Plaque angiogenesis promotes the growth of atheromas, but the functions of plaque capillaries are not fully determined. Neovascularization may act as a conduit for the entry of leukocytes into sites of chronic inflammation. We observe vasa vasorum density correlates highly with the extent of inflammatory cells, not the size of atheromas in apolipoprotein E-deficient mice. We show atherosclerotic aortas contain activities that promote angiogenesis. The angiogenesis inhibitor angiostatin reduces plaque angiogenesis and inhibits atherosclerosis. Macrophages in the plaque and around vasa vasorum are reduced, but we detect no direct effect of angiostatin on monocytes. After angiogenesis blockade in vivo, the angiogenic potential of atherosclerotic tissue is suppressed. Activated macrophages stimulate angiogenesis that can further recruit inflammatory cells and more angiogenesis. Our findings demonstrate that late-stage inhibition of angiogenesis can interrupt this positive feedback cycle. Inhibition of plaque angiogenesis and the secondary reduction of macrophages may have beneficial effects on plaque stability.angiogenesis ͉ inflammation ͉ vasa vasorum ͉ endothelium

Background-Neovascularization within the intima of human atherosclerotic lesions is well described, but its role in the progression of atherosclerosis is unknown. In this report, we first demonstrate that intimal vessels occur in advanced lesions of apolipoprotein E-deficient (apoE Ϫ/Ϫ) mice. To test the hypothesis that intimal vessels promote atherosclerosis, we investigated the effect of angiogenesis inhibitors on plaque growth in apoE Ϫ/Ϫ mice. Methods and Results-ApoE Ϫ/Ϫ mice were fed a 0.15% cholesterol diet. At age 20 weeks, mice were divided into 3 groups and treated for 16 weeks as follows: group 1, recombinant mouse endostatin, 20 mg ⅐ kg Ϫ1 ⅐ d

Macrophage development is regulated by a complex set of hormone-like molecules and cell adhesion events that control the growth and differentiation of progenitor cells. The macrophage scavenger receptor (SR) gene becomes markedly upregulated during the final stages of monocyte-to-macrophage differentiation and provides a model for the identification and characterization of transcription factors that control this process. In this report, we have identified three genomic regulatory elements that are required for transactivation of the SR gene in the THP-1 monocytic leukemia cell line following induction of macrophage differentiation by tetradecanoyl phorbol acetate. Each of these regulatory elements contains a near-consensus binding site for members of the AP-1 gene family, while the two most quantitatively important elements also contain juxtaposed binding sites for ets domain transcription factors. We demonstrate that tetradecanoyl phorbol acetate treatment results in a marked and prolonged increase in AP-1 binding activity on these elements, which can be accounted for almost entirely by c-jun andjunB. These proteins in turn form ternary complexes with additional factors that bind to the adjacent ets recognition motifs. Several indirect lines of evidence indicate that ets2 represents a component of this ternary complex. The combined expression of c-jun, ets2, and a constitutive form of ras result in synergistic increases in transcription from promoters containing the SR regulatory elements. These observations suggest that SR gene expression is regulated via a signal transduction pathway involving ras, AP-1, and ets domain proteins and imply that at least some of the signalling components involved in ras-dependent growth are also utilized to promote the expression of genes involved in terminal differentiation.Macrophages are derived from circulating monocytes that have traversed the endothelium and migrated into tissues or body cavities. This transition from the circulation is temporally correlated with the unfolding of a program of terminal differentiation that involves the transcriptional activation of a diverse set of immediate/early and late genes. The precise pattern of gene expression that is evoked during this process is dependent on the particular cell-cell interactions and the milieu of cytokines and other regulatory molecules encountered by the nascent macrophage in the postcirculatory environment.The type I and II macrophage scavenger receptors (SRs) represent late gene products that are highly restricted in their patterns of expression to macrophages and related cell types (36). These two forms of the SR are encoded by a single gene that gives rise to an alternatively spliced primary transcript (27,42). Although their normal physiologic roles remain uncertain, biochemical studies have demonstrated that both forms of the SR are capable of binding and internalizing a relatively broad spectrum of polyanionic macromolecules. Ligands for SRs include proteins containing lysine residues that have been acetyl...

Age-related macular degeneration (ARMD) with abnormal deposit formation under the retinal pigment epithelium (RPE) is the major cause of blindness in the Western world. basal laminar deposits are found in early ARMD and are composed of excess basement membrane material produced by the RPE. Here, we demonstrate that mice lacking the basement membrane component collagen XVIII/endostatin have massive accumulation of sub-RPE deposits with striking similarities to basal laminar deposits, abnormal RPE, and age-dependent loss of vision. The progressive attenuation of visual function results from decreased retinal rhodopsin content as a consequence of abnormal vitamin A metabolism in the RPE. In addition, aged mutant mice show photoreceptor abnormalities and increased expression of glial fibrillary acidic protein in the neural retina. Our data demonstrate that collagen XVIII/ endostatin is essential for RPE function, and suggest an important role of this collagen in Bruch's membrane. Consistent with such a role, the ultrastructural organization of collagen XVIII/endostatin in basement membranes, including Bruch's membrane, shows that it is part of basement membrane molecular networks.

Background-Plaque neovascularization is thought to promote atherosclerosis; however, the mechanisms of its regulation are not understood. Collagen XVIII and its proteolytically released endostatin fragment are abundant proteoglycans in vascular basement membranes and the walls of major blood vessels. We hypothesized that collagen XVIII in the aortic wall inhibits the proliferation and intimal extension of vasa vasorum. Methods and Results-To test our hypothesis, we bred collagen XVIII-knockout (Col18a1 Ϫ/Ϫ ) mice into the atherosclerosis-prone apolipoprotein E-deficient (ApoE Ϫ/Ϫ ) strain. After 6 months on a cholesterol diet, aortas from ApoE Ϫ/Ϫ ; Col18a1 Ϫ/Ϫ and ApoE Ϫ/Ϫ ;Col18a1 ϩ/Ϫ heterozygote mice showed increased atheroma coverage and enhanced lipid accumulation compared with wild-type littermates. We observed more extensive vasa vasorum and intimal neovascularization in knockout but not heterozygote aortas. Endothelial cells sprouting from Col18a1 Ϫ/Ϫ aortas were increased compared with heterozygote and wild-type aortas. In contrast, vascular permeability of large and small blood vessels was enhanced with even heterozygous loss of collagen XVIII but was not suppressed by increasing serum endostatin to wild-type levels. Conclusions-Our results identify a previously unrecognized function for collagen XVIII that maintains vascular permeability. Loss of this basement membrane proteoglycan enhances angiogenesis and vascular permeability during atherosclerosis by distinct gene-dose-dependent mechanisms.

Greater knowledge of plaque angiogenesis regulation is needed to design treatments that target the most critical regulatory pathways. Evolutions in angiogenesis inhibitor treatments for cancer and other diseases call for a need to understand the distinct cardiovascular profiles of different agents to rationally combine agents for optimal selectivity and efficacy in the intended vascular bed.

Objective Lymphatic vessels collect extravasated fluid and proteins from tissues to blood circulation as well as play an essential role in lipid metabolism by taking up intestinal chylomicrons. Previous studies have shown that impairment of lymphatic vessel function causes lymphedema and fat accumulation, but clear connections between arterial pathologies and lymphatic vessels have not been described. Approach and Results Two transgenic mouse strains with lymphatic insufficiency (sVEGFR3 and Chy) were crossed with atherosclerotic mice (LDLR−/−/ApoB100/100) to study the effects of insufficient lymphatic vessel transport on lipoprotein metabolism and atherosclerosis. Both sVEGFR3 × LDLR−/−/ApoB100/100 mice and Chy × LDLR−/−/ApoB100/100 mice had higher plasma cholesterol levels compared to LDLR−/−/ApoB100/100 control mice during both normal chow diet (16.3 mmol/l and 13.7 mmol/l vs. 8.2 mmol/l, respectively) and Western-type high fat diet (e.g. after 2 weeks of fat diet 45.9 mmol/l and 42.6 mmol/l vs. 30.2 mmol/l, respectively). Cholesterol and triglyceride levels in very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) fractions were increased. Atherosclerotic lesions in young and intermediate cohorts of sVEGFR3 × LDLR−/−/ApoB100/100 mice progressed faster than in control mice (e.g. intermediate cohort mice at 6 weeks 18.3% vs. 7.7% of the whole aorta, respectively). In addition, lesions in sVEGFR3 × LDLR−/−/ApoB100/100 mice and Chy × LDLR−/−/ApoB100/100 mice had much less lymphatic vessels than lesions in control mice (0.33% and 1.07% vs. 7.45% of podoplanin positive vessels, respectively). Conclusions We show a novel finding linking impaired lymphatic vessels to lipoprotein metabolism, increased plasma cholesterol levels and enhanced atherogenesis.

Transcription of the macrophage scavenger receptor A gene is markedly upregulated during monocyte to macrophage differentiation. In these studies, we demonstrate that 291 bp of the proximal scavenger receptor promoter, in concert with a 400-bp upstream enhancer element, is sufficient to direct macrophage-specific expression of a human growth hormone reporter in transgenic mice. These regulatory elements, which contain binding sites for PU