Abstract: PNFBA-11
Sources of Funding: This research was supported by grants from NIH (R01CA190678, 1P01CA165980, and ES00260) and Center of Excellence for Urological Research at New York University School of Medicine.

Introduction

E-cigarette (E-cig) is designed to deliver stimulant nicotine, similar to the conventional cigarette, through an aerosol state. Nicotine is dissolved in harmless organic solvents and then aerosolized with solvents by electric heating. Hence, E-cig smoke (ECS) contains nicotine and the gas phase of the solvents. ECS contains neither carcinogens, allergens, nor odors that result from incomplete combustion in conventional tobacco smoke (TS). E-cig has been advertised as an invention that can deliver a TS &[prime]high&[prime] without TS&[prime]s ill effects. The question, &[prime]Is ECS as harmful as TS or not, particularly its carcinogenicity?&[prime] deserves careful examination. Since 90% of inhaled nicotine and its major metabolite cotinine are excreted to urine, it is possible bladder is a major target of ECS. Using a mouse model, we addressed three questions on E-cig induced effects. 1) Does ECS induce DNA damage in bladder mucosa? 2) If it does, then what is the chemical nature of the DNA damage? 3) Where are the DNA damaging agents coming from? We also examined the effect of nicotine and its metabolites, nitrosamines and formaldehyde (FAL), on DNA adduct induction and their effects on DNA repair and mutational susceptibility in cultured human urothelial cells.

Methods

1.Twenty male mice were randomized into 2 groups. Mice were exposed to ECS (10 mg/ml) or filtered air 6 h/d, 5 d/week for 12 weeks. _x000D_ 2.PdG and O⁶-meth-dG adducts were determined by an immunochemical method and the ³²P post-labeling 2D-TLC/HPLC method. _x000D_ 3.DNA repair activity was determined by an in vitro DNA-damage-dependent repair synthesis method. Mutational susceptibility were determined by the supF system._x000D_

Results

1.ECS induces γ-OH-PdG adducts and O⁶-meth-dG adducts in mouse bladder mucosa. _x000D_ 2.Nicotine, nitrosamine and FAL induce γ-OH-PdG; nicotine and nitrosamine also induce O⁶-meth-dG in urothelial cells._x000D_ 3.Nicotine, nitrosamine and FAL inhibit DNA repair and suppress XPC and OGG1 in urothelial cells._x000D_ 4.Nicotine, nitrosamine and FAL enhance urothelial cell mutational susceptibility. _x000D_

Conclusions

ECS induces tumorigenic γ-OH-PdG and O⁶-meth-dG in bladder mucosa. Nicotine, nitrosamine and FAL can induce the same types of DNA damage in human urothelial cells and also inhibit DNA repair and enhance mutational susceptibility. We conclude that nicotine can be nitrosatized in human and mouse urothelial cells, then further metabolized into carcinogenic nitrosamines and FAL. We predict that E-cig smokers have a high bladder cancer risk.

Funding

This research was supported by grants from NIH (R01CA190678, 1P01CA165980, and ES00260) and Center of Excellence for Urological Research at New York University School of Medicine.