The effect of oestradiol and progesterone on chemerin system expression in the porcine endometrium during early pregnancy and the mid-luteal phase of the oestrous cycle

Abstract

Chemerin is an adipokine which is the product of the RARRES2 gene expressed mainly in adipose tissue. This hormone exerts biological effects via three metabotropic receptors: chemokine like receptor 1 (CMKLR1), G protein-coupled receptor 1 (GPR1), and C-C chemokine receptor-like 2 (CCRL2). Chemerin exerts pleiotropic effects and participates in the regulation of many processes, such as blood pressure control, immune system regulation, inflammation, and angiogenesis. There is a growing body of evidence to indicate that chemerin is involved in the regulation of reproductive system functions. However, little is known about the regulation of chemerin system (chemerin and its receptors) expression. The authors hypothesized that steroid hormones affect the expression of the chemerin system in the uterus of domestic pigs. Thus, the aim of this study was to investigate the influence of steroids, oestradiol (E₂), and progesterone (P₄), on the gene (qPCR) and protein (Western blot) expression of chemerin receptors, RARRES2 gene expression as well as chemerin secretion (ELISA) by endometrial slices during early pregnancy (days 10 to 11, 12 to 13, 15 to 16, and 27 to 28) and the mid-luteal phase of the oestrous cycle (days 10 to 11). Both steroid hormones modulated the expression of chemerin receptor genes and proteins, as well as the abundance of RARRES2 mRNA transcripts. The study also demonstrated that E₂ increased chemerin protein secretion by endometrial cells during the maternal recognition of pregnancy (days 12 to 13) and decreased its release during embryo implantation (days 15 to 16). P₄ had no significant effect on chemerin levels during the studied periods of gestation and the oestrous cycle. These observations suggest that the effects of E₂ and P₄ on the chemerin system are dependent on the period of gestation or the oestrous cycle. Our results support the hypothesis that the hormonal environment could modulate the expression of the chemerin system in the endometrium.

Keywords: Chemerin; Chemerin receptors; Early pregnancy; Endometrium; Pig; Steroid hormones.