Reseda luteola L. extract displays antiproliferative and pro-apoptotic activities that are related to its major flavonoids.

Reseda luteola L. has been used as a dye due to its high luteolin content since ancient times. However, no pharmacological studies have been performed with Reseda extracts so far. Here, we have assessed antiproliferative and apoptosis-inducing effects of the Reseda extract RF-40. It contains 40% flavonoids, primarily luteolin, but also luteolin-7-O-glucoside and apigenin. RF-40 and the isolated flavonoids dose-dependently inhibited cell proliferation and induced apoptotic oligonucleosomes in PHA-stimulated peripheral blood mononuclar cells. These effects were not due to cytotoxicity as shown with a luminometric ATP assay. Dose-response curves of RF-40 and the isolated flavonoids were similar, with luteolin being the most effective isolated flavonoid. Comparison of RF-40 to its major flavonoids revealed that the pharmacological effects of the extract can mostly be attributed to luteolin. We conclude that Reseda extract is an interesting raw material not only for dyeing purposes but also for further pharmacological investigation.

Usnea barbata extract prevents ultraviolet-B induced prostaglandin E2 synthesis and COX-2 expression in HaCaT keratinocytes.

Usnea barbata and its major constituent usnic acid are potent antimicrobial agents. Here, we have investigated anti-inflammatory properties of an U. barbata extract (UBE) containing 4% usnic acid in an ultraviolet-B (UVB) model with HaCaT keratinocytes. UVB irradiation induced PGE(2) production and COX-2 expression in a time and dose-dependent manner. UBE inhibited PGE(2) production at a half-maximal concentration of 60 microg/ml (2.4 microg/ml usnic acid) that did not affect the UVB-induced upregulation of COX-2, suggesting an effect on enzyme activity rather than on protein expression. The inhibition of PGE(2) production by UBE was not due to cytotoxicity. Besides its known antimicrobial properties, UBE displays specific UVB protective effects that might be useful in the topical treatment of UVB-mediated inflammatory skin conditions.

Screening of plant extracts for antimicrobial activity against bacteria and yeasts with dermatological relevance.

There is cumulative resistance against antibiotics of many bacteria. Therefore, the development of new antiseptics and antimicrobial agents for the treatment of skin infections is of increasing interest. We have screened six plant extracts and isolated compounds for antimicrobial effects on bacteria and yeasts with dermatological relevance. The following plant extracts have been tested: Gentiana lutea, Harpagophytum procumbens, Boswellia serrata (dry extracts), Usnea barbata, Rosmarinus officinalis and Salvia officinalis (supercritical carbon dioxide [CO2] extracts). Additionally, the following characteristic plant substances were tested: usnic acid, carnosol, carnosic acid, ursolic acid, oleanolic acid, harpagoside, boswellic acid and gentiopicroside. The extracts and compounds were tested against 29 aerobic and anaerobic bacteria and yeasts in the agar dilution test. U. barbata-extract and usnic acid were the most active compounds, especially in anaerobic bacteria. Usnea CO2-extract effectively inhibited the growth of several Gram-positive bacteria like Staphylococcus aureus (including methicillin-resistant strains - MRSA), Propionibacterium acnes and Corynebacterium species. Growth of the dimorphic yeast Malassezia furfur was also inhibited by Usnea-extract. Besides the Usnea-extract, Rosmarinus-, Salvia-, Boswellia- and Harpagophytum-extracts proved to be effective against a panel of bacteria. It is concluded that due to their antimicrobial effects some of the plant extracts may be used for the topical treatment of skin disorders like acne vulgaris and seborrhoic eczema.

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.

Magnesium ions inhibit the antigen-presenting function of human epidermal Langerhans cells in vivo and in vitro. Involvement of ATPase, HLA-DR, B7 molecules, and cytokines.

The combination of seawater baths and solar radiation at the Dead Sea is known as an effective treatment for patients with psoriasis and atopic dermatitis. Dead Sea water is particularly rich in magnesium ions. In this study we wished to determine the effects of magnesium ions on the capacity of human epidermal Langerhans cells to stimulate the proliferation of alloreactive T cells. Twelve subjects were exposed on four subsequent days on the volar aspects of their forearms to 5% MgCl2, 5% NaCl, ultraviolet B (1 minimal erythemal dose), MgCl2 + ultraviolet B, and NaCl + ultraviolet B. Epidermal sheets were prepared from punch biopsies and were stained for ATPase and HLA-DR. Compared with untreated skin, the number of ATPase+/HLA-DR+ Langerhans cells was significantly reduced after treatment with MgCl2 (p = 0.0063) or ultraviolet B (p = 0.0005), but not after NaCl (p = 0.7744). We next questioned whether this reduced expression of ATPase and HLA-DR on Langerhans cells bears a functional relevance. Six subjects were treated on four subsequent days with 5% MgCl2, ultraviolet B (1 minimal erythemal dose), and MgCl2 + ultraviolet B. Epidermal cell suspensions from treated and untreated skin were assessed for their antigen-presenting capacity in a mixed epidermal lymphocyte reaction with allogeneic naive resting T cells as responder cells. Treatment with MgCl2, similarly to ultraviolet B, significantly reduced the capacity of epidermal cells to activate allogeneic T cells (p = 0.0356). Magnesium ions also suppressed Langerhans cells function when added to epidermal cell suspensions in vitro. The reduced antigen-presenting capacity of Langerhans cells after treatment with MgCl2 was associated with a reduced expression by Langerhans cells of HLA-DR and costimulatory B7 molecules, and with a suppression of the constitutive tumor necrosis factor-alpha production by epidermal cells in vitro. These findings demonstrate that magnesium ions specifically inhibit the antigen-presenting capacity of Langerhans cells and may thus contribute to the efficacy of Dead Sea water in the treatment of inflammatory skin diseases.

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

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).

The photodynamic active plant pigment hypericin is a possible new photosensitizer for photodynamic therapy. Hypericin shows absorption maxima in the ultraviolet (330 nm) and visible light range (550 and 588 nm). The present study compared the photoactivation of hypericin with the incoherent light source PDT 1200 SOA (520-750 nm) to that with a 1000 watt solar simulator (290-2500 nm). Hypericin displayed dose and time dependent phototoxic effects in the keratinocyte cell line HaCaT in vitro and after intracutaneous in vivo application with both light sources. In vivo, delayed (48 h) photosensitivity in hypericin-sensitized skin was observed. With intracutaneous application of 100 ng/ml hypericin, no phototoxic reaction could be produced. The PDT 1200 SOA was about four times more effective in vitro and about ten times more effective in vivo when compared to the solar simulator. Since the PDT 1200 SOA allows homogenous irradiation of large areas, we conclude that the PDT 1200 SOA is an effective and convenient light source for in vitro and in vivo studies using hypericin.

Differential T cell responses to Plasmodium chabaudi chabaudi in peripheral blood and spleens of C57BL/6 mice during infection.

The definition of the immune status of a person is often taken as the responses obtained from lymphocytes isolated from peripheral blood. We therefore analyzed in a mouse model of Plasmodium chabaudi chabaudi the response of T lymphocytes taken from peripheral blood and compared it with the spleen during and after a primary erythrocytic infection. Using limiting dilution conditions, no malaria-specific T cell responses could be measured in the peripheral blood for up to 21 days after infection with P. chabaudi, whereas T cells responding to malaria Ag were readily detected in the spleen. This was true for T cells providing help and for those producing IFN-gamma. After clearance of the parasitemias to subpatent levels (75 days), qualitatively similar T cell responses were found in both compartments of the immune system, i.e., the Th cell response predominated over the inflammatory response. These data suggest that during an active infection with Plasmodium, T cell responses in peripheral blood are not necessarily indicators of the immune status.

CD4+T cell-dependent effector mechanisms important in the immune response to the erythrocytic stages of Plasmodium chabaudi chabaudi (AS).

The ability to produce IFN-gamma during an erythrocytic infection with P. chabaudi chabaudi is not an indicator of resistance or susceptibility of mice to this infection. However, IFN-gamma may play a transient role in immune control of the parasite. We have shown that after its removal in vivo by antibody treatment the acute phase of infection is clearly exacerbated. After the acute phase of infection the T cell response changes from one characterized by IFN-gamma production to one of a T helper response for antibody production. The IFN-gamma response to parasite challenge can be recovered if the challenge infection is given many weeks after the mice have cleared their primary parasitaemias. These data suggest that the CD4+ T cell response is a heterogenous one and regulated by its cytokine production. The protective mechanisms therefore probably reflect the nature of the ongoing immune response.

Role of gamma interferon during infection with Plasmodium chabaudi chabaudi.

A role has been proposed for inflammatory mediators such as gamma interferon (IFN-gamma) and reactive oxygen intermediates in the control of the blood stages of Plasmodium organisms. It was previously shown that IFN-gamma can be detected in the plasma of mice with a primary infection by Plasmodium chabaudi chabaudi (AS). We found that susceptible and other resistant mouse strains produced IFN-gamma, suggesting that susceptibility is not due to a defect in IFN-gamma production. Administration of IFN-gamma to intact C57BL/6 mice slightly decreased and partially delayed parasitemia, whereas in vivo depletion of IFN-gamma through injection of a "cocktail" of monoclonal antibodies against IFN-gamma exacerbated infection. Since CD4+ T cells are essential for the development of a protective immune response to P. chabaudi chabaudi, we tested whether CD4+ T cells are responsible for IFN-gamma production in vivo and whether exogenous IFN-gamma can replace the protective function of the CD4+ T cells. Mice depleted of CD4+ T cells were unable to produce IFN-gamma, but factors in addition to IFN-gamma may be important in parasite clearance.

The role of CD4+ T cells in the protective immune response to Plasmodium chabaudi in vivo.

CD4+ T cells are an essential component of the protective immune response to Plasmodium chabaudi. In order to determine whether the presence of CD4+ T cells is necessary throughout a primary infection for a protective immune response to develop mice were depleted of their CD4+ T cells in vivo by treatment with specific antibodies. Removal of CD4+ T cells during the acute phase of infection renders mice incapable of clearing their infection. In contrast, removal of CD4+ T cells after this time did not affect their ability to control their parasitaemia. The ability to control parasitaemia correlated with appearance of malaria-specific IgG antibodies. Our data, therefore, suggest a mechanism requiring the presence of CD4+ T cells during the acute pre-IgG period. Later, after IgG has been produced, this mechanism is no longer required.