In vitro inhibitory effects of thymol and carvacrol on dendritic cell activation and function.

CONTEXT: Thyme has been used in traditional medicine for medicinal purposes since ancient times. OBJECTIVE: The objective of this study was to investigate the effects of thymol and carvacrol as two major constituents of thyme on dendritic cells (DCs) maturation and T cell activation. MATERIALS AND METHODS: Splenic DCs were treated with non-cytotoxic concentrations of the components and then analyzed for MHC II, CD86, and CD40 expression by flow cytometry. The effects of compounds on mitogenic, as well as allogenic T cell responses in mixed lymphocyte culture (MLR) and the release of cytokines were investigated. RESULTS: At 0.1 µg/ml, reduced mean fluorescent intensity (MFI) of CD86 for thymol (80.3 ± 0.2% of untreated control) and CD40 for carvacrol (79.5 ± 0.14%) was observed (p < 0.001). Decreased mitogenic T cell proliferation by thymol [proliferation index (PI) from 0.93 ± 0.11 at 1 µg/ml to 0.42 ± 0.16 at 100 µg/ml (p < 0.01)] and carvacrol [PI from 1.08 ± 0.3 at 1 µg/ml to 0.28 ± 0.1 at 100 µg/ml (p < 0.001)] was seen. Ten micrograms/ml thymol (PI, 0.85 ± 0.04) and carvacrol (PI, 0.89 ± 0.03) inhibited allogenic T cell response (p < 0.05). Decreased IFN-γ level in MLR supernatant from 1441 ± 27.7 pg/ml in untreated cells to 944 ± 32.1 at 10 µg/ml of thymol and of carvacrol (886 ± 31.7 pg/ml) (p < 0.01) was found. IL-4 levels were decreased in the presence of both compounds (p < 0.01). CONCLUSION: These data showed the suppressive effects of thymol and carvacrol on DCs maturation and function, as well as T cell responses.

Plant components for immune modulation targeting dendritic cells: implication for therapy.

Medicinal plant utilization is as old as human life. There are thousands of herbs consumed for medicinal purposes all over the world, especially in east. Their value has not decreased over time and many modern pharmaceuticals have originated from traditional medicinal plants. Studying the reason for their influence is an attractive field of medicine. Among various types of herbs, some function via their immunomodulatory effects. Experiments have shown the regulatory influences of several plants on each type of immune cell, including T cells, B cells, dendritic cells (DCs), macrophages and NK cells. Because of the prominent role of DCs in antigen presentation as the major APC, this review summarizes the immunomodulatory effects of some plants performed through DC effects.

The effects of cichorium intybus extract on the maturation and activity of dendritic cells.

BACKGROUND: Cichorium intybus is a medicinal plant commonly used in traditional medicine for its benefits in immune-madiated disorders. There are several evidences showing that C. intybus can modulate immune responses. In the present study we have investigated the effects of the ethanolic root extract of this plant on the immune system by targeting dendritic cells (DCs). For this purpose, phenotypic and functional maturity of murine DCs after treatment with the extract was analyzed by flow cytometry and mixed lymphocyte reaction (MLR) assay. RESULTS: C. intybus did not change the expression of CD40, CD86 and MHC-II molecules as important co-stimulatory markers on DCs compared to the control, indicating that it could not promote DCs phenotypic maturation. Treatment of DCs with lower concentrations of the extract resulted in an increased production of IL-12 by these cells with no change in IL-10 release. The capacity of treated DCs to stimulate allogenic T cells proliferation and cytokines secretion was examined in the co-cuture of these cells with T cells in MLR. C. intybus at higher concentrations inhibited proliferation of allogenic T cells and in lower concentrations changed the level of cytokines such that IL-4 decreased and IFN-γ increased. CONCLUSIONS: These results indicated that C. intybus extract at higher concentrations can inhibit T cell stimulating activity of DCs, whereas at lower concentrations can modulate cytokine secretion toward a Th1 pattern. These data may in part explain the traditional use of this plant in treatment of immune-mediated disorders.

Immunomodulatory activity of the water extract of Thymus vulgaris, Thymus daenensis, and Zataria multiflora on dendritic cells and T cells responses.

Thymus vulgaris (thyme), Thymus daenensis, and Zataria multiflora are medicinal plants being used widely for infections and inflammatory diseases in folk medicine. In this study, the effects of the water extract of these plants on the activation of dendritic cells (DCs) and T cells was investigated. Both T. vulgaris and Z. multiflora decreased the proliferation of mitogen-stimulated lymphocytes, whereas T. daenensis induced cell proliferation in a dose-dependent manner (p < 0.001). All the three plants increased the CD40 expression on DCs (p < 0.04). The extent of allogenic T cell proliferation in the presence of T. vulgaris and Z. multiflora extracts was significantly decreased (p < 0.02). The effect of the extracts on secretion of IFN-γ and IL-4 cytokines showed that none of the extracts influenced the pattern of cytokine production by T helper (Th) cells toward a Thl or Th2 profile. In conclusion, all the extracts had the ability to activate DCs. Whereas Z. multiflora and T. vulgaris extracts showed immunoihibitory effects on allogenic T cell proliferation, the main effect of T. daenensis was on mitogenic T cell response. These data may partly explain the mechanisms underlying the beneficial immunomodulatory effects of these extracts in infections and immune-related diseases.

Immunomodulatory effect of Parsley (Petroselinum crispum) essential oil on immune cells: mitogen-activated splenocytes and peritoneal macrophages.

INTRODUCTION: Parsley (Petroselinum crispum) has been traditionally used for the treatment of allergy, autoimmune and chronic inflammatory disorders. The present study aims to investigate the suppressive effects of parsley essential oil on mouse splenocytes and macrophages cells. METHODS AND MATERIALS: Parsley essential oil was harvested. It was treated on splenocytes and phytohemagglutinin (PHA) (5 µg/mL) and lipopolysaccharide (LPS) (10 µg/mL) activated splenocytes in different concentrations (0.01-100 µg/mL); then, proliferation was assayed by methyl tetrazolium (MTT) method. Treatment was also performed on the macrophages and LPS-stimulated macrophages (10 µg/ml) and the nitrite levels were measured using the diazotization method based on the Griess reaction and MTT assay for evaluation of the viability of the macrophages. RESULTS: Proliferation of splenocytes in all the treated groups was suppressed. In PHA-stimulated splenocytes, the suppression was seen in all the examined concentrations (0.01-100 µg/mL), while in the unstimulated and LPS-stimulated groups suppression was relatively dose dependent and in high concentration (10 and100 µg/mL).The viability of the macrophages in all groups was the same and in the unstimulated groups; NO suppression was significant in all the concentrations but in LPS-stimulated groups, it was significant in the three higher concentrations (1, 10, and100 µg/mL). CONCLUSION: The results of this study indicate that parsley essential oil may be able to suppress the cellular and humoral immune response. It can also suppress both NO production and the functions of macrophages as the main innate immune cells. These results may suggest that parsley essential oil is a proper suppressant for different applications.