Prolonged exposure to isoflurane ameliorates infarction severity in the rat pup model of neonatal hypoxia-ischemia

Protocol to optimize the Rice-Vannucci rat pup model of perinatal asphyxia to ensure predictable hypoxic-ischemic cerebral lesions

The Rice-Vannucci model in rodent pups is subject to substantial loss of animals, result inconsistency, and high lab-to-lab variability in extent and composition of induced injury. This protocol allows for highly predictable and reproducible hypoxic-ischemic cerebral injury lesions in post-natal day 10 Wistar rat pups with no mortality. We describe steps for common carotid artery ligation, brief post-operative normothermia, exposure to hypoxia, and post-hypoxic normothermia. Precise timing and temperature control in each step are crucial for a successful procedure. For complete details on the use and execution of this protocol, please refer to Hartman et al.1.

Small animal PET with spontaneous inhalation of 15O-labelled oxygen gases: Longitudinal assessment of cerebral oxygen metabolism in a rat model of neonatal hypoxic-ischaemic encephalopathy

Perinatal hypoxic-ischaemic encephalopathy (HIE) is the leading cause of irreversible brain damage resulting in serious neurological dysfunction among neonates. We evaluated the feasibility of positron emission tomography (PET) methodology with 15O-labelled gases without intravenous or tracheal cannulation for assessing temporal changes in cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) in a neonatal HIE rat model. Sequential PET scans with spontaneous inhalation of 15O-gases mixed with isoflurane were performed over 14 days after the hypoxic-ischaemic insult in HIE pups and age-matched controls. CBF and CMRO2 in the injured hemispheres of HIE pups remarkably decreased 2 days after the insult, gradually recovering over 14 days in line with their increase found in healthy controls according to their natural maturation process. The magnitude of hemispheric tissue loss histologically measured after the last PET scan was significantly correlated with the decreases in CBF and CMRO2.This fully non-invasive imaging strategy may be useful for monitoring damage progression in neonatal HIE and for evaluating potential therapeutic outcomes.

Asymmetry Index Evaluation of Cerebral Volume and Cerebral Blood Flow in Neonatal Hypoxic–Ischemic Encephalopathy

The aim of the present study was to longitudinally evaluate the differences in cerebral volume and cerebral blood flow (CBF) on the right and left sides in rats with neonatal hypoxic–ischemic encephalopathy (HIE) using magnetic resonance imaging and the Rice–Vannucci model. Unilateral ligation of the left common carotid artery was performed on 8-day-old rats, followed by mild (1 h, n = 6) or severe (2 h, n = 7) hypoxic exposure. T2-weighted (T2W) and CBF images were obtained at 1 h and 1, 3, and 7 days following the HI insult. The cerebral volume (Vlesion and Vcontrol), CBF in both hemispheres (lesion and control sides), and asymmetry indices of the cerebral volume (AIvolume) and CBF (AICBF) were calculated for each group. Slight hyperintensities were noted in the lesion-side hemispheres on T2W images at 1 h and 1 day in both groups, as were pronounced hyperintensities at days 3 and 7 in the severe group. AIvolume was positive (Vlesion > Vcontrol) in the mild and severe groups until days 1 and 3, respectively, and changed to negative on days 3 and 7 in the mild and severe groups. These results suggest that the prolonged positive AIvolume prior to day 3 in the severe group was caused by long-term cell swelling following severe HI insult.

A new Hypoxic Ischemic Encephalopathy model in neonatal rats

BACKGROUND

Hypoxic-Ischemic Encephalopathy (HIE) occurs when an infant's brain does not receive adequate blood and oxygen supply, resulting in ischemic and hypoxic brain damage during delivery. Currently, supportive care and hypothermia have been the standard treatment for HIE. However, there are still a 20% mortality and most of the survivors are associated with significant neurodevelopmental disability. HIE animal model was first established by Vannucci et al., in 1981, and has been used extensively to explore the mechanisms of brain damage and its potential treatment. The Vannucci model involves the unilateral common carotid artery occlusion followed by 90 min hypoxia (8% oxygen). The purpose of this study is to define and validate a modified HIE model which mimics closely that of the human neonatal HIE.

METHOD

The classic Vannucci HIE model occludes one common carotid artery followed by 90 min hypoxia. In the new model, common carotid arteries were occluded bilaterally followed by breathing 8% oxygen in a hypoxic chamber for 90, 60 and 30 min, followed by the release of the common carotid artery ligatures, mimicking a reperfusion.

RESULT

We studied 110 neonatal rats in detail, following the modified in comparison with the classical Vannucci models. The classical Vannucci model has a consistent surgical mortality of 18% and the new modified models have a 20%-46%. While mortality depended on the duration of hypoxia, fifty-two animals survived for behavioral assessments and standard histology. The modified HIE model with 60 min of transient carotid occlusion is associated with a moderate brain damage, and has a 30% surgical mortality. This modified experimental model is regarded closer to the human situation than the classical Vannucci model.

Fraxinellone ameliorates intracerebral hemorrhage-induced secondary brain injury by regulating Krüppel-like transcription factor 2 expression in rats

Damage to the blood-brain barrier (BBB) is an important factor leading to intracerebral hemorrhage (ICH)-induced secondary brain injury (SBI). Krüppel-like transcription factor 2 (KLF2) plays an important role in the maintenance of the BBB. This study aims to detect the changes of KLF2 after ICH and evaluate the potential effects of fraxinellone on ICH-induced SBI and its correlation with KLF2. An ICH model was established by injecting autologous blood into the right basal ganglia of Sprague-Dawley (SD) rats. First, after ICH induction, the protein levels of KLF2 were reduced. Then, we found that the decrease of KLF2 protein levels induced by ICH could be effectively reversed with the treatment of fraxinellone in vascular endothelial cells. Furthermore, fraxinellone treatment effectively alleviated brain edema, decreased the levels of TNF-α and IL-1β, and improved neuronal cell degeneration induced by ICH. Meanwhile, fraxinellone ameliorated neurobehavioral disorders, motor and sensory impairments, and neurobehavioral disorders and memory loss caused by ICH. Collectively, these findings reveal that KLF2 may be a potential target for fraxinellone to exert neuroprotective effects after ICH, and fraxinellone could be a potential therapeutic agent for SBI after ICH.

Early neuroimaging and ultrastructural correlates of injury outcome after neonatal hypoxic-ischaemia

Hypoxic ischaemia encephalopathy is the major cause of brain injury in new-borns. However, to date, useful biomarkers which may be used to early predict neurodevelopmental impairment for proper commencement of hypothermia therapy is still lacking. This study aimed to determine whether the early neuroimaging characteristics and ultrastructural correlates were associated with different injury progressions and brain damage severity outcomes after neonatal hypoxic ischaemia. Longitudinal 7 T MRI was performed within 6 h, 24 h and 7 days after hypoxic ischaemia in rat pups. The brain damage outcome at 7 days post-hypoxic ischaemia assessed using histopathology and MRI were classified as mild, moderate and severe. We found there was a spectrum of different brain damage severity outcomes after the same duration of hypoxic ischaemia. The severity of brain damage determined using MRI correlated well with that assessed by histopathology. Quantitative MRI characteristics denoting water diffusivity in the tissue showed significant differences in the apparent diffusion coefficient deficit volume and deficit ratios within 6 h, at 24 h and 7 days after hypoxic ischaemia among the 3 different outcome groups. The susceptible brain areas to hypoxic ischaemia were revealed by the temporal changes in regional apparent diffusion coefficient values among three outcome groups. Within 6 h post-hypoxic ischaemia, a larger apparent diffusion coefficient deficit volume and deficit ratios and lower apparent diffusion coefficient values were highly associated with adverse brain damage outcome. In the apparent diffusion coefficient deficit areas detected early after hypoxic ischaemia which were highly associated with severe damage outcome, transmission electron microscopy revealed fragmented nuclei; swollen rough endoplasmic reticulum and degenerating mitochondria in the cortex and prominent myelin loss and axon detraction in the white matter. Taken together, different apparent diffusion coefficient patterns obtained early after hypoxic ischaemia are highly associated with different injury progression leading to different brain damage severity outcomes, suggesting the apparent diffusion coefficient characteristics may be applicable to early identify the high-risk neonates for hypothermia therapy.

N-acetylserotonin Derivative Exerts a Neuroprotective Effect by Inhibiting the NLRP3 Inflammasome and Activating the PI3K/Akt/Nrf2 Pathway in the Model of Hypoxic-Ischemic Brain Damage

Neonatal hypoxic-ischemic encephalopathy (HIE) is one of the main causes of neonatal disability and death. As a derivative of N-acetylserotonin, N-[2-(5-hydroxy-1H-indol-3-yl) ethyl]-2-oxopiperidine-3-carboxamide (HIOC) can easily cross the blood-brain barrier and have a long half-life in the brain. In this study, the hypothesis was verified that HIOC plays a neuroprotective role in the HIE model and its potential mechanism was evaluated. Firstly, an HIE rat model was established to deliver HIOC, revealing that it can reduce cerebral infarction volume, cerebral edema, and neuronal apoptosis. The results of immunofluorescence staining, Western blots and RT-PCR further showed that HIOC could inhibit the activation of the NLRP3 inflammasome and the expression of related proteins. Finally, the activation of the phosphatidylinositol-3-kinase (PI3K)/Akt/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway by HIOC was verified in vitro and in vivo. It was discovered that HIOC could increase the nuclear translocation of Nrf2, and that this induction can be reversed by the PI3K/Akt pathway inhibitor LY294002. In general terms, the neuroprotective effect of HIOC was confirmed in the HIE model, which is related to the activation of the Pi3k/Akt/Nrf2 signal pathway and the inhibition of the NLRP3 inflammasome.

Effect of Isoflurane Exposure with Administration of Polyunsaturated Fatty Acids on Cognition in Developing Rats

Objective

The developing brain is vulnerable to the negative effects of anaesthetics. We aimed to investigate the effect of isoflurane and polyunsaturated fatty acids (PUFAs) on cognition.

Methods

A total of 64, ten days old rats were randomly divided into 4 groups: group O2 (oxygen group), group Iso (isoflurane group), group Iso-S (isoflurane+saline) and group Iso-PUFAs (isoflurane+intraperitoneal [IP] PUFAs emulsion). Rats in groups Iso, Iso-S and Iso-PUFAs were exposed to 1.5% isoflurane in 50% oxygen for 6 hours. Rats in group O2 breathed only 50% oxygen. Before anaesthesia, rats in group Iso-S were administered 0.5 mL isotonic and rats in group Iso-PUFAs were administered 5 mL kg^-1 PUFAs emulsion by IP injection. The Morris water maze (MWM) test was performed on postnatal 28-33 days. Histological evaluation and immune histochemical staining (Bcl-2 antibody) were performed on postnatal day 11 on rat brains.

Results

As demonstrated by the reduction in the escape latency on days 3, 4 and 5 compared with day 1, all rats learned the task during the acquisition period. In contrast to others, rats in group Iso spent significantly lower time to find the platform on day 2 than on day 1 (p=0.034). No significant difference was found among the groups in terms of time spent in finding the platform. There were no significant differences in probe trials, histological features and Bcl-2 immunoreactivity among the groups.

Conclusion

Isoflurane did not cause cognitive dysfunction and neuronal death, and a single dose of PUFAs emulsion had no effect on cognition either.

Activated WNK3 induced by intracerebral hemorrhage deteriorates brain injury maybe via WNK3/SPAK/NKCC1 pathway

BACKGROUND

Intracerebral hemorrhage (ICH) is the common brain diseases in middle-aged and elderly people, with high disability and/or mortality rate, and is a serious public health concern. Both WNK3 kinase and the WNK3/SPAK/NKCC1 signaling pathway play an integral role in maintaining normal cell homeostasis. However, their role and underlying mechanisms in ICH-induced secondary brain injury (SBI) have yet to be elucidated.

METHODS

We established an ICH model using male Sprague-Dawley (SD) rats by injecting autologous arterial blood into the unilateral basal ganglia. To establish ICH model in vitro, oxyhemoglobin (OxyHb; 20 μM) and neurons were cultured for 6 h at 37 °C, 5% CO₂ atmosphere. To investigate the role of WNK3 and the WNK3/SPAK/NKCC1 signaling pathway in SBI, after genetic interventions, rotation and water maze test, brain edema and neuroinflammation were detected, and terminal-deoxynucleoitidyl transferase mediated dUTP nick end labeling (TUNEL), Fluoro-Jade C (FJC), and Nissl staining were performed.

RESULTS

Our data showed that WNK3 expression in brain tissue were upregulated after ICH induction. In addition, silencing of WNK3 reduced neuronal apoptosis, and inflammatory responses in rats that underwent ICH. Inhibition of WNK3 expression reduced the damaged blood-brain barrier (BBB), alleviated the impaired degree of cerebral edema, and improved disruptive neurobehavioral cognition caused by ICH. Moreover, overexpression of WNK3 had the opposite effects. Finally, WNK3/SPAK/NKCC1 signaling pathway may be involved in the above-mentioned processes.

CONCLUSIONS

In conclusion, our findings showed that WNK3 and WNK3/SPAK/NKCC1 signaling pathway play a vital biological function in ICH-induced SBI. Depletion of WNK3 attenuated brain injury after ICH both in vivo and in vitro. Thus, WNK3 and WNK3/SPAK/NKCC1 signaling pathway are potential targets for treating SBI after ICH.

hUC-MSCs Exert a Neuroprotective Effect via Anti-apoptotic Mechanisms in a Neonatal HIE Rat Model

In this study, we investigated how human umbilical cord mesenchymal stem cells exerted a neuroprotective effect via antiapoptotic mechanisms in a neonatal hypoxic-ischemic encephalopathy rat model. A total of 78 10-day old (P10) rats were used. After human umbilical cord mesenchymal stem cells were collected from human umbilical cords and amplified in culture, they were administered to rat subjects 1 h after induced hypoxic-ischemic encephalopathy treatment. The short-term (48 h) and long-term (28 day) outcomes were evaluated after human umbilical cord mesenchymal stem cells treatment using neurobehavioral function assessment. Triphenyltetrazolium chloride monohydrate staining was performed at 48 h. Beclin-2 and caspase-3 levels were evaluated with Western blot and real time polymerase chain reaction at 48 h. Human umbilical cord mesenchymal stem cells were collected and administrated to hypoxic-ischemic encephalopathy pups by intracerebroventricular injection. Hypoxic-ischemic encephalopathy typically induced significant delay in development and caused impairment in both cognitive and motor functions in rat subjects. Human umbilical cord mesenchymal stem cells were shown to ameliorate hypoxic-ischemic encephalopathy-induced damage and improve both cognitive and motor functions. Although hypoxic-ischemic encephalopathy induced significant expression of caspase-3 and Beclin-2, human umbilical cord mesenchymal stem cells decreased the expression of both of them. Human umbilical cord mesenchymal stem cells may serve as a potential treatment to ameliorate brain injury in hypoxic-ischemic encephalopathy patients.

Osteopontin-Enhanced Autophagy Attenuates Early Brain Injury via FAK-ERK Pathway and Improves Long-Term Outcome after Subarachnoid Hemorrhage in Rats

Osteopontin (OPN) enhances autophagy, reduces apoptosis, and attenuates early brain injury (EBI) after a subarachnoid hemorrhage (SAH). A total of 87 Sprague–Dawley rats were subjected to sham or SAH operations to further investigate the signaling pathway involved in osteopontin-enhanced autophagy during EBI, and the potential effect of recombinant OPN (rOPN) administration to improve long-term outcomes after SAH. Rats were randomly divided into five groups: Sham, SAH + Vehicle (PBS, phosphate-buffered saline), SAH + rOPN (5 μg/rat recombinant OPN), SAH + rOPN + Fib-14 (30 mg/kg of focal adhesion kinase (FAK) inhibitor-14), and SAH + rOPN + DMSO (dimethyl sulfoxide). Short-term and long-term neurobehavior tests were performed, followed by a collection of brain samples for assessment of autophagy markers in neurons, pathway proteins expression, and delayed hippocampal injury. Western blot, double immunofluorescence staining, Nissl staining, and Fluoro-Jade C staining assay were used. Results showed that rOPN administration increased autophagy in neurons and improved neurobehavior in a rat model of SAH. With the administration of FAK inhibitor-14 (Fib-14), neurobehavioral improvement and autophagy enhancement induced by rOPN were abolished, and there were consistent changes in the phosphorylation level of ERK1/2. In addition, early administration of rOPN in rat SAH models improved long-term neurobehavior results, possibly by alleviating hippocampal injury. These results suggest that FAK–ERK signaling may be involved in OPN-enhanced autophagy in the EBI phase after SAH. Early administration of rOPN may be a preventive and therapeutic strategy against delayed brain injury after SAH.

Isoflurane exposure in infant rats acutely increases aquaporin 4 and does not cause neurocognitive impairment

Isoflurane is commonly used in pediatric population, but its mechanism of action in cognition is unclear. Aquaporin 4 (AQP4) regulates water content in blood, brain, and cerebrospinal fluid. Various studies have provided evidence for the role of AQP4 in synaptic plasticity and neurocognition. In this study, we aimed to determine whether a prolonged exposure to isoflurane in infant rats is associated with cognition and what effect this exposure has on AQP4 expression. Ten-day-old [postnatal day (P) 10] Wistar albino rats were randomly allocated to isoflurane group (n = 32; 1.5% isoflurane in 50% oxygen for 6 hours) or control group (n = 32; only 50% oxygen for 6 hours). Acute (P11) and long-term (P33) effects of 6-hour anesthetic isoflurane exposure on AQP4 expression were analyzed in whole brains of P11 and P33 rats by RT-qPCR and Western blot. Spatial learning and memory were assessed on P28 to P33 days by Morris Water Maze (MWM) test. The analysis revealed that isoflurane increased acutely both mRNA (~4.5 fold) and protein (~90%) levels of AQP4 in P11 rats compared with control group. The increasing levels of AQP4 in P11 were not observed in P33 rats. Also, no statistically significant change between isoflurane and control groups was observed in the latency to find the platform during MWM training and probe trial. Our results indicate that a single exposure to isoflurane anesthesia does not influence cognition in infant rats. In this case, acutely increased AQP4 after isoflurane anesthesia may have a protective role in neurocognition.

Isoflurane exposure in infant rats acutely increases aquaporin 4 and does not cause neurocognitive impairment

Isoflurane is commonly used in pediatric population, but its mechanism of action in cognition is unclear. Aquaporin 4 (AQP4) regulates water content in blood, brain, and cerebrospinal fluid. Various studies have provided evidence for the role of AQP4 in synaptic plasticity and neurocognition. In this study, we aimed to determine whether a prolonged exposure to isoflurane in infant rats is associated with cognition and what effect this exposure has on AQP4 expression. Ten-day-old [postnatal day (P) 10] Wistar albino rats were randomly allocated to isoflurane group (n = 32; 1.5% isoflurane in 50% oxygen for 6 hours) or control group (n = 32; only 50% oxygen for 6 hours). Acute (P11) and long-term (P33) effects of 6-hour anesthetic isoflurane exposure on AQP4 expression were analyzed in whole brains of P11 and P33 rats by RT-qPCR and Western blot. Spatial learning and memory were assessed on P28 to P33 days by Morris Water Maze (MWM) test. The analysis revealed that isoflurane increased acutely both mRNA (~4.5 fold) and protein (~90%) levels of AQP4 in P11 rats compared with control group. The increasing levels of AQP4 in P11 were not observed in P33 rats. Also, no statistically significant change between isoflurane and control groups was observed in the latency to find the platform during MWM training and probe trial. Our results indicate that a single exposure to isoflurane anesthesia does not influence cognition in infant rats. In this case, acutely increased AQP4 after isoflurane anesthesia may have a protective role in neurocognition.

Analysis of long non-coding RNA expression profiles in neonatal rats with hypoxic-ischemic brain damage

Hypoxic-ischemic brain damage (HIBD) which is a common cause of acute mortality and neurological dysfunction in neonates still lacks effective therapeutic methods. Long non-coding RNAs (lncRNAs) were demonstrated to play a crucial role in many diseases. To give a foundation for subsequent functional studies of lncRNAs in HIBD, we investigated the profiling of lncRNAs and messenger RNAs (mRNAs) using neonatal HIBD rat model. Six neonatal rats were divided into sham-operated group (n = 3) and HIBD group (n = 3) randomly. Deep RNA sequencing was implemented to find out the meaningful lncRNAs and mRNAs. Quantitative real-time PCR was used to validate expressions of lncRNAs and mRNAs. The Gene Ontology (GO) and kyoto encyclopedia of genes a genomes (KEGG) database were used to predict functions of lncRNAs. A total of 328 differentially expressed lncRNAs (177 down-regulated vs 151 up-regulated) and 7157 differentially expressed mRNAs (2552 down-regulated vs 4605 up-regulated) were identified. The Quantitative real-time PCR results showed significant differential expressions of five lncRNAs and five mRNAs which were consistent with the RNA-Seq data. Gene ontology and KEGG analysis showed these lncRNAs and their expression-correlated mRNAs were closely related to the Janus tyrosine kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway, NF-kappa B signaling pathway, Toll-like receptor signaling pathway, calcium signaling pathway, Notch signaling pathway, mitogen activated protein kinase signaling pathway, neuroactive ligand-receptor interaction pathway and more. The results of our study identified the characterization and expression profiles of lncRNAs in neonatal HIBD and may be a basis for further therapeutic research. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* and *Open Data* because it provided all relevant information to reproduce the study in the manuscript and because it made the data publicly available. The data can be accessed at https://osf.io/yf3da/. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.

Neurogenesis changes and the fate of progenitor cells after subarachnoid hemorrhage in rats

BACKGROUND

Subarachnoid hemorrhage (SAH) is a devastating cerebrovascular disease that leads to poor outcomes. Neurogenesis, an essential recovery mechanism after brain injury, has not been fully elucidated after SAH.

METHODS

A total of 122 SD rats were used in this study. For experiment one, the rats were randomly divided into six groups: sham and SAH with different time points (1,3,5,7,14 days) (n = 12/group). An endovascular perforation method was conducted for SAH model. Rats were injected with 5-Bromo-2'-deoxyuridine (BrdU, 50 mg/kg) 24 h before euthanasia at different time points after SAH. The BrdU labeled cells were detected by immunohistochemistry; Doublecortin (DCX) and glial fibrillary acidic protein (GFAP) were measured by western blot and immunohistochemistry. For experiment two, rats were randomly divided into five groups: sham and SAH with different time points (1, 2, 4, 8 weeks) (n = 6/group). Rats received BrdU (50 mg/kg) once daily for 7 days after the induction of SAH. Double immunofluorescence staining was used to verify proliferation, differentiation and migration of progenitor cells. Rotarod test and water maze used to test the neurobehavioral recovery.

RESULTS

Our results showed that BrdU positive cells in hippocampus changed overtime after SAH. BrdU positive cells decreased as early as 1 day reaching lowest levels at 3 days after SAH, after which it gradually recovered. Similar change patterns were observed with DCX, which was reversed with GFAP. In addition, BrdU did not co-localize with cleaved caspase-3. The BrdU positive cells mainly differentiated into immature neurons for short-term fate, whereas they differentiated into mature neurons for long-term fate but not astrocytes, which facilitated neurobehavioral recovery after SAH.

CONCLUSION

Neurogenesis in the hippocampus changes overtime after SAH. The neuronal progenitor cells may play an essential role in the neurobehavioral recovery after brain injury induced by SAH, since short-term progenitors helped with the recovery of immature neurons in the hippocampus, whereas long-term progenitors differentiated into mature neurons.

Exogenous Neural Precursor Cell Transplantation Results in Structural and Functional Recovery in a Hypoxic-Ischemic Hemiplegic Mouse Model

Cerebral palsy (CP) is a common pediatric neurodevelopmental disorder, frequently resulting in motor and developmental deficits and often accompanied by cognitive impairments. A regular pathobiological hallmark of CP is oligodendrocyte maturation impairment resulting in white matter (WM) injury and reduced axonal myelination. Regeneration therapies based on cell replacement are currently limited, but neural precursor cells (NPCs), as cellular support for myelination, represent a promising regeneration strategy to treat CP, although the transplantation parameters (e.g., timing, dosage, mechanism) remain to be determined. We optimized a hemiplegic mouse model of neonatal hypoxia-ischemia that mirrors the pathobiological hallmarks of CP and transplanted NPCs into the corpus callosum (CC), a major white matter structure impacted in CP patients. The NPCs survived, engrafted, and differentiated morphologically in male and female mice. Histology and MRI showed repair of lesioned structures. Furthermore, electrophysiology revealed functional myelination of the CC (e.g., restoration of conduction velocity), while cylinder and CatWalk tests demonstrated motor recovery of the affected forelimb. Endogenous oligodendrocytes, recruited in the CC following transplantation of exogenous NPCs, are the principal actors in this recovery process. The lack of differentiation of the transplanted NPCs is consistent with enhanced recovery due to an indirect mechanism, such as a trophic and/or “bio-bridge” support mediated by endogenous oligodendrocytes. Our work establishes that transplantation of NPCs represents a viable therapeutic strategy for CP treatment, and that the enhanced recovery is mediated by endogenous oligodendrocytes. This will further our understanding and contribute to the improvement of cellular therapeutic strategies.

Severe-combined immunodeficient rats can be used to generate a model of perinatal hypoxic-ischemic brain injury to facilitate studies of engrafted human neural stem cells

Cerebral palsy (CP) encompasses a group of non-progressive brain disorders that are often acquired through perinatal hypoxic-ischemic (HI) brain injury. Injury leads to a cascade of cell death events, resulting in lifetime motor and cognitive deficits. There are currently no treatments that can repair the resulting brain damage and improve functional outcomes. To date, preclinical research using neural precursor cell (NPC) transplantation as a therapy for HI brain injury has shown promise. To translate this treatment to the clinic, it is essential that human-derived NPCs also be tested in animal models, however, a major limitation is the high risk of xenograft rejection. A solution is to transplant the cells into immune-deficient rodents, but there are currently no models of HI brain injury established in such a cohort of animals. Here, we demonstrate that a model of HI brain injury can be generated in immune-deficient Prkdc knockout (KO) rats. Long-term deficits in sensorimotor function were similar between KO and wildtype (WT) rats. Interestingly, some aspects of the injury were more severe in KO rats. Additionally, human induced pluripotent stem cell derived (hiPSC)-NPCs had higher survival at 10 weeks post-transplant in KO rats when compared to their WT counterparts. This work establishes a reliable model of neonatal HI brain injury in Prkdc KO rats that will allow for future transplantation, survival, and long-term evaluation of the safety and efficacy of hiPSC-NPCs for neonatal brain damage. This model will enable critical preclinical translational research using human NPCs.

IRE1α inhibition decreased TXNIP/NLRP3 inflammasome activation through miR-17-5p after neonatal hypoxic-ischemic brain injury in rats

Background

The endoplasmic reticulum (ER) is responsible for the control of correct protein folding and protein function which is crucial for cell survival. However, under pathological conditions, such as hypoxia–ischemia (HI), there is an accumulation of unfolded proteins thereby triggering the unfolded protein response (UPR) and causing ER stress which is associated with activation of several stress sensor signaling pathways, one of them being the inositol requiring enzyme-1 alpha (IRE1α) signaling pathway. The UPR is regarded as a potential contributor to neuronal cell death and inflammation after HI. In the present study, we sought to investigate whether microRNA-17 (miR-17), a potential IRE1α ribonuclease (RNase) substrate, arbitrates downregulation of thioredoxin-interacting protein (TXNIP) and consequent NLRP3 inflammasome activation in the immature brain after HI injury and whether inhibition of IRE1α may attenuate inflammation via miR-17/TXNIP regulation.

Methods

Postnatal day 10 rat pups (n = 287) were subjected to unilateral carotid artery ligation followed by 2.5 h of hypoxia (8% O₂). STF-083010, an IRE1α RNase inhibitor, was intranasally delivered at 1 h post-HI or followed by an additional one administration per day for 2 days. MiR-17-5p mimic or anti-miR-17-5p inhibitor was injected intracerebroventricularly at 48 h before HI. Infarct volume and body weight were used to evaluate the short-term effects while brain weight, gross and microscopic brain tissue morphologies, and neurobehavioral tests were conducted for the long-term evaluation. Western blots, immunofluorescence staining, reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR), and co-immunoprecipitation (Co-IP) were used for mechanism studies.

Results

Endogenous phosphorylated IRE1α expression was significantly increased after HI. Intranasal administration of STF-083010 alleviated brain injury and improved neurological behavior. MiR-17-5p expression was reduced after HI, and this decrease was attenuated by STF-083010 treatment. MiR-17-5p mimic administration ameliorated TXNIP expression, NLRP3 inflammasome activation, caspase-1 cleavage, and IL-1β production, as well as brain infarct volume. Conversely, anti-miR-17-5p inhibitor reversed IRE1α inhibition-induced decrease in TXNIP expression and inflammasome activation, as well as exacerbated brain injury after HI.

Conclusions

IRE1a-induced UPR pathway may contribute to inflammatory activation and brain injury following neonatal HI. IRE1a activation, through decay of miR-17-5p, elevated TXNIP expression to activate NLRP3 inflammasome and aggravated brain damage.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1077-9) contains supplementary material, which is available to authorized users.

Dihydrolipoic Acid Inhibits Lysosomal Rupture and NLRP3 Through Lysosome-Associated Membrane Protein-1/Calcium/Calmodulin-Dependent Protein Kinase II/TAK1 Pathways After Subarachnoid Hemorrhage in Rat

BACKGROUND AND PURPOSE

The NLRP3 (nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3) inflammasome is a crucial component of the inflammatory response in early brain injury after subarachnoid hemorrhage (SAH). In this study, we investigated a role of dihydrolipoic acid (DHLA) in lysosomal rupture, NLRP3 activation, and determined the underlying pathway.

METHODS

SAH was induced by endovascular perforation in male Sprague-Dawley rats. DHLA was administered intraperitoneally 1 hour after SAH. Small interfering RNA for lysosome-associated membrane protein-1 and CaMKIIα (calcium/calmodulin-dependent protein kinase II α) was administered through intracerebroventricular 48 hours before SAH induction. SAH grade evaluation, short- and long-term neurological function testing, Western blot, and immunofluorescence staining experiments were performed.

RESULTS

DHLA treatment increased the expression of lysosome-associated membrane protein-1 and decreased phosphorylated CaMKIIα and NLRP3 inflammasome, thereby alleviating neurological deficits after SAH. Lysosome-associated membrane protein-1 small interfering RNA abolished the neuroprotective effects of DHLA and increased the level of phosphorylated CaMKIIα, p-TAK1 (phosphorylated transforming growth factor-β-activated kinase), p-JNK (phosphorylated c-Jun-N-terminal kinase), and NLRP3 inflammasome. CaMKIIα small interfering RNA downregulated the expression of p-TAK1, p-JNK, and NLRP3 and improved the neurobehavior after SAH.

CONCLUSIONS

DHLA treatment improved neurofunction and alleviated inflammation through the lysosome-associated membrane protein-1/CaMKII/TAK1 pathway in early brain injury after SAH. DHLA may provide a promising treatment to alleviate early brain injury after SAH.

CpG-ODN exerts a neuroprotective effect via the TLR9/pAMPK signaling pathway by activation of autophagy in a neonatal HIE rat model

Hypoxic Ischemic Encephalopathy (HIE) is an injury caused to the brain due to prolonged lack of oxygen and blood supply which results in death or long-term disabilities. The main aim of this study was to investigate the role of Cytosine-phospho-guanine oligodeoxynucleotide (CpG-ODN) in autophagy after HIE. Ten-day old (P10) rat pups underwent right common carotid artery ligation followed by 2.5h of hypoxia as previously described by Rice-Vannucci. At 1h post HIE, rats were intranasally administered with recombinant CpG-ODN. Time-course expression levels of endogenous key proteins, TLR9, pAMPK/AMPK, LC3II/I, and LAMP1 involved in CpG-ODN's protective effects were measured using western blot. Short (48h) and long (4w) term neurobehavior studies were performed using righting reflex, negative geotaxis, water maze, foot fault and Rota rod tests. Brain samples were collected after long term for histological analysis. Furthermore, to elucidate the pathway via which CpG-ODN confers protection, TLR9 and AMPK inhibitors were used. Time course results showed that the expression of TLR9, pAMPK/AMPK, LC3II/I, LAMP1 increased after HIE. Neurobehavioral studies showed that HIE induced a significant delay in development and resulted in cognitive and motor function deficits. However, CpG-ODN ameliorated HIE-induced outcomes and improved long term neurological deficits. In addition, CpG-ODN increased expression of pAMPK/AMPK, p-ULK1/ULK1, P-AMBRA1/AMBRA1, LC3II/I and LAMP1 while inhibition of TLR9 and AMPK reversed those effects. In summary, CpG-ODN increased HIE-induced autophagy and improved short and long term neurobehavioral outcomes which may be mediated by the TLR9/pAMPK signaling pathway after HIE.

Modification to the Rice-Vannucci perinatal hypoxic-ischaemic encephalopathy model in the P7 rat improves the reliability of cerebral infarct development after 48hours

BACKGROUND

The Rice-Vannucci model of hypoxic-ischaemic encephalopathy (HIE) has been associated with a high degree of variability with respect to the development of cerebral infarction and infarct lesion volume. For this reason, we examined the occurrence of communicational blood flow within the common carotid (CCA), internal (ICA), and external (ECA) carotid arteries following CCA occlusion as a source of variability in the model.

NEW METHOD

We propose a novel modification to the Rice-Vannucci model, whereby both the CCA and ECA are permanently ligated; mitigating communicational blood flow.

RESULTS

Using magnetic resonance angiography, phase-contrast velocity encoding, and pulsed arterial spin labelling, the modified Rice-Vannucci model (CCA/ECA occlusion) was demonstrated to mitigate communicational blood flow, whilst significantly reducing ipsilateral hemispherical cerebral blood flow (CBF). Comparatively, the original Rice-Vannucci model (CCA occlusion) demonstrated anterograde and retrograde blood flow within the ICA and CCA, respectively, with a non-significant reduction in ipsilateral CBF. Furthermore, CCA/ECA occlusion plus hypoxia (8% O₂/92% N₂; 2.5h) resulted in 100% of animals presenting with an infarct (vs 87%), significantly larger infarct volume at 48h (18.5% versus 10.0%; p<0.01), reduced standard deviation (±10% versus ±15%), and significantly worsened functional outcomes when compared to CCA occlusion plus hypoxia.

COMPARISON WITH EXISTING METHOD

We compared a modified Rice-Vannucci model (CCA/ECA occlusion±hypoxia) to the commonly used Rice-Vannucci model (CCA occlusion±hypoxia).

CONCLUSION

This study demonstrates that CCA/ECA occlusion in the Rice-Vannucci model of HIE reduces infarct volume variability by limiting communicational blood flow.

Sestrin2, as a negative feedback regulator of mTOR, provides neuroprotection by activation AMPK phosphorylation in neonatal hypoxic-ischemic encephalopathy in rat pups

Hypoxic-ischemic encephalopathy is a condition caused by reduced oxygen and cerebral blood flow to the brain resulting in neurological impairments. Effective therapeutic treatments to ameliorate these disabilities are still lacking. We sought to investigate the role of sestrin2, a highly conserved stress-inducible protein, in a neonatal rat hypoxic-ischemic encephalopathy model. Ten-day-old rat pups underwent right common carotid artery ligation followed by 2.5 h hypoxia. At 1 h post hypoxic-ischemic encephalopathy, rats were intranasally administered with recombinant human sestrin2 and sacrificed for brain infarct area measurement, Fluoro-Jade C, immunofluorescence staining, Western blot, and neurological function testing. rh-sestrin2 reduced brain infarct area, brain atrophy, apoptosis, ventricular area enlargement, and improved neurological function. Western blot showed that sestrin2 expression levels were increased after treatment with rh-sestrin2, and sestrin2 exerts neuroprotective effects via activation of the adenosine monophosphate-activated protein kinase pathway which in turn inhibits mammalian target of rapamycin signaling resulting in the attenuation of apoptosis. In conclusions: Sestrin2 plays an important neuroprotective role after hypoxic-ischemic encephalopathy via adenosine monophosphate-activated protein kinase signaling pathway and serves as a negative feedback regulator of mammalian target of rapamycin. Administration of rh-sestrin2 not only reduced infarct area and brain atrophy, but also significantly improved neurological function.

TASK channels contribute to neuroprotective action of inhalational anesthetics

Postconditioning with inhalational anesthetics can reduce ischemia-reperfusion brain injury, although the cellular mechanisms for this effect have not been determined. The current study was designed to test if TASK channels contribute to their neuroprotective actions. Whole cell recordings were used to examine effects of volatile anesthetic on TASK currents in cortical neurons and to verify loss of anesthetic-activated TASK currents from TASK^−/− mice. A transient middle cerebral artery occlusion (tMCAO) model was used to establish brain ischemia-reperfusion injury. Quantitative RT-PCR analysis revealed that TASK mRNA was reduced by >90% in cortex and hippocampus of TASK^−/− mice. The TASK^−/− mice showed a much larger region of infarction than C57BL/6 J mice after tMCAO challenge. Isoflurane or sevoflurane administered after the ischemic insult reduced brain infarct percentage and neurological deficit scores in C57BL/6 J mice, these effect were reduced in TASK^−/− mice. Whole cell recordings revealed that the isoflurane-activated background potassium current observed in cortical pyramidal neurons from wild type mice was conspicuously reduced in TASK^−/− mice. Our studies demonstrate that TASK channels can limit ischemia-reperfusion damage in the cortex, and postconditioning with volatile anesthetics provides neuroprotective actions that depend, in part, on activation of TASK currents in cortical neurons.

Rodent Gymnastics: Neurobehavioral Assays in Ischemic Stroke

Despite years of research, most preclinical trials on ischemic stroke have remained unsuccessful owing to poor methodological and statistical standards leading to "translational roadblocks." Various behavioral tests have been established to evaluate traits such as sensorimotor function, cognitive and social interactions, and anxiety-like and depression-like behavior. A test's validity is of cardinal importance as it influences the chance of a successful translation of preclinical results to clinical settings. The mission of choosing a behavioral test for a particular project is, therefore, imperative and the present review aims to provide a structured way to evaluate rodent behavioral tests with implications in ischemic stroke.

Intranasal Administration of Interferon Beta Attenuates Neuronal Apoptosis via the JAK1/STAT3/BCL-2 Pathway in a Rat Model of Neonatal Hypoxic-Ischemic Encephalopathy

Neonatal hypoxic-ischemic encephalopathy (HIE) is an injury that often leads to detrimental neurological deficits. Currently, there are no established therapies for HIE and it is critical to develop treatments that provide protection after HIE. The objective of this study was to investigate the ability of interferon beta (IFNβ) to provide neuroprotection and reduce apoptosis after HIE. Postnatal Day 10 rat pups were subjected to unilateral carotid artery ligation followed by 2.5 hr of exposure to hypoxia (8% O2). Intranasal administration of human recombinant IFNβ occurred 2 hr after HIE and infarct volume, body weight, neurobehavioral tests, histology, immunohistochemistry, brain water content, blood-brain barrier permeability, enzyme-linked immunosorbent assay, and Western blot were all used to evaluate various parameters. The results showed that both IFNβ and the Type 1 interferon receptor expression decreases after HIE. Intranasal administration of human recombinant IFNβ was able to be detected in the central nervous system and was able to reduce brain infarction volumes and improve neurological behavior tests 24 hr after HIE. Western blot analysis also revealed that human recombinant IFNβ treatment stimulated Stat3 and Bcl-2 expression leading to a decrease in cleaved caspase-3 expression after HIE. Positive Fluoro-Jade C staining also demonstrated that IFNβ treatment was able to decrease neuronal apoptosis. Furthermore, the beneficial effects of IFNβ treatment were reversed when a Stat3 inhibitor was applied. Also an intraperitoneal administration of human recombinant IFNβ into the systemic compartment was unable to confer the same protective effects as intranasal IFNβ treatment.

Sestrin2 induced by hypoxia inducible factor1 alpha protects the blood-brain barrier via inhibiting VEGF after severe hypoxic-ischemic injury in neonatal rats

OBJECTIVE

Hypoxic ischemic (HI) encephalopathy remains the leading cause of perinatal brain injury resulting in long term disabilities. Stabilization of blood brain barrier (BBB) after HI is an important target, therefore, in this study we aim to determine the role of sestrin2, a stress inducible protein which is elevated after various insults, on BBB stabilization after moderate and severe HI injuries.

METHODS

Rat pups underwent common carotid artery ligation followed by either 150min (severe model) or 100min (moderate model) of hypoxia. 1h post HI, rats were intranasally administered with recombinant human sestrin2 (rh-sestrin2) and sacrificed for infarct area, brain water content, righting reflex and geotaxis reflex. Sestrin2 was silenced using siRNA and an activator/inhibitor of hypoxia inducible factor1α (HIF1α) was used to examine their roles on BBB permeability.

RESULTS

Rats subjected to severe HI exhibited larger infarct area and higher sestrin2 expression compared to rats in the moderate HI group. rh-sestrin2 attenuated brain infarct and edema, while silencing sestrin2 reversed these protective effects after severe HI. HIF1α induced sestrin2 activation in severe HI but not in moderate HI groups. A HIF1a agonist was shown to increase permeability of the BBB via vascular endothelial growth factor (VEGF) after moderate HI. However, after severe HI, HIF1α activated both VEGF and sestrin2. But HIF1α dependent sestrin2 activation was the predominant pathway after severe HI which inhibited VEGF and attenuated BBB permeability.

CONCLUSIONS

rh-sestrin2 attenuated BBB permeability via upregulation of endogenous sestrin2 which was induced by HIF1α after severe HI. However, HIF1α's effects as a prodeath or prosurvival signal were influenced by the severity of HI injury.

Rodent Hypoxia-Ischemia Models for Cerebral Palsy Research: A Systematic Review

Cerebral palsy (CP) is a complex multifactorial disorder, affecting approximately 2.5-3/1000 live term births, and up to 22/1000 prematurely born babies. CP results from injury to the developing brain incurred before, during, or after birth. The most common form of this condition, spastic CP, is primarily associated with injury to the cerebral cortex and subcortical white matter as well as the deep gray matter. The major etiological factors of spastic CP are hypoxia/ischemia (HI), occurring during the last third of pregnancy and around birth age. In addition, inflammation has been found to be an important factor contributing to brain injury, especially in term infants. Other factors, including genetics, are gaining importance. The classic Rice-Vannucci HI model (in which 7-day-old rat pups undergo unilateral ligation of the common carotid artery followed by exposure to 8% oxygen hypoxic air) is a model of neonatal stroke that has greatly contributed to CP research. In this model, brain damage resembles that observed in severe CP cases. This model, and its numerous adaptations, allows one to finely tune the injury parameters to mimic, and therefore study, many of the pathophysiological processes and conditions observed in human patients. Investigators can recreate the HI and inflammation, which cause brain damage and subsequent motor and cognitive deficits. This model further enables the examination of potential approaches to achieve neural repair and regeneration. In the present review, we compare and discuss the advantages, limitations, and the translational value for CP research of HI models of perinatal brain injury.

Changes in Brain Swelling and Infarction Volume over Four Days After Hypoxia Ischemia in Neonatal Rats

The leading cause of morbidity and mortality in infants is hypoxia-ischemia (HI). The current therapies for HI have limited success, in part due to a lack of understanding of HI pathophysiology and underlying mechanisms. Herein, a neonatal rat model of HI was used to examine the changes in brain swelling and infarct volume over 4 days after HI. Forty-four P10 rat pups were sacrificed at 2, 3, or 4 days post-HI. After sacrifice, the brains were removed, sliced, and stained with TTC (2,3,5-triphenyl-2H-tetrazolium chloride). Images of TTC-stained brains were used for measurement of the ipsilateral hemisphere brain volumes and infarct volumes, calculated using standard equations. The hemispheric brain volumes of HI animals in all groups was lower than that of sham animals and decreased as the post-HI sacrifice time increased. The infarct volume of HI animals was larger than that of sham animals. Infarct volumes tended to decrease over the days post-HI. The change in infarct volume is likely the result of a combination of brain growth and repair mechanisms. However, changes in the hemispheric brain volume may include tissue growth and repair mechanism, so also may be a limitation of the current algorithm used for calculating ipsilateral hemisphere brain volume.

Development of an Infarct Volume Algorithm to Correct for Brain Swelling After Ischemic Stroke in Rats

The primary measure for experimental stroke studies, infarct volume, can be affected by brain swelling. The algorithm by Lin et al. was developed to correct for brain swelling, however, the correction is not adequate. This chapter presents a new infarct volume algorithm that more appropriately corrects for brain hemisphere volume changes (swelling and stunted growth). Fifty-one adult rats were sacrificed 24 h after middle cerebral artery occlusion (MCAO). Forty-four P10 rat pups were sacrificed 48 h after hypoxia-ischemia (HI). Infarct volumes for 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) stained brains were calculated using our algorithm and that of Lin and colleagues. For MCAO animals, the algorithm of Lin et al. computed smaller infarct volumes than those of our algorithm. For HI animals, Lin et al.'s algorithm's infarct volumes were greater than those of our algorithm. For sham animals, Lin et al.'s algorithm's computed infarct volumes were significantly different from those of our algorithm. Our algorithm produces a more robust estimation of infarct volume than Lin et al.'s algorithm because the effects of ipsilesional hemisphere volume changes are minimized. Herein, our algorithm yields an infarct volume that better corrects for brain swelling and stunted brain growth compared with the algorithm of Lin et al.

Neurodevelopmental implications of the general anesthesia in neonate and infants

Each year, about six million children, including 1.5 million infants, in the United States undergo surgery with general anesthesia, often requiring repeated exposures. However, a crucial question remains of whether neonatal anesthetics are safe for the developing central nervous system (CNS). General anesthesia encompasses the administration of agents that induce analgesic, sedative, and muscle relaxant effects. Although the mechanisms of action of general anesthetics are still not completely understood, recent data have suggested that anesthetics primarily modulate two major neurotransmitter receptor groups, either by inhibiting N-methyl-D-aspartate (NMDA) receptors, or conversely by activating γ-aminobutyric acid (GABA) receptors. Both of these mechanisms result in the same effect of inhibiting excitatory activity of neurons. In developing brains, which are more sensitive to disruptions in activity-dependent plasticity, this transient inhibition may have longterm neurodevelopmental consequences. Accumulating reports from preclinical studies show that anesthetics in neonates cause cellular toxicity including apoptosis and neurodegeneration in the developing brain. Importantly, animal and clinical studies indicate that exposure to general anesthetics may affect CNS development, resulting in long-lasting cognitive and behavioral deficiencies, such as learning and memory deficits, as well as abnormalities in social memory and social activity. While the casual relationship between cellular toxicity and neurological impairments is still not clear, recent reports in animal experiments showed that anesthetics in neonates can affect neurogenesis, which could be a possible mechanism underlying the chronic effect of anesthetics. Understanding the cellular and molecular mechanisms of anesthetic effects will help to define the scope of the problem in humans and may lead to preventive and therapeutic strategies. Therefore, in this review, we summarize the current evidence on neonatal anesthetic effects in the developmental CNS and discuss how factors influencing these processes can be translated into new therapeutic strategies.

Isoflurane anesthesia initiated at the onset of reperfusion attenuates oxidative and hypoxic-ischemic brain injury

This study demonstrates that in mice subjected to hypoxia-ischemia (HI) brain injury isoflurane anesthesia initiated upon reperfusion limits a release of mitochondrial oxidative radicals by inhibiting a recovery of complex-I dependent mitochondrial respiration. This significantly attenuates an oxidative stress and reduces the extent of HI brain injury. Neonatal mice were subjected to HI, and at the initiation of reperfusion were exposed to isoflurane with or without mechanical ventilation. At the end of HI and isoflurane exposure cerebral mitochondrial respiration, H2O2 emission rates were measured followed by an assessment of cerebral oxidative damage and infarct volumes. At 8 weeks after HI navigational memory and brain atrophy were assessed. In vitro, direct effect of isoflurane on mitochondrial H2O2 emission was compared to that of complex-I inhibitor, rotenone. Compared to controls, 15 minutes of isoflurane anesthesia inhibited recovery of the compex I-dependent mitochondrial respiration and decreased H2O2 production in mitochondria supported with succinate. This was associated with reduced oxidative brain injury, superior navigational memory and decreased cerebral atrophy compared to the vehicle-treated HI-mice. Extended isoflurane anesthesia was associated with sluggish recovery of cerebral blood flow (CBF) and the neuroprotection was lost. However, when isoflurane anesthesia was supported with mechanical ventilation the CBF recovery improved, the event associated with further reduction of infarct volume compared to HI-mice exposed to isoflurane without respiratory support. Thus, in neonatal mice brief isoflurane anesthesia initiated at the onset of reperfusion limits mitochondrial release of oxidative radicals and attenuates an oxidative stress. This novel mechanism contributes to neuroprotective action of isoflurane. The use of mechanical ventilation during isoflurane anesthesia counterbalances negative effect of isoflurane anesthesia on recovery of cerebral circulation which potentiates protection against reperfusion injury.

G-CSF ameliorates neuronal apoptosis through GSK-3β inhibition in neonatal hypoxia-ischemia in rats

Granulocyte-colony stimulating factor (G-CSF), a growth factor, has known neuroprotective effects in a variety of experimental brain injury models. Herein we show that G-CSF administration attenuates neuronal apoptosis after neonatal hypoxia-ischemia (HI) via glycogen synthase kinase-3β (GSK-3β) inhibition. Ten day old Sprague-Dawley rat pups (n=157) were subjected to unilateral carotid artery ligation followed by 2.5h of hypoxia or sham surgery. HI animals received control siRNA, GSK-3β siRNA (4 μL/pup), G-CSF (50 μg/kg), G-CSF combined with 0.1 or 0.4 nM G-CSF receptor (G-CSFR) siRNA, phosphatidylinositol 3-kinase (PI3K) inhibitor Wortmannin (86 ng/pup), or DMSO (vehicle for Wortmannin). Pups were euthanized 48 h post-HI to quantify brain infarct volume. G-CSFR, activated Akt (p-Akt), activated GSK-3β (p-GSK-3β), Cleaved Caspase-3 (CC3), Bcl-2, and Bax were quantified using Western blot analysis and the localizations of each was visualized via immunofluorescence staining. Neuronal cell death was determined using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). Our results showed p-GSK-3β increased after HI until its peak at 48 h post-ictus, and both GSK-3β siRNA and G-CSF administration reduced p-GSK-3β expression, as well as infarct volume. p-GSK-3β and CC3 were generally co-localized in neurons. Furthermore, G-CSF increased p-Akt expression and the Bcl-2/Bax ratio and also decreased p-GSK-3β and CC3 expression levels in the ipsilateral hemisphere, which were all reversed by G-CSFR siRNA, Wortmannin, and GSK-3β siRNA. In conclusion, G-CSF attenuated caspase activation and reduced brain injury by inhibiting GSK-3β activity after experimental HI in rat pups. This neuroprotective effect was abolished by both G-CSFR siRNA and Wortmannin.

Isoflurane provides neuroprotection in neonatal hypoxic ischemic brain injury

Isoflurane is a volatile anesthetic that is widely used clinically as an inhalational anesthetic. In recent years, several studies have indicated that isoflurane has neuroprotective properties. This has led to the beneficial effects of isoflurane being analyzed in both cell culture and animal models, including various models of brain injury. Neonatal hypoxia ischemia may be characterized as injury that occurs in the immature brain, resulting in delayed cell death via excitotoxicity and oxidative stress. These adverse events in the developing brain often lead to detrimental neurological defects in the future. Currently, there are no well-established effective therapies for neonatal hypoxia ischemia. In line with this, isoflurane, which displays neuroprotective properties in several paradigms and has been shown to improve neurological deficits caused by brain injuries, has the capability to be an extremely relevant clinical therapy for the resolution of deficits concomitant with neonatal hypoxic ischemic brain injuries. This review therefore seeks to explore and analyze the current information on isoflurane, looking at general isoflurane anesthetic properties, and the protection it confers in different animal models, focusing particularly on neuroprotection as shown in studies with neonatal hypoxic ischemic brain injury.

A double-edged sword: volatile anesthetic effects on the neonatal brain

The use of volatile anesthetics, a group of general anesthetics, is an exceedingly common practice. These anesthetics may have neuroprotective effects. Over the last decade, anesthetic induced neurotoxicity in pediatric populations has gained a certain notoriety based on pre-clinical cell and animal studies demonstrating that general anesthetics may induce neurotoxicity, including neuroapoptosis, neurodegeneration, and long-term neurocognitive and behavioral deficits. With hundreds of millions of people having surgery under general anesthesia worldwide, and roughly six million children annually in the U.S. alone, the importance of clearly defining toxic or protective effects of general anesthetics cannot be overstated. Yet, with our expanding body of knowledge, we have come to learn that perhaps not all volatile anesthetics have the same pharmacological profiles; certain ones may have a more favorable neurotoxic profile and may actually exhibit neuroprotection in specific populations and situations. Thus far, very few clinical studies exist, and have not yet been convincing enough to alter our practice. This review will provide an update on current data regarding volatile anesthetic induced neurotoxicity and neuroprotection in neonatal and infant populations. In addition, this paper will discuss ongoing studies and the trajectory of further research over the coming years.

Sildenafil mediates blood-flow redistribution and neuroprotection after neonatal hypoxia-ischemia

BACKGROUND AND PURPOSE

The best conceivable treatment for hypoxia-ischemia (HI) is the restoration of blood flow to the hypoxic-ischemic region(s). Our objective was to examine whether boosting NO-cGMP signaling using sildenafil citrate, a phosphodiesterase-type 5 inhibitor, could modify cerebral blood flow and reduce lesions in the developing brain.

METHODS

HI was induced in P7 Sprague-Dawley rats by unilateral carotid artery occlusion and hypoxia, and followed by either PBS or sildenafil. Blood-flow velocities were measured by ultrasound imaging with sequential Doppler recordings to evaluate collateral recruitment. Cell death, blood-brain barrier integrity, and glial activation were analyzed by immunohistochemistry. Motor behavior was evaluated using an open-field device adapted to neonatal animals.

RESULTS

Sildenafil citrate (10 mg/kg) induced collateral patency, reduced terminal dUTP nick-end labeling-positive cells, reactive astrogliosis, and macrophage/microglial activation at 72 hours and 7 days post-HI. Sildenafil also reduced the number of terminal dUTP nick-end labeling-positive endothelial cells within lesion site. Seven days after HI and sildenafil treatment, tissue loss was significantly reduced, and animals recovered motor coordination.

CONCLUSIONS

Our findings strongly indicate that sildenafil citrate treatment, associated with a significant increase in cerebral blood flow, reduces HI damage and improves motor locomotion in neonatal rats. Sildenafil may represent an interesting therapeutic strategy for neonatal neuroprotection.

Isoflurane provides neuroprotection in neonatal hypoxic ischemic brain injury

Isoflurane is a volatile anesthetic that is widely used clinically as an inhalational anesthetic. In recent years, several studies have indicated that isoflurane has neuroprotective properties. This has led to the beneficial effects of isoflurane being analyzed in both cell culture and animal models, including various models of brain injury. Neonatal hypoxia ischemia may be characterized as injury that occurs in the immature brain, resulting in delayed cell death via excitotoxicity and oxidative stress. These adverse events in the developing brain often lead to detrimental neurological defects in the future. Currently, there are no well-established effective therapies for neonatal hypoxia ischemia. In line with this, isoflurane, which displays neuroprotective properties in several paradigms and has been shown to improve neurological deficits caused by brain injuries, has the capability to be an extremely relevant clinical therapy for the resolution of deficits concomitant with neonatal hypoxic ischemic brain injuries. This review therefore seeks to explore and analyze the current information on isoflurane, looking at general isoflurane anesthetic properties, and the protection it confers in different animal models, focusing particularly on neuroprotection as shown in studies with neonatal hypoxic ischemic brain injury.

Nanoerythropoietin is 10-times more effective than regular erythropoietin in neuroprotection in a neonatal rat model of hypoxia and ischemia

BACKGROUND AND PURPOSE

Erythropoietin (EPO) has been demonstrated to possess significant neuroprotective effects in stroke. We determined if the nano-drug form of human recombinant EPO (PLGA-EPO nanoparticles [PLGA-EPO-NP]) can enhance neuroprotection at lower dosages versus human recombinant EPO (r-EPO).

METHODS

Established neonatal rat model of unilateral ischemic stroke was used to compare r-EPO, PLGA-EPO-NP and phosphate-buffered saline, given by daily intraperitoneal injections, followed by infarction volume and Rotarod Performance Test assessment.

RESULTS

PLGA-EPO-NP significantly reduced infarction volumes 72 hours after injury compared with the same concentrations of r-EPO. Functional deficits were significantly reduced by 300 U/kg PLGA-EPO-NP versus controls, with deficit attenuation apparent at significantly lower dosages of PLGA-EPO-NP versus r-EPO.

CONCLUSIONS

PLGA-EPO-NP is neuroprotective and beneficial against deficits after brain ischemia, at significantly reduced dosages versus r-EPO.