apoE deficiency causes hyperlipidemia and premature atherosclerosis. To determine if macrophage-specific expression of apoE would decrease the extent of atherosclerosis, we expressed human apoE in macrophages of apoE-null mice (apoE-'-) and assessed the effect on lipid accumulation in cells of the arterial wall. Macrophage-specific expression of human apoE in normal mice was obtained by use of the visna virus LTR. These animals were bred with apoE-'-mice to produce animals hemizygous for expression of human apoE in macrophages in the absence of murine apoE (apoE -'-,hTgE '°). Low levels of human apoE mRNA were present in liver and spleen and high levels in lung and peritoneal macrophages. Human apoE was secreted by peritoneal macrophages and was detected in Kupffer cells of the liver. Human apoE in the plasma of apoE-'-,hTgE+'°mice (n = 30) was inversely correlated (P < 0.005) with the plasma cholesterol concentration. After 15 wk on a normal chow diet, atherosclerosis was assessed in apoE-'-,hTgE+'°ani-mals and in apoE-'-,hTgE°'°littermates matched for plasma cholesterol level (-450 mg/dl) and lipoprotein profile. There was significantly less atherosclerosis in both the aortic sinus and in the proximal aorta (P < 0.0001) in the animals expressing the human apoE transgene. In apo-E-'-,hTgE+10 animals, which had detectable atherosclerotic lesions, human apoE was detected in the secretory apparatus of macrophage-derived foam cells in the arterial wall. The data demonstrate that expression of apoE by macrophages is antiatherogenic even in the presence of high levels of atherogenic lipoproteins. The data suggest that apoE prevents atherosclerosis by promoting cholesterol efflux from cells of the arterial wall. (J. Clin. Invest. 1995. 96:2170-2179

No abstract

Although lipid peroxidation in the subendothelial space has been hypothesized to play a central role in atherogenesis, the role of vitamin E in preventing lipid peroxidation and lesion development remains uncertain. Here we show that in atherosclerosis-susceptible apolipoprotein E knockout mice, vitamin E deficiency caused by disruption of the ␣-tocopherol transfer protein gene (Ttpa) increased the severity of atherosclerotic lesions in the proximal aorta. The increase was associated with increased levels of isoprostanes, a marker of lipid peroxidation, in aortic tissue. These results show that vitamin E deficiency promotes atherosclerosis in a susceptible setting and support the hypothesis that lipid peroxidation contributes to lesion development. Ttpa ؊/؊ mice are a genetic model of vitamin E deficiency and should be valuable for studying other diseases in which oxidative stress is thought to play a role.antioxidants O xidative modification of lipoproteins (e.g., low-density lipoproteins) has been hypothesized to play a key role in the pathogenesis of atherosclerosis (1, 2). Because vitamin E is the most potent lipid-soluble antioxidant normally found on lipoproteins in the plasma, there is strong interest in the relationship between vitamin E levels and the development of atherosclerosis. In animal models and human clinical trials, studies of the effects of vitamin E supplementation on atherosclerosis have yielded conf licting results (3-8), and little is known about the effects of vitamin E deficiency on atherosclerosis development (9).The major form of vitamin E in human plasma and tissues is ␣-tocopherol (10). ␣-Tocopherol enrichment of plasma and tissues is mediated by the ␣-tocopherol transfer protein (␣-TTP), a cytosolic lipid-transfer protein expressed in the liver (11)(12)(13)(14). Although the mechanism is unknown (15), ␣-TTP is believed to selectively transfer ␣-tocopherol from lipoproteins taken up by hepatocytes via the endocytic pathway to newly secreted lipoproteins, which facilitate its delivery to peripheral tissues (12). Humans with ␣-TTP gene defects have extremely low plasma ␣-tocopherol concentrations and develop severe neurodegenerative disease unless they are treated with high doses of vitamin E (16-18).To investigate the relationship between vitamin E deficiency and atherosclerosis, we used gene targeting to disrupt the mouse ␣-TTP gene (Ttpa) and generate a genetic model of vitamin E deficiency. We then crossed the ␣-TTP-deficient mice (Ttpa Ϫ/Ϫ ) mice with apolipoprotein (apo) E knockout (Apoe Ϫ/Ϫ ) mice (19), which spontaneously develop atherosclerosis on a chow diet (20,21). This enabled us to generate Apoe Ϫ/Ϫ mice with different Ttpa genotypes (ϩ͞ϩ, ϩ͞Ϫ, and Ϫ͞Ϫ) to test the hypothesis that ␣-TTP and vitamin E deficiency increase atherosclerosis in a susceptible setting. Materials and MethodsGeneration of ␣-TTP Knockout Mice. A 14-kb 129͞Sv genomic clone containing the Ttpa gene was isolated and subcloned into pBSSKII. A sequence replacement vector was constructed by PCR amplifica...