Dietary cholesterol supplementation protects against endothelial cell dysfunction mediated by native and lipolyzed lipoproteins derived from rabbits fed high-corn oil diets

Hamsters fed diets high in saturated fat have increased cholesterol accumulation and cytokine production in the aortic arch compared with cholesterol-fed hamsters with moderately elevated plasma non-HDL cholesterol concentrations

There is growing evidence that dietary fatty acids and/or dietary cholesterol could have a direct role on inflammatory diseases such as atherosclerosis. F(1)B Golden Syrian hamsters (Mesocricetus auratus), in 2 groups of 72, were fed for 10 wk a semipurified diet containing either 20 g/100 g hydrogenated coconut oil without cholesterol or cocoa butter (20 g/100 g) with cholesterol (0.15 g/100 g). After the 10-wk treatment period, plasma was collected from food-deprived hamsters (16 h) for plasma lipid measurements. Hamsters were then ranked according to their plasma VLDL and LDL cholesterol (non-HDL-C) concentrations with 1.86 mmol/L as the cut-off point between low (Low; n = 36) and medium (Med; n = 36) concentrations for each treatment. Hamsters in the Low and Medium groups fed cholesterol (Low-chol) had significantly lower plasma total cholesterol (TC) concentrations than hamsters in the Low group fed coconut oil (Low-CO). However, this difference for the Medium group was reflected in significantly lower plasma HDL cholesterol (HDL-C) concentrations. Hamsters in the Low-CO group had significantly higher aortic total and esterified cholesterol concentrations than hamsters in the Low-chol group. Hamsters in the Low-chol group had significantly higher aortic tumor necrosis factor-alpha concentrations than hamsters in the Low-CO group. Hamsters in the Med-CO group had significantly higher aortic interleukin-1beta concentrations than hamsters in the Med-chol group. In conclusion, the present study suggests that dietary cholesterol and saturated fatty acids could have an effect on atherosclerosis not only beyond their role in affecting plasma lipoproteins but also through increased production of inflammatory cytokines in the arterial wall.

Cholesterol attenuates linoleic acid-induced endothelial cell activation

Vascular endothelial cell activation and dysfunction are critical early events in atherosclerosis. Even though very low or high levels of cholesterol can compromise cellular functions, cholesterol is a critical membrane component and may protect the vascular endothelium from oxidative stress and polyunsaturated fatty acid-mediated inflammatory responses. We have previously shown that the parent omega-6 fatty acid linoleic acid can markedly activate vascular endothelial cells. We now propose that membrane cholesterol can modify and inhibit linoleic acid-mediated endothelial cell dysfunction. To test this hypothesis, pulmonary artery endothelial cells were incubated with cholesterol (0 to 100 micromol/L) for 24 hours and then treated with 90 micromol/L of linoleic acid (18:2n-6) for 6 to 24 hours. In control cells, treatment with linoleic acid reduced intracellular glutathione levels and induced the DNA binding activity of nuclear factor-kappaB (NF-kappaB) leading to the upregulation of interleukin-6 (IL-6). In addition, the expression of endothelial nitric oxide synthase (eNOS) was altered, with linoleic acid increasing eNOS activity. In contrast, enrichment with cholesterol enhanced glutathione levels and reduced the linoleic acid-induced activation of NF-kappaBand the production of IL-6. Prior exposure to 50 micromol/L cholesterol also prevented the fatty acid-induced increase in eNOS activation. Cholesterol loading activated peroxisome proliferator-activated receptor-gamma (PPAR-gamma), a nuclear receptor that can decrease inflammatory responses. Furthermore, the PPAR-gamma agonist thiazolidinedione markedly downregulated the NF-kappaB activation mediated by linoleic acid. Our data suggest that signaling pathways linked to endothelial cell activation by prooxidant and proinflammatory insults may be influenced by cellular cholesterol levels.