Monocyte chemoattractant protein-1 accelerates atherosclerosis in apolipoprotein E-deficient mice. (65/5038)

The pro-inflammatory chemokine, monocyte chemoattractant protein-1 (MCP-1), plays a fundamental role in monocyte recruitment and has been implicated as a contributing factor to atherosclerosis. The predominant cell types within the vessel wall--endothelial cells, smooth muscle cells, and macrophages--all contribute to overexpression of MCP-1 in atherosclerotic tissue. In this report we assess the role of MCP-1 expression by leukocytes on lesion progression in a murine model susceptible to atherosclerosis. Bone marrow cells from mice overexpressing a murine MCP-1 transgene on a background of apoE-deficiency or from control mice were transplanted into irradiated apoE-knockout mice. After repopulation of apoE-knockout mice with bone marrow containing the MCP-1 transgene, macrophages expressing the MCP-1 transgene were found in several tissues, including the aorta. Qualitative assessment of atherosclerosis in these mice revealed increased lipid staining, a 3-fold (P<0.001) increase in the amount of oxidized lipid, and increased immunostaining for macrophage cell surface markers with anti-F4/80 and anti-CD11b antibodies. There were no differences in plasma lipids, plasma lipoprotein profiles, or body weight between the 2 groups. These results provide the first direct evidence that MCP-1 expression by leukocytes, predominately macrophages, increases the progression of atherosclerosis by increasing both macrophage numbers and oxidized lipid accumulation.  (+info)

Direct demonstration of P-selectin- and VCAM-1-dependent mononuclear cell rolling in early atherosclerotic lesions of apolipoprotein E-deficient mice. (66/5038)

Apolipoprotein E-deficient (ApoE-/-) mice develop atherosclerotic lesions throughout the arterial tree, including the carotid bifurcation. Although the expression of adhesion molecules such as ICAM-1, vascular cell adhesion molecule-1 (VCAM-1), and P-selectin on endothelium that overlie atherosclerotic plaques has been implicated in monocyte recruitment to developing lesions, monocyte adhesion in atherosclerotic vessels has not been observed directly. To investigate which adhesion molecules may be important in monocyte adhesion to atherosclerotic lesions, an isolated mouse carotid artery preparation was developed and perfused with mononuclear cells. We show rolling and attachment of the human monocytic cell line U937 and the mouse monocyte-macrophage cell line P388D1 in carotid arteries from 10- to 12-week-old ApoE-/- and C57BL/6 wild-type mice fed a Western-type diet (21% fat wt/wt) for 4 to 5 weeks. No rolling was observed in carotid arteries from C57BL/6 or BALB/c wild-type mice fed a chow diet and little was observed in BALB/c mice fed a Western-type diet. This model represents early lesion development as shown by minimal macrophage infiltration in the intima of carotid arteries from ApoE-/- mice fed a Western-type diet. Rolling was observed at shear stresses that were characteristic of the low-shear recirculation zone near the carotid bifurcation. Mononuclear cell attachment and rolling were significantly inhibited by monoclonal antibody blockade of P-selectin or its leukocyte ligand P-selectin glycoprotein ligand-1. Rolling velocities increased after monoclonal antibody blockade of mononuclear cell alpha4-integrin or VCAM-1, which indicates that alpha4-integrin interacting with VCAM-1 stabilizes rolling interactions and prolongs monocyte transit times.  (+info)

Testing for linkage under robust genetic models. (67/5038)

Robust genetic models are used to assess linkage between a quantitative trait and genetic variation at a specific locus using allele-sharing data. Little is known about the relative performance of different possible significance tests under these models. Under the robust variance components model approach there are several alternatives: standard Wald and likelihood ratio tests, a quasilikelihood Wald test, and a Monte Carlo test. This paper reports on the relative performance (significance level and power) of the robust sibling pair test and the different alternatives under the robust variance components model. Simulations show that (1) for a fixed sample size of nuclear families, the variance components model approach is more powerful than the robust sibling pair approach; (2) when the number of nuclear families is at least approximately 100 and heritability at the trait locus is moderate to high (>0.20) all tests based on the variance components model are equally effective; (3) when the number of nuclear families is less than approximately 100 or heritability at the trait locus is low (<0. 20), on balance, the Monte Carlo test provides the best power and is the most valid. The different testing procedures are applied to determine which are able to detect the known association between low density lipoprotein cholesterol and the common genotypes at the locus encoding apolipoprotein E. Results from this application show that the robust sibling pair method may be more effective in practice than that indicated by simulations.  (+info)

Expression of human apolipoprotein E3 or E4 in the brains of Apoe-/- mice: isoform-specific effects on neurodegeneration. (68/5038)

Apolipoprotein (apo) E isoforms are key determinants of susceptibility to Alzheimer's disease. The apoE4 isoform is the major known genetic risk factor for this disease and is also associated with poor outcome after acute head trauma or stroke. To test the hypothesis that apoE3, but not apoE4, protects against age-related and excitotoxin-induced neurodegeneration, we analyzed apoE knockout (Apoe-/-) mice expressing similar levels of human apoE3 or apoE4 in the brain under control of the neuron-specific enolase promoter. Neuronal apoE expression was widespread in the brains of these mice. Kainic acid-challenged wild-type or Apoe-/- mice had a significant loss of synaptophysin-positive presynaptic terminals and microtubule-associated protein 2-positive neuronal dendrites in the neocortex and hippocampus, and a disruption of neurofilament-positive axons in the hippocampus. Expression of apoE3, but not of apoE4, protected against this excitotoxin-induced neuronal damage. ApoE3, but not apoE4, also protected against the age-dependent neurodegeneration seen in Apoe-/- mice. These differences in the effects of apoE isoforms on neuronal integrity may relate to the increased risk of Alzheimer's disease and to the poor outcome after head trauma and stroke associated with apoE4 in humans.  (+info)

Failure to confirm a synergistic effect between the K-variant of the butyrylcholinesterase gene and the epsilon4 allele of the apolipoprotein gene in Japanese patients with Alzheimer's disease. (69/5038)

To confirm a synergistic effect between the polymorphic K variant of the butyrylcholinesterase (BChE-K) gene and the epsilon4 allele of the apolipoprotein E (APOE) gene in Alzheimer's disease, the frequency of the BChE-K allele was re-examined in a large series of Japanese patients with Alzheimer's disease and controls. Two hundred and three patients with Alzheimer's disease and 288 age and sex matched controls were genotyped by polymerase chain reaction and restriction fragment length polymorphism for BChE-K and APOE. No changes were found in the frequency of BChE-K, either in the Alzheimer's disease group as a whole (0.17 v 0.14; p=0.36) or in early (0.16 v 0.16; p=0.98) or late (0.17 v 0.13; p=0.24) onset patients compared with age matched controls. The study failed to confirm the findings of a previous study which found a significantly higher incidence of BChE-K in patients with Alzheimer's disease with APOE epsilon4 allele than in controls. In the Japanese population studied here, there was no association between BChE-K and Alzheimer's disease, nor an interaction between BChE-K and APOE epsilon4 allele.  (+info)

Impaired collateral vessel development associated with reduced expression of vascular endothelial growth factor in ApoE-/- mice. (70/5038)

BACKGROUND: The impact of disordered lipid metabolism on collateral vessel development was studied in apolipoprotein (apo)E-/- mice with unilateral hindlimb ischemia. METHODS AND RESULTS: Hindlimb blood flow and capillary density were markedly reduced in apoE-/- mice versus C57 controls. This was associated with reduced expression of vascular endothelial growth factor (VEGF) in the ischemic limbs of apoE-/- mice. Cell-specific immunostaining localized VEGF protein expression to skeletal myocytes and infiltrating T cells in the ischemic limbs of C57 mice; in contrast, T-cell infiltrates in ischemic limbs of apoE-/- mice were severely reduced. The critical contribution of T cells to VEGF expression and collateral vessel growth was reinforced by the finding of accelerated limb necrosis in athymic nude mice with operatively induced hindlimb ischemia. Adenoviral VEGF gene transfer to apoE-/- mice resulted in marked augmentation of hindlimb blood flow and capillary density. CONCLUSIONS: These findings thus underscore the extent to which hyperlipidemia adversely affects native collateral development but does not preclude augmented collateral vessel growth in response to exogenous cytokines. Moreover, results obtained in the apoE-/- and athymic nude mice imply a critical role for infiltrating T cells as a source of VEGF in neovascularization of ischemic tissues.  (+info)

Structural characterization by computer experiments of the lipid-free LDL-receptor-binding domain of apolipoprotein E. (71/5038)

The structure and dynamics of the lipid-free LDL-receptor-binding domain of apolipoprotein E (apoE-RBD) has been investigated by Molecular Dynamics Simulations. ApoE-RBD in its monomeric lipid-free form is a singular four-helix bundle made up of four elongated amphipathic helices. Analysis of one 1.5 ns molecular dynamics trajectory of apoE-RBD performed in water indicates that the lipid-free domain adopts a structure that exhibits characteristics found in native proteins: it has very stable helices and presents a compact structure. Yet its interior exhibits a larger number of transient atomic-size cavities relative to that found in other proteins of similar size and its apolar side chains are more mobile. The latter features distinguish the elongated four-helix bundle as a slightly disordered structure, which shows a structural likeness with some de novo designed four-helix bundle proteins and shares with the latter a leucine-rich residue composition. We anticipate that these unique properties compared with other native helix bundles may be related to the postulated ability of apoE-RBD to undergo an opening of its bundle upon interaction with phospholipids. The distribution of empty cavities computed along the trajectory in the interface regions between the different pairs of helices reveals that the tertiary contacts in one of the interfaces are weaker suggesting that this particular interface could be more easily ruptured upon lipid association.  (+info)

Apo A-I inhibits foam cell formation in Apo E-deficient mice after monocyte adherence to endothelium. (72/5038)

We have previously shown that expression of the human apo A-I transgene on the apo E-deficient background increases HDL cholesterol and greatly diminishes fatty streak lesion formation. To examine the mechanism, prelesional events in atherosclerotic plaque development were examined in 6- to 8-week-old apo E-deficient and apo E-deficient/human apo A-I transgenic mice. A quantitative assessment of subendothelial lipid deposition by freeze-fracture and deep-etch electron microscopy indicated that elevated apo A-I did not affect the distribution or amount of aortic arch subendothelial lipid deposits. Immunohistochemical staining for VCAM-1 demonstrated similar expression on endothelial cells at prelesional aortic branch sites from both apo E-deficient and apo E-deficient/human apo A-I transgenic mice. Transmission electron microscopy revealed monocytes bound to the aortic arch in mice of both genotypes, and immunohistochemical staining demonstrated that the area occupied by bound mononuclear cells was unchanged. Serum paraoxonase and aryl esterase activity did not differ between apo E-deficient and apo E-deficient/human apo A-I transgenic mice. These data suggest that increases in apo A-I and HDL cholesterol inhibit foam cell formation in apo E-deficient/human apo A-I transgenic mice at a stage following lipid deposition, endothelial activation, and monocyte adherence, without increases in HDL-associated paraoxonase.  (+info)