Fatty acids play important roles in the regulation of endoplasmic reticulum (ER) stress-induced apoptosis in different cells. Currently, the effects of fatty acids on bovine mammary epithelial cells (MEC) remain unknown. Our study examined bovine MEC viability and measured unfolded protein response (UPR)-related gene and protein expressions following fatty acid treatments. To evaluate the role of fatty acids, we treated MAC-T cells (a line of MEC) with 100 to 400 μM of saturated (palmitic and stearic acid) and unsaturated (palmitoleic, oleic, linoleic, and linolenic acid) fatty acids and 1 to 5 mM of short- and medium-chain fatty acids (acetic, propionic, butyric, and octanoic acid). Thereafter, we determined UPR-related gene expression using quantitative real-time PCR. Palmitic acid stimulated expression of XBP1s, ATF4, ATF6A, and C/EBP homologous protein (CHOP). Stearic acid increased expression of XBP1s and CHOP and decreased expression of ATF4 and ATF6A. Results of Western blot analysis and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay revealed that palmitic and stearic acid reduced MAC-T cell viability and induced extreme ER stress by increasing the protein expression of ER stress markers, such as phospho-PKR-like endoplasmic reticulum kinase, phospho-eIF2α, cleaved CASP-3, and CHOP. Among unsaturated long-chain fatty acids, palmitoleic acid increased expression of ATF4 and ATF6A. Oleic acid increased expression of XBP1s, ATF4, and ATF6A. Linoleic and linolenic acids increased expression of XBP1s, ATF4, and ATF6A but decreased expression of XBP1s and ATF6A at the highest dose. Although palmitoleic, oleic, and linoleic acid decreased CHOP expression, only palmitoleic acid increased MAC-T cell viability. Therefore, unsaturated long-chain fatty acids did not induce severe ER stress. Acetic, propionic, and butyric acids decreased expression of ATF4, ATF6A, and CHOP and increased XBP1s expression. Although only octanoic acid increased ATF4 and ATF6A expressions, it lowered expression of XBP1s and CHOP. Although fatty acid treatment did not increase the levels of ER stress proteins, butyric and octanoic acids reduced cell viability, possibly because of early differentiation. These results suggest that saturated fatty acids play important roles in MEC viability by inducing severe ER stress compared with unsaturated fatty acids. In addition, acetic and propionic acids (short- and medium-chain fatty acids) reduced ER stress. Therefore, the present study reflects the new insight that serum fatty acid concentration plays an important role in maintaining the lactation physiology of dairy cows.

脂肪酸在内质网（ER）应激诱导的不同细胞凋亡的调控中起重要作用。目前，脂肪酸对牛乳腺上皮细胞（MEC）的影响仍然未知。我们的研究检查了牛MEC的生存能力，并测量了脂肪酸处理后未折叠的蛋白应答（UPR）相关基因和蛋白表达。为了评估的脂肪酸的作用，我们处理的MAC-T细胞（MEC的线），具有100至400μ中号饱和（棕榈酸和硬脂酸）和不饱和（棕榈油酸，油酸，亚油酸和亚麻酸）脂肪酸和1至5 m M短链和中链脂肪酸（乙酸，丙酸，丁酸和辛酸）。此后，我们使用定量实时PCR确定了UPR相关基因的表达。棕榈酸刺激XBP1s，ATF4，ATF6A和C / EBP同源蛋白（CHOP）的表达。硬脂酸增加XBP1s和CHOP的表达并降低ATF4和ATF6A的表达。Western印迹分析和3-（4,5-二甲基噻唑-2-基）-2,5-二苯基四唑溴化物（MTT）分析的结果表明，棕榈酸和硬脂酸会通过增加MAC-T细胞的活力并诱导极端的ER应激而引起ER应激标志物的蛋白表达，例如磷酸-PKR样内质网激酶，磷酸-eIF2α，裂解的CASP-3和CHOP。在不饱和长链脂肪酸中，棕榈油酸增加了ATF4和ATF6A的表达。油酸增加XBP1s，ATF4和ATF6A的表达。亚油酸和亚麻酸会增加XBP1s，ATF4和ATF6A的表达，但会降低XBP1s，ATF4和ATF6A的表达。最高剂量的XBP1s和ATF6A。尽管棕榈油酸，油酸和亚油酸会降低CHOP表达，但只有棕榈油酸会增加MAC-T细胞的活力。因此，不饱和长链脂肪酸不会引起严重的内质网应激。乙酸，丙酸和丁酸会降低ATF4，ATF6A和CHOP的表达，并增加XBP1s的表达。尽管只有辛酸会增加ATF4和ATF6A的表达，但会降低XBP1s和CHOP的表达。尽管脂肪酸处理并未增加内质网应激蛋白的水平，但丁酸和辛酸会降低细胞活力，这可能是由于早期分化所致。这些结果表明，与不饱和脂肪酸相比，饱和脂肪酸通过诱导严重的内质网应激，在MEC的存活中起重要作用。此外，乙酸和丙酸（短链和中链脂肪酸）可减少内质网应激。因此，本研究反映了血清脂肪酸浓度在维持奶牛泌乳生理中起重要作用的新见解。