ATORVASTATIN DECREASES LOSS OF HUMAN PANCREATIC ISLET MASS RELATED TO INSTANT BLOOD-MEDIATED INFLAMMATORY REACTION BY DOWN-REGULATION OF TISSUE FACTOR AND MACROPHAGE CHEMOATTRACTANT PROTEIN EXPRESSION.

Abstract

O384 Aims: Pancreatic islets (PI) constitutively express Tissue Factor (TF) and macrophage chemoattractant protein-1 (MCP-1). After exposure to blood, PI trigger a detrimental clotting reaction referred as instant blood-mediated inflammatory reaction (IBMIR), effect associated with significant reduction in islet mass after transplantation. TF as an initiator and MCP-1 as a chemoattractant have been demonstrated to play a critical role in this process. We hypothesized that statins, which decrease the activation of coagulation and inflammation, may down-regulate TF and MCP-1 expression in isolated human PI and therefore reduce loss of islet mass after islet exposure to blood. Methods: Immediately after isolation, groups of human hand-picked PI were incubated with Atorvastatin (10mmol/L) or vehicle for 3 days (n=5). TF and MCP-1 were determined from islet homogenates and supernatants by ELISA. To evaluate the effects of Atorvastatin on IBMIR, 5000 IEQ were perfused with ABO compatible human blood in vitro using loops of heparin-coated PVS (flow 45 mL/min, 37°C, 60 minutes). Plasma pro-insulin (hPI), β-tromboglobulin (TG) and thrombin-antithrombin (TAT) complexes were quantified by ELISA. Results: Atorvastatin decreased spontaneous PI loss during culture (day 3, 91.2±2.4% viable islet cells) compared with vehicle (82.1±3.1, P<0.05). A dose-dependent decrease in TF and MCP-1 was demonstrated after Atorvastatin treatment (10mmol/L, TF=12.3±6.4 pg/IEQ, MCP-1 3.8±2.1 pg/IEQ) compared with controls (TF=38.3±12.4, MCP-1 9.8±4.1, P<0.05). In vitro, Atorvastatin significantly reduced platelet aggregation after PI exposure to blood (platelet counts in the loops: PI media=289±21x109/L, PI=12.3±1.1x109/L, PI + Atorvastatin=160.1±2.1x109/L, n=6, P<0.001), platelet activation (TG: media=366±110 IU/mL; PI=891±156; PI+Atorvastatin=590±89, P<0.05), activation of coagulation (TAT: media=5.1±1.1 mg/L; PI=367±152; PI+Ator=122±88, P<0.05), and complement activation (C3: media=57.1±4 mg/dL; PI=16.3±7; PI+Atorvastatin 33.8±8.9= P<0.05). In parallel with activation of coagulation, PI destruction was higher in controls (proinsulin= 4998±324 pmol/L) compared with Atorvastatin-treated PI (2656±556, P<0.05). Immunohistochemical studies demonstrated reduced platelets, polymorphonuclear cells, monocytes, and fibrin surrounded the PI treated with Atorvastatin compared with controls after exposure to blood. Conclusions: Atorvastatin significantly reduced human islet expression of TF and MCP-1. This effect was associated with reduced loss of islet mass after exposure to blood. Our results suggest that the early use of statins may improve the results in islet transplantation.