Role of TNF-α, IL-1β and IL-6 in the local tissue damage induced by Bothrops asper snake venom: an experimental assessment in mice

Investigating Snake-Venom-Induced Dermonecrosis and Inflammation Using an Ex Vivo Human Skin Model

Snakebite envenoming is a neglected tropical disease that causes >100,000 deaths and >400,000 cases of morbidity annually. Despite the use of mouse models, severe local envenoming, defined by morbidity-causing local tissue necrosis, remains poorly understood, and human-tissue responses are ill-defined. Here, for the first time, an ex vivo, non-perfused human skin model was used to investigate temporal histopathological and immunological changes following subcutaneous injections of venoms from medically important African vipers (Echis ocellatus and Bitis arietans) and cobras (Naja nigricollis and N. haje). Histological analysis of venom-injected ex vivo human skin biopsies revealed morphological changes in the epidermis (ballooning degeneration, erosion, and ulceration) comparable to clinical signs of local envenoming. Immunostaining of these biopsies confirmed cell apoptosis consistent with the onset of necrosis. RNA sequencing, multiplex bead arrays, and ELISAs demonstrated that venom-injected human skin biopsies exhibited higher rates of transcription and expression of chemokines (CXCL5, MIP1-ALPHA, RANTES, MCP-1, and MIG), cytokines (IL-1β, IL-1RA, G-CSF/CSF-3, and GM-CSF), and growth factors (VEGF-A, FGF, and HGF) in comparison to non-injected biopsies. To investigate the efficacy of antivenom, SAIMR Echis monovalent or SAIMR polyvalent antivenom was injected one hour following E. ocellatus or N. nigricollis venom treatment, respectively, and although antivenom did not prevent venom-induced dermal tissue damage, it did reduce all pro-inflammatory chemokines, cytokines, and growth factors to normal levels after 48 h. This ex vivo skin model could be useful for studies evaluating the progression of local envenoming and the efficacy of snakebite treatments.

Photobiomodulation mitigates Bothrops jararacussu venom-induced damage in myoblast cells by enhancing myogenic factors and reducing cytokine production

BACKGROUND

Photobiomodulation has exhibited promise in mitigating the local effects induced by Bothrops snakebite envenoming; however, the mechanisms underlying this protection are not yet fully understood. Herein, the effectiveness of photobiomodulation effects on regenerative response of C2C12 myoblast cells following exposure to Bothrops jararacussu venom (BjsuV), as well as the mechanisms involved was investigated.

METHODOLOGY/PRINCIPAL FINDINGS

C2C12 myoblast cells were exposed to BjsuV (12.5 μg/mL) and irradiated once for 10 seconds with laser light of 660 nm (14.08 mW; 0.04 cm2; 352 mW/cm2) or 780 nm (17.6 mW; 0.04 cm2; 440 mW/ cm2) to provide energy densities of 3.52 and 4.4 J/cm2, and total energies of 0.1408 and 0.176 J, respectively. Cell migration was assessed through a wound-healing assay. The expression of MAPK p38-α, NF-Кβ, Myf5, Pax-7, MyoD, and myogenin proteins were assessed by western blotting analysis. In addition, interleukin IL1-β, IL-6, TNF-alfa and IL-10 levels were measured in the supernatant by ELISA. The PBM applied to C2C12 cells exposed to BjsuV promoted cell migration, increase the expression of myogenic factors (Pax7, MyF5, MyoD and myogenin), reduced the levels of proinflammatory cytokines, IL1-β, IL-6, TNF-alfa, and increased the levels of anti-inflammatory cytokine IL-10. In addition, PBM downregulates the expression of NF-kB, and had no effect on p38 MAKP.

CONCLUSION/SIGNIFICANCE

These data demonstrated that protection of the muscle cell by PBM seems to be related to the increase of myogenic factors as well as the modulation of inflammatory mediators. PBM therapy may offer a new therapeutic strategy to address the local effects of snakebite envenoming by promoting muscle regeneration and reducing the inflammatory process.

Instituto Butantan and Instituto Clodomiro Picado: A long-standing partnership in science, technology, and public health

Instituto Butantan (São Paulo, Brazil) and Instituto Clodomiro Picado (San José, Costa Rica) are public institutions devoted to scientific and technological research, production of antivenoms and other immunobiologicals, and a variety of public health interventions aimed at confronting the problem of snakebite envenoming in their countries and elsewhere. In the context of the 120th anniversary of Instituto Butantan, this work describes the historical developments in the relationship between these institutions, which has evolved into a solid cooperation platform in science, technology, and public health. The relationship between Instituto Butantan and Costa Rica started early in the 20th century, with the provision of Brazilian antivenoms to Costa Rica through the coordination of Instituto Butantan and the health system of Costa Rica, with the leadership of Clodomiro Picado Twight. After the decade of 1980, a prolific collaborative network has been established between Instituto Butantan and Instituto Clodomiro Picado (founded in 1970) in the areas of scientific and technological research in pharmacology, biochemistry, experimental pathology, immunology, and public health, as well as in antivenom development, production, preclinical evaluation, and quality control. In addition, both institutions have played a key role in the integration of regional efforts in Latin America to create a network of public institutions devoted to antivenom production and quality control, in close coordination with the Pan American Health Organization (PAHO). This long-standing partnership is an example of a highly productive south-south cooperation under a frame of solidarity and public well-being.

Basement membrane degradation and inflammation play a role in the pulmonary hemorrhage induced by a P-III snake venom metalloproteinase

Snakebite envenoming is a neglected tropical disease affecting millions of people every year, especially in vulnerable rural populations in the developing world. Viperid snakes cause envenomings characterized by a complex pathophysiology which includes local and systemic hemorrhage due to the action of snake venom metalloproteinases (SVMPs). The pathogenesis of SVMP-induced systemic hemorrhage has not been investigated in detail. This study explored the pulmonary hemorrhage induced in a murine model by a P-III SVMP from the venom of Crotalus simus. Histological analysis revealed extravasation in the lungs as early as 15 min after intravenous injection of the toxin, and hemorrhage increased at 360 min. Western blot analysis demonstrated the cleavage of basement membrane (BM) proteins in lung homogenates and in bronchoalveolar lavage fluid, implying an enzymatic disruption of this extracellular matrix structure at the capillary-alveolar barrier. Likewise, alveolar edema was observed, with an increment in protein concentration in the bronchoalveolar lavage fluid, and a neutrophil-rich inflammatory infiltrate was present in the parenchyma of the lungs as part of the inflammatory reaction. Pretreatment of mice with indomethacin, pentoxifylline and an anti-neutrophil antibody resulted in a significant decrease in pulmonary hemorrhage at 360 min. These findings suggest that this P-III SVMP induces acute lung injury through the direct action of this enzyme in the capillary-alveolar barrier integrity, as revealed by BM degradation, and as a consequence of the inflammatory reaction that develops in lung tissue. Our findings provide novel clues to understand the mechanism of action of hemorrhagic SVMPs in the lungs.

Moringa oleifera Extract Extenuates Echis ocellatus Venom-Induced Toxicities, Histopathological Impairments and Inflammation via Enhancement of Nrf2 Expression in Rats

Echis ocellatus snakebite causes more fatalities than all other African snake species combined. Moringa oleifera reportedly possesses an antivenom property. Therefore, we evaluated the effectiveness of M. oleifera ethanol extract (MOE) against E. ocellatus venom (EOV) toxicities. Thirty male rats were grouped as follows (n = 5): Group 1 (normal control received saline), groups 2 to 6 were administered intraperitoneally, 0.22 mg/kg (LD50) of EOV. Group 2 was left untreated while group 3 to 6 were treated post-envenoming with 0.2 mL of polyvalent antivenom, 200, 400, and 600 mg/kg of MOE respectively. MOE significantly (p < 0.05) normalized the altered haematological indices and blood electrolytes profiles. MOE attenuated venom-induced cellular dysfunctions, characterized by a significant increase in NRF2, and concomitant downregulation of increased antioxidant enzymes (SOD and CAT) activities in the serum and heart of the treated rats. MOE normalized the elevated TNF-α and IL-1β in serum and heart tissues. Furthermore, the IgG titre value was significantly (p < 0.5) higher in the envenomed untreated group compared to the MOE-treated groups. Hemorrhagic, hemolytic and coagulant activities of the venom were strongly inhibited by the MOE dose, dependently. Lesions noticed on tissues of vital organs of untreated rats were abolished by MOE. Our findings substantiate the effectiveness of MOE as a potential remedy against EOV toxicities.

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.

Bothrops alternatus Snake Venom Induces Cytokine Expression and Oxidative Stress on Renal Function

BACKGROUND

Envenomation caused by Bothrops alternatus is common in Southern Brazil. Acute Kidney Injury occurs after Bothrops snakebite and more information is necessaryrequired to understand its mechanism.

OBJECTIVE

The objective was to evaluate the effect of Bothrops alternatus venom (BaV) on renal cells and rat isolated kidney function.

METHODS

Wistar rats (n = 6, weighing 260-320 g) were perfused with a Krebs-Henseleit solution containing 6 g 100 mL-1 of bovine serum albumin. After 30 minutes, the kidneys were perfused with BaV to a final concentration of 1 and 3 μgmL-1; and subsequently were evaluated for Perfusion Pressure (PP), Renal Vascular Resistance (RVR), Urinary Flow (UF), Glomerular Filtration Rate (GFR), and percentage of electrolyte tubular transport. Renal histological analysis, cytokine release, oxidative stress and cytotoxicity in renal proximal tubular cells were assessed.

RESULTS

BaV reduced PP, RVR, GFR, UF, total and proximal sodium transport (%TNa+), and chloride (%TCl-) in the isolated kidney perfusion model. Histological analysis of perfused kidneys disclosed the presence of proteinaceous material in the glomeruli and renal tubules, vacuolar tubular epithelial cell degeneration, Bowman's capsule degeneration, swelling of glomerular epithelial cells, glomerular atrophy and degeneration, and the presence of intratubular protein. Cytokine release (TNF-α, IL-1β, IL-10) and oxidative stress were increased in the kidneys. The viability of LLC-MK2 cells (IC50: 221.3 μg/mL) was decreased by BaV and necrosis was involved in cell death.

CONCLUSION

These findings indicate that BaV modifies functional parameters in an isolated perfused kidney model and has cytotoxic effects on renal lineage cells.

Analysis of effectiveness of Iranian snake antivenom on Viper venom induced effects including analysis of immunologic biomarkers in the Echis carinatus sochureki envenomed victims

Snakebite is an important toxicologic emergency with the potential of triggering local and systemic inflammation. Antivenom has remained the mainstay of treatment for snakebite envenomation. In this study we sought to investigate the effectiveness of Iranian antivenom in a series of 44 viper envenomed patients through analysis of changes in clinical severity and the levels of inflammatory markers. Clinical envenomation severity assessed by snakebite severity score (SSS) and laboratory exams of the patients were recorded before (baseline visit) and after antivenom therapy. During 12-h antivenom therapy, the median (range) score of SSS significantly decreased from 3.5 (2-10) on admission to 1 (0-5) in the last visit (P < 0.001). Moreover, a significant decrease in prothrombin time and international normalized ratio was found (P = 0.006 and 0.008; respectively). Plasma concentrations of interleukin (IL) 1-β, IL-6, IL-8, tumor necrosis factor α (TNF-α), complement hemolytic activity (CH50) were also measured in 10 severely Echis carinatus sochureki envenomed victims and 10 age and gender-matched healthy controls. Except IL-8, the baseline levels of IL-1β, IL-6 and TNF-α in victims were significantly higher than healthy controls (P = 0.005, <0.001 and < 0.001, respectively). Moreover, the baseline level of CH50 was significantly lower in the patients compared to healthy controls (P < 0.001). After 12-h antivenom therapy, the plasma levels of IL-1β, IL-6 and TNF-α significantly decreased (P = 0.032, 0.006 and 0.003, respectively), the levels of IL-8 remained relatively unchanged and the CH50 significantly increased (P = 0.011). Iranian snake antivenom was effective in treating viper bite envenomation as it reversed clinical venom effects and restored near normal underlying inflammatory status. This study is the first to ascertain and report the effectiveness of this antivenom in human subjects.

Effect of Vipera ammodytes ammodytes Snake Venom on the Human Cytokine Network

Local inflammation is a well-known symptom of envenomation by snakes of the family Viperidae, attributed primarily to the phospholipase A₂s, metalloproteinases and L-amino acid oxidases contained in their venom. The inflammatory effect of snake venoms has been associated with a marked increase of the cytokines IL-1β, IL-6, IL-8, IL-10 and TNF-α. To determine the impact of Vipera ammodytes ammodytes snake venom on the expression of inflammation-related genes, we incubated human U937 monocyte cells with dilutions of snake venom. Gene expression was quantified for 28 different genes using a TaqMan^® Array Human Cytokine Network 96-well Plate in a RT-qPCR system. Our results have demonstrated that 1.0 μg/mL Vipera ammodytes ammodytes venom solution induces a notable change in the expression of several cytokine network genes. Among the upregulated genes, there were several that encode interleukins, interferons, and tumor necrosis factors. We further report the downregulation of three interleukin-related genes. Our findings come as supportive information for the known complex effect of snake venoms on the human cytokine network. It also provides relevant new information regarding the expression of genes that have not been previously associated with the effect of snake venoms.

Unresolved issues in the understanding of the pathogenesis of local tissue damage induced by snake venoms

Snakebite envenoming by viperid species, and by some elapids, is characterized by a complex pattern of tissue damage at the anatomical site of venom injection. In severe cases, tissue destruction may be so extensive as to lead to permanent sequelae, with serious pathophysiological, social and psychological consequences. Significant advances have been performed in the study of venom-induced tissue damage, including identification and characterization of the toxins involved, insights into the mechanisms of action of venoms and toxins, and study of tissue responses to venom-induced injury. Nevertheless, much remains to be known and understood on the pathogenesis of these alterations. This review focuses on some of the pending issues in the topic of snake venom-induced local tissue damage. The traditional 'reductionist' approach, which has predominated in the study of snake venoms and their actions, needs to be complemented by more integrative and holistic perspectives aimed at capturing the complexity of these pathological alterations. Future advances in the study of these topics will certainly pave the way for innovative therapeutic interventions, with the goal of reducing the impact of this aspect of snakebite envenoming.

Revisiting the Therapeutic Potential of Bothrops jararaca Venom: Screening for Novel Activities Using Connectivity Mapping

Snake venoms are sources of molecules with proven and potential therapeutic applications. However, most activities assayed in venoms (or their components) are of hemorrhagic, hypotensive, edematogenic, neurotoxic or myotoxic natures. Thus, other relevant activities might remain unknown. Using functional genomics coupled to the connectivity map (C-map) approach, we undertook a wide range indirect search for biological activities within the venom of the South American pit viper Bothrops jararaca. For that effect, venom was incubated with human breast adenocarcinoma cell line (MCF7) followed by RNA extraction and gene expression analysis. A list of 90 differentially expressed genes was submitted to biosimilar drug discovery based on pattern recognition. Among the 100 highest-ranked positively correlated drugs, only the antihypertensive, antimicrobial (both antibiotic and antiparasitic), and antitumor classes had been previously reported for B. jararaca venom. The majority of drug classes identified were related to (1) antimicrobial activity; (2) treatment of neuropsychiatric illnesses (Parkinson’s disease, schizophrenia, depression, and epilepsy); (3) treatment of cardiovascular diseases, and (4) anti-inflammatory action. The C-map results also indicated that B. jararaca venom may have components that target G-protein-coupled receptors (muscarinic, serotonergic, histaminergic, dopaminergic, GABA, and adrenergic) and ion channels. Although validation experiments are still necessary, the C-map correlation to drugs with activities previously linked to snake venoms supports the efficacy of this strategy as a broad-spectrum approach for biological activity screening, and rekindles the snake venom-based search for new therapeutic agents.

Evaluation of pro-inflammatory events induced by Bothrops alternatus snake venom

Inflammation is a major local feature of envenomation by bothropic snakes being characterized by a prominent local edema, pain, and extensive swelling. There are reports demonstrating that whole Bothrops snake venoms and toxins isolated from them are able to activate macrophages functions, such as phagocytosis, production of reactive oxygen, cytokines and eicosanoids, however, little is known about the effects of Bothrops alternatus (B.a.) venom on macrophages. In this work, we evaluated the proinflammatory effects of B.a. venom with in vivo and in vitro experiments using the Raw 264.7 cell line and mouse peritoneal macrophages. We detected that B.a. venom augments cell permeability (2-fold), and cellular extravasation (mainly neutrophils), increase proinflammatory cytokines IL1 (∼300-fold), IL12 (∼200-fold), and TNFα (∼80-fold) liberation and induce the expression of enzymes related to lipid signaling, such as cPLA_2α and COX-2. Additionally, using lipidomic techniques we detected that this venom produces a release of arachidonic acid (∼10 nMol/mg. Protein) and other fatty acids (16:0 and 18:1 n-9c). Although much of these findings were described in inflammatory processes induced by other bothropic venoms, here we demonstrate that B.a. venom also stimulates pro-inflammatory pathways involving lipid mediators of cell signaling. In this sense, lipidomics analysis of macrophages stimulated with B.a. venom evidenced that the main free fatty acids are implicated in the inflammatory response, and also demonstrated that this venom, is able to activate lipid metabolism even with a low content of PLA₂.

Understanding and confronting snakebite envenoming: The harvest of cooperation

During 45 years, the Instituto Clodomiro Picado (ICP, University of Costa Rica) has developed an ambitious scientific, technological, productive, and social program aimed at providing a better understanding of snakes and their venoms, contributing to the development, production and distribution of antivenoms, improving the prevention and management of snakebite envenomings, and strengthening human resources in science and technology. Among other topics, its research agenda has focused on the local tissue alterations induced by viperid snake venoms, i.e. myonecrosis, hemorrhage, dermonecrosis, extracellular matrix degradation, lymphatic vessel damage, and inflammation. In addition, the preclinical efficacy of antivenoms has been thoroughly investigated, together with the technological development of novel antivenoms. ICP's project has been based on a philosophical frame characterized by: (a) An integrated approach for confronting the problem of snakebites, involving research, production, extension activities, and teaching; (b) a cooperative and team work perspective in the pursuit of scientific, technological, productive, and social goals; (c) a search for excellence and continuous improvement in the quality of its activities; and (d) a vision of solidarity and compassion, based on the realization that snakebite envenomings mostly affect impoverished vulnerable populations in the rural settings of developing countries. A key aspect in this program has been the consolidation of international partnerships with groups of all continents, within a frame of academic and social cooperation, some of which are described in this review.

Inflammatory mediators involved in the paw edema and hyperalgesia induced by Batroxase, a metalloproteinase isolated from Bothrops atrox snake venom

Snake venom metalloproteinases have been described as responsible for several inflammatory effects. In this study, we investigated the edema and hyperalgesia induced in rats by Batroxase, a P-I metalloproteinase from Bothrops atrox venom, along with possible inflammatory mediators involved in these responses. Batroxase or sterile saline was injected into rat paws and the edema and hyperalgesic effects were evaluated for 6h by using a plethysmometer and a Von Frey system, respectively. Batroxase induced significant edematogenic and hyperalgesic peak responses in the first hours after administration. The inflammatory mediators involved in these responses were assayed by pretreatment of animals with synthesis inhibitors or receptor antagonists. Peak responses were significantly reduced by administration of the glucocorticoid dexamethasone, the H1 receptor antagonist diphenhydramine and the FLAP inhibitor MK-886. Rat paws injected with compound 48/80, a mast cell degranulating agent, followed by Batroxase injection resulted in significant reduction of the edema and hyperalgesia. However, Batroxase itself induced minor degranulation of RBL-2H3 mast cells in vitro. Additionally, the inflammatory responses did not seem to be related to prostaglandins, bradykinin or nitric oxide. Our results indicate a major involvement of histamine and leukotrienes in the edema and hyperalgesia induced by Batroxase, which could be related, at least in part, to mast cell degranulation.

Bothrops jararacussu snake venom-induces a local inflammatory response in a prostanoid- and neutrophil-dependent manner

Local tissue reactions provoked by Bothrops venoms are characterized by edema, hemorrhage, pain, and inflammation; however, the mechanisms of tissue damage vary depending upon the species of snake. Here, we investigated the mechanisms involved in the local inflammatory response induced by the Bothrops jararacussu venom (BjcuV). Female Swiss mice were injected with either saline, BjcuV (0.125-8 μg/paw) or loratadine (an H1 receptor antagonist), compound 48/80 (for mast cell depletion), capsaicin (for C-fiber desensitization), infliximab (an anti-TNF-α antibody), indomethacin (a non-specific COX inhibitor), celecoxib (a selective COX-2 inhibitor) or fucoidan (a P- and L-selectins modulator) given before BjcuV injection. Paw edema was measured by plethysmography. In addition, paw tissues were collected for the measurement of myeloperoxidase activity, TNF-α and IL-1 levels, and COX-2 immunoexpression. The direct chemotactic effect of BjcuV and the in vitro calcium dynamic in neutrophils were also investigated. BjcuV caused an edematogenic response with increased local production of TNF-α and IL-1β as well as COX-2 expression. Both edema and neutrophil migration were prevented by pretreatment with indomethacin, celecoxib or fucoidan. Furthermore, BjcuV induced a direct in vitro neutrophil chemotaxis by increasing intracellular calcium. Therefore, BjcuV induces an early onset edema dependent upon prostanoid production and neutrophil migration.

Complete regression and systemic protective immune responses obtained in B16 melanomas after treatment with LTX-315

Malignant melanoma is the most aggressive and deadliest form of skin cancer due to its highly metastatic potential, which calls for new and improved therapies. Cationic antimicrobial peptides (CAPs) are naturally occurring molecules found in most species, in which they play a significant role in the first line of defense against pathogens, and several CAPs have shown promising potential as novel anticancer agents. Structure-activity relationship studies on the CAP bovine lactoferricin allowed us to de novo design short chemically modified lytic anticancer peptides. In the present study, we investigated the in vivo antitumor effects of LTX-315 against intradermally established B16 melanomas in syngeneic mice. Intratumoral administration of LTX-315 resulted in tumor necrosis and the infiltration of immune cells into the tumor parenchyma followed by complete regression of the tumor in the majority of the animals. LTX-315 induced the release of danger-associated molecular pattern molecules such as the high mobility group box-1 protein in vitro and the subsequent upregulation of proinflammatory cytokines such as interleukin (IL) 1β, IL6 and IL18 in vivo. Animals cured by LTX-315 treatment were protected against a re-challenge with live B16 tumor cells both intradermally and intravenously. Together, our data indicate that intratumoral treatment with LTX-315 can provide local tumor control followed by protective immune responses and has potential as a new immunotherapeutic agent.

Purification and biochemical characterization of three myotoxins from Bothrops mattogrossensis snake venom with toxicity against Leishmania and tumor cells

Bothrops mattogrossensis snake is widely distributed throughout eastern South America and is responsible for snakebites in this region. This paper reports the purification and biochemical characterization of three new phospholipases A₂ (PLA₂s), one of which is presumably an enzymatically active Asp49 and two are very likely enzymatically inactive Lys49 PLA₂ homologues. The purification was obtained after two chromatographic steps on ion exchange and reverse phase column. The 2D SDS-PAGE analysis revealed that the proteins have pI values around 10, are each made of a single chain, and have molecular masses near 13 kDa, which was confirmed by MALDI-TOF mass spectrometry. The N-terminal similarity analysis of the sequences showed that the proteins are highly homologous with other Lys49 and Asp49 PLA₂s from Bothrops species. The PLA₂s isolated were named BmatTX-I (Lys49 PLA₂-like), BmatTX-II (Lys49 PLA₂-like), and BmatTX-III (Asp49 PLA₂). The PLA₂s induced cytokine release from mouse neutrophils and showed cytotoxicity towards JURKAT (leukemia T) and SK-BR-3 (breast adenocarcinoma) cell lines and promastigote forms of Leishmania amazonensis. The structural and functional elucidation of snake venoms components may contribute to a better understanding of the mechanism of action of these proteins during envenomation and their potential pharmacological and therapeutic applications.

Effect of Bothrops bilineata snake venom on neutrophil function

The aim of the study was to evaluate the in vitro effects of Bothrops bilineata crude venom (BbV) on isolated human neutrophil function. We proved that BbV isn't toxic towards human neutrophils. During an incubation of human neutrophils with BbV hydrogen peroxide was produced. Moreover, BbV was able to stimulate neutrophil release of proinflammatory mediators such as IL-8 and IL-6 as well as PGE2 and NETs liberation. There is no data in the literature showing the effect of BbV on the production of IL-6 and IL-8 or NETs liberation by isolated human neutrophils. Taken together our results testify that BbV triggers relevant proinflammatory events in human neutrophils.

The crucial role of the MyD88 adaptor protein in the inflammatory response induced by Bothrops atrox venom

Most snake accidents in North Brazil are attributed to Bothrops atrox, a snake species of the Viperidae family whose venom simultaneously induces local and systemic effects in the victims. The former are clinically more important than the latter, as they cause severe tissue lesions associated with strong inflammatory responses. Although several studies have shown that inflammatory mediators are produced in response to B. atrox venom (BaV), there is little information concerning the molecular pathways involved in innate immune system signaling. Myeloid differentiation factor 88 (MyD88) is an adaptor molecule responsible for transmitting intracellular signals from most toll-like receptors (TLRs) after they interact with pathogen-associated molecular patterns (PAMPs) or other stimuli such as endogenous damage-associated molecular patterns (DAMPs). The MyD88-dependent pathway leads to activation of transcription factors, which in turn induce synthesis of inflammatory mediators such as eicosanoids, cytokines and chemokines. The aim of this study was to investigate the involvement of MyD88 on the acute inflammatory response induced by BaV. Wild-type (WT) C57BL/6 mice and MyD88 knockout (MyD88(-/-)) mice were intraperitoneally injected with BaV. Compared to WT mice, MyD88(-/-) animals showed an impaired inflammatory response to BaV, with lower influx of polymorphonuclear and mononuclear cells to the peritoneal cavity. Furthermore, peritoneal leukocytes from BaV-injected MyD88(-/-) mice did not induce COX-2 or LTB4 protein expression and released low concentrations of PGE2. These mice also failed to produce Th1 and Th17 cytokines and CCL-2, but IL-10 levels were similar to those of BaV-injected WT mice. Our results indicate that MyD88 signaling is required for activation of the inflammatory response elicited by BaV, raising the possibility of developing new therapeutic targets to treat Bothrops sp. poisoning.

Effects of Bothrops asper snake venom on the expression of cyclooxygenases and production of prostaglandins by peritoneal leukocytes in vivo, and by isolated neutrophils and macrophages in vitro

In this study, the ability of Bothrops asper snake venom (BaV) to increase the production of prostaglandins PGE(2) and PGD(2) was assessed in a mouse model in vivo and in inflammatory cells in vitro. In addition, the expressions of COX-1 and COX-2 were assessed. BaV induced an increment in the in vivo synthesis of PGE(2) and PGD(2), together with an enhanced expression of COX-2, but not of COX-1. However, enzymatic activities of COX-1 and COX-2 were increased. Incubation of isolated macrophages and neutrophils with a sub-cytotoxic concentration of BaV in vitro resulted in increased release of PGE(2) and PGD(2) by macrophages and PGE(2) by neutrophils, concomitantly with an increment in the expression of COX-2, but not of COX-1 by both cell types. Our results demonstrate the ability of BaV to promote the expression of COX-2 and to induce the synthesis of proinflammatory prostaglandins. Macrophages and neutrophils may be important targets for this venom under in vivo situation.

Bothrops jararaca venom (BjV) induces differential leukocyte accumulation in mice genetically selected for acute inflammatory reaction: the role of host genetic background on expression of adhesion molecules and release of endogenous mediators

The dynamics of the local inflammatory events induced by Bothrops jararaca venom (BjV) inoculation in footpad of mice genetically selected for maximal (AIRmax) and minimal (AIRmin) acute inflammatory reactivity (AIR) was investigated. The BjV injection induced a marked inflammatory cell infiltrate with predominance of neutrophils, with increased blood cell numbers before its accumulation, suggesting a stimulatory action of BjV on mechanisms of cell mobilization from bone marrow. The process of cell migration is regulated by different cell-adhesion molecules (CAM). Our results showed that neutrophil cells from both lines had the same pattern of response concerning CAMs expression, presenting the involvement of l-selectin, Mac-1 and PECAM-1 adhesion molecules in BjV-induced neutrophil accumulation. The effect of BjV on the release of pro-inflammatory cytokines and chemokines related with cellular migration was also studied and IL-1beta, IL-6, TNF-alpha and MIP-2 levels could be detected after venom injection. The AIRmax mice were shown to be more responsive than AIRmin with respect to leukocyte influx, expression of MIP-2 and release of IL-1beta and IL-6. These results demonstrate the importance of host genetic background in the local response and the involvement of alleles accumulated in AIRmax mice in the inflammatory events induced by BjV.

Involvement of tumour necrosis factor-alpha in Clostridium perfringens beta-toxin-induced plasma extravasation in mice

BACKGROUND AND PURPOSE

Clostridium perfringens beta-toxin, an important agent of necrotic enteritis, causes plasma extravasation due to the release of a tachykinin NK(1) receptor agonist in mouse skin. In this study, we investigated the role of cytokines in beta-toxin-induced plasma extravasation.

EXPERIMENTAL APPROACH

Male Balb/c, C3H/HeN and C3H/HeJ mice were anaesthetized with pentobarbitone and beta-toxin was injected i.d. into shaved dorsal skin. SR140333, capsaicin, chlorpromazine and pentoxifylline were given as pretreatment when required before the injection of the toxin. Cytokines in the dorsal skin were measured by ELISA.

KEY RESULTS

Injection (i.d.) of beta-toxin induced a dose-dependent increase in dermal TNF-alpha and interleukin (IL)-1beta levels with a concomitant increase in plasma extravasation, but not the release of IL-6. SR140333 and capsaicin significantly inhibited the toxin-induced release of TNF-alpha and IL-1beta. The plasma extravasation and the release of TNF-alpha induced by beta-toxin were significantly inhibited by chlorpromazine and pentoxifylline which inhibit the release of TNF-alpha. The toxin-induced plasma extravasation in mouse skin was attenuated by pretreatment with a monoclonal antibody against TNF-alpha, but not anti-IL-1beta. Furthermore, the toxin caused an increase in plasma extravasation in both C3H/HeN (TLR4-intact) and C3H/HeJ (TLR4-deficient) mice. In C3H/HeN mice, the toxin-induced leakage was not inhibited by pretreatment with anti-TLR4/MD-2 antibody.

CONCLUSIONS AND IMPLICATIONS

These observations show that beta-toxin-induced plasma extravasation in mouse skin is related to the release of TNF-alpha via the mechanism involving tachykinin NK(1) receptors, but not via TLR4.

Inhibition of tumor necrosis factor alpha signaling by anti-tumor necrosis factor alpha antibodies and pentoxifylline is unable to prevent fumonisin hepatotoxicity in mice

Fumonisin B1 (FB1), a mycotoxin from Fusarium verticillioides, disrupts sphingolipid metabolism by inhibiting ceramide synthase leading to modulation of cytokines including tumor necrosis factor (TNF) alpha. Current study investigated the effect of interrupting TNFalpha signaling, known to be involved in FB1 hepatotoxicity. Male C57BL/6N mice were injected intravenously once with anti-TNFalpha antibodies or treated with pentoxifylline at 150 mg/kg intraperitoneally twice a day for 5 days to inhibit TNFalpha production before and during subcutaneous injection of 2.25mg FB1/kg daily for 5 days; mice were sampled one day after the last treatment. Results showed that both anti-TNFalpha antibodies and pentoxifylline did not prevent FB1 hepatotoxicity; the latter was somewhat augmented, indicated by increases in circulating alanine aminotransferase and aspartate aminotransferase, and incidence of apoptotic hepatocytes. Anti-TNFalpha antibodies did not alter FB1-induced accumulation of free sphingoid bases or expression of TNFalpha in liver following the FB1 treatment. Pentoxifylline significantly reduced accumulation of free sphinganine and expression of TNFalpha. Neither anti-TNFalpha antibodies nor pentoxifylline altered FB1-induced expression of interleukin-12, interferongamma, lymphotoxinbeta, and c-myc. Expression of c-myc, an inducer of cell death, increased after interference with TNFalpha signaling. These findings suggest a dual role of TNFalpha signaling activation in FB1 hepatotoxicity.

Pentoxifylline and insulin-like growth factor-I (IGF-I) abrogate kainic acid-induced cognitive impairment in mice

Hippocampal insults involving neuroimmune mechanisms can impair learning and memory in a variety of tasks. The present study was designed to assess the effect of pentoxifylline, an inhibitor of tumor necrosis factor alpha (TNFalpha), and insulin-like growth factor-I (IGF-I) on kainate (KA)-induced impairment in spatial memory. Male mice received a subcutaneous injection of a dose of KA (15 mg/kg) that had no cytotoxic effect on hippocampal neurons as confirmed by Fluorojade B staining. This dose resulted in an impairment of spatial memory in a two-trial recognition task 11 days later. Intraperitoneal administration of pentoxifylline (200 mg/kg) abrogated this effect. Repeated intracerebroventricular injection of IGF-I (2 microg/mouse on day 1 followed by 1 microg/mouse on days 2-5) abrogated KA-induced deficits in spatial memory whereas acute IGF-I (2 microg/mouse on day 1 only) had mixed effects. These findings indicate that endogenous TNFalpha is probably involved in the detrimental effects of kainate on cognition and that exogenous IGF-I can oppose these effects, probably by antagonizing TNFalpha-induced neurotoxicity.