Atherosclerosis: An overview

Chemotaxis of human blood monocytes toward endothelin-1 and the influence of calcium channel blockers

The adherence of monocytes to the arterial endothelium followed by its migration into the arterial intima is the earliest event in atherogenesis. The vasoconstrictive peptide, Endothelin-1 (ET-1), is elevated in patients with atherosclerosis. We were interested to know whether ET-1 was a chemoattractant for blood monocytes. Using the modified membrane filter technique for chemotaxsis assessment, ET-1 increased monocyte chemotaxis in a dose-dependent manner. Ca2+ channel blockers, Nifedipine, Diltiazem and Verapamil (5 microM), reduced ET-1 chemotaxsis more than 60% (P < 0.001). Aspirin and Indomethacin (1 mM and 100 microM, respectively) reduced migration by 23% (P < 0.05). Alpha-Lipoic acid, Probucol and Neomycin (100 microM) were also migration inhibitory (37%, P < 0.01). These results suggest that ET-1 is a strong chemoattractant for blood monocytes; Ca2+ influx is probably the major stimulus for the accelerated migration induced by ET-1.

Effect of skim milk supplementation on blood cholesterol concentration, blood pressure, and triglycerides in a free-living human population

In 82 subjects, aged 21-73, we studied the effect of skim milk supplementation on serum cholesterol concentration, blood pressure, and serum triglyceride level. The study involved a 1-week pretreatment baseline period followed by 8 weeks of milk supplementation. Sixty-four people were designated to a test group and 18 people were placed in a seasonal index group. The study was designed as a free-living trial, i.e., participants were requested to maintain their normal lifestyles, including dietary pattern, except for the supplementation of one quart of 2% solids-not-fat fortified skim milk to the daily diet in the test group. Supplemental milk treatment was associated with a 6.6% reduction (p = 0.0004) of serum cholesterol in the high cholesterol (greater than or equal to 190 mg/dl) test subgroup within the first 4 weeks. No change was noted in serum cholesterol in the low-cholesterol (less than 190 mg/dl) subgroup throughout the study. Body weight and seasonal variation of blood cholesterol did not significantly influence serum cholesterol levels. Reduction (p = 0.0140) in percentage of calories from fat in the high-cholesterol subgroup was not correlated with the decrease in serum cholesterol in this test subgroup. Reductions in systolic and diastolic blood pressure occurred in the test subgroups; the low-cholesterol subgroup had a greater reduction (p = 0.0002) in diastolic blood pressure than the high-cholesterol group (p = 0.0049). Milk supplementation was associated with reduction (p = 0.0370) in serum triglycerides in the high-cholesterol subgroup.

The hyperlipidemic hamster as a model of experimental atherosclerosis

Male hamsters were fed a hyperlipidemic diet consisting of standard chow supplemented with 3% cholesterol and 15% commercial butter for 12 months. In about 3 weeks serum total cholesterol doubled, raised 4-fold after the 4th week and after 10 months attained a 17-fold value. Low density lipoproteins (LDL)-cholesterol increased 4-fold after 4 weeks and about 13-fold after 10 months compared to control animals. In the first 2 weeks mononuclear cells began to adhere to the endothelium and a very intense stromal reaction appeared in the intima of the aortic arch. At the end of the 4th week of diet, Oil Red O stainable deposits were visible on the thoracic aorta, mostly on the arch, some of them as isolated, lipid-laden cells and others distributed on focal areas. Smooth muscle cells (SMC) appeared also in the intima of hyperlipidemic hamsters, compared to normal animals which had no macrophages or smooth muscle cells in the intima of the aortic specimens examined. Up to 6 months, smooth muscle cells in the intima and media began to load with lipids, as well as endothelial cells. After 10 months the affected zones looked like human atherosclerotic plaque with huge cholesterol crystal deposits, calcium deposits and necrosis. The endothelium, though very thinned and loaded with lipids, was morphologically intact.

A possible antiatherogenic role for phosphocitrate through modulation of low density lipoprotein uptake and degradation in aortic smooth muscle cells

The present study reports the influence of a phosphorylated polycarboxylic acid, phosphocitrate, on low density lipoprotein (LDL) metabolism in cultured rabbit aortic smooth muscle cells. Phosphocitrate profoundly influenced both LDL binding and degradation. At the maximal effective concentration (2 mM), phosphocitrate released approximately 90% of the receptor-bound [125I]LDL whilst the total amount of [125I]LDL degraded was reduced by 60%. Measurement of total cholesterol accumulation revealed that even in the presence of high concentrations of added LDL, phosphocitrate (2 mM) diminished cholesterol levels close to the basal levels seen in incubations in lipoprotein-deficient serum. Further, this inhibitory effect of phosphocitrate was demonstrable after 24 h at 37 degrees C. Phosphocitrate, a recognized anticalcifying agent, possesses a strong negative charge to size ratio at physiological pH. It is postulated that the observed effects probably arise from charge interference and/or its ability to modulate cellular calcium concentration.