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A1304 - Dietary Fatty Acids Induce Robust Inflammatory Responses in Human Lung Cells
Author Block: S. Rutting1, D. Xenaki1, L. G. Wood2, J. Horvat3, P. Hansbro4, B. G. Oliver5; 1Respiratory Cellular and Molecular Biology, Woolcock Institute of Medical Research, Sydney, Australia, 2School of Biomedical Science and Pharmacy, University of Newcastle, Newcastle, Australia, 3Priority Research Centre for Asthma and Respiratory Disease, University of Newcastle, Newcastle, Australia, 4Priority Research Centre for Asthma and Respiratory Disease, University of Newcastle, Callaghan, Australia, 5School of Life Science, University of Technology Sydney, Sydney, Australia.
Introduction/Aim:
Obesity is an important risk factor for developing severe asthma. Dietary fatty acids which are increased in sera of obese individuals and after high fat meals, activate the innate immune system, induce inflammation and impair responses to treatment in the airways. This study investigated whether dietary fatty acids directly cause inflammation and/or synergise with obesity-induced cytokines in primary human pulmonary fibroblasts in vitro and the underlying mechanisms.
Methods:
Fibroblasts were challenged with BSA-conjugated ω-6 polyunsaturated fatty acids (PUFAs), ω-3 PUFAs or saturated fatty acids (SFAs) with or without TNFα. Release of the pro-inflammatory cytokines, IL-6 and CXCL8, was measured using ELISA. To investigate underlying mechanisms, specific inhibitors were used to block signaling pathways. Activation of two main pathways, p38 and NF-κB, were investigated using western blotting. To investigate whether other structural lung cells respond the same as pulmonary fibroblasts, selected experiments were repeated in airway smooth muscle (ASM) cells and human bronchial epithelial cells (BEAS-2Bs).
Results:
We found that ω-6 PUFA arachidonic acid (AA), but not ω-3 PUFAs or SFAs up-regulates IL-6 and CXCL8 release from fibroblasts. Combined AA and TNFα-challenge resulted in substantially greater IL-6 and CXCL8 release than either alone, demonstrating synergy. Synergistic upregulation of IL-6, but not CXCL8 was mainly mediated via cyclooxygenase (COX). Inhibition of p38 mitogen-activated protein kinase reduced CXCL8 release induced by AA and TNFα alone, but not in combination. Synergistic CXCL8-release following AA and TNFα challenge was not medicated via a single signaling pathway (MEK1, JNK, PI3K, P38 and NF-κB), nor by hyperactivation of NF-κB or p38. Similar effects were found in ASM cells, but not in BEAS-2Bs.
Conclusion:
Our study demonstrates that in primary mesenchymal lung cells, dietary fatty acids can directly cause inflammation and synergise with the obesity-induced cytokine, TNFα. Exposure to ω-6, but not ω-3 PUFA or SFAs led to IL-6 and CXCL8 release via multiple pathways, including COX dependent- and independent pathways. This suggests that diets rich in ω-6 PUFAs might promote airway inflammation, and in an obese person may lead to more severe airway inflammation.