The Novel Roles of Neutrophils Via Opioid Peptides: Regulation of the Estrous Cycle and Pain

Abstract

Neutrophils are excreted into the vaginal vault at metestrus during the estrous cycle, and this phenomenon has long been used to determine the phase of the estrous cycle. A much smaller number of neutrophils are also detected in the uterus and the ovary. Recently, we provided several lines of evidence supporting the notion that neutrophils infiltrate into the ovary to regulate the estrous cycle by opioid peptides. Upon inflammation, on the other hand, neutrophils infiltrate into the site of infection to suppress pain by opioid peptides. Thus, opioid peptides are key molecules by which neutrophils play a novel role in regulation of the pain and estrous cycle. In both cases, opioid peptides appear to be secreted by neutrophils stimulated with chemokines, such as MIP-2 and KC in mouse, corticotropin-releasing hormone and IL-1.

The role of neutrophil activation in determining the outcome of pregnancy and modulation by hormones and/or cytokines

“…In the oestrous cycle of mammalian therian females, oestrogen produced by the mature follicules initiates the phase of sexual receptivity (oestrus), whereas P4 production either assists with the progression of gestation or a period of inactivity (anoestrus) [24].…”

“…© 2019 British Society for Immunology, Clinical and Experimental Immunology, 198:[24][25][26][27][28][29][30][31][32][33][34][35][36] …”

Intra-uterine experimental infection by Ureaplasma diversum induces TNF-α mediated womb inflammation in mice

“…The presence of infl ammatory cells in uterus tissue and in vaginal lavages seems to be directly related to the estrous cycle in female. During metaestrus, a number of neutrophils infi ltrate the vaginal cavity (Kobayashi 2013, Sasaki et al 2009). Neutrophil infi ltration into the vagina is critical in maintaining the cycle by controlling the levels of steroid hormones and angiogenesis via production of chemoattractants (Jiemtaweeboon et al 2011).…”

Recent Research About the Immune Cells in the Ovary

“…Studies have shown that neutrophils in the ovary are divided into peripherally imported neutrophils and resident neutrophils [38]. However, neutrophils are less abundant in healthy ovaries [39,40]. Neutrophil phenotype is determined by surface markers and receptors as well as chemotaxis to different cytokines [34].…”