Perinatal Hyperoxia and Developmental Consequences on the Lung-Brain Axis

Mechanistic advances of hyperoxia-induced immature brain injury

The impact of hyperoxia-induced brain injury in preterm infants is being increasingly investigated. However, the parameters and protocols used to study this condition in animal models lack consistency. Research is further hampered by the fact that hyperoxia exerts both direct and indirect effects on oligodendrocytes and neurons, with the precise underlying mechanisms remaining unclear. In this article, we aim to provide a comprehensive overview of the conditions used to induce hyperoxia in animal models of immature brain injury. We discuss what is known regarding the mechanisms underlying hyperoxia-induced immature brain injury, focusing on the effects on oligodendrocytes and neurons, and briefly describe therapies that may counteract the effects of hyperoxia. We also identify further studies required to fully elucidate the effects of hyperoxia on the immature brain as well as discuss the leading therapeutic options.

Adverse Skeletal Muscle Adaptations in Individuals Born Preterm-A Comprehensive Review

Infants born preterm face an increased risk of deleterious effects on lung and brain health that can significantly alter long-term function and quality of life and even lead to death. Moreover, preterm birth is also associated with a heightened risk of diabetes and obesity later in life, leading to an increased risk of all-cause mortality in young adults born prematurely. While these preterm-birth-related conditions have been well characterized, less is known about the long-term effects of preterm birth on skeletal muscle health and, specifically, an individual's skeletal muscle hypertrophic potential later in life. In this review, we discuss how a confluence of potentially interrelated and self-perpetuating elements associated with preterm birth might converge on anabolic and catabolic pathways to ultimately blunt skeletal muscle hypertrophy, identifying critical areas for future research.

The emerging role of extracellular vesicles in bronchopulmonary dysplasia

Extracellular vesicle (EV) biology in neonatal lung development and disease is a rapidly growing area of investigation. Although EV research in the neonatal population lags behind EV research in adult lung diseases, recent discoveries demonstrate promise in furthering our understanding of the pathophysiology of bronchopulmonary dysplasia and the potential use of EVs in the clinical setting, as both biomarkers and therapeutic agents. This review article explores some of the recent advances in this field and our evolving knowledge of the role of EVs in bronchopulmonary dysplasia.

Delta like 4 regulates cerebrovascular development and endothelial integrity via DLL4-NOTCH-CLDN5 pathway and is vulnerable to neonatal hyperoxia

The mechanisms governing brain vascularization during development remain poorly understood. A key regulator of developmental vascularization is delta like 4 (DLL4), a Notch ligand prominently expressed in endothelial cells (EC). Exposure to hyperoxia in premature infants can disrupt the development and functions of cerebral blood vessels and lead to long-term cognitive impairment. However, its role in cerebral vascular development and the impact of postnatal hyperoxia on DLL4 expression in mouse brain EC have not been explored. We determined the DLL4 expression pattern and its downstream signalling gene expression in brain EC using Dll4+/+ and Dll4+/LacZ mice. We also performed in vitro studies using human brain microvascular endothelial cells. Finally, we determined Dll4 and Cldn5 expression in mouse brain EC exposed to postnatal hyperoxia. DLL4 is expressed in various cell types, with EC being the predominant one in immature brains. Moreover, DLL4 deficiency leads to persistent abnormalities in brain microvasculature and increased vascular permeability both in vivo and in vitro. We have identified that DLL4 insufficiency compromises endothelial integrity through the NOTCH-NICD-RBPJ-CLDN5 pathway, resulting in the downregulation of the tight junction protein claudin 5 (CLDN5). Finally, exposure to neonatal hyperoxia reduces DLL4 and CLDN5 expression in developing mouse brain EC. We reveal that DLL4 is indispensable for brain vascular development and maintaining the blood-brain barrier's function and is repressed by neonatal hyperoxia. We speculate that reduced DLL4 signalling in brain EC may contribute to the impaired brain development observed in neonates exposed to hyperoxia. KEY POINTS: The role of delta like 4 (DLL4), a Notch ligand in vascular endothelial cells, in brain vascular development and functions remains unknown. We demonstrate that DLL4 is expressed at a high level during postnatal brain development in immature brains and DLL4 insufficiency leads to abnormal cerebral vasculature and increases vascular permeability both in vivo and in vitro. We identify that DLL4  regulates endothelial integrity through NOTCH-NICD-RBPJ-CLDN5 signalling. Dll4 and Cldn5 expression are decreased in mouse brain endothelial cells exposed to postnatal hyperoxia.

Genetic Ablation of Pyruvate Dehydrogenase Kinase Isoform 4 Gene Enhances Recovery from Hyperoxic Lung Injury: Insights into Antioxidant and Inflammatory Mechanisms

BACKGROUND

Pyruvate dehydrogenase kinase isoform 4 (PDK4) plays a pivotal role in the regulation of cellular proliferation and apoptosis. The objective of this study was to examine whether the genetic depletion of the PDK4 gene attenuates hyperoxia-induced lung injury in neonatal mice.

METHODS

Neonatal PDK4-/- mice and wild-type (WT) mice were exposed to oxygen concentrations of 21% (normoxia) and 95% (hyperoxia) for the first 4 days of life. Pulmonary histological assessments were performed, and the mRNA levels of lung PDK4, monocyte chemoattractant protein (MCP)-1 and interleukin (IL)-6 were assessed. The levels of inflammatory cytokines in lung tissue were quantified.

RESULTS

Following convalescence from neonatal hyperoxia, PDK4-/- mice exhibited improved lung alveolarization. Notably, PDK4-/- mice displayed significantly elevated MCP-1 protein levels in pulmonary tissues following 4 days of hyperoxic exposure, whereas WT mice showed increased IL-6 protein levels under similar conditions. Furthermore, neonatal PDK4-/- mice subjected to hyperoxia demonstrated markedly higher MCP-1 mRNA expression at 4 days of age compared to WT mice, while IL-6 mRNA expression remained unaffected in PDK4-/- mice.

CONCLUSIONS

Newborn PDK4-/- mice exhibited notable recovery from hyperoxia-induced lung injury, suggesting the potential protective role of PDK4 depletion in mitigating lung damage.

Maternal exposure to particulate matter from duck houses restricts fetal growth due to inflammatory damage and oxidative stress

The composition of particulate matter (PM) in poultry farms differs significantly from that of atmospheric PM as there is a higher concentration of microbes on farms. To assess the health effects of PM from poultry farms on pregnant animals, we collected PM from duck houses using a particulate sampler, processed it via centrifugation and vacuum concentration, and subsequently exposed the mice to airborne PM at 0.48 mg/m3 (i.e., low concentration group) and 1.92 mg/m3 (i.e., high concentration group) on the fifth day of pregnancy. After exposure until the twentieth day of pregnancy or spontaneous delivery, mice were euthanized for sampling. The effects of PM from duck houses on the pregnancy toxicity of mice were analyzed using histopathological analysis, enzyme-linked immunosorbent assay, and quantitative real-time polymerase chain reaction (qPCR). The results showed that exposure to PM had adverse effects on pregnant mice that reduced their feed intake in both groups. Microscopic lesions were observed in the lungs and placentas of pregnant mice, and the lesions worsened with increased PM concentrations, as shown by alveolar wall thickening, the infiltration of inflammatory cells in pulmonary interstitium, congestion, edema, and cellular degeneration of placenta. In pregnant mice in the high concentration group, exposure to PM significantly increased the expression of inflammatory cytokines in the lungs and placentas, caused oxidative stress, and decreased estrogen level in the blood. Exposure to PM also resulted in the reduced litter sizes of pregnant mice and shorter body and tail lengths in the fetuses delivered. Beyond that, exposure to PM significantly downregulated the levels of antioxidant factor superoxide dismutase and neurotrophic factor Ngf in the brains of fetuses. Collectively, exposure to a high concentration of PM by inhalation among pregnant mice caused significant pregnancy toxicity that led to abnormal fetal development due to inflammatory damage and oxidative stress. These findings established a foundation for future studies on the underlying mechanisms of pregnancy toxicity induced by exposure to PM.

Correlation between the Closure Time of Patent Ductus Arteriosus in Preterm Infants and Long-Term Neurodevelopmental Outcome

In patent ductus arteriosus (PDA) in preterm infants, the relationship between treatment timing and long-term developmental prognosis remains unclear. The purpose of this study was to clarify the relationship between the age in days when ductus arteriosus closure occurred and long-term development. Preterm infants with a birth weight of less than 1500 g who were admitted to our NICU over a period of 9 years (2011-2019) and were diagnosed with PDA were included. A new version of the K-type developmental test for corrected ages of 1.5 and 3 years was used as an index of development. The relationship between the duration of PDA and the developmental index was evaluated using Pearson's correlation coefficient, and multiple regression analysis was performed. Development quotient (DQ) at the ages of 1.5 and 3 years showed a correlation with the PDA closure date and the standard deviation (SD) value of the term birth weight. Multiple regression analysis showed a positive correlation of the DQ at 1.5 and 3 years with the SD value of the term birth weight and a negative correlation with the PDA closure date. In addition, a stronger correlation was found in the "posture/motor" sub-item at 3 years. On the other hand, the analysis including preterm infants without PDA showed that preterm infants with PDA closure on the 6th day or later after birth had a significantly lower 3-year-old DQ than preterm infants with a PDA exposure within 5 days. In conclusion, it is suggested that the decrease in cerebral blood flow due to PDA in preterm infants has an adverse effect on long-term neurodevelopment. Appropriate interventions, including surgical treatment for PDA in preterm infants without delay, ideally within 5 days of birth, may be effective in improving the developmental prognosis.

A review of the effects of early postnatal hyperoxia exposure on the immature brain

Preterm birth is a public health priority worldwide, with approximately 15 million premature babies born each year. Oxygen supplementation is one of the most common interventions for preterm infants. However, prolonged oxygen inhalation at supraphysiological concentrations can lead to the development of bronchopulmonary dysplasia (BPD). In addition to lifelong pulmonary sequelae, clinical evidence suggests that BPD is associated with adverse neurodevelopmental outcomes, such as motor impairment, cognitive impairment, and behavioral deficits, severely affecting the quality of life of preterm infants. However, the mechanisms underlying the combination of neurodevelopmental impairment with BPD remain unclear. Therefore, in recent years, attention has also been focused on the effects of hyperoxia on brain development in preterm infants. In this review, we outline the pathophysiological mechanisms of brain injury caused by developmental hyperoxia exposure in current animal models and briefly describe the pharmacological therapies that may be applicable to the associated brain injury. Overall, more studies are needed to assess the effects of hyperoxia on the immature brain, particularly combined analyses of the lungs and brain in the same experimental setting, to elucidate the potential causes of combined neurodevelopmental impairment in BPD.

Association between bronchopulmonary dysplasia and death or neurodevelopmental impairment at 3 years in preterm infants without severe brain injury

Objective

We investigated the association between bronchopulmonary dysplasia (BPD) and 3 years death or neurodevelopmental impairment (NDI) in very preterm infants without severe brain injury.

Method

Our prospective cohort study recruited preterm infants who were born prior to 32 weeks of gestational age and survived in the neonatal intensive care unit until 36 weeks of corrected age. Upon reaching 3 years of age, each infant was assessed for death or NDI such as cerebral palsy, cognitive deficit, hearing loss, and blindness. Correlations between BPD and death or NDI were determined using multiple logistic regression analyses adjusted for confounding factors.

Result

A total of 1,417 infants without severe brain injury who survived until 36 weeks of corrected age were initially enrolled in the study. Over the study period, 201 infants were lost to follow-up and 5 infants were excluded. Our final dataset, therefore, included 1,211 infants, of which 17 died after 36 weeks of corrected age and 1,194 were followed up to 3 years of age. Among these infants, 337 (27.8%) developed BPD. Interestingly, by 3 years of age, BPD was demonstrated to be independently associated with death or NDI, with an adjusted odds ratio of 1.935 (95% confidence interval: 1.292-2.899, p = 0.001), in preterm infants without severe neonatal brain injury.

Conclusion

Our findings indicate that BPD is strongly associated with death or NDI in preterm infants without severe neonatal brain injury at 3 years of age. Further research is needed to understand the mechanisms linking the development of BPD with death or NDI and whether appropriate treatment of BPD may ameliorate or prevent the development of neurological complications.

Emerging role of metabolic reprogramming in hyperoxia-associated neonatal diseases

Oxygen therapy is common during the neonatal period to improve survival, but it can increase the risk of oxygen toxicity. Hyperoxia can damage multiple organs and systems in newborns, commonly causing lung conditions such as bronchopulmonary dysplasia and pulmonary hypertension, as well as damage to other organs, including the brain, gut, and eyes. These conditions are collectively referred to as newborn oxygen radical disease to indicate the multi-system damage caused by hyperoxia. Hyperoxia can also lead to changes in metabolic pathways and the production of abnormal metabolites through a process called metabolic reprogramming. Currently, some studies have analyzed the mechanism of metabolic reprogramming induced by hyperoxia. The focus has been on mitochondrial oxidative stress, mitochondrial dynamics, and multi-organ interactions, such as the lung-gut, lung-brain, and brain-gut axes. In this article, we provide an overview of the major metabolic pathway changes reported in hyperoxia-associated neonatal diseases and explore the potential mechanisms of metabolic reprogramming. Metabolic reprogramming induced by hyperoxia can cause multi-organ metabolic disorders in newborns, including abnormal glucose, lipid, and amino acid metabolism. Moreover, abnormal metabolites may predict the occurrence of disease, suggesting their potential as therapeutic targets. Although the mechanism of metabolic reprogramming caused by hyperoxia requires further elucidation, mitochondria and the gut-lung-brain axis may play a key role in metabolic reprogramming.

The role of oxygen in the development and treatment of bronchopulmonary dysplasia

Oxygen (O2) is crucial for both the development and treatment of one of the most important consequences of prematurity: bronchopulmonary dysplasia (BPD). In fetal life, the hypoxic environment is important for alveolar development and maturation. After birth, O2 becomes a double-edged sword. While O2 is needed to prevent hypoxia, it also causes oxidative stress leading to a plethora of morbidities, including retinopathy and BPD. The advent of continuous O2 monitoring with pulse oximeters has allowed clinicians to recognize the narrow therapeutic margins of oxygenation for the preterm infant, but more knowledge is needed to understand what these ranges are at different stages of the preterm infant's life, including at birth, in the neonatal intensive care unit and after hospital discharge. Future research, especially in innovative technologies such as automated O2 control and remote oximetry, will improve the understanding and treatment of the O2 needs of infants with BPD.

GSDMD gene knockout alleviates hyperoxia-induced hippocampal brain injury in neonatal mice

BACKGROUND

Neonatal hyperoxia exposure is associated with brain injury and poor neurodevelopment outcomes in preterm infants. Our previous studies in neonatal rodent models have shown that hyperoxia stimulates the brain's inflammasome pathway, leading to the activation of gasdermin D (GSDMD), a key executor of pyroptotic inflammatory cell death. Moreover, we found pharmacological inhibition of caspase-1, which blocks GSDMD activation, attenuates hyperoxia-induced brain injury in neonatal mice. We hypothesized that GSDMD plays a pathogenic role in hyperoxia-induced neonatal brain injury and that GSDMD gene knockout (KO) will alleviate hyperoxia-induced brain injury.

METHODS

Newborn GSDMD knockout mice and their wildtype (WT) littermates were randomized within 24 h after birth to be exposed to room air or hyperoxia (85% O2) from postnatal days 1 to 14. Hippocampal brain inflammatory injury was assessed in brain sections by immunohistology for allograft inflammatory factor 1 (AIF1) and CD68, markers of microglial activation. Cell proliferation was evaluated by Ki-67 staining, and cell death was determined by TUNEL assay. RNA sequencing of the hippocampus was performed to identify the transcriptional effects of hyperoxia and GSDMD-KO, and qRT-PCR was performed to confirm some of the significantly regulated genes.

RESULTS

Hyperoxia-exposed WT mice had increased microglia consistent with activation, which was associated with decreased cell proliferation and increased cell death in the hippocampal area. Conversely, hyperoxia-exposed GSDMD-KO mice exhibited considerable resistance to hyperoxia as O2 exposure did not increase AIF1 + , CD68 + , or TUNEL + cell numbers or decrease cell proliferation. Hyperoxia exposure differentially regulated 258 genes in WT and only 16 in GSDMD-KO mice compared to room air-exposed WT and GSDMD-KO, respectively. Gene set enrichment analysis showed that in the WT brain, hyperoxia differentially regulated genes associated with neuronal and vascular development and differentiation, axonogenesis, glial cell differentiation, hypoxia-induced factor 1 pathway, and neuronal growth factor pathways. These changes were prevented by GSDMD-KO.

CONCLUSIONS

GSDMD-KO alleviates hyperoxia-induced inflammatory injury, cell survival and death, and alterations of transcriptional gene expression of pathways involved in neuronal growth, development, and differentiation in the hippocampus of neonatal mice. This suggests that GSDMD plays a pathogenic role in preterm brain injury, and targeting GSDMD may be beneficial in preventing and treating brain injury and poor neurodevelopmental outcomes in preterm infants.

The emerging roles of SUMOylation in pulmonary diseases

Small ubiquitin-like modifier mediated modification (SUMOylation) is a critical post-translational modification that has a broad spectrum of biological functions, including genome replication and repair, transcriptional regulation, protein stability, and cell cycle progression. Perturbation or deregulation of a SUMOylation and deSUMOylation status has emerged as a new pathophysiological feature of lung diseases. In this review, we highlighted the link between SUMO pathway and lung diseases, especially the sumoylated substrate such as C/EBPα in bronchopulmonary dysplasia (BDP), PPARγ in pneumonia, TFII-I in asthma, HDAC2 in chronic obstructive pulmonary disease (COPD), KLF15 in hypoxic pulmonary hypertension (HPH), SMAD3 in idiopathic pulmonary fibrosis (IPF), and YTHDF2 in cancer. By exploring the impact of SUMOylation in pulmonary diseases, we intend to shed light on its potential to inspire the development of innovative diagnostic and therapeutic strategies, holding promise for improving patient outcomes and overall respiratory health.

Prevention of Chronic Morbidities in Extremely Premature Newborns with LISA-nCPAP Respiratory Therapy and Adjuvant Perinatal Strategies

Less invasive surfactant administration techniques, together with nasal continuous airway pressure (LISA-nCPAP) ventilation, an emerging noninvasive ventilation (NIV) technique in neonatology, are gaining more significance, even in extremely premature newborns (ELBW), under 27 weeks of gestational age. In this review, studies on LISA-nCPAP are compiled with an emphasis on short- and long-term morbidities associated with prematurity. Several perinatal preventative and therapeutic investigations are also discussed in order to start integrated therapies as numerous organ-saving techniques in addition to lung-protective ventilations. Two thirds of immature newborns can start their lives on NIV, and one third of them never need mechanical ventilation. With adjuvant intervention, these ratios are expected to be increased, resulting in better outcomes. Optimized cardiopulmonary transition, especially physiologic cord clamping, could have an additively beneficial effect on patient outcomes gained from NIV. Organ development and angiogenesis are strictly linked not only in the immature lung and retina, but also possibly in the kidney, and optimized interventions using angiogenic growth factors could lead to better morbidity-free survival. Corticosteroids, caffeine, insulin, thyroid hormones, antioxidants, N-acetylcysteine, and, moreover, the immunomodulatory components of mother's milk are also discussed as adjuvant treatments, since immature newborns deserve more complex neonatal interventions.

Dexmedetomidine Protects Cerebellar Neurons against Hyperoxia-Induced Oxidative Stress and Apoptosis in the Juvenile Rat

The risk of oxidative stress is unavoidable in preterm infants and increases the risk of neonatal morbidities. Premature infants often require sedation and analgesia, and the commonly used opioids and benzodiazepines are associated with adverse effects. Impairment of cerebellar functions during cognitive development could be a crucial factor in neurodevelopmental disorders of prematurity. Recent studies have focused on dexmedetomidine (DEX), which has been associated with potential neuroprotective properties and is used as an off-label application in neonatal units. Wistar rats (P6) were exposed to 80% hyperoxia for 24 h and received as pretreatment a single dose of DEX (5µg/kg, i.p.). Analyses in the immature rat cerebellum immediately after hyperoxia (P7) and after recovery to room air (P9, P11, and P14) included examinations for cell death and inflammatory and oxidative responses. Acute exposure to high oxygen concentrations caused a significant oxidative stress response, with a return to normal levels by P14. A marked reduction of hyperoxia-mediated damage was demonstrated after DEX pretreatment. DEX produced a much earlier recovery than in controls, confirming a neuroprotective effect of DEX on alterations elicited by oxygen stress on the developing cerebellum.

Protective effect of resveratrol on mitochondrial biogenesis during hyperoxia-induced brain injury in neonatal pups

BACKGROUND

Neonatal hyperoxic brain injury is caused by exposure to hyperphysiological oxygen content during the period of incomplete development of the oxidative stress defence system, resulting in a large number of reactive oxygen species (ROS) and causing damage to brain tissue. Mitochondrial biogenesis refers to the synthesis of new mitochondria from existing mitochondria, mostly through the PGC-1α/Nrfs/TFAM signalling pathway. Resveratrol (Res), a silencing information regulator 2-related enzyme 1 (Sirt1) agonist, has been shown to upregulate the level of Sirt1 and the expression of peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α). We speculate that Res has a protective effect on hyperoxia-induced brain injury through mitochondrial biogenesis.

METHODS

Sprague-Dawley (SD) pups were randomly divided into the nonhyperoxia (NN) group, the nonhyperoxia with dimethyl sulfoxide (ND) group, the nonhyperoxia with Res (NR) group, the hyperoxia (HN) group, the hyperoxia with dimethyl sulfoxide (HD) group, and the hyperoxia with Res (HR) group within 12 h after birth. The HN, HD, and HR groups were placed in a high-oxygen environment (80‒85%), and the other three groups were placed in the standard atmosphere. The NR and HR groups were given 60 mg/kg Res every day, the ND and HD groups were given the same dose of dimethyl sulfoxide (DMSO) every day, and the NN and HN groups were given the same dose of normal saline every day. On postnatal day (PN) 1, PN7, and PN14, brain samples were acquired for HE staining to assess pathology, TUNEL to detect apoptosis, and real-time quantitative polymerase chain reaction and immunoblotting to detect the expression levels of Sirt1, PGC-1α, nuclear respiratory factor 1 (Nrf1), nuclear respiratory factor 2 (Nrf2) and mitochondrial transcription factor A (TFAM) in brain tissue.

RESULTS

Hyperoxia induced brain tissue injury; increased brain tissue apoptosis; inhibited Sirt1, PGC-1α, Nrf1, Nrf2, TFAM mRNA expression in mitochondria; diminished the ND1 copy number and ND4/ND1 ratio; and decreased Sirt1, PGC-1α, Nrf1, Nrf2, and TFAM protein levels in the brain. In contrast, Res reduced brain injury and attenuated brain tissue apoptosis in neonatal pups and increased the levels of the corresponding indices.

CONCLUSION

Res has a protective effect on hyperoxia-induced brain injury in neonatal SD pups by upregulating Sirt1 and stimulating the PGC-1α/Nrfs/TFAM signalling pathway for mitochondrial biogenesis.

Protective Effect of Dexmedetomidine against Hyperoxia-Damaged Cerebellar Neurodevelopment in the Juvenile Rat

Impaired cerebellar development of premature infants and the associated impairment of cerebellar functions in cognitive development could be crucial factors for neurodevelopmental disorders. Anesthetic- and hyperoxia-induced neurotoxicity of the immature brain can lead to learning and behavioral disorders. Dexmedetomidine (DEX), which is associated with neuroprotective properties, is increasingly being studied for off-label use in the NICU. For this purpose, six-day-old Wistar rats (P6) were exposed to hyperoxia (80% O₂) or normoxia (21% O₂) for 24 h after DEX (5 µg/kg, i.p.) or vehicle (0.9% NaCl) application. An initial detection in the immature rat cerebellum was performed after the termination of hyperoxia at P7 and then after recovery in room air at P9, P11, and P14. Hyperoxia reduced the proportion of Calb1+-Purkinje cells and affected the dendrite length at P7 and/or P9/P11. Proliferating Pax6+-granule progenitors remained reduced after hyperoxia and until P14. The expression of neurotrophins and neuronal transcription factors/markers of proliferation, migration, and survival were also reduced by oxidative stress in different manners. DEX demonstrated protective effects on hyperoxia-injured Purkinje cells, and DEX without hyperoxia modulated neuronal transcription in the short term without any effects at the cellular level. DEX protects hyperoxia-damaged Purkinje cells and appears to differentially affect cerebellar granular cell neurogenesis following oxidative stress.

Neonatal Oxidative Stress Impairs Cortical Synapse Formation and GABA Homeostasis in Parvalbumin-Expressing Interneurons

Neonatal brain injury is often caused by preterm birth. Brain development is vulnerable to increased environmental stress, including oxidative stress challenges. Due to a premature change of the fetal living environment from low oxygen in utero into postnatal high-oxygen room air conditions ex utero, the immature preterm brain is exposed to a relative hyperoxia, which can induce oxidative stress and impair neuronal cell development. To simulate the drastic increase of oxygen exposure in the immature brain, 5-day-old C57BL/6 mice were exposed to hyperoxia (80% oxygen) for 48 hours or kept in room air (normoxia, 21% oxygen) and mice were analyzed for maturational alterations of cortical GABAergic interneurons. As a result, oxidative stress was indicated by elevated tyrosine nitration of proteins. We found perturbation of perineuronal net formation in line with decreased density of parvalbumin-expressing (PVALB) cortical interneurons in hyperoxic mice. Moreover, maturational deficits of cortical PVALB+ interneurons were obtained by decreased glutamate decarboxylase 67 (GAD67) protein expression in Western blot analysis and lower gamma-aminobutyric acid (GABA) fluorescence intensity in immunostaining. Hyperoxia-induced oxidative stress affected cortical synaptogenesis by decreasing synapsin 1, synapsin 2, and synaptophysin expression. Developmental delay of synaptic marker expression was demonstrated together with decreased PI3K-signaling as a pathway being involved in synaptogenesis. These results elucidate that neonatal oxidative stress caused by increased oxygen exposure can lead to GABAergic interneuron damage which may serve as an explanation for the high incidence of psychiatric and behavioral alterations found in preterm infants.