Role of crotoxin, a phospholipase A2 isolated from Crotalus durissus terrificus snake venom, on inflammatory and immune reactions

Crotoxin Modulates Macrophage Phenotypic Reprogramming

Macrophage plasticity is a fundamental feature of the immune response since it favors the rapid and adequate change of the functional phenotype in response to the pathogen or the microenvironment. Several studies have shown that Crotoxin (CTX), the major toxin of the Crotalus durissus terrificus snake venom, has a long-lasting antitumor effect both in experimental models and in clinical trials. In this study, we show the CTX effect on the phenotypic reprogramming of macrophages in the mesenchymal tumor microenvironment or those obtained from the peritoneal cavity of healthy animals. CTX (0.9 or 5 μg/animal subcutaneously) administered concomitantly with intraperitoneal inoculation of tumor cells (1 × 107/0.5 mL, injected intraperitoneally) of Ehrlich Ascitic Tumor (EAT) modulated the macrophages phenotype (M1), accompanied by increased NO• production by cells from ascites, and was evaluated after 13 days. On the other hand, in healthy animals, the phenotypic profile of macrophages was modulated in a dose-dependent way at 0.9 μg/animal: M1 and at 5.0 μg/animal: M2; this was accompanied by increased NO• production by peritoneal macrophages only for the dose of 0.9 μg/animal of CTX. This study shows that a single administration of CTX interferes with the phenotypic reprogramming of macrophages, as well as with the secretory state of cells from ascites, influencing events involved with mesenchymal tumor progression. These findings may favor the selection of new therapeutic targets to correct compromised immunity in different systems.

Pathophysiological and Clinical Significance of Crotalus durissus cascavella Venom-Induced Pulmonary Impairment in a Murine Model

Crotalus venom has broad biological activity, including neurotoxic, myotoxic, hematologic, and cytotoxic compounds that induce severe systemic repercussions. We evaluated the pathophysiological and clinical significance of Crotalus durissus cascavella (Cdc) venom-induced pulmonary impairment in mice. We conducted a randomized experimental study, involving 72 animals intraperitoneally inoculated with saline solution in the control group (CG), as well as venom in the experimental group (EG). The animals were euthanized at predetermined intervals (1 h, 3 h, 6 h, 12 h, 24 h, and 48 h), and lung fragments were collected for H&E and Masson histological analysis. The CG did not present inflammatory alterations in pulmonary parenchyma. In the EG, interstitial and alveolar swelling, necrosis, septal losses followed by alveolar distensions, and areas of atelectasis in the pulmonary parenchyma were observed after three hours. The EG morphometric analysis presented pulmonary inflammatory infiltrates at all time intervals, being more significant at three and six (p = 0.035) and six and 12 h (p = 0.006). The necrosis zones were significant at intervals of one and 24 h (p = 0.001), one and 48 h (p = 0.001), and three and 48 h (p = 0.035). Crotalus durissus cascavella venom induces a diffuse, heterogeneous, and acute inflammatory injury in the pulmonary parenchyma, with potential clinical implications for respiratory mechanics and gas exchange. The early recognition and prompt treatment of this condition are essential to prevent further lung injury and to improve outcomes.

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.

Crotoxin modulates inflammation and macrophages' functions in a murine sepsis model

Sepsis is a syndrome of physiological and biochemical abnormalities induced by an infection that represents a major public health concern. It involves the early activation of inflammatory responses. Crotoxin (CTX), the major toxin of the South American rattlesnake Crotalus durissus terrificus venom, presents longstanding anti-inflammatory properties. Since immune system modulation may be a strategic target in sepsis management, and macrophages' functional and secretory activities are related to the disease's progression, we evaluated the effects of CTX on macrophages from septic animals. Balb/c male mice submitted to cecal ligation and puncture (CLP) were treated with CTX (0.9 μg/animal, subcutaneously) 1 h after the procedure and euthanized after 6 h. We used plasma samples to quantify circulating cytokines and eicosanoids. Bone marrow differentiated macrophages (BMDM) were used to evaluate the CTX effect on macrophages' functions. Our data show that CTX administration increased the survival rate of the animals from 40% to 80%. Septic mice presented lower plasma concentrations of IL-6 and TNF-α after CTX treatment, and higher concentrations of LXA₄, PGE_2, and IL-1β. No effect was observed in IL-10, IFN-γ, and RD1 concentrations. BMDM from septic mice treated with CTX presented decreased capacity of E. coli phagocytosis, but sustained NO and H₂O₂ production. We also observed higher IL-6 concentration in the culture medium of BMDM from septic mice, and CTX induced a significant reduction. CTX treatment increased IL-10 production by macrophages as well. Our data show that the protective effect of CTX in sepsis mortality involves modulation of macrophage functions and inflammatory mediators' production.

Bothrops bilineatus: An Arboreal Pitviper in the Amazon and Atlantic Forest

The two-striped forest-pitviper (Bothrops bilineatus) is an arboreal snake that is currently represented by two subspecies (B. b. bilineatus and B. b. smaragdinus) that comprise a species complex, and its distribution is in the Amazon and the Atlantic Forest. The rarity of encounters with this snake is reflected in the low occurrence of cases of snakebites throughout its geographic distribution and the resulting low number of published clinical reports. However, in some areas, B. bilineatus proves to be more frequent and causes envenomations in a greater proportion. Herein, we review the main aspects of the species complex B. bilineatus, including its biology, ecology, taxonomy, morphology, genetic and molecular studies, geographic distribution, conservation status, venom, pathophysiology and clinical aspects, and epidemiology. In addition, the different antivenoms available for the treatment of envenomations caused by B. bilineatus are presented along with suggestions for future studies that are needed for a better understanding of the snakebites caused by this snake.

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.

The modulatory effect of crotoxin and its phospholipase A2 subunit from Crotalus durissus terrificus venom on dendritic cells interferes with the generation of effector CD4+ T lymphocytes

Dendritic Cells (DCs) direct either cellular immune response or tolerance. The crotoxin (CTX) and its CB subunit (phospholipase A₂) isolated from Crotalus durissus terrificus rattlesnake venom modulate the DC maturation induced by a TLR4 agonist. Here, we analyzed the potential effect of CTX and CB subunit on the functional ability of DCs to induce anti-ovalbumin (OVA) immune response. Thus, CTX and CB inhibited the maturation of OVA/LPS-stimulated BM-DCs from BALB/c mice, which means inhibition of costimulatory and MHC-II molecule expression and proinflammatory cytokine secretion, accompanied by high expression of ICOSL, PD-L1/2, IL-10 and TGF-β mRNA expression. The addition of CTX and CB in cultures of BM-DCs incubated with ConA or OVA/LPS inhibited the proliferation of CD3⁺ or CD4⁺T cells from OVA-immunized mice. In in vitro experiment of co-cultures of purified CD4⁺T cells of DO11.10 mice with OVA/LPS-stimulated BM-DCs, the CTX or CB induced lowest percentage of Th1 and Th2 and CTX induced increase of Treg cells. In in vivo, CTX and CB induced lower percentage of CD4⁺IFNγ⁺ and CD4⁺IL-4⁺ cells, as well as promoted CD4⁺CD25⁺IL-10⁺ population in OVA/LPS-immunized mice. CTX in vivo also inhibited the maturation of DCs. Our findings demonstrate that the modulatory action of CTX and CB on DCs interferes with the generation of adaptive immunity and, therefore contribute for the understanding of the mechanisms involved in the generation of cellular immunity, which can be useful for new therapeutic approaches for immune disorders.

Effects of venoms on neutrophil respiratory burst: a major inflammatory function

Neutrophils play a pivotal role in innate immunity and in the inflammatory response. Neutrophils are very motile cells that are rapidly recruited to the inflammatory site as the body first line of defense. Their bactericidal activity is due to the release into the phagocytic vacuole, called phagosome, of several toxic molecules directed against microbes. Neutrophil stimulation induces release of this arsenal into the phagosome and induces the assembly at the membrane of subunits of the NAPDH oxidase, the enzyme responsible for the production of superoxide anion that gives rise to other reactive oxygen species (ROS), a process called respiratory burst. Altogether, they are responsible for the bactericidal activity of the neutrophils. Excessive activation of neutrophils can lead to extensive release of these toxic agents, inducing tissue injury and the inflammatory reaction. Envenomation, caused by different animal species (bees, wasps, scorpions, snakes etc.), is well known to induce a local and acute inflammatory reaction, characterized by recruitment and activation of leukocytes and the release of several inflammatory mediators, including prostaglandins and cytokines. Venoms contain several molecules such as enzymes (phospholipase A2, L-amino acid oxidase and proteases, among others) and peptides (disintegrins, mastoporan, parabutoporin etc.). These molecules are able to stimulate or inhibit ROS production by neutrophils. The present review article gives a general overview of the main neutrophil functions focusing on ROS production and summarizes how venoms and venom molecules can affect this function.

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.

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-Induced Mice Lung Impairment: Role of Nicotinic Acetylcholine Receptors and COX-Derived Prostanoids

Respiratory compromise in Crotalus durissus terrificus (C.d.t.) snakebite is an important pathological condition. Considering that crotoxin (CTX), a phospholipase A₂ from C.d.t. venom, is the main component of the venom, the present work investigated the toxin effects on respiratory failure. Lung mechanics, morphology and soluble markers were evaluated from Swiss male mice, and mechanism determined using drugs/inhibitors of eicosanoids biosynthesis pathway and autonomic nervous system. Acute respiratory failure was observed, with an early phase (within 2 h) characterized by enhanced presence of eicosanoids, including prostaglandin E2, that accounted for the increased vascular permeability in the lung. The alterations of early phase were inhibited by indomethacin. The late phase (peaked 12 h) was marked by neutrophil infiltration, presence of pro-inflammatory cytokines/chemokines, and morphological alterations characterized by alveolar septal thickening and bronchoconstriction. In addition, lung mechanical function was impaired, with decreased lung compliance and inspiratory capacity. Hexamethonium, a nicotinic acetylcholine receptor antagonist, hampered late phase damages indicating that CTX-induced lung impairment could be associated with cholinergic transmission. The findings reported herein highlight the impact of CTX on respiratory compromise, and introduce the use of nicotinic blockers and prostanoids biosynthesis inhibitors as possible symptomatic therapy to Crotalus durissus terrificus snakebite.

Evaluation of systemic inflammatory response and lung injury induced by Crotalus durissus cascavella venom

This study investigated the systemic inflammatory response and mechanism of pulmonary lesions induced by Crotalus durissus cascavella venom in murine in the state of Bahia. In order to investigate T helper Th1, Th2 and Th17 lymphocyte profiles, we measured interleukin (IL) -2, IL-4, IL-6, IL-10, IL-17, tumor necrosis factor (TNF) and interferon gamma (IFN-γ) levels in the peritoneal fluid and macerated lungs of mice and histopathological alterations at the specific time windows of 1h, 3h, 6h, 12h, 24h and 48h after inoculation with Crotalus durissus cascavella venom. The data demonstrated an increase of acute-phase cytokines (IL-6 and TNF) in the first hours after inoculation, with a subsequent increase in IL-10 and IL-4, suggesting immune response modulation for the Th2 profile. The histopathological analysis showed significant morphological alterations, compatible with acute pulmonary lesions, with polymorphonuclear leukocyte (PMN) infiltration, intra-alveolar edema, congestion, hemorrhage and atelectasis. These findings advance our understanding of the dynamics of envenomation and contribute to improve clinical management and antiophidic therapy for individuals exposed to venom.

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.

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

The Crotalus durissus terrificus rattlesnake venom, its main toxin, crotoxin (CTX), and its crotapotin (CA) and phospholipase A₂ (CB) subunits modulate the immune system. Formyl peptide receptors (FPRs) and lipoxin A₄ (LXA₄) are involved in CTX's effect on macrophages and neutrophils. Dendritic cells (DCs) are plasticity cells involved in the induction of adaptive immunity and tolerance maintenance. Therefore, we evaluated the effect of CTX, CA or CB on the maturation of DCs derived from murine bone marrow (BM). According to data, CTX and CB-but not CA-induced an increase of MHC-II, but not costimulatory molecules on DCs. Furthermore, CTX and CB inhibited the expression of costimulatory and MHC-II molecules, secretion of proinflammatory cytokines and NF-κBp65 and p38/ERK1/2-MAPK signaling pathways by LPS-incubated DCs. Differently, CTX and CB induced IL-10, PGE₂ and LXA₄ secretion in LPS-incubated DCs. Lower proliferation and IL-2 secretion were verified in coculture of CD3⁺ cells and DCs incubated with LPS plus CTX or CB compared with LPS-incubated DCs. The effect of CTX and CB on DCs was abolished in cultures incubated with a FPRs antagonist. Hence, CTX and CB exert a modulation on functional activity of DCs; we also checked the involvement the FPR family on cell activities.

Proof of concept for a banding scheme to support risk assessments related to multi-product biologics manufacturing

A banding scheme theory has been proposed to assess the potency/toxicity of biologics and assist with decisions regarding the introduction of new biologic products into existing manufacturing facilities. The current work was conducted to provide a practical example of how this scheme could be applied. Information was identified for representatives from the following four proposed bands: Band A (lethal toxins); Band B (toxins and apoptosis signals); Band C (cytokines and growth factors); and Band D (antibodies, antibody fragments, scaffold molecules, and insulins). The potency/toxicity of the representative substances was confirmed as follows: Band A, low nanogram quantities exert lethal effects; Band B, repeated administration of microgram quantities is tolerated in humans; Band C, endogenous substances and recombinant versions administered to patients in low (interferons), intermediate (growth factors), and high (interleukins) microgram doses, often on a chronic basis; and Band D, endogenous substances present or produced in the body in milligram quantities per day (insulin, collagen) or protein therapeutics administered in milligram quantities per dose (mAbs). This work confirms that substances in Bands A, B, C, and D represent very high, high, medium, and low concern with regard to risk of cross-contamination in manufacturing facilities, thus supporting the proposed banding scheme.

Crotoxin from Crotalus durissus terrificus is able to down-modulate the acute intestinal inflammation in mice

Inflammatory bowel diseases (IBD) is the result of dysregulation of mucosal innate and adaptive immune responses. Factors such as genetic, microbial and environmental are involved in the development of these disorders. Accordingly, animal models that mimic human diseases are tools for the understanding the immunological processes of the IBD as well as to evaluate new therapeutic strategies. Crotoxin (CTX) is the main component of Crotalus durissus terrificus snake venom and has an immunomodulatory effect. Thus, we aimed to evaluate the modulatory effect of CTX in a murine model of colitis induced by 2,4,6- trinitrobenzene sulfonic acid (TNBS). The CTX was administered intraperitoneally 18 hours after the TNBS intrarectal instillation in BALB/c mice. The CTX administration resulted in decreased weight loss, disease activity index (DAI), macroscopic tissue damage, histopathological score and myeloperoxidase (MPO) activity analyzed after 4 days of acute TNBS colitis. Furthermore, the levels of TNF-α, IL-1β and IL-6 were lower in colon tissue homogenates of TNBS-mice that received the CTX when compared with untreated TNBS mice. The analysis of distinct cell populations obtained from the intestinal lamina propria showed that CTX reduced the number of group 3 innate lymphoid cells (ILC3) and Th17 population; CTX decreased IL-17 secretion but did not alter the frequency of CD4+Tbet+ T cells induced by TNBS instillation in mice. In contrast, increased CD4+FoxP3+ cell population as well as secretion of TGF-β, prostaglandin E2 (PGE2) and lipoxin A4 (LXA4) was observed in TNBS-colitis mice treated with CTX compared with untreated TNBS-colitis mice. In conclusion, the CTX is able to modulate the intestinal acute inflammatory response induced by TNBS, resulting in the improvement of clinical status of the mice. This effect of CTX is complex and involves the suppression of the pro-inflammatory environment elicited by intrarectal instillation of TNBS due to the induction of a local anti-inflammatory profile in mice.

Crotalus durissus collilineatus Venom Induces TNF- α and IL-10 Production in Human Peripheral Blood Mononuclear Cells

Snake venom has been the subject of numerous studies in an attempt to find properties and biological effects that may be beneficial to man. In this study we evaluated in vitro the effects of Crotalus durissus terrificus (Cdt) and Crotalus durissus collilineatus (Cdc) venom in human peripheral blood mononuclear cells (PBMCs). At 24 h, a significant decrease of viable cells was observed in cells stimulated with the Cdc venom at 0.0005 mg/mL and 0.005 mg/mL compared to the negative control. At 48 h, a significant decrease of viable cells was observed only in cells stimulated with Cdc venom at 0.005 mg/mL. A significant increase of TNF-α and IL-10 was detected 48 hours after culture of PBMC with Cdc, but not with Cdt venom. The expression of CD69 and PD1 (programmed death-1), activation and regulatory cell markers, on CD8+ and CD8− T cells did not change in the presence of Cdt and Cdc venom. Our results suggest the presence of proinflammatory and anti-inflammatory components in the Cdc venom. Further analysis should be done to identify those Cdc venom components as it has been done for the Cdt venom by other authors, indicating that modulatory components are found in the venom of different species of Crotalus snakes.

Inhibitory effect of Crotalus durissus terrificus venom on chronic edema induced by injection of bacillus Calmette-Guérin into the footpad of mice

In this study, we evaluated the effect of the Crotalus durissus terrificus (Cdt) venom on the chronic paw edema induced by the injection of bacillus Calmette-Guérin (BCG) into the footpad of mice. The BCG injection evoked chronic edema, which was significantly diminished in animals treated subcutaneously (s.c.) with Cdt venom 1 h before or after the BCG injection. This inhibition persisted throughout the evaluation period (15 days). In mice injected with Cdt venom 6 or 11 days after injection of BCG, we observed a significant reduction in edema only in the period after the venom injection. While studying possible mechanisms involved in this inhibition, we observed that pre-treatment with dexamethasone, zileuton or Boc2 (a selective antagonist of formyl peptide receptors), but not with indomethacin, canceled out the inhibitory effect of Cdt venom on the edema induced by BCG. These results strongly suggest that this rattlesnake venom can stimulate the generation of mediators from the lipoxygenase pathway, which can down-regulate this chronic inflammatory edema. Using fractionated venom, the results indicated that crotoxin was the only component of Cdt venom responsible for this inhibitory effect. These results indicated that crotoxin, the main toxin of the C. durissus terrificus venom, has a significant inhibitory effect on BCG-induced chronic edema, possibly by generating anti-inflammatory mediators from the lipoxygenase pathway.

S1P lyase in skeletal muscle regeneration and satellite cell activation: exposing the hidden lyase

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid whose actions are essential for many physiological processes including angiogenesis, lymphocyte trafficking and development. In addition, S1P serves as a muscle trophic factor that enables efficient muscle regeneration. This is due in part to S1P's ability to activate quiescent muscle stem cells called satellite cells (SCs) that are needed for muscle repair. However, the molecular mechanism by which S1P activates SCs has not been well understood. Further, strategies for harnessing S1P signaling to recruit SCs for therapeutic benefit have been lacking. S1P is irreversibly catabolized by S1P lyase (SPL), a highly conserved enzyme that catalyzes the cleavage of S1P at carbon bond C(2-3), resulting in formation of hexadecenal and ethanolamine-phosphate. SPL enhances apoptosis through substrate- and product-dependent events, thereby regulating cellular responses to chemotherapy, radiation and ischemia. SPL is undetectable in resting murine skeletal muscle. However, we recently found that SPL is dynamically upregulated in skeletal muscle after injury. SPL upregulation occurred in the context of a tightly orchestrated genetic program that resulted in a transient S1P signal in response to muscle injury. S1P activated quiescent SCs via a sphingosine-1-phosphate receptor 2 (S1P2)/signal transducer and activator of transcription 3 (STAT3)-dependent pathway, thereby facilitating skeletal muscle regeneration. Mdx mice, which serve as a model for muscular dystrophy (MD), exhibited skeletal muscle SPL upregulation and S1P deficiency. Pharmacological SPL inhibition raised skeletal muscle S1P levels, enhanced SC recruitment and improved mdx skeletal muscle regeneration. These findings reveal how S1P can activate SCs and indicate that SPL suppression may provide a therapeutic strategy for myopathies. This article is part of a Special Issue entitled Advances in Lysophospholipid Research.

Isolation and functional characterization of proinflammatory acidic phospholipase A2 from Bothrops leucurus snake venom

In the present study, an acidic PLA(2), designated Bl-PLA(2), was isolated from Bothrops leucurus snake venom through two chromatographic steps: ion-exchange on CM-Sepharose and hydrophobic chromatography on Phenyl-Sepharose. Bl-PLA(2) was homogeneous on SDS-PAGE and when submitted to 2D electrophoresis the molecular mass was 15,000Da and pI was 5.4. Its N-terminal sequence revealed a high homology with other Asp49 acidic PLA(2)s from snake venoms. Its specific activity was 159.9U/mg and the indirect hemolytic activity was also higher than that of the crude venom. Bl-PLA(2) induced low myotoxic and edema activities as compared to those of the crude venom. Moreover, the enzyme was able to induce increments in IL-12p40, TNF-α, IL-1β and IL-6 levels and no variation of IL-8 and IL-10 in human PBMC stimulated in vitro, suggesting that Bl-PLA(2) induces proinflammatory cytokine production by human mononuclear cells. Bothrops leucurus venom is still not extensively explored and knowledge of its components will contribute for a better understanding of its action mechanism.

Modulation of the pharmacological activities of secretory phospholipase A2 from Crotalus durissus cascavella induced by naringin

In this work we have characterized the action of the naringin, a flavonoid found in grapefruit and known for its various pharmacological effects, which include antioxidant blood lipid lowering and anticancer activity, on the structure and biochemical activities of a secretory phospholipase A (sPLA2) from Crotalus durissus cascavella, an important protein involved in the releasinge of arachidonic acid in phospholipid membranes. sPLA2 was incubated with naringin (mol:mol) at 37 °C and a discrete reduction in the UV scanning signal and a modification of the circular dichroism spectra were observed after treatment with naringin, suggesting modifications of the secondary structure of the protein. This flavonoid was able to decrease enzymatic activity and some pharmacological effects, such as myonecrosis, platelet aggregation, and neurotoxic activity caused by sPLA2, however, the inflammatory effect was not affected by naringin. In addition, small angle X-ray scattering (SAXS) data were collected for sPLA2 and naringin-treated sPLA2 to evaluate possible modifications of the protein structure. These structural investigations have shown that sPLA2 is an elongated dimer in solution and after treatment with naringin a conformational change in the dimeric configuration was observed. Our results suggest that structural modification may be correlated with the loss of enzymatic activity and alterations in pharmacological properties.

Crotoxin is responsible for the long-lasting anti-inflammatory effect of Crotalus durissus terrificus snake venom: involvement of formyl peptide receptors

In the present study, it was investigated which components are responsible for the anti-inflammatory properties of Crotalus durissus terrificus venom (CdtV). The effect of crotoxin, as well as of other CdtV components was evaluated on edema, cell migration and alterations in leukocyte-endothelium interactions induced by carrageenan. Crotoxin (40 microg kg(-1)) was injected at different time periods before or after the injection of carrageenan (15 mg kg(-1)) into the mouse hind paw, peritoneum or scrotum. Results showed that crotoxin, but not other CdtV components, significantly inhibited inflammatory edema and cell migration when administered before or after carrageenan injection in mice. This toxin also prevented the occurrence of alterations in leukocyte-endothelium interactions induced by carrageenan injection, such as the increase in adhered cells. In animals pretreated with Boc2 (a selective antagonist of formyl peptide receptors), crotoxin showed neither inhibitory effects on edema and cell migration, nor prevented alterations in leukocyte-endothelium interactions induced by carrageenan. These findings demonstrate that crotoxin is the component responsible for the long-lasting anti-inflammatory activity of crude C. durissus terrificus venom, and activation of formyl peptide receptors seems to play a major role in this effect.

Pro- and anti-inflammatory cytokines release in mice injected with Crotalus durissus terrificus venom

The effects of Crotalus durissus terrificus venom (Cdt) were analyzed with respect to the susceptibility and the inflammatory mediators in an experimental model of severe envenomation. BALB/c female mice injected intraperitoneally presented sensibility to Cdt, with changes in specific signs, blood biochemical and inflammatory mediators. The venom induced reduction of glucose and urea levels and an increment of creatinine levels in serum from mice. Significant differences were observed in the time-course of mediator levels in sera from mice injected with Cdt. The maximum levels of IL-6, NO, IL-5, TNF, IL-4 and IL-10 were observed 15 min, 30 min, 1, 2 and 4 hours post-injection, respectively. No difference was observed for levels of IFN-γ. Taken together, these data indicate that the envenomation by Cdt is regulated both pro- and anti-inflammatory cytokine responses at time-dependent manner. In serum from mice injected with Cdt at the two first hours revealed of pro-inflammatory dominance. However, with an increment of time an increase of anti-inflammatory cytokines was observed and the balance toward to anti-inflammatory dominance. In conclusion, the observation that Cdt affects the production of pro- and anti-inflammatory cytokines provides further evidence for the role played by Cdt in modulating pro/anti-inflammatory cytokine balance.

Crotoxin alters lymphocyte distribution in rats: Involvement of adhesion molecules and lipoxygenase-derived mediators

Crotoxin is the main neurotoxic component of Crotalus durissus terrificus snake venom and modulates immune and inflammatory responses, interfering with the activity of leukocytes. In the present work, the effects of crotoxin on the number of blood and lymphatic leukocytes and on lymph nodes and spleen lymphocytes population were investigated. The toxin s.c. administered to male Wistar rats, decreases the number of lymphocytes in blood and lymph circulation and increases the content of B and T-lymphocytes in lymph nodes. These effects were detected 1-2h after treatment. The crotoxin molecule is composed of two subunits, an acidic non-toxic polypeptide, named crotapotin and a toxic basic phospholipase A(2) (PLA(2)). PLA(2), but not crotapotin, decreased the number of circulating blood and lymph lymphocytes. Crotoxin promotes leukocyte adherence to endothelial cells of blood microcirculation and to lymph node high endothelial venules, which might contribute to the drop in the number of circulating lymphocytes. Crotoxin increases expression of the adhesion molecule LFA-1 in lymphocytes. The changes in the expression of the adhesion molecule might contribute, at least in part, for the increased leukocyte adhesion to endothelium. Zileuton, a 5-lipoxygenase inhibitor, blocked the decrease in the number of circulating leukocytes induced by crotoxin and also abolished the changes observed in leukocyte-endothelial interactions, suggesting the involvement of lipoxygenase-derived mediators in the effects of the toxin.

Long-lasting anti-inflammatory properties of Crotalus durissus terrificus snake venom in mice

In the present study, we investigated the effects of Crotalus durissus terrificus venom (CdtV) on vascular and cellular events of inflammation induced by carrageenan (cg) in mice. To evaluate edema, CdtV (75 microg kg(-1)) was administered subcutaneously before (1h, 7 or 14 days) or after (1, 4 or 48 h) subplantar injection of cg (15 mg kg(-1)) into the mouse right hind paw; to analyze leukocyte influx, cg (200 microL) was injected i.p. in mice. The inhibitory action of CdtV on edema, either before or after cg injection, was prolonged, lasting even 72 h after administration. Besides, CdtV significantly inhibited migration of polymorphonuclear cells to peritoneal cavity when administered before or after cg. Such inhibitory effects of CdtV on edema and cell migration were also compared with well-known anti-inflammatory drugs. The results demonstrated that CdtV, when injected either 7 or 14 days or 1h before cg, induced a more effective and long-lasting anti-inflammatory effect than that observed with classical anti-inflammatory drugs. The association of CdtV with different drugs did not potentialize their actions on cell migration. These results demonstrate that CdtV exhibits long-lasting anti-inflammatory effects.

Bothrops jararaca and Crotalus durissus terrificus venoms elicit distinct responses regarding to production of prostaglandins E2 and D2, and expression of cyclooxygenases

Prostaglandins (PGs), synthesized by cyclooxygenases, play important roles in many pathophysiological processes including inflammation and hyperalgesia. In this study the profiles of PGE(2) and PGD(2) production secondary to injection of Bothrops jararaca venom (BjV), with inflammatory activity or Crotalus durissus terrificus venom (CdtV), with anti-inflammatory and antinociceptive properties, into mice were evaluated, and the ability of these venoms to induce expression of cyclooxygenases-1 (COX-1) and -2 (COX-2) was investigated. Intraperitoneal injection of BjV but not of CdtV induced the release and PGD(2) at 30 min and of PGE(2) from 3 up to 12 h after injection. Moreover, BjV up-regulated expression of COX-2 but not of the constitutive COX-1, suggesting that expressed COX-2 provides more substrate for synthesis of PGs by the respective terminal synthases, being the critical enzyme for PGs production in the late periods of BjV effect. In contrast, CdtV does not have any effect on constitutive COX-1 and do not induce expression of COX-2. Therefore, differences between BjV and CdtV in the ability to regulate PGs synthesis can account for their distinct effects with regard to inflammation. Moreover, inhibition of COX-2 by selective drugs may be of value to counteract the severe local inflammation induced by BjV in the victims.

Crotoxin induces actin reorganization and inhibits tyrosine phosphorylation and activity of small GTPases in rat macrophages

Crotoxin is the main neurotoxic component of Crotalus durissus terrificus snake venom. Previous work of our group demonstrated that this toxin or its phospholipase A(2) subunit inhibits macrophage spreading and phagocytosis. The phagocytic activity of macrophages is controlled by the rearrangement of actin cytoskeleton and activity of the small Rho GTPases. The effect of crotoxin and its subunit on actin reorganization and tyrosine phosphorylation in rat peritoneal macrophages, during phagocytosis of opsonized zymosan, was presently investigated. The crude venom was used as positive control. In addition, the effect of crotoxin on the activity of Rho and Rac1 small GTPases was examined. Transmission electron studies showed that the venom or crotoxin decreased the extent of spread cells and increased microprojections often extended from macrophage surface. Immunocytochemical assays demosntrated that the venom or toxins increased F-actin content in the cytoplasm of these cells, but induced a marked decrease of phosphotyrosine. These effects were abolished by treatment with zileuton, a 5-lipoxygenase inhibitor. Furthermore, crotoxin decreased membrane-associated RhoA and Rac1 in translocation assays. The present results indicate that the crotalid venom and crotoxin are able to induce cytoskeleton rearrangement in macrophages. This effect is associated with inhibition of tyrosine phosphorylation and of the activity of proteins involved in intracellular signalling pathways important for the complete phagocytic activity of these cells.

Contribution of mast cells and snake venom metalloproteinases to the hyperalgesia induced by Bothrops jararaca venom in rats

Bothrops jararaca venom (Bjv) is known to induce local inflammation and severe pain. Since, mast cells are able to secrete mediators involved in algesic processes, in this study we examined the putative role of these cells in the hyperalgesia triggered by Bjv in the rat paw. We noted that treatment with mast cell stabilizer sodium cromoglicate as well as with histamine and 5-hydroxytriptamine receptor antagonists meclizine and methysergide, respectively, inhibited the Bjv-induced hyperalgesia. In addition, we showed that stimulation of isolated rat peritoneal mast cells with Bjv in vitro resulted in the release of stored and neo-generated inflammatory mediators such as histamine and leukotriene C(4), respectively. Bjv-induced histamine secretion was clearly sensitive to treatment with sodium cromoglicate and sodium nedocromil. We further observed that metalloproteinase inhibitors 1,10-phenantroline and DM43 inhibited mast cell degranulation in vitro, under conditions where inhibitors of phospholipase A(2) as well as of serine- and cysteine-proteinases were inactive. Altogether, our findings indicate that mast cells seem to contribute to the hyperalgesia caused by Bjv in the rat paw, and also provide evidence that this response might be dependent on the ability of the Bjv to activate directly mast cells.

Inhibitory effect of phospholipase A2 isolated from Crotalus durissus terrificus venom on macrophage function

Recent work demonstrated that crotoxin, the main toxin of Crotalus durissus terrificus venom, inhibits macrophage spreading and phagocytic activities. The crotoxin molecule is composed of two subunits, an acidic non-toxic and non-enzymatic polypeptide named crotapotin and a weakly toxic basic phospholipase A(2) (PLA(2)). In the present work, the active subunit responsible for the inhibitory effect of crotoxin on macrophage function was investigated. Peritoneal macrophages harvested from naive rats were used. Crotapotin (2.12, 3.75, or 8.37nM/ml), added for 2h to the medium of peritoneal cell incubation, did not modify the spreading and phagocytic activities of these cells. On the other hand, the PLA(2) (1.43, 2.86, or 6.43nM/ml) subunit caused a significant reduction (30, 33, and 35%, respectively) of the spreading activity. The PLA(2) also inhibited the phagocytosis of opsonised zymosan, opsonised sheep erythrocytes, and Candida albicans, indicating that this inhibitory effect is not dependent on the type of receptor involved in the phagocytosis process. The inhibitory effect of PLA(2) was not due to loss of cell membrane integrity, since macrophage viability was higher than 95%. These findings indicate that the inhibitory effect of crotoxin on macrophage spreading and phagocytic activities is caused by the phospholipase A(2) subunit.

Crotapotin induced modification of T lymphocyte proliferative response through interference with PGE2 synthesis

The immunosuppressive property has been demonstrated for the venom of the Crotalus durissus terrificus. Using a simple, novel method for obtaining crotapotin and phospholipase A2 isoforms from venom, it was possible to demonstrate that the addition of crotapotin to cultures of isolated lymphocytes resulted in a significant inhibition of the cellular proliferative response to Concanavalin A. This reduction in blastogenic response of lymphocytes is accompanied by a significant increase in the production of PGE2 by macrophages. This effect on the innate immune response suggests that this compound may modify the subsequent adaptative immune response.

Contribution of crotoxin for the inhibitory effect of Crotalus durissus terrificus snake venom on macrophage function

Previous work of our group demonstrated that Crotalus durissus terrificus venom has a dual effect on macrophage function: it inhibits spreading and phagocytosis and stimulates hydrogen peroxide and nitric oxide production, antimicrobial activity and glucose and glutamine metabolism of these cells. Crotalid venom also induces analgesia and this effect is mediated by opioid receptors. The involvement of opioidergic mechanism and the determination of the active component responsible for the inhibitory effect of crotalid venom on macrophage function were investigated. The venom reduced the spreading and phagocytic activities of peritoneal macrophages. This effect was observed in vitro, 2 h after incubation of resident peritoneal macrophages with the venom, and in vivo, 2 h after subcutaneous injection of the venom. The inhibition of phagocytosis was not modified by naloxone, an antagonist of opioid receptors. Venom neutralization with crotalid antivenom abolished the inhibitory effect of the venom, indicating that venom toxins are involved in this effect. Crotoxin, the main toxin of crotalid venom, s.c. injected to rats or added to the medium of peritoneal cell incubation, inhibited macrophage function in a similar manner to that observed for crude venom. The present results suggest that crotoxin causes a direct inhibition of macrophage spreading and phagocytic activities and may contribute to the inhibitory effect of crotalid venom on macrophage function.