Intracellular localisation of hypericin in human glioblastoma and carcinoma cell lines

Hypericin, a natural polycyclic quinone extracted from Hypericum perforatum , has been recently shown to be a powerful sensitiser for photodynamic ther apy (PDT). However, its intracellular localisation remains unclear and cont radictory. In the present work we compared the intracellular localisation o f hypericin in three cultured cell lines (adenocarcinoma cells WiDr, carcin oma cells NHIK 3025 and glioblastoma cells D54Mg) with the distribution of fluorescent probes specific to lysosomes (LysoTracker Blue DND-22), mitocho ndria (MitoTracker Green FM) and endoplasmic reticulum (ERTracker Blue-Whit e DPX). It was shown that the hypericin staining pattern was different comp ared to the intracellular distribution of mitochondria or lysosomes. Hyperi cin was concentrated in the perinucleolar cytoplasmic area mainly on one si de of the nucleus - the region rich in endoplasmic reticulum and Golgi. Som etimes nuclear envelope was also stained. Plasma membrane was not stained b ut the dye was often accumulated in the intercellular space between the tig htly contacting WiDr cells in colonies. Hypericin concentrations of 10 muM or less were not toxic for WiDr cells in the dark. Orange light (lambda (ma x) approximate to 600 mn; 6 mW/cm(2)) killed the cells stained with 1 muM h ypericin with LD50 similar to 1J/cm(2).