Neonatal Rat Model Research Articles

Neuroprotective actions of pterostilbene on hypoxic-ischemic brain damage in neonatal rats through upregulation of heme oxygenase-1

Neonatal hypoxic–ischemic (HI) brain damage causes acute mortality and morbidity in newborns and long-term neurological disorders in the survivors. Pterostilbene (PTE) is a natural compound possessing various biological and pharmacological activities. In the present study, we aimed to investigate the effect of PTE on neonatal HI brain damagein P7 rat model and to explore the possible mechanisms. Neonatal HI brain damage was induced in rat pups (P7). Prior to the induction of HI injury, PTE was injected with or without zinc protoporphyrin IX (ZnPP), an inhibitor of heme oxygenase-1 (HO-1). ZnPP was used to test whether abnormal changes of HO-1 expression were involved in the effect of PTE. The results showed that PTE exhibited excellent neuroprotective effects against neonatal HI brain injury, as evidenced by the decrease of brain infarct volume, brain edema, neurological score, and improvement in motor coordination motor deficit and working memory deficit. PTE pretreatment decreased the expression of several proinflammatory cytokines, including TNFα, IL-1β, IL-6, and key transcription factor p65 NF-κB, and reduced the number of TUNEL-stained neurons, indicating the inhibition of inflammation and programmed cell death. Moreover, PTE pretreatment decreased thiobarbituric acid reactive substances content, increased superoxide dismutase activity and decreased reactive oxygen species level, indicating that PTE played an important antioxidant role. Furthermore, ZnPP was able to inhibit PTE-induced suppression of oxidative stress, programmed cell death, inflammation and brain damage. In conclusion, PTE pretreatment prevented HI-induced brain injury in newborns through HO-1-mediated reduction of oxidative stress, programmed cell death, and inflammation, and final improvement of histological and functional injury. Overall, the data that obtained in rat model provide novel insights into the pathogenesis of neonatal HI brain injury and may be translational to human clinical intervention for HI-associated brain injury in newborns.

Postnatal growth restriction augments oxygen-induced pulmonary hypertension in a neonatal rat model of bronchopulmonary dysplasia

Prematurity and fetal growth restriction are risk factors for pulmonary hypertension (PH) in infants with bronchopulmonary dysplasia (BPD). Neonatal rats develop PH and vascular remodeling when exposed to hyperoxia. We hypothesize that postnatal growth restriction (PNGR) due to under-nutrition increases the severity of PH induced by hyperoxia in neonatal rats. Pups were randomized at birth to litters maintained in room air or 75% oxygen (hyperoxia), together with litters of normal milk intake (10 pups) or PNGR (17 pups). After 14 d, right ventricular hypertrophy (RVH) was assessed by Fulton's index (right ventricular weight/left ventricular plus septal weight) and PH by echocardiography. Lungs were analyzed by immunohistochemistry, morphometrics, western blotting, and metabolomics. Hyperoxia and PNGR each significantly increased pulmonary arterial pressure, RVH and pulmonary arterial medial wall thickness, and significantly decreased pulmonary vessel number. These changes were significantly augmented in pups exposed to both insults. Hyperoxia and PNGR both significantly decreased expression of proteins involved in lung development and vasodilation. PNGR induces right ventricular and pulmonary vascular remodeling and augments the effects of oxygen in neonatal rats. This may be a powerful tool to investigate the mechanisms that induce PH in low-birth-weight preterm infants with BPD.

Helium preconditioning protects the brain against hypoxia/ischemia injury via improving the neurovascular niche in a neonatal rat model

This study aimed to investigate whether helium preconditioning (He-PC) is able to exert neuroprotective effects via improving focal neurovascular niche in a neonatal rat hypoxia/ischemia (HI) brain injury model. Seven day old rat pups were divided into control group, HI group and He-PC group. HI was induced by exposure to 8% oxygen for 90min one day after preconditioning with 70% helium—30% oxygen for three 5-min periods. At 3 and 7 days, the brain was collected for the detection of inflammation related factors (tumor necrosis factor α [TNF-α], interleukin-1β [IL-1β], IL-10) and growth/neurotrophic factors (brain-derived neurotrophic factor [BDNF], basic fibroblast growth factor [bFGF] and nerve growth factor [NGF]); at 7 days, neurobehaviors were evaluated, and the brain was collected for the detection of mRNA expression of vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang-1) by PCR, protein expression of angiogenesis related molecules (VEGF, Ang-1, Tie-2 and Flt-1) by Western blotting and microvessel density (MCD) by immunohistochemistry for vWF. Results showed He-PC was able to reduce TNF-α and IL-1β, further increase IL-10, BDNF, bFGF and NGF, elevate the mRNA expression of VEGF and Ang-1, increase the protein expression of VEGF, Ang-1, Tie-2 and Flt-1, promote angiogenesis and improve neurobehaviors as compared to HI group. These findings suggest that He-PC may improve the post-stroke neurovascular niche to exert neuroprotective effects on neonatal HI brain injury.

Intranasal surfactant protein D as neuroprotective rescue in a neonatal rat model of periventricular leukomalacia

Background: Periventricular leukomalacia (PVL) is the leading cause of neurocognitive deficits in children with prematurity. We previously hypothesized that surfactant protein D (SPD) with its ability to bind toll-like receptors may have a possible ameliorating effect in PVL.Methods: Three groups were defined as: LPS-administered and postnatal intranasal saline administered group, LPS-administered and postnatal intranasal SPD-treated group, and control group. Twenty-eight offspring rats were reared with their dams until their sacrifice for histological evaluation on day 7.Results: A significant loss of brain weight occurred in the LPS group compared with controls. The postnatal intranasal SPD treatment significantly reduced the number of TUNEL-positive cells in the periventricular white matter as compared with the LPS-treated group. Compared with the control group, LPS injection in the rat brain significantly reduced the MBP-positive staining. Postnatal SPD treatment greatly prevented LPS-stimulated loss of MBP staining.Conclusions: Present study demonstrated a neuroprotective effect of SPD in a rat model of PVL. Our results offer future implications towards increasing our understanding about multifactorial mechanisms underlying periventricular leukomalacia and developing plausible therapeutic strategies in order to prevent neurocognitive deficits in preterm infants.

Effect of hyperbaric oxygen on lipid peroxidation and visual development in neonatal rats with hypoxia-ischemia brain damage.

The aim of the present study was to investigate the effect of hyperbaric oxygen (HBO) on lipid peroxidation and visual development in a neonatal rat model of hypoxic-ischemic brain damage (HIBD). The rat models of HIBD were established by delayed uterus dissection and were divided randomly into two groups (10 rats each): HIBD and HBO-treated HIBD (HIBD+HBO) group. Another 20 rats that underwent sham-surgery were also divided randomly into the HBO-treated and control groups. The rats that underwent HBO treatment received HBO (0.02 MPa, 1 h/day) 24 h after the surgery and this continued for 14 days. When rats were 4 weeks old, their flash visual evoked potentials (F-VEPs) were monitored and the ultrastructures of the hippocampus were observed under transmission electron microscope. The levels of superoxide dismutase (SOD) and malonyldialdehyde (MDA) in the brain tissue homogenate were detected by xanthine oxidase and the thiobarbituric acid colorimetric method. Compared with the control group, the ultrastructures of the pyramidal neurons in the hippocampal CA3 area were distorted, the latencies of F-VEPs were prolonged (P<0.01) and the SOD activities were lower while the MDA levels were higher (P<0.01) in the HIBD group. No significant differences in ultrastructure, the latency of F-VEPs or SOD/MDA levels were identified between the HBO-treated HIBD group and the normal control group (P>0.05). HBO enhances antioxidant capacity and reduces the ultrastructural damage induced by hypoxic-ischemia, which may improve synaptic reconstruction and alleviate immature brain damage to promote the habilitation of brain function.

The Akt/mTOR/p70S6K Pathway Is Involved in the Neuroprotective Effect of Erythropoietin on Hypoxic/Ischemic Brain Injury in a Neonatal Rat Model

Background: The mTOR (mammalian target of rapamycin) signaling pathway is a master regulator of cell growth and proliferation in the nervous system. However, the effects of erythropoietin (EPO) treatment on the mTOR signaling pathway have not been elucidated in neonates with hypoxic/ischemic (H/I) brain injury. Objectives: We investigated the mechanism underlying the neuroprotective effect of EPO by analyzing the mTOR signaling pathway after H/I injury in a neonatal rat model. Methods: Seven-day-old rats were subjected to left carotid artery ligation and hypoxic exposure (8%) for 90 min (H/I). EPO at a dose of either 3,000 U/kg or a vehicle (V) was administered by intraperitoneal injection 0, 24 and 48 h after H/I. At 72 h after H/I (postnatal day 10), 2,3,5-triphenyltetrazolium chloride staining, myelin basic protein (MBP) immunofluorescence staining and Western blot analysis of the Akt/mTOR/p70S6K pathway were performed. Neuromotor behavioral tests included Rotarod challenge and cylinder rearing test 1 performed 3 and 6 weeks after H/I. Results: EPO treatment resulted in significant offsetting of MBP depletion ipsilateral (p = 0.001) and contralateral (p = 0.003) to ligation. Western blot analysis showed that the relative immunoreactivity of phosphorylated (p)-Akt, p-mTOR and p-p70S6K ipsilateral to ligation was significantly decreased in the H/I+V group compared with the sham-operated groups. However, EPO treatment significantly upregulated Akt/mTOR/p70S6K signals ipsilateral to ligation compared to the H/I+V group. The behavior tests showed that EPO attenuates long-term impairment in Rotarod challenge and cylinder test performance from 3-6 weeks. Conclusion: This study demonstrates an underlying mechanism of the mTOR signaling pathway after EPO treatment, which is a potential target for treating H/I-induced brain injury.

Impacts of Erythropoietin on Vascular Endothelial Growth Factor Receptor 2 by the Extracellular Signal-regulated Kinase Signaling Pathway in a Neonatal Rat Model of Periventricular White Matter Damage

To explore the impacts of erythropoietin on vascular endothelial growth factor receptor 2 (VEGFR2) by the extracellular signal-regulated kinase (ERK) signaling pathway in a neonatal rat model of periventricular white matter damage. All of postnatal day 4 rats were randomized into three groups: the sham group [without hypoxia-ischemia (HI)], the HI group (HI with saline administration), and the erythropoietin (EPO) group [HI with recombinant human erythropoietin (rh-EPO) administration]. Rat pups underwent permanent ligation of the right common carotid artery, followed by 6% O2 for 2 hours or sham operation and normoxic exposure. Immediately after the HI, rats received a single intraventricular injection of rh-EPO (0.6 IU/g body mass) or saline. ERK and phosphorylation-ERK were examined at 60 minutes and 90 minutes after operation, and VEGFR2 were detected at 2 and 4 days after operation by using Western blot. At 60 minutes and 90 minutes after operation, the proteins of phosphorylation-ERK were significantly higher in HI rats than in the sham rats and significantly higher in HI+EPO rats than in the HI rats (P<0.05). Two days after operation, VEGFR2 was not significantly different between sham and HI rats. However, the proteins of VEGFR2 were increased after administration of rh-EPO (P<0.05). Four days after operation, the proteins of VEGFR2 were significantly higher in HI rats than in the sham rats and significantly higher in HI+EPO rats than in the HI rats (P<0.05). EPO may regulate VEGFR2 expression by affecting the intracranial ERK signaling pathways.

Treatment temperature and insult severity influence the neuroprotective effects of therapeutic hypothermia.

Therapeutic hypothermia (HT) is standard care for moderate and severe neonatal hypoxic-ischaemic encephalopathy (HIE), the leading cause of permanent brain injury in term newborns. However, the optimal temperature for HT is still unknown, and few preclinical studies have compared multiple HT treatment temperatures. Additionally, HT may not benefit infants with severe encephalopathy. In a neonatal rat model of unilateral hypoxia-ischaemia (HI), the effect of five different HT temperatures was investigated after either moderate or severe injury. At postnatal-day seven, rat pups underwent moderate or severe HI followed by 5 h at normothermia (37 °C), or one of five HT temperatures: 33.5 °C, 32 °C, 30 °C, 26 °C, and 18 °C. One week after treatment, neuropathological analysis of hemispheric and hippocampal area loss, and CA1 hippocampal pyramidal neuron count, was performed. After moderate injury, a significant reduction in hemispheric and hippocampal loss on the injured side, and preservation of CA1 pyramidal neurons, was seen in the 33.5 °C, 32 °C, and 30 °C groups. Cooling below 33.5 °C did not provide additional neuroprotection. Regardless of treatment temperature, HT was not neuroprotective in the severe HI model. Based on these findings, and previous experience translating preclinical studies into clinical application, we propose that milder cooling should be considered for future clinical trials.

Expression and distribution of SP and its NK1 receptor in the brain-gut axis in neonatal maternally separated rat model with visceral hypersensitivity

Neurokinin-1 receptor (NK1R) is a high affinity Substance P (SP) receptor and plays a key role in visceral hypersensitivity in irritable bowel syndrome (IBS). Early life stress is a significant risk factor in IBS. The aim of the present study was to investigate the influence of neonatal maternal separation on the expression and distribution of SP and its receptor along the brain-gut axis in a neonatal maternally separated rat model with visceral hypersensitivity. Male neonatal Sprague-Dawley rats, 2-21-day old, were randomly distributed into maternal separation groups of 3 h daily maternal separation (MS) or non-handling (NH). These rats underwent colorectal balloon distention (CRD) upon reaching adulthood. Immunofluorescence was used to examine the distal colon, lumbosacral spinal cord, and the brainstem to semi-quantitatively determine SP and NK1R expression before and after CRD. The following features were assessed: percentage SP-positive area in colonic muscle layer, the number of NK1R-positive myenteric plexus, SP-positive area and NK1-positivity score in the dorsal horn and the brainstem. Neither of these was altered in the MS and NH groups before or after CRD. These results suggest that the SP system might play little role in the development of visceral hyperalgesia in the neonatal maternal separation rat model.

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

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

Enhanced long term potentiation and decreased AMPA receptor desensitization in the acute period following a single kainate induced early life seizure

Neonatal seizures are associated with long term disabilities including epilepsy and cognitive deficits. Using a neonatal seizure rat model that does not develop epilepsy, but develops a phenotype consistent with other models of intellectual disability (ID) and autism spectrum disorders (ASD), we sought to isolate the acute effects of a single episode of early life seizure on hippocampal CA1 synaptic development and plasticity. We have previously shown chronic changes in glutamatergic synapses, loss of long term potentiation (LTP) and enhanced long term depression (LTD), in the adult male rat ~50days following kainic acid (KA) induced early life seizure (KA-ELS) in post-natal (P) 7day old male Sprague–Dawley rats. In the present work, we examined the electrophysiological properties and expression levels of glutamate receptors in the acute period, 2 and 7days, post KA-ELS. Our results show for the first time enhanced LTP 7days after KA-ELS, but no change 2days post KA-ELS. Additionally, we report that ionotropic α-amino-3-hydroxy-5-methyl-isoxazole-propionic acid type glutamate receptor (AMPAR) desensitization is decreased in the same time frame, with no changes in AMPAR expression, phosphorylation, or membrane insertion. Inappropriate enhancement of the synaptic connections in the acute period after the seizure could alter the normal patterning of synaptic development in the hippocampus during this critical period and contribute to learning deficits. Thus, this study demonstrates a novel mechanism by which KA-ELS alters early network properties that potentially lead to adverse outcomes.

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

Objective: To clarify the effects of 3-h hypothermia on learning ability and motor function after growth, employing neonatal rat models with hyperthermic hypoxic-ischemic encephalopathy (HIE). Methods: We divided all rats into three groups: N (adult rats after neonatal hyperthermic HIE without subsequent 3-h hypothermia), H (adult rats after neonatal hyperthermic HIE with subsequent 3-h hypothermia) and Sham (S) groups. We evaluated their malfunctions with the rota-rod test and the step-down passive avoidance test. We also analyzed the cerebrum width and the hippocampal CA1 area of the insulted hemisphere. Results: In the rota-rod test, the result of the N group was significantly worse than that of the S group. In the step-down passive avoidance test, the result of the N group was significantly worse than those of the S and H groups. The longest cerebrum width and the hippocampal CA1 area of the insulted hemisphere of the N group were significantly smaller than those of the S and H groups. Conclusion: Neonatal hyperthermic hypoxic-ischemic insult restricts motor function and learning ability after growth, and such neuronal malfunctions can be relieved by hypothermia for 3 h soon after neonatal HIE.

Sulforaphane is not additive in combination with hypothermia in a neonatal rat model of hypoxia–ischemia

Sulforaphane is not additive in combination with hypothermia in a neonatal rat model of hypoxia–ischemia

The use of broccoli sprouts as a neuropreventative agent in a neonatal rat model of the fetal inflammatory response

The use of broccoli sprouts as a neuropreventative agent in a neonatal rat model of the fetal inflammatory response

Neonatal capsaicin treatment in rats induces chronic hyperthermia resulting in infectious disease.

Treatment of neonatal animals with capsaicin has previously been associated with long-lasting hyperthermia and severe cutaneous lesions. The present study analyzed the effects of capsaicin-induced hyperthermia on the occurrence of infectious disease and pruritic dermatitis in a rat model. Pregnant Sprague-Dawley (SD) rats were obtained 1 week prior to parturition. Pups from each litter were randomly assigned to the following experimental groups: Capsaicin-treated (cap-treated; n=10) or vehicle-treated (n=5). Capsaicin (50 mg/kg) or vehicle were systemically administered to the SD rat pups (age, 48 h), after which body temperature was measured using a biotelemetry system, and the effects of hyperthermia on the ability of the rat pups to resist bacterial infection were analyzed. Furthermore, pruritus-induced scratching behavior and dermatitis were assessed, and changes in interleukin (IL)-4- and IL-13-induced immunoglobulin E expression were measured. Treatment of neonatal rats with capsaicin resulted in chronic hyperthermia, which had negative effects on the host immune defense response. The expression levels of T-helper type 2 cell-associated cytokines were significantly increased (P<0.01) in the cap-treated rats following bacterial infection with Staphylococcus aureus or Streptococcus agalactiae. Furthermore, cap-treated rats exhibited pruritus-induced scratching behavior and dermatitis. The results of the present study suggested that treatment of neonatal rats with capsaicin induces chronic hyperthermia and decreases the effectiveness of the host defense system. Therefore, a cap-treated neonatal rat model may be considered useful when investigating the association between hyperthermia and infectious disease.

Uridine protects against hypoxic-ischemic brain injury by reducing histone deacetylase activity in neonatal rats.

A significant cause of neurological disability in newborns is hypoxic-ischemic encephalopathy (HIE), a disorder which involves an enhancement in histone deacetylase (HDAC) activity among underlying pathological mechanisms. We showed recently that exogenous administration of uridine to newborn rats with HIE reduced brain injury in a dose-dependent manner. The present study was performed to investigate whether uridine modulates histone acetylation/deacetylation balance in a neonatal rat model of HIE. Newborn rats that were subjected to hypoxic-ischemic (HI) insult on postnatal day 7 (P7) were injected intraperitoneally with either saline or uridine (500 mg/kg) for three consecutive days. One day after completion of treatment, brains of pups were collected for evaluation of brain infarct volume, apoptosis, HDAC activity and acetylated-Histone H3 (Ac-H3) and H4 (Ac-H4) protein levels. Results revealed that uridine administration reduced infarct volume, active Caspase-3 levels and HDAC activity while increasing the expressions of Ac-H3 and Ac-H4 proteins. We conclude that one mechanism by which uridine provides neuroprotection in neonatal rat HIE model involves reduction in HDAC activity.

MicroRNA expression profiles and target prediction in neonatal Wistar rat lungs during the development of bronchopulmonary dysplasia.

In this study, we investigated the mechanisms through which microRNAs (miRNAs or miRs) regulate lung development after birth, as well as the role of miRNAs in the development of bronchopulmonary dysplasia (BPD). For this purpose, a total of 90 neonatal Wistar rats were randomly and equally assigned to either a model group or a control group. On postnatal days 3, 7 and 14, the lung tissues were collected for histological analysis to determine morphological changes. The expression levels of proliferating cell nuclear antigen (PCNA) and platelet endothelial cell adhesion molecule-1 (PECAM-1, also known as CD31) were measured by RT-qPCR and western blot analysis. A miRCURY™ LNA array was employed to screen for differentially expressed miRNAs, and the possible target genes of those miRNAs were predicted. Our results revealed that, compared with the control group, the following changes induced by hyperoxia were observed in the model group over time: a decrease in the number, but an increase in the size of the alveoli, and a decrease in the number of secondary septa formed. In the model group, from postnatal days 3–14, the mRNA and protein expression levels of PCNA and CD31 were significantly lower than those in the control group. The differentially expressed miRNAs between the 2 groups were identified on days 3, 7 and 14 after birth. Possible target genes were identified for 32 differentially expressed miRNAs. Taken together, these findings suggest that during the development of BPD, an alveolarization disorder with microvascular dysplasia co-exists with the differential expression of certain miRNAs during the different stages of alveolar development in a neonatal rat model of hyperoxia-induced BPD. This indicates that miRNAs may participate in the occurrence and development of BPD.

Intestinal ischemia–reperfusion induced diaphragm contractility dysfunction: Electrophysiological and ultrastructural study in a neonatal rat model

AimTo evaluate the remote effect of intestinal ischemia reperfusion (IR) injury mediated by tumor necrosis factor alpha (TNF-α) on diaphragm contractility functions and whether administration of NAC may counteract the possible detrimental effects in an experimental neonatal rat model. Methods40 Wistar rat pups were randomized into four groups; ten animals in each. Intestinal ischemia was conducted by obstructing mesentery of intestines by a silk loop. In the control group; only laparotomy was performed. After 1h ischemia, reperfusion was conducted for 1h in 1h group, 24h for 24h group and 24h for 24h+NAC group but administration of NAC (150mg/kg/day) intraperitoneally twice a day was performed. Inflammatory response was evaluated by tissue TNF-α level and contractility functions by mechanic activity studies of the diaphragm. Electrophysiology of the diaphragm and the phrenic nerve was conducted to determine neuropathy or myopathy and transmission electron microscopy was performed to evaluate ultrastructural changes in the phrenic nerve. ResultsDiaphragm tissue TNF-α level significantly increased in 1h and 24h groups (P=0.004, P=0.0001; respectively). Diaphragm mechanic activation force and duration significantly decreased at 1h and 24h (P=0.004, P=0.02 and P=0.0001, P=0.0001; respectively). NAC administration significantly prevented decrease in the maximal contraction and the duration (P<0.001). Phrenic nerve compound action potential (CMAP) amplitude significantly decreased in 1h group (P<0.0001) and NAC administration significantly prevented this decrease when compared with 24h group (P<0.001). In diaphragmatic needle electromyography, the duration of motor unit potentials (MUP) was prolonged significantly when compared with control group. Contractility and electrophysiological studies were indicating primarily neuropathy in diaphragm dysfunction. Histopathology revealed axonal and myelin degeneration in the 1h and 24h group, but less injury in the NAC administered group. ConclusionsIntestinal IR induced elevation of TNF-α level in the diaphragm. Impairment in the diaphragm contractility and neuropathic changes in the phrenic nerve occurred even in the first hour of reperfusion. NAC administration prevented these detrimental effects.

Developmental loss of parvalbumin-positive cells in the prefrontal cortex and psychiatric anxiety after intermittent hypoxia exposures in neonatal rats might be mediated by NADPH oxidase-2

Sleep apnea is more frequently experienced in neonatal life. Here we investigated the causal contribution of NOX2-derived oxidative stress in the prefrontal cortex (PFC) to neurodevelopmental alterations and psychiatric anxiety in a neonatal rat model of sleep apnea. Neonatal postnatal day 5 (P5) rats were exposed to long-term intermittent hypoxia (LTIH) or room air (RA) for 10 days. In the PFC, we determined the impact (I) of LTIH exposures on NADPH oxidase-2 (NOX2) expression and oxidative stress (II) of pharmacological NOX2 inhibition on LTIH-induced neurodevelopmental alterations in the P14 and P49 rats. Endpoints were NOX2-derived oxidative stress, parvalbumin (PV)-positive cells (PV-cells) and psychiatric anxiety. The results showed neonatal LTIH exposures increased NOX2 expression in the PFC of P14 rats, which was accompanied with elevation of NOX activity. Neonatal LTIH exposures increased oxidative stress in cortical PV-cells characterized by elevation of 8-hydroxy-20-deoxyguanosine (8-OHDG) level and reduced PV immunoreactivity, PV-cell counts in the PFC of P14 and P49 rats. Neonatal LTIH exposures increased psychiatric anxiety levels in the P49 rats. Pretreatment of neonatal rats before each neonatal LTIH exposure with the antioxidant/NOX inhibitor apocynin prevented the reduced PV immunoreactivity, PV-cells loss in the PFC and development of anxiety-like behavior. Our data suggest that NOX2-derived oxidative stress might be involved in the developmental loss of PV-cells in the PFC and development of psychiatric anxiety for neonatal rats exposed to LTIH.

Beneficial Effect of Etanercept on Hyperoxic Lung Injury Model in Neonatal Rats

ABSTRACTPurpose: To determine whether prophylaxis with etanercept, an anti-inflammatory drug, would decrease the severity of lung injury in a neonatal rat model of bronchopulmonary dysplasia (BPD); Materials and Methods: Rat pups were divided into three groups: pups exposed to room air (group 1; n = 10), to hyperoxia + placebo (group 2; n = 9), and to hyperoxia + etanercept (group 3; n = 8). Lung morphology was assessed by alveolar surface area percentage, which is a measure of alveolar size. The severities of lung inflammation and antioxidant capacity were assessed by quantifying tumor necrosis factor-α (TNF-α), transforming growth factor-β (TGF-β), malondialdehyde (MDA), and superoxide dismutase (SOD) from lung homogenate; Results: The percentage of alveolar surface areas were significantly higher in group 3 compared to group 2 (p = .004) and similar in both group 1 and group 3 (p = .21). The mean level of lung MDA was significantly higher in group 2 compared to group 1 and group 3 (p < .05 for both). Lung homogenate SOD activities in group 3 was significantly higher than group 2 (p < .001). Furthermore, group 3 pups had lower levels of TNF-α and TGF-β in lung homogenate than that in group 2 (p < .05 for both) but similar in both group 1 and group 3; Conclusion: Etanercept has favorable effects on alveolarization as well as inflammation and oxidative stress markers in a neonatal rat model of BPD.