Atorvastatin and clopidogrel interfere with photosensitization in vitro

Photodynamic therapy (PDT) has been used to eliminate undesired cells by using a combination of photosensitizers and light illumination to generate reactive oxygen species. There is great interest in applying PDT to atherosclerosis; preferential destruction of pro-inflammatory macrophages in atheromata might attenuate plaque growth or rupture-prone vulnerability. Here, we report on a previously unknown interaction between cardiovascular drugs that are commonly prescribed for atherosclerosis patients and the cytolytic effects of photodynamic therapy using Cathepsin B activatable photosensitizer L-SR15 on murine macrophage Raw 264.7 cells in culture. Atorvastatin and clopidogrel significantly interfered with in vitro photosensitization effect while aspirin did this to a lesser extent; these drugs did not change the efficiency of cellular uptake of L-SR15 after in vitro photosensitization. A photosensitization interference effect of atorvastatin and clopidogrel was also observed when using a conventional photosensitizer free Ce6 or NCI-H1299 cancer cells. Considering the clinical implications of PDT, our study merits further investigation in clinical settings as well as in animal models.