Biomedical subjects

Petra Bittigau

Publications and source records attributed to Petra Bittigau.

At least 19 recordsLinked to original sources

PubMed2005

NMDA antagonist inhibits the extracellular signal-regulated kinase pathway and suppresses cancer growth.

Glutamate antagonists limit the growth of human cancers in vitro. The mechanism of anticancer action of NMDA antagonists is not known, however. In this article, we report that the NMDA antagonist dizocilpine inhibits the extracellular signal-regulated kinase 1/2 pathway, an intracellular signaling cascade that is activated by growth factors and controls the proliferation of cancer cells. Dizocilpine reduces the phosphorylation of cAMP-responsive element binding protein, suppresses the expression of cyclin D1, up-regulates the cell cycle regulators and tumor suppressor proteins p21 and p53, and increases the number of lung adenocarcinoma cells in the G(2) and S phases of the cell cycle. Silencing of the tumor suppressor protein p21 abolishes antiproliferative action of dizocilpine. Consistent with inhibition of the extracellular signal-regulated kinase 1/2-signaling cascade, dizocilpine reverses the stimulation of proliferation induced by epidermal, insulin, and basic fibroblast growth factors in lung adenocarcinoma cells. Furthermore, dizocilpine prolongs the survival of mice with metastatic lung adenocarcinoma and slows the growth of neuroblastoma and rhabdomyosarcoma in mice. These findings reveal the mechanism of antiproliferative action of dizocilpine and indicate that it may be useful in the therapy of human cancers.

Antineoplastic Agents↗

PubMed2005

Caspase-1-processed interleukins in hyperoxia-induced cell death in the developing brain.

Infants born prematurely may develop neurocognitive deficits without an obvious cause. Oxygen, which is widely used in neonatal medicine, constitutes one possible contributing neurotoxic factor, because it can trigger neuronal apoptosis in the developing brain of rodents. We hypothesized that two caspase-1-processed cytokines, interleukin (IL)-1beta and IL-18, are involved in oxygen-induced neuronal cell death. Six-day-old Wistar rats or C57/BL6 mice were exposed to 80% oxygen for various time periods (2, 6, 12, 24, and 48 hours). Neuronal cell death in the brain, as assessed by Fluoro-Jade B and silver staining, peaked at 12 to 24 hours and was preceded by a marked increase in mRNA and protein levels of caspase 1, IL-1beta, IL-18, and IL-18 receptor alpha (IL-18Ralpha). Intraperitoneal injection of recombinant human IL-18-binding protein, a specific inhibitor of IL-18, attenuated hyperoxic brain injury. Mice deficient in IL-1 receptor-associated kinase 4 (IRAK-4), which is pivotal for both IL-1beta and IL-18 signal transduction, were protected against oxygen-mediated neurotoxicity. These findings causally link IL-1beta and IL-18 to hyperoxia-induced cell death in the immature brain. These cytokines might serve as useful targets for therapeutic approaches aimed at preserving neuronal function in the immature brain, which is exquisitely sensitive to a variety of iatrogenic measures including oxygen.

Animals↗

PubMed2005

Protection with estradiol in developmental models of apoptotic neurodegeneration.

Medical measures that bear no known danger for the adult brain may trigger active neuronal death in the developing brain. Pharmacological blockade of N-methyl-D-aspartate or activation of GABA(A) receptors, blockade of voltage-dependent sodium channels, and oxygen induce widespread apoptotic neurodegeneration during the period of rapid brain growth in rodents. Because such measures are often necessary in critically ill infants and toddlers, search for adjunctive neuroprotective strategies is warranted. We report that 17beta-estradiol ameliorates neurotoxicity of drugs that block N-methyl-D-aspartate receptors, activate GABA(A) receptors, or block voltage-gated sodium channels and reduces neurotoxicity of oxygen in the infant rat brain. This neuroprotective effect is reversed by tamoxifen and cannot be reproduced by 17alpha-estradiol. 17Beta-estradiol did not affect GABA(A) or N-methyl-D-aspartate currents in hippocampal neuronal cultures, indicating that direct modulation of neurotransmitter receptor/channel properties by this compound cannot explain neuroprotective effect. 17beta-Estradiol did, however, increase levels of phosphorylated extracellular signal-regulated kinase 1/2 and AKT, suggesting that activation of these prosurvival proteins may represent one mechanism for its neuroprotective action. 17Beta-estradiol and related compounds may be neuroprotective agents suitable for use in critically ill infants and toddlers. Its supplementation may particularly help to improve neurocognitive outcome in preterm infants who are prematurely deprived of maternal estrogen.

Animals↗

PubMed2005

Sulthiame but not levetiracetam exerts neurotoxic effect in the developing rat brain.

Antiepileptic drugs (AEDs) used to treat seizures in pregnant women, infants, and young children can cause cognitive impairment. One mechanism implicated in the development of neurocognitive deficits is a pathologic enhancement of physiologically occurring apoptotic neuronal death in the developing brain. We investigated whether the newer antiepileptic drug levetiracetam (LEV) and the older antiepileptic drug sulthiame (SUL) have neurotoxic properties in the developing rat brain. SUL significantly enhanced neuronal death in the brains of rat pups ages 0 to 7 days at doses of 100 mg/kg and above, whereas LEV did not show this neurotoxic effect. Dosages of both drugs used in the context of this study comply with an effective anticonvulsant dose range applied in rodent seizure models. Thus, LEV is an AED which lacks neurotoxicity in the developing rat brain and should be considered in the treatment of epilepsy in pregnant women, infants, and toddlers once general safety issues have been properly addressed.

Age Factors↗

PubMed2004

Anticancer agents are potent neurotoxins in vitro and in vivo.

Neurotoxicity of anticancer agents complicates treatment of children with cancer. We investigated neurotoxic effects of common cytotoxic drugs in neuronal cultures and in the developing rat brain. When neurons were exposed to cisplatin (5-100 microM), cyclophosphamide (5-100 microM), methotrexate (5-100 microM), vinblastin (0.1-1 microM), or thiotepa (5-100 microM), a concentration-dependent neurotoxic effect was observed. Neurotoxicity was potentiated by nontoxic glutamate concentrations. The N-methyl-D-aspartate receptor antagonist MK 801 (10 microM), the AMPA receptor antagonists GYKI 52466 (10 microM) and NBQX (10 microM), and the pancaspase inhibitor Ac-DEVD-CHO (1 nM) ameliorated neurotoxicity of cytotoxic drugs. To investigate neurotoxicity in vivo, we administered to 7-day-old rats the following: cisplatin (5-15 mg/kg i.p.), cyclophosphamide (200-600 mg/kg i.p.), thiotepa (15-45 mg/kg), or ifosfamide (100-500 mg/kg) and their brains were analyzed at 4 to 24 hours. Cytotoxic drugs produced widespread lesions within cortex, thalamus, hippocampal dentate gyrus, and caudate nucleus in a dose-dependent fashion. Early histological analysis demonstrated dendritic swelling and relative preservation of axonal terminals, which are morphological features indicating excitotoxicity. After longer survival periods, degenerating neurons displayed morphological features consistent with active cell death. These results demonstrate that anticancer drugs are potent neurotoxins in vitro and in vivo; they activate excitotoxic mechanisms but also trigger active neuronal death.

Animals↗

PubMed2004

Apoptotic neurodegeneration in the context of traumatic injury to the developing brain.

Head trauma is the leading cause of death and disability in the pediatric population. Some recent studies on neuropathological and biochemical features of traumatic injury to the developing brain revealed interesting aspects and potential targets for future research. Trauma triggers both excitotoxic and apoptotic neurodegeneration in the developing rat brain. Apoptotic neurodegeneration occurs in a delayed fashion over several days and contributes in an age-dependent fashion to neuropathologic outcome following head trauma, with the immature brain being exceedingly sensitive. Biochemical studies indicate that both the extrinsic and the intrinsic apoptotic pathways are involved in pathogenesis of apoptotic cell death following trauma in the developing brain and that caspase inhibition ameliorates apoptotic neurodegeneration in an infant head trauma model. Given the major contribution of apoptotic neurodegeneration to neuropathologic outcome following trauma to the developing brain, interference with apoptotic pathways may comprise a potential therapeutic target in pediatric traumatic brain injury.

Age Factors↗

PubMed2004

Therapeutic doses of topiramate are not toxic to the developing rat brain.

Antiepileptic drugs (AEDs) used to treat seizures in pregnant women, infants, and young children may cause cognitive impairment. One of the implicated mechanisms is enhancement of apoptotic neuronal death, which occurs physiologically in the developing brain. We investigated whether topiramate, one of the newer antiepileptic drugs, has neurotoxic properties in the developing rat brain. Topiramate slightly but significantly enhanced apoptotic neuronal death in the 7-day-old rat brain at doses of 50 mg/kg and above. These doses are several folds higher than reported ED(50) doses in infant rodent seizure models that respond to topiramate. Electron microscopy confirmed that dying neurons following topiramate treatment displayed the same morphological features as neurons undergoing physiological cell death during development. When compared to the neurotoxicity profile of phenytoin, valproate, and phenobarbital, the separation between the effective anticonvulsant dose and the neurotoxic dose was greater for topiramate and the neurotoxic effect was lower.

Age Factors↗

PubMed2004

Erythropoietin protects the developing brain against N-methyl-D-aspartate receptor antagonist neurotoxicity.

Pharmacological blockade of NMDA receptor function induces apoptotic neurodegeneration in the developing rat brain. However, the use of NMDA receptor antagonists as anesthetics and sedatives represents a difficult-to-avoid clinical practice in pediatrics. This warrants the search for adjunctive neuroprotective measures that will prevent or ameliorate neurotoxicity of NMDA receptor antagonists. The NMDA receptor antagonist MK801 triggered apoptosis in the neonatal rat forebrain, most notably in cortex and thalamus. MK801 exposure reduced mRNA levels of erythropoietin (EPO) and the EPO receptor, suggesting that loss of endogenous EPO activity may contribute to MK801-induced apoptosis. Coadministration of recombinant EPO (rEPO) conferred 50% neuroprotection, partially restored MK801-induced reduction of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) mRNA, and prevented decreased phosphorylation levels of extracellular signal-regulated protein kinase-1/2 (ERK1/2) and Akt. These observations indicate that rEPO partly rescues newborn rats from MK801-mediated brain damage by enhancing neurotrophin-associated signaling pathways.

Animals↗

PubMed2004

Mechanisms leading to disseminated apoptosis following NMDA receptor blockade in the developing rat brain.

The developing rodent brain is vulnerable to pharmacological blockade of N-methyl-d-aspartate (NMDA) receptors which can lead to severe and disseminated apoptotic neurodegeneration. Here, we show that systemic administration of the NMDA receptor antagonist MK801 to 7-day-old rats leads to impaired activity of extracellular signal-regulated kinase 1/2 (ERK1/2) and reduces levels of phosphorylated cAMP-responsive element binding protein (CREB) in brain regions which display severe apoptotic neurodegeneration. Impaired ERK1/2 and CREB activity were temporally paralleled by sustained depletion of neurotrophin expression, particularly brain-derived neurotrophic factor (BDNF). BDNF supplementation fully prevented MK801-induced neurotoxicity in immature neuronal cultures and transgenic constitutive activation of Ras was associated with marked protection against MK801-induced apoptotic neuronal death. These data indicate that uncoupling of NMDA receptors from the ERK1/2-CREB signaling pathway in vivo results in massive apoptotic deletion of neurons in the developing rodent brain.

Age Factors↗

PubMed2004

Oxygen causes cell death in the developing brain.

Substantial neurologic morbidity occurs in survivors of premature birth. Premature infants are exposed to partial oxygen pressures that are fourfold higher compared to intrauterine conditions, even if no supplemental oxygen is administered. Here we report that short exposures to nonphysiologic oxygen levels can trigger apoptotic neurodegeneration in the brains of infant rodents. Vulnerability to oxygen neurotoxicity is confined to the first 2 weeks of life, a period characterized by rapid growth, which in humans expands from the sixth month of pregnancy to the third year of life. Oxygen caused oxidative stress, decreased expression of neurotrophins, and inactivation of survival signaling proteins Ras, extracellular signal-regulated kinase (ERK 1/2), and protein kinase B (Akt). The synRas-transgenic mice overexpressing constitutively activated Ras and phosphorylated kinases ERK1/2 in the brain were protected against oxygen neurotoxicity. Our findings reveal a mechanism that could potentially damage the developing brain of human premature neonates.

Aging↗

PubMed2004

Entorhinal cortex lesion in the mouse induces transsynaptic death of perforant path target neurons.

Entorhinal cortex lesion (ECL) is a well described model of anterograde axonal degeneration, subsequent sprouting and reactive synaptogenesis in the hippocampus. Here, we show that such lesions induce transsynaptic degeneration of the target cells of the lesions pathway in the dentate gyrus. Peaking between 24 and 36 hours post-lesion, dying neurons were labeled with DeOlmos silver-staining and antisera against activated caspase 3 (CCP32), a downstream inductor of programmed cell death. Within caspase 3-positive neurons, fragmented nuclei were co-localized using Hoechst 33342 staining. Chromatin condensation and nuclear fragmentation were also evident in semithin sections and at the ultrastructural level, where virtually all caspase 3-positive neurons showed these hallmarks of apoptosis. There is a well-described upregulation of the apoptosis-inducing CD95/L system within the CNS after trauma, yet a comparison of caspase 3-staining patterns between CD95 (Ipr)- and CD95L (gld)-deficient with non-deficient mice (C57/bl6) provided no evidence for CD95L-mediated neuronal cell death in this setting. However, inhibition of NMDA receptors with MK-801 completely suppressed caspase 3 activation, pointing to glutamate neurotoxicity as the upstream inducer of the observed cell death. Thus, these data show that axonal injury in the CNS does not only damage the axotomized neurons themselves, but can also lethally affect their target cells, apparently by activating glutamate-mediated intracellular pathways of programmed cell death.

Animals↗

PubMed2003

Hyperoxia causes inducible nitric oxide synthase-mediated cellular damage to the immature rat brain.

Relative hyperoxia is a condition frequently encountered in premature infants, either spontaneously or during treatment in the Neonatal Intensive Care Unit. The effects of high inspiratory oxygen concentrations on immature brain cells and their signaling cascades are largely unknown. The aim of the study was to investigate the effect of hyperoxia on the amount and topographic distribution of iNOS-expression (inducible nitric oxide synthase) in the immature rat brain, and to localize hyperoxia-induced formation of peroxynitrite as a potential marker of cellular damage to immature cerebral structures. Seven-day-old Wistar rat pups were exposed to >80% oxygen for 24 h and were then transcardially perfused. Following paraformaldehyde fixation, brains were paraffin-embedded and immunohistochemically stained for iNOS and nitrotyrosine. iNOS protein was quantified by Western blot; iNOS mRNA expression was studied by RT-PCR. Total brain iNOS mRNA was up-regulated, demonstrating a peak at 6 h following the onset of hyperoxia. Immunohistochemical staining was predominantly observed in microglial cells of hippocampus and frontal cortex with some iNOS reactivity in endothelial and perivascular cells. Nitrotyrosine staining was positive in apical dendrites of neurons in the frontal cortex. There was no positive staining for iNOS or nitrotyrosine in control animals. Hyperoxia causes iNOS mRNA and protein up-regulation in microglial cells of the immature rat brain. Positive neuronal nitrotyrosine staining indicates formation of peroxynitrite with potential deleterious effects for immature cellular structures in the neonatal brain.

Animals↗

PubMed2003

Neuropathological and biochemical features of traumatic injury in the developing brain.

Trauma to the developing brain constitutes a poorly explored field. Some recent studies attempting to model and study pediatric head trauma, the leading cause of death and disability in the pediatric population, revealed interesting aspects and potential targets for future research. Trauma triggers both excitotoxic and apoptotic neurodegeneration in the developing rat brain. Excitotoxic neurodegeneration develops and subsides rapidly (within hours) whereas apoptotic cell death occurs in a delayed fashion over several days following the initial traumatic insult. Apoptotic neurodegeneration contributes in an age-dependent fashion to neuronal injury following head trauma, with the immature brain being exceedingly sensitive. In the most vulnerable ages the apoptosis contribution to the extent of traumatic brain damage far outweighs that of the excitotoxic component. Molecular and biochemical studies indicate that both extrinsic and intrinsic mechanisms are involved in pathogenesis of apoptotic cell death following trauma. Interestingly, in infant rats a pan-caspase inhibitor ameliorated apoptotic neurodegeneration with a therapeutic time window of up to 8 h after trauma. These results help explain unfavorable outcomes of very young pediatric head trauma patients and imply that regimens which target slow active forms of cell death may comprise a successful neuroprotective approach.

Aging↗

PubMed2003

Antiepileptic drugs and apoptosis in the developing brain.

Epilepsy is the most common neurologic disorder in young humans. Antiepileptic drugs (AEDs), used to treat seizures in children, infants, and pregnant women, cause cognitive impairment, microcephaly, and birth defects by unknown mechanisms. We tested whether common AEDs cause neurodegeneration in the developing rat brain. Rats aged 3-30 days received phenytoin, phenobarbital, diazepam, clonazepam, vigabatrin, or valproic acid. Histologic examination of the brains revealed that these drugs cause widespread and dose-dependent apoptotic neurodegeneration in the developing rat brain during the brain growth spurt period. Apoptotic neurodegeneration was triggered at plasma drug levels relevant for seizure control in humans. Antiepileptic drugs lead to reduced expression of neurotrophins and decreased concentrations of the active forms of ERK1/2, RAF, and AKT. beta-Estradiol, which stimulates pathways that are activated by neurotrophins, ameliorated AEDs-induced apoptotic neurodegeneration. Our findings present one possible mechanism to explain cognitive impairment and reduced brain mass associated with pre- or postnatal exposure of humans to antiepileptic therapy.

Animals↗

PubMed2002

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. beta-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.

Animals↗

PubMed2002

Pathways leading to apoptotic neurodegeneration following trauma to the developing rat brain.

Trauma triggers diffuse apoptotic neurodegeneration in the developing rat brain. To explore the pathogenesis of this phenomenon we investigated the involvement of three possible mechanisms: death receptor activation, activation of the intrinsic apoptotic pathway by cytochrome c release into the cytoplasm, and changes in trophic support provided by endogenous neurotrophins. We detected a decrease in the expression of bcl-2 and bcl-x(L), two antiapoptotic proteins that decrease mitochondrial membrane permeability, an increase in cytochrome c immunoreactivity in the cytosolic fraction, and an activation of caspase-9 in brain regions which show apoptotic neurodegeneration following percussion brain trauma in 7-day-old rats. Increase in the expression of the death receptor Fas was revealed by RT-PCR analysis, Western blotting, and immunohistochemistry, as was activation of caspase-8 in cortex and thalamus. Apoptotic neurodegeneration was accompanied by an increase in the expression of BDNF and NT-3 in vulnerable brain regions. The pancaspase inhibitor z-VAD.FMK ameliorated apoptotic neurodegeneration with a therapeutic time window of up to 8 h after trauma. These findings suggest involvement of intrinsic and extrinsic apoptotic pathways in neurodegeneration following trauma to the developing rat brain. Upregulation of neurotrophin expression may represent an endogenous mechanism that limits this apoptotic process.

Amino Acid Chloromethyl Ketones↗

PubMed2002

The enigma of fetal alcohol neurotoxicity.

The neurotoxic effects of ethanol on the human fetal brain (fetal alcohol syndrome, FAS) have been recognized for three decades, but the underlying mechanisms have remained elusive. Recently, we discovered that a single episode of ethanol intoxication lasting for several hours can trigger a massive wave of apoptotic neurodegeneration in the developing rat or mouse brain. The window of vulnerability coincides with the developmental period of synaptogenesis, also known as the brain growth-spurt period, which in rodents is a postnatal event, but in humans extends from the sixth month of gestation to several years after birth. We propose that the N-methyl-D-aspartate (NMDA) antagonist and gamma-aminobutyric (GABA)mimetic properties of ethanol are responsible for its apoptogenic action, in that we have found that other drugs that block NMDA glutamate receptors or mimic GABA at GABA(A) receptors also trigger apoptotic neurodegeneration in the developing brain. Our findings have clinical significance, not only because they can explain the reduced brain mass and neurobehavioral disturbances associated with the human FAS, but because many agents in the human environment, other than ethanol, have NMDA antagonist or GABAmimetic properties. Such agents include drugs that may be abused by pregnant mothers [phencyclidine (angel dust), ketamine (Special K), nitrous oxide (laughing gas), barbiturates, benzodiazepines], and many medicinals used in obstetric and pediatric neurology (anticonvulsants), and anesthesiology (all general anesthetics are either NMDA antagonists or GABAmimetics).

Alcohol-Induced Disorders, Nervous System↗

PubMed2002

Glutamate and GABA receptor dysfunction in the fetal alcohol syndrome.

The brain damaging effects of ethanol, as the most disabling component of the fetal alcohol syndrome FAS), have been recognized for 3 decades, but the mechanism underlying these effects has remained elusive. Recently, we discovered that ethanol triggers widespread apoptotic neurodegeneration throughout the developing brain when administered to infant rodents during the period of synaptogenesis, also known as the brain growth spurt period. These findings provide a more likely explanation than has heretofore been available for the reduced brain mass and lifelong neurobehavioral disturbances associated with the human FAS. We propose that a dual mechanism - blockade of NMDA glutamate receptors and hyperactivation of GABA(A) receptors - mediates ethanol's apoptogenic action, based on established evidence that ethanol has both NMDA antagonist and GABAmimetic properties, and our recent finding that other drugs with either NMDA antagonist or GABAmimetic properties robustly trigger apoptotic neurodegeneration in the developing brain. The brain growth spurt occurs in different species at different times relative to birth. In rats and mice it is a postnatal event, but in humans it extends from the sixth month of gestation to several years after birth. Thus, there is a period in pre and postnatal human development, lasting for several years, during which immature CNS neurons are prone to commit suicide if exposed to intoxicating concentrations of drugs with NMDA antagonist or GABAmimetic properties. These findings are important, not only because of their relevance to the FAS, but because there are many agents in the human environment, other than ethanol, that have NMDA antagonist or GABAmimetic properties. Such agents include drugs that may be abused by pregnant mothers [ethanol, phencyclidine (angel dust), ketamine (Special K), nitrous oxide (laughing gas), barbiturates, benzodiazepines], and many medicinals used in obstetric and pediatric neurology (anticonvulsants), and anesthesiology (all general anesthetics are either NMDA antagonists or GABAmimetics).

Journal Article↗