Effects of taurine against benzo[α]pyrene-induced cell cycle arrest and reactive oxygen species-mediated nuclear factor-kappa B apoptosis via reduction of mitochondrial stress in A549 cells.

Taurine is a free amino acid that prevents reactive oxygen species (ROS) formation. ROS production is associated with oxidative stress, cell proliferation, apoptosis, inflammation, and DNA alterations in benzo[α]pyrene (BaP)-induced lung cells. Here, we assessed the effect of adding of 25 mM taurine on human pulmonary alveolar epithelial A549 cells treated with different concentrations of BaP. After culturing for 24 h, the cells were tested for biomarkers including cell viability, cellular morphology, Annexin V-FITC/propidium iodide, cell cycle regulation, ROS accumulation, mitochondrial membrane potential (MMP), and expression of related signaling genes and proteins. BaP induced cell cycle arrest and decreased cell viability in a dose-dependent manner. In addition, 50 µM BaP induced a 52.2% increase in ROS levels and inhibited MMP by up to 80%; however, taurine decreased BaP-induced ROS production by 19.5% and restored MMP. The expression of nuclear factor-kappa B (NF-κB), B-cell lymphoma-2 (BCL-2) homologous antagonist killer (Bak), BCL-2-associated X protein (Bax), and cytochrome c at both the mRNA and protein levels were increased, and the expression of BCL-2 and BCL-x1 was decreased by BaP treatment. Furthermore, BaP activated caspase-3/7 expression by up to 25%. However, taurine decreased the expression of NF-κB, Bak, Bax and cytochrome c levels, reduced caspase-3/7 activities, and increased the expression of BCL-2 and BCL-x1. Hence, taurine attenuates BaP-induced oxidative stress and mitochondrial dysfunction by inhibiting the NF-κB-mediated intrinsic apoptosis pathway in A549 cells. Taurine can be considered as a preventive molecule to prevent lung damage.