In vitro and in vivo activation of hypericin with the incoherent light source PDT 1200 SOA (520-750 nm) and with solar simulated radiation (290-2500 nm)

Reduction in hypericin-induced phototoxicity by Hypericum perforatum extracts and pure compounds

Clinical evidence suggests that administration of Hypericum perforatum (Hp) extracts containing the photo-activated hypericin compounds may cause fewer skin photosensitization reactions than administration of pure hypericin. This study was conducted to determine whether the phototoxicity of hypericin in HaCaT keratinocytes could be attenuated by H. perforatum extracts and constituents. Two extracts, when supplemented with 20 microM hypericin: (1) an ethanol re-extraction of residue following a chloroform extraction (denoted ethanol(-chloroform)) (3.35 microM hypericin and 124.0 microM total flavonoids); and (2) a chloroform extract (hypericin and flavonoids not detected), showed 25% and 50% (p<0.0001) less phototoxicity than 20 microM hypericin alone. Two H. perforatum constituents, when supplemented with 20 microM hypericin: (1) 10 microM chlorogenic acid; and (2) 0.25 microM pyropheophorbide, exhibited 24% (p<0.05) and 40% (p<0.05) less phototoxicity than 20 microM hypericin alone. The peroxidation of arachidonic acid was assessed as a measure of oxidative damage by photo-activated hypericin, but this parameter of lipid peroxidation was not influenced by the extracts or constituents. However alpha-tocopherol, a known antioxidant also did not influence the amount of lipid peroxidation induced in this system. These observations indicate that hypericin combined with H. perforatum extracts or constituents may exert less phototoxicity than pure hypericin, but possibly not through a reduction in arachidonic acid peroxidation.

Evaluation of the light-sensitive cytotoxicity of Hypericum perforatum extracts, fractions, and pure compounds

Hypericum perforatum (Hp) is known for possessing antidepressant and antiviral activities. Despite its use as an alternative to conventional antidepressants, the identification of the cytotoxic chemicals derived from this herb is incomplete. In this study, the cytotoxicity of Hp extracts prepared in solvents ranging in polarity, fractions of one extract, and purified compounds were examined in three cell lines. All extracts exhibited significant cytotoxicity; those prepared in ethanol (no hyperforin, 3.6 microM hypericin, and 134.6 microM flavonoids) showed between 7.7 and 77.4% cell survival (p < 0.0001 and 0.01), whereas the chloroform and hexane extracts (hyperforin, hypericin, and flavonoids not detected) showed approximately 9.0 (p < 0.0001) and 4.0% (p < 0.0001) survival. Light-sensitive toxicity was observed primarily with the ethanol extracts sequentially extracted following removal of material extracted in either chloroform or hexane. The absence of light-sensitive toxicity with the Hp extracts suggests that the hypericins were not playing a prominent role in the toxicity of the extracts.

Can St John's wort (hypericin) ingestion enhance the erythemal response during high-dose ultraviolet A1 therapy?

BACKGROUND

St John's wort (SJW) is widely used as a treatment for depression. A phototoxic reaction, due to its content of hypericin, can occur in animals and in cell culture, and has been reported in humans. Hypericin displays absorption within the ultraviolet (UV) A1 spectrum and there may therefore be a potential for phototoxicity if taken during high-dose UVA1 therapy.

OBJECTIVES

To assess the phototoxicity risk of SJW ingestion.

METHODS

Eleven adult volunteers of skin types I and II were exposed to a geometric dose series of UVA1 irradiation from a high-output source (Dermalight Ultra 1; Dr Hönle, Martinsreid, Germany; irradiance 70-77 mW cm(-2)) on the photoprotected lower back skin at eight 1.5-cm(2) test areas. Irradiation was carried out at baseline and after 10 days of SJW extract 1020 mg (equivalent to 3000 microg of hypericin) daily. Four, 8, 24 and 48 h after each exposure, the minimal erythema dose (MED) and the presence or absence of pigmentation were recorded visually and erythema was assessed objectively with an erythema meter.

RESULTS

The median MED and D(0.025), an objective measure of MED, were lower at all time-points after SJW ingestion. The visual erythemal peak (lowest median MED), which was seen at 8 h postirradiation, was lower after SJW (median 14 J cm(-2), range 10-56) than at baseline (median 20 J cm(-2), range 14-56) (P = 0.047). Similarly, the median D(0.025) at 8 h postirradiation was lower after SJW (median 22.0 J cm(-2), range 15.2-53.9) than at baseline (median 33.7 J cm(-2), range 22.9-136.0) (P = 0.014). The MED and D(0.025) were also significantly different at the 48-h and 4-h time-points, respectively. Significance was not reached at the 24-h time-point. Median intensity of postirradiation erythema increased at all time-points after ingestion of SJW. Despite these differences, the maximum slope of the dose-response curve was not increased after SJW ingestion.

CONCLUSIONS

These data suggest that SJW extract has the potential to lower the erythemal threshold to UVA1 irradiation in a significant proportion of individuals and highlight the importance of ascertaining a full drug history, including herbal remedies, before initiating UVA1 phototherapy.

Effect of oral administration ofHypericum perforatum extract (St. John's Wort) on skin erythema and pigmentation induced by UVB, UVA, visible light and solar simulated radiation

Hypericin from St John's wort (Hypericum perforatum L.) is a photosensitizing agent that may cause a severe photodermatitis when higher amounts of St John's wort are ingested by animals. Although Hypericum extracts are widely used in the treatment of depressive disorders, only a little information on the photosensitizing capacity of St John's wort in humans is available. In the present prospective randomized study we investigated the effect of the Hypericum extract LI 160 on skin sensitivity to ultraviolet B (UVB), ultraviolet A (UVA), visible light (VIS) and solar simulated radiation (SIM). Seventy two volunteers of skin types II and III were included and were divided into six groups, each consisting of 12 volunteers. In the single-dose study the volunteers (n = 48) received 6 or 12 coated tablets (5400 or 10 800 microgram hypericin). In the steady-state study the volunteers (n = 24) received an initial dose of 6 tablets (5400 microgram hypericin), and subsequently 3 x 1 tablets (2700 microgram hypericin) per day for 7 days. Phototesting was performed on the volar forearms prior to medication and 6 h after the last administration of Hypericum extract. The erythema-index and melanin-index were evaluated photometrically using a mexameter. After both single-dose and steady-state administration, no significant influence on the erythema-index or melanin-index could be detected, with the exception of a marginal influence on UVB induced pigmentation (p = 0.0471) in the single-dose study. The results do not provide evidence for a phototoxic potential of the Hypericum extract LI 160 in humans when administered orally in typical clinical doses up to 1800 mg daily. This is in accordance with previous pharmacokinetic studies that found hypericin serum and skin levels after oral ingestion of Hypericum extract always to be lower than the assumed phototoxic hypericin threshold level of 1000 ng/mL.

Hypericin photo-induced apoptosis involves the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and activation of caspase-8

Hypericin (HYP) is a photosensitizing pigment from Hypericum perforatum that displays cytotoxic effects in neoplastic cell lines. Therefore, HYP is presently under consideration as a new anticancer drug in photodynamic therapy. Here, we investigated the mechanism of action of HYP photo-induced apoptosis of Jurkat cells compared to the cytostatic drug paclitaxel (PXL). Both photoactivated HYP and PXL similarly increased the activity of caspase-8 and caspase-3, and drug-induced apoptosis of Jurkat cells was completely blocked by inhibitors of caspase-8 (Z-IETD-FMK) and caspase-3 (Z-DEVD-FMK). The involvement of death receptors was analyzed using neutralizing monoclonal antibodies against Fas (SM1/23), FasL (NOK-2) and TNF-R1 (MAB225), and a polyclonal rabbit anti-human TNF-related apoptosis-inducing ligand (TRAIL) antiserum. TRAIL antibody blocked TRAIL-induced and HYP photo-induced, but not PXL-induced apoptosis of Jurkat cells. In contrast, PXL-induced, but not HYP-induced apoptosis was blocked by the SM1/23 and NOK-2 antibodies. Anti-TNF-R1 antibody had no effect. These findings suggest that HYP photo-induced apoptosis of Jurkat cells is mediated in part by the TRAIL/TRAIL-receptor system and subsequent activation of upstream caspases.

Photodynamic therapy of skin cancers: sensitizers, clinical studies and future directives

Photodynamic therapy (PDT) is a new modality of skin cancer treatment. It involves the administration of photosensitizing drugs which, when localized in tumor tissue can produce its destruction by absorbing an adequate dose of light of an appropriate wavelength. A large number of photosensitizing agents have been tested in PDT experiments. Topical application of 5-aminolevulinic acid (5-ALA) followed by light irradiation is the most commonly used method. 5-ALA is a prodrug converted in situ via the heme cycle into protoporphyrin IX, an effective photosensitizer agent. Treatment of nonmelanoma skin cancers by PDT has met with varying degrees of success. In the case of 5-ALA, this therapy's main limitation is the poor penetration of 5-ALA into skin, due to hydrophilic and charge characteristics. However, the efficacy of 5-ALA-PDT may be improved by (a) development of adequate drug delivery systems; (b) use of enhancers of PpIX production and accumulation in target tissue, and (c) modifications of the 5-ALA molecule. Optimal timing, light sources, doses, and number of applications are also important factors for topical 5-ALA therapy and must be well defined. The aim of this review is to highlight recent progress in 5-ALA-PDT of skin cancer, and to present ways holding promise for its improvement.

Topical application of St John's wort (Hypericum perforatum L.) and of its metabolite hyperforin inhibits the allostimulatory capacity of epidermal cells

St John's wort (Hypericum perforatum) is a traditional herbal medicine that is used for the topical treatment of superficial wounds, burns and dermatitis. The characteristic metabolites of St John's wort are the photodynamic active plant pigment hypericin and the phloroglucin-derivative hyperforin. To date, no studies on immunomodulatory properties of topical preparations of St John's wort have been performed. Here, we investigated the alloantigen presenting function of human epidermal cells (EC) exposed to Hypericum ointment in vivo in a mixed EC lymphocyte reaction (MECLR). The effect of Hypericum ointment was compared with the immunosuppressive effect of solar-simulated radiation (SSR). Subsequently, we tested purified hyperforin in vivo and in vitro in a MECLR to evaluate its possible contribution to the effect of the Hypericum ointment. Furthermore, we assessed the effect of hyperforin on the proliferation of peripheral blood mononuclear cells (PBMC) in vitro. Compared with untreated skin, treatment with Hypericum ointment resulted in a significant suppression of the MECLR (P </= 0.001) that was similar to the effect of SSR. The combination of Hypericum ointment plus SSR was not significantly different from either treatment alone. EC isolated from skin treated with the hyperforin containing ointment also showed a reduced capacity to stimulate the proliferation of allogeneic T cells (P </= 0.001). Similarly, in vitro incubation of EC with hyperforin suppressed the proliferation of alloreactive T cells (P </= 0.001). Furthermore, hyperforin inhibited the proliferation of PBMC in a dose-dependent manner, without displaying pronounced toxic effects as determined by Trypan blue staining. The results demonstrate an inhibitory effect of Hypericum extract and of its metabolite hyperforin on the MECLR and on the proliferation of T lymphocytes that may provide a rationale for the traditional treatment of inflammatory skin disorders with Hypericum extracts.