Toxicity of ifosfamide and its metabolite chloroacetaldehyde in cultured renal tubule cells

Summary Renal injury is a common side effect of the chemotherapeutic agent ifosamide. Current evidence suggests that the ifosfamide metabolite chloroacetaldehyde may contribute to this nephrotoxicity. The present study examined the effects of ifosfamide and chloroacetaldehyde on rabbit proximal renal tubule cells in primary culture. The ability of the uroprotectant medication sodium 2-mercaptoethanesulfonate (mesna) to prevent chloroacetaldehyde-induced renal cell injury was also assessed. Chloroacetaldehyde (12.5–150 μM) produced dose-dependent declines in neutral red dye uptake, ATP levels, glutathione content, and cell growth. Coadministration of mesna prevented chloroacetaldehyde toxicity while pretreatment of cells with the glutathione-depleting agent buthionine sulfoximine enhanced the toxicity of chloroacetaldehyde. Ifosfamide (1000–10 000 μM) toxicity was detected only at concentrations of 4000 μM or greater. Analysis of media collected from ifosfamide-treated cell cultures revealed the presence of several ifosfamide metabolites, demonstrating that renal proximal tubule cells are capable of biotransforming this chemotherapeutic agent. This primary renal cell culture system should prove useful in studying the cause and prevention of ifosfamide nephrotoxicity.     

A tubule cell model for ifosfamide nephrotoxicity

Mechanisms leading to ifosfamide (IF)-induced renal damage have not been fully elucidated. Recent work suggests that localized renal tubular metabolism of IF and the production of the nephrotoxic chloroacetaldehyde may lead to nephrotoxicity. Presently no pharmacological method to reduce IF nephrotoxicity has been identified. The objectives of this study were to establish a tubule cell model for IF nephrotoxicity, to verify whether renal proximal tubular cells have the necessary cytochrome P450 (CYP) enzymes to oxidize IF, and whether they can metabolize IF to chloroacetaldehyde. CYP3A, and 2B mRNA and protein were identified in LLCPK-1 cells. The cells metabolized the R- and S-IF enantiomers to their respective 2- and 3-dechloroethylifosfamide metabolites, by-products of chloroacetaldehyde formation. Metabolite production was both time and concentration-dependent. IF did not affect cell viability. In contrast, glutathione-depleted cells showed time and dose-dependent damage. The presence of the relevant CYP enzymes in renal tubular cells along with their ability to metabolize IF to its 2- and 3-dechloroethylifosfamide metabolites suggests that nephrotoxic damage may result from the localized production of chloroacetaldehyde. Glutathione is a major defence mechanism against IF toxicity, thus pharmacological methods for replenishing intracellular glutathione may be effective in modulating IF-induced nephrotoxicity.     

Investigation of ifosfamide nephrotoxicity induced in a liver–kidney co‐culture biochip

In this article, we present a liver–kidney co‐culture model in a micro fluidic biochip. The liver was modeled using HepG2/C3a and HepaRG cell lines and the kidney using MDCK cell lines. To demonstrate the synergic interaction between both organs, we investigated the effect of ifosfamide, an anticancerous drug. Ifosfamide is a prodrug which is metabolized by the liver to isophosforamide mustard, an active metabolite. This metabolism process also leads to the formation of chloroacetaldehyde, a nephrotoxic metabolite and acrolein a urotoxic one. In the biochips of MDCK cultures, we did not detect any nephrotoxic effects after 72 h of 50 µM ifosfamide exposure. However, in the liver–kidney biochips, the same 72 h exposure leads to a nephrotoxicity illustrated by a reduction of the number of MDCK cells (up to 30% in the HepaRG‐MDCK) when compared to untreated co‐cultures or treated MDCK monocultures. The reduction of the MDCK cell number was not related to a modification of the cell cycle repartition in ifosfamide treated cases when compared to controls. The ifosfamide biotransformation into 3‐dechloroethylifosfamide, an equimolar byproduct of the chloroacetaldehyde production, was detected by mass spectrometry at a rate of apparition of 0.3 ± 0.1 and 1.1 ± 0.3 pg/h/biochips in HepaRG monocultures and HepaRG‐MDCK co‐cultures respectively. Any metabolite was detected in HepG2/C3a cultures. Furthermore, the ifosfamide treatment in HepaRG‐MDCK co‐culture system triggered an increase in the intracellular calcium release in MDCK cells on contrary to the treatment on MDCK monocultures. As 3‐dechloroethylifosfamide is not toxic, we have tested the effect of equimolar choloroacetaldehyde concentration onto the MDCK cells. At this concentration, we found a quite similar calcium perturbation and MDCK nephrotoxicity via a reduction of 30% of final cell numbers such as in the ifosfamide HepaRG‐MDCK co‐culture experiments. Our results suggest that ifosfamide nephrotoxicity in a liver–kidney micro fluidic co‐culture model using HepaRG‐MDCK cells is induced by the metabolism of ifosfamide into chloroacetaldehyde whereas this pathway is not functional in HepG2/C3a‐MDCK model. This study demonstrates the interest in the development of systemic organ–organ interactions using micro fluidic biochips. It also illustrated their potential in future predictive toxicity model using in vitro models as alternative methods. Biotechnol. Bioeng. 2013; 110: 597–608. © 2012 Wiley Periodicals, Inc.     

Enantioselective metabolism of ifosfamide by the kidney

Ifosfamide (IF), a potent chemotherapeutic agent for solid tumors, is known to cause high rates of nephrotoxicity, which is most likely due to the renal production of the metabolite chloroacetaldehyde. Enantioselective oxidation of IF has been shown in the liver but has never been reported in the kidney. Using porcine and human kidney samples, as well as the renal porcine cell line LLCPK-1, we document enantioselective metabolism of IF with prevalent production of the N-dechloroethylifosfamide (DCEIF) metabolites from the (S)-IF enantiomer compared to the amount of N-DCEIF metabolites produced from the (R)-IF enantiomers. Since IF enantiomers appear to be equally effective in chemotherapy, these results suggest that replacing the clinically standard racemic mixture of IF with (R)-IF may decrease renal metabolism of the drug and hence may decrease nephrotoxicity.     

The effect of N-acetylcysteine on the antitumor activity of ifosfamide

Ifosfamide-induced nephrotoxicity is a serious adverse effect in children undergoing chemotherapy. Our previous cell and rodent models have shown that the antioxidant N-acetylcysteine (NAC), used extensively as an antidote for acetaminophen poisoning, protects renal tubular cells from ifosfamide-induced nephrotoxicity at a clinically relevant concentration. For the use of NAC to be clinically relevant in preventing ifosfamide nephrotoxicity, we must ensure there is no effect of NAC on the antitumor activity of ifosfamide. Common pediatric tumors that are sensitive to ifosfamide, human neuroblastoma SK-N-BE(2) and rhabdomyosarcoma RD114-B cells, received either no pretreatment or pretreatment with 400 μmol/L of NAC, followed by concurrent treatment with NAC and either ifosfamide or the active agent ifosfamide mustard. Ifosfamide mustard significantly decreased the growth of both cancer cell lines in a dose-dependent manner (p < 0.001). The different combined treatments of NAC alone, sodium 2-mercaptoethanesulfonate alone, or NAC plus sodium 2-mercaptoethanesulfonate did not significantly interfere with the tumor cytotoxic effect of ifosfamide mustard. These observations suggest that NAC may improve the risk/benefit ratio of ifosfamide by decreasing ifosfamide-induced nephrotoxicity without interfering with its antitumor effect in cancer cells clinically treated with ifosfamide.     

Caspase 3/GSDME-dependent pyroptosis contributes to chemotherapy drug-induced nephrotoxicity

Chemotherapy drug-induced nephrotoxicity limits clinical applications for treating cancers. Pyroptosis, a newly discovered programmed cell death, was recently reported to be associated with kidney diseases. However, the role of pyroptosis in chemotherapeutic drug-induced nephrotoxicity has not been fully clarified. Herein, we demonstrate that the chemotherapeutic drug cisplatin or doxorubicin, induces the cleavage of gasdermin E (GSDME) in cultured human renal tubular epithelial cells, in a time- and concentration-dependent manner. Morphologically, cisplatin- or doxorubicin-treated renal tubular epithelial cells exhibit large bubbles emerging from the cell membrane. Furthermore, activation of caspase 3, not caspase 9, is associated with GSDME cleavage in cisplatin- or doxorubicin-treated renal tubular epithelial cells. Meanwhile, silencing GSDME alleviates cisplatin- or doxorubicin-induced HK-2 cell pyroptosis by increasing cell viability and decreasing LDH release. In addition, treatment with Ac-DMLD-CMK, a polypeptide targeting mouse caspase 3-Gsdme signaling, inhibits caspase 3 and Gsdme activation, alleviates the deterioration of kidney function, attenuates renal tubular epithelial cell injury, and reduces inflammatory cytokine secretion in vivo. Specifically, GSDME cleavage depends on ERK and JNK signaling. NAC, a reactive oxygen species (ROS) inhibitor, reduces GSDME cleavage through JNK signaling in human renal tubular epithelial cells. Thus, we speculate that renal tubular epithelial cell pyroptosis induced by chemotherapy drugs is mediated by ROS-JNK-caspase 3-GSDME signaling, implying that therapies targeting GSDME may prove efficacious in overcoming chemotherapeutic drug-induced nephrotoxicity.Subject terms: Apoptosis, Acute kidney injury     

Protective effect of fosfomycin on gentamicin-induced lipid peroxidation of rat renal tissue

Fosfomycin is clinically recognized to reduce the aminoglycoside antibiotics-induced nephrotoxicity. However, little has been clarified why fosfomycin protects the kidney from the aminoglycosides-induced nephrotoxicity. Gentamicin, a typical aminoglycoside, is reported to cause lipid peroxidation. We focused on lipid peroxidation induced by gentamicin as a mechanism for the aminoglycosides-induced nephrotoxicity. The aim of this study is to investigate the effect of fosfomycin on the gentamicin-induced lipid peroxidation. In rat renal cortex mitochondria, fosfomycin was shown to depress the gentamicin-induced lipid peroxidation, which was evaluated by formation of thiobarbituric acid reactive substances (TBARS). Interestingly, this effect was observed in rat renal cortex mitochondria, but not in rat liver microsomes. However, fosfomycin did not affect lipid peroxidation of arachidonic acid caused by gentamicin with iron. Fosfomycin inhibited the gentamicin-induced iron release from rat renal cortex mitochondria. These results indicated that fosfomycin inhibited the gentamicin-induced lipid peroxidation by depressing the iron release from mitochondria. This may possibly be one mechanism for the protection of fosfomycin against the gentamicin-induced nephrotoxicity.     

Detection and quantification of (R) and (S)-dechloroethylifosfamide metabolites in plasma from children by enantioselective LC/MS/MS

Ifosfamide (IF), a potent chemotherapeutic agent for solid tumors, is known to cause high rates of nephrotoxicity in children with cancer, which is most likely due to the renal production of the metabolite chloroacetaldehyde. Using plasma samples obtained from pediatric oncology patients, we developed a simple nonderivatizing enantioselective liquid chromatography mass spectrometry method to detect the (R) and (S)-2- and 3-dechloroethylifosfamide metabolites. The (R) and (S)-enantiomers of the 2- and 3-DCEIF (N-3-dechlroethylifosfamide) were detectable in all 22 patients' samples with levels ranging from 9.9 to 238.7 ng/ml for (R)-2-DCEIF, 15.8 to 663.0 ng/ml for (S)-2-DCEIF, 20.8 to 852.8 ng/l for (R)-3-DCEIF and 28.0 to 862.0 ng/ml for (S)-3-DCEIF. In addition, the lower limit of quantification for this method is 1 ng/ml. Future studies should concentrate on (R) or (S) production of the 2-DCEIF and 3-DCEIF and subsequently chloroacetaldehyde formation with the aim of considering the administration of only the (R)-IF as its metabolism results in a lower production of chloroacetaldehyde.     

Multiple activation of chloroform in kidney microsomes from male and female DBA/2J mice

Microsomes from the renal cortex of DBA/2J mice can metabolize chloroform through oxidative and reductive pathways, similar to hepatic microsomes. The oxidative or reductive nature of CHCl₃ activation is strictly dependent on the oxygenation of the incubation mixture, as indicated by the formation of qualitatively different adducts to phos-pholipids (PLs). The protein and lipid binding levels measured in kidney microsomes from control females differed significantly from the binding levels observed with kidney microsomes from male and testosterone-treated female DBA/2J mice in aerobic conditions only. Therefore, the sex-dependent CHCl₃-induced acute nephrotoxicity seems related only with the oxidative CHCl₃activation. The levels of adducts to PL polar heads and to protein showed a strict correlation with each other. Therefore, the assay of adducts to PL polar heads may be used as a substitute for the assay of adducts to protein. This might be especially convenient when studying the effects of both phosgene and the trichloromethyl radicals.     

Role of MGMT in protecting against cyclophosphamide-induced toxicity in cells and animals

O(6)-Methylguanine-DNA methyltransferase (MGMT) is a DNA repair protein that protects cells from the biological consequences of alkylating agents by removing alkyl groups from the O(6)-position of guanine. Cyclophosphamide and ifosfamide are oxazaphosphorines used clinically to treat a wide variety of cancers; however, the role of MGMT in recognizing DNA damage induced by these agents is unclear. In vitro evidence suggests that MGMT may protect against the urotoxic oxazaphosphorine metabolite, acrolein. Here, we demonstrate that Chinese hamster ovary cells transfected with MGMT are protected against cytotoxicity following treatment with chloroacetaldehyde (CAA), a neuro- and nephrotoxic metabolite of cyclophosphamide and ifosfamide. The mechanism by which MGMT recognizes damage induced by acrolein and CAA is unknown. CHO cells expressing a mutant form of MGMT (MGMT(R128A)), known to have >1000-fold less repair activity towards alkylated DNA while maintaining full active site transferase activity towards low molecular weight substrates, exhibited equivalent CAA- and acrolein-induced cytotoxicity to that of CHO cells transfected with plasmid control. These results imply that direct reaction of acrolein or CAA with the active site cysteine residue of MGMT, i.e. scavenging, is unlikely a mechanism to explain MGMT protection from CAA and acrolein-induced toxicity. In vivo, no difference was detected between Mgmt-/- and Mgmt+/+ mice in the lethal effects of cyclophosphamide. While MGMT may be important at the cellular level, mice deficient in MGMT are not significantly more susceptible to cyclophosphamide, acrolein or CAA. Thus, our data does not support targeting MGMT to improve oxazaphosphorine therapy.     

Cephaloridine-induced lipid peroxidation initiated by reactive oxygen species as a possible mechanism of cephaloridine nephrotoxicity

Rat kidney microsomes reduced cephaloridine when incubated anaerobically with NADPH. Superoxide anion was generated in a concentration- and time-dependent manner when cephaloridine was incubated with rat kidney microsomes. Cephaloridine increased the in vitro peroxidation of rat kidney microsomal lipids in a concentration- and time-dependent manner. Cephaloridine-induced lipid peroxidation was inhibited by a combination of superoxide dismutase and catalase, by the hydroxyl radical scavengers, mannitol, (+)-cyanidanol-3 and by the singlet oxygen scavenger histidine in a concentration-dependent manner. It is proposed that cephaloridine nephrotoxicity may occur through the transfer of an electron from reduced cephaloridine to oxygen and subsequent formation of the superoxide anion, hydrogen peroxide, the hydroxyl radical and singlet oxygen. These activated oxygen species then are very likely to react with membrane lipids to induce lipid peroxidation and nephrotoxicity.     

Use of human-liver microsomes from kidney-transplant donors for the induction of chromatid aberrations and sister-chromatid exchanges by means of pre-carcinogens in Chinese hamster cells in vitro.

Samples of two human livers taken during operation of kidney donor patients were processed for microsome fractions and used for metabolization of cyclophosphamide (CP) and dimethylnitrosamine (DMN) in combination with the NADPH-generating system. Rat-liver microsomes were checked for comparison. Induction of chromatid aberrations and sister-chromatid exchanges in a newly isolated clone of Chinese hamster fibroblasts served as indicators of activity. Human S-9 fractions standardized on protein content showed strong variations of CP and DMN activation. Whereas liver microsomes of one patient (who also suffered from Gaucher's disease) were highly active for both pre-carcinogens and metabolized DMN at the same level as the uninduced rat-liver microsomes, the S-9 fraction from the second patient failed to activate CP, but was distinctly positive for DMN. It is suggested that samples of liver and other organs of renal transplant donors might be a practicable source of freshly prepared human microsome fractions usable in biochemical, genetic and carcinogenetic studies. Problems concerning the extrapolation of results are discussed.     

Human adipose tissue-derived mesenchymal stem cells protect kidneys from cisplatin nephrotoxicity in rats

Cisplatin has multiple cellular targets and modes of action that lead to nephrotoxicity. This suggests novel therapies that act at multiple cisplatin target sites may be effective. We tested whether human adipose tissue-derived mesenchymal stem cells (Ad-MSCs) can affect multiple target sites and protect against cisplatin-induced kidney damage. Rats were divided into four groups: control, infused with Ad-MSCs, injected with cisplatin, and cisplatin followed by infusion of Ad-MSCs. Animal survival and renal function were decreased and histological damage was increased in cisplatin-treated rats at day 3. Infusion of Ad-MSCs ameliorated renal dysfunction and tissue injury caused by cisplatin, leading to increased survival. Apoptotic cell death in the kidney was significantly reduced by infusion of Ad-MSCs. Activation of p53, JNK, and ERK and the expression of inflammation-related molecules were also decreased in the kidney that received Ad-MSCs. Very few Ad-MSCs were detected in the kidney. Conditioned medium from cultured Ad-MSCs had renal-protective functions in vivo and in vitro. Renal dysfunction and tissue damage caused by cisplatin were significantly reduced in rats treated with Ad-MSCs-conditioned medium. The viability of cultured renal proximal tubular cells exposed to cisplatin was also improved by coculture with Ad-MSCs or with conditioned medium. Release of proinflammatory mediators induced by cisplatin was inhibited in coculture with Ad-MSCs. Our results show that human Ad-MSCs exert a paracrine-protective effect on cisplatin nephrotoxicity at multiple target sites and suggest that human Ad-MSCs might be a new therapeutic approach for patients with acute kidney injury.     

Time dependent effects of gentamicin on the enzymes of carbohydrate metabolism, brush border membrane and oxidative stress in rat kidney tissues

Gentamicin (GM), an antibiotic against life threatening bacterial infection, induces remarkable toxicity in the kidney. Histological studies have indicated that mitochondria, microsomes, lysosomes and plasma membranes of renal proximal convoluted tubules in particular are major GM targets. Despite numerous investigations, the biochemical/cellular basis of GM nephrotoxicity is not well understood. Recently reactive oxygen species (ROS) are considered to be important mediators of GM-induced nephrotoxicity. We hypothesize that GM causes damage to intracellular organelles and affects their structural integrity and alters metabolic and other functional capabilities. To address above hypothesis a long-term, time-dependent effect of GM has been studied on blood/urine parameters, enzymes of carbohydrate metabolism, brush border membrane (BBM) and basolateral (BLM), lysosomes and oxidative stress in renal tissues. A nephrotoxic dose of GM (80 mg/kg body weight) was administered to rats daily for 15 days. The long-term treatment with GM induced a significant increase in serum creatinine, blood urea nitrogen followed by massive proteinuria, glucosuria, enzymuria along with loss of electrolytes in the urine. The activities of the enzymes of carbohydrate metabolism, plasma membranes, lysosomes significantly declined. The activities of antioxidant enzymes e.g. superoxide dismutase, catalase and glutathione peroxidase were severely depressed and lipid peroxidation was significantly increased in the renal cortex and medulla. We conclude that GM administration induced oxidative damage to renal tissues that resulted in impaired carbohydrate metabolism and decreased activities of BBM, BLM and lysosomes associated with increased lipid peroxides.     

Predictive Usefulness of Urinary Biomarkers for the Identification of Cyclosporine A-Induced Nephrotoxicity in a Rat Model

The main side effect of cyclosporine A (CsA), a widely used immunosuppressive drug, is nephrotoxicity. Early detection of CsA-induced acute nephrotoxicity is essential for stop or minimize kidney injury, and timely detection of chronic nephrotoxicity is critical for halting the drug and preventing irreversible kidney injury. This study aimed to identify urinary biomarkers for the detection of CsA-induced nephrotoxicity. We allocated salt-depleted rats to receive CsA or vehicle for 7, 14 or 21 days and evaluated renal function and hemodynamics, microalbuminuria, renal macrophage infiltration, tubulointerstitial fibrosis and renal tissue and urinary biomarkers for kidney injury. Kidney injury molecule-1 (KIM-1), tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), fibronectin, neutrophil gelatinase-associated lipocalin (NGAL), TGF-β, osteopontin, and podocin were assessed in urine. TNF-α, IL-6, fibronectin, osteopontin, TGF-β, collagen IV, alpha smooth muscle actin (α -SMA) and vimentin were assessed in renal tissue. CsA caused early functional renal dysfunction and microalbuminuria, followed by macrophage infiltration and late tubulointerstitial fibrosis. Urinary TNF-α, KIM-1 and fibronectin increased in the early phase, and urinary TGF-β and osteopontin increased in the late phase of CsA nephrotoxicity. Urinary biomarkers correlated consistently with renal tissue cytokine expression. In conclusion, early increases in urinary KIM-1, TNF-α, and fibronectin and elevated microalbuminuria indicate acute CsA nephrotoxicity. Late increases in urinary osteopontin and TGF-β indicate chronic CsA nephrotoxicity. These urinary kidney injury biomarkers correlated well with the renal tissue expression of injury markers and with the temporal development of CsA nephrotoxicity.     

Membrane lipid changes in erythrocytes, liver and kidney in acute and chronic experimental liver disease in rats

Lipid molecules in lipoprotein surfaces exchange with their counterparts in cell plasma membranes. In human or experimental liver disease, plasma lipoprotein surfaces are enriched in cholesterol and deficient in arachidonate; corresponding alterations occur in membrane lipids of erythrocytes. To determine whether similar changes take place in membranes of nucleated cells, the lipid content of plasma and of erythrocyte, liver and kidney membranes was measured in rats with acute (3-day) galactosamine-induced hepatitis or chronic (3-week) biliary obstruction. In both models of liver injury the cholesterol:phospholipid ratio in plasma and in erythrocytes was significantly increased (P less than 0.001). Although this ratio was also elevated in liver and kidney microsomes, only in liver microsomes of obstructed rats was the increase significant (P less than 0.001). However, the cholesterol:phospholipid ratio of kidney brush-border membranes, was significantly higher in bile-duct-ligated rats; presumably, compensating mechanisms limit cholesterol accumulation in intracellular membranes. Kidney brush-border membranes from obstructed rats were deficient in arachidonate as were plasma and erythrocytes. However, arachidonate levels were unchanged in kidney microsomes; renal delta 6-desaturase, the rate-limiting enzyme in the conversion of linoleic acid to arachidonic acid, was increased by 50% (P less than 0.001) and may have counteracted a reduced supply of exogenous lipoprotein arachidonate. We conclude that in experimental liver disease lipoprotein-induced lipid abnormalities can occur in renal membranes, although compensatory mechanisms may operate; the alterations seen, cholesterol accumulation and arachidonate depletion, would be expected to interfere with sodium transport and prostaglandin production, respectively. Our findings support the hypothesis that lipid abnormalities in kidney membranes contribute to the renal dysfunction which is a frequent complication of human liver disease.     

Differential expression of cytochrome P-450 1 and related forms in rabbit liver and kidney

Monoclonal antibodies developed to cytochrome P-450 1, some of which react with proteins in addition to P-450 1, were used to investigate the differential expression of P-450 1 dependent 21-hydroxylase activity in renal tissue of rabbits exhibiting differences in hepatic 21-hydroxylase activity. Using immunohistochemical techniques, the monoclonal antibodies, 2F5 and 3C3, localized protein in the S2 and S3 segments of the proximal tubule in the renal cortex. These two monoclonal antibodies, 2F5 and 3C3, reacted with a kidney protein that migrated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a relative electrophoretic mobility that did not correspond to known rabbit hepatic isozymes and was termed P-450 K. Antibodies specific for P-450 1 and 3b, 1F11 and 8-27, respectively, produced no staining in kidney. The protein recognized by the 2F5 and 3C3 antibodies is immunologically distinct from cytochrome P-450s 1, 2, and 3b. The rate of 21-hydroxylation of progesterone was shown to be approximately 100-fold less in kidney than liver microsomes where this pathway is largely catalyzed by P-450 1. The activity of the kidney microsomes was not inhibited by antibodies directed to P-450 1. In addition, the variation observed for the 21-hydroxylase activity in the hepatic microsomal fraction of outbred New Zealand white rabbits was not evident in kidney microsomes from these same animals. The 2F5 antibody was found, however, to be inhibitory (about 50%) of the 11-hydroxylation of lauric acid in kidney microsomes. This suggests that P-450 K participates in lauric acid 11-hydroxylase activity. The treatment of rabbits with phenobarbital, but not 2,3,7,8-tetrachlorodibenzo-p-dioxin, was found to induce the levels of P-450 K.     

Quercetin and allopurinol ameliorate kidney injury in STZ-treated rats with regulation of renal NLRP3 inflammasome activation and lipid accumulation

Hyperuricemia, hyperlipidemia and inflammation are associated with diabetic nephropathy. The NLRP3 inflammasome-mediated inflammation is recently recognized in the development of kidney injury. Urate and lipid are considered as danger signals in the NLRP3 inflammasome activation. Although dietary flavonoid quercetin and allopurinol alleviate hyperuricemia, dyslipidmia and inflammation, their nephroprotective effects are currently unknown. In this study, we used streptozotocin (STZ)-induced diabetic nephropathy model with hyperuricemia and dyslipidemia in rats, and found over-expression of renal inflammasome components NLRP3, apoptosis-associated speck-like protein and Caspase-1, resulting in elevation of IL-1β and IL-18, with subsequently deteriorated renal injury. These findings demonstrated the possible association between renal NLRP3 inflammasome activation and lipid accumulation to superimpose causes of nephrotoxicity in STZ-treated rats. The treatment of quercetin and allopurinol regulated renal urate transport-related proteins to reduce hyperuricemia, and lipid metabolism-related genes to alleviate kidney lipid accumulation in STZ-treated rats. Furthermore, quercetin and allopurinol were found to suppress renal NLRP3 inflammasome activation, at least partly, via their anti-hyperuricemic and anti-dyslipidemic effects, resulting in the amelioration of STZ-induced the superimposed nephrotoxicity in rats. These results may provide a basis for the prevention of diabetes-associated nephrotoxicity with urate-lowering agents such as quercetin and allopurinol.     

Determination of urinary 2- and 3-dechloroethylated metabolites of ifosfamide by high-performance liquid chromatography

In vivo oxidation of chloroethyl side-chains on ifosfamide produces the toxin chloroacetaldehyde. Production of this labile metabolite can be indirectly quantitated by monitoring the excretion of the residual 2- and 3-dechloroethylated ifosfamide. Urinary ifosfamide and the two dechloroethylated metabolites were extracted into chloroform from alkalinized salt-saturated urine, followed by high-performance liquid chromatographic separation using an acetonitrile gradient on a reversed-phase column and ultraviolet detection at 190 nm. In five patients given 1.6 g/m² ifosfamide, 11–30% of the dose was excreted over 24 h as unchanged drug, 11–21% as 3-dechloroethylated and 3–10% as 2-dechloroethylated ifosfamide.