Anti-Inflammatory and Proresolving Effects of the Omega-6 Polyunsaturated Fatty Acid Adrenic Acid.

Polyunsaturated fatty acids (PUFAs) and their metabolites are potent regulators of inflammation. Generally, omega ()-3 PUFAs are considered proresolving whereas -6 PUFAs are classified as proinflammatory. In this study, we characterized the inflammatory response in murine peritonitis and unexpectedly found the accumulation of adrenic acid (AdA), a poorly studied -6 PUFA. Functional studies revealed that AdA potently inhibited the formation of the chemoattractant leukotriene B (LTB), specifically in human neutrophils, and this correlated with a reduction of its precursor arachidonic acid (AA) in free form. AdA exposure in human monocyte-derived macrophages enhanced efferocytosis of apoptotic human neutrophils. In vivo, AdA treatment significantly alleviated arthritis in an LTB-dependent murine arthritis model. Our findings are, to our knowledge, the first to indicate that the -6 fatty acid AdA effectively blocks production of LTB by neutrophils and could play a role in resolution of inflammation in vivo.