DHA- and EPA-derived resolvins, protectins, and maresins in airway inflammation

Essential fatty acids can serve as important regulators of inflammation. A new window into mechanisms for the resolution of inflammation was opened with the identification and structural elucidation of mediators derived from these fatty acids with pro-resolving capacity. Inflammation is necessary to ensure the continued health of the organism after an insult or injury; however, unrestrained inflammation can lead to injury "from within" and chronic changes that may prove both morbid and fatal. The resolution phase of inflammation, once thought to be a passive event, is now known to be a highly regulated, active, and complex program that terminates the inflammatory response once the threat has been contained. Specialized pro-resolving mediators (SPMs) are biosynthesized from omega-3 essential fatty acids to resolvins, protectins, and maresins and from omega-6 fatty acids to lipoxins. Through cell-specific actions mediated through select receptors, these SPMs are potent regulators of neutrophil infiltration, cytokine and chemokine production, and clearance of apoptotic neutrophils by macrophages, promoting a return to tissue homeostasis. This process appears to be defective in several common human lung diseases, such as asthma and COPD, which are characterized by chronic unrestrained inflammation and significant associated morbidity. Here, we highlight translational research in animal models of disease and with human subjects that sheds light on this rapidly evolving area of science and review the molecular and cellular components of the resolution of lung inflammation.