Regional brain shrinkage over two years: individual differences and effects of pro-inflammatory genetic polymorphisms.

We examined regional changes in brain volume in healthy adults (N=167, age 19-79years at baseline; N=90 at follow-up) over approximately two years. With latent change score models, we evaluated mean change and individual differences in rates of change in 10 anatomically-defined and manually-traced regions of interest (ROIs): lateral prefrontal cortex (LPFC), orbital frontal cortex (OF), prefrontal white matter (PFw), hippocampus (Hc), parahippocampal gyrus (PhG), caudate nucleus (Cd), putamen (Pt), insula (In), cerebellar hemispheres (CbH), and primary visual cortex (VC). Significant mean shrinkage was observed in the Hc, CbH, In, OF, and PhG, and individual differences in change were noted in all regions, except the OF. Pro-inflammatory genetic variants modified shrinkage in PhG and CbH. Carriers of two T alleles of interleukin-1ß (IL-1ß C-511T, rs16944) and a T allele of methylenetetrahydrofolate reductase (MTHFR C677T, rs1801133) polymorphisms showed increased PhG shrinkage. No effects of a pro-inflammatory polymorphism for C-reactive protein (CRP-286C>A>T, rs3091244) or apolipoprotein (APOE) ε4 allele were noted. These results replicate the pattern of brain shrinkage observed in previous studies, with a notable exception of the LPFC, thus casting doubt on the unique importance of prefrontal cortex in aging. Larger baseline volumes of CbH and In were associated with increased shrinkage, in conflict with the brain reserve hypothesis. Contrary to previous reports, we observed no significant linear effects of age and hypertension on regional brain shrinkage. Our findings warrant further investigation of the effects of neuroinflammation on structural brain change throughout the lifespan.

A (Sub)field Guide to Quality Control in Hippocampal Subfield Segmentation on Highresolution T2-weighted MRI.

Inquiries into properties of brain structure and function have progressed due to developments in magnetic resonance imaging (MRI). To sustain progress in investigating and quantifying neuroanatomical details in vivo, the reliability and validity of brain measurements are paramount. Quality control (QC) is a set of procedures for mitigating errors and ensuring the validity and reliability of brain measurements. Despite its importance, there is little guidance on best QC practices and reporting procedures. The study of hippocampal subfields in vivo is a critical case for QC because of their small size, inter-dependent boundary definitions, and common artifacts in the MRI data used for subfield measurements. We addressed this gap by surveying the broader scientific community studying hippocampal subfields on their views and approaches to QC. We received responses from 37 investigators spanning 10 countries, covering different career stages, and studying both healthy and pathological development and aging. In this sample, 81% of researchers considered QC to be very important or important, and 19% viewed it as fairly important. Despite this, only 46% of researchers reported on their QC processes in prior publications. In many instances, lack of reporting appeared due to ambiguous guidance on relevant details and guidance for reporting, rather than absence of QC. Here, we provide recommendations for correcting errors to maximize reliability and minimize bias. We also summarize threats to segmentation accuracy, review common QC methods, and make recommendations for best practices and reporting in publications. Implementing the recommended QC practices will collectively improve inferences to the larger population, as well as have implications for clinical practice and public health.

Disruption of the cathepsin K gene reduces atherosclerosis progression and induces plaque fibrosis but accelerates macrophage foam cell formation.

BACKGROUND: Cathepsin K (catK), a lysosomal cysteine protease, was identified in a gene-profiling experiment that compared human early plaques, advanced stable plaques, and advanced atherosclerotic plaques containing a thrombus, where it was highly upregulated in advanced stable plaques. METHODS AND RESULTS: To assess the function of catK in atherosclerosis, catK(-/-)/apolipoprotein (apo) E(-/-) mice were generated. At 26 weeks of age, plaque area in the catK(-/-)/apoE(-/-) mice was reduced (41.8%) owing to a decrease in the number of advanced lesions as well as a decrease in individual advanced plaque area. This suggests an important role for catK in atherosclerosis progression. Advanced plaques of catK(-/-)/apoE(-/-) mice showed an increase in collagen content. Medial elastin fibers were less prone to rupture than those of apoE(-/-) mice. Although the relative macrophage content did not differ, individual macrophage size increased. In vitro studies of bone marrow derived-macrophages confirmed this observation. Scavenger receptor-mediated uptake (particularly by CD36) of modified LDL increased in the absence of catK, resulting in an increased macrophage size because of increased cellular storage of cholesterol esters, thereby enlarging the lysosomes. CONCLUSIONS: A deficiency of catK reduces plaque progression and induces plaque fibrosis but aggravates macrophage foam cell formation in atherosclerosis.

Enhanced development of atherosclerosis in cholesterol-fed rabbits by suppression of cell-mediated immunity.

T lymphocytes are present in atherosclerotic lesions, but the role of this cell type in the disease process has not been determined. To determine whether cell-mediated immunity influences atherogenesis, New Zealand White rabbits fed a cholesterol-supplemented diet (0.5% wt/wt) were treated with cyclosporin A (n = 20) or vehicle alone (n = 16) for 12 wk. The dose of cyclosporin A was adjusted so that a blood concentration between 100 and 200 ng/ml was maintained to achieve a selective action T-lymphocytes. Effectiveness of immunosuppression in cyclosporin A-treated rabbits was confirmed by allogeneic skin graft survival. Cyclosporin A administration did not affect total plasma lipid concentrations, body weight, or renal function. Percentage of aortic intimal area covered with atherosclerotic lesions was increased significantly by immunosuppression in both the arch region (75 +/- 3% [mean +/- SEM] compared with 60 +/- 5% in controls; P < 0.01) and the thoracic region (47 +/- 7% vs 27 +/- 6%; P = 0.04). Enhanced atherogenesis was not associated with diminished numbers of T lymphocytes in lesions, changes in T lymphocyte subtype, or any discernible change in cellular composition. Humoral immune responses to oxidized LDL were similar in the two groups: serum titres of autoantibodies against malondialdehyde-modified LDL were equivalent. These data demonstrate that cyclosporin A-induced suppression of cell-mediated immunity increased the development of macrophage-rich atherosclerotic lesions in cholesterol-fed rabbits.

Angiotensin II promotes atherosclerotic lesions and aneurysms in apolipoprotein E-deficient mice.

Increased plasma concentrations of angiotension II (Ang II) have been implicated in atherogenesis. To examine this relationship directly, we infused Ang II or vehicle for 1 month via osmotic minipumps into mature apoE(-/-) mice. These doses of Ang II did not alter arterial blood pressure, body weight, serum cholesterol concentrations, or distribution of lipoprotein cholesterol. However, Ang II infusions promoted an increased severity of aortic atherosclerotic lesions. These Ang II-induced lesions were predominantly lipid-laden macrophages and lymphocytes; moreover, Ang II promoted a marked increase in the number of macrophages present in the adventitial tissue underlying lesions. Unexpectedly, pronounced abdominal aortic aneurysms were present in apoE(-/-) mice infused with Ang II. Sequential sectioning of aneurysmal abdominal aorta revealed two major characteristics: an intact artery that is surrounded by a large remodeled adventitia, and a medial break with pronounced dilation and more modestly remodeled adventitial tissue. Although no atherosclerotic lesions were visible at the medial break point, the presence of hyperlipidemia was required because infusions of Ang II into apoE(+/+) mice failed to generate aneurysms. These results demonstrate that increased plasma concentrations of Ang II have profound and rapid effects on vascular pathology when combined with hyperlipidemia, in the absence of hemodynamic influences.

Dependence of metabolic and structural heterogeneity of cholesterol ester-rich very low density lipoproteins on the duration of cholesterol feeding in rabbits.

Cholesterol ester-rich (CER) VLDL accumulate rapidly in the plasma of rabbits fed cholesterol-enriched diets. However, the major loci of enhanced synthesis of subfractions of CER-VLDL, their interaction with macrophages, and their relative contribution to atherogenesis have not yet been elucidated. To determine whether anabolism is hepatic or intestinal, subfractions of CER-VLDL were characterized at selected intervals from day 0 to 60 of cholesterol feeding. Rate zonal ultracentrifugation of CER-VLDL from rabbits fed cholesterol for 4 and 60 d demonstrated an early increase of the proportion of cholesterol carried in the intestinally-derived fraction (designated as Fx-I) of VLDL compared with that in hepatically-derived particles (Fx-H). Quantification by size exclusion HPLC also demonstrated that Fx-I was a prominent CER-VLDL component at day 4, while Fx-H particles became increasingly prominent with further cholesterol feeding. At both 4 and 60 d Fx-I stimulated cholesterol esterification and intracellular cholesterol content in macrophages more than the corresponding Fx-H did. In fact, Fx-H harvested at 4 d produced no cholesterol ester deposition. In contrast, Fx-H harvested at 60 d markedly stimulated cholesterol esterification and intracellular cholesterol content. Thus, both compositional and metabolic characteristics of CER-VLDL changed as a function of the duration cholesterol feeding.

Myeloperoxidase, a catalyst for lipoprotein oxidation, is expressed in human atherosclerotic lesions.

Oxidatively modified lipoproteins have been implicated in atherogenesis, but the mechanisms that promote oxidation in vivo have not been identified. Myeloperoxidase, a heme protein secreted by activated macrophages, generates reactive intermediates that oxidize lipoproteins in vitro. To explore the potential role of myeloperoxidase in the development of atherosclerosis, we determined whether the enzyme was present in surgically excised human vascular tissue. In detergent extracts of atherosclerotic arteries subjected to Western blotting, a rabbit polyclonal antibody monospecific for myeloperoxidase detected a 56-kD protein, the predicted molecular mass of the heavy subunit. Both the immunoreactive protein and authentic myeloperoxidase bound to a lectin-affinity column; after elution with methyl mannoside their apparent molecular masses were indistinguishable by nondenaturing size-exclusion chromatography. Peroxidase activity in detergent extracts of atherosclerotic lesions likewise bound to a lectin column and eluted with methyl mannoside. Moreover, eluted peroxidase generated the cytotoxic oxidant hypochlorous acid (HOCl), indicating that enzymatically active myeloperoxidase was present in lesions. Patterns of immunostaining of arterial tissue with antihuman myeloperoxidase antibodies were similar to those produced by an antimacrophage antibody, and were especially prominent in the shoulder region of transitional lesions. Intense foci of myeloperoxidase immunostaining also appeared adjacent to cholesterol clefts in lipid-rich regions of advanced atherosclerotic lesions. These findings identify myeloperoxidase as a component of human vascular lesions. Because this heme protein can generate reactive species that damage lipids and proteins, myeloperoxidase may contribute to atherogenesis by catalyzing oxidative reactions in the vascular wall.

Beta-carotene inhibits atherosclerosis in hypercholesterolemic rabbits.

Oxidatively damaged LDL may be of central importance in atherogenesis. Epidemiological evidence suggests that high dietary intakes of beta-carotene and vitamin E decreases the risk for atherosclerotic vascular disease, raising the possibility that lipid-soluble antioxidants slow vascular disease by protecting LDL from oxidation. To test this hypothesis, we fed male New Zealand White rabbits a high-cholesterol diet or the same diet supplemented with either 1% probucol, 0.01% vitamin E, 0.01% all-trans beta-carotene, or 0.01% 9-cis beta-carotene; then we assessed both the susceptibility of LDL to oxidation ex vivo and the extent of aortic atherosclerosis. As in earlier studies, probucol protected LDL from oxidation and inhibited lesion formation. In contrast, vitamin E modestly inhibited LDL oxidation but did not prevent atherosclerosis. While beta-carotene had no effect on LDL oxidation ex vivo, the all-trans isomer inhibited lesion formation to the same degree as probucol. Moreover, all-trans beta-carotene was undetectable in LDL isolated from rabbits fed the compound, although tissue levels of retinyl palmitate were increased. The effect of all-trans beta-carotene on atherogenesis can thus be separated from the resistance of LDL to oxidation, indicating that other mechanisms may account for the ability of this compound to prevent vascular disease. Our results suggest that metabolites derived from all-trans beta-carotene inhibit atherosclerosis in hypercholesterolemic rabbits, possibly via stereospecific interactions with retinoic acid receptors in the artery wall.

Metabolism of very low density lipoproteins after cessation of cholesterol feeding in rabbits. A factor potentially contributing to the slow regression of atheromatous plaques.

Aortic atheromatous plaques regress slowly in cholesterol-fed rabbits that have been returned to normal laboratory diet. To delineate metabolic factors potentially responsible for persistence of atherosclerosis under these conditions, the physical, chemical, and metabolic characteristics were determined for lipoproteins of d less than 1.006 g/ml; such lipoproteins are thought to be the major determinant of progression of atherosclerotic lesions in cholesterol-fed rabbits. At the time of return to a normal laboratory diet regimen after 3 mo of feeding with cholesterol-enriched laboratory diet, plasma cholesterol concentrations were 2,275 +/- 252 mg/dl, mostly attributable to cholesteryl ester-rich very low density lipoproteins (VLDL). On the hypercholesterolemic diet, fractional catabolic rates of plasma clearance of 125I-labeled VLDL were reduced (0.011 +/- 0.002 vs. 0.151 +/- 0.015 h-1), but the total VLDL catabolic rate was increased considerably (17.1 +/- 2.2 vs. less than 1.2 +/- 0.4 mg of protein/kg X d), because of the expansion of the endogenous pool of cholesteryl ester-rich VLDL. The total catabolic rate of VLDL was maintained above estimated control values (5.8 +/- 0.7 mg protein/kg X d) even 10 wk after return of the rabbits to a normal chow regimen, an effect attributable to continued high rates of cholesteryl ester-rich VLDL synthesis in liver. Accumulation of cholesteryl ester-rich VLDL into aortic tissue persisted at a high rate. Thus the persistence of aortic atheromatous lesions after cessation of cholesterol feeding was attributable in part to continued high rates of hepatic production of cholesteryl ester-rich VLDL and its persistent delivery into the aortic wall.

The effects of total lymphocyte deficiency on the extent of atherosclerosis in apolipoprotein E-/- mice.

Activated T lymphocytes are present in human atherosclerotic lesions and autoantibodies to antigens within lesions have been detected in serum, but the roles of the cellular and humoral immune systems in atherogenesis have not been determined. The effect of total lymphocyte deficiency on atherogenesis was investigated by crossing apo E-deficient mice (which develop atherosclerosis resembling human disease) with mice deficient in RAG2 (which is required for normal B and T lymphocyte development). Mice were placed on a fat- and cholesterol-enriched diet for 12 wk. RAG2-deficient mice had no serum autoantibodies, in contrast to the high titers in RAG2+/- littermates. There were no T lymphocytes and a markedly reduced number of MHC class II-positive macrophages in atherosclerotic lesions of RAG2-deficient mice. Despite these differences, RAG2-deficient mice developed atherosclerosis similar in extent to that in immunocompetent littermates, based on quantification by two independent methods. In conclusion, the absence of autoantibodies and T lymphocytes did not influence the extent of aortic atherosclerotic lesions in apo E-deficient mice.

Jugular Anomalies in Multiple Sclerosis Are Associated with Increased Collateral Venous Flow.

BACKGROUND AND PURPOSE: To date, research on extracranial venous collaterals has been focused on structure, with relatively little attention paid to hemodynamics. We addressed this limitation by quantitatively comparing collateral flow in patients with multiple sclerosis and healthy controls by using phase-contrast MR imaging. We hypothesize that patients with MS with structurally anomalous internal jugular veins will have elevated collateral venous flow compared with healthy controls. MATERIALS AND METHODS: The sample consisted of 276 patients with MS and 106 healthy controls. We used MRV to classify internal jugular veins as stenotic and nonstenotic based on an absolute cross-sectional area threshold in 276 patients with MS and 60 healthy controls; 46 healthy controls lacked this imaging. Individual and total vessel flows were quantified by using phase-contrast MR imaging on all patients. Veins were classified by extracranial drainage type: internal jugular veins (I), paraspinal (II), and superficial (III). Differences among healthy controls, patients with MS, nonstenotic patients, and stenotic subgroups in total venous flow by vessel type were evaluated in a general linear model for statistical analysis. RESULTS: In the MS group, 153 patients (55%) evidenced stenosis, whereas 12 (20%) healthy controls were classified as stenotic (P < .001). Compared with healthy controls, the MS group showed lower type I flow and increased type II flow. Stenosis was associated with reduced flow in the type I vessels [F(1272) = 68; P < .001]. The stenotic MS group had increased flow in the type II vessels compared with the nonstenotic MS group [F(1272) = 67; P < .001]. CONCLUSIONS: Compared with healthy controls, patients with MS exhibit reduced venous flow in the main extracerebral drainage vein (internal jugular vein). In contrast, flow in the paraspinal venous collaterals is elevated in patients with MS and exacerbated by venous stenosis. Collateral drainage may be a compensatory response to internal jugular vein flow reduction.

Myocyte contracture, vascular resistance, and vascular permeability after global ischemia in isolated hearts from alloxan-induced diabetic rabbits.

Coronary vascular hemodynamics, albumin permeation, and myocyte contractility were assessed in isolated hearts from 6-mo alloxan-induced diabetic (ALX-D) rabbits during 3 h of reperfusion after 40 min of global no-flow ischemia. Residue-detection data, generated during the single passage of a bolus of 125I-labeled bovine serum albumin (125I-BSA) through the coronary vasculature, were used to estimate indices of vascular function, including the mean transit time of 125I-BSA, the fractional rate of intravascular clearance of 125I-BSA, and 125I-BSA permeation of coronary vessels. During reflow after ischemia in hearts from control rabbits, vascular resistance increased approximately three times that at baseline, left ventricular end-diastolic pressure (LVEDP) increased 8-10 times, and maximum +dP/dt recovered 0.4 times baseline, whereas the fractional rate of washout of intravascular 125I-BSA decreased to less than one-half of baseline values (was prolonged 2-fold), and albumin permeation and mean-transit time were increased 3 and 5 times baseline, respectively. In hearts from diabetic rabbits, vascular resistance was similar to the control group before ischemia but increased only one-third as much during reflow after ischemia. Increases in LVEDP during reflow were approximately 50% lower than controls, and +dP/dt recovered approximately 2.5 times more than in control hearts. 125I-BSA permeation in diabetics was similar to controls before ischemia, but during reflow increased 6 times (approximately 2 times controls). Washout of intravascular 125I-BSA was prolonged approximately 20% versus baseline during 3 h of reflow in hearts from diabetic rabbits. Thus, ALX-D in the rabbit delayed ischemia-reperfusion injury to myocytes and vascular smooth muscle cells while increasing vascular albumin permeation.

Emerging protein delivery methods.

The efficient and safe delivery of therapeutic proteins is the key to commercial success and, in some cases, the demonstration of efficacy in current and future biotechnology products. Numerous delivery technologies and companies have evolved over the past year. To critically evaluate the available options, each method must be assessed in terms of how easily it can be manufactured, impact on protein quality, bioavailability, and toxicity. Recent advances in depot delivery systems have, for the most part, overcome all of these obstacles except for complex and costly manufacturing. On the other hand, pulmonary delivery usually involves efficient manufacturing, but low protein bioavailability resulting in higher doses compared with injections. Although recent advances in transdermal and oral delivery have been significant, both of these delivery routes require logarithmic increases in bioavailability to make them viable candidates for commercialization. In the next few years, protein delivery for commercial products will probably be limited to injection devices, depot systems and pulmonary administration.

Paradoxical reduction of atherosclerosis in apoE-deficient mice with obesity-related type 2 diabetes.

OBJECTIVE: The effect of obesity and insulin resistance on the development of atherosclerosis was evaluated in apoE-deficient (ApoE(-/-)) mice. A previously described obesity model, in which the hypothalamic satiety center can be destroyed by a single gold thioglucose (GTG) injection, was used. To evaluate the effect of starvation on atherosclerosis ApoE(-/-) mice were food-restricted with 25% less chow than ad libitum-fed control mice. METHODS: Sixty-eight ApoE(-/-) mice were allocated into a control group (n=20), a GTG-injected group (n=28), and a food-restricted group (n=20). The control and food-restricted mice were injected with saline instead of GTG. The control and GTG-injected mice had free access to food, and all mice had free access to water during the study period. RESULTS: After 4 months, the GTG-injected mice were significantly overweight (mean body weight (g): 33 +/- 2.11 vs. 23 +/- 0.24 and 17 +/- 0.31 in control and food-restricted mice, respectively), obese, hypertriglyceridemic, insulin-resistant, hyperinsulinemic (mean plasma insulin (ng/ml): 2.45 and 0.43 in obese and control mice, respectively), and hyperglycemic (mean plasma glucose (mmol/l): 11.03 and 7.80 in obese and control mice, respectively). Unexpectedly, these obese and diabetic mice developed significantly less atherosclerosis compared with lean non-diabetic control mice. Food-restricted mice also developed less atherosclerosis compared to control mice. CONCLUSIONS: These findings may question the usefulness of mouse models in studying the relation of obesity-related type 2 diabetes to atherosclerosis and also the relevance of results obtained in apoE(-/-) mice with reduced weight gain during intervention.

Lipopolysaccharide decreases scavenger receptor mRNA in vivo.

Lipopolysaccharide (LPS) downregulates scavenger receptor (ScR) activity in cultured macrophages through release of tumor necrosis factor-alpha (TNF-alpha). However, LPS administration in vivo stimulates cytokine release from both macrophages and lymphocytes, the combined effects of which could alter ScR expression differently from TNF-alpha in isolation. To investigate whether LPS regulates ScR in vivo, 10 microg/g was injected i.p. into Swiss Webster mice. Administration of LPS produced a profound decrease in hepatic ScR mRNA, with reductions of 74% +/- 8% at 2 h that returned to baseline levels by 6 h. Changes in ScR mRNA abundance coincided with changes in serum concentrations of TNF-alpha, which peaked at 2 h (1320 +/- 309 pg/ml) and returned to preinjection concentrations at 4 h. Serum concentrations of interferon-gamma (IFN-gamma) did not increase until 4 h after injection of LPS. There was no effect on ScR mRNA abundance following LPS administration to LPS-resistant strains of mice, C3H/HeJ and IFN-gamma receptor-/-. The LPS-induced reduction in ScR mRNA in Swiss Webster mice was not sufficiently sustained to affect receptor function, as determined by the kinetics of [(125)I]-acetylated LDL clearance from plasma. Therefore, as observed in cultured cells, LPS administration to mice decreases ScR mRNA despite the release of several cytokines in vivo.

Sidestream cigarette smoke accelerates atherogenesis in apolipoprotein E-/- mice.

Epidemiological studies have strongly implicated active and passive smoking with increased risk of cardiovascular diseases. The present study was performed to determine if exposure to sidestream cigarette smoke (SSCS), a surrogate of environmental tobacco smoke, promotes atherogenesis in a mouse model of human atherosclerosis. Female ApoE-deficient mice, maintained on a Western diet, were exposed to SSCS in a whole-body exposure chamber for a total of 6 h each day, 5 days a week for 7, 10 and 14 weeks. Animals exposed to filtered ambient air served as controls. Elevated concentrations of blood carboxyhemoglobin and pulmonary CYP1A1 ascertained effective exposure of animals to SSCS. There were no consistent changes in serum concentrations of cholesterol between control and SSCS-exposed mice. Morphometric assessment of grossly discernible lesions covering the intimal area of aorta showed remarkable increases in SSCS-exposed mice at all three exposure durations studied. Increases in the lesion area defined by en face measurements were accompanied by parallel increases in the levels of esterified and unesterified cholesterol in the aortic tissues of SSCS mice. These results clearly demonstrate promotion of atherosclerotic lesion development by tobacco smoke in an atherosclerosis-susceptible mouse model.

Short-term interruption of training affects both fasting and post-prandial lipoproteins.

Exercise training alters plasma lipoprotein profiles in a manner compatible with decreased coronary artery disease risk. The aim of this study was to ascertain whether interruption of training (detraining) was associated with potentially undesirable changes in the metabolism of post-prandial lipoproteins and plasma levels of Lp(a). Eight normolipidemic, male runners who ran 30-40 miles/week were studied in the trained state and after 14-22 days of detraining. Two of the subjects were studied in the reverse order to control for any confounding effects of exercise sequence. Detraining resulted in (1) a 12% (P = 0.002) reduction in the subjects' aerobic capacity, (2) a 7.7% (P = 0.007) reduction in fasting concentrations of high density lipoprotein cholesterol (HDL-C), (3) a 21% (P = 0.01) reduction in post-heparin lipoprotein lipase activity. Lp(a) concentrations did not change significantly (mean increase 15%, P = 0.076). Fasting plasma concentrations of total cholesterol (TC), triglycerides (TG) and low density lipoprotein-cholesterol (LDL-C) did not change in the detrained state. There was little fluctuation over 24 h in plasma concentrations of TC, LDL-C and HDL-C in either the trained or detrained states. TG concentrations fluctuated over the 24 h in accord with food intake, but there were no exercise-related changes. Exercise had a dramatic effect on chylomicron and chylomicron remnant metabolism as measured by retinyl palmitate measurements. The mean areas under the concentration vs. time curves (AUC) for chylomicron-retinyl esters increased by 41% (P = 0.013) and for chylomicron remnant-retinyl ester by 37% (P = 0.058) following detraining.(ABSTRACT TRUNCATED AT 250 WORDS)

Freunds adjuvant alone is antiatherogenic in apoE-deficient mice and specific immunization against TNFalpha confers no additional benefit.

TNFalpha participates in the pathogenesis of atherosclerosis. The effect of immunization against TNFalpha on development of advanced vascular lesions in atherosclerosis-susceptible apoE-deficient mice was investigated. At 5-7 weeks of age, animals received immunization with either Freunds adjuvant and a recombinant antigenic TNFalpha molecule (TNF106), Freunds adjuvant alone, or no immunization. All mice received a Western-type high-fat diet for 12 weeks. Aortic sinus lesion area was determined by microscopic morphometry, the total aortic arch cholesterol content was determined by gas chromatography, and antibodies against TNFalpha, malondialdehyde-modified low density lipoprotein, or heat shock protein 60, were assessed by ELISAs. Immunization with TNF106 induced high-titered circulating antibodies against TNFalpha (n=23), and these antibodies were not detected in mice immunized with Freunds adjuvant alone (n=22), or in non-immunized control animals (n=25). After 12 weeks, the atherosclerotic lesion size was significantly reduced in immunized animals, whether they had been immunized with TNF106 or Freunds adjuvant alone, and the total lesional cholesterol content was decreased in mice immunized with TNF106. There were no correlations between circulating antibody titers and plaque size, total aortic arch cholesterol content, or plasma lipid levels, respectively. Administration of Freunds adjuvant alone can thus reduce formation of mature atherosclerotic lesions in apoE-deficient mice and this response is not modified by specific immunization against TNFalpha.

A specific 15-lipoxygenase inhibitor limits the progression and monocyte-macrophage enrichment of hypercholesterolemia-induced atherosclerosis in the rabbit.

Oxidant signalling and lipoprotein oxidation may play important roles in atherosclerotic lesion development. Given coincident localization of 15-lipoxygenase (15-LO), stereospecific products of 15-LO and epitopes of modified LDL in atherosclerotic lesions, we hypothesized that inhibition of 15-LO by PD146176, an inhibitor of 15-LO with an IC50 in cells or isolated enzyme of 0.5-0.8 microM, may limit atherosclerotic lesion development through regulation of monocyte-macrophage enrichment. Rabbits exposed to chronic endothelial denudation of the iliac-femoral artery were meal-fed a 0.25% cholesterol (C), 3% peanut oil (PNO), 3% coconut oil (CNO) diet twice daily with and without 175 mg/kg PD146176 for 12 weeks. In a second study, atherosclerotic lesions were pre-established in rabbits through chronic endothelial denudation and meal-fed a 0.5% C, 3% PNO, 3% CNO diet for 9 weeks and a 0% C/fat diet for 6 weeks prior to an 8 week administration of PD146176 at 175 mg/kg, q.d. Plasma total and lipoprotein cholesterol exposure were similar in control and PD146176-treated animals in both studies but PD146176 increased plasma triglyceride exposure 2- to 4-fold. Plasma PD146176 concentrations ranged from 99 to 214 ng/ml at 2 h post-dose. In the progression study, the iliac-femoral monocyte-macrophage area was reduced 71%, cross-sectional lesion area was unchanged and cholesteryl ester (CE) content was reduced 63%. In the regression study, size and macrophage content of iliac-femoral, fibrous plaque-like lesions were decreased 34%, CE content was reduced 19% and gross extent of thoracic aortic lesions were reduced 41%. We conclude that PD146176 can limit monocyte macrophage enrichment of atherosclerotic lesions and can attenuate development of fibrofoamy and fibrous plaque lesions in the absence of changes in plasma total or lipoprotein cholesterol concentrations.

Metabolic imaging with gallium-68- and indium-111-labeled low-density lipoprotein.

Low-density lipoprotein (LDL) labeled with either gallium-68 (68Ga) or indium-111 (111In) was evaluated as a potential PET or SPECT radiopharmaceutical for determination of hepatic lipoprotein metabolism in rabbits. Gallium-68 or 111In was linked to LDL via diethylenetriaminepentaacetic acid (DTPA) with a 25-70% radiochemical yield. Studies in vivo that compared 68Ga- or 111In-DTPA-LDL with dilactitol-[125I]-tyramine LDL and 131I-LDL showed that both 68Ga- and 111In-labeled LDL behaved as residualizing radiotracers. Localization of radioactivity within the liver of normal rabbits was visualized clearly with [68Ga]DTPA-LDL by PET and with [111In]DTPA-LDL by gamma scintigraphy. Significant differences were observed in hepatic uptake of normal compared with hypercholesterolemic rabbits in which low-capacity LDL receptor-mediated catabolism was saturated. Gallium-68 and 111In-DTPA-LDL are attractive radiopharmaceuticals for noninvasive delineation of tissue LDL metabolism under normal and pathophysiologic conditions.