Renal xenobiotic transporters are differentially expressed in mice following cisplatin treatment

Prophylactic vitamin C supplementation regulates DNA demethylation to protect against cisplatin-induced acute kidney injury in mice

Cisplatin-induced acute kidney injury (AKI) restricts the use of cisplatin as a first-line chemotherapeutic agent. Our previous study showed that prophylactic vitamin C supplementation may act as an epigenetic modulator in alleviating cisplatin-induced AKI in mice. However, the targets of vitamin C and the mechanisms underlying the epigenetics changes remain largely unknown. Herein, whole-genome bisulfite sequencing and bulk RNA sequencing were performed on the kidney tissues of mice treated with cisplatin with prophylactic vitamin C supplementation (treatment mice) or phosphate-buffered saline (control mice) at 24 h after cisplatin treatment. Ascorbyl phosphate magnesium (APM), an oxidation-resistant vitamin C derivative, was found that led to global hypomethylation in the kidney tissue and regulated different functional genes in the promoter region and gene body region. Integrated evidence suggested that APM enhanced renal ion transport and metabolism, and reduced apoptosis and inflammation in the kidney tissues. Strikingly, Mapk15, Slc22a6, Cxcl5, and Cd44 were the potential targets of APM that conferred protection against cisplatin-induced AKI. Moreover, APM was found to be difficult to rescue cell proliferation and apoptosis caused by cisplatin in the Slc22a6 knockdown cell line. These results elucidate the mechanism by which vitamin C as an epigenetic regulator to protects against cisplatin-induced AKI and provides a new perspective and evidence support for controlling the disease process through regulating DNA methylation.

Asperulosidic Acid Ameliorates Renal Interstitial Fibrosis via Removing Indoxyl Sulfate by Up-Regulating Organic Anion Transporters in a Unilateral Ureteral Obstruction Mice Model

Asperulosidic acid is a bioactive iridoid isolated from Hedyotis diffusa Willd. with anti-inflammatory and renal protective effects. However, its mechanism on renal interstitial fibrosis has not been elucidated yet. The present study aims to explore whether asperulosidic acid could retard renal fibrosis by reducing the circulating indoxyl sulfate (IS), which is a uremic toxin and accelerates chronic kidney disease progression by inducing renal fibrosis. In this paper, a unilateral ureteral obstruction (UUO) model of Balb/C mice was established. After the mice were orally administered with asperulosidic acid (14 and 28 mg/kg) for two weeks, blood, liver and kidney were collected for biochemical, histological, qPCR and Western blot analyses. Asperulosidic acid administration markedly reduced the serum IS level and significantly alleviated the histological changes in glomerular sclerosis and renal interstitial fibrosis. It is noteworthy that the mRNA and protein levels of the organic anion transporter 1 (OAT1), OAT3 and hepatocyte nuclear factor 1α (HNF1α) in the kidney were significantly increased, while the mRNA expressions of cytochrome P450 2e1 (Cyp2e1) and sulfotransferase 1a1 (Sult1a1) in the liver were not altered after asperulosidic acid administration. These results reveal that asperulosidic acid could accelerate the renal excretion of IS by up-regulating OATs via HNF1α in UUO mice, thereby alleviating renal fibrosis, but did not significantly affect its production in the liver, which might provide important information for the development of asperulosidic acid.

Study Models of Drug-Drug Interactions Involving P-Glycoprotein: The Potential Benefit of P-Glycoprotein Modulation at the Kidney and Intestinal Levels

P-glycoprotein (P-gp) is a crucial membrane transporter situated on the cell's apical surface, being responsible for eliminating xenobiotics and endobiotics. P-gp modulators are compounds that can directly or indirectly affect this protein, leading to changes in its expression and function. These modulators can act as inhibitors, inducers, or activators, potentially causing drug-drug interactions (DDIs). This comprehensive review explores diverse models and techniques used to assess drug-induced P-gp modulation. We cover several approaches, including in silico, in vitro, ex vivo, and in vivo methods, with their respective strengths and limitations. Additionally, we explore the therapeutic implications of DDIs involving P-gp, with a special focus on the renal and intestinal elimination of P-gp substrates. This involves enhancing the removal of toxic substances from proximal tubular epithelial cells into the urine or increasing the transport of compounds from enterocytes into the intestinal lumen, thereby facilitating their excretion in the feces. A better understanding of these interactions, and of the distinct techniques applied for their study, will be of utmost importance for optimizing drug therapy, consequently minimizing drug-induced adverse and toxic effects.

A State-of-the-Science Review of Interactions of Per- and Polyfluoroalkyl Substances (PFAS) with Renal Transporters in Health and Disease: Implications for Population Variability in PFAS Toxicokinetics

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in the environment and have been shown to cause various adverse health impacts. In animals, sex- and species-specific differences in PFAS elimination half-lives have been linked to the activity of kidney transporters. However, PFAS molecular interactions with kidney transporters are still not fully understood. Moreover, the impact of kidney disease on PFAS elimination remains unclear.

OBJECTIVES

This state-of-the-science review integrated current knowledge to assess how changes in kidney function and transporter expression from health to disease could affect PFAS toxicokinetics and identified priority research gaps that should be addressed to advance knowledge.

METHODS

We searched for studies that measured PFAS uptake by kidney transporters, quantified transporter-level changes associated with kidney disease status, and developed PFAS pharmacokinetic models. We then used two databases to identify untested kidney transporters that have the potential for PFAS transport based on their endogenous substrates. Finally, we used an existing pharmacokinetic model for perfluorooctanoic acid (PFOA) in male rats to explore the influence of transporter expression levels, glomerular filtration rate (GFR), and serum albumin on serum half-lives.

RESULTS

The literature search identified nine human and eight rat kidney transporters that were previously investigated for their ability to transport PFAS, as well as seven human and three rat transporters that were confirmed to transport specific PFAS. We proposed a candidate list of seven untested kidney transporters with the potential for PFAS transport. Model results indicated PFOA toxicokinetics were more influenced by changes in GFR than in transporter expression.

DISCUSSION

Studies on additional transporters, particularly efflux transporters, and on more PFAS, especially current-use PFAS, are needed to better cover the role of transporters across the PFAS class. Remaining research gaps in transporter expression changes in specific kidney disease states could limit the effectiveness of risk assessment and prevent identification of vulnerable populations. https://doi.org/10.1289/EHP11885.

Polymorphic renal transporters and cisplatin's toxicity in urinary bladder cancer patients: current perspectives and future directions

Urinary bladder cancer (UBC) holds a potentially profound social burden and affects over 573,278 new cases annually. The disease's primary risk factors include occupational tobacco smoke exposure and inherited genetic susceptibility. Over the past 30 years, a number of treatment modalities have emerged, including cisplatin, a platinum molecule that has demonstrated effectiveness against UBC. Nevertheless, it has severe dose-limiting side effects, such as nephrotoxicity, among others. Since intracellular accumulation of platinum anticancer drugs is necessary for cytotoxicity, decreased uptake or enhanced efflux are the root causes of platinum resistance and response failure. Evidence suggests that genetic variations in any transporter involved in the entry or efflux of platinum drugs alter their kinetics and, to a significant extent, determine patients' responses to them. This review aims to consolidate and describe the major transporters and their polymorphic variants in relation to cisplatin-induced toxicities and resistance in UBC patients. We concluded that the efflux transporters ABCB1, ABCC2, SLC25A21, ATP7A, and the uptake transporter OCT2, as well as the organic anion uptake transporters OAT1 and OAT2, are linked to cisplatin accumulation, toxicity, and resistance in urinary bladder cancer patients. While suppressing the CTR1 gene's expression reduced cisplatin-induced nephrotoxicity and ototoxicity, inhibiting the expression of the MATE1 and MATE2-K genes has been shown to increase cisplatin's nephrotoxicity and resistance. The roles of ABCC5, ABCA8, ABCC10, ABCB10, ABCG1, ATP7B, ABCG2, and mitochondrial SLC25A10 in platinum-receiving urinary bladder cancer patients should be the subject of further investigation.

The Effect of Donor Rat Gender in Mitochondrial Transplantation Therapy of Cisplatin-Induced Toxicity on Rat Renal Proximal Tubular Cells

Background

Cisplatin-induced nephrotoxicity has been linked to a fundamental mechanism of mitochondrial dysfunction. A treatment called mitochondrial transplantation therapy can be used to replace damaged mitochondria with healthy mitochondria. Mitochondrial-related diseases may benefit from this approach.

Objectives

We investigated the effect of mitochondrial transplantation on cisplatin-induced nephrotoxicity using freshly isolated mitochondria obtained from renal proximal tubular cells (RPTCs).

Methods

Based on our previous findings, we hypothesized that direct exposure of healthy mitochondria to cisplatin-affected RPTCs might improve cytotoxicity markers and restore mitochondrial function. Therefore, the primary objective of this study was to determine whether newly isolated mitochondrial transplantation protected RPTCs from cisplatin-induced cytotoxicity. The supply of exogenous rat kidney mitochondria to cisplatin-affected RPTCs was also a goal of this study to investigate the possibility of gender differences. After the addition of cisplatin (100 µM), rat RPTCs (106 cells/mL) were suspended in Earle's solution (pH = 7.4) at 37°C for two hours. Freshly isolated mitochondria were extracted at 4°C and diluted in 100 and 200 µg/mL mitochondrial protein.

Results

Statistical analysis revealed that transplantation of healthy mitochondria decreased ROS level, mitochondrial membrane potential (MMP) collapse, MDA level, glutathione depletion, lysosomal membrane damage, and caspase-3 activity induced by cisplatin in rat RPTCs. In addition, our results demonstrated that transplantation of female rat kidney mitochondria has higher protective activity at reducing toxicity parameters than male mitochondria.

Conclusions

The findings reaffirmed that mitochondrial transplantation is a novel, potential, and promising therapeutic strategy for xenobiotic-induced nephrotoxicity.

Examination of the emerging role of transporters in the assessment of nephrotoxicity

INTRODUCTION

The kidney is vulnerable to various injuries based on its function in the elimination of many xenobiotics, endogenous substances and metabolites. Since transporters are critical for the renal elimination of those substances, it is urgent to understand the emerging role of transporters in nephrotoxicity.

AREAS COVERED

This review summarizes the contribution of major renal transporters to nephrotoxicity induced by some drugs or toxins; addresses the role of transporter-mediated endogenous metabolic disturbances in nephrotoxicity; and discusses the advantages and disadvantages of in vitro models based on transporter expression and function.

EXPERT OPINION

Due to the crucial role of transporters in the renal disposition of xenobiotics and endogenous substances, it is necessary to further elucidate their renal transport mechanisms and pay more attention to the underlying relationship between the transport of endogenous substances and nephrotoxicity. Considering the species differences in the expression and function of transporters, and the low expression of transporters in general cell models, in vitro humanized models, such as humanized 3D organoids, shows significant promise in nephrotoxicity prediction and mechanism study.

Loss of sphingosine kinase 2 protects against cisplatin-induced kidney injury

Cisplatin is an established chemotherapeutic drug for treatment of solid-organ cancers and is the primary drug used in the treatment of head and neck cancer; however, cisplatin-induced nephrotoxicity largely limits its clinical use. Inhibition of sphingosine kinase 2 (SphK2) has been demonstrated to alleviate various kidney diseases. Therefore, we hypothesized that inhibition of SphK2 could also protect against cisplatin-induced nephrotoxicity. Results from the present study showed that the SphK2 inhibitor ABC294640 or knockdown of SphK2 by siRNA blocked the cisplatin-induced increase of cellular injury markers (neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, and cleaved caspase-3) by Western blot analysis in HK-2 cells, a human renal tubular cell line. In addition, SphK2 inhibition blocked cisplatin-induced activation of NF-κB by Western blot analysis and immunostaining analysis. Furthermore, SphK2 inhibition suppressed cisplatin-induced increases of proinflammatory markers (NLR family pyrin domain containing 3, interleukin-1β, and interleukin-6). Genetic deletion of the SphK2 gene in mice further confirmed that inhibition of SphK2 protected against cisplatin-induced kidney damage in vivo. Compared with wild-type mice, SphK2 knockout mice exhibited less renal dysfunction and reduced promotion of kidney injury markers, inflammatory factors, tubular morphology damage, and fibrotic staining. At the same time, the SphK2 inhibitor ABC294640 failed to interfere with the activity of cisplatin or radiation in two cell culture models of head and neck cancer. It is concluded that inhibition of Sphk2 protects against cisplatin-induced kidney injury. SphK2 may be used as a potential therapeutic target for the prevention or treatment of cisplatin-induced kidney injury.NEW & NOTEWORTHY The present study provides new findings that sphingosine kinase 2 (SphK2) is highly expressed in renal tubules, cisplatin treatment increases the expression of SphK2 in proximal tubular cells and kidneys, and inhibition of SphK2 alleviates cisplatin-induced kidney injury by suppressing the activation of NF-κB, production of inflammatory factors, and apoptosis. SphK2 may serve as a potential therapeutic target for the prevention or treatment of cisplatin-induced nephrotoxicity.

Vitamin C Deficiency Causes Cell Type-Specific Epigenetic Reprogramming and Acute Tubular Necrosis in a Mouse Model

BACKGROUND

Vitamin C deficiency is found in patients with variable kidney diseases. However, the role of vitamin C as an epigenetic regulator in renal homeostasis and pathogenesis remains largely unknown.

METHODS

We showed that vitamin C deficiency leads to acute tubular necrosis (ATN) using a vitamin C-deficient mouse model (Gulo knock-out). DNA/RNA epigenetic modifications and injured S3 proximal tubule cells were identified in the vitamin C-deficient kidneys using whole-genome bisulfite sequencing, methylated RNA immunoprecipitation sequencing, and single-cell RNA sequencing.

RESULTS

Integrated evidence suggested that epigenetic modifications affected the proximal tubule cells and fenestrated endothelial cells, leading to tubule injury and hypoxia through transcriptional regulation. Strikingly, loss of DNA hydroxymethylation and DNA hypermethylation in vitamin C-deficient kidneys preceded the histologic sign of tubule necrosis, indicating the causality of vitamin C-induced epigenetic modification in ATN. Consistently, prophylactic supplementation of an oxidation-resistant vitamin C derivative, ascorbyl phosphate magnesium, promoted DNA demethylation and prevented the progression of cisplatin-induced ATN.

CONCLUSIONS

Vitamin C played a critical role in renal homeostasis and pathogenesis in a mouse model, suggesting vitamin supplementation may be an approach to lower the risk of kidney injury.

Unexpected Enhancement of Cytotoxicity of Cisplatin in a Rat Kidney Proximal Tubular Cell Line Overexpressing Mitochondrial Glutathione Transport Activity

In previous studies, we identified the two principal transporters that mediate the uptake of glutathione (GSH) from cytoplasm into the mitochondrial matrix of rat kidney proximal tubular cells. We hypothesized that genetic modulation of transporter expression could markedly alter susceptibility of renal proximal tubular cells to a broad array of oxidants and mitochondrial toxicants. Indeed, we previously showed that overexpression of either of these transporters resulted in diminished susceptibility to several chemicals. In the present work, we investigated the influence of overexpression of the mitochondrial 2-oxoglutarate carrier (OGC) in NRK-52E cells on the cytotoxicity of the antineoplastic drug cisplatin. In contrast to previous results showing that overexpression of the mitochondrial OGC provided substantial protection of NRK-52E cells from injury due to several toxicants, we found a remarkable enhancement of cellular injury from exposure to cisplatin as compared to wild-type NRK-52E cells. Despite the oxidative stress that cisplatin is known to cause in the renal proximal tubule, the increased concentrations of mitochondrial GSH associated with OGC overexpression likely resulted in increased delivery of cisplatin to molecular targets and increased cellular injury rather than the typical protection observed in the previous work.

Drug Transporters in the Kidney: Perspectives on Species Differences, Disease Status, and Molecular Docking

The kidneys are a pair of important organs that excretes endogenous waste and exogenous biological agents from the body. Numerous transporters are involved in the excretion process. The levels of these transporters could affect the pharmacokinetics of many drugs, such as organic anion drugs, organic cationic drugs, and peptide drugs. Eleven drug transporters in the kidney (OAT1, OAT3, OATP4C1, OCT2, MDR1, BCRP, MATE1, MATE2-K, OAT4, MRP2, and MRP4) have become necessary research items in the development of innovative drugs. However, the levels of these transporters vary between different species, sex-genders, ages, and disease statuses, which may lead to different pharmacokinetics of drugs. Here, we review the differences of the important transports in the mentioned conditions, in order to help clinicians to improve clinical prescriptions for patients. To predict drug-drug interactions (DDIs) caused by renal drug transporters, the molecular docking method is used for rapid screening of substrates or inhibitors of the drug transporters. Here, we review a large number of natural products that represent potential substrates and/or inhibitors of transporters by the molecular docking method.

Wedelolactone protects against cisplatin-induced nephrotoxicity in mice via inhibition of organic cation transporter 2

The balance of cisplatin uptake and efflux, mediated mainly by organic cation transporter 2 (OCT2) and multidrug and toxin extrusion 1 (MATE1), respectively, determines the renal accumulation and nephrotoxicity of cisplatin. Using transporter-mediated cellular uptake assay, we identified wedelolactone (WEL), a medicinal plant-derived natural compound, is a competitive inhibitor of OCT2 and a noncompetitive inhibitor of MATE1. Wedelolactone showed a selectivity to inhibit OCT2 rather than MATE1. Cytotoxicity studies revealed that wedelolactone alleviated cisplatin-induced cytotoxicity in OCT2-overexpressing HEK293 cells, whereas it did not alter the cytotoxicity of cisplatin in various cancer cell lines. Additionally, wedelolactone altered cisplatin pharmacokinetics, reduced kidney accumulation of cisplatin, and ameliorated cisplatin-induced acute kidney injury in the Institute of Cancer Research mice. In conclusion, these findings suggest a translational potential of WEL as a natural therapy for preventing cisplatin-induced nephrotoxicity and highlight the need for drug-drug interaction investigations of WEL with other treatments which are substrates of OCT2 and/or MATE1.

Downregulated expression of organic anion transporting polypeptide (Oatp) 2b1 in the small intestine of rats with acute kidney injury

The expression of transporters on the apical and basal membranes of renal tubular cells is modulated under acute kidney injury (AKI). However, little is known about alterations in non-renal transporters in the tissues other than the kidney under AKI situation. This study aimed to assess the modulation of organic anion transporting polypeptide (Oatp) 1a2 and Oatp2b1 expression/function in the small intestine of rats with drug-induced AKI. AKI was induced by intraperitoneal administration of cisplatin at a dose of 5 mg/kg. On day 3 after cisplatin administration, morphological changes in the small intestine, Oatp1a2 and Oatp2b1 expression, and absorption of pravastatin and theophylline were evaluated. Non-negligible atrophy was observed in the jejunum and ileum of the AKI rats. However, the absorption of theophylline was not affected. While intestinal Oatp2b1 expression was markedly decreased in the AKI rats, no alteration was observed in Oatp1a2 expression. The plasma levels of pravastatin after intraluminal administration declined significantly in the AKI rats. However, no such decline was observed after intravenous administration. This study suggested that the responses of intestinal Oatps to experimentally induced AKI was not unidirectional and that pravastatin absorption was governed more potently by Oatp2b1 than by Oatp1a2 in the rat intestine.

Downregulated expression of intestinal P-glycoprotein in rats with cisplatin-induced acute kidney injury causes amplification of its transport capacity to maintain "gatekeeper" function

The expression of transporters on the apical and basal membranes of renal proximal tubular cells are down- or upregulated to various extents under cisplatin (CDDP)-induced acute kidney injury (AKI). However, little is known about the changes in transporters in tissues other than the kidney under CDDP-induced AKI. This study aimed to investigate the modulation of the expression/function of intestinal efflux transporters, P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp), in CDDP-induced AKI rats. On day 3 after the intraperitoneal administration of CDDP (5 mg/kg) to rats, the expression levels of P-gp and Bcrp were compared with those of normal rats. Further, the absorption of three P-gp substrates (6α-methylprednisolone, rhodamine 123, and gatifloxacin) was evaluated in both groups using conventional loop techniques. In the CDDP-induced AKI rats, P-gp expression in the ileum was markedly decreased to approximately 38% of that in the normal rats. However, no significant changes in Bcrp expression were observed in the AKI rats. In contrast with the reduction in P-gp expression in the AKI rats, the absorption of the three P-gp substrates remained almost the same or decreased in the AKI group. The addition of verapamil (a potent P-gp inhibitor) increased the absorption of the three P-gp substrates to the values obtained from the normal rats. In conclusion, our results suggested that P-gp expression is downregulated in rats with CDDP-induced AKI but that P-gp maintains its potency as a "gatekeeper" against the absorption of xenobiotics by amplifying its individual transport capacity under these conditions.

Air pollution and kidney disease: review of current evidence

Along with amazing technological advances, the industrial revolution of the mid-19th century introduced new sources of pollution. By the mid-20th century, the effects of these changes were beginning to be felt around the world. Among these changes, health problems due to environmental air pollution are increasingly recognized. At the beginning, respiratory and cardiovascular diseases were emphasized. However, accumulated data indicate that every organ system in the body may be involved, and the kidney is no exception. Although research on air pollution and kidney damage is recent, there is now scientific evidence that air pollution harms the kidney. In this holistic review, we have summarized the epidemiology, disease states and mechanisms of air pollution and kidney damage.

Genetic Variations and Cisplatin Nephrotoxicity: A Systematic Review

Background: Nephrotoxicity is a notable adverse effect in cisplatin treated patients characterized by tubular injury and/or increased serum creatinine (SCr) with incidence varying from 20 to 70%. Pharmacogenomics has been shown to identify strongly predictive genetic markers to help determine which patients are more likely to experience, for example, a serious adverse drug reaction or receive optimal benefit through enhanced efficacy. Genetic variations have been reported to influence the risk of cisplatin nephrotoxicity; however, a comprehensive overview is lacking. Methods: A systematic review was performed using Pubmed, Embase and Web of Science on clinical studies that used cisplatin-based chemotherapy as treatment, had available genotyping data, and evaluated nephrotoxicity as an outcome. The quality of reporting was assessed using the STrengthening the REporting of Genetic Association Studies (STREGA) checklist. Results: Twenty-eight eligible studies were included; all were candidate gene studies. Over 300 SNPs across 135 genes were studied; 29 SNPs in 14 genes were significantly associated with cisplatin-induced nephrotoxicity. A variation in SLC22A2 rs316019, a gene involved in platinum uptake by the kidney, was associated with different measures of nephrotoxicity in four independent studies. Further, variants of ERCC1 (rs11615 and rs3212986) and ERCC2 (rs13181), two genes involved in DNA repair, were found to be positively associated with increased risks of nephrotoxicity in two independent studies. Conclusion: Three genes consistently associated with cisplatin-induced nephrotoxicity. Further research is needed to assess the biological mechanism and the clinical value of modifying treatment based on SLCC22A2 and ERCC1/2 genotypes.

Targeting protein-protein interactions for therapeutic discovery via FRET-based high-throughput screening in living cells

We have developed a structure-based high-throughput screening (HTS) method, using time-resolved fluorescence resonance energy transfer (TR-FRET) that is sensitive to protein-protein interactions in living cells. The membrane protein complex between the cardiac sarcoplasmic reticulum Ca-ATPase (SERCA2a) and phospholamban (PLB), its Ca-dependent regulator, is a validated therapeutic target for reversing cardiac contractile dysfunction caused by aberrant calcium handling. However, efforts to develop compounds with SERCA2a-PLB specificity have yet to yield an effective drug. We co-expressed GFP-SERCA2a (donor) in the endoplasmic reticulum membrane of HEK293 cells with RFP-PLB (acceptor), and measured FRET using a fluorescence lifetime microplate reader. We screened a small-molecule library and identified 21 compounds (Hits) that changed FRET by >3SD. 10 of these Hits reproducibly alter SERCA2a-PLB structure and function. One compound increases SERCA2a calcium affinity in cardiac membranes but not in skeletal, suggesting that the compound is acting specifically on the SERCA2a-PLB complex, as needed for a drug to mitigate deficient calcium transport in heart failure. The excellent assay quality and correlation between structural and functional assays validate this method for large-scale HTS campaigns. This approach offers a powerful pathway to drug discovery for a wide range of protein-protein interaction targets that were previously considered “undruggable”.

Pharmacokinetic changes of cefdinir and cefditoren and its molecular mechanisms in acute kidney injury in rats

OBJECTIVES

Acute kidney injury (AKI) was a common organ damage that often occurred after cisplatin. This study was aimed at investigating the pharmacokinetic changes of cefdinir and cefditoren in AKI rats, and elucidating the possible molecular mechanisms.

METHODS

The renal injury model was established by intraperitoneal injection of cisplatin (12 mg/kg). Plasma creatinine, blood urea nitrogen, the mRNA expression of Kim-1, hematoxylin and eosin staining and Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) assay were used to measure the degree of renal damage. On this basis, the pharmacokinetic changes of cefdinir and cefditoren were investigated in normal and AKI rats. RT-PCR and Western blot were performed to clarify the molecular mechanisms for the changes in the related transporters expression.

KEY FINDINGS

The cumulative urinary excretion of cefdinir was significantly decreased and the plasma concentration was remarkably increased in AKI rats. The expression of organic anion transporter 1 (Oat1) and Oat3 in kidney was decreased. However, pharmacokinetics of cefditoren was not influenced. The expression of organic anion-transporting polypeptide 1a1 (Oatp1a1), Oatp1a4, Oatp1b2 and multidrug resistance-associated protein 2 (Mrp2) in liver was unchanged in AKI rats.

CONCLUSIONS

The molecular mechanism of decreased expression of Oat1 and Oat3 was achieved through activating p53, and then increasing the expression of Bax and Caspase-3 and down regulating Bcl-2 in AKI rats. On this basis, the cumulative urinary excretion of cefdinir was significantly decreased and the plasma concentration of cefdinir was remarkably increased in AKI rats. However, the pharmacokinetic changes of cefditoren were not observed. Accordingly, cephalosporin antibiotics such as cefditoren should be firstly selected for the treatment in patients with AKI in clinic.

Environmental pollution and kidney diseases

The burden of disease and death attributable to environmental pollution is becoming a public health challenge worldwide, especially in developing countries. The kidney is vulnerable to environmental pollutants because most environmental toxins are concentrated by the kidney during filtration. Given the high mortality and morbidity of kidney disease, environmental risk factors and their effect on kidney disease need to be identified. In this Review, we highlight epidemiological evidence for the association between kidney disease and environmental pollutants, including air pollution, heavy metal pollution and other environmental risk factors. We discuss the potential biological mechanisms that link exposure to environmental pollutants to kidney damage and emphasize the contribution of environmental pollution to kidney disease. Regulatory efforts should be made to control environmental pollution and limit individual exposure to preventable or avoidable environmental risk. Population studies with accurate quantification of environmental exposure in polluted regions, particularly in developing countries, might aid our understanding of the dose-response relationship between pollutants and kidney diseases.

Activation of the cholinergic anti-inflammatory pathway by GTS-21 attenuates cisplatin-induced acute kidney injury in mice

Acute kidney injury (AKI) is the most common side effect of cisplatin, a widely used chemotherapy drug. Although AKI occurs in up to one third of cancer patients receiving cisplatin, effective renal protective strategies are lacking. Cisplatin targets renal proximal tubular epithelial cells leading to inflammation, reactive oxygen species, tubular cell injury, and eventually cell death. The cholinergic anti-inflammatory pathway is a vagus nerve-mediated reflex that suppresses inflammation via α7 nicotinic acetylcholine receptors (α7nAChRs). Our previous studies demonstrated the renoprotective and anti-inflammatory effects of cholinergic agonists, including GTS-21. Therefore, we examined the effect of GTS-21 on cisplatin-induced AKI. Male C57BL/6 mice received either saline or GTS-21 (4mg/kg, i.p.) twice daily for 4 days before cisplatin and treatment continued through euthanasia; 3 days post-cisplatin mice were euthanized and analyzed for markers of renal injury. GTS-21 significantly reduced cisplatin-induced renal dysfunction and injury (p<0.05). GTS-21 significantly attenuated renal Ptgs2/COX-2 mRNA and IL-6, IL-1β, and CXCL1 protein expression, as well as neutrophil infiltration after cisplatin. GTS-21 blunted cisplatin-induced renal ERK1/2 activation, as well as renal ATP depletion and apoptosis (p<0.05). GTS-21 suppressed the expression of CTR1, a cisplatin influx transporter and enhanced the expression of cisplatin efflux transporters MRP2, MRP4, and MRP6 (p<0.05). Using breast, colon, and lung cancer cell lines we showed that GTS-21 did not inhibit cisplatin’s tumor cell killing activity. GTS-21 protects against cisplatin-AKI by attenuating renal inflammation, ATP depletion and apoptosis, as well as by decreasing renal cisplatin influx and increasing efflux, without impairing cisplatin-mediated tumor cell killing. Our results support further exploring the cholinergic anti-inflammatory pathway for preventing cisplatin-induced AKI.

Sinapic acid modulates Nrf2/HO-1 signaling pathway in cisplatin-induced nephrotoxicity in rats

BACKGROUND

Cisplatin-induced nephrotoxicity is related to increased reactive oxygen species and inflammatory cytokines in the kidney. Sinapic acid (SA) has both antioxidant and anti-inflammatory activities.

AIMS

We determined the effects of SA on cisplatin-induced nephrotoxicity in rats, and the potential mechanisms by which it augments antioxidant responses and attenuates nephrotoxicity related to oxidative/nitrosative stress, apoptosis, and inflammation.

METHODS

Kidney function markers (i.e., serum urea, uric acid, creatinine, and lactate dehydrogenase), oxidative stress markers (i.e., lipid peroxidation and nitric oxide), antioxidant systems (i.e., superoxide dismutase, catalase, and reduced glutathione), inflammation markers (i.e., tumor necrosis factor-α [TNF-α], interleukin-6 [IL-6], and myeloperoxidase [MPO]), apoptotic markers (caspase 3, Bax, and Bcl-2), and the levels of nuclear factor-κB (NF-κB [p65]), Nrf2, and heme oxygenase-1 (HO-1) were assessed. Histopathological examinations of the kidney were also used to evaluate cisplatin-induced nephrotoxicity.

KEY FINDINGS

SA (10 and 20mg/kg) pretreatment ameliorated kidney function, upregulated antioxidant levels, and downregulated lipid peroxidation and nitric oxide levels in cisplatin-injected rats, resulting in significant reductions in oxidative stress and replenishment of endogenous antioxidant enzymes. Cisplatin upregulated cytokines (i.e., TNF-α and IL-6) and MPO, increased apoptosis, and downregulated Nrf2 and HO-1. SA pretreatment downregulated the pro-apoptotic caspase-3 and Bax proteins, and upregulated the anti-apoptotic Bcl-2 protein. SA pretreatment also alleviated the extent of histological impairment and reduced neutrophil infiltration in renal tubules.

SIGNIFICANCE

The results suggest that the Nrf2/HO-1 signaling pathway may be the primary target for protection from cisplatin-induced nephrotoxicity by SA, and that SA reduces oxidative stress, inflammation, and apoptosis by inhibiting NF-κB.

Role of Nigella sativa and Its Constituent Thymoquinone on Chemotherapy-Induced Nephrotoxicity: Evidences from Experimental Animal Studies

Background: Most chemotherapeutic drugs are known to cause nephrotoxicity. Therefore, new strategies have been considered to prevent chemotherapy-induced nephrotoxicity. It is of note that Nigella sativa (NS), or its isolated compound Thymoquinone (TQ), has a potential role in combating chemotherapy-induced nephrotoxicity. AIM: To analyze and report the outcome of experimental animal studies on the protective effects of NS/TQ on chemotherapy-associated kidney complications. Design: Standard systematic review and narrative synthesis. Data Sources: MEDLINE, EMBASE databases were searched for relevant articles published up to March 2017. Additionally, a manual search was performed. Criteria for a study’s inclusion were: conducted in animals, systematic reviews and meta-analysis, containing data on nephroprotective effects of NS/TQ compared to a placebo or other substance. All strains and genders were included. Results: The database search yielded 71 studies, of which 12 (cisplatin-induced nephrotoxicity 8; methotrexate-induced nephrotoxicity 1; doxorubicin-induced nephrotoxicity 2; ifosfamide-induced nephrotoxicity 1) were included in this review. Conclusions: Experimental animal studies showed the protective effect of NS, or TQ, on chemotherapy-induced nephrotoxicity. These effects are caused by decreasing lipid peroxidation and increasing activity of antioxidant enzymes in renal tissue of chemotherapy-treated animals.

Chronic Kidney Disease and Exposure to Nephrotoxic Metals

Chronic kidney disease (CKD) is a common progressive disease that is typically characterized by the permanent loss of functional nephrons. As injured nephrons become sclerotic and die, the remaining healthy nephrons undergo numerous structural, molecular, and functional changes in an attempt to compensate for the loss of diseased nephrons. These compensatory changes enable the kidney to maintain fluid and solute homeostasis until approximately 75% of nephrons are lost. As CKD continues to progress, glomerular filtration rate decreases, and remaining nephrons are unable to effectively eliminate metabolic wastes and environmental toxicants from the body. This inability may enhance mortality and/or morbidity of an individual. Environmental toxicants of particular concern are arsenic, cadmium, lead, and mercury. Since these metals are present throughout the environment and exposure to one or more of these metals is unavoidable, it is important that the way in which these metals are handled by target organs in normal and disease states is understood completely.

Bardoxolone methyl modulates efflux transporter and detoxifying enzyme expression in cisplatin-induced kidney cell injury

Cisplatin is prescribed for the treatment of solid tumors and elicits toxicity to kidney tubules, which limits its clinical use. Nuclear factor erythroid 2-related factor 2 (Nrf2, NFE2L2) is a critical transcription factor that has been shown to protect against kidney injury through activation of antioxidant mechanisms. We aimed to evaluate the ability of short-term treatment with the Nrf2 activator bardoxolone methyl (CDDO-Me) to protect against cisplatin-induced kidney cell toxicity. Cell viability was assessed in human kidney proximal tubule epithelial cells (hPTCs) exposed to low, intermediate, and high cisplatin concentrations in the presence and absence of CDDO-Me, administered either prior to or after cisplatin. Treatment with cisplatin alone resulted in reductions in hPTC viability, while CDDO-Me administered prior to or after cisplatin exposure yielded significantly higher cell viability (17%-71%). Gene regulation (mRNA expression) studies revealed the ability of CDDO-Me to modify protective pathways including Nrf2 induced detoxifying genes [GCLC (increased 1.9-fold), NQO1 (increased 9.3-fold)], and an efflux transporter [SLC47A1 (increased 4.5-fold)] at 12h. Protein assessments were in agreement with gene expression. Immunofluorescence revealed localization of GCLC and NQO1 to the nucleus and cytosol, respectively, with CDDO-Me administered prior to or after cisplatin exposure. The findings of enhanced cell viability and increased expression of detoxifying enzymes (GCLC and NQO1) and the multidrug and toxin extrusion protein 1 (MATE1) efflux transporter (SLC47A1) in hPTCs exposed to CDDO-Me, suggest that intermittent treatment with CDDO-Me prior to or after cisplatin exposure may be a promising approach to mitigate acute kidney injury.

Anatomical and physiological basis for the allometric scaling of cisplatin clearance in dogs

Cisplatin is a platinum-containing cytotoxic drug indicated for the treatment of solid tumors in veterinary and human patients. Several of the algorithms used to standardize the doses of cytotoxic drugs utilize allometry, or the nonproportional relationships between anatomical and physiological variables, but the underlying basis for these relationships is poorly understood. The objective of this proof of concept study was to determine whether allometric equations explain the relationships between body weight, kidney weight, renal physiology, and clearance of a model, renally cleared anticancer agent in dogs. Postmortem body, kidney, and heart weights were collected from 364 dogs (127 juveniles and 237 adults, including 51 dogs ≥ 8 years of age). Renal physiological and cisplatin pharmacokinetic studies were conducted in ten intact male dogs including two juvenile and eight adult dogs (4-55 kg). Glomerular filtration rate (GFR), effective renal plasma flow, effective renal blood flow, renal cisplatin clearance, and total cisplatin clearance were allometrically related to body weight with powers of 0.75, 0.59, 0.61, 0.71, and 0.70, respectively. The similar values of these diverse mass exponents suggest a common underlying basis for the allometry of kidney size, renal physiology, and renal drug handling.

Mechanism of kidney injury caused by bevacizumab in rats

OBJECTIVE

We investigate kidney injury caused by high dose bevacizumab to uncover the possible mechanisms involving in this process.

METHODS

Forty rats were divided into four groups: cisplation group (treated with 1 mg/kg cisplation), Bev-high group (treated with 5 mg/kg bevacizumab); Bev-low group (treated with 2.5 mg/kg bevacizumab) and control group (treated with saline). The urine microalbumin, serum cystatin C, blood urea nitrogen and serum creatinine were detected in the four group rats, respectively. The immunoglobulin of IgG, IgA and IgM and protein of VEGF (vascular endothelial growth factor) and nephrin were detected by immunohistochemical methods.

RESULTS

All the levels of microalbumin, cystatin C, serum creatinine and blood urea nitrogen in Bev-high group were significantly higher than those in normal control group (P < 0.05). The cystatin C was much more increased in kidney Bev-high group than cisplatin and Bev-low groups (P < 0.05). The light microscope showed a normal glomerular morphology in the four groups, while the electronic microscopy showed the podocytes were extensively fused in cisplatin group and Bev-high group. The two groups were found IgG and IgM deposition as well. The VEGF in kidney amples were down regulated in high dose bevacizumab group, whereas the nephrin and IgA showed no significant expression changes at all.

CONCLUSION

Bevacizumab increases the risk of injury in glomerular filtration barrier in a dose dependent model. The injury may not only associate with the rising level of proteinuria but also with podocyte-dependent membrane structures.

Therapeutic effect of Xue Niao An on glyoxylate-induced calcium oxalate crystal deposition based on urinary metabonomics approach

The anti-nephrolithiasis effect of Xue Niao An (XNA) capsules is explored by analyzing urine metabolic profiles in mouse models, with ultra-high performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS). An animal model of calcium oxalate crystal renal deposition was established in mice by intra-abdominal injection of glyoxylate. Then, treatment with XNA by intra-gastric administration was performed. At the end of the study, calcium deposition in kidney was measured by Von Kossa staining under light microscopy, and the Von Kossa staining changes showed that XNA significantly alleviated the calcium oxalate crystal deposition. Meanwhile, urine samples for fifteen metabolites, including amino acids and fatty acids, with significant differences were detected in the calcium oxalate group, while XNA treatment attenuated metabolic imbalances. Our study indicated that the metabonomic strategy provided comprehensive insight on the metabolic response to XNA treatment of rodent renal calcium oxalate deposition.

Magnesium protects against cisplatin-induced acute kidney injury by regulating platinum accumulation

Despite its success as a potent antineoplastic agent, ∼25% of patients receiving cisplatin experience acute kidney injury (AKI) and must discontinue therapy. Impaired magnesium homeostasis has been linked to cisplatin-mediated AKI, and because magnesium deficiency is widespread, we examined the effect of magnesium deficiency and replacement on cisplatin-induced AKI in physiologically relevant older female mice. Magnesium deficiency significantly increased cisplatin-associated weight loss and markers of renal damage (plasma blood urea nitrogen and creatinine), histological changes, inflammation, and renal cell apoptosis and modulated signaling pathways (e.g., ERK1/2, p53, and STAT3). Conversely, these damaging effects were reversed by magnesium. Magnesium deficiency alone significantly induced basal and cisplatin-mediated oxidative stress, whereas magnesium replacement attenuated these effects. Similar results were observed using cisplatin-treated LLC-PK1 renal epithelial cells exposed to various magnesium concentrations. Magnesium deficiency significantly amplified renal platinum accumulation, whereas magnesium replacement blocked the augmented platinum accumulation after magnesium deficiency. Increased renal platinum accumulation during magnesium deficiency was accompanied by reduced renal efflux transporter expression, which was reversed by magnesium replacement. These findings demonstrate the role of magnesium in regulating cisplatin-induced AKI by enhancing oxidative stress and thus promoting cisplatin-mediated damage. Additional in vitro experiments using ovarian, breast, and lung cancer cell lines showed that magnesium supplementation did not compromise cisplatin's chemotherapeutic efficacy. Finally, because no consistently successful therapy to prevent or treat cisplatin-mediated AKI is available for humans, these results support developing more conservative magnesium replacement guidelines for reducing cisplatin-induced AKI in cancer patients at risk for magnesium deficiency.

Effect of lycopene against cisplatin-induced acute renal injury in rats: organic anion and cation transporters evaluation

In the present study, we investigated the effects of lycopene on the expression of organic anion transporters (OATs), organic cation transporters (OCTs), and multidrug resistance-associated proteins (MRPs) of cisplatin-induced nephrotoxicity in rats. Twenty-eight 8-week-old Wistar rats were divided into four groups: control, lycopene-treated (6 mg/kg BW by oral gavage), cisplatin-treated (7 mg/kg BW, IP), and lycopene in combination with cisplatin-treated groups. In the presence of cisplatin, serum urea nitrogen (urea-N) (48.5 vs. 124.3 mg/dl) and creatinine (0.29 vs. 1.37 mg/dl) levels and the kidney efflux transporters MRP2 and MRP4 levels were significantly increased, whereas OAT1, OAT3, OCT1, and OCT2 levels in kidney were decreased in the treated rats compared with normal control rats. However, administration of lycopene in combination with cisplatin resulted in a reduction in the serum urea-N (124.3 vs. 62.4) and creatinine (1.37 vs. 0.40) levels and the kidney efflux transporters MRP2 and MRP4 proteins in the kidneys. Administration of lycopene to acute renal injury-induced rats largely upregulated the organic anion transporters (OAT1 and 3) and organic cation transporters (OCT1 and 2) to decrease the side effects of cisplatin. The present study suggests that lycopene synergizes with its nephroprotective effect against cisplatin-induced acute kidney injury in rats.

Comparative in vivo evaluations of curcumin and its analog difluorinated curcumin against cisplatin-induced nephrotoxicity

Curcumin, a polyphenol, has pharmacological effects including antioxidant, anti-inflammatory and anti-cancer features. In this study, we have performed comparative in vivo evaluations of CDF (curcumin difluorinated) and curcumin in cisplatin-induced nephrotoxicity in rats. Male Wistar rats were divided into four groups: (1) Control; (2) Cisplatin (7 mg/kg body wt, intraperitoneal as a single dose); (3) Cisplatin and CDF (50 mg/rat/day; for 12 days); (4) Cisplatin and curcumin (50 mg/rat/day), for 12 days). Cisplatin treated rats exhibited kidney injury manifested by increased serum N-urea and creatinine (P < 0.001). Kidney from cisplatin treated rats also exhibited significant increase in malondialdehyde (MDA) and 8-isoprostane levels (P < 0.001). Treatment with CDF and curcumin prevented the rise in serum N-urea, creatinine, MDA and 8-isoprostane as compared to experimental control group in kidney (P < 0.05). Compared to curcumin, CDF had greater potential in suppressing cisplatin-induced pro-inflammatory factors NF-κB and COX-2 as well as downstream markers Nrf2 and HO-1 (P < 0.05) in kidney. The analysis on anion transport markers (OAT1 and OAT3) showed a similar trend (CDF > curcumin). CDF could reduce the expression of multi-drug resistance markers OCT1, OCT2, MRP2 and MRP4 to a much greater extent than curcumin (P < 0.05). We also demonstrate that CDF influenced the expression of p-mTOR, p-p70S6K1, p-4E-BP1 and p-Akt. These data suggest that CDF can potentially be used to reduce the chemotherapy induced nephrotoxicity thereby enhancing the therapeutic window of cisplatin. The results also proved that compared to curcumin, CDF has superior protective effect in nephrotoxicity.

C-Phycocyanin prevents cisplatin-induced nephrotoxicity through inhibition of oxidative stress

The aim of this study was to evaluate whether the antioxidant C-phycocyanin (C-PC, 5–30 mg kg⁻¹ i.p.) was able to prevent cisplatin (CP, 18 mg kg⁻¹ i.p.) induced nephrotoxicity by reducing oxidative stress in CD-1 mice.

Fructus Gardenia Extract ameliorates oxonate-induced hyperuricemia with renal dysfunction in mice by regulating organic ion transporters and mOIT3

The potent anti-hyperuricemia activities of Fructus Gardenia Extract (FGE) have been well reported. The aim of this study was to evaluate the uricosuric and nephro-protective effects of FGE and explore its possible mechanisms of action in oxonate-induced hyperuricemic mice. FGE was orally administered to hyperuricemic and normal mice for 1 week. Serum and urinary levels of uric acid, creatinine and blood urea nitrogen (BUN), and fractional excretion of uric acid (FEUA) were measured. The mRNA and protein levels of mouse urate transporter 1 (mURAT1), glucose transporter 9 (mGLUT9), ATP-binding cassette, subfamily G, 2 (mABCG2), organic anion transporter 1 (mOAT1), mOAT3, oncoprotein induced transcript 3 (mOIT3), organic cation/carnitine transporters in the kidney were analyzed. Simultaneously, Tamm-Horsfall glycoprotein (THP) levels in urine and kidney were detected. FGE significantly reduced serum urate levels and increased urinary urate levels and FEUA in hyperuricemic mice. It could also effectively reverse oxonate-induced alterations in renal mURAT1, mGLUT9, mOAT1 and mOIT3 expressions, as well as THP levels, resulting in the enhancement of renal uric acid excretion. Moreover, FGE decreased serum creatinine and BUN levels, and up-regulated expression of organic cation/carnitine transporters, improving renal dysfunction in this model. Furthermore, FGE decreased renal mABCG2 expressions in hyperuricemic mice, contributing to its beneficial actions. However, further investigation is needed in clinical trials of FGE and its bioactive components.

Luteolin ameliorates cisplatin-induced nephrotoxicity in mice through inhibition of platinum accumulation, inflammation and apoptosis in the kidney

The aim of this study was to investigate the effects of flavone luteolin against cisplatin (CP)-induced kidney injury in mice. Luteolin at doses of 10mg/kg was administered intraperitoneally (ip) once daily for 3 days following single CP (10 or 20mg/kg) ip injection. Mice were sacrificed 24h after the last dose of luteolin. The CP treatment significantly increased serum creatinine and blood urea nitrogen and induced pathohistological changes in the kidneys. Renal oxidative/nitrosative stress was evidenced by decreased glutathione (GSH) levels and increased 3-nitrotyrosine (3-NT) and 4-hydroxynonenal (4-HNE) formation as well as cytochrome P450 2E1 (CYP2E1) expression. The CP administration triggered inflammatory response in mice kidneys through activation of nuclear factor-kappaB (NF-κB) and overexpression of tumor necrosis factor-alpha (TNF-α) and cyclooxygenase-2 (COX-2). Simultaneously, the increase in renal p53 and caspase-3 expression indicated apoptosis of tubular cells. The administration of luteolin significantly reduced histological and biochemical changes induced by CP, decreased platinum (Pt) levels and suppressed oxidative/nitrosative stress, inflammation and apoptosis in the kidneys. These results suggest that luteolin is an effective nephroprotective agent, with potential to reduce Pt accumulation in the kidneys and ameliorate CP-induced nephrotoxicity.

Organic anion transporter 5 (Oat5) renal expression and urinary excretion in rats treated with cisplatin: a potential biomarker of cisplatin-induced nephrotoxicity

Cisplatin is one of the most potent chemotherapeutic antitumor drugs used in the treatment of a wide range of solid tumors. Its primary dose-limiting side effect is nephrotoxicity. The organic anion transporter 5 (Oat5) is exclusively localized in the kidney. Oat5 urinary excretion was recently proposed as a potential early biomarker of acute kidney injury (AKI). The aim of this study was to evaluate Oat5 renal expression and its urinary excretion in rats exposed to different doses of cisplatin, in comparison with traditional markers of renal injury, like renal histology, creatinine and urea plasma levels, creatinine clearance, protein and glucose urinary levels and urinary alkaline phosphatase (AP) activity. Male Wistar rats were treated with a single injection of cisplatin at different doses of 1, 2, 5 and 10 mg/kg b.w., i.p. (Cis1, Cis2, Cis5 and Cis10, n = 4, respectively) and experiments were carried out 48 h after cisplatin administration. The renal expression of Oat5 was evaluated by immunohistochemistry and Western blotting. Oat5 abundance, AP activity, creatinine, glucose and proteins were assayed in urine. Creatinine clearance and creatinine and urea plasma levels were also evaluated. In this experimental model, plasma urea and creatinine levels, creatinine clearance, AP urinary activity and protein and glucose urinary levels were significantly modified only at the highest cisplatin dose of 10 mg/kg b.w., i.p., as compared to control rats. In contrast, Oat5 urinary abundance was increased in a dose-related manner after the administration of cisplatin. Oat5 urinary abundance was elevated at a dose as low as 1 mg/kg b.w., i.p., implying renal perturbation, when no modifications of traditional markers of renal injury are yet observed. Oat5 renal expression was decreased in a dose-related manner, both in homogenates and apical membranes from cisplatin-treated kidneys. The increase in urinary Oat5 excretion might explain the decrease in the amount of Oat5 molecules in the renal tubule cells. Hence, the preclinical animal results showed in this work propose that Oat5 urinary excretion might potentially serve as a non-invasive early biomarker of cisplatin-induced AKI.

ABCC4/MRP4: a MYCN-regulated transporter and potential therapeutic target in neuroblastoma

Resistance to cytotoxic drugs is thought to be a major cause of treatment failure in childhood neuroblastoma, and members of the ATP-binding cassette (ABC) transporter superfamily may contribute to this phenomenon by active efflux of chemotherapeutic agents from cancer cells. As a member of the C subfamily of ABC transporters, multidrug resistance-associated protein MRP4/ABCC4 has the ability to export a variety of endogenous and exogenous substances across the plasma membrane. In light of its capacity for chemotherapeutic drug efflux, MRP4 has been studied in the context of drug resistance in a number of cancer cell types. However, MRP4 also influences cancer cell biology independently of chemotherapeutic drug exposure, which highlights the potential importance of endogenous MRP4 substrates in cancer biology. Furthermore, MRP4 is a direct transcriptional target of Myc family oncoproteins and expression of this transporter is a powerful independent predictor of clinical outcome in neuroblastoma. Together, these features suggest that inhibition of MRP4 may be an attractive therapeutic approach for neuroblastoma and other cancers that rely on MRP4. In this respect, existing options for MRP4 inhibition are relatively non-selective and thus development of more specific anti-MRP4 compounds should be a major focus of future work in this area.

Impairment of bilirubin clearance and intestinal interleukin-6 expression in bile duct-ligated vitamin D receptor null mice

The vitamin D receptor (VDR) mediates the physiological and pharmacological actions of 1α,25-dihydroxyvitamin D₃ in bone and calcium metabolism, cellular growth and differentiation, and immunity. VDR also responds to secondary bile acids and belongs to the NR1I subfamily of the nuclear receptor superfamily, which regulates expression of xenobiotic metabolism genes. When compared to knockout mouse investigations of the other NR1I nuclear receptors, pregnane X receptor and constitutive androstane receptor, an understanding of the role of VDR in xenobiotic metabolism remains limited. We examined the effect of VDR deletion in a mouse model of cholestasis. We performed bile duct ligation (BDL) on VDR-null mice and compared blood biochemistry, mRNA expression of genes involved in bile acid and bilirubin metabolism, cytokine production, and expression of inflammatory regulators with those of wild-type mice. VDR-null mice had elevated plasma conjugated bilirubin levels three days after BDL compared with wild-type mice. Urine bilirubin levels and renal mRNA and/or protein expression of multidrug resistance-associated proteins 2 and 4 were decreased in VDR-null mice, suggesting impaired excretion of conjugated bilirubin into urine. While VDR-null kidney showed mRNA expression of interleukin-6 (IL-6) after BDL and VDR-null macrophages had higher IL-6 protein levels after lipopolysaccharide stimulation, the induction of intestinal Il6 mRNA expression and plasma IL-6 protein levels after BDL was impaired in VDR-null mice. Immunoblotting analysis showed that expression of an immune regulator, IκBα, was elevated in the jejunum of VDR-null mice, a possible mechanism for the attenuated induction of Il6 expression in the intestine after BDL. Increased expression of IκBα may be a consequence of compensatory mechanisms for VDR deletion. These results reveal a role of VDR in bilirubin clearance during cholestasis. VDR is also suggested to contribute to tissue-selective immune regulation.

Amelioration of cisplatin-induced nephrotoxicity in peroxiredoxin I-deficient mice

PURPOSE

Cisplatin is one of the most potent chemotherapeutic agents used to treat cancer. However, cisplatin-induced nephrotoxicity, which is partly caused by oxidative damage, is a serious problem. We previously showed that murine embryonic fibroblasts deficient in Peroxiredoxin I (Prx I), a major Nrf2-linked anti-oxidant enzyme, are susceptible to cisplatin-induced cytotoxicity. In the present study, we examined the role of Prx I against cisplatin-induced renal injury in vivo using Prx I-null mice.

METHODS

Prx I-null mice and wild-type (WT) mice were given an intraperitoneal injection of cisplatin, and tissues were removed and evaluated histopathologically. In addition, gene and protein expression of efflux transporters was analyzed.

RESULTS

In contrast to an in vitro cell study, Prx I-null mice exhibited less cisplatin-induced renal damage than WT mice in histological and blood biochemical analyses. Moreover, Prx I-null mice showed a higher clearance rate of cisplatin than WT mice following intraperitoneal cisplatin injection. Consistent with these results, Prx I-null mice exhibited higher expression of renal efflux transporters Mrp2 and Mrp4 compared with WT mice under both basal and the cisplatin-induced conditions. We suggest the enhanced transcriptional activity of c-Myc in Prx I-null mice may partly contribute the enhanced expression of renal efflux transporters.

CONCLUSION

In summary, the enhanced clearance rate of cisplatin significantly attenuates nephrotoxicity in Prx I-null mice.

Regulatory pathways for ATP-binding cassette transport proteins in kidney proximal tubules

The ATP-binding cassette transport proteins (ABC transporters) represent important determinants of drug excretion. Protective or excretory tissues where these transporters mediate substrate efflux include the kidney proximal tubule. Regulation of the transport proteins in this tissue requires elaborate signaling pathways, including genetic, epigenetic, nuclear receptor mediated, posttranscriptional gene regulation involving microRNAs, and non-genomic (kinases) pathways triggered by hormones and/or growth factors. This review discusses current knowledge on regulatory pathways for ABC transporters in kidney proximal tubules, with a main focus on P-glycoprotein, multidrug resistance proteins 2 and 4, and breast cancer resistance protein. Insight in these processes is of importance because variations in transporter activity due to certain (disease) conditions could lead to significant changes in drug efficacy or toxicity.

Changes in expression of renal Oat1, Oat3 and Mrp2 in cisplatin-induced acute renal failure after treatment of JBP485 in rats

The purpose of this study is to investigate whether the effect of cyclo-trans-4-l-hydroxyprolyl-l-serine (JBP485) on acute renal failure (ARF) induced by cisplatin is related to change in expression of renal Oat1, Oat3 and Mrp2 in rats. JBP485 reduced creatinine, blood urea nitrogen (BUN) and indoxyl sulfate (IS) in plasma and malondialdehyde (MDA) in kidney, and recovered the glomerular filtration rate (GFR) and the activity of superoxide dismutase (SOD) in cisplatin-treated rats. The plasma concentration of PAH (para-aminohippurate) determined by LC-MS/MS was increased markedly after intravenous administration of cisplatin, whereas cumulative urinary excretion of PAH and the uptake of PAH in kidney slices were significantly decreased. qRT-PCR and Western-blot showed a decrease in mRNA and protein of Oat1 and Oat3, an increase in mRNA and protein of Mrp2 in cisplatin-treated rats, and an increase in IS (a uremic toxin) after co-treatment with JBP485. It indicated that JBP485 promoted urinary excretion of toxins by upregulating renal Mrp2. This therefore gives in part the explanation about the mechanism by which JBP485 improves ARF induced by cisplatin in rats.

Drug transport by Organic Anion Transporters (OATs)

Common to all so far functionally characterized Organic Anion Transporters (OATs) is their broad substrate specificity and their ability to exchange extracellular against intracellular organic anions. Many OATs occur in renal proximal tubules, the site of active drug secretion. Exceptions are murine Oat6 (nasal epithelium), human OAT7 (liver), and rat Oat8 (renal collecting ducts). In human kidneys, OAT1, OAT2, and OAT3 are localized in the basolateral membrane, and OAT4, OAT10, and URAT1 in the apical cell membrane of proximal tubule cells, respectively. In rats and mice, Oat1 and Oat3 are located basolaterally, and Oat2, Oat5, Oat9, Oat10, and Urat1 apically. Several classes of drugs interact with human OAT1-3, including ACE inhibitors, angiotensin II receptor antagonists, diuretics, HMG CoA reductase inhibitors, β-lactam antibiotics, antineoplastic and antiviral drugs, and uricosuric drugs. For most drugs, interaction was demonstrated in vitro by inhibition of OAT-mediated transport of model substrates; for some drugs, transport by OATs was directly proven. Based on IC₅₀ values reported in the literature, OAT1 and OAT3 show comparable affinities for diuretics, cephalosporins, and nonsteroidal anti-inflammatory drugs whereas OAT2 has a lower affinity to most of these compounds. Drug-drug interactions at OAT1 and OAT3 may retard renal drug secretion and cause untoward effects. OAT4, OAT10, and URAT1 in the apical membrane contribute to proximal tubular urate absorption, and OAT10 to nicotinate absorption. OAT4 is in addition able to release drugs, e.g. diuretics, into the tubule lumen.

Altered arsenic disposition in experimental nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is represented by a spectrum of liver pathologies ranging from simple steatosis to nonalcoholic steatohepatitis (NASH). Liver damage sustained in the progressive stages of NAFLD may alter the ability of the liver to properly metabolize and eliminate xenobiotics. The purpose of the current study was to determine whether NAFLD alters the disposition of the environmental toxicant arsenic. C57BL/6 mice were fed either a high-fat or a methionine-choline-deficient diet to model simple steatosis and NASH, respectively. At the conclusion of the dietary regimen, all mice were given a single oral dose of either sodium arsenate or arsenic trioxide. Mice with NASH excreted significantly higher levels of total arsenic in urine (24 h) compared with controls. Total arsenic in the liver and kidneys of NASH mice was not altered; however, NASH liver retained significantly higher levels of the monomethyl arsenic metabolite, whereas dimethyl arsenic was retained significantly less in the kidneys of NASH mice. NASH mice had significantly higher levels of the more toxic trivalent form in their urine, whereas the pentavalent form was preferentially retained in the liver of NASH mice. Moreover, hepatic protein expression of the arsenic biotransformation enzyme arsenic (3+ oxidation state) methyltransferase was not altered in NASH animals, whereas protein expression of the membrane transporter multidrug resistance-associated protein 1 was increased, implicating cellular transport rather than biotransformation as a possible mechanism. These results suggest that NASH alters the disposition of arsenical species, which may have significant implications on the overall toxicity associated with arsenic in NASH.

Renal efflux transporter expression in pregnant mice with Type I diabetes

Prior research suggests that sex hormones and metabolic changes, such as obesity and hyperglycemia, can alter renal transporter expression in rodents. The purpose of this study was to characterize the expression of kidney efflux transporters and regulatory transcription factors in response to Type I diabetes and pregnancy. Female C57BL/6 mice were treated with multiple low doses of streptozotocin (STZ) to induce hyperglycemia and then mated with normoglycemic male mice. Transporter mRNA and protein expression were quantified in kidneys from vehicle- and STZ-treated non-pregnant and pregnant mice on gestation day 14. Pregnancy decreased the expression of Mdr1b, Mrp4, and 5 proteins and increased the mRNA and protein expression of Mrp3 by 50-60%. STZ treatment elevated Mrp1, 2, 4, and 5 and reduced Mrp3, 6, and Mdr1b mRNA and/or protein in non-pregnant mice. Pregnancy had little effect on STZ-mediated changes in renal efflux transporter expression. Transcriptional profiles of Hnf1α, PXR, AhR, and Nrf2 were altered in patterns similar to some efflux transporters suggesting potential involvement in their regulation. Taken together, these results suggest that renal drug efflux transporters and regulatory signaling pathways are altered by endocrine and metabolic changes that occur during pregnancy and Type I diabetes.

Novel roles of peroxiredoxins in inflammation, cancer and innate immunity

Peroxiredoxins possess thioredoxin or glutathione peroxidase and chaperone-like activities and thereby protect cells from oxidative insults. Recent studies, however, reveal additional functions of peroxiredoxins in gene expression and inflammation-related biological reactions such as tissue repair, parasite infection and tumor progression. Notably, peroxiredoxin 1, the major mammalian peroxiredoxin family protein, directly interacts with transcription factors such as c-Myc and NF-κB in the nucleus. Additionally, peroxiredoxin 1 is secreted from some cells following stimulation with TGF-β and other cytokines and is thus present in plasma and body fluids. Peroxiredoxin 1 is now recognized as one of the pro-inflammatory factors interacting with toll-like receptor 4, which triggers NF-κB activation and other signaling pathways to evoke inflammatory reactions. Some cancer cells release peroxiredoxin 1 to stimulate toll-like receptor 4-mediated signaling for their progression. Interestingly, peroxiredoxins expressed in protozoa and helminth may modulate host immune responses partly through toll-like receptor 4 for their survival and progression in host. Extracellular peroxiredoxin 1 and peroxiredoxin 2 are known to enhance natural killer cell activity and suppress virus-replication in cells. Peroxiredoxin 1-deficient mice show reduced antioxidant activities but also exhibit restrained tissue inflammatory reactions under some patho-physiological conditions. Novel functions of peroxiredoxins in inflammation, cancer and innate immunity are the focus of this review.