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

Introduction: Workplace exposure to respirable crystalline silica (cSiO2)
is associated with chronic inflammatory and autoimmune diseases. At the
mechanistic level, cSiO2 particles are quickly phagocytosed by resident
alveolar macrophages (AMs) in the lung, causing a robust cycle of
proinflammatory cytokine release, lysosomal rupture, mitochondrial
toxicity, and immunogenic cell death if the particle is not efficiently
cleared by the lung. We and others have demonstrated in bone
marrow-derived and transformed macrophage models that supplementation with
the ω-3 polyunsaturated fatty acid (PUFA) docosahexaenoic acid (DHA)
contributes to increased membrane phospholipid content of DHA and
subsequent suppression of cSiO2-triggered inflammatory responses. However,
mechanistic exploration of ω-3 PUFA effects in AMs is challenging due to
reliance on short-lived primary AMs derived from lung lavage fluid.
Methods: To address these limitations, we have employed a recently
developed novel self-renewing AM model from C57BL/6 mice, fetal
liver-derived alveolar-like macrophages (FLAMs), that is phenotypically
representative of primary lung AM populations. We found that incubation of
FLAMs with 25 µM  DHA as ethanolic suspensions or as complexes
with bovine serum albumin were equally effective at increasing ω-3 PUFA
content of phospholipids at the expense of the ω-6 PUFA arachidonic acid
(ARA) and the ω-9 monounsaturated fatty acid oleic acid. Based on these
findings, FLAMs were treated with 25 µM DHA in EtOH or EtOH vehicle (VEH)
for 24 h, with or without LPS for 2 h, and with or without cSiO2 for 1.5
or 4 h then proinflammatory cytokine release, lysosomal membrane
permeabilization, and mitochondrial depolarization assessed. In addition,
oxylipin metabolites were measured using a targeted LC-MS lipidomics panel
of 156 metabolites. Results: Regardless of whether FLAMs were LPS-primed,
cSiO2-triggered lysosomal permeability, mitochondrial toxicity, and cell
death were not impacted by DHA. LPS+cSiO2 elicited marked IL-1α, IL-1β,
and TNF-α release after 1.5 and 4 h of cSiO2 exposure, which was
significantly inhibited by DHA. In VEH-treated cells, cSiO2 alone and
LPS+cSiO2 induced synthesis of ARA-derived proinflammatory oxylipins
including prostaglandins, leukotrienes, and thromboxanes that was
suppressed by DHA. In addition, DHA promoted synthesis of pro-resolving
DHA-derived oxylipins at the expense of ARA-derived oxylipins.
Discussion:  FLAMs were amenable to lipidome modulation by DHA,
which suppressed cSiO2-triggered proinflammatory cytokine responses and
ARA-derived oxylipins that potentially contribute to the particle’s
toxicity in the lung. FLAMs are a promising in vitro alternative to
primary AMs for investigating interventions against toxicant-triggered
inflammation and autoimmunity in the lung.