Fibrotic diseases account for nearly half of all deaths in the developed world. Despite its importance, the pathogenesis of fibrosis remains poorly understood. Recently, the two mechanosensitive transcription cofactors YAP and TAZ have emerged as important profibrotic regulators in multiple murine tissues. Despite this growing recognition, a number of important questions remain unanswered, including which cell types require YAP/TAZ activation for fibrosis to occur and the time course of this activation. Here, we present a detailed analysis of the role that myofibroblast YAP and TAZ play in organ fibrosis and the kinetics of their activation. Using analyses of cells, as well as multiple murine and human tissues, we demonstrated that myofibroblast YAP and TAZ were activated early after organ injury and that this activation was sustained. We further demonstrated the critical importance of myofibroblast YAP/TAZ in driving progressive scarring in the kidney, lung, and liver, using multiple transgenic models in which YAP and TAZ were either deleted or hyperactivated. Taken together, these data establish the importance of early injury-induced myofibroblast YAP and TAZ activation as a key event driving fibrosis in multiple organs. This information should help guide the development of new antifibrotic YAP/TAZ inhibition strategies.
Xiaolin He, Monica F. Tolosa, Tianzhou Zhang, Santosh Kumar Goru, Luisa Ulloa Severino, Paraish S. Misra, Caitríona M. McEvoy, Lauren Caldwell, Stephen G. Szeto, Feng Gao, Xiaolan Chen, Cassandra Atin, Victoria Ki, Noah Vukosa, Catherine Hu, Johnny Zhang, Christopher Yip, Adriana Krizova, Jeffrey L. Wrana, Darren A. Yuen
IgA nephropathy (IgAN) is a leading cause of kidney failure, yet little is known about the immunopathogenesis of this disease. IgAN is characterized by deposition of IgA in the kidney glomeruli, but the source and stimulus for IgA production is not known. Clinical and experimental data suggest a role for aberrant immune responses to mucosal microbiota in IgAN, and in some countries of high disease prevalence tonsillectomy is regarded as standard-of-care therapy. To evaluate the relationship between microbiota and mucosal immune responses we characterized the tonsil microbiota in patients with IgAN versus non-related household-matched control subjects and identified increased carriage of the genus Neisseria and elevated Neisseria-targeted serum IgA in IgAN cases. We reverse-translated these findings in experimental IgAN driven by BAFF overexpression in BAFF-transgenic mice, rendered susceptible to Neisseria infection by introduction of a humanized CEACAM-1 transgene (B x hC-Tg). Colonization of B x hC-Tg mice with Neisseria yielded augmented levels of systemic Neisseria-specific IgA. Using a custom ELISPOT assay, we discovered anti-Neisseria-specific IgA-secreting cells within in the kidneys of these mice. These findings suggest a role for cytokine-driven aberrant mucosal immune responses to oropharyngeal pathobionts such as Neisseria in the immunopathogenesis of IgAN. Furthermore, in the presence of excess BAFF, pathobiont-specific IgA can be produced in situ within the kidney.
Elissa G. Currie, Bryan Coburn, Elisa A. Porfilio, Ping Lam, Olga L. Rojas, Jan Novak, Stuart Yang, Raad B. Chowdhury, Lesley A. Ward, Pauline W. Wang, Khashayar Khaleghi, James An, Sarah Q. Crome, Michelle A. Hladunewich, Sean J. Barbour, Daniel C. Cattran, Rulan S. Parekh, Christoph Licht, Rohan John, Rupert Kaul, Kenneth Croitoru, Scott D. Gray-Owen, David S. Guttman, Jennifer L. Gommerman, Heather N. Reich
Molecular chaperones are responsible for maintaining cellular homeostasis, and one such chaperone, GRP170, is an endoplasmic reticulum (ER) resident that oversees both protein biogenesis and quality control. We previously discovered that GRP170 regulates the degradation and assembly of the epithelial sodium channel (ENaC), which reabsorbs sodium in the distal nephron and thereby regulates salt-water homeostasis and blood pressure. To define the role of GRP170 and more generally molecular chaperones in kidney physiology, we developed an inducible, nephron-specific GRP170 knockout mouse. Here we show that GRP170 deficiency causes a dramatic phenotype: profound hypovolemia, hyperaldosteronemia, and dysregulation of ion homeostasis, all of which are associated with the loss of ENaC. Additionally, the GRP170 KO mouse exhibits hallmarks of acute kidney injury (AKI). We further demonstrate that the unfolded protein response (UPR) is activated in the GRP170 deficient mouse. Notably, the UPR is also activated in AKI when originating from various other etiologies, including ischemia, sepsis, glomerulonephritis, nephrotic syndrome, and transplant rejection. Our work establishes the central role of GRP170 in kidney homeostasis and directly links molecular chaperone function to kidney injury.
Aidan W. Porter, Diep N. Nguyen, Dennis R. Clayton, Wily G. Ruiz, Stephanie M. Mutchler, Evan C. Ray, Allison L. Marciszyn, Lubika J. Nkashama, Arohan R. Subramanya, Sebastien Gingras, Thomas R. Kleyman, Gerard Apodaca, Linda M. Hendershot, Jeffrey L. Brodsky, Teresa M. Buck
Aristolochic acid (AA) is the causative nephrotoxic alkaloid in aristolochic acid nephropathy, which results in a tubulointerstitial fibrosis. AA causes direct proximal tubule damage. There is also an influx of macrophages, although their role in the pathogenesis is poorly understood. Here we demonstrate that AA directly stimulates migration, inflammation, and reactive oxygen species (ROS) production in macrophages ex vivo. Cells lacking interferon regulatory factor 4 (IRF4), a known regulator of macrophage migration and phenotype, had a reduced migratory response, though effects on ROS production and inflammation were preserved or increased relative to wild-type cells. Macrophage-specific IRF4 knockout mice were protected from both acute and chronic kidney effects of AA administration based on functional and histological analysis. Renal macrophages from kidneys of AA-treated macrophage-specific IRF4 knockout mice demonstrated increased apoptosis and ROS production compared with wildtype controls, indicating that AA directly polarizes macrophages to a promigratory and proinflammatory phenotype. However, knockout mice had reduced renal macrophage abundance following AA administration. While macrophages lacking IRF4 can adopt a proinflammatory phenotype upon AA exposure, their inability to migrate to the kidney and increased rates of apoptosis upon infiltration provide protection from AA in vivo. These results provide evidence of direct AA effects on macrophages in AAN and add to the growing body of evidence that supports a key role of IRF4 in modulating macrophage function in kidney injury.
Kensuke Sasaki, Andrew S. Terker, Jiaqi Tang, Shirong Cao, Juan Pablo Arroyo, Aolei Niu, Suwan Wang, Xiaofeng Fan, Yahua Zhang, Stephanie R. Bennett, Ming-zhi Zhang, Raymond C. Harris
The G-protein coupled C-X-C chemokine receptor 4 (CXCR4) is a candidate therapeutic target for tissue fibrosis. A novel fully human single-domain antibody-like scaffold i-body AD-114-PA600 (AD-114) with specific high binding affinity to CXCR4 has been developed. To define the renoprotective role, AD-114 was administrated in a mouse model of renal fibrosis induced by folic acid (FA). Increased extracellular matrix (ECM) accumulation, macrophage infiltration, inflammatory response, transforming growth factor beta-1 (TGF-β1) expression and fibroblasts activation were observed in kidneys of mice with FA-induced nephropathy. These markers were normalized or partially reversed by AD-114 treatment. In vitro studies demonstrated AD-114 blocked TGF-β1-induced upregulated expression of ECM, matrix metallopeptidase-2 (MMP-2) and downstream p38 mitogen-activated protein kinases (p38 MAPK) and Phosphoinositide 3-kinases (PI3K)/AKT/ mammalian target of rapamycin (mTOR) signaling pathways in a renal proximal tubular cell line. Additionally, these renoprotective effects were validated in a second model of unilateral ureteral obstruction (UUO) using a second generation of AD-114 (Fc-fused AD-114, also named AD-214). Collectively, these results suggest a renoprotective role of AD-114 as it inhibited the chemotactic function of CXCR4 as well as blocked CXCR4 downstream p38 MAPK and PI3K/AKT/mTOR signaling, which establish a therapeutic strategy for AD-114 targeting CXCR4 to limit renal fibrosis.
Qinghua Cao, Chunling Huang, Hao Yi, Anthony J. Gill, Angela Chou, Michael Foley, Chris G. Hosking, Kevin K. Lim, Cristina F. Triffon, Ying Shi, Xin-Ming Chen, Carol A. Pollock
Discoidin domain receptor 1 (DDR1), a receptor tyrosine kinase activated by collagen, contributes to chronic kidney disease (CKD). However, its role in acute kidney injury (AKI) and subsequent development of kidney fibrosis is not clear. Thus, we performed a model of severe ischemia-reperfusion-induced AKI that progresses to kidney fibrosis in wild-type and Ddr1-null mice. We show that Ddr1-null mice had reduced acute tubular injury, inflammation, and tubulointerstitial fibrosis with overall decreased renal monocyte chemoattractant protein (MCP-1) levels and STAT3 activation. We identified breakpoint cluster region (BCR) protein as a phosphorylated target of DDR1 that controls MCP-1 production in renal proximal tubule epithelial cells. DDR1-induced BCR phosphorylation or BCR downregulation increased MCP-1 secretion, suggesting that BCR negatively regulates the levels of MCP-1. Mechanistically, phosphorylation or downregulation of BCR increases β-catenin activity and in turn MCP-1 production. Finally, we show that DDR1-mediated STAT3 activation is required to stimulate the secretion of TGF-β. Thus, DDR1 contributes to acute and chronic kidney injury by regulating BCR and STAT3 phosphorylation and in turn the production of MCP-1 and TGF-β. These findings identify DDR1 an attractive therapeutic target for ameliorating both pro-inflammatory and pro-fibrotic signaling in kidney disease.
Corina M. Borza, Gema Bolas, Fabian Bock, Xiuqi Zhang, Favour C. Akabogu, Ming-Zhi Zhang, Mark de Caestecker, Min Yang, Hai-chun Yang, Ethan Lee, Leslie Gewin, Agnes B. Fogo, W. Hayes McDonald, Roy Zent, Ambra Pozzi
Exchange proteins directly activated by cAMP (Epacs) are abundantly expressed in the renal tubules. We used genetic and pharmacological tools in combination with balance, electrophysiological and biochemical approaches to examine the role of Epac1 and Epac2 in renal sodium handling. We demonstrate that Epac1-/- and Epac2-/- mice exhibit a delayed anti-natriuresis to dietary sodium restriction despite augmented aldosterone levels. This was associated with a significantly lower response to the epithelial Na+ channel (ENaC) blocker amiloride, reduced ENaC activity in split-opened collecting ducts, and defective posttranslational processing of α and γENaC subunits in the knockout mice fed with Na+ deficient diet. Concomitant deletion of both isoforms led to a marginally greater natriuresis but further increased aldosterone levels. Epac2 blocker, ESI-05 and Epac1&2 blocker, ESI-09 decreased ENaC activity in EpacWT mice kept on Na+ deficient diet but not on the regular diet. ESI-09 injections led to natriuresis in EpacWT mice on Na+ deficient diet, which was caused by ENaC inhibition. In summary, our results demonstrate non-redundant actions of Epac1 and Epac2 in stimulation of ENaC activity during variations in dietary salt intake. We speculate that inhibition of Epac signaling could be instrumental in treatment of hypertensive states associated with ENaC over-activation.
Victor N. Tomilin, Kyrylo Pyrshev, Anna Stavniichuk, Naghmeh Hassanzadeh Khayyat, Guohui Ren, Oleg Zaika, Sherif Khedr, Alexander Staruschenko, Fang C. Mei, Xiaodong Cheng, Oleh Pochynyuk
We performed next generation sequencing in patients with familial steroid sensitive nephrotic syndrome (SSNS) and identified a homozygous segregating variant (p.H310Y) in the gene encoding clavesin-1 (CLVS1) in a consanguineous family with three affected individuals. Knockdown of the clavesin gene in zebrafish (clvs2) produced edema phenotypes due to disruption of podocyte structure and loss of glomerular filtration barrier integrity that can be rescued by WT CLVS1 but not the p.H310Y variant. Analysis of cultured human podocytes with CRISPR-Cas9 mediated CLVS1 knockout or homozygous H310Y knockin revealed deficits in clathrin-mediated endocytosis and increased susceptibility to apoptosis that could be rescued with corticosteroid treatment, mimicking the steroid-responsiveness observed in SSNS patients. The p.H310Y variant also disrupts binding of clavesin-1 to alpha-tocopherol transfer protein, resulting in increased reactive oxygen species (ROS) accumulation in CLVS1-deficient podocytes. Treatment of CLVS1 knockout or homozygous H310Y knockin podocytes with pharmacological ROS inhibitors restored viability to control levels. Taken together, this data identifies CLVS1 as a candidate gene for SSNS, provides insight into therapeutic effects of corticosteroids on podocyte cellular dynamics and adds to the growing evidence on the importance of endocytosis and oxidative stress regulation to podocyte function.
Brandon M. Lane, Megan Chryst-Stangl, Guanghong Wu, Mohamed Shalaby, Sherif El Desoky, Claire C. Middleton, Kinsie Huggins, Amika Sood, Alejandro Ochoa, Andrew F. Malone, Ricardo Vancini, Sara E. Miller, Gentzon Hall, So Young Kim, David N. Howell, Jameela A. Kari, Rasheed Gbadegesin
Cisplatin is a commonly used chemotherapeutic agent to treat a wide array of cancers that is frequently associated with toxic injury to the kidney due to oxidative DNA damage and perturbations in cell cycle progression leading to cell death. In this study, we investigated whether thyroid receptor interacting protein 13 (TRIP13) plays a central role in the protection of the tubular epithelia following cisplatin treatment by circumventing DNA damage. Following cisplatin treatment, double-stranded DNA repair pathways were inhibited using selective blockers to proteins involved in either homologous recombination or non-homologous end joining. This led to increased blood markers of acute kidney injury (AKI) (creatinine and neutrophil gelatinase–associated lipocalin), tubular damage, activation of DNA damage marker (γ-H2AX), elevated appearance of G2/M blockade (phosphorylated histone H3 Ser10 and cyclin B1), and apoptosis (cleaved caspase-3). Conditional proximal tubule–expressing Trip13 mice were observed to be virtually protected from the cisplatin nephrotoxicity by restoring most of the pathological phenotypes back toward normal conditions. Our findings suggest that TRIP13 could circumvent DNA damage in the proximal tubules during cisplatin injury and that TRIP13 may constitute a new therapeutic target in protecting the kidney from nephrotoxicants and reduce outcomes leading to AKI.
Taketsugu Hama, Prashanth K.B. Nagesh, Pallabita Chowdhury, Bob M. Moore II, Murali M. Yallapu, Kevin R. Regner, Frank Park
Alport syndrome (AS) is a genetic disorder caused by mutations in type IV collagen that leads to defective glomerular basement membrane, glomerular filtration barrier (GFB) damage, and progressive chronic kidney disease. While the genetic basis of AS is well known, the molecular and cellular mechanistic details of disease pathogenesis have been elusive, hindering the development of mechanism-based therapies. Here we performed intravital multiphoton imaging of the local kidney tissue microenvironment in a X-linked AS mouse model to directly visualize the major drivers of AS pathology. Severely distended glomerular capillaries and aneurysms were found accompanied by numerous microthrombi, increased glomerular endothelial surface layer (glycocalyx) and immune cell homing, GFB albumin leakage, glomerulosclerosis and interstitial fibrosis by 5 months of age with an intermediate phenotype at 2 months. Renal histology in mouse or patient tissues largely failed to detect capillary aberrations. Treatment of AS mice with hyaluronidase or the ACE inhibitor enalapril reduced the excess glomerular endothelial glycocalyx and blocked immune cell homing, and GFB albumin leakage. This study identified central roles of glomerular mechanical forces and endothelial and immune cell activation early in AS, which could be therapeutically targeted to reduce mechanical strain and local tissue inflammation and improve kidney function.
Georgina Gyarmati, Urvi Nikhil Shroff, Audrey Izuhara, Xiaogang Hou, Stefano Da Sacco, Sargis Sedrakyan, Kevin V. Lemley, Kerstin Amann, Laura Perin, János Peti-Peterdi
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