Crotoxin Isolated from Crotalus durissus terrificus Venom Modulates the Functional Activity of Dendritic Cells via Formyl Peptide Receptors

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.

Effect of animal venom toxins on the main links of the homeostasis of mammals (Review)

The human body is affected by environmental factors. The dynamic balance between the organism and its environment results from the influence of natural, anthropogenic and social aspects. The factors of exogenous origin determine development of adaptive changes. The present article summarises the mechanisms of animal venom toxins and homeostasis disruption in the body of mammals. The mechanisms underlying pathological changes are associated with shifts in biochemical reactions. Components of the immune, nervous and endocrine systems are key in the host defense and adaptation processes in response to venom by triggering signalling pathways (PI3kinase pathway, arachidonic acid cascade). Animal venom toxins initiate the development of inflammatory processes, the synthesis of pro-inflammatory mediators (cytokines), ROS, proteolytic enzymes, activate the migration of leukocytes and macrophages. Keratinocytes and endothelial cells act as protective barriers under the action of animal venom toxins on the body of mammals. In addition, the formation of pores in cell membranes, structural changes in cell ion channels are characteristic of the action of animal venom toxins.

A Review of Rattlesnake Venoms

Venom components are invaluable in biomedical research owing to their specificity and potency. Many of these components exist in two genera of rattlesnakes, Crotalus and Sistrurus, with high toxicity and proteolytic activity variation. This review focuses on venom components within rattlesnakes, and offers a comparison and itemized list of factors dictating venom composition, as well as presenting their known characteristics, activities, and significant applications in biosciences. There are 64 families and subfamilies of proteins present in Crotalus and Sistrurus venom. Snake venom serine proteases (SVSP), snake venom metalloproteases (SVMP), and phospholipases A2 (PLA2) are the standard components in Crotalus and Sistrurus venom. Through this review, we highlight gaps in the knowledge of rattlesnake venom; there needs to be more information on the venom composition of three Crotalus species and one Sistrurus subspecies. We discuss the activity and importance of both major and minor components in biomedical research and drug development.

Affected inflammation-related signaling pathways in snake envenomation: A recent insight

Snake envenomation is well known to cause grievous pathological signs, including haemorrhagic discharge, necrosis, and respiratory distress. However, inflammatory reactions are also common envenoming manifestations that lead to successive damage, such as oedema, ulceration, lymphadenectasis, systemic inflammatory response syndrome (SIRS) and even multiple organ dysfunction syndrome (MODS). Interference with the inflammatory burst is hence important in the clinical treatment of snake envenomation. Here, we summarize the typical snake toxins (or venoms) that cause inflammatory reactions and the underlying signaling pathways. In brief, inflammatory reactions are usually triggered by snake venom phospholipase A2 (svPLA2), snake venom metalloprotease (SVMP), snake venom serine protease (SVSP) and C-type lectin/snaclec (CTL) as well as disintegrin (DIS) via multiple signaling pathways. They are nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 3 (NLRP3), nuclear factor kappa-B (NF-κB), mitogen-activated protein kinase (MAPK), janus kinase/signal transducer and activator of transcription (JAK-STAT) and phosphoinositide 3-Kinase/protein kinase B (PI3K/PKB also called PI3K-AKT) signaling pathways. Activation of these pathways promotes the expression of pro-inflammatory molecules such as cytokines, especially interleukin-1β (IL-1β) which causes further inflammatory cascades and manifestations, such as swelling, fever, pain, and severe complications. Remarkably, almost half of introduced snake toxins (or venoms) have anti-inflammatory effects through blocking these pathways and suppressing the expression of pro-inflammatory molecules. Investigation of affected inflammation-related signaling pathways is meaningful to achieve better clinical treatment.

Immune response to neurotoxic South American snake venoms

South American rattlesnakes (Crotalus durissus spp) and coral snakes (Micrurus sp) venoms are characterized by inducing a limited inflammatory innate immune response, in contrast to Bothrops sp snake venoms which exert a prominent inflammatory activity. Some Crotalus durissus spp venoms, in addition, exert immunosuppressive activities that hamper the development of neutralizing antibodies in animals immunized for antivenom production. Micrurus sp venoms are rich in low molecular mass neurotoxins that elicit a limited immune response. These characteristics make it difficult to generate antivenoms of high neutralizing activity. Therefore, the study of the mechanisms operating behind this limited immune response to venoms is relevant from both fundamental and practical perspectives. This review summarizes key aspects of the immune response to these venoms and discusses some pending challenges to further understand these phenomena and to improve antivenom production.

Formyl peptide receptors are involved in CTX-induced impairment of lymphocyte functions

Crotoxin (CTX) is a neurotoxin that is isolated from the venom of Crotalus durissus terrificus, which displays immunomodulatory, anti-inflammatory, and anti-tumoral effects. Previous research has demonstrated that CTX promotes the adherence of leukocytes to the endothelial cells in blood microcirculation and the high endothelial venules of lymph nodes, which reduces the number of blood cells and lymphocytes. Studies have also shown that these effects are mediated by lipoxygenase-derived mediators. However, the exact lipoxygenase-derived eicosanoid involved in the CTX effect on lymphocytes is yet to be characterized. As CTX stimulates lipoxin-derived mediators from macrophages and lymphocyte effector functions could be modulated by activating formyl peptide receptors, we aimed to investigate whether these receptors were involved in CTX-induced redistribution and functions of lymphocytes in rats. We used male Wistar rats treated with CTX to demonstrate that Boc2 (butoxycarbonyl-Phe-Leu-Phe-Leu-Phe), an antagonist of formyl peptide receptors, prevented CTX-induced decrease in the number of circulating lymphocytes and increased the expression of the lymphocyte adhesion molecule LFA1. CTX reduced the T and B lymphocyte functions, such as lymphocyte proliferation in response to the mitogen Concanavalin A and antibody production in response to BSA immunization, respectively, which was prevented by the administration of Boc2. Importantly, mesenteric lymph node lymphocytes from CTX-treated rats showed an increased release of 15-epi-LXA₄. These results indicate that formyl peptide receptors mediate CTX-induced redistribution of lymphocytes and that 15-epi-LXA₄ is a key mediator of the immunosuppressive effects of CTX.

Biological and Medical Aspects Related to South American Rattlesnake Crotalus durissus (Linnaeus, 1758): A View from Colombia

In Colombia, South America, there is a subspecies of the South American rattlesnake Crotalus durissus, C. d. cumanensis, a snake of the Viperidae family, whose presence has been reduced due to the destruction of its habitat. It is an enigmatic snake from the group of pit vipers, venomous, with large articulated front fangs, special designs on its body, and a characteristic rattle on its tail. Unlike in Brazil, the occurrence of human envenomation by C. durisus in Colombia is very rare and contributes to less than 1% of envenomation caused by snakes. Its venom is a complex cocktail of proteins with different biological effects, which evolved with the purpose of paralyzing the prey, killing it, and starting its digestive process, as well as having defense functions. When its venom is injected into humans as the result of a bite, the victim presents with both local tissue damage and with systemic involvement, including a diverse degree of neurotoxic, myotoxic, nephrotoxic, and coagulopathic effects, among others. Its biological effects are being studied for use in human health, including the possible development of analgesic, muscle relaxant, anti-inflammatory, immunosuppressive, anti-infection, and antineoplastic drugs. Several groups of researchers in Brazil are very active in their contributions in this regard. In this work, a review is made of the most relevant biological and medical aspects related to the South American rattlesnake and of what may be of importance for a better understanding of the snake C. d. cumanensis, present in Colombia and Venezuela.

Modern venomics-Current insights, novel methods, and future perspectives in biological and applied animal venom research

Venoms have evolved >100 times in all major animal groups, and their components, known as toxins, have been fine-tuned over millions of years into highly effective biochemical weapons. There are many outstanding questions on the evolution of toxin arsenals, such as how venom genes originate, how venom contributes to the fitness of venomous species, and which modifications at the genomic, transcriptomic, and protein level drive their evolution. These questions have received particularly little attention outside of snakes, cone snails, spiders, and scorpions. Venom compounds have further become a source of inspiration for translational research using their diverse bioactivities for various applications. We highlight here recent advances and new strategies in modern venomics and discuss how recent technological innovations and multi-omic methods dramatically improve research on venomous animals. The study of genomes and their modifications through CRISPR and knockdown technologies will increase our understanding of how toxins evolve and which functions they have in the different ontogenetic stages during the development of venomous animals. Mass spectrometry imaging combined with spatial transcriptomics, in situ hybridization techniques, and modern computer tomography gives us further insights into the spatial distribution of toxins in the venom system and the function of the venom apparatus. All these evolutionary and biological insights contribute to more efficiently identify venom compounds, which can then be synthesized or produced in adapted expression systems to test their bioactivity. Finally, we critically discuss recent agrochemical, pharmaceutical, therapeutic, and diagnostic (so-called translational) aspects of venoms from which humans benefit.

Biological Effects of Animal Venoms on the Human Immune System

Venoms are products of specialized glands and serve many living organisms to immobilize and kill prey, start digestive processes and act as a defense mechanism. Venoms affect different cells, cellular structures and tissues, such as skin, nervous, hematological, digestive, excretory and immune systems, as well as the heart, among other structures. Components of both the innate and adaptive immune systems can be stimulated or suppressed. Studying the effects on the cells and molecules produced by the immune system has been useful in many biomedical fields. The effects of venoms can be the basis for research and development of therapeutic protocols useful in the modulation of the immunological system, including different autoimmune diseases. This review focuses on the understanding of biological effects of diverse venom on the human immune system and how some of their components can be useful for the study and development of immunomodulatory drugs.

Correlating biological activity to thermo-structural analysis of the interaction of CTX with synthetic models of macrophage membranes

The important pharmacological actions of Crotoxin (CTX) on macrophages, the main toxin in the venom of Crotalus durissus terrificus, and its important participation in the control of different pathophysiological processes, have been demonstrated. The biological activities performed by macrophages are related to signaling mediated by receptors expressed on the membrane surface of these cells or opening and closing of ion channels, generation of membrane curvature and pore formation. In the present work, the interaction of the CTX complex with the cell membrane of macrophages is studied, both using biological cells and synthetic lipid membranes to monitor structural alterations induced by the protein. Here we show that CTX can penetrate THP-1 cells and induce pores only in anionic lipid model membranes, suggesting that a possible access pathway for CTX to the cell is via lipids with anionic polar heads. Considering that the selectivity of the lipid composition varies in different tissues and organs of the human body, the thermostructural studies presented here are extremely important to open new investigations on the biological activities of CTX in different biological systems.

Inflammatory Effects of Bothrops Phospholipases A2: Mechanisms Involved in Biosynthesis of Lipid Mediators and Lipid Accumulation

Phospholipases A₂s (PLA₂s) constitute one of the major protein groups present in the venoms of viperid and crotalid snakes. Snake venom PLA₂s (svPLA₂s) exhibit a remarkable functional diversity, as they have been described to induce a myriad of toxic effects. Local inflammation is an important characteristic of snakebite envenomation inflicted by viperid and crotalid species and diverse svPLA₂s have been studied for their proinflammatory properties. Moreover, based on their molecular, structural, and functional properties, the viperid svPLA₂s are classified into the group IIA secreted PLA₂s, which encompasses mammalian inflammatory sPLA₂s. Thus, research on svPLA₂s has attained paramount importance for better understanding the role of this class of enzymes in snake envenomation and the participation of GIIA sPLA₂s in pathophysiological conditions and for the development of new therapeutic agents. In this review, we highlight studies that have identified the inflammatory activities of svPLA₂s, in particular, those from Bothrops genus snakes, which are major medically important snakes in Latin America, and we describe recent advances in our collective understanding of the mechanisms underlying their inflammatory effects. We also discuss studies that dissect the action of these venom enzymes in inflammatory cells focusing on molecular mechanisms and signaling pathways involved in the biosynthesis of lipid mediators and lipid accumulation in immunocompetent cells.

A Meta-Analysis of the Protein Components in Rattlesnake Venom

The specificity and potency of venom components give them a unique advantage in developing various pharmaceutical drugs. Though venom is a cocktail of proteins, rarely are the synergy and association between various venom components studied. Understanding the relationship between various components of venom is critical in medical research. Using meta-analysis, we observed underlying patterns and associations in the appearance of the toxin families. For Crotalus, Dis has the most associations with the following toxins: PDE; BPP; CRL; CRiSP; LAAO; SVMP P-I and LAAO; SVMP P-III and LAAO. In Sistrurus venom, CTL and NGF have the most associations. These associations can predict the presence of proteins in novel venom and understand synergies between venom components for enhanced bioactivity. Using this approach, the need to revisit the classification of proteins as major components or minor components is highlighted. The revised classification of venom components is based on ubiquity, bioactivity, the number of associations, and synergies. The revised classification can be expected to trigger increased research on venom components, such as NGF, which have high biomedical significance. Using hierarchical clustering, we observed that the genera's venom compositions were similar, based on functional characteristics rather than phylogenetic relationships.

Formyl Peptide Receptor (FPR)1 Modulation by Resveratrol in an LPS-Induced Neuroinflammatory Animal Model

Among therapeutic approaches that have been investigated, targeting of receptors implicated in managing neuroinflammation has been described. One such family of receptors comprises the formyl peptide receptors (FPRs) whose ligands could play a role in host defense. The murine FPR gene family includes at least six members while in humans there are only three. The two most important members are the Fpr1 and Fpr2. Fpr1encodes murine FPR1, which is considered the murine orthologue of human FPR. Resveratrol, a non-flavonoid polyphenol rich in red wine and grapes, apart from its beneficial health effects and anti-inflammatory properties, has been reported to reduce neuroinflammation in different neurodegenerative disease models. Resveratrol anti-inflammatory responses involve the activation of the protein deacetylase sirtuin 1 (SIRT1) gene. In this work we have investigated in an LPS-based murine model of neuroinflammation the role of FPR1, examining not only if this receptor undergoes a reduction of its expression during neuroinflammation, but also whether treatment with resveratrol was able to modulate its expression leading to an amelioration of neuroinflammatory picture in a murine model of neuroinflammation. Results of this work showed that FPR1 together with SIRT1 resulted upregulated by resveratrol treatment and that this increase is associated with an amelioration of the neuroinflammatory picture, as demonstrated by the induction of IL-10 and IL1-RA expression and the downregulation of proinflammatory mediators, such as TNF-α and IL-1β. The expression and the modulation of FPR1 by resveratrol may be evaluated in order to propose a novel anti-inflammatory and pro-resolving therapeutic approach for the reduction of the detrimental effects associated with neuro-inflammation based neurodegenerative diseases and also as a promising strategy to promote human health by a diet rich in antioxidative bioactive compounds.

Immunomodulatory properties of molecules from animal venoms

The immune system can amplify or decrease the strength of its response when it is stimulated by chemical or biological substances that act as immunostimulators, immunosuppressants, or immunoadjuvants. Immunomodulation is a progressive approach to treat a diversity of pathologies with promising results, including autoimmune disorders and cancer. Animal venoms are a mixture of chemical compounds that include proteins, peptides, amines, salts, polypeptides, enzymes, among others, which produce the toxic effect. Since the discovery of captopril in the early 1980s, other components from snakes, spiders, scorpions, and marine animal venoms have been demonstrated to be useful for treating several human diseases. The valuable progress in fields such as venomics, molecular biology, biotechnology, immunology, and others has been crucial to understanding the interaction of toxins with the immune system and its application on immune pathologies. More in-depth knowledge of venoms' components and multi-disciplinary studies could facilitate their transformation into effective novel immunotherapies. This review addresses advances and research of molecules from venoms that have immunomodulatory properties.

Biomedical applications of snake venom: from basic science to autoimmunity and rheumatology

Snake venoms have components with diverse biological actions that are extensively studied to identify elements that may be useful in biomedical sciences. In the field of autoimmunity and rheumatology, various findings useful for the study of diseases and potential drug development have been reported. The study of disintegrins, proteins that block the action of integrins, has been useful for the development of antiplatelet agents and principles for the development of immunosuppressants and antineoplastics. Several proteins in snake venoms act on the coagulation cascade, activating factors that have allowed the development of tests for the study of coagulation, including Russell's viper venom time, which is useful in the diagnosis of antiphospholipid syndrome. Neurotoxins with either pre- or postsynaptic effects have been used to study neurogenic synapses and neuromuscular plaques and the development of analgesics, muscle relaxants and drugs for neurodegenerative diseases. Various components act by inhibiting cells and proteins of the immune system, which will allow the development of anti-inflammatory and immunosuppressive drugs. This review summarizes the usefulness of the components of snake venoms in the fields of autoimmunity and rheumatology, which can serve as a basis for diverse translational research.

Role of crotoxin in coagulation: novel insights into anticoagulant mechanisms and impairment of inflammation-induced coagulation

Background:

Snake venom phospholipases A₂ (svPLA₂) are biologically active toxins, capable of triggering and modulating a wide range of biological functions. Among the svPLA₂s, crotoxin (CTX) has been in the spotlight of bioprospecting research due to its role in modulating immune response and hemostasis. In the present study, novel anticoagulant mechanisms of CTX, and the modulation of inflammation-induced coagulation were investigated.

Methods:

CTX anticoagulant activity was evaluated using platelet poor plasma (PPP) and whole blood (WB), and also using isolated coagulation factors and complexes. The toxin modulation of procoagulant and pro-inflammatory effects was evaluated using the expression of tissue factor (TF) and cytokines in lipopolysaccharide (LPS)-treated peripheral blood mononuclear cells (PBMC) and in WB.

Results:

The results showed that CTX impaired clot formation in both PPP and WB, and was responsible for the inhibition of both intrinsic (TF/factor VIIa) and extrinsic (factor IXa/factor VIIIa) tenase complexes, but not for factor Xa and thrombin alone. In addition, the PLA₂ mitigated the prothrombinase complex by modulating the coagulation phospholipid role in the complex. In regards to the inflammation-coagulation cross talk, the toxin was capable of reducing the production of the pro-inflammatory cytokines IL-1β, IL-6 and TNF-α, and was followed by decreased levels of TF and procoagulant activity from LPS-treated PBMC either isolated or in WB.

Conclusion:

The results obtained in the present study recognize the toxin as a novel medicinal candidate to be applied in inflammatory diseases with coagulation disorders.

Crystal Structure of Isoform CBd of the Basic Phospholipase A2 Subunit of Crotoxin: Description of the Structural Framework of CB for Interaction with Protein Targets

Crotoxin, from the venom of the South American rattlesnake Crotalus durissus terrificus, is a potent heterodimeric presynaptic β-neurotoxin that exists in individual snake venom as a mixture of isoforms of a basic phospholipase A₂ (PLA₂) subunit (CBa₂, CBb, CBc, and CBd) and acidic subunit (CA_1-4). Specific natural mutations in CB isoforms are implicated in functional differences between crotoxin isoforms. The three-dimensional structure of two individual CB isoforms (CBa₂, CBc), and one isoform in a crotoxin (CA₂CBb) complex, have been previously reported. This study concerns CBd, which by interaction with various protein targets exhibits many physiological or pharmacological functions. It binds with high affinity to presynaptic receptors showing neurotoxicity, but also interacts with human coagulation factor Xa (hFXa), exhibiting anticoagulant effect, and acts as a positive allosteric modulator and corrector of mutated chloride channel, cystic fibrosis transmembrane conductance regulator (CFTR), implicated in cystic fibrosis. Thus, CBd represents a novel family of agents that have potential in identifying new drug leads related to anticoagulant and anti-cystic fibrosis function. We determined here the X-ray structure of CBd and compare it with the three other natural isoforms of CB. The structural role of specific amino acid variations between CB isoforms are analyzed and the structural framework of CB for interaction with protein targets is described.

Venom of the Red-Bellied Black Snake Pseudechis porphyriacus Shows Immunosuppressive Potential

Venoms act with remarkable specificity upon a broad diversity of physiological targets. Venoms are composed of proteins, peptides, and small molecules, providing the foundation for the development of novel therapeutics. This study assessed the effect of venom from the red-bellied black snake (Pseudechis porphyriacus) on human primary leukocytes using bead-based flow cytometry, mixed lymphocyte reaction, and cell viability assays. We show that venom treatment had a significant immunosuppressive effect, inhibiting the secretion of interleukin (IL)-2 and tumor necrosis factor (TNF) from purified human T cells by 90% or greater following stimulation with mitogen (phorbol 12-myristate 13-acetate and ionomycin) or via cluster of differentiation (CD) receptors, CD3/CD28. In contrast, venom treatment did not inhibit TNF or IL-6 release from antigen-presenting cells stimulated with lipopolysaccharide. The reduced cytokine release from T cells was not associated with inhibition of T cell proliferation or reduction of cell viability, consistent with an anti-inflammatory mechanism unrelated to the cell cycle. Deconvolution of the venom using reverse-phase HPLC identified four fractions responsible for the observed immunosuppressive activity. These data suggest that compounds from P. porphyriacus venom may be potential drug leads for T cell-associated conditions such as graft versus host disease, rheumatoid arthritis, and inflammatory bowel disease.

Immunotoxicological effects triggered by the rattlesnake Crotalus durissus cumanensis, mapanare (Bothrops colombiensis) venoms and its purified fractions on spleen and lymph nodes cells

Purpose: The snakes in Venezuela vary in their different venom composition amid the species. In this sense, studies have been carried out elucidating mechanisms related to their immunostimulatory and/or immunosuppressive effects in vitro, measuring inhibition or stimulation on the mice spleen and lymph nodes lymphocytes under the rattlesnake (Crotalus durissus cumanensis) (Cdc) and mapanare (Bothrops colombiensis) crude venoms actions, and also its purified fraction crotoxin (CTX) (Cdc) and a semi-purified fraction (SPF) (Bc) activities. Material and methods: The stimulation of lymphocyte proliferation was carried out in the presence or absence of Concanavalin A (ConA) and lipopolysaccharides (LPS). Results: The lymphocyte response was measured by the Alamar Blue^® (Resazurin) assay, observing that the Crotalus crude venom increased basal proliferation in the spleen and lymph nodes, being also increased with ConA and LPS. CTX slightly decreased the proliferative response in the presence of mitogens. Both Bc venom and its SPF fraction had no significant effect on basal proliferation in the spleen and lymph nodes, but a decrease in the response with ConA was observed. These results suggest that CTX has an inhibitory action on lymphocyte proliferation, while Cdc crude venom has a stimulatory action on T and B cell populations. Bothrops colombiensis venom had no effect on these two types of cell populations. As it is known, lymphocytes are cells of enormous flexibility and can operate in diverse aspects, warranting that the correct immune response persists controlled. Conclusions: These results suggested that these different toxins can modulate lymphocyte functional activation toward an inhibitory or stimulatory state.

Crotoxin down-modulates pro-inflammatory cells and alleviates pain on the MOG35-55-induced experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis

Multiple sclerosis (MS) is a Central Nervous System inflammatory demyelinating disease that has as primary symptoms losses of sensory and motor functions, including chronic pain. To date, however, few studies have investigated the mechanisms of chronic pain in animal models of MS since locomotor impairments render difficult its evaluation. It was previously demonstrated that in the MOG_35-55-induced EAE, an animal model of MS, the hypernociception appears before the onset of motor disability, allowing for the study of these two phenomena separately. Here, we evaluated the effect of crotoxin (CTX), a neurotoxin isolated from the Crotalus durissus terrificus snake venom that displays, at non-toxic dose, antinociceptive, anti-inflammatory and immunomodulatory effects, in the pain and in symptoms progression of EAE. The pain threshold of female C57BL/6 mice decreased at the 4th day after immunization, while the first sign of disease appeared around the 11st-12nd days, coinciding with the onset of motor abnormalities. CTX (40 µg/kg, s.c.) administered in a single dose on the 5th day after immunization, induced a long-lasting analgesic effect (5 days), without interfering with the clinical signs of the disease. On the other hand, when crotoxin was administered for 5 consecutive days, from 5th-9th day after immunization, it induced analgesia and also reduced EAE progression. The antinociceptive effect of crotoxin was blocked by Boc-2 (0.5 mg/kg, i.p.), a selective antagonist of formyl peptide receptors, by NDGA (30 μg/kg, i.p.), a lipoxygenase inhibitor and by atropine sulfate (10 mg/kg, i.p.), an antagonist of muscarinic receptors, administered 30 min before CTX. CTX was also effective in decreasing EAE clinical signs even when administered after its onset. Regarding the interactions between neurons and immunocompetent cells, CTX, in vitro, was able to reduce T cell proliferation, decreasing Th1 and Th17 and increasing Treg cell differentiation. Furthermore, in EAE model, the treatment with 5 consecutive doses of CTX inhibited IFN-γ-producing T cells, GM-CSF-producing T cells, reduced the frequency of activated microglia/macrophages within the CNS and decreased the number of migrating cell to spinal cord and cerebellum at the peak of the disease. These results suggest that CTX is a potential treatment not only for pain alteration but also for clinical progression induced by the disease as well as an useful tool for the development of new therapeutic approaches for the multiple sclerosis control.

Crotoxin Conjugated to SBA-15 Nanostructured Mesoporous Silica Induces Long-Last Analgesic Effect in the Neuropathic Pain Model in Mice

Neuropathic pain is a disease caused by structural and functional plasticity in central and peripheral sensory pathways that produce alterations in nociceptive processing. Currently, pharmacological treatment for this condition remains a challenge. Crotoxin (CTX), the main neurotoxin of Crotalus durissus terrificus rattlesnake venom, has well described prolonged anti-inflammatory and antinociceptive activities. In spite of its potential benefits, the toxicity of CTX remains a limiting factor for its use. SBA-15 is an inert nanostructured mesoporous silica that, when used as a vehicle, may reduce toxicity and potentiate the activity of different compounds. Based on this, we propose to conjugate crotoxin with SBA-15 (CTX:SBA-15) in order to investigate if when adsorbed to silica, CTX would have its toxicity reduced and its analgesic effect enhanced in neuropathic pain induced by the partial sciatic nerve ligation (PSNL) model. SBA-15 enabled an increase of 35% of CTX dosage. Treatment with CTX:SBA-15 induced a long-lasting reduction of mechanical hypernociception, without modifying the previously known pathways involved in antinociception. Moreover, CTX:SBA-15 reduced IL-6 and increased IL-10 levels in the spinal cord. Surprisingly, the antinociceptive effect of CTX:SBA-15 was also observed after oral administration. These data indicate the potential use of the CTX:SBA-15 complex for neuropathic pain control and corroborates the protective potential of SBA-15.

Crotalus durissus ruruima Snake Venom and a Phospholipase A2 Isolated from This Venom Elicit Macrophages to Form Lipid Droplets and Synthesize Inflammatory Lipid Mediators

Viper snake Crotalus durissus ruruima (Cdr) is a subspecies found in northern area of Brazil. Among the snakes of Crotalus genus subspecies, the venom of Cdr presents highest level of crotoxin, which is the major component of Crotalus snake venoms, formed by two subunits (crotapotin and a phospholipase A₂ named CBr) and presents potent neurotoxic activity. Curiously, the venom of C. d. ruruima (CdrV) is better neutralized by antibothropic than by anticrotalic serum, strongly suggesting that this venom has similarities with venom of Bothrops genus snakes with regard to the ability to induce inflammation. Macrophages are cells with a central role in inflammatory and immunological responses. Upon inflammatory stimuli, these cells exhibit increased numbers of lipid droplets, which are key organelles in the synthesis and release of inflammatory mediators. However, the effects of CdrV and CBr in macrophage functions are unknown. We herein investigated the ability of CdrV and CBr to activate macrophages with focus on the formation of lipid droplets (LDs), synthesis of lipid mediators, and mechanisms involved in these effects. The involvement of LDs in PGE₂ biosynthesis was also assessed. Stimulation of murine macrophages with CdrV and CBr induced an increased number of LDs and release of prostanoids (PGE₂, PGD₂, and TXB₂). Neither CdrV nor CBr induced the expression of COX-1 and COX-2 by macrophages. LDs induced by both CdrV and CBr are associated to PLIN2 recruitment and expression and were shown to be dependent on COX-1, but not COX-2 activity. Moreover, PGE₂ colocalized to CdrV- and CBr-induced LDs, revealing the role of these organelles as sites for the synthesis of prostanoids. These results evidence, for the first time, the ability of a whole snake venom to induce formation of LDs and the potential role of these organelles for the production of inflammatory mediators during envenomation by Crotalus snakes.

Immunotherapeutic potential of Crotoxin: anti-inflammatory and immunosuppressive properties

For the past 80 years, Crotoxin has become one of the most investigated isolated toxins from snake venoms, partially due to its major role as the main toxic component in the venom of the South American rattlesnake Crotalus durissus terrificus. However, in the past decades, progressive studies have led researchers to shift their focus on Crotoxin, opening novel perspectives and applications as a therapeutic approach. Although this toxin acts on a wide variety of biological events, the modulation of immune responses is considered as one of its most relevant behaviors. Therefore, the present review describes the scientific investigations on the capacity of Crotoxin to modulate anti-inflammatory and immunosuppressive responses, and its application as a medicinal immunopharmacological approach. In addition, this review will also discuss its mechanisms, involving cellular and molecular pathways, capable of improving pathological alterations related to immune-associated disorders.