Abstract
Pelizaeus‐Merzbacher disease (PMD) is a fatal hypomyelinating disorder characterized by early impairment of motor development, nystagmus, choreoathetotic movements, ataxia and progressive ...spasticity. PMD is caused by variations in the proteolipid protein gene
PLP1
, which encodes the two major myelin proteins of the central nervous system, PLP and its spliced isoform DM20, in oligodendrocytes. Large duplications including the entire
PLP1
gene are the most frequent causative mutation leading to the classical form of PMD. The Plp1 overexpressing mouse model (PLP‐tg
66/66
) develops a phenotype very similar to human PMD, with early and severe motor dysfunction and a dramatic decrease in lifespan. The sequence of cellular events that cause neurodegeneration and ultimately death is poorly understood. In this work, we analyzed patient‐derived fibroblasts and spinal cords of the PLP‐tg
66/66
mouse model, and identified redox imbalance, with altered antioxidant defense and oxidative damage to several enzymes involved in ATP production, such as glycolytic enzymes, creatine kinase and mitochondrial proteins from the Krebs cycle and oxidative phosphorylation. We also evidenced malfunction of the mitochondria compartment with increased ROS production and depolarization in PMD patient's fibroblasts, which was prevented by the antioxidant N‐acetyl‐cysteine. Finally, we uncovered an impairment of mitochondrial dynamics in patient's fibroblasts which may help explain the ultrastructural abnormalities of mitochondria morphology detected in spinal cords from PLP‐tg
66/66
mice. Altogether, these results underscore the link between redox and metabolic homeostasis in myelin diseases, provide insight into the pathophysiology of PMD, and may bear implications for tailored pharmacological intervention.
The murine F9-derived 1C11 clone exhibits a stable epithelial morphology, expresses nestin, an early neuroectodermal marker, and expresses genes involved in neuroectodermal cell fate. Upon ...appropriate induction, 100% of 1C11 precursor cells develop neurite extensions and acquire neuronal markers (N-CAM, synaptophysin, γγ-enolase, and neurofilament) as well as the general functions of either serotonergic (1C11*/5HT) (5HT, 5-hydroxytryptamine) or noradrenergic (1C11**/NE) (NE, norepinephrine) neurons. The two programs are shown to be mutually exclusive. 1C11 thus behaves as a neuroepithelial cell line with a dual bioaminergic fate. 1C11*/5HT cells implement a functional 5-HT transporter and thereby a complete serotonergic phenotype within 4 days, whereas 5-HT1B/D, 5-HT2B, and 5-HT2Areceptors are sequentially induced. The accurate time schedule of catecholaminergic differentiation was defined. Catecholamine synthesis, storage, and catabolism are acquired within 4 days; the noradrenergic phenotype is complete at day 12 and includes a functional norepinephrine transporter and an α1D-adrenoreceptor (day 8). The time-dependent onset of neurotransmitter-associated functions proper to either program is similar to in vivoobservations. Along each pathway, the selective induction of serotonergic or adrenergic receptors is shown to be an essential part of the differentiation program, since they promote an autoregulation of the corresponding phenotype.
During development, antagonists of 5-HT(2) receptor subtypes cause morphological defects of mesodermal and neural crest derivatives including the craniofacial skeleton. We used an inducible ...mesoblastic cell line, C1, able to fully convert into osteocytes within 12 days, to assess the involvement of 5-HT(2) receptors during osteogenic differentiation. On day 5 of the osteogenic program, immediately before matrix mineralization, the cells selectively implement 5-HT(2B) receptors (5-HT(2B)R) which remain functional until terminal differentiation. In 5-HT-depleted medium, the receptor exhibits a constitutive activity leading to basal nitric oxide (NO) release and phospholipase A2 (PLA2)-dependent arachidonic acid (AA) production. Blockade of this intrinsic activity affects the efficiency of mineralization by decreasing calcium incorporation within the matrix by 40%. Optimal bone matrix mineralization involves both NO and PLA2 signaling pathways. Moreover, between day 5 and day 10, at the beginning of mineral deposition, the 5-HT(2B)R promotes prostaglandin E2 production through AA-dependent cyclooxygenase (COX) activation. From day 10 onwards, when C1 osteoblasts undergo conversion into osteocyte-like cells, COX activity is quenched. Altogether these observations indicate that the 5-HT(2B)R contributes in an autocrine manner to osteogenic differentiation and highlight a switch in the downstream targets of the receptor at the terminal stage of the program. Finally, in addition to its autocrine function, the 5-HT(2B)R responds to 5-HT by increasing NO production and AA release. These findings raise concern regarding the use of 5-HT(2B)R-related drugs that may interfere with bone metabolism in physiological or pathological situations.
Corruption of the normal function of the cellular prion protein (PrP
C) by the scrapie isoform (PrP
Sc) emerges as a critical causal event in Transmissible Spongiform Encaphalopathies (TSE) ...pathogenesis. However, PrP
C physiological role remains unclear. By exploiting the properties of the 1C11 neuroectodermal cell line, able to convert into 1C11
5-HT serotonergic or 1C11
NE noradrenergic neuronal cells, we assigned a signaling function to PrP
C. Here, we establish that antibody-mediated PrP
C ligation promotes the recruitment of the cAMP responsive element binding protein (CREB) transcription factor downstream from the MAPK ERK1/2, in 1C11 precursor cells and their 1C11
5-HT and 1C11
NE neuronal progenies. Whatever the differentiation state of 1C11 cells, the PrP
C-dependent CREB activation triggers Egr-1 and c-
fos transcription, two immediate early genes that relay CREB’s role in cell survival and proliferation as well as in neuronal plasticity. Furthermore, in 1C11-derived neuronal cells, we draw a link between the PrP
C–CREB coupling and a transcriptional regulation of the metalloproteinase MMP-9 and its inhibitor TIMP-1, which play pivotal roles in neuronal pathophysiology. Finally, the PrP
C-dependent control on MMP-9 impacts on the processing of the transmembrane protein, β-dystroglycan. Taken together, our data define molecular mechanisms that likely mirror PrP
C ubiquitous contribution to cytoprotection and its involvement in neuronal plasticity.
Botulinum toxin injection reduces spasticity level. However, the effects on gait parameters and daily living activities remain controversial, and the prediction of results remains poorly evaluated. ...The aim of this open study was to investigate these effects, and the predictability of results. Forty-seven injections were given to 47 patients with stroke (males: 24; mean age: 51.7), in the soleus, gastrocnemius, tibialis posterior and anterior, and flexor digitorum longus, with a global dose of 300 U (Botox®). Each was evaluated at day 1 (D1), day 15 (D15), month 2 (M2) and month 5 (M5). We observed a significant but moderate reduction in spasticity (Ashworth) of the ankle plantar flexors (0.72/5) and dorsiflexors, which was greater at D15, and an improvement in distal positioning in the upright situation. Upright balance and gait (Functional Ambulation Categories) were improved, especially at M2 and in the barefoot condition. Gait velocity and step length with usual aids (10 m) were discretely increased, and this was especially evident in about 15 patients. We also found improvement in the Rivermead Motor Assessment. Patients reported better foot positioning, facilitation in limb propulsion, and better static and dynamic balance. For each assessment, high variability in the effects was also shown. Improvement in functional tests was partially predicted by age (negative relation), delay since stroke (negative relation), gender (better in men), spasticity of hip adductors and knee extensors (negative relation), active ankle dorsiflexion (positive relation) and heel–ground distance (positive relation). In conclusion, the effects on spasticity, balance and gait were relatively modest, and with a large variability between patients. Functional improvement could be partially predicted by several general or specific factors, the knowledge of which is important in the selection of patients to be injected, and for future trials aiming to demonstrate the efficacy of botulinum toxin injection.
The conversion of the cellular prion protein, PrPC, to an abnormal isoform, PrPSc, is a central event leading to neurodegeneration in prion diseases. Deciphering the molecular and cellular changes ...imparted by PrPSc accumulation remains an arduous task due to the small number of cell lines supporting prion replication. Here we introduce the 1C11 cell line as a new in vitro model to investigate prion pathogenesis. This cell line is a committed neuroectodermal progenitor able to differentiate into fully functional serotonergic or catecholaminergic neurons. 1C11 cells, which naturally express PrPC from the undifferentiated state, can be chronically infected with various prion strains. Prion infection does not promote any noticeable phenotypic change in the progenitor cells nor prevent the onset of the serotonergic and catecholaminergic differentiation programs. Pathogenic prions, however, deviate the overall neurotransmitter-metabolism in both pathways by decreasing bioamine synthesis, storage, and transport, and enhancing catabolism. Noteworthy, oxidized derivatives of both serotonin and catecholamines are selectively detected in the differentiated progenies of infected cells and contribute to irreversible impairment in bioamine synthesis. Finally, the level of PrPSc accumulation, that of infectivity, and the extent of all prion-induced changes in infected cells appear to be correlated. The report of such specific effects of infection on neuronal functions provides a foundation for dissecting the events underlying loss of neuronal homeostasis in prion diseases.
In lung vasculature, reversible constriction of smooth muscle cells exists in response to acute decrease in oxygen levels (hypoxia). Progressive and irreversible structural remodeling that reduces ...blood vessel lumen takes place in response to chronic hypoxia and results in pulmonary hypertension. Several studies have shown a role of serotonin in regulating acute and chronic hypoxic responses. In this review the contribution of serotonin, its receptors and transporter in lung hypoxic responses is discussed. Hypoxic conditions modify plasma levels of serotonin, serotonin transporter activity, and expression of 5-HT1B and 5-HT2B receptors. These appear to be required for pulmonary vascular cell proliferation, which depends on the ratio between reactive oxygen species and nitric oxide. A heterozygous mutation was identified in the 5-HT2B receptor gene of a patient who developed pulmonary hypertension after fenfluramines anorexigen treatment. This C-terminus truncated 5-HT2B mutant receptor presents lower nitric oxide coupling, and higher cell proliferation capacity than the wild-type receptor. Under low oxygen tension, cells increase the transcription of specific genes via stabilization of the transcription factor hypoxia-inducible factor (HIF)-1. Factors such as angiotensin II or thrombin that can also control HIF-1 pathway contribute to pulmonary vascular remodeling. The 5-HT2B receptor via phosphatidylinositol-3 kinase/Akt activates nuclear factor-kappaB, which is involved in the regulation of HIF-1 expression. Acontrol of HIF- 1 by 5-HT2B receptors explains why expression of pulmonary vascular remodeling factors, such as endothelin-1 or transforming growth factor-beta, which is HIF-1-alpha regulated, is not modified in hypoxic 5-HT2B receptor mutant mice. Understanding the detailed mechanisms involved in lung hypoxic responses may provide general insight into pulmonary hypertension pathogenesis.
Background Tobacco smoking is associated with reduced monoamine oxidase A (MAOA) activity. Smoking-associated low MAOA activities in pregnancy and in newborns may have negative perinatal and ...postnatal consequences. We aimed to compare, in everyday clinical conditions, biomarkers of MAOA activity in smoking (SPW) and lifetime nonsmoking pregnant women (NSPW) and in cord blood and to assess the newborns' behavior during the first 48 hours of life. Methods Thirty SPW and 29 NSPW in their second trimester of pregnancy were included. Plasma MAOA dependent metabolites of norepinephrine: dihydroxyphenylglycol; dopamine: homovanillic and dihydroxyphenylacetic acid; and serotonin: 5-hydroxy-indol acetic acid were measured at the end of the second trimester, at delivery, and in arterial cord blood along with plasma cotinine. The newborns' discomfort was evaluated every 8 hours by a standardized questionnaire. Results The SPW smoked, on average, 73 cigarettes per week at the end of second trimester and 80 cigarettes per week at delivery. Mean plasma cotinine was 84 ng/mL, 105 ng/mL, and 95 ng/mL at the end of second trimester, at delivery, and in cord blood, respectively (NSPW < 10 ng/mL). Plasma markers of MAOA activity, in particular those reflecting dopamine's catabolism, were significantly lower in SPW and in the arterial cord blood of their newborns than in NSPW and their newborns. Newborns of SPW showed significantly more facial discomfort than those of NSPW. Conclusions Smoking is associated with MAOA inhibition in pregnant women and in their newborns at birth. Further studies are needed to estimate the behavioral significance of these findings.
Serotonin, first described as a neurotransmitter in invertebrates, has been investigated mostly for its functions in the mature central nervous system of higher vertebrates. Serotonin receptor ...diversity has been described in the mammalian brain and in insects. We report the isolation of a cDNA coding for a Drosophila melanogaster serotonin receptor that displays a sequence, a gene organization, and pharmacological properties typical of the mammalian 5-HT2 serotonin receptor subtype. Its mRNA can be detected in the adult fly; moreover, a high level of expression occurs at 3 hr of Drosophila embryogenesis. This early embryonic expression is surprisingly organized in a seven-stripe pattern that appears at the cellular blastoderm stage. In addition, this pattern is in phase with that of the even-parasegment-expressed pair-rule gene fushi-tarazu and is similarly modified by mutations affecting segmentation genes. Simultaneously with this pair-rule expression, the complete machinery of serotonin synthesis is present and leads to a peak of ligand concomitant with a peak of 5-HT2-specific receptor sites in blastoderm embryos.
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