title: Degraded λ-carrageenan activates NF-κB and AP-1 pathways in macrophages and enhances LPS-induced TNF-α secretion through AP-1.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  λ-dCGN induced an inflammatory reaction via both NF-κB and AP-1, and enhanced the inflammatory effect of LPS through AP-1 activation.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Ningbo University, Key Laboratory of Applied Marine Biotechnology, Ministry of Education, Ningbo, Zhejiang 315211, China. Electronic address: haiminch75@hotmail.com.
authors.forename: Haimin
authors.initials: H
authors.lastname: Chen
authors.affiliation: Department of Clinical Laboratory, Lihuili Hospital, Ningbo Medical Center, Ningbo, Zhejiang 315041, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Wang
authors.affiliation: Ningbo University, Key Laboratory of Applied Marine Biotechnology, Ministry of Education, Ningbo, Zhejiang 315211, China.
authors.forename: Haihua
authors.initials: H
authors.lastname: Mao
authors.affiliation: Ningbo University, Key Laboratory of Applied Marine Biotechnology, Ministry of Education, Ningbo, Zhejiang 315211, China.
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Yan
mesh_terms: D000818:Animals; D002273:Carcinogens / Q000378:metabolism / Q000633:toxicity*; D002351:Carrageenan / Q000378:metabolism / Q000633:toxicity*; D002460:Cell Line; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007249:Inflammation / Q000139:chemically induced / Q000378:metabolism; D018950:Lipopolysaccharide Receptors / Q000096:biosynthesis; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D016328:NF-kappa B / Q000096:biosynthesis*; D051197:Toll-Like Receptor 4 / Q000096:biosynthesis; D018808:Transcription Factor AP-1 / Q000096:biosynthesis*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000378:metabolism
chemical_list: D002273:Carcinogens; D018950:Lipopolysaccharide Receptors; D016328:NF-kappa B; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; D002351:Carrageenan
keywords: AP-1; Degraded λ-carrageenan (λ-dCGN); LPS; NF-κB; TLR4