Nephrology
Abstract
Membranous nephropathy (MN) is an autoimmune kidney disease and a major cause of nephrotic syndrome in adults. Although autoantibodies against phospholipase A2 receptor 1 (PLA2R) and complement activation are central to disease pathogenesis, the mechanisms by which anti-PLA2R antibodies activate complement at the podocyte surface remain incompletely defined. Here, we cloned 14 patient-derived anti-PLA2R monoclonal antibodies (mAbs) and found that they predominantly recognized the N-terminal cysteine-rich (CysR) and C-type lectin domain 1 (CTLD1) regions of PLA2R. Individual anti-PLA2R mAbs induced little or no complement-dependent cytotoxicity (CDC) of PLA2R-expressing podocytes in vitro. In contrast, paired mAbs targeting distinct epitopes, particularly CysR and CTLD1, markedly enhanced CDC. This effect was strongest for IgG1 and IgG3 antibodies, whereas IgG4 alone did not activate complement but modulated CDC in combination with IgG1. Purified IgG from patients with PLA2R-associated MN similarly induced CDC, which was augmented by addition of anti-PLA2R IgG1 and reduced by anti-PLA2R IgG4 or Fab fragments targeting CysR or CTLD1. In human PLA2R-expressing mice, paired anti-PLA2R antibodies increased glomerular complement deposition and induced albuminuria. These findings identify epitope pairing as a key determinant of complement activation in PLA2R-associated MN and support epitope-specific targeting strategies as a promising avenue for therapeutic intervention.
Authors
Tsai-Yi Wu, Kun-Hua Tu, Larissa Seifert, Kung-Wei Lin, Han-Po Shih, Yu-Fang Lo, Jhan-Jie Peng, Gunther Zahner, Oliver Kretz, You-Ning Lin, Chen-Xuan Kang, Jing-Ya Ding, Yi-Ran Tu, Li-Yi Ma, Ya-Ting Chuang, Chia-Chi Lo, Yu-Huan Tsai, Chih-Wei Yang, Nicola M. Tomas, Cheng-Lung Ku
Abstract
Authors
Chenjian Gu, Yili Fang, Yixuan Wang, Eric Tycksen, Gayathri Kondepati, Chuang Li, Kendrah O. Kidd, Jun Liu, Fumihiko Urano, Maria Lindahl, Anthony J. Bleyer, Srikanth Singamaneni, Zhao Sun, Ying Maggie Chen
Abstract
Following acute kidney injury (AKI), a substantial subset of patients experiences an irreversible progression to chronic kidney disease (CKD), yet the molecular determinants governing this maladaptive transition remain elusive, and effective clinical interventions are lacking. Here, we identify lactate as a key metabolic determinant orchestrating the transition from AKI to CKD. Analysis of the UK Biobank cohort reveals that elevated circulating lactate independently predicts CKD development in AKI patients and correlates with fibrotic progression. Using murine ischemia-reperfusion injury models, we demonstrate that lactate drives sustained renal damage through post-translational lactylation of the RNA helicase DDX18. Mechanistically, p300-mediated lactylation of DDX18 at lysine 116 disrupts its nucleolar retention, causing redistribution to the nucleoplasm where it acquires enhanced binding affinity for CD44 mRNA. This subcellular relocalization stabilizes CD44 mRNA through altered RNA-protein interactions, thereby amplifying fibrotic signaling pathways. Therapeutically, we developed a kidney-targeted, cell-penetrating peptide that specifically inhibits DDX18 K116 lactylation, effectively attenuating fibrotic progression in injured kidneys. Our findings establish protein lactylation as a regulatory mechanism governing RNA helicase nucleolar localization and subsequent control of mRNA stability, revealing a potential therapeutic target for interrupting fibrotic processes in chronic kidney disease.
Authors
Lijun Dong, Jingwen Xie, Mengyuan Tao, Shuai Liu, Yueyang Lu, Tianxing Wu, Jian Geng, Qingyun Chen, Xiaoshan Zhao, Jianbo Zhao, Jia Zhou, Honghao Hou, Jun Ai, Tao Tao, Daming Zuo
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) accounts for 5-10% of prevalent end-stage kidney failure (ESKD). ADPKD cysts result from a loss of sufficient functional expression of PKD1/Polycystin-1 (PC1) in approximately 80% of families. Kidney disease severity correlates with the extent to which PC1 dosage is reduced below a critical level, and evidence suggests therapeutic benefit from increasing PC1 expression in these conditions. Upstream open reading frame (uORF) translation can reduce translation of a protein’s coding sequence. Ribosome profiling data and bioinformatic predictions suggested the presence of conserved PKD1 uORFs, so we sought to explore their biological role. We generated luciferase reporters and two humanized PKD1 5’UTR mouse models with or without single nucleotide edits removing uORF start codons (“delta-uORF”) to define active uORFs and test their impact on PC1 translation. PKD1 uORF start codons can robustly initiate translation and delta-uORF conveys a 2-4-fold increase in PC1 protein expression and resultant prevention of kidney cysts in Dnajb11 as well as in Pkd1 missense models. PKD1 uORF1-blocking steric antisense oligonucleotides (ASOs) substantially increase PC1 expression in vitro. PKD1 uORFs play an important role in the low basal expression of wild-type PKD1, and their inhibition represents an opportunity to therapeutically increase PC1 translation in polycystic kidney and liver disease resulting from reduced dosage of PC1.
Authors
Zhigui Li, Zi Guo, Soyoung Cho, Rishi Bhardwaj, Ke Dong, Sorin Fedeles, Whitney Besse
Abstract
The inflammatory response resulting from the abnormal accumulation of metabolites has been implicated in the pathogenesis of organ fibrosis; however, its role and underlying mechanisms in renal fibrosis remain unclear. In this study, we observed a negative correlation between fumarate hydratase (FH) expression and the degree of renal fibrosis. Loss of FH function was associated with heightened inflammation and exacerbated tubulointerstitial damage in the kidney. Moreover, FH deficiency aggravated fibrosis in both the liver and lungs. Mechanistically, the depletion of FH in renal tubular cells led to fumarate accumulation. Fumarate directly succinated A-kinase anchoring protein 12 at cysteine 670, thereby diminishing its capacity to inhibit the activity of protein kinase Cζ (PKCζ). This process exacerbated renal inflammation and fibrosis by activating the downstream PKCζ/NF-κB and PKCζ/β-catenin pathways. Additionally, the upregulation of FH through adeno-associated virus 2/9-mediated FH overexpression markedly mitigated renal inflammation and fibrosis. These findings highlighted the important role of fumarate accumulation in the advancement of renal fibrosis, supporting FH as a potential therapeutic target in renal fibrosis.
Authors
Shuai Sun, Xu-yang Yan, Yu-hang Dong, Jian-min You, Zhen-yu Guo, Dong-xue Lv, Shuai-shuai Xie, Rui Hou, Xiang-yu Li, Ju-tao Yu, Xiao-yu Shen, Jie Wei, Zhen-yu Song, Zi-qi Chen, Yun-long Zhu, Xing-xin Xu, Juan Jin, Jia-gen Wen, Hao Wang, Xiao-ming Meng, Wei Wang
Abstract
Autosomal dominant polycystic kidney disease (ADPKD), the leading genetic cause of kidney failure, results from loss-of-function mutations in PKD1, encoding polycystin-1 (PC1). PC1 localizes to the primary cilium. In the absence of PC1, adverse signaling from the primary cilium orchestrates cyst formation, but the biomechanical underpinnings of this cilia-dependent cyst activation (CDCA) remain unclear. Combining tubule-specific orthologous mouse models with a tubule-on-chip platform, we show that PC1 and cilia govern the composition, mechanical properties and shape of the tubular basement membrane (TBM), the principal rigid determinant of tubule geometry. PC1 loss triggers TBM thinning, heparan sulfate enrichment and deformation, leading to distension, preferentially of the distal nephron. These changes are driven by a cilia-dependent transcriptional program, with GLIS2 — a key CDCA effector — participating as a downstream mediator. Reduction of TBM stiffness amplifies Pkd1−/− tubule-on-chip dilation and increases cyst formation in vivo. Conversely, increasing luminal pressure through ureteral obstruction induces disproportionate distension of Pkd1-deficient tubules and triggers an irreversible cystogenic program. Together, these findings establish a TBM-centered biomechanical model of ADPKD in which tubule deformation is governed by both basolateral and luminal mechanical factors, and identify the cilium–TBM axis, operating in part through GLIS2, as a central driver of cystogenesis.
Authors
Manal Mazloum, Brice Lapin, Rushdi Alghamdi, Jessica Vandensteen, Martine Burtin, Pascal Houillier, Lydie Cheval, Gilles Crambert, Vicky Scata, Camille Cohen, Christoph Schell, Michael Rehman, Amandine Aka, Karim Ourahmoun, Rui Benedito, E. Wolfgang Kuehn, Stéphanie Descroix, Tilman Busch, Michael Köttgen, Serge Garbay, Marie-Christine Verpont, Ellie Tang, Brigitte Lelongt, Nicolas Cagnard, Stefan Somlo, Sylvie Coscoy, Fabiola Terzi, Amandine Viau, Frank Bienaimé
Abstract
Renal water reabsorption is classically regulated by vasopressin V2 receptor (V2R) signaling through cyclic AMP and protein kinase A, driving apical accumulation of aquaporin-2 (AQP2). However, collecting duct water handling is also modulated by vasopressin-independent mechanisms. Here, we examined intracellular soluble urate as a vasopressin-independent regulator of AQP2 trafficking. Intracellular urate accumulation in collecting duct cells was mediated by enhanced apical urate uptake via GLUT9b and reduced apical urate efflux through ABCG2, triggering phosphodiesterase-4 activation, reduced cAMP, and downstream AMP-activated protein kinase (AMPK) activation. The resulting AQP2 accumulation at the apical membrane was independent of V2R signaling, required ongoing endocytosis and was associated with features of post-endocytic apical trafficking of internalized AQP2. In vivo ABCG2 inhibition with probenecid increased apical AQP2 abundance and markedly attenuated tolvaptan-induced polyuria in both wild-type and Pkd1RC/RC autosomal dominant polycystic kidney disease (ADPKD) mice in a uricase-independent manner, while preserving tolvaptan’s ADPKD-modifying efficacy. In a Phase 2 trial with tolvaptan-treated ADPKD patients, probenecid reduced urine volume and nocturia frequency. Together, these findings support a vasopressin-independent urate–AMPK–AQP2 pathway that regulates renal water handling and, in a preclinical ADPKD model, can uncouple cyst growth attenuation from the dose-limiting aquaretic effects of V2R antagonism.
Authors
Mohamad Hadla, Jean Marc Mardirossian, Daniel G. Bichet, Abdul Hamid Borghol, Georges Abboud, Ahmad Ghanem, Eduardo N. Chini, Peter C. Harris, Vicente E. Torres, Seth L. Alper, Volker Vallon, Fouad T. Chebib
Abstract
Exonic variants in Apolipoprotein-L1 (G1 and G2) are linked to increased risk of kidney disease as well as kidney transplant rejection. Outside of the association of these prevalent variants with African ancestry, underpinning causal mechanisms for rejection are unknown. We investigated T-cell function using transgenic mice with physiologic expression of wild type (G0-), G1-APOL1 (G1), or G2-APOL1 (G2). Mice with either variant showed greater CD8+T-cell activation with expansion of a central memory (TCM) subset. Stimulated G1-CD8+T-cells showed enhanced proliferation and cytokine production, which reversed with APOL1 inhibition. In MHC-mismatched cardiac transplants, G1-mice demonstrated greater CD8+T-cell infiltration and reduced survival. Bulk transcriptome of G1-CD8+T-cells, and single-cell transcriptome of graft infiltrating TCMs, showed enrichment of canonical T-cell receptor (TCR) pathways including Ca2+-signaling. G1-CD8+T-cells demonstrated baseline ER-Ca2+ depletion followed by sustained increases in cytosolic-Ca2+ upon TCR stimulation. G1-CD8+T-cells were more sensitive to Ca2+ chelation, or store-operated Ca2+ entry inhibition, and were relatively resistant to calcineurin antagonism compared to G0-CD8+T-cells. Analogously, in a kidney transplant cohort, APOL1-variant recipients that had elevated peripheral TCMs before transplantation, developed rejection despite significantly higher tacrolimus levels vs G0/G0 recipients. In summary, we unravel an excitatory mechanism for APOL1 variants in T-cells that causally links them to kidney rejection.
Authors
John Pell, EM Tanvir, Zeguo Sun, Irene Chernova, Anand Reghuvaran, Soichiro Nagata, Mateus T. Guerra, John Choi, Soltan Al Chaar, Hiroki Mizuno, Ke Dong, Xin Tian, Reika Ishibe, Barbara Franchin, Paolo Cravedi, Ashwani Kumar, Gabriel Barsotti, Hongmei Shi, Bony De Kumar, Shinobu Smithson, Wenzhi Song, John Cijiang He, Anita S. Chong, Jordan S. Pober, Stefan Somlo, Ian W. Gibson, Waldemar Popik, Zhongyang Zhang, Joseph Craft, Jamil Azzi, Naoka Murakami, Shuta Ishibe, Peter S. Heeger, Madhav C Menon
Abstract
BACKGROUND. Anti-nephrin autoantibodies have emerged as a putative pathogenic driver in a subset of patients with podocytopathies, including those with post-transplant disease recurrence. METHODS. We measured anti-nephrin autoantibodies in a cohort of 65 patients with podocytopathy associated with steroid-sensitive nephrotic syndrome (n = 39) and steroid-resistant nephrotic syndrome (n = 26), and in 34 patients with post-transplant podocytopathy recurrence. Fourteen patients with membranous nephropathy and 20 healthy volunteers served as controls. ELISA and immunoprecipitation assays were performed to detect anti-nephrin IgG using two different recombinant human nephrin proteins. Immunofluorescence analysis was performed to assess the deposition of IgG and their colocalization with nephrin in renal biopsies. RESULTS. When using murine antigen-based ELISA, the highest positivity was found in healthy volunteers (55%), correlating with levels of circulating natural anti-α-galactose-α-1,3-galactose antibodies. This cross-reactivity was abrogated with recombinant human nephrin expressed in human cells. In this setting, very low prevalence (<5%) of anti-nephrin antibody-positive patients was found in steroid-sensitive and steroid-resistant nephrotic syndrome cohorts and in patients with post-transplant disease recurrence. These frequencies were comparable to healthy volunteers. Using confocal and super-resolution microscopy, only trace amounts of IgM, but no IgG, were found in the glomeruli of analyzed biopsies, which did not colocalize with nephrin. CONCLUSIONS. With the methodology presented here, anti-nephrin reactivity was extremely rare and occurred at comparably low frequencies in healthy controls, native-kidney podocytopathies, and post-transplant disease recurrence. This suggests that these autoantibodies are not inherently disease-specific and may not serve as a broad biomarker across podocytopathies. TRIAL REGISTRATION. ClinicalTrials.gov NCT06334692. FUNDING. Private donation.
Authors
Francesco Pecoraro, Luca Perico, Federica Casiraghi, Paola Rizzo, Matias Trillini, Andrea Angeletti, Manuel Alfredo Podestà, Xhuliana Kajana, Agnese Spennacchio, Marta Todeschini, Marilena Mister, Giuseppe Castellano, Ariela Benigni, Giuseppe Remuzzi
Abstract
Sphingosine-1-phosphate lyase (SPL) insufficiency syndrome (SPLIS) or nephrotic syndrome type 14 (NPHS14), is an autosomal recessive multisystem disorder caused by loss-of-function mutations in SGPL1, encoding the enzyme responsible for the terminal degradation of sphingosine-1-phosphate (S1P). We investigated a patient carrying a previously undescribed c.1084T>A (p.Ser362Thr) SGPL1 variant and analyzed the metabolic and cellular consequences of SPL deficiency using patient fibroblasts, SGPL1-knockout HEK293T cells, and Sgpl1–/– and Sgpl1rosa+fl/fl mice. Metabolic stable isotope labelling revealed that SPL deficiency does not invariably result in S1P accumulation. Instead, SPL-deficient cells maintain near-normal S1P levels through (i) feedback regulation of de novo sphingolipid synthesis via the ORMDL–ceramide axis and (ii) increased diversion of excess ceramides into glycosphingolipids. However, perturbation of sphingolipid homeostasis — either by exogenous sphingolipid load or disruption of compensatory regulation — induces pathological intracellular S1P accumulation. In vivo, Sgpl1–/– mice exhibited pronounced urinary S1P excretion and renal S1P enrichment, accompanied by cytoskeletal disorganization and impaired epithelial morphogenesis. Mechanistically, we identify aberrant Rho–ROCK signaling as a key mediator of S1P-driven cytoskeletal dysregulation. Pharmacological ROCK inhibition with Fasudil mitigated renal cytoskeletal defects in Sgpl1–/– and Sgpl1rosa+fl/fl mice and partially restored epithelial architecture. These findings redefine the metabolic consequences of SPL deficiency and identify S1P-driven Rho–ROCK hyperactivation as a tractable therapeutic target in SPLIS.
Authors
Adam Majcher, Ranjha Khan, Kathrin Buder, Florence Bourquin, Julie D. Saba, Thorsten Hornemann
Copyright © 2026 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)