Scorpion envenomation and inflammation: Beyond neurotoxic effects

Clinical outcomes in a murine model after envenoming by the Amazonian scorpions Tityus strandi and Tityus dinizi

The Brazilian Amazon is home to a rich fauna of scorpion species of medical importance, some of them still poorly characterized regarding their biological actions and range of clinical symptoms after envenoming. The Amazonian scorpion species Tityus strandi and Tityus dinizi constitute some of the scorpions in this group, with few studies in the literature regarding their systemic repercussions. In the present study, we characterized the clinical, inflammatory, and histopathological manifestations of T. strandi and T. dinizi envenoming in a murine model using Balb/c mice. The results show a robust clinical response based on clinical score, hyperglycemia, leukocytosis, increased cytokines, and histopathological changes in the kidneys and lungs. Tityus strandi envenomed mice presented more prominent clinical manifestations when compared to Tityus dinizi, pointing to the relevance of this species in the medical scenario, with both species inducing hyperglycemia, leukocytosis, increased cytokine production in the peritoneal lavage, increased inflammatory infiltrate in the lungs, and acute tubular necrosis after T. strandi envenoming. The results presented in this research can help to understand the systemic manifestations of scorpion accidents in humans caused by the target species of the study and point out therapeutic strategies in cases of scorpionism in remote regions of the Amazon.

Cytokines and their regulators in rat lung following scorpion envenomation

Nowadays, more than two billion inhabitants of underdeveloped tropical and subtropical countries are at risk of being stung by scorpions. Scorpion stings annually cause 2000-3000 deaths as they can lead to the respiratory and/or cardiovascular complications. Pathogenesis of lung damage under scorpion envenomation is often comprehensive. Respiratory failure can have a cardiogenic origin, associated with venom neurotoxin action. However, some venom components can stimulate pro-inflammatory signaling cascades followed by cytokines synthesis, recruit and activate immune cells, participating in the inflammatory response in lung injury. Scorpions of the Leiurus genus ("deathstalker") are one of the most dangerous Arthropoda. To date, 22 species of this genus have been described, but the venom composition and the mechanisms of tissues damage under envenomation have been studied to some extent only for L. quinquestriatus, L. hebraeus, and L. abdullahbayrami. Scorpions of L. macroctenus species are expected to be very hazardous, but the possibility of their venom cause inflammation in the lung tissue has not been investigated to date. Therefore, in this study, we focused on evaluating the levels of cytokines and their regulators - transcription factors (HIF-1α and NF-κB) and growth factors (FGF-2, VEGF, and EGF) - in rat lung homogenates after L. macroctenus envenomation. The results revealed a decrease in the levels of most pro-inflammatory cytokines (IL-6, IL-8, IL-1β and TNF-α) with simultaneous rise in the content of both anti-inflammatory cytokines (IL-4 and IL-10) and interferon-γ. Furthermore, the levels of all researched transcription factors and growth factors were shown to be increased too. The detected changes peak occurred at 24 h, whereas a tendency towards all indicators values normalization was observed in 72 h after venom injection. Thus, our results did not reveal signs of a classic inflammatory process in the lungs of rats injected with L. macroctenus venom. However, the obtained data indicate venom influence both on cytokine profile and on their regulators content in the rat lungs, which is a feature of certain alterations in the innate immune response, caused by studied venom components. But, the mechanisms of the changes we found require additional researches.

F1 fraction isolated from Mesobuthus eupeus scorpion venom induces macrophage polarization toward M1 phenotype and exerts anti-tumoral effects on the CT26 tumor cell line

Scorpion venoms identified as agents with anti-tumor and anti-angiogenic features. Tumor microenvironment (TME) plays a pivotal role in the process of tumorigenesis, tumor development, and polarization of M2 phenotype tumor associated macrophages (TAMs). M2 polarized cells are associated with tumor growth, invasion, and metastasis. The fractionation process was performed by gel filtration chromatography on a Sephadex G50 column. To elucidate whether scorpion venom can alter macrophage polarization, we treated interleukin (IL)-4-polarized M2 cells with isolated fractions from Mesobuthus eupeus. Next, we evaluated the cytokine production and specific markers expression for M2 and M1 phenotype using enzyme linked immunosorbent assay (ELISA) and real-time polymerase chain reaction (PCR), respectively. The phagocytic capacity of macrophages was also assessed. In addition, the migration assay and MTT analysis were performed to investigate the effects of reprogrammed macrophages on the CT-26 colon cancer cells. The results indicated that F1 fraction of venom significantly upregulated the levels and expression of M1-associated cytokines and markers, including tumor necrosis factor-alpha (TNF-α) (p < 0.001), IL-1 (p < 0.01), interferon regulatory factor 5 (IRF5) (p < 0.0001), induced nitric oxide synthase (iNOS) (p < 0.0001), and CD86 (p < 0.0001), and downregulated M2-related markers, including transforming growth factor-beta (TGF-β) (p < 0.05), IL-10 (p < 0.05), Fizz1 (p < 0.0001), arginase-1 (Arg-1) (p < 0.0001), and CD206 (p < 0.001). The macrophage phagocytic capacity was enhanced after treatment with F1 fraction (p < 0.01). Moreover, incubation of CT-26 cell line with conditioned media of F1-treated macrophages suppressed migration (p < 0.0001) and proliferation (p < 0.01) of tumor cells. In conclusion, our findings demonstrated the potential of Mesobuthus eupeus venom in M2-to-M1 macrophage polarization as a promising therapeutic approach against proliferation and metastasis of colon cancer cells.

Scorpion sting in Hafizabad, Pakistan: Facility based epidemiological study

Scorpion envenomation is a widespread issue in tropical and subtropical countries. In the present study epidemiology of scorpion sting cases and potential treatment options in district Hafizabad, Pakistan are documented. Hafizabad city and the adjacent villages were selected for the data collection. Age, gender, time, site of scorpion sting on the body, scorpion sting symptoms, number of patients obtaining medical attention and the number of fatalities (if any) were noted. Data showed that scorpion envenomation often occurs in people between the ages of 16-47 years. There were more female victims (55%) and most of the scorpion sting incidences (55.49%) occurred between 07 PM and 02 AM Among body parts, both the hands (41.71%) and feet (48.57%) were more vulnerable to scorpion stings. In rural areas, the incidences of scorpion stings were higher (68.57%). The reported symptoms of scorpion stings include pain, hypertension, nausea and allergy. Out of all the victims, only 56.05% sought treatment from health care units as well as traditional medicine practitioners. However, others (43.94%) fully healed on their own without any treatment. People were using different types of plant-based materials and dead scorpions with mustard oil as a potent remedy against scorpion stings. Moreover, in the health care units there was no antivenom available and medical staff usually used common pain killers such as Xylocain and Lignocain for the treatment of scorpion sting.

The complex repertoire of Tityus spp. venoms: Advances on their composition and pharmacological potential of their toxins

Animal venoms are a rich and complex source of components, including peptides (such as neurotoxins, anionic peptides and hypotensins), lipids, proteins (such as proteases, hyaluronidases and phospholipases) and inorganic compounds, which affect all biological systems of the envenoming victim. Their action may result in a wide range of clinical manifestations, including tachy/bradycardia, hyper/hypotension, disorders in blood coagulation, pain, edema, inflammation, fever, muscle paralysis, coma and even death. Scorpions are one of the most studied venomous animals in the world and interesting bioactive molecules have been isolated and identified from their venoms over the years. Tityus spp. are among the scorpions with high number of accidents reported in the Americas, especially in Brazil. Their venoms have demonstrated interesting results in the search for novel agents with antimicrobial, anti-viral, anti-parasitic, hypotensive, immunomodulation, anti-insect, antitumor and/or antinociceptive activities. Furthermore, other recent activities still under investigation include drug delivery action, design of anti-epileptic drugs, investigation of sodium channel function, treatment of erectile disfunction and priapism, improvement of scorpion antivenom and chelating molecules activity. In this scenario, this paper focuses on reviewing advances on Tityus venom components mainly through the modern omics technologies as well as addressing potential therapeutic agents from their venoms and highlighting this abundant source of pharmacologically active molecules with biotechnological application.

Pulmonary involvement from animal toxins: the cellular mechanisms

Venomous animals and their venom have always been of human interest because, despite species differences, coevolution has made them capable of targeting key physiological components of our bodies. Respiratory failure from lung injury is one of the serious consequences of envenomation, and the underlying mechanisms are rarely discussed. This review aims to demonstrate how toxins affect the pulmonary system through various biological pathways. Herein, we propose the common underlying cellular mechanisms of toxin-induced lung injury: interference with normal cell function and integrity, disruption of normal vascular function, and provocation of excessive inflammation. Viperid snakebites are the leading cause of envenomation-induced lung injury, followed by other terrestrial venomous animals such as scorpions, spiders, and centipedes. Marine species, particularly jellyfish, can also inflict such injury. Common pulmonary manifestations include pulmonary edema, pulmonary hemorrhage, and exudative infiltration. Severe envenomation can result in acute respiratory distress syndrome. Pulmonary involvement suggests severe envenomation, thus recognizing these mechanisms and manifestations can aid physicians in providing appropriate treatment.

Mitochondrial swelling in cardiomyocytes: Insights from a murine model of Tityus serrulatus scorpion envenomation

Immune system hyperactivation is involved with clinical severity and pathological alterations during scorpion envenomation. In a murine model, mice inoculated with a lethal dose of Tityus serrulatus scorpion venom presented mitochondrial swelling in cardiomyocytes, with other structures such as sarcomeres and intercalated disks preserved. Treatment with dexamethasone or knockout animals to the interleukin-1β receptor do not undergo mitochondrial changes in cardiomyocytes during envenomation.

Pioneering in vitro characterization of macrophage response induced by scorpion venoms from the Brazilian Amazon

There are several scorpion species of medical relevance around the world. Some of them are well characterized by their toxins and clinical outcomes. Brazilian Amazon has a great amount of these arthropods that have an impact in the scorpionism events specifically in this region of Brazil. Recently, several studies pointed out the immune system activation during scorpion envenouming as an important facet of scorpionism, inducing a sepsis-like state that culminates in clinical severity and death. In this work, we characterized the macrophage response of three species of clinical relevance in Brazilian Amazon: Tityus silvestris, T. metuendus and T. obscurus and one specie with no toxic effects to humans, Brotheas amazonicus. All the four species analyzed were able to induce pro- and anti-inflammatory cytokine production in a J774.1 murine macrophage model. This activation was dependent on TLR2/TLR4/MyD88 activation and abolished by TLRs antagonists. These results suggest that the venoms of the four species analyzed were able to induce macrophage response in agreement to the well-established immune activation by T. serrulatus venom. Our findings provide new insights into the clinical repercussions of scorpionism of uncharacterized species and point to new biotechnological applications of these venoms and possible supportive therapies in scorpionism.

Protein and peptide profiles of rats' organs in scorpion envenomation

Problem of scorpion envenomation becomes more alarming each year. Main effects of scorpion venom are commonly believed to be related to its neurotoxic properties, yet severe symptoms may also be developed due to the uncontrolled enzymatic activity and formation of various bioactive molecules, including middle-mass molecules (MMMs). MMMs are considered as endogenous intoxication markers, their presence may indicate multiple organ failure. Scorpions, belong to the Leiurus macroctenus species, are very dangerous, nevertheless, effects of their venom on protein and peptide composition within the tissues remains unclear. In this work we have focused the attention on changes in protein and MMM levels and peptide composition in various organs during Leiurus macroctenus envenomation. The results revealed a decrease in protein level during envenomation as well as a significant increment of MMM₂₁₀ and MMM₂₅₄ levels in all assessed organs. Quantitative and qualitative compositions of various protein and peptide factions were continually changing. All of this may suggest that Leiurus macroctenus sting causes considerable destruction of cell microenvironment across all essential organs, providing systemic envenomation. In addition, MMM level increment may indicate endogenous intoxication development. Peptides, formed during envenomation, may possess various bioactive properties, analysis of which constitutes an area of further studies.

Lipidomic profiling of the Brazilian yellow scorpion venom: new insights into inflammatory responses following Tityus serrulatus envenomation

Due to the high prevalence and clinical relevance, scorpionism is a critical public health issue in several Brazilian regions. Tityus serrulatus, commonly known as the Brazilian yellow scorpion, is the most venomous genus found in Brazilian fauna and associated with severe clinical manifestations such as localized pain, hypertension, sweating, tachycardia and complex hyperinflammatory responses. In general, T. serrulatus venom contains a complex mixture of active compounds, including proteins, peptides, and amino acids. Although knowledge of the protein fractions of scorpion venom is available, venom lipid components are not yet comprehensively known. The aim of the present study was to determine and characterize the lipid constituents/profile of the T. serratus venom utilizing liquid chromatography coupled with high-resolution mass spectrometry. Lipid species (164 in total) belonging to 3 different lipid categories, glycerophospholipids, sphingolipids, and glycerolipids, were identified. A further search on MetaCore/MetaDrug platform, which is based upon a manually curated database of molecular interactions, molecular pathways, gene-disease associations, chemical metabolism, and toxicity information, exhibited several metabolic pathways for 24 of previously identified lipid species, including activation of nuclear factor kappa B and oxidative stress pathways. Further several bioactive compounds, such as plasmalogens, lyso-platelet-activating factors, and sphingomyelins, associated with systemic responses triggered by T. serrulatus envenomation were detected. Finally, lipidomic data presented provide advanced and valuable information to better comprehend the mechanisms underlying the complex pathophysiology induced by T. serrulatus envenomation.

Ethnomedicines for the treatment of scorpion stings: A perspective study

ETHNOPHARMACOLOGICAL RELEVANCE

Scorpion sting is a public health concern with limited clinical symptomatic treatment. The clinical treatment uses anti-scorpion antivenom and prazosin (α-adrenergic inhibitor), often in combination with insulin, to reduce scorpion venom-induced hyperglycemia and other complications. However, these therapies also possess some limitations, necessitating urgent exploration of ethnomedicines, mainly traditional medicinal plants, to treat scorpion stings. Unfortunately, several conventional treatments are not scientifically validated, thus raising questions about their quality and utility. Therefore, pharmacological re-assessment of such medicinal plants to alleviate scorpion stings' complications is essential.

AIM OF THE STUDY

The principal objectives of this study are to provide a brief overview of medically important scorpions of the world, outline the extant traditional practices, and comprehensively review plants used in conventional ethnic medicines to treat scorpion stings over time. Modern technological advances in identifying and characterizing plant bioactive molecules are also mentioned in this review.

MATERIALS AND METHODS

The traditionally used medicinal plants against scorpion stings were reviewed from the available literature in the database. The Plant List (http://www.theplantlist.org/) was used to validate the scientific names of the plants mentioned in this study. The search targeted literature on conventional treatments and crude plant extracts or their bioactive components with proven neutralization capacity against scorpion stings. Search words used were 'scorpion sting,' 'treatment for a scorpion sting,' 'antivenom and scorpion sting,' 'traditional treatment for scorpion stings, and 'natural compounds against scorpion stings'.

RESULTS

A list of more than 200 medicinal plants traditionally used in several countries for treating scorpion stings is presented in this review. Though some myth-based remedies are practiced to treat scorpion stings, no empirical evidence exists to validate this aspect of traditional knowledge. Only 38 traditional medicinal plant extracts have been tested under in-vivo and in-vitro conditions to determine their neutralization potency of scorpion envenomation. Although a few bioactive plant constituents showing scorpion venom neutralization potency have been characterized, they are not yet commercially available for clinical application.

CONCLUSIONS

There is tremendous potential locked in medicinal plants' traditional knowledge for scorpion envenomation treatment. Translating this knowledge into the clinical application will require pharmacological reassessment, in tandem with isolation and characterization of active compounds to prove their prophylactic prowess. Almost equally important would be the formulation of stringent strategies to conserve such medicinal plants from overexploitation.

Epidemiological, toxicological and physiopathological characteristics of scorpion stings and their management in Morocco: A literature review

All around the world, scorpion envenomation represents a public health issue. In Morocco, it represents the first cause of poisoning. The aim of this review is to highlight the epidemiological, toxicological and physiopathological characteristics of scorpion stings and envenomation in Morocco as well as their management. According to the bibliography, the most areas affected by scorpion stings and envenomation are those in the center and south of Morocco. Lethality rate is more important in children than adult. Age, admission class, season, serum venom concentration, and the time elapsed between the scorpion sting and medical intervention are risk factors for a poor prognosis. Until now, we have only known the LD50 of 14 scorpion species from three genera: Androctonus, Buthus and Hottentota, and only 6 species, out of 61 moroccan scorpions, have been assessed for their venom toxicity on mice organs. The venom of harmful moroccan scorpions induces several histopathological changes in the myocardium, brain, liver, pulmonary alveoli, and kidneys in rats, as well as severe consequences in the lungs with intra-alveolar hemorrhage. There was also a significant increase in serum enzyme levels of aspartate transaminase (AST), alanine transaminase (ALT), creatine phosphokinase (CPK), and lactate dehydrogenase (LDH), as well as high levels of plasma albumin, creatine and glucose. In the absence of a specific treatment, the management of scorpion envenomation is based only on symptomatic therapy. We noted a widely use of traditional remedies. Despite the magnitude of the scorpion problem in Morocco, it remains understudied and continues to claim lives, particularly given the lack of an efficient etiological cure.

Scorpion Envenomation of Lactating Rats Decreases the Seizure Threshold in Offspring

Few data are available in the literature describing the long-term effects of envenoming in the perinatal period. In this study, the relationship between envenoming of lactating rats and possible behavioral changes in the mother and in her offspring were investigated. Lactating Wistar rats received a single dose of T. serrulatus crude venom on postnatal days 2 (V2), 10 (V10) or 16 (V16), and had their maternal behavior evaluated. The seizure threshold was evaluated in adulthood offspring. A decrease in maternal care during envenoming was observed in V2 and V10 groups. The retrieval behavior was absent in the V2 group, and a lower seizure threshold in the adult offspring of all groups was observed. During envenoming, mothers stayed away from their offspring for a relatively long time. Maternal deprivation during the early postnatal period is one of the most potent stressors for pups and could be responsible, at least in part, for the decrease in the convulsive threshold of the offspring since stress is pointed to as a risk factor for epileptogenesis. Furthermore, the scorpionic accident generates an intense immune response, and inflammation in neonates increases the susceptibility to seizures in adulthood. Therefore, maternal envenoming during lactation can have adverse effects on offspring in adulthood.

Biochemical and Proteomic Characterization, and Pharmacological Insights of Indian Red Scorpion Venom Toxins

The Indian red scorpion (Mesobuthus tamulus) is one of the world's deadliest scorpions, with stings representing a life-threatening medical emergency. This species is distributed throughout the Indian sub-continent, including eastern Pakistan, eastern Nepal, and Sri Lanka. In India, Indian red scorpions are broadly distributed in western Maharashtra, Saurashtra, Kerala, Andhra Pradesh, Tamil Nadu, and Karnataka; however, fatal envenomations have been recorded primarily in the Konkan region of Maharashtra. The Indian red scorpion venom proteome comprises 110 proteins belonging to 13 venom protein families. The significant pharmacological activity is predominantly caused by the low molecular mass non-enzymatic Na+ and K+ ion channel toxins. Other minor toxins comprise 15.6% of the total venom proteome. Indian red scorpion stings induce the release of catecholamine, which leads to pathophysiological abnormalities in the victim. A strong correlation has been observed between venom proteome composition and local (swelling, redness, heat, and regional lymph node involvement) and systemic (tachycardia, mydriasis, hyperglycemia, hypertension, toxic myocarditis, cardiac failure, and pulmonary edema) manifestations. Immediate administration of antivenom is the preferred treatment for Indian red scorpion stings. However, scorpion-specific antivenoms have exhibited poor immunorecognition and neutralization of the low molecular mass toxins. The proteomic analysis also suggests that Indian red scorpion venom is a rich source of pharmacologically active molecules that may be envisaged as drug prototypes. The following review summarizes the progress made towards understanding the venom proteome of the Indian red scorpion and addresses the current understanding of the pathophysiology associated with its sting.

Scorpion species of medical importance in the Brazilian Amazon: a review to identify knowledge gaps

Scorpionism is a relevant medical condition in Brazil. It is responsible for most accidents involving venomous animals in the country, which leads to severe symptoms that can evolve to death. In recent years, an increase of almost 50% in the incidence of scorpionism has been observed in the Northern Region, where the highest severity of envenoming has been notified since the beginning of the 21st century. This review aims to provide an in-depth assessment of public data and reports on symptoms and epidemiology of envenoming, ecological aspects of scorpions, and characterization of venoms and toxins to access the gaps that need to be filled in the knowledge of the scorpion species of medical importance from the Brazilian Amazon. A systematic search using the string words "Amazon" and "scorpion" was performed on 11 databases. No restriction on date, language or status of the publication was applied. Reports not related to the Brazilian Amazon were excluded. Therefore, 88 studies remained. It is shown that populations of scorpions of medical importance, even of the same species, may present significant toxic variations peculiar to some regions in the Brazilian Amazon, and commercial scorpion antivenoms were not able to shorten the intensity and duration of neurological manifestations in patients stung by T. silvestris, T. apiacas or T. obscurus. It is also highlighted that the toxins responsible for triggering these alterations have not been elucidated yet and this is a fruitful field for the development of more efficient antivenoms. Furthermore, the geographic distribution of scorpions of the genus Tityus in the Brazilian Amazon was revised and updated. The cumulative and detailed information provided in this review may help physicians and scientists interested in scorpionism in the Brazilian Amazon.

A new insight into the cellular mechanisms of envenomation: Elucidating the role of extracellular vesicles in Loxoscelism

Envenomation by the Loxosceles genus spiders is a recurring health issue worldwide and specially in the Americas. The physiopathology of the envenomation is tightly associated to the venom's rich toxin composition, able to produce a local dermonecrotic lesion that can evolve systemically and if worsened, might result in multiple organ failure and lethality. The cellular and molecular mechanisms involved with the physiopathology of Loxoscelism are not completely understood, however, the venom's Phospholipases D (PLDs) are known to trigger membrane injury in various cell types. Here, we report for the first time the Loxosceles venom's ability to stimulate the production of extracellular vesicles (EVs) in various human cell lineages. Components of the Loxosceles venom were also detectable in the cargo of these vesicles, suggesting that they may be implicated in the process of extracellular venom release. EVs from venom treated cells exhibited phospholipase D activity and were able to induce in vitro hemolysis in human red blood cells and alter the HEK cell membranes' permeability. Nonetheless, the PLD activity was inhibited when an anti-venom PLDs monoclonal antibody was co-administered with the whole venom. In summary, our findings shed new light on the mechanisms underlying cellular events in the context of loxoscelism and suggest a crucial role of EVs in the process of envenomation.

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

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

Immunological Responses to Envenomation

Venoms are complex mixtures of toxic compounds delivered by bite or sting. In humans, the consequences of envenomation range from self-limiting to lethal. Critical host defence against envenomation comprises innate and adaptive immune strategies targeted towards venom detection, neutralisation, detoxification, and symptom resolution. In some instances, venoms mediate immune dysregulation that contributes to symptom severity. This review details the involvement of immune cell subtypes and mediators, particularly of the dermis, in host resistance and venom-induced immunopathology. We further discuss established venom-associated immunopathology, including allergy and systemic inflammation, and investigate Irukandji syndrome as a potential systemic inflammatory response. Finally, this review characterises venom-derived compounds as a source of immune modulating drugs for treatment of disease.

COVID-19: Integrating the Complexity of Systemic and Pulmonary Immunopathology to Identify Biomarkers for Different Outcomes

In the last few months, the coronavirus disease 2019 (COVID-19) pandemic has affected millions of people worldwide and has provoked an exceptional effort from the scientific community to understand the disease. Clinical evidence suggests that severe COVID-19 is associated with both dysregulation of damage tolerance caused by pulmonary immunopathology and high viral load. In this review article, we describe and discuss clinical studies that show advances in the understanding of mild and severe illness and we highlight major points that are critical for improving the comprehension of different clinical outcomes. The understanding of pulmonary immunopathology will contribute to the identification of biomarkers in an attempt to classify mild, moderate, severe and critical COVID-19 illness. The interface of pulmonary immunopathology and the identification of biomarkers are critical for the development of new therapeutic strategies aimed to reduce the systemic and pulmonary hyperinflammation in severe COVID-19.

Pioneering Study on Rhopalurus crassicauda Scorpion Venom: Isolation and Characterization of the Major Toxin and Hyaluronidase

Scorpionism is responsible for most accidents involving venomous animals in Brazil, which leads to severe symptoms that can evolve to death. Scorpion venoms consist of complexes cocktails, including peptides, proteins, and non-protein compounds, making separation and purification procedures extremely difficult and time-consuming. Scorpion toxins target different biological systems and can be used in basic science, for clinical, and biotechnological applications. This study is the first to explore the venom content of the unexplored scorpion species Rhopalurus crassicauda, which inhabits exclusively the northernmost state of Brazil, named Roraima, and southern region of Guyana. Here, we pioneer the fractionation of the R. crassicauda venom and isolated and characterized a novel scorpion beta-neurotoxin, designated Rc1, and a monomeric hyaluronidase. R. crassicauda venom and Rc1 (6,882 Da) demonstrated pro-inflammatory activities in vitro and a nociceptive response in vivo. Moreover, Rc1 toxin showed specificity for activating Na_v1.4, Na_v1.6, and BgNa_v1 voltage-gated ion channels. This study also represents a new perspective for the treatment of envenomings in Roraima, since the Brazilian scorpion and arachnid antivenoms were not able to recognize R. crassicauda venom and its fractions (with exception of hyaluronidase). Our work provides useful insights for the first understanding of the painful sting and pro-inflammatory effects associated with R. crassicauda envenomings.

Characterization of Synthetic Tf2 as a NaV1.3 Selective Pharmacological Probe

Na_V1.3 is a subtype of the voltage-gated sodium channel family. It has been implicated in the pathogenesis of neuropathic pain, although the contribution of this channel to neuronal excitability is not well understood. Tf2, a β-scorpion toxin previously identified from the venom of Tityus fasciolatus, has been reported to selectively activate Na_V1.3. Here, we describe the activity of synthetic Tf2 and assess its suitability as a pharmacological probe for Na_V1.3. As described for the native toxin, synthetic Tf2 (1 µM) caused early channel opening, decreased the peak current, and shifted the voltage dependence of Na_V1.3 activation in the hyperpolarizing direction by −11.3 mV, with no activity at Na_V1.1, Na_V1.2, and Na_V1.4-Na_V1.8. Additional activity was found at Na_V1.9, tested using the hNav1.9_C4 chimera, where Tf2 (1 µM) shifted the voltage dependence of activation by −6.3 mV. In an attempt to convert Tf2 into an Na_V1.3 inhibitor, we synthetized the analogue Tf2[S14R], a mutation previously described to remove the excitatory activity of related β-scorpion toxins. Indeed, Tf2[S14R](10 µM) had reduced excitatory activity at Na_V1.3, although it still caused a small −5.8 mV shift in the voltage dependence of activation. Intraplantar injection of Tf2 (1 µM) in mice caused spontaneous flinching and swelling, which was not reduced by the Na_V1.1/1.3 inhibitor ICA-121431 nor in Na_V1.9^-/- mice, suggesting off-target activity. In addition, despite a loss of excitatory activity, intraplantar injection of Tf2[S14R](10 µM) still caused swelling, providing strong evidence that Tf2 has additional off-target activity at one or more non-neuronal targets. Therefore, due to activity at Na_V1.9 and other yet to be identified target(s), the use of Tf2 as a selective pharmacological probe may be limited.

Venom components of the scorpion Centruroides limpidus modulate cytokine expression by T helper lymphocytes: Identification of ion channel-related toxins by mass spectrometry

The study of the effector mechanisms of T helper cells has revealed different phenotypic characteristics that can be manipulated for designing new therapeutic schemes in different pathological scenarios. Ion channels are significant targets in T lymphocyte modulation since they are closely related to their effector activity. Remarkably, some toxins produced by scorpions specifically affect the function of these membrane proteins. For that reason, these toxins are important candidates in the search for new immunomodulators. Here, the effect of two venom fractions of the scorpion Centruroides limpidus was assessed on T lymphocyte proliferation and cytokine production. The venom fractions ClF8 and ClF9 were separated by reversed-phase high-performance liquid chromatography (RP-HPLC) and cultured at 25 and 35 µg/ml with murine T lymphocytes. The results indicate that the fraction ClF8 increased both production and secretion levels of IFN-γ, IL-4, IL-17A and IL-10 by CD4⁺ T cells at 24 h. In contrast, fraction ClF9 only promoted the secretion of IL-17A and IL-10 at its highest concentration (35 µg/ml). Both fractions did not show any effect on T cell proliferation. Subsequent analyses by liquid chromatography-tandem mass spectrometry (LC-MS/MS) revealed seventeen toxins in the fraction ClF8 and five toxins in the fraction ClF9, most of them with voltage-gated sodium (NaScTx) and potassium (KScTx) channels as molecular targets. These toxins might probably interact with ion channels involved in T lymphocyte activity. Our findings suggest that the difference in composition between the two fractions could be related to the observed effects, and the components identified could be isolated to search for possible immunomodulatory molecules.

BmK NSP, a new sodium channel activator from Buthus martensii Karsch, promotes neurite outgrowth in primary cultured spinal cord neurons

Scorpion venom is a rich source of bioactive compounds that affect neuronal excitability by modulating the activities of various channels/receptors. In the current study, guided by a Ca²⁺ mobilization assay, we purified a new neuroactive peptide designated as BmK NSP (Buthus martensii Karsch neurite-stimulating peptide, MW: 7064.30 Da). The primary structure of BmK NSP was determined by Edman degradation. BmK NSP concentration-dependently elevated intracellular Ca²⁺ concentration ([Ca²⁺]_i) with an EC₅₀ value of 4.18 μM in primary cultured spinal cord neurons (SCNs). Depletion of extracellular Ca²⁺ abolished BmK NSP-triggered Ca²⁺ response. Moreover, we demonstrated that BmK NSP-induced Ca²⁺ response was partially suppressed by the inhibitors of L-type Ca²⁺ channels, Na⁺-Ca²⁺ exchangers and NMDA receptors and was abolished by voltage-gated sodium channel (VGSC) blocker, tetrodotoxin. Whole-cell patch clamp recording demonstrated that BmK NSP delayed VGSC inactivation (EC₅₀ = 1.10 μM) in SCNs. BmK NSP enhanced neurite outgrowth in a non-monotonic manner that peaked at ~30 nM in SCNs. BmK NSP-promoted neurite outgrowth was suppressed by the inhibitors of L-type Ca²⁺ channels, NMDA receptors, and VGSCs. Considered together, these data demonstrate that BmK NSP is a new α-scorpion toxin that enhances neurite outgrowth through main routes of Ca²⁺ influx. Modulation of VGSC activity by α-scorpion toxin might represent a novel strategy to regulate the neurogenesis in SCNs.

Correlation of Venom Toxinome Composition of Indian Red Scorpion (Mesobuthus tamulus) with Clinical Manifestations of Scorpion Stings: Failure of Commercial Antivenom to Immune-Recognize the Abundance of Low Molecular Mass Toxins of This Venom

The Indian red scorpion (Mesobuthus tamulus), with its life-threatening sting, is the world's most dangerous species of scorpion. The toxinome composition of M. tamulus venom was determined by tandem mass spectrometry (MS) analysis of venom protein bands separated by SDS-PAGE. A total of 110 venom toxins were identified from searching the MS data against the Buthidae family (taxid: 6855) of toxin entries in nonredundant protein databases. The Na⁺ and K⁺ ion channel toxins taken together are the most abundant toxins (76.7%) giving rise to the neurotoxic nature of this venom. The other minor toxin classes in the M. tamulus venom proteome are serine protease-like protein (2.9%), serine protease inhibitor (2.2%), antimicrobial peptide (2.3%), hyaluronidase (2.2%), makatoxin (2.1%), lipolysis potentiating peptides (1.2%), neurotoxin affecting Cl^- channel (1%), parabutoporin (0.6%), Ca²⁺ channel toxins (0.8%), bradykinin potentiating peptides (0.2%), HMG CoA reductase inhibitor (0.1%), and other toxins with unknown pharmacological activity (7.7%). Several of these toxins have been shown to be promising drug candidates. M. tamulus venom does not show enzymatic activity (phospholipase A₂, l-amino acid oxidase, adenosine tri-, di-, and monophosphatase, hyaluronidase, metalloproteinase, and fibrinogenolytic), in vitro hemolytic activity, interference with blood coagulation, or platelet modulation properties. The clinical manifestations post M. tamulus sting have been described in the literature and are well correlated with its venom proteome composition. An abundance of low molecular mass toxins (3-15 kDa) are responsible for exerting the major pharmacological effects of M. tamulus venom, though they are poorly immune-recognized by commercial scorpion antivenom. This is a major concern for the development of effective antivenom therapy against scorpion stings.

Interleukin-1 Receptor-Induced Nitric Oxide Production in the Pancreas Controls Hyperglycemia Caused by Scorpion Envenomation

Tityus serrulatus causes numerous scorpion envenomation accidents and deaths worldwide. The symptoms vary from local to systemic manifestations, culminating in pulmonary edema and cardiogenic shock. Among these events, transitory hyperglycemia is a severe manifestation that influences pulmonary edema, hemodynamic alterations, and cardiac disturbances. However, the molecular mechanism that leads to increased glucose levels after T. serrulatus envenomation remains unknown. This study aimed to investigate our hypothesis that hyperglycemia due to scorpion envenomation involves inflammatory signaling in the pancreas. The present study showed that T. serrulatus venom induces the production of IL-1α and IL-1β in the pancreas, which signal via IL-1R and provoke nitric oxide (NO) production as well as edema in β-cells in islets. Il1r1^−/− mice were protected from transitory hyperglycemia and did not present disturbances in insulin levels in the serum. These results suggest that the pathway driven by IL-1α/IL-1β-IL-1R-NO inhibits insulin release by β-cells, which increases systemic glucose concentration during severe scorpion envenomation. A supportive therapy that inhibits NO production, combined with antiserum, may help to prevent fatal outcomes of scorpion envenomation. Our findings provide novel insights into the design of supportive therapy with NO inhibitors combined with antiscorpion venom serum to overcome fatal outcomes of scorpion envenomation.