Effect of smoking on gene expression profile - overall mechanism, impact on respiratory system function, and reference to electronic cigarettes.

Cigarette smoke has a crucial impact on transcriptome alteration by its effect on chromatin remodeling and DNA methylation status. The first mechanism is associated with the histone acetylation/deacetylation balance damage as a result of increased activity of NFĸB and lipid peroxidation products, which lead to an increased activity of HATs and DNMTs and reduced HDACs. The second mechanism is connected with direct damaging of DNA by smoke components, activation of downstream repair mechanism and recruitment of DNMTs into the breakage site, 'nicotine effect' and carbon monoxide (CO) activity on gene transcription and DNA methylation reduction. Cigarette smoking activates oxidative and inflammatory response and leads to uncontrolled structural changes in airways and alters gene expression. Such changes have a characteristic similar to that for COPD patients. Therefore, smoking is determined as a key risk factor for chronic respiratory disease development. Furthermore, electronic cigarettes, an alternative of tobacco cigarettes, also affect gene expression profile, which suggests some similarities in action mechanisms for both conventional and electronic cigarettes. However, there is only a limited number of trials discussing this issue and future investigations are needed.