Degraded λ-carrageenan activates NF-κB and AP-1 pathways in macrophages and enhances LPS-induced TNF-α secretion through AP-1

• Published in: Biochimica et biophysica acta Vol. 1840; no. 7; pp. 2162 - 2170
• Main Authors: Chen, Haimin, Wang, Feng, Mao, Haihua, Yan, Xiaojun
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.07.2014
• Subjects: Animals; AP-1; B-lymphocytes; carcinogens; Carcinogens - metabolism; Carcinogens - toxicity; Carrageenan - metabolism; Carrageenan - toxicity; Cell Line; Degraded λ-carrageenan (λ-dCGN); digestion; food industry; food processing; Gene Expression Regulation - drug effects; genes; Humans; IKappaB kinase; Inflammation - chemically induced; Inflammation - metabolism; ingredients; lambda-carrageenan; leukemia; Lipopolysaccharide Receptors - biosynthesis; LPS; lymphoma; macrophages; Macrophages - metabolism; Mice; mitogen-activated protein kinase; molecular weight; NF-kappa B - biosynthesis; NF-κB; phosphorylation; polypeptides; secretion; TLR4; Toll-like receptor 4; Toll-Like Receptor 4 - biosynthesis; Transcription Factor AP-1 - biosynthesis; transcription factor NF-kappa B; tumor necrosis factor-alpha; Tumor Necrosis Factor-alpha - biosynthesis; Tumor Necrosis Factor-alpha - secretion; JECFA; NF-κB; λ-dCGN; NOSB; Degraded λ-carrageenan (λ-dCGN); CGN; CCTCC; TLR4; AP-1; LPS
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/j.bbagen.2014.03.011

Carrageenan (CGN), a high molecular weight sulfated polysaccharide, is a traditional ingredient used in food industry. Its degraded forms have been identified as potential carcinogens, although the mechanism remains unclear. The effects of degraded λ-carrageenan (λ-dCGN) on murine RAW264.7 cells and human THP-1-derived macrophage cells were investigated by studying its actions on tumor necrosis factor alpha (TNF-α) secretion, Toll-like receptor 4 (TLR4) expression, and activation of nuclear factor-κb (NF-κB) and activation protein-1 (AP-1) pathways. We found that λ-dCGN was much stronger than native λ-CGN in the activation of macrophages to secrete TNF-α. Treatment of RAW264.7 cells with λ-dCGN resulted in the upregulation of TLR4, CD14 and MD-2 expressions, but it did not increase the binding of lipopolysacchride (LPS) with macrophages. Meanwhile, λ-dCGN treatment activated NF-κB via B-cell lymphoma/leukemia 10 (Bcl10) and nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IκBα) phosphorylation. In addition, λ-dCGN induced extracellular signal-regulated kinases/1/2/mitogen-activated protein kinases (ERK1/2/MAPK) and AP-1 activation. Interestingly, pretreatment of RAW264.7 cells with λ-dCGN markedly enhanced LPS-stimulated TNF-α secretion. This pretreatment resulted in the enhanced phosphorylation of ERK1/2 and c-Jun N-terminal kinase (JNK) and intensified activation of AP-1. λ-dCGN induced an inflammatory reaction via both NF-κB and AP-1, and enhanced the inflammatory effect of LPS through AP-1 activation. The study demonstrated the role of λ-dCGN to induce the inflammatory reaction and to aggravate the effect of LPS on macrophages, suggesting that λ-dCGN produced during food processing and gastric digestion may be a safety concern. •λ-dCGN induced a stronger secretion of TNF-α in macrophages than λ-CGN.•λ-dCGN induced TNF-α secretion by TLR4–Bcl10–NF-κB and ERK1/2–AP-1 pathways.•λ-dCGN markedly enhanced LPS-stimulated TNF-α secretion.•λ-dCGN promoted the inflammation of LPS by ERK1/2–JNK–AP-1 pathway.