Acute exposure to cigarette smoke or its components has been known to trigger diverse cellular effects, such as oxidative stress, DNA damage and cell death in a number of cell culture models. However, available data regarding the potential cytotoxic effects of Smokeless Tobacco (ST) lacks consensus. This research was initiated to investigate the relative biological effects of ST, and whether ST elicits differential biological responses compared to the combustible tobacco preparations.

Total Particulate Matter (TPM) and whole smoke conditioned medium (WS-CM) were prepared from 3R4F reference cigarettes, while 10% 2S3 reference moist tobacco extract was prepared in artificial saliva with enzymes (ST/CAS). Human peripheral blood mononuclear cells (PBMCs), isolated from non-tobacco consumer donors, were used as a model to examine the systemic effects of exposure to the tobacco preparations and nicotine, in short-term cell culture.

Corresponding EC₅₀ values, normalized for nicotine content of the tobacco preparations, suggest that combustible tobacco preparations induced markedly higher cytotoxicity as follows: WS-CM ≥ TPM >> ST/CAS > nicotine. WS-CM and TPM similarly induced time-dependent cytotoxicity in PBMCs. While all three tobacco preparations induced detectable levels of DNA damage in a dose-dependent manner, the combustible tobacco preparations were significantly more potent than ST/CAS. Further, the leukocyte subsets exhibited differential cytotoxicity when exposed to combustible tobacco preparations in the following order: T helper cells > cytotoxic T cells > monocytes > NK cells. In contrast, the treatment with nicotine and ST/CAS was less cytotoxic and did not exhibit cell type selectivity.

Thus, the data presented herein suggest that in terms of nicotine content/unit, the combustible tobacco preparations are markedly more cytotoxic than ST/CAS or nicotine to human PBMCs.