Extracellular inflammasome specks are released after marathon running and induce proinflammatory effects in endothelial cells

Abstract Objectives The intracellular NLRP3 inflammasome is an important regulator of sterile inflammation. Recent data suggest that inflammasome particles can be released into the circulation. The effects of exercise on circulating extracellular apoptosis-associated speck-like protein (ASC) particles and their effects on endothelial cells are not known. Methods We established a flow cytometric method to quantitate extracellular ASC specks in human serum. ASC specks were quantitated in 52 marathon runners 24–72 hours before, immediately after, and again 24–58 hours after the run. For mechanistic characterization, NLRP3 inflammasome particles were isolated from a stable mutant NLRP3 (p.D303N)-YFP HEK cell line and used to treat primary human coronary artery endothelial cells (HCAEC). Results Athletes showed a significant increase in serum concentration of circulating ASC specks immediately after the marathon (t1, +52% compared to baseline, p<0.05) and a decrease during follow-up after 24–58 hours (t2, 12% reduction compared to immediately after the run, p<0.01). Confocal microscopy revealed that HCAEC can internalize extracellular NLRP3 inflammasome specks. After internalization, endothelial cells showed an inflammatory response with higher expression of the cell adhesion molecule ICAM1 (6.9-fold, p<0.05) and increased adhesion of monocytes (1.5-fold, p<0.05). Conclusion These findings identify extracellular inflammasome specks as novel systemic mediators of cell-cell communication that are transiently increased after acute high-intensity exercise. Funding Acknowledgement Type of funding sources: Public hospital(s). Main funding source(s): University Hospital Leipzig