Lipid deposition in the aorta of adjuvant arthritic rats with hypercholesterolemia

[Oxidative stress and atherosclerosis]

Oxidative stress is a continuous level of oxidative damage in animal cells, which is caused by an overabundance of reactive oxygen species or a decline in antioxidant ability against them. Oxidative stress increases with individual risk factors of atherosclerosis such as obesity, hypertension, hyperlipidemia, diabetes and smoking. Thus, oxidative stress is considered to play a key role in the pathogenesis of atherosclerosis. This review discusses the relationship between oxidative stress and atherosclerosis based on findings from our research group. We have found that atherosclerotic lesions are formed in the aorta of mice fed a high-cholesterol and high-linoleic diet, in parallel with elevated serum lipid peroxide levels. This model is useful for primary screening of antiatherosclerotic agents with antioxidative activity. One notable factor in the development of atherosclerosis is oxidized low-density lipoprotein (OxLDL). In order to examine OxLDL levels in blood, we have developed anion-exchange HPLC methods using stepwise elution. Using these methods, we have found that OxLDL markedly increases in a rat model of metabolic syndrome, in animals exposed to cigarette smoke and in smokers in parallel with other oxidative stress markers. These oxidative stress markers have been attenuated by administration of several antioxidants. In addition, we have found that smoking accelerates atherogenesis in the aorta of apoE-deficient mice and this acceleration can be ameliorated by administration of vitamin E. These observations suggest that antioxidant supplementation may be an effective therapeutic strategy for metabolic syndrome and smoking-induced diseases in which elevated oxidative stress plays a pivotal role.

Changes of oxidative stress in various tissues by long-term administration of vitamin E in hypercholesterolemic rats

BACKGROUND

Free radical-mediated oxidative stress has been implicated in the genesis and progression of atherosclerosis.

METHODS

The lipid peroxides and antioxidant status of various tissues were investigated in hypercholesterolemic rats and the effect of vitamin E supplementation on defense systems.

RESULTS

Cholesterol-feeding caused a significant increase in the lipid peroxide concentrations of plasma, erythrocytes, liver and brain. In addition, a significant decrease in glutathione (GSH) content, glutathione peroxidase (GSH-Px) and glutathione transferase (GSH-ST) activities were found in erythrocytes and liver but superoxide dismutase (SOD) activity remained unchanged in these tissues in comparison to the control group. Vitamin E supplementation to hypercholesterolemic rats induced a significantly decrease in lipid peroxide concentrations and a significant increase in the GSH content, GSH-Px and GSH-ST activities in erythrocytes and liver.

CONCLUSIONS

Long-term administration of vitamin E may play an important role in suppressing oxidative stress, and thus, may be useful for the prevention and/or early treatment of hypercholesterolemia.

Suppression of adjuvant arthritis in rats by cholesterol

Dietary cholesterol suppressed adjuvant arthritis, a chronic inflammatory disease, in rats, but did not significantly affect carrageenin edema, an acute inflammation. When rats were fed a high-cholesterol diet beginning 10 days before injection of adjuvant, the development of the adjuvant-induced arthritis was greatly suppressed. Cholesterol feeding prevented hypertrophy of the adrenal gland in arthritic rats, but had little influence on the serum corticosterone level. A significant positive correlation was observed between the adrenal weight and the severity of the arthritis. These findings suggest that the effect of cholesterol feeding is not due to increased adrenal sterol synthesis. Dietary cholesterol also prevented hypertrophy of the spleen, but had no effect on atrophy of the thymus in adjuvant-treated rats. Cholesterol-fed rats showed a significant decrease in the serum lipid peroxide level and a significant increase in the serum copper level. Adjuvant treatment not only enhanced hypercholesterolemia produced by cholesterol feeding, but also the level of free cholesterol in serum. These results suggest that dietary cholesterol may exert some effect on the immune response through changes in spleen and liver functions.