Photodynamic therapy with hexyl aminolevulinate induces carbonylation, posttranslational modifications and changed expression of proteins in cell survival and cell death pathways

Photodynamic therapy (PDT) using blue light and the potent precursor for protoporphyrin IX, hexyl aminolevulinate (HAL), has been shown to induce apoptosis and necrosis in cancer cells, but the mechanism remains obscure. In the present study, we examined protein carbonylation, expression levels and post-translational modifications in rat bladder cells (AY-27) after PDT with HAL. Altered levels of expression and/or post-translational modifications induced by PDT were observed for numerous proteins, including proteins required for cell mobility, energy supply, cell survival and cell death pathways, by using two-dimensional difference gel electrophoresis (2D-DIGE) and mass spectrometry (MS). Moreover, 10 carbonylated proteins associated with cytoskeleton, transport, oxidative stress response, protein biosynthesis and stability, and DNA repair were identified using immunoprecipitation, two-dimensional gel electrophoresis and MS. Overall, the results indicate that HAL-mediated PDT triggers a complex cellular response involving several biological pathways. Our findings may account for the elucidation of mechanisms modulated by PDT, paving the way to improve clinic PDT-efficacy.