Nephrology
Abstract
Tissue regeneration is limited in several organs including the kidney, contributing to the high prevalence of kidney disease globally. However, evolutionary and physiological adaptive responses and the presence of renal progenitor cells suggest existing remodeling capacity. This study uncovered endogenous tissue remodeling mechanisms in the kidney that were activated by the loss of body fluid and salt and regulated by a unique niche of a minority renal cell type called the macula densa (MD). Here we identified neuronal differentiation features of MD cells that sense the local and systemic environment, secrete angiogenic, growth and extracellular matrix remodeling factors, cytokines and chemokines, and control resident progenitor cells. Serial intravital imaging, MD nerve growth factor receptor and Wnt mouse models and transcriptome analysis revealed cellular and molecular mechanisms of these MD functions. Human and therapeutic translation studies illustrated the clinical potential of MD factors including CCN1 as a urinary biomarker and therapeutic target in chronic kidney disease. The concept that a neuronally differentiated key sensory and regulatory cell type responding to organ-specific physiological inputs controls local progenitors to remodel or repair tissues may be applicable to other organs and diverse tissue regenerative therapeutic strategies.
Authors
Georgina Gyarmati, Urvi Nikhil Shroff, Anne Riquier-Brison, Dorinne Desposito, Wenjun Ju, Sean D. Stocker, Audrey Izuhara, Sachin Deepak, Alejandra Becerra Calderon, James L. Burford, Hiroyuki Kadoya, Ju-Young Moon, Yibu Chen, Markus M. Rinschen, Nariman Ahmadi, Lester Lau, Daniel Biemesderfer, Aaron W. James, Liliana Minichiello, Berislav Zlokovic, Inderbir S. Gill, Matthias Kretzler, János Peti-Peterdi
Abstract
Uncontrolled accumulation of extracellular matrix leads to tissue fibrosis and loss of organ function. We previously demonstrated in vitro that the DNA/RNA-binding protein fused in sarcoma (FUS) promotes fibrotic responses by translocating to the nucleus, where it initiates collagen gene transcription. However, it is still not known whether FUS is profibrotic in vivo and whether preventing its nuclear translocation might inhibit development of fibrosis following injury. We now demonstrate that levels of nuclear FUS are significantly increased in mouse models of kidney and liver fibrosis. To evaluate the direct role of FUS nuclear translocation in fibrosis, we used mice that carry a mutation in the FUS nuclear localization sequence (FUSR521G) and the cell-penetrating peptide CP-FUS-NLS that we previously showed inhibits FUS nuclear translocation in vitro. We provide evidence that FUSR521G mice or CP-FUS-NLS–treated mice showed reduced nuclear FUS and fibrosis following injury. Finally, differential gene expression analysis and immunohistochemistry of tissues from individuals with focal segmental glomerulosclerosis or nonalcoholic steatohepatitis revealed significant upregulation of FUS and/or collagen genes and FUS protein nuclear localization in diseased organs. These results demonstrate that injury-induced nuclear translocation of FUS contributes to fibrosis and highlight CP-FUS-NLS as a promising therapeutic option for organ fibrosis.
Authors
Manuel Chiusa, Youngmin A. Lee, Ming-Zhi Zhang, Raymond C. Harris, Taylor Sherrill, Volkhard Lindner, Craig R. Brooks, Gang Yu, Agnes B. Fogo, Charles R. Flynn, Jozef Zienkiewicz, Jacek Hawiger, Roy Zent, Ambra Pozzi
Abstract
Ca2+-activated BK channels in renal intercalated cells (ICs) mediate luminal flow–induced K+ secretion (FIKS), but how ICs sense increased flow remains uncertain. We examined whether PIEZO1, a mechanosensitive Ca2+-permeable channel expressed in the basolateral membranes of ICs, is required for FIKS. In isolated cortical collecting ducts (CCDs), the mechanosensitive cation-selective channel inhibitor GsMTx4 dampened flow-induced increases in intracellular Ca2+ concentration ([Ca2+]i), whereas the PIEZO1 activator Yoda1 increased [Ca2+]i and BK channel activity. CCDs from mice fed a high-K+ (HK) diet exhibited a greater Yoda1-dependent increase in [Ca2+]i than CCDs from mice fed a control K+ diet. ICs in CCDs isolated from mice with a targeted gene deletion of Piezo1 in ICs (IC-Piezo1-KO) exhibited a blunted [Ca2+]i response to Yoda1 or increased flow, with an associated loss of FIKS in CCDs. Male IC-Piezo1-KO mice selectively exhibited an increased blood [K+] in response to an oral K+ bolus and blunted urinary K+ excretion following a volume challenge. Whole-cell expression of BKα subunit was reduced in ICs of IC-Piezo1-KO mice fed an HK diet. We conclude that PIEZO1 mediates flow-induced basolateral Ca2+ entry into ICs, is upregulated in the CCD in response to an HK diet, and is necessary for FIKS.
Authors
Rolando Carrisoza-Gaytan, Stephanie M. Mutchler, Francisco Carattino, Joanne Soong, Marianela G. Dalghi, Peng Wu, WenHui Wang, Gerard Apodaca, Lisa M. Satlin, Thomas R. Kleyman
Abstract
Authors
Maggie E. Jones-Carr, Huma Fatima, Vineeta Kumar, Douglas J. Anderson, Julie Houp, Jackson C. Perry, Gavin A. Baker, Leigh McManus, Andrew J. Shunk, Paige M. Porrett, Jayme E. Locke
Abstract
Two coding variants of apolipoprotein L1 (APOL1) called G1 and G2 explain much of the excess risk of kidney disease in African Americans. While various cytotoxic phenotypes have been reported in experimental models, the proximal mechanism by which G1 and G2 cause kidney disease is poorly understood. Here, we leveraged three experimental models and a recently reported small molecule blocker of APOL1 protein, VX-147, to identify the upstream mechanism of G1-induced cytotoxicity. In HEK293 cells, we demonstrated that G1-mediated Na+ import/K+ efflux triggered activation of G protein-coupled receptor (GPCR)-IP3-mediated calcium release from the endoplasmic reticulum (ER), impaired mitochondrial ATP production, and impaired translation, which were all reversed by VX-147. In human podocyte-like epithelial cells (HUPEC), we demonstrated that G1 caused cytotoxicity that was again reversible by VX-147. Finally, in podocytes isolated from APOL1 G1 transgenic mice, we showed that Interferon gamma (IFNγ)-mediated induction of G1 caused K+ efflux, activation of GPCR-IP3 signaling, and inhibition of translation, podocyte injury, and proteinuria, all reversed by VX-147. Together, these results establish APOL1-mediated Na+/K+ transport as the proximal driver of APOL1-mediated kidney disease.
Authors
Somenath Datta, Brett M. Antonio, Nathan H. Zahler, Jonathan W. Theile, Doug Krafte, Hengtao Zhang, Paul B. Rosenberg, Alec B. Chaves, Deborah M. Muoio, Guofang Zhang, Daniel Silas, Guojie Li, Karen Soldano, Sarah Nystrom, Davis Ferreira, Sara E. Miller, James R. Bain, Michael J. Muehlbauer, Olga Ilkayeva, Thomas C. Becker, Hans-Ewald Hohmeier, Christopher B. Newgard, Opeyemi A. Olabisi
Abstract
Worldwide, over 800 million people are affected by kidney disease, yet its pathogenesis remains elusive, hindering the development of novel therapeutics. In this study, we employed kidney-specific expression of quantitative traits and single-nuclear open chromatin analysis to show that genetic variants linked to kidney dysfunction on chromosome 20 target the acyl-CoA synthetase short-chain family 2 (ACSS2). By generating ACSS2 knock-out mice, we demonstrated their protection from kidney fibrosis in multiple disease models. Our analysis of primary tubular cells revealed that ACSS2 regulates de novo lipogenesis (DNL), causing NADPH depletion and increasing ROS levels, ultimately leading to NLRP3-dependent pyroptosis. Additionally, we discovered that pharmacological inhibition or genetic ablation of fatty acid synthase safeguarded kidney cells against profibrotic gene expression and prevented kidney disease in mice. Lipid accumulation and the expression of genes related to DNL were elevated in the kidneys of patients with fibrosis. Our findings pinpoint ACSS2 as a critical kidney disease gene and reveal the role of DNL in kidney disease.
Authors
Dhanunjay Mukhi, Lingzhi Li, Hongbo Liu, Tomohito Doke, Lakshmi P. Kolligundla, Eunji Ha, Konstantin A. Klötzer, Amin Abedini, Sarmistha Mukherjee, Junnan Wu, Poonam Dhillon, Hailong Hu, Dongyin Guan, Katsuhiko Funai, Kahealani Uehara, Paul M. Titchenell, Joseph A. Baur, Kathryn E. Wellen, Katalin Susztak
Abstract
Mineralocorticoid excess commonly leads to hypertension and kidney disease. In our study, we employed single-cell expression and chromatin accessibility tools to characterize the mineralocorticoid target genes and cell types. We demonstrated that mineralocorticoid effects are established through open chromatin and target gene expression, primarily in principal and connecting tubule cells, and to a lesser extent, in segments of the distal convoluted tubule cells. We examined the kidney-protective effects of steroidal and non-steroidal mineralocorticoid antagonists (MRAs), as well as amiloride, an epithelial sodium channel inhibitor, in a rat model of deoxycorticosterone acetate, unilateral nephrectomy, and high salt consumption-induced hypertension and cardiorenal damage. All antihypertensive therapies protected from cardiorenal damage. However, finerenone was particularly effective in reducing albuminuria and improving gene expression changes in podocytes and proximal tubule cells, even with equivalent blood pressure reduction. There was a strong correlation between the accumulation of injured/profibrotic tubule cells expressing Spp1, Il34, and Pdgfb and the degree of fibrosis in rat kidneys. This gene signature also showed potential for classifying human kidney samples. Our multi-omics approach provides fresh insights into the possible mechanisms underlying hypertension associated kidney disease, the target cell types, and the protective effects of steroidal, non-steroidal MRAs, and amiloride.
Authors
Amin Abedini, Andrea Sanchez-Navarro, Junnan Wu, Konstantin A. Klötzer, Ziyuan Ma, Bibek Poudel, Tomohito Doke, Michael S. Balzer, Julia Frederick, Hana Cernecka, Hongbo Liu, Xiujie Liang, Steven Vitale, Peter Kolkhof, Katalin Susztak
Abstract
The progression of proteinuric kidney diseases is associated with podocyte loss but the mechanisms underlying this process remain unclear. Podocytes re-enter the cell cycle to repair double-stranded DNA (dsDNA) breaks. However, the unsuccessful repair can result in podocytes crossing the G1/S checkpoint and undergoing abortive cytokinesis. In this study, we identified Pfn1 as indispensable in maintaining glomerular integrity - its tissue-specific loss in mouse podocytes results in severe proteinuria and kidney failure. Our results suggest that this phenotype is due to podocyte mitotic catastrophe (MC), characterized histologically and ultrastructurally by abundant multinucleated cells, irregular nuclei, and mitotic spindles. Podocyte cell cycle re-entry was identified using FUCCI2aR mice and observed altered expression of cell-cycle associated proteins such as p21, p53, Cyclin B1, and Cyclin D1. Podocyte-specific translating ribosome affinity purification (TRAP) and RNAseq revealed the downregulation of Ribosomal RNA-processing protein 8 (Rrp8). Over-expression of Rrp8 in Pfn1 KO podocytes partially rescued the phenotype in vitro. Clinical and ultrastructural tomographic analysis of patients with diverse proteinuric kidney diseases further validated the presence of MC podocytes and reduction in podocyte PFN1 expression within kidney tissues. These results suggest that profilin1 is essential in regulating the podocyte cell cycle and its disruption leads to MC and subsequent podocyte loss.
Authors
Xuefei Tian, Christopher E. Pedigo, Ke Li, Xiaotao Ma, Patricia Bunda, John Pell, Angela Lek, Jianlei Gu, Yan Zhang, Paulina X. Medina Rangel, Wei Li, Eike Schwartze, Soichiro Nagata, Gabriel Lerner, Sudhir Perincheri, Anupama Priyadarshini, Hongyu Zhao, Monkol Lek, Madhav C. Menon, Rongguo Fu, Shuta Ishibe
Abstract
Consumption of low dietary potassium, common with ultra-processed foods, activates the thiazide-sensitive sodium chloride cotransporter (NCC) via the WNK-SPAK kinase pathway to induce salt retention and elevate blood pressure (BP). However, it remains unclear how high potassium “DASH-like” diets inactivate the cotransporter and whether this decreases BP. A transcriptomic screen identified Ppp1C⍺, encoding PP1A, as a potassium up-regulated gene, and its negative regulator, Ppp1r1a, as a potassium-suppressed gene in the kidney. PP1A directly binds to and dephosphorylates NCC when extracellular potassium is elevated. Using mice genetically engineered to constitutively activate the NCC-regulatory kinase SPAK and thereby eliminate the effects of the WNK-SPAK kinase cascade, we confirmed that PP1A dephosphorylates NCC directly in a potassium-regulated manner. Prior adaptation to a high potassium diet was required to maximally dephosphorylate NCC and lower BP in the constitutively active SPAK mice, and this was associated with potassium-dependent suppression of Ppp1r1a, and dephosphorylation of its cognate protein, Inhibitory Subunit 1 (I1). In conclusion, potassium-dependent activation of PP1A and inhibition of I1 drives NCC dephosphorylation, providing a mechanism to explain how high dietary K+ lowers BP. Shifting signaling of PP1A in favor of activation of WNK-SPAK may provide an improved therapeutic approach for treating salt-sensitive hypertension.
Authors
Paul Richard Grimm, Anamaria Tatomir, Lena L. Rosenbaek, Bo Young Kim, Dimin Li, Eric J. Delpire, Robert A. Fenton, Paul A. Welling
Abstract
Diabetic kidney disease (DKD) can lead to end-stage kidney disease (ESKD) and mortality, however, few mechanistic biomarkers are available for high risk patients, especially those without macroalbuminuria. Urine from participants with diabetes from Chronic Renal Insufficiency Cohort (CRIC), Singapore Study of Macro-Angiopathy and Reactivity in Type 2 Diabetes (SMART2D), and the Pima Indian Study determined if urine adenine/creatinine ratio (UAdCR) could be a mechanistic biomarker for ESKD. ESKD and mortality were associated with the highest UAdCR tertile in CRIC (HR 1.57, 1.18, 2.10) and SMART2D (HR 1.77, 1.00, 3.12). ESKD was associated with the highest UAdCR tertile in patients without macroalbuminuria in CRIC (HR 2.36, 1.26, 4.39), SMART2D (HR 2.39, 1.08, 5.29), and Pima Indian study (HR 4.57, CI 1.37-13.34). Empagliflozin lowered UAdCR in non-macroalbuminuric participants. Spatial metabolomics localized adenine to kidney pathology and transcriptomics identified ribonucleoprotein biogenesis as a top pathway in proximal tubules of patients without macroalbuminuria, implicating mammalian target of rapamycin (mTOR). Adenine stimulated matrix in tubular cells via mTOR and stimulated mTOR in mouse kidneys. A specific inhibitor of adenine production was found to reduce kidney hypertrophy and kidney injury in diabetic mice. We propose that endogenous adenine may be a causative factor in DKD.
Authors
Kumar Sharma, Guanshi Zhang, Jens Hansen, Petter Bjornstad, Hak Joo Lee, Rajasree Menon, Leila Hejazi, Jian-Jun Liu, Anthony Franzone, Helen C. Looker, Byeong Yeob Choi, Roman Fernandez, Manjeri A. Venkatachalam, Luxcia Kugathasan, Vikas S. Sridhar, Loki Natarajan, Jing Zhang, Varun S. Sharma, Brian Kwan, Sushrut S. Waikar, Jonathan Himmelfarb, Katherine R. Tuttle, Bryan Kestenbaum, Tobias Fuhrer, Harold Feldman, Ian H. de Boer, Fabio C. Tucci, John Sedor, Hiddo Lambers Heerspink, Jennifer Schaub, Edgar A. Otto, Jeffrey B. Hodgin, Matthias Kretzler, Christopher R. Anderton, Theodore Alexandrov, David Cherney, Su Chi Lim, Robert G. Nelson, Jonathan Gelfond, Ravi Iyengar
Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)