interleukin-8 and lauric-acid

Increased circulating free fatty acids in subjects with type 2 diabetes may contribute to activation of macrophages, and thus the development of atherosclerosis. In this study, we investigated the effect of the saturated fatty acids (SFA) palmitate, stearate, myristate and laurate, and the unsaturated fatty acid linoleate, on the production of proinflammatory cytokines in phorbol ester-differentiated THP-1 cells, a model of human macrophages. Palmitate induced secretion and mRNA expression of TNF-alpha, IL-8 and IL-1 beta, and enhanced lipopolysaccharide (LPS)-induced IL-1 beta secretion. Proinflammatory cytokine secretion was also induced by stearate, but not by the shorter chain SFA, myristate and laurate, or linoleate. Triacsin C abolished the palmitate-induced cytokine secretion, suggesting that palmitate activation to palmitoyl-CoA is required for its effect. Palmitate-induced cytokine secretion was decreased by knockdown of serine palmitoyltransferase and mimicked by C(2)-ceramide, indicating that ceramide is involved in palmitate-induced cytokine secretion. Palmitate phosphorylated p38 and JNK kinases, and blocking of these kinases with specific inhibitors diminished the palmitate-induced cytokine secretion. Palmitate also activated the AP-1 (c-Jun) transcription factor. Knockdown of MyD88 reduced the palmitate-induced IL-8, but not TNF-alpha or IL-1 beta secretion. In conclusion, our data suggest that the long-chain SFA induce proinflammatory cytokines in human macrophages via pathways involving de novo ceramide synthesis. This might contribute to the activation of macrophages in atherosclerotic plaques, especially in type 2 diabetes.

Topics: Cell Line, Tumor; Ceramides; Cytokines; Fatty Acids; Humans; Interleukin-1beta; Interleukin-8; JNK Mitogen-Activated Protein Kinases; Lauric Acids; Leukemia; Linoleic Acid; Monocytes; Myeloid Differentiation Factor 88; Myristic Acid; p38 Mitogen-Activated Protein Kinases; Palmitic Acid; Palmitoyl Coenzyme A; RNA, Messenger; RNA, Small Interfering; Stearic Acids; Transcription Factor AP-1; Tumor Necrosis Factor-alpha

Nucleotide-binding oligomerization domain-containing proteins (Nods) are intracellular pattern recognition receptors recognizing conserved moieties of bacterial peptidoglycan through their leucine-rich repeats domain. The agonists for Nods activate proinflammatory signaling pathways, including NF-kappaB pathways. The results from our previous studies showed that the activation of TLR4 and TLR2, leucine-rich repeat-containing pattern recognition receptors, were differentially modulated by saturated and n-3 polyunsaturated fatty acids in macrophages and dendritic cells. Here, we show the differential modulation of NF-kappaB activation and interleukin-8 (IL-8) expression in colonic epithelial cells HCT116 by saturated and unsaturated fatty acids mediated through Nods proteins. Lauric acid (C12:0) dose dependently activated NF-kappaB and induced IL-8 expression in HCT116 cells, which express both Nod1 and Nod2, but not detectable amounts of TLR2 and TLR4. These effects of lauric acid were inhibited by dominant negative forms of Nod1 or Nod2, but not by dominant negative forms of TLR2, TLR4, and TLR5. The effects of lauric acid were also attenuated by small RNA interference targeting Nod1 or Nod2. In contrast, polyunsaturated fatty acids, especially n-3 polyunsaturated fatty acids, inhibited the activation of NF-kappaB and IL-8 expression induced by lauric acid or known Nods ligands in HCT116. Furthermore, lauric acid induced, but docosahexaenoic acid inhibited lauric acid- or Nod2 ligand MDP-induced, Nod2 oligomerization in HEK293T cells transfected with Nod2. Together, these results provide new insights into the role of dietary fatty acids in modulating inflammation in colon epithelial cells. The results suggest that Nods may be involved in inducing sterile inflammation, one of the key etiological conditions in the development of many chronic inflammatory diseases.

Topics: Cell Line; Colon; Epithelial Cells; Fatty Acids; Gene Expression Regulation; Humans; Inflammation; Interleukin-8; Lauric Acids; NF-kappa B; Nod1 Signaling Adaptor Protein; Nod2 Signaling Adaptor Protein; Protein Structure, Tertiary; Signal Transduction; Transcriptional Activation