title: Dual regulation of osteopontin production by TLR stimulation in dendritic cells.
abstract: OPN, a cytokine produced, among others, by DCs, is involved in inflammation and defense against pathogens. Here, we report that the activation of the MyD88 pathway by TLR2, TLR5, and TLR7/8 agonists or IL-1β induces high levels of OPN in human DCs. Conversely, LPS and Poly I:C, two TLR3 and TLR4 agonists that engage the TRIF pathway, were ineffective. TLR2 agonists were the strongest OPN inducers, and OPN production was highly stimulated by TLR2-triggering bacteria (Staphylococcus aureus) but not by TLR4-triggering Escherichia coli. Costimulation experiments revealed that TLR3 and TLR4 agonists, beyond being inactive by themselves, sharply limited TLR2-dependent OPN production by activating a TRIF-dependent inhibition of the MyD88-dependent OPN production. MyD88 silencing impaired TLR2-dependent OPN induction, whereas TRIF pathway blockage by chloroquine, dynasore, or TRIF knockdown prevented the TLR3/4 agonist-mediated inhibition, which was independent from the endogenous production of type I IFN, IL-29, IL-10, or TGF-β. LPS and Poly I:C inhibitory activity was associated with the release of a >10-kDa protein factor(s). We also demonstrated that the higher OPN levels produced by S. aureus-treated DCs compared with E. coli-treated DCs were responsible for a markedly increased production of IL-17 by CD4⁺ T cells. These results highlight the biological relevance of the differential OPN induction by TLR2 and TLR4 agonists and emphasize the importance of TLR cross-talk in OPN induction. This implies that OPN regulation by TLR signaling is critical in shaping inflammatory responses and may modulate IL-17 production in response to pathogens.
authors.affiliation: Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Salvi
authors.forename: Sara
authors.initials: S
authors.lastname: Scutera
authors.forename: Silvia
authors.initials: S
authors.lastname: Rossi
authors.forename: Mario
authors.initials: M
authors.lastname: Zucca
authors.forename: Manuela
authors.initials: M
authors.lastname: Alessandria
authors.forename: Deborah
authors.initials: D
authors.lastname: Greco
authors.forename: Daniela
authors.initials: D
authors.lastname: Bosisio
authors.forename: Silvano
authors.initials: S
authors.lastname: Sozzani
authors.forename: Tiziana
authors.initials: T
authors.lastname: Musso
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D003713:Dendritic Cells / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli / Q000276:immunology* / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D020381:Interleukin-17 / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D053594:Myeloid Differentiation Factor 88 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D053495:Osteopontin / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D013211:Staphylococcus aureus / Q000276:immunology* / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D017077:Culture Media, Conditioned; D016207:Cytokines; D020381:Interleukin-17; D008070:Lipopolysaccharides; C507779:MYD88 protein, human; D053594:Myeloid Differentiation Factor 88; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C470409:TICAM1 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D016212:Transforming Growth Factor beta; D053495:Osteopontin
keywords: MyD88-dependent pathway; TRIF-dependent pathway; bacteria; cytokines; monocytes