Effects of cooling and warming on 5-hydroxytryptamine- and acetylcholine-induced contractions of human umbilical vessels: role of nitric oxide

Prostacyclin Synthase Deficiency Leads to Exacerbation or Occurrence of Endothelium-Dependent Contraction and Causes Cardiovascular Disorders Mainly via the Non-TxA2 Prostanoids/TP Axis

BACKGROUND

Prostaglandin I2 synthesized by endothelial COX (cyclooxygenase) evokes potent vasodilation in some blood vessels but is paradoxically responsible for endothelium-dependent constriction (EDC) in others. Prostaglandin I2 production and EDC may be enhanced in diseases such as hypertension. However, how PGIS (prostaglandin I2 synthase) deficiency affects EDC and how this is implicated in the consequent cardiovascular pathologies remain largely unknown.

METHODS

Experiments were performed with wild-type, Pgis knockout (Pgis-/-) and Pgis/thromboxane-prostanoid receptor gene (Tp) double knockout (Pgis-/-Tp-/-) mice and Pgis-/- mice transplanted with unfractionated wild-type or Cox-1-/- bone marrow cells, as well as human umbilical arteries. COX-derived prostanoids were measured by high-performance liquid chromatography-mass spectrometry. Vasomotor responses of distinct types of arteries were assessed by isometric force measurement. Parameters of hypertension, vascular remodeling, and cardiac hypertrophy in mice at different ages were monitored.

RESULTS

PGF2α, PGE2, and a trace amount of PGD2, but not thromboxane A2 (TxA2), were produced in response to acetylcholine in Pgis-/- or PGIS-inhibited arteries. PGIS deficiency resulted in exacerbation or occurrence of EDC ex vivo and in vivo. Endothelium-dependent hyperpolarization was unchanged, but phosphorylation levels of eNOS (endothelial nitric oxide synthase) at Ser1177 and Thr495 were altered and NO production and the NO-dependent relaxation evoked by acetylcholine were remarkably reduced in Pgis-/- aortas. Pgis-/- mice developed high blood pressure and vascular remodeling at 16 to 17 weeks and subsequently cardiac hypertrophy at 24 to 26 weeks. Meanwhile, blood pressure and cardiac parameters remained normal at 8 to 10 weeks. Additional ablation of TP (TxA2 receptor) not only restrained EDC and the downregulation of NO signaling in Pgis-/- mice but also ameliorated the cardiovascular abnormalities. Stimulation of Pgis-/- vessels with acetylcholine in the presence of platelets led to increased TxA2 generation. COX-1 disruption in bone marrow-derived cells failed to affect the development of high blood pressure and vascular remodeling in Pgis-/- mice though it largely suppressed the increase of plasma TxB2 (TxA2 metabolite) level.

CONCLUSIONS

Our study demonstrates that the non-TxA2 prostanoids/TP axis plays an essential role in mediating the augmentation of EDC and cardiovascular disorders when PGIS is deficient, suggesting TP as a promising therapeutic target in diseases associated with PGIS insufficiency.

Neonatal Outcomes of Water Delivery versus Land Delivery: A Retrospective Propensity Score Weighted Study

OBJECTIVE

Recent evidence has shown that water delivery is safe for the mother, but high-quality evidence is not available for the newborn. Therefore, obstetric guidelines do not support it. This retrospective study aimed to contribute to the available evidence on maternal and neonatal outcomes associated with water delivery.

STUDY DESIGN

Retrospective cohort study from prospectively collected birth registry data from 2015 to 2019. A total of 144 consecutive water deliveries and 265 land deliveries eligible for waterbirth were identified. The inverse probability of treatment weighting (IPTW) method was applied to address for confounders.

RESULTS

We identified 144 women who delivered in water (water group) and 265 women who delivered on land (land group). One (0.7%) neonatal death was observed in the water delivery group. After IPTW adjustment, water delivery was significantly associated with a higher risk of maternal fever in puerperium (odds ratio [OR]: 4.98; 95% confidence interval [CI]: 1.86-17.02; p = 0.004), of neonatal cord avulsion (OR: 20.73; 95% CI: 2.63-2,674; p = 0.001), and of positive neonatal C-reactive protein (CRP > 5 mg/L; OR: 2.59; 95% CI: 1.05-7.24; p = 0.039); delivering in water was associated with lower maternal blood loss (mean difference: 110.40 mL; 95% CI: 191.01-29.78; p = 0.007), a lower risk of major (≥1,000 mL) postpartum hemorrhage (OR: 0.96; 95% CI: 0.92-0.99; p = 0.016), lower risk of manual placenta delivery (OR: 0.18; 95% CI: 0.03-0.67; p = 0.008) and curettage (OR: 0.24; 95% CI: 0.08-0.60; p = 0.002), lower use of episiotomy (OR: 0.02; 95% CI: 0-0.12; p < 0.001), and lower risk of neonatal ward admission (OR: 0.35; 95% CI: 0.25-0.48; p < 0.001).

CONCLUSION

The present study showed that differences are present between water and land delivery, and among them is the risk of cord avulsion, a severe and potentially fatal event. In women choosing to deliver in water, a trained staffmust be present and immediate recognition of cord avulsion is key for a prompt management to avoid possible serious complications.

KEY POINTS

· High-quality evidence is not available for neonatal safety of waterbirth; therefore, retrospective studies still represent the main body of evidence.. · Differences are present between water and land delivery, and among them, the increased risk of cord avulsion is a potentially fatal event.. · A trained staff must assist women who chose to deliver in water and cord avulsion must be promptly recognized and managed to avoid severe neonatal complications..

Placental gas exchange during amniotic carbon dioxide insufflation in sheep

OBJECTIVE

Insufflation of the amniotic cavity with carbon dioxide (CO₂ ) is used clinically to improve visibility during complex fetoscopic surgery. Insufflation with heated, humidified CO₂ has recently been shown to reduce fetal hypercapnia and acidosis in sheep, compared with use of cold and dry CO₂ , but the underlying mechanisms are unclear. The aim of this study was to investigate whether differences in placental CO₂ and oxygen (O₂ ) exchange during insufflation with heated and humidified vs cold and dry CO₂ could explain these findings.

METHODS

Thirteen fetal lambs at 105 days of gestation (term, 146 days) were exteriorized partially, via a midline laparotomy and hysterotomy, and instrumented with an umbilical artery catheter, an umbilical vein catheter and a common umbilical vein flow probe. Arterial and venous catheters and flow probes were also inserted into the maternal uterine circulation. Six ewes were insufflated with cold, dry CO₂ (22°C; 0-5% humidity) and seven with heated, humidified CO₂ (40°C; 95-100% humidity) at 15 mmHg for 180 min. Blood-flow recordings and paired arterial and venous blood gases were sampled from uterine and umbilical vessels. Rates of placental CO₂ and O₂ exchange were calculated.

RESULTS

After 180 min of insufflation, fetal survival was 33% (2/6) using cold, dry CO₂ and 71% (5/7) using heated, humidified CO₂ . By 120 min, fetuses insufflated with heated, humidified CO₂ had lower arterial CO₂ levels and higher arterial pH compared to those insufflated with cold, dry gas. Insufflation decreased significantly placental gas exchange in both groups, as measured by rates of both (i) fetal CO₂ clearance and O₂ uptake and (ii) maternal O₂ delivery and CO₂ uptake from the fetal compartment.

CONCLUSIONS

Lower arterial CO₂ and higher pH levels in fetuses insufflated with heated and humidified, compared to cold and dry, CO₂ could not be explained by differences in placental gas exchange. Instead, heated and humidified insufflation appeared to reduce fetal CO₂ absorption from the uterus, supporting its use in preference to cold, dry CO₂ . © 2019 International Society of Ultrasound in Obstetrics and Gynecology.

Moderate hypothermia and responses to calcium channel blockers - Role of the nitric oxide

Moderate hypothermia (25-31 °C) may have a significant influence on vascular tone. At present, very little is known about the role of endothelial nitric oxide on the hypothermia-induced responses. In this study, we investigated the effect of hypothermia (to 28 °C) on the vasodilatation induced by verapamil, a phenylalkylamine calcium channel blocker (10^-9-3 × 10^-4 M) and dihydropyridines, amlodipine (10^-9-3 × 10^-4 M), and benidipine (10^-9-10^-3 M) on 5-hydroxytryptamine (5-HT or serotonin) precontracted calf cardiac veins. Furthermore, the role of nitric oxide in the hypothermia-induced responses was analyzed. Ring preparations of veins obtained from calf hearts were suspended in organ baths containing 15 ml of Krebs-Henseleit solution, maintained at 37 °C, and continuously gassed with 95% O₂-5% CO₂. After a resting period, verapamil, amlodipine, and benidipine were applied cumulatively on serotonin (10^-6 M) precontracted calf cardiac vein rings and induced concentration-dependent relaxations. In another part of the study, the medium temperature was decreased to 28 °C after the preparations were contracted with 5-HT, then cumulative concentrations of verapamil, amlodipine, or benidipine were added. During hypothermia, the pIC₅₀ value, but not the maximal response, to all blockers were significantly higher than at 37 °C. Hypothermia in the presence of N^G-nitro-l-arginine methyl ester (L-NAME, 10^-4 M) decreased the pIC₅₀ and E_max values to verapamil, amlodipine, and benidipine. Only one blocker was tested in each preparation. These results suggest that nitric oxide may play a role in the hypothermia-induced changes in vasodilation caused by verapamil, amlodipine, and benidipine in calf cardiac vein, but further research is needed to explain the complete mechanism.

Role of the nitric oxide on relaxation of the human umbilical artery during cooling

In the present study, the effects of cooling (to 28°C) on the vasodilatation induced by diazoxide (10(-9)-3×10(-4) M), isoproterenol (10(-9)-3×10(-4) M) and magnesium sulphate (0.1-30 mM) on serotonin-pre-contracted human umbilical artery and the role of nitric oxide in these effects were analyzed. Diazoxide, isoproterenol and magnesium produced concentration-dependent relaxation of human umbilical artery precontracted with serotonin (10(-6) M). During cooling, the pIC(50) values and maximal responses to these agents were significantly lower than at 37°C. Cooling to 28°C in the presence of N(G)-nitro-L-arginine methyl ester (L-NAME, 10(-4) M) did not modify the effects of temperature on diazoxide, isoproterenol and magnesium-induced relaxations. These results suggest that cooling-induced changes of diazoxide, isoproterenol, and magnesium sulphate in human umbilical artery are independent of nitric oxide.