Consequential apoptosis in the cerebellum following injury to the developing rat forebrain

The Emerging Landscape of the Cerebellum after a Pediatric Traumatic Brain Injury: From Diaschisis to Sociality

There is an expanding interest in the cerebellum in the context of focal and diffuse traumatic injuries to the cerebral cortex. In the adult brain, preclinical studies have revealed acute as well as progressive loss of Purkinje cells in the cerebellum coincident with microglial activation. This pathogenesis, remote to the site of the primary injury, is termed "diaschisis." Here we consider traumatic injuries to the developing brain, where the cerebellum likewise undergoes neurodegeneration. As injury is superimposed on a young brain, long-term adverse consequences may reflect diaschisis that is compounded by disruption of brain development.

Hypothermia increases cold-inducible protein expression and improves cerebellar-dependent learning after hypoxia ischemia in the neonatal rat

BACKGROUND

Hypoxic ischemic encephalopathy remains a significant cause of developmental disability.1,2 The standard of care for term infants is hypothermia, which has multifactorial effects.3-5 Therapeutic hypothermia upregulates the cold-inducible protein RNA binding motif 3 (RBM3) that is highly expressed in developing and proliferative regions of the brain.6,7 The neuroprotective effects of RBM3 in adults are mediated by its ability to promote the translation of mRNAs such as reticulon 3 (RTN3).8 METHODS: Hypoxia ischemia or control procedure was conducted in Sprague Dawley rat pups on postnatal day 10 (PND10). Pups were immediately assigned to normothermia or hypothermia at the end of the hypoxia. In adulthood, cerebellum-dependent learning was tested using the conditioned eyeblink reflex. The volume of the cerebellum and the magnitude of cerebral injury were measured. A second study quantified RBM3 and RTN3 protein levels in the cerebellum and hippocampus collected during hypothermia.

RESULTS

Hypothermia reduced cerebral tissue loss and protected cerebellar volume. Hypothermia also improved learning of the conditioned eyeblink response. RBM3 and RTN3 protein expression were increased in the cerebellum and hippocampus of rat pups subjected to hypothermia on PND10.

CONCLUSIONS

Hypothermia was neuroprotective in male and female pups and reversed subtle changes in the cerebellum after hypoxic ischemic.

IMPACT

Hypoxic ischemic produced tissue loss and a learning deficit in the cerebellum. Hypothermia reversed both the tissue loss and learning deficit. Hypothermia increased cold-responsive protein expression in the cerebellum and hippocampus. Our results confirm cerebellar volume loss contralateral to the carotid artery ligation and injured cerebral hemisphere, suggesting crossed-cerebellar diaschisis in this model. Understanding the endogenous response to hypothermia might improve adjuvant interventions and expand the clinical utility of this intervention.

Neonatal hypoxia ischemia redistributes L1 cell adhesion molecule into rat cerebellar lipid rafts

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) is a devastating disease with lifelong disabilities. Hypothermia is currently the only treatment. At term, the neonatal cerebellum may be particularly vulnerable to the effects of HIE. At this time, many developmental processes depend on lipid raft function. These microdomains of the plasma membrane are critical for cellular signaling and axon extension. We hypothesized that HIE alters the protein content of lipid rafts in the cerebellum.

METHODS

Postnatal day (PN) 10 animals, considered human term equivalent, underwent hypoxic-ischemic (HI) injury by a right carotid artery ligation followed by hypoxia. For some animals, LPS was administered on PN7, and hypothermia (HT) was conducted for 4 h post-hypoxia. Lipid rafts were isolated from the right and left cerebella. The percent of total L1 cell adhesion molecule in lipid rafts was determined 4 and 72 h after hypoxia.

RESULTS

No sex differences were found. HI alone caused significant increases in the percent of L1 in lipid rafts which persisted until 72 h in the right but not the left cerebellum. A small but significant effect of LPS was detected in the left cerebellum 72 h after HI. Hypothermia had no effect.

CONCLUSIONS

Lipid rafts may be a new target for interventions of HIE.

IMPACT

This article investigates the effect of neonatal exposure to hypoxic-ischemic encephalopathy (HIE) on the distribution of membrane proteins in the cerebellum. This article explores the effectiveness of hypothermia as a prevention for the harmful effects of HIE on membrane protein distribution. This article shows an area of potential detriment secondary to HIE that persists with current treatments, and explores ideas for new treatments.

Pretreatment Normal WM Magnetization Transfer Ratio Predicts Risk of Radiation Necrosis in Patients with Medulloblastoma

BACKGROUND AND PURPOSE

Radiation necrosis, for which abnormal WM enhancement is a hallmark, is an uncommon complication of craniospinal irradiation in children with medulloblastoma. The magnetization transfer ratio measures macromolecular content, dominated by myelin in the WM. We investigated whether the pretreatment supratentorial (nonsurgical) WM magnetization transfer ratio could predict patients at risk for radiation necrosis after radiation therapy for medulloblastoma.

MATERIALS AND METHODS

Ninety-five eligible patients with medulloblastoma (41% female; mean age, 11.0 [SD, 5.4]  years) had baseline balanced steady-state free precession MR imaging before proton or photon radiation therapy. Associations among baseline supratentorial magnetization transfer ratio, radiation necrosis (spontaneously resolving/improving parenchymal enhancement within the radiation field)³, age, and the presence of visible brain metastases were explored by logistic regression and parametric/nonparametric techniques as appropriate.

RESULTS

Twenty-three of 95 (24.2%) children (44% female; mean age, 10.7 [SD, 6.7] years) developed radiation necrosis after radiation therapy (19 infratentorial, 1 supratentorial, 3 both). The mean pretreatment supratentorial WM magnetization transfer ratio was significantly lower in these children (43.18 versus 43.50, P = .03). There was no association between the supratentorial WM magnetization transfer ratio and age, sex, risk/treatment stratum, or the presence of visible brain metastases.

CONCLUSIONS

A lower baseline supratentorial WM magnetization transfer ratio may indicate underlying structural WM susceptibility to radiation necrosis and may identify children at risk for developing radiation necrosis after craniospinal irradiation for medulloblastoma.

Withania coagulans extract attenuates oxidative stress-mediated apoptosis of cerebellar purkinje neurons after ischemia/reperfusion injury

Cerebral ischemia/reperfusion (I/R) is known to increase reactive oxygen species (ROS) generation, consequences of oxidative stress (OS), and neuronal death in the susceptible brain areas including the cerebellum. Newly, remarkable attention has been paid to a natural diet with the capability to scavenge ROS. Withania coagulans root extract (WCE) is rich in components with antioxidants properties. Therefore, this study aimed to evaluate the effect of WCE on cerebellar Purkinje cells (PCs) against OS-mediated apoptosis after I/R injury. In this experimental study 64 male adult Wistar rats were randomly divided into 4 groups (n = 16) as follows: control, sham, I/R, and WCE 1000 + I/R. I/R animals were pretreated with daily administration of hydro-alcoholic WCE (1000 mg/kg) or distilled water as a vehicle for 30 days before I/R injury. After 72 h, the animals were sacrificed, the cerebellum tissue was removed and used for biochemical (CAT, SOD, GPx, and MDA levels) and histopathological (Nissl and TUNEL staining) assays. Findings showed that the MDA level and the number of apoptotic neurons significantly increased and viable Purkinje neurons decreased in I/R injury (p < 0.05). Administration of 1000 mg/kg WCE reduced MDA level and enhanced antioxidants activity including CAT, SOD, and GPx significantly. In addition, intact surviving PCs increased. At the same time, TUNEL-positive neurons decreased significantly in the WCE pre-treated group (p < 0.05). These findings suggest that WCE can counteract cerebral I/R-induced OS and associated neuronal death by enhancement of ROS scavenging and antioxidant capacity. It appears that pre-treatment with 1000 mg/kg WCE for thirty days can protect PCs against OS-mediated apoptosis after I/R injury.

Mild Neonatal Brain Hypoxia-Ischemia in Very Immature Rats Causes Long-Term Behavioral and Cerebellar Abnormalities at Adulthood

Systemic hypoxia-ischemia (HI) often occurs during preterm birth in human. HI induces injuries to hinder brain cells mainly in the ipsilateral forebrain structures. Such HI injuries may cause lifelong disturbances in the distant regions, such as the contralateral side of the cerebellum. We aimed to evaluate behavior associated with the cerebellum, to acquire cerebellar abundant metabolic alterations using in vivo 1H magnetic resonance spectroscopy (1H MRS), and to determine GFAP, NeuN, and MBP protein expression in the left cerebellum, in adult rats after mild early postnatal HI on the right forebrain at day 3 (PND3). From PND45, HI animals exhibited increased locomotion in the open field while there is neither asymmetrical forelimb use nor coordination deficits in the motor tasks. Despite the fact that metabolic differences between two cerebellar hemispheres were noticeable, a global increase in glutamine of HI rats was observed and became significant in the left cerebellum compared to the sham-operated group. Furthermore, increases in glutamate, glycine, the sum of glutamate and glutamine and total choline, only occurred in the left cerebellum of HI rats. Remarkably, there were decreased expression of MBP and NeuN but no detectable reactive astrogliosis in the contralateral side of the cerebellum of HI rats. Taken together, the detected alterations observed in the left cerebellum of HI rats may reflect disequilibrium in the glutamate-glutamine cycle and a delay in the return of glutamine from astrocytes to neurons from hypoxic-ischemic origin. Our data provides in vivo evidence of long-term changes in the corresponding cerebellum following mild neonatal HI in very immature rats, supporting the notion that systemic HI could cause cell death in the cerebellum, a distant region from the expected injury site.

HIGHLIGHTS

-Neonatal hypoxia-ischemia (HI) in very immature rats induces hyperactivity toward adulthood.-1H magnetic resonance spectroscopy detects long-term cerebellar metabolic changes in adult rats after neonatal HI at postnatal day 3.-Substantial decreases of expression of neuronal and myelin markers in adult rats cerebellum after neonatal cortical mild HI.

Nitric Oxide Donor Prevents Neonatal Isoflurane-induced Impairments in Synaptic Plasticity and Memory

WHAT WE ALREADY KNOW ABOUT THIS TOPIC

Some general anesthetics have been shown to have adverse effects on neuronal development that affect neural function and cognitive behavior.Clinically relevant concentrations of inhalational anesthetics inhibit the postsynaptic density (PSD)-95, discs large homolog, and zona occludens-1 (PDZ) domain-mediated protein-protein interaction between PSD-95 or PSD-93 and N-methyl-D-aspartate receptors or neuronal NO synthase.

WHAT THIS ARTICLE TELLS US THAT IS NEW

Neonatal PSD-95 PDZ2WT peptide treatment mimics the effects of isoflurane (~1 minimum alveolar concentration) by altering dendritic spine morphology, neural plasticity, and memory without inducing detectable increases in apoptosis or changes in synaptic density.These results indicate that a single dose of isoflurane (~1 minimum alveolar concentration) or PSD-95 PDZ2WT peptide alters dendritic spine architecture and functions important for cognition in the developing brain. This impairment can be prevented by administration of the NO donor molsidomine.

BACKGROUND

In humans, multiple early exposures to procedures requiring anesthesia constitute a significant risk factor for development of learning disabilities and disorders of attention. In animal studies, newborns exposed to anesthetics develop long-term deficits in cognition. Previously, our laboratory showed that postsynaptic density (PSD)-95, discs large homolog, and zona occludens-1 (PDZ) domains may serve as a molecular target for inhaled anesthetics. This study investigated a role for PDZ interactions in spine development, plasticity, and memory as a potential mechanism for early anesthetic exposure-produced cognitive impairment.

METHODS

Postnatal day 7 mice were exposed to 1.5% isoflurane for 4 h or injected with 8 mg/kg active PSD-95 PDZ2WT peptide. Apoptosis, hippocampal dendritic spine changes, synapse density, long-term potentiation, and cognition functions were evaluated (n = 4 to 18).

RESULTS

Exposure of postnatal day 7 mice to isoflurane or PSD-95 PDZ2WT peptide causes a reduction in long thin spines (median, interquartile range [IQR]: wild type control [0.54, 0.52 to 0.86] vs. wild type isoflurane [0.31, 0.16 to 0.38], P = 0.034 and PDZ2MUT [0.86, 0.67 to 1.0] vs. PDZ2WT [0.55, 0.53 to 0.59], P = 0.028), impairment in long-term potentiation (median, IQR: wild type control [123, 119 to 147] and wild type isoflurane [101, 96 to 118], P = 0.049 and PDZ2MUT [125, 119 to 131] and PDZ2WT [104, 97 to 107], P = 0.029), and deficits in acute object recognition (median, IQR: wild type control [79, 72 to 88] vs. wild type isoflurane [63, 55 to 72], P = 0.044 and PDZ2MUT [81, 69 to 84] vs. PDZ2WT [67, 57 to 77], P = 0.039) at postnatal day 21 without inducing detectable differences in apoptosis or changes in synaptic density. Impairments in recognition memory and long-term potentiation were preventable by introduction of a NO donor.

CONCLUSIONS

Early disruption of PDZ domain-mediated protein-protein interactions alters spine morphology, synaptic function, and memory. These results support a role for PDZ interactions in early anesthetic exposure-produced cognitive impairment. Prevention of recognition memory and long-term potentiation deficits with a NO donor supports a role for the N-methyl-D-aspartate receptor/PSD-95/neuronal NO synthase pathway in mediating these aspects of isoflurane-induced cognitive impairment.

Parthenolide attenuates cerebral ischemia/reperfusion injury via Akt/GSK-3β pathway in PC12 cells

Parthenolide (PN), a sesquiterpene lactone isolated from the herbal medicine feverfew (Tanacetum parthenium), was reported to possess neuroprotective activity. However, the neuroprotective effect of PN against cerebral ischemia/reperfusion (I/R) injury remains unclear. Therefore, the aim of the present study was to explore the neuroprotective effects of PN against oxygen-glucose deprivation (OGD)-induced apoptosis in PC12 cells and the underlying mechanisms. Our results demonstrated that PN ameliorated OGD/R-evoked neuronal injury and oxidative stress in PC12 cells. In addition, PN notably decreased HIF-1α expression, as well as inhibited apoptosis in PC12 cells after OGD/R. Furthermore, PN pretreatment significantly enhanced the phosphorylation of Akt and GSK-3β in PC12 cells exposed to OGD/R. In conclusion, the present study demonstrated that PN exhibits a neuroprotective effect against OGD/R through activation of the Akt/GSK-3β signaling pathway. Our findings suggest that PN has the potential to serve as a novel therapeutic agent for cerebral I/R injury.

Crossed Cerebellar Atrophy of the Lateral Cerebellar Nucleus in an Endothelin-1-Induced, Rodent Model of Ischemic Stroke

Crossed cerebellar diaschisis (CCD) is a functional deficit of the cerebellar hemisphere resulting from loss of afferent input consequent to a lesion of the contralateral cerebral hemisphere. It is manifested as a reduction of metabolism and blood flow and, depending on severity and duration, it can result in atrophy, a phenomenon known as crossed cerebellar atrophy (CCA). While CCA has been well-demonstrated in humans, it remains poorly characterized in animal models of stroke. In this study we evaluated the effects of cerebral cortical ischemia on contralateral cerebellar anatomy using an established rodent model of chronic stroke. The effects of cortical ischemia on the cerebellar hemispheres, vermis and deep nuclei were characterized. Intracortical microinjections of endothelin-1 (ET-1) were delivered to the motor cortex of Long Evans rats to induce ischemic stroke, with animals sacrificed 6 weeks later. Naive animals served as controls. Cerebral sections and cerebellar sections including the deep nuclei were prepared for analysis with Nissl staining. Cortical ischemia was associated with significant thickness reduction of the molecular layer at the Crus 1 and parafloccular lobule (PFL), but not in fourth cerebellar lobule (4Cb), as compared to the ipsilesional cerebellar hemisphere. A significant reduction in volume and cell density of the lateral cerebellar nucleus (LCN), the rodent correlate of the dentate nucleus, was also noted. The results highlight the relevance of corticopontocerebellar (CPC) projections for cerebellar metabolism and function, including its direct projections to the LCN.

Regional volumes in brain stem and cerebellum are associated with postural impairments in young brain-injured patients

Many patients with traumatic brain injury (TBI) suffer from postural control impairments that can profoundly affect daily life. The cerebellum and brain stem are crucial for the neural control of posture and have been shown to be vulnerable to primary and secondary structural consequences of TBI. The aim of this study was to investigate whether morphometric differences in the brain stem and cerebellum can account for impairments in static and dynamic postural control in TBI. TBI patients (n = 18) and healthy controls (n = 30) completed three challenging postural control tasks on the EquiTest® system (Neurocom). Infratentorial grey matter (GM) and white matter (WM) volumes were analyzed with cerebellum-optimized voxel-based morphometry using the spatially unbiased infratentorial toolbox. Volume loss in TBI patients was revealed in global cerebellar GM, global infratentorial WM, middle cerebellar peduncles, pons and midbrain. In the TBI group and across both groups, lower postural control performance was associated with reduced GM volume in the vermal/paravermal regions of lobules I-IV, V and VI. Moreover, across all participants, worse postural control performance was associated with lower WM volume in the pons, medulla, midbrain, superior and middle cerebellar peduncles and cerebellum. This is the first study in TBI patients to demonstrate an association between postural impairments and reduced volume in specific infratentorial brain areas. Volumetric measures of the brain stem and cerebellum may be valuable prognostic markers of the chronic neural pathology, which complicates rehabilitation of postural control in TBI.

Hippocampus and medial prefrontal cortex contributions to trace and contextual fear memory expression over time

Previous work has shown that damage to the dorsal hippocampus (DH) occurring at recent, but not remote, timepoints following acquisition produces a deficit in trace conditioned fear memory expression. The opposite pattern has been observed with lesions to the medial prefrontal cortex (mPFC). The present studies address: (1) whether these lesion effects are observable within 30 d of training; (2) whether lesions of the ventral hippocampus (VH) produce temporally graded retrograde amnesia similar to DH lesions; and (3) whether the lesion-to-test interval critically contributes to these lesion deficits. In Experiment 1, excitotoxic lesions of the DH, VH, or mPFC were made at 1 or 30 d following trace fear conditioning. DH and VH lesioned animals showed a deficit in freezing to the tone at the recent, but not remote, timepoint. Medial PFC lesioned animals showed the opposite pattern. In Experiment 2, lesions to DH, VH, or mPFC were made 1 d following training, while testing occurred 30 d later. There were no deficits in freezing to the tone in any lesion condition compared to controls. These results suggest that systems consolidation of trace fear memory occurs within 30 d of acquisition, but does not depend on hippocampus-mPFC interactions during this period.

Perinatal intermittent hypoxia alters γ-aminobutyric acid: a receptor levels in rat cerebellum

Perinatal hypoxia commonly causes brain injury in infants, but the time course and mechanisms underlying the preferential male injury are unclear. Intermittent hypoxia disturbs cerebellar γ-aminobutyric (GABA)-A receptor profiles during the perinatal period, possibly responding to transient excitatory processes associated with GABA(A) receptors. We examined whether hypoxic insults were particularly damaging to the male rodent cerebellum during a specific developmental time window. We evaluated cerebellar injury and GABA(A) receptor profiles following 5-h intermittent hypoxia (IH: 20.8% and 10.3% ambient oxygen, switched every 240s) or room-air control in groups of male and female rat pups on postnatal d 1-2, wk 1, or wk 3. The cerebella were harvested and compared between groups. The mRNA levels of GABA(A) receptors α6, normalized to a house-keeping gene GAPDH, and assessed using real-time reverse-transcriptase PCR assays were up-regulated by IH at wk 1, more extensively in male rats, with sex influencing the regulatory time-course. In contrast, GABA(A) α6 receptor protein expression levels, assessed using Western blot assays, reached a nadir at wk 1 in both male and female rats, possibly indicating involvement of a post-transcriptional mechanism. The extent of cerebellar damage and level of apoptosis, assessed by DNA fragmentation, were greatest in the wk 3 IH-exposed group. The findings suggest partial protection for female rats against early hypoxic insult in the cerebellum, and that down-regulation of GABA(A) receptors, rather than direct neural injury assessed by DNA fragmentation may modify cerebellar function, with potential later motor and other deficits.

Height of the cerebellar vermis and gestational age at birth

OBJECTIVES

The objective of this study was to construct reference ranges of the neonatal cerebellar vermis height with respect to the gestational age at birth.

METHODS

This observational study assessed 434 neonates born at 25-42 weeks' gestation. The neonates were singleton and appropriate in size for gestational age, and did not exhibit any abnormalities or neonatal disease. Gestational age was based on the date of the last menstrual period and confirmed by ultrasound examination performed within the 12(th) week of pregnancy. Sonographic measurements of the height of the cerebellar vermis in the mid-sagittal plane were performed within 24 h of birth by the same neonatal sonographer. Reference ranges (5(th), 50(th) and 95(th) centiles) were estimated by a mean and SD model based on least-squares polynomial regression.

RESULTS

Neonatal sonographic measurements were obtained in all cases. Mean (SD) maternal age was 30.2 (4.3) years. Mean cerebellar vermis height adjusted for gestational age did not differ between males and females, the mean adjusted difference being 0.012 (95% CI, - 0.009 to 0.033) cm. Mean cerebellar vermis height (cm) against gestational age (weeks) was suitably modeled by a linear-cubic polynomial as - 1.784 + 0.137 x GA - 0.000019 x GA(3) (SD = - 0.147 + 0.008 x GA), where GA = gestational age.

CONCLUSIONS

Reference ranges for the height of the cerebellar vermis at birth with respect to gestational age at birth have been constructed in appropriate-for-gestational-age neonates.