Systemic arterial pressure at maturity in rats following chronic hypoxia in early life

Perinatal intermittent hypoxia increases early susceptibility to ANG II-induced hypertension in adult male but not in female Sprague-Dawley rats

Prenatal, perinatal, and adulthood exposure to chronic intermittent hypoxia (IH) increases blood pressure in rodents. Males exposed to chronic IH have higher blood pressure versus females. However, it is unknown if this same-sex difference exists with acute perinatal IH. We tested the hypothesis that acute perinatal IH increases baseline blood pressure and enhances sensitivity to angiotensin II (ANG II)-induced hypertension in male Sprague-Dawley rats. Male and female pups were randomized to control (room air) or IH (10 min of ∼10% O2 for 3 times/day) for the first 8 days of life. IH decreased oxygen saturation, as confirmed via a pulse oximeter. Pups were weaned at postnatal day 21. Blood pressure was measured via telemetry beginning at 14 wk of age and analyzed separately into light and dark phases to assess circadian rhythm. Osmotic minipumps to deliver ANG II were implanted at 15 wk of age. Perinatal IH exposure did not alter baseline blood pressure. One week of ANG II treatment increased blood pressure in light and dark periods in males exposed to IH versus control; there was no effect in females. Blood pressure among the groups was comparable following 2 wk of ANG II infusion. Perinatal IH did not change the circadian rhythm. Following ANG II treatment, indexes of renal injury were measured. Perinatal IH did not alter kidney size, structure, nephron number, or creatinine clearance. These data indicate that acute perinatal IH enhances early ANG II-induced hypertension in males, independent of nephron loss or decreases in body weight or kidney function.NEW & NOTEWORTHY The impact of acute intermittent hypoxia (IH) in early life on blood pressure in adulthood is unknown. This study used a new model exposing female and male rat pups to acute IH in the first 8 days of life, without exposing the dam. Although baseline blood pressure was not altered in adulthood, IH increased susceptibility to angiotensin II hypertension only in males, supporting increased susceptibility of males exposed to IH to a second cardiovascular stressor.

Novel Size-Variable Dedicated Rodent Oxygenator for ECLS Animal Models-Introduction of the "RatOx" Oxygenator and Preliminary In Vitro Results

The overall survival rate of extracorporeal life support (ECLS) remains at 60%. Research and development has been slow, in part due to the lack of sophisticated experimental models. This publication introduces a dedicated rodent oxygenator ("RatOx") and presents preliminary in vitro classification tests. The RatOx has an adaptable fiber module size for various rodent models. Gas transfer performances over the fiber module for different blood flows and fiber module sizes were tested according to DIN EN ISO 7199. At the maximum possible amount of effective fiber surface area and a blood flow of 100 mL/min, the oxygenator performance was tested to a maximum of 6.27 mL O₂/min and 8.2 mL CO₂/min, respectively. The priming volume for the largest fiber module is 5.4 mL, while the smallest possible configuration with a single fiber mat layer has a priming volume of 1.1 mL. The novel RatOx ECLS system has been evaluated in vitro and has demonstrated a high degree of compliance with all pre-defined functional criteria for rodent-sized animal models. We intend for the RatOx to become a standard testing platform for scientific studies on ECLS therapy and technology.

Insights into the Mechanisms of Fetal Growth Restriction-Induced Programming of Hypertension

In recent decades, both clinical and animal studies have shown that fetal growth restriction (FGR), caused by exposure to adverse uterine environments, is a risk factor for hypertension as well as for a variety of adult diseases. This observation has shaped and informed the now widely accepted theory of developmental origins of health and disease (DOHaD). There is a plethora of evidence supporting the association of FGR with increased risk of adult hypertension; however, the underlying mechanisms responsible for this correlation remain unclear. This review aims to explain the current advances in the field of fetal programming of hypertension and a brief narration of the underlying mechanisms that may link FGR to increased risk of adult hypertension. We explain the theory of DOHaD and then provide evidence from both clinical and basic science research which support the theory of fetal programming of adult hypertension. In addition, we have explored the underlying mechanisms that may link FGR to an increased risk of adult hypertension. These mechanisms include epigenetic changes, metabolic disorders, vascular dysfunction, neurohormonal impairment, and alterations in renal physiology and function. We further describe sex differences seen in the developmental origins of hypertension and provide insights into the opportunities and challenges present in this field.

Beta Blockers and Chronic Obstructive Pulmonary Disease (COPD): Sum of Evidence

Approximately, half a century has passed since the discovery of beta blockers. Then, their prime therapeutic purpose was to treat angina and cardiac arrhythmias, nowadays, beta blockers' usage and effectiveness is extended to treat other cardiovascular diseases, such as hypertension, congestive heart failure, and coronary artery disease. Safety concerns were raised about beta blockers and their use for chronic obstructive pulmonary disease (COPD) patients with concurrent cardiovascular disease. After a thorough research of the literature, this review summarizes the evidence proving that beta blockers not only might be well tolerated in COPD patients, but they might also have a beneficial effect in this group of patients.

Neonatal oxygen saturations and blood pressure at school-age in children born extremely preterm: a cohort study

OBJECTIVE

To explore the relationship between neonatal oxygen saturation and BP at age 6-7 years in a cohort of infants born extremely preterm.

STUDY DESIGN

Infants <28 weeks gestation were assigned to a higher or lower oxygen saturation target. Oximeter data were monitored throughout the neonatal period. A subset of survivors was seen at age 6. BP was measured and compared by group assignment, achieved saturations, and time spent in hypoxemia (saturations <80%).

RESULTS

There was no difference in systolic or diastolic BP between assigned groups. Median achieved weekly oxygen saturation was not associated with BP. Longer duration of hypoxemia during the first week of age was associated with higher systolic BP.

CONCLUSIONS

Neither target nor actual median oxygen saturations in this study was associated with BP at school age. Increased duration of hypoxemia in the first postnatal week was associated with higher systolic BP at 6-7 years of age.

Effects of vagotomy on cardiovascular and heart rate variability alterations following chronic normobaric hypoxia in adult rabbits

BACKGROUND

chronic hypoxia increases basal ventilation and pulmonary vascular resistance, with variable changes in arterial blood pressure and heart rate, but it's impact on heart rate variability and autonomic regulation have been less well examined. We studied changes in arterial blood pressure, heart rate and heart rate variability (HRV) in rabbits subjected to chronic normobaric hypoxia (CNH; PB ~ 719 mmHg; F_IO₂ ~ 9.2%) for 14 days and assess the effect of autonomic control by acute bilateral vagal denervation.

RESULTS

exposure to CNH stalled animal weight gain and increased the hematocrit, without affecting heart rate or arterial blood pressure. Nevertheless, Poincaré plots of the electrocardiographic R-R intervals showed a reduced distribution parallel to the line of identity, which interpreted as reduced long-term HRV. In the frequency domain, CNH reduced the very-low- (< 0.2 Hz) and high-frequency components (> 0.8 Hz) of the R-R spectrograms and produced a prominent component in the low-frequency component (0.2-0.5 Hz) of the power spectrum. In control and CNH exposed rabbits, bilateral vagotomy had no apparent effect on the short- and long-term HRV in the Poincaré plots. However, bilateral vagotomy differentially affected higher-frequency components (> 0.8 Hz); reducing it in control animals without modifying it in CNH-exposed rabbits.

CONCLUSIONS

These results suggest that CNH exposure shifts the autonomic balance of heart rate towards a sympathetic predominance without modifying resting heart rate or arterial blood pressure.

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.

Arterial stiffness and arterial function in adult cyanotic patients with congenital heart disease

BACKGROUND

Mortality in cyanotic patients with congenital heart diseases (CHD) is high, mainly due to cardiovascular complications. It is known that endothelial dysfunction, increased arterial stiffness, and impaired vascular function have negative influence on cardiovascular prognosis. The aim of the study was to assess parameters of arterial stiffness and vascular dysfunction in cyanotic patients with CHD as well as their potential relation to impaired blood oxygen saturation and polycythemia parameters typical for cyanosis.

METHODS

A total of 36 CHD cyanotic patients (17 males) (42.3±16.3 years) and 35 healthy individuals (16 males) (39.6±10.4 years) were enrolled. Assessed parameters were intima media thickness and flow-mediated dilatation (FMD). Assessed parameters using applanation tonometry methods were aortic systolic pressure, aortic pulse pressure (AoPP), augmentation pressure (AP), augmentation index (AI), pulse pressure amplification (PPampl), and pulse wave velocity (PWV).

RESULTS

AoPP (37.3±11.1mmHg vs. 29±6.5mmHg; p=0.002), AP (10.1±7.3mmHg vs. 1.1±3.9mmHg; p=0.00001), AI (24.7±13.5% vs. 3.0±13.6%; p=0.00001), and PWV (7.4±2.1m/s vs. 6.3±0.7m/s; p=0.003) were higher, and PPampl was lower (135.3±16.1% vs. 160.4±12.8%; p=0.00001) in the studied group compared to controls and proved the presence of the increased stiffness of arteries. Impairment of FMD was observed (9.0±5.6 vs. 10.9±4.7; p=0.04). No significant correlations were found between analyzed arterial parameters and biochemical ones characterizing cyanotic patients depicting rheological properties of blood.

CONCLUSIONS

Cyanotic patients with CHD are characterized by increased arterial stiffness estimated with pulse wave analysis parameters and by deteriorated arterial function expressed with worse vasodilatative response in comparison with healthy population. It may confirm relevance of those mechanisms in development of increased rate of cardiovascular events in this population. Association between oxygen saturation or polycythemia and arterial stiffening or vascular dysfunction was not found in these patients.

Influence of metabolic dysfunction on cardiac mechanics in decompensated hypertrophy and heart failure

Alterations in energetic state of the myocardium are associated with decompensated heart failure in humans and in animal models. However, the functional consequences of the observed changes in energetic state on mechanical function are not known. The primary aim of the study was to quantify mechanical/energetic coupling in the heart and to determine if energetic dysfunction can contribute to mechanical failure. A secondary aim was to apply a quantitative systems pharmacology analysis to investigate the effects of drugs that target cross-bridge cycling kinetics in heart failure-associated energetic dysfunction. Herein, a model of metabolite- and calcium-dependent myocardial mechanics was developed from calcium concentration and tension time courses in rat cardiac muscle obtained at different lengths and stimulation frequencies. The muscle dynamics model accounting for the effect of metabolites was integrated into a model of the cardiac ventricles to simulate pressure-volume dynamics in the heart. This cardiac model was integrated into a simple model of the circulation to investigate the effects of metabolic state on whole-body function. Simulations predict that reductions in metabolite pools observed in canine models of heart failure can cause systolic dysfunction, blood volume expansion, venous congestion, and ventricular dilation. Simulations also predict that myosin-activating drugs may partially counteract the effects of energetic state on cross-bridge mechanics in heart failure while increasing myocardial oxygen consumption. Our model analysis demonstrates how metabolic changes observed in heart failure are alone sufficient to cause systolic dysfunction and whole-body heart failure symptoms.

Role of the kidney in the fetal programming of adult cardiovascular disease: an update

It is well established that an adverse in utero environment can impinge upon fetal development and place the offspring on a track leading to future cardiovascular disease. Significantly, this may occur in the absence of any outward manifestations at birth. In this brief review, we focus on potential renal mechanisms that lead to adaptations in glomerular and tubular function that initiate hypertension of developmental origin and examine potential therapeutic interventions. This report updates recent data in this field.

Exaggerated blood pressure variability in patients with pneumoconiosis: a pilot study

BACKGROUND

Chronic hypoxia is a risk factor for cardiovascular disease, but its association with blood pressure (BP) remains unclear. We performed this study to clarify the hypothesis that chronic hypoxia is associated with abnormal BP variability in patients with pneumoconiosis.

METHODS

We recruited 19 patients with pneumoconiosis and 30 age- and BP level-matched control subjects. We used simultaneous pulse oximetry and ambulatory BP monitoring for all subjects. We evaluated their BP levels and variability by determining the SD and coefficient of variation (CV) of the BP data. The dipper pattern was defined as nocturnal BP fall ≥10%; the nondipper pattern was defined as nocturnal BP fall ≥0% but <10%; the riser pattern was defined as nocturnal BP fall <0%. Pearson and Spearman correlation coefficients were used to calculate the correlations between parameters.

RESULTS

In patients with pneumoconiosis, the daytime systolic BP (SBP) level was lower, the CV in 24-hour SBP (P < 0.05) and diastolic BP (P < 0.001) were higher than that in control subjects. And although not statistically significant (P = 0.13), the odds ratio of riser pattern was 3.73 in patients with pneumoconiosis, and their nighttime pulse rate was significantly higher (P < 0.05) than that in control subjects. The median daytime pulse oximetry oxygen saturation was inversely associated with mean (r = -0.30; P < 0.01) and SD (r = -0.38; P < 0.001) in daytime SBP. The median nighttime pulse oximetry oxygen saturation was inversely associated (r = -0.55; P < 0.001) and the mean nighttime pulse rate was associated (r = 0.51; P < 0.001) with CV in nighttime SBP. Partial pressure of oxygen was inversely associated with CV in daytime SBP (r = -0.24; P < 0.05).

CONCLUSIONS

Exaggerated BP variability was seen in patients with pneumoconiosis, and the measures of hypoxia were associated with large fluctuations in ambulatory BP. Chronic and intermittent hypoxia could be the contributing factors of these findings.

CLINICAL TRIAL REGISTRATION

Clinical Trial Number UMIN000000894 (University Hospital Medical Information Network Clinical Trials Registry website).

Lung Disease and Hypertension

Chronic obstructive pulmonary disease (COPD) patients are at a high risk of developing cardiovascular diseases. Airflow limitation is a predictor of future risks of hypertension and cardiovascular events. COPD is now understood as a systemic inflammatory disease, with the focus on inflammation of the lungs. An association between inflammation and sympathetic overactivity has also been reported. In this article, we review the association between chronic lung disease and the risks of hypertension, cardiovascular morbidity, the underlying mechanisms, and the therapeutic approach to hypertension and cardiovascular diseases in patients with lung diseases.

Petrosal ganglion responses to acetylcholine and ATP are enhanced by chronic normobaric hypoxia in the rabbit

In mammals, adaptation to chronic hypoxia requires the integrity of the arterial chemoreceptors, specially the carotid body (CB). Chronic hypoxia increases the sensibility of the CB by acting on the receptor cells, but there is limited information on the effects of chronic hypoxia on the sensory neurons that innervate the CB. Therefore, we studied the responses evoked by ACh and ATP, the main transmitters that generate the chemoafferent activity, on the petrosal ganglion (PG) of rabbits exposed to chronic normobaric hypoxia (CNH) during fourteen days. ATP and ACh increased the activity of PG neurons in a dose-dependent manner, in a similar way than in rabbits not exposed to hypoxia (naïve). However, the duration of the responses were significantly increased by CNH, with the mean maximal responses to ACh and ATP increased by a factor of two and four, respectively. Our results suggest that CNH increases duration of the responses by modifying the expression and/or content of ACh and ATP receptors.

Gestation dependant changes in angiogenic factors and their associations with fetal growth measures in normotensive pregnancy

Background

Earlier studies indicate that altered angiogenesis at birth is associated with poor birth outcome in women with preeclampsia. Now, we hypothesize that the progressive gestation dependant changes in markers of angiogenesis will be more useful to predict birth weight early even in a normotensive pregnancy. This study for the first time examines the association of gestation dependant changes in the levels of maternal angiogenic factors in addition to their levels in cord with birth weight.

Method

Ninety two pregnant women were followed at three different time points: 16–20 weeks, 26–30 weeks and at delivery during pregnancy. Plasma levels of angiogenic and anti angiogenic factors were determined by commercial enzyme-linked immunosorbent assay (ELISA) kits.

Results

Maternal plasma VEGF levels increased (p<0.01) till the second time point and decreased (p<0.05) up to delivery while plasma sFlt-1 levels increased (p<0.01) at delivery. PlGF levels peaked (p<0.01) at second time point and decreased (p<0.01) at delivery. Cord plasma VEGF levels were higher (p<0.01) and sFlt-1 levels were lower (p<0.01) as compared to maternal values at all time points. Maternal plasma VEGF levels at first time point and PlGF levels at delivery were positively (p<0.05 and p<0.01 respectively), while sFlt-1/PlGF ratio at delivery was negatively associated (p<0.05) with birth weight.

Conclusion

Levels of pro- and anti-angiogenic factors may be differentially regulated across gestation. Maternal VEGF levels at early gestation (16–20 weeks) may be predictive of birth weight in healthy term pregnancies.

Hypoxia in early life is associated with lasting changes in left ventricular structure and function at maturity in the rat

BACKGROUND

There is a growing population of adults with repaired cyanotic congenital heart disease. These patients have increased risk of impaired cardiac health and premature death. We hypothesized that hypoxia in early life before surgical intervention causes lasting changes in left ventricular structure and function with physiological implications in later life.

METHODS

Sprague-Dawley rats reared initially hypoxic conditions (FiO(2)=0.12) for days 1-10 of life were compared to rats reared only in ambient air. Cellular morphology and viability were compared among LV cardiomyocytes and histological analyses were performed on LV myocardium and arterioles. Intracellular calcium transients and cell shortening were measured in freshly-isolated cardiomyocytes, and mitochondrial hexokinase 2 (HK2) expression and activity were determined. Transthoracic echocardiography was used to assess LV function in anesthetized animals.

RESULTS

Cardiomyocytes from adult animals following hypoxia in early life had greater cellular volumes but significantly reduced viability. Echocardiographic analyses revealed LV hypertrophy and diastolic dysfunction, and alterations in cardiomyocyte calcium transients and cell shortening suggested impaired diastolic calcium reuptake. Histological analyses revealed significantly greater intima-media thickness and decreased lumen area in LV arterioles from hypoxic animals. Alterations in mitochondrial HK2 protein distribution and activity were also observed which may contribute to cardiomyocyte fragility.

CONCLUSIONS

Hypoxia in early life causes lasting changes in left ventricular structure and function that may negatively influence myocardial and vascular responses to physiological stress in later life. These data have implications for the growing population of adults with repaired or palliated cyanotic congenital heart disease.