Generation of plasma kinin by three types of protease isolated from Porphyromonas gingivalis 381

The enhanced permeability retention effect: a new paradigm for drug targeting in infection

Multidrug-resistant, Gram-negative infection is a major global determinant of morbidity, mortality and cost of care. The advent of nanomedicine has enabled tailored engineering of macromolecular constructs, permitting increasingly selective targeting, alteration of volume of distribution and activity/toxicity. Macromolecules tend to passively and preferentially accumulate at sites of enhanced vascular permeability and are then retained. This enhanced permeability and retention (EPR) effect, whilst recognized as a major breakthrough in anti-tumoral targeting, has not yet been fully exploited in infection. Shared pathophysiological pathways in both cancer and infection are evident and a number of novel nanomedicines have shown promise in selective, passive, size-mediated targeting to infection. This review describes the similarities and parallels in pathophysiological pathways at molecular, cellular and circulatory levels between inflammation/infection and cancer therapy, where use of this principle has been established.

Activation of the kallikrein-kinin system and release of new kinins through alternative cleavage of kininogens by microbial and human cell proteinases

Kinins are released from kininogens through the activation of the Hageman factor-prekallikrein system or by tissue kallikrein. These peptides exert various biological activities, such as vascular permeability increase, smooth muscle contraction, pain sensation and induction of hypotension. In many instances kinins are thought to be involved in the pathophysiology of various diseases. Recent studies have revealed that microbial and human cell proteinases activate Hageman factor and/or prekallikrein, or directly release kinin from kininogens. This review discusses the activation of the kinin-release system by mast-cell tryptase and microbial proteinases, including gingipains, which are cysteine proteinases from Porphyromonas gingivalis , the major pathogen of periodontal disease. Each enzyme is evaluated in the context of its association to allergy and infectious diseases, respectively. Furthermore, a novel system of kinin generation directly from kininogens by the concerted action of two proteinases is described. An interesting example of this system with implications to bacterial pathogenicity is the release of kinins from kininogens by neutrophil elastase and a synergistic action of cysteine proteinases from Staphylococcus aureus . This alternative production of kinins by proteinases present in diseased sites indicates a significant contribution of proteinases other than kallikreins in kinin generation. Therefore kinin receptor antagonists and proteinase inhibitors may be useful as therapeutic agents.

The role of gingipains in the pathogenesis of periodontal disease

Gingipains are trypsin-like cysteine proteinases produced by Porphyromonas gingivalis, a major causative bacterium of adult periodontitis. HRgpA (95 kDa) and RgpB (50 kDa), products of 2 distinct but related genes, rgpA and rgpB, respectively, are specific for Arg-Xaa peptide bonds. Kgp, a product of the kgp gene, is specific for Lys-Xaa bonds. HRgpA and Kgp are non-covalent complexes containing separate catalytic and adhesion/ hemagglutinin domains, while RgpB has only a catalytic domain with a primary structure essentially identical to that of the catalytic subunit of HRgp. HRgpA and RgpB induce vascular permeability enhancement through activation of the kallikrein/kinin pathway and activate the blood coagulation system, which, respectively, are potentially associated with gingival crevicular fluid production and progression of inflammation leading to alveolar bone loss in the periodontitis site. Kgp is the most potent fibrinogen/fibrin degrading enzyme of the 3 gingipains in human plasma and is involved in the bleeding tendency at the diseased gingiva. HRgpA activates coagulation factors and degrades fibrinogen/fibrin more efficiently than RgpB due to the adhesion/hemagglutinin domains, which have affinity for phospholipids and fibrinogen. Gingipains degrade macrophage CD14, thus inhibiting activation of the leukocytes through the lipopolysaccharide (LPS) receptor, and thereby facilitating sustained colonization of P. gingivalis. Gingipains play a role in bacterial housekeeping and infection, including amino acid uptake from host proteins and fimbriae maturation. Based on the important activities of gingipains in the bacterial infection and the pathogenesis of periodontitis, the bacterial proteinases can be targets for periodontal disease therapy. Immunization with RgpB, HRgpA, or a portion of HRgpA catalytic domain attenuated P. gingivalis induced disorders in mice. In addition, a trypsin-like proteinase inhibitor retarded P. gingivalis growth specifically. Gingipains are potent virulence factors of P. gingivalis, and are likely to be associated with the development of periodontitis. It is, therefore, suggested that gingipain inhibition by vaccination and gingipain-specific inhibitors is a useful therapy for adult periodontitis caused by P. gingivalis infection.

Mechanisms mediating Porphyromonas gingivalis gingipain RgpA-induced oral mucosa inflammation in vivo

Suffusion of gingipain RgpA (GRgpA) elicited a significant concentration-dependent increase in the clearance of macromolecules from in situ hamster cheek pouch which was attenuated by NPC 17647, a selective bradykinin B(2) receptor antagonist. Leupeptin and a mixture of proteinase inhibitors also attenuated GRgpA-induced responses. These data indicate that GRgpA elicits plasma exudation from in situ oral mucosa in a catalytic site-dependent fashion by elaborating bradykinin.

Prolyl tripeptidyl peptidase from Porphyromonas gingivalis. A novel enzyme with possible pathological implications for the development of periodontitis

Porphyromonas gingivalis possesses a complex proteolytic system, which is essential for both its growth and evasion of host defense mechanisms. In this report we characterized, both at a protein and genomic level, a novel peptidase of this system with prolyl tripeptidyl peptidase activity. The enzyme was purified to homogeneity, and its enzymatic activity and biochemical properties were investigated. The amino acid sequence at the amino terminus and of internal peptide fragments enabled identification of the gene encoding this enzyme, which we refer to as PtpA for prolyl tripeptidyl peptidase A. The gene encodes an 82-kDa protein, which contains a GWSYGG motif, characteristic for members of the S9 prolyl oligopeptidase family of serine proteases. However, it does not share any structural similarity to other tripeptidyl peptidases, which belong to the subtilisin family. The production of prolyl tripeptidyl peptidase may contribute to the pathogenesis of periodontal tissue destruction through the mutual interaction of this enzyme, host and bacterial collagenases, and dipeptidyl peptidases in the degradation of collagen during the course of infection.

Comparative properties of two cysteine proteinases (gingipains R), the products of two related but individual genes of Porphyromonas gingivalis

Proteolytic enzymes produced by Porphyromonas gingivalis are important virulence factors of this periodontopathogen. Two of these enzymes, referred to as arginine-specific cysteine proteinases (gingipains R), are the product of two related genes. Here, we describe the purification of an enzyme translated from the rgpB/rgp-2 gene (gingipain R2, RGP-2) and secreted as a single chain protein of 422 residues. The enzyme occurs in several isoforms differing in pI, molecular mass, mobility in gelatin zymography gels, and affinity to arginine-Sepharose. In comparison to the 95-kDa gingipain R1, a complex of catalytic and hemagglutinin/adhesin domains, RGP-2 showed five times lower proteolytic activity, although its activity on various P1-arginine p-nitroanilide substrates was generally higher. Gingipains R amidolytic activity, but not general proteolytic activity, was stimulated by glycyl-glycine. However, in cases of limited proteolysis, such as the inactivation of alpha-1-antichymotrypsin, glycyl-glycine potentiated inhibitor cleavage. In contrast, alpha-1-proteinase inhibitor was not inactivated by gingipains R and only underwent proteolytic degradation during boiling in reducing SDS-polyacrylamide gel electrophoresis treatment buffer. Similarly, native type I collagen was completely resistant to cleavage by gingipains but readily degraded after denaturation. Together, these data explain much of the controversy regarding gingipains structure and substrate specificity and indicate that these enzymes function as P. gingivalis virulence factors by proteolysis of selected target proteins rather than random degradation of host connective tissue components.

Involvement of a lysine-specific cysteine proteinase in hemoglobin adsorption and heme accumulation by Porphyromonas gingivalis

The oral anaerobic bacterium Porphyromonas gingivalis, a major pathogen of advanced adult periodontitis, produces a novel class of cysteine proteinases in both cell-associated and secretory forms. A lysine-specific cysteine proteinase (Lys-gingipain, KGP), as well as an arginine-specific cysteine proteinase (Arg-gingipain), is a major trypsin-like proteinase of the organism. Recent studies indicate that the secreted KGP is implicated in the destruction of periodontal tissue and the disruption of host defense mechanisms. In this study, we have constructed a KGP-deficient mutant to determine whether the cell-associated KGP is important for pathophysiology of the organism. Although the mutant retained the strong ability to disrupt the bactericidal activity of polymorphonuclear leukocytes, its hemagglutination activity was reduced to about one-half that observed with the wild-type strain. More important, the mutant did not form black-pigmented colonies on blood agar plates, indicating the defect of hemoglobin adsorption and heme accumulation. Immunoblot analysis showed that the expression of a 19-kDa hemoglobin receptor protein, which is thought to be responsible for hemoglobin binding by the organism, was greatly retarded in this mutant. The mutant also showed a marked decrease in the ability to degrade fibrinogen. These results suggest the possible involvement of KGP in the hemoglobin binding and heme accumulation of the organism and in the bleeding tendency in periodontal pockets.

Inactivation of tumor necrosis factor-alpha by proteinases (gingipains) from the periodontal pathogen, Porphyromonas gingivalis. Implications of immune evasion

Porphyromonas gingivalis is one of the major pathogens associated with adult periodontitis, a major chronic inflammatory disease. Potent proteinases elaborated by these bacteria aid directly and indirectly in both the development of the pathophysiology of the disease and in host defense evasion. For these reasons they are considered key virulence factors. To investigate whether possible immune evasion mechanisms involve the dysregulation of the host cytokine network, we examined the ability of P. gingivalis cysteine proteinases, including Arg-specific gingipains HRGP and RGP2 and Lys-specific KGP, to degrade the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha). All three gingipains rapidly degraded TNF-alpha as exhibited by immunoblot analysis. Moreover, all biological activity was significantly reduced over extended incubation periods with the proteinases tested, whereas the host neutrophil proteinases were ineffective. These results indicate that the gingipain proteinases elaborated by P. gingivalis are capable of disrupting the cytokine network at the site of infection through the degradation of the proinflammatory cytokine TNF-alpha, suggesting the removal of one of several mediators important to the function of polymorphonuclear leukocytes. Such a mechanism is likely to be utilized by other infective organisms not only for survival but also for growth and proliferation.

Modification of cystatin C activity by bacterial proteinases and neutrophil elastase in periodontitis

AIM

To study the interaction between the human cysteine proteinase inhibitor, cystatin C, and proteinases of periodontitis associated bacteria.

METHODS

Gingival crevicular fluid samples were collected from discrete periodontitis sites and their cystatin C content was estimated by enzyme linked immunosorbent assay (ELISA). The interaction between cystatin C and proteolytic enzymes from cultured strains of the gingival bacteria Porphyromonas gingivalis, Prevotella intermedia, and Actinobacillus actinomycetemcomitans was studied by measuring inhibition of enzyme activity against peptidyl substrates, by detection of break down patterns of solid phase coupled and soluble cystatin C, and by N-terminal sequence analysis of cystatin C products resulting from the interactions.

RESULTS

Gingival crevicular fluid contained cystatin C at a concentration of approximately 15 nM. Cystatin C did not inhibit the principal thiol stimulated proteinase activity of P gingivalis. Instead, strains of P gingivalis and P intermedia, but not A actinomycetemcomitans, released cystatin C modifying proteinases. Extracts of five P gingivalis and five P intermedia strains all hydrolysed bonds in the N-terminal region of cystatin C at physiological pH values. The modified cystatin C resulting from incubation with one P gingivalis strain was isolated and found to lack the eight most N-terminal residues. The affinity of the modified inhibitor for cathepsin B was 20-fold lower (Ki 5 nM) than that of full length cystatin C. A 50 kDa thiol stimulated proteinase, gingipain R, was isolated from P gingivalis and shown to be responsible for the Arg8-bond hydrolysis in cystatin C. The cathepsin B inhibitory activity of cystatin C incubated with gingival crevicular fluid was rapidly abolished after Val10-bond cleavage by elastase from exudate neutrophils, but cleavage at the gingipain specific Arg8-bond was also demonstrated.

CONCLUSIONS

The physiological control of cathepsin B activity is impeded in periodontitis, owing to the release of proteinases from infecting P gingivalis and neutrophils, with a contribution to the tissue destruction seen in periodontitis as a probable consequence.

Titration and mapping of the active site of cysteine proteinases from Porphyromonas gingivalis (gingipains) using peptidyl chloromethanes

Porphyromonas gingivalis is one of the major pathogens associated with periodontal disease and releases powerful cysteine proteinases known as the gingipains, which are key virulence factors for this organism. The three forms of gingipains, gingipain R1, gingipain R2 (gingipain Rs) and gingipain K, which cleave specifically after arginine (R) or lysine (K) residues, were characterized in terms of the kinetics of their interaction with a wide range of synthetic peptidyl chloromethane inhibitors and a peptidyl (acyloxy)methane. Chloromethane inhibitors were found to inhibit all the enzymes to varying degree dependent on the peptidyl components of the inhibitor. Thus, inhibitors containing a basic residue at P1 rapidly inactivated the gingipains and some specificity could be seen at the P2 site. The (acyloxy)methane inhibitor, Cbz-Phe-Lys-CH2OCO-2,4,6-Me3-Ph, was very specific in its rapid inhibition of gingipain K over the gingipains R. This inhibitor, together with the peptidyl chloromethanes, D-Phe-Pro-Arg-CH2Cl and D-Phe-Phe-Arg-CH2Cl, which reacted most rapidly with the Arg-specific proteinases, could be used to active site titrate purified forms of the enzymes and enzymes found in crude fractions such as intact P. gingivalis cells, vesicles or membrane fractions. From these titrations it was evident that gingipains R were always in an excess of about 3-fold over gingipain K and that the gingipains as a whole made up 85% of the proteolytic activity associated with the bacterium. The elucidation of the kinetics of inhibition by the range of compounds and the development of the titration method for gingipains will considerably aid in future studies on the proteases elaborated by P. gingivalis.

Hemagglutinin activity and heterogeneity of related Porphyromonas gingivalis proteinases

Thiol-dependent proteinases that are expressed and released by Porphyromonas gingivalis are considered virulence factors in periodontitis because of their potential to effect matrix degradation and inflammation. A number of P. gingivalis thiol-proteinases have been described, however, with similar biochemical characteristics. In this report we demonstrate that an isolate P. gingivalis proteinase consists of noncovalently associated peptides and that slight variations in the association pattern of these peptides could result in different proteinases with different affinities and activities. We also describe the co-purification of thiol-proteinase activity with hemagglutinin activity and demonstrate that each type of activity has similar inhibition profiles. With the use of monoclonal antibodies against the P. gingivalis proteinase we follow proteinase released into the culture medium over the course of 10 days and, by Western blot analysis, demonstrate that many of the proteinases with varying molecular weight are related. The identification of a single, immunoreactive, 140 kDa proteinase detected early in the culture and in association with the P. gingivalis cells suggests that multiple proteinase may originate from a single 140 kDa proteinase.

Biological and antigenic characterization of three BApNA-hydrolyzing proteases from the culture supernatant of Porphyromonas gingivalis

Biological and antigenic distinction of 3-N-alpha-benzoyl-DL-arginine p-nitroanilide (BApNA)-hydrolyzing proteases (Pase-B, Pase-C and Pase-S) isolated from the culture supernatant of Porphyromonas gingivalis were determined. Immunoblotting analysis of these enzymes using a polyclonal antibody against Pase-S, which is a soluble, clostripain-like protease, revealed immunological distinction from Pase-C, a vesicle-associated thiol-protease. Pase-B, a vesicle-associated clostripain-like protease, reacted with the antibody and was also found to contain a considerable amount of carbohydrates in its structure, as compared with the others. Analysis of N-terminal amino acids of Pase-B provided a sequence not found in the SwissProt data bank or previously reported as N-terminal sequences of proteases from P. gingivalis. Pase-S, resembling Pase-B in its hydrolytic specificity, cleaved only arginine residues of peptides and degraded type IV and denatured type I collagen. Pase-C hydrolyzed N-alpha-benzoyl-DL-lysine p-nitroanilide and showed the strongest capacity of degrading native type I collagen. This enzyme was also the only one to possess hemagglutinating activity. Our findings suggest that Pase-S from P. gingivalis is less active than Pase-C and that the enzyme may be an isozyme of Pase-B.

Dependence of vascular permeability enhancement on cysteine proteinases in vesicles of Porphyromonas gingivalis

Infection with Porphyromonas gingivalis is strongly associated with adult periodontitis, and proteinases are considered to be important virulent factors of the bacterium. In order to investigate the function of proteinases in disease development we examined vesicles, a biological carrier of these enzymes, for the generation of vascular permeability enhancement (VPE) activity, believed to correlate with the exudation of gingival crevicular fluid. The vesicles generated VPE activity from human plasma in a dose-dependent manner which could be inhibited 90% by antipain, a specific inhibitor of the Arg-specific cysteine proteinases (Arg-gingipains [RGPs] from P. gingivalis. Incubation of vesicles with high-molecular-weight-kininogen (HMWK)-deficient plasma did not result in VPE activity. On this basis, RGPs associated with vesicles were assumed to be responsible for most of the VPE activity generation via plasma prekallikrein activation and subsequent bradykinin production. The secondary pathway for VPE activity production was dependent on the direct release of bradykinin from HMWK by the concerted action of RGP and a Lys-specific cysteine proteinase (Lys-gingipain [KGP]), also associated with vesicles. These results indicate that RGP and KGP are biologically important VPE factors acting either via prekallikrein activation (RGP) and/or HMWK cleavage (RGP and KGP) to release BK and, thereby, contributing to the production of gingival crevicular fluid at periodontal sites infected with P. gingivalis.

Anti-inflammatory and analgesic activity of the bradykinin antagonist, icatibant (Hoe 140), against an extract from Porphyromonas gingivalis

1. Porphyromonas gingivalis is one of the bacteria likely to be related to pain in periodontitis. Several enzymes isolated from P. gingivalis have been reported to have kininogenase activity. Since kinin release could be held responsible for inflammatory symptoms and pain in periodontitis, we investigated whether the inflammatory and algesic effects of a sonic extract from P. gingivalis (PGSE) could be inhibited by the potent bradykinin B2 receptor antagonist, icatibant (Hoe 140). 2. In anaesthetized rats, the subplantar injection of PGSE (0.1 and 1.0 mg) caused a dose-dependent oedema of the hind paws. The net increase of the paw volume 60 min after the injection was 23 +/- 5% and 77 +/- 12%, respectively. The oedema was rich in plasma proteins as determined by the Evans blue method. Pretreatment with icatibant (300 nmol kg-1, s.c.) significantly reduced the effect of 1.0 mg of PGSE whereas the effects of 0.1 mg of PGSE remained unaffected. 3. The subplantar injection of 1.0 mg of PGSE in unanaesthetized rats caused nociceptive behavioural responses which started about 5 min after the injection and lasted for about 10-15 min. These responses were completely prevented by pretreatment with icatibant (300 nmol kg-1, s.c.). 4. The present results show that the plasma extravasation induced by non-algesic doses of a sonic extract from P. gingivalis are caused by mechanisms other than B2 kinin receptor activation whereas inflammatory effects of algesic doses are due to the action of kinins. The pain elicited by the extract is solely mediated by kinins and can be prevented by icatibant. The bradykinin antagonist could thus have a potential for a clinical use against pain associated with periodontal inflammation.

Pathogenesis of periodontitis: a major arginine-specific cysteine proteinase from Porphyromonas gingivalis induces vascular permeability enhancement through activation of the kallikrein/kinin pathway

To elucidate the mechanism of production of an inflammatory exudate, gingival crevicular fluid (GCF), from periodontal pockets in periodontitis, we examined the vascular permeability enhancement (VPE) activity induced by an arginine-specific cysteine proteinase, Arg-gingipain-1 (RGP-1), produced by a major periopathogenic bacterium, Porphyromonas gingivalis. Intradermal injections into guinea pigs of RGP-1 (> 10(-8) M), or human plasma incubated with RGP-1 (> 10(-9) M), induced VPE in a dose- and activity-dependent manner but with different time courses for the two routes of production. VPE activity induced by RGP-1 was augmented by kininase inhibitors, inhibited by a kallikrein inhibitor and unaffected by an antihistamine drug. The VPE activity in human plasma incubated with RGP-1 also correlated closely with generation of bradykinin (BK). RGP-1 induced 30-40% less VPE activity in Hageman factor-deficient plasma and no VPE in plasma deficient in either prekallikrein (PK) or high molecular weight kininogen (HMWK). After incubation with RGP-1, plasma deficient in PK or HMWK, reconstituted with each missing protein, caused VPE, as did a mixture of purified PK and HMWK, but RGP-1 induced no VPE from HMWK. The VPE of extracts of clinically isolated P. gingivalis were reduced to about 10% by anti-RGP-1-IgG, leupeptin, or tosyl-L-lysine chloromethyl ketone, which paralleled effects observed with RGP-1. These results indicate that RGP-1 is the major VPE factor of P. gingivalis, inducing this activity through PK activation and subsequent BK release, resulting in GCF production at sites of periodontitis caused by infection with this organism.