ABSTRACT
X-linked adrenoleukodystrophy (X-ALD) is a demyelinating disease due to mutations in the ABCD1 (ALD) gene, encoding a peroxisomal ATP-binding cassette transporter (ALDP). Overexpression of adrenoleukodystrophy-related protein, an ALDP homologue encoded by the ABCD2 (adrenoleukodystrophy-related) gene, can compensate for ALDP deficiency. 4-Phenylbutyrate (PBA) has been shown to induce both ABCD2 expression and peroxisome proliferation in human fibroblasts. We show that peroxisome proliferation with unusual shapes and clusters occurred in liver of PBA-treated rodents in a PPARalpha-independent way. PBA activated Abcd2 in cultured glial cells, making PBA a candidate drug for therapy of X-ALD. The Abcd2 induction observed was partially PPARalpha independent in hepatocytes and totally independent in fibroblasts. We demonstrate that a GC box and a CCAAT box of the Abcd2 promoter are the key elements of the PBA-dependent Abcd2 induction, histone deacetylase (HDAC)1 being recruited by the GC box. Thus, PBA is a nonclassical peroxisome proliferator inducing pleiotropic effects, including effects at the peroxisomal level mainly through HDAC inhibition.
Subject(s)
ATP-Binding Cassette Transporters/metabolism , Adrenoleukodystrophy/genetics , Peroxisome Proliferators/pharmacology , Peroxisomes/ultrastructure , Phenylbutyrates/pharmacology , Up-Regulation/drug effects , ATP Binding Cassette Transporter, Subfamily D , ATP Binding Cassette Transporter, Subfamily D, Member 1 , ATP-Binding Cassette Transporters/genetics , Adrenoleukodystrophy/pathology , Animals , COS Cells , Cells, Cultured , Chlorocebus aethiops , Fibroblasts , Hepatocytes/metabolism , Hepatocytes/ultrastructure , Histone Deacetylases/genetics , Histone Deacetylases/metabolism , Humans , Liver/pathology , Neuroglia/metabolism , Neuroglia/ultrastructure , PPAR alpha/genetics , PPAR alpha/metabolism , Peroxisomes/genetics , Peroxisomes/metabolism , Promoter Regions, Genetic , Rats , Rats, Wistar , Up-Regulation/genetics , Up-Regulation/physiologyABSTRACT
Adrenoleukodystrophy protein (ABCD1), a peroxisomal membrane protein, is mutated in patients affected by X-linked adrenoleukodystrophy (X-ALD). Adrenoleukodystrophy-related protein (ABCD2) is the closest relative of ABCD1. Pharmacological induction of ABCD2 gene expression has been proposed as a novel therapy strategy for X-ALD. Fibrates induce peroxisome proliferation and Abcd2 expression in rodent liver. Here we evaluate the possibility of using peroxisome proliferator-activated receptor alpha (PPARalpha) agonists for pharmacological induction of ABCD2 expression. In the liver of PPARalpha-deficient mice, both the constitutive and the fenofibrate-inducible Abcd2 gene expression was found to be PPARalpha-dependent. In the brain, PPARalpha-deficiency has no effect on Abcd2 expression. In mice orally treated with the novel, highly selective, and potent PPARalpha agonists GW 7647, GW 6867, and tetradecylthioacetic acid, Abcd2 expression was induced in liver and adrenal glands, but not in brain and testis. None of four putative PPREs identified in the 5(')-flanking DNA and in intron 1 of the Abcd2 gene conferred fibrate response in luciferase reporter assays. Thus, although fibrate-mediated Abcd2 induction is PPARalpha-dependent, it appears to be an indirect mechanism. Within the mouse Abcd2 promoter, a putative sterol regulatory element (SRE) similar in sequence and position to the characterized SRE sequence of the human ABCD2 promoter, was identified. A PPARalpha dependent induction of the sterol regulatory-binding protein 2 (SREBP2) and a down-regulation of SREBP1c mRNA levels could be demonstrated after fenofibrate treatment of mice. Our results suggest that the PPARalpha agonist-mediated induction of Abcd2 expression seems to be indirect and possibly mediated by SREBP2.
Subject(s)
Adrenoleukodystrophy/drug therapy , Receptors, Cytoplasmic and Nuclear/agonists , Transcription Factors/agonists , ATP Binding Cassette Transporter, Subfamily D , ATP-Binding Cassette Transporters/drug effects , ATP-Binding Cassette Transporters/genetics , Animals , Brain/drug effects , Brain/metabolism , Butyrates/pharmacology , CCAAT-Enhancer-Binding Proteins/drug effects , CCAAT-Enhancer-Binding Proteins/metabolism , DNA-Binding Proteins/drug effects , DNA-Binding Proteins/metabolism , Drug Evaluation, Preclinical/methods , Gene Expression Regulation/drug effects , Introns , Liver/drug effects , Liver/metabolism , Male , Mice , Mice, Inbred C57BL , Mice, Mutant Strains , Molecular Sequence Data , Phenylurea Compounds/pharmacology , Receptors, Cytoplasmic and Nuclear/deficiency , Response Elements/drug effects , Response Elements/genetics , Sterol Regulatory Element Binding Protein 1 , Sterol Regulatory Element Binding Protein 2 , Sterols/metabolism , Sulfides/pharmacology , Transcription Factors/deficiency , Transcription Factors/drug effects , Transcription Factors/metabolismABSTRACT
X-linked adrenoleukodystrophy (X-ALD) is a demyelinating disorder associated with impaired very-long-chain fatty-acid (VLCFA) beta-oxidation caused by mutations in the ABCD1 (ALD) gene that encodes a peroxisomal membrane ABC transporter. ABCD2 (ALDR) displays partial functional redundancy because when overexpressed, it is able to correct the X-ALD biochemical phenotype. The ABCD2 promoter contains a putative thyroid hormone-response element conserved in rodents and humans. In this report, we demonstrate that the element is capable of binding retinoid X receptor and 3,5,3'-tri-iodothyronine (T3) receptor (TRbeta) as a heterodimer and mediating T3 responsiveness of ABCD2 in its promoter context. After a T3 treatment, an induction of the ABCD2 gene was observed in the liver of normal rats but not that of TRbeta-/- mice. ABCD2 was not induced in the brain of the T3-treated rats. However, we report for the first time that induction of the ABCD2 redundant gene is feasible in myelin-producing cells (differentiated CG4 oligodendrocytes). The induction was specific for this cell type because it did not occur in astrocytes. Furthermore, we observed T3 induction of ABCD2 in human and mouse ABCD1-deficient fibroblasts, which was correlated with normalization of the VLCFA beta-oxidation. Finally, ABCD3 (PMP70), a close homolog of ABCD2, was also induced by T3 in the liver of control rats, but not that of TRbeta-/- mice, and in CG4 oligodendrocytes.
Subject(s)
Adrenoleukodystrophy/genetics , Chemokines, CC/biosynthesis , Promoter Regions, Genetic/physiology , Thyroid Hormones/biosynthesis , Triiodothyronine/physiology , Animals , Astrocytes/metabolism , Cells, Cultured , Chemokine CCL17 , Chemokine CCL22 , Chemokines, CC/genetics , Gene Expression , Humans , Liver/metabolism , Male , Mice , Mice, Knockout , Oligodendroglia/metabolism , Rats , Rats, Sprague-Dawley , Receptors, Retinoic Acid/metabolism , Receptors, Thyroid Hormone/metabolism , Repetitive Sequences, Nucleic Acid , Retinoid X Receptors , Transcription Factors/metabolism , Up-RegulationSubject(s)
ATP-Binding Cassette Transporters/genetics , Dehydroepiandrosterone/pharmacology , ATP Binding Cassette Transporter, Subfamily D , Adrenoleukodystrophy/drug therapy , Adrenoleukodystrophy/genetics , Animals , Cells, Cultured , Gene Expression Regulation/drug effects , Hepatocytes/drug effects , Hepatocytes/metabolism , Humans , Membrane Proteins/genetics , RatsSubject(s)
Adrenoleukodystrophy/drug therapy , Adrenoleukodystrophy/genetics , Phenylbutyrates/therapeutic use , ATP-Binding Cassette Transporters/genetics , Adrenoleukodystrophy/metabolism , Animals , Fatty Acids/metabolism , Gene Expression Regulation/drug effects , Humans , Male , Mice , Mice, Knockout , Multigene Family , RatsABSTRACT
The expression of peroxisome proliferator-activated receptors alpha (PPARalpha) and gamma (PPARgamma) was studied in the human adenocarcinoma Caco-2 cells induced to differentiate by long term culture (15 days). The differentiation of Caco-2 cells was attested by increases in the activities of sucrase-isomaltase and alkaline phosphatase (two brush border enzymes), fatty acyl-CoA oxidase (AOX) and catalase (two peroxisomal enzymes), by an elevation in the protein levels of villin (a brush border molecular marker), AOX, peroxisomal bifunctional enzyme (PBE), catalase and peroxisomal membrane protein of 70 kDa (PMP70). and by the appearance of peroxisomes. The expression of PPARalpha and PPARgamma was investigated by Western blotting, immunocytochemistry, Northern blotting and S1 nuclease protection assay during the differentiation of Caco-2 cells. The protein levels of PPARalpha, PPARgamma, and PPARgamma2 increased gradually during the time-course of Caco-2 cell differentiation. Immunocytochemistry revealed that PPARalpha and gamma were localized in cell nuclei. The PPARgamma1 protein was encoded by PPARgamma3 mRNA because no signal was obtained for PPARgamma1 mRNA using a specific probe in S1 nuclease protection assay. The amount of PPARgamma3 mRNA increased concomitantly to the resulting PPARgamma1 protein. On the other hand, the mRNA of PPARalpha and PPARgamma2 were not significantly changed, suggesting that the increase in their respective protein was due to an elevation of the translational rate. The role played by the PPAR subtypes in Caco-2 cell differentiation is discussed.
