Many neurodegenerative diseases have a multifactorial etiology and variable course of progression that cannot be explained by current models. Neurotropic viruses have long been suggested to play a ...role in these diseases, although their exact contributions remain unclear. Human herpesvirus 6A (HHV-6A) is one of the most common viruses detected in the adult brain, and has been clinically associated with multiple sclerosis (MS), and, more recently, Alzheimer's disease (AD). HHV-6A is a ubiquitous viral pathogen capable of infecting glia and neurons. Primary infection in childhood is followed by the induction of latency, characterized by expression of the U94A viral transcript in the absence of viral replication. Here we examine the effects of U94A on cells of the central nervous system. We found that U94A expression inhibits the migration and impairs cytoplasmic maturation of human oligodendrocyte precursor cells (OPCs) without affecting their viability, a phenotype that may contribute to the failure of remyelination seen in many patients with MS. A subsequent proteomics analysis of U94A expression OPCs revealed altered expression of genes involved in tubulin associated cytoskeletal regulation. As HHV-6A seems to significantly be associated with early AD pathology, we extended our initially analysis of the impact of U94A on human derived neurons. We found that U94A expression inhibits neurite outgrowth of primary human cortical neurons and impairs synapse maturation. Based on these data we suggest that U94A expression by latent HHV-6A in glial cells and neurons renders them susceptible to dysfunction and degeneration. Therefore, latent viral infections of the brain represent a unique pathological risk factor that may contribute to disease processes.
Ataxia-telangiectasia (A-T) is a rare multi-system disorder caused by mutations in the ATM gene. Significant heterogeneity exists in the underlying genetic mutations and clinical phenotypes. A number ...of mouse models have been generated that harbor mutations in the distal region of the gene, and a recent study suggests the presence of residual ATM protein in the brain of one such model. These mice recapitulate many of the characteristics of A-T seen in humans, with the notable exception of neurodegeneration. In order to study how an N-terminal mutation affects the disease phenotype, we generated an inducible Atm mutant mouse model (Atm(tm1Mmpl/tm1Mmpl), referred to as A-T M) predicted to express only the first 62 amino acids of Atm. Cells derived from A-T M mutant mice exhibited reduced cellular proliferation and an altered DNA damage response, but surprisingly, showed no evidence of an oxidative imbalance. Examination of the A-T M animals revealed an altered immunophenotype consistent with A-T. In contrast to mice harboring C-terminal Atm mutations that disproportionately develop thymic lymphomas, A-T M mice developed lymphoma at a similar rate as human A-T patients. Morphological analyses of A-T M cerebella revealed no substantial cellular defects, similar to other models of A-T, although mice display behavioral defects consistent with cerebellar dysfunction. Overall, these results suggest that loss of Atm is not necessarily associated with an oxidized phenotype as has been previously proposed and that loss of ATM protein is not sufficient to induce cerebellar degeneration in mice.
Ataxia-telangiectasia (A-T), caused by mutations in the A-T mutated (
) gene, is a neurodegenerative disorder affecting ∼1 in 40,000-100,000 children. Recurrent respiratory infections are a common ...and challenging comorbidity, often leading to the development of bronchiectasis in individuals with A-T. The role of ATM in development of immune memory in response to recurrent respiratory viral infections is not well understood. Here, we infect wild-type (WT) and Atm-null mice with influenza A virus (IAV; HKx31, H3N2) and interrogate the immune memory with secondary infections designed to challenge the B cell memory response with homologous infection (HKx31) and the T cell memory response with heterologous infection (PR8, H1N1). Although Atm-null mice survived primary and secondary infections, they lost more weight than WT mice during secondary infections. This enhanced morbidity to secondary infections was not attributed to failure to effectively clear virus during the primary IAV infection. Instead, Atm-null mice developed persistent peribronchial inflammation, characterized in part by clusters of B220
B cells. Additionally, levels of select serum antibodies to hemagglutinin-specific IAV were significantly lower in Atm-null than WT mice. These findings reveal that Atm is required to mount a proper memory response to a primary IAV infection, implying that vaccination of children with A-T by itself may not be sufficiently protective against respiratory viral infections.
Genome-wide association studies are identifying multiple genetic risk factors for several diseases, but the functional role of these changes remains mostly unknown. Variants in the ...galactocerebrosidase (GALC) gene, for example, were identified as a risk factor for Multiple Sclerosis (MS); however, the potential biological relevance of GALC variants to MS remains elusive. We found that heterozygote GALC mutant mice have reduced myelin debris clearance and diminished remyelination after a demyelinating insult. We found no histological or behavioral differences between adult wild-type and GALC +/- animals under normal conditions. Following exposure to the demyelinating agent cuprizone, however, GALC +/- animals had significantly reduced remyelination during recovery. In addition, the microglial phagocytic response and elevation of Trem2, both necessary for clearing damaged myelin, were markedly reduced in GALC +/- animals. These altered responses could be corrected in vitro by treatment with NKH-477, a compound discovered as protective in our previous studies on Krabbe disease, which is caused by mutations in both GALC alleles. Our data are the first to show remyelination defects in individuals with a single mutant GALC allele, suggesting such carriers may have increased vulnerability to myelin damage following injury or disease due to inefficient myelin debris clearance. We thus provide a potential functional link between GALC variants and increased MS susceptibility, particularly due to the failure of remyelination associated with progressive MS. Finally, this work demonstrates that genetic variants identified through genome-wide association studies may contribute significantly to complex diseases, not by driving initial symptoms, but by altering repair mechanisms.
Neurodegenerative lysosomal storage disorders (LSDs) are severe and untreatable, and mechanisms underlying cellular dysfunction are poorly understood. We found that toxic lipids relevant to three ...different LSDs disrupt multiple lysosomal and other cellular functions. Unbiased drug discovery revealed several structurally distinct protective compounds, approved for other uses, that prevent lysosomal and cellular toxicities of these lipids. Toxic lipids and protective agents show unexpected convergence on control of lysosomal pH and re-acidification as a critical component of toxicity and protection. In twitcher mice (a model of Krabbe disease KD), a central nervous system (CNS)-penetrant protective agent rescued myelin and oligodendrocyte (OL) progenitors, improved motor behavior, and extended lifespan. Our studies reveal shared principles relevant to several LSDs, in which diverse cellular and biochemical disruptions appear to be secondary to disruption of lysosomal pH regulation by specific lipids. These studies also provide novel protective strategies that confer therapeutic benefits in a mouse model of a severe LSD.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Air pollution has been associated with adverse neurological and behavioral health effects in children and adults. Recent studies link air pollutant exposure to adverse neurodevelopmental outcomes, ...including increased risk for autism, cognitive decline, ischemic stroke, schizophrenia, and depression.
We sought to investigate the mechanism(s) by which exposure to ultrafine concentrated ambient particles (CAPs) adversely influences central nervous system (CNS) development.
We exposed C57BL6/J mice to ultrafine (< 100 nm) CAPs using the Harvard University Concentrated Ambient Particle System or to filtered air on postnatal days (PNDs) 4-7 and 10-13, and the animals were euthanized either 24 hr or 40 days after cessation of exposure. Another group of males was exposed at PND270, and lateral ventricle area, glial activation, CNS cytokines, and monoamine and amino acid neurotransmitters were quantified.
We observed ventriculomegaly (i.e., lateral ventricle dilation) preferentially in male mice exposed to CAPs, and it persisted through young adulthood. In addition, CAPs-exposed males generally showed decreases in developmentally important CNS cytokines, whereas in CAPs-exposed females, we observed a neuroinflammatory response as indicated by increases in CNS cytokines. We also saw changes in CNS neurotransmitters and glial activation across multiple brain regions in a sex-dependent manner and increased hippocampal glutamate in CAPs-exposed males.
We observed brain region- and sex-dependent alterations in cytokines and neurotransmitters in both male and female CAPs-exposed mice. Lateral ventricle dilation (i.e., ventriculomegaly) was observed only in CAPs-exposed male mice. Ventriculomegaly is a neuropathology that has been associated with poor neurodevelopmental outcome, autism, and schizophrenia. Our findings suggest alteration of developmentally important neurochemicals and lateral ventricle dilation may be mechanistically related to observations linking ambient air pollutant exposure and adverse neurological/neurodevelopmental outcomes in humans.
Celotno besedilo
Dostopno za:
CEKLJ, DOBA, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK, VSZLJ
Chemotherapy in cancer patients can be associated with serious short- and long-term adverse neurological effects, such as leukoencephalopathy and cognitive impairment, even when therapy is delivered ...systemically. The underlying cellular basis for these adverse effects is poorly understood.
We found that three mainstream chemotherapeutic agents--carmustine (BCNU), cisplatin, and cytosine arabinoside (cytarabine), representing two DNA cross-linking agents and an antimetabolite, respectively--applied at clinically relevant exposure levels to cultured cells are more toxic for the progenitor cells of the CNS and for nondividing oligodendrocytes than they are for multiple cancer cell lines. Enhancement of cell death and suppression of cell division were seen in vitro and in vivo. When administered systemically in mice, these chemotherapeutic agents were associated with increased cell death and decreased cell division in the subventricular zone, in the dentate gyrus of the hippocampus and in the corpus callosum of the CNS. In some cases, cell division was reduced, and cell death increased, for weeks after drug administration ended.
Identifying neural populations at risk during any cancer treatment is of great importance in developing means of reducing neurotoxicity and preserving quality of life in long-term survivors. Thus, as well as providing possible explanations for the adverse neurological effects of systemic chemotherapy, the strong correlations between our in vitro and in vivo analyses indicate that the same approaches we used to identify the reported toxicities can also provide rapid in vitro screens for analyzing new therapies and discovering means of achieving selective protection or targeted killing.
Generating patient-specific oligodendrocyte progenitors capable of repairing myelination defects observed in multiple neurological afflictions holds great therapeutic potential. Recently in Nature ...Biotechnology, Najm et al. (2013) and Yang et al. (2013) generated these progenitors by direct reprogramming, bringing us closer to their use in disease analysis and autologous transplantation strategies.
The deleterious effects of anemia on auditory nerve (AN) development have been well investigated; however, we have previously reported that significant functional consequences in the auditory ...brainstem response (ABR) can also occur as a consequence of marginal iron deficiency (ID). As the ABR has widespread clinical use, we evaluated the ability of this electrophysiological method to characterize the threshold of tissue ID in rats by examining the relationship between markers of tissue ID and severity of ABR latency defects. To generate various levels of ID, female Long-Evans rats were exposed to diets containing sufficient, borderline, or deficient iron (Fe) concentrations throughout gestation and offspring lifetime. We measured hematological indices of whole body iron stores in dams and offspring to assess the degree of ID. Progression of AN ID in the offspring was measured as ferritin protein levels at different times during postnatal development to complement ABR functional measurements. The severity of ABR deficits correlated with the level of Fe restriction in each diet. The sufficient Fe diet did not induce AN ID and consequently did not show an impaired ABR latency response. The borderline Fe diet, which depleted AN Fe stores but did not cause systemic anemia resulted in significantly increased ABR latency isolated to Peak I.The low Fe diet, which induced anemia and growth retardation, significantly increased ABR latencies of Peaks I to IV. Our findings indicate that changes in the ABR could be related to various degrees of ID experienced throughout development.
: In our attempts to understand how the balance between self‐renewal and differentiation is regulated in dividing precursor cells, we have discovered that intracellular redox state appears to be a ...critical modulator of this balance in oligodendrocyte‐type‐2 astrocyte (O‐2A) progenitor cells. The intracellular redox state of freshly isolated progenitor cells allows prospective isolation of cells with different self‐renewal characteristics, which can be further modulated in opposite directions by prooxidants and antioxidants. Redox state is itself modulated by cell‐extrinsic signaling molecules that alter the balance between self‐renewal and differentiation: growth factors that promote self‐renewal cause progenitors to become more reduced, while exposure to signaling molecules that promote differentiation causes progenitors to become more oxidized. Moreover, pharmacological antagonists of the redox effects of these cell‐extrinsic signaling molecules antagonize their effects on self‐renewal and differentiation, further suggesting that cell‐extrinsic signaling molecules that modulate this balance converge on redox modulation as a critical component of their effector mechanism. A further example of the potential relevance of intracellular redox state to development processes emerges from our attempts to understand why different central nervous system (CNS) regions exhibit different temporal patterns of oligodendrocyte generation and myelinogenesis. Characterization of O‐2A progenitor cells (O‐2A/OPCs) isolated from different regions indicates that these developmental patterns are consistent with properties of the specific O‐2A/OPCs resident in each region. Marked differences were seen in self‐renewal and differentiation characteristics of O‐2A/OPCs isolated from cortex, optic nerve, and optic chiasm. In conditions where optic nerve‐derived O‐2A/OPCs generated oligodendrocytes within 2 days, oligodendrocytes arose from chiasm‐derived cells after 5 days and from cortical O‐2A/OPCs after only 7–10 days. These differences, which appear to be cell intrinsic, were manifested both in reduced percentages of clones producing oligodendrocytes and in a lesser representation of oligodendrocytes in individual clones. In addition, responsiveness of optic nerve‐, chiasm‐, and cortex‐derived O‐2A/OPCs to thyroid hormone (TH) and ciliary neurotrophic factor (CNTF), well‐characterized inducers of oligodendrocyte generation, was inversely related to the extent of self‐renewal observed in basal division conditions. These results demonstrate hitherto unrecognized complexities among the precursor cells thought to be the immediate ancestors of oligodendrocytes and suggest that the properties of these different populations may contribute to the diverse time courses of myelination in different CNS regions. Strikingly, O‐2A/OPCs isolated from cortex and analyzed immediately upon isolation were more reduced in their redox state than were optic nerve‐derived cells, precisely as would be predicted from our analysis of the role of redox state in modulating the balance between self‐renewal and differentiation. Chiasm‐derived cells, which exhibited self‐renewal properties intermediate between cortex‐ and optic nerve‐derived cells, were more reduced than optic nerve cells but more oxidized that cortical O‐2A/OPCs.
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