Photosensitizer effect of curcumin on UVB-irradiated HaCaT cells through activation of caspase pathways.

Photodynamic therapy (PDT) using photosensitizer can induce diverse cellular responses, including apoptosis. Recently, it has been reported that PDT using methylaminolaevulinate may be effective in basal cell carcinoma. However, it is largely unknown whether PDT using a natural product such as curcumin can induce apoptosis in skin cancer. In this study, to confirm the photodynamic effect of curcumin, we investigated the synergistic effect of the combination of UVB with curcumin on apoptotic cell death in HaCaT cells and molecular mechanisms underlying apoptosis. Our data showed that HaCaT cells were markedly undergoing apoptosis, evidenced by DNA laddering, by combination of UVB with curcumin, compared to UVB or curcumin alone. Furthermore, combination of UVB irradiation with curcumin synergistically induces apoptotic cell death in HaCaT cells through activation of caspase-8, and -3 as well as caspase-9 activation followed by release of cytochrome c. Thus, our data indicate that curcumin may be a promising photosensitizer used in PDT to induce apoptosis in skin cancer cells.