BackgroundInterleukin (IL)-1β, IL-18, and downstream IL-6 are key inflammatory cytokines in the pathogenesis of coronary artery disease. Colchicine is believed to block the NLRP3 inflammasome, a cytosolic complex responsible for the production of IL-1β and IL-18. In vivo effects of colchicine on cardiac cytokine release have not been previously studied. This study aimed to (1) assess the local cardiac production of inflammatory cytokines in patients with acute coronary syndromes (ACS), stable coronary artery disease and in controls; and (2) determine whether acute administration of colchicine inhibits their production.Methods and ResultsForty ACS patients, 33 with stable coronary artery disease, and 10 controls, were included. ACS and stable coronary artery disease patients were randomized to oral colchicine treatment (1 mg followed by 0.5 mg 1 hour later) or no colchicine, 6 to 24 hours prior to cardiac catheterization. Blood samples from the coronary sinus, aortic root (arterial), and lower right atrium (venous) were collected and tested for IL-1β, IL-18, and IL-6 using ELISA. In ACS patients, coronary sinus levels of IL-1β, IL-18, and IL-6 were significantly higher than arterial and venous levels (P=0.017, <0.001 and <0.001, respectively). Transcoronary (coronary sinus-arterial) gradients for IL-1β, IL-18, and IL-6 were highest in ACS patients and lowest in controls (P=0.077, 0.033, and 0.014, respectively). Colchicine administration significantly reduced transcoronary gradients of all 3 cytokines in ACS patients by 40% to 88% (P=0.028, 0.032, and 0.032, for IL-1β, IL-18, and IL-6, respectively).ConclusionsACS patients exhibit increased local cardiac production of inflammatory cytokines. Short-term colchicine administration rapidly and significantly reduces levels of these cytokines.

Rationale: Inflammasome activation, with subsequent release of pro-inflammatory cytokines IL-1β and IL-18, has recently been implicated in atherosclerosis-associated inflammation.Objective: To assess in acute coronary syndrome (ACS) patients (1) inflammasome activation in circulating monocytes and (2) whether short-term oral colchicine, a recognised anti-inflammatory agent that has been shown to be cardio-protective in clinical studies, might acutely suppress inflammasome-dependent inflammation. Methods and Results:ACS patients (n=21) were randomised to oral colchicine (1 mg followed by 0.5 mg 1 hour later) or no treatment, and compared with untreated healthy controls (n=9). Peripheral venous blood was sampled pre-(day 1) and 24 hours post-(day 2) treatment. Monocytes were cultured and stimulated with ATP. Analysis of key inflammasome markers was performed by ELISA. IL-1β secretion increased by 580.4 % (p<0.01) in ACS patients compared to controls but only with ATP stimulation. Untreated ACS patients secreted significantly higher levels of IL-18 vs healthy controls independent of ATP stimulation (p< 0.05). Colchicine treatment in ACS patients markedly reduced intracellular and secreted levels of IL-1β vs pre-treatment levels (p<0.05 for both), as well as significantly reducing pro-caspase-1 mRNA levels by 57.7 % and secreted caspase-1 protein levels by 30.2 % vs untreated patients (p<0.05 for both). Conclusions:Monocytes from ACS patients are "primed" to secrete inflammasome-related cytokines and short-term colchicine acutely and markedly suppresses monocyte caspase-1 activity, thereby reducing monocyte secretion of IL-1β. SUMMARY STATEMENTInflammasome activation in monocytes is elevated in ACS patients versus healthy subjects.Acute colchicine therapy dramatically suppresses this activation, via inhibition of caspase-1 gene transcription leading to reduced secretion of IL-1β, supporting a beneficial role for colchicine in atherosclerosis.

Disordered neovascularization and impaired wound healing are important contributors to diabetic vascular complications. We recently showed that high-density lipoproteins (HDLs) enhance ischemia-mediated neovascularization, and mounting evidence suggests HDL have antidiabetic properties. We therefore hypothesized that HDL rescue diabetes-impaired neovascularization. Streptozotocin-induced diabetic mice had reduced blood flow recovery and neovessel formation in a hindlimb ischemia model compared with nondiabetic mice. Reconstituted HDL (rHDL) infusions in diabetic mice restored blood flow recovery and capillary density to nondiabetic levels. Topical rHDL application rescued diabetes-impaired wound closure, wound angiogenesis, and capillary density. In vitro, rHDL increased key mediators involved in hypoxia-inducible factor-1α (HIF-1α) stabilization, including the phosphoinositide 3-kinase/Akt pathway, Siah1, and Siah2, and suppressed the prolyl hydroxylases (PHD) 2 and PHD3. rHDL rescued high glucose–induced impairment of tubulogenesis and vascular endothelial growth factor (VEGF) A protein production, a finding associated with enhanced phosphorylation of proangiogenic mediators VEGF receptor 2 and endothelial nitric oxide synthase. Siah1/2 small interfering RNA knockdown confirmed the importance of HIF-1α stability in mediating rHDL action. Lentiviral short hairpin RNA knockdown of scavenger receptor class B type I (SR-BI) in vitro and SR-BI−/− diabetic mice in vivo attenuated rHDL rescue of diabetes-impaired angiogenesis, indicating a key role for SR-BI. These findings provide a greater understanding of the vascular biological effects of HDL, with potential therapeutic implications for diabetic vascular complications.