Differential responses of mesenteric arterial bed to vasoactive substances in L-NAME-induced preeclampsia: Role of oxidative stress and endothelial dysfunction

Upregulation of SEMP1 Contributes to Improving the Biological Functions of Trophoblast via the PI3K/AKT Pathway in Preeclampsia

Disturbance of extravillous trophoblast infiltration is associated with preeclampsia (PE), a severe condition of pregnancy characterized by hypertension and proteinuria. Senescence-associated epithelial membrane protein 1 (SEMP1), an integral membrane protein, is a vital component of tight junction strands in epithelial or endothelial cells, with no clear function reported in PE. Gene Expression Omnibus (GEO) datasets showed that SEMP1 expression was downregulated in the placental tissues of PE patients, which was confirmed by assessing SEMP1 levels in placental samples collected in our hospital. Furthermore, less SEMP1 was detected in cytokeratin 7 positive trophoblast cells in the spiral arteries of rat placentas post L-arginine methyl ester hydrochloride (L-NAME) treatment. Trophoblast cells acquired robust ability of proliferation, migration, and invasion when SEMP1 was overexpressed. Such capability was weakened in SEMP1-silenced cells. Trophoblast cells overexpressing SEMP1 secreted more vascular endothelial growth factor A (VEGFA), which facilitated the tube formation of human umbilical vein endothelial cells. Blockade of PI3K/AKT signaling transduction with LY294002 dampened the effects of SEMP1 on trophoblast cells. Collectively, we firstly indicated that SEMP1 inhibition is a potential driver for PE, which may be associated with the deactivation of the PI3K/AKT pathway.

Association between micronutrients, oxidative stress biomarkers and angiogenic growth mediators in early and late-onset preeclamptic Ghanaian women

Objectives

Micronutrients, especially calcium (Ca) and magnesium (Mg) are reported to reduce preeclampsia events via several factors such as endothelial cell control, optimal oxidative stress and a balanced angiogenic growth mediator. We evaluated the association of micronutrients with oxidative stress biomarkers, and angiogenic growth mediators in early-onset preeclampsia and late-onset preeclampsia.

Methods

This case-control study recruited 197 preeclampsia (early-onset preeclampsia = 70 and late-onset preeclampsia = 127) as cases and 301 normotensive pregnant women as controls from the Komfo Anokye Teaching Hospital, Ghana. Samples were collected after 20 weeks of gestation for both cases and controls and estimated for Ca, Mg, soluble fms-like tyrosine kinase-1, placental growth factor, vascular endothelial growth factor-A, soluble endoglin, 8-hydroxydeoxyguanosine, 8-epiprostaglandinF2-alpha and total antioxidant capacity.

Results

Early-onset preeclampsia women had significantly lower levels of Ca, Mg, placental growth factor, vascular endothelial growth factor-A and total antioxidant capacity but higher levels of soluble fms-like tyrosine kinase-1, soluble endoglin, 8-epiprostaglandinF2-alpha, 8-hydroxydeoxyguanosine, soluble fms-like tyrosine kinase-1/placental growth factor ratio, 8-epiprostaglandinF2-alpha /placental growth factor ratio, 8-hydroxydeoxyguanosine/placental growth factor ratio and soluble endoglin/placental growth factor ratio than late-onset preeclampsia and normotensive pregnant women (p < 0.0001). Among the early-onset preeclampsia women, the first and second quartile for serum placental growth factor, first quartile for vascular endothelial growth factor-A and total antioxidant capacity and the fourth quartiles for serum sEng, serum sFlt-1, 8-epiPGF2α and 8-OHdG were independently associated with low Ca and Mg (p < 0.05). Among late-onset preeclampsia women, the fourth quartile for soluble fms-like tyrosine kinase-1 was independently associated with low Ca and Mg (p < 0.05).

Conclusion

Magnesium and calcium are associated with an imbalance in angiogenic growth mediators and oxidative stress biomarkers among preeclampsia women, particularly early-onset preeclampsia. Serial and routine measurement of these micronutrients would allow the monitoring of poor placental angiogenesis while enabling an understanding of the triggers of increased oxidative stress and reduced antioxidant in preeclampsia.

Evidence of Nitric Oxide Impairment During Hypertensive Pregnancies

Hypertensive disorders of pregnancy complicate up to 10% of pregnancies worldwide, and they can be classified into (1) gestational hypertension, (2) preeclampsia, (3) chronic hypertension and (4) chronic hypertension with preeclampsia. Nitric oxide (NO) plays an essential role in the haemodynamic adaptations observed during pregnancy. It has been shown that the nitric oxide pathway's dysfunction during pregnancy is associated with placental- and vascular-related diseases such as hypertensive disorders of pregnancy. This review aims to present a brief definition of hypertensive disorders of pregnancy and physiological maternal cardiovascular adaptations during pregnancy. We also detail how NO signalling is altered in the (a) systemic vasculature, (b) uterine artery/spiral arteries, (c) implantation and (d) placenta of hypertensive disorders during pregnancy. We conclude by summarizing the anti-hypertensive therapy of hypertensive disorders of pregnancy as a specific management strategy.

Pathophysiology of Preeclampsia and L-Arginine/L-Citrulline Supplementation as a Potential Strategy to Improve Birth Outcomes

In preeclampsia, the shallow invasion of cytotrophoblast cells to uterine spiral arteries, leading to a reduction in placental blood flow, is associated with an imbalance of proangiogenic/antiangiogenic factors to impaired nitric oxide (NO) production. Proangiogenic factors, such as vascular endothelial growth factor (VEGF) and placental growth factor (PlGF), require NO to induce angiogenesis through antioxidant regulation mechanisms. At the same time, there are increases in antiangiogenic factors in preeclampsia, such as soluble fms-like tyrosine kinase type 1 receptor (sFIt1) and toll-like receptor 9 (TLR9), which are mechanism derivates in the reduction of NO bioavailability and oxidative stress in placenta.Different strategies have been proposed to prevent or alleviate the detrimental effects of preeclampsia. However, the only intervention to avoid the severe consequences of the disease is the interruption of pregnancy. In this scenario, different approaches have been analysed to treat preeclamptic pregnant women safely. The supplementation with amino acids is one of them, especially those associated with NO synthesis. In this review, we discuss emerging concepts in the pathogenesis of preeclampsia to highlight L-arginine and L-citrulline supplementation as potential strategies to improve birth outcomes. Clinical and experimental data concerning L-arginine and L-citrulline supplementation have shown benefits in improving NO availability in the placenta and uterine-placental circulation, prolonging pregnancy in patients with gestational hypertension and decreasing maternal blood pressure.

The L-NAME mouse model of preeclampsia and impact to long-term maternal cardiovascular health

Preeclampsia affects ∼2–8% of pregnancies worldwide. It is associated with increased long-term maternal cardiovascular disease risk. This study assesses the effect of the vasoconstrictor N(ω)-nitro-L-arginine methyl ester (L-NAME) in modelling preeclampsia in mice, and its long-term effects on maternal cardiovascular health. In this study, we found that L-NAME administration mimicked key characteristics of preeclampsia, including elevated blood pressure, impaired fetal and placental growth, and increased circulating endothelin-1 (vasoconstrictor), soluble fms-like tyrosine kinase-1 (anti-angiogenic factor), and C-reactive protein (inflammatory marker). Post-delivery, mice that received L-NAME in pregnancy recovered, with no discernible changes in measured cardiovascular indices at 1-, 2-, and 4-wk post-delivery, compared with matched controls. At 10-wk post-delivery, arteries collected from the L-NAME mice constricted significantly more to phenylephrine than controls. In addition, these mice had increased kidney Mmp9:Timp1 and heart Tnf mRNA expression, indicating increased inflammation. These findings suggest that though administration of L-NAME in mice certainly models key characteristics of preeclampsia during pregnancy, it does not appear to model the adverse increase in cardiovascular disease risk seen in individuals after preeclampsia.

Antihypertensive effect of Mali-Nil surin rice bran hydrolysate and its mechanisms related to the EDHF-mediated vasorelaxation and L-type Ca2+ channel-mediated vasoconstriction in L-NAME hypertensive rats

Mali-Nil Surin rice bran hydrolysate (MRH) contains highly nutritional proteins and beneficial phenolic compounds. This study investigated an antihypertensive effect of MRH and evaluated the mechanisms mediating this action in N^ω-nitro-L-arginine-methyl ester (L-NAME)-induced hypertensive rats. Antihypertensive activity was determined in male rats orally administered with MRH (100 or 300 mg/kg) or enalapril (15 mg/kg) daily together with L-NAME (50 mg/kg/day) in drinking water, for 21 days. Concurrent oral treatment with MRH lowered the high blood pressure in the L-NAME-induced hypertensive rats. MRH treatment improved endothelial function and increased the endothelium-derived hyperpolarizing factor-mediated vasorelaxation in L-NAME hypertensive rats. L-NAME rats treated with MRH had reduced adrenergic hypercontractility, which was associated with a decrease in L-type calcium channel-mediated vasoconstriction. In addition, MRH exhibited antioxidant activity in hypertensive rats, as indicated by suppression of vascular superoxide anion production and reduction of malondialdehyde levels, as well as magnification of superoxide dismutase and catalase activities in serum. This study demonstrated the nutraceutical potential of MRH to prevent oxidative stress-related vascular dysfunction in hypertension.

Ginsenoside Rg2 Ameliorates Brain Injury After Intracerebral Hemorrhage in a Rat Model of Preeclampsia

The incidence of maternal hemorrhagic stroke is elevated in women with preeclampsia during pregnancy. Panax ginseng is a traditional medicinal herb with numerous applications, and ginsenosides are the key bioactive compounds in Panax ginseng. This study aims to evaluate the effects of ginsenoside Rg2 on pregnancy outcomes and brain injury after intracerebral hemorrhage (ICH) in a rat model of preeclampsia. Preeclampsia was induced in rats by N(ω)-nitro-L-arginine methyl ester. Then, an ICH model was prepared by intrastriatal injection of bacterial collagenase. Ginsenoside Rg2 markedly elevated the survival ratio of fetuses. The placental and body weights were increased in the ginsenoside Rg2 group. Compared with the preeclampsia group, the Garcia test score of ginsenoside Rg2-treated rats was significantly increased. Ginsenoside Rg2 treatment ameliorated the ICH-induced augmentation of Evans blue extravasation, inhibited the ICH-induced elevation of brain water content, and reduced the interleukin-1β and tumor necrosis factor-α levels in the hemorrhagic hemisphere after ICH in preeclampsia model rats. Furthermore, ginsenoside Rg2 treatment not only inhibited augmentation of TLR-4, MyD88, p-IκBα, and p-NF-κB expression but also abated the reduction of occludin and claudin-5 expression in the hemorrhagic hemisphere. The findings indicated that ginsenoside Rg2 improved pregnancy outcomes in a rat model of preeclampsia without decreasing the blood pressure and urine protein level. The findings also demonstrated that ginsenoside Rg2 ameliorated ICH-induced neurological disorder and blood-brain barrier dysfunction in an animal model of preeclampsia by regulating the TLR4/NF-κB signaling pathway.

Fibroblast Growth Factor Type 2 (FGF2) Administration Attenuated the Clinical Manifestations of Preeclampsia in a Murine Model Induced by L-NAME

Background: In preeclampsia, a hypertensive disorder of pregnancy, the poor remodeling of spiral arteries leads to placental hypoperfusion and ischemia, provoking generalized maternal endothelial dysfunction and, in severe cases, death. Endothelial and placental remodeling is important for correct pregnancy evolution and is mediated by cytokines and growth factors such as fibroblast growth factor type 2 (FGF2). In this study, we evaluated the effect of human recombinant FGF2 (rhFGF2) administration in a murine model of PE induced by NG-nitro-L-arginine methyl ester (L-NAME) to test if rhFGF2 administration can lessen the clinical manifestations of PE.

Methods: Pregnant rats were administrated with 0.9% of NaCl (vehicle), L-NAME (60 mg/kg), FGF2 (666.6 ng/kg), L-NAME+FGF2 or L-NAME + hydralazine (10 mg/kg) from the 10th to 19th days of gestation. Blood pressure (BP), urine protein concentrations and anthropometric values both rat and fetuses were assessed. Histological evaluation of organs from rats delivered by cesarean section was carried out using hematoxylin and eosin staining.

Results: A PE-like model was established, and it included phenotypes such as maternal hypertension, proteinuria, and fetal growth delay. Compared to the groups treated with L-NAME, the L-NAME + FGF2 group was similar to vehicle: the BP remained stable and the rats did not develop enhanced proteinuria. Both the fetuses and placentas from rats treated with L-NAME + FGF2 had similar values of weight and size compared with the vehicle.

Conclusion: The intravenous administration of rhFGF2 showed beneficial and hypotensive effects, reducing the clinical manifestations of PE in the evaluated model.

Vagus nerve stimulation ameliorates L-NAME-induced preeclampsia-like symptoms in rats through inhibition of the inflammatory response

Background

Preeclampsia is characterized by an excessive inflammatory response. Recent studies have shown that vagus nerve stimulation (VNS) has anti-inflammatory properties in vivo. This study aims to investigate whether VNS is safe for use during pregnancy and to explore the therapeutic potential and underlying mechanisms of VNS in PE.

Methods

Pregnant Sprague-Dawley rats were randomly chosen to receive N-nitro-L-arginine methyl ester (L-NAME)-containing water (preeclampsia-like mouse model) or saline (normal pregnancy control) daily at gestational days 14.5–20.5. VNS and the α7nAChR antagonist methyllycaconitine citrate (MLA, 1 mg/kg/d) were given daily at the same time.

Results

VNS decreased the high systolic blood pressure and urinary protein observed in the PE rats. In addition, VNS mitigated abnormal pregnancy outcomes. Moreover, VNS alleviated the inflammatory response by decreasing the levels of inflammatory cytokines. VNS significantly increased the expression of α7nAChR and attenuated the activation of NF-κB p65 in the placenta.

Discussion

Our findings indicate that maternal VNS treatment is safe during pregnancy and has a protective effect in a pregnant rat model of preeclampsia induced by L-NAME.

Animal Models of Preeclampsia: Causes, Consequences, and Interventions

Preeclampsia is a common pregnancy complication, affecting 2% to 8% of pregnancies worldwide, and is an important cause of both maternal and fetal morbidity and mortality. Importantly, although aspirin and calcium are able to prevent preeclampsia in some women, there is no cure apart from delivery of the placenta and fetus, often necessitating iatrogenic preterm birth. Preclinical models of preeclampsia are widely used to investigate the causes and consequences of preeclampsia and to evaluate safety and efficacy of potential preventative and therapeutic interventions. In this review, we provide a summary of the published preclinical models of preeclampsia that meet human diagnostic criteria, including the development of maternal hypertension, together with new-onset proteinuria, maternal organ dysfunction, and uteroplacental dysfunction. We then discuss evidence from preclinical models for multiple causal factors of preeclampsia, including those implicated in early-onset and late-onset preeclampsia. Next, we discuss the impact of exposure to a preeclampsia-like environment for later maternal and progeny health. The presence of long-term impairment, particularly cardiovascular outcomes, in mothers and progeny after an experimentally induced preeclampsia-like pregnancy, implies that later onset or reduced severity of preeclampsia will improve later maternal and progeny health. Finally, we summarize published intervention studies in preclinical models and identify gaps in knowledge that we consider should be targets for future research.

Pre-eclamptic Fetal Programming Alters Neuroinflammatory and Cardiovascular Consequences of Endotoxemia in Sex-Specific Manners

Pre-eclampsia (PE)-induced fetal programming predisposes offspring to health hazards in adult life. Here, we tested the hypothesis that pre-eclamptic fetal programming elicits sexually dimorphic inflammatory and cardiovascular complications to endotoxemia in adult rat offspring. PE was induced by oral administration of L-NAME (50 mg/kg per day for seven consecutive days) starting from day 14 of conception. Cardiovascular studies were performed in conscious adult male and female offspring preinstrumented with femoral indwelling catheters. Compared with non-PE male counterparts, intravenous administration of lipopolysaccharide (LPS, 5 mg/kg) to PE male offspring caused significantly greater 1) falls in blood pressure, 2) increases in heart rate, 3) rises in arterial dP/dtmax, a correlate of left ventricular contractility, and 4) decreases in time- and frequency-domain indices of heart rate variability (HRV). By contrast, the hypotensive and tachycardic actions of LPS in female offspring were independent of the pre-eclamptic state and no clear changes in HRV or dP/dtmax were noted. Measurement of arterial baroreflex activity by vasoactive method revealed no sex specificity in baroreflex dysfunction induced by LPS. Immunohistochemical studies showed increased protein expression of toll-like receptor 4 in heart as well as in brainstem neuronal pools of the nucleus of solitary tract and rostral ventrolateral medulla in endotoxic PE male, but not female, offspring. Enhanced myocardial, but not neuronal, expression of monocyte chemoattractant protein-1 was also demonstrated in LPS-treated male offspring. Together, pre-eclamptic fetal programming aggravates endotoxic manifestations of hypotension and autonomic dysfunction in male offspring via exacerbating myocardial and neuromedullary inflammatory pathways. SIGNIFICANCE STATEMENT: Current molecular and neuroanatomical evidence highlights a key role for pre-eclamptic fetal programming in offspring predisposition to health hazards induced by endotoxemia in adult life. Pre-eclampsia accentuates endotoxic manifestations of hypotension, tachycardia, and cardiac autonomic dysfunction in male offspring via exacerbating myocardial and central inflammatory pathways. The absence of such detrimental effects in female littermates suggests sexual dimorphism in the interaction of pre-eclamptic fetal programming with endotoxemia.

Reductions of Circulating Nitric Oxide are Followed by Hypertension during Pregnancy and Increased Activity of Matrix Metalloproteinases-2 and -9 in Rats

Hypertensive pregnancy has been associated with reduced nitric oxide (NO), bioavailability, and increased activity of matrix metalloproteinases (MMPs). However, it is unclear if MMPs activation is regulated by NO during pregnancy. To this end, we examined activity of MMP-2 and MMP-9 in plasma, placenta, uterus and aorta, NO bioavailability, oxidative stress, systolic blood pressure (SBP), and fetal-placental development at the early, middle, and late pregnancy stages in normotensive and Nω-Nitro-L-arginine methyl-ester (L-NAME)-induced hypertensive pregnancy in rats. Reduced MMP-2 activity in uterus, placenta, and aorta and reduced MMP-9 activity in plasma and placenta with concomitant increased NO levels were found in normotensive pregnant rats. By contrast, increased MMP-2 activity in uterus, placenta, and aorta, and increased MMP-9 activity in plasma and placenta with concomitant reduced NO levels were observed in hypertensive pregnant rats. Also, elevated oxidative stress was displayed by hypertensive pregnant rats at the middle and late stages. These findings in the L-NAME-treated pregnant rats were also followed by increases in SBP and associated with fetal growth restrictions at the middle and late pregnancy stages. We concluded that NO bioavailability may regulate MMPs activation during normal and hypertensive pregnancy.

Silencing of Annexin A1 suppressed the apoptosis and inflammatory response of preeclampsia rat trophoblasts

Preeclampsia (PE) is a disorder that is characterized by pregnancy-induced hypertension. It has been reported that Annexin A1 (ANXA1) is highly expressed in the plasma of women diagnosed with PE. Therefore, the present study aimed to examine the effect of ANXA1 on PE rats. The PE animal model was constructed in rats using Nω-nitro-L-arginine methyl ester (L-NAME), and the blood pressure and urine protein levels of rats were detected. The pathological features of placental tissue, and the levels of inflammatory factors and ANXA1 were respectively measured by hematoxylin-eosin staining, enzyme-linked immunosorbent assay and immunohistochemical assay. The activity of trophoblasts obtained from PE placental tissue was measured using immunofluorescence staining, while cell apoptosis was assessed using flow cytometry. The levels of associated factors were determined by reverse transcription-quantitative polymerase chain reaction and western blot analysis. The results identified that systolic blood pressure, diastolic blood pressure, mean arterial pressure and urine protein levels were enhanced, and that the contents of ANXA1, tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, IL-6 and IL-8 were increased in the L-NAME group. Transfection with small interfering RNA (siRNA)-ANXA1 markedly decreased the apoptosis and inflammatory response of trophoblasts. In addition, siRNA-ANXA1 upregulated the levels of B-cell lymphoma-2 (Bcl-2) and pro-caspase-3, and downregulated the levels of Bcl-2-associated X protein, cleaved-caspase-3, TNF-α, IL-1β, IL-6 and IL-8. Furthermore, siRNA-ANXA1 repressed the phosphorylation of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3); however, siRNA-ANXA1 did not alter the levels of JAK2 and STAT3. Therefore, silencing of ANXA1 suppressed the apoptosis and inflammatory response of PE rat trophoblasts, and downregulated JAK2/STAK3 pathway.

Evaluation of blood vessel injury, oxidative stress and circulating inflammatory factors in an L-NAME-induced preeclampsia-like rat model

Preeclampsia is a pregnancy-specific disease characterized by hypertension as well as proteinuria after the 20th week of pregnancy. Animal models are effective tools for studying the pathogenesis, diagnostic criteria and treatment methods of preeclampsia. The present study sought to establish and evaluate a preeclampsia-like Sprague Dawley (SD) rat model using N-nitro-L-arginine methyl ester (L-NAME). Rats were randomly assigned to 7 groups (n=10 in each): Control rats and rats treated with low-dose L-NAME (40 mg/kg body weight/day) starting from gestational day (GD) 9, medium-L-NAME (75 mg/kg body weight/day) starting from GD 9 (9D ML group), high-dose L-NAME (125 mg/kg body weight/day) starting from GD 9, low-dose L-NAME starting from GD 10, medium-dose L-NAME starting from GD 10 and high-dose L-NAME starting from GD 10. Blood pressure (BP), 24-h proteinuria, fetal intrauterine growth, histopathological changes, the plasma soluble fms-like tyrosine kinase-1 (sFlt-1)/placental growth factor (PLGF) ratio and cytokine levels were evaluated. Elevated BP, increased urinary albumin excretion, severe endotheliosis, mesangial expansion and increased sFlt-1/PLGF ratios were observed in the experimental groups compared with the control group (P<0.05), particularly in the 9D ML group. The results of the present study may optimize the conditions of the previously established L-NAME-induced preeclampsia SD rat model and aid further study into the pathogenesis of preeclampsia.