Innate immune cell activation and epigenetic remodeling in symptomatic and asymptomatic atherosclerosis in humans in vivo

• Published in: Atherosclerosis Vol. 254; pp. 228 - 236
• Main Authors: Bekkering, Siroon, van den Munckhof, Inge, Nielen, Tim, Lamfers, Evert, Dinarello, Charles, Rutten, Joost, de Graaf, Jacqueline, Joosten, Leo A.B., Netea, Mihai G., Gomes, Marc E.R., Riksen, Niels P.
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier B.V 01.11.2016
• Subjects: Aged; Atherosclerosis; Atherosclerosis - pathology; Cardiovascular; Carotid Arteries - pathology; Coronary Artery Disease - immunology; Cytokines - metabolism; Epigenesis, Genetic; Epigenetics; Female; Glycolysis; Histones - metabolism; Humans; Immunity, Innate; Inflammation; Lipoproteins, LDL - chemistry; Macrophages - metabolism; Male; Metabolism; Methylation; Middle Aged; Monocytes; Monocytes - cytology; Phenotype; Plaque, Atherosclerotic - metabolism; Epigenetics; Monocytes; Inflammation; Metabolism; Atherosclerosis
• ISSN: 0021-9150; 1879-1484; 1879-1484
• DOI: 10.1016/j.atherosclerosis.2016.10.019

We have recently reported that monocytes can undergo functional and transcriptional reprogramming towards a long-term pro-inflammatory phenotype after brief in vitro exposure to atherogenic stimuli such as oxidized LDL. This process is termed ‘trained immunity’, and is mediated by epigenetic remodeling and a metabolic switch towards increased aerobic glycolysis. We hypothesize that trained immunity contributes to atherogenesis. Therefore, we investigated the inflammatory phenotype and epigenetic remodeling of monocytes from patients with and without established atherosclerosis. Monocytes were isolated from 20 patients with severe symptomatic coronary atherosclerosis (total plaque score >4 on coronary computed tomography angiography) and 17 patients with asymptomatic carotid atherosclerosis and matched controls for both groups. Ex vivo stimulation, RNA analysis and chromatin immunoprecipitation were performed. Monocytes from patients with symptomatic atherosclerosis have a higher production of pro-inflammatory cytokines upon LPS stimulation than healthy controls (TNFα 499 ± 102 vs. 267 ± 45 pg/ml, p = 0.01). This was associated with lower histone 3 lysine 4 trimethylation (H3K4me3) (19% vs. 33%, p = 0.002), and lower H3K27me3 (0.005% vs. 0.8%, p < 0.0001) on the TNFα promoter. Furthermore, relative mRNA expression of the glycolytic rate limiting enzymes hexokinase 2 and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 was higher in patients (0.7 ± 0.2 vs. 0.3 ± 0.1 resp. 1.7 ± 0.2 vs. 1.0 ± 0.1, p = 0.007 resp. 0.003) compared to control individuals. Interestingly, this pro-inflammatory phenotype was only present in patients with symptomatic atherosclerosis, and not in patients with asymptomatic carotid atherosclerosis. Circulating monocytes of patients with symptomatic, but not asymptomatic, atherosclerosis have a pro-inflammatory phenotype and increased expression of glycolytic enzymes, associated with epigenetic remodeling at the level of histone methylation. [Display omitted] •Monocytes from patients with symptomatic coronary atherosclerosis have a pro-inflammatory phenotype.•This is associated with metabolic reprogramming towards increased glycolysis on RNA expression level.•And this is associated with epigenetic remodeling at the level of histone methylation.•These differences were not observed in subjects with asymptomatic atherosclerotic plaques in the carotid artery.•Trained innate immunity could play a role in the progression of atherosclerosis.