New fluorogenic substrates for alpha-thrombin, factor Xa, kallikreins, and urokinase

The Role of the Complement in Clear Cell Renal Carcinoma (ccRCC)-What Future Prospects Are There for Its Use in Clinical Practice?

In recent years, the first-line available therapeutic options for metastatic renal cell carcinoma (mRCC) have radically changed with the introduction into clinical practice of new immune checkpoint inhibitor (ICI)-based combinations. Many efforts are focusing on identifying novel prognostic and predictive markers in this setting. The complement system (CS) plays a central role in promoting the growth and progression of mRCC. In particular, mRCC has been defined as an "aggressive complement tumor", which encompasses a group of malignancies with poor prognosie and highly expressed complement components. Several preclinical and retrospective studies have demonstrated the negative prognostic role of the complement in mRCC; however, there is little evidence on its possible role as a predictor of the response to ICIs. The purpose of this review is to explore more deeply the physio-pathological role of the complement in the development of RCC and its possible future use in clinical practice as a prognostic and predictive factor.

Intersection of Coagulation and Fibrinolysis by the Glycosylphosphatidylinositol (GPI)-Anchored Serine Protease Testisin

Hemostasis is a delicate balance between coagulation and fibrinolysis that regulates the formation and removal of fibrin, respectively. Positive and negative feedback loops and crosstalk between coagulation and fibrinolytic serine proteases maintain the hemostatic balance to prevent both excessive bleeding and thrombosis. Here, we identify a novel role for the glycosylphosphatidylinositol (GPI)-anchored serine protease testisin in the regulation of pericellular hemostasis. Using in vitro cell-based fibrin generation assays, we found that the expression of catalytically active testisin on the cell surface accelerates thrombin-dependent fibrin polymerization, and intriguingly, that it subsequently promotes accelerated fibrinolysis. We find that the testisin-dependent fibrin formation is inhibited by rivaroxaban, a specific inhibitor of the central prothrombin-activating serine protease factor Xa (FXa), demonstrating that cell-surface testisin acts upstream of factor X (FX) to promote fibrin formation at the cell surface. Unexpectedly, testisin was also found to accelerate fibrinolysis by stimulating the plasmin-dependent degradation of fibrin and enhancing plasmin-dependent cell invasion through polymerized fibrin. Testisin was not a direct activator of plasminogen, but it is able to induce zymogen cleavage and the activation of pro-urokinase plasminogen activator (pro-uPA), which converts plasminogen to plasmin. These data identify a new proteolytic component that can regulate pericellular hemostatic cascades at the cell surface, which has implications for angiogenesis, cancer biology, and male fertility.

Infection Responsive Smart Delivery of Antibiotics Using Recombinant Spider Silk Nanospheres

Frequent and inappropriate usage of antibiotics has changed the natural evolution of bacteria by reducing susceptibility and increasing resistance towards antibacterial agents. New resistance mechanisms evolved in the response to host defenses and pharmaceutical interventions are threatening our ability to treat common infections, resulting in increased mortality. In the face of this rising epidemic, antibiotic drug discovery, which has long been overlooked by big pharma, is reaching a critical low. Thus, the development of an infection-responsive drug delivery system, which may mitigate multidrug resistance and preserve the lifetime of our current antibiotic arsenal, has garnered the attention of both popular science and funding agencies. The present work describes the development of a thrombin-sensitive linker embedded into a recombinant spider silk copolymer to create a nanosphere drug delivery vehicle. Recent studies have suggested that there is an increase in thrombin-like activity during Staphylococcus aureus infection; thus, drug release from this new "smart" nanosphere can be triggered in the presence of infection. A thrombin sensitive peptide (TSP) was synthesized, and the thrombin cleavage sensitivity was determined by HPLC. The results showed no cleavage of the peptide when exposed to human serum whereas the peptide was cleaved when incubated with S. aureus exudate. Subsequently, the peptide was coupled with a silk copolymer via EDC-NHS chemistry and formulated into nanospheres encapsulating antibiotic vancomycin. These nanospheres were evaluated for in vitro infection-responsive drug release and antimicrobial activity. Finally, the drug responsive nanospheres were assessed for efficacy in an in vivo septic arthritis model. Our study provides evidence that the protein conjugate was enzyme responsive and can be used to formulate targeted drug release to combat infections against multidrug-resistant bacterial strains.

Molecular probes for selective detection of cysteine cathepsins

Cysteine cathepsins are proteases critical in physiopathological processes and show potential as targets or biomarkers for diseases and medical conditions. The 11 members of the cathepsin family are redundant in some cases but remarkably independent of others, demanding the development of both pan-cathepsin targeting tools as well as probes that are selective for specific cathepsins with little off-target activity. This review addresses the diverse design strategies that have been employed to accomplish this tailored selectivity among cysteine cathepsin targets and the imaging modalities incorporated. The power of these diverse tools is contextualized by briefly highlighting the nature of a few prominent cysteine cathepsins, their involvement in select diseases, and the application of cathepsin imaging probes in research spanning basic biochemical studies to clinical applications.

Serine proteases profiles of Leishmania (Viannia) braziliensis clinical isolates with distinct susceptibilities to antimony

Glucantime (Sb^V) is the first-line treatment against American Tegumentary Leishmaniasis. Resistance cases to this drug have been reported and related to host characteristics and parasite phenotypes. In this study, 12 Leishmania (Viannia) braziliensis isolates from patients that presented clinical cure (Responders—R) and relapse or therapeutic failure (Non-responders—NR) after treatment with antimony, were analyzed. These parasites were assessed by in vitro susceptibility to Sb^III and Sb^V, serine proteases activity measured with substrate (z-FR-AMC) and specific inhibitors (TLCK, AEBSF and PMSF). In vitro susceptibility of axenic amastigotes to Sb^III showed a significant difference between R and NR groups. The protease assays showed that TLCK inhibited almost 100% of activity in both axenic amastigotes and promastigotes while AEBSF inhibited around 70%, and PMSF showed lower inhibition of some isolates. Principal component and clustering analysis performed with these data yielded one homogeneous cluster with only NR isolates and three heterogeneous clusters with R and NR isolates. Additionally, differential expression of subtilisins (LbrM.13.0860 and LbrM.28.2570) and TXNPx (LbrM.15.1080) was evaluated in promastigotes and axenic amastigotes from both groups. The results showed a higher expression of LbrM.13.0860 and LbrM.15.1080 genes in axenic amastigotes, while LbrM.28.2570 gene had the lowest expression in all isolates, regardless of the parasite form. The data presented here show a phenotypic heterogeneity among the parasites, suggesting that exploration of in vitro phenotypes based on Sb^III and serine proteases profiles can aid in the characterization of L. (V.) braziliensis clinical isolates.

Dual-Mechanism Quenched Fluorogenic Probe Provides Selective and Rapid Detection of Cathepsin L Activity*

Cathepsin L (CTL) is a cysteine protease demonstrating upregulated activity in many disease states. Overlapping substrate specificity makes selective detection of CTL activity difficult to parse from that of its close homologue CTV and the ubiquitous CTB. Current probes of CTL activity have limited applications due to either poor contrast or extra assay steps required to achieve selectivity. We have developed a fluorogenic probe, CTLAP, that displays good selectivity for CTL over CTB and CTV while exhibiting low background fluorescence attributed to dual quenching mechanisms. CTLAP achieves optimum CTL selectivity in the first 10 min of incubation, thus suggesting that it is amenable for rapid detection of CTL, even in the presence of competing cathepsins.

Methods for the discovery of small molecules to monitor and perturb the activity of the human proteasome

Regulating protein production and degradation is critical to maintaining cellular homeostasis. The proteasome is a key player in keeping proteins at the proper levels. However, proteasome activity can be altered in certain disease states, such as blood cancers and neurodegenerative diseases. Cancers often exhibit enhanced proteasomal activity, as protein synthesis is increased in these cells compared with normal cells. Conversely, neurodegenerative diseases are characterized by protein accumulation, leading to reduced proteasome activity. As a result, the proteasome has emerged as a target for therapeutic intervention. The potential of the proteasome as a therapeutic target has come from studies involving chemical stimulators and inhibitors, and the development of a suite of assays and probes that can be used to monitor proteasome activity with purified enzyme and in live cells.

High-Resolution Mass Spectrometry-Based Approaches for the Detection and Quantification of Peptidase Activity in Plasma

Proteomic technologies have identified 234 peptidases in plasma but little quantitative information about the proteolytic activity has been uncovered. In this study, the substrate profile of plasma proteases was evaluated using two nano-LC-ESI-MS/MS methods. Multiplex substrate profiling by mass spectrometry (MSP-MS) quantifies plasma protease activity in vitro using a global and unbiased library of synthetic peptide reporter substrates, and shotgun peptidomics quantifies protein degradation products that have been generated in vivo by proteases. The two approaches gave complementary results since they both highlight key peptidase activities in plasma including amino- and carboxypeptidases with different substrate specificity profiles. These assays provide a significant advantage over traditional approaches, such as fluorogenic peptide reporter substrates, because they can detect active plasma proteases in a global and unbiased manner, in comparison to detecting select proteases using specific reporter substrates. We discovered that plasma proteins are cleaved by endoproteases and these peptide products are subsequently degraded by amino- and carboxypeptidases. The exopeptidases are more active and stable in plasma and therefore were found to be the most active proteases in the in vitro assay. The protocols presented here set the groundwork for studies to evaluate changes in plasma proteolytic activity in shock.

Serine proteases as luminal mediators of intestinal barrier dysfunction and symptom severity in IBS

OBJECTIVE

The intestinal lumen contains several proteases. Our aim was to determine the role of faecal proteases in mediating barrier dysfunction and symptoms in IBS.

DESIGN

39 patients with IBS and 25 healthy volunteers completed questionnaires, assessments of in vivo permeability, ex vivo colonic barrier function in Ussing chambers, tight junction (TJ) proteins, ultrastructural morphology and 16 s sequencing of faecal microbiota rRNA. A casein-based assay was used to measure proteolytic activity (PA) in faecal supernatants (FSNs). Colonic barrier function was determined in mice (ex-germ free) humanised with microbial communities associated with different human PA states.

RESULTS

Patients with IBS had higher faecal PA than healthy volunteers. 8/20 postinfection IBS (PI-IBS) and 3/19 constipation- predominant IBS had high PA (>95th percentile). High-PA patients had more and looser bowel movements, greater symptom severity and higher in vivo and ex vivo colonic permeability. High-PA FSNs increased paracellular permeability, decreased occludin and increased phosphorylated myosin light chain (pMLC) expression. Serine but not cysteine protease inhibitor significantly blocked high-PA FSN effects on barrier. The effects on barrier were diminished by pharmacological or siRNA inhibition of protease activated receptor-2 (PAR-2). Patients with high-PA IBS had lower occludin expression, wider TJs on biopsies and reduced microbial diversity than patients with low PA. Mice humanised with high-PA IBS microbiota had greater in vivo permeability than those with low-PA microbiota.

CONCLUSION

A subset of patients with IBS, especially in PI-IBS, has substantially high faecal PA, greater symptoms, impaired barrier and reduced microbial diversity. Commensal microbiota affects luminal PA that can influence host barrier function.

Discovery and characterization of a small-molecule enteropeptidase inhibitor, SCO-792

Enteropeptidase, localized into the duodenum brush border, is a key enzyme catalyzing the conversion of pancreatic trypsinogen proenzyme to active trypsin, thereby regulating protein digestion and energy homeostasis. We report the discovery and pharmacological profiles of SCO-792, a novel inhibitor of enteropeptidase. A screen employing fluorescence resonance energy transfer was performed to identify enteropeptidase inhibitors. Inhibitory profiles were determined by in vitro assays. To evaluate the in vivo inhibitory effect on protein digestion, an oral protein challenge test was performed in rats. Our screen identified a series of enteropeptidase inhibitors, and compound optimization resulted in identification of SCO-792, which inhibited enteropeptidase activity in vitro, with IC 50 values of 4.6 and 5.4 nmol/L in rats and humans, respectively. In vitro inhibition of enteropeptidase by SCO-792 was potentiated by increased incubation time, and the calculated Kinact/KI was 82 000/mol/L s. An in vitro dissociation assay showed that SCO-792 had a dissociation half-life of almost 14 hour, with a calculated koff rate of 0.047/hour, which suggested that SCO-792 is a reversible enteropeptidase inhibitor. In normal rats, a ≤4 hour prior oral dose of SCO-792 effectively inhibited plasma elevation of branched-chain amino acids in an oral protein challenge test, which indicated that SCO-792 effectively inhibited protein digestion in vivo. In conclusion, our new screen system identified SCO-792 as a potent and reversible inhibitor against enteropeptidase. SCO-792 slowly dissociated from enteropeptidase in vitro and inhibited protein digestion in vivo. Further study using SCO-792 could reveal the effects of inhibiting enteropeptidase on biological actions.

Blood anticlotting activity of a Rhipicephalus microplus cathepsin L-like enzyme

In parasites, cathepsins are implicated in mechanisms related to organism surveillance and host evasion. Some parasite cathepsins have fibrinogenolytic and fibrinolytic activity, suggesting that they may contribute to maintain blood meal fluidity for extended feeding periods. Here, it is shown that BmGTI (Rhipicephalus [Boophilus] microplus Gut Thrombin Inhibitor), a protein previously described as an inhibitor of fibrinogen hydrolysis and platelet aggregation by thrombin, and BmCL1 (Rhipicephalus [Boophilus] microplus Cathepsin-L like 1) are the same protein, hereinafter referred to using the earliest name (BmCL1). To further characterize BmCL1, Rhipicephalus microplus native and recombinant (rBmCL1) proteins were obtained. Native BmCL1 was isolated using thrombin-affinity chromatography, and it displays thrombin inhibition activity. We subsequently investigated rBmCL1 interaction with thrombin. We show that rBmCL1 and thrombin have a dissociation constant (Κ_D) of 130.2 ± 11.2 nM, and this interaction likely occurs due to a more electronegative surface of BmCL1 at pH 7.5 than at pH 5.0, which may favor an electrostatic binding to positively charged thrombin exosites. During BmCL1-thrombin interaction, thrombin is not degraded or inhibited. rBmCL1 impairs thrombin-induced fibrinogen clotting via a fibrinogenolytic activity. Fibrinogen degradation by BmCL1 occurs by the hydrolysis of Aα- and Bβ-chains, generating products similar to those produced by fibrinogenolytic cathepsins from other organisms. In conclusion, BmCL1 likely has an additional role in R. microplus blood digestion, besides its role in hemoglobin degradation at acid pH. BmCL1 fibrinogenolytic activity indicates a proteolytic activity in the neutral lumen of tick midgut, contributing to maintain the fluidity of the ingested blood, which remains to be confirmed in vivo.

Purification and enzymatic assay of class I histone deacetylase enzymes

The reversible acetylation of histones has a profound influence on transcriptional status. Histone acetyltransferases catalyze the addition of these chemical modifications to histone lysine residues. Conversely, histone deacetylases (HDACs) catalyze the removal of these acetyl groups from histone lysine residues. As modulators of transcription, HDACs have found themselves as targets of several FDA-approved chemotherapeutic compounds which aim to inhibit enzyme activity. The ongoing efforts to develop targeted and isoform-specific HDAC inhibitors necessitates tools to study these modifications and the enzymes that maintain an equilibrium of these modifications. In this chapter, we present an optimized workflow for the isolation of recombinant protein and subsequent assay of class I HDAC activity. We demonstrate the application of this assay by assessing the activities of recombinant HDAC1, HDAC2, and SIN3B. This assay system utilizes readily available reagents and can be used to assess the activity and responsiveness of class I HDAC complexes to HDAC inhibitors.

Kinetic Measurement of Serpin Inhibitory Activity by Real-Time Fluorogenic Biochemical Assay

Biochemical fluorogenic and chromogenic assays facilitate real-time study of enzyme function. Based on the principle of enzymatic inhibition, these kinetic assays can be adapted to measure the function of serpins. Compared to traditional, electrophoretic study of serpin inhibitory complex formation, kinetic assays allow for finer temporal resolution as well as more quantitative comparisons between different conditions. This chapter describes methodology for performing real-time, kinetic measurement of serpin inhibitory activity by fluorogenic substrate conversion assay. Specifically, the methods covered include measurement of alpha-1-antitrypsin inhibitory activity against trypsin and heparin-dependent anti-thrombin III inhibitory activity against thrombin. These methods are scalable to small-volume, high-density format and can be applied for high-throughput screening of serpin activity modulators.

Protein-Templated Formation of an Inhibitor of the Blood Coagulation Factor Xa through a Background-Free Amidation Reaction

Protein‐templated reactions enable the target‐guided formation of protein ligands from reactive fragments, ideally with no background reaction. Herein, we investigate the templated formation of amides. A nucleophilic fragment that binds to the coagulation factor Xa was incubated with the protein and thirteen differentially activated dipeptides. The protein induced a non‐catalytic templated reaction for the phenyl and trifluoroethyl esters; the latter was shown to be a completely background‐free reaction. Starting from two fragments with millimolar affinity, a 29 nm superadditive inhibitor of factor Xa was obtained. The fragment ligation reaction was detected with high sensitivity by an enzyme activity assay and by mass spectrometry. The reaction progress and autoinhibition of the templated reaction by the formed ligation product were determined, and the structure of the protein–inhibitor complex was elucidated.

Characterization of Venom and Oviduct Components of Parasitoid Wasp Asobara japonica

During natural parasitization, Asobara japonica wasps introduce lateral oviduct (LO) components into their Drosophila hosts soon after the venom injection to neutralize its strong toxicity; otherwise, the host will die. Although the orchestrated relationship between the venom and LO components necessary for successful parasitism has attracted the attention of many researchers in this field, the molecular natures of both factors remain ambiguous. We here showed that precipitation of the venom components by ultracentrifugation yielded a toxic fraction that was inactivated by ultraviolet light irradiation, boiling, and sonication, suggesting that it is a virus-like entity. Morphological observation of the precipitate after ultracentrifugation showed small spherical heterogeneous virus-like particles 20-40 nm in diameter. The venom's detrimental effect on D. melanogaster larvae was not directly neutralized by the LO components but blocked by a hemolymphal neutralizing factor activated by the LO factor. Furthermore, we found that A. japonica venom and LO components acted similarly on the larvae of the common cutworm Spodoptera litura: the venom injection caused mortality but coinjection of the LO factor protected S. litura larvae from the venom's toxicity. In contrast, D. ficusphila and D. bipectinata, which are closely related to D. melanogaster but non-habitual host species of A. japonica, were not negatively affected by A. japonica venom due to an intrinsic neutralizing activity in their hemolymph, indicating that these species must have acquired a neutralizer of A. japonica venom during evolution. These results give new insights into the characteristics of both the venom and LO components: A. japonica females have utilized the virus-like toxic venom factor to exploit a wider range of host species after the evolutionary process enabled them to use the LO factor for activation of the host hemolymph neutralizer precursor, although the non-habitual host Drosophila species possess an active intrinsic neutralizer in their hemolymph.

The Activity of Immobilized Heparin via Long Poly(Ethylene Oxide) Spacers

Heparin was immobilized onto BrCN-activated Sepharose gel us ing α,ω-diaminopoly(ethylene oxide) (diamino PEO) with various chain lengths as a spacer. The heparin activity was measured on the basis of prolongation of activated partial thromboplastin time (APTT). The activity of immobilized heparin was observed after the amino groups at the terminal end of the spacer molecule, not used for immobilization of heparin, were blocked with formalde hyde. The flexible PEO spacer appeared to relieve the steric hindrance by the carrier to the formation of a heparin complex with cofactor AT III. The activity of immobilized heparin increased with elongation of the spacer chain and the highest activity was obtained when the chain length of the spacer was between 10 to 20. Longer spacer groups decreased the activity because the high mobil ity of the hydrated PEO chain hindered AT III access to the immobilized heparin.

Effect of Excess Charge in Cellulosic Polyelectrolyte Complexes on the Blood Compatibility

The effect of excess charge in cellulosic polyelectrolyte complexes (PECs) on the blood compatibility was examined in detail. For this purpose, various ex cess charge PECs were prepared from a quaternary ammonium derivative of hydroxyethyl cellulose (Q-HEC) and carboxymethyl cellulose (CMC). The blood compatibility of the PECs was evaluated by three different test methods; Lee- White, platelet adhesion and contact phase activation tests, as well as by the "Quenched Lee-White test" which determines time-variant changes in the differentiated hematological responses during whole blood coagulation.

The three test results showed that relative coagulation time of whole blood is very long and almost independent of the mole ratio of polycation to polyanion components within the mole ratios examined, but platelet adhesion increases with increasing mole ratios of polycation/polyanion in the PEC, while contact phase activation of plasma coagulation increases with decreasing mole ratio. However, the "Quenched Lee-White test" revealed that platelet counts and quantity of the hematological factors measured after 15 min are independent of the excess charge on PECs and maintained at the considerably high level even at 60 min of exposure time, indicating weak interaction of blood with PECs irrespective of surface charge excess. This may result in good antithrom bogenicity in both in vivo and in vitro under longer-term experiments.

Epoxy-α-lapachone has in vitro and in vivo anti-leishmania (Leishmania) amazonensis effects and inhibits serine proteinase activity in this parasite

Leishmania (Leishmania) amazonensis is a protozoan that causes infections with a broad spectrum of clinical manifestations. The currently available chemotherapeutic treatments present many problems, such as several adverse side effects and the development of resistant strains. Natural compounds have been investigated as potential antileishmanial agents, and the effects of epoxy-α-lapachone on L. (L.) amazonensis were analyzed in the present study. This compound was able to cause measurable effects on promastigote and amastigote forms of the parasite, affecting plasma membrane organization and leading to death after 3 h of exposure. This compound also had an effect in experimentally infected BALB/c mice, causing reductions in paw lesions 6 weeks after treatment with 0.44 mM epoxy-α-lapachone (mean lesion area, 24.9 ± 2.0 mm(2)), compared to untreated animals (mean lesion area, 30.8 ± 2.6 mm(2)) or animals treated with Glucantime (mean lesion area, 28.3 ± 1.5 mm(2)). In addition, the effects of this compound on the serine proteinase activities of the parasite were evaluated. Serine proteinase-enriched fractions were extracted from both promastigotes and amastigotes and were shown to act on specific serine proteinase substrates and to be sensitive to classic serine proteinase inhibitors (phenylmethylsulfonyl fluoride, aprotinin, and antipain). These fractions were also affected by epoxy-α-lapachone. Furthermore, in silico simulations indicated that epoxy-α-lapachone can bind to oligopeptidase B (OPB) of L. (L.) amazonensis, a serine proteinase, in a manner similar to that of antipain, interacting with an S1 binding site. This evidence suggests that OPB may be a potential target for epoxy-α-lapachone and, as such, may be related to the compound's effects on the parasite.

Human mannose-binding lectin inhibitor prevents myocardial injury and arterial thrombogenesis in a novel animal model

Myocardial infarction and coagulation disorders are leading causes of disability and death in the world. An important role of the lectin complement pathway in myocardial infarction and coagulation has been demonstrated in mice genetically deficient in lectin complement pathway proteins. However, these studies are limited to comparisons between wild-type and deficient mice and lack the ability to examine reversal/inhibition of injury after disease establishment. We developed a novel mouse that expresses functional human mannose-binding lectin (MBL) 2 under the control of Mbl1 promoter. Serum MBL2 concentrations averaged approximately 3 μg/mL in MBL2(+/+)Mbl1(-/-)Mbl2(-/-) [MBL2 knock in (KI)] mice. Serum MBL2 level in MBL2 KI mice significantly increased after 7 (8 μg/mL) or 14 (9 μg/mL) days of hyperglycemia compared to normoglycemic mice (P < 0.001). Monoclonal antibody 3F8 inhibited C3 deposition on mannan-coated plates in MBL2 KI, but not wild-type, mice. Myocardial ischemia/reperfusion in MBL2 KI mice revealed that 3F8 preserved cardiac function and decreased infarct size and fibrin deposition in a time-dependent manner. Furthermore, 3F8 prevented ferric chloride-induced occlusive arterial thrombogenesis in vivo. MBL2 KI mice represent a novel animal model that can be used to study the lectin complement pathway in acute and chronic models of human disease. Furthermore, these novel mice demonstrate the therapeutic window for MBL2 inhibition for effective treatment of disease and its complications.

Real-time measurement of thrombin generation using continuous droplet microfluidics

Thrombin, which has the leading role in the blood coagulation cascade, is an important biomarker in hemostasis and cardiovascular disease (CVD) development. In this study, a measurement system capable of continuously monitoring individual thrombin generation using droplet microfluidic technology is manipulated. The thrombin generation assay based on fluogenic substrate is performed within the droplets and the thrombin generation curve of plasma sample activated by tissue factor is measured in real-time to reflect the sample conditions dynamically. The injection of the inhibitor of thrombin generation is developed to assay the inhibited curve which relates to thrombin self-inhibition in biological systems. This microfluidic system is integrated with the microdialysis probe, which is useful to connect to the living animals for future in vivo real time thrombin measurements for rapid CVD diagnosis.

Development and prospects of dedicated tracers for the molecular imaging of bacterial infections

Bacterial infections have always been, and still are, a major global healthcare problem. For accurate treatment it is of upmost importance that the location(s), severity, type of bacteria, and therapeutic response can be accurately staged. Similar to the recent successes in oncology, tracers specific for molecular imaging of the disease may help advance patient management. Chemical design and bacterial targeting mechanisms are the basis for the specificity of such tracers. The aim of this review is to provide a comprehensive overview of the molecular imaging tracers developed for optical and nuclear identification of bacteria and bacterial infections. Hereby we envision that such tracers can be used to diagnose infections and aid their clinical management. From these compounds we have set out to identify promising targeting mechanisms and select the most promising candidates for further development.

Venom components of Asobara japonica impair cellular immune responses of host Drosophila melanogaster

The endoparasitoid wasp Asobara japonica has highly poisonous venom: the host Drosophila larvae are killed by envenomation at a dose that is naturally injected by the female wasp at parasitism. This insecticidal venom is neutralized, however, because A. japonica introduces lateral oviduct components soon after venom injection at oviposition. Although the venom and lateral oviduct components of this parasitoid have been partially characterized, how the venom components favor successful development of wasp eggs and larvae in the host remains ambiguous. Here, we demonstrated that A. japonica venom did not affect host humoral immune responses, determined as expression of antimicrobial peptide (AMP) genes, but significantly diminished two cellular responses, spreading and phagocytosis, by host hemocytes. Moreover, venom components drastically elevated a serine protease-like activity 4 h after its injection. The lateral oviduct components did not negate the detrimental effects of the venom on host cellular immunities, but significantly reduced the venom-induced elevation of protease activity. Both active factors in venom and lateral oviduct components were roughly characterized as heat-labile substances with a molecular mass of at least 10 kDa. Finally, venom of A. japonica, with a wide host range, was found to be much more toxic than that of Asobara rossica, which has a limited host range. These results reveal that A. japonica venom toxicity allows exploitation of a broader range of host insects because it is essential to overcome cellular immune responses of the host for successful parasitism.

Zebrafish high-throughput screening to study the impact of dissolvable metal oxide nanoparticles on the hatching enzyme, ZHE1

The zebrafish is emerging as a model organism for the safety assessment and hazard ranking of engineered nanomaterials. In this Communication, the implementation of a roboticized high-throughput screening (HTS) platform with automated image analysis is demonstrated to assess the impact of dissolvable oxide nanoparticles on embryo hatching. It is further demonstrated that this hatching interference is mechanistically linked to an effect on the metalloprotease, ZHE 1, which is responsible for degradation of the chorionic membrane. The data indicate that 4 of 24 metal oxide nanoparticles (CuO, ZnO, Cr2 O3 , and NiO) could interfere with embryo hatching by a chelator-sensitive mechanism that involves ligation of critical histidines in the ZHE1 center by the shed metal ions. A recombinant ZHE1 enzymatic assay is established to demonstrate that the dialysates from the same materials responsible for hatching interference also inhibit ZHE1 activity in a dose-dependent fashion. A peptide-based BLAST search identifies several additional aquatic species that express enzymes with homologous histidine-based catalytic centers, suggesting that the ZHE1 mechanistic paradigm could be used to predict the toxicity of a large number of oxide nanoparticles that pose a hazard to aquatic species.

Fluorogenic peptide-based substrates for monitoring thrombin activity

The synthesis of a series of peptides containing C-terminal 7-amino-4-methylcoumarin (AMC) for use in the thrombin generation test (TGT) is described. The lead structure in this project was H-Gly-Gly-Arg-AMC, of which the water solubility and kinetic parameters (K(M) and k(cat)) are greatly improved over those of the substrate in current use in the TGT: Cbz-Gly-Gly-Arg-AMC. A series of N-terminally substituted Gly-Gly-Arg-AMC derivatives were synthesized, as well as implementation of structural changes at either the P(2) or P(3) position of the peptide backbone. Furthermore, two substrates were synthesized that have structural similarities to the chromogenic thrombin substrate SQ68 or that contain a 1,2,3-triazole moiety in the peptide chain, mimicking an amide bond. To determine the applicability of newly synthesized fluorogenic substrates for monitoring continuous thrombin generation, the K(M) and k(cat) values of the conversion of these fluorogenic substrates by thrombin (FIIa) and factor Xa (FXa) were quantified. An initial selection was made on basis of these data, and suitable substrates were further evaluated as substrates in the thrombin generation assay. Assessment of the acquired data showed that several substrates, including the SQ68 derivative Et-malonate-Gly-Arg-AMC and N-functionalized Gly-Gly-Arg-AMC derivatives, are suitable candidates for replacement of the substrate currently in use.

Noninvasive biosensor for cathepsin L in the stratum corneum

PURPOSE

The objective is to propose an on-site testing biosensor of cathepsin L (CatL) activity in the stratum corneum, which can be used for the evaluation of skin conditions noninvasively and easily.

METHODS

The biosensor comprises of a disposable test strip and a desktop-sized reader (260 × 150 × 290 mm(3), 1.9 kg), incorporating a charge-coupled device image sensor (CCD) unit to measure the reflectance of the test strip. A novel immuno-chromatographic test strip was proposed for CatL analysis in the stratum corneum. In order to realize the test strip, a colloidal gold technique was selected as the molecular recognition method for the CatL. A human skin sample was collected noninvasively by adhesive tape stripping.

RESULTS

Based on optimal assay conditions, the sensitivity of the biosensor was evaluated. It required 10 min from a sample dropping to appear the test line on the test strip. The optical density was proportion to the CatL. Bioanalytical validation indicated that, within the biosensor's detection limit (172.2 μU/mL), its accuracy (R(2) = 0.94), and precision (CV = 15%) approach more elaborate laboratory-based analyzers. In addition, the truncated sampling-reporting cycle (<15 min) allows speedy reporting of CatL levels.

CONCLUSION

It was indicated that this noninvasive and easy-to use biosensor might be a novel tool for the semi-quantitative analysis of CatL in the stratum corneum.

Anatomical localization of protease-activated receptor-1 and protease-mediated neuroglial crosstalk on peri-synaptic astrocytic endfeet

We studied the localization, activation and function of protease-activated receptor 1 (PAR-1) at the CNS synapse utilizing rat brain synaptosomes and slices. Confocal immunofluoresence and transmission electron microscopy in brain slices with pre-embedding diaminobenzidine (DAB) immunostaining found PAR-1 predominantly localized to the peri-synaptic astrocytic endfeet. Structural confocal immunofluorescence microscopy studies of isolated synaptosomes revealed spherical structures stained with anti-PAR-1 antibody which co-stained mainly for glial-filament acidic protein compared with the neuronal markers synaptophysin and PSD-95. Immunoblot studies of synaptosomes demonstrated an appropriate major band corresponding to PAR-1 and activation of the receptor by a specific agonist peptide (SFLLRN) significantly modulated phosphorylated extracellular signal-regulated kinase. A significant membrane potential depolarization was produced by thrombin (1 U/mL) and the PAR-1 agonist (100 μM) and depolarization by high K(+) elevated extracellular thrombin-like activity in the synaptosomes preparation. The results indicate PAR-1 localized to the peri-synaptic astrocytic endfeet is most likely activated by synaptic proteases and induces cellular signaling and modulation of synaptic electrophysiology. A protease mediated neuron-glia pathway may be important in both physiological and pathological regulation of the synapse.

Simultaneous thrombin and plasmin generation capacities in normal and abnormal states of coagulation and fibrinolysis in children and adults

INTRODUCTION

Thrombin and plasmin are the key enzymes involved in coagulation and fibrinolysis, respectively. Plasma coagulative and fibrinolytic potentials in normal children and adults, and in representative pathologically altered hemostatic states, were evaluated via simultaneous assessment of thrombin and plasmin generation.

MATERIALS AND METHODS

An assay of Simultaneous Thrombin and Plasmin generation (STP) was developed to measure thrombin and plasmin in plasma using individual fluorometric substrates. Coagulation is initiated with dilute tissue factor, phospholipid, and calcium in platelet-poor plasma; fibrinolysis is accelerated via tissue plasminogen activator (tPA). Abnormal states of hemostasis were investigated.

RESULTS

STP assay reproducibility and normal adult and pediatric values for measured and calculated parameters have been established. Onset of both thrombin and plasmin generation was significantly delayed in children relative to adults (p<0.001) and the maximum amplitudes of thrombin and plasmin generation were less in children than adults (p<0.01). No significant differences were measured among pediatric age groups. The most profound impairments in thrombin generation were observed for extrinsic and common pathway factor deficiencies, with the exception of afibrinogenemia. Plasmin generation was severely impaired in deficiencies of fibrinogen and plasminogen as well as with decreased tPA reagent concentration and addition of aminocaproic acid. Plasmin generation was greatly enhanced by alpha-2-antiplasmin deficiency and excess tPA reagent.

CONCLUSION

Simultaneous assessment of thrombin and plasmin generation in plasma shows promise for affording an enhanced understanding of overall coagulative and fibrinolytic functions in physiological and pathologically altered states of hemostasis in children and adults.

Protein association and dissociation regulated by extension peptide: a mode for iron control by phytoferritin in seeds

Most of the iron in legume seeds is stored in ferritin located in the amyloplast, which is used during seed germination. However, there is a lack of information on the regulation of iron by phytoferritin. In this study, soluble and insoluble forms of pea (Pisum sativum) seed ferritin (PSF) isolated from dried seeds were found to be identical 24-mer ferritins comprising H-1 and H-2 subunits. The insoluble form is favored at low pH, whereas the two forms reversibly interconvert in the pH range of 6.0 to 7.8, with an apparent pK(a) of 6.7. This phenomenon was not observed in animal ferritins, indicating that PSF is unique. The pH of the amyloplast was found to be approximately 6.0, thus facilitating PSF association, which is consistent with the role of PSF in long-term iron storage. Similar to previous studies, the results of this work showed that protein degradation occurs in purified PSF during storage, thus proving that phytoferritin also undergoes degradation during seedling germination. In contrast, no degradation was observed in animal ferritins, suggesting that this degradation of phytoferritin may be due to the extension peptide (EP), a specific domain found only in phytoferritin. Indeed, removal of EP from PSF significantly increased protein stability and prevented degradation under identical conditions while promoting protein dissociation. Correlated with such dissociation was a considerable increase in the rate of ascorbate-induced iron release from PSF at pH 6.0. Thus, phytoferritin may have facilitated the evolution of EP to enable it to regulate iron for storage or complement in seeds.

Activation of mannan-binding lectin-associated serine proteases leads to generation of a fibrin clot

The lectin pathway of complement is activated upon binding of mannan-binding lectin (MBL) or ficolins (FCNs) to their targets. Upon recognition of targets, the MBL-and FCN-associated serine proteases (MASPs) are activated, allowing them to generate the C3 convertase C4b2a. Recent findings indicate that the MASPs also activate components of the coagulation system. We have previously shown that MASP-1 has thrombin-like activity whereby it cleaves and activates fibrinogen and factor XIII. MASP-2 has factor Xa-like activity and activates prothrombin through cleavage to form thrombin. We now report that purified L-FCN-MASPs complexes, bound from serum to N-acetylcysteine-Sepharose, or MBL-MASPs complexes, bound to mannan-agarose, generate clots when incubated with calcified plasma or purified fibrinogen and factor XIII. Plasmin digestion of the clot and analysis using anti-D-dimer antibodies revealed that the clot was made up of fibrin and was similar to that generated by thrombin in normal human plasma. Fibrinopeptides A and B (FPA and FPB, respectively) were released after fibrinogen cleavage by L-FCN-MASPs complexes captured on N-acetylcysteine-Sepharose. Studies of inhibition of fibrinopeptide release indicated that the dominant pathway for clotting catalysed by the MASPs is via MASP-2 and prothrombin activation, as hirudin, a thrombin inhibitor that does not inhibit MASP-1 and MASP-2, substantially inhibits fibrinopeptide release. In the light of their potent chemoattractant effects on neutrophil and fibroblast recruitment, the MASP-mediated release of FPA and FPB may play a role in early immune activation. Additionally, MASP-catalysed deposition and polymerization of fibrin on the surface of micro-organisms may be protective by limiting the dissemination of infection.

A novel EP-involved pathway for iron release from soya bean seed ferritin

Iron in phytoferritin from legume seeds is required for seedling germination and early growth. However, the mechanism by which phytoferritin regulates its iron complement to these physiological processes remains unknown. In the present study, protein degradation is found to occur in purified SSF (soya bean seed ferritin) (consisting of H-1 and H-2 subunits) during storage, consistent with previous results that such degradation also occurs during seedling germination. In contrast, no degradation is observed with animal ferritin under identical conditions, suggesting that SSF autodegradation might be due to the EP (extension peptide) on the exterior surface of the protein, a specific domain found only in phytoferritin. Indeed, EP-deleted SSF becomes stable, confirming the above hypothesis. Further support comes from a protease activity assay showing that EP-1 (corresponding to the EP of the H-1 subunit) exhibits significant serine protease-like activity, whereas the activity of EP-2 (corresponding to the EP of the H-2 subunit) is much weaker. Consistent with the observation above, rH-1 (recombinant H-1 ferritin) is prone to degradation, whereas its analogue, rH-2, becomes very stable under identical conditions. This demonstrates that SSF degradation mainly originates from the serine protease-like activity of EP-1. Associated with EP degradation is a considerable increase in the rate of iron release from SSF induced by ascorbate in the amyloplast (pH range, 5.8-6.1). Thus phytoferritin may have facilitated the evolution of the specific domain to control its iron complement in response to cell iron need in the seedling stage.

Effects of ergothioneine from mushrooms (Flammulina velutipes) on melanosis and lipid oxidation of kuruma shrimp (Marsupenaeus japonicus)

The antimelanosic and antioxidative properties of a hot water extract prepared from the fruiting body of the edible mushroom (Flammulina velutipes) were evaluated by dietary supplementation in Kuruma shrimp (Marsupenaeus japonicus) for possible aquaculture application. The extract contained ergothioneine (ERT) at a level of 2.05 mg/mL. A commercial standard of l-ergothioneine (l-ERT) and the mushroom extract showed inhibitory activity against mushroom polyphenoloxidase (PPO). Feeding of the extract had no adverse effects on the immune systems of the shrimp under the present experimental conditions. Supplementation of the extract in the diet significantly suppressed PPO activities in the hemolymphs of the shrimp. Expression of the prophenoloxidase (proPO) gene decreased in the hemocyte of the Kuruma shrimp fed with the mushroom extract. Consequently, development of melanosis was significantly suppressed in the supplement fed shrimp during ice storage. Lipid oxidation was also effectively controlled in the supplement fed group throughout the storage period. In vitro experiments showed that l-ERT effectively inhibited the activation of proPO in the hemocyte lysate supernatant (HLS). The transcript of the proPO gene in the hemocyte showed lower expression in the l-ERT-treated HLS. It was concluded that dietary supplementation of the mushroom extract in shrimp could be a promising approach to control post mortem development of melanosis and lipid oxidation in shrimp muscles.

Foam nest components of the túngara frog: a cocktail of proteins conferring physical and biological resilience

The foam nests of the túngara frog (Engystomops pustulosus) form a biocompatible incubation medium for eggs and sperm while resisting considerable environmental and microbiological assault. We have shown that much of this behaviour can be attributed to a cocktail of six proteins, designated ranaspumins (Rsn-1 to Rsn-6), which predominate in the foam. These fall into two discernable classes based on sequence analysis and biophysical properties. Rsn-2, with an amphiphilic amino acid sequence unlike any hitherto reported, exhibits substantial detergent-like surfactant activity necessary for production of foam, yet is harmless to the membranes of eggs and spermatozoa. A further four (Rsn-3 to Rsn-6) are lectins, three of which are similar to fucolectins found in teleosts but not previously identified in a land vertebrate, though with a carbohydrate binding specificity different from previously described fucolectins. The sixth, Rsn-1, is structurally similar to proteinase inhibitors of the cystatin class, but does not itself appear to exhibit any such activity. The nest foam itself, however, does exhibit potent cystatin activity. Rsn-encoding genes are transcribed in many tissues of the adult frogs, but the full cocktail is present only in oviduct glands. Combinations of lectins and cystatins have known roles in plants and animals for defence against microbial colonization and insect attack. Túngara nest foam displays a novel synergy of selected elements of innate defence plus a specialized surfactant protein, comprising a previously unreported strategy for protection of unattended reproductive stages of animals.

Isolation of human renin inhibitor from soybean: soyasaponin I is the novel human renin inhibitor in soybean

We found human renin inhibitory activity in soybean and isolated the active compound, soybean renin inhibitor (SRI). The physico-chemical data on the isolated SRI were identical with those of soyasaponin I. SRI showed significant inhibition against recombinant human renin, with an IC(50) value of 30 microg/ml. Kinetic studies with SRI indicated partial noncompetitive inhibition, with a K(i) value of 37.5 microM. On the other hand, SRI weakly inhibited pepsin, papain, and bromeline activities, but did not inhibit other proteinases, such as trypsin, kallikrein, angiotensin converting enzyme, and aminopeptidase M. Moreover, a significant (p<0.05) decrease in the systolic blood pressure of spontaneously hypertensive rats was observed when partially purified SRI was orally administrated at 40 mg/kg/d for 7 weeks. This is the first demonstration of a renin inhibitor from soybean, soyasaponin I.

A new type of plasma prekallikrein deficiency associated with homozygosity for Gly104Arg and Asn124Ser in apple domain 2 of the heavy-chain region

Three Japanese patients demonstrated plasma prekallikrein (PK) deficiency (PKD) after an examination of the proband family line named 'PKD Seki'. A molecular genetic analysis of these PK genes showed homozygous amino acid substitutions Gly104Arg and Asn124Ser in exon 5, which encodes part of the apple domain 2 (A2) of the heavy chain. This is the first case involving substitutions in the heavy chain of the PK gene which affected blood coagulation. Because the apple domains of PK bind to the C-terminal domain (D6(H)) of high-molecular weight kininogen (HMWK), the two substitutions in A2 may therefore be the main cause of PKD Seki. We subsequently investigated the effects of amino acid substitutions in A2 to elucidate the binding activity of PK to HMWK using mutant A2 proteins produced in Escherichia coli. We clearly demonstrated that the Gly104Arg-substitution with the Asn124Ser-substitution in A2 reduce the binding activity of A2 to HMWK. PKD Seki is the first significant case to show the amino acid substitutions in the A2 affecting the binding capacity of PK with HMWK. Our findings therefore suggest that the binding of PK to HMWK may play a crucial role in the first step of blood coagulation.

Induction of vascular leakage and blood pressure lowering through kinin release by a serine proteinase from Aeromonas sobria

Aeromonas sobria causes septic shock, a condition associated with high mortality. To study the mechanism of septic shock by A. sobria infection, we examined the vascular leakage (VL) activity of A. sobria serine proteinase (ASP), a serine proteinase secreted by this pathogen. Proteolytically active ASP induced VL mainly in a bradykinin (BK) B(2) receptor-, and partially in a histamine-H(1) receptor-dependent manner in guinea pig skin. The ASP VL activity peaked at 10 min to 1.8-fold of the initial activity with an increased BK B(2) receptor dependency, and attenuated almost completely within 30 min. ASP produced VL activity from human plasma apparently through kallikrein/kinin system activation, suggesting that ASP can generate kinin in humans. Consistent with the finding that a major part of the ASP-induced VL was reduced by a potent kallikrein inhibitor, soybean trypsin inhibitor that does not affect ASP enzymatic activity, ASP activated prekallikrein but not factor XII to generate kallikrein in a dose- and incubation time-dependent manner. ASP produced more VL activity directly from human low m.w. kininogen than high m.w. kininogen when both were used at their normal plasma concentrations. Intra-arterial injection of ASP into guinea pigs lowered blood pressure specifically via the BK B(2) receptor. These data suggest that ASP induces VL through prekallikrein activation and direct kinin release from kininogens, which is a previously undescribed mechanism of A. sobria virulence and could be associated with the induction of septic shock by infection with this bacterium. ASP-specific inhibitors, and kinin receptor antagonists, might prove useful for the treatment or prevention of this fatal disease.