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Effect of hypericin on confocal imaging of Ca2+ signaling in cultured human retinal pigment epithelium.

PURPOSE
To investigate the mechanism of the Ca2+ signaling in cultured human retinal pigment epithelial (RPE) cells with the protein kinase C(PKC) specific inhibitor-hypericin stimulation.


METHODS
Cultured human RPE cells were analyzed using the fluorescence Ca2+ dye fluo-3 AM and laser scanning confocal microscope(LSCM) after stimulation with 100 nM phorbol 12-myristate 13-acetate(PMA) and (or) 5 concentrations of hypericin(1, 2, 3, 4 and 5 microM).


RESULTS
The normal fluorescence in RPE cells was strong and distributed throughout the cells. The nucleus appeared to be more fluorescent than the cytoplasm. After stimulation with PMA alone or 5 concentrations of hypericin, a rapid decrease in flurescence intensity was observed. There was no obvious difference in decreased curve among 5 concentrations. However, after stimulation with a 24 hr preincubation of PMA and 5 concentrations of hypericin, a further decrease was not observed.


CONCLUSION
Fluo-3 AM appears to be a good indicator of the change in Ca2+ occurring in RPE cells and hypericin is a strong inhibitor of Ca2+ influx channel. Hypericin has potential as a therapeutic drug for proliferative vitreoretinopathy(PVR), the inhibitory effect on PVR might be caused by blocking the PKC activity and inhibiting Ca2+ influx pathway.