title: Macrophages from the synovium of active rheumatoid arthritis exhibit an activin A-dependent pro-inflammatory profile.
abstract: Rheumatoid arthritis (RA) is a chronic inflammatory disease whose pathogenesis and severity correlates with the presence of macrophage-derived pro-inflammatory cytokines within the inflamed synovium. Macrophage-derived cytokines fuel the pathological processes in RA and are targets of clinically successful therapies. However, although macrophage polarization determines cytokine production, the polarization state of macrophages in RA joints remains poorly defined. To dissect the molecular basis for the tissue-damaging effects of macrophages in RA joints, we undertook the phenotypic and transcriptomic characterization of ex vivo isolated CD14(+) RA synovial fluid (RA-SF) macrophages. Flow cytometry and gene profiling indicated that RA-SF macrophages express pro-inflammatory polarization markers (MMP12, EGLN3, CCR2), lack expression of markers associated with homeostatic and anti-inflammatory polarization (IGF1, HTR2B) and exhibit a transcriptomic profile that resembles the activin A-dependent gene signature of pro-inflammatory in vitro-generated macrophages. In fact, high levels of Smad-activating activin A were found in RA-SF and, accordingly, the Smad signalling pathway was activated in ex vivo-isolated RA-SF macrophages. In vitro experiments on monocytes and macrophages indicated that RA-SF promoted the acquisition of pro-inflammatory markers (INHBA, MMP12, EGLN3, CCR2) but led to a significant reduction in the expression of genes associated with homeostasis and inflammation resolution (FOLR2, SERPINB2, IGF1, CD36), thus confirming the pro-inflammatory polarization ability of RA-SF. Importantly, the macrophage-polarizing ability of RA-SF was inhibited by an anti-activin A-neutralizing antibody, thus demonstrating that activin A mediates the pro-inflammatory macrophage-polarizing ability of RA-SF. Moreover, and in line with these findings, multicolour immunofluorescence evidenced that macrophages within RA synovial membranes (RA-SM) also express pro-inflammatory polarization markers whose expression is activin A-dependent. Altogether, our results demonstrate that macrophages from RA synovial fluids and membranes exhibit an MMP12(+) EGLN3(+) CCR2(+) pro-inflammatory polarization state whose acquisition is partly dependent on activin A from the synovial fluid.
authors.affiliation: Laboratorio de Inmuno-Metabolismo, Hospital General Universitario Gregorio Marañón, Madrid, Spain.
authors.forename: Blanca
authors.initials: B
authors.lastname: Soler Palacios
authors.forename: Lizbeth
authors.initials: L
authors.lastname: Estrada-Capetillo
authors.forename: Elena
authors.initials: E
authors.lastname: Izquierdo
authors.forename: Gabriel
authors.initials: G
authors.lastname: Criado
authors.forename: Concha
authors.initials: C
authors.lastname: Nieto
authors.forename: Cristina
authors.initials: C
authors.lastname: Municio
authors.forename: Isidoro
authors.initials: I
authors.lastname: González-Alvaro
authors.forename: Paloma
authors.initials: P
authors.lastname: Sánchez-Mateos
authors.forename: Jose Luis
authors.initials: JL
authors.lastname: Pablos
authors.forename: Angel L
authors.initials: AL
authors.lastname: Corbí
authors.forename: Amaya
authors.initials: A
authors.lastname: Puig-Kröger
mesh_terms: D028341:Activins / Q000378:metabolism*; D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases / Q000378:metabolism; D066298:In Vitro Techniques; D007249:Inflammation / Q000378:metabolism* / Q000473:pathology; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism* / Q000473:pathology; D008297:Male; D053508:Matrix Metalloproteinase 12 / Q000378:metabolism; D008875:Middle Aged; D010641:Phenotype; D054390:Receptors, CCR2 / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D051785:Smad Proteins / Q000378:metabolism; D013583:Synovial Membrane / Q000378:metabolism* / Q000473:pathology; D059467:Transcriptome
chemical_list: C515334:CCR2 protein, human; D018950:Lipopolysaccharide Receptors; D054390:Receptors, CCR2; D051785:Smad Proteins; C422405:activin A; D028341:Activins; C488894:EGLN3 protein, human; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D053508:Matrix Metalloproteinase 12
keywords: activin A; macrophages; rheumatoid arthritis; synovial fluid