In autophagy long‐lived proteins, protein aggregates or damaged organelles are engulfed by vesicles called autophagosomes prior to lysosomal degradation. Autophagy dysfunction is a hallmark of ...several neurodegenerative diseases in which misfolded proteins or dysfunctional mitochondria accumulate. Excessive autophagy can also exacerbate brain injury under certain conditions. In this review, we provide specific examples to illustrate the critical role played by autophagy in pathological conditions affecting the brain and discuss potential therapeutic implications. We show how a singular type of autophagy‐dependent cell death termed autosis has attracted attention as a promising target for improving outcomes in perinatal asphyxia and hypoxic‐ischaemic injury to the immature brain. We provide evidence that autophagy inhibition may be protective against radiotherapy‐induced damage to the young brain. We describe a specialized form of macroautophagy of therapeutic relevance for motoneuron and neuromuscular diseases, known as chaperone‐assisted selective autophagy, in which heat shock protein B8 is used to deliver aberrant proteins to autophagosomes. We summarize studies pinpointing mitophagy mediated by the serine/threonine kinase PINK1 and the ubiquitin–protein ligase Parkin as a mechanism potentially relevant to Parkinson's disease, despite debate over the physiological conditions in which it is activated in organisms. Finally, with the example of the autophagy‐inducing agent rilmenidine and its discrepant effects in cell culture and mouse models of motor neuron disorders, we illustrate the importance of considering aspects such a disease stage and aggressiveness, type of insult and load of damaged or toxic cellular components, when choosing the appropriate drug, timepoint and duration of treatment.
Autophagy is a process whereby damaged or abnormal components, such as proteins or organelles, are degraded in the cell. In this manuscript, we use specific examples to illustrate how alterations in this process are involved in various pathological conditions of the brain, reviewing selected mechanisms associated with its detrimental enhancement or impairment. Further, we provide prospects for therapy and discuss key issues to be considered when exploring therapeutic avenues based on the manipulation of autophagy.
There are inherent structural and functional differences in the central nervous systems (CNS) of females and males. It has been gradually established that these sex-specific differences are due to a ...spectrum of genetic, epigenetic, and hormonal factors which actively contribute to the differential incidences, disease courses, and even outcomes of CNS diseases between sexes. Microglia, as principle resident macrophages in the CNS, play a crucial role in both CNS physiology and pathology. However, sex differences of microglia have been relatively unexplored until recently. Emerging data has convincingly demonstrated the existence of sex-dependent structural and functional differences of rodent microglia, consequently changing our current understanding of these versatile cells. In this review, we attempt to comprehensively outline the current advances revealing microglial sex differences in rodent and their potential implications for specific CNS diseases with a stark sex difference. A detailed understanding of molecular processes underlying microglial sex differences is of major importance in design of translational sex- and microglia-specific therapeutic approaches.
Microglia are the resident innate immune cells of the immune-privileged CNS and, as such, represent the first line of defence against tissue injury and infection. Given their location, microglia are ...undoubtedly the first immune cells to encounter a developing primary brain tumour. Our knowledge of these cells is therefore important to consider in the context of such neoplasms. As the heterogeneous nature of the most aggressive primary brain tumours is thought to underlie their poor prognosis, this Review places a special emphasis on the heterogeneity of the tumour-associated microglia and macrophage populations present in primary brain tumours. Where available, specific information on microglial heterogeneity in various types and subtypes of brain tumour is included. Emerging evidence that highlights the importance of considering the heterogeneity of both the tumour and of microglial populations in providing improved treatment outcomes for patients is also discussed.
The immature brain is particularly susceptible to free radical injury because of its poorly developed scavenging systems and high availability of iron for the catalytic formation of free radicals. ...Neurons are more vulnerable to free radical damage than glial cells, but oligodendrocyte progenitors and immature oligodendrocytes in very prematurely born infants are selectively vulnerable to depletion of antioxidants and free radical attack. Reactive oxygen and nitrogen species play important roles in the initiation of apoptotic mechanisms and in mitochondrial permeability transition, and therefore constitute important targets for therapeutic intervention. Oxidative stress is an early feature after cerebral ischemia and experimental studies targeting the formation of free radicals demonstrate various degrees of protection after perinatal insults. Oxidative stress-regulated release of proapoptotic factors from mitochondria appears to play a much more important role in the immature brain. This review will summarize and compare with the adult brain some of the current knowledge of free radical formation in the developing brain and its roles in the pathophysiology after cerebral hypoxia–ischemia.
Cranial radiotherapy in the treatment of pediatric malignancies may lead to cognitive deficits, and girls suffer more severe deficits than boys. However, most experimental studies are performed on ...male animals only. Our aim was to investigate possible long‐term gender differences in response to cranial irradiation (IR). Basal neurogenesis in non‐irradiated mice was higher in females but this was not apparent until the animals were adult. Male and female C57BL/6J mice received a single dose of 8 Gy to the whole brain on postnatal day 14 and were killed 6 h or 4 months later. Proliferation in the subgranular zone of the dentate gyrus in the hippocampus, as judged by the number of phosphohistone H3‐positive cells, was reduced by half 6 h after IR in both males and females. The reduced proliferation was still obvious 4 months after IR. Consequently, the continuous addition of new neurons to the granule cell layer (GCL) during brain growth was reduced in irradiated mice, and the reduction was more pronounced in females. This resulted in hampered growth of the GCL, reduced bromodeoxyuridine incorporation in adulthood, and severely reduced adult neurogenesis, as judged by the number of doublecortin‐positive cells in the GCL. In an open‐field test, locomotor activity was increased in both males and females after IR and anxiety levels were increased, more so in females. In an IntelliCage test, place learning was impaired by IR in females but not males.
The upper panel shows a representative microphotograph of BrdU+ cells in the GCL from adult control mouse brain. The lower panel shows the number of BrdU+ cells in the GCL 4 months after IR. There was a significant interaction between gender and treatment showing that BrdU incorporation was more affected in irradiated females than males. Females not subjected to IR showed higher BrdU incorporation than males not subjected to IR. Data shown as mean ± SEM. **P < 0.01 for interaction between treatment and gender.
Background:
Providing oncological care to children is demanding and ethical issues concerning what is best for the child can contribute to moral distress.
Objectives:
To explore healthcare ...professionals’ experiences of situations that generate moral distress in Swedish paediatric oncology.
Research design:
In this national study, data collection was conducted using the Swedish Moral Distress Scale-Revised. The data analysis included descriptive statistics and non-parametric analysis of differences between groups.
Participants and research context:
Healthcare professionals at all paediatric oncology centres in Sweden were invited to participate. A total of 278 healthcare professionals participated. The response rate was 89%.
Ethical considerations:
In its advisory statement, the Regional Ethical Review Board decided that the study was of such a nature that the legislation concerning ethical reviews was not applicable. All participants received written information about the aim of the study and confidentiality. Participants demonstrated their consent by returning the survey.
Findings:
The two situations with the highest moral distress scores concerned lack of competence and continuity of personnel. All professional groups reported high levels of disturbance. Nurses rated significantly higher frequencies and higher total Moral Distress Scale scores compared to medical doctors and nursing assistants.
Discussion:
Lack of competence and continuity, as the two most morally distressing situations, confirms the findings of studies from other countries, where inadequate staffing was reported as being among the top five morally distressing situations. The levels of total Moral Distress Scale scores were more similar to those reported in intensive care units than in other paediatric care settings.
Conclusion:
The two most morally distressing situations, lack of competence and continuity, are both organisational in nature. Thus, clinical ethics support services need to be combined with organisational improvements in order to reduce moral distress, thereby maintaining job satisfaction, preventing a high turnover of staff and ensuring the quality of care.
Optic pathway glioma (OPG) is a feared complication to neurofibromatosis type 1 (NF1) since it can cause visual impairment in young children. The main goal of screening is to detect symptomatic OPGs ...that require treatment. Optical coherence tomography (OCT) has been suggested as a tool for detection of neuro-retinal damage. To investigate whether the ganglion cell layer assessed by OCT is a reliable measure to identify and detect relapses of symptomatic OPGs in children with NF1. Children (3-6 years) with NF1, with and without known OPG and children with sporadic OPG (S-OPG) resident in the Stockholm area, were invited and followed in a prospective study during a three-year period. Brain magnetic resonance tomography (MRI) had been performed in children with symptoms of OPG. Outcome measures were VA in logMAR, visual field index (VFI), average thicknesses of the ganglion cell-inner plexiform layer (GC-IPL), and peripapillary retinal nerve fiber layer (pRNFL). There were 25 children with MRI-verified OPG and 52 with NF1 without symptomatic OPG. Eyes from NF1 patients without symptoms of OPG showed significantly better results in all four analyzed parameters compared to eyes with NF1-associated OPG. Mean GC-IPL measurements seemed stable and reliable, significantly correlated to pRNFL (correlation coefficient (r) = 0.662, confidence interval (CI) = .507 to .773 p<0.001), VA (r = -0.661, CI = -7.45 to -.551, p<0.001) and VFI (r = 0.644, CI = .452 to .774, p<0.001). GC-IPL measurements were easy to obtain and acquired at considerably younger age than pRNFL (5.6±1.5 vs 6.8±1.3; p<0.001). The mean GC-IPL thickness could distinguish well between eyes with OPG and eyes without symptomatic OPG in children with NF1. As thinning of GC-IPL assessed with OCT could indicate underlying OPG, it should be included in the screening protocol of children with questionable VA measurements and in particular in children with NF1.
Inflammatory response induced by microglia plays a critical role in the demise of neuronal populations in neuroinflammatory diseases. Although the role of toll-like receptor 4 (TLR4) in microglia’s ...inflammatory response is fully acknowledged, little is known about endogenous ligands that trigger TLR4 activation. Here, we report that galectin-3 (Gal3) released by microglia acts as an endogenous paracrine TLR4 ligand. Gal3-TLR4 interaction was further confirmed in a murine neuroinflammatory model (intranigral lipopolysaccharide LPS injection) and in human stroke subjects. Depletion of Gal3 exerted neuroprotective and anti-inflammatory effects following global brain ischemia and in the neuroinflammatory LPS model. These results suggest that Gal3-dependent-TLR4 activation could contribute to sustained microglia activation, prolonging the inflammatory response in the brain.
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•Gal3 acts as an endogenous TLR4 ligand with a Kd value around 1 μM•Gal3 can initiate a TLR4-dependent inflammatory response in microglia•Gal3 is required for complete activation of TLR4 upon LPS treatment•Gal3-TLR4 interaction is confirmed in vivo and in stroke patients
In this publication, Burguillos et al. demonstrate how galectin-3 (Gal3) released from reactive microglia cells can activate other surrounding immune cells in a paracrine manner by binding to and activating Toll-like receptor 4 (TLR4). This finding could explain the propagation of the inflammatory response once the initial stimulus is gone.
Perinatal asphyxia induces neuronal cell death and brain injury, and is often associated with irreversible neurological deficits in children. There is an urgent need to elucidate the neuronal death ...mechanisms occurring after neonatal hypoxia-ischemia (HI). We here investigated the selective neuronal deletion of the Atg7 (autophagy related 7) gene on neuronal cell death and brain injury in a mouse model of severe neonatal hypoxia-ischemia. Neuronal deletion of Atg7 prevented HI-induced autophagy, resulted in 42% decrease of tissue loss compared to wild-type mice after the insult, and reduced cell death in multiple brain regions, including apoptosis, as shown by decreased caspase-dependent and -independent cell death. Moreover, we investigated the lentiform nucleus of human newborns who died after severe perinatal asphyxia and found increased neuronal autophagy after severe hypoxic-ischemic encephalopathy compared to control uninjured brains, as indicated by the numbers of MAP1LC3B/LC3B (microtubule-associated protein 1 light chain 3)-, LAMP1 (lysosomal-associated membrane protein 1)-, and CTSD (cathepsin D)-positive cells. These findings reveal that selective neuronal deletion of Atg7 is strongly protective against neuronal death and overall brain injury occurring after HI and suggest that inhibition of HI-enhanced autophagy should be considered as a potential therapeutic target for the treatment of human newborns developing severe hypoxic-ischemic encephalopathy.
Central nervous system (CNS) tumors account for almost a third of pediatric cancers and are the largest contributor to cancer-related death in children. Cranial radiation therapy (CRT) is, often in ...combination with chemotherapy and surgery, effective in the treatment of high-grade childhood brain cancers, but it has been associated with late complications in 50-90% of survivors, such as decline in cognition and mood, decreased social competence, and fatigue. A leading hypothesis to explain the decline in cognition, at least partially, is injury to the neural stem and progenitor cells (NSPCs), which leads to apoptosis and altered fate choice, favoring gliogenesis over neurogenesis. Hence, treatments harnessing neurogenesis are of great relevance in this context. Lithium, a well-known mood stabilizer, has neuroprotective and antitumor effects and has been found to reverse irradiation-induced damage in rodents, at least in part by regulating the expression of the glutamate decarboxylase 2 gene (Gad2) via promoter demethylation in rat NSPCs. Additionally, lithium was shown to rescue irradiation-induced cognitive defects in mice. Here, we show that irradiation (IR) alone or in combination with lithium chloride (LiCl) caused major changes in gene expression and global DNA methylation in iPSC-derived human NSPCs (hNSPCs) compared to untreated cells, as well as LiCl-only-treated cells. The pattern of DNA methylation changes after IR-treatment alone was stochastic and observed across many different gene groups, whereas differences in DNA methylation after LiCl-treatment of irradiated cells were more directed to specific promoters of genes, including genes associated with neurogenesis, for example GAD2. Interestingly, IR and IR + LiCl treatment affected the promoter methylation and expression of several genes encoding factors involved in BMP signaling, including the BMP antagonist gremlin1. We propose that lithium in addition to promoting neuronal differentiation, also represses glial differentiation in hNSPCs with DNA methylation regulation being a key mechanism of action.
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