Focal segmental glomerulosclerosis (FSGS) is a syndrome that involves kidney podocyte dysfunction and causes chronic kidney disease. Multiple factors including chemical toxicity, inflammation, and infection underlie FSGS; however, highly penetrant disease genes have been identified in a small fraction of patients with a family history of FSGS. Variants of apolipoprotein L1 (
Haiyang Yu, Mykyta Artomov, Sebastian Brähler, M. Christine Stander, Ghaidan Shamsan, Matthew G. Sampson, J. Michael White, Matthias Kretzler, Jeffrey H. Miner, Sanjay Jain, Cheryl A. Winkler, Robi D. Mitra, Jeffrey B. Kopp, Mark J. Daly, Andrey S. Shaw
Chronic kidney disease (CKD) has been associated with impaired host response and increased susceptibility to infections. Leukocyte recruitment during inflammation must be tightly regulated to protect the host against pathogens. FGF23 levels are increased in blood during CKD, and levels of this hormone have been associated with a variety of adverse effects in CKD patients. Here, we have shown that CKD impairs leukocyte recruitment into inflamed tissue and host defense in mice and humans. FGF23 neutralization during CKD in murine models restored leukocyte recruitment and host defense. Intravital microscopy of animals with chronic kidney failure showed that FGF23 inhibits chemokine-activated leukocyte arrest on the endothelium, and downregulation of FGF receptor 2 (FGFR2) on PMNs rescued host defense in these mice. In vitro, FGF23 inhibited PMN adhesion, arrest under flow, and transendothelial migration. Mechanistically, FGF23 binding to FGFR2 counteracted selectin- and chemokine-triggered β2 integrin activation on PMNs by activating protein kinase A (PKA) and inhibiting activation of the small GTPase Rap1. Moreover, knockdown of PKA abolished the inhibitory effect of FGF23 on integrin activation. Together, our data reveal that FGF23 acts directly on PMNs and dampens host defense by direct interference with chemokine signaling and integrin activation.
Jan Rossaint, Jessica Oehmichen, Hugo Van Aken, Stefan Reuter, Hermann J. Pavenstädt, Melanie Meersch, Mark Unruh, Alexander Zarbock
Renal erythropoietin-producing cells (REPCs) remain in the kidneys of patients with chronic kidney disease, but these cells do not produce sufficient erythropoietin in response to hypoxic stimuli. Treatment with HIF stabilizers rescues erythropoietin production in these cells, but the mechanisms underlying the decreased response of REPCs in fibrotic kidneys to anemic stimulation remain elusive. Here, we show that fibroblast-like FOXD1+ progenitor-derived kidney pericytes, which are characterized by the expression of α1 type I collagen and PDGFRβ, produce erythropoietin through HIF2α regulation but that production is repressed when these cells differentiate into myofibroblasts. DNA methyltransferases and erythropoietin hypermethylation are upregulated in myofibroblasts. Exposure of myofibroblasts to nanomolar concentrations of the demethylating agent 5-azacytidine increased basal expression and hypoxic induction of erythropoietin. Mechanistically, the profibrotic factor TGF-β1 induced hypermethylation and repression of erythropoietin in pericytes; these effects were prevented by 5-azacytidine treatment. These findings shed light on the molecular mechanisms underlying erythropoietin repression in kidney myofibroblasts and demonstrate that clinically relevant, nontoxic doses of 5-azacytidine can restore erythropoietin production and ameliorate anemia in the setting of kidney fibrosis in mice.
Yu-Ting Chang, Ching-Chin Yang, Szu-Yu Pan, Yu-Hsiang Chou, Fan-Chi Chang, Chun-Fu Lai, Ming-Hsuan Tsai, Huan-Lun Hsu, Ching-Hung Lin, Wen-Chih Chiang, Ming-Shiou Wu, Tzong-Shinn Chu, Yung-Ming Chen, Shuei-Liong Lin
Vascular oxidative injury accompanies many common conditions associated with hypertension. In the present study, we employed mouse models with excessive vascular production of ROS (tgsm/p22phox mice, which overexpress the NADPH oxidase subunit p22
Jing Wu, Mohamed A. Saleh, Annet Kirabo, Hana A. Itani, Kim Ramil C. Montaniel, Liang Xiao, Wei Chen, Raymond L. Mernaugh, Hua Cai, Kenneth E. Bernstein, Jörg J. Goronzy, Cornelia M. Weyand, John A. Curci, Natalia R. Barbaro, Heitor Moreno, Sean S. Davies, L. Jackson Roberts II, Meena S. Madhur, David G. Harrison
The nephron cortical collecting duct (CCD) is composed of principal cells, which mediate Na, K, and water transport, and intercalated cells (ICs), which are specialized for acid-base transport. There are two canonical IC forms: acid-secreting α-ICs and HCO3-secreting β-ICs. Chronic acidosis increases α-ICs at the expense of β-ICs, thereby increasing net acid secretion by the CCD. We found by growth factor quantitative PCR array that acidosis increases expression of mRNA encoding SDF1 (or CXCL12) in kidney cortex and isolated CCDs from mouse and rabbit kidney cortex. Exogenous SDF1 or pH 6.8 media increased H+ secretion and decreased HCO3 secretion in isolated perfused rabbit CCDs. Acid-dependent changes in H+ and HCO3 secretion were largely blunted by AMD3100, which selectively blocks the SDF1 receptor CXCR4. In mice, diet-induced chronic acidosis increased α-ICs and decreased β-ICs. Additionally, IC-specific
George J. Schwartz, XiaoBo Gao, Shuichi Tsuruoka, Jeffrey M. Purkerson, Hu Peng, Vivette D’Agati, Nicolas Picard, Dominique Eladari, Qais Al-Awqati
Inhibition of prostaglandin (PG) production with either nonselective or selective inhibitors of cyclooxygenase-2 (COX-2) activity can induce or exacerbate salt-sensitive hypertension. This effect has been previously attributed to inhibition of intrinsic renal COX-2 activity and subsequent increase in sodium retention by the kidney. Here, we found that macrophages isolated from kidneys of high-salt–treated WT mice have increased levels of COX-2 and microsomal PGE synthase–1 (mPGES-1). Furthermore, BM transplantation (BMT) from either COX-2–deficient or mPGES-1–deficient mice into WT mice or macrophage-specific deletion of the PGE2 type 4 (EP4) receptor induced salt-sensitive hypertension and increased phosphorylation of the renal sodium chloride cotransporter (NCC). Kidneys from high-salt–treated WT mice transplanted with
Ming-Zhi Zhang, Bing Yao, Yinqiu Wang, Shilin Yang, Suwan Wang, Xiaofeng Fan, Raymond C. Harris
A high intake of dietary salt (NaCl) has been implicated in the development of hypertension, chronic inflammation, and autoimmune diseases. We have recently shown that salt has a proinflammatory effect and boosts the activation of Th17 cells and the activation of classical, LPS-induced macrophages (M1). Here, we examined how the activation of alternative (M2) macrophages is affected by salt. In stark contrast to Th17 cells and M1 macrophages, high salt blunted the alternative activation of BM-derived mouse macrophages stimulated with IL-4 and IL-13, M(IL-4+IL-13) macrophages. Salt-induced reduction of M(IL-4+IL-13) activation was not associated with increased polarization toward a proinflammatory M1 phenotype. In vitro, high salt decreased the ability of M(IL-4+IL-13) macrophages to suppress effector T cell proliferation. Moreover, mice fed a high salt diet exhibited reduced M2 activation following chitin injection and delayed wound healing compared with control animals. We further identified a high salt–induced reduction in glycolysis and mitochondrial metabolic output, coupled with blunted AKT and mTOR signaling, which indicates a mechanism by which NaCl inhibits full M2 macrophage activation. Collectively, this study provides evidence that high salt reduces noninflammatory innate immune cell activation and may thus lead to an overall imbalance in immune homeostasis.
Katrina J. Binger, Matthias Gebhardt, Matthias Heinig, Carola Rintisch, Agnes Schroeder, Wolfgang Neuhofer, Karl Hilgers, Arndt Manzel, Christian Schwartz, Markus Kleinewietfeld, Jakob Voelkl, Valentin Schatz, Ralf A. Linker, Florian Lang, David Voehringer, Mark D. Wright, Norbert Hubner, Ralf Dechend, Jonathan Jantsch, Jens Titze, Dominik N. Müller
Calcium/calcineurin signaling is critical for normal cellular physiology. Abnormalities in this pathway cause many diseases, including podocytopathy; therefore, understanding the mechanisms that underlie the regulation of calcium/calcineurin signaling is essential. Here, we showed that critical components of calcium/calcineurin signaling, including
Junnan Wu, Chunxia Zheng, Xiao Wang, Shifeng Yun, Yue Zhao, Lin Liu, Yuqiu Lu, Yuting Ye, Xiaodong Zhu, Changming Zhang, Shaolin Shi, Zhihong Liu
Juvenile ciliopathy syndromes that are associated with renal cysts and premature renal failure are commonly the result of mutations in the gene encoding centrosomal protein CEP290. In addition to centrosomes and the transition zone at the base of the primary cilium, CEP290 also localizes to the nucleus; however, the nuclear function of CEP290 is unknown. Here, we demonstrate that reduction of cellular CEP290 in primary human and mouse kidney cells as well as in zebrafish embryos leads to enhanced DNA damage signaling and accumulation of DNA breaks ex vivo and in vivo. Compared with those from WT mice, primary kidney cells from
Gisela G. Slaats, Joshua C. Saldivar, Julien Bacal, Michelle K. Zeman, Andrew C. Kile, Ann Marie Hynes, Shalabh Srivastava, Jekaterina Nazmutdinova, Krista den Ouden, Miriam S. Zagers, Veronica Foletto, Marianne C. Verhaar, Colin Miles, John A. Sayer, Karlene A. Cimprich, Rachel H. Giles
The thiazide-sensitive NaCl cotransporter (NCC) is important for renal salt handling and blood-pressure homeostasis. The canonical NCC-activating pathway consists of With-No-Lysine (WNK) kinases and their downstream effector kinases SPAK and OSR1, which phosphorylate NCC directly. The upstream mechanisms that connect physiological stimuli to this system remain obscure. Here, we have shown that aldosterone activates SPAK/OSR1 via WNK1. We identified 2 alternatively spliced exons embedded within a proline-rich region of WNK1 that contain PY motifs, which bind the E3 ubiquitin ligase NEDD4-2. PY motif–containing WNK1 isoforms were expressed in human kidney, and these isoforms were efficiently degraded by the ubiquitin proteasome system, an effect reversed by the aldosterone-induced kinase SGK1. In gene-edited cells, WNK1 deficiency negated regulatory effects of NEDD4-2 and SGK1 on NCC, suggesting that WNK1 mediates aldosterone-dependent activity of the WNK/SPAK/OSR1 pathway. Aldosterone infusion increased proline-rich WNK1 isoform abundance in WT mice but did not alter WNK1 abundance in hypertensive
Ankita Roy, Lama Al-Qusairi, Bridget F. Donnelly, Caroline Ronzaud, Allison L. Marciszyn, Fan Gong, Y.P. Christy Chang, Michael B. Butterworth, Núria M. Pastor-Soler, Kenneth R. Hallows, Olivier Staub, Arohan R. Subramanya