Characterization of the inflammatory effects of λ-carrageenan at the genomic and proteomic levels

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Abstract λ-Carrageenan (λCGN) is often used to model local inflammation, but the mechanism by which this compound functions at the genomic and proteomic level has not been delineated. Whole blood from swine was stimulated with λCGN to determine inflammatory biomarkers. We also utilized a HEK-293 (human embryonic kidney) cell line transfected with a SEAP (secreted embryonic alkaline phosphatase)-release plasmid to determine which TLR (Toll-Like Receptor; TLR) signaling cascade was stimulated. Results indicated that Monocyte Chemotactic Protein-1 gene expression and protein were increased by λCGN stimulation while Serum Amyloid A gene expression and protein remained unchanged. λCGN stimulation increased mRNA levels of Phosphatidylinositol 3-Kinase and Alveolar Macrophage Chemotactic –II, decreased mRNA levels of Thrombospondin-2 Precursor, and had no effect on Interleukin-6 mRNA levels. λCGN stimulation increased protein levels of Interleukin-8 and had no effect on protein levels of Tumor Necrosis Factor-α. SEAP release from HEK-293 cells stimulated with λCGN indicated that both TLR2 and TLR4 signaling cascades were initiated. λCGN stimulation did not activate TLR3, TLR5, TLR7, TLR8, TLR9, NOD1, NOD2, Dectin-1a, or Dectin-1b. Experiments silencing either TLR1 or TLR6 to determine which TLR2 heterodimer is activated by λCGN are currently underway. In conclusion, while λCGN stimulation appears to signal through both the TLR2 and TLR4 pathways, significant differences exist between the genes and proteins stimulated by λCGN and pure TLR4 agonists such as E. coli-derived lipopolysaccharide.