Tetracycline inhibition identifies the cellular sources of collagenase in gingival crevicular fluid in different forms of periodontal diseases

Abstract

Tetracyclines have recently been shown to inhibit the activity of mammalian matrix metalloproteinases, i.e. type I collagenase (MMP-1) and type IV collagenase/gelatinase (MMP-2). The specificity of this effect, however, has not been examined in detail. In the present study, doxycycline (a clinically widely used commercial tetracycline) and 4-de-dimethylaminotetracycline (CMT-1, a chemically modified non-antimicrobial tetracycline) were tested, at a wide range of concentrations, for their ability to inhibit human neutrophil and fibroblast interstitial collagenases, which are distinct gene products, as well as collagenase in human gingival crevicular fluid (an inflammatory exudate in periodontal lesions) obtained from adult, juvenile and diabetic adult periodontitis patients. The concentrations of these two tetracyclines, required to inhibit 50% of the collagenase activity (IC50), were found to be 15-30 μM for purified human neutrophil collagenase as well as collagenase in gingival crevicular fluid of adult periodontitis patients and diabetic adult periodontitis patients, thus approximating in vivo therapeutic tetracycline levels. In contrast, the fibroblast collagenase and collagenase in gingival crevicular fluid of patients with juvenile periodontitis were relatively resistant to tetracycline inhibition: the IC50 for doxycycline and CMT-1 were 280 and 500μM, respectively. The authors propose that (1) systemic levels of tetracyclines can inhibit pathological proteolysis by inhibiting collagenolysis involving neutrophil collagenase, but do not inhibit fibroblast type collagenase; (2): the therapeutic importance of neutrophil collagenase inhibition by tetracyclines is evident in the light of the fact that this proteinase, unlike fibroblast collagenase, is relatively resistant to the potent endogenous metalloproteinase inhibitors, α2-macroglobulin and tissue inhibitor of metalloproteinases; and (3) tetracycline inhibition (IC50) analysis of collagenases in tissue and biological fluid samples may serve as a convenient 'probe' to identify the cellular origin of the enzyme. Furthermore, tetracycline treatment may be an effective adjunct in treatment aimed at controlling periodontal breakdown in adult/diabetic periodontitis patients. On the other hand, in juvenile periodontitis the anti-collagenase property of tetracyclines may be less important to the control of periodontal tissue destruction because of the tetracycline resistance of fibroblast-type collagenase.