Studies on the metabolism and biological effects of nitropyrene and related nitro-polycyclic aromatic compounds in diploid human fibroblasts.

Nitro derivatives of polycyclic aromatic hydrocarbons are produced primarily as the result of incomplete combustion. Nitropyrenes have been identified as primary mutagenic compounds of diesel emission particulate and are tumorigenic in laboratory animals. Since nitropyrenes do not react directly with DNA, their effects presumably are mediated through cellular conversion of the parent compounds into reactive species. For example, 1-nitropyrene (1-NP) is activated by enzymatic reduction to 1-nitrosopyrene (1-NOP), followed by reduction to the hydroxylamine, which undergoes decomposition to yield a nitrenium ion, that reacts with DNA. The cytotoxic effects of 1-nitropyrene and 1-nitrosopyrene were compared in fibroblasts from normal persons, from excision-repair-deficient xeroderma pigmentosum (XP) patients, and from a patient with an inherited predisposition to malignant melanoma of the skin (hereditary cutaneous malignant melanoma [HCMM]). HCMM cells are more sensitive than normal cells to the cytotoxic and mutagenic effects of 4-nitroquinoline-1-oxide, and they form more DNA adducts per concentration of this agent than do normal cells. However, the HCMM cells exhibit the same sensitivity as normal cells to 4-hydroxyaminoquinoline-1-oxide, which suggests they are more capable than normal cells of metabolizing the parent compound into a more reactive form. On the basis of concentration, 1-NOP was much more cytotoxic than 1-NP. With both compounds, the normal cells exhibited a shoulder on their survival curves that was lacking for the XP cells. The dose of 1-NP giving 37% survival was 46 microM for a series of four normal cell lines, 22 microM for the HCMM cell line tested, and 12 microM for the XP cell line. The slope of the 1-nitropyrene survival curve for XP cells was 2.5 times steeper than the slope of the curve of the normal cells; the slope of the 1-NP survival curve for the HCMM cells was intermediate between the XP cells and the normal fibroblasts. The slope of the 1-nitrosopyrene survival curve for XP cells was also 2.5 times steeper than that for the normal cells, but the HCMM cells showed a normal response. If the resistance of normal cells to the cytotoxic effect of these compounds reflects their ability to remove potentially cytotoxic adducts from their DNA before these lesions cause cell death, normal cells should require a higher initial number of DNA adducts than XP cells do to cause a particular degree of cell killing.(ABSTRACT TRUNCATED AT 400 WORDS)