Androctonus Australis Hector Venom Research Articles

Analysis of the effect of the scorpion toxin AaH-II on action potential generation in the axon initial segment

The toxin AaH-II, from the scorpion Androctonus australis Hector venom, is a 64 amino acid peptide that targets voltage-gated Na+ channels (VGNCs) and slows their inactivation. While at macroscopic cellular level AaH-II prolongs the action potential (AP), a functional analysis of the effect of the toxin in the axon initial segment (AIS), where VGNCs are highly expressed, was never performed so far. Here, we report an original analysis of the effect of AaH-II on the AP generation in the AIS of neocortical layer-5 pyramidal neurons from mouse brain slices. After determining that AaH-II does not discriminate between Nav1.2 and Nav1.6, i.e. between the two VGNC isoforms expressed in this neuron, we established that 7 nM was the smallest toxin concentration producing a minimal detectable deformation of the somatic AP after local delivery of the toxin. Using membrane potential imaging, we found that, at this minimal concentration, AaH-II substantially widened the AP in the AIS. Using ultrafast Na+ imaging, we found that local application of 7 nM AaH-II caused a large increase in the slower component of the Na+ influx in the AIS. Finally, using ultrafast Ca2+ imaging, we observed that 7 nM AaH-II produces a spurious slow Ca2+ influx via Ca2+-permeable VGNCs. Molecules targeting VGNCs, including peptides, are proposed as potential therapeutic tools. Thus, the present analysis in the AIS can be considered a general proof-of-principle on how high-resolution imaging techniques can disclose drug effects that cannot be observed when tested at the macroscopic level.

Neuromodulation of neurological disorders in a demyelination model: effect of a potassium channel inhibitor from Androctonus scorpion venom

Scorpion’s toxins have attracted attention as a treatment for diverse neurological diseases related to myelin loss. This study aimed to investigate the effect of kaliotoxin2 (KTX2), a potassium-channel blocker from Androctonus australis hector venom on cuprizone model of demyelination. Results showed that KTX2 modulates the behavioral functions, the demyelination, and reduces the recruitment of microglia, astrocytes, and granulocyte in the brain. KTX2 modulates the inflammatory response by increasing the IL-10 release, attenuating NFκB activation, and decreasing the oxidative stress markers and IL-6 levels. Results highlight the modulating effects of KTX2 on cuprizone model and confirm its therapeutic potential in demyelination diseases. Highlights Kaliotoxin2 (KTX2) prevents the excessive reduction in body weight gain and modulate motor coordination disorder induced by cuprizone. KTX2 from Aah venom protect myelin from the destructive effects of cuprizone. KTX2 inoculation to the CNS reduce microglia, astrocytes and granulocyte infiltration in the brain. KTX2 increases the production of the anti-inflammatory cytokine IL-10 and attenuates the activation of NFκB. KTX2 counterbalances cuprizone-induced brain unbalance of neurochemical redox parameters.

Cross Pharmacological, Biochemical and Computational Studies of a Human Kv3.1b Inhibitor from Androctonus australis Venom

The voltage-gated K+ channels Kv3.1 display fast activation and deactivation kinetics and are known to have a crucial contribution to the fast-spiking phenotype of certain neurons. AahG50, as a natural product extracted from Androctonus australis hector venom, inhibits selectively Kv3.1 channels. In the present study, we focused on the biochemical and pharmacological characterization of the component in AahG50 scorpion venom that potently and selectively blocks the Kv3.1 channels. We used a combined optimization through advanced biochemical purification and patch-clamp screening steps to characterize the peptide in AahG50 active on Kv3.1 channels. We described the inhibitory effect of a toxin on Kv3.1 unitary current in black lipid bilayers. In silico, docking experiments are used to study the molecular details of the binding. We identified the first scorpion venom peptide inhibiting Kv3.1 current at 170 nM. This toxin is the alpha-KTx 15.1, which occludes the Kv3.1 channel pore by means of the lysine 27 lateral chain. This study highlights, for the first time, the modulation of the Kv3.1 by alpha-KTx 15.1, which could be an interesting starting compound for developing therapeutic biomolecules against Kv3.1-associated diseases.

Kidney Sensitivity to the Non-Toxic Fraction F1 in Physiological and Non-Physiological State

Background: Scorpion venom contains several bioactive components that could be useful in therapeutic. Methods: In this study, the effects of the repeated administration of the nontoxic fraction of Androctonus australis hector (Aah) venom after carcinogenesis induced by N-Nitrosodiethylamine (DEN) were investigated on rats. Metabolic parameters and oxidative stress markers were evaluated in sera and kidney. Results: The obtained result revealed that DEN had disturbed the metabolic activities (an increase of transaminases and LDH activities) and had led to oxidative stress (a significant increase of NO and MDA levels and depletion of GSH rate) compared to the control. However, repeated injection of F1 shows a kind of modulatory effect on metabolism and oxidative stress. It shows a variable effect on metabolic markers (turn ASAT activity to normal level, recovered ALAT, and activities). A decrease of MDA level in sera and kidney and noticed an increase of GSH level in the kidney were observed. Conclusion: F1 fraction purified from Aah venom contains many bioactive components. These biomolecules lead to enzymatic activity changes and to modulate oxidative stress in the kidney in normal and carcinogenic model. These changes seem to be beneficial in the pathological case.

Immune-toxicity effects of scorpion venom on the hypothalamic pituitary adrenal axis during rest and activity phases in a rodent model

Scorpion venom is a complex mixture of peptides and proteins, rich in toxins. Its toxicological effects are related to central disruptions and autonomic disturbances, organ failure, as well as an excessive systemic inflammatory response. Since the role of the hypothalamic pituitary adrenal (HPA) axis is central in the neuroendocrine-immunological axis, the purpose of this study was, therefore, to examine the immunotoxic effect of Androctonus australis hector (Aah) venom on HPA-axis in synchronised-mice model. Taking into account the circadian activity of the HPA-axis, the variations of adrenocorticotropic hormone and corticosterone plasma levels, oxidative stress as well as inflammatory markers in cerebral, hypothalamic and adrenal tissue homogenates were investigated during the rest and activity phases of animals. Histopathology study was also performed. Results showed that Aah venom activated the HPA axis. This response seems to be dependent on time of envenomation, as a higher hormone levels were more operative during the active phase than in the rest phase when compared to time-matched control. The local toxicity-effects following Aah envenomation revealed an imbalance in oxidative stress with a higher antioxidant defences in darkness hypothalamic and cerebral tissues. Furthermore, there were significantly higher levels in vascular permeability in hypothalamic and cerebral tissues accompanied by a concomitant increase in immune-cell infiltration and/or activation as shown by expression of CD68 and myeloperoxidase activity during the active phase compared with the rest phase. Overall results suggested that Aah venom had a toxic impact on different HPA-axis areas and the effect varies according to the time of envenomation.

Chitosan nanoparticles as a delivery platform for neurotoxin II from Androctonus australis hector scorpion venom: Assessment of toxicity and immunogenicity

In recent years, biodegradable polymers based nanoparticles received high interest for the development of vaccine delivery vehicles. In this study, chitosan nanoparticles encapsulating Aah II toxin (AahII-CNPs) isolated from Androctonus australis hector venom, were investigated as vaccine delivery system. Particles obtained by ionotropic gelation were characterized for their size, surface charge, morphology and toxin release profile from Aah II-CNPs. Toxin-nanoparticles interactions were assessed by Fourier Transform Infrared Spectrometry and X-Ray Diffraction. An immunization protocol was designed in mice to investigate anti-toxin immunity and the protective status induced by different Aah II immune formulations.Unloaded chitosan nanoparticles presenting a spherical shape and smooth surface, were characterized by a size of 185 nm, a dispersion index (PDI) of 0.257 and a zeta potential of +34.6 mV. Aah II toxin was successfully entrapped into chitosan nanoparticles as revealed by FTIR and XRD data. Entrapment efficiency (EE) and Loading capacity (LC) were respectively of 96.66 and 33.5%. Aah II-CNPs had a diameter of 208 nm, a PDI of 0.23 and a zeta potential of +30 mV. Encapsulation of Aah II reduced its toxicity and protected mice until 10 LD50.Mice were immunized via a dual prime-boost scheme. Nanoentrapped Aah II immunogen elicited systemic innate and humoral immune responses as well as local spleen parenchyma hyperplasic alterations. Aah II-CNPs immunized mice withstood high lethal doses of native Aah II, one-month post-boost inoculation. This study provided encouraging and promising results for the development of preventive therapies against scorpion envenoming mainly for the populations at-risk.

Involvement of Toll-like Receptor 4 in Neutrophil-Mediated Inflammation, Oxidative Stress and Tissue Damage Induced by Scorpion Venom.

Systemic inflammatory response and generation of oxidative stress are known to contribute to scorpion venom-induced tissue damage. TLR receptors might represent a link between oxidative stress and inflammation; we therefore investigated whether or not TLR4 is involved in venom-induced immunopathology. The obtained results showed that pharmacological targeting of TLR4 with the selective inhibitor TAK-242 (Resatorvid) prevents the inflammatory response induced by subcutaneous administration of Androctonus australis hector (Aah) venom, as revealed by a significant decrease of neutrophil cell count in peripheral blood associated with significant decline of neutrophil degranulation and sequestration to the lung, liver, and kidney tissues. Moreover, TAK-242 administration inhibited nitrite levels increase in serum, malondialdehyde (MDA), and protein carbonyl tissue contents concomitantly with a significant increase of catalase activity and reduced glutathione (GSH) level in tissue homogenates. Furthermore, venom-induced increases in serum levels of organ dysfunction markers (lactate deshydrogenase, aminotransferase ALT and AST, creatinine and urea) were also significantly suppressed by pre-treatment with TLR4 inhibitor, concordantly with a remarkable improvement in the histological features in lung and liver tissues. The results of the present study indicate the potential role of TLR4 in venom-induced immunopathology and show the in vivo requirement of TLR4 signaling in mediating venom-induced tissue damage.

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

Neurotoxins of scorpion venoms modulate ion channels. Voltage-gated potassium (KV) 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 KV 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 500µg/ml) significantly decreased cell viability, while concentrations of 0.1-25µg/ml were not cytotoxic towards peritoneal macrophages. Electrophysiological data revealed a differential block of KV current between resting and LPS-activated macrophages. Aah venom significantly reduced KV 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 KV current in LPS-activated macrophages. Unlike cloned KV1.5channels, Aah venom exerted a similar blocking effect on KV1.3 compared to KV current in LPS-activated macrophages, along with a hyperpolarizing shift in the voltage dependence of KV1.3 inactivation, indicating a direct mechanism of current inhibition by targeting KV1.3 subunits. The obtained results, demonstrating that Aah venom differentially targets KV channels in macrophages, suggest differentialoutcomesfor their inhibitions, and that further investigations of scorpion venom immunomodulatory potential are required.

TNF-α antagonist improves oxidative stress and lipid disorders induced by scorpion venom in the intestinal tissue

We previously reported that Androctonus australis hector (Aah) venom induces inflammation in several tissues, however limited information is available on its role in gastrointestinal tract. Here we evaluate the involvement of TNF-α in lipid metabolism in the small intestine after Aah envenomation. To address these issues, NMRI mice (3-month-old) were pre-treated with a TNF-α antagonist, 30 min prior to Aah venom injection. Redox status, cytotoxicity and histopathological changes were analyzed in small intestine 3 and 24 h after Aah injection. Lipid metabolism was evaluated through lipid tolerance test in sera. Lipid content in small intestine was also evaluated at different times after envenomation. Obtained results showed that Aah venom affects the intestinal integrity. This cytotoxicity could be associated with lipid peroxidation and altered or insufficient antioxidant system. These results also highlight the perturbation of lipid absorption in intestine tissue of envenomed mice. The use of TNF-α antagonist prior to Aah venom injection seems to be able to improve lipid profile, oxidative stress and antioxidant activity. These findings suggest that Aah venom induces lipid alterations in the intestinal tissue mechanisms involving of TNF- α.

Kidney inflammation and tissue injury induced by scorpion venom: comparison with a nephrotoxic model

The effect of Androctonus australis hector (Aah) venom in comparison with nephrotoxic model was investigated in vivo. Aah venom induced a rapid inflammatory response characterized by recruitment of neutrophil and eosinophil cells, increased levels of cytokines, and lipid peroxidation. These results were in accordance with the histological findings showing structural damage in the nephrons, similar and faster to that induced by cisplatin model. The modifications in renal function parameters as an elevation of blood urea and creatinine levels with a significant increase in the serum aspartate aminotransferase and lactate dehydrogenase were indicative of tissue damages responsible for the renal failure.

Reactogenicity and safety assessment of an attenuated nanovaccine against scorpion envenomation: Preclinical study.

An attenuated nanovaccine (Nps - V∗) has been developed to protect humans from fatal scorpion envenomation in at-risk regions. This study was conducted to evaluate the toxicity and the local reactogenicity of the Nps - V∗ nanovaccine developed against Androctonus australis hector (Aah) venom. Assessment of the systemic inflammatory response and serum cytokine levels were evaluated in vaccinated mice with 100μg of irradiated Aah venom (V∗) encapsulated or not into polymeric calcium-alginate nanoparticles (Nps) and injected by subcutaneous (s.c) route. The local reactogenicity was evaluated by dermal Draize observations and skin tissue analysis at the injection site of vaccinated rabbits with 250 or 500μg of V∗-loaded into Nps. All animals gained weight and had normal food consumption during the study. Additionally, results showed that the nanoformulation Nps - V∗ did not cause clinical evidence of systemic toxicity in mice or rabbits, a transient edema/erythema at the injection site was only recorded as treatment-related reactogenicity. These results indicated a favorable safety profile for Nps - V∗ and supported its use in superior animal tests, then in a Phase 1 clinical trial.

Oxygénothérapie à haut débit au cours de l’insuffisance respiratoire aiguë : nouvelles avancées physiologiques et cliniques: High-flow oxygen therapy in acute respiratory failure: New physiological and clinical advances

To evaluate the dose-effects of Androctonus australis hector (Aah) venom injected subcutaneously on hemodynamics and neurohormonal secretions, 10 anesthetized and ventilated mongrel dogs, were split in two groups (n = 5/group). Subcutaneous injection was done with either 0.2 mg/kg or 0.125 mg/kg of the purified G50 scorpion toxic fraction. Hemodynamic parameters using right heart catheter were recorded and plasma concentrations of catecholamine, troponin, and serum toxic fraction were measured sequentially from baseline to 120 min.We identified the dose of toxic fraction evoking characteristic hemodynamic perturbation of severe envenomation, the time-lapse to envenomation, and the associated plasma level.The injection of 0.125 mg/kg toxic fraction was not associated with significant variations in hemodynamic parameters, whereas the 0.2 mg/kg dose caused envenomation characterized by significant increase in plasma catecholamines, increased pulmonary artery occluded pressure, mean arterial pressure, and systemic vascular resistance (p < 0.05), in association with sustained decline in cardiac output (p < 0.001). Envenomation occurred by the 30th minute, and the corresponding concentration of toxic fraction was 1.14 ng/ml.The current experiment allowed the identification of the sub-lethal dose (0.2 mg/kg) of the toxic fraction of Aah administered by the subcutaneous route. Two parameters with potential clinical relevance were also uncovered: the time-lapse to envenomation and the corresponding concentration of toxic fraction.

Safety and efficiency of active immunization with detoxified antigen against scorpion venom: side effect evaluation.

The efficiency and safety of vaccine are the most important properties, however, as any medication, it can induce side effects. This prophylactic therapy could be used to prevent the lethal and pathophysiological effects induced after scorpion envenomation. In this study, detoxified venom associated to alum adjuvant (V*alum) is used as a vaccine against scorpion venom for immunization of mice. We evaluate the safety and the inflammatory response of this vaccine. We also investigated the protective effect of this formulation against the toxicity of native Androctonus australis hector venom. Results showed no adverse events occurred after immunization of animals. This active immunization of animals did not cause change in vascular permeability, no edema formation in the studied organs. Furthermore, there are no IgE production in sera, nor change in the morphology of the mast cells in skin tissues. However, low inflammatory response triggered by activating the recruitment of eosinophils associated to IL-4 and IL-5 release was observed. All immunized animals are protected from the toxic effects of native venom until 6 LD50 and to 7 LD50 after the second challenge. This safe vaccine preparation seems to induce a long-term protection without any risk of deleterious inflammatory response.

Cytotoxicity and actin cytoskeleton damage induced in human alveolar epithelial cells by Androctonus australis hector venom

Scorpion venom may injure the lung either by direct toxic effects on alveolar cells or by indirect effects mediated by inflammatory response to the lung. We aimed at investigating the effect of Androctonus australis hector (Aah) venom on the cell adhesion, migration and actin shape on human alveolar epithelial cells (A549). We showed that Aah venom affects the cell integrity of A549 cells. This cytotoxicity is associated with enhanced cell spreading and a decrease of cell motility. Furthermore, the actin distribution is altered. These results bring new insights into the direct effect of Aah, linking lung injury to actin dynamics

Age-Related Changes in Inflammatory Response after Experimental Envenomation: Impact on the Susceptibility to Androctonus australis hector Venom.

In regions at risk of scorpion envenomation, children remain the principal victims; they exhibit severe symptoms and represent a higher mortality rate compared to adults. The pathophysiology of envenomation is related to an excessive inflammatory response; however, no studies have identified the differences in immune responses to scorpion stings and mainly the mechanisms of inflammation between children and adults, which may be a determinant key of the susceptibility of children to scorpion envenomation. In this study, we compared the systemic (blood and lung) and the central (brain) inflammatory responses after injection of Androctonus australis hector (Aah) venom to 7 and 21 postnatal days (pnds) and adult mice by subcutaneous route. Results revealed that 7 and 21 pnd mice were more sensitive to Aah venom than adults and presented also severe systemic and central inflammatory responses characterized by a high activation of immune cells, NO liberation, and lipid peroxidation. Lymphocyte levels were much lower in young animals than in adults; however, neutrophil levels seemed to be higher in immature mice. The antioxidant GSH and catalase levels were more reduced in 7 and 21 pnd mice compared to adults leading to more pronounced tissular alterations and edema formation in lung and brain. These findings show a relationship between the severity of the pathophysiological effects of Aah venom and the age. The vulnerability of immature animals to Aah venom might result from uncontrolled inflammatory response and central nervous system alterations. Data from the present study emphasize the need for the development of age-specific therapeutic modalities.

Switch of Steady-State to an Accelerated Granulopoiesis in Response to Androctonus australis hector Venom

Although several studies have shown that scorpion venoms cause a systemic inflammatory response syndrome, little is known about the contribution of the hematopoietic organs. The aim of this study was to investigate the effect of Androctonus australis hector venom on the bone marrow and on local inflammatory mediators, in concordance with the systemic inflammatory reaction elicited in mice. The consequences of a direct interaction of venom with murine bone marrow cells were also assessed by in vitro study. Obtained results showed that the early systemic neutrophilia correlated with a rapid granulocyte mobilization. This response was followed by an accelerated granulopoiesis that was supported by TNF-α and IL-6 signals. In vitro data revealed that the venom exerted a proliferative effect on murine hematopoietic cells and stimulated their differentiation towards granulocyte lineage mainly through cytokine secretion. In conclusion, this study indicated that the bone marrow rapidly exerts its activity in response to the experimental envenomation via the granulopoiesis process and inflammatory mediators in concert with the development of a systemic response. The ability of venom to directly switch steady-state granulopoiesis to an accelerated state in vitro could aggravate the disturbance caused by the venom. Better understanding of the mechanisms involved may lead to the emergence of new targets to avoid cell spreading and accumulation by acting on the very early stage of the systemic inflammatory response.

Cytotoxic activity of Androctonus australis hector venom and its toxic fractions on human lung cancer cell line

BackgroundSeveral studies have showed that animal venoms are a source of bioactive compounds that may inhibit the growth of cancer cells, which makes them useful agents for therapeutic applications. Recently, it was established that venom toxins from scorpions induced cytotoxic, antiproliferative and apoptogenic effects on cancer cells. Therefore, the present study aims to investigate the cytotoxic activity of Androctonus australis hector (Aah) scorpion venom and its toxic fractions (FtoxG-50 and F3) on NCI-H358 human lung cancer cells.MethodsThe cytotoxic and antiproliferative activities were estimated using MTT assay, lactate dehydrogenase release and clonogenic assays. Apoptosis was evaluated by Hoechst 33258 staining, DNA fragmentation assay and caspase-3 activity. Oxidative stress was analyzed by reactive oxygen species, nitric oxide, malondialdehyde and protein carbonyl levels along with assessment of antioxidant status. In addition, alteration of mitochondrial membrane potential was analyzed by JC1 fluorescent dye.ResultsThe present findings showed that F3 fraction was more cytotoxic towards NCI-H358 lung cancer cells with an IC50 of 27.05 ± 0.70 μg/mL than venom alone (396.60 ± 1.33 μg/mL) and its toxic fraction FtoxG-50 (45.86 ± 0.91 μg/mL). Nevertheless, F3 fraction was not cytotoxic at these concentrations on normal human lung fibroblast MRC-5 cells. Inhibition of NCI-H358 cell proliferation after F3 fraction exposure occurred mainly by apoptosis as evidenced by damaged nuclei, significant DNA fragmentation level and caspase-3 activation in a dose dependent manner. Moreover, F3 fraction enhanced oxidative and nitrosative stress biomarkers and dissipated mitochondrial membrane potential in lung cancer cells along with significant depletion in cellular enzymatic and non-enzymatic antioxidants. Further, the apoptosis induced by F3 fraction was markedly prevented by the antioxidant N-acetylcysteine (NAC) suggesting the potential mechanism of oxidative stress.ConclusionThese findings suggest that F3 fraction could induce apoptosis in lung cancer cells through involvement of oxidative stress and mitochondrial dysfunction. Hence, these properties make F3 fraction a promising candidate for development of new anticancer agents.

Development and characterization of a new carrier for vaccine delivery based on calcium-alginate nanoparticles: Safe immunoprotective approach against scorpion envenoming

To enhance humoral defense against diseases, vaccine formulation is routinely prepared to improve immune response. Studies in nanomaterials as a carrier of vaccine delivery are promising and interesting. In this study, attenuated Androctonus australis hector (Aah) venom and its toxic fraction were encapsulated into different formulations inside calcium–alginate nanoparticles (Ca–Alg Nps), and used as a vaccine delivery system against scorpion envenomation. Ca–Alg Nps were prepared by ionic gelation and characterized. An immunization schedule was undertaken in rabbits in order to study how Aah venom entrapped in Ca–Alg Nps might induce protective immunity. Results showed the influence of different parameters on the suitable nanoparticle formation. They also showed no toxicity of free Ca–Alg Nps and a different inflammatory profile depending on the nanovaccine formulations. More interestingly, evaluation of specific IgG titer and IgG1/IgG2a isotype balance revealed a protective effect with the nanoparticles encapsulating the attenuated antigens. Challenge up to 6 LD 50 of native venom, allowed to an important immunoprotection of all immunized rabbits, with no recorded death. Taken together and with respect to the properties of nanoparticles and high immunogenicity, calcium–alginate nanoparticles could be considered as a new promising adjuvant system and a vaccine delivery against scorpion envenomation.

TNF-alpha modulates adipose macrophage polarization to M1 phenotype in response to scorpion venom.

We previously reported that Androctonus australis hector (Aah) venom and its toxic fraction affect adipose tissue metabolism. However, the contribution of immune system and the role of adipose tissue macrophages (ATMs) in the progression of inflammation induced by scorpion venom remain largely unknown. Here we evaluate the capacity of the toxic fraction of Aah venom (FTox-G50) to induce the expression of M1 and M2 markers genes on adipose tissue and isolated stromal vascular cells (SVC). Quantitative real-time PCR was performed on the SVC 24h after FTox-G50 venom injection to assess the gene expressions of IL12p40, IL23, and other macrophages-associated markers. We found that ATM from FTox-G50-venom-injected mice markedly increased the expressions of IL-12p40 and IL-23. Furthermore, the expression of nitric oxide synthase 2 (an M1 marker) was up-regulated, but the expression of Arginase1 (an M2 marker) was not. Systemic injection of a chemical inhibitor directed against TNF-α binding reduced the expression of inflammatory M1 macrophage markers and the MAPKpk2 gene, a key mediator of inflammatory signaling. These results indicate that TNF-α is a physiological regulator of inflammation and macrophage activation induced by scorpion venom.

Study of severe scorpion envenoming following subcutaneous venom injection into dogs: Hemodynamic and concentration/effect analysis.

To evaluate the dose-effects of Androctonus australis hector (Aah) venom injected subcutaneously on hemodynamics and neurohormonal secretions, 10 anesthetized and ventilated mongrel dogs, were split in two groups (n = 5/group). Subcutaneous injection was done with either 0.2 mg/kg or 0.125 mg/kg of the purified G50 scorpion toxic fraction. Hemodynamic parameters using right heart catheter were recorded and plasma concentrations of catecholamine, troponin, and serum toxic fraction were measured sequentially from baseline to 120 min. We identified the dose of toxic fraction evoking characteristic hemodynamic perturbation of severe envenomation, the time-lapse to envenomation, and the associated plasma level. The injection of 0.125 mg/kg toxic fraction was not associated with significant variations in hemodynamic parameters, whereas the 0.2 mg/kg dose caused envenomation characterized by significant increase in plasma catecholamines, increased pulmonary artery occluded pressure, mean arterial pressure, and systemic vascular resistance (p < 0.05), in association with sustained decline in cardiac output (p < 0.001). Envenomation occurred by the 30th minute, and the corresponding concentration of toxic fraction was 1.14 ng/ml. The current experiment allowed the identification of the sub-lethal dose (0.2 mg/kg) of the toxic fraction of Aah administered by the subcutaneous route. Two parameters with potential clinical relevance were also uncovered: the time-lapse to envenomation and the corresponding concentration of toxic fraction.