Myeloperoxidase isoform activities released by human neutrophils in response to dental and periodontal bacteria

Myeloperoxidase is an enzyme released by polymorphonuclear leukocytes which has been used, experimentally, as an indicator of periodontal disease activity when measured in gingival crevicular fluid. There are three myeloperoxidase isoforms: MPOI, MPO II and MPO III. We examined the activities of myeloperoxidase isoforms released by neutrophils in response to serum-opsonized Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, Eikenella corrodens, Capnocytophaga sputigena and Streptococcus sanguis. Isoform activities were determined using intermediate-pressure liquid chromatography and microenzyme assay. A. actinomycetemcomitans tans stimulated higher levels of myeloperoxidase release than any other oral bacteria unless pre-opsonized with serum (or protein-A purified immunoglobulin) from an individual with localized juvenile periodontitis. Most oral bacteria stimulated the release of all myeloperoxidase isoforms with a profile enriched in MPO I and diminished in MPO III. Exceptionally, serum-opsonized A. actinomycetemcomitans stimulated myeloperoxidase isoform release in proportion to the neutrophil granule constituency with or without localized juvenile periodontitis serum pre-opsonization. Because myeloperoxidase isoform profiles reflect how neutrophils were stimulated, isoform analysis may refine future diagnostic tests based upon myeloperoxidase.