Tetranitromethane (TNM) was recently found to be one of the most potent pulmonary carcinogens studied by the NTP, yet the toxic and carcinogenic mechanisms of TNM and related nitro-compounds are unknown. The objective of this project is to investigate the mechanism(s) of tetranitromethane (TNM) pulmonary toxicity and carcinogenicity. Studies were conducted to investigate the biochemical reactions of TNM with nucleosides and DNA in vitro. Purified nucleosides were incubated with TNM in a buffered solution at different pHs for up to 24 hours and then analyzed by HPLC for reaction products. No altered nucleosides were detected, indicating that TNM does not react with purified nucleosides in this experimental system. The potential reaction of TNM with DNA was investigated by incubating TNM with purified herring sperm DNA in a buffered solution for up to 24 hours. After reaction, the DNA was hydrolyzed to individual nucleotides, and the hydrolysate analyzed by HPLC for altered bases. The only products detected were the four unchanged nucleotides, TNM, and nitroform (a breakdown product of TNM), indicating that TNM does not react with purified DNA. These data suggest that TNM may require metabolism to a reactive intermediate before binding to DNA and other macromolecules, and/or TNM interacts with DNA indirectly (e.g. by modification of histones). Studies to evaluate the potential metabolism of TNM by lung microsomes are in progress. These studies will provide the basis for subsequent mechanistic studies performed in cultured cells exposed to TNM.
