Jaburetox, a urease-derived peptide: Effects on enzymatic pathways of the cockroach Nauphoeta cinerea.

Jaburetox is a recombinant peptide derived from one of the Canavalia ensiformis urease isoforms. This peptide induces several toxic effects on insects of different orders, including interference on muscle contractility in cockroaches, modulation of UDP-N-acetylglucosamine pyrophosphorylase (UAP) and nitric oxide synthase (NOS) activities in the central nervous system of triatomines, as well as activation of the immune system in Rhodnius prolixus. When injected, the peptide is lethal for R. prolixus and Triatoma infestans. Here, we evaluated Jaburetox toxicity to Nauphoeta cinerea cockroaches, exploring the effects on the central nervous system through the activities of UAP, NOS, acid phosphatases (ACP), and acetylcholinesterase (AChE). The results indicated that N. cinerea is not susceptible to the lethal effect of the peptide. Moreover, both in vivo and in vitro treatments with Jaburetox inhibited NOS activity, without modifying the protein levels. No alterations on ACP activity were observed. In addition, the enzyme activity of UAP only had its activity affected at 18 hr after injection. The peptide increased the AChE activity, suggesting a mechanism involved in overcoming the toxic effects. In conclusion, our findings indicate that Jaburetox affects the nitrinergic signaling as well as the AChE and UAP activities and establishes N. cinerea as a Jaburetox-resistant model for future comparative studies.

The role of extracellular nucleic acids in the immune system modulation of Rhodnius prolixus (Hemiptera: Reduviidae).

Extracellular traps (ETs) are extracellular nucleic acids associated with cytoplasmic proteins that may aid in the capture and killing of pathogens. To date, only a few insects were shown to display this kind of immune response. Jaburetox, a peptide derived from jack bean urease, showed toxic effects in Rhodnius prolixus, affecting its immune response. The present study aims to evaluate the role of extracellular nucleic acids in R. prolixus' immune response, using Jaburetox as a model entomotoxin. The insects were treated with extracellular nucleic acids and/or Jaburetox, and the cellular and humoral responses were assessed. We also evaluated the release of extracellular nucleic acids induced by toxins, and performed immunocompetence assays using pathogenic bacteria. Our results demonstrated that extracellular nucleic acids can modulate the insect immune responses, either alone or associated with the toxin. Although RNA and DNA induced a cellular immune response, only DNA was able to neutralize the Jaburetox-induced aggregation of hemocytes. Likewise, the activation of the humoral response was different for RNA and DNA. Nevertheless, it was observed that both, extracellular DNA and RNA, immunocompensated the Jaburetox effects on insect defenses upon the challenge of a pathogenic bacterium. The toxin was not able to alter cellular viability, in spite of inducing an increase in the reactive species of oxygen formation. In conclusion, we have demonstrated a protective role for extracellular nucleic acids in R. prolixus´ immune response to toxins and pathogenic bacteria.

Jaburetox-induced toxic effects on the hemocytes of Rhodnius prolixus (Hemiptera: Reduviidae).

Jaburetox is a recombinant peptide derived from a Canavalia ensiformis urease that presents toxic effects upon several species of insects, phytopathogenic fungi and yeasts of medical importance. So far, no toxicity of Jaburetox to mammals has been shown. Previous reports have identified biochemical targets of this toxic peptide in insect models, although its mechanism of action is not completely understood. In this work, we aimed to characterize the effects of Jaburetox in hemolymphatic insect cells. For this purpose, the model insect and Chagas' disease vector Rhodnius prolixus was used. In vivo and in vitro experiments indicated that Jaburetox interacts with a subset of hemocytes and it can be found in various subcellular compartments. In insects injected with Jaburetox there was an increase in the gene expression of the enzymes UDP-N-acetylglucosamine pyrophosphorylase (UAP), chitin synthase and nitric oxide synthase (NOS). Nevertheless, the expression of NOS protein, the enzyme activities of UAP and acid phosphatase (a possible link between UAP and NOS) as well as the phosphorylation state of proteins remained unchanged upon the in vivo Jaburetox treatment. Nitric oxide (NO) imaging using fluorescent probes showed that Jaburetox augmented NO production in the hemocyte aggregates when compared to controls. Even though Jaburetox activated the hemocytes, as demonstrated by wheat germ agglutinin binding assays, the peptide did not lead to an increase of their phagocytic behavior. Taken together, these findings contribute to our understanding of toxic effects of Jaburetox, a peptide with biotechnological applications and a prospective tool for rational insect control.