Hypericium perforatum extract (St. John's Wort) and hypericin induce apoptosis in leukemic HL-60 cells by effecting h-TERT activity.

Hypericin is the main active component of Hypericium perforatum (St. John's Wort). Hypericin has been proven to have antitumoral effect in in vitro condition against solid tumors by deteriorating the mitochondrial functions. It has also anti-leukemic effect in in vitro conditions. However, there has not been any comparative study with hypericin and extract obtained from Hypericium perforatum L. In this study, it has been aimed to investigate the potential cytotoxic role of the extract obtained from Hypericium perforatum grown in Ege region on leukemic cell line, to compare the cytotoxic effects of both extract and hypericin in HL-60 cells, and to clarify the underlying mechanism(s) of this cytotoxicity. Hypericium perforatum extract was used in dilutions as 1/1000, 1/5000, 1/10.000, 1/50.000 and the IC50 value was found to be as 1/10.000 dilution. Hypericin was found to have cytotoxicity in HL-60 cells in time and dose dependent manner between the doses of 1nM to 100 μM with IC50 dose of 0.5 μM. Hypericin with the dose of 0.5 μM had similar cytotoxicity pattern with the cytotoxicity curve obtained with 1/10000 diluted extract. Apoptosis as an underlying mechanism of this cytoxocity was shown in HL-60 cells after incubation with IC50 dose of hypericin which was more remarkable at 48th hours by using acridine orange/ethidium bromide dye method. Total RNA was isolated concomittantly and h-TERT mRNA expression was analyzed at Light Cycler Real-time online polymerase chain reaction and it was found that the mRNA expression was meaningfully decreased at 48th hour of incubation of cells with hypericin. According to results of this study, we have shown that hypericin, as main cytotoxic compound of Hypericium perforatum L, induces apoptosis in HL-60 cells via effecting h-TERT mRNA expression.