Anti-inflammatory effects of EPA and DHA are dependent upon time and dose-response elements associated with LPS stimulation in THP-1-derived macrophages

Abstract

The long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) of fish oil, eicosapentanoic (EPA) and docosahexanoic (DHA) acids are considered cardioprotective. Inflammation elicited by macrophages is increasingly recognised in the aetiology of metabolic syndrome. This study investigated the differential anti-inflammatory potential of EPA and DHA through cytokine production and nuclear factor (NF)-κB signalling in a human macrophage model. We investigated the dependency of LC n-3 PUFA immune-modulation on concentration and duration of lipopolysaccharide (LPS) activation. Interleukin (IL)-1β, IL-6 and tumor necrosis factor-α secretion from EPA, DHA and control cells were differentially limited by LPS concentration. In all cases, there was no benefit in activating cells with >0.1 μg/ml LPS. LC n-3 PUFA decreased proinflammatory cytokines production, an effect modulated by LPS concentration. Expression of the transcription factor NF-κB p65 was significantly reduced in the nucleus and retained in the cytoplasm of EPA- and/or DHA-treated macrophages during 5-h activation with 0.1 μg/ml LPS. Nuclear binding of p65 was significantly reduced in EPA- and DHA-treated cells at 2-h LPS activation. Over the time course, expression of nuclear IκBα was significantly reduced, cytoplasmic NF-κB p50 significantly increased and cytoplasmic cleaving enzyme IκB inhibitor complex significantly reduced in LC n-3 PUFA-treated cells. EPA and DHA down-regulated the production of proinflammatory cytokines associated with the aetiology of metabolic syndrome, NF-κB transcriptional activity and upstream cytoplasmic signalling events. Immune responses are dynamic, and the present study suggests a nutrient sensitive window of LPS activation at which EPA and DHA are strongly anti-inflammatory.