Alterations in hepatic and renal levels of glutathione and activities of glutathione S-transferase from rats treated with cis-dichlorodiammineplatinum-II

Protective Effect of Reduced Glutathione against CIS-Dichlorodiammine Platinum (II)–Induced Nephrotoxicity and Lethal Toxicity

Pretreatment of Swiss mice and Sprague-Dawley rats with glutathione (GSH) reduced the acute lethal toxicity of cis-dichlorodiammine platinum (II) (cis-DDP) in a dose-dependent manner. The protection was accompanied by reduction of both body weight loss and by reduction of nephrotoxicity, as measured by a rise in serum blood urea nitrogen (BUN), creatinine levels and by histopathologic changes, which occurred 4 days following cis-DDP treatment. The antitumor effects of cis-DDP on experimental tumor models (P388 and Gross leukemia) were not significantly altered by GSH treatment. It is suggested that the partial protection by GSH from acute toxicity of the antitumor drug is directly related to protection of renal function.

Usefulness of liposomes loaded with cytostatic bile acid derivatives to circumvent chemotherapy resistance of enterohepatic tumors

We have investigated the sensitivity of the cisplatin-resistant enterohepatic tumor cell lines LS174T/R (human colon adenocarcinoma), WIF-B9/R (rat hepatoma-human fibroblast hybrid), and Hepa 1-6/R (mouse hepatoma) to free and liposome-encapsulated cytostatic bile acid derivatives Bamet-R2 and bamet-UD2. Expression of resistance associated genes was measured by quantitative reverse transcription-polymerase chain reaction or Western blotting. Drug uptake was determined by atomic absorption spectrophotometry. In resistant cells, overexpression of MRP1 and MRP2 was accompanied by reduced accumulation of cisplatin. The expression of MDR1 and GST-P was only enhanced in LS 174T/R. A higher expression of p53 was seen in LS 174T/R and Hepa 1-6/R cell lines but not in WIF-B9/R cells. In wild-type counterparts, uptake and cytostatic ability of Bamets were markedly higher (UD2 > R2) than that of cisplatin. Both effects were further enhanced by liposome formulation. Bamets were able to overcome cisplatin resistance in all cell lines. Cisplatin prolonged the survival time of nude mice in whose livers a Hepa 1-6 tumor had been implanted, but failed to exert a beneficial effect when the tumor was Hepa 1-6/R. In both cases, tissue distribution of cisplatin was: kidney >> liver > tumor. Survival was markedly longer in animals receiving Bamet-UD2, even if the implanted tumor was resistant. The accumulation of Bamet-UD2 in tissues was: liver > tumor > kidney. Liposome formulation further enhanced the beneficial properties of Bamet-UD2. Thus, the amount of drug in the tumor was increased and that in liver and kidney was reduced (tumor > liver > kidney), and life span was prolonged. In conclusion, liposomal Bamet-UD2 may be a useful tool to circumvent resistance to chemotherapy, particularly in tumors of the enterohepatic circuit.

Protective effect of N-benzyl-D-glucamine dithiocarbamate against renal toxicity in rats during repeated cis-diamminedichloroplatinum administrations

The protective effects of N-benzyl-D-glucamine dithiocarbamate (BGD) against the renal toxicity caused by repeated injections of cis-diamminedichloroplatinum (DDP) were studied in rats. The rats were injected i.p. with BGD (2.0 mmol/kg) immediately after i.v. injection of DDP (20 mumol/kg), and after 10 and 20 days they received repeated treatments with the same doses of DDP and BGD. Treatment with BGD prevented nephrotoxicity after repeated DDP administrations. Repeated DDP injections increased lipid peroxidation in the kidney and decreased GSH concentration in the kidney at 5 days after the third injection of DDP. BGD treatment prevented the increase in lipid peroxidation and the decrease in the GSH concentration caused by repeated administration of DDP. The determination of activities of antioxidant enzymes in the kidney showed that catalase activity decreased after repeated DDP administrations and that superoxide dismutase activity tended to decrease. Changes in activities of these enzymes were prevented by BGD treatment. The platinum concentrations in kidney and liver were decreased by BGD treatment. These results indicate that BGD treatment prevents the accumulation of platinum in the kidney after repeated administrations of DDP, resulting in protection against the DDP-induced renal toxicity.

Beneficial effect of acetylcysteine on cisplatin nephrotoxicity in rats

The influence of acetylcysteine (ac-cys) on cisplatin (CP) nephrotoxicity was investigated in female Wistar rats. Administration of 0.6 mg CP 100 g-1 body wt. was followed by oliguria and proteinuria, as well as a significant increase of blood urea nitrogen concentration. The i.p. administration of 0.6 mg CP 100 g-1 body wt. concomitantly with 100 mg ac-cys 100 g-1 body wt. s.c. completely abolished the nephrotoxic effects of CP. However, following this, the Pt concentration in kidney was decreased significantly by ac-cys treatment. This was caused by the enhanced urinary excretion of Pt. The same effect on CP nephrotoxicity appeared when CP and ac-cys were dissolved together in solution prior to injection. It could be shown that in this solution a ligand exchange reaction of CP by ac-cys started immediately, resulting in increased renal excretion and decreased Pt concentration in kidney. From our results we concluded that the protective effect of ac-cys on CP nephrotoxicity is based on the formation of a complex unsuitable for tubular reabsorption.

Role of glutathione for cisplatin nephrotoxicity in young and adult rats

Investigations were done in 10- and 55-day-old Wistar rats. Glutathione (GSH) level in kidney was decreased by 8 mmol buthionine sulfoximine (BSO)/100 g BW. There was no effect on the renal function and nephrotoxicity of cisplatin (0.6 mg CP/100 g BW) in adult rats. In young rats BSO treatment was followed by nephrotoxic effects. Pt concentration remained unaffected by BSO in young and adult rats. GSH concentration in kidney was increased by 100 mg acetyl-cysteine (accys)/100 g BW. CP nephrotoxicity was lower in young as well as in adult ac-cys-treated rats. Pt levels in renal tissue were significantly decreased in rats from both age groups. From our results we conclude that the beneficial effect of high GSH concentration in renal tissue on CP nephrotoxicity is the result of decreased Pt concentration in kidney.

Importance of cell cycle perturbations on the effectiveness of N-methylformamide and anti-neoplastic drugs in combination

The effect of N-methylformamide (NMF) in combination with Adriamycin (ADM) and cis-diamminedichloroplatinum (DDP) on the cell survival and cell cycle kinetics of two human tumour lines was assessed: HT29 colon carcinoma and M14 melanoma cells were exposed to ADM and DDP alone or in combination with a non-cytotoxic dose of NMF, according to different schedules. The results demonstrate that NMF exposure sensitized both tumour cell lines to the lethal activity of ADM and DDP; however, reverse sequences had to be applied to reach an increase in the lethal activity of the two different drugs. The ADM-NMF combination determined a powerful decrease in the surviving fraction of the two cell lines when ADM was given as the first agent (ADM----NMF), while the reverse sequence did not increase the ADM cytotoxic effect. With respect to the DDP-NMF association, the sequence which accounted for a greater sensitizing effect was NMF administration followed by DDP treatment (NMF----DDP). This work demonstrates the importance of timing in combined treatments which involve NMF. A delay in cell proliferation elicited by NMF exposure could be responsible for the effectiveness of the combined treatment.

Triiodothyronine (T3) increases cisplatin nephrotoxicity in young and adult rats

The influence of pretreatment with triiodothyronine (T3) on cisplatin (CP)-induced nephrotoxicity was investigated in 10- and 55-day-old rats. Triiodothyronine pretreatment enhanced CP proteinuria in young and adult rats, and increased blood urea nitrogen concentration in 55-day-old rats. As T3 decreased Pt concentrations in renal tissue, the enhanced nephrotoxicity of CP by T3 must have another mechanism. Enhanced CP nephrotoxicity is discussed in connection with an increase of glutathione concentration obtained in renal tissue as a consequence of T3 pretreatment.

Cisplatin-induced lipid peroxidation and decrease of gluconeogenesis in rat kidney cortex: different effects of antioxidants and radical scavengers

The present in vitro study was performed to investigate the effect of the nephrotoxic anticancer agent cisplatin (CP) on lipid peroxidation, on pyruvate-stimulated gluconeogenesis and on p-aminohippurate (PAH) accumulation in rat renal cortical slices. In addition, the inhibitory effects of the antioxidants and radical scavengers N,N'-diphenyl-p-phenylenediamine (DPPD), (+)-cyanidanol-3 or alpha-tocopherol on CP-induced lipid peroxidation and CP-induced decrease of gluconeogenesis and the inhibitory effect of DPPD on CP-induced decrease of PAH accumulation were evaluated. Slices were incubated in a CP-containing medium for different periods of time (7.5-300 min) and at different concentrations (0.025-1.5 mg/ml). Lipid peroxidation was monitored by measuring the production of malondialdehyde (MDA). Accumulation of PAH was expressed as slice to medium concentration ratio. Pyruvate-stimulated gluconeogenesis, measured as glucose production, was determined after a subsequent 60- or 15-min incubation in a pyruvate-containing, CP-free medium. CP led to a time- and concentration-dependent increase in MDA production, a time- and concentration-dependent decrease of pyruvate-stimulated gluconeogenesis and a time-dependent decrease of PAH accumulation in renal cortical slices. Decrease of gluconeogenesis preceded MDA production and decrease of PAH accumulation. Antioxidants reduced CP-induced MDA production and CP-induced decrease of accumulation of PAH, but did not reverse CP-induced decrease of gluconeogenesis. This might indicate, that the generation of free radicals and subsequent lipid peroxidation may play a role, at least in part, in inducing CP nephrotoxicity. There could be more than one mechanism of CP-induced nephrotoxicity, since decrease of gluconeogenesis preceded MDA production and decrease of PAH accumulation and could not be inhibited by antioxidants and radical scavengers.

Sequence dependence of the antitumor and toxic effects of 5-fluorouracil and cis-diamminedichloroplatinum combination on primary colon tumors in mice

Primary colon tumors of different sizes and malignancy, chemically induced by methylazoxymethanol in outbred CF-1 mice, were used to investigate the antitumor effects of 5-Fluorouracil (5FU) and cis-diammine-dichloroplatinum (DDP), given weekly i.v. as single agents or in combination. When single-drug chemotherapy was tested, DDP showed higher efficacy than 5FU. In fact, in two separate experiments a significant reduction (P less than 0.05) of tumor number (TN) and tumor burden was obtained by treatment with the optimal dose of DDP (4.5 mg/kg per injection) and not by that of 5FU (52 mg/kg). When the two drugs were combined (24-h interval), studies carried out on healthy mice treated weekly i.v. showed a lower toxicity with the same doses given in the sequence 5FU-DDP than in the opposite sequence. The two drugs, delivered in the sequence 5FU followed by DDP, statistically reduced the TN and total tumor burden compared to control mice (P less than 0.05). On the other hand, the same doses in the sequence DDP followed by 5FU did not attain significant tumor reduction. The sequence dependence of the activity and toxicity of the 5FU and DDP combination observed in this experimental model should be taken into account in the design of clinical trials.

Inhibition of cisplatin-induced nephrotoxicity in rats by buthionine sulfoximine, a glutathione synthesis inhibitor

DL-Buthionine-(S,R)-sulfoximine (BSO), a glutathione-depleting agent, was found to diminish the nephrotoxic effect of cisplatin (cis-diamminedichloroplatinum). Pretreatment of rats with BSO (4 mmol/kg s.c.) 2 h prior to cisplatin, either as a single dose of 5 mg/kg or at a daily dose of 2.5 mg/kg for 3 consecutive days, resulted in diminished elevations of plasma BUN concentration and decreased cisplatin-induced inhibition of renal gamma-glutamylcysteine synthetase and gamma-glutamyl transpeptidase activity measured 6 days following treatment. Administration of BSO prior to cisplatin at 7.5 mg/kg did not significantly alter the effect of cisplatin on either BUN concentration or enzyme activity. The influence of BSO pretreatment on the antitumor activity of cisplatin was studied using implantation of a murine bladder cancer (MBT-2) in C3H mice. Pretreatment of mice with BSO (5 mmol/kg) did not influence cisplatin antitumor efficacy.

Possible mechanism for differences in sensitivity to cis-platinum in human prostate tumor cell lines

Two human prostate tumor cell lines which exhibit a 2.4-fold difference in sensitivity to cis-platinum (cis-Pt) were found to possess slightly different sulphydryl contents, and the presence of a metallothionein-like zinc-binding protein was demonstrated in the line exhibiting relative resistance to cis-Pt. Although these factors have been postulated to play a role in the mechanism(s) of resistance to cis-Pt in other cell types, preliminary data in this report suggest that differences found in drug uptake and subsequent binding to DNA are most likely responsible for variations in cis-Pt sensitivity displayed by these prostate tumor cell lines.

Physiological model for the pharmacokinetics of cis-dichlorodiammineplatinum (II) (DDP) in the tumored rat

A physiological model has been developed to describe the disposition of cis-dichlorodiammine-platinum(II) (DDP) following i.v. dosing in the female rat bearing the Walker 256 carcinoma. The model simulates concentrations of DDP and its mobile and fixed metabolites in plasma, liver, gut, skin, muscle, tumor, carcass, and kidney, and DDP and mobile metabolite excretion following a 4 mg/kg dose. In the kinetic model, DDP binds irreversibly to low MW nucleophiles and macromolecules (largely proteins) within the plasma and tissue compartments to form mobile and fixed metabolites, respectively. Reaction rates for the formation of each metabolite are tissue/organ specific. The rate constant for the biotransformation of DDP to fixed metabolite in plasma (k2P = 0.0082 min-1) was determined from in vitro incubation studies. This rate was used as the basis for estimating the biotransformation rate constants for DDP to fixed and mobile metabolites in other compartments. Both DDP and mobile metabolite are assumed to follow flow-limited transport, to freely traverse compartmental barriers, and to partition equally in all compartments. Both are excreted in the urine, the major route of Pt elimination. Urinary excretion is modeled as a linear process involving filtration only; an assumption based on a calculated renal clearance of 1.1 ml/min, a value very similar to the estimated GFR. Biliary excretion is a minor route of mobile metabolite elimination and is modeled as a linear process occurring in the liver. Four hours after dosing, approximately 60% of the administered Pt remains in the tissues and plasma. Of this, over 75% of the plasma Pt and 90% of the metal ion in every other compartment is fixed (protein bound). Fixed Pt can be eliminated from a compartment only after its biotransformation to mobile metabolite. In most compartments this rate of elimination corresponds closely to the average rate of protein turnover in that compartment.

A high-performance liquid chromatographic assay with improved selectivity for cisplatin and active platinum (II) complexes in plasma ultrafiltrate

cis-Diamminedichloroplatinum(II) (DDP) was measured in plasma ultrafiltrate following derivatization with sodium diethyldithiocarbamate (DDTC) by quantitation against a nickel chloride internal standard. A chloroform extract containing the Pt(DDTC)2 and Ni(DDTC)2 complexes was separated by reversed-phase high-performance liquid chromatography on a C18 radial compression column. The complex was eluted with methanol/water, 4/1, at a flow rate of 1.5 ml/min, and was detected at 254 nm. The limit of sensitivity was 0.1 microgram/ml DDP in the ultrafiltrate. This analytical approach was validated by comparison to graphite furnace atomic absorption spectrophotometric determinations of duplicate samples. There was clearly a component of the ultrafiltrable platinum present that was resistant to derivatization by DDTC. Evidence is presented that this component, presumably Pt(II) complexed with endogenous small molecules, is non cytotoxic and, hence, that this method may be selective for "active Pt(II)." This method offers an advantage over atomic absorption determination of total platinum in ultrafiltrate which does not discriminate between active and inactive forms, and over off-line FAA detection of parent DDP in HPLC eluates which ignores other active forms. Using this technique we have measured the pharmacokinetics of DDTC-reactive Pt(II) in humans after either i.v. infusion or infusion of DDP into the peritoneal cavity of patients with ovarian carcinoma.

Uptake and metabolism of cisplatin by rat kidney

Cisplatin, an effective antineoplastic agent, is toxic to the kidney. Since the kidney's vulnerability to cisplatin may originate in its ability to accumulate and retain platinum to a greater degree than other organs, we studied the characteristics of the renal accumulation of platinum and investigated the nature of intracellular platinum. Cisplatin and ethylenediamminedichloroplatinum, nephrotoxic and antineoplastic liganded platinum compounds, were concentrated in rat renal cortical slices fivefold above medium concentration. Platinum uptake was energy- and temperature-dependent and could be inhibited by drugs which inhibit base transport. The organic anions para-aminohippurate and pyrazinoate did not reduce renal slice platinum uptake. Unbound platinum in the blood and urine was predominantly cisplatin but unbound platinum in kidney cytosol was not. This latter compound, in contrast to cisplatin, was not active as a mutagen. These studies suggest that the kidney accumulates platinum in part by transport or specific binding to the base transport system in the kidney and biotransforms it intracellularly. Unbound platinum in the cell is not cisplatin and may no longer be toxic.

The effects of cisplatin on the concentration of protein thiols and glutathione in the rat kidney

The effect of a nephrotoxic dose of cisplatin (5 mg/kg) on the concentrations in the rat kidney of both glutathione and protein-bound thiols was investigated. Total glutathione and oxidised glutathione were measured in the cortex and outer medulla using specific enzyme-based assays. The high-molecular-weight thiols were quantified in cells of the proximal tubule using a cyto-chemical technique. The concentration of total glutathione (oxidised and reduced) in the kidney cortex and outer medulla was significantly higher than that of controls at 1 h following cisplatin administration. The amount by which the concentration in treated animals exceeded that in controls increased to 50% at 72 h and remained significantly elevated for 120 h following treatment. This increase was mainly attributable to an increase in the concentration of reduced glutathione. In contrast, the concentration of protein thiols in the proximal tubules decreased significantly at 8 h after dosing, reaching a nadir 29% below that of controls at 120 h, thus coinciding with the maximal functional disturbance in the kidney as reflected by the concentration of blood urea. The decrease in protein thiols could not be correlated stoichiometrically with the platinum concentration in the cortex and outer medulla, which reached a peak of 16.3 +/- 0.3 micrograms/g wet tissue at 72 h after treatment. Evidently cisplatin perturbs the equilibrium that is said to exist between the concentration of reduced glutathione and that of protein thiols. This perturbation occurs well before the onset of overt functional disturbance of the kidney and is evident before the point at which the damage to the kidney caused by cisplatin becomes irreversible.