Bruckmaier Rupert M
Lehrstuhl für Physiologie, Technische Universität München-Weihenstephan, 85354 Freising, Germany.
J Dairy Res. 2005;72 Spec No:120-4. doi: 10.1017/s0022029905001159.
Pathogenic microorganisms invading the mammary gland induce an inflammatory reaction which includes an increase of somatic cells in milk and activation of bacteriostatic enzymes and proteins in milk. During spontaneously occurring subclinical mastitis the somatic milk cells, mainly macrophages, secrete cytokines, eicosanoids, acute phase proteins and other immunomediators. In contrast, the bacteriostatic protein lactoferrin is mainly secreted by mammary epithelial tissue, while major milk proteins like alpha-lactalbumin and kappa-casein are down-regulated already during subclinical infection. Changes of the mRNA expression of various immunomediators in the mammary tissue of cows during 12 h after induction of mastitis via intramammary administration of lipopolysaccharide (LPS) in several studies are reported. Six healthy lactating cows were injected in one quarter with 100 microg Escherichia coli-LPS (O26: B6) and the contralateral quarter with saline (9 g/l) serving as control. mRNA expression in mammary biopsy samples of various inflammatory factors and milk proteins at 0, 3, 6, 9 and 12 h after LPS administration was quantified by real-time reverse transcription-PCR. In LPS-challenged quarters tumour necrosis factor alpha and cyclooxygenase-2 mRNA expression increased to their highest values (P<0.05) at 3 h after LPS-challenge. Expression of lactoferrin, lysozyme, inducible nitric oxide synthase, and of the apoptotic factors caspase-3, caspase-7 and FAS was elevated (P<0.05) and peaked at 6 h after challenge. No significant increase in mRNA expression of platelet-activating factor acethylhydrolase, 5-lipoxygenase, and insulin-like growth factor 1 was found. None of the parameters tested did change significantly in the control quarters. mRNA expression of major milk proteins did not change significantly in response to the LPS challenge (alphaS1-casein, alphaS2-CN, beta-CN and beta-lactoglobulin) except for alpha-lactalbumin which decreased (P<0.05) in LPS-treated and control quarters and for kappa-CN which decreased in the LPS-treated quarters. In conclusion, mRNA expression of the majority albeit not all inflammatory factors changed within hours of LPS challenge. Decreased gene expression of alpha-lactalbumin and kappa-CN may reduce milk yield and suitability for cheese production.
侵入乳腺的致病微生物会引发炎症反应，包括乳汁中体细胞数量增加以及乳汁中抑菌酶和蛋白质的激活。在自然发生的亚临床乳腺炎期间，体细胞性乳汁细胞（主要是巨噬细胞）会分泌细胞因子、类花生酸、急性期蛋白和其他免疫介质。相比之下，抑菌蛋白乳铁蛋白主要由乳腺上皮组织分泌，而主要的乳蛋白如α-乳白蛋白和κ-酪蛋白在亚临床感染期间就已下调。在多项研究中，报道了通过乳房内注射脂多糖（LPS）诱导奶牛乳腺炎后12小时内，乳腺组织中各种免疫介质mRNA表达的变化。六头健康的泌乳奶牛，在一个乳区注射100微克大肠杆菌LPS（O26:B6），对侧乳区注射生理盐水（9克/升）作为对照。通过实时逆转录PCR定量LPS给药后0、3、6、9和12小时时，乳腺活检样本中各种炎症因子和乳蛋白的mRNA表达。在LPS刺激的乳区，肿瘤坏死因子α和环氧化酶-2的mRNA表达在LPS刺激后3小时升至最高值（P<0.05）。乳铁蛋白、溶菌酶、诱导型一氧化氮合酶以及凋亡因子半胱天冬酶-3、半胱天冬酶-7和FAS的表达升高（P<0.05），并在刺激后6小时达到峰值。未发现血小板活化因子乙酰水解酶、5-脂氧合酶和胰岛素样生长因子1的mRNA表达有显著增加。在对照乳区，所测试的参数均未发生显著变化。除α-乳白蛋白在LPS处理和对照乳区均下降（P<0.05）以及κ-酪蛋白在LPS处理乳区下降外，主要乳蛋白的mRNA表达对LPS刺激无显著变化（αS1-酪蛋白、αS2-CN、β-CN和β-乳球蛋白）。总之，尽管并非所有炎症因子，但大多数炎症因子的mRNA表达在LPS刺激后数小时内发生了变化。α-乳白蛋白和κ-酪蛋白基因表达的降低可能会降低产奶量和奶酪生产的适用性。
