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. 2023 Oct 31;12(21):2552. doi: 10.3390/cells12212552

Figure 3.

Figure 3

Types of e-cig-induced DNA damage. The dominant pathway of nicotine metabolism in humans is the formation of cotinine, the first step of which is catalyzed by cytochrome P450 (CYP P450). Nicotine can be metabolized to 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N’-nitrosonornicotine (NNN). Both of these compounds, as well as acrolein (y-OH-Acr-dGUO), can lead to DNA adduct formation. E-cig aerosol-induced reactive oxygen species (ROS) can also induce DNA oxidation, such as 8-oxo-dG. Usually detected by XPC and repaired via excision by OGG1, aldehydes in the e-cig vape inhibit this repair step causing potential mutations. Nicotine and nicotine-free vape induce DNA fragmentation, including DNA single (SS)- and double-strand breaks (DSB), which require DNA damage repair proteins such as pH2AX to be recruited. Transversions (base-pair substitutions) lead to mutations, e.g., in genes such as Ras and p53. Aldehydes suppress DNA damage repair as they inhibit cytochrome (CYP)-mediated detoxification. Overall, levels of DNA damage correlate with the amount of vape consumed as well as additives such as flavoring, especially sweet, fruit, and menthol flavors.