1. ¹pharmazentrum frankfurt, Institute of Clinical Pharmacology, Frankfurt am Main, Germany
2. ²Funktionsbereich Nephrologie, Medizinische Klinik IV, Klinikum der Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany
3. ³Transplantationsambulanz, KfH Nierenzentrum, Frankfurt am Main, Germany

Correspondence: Jochen Graff, MD, Institute of Clinical Pharmacology, pharmazentrum frankfurt, University Hospital, Theodor Stern Kai 7, D-60590 Frankfurt am Main, Germany E-mail: graff@em.uni-frankfurt.de

^*This study was supported in part by a grant from Fujisawa, Munich, Germany, and Sanofi-Synthelabo, Berlin, Germany.

Received 19 May 2005; Accepted 1 August 2005.

Abstract

Background: Increased platelet activation has been described during treatment with various immunosuppressive agents and may contribute to the high cardiovascular mortality rate in renal transplant patients. Platelets are thought to propagate the inflammatory process of atherosclerosis by interaction with leukocytes.

Methods: We tested an experimental therapy with clopidogrel in renal transplant patients treated with either tacrolimus (n = 20) or cyclosporine (INN, ciclosporin) (n = 19). All patients took low-dose steroids and had stable transplant function. Untreated healthy volunteers (n = 11) were included as the reference group. Degranulation (CD62P), glycoprotein IIb/IIIa receptor activation (PAC1), formation of platelet-leukocyte aggregates (monocyte–platelet-leukocyte aggregate, CD11b, mean fluorescence intensity), and platelet CD40 ligand (CD40L) expression (percent positive) were assessed by flow cytometry before therapy (visit 1) and after 4 weeks of clopidogrel (75 mg/d) intake (visit 2). To assess systemic anti-inflammatory effects, we measured levels of high-sensitivity C-reactive protein, soluble CD40L (sCD40L), monocyte chemoattractant protein 1, and matrix metalloproteinase 9 (MMP-9) by enzyme-linked immunosorbent assay.

Results: At visit 1, cyclosporine-treated patients had significantly enhanced CD62P and PAC1 expression and platelet-leukocyte aggregate formation, as well as elevated sCD40L concentrations, compared with tacrolimus-treated patients (all P<.03). Clopidogrel intake led to a significant decrease in platelet-leukocyte aggregate formation in tacrolimus-treated patients (median, 237 [interquartile range, 177-510] to 194 [interquartile range, 159-275] mean fluorescence intensity; P<.035) and cyclosporine-treated patients (median, 450 [interquartile range, 362-782] to 254 [interquartile range, 211-458] mean fluorescence intensity; P<.035). CD40L expression was reduced in tacrolimus-treated patients (median, 34 [interquartile range, 28-41] to 21 [interquartile range, 12-26] mean fluorescence intensity; P<.002) and cyclosporine-treated patients (median, 33 [interquartile range, 30-37] to 26 [interquartile range, 19-26] mean fluorescence intensity; P<.02). In addition, CD62P, PAC1, and CD11b were significantly reduced in both groups at visit 2 (P<.02). MMP-9 decreased from 88 ng/mL (range, 49-135 ng/mL) to 57 ng/mL (range, 38-73 ng/mL) (P<.05) in tacrolimus-treated patients and from 79 ng/mL (range, 54-148 ng/mL) to 66 ng/mL (range, 41-97 ng/mL) (P<.01) in cyclosporine-treated patients. The sCD40L concentration decreased significantly only in cyclosporine-treated patients (P<.004). In contrast, high-sensitivity C-reactive protein and monocyte chemoattractant protein 1 were not affected.

Conclusion: The P2Y₁₂ receptor antagonist clopidogrel inhibits the expression of platelet activation markers and the interaction of platelets and leukocytes. Because the synthesis of vascular disease markers and inflammatory products such as sCD40L and MMP-9 has been inhibited, anti-inflammatory properties of clopidogrel are likely to be a result of decreasing platelet activation.