Abstract
Hypertrehalosemic hormone (HTH) is a peptide hormone that belongs to the adipokinetic hormone/red pigment concentrating hormone (AKH/RPCH) family, which exerts pleiotropic actions related to catabolic reaction and stress response. AKH peptides have been demonstrated to participate in stress response including oxidative stress in several insects. In order to study the signaling pathway of HTH involved in anti-oxidative stress, we have characterized a HIH receptor cDNA in Blattella germanica (Blage-HTHR) in structural and in functional terms using RNA interference (RNAi). Blage-HTHR is expressed in various female adult tissues (brain–CC–CA, ventral nerve cord, midgut, fat body, oviduct), but maximal expression is observed in the fat body. RNAi-mediated knockdown of Blage-HTHR expression results in a significantly lower level of hemolymph trehalose, even though HTH is exogenously administered. Paraquat elicits lethal oxidative stress in B. germanica, and co-injection of paraquat and HTH reduces this detrimental effect and extends the median survival time. Interestingly, the “rescue” effect of HTH on mortality caused by paraquat is diminished in specimens with depleted expression of Blage-HTH and Blage-HTHR. Finally, lipid peroxidation in the hemolymph increases 4 h after paraquat treatment, in comparison with control specimens or with HTH-treated specimens. However, lipid peroxidation induced by paraquat was not “rescued” by HTH in Blage-HTH and Blage-HTHR knockdown specimens. Our results demonstrate that HTH acts as a stress hormone mediating anti-oxidative protection in B. germanica, and that its receptor, Blage-HTHR, is essential for this action.
Highlights
The adipokinetic hormone/red pigment concentrating hormone (AKH/RPCH) family is one of the extensively characterized group of neuropeptides whose members play important roles on energy homeostasis, as well as on other physiological and behavioral processes in insects (Schooley et al, 2005)
In the present study we report the cloning of the cDNA of the hypertrehalosemic hormone (HTH) receptor (Blage-HTHR) and the effect of PQ when both Blage-HTH and Blage-HTHR expression are silenced by RNA interference (RNAi) in B. germanica, a species that is sensitive to this knockdown technique (Belles, 2010)
CLONING AND EXPRESSION PATTERN OF BLAGE-HTH RECEPTOR Cloning of the HTH receptor (Blage-HTHR) cDNA of B. germanica was accomplished by a RT-PCR approach, combining the use of degenerate primers based on AKHR conserved motifs to obtain a partial sequence, and 5 -rapid amplification of cDNA ends (RACE) and 3 -RACE experiments to complete it
Summary
The adipokinetic hormone/red pigment concentrating hormone (AKH/RPCH) family is one of the extensively characterized group of neuropeptides whose members play important roles on energy homeostasis, as well as on other physiological and behavioral processes in insects (Schooley et al, 2005). Earlier studies have related the release of AKHs as a result of insecticide poisoning through recording the increase of metabolites such as trehalose and lipids in the hemolymph of the cockroach Periplaneta americana (Granett and Leeling, 1972) and the locust Schistocerca gregaria (Samaranayaka, 1974). AKHs participate in anti-oxidative mechanisms by increasing reduced glutathione efflux and decreasing protein carbonyl levels in response to treatment with paraquat (PQ), a bipyridylium herbicide that is currently used to elicit oxidative stress in animals through redoxcycling reactions (Hassan, 1984); it has been used in this way, for example, in the potato beetle Leptinotarsa decemlineata (Kodrik et al, 2007) and in P. apterus (Vecera et al, 2007)
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