Inhibition of Apoptotic Signaling Cascade in Photosensitized Human Epidermal Carcinoma A431 Cells by Genistein

Abstract

Photodynamic treatment (PDT) elicits a diverse cellular response and can also cause apoptotic cell death. Previously we showed that PDT can elicit caspase-3 activation and the subsequent biochemical apoptotic changes in human epidermal carcinoma A431 cells. In this report, we use Rose Bengal (RB) as the photosensitizer to investigate the inhibition mechanism of genistein with PDT-induced apoptotic signaling cascades in human epidermal carcinoma A431 cells. Our results demonstrate that genistein, an isoflavone compound with known inhibitory activities to protein tyrosine kinases (PTKs) and topoisomerase-II (topo-II), can prevent PDT-induced apoptotic changes, including DNA fragmentation, mitochondrial release of cytochrome C, and caspase-3 activation in A431 cells. Using the cell permeable dye DCF-DA as an indicator of reactive oxygen species (ROS) generation revealed that increase in intracellular oxidative stress caused by PDT could be abolished by genistein. Collectively, our results demonstrate that genistein significantly attenuates PDT-induced singlet oxygen formation, and suggest that singlet oxygen triggers cytochrome C release, caspase activation and subsequent apoptotic biochemical changes.