丙丁酚对动脉粥样硬化小鼠抗氧化作用的比较

目的观察丙丁酚对高脂高胆固醇饲养的C57BL/6J小鼠和载脂蛋白E基因缺陷(载脂蛋白E-/-)小鼠抗氧化作用的影响,比较丙丁酚对两种小鼠的作用差异。方法以高脂高胆固醇饲料饲喂小鼠,制作高脂血症模型。采用酶比色法及相关检测试剂盒分别测定小鼠血脂水平及与氧化应激相关的指标;采用双抗夹心ELISA法测定氧化型低密度脂蛋白的水平;采用改良的Eckerson方法测定对氧磷酶1的活性,采用逆转录聚合酶链式反应检测对氧磷酶1mRNA的表达。结果与两种小鼠各自的基础饲料组比较,高脂高胆固醇组血脂水平均有升高;与各自的高脂高胆固醇组比较,丙丁酚处理后,C57BL/6J小鼠血清的甘油三酯、总胆固醇、高密度脂蛋白胆固醇和低密度脂蛋白胆固醇水平分别降低了41.0%、43.6%、44.8%和41.3%(P<0.05),载脂蛋白E-/-小鼠血清的甘油三酯、总胆固醇、高密度脂蛋白胆固醇和低密度脂蛋白胆固醇水平,分别降低了36.2%、28.2%、31.3%、33.9%(P<0.05)。小鼠主动脉内膜的动脉粥样硬化病变与各自高脂高胆固醇组比较,C57BL/6J小鼠经丙丁酚处理后病变面积减少了61.1%,载脂蛋白E-/-小鼠经丙丁酚处理后病变面积减少了27.2%(P<0.05)。与各自基础饲料组比较,高脂血症小鼠丙二醛及氧化型低密度脂蛋白的水平增高,而总抗氧化能力和超氧化物歧化酶水平降低(P<0.05);与各自的高脂高胆固醇组比较,丙丁酚处理组小鼠的总抗氧化能力和超氧化物歧化酶水平上升,丙二醛及氧化型低密度脂蛋白的水平则降低(P<0.05)。两组小鼠高脂高胆固醇组血清对氧磷酶1的活性较基础饲料组均下降,经高脂饮食加丙丁酚处理后对氧磷酶1活性比单纯高脂饮食组有所增加;肝脏对氧磷酶1mRNA的表达在高脂高胆固醇组下调,而丙丁酚处理组则上调(P<0.05)。结论丙丁酚可以减轻高脂血症小鼠动脉粥样硬化病变,减轻高脂高胆固醇饮食诱导的氧化应激,而载脂蛋白E基因缺陷则一定程度减弱丙丁酚的上述作用。     

Plasma insulin levels predict atherosclerotic lesion burden in obese hyperlipidemic mice

Despite a clear association between obesity, insulin resistance and atherosclerosis in humans, to date, no animal models have been described in which insulin resistance is associated with atherosclerotic lesion burden. Using two mouse models of obesity-induced hyperlipidemia:leptin deficient (ob/ob) mice on an apolipoprotein E deficient (apoE-/-) or low density lipoprotein receptor deficient (LDLR-/-) background, we sought to determine metabolic parameters most closely associated with atherosclerotic lesion burden. Total plasma cholesterol (TC) levels in ob/ob;apoE-/- mice and ob/ob;LDLR-/- mice were indistinguishable (682+/-48 versus 663+/-16, respectively). Analysis of lipoprotein profiles showed that cholesterol was carried primarily on VLDL in the ob/ob;apoE-/- mice and on LDL in the ob/ob;LDLR-/- mice. Plasma triglycerides (TG) were 55% lower (P<0.001), non-esterified fatty acids (NEFA) were 1.5-fold higher (P<0.01), and insulin levels were 1.7-fold higher (NS) in ob/ob;apoE-/- mice compared to ob/ob;LDLR-/- mice. Other parameters such as body weight, fat pad weight, and glucose levels were not different between the groups. Aortic sinus lesion area of ob/ob;apoE-/- mice was increased 3.2-fold above ob/ob;LDLR-/- mice (102,455+/-8565 microm2/section versus 31,750+/-4478 microm2/section, P<0.001). Lesions in ob/ob;apoE-/- mice were also more complex as evidenced by a 7.7-fold increase in collagen content (P<0.001). Atherosclerotic lesion area was positively correlated with body weight (P<0.005), NEFA (P=0.007), and insulin (P=0.002) levels in the ob/ob;LDLR-/- mice and with insulin (P=0.014) in the ob/ob;apoE-/- mice. In contrast, lesion burden was neither associated with TC and TG, nor with individual lipoprotein pools, in either animal model. These data provide a direct demonstration of the pathophysiologic relevance of hyperinsulinemia, NEFA, and increased body weight to atherosclerotic lesion formation.     

Cyclooxygenase-2 promotes early atherosclerotic lesion formation in ApoE-deficient and C57BL/6 mice

Cyclooxygenase (COX) 2 is expressed in atherosclerotic lesions. We have previously reported that selective inhibition of COX-2 reduces early atherosclerosis in LDLR deficient mice. To examine the role of COX-2 in atherosclerosis in other mouse models, we studied the effects of selective COX-2 inhibition (by rofecoxib and NS-398) and nonselective COX inhibition (by indomethacin) on early atherosclerotic lesion formation in apolipoprotein E-deficient (apoE(-/-)) mice. Selective COX-2 and nonselective COX inhibition reduced atherosclerosis in female apoE(-/-) mice by 35-38% and 38-51% in the proximal and en face aortas, respectively. Next we investigated the role of macrophage COX-2 by transplanting COX-2(-/-) fetal liver cells into C57BL/6 mice and challenging the mice with an atherogenic diet. Genetic deletion of COX-2 from hematopoietic cells reduced atherosclerosis by 51%. In addition, LPS activated COX-2(-/-) macrophages had decreased expression of monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-alpha (TNFalpha). The results demonstrate that selective inhibition of COX-2 and elimination of COX-2 from macrophages significantly reduces early atherosclerotic lesion formation in apoE-deficient and C57BL/6 mice. These results are compatible with COX-2 expression by macrophages having a proatherogenic role, and support the potential of anti-inflammatory therapeutic approaches for atherosclerosis.     

Bone marrow chimerism prevents atherosclerosis in arterial walls of mice deficient in apolipoprotein E

OBJECTIVE: apolipoprotein E (apoE) is a key regulator in cholesterol-rich lipoprotein metabolism. Inherited deficiency of this protein results in type III hyperlipoproteinemia in humans. ApoE, especially that derived from macrophages, can efficiently protect against development of atherosclerotic lesion. To use stem cell gene therapy or mini-transplant in treating abnormal lipid metabolism and preventing atherosclerosis, a minimal level of bone marrow chimerism must be determined. METHODS: lethally irradiated apoE deficient mice (12-16 weeks of age) fed on normal chow were transplanted with normal bone marrow cells (C57BL/6.Ly5.1) mixed with those of apoE deficient mice (C57BL/6.Ly5.2) at various ratios. Plasma cholesterol levels were determined every 3 weeks for up to 42 weeks. Areas of atherosclerotic lesion in the aortas were quantified 6 months post-transplant. Plasma apoE was measured by Western blot analysis. RESULTS: bone marrow transplantation (BMT) in apoE (-/-) mice resulted in a detectable level of plasma apoE as determined by Western blot analysis. The plasma cholesterol levels in mice with > or = 60% chimerism were normalized by 6 weeks post-transplant. Mice with < or = 40% chimerism showed significant reductions, but not normalization, in the plasma cholesterol levels even at 42 weeks posttransplant. However, atherosclerotic areas observed in 10%-chimeric mice were significantly smaller than those in control mice (P<0.01). Immunohistochemical studies in 10%-chimeric mice revealed foam cells derived from donor marrow (apoE (+/+)) and expressed immunoreactive apoE in the atherosclerotic lesion. The positive signals by Western blot analysis were represented in the plasma of up to 8% of the chimeric mice. CONCLUSION: chimerism of 10%, the minimum level analyzed, was sufficient to reduce the severity of atherosclerosis, although the plasma cholesterol levels were not completely normalized. The results indicate that stem cell gene therapy and mini-transplant may provide possible therapeutic approaches to treat patients with abnormal lipid metabolism and atherosclerosis.     

Disruption of tumor necrosis factor-alpha gene diminishes the development of atherosclerosis in ApoE-deficient mice

Inflammatory cytokines, including tumor necrosis factor-alpha (TNF-alpha) have been implicated in atherogenesis. However, the precise role of TNF-alpha in atherogenesis is still unclear. To examine the effect of TNF-alpha on atherogenesis, we generated compound-deficient mice in apolipoprotein E (apoE) and TNF-alpha (apoE-/-/TNF-alpha-/-) and compared them with apoE-/- mice. Although serum total cholesterol levels were markedly elevated in both apoE-/-/TNF-alpha-/- and apoE-/- mice compared to wild-type mice, no differences were observed between apoE-/-/TNF-alpha-/- and apoE-/- mice. The atherosclerotic plaque area in the aortic luminal surface of apoE-/-/TNF-alpha-/- mice (n=8, 3.1+/-0.4%) was significantly smaller than that of apoE-/- mice (n=7, 4.7+/-0.4%, p<0.001) despite the lack of difference in serum cholesterol levels. The atherosclerotic lesion size in the aortic sinus of apoE-/-/TNF-alpha-/- mice (n=10, 5.1+/-0.3 x 10(5)microm(2)) was also significantly smaller than that of apoE-/- mice (n=11, 7.0+/-0.3 x 10(5)microm(2), p<0.0001). RT-PCR analysis indicated that the expression levels of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP-1) were significantly higher in apoE-/- than apoE-/-/TNF-alpha-/- mice. Macrophages from apoE(-/-) mice showed higher uptake level of oxidized LDL and increased expression level of scavenger receptor class A (SRA) compared to those from apoE-/-/TNF-alpha-/- mice. These results indicate that TNF-alpha plays an atherogenic role by upregulating the expressions of ICAM-1, VCAM-1 and MCP-1 in the vascular wall, and by inducing SRA expression and oxidized LDL uptake in macrophages.     

瑞舒伐他汀对载脂蛋白E基因敲除小鼠动脉粥样硬化的影响

目的 探讨瑞舒伐他汀对载脂蛋白E基因敲除(apoE-/-)小鼠主动脉粥样硬化的影响.方法 取apoE-/-小鼠18只建立动脉粥样硬化模型,C57BL/6小鼠12只为对照组.apoE-/-小鼠予高脂饲料,C57BL/6小鼠予普通饲料.12周后,随机抽取C57BL/6小鼠和apoE-/-小鼠各6只,判断是否成模.将成模后余下的12只apoE-/-小鼠随机分为模型组和瑞舒伐他汀治疗组(瑞舒伐他汀10 mg·kg-1·d-1灌胃),每组6只.余下的6只C57BL/6小鼠作为对照组.再过12周后处死小鼠,行血脂及主动脉HE、Masson、油红O染色观察动脉斑块,免疫组织化学方法检测主动脉组织平滑肌肌动蛋白(α-SMA)、转化生长因子β1(TGF-β1)、巨噬细胞表面分子-3(Mac-3)表达.结果 模型组小鼠胆固醇、低密度脂蛋白水平均高于对照组(P均＜0.01),甘油三酯水平与对照组比较差异无统计学意义.模型组小鼠主动脉组织内可见明显动脉粥样硬化斑块形成,α-SMA、TGF-β1和Mac-3表达均较高于对照组(P均＜0.01).瑞舒伐他汀治疗组小鼠胆固醇、低密度脂蛋白、甘油三酯水平与模型组比较差异无统计学意义,但斑块内脂肪含量少于模型组,胶原含量多于模型组.治疗组α-SMA表达与模型组比较差异无统计学意义,治疗组TGF-β1、Mac-3表达均低于较模型组(P均＜0.01).结论 瑞舒伐他汀可以减轻apoE-/-小鼠动脉粥样硬化模型中的脂质沉积和炎症反应,可以增加其胶原含量,利于斑块的稳定,具有抗动脉粥样硬化的作用,对血脂无影响.

Abstract：

Objective To investigate the effect of rosuvastatin on atherosclerosis in apoE-knockout ( apoE - / - ) mice. Methods Eighteen 6-week-old apoE - / - mice fed with high fat diet were used as atherosclerosis models, twelve 6-week-old C57BL/6 mice fed with normal diet were used as control. After twelve weeks, six apoE -/ - mice were used to observe the formation of atherosclerosis. Another 12 apoE -/- mice were divided into placebo treated group (n =6) and rosuvastatin group (n =6,10 mg· kg-1 ·d -1 per gavage) and treated for 12 weeks. Then, blood was collected for measuring lipid, aorta was prepared for morphologic study (HE, Oil red O, Masson) and immunohistochemical analysis (α-smooth activor protein, transforming growth factor β1, macrophage surface molecule-3 ). Results Serum cholesterol and low density lipoprotein levels were significantly higher in apoE -/- mice fed with high fat diet than in C57/ BL6 mice( all P ＜0. 01 )while triglyceride level was similar between the two groups, these were not affected by rosuvastatin. Similarly, atherosclerotic lesion area in apoE -/ - mice fed with high fat diet was also not significantly reduced by rosuvastatin, while lipid deposition could be significantly reduced and collagen deposition could be significantly increased in the aortic atherosclerotic lesions by treatment with rosuvastatin.Upregulated TGF-β1 and Mac-3 expression in the aortic atherosclerotic lesions in apoE -/- mice fed with high fat diet could also be significantly reduced by rosuvastatin (all P ＜ 0. 01 ), suggesting reduce inflammatory responses in the atherosclerotic lesion and stable atherosclerotic plaque post rosuvastatin treatment. Conclusion Reducing inflammatory responses and stabilizing plaque properties might contribute to the anti-atherosclerosis effects of rosuvastatin in mice high fat diet fed apoE -/- mice.     

C3H apoE(-/-) mice have less atherosclerosis than C57BL apoE(-/-) mice despite having a more atherogenic serum lipid profile

Wild-type C57BL mice are known to be susceptible to diet-induced atherosclerosis, whilst C3H mice are resistant. We investigated the effect of these background strains on the hyperlipidaemia and atherosclerosis that develops in mice deficient in apolipoprotein E (apoE(-/-)). Male and female apoE(-/-) mice on C3H/HeNHsd (C3H) and C57BL/6J (C57) backgrounds were fed atherogenic Western diet for 12 weeks. Serum cholesterol and triglyceride concentrations were measured and atherosclerosis quantified in the aortic sinus. C3H apoE(-/-) mice fed normal diet had 1.5 2 fold higher serum cholesterol levels than C57 apoE(-/-) mice and 4-5 fold higher serum triglyceride concentrations. Feeding Western diet caused a 4-5 fold increase in serum cholesterol in all mice, but levels of triglyceride were either attenuated or were unaffected in C3H apoE(-/-) and C57 apoE(-/-) mice, respectively. C3H apoE(-/-) mice had approximately 2 fold higher serum cholesterol and 4 fold higher triglyceride concentrations than the C57 apoE(-/-) mice throughout the study. Serum triglyceride concentrations were 35-108% higher in male C3H apoE(-/-) than female C3H apoE(-/-) mice. Most of the lipids were present in the very low density lipoprotein (VLDL)/chylomicron fraction in both strains of mice whether they were fed normal or Western diet. Notwithstanding the lower plasma lipid concentrations, atherosclerotic lesion areas were more than 2-fold larger in C57 apoE(-/-) than in C3H apoE(-/-) mice (males 68 +/- 11 x 10(3) vs 30 +/- 6 x 10(3) females 102 +/- 12 x 10(3) vs 41 +/- 8 x 10(3) microm2. mean +/- SEM).     

Urokinase-type plasminogen activator plays a critical role in angiotensin II-induced abdominal aortic aneurysm

We have previously demonstrated that urokinase-type plasminogen activator (uPA) is highly expressed in the aneurysmal segment of the abdominal aorta (AAA) in apolipoprotein E-deficient (apoE-/-) mice treated with angiotensin II (Ang II). In the present study, we tested the hypothesis that uPA is essential for AAA formation in this model. An osmotic minipump containing Ang II (1.44 mg/kg per day) was implanted subcutaneously into 7- to 11-month-old male mice for 1 month. Ang II induced AAA in 9 (90%) of 10 hyperlipidemic mice deficient in apoE (apoE-/-/uPA+/+ mice) but in only 2 (22%) of 9 mice deficient in both apoE and uPA (apoE-/-/uPA-/- mice) (P<0.05). Although the expansion of the suprarenal aorta was significantly less in apoE-/-/uPA-/- mice than in apoE-/-/uPA+/+ mice, the aortic diameters of the aorta immediately above or below the suprarenal aorta were similar between the 2 groups. Ang II induced AAA in 7 (39%) of 18 strain-matched wild-type C57 black/6J control mice. The incidence was significantly higher in atherosclerotic apoE-deficient (apoE-/-) mice, in which 8 (100%) of 8 mice developed AAA. Only 1 (4%) of 27 uPA-/- mice developed AAA after Ang II treatment. We conclude the following: (1) uPA plays an essential role in Ang II-induced AAA in mice with or without preexisting hyperlipidemia and atherosclerosis; (2) uPA deficiency does not affect the diameter of the nonaneurysmal portion of the aorta; and (3) atherosclerosis and/or hyperlipidemia promotes but is not essential for Ang II-induced AAA formation in this model.     

The TNF alpha converting enzyme (TACE/ADAM17) is expressed in the atherosclerotic lesions of apolipoprotein E-deficient mice: possible contribution to elevated plasma levels of soluble TNF alpha receptors

TNF alpha converting enzyme (TACE) critically regulates the inflammatory processes as it releases from the cell surface several transmembrane proteins, including TNFalpha (TNF) and its receptors TNFR1 and TNFR2. We investigated the expression of TACE in atherosclerotic lesions of apolipoproteinE-deficient (apoE (-/-)) mice. Five-week-old apoE(-/-) male mice were fed a high-fat diet and examined at 5, 10, 15 and 25 weeks of age. A group of wild-type C57BL/6 mice (WT) fed the high-fat diet for 25 weeks was included. In apoE(-/-) mice, lesions progressed with time in both aortic sinus and arch, in which TACE immunostaining also increased particularly between 5 and 15 weeks. TACE expression was also observed in human atherosclerotic plaques. The plasma levels of soluble TNFR1 and TNFR2 rose with atherosclerosis. In the 25-week-old WT mice, no lesions were observed and the plasma levels of TNFRs were 17% of those of age-matched apoE(-/-) mice. Incubated aortas of 25-week-old apoE(-/-) mice released much higher amounts of sTNF and sTNFRs than did aortas of 5-week-old apoE(-/-) mice or 25-week-old WT mice. Active TACE was expressed at the surface of macrophages isolated from apoE(-/-) mice. In conclusion, TACE expression is associated with lesions in atherosclerosis-prone sites. Our data suggest that atherosclerotic lesions-expressing TACE may contribute to the elevated levels of circulating sTNFRs.     

Genetic alterations of IL-1 receptor antagonist in mice affect plasma cholesterol level and foam cell lesion size

Inflammatory cytokines have been linked to atherosclerosis by using cell culture models and acute inflammation in animals. The goal of this study was to examine lipoprotein levels and early atherosclerosis in chronic animal models of altered IL-1 physiology by using mice with deficient or excess IL-1 receptor antagonist (IL-1ra). IL-1ra knockout C57BL/6J mice fed a cholesterol/cholate diet for 3 mo had a 3-fold decrease in non-high-density lipoprotein cholesterol and a trend toward increased foam-cell lesion area compared to wild-type littermate controls. IL-1ra transgenic/low-density lipoprotein receptor (LDLR) knockout mice fed a cholesterol-saturated fat diet for 10 wk showed a 40% increase in non-high-density lipoprotein cholesterol, consistent with the IL-1ra knockout data, although there was no change in lesion size. When these IL1-ra overexpressing transgenic mice on the LDLR knockout background were fed a high-cholesterol/high-fat diet containing cholate, however, a statistically significant 40% decrease in lesion area was observed compared to LDLR knockout mice lacking the transgene. By immunohistochemistry, IL-1ra was present in C57BL/6J and LDLR knockout aortae, absent in IL-1ra knockout aortae, and present at high levels in LDLR knockout/IL-1ra transgene aortae. In summary, IL-1ra tended to increase plasma lipoprotein levels and, when fed a cholate-containing diet, decrease foam-cell lesion size. These data demonstrate that in selected models of murine atherosclerosis, chronic IL-1ra depletion or overexpression has potentially important effects on lipoprotein metabolism and foam-cell lesion development.     

Atherosclerosis progression in LDL receptor-deficient and apolipoprotein E-deficient mice is independent of genetic alterations in plasminogen activator inhibitor-1

Impaired fibrinolysis has been linked to atherosclerosis in a number of experimental and clinical studies. Plasminogen activator inhibitor type 1 (PAI-1) is the primary inhibitor of plasminogen activation and has been proposed to promote atherosclerosis by facilitating fibrin deposition within developing lesions. We examined the contribution of PAI-1 to disease progression in 2 established mouse models of atherosclerosis. Mice lacking apolipoprotein E (apoE-/-) and mice lacking the low density lipoprotein receptor (LDLR-/-) were crossbred with transgenic mice overexpressing PAI-1 (resulting in PAI-1 Tg(+)/apoE-/- and PAI-1 Tg(+)/LDLR-/-, respectively) or were crossbred with mice completely deficient in PAI-1 gene expression (resulting in PAI-1-/-/apoE-/- and PAI-1-/-/LDLR-/-, respectively). All animals were placed on a western diet (21% fat and 0.15% cholesterol) at 4 weeks of age and analyzed for the extent of atherosclerosis after an additional 6, 15, or 30 weeks. Intimal and medial areas were determined by computer-assisted morphometric analysis of standardized microscopic sections from the base of the aorta. Atherosclerotic lesions were also characterized by histochemical analyses with the use of markers for smooth muscle cells, macrophages, and fibrin deposition. Typical atherosclerotic lesions were observed in all experimental animals, with greater severity at the later time points and generally more extensive lesions in apoE-/- than in comparable LDLR-/- mice. No significant differences in lesion size or histological appearance were observed among PAI-1-/-, PAI-1 Tg(+), or PAI-1 wild-type mice at any of the time points on either the apoE-/- or LDLR-/- genetic background. We conclude that genetic modification of PAI-1 expression does not significantly alter the progression of atherosclerosis in either of these well-established mouse models. These results suggest that fibrinolytic balance (as well as the potential contribution of PAI-1 to the regulation of cell migration) plays only a limited role in the pathogenesis of the simple atherosclerotic lesions observed in the mouse.     

Impaired superoxide production due to a deficiency in phagocyte NADPH oxidase fails to inhibit atherosclerosis in mice

Superoxide, the reduced form of molecular oxygen, has been implicated in the genesis of vascular disease. One potential mechanism involves oxidation of low density lipoprotein into an atherogenic particle. A second involves reaction with nitric oxide to generate peroxynitrite, a highly oxidizing intermediate. A third involves regulation of signal transduction in artery wall cells. One well-characterized pathway for superoxide production resides in macrophages, the cellular hallmark of the early atherosclerotic lesion. Macrophages contain a membrane-bound NADPH oxidase that reduces oxygen to superoxide. In the current studies, we used mice that are deficient in the gp91-phox subunit of the NADPH oxidase-a model of chronic granulomatous disease (CGD)-to explore the role of superoxide in atherosclerotic vascular disease. Wild-type and CGD mice on the C57BL/6 background received a high-fat diet for 20 weeks to induce hypercholesterolemia. At the end of this period, the 2 strains of mice had comparable plasma lipid levels, and their atherosclerotic lesions were similar in size. We also crossed CGD mice with apolipoprotein E-deficient (apoE-/-) mice to generate spontaneously hypercholesterolemic animals that lacked functional NADPH oxidase. After 24 weeks, the CGD-apoE-/- animals had lower plasma cholesterol and triglyceride levels than did the apoE-/- animals, but there was no difference in the extent of atherosclerotic plaque. Our findings suggest that superoxide generated by the NADPH oxidase of phagocytes does not promote atherosclerosis in mice with either diet-induced or genetic forms of hypercholesterolemia.     

Association of a Vcam1 mutation with atherosclerosis susceptibility in diet-induced models of atherosclerosis

We previously identified a G>A single nucleotide polymorphism (SNP) between C57BL/6J (B6) and C3H/HeJ (C3H) mouse strains at position 2077 in the coding region of Vcam1 that leads to substitution of an amino acid from aspartic acid (D) to asparagine (N) in the protein product. In the present study, we investigated the association of this SNP with atherosclerosis susceptibility using a panel of inbred mouse strains, a set of recombinant inbred (RI) strains derived from B6 and C3H mice, and a cohort of F2 mice derived from B6 and C3H apolipoprotein E-deficient (apoE(-/-)) mice. Inbred strain analysis revealed that mouse strains with the B6 Vcam1 genotype developed significantly larger atherosclerotic lesions than strains with the C3H genotype (4622+/-2816 microm(2)/section versus 362+/-697 microm(2)/section; P=0.029). BXH RI strains with the B6 Vcam1 genotype also developed larger atherosclerotic lesions than those with the C3H genotype (8305+/-9031 microm(2)/section versus 2139+/-2931 microm(2)/section) although the difference was not statistically significant (P=0.13). In contrast, no association was detected between Vcam1 and atherosclerotic lesion size in F2 mice. The present data indicate that the G>A mutation of Vcam1 is associated with atherosclerotic lesion formation in the dietary but not apoE(-/-) models of atherosclerosis and this association suggests a role for the Vcam1 gene in influencing atherosclerosis susceptibility.     

Mouse models of C. pneumoniae infection and atherosclerosis

Mouse models were used to determine whether Chlamydia pneumoniae establishes chronic infection of the aorta and contributes to atherogenesis. Persistent infection of the aorta occurred in 11 of 31 hyperlipidemic apolipoprotein E-deficient (apoE(-/-)) mice but not in C57BL/6J mice fed a normal diet after a single inoculation and in both models following repeated inoculation with C. pneumoniae. Repeated inoculation of C57BL/6J mice resulted in inflammatory changes in the heart and aorta in 8 of 40 of mice; however, no atherosclerotic lesion development was observed. Repeated inoculation of apoE(-/-) mice resulted in a statistically significant increase in lesion area (n=43; P=.05). Although Chlamydia trachomatis disseminated to the aorta, persistent infection was not established and no statistically significant increase in lesion area occurred. These studies suggest that persistent infection of the aorta can lead to inflammatory changes in the absence of hyperlipidemia and accelerate lesion progress in concert with hyperlipidemia.     

Ontogenetic development and spatial distribution of the ileal apical sodium-dependent bile acid transporter and the ileal lipid-binding protein in apoE knockout and C57BL/6 mice

BACKGROUND: Although apoE-/- mice are characterized by hypercholesterolemia, the bile acid enterohepatic circulation, which plays a crucial role in cholesterol homeostasis, has not been examined in these mice. The differences between apoE-/- and C57BL/6 mice in expression of the ileal ASBT and ILBP and in intestinal bile acid absorption were studied. METHODS: The intestinal tissues of the fetal, neonatal and post-weaning mice were processed for immunohistochemistry. Body retention and fecal excretion of 75SeHCAT were measured. The bile acid pool size and its composition were analysed by HPLC. RESULTS: In apoE-/- and C57BL/6 mice, the bile acid pool size was 75 +/- 13 and 78 +/- 13 micromol/ 100 g body weight, respectively, while the ratio of cholic acid/beta-muricholic acid was 1.8 +/- 0.3 and 1.4 +/- 0.3 (P < 0.05), respectively. The daily body retention of 75SeHCAT was 48% = 1.8% in C57 black mice and 58.4% +/- 2.7% in apoE-/- mice (P < 0.05). In both mouse strains, ASBT expression in the small intestine was found in the near-term fetal and post-weaning mice, while ILBP expression was found in all postnatal mice. In the post-weaning mice, ILBP expression was limited to the distal 25%-30% of the small intestine, while ASBT expression was limited to the distal 18%. CONCLUSIONS: The bile acid enterohepatic circulation in apoE-/- mice probably does not differ greatly from that in C57BL/6 mice.     

Increased atherosclerosis in ApoE and LDL receptor gene knock-out mice as a result of human cholesteryl ester transfer protein transgene expression

The plasma cholesteryl ester transfer protein (CETP) plays a major role in the catabolism of HDL cholesteryl ester (CE). CETP transgenic mice have decreased HDL cholesterol levels and have been reported to have either increased or decreased early atherosclerotic lesions. To evaluate the impact of CETP expression on more advanced forms of atherosclerosis, we have cross-bred the human CETP transgene into the apoE knock-out (apoE0) background with and without concomitant expression of the human apo A-I transgene. In this model the CETP transgene is induced to produce plasma CETP levels 5 to 10 times normal human levels. CETP expression resulted in moderately reduced HDL cholesterol (34%) in apoE0 mice and markedly reduced HDL cholesterol (76%) in apoE0/apoA1 transgenic mice. After injection of radiolabeled HDL CE, the CETP transgene significantly delayed the clearance of CE radioactivity from plasma in apoE0 mice, but accelerated the clearance in apoE0/apoA1 transgenic mice. ApoE0/CETP mice displayed an increase in mean atherosclerotic lesion area on the chow diet (approximately 2-fold after 2 to 4 months, and 1.4- to 1.6-fold after 7 months) compared with apoE0 mice (P<0.02). At 7 months apoA1 transgene expression resulted in a 3-fold reduction in mean lesion area in apoE0 mice (P<0.001). In the apoE0/apoA1 background, CETP produced an insignificant 1.3- to 1.7-fold increase in lesion area. In further studies the CETP transgene was bred onto the LDL receptor knock-out background (LDLR0). After 3 months on the Western diet, the mean lesion area was increased 1.8-fold (P<0.01) in LDLR0/CETP mice, compared with LDLR0 mice. These studies indicate that CETP expression leads to a moderate increase in atherosclerosis in apoE0 and LDLR0 mice, and suggest a proatherogenic effect of CETP activity in metabolic settings in which clearance of remnants or LDL is severely impaired. However, apoA1 overexpression has more dramatic protective effects on atherosclerosis in apoE0 mice, which are not significantly reversed by concomitant expression of CETP.