Inhibition of trypsin-like cysteine proteinases (gingipains) from Porphyromonas gingivalis by tetracycline and its analogues

Influence of antibacterial effects of tetracycline, laser, and photodynamic therapy on cell viability, cell damage, and virulence of Porphyromonas gingivalis

INTRODUCTION

This study compares and evaluates the efficacy of tetracycline, laser and photodynamic therapy on bacterial counts, cell damage, cell viability and neutralization of gingipains.

MATERIAL AND METHODS

P.gingivalis (ATCC 33,277) was cultured anaerobically. The minimal inhibitory concentration (MIC) for 50% inhibition of P.gingivalis by tetracycline, laser, and toluidine blue (TB) was determined using spectrophotometry. The antibacterial effects, cell viability, cell damage and neutralization of gingipains of the treated groups was evaluated by microbial culture and counting, 2,3 Bis 2 Methyloxy-4 Nitro-5 Sulphophenyl 2 H tetrazolium-5-Carboxaanilide (MTT) assay, lactate dehydrogenase (LDH) assay, and gingipain assay (BAPNA).

RESULTS

The MIC of tetracycline, toulidine, diode laser (810nmm; 0.5 Watts) is 1 µg/mL, 50 µg/mL and 15 s respectively. Comparative analysis for bacterial colony reduction was highest in tetracycline followed by PDT and then laser group at p < 0.01. MTT assay shows a significantly lesser number of viable cells in the tetracycline and PDT group when compared to laser group p < 0.01. Comparative analysis for cell damage using LDH shows the highest results for PDT followed by tetracycline and laser at p < 0.01. The highest neutralization of the gingipains is seen in the PDT group followed by tetracycline and laser groups at p < 0.01.

CONCLUSION

PDT shows highest antibacterial activity, gingipain neutralization, cell damage, and least number of viable cells in comparison with tetracycline and laser.

The Effect of a Peptide Substrate Containing an Unnatural Branched Amino Acid on Chymotrypsin Activity

7-Amino-4-methylcoumarin (AMC) is a low molecular weight fluorescent probe that can be attached to a peptide to enable the detection of specific proteases, such as chymotrypsin, expressed in certain diseases. Because this detection depends on the specificity of the protease toward the peptidyl AMC, the development of specific substrates is required. To investigate the specificity of chymotrypsin, peptidyl AMC compounds incorporating four different amino acid residues were prepared by liquid-phase synthesis. Two unnatural amino acids, 2-amino-4-ethylhexanoic acid (AEH) and cyclohexylalanine (Cha), were used to investigate the substrate specificity as these amino acids have structures different from natural amino acids. AEH was synthesized using diethyl acetamidemalonate as a starting material. The substrate containing Cha had high hydrophobicity and showed a high reaction velocity with chymotrypsin. Although the AEH substrate with a branched side chain had high hydrophobicity, it showed a low reaction velocity. The substrate containing the aromatic amino acid phenylalanine was less hydrophobic than the Cha and AEH substrates, but chymotrypsin showed the highest specificity for this compound. These results demonstrated that the substrate specificity of chymotrypsin is not only affected by the hydrophobicity and aromaticity, but also by the structural expanse of amino acid residues in the substrate.

Oxytetracycline versus Doxycycline Collagen Sponges Designed as Potential Carrier Supports in Biomedical Applications

Many research studies are directed toward developing safe and efficient collagen-based biomaterials as carriers for drug delivery systems. This article presents a comparative study of the properties of new collagen sponges prepared and characterized by different methods intended for biomedical applications. The structural integrity is one of the main properties for a biomaterial in order for it to be easily removed from the treated area. Thus, the effect of combining a natural polymer such as collagen with an antimicrobial drug such as oxytetracycline or doxycycline and glutaraldehyde as the chemical cross-linking agent influences the cross-linking degree of the material, which is in direct relation to its resistance to collagenase digestion, the drug kinetic release profile, and in vitro biocompatibility. The enzymatic degradation results identified oxytetracycline as the best inhibitor of collagenase when the collagen sponge was cross-linked with 0.5% glutaraldehyde. The drug release kinetics revealed an extended release of the antibiotic for oxytetracycline-loaded collagen sponges compared with doxycycline-loaded collagen sponges. Considering the behavior of differently prepared sponges, the collagen sponge with oxytetracycline and 0.5% glutaraldehyde could represent a viable polymeric support for the prevention/treatment of infections at the application site, favoring tissue regeneration.

Characterization and production of multifunctional cationic peptides derived from rice proteins

Food proteins have been identified as a source of bioactive peptides. These peptides are inactive within the sequence of the parent protein and must be released during gastrointestinal digestion, fermentation, or food processing. Of bioactive peptides, multifunctional cationic peptides are more useful than other peptides that have specific activity in promotion of health and/or the treatment of diseases. We have identified and characterized cationic peptides from rice enzymes and proteins that possess multiple functions, including antimicrobial, endotoxin-neutralizing, arginine gingipain-inhibitory, and/or angiogenic activities. In particular, we have elucidated the contribution of cationic amino acids (arginine and lysine) in the peptides to their bioactivities. Further, we have discussed the critical parameters, particularly proteinase preparations and fractionation or purification, in the enzymatic hydrolysis process for producing bioactive peptides from food proteins. Using an ampholyte-free isoelectric focusing (autofocusing) technique as a tool for fractionation, we successfully prepared fractions containing cationic peptides with multiple functions.

Inhibition of gingipains and Porphyromonas gingivalis growth and biofilm formation by prenyl flavonoids

BACKGROUND AND OBJECTIVE

Porphyromonas gingivalis is considered a major pathogen of chronic periodontitis, which also may be implicated with systemic diseases such as atherosclerosis. Secreted cysteine proteases, gingipains Rgp and Kgp, are essential for P. gingivalis virulence. Some polyphenols and flavonoids are known to inhibit gingipain activity and interfere with biofilm formation by P. gingivalis. Many bioactive compounds have been isolated from Epimedium species, but availability of these compounds on gingipains and P. gingivalis is still unclear. Therefore, the aim of this study was to evaluate natural products from medical plants to develop a new therapeutic agent against periodontal disease.

MATERIAL AND METHODS

Prenylated flavonoids were isolated from Epimedium species plant using column chromatographies. The inhibitory effect of the prenylated flavonoids against protease activity of gingipains were examined using purified gingipains and fluorogenic substrates. Anti-P. gingivalis activity was evaluated to analyze planktonic growth and biofilm formation in brain heart infusion medium in the presence of the prenylated flavonoids.

RESULTS

We isolated 17 prenylated flavonoids (Limonianin, Epimedokoreanin B, etc.) from Epimedium species. We found that some prenylated flavonoids inhibited gingipain activity in a non-competitive manner with Ki values at μm order. The prenylated flavonoids also hindered growth and biofilm formation of P. gingivalis, in a manner independent of gingipain inhibition by the compounds.

CONCLUSION

The results indicated an inhibitory effect of the prenylated flavonoids against P. gingivalis and would provide useful information for future development of periodontitis treatment that suppresses gingipains, P. gingivalis growth and biofilm formation.

Contribution of cationic amino acids toward the inhibition of Arg-specific cysteine proteinase (Arg-gingipain) by the antimicrobial dodecapeptide, CL(14-25), from rice protein

CL(14-25), a dodecapeptide, exhibits antimicrobial activity against Porphyromonas gingivalis with the 50% growth-inhibitory concentration (IC50 ) value of 145 µM, and arginine-specific gingipain (Rgp)-inhibitory activity. Kinetic analysis revealed that CL(14-25) is a mixed-type inhibitor, with inhibition constants (Ki and Ki ' values) of 1.4 × 10(-6) M and 4.3 × 10(-6) M, respectively. To elucidate the contributions of four cationic amino acid residues at the N- and C-termini of CL(14-25) toward Rgp-inhibitory activity, we investigated the Rgp-inhibitory activities of truncated and alanine-substituted analogs of CL(14-25). Rgp-inhibitory activities significantly decreased by truncated analogs, CL(15-25) and CL(16-25), whereas those of CL(14-24) and CL(14-23) were almost as high as that of CL(14-25). Rgp-inhibitory activities of alanine-substituted analogs, CL(R14A) and CL(R14A, R15A) also significantly decreased, whereas those of CL(K25A) and CL(R24A, K25A) were higher than that of CL(14-25). These results suggest that the arginine residue at position 15 substantially contributes to the Rgp-inhibitory activity and that the arginine residue at position 14 plays important roles in exerting Rgp-inhibitory activity. In this study, we demonstrated that CL(K25A) was a potent, dual function, peptide inhibitor candidate, exhibiting Rgp-inhibitory activity with Ki and Ki ' of 9.6 × 10(-7) M and 1.9 × 10(-6) M, respectively, and antimicrobial activity against P. gingivalis with an IC50 value of 51 µM.

Doxycycline hyclate protects lipopolysaccharide-induced endothelial barrier dysfunction by inhibiting the activation of p38 mitogen-activated protein kinase

Doxycycline hyclate (DOX-h) attenuates inflammatory conditions independent of its antimicrobial effect. This study aimed to observe the effects of DOX-h on lipopolysaccharide (LPS)-induced endothelial barrier dysfunction. The endothelial monolayer permeability of human umbilical vein endothelial cells (HUVECs) was monitored by transendothelial electrical resistance (TEER). The phosphorylation of mitogen-activated protein kinases (MAPKs) and the arrangement of F-actin were detected. The results showed that both pretreatment and simultaneous treatment with DOX-h markedly attenuated the LPS-induced reduction in TEER and the disorganization of F-actin on HUVECs in a dose- and time-dependent manner. LPS mediated the phosphorylation of all three MAPKs (p38, extracellular signal-regulated kinase (ERK)1/2, and c-Jun N-terminal kinase (JNK)), but DOX-h was only able to inhibit the LPS-induced phosphorylation of p38 and JNK. The data further suggested that DOX-h alleviated LPS-evoked TEER reduction and F-actin redistribution by inhibiting the phosphorylation of p38 and its downstream target, heat shock protein (HSP)27. Thus, DOX-h attenuates LPS-induced endothelial barrier dysfunction via inhibition of the p38 MAPK-HSP27-F-actin pathway.

Design, synthesis, and biological evaluation of tetrazole analogs of Cl-amidine as protein arginine deiminase inhibitors

Protein arginine deiminases (PADs) catalyze the post-translational hydrolysis of arginine residues to form citrulline. This once obscure modification is now known to play a key role in the etiology of multiple autoimmune diseases (e.g., rheumatoid arthritis, multiple sclerosis, lupus, and ulcerative colitis) and in some forms of cancer. Among the five human PADs (PAD1, -2, -3, -4, and -6), it is unclear which isozyme contributes to disease pathogenesis. Toward the identification of potent, selective, and bioavailable PAD inhibitors that can be used to elucidate the specific roles of each isozyme, we describe tetrazole analogs as suitable backbone amide bond bioisosteres for the parent pan PAD inhibitor Cl-amidine. These tetrazole based analogs are highly potent and show selectivity toward particular isozymes. Importantly, one of the compounds, biphenyl tetrazole tert-butyl Cl-amidine (compound 13), exhibits enhanced cell killing in a PAD4 expressing osteosarcoma bone marrow (U2OS) cell line and can also block the formation of neutrophil extracellular traps. These bioisosteres represent an important step in our efforts to develop stable, bioavailable, and selective inhibitors for the PADs.

Strategies for the inhibition of gingipains for the potential treatment of periodontitis and associated systemic diseases

Gingipains are the major virulence factors of Porphyromonas gingivalis, the main periodontopathogen. It is expected that inhibition of gingipain activity in vivo could prevent or slow down the progression of adult periodontitis. To date, several classes of gingipain inhibitors have been recognized. These include gingipain N-terminal prodomains, synthetic compounds, inhibitors from natural sources, antibiotics, antiseptics, antibodies, and bacteria. Several synthetic compounds are potent gingipain inhibitors but inhibit a broad spectrum of host proteases and have undesirable side effects. Synthetic compounds with high specificity for gingipains have unknown toxicity effects, making natural inhibitors more promising as therapeutic gingipain blockers. Cranberry and rice extracts interfere with gingipain activity and prevent the growth and biofilm formation of periodontopathogens. Although the ideal gingipain inhibitor has yet to be discovered, gingipain inhibition represents a novel approach to treat and prevent periodontitis. Gingipain inhibitors may also help treat systemic disorders that are associated with periodontitis, including cardiovascular disease, rheumatoid arthritis, aspiration pneumonia, pre-term birth, and low birth weight.

Characterization of the shear stress regulation of CD18 surface expression by HL60-derived neutrophil-like cells

Shear stress-induced cleavage of cell surface CD18 integrins is reported to be part of an anti-inflammatory control mechanism that minimizes neutrophil activity in the blood under physiologic conditions. The cysteine protease, cathepsin B (catB), has been implicated in this mechanoregulatory mechanism, but its molecular dynamics remain to be elucidated. Moreover, attempts to do so using molecular approaches are hindered by the limited ex vivo life span of primary neutrophils. As an alternative, we explored the potential use of HL60-derived neutrophilic cells as a transfectable culture model that exhibits a shear-induced CD18 cleavage response comparable to primary neutrophils. HL60 cells were differentiated into neutrophil-like cells (dHL60-NCs) and exposed to laminar shear stress ([Formula: see text] for 10 min). Based on cytometric analyses, sheared cells cleaved CD18 and CD11a, but not CD11b, integrins. Treatment of cells with E64 or doxycycline prior to and during shear exposure inhibited CD18, but only attenuated CD11a, cleavage. Neither aprotinin nor pepstatin affected shear-induced CD18 or CD11a cleavage. Notably, dHL60-NCs expressed minimal catB. Thus, multiple cysteine proteases in addition to catB may cleave CD18 on sheared leukocytes. In fact, our findings indicate that multiple non-cysteine proteases also participate in the shear-related cleavage of CD11/CD18 heterodimers. Finally, shear-induced cleavage of CD18 and CD11a by dHL60-NCs was inhibited by fMLP concentrations of at least [Formula: see text]. Collectively, our findings indicate that shear-induced CD11/CD18 cleavage is phenotypic of neutrophilic cells, including those derived from HL60 cells. Moreover, our results verify shear stress as a key anti-inflammatory stimulus for neutrophils under physiologic conditions.

Current therapeutic leads for the treatment of autoimmune diseases: stem cell transplantation and inhibition of post-translational modifications of autoantigens

BACKGROUND

The complexity of autoimmune diseases is reflected on their clinicopathological heterogeneity and the failure to find treatments that cure them after over a century of research. Conventional treatments help ameliorate disease activity but they treat the symptoms whereas the diseases remain incurable in the vast majority of patients.

OBJECTIVE

To confront diseases of such nature it is essential to discover therapeutics that will lead to the induction of tolerance or the specific deletion of autoreactive lymphocytes. Current basic and clinical research strategies focus on the better identification of self-antigens, the induction of T regulatory cells that can suppress autoreactive cell activities or, more radically, the 'reformatting' of the immune system through hematopoietic stem cell transplantation (HSCT).

METHODS

We analyzed literature on autoimmune disease therapeutics, focusing on new antigens that may arise from post-translational modifications of common proteins and, also, the area of HSCT.

RESULTS/CONCLUSIONS

With the recent discovery that citrullination of self-epitopes may be a major pathogenic mechanism for, at least, certain types of autoimmune diseases, it becomes apparent that potentially any self-antigen in the body can be a target of an autoimmune attack. In addition, although the available data on HSCT applied to patients suffering from severe refractory autoimmune diseases do not allow for the determination of the efficacy of the various methods employed to re-educate the immune system, they contribute to our understanding of disease pathogenesis and the improvement on the therapeutic approaches.

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.

Porphyromonas gingivalis influences actin degradation within epithelial cells during invasion and apoptosis

Porphyromonas gingivalis, a Gram-negative oral pathogen, has been shown to induce apoptosis in human gingival epithelial cells, yet the underlining cellular mechanisms controlling this process are poorly understood. We have previously shown that the P. gingivalis proteases arginine and lysine gingipains, are necessary and sufficient to induce host cell apoptosis. In the present study, we demonstrate that 'P. gingivalis-induced apoptosis' is mediated through degradation of actin leading to cytoskeleton collapse. Stimulation of human gingival epithelial cells with P. gingivalis strains 33277 and W50 at moi:100 induced β-actin cleavage as early as 1 h and human serum inhibited this effect. By using gingipain-deficient mutants of P. gingivalis and purified gingipains, we demonstrate that lysine gingipain is involved in actin hydrolysis in a dose and time-dependent manner. Use of Jasplakinolide and cytochalasin D revealed that P. gingivalis internalization is necessary for actin cleavage. Further, we also show that lysine gingipain from P. gingivalis can cleave active caspase 3. Taken together, we have identified actin as a substrate for lysine gingipain and demonstrated a novel mechanism involved in microbial host cell invasion and apoptosis.

Microbial and fungal protease inhibitors--current and potential applications

Proteolytic enzymes play essential metabolic and regulatory functions in many biological processes and also offer a wide range of biotechnological applications. Because of their essential roles, their proteolytic activity needs to be tightly regulated. Therefore, small molecules and proteins that inhibit proteases can be versatile tools in the fields of medicine, agriculture and biotechnology. In medicine, protease inhibitors can be used as diagnostic or therapeutic agents for viral, bacterial, fungal and parasitic diseases as well as for treating cancer and immunological, neurodegenerative and cardiovascular diseases. They can be involved in crop protection against plant pathogens and herbivorous pests as well as against abiotic stress such as drought. Furthermore, protease inhibitors are indispensable in protein purification procedures to prevent undesired proteolysis during heterologous expression or protein extraction. They are also valuable tools for simple and effective purification of proteases, using affinity chromatography. Because there are such a large number and diversity of proteases in prokaryotes, yeasts, filamentous fungi and mushrooms, we can expect them to be a rich source of protease inhibitors as well.

Binding of tetracycline and chlortetracycline to the enzyme trypsin: spectroscopic and molecular modeling investigations

Tetracycline (TC) and chlortetracycline (CTC) are common members of the widely used veterinary drug tetracyclines, the residue of which in the environment can enter human body, being potentially harmful. In this study, we establish a new strategy to probe the binding modes of TC and CTC with trypsin based on spectroscopic and computational modeling methods. Both TC and CTC can interact with trypsin with one binding site to form trypsin-TC (CTC) complex, mainly through van der Waals' interactions and hydrogen bonds with the affinity order: TC>CTC. The bound TC (CTC) can result in inhibition of trypsin activity with the inhibition order: CTC>TC. The secondary structure and the microenvironment of the tryptophan residues of trypsin were also changed. However, the effect of CTC on the secondary structure content of trypsin was contrary to that of TC. Both the molecular docking study and the trypsin activity experiment revealed that TC bound into S1 binding pocket, competitively inhibiting the enzyme activity, and CTC was a non-competitive inhibitor which bound to a non-active site of trypsin, different from TC due to the Cl atom on the benzene ring of CTC which hinders CTC entering into the S1 binding pocket. CTC does not hinder the binding of the enzyme substrate, but the CTC-trypsin-substrate ternary complex can not further decompose into the product. The work provides basic data for clarifying the binding mechanisms of TC (CTC) with trypsin and can help to comprehensively understanding of the enzyme toxicity of different members of tetracyclines in vivo.

Porphyromonas gingivalis participates in pathogenesis of human abdominal aortic aneurysm by neutrophil activation. Proof of concept in rats

Background

Abdominal Aortic Aneurysms (AAAs) represent a particular form of atherothrombosis where neutrophil proteolytic activity plays a major role. We postulated that neutrophil recruitment and activation participating in AAA growth may originate in part from repeated episodes of periodontal bacteremia.

Methods and Findings

Our results show that neutrophil activation in human AAA was associated with Neutrophil Extracellular Trap (NET) formation in the IntraLuminal Thrombus, leading to the release of cell-free DNA. Human AAA samples were shown to contain bacterial DNA with high frequency (11/16), and in particular that of Porphyromonas gingivalis (Pg), the most prevalent pathogen involved in chronic periodontitis, a common form of periodontal disease. Both DNA reflecting the presence of NETs and antibodies to Pg were found to be increased in plasma of patients with AAA. Using a rat model of AAA, we demonstrated that repeated injection of Pg fostered aneurysm development, associated with pathological characteristics similar to those observed in humans, such as the persistence of a neutrophil-rich luminal thrombus, not observed in saline-injected rats in which a healing process was observed.

Conclusions

Thus, the control of periodontal disease may represent a therapeutic target to limit human AAA progression.

Porphyromonas gingivalis cysteine proteinase inhibition by kappa-casein peptides

Porphyromonas gingivalis is a major pathogen associated with chronic periodontitis, an inflammatory disease of the supporting tissues of the teeth. The Arg-specific (RgpA/B) and Lys-specific (Kgp) cysteine proteinases of P. gingivalis are major virulence factors for the bacterium. In this study κ-casein(109-137) was identified in a chymosin digest of casein as an inhibiting peptide of the P. gingivalis proteinases. The peptide was synthesized and shown to inhibit proteolytic activity associated with P. gingivalis whole cells, purified RgpA-Kgp proteinase-adhesin complexes, and purified RgpB proteinase. The peptide κ-casein(109-137) exhibited synergism with Zn(II) against both Arg- and Lys-specific proteinases. The active region for inhibition was identified as κ-casein(117-137) using synthetic peptides. Kinetic studies revealed that κ-casein(109-137) inhibits in an uncompetitive manner. A molecular model based on the uncompetitive action and its synergistic ability with Zn(II) was developed to explain the mechanism of inhibition. Preincubation of P. gingivalis with κ-casein(109-137) significantly reduced lesion development in a murine model of infection.

Bacterial and human peptidylarginine deiminases: targets for inhibiting the autoimmune response in rheumatoid arthritis?

Peptidylarginine deiminases (PADs) convert arginine within a peptide (peptidylarginine) into peptidylcitrulline. Citrullination by human PADs is important in normal physiology and inflammation. Porphyromonas gingivalis, a major pathogen in periodontitis, is the only prokaryote described to possess PAD. P. gingivalis infection may generate citrullinated peptides, which trigger anti-citrullinated peptide antibodies. In susceptible individuals, host protein citrullination by human PADs in the joint probably perpetuates antibody formation, paving the way for the development of chronic arthritis. Blockades of bacterial and human PADs may act as powerful novel therapies by inhibiting the generation of the antigens that trigger and sustain autoimmunity in rheumatoid arthritis.

Degradation of collagen-guided tissue regeneration membranes by proteolytic enzymes of Porphyromonas gingivalis and its inhibition by antibacterial agents

Previous studies have shown that whole cells of several periodontal pathogenic bacteria including Porphyromonas gingivalis may degrade the clinically used regeneration membranes Biomend Extend and Bio-Gide. Fractionation of P. gingivalis cells revealed that cell membrane-associated proteases are responsible for the in vitro degradation of the collagen membranes. In the present study, the specific role of extracellular vesicles and the purified Arg-gingipain enzyme of P. gingivalis in the degradation of three differently cross-linked collagen membranes (Ossix; Bio-Gide and Biomend Extend) was examined. In addition, the inhibitory effect of antibacterial agents and antibiotics used in local periodontal therapy on the enzymatic degradation was evaluated. The data presented show that while all tested collagen membranes, are prone to lysis by oral bacterial proteases, cross-linked membranes are more resistant to proteolysis. Furthermore, therapeutical concentrations of the antibacterial and antibiotic agents chlorhexidine, cetylpyridiniumchloride, minocycline and doxycycline were found to partially inhibit the enzymatic breakdown of the membranes, while metronidazole had no such effect. These results suggest that the presence of P. gingivalis cells, extracellular vesicles and enzymes in the vicinity of regeneration membranes in the periodontium, may change their physical structure and therefore alter their biological properties. Furthermore, the use of cross-linked collagen membranes and antibacterial agents may significantly inhibit this proteolytic process.

Proteolytic Activities of Oral Bacteria on ProMMP-9 and the Effect of Synthetic Proteinase Inhibitors

Tissue reactions to bacteria lead to proinflammatory reactions involving matrix metalloproteinases (MMPs). Synthetic protease inhibitors may offer new possibilities to regulate bacterial proteases. We investigated proteolytic activities of certain periodontal bacteria, their effects on the latent proMMP-9, and the effects of synthetic MMP inhibitors and a serine protease inhibitor Pefabloc. The strains studied were Porphyromonas gingivalis, Prevotella intermedia, Peptostreptoccus micros, Prevotella nigrescens, Fusobacterium nucleatum, and 5 Aggregatibacter actinomycetemcomitans serotypes. Their gelatinolytic activities and the effects of certain synthetic MMP inhibitors and Pefabloc were analyzed by zymography. Bacterial effects on proMMP-9 conversion were investigated by Western immunoblot. All investigated periodontal bacteria produced gelatinolytic cell-bound and extracellular proteinases which could fragment latent proMMP-9, suggesting co-operative processing cascades in oral tissue remodeling. A. actinomycetemcomitans produced the weakest gelatinolytic activity. Synthetic proteinase inhibitors exhibited slight but clear reductive effects on the bacterial proteolytic activities. We conclude that targeted anti-proteolytic treatment modalities against bacterial-host proteolytic cascades can be developed.

Doxycycline treatment prevents alveolar destruction in VEGF-deficient mouse lung

In vivo lung-targeted VEGF gene inactivation results in pulmonary cell apoptosis, airspace enlargement, and increased lung compliance consistent with an emphysema-like phenotype. The predominant hypothesis for the cause of lung destruction in emphysema is an imbalance between active lung protease and anti-protease molecules. Therefore, we investigated the role of protease (e.g., matrix metalloproteinases--MMPs) and anti-protease (e.g., tissue inhibitors of metalloproteinases--TIMPs) expression in contributing to the lung structural remodeling observed in pulmonary-VEGF-deficient mice. VEGFLoxP mice instilled through the trachea with an adeno-associated virus expressing Cre recombinase (AAV/Cre) manifest airspace enlargement and a greater (P < 0.05) mean linear intercept (MLI: 44.2 +/- 4.2 microm) compared to mice instilled with a control virus expressing LacZ (31.3 +/- 2.5 microm). Airspace enlargement was prevented by the continuous administration of the general MMP inhibitor, doxycycline (Dox) (Cre + Dox: 32.6 +/- 2.5 microm), and MLI values were not different from either control (LacZ + Dox: 30.5 +/- 1.2 microm). In situ magnetic resonance imaging of VEGF gene inactivated mouse lungs revealed uneven inflation, residual trapped gas volumes upon oxygen absorption deflation/re-inflation, and loss of parenchymal structure; effects that were largely prevented by Dox. Five weeks after AAV/Cre infection Western blot revealed a 9.9-fold increase in pulmonary MMP-3, and 2-fold increases in MMP-9 and TIMP-2. However, the increase in MMP-3 was prevented by Dox administration and was associated with a 2-fold increase in serpin b5 (Maspin) expression. These results suggest that doxycycline treatment largely prevents the aberrant lung remodeling response observed in VEGF-deficient mouse lungs and is associated with changes in protease and anti-protease expression.

Profiling Protein Arginine Deiminase 4 (PAD4): a novel screen to identify PAD4 inhibitors

Protein Arginine Deiminase 4 (PAD4) has emerged as a leading target for the development of a Rheumatoid Arthritis (RA) pharmaceutical. Herein, we describe the development of a novel screen for PAD4 inhibitors that is based on a PAD4-targeted Activity-Based Protein Profiling reagent, denoted Rhodamine-conjugated F-Amidine (RFA). This screen was validated by screening 10 Disease Modifying Anti-Rheumatic Drugs (DMARDs) and identified streptomycin, minocycline, and chlortetracycline as micromolar inhibitors of PAD4 activity.

The RgpB C-terminal domain has a role in attachment of RgpB to the outer membrane and belongs to a novel C-terminal-domain family found in Porphyromonas gingivalis

Porphyromonas gingivalis produces outer membrane-attached proteins that include the virulence-associated proteinases RgpA and RgpB (Arg-gingipains) and Kgp (Lys-gingipain). We analyzed the P. gingivalis outer membrane proteome and identified numerous proteins with C-terminal domains similar in sequence to those of RgpB, RgpA, and Kgp, indicating that these domains may have a common function. Using RgpB as a model to investigate the role of the C-terminal domain, we expressed RgpB as a full-length zymogen (recombinant RgpB [rRgpB]), with a catalytic Cys244Ala mutation [rRgpB(C244A)], or with the C-terminal 72 amino acids deleted (rRgpB435) in an Arg-gingipain P. gingivalis mutant (YH522AB) and an Arg- and Lys-gingipain mutant (YH522KAB). rRgpB was catalytically active and located predominantly attached to the outer membrane of both background strains. rRgpB(C244A) was inactive and outer membrane attached, with a typical attachment profile for both background strains according to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, but in YH522KAB, the prodomain was not removed. Thus, in vivo, RgpB export and membrane attachment are independent of the proteolytic activity of RgpA, RgpB, or Kgp. However, for maturation involving proteolytic processing of RgpB, the proteolytic activity of RgpB, RgpA, or Kgp is required. The C-terminally-truncated rRgpB435 was not attached to the outer membrane and was located as largely inactive, discrete 71-kDa and 48-kDa isoforms in the culture supernatant and the periplasm. These results suggest that the C-terminal domain is essential for outer membrane attachment and may be involved in a coordinated process of export and attachment to the cell surface.

Inhibition of Porphyromonas gingivalis proteinases (gingipains) by chlorhexidine: synergistic effect of Zn(II)

BACKGROUND/AIMS

Gingipains, proteolytic enzymes produced by the periodontal pathogen Porphyromonas gingivalis, are regarded as virulence factors in the pathogenesis of periodontitis. Inhibition of gingipain activity therefore may have therapeutic potential, and it has been suggested that chlorhexidine may inhibit the activities of these enzymes. The purposes of the present study were to examine systematically the inhibitory effects of chlorhexidine on three purified gingipains and to determine the effect of Zn(II) on chlorhexidine inhibition.

METHODS

The activities of lys-gingipain (Kgp) and two forms of arg-gingipain (RgpB and HRgpA) were measured in the presence of varying concentrations of chlorhexidine and with chlorhexidine supplemented with Zn(II). Inhibition constants (K(i)'s) were determined for chlorhexidine alone and in the presence of Zn(II). Fractional inhibitory constant indices were calculated to assess the synergy of the chlorhexidine-Zn(II) inhibition.

RESULTS

RgpB, HRgpA, and Kgp were all inhibited by chlorhexidine with K(i)'s in the micromolar range. For RgpB and HRgpA, the inhibitory effects of chlorhexidine were enhanced 3-30-fold by Zn(II). The chlorhexidine-Zn(II) interaction was synergistic for inhibition of HRgpA and RgpB. For Kgp, the effect of Zn(II) on chlorhexidine inhibition was antagonistic.

CONCLUSIONS

Chlorhexidine is an effective inhibitor of gingipains, and the inhibition of R-gingipains is enhanced by Zn(II). A mixture of chlorhexidine and Zn(II) may be useful as an adjunct in the treatment of periodontitis and in the post-treatment maintenance of periodontitis patients.

Transvascular dissemination of Porphyromonas gingivalis from a sequestered site is dependent upon activation of the kallikrein/kinin pathway

BACKGROUND AND OBJECTIVE

Epidemiological evidence implicates a connection between human periodontitis and systemic diseases. One possible mechanism involves the direct dissemination of periodontopathogens to the target organs through the circulation. The aim of this work was to define the mechanism used by Porphyromonas gingivalis for dissemination from a sequestered infection site.

MATERIAL AND METHODS

BALB/c mice were subcutaneously infected with P. gingivalis via use of a mouse chamber model. Tissue fluids from various sites were collected and cultured to determine the presence of P. gingivalis. Evans Blue dye was used to measure the dissemination ability of P. gingivalis. Kinin-associated molecules were introduced into mice, and their effects on bacterial dissemination and mouse pathology were monitored.

RESULTS

P. gingivalis strain A7436 caused remote lesions and septicemia with severe cachexia, resulting in animal death. Intrachamber challenge with A7436 resulted in vascular permeability enhancement (VPE), as measured by the systemic infiltration of Evans Blue dye into chamber fluids. VPE was blocked by kininase and kinin receptor antagonist and enhanced by exogenous bradykinin and kininase inhibitor. Live bacteria were recovered from the subcutaneous perichamber and abdominal spaces (spreading), and from the blood (disseminating) of infected mice. Both kininase and kinin receptor antagonist reduced animal mortality as a result of infection with strain A7436 and decreased the number of bacteria recoverable from the blood, but they were not associated with bacterial spreading.

CONCLUSIONS

The results suggest that activation of the kinin system is involved in the breach of the vascular barrier that permits dissemination of P. gingivalis.

Exploring the Sn binding pockets in gingipains by newly developed inhibitors: structure-based design, chemistry, and activity

Arg-gingipains (Rgps) and Lys-gingipain (Kgp) are cysteine proteinases secreted by Porphyromonas gingivalis, the major pathogen implicated in periodontal disease. Gingipains are essential to the bacterium for its virulence and survival, and development of inhibitors targeting these proteins provides an approach to treat periodontal diseases. Here, we present the first example of structure-based design of gingipains inhibitors, with the use of the crystal structure of RgpB and the homology model of Kgp. Chloromethyl ketones were selected as suitable compounds to explore the specificity of the Sn binding region of both enzymes. Three series of inhibitors bearing Arg or Lys at P1 and different substituents at P2 and P3 were designed, synthesized, and tested. High potency (k(obs)/[I] approximately 10(7) M(-1) s(-1)) was achieved for small ligands, such as the dipeptide analogues. The detailed analysis of Sn binding pockets revealed the molecular basis of inhibitory affinity and provided insight into the structure-activity relationship.

Reduction of myocardial infarct size by doxycycline: a role for plasmin inhibition

Myocardial ischemia-reperfusion (I/R) is associated with the activation of matrix metalloproteinases (MMPs) and serine proteases. We hypothesized that activation of MMPs and the serine protease plasmin contribute to early cardiac myocyte death following I/R and that broad-spectrum protease inhibition with doxycycline (DOX) preserves myocyte viability. Rats treated daily with or without DOX beginning 48 h prior to experimentation were subjected to 30 min of coronary occlusion and 2 days of reperfusion. DOX pre-treatment reduced infarct size by 37%. DOX attenuated increases in MMP-9 and plasmin levels as determined by gelatin zymography and immunoblot, respectively. Neutrophil extravasation was unaltered by DOX as assessed by myeloperoxidase (MPO) activity. To examine the contribution of MMP-9 and plasmin to myocyte injury, cultures of neonatal rat ventricular myocytes (NRVMs) were treated for 48 h with 83 kDa MMP-9 or plasminogen in the presence or absence of DOX. MMP-9 treatment did not affect myocyte viability. Plasminogen treatment led to increased plasmin activity, resulting in loss of beta1-integrin, NRVM detachment and apoptosis. DOX co-treatment inhibited plasmin activity and preserved NRVM attachment, whereas co-treatment with the broad-spectrum MMP inhibitor GM6001 had no effect. These results indicate that plasmin causes disruption of myocyte attachment and viability independently of MMP activation in vitro and that inhibition of plasmin by DOX may reduce I/R-induced myocyte death in vivo through the inhibition of plasmin.

Tactics for Vascular Protection After Acute Ischemic Stroke

BACKGROUND

The vascular events that happen during ischemic stroke worsen outcomes in patients by causing edema, hemorrhagic transformation, and general neurologic tissue compromise. In the past 2 decades, clinical trials in patients after ischemic stroke focused on neuroprotection, but these strategies have failed in providing actual benefit. Vascular protection represents a new field to be explored in acute ischemic stroke in order to develop new approaches to therapeutic intervention.

PURPOSE

We identified tactics likely to provide vascular protection in patients with ischemic stroke. These tactics are based on knowledge of the molecular processes involved.

SUMMARY OF REVIEW

The pathologic processes due to vascular injury after an occlusion of a cerebral artery can be separated into acute (those occurring within hrs), subacute (hrs to days), and chronic (days to mo). Targets for intervention can be identified for all three stages. In the acute phase, superoxide is the predominant mediator, followed by inflammatory mediators and proteases in the subacute phase. In the chronic phase, proapoptotic gene products have been implicated. Many already-marketed therapeutic agents (statins, angiotensin modulators, erythropoietin, minocycline, and thiazolidinediones), with proven safety in patients, have been shown to have activity against some of the key targets of vascular protection.

CONCLUSION

Currently available pharmacologic agents are poised for clinical trials of vascular protection after acute ischemic stroke.

Inhibitory effect of green tea catechins on cysteine proteinases in Porphyromonas gingivalis

The purpose of this study was to examine the effects of catechins and their derivatives on the activities of Arg-gingipain (Rgp) and Lys-gingipain (Kgp) in Porphyromonas gingivalis. Catechin derivatives, which included (-)-epigallocatechin gallate, (-)-epicatechin gallate, (-)-gallocatechin gallate, and (-)-catechin gallate, significantly inhibited the Rgp activity. The 50% inhibitory concentrations (IC50s) of these catechin derivatives for Rgp ranged from 3 to 5 microm. While (-)-epigallocatechin and (-)-gallocatechin moderately inhibited Rgp activity (IC50s, 20 microm), (-) -epicatechin, (+)-catechin, and gallic acid were not effective, with IC50s greater than 300 microm. Further, some of the catechin derivatives tested also inhibited the Kgp activity, though to a lesser extent than inhibition of the Rgp activity. These findings suggest that green tea catechins may have the potential to reduce periodontal breakdown resulting from the potent proteinase activity of P. gingivalis.

Virulence factors of Porphyromonas gingivalis are modified by polyphenol oxidase and asparaginase

Porphyromonas gingivalis is a well-adapted pathogen of the periodontal pocket distinguished by its wide array of proteolytic activities and its ability to adhere to multiple substrata in the oral cavity. Microbial proteins with binding functions (such as adhesins and enzymes) very often contain critical tyrosine residues, supported by one or more asparagines in the binding cleft. This study investigates the reduction in adhesiveness and in proteolytic activity after treating P. gingivalis with the tyrosine- and asparagine-targeting enzymes polyphenol oxidase (PPO) and asparaginase (ASG). Cysteine protease activity was reduced by pretreatment with both enzymes, while the trypsin-like activity was affected only by PPO. Adhesion to buccal epithelial cells, laminin and fibronectin as well as hemagglutination was reduced by one or both of the enzymes. PPO, but not ASG, reduced the coaggregation of P. gingivalis with Actinomyces naeslundii. Treatment with these enzymes might provide an alternative to traditional antimicrobial strategies.

Modulation ofPorphyromonas GingivalisProteinase Activity by Suboptimal Doses of Antimicrobial Agents

BACKGROUND

Antimicrobial agents are sometimes used as adjuncts for the treatment of aggressive and refractory forms of periodontitis. In this study, we used a culture plate assay to investigate the effect of suboptimal doses of antimicrobial agents on proteinase activity of Porphyromonas gingivalis.

METHODS

A culture plate assay using gelatin as the substrate, which allows a semiquantitative determination of proteinase activity, was developed. Suboptimal inhibitory concentrations of tetracycline, minocycline, doxycycline, metronidazole, penicillin G, or chlorhexidine were added to the medium, and proteolysis zones were determined following the growth of three strains of P. gingivalis. The effect of antimicrobials on outer membrane vesicle-associated gingipains also was determined.

RESULTS

The gelatin plate assay was a convenient, simple procedure for investigating the effect of suboptimal inhibitory concentrations of antimicrobial agents on proteinases produced by P. gingivalis. The largest reduction (> 75%) in the proteolysis zones produced by three strains of P. gingivalis was obtained with minocycline. Tetracycline and doxycycline also reduced the proteolysis zones. A suboptimal inhibitory concentration of chlorhexidine increased the proteolysis zones by up to 70%. Metronidazole and penicillin G produced no noticeable effect. The suboptimal inhibitory concentrations of minocycline, tetracycline, and doxycyline did not reduce the activity of outer membrane vesicle-associated Arg- and Lys-gingipains.

CONCLUSION

Results from this study suggest that sublethal concentrations of some antimicrobial agents in subgingival sites have the potential to affect the physiology of P. gingivalis, notably by increasing or decreasing the proteolytic activity of the bacteria.

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.

Inhibition of arginine gingipains (RgpB and HRgpA) with benzamidine inhibitors: zinc increases inhibitory potency

We assayed several benzamidine derivatives for inhibition potency with HRgpA and RgpB gingipains, enzymes which are involved in the pathogenesis of gingivitis and periodontal disease. The benzamidine derivatives proved to be effective inhibitors of HRgpA and RgpB, with the best inhibitor being a bis-benzamidine with a urea linker (Ki=30 microM). The inhibition potency was increased 2-3 fold in the presence of low concentrations of zinc with the benzamidines containing a urea moiety linking the two aromatic rings. We propose an inhibition model involving a tetrahedral zinc atom coordinated with the active site Cys and His of gingipain and the urea linker in the benzamidine inhibitor. In summary, we have discovered a new series of effective inhibitors for the gingipains and found a novel way to increase inhibitor potency with the HRgpA and RgpB gingipains using zinc.