Mast cell degranulation induced by two phospholipase A2 homologues: dissociation between enzymatic and biological activities

Mapping the Immune Cell Microenvironment with Spatial Profiling in Muscle Tissue Injected with the Venom of Daboia russelii

Pathological and inflammatory events in muscle after the injection of snake venoms vary in different regions of the affected tissue and at different time intervals. In order to study such heterogeneity in the immune cell microenvironment, a murine model of muscle necrosis based on the injection of the venom of Daboia russelii was used. Histological and immunohistochemical methods were utilized to identify areas in muscle tissue with a different extent of muscle cell damage, based on the presence of hypercontracted muscle cells, a landmark of necrosis, and on the immunostaining for desmin. A gradient of inflammatory cells (neutrophils and macrophages) was observed from heavily necrotic areas to less damaged and non-necrotic areas. GeoMx® Digital Spatial Profiler (NanoString, Seattle, WA, USA) was used for assessing the presence of markers of various immune cells by comparing high-desmin (nondamaged) and low-desmin (damaged) regions of muscle. Markers of monocytes, macrophages, M2 macrophages, dendritic cells, neutrophils, leukocyte adhesion and migration markers, and hematopoietic precursor cells showed higher levels in low-desmin regions, especially in samples collected 24 hr after venom injection, whereas several markers of lymphocytes did not. Moreover, apoptosis (BAD) and extracellular matrix (fibronectin) markers were also increased in low-desmin regions. Our findings reveal a hitherto-unknown picture of immune cell microheterogeneity in venom-injected muscle which greatly depends on the extent of muscle cell damage and the time lapse after venom injection.

Lys49 myotoxins, secreted phospholipase A2-like proteins of viperid venoms: A comprehensive review

Muscle necrosis is a potential clinical complication of snakebite envenomings, which in severe cases can lead to functional or physical sequelae such as disability or amputation. Snake venom proteins with the ability to directly damage skeletal muscle fibers are collectively referred to as myotoxins, and include three main types: cytolysins of the "three-finger toxin" protein family expressed in many elapid venoms, the so-called "small" myotoxins found in a number of rattlesnake venoms, and the widespread secreted phospholipase A₂ (sPLA₂) molecules. Among the latter, protein variants that conserve the sPLA₂ structure, but lack such enzymatic activity, have been increasingly found in the venoms of many viperid species. Intriguingly, these sPLA₂-like proteins are able to induce muscle necrosis by a mechanism independent of phospholipid hydrolysis. They are commonly referred to as "Lys49 myotoxins" since they most often present, among other substitutions, the replacement of the otherwise invariant residue Asp49 of sPLA₂s by Lys. This work comprehensively reviews the historical developments and current knowledge towards deciphering the mechanism of action of Lys49 sPLA₂-like myotoxins, and points out main gaps to be filled for a better understanding of these multifaceted snake venom proteins, to hopefully lead to improved treatments for snakebites.

NLRP3 inflammasome activation in human peripheral blood mononuclear cells induced by venoms secreted PLA2s

Bothropic venoms contains high amount of secreted phospholipases A₂ (sPLA₂s) that play a significant role in leukocyte activation and inflammation. Monocytes and lymphocytes are highly functional immune system cells that mediate and provide efficient responses during the inflammation. NLRP3 inflammasome is a multiprotein complex found in immune system cells that is triggered by pathogen- and damage-associated molecular patterns, PAMPs and DAMPs, respectively. PLA₂s' effect on human peripheral blood mononuclear cells (PBMCs) is still incompletely understood. PBMCs were isolated by density gradient and incubated with RPMI (control), LPS, BthTX-I (PLA₂-Lys49) or BthTX-II (PLA₂-Asp49) isolated from Bothrops jararacussu venom, to evaluate viability, and the results showed that there was no cell death. RT-qPCR and immunoblot were used to assess the gene and protein expression of NLRP3 components. Results indicated that there was substantial amplification of ASC, Caspase-1, IL-6, and IL-1β in 1 h and NLRP3 in 2 h. Protein expression was measured, and the results revealed substantial expression of the NLRP3 inflammasome complex after 4 h. IL-1β and LDH was quantified in the supernatant of the cells. Taken together, the findings demonstrate that BthTX-I and BthTX-II activate the NLRP3 inflammasome complex in human PBMCs and contribute to the inflammatory response seen in envenoming.

Pain and Cellular Migration Induced by Bothrops jararaca Venom in Mice Selected for an Acute Inflammatory Response: Involvement of Mast Cells

Bothrops jararaca venom (BjV) can induce mast cell degranulation. In order to investigate the role of mast cells and the interference of the host genetic background in the inflammation induced by BjV, we have used mouse strains selected for maximal (AIRmax) or minimal (AIRmin) acute inflammatory response (AIR). Mice were pretreated with an inhibitor of mast cell degranulation, cromolyn (CROM), and injected in footpads or intraperitoneally (i.p.) with BjV. Pain was measured with von Frey hairs, cell migration in the peritoneum by flow cytometry, and reactive oxygen species (ROS) production by chemiluminescence assays. The nociceptive response to BjV was higher in AIRmax than AIRmin mice; however, this difference was abolished by pretreatment with CROM. BjV induced peritoneal neutrophil (CD11b+ GR-1+) infiltration and ROS secretion in AIRmax mice only, which were partially inhibited by CROM. Our findings evidence a role for mast cells in pain, neutrophil migration, and ROS production triggered by BjV in AIRmax mice that are more susceptible to the action of BjV.

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.

Inflammasome Activation Induced by a Snake Venom Lys49-Phospholipase A2 Homologue

Background: Snake venom phospholipases A₂ (PLA₂s) have hemolytic, anticoagulant, myotoxic, oedematogenic, bactericidal, and inflammatory actions. BthTX-I, a Lys49-PLA₂ isolated from Bothrops jararacussu venom, is an example of Lys49-PLA₂ that presents such actions. NLRP3 is a cytosolic receptor from the NLR family responsible for inflammasome activation via caspase-1 activation and IL-1β liberation. The study of NLRs that recognize tissue damage and activate the inflammasome is relevant in envenomation. Methods: Male mice (18–20 g) received an intramuscular injection of BthTX-I or sterile saline. The serum was collected for creatine-kinase (CK), lactate dehydrogenase (LDH), and interleukin-1β (IL-1β) assays, and muscle was removed for inflammasome activation immunoblotting and qRT-PCR expression for nucleotide and oligomerization domain, leucine-rich repeat-containing protein family, pyrin-containing domain 3 receptor (NLRP3) inflammasome components. Results: BthTX-I-induced inflammation and myonecrosis, shown by intravital microscope, and LDH and CK release, respectively. Mouse treatment with A438079, a P2X7 receptor antagonist, did not modify these effects. BthTX-I induced inflammasome activation in muscle, but P2X7R participation in this effect was not observed. Conclusion: Together, the results showed for the first time that BthTX-I in gastrocnemius muscle induces inflammation and consequently, inflammasome activation via NLRP3 with caspase-1 activation and IL-1β liberation.

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.

Neurogenic mediators contribute to local edema induced by Micrurus lemniscatus venom

Background/Aims

Micrurus is one of the four snake genera of medical importance in Brazil. Coral snakes have a broad geographic distribution from the southern United States to Argentina. Micrurine envenomation is characterized by neurotoxic symptoms leading to dyspnea and death. Moreover, various local manifestations, including edema formation, have been described in patients bitten by different species of Micrurus. Thus, we investigated the ability of Micrurus lemniscatus venom (MLV) to induce local edema. We also explored mechanisms underlying this effect, focusing on participation of neuropeptides and mast cells.

Methodology/Principal findings

Intraplantar injection of MLV (1–10 μg/paw) in rats caused dose- and time-dependent edema with a peak between 15 min and 1 h after injection. MLV also induced degranulation of peritoneal mast cells (MCs). MC depletion by compound 48/80 markedly reduced MLV-induced edema. Pre-treatment (30 min) of rats with either promethazine a histamine H₁ receptor antagonist or methysergide, a nonselective 5-HT receptor antagonist, reduced MLV-induced edema. However, neither thioperamide, a histamine H₃/H₄ receptor antagonist, nor co-injection of MLV with HOE-140, a BK₂ receptor antagonist, altered the response. Depletion of neuropeptides by capsaicin or treatment of animals with NK₁- and NK₂-receptor antagonists (SR 140333 and SR 48968, respectively) markedly reduced MLV-induced edema.

Conclusions/Significance

In conclusion, MLV induces paw edema in rats by mechanisms involving activation of mast cells and substance P-releasing sensory C-fibers. Tachykinins NKA and NKB, histamine, and serotonin are major mediators of the MLV-induced edematogenic response. Targeting mast cell- and sensory C-fiber-derived mediators should be considered as potential therapeutic approaches to interrupt development of local edema induced by Micrurus venoms.

Micrurus venoms have neurotoxic activity that is responsible for the serious sequelae in human envenomation. However, various local manifestations of envenoming have been described in patients bitten by different Micrurus species and edematogenic activity has been experimentally demonstrated. Despite the low frequency of edema in Micrurus envenomation, this effect can worsen the clinical manifestations. However, there are few studies on local inflammatory effects induced by Micrurus snake venom. We investigated the edematogenic effect of Micrurus lemniscatus venom (MLV) and participation of neuropeptides and mast cells in inflammation. Results demonstrate that MLV induces prominent edema with rapid onset. Using specific pharmacological interferences, we found that MLV-induced edema is dependent on activation of mast cells and substance P-releasing sensory C-fibers. NKA and NKB tachykinins, histamine via H₁ receptor and serotonin are major mediators of the MLV-induced edematogenic response. These findings suggest that mast cell- and C-fiber-derived mediators are promising therapeutic targets to efficiently counteract the local edema induced by Micrururs venoms.

Beneficial effects of Heparin and l Arginine on dermonecrosis effect induced by Vipera lebetina venom: Involvement of NO in skin regeneration

It is well known that snake venoms such as Viperidae caused severe local effects such as hemorrhage, myonecrosis and dermonecrosis which can lead to permanent tissue loss or the disability. The aim of this study is to evaluate the skin regeneration using heparin and l-arginine as well as the dermonecrotic effects induced by Vipera lebetina venom (VLV). To better understand the toxic effects induced by VLV and to prevent or treat these effects, we evaluate the local effects and the skin regeneration with or without drugs. The evaluation of NO as a marker of angiogenesis was also undertaken to understand its involvement in tissue wound healing and skin regeneration after envenomation. Obtained results showed that this venom is able to induce severe necrosis characterized by hemorrhage, hair follicles' destruction, glandular structure and increased of the thickness (acanthosis) in the epidermo-dermic junction. Inflammatory cells were also observed in the dermis. Pretreatment with heparin or L arginine seemed to decrease the induced dermonecrotic after one and two weeks improving the skin regeneration. The high level of NO could be involved in this regeneration, since it participates in the skin homeostatic functions' regulation and the maintenance of the skin protective barrier integrity against microorgansims. Nitric oxide plays also a key role in wound healing; it acts as a potent mitogenic stimulus to keratinocytes during skin repair and enhances the hair follicles and sebaceous gland structure that appeared after two weeks of treatment. Thus, these drugs could be used in therapeutic approach for dermonecrotic skin repair.

Articular inflammation induced by an enzymatically-inactive Lys49 phospholipase A2: activation of endogenous phospholipases contributes to the pronociceptive effect

BACKGROUND

Arthritis is a set of inflammatory conditions that induce aching, stiffness, swelling, pain and may cause functional disability with severe consequences to the patient's lives. These are multi-mediated pathologies that cannot be effectively protected and/or treated. Therefore, the aim of this study was to establish a new model of acute arthritis, using a Lys49-PLA₂ (Bothrops asper myotoxin II; MT-II) to induce articular inflammation.

METHODS

The articular inflammation was induced by MT-II (10 μg/joint) injection into the left tibio-tarsal or femoral-tibial-patellar joints. Cellular influx was evaluated counting total and differential cells that migrated to the joint. The plasma extravasation was determined using Evans blue dye. The edematogenic response was evaluated measuring the joint thickness using a caliper. The articular hypernociception was determined by a dorsal flexion of the tibio-tarsal joint using an electronic pressure-meter test. The mediators involved in the articular hypernociception were evaluated using receptor antagonists and enzymatic inhibitors.

RESULTS

Plasma extravasation in the knee joints was observed 5 and 15 min after MT-II (10 μg/joint) injection. MT-II also induced a polymorphonuclear cell influx into the femoral-tibial-patellar joints observed 8 h after its injection, a period that coincided with the peak of the hyperalgesic effect. Hyperalgesia was inhibited by the pretreatment of the animals with cyclooxygenase inhibitor indomethacin, with type-2 cyclooxygenase inhibitor celecoxib, with AACOCF₃ and PACOCF_3, inhibitors of cytosolic and Ca²⁺-independent PLA₂s, respectively, with bradykinin B₂ receptor antagonist HOE 140, with antibodies against TNFα, IL-1β, IL-6 and CINC-1 and with selective ET-A (BQ-123) and ET-B (BQ-788) endothelin receptors antagonists. The MT-II-induced hyperalgesia was not altered by the lipoxygenase inhibitor zileuton, by the bradykinin B₁ receptor antagonist Lys-(Des-Arg9,Leu8)-bradykinin, by the histamine and serotonin antagonists promethazine and methysergide, respectively, by the nitric oxide inhibitor LNMMA and by the inhibitor of matrix 1-, 2-, 3-, 8- and 9- metalloproteinases GM6001 (Ilomastat).

CONCLUSION

These results demonstrated the multi-mediated characteristic of the articular inflammation induced by MT-II, which demonstrates its relevance as a model for arthritis mechanisms and treatment evaluation.

Structural determinants of the hyperalgesic activity of myotoxic Lys49-phospholipase A2

BACKGROUND

Bothropstoxin-I (BthTx-I) is a Lys49-phospholipase A₂ (Lys49-PLA₂) from the venom of Bothrops jararacussu, which despite of the lack of catalytic activity induces myotoxicity, inflammation and pain. The C-terminal region of the Lys49-PLA₂s is important for these effects; however, the amino acid residues that determine hyperalgesia and edema are unknown. The aim of this study was to characterize the structural determinants for the Lys49-PLA₂-induced nociception and inflammation.

METHODS

Scanning alanine mutagenesis in the active-site and C-terminal regions of BthTx-I has been used to study the structural determinants of toxin activities. The R118A mutant was employed as this substitution decreases PLA₂ myotoxicity. In addition, K115A and K116A mutants - which contribute to decrease cytotoxicity - and the K122A mutant - which decreases both myotoxicity and cytotoxicity - were also used. The H48Q mutant - which does not interfere with membrane damage or myotoxic activity - was used to evaluate if the PLA₂ catalytic site is relevant for the non-catalytic PLA₂-induced pain and inflammation. Wistar male rats received intraplantar injections with mutant PLA₂. Subsequently, hyperalgesia and edema were evaluated by the paw pressure test and by a plethysmometer. Native and recombinant BthTx-I were used as controls.

RESULTS

Native and recombinant BthTx-I induced hyperalgesia and edema, which peaked at 2 h. The R118A mutant did not induce nociception or edema. The mutations K115A and K116A abolished hyperalgesia without interfering with edema. Finally, the K122A mutant did not induce hyperalgesia and presented a decreased inflammatory response.

CONCLUSIONS

The results obtained with the BthTx-I mutants suggest, for the first time, that there are distinct residues responsible for the hyperalgesia and edema induced by BthTx-I. In addition, we also showed that cytolytic activity is essential for the hyperalgesic effect but not for edematogenic activity, corroborating previous data showing that edema and hyperalgesia can occur in a non-dependent manner. Understanding the structure-activity relationship in BthTx-I has opened new possibilities to discover the target for PLA₂-induced pain.

Lemnitoxin, the major component of Micrurus lemniscatus coral snake venom, is a myotoxic and pro-inflammatory phospholipase A2

The venom of Micrurus lemniscatus, a coral snake of wide geographical distribution in South America, was fractionated by reverse-phase HPLC and the fractions screened for phospholipase A2 (PLA2) activity. The major component of the venom, a PLA2, here referred to as 'Lemnitoxin', was isolated and characterized biochemically and toxicologically. It induces myotoxicity upon intramuscular or intravenous injection into mice. The amino acid residues Arg15, Ala100, Asn108, and a hydrophobic residue at position 109, which are characteristic of myotoxic class I phospholipases A2, are present in Lemnitoxin. This PLA2 is antigenically related to M. nigrocinctus nigroxin, Notechis scutatus notexin, Pseudechis australis mulgotoxin, and Pseudonaja textilis textilotoxin, as demonstrated with monoclonal and polyclonal antibodies. Lemnitoxin is highly selective in its targeting of cells, being cytotoxic for differentiated myotubes in vitro and muscle fibers in vivo, but not for undifferentiated myoblasts or endothelial cells. Lemnitoxin is not lethal after intravenous injection at doses up to 2μg/g in mice, evidencing its lack of significant neurotoxicity. Lemnitoxin displays anticoagulant effect on human plasma and proinflammatory activity also, as it induces paw edema and mast cell degranulation. Thus, the results of this work demonstrate that Lemnitoxin is a potent myotoxic and proinflammatory class I PLA2.

Ac2-26 Mimetic Peptide of Annexin A1 Inhibits Local and Systemic Inflammatory Processes Induced by Bothrops moojeni Venom and the Lys-49 Phospholipase A2 in a Rat Model

Annexin A1 (AnxA1) is an endogenous glucocorticoid regulated protein that modulates anti-inflammatory process and its therapeutic potential has recently been recognized in a range of systemic inflammatory disorders. The effect of the N-terminal peptide Ac2-26 of AnxA1 on the toxic activities of Bothrops moojeni crude venom (CV) and its myotoxin II (MjTX-II) were evaluated using a peritonitis rat model. Peritonitis was induced by the intraperitoneal injection of either CV or MjTX-II, a Lys-49 phospholipase A2. Fifteen minutes after the injection, the rats were treated with either Ac2-26 or PBS. Four hours later, the CV and MjTX-II-induced peritonitis were characterized by neutrophilia (in the peritoneal exudate, blood and mesentery) and increased number of mesenteric degranulated mast cells and macrophages. At 24 hours post-injection, the local inflammatory response was attenuated in the CV-induced peritonitis while the MjTX-II group exhibited neutrophilia (peritoneal exudates and blood). Ac2-26 treatment prevented the influx of neutrophils in MjTX-II-induced peritonitis and diminished the proportion of mesenteric degranulated mast cells and macrophages in CV-induced peritonitis. Additionally, CV and MjTX-II promoted increased levels of IL-1β and IL-6 in the peritoneal exudates which were significantly reduced after Ac2-26 treatment. At 4 and 24 hours, the endogenous expression of AnxA1 was upregulated in the mesenteric neutrophils (CV and MjTX-II groups) and mast cells (CV group). In the kidneys, CV and MjTX-II administrations were associated with an increased number of macrophages and morphological alterations in the juxtamedullary nephrons in proximal and distal tubules. Ac2-26 promoted significant recovery of the juxtamedullary structures, decreased the number of macrophages and diminished the AnxA1 in epithelial cells from distal tubules and renal capsules. Our results show that Ac2-26 treatment significantly attenuates local and systemic inflammatory processes and indicate this peptide as a potential target for the development of new therapeutic strategies for the snakebite envenomation treatment.

Novel acidic phospholipase A2 from Porthidium hyoprora causes inflammation with mast cell rich infiltrate

Phospholipases A₂ (PLA₂) are a group of enzymes that hydrolyze phospholipids at the sn-2 position, being present in all nature. In venomous animals, these proteins assume a special role, being able to exert diverse pharmacological effects. In this work, authors identified a new isoform of PLA₂ in the venom of Porthidium hyoprora, which was isolated through sequential chromatographic steps and named PhTX-III. The enzyme was characterized biochemically and structurally. Structural studies using mass spectrometry confirmed an acidic secretory PLA₂, family IIA, with molecular mass of 13,620.9 Da and identification of 86% of its primary sequence. PhTX-III did not exhibit myotoxic, anticoagulant or antibacterial effects, often present in this class of enzymes. Although, it was capable of initiate inflammatory response, with local edema and release of cytokines IL-1α, IL-6 and TNF-α, probably due to mast cell degranulation.

Occurrence of sulfated fucose branches in fucosylated chondroitin sulfate are essential for the polysaccharide effect preventing muscle damage induced by toxins and crude venom from Bothrops jararacussu snake

Snake envenoming is an important public health problem around the world, particularly in tropics. Beyond deaths, morbidity induced by snake venoms, such as myotoxicity, is of pivotal consequence to population. Bothrops jararacussu is the main venomous snake in southeast region of Brazil, and particularly presents strong myotoxic effect. The only available therapy, antibothropic antivenom, poorly affects venom-induced myotoxicity. The aim of this study is to assess the ability of fucosylated chondroitin sulfate (fucCS), a glycosaminoglycan with anticoagulant and antithrombotic properties, and its derivatives to inhibit toxic activities of B. jararacussu crude venom and its isolated toxins, named bothropstoxins (BthTX-I and BthTX-II). The in vitro myotoxic activities induced by crude venom, by BthTX-I alone and by toxins together were abolished by fucCS. Carboxyl reduction (fucCS-CR) kept this ability whereas defucosilation (defucCS) abrogates myoprotection. We observed the same pattern in the response of these polysaccharides in antagonizing the increase in plasma creatine kinase (CK) levels, the reduction of skeletal muscle CK content and the rise of myeloperoxidase (MPO) activity induced by crude venom and isolated toxins. FucCS inhibited edematogenic activity and partially prevented the reduction of total leukocytes in blood when pre-incubated with crude venom. Furthermore, the venom procoagulant effect was completely antagonized by increasing concentrations of fucCS, although this polyanion could stop neither the tail bleeding nor the skin hemorrhage induced by Bothrops jararaca venom. The B. jararacussu phospholipase, hyaluronidase, proteolytic and collagenase activities were inhibited in vitro. The results suggest that fucCS could be able to interact with both toxins, and it is able to inhibit BthTX-II phospholipase activity. Light microscopy of extensor digitorum longus muscle (EDL) muscle showed myoprotection by fucCS, once necrotic areas, edema and inflammatory cells were all decreased as compared to venom injection alone. Altogether, data show that fucCS was able to inhibit myotoxicity and inflammation induced by B. jararacussu venom and its phospholipase toxins, BthTX-I and BthTX-II. Thus, fucosylated chondroitin sulfate is a new polyanion with potential to be used as an adjuvant in the treatment of snakebites in the future.

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.

A novel phospholipase A2 (D49) from the venom of the Crotalus oreganus abyssus (North American Grand canyon rattlesnake)

Currently, Crotalus viridis was divided into two species: Crotalus viridis and Crotalus oreganus. The current classification divides "the old" Crotalus viridis into two new and independent species: Crotalus viridis (subspecies: viridis and nuntius) and Crotalus oreganus (subspecies: abyssus, lutosus, concolor, oreganus, helleri, cerberus, and caliginis). The analysis of a product from cDNA (E6d), derived from the gland of a specie Crotalus viridis viridis, was found to produce an acid phospholipase A2. In this study we isolated and characterized a PLA2 (D49) from Crotalus oreganus abyssus venom. Our studies show that the PLA2 produced from the cDNA of Crotalus viridis viridis (named E6d) is exactly the same PLA2 primary sequence of amino acids isolated from the venom of Crotalus oreganus abyssus. Thus, the PLA2 from E6d cDNA is actually the same PLA2 presented in the venom of Crotalus oreganus abyssus and does not correspond to the venom from Crotalus viridis viridis. These facts highlight the importance of performing more studies on subspecies of Crotalus oreganus and Crotalus viridis, since the old classification may have led to mixed results or mistaken data.

Activation of J77A.1 macrophages by three phospholipases A2 isolated from Bothrops atrox snake venom

In the present study, we investigated the in vitro effects of two basic myotoxic phospholipases A2 (PLA2), BaTX-I, a catalytically inactive Lys-49 variant, and BaTX-II, a catalytically active Asp-49, and of one acidic myotoxic PLA2, BaPLA2, a catalytically active Asp-49, isolated from Bothrops atrox snake venom, on the activation of J774A.1 macrophages. At noncytotoxic concentrations, the toxins did not affect the adhesion of the macrophages, nor their ability to detach. The data obtained showed that only BaTX-I stimulated complement receptor-mediated phagocytosis. However, BaTX-I, BaTX-II, and BaPLA2 induced the release of the superoxide anion by J774A.1 macrophages. Additionally, only BaTX-I raised the lysosomal volume of macrophages after 15 min of incubation. After 30 min, all the phospholipases increased this parameter, which was not observed within 60 min. Moreover, BaTX-I, BaTX-II, and BaPLA2 increased the number of lipid bodies on macrophages submitted to phagocytosis and not submitted to phagocytosis. However, BaTX-II and BaPLA2 induced the release of TNF-α by J774A.1 macrophages. Taken together, the data show that, despite differences in enzymatic activity, the three toxins induced inflammatory events and whether the enzyme is acidic or basic does not seem to contribute to these effects.

Characterization of inflamin, the first member of a new family of snake venom proteins that induces inflammation

Unlike other sea snakes, Aipysurus eydouxii feeds exclusively on fish eggs. This unusual feeding habit prompted us to search for unique transcripts in their venom glands. In the present study we expressed a novel cysteine-rich secretory protein containing 94 amino acid residues that was identified in its cDNA library. As it induced inflammation and writhing in animals, this protein was named inflamin. It induced two waves of prostanoid production. The first wave peaked at 10 min and 6-oxo PGF1α (prostaglandin F1α) (6-keto PGF1α) was the major product. The second wave, specifically of 6-oxo PGF1α and PGE2 (prostanglandin E2), started after 2 h. In RAW 264.7 cells, COX-1 (cyclo-oxygenase-1) activity showed a transient increase at 10 min and is responsible for the first wave, but its expression was unaffected. COX-2 was induced after 3 h and is responsible for the second wave. Using specific inhibitors, we showed that cPLA2 (calcium-dependent phospholipase A2), and not sPLA2 (secretory phospholipase A2), iPLA2 (calcium-independent phospholipase A2) or DAG (diacylglycerol) lipase, plays a key role in arachidonate release. The cPLA2 activity showed a transient increase of 62% at 10 min; this increase was due to its phosphorylation and not due to an increase in its expression. Thus inflamin, the first member of a new family of snake venom proteins, leads to an increase in the cPLA2 and COX-1 activity resulting in inflammation and pain.

Action of two phospholipases A2 purified from Bothrops alternatus snake venom on macrophages

The in vitro effects of BaltTX-I, a catalytically inactive Lys49 variant of phospholipase A2 (PLA2), and BaltTX-II, an Asp49 catalytically active PLA2 isolated from Bothrops alternatus snake venom, on thioglycollate-elicited macrophages (TG-macrophages) were investigated. At non-cytotoxic concentrations, the secretory PLA2 BaltTX-I but not BaltTX-II stimulated complement receptor-mediated phagocytosis. Pharmacological treatment of TG-macrophages with staurosporine, a protein kinase C (PKC) inhibitor, showed that this kinase is involved in the increase of serum-opsonized zymosan phagocytosis induced by BaltTX-I but not BaltTX-II secretory PLA2, suggesting that PKC may be involved in the stimulatory effect of this toxin in serum-opsonized zymosan phagocytosis. Moreover, BaltTX-I and -II induced superoxide production by TG-macrophages. This superoxide production stimulated by both PLA2s was abolished after treatment of cells with staurosporine, indicating that PKC is an important signaling pathway for the production of this radical. Our experiments showed that, at non-cytotoxic concentrations, BaltTX-I may upregulate phagocytosis via complement receptors, and that both toxins upregulated the respiratory burst in TG-macrophages.

Antitumoral potential of Tunisian snake venoms secreted phospholipases A2

Phospholipases type A₂ (PLA₂s) are the most abundant proteins found in Viperidae snake venom. They are quite fascinating from both a biological and structural point of view. Despite similarity in their structures and common catalytic properties, they exhibit a wide spectrum of pharmacological activities. Besides being hydrolases, secreted phospholipases A₂ (sPLA₂) are an important group of toxins, whose action at the molecular level is still a matter of debate. These proteins can display toxic effects by different mechanisms. In addition to neurotoxicity, myotoxicity, hemolytic activity, antibacterial, anticoagulant, and antiplatelet effects, some venom PLA₂s show antitumor and antiangiogenic activities by mechanisms independent of their enzymatic activity. This paper aims to discuss original finding against anti-tumor and anti-angiogenic activities of sPLA₂ isolated from Tunisian vipers: Cerastes cerastes and Macrovipera lebetina, representing new tools to target specific integrins, mainly, α5β1 and αv integrins.

Unmasking snake venom of Bothrops leucurus: purification and pharmacological and structural characterization of new PLA2 Bleu TX-III

Bleu TX-III was isolated from Bothrops leucurus snake venom on one-step analytical chromatography reverse phase HPLC, was homogeneous on SDS-PAGE, and was confirmed by Q-Tof Ultima API ESI/MS (TOF MS mode) mass spectrometry in 14243.8 Da. Multiple alignments of Bleu TX-III show high degree of homology with basic PLA2 myotoxins from other Bothrops venoms. Our studies on local and systemic myotoxicity "in vivo" reveal that Bleu TX-III is myotoxin with local but not systemic action due to the decrease in the plasmatic CK levels when Bleu TX-III is administrated by intravenous route in mice (dose 1 and 5  μg). And at a dose of 20  μg myotoxin behaves like a local and systemic action. Bleu TX-III induced moderate marked paw edema, evidencing the local increase in vascular permeability. The inflammatory events induced in the mice (I.M.) were investigated. The increase in the levels of IL-1, IL-6, and TNF-α was observed in the plasma. It is concluded that Bleu TX-III induces inflammatory events in this model. The enzymatic phospholipid hydrolysis may be relevant to these phenomena. Bothrops leucurus venom is still not extensively explored, and the knowledge of its toxins separately through the study of structure/function will contribute for a better understanding of its action mechanism.

Biochemical characterization and pharmacological properties of new basic PLA2 BrTX-I isolated from Bothrops roedingeri (Roedinger's Lancehead) Mertens, 1942, snake venom

BrTX-I, a PLA2, was purified from Bothrops roedingeri venom after only one chromatographic step using reverse-phase HPLC on μ-Bondapak C-18 column. A molecular mass of 14358.69 Da was determined by MALDI-TOF mass spectrometry. Amino acid analysis showed a high content of hydrophobic and basic amino acids as well as 14 half-cysteine residues. The total amino acid sequence was obtained using SwissProt database and showed high amino acid sequence identity with other PLA2 from snake venom. The amino acid composition showed that BrTX-I has a high content of Lys, Tyr, Gly, Pro, and 14 half-Cys residues, typical of a basic PLA2. BrTX-I presented PLA2 activity and showed a minimum sigmoidal behavior, reaching its maximal activity at pH 8.0, 35-45°C, and required Ca(2+). In vitro, the whole venom and BrTX-I caused a neuromuscular blockade in biventer cervicis preparations in a similar way to other Bothrops species. BrTX-I induced myonecrosis and oedema-forming activity analyzed through injection of the purified BrTX-I in mice. Since BrTX-I exerts a strong proinflammatory effect, the enzymatic phospholipid hydrolysis might be relevant for these phenomena; incrementing levels of IL-1, IL-6, and TNF α were observed at 15 min, 30 min, one, two, and six hours postinjection, respectively.

Biochemical, pharmacological, and structural characterization of new basic PLA2 Bbil-TX from Bothriopsis bilineata snake venom

Bbil-TX, a PLA2, was purified from Bothriopsis bilineata snake venom after only one chromatographic step using RP-HPLC on μ-Bondapak C-18 column. A molecular mass of 14243.8 Da was confirmed by Q-Tof Ultima API ESI/MS (TOF MS mode) mass spectrometry. The partial protein sequence obtained was then submitted to BLASTp, with the search restricted to PLA2 from snakes and shows high identity values when compared to other PLA2s. PLA2 activity was presented in the presence of a synthetic substrate and showed a minimum sigmoidal behavior, reaching its maximal activity at pH 8.0 and 25-37°C. Maximum PLA2 activity required Ca(2+) and in the presence of Cd(2+), Zn(2+), Mn(2+), and Mg(2+) it was reduced in the presence or absence of Ca(2+). Crotapotin from Crotalus durissus cascavella rattlesnake venom and antihemorrhagic factor DA2-II from Didelphis albiventris opossum sera under optimal conditions significantly inhibit the enzymatic activity. Bbil-TX induces myonecrosis in mice. The fraction does not show a significant cytotoxic activity in myotubes and myoblasts (C2C12). The inflammatory events induced in the serum of mice by Bbil-TX isolated from Bothriopsis bilineata snake venom were investigated. An increase in vascular permeability and in the levels of TNF-a, IL-6, and IL-1 was was induced. Since Bbil-TX exerts a stronger proinflammatory effect, the phospholipid hydrolysis may be relevant for these phenomena.

A Lys49 phospholipase A2, isolated from Bothrops asper snake venom, induces lipid droplet formation in macrophages which depends on distinct signaling pathways and the C-terminal region

MT-II, a Lys49PLA₂ homologue devoid of catalytic activity from B. asper venom, stimulates inflammatory events in macrophages. We investigated the ability of MT-II to induce formation of lipid droplets (LDs), key elements of inflammatory responses, in isolated macrophages and participation of protein kinases and intracellular PLA₂s in this effect. Influence of MT-II on PLIN2 recruitment and expression was assessed, and the effects of some synthetic peptides on LD formation were further evaluated. At noncytotoxic concentrations, MT-II directly activated macrophages to form LDs. This effect was reproduced by a synthetic peptide corresponding to the C-terminal sequence 115–129 of MT-II, evidencing the critical role of C-terminus for MT-II-induced effect. Moreover, MT-II induced expression and recruitment of PLIN2. Pharmacological interventions with specific inhibitors showed that PKC, PI3K, ERK1/2, and iPLA₂, but not P38^MAPK or cPLA₂, signaling pathways are involved in LD formation induced by MT-II. This sPLA₂ homologue also induced synthesis of PGE₂ that colocalized to LDs. In conclusion, MT-II is able to induce formation of LDs committed to PGE₂ formation in a process dependent on C-terminal loop engagement and regulated by distinct protein kinases and iPLA₂. LDs may constitute an important inflammatory mechanism triggered by MT-II in macrophages.

Induction of mast-cell accumulation by promutoxin, an Arg-49 phospholipase A2

Local inflammation is a prominent characteristic of snakebite wound, and snake-venom phospholipase A2s (PLA2s) are some of the main component that contribute to accumulation of inflammatory cells. However, the action of an R49 PLA2s, promutoxin from Protobothrops mucrosquamatus venom, on mast-cell accumulation has not been previously examined. Using a mouse peritoneal model, we found that promutoxin can induce approximately-6-fold increase in mast-cell accumulation, and the response lasts at least for 16 h. The promutoxin-induced mast cell accumulation was inhibited by cyproheptadine, terfenadine, and Ginkgolide B, indicating that histamine and platelet-activating factor (PAF) is likely to contribute to the mast-cells accumulation. Preinjection of antibodies against adhesion molecules ICAM-1, CD18, CD11a, and L-selectin showed that ICAM-1, and CD18, CD11a are key adhesion molecules of promutoxin-induced mast-cell accumulation. In conclusion, promutoxin can induce accumulation of mast cells, which may contribute to snake-venom wound.

Biological and biochemical characterization of two new PLA2 isoforms Cdc-9 and Cdc-10 from Crotalus durissus cumanensis snake venom

This work reports the purification, biological characterization and amino acid sequence of two new basic PLA(2) isoforms, Cdc-9 and Cdc-10, purified from the Crotalus durissus cumanensis venom by one step analytical chromatography reverse phase HPLC. The molecular masses of the PLA(2) were 14,175+/-2.7 Da for Cdc-9 and 14,228+/-3.5 Da for Cdc-10 both deduced by primary structure and confirmed by MALDI-TOF. The isoforms presented an amino acid sequence of 122 amino acid residues, being Cdc-9: SLVQFNKMIK FETRKSGLPF YAAYGCYCGW GGQRPKDATD RCCFVHDCCY GKVAKCNTKW DIYSYSLKSG YITCGKGTWC KEQICECDRV AAECLRRSLS TYKNEYMFYP DSRCREPPEY TC with pI value of 8.25 and Cdc-10: SLLQFNKMIK FETRKSGVPF YAAYGCYCGW GGRRPKDPTD RCCFVHDCCY GKLTKCNTKW DIYSYSLKSG YITCGKGTWC KEQICECDRV AAECLRRSLN TYKNEYMFYP DSRCRGPPEY TC with a pI value of 8.46, showing highly conserved Ca(2+)-binding and catalytic sites. The PLA(2) activity decreased when the isoforms Cdc-9 and Cdc-10 were incubated with 4-bromophenacyl bromide (p-BPB), anhydrous acetic acid and p-nitrobenzene sulfonyl fluoride (NBSF) when compared with the activity of both native isoforms. In mice, the PLA(2) isoforms Cdc-9 and Cdc-10 induced myonecrosis and edema. Myotoxic and edema activities were reduced after treatment of the isoforms with p-BPB; acetylation of the lysine residues and the treatment of PLA(2) with NBSF have also induced edema reduction. However, p-BPB strongly diminishes the local and systemic myotoxic effects.

Induction of microvascular leakage and histamine release by promutoxin, an Arg49 phospholipase A2

It has been recognized that phospholipase A(2) (PLA(2)) is a crucial factor of snake venom induced inflammation. Recently, promutoxin, a novel member of minor subgroup of snake venom PLA(2) (R49 PLA(2)) has been characterized in our laboratory, but its roles in induction of inflammation remain uninvestigated. Using highly purified promutoxin, we found this enzymatically inactive PLA(2) provoked a dose-dependent increase in microvascular leakage in the skin of rats. Pretreatment of rats with compound 48/80 diminished promutoxin-induced skin reaction and reduced mast cell numbers in rats. Cyproheptadine, terfenadine, Ginkgolide B and heparin inhibited promutoxin elicited microvascular leakage when they were co-injected with the stimulus to rat skin. Moreover, promutoxin was found to induce histamine release from human colon, lung and tonsil mast cells, and both metabolic inhibitors and pertussis toxin were capable of inhibiting promutoxin elicited histamine release. Provocation of microvascular leakage and mast cell activation by promutoxin suggests further that snake venom induced inflammation is related to mast cell activation and certain anti-inflammatory drugs could be therapeutic effective in treating snake wound.

Induction of mast cell accumulation, histamine release and skin edema by N49 phospholipase A2

BACKGROUND

It has been recognized that phospholipase A2 (PLA2) is a crucial component of snake venom, which contributes greatly to snake venom induced inflammation in man. However, the mechanisms through which N49 PLA2 provoke inflammation remain unclear. Recently, a N49 PLA2, TM-N49 from Protobothrops mucrosquamatus crude venom was characterized in our laboratory. Since the purification procedure developed is able to supply us with relatively large quantity of highly purified TM-N49, we investigated the ability of TM-N49 in induction of inflammation.

RESULTS

The results showed that TM-N49 provoked a dose dependent increase in microvascular leakage in the skin of rats. The potency of TM-N49 in induction of skin edema appeared similar potency of bradykinin and histamine. Pretreatment of rats with compound 48/80 diminished TM-N49 induced skin reaction and reduced mast cell numbers in rats. Ginkgolide B and cyproheptadine, but not terfenadine and quinacrine, inhibited TM-N49 elicited microvascular leakage when they were co-injected with the stimulus to rat skin. Moreover, TM-N49 was found to induce histamine release from human colon, lung and tonsil mast cells, and both metabolic inhibitors and pertussis toxin were capable of inhibiting TM-N49 elicited histamine release. TM-N49 induced mast cell accumulation in the peritoneum of mice, which was inhibited by co-injection of ginkgolide B, cyproheptadine and terfenadine. Intravenous injection of monoclonal antibodies against CD18, ICAM-1 and CD11a also blocked TM-N49 induced mast cell accumulation.

CONCLUSION

TM-N49 is a potent stimulus for skin edema, mast cell activation and accumulation.

Inflammatory events induced by brown spider venom and its recombinant dermonecrotic toxin: a pharmacological investigation

Accidents involving Brown spider (Loxosceles sp.) venom produce a massive inflammatory response in injured region. This venom has a complex mixture of different toxins, and the dermonecrotic toxin is the major contributor to toxic effects. The ability of Loxosceles intermedia venom and a recombinant isoform of dermonecrotic toxin to induce edema and increase in vascular permeability was investigated. These toxins were injected into hind paws and caused a marked dose and time-dependent edema and increase in vascular permeability in mice. Furthermore, the enzymatic activity of venom toxins may be primal for these effects. A mutated recombinant isoform of dermonecrotic toxin, that has only residual enzymatic activity, was not able to induce these inflammatory events. Besides the previous heating of toxins markedly reduced the paw edema and vascular permeability showing that thermolabile constituents can trigger these effects. In addition, the ability of these venom toxins to evoke inflammatory events was partially reduced in compound 48/80-pretreated animals, suggesting that mast cells may be involved in these responses. Pretreating mice with histamine (prometazine and cetirizine) and serotonin (methysergide) receptor antagonists significantly attenuated toxins induced edema and vascular permeability. Moreover, HPLC analysis of whole venom showed the presence of histamine sufficient to induce inflammatory responses. In conclusion, these inflammatory events may result from the activation of mast cells, which in turn release bioamines and may be related to intrinsic histamine content of venom.

Ctenus medius and Phoneutria nigriventer spiders venoms share noxious proinflammatory activities

Ctenus medius Keyserling, 1891 (Araneae: Ctenidae) co-occurs in various microhabitats of the Brazilian Atlantic Forest and can be easily misidentified as the medically important spider Phoneutria nigriventer Keyserling, 1981 (Ctenidae). Despite being phylogenetically close to Phoneutria, no data are available about the toxic potential of Ctenus medius venom. Here we show that, although presenting different profile of protein composition, C. medius venom displays some of the toxic properties exhibited by P. nigriventer venom, including proteolytic, hyaluronidasic and phospholipasic activities, as well as the ability of causing hyperalgesia and edema. Moreover, C. medius venom interferes in the activation of the complement system in concentrations that P. nigriventer venom is inactive. Thus, these data show that venoms of spiders from Ctenidae family share important proinflammatory properties and suggest that the C. medius bite may have an important noxious effect in human accidents.

Myotoxic phospholipases A(2) isolated from Bothrops brazili snake venom and synthetic peptides derived from their C-terminal region: cytotoxic effect on microorganism and tumor cells

This paper reports the purification and biochemical/pharmacological characterization of two myotoxic phospholipases A(2) (PLA(2)s) from Bothrops brazili venom, a native snake from Brazil. Both myotoxins (MTX-I and II) were purified by a single chromatographic step on a CM-Sepharose ion-exchange column up to a high purity level, showing M(r) approximately 14,000 for the monomer and 28,000Da for the dimer. The N-terminal and internal peptide amino acid sequences showed similarity with other myotoxic PLA(2)s from snake venoms, MTX-I belonging to Asp49 PLA(2) class, enzymatically active, and MTX-II to Lys49 PLA(2)s, catalytically inactive. Treatment of MTX-I with BPB and EDTA reduced drastically its PLA(2) and anticoagulant activities, corroborating the importance of residue His48 and Ca(2+) ions for the enzymatic catalysis. Both PLA(2)s induced myotoxic activity and dose-time dependent edema similar to other isolated snake venom toxins from Bothrops and Crotalus genus. The results also demonstrated that MTXs and cationic synthetic peptides derived from their 115-129 C-terminal region displayed cytotoxic activity on human T-cell leukemia (JURKAT) lines and microbicidal effects against Escherichia coli, Candida albicans and Leishmania sp. Thus, these PLA(2) proteins and C-terminal synthetic peptides present multifunctional properties that might be of interest in the development of therapeutic strategies against parasites, bacteria and cancer.

Role of substance P and bradykinin in acute pancreatitis induced by secretory phospholipase A2

OBJECTIVES

Secretory phospholipases A2 (sPLA2s) induce acute pancreatitis when injected into the common bile duct of rats. Substance P via neurokinin 1 (NK-1) receptors and bradykinin via B2 receptors are described to play important roles in the pathophysiology of acute pancreatitis. This study was undertaken to evaluate the role of substance P and bradykinin in the sPLA2-induced pancreatitis.

METHODS

Rats were submitted to the common bile duct injection of sPLA2 obtained from Naja mocambique mocambique venom at 300 microg/kg. At 4 hours thereafter, measurement of pancreatic plasma extravasation, pancreatic and lung myeloperoxidase (MPO), serum amylase, and serum tumor necrosis factor alpha levels were evaluated.

RESULTS

Injection of sPLA2 significantly increased all parameters evaluated. Pretreatment with either the NK-1 receptor antagonist SR140333 or the B2 receptor antagonist icatibant largely reduced the increased pancreatic plasma extravasation and circulating levels of tumor necrosis factor alpha. Both treatments partly reduced the MPO levels in the pancreas, whereas in the lungs, icatibant was more efficient to reduce the increased MPO levels. In addition, icatibant largely reduced the serum levels of amylase, whereas SR140333 had no significant effect.

CONCLUSIONS

We concluded that NK-1 and B2 receptors can regulate important steps in the local and remote inflammation during acute pancreatitis induced by sPLA2.