Abstract：
High grain feeding or weaning, which could compromise the rumen epithelium by increasing ruminal short-chain fatty acid (SCFA) concentrations with pH reduction, is associated with high levels of ruminal toll-like receptor 5 (TLR5). This study aimed to determine the role of TLR5 in the rumen epithelium. Immunohistochemistry revealed that TLR5 was localized in cells on the basal side (i.e., basal and spinous layers) rather than in the granular layer in the rumen epithelium, where tight junctions are most potent, in pre- and post-weaning calves (n = 9). Primary bovine rumen epithelial cells (BRECs) obtained from Holstein cows (n = 3) were cultured to investigate the factors that upregulate TLR5; however, SCFA, low pH (pH 5.6), BHBA, L-lactate, D-lactate, and LPS did not upregulate TLR5 gene expression in BREC. Primary BREC treated with flagellin (TLR5 ligand) had higher expression of interleukin-1β (IL-1β) (P < 0.05) than BREC treated with vehicle. In addition, BREC treated with IL-1β had higher expression of antimicrobial peptides and C-X-C motif chemokine ligand 8 than BREC treated with vehicle (P < 0.05). These results suggest that ruminal TLR5 may recognize epithelial disruption via flagellin and mediate the immune response via IL-1β during high-grain feeding or weaning.
摘要：
高谷物饲喂或断奶，这可能会损害瘤胃上皮通过增加瘤胃短链脂肪酸（SCFA）浓度与pH降低，与高水平的瘤胃toll样受体5（TLR5）相关。本研究旨在探讨TLR5在瘤胃上皮中的作用。免疫组织化学显示TLR5位于基底侧的细胞中（即，基底层和棘层），而不是在瘤胃上皮的颗粒层中，在紧密连接最有效的地方，断奶前和断奶后的小牛(n=9)。培养从荷斯坦奶牛（n=3）获得的原代牛瘤胃上皮细胞（BRECs）以研究上调TLR5的因素；然而，SCFA,低pH（pH5.6），BHBA,L-乳酸,D-乳酸,LPS并没有上调BREC中TLR5基因的表达。与用载体处理的BREC相比,用鞭毛蛋白(TLR5配体)处理的原发性BREC具有更高的白细胞介素-1β(IL-1β)表达(P<0.05)。此外,用IL-1β处理的BREC的抗菌肽和C-X-C基序趋化因子配体8的表达高于用载体处理的BREC(P<0.05)。这些结果表明，瘤胃TLR5可能通过鞭毛蛋白识别上皮破坏，并在高粒喂养或断奶期间通过IL-1β介导免疫应答。
