[Show abstract][Hide abstract] ABSTRACT: The authors have previously shown that exposure of the neonatal nonhuman primate (NHP) brain to isoflurane for 5 h causes widespread acute apoptotic degeneration of neurons and oligodendrocyte. The current study explored the potential apoptogenic action of isoflurane in the fetal NHP brain.
Fetal rhesus macaques at gestational age of 120 days (G120) were exposed in utero for 5 h to isoflurane anesthesia (n = 5) or to no anesthesia (control condition; n = 4), and all regions of the brain were systematically evaluated 3 h later for evidence of apoptotic degeneration of neurons or glia.
Exposure of the G120 fetal NHP brain to isoflurane caused a significant increase in apoptosis of neurons and of oligodendrocytes at a stage when oligodendrocytes were just beginning to myelinate axons. The neuroapoptosis response was most prominent in the cerebellum, caudate, putamen, amygdala, and several cerebrocortical regions. Oligodendrocyte apoptosis was diffusely distributed over many white matter regions. The total number of apoptotic profiles (neurons + oligodendrocytes) in the isoflurane-exposed brains was increased 4.1-fold, compared with the brains from drug-naive controls. The total number of oligodendrocytes deleted by isoflurane was higher than the number of neurons deleted.
Isoflurane anesthesia for 5 h causes death of neurons and oligodendrocytes in the G120 fetal NHP brain. In the fetal brain, as the authors previously found in the neonatal NHP brain, oligodendrocytes become vulnerable when they are just achieving myelination competence. The neurotoxic potential of isoflurane increases between the third trimester (G120) and the neonatal period in the NHP brain.
[Show abstract][Hide abstract] ABSTRACT: Maternal ingestion of alcohol during pregnancy can cause a disability syndrome termed Fetal Alcohol Spectrum Disorder (FASD), which may include craniofacial malformations, structural pathology in the brain, and a variety of long-term neuropsychiatric disturbances. There is compelling evidence that exposure to alcohol during early embryogenesis (4th week of gestation) can cause excessive death of cell populations that are essential for normal development of the face and brain. While this can explain craniofacial malformations and certain structural brain anomalies that sometimes accompany FASD, in many cases these features are absent, and the FASD syndrome manifests primarily as neurobehavioral disorders. It is not clear from the literature how alcohol causes these latter manifestations. In this review we will describe a growing body of evidence documenting that alcohol triggers widespread apoptotic death of neurons and oligodendroglia (OLs) in the developing brain when administered to animals, including non-human primates, during a period equivalent to the human third trimester of gestation. This cell death reaction is associated with brain changes, including overall or regional reductions in brain mass, and long-term neurobehavioral disturbances. We will also review evidence that many drugs used in pediatric and obstetric medicine, including general anesthetics (GAs) and anti-epileptics (AEDs), mimic alcohol in triggering widespread apoptotic death of neurons and OLs in the third trimester-equivalent animal brain, and that human children exposed to GAs during early infancy, or to AEDs during the third trimester of gestation, have a significantly increased incidence of FASD-like neurobehavioral disturbances. These findings provide evidence that exposure of the developing human brain to GAs in early infancy, or to alcohol or AEDs in late gestation, can cause FASD-like neurodevelopmental disability syndromes. We propose that the mechanism by which alcohol, GAs and AEDs produce neurobehavioral deficit syndromes is by triggering apoptotic death and deletion of neurons and OLs (or their precursors) from the developing brain. Therefore, there is a need for research aimed at deciphering mechanisms by which these agents trip the apoptosis trigger, the ultimate goal being to learn how to prevent these agents from causing neurodevelopmental disabilities.
[Show abstract][Hide abstract] ABSTRACT: Anesthetic and anti-epileptic drugs used in pediatric and obstetric medicine and several drugs, including alcohol, that are abused by pregnant women, trigger widespread neuroapoptosis in the developing brain of several animal species, including non-human primates. Caffeine (CAF) is often administered to premature infants to stimulate respiration, and these infants are also exposed simultaneously to anesthetic drugs for procedural sedation and/or surgical procedures. Pregnant women who abuse alcohol or other apoptogenic drugs also may heavily consume CAF. We administered CAF to infant mice alone or in combination with alcohol, phencyclidine, diazepam, midazolam, ketamine, or isoflurane, which are drugs of abuse and/or drugs frequently used in pediatric medicine, and found that CAF weakly triggers neuroapoptosis by itself and markedly potentiates the neuroapoptogenic action of each of these other drugs. Exposure of infant mice to CAF + phencyclidine resulted in long-term impairment in behavioral domains relevant to attention deficit/hyperactivity disorder, whereas exposure to CAF + diazepam resulted in long-term learning/memory impairment. At doses used in these experiments, these behavioral impairments either did not occur or were substantially less pronounced in mice exposed to CAF alone or to phencyclidine or diazepam alone. CAF currently enjoys the reputation of being highly beneficial and safe for use in neonatal medicine. Our data suggest the need to consider whether CAF may have harmful as well as beneficial effects on the developing brain, and the need for research aimed at understanding the full advantage of its beneficial effects while avoiding its potentially harmful effects.
[Show abstract][Hide abstract] ABSTRACT: Background:
In utero exposure of the fetal non-human primate (NHP) brain to alcohol on a single occasion during early or late third-trimester gestation triggers widespread acute apoptotic death of cells in both gray and white matter (WM) regions of the fetal brain. In a prior publication, we documented that the dying gray matter cells are neurons, and described the regional distribution and magnitude of this cell death response. Here, we present new findings regarding the magnitude, identity and maturational status of the dying WM cells in these alcohol-exposed fetal NHP brains.
Our findings document that the dying WM cells belong to the oligodendrocyte (OL) lineage. OLs become vulnerable when they are just beginning to generate myelin basic protein in preparation for myelinating axons, and they remain vulnerable throughout later stages of myelination. We found no evidence linking astrocytes, microglia or OL progenitors to this WM cell death response. The mean density (profiles per mm3) of dying WM cells in alcohol-exposed brains was 12.7 times higher than the mean density of WM cells dying by natural apoptosis in drug-naive control brains.
In utero exposure of the fetal NHP brain to alcohol on a single occasion triggers widespread acute apoptotic death of neurons (previous study) and of OLs (present study) throughout WM regions of the developing brain. The rate of OL apoptosis in alcohol-exposed brains was 12.7 times higher than the natural OL apoptosis rate. OLs become sensitive to the apoptogenic action of alcohol when they are just beginning to generate constituents of myelin in their cytoplasm, and they remain vulnerable throughout later stages of myelination. There is growing evidence for a similar apoptotic response of both neurons and OLs following exposure of the developing brain to anesthetic and anticonvulsant drugs. Collectively, this body of evidence raises important questions regarding the role that neuro and oligo apoptosis may play in the human condition known as fetal alcohol spectrum disorder (FASD), and also poses a question whether other apoptogenic drugs, although long considered safe for pediatric/obstetric use, may have the potential to cause iatrogenic FASD-like developmental disability syndromes.
[Show abstract][Hide abstract] ABSTRACT: /st> Exposure of the fetal or neonatal non-human primate (NHP) brain to isoflurane or ketamine for 5 h causes widespread apoptotic degeneration of neurones, and exposure to isoflurane also causes apoptotic degeneration of oligodendrocytes (OLs). The present study explored the apoptogenic potential of propofol in the fetal and neonatal NHP brain. Method Fetal rhesus macaques at gestational age 120 days were exposed in utero, or postnatal day 6 rhesus neonates were exposed directly for 5 h to propofol anaesthesia (n=4 fetuses; and n=4 neonates) or to no anaesthesia (n=4 fetuses; n=5 neonates), and the brains were systematically evaluated 3 h later for evidence of apoptotic degeneration of neurones or glia.
/st> Exposure of fetal or neonatal NHP brain to propofol caused a significant increase in apoptosis of neurones, and of OLs at a stage when OLs were just beginning to myelinate axons. Apoptotic degeneration affected similar brain regions but to a lesser extent than we previously described after isoflurane. The number of OLs affected by propofol was approximately equal to the number of neurones affected at both developmental ages. In the fetus, neuroapoptosis affected particularly subcortical and caudal regions, while in the neonate injury involved neocortical regions in a distinct laminar pattern and caudal brain regions were less affected.
/st> Propofol anaesthesia for 5 h caused death of neurones and OLs in both the fetal and neonatal NHP brain. OLs become vulnerable to the apoptogenic action of propofol when they are beginning to achieve myelination competence.
Preview · Article · Jun 2013 · BJA British Journal of Anaesthesia
[Show abstract][Hide abstract] ABSTRACT: There has been a growing belief in recent decades that unrelieved pain experienced in infancy or fetal life may cause long-term psychological disturbances and/or neurological injury. Accordingly, there has been a trend toward using anesthetic drugs liberally in pediatric medicine to reduce conscious awareness of painful experiences. Currently, a counter trend is gaining momentum, based on mounting evidence from multiple independent laboratories that general anesthetic agents, at clinically relevant doses, cause widespread apoptotic neurodegeneration in the developing brains of several animal species, including fetal and infant non-human primates (NHPs). It has also been shown that neonatal exposure to these agents causes long-term neurobehavioral disturbances in both rodents and NHPs. These preclinical findings prompted several research groups to conduct retrospective epidemiological studies, the results of which suggest that exposure of full term human infants to brief anesthesia more than once, before the age of 4 years, is associated with increased risk for long-term neurocognitive deficits. It remains unclear whether risk is increased by a single prolonged exposure, and no data are available pertaining to premature infants who are often exposed to light anesthesia (procedural sedation) for many hours on multiple occasions.
[Show abstract][Hide abstract] ABSTRACT: Previously we reported that exposure of 6-day-old (P6) rhesus macaques to isoflurane for 5 hours triggers a robust neuroapoptosis response in developing brain. We have also observed (unpublished data) that isoflurane causes apoptosis of cellular profiles in the white matter that resemble glia. We analyzed the cellular identity of the apoptotic white matter profiles and determined the magnitude of this cell death response to isoflurane.
Neonatal (P6) rhesus macaques were exposed for 5 hours to isoflurane anesthesia according to current clinical standards in pediatric anesthesia. Brains were collected 3 hours later and examined immunohistochemically to analyze apoptotic neuronal and glial death.
Brains exposed to isoflurane displayed significant apoptosis in both the white and gray matter throughout the central nervous system. Approximately 52% of the dying cells were glia, and 48% were neurons. Oligodendrocytes (OLs) engaged in myelinogenesis were selectively vulnerable, in contrast to OL progenitors, astrocytes, microglia, and interstitial neurons. When adjusted for control rates of OL apoptosis, the percentage of OLs that degenerated in the forebrain white matter of the isoflurane-treated group was 6.3% of the total population of myelinating OLs.
Exposure of the infant rhesus macaque brain to isoflurane for 5 hours is sufficient to cause widespread apoptosis of neurons and OLs throughout the developing brain. Deletion of OLs at a stage when they are just beginning to myelinate axons could potentially have adverse long-term neurobehavioral consequences that might be additive to the potential consequences of isoflurane-induced neuroapoptosis. ANN NEUROL 2012;72:525-535.
No preview · Article · Oct 2012 · Annals of Neurology
[Show abstract][Hide abstract] ABSTRACT: Exposure of rhesus macaque fetuses for 24 h or neonates for 9 h to ketamine anesthesia causes neuroapoptosis in the developing brain. The current study clarifies the minimum exposure required for and the extent and spatial distribution of ketamine-induced neuroapoptosis in rhesus fetuses and neonates.
Ketamine was administered by IV infusion for 5 h to postnatal day 6 rhesus neonates or to pregnant rhesus females at 120 days' gestation (full term = 165 days). Three hours later, fetuses were delivered by cesarean section, and the fetal and neonatal brains were studied for evidence of apoptotic neurodegeneration, as determined by activated caspase-3 staining.
Both the fetal (n = 3) and neonatal (n = 4) ketamine-exposed brains had a significant increase in apoptotic profiles compared with drug-naive controls (fetal n = 4; neonatal n = 5). Loss of neurons attributable to ketamine exposure was 2.2 times greater in fetuses than in neonates. The pattern of neurodegeneration in fetuses was different from that in neonates, and all subjects exposed at either age had a pattern characteristic for that age.
The developing rhesus macaque brain is sensitive to the apoptogenic action of ketamine at both a fetal and neonatal age, and exposure duration of 5 h is sufficient to induce a significant neuroapoptosis response at either age. The pattern of neurodegeneration induced by ketamine in fetuses was different from that in neonates, and loss of neurons attributable to ketamine exposure was 2.2 times greater in the fetal than neonatal brains.
[Show abstract][Hide abstract] ABSTRACT: The ability of brief exposure to alcohol to cause widespread neuroapoptosis in the developing rodent brain and subsequent long-term neurocognitive deficits has been proposed as a mechanism underlying the neurobehavioral deficits seen in fetal alcohol spectrum disorder (FASD). It is unknown whether brief exposure to alcohol causes apoptosis in the fetal primate brain. Pregnant fascicularis macaques at various stages of gestation (G105 to G155) were exposed to alcohol for 8h, then the fetuses were delivered by caesarean section and their brains perfused with fixative and evaluated for apoptosis. Compared to saline control brains, the ethanol-exposed brains displayed a pattern of neuroapoptosis that was widespread and similar to that caused by alcohol in infant rodent brain. The observed increase in apoptosis was on the order of 60-fold. We propose that the apoptogenic action of alcohol could explain many of the neuropathological changes and long-term neuropsychiatric disturbances associated with human FASD.
Full-text · Article · Oct 2010 · Neurobiology of Disease
[Show abstract][Hide abstract] ABSTRACT: Exposure to NMDA glutamate antagonists during the brain growth spurt period causes widespread neuroapoptosis in the rodent brain. This period in rodents occurs during the first two weeks after birth, and corresponds to the third trimester of pregnancy and several years after birth in humans. The developing human brain may be exposed to NMDA antagonists through drug-abusing mothers or through anesthesia.
We evaluated the long-term neurobehavioral effects of mice exposed to a single dose of the NMDA antagonist, phencyclidine (PCP), or saline, on postnatal day 2 (P2) or P7, or on both P2 and P7. PCP treatment on P2 + P7 caused more severe cognitive impairments than either single treatment. Histological examination of acute neuroapoptosis resulting from exposure to PCP indicated that the regional pattern of degeneration induced by PCP in P2 pups was different from that in P7 pups. The extent of damage when evaluated quantitatively on P7 was greater for pups previously treated on P2 compared to pups treated only on P7.
These findings signify that PCP induces different patterns of neuroapoptosis depending on the developmental age at the time of exposure, and that exposure at two separate developmental ages causes more severe neuropathological and neurobehavioral consequences than a single treatment.
[Show abstract][Hide abstract] ABSTRACT: Several different deletions within the N-terminal tail of the prion protein (PrP) induce massive neuronal death when expressed in transgenic mice. This toxicity is dose-dependently suppressed by coexpression of full-length PrP, suggesting that it results from subversion of a normal physiological activity of cellular PrP. We performed a combined biochemical and morphological analysis of Tg(DeltaCR) mice, which express PrP carrying a 21-aa deletion (residues 105-125) within a highly conserved region of the protein. Death of cerebellar granule neurons in Tg(DeltaCR) mice is not accompanied by activation of either caspase-3 or caspase-8 or by increased levels of the autophagy marker, LC3-II. In electron micrographs, degenerating granule neurons displayed a unique morphology characterized by heterogeneous condensation of the nuclear matrix without formation of discrete chromatin masses typical of neuronal apoptosis. Our data demonstrate that perturbations in PrP functional activity induce a novel, nonapoptotic, nonautophagic form of neuronal death whose morphological features are reminiscent of those associated with excitotoxic stress.
Full-text · Article · Jun 2010 · American Journal Of Pathology
[Show abstract][Hide abstract] ABSTRACT: Brief isoflurane anesthesia induces neuroapoptosis in the developing rodent brain, but susceptibility of non-human primates to the apoptogenic action of isoflurane has not been studied. Therefore, we exposed postnatal day 6 (P6) rhesus macaques to a surgical plane of isoflurane anesthesia for 5 h, and studied the brains 3 h later for histopathologic changes.
With the same intensity of physiologic monitoring typical for human neonatal anesthesia, five P6 rhesus macaques were exposed for 5 h to isoflurane maintained between 0.7 and 1.5 end-tidal Vol% (endotracheally intubated and mechanically ventilated) and five controls were exposed for 5 h to room air without further intervention. Three hours later, the brains were harvested and serially sectioned across the entire forebrain and midbrain, and stained immunohistochemically with antibodies to activated caspase-3 for detection and quantification of apoptotic neurons.
Quantitative evaluation of brain sections revealed a median of 32.5 (range, 18.0-48.2) apoptotic cells/mm of brain tissue in the isoflurane group and only 2.5 (range, 1.1-5.2) in the control group (difference significant at P = 0.008). Apoptotic neuronal profiles were largely confined to the cerebral cortex. In the control brains, they were sparse and randomly distributed, whereas in the isoflurane brains they were abundant and preferentially concentrated in specific cortical layers and regions.
The developing non-human primate brain is sensitive to the apoptogenic action of isoflurane and displays a 13-fold increase in neuroapoptosis after 5 h exposure to a surgical plane of isoflurane anesthesia.
[Show abstract][Hide abstract] ABSTRACT: Millions of human fetuses, infants, and children are exposed to anesthetic drugs every year in the United States and throughout the world. Anesthesia administered during critical stages of neurodevelopment has been considered safe and without adverse long-term consequences. However, recent reports provide mounting evidence that exposure of the immature animal brain to anesthetics during the period of rapid synaptogenesis, also known as the brain growth spurt period, triggers widespread apoptotic neurodegeneration, inhibits neurogenesis, and causes significant long-term neurocognitive impairment. Herein, we summarize currently available evidence for anesthesia-induced pathological changes in the brain and associated long-term neurocognitive deficits and discuss promising strategies for protecting the developing brain from the potentially injurious effects of anesthetic drugs while allowing the beneficial actions of these drugs to be realized.
No preview · Article · Dec 2009 · Anesthesia and analgesia
[Show abstract][Hide abstract] ABSTRACT: Ethanol and anesthetic drugs trigger neuroapoptosis in the developing mouse brain. Recently, it was found that ethanol-induced neuroapoptosis is preceded by suppressed phosphorylation of extracellular signal-regulated protein kinase (ERK), and lithium counteracts both the phosphorylated ERK suppressant action and ethanol-induced neuroapoptosis. The current study was undertaken to address the following questions. (1) Do ketamine and propofol mimic ethanol in suppressing ERK phosphorylation? (2) If they do, does lithium prevent this suppressant action and also prevent these anesthetic drugs from triggering neuroapoptosis?
Postnatal day 5 mice were treated with propofol, ketamine, lithium, a combination of propofol or ketamine with lithium or saline, and their brains were prepared for Western blot analysis or histology. For Western blot, cytosolic lysates of caudate putamen were analyzed for expression of phosphorylated ERK and phosphorylated serine/threonine-specific protein kinase. For histology, brains were stained immunohistochemically with antibodies to activated caspase-3, and the density of activated caspase-3 positive cells was determined.
Ketamine and propofol suppressed phosphorylated ERK, and lithium counteracted both the phosphorylated ERK suppressant action and neuroapoptotic action of these anesthetic drugs.
If further testing finds lithium to be safe for use in pediatric/obstetric medicine, administration of a single dose of lithium before anesthesia induction may be a suitable means of mitigating the risk of anesthesia-induced developmental neuroapoptosis.
[Show abstract][Hide abstract] ABSTRACT: Dimethyl sulfoxide (DMSO) is a solvent that is routinely used as a cryopreservative in allogous bone marrow and organ transplantation. We exposed C57Bl/6 mice of varying postnatal ages (P0–P30) to DMSO in order to study whether DMSO could produce apoptotic degeneration in the developing CNS. DMSO produced widespread apoptosis in the developing mouse brain at all ages tested. Damage was greatest at P7. Significant elevations above the background rate of apoptosis occurred at the lowest dose tested, 0.3 ml/kg. In an in vitro rat hippocampal culture preparation, DMSO produced neuronal loss at concentrations of 0.5% and 1.0%. The ability of DMSO to damage neurons in dissociated cultures indicates that the toxicity likely results from a direct cellular effect. Because children, who undergo bone marrow transplantation, are routinely exposed to DMSO at doses higher than 0.3 ml/kg, there is concern that DMSO might be producing similar damage in human children.
Full-text · Article · Apr 2009 · Neurobiology of Disease
[Show abstract][Hide abstract] ABSTRACT: Magnesium sulfate (MgSO4) is often used as a treatment for pre-eclampsia/eclampsia and preterm labor, resulting in the exposure of a significant number of neonates to this drug despite a lack of evidence suggesting that it is safe, or effective as a tocolytic. While there is evidence that MgSO4 may be neuroprotective in perinatal brain injury, recent reviews have suggested that the effects are dependent upon dose, and that higher doses may actually increase neonatal morbidity and mortality. There is a lack of evidence investigating the neurotoxic effects of neonatal magnesium (Mg) exposure on the developing brain, specifically in terms of neurodevelopmental apoptosis, a cell-killing phenomenon known to be potentiated by other drugs with mechanisms of action at Mg-binding sites (i.e. NMDA receptor antagonists such as MK-801, ketamine, and PCP).
To investigate the effects of Mg exposure on the neonatal mouse brain at different postnatal ages to determine whether MgSO4 treatment causes significant cell death in the developing mouse brain.
C57Bl/6 mice were treated with four doses of MgSO4 (250 mg/kg) on postnatal days 3 (P3), 7 (P7) or 14 (P14). Caspase-3 immunohistochemistry, cupric silver staining, and electron microscopy techniques were used to examine Mg-treated brains for neurotoxic effects.
Qualitative evaluation using cupric silver staining revealed widespread damage throughout the brain in P7 animals. Results of electron microscopy confirmed that the cell death process was apoptotic in nature. Quantitative evaluation of damage to the cortex, caudate-putamen, hippocampus, thalamus, and cerebellum showed that Mg treatment caused significant brain damage in animals treated on P3 and P7, but not P14.
Administration of high doses of Mg may be detrimental to the fetal brain, particularly if exposure occurs during critical periods of neurodevelopment.
[Show abstract][Hide abstract] ABSTRACT: Although a wide range of developmental disabilities following fetal alcohol exposure are observed clinically, the molecular factors that determine the severity of these sequelae remain undefined. In mice exposed to ethanol, deletion of adenylyl cyclases (ACs) 1 and 8 exacerbates the neuroapoptosis that occurs in a prolonged post-treatment period; however, it remains unclear whether AC1 and AC8 are critical to the primary or secondary mechanisms underlying ethanol-induced neurodegeneration. Here we demonstrate that mice lacking AC1 and AC8 (DKO) display significantly increased apoptosis in the striatum, a region sensitive to neuroapoptosis in the acute post-treatment period, compared to WT controls. The enhanced neuroapoptotic response observed in the striatum of DKO mice is accompanied by significant reductions in phosphorylation of known pro-survival proteins, insulin receptor substrate-1 (IRS-1), Akt and extracellular signal-regulated kinases (ERKs). These data suggest that AC1/AC8 are crucial activators of cell survival signaling pathways acutely following ethanol exposure and represent molecular factors that may directly modulate the severity of symptoms associated with Fetal Alcohol Syndrome.
Preview · Article · Nov 2008 · Neurobiology of Disease
[Show abstract][Hide abstract] ABSTRACT: There has been a growing controversy regarding the continued use of glucocorticoid therapy to treat respiratory dysfunction associated with prematurity, as mounting clinical evidence has shown neonatal exposure produces permanent neuromotor and cognitive deficits. Here we report that, during a selective neonatal window of vulnerability, a single glucocorticoid injection in the mouse produces rapid and selective apoptotic cell death of the proliferating neural progenitor cells in the cerebellar external granule layer and permanent reductions in neuronal cell counts of their progeny, the cerebellar internal granule layer neurons. Our estimates suggest that this mouse window of vulnerability would correspond in the human to a period extending from approximately 20 weeks gestation to 6.5 weeks after birth. This death pathway is critically regulated by the proapoptotic Bcl-2 family member Puma and is independent of p53 expression. These rodent data indicate that there exists a previously unknown window of vulnerability during which a single glucocorticoid exposure at clinically relevant doses can produce neural progenitor cell apoptosis and permanent cerebellar pathology that may be responsible for some of the iatrogenically induced neurodevelopmental abnormalities seen in children exposed to this drug. This vulnerability may be related to the physiological role of glucocorticoids in regulating programmed cell death in the mammalian cerebellum.
Full-text · Article · Aug 2008 · Cell Death and Differentiation