Prostaglandins and other eicosanoids in insects: biosynthesis and biological actions

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

Submitted to: Frontiers in Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2018
Publication Date: 2/7/2019
Citation: Stanley, D.W., Kim, Y. 2019. Prostaglandins and other eicosanoids in insects: biosynthesis and biological actions. Frontiers in Physiology. https://doi.org/10.3389/fphys.2018.01927.
DOI: https://doi.org/10.3389/fphys.2018.01927

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.

Technical Abstract: In this essay we review the discoveries, synthesis and biological significance of prostaglandins (PGs) and other eicosanoids in insect biology. We present the most current – and growing – understanding of the insect mechanism of PG biosynthesis, provide an updated treatment of known insect phospholipases A2 (PLA2), and detail contemporary findings on the biological roles of PGs and other eicosanoids in insect physiology, including reproduction, fluid secretion, hormone actions in fat body, immunity and eicosanoid signaling and cross-talk in immunity. We complete the essay with a prospectus meant to illuminate research opportunities for interested readers. In more detail, cellular and secretory types of phospholipase A2 (PLA2), similar to those known on the biomedical background, have been identified in insects and their roles in eicosanoid biosynthesis documented. We highlight recent findings showing that eicosanoid biosynthetic pathway in insects is not identical to the solidly established biomedical picture. The relatively low concentrations of arachidonic acid (AA) present in insect phospholipids (< 0.1% in some species) indicate that PLA2 may hydrolyze linoleic acid (LA) as a precursor of eicosanoid biosynthesis. The free LA is desaturated and elongated into AA. Unlike vertebrates, AA is not oxidized by cyclooxygenase, but by a specific peroxidase called peroxinectin to produce PGH2, which is then isomerized into cell-specific PGs. In particular, we treat the actions and roles of a PGE2 synthase that converts PGH2 into PGE2. In the cross-talk mechanisms, eicosanoids act as downstream signals because any inhibition of eicosanoid signaling leads to significant immunosuppression. Because host immunosuppression favors pathogens and parasitoids, some entomopathogens evolved a PLA2 inhibitory strategy activity to express their virulence.