Cholesterol and Its Derivatives Reversibly Inhibit Proteinase K

Microorganisms express a variety of proteases that degrade many proteins of the host body and subvert host immune response. While elucidating the mechanism/s of an immune stimulatory drug that contains bile lipid, regulation of proteolytic activity was investigated. The drug and bile lipids both stabilize Proteinase K, an aggressive protease of fungal origin against auto-digestion. Among the components of bile lipids, only cholesterol and its derivatives stabilize the enzyme. Biophysical evidences such as scattering of light, intrinsic and extrinsic fluorescence emission spectra, circular dichroism spectra, atomic force microscopy, and transmission electron microscopy images indicated that cholesterol and its derivatives interact with Proteinase K. Inhibition kinetics using esterolysis of ATEE revealed noncompetitive inhibition by cholesterol. Surface Plasmon Resonance and mass spectrometric analysis indicated 1:1 stoichiometry of binding and with dissociation constant in the mM range. Further, the presence of four cholesterol recognition amino acid consensus motifs (CRAC motifs I–IV) was identified in Proteinase K. Bioinformatics analysis revealed that the whole stretch of cholesterol interacts very well with the hydrophobic groove of motif II only among the four CRAC motifs. Variation of cholesterol content of HepG2 human liver carcinoma cells showed positive correlation with binding of fluorescence tagged Proteinase K. Under these conditions, binding of Proteinase K to the cells did not affect their morphology, viability and growth kinetics. Cell bound Proteinase K could be released by an excess of its substrate, thereby restoring reversibly its proteolytic activit

Vaccination with recombinant RgpA peptide protects against Porphyromonas gingivalis : induced bone loss

OBJECTIVE: Following P.gingivalis infection in mice, the efficacy of vaccination by recombinant and native RgpA in modulating the early local anti-inflammatory and immune responses and periodontal bone loss were examined. METHODS: Using the subcutaneous chamber model, exudates were analyzed for cytokines after treatment with native RgpA and adjuvant (test), or adjuvant and saline alone (controls). Mice were also immunized with recombinant RgpA after being orally infected with P. gingivalis. After 6 weeks, serum was examined for anti-P. gingivalis IgG1 and IgG2a titers and for alveolar bone resorption. RESULTS: Immunization with native RgpA shifted the immune response toward an anti-inflammatory response as demonstrated by decreased pro-inflammatory cytokine IL-1β production and greater anti-inflammatory cytokine IL-4 in chamber exudates. Systemically, immunization with recombinant RgpA peptide prevented alveolar bone loss by 50%, similar to immunization with heat-killed whole bacteria. Furthermore, recombinant RgpA shifted the humoral response toward high IgG1 and low IgG2a titers, representing an in vivo anti-inflammatory response. CONCLUSIONS: The present study demonstrates the potential of RgpA to shift the early local immune response toward an anti-inflammatory response while vaccination with recRgpA protected against P. gingivalis-induced periodontitis

Expression and regulation of the NALP3 inflammasome complex in periodontal diseases

Periodontitis is an infectious process characterized by inflammation affecting the supporting structures of the teeth. Porphyromonas gingivalis is a major oral bacterial species implicated in the pathogenesis of periodontitis. Processing of interleukin (IL)-1 family cytokines is regulated by an intracellular innate immune response system, known as the NALP3 [nacht domain-, leucine-rich repeat-, and pyrin domain (PYD)-containing protein 3] inflammasome complex. The aim of the present study was to investigate by quantitative real-time polymerase chain reaction (PCR) the mRNA expression of NALP3, its effector molecule apoptosis associated speck-like protein (ASC), its putative antagonist NLRP2 (NLR family, PYD-containing protein 2), IL-1β and IL-18 (i) in gingival tissues from patients with gingivitis (n = 10), chronic periodontitis (n = 18), generalized aggressive periodontitis (n = 20), as well as in healthy subjects (n = 20), (ii) in vitro in a human monocytic cell line (Mono-Mac-6), in response to P. gingivalis challenge for 6 h. The clinical data indicate that NALP3 and NLRP2, but not ASC, are expressed at significantly higher levels in the three forms of inflammatory periodontal disease compared to health. Furthermore, a positive correlation was revealed between NALP3 and IL-1β or IL-18 expression levels in these tissues. The in vitro data demonstrate that P. gingivalis deregulates the NALP3 inflammasome complex in Mono-Mac-6 cells by enhancing NALP3 and down-regulating NLRP2 and ASC expression. In conclusion, this study reveals a role for the NALP3 inflammasome complex in inflammatory periodontal disease, and provides a mechanistic insight to the host immune responses involved in the pathogenesis of the disease by demonstrating the modulation of this cytokine-signalling pathway by bacterial challenge

Porphyromonas gingivalis: an invasive and evasive opportunistic oral pathogen

Porphyromonas gingivalis is a Gram-negative oral anaerobe that is involved in the pathogenesis of periodontitis, an inflammatory disease that destroys the tissues supporting the tooth, eventually leading to tooth loss. Porphyromonas gingivalis has can locally invade periodontal tissues and evade the host defence mechanisms. In doing so, it utilizes a panel of virulence factors that cause deregulation of the innate immune and inflammatory responses. The present review discusses the invasive and evasive strategies of P. gingivalis and the role of its major virulence factors in these, namely lipopolysaccharide, capsule, gingipains and fimbriae. Moreover, the role of P. gingivalis as a 'keystone' biofilm species in orchestrating a host response, is highlighted