC2 heteromers that required the presence of stalk. Extracellular application of synthetic stalk peptide increased calcium permeation in stalkless PC1/PC2. Application of Wnt9B protein increased calcium permeability in PC1/PC2, but not in heteromers containing cleavage-resistant mutant PC1. Wnt9B interacted with N-terminal leucine-rich repeat (LRR) of PC1. Pretreatment with LRR blunted the increase in calcium permeability by Wnt9B. Thus, PC1 and PC2 form receptor-channel complexes that is activated by exposure of the stalk region following ligand binding to the PC1 N-terminus. The stalk peptide acts as a tethered agonist to activate PC1/PC2 by impacting ion selectivity of the complexes.
Authors
Runping Wang, Danish Idrees, Mohammad Amir, Biswajit Padhy, Jian Xie, Chou-Long Huang
Abstract
Mutations in the transcription factor TFAP2A are linked to congenital anomalies of the kidney and urinary tract in humans. While Tfap2a knockout (KO) in mouse collecting ducts leads to tubular epithelial abnormalities, its precise molecular functions in kidney tubules remain unclear. To investigate Tfap2a-dependent gene regulatory networks in the mouse kidney collecting ducts, we employed conditional knockout (Hoxb7-Cre; Tfap2aflox/flox) models combined with transcriptomics. Histomorphological and physiological assessments of Tfap2a knockout mice revealed progressive postnatal dilation of the outer medullary collecting ducts. Integrating bulk and single-nucleus RNA sequencing with in silico motif mapping in ATAC-seq datasets demonstrated that Tfap2a is highly expressed and active in normal collecting duct principal cells. Comparative transcriptomics between 3-month-old Tfap2a KO and control mice identified dysregulated genes associated with cell adhesion and WNT signaling, including Alcam and Wnt9b. These alterations were confirmed by in situ hybridization. Our findings reveal that Tfap2a regulates medullary collecting duct diameter by orchestrating a transcriptional network involving Wnt9b and Alcam, providing new insights into its role in kidney structural integrity.
Authors
Janna Leiz, Karen I. López-Cayuqueo, Shuang Cao, Louisa M. S. Gerhardt, Christian Hinze, Kai M. Schmidt-Ott
Abstract
BK virus nephropathy is a severe, graft-threatening complication of kidney transplantation that requires an effective T cell response. It typically emerges in the kidney medulla. Elevated osmolyte concentrations that dynamically respond to loop diuretic therapy characterize this environment. BK-viremia development in kidney graft recipients negatively correlated with loop diuretic therapy. The association remained significant in multivariable and propensity score matched analyses. Kidney function was better preserved and CD8+ T cell abundance higher in loop diuretic-exposed allografts. CD8+ T cell densities in healthy human and murine kidney medulla were lower than in cortex and increased upon loop diuretic therapy in mice. As a potential underlying mechanism, kidney medullary NaCl and urea concentrations decreased primary human CD8+ T cell numbers in vitro by induction of cell death and limitation of proliferation, respectively. Both osmolytes downregulated interferon-related gene expression. NaCl induced p53-dependent apoptosis and upregulated Na+-transporter SLC38A2, which promoted caspase 3 activation. Both decreased T cell response and cytokine secretion in response to viral peptide and allogenic tubular epithelial cell killing, components of anti-BKV response in the kidney allograft. Our results propose osmolyte-mediated mitigation of CD8+ T cell function as a what we believe to be novel mechanism that impairs immune response to BK virus, therapeutic potential of which is testable.
Authors
Peyman Falahat, Adrian Goldspink, Lucia Oehler, Jessica Schmitz, Julia Miranda, Islem Gammoudi, Jan Hinrich Bräsen, Niklas Klümper, Olena Babyak, Christian Kurts, Herrmann Haller, Marieta Toma, Sibylle von Vietinghoff
Abstract
Nonresolving inflammation and maladaptive renal repair contribute to the pathogenesis of acute kidney injury (AKI) transition to chronic kidney disease (CKD). Few therapies have been identified that can modulate these injurious pathways following AKI. Spleen tyrosine kinase (SYK) is an immune regulator expressed in the kidney and a potential therapeutic target for AKI. The effect of the selective SYK inhibitor entospletinib was studied in AKI-to-CKD transition. Entospletinib was administered to mice undergoing unilateral renal ischemia-reperfusion injury (IRI), with kidneys analyzed over 14 days. Single-cell RNA sequencing, digital spatial profiling, intravital microscopy, and flow cytometry were employed to study renal phenotypes. Entospletinib administered before and after IRI protected ischemic kidneys and significantly attenuated the transition to CKD. Entospletinib targeted leukocyte-expressed SYK and prevented neutrophil/monocyte recruitment to the kidney. Entospletinib reduced nonresolving tubulointerstitial inflammation after AKI by blocking activation of mannose receptor-1– and C-type lectin domain family 7 member A–expressing proinflammatory macrophages. The resolution of renal inflammation mediated by entospletinib was associated with a reciprocal increase in resident macrophages, reparative gene expression, preserved tubular integrity, and reduced renal fibrosis. The SYK inhibitor entospletinib resolves renal inflammation and promotes repair following AKI.
Authors
Esteban E. Elias, Arthur Lau, Sisay Getie Belay, Afshin Derakhshani, Graciela Andonegui, Craig N. Jenne, Antoine Dufour, Nathan A. Bracey, Justin Chun, Daniel A. Muruve
Abstract
BACKGROUND. Urine proteomics may provide mechanistic insights on why patients experience a higher risk of kidney function decline after hospitalization. METHDOS. In 174 patients with and without acute kidney injury (AKI) from the Assessment, Serial Evaluation, and Subsequent Sequelae in AKI (ASSESS-AKI) cohort, we used Olink to profile 2783 urine proteins collected at 3 months post-hospitalization and determined their association with estimated glomerular filtration rate (eGFR) decline during median [IQR] of 5.1[4.0-6.0] years follow-up. In four independent cohorts including the Kidney Precision Medicine Project (KPMP), we determined if proteins were differentially expressed with AKI. We used weighted correlation network analysis to determine proteins’ cellular enrichment in the kidney transcriptome (single-cell and spatial transcriptomics) in patients with AKI receiving research kidney biopsy. RESULTS. We identified 387 and 10 proteins associated with faster and slower eGFR decline, respectively, most of which were differentially expressed in patients at the time of AKI. Among these proteins, 283 (71%) were expressed by kidney cells in participants with AKI from KPMP. The expression formed 3 clusters enriched in the proximal tubule, degenerative tubule and myeloid cells, and stromal cells, and correlated with histopathological features of AKI, such as tubular injury, interstitial inflammation, and fibrosis, respectively. CONCLUSION. Urinary proteins reflecting degenerative tubular injury, inflammation, and fibrosis are associated with eGFR decline in recently hospitalized patients. FUNDING. The Kidney Precision Medicine Project (KPMP) is supported by the National Institute of Diabetes and Digestive Kidney Diseases (NIDDK) through the following grantsU01DK133081, U01DK133091, U01DK133092, U01DK133093, U01DK133095, U01DK133097, U01DK114866, U01DK114908, U01DK133090, U01DK133113, U01DK133766, U01DK133768, U01DK114907, U01DK114920, U01DK114923, U01DK114933, U24DK114886, UH3DK114926, UH3DK114861, UH3DK114915, and UH3DK114937 We gratefully acknowledge the essential contributions of our patient participants and support of the American public though their tax dollars. SM is supported by NIDDK Grant K23DK128358.
Authors
Yumeng Wen, Steven Menez, Heather Thiessen Philbrook, Dennis Moledina, Steven G. Coca, Jiashu Xue, James Kaufman, Vernon Chinchillil, Paul L. Kimmel, T. Alp Ikizler, Chi-yuan Hsu, Tanika Kelly, Ana Ricardo, Jonathan Himmelfarb, Chirag R. Parikh
Abstract
Anemia is a common and disabling complication of chronic kidney disease (CKD). Current therapies can be burdensome, and full correction of anemia is limited by cardiovascular side effects. New approaches that may offer additional therapeutic options are needed. We explored the anti-anemic effects of erythroferrone, an erythroid hormone that induces iron mobilization by suppressing the master iron-regulatory hormone hepcidin. In a preclinical murine model of adenine-induced CKD, transgenic augmentation of erythroferrone mobilized iron, increased hemoglobin concentrations by approximately 2 g/dl, and modestly improved renal function without affecting systemic or renal inflammation, fibrosis, or markers of mineral metabolism. This study supports the concept that therapeutic augmentation of erythroferrone is a promising approach for alleviating CKD-associated anemia.
Authors
Brian Czaya, Joseph D. Olivera, Moya Zhang, Amber Lundin, Christian D. Castro Andrade, Grace Jung, Mark R. Hanudel, Elizabeta Nemeth, Tomas Ganz
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in PKD1 or PKD2, which encode polycystin-1 (PC1) and polycystin-2 (PC2) respectively. These proteins are thought to form a signaling complex that can flux cations including calcium. One of the earliest symptoms in ADPKD is a decline in the concentrating ability of the kidneys, occurring prior to cyst formation. We reasoned that hyperosmolality stimulates the polycystin complex, and that the loss of this function impairs water reabsorption. We found that hyperosmolality resulted in the phosphorylation of a microtubule associated protein 4 (MAP4) in a PC1-dependent manner which then elicited ER-localized PC2 calcium signals. ER-localized PC2 hyperosmotic calcium signals were required for trafficking of the water channel aquaporin (AQP2). Pre-cystic PC1-KO and PC2-KO murine kidneys had cytosolic localized AQP2, and diluted urine compared to their respective controls. Kidney tissue sections from ADPKD patients showed decreased AQP2 apical membrane localization in cystic and non-cystic tubules. Our study demonstrates that osmolality is a physiological stimulus of the polycystin complex, and loss of polycystin osmosensing results in impaired water reabsorption via AQP2. This likely contributes to the declined concentrating ability of the kidneys and high circulating vasopressin levels in ADPKD patients.
Authors
Karla M. Márquez-Nogueras, Ryne M. Knutila, Virdjinija Vuchkovska, Charlie Yang, Patricia Outeda, Darren P. Wallace, Ivana Y. Kuo
Abstract
Transforming growth factor beta (TGF-β) signaling is the master modulator of renal fibrosis. However, targeting drugs have failed to prevent the progression of chronic kidney disease (CKD) in clinical trials due to the extensive biological regulation of TGF-β signaling. It is necessary to investigate the precise downstream mechanisms of TGF-β signaling that regulate renal fibrosis. In this study, we found that PR-domain containing 16 (PRDM16) expression in human renal tubular epithelial cells was markedly reduced by TGF-β. Mechanistically, activated Smad3 induced by TGF-β interacted with the cofactor H-Ras and bound to the promoter of PRDM16, downregulating its transcription. Tubular-specific knockout of PRDM16 promoted renal fibrosis in models of unilateral ureteral occlusion (UUO) and unilateral ischemia-reperfusion injury (UIRI) by exacerbating mitochondrial dysfunction. In vitro, PRDM16 blocked TGF-β-induced mitochondrial injury and lipid deposition by upregulating Peroxisome Proliferator-Activated Receptor Gamma Coactivator-1α (PGC-1α). Delivery of the exogenous PRDM16 gene preserved renal function and ameliorated the progression of renal fibrosis by protecting mitochondrial function. We report PRDM16 as a novel downstream target of TGF-β signaling that attenuates renal fibrosis by safeguarding tubular mitochondrial function.
Authors
Qian Yuan, Ben Tang, Yuting Zhu, Chao Wan, Yaru Xie, Yajuan Xie, Cheng Wan, Hua Su, Youhua Liu, Chun Zhang
Low‐intensity pulsed ultrasound stimulation to treat renal fibrosis through inhibiting tubular IL-1R
Abstract
Low-intensity pulsed ultrasound stimulation (LIPUS) has become increasingly appreciated for its therapeutic effect on kidney diseases. However, its role and biological mechanism in treating chronic kidney disease (CKD) remain poorly defined. Here, we revealed that LIPUS was applied in a safe range with an intensity of 25-315 mW/cm2. Daily LIPUS at an intensity of 315 mW/cm2 ameliorated ischemia-reperfusion (IR)-induced tubular injury and renal fibrosis, accompanied by the remarkable downregulation of IL-1R. Transcriptome sequencing showed that LIPUS significantly down-regulated IL-1R and its downstream genes in IL-1β-stimulated IR-injured mice. LIPUS effectively reversed IL-1β-induced tubular injury and reduced the production of profibrotic cytokines by down-regulating IL-1R in vivo and in vitro. Renal proximal tubule-specific Il1r1 knockout mice exhibited milder renal tubular injury and fibrosis after IR injury. However, LIPUS did not ameliorate IR injury in proximal tubule-specific Il1r1 knockout mice. Collectively, daily LIPUS at an intensity of 315 mW/cm2 relieves IR-induced tubular injury and fibrosis, potentially through down-regulating tubular IL-1R.
Authors
Zhimin Huang, Jiaxin Dong, Ziqi Fu, Li Li, Simeng liu, Lin Wu, Honglei Guo, Ao Bian, Kang Liu, Wei Sun, Changying Xing, Steven D. Crowley, Jiafa Ren, Xiangqing Kong, Huijuan Mao
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