Docosahexaenoic acid attenuates LPS-stimulated inflammatory response by regulating the PPARγ/NF-κB pathways in primary bovine mammary epithelial cells

Background: Docosahexaenoic acid (DHA) is a major dietary n-3 polyunsaturated fatty acid (n-3 PUFA) in fish oil, and has been reported to possess a number of biological properties, such as anti-inflammatory, antitumor and immune-regulatory properties. However, whether DHA exert anti-inflammatory effect on lipopolysaccharide (LPS)-induced mastitis remains unclear. In this study, we investigate the effect and underlying mechanisms of the effects of DHA on LPS-stimulated primary bovine mammary epithelial cells (bMEC). Methods: The experiment was divided into six groups as followed: control group, GW9662 + LPS + DHA (100 mu M) group, LPS and LPS + DHA (25, 50 and 100 mu M) groups. bMEC were treated with DHA for 3 h before LPS (200 mu g/ml) stimulation, and incubated with the PPAR gamma inhibitor GW9662 for 12 h before DHA treatment. The mRNA levels of TNF-alpha, IL-6 and IL-1 beta were measured by quantitative real-time PCR (qRT-PCR). Western blot was employed for measuring the transcriptional activity of NF-kappa B and PPAR gamma. Results: Our results showed that DHA pretreatment significantly decreased the mRNA expression of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and interleukin-1 beta (IL-1 beta) in bMEC stimulated with LPS. Besides, DHA suppressed the phosphorylation of nuclear transcription factor-kappaB (NF-kappa B) p65 and degradation inhibitor of NF-kappa B alpha (I kappa B alpha) in NF-kappa B signal pathway, and activated proliferator activated receptor gamma (PPAR gamma). But, all those effects were obviously abolished by addition of GW9662, a specific inhibitor of PPAR gamma. Conclusion: In conclusion, these results indicated that DHA may attenuate LPS-stimulated inflammatory response in bMEC by suppressing NF-kappa B activation through a mechanism partly dependent on PPAR gamma activation. (C) 2017 Elsevier Ltd. All rights reserved.