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Peggy Bouzika, Haijiang Lin, Yueran Yan, Yijun Hu, Alp Atik, Joan W Miller, Evangelos S Gragoudas, Demetrios G Vavvas; Verteporfin Without Photodynamic Therapy: Effect of the Photosensitizer on Ocular Cell Lines. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1966.
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Verteporfin is a photosensitizing agent, known primarily for its use in photodynamic therapy (PDT). PDT has been widely applied in treating neoplastic diseases, as well as ocular vascular pathologies, such as age-related macular degeneration (AMD). Recent studies suggested that verteporfin (VP) may actually be able to suppress liver oncogenic growth without the need for photoactivation. We used in vitro cell cultures to evaluate the effect of non-photoactivated VP on normal ocular cell lines.
Retinal pigment epithelial cells (ARPE-19) and retinal vascular endothelial cells (RVEC) were treated with VP; culture plates were incubated under dim lighting and subsequently covered with aluminum foil. The tested concentrations of VP ranged from low doses, currently being used to perform PDT in ophthalmological patients, to much higher doses. ARPE-19 cells were treated while at two different densities, confluent, to simulate resting RPE, and non-confluent, to simulate proliferating RPE that may occur in neovascular AMD. MTT assays (Sigma Aldrich) were performed to assess cell viability at 6h (VP t1/2: 51/2-6h) and at 72h post-incubation, to help determine the LD50 for each cell line. To check the consistency of our MTT results, treated cells were also counted over a course of 7 days and the corresponding growth curves were drawn.
The VP doses used in the clinical setting don’t cause any toxicity to normal RPE cells, while VP concentrations equal to or exceeding 8µM appear to be toxic at 3 days time; the LD50 for confluent ARPE19 cells is 12.89µM VP. Proliferating RPE cells are very sensitive to VP treatment. VP doses as low as 4µM cause significant cell death; the LD50 at 72h post-incubation is 4.38µM VP. On the contrary, treatment of RVEC with doses as high as 16 µM VP for 72h causes no cell toxicity. RVEC’s resistance to VP is confirmed by both the LD50 for this cell line, i.e. 32.22µM VP, and the growth curve data.
VP without light seems to have different effects on RPE and RVEC. RVEC were resistant to VP effects at all doses tested. Confluent RPE cells were affected at high concentrations of the drug, while proliferating RPE cells were affected at much lower doses. The effects of VP on proliferating RPE, even in the absence of light, may be relevant to clinical practice.
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