P2861Elevated cc chemokine receptor 2 expression and higher migratory activity of monocytes in atrial fibrillation patients with progressive structural remodeling

Background Inflammation in atrial tissue underlies structural remodeling of left atrium, which is a hallmark of atrial fibrillation (AF). Activated monocytes mediate inflammation; however, the role of monocytes in AF pathogenesis has not been extensively examined. In this study, we thus investigated the association between structural remodeling of left atrium, represented by left atrial dimension (LAD), and characteristics of peripheral monocytes in patients with AF. Methods Blood samples were collected from patients undergone catheter ablation between July 2017 and October 2018, including AF patients (n=152) and paroxysmal supraventricular tachycardia (PSVT) patients, which serves as a control non-AF group (n=22). AF patients were further divided into two groups by the median of LAD (normal LAD group: LAD <40 mm, n=77, large LAD group: LAD ≥40 mm, n=75). Peripheral blood mononuclear cells (PBMC) were isolated to analyze monocyte subsets by flow cytometry. In a subset of patients, we further isolated monocytes from PBMC by using magnetic bead-based negative selection method then gene products associated with inflammation or monocyte functions were evaluated. We also examined migratory activity of monocytes toward monocyte chemotactic protein-1, a ligand for CC chemokine receptor 2 (CCR2), using a modified Boyden chamber method. Finally, we performed immunofluorescence staining of monocytes and macrophages in left atrial appendages resected from patients underwent coronary bypass graft surgery (CABG) complicated by AF. Results There were no differences in age, body mass index and high-sensitivity C-reactive protein levels among three groups, including non-AF, normal LAD and large LAD groups, except that more female subjects were included in non-AF group. We found that proportions of classical CD14++CD16- and nonclassical CD14+CD16++ monocytes were higher (non-AF: 71.2±7.3% vs. AF: 75.5±8.3%, p<0.05) and lower (non-AF: 16.4±5.9% vs. AF: 13.2±5.5%, p<0.05), respectively, in all AF patients compared with those in non-AF group, while no significant difference was observed between normal and large LAD groups. In monocytes from large LAD group, mRNA levels of CCR2, a receptor to mediate monocyte chemotaxis, were significantly higher compared to those in normal LAD group (Figure A, p<0.05). Furthermore, monocytes isolated from large LAD group exhibited higher migratory capacity compared to normal LAD group (Figure B, p<0.01). Finally, higher monocyte/macrophage infiltrations to left atrial appendages were implicated in patients with large LAD, shown by immunofluorescence staining. Conclusions Monocytes in AF patients with enlarged left atrium expressed higher CCR2 mRNA and were more active in chemotaxis to MCP-1, suggesting the proactive roles of activated monocytes in the pathogenesis of arterial remolding in AF.

CC chemokine receptor 2 promotes recruitment of myeloid cells associated with insulin resistance in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a common disease, closely associated with obesity and insulin resistance. We investigated the presence of a subset of myeloid cells associated with metabolic disturbance in the liver of patients with NAFLD and a murine model of obesity-induced liver disease. Gene and protein expression in liver and serum was investigated with RT-PCR or ELISA and correlated to clinical disease. Liver-infiltrating immune cells were isolated from normal or diseased human liver for flow cytometric analysis. In animal experiments, mice were fed a high-fat diet (60% of calories from fat) for 16 wk, or high-fat diet with 30% fructose for 32 wk to induce steatohepatitis and fibrosis. A small molecule inhibitor of CC chemokine receptor 2 (CCR2), CCX872, was administered to some mice. A subset of CD11c+CD206+ immune cells was enriched in human liver tissue, and greater infiltration was observed in NAFLD. The presence of CD11c+CD206+ myeloid cells correlated with systemic insulin resistance. CD11c+CD206+ cells expressed high levels of CCR2, and liver CC chemokine ligand 2 (CCL2) expression was increased in nonalcoholic steatohepatitis and correlated with disease activity. In mice, CCR2 inhibition reduced infiltration of liver CD11b+CD11c+F4/80+ monocytes, which are functional homologs of human CD11c+CD206+ cells, and improved liver injury and glycemic control. A role for CCR2/CCL2 in human NAFLD has long been postulated. These data confirm a role for this chemokine/receptor axis, through mediating adipose and hepatic infiltration of myeloid cells. Inhibition of CCR2 improved hepatic inflammation and fibrosis in murine models of NAFLD. These data confirm the rationale for targeting CCR2 to treat NAFLD. NEW & NOTEWORTHY These data show for the first time that CD11c+CD206+ myeloid cells, previously associated with human adipose tissue inflammation, infiltrate into liver tissue in nonalcoholic fatty liver disease. These cells express CCR2. Inhibition of CCR2 in mice inhibits hepatic inflammation caused by a murine homolog of these myeloid cells and improves experimental liver disease.