Research articleThe effect of tumor necrosis factor α (TNFα), interleukin 1β (IL1β) and interleukin 6 (IL6) on endometrial PGF2α synthesis, metabolism and release in early-pregnant pigs
Introduction
Cytokines regulate many reproductive functions in pigs including embryo development, implantation, feto-maternal communications as well as endocrine activity of the uterus [1], [2], [3], [4], [5]. In women [6], rodents [7], [8], and cows [9], [10] cytokines are involved in synthesis and secretion of endometrial prostaglandins (PG). We hypothesize that the cytokines most likely to alter uterine activity in pigs during early pregnancy are tumor necrosis factor α (TNFα), interleukin 1 (IL1) and interleukin 6 (IL6).
TNFα is a cytokine produced mainly by activated macrophages, but this cytokine is also expressed in human and rodent embryos, in placentae, ovaries, oviducts, and uteri (reviewed in [11]), as well as the porcine endometrium [12]. TNFα mRNA is expressed in porcine endometrium during early stages of pregnancy [12]. TNFα is involved in the regulation of endometrial PG secretion in cyclic pigs during luteolysis [4] and stimulates expression, synthesis, and secretion of luteotrophic PGE2 by luminal epithelial cells of the porcine endometrium in gravid females during early pregnancy [13]. Interleukin 1 (IL1) is a pleiotropic cytokine involved in the control of endometrial and myometrial secretion of PGE2 [5], [14]. Peri-implantation embryos and pregnant endometrium express interleukin 1β (IL1β), which could affect communication between the conceptus and uterus during early pregnancy [3], [15]. In this species, IL1β sharply increases in the uterine lumen on the 12th day of gestation [3] and the pattern of IL1β expression at the site of embryo-maternal contact is specific and unique for this species [15]. The production of IL6 by peri-implantation porcine conceptuses is associated with maternal recognition of pregnancy [2], [16], [17] suggesting that IL6 may be involved in successfully establishing pregnancy in pigs.
In pigs, successful maintenance of early pregnancy, embryonic development, and implantation all require luteotrophic events in order to prevent luteal regression and transform the endometrium to create environment for the embryo development [18], [19], [20], [21], [22]. During early pregnancy, luteal regression is avoided by exocrine redirection and retrograde transfer of PG [18], [23]. Past studies have shown that the presence of the elongating embryos in the uterine horn on days 11 to 12 of pregnancy initiate this change of PGF2α secretion from endocrine to exocrine [24], [25], [26]. On approximately day 12 of pregnancy, pig conceptuses initiate attachment to the uterine luminal surface following a rapid morphological rearrangement of the trophoblast [19]. Days 10 to 16 of pregnancy coincide with continued antiluteolysis and implantation critical for the success of pregnancy [18]. In cyclic pigs luteolysis occurs by action of uterine prostaglandin F2α (PGF2α) which is transferred to the corpus luteum (CL) via an endocrine route [27], [28]. We suggest that an additional mechanism of luteal protection during early pregnancy is the action of cytokines on the production of PGs in the uterus. Specifically, we hypothesize that TNFα, IL1β and IL6 alter endometrial PGF2α synthesis, secretion and/or metabolism to rescue the CL during early pregnancy.
Past studies have shown a role for IL1β in PGE2 production during luteal rescue in pregnant pigs [5]. Specifically, IL1β increased cyclooxygenase 2 (COX-2) as well as PGE2 synthase (mPGES-1) mRNAs expression in porcine endometrium harvested from pigs on days 10–13 of pregnancy and the estrous cycle [5]. Uterine expression of COX-2 in response to IL1β produced by the uterus and embryos may also be involved in the regulation of PGF2α synthesis and secretion.
Here we determined whether TNFα, IL1β and IL6 regulate synthesis, secretion and metabolism of PGF2α in vitro in the porcine endometrium isolated during days 10–11, 12–13, and 15–16 of pregnancy. The effect of cytokines on pregnant endometrial tissue was compared with the effect in cyclic tissue harvested from pigs on the corresponding days of the estrous cycle. Specifically, we examined the effect of TNFα, IL1β and IL6 on: 1) the secretion of PGF2α; 2) the expression of PGFS mRNA; 3) the release of PGFM by tissue slices of the endometrium harvested from pigs on days 10–11, 12–13, and 15–16 of pregnancy or the estrous cycle.
Section snippets
Animals and collection of endometrial tissue
All experiments were approved by the Animal Ethics Committee, University of Warmia and Mazury in Olsztyn, Poland. Post-pubertal crossbred pigs (Large White × Polish Landrace) weighing 90–110 kg were used during early pregnancy or the estrous cycle. Gilts were observed for estrus behavior in the presence of an intact boar. The onset of the second estrus was designated as day 0 of the estrous cycle. Gilts assigned to the early pregnancy group were naturally bred on the second day of estrus. The
The effect of TNFα, IL1β, IL6 on endometrial PGF2α in vitro release during pregnancy and the estrous cycle
TNFα (10 ng/ml) did not alter PGF2α release from the endometrium of pregnant or cyclic pigs (P > 0.05; Fig. 1). IL1β used at a dose of 1 ng/ml did not change PGF2α release from endometrial slices incubated in vitro after 6 h and 12 h (P > 0.05) in pregnant and cyclic pigs. The higher dose of IL1β (10 ng/ml) increased PGF2α release after 6 and 12 h incubation in pregnant endometrium harvested on days 12–13 (P < 0.01 and P < 0.01) and days 15–16 (P < 0.05 and P < 0.001) of pregnancy. IL6 (1 and
Discussion
The present study demonstrated the effects of TNFα, IL1β and IL6 on the synthesis, secretion and metabolism of uterine PGF2α in endometrial explants during the normal estrous cycle and early pregnancy. IL1β was most stimulatory to endometrial release of PGF2α in cyclic pigs on days 12–13 and pregnant pigs on days 15–16; in cyclic pigs the effect of IL1β depends on the time of IL1β action; 2) during maternal recognition of pregnancy (days 12–13) endometrial expression of PGFS mRNA in response to
Acknowledgments
This research was funded by grant N N311 0685 33 (2007−2010) from the Ministry of Science and Higher Education, Poland. The authors would like to thank Dr. Jan Kotwica, Institute of Animal Reproduction and Food Research of Polish Academy of Science, Poland, for permission of PGFM assay in his laboratory. We also thank Dr. Marek Bogacki (Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, Olsztyn, Poland) for his help.
References (48)
Cytokines during early pregnancy of mammals: a review
Anim Reprod Sci
(2003)- et al.
Elevations of tumor necrosis factor-alpha (TNF-alpha) messenger RNA levels in the uterus of pregnant gilts after oestrogen treatment
Anim Reprod Sci
(1998) - et al.
Developmentally regulated expression of interleukin-1beta by peri-implantation conceptuses in swine
J Reprod Immunol
(1996) - et al.
Presence of leukaemia inhibitory factor and interleukin 6 in porcine uterine secretions prior to conceptus attachment
Cytokine
(1994) - et al.
Sparing effects of intrauterine treatment with prostaglandin E2 on luteal function in cyclic pigs
Prostaglandins
(1986) - et al.
Luteal maintenance during early pregnancy in the pig: role for prostaglandin E2
Prostaglandins
(1994) - et al.
The oestrous cycle and early pregnancy—a new concept of local endocrine regulation
Vet J
(2004) - et al.
Expression of enzymes of cyclooxygenase pathway and secretion of prostaglandin E2 and F2α by porcine myometrium during luteolysis and early pregnancy
Theriogenology
(2006) - et al.
Non-genomic effect of steroids on oxytocin-stimulated mobilization of calcium and on prostaglandin F2α and E2 secretion from bovine endometrial cells
Prostaglandins Other Lipid Mediat
(2005) Steroidal regulation of uterine immune defenses
Anim Reprod Sci
(2004)
A study of prostaglandin F2alpha as the luteolysin in swine: I. Effect of prostaglandin F2alpha in hysterectomized gilts
Prostaglandins
Analysis and characterization of differential gene expression during rapid trophoblastic elongation in the pig using suppression subtractive hybridization
Reprod Biol Endocrinol
Characterization of the interleukin-1beta system during porcine trophoblastic elongation and early placental attachment
Biol Reprod
Role of tumor necrosis factor alpha in stimulation of prostaglandins F(2alpha) and E(2) release by cultured porcine endometrial cells
Reprod Dom Anim
Interleukin 1β-induced synthesis and secretion of PGE2 in the porcine uterus during days 10 to 11, 12 to 13 and 15 to16 of pregnancy and the estrous cycle
J Physiol Pharmacol
Interleukin-1 beta induces cyclooxygenase-2 in cultured human decidual cells
Am J Reprod Immunol
Uterine epithelial cell secretion of interleukin-1 alpha induces prostaglandin E2 (PGE2) and PGF2 alpha secretion by uterine stromal cells in vitro
Endocrinology
Role of interleukin 1 in the regulation of cyclooxygenase gene expression in rat endometrial stromal cells
J Reprod Fertil
Is tumor necrosis factor alpha a trigger for the initiation of endometrial prostaglandin F(2alpha) release at luteolysis in cattle?
Biol Reprod
Roles of tumor necrosis factor-alpha of the estrous cycle in cattle: an in vivo study
Biol Reprod
Expression and regulation of the tumor necrosis factor-alpha gene in the female reproductive tract
Reprod Fertil Dev
Oxytocin and tumor necrosis factor alpha stimulate expression of prostaglandin E2 synthase and secretion of prostaglandin E2 by luminal epithelial cells of the porcine endometrium during early pregnancy
Reproduction
The interleukin-1 system and female reproduction
J Endocrinol
Expression of interleukin-6 in porcine, ovine, and bovine preimplantation conceptuses
Mol Reprod Dev
Cited by (31)
PPARγ ligands modulate the immune response mediators in the pig myometrium — An in vitro study
2021, Animal Reproduction SciencePPARβ/δ ligands regulate the expression of immune response mediators in the porcine endometrium – An in vitro study
2019, TheriogenologyCitation Excerpt :Recent research has demonstrated that IL-1β mRNA expression is higher in the human endometrium during the mid-luteal phase than in the early-luteal phase [43]. IL-1β stimulates the secretion of prostaglandins, PGE2 (luteotropic) and PGF2α (luteolytic) in the porcine endometrium during the late-luteal phase of the estrous cycle [44,45]. Interestingly, our previous study demonstrated a stimulatory effect of the PPARβ/δ agonist (L-165,041) on endometrial PGF2α and PGE2 synthesis during the late-luteal phase of the estrous cycle [7,8].
Peri-conceptional nutritional restriction alters transcriptomic profile in the peri-implantation pig embryos
2018, Animal Reproduction ScienceCitation Excerpt :Interestingly, the MMD protein positively regulates tumor necrosis factor α (TNF-α) synthesis (Liu et al., 2012), which is present in female reproductive tract of pigs (Hunt, 1993). The TNF-α protein affects the production of PGs and steroid hormones in the uterus during early pregnancy (Franczak et al., 2012, 2013b) and altered expression of the TNF-α gene may be the reason of pregnancy failures in mammals (Calleja-Agius et al., 2012). Thus, further studies are necessary to explain the effect of the restricted diets fed to females during the peri-conceptional period on MMD activity during the peri-implantation period.
Expression and regulation of interleukin 6 and its receptor at the maternal-conceptus interface during pregnancy in pigs
2017, TheriogenologyCitation Excerpt :Based on localization of IL6 and its receptors in the uterine endometrium and conceptus tissues, it is likely that IL6 acts on endometrial epithelial cells and conceptus/chorioallantoic tissues in an autocrine and/or paracrine manner to affect the endometrial and conceptus function during pig pregnancy. It has been suggested that IL6 induces endometrial E2 and PGF2α production during early pregnancy and attachment and proliferation of trophoblast cells in vitro in pigs [21–23]. However, it is not clear whether IL6 plays similar roles at the maternal-conceptus interface during mid-to late-pregnancy, when expression of IL6 and its receptors is highest.