Biological effects of urease-related peptides on the central nervous system of a disease vector insect

SETTEMBRINI, B.P.; GONZALEZ, A.; CORONEL, M.F.; NOWICKI, S.; CANAVOSO, L.E.; POSTAL, M.; DEFFERRARI, M.S.; CARLINI, C.R.

San Diego, California

Otro; 40th Annual Meeting Society for Neuroscience; 2010

Society for Neuroscience

Triatoma infestans is the main insect vector of Chagas disease in southern cone countries. Different strategies have been designed to control this disease vector. Entomotoxic compounds aimed to specific insect groups have been isolated from plants, being one of these canatoxin, a form of urease obtained from Canavalia ensiformis seeds. Experimental evidence points to a neurotoxic effect of canatoxin in different species. Artificial feeding of T. infestans adults and nymphs with solutions containing canatoxin produced lethargy, extension of the proboscis and decreased the pulsatility of the dorsal vessel. The insects recovered four hours later. The effects of canatoxin have been attributed to the presence of a 10-12kDa peptide in the canatoxin molecule. The peptide, Jaburetox-2EC, was synthesized from a partial cDNA of the Canavalia ensiformis urease. Injections of Jaburetox-2EC in doses ranging from 0.008 to 0.1 μg/mg body weight at the level of the first sternite in adults and nymphs of IV and V stage produced the same initial effects of canatoxin but caused death of all the insects at different intervals after the injection. Morphological studies of the brain of bugs injected with Jaburetox-2EC showed no clear disorganization of the neuropile. Immunocytochemistry experiments of the brain and ganglia of injected animals showed no evident change in the expression of neuropeptides as FMRFamide and cholecystokinin compared to vehicle injected insects. Western blot studies of nervous tissue using an anti-Jaburetox-2EC antiserum revealed a 35kDa protein band only in peptide injected insects. The activity of nitric oxide synthase (NOS) and the production of nitric oxide (NO) were measured in samples containing the brain, the subesophageal ganglion and thoracic ganglia from control (C, n=8) and injected adult bugs (J, n=8). The insects were killed 3 hours after the injection of the peptide or vehicule solution. NO production was evaluated by measuring its stable degradation products nitrite and nitrate (NOx) using the NO Analyser (Sievers). It was found that the injection of Jaburetox-2EC decreased the content of NOx from 5.91±0.39 (C, n=5) to 2.8±0.0 (J, n=4) pmol/μg prot (p