Molecular Pathways of Altered Brain Development in Fetuses Exposed to Hypoxia (original) (raw)
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Developmental Science, 2006
Hypoxia (H) and hypoxia-ischemia (HI) are major causes of foetal brain damage with long-lasting behavioral implications. The effect of hypoxia has been widely studied in human and a variety of animal models. In the present review, we summarize the latest studies testing the behavioral outcomes following prenatal hypoxia/hypoxia-ischemia in rodent models. Delayed development of sensory and motor reflexes during the first postnatal month of rodent life was observed by various groups. Impairment of motor function, learning and memory was evident in the adult animals. Activation of the signaling leading to cell death was detected as early as three hours following H/HI. An increase in the counts of apoptotic cells appeared approximately three days after the insult and peaked about seven days later. Around 14-20 days following the H/HI, the amount of cell death observed in the tissue returned to its basal levels and cell loss was apparent in the brain tissue. The study of the molecular mechanism leading to brain damage in animal models following prenatal hypoxia adds valuable insight to our knowledge of the central events that account for the morphological and functional outcomes. This understanding provides the starting point for the development and improvement of efficient treatment and intervention strategies.
Progress in Neurobiology, 1996
Hypoxia threatens brain function during the entire life-span starting from early fetal age up to senescence. This review compares the short-term, long-term and life-spanning effects of fetal chronic hypoxia and neonatal anoxia on several behavioural paradigms including novelty-induced spontaneous and learning behaviours. Furthermore, it reveals that perinatal hypoxia is an additional threat to neurodegeneration and decline of cognitive and other behaviours during the aging process. Prenatal hypoxia evokes a temporary delay of ingrowth of cholinergic and serotonergic fibres into the hippocampus and neocortex, and causes an enhanced neurodegeneration of 5-HT-ir axons during aging. Neonatal anoxia suppresses hippocampal ChAT activity and up-regulates muscarinic receptor sites for 3H-QNB and 3H-pirenzepine binding in the hippocampus in the early postnatal age. The altered development of axonal arborization and pre- and postsynaptic cholinergic functions may be an important underlying mechanism to explain the behavioural deficits. As far as the cellular mechanisms of perinatal hypoxia is concerned, our primary aim was to study the putative importance of Ca2+ homeostasis of developing neurons by means of pharmacological interventions and by measuring the development of immunoexpression of Ca(2+)-binding proteins. We assessed that nimodipine, an L-type calcium channel blocker, prevented or attenuated the adverse behavioural and neurochemical effects of perinatal hypoxias, while it enhanced the early postnatal development of ir-Ca(2+)-binding proteins. The results are discussed in the context of different related research areas on brain development and hypoxia and ischaemia.
American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 2010
Late-gestational intrauterine hypoxia represents a well-known risk factor of acquired perinatal brain injury. Cell type and age-specific sensitivity of hypoxia-responsive genes to low-oxygen partial pressure is to be considered in the screening for early indicators of fetoplacental tissue hypoxia. To identify early hypoxia-induced alterations in gene expression during late-gestational hypoxia (6% O2, 6 h; gestational day 20) we compared primary mouse placenta and brain transcriptomes using high-density oligonucleotide microarrays. Upregulation of candidate marker genes for hypoxia was confirmed by quantitative RT-PCR and immunohistochemistry. Both developing brain and placenta were highly responsive to systemic hypoxia at the level of gene expression involving hypoxia-inducible transcription factor (HIF)-dependent genes and immediate early genes (IEG) (Fos, Jun, Egr1, Bhlhb2), apoptosis-promoting factors (Bnip3, Dusp1, Ier3) that were all upregulated, and genes modulating RNA bindin...
Early Gestational Hypoxia and Adverse Developmental Outcomes
Birth defects research, 2017
Hypoxia is a normal and essential part of embryonic development. However, this state may leave the embryo vulnerable to damage when oxygen supply is disturbed. Embryofetal response to hypoxia is dependent on duration and depth of hypoxia, as well as developmental stage. Early postimplantation rat embryos were resilient to hypoxia, with many surviving up to 1.5 hr of uterine clamping, while most mid-gestation embryos were dead after 1 hour of clamping. Survivors were small and many had a range of defects, principally terminal transverse limb reduction defects. Similar patterns of malformations occurred when embryonic hypoxia was induced by maternal hypoxia, interruption of uteroplacental flow, or perfusion and embryonic bradycardia. There is good evidence that high altitude pregnancies are associated with smaller babies and increased risk of some malformations, but these results are complicated by increased risk of pre-eclampsia. Early onset pre-eclampsia itself is associated with sm...
The Journal of Physiology, 2000
Perinatal hypoxia can cause various short-term, long-term or life-spanning sequelae. Early postnatal hypoxic exposure within the first days of life induces adverse and long-term effects on postnatal growth (Soulier et al. 1997), neurobehavioural development (Nyakas et al. 1996), breathing and ventilatory response to hypoxia (Okubo & Mortola, 1988; Hertzberg et al. 1992) and development of central catecholaminergic areas involved in respiratory control (Seidler & Slotkin, 1990; Soulier et al. 1997). Postnatal breathing onset and respiratory control are dependent on the peripheral chemoreceptors. Chemosensitivity is low in the fetus and resets to a higher Oµ level within a couple of days after birth (Hertzberg et al. 1990). However, the peripheral chemoreceptors and their integrative ventilatory response are not mature at birth and are susceptible to modulation by changes in environmental oxygen occurring during the early postnatal period. In fact, prolonged hypoxic exposure from birth increases the basal activity of the carotid bodies (Hertzberg et al. 1992; Soulier et al. 1997), delays the onset of the chemoreflex response to hypoxia (Eden & Hanson, 1987; Hertzberg et al. 1992) and elicits hyperventilation in adults (Okubo & Mortola, 1988). However, prolonged perinatal hyperoxia induces a hypoplasia of carotid bodies (Erickson et al. 1998), may accelerate the chemoreflex response to hypoxia (Eden & Hanson, 1986) and attenuates the hypoxic ventilatory response in adult rats (Ling et al. 1996). Fetal hypoxia might result from several pathophysiological situations including maternal anaemia, reduced uteroplacental blood flow secondary to maternal hypertension, smoking or ethanol consumption, reduced placenta size or reduced oxygen inhalation by the mother at high altitude. Prenatal hypoxia elicits many disturbances which are manifest at and after birth. Reduced fetal growth (De Grauw et al. 1986), as well as cognitive and motor deficiency (Nyakas et al. 1996), results from hypoxic insult during gestation. Rats born after hypoxic gestation present, at 1 day of postnatal age, respiratory as well as metabolic disturbances characteristic of hypoxaemia of the newborn
Developmental changes induced by graded prenatal systemic hypoxic–ischemic insults in rats
Neurobiology of Disease, 2005
In infants, a common consequence of systemic perinatal insults is disruption of neonatal brain development. Such insults can cause cerebral palsy, cognitive delay, epilepsy and other chronic neurologic deficits in children. The mechanisms underlying disruption of brain development after perinatal insults are poorly defined. To mimic human systemic insults, a transient prenatal hypoxic-ischemic insult model was developed in rodents. Ischemic animals showed reproducible histological lesions including oligodendrocyte loss, gliosis, and axonal disruption. Ischemic animals displayed persistent postnatal loss of oligodendrocyte lineage cells and cortical neurons, decreased cell proliferation, increased cell death, elevated pro-inflammatory cytokine levels, and impaired motor skills as young adults. Progressive ischemic intervals produced a graded pattern of injury. This systemic rodent prenatal hypoxicischemic insult accurately models human perinatal brain injury in several important criteria, including functional association of altered brain development with motor delay, and consequently provides novel insights into the pathogenesis of human perinatal brain insults.
New insights into the pathogenesis of perinatal hypoxic-ischemic brain injury
Pediatrics International, 2011
Background: Pathogenesis of perinatal hypoxic-ischemic brain injury (HIE) is complex. In this study, we examined the role of neuroinflammation, oxidative stress and growth factors in perinatal hypoxic-ischemic brain damage. Methods: Ninety neonates (>32 weeks' gestation) with perinatal HIE were enrolled prospectively. Perinatal HIE was categorized into three stages according to the Sarnat and Sarnat clinical scoring system and changes seen on amplitude integrated electroencephalography. Cerebrospinal fluid (CSF) for interleukin-6 (IL-6) and glutathione peroxidase analysis was taken in the first 48 h of life and subsequent CSF for neuron-specific enolase (NSE) and vascular endothelial growth factor (VEGF) analysis 72 h after birth. Neurodevelopmental outcome was assessed at 12 months of corrected gestational age using the Denver Developmental Screening Test. Results: Concentrations of NSE in CSF correlated with severity of HIE (P < 0.0001) and corresponded well with subsequent neurodevelopmental outcome. Concentrations of IL-6 in CSF were markedly increased in neonates with severe HIE (P < 0.0001) and those with subsequent neurological sequels, but were normal in the majority of neonates with mild and moderate HIE. Glutathione peroxidase activity in CSF was significant with the stage of HIE (P < 0.0001) and gestational age (P < 0.0001) and corresponded well with subsequent neurodevelopmental outcome. Advanced stage of HIE was associated with increased concentrations of VEGF in CSF (P < 0.0001). Neurological outcomes at 12 months of age correlated best with CSF level of NSE (P < 0.001) and IL-6 (P < 0.001). Conclusion: Our results suggest that neuroinflammation plays a principal role in perinatal hypoxic-ischemic brain damage and we postulate that oxidative stress and upregulation of VEGF might be important contributing factors in the pathogenesis of hypoxic-ischemic brain injury, particularly in preterm neonates.
Systemic hypoxia differentially affects neurogenesis during early mouse brain maturation
Brain and Development, 2012
Background: Cerebral tissue oxygen level modifies crucial processes of neurogenesis, glial and neuronal development during physiological and hypoxic conditions. Whether hypoxia-sensitive factors such as doublecortin (DCX) and hypoxia-inducible transcription factor (HIF)-regulated CXCR4 and SDF-1 modify and activate adaptation to hypoxia in developing brain is not well understood. Present study investigated maturational regulation of oxygen-sensitive developmental genes and proteins in developing mouse brain in relation to the degree of hypoxia. Methods: Physiological expression of HIF-1, CXCR4, SDF-1 and DCX were analyzed in the brain of C57/BL6 mice (P0-P60). In addition, mice (P0, P7) were exposed to normoxia, acute (8% O 2 , 6 h) or chronic hypoxia (10% O 2 , 7 d) followed by reoxygenation. Gene expression was analyzed by quantitative PCR, proteins were quantified by Western blot analysis and immunohistochemistry. Results: Cerebral HIF-1a protein, CXCR4 and DCX mRNA levels showed maturational stage-related peak levels at P0/P1, whereas SDF-1 mRNA levels were highest at P17. CXCR4 and SDF-1 mRNA levels were not altered in response to hypoxia. Whereas DCX mRNA levels significantly increased during acute hypoxia, down-regulation of DCX transcripts was found in response to chronic hypoxia compared to controls, and these changes were related to specifically vulnerable brain regions. Conclusions: Maturational stage-related dynamic changes of HIF-1a, CXCR4, SDF-1 and DCX may reflect involvement of hypoxia-regulated systems in important developmental regulatory processes of the developing brain. Extending the knowledge of differential effects of hypoxia on neurogenesis and dynamic regulatory networks present data provide a basis for future research on gestational age-specific neuroprotective options.