Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0155339 (Brown)
 12,436 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Probucol is a drug that lowers plasma cholesterol in both humans and animals. In low density lipoprotein (LDL) receptor-deficient Watanabe rabbits, probucol reduces the progression of atherosclerosis. This effect may be attributed to the antioxidant and/or the cholesterol-lowering properties of the drug. In the present report we studied the antiatherogenic effect of a probucol analogue (MDL 29,311) that possesses antioxidant activity but that does not lower cholesterol. Modified Watanabe rabbits (11-12 weeks of age) produced by crossing British Brown and Japanese Watanabe rabbits were fed normal chow (n = 8), chow containing 1% probucol (n = 9), or chow containing 0.1% (n = 9), 0.5% (n = 8), or 1% (n = 6) probucol analogue. After 70 days serum cholesterol levels and the percent area of sudanophilic lesions in the thoracic region of aortas were determined. Total serum cholesterol was significantly lowered (p less than 0.05) in the probucol group (560 +/- 54 mg/dl) compared with that of controls receiving no drug (731 +/- 67 mg/dl) but was not lowered in the analogue groups (722-802 mg/dl). The lesioned area (mean% +/- SEM) in the probucol group (16 +/- 3) was significantly lower (p less than 0.01) than in the controls (52 +/- 8). There were 43 +/- 7%, 33 +/- 8%, and 35 +/- 5% of lesions for the 0.1%, 0.5%, and 1% analogue groups, respectively. After combining the data for the 0.5% and 1% analogue groups, the value (34%) was lower than that of the controls and almost reached significance (p = 0.066). The mean serum drug concentration in the 1% probucol group was 58 +/- 4 micrograms/ml compared with 13 +/- 2, 44 +/- 8, and 74 +/- 8 micrograms/ml for the 0.1%, 0.5%, and 1% analogue groups, respectively. Thus, the decreased effectiveness of the probucol analogue in preventing atherosclerosis could not be explained by a lack of bioavailability. LDLs isolated from rabbits treated with the drug were resistant to Cu(2+)-induced lipid peroxidation, as determined by thiobarbituric acid-reactive substances. The resistance within the analogue groups was dependent on the number of antioxidant molecules per LDL particle. However, there was no significant difference in atherosclerotic lesions between these two groups, suggesting, although not definitively, that the maximal antiatherogenic effect had been reached. Our data suggest that the antioxidant activity of this class of compounds may play an important role in reducing atherosclerosis, but not in reducing cholesterol levels, and that hypocholesterolemic and possibly other activities of probucol might further enhance its antiatherogenic activity.
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PMID:Attenuation of atherosclerosis in a modified strain of hypercholesterolemic Watanabe rabbits with use of a probucol analogue (MDL 29,311) that does not lower serum cholesterol. 191 12

In 1973, studies with cultured human fibroblasts by Brown, Goldstein, and colleagues showed that receptor-mediated endocytosis of low-density lipoprotein (LDL) is the regulatory principle in cellular cholesterol homeostasis. The complete sequence of metabolic events associated with the binding, uptake, and degradation of these cholesterol-rich lipoprotein particles by mammalian cells has been termed the LDL receptor pathway. This important process has two main tasks. First, it supplies cells with cholesterol, thereby mediating the removal of cholesterol-rich lipoproteins from the circulation. Second, it protects cells from over-accumulation of cholesterol, because the cholesterol derived from lysosomal hydrolysis of LDL cholesterylesters exerts a series of feedback control mechanisms designed to maintain a constant level of cholesterol within the cell. Thus, high extracellular concentrations of LDL reduce cellular synthesis of cholesterol (by suppression of the activities of 3 hydroxy-, 3-methyl-glutaryl-CoA synthase and reductase, rate-limiting enzymes in cholesterol synthesis), stimulate its re-esterification, and decrease the number of LDL receptors, preventing further cellular entry of cholesterol. The suppression of LDL receptor activity by high plasma levels of LDL is beneficial for most cells, but the consequences caused by reduction of LDL receptor activity in the liver can be devastating. This is best documented in familial hypercholesterolemia (FH), in which defects in the LDL receptor gene disrupt the normal functions of the LDL receptor pathway. The clinical manifestation of the failure to remove LDL from the bloodstream at normal rates includes severe hypercholesterolemia and premature atherosclerosis. Some of the important findings that emerged from studies on structure/function relationships of the key player in the process, the LDL receptor itself, are described.
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PMID:Familial hypercholesterolemia: dissection of a receptor disease. 209 41

The main advances since 1980 in our understanding of atherosclerosis can be summarised under four headings. 1) The migration and proliferation of smooth muscle cells from the media into the intima are key-events of atherogenesis, and probably also of restenosis following percutaneous transluminal coronary angioplasty. The experimental study of their regulations, especially looking for inhibitors, has therefore gained increased interest as it may provide original approaches to the prevention of post-angioplasty restenosis. 2) The histiocytes/macrophages, derived from blood monocytes, also take a major part in the initiation of atherosclerotic lesions. An intensive research activity is now being devoted to elucidating the many facets of their participation in atherogenesis. 3) Brown and Goldstein's discoveries have explained the biochemical mechanisms of the increased plasma low-density lipoprotein (LDL) concentration found in familial hypercholesterolemia (type IIa), although they did not completely solve the enigma of lipid deposition in the arterial wall. The metabolic handling of modified LDLs appears to be crucial to the foamy transformation of macrophages and, possibly, of smooth muscle cells. 4) Risk factors identified by epidemiology are usually held responsible for atherosclerosis. Yet this causal interpretation is not entirely satisfactory, and alternative or complementary hypotheses are being but forward. Among them, the most consistent submits that a viral aggression of the arterial wall is involved in the genesis and progression of atherosclerosis.
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PMID:[New concepts of atherogenesis]. 283 18

Aortocoronary vein bypass surgery might not restore normal maximal coronary flow reserve to bypassed coronary vessels because residual diffuse coronary atherosclerosis might limit maximal hyperemia. To investigate the effect of diffuse atherosclerosis and a focal stenosis at the graft-coronary anastomosis, we measured coronary flow reserve with an extensively validated subselective Doppler catheter in 24 patients with 35 bypass grafts perfusing angiographically normal coronary vessels. The Doppler catheter was positioned in the midportion of the graft, and coronary flow reserve was measured as the peak/resting velocity ratio after selective graft injection of a maximally vasodilating dose of papaverine. Luminal dimensions of the bypass graft, graft-coronary insertion, and bypassed coronary vessel were measured by quantitative coronary angiography (Brown/Dodge method). Measurements of coronary flow reserve and coronary dimensions of vein bypass grafts were compared with similar measurements obtained from 13 patients with normal coronary vessels and normal myocardium. Seventeen of the 35 bypass grafts perfused unobstructed coronary-vein graft anastomoses (less than 50% area stenosis) and normal myocardium. The coronary flow reserve of these 17 bypass grafts was normal (5.0 +/- 0.4, mean +/- SEM) and not significantly different from that measured in normal arteries (5.1 +/- 0.6), even though the cross-sectional area of the native coronary artery just distal to the bypass insertion was 40% smaller than in matched normal vessels. Bypass grafts perfusing hypertrophied (n = 2) or infarcted (n = 6) myocardium had significantly reduced coronary flow reserve compared with normal vessels (2.7 +/- 0.3; p less than .01), even when the infarcted wall had only minimal hypokinesis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Does coronary artery bypass surgery restore normal maximal coronary flow reserve? The effect of diffuse atherosclerosis and focal obstructive lesions. 295 10

Studies in animals with normal coronary arteries have shown that coronary flow reserve can be predicted by angiographic measurements of arterial stenosis. Studies in man, however, suggest that even quantitative analysis of coronary angiograms cannot predict the physiologic significance of individual coronary lesions. These studies, however, were carried out in patients with either widespread, diffuse coronary artery disease or by measurement techniques that tend to underestimate maximal coronary flow reserve. To determine the relationship between coronary arterial stenosis and coronary flow reserve (CFR) in patients with discrete limited coronary atherosclerosis, we studied 50 patients with a single discrete coronary stenosis in only one or two vessels. The minimum coronary arterial cross-sectional area (mCSA), percent area stenosis (%AS), and percent diameter stenosis in the left and right anterior oblique projections were determined by the Brown/Dodge method of quantitative coronary angiography. A No. 3F coronary Doppler catheter was placed immediately proximal to the lesion. Measurements of CFR were obtained by intracoronary administration of papaverine in doses sufficient to provide maximal arteriolar vasodilation. In 25 patients, a translesional pressure gradient was obtained with an angioplasty catheter. CFR measured in patients with coronary artery disease was compared with that in 13 patients with normal coronary vessels. In normal patients, CFR averaged 5.0 +/- 0.6 (peak/resting velocity ratio; mean +/- SEM, range 3.7 to 8.2). In patients with limited coronary artery disease, CFR was closely correlated with %AS (r = .85), mCSA (r = .79), and the translesional pressure gradient (r = .83). Additionally, the most severe percent diameter stenosis in either the left or right anterior oblique view was also highly correlated with CFR (r = .82). Importantly, all arteries with lesions producing less than 70% area stenosis and less than 50% diameter stenosis, or with greater than 2.5 mm2 mCSA had CFR of over 3.5. These results suggest that, in contrast to the poor correlation of percent area and percent diameter stenosis to CFR measured in patients with multivessel coronary artery disease, CFR measured at angiography in patients with discrete, limited coronary artery disease correlates closely with luminal stenosis determined precisely with quantitative coronary angiography. Differences in the extent of diffuse arterial narrowing may account for these discrepancies.
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PMID:Prediction of the physiologic significance of coronary arterial lesions by quantitative lesion geometry in patients with limited coronary artery disease. 382 34

Sixty-two subjects from 23 families were evaluated by serum lipid analyses and tissue culture biochemistry in skin fibroblasts. In 53 cases from 19 families with proven familial hypercholesterolemia (FHC), fibroblast cultures were successful. In 45 of these cases (85%) the clinical diagnosis of hyper- or normocholesterolemia was in accordance with the tissue culture findings. Four patients 2-38 years old, had hypercholesterolemia but normal tissue culture results. Four patients, 18-44 years old, had normal serum cholesterol levels for their age and sex, but were heterozygotes according to tissue culture results. In the remaining four families only the propositus had hypercholesterolemia. All members of the families including the propositus had normal tissue culture determinations indicating that not all cases of idiopathic hypercholesterolemia are due to the Goldstein-Brown mechanism of defective LDL receptor function.
Atherosclerosis 1981 Apr
PMID:Serum cholesterol levels in patients with familial hypercholesterolemia confirmed by tissue culture. 724 90

Hypercholesterolemia is a predisposing factor for atherosclerosis. We studied the response to damage of vascular smooth muscle cells (SMC) from normocholesterolemic Brown Norway (BN) and from spontaneously hyper-cholesterolemic Yoshida (YOS) rats (16-24 month old). The regrowth rate of SMC from BN and YOS rats after freeze-induced damage was similar in the presence of fetal calf serum and of serum derived from normocholesterolemic rats, while it was reduced in the presence of serum from hypercholesterolemic rats. Freeze-injury of the abdominal aorta was followed by reduced neointima formation in YOS rats, as compared to BN rats, confirming the impaired response of vascular cells from hypercholesterolemic rats to injury. This defect may be due either to lipids or to unknown factors present in the hyperlypidemic serum.
Atherosclerosis 1994 Dec
PMID:Reduced smooth muscle cell regeneration in Yoshida (YOS) spontaneously hypercholesterolemic rats. 771 25

Vascular smooth muscle cells (SMCs) produce the bulk of the connective tissue of major arteries, including collagen types I, III, and V. Recently, we have shown, they also have the capacity to synthesize the alpha 1 chain of type XI, a collagen related to type V (Brown, K., Lawrence, R., and Sonenshein, G. (1991) J. Biol. Chem. 266, 23268-23273). Furthermore, expression of types V and XI collagen were coordinately regulated with respect to serum deprivation and cell density in a fashion distinct from that for types I and III. To begin to determine the factors that influence vascular SMC production of types V/XI collagen, we have examined the effects of transforming growth factor (TGF)-beta 1, a major modulator of connective tissue expression. In serum-deprived confluent cultures of bovine pulmonary artery SMCs, TGF-beta 1 treatment increased the steady-state levels of the mRNAs of collagen types V and XI, as well as of types I and III, elastin and fibronectin. The largest increase was seen for alpha 2(V) procollagen. The increase in alpha 2(V) mRNA was detectable by 12 h after addition of 2 ng/ml TGF-beta 1, and concentrations as little as 0.5 ng/ml were effective. A similar increase in alpha 2(V) mRNA levels was observed with SMCs derived from the aortic arch and carotid artery. Type V collagen protein was found to be elevated by TGF-beta 1 treatment in both the conditioned media and the cell layer associated fraction of pulse-labeled cultures. A slight decrease in SMC proliferation as judged by DNA content, [3H]thymidine incorporation, and steady-state levels of histone H3.2 mRNA resulted from TGF-beta 1 treatment. These results suggest that the elevated levels of TGF-beta 1 in the vessel wall during atherosclerosis may be, in part, responsible for the increase in type V collagen that typifies advanced fibrotic lesions.
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PMID:Transforming growth factor beta 1 stimulates type V collagen expression in bovine vascular smooth muscle cells. 814 47

The lesions of atherosclerosis represent a protective, inflammatory-fibroproliferative response against the different agents that can cause the disease. If the injury continues chronically over a sufficiently long period of time, and if opportunity is not given for restitution of normal architecture in the artery wall, lesions may progress to a point at which clinical sequelae develop. On the other hand, as demonstrated by Brown et al, Kane et al, and Blankenhorn et al, the advanced lesions of atherosclerosis can be shown to regress. A quantitative, statistical analysis of angiograms in patients who are aggressively treated with lipid-lowering agents, such as HMGCoA reductase inhibitors has clearly shown this to be the case. Thus, it is entirely conceivable that this chronic, excessive, inflammatory, and fibroproliferative response can be reversed, given sufficient opportunity for the factors that have led to the endothelial and arterial wall injury causing these events to be taken into hand and modified.
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PMID:Atherosclerosis: current understanding of mechanisms and future strategies in therapy. 847 Feb 66

An increasing body of evidence indicates that oxidized low density lipoprotein (LDL) is involved in the pathogenesis of atherosclerosis. One of the first biologic actions of oxidized LDL to be identified in vitro was its ability to interact with the 'acetyl LDL receptor' discovered by Goldstein and Brown. Over the past decade, considerable progress has been made in identifying and characterizing cell-surface receptors for oxidized LDL. Most of these receptors are thought to be multifunctional because they interact with several structurally different ligands, and accordingly have been termed 'scavenger receptors'. The objective of this article is to review the most important publications dealing with structure, ligand specificity, regulation, and function of scavenger receptors.
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PMID:Receptors for oxidized low density lipoprotein. 998 60


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