Expression of the estrogen receptor in blood neutrophils of dairy cows during the periparturient period

Abstract

During the period around parturition, cows experience an increased susceptibility to inflammatory disorders in the mammary gland and uterus. This increased susceptibility has been correlated with a decreased functionality of neutrophils, major components in the innate immune defence. As sex steroid levels vary extensively in the period around parturition, an influence of these changes on the functionality of neutrophils has been suggested. Indeed, it has been shown that 17β-estradiol affects some functions of bovine neutrophils. In spite of these observations, receptors for 17β-estradiol have not yet been demonstrated in these cells. The investigation of the presence of estrogen receptors in bovine neutrophils was therefore the main objective of this study. The expression of estrogen receptors was evaluated at the protein level by flow cytometry, and at the mRNA level by polymerase chain reaction. A clear positive signal was obtained using flow cytometry for the estrogen receptor protein in bovine neutrophils. Further discrimination between the estrogen receptor subtypes α and β revealed the expression of the estrogen receptor β, whereas for the estrogen receptor α no reproducible positive signal could be obtained with the available antibodies. Both subtypes were found at the mRNA level. Subsequently, the estrogen receptor protein expression level in neutrophils obtained from cows in early lactation was compared with those from cows in late pregnancy. Additionally, the influence of endogenous 17β-estradiol and progesterone levels was assessed. No difference was found for the estrogen receptor protein expression in neutrophils from cows in early lactation compared with late gestation neither were the endogenous 17β-estradiol and progesterone levels correlated with the protein expression.