CX ₃ CR1 Deficiency Confers Protection From Intimal Hyperplasia After Arterial Injury

Abstract

Objective-A functional polymorphism in the chemokine receptor CX 3 CR1 is associated with protection from vascular diseases including coronary artery disease and internal carotid artery occlusive disease. We investigated the mechanisms by which CX 3 CR1 may be involved by evaluating the inflammatory response to arterial injury in CX 3 CR1-deficient animals. Methods and Results-Femoral arteries of CX 3 CR1Ϫ/Ϫ and wild-type (WT) mice were injured with an angioplasty guide wire. After 1, 5, 14, and 28 days, arteries were harvested and evaluated by histology, morphometry, and immunohistochemistry. Arterial injury upregulated the CX 3 CR1 ligand CX 3 CL1. In CX 3 CR1Ϫ/Ϫ compared with WT animals, the incidence of neointima formation was 58% lower (Pϭ0.0017), accompanied by no difference in the area of platelet accumulation at day 1 (Pϭ0.48) but a significant decrease in intimal monocyte infiltration at day 5 (Pϭ0.006), vascular smooth muscle cell (VSMC) proliferation at days 5 and 14, and intimal area at day 28 (Pϭ0.009). Both animal models and human genetic association studies have implicated an important role for the chemokine receptor CX 3 CR1 and its ligand fractalkine (CX 3 CL1) in vascular disease. Mice that lack both CX 3 CR1 and apolipoprotein E (apoE) exhibit a reduction in atherosclerotic lesion formation in the aorta and aortic root compared with apoE-deficient mice. 4,5 CX 3 CL1-deficient mice have a reduction in atherosclerotic plaque burden in the innominate artery. 6 In humans, the V249I/T280M variant of CX 3 CR1 is associated with protection from coronary artery disease 7-9 and internal carotid artery occlusive disease. 10 While CX 3 CR1 and CX 3 CL1 are emerging as important mediators of vascular disease, the specific mechanisms regulating their involvement remain unclear. CX 3 CL1 is a transmembrane chemokine on activated endothelium that also exists in a soluble form. 11-13 Soluble CX 3 CL1 is a potent chemoattractant, and membrane-tethered CX 3 CL1 promotes cell adhesion by supporting the capture and firm adhesion of circulating CX 3 CR1-expressing cells. 14,15 CX 3 CR1 is expressed on monocytes, 16 VSMCs, 17,18 and platelets. 19 Thus, each of these cell types is a candidate to mediate the effects of CX 3 CR1 on vascular inflammatory responses. Conclusions-InThe prevailing hypothesis is that the mechanism for CX 3 CR1 in the development of vascular diseases such as atherosclerosis is the adherence of CX 3 CR1-expressing monocytes to inflamed endothelium. 5,14 However, recent evidence that smooth muscle cells (SMCs) found in human atherosclerotic plaques also express CX 3 CR1 suggests an alternative mechanism. 18 Stimulation of aortic smooth muscle cells with soluble CX 3 CL1 leads to an increase in cell survival and proliferation. 20 Monocyte adhesion and arrest on neointimal SMC is dependent on CX 3 CL1, 21 and VSMCs undergo chemotaxis toward CX 3 CL1. 17 Thus, CX 3 CL1 may act not only on monocytes, but also may function to stimulate SMC proliferation and recruitment into the neointima.In the pre...

Contribution of Platelet CX 3 CR1 to Platelet–Monocyte Complex Formation and Vascular Recruitment During Hyperlipidemia

“…24 In the following experiment, adhesion of TRAP-6-activated platelets to immobilized rhCX 3 CL1 was specifically increased by 35.8%6.13 ( Figure 4A) (P0.05) as compared with adhesion to plastic and human serum albumin and as shown by preincubation with a CX 3 CR1 neutralizing antibody. In agreement with this finding, adhesion of nonactivated platelets to rhCX 3 CL1 was almost absent (not shown).…”

“…20,21 Accordingly, the important role of the CX 3 CL1-CX 3 CR1 axis in atherosclerosis and vascular remodeling has been highlighted in several studies in hyperlipidemic mice. [22][23][24][25] Given the integral role of platelets and the CX 3 CL1-CX 3 CR1 axis in the development of atherosclerosis and neointima formation, we investigated the expression and function of CX 3 CR1 on human and mouse platelets. The surface expression of CX 3 CR1 was upregulated after stimulation with thrombin and activated platelets reversibly associated with monocytic cells in a CX 3 CR1-dependent manner.…”

Stat3-dependent acute Rantes production in vascular smooth muscle cells modulates inflammation following arterial injury in mice

“…Initial evidence arose from broad knockdown models, including clodronate-induced macrophage depletion (39), anti-CD11b antibody administration (8), and Rag -/-mice with absence of B and T lymphocytes (1), in which depletion of macrophages/lymphocytes/neutrophils led to reduced neointimal formation. While certain regulatory subtypes retard vascular inflammation (6,7), the paradigm that macrophages and T cells generally enhance inflammation and neointimal formation has been reinforced by genetic deletion of key surface antigens such as P-selectin glycoprotein ligand-1 (12), CCR2 (10, 11), CXCR3 (5), and CX3CR1 (13) or the inhibition of specific chemokines including monocyte chemotactic protein-1 (Mcp-1) (11), stromal cell-derived factor-1 (Sdf-1) (2), and Rantes (14). Rantes promoter activity (19,36) and transcription (40) may be stimulated by Tnf-α and mediated by NF-κB in various non-VSMC populations.…”

“…While certain regulatory subtypes differ in their responses (6,7), macrophage and T cell recruitment typically leads to enhanced inflammation and neointimal formation as well as reduced luminal patency (1,2,5,(8)(9)(10)(11). A complex network of cytokines, chemokines, and their receptors is known to regulate recruitment of these cells (2,5,(10)(11)(12)(13)(14). However, surprisingly little data are available regarding acute local cytokine/chemokine production or early vascular inflammatory cell infiltration.…”

Genetic and cellular evidence of vascular inflammation in neurofibromin-deficient mice and humans

“…Fractalkine is cleaved from the cell membrane, resulting in soluble fractalkine, which functions as a potent chemoattractant for monocytes (58), and the inflammatory CD14 + CD16 + monocytes have been demonstrated to preferentially express CX3CR1 (60). In vivo, arterial injury upregulated the expression of fractalkine, and genetic ablation of Cx3cr1 abrogates neointima formation through impaired monocyte recruitment (61). Taken together, the data indicate that upregulation of fractalkine expression in NF1 patients in response to increased inflammatory cytokines would result in increased recruitment and attachment of monocytes to the vessel wall, leading to endothelial dysfunction and subsequent vascular disease.…”