Abstract-C-reactive protein (CRP) is a predictor of cardiovascular risk. It circulates as a pentamer (pentameric CRP) in plasma. The in vivo existence of monomeric (m)CRP has been postulated, but its function and source are not clear. We show that mCRP is deposited in human aortic and carotid atherosclerotic plaques but not in healthy vessels. pCRP is found neither in healthy nor in diseased vessels. As source of mCRP, we identify a mechanism of dissociation of pCRP to mCRP. We report that activated platelets, which play a central role in cardiovascular events, mediate this dissociation via lysophosphatidylcholine, which is present on activated but not resting platelets. Furthermore, the dissociation of pCRP to mCRP can also be mediated by apoptotic monocytic THP-1 and Jurkat T cells. The functional consequence is the unmasking of proinflammatory effects of CRP as demonstrated in experimental settings that are pathophysiologically relevant for atherogenesis: compared to pCRP, mCRP induces enhanced monocyte chemotaxis; monocyte activation, as determined by conformational change of integrin Mac-1; generation of reactive oxygen species; and monocyte adhesion under static and physiological flow conditions. In conclusion, we demonstrate mCRP generation via pCRP dissociation on activated platelets and H 2 O 2 -treated apoptotic THP-1 and Jurkat T cells, thereby identifying a mechanism of localized unmasking of the proinflammatory properties of CRP. This novel mechanism provides a potential link between the established cardiovascular risk marker, circulating pCRP, and localized platelet-mediated inflammatory and proatherogenic effects. Key Words: C-reactive protein Ⅲ atherosclerosis Ⅲ platelets C -reactive protein (CRP) is a highly conserved protein of the pentraxin family that consists of 5 noncovalently linked subunits of Ϸ23 kDa. It is mainly produced in the liver, but under certain conditions can also be secreted by smooth muscle cells 1 and endothelial cells. 2 It was first discovered as an acute phase reactant, with plasma levels increasing from a baseline level of 1 to 2 g/mL up to 100-to 1000-fold within 24 to 72 hours. Because of this rapid cytokinedriven response to tissue injury, infection, and inflammation, CRP is seen as the prototypic inflammatory marker.Small, 2-to 5-fold increases in the baseline level of plasma CRP in asymptomatic individuals have been associated with an increased risk for cardiovascular events such as stroke and myocardial infarction. 3,4 In the recently published Jupiter trial, mildly elevated CRP levels were used to guide primary prevention, resulting in a significant reduction of major cardiovascular events in apparently healthy individuals. 5 Although the exact role of CRP in atherosclerosis and its complications are unknown, evidence is now emerging to suggest that it may be a direct, causative factor. 6,7 In vitro, CRP has been reported to increase interleukin-8 production in monocytes, 8 inhibit endothelial nitric oxide synthase, 9 alter the antioxidant defenses, and promote...

Abstract-Studies have shown a reduction in plaque volume and change in plaque ultrasound characteristics after 4 infusions of reconstituted high-density lipoprotein (rHDL). Whether rHDL infusion leads to acute changes in plaque characteristics in humans is not known. Patients with claudication scheduled for percutaneous superficial femoral artery revascularization were randomized to receive 1 intravenous infusion of either placebo or rHDL (80 mg/kg given over 4 hours). Five to 7 days following the infusion, patients returned and revascularization was performed including atherectomy to excise plaque from the superficial femoral artery. Twenty patients (17 males) average age, 68Ϯ10 years (meanϮSD) were recruited. Eleven patients had a history of documented coronary artery disease, all patients were on aspirin, and 18 were on statins. Ten of the patients received rHDL and 10 placebo. There was significantly less vascular cell adhesion molecule-1 expression (28Ϯ3% versus 50Ϯ3%; PϽ0.05) and a reduction in lipid content in the plaque of HDL-treated subjects compared to placebo. The level of HDL cholesterol increased by 20% after infusion of rHDL and the capacity of apolipoprotein B-depleted plasma to support cholesterol efflux increased. Intravenous infusion of a single dose of reconstituted HDL led to acute changes in plaque characteristics with a reduction in lipid content, macrophage size, and measures of inflammation. These changes may contribute to the cardioprotective effects of HDL.

Background— Heart attacks and strokes, leading causes of deaths globally, arise from thrombotic occlusion of ruptured vulnerable atherosclerotic plaques characterized by abundant apoptosis, large necrotic cores derived from inefficient apoptotic cell clearance, thin fibrous caps, and focal inflammation. The genesis of apoptosis and necrotic cores in these vulnerable atherosclerotic plaques remains unknown. Cytotoxic CD8 + T lymphocytes represent up to 50% of leukocytes in advanced human plaques and dominate early immune responses in mouse lesions, yet their role in atherosclerosis also remains unresolved. Methods and Results— CD8 + T-lymphocyte depletion by CD8α or CD8β monoclonal antibody in apolipoprotein E-deficient mice fed a high-fat diet ameliorated atherosclerosis by reducing lipid and macrophage accumulation, apoptosis, necrotic cores, and monocyte chemoattractant protein 1, interleukin 1β, interferon γ, and vascular cell adhesion molecule 1. Transfer of CD8 + T cells into lymphocyte-deficient, apolipoprotein E-deficient mice partially reconstituted CD8 + T cells in lymphoid compartments and was associated with CD8 + T-cell infiltration in lesions, increased lipid and macrophage accumulation, apoptotic cells, necrotic cores, and interleukin 1β in atherosclerotic lesions. Transfer of CD8 + T cells deficient in perforin, granzyme B, or tumor necrosis factor α but not interferon γ failed to increase atherosclerotic lesions despite partial reconstitution in the lymphoid system and the presence in atherosclerotic lesions. Macrophages, smooth muscle cells, and endothelial cells were identified as apoptotic targets. Conclusions— We conclude that CD8 + T lymphocytes promote the development of vulnerable atherosclerotic plaques by perforin- and granzyme B–mediated apoptosis of macrophages, smooth muscle cells, and endothelial cells that, in turn, leads to necrotic core formation and further augments inflammation by tumor necrosis factor α secretion.

Abstract-Transforming growth factor-␤ (TGF-␤) superfamily members, TGF-␤ and bone morphogenetic proteins (BMPs), are potent regulatory cytokines with diverse functions on vascular cells. They signal through heteromeric type I and II receptor complexes activating Smad-dependent and Smad-independent signals, which regulate proliferation, differentiation, and survival. They are potent regulators of vascular development and vessel remodeling and play key roles in atherosclerosis and restenosis, regulating endothelial, smooth muscle cell, macrophage, T cell, and probably vascular calcifying cell responses. In atherosclerosis, TGF-␤ regulates lesion phenotype by controlling T-cell responses and stimulating smooth muscle cells to produce collagen. It contributes to restenosis by augmenting neointimal cell proliferation and collagen accumulation. Defective TGF-␤ signaling in endothelial cells attributable to mutations in endoglin or the type I receptor ALK-1 leads to hereditary hemorrhagic telangiectasia, whereas defective BMP signaling attributable to mutations in the BMP receptor II has been associated with development of primary pulmonary hypertension. The development of mouse models with either cell type-specific or general inactivation of TGF-␤/BMP signaling has started to reveal the importance of the regulatory network of TGF-␤/BMP pathways in vivo and their significance for atherosclerosis, hereditary hemorrhagic telangiectasia, and primary pulmonary hypertension. This review highlights recent findings that have advanced our understanding of the roles of TGF-␤ superfamily members in regulating vascular cell responses and provides likely avenues for future research that may lead to novel pharmacological therapies for the treatment or prevention of vascular disorders.