Molecular imaging of pulmonary inflammation in electronic and combustible cigarette users: a pilot study

Abstract

Electronic cigarette (EC) use has increased dramatically, particularly among adolescents and young adults, which, like cigarette use, can cause pulmonary inflammation and increase the risk of lung disease. Methods: This preliminary study used positron emission tomography with ¹⁸F-6-(1/2)(2-fluoro-propyl)-4-methylpyridin-2-amine (¹⁸F-NOS) to quantify inducible nitric oxide synthase (iNOS) expression to characterize oxidative stress and inflammation in the lungs in vivo in three age- and sex-matched groups: (1) 5 EC users, (2) 5 cigarette smokers, and (3) 5 never smoke/vape controls. Results: EC users showed greater ¹⁸F-NOS non-displaceable binding potential (BPND) than cigarette smokers (P = 0.03) and never smoke/vape controls (P = 0.01); whereas BPND in cigarette smokers did not differ from controls (p> 0.1). ¹⁸F-NOS lung tissue delivery and iNOS distribution volume did not significantly differ between groups. Although there were no group differences in peripheral inflammatory biomarker concentrations, ¹⁸F-NOS BPND correlated with the pro-inflammatory cytokine tumor necrosis factor-α concentrations (rs= 0.87, P = 0.05) in EC users. Additionally, when EC users and cigarette smokers were pooled together, vaping episodes/cigarettes per day correlated with interleukin-6 levels (rs= 0.86, P = 0.006). Conclusion: This is the first PET imaging study to compare lung inflammation between EC and cigarette users in vivo. We found preliminary evidence EC users had greater pulmonary inflammation than cigarette smokers and never smoke/vape controls, with a positive association between pulmonary and peripheral measures of inflammation.