Protection of the brain from hypoxia: a review

Isorhamnetin Alleviates High Glucose-Aggravated Inflammatory Response and Apoptosis in Oxygen-Glucose Deprivation and Reoxygenation-Induced HT22 Hippocampal Neurons Through Akt/SIRT1/Nrf2/HO-1 Signaling Pathway

This study is aimed at exploring the potential of isorhamnetin in protection against diabetes-exacerbated ischemia/reperfusion-induced brain injury and elucidating its action mechanism. After establishment of the model of high glucose (HG)-aggravated oxygen-glucose deprivation and reoxygenation (OGD/R), HT22 cell viability was detected by CCK-8. Lactate dehydrogenase (LDH) activity, casapase-3 activity, and oxidative stress-related markers in HT22 cells were detected by corresponding commercial kits. The apoptosis of HG-treated HT22 cells following OGD/R was observed with TUNEL staining. The level of pro-inflammatory cytokines was examined by ELISA. The expression of Akt/SIRT1/Nrf2/HO-1 signaling-related proteins was assayed by Western blot. The results showed that HG noticeably worsened the OGD/R-induced apoptosis of HT22 cells. Isorhamnetin relieved the HG-aggravated OGD/R-induced apoptosis, inflammatory response, and oxidative stress of HT22 cells. Isorhamnetin alleviated the HG-aggravated OGD/R injury in HT22 cells through Akt/SIRT1/Nrf2/HO-1 signaling pathway. Meanwhile, treatment with Akt inhibitor LY294002 reversed the protective effects of isorhamnetin against HG-aggravated OGD/R injury in HT22 cells. In a conclusion, Isorhamnetin alleviates HG-aggravated OGD/R in HT22 hippocampal neurons through Akt/SIRT1/Nrf2/HO-1 signaling pathway.

Agomelatine prevents macrophage infiltration and brain endothelial cell damage in a stroke mouse model

Background and purpose: Ischemic/reperfusions are regarded as the clinical consensus for stroke treatment, which results in secondary injury of brain tissues. Increased blood-brain barrier (BBB) permeability and infiltration of inflammatory cells are responsible for the ischemic/reperfusion injury. In the present study, we aimed to investigate the effects of Agomelatine on brain ischemic/reperfusions injury and the underlying mechanism.

Methods: MCAO model was established in mice. The expressions of CD68 and claudin-5 in the cerebral cortex were determined using an immunofluorescence assay. Brain permeability was evaluated using Evans blue staining assay. A two-chamber and two-cell trans-well assay was used to detect the migration ability of macrophages through endothelial cells. The expression levels of claudin-5 and MCP-1 in the endothelial cells were determined using qRT-PCR and ELISA.

Results: CD68 was found to be up-regulated in the cerebral cortex of MCAO mice but was down-regulated by treatment with Agomelatine. The expression level of down-regulated claudin-5 in the cerebral cortex of MCAO mice was significantly suppressed by Agomelatine. Deeper staining of Evans blue was found in the MCAO group, which was however faded significantly in the Agomelatine treated MCAO mice. The migrated macrophages were significantly increased by hypoxia incubation but were greatly suppressed by the introduction of Agomelatine. The down-regulated claudin-5 by hypoxic incubation in endothelial cells was up-regulated by treatment with Agomelatine. Furthermore, the increased expression of MCP-1 in endothelial cells under hypoxic conditions was significantly inhibited by Agomelatine.

Conclusion: Agomelatine prevents macrophage infiltration and brain endothelial cell damage in a stroke mouse model.

Neovascularization following traumatic brain injury: possible evidence for both angiogenesis and vasculogenesis

OBJECTIVE

Our goal was to characterize the angiogenic response following traumatic brain injury (TBI).

METHODS

Western analysis for vascular endothelial growth factor (VEGF) expression, double immunofluorescence labeling of endothelium and vascular endothelial growth factor receptor 2 (VEGFR2), bromodioxyuridine (BrdU) incorporation and measurement of capillary density, were all used to determine the temporal angiogenic response following TBI.

RESULTS

The angiogenic factors, VEGF and VEGFR2, increase following trauma. Capillary density increases and BrdU incorporation confirm the presence of newly formed vessels up to 48 hours post-injury.

DISCUSSION

Our results indicated that following TBI, there is a substantial increase in angiogenesis and based on morphologic characterization of BrdU-positive nuclei within the endothelium, we provide evidence for vasculogenesis following injury.

Cerebral blood flow, cross-brain oxygen extraction, and fontanelle pressure after hypoxic-ischemic injury in newborn infants

The relationship between mean arterial pressure, intracranial pressure, cerebral blood flow, cross-brain oxygen extraction, cerebral metabolic rate, and outcome was studied during therapy in nine neonates on 3 consecutive days after severe hypoxic-ischemic cerebral injury. Cross-brain oxygen extraction was significantly higher (5.06 +/- 0.5 vs 2.05 +/- 0.8 ml/dl; p = 0.012) in the five neonates who survived with normal neurologic outcome than in the four who died or sustained severe brain damage. In contrast, global cerebral blood flow in the five neonates with normal neurologic outcome was significantly lower (25.6 +/- 8.2 vs 83.2 +/- 44.9 ml/100 gm brain/min; p less than 0.05) during the study period. The differences in cross-brain oxygen extraction and global cerebral blood flow between infants who had neurologic recovery and those who died or sustained brain damage occurred in the presence of acceptable values for intracranial pressure, mean arterial pressure, and cerebral perfusion pressure. Our preliminary data suggest that cross-brain oxygen extraction and possibly global cerebral blood flow may be important variables associated with severe neuronal injury and death after hypoxic-ischemic cerebral injury.

Cerebral blood flow, metabolic rate, and cross-brain oxygen consumption in brain injury

In six deeply comatose children, the relationships of intracranial pressure, cerebral perfusion pressure, cerebral blood flow, cross-brain oxygen consumption, and metabolic rate to outcome were studied sequentially during therapy. Intracranial pressure, cross-brain oxygen consumption, and metabolic rate values were significantly different in the three children who survived compared with those in the three who died. The differences in cross-brain oxygen consumption and metabolic rate occurred in the presence of clinically acceptable values for intracranial and cerebral perfusion pressures. Cross-brain oxygen consumption and metabolic rate may be important indicators of degree of neuronal injury, and of outcome.

Energy-requiring cell functions in the ischemic brain. Their critical supply and possible inhibition in protective therapy

✓ The energy-requiring cell functions in the brain are described. The role of specific inhibition of these functions, and their critical low-supply levels of blood flow and oxygen are reviewed in relation to clinical management of focal and complete global cerebral ischemia.

The "milieu interieur"-a model of brain physiology and pathophysiology

The "milieu interieur" or "internal environment" of the brain is determined by the glial cells, the cerebrospinal fluid, the blood-brain barrier, the cerebral blood flow, the central regulation of respiration, and the intracranial pressure. Anaesthetic agents and anoxia-ischaemic insult can disrupt this important but vulnerable neuronal environment. Head injury is used as an example of a common insult to the neuronal environment and the principles of management are discussed, using a model of brain physiology and pathophysiology which can be modified to include other clinical situations.