IMPACT OF E-CIGARETTE LIQUID FLAVORING AGENTS ON ACTIVITY OF MICROSOMAL RECOMBINANT CYP2A6, THE PRIMARY NICOTINE-METABOLIZING-ENZYME.

Nicotine is the primary psychoactive chemical in both traditional and electronic cigarettes (e-cigarettes). Nicotine levels in both traditional cigarettes and e-cigarettes are an important health concern for public health. Nicotine exposure due to e-cigarette use is of importance primarily due to the addictive potential of nicotine, but there is also concern for nicotine poisoning in e-cigarette users. Nicotine concentrations in e-cigarette liquids vary widely. Additionally, there is significant genetic variability in rate of metabolism of nicotine due to polymorphisms of CYP2A6, the enzyme responsible for the metabolism of approximately 80% of nicotine. Recent studies have shown CYP2A6 is also readily inhibited by aromatic aldehydes such as those added to e-cigarette liquids as flavoring agents, which may increase nicotine serum concentrations. However, the impacts of e-cigarette flavorings on metabolism of nicotine by CYP2A6 activity are unknown. In this study, we investigated the impact of three flavored e-cigarette liquids on microsomal recombinant CYP2A6. Microsomal recombinant CYP2A6 was challenged at e-cigarette liquid concentrations ranging up to 0.125% and monitored for metabolic activity using a probe molecule approach. Two e-cigarette liquids exhibited dose-dependent inhibition of CYP2A6 activity. Mass spectrometry was conducted to identify concentration of flavoring agents in flavored e-cigarette liquids that inhibited CYP2A6 Recombinant microsomal CYP2A6 was subsequently exposed to flavoring agents at concentrations ranging from 0.03 μM to 500 μM. Cinnamaldehyde and benzaldehyde were found to be the most potent inhibitors of microsomal CYP2A6 of the flavoring agents tested, with identified IC50 values of 1.1 μM and 3.0 μM, respectively. These data indicate certain aromatic aldehyde flavoring agents are potent inhibitors of CYP2A6, which may reduce nicotine metabolism in vivo. These findings indicate an urgent need to evaluate the effects of e-cigarette flavoring agents on the pharmacokinetics of nicotine in vivo.

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