Acute kidney injury (AKI) secondary to sepsis results in poor outcomes and conventional kidney function indicators lack diagnostic value. Soluble urokinase plasminogen activator receptor (suPAR) is an innate immune–derived molecule implicated in inflammatory organ damage. We characterized the diagnostic ability of longitudinal serum suPAR levels to discriminate severity and course of sepsis-induced AKI (SI-AKI) in 200 critically ill patients meeting Sepsis-3 criteria. The pathophysiologic relevance of varying suPAR levels in SI-AKI was explored in a polymicrobial sepsis model in WT, (s)uPAR-knockout, and transgenic suPAR-overexpressing mice. At all time points studied, suPAR provided a robust classification of SI-AKI disease severity, with improved prediction of renal replacement therapy (RRT) and mortality compared with established kidney biomarkers. Patients with suPAR levels of greater than 12.7 ng/mL were at highest risk for RRT or death, with an adjusted odds ratio of 7.48 (95% CI, 3.00–18.63). suPAR deficiency protected mice against SI-AKI. suPAR-overexpressing mice exhibited greater kidney damage and poorer survival through inflamed kidneys, accompanied by local upregulation of potent chemoattractants and pronounced kidney T cell infiltration. Hence, suPAR allows for an innate immune–derived and kidney function–independent staging of SI-AKI and offers improved longitudinal risk stratification. suPAR promotes T cell–based kidney inflammation, while suPAR deficiency improves SI-AKI.
Christian Nusshag, Changli Wei, Eunsil Hahm, Salim S. Hayek, Jing Li, Beata Samelko, Christoph Rupp, Roman Szudarek, Claudius Speer, Florian Kälble, Matthias Schaier, Florian Uhle, Felix C.F. Schmitt, Mascha O. Fiedler, Ellen Krautkrämer, Yanxia Cao, Ricardo Rodriguez, Uta Merle, Jesper Eugen-Olsen, Martin Zeier, Markus A. Weigand, Christian Morath, Thorsten Brenner, Jochen Reiser
BACKGROUND. Longitudinal investigations of murine acute kidney injury (AKI) suggest that injury and inflammation may persist long after the initial insult. However, the evolution of these processes and their prognostic values are unknown in patients with AKI. METHODS. In a prospective cohort of 656 participants hospitalized with AKI, we measured seven urine and two plasma biomarkers of kidney injury, inflammation, and tubular health at multiple timepoints from the diagnosis to 12 months after AKI. We used linear mixed-effect models to estimate biomarker changes over time, and used Cox proportional hazard regressions to determine their associations with a composite outcome of CKD incidence and progression. We compared the gene expression kinetics of biomarkers in murine models of repair and atrophy after ischemic reperfusion injury (IRI). RESULTS. After 4.3 years, 106 and 52 participants developed incident CKD and CKD progression, respectively. Each standard deviation increases in the change of urine KIM-1, MCP-1 and plasma TNFR1 from baseline to 12 months was associated with 2-3-fold increased risk for CKD, while the increase in urine UMOD was associated with 40% reduced risk for CKD. The trajectories of these biological processes were associated with progression to kidney atrophy in mice after IRI. CONCLUSION. Sustained tissue injury and inflammation, and slower restoration of tubular health are associated with higher risk of kidney disease progression. Further investigation into these ongoing biological processes may help understand and prevent the AKI-to-CKD transition. FUNDING. NIH and NIDDK (grants U01DK082223, U01DK082185, U01DK082192, U01DK082183, R01DK098233, R01DK101507, R01DK114014, K23DK100468, R03DK111881, K01DK120783, and R01DK093771).
Yumeng Wen, Leyuan Xu, Isabel A. Melchinger, Heather Thiessen-Philbrook, Dennis G. Moledina, Steven G. Coca, Chi-yuan Hsu, Alan S. Go, Kathleen D. Liu, Edward D. Siew, T. Alp Ikizler, Vernon M. Chinchilli, James S. Kaufman, Paul L. Kimmel, Jonathan Himmelfarb, Lloyd G. Cantley, Chirag R. Parikh
Cisplatin is a widely used chemotherapy drug but it induces both acute and chronic kidney diseases (CKD) in cancer patients. The pathogenesis of cisplatin-induced CKD is unclear and effective renoprotective approaches are not available. Here, we report that repeated low-dose cisplatin (RLDC) treatment of C57BL/6 mice induced chronic cellular senescence in kidney tubules, accompanied with tubular degeneration and pro-fibrotic phenotype transformation that culminated in maladaptive repair and renal fibrosis. Suppression of tubular senescence by senolytic drugs ABT-263 and Fisetin attenuated renal fibrosis and improved tubular repair as indicated by restoration of tubular regeneration and renal function. In vitro, RLDC also induced senescence in mouse proximal tubular BUMPT cells. ABT-263 eliminated senescent BUMPT cells following RLDC treatment, reversed the pro-fibrotic phenotype of the cells and increased their clonogenic activity. Moreover, ABT-263 alleviated the paracrine effect of RLDC-treated BUMPT cells on fibroblasts for fibrosis. Consistently, knockdown of p16 suppressed post-RLDC senescence and fibrotic changes in BUMPT cells, and alleviated their paracrine effects on renal fibroblast proliferation. These results indicate that persistent induction of tubular senescence plays an important role in promoting cisplatin-induced CKD. Targeting senescent tubular cells may be efficient to improve kidney repair for the prevention and treatment of cisplatin-induced CKD.
Siyao Li, Man J. Livingston, Zhengwei Ma, Xiaoru Hu, Lu Wen, Han-Fei Ding, Daohong Zhou, Zheng Dong
Despite recent progress in the identification of mediators of podocyte injury, mechanisms underlying podocyte loss remain poorly understood, and cell-specific therapy is lacking. We previously reported that KIBRA, KIdney and BRAin expressed protein, encoded by WWC1, promotes podocyte injury in vitro through activation of the Hippo signaling pathway. KIBRA expression is increased in the glomeruli of patients with focal segmental glomerulosclerosis (FSGS), and KIBRA depletion in vivo is protective against acute podocyte injury. Here, we tested the consequences of transgenic podocyte-specific WWC1 expression in immortalized human podocytes and in mice, and we explored the association between glomerular WWC1 expression and glomerular disease progression. We found that KIBRA overexpression in immortalized human podocytes promoted cytoplasmic localization of YAP (Yes-associated protein), induced actin cytoskeletal reorganization, and altered focal adhesion expression and morphology. Transgenic WWC1 (KIBRA OE) mice were more susceptible to acute and chronic glomerular injury, with evidence of YAP inhibition in vivo. Of clinical relevance, glomerular WWC1 expression negatively correlated with renal survival among patients with primary glomerular diseases. These findings highlight the importance of KIBRA-YAP signaling to the regulation of podocyte structural integrity and identify KIBRA-mediated injury as a potential target for podocyte-specific therapy in glomerular disease.
Kristin Meliambro, Yanfeng Yang, Marina de Cos, Estefania Rodriguez-Ballestas, Caroline Malkin, Jonathan C. Haydak, John R. Lee, Fadi Salem, Laura H. Mariani, Ronald E. Gordon, John M. Basgen, Huei Hsun Wen, Jia Fu, Evren U. Azeloglu, John Cijiang He, Jenny S. Wong, Kirk N. Campbell
We examine whether calcineurin or protein-phosphatase-2B (PP2B) regulates the basolateral Kir4.1/Kir5.1 in distal-convoluted-tubule (DCT). Application of tacrolimus (FK506) or cyclosporine-A (CsA) increased whole-cell-Kir4.1/Kir5.1-mediated-K+-currents and hyperpolarized DCT-membrane. Moreover, FK506-induced-stimulation of Kir4.1/Kir5.1 was absent in kidney-tubule-specific 12-kDa-FK506-binding-protein knockout-mice (Ks-FKBP-12-KO). In contrast, CsA still stimulated Kir4.1/Kir5.1 of the DCT in Ks-FKBP-12-KO mice, suggesting that FK506-induced stimulation of Kir4.1/Kir5.1 was due to inhibiting PP2B. Single-channel-patch-clamp experiments demonstrated that FK506 or CsA stimulated the basolateral Kir4.1/Kir5.1-activity of DCT, defined by NPo (a product of channel-Number- and- Open-Probability). However, this effect was absent in the DCT treated with Src-family-protein-tyrosine-kinase (SFK) inhibitor or hydroxyl-peroxide which stimulates SFK. Fluorescence-image demonstrated that CsA-treatment increased membrane-staining-intensity of Kir4.1 in the DCT of Kcnj10flox/flox mice. Moreover, CsA-treatment has no obvious effect on pNCC expression in Ks-Kir4.1-KO mice. Immunoblotting showed that acute FK506 treatment increased pNCC-expression in Kcnj10flox/flox mice, but this effect was attenuated in Ks-Kir4.1-KO mice. In vivo measurement of thiazide-induced-renal-Na+ excretion demonstrated that FK506 enhanced thiazide-induced natriuresis. This effect was absent in Ks-FKBP-12-KO mice and blunted in Ks-Kir4.1-KO mice. We conclude that inhibition of PP2B stimulates Kir4.1/Kir5.1 of DCT and NCC, and that PP2B-inhibition-induced stimulation of NCC is partially achieved by stimulation of the basolateral Kir4.1/Kir5.1.
Dan-Dan Zhang, Xin-Peng Duan, Kerim Mutig, Franziska Rausch, Yu Xiao, Jun-Ya Zheng, Dao-Hong Lin, Wen-Hui Wang
The transcription factor c-Maf has been widely studied and has been reported to play a critical role in embryonic kidney development; however, the postnatal functions of c-Maf in adult kidneys remain unknown as c-Maf null C57BL/6J mice exhibit embryonic lethality. In this study, we investigated the role of c-Maf in adult mouse kidneys by comparing the phenotypes of tamoxifen (TAM)-inducible c-Maf knockout mice (c-Maf flox/flox; CAG-Cre-ERTM mice named “c-Maf ΔTAM”) with c-Maf flox/flox control mice10 days after TAM injection (TAM(10d)). In addition, we examined the effects of c-Maf deletion on diabetic conditions by injecting the mice with streptozotocin (STZ) four weeks before TAM injection. c-Maf ΔTAM mice displayed primary glycosuria caused by Sglt2 and Glut2 downregulation in the kidneys without diabetes, as well as morphological changes and life-threatening injuries in the kidneys on TAM(10d). Under diabetic conditions, c-Maf deletion promoted recovery from hyperglycemia and suppressed albuminuria and diabetic nephropathy by causing similar effects to Sglt2 knockout and SGLT2 inhibitors. In addition to demonstrating the unique gene regulation of c-Maf, these findings highlight the renoprotective effects of c-Maf deficiency under diabetic conditions and suggest that c-Maf could be a novel therapeutic target gene for treating diabetic nephropathy.
Mitsunori Fujino, Naoki Morito, Takuto Hayashi, Masami Ojima, Shun Ishibashi, Akihiro Kuno, Seizo Koshiba, Kunihiro Yamagata, Satoru Takahashi
Acute kidney failure and chronic kidney disease are global health issues steadily rising in incidence and prevalence. Animal models on a single genetic background have so far failed to recapitulate the clinical presentation of human nephropathies. Here, we used a simple model of folic acid–induced kidney injury in 7 highly diverse mouse strains. We measured plasma and urine parameters, as well as renal histopathology and mRNA expression data, at 1, 2, and 6 weeks after injury, covering the early recovery and long-term remission. We observed an extensive strain-specific response ranging from complete resistance of the CAST/EiJ to high sensitivity of the C57BL/6J, DBA/2J, and PWK/PhJ strains. In susceptible strains, the severe early kidney injury was accompanied by the induction of mitochondrial stress response (MSR) genes and the attenuation of NAD+ synthesis pathways. This is associated with delayed healing and a prolonged inflammatory and adaptive immune response 6 weeks after insult, heralding a transition to chronic kidney disease. Through a thorough comparison of the transcriptomic response in mouse and human disease, we show that critical metabolic gene alterations were shared across species, and we highlight the PWK/PhJ strain as an emergent model of transition from acute kidney injury to chronic disease.
Jean-David Morel, Maroun Bou Sleiman, Terytty Yang Li, Giacomo von Alvensleben, Alexis M. Bachmann, Dina Hofer, Ellen Broeckx, Jing Ying Ma, Vinicius Carreira, Tao Chen, Nabil Azhar, Romer A. Gonzalez-Villalobos, Matthew Breyer, Dermot Reilly, Shannon Mullican, Johan Auwerx
The glomerular endothelial glycocalyx (GEnGlx) forms the first part of the glomerular filtration barrier. Previously we showed that mineralocorticoid receptor (MR) activation caused GEnGlx damage and albuminuria. Here we investigated whether MR antagonism could limit albuminuria in diabetes and studied the site of action. Streptozotocin-induced diabetic Wistar rats developed albuminuria, increased glomerular albumin permeability (Ps’alb) and increased glomerular matrix metalloproteinase (MMP) activity with corresponding GEnGlx loss. MR antagonism prevented albuminuria progression, restored Ps’alb, preserved GEnGlx and reduced MMP activity. Enzymatic degradation of the GEnGlx negated the benefits of MR antagonism, confirming their dependence on GEnGlx integrity. Exposing human glomerular endothelial cells (GEnC) to diabetic conditions in vitro increased MMPs and caused glycocalyx damage. Amelioration of these effects confirmed a direct effect of MR antagonism on GEnC. To confirm relevance to human disease, we used a novel confocal imaging method to show loss of GEnGlx in renal biopsy specimens from patients with diabetic nephropathy (DN). In addition, DN patients randomised to receive an MR antagonist had reduced urinary MMP2 activity and albuminuria compared with placebo and baseline levels. Taken together our work suggests MR antagonists reduce MMP activity and thereby preserve GEnGlx resulting in reduced glomerular permeability and albuminuria in diabetes.
Michael Crompton, Joanne K. Ferguson, RainaD. Ramnath, Karen L. Onions, Anna S. Ogier, Monica Gamez, Colin J. Down, Laura J. Skinner, Kitty H.F. Wong, Lauren Kari Dixon, Judit Sutak, Steven J. Harper, Paola Pontrelli, Loreto Gesualdo, Hiddo L. Heerspink, Robert D. Toto, Gavin I. Welsh, Rebecca R. Foster, Simon C. Satchell, Matthew J. Butler
Acute kidney injury (AKI) is one of the most important complications in COVID-19 patients and is considered a negative prognostic factor with respect to patient survival. The occurrence of direct infection of the kidney by SARS-CoV-2, and its contribution to the renal deterioration process, remains a controversial issue. By studying 32 renal biopsies from COVID-19 patients we confirmed that the major pathological feature of COVID-19 is acute tubular injury (ATI). Using smFISH, we showed that the SARS-CoV-2 infects living renal cells and that infection, which parallels renal ACE2 expression levels, is associated to increase death. Mechanistically, a transcriptomic analysis uncovered specific molecular signatures in SARS-CoV-2 infected kidneys as compared to healthy kidneys and non-COVID-19 ATI kidneys. On the other hand, we demonstrated that SARS-CoV-2 and Hantavirus, two RNA viruses, activated different genetic networks despite they triggered the same pathological lesions. Finally, we identified XAF1 as a critical target of SARS-CoV-2 infection. In conclusion, this study demonstrates that SARS-CoV2 can directly infect living renal cells and identified specific druggable molecular targets that can potentially aid in the design of novel therapeutic strategies to preserve renal function in severely affected COVID-19 patients.
Pierre Isnard, Paul Vergnaud, Serge Garbay, Matthieu Jamme, Maeva Eloudzeri, Alexandre Karras, Dany Anglicheau, Valerie Galantine, Arwa Jalal Eddine, Clément Gosset, Franck Pourcine, Mohammed Zarhrate, Jean-Baptiste Gibier, Elena Rensen, Stefano Pietropaoli, Giovanna Barba-Spaeth, Jean-Paul Duong-Van-Huyen, Thierry J. Molina, Florian Mueller, Christophe Zimmer, Marco Pontoglio, Fabiola Terzi, Marion Rabant
Dietary potassium (K+) supplementation is associated with a blood pressure (BP) lowering effect, but not all studies agree. Here we examined the effects of short and long-term K+ supplementation on BP in mice, whether differences depend on the accompanying anion or the sodium (Na+) intake and molecular alterations in the kidney that may underlie BP changes. Relative to the control diet, BP was higher in mice fed a high NaCl (1.57% Na+) for 7 weeks or 2 weeks with a K+-free diet. BP was highest on a K+-free/high NaCl diet. Commensurate with increased abundance and phosphorylation of the thiazide sensitive sodium-chloride-cotransporter (NCC) on the K+-free/high NaCl diet, BP returned to normal with thiazides. Three weeks of a high K+ diet (5% K+) increased BP (predominantly during night-time) independently of dietary Na+ or anion intake. Conversely, 4 days of KCl feeding reduced BP. Both feeding periods resulted in lower NCC levels, but increased levels of cleaved (active) α and γ subunits of the epithelial Na+ channel ENaC. The elevated BP after chronic K+ feeding was reduced by amiloride but not thiazide. Our results suggest that dietary K+ has an optimal threshold where it may be most effective for cardiovascular health.
Robert Little, Sathish K. Murali, Søren B. Poulsen, Paul R. Grimm, Adrienne Assmus, Lei Cheng, Jessica R. Ivy, Ewout J. Hoorn, Vladimir V. Matchkov, Paul A. Welling, Robert A. Fenton
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