Dose-dependent effects of meloxicam administration on cyclooxygenase-1 and cyclooxygenase-2 protein expression in intrauterine tissues and fetal tissues of a sheep model of preterm labor

Analgesia during Parturition in Domestic Animals: Perspectives and Controversies on Its Use

This article analyzes the physiological role of pain during parturition in domestic animals, discusses the controversies surrounding the use of opioids, non-steroidal anti-inflammatory drugs (NSAIDs), and local analgesics as treatments during labor, and presents the advantages and disadvantages for mother and offspring. Labor is a potentially stressful and painful event, due to the contractions that promote expulsion of the fetus. During labor, neurotransmitters such as the prostaglandins contribute to the sensitization of oxytocin receptors in the myometrium and the activation of nociceptive fibers, thus supporting the physiological role of pain. Endogenously, the body secretes opioid peptides that modulate harmful stimuli and, at the same time, can inhibit oxytocin's action in the myometrium. Treating pain during the different stages of parturition is an option that can help prevent such consequences as tachycardia, changes in breathing patterns, and respiratory acidosis, all of which can harm the wellbeing of offspring. However, studies have found that some analgesics can promote myometrial contractility, increase expulsion time, affect fetal circulation, and alter mother-offspring recognition due to hypnotic effects. Other data, however, indicate that reducing the number of uterine contractions with analgesics increases their potency, thus improving maternal performance. Managing pain during labor requires understanding the tocolytic properties of analgesics and their advantages in preventing the consequences of pain.

Prostaglandin dehydrogenase is a target for successful induction of cervical ripening

The cervix represents a formidable structural barrier for successful induction of labor. Approximately 10% of pregnancies undergo induction of cervical ripening and labor with prostaglandin (PG) E₂ or PGE analogs, often requiring many hours of hospitalization and monitoring. On the other hand, preterm cervical ripening in the second trimester predicts preterm birth. The regulatory mechanisms of this paradoxical function of the cervix are unknown. Here, we show that PGE₂ uses cell-specific EP2 receptor-mediated increases in Ca²⁺ to dephosphorylate and translocate histone deacetylase 4 (HDAC4) to the nucleus for repression of 15-hydroxy prostaglandin dehydrogenase (15-PGDH). The crucial role of 15-PGDH in cervical ripening was confirmed in vivo. Although PGE₂ or 15-PGDH inhibitor alone did not alter gestational length, treatment with 15-PGDH inhibitor + PGE₂ or metabolism-resistant dimethyl-PGE₂ resulted in preterm cervical ripening and delivery in mice. The ability of PGE₂ to selectively autoamplify its own synthesis in stromal cells by signaling transcriptional repression of 15-PGDH elucidates long sought-after molecular mechanisms that govern PG action in the cervix. This report details unique mechanisms of action in the cervix and serves as a catalyst for (i) the use of 15-PGDH inhibitors to initiate or amplify low-dose PGE₂-mediated cervical ripening or (ii) EP2 receptor antagonists, HDAC4 inhibitors, and 15-PGDH activators to prevent preterm cervical ripening and preterm birth.

miR-144 and targets, c-fos and cyclooxygenase-2 (COX2), modulate synthesis of PGE2 in the amnion during pregnancy and labor

Labor is initiated as a result of hormonal changes that are induced by the activation of the inflammatory response and a series of biochemical events. The amnion, which is the primary source of prostaglandin E2 (PGE2), plays an important role in the process of labor. In the present study, we uncovered a pathway in which c-fos, cyclooxygenase-2 (COX2) and miR-144 function as hormonal modulators in the amnions of pregnant mice and humans. miR-144 down-regulated the synthesis of PGE2 during pregnancy by directly and indirectly inhibiting COX2 expression and by directly inhibiting the expression of c-fos, a transcriptional activator of COX2 and miR-144. Estrogen (E₂) activated c-fos, thus promoting the expression of miR-144 and COX2 during labor. However, the increase in COX2 resulted in the partial inhibition of COX2 expression by miR-144, thereby slightly reducing the secretion of PGE2. These observations suggest that miR-144 inhibits PGE2 secretion by section to prevent the initiation of premature labor. Up-regulated expression of miR-144, c-fos and COX2 was also observed both in preterm mice and in mice undergoing normal labor. In summary, miR-144, c-fos and COX2 play important roles in regulating PGE2 secretion in the amnion during pregnancy and labor.

Cortisol and interferon tau regulation of endometrial function and conceptus development in female sheep

During early pregnancy in sheep, the elongating conceptus secretes interferon-τ (IFNT) and the conceptus as well as endometrial epithelia produce prostaglandins (PG) via PG synthase 2 (PTGS2) and cortisol via hydroxysteroid (11-β) dehydrogenase 1 (HSD11B1). Ovarian progesterone induces and PG and IFNT stimulates endometrial HSD11B1 expression and keto-reductase activity as well as many epithelial genes that govern trophectoderm proliferation, migration, and attachment during elongation. The primary aim of these studies was to test the hypothesis that HSD11B1-derived cortisol has a biological role in endometrial function and conceptus development during early pregnancy in sheep. In study 1, cyclic ewes received vehicle, cortisol, PF 915275 (PF; a selective inhibitor of HSD11B1), cortisol and PF, meloxicam (a selective inhibitor of PTGS2), cortisol and meloxicam, recombinant ovine IFNT, or IFNT and PF into the uterus from day 10 to day14 after estrus. Cortisol and IFNT stimulated endometrial HSD11B1 expression and activity, increased endometrial PTGS2 activity and the amount of PG in the uterine lumen, and up-regulated many conceptus elongation-related genes in the endometrium. Some effects of cortisol and IFNT were mediated by PTGS2-derived PG. In study 2, bred ewes received PF 915275 or recombinant ovine IFNT and into the uterus from day 10 to day 14 after mating. Inhibition of HSD11B1 activity in utero prevented conceptus elongation, whereas IFNT rescued conceptus elongation in PF-infused ewes. These results suggest that HSD11B1-derived cortisol mediates, in part, actions of ovarian progesterone and the conceptus on endometrial function and support the hypothesis that IFNT, PG, and cortisol coordinately regulate endometrial functions important for conceptus elongation and implantation during early pregnancy in sheep.

Dual effect of nitric oxide on uterine prostaglandin synthesis in a murine model of preterm labour

BACKGROUND AND PURPOSE

Maternal infections are one of the main causes of adverse developmental outcomes including embryonic resorption and preterm labour. In this study a mouse model of inflammation-associated preterm delivery was developed, and used to study the relationship between nitric oxide (NO) and prostaglandins (PGs).

EXPERIMENTAL APPROACH

The murine model of preterm labour was achieved by assaying different doses of bacterial lipopolysaccharides (LPS). Once established, it was used to analyse uterine levels of prostaglandins E(2) and F(2α) (by radioimmunoassay), cyclooxygenases (COX) and NOS proteins (by Western blot) and NO synthase (NOS) activity. Effects of inhibitors of COX and NOS on LPS-induced preterm labour were also studied. In vitro assays with a nitric oxide donor (SNAP) were performed to analyse the modulation of prostaglandin production by NO.

KEY RESULTS

Lipopolysaccharide increased uterine NO and PG synthesis and induced preterm delivery. Co-administration of meloxicam, a cyclooxygenase-2 inhibitor, or aminoguanidine, an inducible NOS inhibitor, prevented LPS-induced preterm delivery and blocked the increase in PGs and NO. Notably, the levels of NO were found to determine its effect on PG synthesis; low concentrations of NO reduced PG synthesis whereas high concentrations augmented them.

CONCLUSIONS AND IMPLICATIONS

An infection-associated model of preterm labour showed that preterm delivery can be prevented by decreasing PG or NO production. NO was found to have a dual effect on PG synthesis depending on its concentration. These data contribute to the understanding of the interaction between NO and PGs in pregnancy and parturition, and could help to improve neonatal outcomes.