Quantitation of phenanthrenols in human urine: Application to development of a urinary biomarker phenotyping method for metabolic activation and detoxification of polycyclic aromatic hydrocarbons

Abstract

1957

Polycyclic aromatic hydrocarbons (PAH) are a major class of environmental carcinogens that are likely to be involved as causative factors for cancers of the lung, skin, and other organs in smokers and occupationally exposed individuals. A major metabolic activation pathway of PAH proceeds through diol epoxides while phenol formation is a detoxification pathway. The balance of PAH activation vs. detoxification is likely to affect cancer risk in exposed individuals. This balance has been extensively investigated by genotyping approaches in recent years but the results have been inconsistent, probably because of the complexity of PAH metabolism. We propose that PAH metabolite phenotyping will be a more useful approach. Our phenotyping approach focuses on urinary metabolites of phenanthrene, the simplest PAH with a bay region, a feature closely associated with carcinogenicity of other PAH. We have already described a method for the quantitation of phenanthrene tetraol in human urine as a biomarker of metabolic activation via the diol epoxide pathway. However, levels of phenanthrene tetraol could be affected by both exposure and metabolic activation. To correct for exposure and to establish an activation detoxification ratio, we have now developed a method for quantitation of phenanthrenols, representative of PAH detoxification. The internal standard, [¹³C₆]3-hydroxyphenanthrene, is added to urine and the urine is treated with β-glucuronidase and arylsulfatase. It is then passed through a Chem-Elute extraction cartridge with elution by toluene. The toluene eluate is treated with the antioxidant Na₂S₂O₄ to prevent loss of 9-hydroxyphenanthrene, and further purified by blue rayon solid phase extraction. The resulting eluate is silylated and analyzed by GC-positive ion chemical ionization-MS with selected ion monitoring at m/z 267 for phenanthrenols and m/z 273 for the internal standard. We quantified 1-, 2-, 3-, 4-, and 9-hydroxyphenanthrene using this method. In smokers, total phenanthrenols were 3.69 ± 1.78 pmol/ml. 1-Hydroxyphenanthrene and 3-hydroxyphenanthrene were the most abundant. 3-Hydroxyphenanthrene was highly correlated with total phenanthrenols and all other phenanthrenols except 9-hydroxyphenanthrene. Ratios of phenanthrene tetraols to phenanthrenols ranged from <0.25->2 in non-smokers and <0.5->4 in smokers indicating considerable dispersion of ratio values. This suggests that these ratios may be useful phenotypic biomarkers of PAH metabolic activation and detoxification in humans.