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

Systemic loxoscelism leading to autoimmune haemolytic anaemia in a healthy young adult

The brown recluse spider (Loxosceles reclusa) is endemic to the southcentral Midwest and the Southern United States. A bite from a brown recluse spider may result in symptoms that range from local skin necrosis to systemic complications such as acute haemolytic anaemia, disseminated intravascular coagulopathy, rhabdomyolysis and death. Although rare, systemic loxoscelism is a clinical diagnosis of exclusion that should be considered in a patient with acute autoimmune haemolytic anaemia. We describe a case of a young man with autoimmune haemolytic anaemia secondary to systemic loxoscelism successfully treated with intravenous immunoglobulin and steroids.

A Brief Overview of the Toxic Sphingomyelinase Ds of Brown Recluse Spider Venom and Other Organisms and Simple Methods To Detect Production of Its Signature Cyclic Ceramide Phosphate

A special category of phospholipase D (PLD) in the venom of the brown recluse spider (Loxosceles reclusa) and several other sicariid spiders accounts for the dermonecrosis and many of the other clinical symptoms of envenomation. Related proteins are produced by other organisms, including fungi and bacteria. These PLDs are often referred to as sphingomyelinase Ds (SMase Ds) because they cleave sphingomyelin (SM) to choline and "ceramide phosphate." The lipid product has actually been found to be a novel sphingolipid: ceramide 1,3-cyclic phosphate (Cer1,3P). Since there are no effective treatments for the injury induced by the bites of these spiders, SMase D/PLDs are attractive targets for therapeutic intervention, and some of their features will be described in this minireview. In addition, two simple methods are described for detecting the characteristic SMase D activity using a fluorescent SM analog, (N-[12-[(7-nitro-2-1,3-benzoxadiazol-4-yl)amino]dodecanoyl]-SM (C12-NBD-SM), that is cleaved to C12-NBD-Cer1,3P, which is easily separated from other potential metabolites by thin-layer chromatography and visualized under UV light. Besides confirming that C12-NBD-Cer1,3P is the only product detected upon incubation of C12-NBD-SM with brown recluse spider venom, the method was also able to detect for the first time very low levels of activity in venom from another spider, Kukulcania hibernalis The simplicity of the methods makes it relatively easy to determine this signature activity of SMase D/PLD. SIGNIFICANCE STATEMENT: The sphingomyelinase D/phospholipase D that are present in the venom of the brown recluse spider and other sources cause considerable human injury, but detection of the novel sphingolipid product, ceramide 1,3-cyclic phosphate, is not easy by previously published methods. This minireview describes simple methods for detection of this activity that will be useful for studies of its occurrence in spider venoms and other biological samples, perhaps including lesions from suspected spider bites and infections.

Comparative Biochemical, Structural, and Functional Analysis of Recombinant Phospholipases D from Three Loxosceles Spider Venoms

Spiders of Loxosceles genus are widely distributed and their venoms contain phospholipases D (PLDs), which degrade phospholipids and trigger inflammatory responses, dermonecrosis, hematological changes, and renal injuries. Biochemical, functional, and structural properties of three recombinant PLDs from L. intermedia, L. laeta, and L. gaucho, the principal species clinically relevant in South America, were analyzed. Sera against L. gaucho and L. laeta PLDs strongly cross-reacted with other PLDs, but sera against L. intermedia PLD mostly reacted with homologous molecules, suggesting underlying structural and functional differences. PLDs presented a similar secondary structure profile but distinct melting temperatures. Different methods demonstrated that all PLDs cleave sphingomyelin and lysophosphatidylcholine, but L. gaucho and L. laeta PLDs excelled. L. gaucho PLD showed greater "in vitro" hemolytic activity. L. gaucho and L. laeta PLDs were more lethal in assays with mice and crickets. Molecular dynamics simulations correlated their biochemical activities with differences in sequences and conformations of specific surface loops, which play roles in protein stability and in modulating interactions with the membrane. Despite the high similarity, PLDs from L. gaucho and L. laeta venoms are more active than L. intermedia PLD, requiring special attention from physicians when these two species prevail in endemic regions.

Brown recluse spider envenomation with systemic loxoscelism and delayed hemolysis: A case report

The brown recluse spider (Loxosceles reclusa) is endemic to the South, West and Central Midwestern United States, and envenomation from this spider can cause cutaneous and/or systemic symptoms. We present a case of systemic loxocelism in an adolescent male resulting in three emergency department visits and two hospitalizations for a rare case of delayed hemolysis 6 days after envenomation. A 19-year-old male presented to the emergency department twice within two days after envenomation with worsening pain, subjective fever, chills, nausea and vomiting. He required a two-day hospitalization for rhabdomyolysis and acute kidney injury. The patient was discharged with improving symptoms and laboratory results on day four before returning again on day seven with worsening symptoms. He was diagnosed with hemolytic anemia on day seven and was subsequently hospitalized for six days. This case of systemic loxoscelism manifested hemolysis six days after envenomation, following an improvement in symptoms and laboratory studies. This case highlights the need for continuous monitoring and/or follow-up in cases of systemic loxocelism.

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

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

Anti-inflammatory activities of arthropod peptides: a systematic review

Peptides obtained from different animal species have gained importance recently due to research that aims to develop biopharmaceuticals with therapeutic potential. In this sense, arthropod venoms have drawn attention, not only because of their toxicity but mainly for the search for molecules with various bioactivities, including anti-inflammatory activity. The purpose of the present study is to gather data available in the literature on new peptides derived from arthropod species with anti-inflammatory potential. This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Studies on peptides from arthropods that display anti-inflammatory activity were retrieved from PubMed, Scopus, Web of Science, and Google Scholar databases. The bibliographic research started in 2020 and searched papers without a limit on the publication date. The articles were analyzed using a search string containing the following terms: "Peptides" and "Anti-inflammatory", in combinations such as "Ant", "Bee", "Wasp", "Crab", "Shrimp", "Scorpion", "Spider", "Tick" and "Centipedes". Besides, a search was carried out in the databases with the terms: "Peptides", "Antitumor", or "Anticancer", and "Arthropods". Articles that met the inclusion and exclusion criteria totalized 171, and these served for data extraction. Additionally, the present review included anti-inflammatory peptides with anticancer properties. Peptides with confirmed anti-inflammatory activity were from insects (ants, bees, and wasps), crustaceans (shrimp and crabs), arachnids (scorpions, spiders, and ticks), and centipedes. These arthropod peptides act mainly by decreasing pro-inflammatory cytokines as analyzed in vitro and in vivo. Some showed significant antineoplastic activity, working in essential cellular pathways against malignant neoplasms.

A loxoscelism case received therapeutic apheresis and hyperbaric oxygen therapy

Loxosceles reclusa (L.reclusa) is known to bite humans, and its venom includes several enzymes that cause clinical symptoms. Loxoscelism, a condition due to being bitten by Loxosceles spiders, commonly known as recluses, can involve a range of clinical conditions, from local cutaneous lesions to severe systemic involvement. The diagnosis of loxoscelism is usually made by anamnesis and clinical findings. Magnetic resonance imaging is recommended for patients at high risk of necrotizing fasciitis. Treatment modalities are still controversial and there is no standardized treatment approach. Reported here, our case of loxoscelism involved a 24-year-old man presenting with a Loxosceles spider bite, dermonecrotic lesion, vomiting, diarrhea, acute renal injury, and rhabdomyolysis, who was successfully treated with hyperbaric oxygen therapy, therapeutic apheresis, hemodialysis, wound debridement, and cutaneous autografting. Early diagnosis and multidisciplinary approach can be life-saving in spider bites that can cause systemic involvement. Loxoscelism should be considered in patients with skin necrosis, acute renal injury, and rhabdomyolysis.

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

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

Loxoscelism: Advances and Challenges in the Design of Antibody Fragments with Therapeutic Potential

Envenoming due to Loxosceles spider bites still remains a neglected disease of particular medical concern in the Americas. To date, there is no consensus for the treatment of envenomed patients, yet horse polyclonal antivenoms are usually infused to patients with identified severe medical conditions. It is widely known that venom proteins in the 30–35 kDa range with sphingomyelinase D (SMasesD) activity, reproduce most of the toxic effects observed in loxoscelism. Hence, we believe that monoclonal antibody fragments targeting such toxins might pose an alternative safe and effective treatment. In the present study, starting from the monoclonal antibody LimAb7, previously shown to target SMasesD from the venom of L. intermedia and neutralize its dermonecrotic activity, we designed humanized antibody V-domains, then produced and purified as recombinant single-chain antibody fragments (scFvs). These molecules were characterized in terms of humanness, structural stability, antigen-binding activity, and venom-neutralizing potential. Throughout this process, we identified some blocking points that can impact the Abs antigen-binding activity and neutralizing capacity. In silico analysis of the antigen/antibody amino acid interactions also contributed to a better understanding of the antibody’s neutralization mechanism and led to reformatting the humanized antibody fragment which, ultimately, recovered the functional characteristics for efficient in vitro venom neutralization.

Haplopelma hainanum venom induces inflammatory skin lesions

The Haplopelma hainanum is a species of theraphosid spider from China. Its large size and charming appearance make this species a popular pet. According to a previous study, theraphosid spider bites can induce pain, erythema, and edema in humans and can present more severely in domestic animals. The pathological consequences of envenomation by H. hainanum remain unclear. In this study, we investigated the effects and mechanisms of H. hainanum envenomation in mice. We showed that the venom induced slight swelling, intense inflammatory response, and increased the microvascular density in mice skin. Moreover, we found that 50 µg/ml of the spider’s venom induced IL-1β expression in both HaCaT cells and fibroblast cells, but repressed CXCL10 expression in fibroblasts. The venom significantly induced cell senescence and repressed cell proliferation and migration in both HaCaT cells and fibroblast cells. Finally, we examined the expression of Nav channel in HaCaT and fibroblast cells and found that H. hainanum venom effectively inhibited Na⁺ currents in HaCaT cells. Our study calls for further investigation of the pathological consequences and potential mechanisms of H. hainanum envenomation. This information might assist in the development of suitable therapy.

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

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

Design and Production of a Recombinant Hybrid Toxin to Raise Protective Antibodies Against Loxosceles Spider Venom

Human accidents with spiders of the genus Loxosceles are an important health problem affecting thousands of people worldwide. Patients evolve to severe local injuries and, in many cases, to systemic disturbances as acute renal failure, in which cases antivenoms are considered to be the most effective treatment. However, for antivenom production, the extraction of the venom used in the immunization process is laborious and the yield is very low. Thus, many groups have been exploring the use of recombinant Loxosceles toxins, particularly phospholipases D (PLDs), to produce the antivenom. Nonetheless, some important venom activities are not neutralized by anti-PLD antibodies. Astacin-like metalloproteases (ALMPs) are the second most expressed toxin acting on the extracellular matrix, indicating the importance of its inclusion in the antigen’s formulation to provide a better antivenom. Here we show the construction of a hybrid recombinant immunogen, called LgRec1ALP1, composed of hydrophilic regions of the PLD and the ALMP toxins from Loxosceles gaucho. Although the LgRec1ALP1 was expressed as inclusion bodies, it resulted in good yields and it was effective to produce neutralizing antibodies in mice. The antiserum neutralized fibrinogenolytic, platelet aggregation and dermonecrotic activities elicited by L. gaucho, L. laeta, and L. intermedia venoms, indicating that the hybrid recombinant antigen may be a valuable source for the production of protective antibodies against Loxosceles ssp. venoms. In addition, the hybrid recombinant toxin approach may enrich and expand the alternative antigens for antisera production for other venoms.

Arthropod venoms: Biochemistry, ecology and evolution

Comprising of over a million described species of highly diverse invertebrates, Arthropoda is amongst the most successful animal lineages to have colonized aerial, terrestrial, and aquatic domains. Venom, one of the many fascinating traits to have evolved in various members of this phylum, has underpinned their adaptation to diverse habitats. Over millions of years of evolution, arthropods have evolved ingenious ways of delivering venom in their targets for self-defence and predation. The morphological diversity of venom delivery apparatus in arthropods is astounding, and includes extensively modified pedipalps, tail (telson), mouth parts (hypostome), fangs, appendages (maxillulae), proboscis, ovipositor (stinger), and hair (urticating bristles). Recent investigations have also unravelled an astonishing venom biocomplexity with molecular scaffolds being recruited from a multitude of protein families. Venoms are a remarkable bioresource for discovering lead compounds in targeted therapeutics. Several components with prospective applications in the development of advanced lifesaving drugs and environment friendly bio-insecticides have been discovered from arthropod venoms. Despite these fascinating features, the composition, bioactivity, and molecular evolution of venom in several arthropod lineages remains largely understudied. This review highlights the prevalence of venom, its mode of toxic action, and the evolutionary dynamics of venom in Arthropoda, the most speciose phylum in the animal kingdom.

Probable cutaneous loxoscelism with mild systemic symptoms: A case report from Spain

We present a case from Valencia, Spain, of a 25-year-old woman who presented with a painful erythematous skin lesion, initially diagnosed as cellulitis. The lesion was unresponsive to antibiotic treatments and progressed into a hemorrhagic blister with necrotic ulcer formation. Posterior collection of a spider from the patient's home and expert identification of the spider as Loxosceles rufescens was achieved, establishing the diagnosis of probable cutaneous loxoscelism. Symptomatic treatment, general wound care and ultimately surgery, resulted in complete recovery with minor residual scarring. This case illustrates some of the difficulties encountered in the diagnosis and treatment of loxoscelism and adds to the increasing reports of loxoscelism in the Mediterranean Basin.