Inflammation is an immune response triggered by microbial invasion and/or tissue injury. While acute
inflammation is directed toward invading pathogens and injured cells, thus enabling tissue regeneration, chronic
inflammation can lead to severe pathologies and tissue dysfunction. These processes are linked with macrophage polarization into specific inflammatory "M1-like" or regulatory "M2-like" subsets. Nitro-
fatty acids (NO2-FAs), produced endogenously as byproducts of metabolism and oxidative inflammatory conditions, may be useful for treating diseases associated with dysregulated immune homeostasis. The goal of this study was to characterize the role of
nitro-oleic acid (OA-NO2) in regulating the functional specialization of macrophages induced by bacterial
lipopolysaccharide or
interleukin-4, and to reveal specific signaling mechanisms which can account for OA-NO2-dependent modulation of
inflammation and fibrotic responses. Our results show that OA-NO2 inhibits
lipopolysaccharide-stimulated production of both pro-inflammatory and immunoregulatory
cytokines (including
transforming growth factor-β) and inhibits
nitric oxide and
superoxide anion production. OA-NO2 also decreases interleukin-4-induced macrophage responses by inhibiting
arginase-I expression and
transforming growth factor-β production. These effects are mediated via downregulation of signal transducers and activators of transcription,
mitogen-activated protein kinase and nuclear factor-кB signaling responses. Finally, OA-NO2 inhibits fibrotic processes in an in vivo model of
angiotensin II-induced myocardial
fibrosis by attenuating expression of α-smooth muscle actin, systemic
transforming growth factor-β levels and infiltration of both "M1-" and "M2-like" macrophage subsets into afflicted tissue. Overall, the electrophilic
fatty acid derivative OA-NO2 modulates a broad range of "M1-" and "M2-like" macrophage functions and represents a potential therapeutic approach to target diseases associated with dysregulated macrophage subsets.