Papers by German Ebensperger
not for the birds! Last Word on Point:Counterpoint: High altitude is/is
Frontiers in Physiology
Neonatal pulmonary hypertension (NPHT) is produced by sustained pulmonary vasoconstriction and in... more Neonatal pulmonary hypertension (NPHT) is produced by sustained pulmonary vasoconstriction and increased vascular remodeling. Soluble guanylyl cyclase (sGC) participates in signaling pathways that induce vascular vasodilation and reduce vascular remodeling. However, when sGC is oxidized and/or loses its heme group, it does not respond to nitric oxide (NO), losing its vasodilating effects. sGC protein expression and function is reduced in hypertensive neonatal lambs. Currently, NPHT is treated with NO inhalation therapy; however, new treatments are needed for improved outcomes. We used Cinaciguat (BAY-582667), which activates oxidized and/or without heme group sGC in pulmonary hypertensive lambs studied at 3,600 m. Our study included 6 Cinaciguat-treated (35 ug kg−1 day−1x 7 days) and 6 Control neonates. We measured acute and chronic basal cardiovascular variables in pulmonary and systemic circulation, cardiovascular variables during a superimposed episode of acute hypoxia, remodelin...
Beneficial effects of melatonin on prostanoids pathways in pulmonary hypertensive neonates
Vascular Pharmacology, 2021
Pulmonary arterial hypertension of the newborn (PAHN) is a syndrome caused by chronic hypoxia, ch... more Pulmonary arterial hypertension of the newborn (PAHN) is a syndrome caused by chronic hypoxia, characterized by decreased vasodilator function, a marked vasoconstrictor activity, proliferation of smooth muscle cells (SMC) and thickening of the extracellular matrix in the pulmonary circulation, among other characteristics. Prostaglandins are derived from the arachidonic acid (AA) metabolism and are important regulators of pulmonary vascular tone. Since hypoxia induces oxidative stress and has been related to PAHN, a postnatal treatment with melatonin has been proposed due to its antioxidant properties. Here, we determined the effects of melatonin on pulmonary vascular homeostasis given by prostanoids. Ten PAHN newborn lambs were divided in two groups and treated either with vehicle or melatonin. After 1 week of treatment, we assessed pulmonary vascular prostanoids function and expression by wire myography, RT-PCR, Western Blot and immunohistochemistry. Melatonin improved in vivo and ex vivo pulmonary vasodilation. This was associated with an increased function and expression of vasodilator prostanoids at the expense of vasoconstrictor prostanoids. Our study demonstrates for the first time that melatonin may enhance the vasodilator prostanoid pathway in PAHN.
Melatonin treatment during chronic hypoxic gestation improves neonatal cerebrovascular function
Vascular Pharmacology, 2022
BACKGROUND Fetal chronic hypoxia is associated with blood flow redistribution and oxidative damag... more BACKGROUND Fetal chronic hypoxia is associated with blood flow redistribution and oxidative damage in the brain, leading to increased perinatal morbimortality. Melatonin reduces oxidative stress, improves vascular function, and has neuroprotective effects. OBJECTIVES This study aimed to determine the effects of an oral melatonin treatment to pregnant ewes at high-altitude, on the cerebrovascular function of their neonates. STUDY DESIGN Ten high-altitude pregnant sheep received either vehicle or melatonin (10 mg/d) during the last third of gestation until delivery. Postnatal daily hemodynamic measurements were recorded from lambs until 12 days old. In addition, lambs were submitted to a graded oxygenation protocol to assess cerebrovascular responses. Subsequently, lambs were euthanized, and middle cerebral arteries (MCA) were collected for vascular function, protein levels, and morphostructural analyses. RESULTS Antenatal treatment doubled plasma levels of melatonin in pregnant ewes. Melatonin increased carotid flow and decreased carotid vascular resistance in the lambs by the end of the first week. Furthermore, melatonin increased MCA's maximal vasoconstrictor and vasodilator responses, associated with nitric oxide-dependent and independent mechanisms. CONCLUSIONS An oral treatment with melatonin during pregnancy promotes postnatal cerebral perfusion in chronically hypoxic neonates. Melatonin is a potential treatment for cerebrovascular dysfunction due to perinatal chronic hypoxia.
Frontiers in Physiology, 2022
Calcium signaling is key for the contraction, differentiation, and proliferation of pulmonary art... more Calcium signaling is key for the contraction, differentiation, and proliferation of pulmonary arterial smooth muscle cells. Furthermore, calcium influx through store-operated channels (SOCs) is particularly important in the vasoconstrictor response to hypoxia. Previously, we found a decrease in pulmonary hypertension and remodeling in normoxic newborn lambs partially gestated under chronic hypoxia, when treated with 2-aminoethyldiphenyl borinate (2-APB), a non-specific SOC blocker. However, the effects of 2-APB are unknown in neonates completely gestated, born, and raised under environmental hypoxia. Accordingly, we studied the effects of 2-APB-treatment on the cardiopulmonary variables in lambs under chronic hypobaric hypoxia. Experiments were done in nine newborn lambs gestated, born, and raised in high altitude (3,600 m): five animals were treated with 2-APB [intravenous (i.v.) 10 mg kg–1] for 10 days, while other four animals received vehicle. During the treatment, cardiopulmona...
Ca 2+ is a major trigger for pulmonary vasoconstriction and a stimulus for pulmonary vascular smo... more Ca 2+ is a major trigger for pulmonary vasoconstriction and a stimulus for pulmonary vascular smooth muscle cell proliferation. The transient receptor potential cation channels participate in regulating intracellular Ca 2+ and thus vascular contractility and cell proliferation. Upregulation of genes encoding these channels is involved in the development of pulmonary hypertension.
Antioxidants, 2021
Pulmonary arterial hypertension of newborns (PAHN) constitutes a critical condition involving bot... more Pulmonary arterial hypertension of newborns (PAHN) constitutes a critical condition involving both severe cardiac remodeling and right ventricle dysfunction. One main cause of this condition is perinatal hypoxia and oxidative stress. Thus, it is a public health concern for populations living above 2500 m and in cases of intrauterine chronic hypoxia in lowlands. Still, pulmonary and cardiac impairments in PAHN lack effective treatments. Previously we have shown the beneficial effects of neonatal melatonin treatment on pulmonary circulation. However, the cardiac effects of this treatment are unknown. In this study, we assessed whether melatonin improves cardiac function and modulates right ventricle (RV) oxidative stress. Ten lambs were gestated, born, and raised at 3600 m. Lambs were divided in two groups. One received daily vehicle as control, and another received daily melatonin (1 mg·kg−1·d−1) for 21 days. Daily cardiovascular measurements were recorded and, at 29 days old, cardia...
Frontiers in Physiology, 2021
The authors previously demonstrated that newborn llama (NBLL) express high levels of α1 adrenergi... more The authors previously demonstrated that newborn llama (NBLL) express high levels of α1 adrenergic receptors, which provide a potent vasoconstriction response when compared with newborn sheep (NBSH) gestated at sea level. However, data regarding the impact of chronic gestational hypobaric hypoxia on α-adrenergic vasoconstriction in the neonatal life has not been studied. We evaluated if gestation under chronic hypobaric hypoxia modifies α1-adrenergic vasoconstrictor function in NBLL and NBSH. We compared the vasoconstrictor response induced by potassium and α-adrenergic stimuli in isolated small femoral arteries of NBLL and NBSH gestated at high altitude (HA; 3,600 m) or low altitude (LA; 580 m). The maximal contraction (RMAX) and potency (EC50) to potassium, noradrenaline (NA), and phenylephrine (PHE) were larger in HA-NBLL than LA-NBLL. RMAX to potassium, NA, and PHE were lower in HA-NBSH when compared with LA-NBSH and potency results were similar. Competitive blockade with prazos...
The newborn sheep translational model for pulmonary arterial hypertension of the neonate at high altitude
Journal of Developmental Origins of Health and Disease, 2020
Chronic hypoxia during gestation induces greater occurrence of perinatal complications such as in... more Chronic hypoxia during gestation induces greater occurrence of perinatal complications such as intrauterine growth restriction, fetal hypoxia, newborn asphyxia, and respiratory distress, among others. This condition may also cause a failure in the transition of the fetal to neonatal circulation, inducing pulmonary arterial hypertension of the neonate (PAHN), a syndrome that involves pulmonary vascular dysfunction, increased vasoconstrictor tone and pathological remodeling. As this syndrome has a relatively low prevalence in lowlands (~7 per 1000 live births) and very little is known about its prevalence and clinical evolution in highlands (above 2500 meters), our understanding is very limited. Therefore, studies on appropriate animal models have been crucial to comprehend the mechanisms underlying this pathology. Considering the strengths and weaknesses of any animal model of human disease is fundamental to achieve an effective and meaningful translation to clinical practice. The sh...
Journal of Applied Physiology, 2020
Most mammals have a poor tolerance to hypoxia, and prolonged O2 restriction can lead to organ inj... more Most mammals have a poor tolerance to hypoxia, and prolonged O2 restriction can lead to organ injury, particularly during fetal and early postnatal life. Nevertheless, the llama ( Lama Glama) has evolved efficient mechanisms to adapt to acute and chronic perinatal hypoxia. One striking adaptation is the marked peripheral vasoconstriction measured in the llama fetus in response to acute hypoxia, which allows efficient redistribution of cardiac output toward the fetal heart and adrenal glands. This strong peripheral vasoconstrictor tone is triggered by a carotid body reflex and critically depends on α-adrenergic signaling. A second adaptation is the ability of the llama fetus to protect its brain against hypoxic damage. During hypoxia, in the llama fetus there is no significant increase in brain blood flow. Instead, there is a fall in brain O2 consumption and temperature, together with a decrease of Na+-K+-ATPase activity and Na+ channels expression, protecting against seizures and ne...
Cinaciguat Reduces Prolyl Hydroxylase 2 (PHD2) Protein Expression in Chronically Hypoxic and Pulmonary Hypertensive Newborn Lambs
The FASEB Journal, 2020
Journal of Pineal Research, 2019
Pulmonary arterial hypertension of the neonate (PAHN) is a pathophysiological condition character... more Pulmonary arterial hypertension of the neonate (PAHN) is a pathophysiological condition characterized by maladaptive pulmonary vascular remodeling and abnormal contractile reactivity. This is a multifactorial syndrome with chronic hypoxia and oxidative stress as main etiological drivers, and with limited effectiveness in therapeutic approaches. Melatonin is a neurohormone with antioxidant and vasodilator properties at the pulmonary level. Therefore, this study aims to test whether a postnatal treatment with melatonin during the neonatal period improves in a long-lasting manner the clinical condition of PAHN. Ten newborn lambs gestated and born at 3600 m were used in this study, five received vehicle and five received melatonin in daily doses of 1 mg kg −1 for the first 3 weeks of life. After 1 week of treatment completion, lung tissue and small pulmonary arteries (SPA) were collected for wire myography, molecular biology, and morphostructural analyses. Melatonin decreased pulmonary arterial pressure the first 4 days of treatment. At 1 month old, melatonin decreased the contractile response to the vasoconstrictors K + , TX 2 , and ET-1. Further, melatonin increased the endothelium-dependent and muscle-dependent vasodilation of SPA. Finally, the treatment decreased pulmonary oxidative stress by inducing antioxidant enzymes and diminishing pro-oxidant sources. In conclusion, melatonin improved vascular reactivity and oxidative stress at the pulmonary level in PAHN lambs gestated and born in chronic hypoxia. K E Y W O R D S chronic hypoxia, melatonin treatment, oxidative stress, pulmonary hypertension of the neonate, reactive oxygen species How to cite this article: Gonzaléz-Candia A, Candia AA, Figueroa EG, et al. Melatonin long-lasting beneficial effects on pulmonary vascular reactivity and redox balance in chronic hypoxic ovine neonates.
Revista médica de Chile, 2019
Melatonin modulates the expression of pulmonary prostanoids Background: Living above 2,500 meters... more Melatonin modulates the expression of pulmonary prostanoids Background: Living above 2,500 meters in hypobaric conditions induces pulmonary arterial hypertension of the neonate (PAHN), a syndrome whose main features are: pathological remodeling of the pulmonary vessels, abnormal vascular reactivity and increased oxidative stress. Melatonin could have pulmonary antioxidant, anti-remodeling and vasodilating properties for this condition. Aim: To determine the effect of melatonin at the transcript level of prostanoid pathways in the lung of neonatal lambs gestated and born under hypobaric hypoxia. Material and Methods: Vehicle (1.4% of ethanol, n = 6) or melatonin (1 mg * kg-1 , n = 5) were administered from the postnatal day 4 to 21 to lambs gestated and born at 3,600 meters above sea level. After one week of treatment completion, lung tissue was obtained, the transcript and protein levels of prostanoid synthases and receptors were assessed by RT-PCR and Western Blot. Results: Melatonin induced the expression of prostacyclin synthase transcript and increased protein expression of the prostacyclin receptor. In addition, the treatment decreased the expression of transcript and protein of cyclooxygenase-2, without changes in the expression of the prostanoid vasoconstrictor (thromboxane) pathway. Conclusions: Postnatal treatment with melatonin increases the expression of the prostacyclin-vasodilator pathway without changing the vasoconstrictor thromboxane pathway. Further, the decreased COX-2 induced by melatonin could be an index of lesser oxidative stress and inflammation in the lung.
The role of nitric oxide signaling in pulmonary circulation of high- and low-altitude newborn sheep under basal and acute hypoxic conditions
Nitric Oxide, 2019
Nitric oxide (NO) is the main vasodilator agent that drives the rapid decrease of pulmonary vascu... more Nitric oxide (NO) is the main vasodilator agent that drives the rapid decrease of pulmonary vascular resistance for the respiratory onset during the fetal to neonatal transition. Nevertheless, the enhanced NO generation by the neonatal pulmonary arterial endothelium does not prevent development of hypoxic pulmonary hypertension in species without an evolutionary story at high altitude. Therefore, this study aims to describe the limits of the NO function at high-altitude during neonatal life in the sheep as an animal model without tolerance to perinatal hypoxia. We studied the effect of blockade of NO synthesis with l-NAME in the cardiopulmonary response of lowland (580 m) and highland (3600 m) newborn lambs basally and under an episode of acute hypoxia. We also determined the pulmonary expression of proteins that mediate the actions of the NO vasodilator pathway in the pulmonary vasoactive tone and remodeling. We observed an enhanced nitrergic function in highland lambs under basal conditions, evidenced as a markedly greater increase in basal mean pulmonary arterial pressure (mPAP) and resistance (PVR) under blockade of NO synthesis. Further, acute hypoxic challenge in lowland lambs infused with l-NAME markedly increased their mPAP and PVR to values greater than baseline, whilst in highland animals under NO synthesis blockade, these variables did not show additional increase in response to low PO2. Highland animals showed increased pulmonary RhoA expression, decreased PSer188-RhoA fraction, increased PSer311-p65-NFқβ fraction and up-regulated smooth muscle α-actin, relative to lowland controls. Taken together our data suggest that NO-mediated vasodilation is important to keep a low pulmonary vascular resistance under basal conditions and acute hypoxia at low-altitude. At high-altitude, the enhanced nitrergic signaling partially prevents excessive pulmonary hypertension but does not protect against acute hypoxia. The decreased vasodilator efficacy of nitrergic tone in high altitude lambs could be in part due to increased RhoA signaling that opposes to NO action in the hypoxic pulmonary circulation.
Redox Biology, 2019
Chronic hypobaric hypoxia during fetal and neonatal life induces neonatal pulmonary hypertension.... more Chronic hypobaric hypoxia during fetal and neonatal life induces neonatal pulmonary hypertension. Hypoxia and oxidative stress are driving this condition, which implies an increase generation of reactive oxygen species (ROS) and/or decreased antioxidant capacity. Melatonin has antioxidant properties that decrease oxidative stress and improves pulmonary vascular function when administered postnatally. However, the effects of an antenatal treatment with melatonin in the neonatal pulmonary function and oxidative status are unknown. Therefore, we hypothesized that an antenatal therapy with melatonin improves the pulmonary arterial pressure and antioxidant status in high altitude pulmonary hypertensive neonates. Twelve ewes were bred at high altitude (3600 m); 6 of them were used as a control group (vehicle 1.4% ethanol) and 6 as a melatonin treated group (10 mg d-1 melatonin in vehicle). Treatments were given once daily during the last third of gestation (100-150 days). Lambs were born and raised with their mothers until 12 days old, and neonatal pulmonary arterial pressure and resistance, plasma antioxidant capacity and the lung oxidative status were determined. Furthermore, we measured the pulmonary expression and activity for the antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase, and the oxidative stress markers 8-isoprostanes, 4HNE and nitrotyrosine. Finally, we assessed pulmonary pro-oxidant sources by the expression and function of NADPH oxidase, mitochondria and xanthine oxidase. Melatonin decreased the birth weight. However, melatonin enhanced the plasma antioxidant capacity and decreased the pulmonary antioxidant activity, associated with a diminished oxidative stress during postnatal life. Interestingly, melatonin also decreased ROS generation at the main pro-oxidant sources. Our findings suggest that antenatal administration of melatonin programs an enhanced antioxidant/pro-oxidant status, modulating ROS sources in the postnatal lung.
The Journal of physiology, Jan 25, 2018
Llamas are born in the Alto Andino with protection against pulmonary hypertension. The physiology... more Llamas are born in the Alto Andino with protection against pulmonary hypertension. The physiology underlying protection against pulmonary vasoconstrictor responses to acute hypoxia in highland species is unknown. We determined the role of NO in the cardiopulmonary responses to acute hypoxia in high- and low-land newborn llamas. The cardiopulmonary function of newborn llamas, born at low (580 m) or high altitude (3600 m), was studied under acute hypoxia, with and without NO blockade. In pulmonary arteries, we measured the reactivity to potassium and SNP, and in lung we determined the content of cGMP and the expression of the NO-related proteins: BKCa, PDE5, PSer92-PDE5, PKG-1, ROCK1 and 2, MYPT1, PSer695-MYPT1, PThr696-MYPT1, MLC20 and PSer19-MLC20. Pulmonary vascular remodelling was evaluated by morphometry and α-actin expression. High- compared to low-land newborn llamas showed lower in vivo pulmonary arterial pressor responses to acute hypoxia. This protection involved enhanced NO...
Placenta, 2017
absence of TGF-b. HTR8/SVneo cell invasion decreased with TGF-b1 (30 ± 15%), but increased (1.4 ±... more absence of TGF-b. HTR8/SVneo cell invasion decreased with TGF-b1 (30 ± 15%), but increased (1.4 ± 0.5 fold) in the presence of hCG. Conclusion; These results suggest a modulating effect of hCG on TGF-b in ESCs, facilitating the invasion of extravillous trophoblast cells, which may have direct implications in the process of embryo implantation and placentation.
American Journal of Physiology-Lung Cellular and Molecular Physiology, 2016
Calcium signaling through store-operated channels (SOC) is involved in hypoxic pulmonary hyperten... more Calcium signaling through store-operated channels (SOC) is involved in hypoxic pulmonary hypertension. We determined whether a treatment with 2-aminoethyldiphenylborinate (2-APB), a compound with SOC blocker activity, reduces pulmonary hypertension and vascular remodeling. Twelve newborn lambs exposed to perinatal chronic hypoxia were studied, six of them received a 2-APB treatment and the other six received vehicle treatment for 10 days in both cases. Throughout this period, we recorded cardiopulmonary variables and on day 11 we evaluated the response to an acute hypoxic challenge. Additionally, we assessed the vasoconstrictor and vasodilator function in isolated pulmonary arteries as well as their remodeling in lung slices. 2-APB reduced pulmonary arterial pressure between the 3rd and 10th days, cardiac output between the 4th and 8th days, and pulmonary vascular resistance at the 10th day of treatment. The pulmonary vasoconstrictor response to acute hypoxia was reduced by the end ...
American journal of obstetrics and gynecology, Aug 19, 2016
Intrauterine growth restriction is a condition in which the fetus has a birth weight and/or lengt... more Intrauterine growth restriction is a condition in which the fetus has a birth weight and/or length below the 10th percentile for the gestational age. Intrauterine growth restriction can be associated with various causes, among which is the low utero-placental perfusion and chronic hypoxia during gestation. Often, intrauterine growth restricted fetuses have increased oxidative stress, therefore, agents that decrease oxidative stress and increase utero, placental and umbilical perfusion have been proposed as a beneficial therapeutic strategy. In this scenario, melatonin acts as an umbilical vasodilator and a potent antioxidant that has not been evaluated in pregnancies under chronic hypoxia that induce fetal growth restriction. However, this neurohormone has been proposed as a pharmacological therapy for complicated pregnancies. The aim of this study was to determine the effects of prenatal administration of melatonin during the last trimester of pregnancy on the biometry of the growt...
Pharmacological Research, 2015
Hypoxia induces several responses at cardiovascular, pulmonary and reproductive levels, which may... more Hypoxia induces several responses at cardiovascular, pulmonary and reproductive levels, which may lead to chronic diseases. This is relevant in human populations exposed to high altitude (HA), in either chronic continuous (permanent inhabitants) or intermittent fashion (HA workers, tourists and mountaineers). In Chile, it is estimated that 1.000.000 people live at highlands and more than 55.000 work in HA shifts. Initial responses to hypoxia are compensatory and induce activation of cardioprotective mechanisms, such as those seen under intermittent hypobaric (IH) hypoxia, events that could mediate preconditioning. However, whenever hypoxia is prolonged, the chronic activation of cellular responses induces longlasting modifications that may result in acclimatization or produce maladaptive changes with increase in cardiovascular risk. HA exposure during pregnancy induces hypoxia and oxidative stress, which in turn may promote cellular responses and epigenetic modifications resulting in severe impairment in growth and development. Sadly, this condition is accompanied with an increased fetal and neonatal morbi-mortality. Further, developmental hypoxia may program cardio-pulmonary circulations later in postnatal life, ending in vascular structural and functional alterations with augmented risk on pulmonary and cardiovascular failure. Additionally, permanent HA inhabitants have augmented risk and prevalence of chronic hypoxic pulmonary hypertension, right ventricular hypertrophy and cardiopulmonary remodeling. Similar responses are seen in adults that are intermittently exposed to chronic hypoxia (CH) such as shift workers in HA areas. The mechanisms involved determining the immediate, short and long-lasting effects are still unclear. For several years, the study of the responses to hypoxic insults and pharmacological targets has been the motivation of our group. This review describes some of the mechanisms underlying hypoxic responses and potential therapeutic approaches with antioxidants such as melatonin, ascorbate, omega 3 (3) or compounds that increase the nitric oxide (NO) bioavailability.
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Papers by German Ebensperger