Antenatal maternal hypoxic stress: adaptations in fetal lung Renin-Angiotensin system

Nrf2 deficiency exacerbated pulmonary pyroptosis in maternal hypoxia-induced intrauterine growth restriction offspring mice

Maternal prenatal hypoxia is an important contributor to intrauterine growth restriction (IUGR), which impedes fetal lung maturation and leads to the development of chronic lung diseases. Although evidence suggests the involvement of pyroptosis in IUGR, the molecular mechanism of pyroptosis is still unclear. Nuclear factor erythroid 2-related factor 2 (Nrf2) has been found to potentially interact with gasdermin D (GSDMD), the key protein responsible for pyroptosis, indicating its crucial role in inhibiting pyroptosis. Therefore, we hypothesized that Nrf2 deficiency is a key molecular responsible for lung pyroptosis in maternal hypoxia-induced IUGR offspring mice. Pregnant WT and Nrf2-/- mice were exposed to hypoxia (10.5 % O2) to mimic IUGR model. We assessed body weight, lung histopathology, pulmonary angiogenesis, oxidative stress levels, as well as mRNA and protein expressions related to inflammation in the 2-week-old offspring. Additionally, we conducted a dual-luciferase reporter assay to confirm the targeting relationship between Nrf2 and GSDMD. Our findings revealed that offspring with maternal hypoxia-induced IUGR exhibited reduced birth weight, catch-up growth delay, and pulmonary dysplasia. Furthermore, we observed impaired nuclear translocation of Nrf2 and increased GSDMD-mediated pyroptosis in these offspring with IUGR. Moreover, the dual-luciferase reporter assay demonstrated that Nrf2 could directly inhibit GSDMD transcription; deficiency of Nrf2 exacerbated pyroptosis and pulmonary dysplasia in offspring with maternal hypoxia-induced IUGR. Collectively, our findings suggest that Nrf2 deficiency induces GSDMD-mediated pyroptosis and pulmonary dysplasia in offspring with maternal hypoxia-induced IUGR; thus highlighting the potential therapeutic approach of targeting Nrf2 for treating prenatal hypoxia-induced pulmonary dysplasia in offspring.

Molecular mechanisms involved in fetal programming and disease origin in adulthood

Fetal programming occurs during the gestational age when exposure to environmental stimuli can cause long-term changes in the fetus, predisposing it to develop chronic non-communicable diseases (CNCD) in adulthood. Herein, we summarized the role of low-calorie or high-fat diets during pregnancy as fetal programming agents that induce intrauterine growth restriction (IUGR), amplified de novo lipogenesis, and increased amino acid transport to the placenta, which favor the CNCD onset in the offspring. We also outlined how maternal obesity and gestational diabetes act as fetal programming stimuli by reducing iron absorption and oxygen transport to the fetus, stimulating inflammatory pathways that boost neurological disorders and CNCD in the progeny. Moreover, we reviewed the mechanisms through which fetal hypoxia elevates the offspring's risk of developing hypertension and chronic kidney disease in adult life by unbalancing the renin-angiotensin system and promoting kidney cell apoptosis. Finally, we examined how inadequate vitamin B12 and folic acid consumption during pregnancy programs the fetus to greater adiposity, insulin resistance, and glucose intolerance in adulthood. A better understanding of the fetal programming mechanisms may help us reduce the onset of insulin resistance, glucose intolerance, dyslipidemia, obesity, hypertension, diabetes mellitus, and other CNCD in the offspring during adulthood.

Perspectives on frailty as a total life-course disease with consideration of the fetal environment

Frailty attracts research as it represents a significant target for intervention to extend the healthy life span. An unanswered question in this field is the time point during the life-course at which an individual becomes predisposed to frailty. Here, we propose that frailty has a fetal origin and should be regarded as part of the spectrum of the developmental origins of health and disease. The developmental origins of health and disease theory originated from findings linking the fetal environment to lifestyle-related disorders such as hypertension and diabetes. Coincidentally, a recent trend in frailty research also centers on vascular dysfunction and metabolic alterations as the causality of lifestyle-related disorders such as sarcopenia and dementia. Here, we explore the relationship between fetal programming, frailty-related disorders (sarcopenia and dementia), and other age-related diseases mainly based on reports on intrauterine growth restriction. We propose a "total" life-course approach to combat frailty. With this viewpoint, not only physicians and gerontologists but also obstetricians and pediatricians should team up to overcome age-related diseases in the elderly. Geriatr Gerontol Int 2023; ••: ••-••.

Elevated Vascular Sympathetic Neurotransmission and Remodelling Is a Common Feature in a Rat Model of Foetal Programming of Hypertension and SHR

Hypertension is of unknown aetiology, with sympathetic nervous system hyperactivation being one of the possible contributors. Hypertension may have a developmental origin, owing to the exposure to adverse factors during the intrauterine period. Our hypothesis is that sympathetic hyperinnervation may be implicated in hypertension of developmental origins, being this is a common feature with essential hypertension. Two-animal models were used: spontaneously hypertensive rats (SHR-model of essential hypertension) and offspring from dams exposed to undernutrition (MUN-model of developmental hypertension), with their respective controls. In adult males, we assessed systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), sympathetic nerve function (3H-tritium release), sympathetic innervation (immunohistochemistry) and vascular remodelling (histology). MUN showed higher SBP/DBP, but not HR, while SHR exhibited higher SBP/DBP/HR. Regarding the mesenteric arteries, MUN and SHR showed reduced lumen, increased media and adventitial thickness and increased wall/lumen and connective tissue compared to respective controls. Regarding sympathetic nerve activation, MUN and SHR showed higher tritium release compared to controls. Total tritium tissue/tyrosine hydroxylase detection was higher in SHR and MUN adventitia arteries compared to respective controls. In conclusion, sympathetic hyperinnervation may be one of the contributors to vascular remodelling and hypertension in rats exposed to undernutrition during intrauterine life, which is a common feature with spontaneous hypertension.

The pathobiological harmony between the local pulmonary/ bone marrow RAS and its management via tissue-RAS modulating agents in COVID-19

Coronavirus disease 2019 (COVID-19) outbreak, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), poses an unprecedented threat to public health and healthcare systems. It presents unusual pathophysiological effects mainly characterized by immune-inflammatory response and prothrombotic state causing acute respiratory distress syndrome and multiple organ failure. SARS-CoV-2 enters target cells after binding to the angiotensin-converting enzyme 2 (ACE2) receptor and therefore has a direct effect on the renin-angiotensin system (RAS). Apart from affecting numerous organs including lungs, heart, gastrointestinal system, spleen, brain and kidneys, the spike protein of SARS-CoV-2 could attack hematopoietic stem cells and hematopoietic progenitor cells in bone marrow (BM) microenvironment together with the precursor and mature blood cells. Within this hematopoietic viral spread context, it is crucial to search the clinicopathological correlations of COVID-19 in order to develop specific potential therapeutics against pleiotropic SARS-CoV-2 actions. Therefore, pharmacological disruption of the pathological cross-talk of local BM RAS and pulmonary RAS via administration of the tissue-RAS modulating agents such as soluble ACE2, angiotensin (1-7), TXA127 and MAS receptor agonists may prevent the clinical progression of the COVID-19 syndrome via reducing the hematopoietic virus propagation and systemic multi-organ spread.

Programming of Vascular Dysfunction by Maternal Stress: Immune System Implications

A growing body of evidence highlights that several insults during pregnancy impact the vascular function and immune response of the male and female offspring. Overactivation of the immune system negatively influences cardiovascular function and contributes to cardiovascular disease. In this review, we propose that modulation of the immune system is a potential link between prenatal stress and offspring vascular dysfunction. Glucocorticoids are key mediators of stress and modulate the inflammatory response. The potential mechanisms whereby prenatal stress negatively impacts vascular function in the offspring, including poor hypothalamic–pituitary–adrenal axis regulation of inflammatory response, activation of Th17 cells, renin–angiotensin–aldosterone system hyperactivation, reactive oxygen species imbalance, generation of neoantigens and TLR4 activation, are discussed. Alterations in the immune system by maternal stress during pregnancy have broad relevance for vascular dysfunction and immune-mediated diseases, such as cardiovascular disease.

Fetal Undernutrition Modifies Vascular RAS Balance Enhancing Oxidative Damage and Contributing to Remodeling

Fetal stress is known to increase susceptibility to cardiometabolic diseases and hypertension in adult age in a process known as fetal programming. This study investigated the relationship between vascular RAS, oxidative damage and remodeling in fetal programming. Six-month old Sprague-Dawley offspring from mothers that were fed ad libitum (CONTROL) or with 50% intake during the second half of gestation (maternal undernutrition, MUN) were used. qPCR or immunohistochemistry were used to obtain the expression of receptors and enzymes. Plasma levels of carbonyls were measured by spectrophotometry. In mesenteric arteries from MUN rats we detected an upregulation of ACE, ACE2, AT₁ receptors and NADPH oxidase, and lower expression of AT₂, Mas and MrgD receptors compared to CONTROL. Systolic and diastolic blood pressure and plasma levels of carbonyls were higher in MUN than in CONTROL. Vascular morphology evidenced an increased media/lumen ratio and adventitia/lumen ratio, and more connective tissue in MUN compared to CONTROL. In conclusion, fetal undernutrition indices RAS alterations and oxidative damage which may contribute to the remodeling of mesenteric arteries, and increase the risk of adverse cardiovascular events and hypertension.

Role of the Uteroplacental Renin-Angiotensin System in Placental Development and Function, and Its Implication in the Preeclampsia Pathogenesis

Placental development and function implicate important morphological and physiological adaptations to thereby ensure efficient maternal–fetal exchanges, as well as pregnancy-specific hormone secretion and immune modulation. Incorrect placental development can lead to severe pregnancy disorders, such as preeclampsia (PE), which endangers both the mother and the infant. The implication of the systemic renin–angiotensin system (RAS) in the pregnancy-related physiological changes is now well established. However, despite the fact that the local uteroplacental RAS has been described for several decades, its role in placental development and function seems to have been underestimated. In this review, we provide an overview of the multiple roles of the uteroplacental RAS in several cellular processes of placental development, its implication in the regulation of placental function during pregnancy, and the consequences of its dysregulation in PE pathogenesis.

Effects of SARS-COV-2 infection on fetal pulmonary artery Doppler parameters

Purpose

To determine the effect of SARS‐CoV‐2 infection on the fetal pulmonary system using the acceleration time (AT), ejection time (ET), and acceleration/ejection time ratio (PATET) of the fetal main pulmonary artery Doppler waveform.

Methods

We prospectively studied pregnant women attending our hospital with confirmed SARS‐CoV‐2 infection by RT‐PCR test and an age‐matched control group who admitted for routine prenatal care. An ultrasound examination that included measurements of the AT, ET, and AT/ET ratio (PATET) were performed and the results were compared.

Results

Fifty‐five SARS‐CoV‐2‐infected and 93 control group pregnant women were included in this study. AT found higher in the COVID‐19 positive group when compared with controls. When the ET and PATET parameters were compared, no differences were detected between the groups. Eleven neonates had Neonatal Intensive Care Unit (NICU) requirement in the COVID‐19 positive group while there were none in the control group. All fetal pulmonary artery Doppler values were decreased in NICU admitted fetuses. The mean gestational week of this group was lower than non‐NICU COVID‐19 positive group and the control group.

Conclusion

COVID‐19 infection increases fetal pulmonary blood flow, which appears high AT values on Doppler parameters. NICU admission only occurred in the COVID‐19 group and their Doppler values were found significantly lower than non‐NICU COVID‐19 group. The clinical significance of this result must be evaluated with further studies.

Prenatal High-Sucrose Diet Induced Vascular Dysfunction in Thoracic Artery of Fetal Offspring

SCOPE

Maternal nutrition during pregnancy is related to intrauterine fetal development. The authors' previous work reports that prenatal high sucrose (HS) diet impaired micro-vascular functions in postnatal offspring. It is unclear whether/how prenatal HS causes vascular injury during fetal life.

METHODS AND RESULTS

Pregnant rats are fed with normal drinking water or 20% high-sucrose solution during the whole gestational period. Pregnant HS increases maternal weight before delivery. Fetal thoracic aorta is separated for experiments. Angiotensin II (AII)-stimulated vascular contraction of fetal thoracic arteries in HS group is greater, which mainly results from the enhanced AT1 receptor (AT1R) function and the downstream signaling. Nifedipine significantly increases vascular tension in HS group, indicating that the L-type calcium channels (LTCCs) function is strengthened. 2-Aminoethyl diphenylborinate (2-APB), inositol 1,4,5-trisphosphate receptors (IP3Rs) inhibitor, increases vascular tension induced by AII in HS group and ryanodine receptors-sensitive vascular tone shows no difference in the two groups, which suggested that the activity of IP3Rs-operated calcium channels is increased.

CONCLUSION

These findings suggest that prenatal HS induces vascular dysfunction of thoracic arteries in fetal offspring by enhancing AT1R, LTCCs function and IP3Rs-associated calcium channels, providing new information regarding the impact of prenatal HS on the functional development of fetal vascular systems.

Insights into sympathetic nervous system and GPCR interplay in fetal programming of hypertension: a bridge for new pharmacological strategies

Cardiovascular diseases (CVDs) are the most common cause of death from noncommunicable diseases worldwide. In addition to the classical CVD risk factors related to lifestyle and/or genetic background, exposure to an adverse intrauterine environment compromises fetal development leading to low birth weight and increasing offspring susceptibility to develop CVDs later in life, particularly hypertension - a process known as fetal programming of hypertension (FPH). In FPH animal models, permanent alterations have been detected in gene expression, in the structure and function of heart and blood vessels, compromising cardiovascular physiology and favoring hypertension development. This review focuses on the role of the sympathetic nervous system and its interplay with G-protein-coupled receptors, emphasizing strategies that envisage the prevention and/or treatment of FPH through interventions in early life.

Fetal brain sparing in a mouse model of chronic maternal hypoxia

Hypoxic stress is a common occurrence during human pregnancy, yet little is known about its effects on the fetal brain. This study examined the fetal hemodynamic responses to chronic hypoxia in an experimental mouse model of chronic maternal hypoxia (11% O₂ from E14.5 to E17.5). Using high-frequency Doppler ultrasound, we found fetal cerebral and ductus venosus blood flow were both elevated by 69% and pulmonary blood flow was decreased by 62% in the fetuses exposed to chronic hypoxia compared to controls. This demonstrates that brain sparing persists during chronic fetal hypoxia and is mediated by "streaming," where highly oxygenated blood preferentially flows through the ductus venosus towards the cerebral circulation, bypassing the liver and the lungs. Consistent with these changes in blood flow, the fetal brain volume measured by MRI is preserved, while the liver and lung volumes decreased compared to controls. However, hypoxia exposed fetuses were rendered vulnerable to an acute hypoxic challenge (8% O₂ for 3 min), demonstrating global blood flow decreases consistent with imminent fetal demise rather than elevated cerebral blood flow. Despite this vulnerability, there were no differences in adult brain morphology in the mice exposed to chronic maternal hypoxia compared to controls.

Liraglutide Enhances the Activity of the ACE-2/Ang(1-7)/Mas Receptor Pathway in Lungs of Male Pups from Food-Restricted Mothers and Prevents the Reduction of SP-A

In utero growth restriction and being born small for gestational age are risk factors for respiratory morbidity. IUGR (in utero growth retardation) is associated to overall reduction in lung weight, surfactant content and activity, impaired maturation of the alveolar type II cells, and decreased alveolar formation. The renin-angiotensin system (RAS) may be a key target underlying pathophysiological lung alterations. GLP-1 and agonists of its receptor modulate the expression levels of different components of RAS and also are very important for lung maturation and the production of surfactant proteins. The aim of this study was to elucidate the effects of IUGR induced by perinatal food restriction of the mother in the lung function of pups at early stages of life (PD21) and to determine if liraglutide had any effect during gestational period. Sprague-Dawley pregnant rats were randomly assigned to 50% food restriction (MPFR) or ad libitum control (CT) groups at day of pregnancy 12 (GD12). From GD14 to parturition, pregnant MPFR and CT rats were treated with liraglutide or vehicle. At postnatal day 21 and before weaning, 20 CT and 20 FR male pups were sacrificed and lungs were analyzed by RT-PCR. Liraglutide restored surfactant protein A (SP-A) mRNA expression in pup lungs from food-restricted mothers. Surfactant protein B (SP-B) mRNA expression is not affected by neither IUGR nor liraglutide treatment. Moreover, liraglutide modulated different elements of RAS, increasing angiotensin-converting enzyme 2 (ACE2) and MasR mRNA expression only in pups from food-restricted mothers (MPFR), despite food restriction had not any direct effect at this early stage. Liraglutide also increased endothelial nitric oxide synthase (eNOS) expression in MPFR lungs, reflecting the activation of MasR by angiotensin 1-7. In conclusion, liraglutide prevented the alteration in lung function induced by IUGR and promoted the positive effects of ACE2-Ang(1-7)-MasR in restoring lung function.

Fetal Cerebrovascular Maturation: Effects of Hypoxia

The human cerebral vasculature originates in the fourth week of gestation and continues to expand and diversify well into the first few years of postnatal life. A key feature of this growth is smooth muscle differentiation, whereby smooth muscle cells within cerebral arteries transform from migratory to proliferative to synthetic and finally to contractile phenotypes. These phenotypic transformations can be reversed by pathophysiological perturbations such as hypoxia, which causes loss of contractile capacity in immature cerebral arteries. In turn, loss of contractility affects all whole-brain cerebrovascular responses, including those involved in flow-metabolism coupling, vasodilatory responses to acute hypoxia and hypercapnia, cerebral autoregulation, and reactivity to activation of perivascular nerves. Future strategies to minimize cerebral injury following hypoxia-ischemic insults in the immature brain might benefit by targeting treatments to preserve and promote contractile differentiation in the fetal cerebrovasculature. This could potentially be achieved through inhibition of receptor tyrosine kinase-mediated growth factors, such as vascular endothelial growth factor and platelet-derived growth factor, which are mobilized by hypoxic and ischemic injury and which facilitate contractile dedifferentiation. Interruption of the effects of other vascular mitogens, such as endothelin and angiotensin-II, and even some miRNA species, also could be beneficial. Future experimental work that addresses these possibilities offers promise to improve current clinical management of neonates who have suffered and survived hypoxic, ischemic, asphyxic, or inflammatory cerebrovascular insults.

Gestational Hypoxia and Developmental Plasticity

Hypoxia is one of the most common and severe challenges to the maintenance of homeostasis. Oxygen sensing is a property of all tissues, and the response to hypoxia is multidimensional involving complicated intracellular networks concerned with the transduction of hypoxia-induced responses. Of all the stresses to which the fetus and newborn infant are subjected, perhaps the most important and clinically relevant is that of hypoxia. Hypoxia during gestation impacts both the mother and fetal development through interactions with an individual's genetic traits acquired over multiple generations by natural selection and changes in gene expression patterns by altering the epigenetic code. Changes in the epigenome determine "genomic plasticity," i.e., the ability of genes to be differentially expressed according to environmental cues. The genomic plasticity defined by epigenomic mechanisms including DNA methylation, histone modifications, and noncoding RNAs during development is the mechanistic substrate for phenotypic programming that determines physiological response and risk for healthy or deleterious outcomes. This review explores the impact of gestational hypoxia on maternal health and fetal development, and epigenetic mechanisms of developmental plasticity with emphasis on the uteroplacental circulation, heart development, cerebral circulation, pulmonary development, and the hypothalamic-pituitary-adrenal axis and adipose tissue. The complex molecular and epigenetic interactions that may impact an individual's physiology and developmental programming of health and disease later in life are discussed.

Hypoxia: From Placental Development to Fetal Programming

Hypoxia may influence normal and different pathological processes. Low oxygenation activates a variety of responses, many of them regulated by hypoxia-inducible factor 1 complex, which is mostly involved in cellular control of O₂ consumption and delivery, inhibition of growth and development, and promotion of anaerobic metabolism. Hypoxia plays a significant physiological role in fetal development; it is involved in different embryonic processes, for example, placentation, angiogenesis, and hematopoiesis. More recently, fetal hypoxia has been associated directly or indirectly with fetal programming of heart, brain, and kidney function and metabolism in adulthood. In this review, the role of hypoxia in fetal development, placentation, and fetal programming is summarized. Hypoxia is a basic mechanism involved in different pregnancy disorders and fetal health developmental complications. Although there are scientific data showing that hypoxia mediates changes in the growth trajectory of the fetus, modulates gene expression by epigenetic mechanisms, and determines the health status later in adulthood, more mechanistic studies are needed. Furthermore, if we consider that intrauterine hypoxia is not a rare event, and can be a consequence of unavoidable exposures to air pollution, nutritional deficiencies, obesity, and other very common conditions (drug addiction and stress), the health of future generations may be damaged and the incidence of some diseases will markedly increase as a consequence of disturbed fetal programming. Birth Defects Research 109:1377-1385, 2017.© 2017 Wiley Periodicals, Inc.

Regulation of the prorenin - angiotensin system by oxygen and miRNAs; parallels between placentation and tumour development?

Tissue renin-angiotensin systems (RASs) are involved in tissue growth and development as they are important regulators of angiogenesis, cell proliferation and migration. The placental RAS is most highly expressed in early gestation, at a time when the oxygen tension within the conceptus is reduced, and plays a key role in placental growth and development. Similar to the placenta, tumour development relies on proliferation, angiogenesis and invasion in order to grow and metastasize. The RAS is known to be upregulated in a variety of solid tumours, including ovarian, endometrial, cervical, breast and prostate. This review explores the roles of oxygen and microRNAs in regulating the normal expression of the placental RAS, providing insight into regulation of its development as well as the development of disease states in which the RAS is overexpressed. We propose that the placental RAS is downregulated by microRNAs that are suppressed during the physiologically normal 'hypoxic' phase of early placentation. Suppression of these miRNAs allows the placental RAS to stimulate placental growth and angiogenesis. We propose that similar mechanisms may be at play in solid tumours, which are characterised by hypoxia.

In Utero Origins of Hypertension: Mechanisms and Targets for Therapy

The developmental origins of health and disease theory is based on evidence that a suboptimal environment during fetal and neonatal development can significantly impact the evolution of adult-onset disease. Abundant evidence exists that a compromised prenatal (and early postnatal) environment leads to an increased risk of hypertension later in life. Hypertension is a silent, chronic, and progressive disease defined by elevated blood pressure (>140/90 mmHg) and is strongly correlated with cardiovascular morbidity/mortality. The pathophysiological mechanisms, however, are complex and poorly understood, and hypertension continues to be one of the most resilient health problems in modern society. Research into the programming of hypertension has proposed pharmacological treatment strategies to reverse and/or prevent disease. In addition, modifications to the lifestyle of pregnant women might impart far-reaching benefits to the health of their children. As more information is discovered, more successful management of hypertension can be expected to follow; however, while pregnancy complications such as fetal growth restriction, preeclampsia, preterm birth, etc., continue to occur, their offspring will be at increased risk for hypertension. This article reviews the current knowledge surrounding the developmental origins of hypertension, with a focus on mechanistic pathways and targets for therapeutic and pharmacologic interventions.

Prenatal hypoxia enhanced angiotensin II-mediated vasoconstriction via increased oxidative signaling in fetal rats

Toxic factors could cause in utero hypoxia, and prenatal hypoxia (PH) increased incidence of cardiovascular diseases in late life. It is unclear whether/how PH causes vascular injury during fetal life. This study found that PH significantly increased angiotensin II (Ang II)-mediated vessel contractions in fetal thoracic aortas, which was blocked by losartan, not PD123319, indicating that AT1 receptors played a dominant role in the enhanced fetal vasoconstriction following hypoxia. Prenatal hypoxia increased superoxide production and decreased superoxide dismutase (SOD) expression, associated with the enhanced NADPH oxidase (Nox) 4, but not Nox1 or Nox2 in fetal aortas. Ang II-increased vasoconstriction was inhibited by Nox inhibitor apocynin and SOD mimetic blocker tempol. These findings suggested that PH resulted in Ang II/AT1R-mediated fetal vascular hypertensive re-activity via pathways of Nox4-dependent oxidative stress, providing new information regarding the impact of PH on the functional and molecular development of fetal vascular systems.

Developmental acceleration of bradykinin-dependent relaxation by prenatal chronic hypoxia impedes normal development after birth

Bradykinin-induced activation of the pulmonary endothelium triggers nitric oxide production and other signals that cause vasorelaxation, including stimulation of large-conductance Ca(2+)-activated K(+) (BKCa) channels in myocytes that hyperpolarize the plasma membrane and decrease intracellular Ca(2+). Intrauterine chronic hypoxia (CH) may reduce vasorelaxation in the fetal-to-newborn transition and contribute to pulmonary hypertension of the newborn. Thus we examined the effects of maturation and CH on the role of BKCa channels during bradykinin-induced vasorelaxation by examining endothelial Ca(2+) signals, wire myography, and Western immunoblots on pulmonary arteries isolated from near-term fetal (∼ 140 days gestation) and newborn, 10- to 20-day-old, sheep that lived in normoxia at 700 m or in CH at high altitude (3,801 m) for >100 days. CH enhanced bradykinin-induced relaxation of fetal vessels but decreased relaxation in newborns. Endothelial Ca(2+) responses decreased with maturation but increased with CH. Bradykinin-dependent relaxation was sensitive to 100 μM nitro-L-arginine methyl ester or 10 μM 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, supporting roles for endothelial nitric oxide synthase and soluble guanylate cyclase activation. Indomethacin blocked relaxation in CH vessels, suggesting upregulation of PLA2 pathways. BKCa channel inhibition with 1 mM tetraethylammonium reduced bradykinin-induced vasorelaxation in the normoxic newborn and fetal CH vessels. Maturation reduced whole cell BKCa channel α1-subunit expression but increased β1-subunit expression. These results suggest that CH amplifies the contribution of BKCa channels to bradykinin-induced vasorelaxation in fetal sheep but stunts further development of this vasodilatory pathway in newborns. This involves complex changes in multiple components of the bradykinin-signaling axes.

Maternal-pup interaction disturbances induce long-lasting changes in the newborn rat pulmonary vasculature

The factors accounting for the pathological maintenance of a high pulmonary vascular (PV) resistance postnatally remain elusive, but neonatal stressors may play a role in this process. Cross-fostering in the immediate neonatal period is associated with adult-onset vascular and behavioral changes, likely triggered by early-in-life stressors. In hypothesizing that fostering newborn rats induces long-lasting PV changes, we evaluated them at 14 days of age during adulthood and compared the findings with animals raised by their biological mothers. Fostering resulted in reduced maternal-pup contact time when compared with control newborns. At 2 wk of age, fostered rats exhibited reduced pulmonary arterial endothelium-dependent relaxation secondary to downregulation of tissue endothelial nitric oxide synthase expression and tetrahydrobiopterin deficiency-induced uncoupling. These changes were associated with neonatal onset-increased ANG II receptor type 1 expression, PV remodeling, and right ventricular hypertrophy that persisted into adulthood. The pulmonary arteries of adult-fostered rats exhibited a higher contraction dose response to ANG II and thromboxane A2, the latter of which was abrogated by the oxidant scavenger Tempol. In conclusion, fostering-induced neonatal stress induces long-standing PV changes modulated via the renin-angiotensin system.

Antenatal maternal hypoxia: criterion for fetal growth restriction in rodents

Rodents are a useful model for life science research. Accumulating evidence suggests that the offspring of mice and rats suffer from similar disorders as humans when exposed to hypoxia during pregnancy. Importantly, with antenatal hypoxic exposure, human neonates demonstrate low birth weight or growth restriction. Similarly, with antenatal hypoxic exposure rodents also demonstrate the fetal growth restriction (FGR). Surprisingly, there is no consensus on the minimum duration or degree of hypoxic exposure required to cause FGR in rodents. Thus, we have reviewed the available literature in an attempt to answer these questions. Based on studies in rats, birth weight reduction of 31% corresponded to 10th percentile reduction in birth weight curve. With the similar criterion (10th percentile), in mice 3 days or more and in rats 7 days or more of 14% or lower hypoxia administration was required to produce statistically significant FGR.

Antenatal maternal low protein diet: ACE-2 in the mouse lung and sexually dimorphic programming of hypertension

Elevated blood pressure is an important global health problem, and in-utero under-nutrition may be an important factor in the pathogenesis of hypertension. In the present study, we tested the hypothesis that antenatal maternal low protein diet (MLPD) leads to sexually dimorphic developmental programming of the components of the pulmonary renin-angiotensin system. This may be important in the antenatal MLPD-associated development of hypertension. In pregnant mice, we administered normal (control) and isocaloric 50 % protein restricted diet, commencing one week before mating and continuing until delivery of the pups. From the 18th to 24th week postnatal, we measured blood pressure in the offspring by use of a non-invasive tail-cuff method. In the same mice, we examined the mRNA and protein expression of the key components of the pulmonary renin-angiotensin system. Also, we examined microRNA complementary to angiotensin converting enzymes (ACE) 2 in the offspring lungs. Our results demonstrate that as a consequence of antenatal MLPD: 1) pup birthweight was significantly reduced in both sexes. 2) female offspring developed hypertension, but males did not. 3) In female offspring, ACE-2 protein expression was significantly reduced without any change in the mRNA levels. 4) miRNA 429, which has a binding site on ACE-2 - 3’ UTR was significantly upregulated in the female antenatal MLPD offspring. 5) In males, ACE-2 mRNA and protein expression were unaltered. We conclude that in the mouse, antenatal MLPD-induced reduction of ACE-2 in the female offspring lung may be an important mechanisms in sexually dimorphic programming of hypertension.

Maternal protein restriction alters VEGF signaling and decreases pulmonary alveolar in fetal rats

Epidemiological studies have demonstrated that intrauterine growth restriction (IUGR) increases the risk for respiratory morbidity from infancy, throughout childhood and into adulthood. Chronic restriction of nutrients causes abnormalities in the airways and lungs of offspring, but whether IUGR adversely impacts fetal pulmonary vascular development and underlying mechanisms remain under investigation. In this study, we investigated the effects of protein malnutrition in utero on pulmonary alveolarization and vascular growth of the fetal lung and placentae. Pregnant rats were feed with an isocaloric low-protein diet (8% protein) until delivery. Placenta and fetal lungs were harvested on 20th day of gestation (term 21 days of gestation). Lung index (lung weight as a percentage of body weight), total DNA and protein, radial alveolar count, arteriolar wall thickness, lung maturity and angiogenic factor VEGF were assessed. The lung was hypoplastic in IUGR fetus, evidenced by reduction in lung weight, DNA and protein content. Protein restriction in utero led to higher glycogen levels, but reduced number of alveoli as confirmed by the measurement of radial alveolar counts. IUGR fetus had significantly reduced VEGF, Flk-1 levels in lung but no changes in Flt-1 mRNA. Furthermore, IUGR was associated with increased lung miR-126-3p levels, which modulated the expression of angiogenic factor. In contrast, with regard to the placenta, IUGR fetus presented with decreased expression of VEGF, with no changes in VEGF receptors and expression-regulating miRNAs. This work suggested that VEGF signaling defect plays an important role in the defective lung development, which may explain the increased incidence of respiratory infections in IUGR patients.

MicroRNAs: potential regulators of renal development genes that contribute to CAKUT

Congenital anomalies of the kidney and urinary tract (CAKUT) are the leading cause of childhood chronic kidney disease (CKD). While mutations in several renal development genes have been identified as causes for CAKUT, most cases have not yet been linked to known mutations. Furthermore, the genotype-phenotype correlation is variable, suggesting that there might be additional factors that have an impact on the severity of CAKUT. MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at the post-transcriptional level, and are involved in many developmental processes. Although little is known about the function of specific miRNAs in kidney development, several have recently been shown to regulate the expression of, and/or are regulated by, crucial renal development genes present in other organ systems. In this review, we discuss how miRNA regulation of common developmental signaling pathways may be applicable to renal development. We focus on genes that are known to contribute to CAKUT in humans, for which miRNA interactions in other contexts have been identified, with miRNAs that are present in the kidney. We hypothesize that miRNA-mediated processes might play a role in kidney development through similar mechanisms, and speculate that genotypic variations in these small RNAs or their targets could be associated with CAKUT.

Long-term disruption of maternal glucose homeostasis induced by prenatal glucocorticoid treatment correlates with miR-29 upregulation

Excess of glucocorticoids (GCs) during pregnancy is strongly associated with the programming of glucose intolerance in the offspring. However, the impact of high GC levels on maternal metabolism is not clearly documented. This study aimed to test the hypothesis that mothers exposed to elevated levels of GCs might also display long-term disturbances in glucose homeostasis. Dexamethasone (DEX) was administered noninvasively to the mothers via drinking water between the 14th and the 19th days of pregnancy. Mothers were subjected to glucose and insulin tolerance tests at 1, 2, 3, 6, and 12 mo postweaning. Pregnant rats not treated with DEX and age-matched virgin rats were used as controls. Pancreatic islets were isolated at the 20th day of pregnancy and 12 mo postweaning in order to evaluate glucose-stimulated insulin secretion. The expression of the miR-29 family was also studied due to its responsiveness to GCs and its well-documented role in the regulation of pancreatic β-cell function. Rats treated with DEX during pregnancy presented long-term glucose intolerance and impaired insulin secretion. These changes correlated with 1) increased expression of miR-29 and its regulator p53, 2) reduced expression of syntaxin-1a, a direct target of miR-29, and 3) altered expression of genes related to cellular senescence. Our data demonstrate that the use of DEX during pregnancy results in deleterious outcomes to the maternal metabolism, hallmarked by reduced insulin secretion and glucose intolerance. This maternal metabolic programming might be a consequence of time-sustained upregulation of miR-29s in maternal pancreatic islets.

The role of renin-angiotensin system in cellular differentiation: implications in pancreatic islet cell development and islet transplantation

In addition to the well-characterized circulating renin-angiotensin system (RAS), local RAS has been identified recently in diverse tissues and organs. The presence of key components of the RAS in local tissues is important for our understanding of the patho-physiological mechanism(s) of several metabolic diseases, and may serve as a major therapeutic target for cardiometabolic syndromes. Locally generated and physiologically active RAS components have functions that are distinct from the classical vasoconstriction and fluid homeostasis actions of systemic RAS and cater specifically for local tissues. Local RAS can affect islet-cell function and structure in the adult pancreas as well as proliferation and differentiation of pancreatic stem/progenitor cells during development. Differentiation of stem/progenitor cells into insulin-expressing cells suitable for therapeutic transplantation offers a desperately needed new approach for replacement of glucose-responsive insulin producing cells in diabetic patients. Given that the generation of functional and transplantable islet cells has proven to be difficult, elucidation of RAS involvement in cellular regeneration and differentiation may propel pancreatic stem/progenitor cell development and thus β-cell regeneration forward. This review provides a critical appraisal of current research progress on the role of the RAS, including the newly characterized ACE2/Ang-(1-7)/Mas axis in the proliferation, differentiation, and maturation of pancreatic stem/progenitor cells. It is thus plausible to propose that the AT1 stimulation could be a repair mechanism involving the AT2R as well as the ACE2/Ang-(1-7)/Mas axis in directing β-cell development in diabetic patients using genetic and pharmaceutical manipulation of the RAS.

Maternal stress induces epigenetic signatures of psychiatric and neurological diseases in the offspring

The gestational state is a period of particular vulnerability to diseases that affect maternal and fetal health. Stress during gestation may represent a powerful influence on maternal mental health and offspring brain plasticity and development. Here we show that the fetal transcriptome, through microRNA (miRNA) regulation, responds to prenatal stress in association with epigenetic signatures of psychiatric and neurological diseases. Pregnant Long-Evans rats were assigned to stress from gestational days 12 to 18 while others served as handled controls. Gestational stress in the dam disrupted parturient maternal behaviour and was accompanied by characteristic brain miRNA profiles in the mother and her offspring, and altered transcriptomic brain profiles in the offspring. In the offspring brains, prenatal stress upregulated miR-103, which is involved in brain pathologies, and downregulated its potential gene target Ptplb. Prenatal stress downregulated miR-145, a marker of multiple sclerosis in humans. Prenatal stress also upregulated miR-323 and miR-98, which may alter inflammatory responses in the brain. Furthermore, prenatal stress upregulated miR-219, which targets the gene Dazap1. Both miR-219 and Dazap1 are putative markers of schizophrenia and bipolar affective disorder in humans. Offspring transcriptomic changes included genes related to development, axonal guidance and neuropathology. These findings indicate that prenatal stress modifies epigenetic signatures linked to disease during critical periods of fetal brain development. These observations provide a new mechanistic association between environmental and genetic risk factors in psychiatric and neurological disease.

Maternal protein deprivation: sexually dimorphic programming of hypertension in the mouse

Epidemiological data in humans and experiments in laboratory animals have demonstrated that the developmental programming of hypertension may occur as a consequence of dietary manipulations during pregnancy. Surprisingly, there is a scarcity of data regarding the development of hypertension as a consequence of a maternal low-protein diet (MLPD), particularly in the mouse. Furthermore, the role of sex in developmental programming is not well understood. We used FVB/NJ mice, because of their value in genetic/mechanistic analysis, to test the hypothesis that a MLPD during gestation leads to the sexually dimorphic developmental programming of hypertension and related disorders, such as intra-uterine growth restriction (IUGR), type 2 diabetes mellitus and obesity. We administered iso-caloric, normal (control), moderate protein (moderate MLPD) and severe protein (severe MLPD) diets to the mice, beginning 1 week before mating and continuing until the delivery of the pups. From 4 weeks onward, using a non-invasive tail-cuff method, we measured blood pressure and other parameters in the offspring. Our results demonstrate the following: (1) MLPD caused IUGR (low birthweight) in a dose-dependent manner; (2) Female offspring developed severe hypertension, whereas males were affected only moderately; (3) The blood glucose level was elevated only in females from the moderate MLPD group, although their insulin levels remained normal; (4) Rapid catch-up growth was observed in both sexes, with moderate MLPD females and severe MLPD males becoming overweight. Notably, blood leptin levels in the control group were significantly higher in females than in male offspring and were reduced in females from the severe MLPD group. We conclude that an antenatal MLPD during gestation leads to sexually dimorphic programming in mice.

Antenatal maternal protein deprivation: sexually dimorphic programming of the pancreatic renin-angiotensin system

As an underlying mechanism of antenatal maternal malnutrition-induced type 2 diabetes mellitus (T2DM), alterations in the local pancreatic renin-angiotensin system (RAS) may play a significant role. We tested the hypothesis that antenatal maternal protein deprivation (AMPD) leads to increased activity of the local pancreatic RAS, with associated hyperglycemia in the adult progeny. Mice dams were fed either control or 50% protein restricted diet (AMPD) starting one week before conception and maintained during complete gestation. Our results demonstrate low birth weight (control 1.5 ± 0.03 and AMPD 1.3 ± 0.03) and sexually dimorphic programming of the pancreatic RAS, with development of hyperglycemia only in the female mice offspring as a consequence of AMPD. No significant difference in serum insulin concentration was observed; however, AMPD was associated with increased mRNA and protein expression of angiotensinogen, renin and angiotensin-converting enzyme (ACE)-1 in male and female offspring. Of importance, mRNA and protein expression of ACE 2 and angiotensin II receptors was up-regulated only in the male offspring, as a consequence of AMPD. We conclude that sexually dimorphic programming of the pancreatic RAS expression is associated with AMPD diet-mediated development of hyperglycemia.

Local fetal lung renin-angiotensin system as a target to treat congenital diaphragmatic hernia

Antenatal stimulation of lung growth is a reasonable approach to treat congenital diaphragmatic hernia (CDH), a disease characterized by pulmonary hypoplasia and hypertension. Several evidences from the literature demonstrated a possible involvement of renin-angiotensin system (RAS) during fetal lung development. Thus, the expression pattern of renin, angiotensin-converting enzyme, angiotensinogen, type 1 (AT₁) and type 2 (AT₂) receptors of angiotensin II (ANGII) was assessed by immunohisto-chemistry throughout gestation, whereas the function of RAS in the fetal lung was evaluated using fetal rat lung explants. These were morphometrically analyzed and intracellular pathway alterations assessed by Western blot. In nitrofen-induced CDH model, pregnant rats were treated with saline or PD-123319. In pups, lung growth, protein/DNA ratio, radial saccular count, epithelial differentiation and lung maturation, vascular morphometry, right ventricular hypertrophy and overload molecular markers, gasometry and survival time were evaluated. Results demonstrated that all RAS components were constitutively expressed in the lung during gestation and that ANGII had a stimulatory effect on lung branching, mediated by AT₁ receptor, through p44/42 and Akt phosphorylation. This stimulatory effect on lung growth was mimicked by AT₂-antagonist (PD-123319) treatment. In vivo antenatal PD-123319 treatment increased lung growth, ameliorated indirect parameters of pulmonary hypertension, improved lung function and survival time in nonventilated CDH pups, without maternal or fetal deleterious effects. Therefore, this study demonstrated a local and physiologically active RAS during lung morphogenesis. Moreover, selective inhibition of AT₂ receptor is presented as a putative antenatal therapy for CDH.

Ontogeny of angiotensin-converting enzyme 2

INTRODUCTION

This study examined the temporal expression of angiotensin (Ang)-converting enzyme 2 (ACE2) during renal, heart, lung, and brain organogenesis in the mouse.

RESULTS

We demonstrate that kidney ACE2 mRNA levels are low on embryonic day (E) 12.5, increase fourfold during development, and decline in adulthood. In extrarenal tissues, ACE2 mRNA levels are also low during early gestation, increase in perinatal period, and peak in adulthood. The lung shows the highest age-related increase in ACE2 mRNA levels followed by the brain, kidney, and heart. ACE2 protein levels and enzymatic activity are high in all organs studied during gestation and decline postnatally. Ang II decreases ACE2 mRNA levels and enzymatic activity in kidneys grown ex vivo. These effects of Ang II are blocked by the specific Ang II AT(1) receptor (AT(1)R) antagonist candesartan, but not by the AT(2) receptor (AT(2)R) antagonist PD123319.

DISCUSSION

We conclude that ACE2 gene and protein expression and enzymatic activity are developmentally regulated in a tissue-specific manner. Ang II, acting through AT(1)R, exerts a negative feedback on ACE2 during kidney development. We postulate that relatively high ACE2 protein levels and enzymatic activity observed during gestation may play a role in kidney, lung, brain, and heart organogenesis.