Immunological implications of pregnancy: A focus on inflammatory cytokines

Abstract Text:

The present studies aim to 1) determine expression of (C-X-C motif) ligand twelve (CXCL12), CXCR4, and inflammatory cytokines in corpus luteum (CL) and fetal-maternal interface during early pregnancy and when CXCR4 signaling is inhibited in ewes, and 2) determine alterations in CL cytokine expression using an in vivo model with hCG-stimulated P4 levels. Several human studies highlight CXCL12-CXCR4 signaling in regulating cytokine production, but whether similar mechanisms occur in livestock is uncertain. Our laboratory reported activation of CXCL12-CXCR4 signaling axis at the fetal-maternal interface in sheep but whether this axis is involved in modifying reproductive tissue or peripheral blood inflammatory responses is uncertain. We hypothesized CXCL12-CXCR4 signaling acts as a potentiator during early pregnancy in ewes by altering cytokine populations at the fetal-maternal interface and the luteal microenvironment. To test this hypothesis, CL tissue was collected from NP (d 10 of estrous cycle) and pregnant ewes on d 20 and 25. In a separate study, we utilized AMD3100, a potent CXCR4 antagonist, to disrupt CXCR4 signaling to determine inhibition effects on fetal-maternal cytokines. Mini-osmotic pumps were surgically installed on d 12 of gestation and delivered AMD3100 or PBS into the uterine lumen ipsilateral to CL for 7 d. Endometrium (caruncular and intercaruncular) and fetal membrane tissues were collected on d 23 of gestation. Gene expression of inflammatory cytokines were investigated using real time PCR. During gestation, proinflammatory cytokines increased (P < 0.05) in CL from pregnant compared to NP ewes. Similarly, CXCL12 and CXCR4 increased (P < 0.05) on d 20 of gestation in pregnant compared to NP ewes. Under hCG stimulation, interferon gamma (IFNG) decreased (P < 0.01) on d 25 in CL tissue compared to control ewes. In AMD3100-treated ewes, transcripts for tumor necrosis factor (TNF) (P < 0.05) and interleukin 12 (IL12A) (P < 0.01) increased in caruncle, while transforming growth factor beta 1 (TGFB1) and IL12A tended (P = 0.2) to increase in intercaruncular endometrium compared to control. Interleukin 10 (IL10) transcript from treated ewe fetal membrane tended (P = 0.1) to increase compared to control. Using immunofluorescence, IL10 protein was localized to uterine luminal and glandular epithelium, and TNF to uterine glandular epithelium and stroma. Using flow cytometry, we established peripheral blood T lymphocytes are CXCR4-positive. Our results highlight the role CXCL12- CXCR4 signaling may play in regulating localized inflammation at the fetal-maternal interface and immune cell trafficking in peripheral blood, contributing to pregnancy maintenance.

Keywords:

chemokine receptor 4, cytokines, inflammation