Lonomia obliqua venomous secretion induces human platelet adhesion and aggregation.
ABSTRACT The caterpillar Lonomia obliqua is a venomous animal that causes numerous accidents, especially in southern Brazil, where it is considered a public health problem. The clinical manifestations include several haemostatic disturbances that lead to a hemorrhagic syndrome. Considering that platelets play a central role in hemostasis, in this work we investigate the effects of L. obliqua venomous secretion upon blood platelets responses in vitro. Results obtained shows that L. obliqua venom directly induces aggregation and ATP secretion in human washed platelets in a dose-dependent manner. Electron microscopy studies clearly showed that the venomous bristle extract was also able to produce direct platelets shape change and adhesion as well as activation and formation of platelet aggregates. Differently from other enzyme inhibitors, the venom-induced platelet aggregation was significatively inhibited by p-bromophenacyl bromide, a specific inhibitor of phospholipases A2. Additional experiments with different pharmacological antagonists indicate that the aggregation response triggered by the venom active components occurs through a calcium-dependent mechanism involving arachidonic acid metabolite(s) of the cyclooxygenase pathway and activation of phosphodiesterase 3A, an enzyme that leads to the consumption of intracellular cAMP content. It was additionally found that L. obliqua-induced platelet aggregation was independent of ADP release. Altogether, these findings are in line with the need for a better understanding of the complex hemorrhagic syndrome resulting from the envenomation caused by L. obliqua caterpillars, and can also give new insights into the management of its clinical profile.
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ABSTRACT: Erucism is a skin reaction to envenomation from certain poisonous caterpillar bristles. In Brazil, most reports of erucism provoked by Lonomia caterpillars are from the southern region. Most manifestations of erucism are local and include burning pain, itching, local hyperthermia and, rarely, blisters (benign symptoms with spontaneous regression in a few hours). General symptoms such as nausea and vomiting, headache, fever, myalgia, abdominal pain and conjunctivitis may also occur. Uncommon symptoms include arthritis, coagulation disorders (manifested as bruising and bleeding), intracerebral hemorrhage and acute renal failure, which comprise serious complications. The present study reports the case of 60-year-old patient from Rio de Janeiro state, Brazil, who came into contact with a caterpillar and developed, a few days later, chronic renal disease.Journal of Venomous Animals and Toxins including Tropical Diseases 01/2013; 19(1):14. · 0.55 Impact Factor
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ABSTRACT: Despite the nearly worldwide distribution of Lepidoptera, there are few species with clear documentation of adverse reactions in humans. Most syndromes caused by Lepidoptera are consequences of direct contact with the hairs or setae of caterpillars. In most instances, the adverse effects caused by moth and caterpillars are self-limited and the treatment is based on the removal of hairs, application of topical antipruritics and, in some cases, the use of oral antihistamines. However, in the case of envenoming by South American Lonomiaobliqua caterpillars, the antilonomic serum produced at Instituto Butantan in Brazil is the only effective treatment to re-establish the physiological coagulation parameters in poisoned patients and to abolish the complications seen in severe cases (e.g. consumptive coagulopathy, intracerebral hemorrhage, and acute renal failure). Many studies have been carried out to understand the pathophysiological mechanism of envenoming by L. obliqua. Several toxic principles were found in bristle extract and the hemolymph, probably related to the envenoming. An interesting fact is that some toxins from the venom usually have more than one function. With the advent of molecular biology techniques it has become possible to analyze these processes at a molecular level, thus giving rise to hypotheses on the molecular basis of envenomation. This review contributes to enhance our understanding of the dramatic alterations that hemorrhagic syndrome causes in patients, current treatment, and the diversity of the molecules involved in this pathology.Pathophysiology of Haemostasis and Thrombosis 01/2010; 37(1):1-16. · 2.23 Impact Factor
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ABSTRACT: The purpose of this study was to investigate the effects of naloxone and phentolamine on the blood flow changes in rabbit oral tissue induced by remifentanil during sevoflurane anesthesia. Male Japan White rabbits were anesthetized with sevoflurane under mechanical ventilation. Remifentanil was continuously infused at a rate of 0.4 μg/kg/min. Naloxone 0.01 mg/kg or phentolamine 0.01 mg/kg was administered during remifentanil infusion. Observed variables were systolic and diastolic blood pressures, mean arterial pressure, heart rate, common carotid artery blood flow, tongue mucosal blood flow, mandibular bone marrow blood flow, masseter muscle blood flow, and upper and lower alveolar tissue blood flows. The common carotid artery blood flow was monitored continuously using an ultrasonic blood flowmeter. Tongue mucosal blood flow was monitored continuously using a laser Doppler blood flowmeter. Mandibular bone marrow blood flow, masseter muscle blood flow, and upper and lower alveolar tissue blood flows were measured using a hydrogen clearance tissue blood flowmeter. One-way analysis of variance for repeated measurements followed by the Student-Newman-Keuls test was used. Remifentanil produced decreases in the heart rate, systolic blood pressure, and common carotid artery blood flow by about 15% and mandibular bone marrow blood flow, masseter muscle blood flow, and upper and lower alveolar tissue blood flows by about 30%. In the naloxone group, all variables recovered after naloxone administration. In contrast, in the phentolamine group, tissue blood flow recovered, whereas heart rate, systolic blood pressure, and common carotid artery blood flow did not recover after phentolamine administration. Remifentanil deceased oral tissue blood flow and systemic hemodynamic variables. Naloxone and phentolamine produced a recovery of oral tissue blood flow with and without systemic hemodynamic recovery, respectively.Journal of oral and maxillofacial surgery: official journal of the American Association of Oral and Maxillofacial Surgeons 02/2012; 70(4):797-802. · 1.58 Impact Factor