Crystalline silica-induced proinflammatory eicosanoid storm in novel alveolar macrophage model quelled by docosahexaenoic acid supplementation

• Published in: Frontiers in immunology Vol. 14; p. 1274147
• Main Authors: Favor, Olivia K, Rajasinghe, Lichchavi D, Wierenga, Kathryn A, Maddipati, Krishna R, Lee, Kin Sing Stephen, Olive, Andrew J, Pestka, James J
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 2023
• Subjects: alveolar macrophage; Animals; Arachidonic Acid; crystalline silica; Dietary Supplements; docosahexaenoic acid; Docosahexaenoic Acids - pharmacology; Fatty Acids, Omega-3 - metabolism; Fatty Acids, Omega-3 - pharmacology; Fatty Acids, Omega-6 - pharmacology; lipidome; Lipopolysaccharides; Macrophages, Alveolar - metabolism; Mice; Mice, Inbred C57BL; oxylipin; Oxylipins - metabolism; Oxylipins - pharmacology; Silicon Dioxide; alveolar macrophage; oxylipin; lipidome; docosahexaenoic acid; crystalline silica
• ISSN: 1664-3224; 1664-3224
• DOI: 10.3389/fimmu.2023.1274147

Phagocytosis of inhaled crystalline silica (cSiO ) particles by tissue-resident alveolar macrophages (AMs) initiates generation of proinflammatory eicosanoids derived from the ω-6 polyunsaturated fatty acid (PUFA) arachidonic acid (ARA) that contribute to chronic inflammatory disease in the lung. While supplementation with the ω-3 PUFA docosahexaenoic acid (DHA) may influence injurious cSiO -triggered oxylipin responses, investigation of this hypothesis in physiologically relevant AMs is challenging due to their short-lived nature and low recovery numbers from mouse lungs. To overcome these challenges, we employed fetal liver-derived alveolar-like macrophages (FLAMs), a self-renewing surrogate that is phenotypically representative of primary lung AMs, to discern how DHA influences cSiO -induced eicosanoids. We first compared how delivery of 25 µM DHA as ethanolic suspensions or as bovine serum albumin (BSA) complexes to C57BL/6 FLAMs impacts phospholipid fatty acid content. We subsequently treated FLAMs with 25 µM ethanolic DHA or ethanol vehicle (VEH) for 24 h, with or without LPS priming for 2 h, and with or without cSiO for 1.5 or 4 h and then measured oxylipin production by LC-MS lipidomics targeting for 156 oxylipins. Results were further related to concurrent proinflammatory cytokine production and cell death induction. DHA delivery as ethanolic suspensions or BSA complexes were similarly effective at increasing ω-3 PUFA content of phospholipids while decreasing the ω-6 PUFA arachidonic acid (ARA) and the ω-9 monounsaturated fatty acid oleic acid. cSiO time-dependently elicited myriad ARA-derived eicosanoids consisting of prostaglandins, leukotrienes, thromboxanes, and hydroxyeicosatetraenoic acids in unprimed and LPS-primed FLAMs. This cSiO -induced eicosanoid storm was dramatically suppressed in DHA-supplemented FLAMs which instead produced potentially pro-resolving DHA-derived docosanoids. cSiO elicited marked IL-1α, IL-1β, and TNF-α release after 1.5 and 4 h of cSiO exposure in LPS-primed FLAMs which was significantly inhibited by DHA. DHA did not affect cSiO -triggered death induction in unprimed FLAMs but modestly enhanced it in LPS-primed FLAMs. FLAMs are amenable to lipidome modulation by DHA which suppresses cSiO -triggered production of ARA-derived eicosanoids and proinflammatory cytokines. FLAMs are a potential alternative to primary AMs for investigating interventions against early toxicant-triggered inflammation in the lung.