Humoral and cellular immune responses induced by the urease-derived peptide Jaburetox in the model organism Rhodnius prolixus

Abstract

BackgroundAlthough the entomotoxicity of plant ureases has been reported almost 20 years ago, their insecticidal mechanism of action is still not well understood. Jaburetox is a recombinant peptide derived from one of the isoforms of Canavalia ensiformis (Jack Bean) urease that presents biotechnological interest since it is toxic to insects of different orders. Previous studies of our group using the Chagas disease vector and model insect Rhodnius prolixus showed that the treatment with Jack Bean Urease (JBU) led to hemocyte aggregation and hemolymph darkening, among other effects. In this work, we employed cell biology and biochemical approaches to investigate whether Jaburetox would induce not only cellular but also humoral immune responses in this species.ResultsThe findings indicated that nanomolar doses of Jaburetox triggered cation-dependent, in vitro aggregation of hemocytes of fifth-instar nymphs and adults. The use of specific eicosanoid synthesis inhibitors revealed that the cellular immune response required cyclooxygenase products since indomethacin prevented the Jaburetox-dependent aggregation whereas baicalein and esculetin (inhibitors of the lipoxygenases pathway) did not. Cultured hemocytes incubated with Jaburetox for 24 h showed cytoskeleton disorganization, chromatin condensation and were positive for activated caspase 3, an apoptosis marker, although their phagocytic activity remained unchanged. Finally, in vivo treatments by injection of Jaburetox induced both a cellular response, as observed by hemocyte aggregation, and a humoral response, as seen by the increase of spontaneous phenoloxidase activity, a key enzyme involved in melanization and defense. On the other hand, the humoral response elicited by Jaburetox injections did not lead to an increment of antibacterial or lysozyme activities. Jaburetox injections also impaired the clearance of the pathogenic bacteria Staphylococcus aureus from the hemolymph leading to increased mortality, indicating a possible immunosuppression induced by treatment with the peptide.ConclusionsIn our experimental conditions and as part of its toxic action, Jaburetox activates some responses of the immune system of R. prolixus both in vivo and in vitro, although this induction does not protect the insects against posterior bacterial infections. Taken together, these findings contribute to the general knowledge of insect immunity and shed light on Jaburetox’s mechanism of action.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1710-3) contains supplementary material, which is available to authorized users.

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

“…These data is in line with a previous report demonstrating that abdominal injections of JBU did not cause the death of adult cockroaches (Carrazoni et al, 2016). On the contrary, when R. prolixus and T. infestans were tested under similar doses, the triatomines had 100% of mortality after 72 hr or less (Fruttero et al, 2016; Galvani et al, 2015), confirming that they are susceptible to the Jbtx effects and N. cinerea is resistant. Jbtx causes harmful effects and death on several insect species, belonging to the orders Hemiptera ( Oncopeltus fasciatus, Dysdercus peruvianus ), Diptera ( Aedes aegypti ), Lepidoptera ( Spodoptera frugiperda and Helicoverpa armigera ; Becker‐Ritt, Portugal, & Carlini, 2017), and Blattodea ( Blattella germanica ; Carlini & Ligabue‐Braun, 2016).…”

“…In addition, different reports showed higher resistance of N. cinerea against nematode infection and spider venom when compared to other cockroach species, including B. germanica (Cutler, Hughes, & Rae, 2017; Wullschleger & Nentwig, 2002). In R. prolixus , our group reported that the cellular immune response of hemocyte cellular aggregation is dependent on eicosanoids of the cyclooxygenase pathway (prostaglandins and thromboxanes; Fruttero et al, 2016). Future studies will be directed to elucidate whether this enzymatic pathway is involved in the resistant phenotype of N. cinerea .…”

“…In addition, Jbtx induces several toxic effects on insects from different orders, including those not affected by the intact urease (Mulinari et al, 2007; Stanisçuaski & Carlini, 2012). The effects include the interference on muscle contractility in the cockroach Nauphoeta cinerea (Martinelli et al, 2014), the activation of the immune system (Fruttero et al, 2016), and the inhibition of diuresis in the Chagas’ disease vector Rhodnius prolixus (Stanisçuaski, Te Brugge, Carlini, & Orchard, 2009). Moreover, when injected, the peptide is lethal to R. prolixus nymphs (Martinelli et al, 2014).…”

Jaburetox: update on a urease-derived peptide

“…Besides interfering with diuresis, crop physiology and causing effects related to the central nervous system (CNS), JBTX was shown to disrupt the immune response of R. prolixus , affecting the ability of the insect to effectively counteract bacterial infection [24]. …”

The role of a novel Wo l b a c h i a (Rickettsiales: Anaplasmataceae) synthetic peptide, WolFar, in regulating prostaglandin levels in the hemolymph of Acheta domesticus (Orthoptera: Gryllidae)

“…However, a limited number of studies have focused on the introduction of different foreign substances, such as peptides, into the insect's system with the aim of properly understanding the mechanisms of the immune responses of different insect species. Several related studies, including those of Windley et al (2012) and Fruttero et al (2016), developed novel bioinsecticides, as in the present study. For example, Hardy et al (2013) successfully developed an oral insecticidal toxin, OAIP-1, from the Australian tarantula, Selenotypus plumipes, to combat the agronomically important cotton bollworm, Helicoverpa armigera.…”