Platelet aggregation is impaired during severe sepsis but not platelet adhesion and vegf release

Severe sepsis induces Disseminated Intravascular Coagulation (DIG) and organ dysfunction. 50 % of the septic patients have thrombocytopenia related to thrombin generation, which activates platelets, and inflammatory cytokines ( IL-1,TNF) which activate leucocytes and endothelial cells increasing platelet adhesion. We investigate ex vivo the platelets aggregability, adhesiveness and vascular growth factor release of patients with severe sepsis (n=l 1) and septic shock (n=10) at Day 0, 3 and 7. ADP, collagen and thrombin (TRAP) induced platelet rich plasma aggregation were impaired in all the patients by comparison to 10 normal subjects, even in absence of thrombocytopenia. The slope and the percentage of aggregation were decreased after collagen and TRAP but not ADP. Whole blood flow cylometry confirms the aggregation defect. GPIIbllla activation, stained by PAC-1 expression and fibrinogen- FITC fixation, was significantly reduced spontaneously and after activation by collagen and TRAP. In opposit, P selectin (CD62p) and vWF receptor remain unchanged. Adhesion of septic patient's platelet to endothelial cells is under investigation. aggreg ADP ADP collagen collagen TRAP TRAP slope % aggreg slope % aggreg slope % aggreg normal 37.7 ±3.5 73.3 ±5.7 46.4 ±6.4 83.3 ±5.9 64.6 ±5.9 83.6 ±3.4 sepsis 30.1 ±5.8 61.0±14.l 34.5±3.6 70.6+7.9 40.1+12.6 70.5 ±9.7 pvalue 0.679 0.185 0.001 0.014 0.002 0.015 FCM CD62p PAC-1 fibrinogen meanfluo PBS TRAP PBS TRAP PBS TRAP normal 153 626.75 158 505.75 255.5 766 sepsis 115.6 530.9 120.1 275.6 233.9 309.8 pvalue 0.575 0.263 0.045 0.009 0.084 0.002 VEGF and PDGF mesured in the plasma supernatant after TRAP induced platelet aggregation, was differently regulated with an increased release of VEGF (125.99±99 in control vs 376 ±170 in septic p=0.017) and an inhibition of PDGF (2629±491 vs 1959+478 p=0.033). In conclusion severe sepsis is characterized by an impaired platelet aggregation with concerved adhesion and complex angiogenic regulation.