Cyclophilin B attenuates the expression of TNF-α in lipopolysaccharide-stimulated macrophages through the induction of B cell lymphoma-3.
Extracellular cyclophilin A (CyPA) and CyPB have been well described as chemotactic factors for various leukocyte subsets, suggesting their contribution to inflammatory responses. Unlike CyPA, CyPB accumulates in extracellular matrixes, from which it is released by inflammatory proteases. Hence, we hypothesized that it could participate in tissue inflammation by regulating the activity of macrophages. In the current study, we confirmed that CyPB initiated in vitro migration of macrophages, but it did not induce production of proinflammatory cytokines. In contrast, pretreatment of macrophages with CyPB attenuated the expression of inflammatory mediators induced by LPS stimulation. The expression of TNF-α mRNA was strongly reduced after exposure to CyPB, but it was not accompanied by significant modification in LPS-induced activation of MAPK and NF-κB pathways. LPS activation of a reporter gene under the control of TNF-α gene promoter was also markedly decreased in cells treated with CyPB, suggesting a transcriptional mechanism of inhibition. Consistent with this hypothesis, we found that CyPB induced the expression of B cell lymphoma-3 (Bcl-3), which was accompanied by a decrease in the binding of NF-κB p65 to the TNF-α promoter. As expected, interfering with the expression of Bcl-3 restored cell responsiveness to LPS, thus confirming that CyPB acted by inhibiting initiation of TNF-α gene transcription. Finally, we found that CyPA was not efficient in attenuating the production of TNF-α from LPS-stimulated macrophages, which seemed to be due to a modest induction of Bcl-3 expression. Collectively, these findings suggest an unexpected role for CyPB in attenuation of the responses of proinflammatory macrophages.
Unité de Glycobiologie Structurale et Fonctionnelle, Unité Mixte de Recherche 8576 du Centre National de la Recherche Scientifique, Institut Fédératif de Recherche 147, Université Lille Nord de France-Université des Sciences et Technologies, Villeneuve d'Ascq 59655, France.
Adeline
A
Marcant
Agnès
A
Denys
Aurélie
A
Melchior
Pierre
P
Martinez
Audrey
A
Deligny
Mathieu
M
Carpentier
Fabrice
F
Allain
D000081242:B-Cell Lymphoma 3 Protein; D015153:Blotting, Western; D002478:Cells, Cultured; D002634:Chemotaxis, Leukocyte / Q000276:immunology; D047369:Chromatin Immunoprecipitation; D021983:Cyclophilins / Q000276:immunology / Q000378:metabolism*; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000276:immunology; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000276:immunology / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis*; D034741:RNA, Small Interfering; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D014157:Transcription Factors / Q000096:biosynthesis*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000276:immunology
D000081242:B-Cell Lymphoma 3 Protein; C000631344:BCL3 protein, human; D008070:Lipopolysaccharides; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; C081786:cyclophilin B; D021983:Cyclophilins