Serum Amyloid A Induces Contrary Immune Responses via Formyl Peptide Receptor-Like 1 in Human Monocytes (original) (raw)
2006, Molecular Pharmacology
Although the level of serum amyloid A has been reported to be up-regulated during inflammatory response, the role of serum amyloid A on the regulation of inflammation and immune response has not been elucidated. We found that serum amyloid A stimulated the production of tumor necrosis factor-α (TNF-α) and IL-10, which are, proinflammatory and anti-inflammatory cytokines, respectively in human monocytes. Low concentrations of serum amyloid A stimulated TNF-α production with maximal activity at 6 hr after stimulation, whereas high concentrations of serum amyloid A stimulated IL-10 production with maximal activity at 12 hr. The activations of the two cytokines by serum amyloid A occurred at both the transcription and translational levels. Signaling events induced by serum amyloid A included the activation of two mitogen activated protein kinase (extracellular signalregulated kinase and p38 kinase), which were found to be required for TNF-α and IL-10 production, respectively. The stimulation of formyl peptide receptor like 1-expressing RBL-2H3 cells, but not of vector-expressing RBL-2H3 cells with serum amyloid A, induced mitogen activated protein kinases activation and the accumulation of the RNAs of these two cytokines. Taken together, our findings suggest that serum amyloid A modulates contrary immune responses via formyl peptide receptor like 1, by inducing TNF-α or IL-10, and demonstrate that extracellular signal-regulated kinase and p38 kinase play counteracting roles in this process.
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