The modulatory effect of silibinin on T cell immune responses
Date Issued
2008
Date
2008
Author(s)
Kuo, Fu-Hua
Abstract
Silibinin and silymarin have been used as herbal medicines to treat liver disease for a long time. ecent years, silibinin and silymarin has been commonly used as dietary supplements, as well as edicinal products in many countries, including Taiwan. To date, scientific evidence indicates that ilibinin and silymarin possess potential biological activities, including immune modulation (i.e. effects n T cell reactivity and cytokine expression). Although the immunomodulatory activity of silibinin on cell functionality has been documented, contrasting effects on the balance of T helper (Th)1/Th2 ell-mediated immunity were reported. Hence, the objective of the present study was to investigate the ffect of silibinin on Th1/Th2 immune balance. Both animal models and cell culture experiments were mployed to examine the influence of silibinin on T-dependent antibody production, T cell-mediated llergic airway responses, and cytokine expression. The results demonstrated that daily oral dministration of silibinin for 3 days prior to ovalbumin (OVA) sensitization markedly enhanced the roduction of IFN-γ by splenocytes and the serum level of OVA-specific IgG2a in OVA-sensitized ALB/c mice. In contrast, the production of IL-4 and OVA-specific IgE and total IgE was attenuated. hese finding indicates that silibinin administration polarizes the Th1/Th2 balance toward the Th1 irection. In the murine model of allergic airway responses induced by the challenge of OVA aerosol to VA-sensitized mice, no significant effect on the airway allergic immune response by silibinin dministration was observed; however, the steady state mRNA expression of IFN-γ in the lung tissues f OVA-sensitized and challenged mice was markedly enhanced by silibinin administration. urthermore, the direct effect of silibinin on T cell-derived cytokine expression was also studied in itro. Splenocytes obtained from OVA-sensitized mice were exposed to silibinin in culture and timulated with OVA to induce cytokine production. The results showed that silibinin exposure ignificantly attenuated the production of both IFN-γ and IL-4 by OVA-stimulated splenocytes. These esults demonstrated that the effects of silibinin on T cell cytokine expression between the employed in ivo and in vitro experimental settings are inconsistent. The present study utilized 3 experimental ystems, including animal models and cell culture experiments, to examine the immunomodulatory ffect of silibinin on T cells; however, the results on T cell cytokine expression are contrasting. The nconsistency of silibinin-mediated effects on the Th1/Th2 immune balance has been reported in the iterature, suggesting a very complicated profile of silibinin influence on the immune system. It is oticed that, under the employed condition of cell culture studies, the effective concentration range of IVilibinin (5-10 μM) to affect Th1 (IFN-γ) and Th2 (IL-4) cytokine expression is lower than the oncentrations used by many reports in the literature. Together with the demonstrated effects of ilibinin on Th1/Th2 cytokine expression in murine models, it is apparent that T cells are a sensitive arget for silibinin. Further studies to elucidate the mechanism of silibinin-mediated effects on cytokine xpression are warranted.
Subjects
silibinin
T cell
ovalbumin
interferon-gamma
interleukin-4
IgG2a
IgE
Type
thesis
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