Search Results (28)

Nephronophthisis (NPH) is the leading genetic cause of end-stage renal disease in children and young adults, but no effective disease-modifying therapies are currently available. Here, we identify glucagon-like peptide-1 (GLP-1) signaling as a novel therapeutic target for NPH through a systematic drug repurposing screen in zebrafish. By simultaneously depleting nphp1 and nphp4, we developed a robust zebrafish model that reproduces key features of human NPH, including glomerular cyst formation. Our screen revealed that dipeptidyl peptidase-4 (DPP4) inhibitors (Omarigliptin and Linagliptin) and GLP-1 receptor agonists (Semaglutide) significantly reduce cystogenesis in a dose-dependent manner. Genetic analysis demonstrated that GLP-1 receptor signaling is important for maintaining pronephros integrity, with gcgra and gcgrb (GLP-1 receptor genes) playing a particularly important role. Transcriptomic profiling identified adenosine receptor A2ab (adora2ab) as a key downstream effector of GLP-1 signaling, which regulates ciliary morphology and prevents cyst formation. Notably, nphp1/nphp4 double mutant zebrafish exhibited the upregulation of gcgra as a compensatory mechanism, which might explain their resistance to cystogenesis. This compensation was disrupted by the targeted depletion of GLP-1 receptors or the inhibition of adenylate cyclase, resulting in enhanced cyst formation, specifically in the mutant background. Our findings establish a signaling cascade from GLP-1 receptors to adora2ab in terms of regulating ciliary organization and preventing cystogenesis, offering new therapeutic opportunities for NPH through the repurposing of FDA-approved medications with established safety profiles. Full article

Autosomal dominant polycystic kidney disease (ADPKD) is a prevalent hereditary renal disorder characterized by the progressive formation of numerous fluid-filled cysts, ultimately leading to end-stage kidney disease. The results of recent studies have demonstrated that metabolic reprogramming plays a crucial role in cystogenesis and disease progression, including enhanced aerobic glycolysis, impaired fatty acid oxidation, glutamine dependence, and mitochondrial dysfunction; these metabolic alterations are regulated by signaling pathways such as mTOR, cAMP/PKA, and HIF-1α, which can modulate cell proliferation, fluid secretion, and energy metabolism. Furthermore, hypoxia and the oxidative microenvironment also promote the growth of cysts. In this review, we summarized the complex interactions between metabolic pathway alterations and key signaling cascades in ADPKD, in addition to exploring new therapeutic strategies targeting these metabolic pathways, including drug and dietary interventions. A comprehensive understanding of these mechanisms may contribute to the development of innovative treatment methods aiming to slow the disease progression of patients with ADPKD. Full article

Pathogenic variants in type IV collagen genes (COL4A3, COL4A4, COL4A5) are classically associated with Alport syndrome (AS), a hereditary nephropathy primarily affecting the glomerular basement membrane (GBM). Recent findings, however, suggest a broader phenotypic spectrum that includes renal cyst formation, raising questions about overlapping mechanisms with other cystic kidney diseases. Clinically, renal cysts have been increasingly reported in patients with autosomal dominant and X-linked forms of Alport syndrome, particularly in association with glycine missense variants. The most recent studies focusing on the cystic phenotype in Alport syndrome provide growing support for the idea that variants in type IV collagen genes are associated with an increased likelihood of developing renal cysts, likely through mechanisms involving the structural integrity of renal basement membranes. In this review, we explore evidence from murine models and human studies indicating defects in collagen IV and discuss their contribution to cystogenesis. These observations underscore the need for broader genetic screening strategies and further investigation into the molecular mechanisms underlying this emerging phenotype. Full article

Tuberous sclerosis complex (TSC) is caused by mutations in TSC1 or TSC2 genes and affects multiple organs. TSC proteins control cell growth by regulating the activity of the mechanistic target of rapamycin complex 1. Extracellular vesicles (EVs) are membrane-bound particles produced by cells that mediate cellular communication, function, and growth. Although extensive studies regarding the genetic basis of TSC exist, the exact mechanism contributing to its pathogenesis remains unresolved. It has been proposed that EVs generated by renal cyst epithelia of mice and cells with Tsc gene mutations contain factors that alter the function and proliferation of TSC-sufficient cells. To test this, EVs from the kidneys and kidney explants of wildtype and Tsc1KO mice were isolated and characterized by Western blotting, transmission electron microscopy, dynamic light scattering, and fluorescent nanoparticle tracking. Our results show an enrichment in EV-associated markers and particle sizes of similar ranges. RNA-seq and proteomic analyses identified EV shuttle factors. EV RNA and protein shuttle factors showed significant differences. Furthermore, EVs isolated from Tsc1KO mice inhibited the proliferation of M-1 cells. Understanding the role of EVs in cell proliferation and cystogenesis in TSC may lead to the development of new approaches for the treatment of this disease. Full article

Polycystic kidney disease (PKD) is the most common hereditary disorder that disrupts renal function and frequently progresses to end-stage renal disease. Recent advances have elucidated the critical role of primary cilia and ciliary ion channels, including transient receptor potential (TRP) channels, cystic fibrosis transmembrane conductance regulator (CFTR), and polycystin channels, in the pathogenesis of PKD. While some channels primarily function as chloride conductance channels (e.g., CFTR), others primarily regulate calcium (Ca⁺²) homeostasis. These ion channels are essential for cellular signaling and maintaining the normal kidney architecture. Dysregulation of these pathways due to genetic mutations in PKD1 and PKD2 leads to disrupted Ca⁺² and cAMP signaling, aberrant fluid secretion, and uncontrolled cellular proliferation, resulting in tubular cystogenesis. Understanding the molecular mechanisms underlying these dysfunctions has opened the door for innovative therapeutic strategies, including TRPV4 activators, CFTR inhibitors, and calcimimetics, to mitigate cyst growth and preserve renal function. This review summarizes the current knowledge on the roles of ciliary ion channels in PKD pathophysiology, highlights therapeutic interventions targeting these channels, and identifies future research directions for improving patient outcomes. Full article

Understanding chronic kidney disease (CKD) through the lens of evolutionary biology highlights the mismatch between our Paleolithic-optimized genes and modern diets, which led to the dramatically increased prevalence of CKD in modern societies. In particular, the Standard American Diet (SAD), high in carbohydrates and ultra-processed foods, causes conditions like type 2 diabetes (T2D), chronic inflammation, and hypertension, leading to CKD. Autosomal dominant polycystic kidney disease (ADPKD), a genetic form of CKD, is characterized by progressive renal cystogenesis that leads to renal failure. This review challenges the fatalistic view of ADPKD as solely a genetic disease. We argue that, just like non-genetic CKD, modern dietary practices, lifestyle, and environmental exposures initiate and accelerate ADPKD progression. Evidence shows that carbohydrate overconsumption, hyperglycemia, and insulin resistance significantly impact renal health. Additionally, factors like dehydration, electrolyte imbalances, nephrotoxin exposure, gastrointestinal dysbiosis, and renal microcrystal formation exacerbate ADPKD. Conversely, carbohydrate restriction, ketogenic metabolic therapy (KMT), and antagonizing the lithogenic risk show promise in slowing ADPKD progression. Addressing disease triggers through dietary modifications and lifestyle changes offers a conservative, non-pharmacological strategy for disease modification in ADPKD. This comprehensive review underscores the urgency of integrating diet and lifestyle factors into the clinical management of ADPKD to mitigate disease progression, improve patient outcomes, and offer therapeutic choices that can be implemented worldwide at low or no cost to healthcare payers and patients. Full article

Polycystic kidney disease (PKD) is characterized by extensive cyst formation and progressive fibrosis. However, the molecular mechanisms whereby the loss/loss-of-function of Polycystin 1 or 2 (PC1/2) provokes fibrosis are largely unknown. The small GTPase RhoA has been recently implicated in cystogenesis, and we identified the RhoA/cytoskeleton/myocardin-related transcription factor (MRTF) pathway as an emerging mediator of epithelium-induced fibrogenesis. Therefore, we hypothesized that MRTF is activated by PC1/2 loss and plays a critical role in the fibrogenic reprogramming of the epithelium. The loss of PC1 or PC2, induced by siRNA in vitro, activated RhoA and caused cytoskeletal remodeling and robust nuclear MRTF translocation and overexpression. These phenomena were also manifested in PKD1 (RC/RC) and PKD2 (WS25/−) mice, with MRTF translocation and overexpression occurring predominantly in dilated tubules and the cyst-lining epithelium, respectively. In epithelial cells, a large cohort of PC1/PC2 downregulation-induced genes was MRTF-dependent, including cytoskeletal, integrin-related, and matricellular/fibrogenic proteins. Epithelial MRTF was necessary for the paracrine priming of the fibroblast–myofibroblast transition. Thus, MRTF acts as a prime inducer of epithelial fibrogenesis in PKD. We propose that RhoA is a common upstream inducer of both histological hallmarks of PKD: cystogenesis and fibrosis. Full article

Tuberous sclerosis complex (TSC) presents with renal cysts and benign tumors, which eventually lead to kidney failure. The factors promoting kidney cyst formation in TSC are poorly understood. Inactivation of carbonic anhydrase 2 (Car2) significantly reduced, whereas, deletion of Foxi1 completely abrogated the cyst burden in Tsc1 KO mice. In these studies, we contrasted the ontogeny of cyst burden in Tsc1/Car2 dKO mice vs. Tsc1/Foxi1 dKO mice. Compared to Tsc1 KO, the Tsc1/Car2 dKO mice showed few small cysts at 47 days of age. However, by 110 days, the kidneys showed frequent and large cysts with overwhelming numbers of A-intercalated cells in their linings. The magnitude of cyst burden in Tsc1/Car2 dKO mice correlated with the expression levels of Foxi1 and was proportional to mTORC1 activation. This is in stark contrast to Tsc1/Foxi1 dKO mice, which showed a remarkable absence of kidney cysts at both 47 and 110 days of age. RNA-seq data pointed to profound upregulation of Foxi1 and kidney-collecting duct-specific H⁺-ATPase subunits in 110-day-old Tsc1/Car2 dKO mice. We conclude that Car2 inactivation temporarily decreases the kidney cyst burden in Tsc1 KO mice but the cysts increase with advancing age, along with enhanced Foxi1 expression. Full article

The progression of autosomal dominant polycystic kidney disease (ADPKD), an inherited kidney disease, is associated with renal interstitial inflammation and fibrosis. CD74 has been known not only as a receptor of macrophage migration inhibitory factor (MIF) it can also have MIF independent functions. In this study, we report unknown roles and function of CD74 in ADPKD. We show that knockout of CD74 delays cyst growth in Pkd1 mutant kidneys. Knockout and knockdown of CD74 (1) normalize PKD associated signaling pathways, including ERK, mTOR and Rb to decrease Pkd1 mutant renal epithelial cell proliferation, (2) decrease the activation of NF-κB and the expression of MCP-1 and TNF-alpha (TNF-α) which decreases the recruitment of macrophages in Pkd1 mutant kidneys, and (3) decrease renal fibrosis in Pkd1 mutant kidneys. We show for the first time that CD74 functions as a transcriptional factor to regulate the expression of fibrotic markers, including collagen I (Col I), fibronectin, and α-smooth muscle actin (α-SMA), through binding on their promoters. Interestingly, CD74 also regulates the transcription of MIF to form a positive feedback loop in that MIF binds with its receptor CD74 to regulate the activity of intracellular signaling pathways and CD74 increases the expression of MIF in ADPKD kidneys during cyst progression. We further show that knockout of MIF and targeting MIF with its inhibitor ISO-1 not only delay cyst growth but also ameliorate renal fibrosis through blocking the activation of renal fibroblasts and CD74 mediated the activation of TGF-β-Smad3 signaling, supporting the idea that CD74 is a key and novel upstream regulator of cyst growth and interstitial fibrosis. Thus, targeting MIF-CD74 axis is a novel therapeutic strategy for ADPKD treatment. Full article

Recently, arginine has been proven to play an important role in ADPKD physiopathology. Arginine auxotrophy in ADPKD induces cell hyperproliferation, blocking the normal differentiation of renal tube cells and causing cyst formation. We explored the L-arginine (Arg)–nitric oxide (NO) molecular pathway in ADPKD, a multisystemic arginine auxotrophe disease. We developed a prospective case–control study that included a group of 62 ADPKD subjects with an estimated filtration rate over 60 mL/min/1.73 mp, 26 subjects with chronic kidney disease with an eGFR > 60 mL/min/1.73 mp, and a group of 37 healthy subjects. The laboratory determinations were the serum level of arginine, the enzymatic activity of arginase 2 and inducible nitric oxide synthase, the serum levels of the stable metabolites of nitric oxide (nitrate, direct nitrite, and total nitrite), and the endogenous inhibitors of nitric oxide synthesis (asymmetric dimethylarginine and symmetric dimethylarginine). In the ADPKD group, the levels of the arginine and nitric oxide metabolites were low, while the levels of the metabolization enzymes were higher compared to the control group. Statistical analysis of the correlations showed a positive association between the serum levels of Arg and the eGFR and a negative association between Arg and albuminuria. ADPKD is a metabolic kidney disease that is auxotrophic for arginine. Exploring arginine reprogramming and L-Arg–NO pathways could be an important element in the understanding of the pathogenesis and progression of ADPKD. Full article

Mutations of PKD1 coding for polycystin-1 (PC1) account for most cases of autosomal-dominant polycystic kidney disease (ADPKD). The extracellular region of PC1 contains many evolutionarily conserved domains for ligand interactions. Among these are the leucine-rich repeats (LRRs) in the far N-terminus of PC1. Using zebrafish (Danio rerio) as an in vivo model system, we explored the role of LRRs in the function of PC1. Zebrafish expresses two human PKD1 paralogs, pkd1a and pkd1b. Knockdown of both genes in zebrafish by morpholino antisense oligonucleotides produced phenotypes of dorsal-axis curvature and pronephric cyst formation. We found that overexpression of LRRs suppressed both phenotypes in pkd1-morphant zebrafish. Purified recombinant LRR domain inhibited proliferation of HEK cells in culture and interacted with the heterotrimeric basement membrane protein laminin-511 (α5β1γ1) in vitro. Mutations of amino acid residues in LRRs structurally predicted to bind laminin-511 disrupted LRR–laminin interaction in vitro and neutralized the ability of LRRs to inhibit cell proliferation and cystogenesis. Our data support the hypothesis that the extracellular region of PC1 plays a role in modulating PC1 interaction with the extracellular matrix and contributes to cystogenesis of PC1 deficiency. Full article

Autosomal Dominant Polycystic Kidney Disease (ADPKD) stands as the most prevalent hereditary renal disorder in humans, ultimately culminating in end-stage kidney disease. Animal models carrying mutations associated with polycystic kidney disease have played an important role in the advancement of ADPKD research. The Han:SPRD rat model, carrying an R823W mutation in the Anks6 gene, is characterized by cyst formation and kidney enlargement. The mutated protein, named Samcystin, is localized in cilia of tubular epithelial cells and seems to be involved in cystogenesis. The homozygous Anks6 mutation leads to end-stage renal disease and death, making it a critical factor in kidney development and function. This review explores the utility of the Han:SPRD rat model, highlighting its phenotypic similarity to human ADPKD. Specifically, we discuss its role in preclinical trials and its importance for investigating the pathogenesis of the disease and developing new therapeutic approaches. Full article

The progressive formation of single or multiple cysts accompanies several renal diseases. Specifically, (i) genetic forms, such as adult dominant polycystic kidney disease (ADPKD), and (ii) acquired cystic kidney disease (ACKD) are probably the most frequent forms of cystic diseases. Adult dominant polycystic kidney disease (ADPKD) is a genetic disorder characterized by multiple kidney cysts and systemic alterations. The genes responsible for the condition are known, and a large amount of literature focuses on the molecular description of the mechanism. The present manuscript shows that a multiscale approach that considers supramolecular physical phenomena captures the characteristics of both ADPKD and acquired cystic kidney disease (ACKD) from the pathogenetic and therapeutical point of view, potentially suggesting future treatments. We first review the hypothesis of cystogenesis in ADPKD and then focus on ACKD, showing that they share essential pathogenetic features, which can be explained by a localized obstruction of a tubule and/or an alteration of the tubular wall tension. The consequent tubular aneurysms (cysts) follow Laplace’s law. Reviewing the public databases, we show that ADPKD genes are widely expressed in various organs, and these proteins interact with the extracellular matrix, thus potentially modifying wall tension. At the kidney and liver level, the authors suggest that altered cell polarity/secretion/proliferation produce tubular regions of high resistance to the urine/bile flow. The increased intratubular pressure upstream increases the difference between the inside (Pi) and the outside (Pe) of the tubules (∆P) and is counterbalanced by lower wall tension by a factor depending on the radius. The latter is a function of tubule length. In adult dominant polycystic kidney disease (ADPKD), a minimal reduction in the wall tension may lead to a dilatation in the tubular segments along the nephron over the years. The initial increase in the tubule radius would then facilitate the progressive expansion of the cysts. In this regard, tubular cell proliferation may be, at least partially, a consequence of the progressive cysts’ expansion. This theory is discussed in view of other diseases with reduced wall tension and with cysts and the therapeutic effects of vaptans, somatostatin, SGLT2 inhibitors, and potentially other therapeutic targets. Full article

Nephronophthisis (NPHP) is the most prevalent monogenic disease leading to end-stage renal failure in childhood. RhoA activation is involved in NPHP pathogenesis. This study explored the role of the RhoA activator guanine nucleotide exchange factor (GEF)-H1 in NPHP pathogenesis. We analyzed the expression and distribution of GEF-H1 in NPHP1 knockout (NPHP1^KO) mice using Western blotting and immunofluorescence, followed by GEF-H1 knockdown. Immunofluorescence and renal histology were used to examine the cysts, inflammation, and fibrosis. A RhoA GTPase activation assay and Western blotting were used to detect the expression of downstream GTP-RhoA and p-MLC2, respectively. In NPHP1 knockdown (NPHP1^KD) human kidney proximal tubular cells (HK2 cells), we detected the expressions of E-cadherin and α-smooth muscle actin (α-SMA). In vivo, increased expression and redistribution of GEF-H1, and higher levels of GTP-RhoA and p-MLC2 in renal tissue of NPHP1^KO mice were observed, together with renal cysts, fibrosis, and inflammation. These changes were alleviated by GEF-H1 knockdown. In vitro, the expression of GEF-H1 and activation of RhoA were also increased, with increased expression of α-SMA and decreased E-cadherin. GEF-H1 knockdown reversed these changes in NPHP1^KD HK2 cells. Thus, the GEF-H1/RhoA/MLC2 axis is activated in NPHP1 defects and may play a pivotal role in NPHP pathogenesis. Full article

Tuberous sclerosis complex (TSC) is caused by mutations in the hamartin (TSC1) or tuberin (TSC2) genes. Using a mouse model of TSC renal cystogenesis that we have previously described, the current studies delineate the metabolic changes in the kidney and their relation to alterations in renal gene expression. To accomplish this, we compared the metabolome and transcriptome of kidneys from 28-day-old wildtype (Wt) and principal cell-specific Tsc1 KO (Tsc1 KO) mice using targeted ¹H nuclear magnetic resonance targeted metabolomic and RNA-seq analyses. The significant changes in the kidney metabolome of Tsc1 KO mice included reductions in the level of several amino acids and significant decreases in creatine, NADH, inosine, UDP-galactose, GTP and myo-inositol levels. These derangements may affect energy production and storage, signal transduction and synthetic pathways. The pertinent derangement in the transcriptome of Tsc1 KO mice was associated with increased collecting duct acid secretion, active cell division and the up-regulation of signaling pathways (e.g., MAPK and AKT/PI3K) that suppress the TSC2 GTPase-activating function. The combined renal metabolome and transcriptome alterations observed in these studies correlate with the unregulated growth and predominance of genotypically normal A-intercalated cells in the epithelium of renal cysts in Tsc1 KO mice. Full article