Abstract
F2-isoprostanes (F2-IsoP) are formed in vivo via free radical peroxidation of arachidonic acid. Enhanced oxidative stress is implicated in the development of atherosclerosis in humans and F2-IsoP have been detected in atherosclerotic plaque. Colony stimulating factor-1 (CSF-1) is essential to macrophage survival, proliferation and differentiation and has been detected in human atherosclerotic plaques. Accumulation of macrophages within the vascular wall is an important component of atherosclerosis but little is known about the effect of F2-IsoP on the migration of these cells. Our aim was to examine the effect of free and lipid-bound 15-F2t-isoprostane (15-F2t-IsoP) on macrophage migration and investigate the signalling pathways involved. Mouse macrophages (cell line BAC1.2F5) were pre-incubated with 15-F2t-IsoP (free, bound to cholesterol or monoacylglycerol or within oxidized phospholipid) and cell migration was assessed using chemotaxis towards CSF-1 in Boyden chambers. Migration was also measured using the wound healing assay with primary mouse bone marrow derived macrophages. We showed that 15-F2t-IsoP dose-dependently inhibited BAC1.2F5 macrophage spreading and adhesion but stimulated their migration towards CSF-1, with maximum effect at 10 µM. Analysis of CSF-1 stimulated signalling pathways in BAC1.2F5 macrophages showed that phosphorylation of Akt, a key mediator of cell migration, and one of its regulators, the mTORC2 component, Rictor, was significantly decreased. In contrast, phosphorylation of the adhesion kinases, FAK and Pyk2, and the adhesion scaffold protein, paxillin, was enhanced after treatment with 15-F2t-IsoP. Mouse bone marrow macrophages were transfected with FAK or Pyk2 small interfering RNA (siRNA) to examine the role of FAK and Pyk2 in 15-F2t-IsoP signalling. Pyk2 silencing inhibited 15-F2t-IsoP-induced reduction in cell area and phospho-paxillin adhesion numbers. The size distribution of adhesions in the presence of 15-F2t-IsoP was also affected by Pyk2 silencing and there was a trend for Pyk2 silencing to reduce 15-F2t-IsoP-stimulated macrophage migration. These results demonstrate that 15-F2t-IsoP affects macrophage adhesions and migration, which are integral components of macrophage involvement in atherosclerosis.