Electrophysiological characterization of the first Tityus serrulatus alpha-like toxin, Ts5: Evidence of a pro-inflammatory toxin on macrophages

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.

Effect of animal venom toxins on the main links of the homeostasis of mammals (Review)

The human body is affected by environmental factors. The dynamic balance between the organism and its environment results from the influence of natural, anthropogenic and social aspects. The factors of exogenous origin determine development of adaptive changes. The present article summarises the mechanisms of animal venom toxins and homeostasis disruption in the body of mammals. The mechanisms underlying pathological changes are associated with shifts in biochemical reactions. Components of the immune, nervous and endocrine systems are key in the host defense and adaptation processes in response to venom by triggering signalling pathways (PI3kinase pathway, arachidonic acid cascade). Animal venom toxins initiate the development of inflammatory processes, the synthesis of pro-inflammatory mediators (cytokines), ROS, proteolytic enzymes, activate the migration of leukocytes and macrophages. Keratinocytes and endothelial cells act as protective barriers under the action of animal venom toxins on the body of mammals. In addition, the formation of pores in cell membranes, structural changes in cell ion channels are characteristic of the action of animal venom toxins.

Biphasic Hormetic-like Effect of Lebecetin, a C-type Lectin of Snake Venom, on Formalin-induced Inflammation in Mice

BACKGROUND

Integrins, important extracellular matrix (ECM) receptor proteins, are affected by inflammation and can participate in the maintenance of many painful conditions. Although they are ubiquitous and changeable across all cell types, the roles of these cell adhesion molecules in pathological pain have not been fully explored.

OBJECTIVE

We evaluated the effects of the subcutaneous injection of lebecetin, a C-type lectin isolated from Macrovipera lebetina snake venom, previously reported to inhibit α5β1 and αv integrin activity, on different components of inflammation induced by the formalin administration in the hind paw of mice.

METHODS

The formalin-induced nocifensive behavior, edema, and histopathological changes in the hind paw associated with cytokine, iNOS, and COX2 expression, nociceptive-specific neuron activity, and microglial activation analysis in the spinal cord were evaluated in mice receiving vehicle or lebecetin pretreatment.

RESULTS

Lebecetin inhibited the nocifensive responses in the formalin test, related edema, and cell infiltration in the injected paw in a biphasic, hormetic-like, and dose-dependent way. According to that hormetic trend, a reduction in pro-inflammatory cytokines IL-6, IL-8, and TNF-alpha and upregulation of the anti-inflammatory cytokine IL-10 in the spinal cord were found with the lowest doses of lebecetin. Moreover, COX2 and iNOS expression in serum and spinal cord followed the same biphasic pattern of cytokines. Finally, nociceptive neurons sensitization and activated microglia were normalized in the dorsal horn of the spinal cord by lebecetin.

CONCLUSION

These findings implicate specific roles of integrins in inflammation and tonic pain, as well as in the related central nervous system sequelae.

The nociceptive response induced by different classes of Tityus serrulatus neurotoxins: The important role of Ts5 in venom-induced nociception

Scorpion sting envenomations (SSE) are feared by the intense pain that they produce in victims. Pain from SSE is triggered mainly by the presence of neurotoxins in the scorpion venom that modulates voltage-gated ion channels. In Brazil, SSE is mostly caused by Tityus serrulatus, popularly known as yellow scorpion. Here, we evaluated experimental spontaneous nociception induced by T. serrulatus venom as well as its isolated neurotoxins Ts1, Ts5, Ts6, Ts8, and Ts19 frag II, evidencing different degrees of pain behavior in mice. In addition, we developed a mice-derived polyclonal antibody targeting Ts5 able to neutralize the effect of this neurotoxin, showing that Ts5 presents epitopes capable of activating the immune response, which decreased considerably the nociception produced by the whole venom. This is the pioneer study to explore nociception using different classes of T. serrulatus neurotoxins on nociception (α-NaTx, β-NaTx, α-KTx, and β-KTx), targeting potassium and sodium voltage-gated channels, besides demonstrating that Ts5 plays an important role in the scorpion sting induced-pain.

Ts17, a Tityus serrulatus β-toxin structurally related to α-scorpion toxins

Ts17 was purified from the venom of the scorpion Tityus serrulatus, the most dangerous scorpion species in Brazil. The activity on Na_v1.1-Na_v1.7 channels was electrophysiologically characterized by patch-clamp technique. Ts17 amino acid sequence indicated high similarity to alpha-scorpion toxins; however, it presented beta-toxin activity, altering the kinetics of the Na⁺-channels. The most affected subtypes during activation (with and without prepulse) and inactivation phases were Na_v1.2 and Na_v1.5, respectively. For recovery from inactivation, the most affected voltage-gated sodium channel was Na_v1.5. Circular dichroism spectra showed that Ts17 presents mainly β-sheet and unordered structures at all analyzed pHs, and the maximum value of α-helix was found at pH 4.0 (13.3 %). Based on the results, Ts17 might be used as a template to develop a new cardiac drug. Key contribution Purification of Ts17 from Tityus serrulatus, electrophysiological characterization of Ts17 on voltage-gated sodium channel subtypes, β-toxin classification.

Unraveling the structure and function of CdcPDE: A novel phosphodiesterase from Crotalus durissus collilineatus snake venom

This study reports the isolation, structural, biochemical, and functional characterization of a novel phosphodiesterase from Crotalus durissus collilineatus venom (CdcPDE). CdcPDE was successfully isolated from whole venom using three chromatographic steps and represented 0.7% of total protein content. CdcPDE was inhibited by EDTA and reducing agents, demonstrating that metal ions and disulfide bonds are necessary for its enzymatic activity. The highest enzymatic activity was observed at pH 8-8.5 and 37 °C. Kinetic parameters indicated a higher affinity for the substrate bis(p-nitrophenyl) phosphate compared to others snake venom PDEs. Its structural characterization was done by the determination of the protein primary sequence by Edman degradation and mass spectrometry, and completed by the building of molecular and docking-based models. Functional in vitro assays showed that CdcPDE is capable of inhibiting platelet aggregation induced by adenosine diphosphate in a dose-dependent manner and demonstrated that CdcPDE is cytotoxic to human keratinocytes. CdcPDE was recognized by the crotalid antivenom produced by the Instituto Butantan. These findings demonstrate that the study of snake venom toxins can reveal new molecules that may be relevant in cases of snakebite envenoming, and that can be used as molecular tools to study pathophysiological processes due to their specific biological activities.

Oliveira I, Rimbault C, A. Cerni F, Wen FH, Sachett J, Sartim MA, Laustsen AH, Monteiro WM. Current Knowledge on Snake Dry Bites

Snake 'dry bites' are characterized by the absence of venom being injected into the victim during a snakebite incident. The dry bite mechanism and diagnosis are quite complex, and the lack of envenoming symptoms in these cases may be misinterpreted as a miraculous treatment or as proof that the bite from the perpetrating snake species is rather harmless. The circumstances of dry bites and their clinical diagnosis are not well-explored in the literature, which may lead to ambiguity amongst treating personnel about whether antivenom is indicated or not. Here, the epidemiology and recorded history of dry bites are reviewed, and the clinical knowledge on the dry bite phenomenon is presented and discussed. Finally, this review proposes a diagnostic and therapeutic protocol to assist medical care after snake dry bites, aiming to improve patient outcomes.

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.

Scorpion Venom: Detriments and Benefits

Scorpion venom may cause severe medical complications and untimely death if injected into the human body. Neurotoxins are the main components of scorpion venom that are known to be responsible for the pathological manifestations of envenoming. Besides neurotoxins, a wide range of other bioactive molecules can be found in scorpion venoms. Advances in separation, characterization, and biotechnological approaches have enabled not only the development of more effective treatments against scorpion envenomings, but have also led to the discovery of several scorpion venom peptides with interesting therapeutic properties. Thus, scorpion venom may not only be a medical threat to human health, but could prove to be a valuable source of bioactive molecules that may serve as leads for the development of new therapies against current and emerging diseases. This review presents both the detrimental and beneficial properties of scorpion venom toxins and discusses the newest advances within the development of novel therapies against scorpion envenoming and the therapeutic perspectives for scorpion toxins in drug discovery.

Spider Knottin Pharmacology at Voltage-Gated Sodium Channels and Their Potential to Modulate Pain Pathways

Voltage-gated sodium channels (Na_Vs) are a key determinant of neuronal signalling. Neurotoxins from diverse taxa that selectively activate or inhibit Na_V channels have helped unravel the role of Na_V channels in diseases, including chronic pain. Spider venoms contain the most diverse array of inhibitor cystine knot (ICK) toxins (knottins). This review provides an overview on how spider knottins modulate Na_V channels and describes the structural features and molecular determinants that influence their affinity and subtype selectivity. Genetic and functional evidence support a major involvement of Na_V subtypes in various chronic pain conditions. The exquisite inhibitory properties of spider knottins over key Na_V subtypes make them the best lead molecules for the development of novel analgesics to treat chronic pain.

An Immunological Stairway to Severe Tissue Complication Assembly in Bothrops atrox Snakebites

Snakebites are a serious public health problem and, in the Amazon, the Bothrops atrox snake is the most frequent cause of envenomation. B. atrox venom (BaV) causes pathophysiological changes with intense, local inflammatory processes, such as severe tissue complication (STC). However, mechanisms associated with the inflammatory process in humans are still poorly understood. Thus, in this study, we sought to describe the profile of local and systemic immunological soluble molecules in Bothrops envenomation patients treated at a specialist tertiary healthcare unit in the Brazilian Amazon. An analytical and prospective study was performed with patients who had snakebites with different clinical outcomes (STC and Mild Tissue Complication-MTC) using venous blood and blister exudate in order to measure immunological soluble molecules present in the response process. Twenty STC patients and 20 MTC patients were eligible for the study. In addition, 20 healthy donors (HD) who had never been bitten by a snake were used as controls. The biomarkers CXCL-8, CCL-5, CXCL-9, CCL-2 and CXCL-10; C3a, C4a, and C5a; IL-1, IL-2, IL-4, IL-5, IL-6, IL-10, TNF, IFN-γ and IL-17A were quantified using flow cytometry and ELISA. The circulating response profile differs between the studied groups, with MTC patients presenting a mixed profile and STC patients presenting a more polarized profile for Th1 response. In addition, individuals who develop STC have a more intense local immune response, because the tissue response differs from the circulating immunological soluble molecules and presents Th1/Th2/Th17 response polarization. Furthermore, these results suggest that CCL-2 and CXCL-10 are biomarkers for STC and the response profile they assume against Bothrops snakebite should reflect in the clinical practice for the patient.

Peptides ToAP3 and ToAP4 decrease release of inflammatory cytokines through TLR-4 blocking

Antimicrobial peptides (AMPs) are small molecules with microbicidal and immunoregulatory activities. In this study we evaluated the anti-inflammatory and antimicrobial activities of peptides ToAP3 and ToAP4, AMPs from the venom of the Brazilian scorpion Tityus obscurus. To test the peptides' activity, murine bone marrow-derived macrophages (BMDMs) or dendritic cells (BMDCs) were stimulated with peptides plus LPS to analyze their ability to modulate cytokine release as well as phenotypic markers. For antimicrobial analysis, we evaluated the indirect activity against macrophage-internalized Cryptococcus neoformans and direct activity against Mycobacterium massiliense. Our data demonstrate that they were able to reduce TNF-α and IL-1β transcript levels and protein levels for BMDM and BMDC. Furthermore, the reduction of TNF-α secretion, before LPS- inflammatory stimuli, is associated with peptide interaction with TLR-4. ToAP4 increased MHC-II expression in BMDC, while ToAP3 decreased co-stimulatory molecules such as CD80 and CD86. Although these peptides were able to modulate the production of cytokines and molecules associated with antigen presentation, they did not increase the ability of clearance of C. neoformans by macrophages. In antimicrobial analysis, only ToAP3 showed potent action against bacteria. Altogether, these results demonstrate a promising target for the development of new immunomodulatory and anti-bacterial therapies.

Differential effect of Androctonus australis hector venom components on macrophage KV channels: electrophysiological characterization

Neurotoxins of scorpion venoms modulate ion channels. Voltage-gated potassium (K_V) channels regulate the membrane potential and are involved in the activation and proliferation of immune cells. Macrophages are key components of the inflammatory response induced by scorpion venom. The present study was undertaken to investigate the effect of Androctonus australis hector (Aah) venom on K_V channels in murine resident peritoneal macrophages. The cytotoxicity of the venom was assessed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) -based assay and electrophysiological recordings were performed using the whole-cell patch clamp technique. High doses of Aah venom (50, 125, 250 and 500 µg/ml) significantly decreased cell viability, while concentrations of 0.1-25 µg/ml were not cytotoxic towards peritoneal macrophages. Electrophysiological data revealed a differential block of K_V current between resting and LPS-activated macrophages. Aah venom significantly reduced K_V current amplitude by 62.5 ± 4.78% (n = 8, p < 0.05), reduced the use-dependent decay of the current, decreased the degree of inactivation and decelerated the inactivation process of K_V current in LPS-activated macrophages. Unlike cloned K_V1.5 channels, Aah venom exerted a similar blocking effect on K_V1.3 compared to K_V current in LPS-activated macrophages, along with a hyperpolarizing shift in the voltage dependence of K_V1.3 inactivation, indicating a direct mechanism of current inhibition by targeting K_V1.3 subunits. The obtained results, demonstrating that Aah venom differentially targets K_V channels in macrophages, suggest differential outcomes for their inhibitions, and that further investigations of scorpion venom immunomodulatory potential are required.

Effects of Brazilian scorpion venoms on the central nervous system

In Brazil, the scorpion species responsible for most severe incidents belong to the Tityus genus and, among this group, T. serrulatus, T. bahiensis, T. stigmurus and T. obscurus are the most dangerous ones. Other species such as T. metuendus, T. silvestres, T. brazilae, T. confluens, T. costatus, T. fasciolatus and T. neglectus are also found in the country, but the incidence and severity of accidents caused by them are lower. The main effects caused by scorpion venoms - such as myocardial damage, cardiac arrhythmias, pulmonary edema and shock - are mainly due to the release of mediators from the autonomic nervous system. On the other hand, some evidence show the participation of the central nervous system and inflammatory response in the process. The participation of the central nervous system in envenoming has always been questioned. Some authors claim that the central effects would be a consequence of peripheral stimulation and would be the result, not the cause, of the envenoming process. Because, they say, at least in adult individuals, the venom would be unable to cross the blood-brain barrier. In contrast, there is some evidence showing the direct participation of the central nervous system in the envenoming process. This review summarizes the major findings on the effects of Brazilian scorpion venoms on the central nervous system, both clinically and experimentally. Most of the studies have been performed with T. serrulatus and T. bahiensis. Little information is available regarding the other Brazilian Tityus species.

Tityus serrulatus envenoming in non-obese diabetic mice: a risk factor for severity

BACKGROUND

In Brazil, accidents with venomous animals are considered a public health problem. Tityus serrulatus (Ts), popularly known as the yellow scorpion, is most frequently responsible for the severe accidents in the country. Ts envenoming can cause several signs and symptoms classified according to their clinical manifestations as mild, moderate or severe. Furthermore, the victims usually present biochemical alterations, including hyperglycemia. Nevertheless, Ts envenoming and its induced hyperglycemia were never studied or documented in a patient with diabetes mellitus (DM). Therefore, this is the first study to evaluate the glycemia during Ts envenoming using a diabetic animal model (NOD, non-obese diabetic).

METHODS

Female mice (BALB/c or NOD) were challenged with a non-lethal dose of Ts venom. Blood glucose level was measured (tail blood using a glucose meter) over a 24-h period. The total glycosylated hemoglobin (HbA1c) levels were measured 30 days after Ts venom injection. Moreover, the insulin levels were analyzed at the glycemia peak.

RESULTS

The results demonstrated that the envenomed NOD animals presented a significant increase of glycemia, glycosylated hemoglobin (HbA1c) and insulin levels compared to the envenomed BALB/c control group, corroborating that DM victims present great risk of developing severe envenoming. Moreover, the envenomed NOD animals presented highest risk of death and sequelae.

CONCLUSIONS

This study demonstrated that the diabetic victims stung by Ts scorpion should be always considered a risk group for scorpion envenoming severity.

Non-disulfide-bridged peptides from Tityus serrulatus venom: Evidence for proline-free ACE-inhibitors

The present study purifies two T. serrulatus non-disulfide-bridged peptides (NDBPs), named venom peptides 7.2 (RLRSKG) and 8 (KIWRS) and details their synthesis and biological activity, comparing to the synthetic venom peptide 7.1 (RLRSKGKK), previously identified. The synthetic replicate peptides were subjected to a range of biological assays: hemolytic, antifungal, antiviral, electrophysiological, immunological and angiotensin-converting enzyme (ACE) inhibition activities. All venom peptides neither showed to be cytolytic nor demonstrated significant antifungal or antiviral activities. Interestingly, peptides were able to modulate macrophages' responses, increasing IL-6 production. The three venom peptides also demonstrated potential to inhibit ACE in the following order: 7.2>7.1>8. The ACE inhibition activity was unexpected, since peptides that display this function are usually proline-rich peptides. In attempt to understand the origin of such small peptides, we discovered that the isolated peptides 7.2 and 8 are fragments of the same molecule, named Pape peptide precursor. Furthermore, the study discusses that Pape fragments could be originated from a post-splitting mechanism resulting from metalloserrulases and other proteinases cleavage, which can be seen as a clever mechanism used by the scorpion to enlarge its repertoire of venom components. Scorpion venom remains as an interesting source of bioactive proteins and this study advances our knowledge about three NDBPs and their biological activities.

Ts8 scorpion toxin inhibits the Kv4.2 channel and produces nociception in vivo

The venom from the scorpion Tityus serrulatus (Ts) has been extensively studied mainly because of its rich cocktail of neurotoxins. Neurotoxins are the major and the most known components based on their modulation of voltage-gated ion channels. Until now, electrophysiological studies demonstrated that the Ts venom comprises toxins that affect Nav and Kv channels. However, although many studies have been conducted in this field, many peptides from Ts venom await further studies, including Ts8 toxin. Here we report the isolation and electrophysiological study of Ts8. The toxin Ts19 Frag-II was used as negative control. Ts8 demonstrates, among 20 tested channels, to be a selective modulator of Kv4.2 channels. Based on studies investigating the involvement of Kv4.2 on controlling nociception, we further investigated the modulation of pain by Ts8. Using intraplantar injections, Ts8 induced overt nociception (licking and lifting behaviors) and decreased the mechanical nociceptive threshold (hyperalgesia). Furthermore, the hyperalgesia was prolonged when intrathecal injections were performed. Independent of the severity, most of the victims stung by Ts scorpions report an intense and persistent pain as the major manifestation. The new role of Ts8 on nociception could explain, at least partially, this phenomenon. Additionally, our study also stresses the involvement of toxins specific to Nav channels and inflammatory mediators on the Ts painful sting. This work provides useful insights for a better understanding of the prolonged and intense pain associated with Ts envenoming for the development of specific therapies.

Immunosuppressive evidence of Tityus serrulatus toxins Ts6 and Ts15: insights of a novel K(+) channel pattern in T cells

The voltage-gated potassium channel Kv1.3 is a novel target for immunomodulation of autoreactive effector memory T cells, which play a major role in the pathogenesis of autoimmune diseases. In this study, the Ts6 and Ts15 toxins isolated from Tityus serrulatus (Ts) were investigated for their immunosuppressant roles on CD4(+) cell subsets: naive, effector (TEF ), central memory (TCM) and effector memory (TEM). The electrophysiological assays confirmed that both toxins were able to block Kv1.3 channels. Interestingly, an extended Kv channel screening shows that Ts15 blocks Kv2.1 channels. Ts6 and Ts15 significantly inhibit the proliferation of TEM cells and interferon-γ production; however, Ts15 also inhibits other CD4(+) cell subsets (naive, TEF and TCM). Based on the Ts15 inhibitory effect of proliferation of all CD4(+) cell subsets, and based on its blocking effect on Kv2.1, we investigated the Kv2.1 expression in T cells. The assays showed that CD4(+) and CD8(+) cells express the Kv2.1 channels mainly extracellularly with TCM cells expressing the highest number of Kv2.1 channels. We also provide in vivo experimental evidence to the protective effect of Ts6 and Ts15 on delayed-type hypersensitivity reaction. Altogether, this study presents the immunosuppressive behaviour of Ts6 and Ts15 toxins, indicating that these toxins could be promising candidates for autoimmune disease therapy. Moreover, this is the first report illustrating the involvement of a novel K(+) channel subtype, Kv2.1, and its distribution in T-cell subsets.

Partial purification and functional characterization of Ts19 Frag-I, a novel toxin from Tityus serrulatus scorpion venom

BACKGROUND

The yellow scorpion Tityus serrulatus (Ts) is responsible for the highest number of accidents and the most severe scorpion envenoming in Brazil. Although its venom has been studied since the 1950s, it presents a number of orphan peptides that have not been studied so far. The objective of our research was to isolate and identify the components present in the fractions VIIIA and VIIIB of Ts venom, in order to search for a novel toxin. The major isolated toxins were further investigated for macrophage modulation.

METHODS

The fractions VIIIA and VIIIB, obtained from Ts venom cation exchange chromatography, were rechromatographed on a C18 column (4.6 × 250 mm) followed by a reversed-phase chromatography using another C18 column (2.1 × 250 mm). The main eluted peaks were analyzed by MALDI-TOF and Edman's degradation and tested on macrophages.

RESULTS

The previously described toxins Ts2, Ts3-KS, Ts4, Ts8, Ts8 propeptide, Ts19 Frag-II and the novel peptide Ts19 Frag-I were isolated from the fractions VIIIA and VIIIB. Ts19 Frag-I, presenting 58 amino acid residues, a mass of 6,575 Da and a theoretical pI of 8.57, shares high sequence identity with potassium channel toxins (KTx). The toxins Ts4, Ts3-KS and the partially purified Ts19 Frag-I did not produce cytotoxic effects on macrophage murine cells line (J774.1). On the other hand, Ts19 Frag-I induced the release of nitric oxide (NO) by macrophages, while Ts4 and Ts3-KS did not affect the NO production at the tested concentration (50 μg/mL). At the same concentration, Ts19 Frag-I and Ts3-KS increased the production of interleukin-6 (IL-6). Ts19 Frag-I and Ts4 did not induce the release of IL-10, IL-1β or tumor necrosis factor-α by macrophage cells using the tested concentration (50 μg/mL).

CONCLUSIONS

We partially purified and determined the complete sequence and chemical/physical parameters of a new β-KTx, denominated Ts19 Frag-I. The toxins Ts4, Ts3-KS and Ts19 Frag-I showed no cytotoxicity toward macrophages and induced IL-6 release. Ts19 Frag-I also induced the release of NO, suggesting a pro-inflammatory activity.

Tityus serrulatus venom--A lethal cocktail

Tityus serrulatus (Ts) is the main scorpion species of medical importance in Brazil. Ts venom is composed of several compounds such as mucus, inorganic salts, lipids, amines, nucleotides, enzymes, kallikrein inhibitor, natriuretic peptide, proteins with high molecular mass, peptides, free amino acids and neurotoxins. Neurotoxins are considered the most responsible for the envenoming syndrome due to their pharmacological action on ion channels such as voltage-gated sodium (Nav) and potassium (Kv) channels. The major goal of this review is to present important advances in Ts envenoming research, correlating both the crude Ts venom and isolated toxins with alterations observed in all human systems. The most remarkable event lies in the Ts induced massive releasing of neurotransmitters influencing, directly or indirectly, the entire body. Ts venom proved to extremely affect nervous and muscular systems, to modulate the immune system, to induce cardiac disorders, to cause pulmonary edema, to decrease urinary flow and to alter endocrine, exocrine, reproductive, integumentary, skeletal and digestive functions. Therefore, Ts venom possesses toxins affecting all anatomic systems, making it a lethal cocktail. However, its low lethality may be due to the low venom mass injected, to the different venom compositions, the body characteristics and health conditions of the victim and the local of Ts sting. Furthermore, we also described the different treatments employed during envenoming cases. In particular, throughout the review, an effort will be made to provide information from an extensive documented studies concerning Ts venom in vitro, in animals and in humans (a total of 151 references).

Revealing the Function and the Structural Model of Ts4: Insights into the "Non-Toxic" Toxin from Tityus serrulatus Venom

The toxin, previously described as a "non-toxic" toxin, was isolated from the scorpion venom of Tityus serrulatus (Ts), responsible for the most severe and the highest number of accidents in Brazil. In this study, the subtype specificity and selectivity of Ts4 was investigated using six mammalian Nav channels (Nav1.2→Nav1.6 and Nav1.8) and two insect Nav channels (DmNav1 and BgNav). The electrophysiological assays showed that Ts4 specifically inhibited the fast inactivation of Nav1.6 channels, the most abundant sodium channel expressed in the adult central nervous system, and can no longer be classified as a "non-toxic peptide". Based on the results, we could classify the Ts4 as a classical α-toxin. The Ts4 3D-structural model was built based on the solved X-ray Ts1 3D-structure, the major toxin from Ts venom with which it shares high sequence identity (65.57%). The Ts4 model revealed a flattened triangular shape constituted by three-stranded antiparallel β-sheet and one α-helix stabilized by four disulfide bonds. The absence of a Lys in the first amino acid residue of the N-terminal of Ts4 is probably the main responsible for its low toxicity. Other key amino acid residues important to the toxicity of α- and β-toxins are discussed here.