Tangier disease (TD) is an autosomal recessive disorder of lipid metabolism. It is characterized by absence of plasma high-density lipoprotein (HDL) and deposition of cholesteryl esters in the reticulo-endothelial system with splenomegaly and enlargement of tonsils and lymph nodes. Although low HDL cholesterol is associated with an increased risk for coronary artery disease, this condition is not consistently found in TD pedigrees. Metabolic studies in TD patients have revealed a rapid catabolism of HDL and its precursors. In contrast to normal mononuclear phagocytes (MNP), MNP from TD individuals degrade internalized HDL in unusual lysosomes, indicating a defect in cellular lipid metabolism. HDL-mediated cholesterol efflux and intracellular lipid trafficking and turnover are abnormal in TD fibroblasts, which have a reduced in vitro growth rate. The TD locus has been mapped to chromosome 9q31. Here we present evidence that TD is caused by mutations in ABC1, encoding a member of the ATP-binding cassette (ABC) transporter family, located on chromosome 9q22-31. We have analysed five kindreds with TD and identified seven different mutations, including three that are expected to impair the function of the gene product. The identification of ABC1 as the TD locus has implications for the understanding of cellular HDL metabolism and reverse cholesterol transport, and its association with premature cardiovascular disease.

Humanin (HN) is a recently identified neuroprotective and antiapoptotic peptide derived from a portion of the mitochondrial MT-RNR2 gene. We provide bioinformatic and expression data suggesting the existence of 13 MT-RNR2-like nuclear loci predicted to maintain the open reading frames of 15 distinct full-length HN-like peptides. At least ten of these nuclear genes are expressed in human tissues, and respond to staurosporine (STS) and beta-carotene. Sequence comparisons of the nuclear HN isoforms and their homologues in other species reveal two consensus motifs, encompassing residues 5-11 (GFS/NCLLL), and 14-19 (SEIDLP/S). Proline vs serine in position 19 may determine whether the peptide is secreted or not, while threonine in position 13 may be important for cell surface receptor binding. Cytoprotection against the STS-induced apoptosis conferred by the polymorphic HN5 variant, in which threonine in position 13 is replaced with isoleucine, is reduced compared to the wild type HN5 peptide.

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Activated lipid-laden macrophages in the vascular wall are key modulators of the inflammatory processes underlying atherosclerosis. We demonstrate here that the ATP-binding cassette (ABC) transporter ABCA1 is induced during differentiation of human monocytes into macrophages. ABCA1 has been implicated in macrophage interleukin-1β secretion and apoptosis. Moreover, ABCA1 mRNA and protein levels are strongly upregulated by uptake of modified LDL and downregulated by HDL₃-mediated lipid efflux in macrophages. Mutation analysis in patients with the classical Tangier disease (TD), a monogenetic disorder characterized by hypersplenism, macrophage accumulation and deposition of cholesteryl esters in the reticuloendothelial system, low plasma HDL and premature atherosclerosis, revealed deleterious mutations in their ABCA1 gene. The localization pattern of the mutations within the ABCA1 protein appears to determine the tropism for either the reticuloendothelial system, as seen in the classical TD phenotype, or the artery wall, as in the case of HDL deficiency in the absence of splenomegaly. In a comprehensive analysis of the expression and regulation of all currently known human ABC transporters, we identified additional cholesterol-responsive genes that are induced during monocyte differentiation into macrophages. Our results indicate a dual regulatory function for ABCA1 in macrophage lipid metabolism and inflammation.

Endothelial cells play an important role in angiogenesis (formation of new vessels from preexisting ones), which is essential for organogenesis, tissue remodeling but also inflammatory response, carcinogenesis in all periods of our life. Beta-carotene (BC) in non-toxic concentrations (up to 3 microM) had no detectable effect on HUVECs (human umbilical vein endothelial cells) proliferation or apoptosis, despite significant changes of the expression patterns of pro- and anti-apoptotic genes. However beta-carotene did not change the tubulogenic activity of HUVEC in the in vitro angiogenesis model, it potently accelerated the bFGF-induced development of microcapillaries, as well as the migration of endothelial cells, in matrigel plug injected subcutaneously to mice. Potent activation of endothelial cell migration in the in vitro model of chemotaxis was also observed. According to the microarray data, genes involved in cell/cell and cell/matrix adhesion, matrix reorganization, activation of chemotaxis, the G-protein regulated intracellular signaling as well as genes involved in the rapid remodeling of protein cytoskeleton were the most affected by BC in HUVEC. We conclude that beta-carotene in the physiological concentration range stimulates early steps of angiogenesis by the activation of cellular migration as well as matrix reorganization and decrease of cell adhesion.

It was shown that high doses of beta-carotene (>30 microM) decrease proliferation of prostate cancer cells in vitro. However, it is rather doubtful whether such concentration of beta-carotene is really accessible at cellular level. We studied the effect of 3 and 10 microM beta-carotene on proliferation and gene expression in LNCaP and PC-3 prostate cancer cell lines. Beta-carotene--more efficiently absorbed from medium by androgen-sensitive LNCaP cells--increased proliferation of LNCaP cells whereas it had weaker effect on PC-3 cells. Initial global analysis of expression of genes in both cell lines treated with 10 microM beta-carotene (Affymetrix HG-U133A) showed remarkable differences in number of responsive genes. Their recognition allows for conclusion that differences between prostate cancer cell lines in response to beta-carotene treatment are due to various androgen sensitivities of LNCaP and PC-3 cells. Detailed analysis of expression of selected genes in beta-carotene treated LNCaP cells at the level of mRNA and protein indicated that the observed increase of proliferation could have been the result of slight induction of a few genes affecting proliferation (c-myc, c-jun) and apoptosis (bcl-2) with no significant effect on major cell cycle control genes (cdk2, RB, E2F-1).

The influence of beta-carotene (BC) and its derivatives on differentiation, proliferation and apoptosis in three human acute leukemia cell lines was studied. We investigated: (i) the cellular uptake of BC, (ii) the cytotoxicity, (iii) the effect on cell cycle progression and/or apoptosis. The dose- and time-dependent pattern of cellular BC uptake in all studied cell lines was seen. We did not observe any cytotoxic effect of BC and ATRA in the chosen concentrations. There was only limited effect of BC on gene expression. The microarrray analysis of U-937 cell line exposed to BC for 72 h showed an increased expression of BAX gene. This finding was confirmed by real-time Q-PCR analysis, and supported by a flow cytometry apoptosis tests. We did not observe any influence of studied components on cellular proliferation. The induction of differentiation after incubation with ATRA in HL-60 cells was noted. The induction of cellular apoptosis by BC was seen in all studied cell lines. We demonstrated that BC used in the concentrations achievable in vivo does not affect the proliferation and differentiation process of the studied leukemic cell lines, but can influence and enhance the apoptosis by modulating the expression of the regulatory genes.

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