The cardiovascular system after scorpion envenomation. A review

Scorpion-Induced Acute Coronary Syndrome: A Stinging Complication

The Tityus trinitatis, a black scorpion species endemic to the fauna of Trinidad, has been implicated in envenomation with devastating clinical sequelae such as acute pancreatitis and major adverse cardiovascular events. We present the first in-Caribbean case of a 59-year-old Caribbean South Asian male with human immunodeficiency virus who presented with a non-ST-segment-elevation acute coronary syndrome after being stung, which was managed with comprehensive, guideline-directed medical therapy. The clinician should be cognizant of scorpion-induced acute coronary syndrome (ACS) as a potential sequela of envenomation and its clinical management.

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.

Structural basis for the binding of the cancer targeting scorpion toxin, ClTx, to the vascular endothelia growth factor receptor neuropilin-1

Chlorotoxin (ClTx) is a 36-residue disulfide-rich peptide isolated from the venom of the scorpion Leiurus quinquestriatus. This peptide has been shown to selectively bind to brain tumours (gliomas), however, with conflicting reports regarding its direct cellular target. Recently, the vascular endothelial growth factor receptor, neuropilin-1 (NRP1) has emerged as a potential target of the peptide. Here, we sought to characterize the details of the binding of ClTx to the b1-domain of NRP1 (NRP1-b1) using solution state nuclear magnetic resonance (NMR) spectroscopy. The 3D structure of the isotope labelled peptide was solved using multidimensional heteronuclear NMR spectroscopy to produce a well-resolved structural ensemble. The structure points to three putative protein-protein interaction interfaces, two basic patches (R14/K15/K23 and R25/K27/R36) and a hydrophobic patch (F6/T7/T8/H10). The NRP1-b1 binding interface of ClTx was elucidated using ¹⁵N chemical shift mapping and included the R25/K27/R36 region of the peptide. The thermodynamics of binding was determined using isothermal titration calorimetry (ITC). In both NMR and ITC measurements, the binding was shown to be competitive with a known NRP1-b1 inhibitor. Finally, combining all of this data we generate a model of the ClTx:NRP1-b1 complex. The data shows that the peptide binds to the same region of NRP1 that is used by the SARS-CoV-2 virus for cell entry, however, via a non-canonical binding mode. Our results provide evidence for a non-standard NRP1 binding motif, while also providing a basis for further engineering of ClTx to generate peptides with improved NRP1 binding for future biomedical applications.

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Structural details of the binding of the scorpion toxin, chlorotoxin (ClTx) to the VEGF receptor neuropilin-1 (NRP1).

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ClTx was produced in its native fold and isotope labelled using a new, high-yield, bacterial expression system.

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Multidimensional heteronuclear NMR experiments reveal the high-resolution structure of ClTx and its binding to NRP1.

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ClTx binds to NRP1 via a non-canonical primary sequence that satisfies the receptor binding motif through its tertiary fold.

Severe Troponin I Elevation and Myocardial Dysfunction in a Child with Scorpion Sting

Background  Scorpion sting is a common medical problem and major cause of mortality and morbidity in many countries. The symptoms of envenomation are more severe in the pediatric population. The clinical manifestations of scorpion envenomation appear by activation of sympathetic and parasympathetic nervous system. Envenomation can cause multiorgan dysfunction and death. Case Presentation and Findings  In this case report, we present a pediatric patient from Adana, Southeast Anatolia, with severe scorpion envenomation with Leiurus abdullahbayrami which is an especially dangerous species for children. Severe systolic dysfunction was detected by echocardiography. Troponin I levels elevated significantly and rapidly responded to three doses of antivenom therapy. Conclusion  Early echocardiographic examination is an important procedure for patients with scorpion envenomation. Troponin I is a significant parameter to monitor the degree of cardiac injury. Antivenom therapy is the only recommended specific therapy for children with severe scorpion envenomation due to Leiurus abdullahbayrami . Abnormal echocardiography findings may require repeated doses of scorpion antivenom.

Determination of median effective dose (ED50) of scorpion antivenom against scorpion envenomation using a newly developed formula

BACKGROUND

About 50 species of scorpions cause fatal scorpionism worldwide. Most of these are members of the Buthidae family, and include, among others, Mesobuthus eupeus, Androctonus crassicauda, Leiurus abdullahbayrami, Leiurus quinquestriatus, Tityus pachyurus and Androctonus australis. Because high doses of scorpion venom and antivenom can cause death and hypersensitive reactions, there is a need to develop a formula that can be used to calculate both lethal and effective doses for scorpion venom and antivenom, respectively, thereby obviating the need for laboratory experiments.

METHODS

In view of this, a literature search was carried out with the aim of modifying the formula (LD 50 = ED 50 3 × W a × 10 - 4 ) for calculation of the median lethal dose (LD50) of scorpion venom and the ED50 of antivenom. The human equivalent dose (HED) formula was assessed for extrapolation of LD50 and ED50 from animals to human for comparison and relevance with the new formula.

RESULTS

The findings showed that the newly developed formula (LD50 = ED50 1/3 × W a  × 10-4) yielded results that are very close to the reported values. Therefore, the newly developed and HED formulas can be used for calculation of LD50 and ED50 values for scorpion venom and antivenom, respectively.

CONCLUSION

The new formula yielded better results than the HED formula, confirming its predictive validity, precision, and reliability, thereby obviating the need for rigorous experiments and justifying the principles of reduction, refinement, and replacement (3Rs).

Study on Distribution of Scorpions to Provide Prevention and Interventions in Combating Scorpionism in Poldokhtar County, Lorestan Province, Iran

INTRODUCTION

Scorpions are arthropods of medical importance classified in the class Arachnida, inhabiting hot and dry environments. All scorpions have a venomous sting and several thousand people die each year from scorpion stings, but this mortality is due to the venom of about 25 species located in northern Africa, the Middle East, India, Mexico and parts of South America. Poldokhtar County belongs to one of the southern cities of Lorestan Province, providing suitable habitats for many different species of scorpions due to its specific climatic conditions.

AIM

To examine the fauna of scorpion and its distribution in the Poldokhtar County and to provide appropriate preventive and medical interventions in combating scorpionism.

MATERIALS AND METHODS

This present study was a descriptive and analytical cross-sectional study. This study was conducted from April 2014 to November 2014 in regions of Poldokhtar County, Lorestan Province, and west of Iran. Cluster sampling methodology was employed in the sampling and scorpion collection procedure. Sampling was undertaken for an eight-month period, in villages and districts, namely, Myankuhe sharqi, Jayedar, Jelogir and Malavi within the county. The Chi-square test and the Fisher-exact test for homogeneity of proportions were used to compare quantitative variables.

RESULTS

Totally, 393 specimens were captured entailing 193 (49.1%) males and 200 (50.9%) females. There were at least seven species of scorpions belonging to three families; BU= Buthidae, HE = Hemiscorpiidae, SCN = Scorpionidae in Poldokhtar. Out of 393 collected scorpions, seven species, Androctonus crassicauda, Hottentotta (Buthotus) saulcyi, Compsobuthus matthiesseni, Compsobuthus rugosulus, Orthochirus scrobiculosus, Scorpio maurus and Hemiscorpius lepturus were identified. The overall sex ratio of females to males was 1:1.03.

CONCLUSION

It is crucial to improve the knowledge of residents in this region regarding preventive methods towards scorpion stinging. All the known dangerous Iranian scorpions having medical importance, including Hemiscorpius lepturus and Androctonus crassicauda were found in the study area. Additionally, other complementary research detailing the fauna of scorpions and their morphological, ecological and molecular variety in this region is highly recommended to estimate the correlation between particular scorpions' species and ensuring clinical signs and symptoms.

Some pharmacological effects of Tityus obscurus venom in rats and mice

There are a great number of studies about Brazilian scorpions. However, little is known about the venom of scorpions of northern Brazil, mainly about Tityus obscurus, which is responsible for the most number of accidents in the Amazon. Thus, this study aimed to evaluate some pharmacological effects of T. obscurus venom in rats and mice. In rats, the venom (10 mg/kg i.p.) caused hemorrhagic patches in the lung parenchyma but did not lead to pulmonary edema. There was a decrease in general activity, observed in the activity box after venom injection. The venom did not induce changes in the occurrence and intensity of experimentally induced convulsions, nor did it cause hippocampal neuronal loss. In mice, the LD₅₀ obtained was 3.13 mg/kg (i.p.). Different doses of the venom (0.2; 1; 5; 10; 15 μg/30 μL per hind paw) induced edematogenic and moderate nociceptive activity in mice. The Tiyus serrulatus venom used as comparison caused more intense symptomatology in mice. Comparing to the venom of other Tityus scorpions of medical importance, that have convulsant and intense nociceptive effects and cause lung edema, as described in the literature, we can conclude that the venom of T. obscurus probably has different characteristics.

Acute myocarditis and pulmonary edema due to scorpion sting

Objective: To present a case of a serious manifestation of scorpion sting, which was not reported before in Qatar, review the literature, and compare with previously reported similar cases.

Case presentation and intervention: A young male patient was admitted to CCU with a clinical picture of acute toxic myocarditis and cardiogenic shock with abnormal ECG and elevated cardiac markers after a scorpion sting to his right big toe. Thorough investigations, including echocardiography, cardiac MRI and right heart catheterization, supported the diagnosis. Coronary angiography was normal. Patient was managed conservatively with supportive measures, mechanical ventilation, IV fluids, inotropic agents, steroids, antibiotics and Prazocin. Over 9 days of hospital course, patient gradually improved, was successfully extubated, and was discharged in a stable condition.

Conclusion: Toxic myocarditis (with myocardial damage), pulmonary edema and cardiogenic shock are reported manifestations of scorpion venom intoxication.

Endocrinological and biochemical changes of scorpionism in children in Upper Egypt

AIM

The aim of this study was to determine some endocrinological and biochemical changes of scorpionism in children in Upper Egypt. In addition, it aimed to find any possible relationship between these changes and the severity of scorpionism.

PATIENTS AND METHODS

The present study was carried out at two university hospitals in Upper Egypt and included 42 children with envenomation and 20 apparently healthy children as controls. In all subjects, levels were measured of noradrenaline, aldosterone, insulin and cortisol, and some biochemical parameters and electrolytes including nitric oxide (NO), creatine phosphokinase (CPK), Na+ and K+.

RESULTS

Na+, NO and CPK levels were significantly higher in children with envenomation compared with the controls. Also, there was a significant reduction in K+ in patients compared with controls. Children with severe envenomation had significantly higher levels of noradrenaline, cortisol and aldosterone compared with the controls and mild cases. However, insulin levels were significantly decreased in severe cases of scorpionism compared with mild ones. Moreover, hyperglycemia was detected in all patients with envenomation compared with controls, with significantly higher blood glucose levels among children with severe envenomation compared with mild cases.

CONCLUSION

Endocrinological changes were common in all children with scorpion envenomation and more obvious in cases of severe envenomation. The released mediators may account for several inflammatory manifestations such as pulmonary edema, myocardial failure, systemic inflammatory response syndrome and multiple organ failure. The use of insulin is recommended in cases of severe envenomation to improve the outcome.

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.

Beneficial effects of Androctonus australis hector venom and its non-toxic fraction in the restoration of early hepatocyte-carcinogenesis induced by FB1 mycotoxin: Involvement of oxidative biomarkers

Some venom components are known to present potential biological activities that are useful as tools in therapeutics. In this study anti-tumoral activity of Androctonus australis hector (Aah) venom and its purified fraction on early step of hepato-carcinogenesis initiated by Fumonisin (FB1), was tested. Initiated hepatic tumor was assessed in mice by decreased doses of Fumonisin B1 associated to phenobarbital. Scorpion venom was used to investigate its activity on initiated tumor by FB1. Evaluation of oxidative unbalance, enzymatic activities and DNA quantification in the liver were correlated with tissue analysis. Obtained results showed that the initiated pathogenesis by FB1 at seven months was characterized by tissue alterations and biomarker variations. These alterations were characterized by atypical lesions such as muffled nucleus, karyo- and cyto-megaly; up normal and large number of nuclei into hepatocytes. These alterations were confirmed by DNA alteration. An unbalance of oxidative status was also observed, characterized by an increased levels of respectively oxidant (NO and MDA) and antioxidant (GSH and catalase activity) mediators. Aah venom and its non-toxic fraction used at low doses seemed to be able to restore partially the hepatic altered tissue induced by FB1. Decreased levels of oxidative and anti-oxidative mediators were also observed. DNA in hepatocytes returned also to the physiological values. Structure of hepatic tissue showed restoration of some alterations such as karyo- and cyto-megaly; decrease of polyploidy hepatocytes induced by FB1. Aah venom and its non-toxic fraction seem to contain some bioactive components with anti-tumoral activity. Purification of this activity from non-toxic fraction F1 could be of interest to identify the components with anti-tumoral activities.

Mesobuthus tamulus venom induces acute respiratory distress syndrome in rats involving additional mechanisms as compared to oleic acid model

The present study was undertaken to determine whether acute respiratory distress syndrome (ARDS) is produced after Mesobuthus tamulus (MBT) envenomation and compared it with oleic acid (OA)-induced ARDS. The trachea, jugular vein and femoral artery were cannulated in anesthetized adult rats. Lethal dose of MBT venom (5 mg/kg) or OA (75 μL) was administered intravenously and the time-dependent changes in respiratory frequency (RF), heart rate (HR) and mean arterial pressure (MAP) were recorded. Minute ventilation (MV) and the PaO2/FiO2 (P/F) ratio were also determined. At the end lungs were excised, one lung was used for histopathological examination and the other was used for determination of pulmonary water content physically. MBT venom or OA produced hypoxemia, pulmonary pathology (alveolar damage, infiltration of inflammatory cells, capillary damage and exudation) and pulmonary edema implicating for ARDS. However, the hypoxemia in MBT venom group was associated with decreased MV, apnea/bradypnea, and bradycardia whereas, in OA group it was seen with increased MV, tachypnea, and tachycardia. Lack of effect of hypoxemic drive on RF/MV or HR in MBT venom group unlike OA group, suggests the involvement of medullary centers. The present results demonstrate that MBT venom produces ARDS. However MBT venom-induced ARDS involves pulmonary as well as extrapulmonary mechanisms.

A randomized trial comparing intravenous paracetamol, topical lidocaine, and ice application for treatment of pain associated with scorpion stings

OBJECTIVE

Appropriate treatment for scorpion-associated pain was not previously studied in detail in the literature. The aim of this study was to compare the efficacy of three treatment modalities in patients with painful scorpion stings using visual analog scale (VAS) scores.

MATERIALS AND METHODS

A randomized study was carried out during a 1-year period in patients with scorpion stings who did not have any systemic signs or symptoms. Patients were treated with intravenous paracetamol, topical lidocaine, or ice application. Pain intensity was evaluated using VAS score at the time of presentation to emergency department and at 30th, 60th, 120th, and 240th minutes. Changes in VAS scores from baseline were recorded.

RESULTS

A total of 130 patients were included in the statistical analysis. Significant reduction in pain intensity was observed with topical lidocaine group when compared with the ice application group (p < 0.001) and paracetamol group (p < 0.001) in all selected time intervals. The median reduction in scores at 30 min after therapeutic intervention was 25.0 mm for topical lidocaine, 14.5 mm for ice application, and 10.0 mm for intravenous paracetamol. No adverse events were reported.

DISCUSSION

Our results revealed that topical lidocaine is superior to both intravenous paracetamol and local ice application and its effect lasts several hours after envenomation.

CONCLUSION

Topical lidocaine is an effective and safe treatment in scorpion sting associated with pain in patients with nonsystemic signs and symptoms.

Clinical comparison of scorpion envenomation by Androctonus mauritanicus and Buthus occitanus in children

The clinical results of scorpion stings by Androctonus mauritanicus (Am) and Buthus occitanus (Bo) (main sources of scorpionism in Morocco) were evaluated in this work. The objective was to compare the clinical manifestations of envenoming from these species by investigating possible correlations among symptoms/signs and laboratory abnormalities of envenomed patients. 41 children (25 males, 18 months - 11 years) were admitted at the Provincial Hospital of El Jadida-Morocco. Their minor (18 children) or severe (23 children) systemic signs such as pallor (48.8%), pulmonary edema (APE) (36.6%), convulsion (26.8%), coma (7.3%) were more frequent in children envenomed by Am than Bo, but angioedema (Quincke's edema) (4.9%) was particularly developed in the latter group. The laboratory blood abnormalities (hyperglycemia, high levels of aspartate aminotransferase (AST), lactate dehydrogenase (LDH), creatinine, bilirubin, leukocytes, neutrophils, monocytes, platelets and low levels of lymphocytes and hemoglobin) were significantly higher (p < 0.05) in patients envenomed by Am than Bo, and in all population in comparison to control group. The correlation among these biological analyzes and clinical status showed that higher levels of LDH and value of leukocytes ≥19 × 10(3)/mm(3) were indices of cardiac dysfunction with APE. Pallor sign was correlated with a state of shock and/or low level of hemoglobin, associated or not to bilirubin increase. Fatalities (7.3%), presenting toxic myocarditis, had lowest count of lymphocytes (≤4.2%) in comparison to survivors. This is the first report on lymphopenia which may be useful for forecast the fatal outcome in scorpion envenomation.

Effects of atropine and propranolol on lung inflammation in experimental envenomation: comparison of two buthidae venoms

Background

Previous works had shown that scorpion venom induced neurotransmitter elevation and an inflammatory response associated with various anatomo-pathological modifications. The most dangerous scorpions species in Algeria responsible for these effects are Androctonus australis hector (Aah) and Androctonus amoreuxi (Aam).

Results

Comparison of the physiopathological effects induced by the two venoms showed differences in the kinetic of cytokine release and in lung injury.

The lung edema was only observed in response to Aah venom and it was correlated with cell infiltration. In order to better understand the involved mechanism in inflammatory response, we used two antagonists, atropine (non-selective muscarinic antagonist) and propranolol (β adrenergic antagonist), which lead to a decrease of cell infiltration but has no effect on edema forming.

Conclusion

These results suggest another pathway in the development of lung injury following envenomation with Aam or Aah venom.

Amelioration of cardio-respiratory perturbations following Mesobuthus eupeus envenomation in anesthetized rabbits with commercial polyvalent F(ab')2 antivenom

Immunotherapy is the only specific treatment for scorpion sting. In the present study, protective effects of polyvalent antivenom against hemodynamic disturbances, biomarkers (troponin T, creatinine kinase isoenzyme MB, Lactate dehydrogenase) changes, electrocardiogram abnormalities and histopathological complications in heart and lung induced by Mesobuthus eupeus scorpion venom was investigated in anesthetized rabbits. Twenty four rabbits were randomized into four equal groups: six rabbits in control group received 1 ml ultra-pure water subcutaneously (group 1). Group two received LD50 of venom (4.5 mg/kg). In the third and fourth groups, 5 ml of scorpion antivenom was administrated intravenously simultaneous with venom injection and 60 min following envenomation, respectively. Results of the present study indicate significant decrease in hemodynamic parameters following envenomation in the second group of animals. Venom injection caused edema, myocytolysis, coagulation necrosis, hemorrhage in heart as well as edema, hemorrhage and vascular thrombus in lungs. Although envenomed rabbits presented rises in LDH and TnT but no alteration in CK-MB was observed. Electrocardiogram monitoring of rabbits showed ST elevation and inverted T waves. Simultaneous administration of antivenom and venom prevented entirely the clinical signs, hemodynamic disturbances, markers changes, ECG abnormalities and histopathological damages. Delayed immunotherapy gradually ameliorated clinical signs, hemodynamic disturbances and markers changes related to envenomation. Histopathological evaluation showed slight alterations such as mild myocytolysis in heart and mild edema in lung following delayed immunotherapy. In conclusion, scorpion antivenom administration has preventive, neutralizing and curative properties for M. eupeus scorpion envenomation, if it would be applied at optimum time, dose and route.

Scorpion envenomation among children: clinical manifestations and outcome (analysis of 685 cases)

Our objective was to characterize both epidemiologically and clinically manifestations after severe scorpion envenomation and to define simple factors indicative of poor prognosis in children. We performed a retrospective study over 13 years (1990-2002) in the medical intensive care unit (ICU) of a university hospital (Sfax-Tunisia). The diagnosis of scorpion envenomation was based on a history of scorpion sting. The medical records of 685 children aged less than 16 years who were admitted for a scorpion sting were analyzed. There were 558 patients (81.5%) in the grade III group (with cardiogenic shock and/or pulmonary edema or severe neurological manifestation [coma and/or convulsion]) and 127 patients (18.5%) in the grade II group (with systemic manifestations). In this study, 434 patients (63.4%) had a pulmonary edema, and 80 patients had a cardiogenic shock; neurological manifestations were observed in 580 patients (84.7%), 555 patients (81%) developed systemic inflammatory response syndrome (SIRS), and 552 patients (80.6%) developed multi-organ failure. By the end of the stay in the ICU, evolution was marked by the death in 61 patients (8.9%). A multivariate analysis found the following factors to be correlated with a poor outcome: coma with Glasgow coma score ≤ 8/15 (odds ratio [OR] = 1.3), pulmonary edema (OR = 2.3), and cardiogenic shock (OR = 1.7). In addition, a significant association was found between the development of SIRS and heart failure. Moreover, a temperature > 39°C was associated with the presence of pulmonary edema, with a sensitivity at 20.6%, a specificity at 94.4%, and a positive predictive value at 91.7%. Finally, blood sugar levels above 15 mmol/L were significantly associated with a heart failure. In children admitted for severe scorpion envenomation, coma with Glasgow coma score ≤ 8/15, pulmonary edema, and cardiogenic shock were associated with a poor outcome. The presence of SIRS, a temperature > 39°C, and blood sugar levels above 15 mmol/L were associated with heart failure.

Scorpion venom and the inflammatory response

Scorpion venoms consist of a complex of several toxins that exhibit a wide range of biological properties and actions, as well as chemical compositions, toxicity, and pharmacokinetic and pharmacodynamic characteristics. These venoms are associated with high morbility and mortality, especially among children. Victims of envenoming by a scorpion suffer a variety of pathologies, involving mainly both sympathetic and parasympathetic stimulation as well as central manifestations such as irritability, hyperthermia, vomiting, profuse salivation, tremor, and convulsion. The clinical signs and symptoms observed in humans and experimental animals are related with an excessive systemic host inflammatory response to stings and stings, respectively. Although the pathophysiology of envenomation is complex and not yet fully understood, venom and immune responses are known to trigger the release of inflammatory mediators that are largely mediated by cytokines. In models of severe systemic inflammation produced by injection of high doses of venom or venoms products, the increase in production of proinflammatory cytokines significantly contributes to immunological imbalance, multiple organ dysfunction and death. The cytokines initiate a cascade of events that lead to illness behaviors such as fever, anorexia, and also physiological events in the host such as activation of vasodilatation, hypotension, and increased of vessel permeability.

Differential effects of Tityus bahiensis scorpion venom on tetrodotoxin-sensitive and tetrodotoxin-resistant sodium currents

We examined modification of sodium channel gating by Tityus bahiensis scorpion venom (TbScV), and compared effects on native tetrodotoxin-sensitive and tetrodotoxin-resistant sodium currents from rat dorsal root ganglion neurons and cardiac myocytes. In neurons, TbScV dramatically reduced the rate of sodium current inactivation, increased current amplitude, and caused a negative shift in the voltage-dependence of activation and inactivation of tetrodotoxin-sensitive channels. Enhanced activation of modified sodium channels was independent of a depolarizing prepulse. We identified two components of neuronal tetrodotoxin-resistant current with biophysical properties similar to those described for NaV1.8 and NaV1.9. In contrast to its effects on neuronal tetrodotoxin-sensitive current, TbScV caused a small decrease in neuronal tetrodotoxin-resistant sodium current amplitude and the gating modifications described above were absent. A third tetrodotoxin-resistant current, NaV1.5 recorded in rat cardiac ventricular myocytes, was inhibited approximately 50% by TbScV, and the remaining current exhibited markedly slowed activation and inactivation. In conclusion, TbScV has very different effects on different sodium channel isoforms. Among the neuronal types, currents resistant to tetrodotoxin are also resistant to gating modification by TbScV. The cardiac tetrodotoxin-resistant current has complex sensitivity that includes both inhibition of current amplitude and slowing of activation and inactivation.

Comparative study between the protective effects of Saudi and Egyptian antivenoms, alone or in combination with ion channel modulators, against deleterious actions of Leiurus quinquestriatus scorpion venom

This study compared efficacy of two polyvalent antivenoms (Saudi Arabian and Egyptian), against lethality and pathophysiological changes of Leiurus quinquestriatus quinquestriatus (LQQ) scorpion venom in mice. Additionally, the study examined whether treatment with selected ion channel modulators, lidocaine, nimodipine or amiodarone would be effective, alone or combined with the antivenoms. The protein concentration of the Saudi antivenom was 1/3 of Egyptian, indicating lesser immunogenicity, while both preservative contents were within limits. In immunodiffusion experiments, both exhibited prominent precipitin bands indicating high concentrations of specific antibodies. Neutralizing capacities (60-70 LD(50)) stated on labels were confirmed. Both antivenoms significantly (P < 0.001) prolonged survival time (from 26.9 +/- 1.18 min, 100% dead with venom to 224-300 min, 0-30% dead) of envenomed mice, whether injected iv before or 5 min after venom. Injection of either antivenom plus ion channel modulators, gave comparable results to that observed in mice treated with antivenoms alone. The Na(+) channel blocker lidocaine and the Ca(2+) channel blocker nimodipine on their own significantly protected the animals (P < 0.05), but to a lesser extent. The two antivenoms, significantly ameliorated the venom-evoked changes in serum LDH (P < 0.001) and CKMB (P < 0.01) plus cardiac TNFalpha and nitrate/nitrite levels (P < 0.001). When combined with lidocaine or nimodipine, the effects were not greater than antivenom alone. Moreover, the antivenoms ameliorated characteristic venom-evoked changes in the isolated perfused Langendorff hearts. Lidocaine and amiodarone were more effective than nimodipine. In Conclusion both Saudi and Egyptian antivenoms protected mice from the pathological and lethal effects of LQQ scorpion. Sodium and calcium channel blockers, lidocaine and nimodipine, may be useful when antivenoms are not available.

Scorpion toxin of Androctonus australis garzonii induces neuropeptide Y release via bradykinin stimulation in rat atria and kidneys

The ability of scorpion toxins to produce hemodynamic alterations is well documented but all mediators implied in cardiovascular disturbances are not known. In the present investigation we studied the effect of North African Androctonus australis garzonii scorpion toxin on neuropeptide Y (NPY) release from rat atria and kidneys by a perifusion system in vitro. To further understand the mechanisms of the scorpion toxin action on NPY release, the effects of icatibant (HOE 140, a selective bradykinin-B2 receptor antagonist), tetrodotoxin (TTX, a sodium channel antagonist) and diltiazem (a calcium channel antagonist), and the effect of the scorpion toxin on bradykinin (BK, a potent vasorelaxant peptide of the kinin group) release were studied in both tissues. We showed that the scorpion toxin (10(-6)M) increased the NPY release from both atria (35%) and kidneys (40%). This increase was significantly (p<0.001) inhibited by HOE 140 (10(-5)M). The scorpion toxin (10(-6)M) enhanced BK secretion in both atria (52%) and kidneys (55%). Diltiazem (10(-5)M) and TTX (10(-5)M) decreased by 45-75% NPY levels induced by scorpion toxin in both organs. The results show that A. australis garzonii scorpion toxin stimulates NPY release from both rat atria and kidneys, and suggest that the toxin induces NPY release via BK stimulation through B2 receptors. This effect appears to involve calcium and sodium channel activation.

Antepartum fetal death following a yellow scorpion sting

Scorpion envenomation in pregnant victims has been scarcely studied. We would like to suggest an association between yellow scorpion sting during the third trimester of pregnancy and adverse fetal outcome. The particular deleterious mechanism of scorpion venom has not been elucidated yet.

Asymmetric pulmonary edema after scorpion sting: a case report

A 12-year-old boy was referred with acute asymmetric pulmonary edema (APE) four-hour after scorpion sting to Emergency department. On admission, the main clinical manifestations were: dyspnea, tachypnea, and tachycardia. Chest x-ray revealed APE predominantly on the right hemithorax. The patient was treated with oxygen, intravenous frusemide and digoxin and discharged on the sixth hospital day in a good condition. This case report emphasizes the occurrence of asymmetric pulmonary edema after severe scorpion envenomation within few hours immediately after the sting.

Carbamazepine is effective in the treatment of 21-day-old Wistar rats injected with Tityus serrulatus crude venom

The scorpion-envenoming syndrome has an incidence of approximately 8000 accidents/year in Brazil; with most severe cases occurring during childhood and elderly. Previous results from our laboratory suggest that the effects of scorpion toxins on the central nervous system play a major role on the lethality induced by scorpion envenoming. Our group has shown that the pre-treatment with carbamazepine (CBZ) is able to increase the latency-to-death in developing animals inoculated with tityustoxin, a toxic fraction of the Tityus serrulatus crude venom. Nevertheless, in order to perceive CBZ as potentially useful in clinical practice, the efficiency of CBZ against crude venom inoculation and the pharmacological treatment introduced after envenomation must be addressed. Thus, the objective of this work was to evaluate CBZ therapeutic efficiency against scorpion envenomation in developing rats. Animals were treated with i.p. injections of either vehicle or CBZ (50 mg/kg or 100 mg/kg) 10 min after injected with a s.c. fixed volume of either saline or crude T. serrulatus venom extract (48 mg/kg). The dose chosen for venom inoculation was 16 times its DL50 for 21-day-old Wistar rats, invariably inducing death within 2 h. Although CBZ did not significantly reduce the pulmonary edema, it was effective in increasing survival rate by approximately 75% in treated rats. In conclusion, CBZ was effective in the treatment of T. serrulatus envenomation even though not blocking the pulmonary edema.

Pathophysiological effects of Androctonus australis hector scorpion venom: tissue damages and inflammatory response

In this study, the effects of sublethal dose of Androctonus australis hector (Aah) venom on the enzymatic activities (creatine phospho-kinase and lactate dehydrogenase) and histopathological changes of heart and lungs' organs were determined 24h following envenoming NMRI mice. The effects of Aah venom on the lytic activity of the complement system, plasma cytokine rates (IL1-beta, IL-6, TNF-alpha, IL-4 and IL-10) and the peripheral blood cell infiltration were also studied. Microscopically, treated animals showed severe myocardial edema, hemorrhages and necroses and severe acute bronchopneumonia with alveolar edema and hemorrhages. High serum levels of lactate dehydrogenase and creatine kinase correlate to the tissue lesions. The results showed fast kinetics of production of pro-inflammatory (IL1-beta, IL-6, TNF-alpha) and anti-inflammatory (IL-4 and IL-10) cytokines at 30min in blood sera. An increase in serum lytic activity of envenomed animals and leucocytosis in peripheral blood with predominance of mononuclear and neutrophil cells were also observed. In conclusion, the results reported in the present study suggest that pathophysiological manifestations of Aah envenomation may be mediated sequentially or simultaneously by cytokines and the complement system, which in turn activate leukocyte to produce tissue damage.

Effect of leukocyte inhibitors benzydamine and cyclophosphamide, on lung injury caused by Tityus discrepans scorpion venom

We studied the effects of benzydamine (BZ) and cyclophosphamide (CP) on acute lung injury caused by Tityus discrepans venom. Mice (male, IVIC strain, approximately 25g) were pretreated with either BZ (20microg/g) or CP (100microg/g) i.p. or saline. Envenoming (2microg/g mouse) was induced sc. Lung fraction area occupied by fibrin (FF), nuclei (NF), alveolar space (AS) and parenchyma (PF) were determined. Venom increased FF, NF and PF, significantly, and decreased AS. BZ antagonised venom's effect on FF sharply, antagonised partially effects on PF and AS, but was not able to antagonise effect on NF. CP abolished venom effects on NF, AS and PF, but was not able to antagonise the effect on FF. CP was slightly less effective than BZ in reducing FF. Fibrin deposition was associated to leukocyte sequestration. Blocking pro-inflammatory leukocyte metabolic pathways with BZ diminished FF, suggesting that neutrophil activation, inflammation and coagulation are correlated in the genesis of scorpionism acute lung injury.

INVESTIGATION OF THE MICROCIRCULATION AND THE STATE OF OXIDATIVE STRESS IN THE RAT AFTER SCORPION ENVENOMATION

1. Severe cases of scorpion envenomation (SE) generally show both respiratory and cardiocirculatory dysfunction. However, the pathophysiology of SE remains controversial. In the present study, we tried to explain the pathophysiology of the haemodynamic perturbations and cardiac failure in rats poisoned by the venom of Buthus occitanus tunetanus through a histomorphometric study of myocardial and muscular skeletal microcirculation and analysis of the oxidative stress state in order to evaluate the implication of the inflammatory process in the pathogenesis of SE. 2. Experiments were performed on 96 rats divided into 16 groups (n = 6 in each group). Two groups were used to determine the optimum conditions of venom administration and times when to measure haemodynamic parameters. The B. occitanus tunetanus venom was administered at a dose of 800 microg/kg and tissues were removed 5 and 20 min after envenomation. Six groups were used for histomorphometric study: two control groups, two poisoned groups an two melatonin-pretreated and poisoned groups. The histomorphometric study was performed on isolated hearts and skeletal muscles. The final eight groups of rats (two control groups, two envenomated groups, two control groups pretreated with melatonin and two groups pretreated and envenomated) were used to investigate the state of tissue oxidative stress during SE and to evaluate the anti-oxidant effect of melatonin on rats poisoned with B. occitanus tunetanus venom. This study was based on the determination of tissue malondialdehyde in isolated organs as an indicator of thiobarbituric acid-reactive substances (TBARS). Melatonin was injected at a dose of 5 mg/kg, i.v., 15 min before the administration of serum or venom. Data were compared using analysis of variance and Tukey's test for multiple pair-wise comparisons. 3. Five minutes after venom injection, a significant reduction in the mean relative volume of venules and arterioles in the heart and skeletal muscles of poisoned rats was noted. Twenty minutes after venom injection, these volumes were significantly increased in the heart and skeletal muscles of poisoned rats. Pretreatment of envenomated rats with melatonin resulted in a significant decrease in the mean relative volume of the venules and arterioles in the heart and skeletal muscles 5 and 20 min after venom injection compared with untreated envenomated rats. Investigation of the oxidative stress state showed a highly significant increase in TBARS in poisoned rats compared with control groups 5 and 20 min after venom injection. Melatonin pretreatment of rats poisoned with B. occitanus tunetanus venom resulted in an important and highly significant reduction of TBARS compared with untreated envenomated rats. 4. It appears from the results of the present study that administration of B. occitanus tunetanus venom engendered an excessive myocardial and skeletal muscular vasoconstriction attributed to massive catecholamine release followed by arteriolar and venular vasodilatation. This venous stasis at the muscular microcirculation could be due to myocardiac failure. However, the concomitant presence of arteriolar vasodilatation suggests an inflammatory process in the pathophysiology of SE. This process was suggested by the genesis of a state of oxidative stress in relation to the important lipoperoxidation, which was inhibited by administration of the anti-oxidant melatonin. Thus, melatonin pretreatment seemed to accentuate the first phase of vascular reactivity in envenomed rats and inhibit the second vasodilator phase observed 20 min after administration of the venom.

Indirect activation of neuronal noncapacitative Ca2+entry is the final step involved in the neurotoxic effect ofTityus serrulatusscorpion β-toxin

Interweaving strategies of electrophysiology, calcium imaging and immunocytochemistry bring new insights into the mode of action of the Brazilian scorpion Tityus serrulatusbeta-toxin VII. Pacemaker dorsal unpaired median neurons isolated from the cockroach central nervous system were used to study the effects of toxin VII. In current-clamp, 50 nm toxin VII produced a membrane depolarization and reduced spiking. At 200 nM, depolarization associated with multiphasic effects was seen. After artificial hyperpolarization, plateau potentials on which spontaneous electrical activity appeared were observed. In voltage clamp, toxin VII induced a negative shift of the voltage dependence of sodium current activation without significant effect on steady-state inactivation. In addition, toxin VII produced a permanent TTX-sensitive holding inward current, indicating that background sodium channels were targeted by beta-toxin. Cell-attached patch recordings indicated that these channels were switched from unclustered single openings to current fluctuating between distinct subconductance levels exhibiting increased open probability and open-time distribution. Toxin VII also produced a TTX-sensitive [Ca2+]i rise. Immunostaining with Cav2.2(alpha1b) antibodies and calcium imaging data obtained with omega-CgTx GVIA indicated that N-type high-voltage-activated calcium channels initiated calcium influx and were an essential intermediate in the pathway linking toxin VII-modified sodium channels to the activation of an additional route for calcium entry. By using inhibitors of (i) noncapacitative calcium entry (inhibitor LOE-908), (ii) NO-sensitive guanylyl cyclase (ODQ) and (iii) phosphodiesterase 2 (EHNA), together with cGMP antibodies, we demonstrated that noncapacitative calcium entry was the final step in a complex combination of events that was initiated by toxin VII-alteration of sodium channels and then involved successive activation of other membrane ion channels.

Infective Endocarditis Associated With a Scorpion Sting

We report the successful surgical intervention in two cases of aortic valve bacterial endocarditis after scorpion stings. Infective endocarditis developed in both patients several weeks after they suffered repeated scorpion stings. Both patients had similar, but uncommon features: (1) the isolated organisms were unusual causes of infective endocarditis (streptococcus group G and Streptococcus milleri), (2) annular abscesses developed that required either aortic root replacement with a homograft or annular patch repair with pericardium, and (3) complete heart block developed postoperatively, requiring permanent pacemaker implantation. Both patients completed a 6-week postoperative course of antibiotic therapy and are without recurrent infection.

Neurohormonal activation in severe scorpion envenomation: correlation with hemodynamics and circulating toxin

We studied the effects of scorpion (Androctonus australis hector) venom on hemodynamics and on the release of catecholamines, neuropeptide Y (NPY), endothelin-1 (ET-1) and atrial natriuretic peptide (ANP) in dog model of severe scorpion envenomation. Nine mongrel anesthetized dogs were submitted to mechanical ventilation through intubation and were administered intravenously purified dried scorpion venom (Androctonus autstralis) 0.05 mg/kg. Measurements including pulmonary artery catheter derived parameters, serum toxin levels and humoral variables were performed at baseline (before venom injection) and 5, 15, 30 and 60 min after venom injection. Humoral variables included: serum lactate, epinephrine (EP), norepinephrine (NE), NPY, ET-1 and ANP plasma concentrations. Scorpion venom caused rapid and transient increase of mean arterial pressure (MAP) and PAOP associated with a marked and sustained decline in cardiac output (-55% at 60 min; P < 0.001). Hemodynamic changes were associated with a rapid and significant increase of all measured hormones. The highest increase was for NE (28-fold) and EP (25-fold). MAP was closely correlated with NE and less significantly correlated with toxin levels. Similarly, significant correlation was observed between PAPO and ANP plasma levels. These findings support the implication of excessive catecholamines release in hemodynamic disturbances of severe SE and suggest that NPY and ET-1 could be involved in this process. Serum toxin does not appear to consistently contribute to these effects. Through its correlation with PAOP, ANP could be a reliable and useful marker of cardiac dysfunction in SE.

Effects of voltage-gated Na+ channel toxins from Tityus serrulatus venom on rat arterial blood pressure and plasma catecholamines

Scorpion toxins interact with ionic channels of excitable cells, leading to a massive release of neurotransmitters. Voltage-gated Na+ channel toxins are mainly responsible for the toxic effects of scorpion envenoming and can be classified into two classes: alpha- and beta-neurotoxins. TsTX-V and TsTX-I from Tityus serrulatus venom (TsV) are, respectively, examples of these toxins. In this work, we compared the effects of these toxins on mean arterial pressure (MAP) and catecholamines release in rats. Toxins were isolated by ion exchange chromatography (TsTX-I) followed by RP-HPLC (TsTX-V). All experiments were performed on conscious unrestrained rats previously catheterised. The toxins (15 and 30 microg/kg) and TsV (50 and 100 microg/kg) were injected intravenously. MAP was continuously monitored through femoral catheter. Epinephrine (E) and norepinephrine (NE) levels were determined by RP-HPLC with electrochemical detection, at 10 min before and 2.5, 30 and 90 min after treatments. Maximal pressor effects were observed at 2.5-3.5 min. TsV induced intense long lasting increase in MAP, as did TsTX-I. TsTX-V showed the lowest pressor effects. TsV showed the highest effects on catecholamines release, followed by TsTX-I and TsTX-V with maximal effect at 2.5 min, followed by a gradual reduction, however remaining higher than controls. Although both toxins act on Na+ channels, TsTX-I displayed significant and more intense effects on catecholamines release and blood pressure than TsTX-V. It seems that the toxicity of TsTX-V is not related only with its ability to release catecholamines, indicating that other neurotransmitters, may be involved in its toxicity.

Evidence that free radical generation occurs during scorpion envenomation

Although it is well established that symptomatology, morbidity and death following scorpion envenomation are due to increases in neurotransmitter release secondary to toxins binding to voltage-sensitive sodium channels, the mechanism by which venom action is involved in damaging heart, liver, lungs and kidneys remains unclear. We hypothesized that scorpion toxins could induce the generation of high levels of free radicals responsible for membrane damage in organs targeted by venom action. We have investigated lipid peroxidation in different organs, through the evaluation of thiobarbituric acid reactive substances (TBARS), after experimental envenomation of rats by toxic fractions of Androctonus australis Hector venom. We have shown that scorpion toxins cause considerable lipid peroxidation in most vital organs. We also evaluated the protective effects of antioxidants in mice injected with lethal doses of toxins. Among the drugs tested, N-acetylcysteine (NAC) was effective in protecting the mice when injected prior to toxin application. However, the free radical scavenging properties of NAC seem less implicated in these protective effects than its ability to increase the fluidity of bronchial secretions. We therefore conclude that free radical generation only plays a minor role in the toxicity of scorpion venom.

Direct vs. mediated effects of scorpion venom: an experimental study of the effects of a second challenge with scorpion venom

OBJECTIVE

To assess the respective roles of venom and of catecholamines following scorpion envenomation and to verify whether a second challenge with scorpion venom induces the same consequences than a first one.

DESIGN AND SETTING

Controlled animal study in a university research laboratory.

SUBJECTS

Anesthetized and ventilated dogs.

INTERVENTIONS

Fifteen dogs received intravenously a sublethal dose of scorpion venom (0.05 mg/kg). In the reenvenomated group (n=5) a second venom challenge with one-half sublethal venom dose was performed 30 min after the first one. The control group (n=10) received saline. Five additional animals served as sham.

MEASUREMENTS AND RESULTS

Plasma toxin and catecholamine levels and a set of usual hemodynamic measurements were repeatedly measured in the first hour following envenomation. In the reenvenomated group another set of measurements was performed 5 min after the second challenge. Changes in toxin, catecholamines, and the main hemodynamic parameters were compared between the study groups. Initial peak toxin levels were similar in the two groups. They induced a striking increase in circulating catecholamines, a fall in heart rate, and an increase in mean arterial and pulmonary artery occluded pressures and in systemic vascular resistance. In the reenvenomated group the second challenge with scorpion venom achieved a toxin blood level similar to the first peak. However, it was not associated with a significant effect either on catecholamines release or on hemodynamics. Subsequent trends in hemodynamic changes were similar to those observed in the control group.

CONCLUSIONS

These data emphasize the limited role of direct effects of scorpion venom on the cardiovascular system and the key role of catecholamines.

Pediatric electrocardiograph abnormalities following Centruroides limpidus tecomanus scorpion envenomation

Scorpionism is an endemic public health problem in Mexico [Hoffmann, C.C., 1936. La distribucion geografica de los alacranes peligrosos en la Republica Mexicana. Bol. Inst. Hygiene Mex. 2, 321; Hoffmann, C.C., Nieto, D.R., 1939. Segunda contribucion al conocimiento de los alacranes mexicanos. Anal. Inst. Biol. 10, 83-92; Mazzoti, L., Bravo-Becherelle, M.A., 1963. Scorpionism in the Mexican Republic. In: Keegan, H.L., McFarlane, W.V. (Eds.), Venomous and Poissonous Animals and Noxious Plants of the Pacific Area. Pergamon Press, London, pp. 119-131; Monroy-Velasco, J., 1961. Alacranes venenosos de Mexico. Rev. Mex. Cien. Med. Biol., Mex. 1, 1-23; Diaz-Najera, A., 1975. Listas y datos de distribucion geografica de los alacranes de Mexico. Rev. Inv. Salud. Publica. (Mex.) 35, 1; Velasco-Castrejon, O., Lara-Aguilera, R., Alatorre, H., 1976. Aspectos epidemiologicos y clinicos de la picadura de alacran en una area hiperendemica. Rev. Inv. Salud Publica. (Mex.) 36, 93-103; Dehesa-Davila, M., Possani, L.D., 1994. Scorpionism and serotherapy in Mexico. Toxicon 32 (9), 1015-1018]. In this prospective study, we assess cardiovascular disorders in children via electrocardiographic (ECG) recordings following envenomation by scorpion species Centruroides limpidus tecomanus found in the state of Colima, Mexico. We analyzed 113 cases between the ages of 5 and 14 years. Among the most frequent symptoms presented included local pain (99.1%) and paresthesia (75.2%), pruritus (36.3%), sialorrhoea (35.4%), and nystagmus (24.8%). Cardiovascular disorders were observed in 39.8% of cases, 71% of which were rhythm abnormalities. We find a significant association between the frequency of ECG alterations and age, whereby 8-9-year-old children are more likely to experience ECG alterations when compared with other tested age groups.

Blockade of neuronal nitric oxide synthase abolishes the toxic effects of Tx2-5, a lethal Phoneutria nigriventer spider toxin

The primary goal of this study was to determine whether Tx2-5, a sodium channel selective toxin obtained from the venom of the spider Phoneutria nigriventer, produced penile erection by means of nitric oxide mechanism. Toxin identity was analyzed by MALDI-TOF, ES-MS and N-terminal amino acid sequencing. Pretreating mice with the non-selective nitric oxide synthase (NOS) inhibitor N(omega)-Nitro-L-arginine methyl ester hydrochloride (L-NAME) and the selective neuronal-NOS inhibitor 7-Nitroindazole (7-NI) prior to Tx2-5 i.p. (10 microg/25 g mouse) injection challenged the hypothesis above. Controls were injected with the D-isomer or DMSO or saline. Results demonstrated that L-NAME inhibited penile erections in about half the animals treated, while 7-NI completely abolished this effect. Interestingly 7-NI also abolished all the other symptoms of intoxication induced by Tx2-5, including salivation, respiratory distress and death. Tx2-5 killed all the animals of the control group and no one in the 7-NI-treated group. We conclude that (1) intraperitoneal injections of Tx2-5 induce a toxic syndrome that include penile erection, hypersalivation and death by respiratory distress or pulmonary edema; (2) pretreatment with the non-selective NOS inhibitor L-NAME reduces the penile erection and partially protects from the lethal effects of Tx2-5; (3) pretreatment with the nNOS-selective inhibitor 7-NI completely abolishes all the toxic effects of Tx2-5, including penile erection and death suggesting that nNOS is the major player in this intoxication; (4) toxins from other animals that affect sodium channels in the same way as Tx2-5 and induce similar toxic syndromes may have as a major common target, the activation of nitric oxide synthases.

The indirect effect of Tityus discrepans on rabbit pulmonary vasculature

Serum (IS) was obtained 0.5, 2, 4 or 6 h after inoculating s.c. six rabbits (approximately 2 kg) in each time period with 1 mg/kg of Tityus discrepans (Td) venom; the control was serum obtained from four rabbits 4 h after injecting them 1 ml s.c. of 0.9% NaCl. IS produced a transient (<25 min) rise in pulmonary artery pressure of isolated and perfused rabbit lungs, other lung parameters were not altered. We found that both scorpion venom and IS produced a approximately 50% transient increase of transendothelial electric resistance in cultured tissue human umbilical cord vein. Neither venom nor IS changed the transepithelial electrical resistance of tissue cultured human airway epithelia. The experiments suggest that humoral factors contained in the inoculated serum modify vascular endothelium in a much more effective manner than the venom by itself. These experiments also make it unlikely that vascular endothelium is the source of the humoral factors contained in inflammatory serum.

Significance of assessment of serum cardiac troponin I and interleukin-8 in scorpion envenomed children

In the present study, 41 children in Upper Egypt were admitted to Pediatric Intensive Care Unit, Assiut University Hospital, for scorpion envenomation. They were compared with 15 apparently healthy children of matching age as controls. The victims and controls were subjected to complete clinical examination, full blood count and arterial blood gases analysis. According to severity of scorpion envenomation, 17 children had manifestations of severe envenomation and clinical signs of toxic myocarditis (severe cases), 14 children had moderate manifestations of envenomation without clinical evidence of carditis (moderate cases) and 10 cases showing only mild symptoms of envenomation (mild cases). The serum levels of cardiac troponin I (cTnI) and interleukin-8 (IL-8) beside the enzymatic activities of creatine phosphokinase (CPK), CPK-isoenzyme-MB (CPK-MB) and lactate dehydrogenase (LDH) were determined once for mild cases and controls on admission and twice for severe and moderate cases on admission and after 24. Electrocardiography and measurements of echocardiographic (Echo) of % fractional shortening of left ventricule (% SF), left ventricular ejection fraction (LVEF) and cardiac chambers dilatation were done for severe and moderate cases. All the envenomed victims showed significantly higher mean values of CPK, CPK-MB, LDH, and IL-8 on admission in comparison to control group. cTnI was not detectable in the sera of control group as well as patients of mild envenomation. The mean values of CPK, CPK-MB, LDH, and IL-8 were significantly higher in severe cases while only IL-8 and CPK-MB were significantly higher in moderate cases in comparison with mild cases. The mean values of IL-8, cTnI, CPK, CPK-MB and LDH were significantly higher in severe cases both on admission and on follow-up comparing with moderate cases. The case fatality rate was 12.5% and all were from severe cases with toxic myocarditis. The non-survivors victims showed significant higher mean values of only cTnI on admission and both cTnI and IL-8 on follow up in comparison to the survivors. Significant reduction of % SF and LVEF were noticed among the non-survivors in comparison to survivors. The cTnI showed 100% specificity and sensitivity for diagnosis of myocardial injury in relation to Echo finding in the envenomed victims. In severe cases, cTnI was positively correlated with IL-8 while negatively correlated with %SF and LVEF. In conclusion, cTnI is a specific marker for diagnosis of myocardial injury in scorpion envenomation while other biochemical markers did not show such specificity. Also, IL-8 may be involved in the pathogenesis of myocardial injury of scorpion envenomation. Both cTnI and IL-8 may be useful to forecast the fatal outcome in scorpion envenomation.

Treatment of the scorpion envenoming syndrome: 12-years experience with serotherapy

The pathophysiology of the scorpion envenoming syndrome is described with emphasis on the body systems commonly affected. Concepts of the mechanisms underlying venom action, as can be explained by the recently discovered effects on ionic channels, are discussed. A protocol for the treatment of scorpion stings based mainly on antivenom therapy was applied nationwide in Saudi Arabia. A list of drugs with alternatives was specified to be used in adjunctive therapy, when required. Analysis of the outcome from 1,033 cases at Al-Baha region, 791 cases at Al-Qassim region and more than 2,000 cases from 12 central and specialist hospitals in the Central Province, Saudi Arabia gave impressive results. The incidence of severe venom toxicity following antivenom administration was almost negligible. The period of stay in the hospital was reduced. The early reaction to antivenom administration was lower than expected the severity of the reaction consisting mainly of skin rashes, urticaria, wheezing and bronchial hypersensitivity, but no anaphylaxis. About 13.8% of the victims had been previously treated with antivenom but only 1.7% of the patients showed positive skin tests. This might be due to the low protein content of the antivenom and the action of the venom in releasing massive amounts of catecholamines.

Increased plasma levels of IL-1beta, IL-6, IL-8, IL-10 and TNF-alpha in patients moderately or severely envenomed by Tityus serrulatus scorpion sting

Scorpion envenomation is a common medical problem in many countries and an important cause of morbidity and mortality, especially among children. The plasma levels of pro-inflammatory (IL-1beta, IL-6, IL-8 and TNF-alpha) and anti-inflammatory (IL-10) cytokines were measured in individuals stung by Tityus serrulatus (Ts) scorpions. According to clinical manifestations patients were classified, as defined by the Brazilian Ministry of Health, as having mild (n=15, mean age=42.2 years), moderate (n=8, mean age=26 years) or severe (n=4, mean age=14 years) envenomation. Blood samples were taken immediately (T1) and 6h (T2) after admission to the hospital. Eighteen age-matched healthy volunteers were used as control. TNF-alpha, IL-1beta, IL-6 and IL-8 levels were significantly increased in moderate and severe cases and the levels of these cytokines were positively correlated with the severity of envenomation, as evaluated by clinical profile and plasma venom concentration. IL-10 levels were increased in severe and moderate cases and reduced in mild cases. The results reported in the present study suggest that the physiopathological manifestation of Ts envenomation may be mediated, at least in part, by cytokines, and that the early treatment after scorpion sting with drugs that inhibit cytokine production, such as glucocorticoids, may have a potential beneficial effect, ameliorating the severity of the clinical manifestations observed, particularly in severe and moderate cases.