Pharmacological studies of scorpion (Androctonus amoreuxi Aud. & Sav.) venom

Toxicology of Androctonus scorpion

The following paper is a summary of studies of the biology of the Androctonus scorpion and its toxicology. A materia medica based on human envenomation by Androctonus is also provided.

Anti-scorpion venom activity of Thapsia garganica methanolic extract: Histopathological and biochemical evidences

ETHNOPHARMACOLOGICAL RELEVANCE

Thapsia garganica, is a herbal medicine traditionally used as diuretic, emetic and purgative. It is also used as anti-scorpion venom in Morocco; however, its protective effects against scorpion venom remain elusive.

AIM OF THE STUDY

The present study was undertaken to evaluate anti-venom activity of T. garganica in vivo through histological and biochemical studies.

MATERIALS AND METHODS

Methanolic leaves extract of T. garganica was evaluated for anti-venom activity against buthus. occitanus under in vivo conditions. Histopathological and biochemical changes in envenomed and treated mice were also examined. Phytochemical screening was conducted to estimate the major constituents whereas DPPH, β -Carotene-linoleic acid and reducing power assays were performed to evaluate the anti-oxidant activity of T. garganica extract.

RESULTS

Methanolic leaves extract of T. garganica (2g/kg) increased the survival time (> 18h) of mice injected with lethal doses of B. occitanus venom, with remarkable recovery of histology damage. Furthermore T. garganica induced a significant decreased of biochemical markers of kidney, liver and heart function. Phytochemistry screening revealed the presence of phenolic compounds, flavonoids, tannins and steroids/terpenoids, which might explain the bioactivity of the extract. It was also shown that the extract has an exceptionally high antioxidant activity compared to well-known antioxidants used as standards.

CONCLUSION

The present study provides strong evidence that support the use of T. garganica as anti-scorpion venom in traditional medicine in Morocco. However, additional studies are required to isolate and identify the metabolites responsible for the activity.

Involvement of Cholinergic and Adrenergic Receptors in Pathogenesis and Inflammatory Response Induced by Alpha-Neurotoxin Bot III of Scorpion Venom

Bot III neurotoxin is the most lethal α neurotoxin purified from Buthus occitanus tunetanus scorpion venom. This toxin binds to the voltage-gated sodium channel of excitable cells and blocks its inactivation, inducing an increased release of neurotransmitters (acetylcholine and catecholamines). This study aims to elucidate the involvement of cholinergic and adrenergic receptors in pathogenesis and inflammatory response triggered by this toxin. Injection of Bot III to animals induces an increase of peroxidase activities, an imbalance of oxidative status, tissue damages in lung parenchyma, and myocardium correlated with metabolic disorders. The pretreatment with nicotine (nicotinic receptor agonist) or atropine (muscarinic receptor antagonist) protected the animals from almost all disorders caused by Bot III toxin, especially the immunological alterations. Bisoprolol administration (selective β1 adrenergic receptor antagonist) was also efficient in the protection of animals, mainly on tissue damage. Propranolol (non-selective adrenergic receptor antagonist) showed less effect. These results suggest that both cholinergic and adrenergic receptors are activated in the cardiopulmonary manifestations induced by Bot III. Indeed, the muscarinic receptor appears to be more involved than the nicotinic one, and the β1 adrenergic receptor seems to dominate the β2 receptor. These results showed also that the activation of nicotinic receptor leads to a significant protection of animals against Bot III toxin effect. These findings supply a supplementary data leading to better understanding of the mechanism triggered by scorpionic neurotoxins and suggest the use of drugs targeting these receptors, especially the nicotinic one in order to counteract the inflammatory response observed in scorpion envenomation.

Systemic responses following brain injuries and inflammatory process activation induced by a neurotoxin of Androctonus scorpion venom

OBJECTIVE

Kaliotoxin 2 (KTX2), a neurotoxin isolated from Androctonus australis hector scorpion venom, presents a high affinity with the voltage-gated potassium channels. The targets of KTX2 in the brain and its toxic effects on the cerebral cortex have been extensively studied; however, its deleterious systemic effects on other organ systems have not yet been investigated. Inflammatory response induced by KTX2 is supported by cytokine release which could provoke multiple organ dysfunction and diverse biological disorders in mammals. The possibility that inflammatory response and brain injuries induced by KTX2 may lead to functional disturbances, e.g. in the pancreas and the liver, were investigated. The contribution of IL-6 and TNF-α to the modulation of pathophysiological effects induced by KTX2 was also tested.

METHODS

NMRI mice were injected by the intracerebroventricular route with a sublethal dose of KTX2 or saline solution. Inflammatory response and oxidative stress were assessed in sera and tissue homogenates. Biomarkers of pancreatic and hepatic functions and the correlation with tissue damage in the brain, liver and pancreas were also analyzed.

RESULTS

The obtained results revealed that KTX2 injection induced an inflammatory process activation and imbalanced redox status. It also induced severe alterations in cerebral cortex, hepatic and pancreatic tissues associated with a significant increase in pancreatic and hepatic pathological biomarkers. Cytokine antagonists injected 30 min prior to KTX2 led to a significant reduction of all disturbances induced by KTX2.

CONCLUSION

In addition to its significant toxicity on the central nervous system, KTX2 can also affect pancreatic and hepatic functions, probably by an indirect mechanism involving activation of the inflammatory response with release of IL-6 and TNF-α.

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.

Evidence for a direct action of Tityus serrulatus scorpion venom on the cardiac muscle

The ability of toxins to activate the cardiovascular system plays an important role in the morbidity and lethality of the Tityus serrulatus scorpion envenoming. Most of the actions of the scorpion toxins are indirect and due to the release of adrenergic and cholinergic neurotransmitters. Accordingly, treatment following envenoming is targeted towards inhibition of adrenergic and cholinergic receptors. Here, we have sought evidence for a direct action of T. serrulatus venom on the isolated rat heart (Langendorff's method). We show that the bradycardia induced by T. serrulatus venom was completely blocked by atropine, a muscarinic receptor antagonist. Similarly, the increase in heart rate that follows the venom-induced bradycardia was totally inhibited by a beta(1)-adrenoceptor antagonist or by chemical sympathetic denervation with 6-hydroxydopamine. In contrast to these findings, the venom-induced increase in contractile force was not modified by beta(1)-adrenoceptor blockade or by chemical sympathetic denervation. The results clearly demonstrate that the chronotropic effects of T. serrulatus are dependent on neurotransmitter release, but the inotropic effects are not. The neurotransmitter-independent increase in contractility seems to be a direct action of the venom on cardiomyocytes. We suggest that this direct effect on cardiac fibers may play a role in the development of cardiac arrhythmias and contractility defects following envenoming with T. serrulatus scorpion.

The scorpion envenoming syndrome

The pathophysiology of the scorpion envenoming syndrome is reviewed 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. The results of clinical analysis of cases of scorpion sting victims and animal experiments with scorpion envenomation supporting these concepts are presented. The pharmacokinetic characteristics of scorpion venoms and their correlation to the magnitude of toxic effects are presented in relation to the potentials of therapeutic intervention. The pharmacological basis of the therapeutic usefulness and toxicities of the drugs commonly used in the treatment of scorpion envenoming is also projected. Finally, the results of a successful nation-wide clinical study with serotherapy of scorpion envenoming are presented and evaluated.

Scorpion sting sydrome - a ten year experience

A 10-year retrospective review was undertaken of patients presenting with "scorpion sting" to the Emergency Department of the King Fahad National Guard Hospital in Riyadh. The purpose of the study was 1) to assess the risk of morbidity and mortality following scorpion envenomation in the Riyadh area; 2) to define patient demographics of the study group and identify high risk groups for systemic toxicity; 3) to develop guidelines for patient management. Four hundred and thirty-four cases were studied. Local pain was the primary presenting complaint (92%). Systemic toxicity occurred in 25.6% (n=111). Anxiety-related presentations were the most common systemic symptoms (6%). Hypertension (17%) and/or tachycardia (4%) were the most common systemic signs. Only four patients (<1%) had signs of serious envenomation requiring admission. There were no deaths. The higher risk groups for systemic toxicity were identified as those with age less than eight years or greater than 30 years, with highest risk in those over 50 years, those with history of hypertension or diabetes, and patients with multiple stings. The great majority of patients can be treated with analgesia, local application of ice, and a period of observation dictated by clinical findings. The use of antivenin should be restricted to patients with signs of serious systemic toxicity only.

Androctonus crassicauda (Olivier), a dangerous and unduly neglected scorpion--I. Pharmacological and clinical studies

Androctonus crassicauda venom has an i.v. LD50 in mice of 0.32 +/- 0.02 mg/kg, which makes the scorpion among the most toxic species in the world. Fifty-one non-fatal and one fatal cases of scorpion sting were presented. Pain and tenderness were very common following the sting. Generalized erythema occurred in 20-25% of all infants and children below the age of 5 years. Severe CNS manifestations including seizures, unconsciousness and marked irritability occurred mainly in infants and young children, while hypertension occurred in the majority of victims below the age of 11 years. Two pregnant victims were treated with antivenom with no bad consequences on mothers or foetuses. The fatal case described was inadequately treated with antivenom and presented a rare situation of intracranial coagulation in the basal cisterns or low in the cranial subarachnoid space. The victim developed moderate hydrocephalus of the communicating type with clear ventricular CSF and strongly xanthocromic fluid from lumbar puncture. The effects of A. crassicauda venom on isolated hearts, atria and anaesthetized rat blood pressure appeared to be mediated largely through stimulation of the autonomic nervous system with predominance of sympathetic stimulation and release of tissue catecholamines. Electrocardiograms recorded simultaneously with blood pressure changes showed evidence of ectopic foci during the hypertensive phase and ischaemia, inferior wall infarction and different degrees of heart block during the late hypotensive phase. Androctonus crassicauda venom was unique in following a three-compartment open model comprising a central compartment 'blood', a rapidly equilibrating 'shallow' tissue compartment and a slowly equilibrating 'deep' tissue compartment. The overall elimination half-life, t1/2 beta, was 24 hr, indicating that the venom has the slowest elimination among all known scorpion venoms. The long stay of the venom in the body might explain the increased risk of toxicity and the good potential for treatment with serotherapy even hours after the sting.

The treatment of the scorpion envenoming syndrome: the Saudi experience with serotherapy

A protocol for treatment of scorpion sting based mainly on antivenom therapy was applied nation-wide in Saudi Arabia. At least 5 x 1 ml ampoules of antivenom diluted in 20-50 ml saline were injected slowly i.v. in all patients confirmed to have scorpion stings or suspected stings with systemic manifestations. A list of drugs was specified to be used in adjunctive therapy, when required. Analysis of 1033 cases at Al-Baha region, 791 cases at Al-Qassim region and more than 600 cases from 12 central and specialist hospitals in the Central Province revealed impressive results. Except for a 12-year-old boy who was inadequately treated with antivenom and died from pulmonary oedema, haematemesis, severe neurotoxicity and circulatory failure, no other fatalities occurred. The incidence of pulmonary oedema, hypertension, hypotension, cardiac dysrhythmias and neurological symptoms requiring drug therapy following antivenom administration was very slight. The period of stay in the hospital was reduced; most patients were symptom-free within 1-2 days. The early reaction to antivenom administration was lower than expected, amounting to 6.6% and 1.7% among Al-Qassim and Al-Baha victims, respectively. The severity of the reaction in both groups was low, consisting mainly of skin rashes, urticaria, wheezing and bronchial secretion, but no anaphylaxis. About 13.8% of Al-Baha victims were 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.

Experimental treatment protocols for scorpion envenomation: a review of common therapies and an effect of kallikrein-kinin inhibitors

Nine fatal cases from the sting of the scorpion Leiurus quinquestriatus are presented. All victims showed association of CNS and cardiovascular manifestations. Either the CNS or the cardiovascular effects could occur first in the early phases of the scorpion envenoming syndrome; the CNS manifestations, however, always preceded the terminal hypotension and cardiac arrest. Pharmacokinetic studies in rabbits following s.c. injection of the labelled venom showed that rapid absorption took place with about 70% of the maximum blood concentration reached within 15 min. Intramuscular injection of antivenom did not significantly affect the absorption of the venom or the other pharmacokinetic parameters. The total area under concentration time curve was not significantly different from that following i.v. injection, showing that nearly complete absorption of the venom from the s.c. site would occur in 7-8 hr. The i.v. infusion of venom into anaesthetized rats, at a rate comparable to the absorption rate from s.c. sites, allowed the determination of the minimum lethal dose (MLD) with reasonable accuracy. In rescue experiments, anaesthetized rats were injected s.c. with multiple MLD of venom and infused i.v. with drugs commonly used in the treatment of scorpion envenomation. The prepared potent specific antivenoms, but not the commercial polyvalent antivenom, rescued all animals from the lethal effect of the venom, even when injected late. Atropine, atropine+phentolamine, chlorpromazine, hydrocortisone and indomethacin were able, in varying degrees, to rescue some rats injected with 2 MLD of venom. Phentolamine, propranolol, hydralazine and calcium gluconate significantly prolonged the survival time, but did not rescue any animals. Chlorpheniramine, saline and 1/4 saline + 5% dextrose were without any effect. Aprotinin, the kallikrein-kinin inhibitor, was able to rescue half of the animals from the lethal action of the venom. Electrocardiographic studies showed that L. quinquestriatus venom, irrespective of the route of administration, causes myocardial ischaemia and either inferior or anterior wall infarction. This was associated with an initial moderate and a terminal severe bradycardia together with a variety of rhythm and conduction defects. Except for minor and transient electrocardiographic changes, either the prepared antivenoms or aprotinin protected rabbits and rats from the cardiac effects of the venom.

Do changes in body temperature following envenomation by the scorpion Leiurus quinquestriatus influence the course of toxicity?

Four fatal cases following scorpion sting in children are presented. Two victims had rectal temperature above 41 degrees C, the third exhibited a temperature of 40.9 degrees C from the combined effects of scorpion sting and heat stroke, while the fourth was hypothermic. All victims developed hypothermia 48 hr following the sting. The hyperthermia was effectively treated by acetaminophen suppositories, ice packs and water sponges. All victims showed late hypotension that was refractory to dopamine infusion. This was explained by bradykinin released by the venom blocking the dopaminergic receptors. Deterioration of the cortical activity of the victims maintained on mechanical ventilation before the incidence of asystole suggests a central component in the cardiovascular manifestations of envenomation. A. amoreuxi venom was selected as a model for the pharmacokinetic and quantitative toxicological studies since it has no effect on body temperature. In hyperthermic rabbits injected with labelled lethal fraction of A. amoreuxi venom, there was a significant decrease in the elimination half-life, t1/2 beta, the apparent volume of the tissue compartment, Vt, the apparent volume of distribution, Vdss, and the intercompartmental rate constant, kCT. Hypothermic rabbits showed a significant decrease in the apparent first-order elimination rate constant, kd, and a significant increase in the elimination half-life. In both states a higher concentration of the lethal fraction in the blood was calculated. This would explain the rapidity of onset of the electrocardiographic effects and the decreased survival time in both the hyperthermic and hypothermic rabbits injected with venom when compared to normothermic animals. The s.c. LD50 in mice and the i.v. MLD in rats were significantly reduced in the hypothermic mice and hypothermic and hyperthermic rats.

Are the toxicological effects of scorpion envenomation related to tissue venom concentration?

The pharmacokinetics of 125I-labelled Androctonus amoreuxi venom and its lethal fraction was studied in rabbits. Comparative pharmacokinetic studies of labelled A. amoreuxi, Leisurus quinquestriatus and Buthotus judaicus venoms were carried out in guinea-pigs. The pharmacokinetics of A. amoreuxi venom was also studied in rats. Groups of rats were injected with labelled A. amoreuxi venom and killed at frequent time intervals for the determination of the relative tissue venom concentration as a function of time. Several groups of rabbits were injected with A. amoreuxi venom and serial blood samples withdrawn at time intervals comparable with those used in the pharmacokinetic studies for the determination of serum glucose, insulin, cortisol, total proteins, albumin, globulins, cholesterol, total bilirubin, urea, uric acid, bicarbonate, alkaline phosphatase, aspartate aminotransferase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase, sodium, potassium, calcium and phosphorus. The packed cell volume, and total and differential leucocyte counts were also determined. In another series of experiments continuous monitoring of the electrocardiograms of rabbits following venom injection was made to correlate any abnormalities with tissue venom concentration. All three venoms and the lethal fraction showed an open two-compartment behaviour with rapid distribution half-lives ranging between 4 and 7 min and overall elimination half-lives of 4.2 to 13.4 hr. The behaviour of A. amoreuxi venom was not markedly different in the three species of animals used. In a given species (guinea-pigs) the behaviour of the three venoms was not markedly different. Correlation of the ECG changes with cardiac venom concentration showed that arrhythmias and infarction occurred at times when cardiac concentration was very low, indicating that the cardiac abnormalities might result from indirect factors. Comparison of the course of the biochemical changes with venom concentration in the central compartment indicated that the site of action of the venom is not located in the central compartment. Correlation of the intensity of the biochemical effects with venom concentration in the peripheral compartment revealed an apparent delay in the onset and peak of action. This was explained by assuming that the tissue compartment could be divided into a rapidly accessible and a slowly accessible compartment with the venom acting through the slowly accessible compartment. There was also the possibility of the venom acting indirectly through the release of other substances or transformation to an intermediate.(ABSTRACT TRUNCATED AT 400 WORDS)

Teratogenicity in the rat of the venom from the scorpion Androctonus amoreuxi (Aud. & Sav.)

A. amoreuxi venom caused a high foetal resorption rate in rats, particularly when injected on days 9-11 of gestation. Vertebral and ossification defects and foetal weight loss were observed in many of the viable foetuses obtained from mothers treated with scorpion venom. Treatment of the rats with phentolamine in addition to the venom significantly reduced the venom-induced hyperglycemia. It also conferred some protection against foetal resorption but had only a slight effect on chondrification or foetal weight loss. This shows that hyperglycemia might be responsible for foetal mortality, but alone is not a decisive factor in the effect of the venom on the chondrification process. Treatment of the rats with triamterene reduced the foetal resorption rate and significantly decreased the effects of the venom on chondrification. However, marked stippling was observed in the long bones and was ascribed to marked mobilization of ionized calcium in the foetus. Foetuses removed from rats treated with phentolamine or triamterene in addition to the venom, however, showed flattened and depressed skulls, possibly from a missing 1st cervical vertebra or failure of the occipital fontanel to close. Treatment of the rats with the scorpion venom over a longer period of time and starting at an earlier time of gestation (days 7-14) caused total foetal resorption, which may be due to inhibition of histamine formation by the venom. The teratogenic effect of the venom appears to be the result of its metabolic effect and action on body electrolytes of the maternal animal, rather than to a direct effect on the foetuses. This was evidenced from experiments with labelled venom, where only a small fraction (0.08-0.33%) was detected in foetuses or placenta.