Neurotrophic factor expression in three infants with Ondine's curse

The Influence of Neurotrophins on the Brain-Lung Axis: Conception, Pregnancy, and Neonatal Period

Neurotrophins (NTs) are four small proteins produced by both neuronal and non-neuronal cells; they include nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4). NTs can exert their action through both genomic and non-genomic mechanisms by interacting with specific receptors. Initial studies on NTs have identified them only as functional molecules of the nervous system. However, recent research have shown that some tissues and organs (such as the lungs, skin, and skeletal and smooth muscle) as well as some structural cells can secrete and respond to NTs. In addition, NTs perform several roles in normal and pathological conditions at different anatomical sites, in both fetal and postnatal life. During pregnancy, NTs are produced by the mother, placenta, and fetus. They play a pivotal role in the pre-implantation process and in placental and embryonic development; they are also involved in the development of the brain and respiratory system. In the postnatal period, it appears that NTs are associated with some diseases, such as sudden infant death syndrome (SIDS), asthma, congenital central hypoventilation syndrome (CCHS), and bronchopulmonary dysplasia (BPD).

Congenital central hypoventilation syndrome: An overview of etiopathogenesis, associated pathologies, clinical presentation, and management

Congenital central hypoventilation syndrome (CCHS), known colloquially as Ondine's curse, is a rare disorder characterized by impaired autonomic control of breathing during sleep from the loss of vagal input and diminished sensitivity of CO₂ receptors in the medulla. CCHS correlates to the malformation of the neural crest located in the brainstem; this consequently affects the loss of sensitivity of CO₂ chemoreceptors, bringing about hypoventilation during sleep. The primary cause of CCHS is the mutation of the paired-like homeobox PHO2XB gene, found in 90% of the patients. This mutation not only affects breathing but also drives neurological abnormalities such as autonomic and neurocognitive dysfunction. Though typically congenital, there have been late-onset (i.e., acquired) cases reported. It is vital for physicians and clinicians to be able to diagnose CCHS due to its similar presentation to other syndromes and disorders, which may cause it to be misdiagnosed and may account for its deleterious effects. CCHS can lead to a constellation of symptoms, and consideration of diseases that present concomitantly with CCHS affords us a better understanding of the etiology of this illness. Although a rare syndrome, we aim to review the current literature to emphasize the pathogenesis, etiology, clinical presentation, symptoms, diagnosis, and current treatment methods of CCHS for clinicians to better identify and understand this condition.

Psycho-cognitive behavioral problems in sleep disordered children

Sleep disturbances are common in childhood and adolescence. Sleep problems in early infants tend to be persistent and prominent in preschool and school-aged children. Chronic sleep disorders, especially in young children may lead to neurobehavioral problems and psycho-cognitive impairment. Sleep difficulties may be the result of underlying medical conditions, (breathing disorders) or psychological problems. Research studies have shown the association between sleep disorders and day time cognitive impairment, behavioral problems, poor school performance and inattention in children. Appropriate diagnosis and early management of sleep disorders in children lead to improvement of neurocognitive function and behavioral problems in these children.

Disruption of the brain-derived neurotrophic factor (BDNF) immunoreactivity in the human Kölliker-Fuse nucleus in victims of unexplained fetal and infant death

Experimental studies have demonstrated that the neurotrophin brain-derived neutrophic factor (BDNF) is required for the appropriate development of the central respiratory network, a neuronal complex in the brainstem of vital importance to sustaining life. The pontine Kölliker-Fuse nucleus (KFN) is a fundamental component of this circuitry with strong implications in the pre- and postnatal breathing control. This study provides detailed account for the cytoarchitecture, the physiology and the BDNF behavior of the human KFN in perinatal age. We applied immunohistochemistry in formalin-fixed and paraffin-embedded brainstem samples (from 45 fetuses and newborns died of both known and unknown causes), to analyze BDNF, gliosis and apoptosis patterns of manifestation. The KFN showed clear signs of developmental immaturity, prevalently associated to BDNF altered expression, in high percentages of sudden intrauterine unexplained death syndrome (SIUDS) and sudden infant death syndrome (SIDS) victims. Our results indicate that BDNF pathway dysfunctions can derange the normal KFN development so preventing the breathing control in the sudden perinatal death. The data presented here are also relevant to a better understanding of how the BDNF expression in the KFN can be involved in several human respiratory pathologies such as the Rett's and the congenital central hypoventilation syndromes.

Brain-derived neurotrophic factor interacts with astrocytes and neurons to control respiration

Respiratory rhythm is generated and modulated in the brainstem. Neuronal involvement in respiratory control and rhythmogenesis is now clearly established. However, glial cells have also been shown to modulate the activity of brainstem respiratory groups. Although the potential involvement of other glial cell type(s) cannot be excluded, astrocytes are clearly involved in this modulation. In parallel, brain-derived neurotrophic factor (BDNF) also modulates respiratory rhythm. The currently available data on the respective roles of astrocytes and BDNF in respiratory control and rhythmogenesis lead us to hypothesize that there is BDNF-mediated control of the communication between neurons and astrocytes in the maintenance of a proper neuronal network capable of generating a stable respiratory rhythm. According to this hypothesis, progression of Rett syndrome, an autism spectrum disease with disordered breathing, can be stabilized in mouse models by re-expressing the normal gene pattern in astrocytes or microglia, as well as by stimulating the BDNF signaling pathway. These results illustrate how the signaling mechanisms by which glia exerts its effects in brainstem respiratory groups is of great interest for pathologies associated with neurological respiratory disorders.

Congenital central hypoventilation syndrome and the PHOX2B gene: a model of respiratory and autonomic dysregulation

The paired-like homeobox 2B gene (PHOX2B) is the disease-defining gene for congenital central hypoventilation syndrome (CCHS). Individuals with CCHS typically present in the newborn period with alveolar hypoventilation during sleep and often during wakefulness, altered respiratory control including reduced or absent ventilatory responses to hypercarbia and hypoxemia, and autonomic nervous system (ANS) dysregulation; however, a subset of individuals present well into adulthood. Thermoregulation is altered and perception of shortness of breath is absent, but voluntary breathing is retained. Structural and functional magnetic resonance imaging (MRI) and limited post-mortem studies in subjects with CCHS reveal abnormalities in both forebrain and brainstem. MRI changes appear in the hypothalamus (responsible for thermal drive to breathing), posterior thalamus and midbrain (mediating O(2) and oscillatory motor patterns), caudal raphé and locus coeruleus (regulating serotonergic and noradrenergic systems), the lateral medulla, parabrachial pons, and cerebellum (coordinating chemoreceptor and somatic afferent activity with breathing), and insular and cingulate cortices (mediating shortness of breath perception). Structural and functional alterations in these sites may result from PHOX2B mutations or be secondary to hypoxia/perfusion alterations from suboptimal management/compliance. The study of CCHS, with collaboration between physician-scientists and basic scientists, offers a rare opportunity to investigate control of breathing within the complex physiological network of the ANS.

Carbon dioxide chemoreception and hypoventilation syndromes with autonomic dysregulation

Respiratory and autonomic disorders of infancy, childhood, and adulthood are a group of disorders that have varying presentation, combined with a range of severity of respiratory control and autonomic nervous system dysfunction. Within this group, congenital central hypoventilation syndrome and rapid onset obesity with hypothalamic dysfunction, hypoventilation, and autonomic dysregulation, exhibit the greatest respiratory control deficits, requiring supported ventilation as a mainstay of care. The discovery of the key role of the paired-like homeobox 2B gene in autonomic nervous system development, along with the identification of paired-like homeobox 2B gene mutations causing congenital central hypoventilation syndrome, has led to a fruitful dialog between basic scientists and physician-scientists, producing an explosion of knowledge regarding genotype-phenotype correlations in this disorder, as well as important animal models of chemosensory regulation deficit. Though the etiology of rapid onset obesity with hypothalamic dysfunction, hypoventilation, and autonomic dysregulation is still to be determined, recent studies have begun to carefully delineate the phenotype, suggesting that it too may provide fertile ground for research that both advances our knowledge and improves patient care.

Changes in cerebrospinal fluid nerve growth factor levels during chick embryonic development

In the early stages of brain development, cells within the ependymal lining of the neural tube are thought to secrete cerebrospinal fluid (CSF), the so-called neural tube fluid (NTF), whereas before fusion of the neural folds, the neuroepithelium that lines the inside of the neural tube is in contact with amniotic fluid. As the neural tube closes, a membrane formed from these cells invaginates to form the specialized choroid plexus. The choroid plexus is a highly vascularized epithelial cell structure that secretes proteins, including growth factors, into the CSF. Embryonic CSF (e-CSF) contains high concentrations of proteins compared to adult CSF. CSF has been reported to contain nerve growth factor (NGF) and other neurotrophic factors. In this study, total protein concentration and NGF level in e-CSF samples from chick embryos were measured using a dye-based protein assay, enzyme-linked immunosorbent assay (ELISA) and Western blot. The total protein concentration and NGF levels in the CSF decreased from days E10 to E16. There was a rapid increase in total protein content on days E17 and E18, and thereafter the levels decreased from day E19 to day E21. Days E17 and E18 coincide with the onset of neuron migration, proliferation and organization of the cytoarchitecture of the developing cerebral cortex. After that time the total protein concentration and NGF levels decrease until hatching. Since CSF is in contact with the cerebral cortical germinal epithelium, changes in the protein concentration in the CSF could affect neuroepithelial cell proliferation, survival and migration. It is concluded that NGF is not only a constant component of CSF during chick embryogenesis but it might also be involved in cerebral cortical development.

Acute role of the brain-derived neurotrophic factor (BDNF) on the respiratory neural network activity in mice in vitro

In humans, several pathologies are associated with disturbances of the respiratory control, some of them including alteration in the brain-derived neurotrophic factor (BDNF) signalling pathway. BDNF has long been known as a neurotrophic factor involved in survival, differentiation and maintenance of neuronal populations in the peripheral and central nervous system. More recently BDNF has also been discovered to be a potent neuromodulator with acute effects on neuronal excitability and synaptic plasticity. Animals deleted for the gene encoding BDNF exhibit respiratory alteration suggesting an important but yet undefined role of the neurotrophin in respiratory rhythmogenesis either by a trophic and/or an acute action. The possibility that BDNF might exert an acute regulatory role on the rhythmic activity of the respiratory generator of the pre-Bötzinger complex has been recently examined in newborn mice in vitro. Results obtained, reviewed in the present paper, will help getting insights in respiratory rhythm regulatory mechanisms that involve BDNF signalling.