The Mechanism of Antiviral Phototoxicity of the Furanochromones Visnagin and Khellin

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Abstract
The naturally occurring furanochromones, visnagin and khellin, and the furanocoumarin 8-methoxypsoralen, were compared with respect to their mechanisms of antiviral phototoxicity. Cultured mouse cells were infected with murine cytomegalovirus (MCMV) which had been treated with each compound in long wave ultraviolet (UVA) or dark, and the infected cells were analyzed for the production of viral specific proteins (early and late, by polyacrylamide gel electrophoresis), DNA and RNA (by hybridization with labelled MCMV DNA). No viral macromolecules were synthesized in cells infected with methoxypsoralen + UVA, or visnagin + UVA-treated viruses, although viruses treated similarly in the dark gave rise to normal growth cycles. In the case of khellin + UVA treated virus the inhibition in viral macromolecule synthesis was partial, in accordance with the relatively lower phototoxicity of this compound. The results are consistent with a mechanism involving a photo-induced block in viral gene expression for all the compounds.