Oxygen-dependent modulation of release and activity of polymorphonuclear leukocyte granule products

Are proteinase 3 and cathepsin C enzymes related to pathogenesis of periodontitis?

Aim. Cathepsin C is the activator of the polymorphonuclear leukocyte-derived proteinase 3, which contributes to inflammatory processes. The aim of the present study was to investigate gingival crevicular fluid (GCF) proteinase 3 and cathepsin C levels in periodontal diseases. Design. Eighteen patients with chronic periodontitis (CP), 20 patients with generalized aggressive periodontitis (G-AgP), 20 patients with gingivitis, and 18 healthy subjects were included in the study. Periodontal parameters including probing depth, clinical attachment level, papilla bleeding index, and plaque index were assessed in all study subjects. GCF proteinase 3 and cathepsin C levels were analyzed by ELISA. Results. GCF proteinase 3 total amount was significantly higher in diseased groups compared to control group, after adjusting age (P < 0.05). No differences were found in GCF cathepsin C levels among the study groups (P > 0.05). Periodontal parameters of sampling sites were positively correlated with GCF proteinase 3 total amounts (P < 0.01) but not with cathepsin C total amounts (P > 0.05). Conclusions. Elevated levels of GCF proteinase 3 in CP, G-AgP, and gingivitis might suggest that proteinase 3 plays a role during inflammatory periodontal events in host response. However, cathepsin C in GCF does not seem to have an effect on the pathogenesis of periodontal diseases.

Hyper-reactive PMNs in FcγRIIa 131 H/H genotype periodontitis patients

BACKGROUND

Receptors for the Fc part of IgG (FcgammaRIIa) on polymorphonuclear leukocytes (PMN) mediate phagocytosis and cell activation. Previous results show that one of the genetic variants of the FcgammaRIIa, the 131 H/H, is associated with more periodontal breakdown than the R/R. This may be due to hyper-reactivity of the H/H-PMNs upon interaction with bacteria.

AIM

To study whether the FcgammaRIIa genotype modifies the PMN reactivity in periodontitis patients.

MATERIAL AND METHODS

A cohort of 98 periodontitis patients was genotyped. From these, 10 H/H and 10 R/R consented to participate. PMNs were incubated with immune serum-opsonized Actinobacillus actinomycetemcomitans (A.a.). Phagocytosis, degranulation (CD63 and CD66b expression), respiratory burst and elastase release were assessed.

RESULTS

Patients of the H/H genotype showed more bone loss than those with the H/R or R/R genotype (p=0.038). H/H-PMNs phagocytosed more opsonized A.a. than did R/R-PMNs (p=0.019). The H/H-PMNs also expressed more CD63 and CD66b than did the R/R-PMNs (p=0.004 and 0.002, respectively) and released more elastase (p=0.001).

CONCLUSIONS

The genotyping results confirm previous reports that more periodontal destruction occurs in the H/H genotype than in the H/R or R/R genotype. The functional studies indicate a hyper-reactivity of the H/H-PMN in response to bacteria, which may be one of several pathways leading to more periodontal breakdown.

Role of polymorphonuclear leukocyte-derived serine proteinases in defense against Actinobacillus actinomycetemcomitans

Periodontitis is a chronic destructive infection of the tooth-supportive tissues, which is caused by pathogenic bacteria such as Actinobacillus actinomycetemcomitans. A severe form of periodontitis is found in Papillon-Lefèvre syndrome (PLS), an inheritable disease caused by loss-of-function mutations in the cathepsin C gene. Recently, we demonstrated that these patients lack the activity of the polymorphonuclear leukocyte (PMN)-derived serine proteinases elastase, cathepsin G, and proteinase 3. In the present study we identified possible pathways along which serine proteinases may be involved in the defense against A. actinomycetemcomitans. Serine proteinases are capable to convert the PMN-derived hCAP-18 into LL-37, an antimicrobial peptide with activity against A. actinomycetemcomitans. We found that the PMNs of PLS patients released lower levels of LL-37. Furthermore, because of their deficiency in serine proteases, the PMNs of PLS patients were incapable of neutralizing the leukotoxin produced by this pathogen, which resulted in increased cell damage. Finally, the capacity of PMNs from PLS patients to kill A. actinomycetemcomitans in an anaerobic environment, such as that found in the periodontal pocket, seemed to be reduced. Our report demonstrates a mechanism that suggests a direct link between an inheritable defect in PMN functioning and difficulty in coping with a periodontitis-associated pathogen.

Release and activation of matrix metalloproteinase 8 from human neutrophils triggered by the leukotoxin of Actinobacillus actinomycetemcomitans

Matrix metalloproteinase 8 (MMP 8) degrades type I collagen and may be involved in the pathogenesis of periodontitis. Latent MMP 8 is stored in neutrophil granules and can be activated when released extracellularly. The periodontitis-associated bacterium Actinobacillus actinomycetemcomitans produces an RTX-toxin, leukotoxin, that degranulates and lyses human neutrophils. This study deals with the ability of leukotoxic A. actinomycetemcomitans to trigger the release and activation of MMP 8. Whole bacteria of three A. actinomycetemcomitans strains or leukotoxin purified from the highly toxic strain HK 1519 were incubated with human neutrophils. The extracellularly released latent and active forms of MMP 8 were detected by an immunoblot technique using specific antibodies against the protease. The activity of MMP 8 was determined by a collagen degradation assay. All strains induced release and activation of MMP 8. The effect was more pronounced under aerobic than anaerobic conditions and correlated with the leukotoxicity of the strains. Pure leukotoxin also induced MMP 8 release and activation in a concentration-dependent manner. Under aerobic conditions, oxidising substances formed by the neutrophils contributed to the rapid activation of the latent enzyme. Upon anaerobic incubation, the activation was slow and mainly caused by other proteases released during neutrophil degranulation. The activation was totally abolished in the presence of serum, probably due to the serum-protease inhibitors. Compared to the calcium ionophore A 23187, a well-known stimulus of neutrophil degranulation, leukotoxin was a more powerful inducer of MMP 8 release, since it triggered the process at a 1000-fold lower concentration. The present findings reveal a specific mechanism that can be induced by A. actinomycetemcomitans leukotoxin and which may contribute to the degradation of periodontal tissues under certain conditions.

Protease inhibitors, the responsible components for the serum-dependent enhancement of Actinobacillus actinomycetemcomitans leukotoxicity

Serum enhances the leukotoxic activity of Actinobacillus actinomycetemcomitans against human polymorphonuclear leukocytes (PMNL) by a mechanism that still is unknown. Early attempts to identify the serum components responsible for this enhancement gave no conclusive results, but indicated that the lipoprotein-containing fraction of the serum was involved in the interaction. This study aimed to clarify the role of serum lipoproteins in the leukotoxin interaction, and to identify other serum components involved. The main hypothesis examined was that the leukotoxicity enhancement might depend on serum protease inhibitors that block proteolytic cleavage of leukotoxin by enzymes released from the leukocytes. PMNL were isolated from human peripheral blood and incubated with purified leukotoxin in the presence of serum or purified serum components or lipoprotein-deficient serum. Leukotoxin was also incubated with purified elastase and cathepsin G or with enzyme mixtures from degranulated PMNL. The leukotoxic activity in these mixtures was determined as the extracellular release of lactate dehydrogenase from PMNL. Cleavage of the toxin was showed by gel electrophoresis and Western blot. Morphological changes in PMNL from the above mixtures were examined by electron microscopy. Enzymes from degranulated PMNL cleaved leukotoxin to non-cytotoxic fragments. Elastase and cathepsin G were mainly responsible for the cleavage. Inhibition of leukotoxin degradation was found in the presence of whole serum or of the serum protease inhibitors alpha2-macroglobulin and alpha1-proteinase inhibitor. Under these conditions enhanced PMNL lysis was also observed. A similar enhancement of PMNL lysis was found when PMNL degranulation was blocked by EDTA. On the other hand, lipoprotein-deficient serum had no influence on the leukotoxic activity. The results indicate that the increased leukotoxicity of A. actinomycetemcomitans observed in the presence of human serum is caused by the serum protease inhibitors that counteract proteolytic degradation of leukotoxin. The degradation is caused by enzymes from degranulated PMNL triggered by leukotoxin.

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: MPO I, 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 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.