Mark Dzietko

Antiepileptic drugs and apoptotic neurodegeneration in the developing brain.

Epilepsy is the most common neurological disorder of young humans. Each year 150,000 children in the United States experience their first seizure. Antiepileptic drugs (AEDs), used to treat seizures in children, infants, and pregnant women, cause cognitive impairment, microcephaly, and birth defects. The cause of unwanted effects of therapy with AEDs is unknown. Here we reveal that phenytoin, phenobarbital, diazepam, clonazepam, vigabatrin, and valproate cause apoptotic neurodegeneration in the developing rat brain at plasma concentrations relevant for seizure control in humans. Neuronal death is associated with reduced expression of neurotrophins and decreased concentrations of survival-promoting proteins in the brain. β-Estradiol, which stimulates pathways that are activated by neurotrophins, ameliorates AED-induced apoptotic neurodegeneration. Our findings present one possible mechanism to explain cognitive impairment and reduced brain mass associated with prenatal or postnatal exposure of humans to antiepileptic therapy.

Estradiol attenuates hyperoxia-induced cell death in the developing white matter

Periventricular leukomalacia is the predominant type of brain injury in preterm infants underlying the development of cerebral palsy. Periventricular leukomalacia has its peak incidence at 23 to 32 weeks postconceptional age characterized by extensive oligodendrocyte migration and maturation. Oxygen toxicity has been identified as a possible contributing factor to the pathogenesis of cerebral palsy in survivors of preterm birth. 17β‐estradiol (E2) is important for the development and function of the central nervous system. Furthermore, neuroprotective properties have been attributed to estrogens. We examined the effect of E2 on hyperoxia‐induced cell death in the developing white matter in the rat brain.

Effects of Repetitive Exposure to Pain and Morphine Treatment on the Neonatal Rat Brain

Background: Untreated exposure to pain in preterm neonates might damage the vulnerable premature brain and alter development. Pain treatment is limited because analgesic agents may also have adverse neurodevelopmental consequences in newborns. Objective: To study the effects of neonatal pain and morphine treatment on the developing brain in a neonatal rat model. Methods: Newborn rats were randomly assigned to: treatment with formalin injections (group 1), saline injections (group 2) and controls receiving no injections (group 3). Treatment was given on postnatal days 1–3 (model A), 1–5 (model B) and 10–12 (model C). Brains were studied histologically and protein expression was evaluated (protein kinase C epsilon and doublecortin). Effects of preemptive morphine treatment were studied in the same models (models A+M and B+M). Results: Formalin injections resulted in increased apoptotic scores in models A and B. Saline injections increased the number of degenerative cells only in model B. Morphine showed protective effects in formalin-treated animals of model A+M and saline-treated animals of model B+M only. In model C, no neurodegenerative effects were detected. The protein expression of doublecortin showed a pain-related upregulation in the thalamus region, whereas protein kinase C epsilon expression was upregulated in the cortex. Conclusions: Severe inflammatory pain and pain caused by repetitive injections in neonatal rats may cause major changes in the developing brain during the first week of life. Morphine may only protect the newborn brain against these changes in specific situations.

A critical role for Fas/CD‐95 dependent signaling pathways in the pathogenesis of hyperoxia‐induced brain injury

Prematurely born infants are at risk for development of neurocognitive impairment in later life. Oxygen treatment has been recently identified as a trigger of neuronal and oligodendrocyte apoptosis in the developing rodent brain. We investigated the role of the Fas death receptor pathway in oxygen‐triggered developmental brain injury.

Activation of caspase-1 dependent interleukins in developmental brain trauma

Focal mechanical cortical trauma triggers diffuse apoptotic neurodegeneration in the developing rat brain which is associated with invasion of brain tissue with inflammatory mediators. We hypothesized that caspase-1 and the two caspase-1-processed cytokines, interleukin (IL)-1beta and IL-18, are involved in trauma-induced neuronal cell death in the developing brain. 7-day-old Wistar rats or C57/BL6 mice were subjected to head trauma using a weight drop device. Animals were sacrificed at defined time points following trauma and brains were processed for histology and molecular analyses. Neuronal cell death in the immature brain peaked at 12-24 h and was accompanied by a marked increase of mRNA and protein levels for caspase-1, IL-1beta and IL-18 within 2 to 12 h following the injury. Caspase-1 levels were elevated for 72 h, whereas IL-1beta decreased earlier at 48 h. IL-18 remained high over a period of 3 days and decreased to normal levels by day 7 after the injury. Intraperitoneal injection of recombinant human IL-18-binding protein (IL-18BP), a specific inhibitor of IL-18, attenuated traumatic brain injury. Mice deficient in IL-18 (IL-18-/-) were protected against trauma-induced brain damage. These findings indicate that IL-18 is involved in trauma-induced neuronal cell death in the immature rodent brain and might serve as a potential therapeutic target.

Elective High-Frequency Oscillatory Ventilation versus Conventional Ventilation for Acute Pulmonary Dysfunction in Preterm Infants

BACKGROUND Respiratory failure due to lung immaturity is a major cause of mortality in preterm infants. Although the use of intermittent positive pressure ventilation in neonates with respiratory failure saves lives, its use is associated with lung injury and chronic lung disease (CLD). A newer form of ventilation called high-frequency oscillatory ventilation (HFOV) has been shown to result in less lung injury in experimental studies. OBJECTIVES The objective of this review is to determine the effect of the elective use of HFOV as compared to conventional ventilation (CV) on the incidence of CLD, mortality and other complications associated with prematurity and assisted ventilation in preterm infants who are mechanically ventilated for respiratory distress syndrome (RDS). SEARCH METHODS Searches were made of the Oxford Database of Perinatal Trials, MEDLINE, EMBASE, previous reviews including cross-references, abstracts, conferences and symposia proceedings, expert informants, journal hand searching by the Cochrane Collaboration, mainly in the English language. The search was updated in January 2009. SELECTION CRITERIA Randomized controlled trials comparing HFOV and CV in preterm or low birth weight infants with pulmonary dysfunction, mainly due to RDS, who required assisted ventilation. Randomization and commencement of treatment needed to be as soon as possible after the start of CV and usually in the first 12 h of life. DATA COLLECTION AND ANALYSIS The methodological quality of each trial was independently reviewed by the various authors. The standard effect measures are relative risk (RR) and risk difference (RD). From 1/RD the number needed to treat to produce one outcome were calculated. For all measures of effect, 95% confidence intervals were used. In subgroup analyses the 99% CIs are also given for summary RRs in the text. Meta-analysis was performed using a fixed effect model. Where heterogeneity was over 50%, the random effects RR is also given. MAIN RESULTS Seventeen eligible studies of 3,652 infants were included. Meta-analysis comparing HFOV with CV revealed no evidence of effect on mortality at 28-30 days of age or at approximately term equivalent age. These results were consistent across studies and in subgroup analyses. The effect of HFOV on CLD in survivors at term equivalent gestational age was inconsistent across studies and the reduction was of borderline significance overall. The effect was similar in trials with a high lung volume strategy for HFOV targeting at very low FiO(2) and trials with a high lung volume strategy with somewhat higher or unspecified target FiO(2). Subgroups of trials showed a significant reduction in CLD with HFOV when no surfactant was used, when piston oscillators were used for HFOV, when lung protective strategies for CV were not used, when randomization occurred at two to six hours of age, and when inspiratory:expiratory ratio of 1:2 was used for HFOV. In the meta-analysis of all trials, pulmonary air leaks occurred more frequently in the HFOV group. In some studies, short-term neurological morbidity with HFOV was found, but this effect was not statistically significant overall. The subgroup of two trials not using a high-volume strategy with HFOV found increased rates of grade 3 or 4 intraventricular hemorrhage and of periventricular leukomalacia. An adverse effect of HFOV on long-term neurodevelopment was found in one large trial but not in the five other trials that reported this outcome. The rate of retinopathy of prematurity is reduced overall in the HFOV group.

Effects of PMA (PHORBOL-12-MYRISTATE-13-ACETATE) on the Developing Rodent Brain

Perinatal infections have a negative impact on brain development. However, the underlying mechanisms leading to neurological impairment are not completely understood and reliable models of inflammation are urgently needed. Using phorbol-myristate-acetate as an activator of inflammation, we investigated the effect on the developing rodent brain. Neonatal rats and mice deficient in IL-18 or IRAK-4 were exposed to PMA. Brains were assessed for regulation of pro- and anti-inflammatory cytokines and cell death 24 hrs, 7 and 14 days after treatment. PMA induced an inflammatory response and caused widespread neurodegeneration in the brains of 3- and 7-day-old rats. In contrast, 14-day-old rats were resistant to the neurotoxic effect of PMA. Histological evaluation at the age of 14 and 21 days revealed a destruction of the cortical microstructure with decreased numerical density of neuronal cells. Mice deficient in IL-18 or IRAK-4 were protected against PMA induced brain injury. PMA treatment during a vulnerable period can alter brain development. IL-18 and IRAK-4 appear to be important for the development of PMA induced injury.

Sildenafil Enhances Quantity of Immature Neurons and Promotes Functional Recovery in the Developing Ischemic Mouse Brain

Background: Hypoxic-ischemic (HI) injury to the developing brain occurs in 1 out of 1,000 live births and remains a major cause of significant morbidity and mortality. A large number of survivors suffer from long-term sequelae including seizures and neurological deficits. However, the pathophysiological mechanisms of recovery after HI insult are not clearly understood, and preventive measures or clinical treatments are nonexistent or not sufficiently effective in the clinical setting. Sildenafil as a specific phosphodiesterase 5 inhibitor leads to increased levels of the second messenger cyclic guanosine monophosphate (cGMP) and promotes functional recovery and neurogenesis after ischemic injury to the adult brain. Objective: Here, we investigated the effect of sildenafil treatment on activation of intracellular signaling pathways, histological and neurogenic response including functional recovery after an ischemic insult to the developing brain. Design/Methods: Nine-day-old C57BL/6 mice were subjected either to sham operation or underwent ligation of the right common carotid artery followed by hypoxia (8%) for 60 min. Animals were either administered sildenafil (10 mg/kg, i.p.) or vehicle 2 h after hypoxia. A subgroup of animals received multiple injections of 10 mg/kg daily on 5 consecutive days. Pups were either perfusion fixed at postnatal days 14 or 47 for immunohistochemical analysis, or brains were dissected 2, 6, 12, and 24 h after the end of hypoxia and analyzed for cGMP, pAkt, pGSK-3β, and β-catenin by means of ELISA or immunoblotting. In addition, behavioral studies using the wire hang test and elevated plus maze were conducted 21 and 38 days after HI injury. Results: Based on cresyl violet staining, single or multiple sildenafil injections did not reveal any differences in injury scoring compared to sham animals. However, cerebral levels of cGMP were altered after sildenafil therapy. Treatment significantly increased numbers of immature neurons, as indicated by doublecortin immunoreactivity in the ipsilateral subventricular zone and striatum. In addition, animals treated with sildenafil after HI insult demonstrated improved functional recovery. pAkt, pGSK-3β, and β-catenin levels vary after HI injury but additional sildenafil treatment had no impact on protein expression compared to the level of sham controls. Conclusions: Here, we report that treatment with sildenafil after HI insult did not improve histological brain injury scores. Nevertheless, our results suggest involvement of the cGMP and PI3K/Akt/GSK-3β signaling pathway with promotion of a neurogenic response and reduction of neurological deficits. In summary, sildenafil may have a role in promoting recovery from HI injury in the developing brain.

Apolipoprotein E gene polymorphisms and intraventricular haemorrhage in infants born preterm: a large prospective multicentre cohort study

Infants born preterm are at risk of intraventricular haemorrhage (IVH) but individual susceptibility related to genes is not well defined in this vulnerable population. Apolipoprotein genotypes APOE2 and APOE4 increase the hazard of cerebral haemorrhages in adults. We investigated whether APOE is associated with prevalence of IVH and is likely to have a particular genotype.

Neonatal Arterial Ischemic Stroke – A Hospital Based Active Surveillance Study in Germany

Background Neonatal arterial ischemic stroke (NAIS) accounts for substantial long term sequelae in children. The potential effectiveness of neuroprotective therapies needs to be evaluated in appropriate studies with sufficient power. Objective To identify annual number of NAIS cases in Germany potentially eligible for randomized interventional trials. Methods Active surveillance for NAIS in 345 pediatric hospitals with questionnaire based validation of reported cases. Results Incidence of NAIS (7.1/100000 births) was in the range of other population-based studies. To design future clinical trials with anticoagulative or regenerative therapies, it is of major importance to distinguish between cases with or without relevant perinatal pathology. Children without underlying disease or premature birth accounted for 56% of all reported NAIS cases (primary NAIS). In 69% of the primary cases clinical seizures were observed. Although 31% showed other, less pathognomonic symptoms, NAIS was diagnosed. Mean time span between onset of symptoms and diagnosis was 2.9 days. The sensitivity of the initial ultrasound performed in all cases was 69%. Conclusions NAIS is a rare but not negligible morbidity in newborns. Asymptomatic children account for 56% of NAIS in all neonates. In these, not only seizures but also other unexplained symptoms should trigger diagnostic work-up with cUS and cMRI. Negative initial ultrasound results do not exclude NAIS.