Omega-3 Fatty Acid and Glucocorticoid Additively Suppress Pro-inflammatory/ Interferon-Regulated Gene Responses and Inflammasome Activation in Novel Alveolar Macrophage Model

Glucocorticoids (GCs, a.k.a. steroids) are a widely used treatment in chronic inflammatory and autoimmune diseases, but have many injurious side effects. Dietary omega‐3 fatty acids (O3FA) are effective anti‐inflammatory agents with potentially distinct and overlapping mechanisms of action with GCs. However, the potential for combining these anti‐inflammatory agents as a steroid‐sparing strategy is understudied. The goal of this study was to assess the interactive effects of the O3FA docosahexaenoic acid (DHA) and GC dexamethasone (DEX) in modulating inflammasome activation and interferon‐regulated gene (IRG) response in Max Planck Institute (MPI) cells, a novel murine alveolar macrophage model derived from fetal liver. MPI cells were pre‐treated with 0, 5, 10 or 20 μM DHA‐BSA conjugate for 24 hr, followed by 0, 0.01, 0.1, or 1 μM DEX for 1 hr. This was followed by stimulation with 20 ng/mL lipopolysaccharide (LPS) for 2 or 4 hr. At this point, cells were either i) directly harvested and analyzed for pro‐inflammatory and IRG gene expression by qRT‐PCR, or ii) incubated with 5 μM nigericin for 45 min to achieve inflammasome activation, as measured by IL‐1β in the supernatant. LPS treatment significantly induced both pro‐inflammatory and IRG responses in this cell line, and was also required for nigericin‐induced IL‐1β release. Singular treatment with either DHA or DEX alone both exhibited concentration‐dependent reduced inflammatory gene expression and inflammasome activation. When combined, DHA and DEX suppressed these responses in an additive manner. Taken together, this model offers a tool to identify interrelated mechanisms of action of O3FAs and GCs with the long‐term goal of implementing this combination in new steroid‐sparing therapies against inflammatory and autoimmune diseases. Support or Funding Information Research funded in part by the Dr. Robert and Carol Deibel Family Endowment fund