Cyclophosphamide, an orally active alkylating agent, is widely used to treat a variety of malignant and nonmalignant disorders. Although it has some tumour selectivity, it also possesses a wide spectrum of toxicities. The requirement of metabolic activation before cyclophosphamide exerts either its therapeutic or toxic effects is well established, but has not led to effective counter-measures. Clinically, damage to the bladder (haemorrhagic cystitis), immunosuppression (when not desired) and alopecia are the most significant toxicities associated with cyclophosphamide. Cardiotoxicity is also a possibility when very high doses are given. Preventing these toxicities has focused on modifications of the treatment regimens and, in the case of haemorrhagic cystitis, the administration of a drug which is excreted in the urine where it inactivates the bladder-toxic species. As treatment regimens for cancer become more effective in prolonging a patient's life, and as cyclophosphamide receives increasing use for nonmalignant disorders, the potential for cyclophosphamide-induced cancers, particularly in the bladder, must be recognised. Although the toxicities associated with cyclophosphamide are serious, this agent remains a highly effective drug in many situations. Research on the pathways which play an important role in activating this drug may improve our ability to target particular diseases and decrease unwanted side effects.

Acrolein is the metabolite of cyclophosphamide (CP) believed to be involved in the bladder toxicity associated with this anticancer drug. The mechanism by which this extremely reactive intermediate is delivered to the bladder is not known. Glutathione (GSH) readily conjugates with acrolein, and the acrolein mercapturate S-(3-hydroxypropyl)-N-acetylcysteine (3-hydroxy-PrMCA) has been found in the urine of animals and man given CP. The objectives of this study were to prepare and characterize synthetic standards of the GSH acrolein adduct (3-oxopropyl)glutathione (3-oxoPrGSH), the acrolein mercapturates S-(3-oxopropyl)-N-acetylcysteine (3-oxoPrMCA) and 3-hydroxyPrMCA, and the S-oxidation product of 3-oxoPrMCA (3-oxoPrMCA S-oxide). In addition, the release of acrolein from, and the bladder toxicity of, these conjugates was determined. 3-OxoPrGSH and 3-oxoPrMCA were prepared with a 99% yield by condensing acrolein with GSH and N-acetylcysteine, respectively. 3-HydroxyPrMCA was prepared with a 63% yield by refluxing 3-chloropropanol and N-acetylcysteine in a basic medium. Oxidation of 3-oxoPrMCA with H2O2 was used to prepare 3-oxoPrMCA S-oxide. By decreasing the reaction time to 1 h, and adjusting the ratio of 3-oxoPrMCA to H2O2, the yield of 3-oxoPrMCA S-oxide was increased to 96%. The anhydrous aldehyde, 3-oxoPrMCA, afforded characteristic aldehydic proton resonances (1H NMR) in deuterated dimethyl sulfoxide. New resonances were observed in deuterated water, indicating a 75% hydration of the aldehyde to the corresponding geminal diol. This phenomenon was enhanced with 3-oxoPrMCA S-oxide where approximately 100% hydration of the aldehyde to the corresponding geminal diol was observed. When incubated at 25 degrees C in 100 mM potassium phosphate buffer containing 1 M KCl, pH 8.0, 3-oxoPrMCA released approximately 6% and 3-oxoPrMCA S-oxide released approximately 16-18% of the theoretical maximum yield of acrolein after 30 min, as indicated by an increase in absorbance at 210 nm and confirmed by trapping this aldehyde as a semicarbazone. There was less than a 2% yield of acrolein from 3-hydroxyPrMCA or 3-oxoPrGSH under similar conditions. At pH 7.4 the release of acrolein from 3-oxoPrMCA and 3-oxoPrMCA S-oxide was decreased by 50%. An assay where aldehydes are reacted with m-aminophenol in acid media produced fluorescence consistent with 72%, 46%, 23%, and 1% yields of acrolein from 3-oxoPrMCA S-oxide, 3-oxoPrMCA, 3-oxoPrGSH, and 3-hydroxyPrMCA, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

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Information from highly respected sources, such as the American Cancer Society, indicates that only about 2 percent of cancer deaths in the United States are the result of exposures to carcinogenic agents in the workplace, community, and other settings. But the news about health risks from environmental exposures to air pollutants is almost constant. Although the US air quality has improved dramatically in the last 30 years, each recent review of a National Ambient Air Quality Standard (NAAQS) by the US Environmental Protection Agency (EPA) has resulted in a reduction in existing standards or replacement by a completely different and generally more stringent standard.