Periods Of Hypoxia Research Articles

Impaired Chemoreflex Response to Acute Hypoxia Correlates with Decreased Activation of the Medial Nucleus Tractus Solitarii in the STZ‐Induced Rat Model of Alzheimer's Disease

BackgroundAlzheimer's disease (AD) is the most common cause of dementia and clinically diagnosed largely based on cognitive decline. Most AD patients also present with disorders of respiration, swallowing, and autonomic function. Current studies suggest that pathological changes in the brainstem manifest simultaneously or even before those in forebrain regions, and may account for non‐cognitive symptoms. Identifying the pathologic changes in brainstem centers may elucidate the mechanisms behind cardiorespiratory dysfunction in AD. This study concentrated on the respiratory deficits. Using the streptozotocin (STZ)‐induced model of AD, we determined cell activation in response to acute hypoxia in the nucleus tractus solitarii (nTS), a brainstem area that is integral for chemoreflex function.MethodsSporadic AD was induced in Sprague Dawley rats (280 ± 17g, n = 6 rats/group) by intracerebroventricular injections of streptozotocin (1.5 mg/kg STZ in citrate buffer; day 1 and 3). Vehicle injections served as control (CTL). Peripheral chemoreflex function was tested with two hours of acute hypoxia (10% O2) in a plethysmography chamber. Immediately following the hypoxic period, the brains were fixed with 4% paraformaldehyde. Four representative areas of the nTS were immunohistochemically analyzed for cell activation (c‐Fos).ResultsThe chemoreflex‐mediated increase of minute ventilation in response to acute hypoxia was significantly blunted by ~20% in STZ rats when compared to CTL (p = 0.03). The diminished response continued over the entire 2 hours of hypoxia and was mainly due to alterations in respiratory rate. Immunohistochemical analysis revealed a ~25% decrease of hypoxia‐mediated cell activation in the medial nTS of STZ rats (−14.04 mm from bregma, p = 0.02). This decline in cell activation was not due to a general decrease in cell density as shown by DAPI staining. The level of activation in commissural and rostral nTS sections was not different from CTL.ConclusionWe had previously found respiratory dysregulation in the STZ model of sporadic AD. This follow‐up study analyzed respiratory parameters over a two‐hour hypoxic period and the underlying pattern of cell activation in the nTS. Our data document a reduced activation of the medial nTS in the chemoreflex pathway of AD rats. This finding may help explain the respiratory symptoms observed in AD patients.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A Translational Model of Incomplete Catch-Up Growth: Early-Life Hypoxia and the Effect of Physical Activity.

Advances in therapies have led to prolonged survival from many previously lethal health threats in children, notably among prematurely born babies and those with congenital heart disease. Evidence for catch‐up growth is common in these children, but in many cases the adult phenotype is never achieved. A translational animal model is required in which specific tissues can be studied over a reasonable time interval. We investigated the impact of postnatal hypoxia (HY) (12%O2 (HY12) or 10% O2 (HY10)) on growth in rats relative to animals raised in room air. Subgroups had access to running wheels following the HY period. Growth was fully compensated in adult HY12 rats but not HY10 rats. The results of this study indicate that neonatal hypoxia can be a useful model for the elucidation of mechanisms that mediate successful catch‐up growth following neonatal insults and identify the critical factors that prevent successful catch‐up growth.

Time-dependent changes in cardiorespiratory functions of anesthetized rats exposed to sustained hypoxia.

Although cardiovascular responses may be altered by respiratory changes under prolonged hypoxia, the relationship between respiratory and cardiovascular changes remains unknown. The aim of the present study is to clarify cardiorespiratory changes in anesthetized rats during and after hypoxic conditions using simultaneous recordings of cardiorespiratory variables with 20-sec recording intervals. After air breathing for 20 min (pre-exposure period), rats were subjected to 10% O2 for 2 h (hypoxic exposure period) and then air for 30 min (recovery period). Minute ventilation (VE), respiratory frequency, tidal volume, arterial blood pressure (BP), and heart rate (HR) were continuously monitored during the experimental period. Just after hypoxic exposure, VE, BP, and HR exhibited an overshoot, undershoot, and overshoot followed by a decrease, respectively. During the remaining hypoxic exposure period, continuous high VE and low BP were observed, whereas HR re-increased. In the recovery period, VE, BP, and HR showed an undershoot, increase, and decrease followed by an increase, respectively. These results suggest that the continuation of enhanced VE and re-increased HR, probably, due to carotid body excitation and accompanying sympathetic activation, during the late period of hypoxic exposure are protective responses to avoid worsening hypoxemia and further circulatory insufficiencies under sustained hypoxia.

Uncovering the metabolic response of abalone (Haliotis midae) to environmental hypoxia through metabolomics.

Oxygen is essential for metabolic processes and in the absence thereof alternative metabolic pathways are required for energy production, as seen in marine invertebrates like abalone. Even though hypoxia has been responsible for significant losses to the aquaculture industry, the overall metabolic adaptations of abalone in response to environmental hypoxia are as yet, not fully elucidated. To use a multiplatform metabolomics approach to characterize the metabolic changes associated with energy production in abalone (Haliotis midae) when exposed to environmental hypoxia. Metabolomics analysis of abalone adductor and foot muscle, left and right gill, hemolymph, and epipodial tissue samples were conducted using a multiplatform approach, which included untargeted NMR spectroscopy, untargeted and targeted LC-MS spectrometry, and untargeted and semi-targeted GC-MS spectrometric analyses. Increased levels of anaerobic end-products specific to marine animals were found which include alanopine, strombine, tauropine and octopine. These were accompanied by elevated lactate, succinate and arginine, of which the latter is a product of phosphoarginine breakdown in abalone. Primarily amino acid metabolism was affected, with carbohydrate and lipid metabolism assisting with anaerobic energy production to a lesser extent. Different tissues showed varied metabolic responses to hypoxia, with the largest metabolic changes in the adductor muscle. From this investigation, it becomes evident that abalone have well-developed (yet understudied) metabolic mechanisms for surviving hypoxic periods. Furthermore, metabolomics serves as a powerful tool for investigating the altered metabolic processes in abalone.

Dissolved oxygen concentration affects δ15N values in oyster tissues: implications for stable isotope ecology

AbstractTo investigate the potential effects of physiological stress on stable isotope (SI) ratios in oysters, we transplanted hatchery‐reared oysters to reefs that experienced different concentrations of dissolved oxygen (DO) in Mobile Bay, Alabama, USA, a freshwater dominated estuary that experiences periodic hypoxia. We monitored physical, biological, and chemical parameters of the environment and biological responses in oysters, including growth, survival, and carbon and nitrogen SI ratios in tissues. Oysters at the low DO site (3.66 ± 0.05 mg/L) had ~1 ‰ higher δ15N values in tissue than oysters at the higher DO site (6.00 ± 0.06 mg/L). Oysters grown at the low DO site also had lower survival (25%) and no growth compared to oysters at the higher DO site, which had 96% survival and growth rates up to 38 mm/d. Multivariate and regression statistics related DO concentration to changes in δ15N values in three different oyster tissues (adductor muscle, gut gland, and gill), regardless of similarity in suspended particulate matter and chlorophyll a concentrations (food quantity), C:N (food quality), and SI composition in available foods between sites. The increased δ15N values in oyster tissues under low DO conditions during this study were consistent with known starvation responses in which oysters stop feeding and catabolize tissues. These data indicate that environmental conditions related to physiological stress can affect SI ratios in oysters in a similar manner to changes in diet composition. Small changes in SI ratios, therefore, may be physiologically significant indicators of environmental stress. When analyzing SI ratios for food web dynamics and source tracing, potential for confounding effects of environmental stressors should be considered.

Long-term effects of brief hypoxia due to cardiac arrest: Hippocampal reductions and memory deficits

ObjectiveTo examine the effects of brief hypoxia (<7 min) due to cardiac arrest on the integrity of the brain and performance on memory and executive functions tasks. MethodsPatients after out-of-hospital cardiac arrest (CA) (n = 9), who were deemed neurologically intact on discharge, were compared to matched patients with myocardial infarction (MI) (n = 9). A battery of clinical and experimental memory and executive functions neuropsychological tests were administered and MRI scans for all patients were collected. Measures of subcortical and cortical volumes and cortical thickness were obtained using FreeSurfer. Manual segmentations of the hippocampus were also performed. APACHE-II scores were calculated based on metrics collected at admission to ICCU for all patients. ResultsSignificant differences between the two groups were observed on several verbal memory tests. Both hippocampi were significantly reduced (p < 0.05) in the CA patients, relative to MI patients. Hippocampal subfields segmentation showed significantly reduced presubiculum volumes bilaterally. CA patients had on average 10% reduction in volumes bilaterally across hippocampal subfields. No cortical thickness differences survived correction. Significant correlations were observed in the CA group only between the hippocampal volumes and performance on verbal memory tasks, including recollection. Hippocampal volumes and several memory measures (but not other cognitive domains) were strongly correlated with APACHE-II scores on admission in the CA group, but not in the MI group ConclusionsChronic patients with cardiac arrest who were discharged from hospital in “good neurological condition” showed an average of 10% reduction in hippocampal volume bilaterally and significant verbal memory deficits relative to matched controls with myocardial infarction, suggesting even brief hypoxic periods suffice to lead to specific hippocampal damage.

Increased Small Intestinal Permeability during Severe Acute Exacerbations of COPD

Background: Disturbances of intestinal integrity, manifested by increased gastro-intestinal (GI) permeability, have been found in chronic obstructive pulmonary disease (COPD) patients during physical activity, often associated with intermittent hypoxic periods. Evidence about extrapulmonary organ disturbances, especially of the GI tract, during hospitalised acute exacerbation of COPD (AE-COPD) with hypoxaemic respiratory failure (RF) is lacking. Objective: The aim was to assess changes in GI permeability in patients with AE-COPD and during recovery 4 weeks later. Methods: All patients admitted to our hospital with AE-COPD accompanied by hypoxaemia at admission (PaO₂ <8.7 kPa or O₂ saturation <93%) were screened between October 2013 and February 2014. Patients with a history of GI or renal disease, chronic heart failure, or use of non-steroidal anti-inflammatory drugs in the 48 h before the test were excluded. GI permeability was assessed by evaluating urinary excretion ratios of the orally ingested sugars lactulose/L-rhamnose (L/R ratio), sucrose/L-rhamnose (Su/R ratio) and sucralose/erythritol (S/E ratio). Results: Seventeen patients with severe to very severe COPD completed the study. L/R ratio (×10³) at admission of AE-COPD was significantly higher than in the recovery condition (40.9 [29.4–49.6] vs. 27.3 [19.5–47.7], p = 0.039), indicating increased small intestinal permeability. There were no significant differences in the individual sugar levels in urine nor in the 0- to 5-h urinary S/E and Su/R ratios between the 2 visits. Conclusion: This is the first study showing increased GI permeability during hospitalised AE-COPD accompanied by hypoxaemic RF. Therefore, GI integrity in COPD patients is an attractive target for future research and for the development of interventions to alleviate the consequences of AE-COPD.

ОСОБЕННОСТИ ДИНАМИКИ СПЕКТРА ЭЭГ ЧЕЛОВЕКА ПРИ ПОСТОЯННОМ УРОВНЕ ОСТРОГО ГИПОКСИЧЕСКОГО ВОЗДЕЙСТВИЯ, "Российский физиологический журнал им. И.М. Сеченова"

У 12 испытуемых с помощью Фурье-анализа исследованы изменения амплитудно-частотного спектра ЭЭГ при постоянном уровне нормобарического гипоксического воздействия (дыхание кислородо-азотной смесью с 8%-ным содержанием кислорода в течение 25 мин). При помощи кластерного анализа 16-канальных ЭЭГ были выделены две группы испытуемых, различающихся по средней за период гипоксического воздействия относительной спектральной мощности (СМ) дельта-диапазона ЭЭГ. У 6 испытуемых первой группы (п = 7), имеющих более высокую относительную СМ дельта-диапазона при гипоксии, после 6 мин гипоксии во всех последующих одноминутных отрезках и во всех отведениях отмечалось доминирование дельта-активности. У испытуемых второй группы (п = 5) в затылочных отведениях в целом за 25 мин гипоксии доминировала альфа-активность. В последовательных одноминутных отрезках записи доминирование альфа-активности у некоторых испытуемых данной группы перемежалось с доминированием активности дельта- и тета-диапазонов. Показано, что динамика амплитудно-частотного спектра ЭЭГ при постоянном уровне гипоксического воздействия не всегда соответствует последовательному «замедлению» ЭЭГ, описанному для нарастающего по силе гипоксического воздействия.

Synaptic densities in hypoxia exposed and electrically stimulated primary neural cultures

Synaptic densities in hypoxia exposed and electrically stimulated primary neural cultures

Abstract 312: Visualization of Cardiomyocyte cGMP Dynamics in Hypoxia/Reoxygenation

The second messenger cyclic guanosine 3′5′-monophosphate (cGMP) plays an important role in the regulation of multiple physiologic processes in the cardiovascular system for example it is known to inhibit hypertrophy and to protect against ischemia-reperfusion injury. As a consequence of hypoxia in the heart, maladaptive signaling cascades are activated that can result in cardiac damage and finally lead to heart failure. However, cellular responses to hypoxia/reoxygenation (H/R) are still incompletely understood and almost nothing is known about cGMP dynamics in the context of H/R. The aim of this project was to investigate the effects of H/R on cGMP dynamics in mammalian cardiomyocytes. Therefore transgenic mice with cardiomyocyte-specific expression of the cytosolic Förster resonance energy transfer (FRET)-based cGMP sensor red cGES-DE5 were used to study cGMP dynamics in single adult cardiomyocytes exposed to H/R. In addition, a Langendorff system was used for FRET measurements in whole-heart. Basal cGMP levels in single adult cardiomyocytes exposed to H/R were increased. This increase was generated already during the hypoxic period and was maintained during reoxygenation. PDE3 protein expression and activity were significantly downregulated after H/R, however RNA expression level of PDE3 was not significantly changed. At the same time, protein levels of the soluble guanylyl cyclase β-subunit showed a tendency towards downregulation during H/R. In whole heart measurements, we could show that cGMP levels increase during anoxia and decrease during reoxygenation. This indicates that there is also an influence of other cell-types on cGMP dynamics or on cGMP cell-cell transfer. In conclusion, we developed FRET-based cGMP measurements in single cardiomyocytes and whole hearts in context of H/R and found an increase of intracellular cGMP in hypoxia. This offers great opportunities to dissect the molecular mechanism of cGMP signaling regulation during ischemic injury and should help to distinguish between direct protective effects on cardiomyocytes and indirect mechanisms such as cell-cell interactions in cGMP signaling during and after H/R.

Correction of tissue oxygen saturations using arterial oxygen levels for cerebrovascular autoregulation analysis.

Adequate perfusion of blood is fundamental to brain tissue viability, and failure to appropriately regulate cerebral blood flow is related to neurological damage. Cerebral tissue oxygenation is commonly used as a surrogate of cerebral blood flow for non-invasive measures of autoregulation, but may only be valid during periods of constant oxygen delivery. We present a new algorithm to correct for supply oxygen-induced variations in cerebral tissue oxygenation, and we validate it by measuring the improved correlation of the corrected tissue oxygenation with blood flow. The algorithm corrects tissue oxygenation by calculating its linear dependence with arterial oxygen saturation below a baseline level. A porcine model (N=8) of hypoxia is used to test the algorithm and compare the tissue oxygen correction with a blood flow reference signal. The correction provides significant improvement in the correlation between flow and tissue oxygenation (Wilcoxon signed rank, p<;0.01), and for the root mean square distance between the corrected hypoxic periods and the rSO2-flow regression line (Wilcoxon signed rank, p<;0.01). This method allows the correction of tissue oxygenation levels used in the non-invasive monitoring of autoregulation.

High salmon density and low discharge create periodic hypoxia in coastal rivers

AbstractDissolved oxygen (DO) is essential to the survival of almost all aquatic organisms. Here, we examine the possibility that abundant Pacific salmon (Oncorhynchus spp.) and low streamflow combine to create hypoxic events in coastal rivers. Using high‐frequency DO time series from two similar watersheds in southeastern Alaska, we summarize DO regimes and the frequency of hypoxia in relationship to salmon density and stream discharge. We also employ a simulation model that links salmon oxygen respiration to DO dynamics and predicts combinations of salmon abundance, discharge, and water temperature that may result in hypoxia. In the Indian River, where DO was monitored hourly during the ice‐free season from 2010 to 2015, DO levels decreased when salmon were present. In 2013, a year with extremely high spawning salmon densities, DO dropped to 1.7 mg/L and 16% saturation, well below lethal limits. In Sawmill Creek, where DO was monitored every six minutes across an upstream–downstream gradient during the 2015 spawning season, DO remained fully saturated upstream of spawning reaches, but declined markedly downstream to 2.9 mg/L and 26% saturation during spawning. Modeled DO dynamics in the Indian River closely tracked field observations. Model sensitivity analysis illustrates that low summertime river discharge is a precursor to salmon‐induced oxygen depletion in our study systems. Our results provide compelling evidence that dense salmon populations and low discharge can trigger hypoxia, even in rivers with relatively cold thermal regimes. Although climate change modeling for southeastern Alaska predicts an increase in annual precipitation, snowfall in the winter and rainfall in the summer are likely to decrease, which would in turn decrease summertime discharge in rain‐ and snow‐fed streams and potentially increase the frequency of hypoxia. Our model template can be adapted by resource managers and watershed stakeholders to create real‐time predictive models of DO trends for individual streams. While preserving thermally suitable stream habitat for cold‐water taxa facing climate change has become a land management priority, managers should also consider that some protected watersheds may still be at risk of increasingly frequent hypoxia due to human impacts such as water diversion and artificially abundant salmon populations caused by hatchery straying.

Hypoxic Induced Decrease in Oxygen Consumption in Cuttlefish (Sepia officinalis) Is Associated with Minor Increases in Mantle Octopine but No Changes in Markers of Protein Turnover.

The common cuttlefish (Sepia officinalis), a dominant species in the north-east Atlantic ocean and Mediterranean Sea, is potentially subject to hypoxic conditions due to eutrophication of coastal waters and intensive aquaculture. Here we initiate studies on the biochemical response to an anticipated level of hypoxia. Cuttlefish challenged for 1 h at an oxygen level of 50% dissolved oxygen saturation showed a decrease in oxygen consumption of 37% associated with an 85% increase in ventilation rate. Octopine levels were increased to a small but significant level in mantle, whereas there was no change in gill or heart. There were no changes in mantle free glucose or glycogen levels. Similarly, the hypoxic period did not result in changes in HSP70 or polyubiquinated protein levels in mantle, gill, or heart. As such, it appears that although there was a decrease in metabolic rate there was only a minor increase in anaerobic metabolism as evidenced by octopine accumulation and no biochemical changes that are hallmarks of alterations in protein trafficking. Experiments with isolated preparations of mantle, gill, and heart revealed that pharmacological inhibition of protein synthesis could decrease oxygen consumption by 32 to 42% or Na+/K+ ATPase activity by 24 to 54% dependent upon tissue type. We propose that the decrease in whole animal oxygen consumption was potentially the result of controlled decreases in the energy demanding processes of both protein synthesis and Na+/K+ ATPase activity.

Role of carbonic anhydrases in skin wound healing

Skin wound closure occurs when keratinocytes migrate from the edge of the wound and re-epithelialize the epidermis. Their migration takes place primarily before any vascularization is established, that is, under hypoxia, but relatively little is known regarding the factors that stimulate this migration. Hypoxia and an acidic environment are well-established stimuli for cancer cell migration. The carbonic anhydrases (CAs) contribute to tumor cell migration by generating an acidic environment through the conversion of carbon dioxide to bicarbonate and a proton. On this basis, we explored the possible role of CAs in tissue regeneration using mouse skin wound models. We show that the expression of mRNAs encoding CA isoforms IV and IX are increased (~25 × and 4 ×, respectively) during the wound hypoxic period (days 2–5) and that cells expressing CAs form a band-like structure beneath the migrating epidermis. RNA-Seq analysis suggested that the CA IV-specific signal in the wound is mainly derived from neutrophils. Due to the high level of induction of CA IV in the wound, we treated skin wounds locally with recombinant human CA IV enzyme. Recombinant CA IV significantly accelerated wound re-epithelialization. Thus, CA IV could contribute to wound healing by providing an acidic environment in which the migrating epidermis and neutrophils can survive and may offer novel opportunities to accelerate wound healing under compromised conditions.

Hypoxic Preconditioning Improves Respiratory Muscle Function during Hypoxia by Regulating Mitochondria in COPD Mice

Diaphragm weakness has been observed in patients with chronic obstructive pulmonary disease (COPD), which may be associated with the prolonged hypoxic conditions in the disease. We found that hypoxic preconditioning (HPC) can strengthen diaphragm under hypoxic conditions in COPD mice by treating the muscle with alternating low and high O2 concentrations. In this study, we tested the hypothesis that the protective effects offered by HPC are linked with the opening of mitochondrial ATP‐sensitive potassium channel (KATP) and the closing of the mitochondrial permeability transition pore (mPTP) in COPD mice. Adult C57BL6 mice were smoked for three months to develop COPD symptoms. Following the completion of smoking, diaphragms of the mice were isolated and mounted in a contractile chamber. Each muscle strip was treated (n = 6) or non‐treated with HPC (n = 6), or pre‐incubated with a combination of KATP channel inhibitor (glibenclamide; 100 μM) and mPTP opener (carboxyatractyloside; 50 μM; n = 6) for 30 min prior to HPC. Another two groups of muscles were treated either with KATP channel activator (diazoxide; 100 μM; n = 6) or mPTP inhibitor (cyclosporine A; 100 μM; n = 6) in the absence of HPC. The muscles were then consecutively stimulated for five minutes (0.5 Hz) during a 30‐min hypoxic period. Fatigue tolerance was determined as the ratio of residual force at the end of the five‐min contraction to the initial force. Data were expressed as means ± SE, and analyzed using multi‐way ANOVA. P &lt; 0.05 was considered statistically different. Our results show that HPC significantly improved diaphragm function during hypoxia (29 ± 2.8% for HPC vs. 6 ± 1.3% for control, p &lt; 0.05). However, such protective effects were eliminated via the simultaneous inhibition of KATP channel and the opening of mPTP (5 ± 2.1%, p &lt; 0.05 vs. HPC). On the other hand, either the activation of KATP channel (27 ± 2.6%) or the inhibition of mPTP (24 ± 3.6%) significantly mitigates diaphragm fatigue (p &lt; 0.05 vs. control) to an extent similar to that of HPC. These data collectively indicate that the mechanisms of HPC protection on diaphragm under hypoxia may involve the opening of mitochondrial KATP channel and inhibition of mPTP in COPD mice.Support or Funding InformationAmerican Physiological Society (APS) 2016 S&amp;R Foundation Ryuji Ueno Award

Rebuilding of Carbohydrate and Lipid Metabolism Under Hypoxia: Regularities and Therapeutic Possibilities

Previously, we have found that the effects of chronic (staying in midlands) or moderate periodic hypoxia as well as hypoxic preconditioning is accompanied by beneficial refbuilding in lipid and carbohydrate metabolism in human and animals: a reduction of total cholesterol and its fractions in blood plasma, a hypoglycemic reaction or normalization of elevated blood glucose, and a decrease of impaired glucose tolerance. This metabolic rebuilding has a phase character during the adaptation to hypoxia and following deadaptation. Changes in metabolism during hypoxia occur in a consecutive manner and mediate by induction and repression of target genes following activation of hypoxia responsible signal ways and transcription factors. In particular, we showed the alternate transactivation of HIF-1alpha and -3alpha subunits, and the restructuring of glucose transport by consecutive induction of GLUT-4 and -1 in rat myocardium and lungs. Mitochondrial respiration is consequentially shifted from down - to up- regulation, and from carbohydrate to mainly lipid substrate using. In human, we found attenuation of transcriptional regulator of cholesterol synthesis SREBP-1, leptin and insulin-like growth factor IGF-1 levels in blood plasma under prolonged hypoxic conditions, as well as positive correlation with HIF-dependent protein IGF-1 and HDL-cholesterol level. In middle-aged people with metabolic disorders (metabolic syndrome, diabetes mellitus, dyslipidemia), favorable influence of staying in midlands, moderate acute or periodic hypoxia was found, but metabolic pathology was associated with altered pattern of regulatory protein expression. The data suggest the close relationship between carbohydrate and lipid metabolism under hypoxia, and evidence the possibility of hypoxic correction of metabolic disorders as diabetes, dyslipidemia and metabolic syndrome based on phase processes of metabolic rebuilding.

Positron emission tomography of cerebral angiogenesis and TSPO expression in a mouse model of chronic hypoxia

The present study aimed to examine whether positron emission tomography (PET) could evaluate cerebral angiogenesis. Mice were housed in a hypoxic chamber with 8–9% oxygen for 4, 7, and 14 days, and the angiogenic responses were evaluated with a radiotracer, 64Cu-cyclam-RAFT-c(-RGDfK-)4, which targeted αVβ3 integrin and was imaged with PET. The PET imaging results showed little uptake during all of the hypoxic periods. Immunofluorescence staining of the β3 integrin, CD61, revealed weak expression, while the microvessel density assessed by CD31 staining increased with the hypoxic duration. These observations suggest that the increased vascular density originated from other types of vascular remodeling, unlike angiogenic sprouting. We then searched for any signs of vascular remodeling that could be detected using PET. PET imaging of 11C-PK11195, a marker of the 18-kDa translocator protein (TSPO), revealed a transient increase at day 4 of hypoxia. Because the immunofluorescence of glial markers showed unchanged staining over the early phase of hypoxia, the observed upregulation of TSPO expression probably originated from non-glial cells (e.g. vascular cells). In conclusion, a transient increase in TSPO probe uptake was detected with PET at only the early phase of hypoxia, which indicates an early sign of vascular remodeling induced by hypoxia.

Shock Wave Therapy Promotes Cardiomyocyte Autophagy and Survival during Hypoxia

Background: Autophagy plays an important role in cardiovascular disease. Controversy still exists regarding the effect of autophagy on ischemic/hypoxic myocardium. Cardiac shock wave therapy (CSWT) is an effective alternative treatment for refractory ischemic heart disease. Whether CSWT can regulate cardiomyocyte autophagy under hypoxic conditions is not clear. We established a myocardial hypoxia model using the H9c2 cell line and performed shock waves (SWs) treatment to evaluate the effect of SW on autophagy. Methods: The H9c2 cells were incubated under hypoxic conditions, and SW treatment was then performed at energies of 0.02, 0.05, or 0.10 mJ/mm². The cell viability and intracellular ATP level were examined. Western blot analysis was used to assess the expression of LC3B, AMPK, mTOR, Beclin-1, Sirt1, and HIF-1α. Autophagic vacuoles were visualized by monodansylcadaverine staining. Results: After the 24-hour hypoxic period, cardiomyocyte viability and ATP levels were decreased and autophagy was significantly increased in H9c2 cells. SW treatment with an energy of 0.05 mJ/mm² significantly increased the cellular viability, ATP level, LC3B-II/I, and number of autophagic vacuoles. In addition, phosphorylated AMPK and Sirt1 were increased and phosphorylated mTOR and HIF-1α were decreased after SW treatment. Conclusion: SW treatment can potentially promote cardiomyocyte autophagy during hypoxia and protect cardiomyocyte function by regulating the AMPK/mTOR pathway.

Is levetiracetam neuroprotective in neonatal rats with hypoxic ischemic brain injury?

The aim of this study was to determine if levetiracetam (LEV) is neuroprotective in neonatal rats with hypoxic-ischemic brain injury (HIBI). The study included 7-d-old male Wistar rats that were randomly divided into the LEV400, LEV800, control, and sham groups. All the rats, except those in the sham group, underwent ligation of the carotid artery and were then kept in a hypoxic chamber containing 8% oxygen for 2 h. At the end of the hypoxic period the rats in the control group were administered saline solution 0.5 mL, the rats in the LEV400 group were administered LEV 400 mg.kg-1, and rats in the LEV800 group were administered LEV 800 mg.kg-1 via the intraperitoneal route. The terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) method was used to evaluate neuronal apoptosis in the rats. The Morris Water Maze (MWM) test was performed at age 14 weeks in order to evaluate cognitive function. The number of apoptotic neurons in the right hemispheres was significantly lower in the sham, LEV400, and LEV800 groups than in the control group (p < 0.001, p < 0.001, and p < 0.001, respectively). In addition, the number of apoptotic neurons in the right hemispheres was significantly lower in the LEV800 group than in the LEV400 group (p = 0.001). Platform finding time (PFT) during MWM testing was significantly shorter in the sham and LEV800 groups on d 4 than on d 1 (p = 0.001 and p = 0.006, respectively); however, PFT did not significantly change between d 1 and d 4 in the control or LEV400 groups (p = 0.91 and p = 0.096, respectively). Based on the present findings, LEV exhibited a dose-dependent neuroprotective effect in neonatal rats with HIBI (Ref. 27).

Longer hypoxia–ischemia periods to neonatal rats causes motor impairments and muscular changes

Prematurity and hypoxia–ischemia (HI) can lead to movement disorders in infants. Considering that mild-moderate HI induced at postnatal day (PND) 3 has failed to produce motor disabilities similar to those seen in pre-term newborns, the main goal of the present study was to verify whether longer hypoxia periods would mimic motor function impairment, brain and muscle morphological alterations. Forty-nine Wistar rat pups of both sexes were randomly assigned to surgical control (CG) and HI groups. HI animals were submitted to the Levine-Rice model at PND 3, and exposed to 120 (HI-120′), 180 (HI-180′) or 210 (HI-210′) minutes of hypoxia (FiO2: 0.08). Sensorimotor function was assessed as from PND 35–45, by means of grasping strength, adhesive removal, cylinder and ladder walking tests. Histological staining was used to quantify the striatal volume and the cross-sectional area (CSA) of skeletal muscles. Cylinder and adhesive removal test evidenced that HI-180′ and HI-210′ groups had asymmetrical use of the forepaws when compared to controls. HI animals showed a decrease in the step placement quality and an increase in step errors when compared to CG (P⩽0.05). Reduction in striatal volume correlates with behavioral assessment, HI-180′ and HI-210′ groups presented lower biceps brachii and tibialis anterior CSA. These results show that rats exposed to longer hypoxic periods at PND3 have encephalic and sensorimotor impairments that mimic those observed in preterm infants. Morphological changes in muscle tissue evidence a new pathophysiological characteristic of the HI model that might be of relevance for the study of sensorimotor deficits.