Dong GC, Chuang PH, Chang KC, Jan PS, Hwang PI, Wu HB, Yi M, Zhou HX, Chen HM. Blocking effect of an immuno-suppressive agent, cynarin, on CD28 of T-cell receptor.
Pharm Res 2008;
26:375-81. [PMID:
18989760 DOI:
10.1007/s11095-008-9754-5]
[Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2008] [Accepted: 10/09/2008] [Indexed: 11/26/2022]
Abstract
PURPOSE
Cynarin, a potential immunosuppressant that blocks the interaction between the CD28 of T-cell receptor and CD80 of antigen presenting cells, was found in Echinacea purpurea by a new pharmaceutical screening method: After Flowing Through Immobilized Receptor (AFTIR; Dong et al., J Med Chem, 49: 1845-1854, 2006). This Echinacea component is the first small molecule that is able to specifically block "signal 2" of T-cell activation.
METHODS
In this study, we used the AFTIR method to further confirm that cynarin effectively blocked the binding between CD80 of B-cells and CD28 of T-cells, and provide details of its mechanism of action.
RESULTS
The experimental results showed that cynarin blocked about 87% of the CD28-dependent "signal 2" pathway of T-cell activation under the condition of one to one ratio of T-cell and B-cell in vitro. Theoretical structure modeling showed that cynarin binds to the "G-pocket" of CD28 (Evans et al., Nat Immunol, 6:271-279, 2005), and thus interrupts the site of interaction between CD28 and CD80.
CONCLUSIONS
These results confirm both that AFTIR is a promising method for screening selective active compounds from herbal medicine and that cynarin has great potential as an immuno-suppressive agent.
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