LINC00938 alleviates hypoxia ischemia encephalopathy induced neonatal brain injury by regulating oxidative stress and inhibiting JNK/p38 MAPK signaling pathway

Hypoxic-ischemic encephalopathy (HIE) is an important factor leading to permanent damage of central nervous system (CNS) and even neonatal death. Long non-coding RNAs (lncRNAs) has been shown to get involved in the pathogenesis of nervous system diseases. LINC00938 is an intergenic lncRNA which is reported to be involved in neurodegenerative disease. However, the potential role of LINC00938 in nerve injury of neonatal HIE is undetermined. Here, we found that the expression of LINC00938 in the whole blood of neonates with HIE was downregulated compared with the non-HIE group. Functional study revealed that the expression of LINC00938 was significantly decreased in oxygen-glucose deprivation (OGD)-induced SH-SY5Y. Knockdown of LINC00938 induced the neural cell apoptosis by increased the protein level of Bax, Cleaved-Caspase3 and decreased the expression of Bcl-2. In addition, overexpression of LINC00938 prevented the apoptosis of SH-SY5Y from OGD injury. RNA-seq analysis showed that MAPK signaling was involved in the anti-apoptosis function of LINC00938. LINC00938 knockdown induced the activation of c-Jun-N-terminal kinase (JNK), p38 mitogen-activated protein kinase, and inhibited the activation of ERK signaling. However, LINC00938 play neuroprotective role in OGD-induced SH-SY5Y by suppression the phosphorylation of JNK and p38 MAPK rather than regulation of ERK signaling pathway. Further analyses illustrated that the cell apoptosis of neuronal cell was dependent on the elevation of reactive oxygen species (ROS) and result in mitochondria dysfunction in LINC00938 knockdown SH-SY5Y. Pretreated with ROS inhibitor N-acetylcysteine amide (NACA) dramatically suppressed LINC00938 knockdown induced oxidative stress and mitochondria dysfunction which induced cell apoptosis. In addition, NACA treatment significantly reduced the expression of p-JNK and p-p38 in OGD-induced SH-SY5Y. Furthermore, overexpression of LINC00938 displayed a notably neuroprotective effect by suppress central nervous system cell apoptosis via alleviating oxidative stress in CoCl2-induced hypoxic HIE model of zebrafish. Taken together, these results suggested that LINC00938 can act as a neuroprotective factor to inhibit oxidative stress and apoptosis of CNS under HIE conditions.

Can radiomics be used to detect hypoxic-ischemic encephalopathy in neonates without magnetic resonance imaging abnormalities?

BACKGROUND

No study has assessed normal magnetic resonance imaging (MRI) findings to predict potential brain injury in neonates with hypoxic-ischemic encephalopathy (HIE).

OBJECTIVE

We aimed to evaluate the efficacy of MRI-based radiomics models of the basal ganglia, thalami and deep medullary veins to differentiate between HIE and the absence of MRI abnormalities in neonates.

MATERIALS AND METHODS

In this study, we included 38  full-term neonates with HIE and normal MRI findings and 89 normal neonates. Radiomics features were extracted from T1-weighted images, T2-weighted images, diffusion-weighted imaging and susceptibility-weighted imaging (SWI). The different models were evaluated using receiver operating characteristic curve analysis. Clinical utility was evaluated using decision curve analysis.

RESULTS

The SWI model exhibited the best performance among the seven single-sequence models. For the training and validation cohorts, the area under the curves (AUCs) of the SWI model were 1.00 and 0.98, respectively. The combined nomogram model incorporating SWI Rad-scores and independent predictors of clinical characteristics was not able to distinguish HIE in patients without MRI abnormalities from the control group (AUC, 1.00). A high degree of fitting and favorable clinical utility was detected using the calibration curve with the Hosmer-Lemeshow test. Decision curve analysis was used for the SWI, clinical and combined nomogram models. The decision curve showed that the SWI and combined nomogram models had better predictive performance than the clinical model.

CONCLUSIONS

HIE can be detected in patients without MRI abnormalities using an MRI-based radiomics model. The SWI model performed better than the other models.

Biomarkers of hypoxic-ischemic encephalopathy: a systematic review

BACKGROUND

Current diagnostic criteria for hypoxic-ischemic encephalopathy in the early hours lack objective measurement tools. Therefore, this systematic review aims to identify putative molecules that can be used in diagnosis in daily clinical practice (PROSPERO ID: CRD42021272610).

DATA SOURCES

Searches were performed in PubMed, Web of Science, and Science Direct databases until November 2020. English original papers analyzing samples from newborns > 36 weeks that met at least two American College of Obstetricians and Gynecologists diagnostic criteria and/or imaging evidence of cerebral damage were included. Bias was assessed by the Newcastle-Ottawa Scale. The search and data extraction were verified by two authors separately.

RESULTS

From 373 papers, 30 met the inclusion criteria. Data from samples collected in the first 72 hours were extracted, and increased serum levels of neuron-specific enolase and S100-calcium-binding protein-B were associated with a worse prognosis in newborns that suffered an episode of perinatal asphyxia. In addition, the levels of glial fibrillary acidic protein, ubiquitin carboxyl terminal hydrolase isozyme-L1, glutamic pyruvic transaminase-2, lactate, and glucose were elevated in newborns diagnosed with hypoxic-ischemic encephalopathy. Moreover, pathway analysis revealed insulin-like growth factor signaling and alanine, aspartate and glutamate metabolism to be involved in the early molecular response to insult.

CONCLUSIONS

Neuron-specific enolase and S100-calcium-binding protein-B are potential biomarkers, since they are correlated with an unfavorable outcome of hypoxic-ischemic encephalopathy newborns. However, more studies are required to determine the sensitivity and specificity of this approach to be validated for clinical practice.

Hypothermia for neonatal hypoxic-ischemic encephalopathy: Retrospective descriptive study of features associated with poor outcome

AIM

To investigate the clinical, laboratory, electrophysiological, and imaging features associated with death or neurological impairment at 1 year of age in term neonates with hypoxic-ischemic encephalopathy (HIE) treated by therapeutic hypothermia (TH).

METHODS

This was a single-center retrospective and descriptive study conducted over a period of 2 years. We included consecutive term newborns with moderate or severe HIE who were treated by TH initiated within the sixth hour after birth and continued for 72 h,. For all patients, brain magnetic resonance imaging (MRI) was performed before the eighth day and a score was established; furthermore, at least two electroencephalograms were recorded.

RESULTS

Among the 33 patients included, 20 neonates had a favorable outcome and 13 had an unfavorable outcome. Early clinical seizures (15% vs. 53.8%, p = 0.047), the persistence of a poor prognosis according to the electroencephalogram pattern after TH (0% vs. 69.2%, p = 0.0001), and an elevated score on the early brain MRI (2 vs. 11, p < 0.001) combined with a high lactate/N-acetyl-aspartate ratio (0.52 vs. 1.33, p = 0.008) on spectroscopy were associated with death and a poor outcome.

CONCLUSION

A combination of tools can help the medical team to establish the most reliable prognosis for these full-term neonates, to guide care, and to inform parents most appropriately and sincerely.

Therapeutic Hypothermia for Perinatal Asphyxia in India-Experience and Evidence

Therapeutic hypothermia is an established therapy with proven benefit for term neonates with moderate and severe hypoxic-ischemic encephalopathy (HIE). Many centers in India have started therapeutic cooling of asphyxiated infants. There is enough evidence for the beneficial effect of cooling from the randomized trials conducted in India. However, the recently published hypothermia for encephalopathy in low- and middle-income countries (HELIX) trial has contrasting findings. In this context, this review is written summarizing the available experience and evidence for therapeutic hypothermia for perinatal asphyxia in India.

Diffusion restriction in the corticospinal tract and the corpus callosum of term neonates with hypoxic-ischemic encephalopathy

BACKGROUND

Diffusion-weighted imaging performed shortly after brain injury has been shown to facilitate visualization of acute corticospinal tract injury known as "pre-Wallerian degeneration."

OBJECTIVE

The aim of this study was to determine whether diffusion restriction in the corticospinal tract and corpus callosum occurs within the first 2 weeks after birth in neonates with neonatal hypoxic-ischemic encephalopathy.

MATERIALS AND METHODS

We enrolled a consecutive series of 66 infants diagnosed with hypoxic-ischemic encephalopathy who underwent MRI. We evaluated diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) values to assess the presence of restricted diffusion in the corticospinal tract and corpus callosum. Next, we compared ADC values in the corticospinal tract and in the splenium and genu of the corpus callosum of infants with abnormal pattern on MRI with those of control infants, who showed a normal pattern on MRI. We attempted to follow all infants with hypoxic-ischemic encephalopathy until 18 months of age and assess them using a standardized neurologic examination.

RESULTS

After exclusions, we recruited 25 infants with abnormal MRI and 20 with normal MRI (controls). Among these 45 neonates, pre-Wallerian degeneration was visualized in the corticospinal tract in 10 neonates and in the corpus callosum in 12. The ADC values in the corticospinal tract in the first week were significantly lower than they were in the second week. Infants with pre-Wallerian degeneration in the corticospinal tract showed an unfavorable outcome.

CONCLUSION

Pre-Wallerian degeneration was visualized in the corticospinal tract and corpus callosum and was associated with extensive brain injury caused by hypoxic-ischemic encephalopathy. The changes in signal were observed to evolve over time within the first 2 weeks. The clinical outcome of infants having pre-Wallerian degeneration in the corticospinal tract was unfavorable.

Neuroprotective strategies of cerebrolysin for the treatment of infants with neonatal hypoxic-ischemic encephalopathy

BACKGROUND

Perinatal asphyxia (PA) is a devastating neonatal condition characterized by a lack of oxygen supporting the organ systems. PA can lead to hypoxic-ischemic encephalopathy (HIE), a brain dysfunction due to oxygen deprivation with a complex neurological sequela. The pathophysiology of HIE and PA is not entirely understood, with therapeutic hypothermia being the standard treatment with only limited value. However, alternative neuroprotective therapies can be a potential treatment modality.

METHODS

In this review, we will characterize the biochemical mechanisms of PA and HIE, while also giving insight into cerebrolysin, a neuroprotective treatment used for HIE and PA.

RESULTS

We found that cerebrolysin has up to 6-month treatment window post-ischemic insult. Cerebrolysin injections of 0.1 ml/kg of body weight twice per week were found to provide gross motor and speech deficit improvement.

CONCLUSION

Our literature search emphasizes the positive effects of cerebrolysin for general improvement outcomes. Nevertheless, biomarker establishment is warranted to improve patient outcomes.

Tubular calcium, magnesium, and phosphate excretion during therapeutic hypothermia for neonatal hypoxic-ischemic encephalopathy: A prospective study

OBJECTIVES

Hypocalcemia, hypomagnesemia, and hyperphosphatemia are common electrolyte disturbances in perinatal asphyxia (PA). Different reasons have been proposed for these electrolyte disturbances. This study investigated the effect of the urinary excretion of calcium (Ca), magnesium (Mg), and phosphorus (P) on the serum levels of these substances in babies who were treated using therapeutic hypothermia for hypoxic ischemic encephalopathy (HIE) caused by PA. This study sheds light on the pathophysiology that may cause changes in the serum values of these electrolytes.

METHODS

This study included 21 healthy newborns (control group) and 38 patients (HIE group) who had undergone therapeutic hypothermia due to HIE. Only infants with a gestational age of 36 weeks and above and a birth weight of 2000 g and above were evaluated. The urine and serum Ca, Mg, P, and creatinine levels of all infants were evaluated at 24, 48, and 72 h.

RESULTS

The lower serum Ca value and the higher serum P value of the HIE group were found to be statistically significant compared to the control group (p<0.05). There was no significant difference in serum Mg values between the groups. However, hypomagnesemia was detected in five patients from the HIE group. The urine excretion of FeCa and FeMg at 24 h, and FeP excretion at 48 and 72 h were found to be significantly higher in the HIE group compared to the control group.

CONCLUSIONS

This study determined that the urinary excretion of Ca, Mg, and P has an effect on the serum Ca, Mg, and P levels of infants with HIE.

Activation of GPR39 with TC-G 1008 attenuates neuroinflammation via SIRT1/PGC-1α/Nrf2 pathway post-neonatal hypoxic-ischemic injury in rats

Background

Hypoxic–ischemic encephalopathy (HIE) is a severe anoxic brain injury that leads to premature mortality or long-term disabilities in infants. Neuroinflammation is a vital contributor to the pathogenic cascade post-HIE and a mediator to secondary neuronal death. As a plasma membrane G-protein-coupled receptor, GPR39, exhibits anti-inflammatory activity in several diseases. This study aimed to explore the neuroprotective function of GPR39 through inhibition of inflammation post-hypoxic–ischemic (HI) injury and to elaborate the contribution of sirtuin 1(SIRT1)/peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α)/nuclear factor, erythroid 2 like 2(Nrf2) in G-protein-coupled receptor 39 (GPR39)-mediated protection.

Methods

A total of 206 10-day-old Sprague Dawley rat pups were subjected to HIE or sham surgery. TC-G 1008 was administered intranasally at 1 h, 25 h, 49 h, and 73 h post-HIE induction. SIRT1 inhibitor EX527, GPR39 CRISPR, and PGC-1α CRISPR were administered to elucidate the underlying mechanisms. Brain infarct area, short-term and long-term neurobehavioral tests, Nissl staining, western blot, and immunofluorescence staining were performed post-HIE.

Results

The expression of GPR39 and pathway-related proteins, SIRT1, PGC-1α and Nrf2 were increased in a time-dependent manner, peaking at 24 h or 48-h post-HIE. Intranasal administration of TC-G 1008 reduced the percent infarcted area and improved short-term and long-term neurological deficits. Moreover, TC-G 1008 treatment significantly increased the expression of SIRT1, PGC-1α and Nrf2, but downregulated the expressions of IL-6, IL-1β, and TNF-α. GPR39 CRISPR EX527 and PGC-1α CRISPR abolished GPR39’s neuroprotective effects post-HIE.

Conclusions

TC-G 1008 attenuated neuroinflammation in part via the SIRT1/PGC-1α/Nrf2 pathway in a neonatal rat model of HIE. TC-G 1008 may be a novel therapeutic target for treatment post-neonatal HIE injury.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02289-7.

Development, Reliability, and Testing of a New Rating Scale for Neonatal Encephalopathy

OBJECTIVE

To develop and test the Neonatal Encephalopathy-Rating Scale (NE-RS), a new rating scale to grade the severity of neonatal encephalopathy (NE) within the first 6 hours after birth.

STUDY DESIGN

A 3-phase process was conducted: (1) design of a comprehensive scale that would be specific, sensitive, brief, and unsophisticated; (2) evaluation in a cohort of infants with neonatal encephalopathy and healthy controls; and (3) validation with brain magnetic resonance imaging findings and outcome at 2 years of age.

RESULTS

We evaluated the NE-RS in 54 infants with NE and 28 healthy infants. The NE-RS had excellent internal consistency (Cronbach alpha coefficient: 0.93 [95% CI 0.86-0.94]) and reliability (intraclass correlation coefficient in the NE cohort 0.996 [95% CI 0.993-0.998; P < .001]). Alertness, posture, motor response, and spontaneous activity were the top discriminators for degrees of NE. The cut-off value for mild vs moderate NE was 8 points (area under the curve [AUC] 0.99, 95% CI 0.85-1.00) and for moderate vs severe NE, 30 points (AUC 0.93, 95% CI 0.81-0.99). The NE-RS was significantly correlated with the magnetic resonance imaging score (Spearman Rho 0.77, P < .001) and discriminated infants who had an adverse outcome (AUC 0.91, 95% CI 0.83-0.99, sensitivity 0.82, specificity 0.81, positive predictive value 0.87, negative predictive value 0.74).

CONCLUSIONS

The NE-RS is reliable and performs well in reflecting the severity of NE within the first 6 hours after birth. This tool could be useful when assessing clinical criteria for therapeutic hypothermia in NE.

Delayed cerebral enhancement on post-mortem computed tomography due to residual contrast medium administered shortly before death

Postmortem computed tomography (CT) is currently a well-known procedure and helps in postmortem investigations. In this case report, we report a unique postmortem CT finding: delayed cerebral enhancement associated with the antemortem infusion of contrast medium. A 72-year-old female lost consciousness at a restaurant and was taken to a hospital in an ambulance. Despite resuscitation efforts, she died of hypoxic–ischemic encephalopathy caused by cardiac arrest. About 6 h before her death, she underwent enhanced antemortem CT of the head. No abnormal enhancement was observed in the cerebral parenchyma. Then, 11 h after her death, she underwent unenhanced postmortem CT, which showed bilateral hyperdense caudate nucleus and putamina, due to residual iodinated contrast medium, in addition to other characteristic findings of hypoxic–ischemic encephalopathy. The mechanism underlying this phenomenon could be the destruction of the blood–brain barrier, and/or selective vulnerability, due to hypoxic–ischemic changes in the gray matter. Enhancement of basal ganglia on postmortem CT due to antemortem infusion of iodinated contrast medium might suggest hypoxic–ischemic encephalopathy, which should be noted in postmortem CT interpretations.

Crocin enhances hypothermia therapy in hypoxic ischemia-induced brain injury in mice

Hypoxic-ischemic encephalopathy (HIE) is a serious medical situation at labor which leads to severe brain damage. Hypothermia therapy is the standard treatment for infants with HIE, but the efficacy is limited. Combination treatments are considered to enhance the efficacy of hypothermia. Crocin is an extract from saffron which has anti-inflammatory, anti-oxidant, and neuroprotective properties. The present study sought to investigate whether crocin could act as a combined treatment with hypothermia in a mouse model of HIE. C57BL/6J mice at post-natal day 7 were subjected to left common carotid artery ligation, followed by treatment of crocin (10 mg/kg) and hypothermia, either alone or in combination. Brain edema and tissue infarct were measured to evaluate brain damage. Mediators involved in inflammatory response and oxidative stress were measured. Neurological severity score test was performed to evaluate the functional outcome. Results show that crocin treatment alone could reduce inflammation and brain damage after hypoxia-ischemia. Combined treatment of crocin and hypothermia exerted enhanced therapeutic effect compared with single treatment, resulting in significantly less brain damage, reduced inflammatory and oxidative responses, and improved functional outcome. Together, these data suggest that crocin plays a beneficial effect in the mouse model of HIE. It could also enhance the neuroprotective effect of hypothermia and might be considered as a combination therapeutic treatment with hypothermia in HIE.

Validation of the suppression ratio from a simplified EEG montage during targeted temperature management after cardiac arrest

AIM

The Suppression Ratio (SR) estimates the percent of the electroencephalography (EEG) epoch with very low voltage, and is associated with neurological outcome after cardiac arrest. We aimed to compare the SR generated by two monitoring devices and determine the association between SR and patterns on amplitude integrated EEG (aEEG) and full conventional EEG (cEEG).

METHODS

Consecutive adult patients treated with TTM after cardiac arrest were enrolled. We compared the SR from the Medtronic Vista monitor (MSR) to the SR generated from the full montage cEEG with Persyst Magic-Marker software (PSR). A blinded neurologist, board certified in epilepsy, scored the 4-channel aEEG pattern and the cEEG background using standardized terminology. Values for SR were compared to aEEG and cEEG categories using Kruskal-Wallis ANOVA, and to each other using Altman-Bland methodology.

RESULTS

23 adults treated with TTM had a mean core temperature of 33.8 °C at the time of SR and EEG background analysis. The MSR was 0% during continuous cEEG background, 23% when cEEG was discontinuous, and 64% during cEEG burst suppression (p = 0.01). The MSR was 0% during aEEG continuous patterns, 34% during aEEG burst suppression, and 46% during flat aEEG (p < 0.001). The MSR and PSR were highly correlated (0.88, p < 0.0001), with minimal bias (0.3%) and excellent 95% limits of agreement (-2.9 to 2.4%).

CONCLUSION

The Suppression Ratio from the Medtronic Vista monitor is highly correlated with the full montage SR from Persyst software. The MSR values are valid, changing with different aEEG patterns and cEEG background categories.

Pathophysiology of hypoxic-ischemic encephalopathy: a review of the past and a view on the future

Hypoxic-ischemic encephalopathy, also referred as HIE, is a type of brain injury or damage that is caused by a lack of oxygen to the brain during neonatal period. The incidence is approximately 1.5 cases per 1000 live births in developed countries. In low and middle-income countries, the incidence is much higher (10‒20 per 1000 live births). The treatment for neonatal HIE is hypothermia that is only partially effective (not more than 50% of the neonates treated achieve an improved outcome). HIE pathophysiology involves oxidative stress, mitochondrial energy production failure, glutaminergic excitotoxicity, and apoptosis. So, in the last years, many studies have focused on peptides that act somewhere in the pathway activated by severe anoxic injury leading to HIE. This review describes the pathophysiology of perinatal HIE and the mechanisms that could be the target of innovative HIE treatments.

Overexpression of miR-124 Protects Against Neurological Dysfunction Induced by Neonatal Hypoxic-Ischemic Brain Injury

Neonatal hypoxic-ischemic encephalopathy (HIE) is a major cause of lifelong disabilities worldwide, without effective therapies and clear regulatory mechanisms. MicroRNAs (miRNAs) act as a significant regulator in neuroregeneration and neuronal apoptosis, thus holding great potential as therapeutic targets in HIE. In this study, we established the hypoxia-ischemia (HI) model in vivo and oxygen-glucose deprivation (OGD) model in vitro. Zea-longa score and magnetic resonance imaging were applied to verify HI-induced neuronal dysfunction and brain infarction. Subsequently, a miRNA microarray analysis was employed to profile miRNA transcriptomes. Down-regulated miR-124 was found 24 h after HIE, which corresponded to the change in PC12, SHSY5Y, and neurons after OGD. To determine the function of miR-124, mimics and lentivirus-mediated overexpression were used to regulate miR-124 in vivo and in vitro, respectively. Our results showed that miR-124 overexpression obviously promoted cell survival and suppressed neuronal apoptosis. Further, the memory and neurological function of rats was also obviously improved at 1 and 2 months after HI, indicated by the neurological severity score, Y-maze test, open field test, and rotating rod test. Our findings showed that overexpression of miR-124 can be a promising new strategy for HIE therapy in future clinical practice.

Maternal hypertensive disorders in pregnancy and risk of hypoxic-ischemia encephalopathy

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) is one of the most serious birth complications for neonates. Few studies reported the relationship between maternal blood pressure disorders and risk of neonatal HIE.

OBJECTIVE

This study was conducted to examine whether maternal hypertensive disorders in pregnancy increase the risk of HIE.

METHODS

The analyses were performed using data from a large population-based cohort study aiming to prevent neural tube defects by supplementation with folic acid. The subjects comprised 183,981 women with singleton live births delivered at gestational ages of 32-42 weeks, who registered in two southern provinces in China. Blood pressure was measured by trained health care workers at each prenatal visit. Diagnosis information on HIE was recorded at the time of delivery.

RESULTS

Totally 19,298 women (10.49%) were diagnosed with maternal hypertensive disorders in pregnancy and 255 infants (1.4 per 1000) with HIE, respectively. Compared with the normotensive group, a great increment in the risk of HIE was observed in women with hypertensive disorders (adjusted RR = 2.40, 95% confidence interval [CI]: 1.79-3.22) after adjusting for maternal confounding factors. A greater association was presented among preterm (32-36 weeks) infants with an adjusted RR of 5.45 (95% CI: 2.79, 10.65) compared to a RR of 2.09 (95% CI: 1.49, 2.92) among full-term (37-42 weeks) infants (p for heterogeneity < .05). Further stratification analyses showed that no matter with or without small for gestational age (SGA), maternal hypertensive disorders were associated with the increased risk for HIE. Sensitivity analyses excluding infants with low or high birth weight did not appreciably change the findings.

CONCLUSIONS

Our present study demonstrated a positive association of maternal hypertensive disorders in pregnancy with the risk of neonatal HIE.

Early proton magnetic resonance spectroscopy during and after therapeutic hypothermia in perinatal hypoxic-ischemic encephalopathy

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) remains a significant cause of mortality and neurodevelopmental impairment despite treatment with therapeutic hypothermia. Magnetic resonance H¹-spectroscopy measures concentrations of cerebral metabolites to detect derangements in aerobic metabolism.

OBJECTIVE

We assessed MR spectroscopy in neonates with HIE within 18-24 h of initiating therapeutic hypothermia and at 5-6 days post therapeutic hypothermia.

MATERIALS AND METHODS

Eleven neonates with HIE underwent MR spectroscopy of the basal ganglia and white matter. We compared metabolite concentrations during therapeutic hypothermia and post-therapeutic hypothermia and between moderate and severe HIE.

RESULTS

During therapeutic hypothermia, neonates with severe HIE had decreased basal ganglia N-acetylaspartate (NAA; 0.62±0.08 vs. 0.72±0.05; P=0.02), NAA + N-acetylaspartylglutamate (NAAG; 0.66±0.11 vs. 0.77±0.06; P=0.05), glycerophosphorylcholine + phosphatidylcholine (GPC+PCh; 0.28±0.05 vs. 0.38±0.06; P=0.02) and decreased white matter GPC+PCh (0.35±0.13 vs. 0.48±0.04; P=0.02) compared to neonates with moderate HIE. For all subjects, basal ganglia NAA decreased (-0.08±0.07; P=0.01), whereas white matter GPC+PCh increased (0.03±0.04; P=0.04) from therapeutic hypothermia MRI to post-therapeutic-hypothermia MRI. All metabolite values are expressed in mmol/L.

CONCLUSION

Decreased NAA and GPC+PCh were associated with greater HIE severity and could distinguish neonates who might benefit most from targeted additional neuroprotective therapies.

Cerebral oxygen metabolism during and after therapeutic hypothermia in neonatal hypoxic-ischemic encephalopathy: a feasibility study using magnetic resonance imaging

BACKGROUND

Therapeutic hypothermia is the standard-of-care treatment for infants diagnosed with moderate-to-severe hypoxic-ischemic encephalopathy (HIE). MRI for assessing brain injury is usually performed after hypothermia because of logistical challenges in bringing acutely sick infants receiving hypothermia from the neonatal intensive care unit (NICU) to the MRI suite. Perhaps examining and comparing early cerebral oxygen metabolism disturbances to those after rewarming will lead to a better understanding of the mechanisms of brain injury in HIE and the effects of therapeutic hypothermia.

OBJECTIVE

The objectives were to assess the feasibility of performing a novel T2-relaxation under spin tagging (TRUST) MRI technique to measure venous oxygen saturation very early in the time course of treatment, 18-24 h after the initiation of therapeutic hypothermia, to provide a framework to measure neonatal cerebral oxygen metabolism noninvasively, and to compare parameters between early and post-hypothermia MRIs.

MATERIALS AND METHODS

Early (18-24 h after initiating hypothermia) MRIs were performed during hypothermia treatment in nine infants with HIE (six with moderate and three with severe HIE). Six infants subsequently had an MRI after hypothermia. Mean values of cerebral blood flow, oxygen extraction fraction, and cerebral metabolic rate of oxygen from MRIs during hypothermia were compared between infants with moderate and severe HIE; and in those with moderate HIE, we compared cerebral oxygen metabolism parameters between MRIs performed during and after hypothermia.

RESULTS

During the initial hypothermia MRI at 23.5±5.2 h after birth, infants with severe HIE had lower oxygen extraction fraction (P=0.04) and cerebral metabolic rate of oxygen (P=0.03) and a trend toward lower cerebral blood flow (P=0.33) compared to infants with moderate HIE. In infants with moderate HIE, cerebral blood flow decreased and oxygen extraction fraction increased between MRIs during and after hypothermia (although not significantly); cerebral metabolic rate of oxygen (P=0.93) was not different.

CONCLUSION

Early MRIs were technically feasible while maintaining hypothermic goal temperatures in infants with HIE. Cerebral oxygen metabolism early during hypothermia is more disturbed in severe HIE. In infants with moderate HIE, cerebral blood flow decreased and oxygen extraction fraction increased between early and post-hypothermia scans. A comparison of cerebral oxygen metabolism parameters between early and post-hypothermia MRIs might improve our understanding of the evolution of HIE and the benefits of hypothermia. This approach could guide the use of adjunctive neuroprotective strategies in affected infants.

Neonatal encephalopathy and hypoxic-ischemic encephalopathy

Acute hypoxic-ischemic encephalopathy around the time of birth remains a major cause of death and life-long disability. The key insight that led to the modern revival of studies of neuroprotection was that, after profound asphyxia, many brain cells show initial recovery from the insult during a short "latent" phase, typically lasting approximately 6h, only to die hours to days later after a "secondary" deterioration characterized by seizures, cytotoxic edema, and progressive failure of cerebral oxidative metabolism. Studies designed around this framework showed that mild hypothermia initiated as early as possible before the onset of secondary deterioration and continued for a sufficient duration to allow the secondary deterioration to resolve is associated with potent, long-lasting neuroprotection. There is now compelling evidence from randomized controlled trials that mild to moderate induced hypothermia significantly improves survival and neurodevelopmental outcomes in infancy and mid-childhood.

Diagnosis of seizures and encephalopathy using conventional EEG and amplitude integrated EEG

Seizures are more common in the neonatal period than at any other time of life, partly due to the relative hyperexcitability of the neonatal brain. Brain monitoring of sick neonates in the NICU using either conventional electroencephalography or amplitude integrated EEG is essential to accurately detect seizures. Treatment of seizures is important, as evidence increasingly indicates that seizures damage the brain in addition to that caused by the underlying etiology. Prompt treatment has been shown to reduce seizure burden with the potential to ameliorate seizure-mediated damage. Neonatal encephalopathy most commonly caused by a hypoxia-ischemia results in an alteration of mental status and problems such as seizures, hypotonia, apnea, and feeding difficulties. Confirmation of encephalopathy with EEG monitoring can act as an important adjunct to other investigations and the clinical examination, particularly when considering treatment strategies such as therapeutic hypothermia. Brain monitoring also provides useful early prognostic indicators to clinicians. Recent use of machine learning in algorithms to continuously monitor the neonatal EEG, detect seizures, and grade encephalopathy offers the exciting prospect of real-time decision support in the NICU in the very near future.

Biomarkers in neonatal hypoxic-ischemic encephalopathy-Review of the literature to date and future directions for research

The widespread introduction of therapeutic hypothermia as a standard of care in hypoxic-ischemic encephalopathy (HIE) has brought increasing pressure on clinicians to make an early and accurate assessment of the degree of hypoxic injury (HI) that has occurred and the severity of the encephalopathy that will ensue. No single blood-based marker is currently robust enough to detect significant HI or predict outcome. However, research in the field has been active in the last 10 years and we know that HIE is associated with predictable alterations in the expression of a number of inflammatory proteins, neuron-specific proteins, metabolite pathways, and microRNA. These alterations evolve quickly over the first hours and days of life. Predictive power varies depending on the timing of measurement of the biomarker, the sample type, and the case mix of the cohort examined. Combining clinical data with biochemical measurements is currently the most likely path toward improved detection and prediction of outcome in neonatal HIE.

Diffusion pseudonormalization and clinical outcome in term neonates with hypoxic-ischemic encephalopathy

BACKGROUND

Pseudonormalization of diffusion-weighted magnetic resonance imaging (MRI) can lead to underestimation of brain injury in newborns with hypoxic-ischemic encephalopathy (HIE), posing a significant problem. We have noticed that some neonates show pseudonormalization negativity on diffusion-weighted imaging.

OBJECTIVE

To compare pseudonormalization negativity with clinical outcomes.

MATERIALS AND METHODS

Seventeen term neonates with moderate or severe HIE underwent therapeutic hypothermia. They were examined by MRI twice at mean ages of 3 days and 10 days. We evaluated the presence of restricted diffusion, and also the presence or absence of pseudonormalization, by diffusion-weighted imaging at the time of the second MRI, and correlated the results with clinical outcome.

RESULTS

DWI demonstrated no abnormality in seven neonates. Among the 10 neonates with abnormal diffusion-weighted imaging findings, 2 were positive for pseudonormalization and 8 were negative. Among neonates with normal diffusion-weighted imaging findings and with positivity for pseudonormalization, none had major disability. Among the eight neonates with pseudonormalization negativity, all but one, who was lost to follow-up, had major disability.

CONCLUSION

Abnormal diffusion-weighted imaging with pseudonormalization negativity might be predictive of severe brain injury and major disability. The second-week MRI is important for the judgment of pseudonormalization.

Outcomes after acute symptomatic seizures in neonates

Acute symptomatic seizures are a common sign of neurological dysfunction and brain injury in neonates and occur in approximately one to three per 1000 live births. Seizures in neonates are usually a sign of underlying brain injury and, as such, are commonly associated with adverse outcomes. Neurological morbidities in survivors often co-occur; epilepsy, cerebral palsy, and intellectual disability often occur together in the most severely affected children. Risk factors for adverse outcome include prematurity, low Apgar scores, low pH on the first day of life, seizure onset <24 or >72 h after birth, abnormal neonatal neurological examination, abnormal neonatal electroencephalographic background, status epilepticus, and presence and pattern of brain injury (particularly deep gray or brainstem injury). Despite this list of potential indicators, accurate prediction of outcome in a given child remains challenging. There is great need for long-term, multicenter studies to examine risk factors for, and pathogenesis of, adverse outcomes following acute symptomatic seizures in neonates.

Acute symptomatic seizures in term neonates: Etiologies and treatments

Acute symptomatic seizures caused by either diffuse or focal perinatal hypoxic-ischemic insults and intracranial hemorrhage in term newborns make up the large majority of all neonatal seizures. Acute seizures are one of the most common neurological disorders in term newborns who require admission to the neonatal intensive care unit. Despite elucidation of seizure pathogenesis in this population using animal models, treatment is limited by a lack of good evidence-based guidelines because of a paucity of rigorously conducted clinical trials or prospective studies in human newborns. A result of this knowledge gap is that management, particularly drug choice, is guided by clinical experience rather than by data informing drug efficacy and safety. This review summarizes the common etiologies and pathogenesis of acute symptomatic seizures, and the current data informing their treatment, including potential novel drugs, together with a suggested treatment algorithm.

Inflammatory Responses are Sex Specific in Chronic Hypoxic-Ischemic Encephalopathy

Neonatal hypoxic-ischemic encephalopathy (HIE) is increasingly recognized as a sexually dimorphic disease. Male infants are not only more vulnerable to ischemic insult; they also suffer more long-term cognitive deficits compared with females with comparable brain damage. The innate immune response plays a fundamental role in mediating acute neonatal HIE injury. However, the mechanism underlying the sex difference in chronic HIE is still elusive. The present study investigated the sex difference in HIE outcomes and inflammatory response in the chronic stage (30 days after HIE). Postnatal day 10 (P10) male and female C57BL/6 pups were subjected to 60-min Rice-Vanucci model (RVM) to induce HIE. Brain atrophy and behavioral deficits were analyzed to measure stroke outcomes at 30 days of HIE. Flow cytometry (FC) was performed to examine central (microglial activation) and peripheral immune responses. Serum levels of cytokines and sex hormones were determined by enzyme-linked immunosorbent assay (ELISA). Neurogenesis was quantified by 5-Bromo-2'-deoxyuridine (BrdU) incorporation with neurons. Results showed males had worse HIE outcomes than females at the endpoint. Female microglia exhibited a more robust anti-inflammatory response that was corresponding to an enhanced expression of CX3C chemokine receptor 1 (CX3CR1) than males. More infiltration of peripheral lymphocytes was seen in male vs. female HIE brains. Cytokine levels of tumor necrosis factor (TNF)-α and interleukin (IL)-10 were more upregulated in males and females respectively than their counterparts. Neurogenesis was more highly induced in females vs. males. No significant difference in circulating hormonal level was found between males and females after HIE. We conclude that a sex dichotomy in pro- and anti-inflammatory response underlies the sex-specific chronic HIE outcomes, and an enhanced neurogenesis in females also contribute to the sex difference.

The use of phenobarbital and other anti-seizure drugs in newborns

Neonatal seizures constitute the most frequent presenting neurologic sign encountered in the neonatal intensive care unit. Despite limited efficacy and safety data, phenobarbital continues to be used near-universally as the first-line anti-seizure drug (ASD) in neonates. The choice of second-line ASDs varies by provider and institution, and is still not supported by sufficient scientific evidence. In this review, we discuss the available evidence supporting the efficacy, mechanism of action, potential adverse effects, key pharmacokinetic characteristics such as interaction with therapeutic hypothermia, logistical issues, and rationale for use of neonatal ASDs. We describe the widely used neonatal ASDs, namely phenobarbital, phenytoin, midazolam, and levetiracetam, in addition to potential ASDs, including lidocaine, topiramate, and bumetanide.

Therapeutic hypothermia in infants with hypoxic-ischemic encephalopathy and reversible persistent pulmonary hypertension: short-term hospital outcomes

AIM

Neonatal hypoxic ischemic encephalopathy (HIE) patients are at times accompanied by persistent pulmonary hypertension (PPHN), which is by itself another risk factor of adverse outcomes. We aimed to assess the outcome of therapeutic hypothermia (TH) in these patients whom we managed to reverse the shunt flow, as they are expected to be at much higher risk of adverse neurodevelopmental outcome.

METHODS

We reviewed the medical records of 116 HIE infants (13 with PPHN and 103 without PPHN) who underwent TH between 2012 and 2016. We analyzed the short-term hospital outcomes and brain study results (electroencephalogram and magnetic resonance imaging) of TH in these patients.

RESULTS

While infants with PPHN were significantly more likely to be outborn or have meconium aspiration syndrome, and required a longer duration of inotrope and intensive care support, electroencephalographic and brain magnetic resonance findings did not significantly differ according to PPHN status.

CONCLUSION

Based on our study, the hospital outcomes of infants with HIE accompanied by reversible PPHN who underwent TH were in general not significantly graver than those not accompanied by PPHN. Our results suggest that undergoing TH may be more beneficial in HIE infants with PPHN and the risks for possible adverse effects may not be as so high.

The paracrine effect of cobalt chloride on BMSCs during cognitive function rescue in the HIBD rat

Hypoxia-ischemia (HI)-induced perinatal encephalopathy frequently causes chronic neurological morbidities and acute mortality. Bone mesenchymal stem cell (BMSC) transplantation could potentially promote functional and anatomical recovery of ischemic tissue. In vitro hypoxic preconditioning is an effective strategy to improve the survival of BMSCs in ischemic tissue. In this study, cobalt chloride (CoCl₂) preconditioned medium from BMSC cultures was injected into the left lateral ventricle of HI rats using a micro-osmotic pump at a flow rate 1.0μl/h for 7 days. The protein levels of HIF-1α and its target genes, vascular endothelial growth factor and erythropoietin, markedly increased after CoCl₂ preconditioning in BMSCs. In 7-week-old rats that received CoCl₂ preconditioned BMSC medium, results of the Morris water maze test indicated ameliorated spatial working memory function following hypoxia-ischemia damage. Neuronal loss, cellular disorganization, and shrinkage in brain tissue were also ameliorated. Extracellular field excitatory postsynaptic potentials (fEPSPs) in the brain slices of 8-week-old rats were recorded; administration of CoCl₂ preconditioned BMSC culture medium induced a progressive increment of baseline and amplitude of the fEPSPs. Immunohistochemical quantification showed that GluR2 protein expression increased. In conclusion, CoCl₂ activates HIF-1α signals in BMSCs. CoCl₂ preconditioned BMSC culture medium likely effects neuroprotection by inducing long-term potentiation (LTP), which could be associated with GluR2 expression. The paracrine effects of hypoxia preconditioning on BMSCs could have applications in novel cell-based therapeutic strategies for hypoxic and ischemic brain injury.

Biochemical and clinical predictors of hypoxic-ischemic encephalopathy after perinatal asphyxia

OBJECTIVE

To determine the usefulness of measures, available shortly after birth, as predictors of hypoxic-ischemic encephalopathy (HIE) following perinatal asphyxia.

PATIENTS

All inborn patients at Southmead Hospital between January 2012 and March 2014 at ≥36 weeks gestation with a pH <7 or BE >16 on cord or baby's blood within one hour of birth or 10-minute Apgar score ≤5 or requiring intermittent positive pressure ventilation at 10 minutes were eligible for inclusion.

METHODS

ROC curves were derived for the perinatal clinical and biochemical measures to establish their predictive values for the development of HIE and the area under the curve (AUC) used as the measure of prediction.

RESULTS

We identified 79 eligible babies. Infants qualifying for therapeutic hypothermia (TH) based on aEEG abnormalities were considered to have HIE (n = 13; 16.5%), whereas babies with normal aEEG were classified as "non-HIE" (n = 66; 83.5%). The highest AUC measure was associated with the five-minute Apgar score (0.89 (0.79-0.99)). Troponin T (0.81 (0.64-0.98)) and ALT (0.78 (0.60-96)) also showed high values.

CONCLUSIONS

In this work, the Apgar score, troponin T and ALT were found to be strong and useful predictors of HIE.

Pathophysiology of Birth Asphyxia

The pathophysiology of asphyxia generally results from interruption of placental blood flow with resultant fetal hypoxia, hypercarbia, and acidosis. Circulatory and noncirculatory adaptive mechanisms exist that allow the fetus to cope with asphyxia and preserve vital organ function. With severe and/or prolonged insults, these compensatory mechanisms fail, resulting in hypoxic ischemic injury, leading to cell death via necrosis and apoptosis. Permanent brain injury is the most severe long-term consequence of perinatal asphyxia. The severity and location of injury is influenced by the mechanisms of injury, including degree and duration, as well as the developmental maturity of the brain.

Can postmortem computed tomography detect antemortem hypoxic-ischemic encephalopathy?

The purpose of this study was to evaluate the usefulness of brain postmortem computed tomography (PMCT) findings for the detection of global hypoxia or hypoperfusion leading to hypoxic-ischemic encephalopathy (HIE) prior to death. Cadavers of individuals who died from non-traumatic causes were subjected to PMCT and pathological autopsy. Cases with an episode of cardiopulmonary arrest, hypoxia, or hypoperfusion that required intensive respiratory management at least 24 h before death and exhibited findings of HIE in conventional autopsy (HIE group, n = 6) were compared with those without such episodes prior to death (control group; overall, n = 37; age-matched, n = 8) with regard to four parameters: (1) width of the central sulcus (CS), (2) attenuation difference at the basal ganglia (BG) level, (3) attenuation difference between cerebral gray matter (GM) and cerebral white matter (WM), and (4) attenuation difference between cerebellar GM and cerebral GM. The results revealed significant differences in the width of the CS (P < 0.001), attenuation difference at the BG level (P < 0.001), and attenuation difference between cerebral GM and cerebral WM (P = 0.009) between the HIE group and the overall control group. When the age-matched control group and the HIE group were compared, there was a significant difference in the width of the CS (P = 0.026) and attenuation difference at the BG level (P < 0.001). Our results suggest that effacement of the sulcus of the cerebral hemisphere and the loss of contrast at the BG level on brain PMCT indicate the existence of HIE prior to death.

Excitotoxicity as a Common Mechanism for Fetal Neuronal Injury with Hypoxia and Intrauterine Inflammation

Excitotoxicity is a mechanism of neuronal injury, implicated in the pathogenesis of many acute and chronic neurologic disorders, including perinatal brain injury associated with hypoxia-ischemia and exposure to intrauterine inflammation. Glutamate, the primary excitatory neurotransmitter, signals through N-methyl-d-aspartic acid (NMDA)/α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptors. Proper functioning of both of these receptors, in conjunction with glutamate signaling, is crucial for normal development. However, even a small imbalance can result in perinatal neuronal injury. Therefore, a mechanistic understanding of the role of excitotoxicity and the NMDA/AMPA receptor functions is critical to establishing the pathogenesis of hypoxic-ischemic encephalopathy (HIE) and perinatal brain injury due to exposure to intrauterine inflammation. Evidence from experimental animal models and clinical studies indicates that both oxygen and glucose deficiencies play a major role in fetal neuronal injury. However, the connection between these deficiencies, excitotoxicity, and HIE is not well established. The excitotoxic mechanisms in animal models and humans have many parallels, suggesting that detailed animal studies can elicit clinically relevant discoveries. While current therapies for HIE include hypothermia and other neuroprotective measures, emphasizing prevention of acute injuries, increase of therapeutic time window, and increased neural repair, there are no effective widely used treatment modalities for fetuses and neonates exposed to intrauterine inflammation. Further studies of HIE and intrauterine inflammation (as in cases of preterm birth and chorioamnionitis) will provide a better insight into development of effective therapeutic interventions for these conditions.

Metabolic Alterations in Developing Brain After Injury: Knowns and Unknowns

Brain development is a highly orchestrated complex process. The developing brain utilizes many substrates including glucose, ketone bodies, lactate, fatty acids and amino acids for energy, cell division and the biosynthesis of nucleotides, proteins and lipids. Metabolism is crucial to provide energy for all cellular processes required for brain development and function including ATP formation, synaptogenesis, synthesis, release and uptake of neurotransmitters, maintaining ionic gradients and redox status, and myelination. The rapidly growing population of infants and children with neurodevelopmental and cognitive impairments and life-long disability resulting from developmental brain injury is a significant public health concern. Brain injury in infants and children can have devastating effects because the injury is superimposed on the high metabolic demands of the developing brain. Acute injury in the pediatric brain can derail, halt or lead to dysregulation of the complex and highly regulated normal developmental processes. This paper provides a brief review of metabolism in developing brain and alterations found clinically and in animal models of developmental brain injury. The metabolic changes observed in three major categories of injury that can result in life-long cognitive and neurological disabilities, including neonatal hypoxia-ischemia, pediatric traumatic brain injury, and brain injury secondary to prematurity are reviewed.

Metabolic Alterations in Developing Brain After Injury: Knowns and Unknowns

Brain development is a highly orchestrated complex process. The developing brain utilizes many substrates including glucose, ketone bodies, lactate, fatty acids and amino acids for energy, cell division and the biosynthesis of nucleotides, proteins and lipids. Metabolism is crucial to provide energy for all cellular processes required for brain development and function including ATP formation, synaptogenesis, synthesis, release and uptake of neurotransmitters, maintaining ionic gradients and redox status, and myelination. The rapidly growing population of infants and children with neurodevelopmental and cognitive impairments and life-long disability resulting from developmental brain injury is a significant public health concern. Brain injury in infants and children can have devastating effects because the injury is superimposed on the high metabolic demands of the developing brain. Acute injury in the pediatric brain can derail, halt or lead to dysregulation of the complex and highly regulated normal developmental processes. This paper provides a brief review of metabolism in developing brain and alterations found clinically and in animal models of developmental brain injury. The metabolic changes observed in three major categories of injury that can result in life-long cognitive and neurological disabilities, including neonatal hypoxia-ischemia, pediatric traumatic brain injury, and brain injury secondary to prematurity are reviewed.

Analgesics, sedatives, anticonvulsant drugs, and the cooled brain

Multiple randomized controlled trials have shown that prolonged, moderate cerebral hypothermia initiated within a few hours after severe hypoxia-ischemia and continued until resolution of the acute phase of delayed cell death reduces mortality and improves neurodevelopmental outcome in term infants. The challenge is now to find ways to further improve outcomes. In the present review, we critically examine the evidence that conventional analgesic, sedative, or anticonvulsant agents might improve outcomes, in relation to the known window of opportunity for effective protection with hypothermia. This review strongly indicates that there is insufficient evidence to recommend routine use of these agents during therapeutic hypothermia. Further systematic research into the effects of pain and stress on the injured brain, and their treatment during hypothermia, is essential to guide the rational development of clinical treatment protocols.

Who should we cool after perinatal asphyxia?

Three ongoing challenges have arisen after the introduction of therapeutic hypothermia (TH) as standard of care for term newborns with moderate or severe perinatal asphyxia: (i) to ensure that the correct group of infants are cooled; (ii) to optimize the delivery of TH and intensive care in relation to the severity of the encephalopathy; (iii) to systematically follow up the long-term efficacy of TH using comparable outcome data between centers and countries. This review addresses the entry criteria for TH, and discusses potential issues regarding patient selection, and management of TH: cooling mild, moderate, and very severe perinatal asphyxia, cooling longer or deeper, and/or starting with a greater delay. This includes cooling of patients outside of standard trial entry criteria, such as after postnatal collapse, premature infants, those with infection, and infants with metabolic, chromosomal or surgical diagnoses in addition to perinatal asphyxia.

The importance of temperature on the neurovascular unit

Therapeutic hypothermia is the only treatment that has been shown to be of benefit to infant's ≥ 36 weeks of gestation with hypoxic-ischemic encephalopathy. The evidence for the benefit is based on multiple, well-designed randomized clinical trials. Based on this data, the use of therapeutic hypothermia has been widely disseminated throughout the neonatal community. An important concept in hypoxic-ischemic brain injury is the functioning of the neurovascular unit which links neurons, non-neuronal cellular elements and the capillary endothelial cells to promote optimal barrier maintenance between the brain and systemic circulation, regulation of blood flow and neuro-immunologic functioning. Hypoxic-ischemic injury can trigger increased permeability of the blood-brain-barrier via molecular events within the neurovascular unit and initiate pathways to brain injury. In addition, exposure of the brain to cellular elements from the systemic circulation can further propagate the neuro-inflammatory response. The influence of temperature on injury to the neurovascular unit has received relatively little attention. This review will focus on one component of the neurovascular unit, the blood-brain barrier and its constituents. Specifically, this review will address the effects of hypoxia-ischemia and temperature on the neurovascular unit and potential knowledge gaps which may serve as areas for further investigation.

Serum tau protein level serves as a predictive factor for neurological prognosis in neonatal asphyxia

BACKGROUND

Tau protein is a microtubule-associated protein that is present in axons. Elevated tau protein levels in cerebrospinal fluid or serum are associated with several central nervous system diseases and can indicate neuronal injury.

OBJECTIVE

In the present study, we measured and then compared serum tau protein levels between infants with neonatal asphyxia and control subjects. We examined these data to investigate the correlation between serum tau protein levels and neurological outcomes after neonatal asphyxia.

PATIENTS AND METHODS

Serum tau protein levels were determined by an enzyme-linked immunosorbent assay in 19 neonates with neonatal asphyxia. Of these 19 neonates, 3 had severe spastic tetraplegia, and 1 had west syndrome. A group of 19 unaffected neonates was included in the study as a control group.

RESULTS

Serum tau protein levels on postnatal day 3 were significantly higher in the poor outcome group than those in the good outcome (p=0.010) and control groups (p=0.006). On postnatal day 7, serum tau protein levels again were significantly higher in the poor outcome group than those in the good outcome (p=0.007) and control groups (p=0.006).

CONCLUSIONS

The present findings indicate serum tau protein levels measured on postnatal days 3 and 7 can predict neurological prognosis following neonatal asphyxia.

Measurement of brain perfusion in newborns: pulsed arterial spin labeling (PASL) versus pseudo-continuous arterial spin labeling (pCASL)

BACKGROUND

Arterial spin labeling (ASL) perfusion-weighted imaging (PWI) by magnetic resonance imaging (MRI) has been shown to be useful for identifying asphyxiated newborns at risk of developing brain injury, whether or not therapeutic hypothermia was administered. However, this technique has been only rarely used in newborns until now, because of the challenges to obtain sufficient signal-to-noise ratio (SNR) and spatial resolution in newborns.

OBJECTIVE

To compare two methods of ASL-PWI (i.e., single inversion-time pulsed arterial spin labeling [single TI PASL], and pseudo-continuous arterial spin labeling [pCASL]) to assess brain perfusion in asphyxiated newborns treated with therapeutic hypothermia and in healthy newborns.

DESIGN/METHODS

We conducted a prospective cohort study of term asphyxiated newborns meeting the criteria for therapeutic hypothermia; four additional healthy term newborns were also included as controls. Each of the enrolled newborns was scanned at least once during the first month of life. Each MRI scan included conventional anatomical imaging, as well as PASL and pCASL PWI-MRI. Control and labeled images were registered separately to reduce the effect of motion artifacts. For each scan, the axial slice at the level of the basal ganglia was used for comparisons. Each scan was scored for its image quality. Quantification of whole-slice cerebral blood flow (CBF) was done afterwards using previously described formulas.

RESULTS

A total number of 61 concomitant PASL and pCASL scans were obtained in nineteen asphyxiated newborns treated with therapeutic hypothermia and four healthy newborns. After discarding the scans with very poor image quality, 75% (46/61) remained for comparison between the two ASL methods. pCASL images presented a significantly superior image quality score compared to PASL images (p < 0.0001). Strong correlation was found between the CBF measured by PASL and pCASL (r = 0.61, p < 0.0001).

CONCLUSION

This study demonstrates that both ASL methods are feasible to assess brain perfusion in healthy and sick newborns. However, pCASL might be a better choice over PASL in newborns, as pCASL perfusion maps had a superior image quality that allowed a more detailed identification of the different brain structures.

Nucleated red blood cell counts: an early predictor of brain injury and 2-year outcome in neonates with hypoxic-ischemic encephalopathy in the era of cooling-based treatment

BACKGROUND

Raised nucleated red blood cell (NRBC) counts in neonates may indicate in utero hypoxia and brain damage.

OBJECTIVE

The study aimed to examine the use of NRBC counts as a predictor of brain injury and neurodevelopmental outcomes in neonates with hypoxic-ischemic encephalopathy (HIE) treated under current cooling-based strategy.

METHODS

Forty-three neonates with asphyxia between 2004 and 2010 were retrospectively investigated. Twenty neonates with moderate/severe HIE underwent hypothermia (HT), and 23 with mild HIE were treated in normothermia (NT). Neonates were divided into groups according to the presence of cerebral parenchymal lesions on magnetic resonance imaging (MRI) at 2 weeks after birth. All patients were followed-up neurologically for ⩾ 24 months. NRBC counts during the first 3 days were compared between groups.

RESULTS

Eleven HT (HT-N) and 21 NT (NT-N) neonates had normal MRI, and 9 HT (HT-L) and 2 NT (NT-L) neonates had parenchymal lesions. NRBC counts, both absolute and /100 white blood cells (WBC) counts, during the first 3 days in HT-L and NT-L were significantly higher than those in HT-N and NT-N, particularly within 6 hours after birth (HT-N: 502 [0-3060]/mm(3) vs HT-L: 2765 [496-6192]; 0 [0-3417] vs NT-L: 4384 [3978-4789], median [range]). Neonates with /100 white blood cells ⩾ 6/mm(3) and absolute NRBC counts ⩾ 1324/mm(3) within 6 hours of birth had high risks of abnormal MRIs and 2-year outcomes.

CONCLUSIONS

NRBC counts can predict brain injury and neurological outcomes in cooled and non-cooled asphyxiated neonates.

Preconditioning and post-treatment with cobalt chloride in rat model of perinatal hypoxic-ischemic encephalopathy

BACKGROUND

Hypoxia-ischemia (HI)-induced perinatal encephalopathy is a major cause of acute mortality and chronic neurologic morbidities such as cerebral palsy, mental retardation, and epilepsy. As the essential transcription factor for the activation of hypoxia-inducible genes, hypoxia-inducible factor 1 alpha (HIF-1α) plays an important role in the pathophysiological response to the stress of HI brain damage. Whether HIF-1α activation promotes neuroprotection in HI tissues is controversial.

METHODS

The left common carotid artery of rats aged 7days was ligated under anesthesia. The pups were then exposed to hypoxia in a normobaric chamber filled with 8% oxygen and 92% nitrogen for 2.5h. In the sham control group, the left common carotid artery was exposed but was not ligated or exposed to hypoxia. To assess the time window for effective treatment, the HIF-1α inducer cobalt chloride (CoCl2) was injected subcutaneously 1day before surgery, immediately or 1day after surgery. The brain tissues were harvested from the pups of each groups at 1, 2 and 7days after insult for HIF-1α protein ant its target genes expression and for investigating the injury. Morris water maze tests were performed at postnatal 7weeks.

RESULTS

HIF-1α protein levels and its target genes vascular endothelial growth factor, heme oxygenase-1, and insulin-like growth factor 1 were markedly increased after intraperitoneal injection of CoCl2 (60mg/kg). The target gene inducible nitric oxide synthase exhibited a biphasic time course. HI caused apoptosis and reduced capillary density, which were ameliorated by CoCl2. Both preconditioning with CoCl2 24h before HI and administration of CoCl2 24h after HI improved long-term reference memory compared with that in vehicle-injected littermate controls. Administration of CoCl2 immediately after HI did not improve spatial working memory.

CONCLUSIONS

CoCl2 activates HIF-1α and protects against brain damage in vivo. The time of administration could be used to manipulate the activity of HIF-1α pathways and promote recovery.

Protection by vascular prostaglandin E2 signaling in hypoxic-ischemic encephalopathy

Hypoxic-ischemic encephalopathy (HIE) in neonates is a leading cause of neurological impairment. Significant progress has been achieved investigating the pathologic contributions of excitotoxicity, oxidative stress, and neuroinflammation to cerebral injury in HIE. Less extensively investigated has been the contribution of vascular dysfunction, and whether modulation of cerebral perfusion may improve HIE outcome. Here, we investigated the function of the prostaglandin E2 (PGE2) EP4 receptor, a vasoactive Gαs-protein coupled receptor (GPCR), in rodent models of neonatal HIE. The function of PGE2 signaling through the EP4 receptor was investigated using pharmacological and conditional knockout genetic strategies in vivo in rodent models of HIE. Pharmacologic activation of the EP4 receptor with a selective agonist was significantly cerebroprotective both acutely and after 7days. Measurement of cerebral perfusion during and after hypoxia-ischemia demonstrated that EP4 receptor activation improved cerebral perfusion in both the contralateral and ipsilateral hypoxic-ischemic hemispheres. To test whether vascular EP4 signaling exerted a critical function in HIE injury, cell specific conditional knockout mouse pups were generated in which endothelial EP4 receptor was selectively deleted postnatally. VE-Cadherin Cre-ER(T2);EP4(lox/lox) pups demonstrated significant increases in cerebral injury as compared to VE-Cadherin Cre-ER(T2);EP4(+/+) control littermates, indicating that endothelial EP4 signaling is protective in HIE. Our findings identify vascular PGE2 signaling through its EP4 receptor as protective in HIE. Given the pharmacologic accessibility of endothelial EP4 GPCRs, these data support further investigation into novel approaches to target cerebral perfusion in neonatal HIE.

Promoter methylation represses AT2R gene and increases brain hypoxic-ischemic injury in neonatal rats

Perinatal nicotine exposure downregulated angiotensin II type 2 receptor (AT2R) in the developing brain and increased brain vulnerability to hypoxic-ischemic injury in male neonatal rats. We tested the hypothesis that site-specific CpG methylation at AT2R gene promoter contributes to the increased vulnerability of brain injury in the neonate. Nicotine was administered to pregnant rats from day 4 of gestation to day 10 after birth. Brain hypoxic-ischemic injury was induced in day 10 male pups. CpG methylation at AT2R promoter was determined in the brain by quantitative methylation-specific PCR. Nicotine exposure significantly increased the methylation of a single CpG-52 locus near the TATA-box at AT2R promoter. Electrophoretic mobility shift assay indicated that the methylation of CpG-52 significantly decreased the binding affinity of TATA-binding protein (TBP). Chromatin immunoprecipitation assay further demonstrated an increase in the binding of a methyl-binding protein and a decrease in TBP binding to AT2R promoter in vivo in neonatal brains of nicotine-treated animals. This resulted in AT2R gene repression in the brain. Intracerebroventricular administration of a demethylating agent 5-aza-2'-deoxycytidine abrogated the enhanced methylation of CpG-52, rescued the TBP binding, and restored AT2R gene expression. Of importance, 5-aza-2'-deoxycytidine reversed the nicotine-increased vulnerability of brain hypoxic-ischemic injury in the neonate. The finding provides mechanistic evidence of increased promoter methylation and resultant AT2R gene repression in the developing brain linking perinatal stress and a pathophysiological consequence of heightened vulnerability of brain hypoxic-ischemic encephalopathy in the neonate.

Systemic G-CSF attenuates cerebral inflammation and hypomyelination but does not reduce seizure burden in preterm sheep exposed to global hypoxia-ischemia

Hypoxic-ischemic encephalopathy (HIE) is common in preterm infants, but currently no curative therapy is available. Cell-based therapy has a great potential in the treatment of hypoxic-ischemic preterm brain injury. Granulocyte-colony stimulating factor (G-CSF) is known to mobilize endogenous hematopoietic stem cells (HSC) and promotes proliferation of endogenous neural stem cells. On these grounds, we hypothesized that systemic G-CSF would be neuroprotective in a large translational animal model of hypoxic-ischemic injury in the preterm brain. Global hypoxia-ischemia (HI) was induced by transient umbilical cord occlusion in instrumented preterm sheep. G-CSF treatment (100μg/kg intravenously, during five consecutive days) was started one day before the global HI insult to ascertain mobilization of endogenous stem cells within the acute phase after global HI. Mobilization of HSC and neutrophils was studied by flow cytometry. Brain sections were stained for microglia (IBA-1), myelin basic protein (MBP) and myeloperoxidase (MPO) to study microglial proliferation, white matter injury and neutrophil invasion respectively. Electrographic seizure activity was analyzed using amplitude-integrated electroencephalogram (aEEG). G-CSF effectively mobilized CD34-positive HSC in the preterm sheep. In addition, G-CSF caused marked mobilization of neutrophils, but did not influence enhanced invasion of neutrophils into the preterm brain after global HI. Microglial proliferation and hypomyelination following global HI were reduced as a result of G-CSF treatment. G-CSF did not cause a reduction of the electrographic seizure activity after global HI. In conclusion, G-CSF induced mobilization of endogenous stem cells which was associated with modulation of the cerebral inflammatory response and reduced white matter injury in an ovine model of preterm brain injury after global HI. G-CSF treatment did not improve neuronal function as shown by seizure analysis. Our study shows that G-CSF treatment has neuroprotective potential following hypoxic-ischemic injury in the preterm brain.

Connexin hemichannel blockade is neuroprotective after, but not during, global cerebral ischemia in near-term fetal sheep

There is increasing evidence that connexin hemichannels, the half gap junctions that sit unopposed in the cell membrane, can open during ischemia and that blockade of connexin43 hemichannels after cerebral ischemia can improve neural outcomes. However, it is unclear whether connexin blockade during ischemia is protective. In the present study global cerebral ischemia was induced by 30 min of bilateral carotid artery occlusion in near-term (128 ± 1 day gestation age) fetal sheep. A specific mimetic peptide that blocks connexin43 hemichannels was infused into the lateral ventricle for either 1h before and during ischemia (intra-ischemia group, n=6) or for 25 h starting 90 min after the end of ischemia (post-ischemia group, n=7). The vehicle was infused in the ischemia-vehicle group (n=6) and sham-controls received sham occlusion plus vehicle (n=10). The post-ischemia group showed enhanced recovery of EEG power from day five until the end of the experiment (-5 ± 1.6 dB) compared to ischemia-vehicle (-13 ± 1.9 dB, p<0.05) and intra-ischemia infusion (-14.4 ± 3.6 dB, p<0.05). Post-ischemic infusion was associated with higher neuronal counts compared to ischemia-vehicle and intra-ischemia in the cortex (p<0.05) but not the CA1 and CA3 regions of the hippocampus. Oligodendrocyte cell counts in the intragyral and periventricular white matter were significantly higher in the post-ischemia group compared to ischemia-vehicle and intra-ischemia infusion (p<0.05). These large animal data support the hypothesis that connexin hemichannel opening after, but not during, ischemia contributes to the spread of white and gray matter injury of the developing brain.

Near-infrared spectroscopy versus magnetic resonance imaging to study brain perfusion in newborns with hypoxic-ischemic encephalopathy treated with hypothermia

BACKGROUND

The measurement of brain perfusion may provide valuable information for assessment and treatment of newborns with hypoxic-ischemic encephalopathy (HIE). While arterial spin labeled perfusion (ASL) magnetic resonance imaging (MRI) provides noninvasive and direct measurements of regional cerebral blood flow (CBF) values, it is logistically challenging to obtain. Near-infrared spectroscopy (NIRS) might be an alternative, as it permits noninvasive and continuous monitoring of cerebral hemodynamics and oxygenation at the bedside.

OBJECTIVE

The purpose of this study is to determine the correlation between measurements of brain perfusion by NIRS and by MRI in term newborns with HIE treated with hypothermia.

DESIGN/METHODS

In this prospective cohort study, ASL-MRI and NIRS performed during hypothermia were used to assess brain perfusion in these newborns. Regional cerebral blood flow (CBF) values, measured from 1-2 MRI scans for each patient, were compared to mixed venous saturation values (SctO2) recorded by NIRS just before and after each MRI. Analysis included groupings into moderate versus severe HIE based on their initial background pattern of amplitude-integrated electroencephalogram.

RESULTS

Twelve concomitant recordings were obtained of seven neonates. Strong correlation was found between SctO2 and CBF in asphyxiated newborns with severe HIE (r=0.88; p value=0.0085). Moreover, newborns with severe HIE had lower CBF (likely lower oxygen supply) and extracted less oxygen (likely lower oxygen demand or utilization) when comparing SctO2 and CBF to those with moderate HIE.

CONCLUSIONS

NIRS is an effective bedside tool to monitor and understand brain perfusion changes in term asphyxiated newborns, which in conjunction with precise measurements of CBF obtained by MRI at particular times, may help tailor neuroprotective strategies in term newborns with HIE.