| Objective:In order to develop a new immunosuppressant on the basis of natural chemicals, studies of quercetin, a kind of flavonoids, on the pharmacological effects on the T cell behaviors as well as its mechanism were performed respectively.Methods:FACS technology in association with fluorescent antibody, CFSE and Annexin V ,7-AAD staining were used to assess the expression lever of CD69 and CD25, the intensity of CFSE and the percentages of Annexin V+ 7-AAD- of T cells stimulated by ConA or (PDB+Ion) at different time points. The effects of different concentrations of quercetin on these parameters are also assessed. Therefore, the effects of quercetin on the activation, the proliferation and the apoptosis could be determined.Results:The expression rates of CD69 and CD25, the declining degree of CFSE of T cells were significantly lower in the quercetin-adding groups than the control ones, while the percentages of Annexin V+ 7-AAD- were significantly higher in the quercetin-adding groups (P<0.01). The effects of quercetin are concentration-depend for the three behaviors.Conclusion:The activation and proliferation of murine T cells stimulated by Con A or (PDB+Ion ) were significantly inhibited by quercetin, suggesting that quercetin could act on PKC9 by binding to the orthosteric or allosteric binding site of PDB to interfere with the activation of PKC6, then suppress the activities of transcriptors such as AP-1 , NFAT and NF-kB and finally decrease the production of IL-2 et al., so quercetin could change the microenvironment within T cells and at last inhibit the activation and proliferation of T cells. At the same time, the activation induced T cell death was significantly increased by quercetin, suggesting quercetin maybe act on the upstream and/or downstream of Fas/FasL to induce activated T cells to apoptosis. Therefore quercetin is a potential immunosuppressant that may be used together with Cyclosporin A to attenuate the side- effect of the latter.
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