Low dose thirdhand smoke exposure enhances platelet functional responses in mice

Although cigarette smoking is the most preventable cause of cardiovascular diseases, most researchers have focused on either direct/firsthand or secondhand smoke exposures. Recently though, attention has shifted to an emerging/indirect exposure trend-known as thirdhand smoke (THS)- which was previously "overlooked." This phenomenon, which was/is thought to be harmless, has been identified as a serious health risk, including in the context of thrombogenesis/platelets. However, whether low dose THS exposure has the capacity to modulate platelets has not been investigated. Two sets of household materials were exposed to 20 cigarettes/day for a week on an alternating basis, with controls exposed to clean air. After the first set of exposed materials is placed in mice cages, exposure of the second set is initiated. The materials were interchanged weekly, for a total exposure duration of 1 month. Mice were then subjected to multiple platelet function assays. THS exposed mice exhibited shortened tail bleeding and occlusion times, indicating a prothrombotic phenotype. Moreover, we also observed that platelets from the exposed mice exhibited an enhanced aggregation response. However, we did not observe any gender differences in our in vivo as well as aggregation experiments; hence, subsequent characterization was carried out on male mice. It was also found that dense granules release, integrin activation, and PS exposure were also potentiated in the exposed platelets compared to the controls. Finally, we observed for the first time that the tobacco-specific nitrosamine and THS toxicant NNK enhanced platelet aggregation and thrombus formation. Collectively, we provide documentation that low dose of THS exposure is detrimental to health by increasing the risk of thrombosis through a hyperactive platelet phenotype that involves the toxicant NNK.