DNA adduct formation in mice following dermal application of smoke condensates from cigarettes that burn or heat tobacco

Abstract

A prototype cigarette that heats tobacco (test cigarette), developed by R.J. Reynolds Tobacco Company, has yielded consistently negative results in several in vivo and in vitro genetic toxicology tests. The objective of the present study was to evaluate the potential of cigarette smoke condensate (CSC) from the test cigarette to induce DNA adducts in mouse tissues and compare the results with those obtained with CSC from a reference tobacco-burning cigarette (1R4F). CD-1 mice were skin-painted with CSC from reference and test cigarettes three times a week for 4 weeks. The highest mass of CSC applied was 180 mg "tar" per week per animal for both reference and test cigarette. DNA adducts were analyzed in skin and lung tissues using the 32P-postlabeling method with the P1 nuclease modification. Distinct diagonal radioactive zones (DRZ) were observed in the DNA from both skin and lung tissues of animals dosed with reference CSC, whereas no corresponding DRZ were observed from the DNA of animals dosed with either test CSC or acetone (solvent control). The relative adduct labeling (RAL) values of skin and lung DNA from reference CSC-treated animals were significantly greater than those of the test CSC-treated animals. The RAL values of the test CSC-treated animals were no greater than those of solvent controls. The negative results in DNA adduct assays with test CSC are consistent with all previous results of in vivo and in vitro genetic toxicology testing on this cigarette and provide additional evidence that smoke condensate from the test cigarette is not genotoxic.

Selection and Characterization of Human Cytochrome P450 1A2 Mutants with Altered Catalytic Properties

“…Mutants at Thr-321 (T321S, T321P) varied in activity, with less efficiency in some cases but more in others (Figure 3B). Shimizu also reported that the rat P450 1A2 T319A mutant had low activity in some reactions but elevated activity in others (28,31,32). These shifts in activity were typically accompanied by increases in the respective K m .…”