Neuroprotective effect of rLosac on supplement-deprived mouse cultured cortical neurons involves maintenance of monocarboxylate transporter MCT2 protein levels.

The recombinant Lonomia obliqua Stuart-factor activator (rLosac) is a recombinant hemolin which belongs to the immunoglobulin superfamily of cell adhesion molecules. It is capable of inducing pro-survival activity in serum-deprived human umbilical vein endothelial cells (HUVECs) and fibroblasts by increasing mitochondrial metabolism. We hypothesize that it could promote neuronal survival by acting on neuroenergetics. Our study reveals that treatment of primary mouse cortical neurons cultured in neurobasal medium lacking B27 supplement with rLosac led to an enhancement of cell viability in a time- and concentration-dependent manner. In parallel, preserved or enhanced phosphorylation of Akt, p44, and p42 MAPK, as well as mTOR was observed following treatment with rLosac. During deprivation, as assessed by western blot and qRT-PCR, protein and mRNA expression of MCT2 (the predominant neuronal monocarboxylate transporter allowing lactate use as an alternative energy substrate) decreased significantly in B27 supplement-deprived cortical neurons and was hardly detected after 24 h of deprivation. Interestingly, rLosac maintained MCT2 protein expression after 24 h of deprivation including at the cell surface without preventing mRNA loss. MCT2 knockdown reduced rLosac-enhanced cell viability, confirming its involvement in rLosac effect. Enhanced uptake of lactate was detected following rLosac treatment and might contribute to rLosac-enhanced viability during deprivation. In the presence of both lactate and rLosac, cell viability was higher than in the presence of lactate alone. Our observations suggest that rLosac promotes cell viability in stressed (B27 supplement-deprived) neurons by facilitating the use of lactate as energy substrate via the preservation of MCT2 protein expression. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.

Amblyomin-X having a Kunitz-type homologous domain, is a noncompetitive inhibitor of FXa and induces anticoagulation in vitro and in vivo.

BACKGROUND: Cancer has long been associated with thrombosis and many of the standard chemotherapeutics used to treat cancer are pro-thrombotic. Thus, the identification of novel selective anticancer drugs that also have antithrombotic properties is of enormous significance. Amblyomin-X is an anticancer protein derived from the salivary glands of the Amblyomma cajennense tick. METHODS: In this work, we determined the inhibition profile of Amblyomin-X and its effect on activated partial thromboplastin time (aPTT) and prothrombin time (PT), using various approaches such as, kinetic analyses, amidolytic assays, SDS-PAGE, and mass spectrometry. RESULTS: Amblyomin-X inhibited factor Xa, prothrombinase and tenase activities. It was hydrolyzed by trypsin and plasmin. MS/MS data of tryptic hydrolysate of Amblyomin-X suggested the presence of Cys(8)-Cys(59) and Cys(19)-Cys(42) but not Cys(34)-Cys(55) disulfide bond. Instead of Cys(34)-Cys(55), two noncanonical Cys(34)-Cys(74) and Cys(55)-Cys(74) disulfide bonds were identified. Furthermore, when Amblyomin-X (1mg/kg) injected in rabbits, it prolonged aPTT and PT. CONCLUSION: Amblyomin-X is a noncompetitive inhibitor (Ki=3.9µM) of factor Xa. It is a substrate for plasmin and trypsin, but not for factor Xa and thrombin. The disulfide Cys(34)-Cys(55) bond probably scrambles with interchain seventh free cysteine residues (Cys(74)) of Amblyomin-X. The prolongation of PT and aPTT is reversible. GENERAL SIGNIFICANCE: In term of anticoagulant property, this is structural and functional characterization of Amblyomin-X. All together, these results and previous findings suggest that Amblyomin-X has a potential to become an anticancer drug with antithrombotic property.

Interaction of Leptospira interrogans with human proteolytic systems enhances dissemination through endothelial cells and protease levels.

We have recently reported the ability of Leptospira to capture plasminogen (PLG) and generate plasmin (PLA) bound on the microbial surface in the presence of exogenous activators. In this work, we examined the effects of leptospiral PLG binding for active penetration through the endothelial cell barrier and activation. The results indicate that leptospires with PLG association or PLA activation have enhanced migration activity through human umbilical vein endothelial cell (HUVEC) monolayers compared with untreated bacteria. Leptospira cells coated with PLG were capable of stimulating the expression of PLG activators by HUVECs. Moreover, leptospires endowed with PLG or PLA promoted transcriptional upregulation matrix metalloprotease 9 (MMP-9). Serum samples from patients with confirmed leptospirosis showed higher levels of PLG activators and total MMP-9 than serum samples from normal (healthy) subjects. The highest level of PLG activators and total MMP-9 was detected with microscopic agglutination test (MAT)-negative serum samples, suggesting that this proteolytic activity stimulation occurs at the early stage of the disease. Furthermore, a gelatin zymography profile obtained for MMPs with serum samples from patients with leptospirosis appears to be specific to leptospiral infection because serum samples from patients with unrelated infectious diseases produced no similar degradation bands. Altogether, the data suggest that the Leptospira-associated PLG or PLA might represent a mechanism that contributes to bacterial penetration of endothelial cells through an activation cascade of events that enhances the proteolytic capability of the organism. To our knowledge, this is the first proteolytic activity associated with leptospiral pathogenesis described to date.

A Kunitz-type inhibitor from tick salivary glands: A promising novel antitumor drug candidate.

Salivary glands are vital structures responsible for successful tick feeding. The saliva of ticks contains numerous active molecules that participate in several physiological processes. A Kunitz-type factor Xa (FXa) inhibitor, similar to the tissue factor pathway inhibitor (TFPI) precursor, was identified in the salivary gland transcriptome of Amblyomma sculptum ticks. The recombinant mature form of this Kunitz-type inhibitor, named Amblyomin-X, displayed anticoagulant, antiangiogenic, and antitumor properties. Amblyomin-X is a protein that inhibits FXa in the blood coagulation cascade and acts via non-hemostatic mechanisms, such as proteasome inhibition. Amblyomin-X selectively induces apoptosis in cancer cells and promotes tumor regression through these mechanisms. Notably, the cytotoxicity of Amblyomin-X seems to be restricted to tumor cells and does not affect non-tumorigenic cells, tissues, and organs, making this recombinant protein an attractive molecule for anticancer therapy. The cytotoxic activity of Amblyomin-X on tumor cells has led to vast exploration into this protein. Here, we summarize the function, action mechanisms, structural features, pharmacokinetics, and biodistribution of this tick Kunitz-type inhibitor recombinant protein as a promising novel antitumor drug candidate.

EcTI impairs survival and proliferation pathways in triple-negative breast cancer by modulating cell-glycosaminoglycans and inflammatory cytokines.

Breast cancer is the most common malignant tumor among women worldwide, and triple-negative breast cancer is the most aggressive type of breast cancer, which does not respond to hormonal therapies. The protease inhibitor, EcTI, extracted from seeds of Enterolobium contortisiliquum, acts on the main signaling pathways of the MDA-MB-231 triple-negative breast cancer cells. This inhibitor, when bound to collagen I of the extracellular matrix, triggers a series of pathways capable of decreasing the viability, adhesion, migration, and invasion of these cells. This inhibitor can interfere in the cell cycle process through the main signaling pathways such as the adhesion, Integrin/FAK/SRC, Akt, ERK, and the cell death pathway BAX and BCL-2. It also acts by reducing the main inflammatory cytokines such as TGF-α, IL-6, IL-8, and MCP-1, besides NFκB, a transcription factor, responsible for the aggressive and metastatic characteristics of this type of tumor. Thus, the inhibitor was able to reduce the main processes of carcinogenesis of this type of cancer.

Preclinical evaluation of Amblyomin-X, a Kunitz-type protease inhibitor with antitumor activity.

Amblyomin-X, a Kunitz-type protease inhibitor, is a recombinant protein that selectively induces apoptosis in tumor cells and promotes tumor reduction in vivo in melanoma animal models. Furthermore, Amblyomin-X was able to drastically reduce lung metastasis in a mice orthotopic kidney tumor model. Due to its antitumor activity, Amblyomin-X potential to become a new drug is currently under investigation, therefore the aim of the present study was to perform preclinical assays to evaluate Amblyomin-X toxicity in healthy mice. Exploratory toxicity assays have shown that treatment with 512 mg/kg of Amblyomin-X lead to animal mortality, therefore two groups of treatment were evaluated in the present work: in the acute toxicity assay, animals were injected once with doses ranging from 4 to 256 mg/kg of Amblyomin-X, while in the subacute toxicity assay, animals were injected with 0.25, 0.57 and 1 mg/kg of Amblyomin-X daily, during 28 days. Following this treatment regimens, Amblyomin-X did not cause any mortality; moreover, toxicity signs were discrete, reversible and observed only at the higher doses, thus establishing a safety profile for administration in mice, which can be further used to determine the dose translation of this novel drug candidate for treatment in other species.

Expressed sequence tags (ESTs) from the salivary glands of the tick Amblyomma cajennense (Acari: Ixodidae).

The neotropical tick Amblyomma cajennense is a significant pest to domestic animals, the most frequently human-biting tick in South America and the main vector of Brazilian spotted fever (caused by Rickettsia rickettsii), a deadly human disease. The purpose of this study is to characterize the adult A. cajennense salivary gland transcriptome by expressed sequence tags (ESTs). We report the analysis of 1754 clones obtained from a cDNA library, which reveal mainly transcripts related to proteins involved in the hemostatic processes, especially proteases and their inhibitors. Remarkably, five types of possible serine protease inhibitors were found, including a molecule with a distinguished structure that contains repeats of the active motif of hirudin inhibitors. Besides, other components that may be active over the host immune system or acting as defensins against infecting microorganisms were also described, including a molecule similar to insect venom allergens. The conjunction of components from this transcriptome suggests a diverse strategy of A. cajennense tick during feeding, but emphasized in the coagulation system.

Gene expression in the salivary complexes from Haementeria depressa leech through the generation of expressed sequence tags.

A survey of the transcriptional profile of Haementeria depressa Ringuelet, 1972 (Annelida, Hirudinea) salivary complexes was produced through expressed sequence tag (EST). Sequences from 898 independent clones were assembled in 555 clusters, representing the transcript profile of this tissue. The repertoire of possible proteins involved in feeding and host interaction processes of the leech corresponded to 10.6% of all identified transcripts (67 clusters), being the carbonic anhydrases (30%), several coagulation inhibitors (25%) and hemerythrin-like molecules (19%), the major components. Among the 387 clusters matching cellular proteins, the majority represents molecules involved in gene and protein expression, reflecting a high specialization of this tissue for protein synthesis. Our H. depressa dbEST was also compared to those from other blood-feeding organisms, providing evidences that among the secreted proteins, the coagulation inhibitors present a profile very characteristic of this animal class.

Blood coagulation and fibrinolytic factors in 105 patients with hemorrhagic syndrome caused by accidental contact with Lonomia obliqua caterpillar in Santa Catarina, southern Brazil.

Haemostatic disorders caused by Lonomia obliqua caterpillars has reached epidemic proportions in southern Brazil. Here we evaluated coagulation and fibrinolysis in 105 patients after accidental contact with Lonomia obliqua caterpillars. Global coagulation tests were prolonged in most cases and patients were divided into 3 groups according to fibrinogen (Fg) level: 1.5 g/l (group C). There was a significant reduction of factors V, XIII, VIII and prekallikrein in group A, with no change in factors X, II and von Willebrand factor. Thrombin-antithrombin and prothrombin F1+2 were elevated in most patients. Antithrombin and protein S were not changed whereas protein C levels were reduced in group A. Plasminogen and alfa2-antiplasmin levels were significantly reduced in group A and D-Dimer levels were extremely high in all groups, showing that fibrinolysis had been activated, possibly secondary to fibrin production. Levels of t-PA were normal and PAI-1 was mildly elevated in group A. The platelet count remained above 150 x 109 platelets/ml in 97% of cases. In summary, our results suggest that Lonomia obliqua envenoming is characterized by a consumption coagulopathy and secondary fibrinolysis.

Dynein function and protein clearance changes in tumor cells induced by a Kunitz-type molecule, Amblyomin-X.

Amblyomin-X is a Kunitz-type recombinant protein identified from the transcriptome of the salivary glands of the tick Amblyomma cajennense and has anti-coagulant and antitumoral activity. The supposed primary target of this molecule is the proteasome system. Herein, we elucidated intracellular events that are triggered by Amblyomin-X treatment in an attempt to provide new insight into how this serine protease inhibitor, acting on the proteasome, could be comparable with known proteasome inhibitors. The collective results showed aggresome formation after proteasome inhibition that appeared to occur via the non-exclusive ubiquitin pathway. Additionally, Amblyomin-X increased the expression of various chains of the molecular motor dynein in tumor cells, modulated specific ubiquitin linkage signaling and inhibited autophagy activation by modulating mTOR, LC3 and AMBRA1 with probable dynein involvement. Interestingly, one possible role for dynein in the mechanism of action of Amblyomin-X was in the apoptotic response and its crosstalk with autophagy, which involved the factor Bim; however, we observed no changes in the apoptotic response related to dynein in the experiments performed. The characteristics shared among Amblyomin-X and known proteasome inhibitors included NF-κB blockage and nascent polypeptide-dependent aggresome formation. Therefore, our study describes a Kunitz-type protein that acts on the proteasome to trigger distinct intracellular events compared to classic known proteasome inhibitors that are small-cell-permeable molecules. In investigating the experiments and literature on Amblyomin-X and the known proteasome inhibitors, we also found differences in the structures of the molecules, intracellular events, dynein involvement and tumor cell type effects. These findings also reveal a possible new target for Amblyomin-X, i.e., dynein, and may serve as a tool for investigating tumor cell death associated with proteasome inhibition.

Nitridergic platelet pathway activation by hementerin, a metalloprotease from the leech Haementeria depressa.

Hementerin (HT) is an 80 kDa fibrino(geno)lytic metalloprotease, purified from saliva of the leech Haementeria depressa. In the present report, the effect of HT on several functional parameters of human platelets was assessed. HT inhibited platelet aggregation and ATP release induced by different agonists such as ADP, adrenaline, collagen, thrombin, and arachidonic acid. HT did neither modify the expression of platelet glycoproteins (Ib, IIb-IIIa, Ia-IIa, IV) nor intraplatelet fibrinogen levels, whereas it markedly decreased CD62P and CD63 levels after the stimulation with thrombin. HT significantly increased thrombin-induced platelet Ca2+ intracellular levels, cGMP content and nitric oxide synthase (NOS) activity. The effect of HT on platelet aggregation was reversed by two NOS inhibitors, N(omega)-Nitro-L-arginine methyl ester and 2 N(G)-Nitro-L-arginine. In summary, these results indicate that HT is an effective inhibitor of human platelet aggregation, presumably through activation of the platelet's nitridergic pathway.

Bauhinia proteinase inhibitor-based synthetic fluorogenic substrates for enzymes isolated from insect midgut and caterpillar bristles.

Bauhinia ungulata factor Xa inhibitor (BuXI) inactivates factor Xa and LOPAP, a prothrombin activator proteinase isolated from the venom of Lonomia obliqua caterpillar bristles. The reactive site of the enzyme-inhibitor interaction was explored to design specific substrates for both enzymes. Methionine is crucial for LOPAP and factor Xa substrate interaction, since the change of both Met residues in the substrates abolished the hydrolysis. Synthetic substrates containing the sequence around the reactive site of BbKI, a plasma kallikrein inhibitor, were shown to be specific for trypsin hydrolysis. Therefore, these substrates may be an alternative in studies aiming at a characterization of trypsin-like enzyme activities, especially non-mammalian enzymes.

A prothrombin activator from Bothrops erythromelas (jararaca-da-seca) snake venom: characterization and molecular cloning.

A novel prothrombin activator enzyme, which we have named 'berythractivase', was isolated from Bothrops erythromelas (jararaca-da-seca) snake venom. Berythractivase was purified by a single cation-exchange-chromatography step on a Resource S (Amersham Biosciences) column. The overall purification (31-fold) indicates that berythractivase comprises about 5% of the crude venom. It is a single-chain protein with a molecular mass of 78 kDa. SDS/PAGE of prothrombin after activation by berythractivase showed fragment patterns similar to those generated by group A prothrombin activators, which convert prothrombin into meizothrombin, independent of the prothrombinase complex. Chelating agents, such as EDTA and o -phenanthroline, rapidly inhibited the enzymic activity of berythractivase, like a typical metalloproteinase. Human fibrinogen A alpha-chain was slowly digested only after longer incubation with berythractivase, and no effect on the beta- or gamma-chains was observed. Berythractivase was also capable of triggering endothelial proinflammatory and procoagulant cell responses. von Willebrand factor was released, and the surface expression of both intracellular adhesion molecule-1 and E-selectin was up-regulated by berythractivase in cultured human umbilical-vein endothelial cells. The complete berythractivase cDNA was cloned from a B. erythromelas venom-gland cDNA library. The cDNA sequence possesses 2330 bp and encodes a preproprotein with significant sequence similarity to many other mature metalloproteinases reported from snake venoms. Berythractivase contains metalloproteinase, desintegrin-like and cysteine-rich domains. However, berythractivase did not elicit any haemorrhagic response. These results show that, although the primary structure of berythractivase is related to that of snake-venom haemorrhagic metalloproteinases and functionally similar to group A prothrombin activators, it is a prothrombin activator devoid of haemorrhagic activity. This is a feature not observed for most of the snake venom metalloproteinases, including the group A prothrombin activators.