Aernoud Fiolet

269 Colchicine reduces extracellular vesicle NLRP3 inflammasome protein levels INTRODUCTION I nflammation is one of the major processes underlying the progression of atherosclerosis leading to atherothrombotic complications such as myocardial infarction and stroke. 1,2 An effective anti-inflammatory treatment for atherosclerosis, reducing cardiovascular events independent of lipid lowering, proved elusive for decades. The Canakinumab Antiinflammatory Thrombosis Outcome Study (CANTOS) demonstrated that targeted anti-inflammatory therapy with selective inhibition of interleukin (IL)-1 β reduced the risk of major cardiovascular events in patients with recent myocardial infarction. 3 Subsequently, the Colchicine Cardiovascular Outcomes Trial (COLCOT) showed that 0.5 mg of colchicine, an anti-inflammatory drug used for gout, pericarditis and familial Mediterranean fever, administered once daily reduced the risk of cardiovascular events in patients with recent myocardial infarction. 4 Recently, the second Low-Dose Colchicine (LoDoCo2) trial demonstrated that a similar dose of colchicine reduced the risk of cardiovascular events in patients with chronic coronary disease. 5 Colchicine is a drug with broad anti-inflammatory effects and, although it has been used for centuries, its exact mechanisms of action remain unclear. Among others, colchicine acts through the inhibition of tubulin polymerization, adhesion molecules and cytokines, and the inhibition of the nucleotide-binding oligomerization domain-, leucine-rich repeat-, and pyrin domain-containing protein 3 (NLRP3) inflammasome. 6,7 NLRP3 is an intracellular innate receptor that, after activation, forms the intracellular inflammasome multiprotein complex that results in caspase 1-dependent cleavage and subsequent release of the mature pro-inflammatory cytokines IL-1 β and IL-18. 8–10 Both IL-1 β and IL-18 are known to drive atherosclerotic plaque progression and increase the risk for instability. 9,11,12 IL-1 β levels are generally low and cleavage of its precursor pro-IL-1 β is driven by several other pathways aside from the NLRP3 inflammasome. 13–15 IL-1 β thus proves to be a difficult indicator for NLRP3 inflammasome activity. NLRP3 inflammasome activation also results in the secretion of its intracellular components, including NLRP3 protein, in extracellular vesicles (EVs). 16,17 EVs are small bilayer membrane vesicles including microvesicles, microparticles and exosomes, ranging from 50-1000 nm in diameter, that are released during cell