Merriman Kathryn E, Poindexter Michael B, Kweh Mercedes F, Santos Jose E P, Nelson Corwin D
Department of Animal Sciences, University of Florida, Gainesville, FL, United States.
Department of Animal Sciences, University of Florida, Gainesville, FL, United States.
J Steroid Biochem Mol Biol. 2017 Oct;173:33-41. doi: 10.1016/j.jsbmb.2017.02.006. Epub 2017 Feb 14.
Bacterial infection of the mammary gland activates an intracrine vitamin D pathway in macrophages of dairy cows. The active hormone of the vitamin D pathway, 1,25-dihydroxyvitamin D (1,25D), stimulates nitric oxide and β-defensin responses in bovine monocyte cultures, but the effect of 1,25D on innate immune genes in the mammary gland remained unknown. Therefore, the objective of this study was to determine the effects intramammary 1,25D treatment on expression of vitamin D associated host-defenses of the bovine mammary gland. Intramammary treatment of normal, healthy mammary glands of lactating dairy cows (n=14) with 10μg 1,25D increased inducible nitric oxide synthase (iNOS) and β-defensin 7 (DEFB7) gene expression in total milk somatic cells more than two-fold relative to placebo-treated glands within 8h after treatment. The vitamin D 24-hydroxylase gene (CYP24A1) also was increased nearly 100-fold in 1,25D-treated glands within 4h after treatment but was not affected in placebo-treated glands. Both macrophages and neutrophils isolated from milk had increased CYP24A1 expression in response to 1,25D treatment but only macrophages had increased iNOS expression. Repeated intramammary 1,25D treatment, every 12h for 48h, of infected mammary glands of cows diagnosed with subclinical mastitis resulted in increased expression of CYP24A1, DEFB4, DEFB7 and iNOS genes compared to placebo-treated glands. The 1,25D treatment resulted in elevated serum 1,25D concentrations (55 vs 33pg/mL) compared to placebo but it did not change serum calcium concentrations or bacteria counts in milk of infected mammary glands. In conclusion, 1,25D upregulates iNOS and β-defensin genes in vivo in cattle and affirms earlier reports that vitamin D supports innate immune functions of cattle.
乳腺的细菌感染会激活奶牛巨噬细胞中的一种内分泌维生素D途径。维生素D途径的活性激素1,25-二羟基维生素D（1,25D）可刺激牛单核细胞培养物中的一氧化氮和β-防御素反应，但1,25D对乳腺中固有免疫基因的影响尚不清楚。因此，本研究的目的是确定乳腺内注射1,25D对牛乳腺维生素D相关宿主防御表达的影响。用10μg 1,25D对泌乳奶牛（n = 14）的正常、健康乳腺进行乳腺内治疗，与安慰剂处理的腺体相比，处理后8小时内，总乳体细胞中诱导型一氧化氮合酶（iNOS）和β-防御素7（DEFB7）基因表达增加了两倍多。维生素D 24-羟化酶基因（CYP24A1）在处理后4小时内，1,25D处理的腺体中也增加了近100倍，但在安慰剂处理的腺体中未受影响。从牛奶中分离出的巨噬细胞和中性粒细胞对1,25D处理均有CYP24A1表达增加，但只有巨噬细胞有iNOS表达增加。对诊断为亚临床乳腺炎的奶牛感染乳腺每12小时重复进行1,25D乳腺内治疗，持续48小时，与安慰剂处理的腺体相比，CYP24A1、DEFB4、DEFB7和iNOS基因表达增加。与安慰剂相比，1,25D处理导致血清1,25D浓度升高（55对33pg/mL），但它没有改变血清钙浓度或感染乳腺牛奶中的细菌计数。总之，1,25D在牛体内上调iNOS和β-防御素基因，并证实了早期关于维生素D支持牛固有免疫功能的报道。
