Neurotoxicity of Jaburetox, a Urease-derived peptide: Effect on enzymatic pathways of the cockroach Nauphoeta cinerea

PERIN, A.P.A.; NORONHA, M.S.; MOYETTA, N.R.; CARLINI, C.R.; FRUTTERO, L.L.; MARGIS, R.R.

Porto Alegre

Encuentro; XVIII Encontro Anual do Programa de Pós-Graduação em Biologia Celular e Molecular (PPGBCM); 2017

Universidade Federal do Rio Grande do Sul

Introduction: Jaburetox (Jbtx) is a recombinant peptide (~11 kDa) derived from one of the Canavalia ensiformis (Jack Bean) urease isoforms. The peptide induces several toxic effects on insects of different orders, including the interference on muscle contractility in the cockroach Nauphoeta cinerea as well as the activation of the immune system and the inhibition of diuresis in the Chagas? disease vector Rhodnius prolixus. Moreover, when injected, the peptide is lethal for R. prolixus nymphs. Previous data from our group demonstrated that the central nervous system (CNS) of the triatomines, Triatoma infestans and R. prolixus, is a target organ for Jbtx. In addition, recent works reported that the Jbtx modulates the enzyme activities of the UDP-N-acetylglucosamine pyrophosphorylase (UAP, involved in chitin synthesis and glycosylation pathways) and nitric oxide synthase (NOS, nitrinergic signaling and immunity response) in the CNS of those species. Objectives: In order to better understand the mechanism of action of Jbtx, we employed adult cockroachs of N. cinerea to explore the effects induced by the peptide on the CNS, focusing on the enzymatic activities of UAP, NOS, acid phosphatases (APs), and acetylcholinesterase (AChE). In addition, we evaluated the insecticidal effect of Jbtx upon the N. cinerea nymphs. Material and Methods: The enzymatic experiments were performed after in vitro and in vivo treatments with Jbtx using organs from adult cockroaches. The in vitro treatment with Jbtx was carried out pre-incubating the CNS homogenates with different concentrations of the peptide or with the same volume of buffer for the controls. The in vivo treatment was performed by abdominal injection of different doses of Jbtx or the same volume of buffer for the controls and 6 hours after the injections, CNS were dissected. Spectrophotometric assays were employed to measure the enzyme activities. The insecticidal assay against N. cinerea nymphs was performed by abdominal injections of 50 µg of Jbtx per g of insect or the same volume of buffer for the controls. Five groups with four insects were used to test each condition. Survival rate was followed up for 10 days. Results and Discussion: In N. cinerea, both in vivo and in vitro treatments with Jbtx partially inhibited the activity of NOS and a similar inhibition profile was previously observed in R. prolixus. Interestingly, Jbtx has no effect upon N. cinerea?s UAP activity, contrasting with R. prolixus? findings in which the activity was increased. Also in contrast with the profile observed in R. prolixus, the in vivo Jbtx treatment increased the activity of APs (a possible link between UAP and NOS) in the cockroach. Finally, Jbtx injections decreased the AChE activity in adult cockroachs and had no insecticidal effect on nymphs. In previous studies using R. prolixus nymphs, almost 100 % of nymphs died after 3 days post- injection. Conclusions: Taken together, our findings indicate that Jbtx affects the nitrinergic signaling, the AChE and APs activities. The fact that Jbtx affects differently the enzyme activities in R. prolixus and N. cinerea, may explain why the cockroach is not susceptible to the lethal effect of the peptide. Financial support: CNPq and CAPES.