One of the major causes of early pregnancy loss is heat stress. In ruminants, interferon tau (IFNT) is the embryo signal to the mother. Once the interferon signaling pathway is activated, it drives gene expression for interferon-stimulated genes (ISGs) and alters neutrophils responses. The aim of the present study was to evaluate interferon (IFN) pathway, ISGs and gene expression in polymorphonuclear leukocytes (PMN) and oxidative stress in dairy cows under heat stress. Pregnant cows had their estrous cycle synchronized and randomly assigned to a comfort or heat stress group. Blood samples were collected at artificial insemination (AI) and on Days 10, 14 and 18 following AI. Pregnant cows were pregnancy checked by ultrasound on Day 30 and confirmed on Day 60 post-AI. Results are presented as mean ± SEM. The corpus luteum (CL) diameter was not different between groups of pregnant cows; concentration of progesterone of pregnant cows on Day 18 following AI was greater in comfort group compared to heat stressed group. Comfort pregnant cows had higher expression of all analyzed genes from interferon pathway, except for IFNAR1, on both Days 14 and 18. Conversely, heat stressed cows did not show altered expression of IFNT pathway genes and ISGs between Days 10, 14, and 18 after AI. The oxidative stress, determined as malondialdehyde (MDA) levels, was greater in heat stress group on Days 10, 14 and 18, independent of pregnancy status. Heat stress negatively influences expression of ISGs, IFN pathway gene expression in neutrophils, and oxidative stress. Our data suggest that lower conception rates in cows under heat stress are multifactorial, with the association of interferon pathway activation and the unbalanced oxidative stress being main contributing factors.

中文翻译：

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热应激调节早孕奶牛的多形核细胞反应：I.干扰素途径和氧化应激。

早期流产的主要原因之一是热应激。在反刍动物中，干扰素 tau (IFNT) 是给母亲的胚胎信号。一旦干扰素信号通路被激活，它就会驱动干扰素刺激基因 (ISG) 的基因表达并改变中性粒细胞的反应。本研究的目的是评估热应激下奶牛的多形核白细胞 (PMN) 中的干扰素 (IFN) 通路、ISG 和基因表达以及氧化应激。怀孕奶牛的发情周期同步并随机分配到舒适或热应激组。在人工授精 (AI) 和人工授精后第 10、14 和 18 天收集血液样本。怀孕的母牛在第 30 天通过超声检查怀孕并在 AI 后第 60 天确认。结果表示为平均值±SEM。妊娠母牛组之间的黄体（CL）直径没有差异；与热应激组相比，舒适组妊娠母牛在 AI 后第 18 天的黄体酮浓度更高。在第 14 天和第 18 天，舒适怀孕奶牛的所有干扰素途径分析基因的表达均较高，但 IFNAR1 除外。人工智能。在第 10、14 和 18 天，热应激组中以丙二醛 (MDA) 水平确定的氧化应激更大，与妊娠状态无关。热应激会对 ISG 的表达、中性粒细胞中的 IFN 通路基因表达和氧化应激产生负面影响。我们的数据表明，热应激下奶牛的受孕率较低是多因素的，