Evaluation of protective effects of eucalyptol (EUC) and curcumin (CUR) on cigarette smoke extract (CSE) induced lung cell toxicity in vitro

Smoking is one of the most important leading cause of worldwide death, over millions of people each year. From toxicological perspective, cigarette smoke (CS) also serving an environmental issue for all living organism, especially human being exposed to passive smoke. Last decades, effects of natural compounds on pulmonary system have been under investigation in order to enlighten their effects on CS mediated respiratory diseases such as chronic obstructive pulmonary disease, asthma and lung cancer. Therefore, protective mechanism of traditionally used eucalyptol (EUC), curcumin (CUR) and their combination on BEAS-2B human bronchial epithelial cell line was investigated in vitro in order to understand their impact on adverse outcome pathways involved in cell death, oxidative cell injury and inflammatory response induced by CS extract (CSE). According to exhibited results, EUC, CUR and their combination improved BEAS-2B cell viability, attenuated CSE induced apoptosis and autophagy-dependent cell death. Further, CSE induced oxidative stress remarkably reduced by combination treatment through increase in SOD and CAT antioxidant enzymatic activity and elevated GSH level. Also, intracellular ROS production induced by CSE exposure was prominently decreased with treatments. In parallel, lipid peroxidation was diminished with pre-treatment of combination, significantly. Moreover, Nrf2, master regulator of indirect antioxidant activity, was significantly activated with combination treatment compared to CSE group. Also CSE induced inflammatory response through nitrite and IL-6 release is significantly reduced by combination treatment. In the light of observed results, EUC, CUR and especially their combination might be potential therapeutics through investigated pathways. Furthermore, these results may represent a valuable background for future in vivo studies.