Candida albicans and its metabolite gliotoxin inhibit platelet function via interaction with thiols

Summary

Platelets bind to Candida albicans, the major cause of candidiasis. But in contrast to other microorganisms the fungus does not aggregate platelets. Gliotoxin (GT), which possesses immunosuppressive properties, is produced by various fungi, including the opportunistic pathogens Aspergillus fumigatus and C. albicans. Its mode of action involves the formation of mixed disulfides with host proteins. Disulfide exchanges play an important role in platelet activation. Therefore, the effect of C. albicans and GT on platelet function was tested. C. albicans yeast cells (5,000–10,000 cells/μl) and GT, in pathophysiologically relevant concentrations (0.05–0.5 μM), inhibited platelet fibrinogen binding, anti gp IIb/IIIa antibody PAC-1 binding, aggregation and procoagulant activity in a dose-dependent manner. Alpha granule release, measured via CD62P surface expression, was not affected. Addition of reduced glutathione partially counteracted the effect of C. albicans and GT on platelet fibrinogen binding and platelet aggregation. The C. albicans metabolite GT features antithrombotic properties in addition to its immunosuppressive functions. Since treatment with reduced glutathione partially counteracted the inhibitory effect of C. albicans yeast cells and GT on platelet fibrinogen binding, the antithrombotic activity is likely to depend on the disulfide bridge of this mycotoxin. GT production by C. albicans could contribute to its survival in the blood stream during vascular infections. The knowledge of the underlying mechanisms of the antithrombotic properties might help to treat fungal infections as well as thrombosis.

Keywords

Cell-cell interactions - infectious diseases - platelet physiology

• References

• 1 van Burik JA, Magee PT. Aspects of fungal pathogenesis in humans. Annu Rev Microbiol 2001; 55: 743-772.
• 2 Maisch PA, Calderone RA. Adherence of Candida albicans to a fibrin-platelet matrix formed in vitro. Infect Immun 1980; 27: 650-656.
• 3 Klotz SA, Harrison JL, Misra RP. Aggregated platelets enhance adherence of Candida yeasts to endothelium. J Infect Dis 1989; 160: 669-677.
• 4 Robert R, Mahaza C, Miegeville M. et al. Binding of resting platelets to Candida albicans germ tubes. Infect Immun 1996; 64: 3752-3757.
• 5 Robert R, Nail S, Marot-Leblond A. et al. Adherence of platelets to Candida species in vivo. Infect Immun 2000; 68: 570-576.
• 6 Yeaman MR, Ibrahim AS, Edwards JE. et al. Thrombininduced rabbit platelet microbicidal protein is fungicidal in vitro. Antimicrob Agents Chemother 1993; 37: 546-553.
• 7 Willcox MD, Webb BC, Thakur A. et al. Interactions between Candida species and platelets. J Med Microbiol 1998; 47: 103-110.
• 8 Carvalho Neiva Tde J, dos Santos JI. Effect of pathogenic yeasts on human platelet aggregation. Braz J Infect Dis 2003; 07: 370-374.
• 9 Lahav J, Jurk K, Hess O. et al. Sustained integrin ligation involves extracellular free sulfhydryls and enzymatically catalyzed disulfide exchange. Blood 2002; 100: 2472-2478.
• 10 Waring P, Beaver J. Gliotoxin and related epipolythiodioxopiperazines. Gen Pharmacol 1996; 27: 1311-1316.
• 11 Waring P, Sjaarda A, Lin QH. Gliotoxin inactivates alcohol dehydrogenase by either covalent modification or free radical damage mediated by redox cycling. Biochem Pharmacol 1995; 49: 1195-1201.
• 12 Hurne AM, Chai CL, Waring P. Inactivation of rabbit muscle creatine kinase by reversible formation of an internal disulfide bond induced by the fungal toxin gliotoxin. J Biol Chem 2000; 275: 25202-25206.
• 13 Pahl HL, Krauss B, Schulze-Osthoff K. et al. The immunosuppressive fungal metabolite gliotoxin specifically inhibits transcription factor NF-kappaB. J Exp Med 1996; 183: 1829-1840.
• 14 Xia Z, Wong T, Liu Q, Kasirer-Friede A. et al. Optimally functional fluorescein isothiocyanate-labelled fibrinogen for quantitative studies of binding to activated platelets and platelet aggregation. Br J Haematol 1996; 93: 204
• 15 Rauterberg J, Kuhn K. The renaturation behaviour of modified collagen molecules. Hoppe Seylers Z Physiol Chem 1968; 349: 611-622.
• 16 Doermann D, Clemetson KJ, Kehrel BE. The GPIb thrombinbinding site is essen-tial for thrombin-induced platelet procoagulant activity. Blood 2000; 96: 2469-2478.
• 17 Born GV. Aggregation of blood platelets by adenosine diphosphate and its reversal. Nature 1962; 194: 927-929.
• 18 Doermann D, Kardoeus J, Zimmermann RE. et al. Flow cytometric analysis of agonistinduced annexin V, factor Va and factor Xa binding to human platelets. Platelets 1998; 09: 171-177.
• 19 Niemann S, Spehr N, Van Aken H. et al. Soluble fibrin is the main mediator of Staphylococcus aureus adhesion to platelets. Circulation 2004; 110: 193-200.
• 20 Gofer-Dadosh N, Klepfish A, Schmilowitz H. et al. Affinity modulation in platelet alpha 2 beta 1 following ligand binding. Biochem Biophys Res Commun 1997; 232: 724-727.
• 21 Lahav J, Gofer-Dadosh N, Luboshitz J. et al. Protein disulfide isomerase mediates integrindependent adhesion. FEBS Lett 2000; 475: 89-92.
• 22 Bernardo PH, Chai CL, Deeble GJ. et al. Evidence for gliotoxin-glutathione conjugate adducts. Bioorg Med Chem Lett 2001; 11: 483-485.
• 23 Shah DT, Larsen B. Clinical isolates of yeast produce a gliotoxin-like substance. Mycopathologia 1991; 116: 203-208.
• 24 Shah DT, Glover DD, Larsen B. In situ mycotoxin production by Candida albicans in women with vaginitis. Gynecol Obstet Invest 1995; 39: 67-69.
• 25 Lewis RE, Wiederhold NP, Chi J. et al. Detection of gliotoxin in experimental and human aspergillosis. Infect Immun 2005; 73: 635-637.
• 26 Stief TW, Kurz J, Doss MO. et al. Singlet oxygen inactivates fibrinogen, factor V, factor VIII, factor X, and platelet aggregation of human blood. Thromb Res 2000; 97: 473-480.
• 27 Austen DE. Thiol groups in the blood clotting action of factor VIII. Br J Haematol 1970; 19: 477-484.