Nephrology
Abstract
Vaso-occlusive episodes (VOEs) in the setting of hyperhemolysis can rapidly evolve into multiorgan failure in sickle cell disease (SCD). Although the mechanisms for rapid progression to multiorgan failure are unclear, a systemic vasculopathy with thrombotic microangiopathy-type features has been described. Reduced thrombomodulin (TM) function is implicated in some thrombotic microangiopathy syndromes. We observed a greater decline in platelet count and hemoglobin concentration and increase in vascular injury biomarkers within 24-hours of admission for a VOE in 12 SCD patients with versus 12 without multiorgan failure. We observed decreased TM expression on the lung and kidney vasculature of three additional SCD patients with multiorgan failure and an autopsy performed compared to a non-SCD control. Transgenic SCD mice challenged with cell-free hemoglobin had reduced TM function, increased vascular injury biomarkers, and reduced renal cortical blood flow. Infusion of recombinant TM 2- or 24-hours after the challenge restored cortical blood flow, mitigated increases in vascular injury, complement activation, and tubular injury biomarkers, and protected against acute kidney and lung injury. We demonstrated that impaired TM function may be involved in the systemic vasculopathy of SCD-related multiorgan failure and infusion of recombinant TM may restore vascular function and protect against acute organ damage.
Authors
Guohui Ren, Dustin R. Fraidenburg, Suman Setty, Jiwang Chen, Janae Gonzales, Maria Armila Ruiz, Zalaya Ivy, Najmeh Eskandari, Richard D. Minshall, James P. Lash, Victor R. Gordeuk, Santosh L. Saraf
Abstract
Urinary tract infections (UTIs) are the most common severe bacterial infections in young children, often associated with vesicoureteral reflux (VUR). To explore host genetic-microbiota interactions and their clinical implications, we analyzed the urinary microbiota (urobiota) and conducted genome-wide association studies (GWAS) for bacterial abundance traits in pediatric UTI and VUR patients from the RIVUR and CUTIE cohorts. We identified four urobiota community types based on relative abundance, characterized by the genera Enterococcus, Prevotella, Pseudomonas, and Escherichia/Shigella, and their associations with VUR, age, and toilet training. Children with VUR exhibited decreased microbial diversity and increased abundance of genera that included opportunistic pathogens, suggesting a disrupted urobiota. We detected genome-wide significant genetic associations with urinary bacterial relative abundances, in or near candidate genes including CXCL12, ABCC1, and ROBO1, which are implicated in urinary tract development and response to infection. We showed that Cxcl12 is induced 12 hours after uropathogenic bacterial infection in mouse bladder. The association with CXCL12 suggests a genetic link between UTI, VUR and cardiovascular phenotypes later in life. These findings provide the first characterization of host genetic influences on the pediatric urobiota in UTI and VUR, offering insights into the interplay between disease, host genetics and the urobiota composition.
Authors
Miguel Verbitsky, Pavan Khosla, Daniel Bivona, Atlas Khan, Yask Gupta, Heekuk Park, Tian H. Shen, Aryan Ghotra, Katherine Xu, Iman A. Ghavami, Priya Krithivasan, Jeremiah Martino, Tanya Sezin, Tze Y. Lim, Victoria Kolupaeva, Nita A. Limdi, Yuan Luo, Hakon Hakonarson, Simone Sanna-Cherchi, Krzysztof Kiryluk, Cathy L. Mendelsohn, Anne-Catrin Uhlemann, Jonathan Barasch, Ali G. Gharavi
Abstract
Mitochondrial dysfunction is a major mechanism of acute kidney injury (AKI), and increased circulating interleukin 6 (IL-6) is associated with systemic inflammation and death due to sepsis. We tested whether kidney mitochondrial DNA (mtDNA) contributes to IL-6 release in sepsis-associated AKI via Toll-like receptor 9 (TLR9). In a murine model of sepsis via cecal ligation and puncture (CLP), we used next-generation sequencing of plasma mtDNA to inform the design of optimal target sequences for quantification by droplet digital PCR, and to identify single-nucleotide polymorphisms (SNPs) to infer tissue origin. We found significantly higher concentrations of plasma mtDNA after CLP versus shams and that plasma mtDNA SNPs matched kidney SNPs more than other organs. Kidney mtDNA contributed directly to IL-6 and mtDNA release from dendritic cells in vitro and kidney mitochondria solution led to higher IL-6 concentrations in vivo. IL-6 release was mitigated by a TLR9 inhibitor. Finally, plasma mtDNA was significantly higher in septic patients with AKI compared with those without AKI and correlated significantly with plasma IL-6. We conclude that AKI contributes to increased circulating IL-6 in sepsis via mtDNA release. Targeting kidney mitochondria and mtDNA release are potential translational avenues to decrease mortality from sepsis-associated AKI.
Authors
Avnee J. Kumar, Katharine Epler, Jing Wang, Alice Shen, Negin Samandari, Mark L. Rolfsen, Laura A. Barnes, Gerald S. Shadel, Alexandra G. Moyzis, Alva G. Sainz, Karlen Ulubabyan, Kefeng Li, Kristen Jepsen, Xinrui Li, Mark M. Fuster, Roger G. Spragg, Roman Sasik, Volker Vallon, Helen Goodluck, Joachim H. Ix, Prabhleen Singh, Mark L. Hepokoski
Abstract
Renal polycystins (PKD1, PKD2) are ion channel–forming subunits that traffic to principal cell primary cilia. Variants in these proteins cause approximately 95% of autosomal dominant polycystic kidney disease (ADPKD), a common, lethal genetic disorder that lacks effective drug treatments. We assessed the mechanistic impact and pathogenic propensity of 2 disease-associated PKD2 truncating variants, R803X and R654X. Worldwide, hundreds of individuals with ADPKD harbor these germline mutations, including the R803X founder variant first identified within the patient population of Taiwan. Our biochemical, electrophysiological, and super-resolution imaging analyses demonstrated that the pore-truncating R654X variant abolished channel assembly and ciliary trafficking, whereas the R803X variant retained partial cilia trafficking and channel function. To assess disease impact, we generated transgenic mice with analogous truncation mutations. Homozygous mutants were embryonic lethal, whereas heterozygous mice expressing both variant and conditional Pkd2 repression alleles developed pronounced renal cysts. Cyst progression was slower in mice carrying the equivalent Taiwan mutation, reflecting the milder clinical course observed in patients. These findings revealed that the degree of impaired PKD2 channel trafficking to primary cilia correlated with cystic disease severity, providing insight into variant-specific ADPKD pathogenesis and newly developed animal models expressing clinically relevant variants for therapeutic testing.
Authors
Louise F. Kimura, Orhi Esarte Palomero, Megan Larmore, Paul G. DeCaen, Thuy N. Vien
Abstract
Prolonged and dysregulated neutrophilic inflammation causes tissue damage in chronic inflammatory diseases, including antibody-mediated glomerulonephritis (AGN). An increase in glycolysis, supported by enhanced glucose uptake, is a hallmark of hyperneutrophilic inflammation. Neutrophils upregulate glucose transporter 1–mediated (Glut1-mediated) glucose incorporation for renal antimicrobial activities. However, little is known about the role of neutrophil-specific Glut1 function in the pathogenesis of AGN. Using a well-vetted mouse model of AGN, we show that neutrophils upregulate Glut1 expression and function in the nephritic kidney. We demonstrate that Glut1 function in the hematopoietic cells during the early stage of the disease is necessary for kidney pathology. Most importantly, neutrophil-intrinsic Glut1 function is critical for AGN. While neutrophil-specific Glut1 ablation diminished the expression of tissue-damaging effector molecules in both the early and late stages, renal cytokines’ and chemokines’ production were compromised only in the late stage of the disease. Consequently, Glut1 inhibitor treatment ameliorated renal pathology in AGN mice. These data identify a Glut1-driven inflammatory circuit in neutrophils, which is amenable to therapeutic targeting in AGN.
Authors
Hossein Rahimi, Wonseok Choi, Doureradjou Peroumal, Shuxia Wang, Partha S. Biswas
Abstract
The mechanisms underlying cyst growth and progression in Autosomal Dominant Polycystic Kidney Disease (ADPKD) remain unresolved. Since cyst expansion requires epithelial salt and water secretion likely involving basolateral membrane K+ recycling, we investigated the role of KCNN4-encoded K+ channel KCa3.1, inhibited by the potent, pharmacospecific, well-tolerated antagonist, senicapoc. We hypothesized that genetic and/or pharmacological inactivation of KCNN4/KCa3.1 would slow PKD progression. KCNN4 was upregulated in kidneys of patients with ADPKD and of mechanistically distinct PKD mouse models. Cyst expansion in Pkd1–/– murine metanephroi was stimulated by KCa3.1 agonist and was prevented/reversed by senicapoc. In rapidly and/or slowly progressive mouse Pkd1 models, Kcnn4 inactivation slowed renal cyst growth; attenuated PKD-stimulated cAMP and ERK/Myc signaling pathways; reduced PKD-associated ciliary elongation, cell proliferation, and fibrosis; improved renal function; and prolonged survival. Importantly, senicapoc treatment of Pkd1 mouse models phenocopied most effects of Kcnn4 inactivation. This first study on the efficacy of KCa3.1 inhibition in PKD progression recommends senicapoc as a clinical trial candidate for ADPKD.
Authors
Guanhan Yao, Almira Kurbegovic, Camila Parrot, William Foley, William Roman, Seth L. Alper, Marie Trudel
Abstract
Glomerular inflammation and podocyte loss are the hallmarks of chronic kidney disease (CKD) progression. Understanding how podocytes and their microenvironment regulate inflammation is critical for developing effective therapies. In this study, we identified C-C chemokine ligand 5 (CCL5) as an inflammatory mediator elevated in injured podocytes, based on analyses of both human kidney biopsies and mouse models of CKD. We discovered that CCL5 exerts paradoxical effects in nephropathy: while it protects podocytes in vitro, it exacerbates glomerular injury in vivo. Recombinant CCL5 and podocyte-specific CCL5 overexpression promoted cell survival and reduced apoptosis in cultured podocytes. However, in Adriamycin-induced nephropathy, CCL5 worsened glomerular injury, increasing proteinuria, glomerulosclerosis, and podocyte loss. Bone marrow (BM) transplantation experiments revealed that CCL5 in BM-derived cells—not kidney-resident cells—drove disease progression. CCL5 deficiency in BM-derived cells conferred protection by increasing reparative M2 macrophages, whereas endogenous CCL5 promoted M1 polarization, inhibited M2 differentiation, and triggered M2-to-M1 transition. These findings demonstrate that while CCL5 supports podocyte survival, its expression in BM-derived cells promotes inflammatory macrophage phenotypes and glomerular injury. The harmful immune effects of CCL5 in BM-derived cells outweigh its podocyte-protective role, highlighting the importance of cell-targeted strategies to mitigate kidney damage.
Authors
Ika N. Kadariswantiningsih, Issei Okunaga, Kaho Yamasaki, Maulana A. Empitu, Hiroyuki Yamada, Shin-ichi Makino, Akitsu Hotta, Hideo Yagita, Masashi Aizawa, Ryo Koyama-Nasu, Motoko Y. Kimura, Narihito Tatsumoto, Katsuhiko Asanuma
Abstract
Normothermic machine perfusion (NMP) has become a valuable tool to expand the pool of transplantable organs. However, the application of NMP to kidneys presents substantial challenges, mostly due to high variability in the composition of currently used perfusion solutions. Here, we provide a multimodal cross-species cellular atlas of kidney injury associated with NMP using a literature-based consensus buffer. This resource provided a systematic framework that was used to develop a metabolite-enhanced perfusion solution, which protected renal proximal tubular cells, improving cellular viability and transplantation outcomes across species, including human kidneys.
Authors
Jan Czogalla, Fabian Hausmann, Simon Lagies, Sydney E. Gies, Sabrina Christiansen, Nico Kaiser, Fabian Haas, Yusuke Okabayashi, Dominik Kylies, Smilla Hofmann, Rossana Franzin, Niklas Sabra, Sarah Bouari, Yitian Fang, Gisela Ambagtsheer, Ilka Edenhofer, Silvia Chilla, Anne K. Mühlig, Marina Zimmermann, Milagros N. Wong, Takashi Yokoo, Oliver Kretz, Maja Lindenmeyer, Florian Grahammer, Martin J. Hoogduijn, Ron de Bruin, Malte Kuehl, Sonja Hänzelmann, Bernd Kammerer, Loreto Gesualdo, Stefan Bonn, Robert C. Minnee, Tobias B. Huber, Victor G. Puelles
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
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