Delayed postischemic hypothermia improves long-term behavioral outcome after cerebral hypoxia-ischemia in neonatal rats

Therapeutic hypothermia success for hypoxic-ischaemic encephalopathy in Latin America: Eight-year experience in EpicLatino Neonatal Network

AIM

A study reported that therapeutic hypothermia (TH) did not reduce the combined prognosis of mortality and disability at 18 months, in low- and middle-income countries for patients with hypoxic ischaemic encephalopathy (HIE) who received TH, suggesting its no implementation in these regions. We described characteristics, mortality, and neurological response before and after the use of TH in newborns with HIE within the EpicLatino Neonatal Network (ENN) and described the population of infants with HIE treated and not treated with TH.

METHODS

Data were collected from 2015 to 2022 for patients with HIE. Mortality rates and Sarnat scores were compared before and after TH. The Wilcoxon Signed-Rank Test was used for comparisons.

RESULTS

In this observational study 518 neonates of our total population of 26 970, had HIE (1.92%) of whom 150 underwent TH. Ten out of 21 neonatal intensive care units (NICUs) provided TH. The Wilcoxon Signed Rank Test for 138 cases with complete data showed a significant difference.

CONCLUSION

The findings support the benefits of TH in HIE within this cohort. TH should not be withheld solely due to the economic status of the country. A strict patient selection and TH protocol are essential.

Time to Reaching Target Cooling Temperature and 2-year Outcomes in Infants with Hypoxic-Ischemic Encephalopathy

OBJECTIVE

To determine if time to reaching target temperature (TT) is associated with death or neurodevelopmental impairment (NDI) at 2 years of age in infants with hypoxic-ischemic encephalopathy (HIE).

STUDY DESIGN

Newborn infants ≥36 weeks of gestation diagnosed with moderate or severe HIE and treated with therapeutic hypothermia were stratified based on time at which TT was reached, defined as early (ie, ≤4 hours of age) or late (>4 hours of age). Primary outcomes were death or NDI. Secondary outcomes included neurodevelopmental assessment with Bayley Scales of Infant and Toddler Development, third edition (BSID-III) at age 2.

RESULTS

Among 500 infants, the median time to reaching TT was 4.3 hours (IWR, 3.2-5.7 hours). Infants in early TT group (n = 211 [42%]) compared with the late TT group (n = 289 [58%]) were more likely to be inborn (23% vs 13%; P < .001) and have severe HIE (28% vs 19%; P = .03). The early and late TT groups did not differ in the primary outcome of death or any NDI (adjusted RR, 1.05; 95% CI, 0.85-0.30; P = .62). Among survivors, neurodevelopmental outcomes did not differ significantly in the 2 groups (adjusted mean difference in Bayley Scales of Infant Development-III scores: cognitive, -2.8 [95% CI, -6.1 to 0.5], language -3.3 [95% CI, -7.4 to 0.8], and motor -3.5 [95% CI, -7.3 to 0.3]).

CONCLUSIONS

In infants with HIE, time to reach TT is not independently associated with risk of death or NDI at age 2 years. Among survivors, developmental outcomes are similar between those who reached TT at <4 and ≥4 hours of age.

TRIAL REGISTRATION

High-dose Erythropoietin for Asphyxia and Encephalopathy (HEAL); NCT02811263; https://beta.

CLINICALTRIALS

gov/study/NCT02811263.

MR imaging and outcome in neonatal HIBD models are correlated with sex: the value of diffusion tensor MR imaging and diffusion kurtosis MR imaging

Objective

Hypoxic-ischemic encephalopathy can lead to lifelong morbidity and premature death in full-term newborns. Here, we aimed to determine the efficacy of diffusion kurtosis (DK) [mean kurtosis (MK)] and diffusion tensor (DT) [fractional anisotropy (FA), mean diffusion (MD), axial diffusion (AD), and radial diffusion (RD)] parameters for the early diagnosis of early brain histopathological changes and the prediction of neurodegenerative events in a full-term neonatal hypoxic-ischemic brain injury (HIBD) rat model.

Methods

The HIBD model was generated in postnatal day 7 Sprague-Dawley rats to assess the changes in DK and DT parameters in 10 specific brain structural regions involving the gray matter, white matter, and limbic system during acute (12 h) and subacute (3 d and 5 d) phases after hypoxic ischemia (HI), which were validated against histology. Sensory and cognitive parameters were assessed by the open field, novel object recognition, elevated plus maze, and CatWalk tests.

Results

Repeated-measures ANOVA revealed that specific brain structures showed similar trends to the lesion, and the temporal pattern of MK was substantially more varied than DT parameters, particularly in the deep gray matter. The change rate of MK in the acute phase (12 h) was significantly higher than that of DT parameters. We noted a delayed pseudo-normalization for MK. Additionally, MD, AD, and RD showed more pronounced differences between males and females after HI compared to MK, which was confirmed in behavioral tests. HI females exhibited anxiolytic hyperactivity-like baseline behavior, while the memory ability of HI males was affected in the novel object recognition test. CatWalk assessments revealed chronic deficits in limb gait parameters, particularly the left front paw and right hind paw, as well as poorer performance in HI males than HI females.

Conclusions

Our results suggested that DK and DT parameters were complementary in the immature brain and provided great value in assessing early tissue microstructural changes and predicting long-term neurobehavioral deficits, highlighting their ability to detect both acute and long-term changes. Thus, the various diffusion coefficient parameters estimated by the DKI model are powerful tools for early HIBD diagnosis and prognosis assessment, thus providing an experimental and theoretical basis for clinical treatment.

Effects of Cannabidiol, Hypothermia, and Their Combination in Newborn Rats with Hypoxic-Ischemic Encephalopathy

Therapeutic hypothermia is well established as a standard treatment for infants with hypoxic-ischemic (HI) encephalopathy but it is only partially effective. The potential for combination treatments to augment hypothermic neuroprotection has major relevance. Our aim was to assess the effects of treating newborn rats following HI injury with cannabidiol (CBD) at 0.1 or 1 mg/kg, i.p., in normothermic (37.5°C) and hypothermic (32.0°C) conditions, from 7 d of age (neonatal phase) to 37 d of age (juvenile phase). Placebo or CBD was administered at 0.5, 24, and 48 h after HI injury. Two sensorimotor (rotarod and cylinder rearing) and two cognitive (novel object recognition and T-maze) tests were conducted 30 d after HI. The extent of brain damage was determined by magnetic resonance imaging, histologic evaluation, magnetic resonance spectroscopy, amplitude-integrated electroencephalography, and Western blotting. At 37 d, the HI insult produced impairments in all neurobehavioral scores (cognitive and sensorimotor tests), brain activity (electroencephalography), neuropathological score (temporoparietal cortexes and CA1 layer of hippocampus), lesion volume, magnetic resonance biomarkers of brain injury (metabolic dysfunction, excitotoxicity, neural damage, and mitochondrial impairment), oxidative stress, and inflammation (TNFα). We observed that CBD or hypothermia (to a lesser extent than CBD) alone improved cognitive and motor functions, as well as brain activity. When used together, CBD and hypothermia ameliorated brain excitotoxicity, oxidative stress, and inflammation, reduced brain infarct volume, lessened the extent of histologic damage, and demonstrated additivity in some parameters. Thus, coadministration of CBD and hypothermia could complement each other in their specific mechanisms to provide neuroprotection.

Therapeutic hypothermia for the treatment of neonatal hypoxia-ischemia: sex-dependent modulation of reactive astrogliosis

Therapeutic hypothermia (TH) is the standard treatment for neonatal hypoxia-ischemia (HI) with a time window limited up to 6 h post injury. However, influence of sexual dimorphism in the therapeutic window for TH has not yet been elucidated in animal models of HI. Therefore, the aim of this study was to investigate the most effective time window to start TH in male and female rats submitted to neonatal HI. Wistar rats (P7) were divided into the following groups: NAÏVE and SHAM (control groups), HI (submitted to HI) and TH (submitted to HI and TH; 32ºC for 5 h). TH was started at 2 h (TH-2 h group), 4 h (TH-4 h group), or 6 h (TH-6 h group) after HI. At P14, animals were subjected to behavioural tests, volume of lesion and reactive astrogliosis assessments. Male and female rats from the TH-2 h group showed reduction in the latency of behavioral tests, and decrease in volume of lesion and intensity of GFAP immunofluorescence. TH-2 h females also showed reduction of degenerative cells and morphological changes in astrocytes. Interestingly, females from the TH-6 h group showed an increase in volume of lesion and in number of degenerative hippocampal cells, associated with worse behavioral performance. Together, these results indicate that TH neuroprotection is time- and sex-dependent. Moreover, TH started later (6 h) can worsen volume of brain lesion in females. These data indicate the need to develop specific therapeutic protocols for each sex and reinforce the importance of early onset of the hypothermic treatment.

Therapeutic Hypothermia in Transport Permits Earlier Treatment Regardless of Transfer Distance

OBJECTIVE

Therapeutic hypothermia (TH) is currently the only effective therapy available to improve outcomes in neonates with hypoxic-ischemic encephalopathy (HIE) and has maximal effect when initiated within 6 hours of birth. Neonates affected by HIE are commonly born outside of cooling centers and transport is a barrier to timely initiation. In this study, we sought to determine if the initiation of servo-controlled TH in transport allowed neonates to reach target temperature earlier, without a significant delay in the transfer process, for both local and long-distance transport.

STUDY DESIGN

In this single-center cohort study of neonates referred to a level IV neonatal intensive care unit for TH, we determined the chronologic age at which target temperature was reached for those cooled in transport. Short-term outcome measures were assessed, including survival, incidence of electrographic seizures, discharge feeding method, and length of hospitalization.

RESULTS

In a study population of 85 neonates, those receiving TH during transport (n = 23), achieved target temperature (33-34°C) 77 minutes sooner (230 ± 71 vs. 307 ± 79 minutes of life (MOL); p < 0.001). Locally transported neonates (<15 miles) achieved target temperature 69 minutes earlier (215 ± 48 vs. 284 ± 74 MOL; p < 0.01). TH during long-distance transports allowed neonates to reach target temperature 81 minutes sooner (213 ± 85 vs. 294 ± 79 MOL; p < 0.01). Infants who were cooled in transport discharged 4 days earlier (13.7 ± 8 vs. 17.8 ± 13 days; p = 0.18) and showed a significantly higher rate of oral feeding at discharge (95 vs. 71%; p = 0.03).

CONCLUSION

For those starting TH in transport, time to target temperature was decreased. In our cohort, cooling in transport was associated with improved short-term outcomes, although additional studies are needed to correlate these findings with long-term outcomes.

KEY POINTS

· Therapeutic hypothermia started during transport allows shorter time to target temperature.. · Transfer was minimally delayed by starting cooling in transport.. · Cooling in transport was associated with increased rate of oral feeding at hospital discharge..

Neuroprotective role of lactate in rat neonatal hypoxia-ischemia

Hypoxic-ischemic (HI) encephalopathy remains a major cause of perinatal mortality and chronic disability in newborns worldwide (1-6 for 1000 births). The only current clinical treatment is hypothermia, which is efficient for less than 60% of babies. Mainly considered as a waste product in the past, lactate, in addition to glucose, is increasingly admitted as a supplementary fuel for neurons and, more recently, as a signaling molecule in the brain. Our aim was to investigate the neuroprotective effect of lactate in a neonatal (seven day old) rat model of hypoxia-ischemia. Pups received intra-peritoneal injection(s) of lactate (40 μmol). Size and apparent diffusion coefficients of brain lesions were assessed by magnetic resonance diffusion-weighted imaging. Oxiblot analyses and long-term behavioral studies were also conducted. A single lactate injection induced a 30% reduction in brain lesion volume, indicating a rapid and efficient neuroprotective effect. When oxamate, a lactate dehydrogenase inhibitor, was co-injected with lactate, the neuroprotection was completely abolished, highlighting the role of lactate metabolism in this protection. After three lactate injections (one per day), pups presented the smallest brain lesion volume and a complete recovery of neurological reflexes, sensorimotor capacities and long-term memory, demonstrating that lactate administration is a promising therapy for neonatal HI insult.

Effects of Juvenile or Adolescent Working Memory Experience and Inter-Alpha Inhibitor Protein Treatment after Neonatal Hypoxia-Ischemia

Hypoxic-Ischemic (HI) brain injury in the neonate contributes to life-long cognitive impairment. Early diagnosis and therapeutic interventions are critical but limited. We previously reported in a rat model of HI two interventional approaches that improve cognitive and sensory function: administration of Inter-alpha Inhibitor Proteins (IAIPs) and early experience in an eight-arm radial water maze (RWM) task. Here, we expanded these studies to examine the combined effects of IAIPs and multiple weeks of RWM assessment beginning with juvenile or adolescent rats to evaluate optimal age windows for behavioral interventions. Subjects were divided into treatment groups; HI with vehicle, sham surgery with vehicle, and HI with IAIPs, and received either juvenile (P31 initiation) or adolescent (P52 initiation) RWM testing, followed by adult retesting. Error rates on the RWM decreased across weeks for all conditions. Whereas, HI injury impaired global performance as compared to shams. IAIP-treated HI subjects tested as juveniles made fewer errors as compared to their untreated HI counterparts. The juvenile group made significantly fewer errors on moderate demand trials and showed improved retention as compared to the adolescent group during the first week of adult retesting. Together, results support and extend our previous findings that combining behavioral and anti-inflammatory interventions in the presence of HI improves subsequent learning performance. Results further indicate sensitive periods for behavioral interventions to improve cognitive outcomes. Specifically, early life cognitive experience can improve long-term learning performance even in the presence of HI injury. Results from this study provide insight into typical brain development and the impact of developmentally targeted therapeutics and task-specific experience on subsequent cognitive processing.

Maternal alcoholism and neonatal hypoxia-ischemia: Neuroprotection by stilbenoid polyphenols

The impact of maternal nutrition on neurodevelopment and neonatal neuroprotection is a research topic with increasing interest. Maternal diet can also have deleterious effects on fetal brain development. Fetal exposure to alcohol is responsible for poor neonatal global development, and may increase brain vulnerability to hypoxic-ischemic encephalopathy, one of the major causes of acute mortality and chronic neurological disability in newborns. Despite frequent prevention campaigns, about 10% of women in the general population drinks alcohol during pregnancy and breastfeeding. This study was inspired by this alarming fact. Its aim was to evaluate the beneficial effects of maternal supplementation with two polyphenols during pregnancy and breastfeeding, on hypoxic-ischemic neonate rat brain damages, sensorimotor and cognitive impairments, in a context of moderate maternal alcoholism. Both stilbenoid polyphenols, trans-resveratrol (RSV - 0.15 mg/kg/day), and its hydroxylated analog, trans-piceatannol (PIC - 0.15 mg/kg/day), were administered in the drinking water, containing or not alcohol (0.5 g/kg/day). In a 7-day post-natal rat model of hypoxia-ischemia (HI), our data showed that moderate maternal alcoholism does not increase brain lesion volumes measured by MRI but leads to higher motor impairments. RSV supplementation could not reverse the deleterious effects of HI coupled with maternal alcoholism. However, PIC supplementation led to a recovery of all sensorimotor and cognitive functions. This neuroprotection was obtained with a dose of PIC corresponding to the consumption of a single passion fruit per day for a pregnant woman.

Potential biomarkers for neuroinflammation and neurodegeneration at short and long term after neonatal hypoxic-ischemic insult in rat

BACKGROUND

Hypoxic-ischemic (HI) encephalopathy causes life-long morbidity and premature mortality in term neonates. Therapies in addition to whole-body cooling are under development to treat the neonate at risk for HI encephalopathy, but are not a quickly measured serum inflammatory or neuronal biomarkers to rapidly and accurately identify brain injury in order to follow the efficacy of therapies.

METHODS

In order to identify potential biomarkers for early inflammatory and neurodegenerative events after neonatal hypoxia-ischemia, both male and female Wistar rat pups at postnatal day 7 (P7) were used and had their right carotid artery permanently doubly occluded and exposed to 8% oxygen for 90 min. Sensory and cognitive parameters were assessed by open field, rotarod, CatWalk, and Morris water maze (MWM) test. Plasma and CSF biomarkers were investigated on the acute (24 h and 72 h) and chronic phase (4 weeks). Brains were assessed for gene expression analysis by quantitative RT-PCR Array.

RESULTS

We found a delay of neurological reflex maturation in HI rats. We observed anxiolytic-like baseline behavior in males more than females following HI injury. HI rats held on the rotarod for a shorter time comparing to sham. HI injury impaired spatial learning ability on MWM test. The CatWalk assessment demonstrated a long-term deficit in gait parameters related to the hind paw. Proinflammatory biomarkers such as IL-6 in plasma and CCL2 and TNF-α in CSF showed an upregulation at 24 h after HI while other cytokines, such as IL-17A and CCL5, were upregulated after 72 h in CSF. At 24 h post-injury, we observed an increase of Edn1, Hif1-α, and Mmp9 mRNA levels in the ipsilateral vs the contralateral hemisphere of HI rats. An upregulation of genes involved with clotting and hematopoietic processes was observed 72 h post-injury.

CONCLUSIONS

Our work showed that, in the immature brain, the HI injury induced an early increased production of several proinflammatory mediators detectable in plasma and CSF, followed by tissue damage in the hypoxic hemisphere and short-term as well as long-lasting neurobehavioral deficits.

Maternal consumption of piceatannol: A nutritional neuroprotective strategy against hypoxia-ischemia in rat neonates

Hypoxia-ischemia (HI) remains a major cause of perinatal mortality and chronic disability in newborns worldwide (1-6 for 1000 births) with a high risk of future motor, behavioral and neurological deficits. Keeping newborns under moderate hypothermia is the unique therapeutic approach but is not sufficiently successful as nearly 50% of infants do not respond to it. In a 7-day post-natal rat model of HI, we used pregnant and breastfeeding female nutritional supplementation with piceatannol (PIC), a polyphenol naturally found in berries, grapes and passion fruit, as a neuroprotective strategy. Maternal supplementation led to neuroprotection against neonate brain damage and reversed their sensorimotor deficits as well as cognitive impairments. Neuroprotection of per os maternal supplementation with PIC is a preventive strategy to counteract brain damage in pups induced by HI. This nutritional approach could easily be adopted as a preventive strategy in humans.

Perinatal hypoxic-ischemic brain injury in large animal models: Relevance to human neonatal encephalopathy

Perinatal hypoxia-ischemia resulting in death or lifelong disabilities remains a major clinical disorder. Neonatal models of hypoxia-ischemia in rodents have enhanced our understanding of cellular mechanisms of neural injury in developing brain, but have limitations in simulating the range, accuracy, and physiology of clinical hypoxia-ischemia and the relevant systems neuropathology that contribute to the human brain injury pattern. Large animal models of perinatal hypoxia-ischemia, such as partial or complete asphyxia at the time of delivery of fetal monkeys, umbilical cord occlusion and cerebral hypoperfusion at different stages of gestation in fetal sheep, and severe hypoxia and hypoperfusion in newborn piglets, have largely overcome these limitations. In monkey, complete asphyxia produces preferential injury to cerebellum and primary sensory nuclei in brainstem and thalamus, whereas partial asphyxia produces preferential injury to somatosensory and motor cortex, basal ganglia, and thalamus. Mid-gestational fetal sheep provide a valuable model for studying vulnerability of progenitor oligodendrocytes. Hypoxia followed by asphyxia in newborn piglets replicates the systems injury seen in term newborns. Efficacy of post-insult hypothermia in animal models led to the success of clinical trials in term human neonates. Large animal models are now being used to explore adjunct therapy to augment hypothermic neuroprotection.

Differential regulation of estrogen in iron metabolism in astrocytes and neurons

Previous studies have demonstrated an effect of estrogen on iron metabolism in peripheral tissues. The role of estrogen on brain iron metabolism is currently unknown. In this study, we investigated the effect and mechanism of estrogen on iron transport proteins. We demonstrated that the iron exporter ferroportin 1 (FPN1) and iron importer divalent metal transporter 1 (DMT1) were upregulated and iron content was decreased after estrogen treatment for 12 hr in primary cultured astrocytes. Hypoxia-inducible factor-1 alpha (HIF-1α) was upregulated, but HIF-2α remained unchanged after estrogen treatment for 12 hr in primary cultured astrocytes. In primary cultured neurons, DMT1 was downregulated, FPN1 was upregulated, iron content decreased, iron regulatory protein (IRP1) was downregulated, but HIF-1α and HIF-2α remained unchanged after estrogen treatment for 12 hr. These results suggest that the regulation of iron metabolism by estrogen in astrocytes and neurons is different. Estrogen increases FPN1 and DMT1 expression by inducing HIF-1α in astrocytes, whereas decreased expression of IRP1 may account for the decreased DMT1 and increased FPN1 expression in neurons.

2-Iminobiotin Superimposed on Hypothermia Protects Human Neuronal Cells from Hypoxia-Induced Cell Damage: An in Vitro Study

Perinatal asphyxia represents one of the major causes of neonatal morbidity and mortality. Hypothermia is currently the only established treatment for hypoxic-ischemic encephalopathy (HIE), but additional pharmacological strategies are being explored to further reduce the damage after perinatal asphyxia. The aim of this study was to evaluate whether 2-iminobiotin (2-IB) superimposed on hypothermia has the potential to attenuate hypoxia-induced injury of neuronal cells. In vitro hypoxia was induced for 7 h in neuronal IMR-32 cell cultures. Afterwards, all cultures were subjected to 25 h of hypothermia (33.5°C), and incubated with vehicle or 2-IB (10, 30, 50, 100, and 300 ng/ml). Cell morphology was evaluated by brightfield microscopy. Cell damage was analyzed by LDH assays. Production of reactive oxygen species (ROS) was measured using fluorometric assays. Western blotting for PARP, Caspase-3, and the phosphorylated forms of akt and erk1/2 was conducted. To evaluate early apoptotic events and signaling, cell protein was isolated 4 h post-hypoxia and human apoptosis proteome profiler arrays were performed. Twenty-five hour after the hypoxic insult, clear morphological signs of cell damage were visible and significant LDH release as well as ROS production were observed even under hypothermic conditions. Post-hypoxic application of 2-IB (10 and 30 ng/ml) reduced the hypoxia-induced LDH release but not ROS production. Phosphorylation of erk1/2 was significantly increased after hypoxia, while phosphorylation of akt, protein expression of Caspase-3 and cleavage of PARP were only slightly increased. Addition of 2-IB did not affect any of the investigated proteins. Apoptosis proteome profiler arrays performed with cellular protein obtained 4 h after hypoxia revealed that post-hypoxic application of 2-IB resulted in a ≥ 25% down regulation of 10/35 apoptosis-related proteins: Bad, Bax, Bcl-2, cleaved Caspase-3, TRAILR1, TRAILR2, PON2, p21, p27, and phospho Rad17. In summary, addition of 2-IB during hypothermia is able to attenuate hypoxia-induced neuronal cell damage in vitro. Combination treatment of hypothermia with 2-IB could be a promising strategy to reduce hypoxia-induced neuronal cell damage and should be considered in further animal and clinical studies.

Effects of therapeutic hypothermia on white matter injury from murine neonatal hypoxia-ischemia

BackgroundTherapeutic hypothermia (TH) is the standard of care for neonates with hypoxic-ischemic encephalopathy, but it is not fully protective in the clinical setting. Hypoxia-ischemia (HI) may cause white matter injury (WMI), leading to neurological and cognitive dysfunction.MethodsP9 mice were subjected to HI as previously described. Pups underwent 3.5 h of systemic hypothermia or normothermia. Cresyl violet and Perl's iron staining for histopathological scoring of brain sections was completed blindly on all brains. Immunocytochemical (ICC) staining for myelin basic protein (MBP), microglia (Iba1), and astrocytes (glia fibrillary acidic protein (GFAP)) was performed on adjacent sections. Volumetric measurements of MBP coverage were used for quantitative analysis of white matter.ResultsTH provided neuroprotection by injury scoring for the entire group (n=44; P<0.0002). ICC analysis of a subset of brains showed that the lateral caudate was protected from WMI (P<0.05). Analysis revealed decreased GFAP and Iba1 staining in hippocampal regions, mostly CA2/CA3. GFAP and Iba1 directly correlated with injury scores of normothermic brains.ConclusionTH reduced injury, and qualitative data suggest that hippocampus and lateral caudate are protected from HI. Mildly injured brains may better show the benefits of TH. Overall, these data indicate regional differences in WMI susceptibility and inflammation in a P9 murine HI model.

Hypoxic postconditioning improves behavioural deficits at 6 weeks following hypoxic-ischemic brain injury in neonatal rats

Hypoxic-ischemic (HI) brain injury in newborns is associated with high morbidity and mortality, with many babies suffering neurological deficits. Recently, we showed that hypoxic postconditioning (PostC) immediately post injury can protect against HI up to one week in neonatal rats. Here, we aimed to examine whether long term functional deficits were also improved by PostC. Sprague-Dawley rats were assigned to control (C) or HI group on postnatal day 7 (P7). The HI group underwent unilateral carotid artery occlusion followed by hypoxia (7% oxygen, 3h). Half of each group were randomly assigned to the PostC group (8% oxygen, 1h/day for 5days post-injury), or normoxic group, where animals were kept under ambient conditions. Righting reflex and negative geotaxis tests were performed on P8 and P14. On P42, rats underwent further behavioural tests of motor function and memory (forelimb grip strength, grid walking and novel object recognition tasks). Brain injury was assessed using histological scoring of brain sections. At P14, PostC reduced the righting reflex deficit compared to HI alone. Long-term (6 weeks) behavioural deficits were observed in grid walking and novel object recognition tests after HI alone, with both functions improved following PostC. Following HI, there was an increase in brain injury assessed by histological scoring compared to control, and this damage was reduced by PostC. This novel finding of long-term histological neuroprotection accompanied by functional improvements by PostC further demonstrates the clinical potential of mild hypoxia for the treatment of HI brain injury.

Therapeutic hypothermia protects against ischemia-induced impairment of synaptic plasticity following juvenile cardiac arrest in sex-dependent manner

Pediatric cardiac arrest (CA) often leads to poor neurologic outcomes, including deficits in learning and memory. The only approved treatment for CA is therapeutic hypothermia, although its utility in the pediatric population remains unclear. This study analyzed the effect of mild therapeutic hypothermia after CA in juvenile mice on hippocampal neuronal injury and the cellular model of learning and memory, termed long-term potentiation (LTP). Juvenile mice were subjected to cardiac arrest and cardiopulmonary resuscitation (CA/CPR) followed by normothermia (37°C) and hypothermia (30°C, 32°C). Histological injury of hippocampal CA1 neurons was performed 3days after resuscitation using hematoxylin and eosin (H&E) staining. Field excitatory post-synaptic potentials (fEPSPs) were recorded from acute hippocampal slices 7days after CA/CPR to determine LTP. Synaptic function was impaired 7days after CA/CPR. Mice exposed to hypothermia showed equivalent neuroprotection, but exhibited sexually dimorphic protection against ischemia-induced impairment of LTP. Hypothermia (32°C) protects synaptic plasticity more effectively in females, with males requiring a deeper level of hypothermia (30°C) for equivalent protection. In conclusion, male and female juvenile mice exhibit equivalent neuronal injury following CA/CPR and hypothermia protects both males and females. We made the surprising finding that juvenile mice have a sexually dimorphic response to mild therapeutic hypothermia protection of synaptic function, where males may need a deeper level of hypothermia for equivalent synaptic protection.

Effects of 3-h hypothermia after neonatal hyperthermic hypoxic-ischemic encephalopathy in rat models on behavioral prognosis and anatomical and histological features after growth

OBJECTIVE

To clarify the effects of 3-h hypothermia on learning ability and motor function after growth, employing neonatal rat models with hyperthermic hypoxic-ischemic encephalopathy (HIE).

METHODS

We divided all rats into three groups: N (adult rats after neonatal hyperthermic HIE without subsequent 3-h hypothermia), H (adult rats after neonatal hyperthermic HIE with subsequent 3-h hypothermia) and Sham (S) groups. We evaluated their malfunctions with the rota-rod test and the step-down passive avoidance test. We also analyzed the cerebrum width and the hippocampal CA1 area of the insulted hemisphere.

RESULTS

In the rota-rod test, the result of the N group was significantly worse than that of the S group. In the step-down passive avoidance test, the result of the N group was significantly worse than those of the S and H groups. The longest cerebrum width and the hippocampal CA1 area of the insulted hemisphere of the N group were significantly smaller than those of the S and H groups.

CONCLUSION

Neonatal hyperthermic hypoxic-ischemic insult restricts motor function and learning ability after growth, and such neuronal malfunctions can be relieved by hypothermia for 3 h soon after neonatal HIE.

Sex differences in behavioral outcomes following temperature modulation during induced neonatal hypoxic ischemic injury in rats

Neonatal hypoxia ischemia (HI; reduced oxygen and/or blood flow to the brain) can cause various degrees of tissue damage, as well as subsequent cognitive/behavioral deficits such as motor, learning/memory, and auditory impairments. These outcomes frequently result from cardiovascular and/or respiratory events observed in premature infants. Data suggests that there is a sex difference in HI outcome, with males being more adversely affected relative to comparably injured females. Brain/body temperature may play a role in modulating the severity of an HI insult, with hypothermia during an insult yielding more favorable anatomical and behavioral outcomes. The current study utilized a postnatal day (P) 7 rodent model of HI injury to assess the effect of temperature modulation during injury in each sex. We hypothesized that female P7 rats would benefit more from lowered body temperatures as compared to male P7 rats. We assessed all subjects on rota-rod, auditory discrimination, and spatial/non-spatial maze tasks. Our results revealed a significant benefit of temperature reduction in HI females as measured by most of the employed behavioral tasks. However, HI males benefitted from temperature reduction as measured on auditory and non-spatial tasks. Our data suggest that temperature reduction protects both sexes from the deleterious effects of HI injury, but task and sex specific patterns of relative efficacy are seen.

Hypoxia-ischemia and therapeutic hypothermia in the neonatal mouse brain--a longitudinal study

Therapeutic hypothermia is standard of care for infants with hypoxic ischemic encephalopathy. Murine models of hypoxic-ischemic injury exist; however, a well-established mouse model of therapeutic hypothermia following hypoxic-ischemic injury is lacking. The goal of this study was to develop a full-term-equivalent murine model of therapeutic hypothermia after hypoxia-ischemia and examine magnetic resonance imaging, behavior, and histology in a region and sex specific manner. Hypoxic-ischemic injury was induced at postnatal day 10 in C57BL6 mice using a modified Vannucci model. Mice were randomized to control, hypothermia (31˚C for 4h), or normothermia (36˚C) following hypoxic-ischemic injury and stratified by sex. T2-weighted magnetic resonance imaging was obtained at postnatal day 18 and 30 and regional and total cerebral and cerebellar volumes measured. Behavioral assessments were performed on postnatal day 14, 21, and 28. On postnatal day 18, normothermic mice had smaller cerebral volumes (p < 0.001 vs. controls and p = 0.009 vs. hypothermia), while at postnatal day 30 both injured groups had smaller volumes than controls. When stratified by sex, only normothermia treated male mice had smaller cerebral volumes (p = 0.001 vs. control; p = 0.008 vs. hypothermia) at postnatal day 18, which persisted at postnatal day 30 (p = 0.001 vs. control). Female mice had similar cerebral volumes between groups at both day 18 and 30. Cerebellar volumes of hypothermia treated male mice differed from control at day 18, but not at 30. Four hours of therapeutic hypothermia in this murine hypoxic-ischemic injury model provides sustained neuroprotection in the cerebrum of male mice. Due to variable degree of injury in female mice, response to therapeutic hypothermia is difficult to discern. Deficits in female behavior tests are not fully explained by imaging measures and likely represent injury not detectable by volume measurements alone.

Therapeutic effect of placenta-derived mesenchymal stem cells on hypoxic-ischemic brain damage in rats

BACKGROUND

Oxidative stress is involved in the development of hypoxic-ischemic brain damage (HIBD). In this study, we investigated the therapeutic effects of placenta-derived mesenchymal stem cells (PD-MSCs) and explored the NF-E2-related factor-2/heme oxygenase-1 (Nrf2/HO-1) signaling pathway in treating HIBD.

METHODS

P7 rats were subjected to hypoxic-ischemic brain injury and randomly divided into four groups (control, HIBD, HIBD+PD-MSCs, and HIBD+fibroblasts). Forty-eight hours after the induction of HIBD, 5×10(5) of PD-MSCs were injected into cerebral tissue in the HIBD+PD-MSCs group, while the same dose of fibroblasts were injected in the HIBD+fibroblasts group. Morris Water Maze, gross and pathological changes were tested at P28. The level of malondialdehyde (MDA) was detected in rats' hippocampus. RT-PCR and western blot analysis were used to evaluate the changes of Nrf2/HO-1.

RESULTS

The HIBD group showed significantly longer escape latency and a lower frequency of original platform crossing in the Morris Water Maze compared with the control group. Rats receiving PD-MSCs showed significant improvement of HIBD. The pathological changes were evident after HIBD, but ameliorated in the PD-MSCs group. Compared with the control group, HO-1 and Nrf2 were up-regulated at gene and protein levels in the HI brain, beginning at 6 hours and peaking at 48 hours (P<0.05). The expression of HO-1 and Nrf2 in the PD-MSCs treatment group was more pronounced than in the HIBD group (P<0.01). PD-MSCs also decreased MDA production in the brain tissue.

CONCLUSION

These results demonstrate that PD-MSCs have neuroprotective effect during the treatment of HIBD and that the mechanism may be partly due to alleviating oxidative stress.

Mild hypothermia combined with neural stem cell transplantation for hypoxic-ischemic encephalopathy: neuroprotective effects of combined therapy

Neural stem cell transplantation is a useful treatment for ischemic stroke, but apoptosis often occurs in the hypoxic-ischemic environment of the brain after cell transplantation. In this study, we determined if mild hypothermia (27-28°C) can increase the survival rate of neural stem cells (1.0 × 10(5)/μL) transplanted into neonatal mice with hypoxic-ischemic encephalopathy. Long-term effects on neurological functioning of the mice were also examined. After mild hypothermia combined with neural stem cell transplantation, we observed decreased expression levels of inflammatory factor nuclear factor-kappa B and apoptotic factor caspase-3, reduced cerebral infarct volumes, increased survival rate of transplanted cells, and marked improvements in neurological function. Thus, the neuroprotective effects of mild hypothermia combined with neural stem cell transplantation are superior to those of monotherapy. Moreover, our findings suggest that the neuroprotective effects of mild hypothermia combined with neural stem cell transplantation on hypoxic-ischemic encephalopathy are achieved by anti-inflammatory and anti-apoptotic mechanisms.

Hypothermia modulates cytokine responses after neonatal rat hypoxic-ischemic injury and reduces brain damage

While hypothermia (HT) is the standard-of-care for neonates with hypoxic ischemic injury (HII), the mechanisms underlying its neuroprotective effect are poorly understood. We examined ischemic core/penumbra and cytokine/chemokine evolution in a 10-day-old rat pup model of HII. Pups were treated for 24 hr after HII with HT (32℃; n = 18) or normothermia (NT, 35℃; n = 15). Outcomes included magnetic resonance imaging (MRI), neurobehavioral testing, and brain cytokine/chemokine profiling (0, 24, 48, and 72 hr post-HII). Lesion volumes (24 hr) were reduced in HT pups (total 74%, p < .05; penumbra 68%, p < .05; core 85%, p = .19). Lesion volumes rebounded at 72 hr (48 hr post-HT) with no significant differences between NT and HT pups. HT reduced interleukin-1β (IL-1β) at all time points (p < .05); monocyte chemoattractant protein-1 (MCP-1) trended toward being decreased in HT pups (p = .09). The stem cell signaling molecule, stromal cell-derived factor-1 (SDF-1) was not altered by HT. Our data demonstrate that HT reduces total and penumbral lesion volumes (at 24 and 48 hr), potentially by decreasing IL-1β without affecting SDF-1. Disassociation between the increasing trend in HII volumes from 48 to 72 hr post-HII when IL-1β levels remained low suggests that after rewarming, mechanisms unrelated to IL-1β expression are likely to contribute to this delayed increase in injury. Additional studies should be considered to determine what these mechanisms might be and also to explore whether extending the duration or degree of HT might ameliorate this delayed increase in injury.

Hypothermia in hypoxic ischemic encephalopathy: a 5-year experience at Phoenix Children's Hospital Neuro NICU

We found TH to be safe and effective in improving survival and neurodevelopmental outcomes following HIE in term children. Additionally, the use of a multidisciplinary team involved with these complex patients and the use of advanced monitoring techniques will likely assist in identifying second insults (ie, seizures), leading to more rapidly instituted treatments. Our study, however, had the limitation of including only retrospective data from patients in whom TH was provided. This makes it difficult to identify the specific sources for the improved outcomes and/or the presence of complications.

Obstetric antecedents to body-cooling treatment of the newborn infant

OBJECTIVE

Obstetric antecedents were analyzed in births in which the infant received whole-body cooling for neonatal encephalopathy.

STUDY DESIGN

This retrospective cohort study included all live-born singleton infants delivered at or beyond 36 weeks' gestation from October 2005 through December 2011. Infants who had received whole-body cooling identified by review of a prospective neonatal registry were compared with a control group comprising the remaining obstetric population delivered at greater than 36 weeks but not cooled. Univariable analysis was followed up by a staged, stepwise selection of variables with the intent to rank significant risk factors for cooling.

RESULTS

A total of 86,371 women delivered during the study period and 98 infants received whole-body cooling (1.1 per 1000 live births). Of these 98 infants, 80 newborns (88%) had moderate encephalopathy and 10 (12%) had severe encephalopathy prior to cooling. Maternal age of 15 years or younger, low parity, maternal body habitus (body mass index of ≥40 kg/m(2)), diabetes, preeclampsia, induction, epidural analgesia, chorioamnionitis, length of labor, and mode of delivery were associated with significantly increased risk of infant cooling during a univariable analysis. Catastrophic events to include umbilical cord prolapse (odds ratio [OR], 14; 95% confidence interval [CI], 3-72), placental abruption (OR, 17; 95% CI, 7-44), uterine rupture (OR, 130; 95% CI, 11-1477) were the strongest factors associated with infant cooling after staged-stepwise logistic analysis.

CONCLUSION

A variety of intrapartum characteristics were associated with infant cooling for neonatal encephalopathy, with the most powerful antecedents being umbilical cord prolapse, placental abruption, and uterine rupture.

Spatial working memory deficits in male rats following neonatal hypoxic ischemic brain injury can be attenuated by task modifications

Hypoxia-ischemia (HI; reduction in blood/oxygen supply) is common in infants with serious birth complications, such as prolonged labor and cord prolapse, as well as in infants born prematurely (<37 weeks gestational age; GA). Most often, HI can lead to brain injury in the form of cortical and subcortical damage, as well as later cognitive/behavioral deficits. A common domain of impairment is working memory, which can be associated with heightened incidence of developmental disorders. To further characterize these clinical issues, the current investigation describes data from a rodent model of HI induced on postnatal (P)7, an age comparable to a term (GA 36–38) human. Specifically, we sought to assess working memory using an eight-arm radial water maze paradigm. Study 1 used a modified version of the paradigm, which requires a step-wise change in spatial memory via progressively more difficult tasks, as well as multiple daily trials for extra learning opportunity. Results were surprising and revealed a small HI deficit only for the final and most difficult condition, when a delay before test trial was introduced. Study 2 again used the modified radial arm maze, but presented the most difficult condition from the start, and only one daily test trial. Here, results were expected and revealed a robust and consistent HI deficit across all weeks. Combined results indicate that male HI rats can learn a difficult spatial working memory task if it is presented in a graded multi-trial format, but performance is poor and does not appear to remediate if the task is presented with high initial memory demand. Male HI rats in both studies displayed impulsive characteristics throughout testing evidenced as reduced choice latencies despite more errors. This aspect of behavioral results is consistent with impulsiveness as a core symptom of ADHD—a diagnosis common in children with HI insult. Overall findings suggest that task specific behavioral modifications are crucial to accommodating memory deficits in children suffering from cognitive impairments following neonatal HI.

Sex differences in behavioral outcome following neonatal hypoxia ischemia: insights from a clinical meta-analysis and a rodent model of induced hypoxic ischemic brain injury

Hypoxia ischemia (HI; reduced oxygen and/or blood flow to the brain) is one of the most common injuries among preterm infants and term infants with birth complications. Both populations show cognitive/behavioral deficits, including impairments in sensory, learning/memory, and attention domains. Clinical data suggests a sex difference in HI outcomes, with males exhibiting more severe cognitive/behavioral deficits relative to matched females. Our laboratory has also reported more severe behavioral deficits among male rats with induced HI relative to females with comparable injury (Hill et al., 2011a,b). The current study initially examined published clinical studies from the past 20years where long-term IQ outcome scores for matched groups of male and female premature infants were reported separately (IQ being the most common outcome measure). A meta-analysis revealed a female "advantage," as indicated by significantly better scores on performance and full scale IQ (but not verbal IQ) for premature females. We then utilized a rodent model of neonatal HI injury to assess sham and postnatal day 7 (P7) HI male and female rats on a battery of behavioral tasks. Results showed expected deficits in HI male rats, but also showed task-dependent sex differences, with HI males having significantly larger deficits than HI females on some tasks but equivalent deficits on other tasks. In contrast to behavioral results, post mortem neuropathology associated with HI was comparable across sex. These findings suggest: 1) neonatal female "protection" in some behavioral domains, as indexed by superior outcome following early injury relative to males; and 2) female protection may entail sex-specific plasticity or compensation, rather than a reduction in gross neuropathology. Further exploration of the mechanisms underlying this sex effect could aid in neuroprotection efforts for at-risk neonates in general, and males in particular. Moreover, our current report of comparable anatomical damage coupled with differences in cognitive outcomes (by sex) provides a framework for future studies to examine neural mechanisms underlying sex differences in cognition and behavior in general.

Therapeutic hypothermia after cardiopulmonary resuscitation

Full cerebral recovery after cardiopulmonary resuscitation is still a rare event. Unfortunately, up to now, no specific and outcome-improving therapy was available after such events. From several cases it is known that low body and brain temperature during a cardiocirculatory arrest improves the neurological outcome following these events. As it is not possible in acute events to induce hypothermia beforehand, whether cooling after the insult could also be protective was evaluated. After animal studies in the 1990s and first clinical pilot trials of mild therapeutic and induced hypothermia, two randomized trials of hypothermic therapy after successful resuscitation after cardiac arrest were conducted. These studies demonstrated that hypothermia after cardiac arrest could improve neurological outcome as well as overall mortality.

Short-term treadmill exercise preserves sensory-motor function through inhibiting apoptosis in the hippocampus of hypoxic ischemia injury rat pups

Perinatal hypoxic ischemia injury is a common cause of morbidity and mortality in neonates. Physical exercise may ameliorate neurological impairment by impeding neuronal loss following various brain insults. In the present study, the effect of treadmill exercise on sensory-motor function in relation with hippocampal apoptosis following hypoxic ischemia brain injury was investigated. Sensory-motor function was determined by walking initiation test and apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining and caspase-3 immunohistochemistry. On postnatal 7 day, left common carotid artery of the neonatal rats was ligated for two hours and then the neonatal rats were exposed to hypoxia conditions for one hour. The rat pups in the exercise groups were forced to run on a motorized treadmill for 30 min once a day for 10 days, starting 22 days after induction of hypoxic ischemia brain injury. Hypoxic ischemia caused sensory-motor disturbance with enhancement of apoptosis in the hippocampus. Short-term treadmill exercise suppressed hypoxic ischemia injury-induced apoptosis in the hippocampus, and preserved sensory-motor function of hypoxic ischemia injury rat pups.

Cooling in the real world: therapeutic hypothermia in hypoxic-ischemic encephalopathy

BACKGROUND AND AIM

The benefits of therapeutic hypothermia have not been assessed from the perspective of the neurology clinic. We aimed to report the impact of the implementation of a local regional therapeutic hypothermia program on the neurodevelopmental outcomes of surviving hypoxic-ischemic encephalopathy (HIE) infants who were followed in the neonatal neurology clinic.

METHODS

Retrospective analysis of term infants referred to the neonatal neurology clinic after having been diagnosed with HIE and meeting eligibility criteria for therapeutic hypothermia between March 1999 and June 2010. Therapeutic hypothermia was implemented in September 2008. Outcome measures were dichotomously defined as: normal or adverse, which included cerebral palsy, global developmental delay, and epilepsy.

RESULTS

Thirty infants were included in the pre-therapeutic hypothermia group. Thirty-one infants received therapeutic hypothermia and 27 were adequately followed and included in the post-therapeutic hypothermia group. The frequency of an adverse outcome was significantly higher in the pre-therapeutic hypothermia infants (19/30 [63%] versus 4/27 [15%]; OR = 0.10; 95% CI, 0.03-0.37; P < 0.001). Neonatal clinical seizures were more frequent in the pre-therapeutic hypothermia group (P = 0.012). There were no differences regarding frequency of fetal distress, rate of caesarean sections, Apgar scores, need of resuscitation, cord/initial blood gases, and degrees of encephalopathy between the two groups.

CONCLUSIONS

The implementation of a regional therapeutic hypothermia program in our institution has vastly reduced the observed neurological morbidity of surviving HIE infants followed in our neonatal neurology clinic. A similar change in outcomes of infants with HIE can be anticipated by other centers and other clinics adopting this therapy.

The effect of hypothermia therapy on cortical laminar disruption following ischemic injury in neonatal mice

Hypothermia has been proposed as a treatment for reducing neuronal damage in the brain induced by hypoxic ischemia. In the developing brain, hypoxic ischemia-induced injury may give rise to cerebral palsy (CP). However, it is unknown whether hypothermia might affect the development of CP. The purpose of this study was to investigate whether hypothermia would have a protective effect on the brains of immature, 3-day old (P3) mice after a challenge of cerebral ischemia. Cerebral ischemia was induced in P3 mice with a right common carotid artery ligation followed by hypoxia (6% O2, 37°C) for 30 min. Immediately after hypoxic ischemia, mice were exposed to hypothermia (32°C) or normothermia (37°C) for 24 h. At 4 weeks of age, mouse motor development was tested in a behavioral test. Mice were sacrificed at P4, P7, and 5 weeks to examine brain morphology. The laminar structure of the cortex was examined with immunohistochemistry (Cux1/Ctip2); the number of neurons was counted; and the expression of myelin basic protein (MBP) was determined. The hypothermia treatment was associated with improved neurological outcomes in the behavioral test. In the normothermia group, histological analyses indicated reduced numbers of neurons, reduced cortical laminar thickness in the deep, ischemic cortical layers, and significant reduction in MBP expression in the ischemic cortex compared to the contralateral cortex. In the hypothermia group, no reductions were noted in deep cortical layer thickness and in MBP expression in the ischemic cortex compared to the contralateral cortex. At 24 h after the hypothermia treatment prevented the neuronal cell death that had predominantly occurred in the ischemic cortical deep layers with normothermia treatment. Our findings may provide a preclinical basis for testing hypothermal therapies in patients with CP induced by hypoxic ischemia in the preterm period.

Pathophysiology of an hypoxic–ischemic insult during the perinatal period

Hypoxia-ischemia is a leading cause of morbidity and mortality in the perinatal period with an incidence of 1/4000 live births. Biochemical events such as energy failure, membrane depolarization, brain edema, an increase of neurotransmitter release and inhibition of uptake, an increase of intracellular Ca(2+), production of oxygen-free radicals, lipid peroxidation, and a decrease of blood flow are triggered by hypoxia-ischemia and may lead to brain dysfunction and neuronal death. These abnormalities can result in mental impairments, seizures, and permanent motor deficits, such as cerebral palsy. The physical and emotional strain that is placed on the children affected and their families is enormous. The care that these individuals need is not only confined to childhood, but rather extends throughout their entire life span, so it is very important to understand the pathophysiology that follows a hypoxic-ischemic insult. This review will highlight many of the mechanisms that lead to neuronal death and include the emerging area of white matter injury as well as the role of inflammation and will provide a summary of therapeutic strategies. Hypothermia and oxygen will also be discussed as treatments that currently lack a specific target in the hypoxic/ischemic cascade.

Comparison of three hypothermic target temperatures for the treatment of hypoxic ischemia: mRNA level responses of eight genes in the piglet brain

Hypothermia can reduce neurodevelopmental disabilities in asphyxiated newborn infants. However, the optimal cooling temperature for neuroprotection is not well defined. We studied the effects of transient piglet brain hypoxic ischemia (HI) on transcriptional activity of eight genes and if mRNA level alterations could be counteracted by whole body cooling to 35, 33.5 or 30 °C. BDNF mRNA was globally upregulated by the insult, and none of the cooling temperatures counteracted this change. In contrast, MANF mRNA was downregulated, and these changes were modestly counteracted in different brain regions by hypothermic treatment at 33.5 °C, while 30 °C aggravated the MANF mRNA loss. MAP2 mRNA was markedly downregulated in all brain regions except striatum, and cooling to 33.5 °C modestly counteract this downregulation in the cortex cerebri. There was a tendency for GFAP mRNA levels in core, but not mantle regions to be downregulated and for these changes to be modestly counteracted by cooling to 33.5 or 35 °C. Cooling to 30 °C caused global GFAP mRNA decrease. HSP70 mRNA tended to become upregulated by HI and to be more pronounced in cortex and CA1 of hippocampus during cooling to 33.5 °C. We conclude that HI causes alterations of mRNA levels of many genes in superficial and deep piglet brain areas. Some of these changes may be beneficial, others detrimental, and lowering body temperature partly counteracts some, but not all changes. There may be general differences between core and mantle regions, as well as between the different cooling temperatures for protection. Comparing the three studied temperatures, cooling to 33.5 °C, appears to provide the best cooling temperature compromise.

Attenuating systemic inflammatory markers in simulated high-altitude exposure by heat shock protein 70-mediated hypobaric hypoxia preconditioning in rats

BACKGROUND/PURPOSE

The primary goal of this study was to test whether high-altitude exposure (HAE: 0.9% O(2) at 0.47 ATA for 24 hours) was capable of increasing the systemic inflammatory markers as well as the toxic organ injury indicators in rats, with a secondary goal to test whether preinduction of heat shock protein (HSP) 70 by hypobaric hypoxia preconditioning (HHP: 18.3% O(2) at 0.66 ATA for 5 h/day on 5 days consecutively for 2 weeks) attenuated the proposed increased serum levels of both the systemic inflammatory markers and the toxic organ injury indicators.

METHODS

Rats were assigned to: (1) non-HHP (21% O(2) at 1.0 ATA)+non-HAE (21% O(2) at 1.0 ATA) group; (2) non-HHP+HAE group; (3) HHP+non-HAE group; (4) HHP+HAE group; and (5) HHP+HSP70 antibodies (Ab)+HAE group. For the HSP70Ab group, a neutralizing HSP70Ab was injected intravenously at 24 hours prior to HAE. All the physiological and biochemical parameters were obtained at the end of HAE or the equivalent time period of non-HAE. Blood samples were obtained for determination of both the systemic inflammatory markers (e.g., serum tumor necrosis factor-α, interleukin-1β, E-selectin, intercellular adhesion molecule-1, and liver myeloperoxidase activity) and the toxic organ injury indicators (e.g., nitric oxide metabolites, 2,3-dihydroxybenzoic acid, and lactate dehydrogenase).

RESULTS

HHP, in addition to inducing overexpression of tissue HSP70, significantly attenuated the HAE-induced hypotension, bradycardia, hypoxia, acidosis, and increased tissue levels of both the systemic inflammatory markers and the toxic organ injury indicators. The beneficial effects of HHP in inducing tissue overexpression of HSP70 as well as in preventing the HAE-induced increased levels of the systemic inflammatory markers and the toxic organ injury indicators could be significantly reduced by HSP70Ab preconditioning.

CONCLUSION

These results suggest that HHP may downgrade both the systemic inflammatory markers and the toxic organ injury indicators in HAE by upregulating tissue HSP70.

Safety and efficacy of topiramate in neonates with hypoxic ischemic encephalopathy treated with hypothermia (NeoNATI)

BACKGROUND

Despite progresses in neonatal care, the mortality and the incidence of neuro-motor disability after perinatal asphyxia have failed to show substantial improvements. In countries with a high level of perinatal care, the incidence of asphyxia responsible for moderate or severe encephalopathy is still 2-3 per 1000 term newborns. Recent trials have demonstrated that moderate hypothermia, started within 6 hours after birth and protracted for 72 hours, can significantly improve survival and reduce neurologic impairment in neonates with hypoxic-ischemic encephalopathy. It is not currently known whether neuroprotective drugs can further improve the beneficial effects of hypothermia. Topiramate has been proven to reduce brain injury in animal models of neonatal hypoxic ischemic encephalopathy. However, the association of mild hypothermia and topiramate treatment has never been studied in human newborns. The objective of this research project is to evaluate, through a multicenter randomized controlled trial, whether the efficacy of moderate hypothermia can be increased by concomitant topiramate treatment.

METHODS/DESIGN

Term newborns (gestational age ≥ 36 weeks and birth weight ≥ 1800 g) with precocious metabolic, clinical and electroencephalographic (EEG) signs of hypoxic-ischemic encephalopathy will be randomized, according to their EEG pattern, to receive topiramate added to standard treatment with moderate hypothermia or standard treatment alone. Topiramate will be administered at 10 mg/kg once a day for the first 3 days of life. Topiramate concentrations will be measured on serial dried blood spots. 64 participants will be recruited in the study. To evaluate the safety of topiramate administration, cardiac and respiratory parameters will be continuously monitored. Blood samplings will be performed to check renal, liver and metabolic balance. To evaluate the efficacy of topiramate, the neurologic outcome of enrolled newborns will be evaluated by serial neurologic and neuroradiologic examinations. Visual function will be evaluated by means of behavioural standardized tests.

DISCUSSION

This pilot study will explore the possible therapeutic role of topiramate in combination with moderate hypothermia. Any favourable results of this research might open new perspectives about the reduction of cerebral damage in asphyxiated newborns.

Hypoxic ischaemic hypothermia promotes neuronal differentiation and inhibits glial differentiation from newly generated cells in the SGZ of the neonatal rat brain

Hypothermia is a potential therapy for cerebral hypoxic ischaemic injury in adults and neonates. The mechanism of the neuroprotective effects of hypothermia after hypoxia-ischaemia (HI) in the developing rat brain remains unclear. In this research, 7-day-old rats underwent left carotid artery ligation followed by the administration of 8% oxygen for 2 h. These rats were divided into hypothermic (rectal temperature, 32-33 °C for 24 h) and normothermic (36-37 °C for 24 h) groups immediately after HI. All rats were given 50 mg/kg/day 5-bromodeoxyuridine (BrdU) intraperitoneally at 4-6 days and sacrificed at 1 or 2 weeks after HI. We found a significant decrease in infarct volume and the neuron loss were also detected in the subgranular zone (SGZ) in the hypothermic group at 7 and 14 days after HI compared with the normothermic group. BrdU immunopositive cells were reduced greatly in the hypothermic group compared with the normothermic group. Hypothermia did not change the number of nestin-labelled cells in the ipsilateral SGZ at 1 and 2 weeks after HI. The differentiation of newly generated cells was assessed by double immunolabelling of BrdU with glial fibrillary acidic protein (GFAP), O4 or Neuronal Nuclei (NeuN). The ratio of BrdU(+)-GFAP(+) or BrdU(+)-O4(+) to total BrdU(+) staining decreased dramatically, but the ratio of BrdU(+)-NeuN(+) to total BrdU(+) staining increased significantly in the hypothermic group compared to the normothermic group at 2 and 6 weeks after HI. These results suggest that the reduction in neuron loss observed after mild hypothermia may be associated with enhanced neuronal differentiation and decreased glial differentiation in the SGZ after HI. These observations are noteworthy for clinical hypothermia therapy following cerebral HI injury during the perinatal period.

Cannabidiol administration after hypoxia-ischemia to newborn rats reduces long-term brain injury and restores neurobehavioral function

Cannabidiol (CBD) demonstrated short-term neuroprotective effects in the immature brain following hypoxia-ischemia (HI). We examined whether CBD neuroprotection is sustained over a prolonged period. Newborn Wistar rats underwent HI injury (10% oxygen for 120 min after left carotid artery electrocoagulation) and then received vehicle (HV, n = 22) or 1 mg/kg CBD (HC, n = 23). Sham animals were similarly treated (SV, n = 16 and SC, n = 16). The extent of brain damage was determined by magnetic resonance imaging, histological evaluation (neuropathological score, 0-5), magnetic resonance spectroscopy and Western blotting. Several neurobehavioral tests (RotaRod, cylinder rear test[CRT],and novel object recognition[NOR]) were carried out 30 days after HI (P37). CBD modulated brain excitotoxicity, oxidative stress and inflammation seven days after HI. We observed that HI led to long-lasting functional impairment, as observed in all neurobehavioral tests at P37, whereas the results of HC animals were similar to those of sham animals (all p < 0.05 vs. HV). CBD reduced brain infarct volume by 17% (p < 0.05) and lessened the extent of histological damage. No differences were observed between the SV and SC groups in any of the experiments. In conclusion, CBD administration after HI injury to newborn rats led to long-lasting neuroprotection, with the overall effect of promoting greater functional rather than histological recovery. These effects of CBD were not associated with any side effects. These results emphasize the interest in CBD as a neuroprotective agent for neonatal HI.

Reducing pulmonary injury by hyperbaric oxygen preconditioning during simulated high altitude exposure in rats

BACKGROUND

Hyperbaric oxygen preconditioning (HBO₂P + HAE) has been found to be beneficial in preventing the occurrence of ischemic damage to brain, spinal cord, heart, and liver in several disease models. In addition, pulmonary inflammation and edema are associated with a marked reduction in the expression levels of both aquaporin (AQP) 1 and AQP5 in the lung. Here, the aims of this study are first to ascertain whether acute lung injury can be induced by simulated high altitude in rats and second to assess whether HBO2P + HAE is able to prevent the occurrence of the proposed high altitude-induced ALI.

METHODS

Rats were randomly divided into the following three groups: the normobaric air (NBA; 21% O₂ at 1 ATA) group, the HBO₂P + high altitude exposure (HAE) group, and the NBA + HAE group. In HBO₂P + HAE group, animals received 100% O₂ at 2.0 ATA for 1 hour per day, for five consecutive days. In HAE groups, animals were exposed to a simulated HAE of 6,000 m in a hypobaric chamber for 24 hours. Right after being taken out to the ambient, animals were anesthetized generally and killed and thoroughly exsanguinated before their lungs were excised en bloc. The lungs were used for both histologic and molecular evaluation and analysis.

RESULTS

In NBA + HAE group, the animals displayed higher scores of alveolar edema, neutrophil infiltration, and hemorrhage compared with those of NBA controls. In contrast, the levels of both AQP1 and AQP5 proteins and mRNA expression in the lung in the NBA + HAE group were significantly lower than those of NBA controls. However, the increased lung injury scores and the decreased levels of both AQP1 and AQP5 proteins and mRNA expression in the lung caused by HAE was significantly reduced by HBO₂P + HAE.

CONCLUSIONS

Our results suggest that high altitude pulmonary injury may be prevented by HBO2P + HAE in rats.

The effect of postischemic hypothermia on apoptotic cell death in the neonatal rat brain

BACKGROUND AND OBJECTIVE

Hypothermia is the most effective neuroprotective therapy against ischemic injury in the developing brain. However, the mechanism of hypothermic neuroprotection is not well understood. We sought to investigate whether hypothermia mediates neuroprotection by modulating ischemia-induced apoptosis.

METHODS

Seven-day-old rat pups were randomly assigned to either control or hypoxia-ischemia (HI) groups. In the HI group, the internal carotid artery was ligated and cut. This was followed by transient hypoxia at 8% oxygen for 90 min. In the control rats, the internal carotid was isolated but not ligated. Immediately after the hypoxic episode, pups in the HI group were either placed in water baths maintained at 28°C for 24 h (core temperatures at 31°C) or they remained in a normothermic environment. Animals were sacrificed at 24, 48 and 72 h and 1 week after the HI insult. Brain sections were processed for immunohistochemistry and Western blots.

RESULTS

Caspase 3 expression was significantly higher in the core compared with the peri-infarct area at all time points in normothermic rats. Hypothermia reduced caspase 3 expression in the core but had little effect in the peri-infarct area. Hypothermia reduced apoptosis-inducing factor translocation to the nucleus in the core and peri-infarct area. Concurrently, X-linked inhibitor of apoptosis (XIAP) expression was significantly potentiated in the hypothermic-ischemic core but not in the peri-infarct area.

CONCLUSION

Hypothermic modulation of caspase-dependent apoptosis may be mediated by upregulating XIAP. However, the effect of hypothermia on caspase-independent apoptosis may be mediated by XIAP-independent mechanisms. Importantly, these effects are mediated in both the core and the penumbral regions of ischemic lesion.

Short- and long-term behavioral effects of exposure to 21%, 40% and 100% oxygen after perinatal hypoxia-ischemia in the rat

Until recently, supplementation with 100% oxygen was standard therapy for newborns who required resuscitation at birth or suffered later hypoxic-ischemic events. Exposure to high concentrations of oxygen, however, may worsen oxidative stress induced by ischemic injury. In this study we investigated the short- and long-term behavioral outcomes in rats that had undergone hypoxic-ischemic brain injury on postnatal day 7, followed by 2h exposure to 21%, 40%, or 100% oxygen, compared to normal controls. There were no differences in the development of walking, head lifting and righting reflexes from postnatal days 9 to 15. Cliff avoidance showed some abnormal responses in the H21 animals. From postnatal days 28 to 56, three tests of sensorimotor coordination were performed weekly: ledged tapered beam, cylinder, and bilateral tactile stimulation. The ledged tapered beam test without prior training of animals was sensitive to injury, but did not distinguish between treatment groups. The cylinder test showed a greater use of the unimpaired limb in female 21% and 40% oxygen groups compared to controls. Performance in both cylinder and the beam tests showed a correlation with the degree of brain injury. The bilateral tactile stimulation test showed that the male 21% oxygen groups had worse sensory asymmetry than male 40% or 100% oxygen groups, but was not statistically significantly different from controls. We thus found a minor benefit to post-hypoxia-ischemic treatment with 100% and 40% oxygen compared to 21% in one test of early motor skills. Our results for long-term sensorimotor behavior, however, showed conflicting results, however, as males treated with 40% or 100% oxygen had less sensory asymmetry (better performance) in the bilateral tactile stimulation test than males treated with 21% oxygen, while females had impaired motor performance in the cylinder test with both 21% and 40% oxygen.

Animal models of intellectual disability: towards a translational approach

Intellectual disability is a prevalent form of cognitive impairment, affecting 2-3% of the general population. It is a daunting societal problem characterized by significant limitations both in intellectual functioning and in adaptive behavior as expressed in conceptual, social and practical adaptive skills. Intellectual disability is a clinically important disorder for which the etiology and pathogenesis are still poorly understood. Moreover, although tremendous progress has been made, pharmacological intervention is still currently non-existent and therapeutic strategies remain limited. Studies in humans have a very limited capacity to explain basic mechanisms of this condition. In this sense, animal models have been invaluable in intellectual disability investigation. Certainly, a great deal of the knowledge that has improved our understanding of several pathologies has derived from appropriate animal models. Moreover, to improve human health, scientific discoveries must be translated into practical applications. Translational research specifically aims at taking basic scientific discoveries and best practices to benefit the lives of people in our communities. In this context, the challenge that basic science research needs to meet is to make use of a comparative approach to benefit the most from what each animal model can tell us. Intellectual disability results from many different genetic and environmental insults. Taken together, the present review will describe several animal models of potential intellectual disability risk factors.

Long-term neuroprotective effect of postischemic hypothermia in a neonatal rat model of severe hypoxic ischemic encephalopathy: a comparative study on the duration and depth of hypothermia

It is not known whether deeper or longer hypothermia (HT) can achieve better neuroprotection against hypoxic ischemic encephalopathy (HIE) in neonates. To compare the neuroprotective effects of different durations and temperatures of postischemic HT in neonatal rats with severe HIE, 7-d-old rats were subjected to the Rice-Vannucci model for 150 min hypoxia. Only the rats with identified brain lesions in diffusion-weighted MRI were assigned to normothermia (NT, 36° C/48 h) or four HT (HT-30° C/48 h; HT-30° C/24 h; HT-33° C/48 h; and HT-33° C/24 h) groups. H-magnetic resonance spectroscopy (H-MRS) and T2-weighted MRI were obtained serially, and functional studies were performed. HT groups showed significantly greater residual hemispheric volume and better rotarod and cylinder tests than did the NT group at 5 wk postischemia. HT groups also showed lower lactate-plus-lipid level in H-MRS than did the NT group at 7 d postischemia. All of these outcome variables, however, did not differ among the 4 HT subgroups, despite a trend toward greater residual brain volume in the 48-h HT versus 24-h HT subgroups. In conclusion, neither reducing the target temperature from 33 to 30° C nor prolonging the duration from 24 to 48 h produced further improvements in neurologic outcomes in neonatal rat with HIE.

Selective head cooling with mild systemic hypothermia after neonatal hypoxic-ischemic encephalopathy: a multicenter randomized controlled trial in China

OBJECTIVE

To investigate the efficacy and safety of selective head cooling with mild systemic hypothermia in hypoxic-ischemic encephalopathy (HIE) in newborn infants.

STUDY DESIGN

Infants with HIE were randomly assigned to the selective head cooling or control group. Selective head cooling was initiated within 6 hours after birth to a nasopharyngeal temperature of 34 degrees+/-0.2 degrees C and rectal temperature of 34.5 degrees to 35.0 degrees C for 72 hours. Rectal temperature was maintained at 36.0 degrees to 37.5 degrees C in the control group. Neurodevelopmental outcome was assessed at 18 months of age. The primary outcome was a combined end point of death and severe disability.

RESULTS

One hundred ninety-four infants were available for analysis (100 and 94 infants in the selective head cooling and control group, respectively). For the selective head cooling and control groups, respectively, the combined outcome of death and severe disability was 31% and 49% (OR: 0.47; 95% CI: 0.26-0.84; P=.01), the mortality rate was 20% and 29% (OR:0.62; 95% CI: 0.32-1.20; P=.16), and the severe disability rate was 14% (11/80) and 28% (19/67) (OR: 0.40; 95% CI: 0.17-0.92; P=.01).

CONCLUSIONS

Selective head cooling combined with mild systemic hypothermia for 72 hours may significantly decrease the combined outcome of severe disability and death, as well as severe disability.