IL-6 plays a critical role in the synergistic induction of human serum amyloid A (SAA) gene when stimulated with proinflammatory cytokines as analyzed with an SAA isoform real-time quantitative RT-PCR assay system |
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Authors: | Hagihara Keisuke Nishikawa Teppei Isobe Tomoyasu Song Jian Sugamata Yasuhiro Yoshizaki Kazuyuki |
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Institution: | Department of Medical Science I, School of Health and Sport Sciences, Osaka University, Osaka, Japan. |
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Abstract: | Serum amyloid A (SAA) is known to be a precursor of amyloid A (AA) protein in AA (secondary) amyloidosis and SAA1 to be mainly involved in AA amyloidosis. We established an SAA isoform real-time quantitative RT-PCR assay and found that beta-2 microglobulin is more stable as an internal control than GAPDH and beta-actin for our system. Either IL-6 and IL-1beta or IL-6 and TNFalpha, but not IL-1beta and TNFalpha, induced the synergistic induction of SAA1 and SAA2 genes. Anti-IL-6 receptor monoclonal antibody completely inhibited the synergistic induction of SAA1 and SAA2 during triple stimulation with IL-6, IL-1beta, and TNFalpha, but, IL-1 receptor antagonist or anti-TNFalpha monoclonal antibody was only partially inhibited in HepG2, Hep3B, and PLC/PRF/5 cells. Although the SAA1 promoter has no STAT3 consensus sequence, the JAK2 inhibitor-AG490 reduced SAA1 gene expression to 30%, suggesting the involvement of STAT3. We were able to demonstrate that IL-6 plays a critical role in the synergistic induction of human SAA gene when stimulated with proinflammatory cytokines. |
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Keywords: | SAA AA amyloidosis Real-time quantitative PCR IL-6 Anti-IL-6 receptor antibody STAT3 |
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