TNF-alpha plus IFN-gamma induce connexin43 expression and formation of gap junctions between human monocytes/macrophages that enhance physiological responses.
In this work, the effects of bacterial LPS, TNF-alpha, and IFN-gamma on gap junctional communication (dye coupling) and on the expression of connexin43 (immunofluorescence, immunoblotting, and RT-PCR) in monocytes/macrophages were studied. Freshly isolated human monocytes plated at high density and treated either with LPS plus IFN-gamma or TNF-alpha plus IFN-gamma became transiently dye coupled (Lucifer yellow) within 24 h. Cells treated with LPS, TNF-alpha, or IFN-gamma alone remained dye uncoupled. In dye-coupled cells, the spread of Lucifer yellow to neighboring cells was reversibly blocked with 18 alpha-glycyrrhetinic acid, a gap junction blocker, but it was unaffected by oxidized ATP or probenecid, which block ionotropic ATP-activated channels and organic anion transporters, respectively. Abs against TNF-alpha significantly reduced the LPS plus IFN-gamma-induced increase in dye coupling. In dye-coupled monocytes/macrophages, but not in control cells, both connexin43 protein and mRNA were detected, and their levels were higher in cells with an elevated incidence of dye coupling. In dye-coupled cells, the localization of connexin43 immunoreactivity was diffuse at perinuclear regions and thin cell processes. The addition of 18-alpha-glycyrrhetinic acid induced a profound reduction of monocyte/macrophage transmigration across a blood brain barrier model. It also induced a significant reduction in the secretion of metalloproteinase-2 in cells treated with TNF-alpha plus IFN-gamma. We propose that some monocyte/macrophage responses are coordinated by connexin-formed membrane channels expressed transiently at inflammatory sites in which these cells form aggregates.
Eugenín
Eliseo A
EA
Departamento de Ciencias Fisiológicas, Pontificia Universidad Católica de Chile, Santiago, Chile. eeugenin@aecom.yu.edu
Brañes
María C
MC
Berman
Joan W
JW
Sáez
Juan C
JC
D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D001812:Blood-Brain Barrier / Q000276:immunology / Q000502:physiology; D002450:Cell Communication / Q000276:immunology / Q000502:physiology*; D002465:Cell Movement / Q000276:immunology / Q000502:physiology; D002478:Cells, Cultured; D018031:Connexin 43 / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D004357:Drug Synergism; D017629:Gap Junctions / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D007249:Inflammation / Q000276:immunology / Q000378:metabolism; D007371:Interferon-gamma / Q000494:pharmacology*; D007546:Isoquinolines / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000276:immunology / Q000502:physiology*; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D009000:Monocytes / Q000166:cytology / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D000276:Adjuvants, Immunologic; D018031:Connexin 43; D007546:Isoquinolines; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; C017475:lucifer yellow; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9