title: IFN-gamma down-regulates ABCA1 expression by inhibiting LXRalpha in a JAK/STAT signaling pathway-dependent manner.
abstract: Interferon gamma (IFN-gamma) is an immunomodulatory and anti-microbial cytokine, which has a variety of proatherogenic effects. It has been reported that IFN-gamma can down-regulate ABCA1 expression. However, its mechanism is elusive. In the present study, we have investigated the effect of IFN-gamma on ABCA1 expression and cholesterol efflux in THP-1 macrophage-derived foam cells. IFN-gamma decreased ABCA1 expression at both transcriptional and translational levels in a dose-dependent manner. Cellular cholesterol content was increased while cholesterol efflux was decreased by IFN-gamma treatment. Liver X receptor alpha (LXRalpha), which can regulate the expression of ABCA1, was also down-regulated by IFN-gamma treatment. LXRalpha-specific activation by LXRalpha agonist almost compensated the down-regulation of ABCA1 expression by IFN-gamma, while siRNA of LXRalpha led to down-regulation of ABCA1 expression more significantly than IFN-gamma. IFN-gamma induced phosphorylation of STAT1 and expression of STAT1alpha in the nucleus, which was inhibited by a JAK inhibitor AG-490. Treatment with STAT1 siRNA further enhanced down-regulation of LXRalpha mRNA by IFN-gamma. Furthermore, AG-490 and STAT1 siRNA almost compensated the effect of IFN-gamma on ABCA1 expression and cholesterol efflux. In conclusion, IFN-gamma may first down-regulate expression of LXRalpha through the JAK/STAT1 signaling pathway and then decrease expression of ABCA1 and cholesterol efflux in THP-1 macrophage-derived foam cells. Therefore, our study may be useful in understanding the critical effect of IFN-gamma in pathogenesis of atherosclerosis.
authors.affiliation: Institute of Cardiovascular Research, Life Science Research Center, University of South China, Nanhua University, Hengyang, Hunan, China.
authors.forename: Xin-rui
authors.initials: XR
authors.lastname: Hao
authors.forename: Dong-li
authors.initials: DL
authors.lastname: Cao
authors.forename: Yan-wei
authors.initials: YW
authors.lastname: Hu
authors.forename: Xiao-xu
authors.initials: XX
authors.lastname: Li
authors.forename: Xie-hong
authors.initials: XH
authors.lastname: Liu
authors.forename: Ji
authors.initials: J
authors.lastname: Xiao
authors.forename: Duan-fang
authors.initials: DF
authors.lastname: Liao
authors.forename: Jim
authors.initials: J
authors.lastname: Xiang
authors.forename: Chao-ke
authors.initials: CK
authors.lastname: Tang
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis*; D050197:Atherosclerosis / Q000378:metabolism; D002784:Cholesterol / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D005786:Gene Expression Regulation; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism*; D053613:Janus Kinase 1 / Q000378:metabolism*; D000071518:Liver X Receptors; D008264:Macrophages / Q000378:metabolism; D057093:Orphan Nuclear Receptors; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000096:biosynthesis*; D050794:STAT1 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction; D020032:Tyrphostins / Q000494:pharmacology
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D004268:DNA-Binding Proteins; D000071518:Liver X Receptors; C000605213:NR1H3 protein, human; D057093:Orphan Nuclear Receptors; D034741:RNA, Small Interfering; D018160:Receptors, Cytoplasmic and Nuclear; D050794:STAT1 Transcription Factor; D020032:Tyrphostins; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; D007371:Interferon-gamma; D002784:Cholesterol; D053613:Janus Kinase 1