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A.R. Wielgus, C.F. Chignell, D.S. Miller, D.–N. Hu, J.E. Roberts; Visible Light Toxicity of Hypericin to Human Retinal Pigment Epithelial Cells . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1598.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine the potential visible light induced toxicity of hypericin, the active ingredient in St. John’s Wort, in vitro with human retinal pigment epithelial (hRPE) cells. Methods: Human RPE cells from donor eyes were incubated in the dark for 1 hour with 10–7 to 10–5 M hypericin in F–12 medium supplemented with 10% FBS. Uptake of hypericin into the hRPE cells was confirmed by both confocal microscopy and extraction in methanol/ethyl acetate mixture. Cells were washed and resuspended in PBS buffer. Then they were exposed to visible light emitted by 2 Philips, F40 AX50, 5000 K Advantage lamps equipped with a filter which transmitted only wavelengths above 400 nm. The visible light exposures used in our experiments (710, 2140, and 7140 lx·s) are lower than the daily dose which reaches the human retina. Cell viability was estimated using MTS and LDH assays. Light dependent changes of redox potential expressed in GSH/GSSG relation and TBARS concentration were monitored. Protein content was determined by the BCA method. Results: Fluorescence emission spectra detected from the cells (exc = 550 nm; em = 601 and 651 nm) confirmed hypericin uptake by human RPE. Visible light exposure of hRPE cells with incorporated hypericin caused a decrease in cell viability. The presence of hypericin in irradiated hRPE cells significantly changed the redox equilibrium of glutathione. Increasing concentrations of hypericin in the light exposed cells led to a decrease in the intracellular amount of both total and reduced glutathione with a concomitant increase in the oxidized form of glutathione. Extracellular modifications of either oxidized or reduced glutathione forms were not observed. Increased TBARS production induced by light was correlated to hypericin concentration in hRPE cells. Conclusions: Hypericin, a component of the herbal antidepressant St. John’s Wort, is photoxic to hRPE cells at low concentrations and weak visible light. These studies suggest that similar phototoxic effects may also take place in vivo, however further research in that area is required.
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