The role of soluble interleukin (IL)-6 receptor in mediating the effects of IL-6 on matrix metalloproteinase-1 and tissue inhibitor of metalloproteinase-1 expression by gingival fibroblasts.
BACKGROUND
Interleukin-6 (IL-6) is a multifunctional cytokine thought to play a role in the tissue destruction that characterizes periodontal disease. IL-6 exerts its cellular effects through a cell-surface receptor which also exists in a soluble form (sIL-6r). This study investigated the effects of IL-6 on matrix metalloproteinase (MMP)-1 activity in gingival fibroblast cultures, specifically determining the role of the sIL-6r in mediating these actions.


METHODS
Fibroblasts were grown to confluence, washed in Hank's balanced saline solution (HBSS), and then cultured for 72 hours in serum-free medium supplemented with 0.2% bovine serum albumin, 1 microgram/ml Escherichia coli LPS and containing various combinations of IL-6 and its soluble receptor over the concentration range 0 to 1,000 ng/ml. MMP-1 and tissue inhibitor of MMP (TIMP)-1 protein levels in the conditioned medium were assessed by enzyme-linked immunosorbent assay (ELISA) and collagenolytic activity determined using a 3H-acetylated type I collagen degradation assay.


RESULTS
Results indicated that the addition of IL-6 alone to cultures, over the concentration range 0 to 1,000 ng/ml, had no significant effect on MMP-1 protein expression. However, addition of IL-6 in combination with its soluble receptor resulted in a statistically significant, dose-dependent upregulation in MMP-1 expression. The IL-6/sIL-6r combination also induced a significant increase in collagenolytic activity in cultures. IL-6 and sIL-6r, either alone or in combination, had no marked effect on TIMP expression or cell growth.


CONCLUSIONS
These data strongly suggest that future clinical studies investigating the role of IL-6 in periodontal disease must also determine the levels of sIL-6r within the periodontal tissues.
Irwin
Chris R
CR
Department of Periodontology, School of Dentistry, Queen's University, Belfast, N. Ireland. c.r.irwin@qub.ac.uk
Myrillas
Theofilos T
TT
Traynor
Patrick
P
Leadbetter
Nicola
N
Cawston
Timothy E
TE
D000328:Adult; D000704:Analysis of Variance; D002478:Cells, Cultured; D003094:Collagen / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005347:Fibroblasts / Q000201:enzymology; D005881:Gingiva / Q000166:cytology / Q000201:enzymology*; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism* / Q000494:pharmacology; D008070:Lipopolysaccharides; D008297:Male; D020781:Matrix Metalloproteinase 1 / Q000096:biosynthesis* / Q000502:physiology; D010510:Periodontal Diseases / Q000139:chemically induced / Q000201:enzymology*; D019947:Receptors, Interleukin-6 / Q000378:metabolism*; D012995:Solubility; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000096:biosynthesis; D015854:Up-Regulation
D015850:Interleukin-6; D008070:Lipopolysaccharides; D019947:Receptors, Interleukin-6; D019715:Tissue Inhibitor of Metalloproteinase-1; D003094:Collagen; D020781:Matrix Metalloproteinase 1