Inhibition of eicosanoid signaling leads to increased lipid peroxidation in a host/parasitoid system

Authors: BÜYÜKGÜZEL, ENDER - Bülent Ecevit University; ERDEM, MELTEM - Bülent Ecevit University; TUNAZ, HASAN - Kahramanmaras Sutcu University; KÜÇÜK, CEYHUN - Bülent Ecevit University; ATILGAN, UTKU CAN - Bülent Ecevit University; Stanley, David; BÜYÜKGÜZEL, KEMEL - Bülent Ecevit University

Submitted to: Comparative Biochemistry and Physiology - Part A: Molecular & Integrative Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2016
Publication Date: 11/23/2016
Publication URL: http://handle.nal.usda.gov/10113/5695354
Citation: Büyükgüzel, E., Erdem, M., Tunaz, H., Küçük, C., Atilgan, U., Stanley, D.W., Büyükgüzel, K. 2016. Inhibition of eicosanoid signaling leads to increased lipid peroxidation in a host/parasitoid system. Comparative Biochemistry and Physiology - Part A: Molecular & Integrative Physiology. 204 (2017) 121-128.

Interpretive Summary: Application of classical insecticides has introduced severe problems in agricultural sustainability. Pest insect biological control programs are based on using beneficial agents to reduce pest insect populations. Such programs reduce use in insecticides globally. Among biological control agents, endoparasitoids are small insects that develop inside another insect. They are highly efficacious. The problem, however, is the lack of detailed understanding of the mechanisms involved in the relationship between parasites and their pest insect hosts. On the background that certain biochemical signal molecules operate within the hosts and their parasitoids. We investigated the possibility that chemical inhibitors of the signal molecules in the host diet can move into the hosts and then into the internal parasitoids. Our results show such inhibitors move through all three feeding levels, from host diet to host to parasitoid. The inhibitors blocked the synthesis of the biochemical signal molecules within the parasitoids, which exerted a strong negative influence on the parasitoids. The significance of our finding is that host/parasitoid relationships are more intricate than commonly thought. Whereas parasitoids influence their hosts by injecting chemicals into their hosts during egg laying, hosts can also influence parasitoids with chemicals present in host blood. This new information will be will be directly useful to scientists who are working to improve the efficacy of biological control methods. The ensuing improved biological control methods will benefit a wide range of agricultural producers by reducing use of classical insecticides and supporting the long-term sustainability of agriculture.

Technical Abstract: We posed the hypothesis that eicosanoids act in reduction of oxidative stress in insects. Here we report that inhibiting eicosanoid biosynthesis throughout the larval, pupal and adult life led to major alterations on some oxidative and antioxidative parameters of the greater wax moth, Galleria mellonella and its ectoparasitoid, Bracon hebetor. Dietary dexamethasone (Dex), esculetin (Esc) and phenidone (Phe) led to increased malondialdehyde (MDA) levels and to elevated catalase (CAT) and glutathione-S-transferase (GST) activities in all developmental stages of host larvae. Dietary Phe resulted in increased MDA levels, and CAT activity in Galleria adults by about 4-fold and about 2-fold, respectively. The Phe effect on GST activity in larval, pupal and adult stages of the wax moth was expressed in a dose-dependent manner, increased to 140 nmol/mg protein/min in larvae. MDA levels were increased by over 30-fold in adult wasps reared on Dex- and Esc-treated hosts. CAT and GST activities were also increased in adult parasitoids reared on Esc-and Phe-treated hosts. GST activity of Dex-treated parasitoid larvae increased from about 4 to over 30 nmol/mg protein/min. Dietary Phe led to increased GST activity, by about 25-fold, in adult wasps. These data indicate that chronic inhibition of eicosanoid biosynthesis leads to increased oxidative stress, which strongly supports our hypothesis. The significance of this work lies in understanding the roles of eicosanoids in insect biology. Aside from other well-known eicosanoids actions, we propose that eicosanoids mediate reductions in oxidative stress.