Tangier disease (TD) was first discovered nearly 40 years ago in two siblings living on Tangier Island. This autosomal co-dominant condition is characterized in the homozygous state by the absence of HDL-cholesterol (HDL-C) from plasma, hepatosplenomegaly, peripheral neuropathy and frequently premature coronary artery disease (CAD). In heterozygotes, HDL-C levels are about one-half those of normal individuals. Impaired cholesterol efflux from macrophages leads to the presence of foam cells throughout the body, which may explain the increased risk of coronary heart disease in some TD families. We report here refining of our previous linkage of the TD gene to a 1-cM region between markers D9S271 and D9S1866 on chromosome 9q31, in which we found the gene encoding human ATP cassette-binding transporter 1 (ABC1). We also found a change in ABC1 expression level on cholesterol loading of phorbol ester-treated THP1 macrophages, substantiating the role of ABC1 in cholesterol efflux. We cloned the full-length cDNA and sequenced the gene in two unrelated families with four TD homozygotes. In the first pedigree, a 1-bp deletion in exon 13, resulting in truncation of the predicted protein to approximately one-fourth of its normal size, co-segregated with the disease phenotype. An in-frame insertion-deletion in exon 12 was found in the second family. Our findings indicate that defects in ABC1, encoding a member of the ABC transporter superfamily, are the cause of TD.

Abstract-The potential role of anti-inflammatory cytokines in the modulation of the atherosclerotic process remains unknown. Interleukin (IL)-10 has potent deactivating properties in macrophages and T cells and modulates many cellular processes that may interfere with the development and stability of the atherosclerotic plaque. IL-10 is expressed in human atherosclerosis and is associated with decreased signs of inflammation. In the present study, we show that IL-10 -deficient C57BL/6J mice fed an atherogenic diet and raised under specific pathogen-free conditions exhibit a significant 3-fold increase in lipid accumulation compared with wild-type mice. Interestingly, the susceptibility of IL-10 -deficient mice to atherosclerosis was exceedingly high (30-fold increase) when the mice were housed under conventional conditions. Atherosclerotic lesions of IL-10 -deficient mice showed increased T-cell infiltration, abundant interferon-␥ expression, and decreased collagen content. In vivo, transfer of murine IL-10 achieved 60% reduction in lesion size. These results underscore the critical roles of IL-10 in both atherosclerotic lesion formation and stability. Moreover, IL-10 appears to be crucial as a protective factor against the effect of environmental pathogens on atherosclerosis. The full text of this article is available at http://www.circresaha.org. (Circ Res. 1999;85:e17-e24.)

Apolipoproteins are protein constituents of plasma lipid transport particles. Human apolipoprotein A-IV (apoA-IV) was expressed in the liver of C57BL/6 mice and mice deficient in apoE, both of which are prone to atherosclerosis, to investigate whether apoA-IV protects against this disease. In transgenic C57BL/6 mice on an atherogenic diet, the serum concentration of high density lipoprotein (HDL) cholesterol increased by 35 percent, whereas the concentration of endogenous apoA-I decreased by 29 percent, relative to those in transgenic mice on a normal diet. Expression of human apoA-IV in apoE-deficient mice on a normal diet resulted in an even more severe atherogenic lipoprotein profile, without affecting the concentration of HDL cholesterol, than that in nontransgenic apoE-deficient mice. However, transgenic mice of both backgrounds showed a substantial reduction in the size of atherosclerotic lesions. Thus, apoA-IV appears to protect against atherosclerosis by a mechanism that does not involve an increase in HDL cholesterol concentration.

The regulation of liver apolipoprotein (apo) A-I gene expression by fibrates was studied in human apo A-I transgenic mice containing a human genomic DNA fragment driving apo A-I expression in liver. Treatment with fenofibrate (0.5% wt/wt) for 7 d increased plasma human apo A-I levels up to 750% and HDL-cholesterol levels up to 200% with a shift to larger particles. The increase in human apo A-I plasma levels was time and dose dependent and was already evident after 3 d at the highest dose (0.5% wt/wt) of fenofibrate. In contrast, plasma mouse apo A-I concentration was decreased after fenofibrate in nontransgenic mice. The increase in plasma human apo A-I levels after fenofibrate treatment was associated with a 97% increase in hepatic human apo A-I mRNA, whereas mouse apo A-I mRNA levels decreased to 51%. In nontransgenic mice, a similar down-regulation of hepatic apo A-I mRNA levels was observed. Nuclear run-on experiments demonstrated that the increase in human apo A-I and the decrease in mouse apo A-I gene expression after fenofibrate occurred at the transcriptional level. Since part of the effects of fibrates are mediated through the nuclear receptor PPAR (peroxisome proliferator-activated receptor), the expression of the acyl CoA oxidase (ACO) gene was measured as a control of PPAR activation. Both in transgenic and nontransgenic mice, fenofibrate induced ACO mRNA levels up to sixfold. When transgenic mice were treated with gemfibrozil (0.5% wt/wt) plasma human apo A-I and HDL-cholesterol levels increased 32 and 73%, respectively, above control levels. The weaker effect of this compound on human apo A-I and HDL-cholesterol levels correlated with a less pronounced impact on ACO mRNA levels (a threefold increase) suggesting that the level of induction of human apo A-I gene is related to the PPAR activating potency of the fibrate used. Treatment of human primary hepatocytes with fenofibric acid (500 M) provoked an 83 and 50% increase in apo A-I secretion and mRNA levels, respectively, supporting that a direct action of fibrates on liver human apo A-I production leads to the observed increase in plasma apo A-I and HDLcholesterol. ( J. Clin. Invest. 1996. 97:2408-2416.)

Ischemia induces both hypoxia and inflammation that trigger angiogenesis. The inflammatory reaction is modulated by production of anti-inflammatory cytokines. This study examined the potential role of a major anti-inflammatory cytokine, interleukin (IL)-10, on angiogenesis in a model of surgically induced hindlimb ischemia. Ischemia was produced by artery femoral occlusion in both C57BL/6J IL-10(+/+) and IL-10(-/-) mice. After 28 days, angiogenesis was quantified by microangiography, capillary, and arteriole density measurement and laser Doppler perfusion imaging. The protein levels of IL-10 and vascular endothelial growth factor (VEGF) were determined by Western blot analysis in hindlimbs. IL-10 was markedly expressed in the ischemic hindlimb of IL-10(+/+) mice. Angiogenesis in the ischemic hindlimb was significantly increased in IL-10(-/-) compared with IL-10(+/+) mice. Indeed, angiographic data showed that vessel density in the ischemic leg was 10.2+/-0.1% and 5.7+/-0.4% in IL-10(-/-) and IL-10(+/+) mice, respectively (P:<0.01). This corresponded to improved ischemic/nonischemic leg perfusion ratio by 1.4-fold in IL-10(-/-) mice compared with IL-10(+/+) mice (0.87+/-0. 05 versus 0.63+/-0.01, respectively; P:<0.01). Revascularization was associated with a 1.8-fold increase in tissue VEGF protein level in IL-10(-/-) mice compared with IL-10(+/+) mice (P:<0.01). In vivo electrotransfer of murine IL-10 cDNA in IL-10(-/-) mice significantly inhibited both the angiogenic process and the rise in VEGF protein level observed in IL-10(-/-) mice. No changes in vessel density or VEGF content were observed in the nonischemic hindlimb. These findings underscore the antiangiogenic effect of IL-10 associated with the downregulation of VEGF expression and suggest a role for the inflammatory balance in the modulation of ischemia-induced angiogenesis.

Background-Hypoalphalipoproteinemia is the most common lipoprotein abnormality in patients with coronary artery disease, yet its causes are unknown. Methods and Results-We show that the homozygous staggerer (sg/sg) mutant mouse, which carries a deletion within the nuclear receptor ROR␣ gene, develops severe atherosclerosis when maintained on an atherogenic diet. In addition, sg/sg mice display a profound hypoalphalipoproteinemia, which is associated with decreased plasma levels of the major HDL proteins, apolipoprotein (apo) A-I and apoA-II. This decrease in HDL levels in sg/sg mice is due to lowered apoA-I gene expression in the intestine but not in the liver. ApoA-II gene expression is unaffected. Conclusions-These results suggest that the ROR␣ gene contributes to the plasma HDL level and susceptibility to atherosclerosis. (Circulation. 1998;98:2738-2743.)

Overexpression of human apo A-I in rabbits inhibits the development of atherosclerosis in this animal model that resembles, in many respects, human atherosclerosis.

The reality of the atheroprotective effect of estrogens is still a matter of debate, and its unknown mechanisms could involve favorable changes in blood lipids and lipoproteins and/or direct action at the level of the arterial wall. We used the recently developed animal model of atherosclerosis constituted by apolipoprotein E-deficient mice in an attempt to clarify these issues. Male and female animals, fed a low-fat chow diet, were treated with increasing doses of 17 beta-estradiol (E2) after castration and compared with testosterone treated and uncastrated (intact) animals. Total serum cholesterol, LDL-cholesterol, and HDL-cholesterol concentrations decreased under E2 treatment in each sex and were weakly correlated with lesion area. However, a highly significant correlation between lesion area and serum E2 levels also suggested a direct action of E2 on cells of the vascular wall. A dose-response curve analysis revealed that these activities were sex-dependent, with females being nearly twice as sensitive to E2 as males. It also revealed that the atheroprotective activity was recruited at higher E2 concentrations than those needed by other E2 target tissues such as uterus or functions such as apoA-1 and LDL production and/or clearance rates.