Galleria mellonella como modelo experimental para avaliar os efeitos nocivos de cocaína: resposta imune e comportamental

Abstract

Galleria mellonella (“wax moth”) has been used to study the pathogenesis of microorganisms, the toxicity of antimicrobials and physical and chemical agents. The use of this insect as a model system in animal research is possible because the immune system of G. mellonella shares functional and structural homology with the innate immune system of vertebrates. The present study evaluated the use of G. mellonella larvae as a model organism to investigate the effects and toxicity of cocaine using negative control groups (PBS), positive control groups (DMSO) and test groups with different concentrations of cocaine. A pilot test was carried out with concentrations of 5 mg/mL, 7.5 mg/mL, 10 mg/mL and 20 mg/mL of cocaine and behavioral changes were observed for 120 min. Based on the survival data, concentrations of 10 mg/mL, 20 mg/mL, 40 mg/mL, 80 mg/mL and 200 mg/mL of cocaine were standardized to assess the health of the larvae, the percentage of survival and death and the average lethal concentration (LC50), which were analyzed over 120 h. To assess the immune response and tissue damage, concentrations of 10 mg/mL, 20 mg/mL, 40 mg/mL and 80 mg/mL were used 24 h after drug administration. The behavioral changes observed were: immediate and intermittent hyperexcitation (rhythmic tremors, sweating and regurgitation), followed by paralysis with sporadic spasms and, finally, complete paralysis, not necessarily followed by death. Cocaine did not inhibit silk production and cocoon formation (except at a concentration of 200 mg/mL, where all the individuals died less than 24 hours after administration of the drug). The death of at least one individual was observed in the test groups during the 120 hours of the experiments. The administration of different concentrations of cocaine produced immune responses in G. mellonella larvae: with regard to cellular immunity, activation of granulocytes, spherulocytes and oenocytoids was observed; and with regard to humoral immunity, activation of the pro-phenoloxidase cascade was observed, with subsequent melanization at the highest concentrations of the drug (80 mg/mL and 200 mg/mL) in nearly half of the body surface of the lower region (caudal). There was tissue damage in the digestive system of G. mellonella larvae characterized by a reduction in the haemocyte layer and rupture of part of the intestine (middle or final) which may be related to the administration of different concentrations of cocaine. The LC50 was 73.53 mg/mL. Cocaine had an immunosuppressive and immunotoxic effect on G. mellonella larvae. In conclusion, G. mellonella larvae can be used as a model system for initial studies of the acute effects of cocaine, with the potential for studies of chronic abuse (addiction).