Role of the complement system in kidney cell death induced by Loxosceles venom Sphingomyelinases D

Envenomation by Loxosceles spiders can result in local and systemic pathologies. Systemic loxoscelism, which can lead to death, is characterized by intravascular hemolysis, platelet aggregation, and acute kidney injury. Sphingomyelinase D (SMase D) in Loxosceles spider venom is responsible for both local and systemic pathologies, and has been shown to induce metalloprotease activity. As the complement system is involved in many renal pathologies and is involved in hemolysis in systemic loxoscelism, the aim of this study was to investigate its role and the role of complement regulators and metalloproteases in an in vitro model of Loxosceles venom induced renal pathology. We investigated the effects of the venom/SMase D and the complement system on the HK-2 kidney cell line. Using cell viability assays, western blotting, and flow cytometry, we show that human serum, as a source of complement, enhanced the venom/SMase D induced cell death and the deposition of complement components and properdin. Inhibitors for ADAM-10 and ADAM-17 prevented the venom induced release of the of the complement regulator MCP/CD46 and reduced the venom/SMase D induced cell death. Our results show that the complement system can contribute to Loxosceles venom induced renal pathology. We therefore suggest that patients experiencing systemic loxoscelism may benefit from treatment with metalloproteinase inhibitors and complement inhibitors, but this proposition should be further analyzed in future pre-clinical and clinical assays.

Snake and arthropod venoms: Search for inflammatory activity in human cells involved in joint diseases

Most anti-inflammatory drugs currently adopted to treat chronic inflammatory joint diseases can alleviate symptoms but they do not lead to remission. Therefore, new and more efficient drugs are needed to block the course of joint inflammatory diseases. Animal venoms, rich in bioactive compounds, can contribute as valuable tools in this field of research. In this study, we first demonstrate the direct action of venoms on cells that constitute the articular joints. We established a platform consisting of cell-based assays to evaluate the release of cytokines (IL-6, IL-8, TNFα, IL-1β, and IL-10) by human chondrocytes, synoviocytes and THP1 macrophages, as well as the release of neuropeptides (substance-P and β-endorphin) by differentiated sensory neuron-like cells, 24 h after stimulation of cells with 21 animal venoms from snake and arthropod species, sourced from different taxonomic families and geographic origins. Results demonstrated that at non-cytotoxic concentrations, the venoms activate at varying degrees the secretion of inflammatory mediators involved in the pathology of articular diseases, such as IL-6, IL-8, and TNF-α by chondrocytes, synoviocytes, and macrophages and of substance P by neuron-like cells. Venoms of the Viperidae snake family were more inflammatory than those of the Elapidae family, while venoms of Arthropods were less inflammatory than snake venoms. Notably, some venoms also induced the release of the anti-inflammatory IL-10 by macrophages. However, the scorpion Buthus occitanus venom induced the release of IL-10 without increasing the release of inflammatory cytokines by macrophages. Since the cell types used in the experiments are crucial elements in joint inflammatory processes, the results of this work may guide future research on the activation of receptors and inflammatory signaling pathways by selected venoms in these particular cells, aiming at discovering new targets for therapeutic intervention.

Role of ErbB and IL-1 signaling pathways in the dermonecrotic lesion induced by Loxosceles sphingomyelinases D

Sphingomyelinase D (SMase D), the main toxic component of Loxosceles venom, has a well-documented role on dermonecrotic lesion triggered by envenomation with these species; however, the intracellular mechanisms involved in this event are still poorly known. Through differential transcriptomics of human keratinocytes treated with L. laeta or L. intermedia SMases D, we identified 323 DEGs, common to both treatments, as well as upregulation of molecules involved in the IL-1 and ErbB signaling. Since these pathways are related to inflammation and wound healing, respectively, we investigated the relative expression of some molecules related to these pathways by RT-qPCR and observed different expression profiles over time. Although, after 24 h of treatment, both SMases D induced similar modulation of these pathways in keratinocytes, L. intermedia SMase D induced earlier modulation compared to L. laeta SMase D treatment. Positive expression correlations of the molecules involved in the IL-1 signaling were also observed after SMases D treatment, confirming their inflammatory action. In addition, we detected higher relative expression of the inhibitor of the ErbB signaling pathway, ERRFI1, and positive correlations between this molecule and pro-inflammatory mediators after SMases D treatment. Thus, herein, we describe the cell pathways related to the exacerbation of inflammation and to the failure of the wound healing, highlighting the contribution of the IL-1 signaling pathway and the ERRFI1 for the development of cutaneous loxoscelism.

Complement System Inhibitory Drugs in a Zebrafish (Danio rerio) Model: Computational Modeling

The dysregulation of complement system activation usually results in acute or chronic inflammation and can contribute to the development of various diseases. Although the activation of complement pathways is essential for innate defense, exacerbated activity of this system may be harmful to the host. Thus, drugs with the potential to inhibit the activation of the complement system may be important tools in therapy for diseases associated with complement system activation. The synthetic peptides Cp40 and PMX205 can be highlighted in this regard, given that they selectively inhibit the C3 and block the C5a receptor (C5aR1), respectively. The zebrafish (Danio rerio) is a robust model for studying the complement system. The aim of the present study was to use in silico computational modeling to investigate the hypothesis that these complement system inhibitor peptides interact with their target molecules in zebrafish, for subsequent in vivo validation. For this, we analyzed molecular docking interactions between peptides and target molecules. Our study demonstrated that Cp40 and the cyclic peptide PMX205 have positive interactions with their respective zebrafish targets, thus suggesting that zebrafish can be used as an animal model for therapeutic studies on these inhibitors.

New Insights into Immunopathology Associated to Bothrops lanceolatus Snake Envenomation: Focus on PLA2 Toxin

The systemic increase in inflammatory mediator levels can induce diverse pathological disorders, including potentially thrombus formation, which may be lethal. Among the clinical conditions in which the formation of thrombi dictates the patient's prognosis, envenomation by Bothrops lanceolatus should be emphasized, as it can evolve to stroke, myocardial infarction and pulmonary embolism. Despite their life-threatening potential, the immunopathological events and toxins involved in these reactions remain poorly explored. Therefore, in the present study, we examined the immunopathological events triggered by a PLA₂ purified from B. lanceolatus venom, using an ex vivo human blood model of inflammation. Our results showed that the purified PLA₂ from the venom of B. lanceolatus damages human erythrocytes in a dose dependent way. The cell injury was associated with a decrease in the levels of CD55 and CD59 complement regulators on the cell surface. Moreover, the generation of anaphylatoxins (C3a and C5a) and the soluble terminal complement complex (sTCC) indicates that human blood exposure to the toxin activates the complement system. Increased production of TNF-α, CXCL8, CCL2 and CCL5 followed complement activation. The venom PLA₂ also triggered the generation of lipid mediators, as evidenced by the detected high levels of LTB₄, PGE₂ and TXB₂. The scenario here observed of red blood cell damage, dysfunctions of the complement regulatory proteins, accompanied by an inflammatory mediator storm, suggests that B. lanceolatus venom PLA₂ contributes to the thrombotic disorders present in the envenomed individuals.

Hyaluronan breakdown by snake venom hyaluronidases: From toxins delivery to immunopathology

Snake venom enzymes have a broad range of molecular targets in plasma, tissues, and cells, among which hyaluronan (HA) is outstanding. HA is encountered in the extracellular matrix of diverse tissues and in the bloodstream, and its different chemical configurations dictate the diverse morphophysiological processes in which it participates. Hyaluronidases are highlighted among the enzymes involved in HA metabolism. This enzyme has been detected along the phylogenetic tree, suggesting that hyaluronidases exert multiple biological effects on different organisms. Hyaluronidases have been described in tissues, blood and snake venoms. Snake venom hyaluronidases (SVHYA) contribute to tissue destruction in envenomations and are called spreading factors since their action potentiates venom toxin delivery. Interestingly, SVHYA are clustered in Enzyme Class 3.2.1.35 together with mammalian hyaluronidases (HYAL). Both HYAL and SVHYA of Class 3.2.1.35 act upon HA, generating low molecular weight HA fragments (LMW-HA). LMW-HA generated by HYAL becomes a damage-associated molecular pattern that is recognized by Toll-like receptors 2 and 4, triggering cell signaling cascades culminating in innate and adaptive immune responses that are characterized by lipid mediator generation, interleukin production, chemokine upregulation, dendritic cell activation and T cell proliferation. In this review, aspects of the structures and functions of HA and hyaluronidases in both snake venoms and mammals are presented, and their activities are compared. In addition, the potential immunopathological consequences of HA degradation products generated after snakebite envenoming and their use as adjuvant to enhance venom toxin immunogenicity for antivenom production as well as envenomation prognostic biomarker are also discussed.

Complement System Inhibition Modulates the Inflammation Induced by the Venom of Premolis semirufa, an Amazon Rainforest Moth Caterpillar

The caterpillar of the Premolis semirufa moth, commonly called Pararama, is found in the Brazilian Amazon region. Contact with the hairs can cause a chronic inflammatory reaction, termed "pararamosis". To date, there is still no specific treatment for pararamosis. In this study, we used a whole human blood model to evaluate the involvement of the complement in the proinflammatory effects of P. semirufa hair extract, as well as the anti-inflammatory potential of complement inhibitors in this process. After treatment of blood samples with the P. semirufa hair extract, there was a significant increase in the generation of soluble terminal complement complex (sTCC) and anaphylatoxins (C3a, C4a, and C5a), as well as the production of the cytokines TNF-α and IL-17 and the chemokines IL-8, RANTES, MIG, MCP-1, and IP-10. The inhibition of C3 with compstatin significantly decreased IL-17, IL-8, RANTES, and MCP-1 production. However, the use of the C5aR1 antagonist PMX205 promoted a reduction in the production of IL-8 and RANTES. Moreover, compstatin decreased CD11b, C5aR1, and TLR2 expression induced by P. semirufa hair extract in granulocytes and CD11b, TLR4, and TLR2 in monocytes. When we incubated vascular endothelial cells with extract-treated human plasma, there was an increase in IL-8 and MCP-1 production, and compstatin was able to decrease the production of these chemokines. C5aR1 antagonism also decreased the production of MCP-1 in endothelial cells. Thus, these results indicate that the extract of the Pararama bristles activates the complement system and that this action contributes to the production of cytokines and chemokines, modulation of the expression of surface markers in leukocytes, and activation of endothelial cells.

Bothrops jararaca Snake Venom Inflammation Induced in Human Whole Blood: Role of the Complement System

The clinical manifestations of envenomation by Bothrops species are complex and characterized by prominent local effects that can progress to tissue loss, physical disability, or amputation. Systemic signs can also occur, such as hemorrhage, coagulopathy, shock, and acute kidney failure. The rapid development of local clinical manifestations is accompanied by the presence of mediators of the inflammatory process originating from tissues damaged by the bothropic venom. Considering the important role that the complement system plays in the inflammatory response, in this study, we analyzed the action of Bothrops jararaca snake venom on the complement system and cell surface receptors involved in innate immunity using an ex vivo human whole blood model. B. jararaca venom was able to induce activation of the complement system in the human whole blood model and promoted a significant increase in the production of anaphylatoxins C3a/C3a-desArg, C4a/C4a-desArg, C5a/C5a-desArg and sTCC. In leukocytes, the venom of B. jararaca reduced the expression of CD11b, CD14 and C5aR1. Inhibition of the C3 component by Cp40, an inhibitor of C3, resulted in a reduction of C3a/C3a-desArg, C5a/C5a-desArg and sTCC to basal levels in samples stimulated with the venom. Exposure to B. jararaca venom induced the production of inflammatory cytokines and chemokines such as TNF-α, IL-8/CXCL8, MCP-1/CCL2 and MIG/CXCL9 in the human whole blood model. Treatment with Cp40 promoted a significant reduction in the production of TNF-α, IL-8/CXCL8 and MCP-1/CCL2. C5aR1 inhibition with PMX205 also promoted a reduction of TNF-α and IL-8/CXCL8 to basal levels in the samples stimulated with venom. In conclusion, the data presented here suggest that the activation of the complement system promoted by the venom of the snake B. jararaca in the human whole blood model significantly contributes to the inflammatory process. The control of several inflammatory parameters using Cp40, an inhibitor of the C3 component, and PMX205, a C5aR1 antagonist, indicates that complement inhibition may represent a potential therapeutic tool in B. jararaca envenoming.

Oral Tolerance Induction by Bothrops jararaca Venom in a Murine Model and Cross-Reactivity with Toxins of Other Snake Venoms

Oral tolerance is defined as a specific suppression of cellular and humoral immune responses to a particular antigen through prior oral administration of an antigen. It has unique immunological importance since it is a natural and continuous event driven by external antigens. It is characterized by low levels of IgG in the serum of animals after immunization with the antigen. There is no report of induction of oral tolerance to Bothrops jararaca venom. Here, we induced oral tolerance to B. jararaca venom in BALB/c mice and evaluated the specific tolerance and cross-reactivity with the toxins of other Bothrops species after immunization with the snake venoms adsorbed to/encapsulated in nanostructured SBA-15 silica. Animals that received a high dose of B. jararaca venom (1.8 mg) orally responded by showing antibody titers similar to those of immunized animals. On the other hand, mice tolerized orally with three doses of 1 µg of B. jararaca venom showed low antibody titers. In animals that received a low dose of B. jararaca venom and were immunized with B. atrox or B. jararacussu venom, tolerance was null or only partial. Immunoblot analysis against the venom of different Bothrops species provided details about the main tolerogenic epitopes and clearly showed a difference compared to antiserum of immunized animals.

C5a-C5aR1 Axis Activation Drives Envenomation Immunopathology by the Snake Naja annulifera

Systemic complement activation drives a plethora of pathological conditions, but its role in snake envenoming remains obscure. Here, we explored complement's contribution to the physiopathogenesis of Naja annulifera envenomation. We found that N. annulifera venom promoted the generation of C3a, C4a, C5a, and the soluble Terminal Complement Complex (sTCC) mediated by the action of snake venom metalloproteinases. N. annulifera venom also induced the release of lipid mediators and chemokines in a human whole-blood model. This release was complement-mediated, since C3/C3b and C5a Receptor 1 (C5aR1) inhibition mitigated the effects. In an experimental BALB/c mouse model of envenomation, N. annulifera venom promoted lipid mediator and chemokine production, neutrophil influx, and swelling at the injection site in a C5a-C5aR1 axis-dependent manner. N. annulifera venom induced systemic complementopathy and increased interleukin and chemokine production, leukocytosis, and acute lung injury (ALI). Inhibition of C5aR1 with the cyclic peptide antagonist PMX205 rescued mice from these systemic reactions and abrogated ALI development. These data reveal hitherto unrecognized roles for complement in envenomation physiopathogenesis, making complement an interesting therapeutic target in envenomation by N. annulifera and possibly by other snake venoms.

Searching for the toxic potential of Loxosceles amazonica and Loxosceles willianilsoni spiders' venoms

The Loxosceles genus belongs to the Sicariidae family and it comprises species whose venom can cause accidents with potentially fatal consequences. We have previously shown that SMase D is the enzyme responsible for the main pathological effects of Loxosceles venom. Despite the severity of accidents with Loxosceles, few species are considered to be of medical importance. Little is known about the venom of non-synanthropic species that live in natural environments. To contribute to a better understanding about the venom's toxicity of Loxosceles genus, the aim of this study was to (i) characterize the toxic properties of Loxosceles amazonica from two different localities and a recent described cave species Loxosceles willianilsoni and (ii) compare these venoms with that from Loxosceles laeta, which is among the most toxic ones. We show here that both L. amazonica venoms (from the two studied locations) and L. willianilsoni presented SMase D activity similar to that exhibited by L. laeta venom. Although L. amazonica and L. willianilsoni venoms were able to induce complement dependent human erythrocytes lysis, they were not able to induce cell death of human keratinocytes, as promoted by L. laeta venom, in the concentrations tested. These results indicate that other species of Loxosceles, in addition to those classified as medically important, have toxic potential to cause accidents in humans, despite interspecific variations that denote possible less toxicity.

Self-Assembled Cationic-Covered Nanoemulsion as A Novel Biocompatible Immunoadjuvant for Antiserum Production Against Tityus serrulatus Scorpion Venom

This study assesses the efficacy of different nanoemulsion formulations as new and innovative adjuvants for improving the in vivo immunization against the Tityus serrulatus scorpion venom. Nanoemulsions were designed testing key-variables such as surfactants, co-solvents, and the influence of the temperature, which would be able to induce the phase transition from a liquid crystal to a stable nanoemulsion, assessed for four months. Additionally, cationic-covered nanoemulsion with hyper-branched poly(ethyleneimine) was prepared and its performance was compared to the non-cationic ones. The physicochemical properties of the selected nanoemulsions and the interactions among their involved formulation compounds were carefully monitored. The cytotoxicity studies in murine macrophages (RAW 264.7) and red blood cells were used to compare different formulations. Moreover, the performance of the nanoemulsion systems as biocompatible adjuvants was evaluated using mice immunization protocol. The FTIR shifts and the zeta potential changes (from -18.3 ± 1.0 to + 8.4 ± 1.4) corroborated with the expected supramolecular anchoring of venom proteins on the surface of the nanoemulsion droplets. Cell culture assays demonstrated the non-toxicity of the formulations at concentrations less than 1.0 mg/mL, which were able to inhibit the hemolytic effect of the scorpion venom. The cationic-covered nanoemulsion has shown superior adjuvant activity, revealing the highest IgG titer in the immunized animals compared to both the non-cationic counterpart and the traditional aluminum adjuvant. In this approach, we demonstrate the incredible potential application of nanoemulsions as adjuvants, using a nanotechnology platform for antigen delivery system on immune cells. Additionally, the functionalization with hyper-branched poly(ethyleneimine) enhances this recognition and improves its action in immunization.

Human Chondrocyte Activation by Toxins From Premolis semirufa, an Amazon Rainforest Moth Caterpillar: Identifying an Osteoarthritis Signature

Pararamosis is a disease that occurs due to contact with the hairs of the larval stage of the Brazilian moth Premolis semirufa. Envenomation induces osteoarticular alterations with cartilage impairment that resembles joint synovitis. Thus, the toxic venom present in the caterpillar hairs interferes with the phenotype of the cells present in the joints, resulting in inflammation and promoting tissue injury. Therefore, to address the inflammatory mechanisms triggered by envenomation, we studied the effects of P. semirufa hair extract on human chondrocytes. We have selected for the investigation, cytokines, chemokines, matrix metalloproteinases (MMPs), complement components, eicosanoids, and extracellular matrix (ECM) components related to OA and RA. In addition, for measuring protein-coding mRNAs of some molecules associated with osteoarthritis (OA) and rheumatoid arthritis (RA), reverse transcription (RT) was performed followed by quantitative real-time PCR (RT-qPCR) and we performed the RNA-sequencing (RNA-seq) analysis of the chondrocytes transcriptome. In the supernatant of cell cultures treated with the extract, we observed increased IL-6, IL-8, MCP-1, prostaglandin E2, metalloproteinases (MMP-1, MMP-2, MMP-3 and MMP-13), and complement system components (C3, C4, and C5). We noticed a significant decrease in both aggrecan and type II collagen and an increase in HMGB1 protein in chondrocytes after extract treatment. RNA-seq analysis of the chondrocyte transcriptome allowed us to identify important pathways related to the inflammatory process of the disease, such as the inflammatory response, chemotaxis of immune cells and extracellular matrix (ECM) remodeling. Thus, these results suggest that components of Premolis semirufa hair have strong inflammatory potential and are able to induce cartilage degradation and ECM remodeling, promoting a disease with an osteoarthritis signature. Modulation of the signaling pathways that were identified as being involved in this pathology may be a promising approach to develop new therapeutic strategies for the control of pararamosis and other inflammatory joint diseases.

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.

Sphingomyelinases D From Loxosceles Spider Venoms and Cell Membranes: Action on Lipid Rafts and Activation of Endogenous Metalloproteinases

Loxosceles spider venom contains Sphingomyelinase D (SMase D), the key toxin causing pathology. SMase D hydrolyzes the main component of lipid rafts, sphingomyelin, which changes the membrane microenvironment resulting in the activation of endogenous metalloproteinase from the ADAMs family. Alterations in membrane microenvironment of lipid rafts contribute to the activation of several cell surface molecules. Serine proteinases convertases acting on the pro-domain of membrane metalloproteinases, such as ADAMs, increase the cleavage and the release of proteins ectodomains and receptors located at the cell surface areas containing lipid rafts. We, therefore, investigated the interaction of SMases D with these membrane microdomains (lipid rafts) in human keratinocytes, to better understand the molecular mechanism of SMases D action, and identify the ADAM(s) responsible for the cleavage of cell surface molecules. Using specific inhibitors, we observed that ADAMs 10 and 17 are activated in the cell membrane after SMase D action. Furthermore, proproteins convertases, such as furin, are involved in the SMase D induced ADAMs activation. One of the signaling pathways that may be involved in the activation of these proteases is the MAPK pathway, since phosphorylation of ERK1/2 was observed in cells treated with SMase D. Confocal analysis showed a strong colocalization between SMase D and GM1 ganglioside present in rafts. Analysis of structural components of rafts, such as caveolin-1 and flotillin-1, showed that the action of SMase D on cell membranes leads to a reduction in caveolin-1, which is possibly degraded by toxin-induced superoxide production in cells. The action of the toxin also results in flotilin-1 increased detection in the cell membrane. These results indicate that SMases D from Loxosceles venoms alter membrane rafts structure, leading to the activation of membrane bound proteases, which may explain why the lipase action of this toxin can result in proteolytic cleavage of cell surface proteins, ultimately leading to pathology.

Clinical aspects, diagnosis and management of Loxosceles spider envenomation: literature and case review

The genus Loxosceles comprises 140 species widely distributed around the world. These spiders are nocturnal, sedentary and remarkably nonaggressive, although they cause accidents in humans with wide degrees of severity, generating signs and symptoms that define the clinical condition known as loxoscelism. Its local signs and symptoms were first reported in 1872, and over the years, a large medical literature has been accumulated; unfortunately, it is not always trustworthy. Assessing the reliability of such information, we reviewed 120 case reports of loxoscelism published in 84 articles over the past 20 years. This search allowed us to gather information on the clinical aspects, diagnosis and treatment of loxoscelism, showing that the severity of these accidents has multiple degrees and that it is influenced by many factors. Thus, coupled with epidemiological and species occurrence information, this study can be a useful tool for the clinical practice of loxoscelism. It may support and provide a multidisciplinary view that should be taken into consideration when establishing the therapeutic approach in cases of Loxosceles envenomation.

Corrigendum: Complement System Inhibition Modulates the Pro-Inflammatory Effects of a Snake Venom Metalloproteinase

[This corrects the article DOI: 10.3389/fimmu.2019.01137.].

Complement System Inhibition Modulates the Pro-Inflammatory Effects of a Snake Venom Metalloproteinase

Envenomation by Bothrops snakes causes prominent local effects, including pain, oedema, local bleeding, blistering and necrosis, and systemic manifestations, such as hemorrhage, hypotension, shock and acute renal failure. These snake venoms are able to activate the complement system and induce the generation of anaphylatoxins, whose mechanisms include the direct cleavage of complement components by snake venom metalloproteinases and serine proteinases present in the venoms. A metalloproteinase able to activate the three complement pathways and generate active anaphylatoxins, named C-SVMP, was purified from the venom of Bothrops pirajai. Considering the inflammatory nature of Bothrops venoms and the complement-activation property of C-SVMP, in the present work, we investigated the inflammatory effects of C-SVMP in a human whole blood model. The role of the complement system in the inflammatory process and its modulation by the use of compstatin were also investigated. C-SVMP was able to activate the complement system in the whole blood model, generating C3a/C3a desArg, C5a/C5a desArg and SC5b-9. This protein was able to promote an increase in the expression of CD11b, CD14, C3aR, C5aR1, TLR2, and TLR4 markers in leukocytes. Inhibition of component C3 by compstatin significantly reduced the production of anaphylatoxins and the Terminal Complement Complex (TCC) in blood plasma treated with the toxin, as well as the expression of CD11b, C3aR, and C5aR on leukocytes. C-SVMP was able to induce increased production of the cytokines IL-1β and IL-6 and the chemokines CXCL8/IL-8, CCL2/MCP-1, and CXCL9/MIG in the human whole blood model. The addition of compstatin to the reactions caused a significant reduction in the production of IL-1β, CXCL8/IL-8, and CCL2/MCP-1 in cells treated with C-SVMP. We therefore conclude that C-SVMP is able to activate the complement system, which leads to an increase in the inflammatory process. The data obtained with the use of compstatin indicate that complement inhibition may significantly control the inflammatory process initiated by Bothrops snake venom toxins.

Targeting Loxosceles spider Sphingomyelinase D with small-molecule inhibitors as a potential therapeutic approach for loxoscelism

Loxosceles spiders’ venoms consist of a mixture of proteins, including the sphingomyelinases D (SMases D), which are the main toxic components responsible for local and systemic effects in human envenomation. Herein, based on the structural information of SMase D from Loxosceles laeta spider venom and virtual docking-based screening approach, three benzene sulphonate compounds (named 1, 5 and 6) were identified as potential Loxosceles SMase D inhibitors. All compounds inhibited the hydrolysis of the sphingomyelin substrate by both recombinant and native SMases D. Compounds 5 and 6 acted as SMases D uncompetitive inhibitors with Ki values of 0.49 µM and 0.59 µM, respectively. Compound 1 is a mixed type inhibitor, and presented a Ki value of 0.54 µM. In addition, the three compounds inhibited the binding of SMases D to human erythrocytes and the removal of glycophorin C from the cell surface, which are important events in the complement-dependent haemolysis induced by Loxosceles venom. Moreover, compounds 5 and 6 reduced the binding of SMases to human keratinocytes membrane and the venom induced cell death. Importantly, compounds 5 and 6 also controlled the development of the necrotic lesion in an in vivo model of loxoscelism. Together, our findings indicate that the novel SMase D inhibitors presented here are able to suppress both local and systemic reactions induced by Loxosceles venoms. Since the number of Loxosceles envenomation accidents is currently growing worldwide, our results indicate that both inhibitors are promising scaffolds for the rational design of new drugs targeting SMases D from these spiders.

Kn-Ba: a novel serine protease isolated from Bitis arietans snake venom with fibrinogenolytic and kinin-releasing activities

Background

Bitis arietans is a venomous snake found in sub-Saharan Africa and in parts of Morocco and Saudi Arabia. The envenomation is characterized by local and systemic reactions including pain, blistering, edema and tissue damage, besides hemostatic and cardiovascular disturbances, which can cause death or permanent disabilities in its victims. However, the action mechanisms that provoke these effects remain poorly understood, especially the activities of purified venom components. Therefore, in order to elucidate the molecular mechanisms that make the Bitis arietans venom so potent and harmful to human beings, this study reports the isolation and biochemical characterization of a snake venom serine protease (SVSP).

Methods

Solubilized venom was fractionated by molecular exclusion chromatography and the proteolytic activity was determined using fluorescent substrates. The peaks that showed serine protease activity were determined by blocking the proteolytic activity with site-directed inhibitors. In sequence, the fraction of interest was submitted to another cycle of molecular exclusion chromatography. The purified serine protease was identified by mass spectrometry and characterized biochemically and immunochemically.

Results

A serine protease of 33 kDa with fibrinogen-degrading and kinin-releasing activities was isolated, described, and designated herein as Kn-Ba. The experimental Butantan Institute antivenom produced against Bitis arietans venom inhibited the Kn-Ba activity.

Conclusions

The in vitro activities of Kn-Ba can be correlated with the capacity of the venom to provoke bleeding and clotting disorders as well as hypotension, which are common symptoms presented by envenomed victims. Obtaining satisfactory Kn-Ba inhibition through the experimental antivenom is important, given the WHO’s recommendation of immunotherapy in cases of human accidents with venomous snakes.

Electronic supplementary material

The online version of this article (10.1186/s40409-018-0176-5) contains supplementary material, which is available to authorized users.

Persistence and Intra-Host Genetic Evolution of Zika Virus Infection in Symptomatic Adults: A Special View in the Male Reproductive System

We followed the presence of Zika virus (ZIKV) in four healthy adults (two men and two women), for periods ranging from 78 to 298 days post symptom onset. The patients were evaluated regarding the presence of the virus in different body fluids (blood, saliva, urine and semen), development of immune responses (including antibodies, cytokines and chemokines), and virus genetic variation within samples collected from semen and urine during the infection course. The analysis was focused primarily on the two male patients who shed the virus for up to 158 days after the initial symptoms. ZIKV particles were detected in the spermatozoa cytoplasm and flagella, in immature sperm cells and could also be isolated from semen in cell culture, confirming that the virus is able to preserve integrity and infectivity during replication in the male reproductive system (MRS). Despite the damage caused by ZIKV infection within the MRS, our data showed that ZIKV infection did not result in infertility at least in one of the male patients. This patient was able to conceive a child after the infection. We also detected alterations in the male genital cytokine milieu, which could play an important role in the replication and transmission of the virus which could considerably increase the risk of ZIKV sexual spread. In addition, full genome ZIKV sequences were obtained from several samples (mainly semen), which allowed us to monitor the evolution of the virus within a patient during the infection course. We observed genetic changes over time in consensus sequences and lower frequency intra-host single nucleotide variants (iSNV), that suggested independent compartmentalization of ZIKV populations in the reproductive and urinary systems. Altogether, the present observations confirm the risks associated with the long-term replication and shedding of ZIKV in the MRS and help to elucidate patterns of intra-host genetic evolution during long term replication of the virus.

Leptospira interrogans outer membrane protein LipL21 is a potent inhibitor of neutrophil myeloperoxidase

Leptospirosis is a widespread zoonotic and neglected infectious disease of human and veterinary concern that is caused by pathogenic Leptospira species. After entrance in the host, pathogenic leptospires evade the host natural defense mechanisms in order to propagate and disseminate to multiple organs. Myeloperoxidase is an enzyme stored in neutrophils azurophilic granules, and is released upon neutrophil activation to produce mainly hypochlorous acid, a strong oxidant and potent antimicrobial agent. In the present investigation, we studied the modulation of myeloperoxidase activity by L. interrogans serovar Copenhageni. We show that leptospires and their culture supernatants are able to inhibit both peroxidase and chlorination activities of myeloperoxidase, without interfering with neutrophil degranulation. By leptospiral outer membrane protein extraction and fractionation, we identified the proteins LipL21 and LipL45 as myeloperoxidase inhibitors, constituting new Leptospira virulence factors. Accordingly, we propose a function for the protein LipL21, one of the most expressed leptospiral outer membrane proteins. Our results show a novel innate immune evasion mechanism by which leptospires interfere with the host response in order to cope with the host oxidative stress and efficiently achieve dissemination and colonization.

Venomous caterpillars: From inoculation apparatus to venom composition and envenomation

Envenomation by the larval or pupal stages of moths occurs when the victim presses their hairs. They penetrate the subcutaneous tissue, releasing toxins such as proteolytic enzymes, histamine and other pro-inflammatory substances. Cutaneous reactions, including severe pain, oedema and erythema are frequent local manifestations of caterpillar envenomation, but, in some cases, the reactions can evolve into vesicles, bullae, erosions, petechiae, superficial skin necrosis and ulcerations. Alternatively, some individual can develop allergic reactions, renal failure, osteochondritis, deformity and immobilization of the affected joints and intracerebral bleeding. Caterpillars produce venom to protect themselves from predators; contact with humans is accidental and deserves close attention. Their venoms have not been well studied, except for toxins from some few species. The present review brings together data on venomous caterpillars of moths, primarily addressing the available literature on diversity among the different families that cause accident in humans, the structures used in their defense, venom composition and clinical aspects of the envenomations. Understanding the molecular mechanisms of action of caterpillars' toxins may lead to the development of more adequate treatments.

Quality of horse F(ab')2 antitoxins and anti-rabies immunoglobulins: protein content and anticomplementary activity

Background

Among other applications, immunotherapy is used for the post-exposure treatment and/or prophylaxis of important infectious diseases, such as botulism, diphtheria, tetanus and rabies. The effectiveness of serum therapy is widely proven, but improvements on the immunoglobulin purification process and on the quality control are necessary to reduce the amount of protein aggregates. These may trigger adverse reactions in patients by activating the complement system and inducing the generation of anaphylatoxins. Herein, we used immunochemical methods to predict the quality of horse F(ab’)₂ anti-botulinum AB, anti-diphtheric, antitetanic and anti-rabies immunoglobulins, in terms of amount of proteins and protein aggregates.

Methods

Samples were submitted to protein quantification, SDS-PAGE, Western blot analysis and molecular exclusion chromatography. The anticomplementary activity was determined in vitro by detecting the production of C5a/C5a desArg, the most potent anaphylatoxin. Data were analyzed by one-way ANOVA followed by Tukey’s post-test, and differences were considered statistically significant when p < 0.05.

Results

Horse F(ab’)₂ antitoxins and anti-rabies immunoglobulin preparations presented different amounts of protein. SDS-PAGE and Western blot analyses revealed the presence of protein aggregates, non-immunoglobulin contaminants and, unexpectedly, IgG whole molecules in the samples, indicating the non-complete digestion of immunoglobulins. The chromatographic profiles of antitoxins and anti-rabies immunoglobulins allowed to estimate the percentage of contaminants and aggregates in the samples. Although protein aggregates were present, the samples were not able to induce the generation of C5a/C5a desArg in vitro, indicating that they probably contain acceptable levels of aggregates.

Conclusions

Anti-botulinum AB (bivalent), anti-diphtheric, antitetanic and anti-rabies horse F(ab’)₂ immunoglobulins probably contain acceptable levels of aggregates, although other improvements on the preparations must be carried out. Protein profile analysis and in vitro anticomplementary activity of F(ab’)₂ immunoglobulin preparations should be included as quality control steps, to ensure acceptable levels of aggregates, contaminants and whole IgG molecules on final products, reducing the chances of adverse reactions in patients.

The Ex vivo Eye Irritation Test (EVEIT) model as a mean of improving venom ophthalmia understanding

Snakes belonging to the genus Naja (Elapid family), also known as "spitting cobras", can spit venom towards the eyes of the predator as a defensive strategy, causing painful and potentially blinding ocular envenoming. Venom ophthalmia is characterized by pain, hyperemia, blepharitis, blepharospasm and corneal erosions. Elapid venom ophthalmia is not well documented and no specific treatment exists. Furthermore, accidental ejection of venom by non-spitting vipers, as Bothrops, also occurs. The Ex vivo Eye Irritation Test model (EVEIT) has enabled important progress in the knowledge of chemical ocular burns. Considering the lack of experimental animal model, we adapted the EVEIT to study venom ophthalmia mechanisms. Ex vivo rabbit corneas were exposed to venoms from spitting (Naja mossambica, Naja nigricollis) and non-spitting (Naja naja, Bothrops jararaca and Bothrops lanceolatus) snakes, and rinsed or not with water. The corneal thickness and the depth of damage were assessed using high-resolution optical coherence tomography (HR-OCT) imaging and histological analysis. All Naja venoms induced significant corneal edema, collagen structure disorganization and epithelial necrosis. Corneas envenomed by African N. mossambica and N. nigricollis venoms were completely opaque. Opacification was not observed in corneas treated with venoms from non-spitting snakes, such as the Asian cobra, N. naja, and the vipers, B. jararaca and B. lanceolatus. Moreover, Bothrops venoms were able to damage the epithelium and cause collagen structure disorganization, but not edema. Immediate water rinsing improved corneal status, though damage and edema could still be observed. In conclusion, the present study shows that the EVEIT model was successfully adapted to set a new experimental ex vivo animal model of ophthalmia, caused by snake venoms, which will enable to explore new therapies for venom ophthalmia.

Comparison of two Jatropha species (Euphorbiaceae) used popularly to treat snakebites in Northeastern Brazil: Chemical profile, inhibitory activity against Bothrops erythromelas venom and antibacterial activity

ETHNOPHARMACOLOGICAL RELEVANCE

Jatropha species (Euphorbiaceae) are largely used in traditional medicine to treat different pathologies in Africa, Asia and Latin America. In Northeastern Brazilian folk medicine, several Jatropha species, such as Jatropha gossypiifolia L. and Jatropha mollissima (Pohl) Baill., are indistinctly used to treat snakebites.

AIM OF THE STUDY

To compare two of the Brazilian most used Jatropha species for snakebites (J. gossypiifolia and J. mollissima), in relation to their ability to inhibit local edematogenic activity of Bothrops erythromelas snake venom in mice, their in vitro antibacterial activity and phytochemical profile.

MATERIAL AND METHODS

Aqueous leaf extracts of J. gossypiifolia (AEJg) and J. mollissima (AEJm) were prepared by decoction. AEJg and AEJm were compared chemically, by thin layer chromatography (TLC) and high-performance liquid chromatography with diode array detection (HPLC-DAD) analysis. They were also pharmacologically compared, using the mouse model of paw edema induced by Bothrops erythromelas snake venom (BeV), and in vitro by broth microdilution and agar dilution antimicrobial tests.

RESULTS

Flavonoids were detected as the major compounds in both extracts. However, AEJg and AEJm showed quantitatively different chemical profiles by HPLC-DAD. AEJg presented fewer peaks of flavonoids than AEJm, however, when the intensity of peaks were analyzed, these compounds were at high concentration in AEJg, even using the same concentration of both extracts. Differences were also observed in the biological activity of the two extracts. While no difference was observed when the extracts were administered by oral route (P > 0.05), by the intraperitoneal route AEJg presented anti-edematogenic activity significantly (P < 0.001) higher than AEJm. In antimicrobial assays, only AEJg presented antibacterial activity against Staphylococcus epidermidis, Staphylococcus aureus and Bacillus cereus.

CONCLUSIONS

Although used indistinctly by folk medicine, our results suggested that AEJg is more active than AEJm in relation to its antiedematogenic and antibacterial activities. Significant differences were observed in their phytochemical profiles, especially a higher content of C-glycosylated flavonoids in the most active species, which could justify the different biological effects observed. These findings strengthen the potentiality of J. gossypiifolia species for use as complementary treatment for local effects induced by Bothrops venoms and could be helpful for distinction of the species and control quality assessment of future herbal medicines based on Jatropha plants.

Loxosceles venom Sphingomyelinase D activates human blood leukocytes: Role of the complement system

Envenomation by Loxosceles spiders can result in severe systemic and local reactions, which are mainly triggered by Sphingomyelinase D (SMase D), a toxic component of Loxosceles venom. SMase D induces a systemic inflammatory condition similar to the reaction observed during an endotoxic shock. Considering the potent pro-inflammatory potential of Loxosceles venom and the SMase D, in this study we have used the whole human blood model to study the endotoxic-like shock triggered by SMase D. Recombinant purified SMase D from L. intermedia venom, similarly to LPS, induced activation of blood leukocytes, as observed by the increase in the expression of CD11b and TLR4, production of reactive oxygen and nitrogen species (superoxide anion and peroxynitrite) and release of TNF-α. Complement consumption in the plasma was also detected, and complement inhibition by compstatin decreased the SMase D and LPS-induced leukocyte activation, as demonstrated by a reduction in the expression of CD11b and TLR4 and superoxide anion production. Similar results were found for the L. intermedia venom, except for the production of TNF-α. These findings indicate that SMase D present in Loxosceles venom is able to activate leukocytes in a partially complement-dependent manner, which can contribute to the systemic inflammation that follows envenomation by this spider. Thus, future therapeutic management of systemic Loxosceles envenomation could include the use of complement inhibitors as adjunct therapy.

Enzymatic and Pro-Inflammatory Activities of Bothrops lanceolatus Venom: Relevance for Envenomation

Bothrops lanceolatus, commonly named ‘Fer-de-Lance’, is an endemic snake of the French Caribbean Island of Martinique. Envenomations by B. lanceolatus present clinical aspects characterized by systemic thrombotic syndrome and important local inflammation, involving edema and pain but limited hemorrhage. To investigate mechanisms of venom-induced inflammation, B. lanceolatus venom was characterized, its cross-reactivity with bothropic antivenom explored, its cytotoxicity on human keratinocytes and vascular cells, and the production of cytokines and chemokines were analyzed. We used electrophoretic separation, zymography, colorimetric or fluorimetric enzymatic assays, and immunochemical assays. Therapeutic South American bothropic antivenom cross-reacted with B. lanceolatus venom and completely or partially abolished its PLA2, hyaluronidase, and proteolytic activities, as well as its cytotoxicity for keratinocytes. The substrate specificity of B. lanceolatus venom proteases was emphasized. B. lanceolatus venom cytotoxicity was compared to the B. jararaca venom. Both venoms were highly cytotoxic for keratinocytes (HaCaT), whereas B. lanceolatus venom showed particularly low toxicity for endothelial cells (EAhy926). Patterns of cytokine and chemokine production by cells exposed to the venoms were highly pro-inflammatory. Thus, the results presented here show that B. lanceolatus venom toxins share important antigenic similarities with South American Bothrops species toxins, although their proteases have acquired particular substrate specificity. Moreover, the venom displays important cytotoxic and pro-inflammatory action on human cell types such as keratinocytes and endothelial cells, which are important players in the local and systemic compartments affected by the envenomation.

Characterization of the gene encoding component C3 of the complement system from the spider Loxosceles laeta venom glands: Phylogenetic implications

A transcriptome analysis of the venom glands of the spider Loxosceles laeta, performed by our group, in a previous study (Fernandes-Pedrosa et al., 2008), revealed a transcript with a sequence similar to the human complement component C3. Here we present the analysis of this transcript. cDNA fragments encoding the C3 homologue (Lox-C3) were amplified from total RNA isolated from the venom glands of L. laeta by RACE-PCR. Lox-C3 is a 5178 bps cDNA sequence encoding a 190kDa protein, with a domain configuration similar to human C3. Multiple alignments of C3-like proteins revealed two processing sites, suggesting that Lox-C3 is composed of three chains. Furthermore, the amino acids consensus sequences for the thioester was found, in addition to putative sequences responsible for FB binding. The phylogenetic analysis showed that Lox-C3 belongs to the same group as two C3 isoforms from the spider Hasarius adansoni (Family Salcitidae), showing 53% homology with these. This is the first characterization of a Loxosceles cDNA sequence encoding a human C3 homologue, and this finding, together with our previous finding of the expression of a FB-like molecule, suggests that this spider species also has a complement system. This work will help to improve our understanding of the innate immune system in these spiders and the ancestral structure of C3.

Sphingomyelinase D from Loxosceles laeta Venom Induces the Expression of MMP7 in Human Keratinocytes: Contribution to Dermonecrosis

Envenomation by Loxosceles spider is characterized by the development of dermonecrosis. In previous studies, we have demonstrated that increased expression/secretion of matrix metalloproteinases 2 and 9, induced by Loxosceles intermedia venom Class 2 SMases D (the main toxin in the spider venom), contribute to the development of cutaneous loxoscelism. In the present study we show that the more potent venom containing the Class 1 SMase D from Loxosceles laeta, in addition to increasing the expression/secretion of MMP2 and MMP9, also stimulates the expression of MMP7 (Matrilysin-1), which was associated with keratinocyte cell death. Tetracycline, a matrix metalloproteinase inhibitor, prevented cell death and reduced MMPs expression. Considering that L. laeta venom is more potent at inducing dermonecrosis than L. intermedia venom, our results suggest that MMP7 may play an important role in the severity of dermonecrosis induced by L. laeta spider venom SMase D. In addition, the inhibition of MMPs by e.g. tetracyclines may be considered for the treatment of the cutaneous loxoscelism.

Adaptive evolution in the toxicity of a spider's venom enzymes

Background

Sphingomyelinase D is the main toxin present in the venom of Loxosceles spiders. Several isoforms present in these venoms can be structurally classified in two groups. Class I Sphingomyelinase D contains a single disulphide bridge and variable loop. Class II Sphingomyelinase D presents an additional intrachain disulphide bridge that links a flexible loop with a catalytic loop. These classes exhibit differences in their toxic potential. In this paper we address the distribution of the structural classes of SMase D within and among species of spiders and also their evolutionary origin by means of phylogenetic analyses. We also conducted tests to assess the action of natural selection in their evolution combined to structural modelling of the affected sites.

Results

The majority of the Class I enzymes belong to the same clade, which indicates a recent evolution from a single common ancestor. Positively selected sites are located on the catalytic interface, which contributes to a distinct surface charge distribution between the classes. Sites that may prevent the formation of an additional bridge were found in Class I enzymes.

Conclusions

The evolution of Sphingomyelinase D has been driven by natural selection toward an increase in noxiousness, and this might help explain the toxic variation between classes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-015-0561-4) contains supplementary material, which is available to authorized users.

A serine protease isolated from the bristles of the Amazonic caterpillar, Premolis semirufa, is a potent complement system activator

Background

The caterpillar of the moth Premolis semirufa, commonly named pararama, is found in the Brazilian Amazon region. Accidental contact with the caterpillar bristles causes an intense itching sensation, followed by symptoms of an acute inflammation, which last for three to seven days after the first incident. After multiple accidents a chronic inflammatory reaction, called “Pararamose”, characterized by articular synovial membrane thickening with joint deformities common to chronic synovitis, frequently occurs. Although complement mediated inflammation may aid the host defense, inappropriate or excessive activation of the complement system and generation of anaphylatoxins can lead to inflammatory disorder and pathologies. The aim of the present study was to evaluate, in vitro, whether the Premolis semirufa’s bristles extract could interfere with the human complement system.

Results

The bristles extract was able to inhibit the haemolytic activity of the alternative pathway, as well as the activation of the lectin pathway, but had no effect on the classical pathway, and this inhibition seemed to be caused by activation and consumption of complement components. The extract induced the production of significant amounts of all three anaphylatoxins, C3a, C4a and C5a, promoted direct cleavage of C3, C4 and C5 and induced a significant generation of terminal complement complexes in normal human serum. By using molecular exclusion chromatography, a serine protease of 82 kDa, which activates complement, was isolated from P. semirufa bristles extract. The protease, named here as Ps82, reduced the haemolytic activity of the alternative and classical pathways and inhibited the lectin pathway. In addition, Ps82 induced the cleavage of C3, C4 and C5 and the generation of C3a and C4a in normal human serum and it was capable to cleave human purified C5 and generate C5a. The use of Phenanthroline, metalloprotease inhibitor, in the reactions did not significantly interfere with the activity of the Ps82, whereas the presence of PMSF, serine protease inhibitor, totally blocked the activity.

Conclusion

These data show that a serine protease present in the Premolis semirufa’s bristles extract has the ability to activate the complement system, which may contribute to the inflammatory process presented in humans after envenomation.

New proline-rich oligopeptides from the venom of African adders: Insights into the hypotensive effect of the venoms

BACKGROUND

The snakes from the Bitis genus are some of the most medically important venomous snakes in sub Saharan Africa, however little is known about the composition and effects of these snake venom peptides. Considering that the victims with Bitis genus snakes have exacerbate hypotension and cardiovascular disorders, we investigated here the presence of angiotensin-converting enzyme modulators on four different species of venoms.

METHODS

The peptide fractions from Bitis gabonica gabonica, Bitis nasicornis, Bitis gabonica rhinoceros and Bitis arietans which showed inhibitory activity on angiotensin-converting enzyme were subjected to mass spectrometry analysis. Eight proline-rich peptides were synthetized and their potencies were evaluated in vitro and in vivo.

RESULTS

The MS analysis resulted in over 150 sequences, out of which 32 are new proline-rich oligopeptides, and eight were selected for syntheses. For some peptides, inhibition assays showed inhibitory potentials of cleavage of angiotensin I ten times greater when compared to bradykinin. In vivo tests showed that all peptides decreased mean arterial pressure, followed by tachycardia in 6 out of 8 of the tests.

CONCLUSION

We describe here some new and already known proline-rich peptides, also known as bradykinin-potentiating peptides. Four synthetic peptides indicated a preferential inhibition of angiotensin-converting enzyme C-domain. In vivo studies show that the proline-rich oligopeptides are hypotensive molecules.

GENERAL SIGNIFICANCE

Although proline-rich oligopeptides are known molecules, we present here 32 new sequences that are inhibitors of the angiotensin-converting enzyme and consistent with the symptoms of the victims of Bitis spp, who display severe hypotension.

Neuropeptide Y family-degrading metallopeptidases in the Tityus serrulatus venom partially blocked by commercial antivenoms

Accidents caused by scorpions represent a relevant public health issue in Brazil, being more recurring than incidents with snakes and spiders. The main species responsible for this situation is the yellow scorpion, Tityus serrulatus, due especially to the great frequency with which accidents occur and the potential of its venom to induce severe clinical manifestations, even death, mainly among children. Although neurotoxins are well characterized, little information is known about other components of scorpion venoms, such as peptidases, and their effect on envenomation. Previous results from our group showed that the metallopeptidases present in this venom are capable of hydrolyzing the neuropeptide dynorphin 1-13 in vitro, releasing Leu-enkephalin, which may interact with ion channels and promote indirect neurotoxicity. Thus, this study aims to get more information about the effect of toxic peptidase activity present in the venom on biologically active peptides, and to evaluate the in vitro neutralizing potential of commercial antivenoms produced by the Butantan Institute. A set of human bioactive peptides were studied as substrates for the peptidases, and the members of the neuropeptide Y family were found to be the most susceptible ones. All new substrate hydrolyses were totally inhibited by ethylenediaminetetracetic and not blocked by phenylmethanesulfonylfluoride, indicating that metallopeptidases were responsible for the peptidase activity. Also, peptidase activities were only partially inhibited by therapeutic Brazilian scorpion antivenom (SAV) and arachnid antivenom (AAV). The dose-response inhibition by both antivenoms indicates that AAV neutralizes better than SAV at the used doses. These characterizations, unpublished until now, can contribute to the improvement of our knowledge about the venom and envenomation processes by T. serrulatus.

Animal venoms/toxins and the complement system

Nature is a wealthy source of agents that have been shown to be beneficial to human health, but nature is also a rich source of potential dangerous health damaging compounds. This review will summarise and discuss the agents from the animal kingdom that have been shown to interact with the human complement (C) system. Most of these agents are toxins found in animal venoms and animal secretions. In addition to the mechanism of action of these toxins, their contribution to the field of complement, their role in human pathology and the potential benefit to the venomous animal itself will be discussed. Potential therapeutic applications will also be discussed.

Anticomplementary activity of horse IgG and F(ab')2 antivenoms

Envenomation by poisonous animals is a neglected condition according to the World Health Organization (WHO). Antivenoms are included in the WHO Essential Medicines List. It has been assumed that immunoglobulin G (IgG) antivenoms could activate the complement system through Fc and induce early adverse reactions (EARs). However, data in the literature indicate that F(ab')2 fragments can also activate the complement system. Herein, we show that several batches of IgG and F(ab')2 antivenoms from the Butantan, Vital Brazil, and Clodomiro Picado Institutes activated the complement classical pathway and induced the production of C3a; however, only those antivenoms from Clodomiro Picado generated C5a. Different protein profiles (IgG heavy chain, protein contaminants, and aggregates) were observed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analyses. Our results show that various antivenoms from different producers are able to activate the classical pathway of the complement system and generate anaphylatoxins, and these findings suggest that factors, such as composition, contaminant proteins, and aggregates, may influence the anticomplementary activity of antivenoms in vitro. Therefore, there is a need to further improve antivenom production methods to reduce their anticomplementary activity and potential to cause EARs.

Mechanism of neutrophil dysfunction: neutrophil serine proteases cleave and inactivate the C5a receptor

Neutrophil dysfunction, resulting in inefficient bacterial clearance, is a feature of several serious medical conditions, including cystic fibrosis (CF) and sepsis. Poorly controlled neutrophil serine protease (NSP) activity and complement activation have been implicated in this phenomenon. The capacity for excess NSP secretion and complement activation to influence the expression and function of the important neutrophil-activating receptor C5aR was investigated. Purified NSPs cathepsin G (CG), neutrophil elastase (NE), and proteinase 3 cleaved C5aR to a 26- to 27-kDa membrane-bound fragment, thereby inactivating its C5a-induced signaling ability. In a supernatant transfer assay, NSPs released from neutrophils in response to C5a induced the cleavage of the C5aR on unstimulated cells. Stimulation of myeolomonocytic U937 cells and purified neutrophils with C5a resulted in downregulation of the C5aR on these cells, which, in the case of U937 cells, was largely caused by NSP-mediated cleavage of C5aR, but in the case of neutrophils, intracellular degradation was likely the main mediator in addition to a small role for NSPs. CG and NE in bronchoalveolar lavage fluid from CF patients both contributed to C5aR cleavage. We propose two converging models for C5a- and NSP-mediated neutrophil dysfunction whereby C5aR cleavage is induced by NSPs, secreted in response to: 1) excess C5a generation or other stimuli; or 2) necrosis. The consequent impairment of C5aR activity contributes to suboptimal local neutrophil priming and bacterial clearance. NSP inhibitors with specificity for both CG and NE may aid the treatment of pathologies associated with neutrophil dysfunction including sepsis and CF.

Venom of the Brazilian spider Sicarius ornatus (Araneae, Sicariidae) contains active sphingomyelinase D: potential for toxicity after envenomation

Background

The spider family Sicariidae includes two genera, Sicarius and Loxosceles. Bites by Sicarius are uncommon in humans and, in Brazil, a single report is known of a 17-year old man bitten by a Sicarius species that developed a necrotic lesion similar to that caused by Loxosceles. Envenomation by Loxosceles spiders can result in dermonecrosis and severe ulceration. Sicarius and Loxosceles spider venoms share a common characteristic, i.e., the presence of Sphingomyelinases D (SMase D). We have previously shown that Loxosceles SMase D is the enzyme responsible for the main pathological effects of the venom. Recently, it was demonstrated that Sicarius species from Africa, like Loxosceles spiders from the Americas, present high venom SMase D activity. However, despite the presence of SMase D like proteins in venoms of several New World Sicarius species, they had reduced or no detectable SMase D activity. In order to contribute to a better understanding about the toxicity of New World Sicarius venoms, the aim of this study was to characterize the toxic properties of male and female venoms from the Brazilian Sicarius ornatus spider and compare these with venoms from Loxosceles species of medical importance in Brazil.

Methodology/Principal Findings

SDS-PAGE analysis showed variations in the composition of Loxosceles spp. and Sicarius ornatus venoms. Differences in the electrophoretic profiles of male and female venoms were also observed, indicating a possible intraspecific variation in the composition of the venom of Sicarius spider. The major component in all tested venoms had a Mr of 32–35 kDa, which was recognized by antiserum raised against Loxosceles SMases D. Moreover, male and female Sicarius ornatus spiders' venoms were able to hydrolyze sphingomyelin, thus showing an enzymatic activity similar to that determined for Loxosceles venoms. Sicarius ornatus venoms, as well as Loxosceles venoms, were able to render erythrocytes susceptible to lysis by autologous serum and to induce a significant loss of human keratinocyte cell viability; the female Sicarius ornatus venom was more efficient than male.

Conclusion

We show here, for the first time, that the Brazilian Sicarius ornatus spider contains active Sphingomyelinase D and is able to cause haemolysis and keratinocyte cell death similar to the South American Loxosceles species, harmful effects that are associated with the presence of active SMases D. These results may suggest that envenomation by this Sicarius spider has the potential to cause similar pathological events as that caused by Loxosceles envenomation. Our results also suggest that, in addition to the interspecific differences, intraspecific variations in the venoms composition may play a role in the toxic potential of the New World Sicarius venoms species.

The spider family Sicariidae includes two genera, Sicarius and Loxosceles. These spiders' venoms share a common characteristic, i.e., the presence of Sphingomyelinases D (SMase D). This toxin is the main component responsible for the local and systemic effects observed in loxoscelism. In the present study, we have investigated the toxic potential of male and female Brazilian Sicarius ornatus spider venoms and compared these with the venoms from Loxosceles species of medical importance in Brazil. We show here that Brazilian Sicarius ornatus venom is endowed with all toxic in vitro and ex vivo biological properties ascribed to the venoms from Loxosceles species, including the abilities to hydrolyze sphingomyelin and to induce keratinocyte cell death and complement dependent haemolysis, detrimental effects that were positively associated with the presence of active SMases D and with in vivo pathologies. Therefore, the venom of Sicarius ornatus spider can potentially lead to a similar pathology as that observed for Loxosceles envenomation.