Mechanisms underlying maternal venous adaptation in pregnancy

Placental protein 13 dilation of pregnant rat uterine vein is endothelium dependent and involves nitric oxide/calcium activated potassium channels signals

INTRODUCTION

Accumulating evidence demonstrates the importance of the galectin protein Placental Protein 13 (PP13) in predicting Preeclampsia (PE), a gestational disorder that has no cure and is associated with a compromised uterine vascular adaptation to pregnancy. Uterine vasculature undergoes significant remodeling (growth in length and in circumference) during normal pregnancy to accommodate the increased blood volume to the feto-placental unit. The aim of this study was to demonstrate the role of PP13 on the uterine veins (UVs).

METHODS

PP13 was tested on UVs isolated from rat by using a pressurized myograph. The PP13 investigation was carried out in the presence of: a) nitric oxide synthases inhibitors (l-NAME + L-NNA, 2 x 10^-4 M); b) small conductance Ca²⁺-activated K⁺ channels (SK_ca) inhibitor (Apamin, 10^-7 M); c) intermediate conductance Ca²⁺-activated K⁺ channels (IK_ca) inhibitor (TRAM-34, 10^-5 M); d) big conductance Ca²⁺-activated K⁺ channels (BK_ca) inhibitor (Paxilline, 10^-5 M) and in the absence of endothelium.

RESULTS

Our results showed that in late pregnancy, PP13 induced a significant dilation of UVs that is endothelium dependent. Further, PP13-dilation is mediated by the SKca - NO - BKca pathway.

DISCUSSION

For the first time, this study provides evidence that in pregnancy, the UVs are dilated by PP13 and suggests SK_Ca as a potential target for treatments aimed at restoring pregnancy complication associated with deficiency in uterine adaptation.

Monocytes from preeclamptic women previously treated with silibinin attenuate oxidative stress in human endothelial cells

Objective: To investigate whether the supernatant from monocytes of preeclamptic and normotensive pregnant women, cultured in vitro with silibinin, can modulate oxidative stress in HUVEC.Methods: Concentrations of IL-1β, IL-10, and TNF-α in monocyte culture supernatants were determined by ELISA. HUVEC and their supernatant cultures were employed for determination of NO, nitrite and nitrate, lipid peroxidation, and hemeoxygenase-1 (HO-1).Results: HUVEC treatment with supernatant of preeclamptic monocytes cultured with silibinin produced increased levels of nitrite, reduced lipid peroxidation, and increased HO-1.Conclusion: Supernatant of monocytes from preeclamptic women induce oxidative stress in HUVEC which can be reduced by silibinin treatment.Abbreviations: DAF-FM^TM, Diaminofluorescein-FM; EDTA, Ethylenediaminetetraacetic acid; HO-1, heme oxygenase-1; HPLC, high-performance liquid chromatography; HUVEC, human umbilical vein endothelial cell; MDA, malondialdehyde; NO, nitric oxide; NT, normotensive; PE, preeclampsia; ROS, reactive oxygen species; Sb, silibinin.

Peripartum clinical manifestations of a mesentericorenocaval shunt in a Burmese cat

Case summary

A 3-year-old entire female Burmese cat was presented for investigation of intermittent lethargy during gestation followed by persistent hypersalivation and ataxia postpartum. The cat had queened three litters in total, with clinical signs worsening during the most recent lactation period. Mild anaemia (26%), hypoglycaemia (2.4 mmol/l; reference interval [RI] 3.9–8.3 mmol/l) and increased postprandial serum bile acids (74 µmol/l; RI <25 µmol/l) were identified on initial bloodwork. Multiphase contrast-enhanced CT identified a mesentericorenocaval portosystemic shunt; this was attenuated surgically with an ameroid constrictor. Clinical signs resolved after surgery. Follow-up 3 months postoperatively revealed normal pre- and postprandial serum bile acids (2 µmol/l and 3 µmol/l, respectively) with repeat CT identifying evidence of shunt attenuation. The cat continued to be healthy and free of clinical signs 12 months postoperatively.

Relevance and novel information

Mesentericorenocaval portosystemic shunt morphology has not been previously reported in the cat and should be considered as a differential diagnosis for cats presenting with peripartum onset of malaise, ptyalism or ataxia.

Maternal Venous Hemodynamic Dysfunction in Proteinuric Gestational Hypertension: Evidence and Implications

This review summarizes current knowledge from experimental and clinical studies on renal function and venous hemodynamics in normal pregnancy, in gestational hypertension (GH) and in two types of preeclampsia: placental or early-onset preeclampsia (EPE) and maternal or late-onset (LPE) preeclampsia, presenting at <34 weeks and ≥34 weeks respectively. In addition, data from maternal venous Doppler studies are summarized, showing evidence for (1) the maternal circulation functioning closer to the upper limits of capacitance than in non-pregnant conditions, with intrinsic risks for volume overload, (2) abnormal venous Doppler measurements obtainable in preeclampsia, more pronounced in EPE than LPE, however not observed in GH, and (3) abnormal venous hemodynamic function installing gradually from first to third trimester within unique pathways of general circulatory deterioration in GH, EPE and LPE. These associations have important clinical implications in terms of screening, diagnosis, prevention and management of gestational hypertensive diseases. They invite for further hypothesis-driven research on the role of retrograde venous congestion in the etiology of preeclampsia-related organ dysfunctions and their absence in GH, and also challenge the generally accepted view of abnormal placentation as the primary cause of preeclampsia. The striking similarity between abnormal maternal venous Doppler flow patterns and those observed at the ductus venosus and other abdominal veins of the intra-uterine growth restricted fetus, also invites to explore the role of venous congestion in the intra-uterine programming of some adult diseases.

The Piezo1 cation channel mediates uterine artery shear stress mechanotransduction and vasodilation during rat pregnancy

During mammalian pregnancy, the uterine circulation must undergo substantial vasodilation and growth to maintain sufficient uteroplacental perfusion. Although we and others have shown that nitric oxide (NO) is a key mediator of these processes, the mechanisms that augment uterine artery NO signaling during gestation have not been identified. We hypothesized that Piezo1, a recently discovered cation channel, may be involved in the process of shear stress mechanotransduction, as other studies have shown that it is both mechanosensitive and linked to NO production. Surprisingly, there are no studies on Piezo1 in the uterine circulation. Our aims in the present study were to determine whether this novel channel is 1) present in uterine arteries, 2) regulated by gestation, 3) functionally relevant (able to elicit rises in intracellular Ca²⁺ concentration and vasodilation), and 4) linked to NO. Immunohistochemistry confirmed that Piezo1 is present in uterine arteries, primarily but not exclusively in endothelial cells. Western blot analysis showed that its protein expression was elevated during gestation. In pressurized main uterine arteries, pharmacological activation of Piezo1 by Yoda1 produced near maximal vasodilation and was associated with significant increases in intracellular Ca²⁺ concentration in endothelial cell sheets. Shear stress induced by intraluminal flow produced reversible vasodilations that were inhibited >50% by GsMTx-4, a Piezo1 inhibitor, and by N^ω-nitro-l-arginine methyl ester/ N^ω-nitro-l-arginine, inhibitors of NO synthase. These findings are the first to implicate a functional role for Piezo1 in the uterine circulation as a mechanosensor of endothelial shear stress. Moreover, our data demonstrate that Piezo1 activation leads to vasodilation via NO and indicate that its molecular expression is upregulated during pregnancy. NEW & NOTEWORTHY This is the first study to highlight Piezo1 in the uterine circulation. As a potentially important endothelial mechanosensor of shear stress, Piezo1 may be linked to mechanisms that support increased uteroplacental perfusion during pregnancy. Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/piezo1-mechanotransduction-in-the-uterine-circulation/ .

Placental protein 13 (PP13)-induced vasodilation of resistance arteries from pregnant and nonpregnant rats occurs via endothelial-signaling pathways

Placental protein 13 (PP13) induces hypotension in rats. This study aims to evaluate PP13 effects on isolated uterine arteries from nonpregnant and mid-pregnant rats. Vessels were isolated, cannulated, and pressurized to 50 mmHg within an arteriograph, preconstricted and exposed to increasing PP13 concentrations (10^-13-10^-8 M). PP13 elicited 38-50% arterial vasodilation with half-maximum response (EC₅₀) = 1 pM. The relaxation was mediated by activating the endothelial-signaling pathways of prostaglandin and nitric oxide (NO). Accordingly, these results encourage evaluation of PP13 as a possible therapy for gestational diseases characterized by insufficient uteroplacental blood flow and/or maternal hypertension.

Longitudinal changes in serum catecholamines, dopamine, serotonin, ACTH and cortisol in pregnant Spanish mares

Systemic physiological changes required for placental and fetal development during pregnancy are associated with an activation of the sympathetic nervous system (SNS) and the hypothalamus-pituitary-adrenal axis (HPA) in women, but this fact has not been investigated in mares. Venous blood samples were taken monthly from 31 successful Spanish mares during the 11months of pregnancy. During the first 4months of pregnancy, adrenaline (AD), dopamine (DOPA) and ACTH increases, whereas 5-hydroxitryptamine (5-HT) decreased, and noradrenaline (NAD) and cortisol (CORT) did not change. Serum NAD increased at 8th month, 5-HT at 5th, 7th months, and DOPA increased progressively between the 5th and 8th months and CORT concentrations peak at 5th month. During the three last months of pregnancy, NAD, 5-TH and DOPA decreased, particularly at the 11th month. These results confirmed an activation of the SNS and the HPA axis in pregnant mares during successful pregnancies. The next step would be to elucidate whether these changes also appear in unsuccessful pregnancies.

Impact of Immune Deficiency on Remodeling of Maternal Resistance Vasculature 4 Weeks Postpartum in Mice

Pregnancy manifests changes in the vascular and immune systems that persist postpartum (PP), have important implications for future pregnancies, and may modify responses to cardiovascular stress in late life. The association between immune and vascular function and the generation or progression of cardiovascular disease beg the question of whether altered immunity modifies pregnancy-induced changes in the vasculature. Our objective was to compare changes in the function and remodeling of systemic resistance vessels 4 weeks PP in normal C57BL/6 (B6), and immunodeficient mice recombinase 1-deficient/B6 ( Rag1^-/-). Immune deficiency did not change the responsiveness to acetylcholine (ACh) and phenylephrine at baseline but decreased arterial distensibility and increased stiffness PP. Adoptive transfer of CD8 T cells into Rag1^-/- mice decreased the response to ACh while increasing distensibility and wall thickness. When compared to PP Rag1^-/-, vessels from PP CD4-deficient mice, which have B cells and CD8 T cells, but no CD4 cells, show increased distensibility and decreased responsiveness to ACh in a pattern similar to that seen in Rag1^-/- given CD8 T cells prior to mating. These studies suggest a key role for T cell, particularly CD8 T cell, associated factors in the PP remodeling of maternal resistance vessels.

Impairments in microvascular function and skeletal muscle oxygenation in women with gestational diabetes mellitus: links to cardiovascular disease risk factors

AIMS/HYPOTHESIS

Gestational diabetes mellitus (GDM) is a risk factor for the development of endothelial dysfunction and cardiovascular disease. However, in vivo microvascular endothelial function in GDM has not been investigated. This study aimed to examine, using near-infrared spectroscopy (NIRS), whether: (1) there are differences in microvascular reactivity and skeletal muscle oxygen consumption (m[Formula: see text]) at rest and during exercise between GDM and uncomplicated pregnancies; and (2) there is an association of NIRS indices with macrovascular function and cardiovascular disease risk factors.

METHODS

Twenty-nine pregnant women (13 with GDM and 16 women with uncomplicated pregnancy, 28 ± 2 gestational weeks) underwent arterial stiffness (pulse wave velocity [PWV]) and 24 h ambulatory BP (24 h BP) evaluation. NIRS continuously monitored, non-invasively, changes in muscle oxygenated and deoxygenated haemoglobin and tissue O₂ saturation index (TSI, %) during arterial occlusion/reperfusion and intermittent handgrip exercise. m[Formula: see text] and vascular reactivity indices were calculated.

RESULTS

During occlusion and reperfusion, women with GDM exhibited slower TSI response (occlusion slope: -0.06 ± 0.02 vs -0.10 ± 0.04, in GDM and controls, respectively; reperfusion slope: 0.65 ± 0.26 vs 1.05 ± 0.41, respectively), lower m[Formula: see text] (1.3 ± 1.2 vs 3.8 ± 2.3 μmol l^-1 min^-1) and blunted hyperaemia (ΔTSI 6.8 ± 2.9 vs 9.5 ± 3.4) compared with controls (p < 0.01). Despite similar handgrip strength in the GDM and control groups (29.1 ± 8.1 vs 26.2 ± 10.4 kg, respectively), during repeated forearm contractions, women with GDM presented a blunted TSI response (6.5 ± 3.9 vs 19.2 ± 10.9; p < 0.01) and a reduced capacity to maintain the predetermined handgrip (23.4 ± 2.9 vs 27.4 ± 3.8%, p < 0.05). NIRS indices correlated with PWV, 24 h BP and blood glucose concentration earlier in pregnancy (r = 0.40-0.60; p < 0.05).

CONCLUSIONS/INTERPRETATION

Women with GDM exhibited a characteristic blunted TSI curve, showing alterations in muscle oxygenation and microvascular responsiveness compared with women with uncomplicated pregnancies. These alterations were manifested during exercise and possibly contribute to the reduced exercise tolerance in GDM. NIRS indices correlated with macrovascular indices (arterial stiffness) and 24 h BP.

Assessment of endothelial function in pregnant women with preeclampsia and gestational diabetes mellitus by flow-mediated dilation of brachial artery

PURPOSE

To compare endothelial function, as assessed by flow-mediated dilation (FMD) in pregnant women with preeclampsia (PE), gestational diabetes mellitus (GDM) and healthy pregnant women.

METHODS

We conducted a cross-sectional study of eighty women who were selected and divided into three groups: Group A comprising 42 pregnant women with PE, Group B (control) consisting of 19 normotensive pregnant women with no comorbidities and Group C consisting of 19 pregnant women with GDM. The women underwent FMD and the results were compared between groups. The data were obtained from the Center for Fetal Medicine, Hospital das Clínicas, Federal University of Minas Gerais, Brazil (CEMEFE-HC-UFMG) after approval by the Ethics and Research Committee on June 4, 2008 under no CAAE-0280.0.203.000-08.

RESULTS

Nonparametric variance analysis showed no statistically significant difference between the characteristics of the three groups. The comparison between the results of the mean values of brachial artery FMD groups of pregnant women with preeclampsia (FMD = 5.36 ± 4.61 %), gestational diabetes (FMD = 9,18 ± 5.98 %) and pregnant women in the control group (FMD = 17.55 ± 8.35 %) showed that a statistically significant difference was found between groups using the Dunn test. The comparison between groups PE × GDM was not statistically significant. The group consisting of pregnant women with GDM associated with those with PE had significantly lower results for FMD (6.55 ± 5.33 %) than the control group (17.55 ± 8.35 %, p = 0.00).

CONCLUSIONS

The group consisting of pregnant women with GDM or PE showed results for FMD significantly lower than the control group, suggesting possible endothelial injury in these patients.

Pregnancy causes diminished myogenic tone and outward hypotrophic remodeling of the cerebral vein of Galen

Pregnancy increases the risk of several complications associated with the cerebral veins, including thrombosis and hemorrhage. In contrast to the cerebral arteries and arterioles, few studies have focused on the effect of pregnancy on the cerebral venous side. Here, we investigated for the first time the effect of pregnancy on the function and structure of the cerebral vein of Galen in rats. Our major finding was that cerebral veins from late-pregnant (LP, n=11) rats had larger lumen diameters and thinner walls than veins from nonpregnant (NP, n=13) rats, indicating that pregnancy caused outward hypotrophic remodeling of the vein of Galen. Moreover, veins from NP animals had a small amount of myogenic tone at 10 mm Hg (3.9±1.0%) that was diminished in veins during pregnancy (0.8±0.3%; P<0.01). However, endothelium-dependent and -independent vasodilation of the veins was unchanged during pregnancy. Using immunohistochemistry, we show that the vein of Galen receives perivascular innervation, and that serotonergic innervation of cerebral veins is significantly higher in veins from LP animals. Outward hypotrophic remodeling and diminished tone of cerebral veins during pregnancy may contribute to the development of venous pathology through elevated wall tension and wall stress, and possibly by promoting venous blood stasis.

Hemodynamic, vascular, and reproductive impact of FMS-like tyrosine kinase 1 (FLT1) blockade on the uteroplacental circulation during normal mouse pregnancy

To investigate the role of FMS-like tyrosine kinase 1 (FLT1, also known as VEGFR1) signaling during pregnancy, mice were injected with anti-FLT1 neutralizing antibody (Ab) beginning on Gestational Day 8 or 12 and every other day thereafter until Day 18; vehicle-only injected mice served as controls. Uterine artery blood flow was measured with ultrasound on Days 13 and 18, and morphometric measurements of the uterine arcade were carried out on Day 19 to provide a measure of gestational vascular remodeling; reproductive performance was evaluated by determining litter size, resorption rates, and pup and placental weights. Ab injections beginning on Day 8 or Day 12 resulted in significant reductions of uterine artery peak systolic and diastolic flows at Days 13 and 18. In addition, normal reproductive function was compromised, as evidenced by a significant reduction in average number of viable pups along with enhanced resorption rates. Reproductive performance was also significantly compromised in this group, although less severely. There was no evidence of a reduction in main uterine artery diameters, though arterial distensibility was reduced, and the diameter of the main uterine vein was significantly smaller in the Ab-injected mice. Significant reductions in main uterine artery and segmental artery length were also noted. Placental and pup weights were similar in all the groups. FLT1 inhibition during murine pregnancy impaired blood flow to the fetal-placental unit, compromised several indices of vascular remodeling, reduced fecundity, and increased fetal reabsorptions. The effects of FLT1 inhibition are most pronounced when targeted during early pregnancy.