Search Results (317)

Background and Objectives: Hypocitraturia is a major risk factor for calcium-containing kidney stone disease. Citrate inhibits stone formation by binding calcium in the urine. The SLC13A2 gene encodes the sodium-dependent dicarboxylate cotransporter 1 (NaDC1), a membrane transport protein that facilitates citrate reabsorption in the proximal renal tubules. Variants in this gene, such as rs11568476 (V477M), have been shown to significantly impair transporter activity. This study aimed to investigate the presence of the rs11568476 polymorphism in SLC13A2 and its association with hypocitraturia in Turkish patients with calcium-containing kidney stones. To our knowledge, this is the first genetic study evaluating this polymorphism in a Turkish cohort. Materials and Methods: This prospective cross-sectional study included 90 patients diagnosed with calcium-containing kidney stones at Düzce University Faculty of Medicine, Department of Urology. Based on 24 h urinary citrate levels, patients were divided into two groups: normocitraturic (n = 38) and hypocitraturic (n = 52). Blood and 24 h urine samples were analyzed for biochemical parameters. The rs11568476 polymorphism in SLC13A2 was analyzed using Real-Time PCR. Results: There were no significant differences between the two groups in terms of age, gender, and most biochemical parameters. Serum uric acid levels were significantly higher in the hypocitraturic group (p = 0.002), whereas family history of stone disease was more prevalent in the normocitraturic group (p = 0.024). Genetic analysis revealed no polymorphism in the rs11568476 region; all patients exhibited the homozygous wild-type genotype (GG). Conclusions: No association was observed between the rs11568476 polymorphism and hypocitraturia in this cohort. The absence of the polymorphism suggests that this variant may be rare or absent in the Turkish population. These findings highlight the importance of investigating additional genetic and environmental contributors to hypocitraturia and nephrolithiasis through larger, multicenter studies. Full article

Background: Accumulating evidence indicates that SARS-CoV-2 infection results in long-term multiorgan complications, with the kidney being a primary target. This study aimed to characterize the long-term transcriptomic changes in the kidney following coronavirus infection using a murine model of MHV-1-induced SARS-like illness and to evaluate the therapeutic efficacy of SPIKENET (SPK). Methods: A/J mice were infected with MHV-1. Renal tissues were collected and subjected to immunofluorescence analysis and Next Generation RNA Sequencing to identify differentially expressed genes associated with acute and chronic infection. Bioinformatic analyses, including PCA, volcano plots, and GO/KEGG pathway enrichment, were performed. A separate cohort received SPK treatment, and comparative transcriptomic profiling was conducted. Gene expression profile was further confirmed using real-time PCR. Results: Acute infection showed the upregulation of genes involved in inflammation and fibrosis. Long-term MHV-1 infection led to the sustained upregulation of genes involved in muscle regeneration, cytoskeletal remodeling, and fibrotic responses. Notably, both expression and variability of SLC22 and SLC22A8, key proximal tubule transporters, were reduced, suggesting a loss of segment-specific identity. Further, SLC12A1, a critical regulator of sodium reabsorption and blood pressure, was downregulated and is associated with the onset of polyuria and hydronephrosis. SLC transporters exhibited expression patterns consistent with tubular dysfunction and inflammation. These findings suggest aberrant activation of myogenic pathways and structural proteins in renal tissues, consistent with a pro-fibrotic phenotype. In contrast, SPK treatment reversed the expression of most genes, thereby restoring the gene profiles to those observed in control mice. Conclusions: MHV-1-induced long COVID is associated with persistent transcriptional reprogramming in the kidney, indicative of chronic inflammation, cytoskeletal dysregulation, and fibrogenesis. SPK demonstrates robust therapeutic potential by normalizing these molecular signatures and preventing long-term renal damage. These findings underscore the relevance of the MHV-1 model and support further investigation of SPK as a candidate therapy for COVID-19-associated renal sequelae. Full article

Chronic kidney disease (CKD) significantly affects canine health, but the precise cellular mechanisms of this condition remain elusive. In this study, we used single-cell RNA sequencing (scRNA-seq) to profile renal cellular gene expression in a canine model of X-linked hereditary nephropathy (XLHN). Dogs with this condition exhibit juvenile-onset CKD similar to that seen in human Alport syndrome. Post-mortem renal cortical tissues from an affected male dog and a heterozygous female dog were processed to obtain single-cell suspensions. In total, we recovered up to 13,190 cells and identified 11 cell types, including major kidney cells and immune cells. Differential gene expression analysis comparing the affected male and heterozygous female dogs identified cell-type specific pathways that differed in a subpopulation of proximal tubule cells. These pathways included the integrin signaling pathway and the pathway for inflammation mediated by chemokine and cytokine signaling. Additionally, using machine learning-empowered digital cytometry, we deconvolved bulk mRNA-seq data from a previous canine study, revealing changes in cell type proportions across CKD stages. These results underline the utility of single-cell methodologies and digital cytometry in veterinary nephrology. Full article

Background and Clinical Significance: Although dietary supplements have often been deemed safe, some have been linked to drug-induced nephropathy due to their diverse ingredients. The aim of this report is to enhance clinical awareness of a novel and emerging cause of Fanconi syndrome due to red yeast rice supplements and to contribute new histopathological and clinical data. Case Presentation: We report two cases of renal dysfunction and Fanconi syndrome associated with the use of red yeast rice supplements. Both patients presented with renal impairment accompanied by elevated markers of tubular injury, hypouricemia, hypokalemia, and glucosuria, consistent with Fanconi syndrome. Following the discontinuation of the red yeast rice supplement and initiation of steroid therapy, Fanconi syndrome resolved, however, moderate renal dysfunction persisted. Urinary NGAL levels improved after treatment in both cases. KIM-1 normalized in one case but remained elevated in the other. Uromodulin recovery was complete in one case and partial in the other. Renal biopsy revealed mild tubulointerstitial nephritis, with notable shedding of proximal tubular epithelial cells. Immunohistochemical analysis demonstrated reduced expression of URAT-1, Na-K ATPase, and Na-Pi IIa in some tubules. Conclusions: These findings suggest that renal injury induced by red yeast rice supplements is mediated by direct proximal tubular necrosis caused by a harmful substance in the supplement, resulting in persistence of tubular dysfunction. Full article

Chronic kidney disease (CKD) is associated with the systemic accumulation of uremic toxins (UTs) due to impaired renal elimination. Among these, indoxyl sulfate (IS) and p-cresyl sulfate (PCS) are particularly challenging because of their high protein binding and limited removal by dialysis. In addition to renal excretion, the transport of IS and PCS, and their microbiota-derived precursors, indole and p-cresol, across key physiological barriers—the intestinal barrier, blood–brain barrier, and renal proximal tubule—critically influences their distribution and elimination. This review provides an overview of transporter-mediated mechanisms involved in the disposition of IS, PCS, and their microbial precursors, indole and p-cresol. It also examines how these UTs may interact with commonly prescribed drugs in CKD, particularly those that share transporter pathways as substrates or inhibitors. These drug–toxin interactions may influence the pharmacokinetics and toxicity of IS and PCS, but remain poorly characterized and largely overlooked in clinical settings. A better understanding of these processes may guide future efforts to optimize pharmacotherapy and support more informed management of CKD patients, particularly in the context of polypharmacy. Full article

Background: Organic anion transporter 3 (OAT3) in the kidney proximal tubule cells plays a critical role in renal clearance of numerous endogenous metabolites and exogenous drugs and toxins. In this study, we discovered that epidermal growth factor (EGF) regulates the expression and activity of OAT3 through palmitoylation, a novel mechanism that has never been described in the OAT field. Methods/Results: Our results showed that treatment of OAT3-expressing cells with EGF led to a ~40% increase in OAT3 expression and OAT3-mediated transport of estrone sulfate, a prototypical substrate for OAT3. EGF-stimulated OAT3 transport activity was abrogated by H-89, a protein kinase A (PKA) inhibitor, indicating that an EGF-PKA signaling pathway is involved in the regulation of OAT3. We also showed that treatment of OAT3-expressing cells with EGF resulted in an enhancement of OAT3 palmitoylation, a novel type of post-translational modification for OATs, and such an enhancement was blocked by H-89, suggesting that the EGF-PKA signaling pathway participated in the modulation of OAT3 palmitoylation. Palmitoylation was catalyzed by a group of palmitoyltransfereases, and we showed that OAT3 palmitoylation and expression were inhibited by 2-BP, a general inhibitor for palmitoyltransfereases. We also explored the relationship among EGF/PKA signaling, OAT palmitoylation, and OAT transport activity. We treated OAT3-expressing cells with EGF or Bt2-cAMP, a PKA activator, in the presence and absence of 2-BP, followed by the measurement of OAT3-mediated transport of estrone sulfate. We showed that both EGF- and Bt2-cAMP-stimulated OAT3 transport activity were abolished by 2-BP, suggesting that palmitoylation mediates the regulation of EGF/PKA on OAT3. Finally, we showed that osimertinib, an anti-cancer drug/EGFR inhibitor, blocked EGF-stimulated OAT3 transport activity. Conclusions: In summary, we provided the first evidence that palmitoylation transduces the EGF/PKA signaling pathway to the modulation of OAT3 expression and function. Our study also provided an important implication that during comorbidity therapies, EGFR inhibitor drugs could potentially decrease the transport activity of renal OAT3, which would subsequently alter the therapeutic efficacy and toxicity of many co-medications that are OAT3 substrates. Full article

Volatile anesthetics, while increasingly utilized in intensive care medicine, are associated with significant renal adverse effects. A critical safety concern—particularly with sevoflurane—involves its potential impact on renal function. Pathophysiologically, inorganic fluoride levels exceeding 50 µmol/L are recognized as a threshold for nephrogenic diabetes insipidus, a condition generally considered reversible. Additionally, the sevoflurane degradation product “compound A” has been implicated in direct renal tubular and glomerular toxicity. Specifically, exposure has been correlated with glomerular damage, evidenced by albuminuria, as well as injury to both proximal and distal tubules, indicated by elevated levels of α-glutathione-S-transferase. Postprandial glycosuria may also be observed. Unlike nephrogenic diabetes insipidus, the structural damage induced by compound A may result in irreversible renal impairment. Full article

Arsenic, in the form of inorganic arsenite, is toxic to the kidney and can cause acute kidney injury, manifesting as destruction of proximal tubule cells. Nephron repair is possible through the proliferation of resident tubular progenitor cells expressing CD133 and CD24 surface markers. We simulated regenerative repair in the continued presence of i-As (III) using a cell culture model of a renal progenitor cell line expressing CD133 (PROM1) and CD24. Continued exposure and subculturing of progenitor cells to i-As (III) led to a reduction in the expression of PROM1 and CD24, as well as a decrease in the ability to differentiate into tubule-like structures. Cessation of i-As (III) and recovery for up to three passages resulted in continued repression of PROM1 and reduced ability to differentiate. Chronically exposed cells exhibited an ability to form colonies in soft agar, suggesting neoplastic transformation. Chronically exposed cells also exhibited an induction of CD44, a cell surface marker commonly found in renal cell carcinoma, as well as in tubular repair in chronic renal injury such as chronic kidney disease. These results demonstrate potential adverse outcomes of renal progenitor cells chronically exposed to a nephrotoxicant, as well as in environmental exposure to arsenic. Full article

Diabetes mellitus has been knowingly associated with increased risk of fractures, so much so that skeletal fragility is considered a complication of diabetes. Determinants of bone fragility in this chronic condition are several, and the diabetes treatment choice could influence bone metabolism. Sodium-glucose cotransporter-2 inhibitors (SGLT2i) have recently expanded the therapeutic armamentarium for type 2 diabetes mellitus (T2D); these antihyperglycemic drugs act by reducing renal glucose reabsorption in the proximal tubule and have a proven cardiorenal benefit. The role of SGLT2i towards phospho-calcium metabolism is still unclear, so we aimed to review the current evidence of the relationship between SGLT2i and calcium and phosphate homeostasis. The PubMed, Scopus, and Web of Knowledge databases were searched to identify original research articles, meta-analyses, and scientific reviews on effects on bone metabolism in T2D patients treated with SGLT2i. Emerging data indicate that SGLT2i may lead to a rise of bone turnover markers, promoting a lower skeletal bone density and an increased fracture risk on murine models, but in real-world studies, results are controversial. Therefore, more clinical trials are needed to further clarify this topic, and the effects of SGLT2i on calcium homeostasis remain to date poorly understood. Full article

Background: Abnormal sodium-dependent hexose reabsorption in the proximal tubule, accompanied by a functional decrease in sodium and water reabsorption under conditions of increased volemia, may be attributed to a dysfunction of primary transporters related to a genetic defect in the Na,K-ATPase gamma subunit. Methods: We examined two sisters, aged 6 and 8 years, who presented with hypercalciuria, glucosuria, fructosuria, galactosuria, and atypical proteinuria. Primary diabetes, galactosemia, and fructosemia were excluded, suggesting a defect in cellular hexose transport in the proximal tubule. We conducted tests on the family members to assess the impact of gradually increasing volemia, using a water-loading test, on tubular H⁺ transport and urinary excretion of calcium, citrate, endothelin-1 (ET-1), and atypical proteins. Whole-exome sequencing was performed in the affected patients to identify the genetic basis of this phenotype. Results: Extended investigations revealed a complex defect in tubular H⁺ transport, calcium and citrate handling, and atypical proteinuria, resulting from water load-driven overproduction of endothelin-1 (ET-1). Genetic analysis identified a heterozygous pathogenic variant, c.80G>A, p.(Arg27His), in the FXYD2 gene, which encodes the gamma subunit of sodium/potassium-transporting ATPase. Conclusions: Our findings provide evidence that a defect in FXYD2 (splice form a) leads to functional impairment of proximal tubular hexose reabsorption. This is the first report on the metabolic consequences of a pathogenic FXYD2 variant affecting the gamma subunit of sodium/potassium-transporting ATPase in humans. The genotype–phenotype correlation in two siblings with a sodium-dependent defect in fructose, galactose, and glucose renal reabsorption allowed us to characterize a disease with a distinct clinical course and biochemical profile, not previously reported in the medical literature or genetic databases. Analysis of this condition was crucial for the early introduction of reno-protective treatment aimed at slowing the progression of nephropathy and for risk assessment in family members, which was essential for genetic counseling. Full article

Physiological control of blood pressure (BP) and extracellular fluid volume is mediated by the action of the renin-angiotensin system (RAS). The presence of RAS components throughout the nephron has been widely discussed. The (pro)renin receptor (PRR) is a member of the RAS widely expressed in the body of humans and rodents. In the kidney, PRR is expressed in mesangial cells, renal vasculature, and tubules of the proximal and distal nephron. Binding of the PRR to renin and prorenin promotes angiotensin (Ang) I-mediated sodium (Na⁺) reabsorption via the epithelial sodium channel (ENaC). The Goldblatt 2-kidney 1-clip (2K1C) is a model of experimental renovascular hypertension that displays activation of systemic and intrarenal RAS. We use the 2K1C hypertension mouse model for 7 days to evaluate the role of the PRR on renal αENaC expression, Na⁺ reabsorption, and BP using pharmacological systemic blockade of the PRR with PRO20 peptide. Mice undergoing or not to 2K1C surgery (0.13 mm clip internal gap) were chronically infused with PRO20 and compared to sham (control) mice to assess changes in systolic BP (SBP) and diastolic BP (DBP), intrarenal angiotensin-converting enzyme (ACE) activity, Ang II, and renal αENaC expression and natriuretic responses after a saline challenge. Renal artery obstruction increased SBP and DBP, intrarenal ACE activity, Ang II levels, Na⁺ retention, and αENaC expression in both kidneys. PRO20 prevented the increases in SBP, DBP, attenuated Na⁺ retention, and blunted intrarenal Ang II and αENaC levels in non-clipped kidneys of 2K1C mice. Chronic infusion of the PRR for 7 days prevents hypertensive responses in part due to impaired αENaC upregulation and intrarenal Ang II formation in the early phase of the development of renovascular hypertension in 2K1C Goldblatt mice. Full article

In this work, the utilization of calcium and strontium by the (Ca²⁺ + Mg²⁺)ATPase of the basolateral plasma membrane of renal proximal convoluted tubules were compared. [⁹⁰Sr]Sr²⁺ and [⁴⁵Ca]Ca²⁺ uptake by vesicles derived from this membrane were strictly dependent on ATP and Mg²⁺, and no other nucleotide was able to support the transport. Each cation inhibited the uptake of the other one in a purely competitive fashion (the same Vmax; increased K_0.5), without causing a significant change in the influx rate. These results indicate that both cations bind at the same transport site on the enzyme, facing the cytosolic surface of the cell. The K_0.5 for Sr²⁺ obtained for (Sr²⁺ + Mg²⁺)ATPase activity was 13.1 ± 0.2 µM and for Sr²⁺ uptake was 13.4 ± 0.1 µM. They were higher than K_0.5 for Ca²⁺ obtained for (Ca²⁺ + Mg²⁺)ATPase activity (0.42 ± 0.03 µM) and for Ca²⁺ uptake (0.28 ± 0.02 µM). It is postulated that the lower ATPase affinity for Sr²⁺ is associated with greater steric difficulties for the occupation by this cation of the binding and transport sites, as a consequence of its greater crystal ionic radius (1.13 Å for Sr²⁺ against 0.99 Å for Ca²⁺). Full article

Primary mouse renal proximal tubule epithelial cells (moRPTECs) were immortalized by lentivirus transduction to create hTERT or SV40LgT (LgT) cell lines. Prior work showed a more pronounced injury and repair response in LgT versus hTERT cells after chemical challenge. We hypothesized that unique genomic changes occurred after immortalization, altering critical genes and pathways. RNA-seq profiling and whole-genome sequencing (WGS) of parent, hTERT, and LgT cells showed that 92.5% of the annotated transcripts were shared, suggesting a conserved proximal tubule expression pattern. However, the cell lines exhibited unique transcriptomic and genomic profiles different from the parent cells. Three transcript classes were quite relevant for chemical challenge response—Cyps, ion channels, and metabolic transporters—each important for renal function. A pathway analysis of the hTERT cells suggested alterations in intermediary and energy metabolism. LgT cells exhibited pathway activation in cell cycle and DNA repair that was consistent with replication stress. Genomic karyotyping by combining WGS and RNA-seq data showed increased gene copy numbers in chromosome 5 for LgT cells, while hTERT cells displayed gene copy losses in chromosomes 4 and 9. These data suggest that the exaggerated transcriptional responses of LgT cells versus hTERT cells result from differences in gene copy numbers, replication stress, and the unique selection processes underlying LgT or hTERT immortalization. Full article

Background: This prospective study aimed to evaluate renal function using retinol binding protein 4 (RBP4), cystatin C, and glomerular filtration rate (GFR) in relation to physical activity and lesion level in children with neurogenic bladder (NB) post-myelomeningocele. Methods: Two groups were studied: 33 children with NB and 20 healthy controls. Data collected included demographic details, physical activity levels, uroflowmetry, urodynamic diagnosis, and renal function parameters. Urinary RBP4 and serum cystatin C were measured using ELISA, and GFR was calculated using the Schwartz formula. Results: The NB group had higher median serum cystatin C and urinary RBP4/creatinine ratios compared to the control group (0.28 vs. 0.22; 18.6 vs. 3.2, respectively). The participants were categorized based on activity levels, lesion levels, catheterization status, and urodynamic diagnosis. No differences in RBP4, cystatin C, or urodynamic diagnosis were observed according to activity and lesion levels. Significant differences in GFR were found based on activity and lesion levels, with higher median GFR in NB children (182.7 vs. 147.3). No differences were found between catheterized and non-catheterized children in the studied parameters. Conclusions: Elevated urinary RBP4 in NB patients suggests possible proximal renal tubule dysfunction. Higher serum cystatin C despite lower creatinine levels indicates altered renal function in NB children. Urinary RBP4 correlates positively with bladder pressure at maximum cystometric capacity, suggesting potential utility in therapy monitoring and modification. Full article

Background/Objectives: The pathogenesis of diabetic kidney disease (DKD) is complex and multifactorial. Because of its complications and reduced number of diagnostic biomarkers, it is important to explore new biomarkers with possible roles in the early diagnosis of DKD. Our study aims to investigate the pattern of previously identified metabolites and their association with biomarkers of endothelial dysfunction, proximal tubule (PT) dysfunction, and podocyte injury. Methods: A total of 110 participants, comprising 20 healthy individuals and 90 patients divided in three groups were enrolled in the study: normoalbuminuria, microalbuminuria, and macroalbuminuria. Untargeted and targeted metabolomic methods were employed to assess urinary and serum biomarkers, as well as indicators of endothelial dysfunction, podocyte damage, and PT dysfunction through ELISA techniques. Results: Our research uncovered specific metabolites that exhibit varying levels across different sub-groups. Notably, glycine serves as a distinguishing factor between group C and the normoalbuminuric group. Furthermore, glycine is correlated with endothelial markers, especially VCAM. We observed a gradual decrease in kynurenic acid levels from group C to group P3; this biomarker also demonstrates an inverse relationship with both p-selectin and VCAM. Additionally, tryptophan levels decline progressively from group C to group P3, accompanied by a negative correlation with p-selectin and VCAM. Urinary tiglylglycine also differentiates among the patient groups, with concentrations decreasing as the condition worsens. It shows a strong positive correlation with nephrin, podocalyxin, KIM1, and NAG. Conclusions: In conclusion, glycine, tiglylglycine, kynurenic acid and tryptophan may be considered putative biomarkers for early diagnosis of DKD and T2DM progression. Full article