MMP-9 from TNF alpha-stimulated keratinocytes binds to cell membranes and type I collagen: a cause for extended matrix degradation in inflammation?
Activated keratinocytes synthesize increased amounts of matrix metalloproteinases during inflammation. Incubation of mucosal keratinocytes with TNFalpha (24 h) increased their expression of MMP-9 mRNA, which was followed by the corresponding increase in the expression of MMP-9 protein. This stimulation was dose dependent and continued for several days after the initial exposure to TNFalpha. In contrast, the expression of MMP-2 was not influenced by TNFalpha. IFNgamma caused a significant dose-dependent inhibition in the TNFalpha-stimulated expression of MMP-9. TNFalpha did not markedly influence keratinocyte growth, while INFgamma potently inhibited cell growth. Cytokine-stimulated keratinocytes secreted most MMP-2 and MMP-9 extracellularly into the culture medium, but MMP-9 was also found in the membrane extract of keratinocytes. Furthermore, wild-type and recombinant MMP-9 were bound to noncollageneous and nonintegrin components of the mucosal keratinocyte cell surface. MMP-9 was not, however, found in the extracellular matrix deposited by the keratinocytes in culture. Type I and IV collagens and gelatin but no other purified extracellular matrix nor basement membrane proteins (types I and IV collagen, laminin-1 and -5, fibronectin) were able to bind MMP-9 from the conditioned medium. Binding of MMP-9 from keratinocyte conditioned medium was demonstrated along the collagen fibers using immunoelectron microscopy. These phenomena may participate in extended matrix degradation in chronic inflammation.
Mäkelä
M
M
Department of Periodontology, University of Turku, Finland. rkumar@mayo.edu
Salo
T
T
Larjava
H
H
D002455:Cell Division / Q000187:drug effects; D002461:Cell Line, Transformed; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism*; D017364:Collagenases / Q000096:biosynthesis / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005109:Extracellular Matrix / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology*; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D018093:Gelatinases / Q000096:biosynthesis; D006801:Humans; D007249:Inflammation / Q000201:enzymology / Q000473:pathology; D007371:Interferon-gamma / Q000494:pharmacology; D015603:Keratinocytes / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology*; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D008666:Metalloendopeptidases / Q000096:biosynthesis; D009092:Mucous Membrane / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D011485:Protein Binding / Q000187:drug effects; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D016326:Extracellular Matrix Proteins; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D003094:Collagen; D017364:Collagenases; D018093:Gelatinases; D008666:Metalloendopeptidases; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9