Too much of a good thing: How modulating LTB4 actions restore host defense in homeostasis or disease

Abstract

The ability to regulate inflammatory pathways and host defense mechanisms is critical for maintaining homeostasis and responding to infections and tissue injury. While unbalanced inflammation is detrimental to the host; inadequate inflammation might not provide effective signals required to eliminate pathogens. On the other hand, aberrant inflammation could result in organ damage and impair host defense. The lipid mediator leukotriene B₄ (LTB₄) is a potent neutrophil chemoattractant and recently, its role as a dominant molecule that amplifies many arms of phagocyte antimicrobial effector function has been unveiled. However, excessive LTB₄ production contributes to disease severity in chronic inflammatory diseases such as diabetes and arthritis, which could potentially be involved in poor host defense in these groups of patients. In this review we discuss the cellular and molecular programs elicited during LTB₄ production and actions on innate immunity host defense mechanisms as well as potential therapeutic strategies to improve host defense.

Keywords: Host defense; Immune regulation; Inflammation; Innate immunity; Leukotriene B(4); Microbicidal activity.

Fig. 1. Host defense mechanisms enhanced by LTB₄/BLT1 axis during microbial infection

Upper panel. Upon infection, microbial recognition triggers 5-LO activation to generate LTB₄ in phagocytes. Lower panel. LTB₄ amplifies macrophage and neutrophil effector function by enhancing the actions of different PRRs and FcR.