Potentiation of uterine effects of prostaglandin F2{alpha} by adenosine 5'-triphosphate

Golgi Reassembly Stacking Protein 2 Modulates Myometrial Contractility during Labor by Affecting ATP Production

The mechanism of maintaining myometrial contractions during labor remains unclear. Autophagy has been reported to be activated in laboring myometrium, along with the high expression of Golgi reassembly stacking protein 2 (GORASP2), a protein capable of regulating autophagy activation. This study aimed to investigate the role and mechanism of GORASP2 in uterine contractions during labor. Western blot confirmed the increased expression of GORASP2 in laboring myometrium. Furthermore, the knockdown of GORASP2 in primary human myometrial smooth muscle cells (hMSMCs) using siRNA resulted in reduced cell contractility. This phenomenon was independent of the contraction-associated protein and autophagy. Differential mRNAs were analyzed using RNA sequencing. Subsequently, KEGG pathway analysis identified that GORASP2 knockdown suppressed several energy metabolism pathways. Furthermore, reduced ATP levels and aerobic respiration impairment were observed in measuring the oxygen consumption rate (OCR). These findings suggest that GORASP2 is up-regulated in the myometrium during labor and modulates myometrial contractility mainly by maintaining ATP production.

The Biosynthesis of Enzymatically Oxidized Lipids

Enzymatically oxidized lipids are a specific group of biomolecules that function as key signaling mediators and hormones, regulating various cellular and physiological processes from metabolism and cell death to inflammation and the immune response. They are broadly categorized as either polyunsaturated fatty acid (PUFA) containing (free acid oxygenated PUFA "oxylipins", endocannabinoids, oxidized phospholipids) or cholesterol derivatives (oxysterols, steroid hormones, and bile acids). Their biosynthesis is accomplished by families of enzymes that include lipoxygenases (LOX), cyclooxygenases (COX), cytochrome P450s (CYP), and aldo-keto reductases (AKR). In contrast, non-enzymatically oxidized lipids are produced by uncontrolled oxidation and are broadly considered to be harmful. Here, we provide an overview of the biochemistry and enzymology of LOXs, COXs, CYPs, and AKRs in humans. Next, we present biosynthetic pathways for oxylipins, oxidized phospholipids, oxysterols, bile acids and steroid hormones. Last, we address gaps in knowledge and suggest directions for future work.

Changes in expression of P2X7 receptors in rat myometrium at different gestational stages and the mechanism of ATP-induced uterine contraction

AIMS

Given the importance of ATP in the control of uterine activity for successful labor and involution, this study was performed to measure the level of P2X7 receptors (P2X7Rs) in rat myometrium at different gestational stages and to investigate the mechanisms of ATP-induced uterine contraction.

MATERIALS AND METHODS

Myometrial tissues were obtained from rats at different gestational stages and the level of P2X7Rs was measured by ELISA. In other experiments, the effect of 1 mM ATP was tested on spontaneous contraction and the underlying mechanisms were investigated.

KEY FINDINGS

P2X7Rs were expressed in nonpregnant uterine tissues, progressively increased throughout pregnancy, and markedly peaked during postpartum involution. ATP significantly increased the force of spontaneous contraction in all uterine strips from different gestational stages with marked increase during labor and postpartum. ATP could not maintain the force when external Ca²⁺ was removed. In addition, ATP was able to cause tonic transient contraction in the absence of external Ca²⁺.

SIGNIFICANCE

P2X7Rs are functionally regulated and contributed to ATP-induced uterine contraction. The sensitivity of the myometrium to ATP increases as pregnancy progresses and it involves Ca²⁺ influx and Ca²⁺ release pathways. The clear effects of ATP on contractility suggest its physiological requirement for successful labor and postpartum involution.

Influence of threatened miscarriage on pregnancy and early postpartum period: a case-control report

OBJECTIVE

To evaluate the influence of threatened miscarriage on obstetric complications during pregnancy and early postpartum period.

METHODS

In this case-control study, hospital records of 12,050 first-trimester patients between January 2011 and December 2012 at the Research and Educational Hospital in Ankara, Turkey, were used. Of the 12,050 patients, 481 threatened miscarriage patients were evaluated. The control group was formed by age- and body mass index-matched cases without first trimester bleeding. Abortion, intrauterine foetal demise, preterm birth, preeclampsia, antenatal haematoma, uterine atony placental abruption and low birth-weights were compared between the study and the control group.

RESULTS

When compared with the control group, the risk of having a preterm birth (p = 0.014; OR: 1.95; 95% CI: 1.15-3.24), low-birth-weight infant (p = 0.001; OR: 2.33; 95% CI: 1.45-3.83) and abortion (p = 0.00; OR: 2.55; 95% CI: 1.62-3.91) increased in cases of threatened miscarriage. However, the risk of uterine atony was decreased (p = 0.006; OR: 0.09; 95% CI: 0.12-0.7) in the threatened miscarriage group when compared with the control group. Threatened miscarriage did not increase the risk of placenta praevia, placental abruption or intrauterine foetal demise.

CONCLUSION

Increased complications after threatened miscarriage is probably due to the persistence of a triggering mechanism. As preterm birth and abortion rate increased, whilst uterine atony rate decreased, one of the mechanisms causing threatened miscarriage might be increased uterine contractility.

The effect of extracellular adenosine triphosphate on the spontaneous contractility of human myometrial strips

OBJECTIVES

Extracellular ATP is involved in cell-cell signalling in a variety of tissues but its effects in tissue level signalling in the myometrium have been poorly studied to date. We hypothesised that extracellular ATP was involved in the control of myometrial contractile frequency and/or force.

STUDY DESIGN

In vitro study of the effect of altering the concentration of extracellular ATP on the spontaneous contractility of human myometrial strips obtained from term elective caesarean sections.

RESULTS

Decreasing extracellular ATP levels by the ectoATP-ase agent apyrase VI (1-50 units/mL) produced a dose dependent decrease in contractile frequency (decrease of 46.3% compared with the baseline frequency at 20 units/mL, p=0.001, n=6). Contractility was unchanged by apyrase VII (20 units/mL), an agent with relatively greater ADPase activity, indicating an effect via ATP and not ADP. Contractile frequency increased after addition of ATP 10-100 microM (an increase to 145.8% of baseline frequency at 100 microM: 126.1-165.5%, p=0.005, n=7) or the ATPase inhibitor ARL at 100 microM (an increase to 136.3% of the baseline frequency: 107.1-165.5, p=0.03, n=7). Contractile force remained unchanged by these agents.

CONCLUSIONS

Extracellular ATP shows a dose-response relationship to contractile frequency but does not affect contractile force. Consequently it may be involved in the pacemaking mechanism for the generation of uterine contractions.

Differences in muscarinic-receptor agonist-, oxytocin-, and prostaglandin-induced uterine contractions

OBJECTIVE

To investigate the contractile response of the perfused swine uterus to various receptor pathways (oxytocin, prostaglandins, and muscarine).

DESIGN

An extracorporeal perfusion model of the swine uterus was used that keeps the uterus in a functional condition and is appropriate for the study of physiologic questions.

INTERVENTION(S)

Oxytocin-, prostaglandin-, and carbachol-induced uterine contractility and peristalsis were assessed using an intrauterine double-chip microcatheter.

SETTING

University hospital.

MAIN OUTCOME MEASURE(S)

Intrauterine pressure profiles.

RESULT(S)

A dose-dependent increase in intrauterine pressure (IUP) in the isthmus uteri and corpus uteri was observed after the administration of prostaglandin F(2alpha) (PGF(2alpha)) and oxytocin, which reached a plateau after further stimulation. A dose-dependent increase in IUP in the isthmus uteri and corpus uteri was also observed after the administration of prostaglandin E(1) (PGE(1)) and prostaglandin E(2) (PGE(2)), with a plateau in IUP in the middle-concentration range and a decrease during the further course of stimulation. After administration of PGE(1), PGE(2), and PGF(2alpha), different directions of contraction waves were also observed. Carbachol also showed a unique contractility pattern, with isolated, very powerful, dose-dependent contractions with an IUP gradient, suggesting directed transport from the upper region to the lower region.

CONCLUSION(S)

This study demonstrated that oxytocin, the prostaglandins, and carbachol modulate contractility in nonpregnant swine uteri in a characteristic way, resulting in different contractility patterns.

Uterine contractility in response to different prostaglandins: results from extracorporeally perfused non-pregnant swine uteri

BACKGROUND

Prostaglandins (PGs) are important stimulators of uterine contractility. Limited data are available at present on the effects of different PGs on uterine contractility, measured using intraluminal pressure changes in the complete uterus. The goal of this study was to assess dynamic changes in uterine contractility and peristalsis in response to PGs in comparison with the effects of oxytocin administration.

METHODS

An extracorporeal perfusion model of swine uteri was used, which keeps the uterus in a functional condition, and is appropriate for the study of physiological questions. Oxytocin- and PG-induced uterine contractility and peristalsis were assessed using an intrauterine double-chip microcatheter.

RESULTS

A dose-dependent increase in intrauterine pressure (IUP) in the isthmus uteri (P < 0.001) and the corpus uteri (P < 0.001) was observed after the administration of PGF(2alpha) and oxytocin, which reached a plateau after further stimulation. A dose-dependent increase in IUP in the isthmus uteri (P < 0.001) and the corpus uteri (P < 0.001) was also observed after the administration of PGE(1) and PGE(2), with a plateau in IUP in the middle-concentration range and a decrease in the course of further stimulation. PGE(2) caused significantly more contractions starting in the corpus uteri and moving to the isthmus uteri (P = 0.008). The direction of most contractions caused by PGE(1), PGE(2) and oxytocin differed from that of PGF(2alpha).

CONCLUSIONS

This study demonstrates that the PGs tested modulate contractility in non-pregnant swine uteri in a characteristic way, resulting in different contractility patterns.

Term-dependency of P2 receptor-mediated contractile responses of isolated human pregnant uterus

OBJECTIVE

The aim of the study was to test the hypothesis that in the human uterus, the effectiveness of P2 receptor-mediated contractile responses is up-regulated during pregnancy.

STUDY DESIGN

Experiments were performed on myometrial samples obtained from women undergoing caesarean section at 28-30 weeks of pregnancy (3 women, Group 1), 32-34 weeks of pregnancy (6 women, Group 2) and 38-41 weeks of pregnancy (16 women, Group 3). Concentration-response relationships for a non-selective P2 receptor agonist, adenosine 5'-triphosphate (ATP), a selective P2X receptor agonist, alpha,beta-methylene-ATP (alpha,beta-meATP), and a frequency-response relationship for non-adrenergic non-cholinergic (NANC) electrical field stimulation (EFS) were obtained using routine pharmacological organ bath technique. Effects of pyridoxalphosphate azophenyl-2',4'-disulphonic acid (PPADS, 10(-5) M), a P2 receptor antagonist, were also evaluated. Parametric Student's t-test, non-parametric Wilcoxon T-test, Mann-Whitney U-test, two-way analysis of variance (ANOVA) and Krushkal-Wallis tests were used for statistical analysis.

RESULTS

ATP (10(-6) to 3 x 10(-4) M), alpha,beta-meATP (10(-7) to 3 x 10(-5) M) and EFS (2-32 Hz) evoked contractions of isolated pregnant uterus in all three groups. Uterus responses to ATP were not correlated with the term of pregnancy while the amplitude of uterine contractions to alpha,beta-meATP and EFS was higher in full term pregnancy than in earlier pregnancy. PPADS antagonized uterus responses to alpha,beta-meATP and EFS, but not to ATP, in all three groups.

CONCLUSION

P2X receptor-mediated contractions of human pregnant uterus to alpha,beta-meATP and EFS, but not to ATP, are increased with the progression of pregnancy.