Functional alteration of endothelium by short-term cholesterol feeding

Attenuation of serum lipid abnormalities and cardiac oxidative stress by eicosapentaenoate-lipoate (EPA-LA) derivative in experimental hypercholesterolemia

BACKGROUND

Dietary cholesterol plays an important role in development of atherogenesis and cardiovascular disease. We explored the lipemic-oxidative injury in the hypercholesterolemic atherogenic animals. The effects of eicosapentaenoic acid (EPA), dl-alpha-lipoic acid (LA) and eicosapentaenoate-lipoate derivative (EPA-LA) were tested for their efficacy in controlling the atherogenic disturbances.

METHODS

Four groups of male Wistar rats were fed with a high cholesterol diet (rat chow supplemented with 4% cholesterol and 1% cholic acid; HCD) for 30 days. Of these groups, 3 groups of rats were treated with either EPA (oral gavage, 35 mg/kg body weight/day), LA (oral gavage, 20 mg/kg body weight/day) or EPA-LA derivative (oral gavage, 50 mg/kg body weight/day) from 16th day to 30th day of the experimental period.

RESULTS

HCD induced abnormal increase in lipid peroxidation and serum cholesterol, triglyceride, LDL and VLDL, and a decreased HDL concentration. Altered activity of cardiac and serum creatine kinase, accompanied by a depressed cardiac enzymatic and nonenzymatic antioxidants defense system were observed in HCD fed rats. These changes were partially restored in the EPA and LA treated groups, however, their combined derivative EPA-LA more effectively restored the altered parameters near to that of control (P<0.05).

CONCLUSION

Lipid abnormalities and oxidative injury were induced by a hypercholesterolemic diet. Administration of the combination treatment of EPA-LA afforded protection against the lipemic-oxidative injury.

Effect of hypercholesterolemia on transendothelial EBD-albumin permeability and lipid accumulation in porcine iliac arteries

Hypercholesterolemia is associated with increased cardiovascular mortality and is known to promote the advancement of atherosclerotic lesions in experimental animal models. Juvenile swine were fed a normal or high-cholesterol diet, and the transendothelial macromolecular permeability of the external iliac arteries of these animals was assessed by measuring the uptake rate of circulating Evans blue dye (EBD). The extent and patterns of lipid-containing lesions were also determined using en face staining with Oil Red O (ORO). Sites of ORO staining often excluded EBD, possibly via the fragmentation of the internal elastic lamina, to which EBD binds. By spatially averaging the EBD uptake in arterial segments relatively free of ORO-positive lesions, it was found that endothelial permeability to albumin was greater in hypercholesterolemic pigs than in those on a normal diet (p=0.056).

Oxidized products of cholesterol: dietary and metabolic origin, and proatherosclerotic effects (review)

Cholesterol oxidation products, termed oxysterols, are increasingly considered of potential interest in the pathogenesis of atherosclerotic lesions. Of dietary or endogenous origin, oxysterols may occur in significant amounts in low density lipoprotein (LDL) particles, especially in hypercholesterolemic subjects. They likely contribute to the uptake of modified LDL by scavenger receptors and some of them finally accumulate in the subintimal space of major arteries; here cholesterol oxides may favor the perpetuation of a chronic inflammatory state, through their ability to trigger irreversible damage of vascular cells with consequent activation of phagocytes. Furthermore, practically all oxysterols of major pathophysiologic interest have been shown to markedly up-regulate expression and synthesis of adhesion molecules, inflammatory cytokines and chemokines. Cholesterol oxidation thus appears to be an important biochemical pathway through which it exerts toxic, inflammatory and finally atherogenic effects.

Transfer of low density lipoprotein into the arterial wall and risk of atherosclerosis

The aim of the review is to summarize the present knowledge on determinants of transfer of low density lipoprotein (LDL) into the arterial wall, particularly in relation to the risk of development of atherosclerosis. The flux of LDL into the arterial wall (in moles of LDL per surface area per unit of time) has two major determinants, i.e. the LDL concentration in plasma and the arterial wall permeability. LDL enters the arterial wall as intact particles by vesicular ferrying through endothelial cells and/or by passive sieving through pores in or between endothelial cells. Estimates in vivo of the LDL permeability of a normal arterial wall vary between 5 and 100 nl/cm2/h. In laboratory animals, the regional variation in the arterial wall permeability predicts the pattern of subsequent dietary induced atherosclerosis. Moreover, mechanical or immunological injury of the arterial wall increases the LDL permeability and is accompanied by accelerated development of experimental atherosclerosis. This supports the idea that an increased permeability to LDL, like an increased plasma LDL concentration, increases the risk of atherosclerosis. Hypertension, smoking, genetic predisposition, atherosclerosis, and a small size of LDL may all increase the arterial wall permeability to LDL and in this way increase the risk of accelerated development of atherosclerosis. The hypothesis that atherosclerosis risk can be reduced by improving the barrier function of the arterial wall towards the entry of LDL remains to be investigated; agents which directly modulate the LDL permeability of the arterial wall in vivo await identification.

High potassium diets reduce endothelial permeability in stroke-prone spontaneously hypertensive rats

1. High potassium (K) diets are known to prevent hypertensive arterial lesions and reduce stroke incidence without affecting blood pressure. 2. To elucidate the mechanism of this beneficial effect, we studied the effect of K supplementation on the extravasation of plasma albumin in high NaCl-fed stroke-prone spontaneously hypertensive rats (SHRSP). Increased permeability of the endothelium to macromolecules is assumed to be an early manifestation of vascular injury. 3. The disappearance of intravenously injected [125I]-albumin was examined in SHRSP rats fed high NaCl diets containing either 0.5% normal K or 2.1% high K for 5 weeks. 4. The bodyweight, blood pressure, plasma volume and urinary protein excretion were not significantly different between the two SHRSP groups. 5. The high K SHRSP showed a slower plasma albumin disappearance rate than the normal K SHRSP (10.3 vs 14.7%/h, P < 0.004). The albumin radioactivity remaining in the aortic wall and in the brain after removing blood after perfusion was lower in the high K SHRSP than in the normal K SHRSP (aorta, -20%, P < 0.02; brain, -26%, P < 0.04). 6. These results suggest that the high K diet reduced the endothelial permeability to albumin in high NaCl-fed SHRSP rats. High K diets may have a protective effect against endothelial dysfunction and thereby contribute to the reduction of vascular lesion formation and stroke incidence.