Project description:Transplanting renal allografts represents the major curative treatment of chronic renal failure. Despite recent advances in immunosuppressive therapy, long-term survival of allografts remains a major clinical problem. Kidney function depends in part on transport proteins such as MRP2 (ABCC2) which facilitates renal secretion of amphiphilic exogenous and endogenous compounds. Inherited variants of genes not related to the immune system have been shown to modify the outcome after renal transplantation. We investigated whether ABCC2 gene variants in the donor kidney affect renal graft function. A congenic rat model was established carrying a single nucleotide deletion in the ABCC2 gene. Renal cross transplantations were performed with wild type rats. Renal excretion of the MRP2 substrates bilirubin glucuronide and p-aminohippuric acid, but not morphine-6-glucuronide, was affected by the donor genotype. Moreover, proteomic analyses and transcriptional profiling revealed modified expression patterns indicative of increased oxidative stress in renal grafts carrying the mutated gene. In the clinical part our study, we assessed ABCC2 haplotypes in renal transplant patients and evaluated graft function. The 3563T>A gene polymorphism was significantly associated with delayed graft function. Together, both experimental and clinical data show that the ABCC2 genotype of the donor kidney affects renal graft function. Keywords: dysfunction of organic anion transporter MRP2 (ABCC2)
Project description:The circadian clock controls a wide variety of metabolic and homeostatic processes in a number of tissues, including the kidney. However, the role of the renal circadian clocks remains largely unknown. To address this question we performed transcriptomic analysis in mice with inducible and conditional ablation of the circadian clock system in the renal tubular cells (Bmal1lox/lox/Pax8-rtTA/LC1 mice). Deep sequencing of the renal transcriptome revealed significant changes in the expression of genes related to metabolic pathways and organic anion transport. In parallel, kidneys from Bmal1lox/lox/Pax8-rtTA/LC1 mice exhibited a significant decrease in the NAD+/NADH ratio suggesting an increased anaerobic glycolysis and/or decreased mitochondrial function. In-depth analysis of two selected pathways revealed (i) a significant increase in plasma urea levels correlating with increased renal arginase 2 (Arg2) activity, hyperargininemia and increase of the kidney arginine content; (ii) a significantly increased plasma creatinine concentration and reduced capacity of the kidney to secrete anionic drugs (furosemide), paralleled by a ~80% decrease in the expression levels of organic anion transporter OAT3 (SLC22a8). Collectively, these results indicate that the renal circadian clocks control a variety of metabolic/homeostatic processes at both the intra-renal and systemic levels and are involved in drug disposition. Mice with a specific ablation of the Arntl gene encoding BMAL1 in the renal tubular cells were compared to wild-type littermate at ZT4 and ZT16 (ZT â Zeitgeber time units; ZT0 is the time of light on and ZT12 is the time of light off).
Project description:The circadian clock controls a wide variety of metabolic and homeostatic processes in a number of tissues, including the kidney. However, the role of the renal circadian clocks remains largely unknown. To address this question we performed transcriptomic analysis in mice with inducible and conditional ablation of the circadian clock system in the renal tubular cells (Bmal1lox/lox/Pax8-rtTA/LC1 mice). Deep sequencing of the renal transcriptome revealed significant changes in the expression of genes related to metabolic pathways and organic anion transport. In parallel, kidneys from Bmal1lox/lox/Pax8-rtTA/LC1 mice exhibited a significant decrease in the NAD+/NADH ratio suggesting an increased anaerobic glycolysis and/or decreased mitochondrial function. In-depth analysis of two selected pathways revealed (i) a significant increase in plasma urea levels correlating with increased renal arginase 2 (Arg2) activity, hyperargininemia and increase of the kidney arginine content; (ii) a significantly increased plasma creatinine concentration and reduced capacity of the kidney to secrete anionic drugs (furosemide), paralleled by a ~80% decrease in the expression levels of organic anion transporter OAT3 (SLC22a8). Collectively, these results indicate that the renal circadian clocks control a variety of metabolic/homeostatic processes at both the intra-renal and systemic levels and are involved in drug disposition.
Project description:Tubuloids are adult stem cell-based kidney organoids with promising application in kidney disease modelling and drug screening. However, tubuloids still present limited transepithelial transport capacity, which is essential for the kidney’s function. The extracellular vesicles (EVs) are cell-derived vesicular structures known to regulate several cellular processes, including development and maturation. This study explores the potential of EVs derived from renal cells to support tubuloid functional maturation by increasing the levels of organic anion transport 1 (OAT1), a protein involved in renal waste handling.
Project description:The proximal tubule plays an important role in the secretion and reabsorption of drugs in the kidney and is a major site of drug interaction and toxicity. Kidney toxicity analysis via in vitro assays is challenging as few provide appropriate proximal tubular cell function. In this study, we aimed to develop a simple and reproducible method to culture human proximal tubular epithelial cells (RPTECs), used in pharmacokinetic and toxicological evaluation by monitoring organic anion transporter (OAT)1 as a selection marker. As a result, by culturing RPTECs in spherical cellular aggregates, OAT1 protein expression, which does not increase in conventional 2D culture, increased over time and reached a similar level to that in human renal cortices from 5 different donors. The expression of proximal tubule markers, AQP1 and CDH6, was maintained, indicating that 3D RPTEC spheroids had proximal tubule characteristics. For SLC transporters, the 3D spheroid culture improved the protein expression of about 7% of the 139 transporter proteins detected and 2.3% of 4,800 proteins detected to about 5-fold that in human renal cortices. Furthermore, the protein expression levels of about 4800 proteins in 3D RPTEC spheroids (cultured for 12 days) were maintained over 20 days. Cisplatin and adefovir exhibited transporter-dependent ATP decreases in 3D RPTEC spheroids. These results indicate that the 3D RPTEC spheroid is a simple and robust in vitro experimental system for pharmacokinetic and toxicological evaluation in drug development.
Project description:Ochratoxin A (OTA) is one of the most abundant mycotoxin contaminants in food stuffs and possesses carcinogenic, nephrotoxic, teratogenic and immunotoxic properties. Especially, severe nephrotoxicity is of great concern, as characterized by degeneration of epithelial cells of the proximal tubules and interstitial fibrosis. However, its mechanism of toxicity, hazard identification as well as genetic risk factors contributing to OTA toxicity in humans has been elusive due to the lack of adequate models that fully recapitulate kidney function in vitro. The present study attempts to evaluate dose-response relationships, identify the contribution of active transport proteins that govern renal disposition of OTA, and determine the role of metabolism in bioactivation and detoxification of OTA using a 3D human kidney proximal tubule microphysiological system (kidney MPS). We demonstrated that IC50 values of OTA in kidney MPS culture (0.375 – 1.21 µM) were in good agreement with clinical toxic concentrations of OTA in urine. Surprisingly, no enhancement of kidney injury biomarkers was evident in the effluents of kidney MPS after OTA exposure despite significant toxicity observed by LIVE/DEAD staining, rather these biomarkers were decreased in OTA concentration-dependent manner. Furthermore, the effect of 1-aminobenzotriazole (ABT) and 6-(NBD-4-ylthio-) hexanol (NBDHEX), pan-inhibitor of P450 and GST enzymes, respectively, on the OTA-induced toxicity in kidney MPS was examined, which resulted in significant enhancement of OTA-induced toxicity by NBDHEX (3 µM) treatment whereas ABT (1 mM) treatment decreased OTA-induced toxicity, suggesting the roles of GSTs and P450 enzymes in the detoxification and bioactivation of OTA, respectively. Additionally, OTA transport studies using kidney MPS in the presence and absence of inhibitor of organic anion transporter(s), probenecid (1 mM), revealed the role of organic anionic membrane transporter(s) in the kidney specific disposition of OTA. Our findings provide a better understanding of the mechanism of OTA-induced kidney injury which may support changes in risk assessment, regulatory agency policies on allowable exposure levels and determination of genetic factors in high-risk populations against OTA nephrotoxicity.
Project description:Approximately 70% of kidney grafts are obtained from deceased donors, and these grafts must be preserved in hypothermic conditions to prolong their viability until transplantation. However, prolonged cold storage (CS) of kidneys results in poor long-term outcomes after transplantation. We reported previously that CS of rat kidneys for 18 h prior to transplant impaired proteasome function, disrupted protein homeostasis, and reduced graft function. The goal of the present study was to identify the renal proteins that are dysregulated by this CS-induced injury. Isolated donor Lewis rat kidneys were subject to 18-h CS and transplanted into recipient Lewis rats (CS+Tx). Autotransplantation (ATx: transplant with 0-h CS) or Sham (right nephrectomy) surgeries served as controls. The proteome of kidney homogenates was analyzed with tandem mass-tag mass spectrometry to identify CS-induced abnormalities in kidney grafts. CS injury disrupted the renal phosphoproteome in kidney grafts and dysregulated numerous signaling pathways. Integrated analysis of global proteomes and phosphoproteomes identified 15 proteins that were significantly regulated in a CS-specific manner. In particular, proteins and pathways such as complement and coagulation cascades were upregulated, while antioxidant pathways, such as glutathione, were suppressed in CS+Tx groups compared to ATx and Sham controls. This study, for the first time, provides deeper insight into the disruption of the renal graft proteome caused by CS injury and provides a novel set of pathways and molecules that can be investigated to delineate their specific role in renal transplant outcomes, ultimately improving outcomes for patients with end-stage kidney disease.