Nephrology
Abstract
Diabetic nephropathy (DN) is a polygenic disorder with few risk variants showing robust replication in large-scale genome-wide association studies. To understand the role of DNA methylation, it is important to have the prevailing genomic view to distinguish key sequence elements that influence gene expression. This is particularly challenging for DN because genome wide methylation patterns are poorly defined. While methylation is known to alter gene expression the importance of this causal relationship is obscured by array-based technologies since coverage outside promoter regions is low. To overcome these challenges, we performed methylation sequencing using leukocytes derived from participants of the Finnish Diabetic Nephropathy (FinnDiane) type 1 diabetes (T1D) study (n=39) that was subsequently replicated in a larger validation cohort (n=296). Gene body related regions made up >60% of the methylation differences and emphasised the importance of methylation sequencing. We observe differentially methylated genes associated with DN (DDN) in three independent T1D registries originating from Denmark (n=445), Hong Kong (n=107) and Thailand (n=130). Reduced DNA methylation at CTCF and Pol2B sites were tightly connected with DN pathways that include insulin signalling, lipid metabolism and fibrosis. To define the pathophysiological significance of these population findings, methylation indices were assessed in human renal cells such as podocytes and proximal convoluted tubules. The expression of core genes was associated with reduced methylation, elevated CTCF and Pol2B binding and the activation of insulin signalling phosphoproteins in hyperglycaemic cells. These experimental observations also closely parallel methylation-mediated regulation in human macrophage and vascular endothelial cells.
Authors
Ishant Khurana, Harikrishnan Kaipananickal, Scott Maxwell, Sørine Birkelund, Anna Syreeni, Carol Forsblom, Jun Okabe, Mark Ziemann, Antony Kaspi, Haloom Rafehi, Anne Jørgensen, Keith Al-Hasani, Merlin C. Thomas, Guozhi Jiang, Andrea O.Y. Luk, Heung Man Lee, Yu Huang, Yotsapon Thewjitcharoen, Soontaree Nakasatien, Thep Himathongkam, Christopher Fogarty, Rachel Njeim, Assaad Eid, Tine Willum Hansen, Nete Tofte, Evy Connie Ottesen, Ronald C.W. Ma, Juliana C.N. Chan, Mark Emmanuel Cooper, Peter Rossing, Per-Henrik Groop, Assam El-Osta
Abstract
Genetic variants in the third intron of the PRDM6 gene have been associated with blood pressure traits in multiple genome-wide association studies (GWAS). By combining fine mapping, massive-ly parallel reporter assays, and gene editing we identified the causal variants for hypertension as super-enhancers that drive the expression of PRDM6 and are partly regulated by STAT1. The het-erozygous SMC-specific Prdm6 knockout mice (Prdm6fl/+ Sm22Cre) exhibited a markedly high-er number of renin-producing cells in the kidneys at embryonic day 18.5 compared to wild-type littermates and developed salt-induced systemic hypertension that was completely responsive to the renin inhibitor aliskiren. Strikingly, RNA-seq analysis of the mice aorta identified a network of PRDM6-regulated genes that are located in GWAS-associated loci for blood pressure, most nota-bly Sox6, which modulates renin-expression in the kidney. Accordingly, the smooth muscle cell-specific disruption of Sox6 in Prdm6fl/+ Sm22Cre mice resulted in a dramatic reduction of renin. Fate mapping and histological studies also showed increased numbers of neural crest-derived cells accompanied by increased collagen deposition in the kidneys of Prdm6fl/+ Wnt1Cre-ZsGreen1Cre compared to wild-type mice. These findings establish the role of PRDM6 as a regulator of renin-producing cells and an attractive target for the development of antihypertensive drugs.
Authors
Kushan L. Gunawardhana, Lingjuan Hong, Trojan Rugira, Severin Uebbing, Joanna Kucharczak, Sameet Mehta, Dineth R. Karunamuni, Brenda Cabrera-Mendoza, Renato Polimanti, James P. Noonan, Arya Mani
Abstract
Acute kidney injury (AKI) occurs in approximately 13% of hospitalized patients and predisposes patients to chronic kidney disease (CKD) through the AKI-to-CKD transition. Studies from our laboratory and others have demonstrated that maladaptive repair of proximal tubule cells (PTCs), including induction of dedifferentiation, G2/M cell cycle arrest, senescence, and profibrotic cytokine secretion, is a key process promoting AKI-to-CKD transition, kidney fibrosis, and CKD progression. The molecular mechanisms governing maladaptive repair and the relative contribution of dedifferentiation, G2/M arrest, and senescence to CKD remain to be resolved. We identified cyclin G1 (CG1) as a factor upregulated in chronically injured and maladaptively repaired PTCs. We demonstrated that global deletion of CG1 inhibits G2/M arrest and fibrosis. Pharmacological induction of G2/M arrest in CG1-knockout mice, however, did not fully reverse the antifibrotic phenotype. Knockout of CG1 did not alter dedifferentiation and proliferation in the adaptive repair response following AKI. Instead, CG1 specifically promoted the prolonged dedifferentiation of kidney tubule epithelial cells observed in CKD. Mechanistically, CG1 promotes dedifferentiation through activation of cyclin-dependent kinase 5 (CDK5). Deletion of CDK5 in kidney tubule cells did not prevent G2/M arrest but did inhibit dedifferentiation and fibrosis. Thus, CG1 and CDK5 represent a unique pathway that regulates maladaptive, but not adaptive, dedifferentiation, suggesting they could be therapeutic targets for CKD.
Authors
Kensei Taguchi, Bertha C. Elias, Sho Sugahara, Snehal Sant, Benjamin S. Freedman, Sushrut S. Waikar, Ambra Pozzi, Roy Zent, Raymond C. Harris, Samir M. Parikh, Craig R. Brooks
Abstract
Cisplatin is a potent chemotherapeutic drug that is widely used in the treatment of various solid cancers. However, its clinical effectiveness is strongly limited by frequent severe adverse effects, in particular nephrotoxicity and chemotherapy-induced peripheral neuropathy. Thus, there is an urgent medical need to identify novel strategies that limit cisplatin-induced toxicity. In the present study, we show that the FDA-approved adenosine A2A receptor antagonist istradefylline (KW6002) protected from cisplatin-induced nephrotoxicity and neuropathic pain in mice with or without tumors. Moreover, we also demonstrate that the antitumoral properties of cisplatin were not altered by istradefylline in tumor-bearing mice and could even be potentiated. Altogether, our results support the use of istradefylline as a valuable preventive approach for the clinical management of patients undergoing cisplatin treatment.
Authors
Edmone Dewaeles, Kévin Carvalho, Sandy Fellah, Jaewon Sim, Nihad Boukrout, Raphaelle Caillierez, Hariharan Ramakrishnan, Cynthia Van der Hauwaert, Jhenkruthi Vijaya Shankara, Nathalie Martin, Noura Massri, Agathe Launay, Joseph K. Folger, Clémentine de Schutter, Romain Larrue, Ingrid Loison, Marine Goujon, Matthieu Jung, Stéphanie Le Gras, Victoria Gomez-Murcia, Emilie Faivre, Julie Lemaire, Anne Garat, Nicolas Beauval, Patrice Maboudou, Viviane Gnemmi, Jean-Baptiste Gibier, Luc Buée, Corinne Abbadie, Francois Glowacki, Nicolas Pottier, Michael Perrais, Rodrigo A. Cunha, Jean-Sébastien Annicotte, Geoffroy Laumet, David Blum, Christelle Cauffiez
Abstract
Authors
Kenar D. Jhaveri, Abhijat Kitchlu, Ala Abudayyeh
Abstract
The Hippo pathway nuclear effector Yes-associated protein 1 (YAP) potentiates the progression of polycystic kidney disease (PKD) arising from ciliopathies. The mechanisms underlying the increase in YAP expression and transcriptional activity in PKD remain obscure. We observed that in kidneys from mice with juvenile cystic kidney (jck) ciliopathy, the aberrant hyperactivity of mechanistic target of rapamycin complex 1 (mTORC1) driven by ERK1/2 and PI3K/AKT cascades induced endoplasmic reticulum (ER) proteotoxic stress. To reduce it by reprogramming translation, the protein kinase R-like ER kinase (PERK)-eukaryotic initiation factor 2α (eIF2α) arm of the integrated stress response (ISR) was activated. PERK-mediated phosphorylation of eIF2α drove the selective translation of activating transcription factor 4 (ATF4), potentiating YAP expression. In parallel, YAP underwent K63-linked polyubiquitination by SCF-S-phase kinase-associated protein 2 (SKP2) E3 ubiquitin ligase, a Hippo-independent, nonproteolytic ubiquitination that enhances YAP nuclear trafficking and transcriptional activity in cancer cells. Defective ISR cellular adaptation to ER stress in eIF2α-phosphorylation-deficient jck mice further augmented YAP-mediated transcriptional activity and renal cyst growth. Conversely, pharmacological tuning down of ER stress-ISR activity and SKP2 expression in jck mice by administration of tauroursodeoxycholic acid (TUDCA) or tolvaptan, impeded these processes. Restoring ER homeostasis, and/or interfering with the SKP2-YAP interaction represent novel potential therapeutic avenues for stemming the progression of renal cystogenesis.
Authors
Dibyendu K. Panda, Xiuying Bai, Yan Zhang, Nicholas A. Stylianesis, Antonis E. Koromilas, Mark L. Lipman, Andrew C. Karaplis
Abstract
To understand how kidney donation leads to excess preeclampsia risk, we studied pregnant outbred mice with prior uninephrectomy and compared them to sham-treated littermates carrying both kidneys. During pregnancy, uninephrectomized mice failed to achieve physiological increase of glomerular filtration rate, and during late gestation developed hypertension, albuminuria, glomerular endothelial damage, and excess placental production of soluble fms-like tyrosine kinase 1 (sFLT1), an anti-angiogenic protein implicated in the pathogenesis of preeclampsia. Maternal hypertension in uninephrectomized mice was associated with low plasma volumes, increased rate of fetal resorption, impaired spiral artery remodeling and placental ischemia. To evaluate potential mechanisms, we studied plasma metabolite changes using mass spectrometry and noted that L-kynurenine, a metabolite of L-tryptophan, was upregulated ~3 fold during pregnancy when compared to pre-pregnant concentrations in the same animals, consistent with prior reports suggesting a protective role for L-kynurenine in placental health. However, uninephrectomized mice failed to upregulate L-kynurenine during pregnancy; furthermore, when uninephrectomized mice were fed L-kynurenine in drinking water throughout pregnancy, their preeclampsia-like state was rescued, including reversal of placental ischemia and normalization of sFLT1 levels. In aggregate, we provide a mechanistic basis for how impaired renal reserve and resulting failure to upregulate L-kynurenine during pregnancy can lead to impaired placentation, placental hypoperfusion, anti-angiogenic state and subsequent preeclampsia.
Authors
Vincent Dupont, Anders H. Berg, Michifumi Yamashita, Chengqun Huang, Ambart E. Covarrubias, Shafat Ali, Aleksandr Stotland, Jennifer E. Van Eyk, Belinda Jim, Ravi Thadhani, S. Ananth Karumanchi
Abstract
The glomerular filtration barrier (GFB) produces primary urine and is composed of a fenestrated endothelium, a glomerular basement membrane (GBM), podocytes, and a slit diaphragm. Impairment of the GFB leads to albuminuria and microhematuria. The GBM is generated via secreted proteins from both endothelial cells and podocytes and is supposed to majorly contribute to filtration selectivity. While genetic mutations or variations of GBM components have been recently proposed to be a common cause of glomerular diseases, pathways modifying and stabilizing the GBM remain incompletely understood. Here, we identified prolyl 3-hydroxylase 2 (P3H2) as a regulator of the GBM in an a cohort of patients with albuminuria. P3H2 hydroxylates the 3′ of prolines in collagen IV subchains in the endoplasmic reticulum. Characterization of a P3h2ΔPod mouse line revealed that the absence of P3H2 protein in podocytes induced a thin basement membrane nephropathy (TBMN) phenotype with a thinner GBM than that in WT mice and the development of microhematuria and microalbuminuria over time. Mechanistically, differential quantitative proteomics of the GBM identified a significant decrease in the abundance of collagen IV subchains and their interaction partners in P3h2ΔPod mice. To our knowledge, P3H2 protein is the first identified GBM modifier, and loss or mutation of P3H2 causes TBMN and focal segmental glomerulosclerosis in mice and humans.
Authors
Hande Aypek, Christoph Krisp, Shun Lu, Shuya Liu, Dominik Kylies, Oliver Kretz, Guochao Wu, Manuela Moritz, Kerstin Amann, Kerstin Benz, Ping Tong, Zheng-mao Hu, Sulaiman M. Alsulaiman, Arif O. Khan, Maik Grohmann, Timo Wagner, Janina Müller-Deile, Hartmut Schlüter, Victor G. Puelles, Carsten Bergmann, Tobias B. Huber, Florian Grahammer
Abstract
The roles of neutrophils in renal inflammation are currently unclear. On examining these cells in the unilateral ureteral obstruction murine model of chronic kidney disease, we found that the injured kidney bore a large and rapidly expanding population of neutrophils that expressed the eosinophil marker Siglec-F. We first confirmed that these cells were neutrophils. Siglec-F+ neutrophils were recently detected for the first time by several studies on other disease contexts. We then showed that (i) these cells were derived from conventional neutrophils in the renal vasculature by TGF-β1 and GM-CSF, (ii) they differed from their parent cells by more frequent hypersegmentation, higher expression of pro-fibrotic inflammatory cytokines, and, notably, expression of Collagen 1, and (iii) their depletion reduced collagen deposition and disease progression, but adoptive transfer increased renal fibrosis. These findings have thus unveiled a subtype of neutrophils that participate in renal fibrosis and maybe a new therapeutic target in chronic kidney disease.
Authors
Seungwon Ryu, Jae Woo Shin, Soie Kwon, Jiwon Lee, Yong Chul Kim, Yoe-Sik Bae, Yong-Soo Bae, Dong Ki Kim, Yon Su Kim, Seung Hee Yang, Hye Young Kim
Abstract
As life expectancy continues to increase, clinicians are challenged by age-related renal impairment that involves podocyte senescence and glomerulosclerosis. There is now compelling evidence that lithium has a potent antiaging activity that ameliorates brain aging and increases longevity in Drosophila and Caenorhabditis elegans. As the major molecular target of lithium action and a multitasking protein kinase recently implicated in a variety of renal diseases, glycogen synthase kinase 3β (GSK3β) is overexpressed and hyperactive with age in glomerular podocytes, correlating with functional and histological signs of kidney aging. Moreover, podocyte-specific ablation of GSK3β substantially attenuated podocyte senescence and glomerular aging in mice. Mechanistically, key mediators of senescence signaling, such as p16INK4A and p53, contain high numbers of GSK3β consensus motifs, physically interact with GSK3β, and act as its putative substrates. In addition, therapeutic targeting of GSK3β by microdose lithium later in life reduced senescence signaling and delayed kidney aging in mice. Furthermore, in psychiatric patients, lithium carbonate therapy inhibited GSK3β activity and mitigated senescence signaling in urinary exfoliated podocytes and was associated with preservation of kidney function. Thus, GSK3β appears to play a key role in podocyte senescence by modulating senescence signaling and may be an actionable senostatic target to delay kidney aging.
Authors
Yudong Fang, Bohan Chen, Zhangsuo Liu, Athena Y. Gong, William T. Gunning, Yan Ge, Deepak Malhotra, Amira F. Gohara, Lance D. Dworkin, Rujun Gong
Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)