Brain Activity after Intermittent Hypoxic Brain Condition in Rats

Hypoxic brain injury is accompanied by a decrease in various functions. It is also known that obstructive sleep apnea (OSA) can cause hypoxic brain injury. This study aimed to produce a model of an intermittent hypoxic brain condition in rats and determine the activity of the brain according to the duration of hypoxic exposure. Forty male Sprague–Dawley rats were divided into four groups: the control group (n = 10), the 2 h per day hypoxia exposure group (n = 10), the 4 h per day hypoxia exposure group (n = 10), and the 8 h per day hypoxia exposure group (n = 10). All rats were exposed to a hypoxic chamber containing 10% oxygen for five days. Positron emission tomography–computed tomography (PET-CT) brain images were acquired using a preclinical PET-CT scanner to evaluate the activity of brain metabolism. All the rats were subjected to normal conditions. After five days, PET-CT was performed to evaluate the recovery of brain metabolism. Western blot analysis and immunohistochemistry were performed with vascular endothelial growth factor (VEGF) and brain-derived neurotrophic factor (BDNF). The mean SUV was elevated in the 2 h per day and 4 h per day groups, and all brain regions showed increased metabolism except the amygdala on the left side, the auditory cortex on the right side, the frontal association cortex on the right side, the parietal association cortex on the right side, and the somatosensory cortex on the right side immediately after hypoxic exposure. However, there was no difference between 5 days rest after hypoxic exposure and control group. Western blot analysis revealed the most significant immunoreactivity for VEGF in the 2, 4, and 8 h per day groups compared with the control group and quantification of VEGF immunohistochemistry showed more expression in 2 and 4 h per day groups compared with the control group. However, there was no significant difference in immunoreactivity for BDNF among the groups. The duration of exposure to hypoxia may affect the activity of the brain due to angiogenesis after intermittent hypoxic brain conditions in rats.

Intensive Care Management of Multiorgan Dysfunction and Hypoxic Brain Injury Secondary to Refractory Status Epilepticus

Refractory Status Epilepticus (RSE) is a medical emergency that may lead to permanent brain damage or death.Mortality rate is 16-39%. It is the life threatening condition in which continuous fits occur, despite treatmentwith benzodiazepines and one antiepileptic drug.A 25-year-old female, brought in emergency department with high-grade fever and frequent fits. GlasgowComa Scale (GCS) was 3/15 with unstable hemodynamics. Resuscitation started immediately and managed asstatus epilepticus. Patient was in multi organ failure on arrival. On the basis of history and examination, hypoxicbrain injury was diagnosed initially. Later on, refractory status epilepticus (RSE) with multi organ dysfunctionsyndrome (MODS) was diagnosed, after necessary investigations and treatment. Patient was managed as ateam with multidisciplinary approach and after continuous effort of 2 weeks, patient was successfullydischarged to home.

The Potential Role of Hypoxia-inducible Factor-1 in the Progression and Therapy of Central Nervous System Diseases

: Hypoxia-inducible factor-1 (HIF-1) is a heterodimer protein composed of an oxygen-regulated functional subunit, HIF-1α, and a structural subunit, HIF-1β, belonging to the basic helix-loop-helix family. Strict regulation of HIF-1 protein stability and subsequent transcriptional activity involves various molecular interactions and is primarily controlled by post-transcriptional modifications. Hypoxia, owing to impaired cerebral blood flow, has been implicated in a range of central nervous system (CNS) diseases by exerting a deleterious effect on brain function. As a master oxygen-sensitive transcription regulator, HIF-1 is responsible for upregulating a broad spectrum of target genes involved in glucose metabolism, angiogenesis, and erythropoiesis to generate the adaptive response to avoid or minimize hypoxic brain injury. However, prolonged, severe oxygen deprivation may directly contribute to the role-conversion of HIF-1, namely. From neuroprotection to the promotion of cell death. Currently, an increasing number of studies support the fact HIF-1 is involved in a variety of CNS-related diseases, such as intracranial atherosclerosis, stroke, and neurodegenerative diseases. This review article chiefly focuses on the effect of HIF-1 on the pathogenesis and mechanism of progression of numerous CNS-related disorders by mediating the expression of various downstream genes and extensive biological functional events. It presents robust evidence that HIF-1 may represent a potential therapeutic target for CNS-related diseases.

Cerebral and Somatic Oxygen Saturation in Neonates with Congenital Heart Disease before Surgery

BACKGROUND: We investigated preoperative cerebral (ScO2) and abdominal (StO2) regional oxygen saturations according to cardiac diagnosis in neonates with critical CHD, their time trends, and the clinical and biochemical parameters associated with them. METHODS: Thirty-seven neonates with a prenatal diagnosis of CHD were included. ScO2 and StO2 values were continuously evaluated using near-infrared spectroscopy. Measurements were obtained hourly before surgery. A linear mixed effects model was used to assess the effects of time and cardiac diagnosis on regional oxygenation and to explore the contributing factors. RESULTS: Regional oxygenation differed according to cardiac diagnosis (p < 0.001). ScO2 was lowest in the patients with severe atrioventricular valvar regurgitation (AVVR) (48.1 ± 8.0%). StO2 tended to be lower than ScO2, and both worsened gradually during the period between birth and surgery. There was also a significant interaction between cardiac diagnosis and time. The factors related to ScO2 were hemoglobin and arterial saturation, whereas no factor was associated with StO2. CONCLUSIONS: Preoperative ScO2 and StO2 in critical CHD differed according to cardiac diagnosis. ScO2 in the patients with severe AVVR was very low, which may imply cerebral hypoxia. ScO2 gradually decreased, suggesting that the longer the time to surgery, the higher the risk of hypoxic brain injury.

The effects of clonidine and yohimbine in the tail flick and hot plate tests in the naked mole rat (Heterocephalus glaber)

Objective The naked mole rat (NMR) (Heterocephalus glaber) is increasingly considered an important biomedical research model for various conditions like hypoxic brain injury, cancer and nociception. This study was designed to investigate the effects of clonidine and yohimbine, an alpha-2 (α2) adrenoceptor agonist and antagonist respectively in the tail flick and hot plate tests. Results A significant difference in tail flick latency was noted between saline control and 30 µg/kg clonidine, which was reduced after administration of 30 µg/kg yohimbine. A significant difference in hot plate latency was also noted between saline control and 30 µg/kg clodinine during the periods 30, 45, 60, 75 and 90 min after administration, and between saline control and 10 µg/kg clonidine during 30 min after administration. The hot plate latency by 30 µg/kg clonidine was also reduced by 30 µg/kg yohimbine during 30 min after administration. Since the tail-flick and hot plate tests mediate the effects at spinal and supraspinal levels respectively, the present study indicates the presence and involvement of noradrenergic receptors in thermal antinociception at spinal and supraspinal levels of the NMR, similar to what has been found in other mammals.

Human fetal neural stem cell-derived astrocytes maintain glutamate transport after hypoxic injury in vitro

Astrocytes are the most abundant glial cells that play many critical roles in the central nervous system physiology including the uptake of excess glutamate from the synapse by Excitatory Amino Acid Transporters (EAATs). Among the EAATs, EAAT2 are predominantly functional, astrocyte-specific glutamate transporters in the forebrain. Hypoxic brain injury is a pathological phenomenon seen in various clinical conditions including stroke and neonatal hypoxic ischemic encephalopathy. Glutamate excitotoxicity is an important cause of neuronal cell death in disorders involving hypoxic brain injury. As findings from rodent models cannot always be reliably extrapolated to humans, we aimed to develop a homogenous population of primary human astrocytes to study the effect of hypoxic injury on astrocyte function, especially glutamate uptake. We successfully isolated, established and characterized cultures of human fetal neural stem cells (FNSCs) from aborted fetal brains. FNSCs were differentiated into astrocytes, and characterized by increased expression of the astrocyte marker, glial fibrillary acidic protein (GFAP), and a concomitant decrease in neural stem cell marker, Nestin. Differentiated astrocytes were exposed to various oxygen concentrations mimicking normoxia (20% and 6%), moderate and severe hypoxia (2% and 0.2% respectively). Interestingly, no change was observed in the expression of glutamate transporter, EAAT2 and glutamate uptake by astrocytes, even after exposure to hypoxia. Our novel model of human FNSC derived astrocytes exposed to hypoxic injury, establishes that astrocytes are able to maintain glutamate uptake even after exposure to severe hypoxia for 48 hours, and thus provides evidence for the neuroprotective role of astrocytes in hypoxic injury.