Effects of the diuretics mannitol or acetazolamide on nephrotoxicity and physiological disposition of cisplatin in rats

Summary The anticancer drug cisplatin has been known to produce severe renal lesions characterized by high levels of blood urea nitrogen (BUN), toxic nephrosis, and platinum (Pt) retention in the kidney. The effect of IV pretreatment with acetazolamide (ACZ) 30 min before or mannitol (MAN) immediately prior to IP administration of 5 mg/kg cisplatin on Pt excretion, tissue distribution, and nephrotoxicity was investigated in male F344 rats.ACZ pretreatment reduced the cisplatin-induced nephrotoxicity, as indicated by only a slight elevation of BUN, a milder histopathologic lesion, and a more rapid recovery of renal function and structure. Although MAN-pretreated animals exhibited similar changes in BUN to ACZ-pretreated animals, the renal damage was similar to that seen in aninals treated with cisplatin alone. A reduction of kidney Pt content was observed with both diuretics, although there was significantly less retention after ACZ pretreatment.The diuretic ACZ was more effective than MAN in reducing the renal lesions induced by cisplatin and it might be clinically useful in preventing cisplatin nephrotoxicity.     

Intracellular metabolites of cisplatin in the rat kidney

Summary The appearance of low-molecular-weight metabolites of cisplatin in the cytosol of cells from the cortex and outer medulla, of the rat kidney has been examined using HPLC up to 24 h following cisplatin administration. Comparison was made between these metabolites and those present in plasma, urine and liver. The effect of sodium chloride (NaCl) pretreatment, which is known to reduce cisplatin-induced nephrotoxicity, on these metabolites was also investigated. Platinum levels in the kidney cortex and medulla and the cytosol reached maximal levels within 1 h of i.p. injection of 5 mg/kg cisplatin. At least six platinum species, including cisplatin, were present 1 h post-dosing, with the principal species being the parent drug; all of these species were either neutral or negatively charged. Although the concentration of most of the platinum species fell with time, that of one species eluting before cisplatin rose, and by 24 h it was the major metabolite. Cisplatin and two other major cytosolic platinum species were also present in urine and plasma, both of which also contained a number of charged species that were absent from the cytosol. The liver cytosol contained at least five metabolites 1 h post-dosing, but, in contrast to the kidney cytosol at the same time, the predominant species was that eluting before cisplatin and not cisplatin itself. One of the metabolites in the cytosol and urine had the same retention time as an adduct of cisplatin with glutathione and with cysteine. Urinary samples also contained a metabolite coeluting with aquated cisplatin. Pretreatment of animals with NaCl significantly reduced the platinum concentration in the kidney, with a corresponding decrease in the cytosolic metabolites; this may have contributed significantly to the reduction in cisplatin-induced nephrotoxicity after NaCl pretreatment. NaCl also significantly reduced a possible aquated species present in the urine, which may also have contributed to the reduction in nephrotoxicity. The data suggest that cisplatin itself may be the nephrotoxic species, since it is the intracellular platinum compound present in highest concentration during the early critical period after its administration.     

(-)-Epigallocatechin gallate can prevent cisplatin-induced lung tumorigenesis in A/J mice

Risks of secondary lung cancer in patients with non-small cell lung cancer and small cell lung cancer are estimated to be 1-2% and 2-10% per patient per year, respectively. Cisplatin is widely used in the treatment of lung cancer and is also known as a carcinogen in experimental animals. In this study, the effect of (-)-epigallocatechin gallate (EGCG) on cisplatin-induced lung tumors in A/J mice was investigated. Female A/J mice (4 weeks old) were divided into four groups: group 1, control without treatment; group 2, EGCG treatment (1 mg/ml in tap water); group 3, weekly cisplatin treatment (1.62 mg/kg body wt, i.p.) for 10 weeks; group 4, cisplatin plus EGCG treatment (EGCG was started 2 weeks before cisplatin treatment). Four groups of mice were killed at week 30 after treatment. Tumor incidence was 26.3% (5/19) in group 1, 30% (6/20) in group 2, 100% (19/19) in group 3 and 94.4% (17/18) in group 4. Tumor multiplicity (the number of tumors per mouse, mean +/- SD) was 0.4 +/- 0.8 in group 1, 0.4 +/- 0.8 in group 2, 5.1 +/- 2.1 in group 3 and 2.8 +/- 2.3 in group 4. Tumor multiplicity was significantly reduced by adding EGCG to cisplatin-treated mice (P < 0.01). Furthermore, EGCG significantly reduced cisplatin-induced weight loss from 24.7-26.3% (cisplatin treatment) to 10.8-11.6% (cisplatin plus EGCG treatment) (P < 0.01). These findings suggest that EGCG can inhibit cisplatin-induced weight loss and lung tumorigenesis in A/J mice.     

灯盏花素对顺铂肾损害的防治及抗氧化的实验

目的观察灯盏花素对小鼠顺铂（cisplatin,DDP）肾损害的防治及抗氧化作用,探究其可能的作用机制。方法以 DDP 8 mg/kg单次腹腔注射制备小鼠肾脏损害模型,再以不同剂量的灯盏花素灌胃,1次/天,连续给药7 d后采样,观察肾脏结构变化,检测血清中肌酐（Scr）、尿素氮（BUN）、丙二醛（MDA）含量及超氧化物歧化酶（SOD）活性,肾皮质 SOD 及 MDA 的变化。 结果灯盏花素可明显改善顺铂肾损害的小鼠肾脏结构,降低血清Scr、BUN及肾皮质 MDA含量（P<0.05,P<0.01）,而 SOD 活性明显升高（P<0.05）。 结论灯盏花素可明显减轻顺铂引起的肾毒性,其机制可能与抑制顺铂肾损害所致血液和肾皮质脂质过氧化反应增强有关。     

三七总皂苷对顺铂肾损害大鼠肾组织差异表达蛋白质的影响

目的 探讨三七总皂苷（panax notoginsenosides,PNS）对顺铂肾损害大鼠肾组织差异表达蛋白质的影响。方法 实验大鼠随机分为正常对照组、顺铂模型组和PNS治疗组,对大鼠给药处理10 d后,检测大鼠血清尿素氮（BUN）、肌酐（Scr）和尿N-乙酰-β-氨基葡萄糖苷酶（NAG）的水平,并做肾脏病理检查;采用SELDI-TOF-MS技术筛选大鼠肾组织的差异表达蛋白质,并通过MALDI-TOF-MS/MS、Western blot实验予以鉴定。结果 顺铂模型组大鼠血清BUN、Scr和尿NAG的水平均显著高于正常对照组（P均〈0.05）。电镜下可见肾小管上皮细胞的线粒体明显损伤,说明顺铂肾损害大鼠模型制作成功。PNS干预可使大鼠血清BUN、Scr和尿NAG的水平显著低于顺铂模型组（P〈0.05）,肾小管上皮细胞的线粒体损害程度较顺铂模型组明显改善,提示PNS对其有保护作用。筛选出顺铂模型组与正常对照组肾组织差异表达的蛋白质20个,其中7个蛋白质在顺铂模型组中的表达下调2倍以上;顺铂模型组与PNS治疗组肾组织差异表达的蛋白质18个,其中11个蛋白质在PNS治疗组中的表达下调;有6个共同的差异表达蛋白质在顺铂模型组较正常对照组的表达上调或下调,在PNS治疗组可回调到接近正常对照组水平。差异表达蛋白质m/z 10815.42被鉴定为线粒体热休克蛋白,m/z 16021.67被鉴定为血红蛋白β1亚基、血红蛋白β2亚基。结论 顺铂肾损害可伴随多种蛋白质的表达变化,这些差异表达蛋白质可能与顺铂损害肾脏以及PNS的保护作用有关。通过对其分离和鉴定,进一步了解其性质,将有助于全面、系统地探讨顺铂肾损害以及PNS保护作用的机制。     

Effect of N-acetylcysteine route of administration on chemoprotection against cisplatin-induced toxicity in rat models

Dosing and route of administration of N-acetylcysteine (NAC) for protection against cisplatin (CDDP) nephrotoxicity was investigated in rats. Two models of toxicity were tested: a single high dose of CDDP (10 mg/kg intraperitoneally (IP)), and multiple low dose treatments (1 mg/kg IP twice a day for 4 days, 10 days rest, then repeated). NAC (50-1,200 mg/kg) was given to the rats by IP, oral (PO), intravenous (IV) and intra-arterial (IA) routes. Renal toxicity was determined by blood urea nitrogen (BUN) and creatinine (CR) levels 3 days after treatment. Blood collected 15 min after NAC was analyzed for total NAC. Both models of CDDP administration produced renal toxicity. In the single dose CDDP model, NAC 400 mg/kg given IP and PO produced no renal protection as measured by BUN (131.8 +/- 8.2 and 123.3 +/- 8.2, respectively) or CR (2.3 +/- 0.38 and 1.77 +/- 0.21, respectively). IV NAC reduced nephrotoxicity, (BUN 26.3 +/- 6.8, CR 0.47 +/- 0.15). NAC 50 mg/kg IA gave better protection than IV. In the repeated-dose CDDP model, nephrotoxicity was blocked by 800 mg/kg NAC given IV but not IP. Blood concentrations of total NAC showed a dose response after IV NAC, but high dose NAC (1,200 mg/kg) by the PO route gave very low levels of NAC. Thus the protective properties of NAC are affected by the dose and route of administration.     

Antitumor activity and toxicity of serum protein-bound platinum formed from cisplatin

When cisplatin was incubated with mouse serum, its cytotoxicity towards P388 leukemia cells decreased with the formation of non-ultrafiltrable or protein-bound platinum. The cytotoxicity of prepared mouse serum protein-bound platinum at 100 microgram/ml (as the cisplatin-equivalent concentration) was less than that of cisplatin at 0.125 microgram/ml. The prepared protein-bound platinum exhibited antitumor activity against colon adenocarcinoma 26 in mice, when administered iv daily for 9 consecutive days at 32 and 64 mg/kg (as the cisplatin-equivalent dose). Cisplatin similarly administered exhibited antitumor activity at daily doses of only 1 and 2 mg/kg. Administration of the protein-bound platinum at such high doses as 32 and 64 mg/kg (as the cisplatin-equivalent dose) caused elevation of serum BUN and reduction of bone marrow cells in mice. After iv administration of cisplatin to mice at 6 mg/kg, ultrafiltrable platinum was detected in the plasma for the first 30 min. Thereafter platinum was found only in protein-bound form. When mice were iv inoculated with colon adenocarcinoma 26 more than 30 min after cisplatin administration, no prolongation of the life span was observed. From these results, it is concluded that mouse serum protein-bound platinum does not contribute significantly to cisplatin antitumor activity and toxicity in mice.     

Regional pharmacokinetic selectivity of intraperitoneal cisplatin in ovarian cancer

Five patients with intraabdominal ovarian cancer, 4 of whom with concomitant ascites, refractory to cisplatin-containing combination chemotherapy were treated with intraperitoneal cisplatin. Cisplatin, 90 mg/m2, was administered intraperitoneally in 2 liters of warm 0.9% NaCl with a 4-hour dwelling time on day 1 q 21 days. Platinum concentrations in plasma, ascites, ultrafiltrates of plasma and ascites, and urine were assayed by flameless atomic absorption spectrophotometry and determinations were verified by neutron activation analysis. Peak total and ultrafiltrable plasma platinum levels were 1.63 +/- 0.6 and 0.76 +/- 0.3 microgram/ml, respectively. Peritoneal clearance of total platinum (PA) was 21 ml/min whereas body clearance of total platinum was on the average 13.8 times PA, varying from 171 to 429 ml/min; the mean AUC (peritoneum) to AUC (plasma) ratio was 11 +/- 3. In 2 patients control of ascites was obtained, in 1 of these patients prior positive cytology became negative after her first intraperitoneal course. No nephrotoxicity was observed and gastrointestinal toxicity was mild. No catheter-related infections were observed. Intraperitoneal cisplatin therapy is well tolerated, pharmacokinetically rational and may be useful in managing ovarian cancer patients with malignant ascites or minimal residual disease at second-look laparotomy.     

Application of cisplatin as intraoperative hyperthermic peritoneal lavage (IHPL) in patients with locally advanced gastric cancer: analysis of pharmacokinetics and of nephrotoxicity

The purpose of this study was to assess the extent of the systemic absorption of cisplatin during intraoperative hyperthermic peritoneal lavage (IHPL) in patients with locally advanced gastric cancer. MATERIALS AND METHODS: The pharmacokinetics and nephrotoxicity of cisplatin were analyzed in patients receiving IHPL (8000 ml of Ringer's solution containing 150 mg/m2 cisplatin and 15 mg/m2 mitomycin C for one hour at 43.5 degrees C). Levels of ultrafiltrable platin were determined by flameless atomic absorption spectrometry. Nephrotoxicity was assessed by nephelometric analyses of urinary marker-proteins. The data were compared to respective analyses in patients receiving intravenous cisplatin. RESULTS: Twenty-four patients received five applications of cisplatin as IHPL (five patients) and 53 applications of intravenous cisplatin (21 patients). Platin levels within the lavage fluid declined monophasically (half-life, 0.48 +/- 10 hours; area under curve (AUC) 29,274 +/- 9075 ng/ml*h). The pharmacokinetic parameters calculated for IHPL vs. intravenous application of cisplatin were: maximum plasma levels 2392 +/- 407 vs. 1349 +/- 692 ng/ml; terminal half-lives 93 +/- 73 vs. 36 +/- 9 hours; AUC 9508 +/- 856 vs. 11,627 +/- 3372 ng/ml*h; total urinary excretion of platinum 24 +/- 6 vs. 49 +/- 13% of dose; renal clearance 127 +/- 34 vs. 145 +/- 35 ml/min. Pathologic urinary albumin excretion occurred on days 9 +/- 0 vs. 5 +/- 2 (maximum 232 +/- 179 vs. 20 +/- 20 mg/l). Plasma creatinine levels rose to 1.5 +/- 0.4 vs. 0.9 +/- 0.1 mg/dl on days 15 +/- 4 vs. 16 +/- 26. The degree of albuminuria was related to the clearance of platin from the lavage fluid (p = 0.048). CONCLUSION: A significant amount of intraperitoneally applied cisplatin is available systemically and probably adds to the nephrotoxicity of IHPL.     

Comparative nephrotoxicity of cisplatin and new octahedral Pt(IV) complexes

Purpose Previously, we have reported that the newly synthesized octahedral Pt(IV) compound, trans,cis-Pt(acetato)₂Cl₂(1,4-butanediamine), K101 and trans,cis-Pt(trifluoroacetato)₂Cl₂(1,4-butanediamine), K102 showed potent antitumor activities in vitro and in vivo. In order to compare the nephrotoxicity of the newly synthesized Pt(IV) complexes, K102 and K102 with cisplatin, we performed various tests. Materials and methods We performed a single dose acute toxicity test for LD₅₀ values determination, biochemical assays in blood serum, acid phosphatase enzyme histochemistry and transmission electron microscopic studies in renal proximal tubular cells in mice in vivo. The route of drugs administration is intraperitoneal injection. Results In biochemical assays, the serum levels of BUN were significantly elevated at 6 h (p < 0.001), 1 day (p < 0.05) and 3 days (p < 0.001) after injection in cisplatin treated mice (6 mg/kg, single dose, i.p.). On the other hand, the serum levels of BUN were slightly elevated at 6 h (p < 0.01) only in K101 treated mice (8.2 mg/kg, single dose, i.p.), and were significantly raised at 6 h, 1 and 3 days (p < 0.05) after injection in K102 treated mice (6.2 mg/kg, single dose, i.p.). The higher serum BUN level in K102 treated mice is considered that K102 possesses more lipophilic fluoro group than acetyl group in K101. The values of creatinine and uric acid were similar in all groups. The ultrastructural morphological changes of K101- or K102-administrated mice were less remarkable than cisplatin-administrated mice. In acid phosphatase enzyme histochemistry, cisplatin treatment induced relevant changes in the distribution pattern of enzyme activity compared with K101 or K102 treatment at 7 days after injection. Conclusions In conclusion, these results show that K101 is less nephrotoxic than cisplatin and a promising new platinum complex.     

Successful use of cisplatin to treat metastatic seminoma during cisplatin-induced acute renal failure

A chemotherapeutic regimen including cisplatin was administered to a man with extragonadal seminoma and cisplatin-induced acute renal failure. Three doses of cisplatin (30, 50, and 100 mg/m2) were given in conjunction with hemodialysis. Pharmacokinetic data for free and total plasma platinum were obtained. The patient also received one dose of carboplatin and a course of radiation therapy. Complete remission was achieved, and useful renal function returned. Cisplatin can be used successfully during acute renal failure.     

Liver and tumor uptake and plasma pharmacokinetic of arterial cisplatin administered with and without starch microspheres in patients with liver metastases

Arterial chemoembolization of liver tumors should improve regional treatment by reducing native blood flow of the whole organ and redistributing residual flow toward hypovascular masses. Plasma cisplatin pharmacokinetics and its tissue uptake and relative tumor and liver vascularity were studied during surgical placement of arterial catheters in four patients and in four patients with colorectal metastases given intraoperative arterial cisplatin (DDP, 25 mg/m2), with an without coadministration of 600 mg degradable starch microspheres (DSM). Mean (+/- standard deviation) filterable plasma platinum levels peaked later (2 minutes) and were significantly lower after DDP with DSM (1.23 +/- 0.69 micrograms/ml) than after DDP alone (2.13 +/- 0.43 micrograms/ml, P less than 0.05), with the area under the curve (AUC0-30 min) values of 15.8 +/- 5.5 and 25.1 +/- 3.8 micrograms x min/ml (P less than 0.05), respectively. No differences in urine excretion, total body clearance, or plasma protein binding of platinum were observed. Tissue biopsies were started 15 minutes after DDP administration and completed in all cases within 5 minutes. Tumor platinum concentrations were significantly higher after DDP with DSM (3.03 +/- 1.60 micrograms/g) than after DDP alone (0.67 +/- 0.49 micrograms/ml, P less than 0.05). Liver concentrations and tumor-liver ratios of platinum also were higher, although not significantly, after DDP with DSM. Preoperative vascularization, studied with arterial perfusion scan, influenced individual tissue drug uptake in cases given DDP alone, with the lowest tumor levels in cold masses. Very high and almost superimposable liver and tumor concentrations were measured in those receiving DDP and DSM. The latter phenomenon was irrespective of native vascularization, indicating that DSM administration induced both an increased whole-liver extraction of the drug and a redistribution of blood flow and flow-dependent tissue uptake of platinum.     

Pharmacokinetic behaviour of the chemoprotectants BNP7787 and mesna after an i.v. bolus injection in rats

In preclinical studies, BNP7787 (disodium 2,2'-dithio-bis-ethane sulphonate), the disulphide form of mesna, has demonstrated selective protection against cisplatin-induced nephrotoxicity due to conversion into mesna inactivating toxic platinum species. Mesna (sodium 2-mercapto ethane sulphonate), however, can affect the antitumour activity of cisplatin, while BNP7787 does not interfere with the antitumour activity. To understand the difference in interference with cisplatin-induced antitumour activity between BNP7787 and mesna as well to characterise the selective nephroprotection by BNP7787, the pharmacokinetics of BNP7787 and mesna, each given i.v. 1000 mg x kg(-1), were determined in plasma, kidney, liver, red blood cells (RBC), skeletal muscle and tumour of Fischer rats bearing subcutaneously implanted WARD colon tumours. The following results were obtained: (1). high concentrations of BNP7787 and mesna were observed in the plasma and kidney after administration of BNP7787 or mesna, except for mesna in plasma after BNP7787 administration; (2). in all other sampled compartments, the AUC values of both compounds were at least 5.5-fold lower than the corresponding values in kidney; (3). the AUC of mesna in plasma after mesna administration was comparable to the AUC of mesna in kidney after a dose of BNP7787 that can completely prevent cisplatin-induced nephrotoxicity in rats; (4). the AUC of mesna in plasma was five-fold higher relative to the AUC of mesna following BNP7787 administration (P<0.01). In conclusion, the five-fold higher AUC of mesna in plasma after mesna administration and the fact that mesna is more reactive with (hydrated) cisplatin than its disulphide form BNP7787 represent a plausible explanation as to why mesna administration can reduce the antitumour activity of cisplatin. After BNP7787 administration, the distribution of BNP7787 and mesna was restricted to the kidney, which confirmed the selective protection of the kidney by BNP7787.     

Uptake enhancement of platinum in the dog kidney by microencapsulation of cisplatin and local injection

Microcapsules containing cisplatin were administered into the renal artery of mongrel dogs. Significant increase of the platinum tissue concentration in the kidney was observed 17 days after administration compared to injection of cisplatin only. The highest drug tissue levels were obtained when the renal artery was ligated after microcapsule injection. In addition the decrease in plasma levels indicated that microencapsulation causes, at least, a 100-fold enhancement of the ratio: exposure of infused tissue to the drug over total body exposure. On the contrary, no major change in drug urine excretion could be related to microencapsulation.     

Molecular hydrogen alleviates nephrotoxicity induced by an anti-cancer drug cisplatin without compromising anti-tumor activity in mice

Purpose  Cisplatin is a widely used anti-cancer drug in the treatment of a wide range of tumors; however, its application is limited by nephrotoxicity, which is affected by oxidative stress. We have reported that molecular hydrogen (H₂) acts as an efficient antioxidant (Ohsawa et al. in Nat Med 13:688–694, 2007). Here we show that hydrogen efficiently mitigates the side effects of cisplatin by reducing oxidative stress. Methods  Mice were administered cisplatin followed by inhaling hydrogen gas (1% H₂ in air). Furthermore, instead of inhaling hydrogen gas, we examined whether drinking water containing hydrogen (hydrogen water; 0.8 mM H₂ in water) is applicable by examining oxidative stress, mortality, and body-weight loss. Nephrotoxicity was assessed by morphological changes, serum creatinine and blood urea nitrogen (BUN) levels. Results  Inhalation of hydrogen gas improved mortality and body-weight loss caused by cisplatin, and alleviated nephrotoxicity. Hydrogen was detected in blood when hydrogen water was placed in the stomach of a rat. Consuming hydrogen water ad libitum also reduced oxidative stress, mortality, and body-weight loss induced by cisplatin in mice. Hydrogen water improved metamorphosis accompanying decreased apoptosis in the kidney, and nephrotoxicity as assessed by serum creatinine and BUN levels. Despite its protective effects against cisplatin-induced toxicity, hydrogen did not impair anti-tumor activity of cisplatin against cancer cell lines in vitro and tumor-bearing mice in vivo. Conclusion  Hydrogen has potential for improving the quality of life of patients during chemotherapy by efficiently mitigating the side effects of cisplatin.     

Ototoxicity,nephrotoxicity and pharmacokinetics of cisplatin and its monohydrated complex in the guinea pig

PURPOSE: To evaluate and compare the ototoxicity and nephrotoxicity of cisplatin and cis-diammineaquachloroplatinum(II) ion (monohydrated complex of cisplatin, MHC, formed in vivo by hydrolysis of cisplatin) after their separate administration to guinea pigs. METHODS: A dose of 4 mg/kg body weight of MHC was deemed suitable for the toxicity evaluation after dose titration. Electrophysiological hearing thresholds (auditory brainstem response, ABR), plasma creatinine and weight were measured in three groups of animals before and after receiving MHC 4 mg/kg (0.0141 mmol/kg), cisplatin 4.24 mg/kg (0.0141 mmol/kg, i.e. equimolar dose) or cisplatin 8 mg/kg (0.0267 mmol/kg) as an i.v. bolus injection. Cisplatin and MHC were analysed using liquid chromatography with post-column derivatization. RESULTS: Administration of MHC 4 mg/kg caused a moderate ABR threshold shift, a significant increase in creatinine and a significant weight loss, changes similar to those seen after administration of cisplatin 8 mg/kg. Animals given cisplatin 4.24 mg/kg had a slight increase in creatinine, but had no ABR threshold shift and gained weight during the experiment. The pharmacokinetic parameters of cisplatin and MHC were estimated after administration of cisplatin 4.24 mg/kg and MHC 4 mg/kg. The area under the blood-ultrafiltrate concentration versus time curve (AUC) for cisplatin after administration of MHC 4 mg/kg was 23% (56+/-5.0 micro g.min.ml(-1)) (means+/-SD) of that after administration of cisplatin 4.24 mg/kg (240+/-25 micro g.min.ml(-1)). The AUC for MHC after administration of cisplatin 4.24 mg/kg was 20% (30+/-4.9 micro g.min.ml(-1)) of that after administration of MHC 4 mg/kg (149+/-26 micro g.min.ml(-1)). CONCLUSIONS: MHC 4 mg/kg causes ototoxicity, nephrotoxicity and weight loss when administered to guinea pigs. The toxic effects were similar to those seen after administration of cisplatin 8 mg/kg and higher than those seen after administration of cisplatin 4.24 mg/kg.     

WR2721 as a modulator of cisplatin-and carboplatin-induced side effects in comparison with other chemoprotective agents: a molecular approach

Cisplatin is an active cytostatic that became successful in the treatment of several types of solid tumours after its nephrotoxic potential was controlled by hydration and diuresis. Thiol compounds were tested to reduce further cisplatin-induced nephrotoxicity. Thiosulphate is rapidly excreted by the kidneys and protects against cisplatin-induced nephrotoxicity by inactivating reactive platinum species in the kidney. Due to inactivation of cisplatin in the circulation, thiosulphate also interferes with its antitumour activity. Therefore, it is mainly used in two-route schedules, whereby cisplatin is delivered locally to the tumour (i.p. or i.a.) while systemic (i.v.) thiosulphate protects the kidneys. Diethyldithiocarbamate was shown to protect against cisplatin-induced nephrotoxicity in several animal models by reversing cellular damage. However, in the clinic it has been less successful, partly due to its central nervous system toxicity. The endogenous thiol compounds glutathione and metallothionein have been shown to reduce cisplatin-induced toxicity both in animal models and in clinical trials. However, the results are rather preliminary and a reduction in therapeutic efficacy may be expected, for both glutathione and metallothionein have been reported to be involved in platinum resistance. The thioether methionine has been shown to reduce cisplatin-induced nephrotoxicity in animal models but it has not yet been tested in the clinic. Cisplatin-induced acute emesis can be sufficiently controlled with a new class of 5-hydroxytryptamine-3 (5HT₃)-receptor blockers, but delayed emesis remains a problem. High-dose cisplatin regimens with protection of the kidneys induces ototoxicity, peripheral neuropathy and myelotoxicity, which become doselimiting. Neurotoxicity was partly reversed by the neurogenerative agent ORG2766, but this agent does not reduce other cisplatin-induced toxicities. Therefore, an agent capable of protecting multiple non-tumour tissues is needed. Carboplatin is a second-generation analogue of cisplatin with less nephro-, neuro-and ototoxicity. Carboplatin is at least as active as cisplatin at its maximum tolerated dose, which is defined by its myelotoxicity. Protection from carboplatin-induced myelotoxicity may be controlled by autologous bone marrow transplantation and/or hematopoietic growth factor infusions. High-dose carboplatin schedules may cause nephrotoxicity, neurotoxicity and ototoxicity. Again, the protection of multiple non-tumour tissues is needed. WR2721 appears to be such a modulating agent capable of protecting multiple non-tumour tissues. It was shown to be preferentially metabolized and taken up as the thiol metabolite WR1065 by non-tumour tissues as compared with *hypoxic) solid tumours. It was shown to protect mice from cisplatin-induced nephrotoxicity and from cisplatin-and carboplatin-induced myelotoxicity without interfering with the antitumour activity. The first clinical studies suggest the same selective protection of multiple non-tumour tissues from cisplatin-induced toxicity. This could be explained by a strong prevention (not reversal) of cisplatin-induced cellular damage by WR1065, whereas WR2721 or its main metabolites will hardly inactivate the intact platinum-based drug in the circulation.     

Thioether suppression of cisplatin nephrotoxicity in the rat

Six compounds containing a thioether group were examined as agents for the reduction of the nephrotoxicity caused by cisplatin (CDDP) in the rat. Of these, five were able to reduce the CDDP- induced nephrotoxicity when administered simultaneously with CDDP (8.0 mg/kg, iv). The compounds capable of reducing CDDP toxicity were L-methioninamide, cystathionine, methionyl-L-alanine, (methythio) acetic acid and 4-(methylthio) benzoic acid. Indices used to evaluate toxicity included body weight changes, BUN and serum creatinine levels and the histopathological examination of renal tissue. The platinum levels of renal tissue were determined but were found not to correlate well with other measures of renal function. Oral administration of the more effective of these compounds was found to provide a reduced level of protection against the nephrotoxicity caused by iv CDDP. The most effective of these compounds caused a very modest reduction in the anti-tumor activity of CDDP as measured against the L1210 murine leukemia.