Yamada T, Miida T, Yamaguchi T, Itoh Y
Department of Clinical Pathology, Jichi Medical School, Tochigi, Japan.
Eur J Clin Chem Clin Biochem. 1997 Jun;35(6):421-6. doi: 10.1515/cclm.1997.35.6.421.
Serum amyloid A, an apolipoprotein of high density lipoproteins, is also present to a lesser degree in low density lipoproteins and is co-localized with apolipoprotein B in atherosclerotic lesions. This study examined the effect of serum amyloid A on cellular affinity of low density lipoprotein in vitro. 125I-labelled low density lipoprotein, when loaded with recombinant serum amyloid A1 (acute phase isotype) or recombinant serum amyloid A4 (constitutive isotype), had enhanced binding to both human skin fibroblasts and a murine macrophage cell line, J774, while its degradation was slightly increased in both cells. The binding of oxidized low density lipoprotein to J774 cells was also enhanced by addition of recombinant serum amyloid A1 or serum amyloid A4, and degradation of oxidized low density lipoprotein was moderately enhanced by recombinant serum amyloid A1. The effects of recombinant serum amyloid A on cellular binding of labelled low density lipoprotein were not competed by non-labelled low density lipoprotein and were diminished in the presence of high density lipoprotein. These findings suggest that serum amyloid A in low density lipoprotein may promote association of low density lipoprotein with cells by non-specific adsorption, and high density lipoprotein may prevent such interactions by removal of serum amyloid A.
血清淀粉样蛋白A是高密度脂蛋白的一种载脂蛋白，在低密度脂蛋白中也有少量存在，并与载脂蛋白B共同定位于动脉粥样硬化病变处。本研究检测了血清淀粉样蛋白A在体外对低密度脂蛋白细胞亲和力的影响。当用重组血清淀粉样蛋白A1（急性期同种型）或重组血清淀粉样蛋白A4（组成型同种型）负载时，125I标记的低密度脂蛋白与人皮肤成纤维细胞和小鼠巨噬细胞系J774的结合均增强，而在这两种细胞中其降解略有增加。添加重组血清淀粉样蛋白A1或血清淀粉样蛋白A4也增强了氧化低密度脂蛋白与J774细胞的结合，并且重组血清淀粉样蛋白A1适度增强了氧化低密度脂蛋白的降解。重组血清淀粉样蛋白A对标记的低密度脂蛋白细胞结合的影响不受未标记的低密度脂蛋白竞争，且在高密度脂蛋白存在时减弱。这些发现表明，低密度脂蛋白中的血清淀粉样蛋白A可能通过非特异性吸附促进低密度脂蛋白与细胞的结合，而高密度脂蛋白可能通过去除血清淀粉样蛋白A来防止这种相互作用。
