Abstract 252: Arterial Wall TNF Receptor-1 Expression Accelerates Atherosclerosis by Enhancing Neointimal Cell Recruitment
The cytokine tumor necrosis factor- α(TNF) promotes endothelial and smooth muscle cell (SMC) adhesion molecule (CAM) expression, induces SMC migration, and signals through TNF receptor-1 (TNFR1) and TNFR2. Arterial wall TNFR1 expression was shown to augment atherosclerosis, when carotid interposition grafts from WT and TNFR10 mice were placed into the common carotids of congenic apoE0 mice. We therefore tested the hypothesis that arterial wall TNFR1 enhances atherosclerosis by augmenting circulating cell recruitment to the atheroma and medial SMC migration into the atheroma. To track atheroma cell origin, we used the carotid graft system, but with congenic ApoE0 recipients, WT and TNFR10 donors that lacked or expressed GFP constitutively, to create 4 donor/recipient groups (≥5/group): WTGFP+/apoE0, WT/apoE0/GFP+, TNFR10/GFP+/apoE0, TNFR10/apoE0/GFP+. Grafts were frozen or perfusion-fixed at harvest. As before, arterial TNFR1 expression doubled neointimal area (P < 0.05). Assessed as the ratio of GFP to DNA fluorescence, the prevalence of donor- (40%) and recipient-derived (60%) neointimal cells in TNFR10 and WT grafts was equivalent. Thus, arterial wall TNFR1 signaling enhanced both graft-intrinsic cell proliferation/migration and graft-extrinsic cell recruitment to atheromata. Oil red O staining (% graft area), as well as the prevalence of TNF, macrophages (Mac3), SMC-actin positive, and CD3-positive cells (immunofluorescence/DNA fluorescence) were equivalent in TNFR10 and WT grafts. However, arterial wall TNFR1 activity increased VCAM-1, ICAM-1, and MCP-1 expression (P < 0.05)–in pre-atherosclerotic (2-wk-old) grafts’ media (by 2- to 3-fold), and in 8-wk-old grafts’ neointima (by 3- to 3.7-fold), judged by protein immunofluorescence/DNA fluorescence. Aortic SMCs from WT and TNFR10 mice (n = 3 each) migrated equivalently to PDGF (9-fold/basal); however, SMC migration toward co-cultured macrophages activated by cholesterol loading was 160% higher in WT (6-fold/basal) than TNFR10 SMCs (P < 0.05). We conclude that arterial wall TNFR1 expression contributes to atherogenesis by mechanisms that include enhancement of SMC migration and expression of CAMs and chemokines that facilitate neointimal cell recruitment and retention.