Thirdhand smoke (THS) is residual smoke after the cigarette is extinguished and adheres to surfaces. Its re-emission into the air also makes THS a health concern for those who suffer from respiratory diseases. The present study evaluated THS's cytotoxic, oxidative, and inflammatory potential in the H2O2-driven respiratory responses in A549 human airway epithelial cells. Extracted THS from terrycloth exposed to 3R4F cigarettes was assessed via MTT to identify cytotoxicity. The reactive oxygen species (ROS) level was set via DCFDA fluorescence intensity in a flow cytometer, where GSH, MDA level, and CAT activity were assessed spectrophotometrically. IL-6 level is measured via ELISA. THS 50% (v/v) with significant cytotoxicity in A549 cells up-regulated the intracellular ROS level via right-shifted fluorescence intensity of DCFDA compared to the control (p<0.05), which was also amplified with H2O2 co-treatment. MDA level remarkably increased with THS (p<0.05) whereas both THS and THS+H2O2 led to a notable GSH depletion, increase in CAT activity as well as increase in IL-6 level, which were attenuated with negative control (NAC, 1mM) (p<0.05). The induction of oxidative stress might be defined as an important key event in THS-induced airway toxicity that may contribute to chronic respiratory disease progression.
Keywords: chronic airway diseases, airway inflammation, oxidative stress, thirdhand smoke, cigarette.