Progress on the role of eicosanoids in insect immunity.

Eicosanoids are synthesized from arachidonic acid, which are oxygenated metabolites of C20 polyunsaturated fatty acids through cyclooxygenases (COXs) or lipoxygenases (LOXs). Eicosanoids include prostaglandins (PGs), thromboxanes (TXs), epoxyeicosatrienoic acids (EETs) and leukotrienes (LTs), etc. Eicosanoids mediate a number of physiological processes in insects, such as Malpighian tubule and ovary development, or immune response. They play the important roles in regulating cellular immune processes to clear bacteria, fungi, parasites and viruses by hemocytes and the humoral immune pathways. In this review, we summarize the pathways of eicosanoids synthesis, different types of insect immune response and relationship between eicosanoids and humoral immune system. Understanding the role of eicosanoids in insect immune system, and key enzymes or inhibitors in the pathway of eicosanoids synthesis, will provide theoretical guide for the research in pathogen and insects interaction.