3310Platelet complement C3 deposition predicts platelet hyperactivity in patients with type II diabetes

Abstract

Abstract Introduction Atherothrombotic disease is associated with significant morbidity and mortality. Diabetes greatly increases the prothrombotic risk of individuals by factors that remain ill defined. Recently, increased plasma levels of complement C3 were associated with prothrombotic alterations in coagulation in patients with diabetes. The aim of this project was to evaluate the role of complement C3 on platelets in patients with type 2 diabetes. Methods Patients with type 2 diabetes (N=20) and controls (N=22) were included in the present study and assessed for platelet complement C3 deposition and expression of complement regulating proteins (e.g. CD35, CD55, CD59 and Factor H). Results Complement C3 was present on the surface of unstimulated platelets and significantly increased upon platelet activation (C3: 194±10 vs. C3-activated: 778±51 p=0.0001). Expression of complement C3 correlated significantly with platelet expression of CD35 and CD55, that are known to impair C3 breakdown, suggesting a key function in regulation of platelet complement deposition of these proteins (CD35 R2=0.374, p=0.001; CD55 R2 = 0.121 p=0.026). Interestingly, in patients with type 2 diabetes complement C3 deposition predicted platelet hyperactivity measured by P-selectin expression in an univariate analysis while this was not the case in control patients (Diabetes: std. β: 0.527; p=0.013 Controls: std.β 0.087 p=0.740). Using a multivariate approach complement C3 deposition remained a predictor for platelet hyperactivity after correction for dual antiplatelet therapy (DAPT), Aspirin treatment, BMI, age and basal platelet activity in patients with type II diabetes (Diabetes: std. β 0.490 p=0.049 Control: std. β −0.152 p=0.612). Since there was no quantitative difference in complement C3 deposition between the patient groups we hypothesised that a difference in complement activation might explain the differential effects of C3 deposition in these patient groups (Control: 186±54 vs. Diabetes: 202±76 p=0.422). Indeed, presence of the complement C3 metabolite iC3b, which is liberated by complement C3 activation, correlated significantly with HbA1c (R20.174; p=0.015) suggesting an increased complement activation in patients with diabetes. To test whether complement C3 activity influences platelet activity, we preincubated platelets with the complement activator cobra venom factor (CVF) or complement inhibitor CP40 (C3 inhibitor) and Eculizumab (C5 Inhibitor). While additive complement activation showed no effect on platelet activity (p=0.87), complement inhibition by either CP40 and Eculizumab led to a significant reduction in platelet activity (CP40% Inhibition: 15.81% ± 2.42 p=0.0006 Eculizumab % Inhibition: 31,71% ± 7.89, p=0.007). Conclusion Our data suggests that complement C3 deposition in patients with type 2 diabetes predicts platelet hyperactivity and these effects might be due to increased complement activation.