Nitric oxide in parturition

Propofol protects against lipopolysaccharide-induced inflammatory response in human amnion-derived WISH cells

Background

Nonobstetric surgery is sometimes required during pregnancy, and neck abscess or facial bone fracture surgery cannot be postponed in pregnant women. However, dental surgery can be stressful and can cause inflammation, and the inflammatory response is a well-known major cause of preterm labor. Propofol is an intravenous anesthetic commonly used for general anesthesia and sedation. Studies investigating the effect of propofol on human amnion are rare. The current study investigated the effects of propofol on lipopolysaccharide (LPS)-induced inflammatory responses in human amnion-derived WISH cells.

Methods

WISH cells were exposed to LPS for 24 h and co-treated with various concentrations of propofol (0.01-1 µg/ml). Cell viability was measured using the MTT assay. Nitric oxide (NO) production was analyzed using a microassay based on the Griess reaction. The protein expression of cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE 2), p38, and phospho-p38 was analyzed using western blotting.

Results

Propofol did not affect the viability and NO production of WISH cells. Co-treatment with LPS and propofol reduced COX-2 and PGE₂ protein expression and inhibited p38 phosphorylation in WISH cells.

Conclusion

Propofol does not affect the viability of WISH cells and inhibits LPS-induced expression of inflammatory factors. The inhibitory effect of propofol on inflammatory factor expression is likely mediated by the inhibition of p38 activation.

Anandamide Exerts a Differential Effect on Human Placenta Before and After the Onset of Labor

The onset of labor involves the action of multiple factors and recent reports have postulated the endocannabinoid system as a new regulator of this process. Our objective was to study the role of anandamide, one of the main endocannabinoids, on the regulation of placental molecules that contribute to the onset of labor at term. Placental samples were obtained from patients with laboring vaginal deliveries and from non-laboring elective cesarean sections. Vaginal delivery placentas produced higher prostaglandins levels than cesarean section samples. Besides, no differences were observed in NOS basal activity between groups. Incubation of vaginal delivery placentas with anandamide increased prostaglandins concentration and decreased NOS activity. Antagonism of type-1cannabinoid receptor (CB1) did not alter the effect observed on NOS activity. Conversely, incubation of cesarean section placentas with anandamide reduced prostaglandins levels and enhanced NOS activity, the latter involving the participation of CB1. Furthermore, we observed a differential expression of the main components of the endocannabinoid system between placental samples, being the change in CB1 localization the most relevant finding. Our results suggest that anandamide acts as a modulator of the signals that regulate labor, exerting differential actions depending on CB1 localization in laboring or non-laboring term placentas.

Anti-inflammatory effects of dexmedetomidine on human amnion-derived WISH cells

Background: To maintain the normal pregnancy, suppression of inflammatory signaling pathway is a crucial physiologic response. Dexmedetomidine has been used for labor analgesia or supplement of inadequate regional analgesia during delivery. And it has been reported that dexmedetomidine has an anti-inflammatory effect. In this study, we examined the influence of dexmedetomidine on the expression of cyclooxygenase-2 (COX-2), prostaglandin E₂ (PGE₂) and inflammatory cytokines in lipopolysaccharide (LPS)-stimulated human amnion-derived WISH cells. In addition, we evaluated the association of mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) pathway in anti-inflammatory effect of dexmedetomidine. Methods: Human amnion-derived WISH cells were pretreated with various concentrations of dexmedetomidine (0.001-1 µg/ml) for 1 h and after then treated with LPS (1 µg/ml) for 24 h. MTT assay was conducted to evaluate the cytotoxicity. Nitric oxide (NO) production was analyzed using Griess-reaction microassay. RT-PCR was performed for analysis of mRNA expressions of COX-2, PGE₂, tumor necrosis factor (TNF)-α and interlukin (IL)-1β. Protein expressions of COX-2, PGE₂, p38 and NF-κB were analyzed by western blotting. Results: LPS and dexmedetomidine had no cytotoxic effect on WISH cells. There was no difference in NO production after dexmedetomidine pretreatment. The mRNA and protein expressions of COX-2 and PGE₂ were decreased by dexmedetomidine pretreatment in LPS-treated WISH cells. Dexmedetomidine also attenuated the LPS-induced mRNA expression of TNF-α and IL-1β. The activation of p38 and NF-κB was suppressed by dexmedetomidine pretreatment in LPS-treated WISH cells. Conclusion: We demonstrated that dexmedetomidine pretreatment suppressed the expressions of inflammatory mediators increased by LPS. In addition, this study suggests that anti-inflammatory effect of dexmedetomidine on WISH cells was mediated by the inhibitions of p38 and NF-κB activation.

Propofol Suppresses LPS-Induced Inflammation in Amnion Cells via Inhibition of NF-κB Activation

Background

Preterm labor is a leading risk factor for neonatal death and long-term impairment and linked closely with inflammation. Non-obstetric surgery is occasionally needed during pregnancy and the anesthetic drugs or surgery itself can give rise to inflammation. Here, we examined the influence of propofol pretreatment on the expression of cyclooxygenase-2 (COX-2) and prostaglandin E₂ (PGE₂) after lipopolysaccharide (LPS) stimulation. In addition, we evaluated the expression of pro-inflammatory cytokines and nuclear factor kappa B (NF-κB).

Methods

Human amnion-derived WISH cells were used to investigate the effect of propofol on the LPS-induced expression of inflammatory substances involved in preterm labor. For the experiment, WISH cells were pretreated with various concentrations propofol (0.01-10 μg/ml) for 1 h and then treated with LPS (1 μg/ml) for 24 h. Cytotoxicity was evaluated using MTT assay. PGE₂ concentration was assessed by ELISA. Protein expressions of COX-2, PGE₂ and NF-κB were analyzed by western blotting analysis. RT-PCR was used for analysis of mRNA expression of COX-2, PGE₂, interlukin (IL)-1β and tumor necrosis factor (TNF)-α.

Results

Propofol showed no cytotoxicity on the WISH cells. LPS-induced PGE₂ production and COX-2 and PGE₂ expression were decreased after propofol pretreatment. Propofol also attenuated the LPS-induced mRNA expression of IL-1β and TNF-α. Moreover, the activation of NF-κB was inhibited by propofol pretreatment on LPS-stimulated WISH cells.

Conclusion

We demonstrated that propofol suppresses the expression of inflammatory substances enhanced by LPS stimulation. Furthermore, this inhibitory effect of propofol on the inflammatory substance expression is mediated by suppression of NF-κB activation.

Systems Pharmacological Approach to the Effect of Bulsu-san Promoting Parturition

Bulsu-san (BSS) has been commonly used in oriental medicine for pregnant women in East Asia. The purpose of this research was to elucidate the effect of BSS on ease of parturition using a systems-level in silico analytic approach. Research results show that BSS is highly connected to the parturition related pathways, biological processes, and organs. There were numerous interactions between most compounds of BSS and multiple target genes, and this was confirmed using herb-compound-target network, target-pathway network, and gene ontology analysis. Furthermore, the mRNA expression of relevant target genes of BSS was elevated significantly in related organ tissues, such as those of the uterus, placenta, fetus, hypothalamus, and pituitary gland. This study used a network analytical approach to demonstrate that Bulsu-san (BSS) is closely related to the parturition related pathways, biological processes, and organs. It is meaningful that this systems-level network analysis result strengthens the basis of clinical applications of BSS on ease of parturition.

Changes in Cervical Nitric Oxide Concentration Correlate With Bishop Score and Cervical Length Modifications in Prostaglandin E2-Mediated Induction of Labor

OBJECTIVE

Nitric oxide (NO) plays a fundamental role in cervical ripening and it is synthesized in the human cervix. We studied the effect of the dinoprostone on cervical NO release in pregnant women, and we investigated the relationship between cervical NO metabolites, cervical length, and Bishop score.

METHODS

Seventy-seven women underwent induction of labor at > or = 37 weeks of gestation, due to post-term pregnancy (23.8%), oligohydramnios (36.3) or preeclampsia (29.9%). Cervical fluid samples for NO metabolites (NOx), Bishop score, and cervical length were assessed immediately before (time 0 [T0]) and 6 hours after (T6) the local application of dinoprostone, a commercially available prostaglandin E2 (PGE2) analog.

RESULTS

The mean patients' age was 34 +/- 3.2 years, mean gestational age at enrollment was 284 +/- 9.2 days, and nulliparous represented 31.2% of the study population. At time 0, Bishop score was less than 4 in 74% (57/77) of the subjects, mean cervical length was 28.6 +/- 5.8 mm, mean NOx concentration was 208.6 +/- 103.8 microM/mL; 6 hours later, at T6, the mean cervical length decreased to 19.5 +/- 8.8 mm, and the mean NOx concentration increased up to 316.7 +/- 240.9 microM/mL. Data were unaffected by parity or by regular uterine contraction patterns. A statistically significant positive correlation was found between changes in cervical NOx levels and Bishop score modification (P < .01; r = .494), as well as between the modification of NO metabolites concentration and cervical shortening (P < .01; r = .307).

CONCLUSIONS

Prostaglandin (PG)-induced cervical ripening is associated with local NO release. NO plays an active role in cervical remodeling since it positively correlates with both cervical shortening and Bishop score increase. NO oxide and PG are the two pathways that, cross activating each other, trigger the cascade of events responsible of cervical ripening.

Glyceryl trinitrate for the treatment of preterm labor

OBJECTIVE

This study was conducted to compare the tocolytic efficacy of glyceryltrinitrate (GTN) with that of magnesium sulfate (MgSO4) and to investigate serum nitric oxide metabolites before and after tocolysis.

MATERIAL AND METHODS

In total, 48 women between 27 and 34 weeks' gestation with threatened preterm labor and intact membranes were randomly allocated to receive either GTN or MgSO4 tocolysis. Main outcome measures included tocolytic efficacy and maternal side effect(s) of the tocolytic agent. Obstetric and neonatal outcomes as well as pretreatment and posttreatment nitric oxide (NO) metabolites were assessed.

RESULTS

Forty-one patients were included into the final analysis. Uterine contraction cessation times were 3.66±1.28 and 6.83±3.47 hours for GTN and MgSO4 groups, respectively. Similarly, maternal side effects were significantly lower in the GTN group than in the MgSO4 group, and no serious maternal side effects were recorded. Serum NO metabolite levels before treatment were significantly lower in the treatment groups than in the controls. Serum nitrite levels were significantly increased after tocolytic treatment both in MgSO4 and GTN groups.

CONCLUSION

GTN effectively delays preterm delivery and reduces neonatal morbidity and mortality with less maternal side effects and seems to be an effective and safe alternative to MgSO4.

Oxytocin, its antagonist Atosiban, and preterm labor: a role for placental nitric oxide

OBJECTIVE

The aim of the present study was to understand the role played by Atosiban, an oxytocin receptor antagonist, on trophoblastic human cells, and the molecular bases of its efficacy and safety in the treatment of preterm labor. NO, peroxinitrite production and NOS expression have been evaluated on placenta obtained from term and preterm labors.

PATIENTS AND METHODS

We studied trophoblast cells isolated from selected placental tissue from 20 controls and 20 preterm patients after cesarean sections. Each sample was studied at basal state and after 2 hours incubation with oxytocin and Atosiban.

RESULTS

Significant variations of NO levels, peroxynitrite production and iNOS and eNOS expression both in the preterm, term samples and in each of the considered groups were observed. In the control group Atosiban re-established NO levels that were reduced after incubation with oxytocin, while in preterm samples NO levels were not only re-established but, after incubation with Atosiban, significantly increased compared to basal levels.

CONCLUSIONS

This confirms the beneficial role of Atosiban in prolonging the pregnancy of spontaneous labor at very early gestational periods. In conclusion, Atosiban might be an effective drug to prevent preterm labor, in the therapeutic approach to this pathology.

Characterization of the myometrial transcriptome in women with an arrest of dilatation during labor

OBJECTIVE

The molecular basis of failure to progress in labor is poorly understood. This study was undertaken to characterize the myometrial transcriptome of patients with an arrest of dilatation (AODIL).

STUDY DESIGN

Human myometrium was prospectively collected from women in the following groups: (1) spontaneous term labor (TL; n=29) and (2) arrest of dilatation (AODIL; n=14). Gene expression was characterized using Illumina® HumanHT-12 microarrays. A moderated Student's t-test and false discovery rate adjustment were used for analysis. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) of selected genes was performed in an independent sample set. Pathway analysis was performed on the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database using Pathway Analysis with Down-weighting of Overlapping Genes (PADOG). The MetaCore knowledge base was also searched for pathway analysis.

RESULTS

(1) Forty-two differentially expressed genes were identified in women with an AODIL; (2) gene ontology analysis indicated enrichment of biological processes, which included regulation of angiogenesis, response to hypoxia, inflammatory response, and chemokine-mediated signaling pathway. Enriched molecular functions included transcription repressor activity, heat shock protein (Hsp) 90 binding, and nitric oxide synthase (NOS) activity; (3) MetaCore analysis identified immune response chemokine (C-C motif) ligand 2 (CCL2) signaling, muscle contraction regulation of endothelial nitric oxide synthase (eNOS) activity in endothelial cells, and triiodothyronine and thyroxine signaling as significantly overrepresented (false discovery rate <0.05); (4) qRT-PCR confirmed the overexpression of Nitric oxide synthase 3 (NOS3); hypoxic ischemic factor 1A (HIF1A); Chemokine (C-C motif) ligand 2 (CCL2); angiopoietin-like 4 (ANGPTL4); ADAM metallopeptidase with thrombospondin type 1, motif 9 (ADAMTS9); G protein-coupled receptor 4 (GPR4); metallothionein 1A (MT1A); MT2A; and selectin E (SELE) in an AODIL.

CONCLUSION

The myometrium of women with AODIL has a stereotypic transcriptome profile. This disorder has been associated with a pattern of gene expression involved in muscle contraction, an inflammatory response, and hypoxia. This is the first comprehensive and unbiased examination of the molecular basis of an AODIL.

Effect of lipopolysaccharide on the production of prostaglandin E2 and inhibition of uterine contractions by nitric oxide in pregnant inducible nitric oxide synthase knockout mice

AIM

The aim of the present study was to evaluate the effect of lipopolysaccharide (LPS) on the production of prostaglandin E2 (PGE2) and inhibition by nitric oxide (NO) of spontaneous contractions of uterine rings from pregnant inducible isoform of nitric oxide synthase knockout (iNOS KO) mice.

MATERIAL AND METHODS

iNOS KO and wild-type mice were sacrificed 6 h after intraperitoneal (i.p.) administration of LPS on day 14 of gestation. Uterine rings were equilibrated in Krebs-Henseleit solution for isometric tension recording. In part of the uterine rings, placental tissues were left attached. The bathing solution was analyzed for PGE2 by radioimmunoassay. Changes in spontaneous contractions in response to cumulative concentrations of L-arginine, diethylamine/nitric oxide (DEA/NO), and 8-bromo-cyclic guanosine monophosphate (8-br-cGMP) were determined.

RESULTS

Treatment with LPS increased PGE2 production by uterine rings from wild-type and iNOS-KO mice. DEA/NO and 8-br-cGMP inhibited spontaneous contractions in uterine rings in the absence or presence of placenta, in both LPS-treated and LPS-untreated animals. LPS treatment attenuated maximal inhibition induced by the agents, both in the absence and presence of placental tissues in iNOS KO and wild-type mice.

CONCLUSION

LPS induces PG production in mice myometrium that is not dependent on the integrity of iNOS, while LPS could induce pathophysiological iNOS obstruct uterine quiescence by physiological iNOS. Infection affects uterine contractile activity through PG production, as well as through placental and genetic factors. NO may be a double-edged sword in pregnant mice myometrium.

Progestin treatment for the prevention of preterm birth

Progestin supplementation appears to be a promising approach to both preventing initiation of preterm labor and treating it once it is already established, given the role of progesterone in maintaining pregnancy, as well as support from basic and clinical research. Progesterone and 17α-hydroxyprogesterone acetate slow the process of cervical ripening, and this is the rationale for prophylactic long-term progestin supplementation mostly studied so far. However, progesterone (but not 17α-hydroxyprogesterone acetate) also inhibits myometrial activity even after the cervix has already ripened. Moreover, these effects depend greatly on the vehicle used and the route of administration. Understanding different mechanisms of action, as well as the importance of progestin formulation, vehicle and route of administration, is the key to finding the optimal progestin treatment for prevention of preterm birth.

The cost-effectiveness of outpatient (at home) cervical ripening with isosorbide mononitrate prior to induction of labour

OBJECTIVES

To assess the cost-effectiveness of outpatient (at home) cervical ripening with isosorbide mononitrate (IMN) prior to induction of labour.

DESIGN

Economic evaluation was conducted alongside a randomised placebo controlled trial (the IMOP trial).

SETTING

Large UK maternity hospital.

POPULATION

A total of 350 nulliparous women with a singleton pregnancy, cephalic presentation > or = 37 weeks gestation, requiring cervical ripening prior to induction of labour.

INTERVENTIONS

Isosorbide mononitrate (n = 177) or placebo (n = 173) self-administered vaginally at home at 48, 32 and 16 hours prior to the scheduled time of admission for induction.

RESULTS

Mean health service costs between the period of randomisation and discharge for mother and infant were 1254.86 pound sterling in the IMN group and 1242.88 pound sterling in the placebo group, generating a mean cost difference of 11.98 pound sterling (bootstrap mean cost difference 12.86 pound sterling; 95%CI: -106.79 pound sterling, 129.39 pound sterling) that was not statistically significant (P = 0.842). The incremental cost per hour prevented from hospital admission to delivery was 7.53 pound sterling. At the notional willingness to pay threshold of 100 pound sterling per hour prevented from hospital admission to delivery, the probability that IMN is cost-effective was estimated at 0.67. This translated into a mean net monetary benefit of 98.13 pound sterling for each woman given IMN.

CONCLUSIONS

Although the probability that IMN is cost-effective approaches 0.7 at seemingly low willingness to pay thresholds for an hour prevented from hospital admission to delivery, our results should be viewed in the light of the clinical findings from the IMOP trial.

Nitric oxide detection by DAF (diaminofluorescein) fluorescence in human myometrial tissue

Nitric oxide (NO) is considered to be involved in the modulation of uterine contractility. In the present pilot study, the direct detection of intracellular NO in pregnant human myometrial tissues has been investigated by using the fluorescent indicator 4,5-diaminofluorescein-2 diacetate (DAF-2DA). Pregnant myometrial tissue samples were obtained during Cesarean sections between week 34 and 40 of gestation before the onset of labor. Living explants were loaded with 10 microM DAF-2DA, stimulated with 1 mM arginine, subsequently fixed with glutaraldehyde and examined by fluorescence microscopy. The presence of NO synthases (NOS) was studied by immunohistochemistry. After application of DAF-2DA, DAF fluorescence was located primarily in blood vessels and to a minor extent in myometrial cells. By immunohistochemistry, strong endothelial NOS (eNOS) staining was found in vessel walls. In myometrial cells weak staining of eNOS and inducible NOS was observed. We conclude that the direct NO detection by DAF-2DA provides a new and independent method to identify sites of NO production in myometrium and other heterogeneous tissues.

Clinical use of nitric oxide donors and L-arginine in obstetrics

Nitric oxide (NO) is a free radical that plays a fundamental role in human physiology, being involved in the homeostasis of different functions. In obstetrics this molecule is determinant in the physiology of labor and cervical ripening; it possibly plays a fundamental role in the etiology of preeclampsia and intrauterine growth restriction, and it could also be utilized in view of its ability to induce smooth muscle relaxation. Several clinical trials have ascertained the ability of the topical application of NO donors to promote cervical ripening, and also labor induction. There is much less evidence on the use of NO donors in the vascular complications of pregnancy, either as prophylactics or therapeutic agents. Due to the capacity of NO to promote relaxation of smooth muscle, NO donors have been employed as tocolytics with performance similar to other agents. Moreover, although anecdotal, the experience of sudden uterine relaxation using NO donors in obstetric emergencies remains of great clinical value.

Reduced Nitric Oxide in Amniotic Fluid of Patients with Chorioamnionitis

OBJECTIVE

Levels of nitric oxide (NO) and cytokines were assessed in amniotic fluid obtained from patients with severe chorioamnionitis (CAM) and appropriate controls.

METHODS

Amniotic fluid was obtained from 12 patients with CAM (17-24 weeks of gestation) and 89 patients undergoing diagnostic amniocentesis (16-18 weeks of gestation). The concentrations of NO, interleukin-6 (IL-6), and leukocyte elastase (LE) in amniotic fluid were then measured and compared.

RESULTS

The concentrations of NO, IL-6, and LE were all higher in CAM cases than in normal pregnant women. Furthermore, an inverse correlation between NO and LE was suggested in the CAM group.

CONCLUSIONS

These results indicate that in severe CAM, the action of NO might be reduced, not only due to blockage of action but also by degradation, despite increased production.

Urinary cyclic guanosine 3',5'-monophosphate and cyclic adenosine 3',5'-monophosphate changes in spontaneous and induced onset active labor

BACKGROUND

The aim of this prospective, randomized study was to investigate the changes in urinary cyclic guanosine 3',5'-monophosphate (cGMP) and cyclic adenosine 3',5'-monophosphate (cAMP) between the latent and the active phases of spontaneous and prostaglandin E(1) (PGE(1))-induced labor.

METHODS

Seventy singleton pregnant women at 36-41(+) weeks' gestation without signs of fetal distress were enrolled. The first group consisted of 35 pregnant women in whom labor was induced by PGE(1) applied intravaginally. The second group consisted of 35 women who had spontaneous active labor. Clinical data of the two groups were assessed as labor progressed.

RESULTS

After the onset of active labor, urinary cGMP/creatinine (U cGMP/Cr) decreased in both groups with the percentage decline of 35.2 and 9.7, respectively, but this difference was only significant in the PGE(1)-induced group (P=0.033). After the onset of active labor, urinary cAMP/creatinine (U cAMP/Cr) decreased in both groups with the percentage decline of 36.5 and 15.6, respectively, but this difference was only significant in the PGE(1)-induced group (P=0.001). The duration of the latent phase was significantly shortened in the PGE(1)-induced group compared with the spontaneous labor group (P<0.05).

CONCLUSIONS

Decreased U cGMP/Cr and U cAMP/Cr may be a transition from the latent to the active phase in PGE(1)-induced labor. Our results suggest that U cGMP/Cr and U cAMP/Cr can serve as easily obtained secondary messenger markers of myometrial contractility and cervical ripening at the onset of active labor. The NO-cGMP system and the G-protein alpha-cAMP system in the human uterus may concomitantly contribute to uterine quiescence during pregnancy and show downregulation in U cGMP/Cr and U cAMP/Cr at the initiation of active labor.

Nitric oxide donor-induced inhibition of pregnant rat uterine spontaneous contractile activity and release of nitric oxide from uterus measured by microdialysis

Our aim was to study whether nitric oxide (NO) donor-induced inhibition of pregnant rat myometrium contractility correlates with the release of NO. Uterine rings from mid-pregnant and late pregnant Sprague-Dawley rats were used for isometric tension recording. Concentration-response relationships to sodium nitroprusside (SNP), nitroglycerine (NTG) and diethylamine (DEA)/NO were assessed. The time course of NO release after addition to the organ chambers of the 3 NO-donors was assessed by the detection of NO products NOx (NO3+NO2) using the microdialysis probe by a HPLC-NO detector system. DEA/ NO induced greater inhibition of the spontaneous contractile activity of uterine rings from mid-pregnant rats than SNP or NTG. In uterine rings from late pregnant rats, however, the maximal inhibition of the contractility by all 3 NO-donors were significantly less. The NOx levels measured in the uterine ring walls from either mid-pregnant or late pregnant rats significantly increased after DEA/ NO as compared to the basal levels or the levels after NTG or SNP. The decrease of NO-donor-induced inhibition of rat myometrium contractility, with unchanged formation of NOx, at term, suggests that the changes in NO signaling are responsible for gestational age-dependent attenuation of the inhibitory effect.

Expression of iNOS mRNA and inhibitory effect of NO on uterine contractile activity in rats are determined by local rather than systemic factors of pregnancy

Our purpose was to investigate whether the local or systemic factors of pregnancy are associated with inducible nitric oxide synthase (iNOS) mRNA expression and to determine the inhibitory effects of pharmacological agents that increase cGMP levels in rat myometrium. iNOS mRNA expression was determined in uterine tissues from nonpregnant rats and on day 17 of gestation in the pregnant and non-pregnant uterine horns by RT-PCR. In addition, uterine rings from the pregnant and non-pregnant uterine horns were placed in Krebs-Henseleit solution for isometric recordings of spontaneous contractions. Concentration-inhibition relationships to diethylamine/nitric oxide complex, 8-bromo-cGMP, and the selective phosphodiesterase V inhibitor were obtained. Compared to nonpregnant rats, expression of iNOS mRNA in myometrium increased during pregnancy, which was maximal on day 17, followed by a decrease on day 21 of gestation. Expression of iNOS mRNA at day 17 of gestation was greater in pregnant uterine horns than in nonpregnant ones. Maximal inhibition of phosphodiesterase V and increasing cGMP induced similar inhibition of spontaneous contractions in nonpregnant and pregnant uterine horns, while NO induced less inhibition in the former. The results suggest that the local pregnancy factor is needed for signal transduction from NO to soluble guanylate cyclase at a time when maximal expression of iNOS mRNA is evident.

Fetal hemodynamic changes after amniotomy

BACKGROUND

The aim of the study was to assess fetal vascular blood flow after amniotomy.

METHODS

This was a prospective observational study. Thirty-five women with singleton pregnancy beyond 36 weeks of gestation, who underwent amniotomy, were recruited. The pulsatility indices of the fetal middle cerebral artery (MCA), the renal artery, and the ductus venosum were measured before and 30 min following amniotomy. The changes in pulsatility index were compared by means of Wilcoxon signed rank test.

RESULTS

There was a significant reduction in pulsatility indices of the MCA (median reduction: 0.23; interquantile range (IQR): -0.04, 0.4) and the renal artery (median reduction: 0.12; IQR: -0.12, 0.54) after amniotomy. However, there was no obvious change in the ductus venosum (median reduction: 0.00; IQR: -0.06, 0.1).

CONCLUSIONS

Amniotomy is associated with significant reduction in the impedance of the fetal MCA and the renal artery. The former may be a result of fetal stress response and the latter could be related to the release of vasoactive substances after amniotomy.

Oxytocin Modulates Nitric Oxide Generation by Human Fetal Membranes at Term Pregnancy

PROBLEM

Nitric oxide (NO), an important mediator of the inflammatory response, is involved in several reproductive processes including pregnancy and labor. Uterus, placenta and fetal membranes are significant sources of NO. Presently, there is no information on factors regulating NO production by fetal membranes.

METHOD OF STUDY

Human fetal membranes at term gestation were cultured for 24 hr in the presence of oxytocin. The concentrations of NO metabolites nitrites in culture medium were determined by the Griess reaction. The presence of inducible nitric oxide synthase (iNOS) was determined by reverse transcriptase-polymerase chain reaction and Western blot.

RESULTS

Oxytocin increased nitrite release by fetal membranes. Messenger ribonucleic acid iNOS expression was also enhanced by oxytocin. These effects were more marked in tissues obtained after labor than before labor.

CONCLUSIONS

Oxytocin exerts an overall stimulatory effect on NO release by fetal membranes. This action might be of relevance in the biomolecular processes leading to parturition.

Expression of inducible nitric oxide synthase messenger RNA, but not guanylate cyclase messenger RNA, depends on gestational age in rat myometrium

We studied the expression of inducible nitric oxide (NO) synthase (iNOS) and soluble guanylate cyclase (sGC) mRNAs in pregnant rat myometrium. Expression of iNOS and sGC alpha1, beta1 and beta2 mRNA was analyzed in non-pregnant and pregnant (days 10, 14, 17 and 21) Wistar rats by reverse transcription-polymerase chain reaction. Expression of iNOS mRNA increased during pregnancy but decreased on day 21 of gestation. Expression of GC alpha1 mRNA was greater than GC beta1 mRNA at all time points. Expression of uterine GC alpha1 and GC beta1 mRNA did not change significantly during pregnancy and did not differ significantly from non-pregnant levels. The values of sGC beta2 mRNA were below the limit of detection. In conclusion, the expression of iNOS mRNA increased during pregnancy in the myometrium and decreased at term, while the expression of sGC mRNA was not affected by pregnancy. Thus, it is the changes in NO production, rather than changes in its target, that are responsible for uterine quiescence during pregnancy and initiation of labor.

Urinary nitric oxide metabolite changes in spontaneous and induced onset active labor

BACKGROUND

The aim of this prospective, randomized study was to investigate the changes in urinary nitric oxide (NO) metabolite between the latent and the active phases of spontaneous and either prostaglandin E(1) (PGE(1)) or prostaglandin E(2) (PGE(2))-induced labors.

METHODS

Eighty-eight singleton pregnant women at 36-41(+) weeks' gestation without signs of fetal distress were enrolled. The first group consisted of 29 pregnant women in whom labor was induced by PGE(1) applied intravaginally. The second group consisted of 29 pregnant women with labor induced by PGE(2) applied intracervically. The third group consisted of 30 women, who had spontaneous active labor. Clinical data of the three groups were assessed as labor progressed.

RESULTS

Urinary nitric oxide/creatinine (U NO/Cr) decreased significantly after the onset of active labor in all three groups (p < 0.005), with the percentage decline of 42.2%, 28.6% and 10.1%, respectively. The magnitude of the difference in decline in U NO/Cr after active labor between the PGE(1)-induced and the spontaneous labor group was significantly reduced (p = 0.0047) after adjustment for potential confounders using the generalized estimating equations test (GEE). The duration of the latent phase was significantly shortened in the PGE(1)-induced group as compared with the spontaneous labor group (p < 0.01).

CONCLUSIONS

Decreased U NO/Cr may facilitate transition from the latent to the active phase either in spontaneous or induced labors. Our results indicate that U NO/Cr can serve as an easily obtained marker for use in controlling myometrial contractility and cervical ripening at the onset of active labor. The nitric oxide system is present in the human uterus and may contribute to uterine quiescence during pregnancy and show down-regulation in U NO/Cr at the initiation of active labor.

The retained placenta

The retained placenta is a significant cause of maternal mortality and morbidity throughout the developing world. It complicates 2% of all deliveries and has a case mortality rate of nearly 10% in rural areas. Ultrasound studies have provided fresh insights into the mechanism of the third stage of labour and the aetiology of the retained placenta. Following delivery of the baby, the retro-placental myometrium is initially relaxed. It is only when it contracts that the placenta shears away from the placental bed and is detached. This leads to its spontaneous expulsion. Retained placenta occurs when the retro-placental myometrium fails to contract. There is evidence that this may also occur during labour leading to dysfunctional labour. It is likely that this is caused by the persistence of one of the placental inhibitory factors that are normally reduced prior to the onset of labour, possibly progesterone or nitric oxide. Presently, the only effective treatment is manual removal of placenta (MROP) under anaesthetic. This needs to be carried out within a few hours of delivery to avoid haemorrhage. For women in rural Africa, facilities for MROP are scarce, leading to high mortality rates. Injection of oxytocin into the umbilical vein has been suggested as an alternative. This method relies on the injected oxytocin passing through the placenta to contract the retro-placental myometrium and cause its detachment. Despite several placebo controlled trials of this technique, no firm conclusion have been reached regarding its efficacy. This may be due to inadequate delivery of the oxytocin to the placenta. Further trials are in progress to assess the optimal dose of oxytocin as well as the efficacy of a new technique designed to improve delivery of the oxytocin to the placental bed.

Nitric oxide-mediated arachidonic acid release from perifused Venus verrucosa oocytes

This study was undertaken in order to investigate the possible interactions between nitric oxide and arachidonic acid (AA) in Venus verrucosa oocytes. We perifused isolated oocytes to determine the effect of the following substances on [3H]arachidonic acid release ([3H]AA): (1) A 23187, a calcium ionophore; (2) nitric oxide (NO) donors; (3) 1,1,1-trifluoromethyl-6,9,12,15 heicosatetraen-2-one (AACOCF(3)), a specific phospholipase A(2) (PLA(2)) inhibitor; (4) [5'-hydroxymethyl-2'-furyl]-1-benzyl indazole (YC-1) and 1H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one (ODQ), specific soluble guanylyl cyclase activator and inhibitor, respectively; (5) L-arginine, the substrate of nitric oxide synthase; (6) L-nitroarginine methyl esther (L-NAME), an inhibitor of nitric oxide synthase. Our results demonstrated that: (a) the calcium ionophore dose-dependently increased [3H]arachidonic acid release; (b) the NO donors sodium nitroprusside (SNP) and linsidomine (SIN-1) highly increased [3H]arachidonic acid output, while S-nitroso-N-acetylpenicillamine (SNAP) was without effect; (c) AACOCF(3) completely blocked the [3H]arachidonic acid release induced by SNP and SIN-1; (d) YC-1 increased [3H]arachidonic acid release, while ODQ completely counteracted SNP response; (e) [3H]arachidonic acid output was also increased by L-arginine; (f) a similar effect was, paradoxically, obtained in the presence of L-NAME. Furthermore, using RT-PCR we demonstrated in the same cells the presence of a nitric oxide synthase (NOS) mRNA, whose expression was not modulated by interleukin 1beta (IL-1beta). These results demonstrate the presence of a both calcium-dependent and NO-sensitive PLA(2) and of nitric oxide synthase in V. verrucosa oocytes. Our data also suggest a co-action of the two pathways in the control of reproduction in this bivalve.

Effect of nitric oxide on arachidonic acid release from human amnion-like WISH cells

In order to clarify the possible interactions between nitric oxide (NO) and arachidonic acid (AA) pathways, human amnion-like WISH cells were perifused to measure the effects of the following substances on [(3)H]arachidonic acid release: (1) sodium nitroprusside (SNP), a nitric oxide donor; (2) 1,1,1-trifluoromethyl-6,9,12,15-heicosatetraen-2-one, a cytosolic phospholipase A(2) (cPLA(2)) inhibitor; (3)L -arginine, the substrate of nitric oxide synthase (NOS); (4) 3-(5'-Hydroxymethyl-2'-furyl)-1-benzylindazole and 1H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one, activator and inhibitor of soluble guanylyl cyclase, respectively; (5) a membrane-permeable non-hydrolyzable analogue of guanosine-3',5'-cyclic monophosphate (cGMP). Furthermore, the effect of SNP on prostaglandin E(2) (PGE(2)) release was tested. Exogenous and endogenous NO, as well as the guanylyl cyclase activator and cGMP analogue, significantly increased [(3)H]arachidonic acid release. Both soluble guanylyl cyclase and PLA(2) inhibitors counteracted SNP response. Exogenous NO increased PGE(2) release, although to a much lesser degree compared with arachidonic acid release. Our results indicate that NO stimulates AA release in WISH cells by activating PLA(2) through a cyclic GMP-dependent mechanism.

New developments in the management of preterm labor

Current management of preterm labor has not changed the incidence of preterm delivery; therefore, significant research effort has been concentrated on the search for new methods of management. New tocolytics like inhibitors of cyclooxygenase 2 and nitric oxide donors have been tested in animal models and in preliminary clinical trials with promising results. Inhibition of cervical ripening may be one alternative to tocolysis. This new approach has a potential to be a valuable method of management of preterm labor if human studies confirm the promising results reported in animals. Growing evidence suggests that premature delivery may be associated with infection or fetal growth abnormalities, with dire consequences to the fetus. If these associations are to be included in risk and benefit assessment, then inhibition of preterm labor may prove to be detrimental to the fetus.

Vaginal application of the nitric oxide donor isosorbide mononitrate for preinduction cervical ripening: a randomized controlled trial to determine effects on maternal and fetal hemodynamics

OBJECTIVE

Our aim was to assess the effects of vaginally administered isosorbide mononitrate (a nitric oxide donor) on maternal and fetal hemodynamics in pregnant women at term.

STUDY DESIGN

We conducted a randomized controlled trial. Women were randomly selected to receive vaginally administered isosorbide mononitrate, 20 mg (n = 13) or 40 mg (n = 11), or to undergo a vaginal examination only (n = 12). Maternal pulse, blood pressure, and fetal heart rate were recorded at baseline and then every 30 minutes until 360 minutes. Umbilical artery resistance index and pulsatility index measurements were performed at 0, 180, and 330 minutes.

RESULTS

Maternal pulse rate was greater after the administration of isosorbide mononitrate, 20 or 40 mg, compared with the pulse rate in the vaginal examination-only group (greatest difference in means, 21 beats/min; P <.01). Maternal systolic and diastolic blood pressures were greater in the 20-mg and 40-mg isosorbide mononitrate groups than in the vaginal examination-only group (greatest difference in mean systolic and diastolic blood pressure, 15 and 16 mm Hg, respectively; P <.02 and P <.001, respectively). Fetal heart rate was greater in the 40-mg isosorbide mononitrate group than in either the 20-mg isosorbide mononitrate group or the vaginal examination-only group (difference in mean, 15 beats/min; P <.05). No woman required treatment for maternal or fetal tachycardia or maternal hypotension. Neither dose of isosorbide mononitrate had a significant effect on umbilical artery resistance or pulsatility index.

CONCLUSIONS

Vaginal administration of 20 or 40 mg isosorbide mononitrate to pregnant women at term has an effect on both maternal and fetal hemodynamics, but this effect is not clinically significant.