Molecular forms and fragments of salivary MMP-8 in relation to periodontitis

To investigate the molecular forms of salivary matrix metalloproteinase (MMP)-8 in relation to periodontitis.

Molecular forms, degree of activation and fragmentation of neutrophilic and mesenchymal-type MMP-8 isoforms were analysed from salivary samples of 81 subjects with generalized periodontitis, 63 subjects with localized periodontitis and 79 subjects without pocket teeth, by using western-immunoblots with computer quantitation. In addition, human recombinant proMMP-8 was in vitro activated by Treponema denticola chymotrypsin-like protease (Td-CTLP), sodium hypochlorite (NaOCl, 1 mM, oxidant) or amino phenyl mercuric acetate (APMA, 1 mM).

In saliva of periodontitis-affected individuals, MMP-8 is found in multiple forms, that is, complexes, active and pro-forms of neutrophilic and mesenchymal-type MMP-8, and especially 20-27 kDa fragments. The quantity of these fragments was elevated in both localized and generalized forms of periodontitis. Moreover, the tested activators (Td-CTLP, NaOCl and APMA) activated inactive proMMP-8, resulting in fragments of 20-27 kDa, in vitro, and salivary concentrations of T. denticola correlated significantly with salivary levels of fragmented MMP-8.

The present results indicate that during the development and progression of periodontitis, MMP-8 appears as activated and fragmented, and treponemal proteases most likely play role in this cascade.