Host Defense Peptides and the Eicosanoid Cascade

Host defense peptides (HDPs) and eicosanoids are two important families in host defense and inflammation. Most of the naturally occurring HDPs are cationic and amphipathic short polypeptides with typical length between 15 and 40 amino acid residues. HDPs not only possess potent antimicrobial activity against a variety of pathogens, they are also widely recognized for their multifunctional roles in both the innate and adaptive immune responses. On the other hand, arachidonic acid-derived eicosanoids, including prostaglandins, thromboxanes, leukotrienes and lipoxins, are small lipid molecules with a 20-carbon backbone, which possess potent biological properties and participate in regulation of physiological and pathophysiological processes. In this article, we discuss the biosynthesis and functions of eicosanoids with emphasis on the roles of eicosanoids in host defense and regulation of HDP production. Moreover, we review how HDPs regulate eicosanoid metabolism and conclude that there are positive feedback circuits between HDP and eicosanoid signaling with implications for certain pathological conditions, such as infection and allergy.