Effect of aspirin and ticlopidine on platelet deposition in carotid atherosclerosis: assessment by indium-111 platelet scintigraphy

The antiplatelet effects of aspirin and ticlopidine were studied by a dual-tracer method, using indium-111 labeled platelets and technetium-99m human serum albumin, in a group of 12 patients with suspected ischemic cerebrovascular disease. The magnitude of platelet accumulation at the carotid bifurcation was expressed as the ratio of radioactivity of indium-111 platelets deposited on the vascular wall to those circulating in the blood-pool (PAI, platelet accumulation index), 48 hr after injection of labeled platelets. PAI values were measured before (baseline studies) and after the antithrombotic therapies (aspirin studies: 325 mg bid for 22.3 +/- 1.3 days, ticlopidine studies: 100 mg tid for 21.8 +/- 2.1 days). At the baseline, the mean PAI value at 24 carotid bifurcations in the patient group was 15.7 +/- 15.3% (mean +/- S.D.) compared to -4.3 +/- 9.1 at 24 carotid bifurcations in 12 normal subjects (p less than 0.01). We defined the upper limit for a normal PAI (%) value to be +13.9, namely the mean PAI plus 2 SD for the carotid bifurcation in normal subjects and used this value for semiquantitative analysis. At the baseline, significant elevation of PAI (more than 13.9%; positive scintigram) was observed at 12 of 24 vessels, while 12 other regions were negative (less than 13.9%). In the lesions with positive scintigraphic results at the baseline, the mean PAI (%) value from the baseline, aspirin and ticlopidine studies was 29.5 +/- 7.0, 11.2 +/- 8.5 (p less than 0.01 versus baseline) and 21.4 +/- 21.3 (not significant from baseline), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Suppressing thrombin generation is compatible with the development of atherosclerosis in mice

Thrombin has been proposed to play a key role in the development of atherosclerosis, both by promoting fibrin deposition into the atherosclerotic vessel wall and also by signalling through thrombin receptors. Unfortunately, mice homozygous for a deletion of the prothrombin gene (FII) die in utero, making a direct assessment of the role of thrombin during atherogenesis difficult. We have assessed the contribution of thrombin-dependent processes to vascular lipid lesion formation in the atherosclerosis-prone apolipoprotein E (ApoE)-deficient mice by inhibiting thrombin generation with warfarin. ApoE-/- mice were treated with warfarin at a dose that increased the prothrombin time (PT) more than 10-fold (250-375 microg/kg body weight/day) for 12 weeks from the age of 12 weeks onwards. The extent and composition of the vascular lipid lesions that developed were assessed using oil red O to measure neutral lipid in the vessel wall and quantitative immunofluoresence to measure fibrin(ogen) levels as well as macrophage and smooth muscle cell numbers. Mice treated with warfarin developed lesions both in the aortic sinus and the descending aorta to the same degree as mice receiving no treatment (28,351+/-350 microm2/mouse treated with warfarin versus 27,952+/-750 micro2/control mouse; P = .86). However, the amount of fibrin(ogen) deposited in the vessel wall was decreased by more than 60% (34+/-11 arbitrary units in warfarin treated mice versus 92+/-11 arbitrary units in control mice; P < .01). Staining of macrophage and for smooth muscle cell markers was unaltered by treatment with warfarin. We conclude that suppressing thrombin generation does not alter the development of vascular lipid lesions in mice with a severe disorder of lipid metabolism, despite a marked reduction in fibrin(ogen) deposition.     

Degradation of the endothelial glycocalyx is associated with chylomicron leakage in mouse cremaster muscle microcirculation

A thick endothelial glycocalyx contributes to the barrier function of vascular endothelium in macro- and microcirculation. We hypothesised in the current study that diet-induced hyperlipidaemia perturbs the glycocalyx, resulting in decreased dimensions of this layer and increased transendothelial lipoprotein leakage in capillaries. Glycocalyx thickness was measured in mouse cremaster muscle capillaries by intravital microscopy from the distance between flowing red blood cells and the endothelial surface. In control C57BL/6 mice on standard chow, glycocalyx thickness measured 0.58 ± 0.01 (mean ± SEM) μm, and no lipoproteins were observed in the tissue. After three months administration of an either mild or severe high-fat / high-cholesterol diet (HFC) to C57BL/6 and ApoE3-Leiden mice, circulating large lipoproteins appeared into the subendothelial space in an increasing proportion of cremaster capillaries, and these capillaries displayed reduced glycocalyx dimensions of 0.40 ± 0.02 and 0.30 ± 0.01 μm (C57BL/6 mice), and 0.37 ± 0.01 and 0.28 ± 0.01 μm (ApoE3-Leiden mice), after the mild and severe HFC diet, respectively. The chylomicron nature of the accumulated lipoproteins was confirmed by observations of subendothelial deposition of DiI-labeled chylomicrons in capillaries after inducing acute glycocalyx degradation by heparitinase in normolipidaemic C57BL/6 mice. It is concluded that while under control conditions the endothelial glycocalyx contributes to the vascular barrier against transvascular lipoprotein leakage in the microcirculation, diet-induced hyperlipidaemia reduces the thickness of the glycocalyx, thereby facilitating leakage of chylomicrons across the capillary wall.     

Reproducibility of noninvasive ultrasonic measurement of carotid atherosclerosis. The Asymptomatic Carotid Artery Plaque Study.

BACKGROUND AND PURPOSE: To determine the effect of a lipid-lowering agent and/or a low-dose antithrombotic agent on the progression of early-stage carotid atherosclerosis, noninvasive B-mode ultrasound was used to measure intimal-medial thickness in asymptomatic individuals with moderately elevated lipids as part of the ongoing multicenter Asymptomatic Carotid Artery Plaque Study. METHODS: Uniform ultrasonic scanning and reading protocols were implemented to obtain maximum intimal-medial thickness measurements in 12 standard segments in patients having a small to moderate wall thickness (1.5-3.5 mm) in at least one of the carotid arteries. Paired B-mode image recordings on 858 patients, performed 1 month apart and read at a core laboratory (each pair by the same reader), determined both within-sonographer (W, n = 405) and between-sonographer (B, n = 453) reproducibility. RESULTS: The primary end point (mean +/- SD), defined in each individual as the mean value of the 12 maximum intimal-medial thickness measurements, was 1.31 +/- 0.21 mm (W) and 1.32 +/- 0.22 (B) at the time of the second examination. The mean difference in the primary end point (exam 2-exam 1) was -0.01 +/- 0.13 mm (W) and 0.00 +/- 0.15 mm (B). The Pearson correlation coefficients were 0.79 (W) and 0.75 (B). In 90% of the patients, the absolute difference in the primary end point was less than 0.22 mm (W) and less than 0.24 mm (B). Variability of the secondary end point, defined as the single largest intimal-medial thickness measurement in a patient, was between three and four times larger than the variability for the primary end point. Differences in sonographer performance between clinical centers were very small. CONCLUSIONS: The results demonstrate that standardized noninvasive ultrasonic techniques yield highly reproducible measures of carotid intimal-medial thickness, which can serve as a measure of carotid atherosclerosis in clinical trials that monitor small rates of lesion progression.     

Platelet-vessel wall interactions with third-generation oral contraceptives: no evidence of detrimental effects.

Because of the association of oral contraceptives (OC) and cigarette smoking with an increased thrombotic risk, we evaluated thromboxane (TX) and prostacyclin urinary (u) metabolites, as in vivo indices of platelet-vessel wall interactions, in women assigned to third generation OC. Twenty-eight women (15 smokers) underwent a 6-month trial of 30 microg ethinylestradiol plus 0.150 mg desogestrel. Cotinine plasma levels were elevated only in persons classified as smokers and serum TXB2 determination confirmed the absence of cyclooxygenase inhibition throughout the study. u-TXB2 and 11-dehydro-TXB2 were higher in smokers than in non-smokers. OC decreased u-11-dehydro-TXB2 both in smokers (from (pg/micromol creatinine) 35.1+/-6.9 to 15.8+/-2.8; P<0.025) and non-smokers (from 31.7+/-9.8 to 20.6+/-4.8, P = N.S.). u-6-keto-prostaglandin(PG)F1alpha excretion, also higher in smokers compared to non-smokers, was also reduced after OC in smokers (from (pg/micromol creatinine) 24.3+/-5.2 to 14.8+/-2.3; P<0.05). Smokers also had a trend to higher u-2,3-dinor-6-keto-PGF1alpha, marginally reduced by OC. Thus, the OC regimen used here improves - if anything - platelet vessel wall interactions as assessed by prostanoid production in vivo. The prothrombotic tendency associated with the use of OC in smokers does not appear to be mediated by changes in platelet-vessel wall interactions.     

Elimination of platelet factor 4 (PF4) from platelets reduces atherosclerosis in C57Bl/6 and apoE-/- mice

Activated platelets, which release platelet factor 4 (PF4) are present in patients with atherosclerosis. To date, no direct in-vivo evidence exists for the involvement of PF4 in atherogenesis. In the current study, we tested the hypothesis that PF4 is atherogenic, and that genetic elimination of PF4 would protect mice from atherosclerosis. We have bred PF4(-/-) mice onto two athero-susceptible backgrounds, WT-C57Bl/6(WT) and apoE(-/-) to examine the importance of PF4 in atherogenesis. In order to induce atherosclerosis, WT and PF4(-/-) mice were fed an atherogenic diet for 30 weeks, while apoE(-/-) and apoE(-/-) PF4(-/-) mice were fed a high-fat Western-style diet for 10 weeks. Examination of lesions in the aortic roots of atherogenic diet fed mice demonstrated reduced atherosclerosis in PF4(-/-) (20% compared to WT). Examination of apoE(-/-) mice demonstrated similar changes, with apoE(-/-) PF4(-/-) mice demonstrating 37% of the aortic atherosclerotic burden compared to apoE(-/-) mice. Although we found similar levels of total and non-HDL cholesterol in WT and PF4(-/-) mice, HDL-cholesterol levels were increased in PF4(-/-) on both backgrounds. These data demonstrate, for the first time, that the platelet specific chemokine PF4 promotes atherosclerotic lesion development in vivo.     

Microvascular platforms for the study of platelet-vessel wall interactions

Platelets interact with the endothelium to regulate vascular integrity and barrier function, mediate inflammation and immune response, and prevent and arrest hemorrhage. In this review, we describe existing tools to study the flow-dependent interactions of platelets with the vessel wall. We also discuss our work on building engineered microvessels to study the roles of platelets on endothelial barrier function, endothelial sprouting, and thrombus formation on both quiescent and stimulated endothelium. In particular, we will show the advantage of using a cell-remodelable system in the studies of platelet-vessel wall interactions.     

Role of P2X4 receptors in synaptic strengthening in mouse CA1 hippocampal neurons

P2X4 receptors are calcium-permeable cation channels gated by extracellular ATP. They are found close to subsynaptic sites on hippocampal CA1 neurons. We compared features of synaptic strengthening between wild-type and P2X4 knockout mice (21-26 days old). Potentiation evoked by a tetanic presynaptic stimulus (100 Hz, 1 s) paired with postsynaptic depolarization was less in P2X4(-/-) mice than in wild-type mice (230 vs. 50% potentiation). Paired-pulse ratios and the amplitude and frequency of spontaneous excitatory postsynaptic currents (EPSCs) were not different between wild-type and knockout mice. Prior hyperpolarization (ten 3 s pulses to -120 mV at 0.17 Hz) potentiated the amplitude of spontaneous EPSCs in wild-type mice, but not in P2X4(-/-) mice; this potentiation was not affected by nifedipine, but was abolished by 10 mM 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid (BAPTA) in the recording pipette. The amplitude of N-methyl-d-aspartate EPSCs (in 6-cyano-7-nitroquinoxaline-2,3-dione, 10 or 30 μm, at -100 mV) facilitated during 20 min recording in magnesium-free solution. In wild-type mice, this facilitation of the N-methyl-d-aspartate EPSC was reduced by about 50% by intracellular BAPTA (10 mM), ifenprodil (3 μm) or 4-(4-fluorophenyl)-2-(4-methylsulphinylphenyl)-5-(4-pyridyl)1H-imidazole (5 μm). In P2X4(-/-) mice, the facilitation was much less, and was unaffected by intracellular BAPTA, ifenprodil (3 μm) or mitogen-activated protein (MAP) kinase inhibitor 4-(4-fluorophenyl)-2-(4-methylsulphinylphenyl)-5-(4-pyridyl)1H-imidazole (5 μm). This suggests that the absence of P2X4 receptors limits the incorporation of NR2B subunits into synaptic N-methyl-d-aspartate receptors.     

NG-monomethyl-L-arginine increases platelet deposition on damaged endothelium in vivo. A scanning electron microscopic study.

There is increasing evidence that nitric oxide (NO) synthetized in vascular endothelium and in platelets by NO synthase influences vascular tone, down regulates platelet function and platelet-vessel wall interaction both in vitro and in vivo. We investigated the effect of a NO synthase inhibitor, NG-mono-methyl-L-arginine (L-NMMA, 100 mg/kg iv) on platelet-endothelial cell interaction in rabbit arteries ex vivo using scanning electron microscope (SEM). The effect of L-NMMA was examined on intact endothelium and on that damaged by arterial constriction. The infusion of L-NMMA increased systemic blood pressure and decreased carotid blood flow, however, it did not change the appearance of an intact endothelium and did not result in platelet activation on intact endothelial cells. In contrast, SEM of endothelial areas damaged by constriction showed extensive platelet adhesion and aggregation on subendothelium. These morphological changes were not detected in control animals with intact or damaged by arterial constriction endothelium. These results show that under physiological conditions, the inhibition of NO synthase alone does not result in platelet activation in vivo. However, when combined with endothelial injury it may lead to platelet activation and thrombosis.     

Rosuvastatin exerts favourable effects on thrombosis and neointimal growth in a mouse model of endothelial injury

Apart from reducing systemic lipid levels, statins may improve the clinical course of atherosclerosis by exerting favourable pleiotropic effects on the vessel wall. We studied the effects of rosuvastatin, a new, potent 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, on vascular remodelling after endothelial injury in the hyperlipidaemic apolipoprotein E-knockout (apoE-/-) mouse. ApoE-/- mice, 22-weeks-old, were injected daily with rosuvastatin at a low (1 mg/kg; n=27) or high dosage (10 mg/kg; n=24), or with vehicle alone (n=26). After treatment for 2 weeks, endothelial injury and thrombosis of the carotid artery was induced with 10% ferric chloride. Treatment was then resumed for a 3-week period. Although statin treatment did not affect the plasma lipid levels of mice, mean times to arterial thrombosis were prolonged in the low-dose and the high-dose group compared to controls (P<0.05 and P<0.01 respectively). Interestingly, rosuvastatin withdrawal 4 days before injury completely reversed the antithrombotic effects of the drug. In follow-up studies 3 weeks after injury, deposition of fibrin in the vessel wall was significantly reduced in the rosuvastatin-treated animals. There was an increase in the content of alpha-actin-positive smooth muscle cells (P=0.008) and collagen fibers (P<0.001), and a concomitant decrease in the number of oxLDL-containing macrophages (P<0.001). Overall, the neointimal area and the severity of luminal stenosis were significantly reduced in statin-treated mice. Thus, rosuvastatin attenuates arterial thrombosis and neointima formation, and it may stabilise vascular lesions developing after endothelial injury in mice. These effects are independent of systemic lipid lowering.     

Interaction of thrombin-stimulated platelets with vitronectin (S-protein of complement) substrate: inhibition by a monoclonal antibody to glycoprotein IIb-IIIa complex

Platelets adhere to vitronectin substrate following activation with physiological concentrations of thrombin. Adhesion of activated platelets to vitronectin substrate is dependent upon the presence of divalent cations, the amount of vitronectin, and the duration of adhesion assay. The adhesion of platelets is inhibited by synthetic peptides containing the sequence of Arg-Gly-Asp. In addition, monoclonal antibodies to glycoprotein IIb-IIIa complex inhibit the adhesion of activated platelets to vitronectin substrate in a dose-dependent manner. These studies suggest that the glycoprotein IIb-IIIa complex on activated platelets may interact with vitronectin substrate through the Arg-Gly-Asp mechanism. Since vitronectin is present in the subendothelial matrix, it might be involved in platelet-vessel wall interactions.     

Differential susceptibity of transgenic mice lacking one or both apolipoprotein alleles to folate and vitamin E deprivation

The E4 allele of apolipoprotein E (ApoE) is associated with neurodegeneration in part due to increased oxidative stress. Transgenic mice lacking ApoE (-/-) represent a model for the consequences of deficiencies in ApoE function. Dietary deficiency in folate and vitamin E has previously been shown to potentiate the impact of ApoE deficiency; ApoE-/- mice deprived of folate and vitamin E for 1 month demonstrated increased oxidative damage in brain tissue and impaired cognitive performance as compared to ApoE+/+ mice. Since individuals homozygous for E4 can demonstrate more increased risk for neurodegeneration and an earlier age of onset than individuals heterozygous for E4, we tested the impact of folate and vitamin E deprivation on ApoE+/- mice. Thiobarbituric acid-reactive substances in brain tissue of ApoE+/- were significantly increased compared to ApoE+/+ mice, but this increase was less than that observed in ApoE-/- mice. By contrast, livers of ApoE+/- and -/- mice displayed an identical increase over that of +/+ mice. ApoE-/- mice, but not +/- or +/+ mice, exhibited impaired cognitive performance in maze trials when deprived of folate and vitamin E. These findings support the notion that homozygous deficiency of ApoE function can be more severe than heterozygous deficiency. They further suggest that the impact of partial deficiency in ApoE function may present a latent risk that may manifest only when compounded by other factors such as dietary deficiency.     

Membrane fluidity and thromboxane synthesis in platelets from patients with severe atherosclerosis

Platelets play an important role in the development of atherosclerosis. The arachidonic acid, whose oxygenated metabolites are potent regulators of the platelet-vessel wall interactions, is released from membrane phospholipids by the phospholipase (s) system (s). These membrane-linked phenomena are strongly modulated by the membrane physical properties. The present study was carried out to investigate the relationship between membrane fluidity and arachidonic acid metabolism in platelets from atherosclerotic patients. Twenty-one patients with peripheral vascular disease and twelve controls were studied. Platelets from patients showed an increase in membrane fluidity and enhanced thrombin-stimulated thromboxane synthesis. No alterations were found, however, in total phospholipid fatty acid composition. A significant decrease in the cholesterol/phospholipid ratio could account for the alterations in the membrane physical properties described in the platelets from patients.     

Relationship between the concentration of antibodies to myosin heavy chains in serum and symptomatic carotid atherosclerosis

It is believed that atherosclerosis could result from inflammatory-fibroproliferative response to various forms of injury of endothelium and smooth muscle cells of arterial wall. The aim of this study was to examine whether immunological reaction against myosin filaments of carotid artery (CA) wall smooth muscle cells is involved in atherogenesis. 43 patients (22 females) with first-ever ischaemic stroke proven by CT were investigated. The results were compared with those obtained in 40 (21 females) healthy sex- and age-matched subjects. Anti-myosin antibodies (AMA) were evaluated by solid phase radioimmunoassay using rabbit myosin heavy chains as an antigen. The intima-media thickness (IMT) of common and CA--a measure for atherosclerosis--was estimated with the use of high-resolution ultrasonography. The AMA serum concentration in stroke patients was significantly greater than in control subjects (p < 0.001). Mean IMT for CA in stroke patients was significantly increased compared with the controls (0.98 +/- 0.17 mm vs. 0.68 +/- 0.13 mm; p < 0.0001). There was a significant correlation between AMA serum antibodies concentration and IMT (r = 0.51; p < 0.001). CONCLUSION: The significant correlation between AMA concentration and IMT of CA is the basis of the hypothesis that immunological reaction against myosin heavy chains of smooth muscle cells in CA is involved in atherogenesis.     

The reduction of platelet thrombi on damaged vessel wall by a thromboxane synthetase inhibitor in rabbits

The role of thromboxane A₂ (TXA₂) in platelet-vessel wall interaction was investigated using 1-benzylimidazole (1-BI), a selective thromboxane synthetase inhibitor. 1-BI (0.9 mM) will reduce the aggregatory response of rabbit platelets to 0.2 mM arachidonate by 50% and their production of TXA₂ by 84%. The effect of 1-BI on platelet thrombus formation was evaluated in vivo on New Zealand white male rabbits using the autologous indium-111 labeled platelet technique. After injection of autologous ¹¹¹In-platelets, 10 cm of the abdominal aorta was de-endothelialized with a balloon catheter. Three hours later the animals were sacrificed and injured and uninjured segments of the aorta removed. The radioactivity and dry weight of the tissue were determined. The radioactivity/gm of tissue was greater for the injured tissue than for the uninjured tissue. 1-BI at 10 mg/kg reduced the specific platelet accumulation at the injured site (n=5; 4.8 ± 0.3 × 10⁵ cpm/gm) compared to the controls (n=10; 11.7 ± 2.1 × 10⁵ cpm/gm). Platelet accumulation on the injured tissue was further reduced by increasing the dosage to 30 mg/kg. Thirty minutes after 1-BI administration (30 mg/kg), platelets were less sensitive to arachidonate-induced aggregation (a 67% decrease) and TXA₂ production was decreased 82%. Alterations in platelet sensitivity persisted for up to 3 hours. These findings indicate that TXA₂ plays an important role in platelet-vessel wall interaction.     

牛磺酸治疗高同型半胱氨酸脑梗死患者动脉粥样硬化的临床观察

目的 探讨牛磺酸对高同型半胱氨酸脑梗死患者动脉粥样硬化的治疗作用. 方法选择自2006年9月至2006年12月哈尔滨医科大学附属第一医院神经内科住院的40例高同型半胱氨酸脑梗死患者,按随机数字表法分为牛磺酸治疗组和叶酸、维生素治疗组,相应的药物治疗6个月.治疗前后分别检查颈动脉彩超,观察颈动脉内膜中层厚度(IMT)和斑块变化情况,采血分离血清,采用高压液相色谱分析仪及相应试剂盒测定血浆同型半胱氨酸水平. 结果经治疗6个月后,叶酸、维生素组颈动脉IMT平均厚度减小0.372 mm,牛磺酸治疗组减小0.551 mm,两组在治疗前后颈动脉IMT比较差异均有统计学意义(P<0.05),且牛磺酸治疗组对颈动脉IMT的控制要优于叶酸、维生素治疗组,差异有统计学意义(P<0.05).牛磺酸治疗组治疗前后血浆同型半胱氨酸水平[(29.832±7.750)μmol/Lvs(19.316±2.240)μmol/L]比较差异有统计学意义(P<0.05). 结论牛磺酸对高同型半胱氨酸脑梗死患者动脉粥样硬化的治疗有效且优于叶酸、维生素,并对血浆同型半胱氨酸水平有控制作用.     

基质金属蛋白酶-3基因多态与颈动脉斑块稳定性的关系

目的 探讨基质金属蛋白酶-3(matrix metalloproteinase-3,MMP-3)血清水平及启动子基因5A/6A多态与颈动脉斑块稳定性的关系.方法 280例急性脑梗死患者根据颈动脉超声结果 分为颈动脉易损斑块组(124例)和颈动脉稳定斑块组(156例).采用ELISA法测定两组患者的血清MMP-3水平,同时采用聚合酶链反应-限制性片段长度多态性(PCR-RFLP)方法分析MMP-3启动子基因5A/6A多态性.结果 易损斑块组发病48 h内的血清MMP-3水平为(23.8±8.3)ng/μl,而稳定斑块组为(20.0±10.0)ng/μl(t=3.39,P=0.00).易损斑块组5A/6A+5A/5A基因型频率为39.5%,稳定斑块组为25.6%,两者比较差异有统计学意义(χ2=6.13,P:0.01,DR=1.90,95%CI,1.14～3.15),5A等位基因频率在易损斑块组为20.6%,稳定斑块组为12.8%,两者比较差异也有统计学意义(χ2=6.09,P=0.01,DR=1.76,95%CI 1.12～2.77).结论 MMP-3血清水平及启动子基因5A/6A多态性可能与中国汉族人群颈动脉易损斑块发生的倾向性有关,5A等位基因可能是颈动脉易损斑块的遗传易患标志之一.     

Differential effects of lovastatin treatment on brain cholesterol levels in normal and apoE-deficient mice

Growing evidence indicates that membrane cholesterol is involved in the development of Alzheimer's disease. Therefore, the availability of pharmacological strategies to modify brain cholesterol is of increasing importance. Accordingly, we investigated the effects of the HMG-CoA reductase inhibitor lovastatin on brain cholesterol levels in vivo. Brain cholesterol was significantly decreased by lovastatin treatment (100 mg/kg/day) in 1- and 12-month-old C57BL/6J mice. Reduced brain cholesterol was associated with decreased pyrene-excimer fluorescence, indicating altered membrane function. Lovastatin had no effect on brain cholesterol ApoE-/- mice. Peripheral cholesterol levels were not affected by lovastatin in all three groups of mice. We demonstrate for the first time that lovastatin represents a valid pharmacological tool to significantly modulate brain cholesterol levels.