Systemic epothilone D improves hindlimb function after spinal cord contusion injury in rats

Following a spinal cord injury (SCI) a growth aversive environment forms, consisting of a fibroglial scar and inhibitory factors, further restricting the already low intrinsic growth potential of injured adult central nervous system (CNS) neurons. Previous studies have shown that local administration of the microtubule-stabilizing drug paclitaxel or epothilone B (Epo B) reduce fibrotic scar formation and axonal dieback as well as induce axonal growth/sprouting after SCI. Likewise, systemic administration of Epo B promoted functional recovery. In this study, we investigated the effects of epothilone D (Epo D), an analog of Epo B with a possible greater therapeutic index, on fibrotic scarring, axonal sprouting and functional recovery after SCI. Delayed systemic administration of Epo D after a moderate contusion injury (150 kDyn) in female Fischer 344 rats resulted in a reduced number of footfalls when crossing a horizontal ladder at 4 and 8 weeks post-injury. Hindlimb motor function assessed with the BBB open field locomotor rating scale and Catwalk gait analysis were not significantly altered. Moreover, formation of laminin positive fibrotic scar tissue and 5-HT positive serotonergic fiber length caudal to the lesion site were not altered after treatment with Epo D. These findings recapitulate a functional benefit after systemic administration of a microtubule-stabilizing drug in rat contusion SCI

Microtubule and microtubule associated protein anomalies in psychiatric disease

Anomalies in neuronal cell architecture, in particular dendritic complexity and synaptic density changes, are widely observed in the brains of subjects with schizophrenia or mood disorders. The concept that a disturbed microtubule cytoskeleton underlies these abnormalities and disrupts synaptic connectivity is supported by evidence from clinical studies and animal models. Prominent changes in tubulin expression levels are commonly found in disease specific regions such as the hippocampus and prefrontal cortex of psychiatric patients. Genetic linkage studies associate tubulin-binding proteins such as the dihydropyrimidinase family with an increased risk to develop schizophrenia and bipolar disorder. For many years, altered immunoreactivity of microtubule associated protein-2 has been a hallmark found in the brains of individuals with schizophrenia. In this review, we present a growing body of evidence that connects a dysfunctional microtubule cytoskeleton with neuropsychiatric illnesses. Findings from animal models are discussed together with clinical data with a particular focus on tubulin post-translational modifications and on microtubule-binding proteins

Microtubule-associated proteins: structuring the cytoskeleton

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Roles of Selenoprotein M (SELENOM) in Hypothalamic Leptin Signaling and Calcium Regulation.

Ph.D. Thesis. University of Hawaiʻi at Mānoa 2018

Axonal Transport, Parkin, And Α-Synuclein; Novel Therapeutic Targets To Treat Methamphetamine Neurotoxicity

Methamphetamine (METH) is a commonly abuse psychostimulant. Exposure to chronic high doses of METH can result in neurotoxicity primarily characterized by damage to striatal dopaminergic (DAergic) axons. There are currently no therapeutic interventions for METH neurotoxicity. To some extent damage to striatal DAergic axons is reversible and DAergic axon function may return following abstinence from METH. The reversible nature of METH neurotoxicity suggests that normal striatal function could be restored following exposure to METH. However, potential targets to treat METH neurotoxicity are needed. Axonal transport is required for restoration of DAergic axon components damaged or lost following METH. Here we investigated several potential novel drug targets to treat METH neurotoxicity including with emphasis on targeting axonal transport. We also investigated the E3 ligase parkin and the aggregation prone nerve terminal protein α-synuclein. To investigate the role of axonal transport in METH neurotoxicity we treated a rat model of METH neurotoxicity with axonal transport enhancing drug, epothilone D. Results show that epothilone D could to some extent prevent METH-induced damage to DAergic axons in the striatum. To investigate parkin’s role in METH neurotoxicity we treated parkin knockout rats with a neurotoxic dose of METH. We found that parkin knockout rats were hypersensitive to the METH induced DAergic neurotoxicity, confirming the neuroprotective role of parkin for DAergic neurons. To investigate the role of α-synuclein in METH neurotoxicity we developed a novel method of measuring α-synuclein oligomerization in complex biological samples. In conclusion, here we lay the experimental foundation for three potential targets of METH neurotoxicity

Genetic and Epigenetic Mechanisms Underlying Stress-Induced Behavioral Change

Social stress is the most common stressor experienced by humans and exposure to social stress is thought to cause or exacerbate neuropsychiatric illness. Social stress also leads to behavioral and physiological responses in many animal models that closely mirror the symptoms of fear and anxiety in humans. Our laboratory uses Syrian hamsters to study behavioral responses to social stress. Hamsters are highly territorial, but after losing an agonistic encounter, hamsters exhibit a striking behavioral change, abandoning all territorial aggression and instead becoming highly submissive. This behavioral shift is termed conditioned defeat. Epigenetic modifications, such as changes in histone acetylation, are a possible molecular mechanism underlying such behavioral shifts. Histone deacetylase (HDAC) inhibitors have been shown to enhance fear learning and conditioned place preference for drugs of abuse, while suppressing histone acetylation with histone acetyltransferase (HAT) inhibitors impairs long-term memory formation. The first goal of this study was to test the hypothesis that histone acetylation is a molecular mechanism underlying conditioned defeat. We found that animals given an HDAC inhibitor systemically before social defeat later exhibited increased conditioned defeat. This treatment also suppressed defeat-induced immediate-early gene activity in the infralimbic cortex but not the basolateral amygdala. Next, we demonstrated that administration of an HDAC inhibitor in the infralimbic cortex before defeat enhanced stress-induced behavioral responses while HAT inhibition blocked these behavioral changes. Although both males and females exhibit conditioned defeat, the behavioral expression is more pronounced in males. We next used transcriptomic analysis to investigate potential genetic mechanisms leading to this sexually dimorphic expression and to further delineate the role of acetylation in stress-induced behavioral changes. We sequenced the whole brain transcriptome of male and female hamsters as well as the transcriptome of basolateral amygdala, a nucleus necessary for the acquisition and expression of conditioned defeat, of dominant, subordinate, and control animals. Our analysis revealed that numerous genes relating to histone acetylation, including several HDACs, were differentially expressed in animals of different social status and between sexes. Together, these data support the hypotheses that histone modifications underlie behavioral responses to social stress and that some of these modifications are sexually dimorphic

Neural plasticity in motor control centres : Analysis of the endocannabinoid system in the cerebellum of the PCD mouse

[ES]El sistema endocannabinoide se ha relacionado en las últimas décadas con procesos de muerte celular e inflamatorios. Asimismo, en el sistema nervioso central se sabe que los receptores endocannabinoides clásicos -CB1 y CB2- tienen efectos neuroprotectores. Recientemente se ha visto que los receptores PPAR¿ y su agonista endógeno la oleiletanolamida (OEA) tienen también efectos neuroprotectores. Sin embargo, a día de hoy se desconoce la expresión de los receptores CB2 y PPAR¿ en el cerebelo, tanto a lo largo del desarrollo postnatal normal como en procesos patológicos. Precisamente, desde hace décadas el cerebelo viene relacionándose no sólo con el comportamiento motor sino también con procesos cognitivos y afectivos. Sin embargo, a día de hoy esta relación no está totalmente aceptada. Con el objetivo de poder estudiar la relación del sistema endocannabinoide con un proceso de desestructuración cerebelosa, así como su efecto en el comportamiento cognitivo y afectivo, se ha empleado como modelo el ratón mutante PCD. Éste tiene una mutación en el gen Nna1/Ccp1, que sintetiza una enzima encargada de la despoliglutamilación de los microtúbulos. Esto nos permite estudiar cómo las alteraciones de los microtúbulos en los animales PCD afecta a la expresión del sistema endocannabinoide y la estructura del cerebelo, así como el impacto de dichas alteraciones en el comportamiento del ratón PCD durante el progreso de la desestructuración cerebelosa. Finalmente, el análisis del sistema endocannabinoide durante el desarrollo post-natal nos permitirá estudiar el efecto de la OEA en los mismos parámetros antes mencionados para el desarrollo del ratón PCD. Los resultados demuestran que la mutación pcd afecta tanto a la dinámica como a la estructura de los microtúbulos, haciendo que estos sean más inestables y parecidos a microtúbulos de neuronas en desarrollo. Estas alteraciones de los microtúbulos van a afectar de manera paulatina tanto a la expresión del sistema endocannabinoide, así como a la estructura cerebelosa a partir de los 15 días de desarrollo post-natal (P15). Así, las alteraciones en la expresión del sistema endocannabinoide comienzan con un aumento en la expresión de los receptores PPAR¿ y posteriormente, a partir de P22, se observa un aumento en la expresión de receptores CB2. Del mismo modo, la morfología de las células de Purkinje comienza a verse alterada a la misma edad (P15), agravándose a medida que avanza la edad de los animales. Todas estas alteraciones cerebelosas van a verse reflejadas en el comportamiento de los animales PCD. Inicialmente (P15) las alteraciones cerebelosas del ratón PCD van a afectar a su comportamiento social y exploratorio. Posteriormente estas alteraciones van a ir agravándose, observándose defectos tanto en el comportamiento de limpiezas como en la memoria de reconocimiento. En relación al efecto de la administración de OEA, se observó que aunque esta afecta a de la misma manera a microtúbulos de animales silvestres como PCD, estos últimos requieren de dosis más altas. Además, la OEA restableció la curvatura de los microtúbulos de animales mutantes. Finalmente, la OEA previno las alteraciones morfológicas y el proceso neurodegenerativo de las células de Purkinje de manera dosis dependiente, confirmándose así las propiedades preventivas de la OEA en procesos neurodegenerativos cerebelosos

Neuronal transport defects of the MAP6 KO mouse - a model of schizophrenia - and alleviation by Epothilone D treatment, as observed using MEMRI.

International audienceThe MAP6 (microtubule-associated protein 6) KO mouse is a microtubule-deficient model of schizophrenia that exhibits severe behavioral disorders that are associated with synaptic plasticity anomalies. These defects are alleviated not only by neuroleptics, which are the gold standard molecules for the treatment of schizophrenia, but also by Epothilone D (Epo D), which is a microtubule-stabilizing molecule. To compare the neuronal transport between MAP6 KO and wild-type mice and to measure the effect of Epo D treatment on neuronal transport in KO mice, MnCl2 was injected in the primary somatosensory cortex. Then, using manganese-enhanced magnetic resonance imaging (MEMRI), we followed the propagation of Mn(2+) through axonal tracts and brain regions that are connected to the somatosensory cortex. In MAP6 KO mice, the measure of the MRI relative signal intensity over 24h revealed that the Mn(2+) transport rate was affected with a stronger effect on long-range and polysynaptic connections than in short-range and monosynaptic tracts. The chronic treatment of MAP6 KO mice with Epo D strongly increased Mn(2+) propagation within both mono- and polysynaptic connections. Our results clearly indicate an in vivo deficit in neuronal Mn(2+) transport in KO MAP6 mice, which might be due to both axonal transport defects and synaptic transmission impairments. Epo D treatment alleviated the axonal transport defects, and this improvement most likely contributes to the positive effect of Epo D on behavioral defects in KO MAP6 mice