Laboratory of Food and Environmental Hygiene, Cooperative Department of Veterinary Medicine, Faculty of Applied Biological Sciences, Gifu University, Gifu 501-1193, Japan.
Laboratory of Veterinary Toxicology, Cooperative Department of Veterinary Medicine, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan.
J Vet Med Sci. 2020 Jun 24;82(6):764-770. doi: 10.1292/jvms.19-0473. Epub 2020 May 1.
Serum amyloid A (SAA) is both an amyloidogenic protein of amyloid A amyloidosis and an acute phase protein in most animal species. Although SAA isoforms, such as SAA1, 2, 3, and 4, have been identified in cattle, their biological functions are not completely understood. Previous studies using mice indicated that SAA3 mRNA expression increased by stimulation with Escherichia coli and lipopolysaccharide (LPS) in colonic epithelial cells, and subsequently the SAA3 protein enhanced the expression of mucin2 (MUC2) mRNA, which is the major component of the colonic mucus layer. These results suggest that SAA3 plays a role in host innate immunity against bacterial infection in the intestine. In this study, a novel anti-bovine SAA3 monoclonal antibody was produced and SAA3 expression levels in bovine epithelia were examined in vitro and in vivo using real-time PCR and immunohistochemistry (IHC). SAA3 mRNA expression, but not that of SAA1, was enhanced by LPS stimulus in bovine small intestinal and mammary glandular epithelial cells in vitro. Moreover, in bovine epithelia (small intestine, mammary gland, lung, and uterus) obtained from four Holstein dairy cows from a slaughterhouse, SAA3 mRNA expression was higher than that of SAA1. Furthermore, using IHC, SAA3 protein expression was observed in bovine epithelia, whereas SAA1 protein was not. These results suggest that in cattle, SAA3 plays an immunological role against bacterial infection in epithelial tissues, including the small intestine, mammary gland, lung, and uterus.
血清淀粉样蛋白 A (SAA) 既是淀粉样 A 淀粉样变性的淀粉样蛋白，也是大多数动物物种中的急性期蛋白。虽然在牛中已经鉴定出 SAA 同工型，如 SAA1、2、3 和 4，但它们的生物学功能尚未完全了解。以前使用小鼠的研究表明，SAA3 mRNA 表达在结肠上皮细胞中受到大肠杆菌和脂多糖 (LPS) 的刺激而增加，随后 SAA3 蛋白增强了粘蛋白 2 (MUC2) mRNA 的表达，MUC2 mRNA 是结肠粘液层的主要成分。这些结果表明 SAA3 在宿主对肠道细菌感染的先天免疫中发挥作用。在这项研究中，生产了一种新型抗牛 SAA3 单克隆抗体，并使用实时 PCR 和免疫组织化学 (IHC) 在体外和体内检查了牛上皮细胞中的 SAA3 表达水平。SAA3 mRNA 表达（而不是 SAA1）在体外被 LPS 刺激增强在牛小肠和乳腺上皮细胞中。此外，在来自屠宰场的 4 头荷斯坦奶牛的牛上皮细胞（小肠、乳腺、肺和子宫）中，SAA3 mRNA 表达高于 SAA1。此外，使用 IHC，观察到 SAA3 蛋白在牛上皮细胞中表达，而 SAA1 蛋白未表达。这些结果表明，在牛中，SAA3 在包括小肠、乳腺、肺和子宫在内的上皮组织中对细菌感染发挥免疫作用。
