title: Molecular mechanism of lipopolysaccharide-induced SOCS-3 gene expression in macrophages and microglia.
abstract: Immunological activation of macrophages/microglia within the CNS leads to the production of cytokines and chemokines that ultimately impact on glial and neuronal function. Suppressor of cytokine signaling (SOCS) proteins are negative regulators of adaptive and innate immune responses. Our previous studies demonstrated that SOCS-3 attenuates macrophage/microglial activation in vitro, suggesting that SOCS-3 may exert beneficial effects for immune-mediated CNS diseases in vivo. In this study, we describe LPS as a potent inducer of SOCS-3 transcription and expression in macrophages/microglia. An analysis of the SOCS-3 promoter indicates that AP-1 and IFN-gamma activation sequence (GAS) elements are involved in LPS-induced SOCS-3 transcription. LPS-induced SOCS-3 expression was diminished in IL-10-deficient macrophages at later time points, indicating the involvement of endogenous IL-10 in this response. Blocking STAT-3 expression and activation using STAT-3 small interfering RNA reduced LPS-induced SOCS-3 gene expression. LPS activated the MAPK-ERK1/2, JNK, and p38 pathways that, in addition to STAT-3, were also involved in LPS-induced SOCS-3 expression. LPS treatment of cells led to the acetylation of histones H3 and H4 on the SOCS-3 promoter and the recruitment of STAT-3, c-Jun, c-Fos, CREB-binding protein, p300, and RNA polymerase II to the endogenous SOCS-3 promoter in a time-dependent manner. These results indicate that LPS-induced MAPK activation, the production of endogenous IL-10, and STAT-3 activation play critical roles in SOCS-3 expression, which provides for feedback attenuation of cytokine-induced immune and inflammatory responses in macrophages and microglia.
authors.affiliation: Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Qin
authors.forename: Kevin L
authors.initials: KL
authors.lastname: Roberts
authors.forename: Sandrine A
authors.initials: SA
authors.lastname: Niyongere
authors.forename: Yingzi
authors.initials: Y
authors.lastname: Cong
authors.forename: Charles O
authors.initials: CO
authors.lastname: Elson
authors.forename: Etty N
authors.initials: EN
authors.lastname: Benveniste
mesh_terms: D000107:Acetylation; D000818:Animals; D002460:Cell Line; D005786:Gene Expression Regulation / Q000187:drug effects*; D006657:Histones / Q000378:metabolism; D050832:Interferon-Stimulated Gene Factor 3 / Q000378:metabolism; D016753:Interleukin-10 / Q000096:biosynthesis; D008070:Lipopolysaccharides / Q000494:pharmacology*; D020935:MAP Kinase Signaling System; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D017628:Microglia / Q000187:drug effects* / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D050796:STAT3 Transcription Factor / Q000378:metabolism; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism
chemical_list: D006657:Histones; D050832:Interferon-Stimulated Gene Factor 3; D008070:Lipopolysaccharides; D050796:STAT3 Transcription Factor; C491411:Socs3 protein, mouse; C494087:Stat3 protein, mouse; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D018808:Transcription Factor AP-1; C079868:gamma interferon activation factor; D016753:Interleukin-10; D020928:Mitogen-Activated Protein Kinases