Acute physiopathological effects of honeybee (Apis mellifera) envenoming by subcutaneous route in a mouse model

Abstract

Bee stings are a health concern in the Americas, where fatal envenomings due to massive attacks by Africanized honeybees have been documented in the last decades. Most studies on the toxic effects of honeybee venom in experimental animals have been performed using the intravenous or intraperitoneal injection routes. The aim of this study was to develop a mouse model that would better resemble a massive honeybee attack by using the subcutaneous (s.c.) route to induce a severe, sublethal systemic envenoming. An array of acute venom effects were characterized, including biochemical, hematological, histological, and inflammatory alterations, after the s.c. injection of 0.5 median lethal dose of venom. Rapid increases in serum alanine (ALT) and aspartate (AST) transaminases, creatinine, urea nitrogen, uric acid, sodium and chloride electrolytes, and creatine kinase (CK) were recorded, indicating damage to liver, kidneys, and skeletal muscle. Also, coagulation disturbances (fibrinogen decrease, and moderate delay in prothrombin and partial thromboplastin times) were demonstrated. Circulating platelet and leukocyte numbers remained unaltered, but a hemoconcentration effect (hematocrit and hemoglobin increase) was observed. This effect might be related to the marked edema induced by the venom. In addition, this inflammatory response included a systemic increase in cytokines (IL-1b, IL-6, TNF-a), together with an elevation of serum malondialdehyde and nitric oxide. The myotoxic effects of venom, melittin, and phospholipase A2 were demonstrated after injection by s.c. route. No synergistic myotoxicity between melittin and PLA2 was observed. Moreover, these two components, when injected at equivalent concentrations to those present in venom, induced a lower increase in serum CK than venom, suggesting that other components also contribute to its strong systemic toxicity towards skeletal muscle. The model here presented may be useful in preclinical studies to assess therapeutic antivenoms developed to cope with the problem of massive bee attacks.