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1 December 2004 Evidence for Intracellular Aggregation of Hypericin and the Impact on its Photocytotoxicity in PAM 212 Murine Keratinocytes
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Abstract

We have assessed photoinduced toxicity of hypericin in PAM 212 murine keratinocytes and the relationship between concentration, incubation time and light fluence to evaluate the effect of intracellular aggregation at high concentrations. Confocal microscopy was used to establish the subcellular localization of hypericin at 5 and 50 μM and incubation times of 1 and 3 h. From fluorescence uptake time course studies, intracellular hypericin was demonstrated to exist predominantly in the monomeric form for up to 26 h incubation at 5 μM. However, there was a pronounced aggregation effect at 50 μM, with intracellular hypericin fluorescence levels initially showing an increase followed by a decrease with incubation time. This effect was subsequently shown to exert an effect on the phototoxicity of hypericin. On irradiation, the photocytotoxicity for 1 and 7 h incubation with 50 μM hypericin was comparable, whereas using 5 μM the photocytotoxicity showed good correlation with the intracellular fluorescence measurements at 1 and 7 h incubation.

Theodossis Theodossiou, Michael D. Spiro, Jake Jacobson, John S. Hothersall, and Alexander J. MacRobert "Evidence for Intracellular Aggregation of Hypericin and the Impact on its Photocytotoxicity in PAM 212 Murine Keratinocytes," Photochemistry and Photobiology 80(3), 438-443, (1 December 2004). https://doi.org/10.1562/0031-8655(2004)080<0438:EFIAOH>2.0.CO;2
Received: 30 June 2004; Accepted: 1 September 2004; Published: 1 December 2004
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