Abstract 1045: E-ntpdase-1/Cd39 Confers Anti-inflammatory And Immunomodulatory Properties To Circulating Membrane-derived Microparticles

Abstract

Background: Microparticles (MPs, <1.5ÂμM) are circulating, membrane-derived micro-vesicles shed from cells and platelets under physiological conditions as well as following stress, such as post-myocardial infarction. MPs have been implicated in inflammation, coagulation and vascular function. CD39, the prototype nucleoside triphosphate diphosphohydrolase (NTP-Dase1) within the vasculature modulates extracellular purinergic signalling through ATP and ADP hydrolysis, conferring anti-inflammatory, anti-thrombotic properties to the intravascular space. The aim of this study was to determine if CD39 is present on MPs and whether this impacts MP phenotype and function. Methods: The proteome, absolute numbers as well as cellular origin of circulating MPs from wild type (wt) and cd39-null C57Bl6 mice were compared by 2D-gel electrophoresis, western blot and flow cytometry. Isolated MPs were incubated with endothelial cells (EC) to analyze their intrinsic pro-inflammatory potential. Results: CD39 can be demonstrated and has ecto-enzymatic activity on circulating MPs from wt mice. 2D-gel analysis revealed that cd39-null MPs express lower levels of talin (component of focal adhesion) and ATP synthase, when compared to wild type MPs. Mutant mice have increased numbers of circulating MPs, with significantly higher fractions derived from platelets and endothelium as compared to wt mice (p<0.05). The presence of CD39 on wt MPs significantly attenuates inflammatory responses following incubation with EC as compared to cd39-null MPs (reduced IL-6 and TNF-alpha secretion, ICAM-1 and VCAM-1 expression, vWF release and NF-kappa B activation, p<0.05). Conclusions: CD39 confers anti-inflammatory and immunomodulatory properties upon circulating MPs. These results highlight the protective potential of CD39; a finding that may be exploited therapeutically, with the prospective of administering soluble CD39 (apyrase) to the site of intravascular injury to ameliorate inflammation, as occurs for instance in acute coronary syndromes.