Presentations

Abstract

Introduction:

Over 70 million Americans report insufficient sleep due to daily responsibilities and lifestyle choices. Altered duration and poor sleep quality are associated with an increased risk of mortality due to a cardiovascular event, such as myocardial infarction or stroke. Atherosclerosis is the major underlying cause of cardiovascular disease. It is a chronic, inflammatory disease characterized by the formation of lipid laden, atherosclerotic plaques in the vessel walls. As the disease progresses, the composition of advanced atherosclerotic plaques increases in complexity and can become unstable and prone to rupture. Ruptured plaques are the main cause of the severe cardiovascular related events that are more likely to result in death. Previous data has shown fragmented sleep to accelerate atherosclerosis development though increased production of neutrophils from the bone marrow. Our previous experiments have demonstrated SF to alter neutrophils towards an activated phenotype that is associated with plaque instability. Here, we hypothesized that SF results in accelerated atherosclerotic plaque development and destabilization by increased production and activation of circulating neutrophils. Furthermore, the depletion of circulating neutrophils would improve plaque stability of sleep fragmented, atherosclerotic mice.

Methods:

Female Apoe−/−mice were placed on a high fat diet (HFD) and sleep fragmented using a slow-moving mechanical sweeper every 2 minutes during the light period each day. To test the role of neutrophils in SF-associated plaque instability, mice were fed a HFD and SF for 8 weeks, to induce the formation of atherosclerotic plaques throughout the aorta, then neutrophils were depleted while HFD-feeding and SF continued for 4 additional weeks. After a total 12 weeks of HFD-feeding and SF blood was collected to confirm successful depletion of circulating neutrophils and aortas were collected to examine immune cell infiltration via flow cytometry. Finally, hearts were collected and stained with picrosirius red and hematoxylin to examine features of plaque stability via light microscopy.

Results:

Following 12 weeks of SF, HFD-fed female Apoe-/- mice showed almost a two-fold increase in aortic plaque formation compared to HFD-fed Apoe-/- mice who received sufficient sleep. Furthermore, SF resulted in increased necrotic cores and decreased plaque collagen with SF Apoe-/- mice having more thin collagen fibers and fewer thick collagen fibers. Importantly, depletion of circulating neutrophils resulted in improved features of plaque stability in SF, HFD-Fed Apoe-/- mice, including increased total plaque collagen with a shift towards thicker collagen fibers surrounding smaller necrotic cores.

Conclusion:

Our data suggests that sleep fragmentation accelerates the development and destabilization of atherosclerotic plaques towards a rupture prone phenotype through the increased production and activation of circulating neutrophils. Furthermore, the depletion of circulating neutrophil improves the characteristics of advanced atherosclerotic plaques towards a more stable phenotype.