Activation of human Hageman factor by Pseudomonas aeruginosa elastase in the presence or absence of negatively charged substance in vitro

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.

Role of bacterial proteases in pseudomonal and serratial keratitis

Pseudomonas aeruginosa and Serratia marcescens can cause refractory keratitis resulting in corneal perforation and blindness. These bacteria produce various kinds of proteases. In addition to pseudomonal elastase (LasB) and alkaline protease, LasA protease and protease IV have recently been found to be more important virulence factors of P. aeruginosa . S. marcescens produces a cysteine protease in addition to metalloproteases. These bacterial proteases have a number of biological activities, such as degradation of tissue constituents and host defense-oriented proteins, as well as activation of zymogens (Hageman factor, prekallikrein and pro-matrix metalloproteinases) through limited proteolysis. In this article, the properties of these bacterial proteases are reviewed and the pathogenic roles of these proteases in pseudomonal keratitis are discussed.

Whale Hageman factor (factor XII): prevented production due to pseudogene conversion

In Southern blot analysis of the Hind III-digested whale genomic DNA obtained from the livers of two individual whales, we detected a single band with a size of five kilobase pairs which hybridized to full length guinea pig Hageman factor cDNA. We amplified two successive segments of the whale Hageman factor gene by polymerase chain reaction (PCR), and sequenced the PCR products with a combined total of 1367 base pairs. Although all of the exon-intron assemblies predicted were identical to those of the human Hageman factor gene, there were two nonsense mutations making stop codons and a single nucleotide insertion causing a reading frame shift. We could not detect any message of the Hageman factor gene expression by northern blot analysis or by reverse transcription-polymerase chain reaction (RT-PCR) analysis. These results suggest that in the whale, production of the Hageman factor protein is prevented due to conversion of its gene to a pseudogene. The deduced amino acid sequence of whale Hageman factor showed the highest homology with the bovine molecule among the land mammals analyzed so far.

Species differences in amino acid sequences of Hageman factor and prekallikrein at region around scissile bond in activation

The initial step in activation of the plasma kinin system is activation of Hageman factor (coagulation factor XII) and/or plasma prekallikrein. Two types of activation mechanisms, contact activation on a negatively charged surface and a cascade activation by exogenous proteases are known. Since these factors are serine protease zymogens, the activation of these molecules usually results from the cleavage of a particular -Arg-Ile(Val)- bond in either mechanism. Hence, these zymogens are regard to be substrates of their activator proteases. Sensitivity of the substrate for the protease basically depends on the amino acid sequence of six to eight residues around the scissile bond of the substrate. We found different activation efficiencies of these zymogens between human and guinea pig in both types of activation, and micro-heterogeneity of the sequence around the scissile bond among human, guinea pig and bovine Hageman factors, or between human and guinea pig prekallikreins. The sequence heterogeneity may explain the different activation efficiencies of these zymogens among mammalian species.

Pathogenic mechanisms induced by microbial proteases in microbial infections

Most bacterial and fungal proteases excreted into infected hosts exhibit a wide range of pathogenic potentials ranging from pain, edema or even shock to translocation of bacteria from the site of infection into systemic circulation, thus resulting in septicemia. The basic mechanism or principle common to all these phenomena is explained by kinin generation, either directly from high- and/or low-molecular weight kininogens or indirectly via activation of the bradykinin generating cascade: i.e. Hageman factor-->activated Hageman factor-->prekallikrein-->kallikrein-->high-molecular weight kininogen-->bradykinin. Some bacterial proteases are also involved in activation of other host protease zymogens such as plasminogen, procollagenase (matrix metallo proteases) and proenzymes of the clotting system. Furthermore, most bacterial proteases are not only resistant to plasma protease inhibitors of the hosts, most of which belong to a group of serine protease inhibitors called serpins (serine protease inhibitors), but they also quickly inactivate serpins. Some bacterial proteases may also activate bacterial toxins thus rendering toxigenic pathogenesis. They are also capable of degrading immunoglobulins and components of the complement system and facilitate propagation of micro organisms. All in all, microbial proteases are very critical in enhancing pathogenesis of severe diseases. It is also noteworthy that bacterial cell wall components themselves, i.e. endotoxin (or lipopolysaccharide) of gram negative bacteria and teichoic/lipoteichoic acid of gram positive bacteria, are also able to activate the bradykinin generating cascade-involving activation of Hageman factor as mentioned above.

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

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

Pseudomonal elastase injection causes low vascular resistant shock in guinea pigs

An intravenous injection of culture supernatants obtained from an elastase producing strain (IFO-3455) of Pseudomonas aeruginosa exhibited immediate fall of mean arterial blood pressure from 63.8 +/- 1.62 to 35.6 +/- 2.31 mmHg (P < 0.001), increased heart rate from 249.6 +/- 3.86 to 272.6 +/- 2.18 beats/min (P < 0.05), and increased respiratory rate from 44.8 +/- 2.33 to 68.6 +/- 1.60/min (P < 0.01) within 5 min in the anesthetized guinea pigs. In contrast, culture supernatants obtained from an elastase non-producing strain (PA-103) did not cause the cardio-respiratory alterations, even though the same dose of endotoxin was contained in the supernatants. Intravenous or intracardiac injection of purified Pseudomonas aeruginosa elastase (1.2 mg/kg) but not endotoxin (up to 2.0 mg/kg) reproduced the immediate shock followed by death within 45 min in anesthetized or in conscious guinea pigs. Consistently, the shock-inducing ability of pseudomonal elastase was prevented by pretreatment with anti-pseudomonal elastase rabbit F(ab')2 antibodies or with a synthetic inhibitor of pseudomonal elastase. Furthermore, intravenous injection of a non-lethal dose of pseudomonal elastase (0.8 mg/kg) immediately decreased peripheral vascular resistance when estimated from a change of perfusion pressure at hindquarter circulation from 74.0 +/- 1.00 to 52.6 +/- 1.76 mmHg (P < 0.05) in association with fall of arterial blood pressure and of cardiac output which was estimated from a change of regional aortic flow. The same low-resistant shock was also observed in rats. We speculate, therefore, that bacterial proteinases may play an important role in human septic shock.

Role of Hageman factor/kallikrein-kinin system in pseudomonal elastase-induced shock model

The role of the Hageman factor dependent pathway in pseudomonal elastase-induced shock was investigated in guinea pigs. Presence of a bradykinin B2 receptor antagonist [D-Arg0,Hyp3,Thi5,8,D-Phe7]-bradykinin (200 nM) in the circulation prevented shock caused by an intrajugular injection of pseudomonal elastase (0.8 mg/kg body weight). During the lethal shock caused by elastase (1.2 mg/kg), a significant consumption of components of the Hageman factor/kallikrein-kinin system was observed such as 45.7 +/- 2.20% consumption of Hageman factor, 100 +/- 0% of prekallikrein, and 85.1 +/- 2.50 of high-molecular-weight kininogen. More striking evidence for the participation of this system was demonstrated in depletion experiments with monospecific F(ab')2 antibodies against the components of the system. After depletion of any one of the components, guinea pigs exhibited unresponsiveness to the same lethal dose of pseudomonal elastase in regard to the cardio-respiratory alterations. In vitro, pseudomonal elastase (60 micrograms/ml) possessed a capacity to generate substantial amount of bradykinin in undiluted plasmas of humans (300.0 +/- 32.16 ng/ml) as well as guinea pigs (460.2 +/- 20.67 ng/ml) at 37 degrees C but not in those deficient in Hageman factor or prekallikrein. These results strongly suggested a pathological role of elastase in pseudomonal sepsis through activation of the Hageman factor dependent pathway.

Difference between human and guinea pig Hageman factors in activation by bacterial proteinases: cleavage site shift due to local amino acid substitutions may determine the activation efficiency of serine proteinase zymogens

Human and guinea pig Hageman factors have been subjected to the action of pseudomonal elastase and serratial E15 proteinase. The pseudomonal elastase cleaved 22-24% of the human molecule at Arg353-Val354, and the remainder at Gly357-Leu358 resulting in the generation of about 20% of potential activity as activated Hageman factor, compared with trypsin activation, while it hydrolyzed Arg340-Ile341 bond in guinea pig molecule and generated about 75% of activity as activated Hageman factor. The serratial proteinase did not hydrolyze the essential cleavage site (Arg353-Val354) of the human zymogen but Gly356-Gly357 (30%) and Gly357-Leu358 (70%) bonds. Both products showed no activity. The guinea pig zymogen, in contrast, was cleaved mostly at Arg340-Ile341 (70%) and less abundantly at Gly344-Leu345 (30%), generating about 85% of the whole potential activity as activated Hageman factor. From the high correspondence between the proportions of activation and of hydrolysis at the essential cleavage site in activation, it was concluded that hydrolysis of the bonds different from the essential bond did not cause activation, even when the spatial separation was only 3 or 4 residues. Considering the amino acid differences between human and guinea pig Hageman factors, -Met351-Thr-Arg-Val-Val-Gly-Gly-Leu-Val-Ala360- and -Leu338-Ser-Arg-Ile-Val-Gly-Gly-Leu-Val-Ala347-, respectively, it was realized that even the minor amino acid substitutions caused the cleavage site shift which resulted in significant differences in activation efficiency of the proteinase zymogens.

Primary structure of guinea-pig Hageman factor: sequence around the cleavage site differs from the human molecule

The guinea-pig and human Hageman factors differ in their sensitivity to activation by particular bacterial proteinases. To understand this difference, the primary structure and cleavage site on activation of the guinea-pig molecule were determined and compared with the human molecule. By the use of a synthetic oligodeoxyribonucleotide probe which encoded a part of human Hageman factor cDNA, a cDNA clone was isolated from a lambda gt11 cDNA library of guinea-pig liver and sequenced. The cDNA clone was identified as that of guinea-pig Hageman factor by the complete identity of the deduced amino-acid sequence with the actual sequence of the amino-terminal portion of guinea-pig Hageman factor molecule and the active form. The cDNA included part of a leader sequence and the entire coding region of the Hageman factor molecule. Guinea-pig Hageman factor was composed of the same domain structures as the human counterpart with an overall 72% homology in the amino-acid sequence. However, the sequences around the cleavage site were surprisingly different; -Met351-Thr-Arg-Val-Val-Gly-Gly-Leu-Val359-(human) and -Leu338-Ser-Arg-Ile-Val-Gly-Gly-Leu-Val346-(guinea-pig). The amino-acid substitutions around the cleavage site might explain the difference in sensitivity to activation between the human and guinea-pig molecules.

Activation mechanism of human Hageman factor-plasma kallikrein-kinin system by Vibrio vulnificus metalloprotease

Vivrio vulnificus, an opportunistic human pathogen, secretes a metalloprotease (VVP). The VVP inoculated into a guinea pig is known to generate bradykinin through activation of the Hageman factor-plasma kallikrein-kinin system. VVP was shown to possess the ability to activate the human system through the same mechanism as that clarified in the guinea pig system, namely, VVP converted both human zymogens (Hageman factor and plasma prekallikrein) to active enzymes (activated Hageman factor and plasma kallikrein), and the then generated kallikrein liberated bradykinin from high-molecular-weight kininogen. However, in the presence of plasma alpha 2-macroglobulin (alpha 2M), the VVP action was drastically decreased. This finding suggests that the human system might be activated only at the interstitial-tissue space which contains negligible amounts of alpha 2M or in the bloodstream of the individuals whose plasma alpha 2M level is extremely reduced.

Activation of human plasma prekallikrein by Pseudomonas aeruginosa elastase in vitro

Human plasma prekallikrein, precursor of the bradykinin-generating enzyme, was activated in a purified system under a near physiological condition (pH 7.8, ionic strength I = 0.14, 37 degrees C) by Pseudomonas aeruginosa elastase which is a tissue-destructive metalloproteinase. Compared with that, Pseudomonas aeruginosa alkaline proteinase poorly activated it with a rate as low as less than one-twentieth of that of elastase. The activation by elastase was blocked with a specific inhibitor of elastase, HONHCOCH(CH2C6H5)CO-Ala-Gly-NH2 (10 microM). Generation of kallikrein-like amidolytic activity was also observed in plasma deficient in Hageman factor by treatment with elastase, but was not in plasma deficient in prekallikrein. The kallikrein-like activity generated in Hageman factor deficient plasma as well as the generation process itself was indeed inhibited by anti-human prekallikrein goat antibody. These results suggest that the pathological activation of the kallikrein-kinin system might occur under certain clinical conditions in pseudomonal infections.

Pseudomonas aeruginosa alkaline proteinase might share a biological function with plasmin

Pseudomonas aeruginosa alkaline proteinase, which is a zinc-dependent bacterial endopeptidase, preferentially hydrolyzed Boc-Val-Leu-Lys-methylcoumarylamide (MCA) which was originally designed as a specific substrate of plasmin, a plasma serine proteinase. The hydrolytic capacity was resistant to tosyl-lysine chloromethylketone at a concentration as high as 1 mM, but was blocked by a treatment with metal chelator such as o-phenanthroline at the concentration of 5 mM. Kinetic parameters of the amidolytic reaction were Km = 21 microM, kcat = 0.067 s-1 and kcat/Km = 3190 M-1 s-1. A synthetic peptide inhibitor which bore a possible ligand for zinc atom at the carboxy terminal was designed. This inhibitor, Ac-Val-Leu-Lys-4-mercaptoanilide, blocked the amidolytic activity of the pseudomonal alkaline proteinase in a competitive manner with the dissociation constant (Ki) value of 24 microM. The results imply that P. aeruginosa alkaline proteinase must be an unusual zinc-dependent 'C (COOH)-type' endopeptidase, which hydrolyzes the peptide bond of certain amino acid residues at the carboxyl group side by specific recognition, like serine- and cysteine-proteinases. In comparison, P. aeruginosa elastase which is a typical 'N (NH2)-type' metalloproteinase did not hydrolyze all of the commercially available peptide-MCA substrates tested at the present study. P. aeruginosa alkaline proteinase also hydrolyzed natural substrates of plasmin, such as fibrin and fibrinogen, with similar specific activities to plasmin. The susceptible subunits of fibrinogen were the A-alpha and B-beta ones, in this order. P. aeruginosa alkaline proteinase also exhibited an anti-coagulant activity in human plasma attributed to the direct fibrinogenolytic function. Such potential anti-coagulant capacity of the P. aeruginosa alkaline proteinase might explain, at least partly, the most characteristic pathologic feature of the P. aeruginosa septicemia, hemorrhagic lesions with lacking thrombi (Fetzer, A.E. et al. (1967) Am. Rev. Respirat. Dis. 96, 1121-1130).