Phototoxicity in Human Retinal Pigment Epithelial Cells Promoted by Hypericin, a Component of St. John’s Wort

Authors


  • A part of the paper was presented at the Association for Research in Vision and Ophthalmology (ARVO) Annual Meeting during 1–5 May 2005 in Fort Lauderdale, FL and at the third Annual NIEHS Science Award Day on 31 October 2005 in Research Triangle Park, NC.

*email: jroberts@fordham.edu (Joan E. Roberts)

ABSTRACT

St. John’s wort (SJW), an over-the-counter antidepressant, contains hypericin, which absorbs light in the UV and visible ranges. In vivo studies have determined that hypericin is phototoxic to skin and our previous in vitro studies with lens tissues have determined that it is potentially phototoxic to the human lens. To determine if hypericin might also be phototoxic to the human retina, we exposed human retinal pigment epithelial (hRPE) cells to 10−7 to 10−5 M hypericin. Fluorescence emission detected from the cells (λex = 488 nm; λem = 505 nm) confirmed hypericin uptake by human RPE. Neither hypericin exposure alone nor visible light exposure alone reduced cell viability. However when irradiated with 0.7 J cm−2 of visible light (λ > 400 nm) there was loss of cell viability as measured by MTS and lactate dehydrogenase assays. The presence of hypericin in irradiated hRPE cells significantly changed the redox equilibrium of glutathione and a decrease in the activity of glutathione reductase. Increased lipid peroxidation as measured by the thiobarbituric acid reactive substances assay correlated to hypericin concentration in hRPE cells and visible light radiation. Thus, ingested SJW is potentially phototoxic to the retina and could contribute to retinal or early macular degeneration.

Ancillary