title: Cholera toxin inhibits IL-12 production and CD8alpha+ dendritic cell differentiation by cAMP-mediated inhibition of IRF8 function.
abstract: Prior studies have demonstrated that cholera toxin (CT) and other cAMP-inducing factors inhibit interleukin (IL)-12 production from monocytes and dendritic cells (DCs). We show that CT inhibits Th1 responses in vivo in mice infected with Toxoplasma gondii. This correlated with low serum IL-12 levels and a selective reduction in the numbers of CD8alpha(+) conventional DCs (cDCs) in lymphoid organs. CT inhibited the function of interferon (IFN) regulatory factor (IRF) 8, a transcription factor known to positively regulate IL-12p35 and p40 gene expression, and the differentiation of CD8alpha(+) and plasmacytoid DCs (pDCs). Fluorescence recovery after photobleaching analysis showed that exposure to CT, forskolin, or dibutyryl (db) cAMP blocked LPS and IFN-gamma-induced IRF8 binding to chromatin. Moreover, CT and dbcAMP inhibited the binding of IRF8 to the IFN-stimulated response element (ISRE)-like element in the mouse IL-12p40 promoter, likely by blocking the formation of ISRE-binding IRF1-IRF8 heterocomplexes. Furthermore, CT inhibited the differentiation of pDCs from fms-like tyrosine kinase 3 ligand-treated bone marrow cells in vitro. Therefore, because IRF8 is essential for IL-12 production and the differentiation of CD8alpha(+) cDCs and pDCs, these data suggest that CT and other Gs-protein agonists can affect IL-12 production and DC differentiation via a common mechanism involving IRF8.
authors.affiliation: Laboratory of Molecular and Cellular Immunology, Istituto di Ricovero e Cura a Carattere Scientifico San Raffaele, 00163 Rome, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: la Sala
authors.forename: Jianping
authors.initials: J
authors.lastname: He
authors.forename: Leopoldo
authors.initials: L
authors.lastname: Laricchia-Robbio
authors.forename: Stefania
authors.initials: S
authors.lastname: Gorini
authors.forename: Akiko
authors.initials: A
authors.lastname: Iwasaki
authors.forename: Michael
authors.initials: M
authors.lastname: Braun
authors.forename: George S
authors.initials: GS
authors.lastname: Yap
authors.forename: Alan
authors.initials: A
authors.lastname: Sher
authors.forename: Keiko
authors.initials: K
authors.lastname: Ozato
authors.forename: Brian
authors.initials: B
authors.lastname: Kelsall
mesh_terms: D000818:Animals; D016827:CD8 Antigens / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology / Q000502:physiology*; D005260:Female; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000235:genetics / Q000378:metabolism; D006801:Humans; D050856:Interferon Regulatory Factor-1 / Q000235:genetics / Q000276:immunology; D050835:Interferon Regulatory Factors / Q000235:genetics / Q000276:immunology*; D007371:Interferon-gamma / Q000276:immunology; D018664:Interleukin-12 / Q000096:biosynthesis* / Q000235:genetics; D053762:Interleukin-12 Subunit p40 / Q000235:genetics / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D013154:Spleen / Q000166:cytology; D014123:Toxoplasmosis / Q000276:immunology; D000099185:Interferon Regulatory Factor-8
chemical_list: D016827:CD8 Antigens; D002772:Cholera Toxin; D000242:Cyclic AMP; D019205:GTP-Binding Protein alpha Subunits, Gs; D050856:Interferon Regulatory Factor-1; D050835:Interferon Regulatory Factors; D007371:Interferon-gamma; D018664:Interleukin-12; D053762:Interleukin-12 Subunit p40; D000099185:Interferon Regulatory Factor-8; C431698:CD8alpha antigen; C494258:Irf1 protein, mouse