Novel interventions to reduce oxidative-stress related brain injury in neonatal asphyxia

Preconditioning and Posttreatment Strategies in Neonatal Hypoxic-Ischemic Encephalopathy: Recent Advances and Clinical Challenges

Neonatal hypoxic-ischemic encephalopathy (HIE) is a severe neurological disorder caused by impaired cerebral blood flow and brain hypoxia, resulting in high morbidity and mortality rates. While therapeutic hypothermia remains the standard treatment and has been shown to reduce mortality to some extent, its therapeutic efficacy is limited, and it applies only to a select group of neonates who meet stringent inclusion criteria. Advances in our understanding of the pathophysiology of HIE have led to the identification of several promising neuroprotective strategies designed to mitigate or prevent the neurological damage induced by hypoxia-ischemia. Among these, preconditioning has emerged as a potent neuroprotective approach, enhancing cellular resilience to subsequent injury and potentially reducing treatment complexity and healthcare costs. Preconditioning/pretreatment and posttreatment offer significant promise in attenuating the neurological damage associated with HIE. Thus, exploring early intervention strategies for neonatal HIE, focusing on the comparative mechanisms and therapeutic targets of preconditioning and postconditioning, is critical to developing more effective treatment modalities. This review summarizes the current understanding of the pathophysiological mechanisms underlying neonatal HIE and its prevention and treatment strategies, providing new perspectives and a theoretical foundation for future neuroprotective interventions.

Hypoxic-Ischemic Encephalopathy: Pathogenesis and Promising Therapies

Hypoxic-ischemic encephalopathy (HIE) is a brain lesion caused by inadequate blood supply and oxygen deprivation, often occurring in neonates. It has emerged as a grave complication of neonatal asphyxia, leading to chronic neurological damage. Nevertheless, the precise pathophysiological mechanisms underlying HIE are not entirely understood. This paper aims to comprehensively elucidate the contributions of hypoxia-ischemia, reperfusion injury, inflammation, oxidative stress, mitochondrial dysfunction, excitotoxicity, ferroptosis, endoplasmic reticulum stress, and apoptosis to the onset and progression of HIE. Currently, hypothermia therapy stands as the sole standard treatment for neonatal HIE, albeit providing only partial neuroprotection. Drug therapy and stem cell therapy have been explored in the treatment of HIE, exhibiting certain neuroprotective effects. Employing drug therapy or stem cell therapy as adjunctive treatments to hypothermia therapy holds great significance. This article presents a systematic review of the pathogenesis and treatment strategies of HIE, with the goal of enhancing the effect of treatment and improving the quality of life for HIE patients.

Effect of vasopressin on brain and cardiac tissue during neonatal cardiopulmonary resuscitation of asphyxiated post-transitional piglets

Background

Epinephrine is currently the only recommended cardio-resuscitative medication for use in neonatal cardiopulmonary resuscitation (CPR), as per consensus of science and treatment recommendations. An alternative medication, vasopressin, may be beneficial, however there is limited data regarding its effect on cardiac and brain tissue following recovery from neonatal CPR.

Aim

To compare the effects of vasopressin and epinephrine during resuscitation of asphyxiated post-transitional piglets on cardiac and brain tissue injury.

Methods

Newborn piglets (n = 10/group) were anesthetized, tracheotomized and intubated, instrumented, and exposed to hypoxia-asphyxia and cardiac arrest. Piglets were randomly allocated to receive intravenous vasopressin (Vaso, 0.4 U/kg) or epinephrine (Epi, 0.02 mg/kg) during CPR until return of spontaneous circulation (ROSC). Left ventricle cardiac tissue, and frontoparietal cerebral cortex and thalamus samples from brain tissue were collected from piglets that survived four hours after ROSC. The concentrations of the pro-inflammatory cytokines interleukin (IL)-1β, IL-6, IL-8, and tumour necrosis factor (TNF)-α, cardiac troponin-1, lactate, and levels of oxidized and total glutathione were quantified in tissue homogenates.

Main Results

The median time (IQR) to ROSC was 127 (98-162)sec with Vaso and 197 (117-480)sec with Epi (p = 0.07). ROSC rate was 10/10 (100 %) with Vaso and 7/10 (70 %) with Epi (p = 0.21); survival to four hours after ROSC was 10/10 (100 %) with Vaso and 5/7 (71 %) with Epi (p = 0.15). Kaplan-Meier survival curves were significantly different between groups (p = 0.011). Cardiac tissue IL-8 concentration was significantly lower with Vaso than Epi (16.9 (2.94)pg/mg vs. 33.0 (6.75)pg/mg, p = 0.026). All other markers of cardiac and brain tissue injury were similar between Vaso and Epi groups.

Conclusions

Vasopressin is effective in the resuscitation of asphyxiated newborn piglets and is associated with reduced inflammation of the myocardium compared to epinephrine, and there was no evidence of increased tissue injury in the frontoparietal cortex and thalamus regions of the brain. Vasopressin might be a viable alternative to epinephrine during neonatal CPR, but further studies are warranted.

Prevalence and risk factors associated with birth asphyxia among neonates delivered in China: a systematic review and meta-analysis

BACKGROUND

Birth asphyxia is a critical condition caused by an insufficient oxygen supply during delivery, and it poses a major threat to the health of newborns. The present meta-analysis aimed to estimate the prevalence of birth asphyxia among neonates and identify its risk factors in China.

METHODS

PubMed, EMBASE, Scopus, Web of Science, the China Academic Journals (CNKI), the Chinese Biomedical Literature (CBM), the China Science and Technology Journal Database (VIP), and the WanFang database were searched for related publications. Two researchers independently selected the literature, extracted the relevant data, and assessed its methodological quality. The meta-analysis applied a random-effects model with Stata 17.0 software to calculate the pooled prevalence of birth asphyxia among neonates delivered in China and to merge the odds ratios (ORs) of risk factors. Subgroup analysis was performed on the included studies. Publication bias was assessed by funnel plots and Egger's test.

RESULTS

Eighty studies were eligible for inclusion. The overall prevalence of birth asphyxia in newborns was 4.8% (95% CI, 4.5%-5.2%). In the subgroup analyses, the northern area presented the highest prevalence (5.1%; 95% CI, 4.1%-6.3%), followed by the southern area (4.1%; 95% CI, 3.3%-5.1%). The rural setting presented the highest prevalence (6%; 95% CI, 4.6%-7.4%), followed by the urban (4.2%; 95% CI, 4.6%-7.4%) and mixed (5.8%; 95% CI, 5.3%-6.3%) settings. The Apgar score demonstrated the highest prevalence (4.6%; 95% CI, 3.8%-5.4%), followed by the Apgar score with the umbilical artery blood pH (3.7%; 95% CI, 2.2%-5.7%). A significant difference in prevalence was found between studies with sample sizes greater than 5,000 (2.2%; 95% CI, 1.6%-3%) and those with 5,000 or fewer participants (6.2%; 95% CI, 5.5%-7.1%). Furthermore, there was a significant decrease in the incidence of birth asphyxia from 1995-2016 (4.9%; 95% CI, 4.2%-5.9%) to 2017-2023 (3.7%; 95% CI, 2.6%-5%). Placental abruption (OR = 5; 95% CI, 3.08-8.13), placenta previa (OR = 2.57; 95% CI, 1.84-3.58), advanced maternal age (OR = 3.94; 95% CI, 1.46-10.62), primigravida (OR = 5.33; 95% CI, 0.41-68.71), premature birth (OR = 3.36; 95% CI, 2.61-4.32), intrauterine distress (OR = 4.48; 95% CI, 3.47-5.80), stained amniotic fluid (OR = 3.28; 95% CI, 2.25-4.79), macrosomia (OR = 6.30; 95% CI, 0.61-65.22), foetal malformation (OR = 7.44; 95% CI, 1.46-38.02), breech birth (OR = 2.42; 95% CI, 1.24-4.73), caesarean section (OR = 1.72; 95% CI, 0.91-3.24), assisted delivery (OR = 13.62; 95% CI, 5.50-33.73), prolonged second stage of labour (OR = 1.43; 95% CI, 0.68-3.01), and malpresentation (OR = 4.20; 95% CI, 2.21-7.99) were major risk factors.

CONCLUSIONS

The prevalence of birth asphyxia among newborns in China is relatively high. In addition, 14 risk factors are related to neonatal birth asphyxia. Urgent attention needs to be focused on regionalized maternal and child management to address this problem in China.

Associations of risk factors and the number of risk factors with the classification, GMFCS level and comorbidities with cerebral palsy: a retrospective study

OBJECTIVE

The objective was to explore the characteristics of risk factors in children with cerebral palsy (CP), focusing on the effects of single risk factors and the number of risk factors on the classification, GMFCS level, and comorbidities of children with CP.

METHODS

The medical records of children with CP hospitalized from 2015 to 2023 were reviewed. The effects of nine risk factors, such as hyperbilirubinemia, asphyxia, and HIE, on the classification, GMFCS level and comorbidities of children with CP were studied.

RESULTS

In Part 1, among the 536 children with CP, 476 (88.8%) had obvious risk factors. Preterm birth and/or low birth weight were the most common risk factor (243 cases (45.3%)). CP combined with two risk factors was the most common, with 147 cases (27.4%). In Part 2, neonatal seizures were associated with epilepsy, and HIE and hyperbilirubinemia were associated with intellectual disability. Asphyxia was associated with high GMFCS levels and mixed CP. Preterm birth and/or low birth weight was associated with spastic diplegia, and hyperbilirubinemia was associated with involuntary movement. In Part 3, the number of risk factors in children with CP with epilepsy and/or hearing impairment seemed to be lower, but those with spastic quadriplegia were more likely to have more risk factors (≥ 4). In the six groups with 1-6 risk factors, intellectual disability and a GMFCS level ≥ level IV were more common in the various risk factor groups, but spastic hemiplegia and ataxia were less common.

CONCLUSION

Most children with CP have apparent risk factors, and the combination of two risk factors is relatively common. Preterm birth/low birth weight is the most common risk factor. The analysis of single risk factors revealed that the risk factors were related to the classification, GMFCS level and comorbidities. This correlation is consistent with the current research. Risk factors were more common in children with severe CP, high GMFCS levels, spastic quadriplegia, and intellectual disability.

The Role and Mechanism of Metformin in the Treatment of Nervous System Diseases

Nervous system diseases represent a significant global burden, affecting approximately 16% of the world's population and leading to disability and mortality. These conditions, encompassing both central nervous system (CNS) and peripheral nervous system (PNS) disorders, have substantial social and economic impacts. Metformin, a guanidine derivative derived from a plant source, exhibits therapeutic properties in various health conditions such as cancer, aging, immune-related disorders, polycystic ovary syndrome, cardiovascular ailments, and more. Recent studies highlight metformin's ability to cross the blood-brain barrier, stimulate neurogenesis, and provide beneficial effects in specific neurological disorders through diverse mechanisms. This review discusses the advancements in research on metformin's role and mechanisms in treating neurological disorders within both the central and peripheral nervous systems, aiming to facilitate further investigation, utilization, and clinical application of metformin in neurology.

Mitochondrial dynamics and sex-specific responses in the developing rat hippocampus: Effect of perinatal asphyxia and mesenchymal stem cell Secretome treatment

AIMS

Perinatal asphyxia is one of the major causes of neonatal death at birth. Survivors can progress but often suffer from long-term sequelae. We aim to determine the effects of perinatal asphyxia on mitochondrial dynamics and whether mesenchymal stem cell secretome (MSC-S) treatment can alleviate the deleterious effects.

MATERIALS AND METHODS

Animals were subjected to 21 min of asphyxia at the time of delivery. MSC-S or vehicle was intranasally administered 2 h post-delivery. Mitochondrial mass (D-loop, qPCR), mitochondrial dynamics proteins (Drp1, Fis1 and OPA1, Western blot), mitochondrial dynamics (TOMM20, Immunofluorescence), as well as mitochondrial membrane potential (ΔΨm) (Safranin O) were evaluated at P1 and P7 in the hippocampus.

KEY FINDINGS

Perinatal asphyxia increased levels of mitochondrial dynamics proteins Drp1 and S-OPA1 at P1 and Fis1 at P7. Mitochondrial density and mass were decreased at P1. Perinatal asphyxia induced sex-specific differences, with increased L-OPA1 in females at P7 and increased mitochondria circularity. In males, asphyxia-exposed animals exhibited a reduced ΔΨm at P7. MSC-S treatment normalised levels of mitochondrial dynamics proteins involved in fission.

SIGNIFICANCE

This study provides novel insights into the effects of perinatal asphyxia on mitochondrial dynamics in the developing brain and on the therapeutic opportunities provided by mesenchymal stem cell secretome treatment. It also highlights on the relevance of considering sex as a biological variable in perinatal brain injury and therapy development. These findings contribute to the development of targeted, personalised therapies for infants affected by perinatal asphyxia.

Hyperbaric Oxygen Improves Cognitive Impairment Induced by Hypoxia via Upregulating the Expression of Oleic Acid and MBOAT2 of Mice

Cognitive impairment (CI) causes severe impairment of brain function and quality of life of patients, which brings a great burden to society. Cerebral hypoxia is an important factor in the pathogenesis of CI. Hyperbaric oxygen (HBO) therapy may mitigate hypoxia-induced CI, but its efficacy and mechanisms are not fully understood. In this study, a mice model of CI induced by hypoxia environment was established, then behavioral tests, pathological examination, metabolomic and lipidomic analyses, and molecular biology were used to assess the impact of HBO on hypoxia-induced CI. HBO was found to alleviate CI and pathological damage of hypoxia mice. Metabolomic, lipidomic, and molecular biology analyses showed that HBO increased the levels of oleic acid (OA) and membrane-bound O-acyltransferase 2 (MBOAT2), thereby altering the composition of membrane phospholipids (PLs) and reducing hypoxia-induced neuronal ferroptosis (FPT) to interfere with cognitive function in mice. In vitro experiments confirmed that OA and MBOAT2 led to membrane PL remodeling in a mutually dependent manner, affecting cell resistance to hypoxia-FPT. The results emphasized the combined effect value of OA and MBOAT2 in HBO for hypoxia-induced CI, and provided a novel perspective for the treatment of CI by HBO.

Xenon and Argon as Neuroprotective Treatments for Perinatal Hypoxic-Ischemic Brain Injury: A Preclinical Systematic Review and Meta-Analysis

Xenon and argon are currently being evaluated as potential neuroprotective treatments for acquired brain injuries. Xenon has been evaluated clinically as a treatment for brain ischemia with equivocal results in small trials, but argon has not yet undergone clinical evaluation. Several preclinical studies have investigated xenon or argon as treatments in animal models of perinatal hypoxic-ischemic encephalopathy (HIE). A systematic review of MEDLINE and Embase databases was performed. After screening of titles, abstracts, and full text, data were extracted from included studies. A pairwise meta-analysis of neuroprotective efficacy was performed using a random effects model. Heterogeneity was investigated using subgroup analysis, funnel plot asymmetry, and Egger's regression. The protocol was prospectively registered on PROSPERO (CRD42022301986). A total of 21 studies met the inclusion criteria. The data extracted included measurements from 1591 animals, involving models of HIE in mice, rats, and pigs. The meta-analysis found that both xenon and argon had significant (P < .0001) neuroprotective efficacies. The summary estimate for xenon was 39.7% (95% confidence interval [CI], 28.3%-51.1%) and for argon it was 70.3% (95% CI, 59.0%-81.7%). The summary effect for argon was significantly (P < .001) greater than that of xenon. Our results provide evidence supporting further investigation of xenon and argon as neuroprotective treatments for HIE.

Multi-omics profiling reveals the molecular mechanisms of H2O2-induced detrimental effects on Thamnaconus septentrionalis

BACKGROUND

Hydrogen peroxide (H2O2), a novel water treatment agent, can be used for disinfection, water quality adjustment, and disease prevention, while excessive H2O2 can injure farm animals, even leading to death. Hydrogen peroxide is a recommended disinfectant and bactericide for treating gill diseases and vibriosis in the greenfin horse-faced filefish Thamnaconus septentrionalis. However, its cumulative effect, toxic molecular mechanism and relevant signal transduction/metabolic networks in marine fishes are largely unknown.

RESULTS

We employed a multi-omics approach to investigate the detrimental effects of 50 mg/L H2O2 exposure (2 h/d) on filefish for 2 d, 4 d, and 6 d. Transcriptome sequencing showed that differentially expressed genes (DEGs) were mainly classified into functions such as signal transduction, nervous system, liver and bile acid metabolism, energy metabolism, cell adhesion and communication, inflammation and immune response. Metabolomic analysis found that the significantly changed metabolites (SCMs) were involved in phenylalanine metabolism, inflammatory mediator regulation, linoleic acid metabolism, and necroptosis. The main SCMs were cholic acid, carnitine C12:1, dimethylmalonic acid, glutamic acid, L-lactic acid, shikimic acid, 2-methylsuccinic acid, and others. Moreover, H2O2-induced oxidative stress also disturbs the balance of the gut microbiota, altering the microbial composition and affecting digestive processes.

CONCLUSIONS

Integrated multiomics analysis revealed that H2O2-induced detrimental impacts include mucosal damage, inflammatory and immune responses, altered energy metabolism, and gut microbiota disorders. These findings offer novel insights into the harmful effects and signal transduction/metabolic pathways triggered by H2O2 exposure in marine fishes.

Towards chlorocytes for therapeutic intravascular photosynthesis

Aerobic metabolism relies on external oxygen production through photosynthesis and its subsequent transport into each cell of the body via the cardiorespiratory system. This mechanism has successfully evolved over millions of years, enabling animals to inhabit most environments on Earth. However, the insufficient oxygen supply leads to several clinical problems, ranging from non-healing wounds to tumor resistance to therapy. Given that photosynthetic microorganisms are capable of producing oxygen and removing carbon dioxide from the environment, over the last decade, several groups worldwide have proposed their potential use as an alternative tissue oxygenation approach. While most studies have demonstrated safety and efficacy after local tissue administration, recent studies have also suggested that systemic administration could trigger intravascular photosynthesis. If successful, the development of a new generation of circulating cells, known as chlorocytes, may partially replace the role of erythrocytes in gas exchange within the body, without relying on external supply and vascular flow. This work reviews the existing literature on local and systemic administration of photosynthetic microorganisms, highlighting the main challenges in the field and potential solutions to unleash the enormous potential clinical impact of chlorocytes and intravascular photosynthesis. KEY POINTS: • Circulating photosynthetic microorganisms could deliver oxygen to tissues • Microalgae and cyanobacteria have shown safety and efficacy for oxygen delivery • Several key challenges need to be addressed for the clinical success of chlorocytes.

Postnatal Development of the Circadian Rhythmicity of Human Pineal Melatonin Synthesis and Secretion (Systematic Review)

Introduction: According to current knowledge, at birth, the pineal gland and melatonin receptors are already present and the suprachiasmatic nucleus is largely functional, and noradrenaline, the key pineal transmitter, can be detected in the early foetal period. It is still unclear why the pineal gland is not able to start its own pulsatile synthesis and secretion of melatonin in the first months of life, and as a result, infants during this time are dependent on an external supply of melatonin. Method: The causes and consequences of this physiological melatonin deficiency in human infancy are examined in a systematic review of the literature, in which 40 of 115 initially selected publications were evaluated in detail. The references of these studies were checked for relevant studies on this topic. References from previous reviews by the author were taken into account. Results: The development and differentiation of the pineal gland, the pinealocytes, as the site of melatonin synthesis, and the development and synaptic coupling of the associated predominantly noradrenergic neural pathways and vessels and the associated Lhx4 homebox only occurs during the first year of life. Discussion: The resulting physiological melatonin deficiency is associated with sleep disorders, infant colic, and increased crying in babies. Intervention studies indicate that this deficiency should be compensated for through breastfeeding, the administration of nonpooled donor milk, or through industrially produced chrononutrition made from nonpooled cow's milk with melatonin-poor day milk and melatonin-rich night milk.

The effects of MEPaL on oxidative stress and motor function in the rats affected by prenatal hypoxia

BACKGROUND AND OBJECTIVES

Maternal hypoxia disrupts neural development and subsequently leads to cerebral palsy and epilepsy in newborns. Hypoxia plays a role in neurodegeneration by increasing oxidative stress. Pistacia atlantica is known as an important antioxidant, and its anti-inflammatory and antioxidant effects have been shown in various studies. This study aims to investigate the effects of methanolic extract of P. atlantica leaves (MEPaLs) on the oxidative parameters in the serum of rats affected by maternal hypoxia.

MATERIAL AND METHODS

In this study, eight pregnant rats were used. The newborns were divided into four groups, including the control and the hypoxia groups, which are affected by maternal hypoxia, hypoxia + MEPaL 100 mg/kg, and hypoxia + MEPaL 150 mg/kg. MEPaL was injected (i.p) for 21 days into the neonatal rats after the lactation period. Hypoxia was induced by keeping pregnant rats in a hypoxic chamber with 7% oxygen and 93% nitrogen intensity for 3 h on the 20th day of pregnancy. Behavioral changes were measured using open-field and rotarod tests. Finally, biomarkers of oxidative stress, nitric oxide (NO), glutathione (GSH), GSSG, TAS, TOS, and oxidative stress index (OSI) were measured in the experimental groups.

RESULTS

Behavioral results showed that the anxiety behavior in the hypoxia group increased, but the motor activity (moved distance and movement speed) decreased. Moreover, the amount of time spent maintaining balance on the rotarod rod was significantly decreased in the hypoxia group. The concentration of NO in the group of hypoxia + MEPaL 100 mg/kg showed a significant decrease, and MEPaL 100, and 150 mg/kg + hypoxia also increased the concentration of GSH and decreased GSSG. In addition, MEPaL100 and 150 mg/kg caused a significant increase in the ratio of GSH to GSSG and decreased OSI and total oxidant capacity.

CONCLUSIONS

Oxidative stress increased in the rats affected by maternal hypoxia and may be the main mechanism for motor activity impairment and balance disturbance, whereas MELaL improved motor performance by decreasing oxidative stress.

Plasmatic profiles of cytokines/chemokines, glial fibrillary acidic protein (GFAP) and MRI brain damage in neonates with hypoxic ischemic encephalopathy (HIE)

BACKGROUND

Perinatal hypoxia triggers the release of cytokines and chemokines by neurons, astrocytes and microglia. In response to hypoxia-ischemia resting/ramified microglia proliferate and undergo activation, producing proinflammatory molecules. The brain damage extension seems to be related to both the severity of hypoxia and the balance between pro and anti-inflammatory response and can be explored with neuroimaging.

AIMS

The aim of this preliminary study was to explore possible relationships between plasma levels of inflammatory cytokines/chemokines and the severe brain damage detectable by Magnetic Resonance Imaging (MRI), performed during the hospitalization.

METHODS

In 10 full terms neonates with hypoxic ischemic encephalopathy (HIE) undergoing therapeutic hypothermia (TH), divided into cases and controls, according to MRI results, we measured and compared the plasma levels of CCL2/MCP-1, CXCL8, GFAP, IFN y, IL-10, IL-18, IL-6, CCL3, ENOLASE2, GM-CSF, IL-1b, IL-12p70, IL-33, TNFα, collected at four different time points during TH (24, 25-48, 49-72 h of life, and 7-10 days from birth). Five of enrolled babies had pathological brain MRI (cases) and 5 had a normal MRI examination (controls). Cytokines were measured by Magnetic Luminex Assay. MRI images were classified according to Barkovich's score.

RESULTS

Mean levels of all cytokines and molecules at time T1 were not significantly different in the two groups. Comparing samples paired by day of collection, the greatest differences between cases and controls were found at times T2 and T3, during TH. At T4, levels tended to get closer again (except for IL-6, IL10 and IL18). Infants with worse MRI showed higher plasmatic GFAP levels than those with normal MRI, while their IL-18 was lower. The mean levels of CCL3MIP1alpha, GMCSF, IL1BETA overlapped throughout the observation period in both groups.

CONCLUSION

In a small number of infants with worse brain MRI, we found higher levels of GFAP and of IL-10 at T4 and a trend toward low IL-18 levels than in infants with normal MRI, considered early biomarker of brain damage and a predictor of adverse outcome, respectively. The greatest, although not significant, difference between the levels of molecules was found in cases and controls at time points T2 and T3, during TH.

Additive interaction between birth asphyxia and febrile seizures on autism spectrum disorder: a population-based study

BACKGROUND

Autism Spectrum Disorder (ASD) is a pervasive neurodevelopmental disorder that can significantly impact an individual's ability to socially integrate and adapt. It's crucial to identify key factors associated with ASD. Recent studies link both birth asphyxia (BA) and febrile seizures (FS) separately to higher ASD prevalence. However, investigations into the interplay of BA and FS and its relationship with ASD are yet to be conducted. The present study mainly focuses on exploring the interactive effect between BA and FS in the context of ASD.

METHODS

Utilizing a multi-stage stratified cluster sampling, we initially recruited 84,934 Shanghai children aged 3-12 years old from June 2014 to June 2015, ultimately including 74,251 post-exclusion criteria. A logistic regression model was conducted to estimate the interaction effect after controlling for pertinent covariates. The attributable proportion (AP), the relative excess risk due to interaction (RERI), the synergy index (SI), and multiplicative-scale interaction were computed to determine the interaction effect.

RESULTS

Among a total of 74,251 children, 192 (0.26%) were diagnosed with ASD. The adjusted odds ratio for ASD in children with BA alone was 3.82 (95% confidence interval [CI] 2.42-6.02), for FS alone 3.06 (95%CI 1.48-6.31), and for comorbid BA and FS 21.18 (95%CI 9.10-49.30), versus children without BA or FS. The additive interaction between BA and FS showed statistical significance (P < 0.001), whereas the multiplicative interaction was statistically insignificant (P > 0.05).

LIMITATIONS

This study can only demonstrate the relationship between the interaction of BA and FS with ASD but cannot prove causation. Animal brain experimentation is necessary to unravel its neural mechanisms. A larger sample size, ongoing monitoring, and detailed FS classification are needed for confirming BA-FS interaction in ASD.

CONCLUSION

In this extensive cross-sectional study, both BA and FS were significantly linked to ASD. The coexistence of these factors was associated with an additive increase in ASD prevalence, surpassing the cumulative risk of each individual factor.

Mitochondrial ferritin upregulation reduced oxidative stress and blood-brain-barrier disruption by maintaining cellular iron homeostasis in a neonatal rat model of germinal matrix hemorrhage

Germinal matrix hemorrhage (GMH) is a devasting neurological disease in premature newborns. After GMH, brain iron overload associated with hemoglobin degradation contributed to oxidative stress, causing disruption of the already vulnerable blood-brain barrier (BBB). Mitochondrial ferritin (FTMT), a novel mitochondrial outer membrane protein, is crucial in maintaining cellular iron homeostasis. We aimed to investigate the effect of FTMT upregulation on oxidative stress and BBB disruption associated with brain iron overload in rats. A total of 222 Sprague-Dawley neonatal rat pups (7 days old) were used to establish a collagenase-induced GMH model and an iron-overload model of intracerebral FeCl2 injection. Deferiprone was administered via gastric lavage 1 h after GMH and given daily until euthanasia. FTMT CRISPR Knockout and adenovirus (Ad)-FTMT were administered intracerebroventricularly 48 h before GMH and FeCl2 injection, respectively. Neurobehavioral tests, immunofluorescence, Western blot, Malondialdehyde measurement, and brain water content were performed to evaluate neurobehavior deficits, oxidative stress, and BBB disruption, respectively. The results demonstrated that brain expressions of iron exporter Ferroportin (FPN) and antioxidant glutathione peroxidase 4 (GPX4) as well as BBB tight junction proteins including Claudin-5 and Zona Occulta (ZO)-1 were found to be decreased at 72 h after GMH. FTMT agonist Deferiprone attenuated oxidative stress and preserved BBB tight junction proteins after GMH. These effects were partially reversed by FTMT CRISPR Knockout. Iron overload by FeCl2 injection resulted in oxidative stress and BBB disruption, which were improved by Ad-FTMT mediated FTMT overexpression. Collectively, FTMT upregulation is neuroprotective against brain injury associated with iron overload. Deferiprone reduced oxidative stress and BBB disruption by maintaining cellular iron homeostasis partially by the upregulating of FTMT after GMH. Deferiprone may be an effective treatment for patients with GMH.

A comparative proteomic analysis for non-invasive early prediction of hypoxic-ischemic injury in asphyxiated neonates

AIM

Hypoxic Ischemic Encephalopathy (HIE) is one of the principal causes of neonatal mortality and long-term morbidity worldwide. The neonatal signs of mild cerebral injury are subtle, making an early precise diagnosis difficult. Delayed detection, poor prognosis, and lack of specific biomarkers for the disease are increasing mortality rates. In this study, we intended to identify specific biomarkers using comparative proteomic analysis to predict the severity of perinatal asphyxia so that its outcome can also be prevented.

EXPERIMENTAL DESIGN

A case-control study was conducted on 38 neonates, and urine samples were collected within 24 and 72 h of life. A tandem mass spectrometry-based quantitative proteomics approach, followed by validation via sandwich ELISA, was performed.

RESULTS

The LC-MS/MS-based proteomics analysis resulted in the identification of 1201 proteins in urine, with 229, 244, and 426 being differentially expressed in HIE-1, HIE-2, and HIE-3, respectively. Axon guidance, Diseases of programmed cell death, and Detoxification of reactive oxygen species pathways were significantly enriched in mild HIE versus severe HIE. Among the differentially expressed proteins in various stages of HIE, we chose to validate four proteins - APP, AGT, FABP1, and FN1 - via sandwich ELISA. Individual and cumulative ROC curves were plotted. AGT and FABP1 together showed high sensitivity, specificity, and accuracy as potential biomarkers for early diagnosis of HIE.

CONCLUSION

Establishing putative urinary biomarkers will facilitate clinicians to more accurately screen neonates for brain injury and monitor the disease progression. Prompt treatment of neonates may reduce mortality and neurodevelopmental impairment.

RCOR1 improves neurobehaviors and neuron injury in rat cerebral palsy by Endothelin-1 targeting-induced Akt/GSK-3β pathway upregulation

BACKGROUND

RE1 Silencing Transcription factor (REST) corepressor 1 (RCOR1) has been reported to orchestrate neurogenesis, while its role in cerebral palsy (CP) remains elusive. Besides, RCOR1 can interact with Endothelin-1 (EDN1), and EDN1 expression is related to brain damage. Therefore, this study aimed to explore the effects of RCOR1/EDN1 on brain damage during the progression of CP.

METHODS

CP rats were established via hypoxia-ischemia insult, and injected with lentivirus-RCOR1, followed by examination of brain pathological conditions. The RCOR1 and EDN1 interaction was recognized using hTFtarget. Healthy rat cortical neuron cells received interference of RCOR1/EDN1 expression, and underwent oxygen-glucose deprivation/reoxygenation (OGD/R) treatment, after which phenotypic and molecular assays were conducted through the biochemical method, qRT-PCR and/or western blot.

RESULTS

RCOR1 was low-expressed but EDN1 was high-expressed in CP model rats and OGD/R-treated neurons. RCOR1 overexpression ameliorated rat neurobehaviors, alleviated brain pathological conditions, reduced TUNEL-positive cells, decreased the levels of reactive oxygen species (ROS) and malondialdehyde (MDA), increased superoxide dismutase (SOD) level and repressed EDN1 expression in the brains of CP model rats. In neurons, RCOR1 overexpression counteracted OGD/R-induced viability decrease, reduction of the levels of RCOR1, SOD, Bcl-2, caspase-3, p-Akt/Akt and p-GSK-3β/GSK-3β, and elevation of the levels of EDN1, ROS, Bax, and cleaved caspase-3, while EDN1 overexpression did contrarily on these events. Moreover, there was a negative interplay between RCOR1 overexpression and EDN1 overexpression in OGD/R-induced neurons.

CONCLUSION

RCOR1 ameliorates neurobehaviors and suppresses neuronal apoptosis and oxidative stress in CP through EDN1 targeting-mediated upregulation of Akt/GSK-3β.

L-F001, a multifunctional fasudil-lipoic acid dimer, antagonizes hypoxic-ischemic brain damage by inhibiting the TLR4/MyD88 signaling pathway

INTRODUCTION

Neonatal hypoxic-ischemic brain damage (HIBD) is a serious inflammatory injury. At present, the standard treatment for this disease is hypothermia therapy, and the effect of drug intervention is still limited. L-F001 is a compound of fasudil and lipoic acid. Previous in vitro experiments have confirmed that L-F001 has anti-inflammatory neuroprotective functions. However, its therapeutic effect on neonates with HIBD remains unknown. This study was aimed at exploring the therapeutic effect of L-F001 on HIBD rats.

METHODS

The newborn rats were divided into three groups: Sham operation group, HIBD group, and HIBD + L-F001 group. HE staining, Nissil staining, the immunofluorescence of iNOS and COX-2, ELISA (IL-1β, IL-6, TNF-α, and IL-10), and western blotting analyses were performed to determine the therapeutic effect of L-F001. Finally, we evaluated the growth and development of each group by measuring body weight.

RESULTS

The hippocampal structure of HIBD rats was disordered, and the Nissil body was small and shallow. The expressions of iNOS and COX-2 in HIBD rats were increased, whereas the expressions of IL-1β, IL-6, and TNF-α in plasma were upregulated, and the expression of IL-10 was decreased. L-F001 could improve the tissue structure and reduce the expression of iNOS and COX-2 in HIBD rats. Meanwhile, L-F001 could also reduce the expression of pro-inflammatory cytokines and restore the content of anti-inflammatory cytokines in plasma. We further found that the TLR4 pathway was activated after hypoxic-ischemia in neonatal rats. L-F001 could inhibit the activation of TLR4 pathway. Finally, we found that after L-F001 treatment, the body weight of HIBD rats increased significantly compared with the untreated group.

CONCLUSIONS

L-F001 antagonizes the inflammatory response after hypoxic-ischemia by inhibiting the activation of the TLR4 signaling pathway, thus playing a neuroprotective role. L-F001 may be a potential therapeutic agent for neonatal HIBD.

A comparative study of CTG monitoring one hour before labor in infants born with and without asphyxia

BACKGROUND AND AIM

Asphyxia is a condition arising when the infant is deprived of oxygen, causing Fetal brain damage or death, which is associated with hypoxia and hypercapnia. Although fetal Cardiotocography (CTG) can show the Fetal health status during labor, some studies have reported cases of fetal asphyxia despite reassuring CTGs. This study hence aimed to compare FHR Monitoring and uterine contractions in the last hour before delivered between two groups of infants born with and without asphyxia.

METHODOLOGY

The study was conducted on 70 pregnant women who delivered Taleghani and Al-Zahra academic teaching hospitals of Tabriz for labor in 2020-2021.

RESULTS

The study data showed no significant difference between mothers of infants with and without asphyxia in terms of demographics (p > 0.05). The prevalence of asphyxia was significantly higher only in mothers with the gravidity of 3 and 4 (p = 0.003). In terms of the methods for labor induction, the use of oxytocin was more common among mothers of infants with asphyxia (74.3%) than in those of infants without asphyxia (p = 0.015). The results also revealed a significant difference between infants with and without asphyxia in the Apgar score (first, fifth, and tenth minutes), need for neonatal resuscitation, umbilical cord artery Acidosis (pH, bicarbonate, and BE), and severity of HIE between two groups of infants with asphyxia and without asphyxia (p < 0.0001). The comparison of fetal CTG 0 to 20 min before the delivery indicated that normal variability was observed in 71.4% of infants born with asphyxia, whereas this figure for infants born without asphyxia was 91.4% (p = 0.031). However, the results showed no significant difference between the two groups of infants in any of the tstudied indicators at 20 and 40 min before the labor(p > 0.05). There was a significant difference between the two groups of infants in terms of deceleration at 40 and 60 min before the labor, as it was observed in 53.6% of infants born with asphyxia and only 11.1% of those born without asphyxia. The results also demonstrated a significant difference between the two groups in the type of deceleration (p = 0.025). Pearson and Spearman correlation coefficients showed a significant and direct relationship between interpretation the CTG of the three Perinatologists(p < 0.0001, r > 0.8).

CONCLUSION

The study results demonstrated a significant difference between infants born with asphyxia and those born without asphyxia in variability at 0 to 20 min before the labor and deceleration at 40 to 60 min before the labor.

Perinatal asphyxia and hypothermic treatment from the endocrine perspective

Introduction

Perinatal asphyxia is one of the three most important causes of neonatal mortality and morbidity. Therapeutic hypothermia represents the standard treatment for infants with moderate-severe perinatal asphyxia, resulting in reduction in the mortality and major neurodevelopmental disability. So far, data in the literature focusing on the endocrine aspects of both asphyxia and hypothermia treatment at birth are scanty, and many aspects are still debated. Aim of this narrative review is to summarize the current knowledge regarding the short- and long-term effects of perinatal asphyxia and of hypothermia treatment on the endocrine system, thus providing suggestions for improving the management of asphyxiated children.

Results

Involvement of the endocrine system (especially glucose and electrolyte disturbances, adrenal hemorrhage, non-thyroidal illness syndrome) can occur in a variable percentage of subjects with perinatal asphyxia, potentially affecting mortality as well as neurological outcome. Hypothermia may also affect endocrine homeostasis, leading to a decreased incidence of hypocalcemia and an increased risk of dilutional hyponatremia and hypercalcemia.

Conclusions

Metabolic abnormalities in the context of perinatal asphyxia are important modifiable factors that may be associated with a worse outcome. Therefore, clinicians should be aware of the possible occurrence of endocrine complication, in order to establish appropriate screening protocols and allow timely treatment.

Exogenous lactate administration: A potential novel therapeutic approach for neonatal hypoxia-ischemia

Neonatal hypoxic-ischemic encephalopathy (HIE) is the primary reason for neonatal mortality and prolonged disablement. Currently, hypothermia is the only approved clinical treatment available for HIE. However, hypothermia's limited therapeutic efficacy and adverse effects suggest an urgent need to advance our knowledge of its molecular pathogenesis and develop novel therapies. The leading cause of HIE is impaired cerebral blood flow and oxygen deprivation-initiated primary and secondary energy failure. Lactate was traditionally regarded as a marker of energy failure or a waste product of anaerobic glycolysis. Recently, the beneficial aspects of lactate as supplementary energy for neurons have been demonstrated. Under the conditions of HI, lactate supports various functions of neuronal cells, including learning and memory formation, motor coordination, and somatosensory. Furthermore, lactate contributes to the regeneration of blood vessels and has shown its beneficial effects on the immune system. This review first introduces the hypoxic or ischemic events-induced fundamental pathophysiological changes in HIE and then discusses the potential neuroprotective properties of lactate for the treatment and prevention of HIE. Finally, we discuss the possible protective mechanisms of lactate in the context of the pathological features of perinatal HIE. We conclude that exogenous and endogenous lactate exert neuroprotective effects in HIE. Lactate administration may be a potential approach to treating HIE injury.

Melatonin Use in Pediatric Intensive Care Units: A Single-Center Experience

Growing evidence indicates that altered melatonin secretion during critical illness may influence the quality and quantity of sleep, delirium, and overall recovery. However, limited data exist regarding the use of melatonin in pediatric critical illness. Data were reviewed over a 5-year period at a tertiary pediatric intensive care unit for pediatric patients (ages 0-18 years) who were prescribed melatonin with the aim of identifying the frequency of and indications for use. Data collection included the hospital day of initiation, the dose, the frequency, the duration of use, and the length of stay. The results demonstrate that melatonin was infrequently prescribed (6.0% of patients admitted; n = 182) and that the majority of patients received melatonin as continuation of home medication (46%; n = 83 of 182). This group had significantly earlier melatonin use (0.9 ± 2.3 day of hospitalization; p < 0.0001) and significantly reduced lengths of stay compared to the other groups (mean LOS 7.2 ± 9.3 days; p < 0.0001). Frequently, clear documentation of indication for melatonin use was absent (20%; n = 37). In conclusion, given that melatonin is infrequently used within a tertiary PICU with the most common indication as the continuation of home medication, and often without clear documentation for indication, this presents an opportunity to emphasize a more attentive and strategic approach regarding melatonin use in the PICU population.

Socioeconomic factors, perceived stress, and social support effect on neonatal nurse burnout in China: a cross-sectional study

BACKGROUND

Neonatal nurses' working environments are highly stressful, and burnout is common. This study examines the effect of socioeconomic factors, perceived stress, and social support on neonatal nurse burnout.

METHODS

A total of 311 neonatal nurses participated in this study. They were administered a validated Maslach Burnout Inventory. The study employed a 14-item perceived stress scale (PSS-14) and a social support rate scale (SSRS) to examine stress, socioeconomic factors, and lifestyles.

RESULTS

Of the neonatal nurses, 40.19% had burnout, 89.60% had mild burnout, and 10.40% had moderate burnout; no neonatal nurse experienced severe burnout. Young nurses and those with low technical skills, poor interpersonal relationships, irregular diet, and insufficient rest were exposed to burnout (all p < 0.05).Most burnout nurses experienced moderate-severe perceived stress, and their PSS-14 scores were higher (all p < 0.05).The scores for objective social support, subjective social support, utilization of social support, total SSRS scores, and the level of social support were all lower in burnout nurses (all p < 0.05). Perceived stress was correlated positively and significantly with emotional exhaustion and personal accomplishment (all p < 0.05). Social support correlated significantly with and reduced personal accomplishments (p < 0.05). Age, poor interpersonal relationships, perceived stress, and social support were all independent factors associated with neonatal nurse burnout (all p < 0.05).

CONCLUSION

The prevalence of burnout in neonatal nurses was higher than average. Socioeconomic factors, higher perceived stress, and lower social support contribute to neonatal nurse burnout. Nursing managers should pay attention to socioeconomic factors, perceived stress, and social support among neonatal nurses and employ strategies to reduce neonatal nurse burnout.

Molecular Pathways of Altered Brain Development in Fetuses Exposed to Hypoxia

Perinatal hypoxia is a major cause of neurodevelopmental impairment and subsequent motor and cognitive dysfunctions; it is associated with fetal growth restriction and uteroplacental dysfunction during pregnancy. This review aims to present the current knowledge on brain development resulting from perinatal asphyxia, including the causes, symptoms, and means of predicting the degree of brain damage. Furthermore, this review discusses the specificity of brain development in the growth-restricted fetus and how it is replicated and studied in animal models. Finally, this review aims at identifying the least understood and missing molecular pathways of abnormal brain development, especially with respect to potential treatment intervention.

MiR-155 promotes inflammation and apoptosis via targeting SIRT1 in hypoxic-ischemic brain damage

Hypoxic-ischemic brain damage (HIBD) is one of the major causes of infant death and long-term neurological disturbances, which puts great pressure on families and society. Previous studies have reported that neuroinflammation regulates the pathogenesis of HIBD. MiR-155 has been reported to participate in many brain injuries; however, its direct implication and related mechanisms are not illuminated in HIBD. Herein, we identified that miR-155 plays a vital role in HIBD both in in vitro and in vivo models. We found that miR-155 promoted inflammation and apoptosis via targeting SIRT1 and negatively regulated its expression levels in oxygen-glucose deprivation/reoxygenation (OGD/R) in an in vitro model. Silencing of SIRT1 reversed the effects of miR-155 inhibitor on apoptosis and the NF-κB pathway in OGD/R-treated PC12 cells and microglia (BV2) cells. Moreover, in a neonatal rat HIBD model, miR-155 enhanced apoptosis and inflammation in the brains of rats with HIBD in vivo. Together, our results demonstrated that miR-155 exerted a negative effect in HIBD by targeting SIRT1, which could contribute to the treatment of neonatal patients with hypoxic-ischemic brain damage.

Systemic Cytokines in Retinopathy of Prematurity

Retinopathy of prematurity (ROP), a vasoproliferative vitreoretinal disorder, is the leading cause of childhood blindness worldwide. Although angiogenic pathways have been the main focus, cytokine-mediated inflammation is also involved in ROP etiology. Herein, we illustrate the characteristics and actions of all cytokines involved in ROP pathogenesis. The two-phase (vaso-obliteration followed by vasoproliferation) theory outlines the evaluation of cytokines in a time-dependent manner. Levels of cytokines may even differ between the blood and the vitreous. Data from animal models of oxygen-induced retinopathy are also valuable. Although conventional cryotherapy and laser photocoagulation are well established and anti-vascular endothelial growth factor agents are available, less destructive novel therapeutics that can precisely target the signaling pathways are required. Linking the cytokines involved in ROP to other maternal and neonatal diseases and conditions provides insights into the management of ROP. Suppressing disordered retinal angiogenesis via the modulation of hypoxia-inducible factor, supplementation of insulin-like growth factor (IGF)-1/IGF-binding protein 3 complex, erythropoietin, and its derivatives, polyunsaturated fatty acids, and inhibition of secretogranin III have attracted the attention of researchers. Recently, gut microbiota modulation, non-coding RNAs, and gene therapies have shown promise in regulating ROP. These emerging therapeutics can be used to treat preterm infants with ROP.

Noble gas and neuroprotection: From bench to bedside

In recent years, inert gases such as helium, argon, and xenon have gained considerable attention for their medical value. Noble gases present an intriguing scientific paradox: although extremely chemically inert, they display a remarkable spectrum of clinically useful biological properties. Despite a relative paucity of knowledge about their mechanisms of action, some noble gases have been used successfully in clinical practice. The neuroprotection elicited by these noble gases has been investigated in experimental animal models of various types of brain injuries, such as traumatic brain injury, stroke, subarachnoid hemorrhage, cerebral ischemic/reperfusion injury, and neurodegenerative diseases. Collectively, these central nervous system injuries are a leading cause of morbidity and mortality every year worldwide. Treatment options are presently limited to thrombolytic drugs and clot removal for ischemic stroke, or therapeutic cooling for other brain injuries before the application of noble gas. Currently, there is increasing interest in noble gases as novel treatments for various brain injuries. In recent years, neuroprotection elicited by particular noble gases, xenon, for example, has been reported under different conditions. In this article, we have reviewed the latest in vitro and in vivo experimental and clinical studies of the actions of xenon, argon, and helium, and discuss their potential use as neuroprotective agents.

Hypoxia Depresses Synaptic Transmission in the Primary Motor Cortex of the Infant Rat-Role of Adenosine A1 Receptors and Nitric Oxide

The acute and long-term consequences of perinatal asphyxia have been extensively investigated, but only a few studies have focused on postnatal asphyxia. In particular, electrophysiological changes induced in the motor cortex by postnatal asphyxia have not been examined so far, despite the critical involvement of this cortical area in epilepsy. In this study, we exposed primary motor cortex slices obtained from infant rats in an age window (16-18 day-old) characterized by high incidence of hypoxia-induced seizures associated with epileptiform motor behavior to 10 min of hypoxia. Extracellular field potentials evoked by horizontal pathway stimulation were recorded in layers II/III of the primary motor cortex before, during, and after the hypoxic event. The results show that hypoxia reversibly depressed glutamatergic synaptic transmission and neuronal excitability. Data obtained in the presence of specific blockers suggest that synaptic depression was mediated by adenosine acting on pre-synaptic A1 receptors to decrease glutamate release, and by a nitric oxide (NO)/cGMP postsynaptic pathway. These effects are neuroprotective because they limit energy failure. The present findings may be helpful in the preclinical search for therapeutic strategies aimed at preventing acute and long-term neurological consequences of postnatal asphyxia.

Treatments and therapeutic protocols for the recovery of an asphyxiated new-born: A review of pre-clinical and clinical studies in human neonates and in different animal models

The objective of this review is to ascertain the advantages and disadvantages of several treatments and therapeutic protocols that have been used for the prevention and treatment of perinatal asphyxia in human neonates and in different animal models. Perinatal asphyxia is one of the main causes of mortality worldwide and is an important factor in triggering physio-metabolic disorders that result in serious neurological consequences and learning disorders not only in human foetuses and neonates, but also in animals. In recent years, the search for new pharmacological protocols to prevent and reverse physio-metabolic disorders and brain damage derived from perinatal asphyxia has been and continues to be the subject of intense research. Currently, within these pharmacological protocols, therapeutic strategies have been evaluated that use respiratory and hormonal stimulants, as well as hypothermic therapies in combination with other putative neuroprotective agents. Similarly, energy supplements have been evaluated with the objective of preventing perinatal asphyxia and treating new-borns with this condition, and to decrease the incidence of neonatal and foetal deaths associated with it. However, despite these promising advances, this pathology has persisted, since the administration of these therapies in low doses may not exert a neuroprotective effect or, in high doses, can trigger adverse effects (such as reduced cardiac contractility, reduced cerebral blood flow, poor perfusion, sympathetic and neuroendocrine stimulation, and increased blood viscosity) in human foetuses and neonates as well as in different animal models (rats, piglets, sheep and rabbits). Therefore, it is important to determine the minimum effective dose with which these therapies exert a neuroprotective effect, as well as the mode of administration, the duration of therapy, etc. Therefore, until a powerful strategy is found to improve the consequences of suffocation, this topic will continue to be the subject of intensive research in the future.

Erythropoietin as a Neuroprotective Drug for Newborn Infants: Ten Years after the First Use

Protective strategies against perinatal brain injury represent a major challenge for modern neonatology. Erythropoietin (Epo) enhances endogenous mechanisms of repair and angiogenesis. In order to analyse the newest evidence on the role of Epo in prematurity, hypoxic ischemic encephalopathy (HIE) and perinatal stroke, a critical review using 2020 PRISMA statement guidelines was conducted. This review uncovered 26 clinical trials examining the use of Epo for prematurity and brain injury-related outcomes. The effects of Epo on prematurity were analysed in 16 clinical trials. Erythropoietin was provided until 32–35 weeks of corrected postnatal age with a dosage between 500–3000 UI/kg/dose. Eight trials reported the Epo effects on HIE term newborn infants: Erythropoietin was administered in the first weeks of life, at different multiple doses between 250–2500 UI/kg/dose, as either an adjuvant therapy with hypothermia or a substitute for hypothermia. Two trials investigated Epo effects in perinatal stroke. Erythropoietin was administered at a dose of 1000 IU/kg for three days. No beneficial effect in improving morbidity was observed after Epo administration in perinatal stroke. A positive effect on neurodevelopmental outcome seems to occur when Epo is used as an adjuvant therapy with hypothermia in the HIE newborns. Administration of Epo in preterm infants still presents inconsistencies with regard to neurodevelopmental outcome. Clinical trials show significant differences mainly in target population and intervention scheme. The identification of specific markers and their temporal expression at different time of recovery after hypoxia-ischemia in neonates might be implemented to optimize the therapeutic scheme after hypoxic-ischemic injury in the developing brain. Additional studies on tailored regimes, accounting for the risk stratification of brain damage in newborns, are required.

Pharmacometric approach to assist dosage regimen design in neonates undergoing therapeutic hypothermia

BACKGROUND

Therapeutic hypothermia (TH) is the treatment of choice for neonates diagnosed with perinatal asphyxia (PA). Dosing recommendations of various therapeutic agents including antimicrobials were not specifically available for the neonates undergoing TH.

METHODS

A systematic search methodology was used to identify pharmacokinetic (PK) studies of antimicrobials during TH. Antimicrobials with multiple PK studies were identified to create a generalizable PK model. Pharmacometric simulations were performed using the PUMAS software platform to reproduce the results of published studies. A suitable model that could reproduce the results of all other published studies was identified. With the help of a generalizable model, an optimal dosage regimen was designed considering the important covariates of the identified model.

RESULTS

With the systematic search, only gentamicin had multiple PK reports during TH. A generalizable model was identified and the model predictions could match the reported/observed concentrations of publications. Birth weight and serum creatinine were the significant covariates influencing the PK of gentamicin in neonates. A dosage nomogram was designed using pharmacometric simulations to maintain gentamicin concentrations below 10 μg/mL at peak and below 2 μg/mL at trough.

CONCLUSIONS

A generalizable PK model for gentamicin during TH in neonates was identified. Using the model, a dosing nomogram for gentamicin was designed.

IMPACT

Dosing guidelines for antimicrobials during TH in neonates is lacking. This is the first study to identify the generalizable model for gentamicin during TH in neonates. Nomogram, proposed in the study, will aid the clinicians to individualize gentamicin dosing regimen for neonates considering the birth weight and serum creatinine.

Neuroprotective Agents for Neonates with Hypoxic-Ischemic Encephalopathy

Hypoxic-ischemic encephalopathy (HIE) remains a significant source of long-term neurodevelopmental impairment despite overall improvements in survival without disability in neonates who undergo therapeutic hypothermia. Each phase in the evolution of hypoxic-ischemic injury presents potential pharmacologic targets for neuroprotective agents. Melatonin is a promising emerging therapy for early phases of ischemic injury, but utility is currently limited by the lack of pharmaceutical-grade products. Magnesium has been extensively studied for its neuroprotective effects in the preterm population. Studies in neonates with HIE have produced mixed outcomes. Erythropoietin use in HIE with or without therapeutic hypothermia appears to be safe and may provide additional benefit. Dexmedetomidine, N-acetylcysteine, xenon, and topiramate all have promising animal data, but need additional human trials to elucidate what role they may play in HIE. Frequent review of existing literature is required to ensure provision of evidence-based pharmacologic agents for neuroprotection following HIE.

Application of transcriptome analysis to understand the adverse effects of hydrogen peroxide exposure on brain function in common carp (Cyprinus carpio)

Hydrogen peroxide (H₂O₂), as a common disinfectant, has been extensively used in aquaculture. The toxicity of high ambient H₂O₂ for gills and liver of fish has received attention from many researchers. However, whether H₂O₂ exposure induced brain injury and neurotoxicity has not been reported in fish. Therefore, this study aimed to explore the potential mechanism of H₂O₂ toxicity in brain of common carp via transcriptome analysis and biochemical parameter detection. The fish were exposed to 0 (control) and 1 mM of H₂O₂ for 1 h per day lasting 14 days. The results showed that H₂O₂ exposure caused oxidative damage in brain evidenced by decreased glutathione (GSH), total antioxidant capacity (T-AOC) and nicotinamide adenine dinucleotide (NAD⁺) levels, and increased formation of malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG). Meanwhile, H₂O₂ exposure reduced 5-hydroxytryptamine (5-HT) level, and down-regulated tryptophan hydroxylase 1 (tph1a), tph2, 5-hydroxytryptamine receptor 1A-beta (htr1ab) and htr2b expression in brain. Transcriptome analysis showed that H₂O₂ exposure up-regulated 604 genes and down-regulated 1209 genes in brain. Go enrichment displayed that the differently expressed genes (DEGs) were enriched mainly in cellular process, single-organism process, metabolic process, and biological regulation in the biological process category. Further, KEGG enrichment indicated that H₂O₂ exposure led to dysregulation of neurotransmitter signals including depression of glutamatergic synapse, GABAergic synapse and endocannabinoid signaling. Also, we found the alteration of three key pathways including calcium, cAMP and HIF-1 in brain after H₂O₂ exposure. In conclusion, our data indicated that H₂O₂ exposure induced oxidative damage and neurotoxicity, possibly related to dysregulation of neurotransmitters and calcium, cAMP and HIF-1 signaling pathways, which may adversely affect learning, memory and social responses of common carp. This study provided novel insight into biological effects and underlying mechanism of H₂O₂ toxicity in aquatic animal, and contributed to proper application of H₂O₂ in aquaculture.

Mitochondrial dysfunction in perinatal asphyxia: role in pathogenesis and potential therapeutic interventions

Perinatal asphyxia (PA)-induced brain injury may present as hypoxic-ischemic encephalopathy in the neonatal period, and long-term sequelae such as spastic motor deficits, intellectual disability, seizure disorders and learning disabilities. The brain injury is secondary to both the hypoxic-ischemic event and oxygenation-reperfusion following resuscitation. Following PA, a time-dependent progression of neuronal insult takes place in terms of transition of cell death from necrosis to apoptosis. This transition is the result of time-dependent progression of pathomechanisms which involve excitotoxicity, oxidative stress, and ultimately mitochondrial dysfunction in developing brain. More precisely mitochondrial respiration is suppressed and calcium signalling is dysregulated. Consequently, Bax-dependent mitochondrial permeabilization occurs leading to release of cytochrome c and activation of caspases leading to transition of cell death in developing brain. The therapeutic window lies within this transition process. At present, therapeutic hypothermia (TH) is the only clinical treatment available for treating moderate as well as severe asphyxia in new-born as it attenuates secondary loss of high-energy phosphates (ATP) (Solevåg et al. in Free Radic Biol Med 142:113-122, 2019; Gunn et al. in Pediatr Res 81:202-209, 2017), improving both short- and long-term outcomes. Mitoprotective therapies can offer a new avenue of intervention alone or in combination with therapeutic hypothermia for babies with birth asphyxia. This review will explore these mitochondrial pathways, and finally will summarize past and current efforts in targeting these pathways after PA, as a means of identifying new avenues of therapeutic intervention.

Current Therapies for Neonatal Hypoxic-Ischaemic and Infection-Sensitised Hypoxic-Ischaemic Brain Damage

Neonatal hypoxic-ischaemic brain damage is a leading cause of child mortality and morbidity, including cerebral palsy, epilepsy, and cognitive disabilities. The majority of neonatal hypoxic-ischaemic cases arise as a result of impaired cerebral perfusion to the foetus attributed to uterine, placental, or umbilical cord compromise prior to or during delivery. Bacterial infection is a factor contributing to the damage and is recorded in more than half of preterm births. Exposure to infection exacerbates neuronal hypoxic-ischaemic damage thus leading to a phenomenon called infection-sensitised hypoxic-ischaemic brain injury. Models of neonatal hypoxia-ischaemia (HI) have been developed in different animals. Both human and animal studies show that the developmental stage and the severity of the HI insult affect the selective regional vulnerability of the brain to damage, as well as the subsequent clinical manifestations. Therapeutic hypothermia (TH) is the only clinically approved treatment for neonatal HI. However, the number of HI infants needed to treat with TH for one to be saved from death or disability at age of 18-22 months, is approximately 6-7, which highlights the need for additional or alternative treatments to replace TH or increase its efficiency. In this review we discuss the mechanisms of HI injury to the immature brain and the new experimental treatments studied for neonatal HI and infection-sensitised neonatal HI.

Creatinine Trends and Patterns in Neonates Undergoing Whole Body Hypothermia: A Systematic Review

Many neonates undergoing whole body hypothermia (WBH) following moderate to severe perinatal asphyxia may also suffer from renal impairment. While recent data suggest WBH-related reno-protection, differences in serum creatinine (Scr) patterns to reference patterns were not yet reported. We therefore aimed to document Scr trends and patterns in asphyxiated neonates undergoing WBH and compared these to centiles from a reference Scr data set of non-asphyxiated (near)term neonates. Using a systematic review strategy, reports on Scr trends (mean ± SD, median or interquartile range) were collected (day 1-7) in WBH cohorts and compared to centiles of an earlier reported reference cohort of non-asphyxia cases. Based on 13 papers on asphyxia + WBH cases, a pattern of postnatal Scr trends in asphyxia + WBH cases was constructed. Compared to the reference 50th centile Scr values, mean or median Scr values at birth and up to 48 h were higher in asphyxia + WBH cases with a subsequent uncertain declining trend towards, at best, high or high-normal creatinine values afterwards. Such patterns are valuable for anticipating average changes in renal drug clearance but do not yet cover the relevant inter-patient variability observed in WBH cases, as this needs pooling of individual Screa profiles, preferably beyond the first week of life.

Alzheimer's Disease Associated Presenilin 1 and 2 Genes Dysregulation in Neonatal Lymphocytes Following Perinatal Asphyxia

Perinatal asphyxia is mainly a brain disease leading to the development of neurodegeneration, in which a number of peripheral lesions have been identified; however, little is known about the expression of key genes involved in amyloid production by peripheral cells, such as lymphocytes, during the development of hypoxic-ischemic encephalopathy. We analyzed the gene expression of the amyloid protein precursor, β-secretase, presenilin 1 and 2 and hypoxia-inducible factor 1-α by RT-PCR in the lymphocytes of post-asphyxia and control neonates. In all examined periods after asphyxia, decreased expression of the genes of the amyloid protein precursor, β-secretase and hypoxia-inducible factor 1-α was noted in lymphocytes. Conversely, expression of presenilin 1 and 2 genes decreased on days 1–7 and 8–14 but increased after survival for more than 15 days. We believe that the expression of presenilin genes in lymphocytes could be a potential biomarker to determine the severity of the post-asphyxia neurodegeneration or to identify the underlying factors for brain neurodegeneration and get information about the time they occurred. This appears to be the first worldwide data on the role of the presenilin 1 and 2 genes associated with Alzheimer’s disease in the dysregulation of neonatal lymphocytes after perinatal asphyxia.

Reciprocal assessment of urinary beta-2-microglobulin and BUN levels in renal dysfunction of neonates with birth asphyxia

OBJECTIVE

Asphyxia at birth is one of the major causes of morbidity and mortality in all neonates due to various organ dysfunctions, for example, kidneys. Recent advances in this area have suggested new urinary proteins for the assessment of renal damage, including beta-2 microglobulin (β2-MG). The aim of this study was to investigate the changes of urinary β2-MG in asphyxiated neonates and to evaluate the value of combined detection of multiple biomarkers in the early diagnosis of acute kidney injury (AKI) in asphyxiated neonates.

STUDY DESIGN

This case-control study was performed on 84 term neonates in two control and case groups who were hospitalized at the neonatal intensive care unit. Using the Sarnat scoring system, the asphyxiated neonates were neurologically divided. Renal function tests and urinary β2-MG (uβ2-MG) levels of participants who registered based on inclusion criteria were measured. The data analyzed using descriptive and inferential statistical tests. The diagnostic value of the biomarker was determined using receiver operating characteristic (ROC) curves.

RESULTS

This study showed that uβ2-MG was not a statistically significant difference in both asphyxiated neonates with AKI and non-AKI (p = .085). Whereas, uβ2-MG levels were statistically significant in neurological grading of asphyxiated infants to two groups (p = .013). A new predictor, uβ2-MG and blood urea nitrogen (BUN); named BB1, was substituted as the diagnostic value in neonates with asphyxia with an area under the receiver operating characteristic curve (AUC) (95% CI) of 0.88 (0.76-1.0). This AUC was significantly greater than the value for uβ2-MG associated with AKI (p = .003).

CONCLUSION

Our findings showed that mutual detection of uβ2-MG levels with BUN should be an early indicator for the diagnosis of renal injury with greater specificity and improved prognostic accuracy after neonatal asphyxia.

Hypoxic postconditioning-induced neuroprotection increases neuronal autophagy via activation of the SIRT1/FoxO1 signaling pathway in rats with global cerebral ischemia

Hypoxic postconditioning (HPC) has been reported to be a beneficial and promising treatment for global cerebral ischemia (GCI). However, its neuroprotective mechanism remains unclear. The aim of the present study was to determine whether the protective effects of HPC in a rat model of GCI were due to the upregulation of autophagy via the silent information regulator transcript-1 (SIRT1)/Forkhead box protein 1 (FoxO1) pathway. Morris water maze test revealed that HPC attenuated cognitive damage in GCI rats. HPC also significantly increased the levels of the autophagy-related protein LC3-II, SIRT1 and FoxO1 compared with those in the GCI group. However, the HPC-induced LC3-II upregulation was blocked by the SIRT1 inhibitor EX527. These results suggested that the beneficial effects of HPC on GCI rats were due to the upregulation of ischemiainduced autophagy and involved the SIRT1/FoxO1 signaling pathway.

Neuroprotective effect of apigenin against hypoxic-ischemic brain injury in neonatal rats via activation of the PI3K/Akt/Nrf2 signaling pathway

Neonatal hypoxic-ischemic (HI) brain injury can lead to mortality and severe long-term disabilities including cerebral palsy and brain injury. However, the treatment options for neonatal hypoxic-ischemic (HI) brain injury are limited. Apigenin is abundantly present in vegetables, celery, and chamomile tea with diverse biological functions, such as anti-inflammatory, anti-apoptotic, antioxidant, and anticancer effects. However, it has not yet been reported whether apigenin exerts a neuroprotective effect against neonatal hypoxic-ischemic (HI) brain injury. In this study, we investigated whether apigenin could ameliorate HI brain injury and explored the associated mechanism using in vivo experiments. We found that apigenin remarkably reduced the infarct volume and ameliorated cerebral edema, decreased inflammatory response, inhibited apoptosis, promoted the recovery of tissue structure, and improved prognosis following HI brain injury. Mechanistically, we found that apigenin exerted a neuroprotective effect against HI brain injury by activating the PI3K/Akt/Nrf2 pathway. In summary, all these results demonstrate that apigenin could be a potential therapeutic approach for neonatal hypoxic-ischemic (HI) brain injury.

White matter injury in the neonatal hypoxic-ischemic brain and potential therapies targeting microglia

Neonatal hypoxic-ischemic (H-I) injury, which mainly causes neuronal damage and white matter injury (WMI), is among the predominant causes of infant morbidity (cerebral palsy, cognitive and persistent motor disabilities) and mortality. Disruptions to the oxygen and blood supply in the perinatal brain affect the cerebral microenvironment and may affect microglial activation, excitotoxicity, and oxidative stress. Microglia are significantly associated with axonal damage and myelinating oligodendrocytes, which are major pathological components of WMI. However, the effects of H-I injury on microglial functions and underlying transformation mechanisms remain poorly understood. The historical perception that these cells are major risk factors for ischemic stroke has been questioned due to our improved understanding of the diversity of microglial phenotypes and their alterable functions, which exacerbate or attenuate injuries in different regions in response to environmental instability. Unfortunately, although therapeutic hypothermia is an efficient treatment, death and disability remain the prognosis for a large proportion of neonates with H-I injury. Hence, novel neuroprotective therapies to treat WMI following H-I injury are urgently needed. Here, we review microglial mechanisms that might occur in the developing brain due to neonatal H-I injury and discuss whether microglia function as a double-edged sword in WMI. Then, we emphasize microglial heterogeneity, notably at the single-cell level, and sex-specific effects on the etiology of neurological diseases. Finally, we discuss current knowledge of strategies aiming to improve microglia modulation and remyelination following neonatal H-I injury. Overall, microglia-targeted therapy might provide novel and valuable insights into the treatment of neonatal H-I insult.

Neurotoxicity of Unconjugated Bilirubin in Neonatal Hypoxic-Ischemic Brain Injury in vitro

Background: The pathophysiology of bilirubin neurotoxicity in course of hypoxic-ischemic encephalopathy (HIE) in term and preterm infants is still poorly understood. We hypothesized that oxidative stress may be a common mechanism that link hyperbilirubinemia and HIE. Objectives: The objective of the present study was to evaluate whether unconjugated bilirubin (UCB) may enhance the HI brain injury by increasing oxidative stress and to test pioglitazone and allopurinol as new antioxidant therapeutic drugs in vitro. Methods: The effects of UCB were tested on organotypic hippocampal slices subjected to 30 min oxygen-glucose deprivation (OGD), used as in vitro model of HIE. The experiments were performed on mature (14 days in culture) and immature (7 days in culture) slices, to mimic the brains of term and preterm infants, respectively. Mature and immature slices were exposed to UCB, human serum albumin (HSA), pioglitazone, and/or allopurinol for 24 h, immediately after 30 min OGD. Neuronal injury was assessed using propidium iodide (PI) fluorescence. ROS formation was quantified by using the 2',7'-dichlorodihydrofluorescein diacetate (DCF-DA) method. Results: In mature slices, we found that the neurotoxicity, as well as oxidative stress, induced by OGD were enhanced by UCB. HSA significantly prevented UCB-increased neurotoxicity, but had a slight reduction on ROS production. Allopurinol, but not pioglitazone, significantly reduced UCB-increased neurotoxicity induced by OGD. In immature slices exposed to OGD, no increase of neuronal death was observed, whereas oxidative stress was detected after UCB exposure. HSA, pioglitazone and allopurinol have no protective effects on both OGD-induced neuronal death and on UCB-induced oxidative stress. For this reason, UCB, pioglitazone and allopurinol was also tested on ischemic preconditioning protocol. We found that UCB abolished the neuroprotection induced by preconditioning and increased oxidative stress. These effects were restored by allopurinol but not pioglitazone. Conclusions: UCB characterized a different path of neuronal damage and oxidative stress in mature and immature hippocampal slice model of HIE. Management of hyperbilirubinemia in a complex pathological condition, such as HIE and hyperbilirubinemia, should be very careful. Allopurinol could deserve attention as a novel pharmacological intervention for hyperbilirubinemia and HIE.

The Neonatal and Juvenile Pig in Pediatric Drug Discovery and Development

Pharmacotherapy in pediatric patients is challenging in view of the maturation of organ systems and processes that affect pharmacokinetics and pharmacodynamics. Especially for the youngest age groups and for pediatric-only indications, neonatal and juvenile animal models can be useful to assess drug safety and to better understand the mechanisms of diseases or conditions. In this respect, the use of neonatal and juvenile pigs in the field of pediatric drug discovery and development is promising, although still limited at this point. This review summarizes the comparative postnatal development of pigs and humans and discusses the advantages of the juvenile pig in view of developmental pharmacology, pediatric diseases, drug discovery and drug safety testing. Furthermore, limitations and unexplored aspects of this large animal model are covered. At this point in time, the potential of the neonatal and juvenile pig as nonclinical safety models for pediatric drug development is underexplored.

Acute symptomatic neonatal seizures, brain injury, and long-term outcome: The role of neuroprotective strategies

INTRODUCTION

Neonatal seizures are frequent but underdiagnosed manifestations of acute brain dysfunction and an important contributor to unfavorable outcomes. Etiology and severity of brain injury are the single strongest outcome determinants.

AREAS COVERED

The authors will discuss the prognostic role of acute symptomatic seizures versus brain injury and the main neuroprotective and neurorestorative strategies for full-term and preterm infants.

EXPERT OPINION

Prolonged acute symptomatic seizures likely contribute to long-term outcomes by independently adding further brain injury to initial insults. Correct timing and dosing of therapeutic interventions, depending on etiology and gestational ages, need careful evaluation. Although promising strategies are under study, the only standard of care is whole-body therapeutic hypothermia in full-term newborns with hypoxic-ischemic encephalopathy.

S100a8 silencing attenuates inflammation, oxidative stress and apoptosis in BV2 cells induced by oxygen‑glucose deprivation and reoxygenation by upregulating GAB1 expression

S100a8 serves an important role in cell differentiation and is abnormally expressed in common tumors, but there are few studies on the association between S100a8 and brain I/R injury. The present study aimed to investigate the role of S100a8 in oxygen-glucose deprivation and reoxygenation (OGD/R)-induced BV2 microglia cell injury, and to elucidate the potential underlying molecular mechanisms. BV2 cells were exposed to OGD/R to mimic ischemia/reperfusion (I/R) injury in vitro. S100a8 expression was detected via reverse transcription-quantitative PCR and western blot analyses. Following transfection with short hairpin RNAs targeting S100a8, the levels of inflammatory cytokines and oxidative stress-related factors were determined using commercial kits. Apoptosis was assessed using flow cytometric analysis and the expression levels of apoptosis-related proteins were determined using western blot analysis. Subsequently, the mRNA and protein levels of Grb2-associated binder 1 (GAB1) were assessed following S100a8 silencing. Immunoprecipitation (IP) was performed to verify the association between S100a8 and GAB1. The levels of inflammation, oxidative stress and apoptosis were assessed following GAB1 silencing, along with S100a8 silencing in BV2 cells subjected to OGD/R. The results indicated that exposure to OGD/R markedly upregulated S100a8 expression in BV2 cells. S100a8 silencing inhibited inflammation, oxidative stress and apoptosis, accompanied by changes in the expression of related proteins. The IP assay revealed a strong interaction between GAB1 and S100a8. In addition, GAB1 silencing reversed the inhibitory effects of S100a8 silencing on inflammation, oxidative stress and apoptosis in OGD/R-stimulated BV2 cells. Taken together, the results of the present study demonstrated that S100a8 silencing alleviated inflammation, oxidative stress and the apoptosis of BV2 cells induced by OGD/R, partly by upregulating the expression of GAB1. Thus, these findings may potentially provide a novel direction to develop therapeutic strategies for cerebral I/R injury.

The Function of the NMDA Receptor in Hypoxic-Ischemic Encephalopathy

Hypoxic-ischemic encephalopathy (HIE) is one of the main forms of neonatal brain injury which could lead to neonatal disability or even cause neonatal death. Therefore, HIE strongly affects the health of newborns and brings heavy burden to the family and society. It has been well studied that N-methyl-D-aspartate (NMDA) receptors are involved in the excitotoxicity induced by hypoxia ischemia in adult brain. Recently, it has been shown that the NMDA receptor also plays important roles in HIE. In the present review, we made a summary of the molecular mechanism of NMDA receptor in the pathological process of HIE, focusing on the distinct role of GluN2A- and GluN2B-containing NMDA receptor subtypes and aiming to provide some insights into the clinical treatment and drug development of HIE.

How to Improve the Antioxidant Defense in Asphyxiated Newborns-Lessons from Animal Models

Oxygen free radicals have been implicated in brain damage after neonatal asphyxia. In the early phase of asphyxia/reoxygenation, changes in antioxidant enzyme activity play a pivotal role in switching on and off the cascade of events that can kill the neurons. Hypoxia/ischemia (H/I) forces the brain to activate endogenous mechanisms (e.g., antioxidant enzymes) to compensate for the lost or broken neural circuits. It is important to evaluate therapies to enhance the self-protective capacity of the brain. In animal models, decreased body temperature during neonatal asphyxia has been shown to increase cerebral antioxidant capacity. However, in preterm or severely asphyxiated newborns this therapy, rather than beneficial seems to be harmful. Thus, seeking new therapeutic approaches to prevent anoxia-induced complications is crucial. Pharmacotherapy with deferoxamine (DFO) is commonly recognized as a beneficial regimen for H/I insult. DFO, via iron chelation, reduces oxidative stress. It also assures an optimal antioxidant protection minimizing depletion of the antioxidant enzymes as well as low molecular antioxidants. In the present review, some aspects of recently acquired insight into the therapeutic effects of hypothermia and DFO in promoting neuronal survival after H/I are discussed.