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

Indoxyl sulphate-TNFα axis mediates uremic encephalopathy in rodent acute kidney injury

Acute kidney injury (AKI) is often accompanied by uremic encephalopathy resulting from accumulation of uremic toxins in brain possibly due to impaired blood-brain barrier (BBB) function. Anionic uremic toxins are substrates or inhibitors of organic anionic transporters (OATs). In this study we investigated the CNS behaviors and expression/function of BBB OAT3 in AKI rats and mice, which received intraperitoneal injection of cisplatin 8 and 20 mg/kg, respectively. We showed that cisplatin treatment significantly inhibited the expressions of OAT3, synaptophysin and microtubule-associated protein 2 (MAP2), impaired locomotor and exploration activities, and increased accumulation of uremic toxins in the brain of AKI rats and mice. In vitro studies showed that uremic toxins neither alter OAT3 expression in human cerebral microvascular endothelial cells, nor synaptophysin and MAP2 expressions in human neuroblastoma (SH-SY5Y) cells. In contrast, tumour necrosis factor alpha (TNFα) and the conditioned medium (CM) from RAW264.7 cells treated with indoxyl sulfate (IS) significantly impaired OAT3 expression. TNFα and CM from IS-treated BV-2 cells also inhibited synaptophysin and MAP2 expressions in SH-SY5Y cells. The alterations caused by TNFα and CMs in vitro, and by AKI and TNFα in vivo were abolished by infliximab, a monoclonal antibody designed to intercept and neutralize TNFα, suggesting that AKI impaired the expressions of OAT3, synaptophysin and MAP2 in the brain via IS-induced TNFα release from macrophages or microglia (termed as IS-TNFα axis). Treatment of mice with TNFα (0.5 mg·kg-1·d-1, i.p. for 3 days) significantly increased p-p65 expression and reduced the expressions of Nrf2 and HO-1. Inhibiting NF-κB pathway, silencing p65, or activating Nrf2 and HO-1 obviously attenuated TNFα-induced downregulation of OAT3, synaptophysin and MAP2 expressions. Significantly increased p-p65 and decreased Nrf2 and HO-1 protein levels were also detected in brain of AKI mice and rats. We conclude that AKI inhibits the expressions of OAT3, synaptophysin and MAP2 due to IS-induced TNFα release from macrophages or microglia. TNFα impairs the expressions of OAT3, synaptophysin and MAP2 partly via activating NF-κB pathway and inhibiting Nrf2-HO-1 pathway.

Hyperoside ameliorates cisplatin-induced acute kidney injury by regulating the expression and function of Oat1

Cisplatin is a widely used chemotherapeutic agent to treat solid tumours in clinics. However, cisplatin-induced acute kidney injury (AKI) limits its clinical application. This study investigated the effect of hyperoside (a flavonol glycoside compound) on regulating AKI.The model of cisplatin-induced AKI was established, and hyperoside was preadministered to investigate its effect on improving kidney injury.Hyperoside ameliorated renal pathological damage, reduced the accumulation of SCr, BUN, Kim-1 and indoxyl sulphate in vivo, increased the excretion of indoxyl sulphate into the urine, and upregulated the expression of renal organic anion transporter 1 (Oat1). Moreover, evaluation of rat kidney slices demonstrated that hyperoside promoted the uptake of PAH (p-aminohippurate, the Oat1 substrate), which was confirmed by transient over-expression of OAT1 in HEK-293T cells. Additionally, hyperoside upregulated the mRNA expression of Oat1 upstream regulators hepatocyte nuclear factor-1α (HNF-1α) and pregnane X receptor (PXR).These findings indicated hyperoside could protect against cisplatin-induced AKI by promoting indoxyl sulphate excretion through regulating the expression and function of Oat1, suggesting hyperoside may offer a potential tactic for cisplatin-induced AKI treatment.

Research Methods and New Advances in Drug-Drug Interactions Mediated by Renal Transporters

The kidney is critical in the human body's excretion of drugs and their metabolites. Renal transporters participate in actively secreting substances from the proximal tubular cells and reabsorbing them in the distal renal tubules. They can affect the clearance rates (CLr) of drugs and their metabolites, eventually influence the clinical efficiency and side effects of drugs, and may produce drug-drug interactions (DDIs) of clinical significance. Renal transporters and renal transporter-mediated DDIs have also been studied by many researchers. In this article, the main types of in vitro research models used for the study of renal transporter-mediated DDIs are membrane-based assays, cell-based assays, and the renal slice uptake model. In vivo research models include animal experiments, gene knockout animal models, positron emission tomography (PET) technology, and studies on human beings. In addition, in vitro-in vivo extrapolation (IVIVE), ex vivo kidney perfusion (EVKP) models, and, more recently, biomarker methods and in silico models are included. This article reviews the traditional research methods of renal transporter-mediated DDIs, updates the recent progress in the development of the methods, and then classifies and summarizes the advantages and disadvantages of each method. Through the sorting work conducted in this paper, it will be convenient for researchers at different learning stages to choose the best method for their own research based on their own subject's situation when they are going to study DDIs mediated by renal transporters.

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.

Renal tubular transporter-mediated interactions between mirogabalin and cimetidine in rats

Cimetidine at a clinical dosage decreased the renal clearance (CLr) of mirogabalin in humans by inhibition of renal secretion. Mirogabalin is a substrate of human OAT1/3, OCT2, MATE1 and/or MATE2-K. To clarify the mechanism behind the above interaction, it was investigated whether cimetidine inhibits the process of mirogabalin uptake at the basolateral side or the process of its efflux at the apical side in rat kidney in vivo.Cimetidine was administered to rats by a constant infusion to achieve an unbound plasma concentration of 7.0 μM and examine its effect on the renal disposition of [¹⁴C]metformin, [³H]p-aminohippuric acid (PAH), and [¹⁴C]mirogabalin.Cimetidine significantly induced the intrarenal accumulation of radioactivity (Kp, kidney) and decreased the renal clearance (CLr) of [¹⁴C]mirogabalin. These effects resulted in significantly decreased total clearance (CLt). Kp, kidney, and CLr of [¹⁴C]metformin, except CLt, were also affected, but no parameters of [³H]PAH were affected by cimetidine.These findings clarified that an unbound plasma concentration of cimetidine of 7.0 μM inhibited the apical efflux not the basolateral uptake of [¹⁴C]mirogabalin in rat kidney, suggesting that mirogabalin/cimetidine interaction was caused by inhibiting the apical efflux transporter, human MATE1 and/or MATE2-K, not the basolateral uptake transporter, human OCT2, in the kidney.

Kidney Drug Transporters in Pharmacotherapy

The kidney functions not only as a metabolite elimination organ but also plays an important role in pharmacotherapy. The kidney tubule epithelia cells express membrane carriers and transporters, which play an important role in drug elimination, and can determine drug nephrotoxicity and drug-drug interactions, as well as constituting direct drug targets. The above aspects of kidney transport proteins are discussed in the review.

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.

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.

Research Progress on the Positive and Negative Regulatory Effects of Rhein on the Kidney: A Review of Its Molecular Targets

Currently, both acute kidney injury (AKI) and chronic kidney disease (CKD) are considered to be the leading public health problems with gradually increasing incidence rates around the world. Rhein is a monomeric component of anthraquinone isolated from rhubarb, a traditional Chinese medicine. It has anti-inflammation, anti-oxidation, anti-apoptosis, anti-bacterial and other pharmacological activities, as well as a renal protective effects. Rhein exerts its nephroprotective effects mainly through decreasing hypoglycemic and hypolipidemic, playing anti-inflammatory, antioxidant and anti-fibrotic effects and regulating drug-transporters. However, the latest studies show that rhein also has potential kidney toxicity in case of large dosages and long use times. The present review highlights rhein's molecular targets and its different effects on the kidney based on the available literature and clarifies that rhein regulates the function of the kidney in a positive and negative way. It will be helpful to conduct further studies on how to make full use of rhein in the kidney and to avoid kidney damage so as to make it an effective kidney protection drug.

JBP485, A Dual Inhibitor of Organic Anion Transporters (OATs) and Renal Dehydropeptidase-I (DHP-I), Protects Against Imipenem-Induced Nephrotoxicity

Imipenem (IMP) possesses a broad spectrum of antibacterial activity; however, nephrotoxicity limits its clinical application in patients with renal insufficiency. In our previous studies, a dipeptide, JBP485, a dipeptide with the chemical structure cyclo-trans-4-L-hydroxyprolyl-L-serine, was found to attenuate drug-induced kidney injury. The current study aimed to explore whether JBP485 could relieve IMP-induced kidney injury and clarify the potential molecular pharmacokinetic mechanism. The effects of JBP485 on IMP nephrotoxicity were evaluated in rabbits and human kidney 2 (HK-2) cells. Drug-drug interactions (DDIs) mediated by organic anion transporters (OATs) and dehydropeptidase-I (DHP-I) were explored through pharmacokinetic studies in rats, metabolism assays in the kidney, and uptake studies in OAT-over-expressing cells. The results revealed that JBP485 significantly ameliorated IMP-induced nephrotoxicity in rabbits. Further, incubation of HK-2 cells with JBP485 or cilastatin markedly improved the cell survival rate, inhibited apoptosis and attenuated mitochondrial damage by improving the stability of IMP and reducing its intracellular accumulation. This suggests that DHP-I and OATs might be involved in the protective effect of JBP485. Furthermore, coadministration with JBP485 significantly increased the IMP's plasma concentration as well as the area under the plasma concentration-time curve (AUC), while decreasing IMP renal clearance and cumulative urinary excretion. Moreover, JBP485 reduced IMP uptake in kidney slices and OAT1/3-human embryonic kidney 293 (HEK293) cells. At the same time, the metabolism of IMP by DHP-I was inhibited by JBP485 with an IC₅₀ value of 12.15 ± 1.22 μM. Finally, the molecular docking assay revealed a direct interaction between JBP485 and OAT1/3 or DHP-I. In conclusion, JBP485 protected against IMP nephrotoxicity in rabbits and HK-2 cells by improving IMP stability and reducing its intracellular accumulation via simultaneous inhibition of renal OATs and DHP-I. JBP485 is a promising renoprotective agent and could serve as an effective supplement to reduce IMP-induced adverse renal reactions in the clinical setting.

Relaxin inhibits renal fibrosis and the epithelial-to-mesenchymal transition via the Wnt/β-catenin signaling pathway

Renal fibrosis is a common characteristic and the final pathological mechanism of chronic kidney disease (CKD). Although CKD remains incurable, inhibition of renal fibrosis is beneficial to inhibit the CKD process. Relaxin alleviates renal fibrosis in some experimental models, but its mechanism remains unclear. In the following, we studied the regulatory effect of relaxin on epithelial-mesenchymal transition (EMT) after unilateral ureteral obstruction (UUO). Our results demonstrate that relaxin could downregulate Wnt/β-catenin signaling and decrease EMT, thus protecting against loss of transporters in tubular epithelial cells (TECs) and abrogate renal interstitial fibrosis following UUO. We confirmed that relaxin can downregulate Wnt/β-catenin signaling and decrease EMT in NRK52E, thus abrogating G2 cell cycle arrest in vitro experiments. Therefore, a novel mechanism by which relaxin is antifibrotic is that relaxin regulates the EMT program of TECs via Wnt/β-catenin signaling pathway. The inhibition of EMT contributes to protecting the functional capabilities of TECs and promoting the regeneration of TECs.

Changes of renal transporters in the kinetic process of VCM-induced nephrotoxicity in mice

Renal transporters involved in tubular excretion pathway are considered to be the key concern in drug evaluations in nephrotoxicity. However, the relationship between the alternation of renal transporters and the kinetic process of vancomycin (VCM)-induced nephrotoxicity has not been fully elucidated. The present study investigated the alteration of renal transporters expression in the kinetic process of VCM-induced nephrotoxicity in mice. C57BL/6 mice were administrated with normal saline or VCM for 7 days. Biochemical and pathological analyses were conducted to investigate the nephrotoxicity induced by VCM administration. Renal oxidative status, plasma, and kidney content of VCM were monitored. Quantitative real-time polymerase chain reaction and immunohistochemistry analyses were performed to analyze the expression of renal transporters. Finally, our data showed that the exposure of VCM (400 mg/kg) caused a slight nephrotoxicity in mice, whereas exposure of VCM (600 mg/kg) resulted in the severe nephrotoxicity in mice as evidenced by biochemical parameters and renal morphological changes. In addition, the accumulation of VCM in kidney is higher than plasma. Interestingly, VCM (600 mg/kg, body weight) resulted in the induction of Oct2-Mate1 and Oat1/3-Mrp2/Mrp4/Bcrp pathways. However, VCM (400 mg/kg, body weight) caused the induction of Oct2-Mate1/Mate2 and Oat1/3-Mrp4/Bcrp pathways. The changes of renal transporters in association with the kinetic process of VCM-induced nephrotoxicity may exert important practical implications for its optimal use in clinic.

Impact of kidney dysfunction on hepatic and intestinal drug transporters

Emerging information suggests that pathology of the kidney may not only affect expression and function of membrane transporters in the organ, but also in the gastrointestinal tract and the liver. Transporter dysfunction may cause effects on handling of drug as well as endogenous compounds with subsequent clinical consequences. A literature search was conducted on Ovid and PubMed databases to select relevant in vitro, animal and human studies that have reported expression, protein abundance and function of the gastrointestinal and liver localized ABC transporters and SLC carriers in kidney dysfunction or uremia states. The altered function of drug transporters in the liver and intestines in kidney failure subjects may provide compensatory activity in handling endogenous compounds (e.g. uremic toxins), which is expected to affect drug pharmacokinetics and local drug actions.

Membrane Carriers and Transporters in Kidney Physiology and Disease

The growing information suggests that chronic kidney disease may affect expression and function of membrane carriers and transporters in the kidney. The dysfunction of carriers and transporters entails deficient elimination of uremic solutes as well as xenobiotics (drugs and toxins) with subsequent clinical consequences. The renal carriers and transporters are also targets of drugs used in clinical practice, and intentional drug-drug interactions in the kidney are produced to increase therapeutic efficacy. The understanding of membrane carriers and transporters function in chronic kidney disease is important not only to better characterize drug pharmacokinetics, drug actions in the kidney, or drug-drug interactions but also to define the organ pathophysiology.

Hypouricemic agents reduce indoxyl sulfate excretion by inhibiting the renal transporters OAT1/3 and ABCG2

Indoxyl sulfate (IS) accumulates in the body in chronic kidney disease (CKD). In the renal proximal tubules, IS excretion is mediated by OAT1/3 and ABCG2. These transporters are inhibited by some hypouricemic agents; OATs by probenecid and benzbromarone, ABCG2 by febuxostat and benzbromarone. Thus, we evaluated whether hypouricemic agents including dotinurad, a novel selective urate reabsorption inhibitor with minimal effect on OATs or ABCG2, affect IS clearance in rats. Intact and adenine-induced acute renal failure rats were orally administered hypouricemic agents, and both endogenous IS and exogenously administered stable isotope-labeled d⁴-IS in the plasma and kidney were measured. Our results demonstrated that OATs inhibitors, such as probenecid, suppress IS uptake into the kidney, leading to increased plasma IS concentration, whereas ABCG2 inhibitors, such as febuxostat, cause renal IS accumulation remarkably by suppressing its excretion in intact rats. The effects of these agents were reduced in adenine-induced acute renal failure rats, presumably due to substantial decrease in renal OAT1/3 and ABCG2 expression. Dotinurad did not significantly affected the clearance of IS under both conditions. Therefore, we suggest that hypouricemic agents that do not affect OATs and ABCG2 are effective therapeutic options for the treatment of hyperuricemia complicated by CKD.

Transient Receptor Potential Channel 6 Knockout Ameliorates Kidney Fibrosis by Inhibition of Epithelial-Mesenchymal Transition

Kidney fibrosis is generally confirmed to have a significant role in chronic kidney disease, resulting in end-stage kidney failure. Epithelial–mesenchymal transition (EMT) is an important molecular mechanism contributing to fibrosis. Tubular epithelial cells (TEC), the major component of kidney parenchyma, are vulnerable to different types of injuries and are a significant source of myofibroblast by EMT. Furthermore, TRPC6 knockout plays an anti-fibrotic role in ameliorating kidney damage. However, the relationship between TRPC6 and EMT is unknown. In this study, TRPC6^−/− and wild-type (WT) mice were subjected to a unilateral ureteric obstruction (UUO) operation. Primary TEC were treated with TGF-β1. Western blot and immunofluorescence data showed that fibrotic injuries alleviated with the inhibition of EMT in TRPC6^−/− mice compared to WT mice. The activation of AKT-mTOR and ERK1/2 pathways was down-regulated in the TRPC6^−/− mice, while the loss of Na⁺/K⁺-ATPase and APQ1 was partially recovered. We conclude that TRPC6 knockout may ameliorate kidney fibrosis by inhibition of EMT through down-regulating the AKT-mTOR and ERK1/2 pathways. This could contribute to the development of effective therapeutic strategies on chronic kidney diseases.

Characteristic and Mechanism of Drug-Herb Interaction Between Acetylsalicylic Acid and Danhong Injection Mediated by Organic Anion Transporters

The mixture of Salvia miltiorrhiza and Carthamus tinctorius (Danhong injection, DHI) is widely prescribed in China for the treatment of cardiovascular and cerebrovascular diseases. In most cases, DHI is used in combination with acetylsalicylic acid (aspirin, ASA). However, the interaction between DHI and ASA remains largely undefined. The purpose of this study is to explore the interaction profile and mechanism between DHI and ASA. The frequency of drug combination of DHI and ASA was analyzed based on 5,183 clinical cases. The interaction characteristics were evaluated by analyzing the pharmacokinetics and disposition profile of salicylic acid (SA, the primary metabolite of ASA) in rats. The interaction mechanisms were explored through evaluating the hydrolysis of ASA regulated by ASA esterase, the tubular secretion of SA mediated by influx and efflux transporters, and the tubular reabsorption of SA regulated by urinary acidity-alkalinity. The inhibitory potential of DHI on organic anion transporters (OATs) was further verified in aristolochic acid I (AAI) induced nephropathy. Clinical cases analysis showed that DHI and ASA were used in combination with high frequency of 70.73%. In drug combination of DHI and ASA, the maximum plasma concentration of SA was significantly increased by 1.37 times, while the renal excretion of SA was significantly decreased by 32.54%. The mechanism study showed that DHI significantly inhibited the transport function, gene transcription and protein expression of OATs. In OATs mediated AAI nephropathy, DHI significantly reduced the renal accumulation of AAI by 55.27%, and alleviated renal damage such as glomerulus swelling, tubular blockage and lymphocyte filtration. In drug combination of DHI and ASA, DHI increased the plasma concentration of SA not through enhancing the hydrolysis of ASA, and the tubular reabsorption of SA was not significantly affected. Inhibition of tubular secretion of SA mediated by OATs might be the reason that contributes to the decrease of SA renal excretion.

Drug Elimination Alteration in Acute Lymphoblastic Leukemia Mediated by Renal Transporters and Glomerular Filtration

PURPOSE

Drug elimination alteration has been well reported in acute lymphoblastic leukemia (ALL). Considering that transporters and glomerular filtration influence, to different extents, the drug disposition, and possible side effects, we evaluated the effects of ALL on major renal transporters and glomerular filtration mediated pharmacokinetic changes, as well as expression of renal drug transporters.

METHODS

ALL xenograft models were established and intravenously injected with substrates of renal transporters and glomerular filtration separately in NOD/SCID mice. The plasma concentrations of substrates, after single doses, were determined using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS).

RESULTS

With the development of ALL, protein expression of MDR1, OAT3 and OCT2 were increased by 2.62-fold, 1.70-fold, and 1.45-fold, respectively, whereas expression of MRP2 and MRP4 were significantly decreased by 30.98% and 45.28% in the kidney of ALL groups compared with control groups. Clearance of MDR1-mediated digoxin, OAT3-mediated furosemide, and OCT2-mediated metformin increased by 3.04-fold, 1.47-fold, and 1.26-fold, respectively. However, clearance of MRPs-mediated methotrexate was reduced by 39.5%. These results are consistent with mRNA expression. Clearance of vancomycin and amikacin, as markers of glomerular filtration rate, had a 2.14 and 1.64-fold increase in ALL mice, respectively.

CONCLUSIONS

The specific alteration of renal transporters and glomerular filtration in kidneys provide a rational explanation for changes in pharmacokinetics for ALL.

Organic anion transporter 1 and 3 contribute to traditional Chinese medicine-induced nephrotoxicity

With the internationally growing popularity of traditional Chinese medicine (TCM), TCM-induced nephropathy has attracted public attention. Minimizing this toxicity is an important issue for future research. Typical nephrotoxic TCM drugs such as Aristolochic acid, Tripterygium wilfordii Hook. f, Rheum officinale Baill, and cinnabar mainly damage renal proximal tubules or cause interstitial nephritis. Transporters in renal proximal tubule are believed to be critical in the disposition of xenobiotics. In this review, we provide information on the alteration of renal transporters by nephrotoxic TCMs, which may be helpful for understanding the nephrotoxic mechanism of TCMs and reducing adverse effects. Studies have proven that when administering nephrotoxic TCMs, the expression or function of renal transporters is altered, especially organic anion transporter 1 and 3. The alteration of these transporters may enhance the accumulation of toxic drugs or the dysfunction of endogenous toxins and subsequently sensitize the kidney to injury. Transporters-related drug combination and clinical biomarkers supervision to avoid the risk of future toxicity are proposed.

Cordyceps cicadae Mycelia Ameliorate Cisplatin-Induced Acute Kidney Injury by Suppressing the TLR4/NF-κB/MAPK and Activating the HO-1/Nrf2 and Sirt-1/AMPK Pathways in Mice

Acute kidney injury (AKI) is a common clinical problem, characterized by a sudden loss of renal function, a high risk of death, and the eventual development of renal fibrosis and renal failure. Cordyceps cicadae is a traditional Chinese medicine with the potential function of kidney protection. We analyze two sputum extracts, a water extract (WCC), and an ethanol extract (ECC), to assess the potential of treating AKI in an animal model of kidney injury induced by cisplatin. A nephrotoxic mouse model was first established by intraperitoneal injection of cisplatin. Subsequently, WCC and ECC were orally administered in these mice. The results show that WCC and ECC significantly alleviated cisplatin-induced AKI renal histological changes, serum creatinine (CRE) and blood urea nitrogen (BUN) production, and the levels of NO, TNF-α, IL-1β, and IL-6. The levels of malondialdehyde (MDA) and glutathione (GSH) were suppressed by administration of WCC and ECC. However, WCC treatment prevented these changes significantly better than ECC treatment. In addition, Western blot data showed that WCC attenuated the cisplatin-induced protein expression of cyclooxygenase-2 (COX-2) and inducible NO synthase (iNOS), as well as inhibiting nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) activation in the kidney tissues. Furthermore, WCC greatly inhibited the expression of Toll-like receptor 4 (TLR4) and cisplatin-induced NF-κB activation, as well as dramatically increasing the production of antioxidative enzymes (i.e., superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase, nuclear factor erythroid 2-related factor 2 (Nrf2), and heme oxygenase 1 (HO-1)), silent information regulator T1 (Sirt1), and p-AMP-activated protein kinase (AMPK) in the kidney tissues. In addition, we found that WCC increased the expression levels of the autophagy-related proteins LC3B and Beclin-1; proapoptotic proteins, including cleaved caspase-3 and cleaved poly (ADP-ribose) polymerase (PARP) 1; and organic anion transporters 1 (OAT1) and 3 (OAT3) in the kidney tissues. Finally, WCC, ECC, and two bioactive compounds-adenosine and N6-(2-hydroxyethyl) adenosine (HEA)-inhibited the production of nitrite oxide (NO) and intracellular reactive oxygen species (ROS) triggered by lipopolysaccharide- (LPS-) stimulated RAW264.7 macrophages in vitro. Collectively, WCC could provide a potential therapeutic candidate for the prevention of cisplatin-induced kidney injury through the inhibition of oxidative stress and inflammation.

Expression of Organic Anion Transporter 1 or 3 in Human Kidney Proximal Tubule Cells Reduces Cisplatin Sensitivity

Cisplatin is a cytostatic drug used for treatment of solid organ tumors. The main adverse effect is organic cation transporter 2 (OCT2)-mediated nephrotoxicity, observed in 30% of patients. The contribution of other renal drug transporters is elusive. Here, cisplatin-induced toxicity was evaluated in human-derived conditionally immortalized proximal tubule epithelial cells (ciPTEC) expressing renal drug transporters, including OCT2 and organic anion transporters 1 (OAT1) or 3 (OAT3). Parent ciPTEC demonstrated OCT2-dependent cisplatin toxicity (TC₅₀ 34 ± 1 μM after 24-hour exposure), as determined by cell viability. Overexpression of OAT1 and OAT3 resulted in reduced sensitivity to cisplatin (TC₅₀ 45 ± 6 and 64 ± 11 μM after 24-hour exposure, respectively). This effect was independent of OAT-mediated transport, as the OAT substrates probenecid and diclofenac did not influence cytotoxicity. Decreased cisplatin sensitivity in OAT-expressing cells was associated directly with a trend toward reduced intracellular cisplatin accumulation, explained by reduced OCT2 gene expression and activity. This was evaluated by V_max of the OCT2-model substrate ASP⁺ (23.5 ± 0.1, 13.1 ± 0.3, and 21.6 ± 0.6 minutes^-1 in ciPTEC-parent, ciPTEC-OAT1, and ciPTEC-OAT3, respectively). Although gene expression of cisplatin efflux transporter multidrug and toxin extrusion 1 (MATE1) was 16.2 ± 0.3-fold upregulated in ciPTEC-OAT1 and 6.1 ± 0.7-fold in ciPTEC-OAT3, toxicity was unaffected by the MATE substrate pyrimethamine, suggesting that MATE1 does not play a role in the current experimental set-up. In conclusion, OAT expression results in reduced cisplatin sensitivity in renal proximal tubule cells, explained by reduced OCT2-mediated uptake capacity. In vitro drug-induced toxicity studies should consider models that express both OCT and OAT drug transporters.

Alteration of renal excretion pathways in gentamicin-induced renal injury in rats

The kidney plays a major part in the elimination of many drugs and their metabolites, and drug-induced kidney injury commonly alters either glomerular filtration or tubular transport, or both. However, the renal excretion pathway of drugs has not been fully elucidated at different stages of renal injury. This study aimed to evaluate the alteration of renal excretion pathways in gentamicin (GEN)-induced renal injury in rats. Results showed that serum cystatin C, creatinine and urea nitrogen levels were greatly increased by the exposure of GEN (100 mg kg^-1 ), and creatinine concentration was increased by 39.7% by GEN (50 mg kg^-1 ). GEN dose-dependently upregulated the protein expression of rOCT1, downregulated rOCT2 and rOAT1, but not affected rOAT2. Efflux transporters, rMRP2, rMRP4 and rBCRP expressions were significantly increased by GEN(100), and the rMATE1 level was markedly increased by GEN(50) but decreased by GEN(100). GEN(50) did not alter the urinary excretion of inulin, but increased metformin and furosemide excretion. However, GEN(100) resulted in a significant decrease of the urinary excretion of inulin, metformin and p-aminohippurate. In addition, urinary metformin excretions in vivo were significantly decreased by GEN(100), but slightly increased by GEN(50). These results suggested that GEN(50) resulted in the induction of rOCTs-rMATE1 and rOAT3-rMRPs pathway, but not changed the glomerular filtration rate, and GEN(100)-induced acute kidney injury caused the downregulated function of glomerular filtration -rOCTs-rMATE1 and -rOAT1-rMRPs pathway.

Renal organic anion transporters in drug-drug interactions and diseases

The kidney plays a vital role in maintaining systemic homeostasis. Active tubular secretion and reabsorption, which are mainly mediated by transporters, is an efficient mechanism for retaining glucose, amino acids, and other nutrients and for the clearance of endogenous waste products and xenobiotics. These substances are recognized by uptake transporters located in the basolateral and apical membranes of renal proximal tubule cells and are extracted from plasma and urine. Organic anion transporters (OATs) belong to the solute carrier (SLC) 22 superfamily and facilitate organic anions across the plasma membranes of renal proximal tubule cells. OATs are responsible for the transmembrane transport of anionic and zwitterionic organic molecules, including endogenous substances and many drugs. The alteration in OAT expression and function caused by diseases, drug-drug interactions (DDIs) or other issues can thus change the renal disposition of substrates, induce the accumulation of toxic metabolites, and lead to unexpected clinically outcome. This review summarizes the recent information regarding the expression, regulation, and substrate spectrum of OATs and discusses the roles of OATs in diseases and DDIs. These findings will enables us to have a better understanding of the related disease therapy and the potential risk of DDIs mediated by OATs.

Effect of Disease Pathologies on Transporter Expression and Function

Transporters are important determinants of drug absorption, distribution, and excretion. The clinical relevance of drug transporters in drug disposition and toxicology depends on their localization in liver, kidney, and brain. There has been growing evidence regarding the importance of disease status on alterations in metabolizing enzymes and transporter proteins. This review focuses on uptake and efflux transporter proteins in liver, kidney, and brain and discusses mechanisms of altered transporter expression and function secondary to disease.

Identification and Quantitative Assessment of Uremic Solutes as Inhibitors of Renal Organic Anion Transporters, OAT1 and OAT3

One of the characteristics of chronic kidney disease (CKD) is the accumulation of uremic solutes in the plasma. Less is known about the effects of uremic solutes on transporters that may play critical roles in pharmacokinetics. We evaluated the effect of 72 uremic solutes on organic anion transporter 1 and 3 (OAT1 and OAT3) using a fluorescent probe substrate, 6-carboxyfluorescein. A total of 12 and 13 solutes were identified as inhibitors of OAT1 and OAT3, respectively. Several of them inhibited OAT1 or OAT3 at clinically relevant concentrations and reduced the transport of other OAT1/3 substrates in vitro. Review of clinical studies showed that the active secretion of most drugs that are known substrates of OAT1/3 deteriorated faster than the renal filtration in CKD. Collectively, these data suggest that through inhibition of OAT1 and OAT3, uremic solutes contribute to the decline in renal drug clearance in patients with CKD.

Protective effects of formononetin against rhabdomyolysis-induced acute kidney injury by upregulating Nrf2 in vivo and in vitro

Acute kidney injury (AKI) is a well-known organ injury frequently observed after rhabdomyolysis (RM).

JBP485 promotes corneal epithelial wound healing

Proper wound healing is vital for maintenance of corneal integrity and transparency. Corneal epithelial damage is one of the most frequently observed ocular disorders. Because clinical options are limited, further novel treatments are needed to improve clinical outcomes for this type of disease. In the present study, it was found that placental extract-derived dipeptide (JBP485) significantly increased the proliferation and migration of corneal epithelial cells (CECs). Moreover, JBP485 accelerated corneal epithelial wound healing in vivo without inflammation and neovascularization and was found to be effective for the treatment of corneal damage. These data indicate that JBP485 efficiently activates the viability of CECs and has potential as a novel treatment for various kinds of corneal epithelial disease.

Organic Anion Transporter 5 (Oat5) Urinary Excretion Is a Specific Biomarker of Kidney Injury: Evaluation of Urinary Excretion of Exosomal Oat5 after N-Acetylcysteine Prevention of Cisplatin Induced Nephrotoxicity

Cisplatin is a commonly used chemotherapeutic agent. Its main side-effect is nephrotoxicity. It was reported that the organic anion transporter 5 (Oat5) urinary excretion is elevated, implying renal perturbation, when no modifications of traditional markers of renal damage are still observed in cisplatin-induced acute kidney injury (AKI). It was also demonstrated that Oat5 is excreted in urine by the exosomal pathway. This study was designated to demonstrate the specific response of the urinary excretion of exosomal Oat5 to kidney injury independently of other cisplatin toxic effects, in order to strengthen Oat5 urinary levels as a specific biomarker of AKI. To accomplish that aim, we evaluated if urinary excretion of exosomal Oat5 returns to its basal levels when cisplatin renal damage is prevented by the coadministration of the renoprotective compound N-acetylcysteine. Four days after cisplatin administration, AKI was induced in cisplatin-treated male Wistar rats (Cis group), as it was corroborated by increased urea and creatinine plasma levels. Tubular damage was also observed. In cotreated animals (Cis + NAC group), plasma urea and creatinine concentrations tended to return to their basal values, and tubular damage was improved. Urinary excretion of exosomal Oat5 was notably increased in the Cis group, but when renal injury was ameliorated by N-acetylcysteine coadministration, that increase was undetected. So, in this work we observed that urinary excretion of exosomal Oat5 was only increased if renal insult is produced, demonstrating its specificity as a renal injury biomarker.

Epithelial-to-mesenchymal transition induces cell cycle arrest and parenchymal damage in renal fibrosis

Kidney fibrosis is marked by an epithelial–to–mesenchymal transition (EMT) by tubular epithelial cells (TECs). Here we find that during renal fibrosis TECs acquire a partial EMT program during which they remain associated with their basement membrane and express markers of both epithelial and mesenchymal cells. The functional consequence of EMT program during fibrotic injury is an arrest in the G2 phase of the cell cycle and lower expression of several transporters in TECs. We also found that transgenic expression of Twist or Snai1 expression is sufficient to promote prolonged TGF-β1–induced G2 arrest of TECs, limiting their potential for repair and regeneration. Also, in mouse models of experimentally-induced renal fibrosis, conditional deletion of Twist1 or Snai1 in proximal TECs resulted in inhibition of the EMT program and the maintenance of TEC integrity, while restoring proliferation, de–differentiation–associated repair and regeneration of the kidney parenchyma and attenuating interstitial fibrosis. Thus, inhibition of EMT program in TECs during chronic renal injury represents a potential anti–fibrosis therapy

A 2-DE-based proteomic study on the toxicological effects of cisplatin in L02 cells

Cisplatin is a chemotherapeutic agent for the treatment of various cancers. In this study, cisplatin-induced effects were characterized in vitro model of human liver cells (L02) using 2-DE-based proteomics. Results indicated that different cisplatin treatments primarily induced disturbances in protein synthesis and oxidative stress via differential mechanisms. Since the experimental concentrations of cisplatin described a hormesis effect in cell proliferation of L02 cells, it was expected to reveal the hormesis effects using proteomic markers. However, only confilin-1 was commonly up-regulated in three concentrations of cisplatin treatments showing a hormesis effects with a U-shape regulation. These results were highly consistent with many other toxico-proteomic studies, indicating that the toxico-proteomic responses based on dose-dependent protein responses were incongruent with the theoretically linear or hormetic concentration-effect relationship. Our findings suggested that a macroscopic hormesis phenomenon on the cell proliferation could not be reflected by proteomic responses induced by cisplatin treatments.

Dose responsive effects of cisplatin in L02 cells using NMR-based metabolomics

Cisplatin is an effective chemotherapeutic agent for the treatment of various cancers, such as bladder cancer, epithelial ovarian cancer, cervical cancer, and so on. However, cisplatin can cause various side effects. In this study, the dose-responsive effects of cisplatin were investigated in an in vitro model of human liver cells (L02) using NMR-based metabolomics. The inverted U-shaped curve of cell proliferation confirmed the hormetic effects of cisplatin (from 1 nM to 1 mM) in L02 cells. However, the metabolite changes revealed both U-shaped (ethanol, lactate, aspartate, choline, etc.) and inverted U-shaped (glutamate, glutamine, 4-aminobutyrate, myo-inositol, etc.) curves induced by three typical concentrations of cisplatin which covered the inverted U-shaped curve as indicated by the cell proliferation assay. These findings suggested that a macroscopic hormesis phenomenon on the cell proliferation could be reflected by both stimulated and inhibited metabolites and corresponding metabolic pathways to cisplatin treatments. Therefore, a global analysis using metabolomics may give a broader view into the dose-response relationship than using a single endpoint at molecular levels.

'Biologic memory' in response to acute kidney injury: cytoresistance, toll-like receptor hyper-responsiveness and the onset of progressive renal disease

Following the induction of ischemic or toxin-mediated acute kidney injury (AKI), cellular adaptations occur that 're-program' how the kidney responds to future superimposed insults. This re-programming is not simply a short-lived phenomenon; rather it can persist for many weeks, implying that a state of 'biologic memory' has emerged. These changes can be both adaptive and maladaptive in nature and they can co-exist in time. A beneficial adaptation is the emergence of acquired cytoresistance, whereby a number of physiologic responses develop that serve to protect the kidney against further ischemic or nephrotoxic attack. Conversely, some changes are maladaptive, such as a predisposition to Gram-negative or Gram-positive bacteremia due to a renal tubular up-regulation of toll-like receptor responses. This latter change culminates in exaggerated cytokine production, and with efflux into the systemic circulation, extra-renal tissue injury can result (so-called 'organ cross talk'). Another maladaptive response is a persistent up-regulation of pro-inflammatory, pro-fibrotic and vasoconstrictive genes, culminating in progressive renal injury and ultimately end-stage renal failure. The mechanisms by which this biologic re-programming, or biologic memory, is imparted remain subjects for considerable debate. However, injury-induced, and stable, epigenetic remodeling at pro-inflammatory/pro-fibrotic genes seems likely to be involved. The goal of this editorial is to highlight that the so-called 'maintenance phase' of acute renal failure is not a static one, somewhere between injury induction and the onset of repair. Rather, this period is one in which the induction of 'biologic memory' can ultimately impact renal functional recovery, extra-renal injury and the possible transition of AKI into chronic, progressive renal disease.