The process of luteal regression is tightly regulated by the immune system and chemokines-small cytokines responsible mostly for the activation and migration of immune cells. The role of chemokines in porcine corpus luteum (CL) function is still not well understood. The aim of this study was to investigate the expression profile and distribution of CC chemokines in the porcine CL during the natural oestrous cycle and early pregnancy. Additionally, the effect of PGF2α on the expression of selected chemokines and their luteotropic and apoptotic influence on CL cells were studied in vitro. The expression levels of the chemokines CCL2, CCL4, and CCL5 and the chemokine receptor CCR5 were time-dependent (low on Days 8-10 and high on Days 12-14 of the oestrous cycle). Moreover, CCL8 and CCR2 transcript levels were also elevated during the period of luteolysis. The immunolocalization of CCL2, CCL4, CCL5, CCR1, CCR2 and CCR5 was determined using CL sections obtained from cycling and pregnant pigs. The immunofluorescence signals were localized mainly in luteal cells. PGF2α treatment of CL cells caused increased mRNA expression of CCL2 and CCR1. CCL2 treatment alone upregulated the expression of genes BAX, BCL2 and StAR in CL cells in vitro, but additional experiments showed that the chemokines CCL2, CCL4 and CCL5 alone do not cause apoptosis in a mixed population of CL cells. The chemokine CCL4 increased the transcript levels of StAR and HSD3-β1. Additionally, CCL5 led to the inhibition of BAX gene expression. The differential spatiotemporal expression of CCL2, CCL4, CCL5 and CCR5 throughout the oestrous cycle and the direct but aberrant effect of these three chemokines on genes associated with apoptosis and progesterone synthesis indicate the complicated involvement of these factors in the regulation of luteolysis in pigs.

中文翻译：

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CC趋化因子的存在及其在猪黄体中的异常作用。

黄体退化的过程受到免疫系统和趋化因子-小细胞因子（主要负责免疫细胞的活化和迁移）的严格调控。趋化因子在猪黄体（CL）功能中的作用仍不十分清楚。这项研究的目的是调查在自然雌性周期和早期妊娠期间猪CL中CC趋化因子的表达情况和分布。此外，在体外研究了PGF2α对所选趋化因子表达的影响及其对CL细胞的亲黄性和凋亡性。趋化因子CCL2，CCL4和CCL5以及趋化因子受体CCR5的表达水平是时间依赖性的（在雌性周期的第8-10天低，在第12-14天高）。此外，在黄体溶解期间，CCL8和CCR2转录水平也升高。CCL2，CCL4，CCL5，CCR1，CCR2和CCR5的免疫定位是使用从循环猪和怀孕猪身上获得的CL切片确定的。免疫荧光信号主要定位在黄体细胞中。PGF2α处理CL细胞导致CCL2和CCR1的mRNA表达增加。单独的CCL2处理在体外会上调CL细胞中BAX，BCL2和StAR基因的表达，但另外的实验表明，单独的趋化因子CCL2，CCL4和CCL5不会在混合的CL细胞群体中引起凋亡。趋化因子CCL4增加了StAR和HSD3-β1的转录水平。另外，CCL5导致BAX基因表达的抑制。CCL2，CCL4，