Matrix metalloproteinases (MMPs) in oral diseases

Effect of E. faecalis on the release of serine proteases elastase and cathepsin G, and collagenase-2 (MMP-8) by human polymorphonuclear leukocytes (PMNs)

AIM

To measure the release of hydrolytic enzymes [elastase, cathepsin G and collagenase-2 (MMP-8)] from human polymorphonuclear leukocytes (PMNs) during interaction with strains of Enterococcus faecalis isolated from endodontic infections.

METHODOLOGY

Six E. faecalis strains isolated from treatment resistant cases of apical periodontitis were included in the study. Overnight cultures of the microbes were used for the experiments. PMNs were isolated using the Ficoll Paque technique, and their vitality was assessed throughout the experiments by the Trypan Blue exclusion test. A known amount of microbes and PMNs were mixed in PBS at +37 degrees C in air, and the release of elastase, cathepsin G and MMP-8 was measured at 0, 20, 60 and 120 min after initiation of incubation. The activities of elastase and cathepsin G were analysed by spectrophotometer assays using specific synthetic peptide substrates, and MMP-8 by western immunoblotting quantitated by computer densitometry. PMNs incubated in buffer without any added microbes served as negative controls, cells incubated with 5 ng mL(-1) phorbol myristic acetate (PMA) served as a positive control. The 95% confidence interval was used to compare the relative amount of elastase and cathepsin G released from the samples.

RESULTS

One E. faecalis strain induced a similar or higher elastase, cathepsin G and MMP-8 release than the positive control, whereas the other five strains induced only moderate or no release of the three enzymes examined as compared with the negative and positive controls. Western immunoblot revealed that released MMP-8 had molecular sizes of 60 and 75 kDa representing active and latent forms of MMP-8. In addition, >110 kDa high molecular size and a fragmented 20-30 kDa MMP-8 species could be observed.

CONCLUSIONS

The majority of the E. faecalis strains induced little or no release of hydrolytic enzymes from the PMN cells. The finding may partly explain the clinical observation that root canal infections dominated by E. faecalis are usually symptom free.

In vivo relationship between collagenase-2 and interleukin-8 but not tumour necrosis factor-alpha in chronic rhinosinusitis with nasal polyposis

BACKGROUND

The characteristic feature of chronic rhinosinusitis with nasal polyposis (CRSwNP) is eosinophilic inflammation of the sinus mucosa; a type of inflammation also seen in asthmatic airways. Similar histopathologic findings of airway remodelling are present in both diseases. Remodelling is tightly controlled by matrix metalloproteinases (MMP). Increase of collagenase-2 (MMP-8) expression in the bronchial epithelial cells has been described in asthmatic patients, but it has not been studied in CRSwNP.

METHODS

The concentrations and degree of activation of MMP-8 were analysed by immunofluorometric assay and Western blotting, respectively, in sinus mucus samples from CRSwNP patients and in nasal lavages from healthy controls in relation to inductive cytokines interleukin-8 (IL-8) and tumour necrosis factor-alpha (TNF-alpha).

RESULTS

Significantly elevated levels of MMP-8 and IL-8 but not TNF-alpha were found in CRSwNP patients relative to controls. In particular, the activation of mesenchymal-type MMP-8 but not polymorphonuclear-type MMP-8 was associated with elevated IL-8 levels.

CONCLUSIONS

The IL-8 and MMP-8 seemingly form an inductive cytokine-proteinase cascade in CRSwNP pathogenesis. Together they provide a target for novel therapies and a diagnostic tool for monitoring CRSwNP treatment.

Pancreatic trypsin activates human promatrix metalloproteinase-2

In contrast to the prevalent view in the literature hitherto, the present study shows that pancreatic trypsin can activate human promatrix metalloproteinase-2 (proMMP-2). It is shown that trypsin's ability to activate proMMP-2 is dependent on various environmental factors such as the level of exogenously added Ca(2+) and Brij-35, temperature, as well as trypsin concentration. The activation occurred as a sequential processing of the proenzyme, initially generating an active 62kDa species. This was followed by successive truncation of the C-terminal domain, giving rise to active species of 56kDa, 52kDa and 50kDa. Tissue inhibitor of matrix metalloproteinases-2 (TIMP-2) prevented the trypsin-mediated C-terminal truncation, without affecting the generation of the 62kDa species, while the presence of EDTA increased the rate of the trypsin-mediated activation of proMMP-2. MALDI-TOF MS analysis of the 50kDa form indicated that trypsin generated active forms with either Lys87 or Trp90 as the N-terminal residue and Arg538 as a C-terminal residue. The trypsin-activated MMP-2 was active in solution against both synthetic and physiologic substrates, and the steady-state kinetic coefficients k(cat), K(m) and k(cat)/K(m) were determined for the enzyme activated either by APMA, membrane-type 1 matrix metalloproteinase (MT1-MMP) or trypsin. The trypsin-activated MMP-2 exhibited slightly lower k(cat) and k(cat)/K(m) values as well as a slightly higher K(i) value against TIMP-1 compared to the enzyme activated by APMA or MT1-MMP. Docking studies of TIMP-1 revealed that the slightly weaker binding of the inhibitor to the trypsin-activated MMP-2 could be attributed to its shorter N terminus (Lys87/Trp90 versus Tyr81), as Phe83 and Arg86 interacted directly with the inhibitor. Our results suggest that the trypsin-activated MMP-2 possesses the catalytic and regulatory potential to be of significance in vivo.