title: Fibronectin-bound TNF-alpha stimulates monocyte matrix metalloproteinase-9 expression and regulates chemotaxis.
abstract: Tumor necrosis factor alpha (TNF-alpha) is a proinflammatory cytokine implicated in the stimulation of matrix metalloproteinase (MMP) production by several cell types. Our previous studies demonstrated that TNF-alpha avidly binds fibronectin (FN) and laminin, major adhesive glycoproteins of extracellular matrix (ECM) and basement membranes. These findings suggested that TNF-alpha complexing to insoluble ECM components may serve to concentrate its activities to distinct inflamed sites. Herein, we explored the bioactivity and possible function of ECM-bound TNF-alpha by examining its effects on MMP-9 secretion by monocytes. Immunofluorescent staining indicated that LPS-activated monocytes deposited newly synthesized TNF-alpha into ECM-FN. FN-bound TNF-alpha (FN/TNF-alpha) significantly up-regulated MMP-9 expression and secretion by the human monocytic cell line MonoMac-6 and peripheral blood monocytes. Such secretion could be inhibited by antibodies that block TNF-alpha activity and binding to its receptors TNF RI (p55) and TNF RII (p75). Cheniotaxis through ECM gels in the presence of soluble or bound TNF-alpha was inhibited by a hydroxamic acid inhibitor of MMPs (GM6001). It is interesting that, although the adhesion of MonoMac-6 cells to FN/TNF-alpha required functional activated beta1 integrins, FN/TNF-alpha-induced MMP-9 secretion was independent of binding to beta1 integrins, since MMP-9 secretion was unaffected by: (1) neutralizing nAb to alpha4, alpha5, and beta1 subunits, which blocked cell adhesion; (2) a mAb that stimulated beta1 integrin-mediated adhesion; and (3) binding TNF-alpha to the 30-kDa amino-terminal fragment of FN, which lacks the major cell adhesive binding sites. Thus, in addition to their cell-adhesive roles, ECM glycoproteins, such as FN, may play a pivotal role in presenting proinflammatory cytokines to leukocytes within the actual inflamed tissue, thereby affecting their capacities to secrete ECM-degrading enzymes. These TNF-alpha-ECM interactions may serve to limit the cytokine's availability and bioactivity to target areas of inflammation.
authors.affiliation: Department of Immunology, The Weizmann Institute of Science, Rehovot, Israel.
authors.forename: G G
authors.initials: GG
authors.lastname: Vaday
authors.forename: R
authors.initials: R
authors.lastname: Hershkoviz
authors.forename: M A
authors.initials: MA
authors.lastname: Rahat
authors.forename: N
authors.initials: N
authors.lastname: Lahat
authors.forename: L
authors.initials: L
authors.lastname: Cahalon
authors.forename: O
authors.initials: O
authors.lastname: Lider
mesh_terms: D000818:Animals; D002417:Cattle; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D002634:Chemotaxis, Leukocyte / Q000187:drug effects* / Q000502:physiology; D005109:Extracellular Matrix / Q000378:metabolism / Q000502:physiology; D005353:Fibronectins / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D016023:Integrins / Q000502:physiology; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis* / Q000378:metabolism; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D018124:Receptors, Tumor Necrosis Factor / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D005353:Fibronectins; D016023:Integrins; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D020780:Matrix Metalloproteinase 9