Insect prostaglandins and other eicosanoids: from molecular to physiological actions

Authors: Stanley, David; KIM, YOUNGGYUN - Andong National University

Submitted to: Advances in Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2018
Publication Date: 2/22/2019
Citation: Stanley, D.W., Kim, Y. 2019. Insect prostaglandins and other eicosanoids: from molecular to physiological actions. Advances in Insect Physiology. 56:283-343. https://doi.org/10.1016/bs.aiip.2019.01.003.
DOI: https://doi.org/10.1016/bs.aiip.2019.01.003

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 management 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 insect pathogenic microbes, and show how research to discover the signals also points to promising directions in future research to compromise insect immune functions. This important information will be used by research teams globally and ultimately benefit citizens of the United States and other countries with improved nutrition and food security.

Technical Abstract: Phospholipase A2 (PLA2) is the first biochemical step in eicosanoid biosynthesis. Cellular and secretory PLA2 types, similar to those of vertebrates, have been identified and demonstrated to act in insect eicosanoid biosynthesis. However, eicosanoid biosynthetic pathways in insects are not identical to those of vertebrates. The relatively low concentrations of arachidonic acid (AA)in phospholipids of insect tissues suggest that PLA2 may hydrolyze linoleic acid as a precursor of eicosanoid biosynthesis and its subsequent desaturation and elongation leads to AA. Unlike vertebrates, AA is not oxidized by cyclooxygenase, but by a specific peroxidase called peroxinectin to produce a prostaglandin (PG) precursor, PGH2, which is then isomerized into PGE2 by PGE2 synthase. PGs and other eicosanoids mediate insect reproduction such as oocyte development and egg-laying behavior, trehalose metabolism, fluid secretion, and immunity. They also interact with insect cytokine and other immune mediators to propagate non-self recognition signals to immune effector tissues. In the cross-talks, eicosanoids act as downstream signals because any intervention of eicosanoid signaling leads to substantial immunosuppression. Because host immunosuppression favors pathogens, some entomopathogens exploit a PLA2 inhibitory strategy to express their virulence. We propose PGs and other eicosanoids as central signaling systems in insect biology.