Involvement of bradykinin generation in intravascular dissemination of Vibrio vulnificus and prevention of invasion by a bradykinin antagonist

The role of Vibrio vulnificus virulence factors and regulators in its infection-induced sepsis

Due to the development of Marine aquaculture, infections caused by Vibrio vulnificus are common all over the world. Symptoms of V. vulnificus infection vary from gastrointestinal illness to septicemia. After infection with V. vulnificus, some patients showed gastrointestinal symptoms, including vomiting, fever, diarrhea, and so on. Others appeared wound infection at the site of contact with bacteria, and even developed sepsis. Once it develops into sepsis, the prognosis of patients is very poor. However, its underlying pathogenic mechanism remains largely undetermined. Growing evidence shows that it can induce primary septicemia mainly via essential virulence factors and regulators. Therefore, it is important to identify the factors that play roles in sepsis. In this review, we systematically expounded the role of V. vulnificus virulence factors and regulators in its infection-induced sepsis in order to provide useful information for the treatment and prevention of V. vulnificus.

Degradation of bradykinin by a metalloendopeptidase from Streptococcus pyogenes

OBJECTIVES

Streptococcus pyogenes secretes streptococcal pyrogenic exotoxin B (SpeB), which cleaves kininogen to liberate bradykinin. In addition, this bacterium also has cell-associated bradykinin-degrading activity. Here, we characterized the bradykinin-degrading enzyme produced by S. pyogenes.

METHODS

The effects of various peptidase inhibitors on bradykinin degradation by intact S. pyogenes and cell lysates were assessed. Cleavage of bradykinin and other peptides by a recombinant putative metalloendopeptidase (Sp-Pep) from S. pyogenes was analyzed by mass spectrometry. The enhancement of vascular permeability induced by bradykinin (before and after treatment with Sp-Pep) was evaluated in guinea pig skin.

RESULTS

Various S. pyogenes strains expressed Sp-Pep. Immunoadsorption of S. pyogenes with an anti-Sp-Pep antibody showed that 80% of the bradykinin-degrading activity in S. pyogenes was due to Sp-Pep. Recombinant Sp-Pep cleaved bradykinin, and cleavage caused a loss of its extravasation-inducing potential. Sp-Pep-mediated degradation of bradykinin was 40 times more efficient than degradation of substance P and angiotensin II. While S. pyogenes secreted mature SpeB in stationary phase, this bacterium produced Sp-Pep during all tested growth phases.

CONCLUSIONS

S. pyogenes produces a cell-associated metalloendopeptidase that degrades bradykinin.

Hen egg white ovomacroglobulin promotes fibroblast migration via mediating cell adhesion and cytoskeleton

BACKGROUND

Hen egg white ovomacroglobulin (OVM) possesses a variety of bioactivities and could potentially be used as a pharmaceutical agent. It has been reported that OVM is involved in wound healing and cancer pathological processes, and previous results suggest that OVM plays a potential role in cell proliferation and migration; however, this has not yet been proven. In the present study, the effects of OVM on fibroblast proliferation and migration were evaluated.

RESULTS

Results of cell counting, cell viability, and cell cycle indicated that proliferation of fibroblasts was not altered by OVM treatment. However, scratch assays showed that OVM could promote the migration of 3 T6 mouse embryonic fibroblasts and human skin fibroblasts (HSF). Also, the adhesion of HSF to the collagen matrix was also enhanced by OVM treatment. RT-qPCR and western blot analysis showed that β1 -integrin, β-tubulin, and β-actin were up-regulated while E-cadherin was down-regulated in OVM-treated HSF cells. The effect of OVM was silenced after forming a complex with trypsin, suggesting that the protease inhibitory ability of OVM is important for its effect on cell migration.

CONCLUSION

These results suggested that promotion of OVM on cell migration was achieved by enhancing cell adhesion to extracellular matrix, reducing intercellular aggregation, and strengthening cytoskeleton. The finding of the promotion effect of OVM on cell migration is important for understanding its role in wound healing and cancer pathological processes. © 2015 Society of Chemical Industry.

Alpha 2 macroglobulin is a maternally-derived immune factor in amphioxus embryos: New evidence for defense roles of maternal immune components in invertebrate chordate

In fish, a series of maternal derived immune components have been identified in their eggs or embryos at very early stages, which are proposed to provide protections to themselves against pathogenic attacks from hostile environment. The phenomenon of maternal immunity has been also recorded in several invertebrate species, however, so far, very limited information about the maternal immune molecules are available. In this study, it was demonstrated maternal alpha2 macroglobulin (A2m) protein, an important innate immune factor, exists in the fertilized eggs of amphioxus Branchiostoma japonicum, an invertebrate chordate. Maternal mRNA of A2m was also detected in amphioxus embryos at very early developing stages. In addition, it was recorded that the egg lysate prepared from the newly fertilized eggs can inhibit the growth of both Gram-negative bacterium Escherichia coli and Gram-positive bacterium Staphylococcus aureus in a concentration dependent manner. The bacteriostatic activity can be reduced notably after precipitated A2m with anti-A2m antibody. Thus maternal A2m is partly attributed to the bacteriostatic activity. It was further demonstrated that recombinant A2m can bind to E. coli cells directly. All these points come to a result that A2m is a maternal immune factor existing in eggs of invertebrate chordate, which may be involved in defense their embryos against harmful microbes' attacks.

Bioactive peptides from egg: a review

Purpose

– The aim of the article was to focus on various peptides identified in the egg and their probable application as novel ingredients in the development of functional food products. Bioactive peptides of egg origin have attracted increasing interest as one of the prominent candidates for development of various health-promoting functional and designer foods.

Design/methodology/approach

– Traditionally known as a source of highly valuable proteins in human nutrition, eggs are nowadays also considered as an important source of many bioactive peptides which may find wide application in medicine and food production. These specific protein fragments from egg proteins which, above and beyond their nutritional capabilities, have a positive impact on the body’s function or condition by affecting the digestive, endocrine, cardiovascular, immune and nervous systems, and may ultimately influence health.

Findings

– Several peptides that are released in vitro or in vivo from egg proteins have been attributed to different health effects, including antihypertensive effects, antimicrobial properties, antioxidant activities, anticancer activity, immunomodulating activity, antiadhesive properties and enhancement of nutrient absorption and/or bioavailability. Extensive research has been undertaken to identify and characterize these biologically active peptides of egg origin which has changed the image of egg as a new source of biologically active ingredients for the development of functional foods with specific benefits for human health and treatment and prevention of diseases.

Originality/value

– The paper mainly describes the above-stated properties of bioactive peptides derived from egg proteins.

The Kallikrein Inhibitor from Bauhinia bauhinioides (BbKI) shows antithrombotic properties in venous and arterial thrombosis models

The Bauhinia bauhinioides Kallikrein Inhibitor (BbKI) is a Kunitz-type serine peptidase inhibitor of plant origin that has been shown to impair the viability of some tumor cells and to feature a potent inhibitory activity against human and rat plasma kallikrein (Kiapp 2.4 nmol/L and 5.2 nmol/L, respectively). This inhibitory activity is possibly responsible for an effect on hemostasis by prolonging activated partial thromboplastin time (aPTT). Because the association between cancer and thrombosis is well established, we evaluated the possible antithrombotic activity of this protein in venous and arterial thrombosis models. Vein thrombosis was studied in the vena cava ligature model in Wistar rats, and arterial thrombosis in the photochemical induced endothelium lesion model in the carotid artery of C57 black 6 mice. BbKI at a concentration of 2.0 mg/kg reduced the venous thrombus weight by 65% in treated rats in comparison to rats in the control group. The inhibitor prolonged the time for total artery occlusion in the carotid artery model mice indicating that this potent plasma kallikrein inhibitor prevented thrombosis.

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.

Proteases produced by vibrios

Bacteria of the genus Vibrio are normal habitants of the aquatic environment but the some species are believed to be human pathogens. Pathogenic vibrios produce various pathogenic factors, and the proteases are also recognized to play pathogenic roles in the infection: the direct roles by digesting many kinds of host proteins or indirect roles by processing other pathogenic protein factors. Especially VVP from Vibrio vulnificus is thought to be a major pathogenic factor of the vibrio. Although HA/P, the V. cholerae hemagglutinin/protease, is not a direct toxic factor of cholera vibrio, its significance is an undeniable fact. Production of HA/P is regulated together with major pathogenic factors such as CT (cholera toxin) or TCP (toxin co-regulated pilus) by a quorum-sensing system. HA/P is necessary for full expression of pathogenicity of the vibrio by supporting growth and translocation in the digestive tract. Processing of protein toxins such as CT or El Tor hemolysin is also an important pathogenic role.

Degradation of human kininogens with the release of kinin peptides by extracellular proteinases of Candida spp

The secretion of proteolytic enzymes by pathogenic microorganisms is one of the most successful strategies used by pathogens to colonize and infect the host organism. The extracellular microbial proteinases can seriously deregulate the homeostatic proteolytic cascades of the host, including the kinin-forming system, repeatedly reported to be activated during bacterial infection. The current study assigns a kinin-releasing activity to secreted proteinases of Candida spp. yeasts, the major fungal pathogens of humans. Of several Candida species studied, C. parapsilosis and C. albicans in their invasive filamentous forms are shown to produce proteinases which most effectively degrade proteinaceous kinin precursors, the kininogens. These enzymes, classified as aspartyl proteinases, have the highest kininogen-degrading activity at low pH (approx. 3.5), but the associated production of bradykinin-related peptides from a small fraction of kininogen molecules is optimal at neutral pH (6.5). The peptides effectively interact with cellular B2-type kinin receptors. Moreover, kinin-related peptides capable of interacting with inflammation-induced B1-type receptors are also formed, but with a reversed pH dependence. The presented variability of the potential extracellular kinin production by secreted aspartyl proteinases of Candida spp. is consistent with the known adaptability of these opportunistic pathogens to different niches in the host organism.

A comprehensive review of Vibrio vulnificus: an important cause of severe sepsis and skin and soft-tissue infection

Vibrio vulnificus is a halophilic Gram-negative bacillus found worldwide in warm coastal waters. The pathogen has the ability to cause primary sepsis in certain high-risk populations, including patients with chronic liver disease, immunodeficiency, iron storage disorders, end-stage renal disease, and diabetes mellitus. Most reported cases of primary sepsis in the USA are associated with the ingestion of raw or undercooked oysters harvested from the Gulf Coast. The mortality rate for patients with severe sepsis is high, exceeding 50% in most reported series. Other clinical presentations include wound infection and gastroenteritis. Mild to moderate wound infection and gastroenteritis may occur in patients without obvious risk factors. Severe wound infection is often characterized by necrotizing skin and soft-tissue infection, including fasciitis and gangrene. V. vulnificus possesses several virulence factors, including the ability to evade destruction by stomach acid, capsular polysaccharide, lipopolysaccharide, cytotoxins, pili, and flagellum. The preferred antimicrobial therapy is doxycycline in combination with ceftazidime and surgery for necrotizing soft-tissue infection.

Captopril increases the intensity of monocyte infection by Trypanosoma cruzi and induces human T helper type 17 cells

The anti-hypertensive drug captopril is used commonly to reduce blood pressure of patients with severe forms of Chagas disease, a cardiomyopathy caused by chronic infection with the intracellular protozoan Trypanosoma cruzi. Captopril acts by inhibiting angiotensin-converting enzyme (ACE), the vasopressor metallopeptidase that generates angiotensin II and promotes the degradation of bradykinin (BK). Recent studies in mice models of Chagas disease indicated that captopril can potentiate the T helper type 1 (Th1)-directing natural adjuvant property of BK. Equipped with kinin-releasing cysteine proteases, T. cruzi trypomastigotes were shown previously to invade non-professional phagocytic cells, such as human endothelial cells and murine cardiomyocytes, through the signalling of G protein-coupled bradykinin receptors (B(2) KR). Monocytes are also parasitized by T. cruzi and these cells are known to be important for the host immune response during infection. Here we showed that captopril increases the intensity of T. cruzi infection of human monocytes in vitro. The increased parasitism was accompanied by up-regulated expression of ACE in human monocytes. While T. cruzi infection increased the expression of interleukin (IL)-10 by monocytes significantly, compared to uninfected cells, T. cruzi infection in association with captopril down-modulated IL-10 expression by the monocytes. Surprisingly, studies with peripheral blood mononuclear cells revealed that addition of the ACE inhibitor in association with T. cruzi increased expression of IL-17 by CD4(+) T cells in a B(2) KR-dependent manner. Collectively, our results suggest that captopril might interfere with host-parasite equilibrium by enhancing infection of monocytes, decreasing the expression of the modulatory cytokine IL-10, while guiding development of the proinflammatory Th17 subset.

gC1qR/p33 blockade reduces Staphylococcus aureus colonization of target tissues in an animal model of infective endocarditis

gC1qR/p33 (gC1qR) is a ubiquitously expressed cellular protein that is also found in plasma and the extracellular matrix. In addition to its role in modulating the activation of complement and kinin cascades, gC1qR has been identified as a putative host ligand for endovascular pathogens, including Staphylococcus aureus. The present study provides evidence of the ability of soluble gC1qR to enhance S. aureus-fibrinogen interactions via simultaneously binding fibrinogen and S. aureus. This interaction was inhibited in vitro by two monoclonal antibodies (MAbs 74.5.2 and 60.11) recognizing distinct structural and functional domains of gC1qR. To evaluate the in vivo role of gC1qR, MAbs 74.5.2 and 60.11 were used in an experimental rat model of S. aureus endocarditis. Each MAb (100 mg/kg of body weight, given intraperitoneally) reached sustained (>60 h) and high (100 to 200 microg/ml) serum levels. Prophylaxis with MAb 60.11 or 74.5.2 caused substantial reductions in S. aureus colonization of aortic valves, kidneys, and the spleen compared to untreated controls. However, only MAb 74.5.2 prophylaxis therapy reached statistical significance, and only sera from animals protected with MAb 74.5.2 inhibited gC1qR-mediated S. aureus interactions with fibrinogen. Although not statistically significant, the reductions in bacterial colonization achieved with MAb 60.11 alone and in combination with MAb 74.5.2 (versus MAb 74.5.2 alone) suggest that there are effects of gC1qR blockade on S. aureus infective endocarditis in addition to blocking gC1qR-mediated S. aureus binding to fibrinogen. Such impacts may include direct modulation of complement (MAb 60.11) and kinin cascades (MAb 74.5.2) and/or activation of immune and inflammatory responses via localized immune complex formation.

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.

Specificity of a Vibrio vulnificus aminopeptidase toward kinins and other peptidyl substrates

Recently, phosphoglucose isomerase with a lysyl aminopeptidase (PGI-LysAP) activity was identified in Vibrio vulnificus. In this paper, we demonstrate the proteolytic cleavage of human-derived peptides by PGI-LysAP of V. vulnificus using three approaches: (i) a quantitative fluorescent ninhydrin assay for free lysine, (ii) matrix-assisted laser desorption ionization-two-stage time of flight mass spectrometry (MALDI-TOF-TOF), and (iii) Tricine gel electrophoresis. PGI-LysAP hydrolyzed bradykinin, Lys-bradykinin, Lys-(des-Arg9)-bradykinin, neurokinin A, Met-Lys-bradykinin, histatin 8, and a myosin light chain fragment. We detected the proteolytic release of free L-lysine from peptide digests using a rapid, simple, sensitive, and quantitative fluorescent ninhydrin assay, and results were confirmed by MALDI-TOF-TOF. The use of the fluorescent ninhydrin assay to quantitatively detect free lysine hydrolyzed from peptides is the first application of its kind and serves as a paradigm for future studies. The visualization of peptide hydrolysis was accomplished by Tricine gel electrophoresis. Proteolytic processing of kinins alters their affinities toward specific cellular receptors and initiates signal transduction mechanisms responsible for inflammation, vasodilation, and enhanced vascular permeability. By applying novel approaches to determine the proteolytic potential of bacterial enzymes, we demonstrate that PGI-LysAP has broad exopeptidase activity which may enhance V. vulnificus invasiveness by altering peptides involved in signal transduction pathways.

Advances in the value of eggs and egg components for human health

The avian egg is an important source of nutrients, containing all of the proteins, lipids, vitamins, minerals, and growth factors required by the developing embryo, as well as a number of defense factors to protect against bacterial and viral infection. Moreover, eggs are now understood to contain substances with biological functions beyond basic nutrition, and extensive research has been undertaken to identify and characterize these biologically active components. This review mainly focused on biological activities of proteins and peptides derived from egg components. Several biological activities have now been associated with egg components, including novel antimicrobial activities, antiadhesive properties, immunomodulatory, anticancer, and antihypertensive activities, antioxidant properties, protease inhibitors, nutrient bioavailability, and functional lipids, highlighting the importance of egg and egg components in human health and in disease prevention and treatment. Continued research to identify new and existing biological functions of hen egg components will help to define new methods to further improve the value of eggs as a source of numerous biologically active compounds with specific benefits for human and animal health and secure their role in the therapy and prevention of chronic and infectious disease.

Inactivation of Vibrio vulnificus hemolysin by oligomerization but not proteolysis

Vibrio vulnificus extracellular protease (VvpE) is believed to destroy its hemolysin (VvhA) in the late growth phase, without obvious experimental evidence. So, we attempted to elucidate the mechanism. The hemolytic activity steeply increased with the expression of the VvhA in the early growth phase, and then abruptly declined with the expression of VvpE in the late growth phase. However, the VvhA activity also abruptly declined in a VvpE-deficient mutant. In Western blot, the degradation of VvhA was not observed; instead, the oligomerization of VvhA increased with the concomitant loss of hemolytic activity. These results evidently indicate that the inactivation of VvhA is due to the novel oligomerization of VvhA by unknown mechanism, but not to the destruction of VvhA by VvpE, so that the routine functional assay measuring hemolytic activity cannot reflect the actual production of VvhA.

Pathogenic Factors of Vibrios with Special Emphasis on Vibrio vulnificus

Bacteria of the genus Vibrio are normal habitants of the aquatic environment and play roles for biocontrole of aquatic ecosystem, but some species are believed to be human pathogens. These species can be classified into two groups according to the types of diseases they cause: the gastrointestinal infections and the extraintestinal infections. The pathogenic species produce various pathogenic factors including enterotoxin, hemolysin, cytotoxin, protease, siderophore, adhesive factor, and hemagglutinin. We studied various pathogenic factors of vibrios with special emphasis on protease and hemolysin of V. vulnificus. V. vulnificus is now recognized as being among the most rapidly fatal of human pathogens, although the infection is appeared in patients having underlying disease(s) such as liver dysfunction, alcoholic cirrhosis or haemochromatosis. V. vulnificus protease (VVP) is thought to be a major toxic factor causing skin damage in the patients having septicemia. VVP is a metalloprotease and degrades a number of biologically important proteins including elastin, fibrinogen, and plasma proteinase inhibitors of complement components. VVP causes skin damages through activation of the Factor XII-plasma kallikrein-kinin cascade and/or exocytotic histamine release from mast cells, and a haemorrhagic lesion through digestion of the vascular basement membrane. Thus, the protease is the most probable candidate for tissue damage and bacterial invasion during an infection. Pathogenic roles and functional mechanism of other factors including hemolysins of V. vulnificus and V. mimicus are also shown in this review article.

A survey for phosphoglucose isomerase with lysyl aminopeptidase activity in Vibrionaceae and non-Vibrio pathogens

Phosphoglucose isomerase (PGI) with a novel lysyl aminopeptidase (LysAP) activity was recently purified and characterized from Vibrio vulnificus. We showed that it cleaves the amino-terminal lysyl residue from des-Arg(10)-kallidin to produce des-Arg(9)-bradykinin, suggesting that it plays a role in virulence. A survey was conducted to determine the presence of this potential virulence-enhancing enzyme among twenty-three halotolerant human and fish pathogens from eleven species within the Vibrionaceae family, including V. vulnificus, V. parahaemolyticus, V. cholerae, Aeromonas hydrophila, and Plesiomonas shigelloides. In addition, fourteen species of non-Vibrionaceae pathogens were screened for LysAP activity. Cell lysates were partially purified by anion exchange chromatography and fractions were screened for LysAP and isomerase activities. PGI-LysAP activity was detected in chromatographic fractions from all the Vibrio species tested, but was not detected in any of the non-Vibrionaceae pathogens. Levels of isomerase and LysAP activity correlated (R(2)=0.92) for nine strains of V. vulnificus. Since the Vibrionaceae represent an important family of human and fish pathogens, our identification of PGI-LysAP activity in a broad array of vibrios may lead to the development of improved analytical methods for their identification as well as interventions to reduce the high morbidity and mortality associated with some Vibrionaceae infections in clinical, veterinary, and aquaculture settings.

Structural and functional analyses of phosphoglucose isomerase from Vibrio vulnificus and its lysyl aminopeptidase activity

Phosphoglucose isomerase (PGI) with a novel lysyl aminopeptidase (LysAP) activity was recently isolated and partially characterized from the human pathogen, Vibrio vulnificus. This PGI is a heterodimer consisting of 60.8- and 23.4-kDa subunits, which together provide LysAP activity. The present study further characterizes the complex structure and functions of Vibrio PGI and draws parallels with rabbit and human PGI. A Proscan search of Vibrio PGI revealed 194 different structural motifs of which 124 and 127 were also found in rabbit and human PGI, respectively. Vibrio PGI contains motifs for the serine, histidine and aspartic acid active sites of the subtilase family of serine proteases which form a putative catalytic triad consisting of His534 and Ser159 on the 60.8-kDa subunit and Asp53 on the 23.4-kDa subunit. Together, they form one LysAP site for each heterodimer. Each active site motif is overlapped by motifs for EF-hand calcium binding domains. The LysAP activity was inhibited by the addition of > or =10 microM Ca2+, suggesting that the EF-hand calcium-binding domain may be a natural regulatory region for LysAP activity. In contrast, PGI's isomerase activity was enhanced at Ca2+ concentrations >100 microM. PGI-LysAP cleaved the amino-terminal lysyl residue from des-Arg10-kallidin producing des-Arg9-bradykinin; therefore, Vibrio PGI-LysAP may serve as a virulence factor to enhance Vibrio invasiveness. Together, these data provide a framework to account for PGI's LysAP activity and further demonstrate the structural complexity and functional importance of this molecule.

Captopril ameliorates myocarditis in acute experimental Chagas disease

BACKGROUND

Captopril, an angiotensin-converting enzyme inhibitor, is commonly prescribed to patients with Chagas heart disease (CHD). There are few human studies and no animal studies on the effects of captopril in CHD. We investigated the effects of captopril on myocarditis and the host immune response to Trypanosoma cruzi in an experimental model of acute CHD.

METHODS AND RESULTS

A/J mice infected with Brazil strain of T cruzi developed acute myocarditis by day 21 after infection, consisting of severe focal inflammation, necrosis, fibrosis, and T cruzi pseudocysts. Administration of captopril (5 mg/L in the water) significantly reduced necrosis and fibrosis in infected mice. Increasing the captopril dose also led to a decrease in inflammation. Captopril did not affect overall mortality but did delay death while having no effect on parasitemia or cardiac parasite load. Treatment did not affect humoral immunity against T cruzi or cardiac myosin (autoimmunity) but did decrease delayed-type hypersensitivity responses against both antigens. Interestingly, increasing the dose of captopril induced mortality in infected mice in a dose-dependent manner. Mortality was apparently not due to T cruzi because neither parasitemia nor cardiac parasitosis was affected. The combination of captopril and infection may have impaired renal function because these mice had increased water consumption, decreased body mass, and increased serum BUN/creatinine ratio.

CONCLUSIONS

Captopril ameliorates the myocarditis associated with acute T cruzi infection.

Vascular permeability enhancement in solid tumor: various factors, mechanisms involved and its implications

Most solid tumors are known to exhibit highly enhanced vascular permeability, similar to or more than the inflammatory tissues. Common denominators affecting both cancer and inflammatory lesions are now well known: bradykinin (BK), nitric oxide (NO), peroxynitrite (ONOO(-)), prostaglandins (PGs), collagenases or matrix metalloproteinases (MMPs) and others. Incidentally, enzymes involved in these mediator syntheses are upregulated or activated. Initially described vascular permeability factor (VPF) (proteinaceous) was later identified to be the same as vascular endothelial growth factor (VEGF), which promotes angiogenesis of cancer tissues as well. These mediators cross-talk or co-upregulate each other, such as BK-NO-PGs system. Therefore, vascular permeability observed in solid tumor may reflect the other side of the coin (angiogenesis). The vascular permeability and accumulation of plasma components in the interstitium described here is applicable for predominantly macromolecules (molecular weight, Mw>45 kDa), but not for low molecular compounds as most anticancer agents are. Macromolecular compounds (e.g., albumin, transferrin) or many biocompatible water-soluble polymers show this effect. Furthermore, they are not cleared rapidly from the sites of lesion (cancer/inflammatory tissue), thus, remain for prolonged time, usually for more than a few days. This phenomenon of "enhanced permeability and retention effect" observed in cancer tissue for macromolecules and lipids is coined "EPR effect", which is now widely accepted as a gold standard for anticancer drug designing to seek more cancer-selective targeting using macromolecular drugs. Consequently, drastic reduction of the systemic side effect is observed, while the macromolecular drugs will continuously exert antitumor activity. Other advantages of macromolecular drugs are also discussed.

Vibrio vulnificus septicaemia

Vibrio vulnificus is an opportunistic pathogen capable of causing a fulminant septicaemia in susceptible patients. Underlying chronic diseases such as liver impairment and immunosuppression are important factors contributing to the severity of the infection and outcome. Early suspicion and diagnosis with appropriate antibiotic therapy is important as delay can adversely affect outcome. For those who develop tissue necrotizing fasciitis, early surgical debridement is recommended to allow better penetration of antibiotics and also to reduce the severity of the septicaemia. Mortality is quoted as between 50% and 90%. Current antibiotic recommendations are intravenous ceftazidime 2 g tds and doxycycline 100 mg od.

Staphylococcus aureus induces release of bradykinin in human plasma

Staphylococcus aureus is a prominent human pathogen. Here we report that intact S. aureus bacteria activate the contact system in human plasma in vitro, resulting in a massive release of the potent proinflammatory and vasoactive peptide bradykinin. In contrast, no such effect was recorded with Streptococcus pneumoniae. In the activation of the contact system, blood coagulation factor XII and plasma kallikrein play central roles, and a specific inhibitor of these serine proteinases inhibited the release of bradykinin by S. aureus in human plasma. Furthermore, fragments of the cofactor H-kininogen of the contact system efficiently blocked bradykinin release. The results suggest that activation of the contact system at the surface of S. aureus and the subsequent release of bradykinin could contribute to the hypovolemic hypotension seen in patients with severe S. aureus sepsis. The data also suggest that the contact system could be used as a target in the treatment of S. aureus infections.

Enhanced vascular permeability in solid tumor involving peroxynitrite and matrix metalloproteinases

Peroxynitrite (ONOO(-)), which is generated from nitric oxide (NO) and superoxide anion (O(2)(.-)) under pathological conditions, plays an important role in pathophysiological processes. Activation of matrix metalloproteinases (MMPs) contributes to tumor angiogenesis and metastasis. NO mediates the enhanced vascular permeability and retention (EPR) effect in solid tumors, and ONOO(-)activates proMMP to MMP in vitro. In this study, we examined the role of ONOO(-)in the EPR effect in solid tumors and normal tissues as related to MMP activation. Authentic ONOO(-), at 50 nmol or higher concentrations, induced the enhanced vascular permeability in normal dorsal skin of mice. ONOO(-)scavengers ebselen and uric acid significantly suppressed the EPR effect in mouse sarcoma 180 (S-180) tumors. Indirect evidence for formation of ONOO(-)in S-180 and mouse colon adenocarcinoma (C-38) tumors included strong immunostaining for nitrotyrosine in the tumor tissue, predominantly surrounding the tumor vessels. MMP inhibitor BE16627B (66.6 mg / kg i.v., given 2 times) or SI-27 (10 mg / kg i.p., given 2 times) significantly suppressed the ONOO(-)-induced EPR effect in S-180 tumors and in normal skin. Soybean trypsin inhibitor (Kunitz type), broad-spectrum proteinase inhibitor ovomacroglobulin, and bradykinin receptor antagonist HOE 140 also significantly suppressed the ONOO(-)-induced EPR effect in normal skin tissues. These data suggest that ONOO(-)may be involved in and promote the EPR effect in tumors, which could be mediated partly through activation of MMPs and a subsequent proteinase cascade to generate potent vasoactive mediators such as bradykinin.

Construction and phenotypic evaluation of a Vibrio vulnificus vvpE mutant for elastolytic protease

Vibrio vulnificus is an opportunistic gram-negative pathogen that commonly contaminates oysters. Predisposed individuals who consume raw oysters can die within days from sepsis, and even otherwise healthy people are susceptible to serious wound infection after contact with contaminated seafood or seawater. Numerous secreted and cell-associated virulence factors have been proposed to account for the fulminating and destructive nature of V. vulnificus infections. Among the putative virulence factors is an elastolytic metalloprotease. We cloned and sequenced the vvpE gene encoding an elastase of V. vulnificus ATCC 29307. The functions of the elastase were assessed by constructing vvpE insertional knockout mutants and evaluating phenotypic changes in vitro and in mice. Although other types of protease activity were still observed in vvpE mutants, elastase activity was completely absent in the mutants and was restored by reintroducing the recombinant vvpE gene. In contrast to previous characterization of elastase as a potential virulence factor, which was demonstrated by injecting the purified protein into animals, inactivation of the V. vulnificus vvpE gene did not affect the ability of the bacteria to infect mice and cause damage, either locally in subcutaneous tissues or systemically in the liver, in both iron-treated and normal mice. Furthermore, a vvpE mutant was not affected with regard to cytolytic activity toward INT407 epithelial cells or detachment of INT407 cells from culture dishes in vitro. Therefore, it appears that elastase is less important in the pathogenesis of V. vulnificus than would have been predicted by examining the effects of administering purified proteins to animals. However, V. vulnificus utilizes a variety of virulence factors; hence, the effects of inactivation of elastase alone could be masked by other compensatory virulence factors.

Metalloprotease is not essential for Vibrio vulnificus virulence in mice

Previous work suggested that a metalloprotease, Vvp, may be a virulence factor of Vibrio vulnificus, which causes severe wound infection and septicemia in humans. To determine the role of Vvp in pathogenesis, we isolated an isogenic protease-deficient (PD) mutant of Vibrio vulnificus by in vivo allelic exchange. This PD mutant was as virulent as its parental strain in mice infected intraperitoneally and was 10-fold more virulent in mice infected via the oral route. Furthermore, the PD mutant was indistinguishable from its parental strain in invasion from peritoneal cavity into blood stream, enhancement of vascular permeability, growth in murine blood, and utilization of hemoglobin and transferrin. These data suggest that Vvp is not essential for virulence in the mouse. However, the cytolysin activity in the culture supernatant of the PD mutant was found to be twofold higher than that of the wild-type strain and remained for a much longer period. The higher cytolysin activity of the PD mutant may be associated with the enhanced virulence in mice infected via the oral route.

The marine pathogen Vibrio vulnificus encodes a putative homologue of the Vibrio harveyi regulatory gene, luxR: a genetic and phylogenetic comparison

Vibrio vulnificus is an opportunistic pathogen that exhibits numerous virulence factors, including the secretion of a zinc metalloprotease and the production of a capsule. We have cloned and sequenced a gene from V. vulnificus that is a homologue of the positive transcriptional regulator, luxR, of the lux operon in Vibrio harveyi. This gene encodes a putative, single complete open reading frame designated smcR, which shares greater than 75% nucleotide identity with luxR of V. harveyi. The deduced amino acid sequence of the putative SmcR protein is more than 90% identical and 95% similar to that of LuxR of V. harveyi, suggesting that V. vulnificus possesses a member of the family of signal-response genes recently described in Vibrio cholerae and in Vibrio parahaemolyticus. Our data also demonstrate that, in addition to V. vulnificus, all six Vibrio spp. tested contained genes that hybridized with the luxR probe. We also present evidence that this regulatory protein was inherited from a common ancestor, and that the gene is ancient and widespread in marine Vibrio spp.

Bacterial proteinases as targets for the development of second-generation antibiotics

The emergence of bacterial pathogen resistance to common antibiotics strongly supports the necessity to develop alternative mechanisms for combating drug-resistant forms of these infective organisms. Currently, few pharmaceutical companies have attempted to investigate the possibility of interrupting metabolic pathways other than those that are known to be involved in cell wall biosynthesis. In this review, we describe multiple, novel roles for bacterial proteinases during infection using, as a specific example, the enzymes from the organism Porphyromonas gingivalis, a periodontopathogen, which is known to be involved in the development and progression of periodontal disease. In this manner, we are able to justify the concept of developing synthetic inhibitors against members of this class of enzymes as potential second-generation antibiotics. Such compounds could not only prove valuable in retarding the growth and proliferation of bacterial pathogens but also lead to the use of this class of inhibitors against invasion by other infective organisms.

Tumor vascular permeability and the EPR effect in macromolecular therapeutics: a review

Most solid tumors possess unique pathophysiological characteristics that are not observed in normal tissues or organs, such as extensive angiogenesis and hence hypervasculature, defective vascular architecture, impaired lymphatic drainage/recovery system, and greatly increased production of a number of permeability mediators. The phenomenon now known as the enhanced permeability and retention (EPR) effect for lipid and macromolecular agents has been observed to be universal in solid tumors. Primarily, enhanced vascular permeability will sustain an adequate supply of nutrients and oxygen for rapid tumor growth. The EPR effect also provides a great opportunity for more selective targeting of lipid- or polymer-conjugated anticancer drugs, such as SMANCS and PK-1, to the tumor. In the present review, the basic characteristics of the EPR effect, particularly the factors involved, are described, as well as its modulation for improving delivery of macromolecular drugs to the tumor. Tumor-specific vascular physiology is also described.

Kallikrein-kinin in infection and cancer

This review article describes the mechanism of enhancement of vascular permeability in infectious disease and cancer. This phenomenon is primarily mediated by bradykinin, nitric oxide and other unique vascular mediators. They are highly intermingled with each other in these disease states. Furthermore, these mediators are elicited in various in vivo settings most frequently induced by bacterial proteases, and indirect or direct activation of kallikrein-kinin cascade at one or more steps. The key steps involve bacterial proteases or cellular components including lipopolysaccharides. Thus, the use of appropriate protease inhibitors or antagonists, or scavengers in the case of nitric oxide, superoxide or peroxynitrite, are anticipated to attenuate the clinical manifestation induced by such mediators. It also explained that fluid accumulation in ascitic or pleural compartments in the case of carcinomatosis in terminal cancer patients can be largely attributed to bradykinin or related mechanism. Systemic bacterial dissemination is also facilitated by bradykinin, or suppressed by kinin antagonists as well as by the inhibition of kinin production, respectively. Thus, control of the level of such vascular mediators appears important both in infectious disease and in cancer. alpha1-Protease inhibitor, which inhibits neutrophil elastase, is inactivated by oxidative metabolites such as superoxide and peroxynitrite, and this effect activates matrix metalloproteinases. This indicates that oxidative stress activates proteolytic potential, and thus accelerates the degenerative process upon infection.

Pathogenesis of Vibrio vulnificus

This review describes the factors which are currently recognized as being central to the virulence of the human pathogen, Vibrio vulnificus. This estuarine/marine bacterium occurs in high numbers in molluscan shellfish, primarily oysters, and its ingestion in raw oysters results in a ca. 60% mortality in those persons who are susceptible to this bacterium. The organism is also able to produce life-threatening wound infections. We describe here the nature of both the wound and primary septicemia infections, the virulence factors known or believed to be involved in these infections, possible immunotherapy, and some thoughts on the possibility that not all strains of this pathogen are virulent.