Punicalagin induces apoptosis in A549 cell line through mitochondria-mediated pathway

Lung cancer is the most common cause of cancer-related deaths worldwide. Punicalagin is an ellagitannin mostly found in pomegranate husk and shows very strong antitumoral activity. The purpose of this study was to investigate the mechanism in which punicalagin acts as an antiproliferative agent on A549 cell line (adenocarcinomic human alveolar basal epithelial cells) and MRC-5 cell line (normal lung fibroblast cells). The cultured cells were treated with punicalagin at concentrations of 1-100 μM for 24 h. For this aim, cell growth inhibition, percentage of apoptotic cells, cell cycle distribution, morphological changes, cellular and mitochondrial reactive oxygen species (ROS) production, and expression of apoptotic proteins were evaluated. Cell viability test and morphological examinations showed that punicalagin at 50 and 75 µM concentrations exhibited toxic effect against lung cancer cells but not toxic against normal lung cells. Cytoplasmic ROS production decreased with the application of punicalagin, while the level of ROS released from mitochondria increased due to mitochondrial dysfunction. Studies of apoptosis indicated that both punicalagin concentrations induced apoptotic process in A549 cells. However, cell cycle was arrested in the G1/S phase after punicalagin treatment. These findings suggest that punicalagin has antiproliferative and apoptotic properties in these concentrations.