The cholesterol trafficking defect in Niemann-Pick type C (NPC) disease leads to impaired regulation of cholesterol esterification, cholesterol synthesis, and low density lipoprotein receptor activity. The ATP-binding cassette transporter A1 (ABCA1), which mediates the rate-limiting step in high density lipoprotein (HDL) particle formation, is also regulated by cell cholesterol content. To determine whether the Niemann-Pick C1 protein alters the expression and activity of ABCA1, we determined the ability of apolipoprotein A-I (apoA-I) to deplete pools of cellular cholesterol and phospholipids in human fibroblasts derived from NPC1 and NPC1؉/؊ cells but showed low levels at base line and in response to cholesterol loading in NPC1 ؊/؊ cells. Consistent with impaired ABCA1-dependent lipid mobilization to apoA-I for HDL particle formation, we demonstrate for the first time decreased plasma HDL-cholesterol levels in 17 of 21 (81%) NPC1 ؊/؊ subjects studied. These results indicate that the cholesterol trafficking defect in NPC disease results in reduced activity of ABCA1, which we suggest is responsible for the low HDL-cholesterol in the majority of NPC subjects and partially responsible for the overaccumulation of cellular lipids in this disorder.

Transforming growth factor-beta (TGF-beta) isoforms are multifunctional cytokines that play an important role in wound healing. Transgenic mice overexpressing TGF-beta in the skin under control of epidermal-specific promoters have provided models to study the effects of increased TGF-beta on epidermal cell growth and cutaneous wound repair. To date, most of these studies used transgenic mice that overexpress active TGF-beta in the skin by modulating the latency-associated-peptide to prevent its association with active TGF-beta. The present study is the first to use transgenic mice that overexpress the natural form of latent TGF-beta 1 in the epidermis, driven by the keratin 14 gene promoter to investigate the effects of locally elevated TGF-beta 1 on the healing of partial-thickness burn wounds made on the back of the mice using a CO(2) laser. Using this model, we demonstrated activation of latent TGF-beta after wounding and determined the phenotypes of burn wound healing. We found that introduction of the latent TGF-beta1 gene into keratinocytes markedly increases the release and activation of TGF-beta after burn injury. Elevated local TGF-beta significantly inhibited wound re-epithelialization in heterozygous (42% closed versus 92% in controls, P < 0.05) and homozygous (25% versus 92%, P < 0.01) animals at day 12 after wounding. Interestingly, expression of type I collagen mRNA and hydroxyproline significantly increased in the wounds of transgenic mice, probably as a result of a paracrine effect of the transgene.

Background-Accumulation of excess cholesterol by intimal arterial smooth muscle cells (SMCs) contributes to the formation of foam cells in atherosclerotic lesions. The purpose of this study was to examine the expression and activity of ATP-binding cassette transporter A1 (ABCA1) in model intimal and medial arterial SMCs, in human atherosclerotic coronary artery intimal and medial layers, and in human intimal and medial SMCs. Methods and Results-Model intimal arterial SMCs showed increased cholesteryl ester accumulation, absence of apolipoprotein A-I-mediated lipid efflux, markedly diminished ABCA1 expression, and poor apoA-I binding compared with medial-layer SMCs. Total ABCA1 mRNA and SMC-specific ABCA1 protein levels were diminished in the intimal layer compared with the medial layer of atherosclerotic human coronary arteries. Increased expression of ABCA1 by liver X receptor agonist treatment or gene transfection failed to correct apolipoprotein A-I binding, lipid efflux, or high-density lipoprotein particle formation by intima-type SMCs. In addition to impaired ABCA1 expression, intima-type SMCs appear to lack a critical binding factor or factors required for the apolipoprotein A-I-ABCA1 interaction, cholesterol efflux, and high-density lipoprotein particle formation. Key Words: apolipoproteins Ⅲ atherosclerosis Ⅲ cholesterol Ⅲ lipoproteins Ⅲ muscle, smooth S mooth muscle cells (SMCs) constitute a, or the, major cell type in most stages of atherosclerosis. 1 Relatively little is known, however, about cholesterol homeostasis in arterial SMCs compared with macrophages. Like macrophages, intima-type SMCs express scavenger receptors and develop into smooth muscle foam cells containing excess cholesteryl esters. [2][3][4][5][6] Removal of cholesterol from SMCs, like other cells, is dependent on the binding of apolipoprotein A-I (apoA-I) to the cell surface and the transfer of cellular phospholipids and cholesterol to apoA-I through the actions of the ATP-binding cassette transporter A1 (ABCA1). 7,8 Previous studies have reported marked variability in apoA-I binding and apoA-I-mediated lipid efflux from arterial SMCs obtained from different species, 9,10 suggesting that the apoA-I-SMC interaction may differ depending on SMC phenotype. Recent studies have reported both increased and decreased expression of ABCA1 in atherosclerotic arteries, [11][12][13] but the relative expression of ABCA1 in intimal versus medial layers has not been described. Although ABCA1 is expressed in SMCs originating from the medial layer of normal arteries, 7 its expression in intimal SMCs has not been reported. Conclusion-ABCA1 expression is reduced in cultured model intimal and human atherosclerotic lesion Clinical Perspective on p 3231In addition to excess cholesterol accumulation, intimal SMCs are characterized by a dedifferentiated state, an increased rate of proliferation, a loss of contractility, an increased synthesis of extracellular matrix components, and a reduced expression of SMC markers, including smooth muscle ␣-actin and...