Docosahexaenoic acid decreases pro-inflammatory mediators in an in vitro murine adipocyte macrophage co-culture model

PLoS One. 2014 Jan 20;9(1):e85037. doi: 10.1371/journal.pone.0085037. eCollection 2014.

Abstract

Paracrine interactions between adipocytes and macrophages contribute to chronic inflammation in obese adipose tissue. Dietary strategies to mitigate such inflammation include long-chain polyunsaturated fatty acids, docosahexaenoic (DHA) and eicosapentaenoic (EPA) acids, which act through PPARγ-dependent and independent pathways. We utilized an in vitro co-culture model designed to mimic the ratio of macrophages:adipocytes in obese adipose tissue, whereby murine 3T3-L1 adipocytes were cultured with RAW 264.7 macrophages in direct contact, or separated by a trans-well membrane (contact-independent mechanism), with 125 µM of albumin-complexed DHA, EPA, palmitic acid (PA), or albumin alone (control). Thus, we studied the effect of physical cell contact versus the presence of soluble factors, with or without a PPARγ antagonist (T0070907) in order to elucidate putative mechanisms. After 12 hr, DHA was the most anti-inflammatory, decreasing MCP1 and IL-6 secretion in the contact system (-57%, -63%, respectively, p ≤ 0.05) with similar effects in the trans-well system. The trans-well system allowed for isolation of cell types for inflammatory mediator analysis. DHA decreased mRNA expression (p<0.05) of Mcp1 (-7.1 fold) and increased expression of the negative regulator, Mcp1-IP (+1.5 fold). In macrophages, DHA decreased mRNA expression of pro-inflammatory M1 polarization markers (p ≤ 0.05), Nos2 (iNOS; -7 fold), Tnfα (-4.2 fold) and Nfκb (-2.3 fold), while increasing anti-inflammatory Tgfβ1 (+1.7 fold). Interestingly, the PPARγ antagonist co-administered with DHA or EPA in co-culture reduced (p ≤ 0.05) adiponectin cellular protein, without modulating other cytokines (protein or mRNA). Overall, our findings suggest that DHA may lessen the degree of MCP1 and IL-6 secreted from adipocytes, and may reduce the degree of M1 polarization of macrophages recruited to adipose tissue, thereby decreasing the intensity of pro-inflammatory cross-talk between adipocytes and macrophages in obese adipose tissue.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3-L1 Cells
  • Adipocytes / drug effects*
  • Adipocytes / metabolism*
  • Animals
  • Cell Line
  • Chemokine CCL2 / metabolism
  • Coculture Techniques
  • Docosahexaenoic Acids / pharmacology*
  • Eicosapentaenoic Acid / pharmacology
  • Interleukin-10 / metabolism
  • Interleukin-6 / metabolism
  • Macrophages / drug effects*
  • Macrophages / metabolism*
  • Mice
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • Chemokine CCL2
  • Interleukin-6
  • Tumor Necrosis Factor-alpha
  • Interleukin-10
  • Docosahexaenoic Acids
  • Eicosapentaenoic Acid

Grants and funding

This study was funded by the Natural Science and Engineering Research Council of Canada (LER; 400536). AAD was supported by the CBS PhD award from the College of Biological Sciences, University of Guelph. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.