A novel, potent dual inhibitor of Arg-gingipains and Lys-gingipain as a promising agent for periodontal disease therapy.

The periodontal pathogen Porphyromonas gingivalis produces a unique class of cysteine proteinases termed gingipains that comprises Arg-gingipain (Rgp) and Lys-gingipain (Kgp). Growing evidence indicates that these 2 types of gingipains synergistically contribute to the entire virulence of the organism and increase the risk of periodontal disease (PD) by disrupting the host immune system and degrading the host tissue and plasma proteins. Therefore, a dual inhibitor of both gingipains would have attractive clinical potential for PD therapy. In this study, a novel, potent, dual inhibitor of Rgp and Kgp was developed through structure-based drug design, and its biological potency was evaluated in vitro and in vivo. This inhibitor had low nanomolar inhibitory potency (Ki=40 nM for Rgp, Ki=0.27 nM for Kgp) and good selectivity for host proteases and exhibited potent antibacterial activity against P. gingivalis by abrogating its manifold pathophysiological functions. The therapeutic potential of this inhibitor in vivo was also verified by suppressing the vascular permeability that was enhanced in guinea pigs by the organism and the gingival inflammation in beagle dog PD models. These findings suggest that a dual inhibitor of Rgp and Kgp would exhibit noteworthy anti-inflammatory activity in the treatment of PD.

Inhibition of gingipains prevents Porphyromonas gingivalis-induced preterm birth and fetal death in pregnant mice.

Accumulating epidemiological evidence indicates that infection with Porphyromonas gingivalis which is a major periodontal pathogen, causes preterm birth and low birth weight. However, virulence factors of P. gingivalis responsible for preterm birth/low birth weight remain to be elucidated. In this study, using P. gingivalis-infected pregnant mice as an in vivo model, we investigated whether gingipains-cysteine proteinases produced by P. gingivalis-affect preterm birth and low birth weight. We found that intravenous infection of pregnant mice with P. gingivalis induced higher accumulation of the bacterium in the placenta than that in other organs. Compared to infection with P. gingivalis wild-type, infection with a gingipain-deficient P. gingivalis mutant KDP136 led to significant reduction in preterm birth and pregnancy loss. Although repetitive low-level infections of P. gingivalis failed to induce preterm birth and fetal death, it induced suppressive effects on IFN-γ production. Therapeutically, treatment with ginginpain inhibitors prevented fetal death and preterm birth caused by P. gingivalis infection and resulted in recovery of IFN-γ suppression caused by repetitive chronic P. gingivalis infection. These results indicate that gingipains are major virulence factors of P. gingivalis responsible for preterm birth/low birth, and gingipain inhibitors may be useful not only as a therapeutic agent for periodontal diseases, but also as a preventive medicine for preterm birth/low birth weight.

A role for gingipains in cellular responses and bacterial survival in Porphyromonas gingivalis-infected cells.

Porphyromonas gingivalis is one of the primary etiologic agents of adult periodontitis and is known to produce a unique class of cysteine proteinases, termed gingipains. They consist of Arg-gingipain (Rgp) and Lys-gingipain (Kgp) and exist in the cell-associated and secreted forms. In the current review, we summarize recent knowledge on the pathophysiological role of gingipains in the virulence of P. gingivalis including host cell responses to bacterial infection and its evasion from host defense mechanisms. Studies with various P. gingivalis mutants deficient in Rgp- and/or Kgp-encoding genes and proteinase inhibitors specific for each enzyme have demonstrated that both enzymes play a substantial role in disruption of host defense mechanisms by the bacterium and its survival in vivo. Gingipains are also important in the bacterium-mediated host cell responses and the subsequent intracellular signaling in the infected cells. P. gingivalis can evade the autophagic pathway and instead directly traffic to the endocytic pathway to lysosomes in the infected cells. In addition, gingipains play an important role in acquiring resistance against destruction of the bacterium in the lysosomal system. Furthermore, a major form of the cell-associated gingipain complex composed of the catalytic domains of both enzymes, their adhesin domains, phospholipids, and lipopolysaccharide has recently been isolated and shown to contribute the bacterial evasion of host defense mechanisms and the host tissue breakdown.

Role for gingipains in Porphyromonas gingivalis traffic to phagolysosomes and survival in human aortic endothelial cells.

Gingipains are cysteine proteinases that are responsible for the virulence of Porphyromonas gingivalis. Recent studies have shown that P. gingivalis is trapped within autophagic compartments of infected cells, where it promotes survival. In this study we investigated the role of gingipains in the intracellular trafficking and survival of this bacterium in human aortic endothelial cells and any possible involvement of these enzymes in the autophagic pathway. Although autophagic events were enhanced by infection with either wild-type (WT) P. gingivalis strains (ATCC 33277, 381, and W83) or an ATCC 33277 mutant lacking gingipains (KDP136), we have found that more than 90% of intracellular WT and KDP136 colocalized with cathepsin B, a lysosome marker, and only a few of the internalized cells colocalized with LC3, an autophagosome marker, during the 0.5- to 4-h postinfection period. This was further substantiated by immunogold electron microscopic analyses, thus implying that P. gingivalis evades the autophagic pathway and instead directly traffics to the endocytic pathway to lysosomes. At the late stages after infection, WT strains in phagolysosomes retained their double-membrane structures. KDP136 in these compartments, however, lost its double-membrane structures, representing a characteristic feature of its vulnerability to rupture. Together with the ultrastructural observations, we found that the number of intracellular viable WT cells decreased more slowly than that of KDP136 cells, thus suggesting that gingipains contribute to bacterial survival, but not to trafficking, within the infected cells.

A functional virulence complex composed of gingipains, adhesins, and lipopolysaccharide shows high affinity to host cells and matrix proteins and escapes recognition by host immune systems.

Arg-gingipain (Rgp) and Lys-gingipain (Kgp) are Porphyromonas gingivalis cysteine proteinases implicated as major virulence factors in pathologies of periodontitis. We purified a 660-kDa cell-associated gingipain complex existing as a homodimer of two catalytically active monomers which comprises their catalytic and adhesin domains. Electron microscopy revealed that the complex was composed of a globular particle with a 10-nm external diameter possessing one or two electron-dense hole-like structures. Two-dimensional gel electrophoresis and immunoblot analyses revealed the association of lipopolysaccharide (LPS) with the catalytic domains and a hemagglutinin domain, Hgp44, of Rgp and Kgp in the complex. The complex significantly degraded human type I collagen and elastin and strongly disrupted viability of human gingival fibroblasts and umbilical vein endotherial cells with an efficiency which was higher than that of the monomeric gingipains. The native complex produced only a small amount of nitrogen dioxide, tumor necrosis factor alpha, and interleukin-6 by macrophages, whereas the heat-denatured complex resulted in increased production. Inhibition of the proteolytic activities of the gingipain complex did not up-regulate the cytokine production, indicating that the functional domains in LPS are structurally masked by the complex proteins. These results indicate the importance of the complex in evasion of host defense mechanisms as well as in host tissue breakdown.

[Gingipains as the determinants of periodontopathogenicity].

The arginine-specific cysteine proteinase (Arg-gingipain, Rgp) and lysine-specific cysteine proteinase (Lys-gingipain, Kgp) are produced by Porphyromonas gingivalis, an etiological bacterium of periodontal disease. Rgp and Kgp have been implicated as the major virulent factors because of their degrading activity to a broad range of host proteins and of the essential roles in bacterial cell viability. Recent studies have demonstrated the association of P. gingivalis with systemic diseases such as cardiovascular diseases, preterm birth, and low birth weight. The majority of gingipains exist as the membrane-associated complexes composed of the proteinase domains of both Rgp and Kgp, the C-terminal adhesin domains of RgpA and Kgp, phospholipids, and LPS. The complex induced potent viability loss of human endothelial cells and fibroblasts. As the suppression of Rgp and Kgp seems to be the most important to overcome the P. gingivalis-induced systemic disorders as well as the periodontal disease, we have thus designed and synthesized novel proteinase inhibitors specific to Rgp and Kgp on the basis of cleavage sites. Some of them suppressed the characteristic features of P. gingivalis associated with its pathogenicity such as degradation of host proteins, hemagglutination, enhancement of vascular permeability, disruption of leukocytes function, and induction of host cell death.

Isolation and characterization of a novel and potent inhibitor of Arg-gingipain from Streptomyces sp. strain FA-70.

Arg-gingipain (Rgp) is a major cysteine proteinase produced by the oral bacterium Porphyromonas gingivalis, which is a major pathogen of advanced periodontal diseases. This enzyme is important for the bacterium both to exhibit its virulence and to survive in periodontal pockets. The development of Rgp inhibitors thus provides new therapeutic approaches to periodontal diseases. In this study, we first isolated and purified a novel and potent inhibitor of Rgp from the culture supernatant of Streptomyces species strain FA-70, now designated as FA-70C1. This compound was found to be an antipain analog composed of phenylalanyl-ureido-citrullinyl-valinyl-cycloarginal (C27H43N9O7). The Ki value was calculated to be 4.5x10(-9) M when benzyloxycarbonyl-phenylalanyl-arginine-4-methly-coumaryl-7-amide was used as a substrate. This compound also inhibited cathepsins B, L, and H, though their Ki values were much higher than that of Rgp. FA-70C1 had little or no inhibitory activity on Lys-gingipain, another cysteine proteinase of P. gingivalis. The Rgp-induced degradation of various human proteins was completely blocked by this inhibitor. Disruption of both the bactericidal activity of polymorphonuclear leukocytes and the viability of human fibroblasts and umbilical vein endothelial cells induced by the culture supernatant of P. gingivalis was suppressed by the inhibitor in a dose-dependent manner. The enhancement of vascular permeability induced by in vivo administration of the culture supernatant of P. gingivalis was strongly inhibited by the inhibitor. Furthermore, the growth of P. gingivalis was suppressed by FA-70C1 in a dose-dependent manner. These results strongly suggest that FA-70C1 is a useful tool to prevent the virulence of P. gingivalis.

Roles of Arg- and Lys-gingipains in coaggregation of Porphyromonas gingivalis: identification of its responsible molecules in translation products of rgpA, kgp, and hagA genes.

Arg- (Rgp) and Lys-gingipains (Kgp) are two individual cysteine proteinases produced by Porphyromonas gingivalis , an oral anaerobic bacterium, and are implicated as major virulence factors in a wide range of pathologies of adult periodontitis. Coaggregation of this bacterium with other oral bacteria is an initial and critical step in infectious processes, yet the factors and mechanisms responsible for this process remain elusive. Here we show that the initial translation products of the rgpA , kgp and hemagglutinin hagA genes are responsible for coaggregation of P. gingivalis and that the proteolytic activity of Rgp and Kgp is indispensable in this process. The rgpA rgpB kgp- and rgpA kgp hagA -deficient triple mutants exhibited no coaggregation activity with Actinomyces viscosus , whereas the kgp -null and rgpA rgpB -deficient double mutants significantly retained this activity. Consistently, the combined action of Rgp- and Kgp-specific inhibitors strongly inhibited the coaggregation activity of the bacterium, although single use of Rgp- or Kgp-specific inhibitor significantly retained this activity. We also demonstrate that the 47- and 43-kDa proteins produced from the translation products of the rgpA , kgp , and hagA genes by proteolytic activity of both Rgp and Kgp are responsible for the coaggregation of P. gingivalis.

Suppression of pathogenicity of Porphyromonas gingivalis by newly developed gingipain inhibitors.

Arg-gingipain (Rgp) and Lys-gingipain (Kgp) are cysteine proteinases produced by Porphyromonas gingivalis, a major etiological bacterium of periodontal diseases. Here we show a series of small peptide analogs able to inhibit either Rgp or Kgp, which are synthesized on the basis of the cleavage site specificity of human salivary histatins by each enzyme. Among this series of compounds, carbobenzoxy-Lys-Arg-CO-Lys-N-(CH2)2 (KYT-1) and carbobenzoxy-Glu(NHN(CH3)Ph)-Lys-CO-NHCH2Ph (KYT-36) were found to be the most potent inhibitors of Rgp and Kgp, respectively, with Ki values of 10(-11) to 10(-10) M order. Both inhibitors exhibited slight or no inhibition on mammalian proteinases such as trypsin and cathepsins B, L, and H. All of the virulence induced by the culture supernatant of P. gingivalis tested, including the degradation of various host proteins such as human type I collagen, immunoglobulins, fibronectin, and fibrinogen, disruption of the bactericidal activity of polymorphonuclear leukocytes, and enhancement of the vascular permeability, were strongly inhibited by a combined action of both inhibitors. The functions essential for the bacterium to grow and survive in the periodontal pocket, such as coaggregation and acquisition of amino acids, were also strongly inhibited by the combined action of both inhibitors. The disruption of the adhesion and viability of human fibroblasts and hemagglutination by the organism were strongly suppressed by a single use of KYT-1. These results thus indicate that the newly developed KYT-1 and KYT-36 both should provide a broader application in studies of this important class of enzymes and facilitate the development of new approaches to periodontal diseases.