Severe glomerular injury ultimately leads to tubulointerstitial fibrosis which determines patient outcome, but the immunological molecules connecting these two processes remain unresolved. The present study addressed whether V-domain Ig suppressor of T cell activation (VISTA), constitutively expressed in kidney macrophages, plays a protective role in tubulointerstitial fibrotic transformation after acute antibody-mediated glomerulonephritis. After acute glomerular injury using nephrotoxic serum, tubules in the VISTA-deficient (Vsir–/–) kidney suffered more damage than in wild type kidneys. When interstitial immune cells were examined, the contact frequency of macrophages with infiltrated T cells increased, and the immunometabolic features of T cells changed to high oxidative phosphorylation and fatty acid metabolism and overproduction of interferon-γ. The Vsir–/– parenchymal tissue cells responded to this altered milieu of interstitial immune cells as more interleukin-9 was produced, which augmented tubulointerstitial fibrosis. Blocking antibodies against interferon-γ and interleukin-9 protected the above pathological process in VISTA-depleted conditions. In human samples with acute glomerular injury (e.g., anti-neutrophil cytoplasmic autoantibody vasculitis), high VISTA expression in tubulointerstitial immune cells was associated with low tubulointerstitial fibrosis and good prognosis. Therefore, VISTA is a sentinel protein expressed in kidney macrophages that prevents tubulointerstitial fibrosis via the interferon-γ-interleukin-9 axis after acute antibody-mediated glomerular injury.
Min-Gang Kim, Donghwan Yun, Chae Lin Kang, Minki Hong, Juhyeon Hwang, Kyung Chul Moon, Chang Wook Jeong, Cheol Kwak, Dong Ki Kim, Kook-Hwan Oh, Kwon Wook Joo, Yon Su Kim, Dong-Sup Lee, Seung Seok Han
Coding variants in apolipoprotein L1 (APOL1), termed G1 and G2, can explain most excess kidney disease risk in African Americans; however, the molecular pathways of APOL1-induced kidney dysfunction remain poorly understood. Here, we report that expression of G2 APOL1 in the podocytes of Nphs1rtTA/TRE-G2APOL1 (G2APOL1) mice leads to early activation of the cytosolic nucleotide sensor, stimulator of interferon genes (STING), and the NLR family pyrin domain–containing 3 (NLRP3) inflammasome. STING and NLRP3 expression was increased in podocytes from patients with high-risk APOL1 genotypes, and expression of APOL1 correlated with caspase-1 and gasdermin D (GSDMD) levels. To demonstrate the role of NLRP3 and STING in APOL1-associated kidney disease, we generated transgenic mice with the G2 APOL1 risk variant and genetic deletion of Nlrp3 (G2APOL1/Nlrp3 KO), Gsdmd (G2APOL1/Gsdmd KO), and STING (G2APOL1/STING KO). Knockout mice displayed marked reduction in albuminuria, azotemia, and kidney fibrosis compared with G2APOL1 mice. To evaluate the therapeutic potential of targeting NLRP3, GSDMD, and STING, we treated mice with MCC950, disulfiram, and C176, potent and selective inhibitors of NLRP3, GSDMD, and STING, respectively. G2APOL1 mice treated with MCC950, disulfiram, and C176 showed lower albuminuria and improved kidney function even when inhibitor treatment was initiated after the development of albuminuria.
Junnan Wu, Archana Raman, Nathan J. Coffey, Xin Sheng, Joseph Wahba, Matthew J. Seasock, Ziyuan Ma, Pazit Beckerman, Dorottya Laczkó, Matthew B. Palmer, Jeffrey B. Kopp, Jay J. Kuo, Steven S. Pullen, Carine M. Boustany-Kari, Andreas Linkermann, Katalin Susztak
Apolipoprotein L1 (APOL1) risk-alleles in donor kidneys associate with graft loss but whether recipient risk-allele expression impacts transplant outcomes is unclear. To test whether recipient APOL1 risk-alleles independently correlate with transplant outcomes, we analyzed genome-wide SNP genotyping data of donors and recipients from two kidney transplant cohorts, Genomics of Chronic Allograft Rejection (GOCAR) and Clinical Trials in Organ Transplantation (CTOT1/17). We estimated genetic ancestry (quantified as proportion of African ancestry or pAFR) by ADMIXTURE and correlated APOL1 genotypes and pAFR with outcomes. In the GOCAR discovery set, we observed that the number of recipient APOL1 G1/G2 alleles (R-nAPOL1) associated with increased risk of death-censored allograft loss (DCAL), independent of ancestry (HR = 2.14; P = 0.006), and within the subgroup of African American and Hispanic (AA/H) recipients (HR = 2.36; P = 0.003). R-nAPOL1 also associated with increased risk of any T cell-mediated rejection (TCMR) event. These associations were validated in CTOT1/17. Ex vivo studies of peripheral blood mononuclear cells revealed unanticipated high APOL1 expression in activated CD4+/CD8+ T cells and natural killer cells. We detected enriched immune response gene pathways in risk-allele carriers vs. non-carriers on the kidney transplant waitlist and among healthy controls. Our findings demonstrate an immunomodulatory role for recipient APOL1 risk-alleles associating with TCMR and DCAL. This finding has broader implications for immune mediated injury to native kidneys.
Zhongyang Zhang, Zeguo Sun, Jia Fu, Qisheng Lin, Khadija Banu, Kinsuk Chauhan, Marina Planoutene, Chengguo Wei, Fadi Salem, Zhengzi Yi, Ruijie Liu, Paolo Cravedi, Haoxiang Cheng, Ke Hao, Philip J. O’Connell, Shuta Ishibe, Weijia Zhang, Steven G. Coca, Ian W. Gibson, Robert B. Colvin, John C. He, Peter S. Heeger, Barbara T. Murphy, Madhav C. Menon
The western pattern diet is rich not only in fat and calorie but also in phosphate. Negative impacts of excessive fat and calorie intake on health are widely accepted, whereas potential harms of excessive phosphate intake are poorly recognized. Here we show the mechanism by which dietary phosphate damages the kidney. When phosphate intake was excessive relative to the functioning nephron number, circulating fibroblast growth factor-23 (FGF23), a hormone that increases phosphate excretion per nephron, was increased to maintain phosphate homeostasis. FGF23 suppressed phosphate reabsorption in renal tubules and thus raised the phosphate concentration in the tubular fluid. Once it exceeded a threshold, microscopic particles containing calcium phosphate crystals appeared in the tubular lumen, which damaged tubular cells through binding to Toll-like receptor-4 expressed on them. Persistent tubular damage induced interstitial fibrosis, reduced the nephron number, and further boosted FGF23 to trigger a deterioration spiral leading to progressive nephron loss. In humans, progression of chronic kidney disease (CKD) ensued when the serum FGF23 level exceeded 53 pg/mL. The present study identified the calcium phosphate particles in the renal tubular fluid as an effective therapeutic target to decelerate nephron loss during the course of aging and CKD progression.
Kazuhiro Shiizaki, Asako Tsubouchi, Yutaka Miura, Kinya Seo, Takahiro Kuchimaru, Hirosaka Hayashi, Yoshitaka Iwazu, Marina Miura, Batpurev Battulga, Nobuhiko Ohno, Toru Hara, Rina Kunishige, Mamiko Masutani, Keita Negishi, Kazuomi Kario, Kazuhiko Kotani, Toshiyuki Yamada, Daisuke Nagata, Issei Komuro, Hiroshi Itoh, Hiroshi Kurosu, Masayuki Murata, Makoto Kuro-o
Skeletal muscle wasting is commonly associated with chronic kidney disease (CKD), resulting in increased morbidity and mortality. However, the link between kidney and muscle function remains poorly understood. Here, we took a complementary interorgan approach to investigate skeletal muscle wasting in CKD. We identified increased production and elevated blood levels of soluble pro-cachectic factors, including activin A, directly linking experimental and human CKD to skeletal muscle wasting programs. Single-cell sequencing data identified the expression of activin A in specific kidney cell populations of fibroblasts and cells of the juxtaglomerular apparatus. We propose that persistent and increased kidney production of pro-cachectic factors, combined with a lack of kidney clearance, facilitates a vicious kidney/muscle signaling cycle, leading to exacerbated blood accumulation and, thereby, skeletal muscle wasting. Systemic pharmacological blockade of activin A using soluble activin receptor type IIB ligand trap as well as muscle-specific adeno-associated virus–mediated downregulation of its receptor ACVR2A/B prevented muscle wasting in different mouse models of experimental CKD, suggesting that activin A is a key factor in CKD-induced cachexia. In summary, we uncovered a crosstalk between kidney and muscle and propose modulation of activin signaling as a potential therapeutic strategy for skeletal muscle wasting in CKD.
Francesca Solagna, Caterina Tezze, Maja T. Lindenmeyer, Shun Lu, Guochao Wu, Shuya Liu, Yu Zhao, Robert Mitchell, Charlotte Meyer, Saleh Omairi, Temel Kilic, Andrea Paolini, Olli Ritvos, Arja Pasternack, Antonios Matsakas, Dominik Kylies, Julian Schulze zur Wiesch, Jan-Eric Turner, Nicola Wanner, Viji Nair, Felix Eichinger, Rajasree Menon, Ina V. Martin, Barbara M. Klinkhammer, Elion Hoxha, Clemens D. Cohen, Pierre-Louis Tharaux, Peter Boor, Tammo Ostendorf, Matthias Kretzler, Marco Sandri, Oliver Kretz, Victor G. Puelles, Ketan Patel, Tobias B. Huber
Lupus nephritis is a severe organ manifestation in systemic lupus erythematosus leading to kidney failure in a subset of patients. In lupus-prone mice, controlled infection with Plasmodium parasites protects against the progression of autoimmune pathology including lethal glomerulonephritis. Here, we demonstrate that parasite-induced protection was not due to a systemic effect of infection on autoimmunity as previously assumed, but rather to specific alterations in immune cell infiltrates into kidneys and renal draining lymph nodes. Infection of lupus-prone mice with a Plasmodium parasite did not reduce the levels or specificities of autoreactive antibodies, vasculitis, immune complex–induced innate activation, or hypoxia. Instead, infection uniquely reduced kidney-infiltrating CCL17-producing bone marrow–derived type 2 inflammatory dendritic cells (iDC2s). Bone marrow reconstitution experiments revealed that infection with Plasmodium caused alterations in bone marrow cells that hindered the ability of DC2s to infiltrate the kidneys. The essential role for CCL17 in lupus nephritis was confirmed by in vivo depletion with a blocking antibody, which reduced kidney pathology and immune infiltrates, while bypassing the need for parasitic infection. Therefore, infiltration into the kidneys of iDC2s, with the potential to prime local adaptive responses, is an essential regulated event in the transition from manageable glomerulonephritis to lethal tubular injury.
Laura Amo, Hemanta K. Kole, Bethany Scott, Chen-Feng Qi, Juan Wu, Silvia Bolland
Genome-wide association studies (GWAS) for kidney function identified hundreds of risk regions; however, the causal variants, target genes, cell types, and disease mechanisms remain poorly understood. Here, we performed transcriptome-wide association studies (TWAS), summary Mendelian randomization, and MetaXcan to identify genes whose expression mediates the genotype effect on the phenotype. Our analyses identified Dachshund homolog 1 (DACH1), a cell-fate determination factor. GWAS risk variant was associated with lower DACH1 expression in human kidney tubules. Human and mouse kidney single-cell open chromatin data (snATAC-Seq) prioritized estimated glomerular filtration rate (eGFR) GWAS variants located on an intronic regulatory region in distal convoluted tubule cells. CRISPR-Cas9–mediated gene editing confirmed the role of risk variants in regulating DACH1 expression. Mice with tubule-specific Dach1 deletion developed more severe renal fibrosis both in folic acid and diabetic kidney injury models. Mice with tubule-specific Dach1 overexpression were protected from folic acid nephropathy. Single-cell RNA sequencing, chromatin immunoprecipitation, and functional analysis indicated that DACH1 controls the expression of cell cycle and myeloid chemotactic factors, contributing to macrophage infiltration and fibrosis development. In summary, integration of GWAS, TWAS, single-cell epigenome, expression analyses, gene editing, and functional validation in different mouse kidney disease models identified DACH1 as a kidney disease risk gene.
Tomohito Doke, Shizheng Huang, Chengxiang Qiu, Hongbo Liu, Yuting Guan, Hailong Hu, Ziyuan Ma, Junnan Wu, Zhen Miao, Xin Sheng, Jianfu Zhou, Aili Cao, Jianhua Li, Lewis Kaufman, Adriana Hung, Christopher D. Brown, Richard Pestell, Katalin Susztak
Dachshund homolog 1 (DACH1), a key cell-fate determinant, regulates transcription by DNA sequence–specific binding. We identified diminished Dach1 expression in a large-scale screen for mutations that convert injury-resistant podocytes into injury-susceptible podocytes. In diabetic kidney disease (DKD) patients, podocyte DACH1 expression levels are diminished, a condition that strongly correlates with poor clinical outcomes. Global Dach1 KO mice manifest renal hypoplasia and die perinatally. Podocyte-specific Dach1 KO mice, however, maintain normal glomerular architecture at baseline, but rapidly exhibit podocyte injury after diabetes onset. Furthermore, podocyte-specific augmentation of DACH1 expression in mice protects from DKD. Combined RNA sequencing and in silico promoter analysis reveal conversely overlapping glomerular transcriptomic signatures between podocyte-specific Dach1 and Pax transactivation-domain interacting protein (Ptip) KO mice, with upregulated genes possessing higher-than-expected numbers of promoter Dach1-binding sites. PTIP, an essential component of the activating histone H3 lysine 4 trimethylation (H3K4Me3) complex, interacts with DACH1 and is recruited by DACH1 to its promoter-binding sites. DACH1-PTIP recruitment represses transcription and reduces promoter H3K4Me3 levels. DACH1 knockdown in podocytes combined with hyperglycemia triggers target gene upregulation and increases promoter H3K4Me3. These findings reveal that in DKD, diminished DACH1 expression enhances podocyte injury vulnerability via epigenetic derepression of its target genes.
Aili Cao, Jianhua Li, Morad Asadi, John M. Basgen, Bingbing Zhu, Zhengzi Yi, Song Jiang, Tomohito Doke, Osama El Shamy, Niralee Patel, Paolo Cravedi, Evren U. Azeloglu, Kirk N. Campbell, Madhav Menon, Steve Coca, Weijia Zhang, Hao Wang, Ke Zen, Zhihong Liu, Barbara Murphy, John C. He, Vivette D. D’Agati, Katalin Susztak, Lewis Kaufman
Podocytes are key to kidney glomerular filtration barrier by forming slit diaphragm between interdigitating foot processes; however, molecular details and functional importance of protein folding and degradation in the ER remain unknown. Here we show that SEL1L-HRD1 protein complex of endoplasmic reticulum (ER)-associated degradation (ERAD) is required for slit diaphragm formation and glomerular filtration function. SEL1L-HRD1 ERAD is highly expressed in podocytes of both mouse and human kidneys. Mice with podocyte-specific Sel1L deficiency develop podocytopathy and severe congenital nephrotic syndrome shortly after weaning with impaired slit diaphragm, and die prematurely with a median life span of ~3 months. Mechanistically, we show that nephrin, a type-1 membrane protein causally linked to congenital nephrotic syndrome, is an endogenous ERAD substrate. ERAD deficiency attenuates the maturation of nascent nephrin, leading to its retention in the ER. Lastly, we show that various autosomal-recessive nephrin disease mutants are highly unstable and degraded by Sel1L-Hrd1 ERAD, which attenuates the pathogenicity of the mutants towards the wildtype allele. Hence, this study uncovers a critical role of Sel1L-Hrd1 ERAD in glomerular filtration barrier function and provides new insights into the pathogenesis associated with autosomal recessive disease mutants.
Sei Yoshida, Xiaoqiong Wei, Gensheng Zhang, Christopher L. O’Connor, Mauricio Torres, Zhangsen Zhou, Liangguang Lin, Rajasree Menon, Xiaoxi Xu, Wenyue Zheng, Yi Xiong, Edgar A. Otto, Chih-Hang Anthony Tang, Rui Hua, Rakesh Verma, Hiroyuki Mori, Yang Zhang, Chih-Chi Andrew Hu, Ming Liu, Puneet Garg, Jeffrey B. Hodgin, Shengyi Sun, Markus Bitzer, Ling Qi
Renal fibrosis, a common pathological manifestation of virtually all types of chronic kidney diseases (CKD), often results in diffuse kidney scarring and predisposes to end-stage renal disease. Currently, there is no effective therapy against renal fibrosis. Recently, our laboratory identified an ER-resident protein, thioredoxin domain containing 5 (TXNDC5), as a critical mediator of cardiac fibrosis. Transcriptome analyses of renal biopsy specimens from CKD patients revealed marked TXNDC5 upregulation in fibrotic kidneys, suggesting a potential role of TXNDC5 in renal fibrosis. Employing multiple fluorescent reporter mouse lines, we showed that TXNDC5 was specifically upregulated in collagen-secreting fibroblasts in fibrotic mouse kidneys. In addition, we showed that TXNDC5 was required for TGFβ1-induced fibrogenic responses in human kidney fibroblasts (HKF), whereas TXNDC5 over-expression was sufficient to promote HKF activation, proliferation and collagen production. Mechanistically, we showed that TXNDC5, transcriptionally controlled by ATF6-dependent ER stress pathway, mediates its pro-fibrogenic effects by enforcing TGFβ signaling activity through post-translational stabilization and upregulation of type I TGFβ receptor in kidney fibroblasts. Using a tamoxifen-inducible, fibroblast-specific Txndc5 knockout mouse line, we demonstrated that deletion of Txndc5 in kidney fibroblasts mitigated the progression of established kidney fibrosis, suggesting the therapeutic potential of TXNDC5 targeting for renal fibrosis and CKD.
Yen-Ting Chen, Pei-Yu Jhao, Chen-Ting Hung, Yueh-Feng Wu, Sung-Jan Lin, Wen-Chih Chiang, Shuei-Liong Lin, Kai-Chien Yang