Cigarette smoke extract and isoprene resulted in the induction of apoptosis and autophagy in human placenta choriocarcinoma JEG-3 cells

Abstract

In this study, the effects of cigarette smoke (CS) on the induction of apoptosis via reactive oxygen species (ROS) production and endoplasmic reticulum stress (ER stress) of JEG-3 human choriocarcinoma cells were examined to confirm the relationship between CS and placenta development. Upon TUNEL assay, CS extract (3R4F; 0.3 and 2.1 μM) increased JEG-3 apoptosis. Western blot assay revealed that the protein expressions of p53, Bax, and CCAAT-enhancer-binding protein homologous protein (CHOP) increased, while the levels of Bcl-2 were reduced following CS extract treatment. Moreover, 2',7'-dichlorofluorescein diacetate (DCFH-DA) assay revealed increased ROS production. Upon 3-(4-5-dimethylthiazol-2-yl)-2.5-dyhphenyltetrazolium bromide (MTT) assay, isoprene (IP), one of ingredients of CS, deceased JEG-3 cell viability (10^-11 to 10^-6 M). After based on the MTT assay, two IP concentrations of 10^-11 and 10^-8 M were selected and the protein expressions of cyclin D1, cyclin E1, p21, and p27 decreased in response to IP. Furthermore, IP showed the greatest increase in autophagy at 24 hours and further induction of cell death at 72 hours upon monodansylacadaverine and TUNEL assay. Western blot analysis confirmed the increase in autophagy markers, LC3β and p62, as well as the increase or decrease of apoptosis markers p53, Bax, CHOP, and Bcl-2 in response to its treatments. In addition to confirming increases in ROS through DCFH-DA, we also confirmed the expression of Nrf2, an antioxidant marker, and the expression of Kelch-like ECH-associated protein 1 (KEAP1), which specifically degrades Nrf2, by Western blot. Taken together, these results indicate that CS and IP may inhibit the development of placenta via activation of ROS by inducing apoptosis and autophagy by affecting the expression of KEAP1, which regulates Nrf2 expression.

Keywords: EMT; cell cycle; cigarette smoke; isoprene; placenta choriocarcinoma.