Elevated expression and activation of matrix metalloproteinase 8 in tear fluid in atopic blepharoconjunctivitis

Matrix metalloproteinase 8 (MMP-8) is an effective collagenolytic enzyme that is associated with many ocular inflammatory diseases, such as uveitis, keratitis, and ocular rosacea. We studied the tear fluid concentration and activation of MMP-8 in atopic blepharoconjunctivitis (ABC) and the presence of the enzyme in conjunctival inflammatory cells in vivo.

Tear fluid samples were collected from 26 patients with ABC and 26 healthy controls. MMP-8 concentrations were determined by immunofluorometric assay, and its molecular forms and degrees of activation were studied by Western blotting. Conjunctival brush cytology samples from patients with ABC were used for MMP-8 immunocytochemistry.

: The mean MMP-8 concentration was statistically significantly higher among the patients with ABC (545.6 +/- 879.3 microg/L) than among the healthy controls (50.4 +/- 62.3 microg/L, P = 0.0001). There was a statistically significant correlation between neutrophils detected in brush cytology and tear fluid MMP-8 (P = 0.032, r = 0.47). Both the control and ABC tear fluid samples contained predominantly the larger (60-80 kDa), highly glycosylated polymorphonuclear leukocyte-type MMP-8 isoform, as identified by Western blotting, but neither was found to contain the mesenchymal-type isoform. The active enzyme was in practice present only in the ABC samples. Immunostainings show the MMP-8 protein to be present in all the main inflammatory cell types within the conjunctiva.

: A higher mean concentration and activation of MMP-8 is present in tear fluid in ABC. This finding probably reflects persistent inflammatory and collagenolytic activity associated with the disease.