Eicosanoid-mediated immunity in insects

Authors: KIM, YONGGYUN - Andong National University; AHMED, SHABIR - Andong National University; Stanley, David; AN, CHUNJU - China Agricultural University

Submitted to: Developmental and Comparative Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2017
Publication Date: 12/7/2017
Citation: Kim, Y., Ahmed, S., Stanley, D.W., An, C. 2017. Eicosanoid-mediated immunity in insects. Developmental and Comparative Immunology. 83:130-143. https://doi.org/10.1016/j.dci.2017.12.005.
DOI: https://doi.org/10.1016/j.dci.2017.12.005

Interpretive Summary: Chemical insecticides are effective pest insect management tools, however, negative effects, including environmental contamination and insect resistance to the insecticides attend use of these products. These negative effects drive research into alternative insect management technologies such as biological control based on deploying insect pathogenic microbes, known as microbial control. The problem with microbial insect control is insects have very powerful immune responses to pathogenic microbes, which reduces the efficacy of these microbes. Research is necessary to identify and compromise insect immune mechanisms to improve microbial control effectiveness. In this paper we clarify biochemical signaling that acts in mediating immune reactions to applied insect pathogenic microbes, and show how research to discover the signals also points to promising directions in future research to compromise insect immune functions.

Technical Abstract: Eicosanoid is a collective term for oxygenated metabolites of C20 polyunsaturated fatty acids. As seen in mammals, eicosanoids play crucial roles in mediating various physiological processes, including immune responses, in insects. Upon microbial pathogen infection, non-self recognition signals are propagated to nearly immune effectors such as hemocytes and fat body using various immune mediators, in which eicosanoid signals act as the ultimate downstream mediator. The chemical diversity of eicosanoids may operate to mediate various immune responses. Some entomopathogenic bacteria suppress eicosanoid biosynthesis, which inhibits host insect immunity and promotes their pathogenicity. This review introduces immune responses mediated by various eicosanoids. Then it explains the cross-talks of eicosanoids with other immune mediators including cytokines, biogenic monoamines, and nitric oxide to clarify the complexity of insect immune mediation. Finally, we highlight the biological significance of eicosanoids by demonstrating bacterial pathogenicity inhibiting a key enzyme – phospholipase A2 – in eicosanoid biosynthesis using their secondary metabolites to defend host insect immune attack.