RESUMEN
Myelin regeneration is a major therapeutic goal in demyelinating diseases, and the failure to remyelinate rapidly has profound consequences for the health of axons and for brain function. However, there is no efficient treatment for stimulating myelin repair, and current therapies are limited to anti-inflammatory agents. Males are less likely to develop multiple sclerosis than females, but often have a more severe disease course and reach disability milestones at an earlier age than females, and these observations have spurred interest in the potential protective effects of androgens. Here, we demonstrate that testosterone treatment efficiently stimulates the formation of new myelin and reverses myelin damage in chronic demyelinated brain lesions, resulting from the long-term administration of cuprizone, which is toxic for oligodendrocytes. In addition to the strong effect of testosterone on myelin repair, the number of activated astrocytes and microglial cells returned to low control levels, indicating a reduction of neuroinflammatory responses. We also identify the neural androgen receptor as a novel therapeutic target for myelin recovery. After the acute demyelination of cerebellar slices in organotypic culture, the remyelinating actions of testosterone could be mimicked by 5α-dihydrotestosterone, a metabolite that is not converted to oestrogens, and blocked by the androgen receptor antagonist flutamide. Testosterone treatment also failed to promote remyelination after chronic cuprizone-induced demyelination in mice with a non-functional androgen receptor. Importantly, testosterone did not stimulate the formation of new myelin sheaths after specific knockout of the androgen receptor in neurons and macroglial cells. Thus, the neural brain androgen receptor is required for the remyelination effect of testosterone, whereas the presence of the receptor in microglia and in peripheral tissues is not sufficient to enhance remyelination. The potent synthetic testosterone analogue 7α-methyl-19-nortestosterone, which has been developed for long-term male contraception and androgen replacement therapy in hypogonadal males and does not stimulate prostate growth, also efficiently promoted myelin repair. These data establish the efficacy of androgens as remyelinating agents and qualify the brain androgen receptor as a promising drug target for remyelination therapy, thus providing the preclinical rationale for a novel therapeutic use of androgens in males with multiple sclerosis.
Asunto(s)
Encéfalo/metabolismo , Enfermedades Desmielinizantes/metabolismo , Vaina de Mielina/metabolismo , Oligodendroglía/metabolismo , Receptores Androgénicos/metabolismo , Andrógenos/farmacología , Andrógenos/uso terapéutico , Animales , Encéfalo/efectos de los fármacos , Encéfalo/patología , Cuprizona , Enfermedades Desmielinizantes/inducido químicamente , Enfermedades Desmielinizantes/tratamiento farmacológico , Enfermedades Desmielinizantes/patología , Femenino , Masculino , Ratones , Ratones Noqueados , Vaina de Mielina/efectos de los fármacos , Vaina de Mielina/patología , Fibras Nerviosas Mielínicas/efectos de los fármacos , Fibras Nerviosas Mielínicas/metabolismo , Fibras Nerviosas Mielínicas/patología , Oligodendroglía/efectos de los fármacos , Oligodendroglía/patología , Receptores Androgénicos/genética , Testosterona/farmacología , Testosterona/uso terapéuticoRESUMEN
Patent Blue V (PBV), a dye used clinically for sentinel lymph node detection, was mixed with human serum albumin (HSA). After binding to HSA, the fluorescence quantum yield increased from 5 × 10(-4) to 1.7 × 10(-2), which was enough to allow fluorescence detection and imaging of its distribution. A detection threshold, evaluated in scattering test objects, lower than 2.5 nmol × L(-1) was obtained, using a single-probe setup with a 5-mW incident light power. The detection sensitivity using a fluorescence imaging device was in the µmol × L(-1) range, with a noncooled CCD camera. Preclinical evaluation was performed on a rat model and permitted to observe inflamed nodes on all animals.
RESUMEN
We present a new near infrared optical probe for the sentinel lymph node detection, based on the recording of scattered photons. A two wavelengths setup was developed to improve the detection threshold of an injected dye: the Patent Blue V dye. The method used consists in modulating each laser diode at a given frequency. A Fast Fourier Transform of the recorded signal separates both components. The signal amplitudes are used to compute relative Patent Blue V concentration. Results on the probe using phantoms model and small animal experimentation exhibit a sensitivity threshold of 3.2 µmol/L, which is thirty fold better than the eye visible threshold.
RESUMEN
A new dendritic manganese(II) chelate 1 has been evaluated by in vivo (relaxivity) and in vitro (toxicity and relaxivity) experiments as a manganese enhanced magnetic resonance imaging (MEMRI) contrast agent. Also, a comparison with its corresponding gadolinium(III) homologue 2 and the commercially available MEMRI agent MnDPDP (Teslascan, Amersham Health) was achieved in order to determine respectively the real influence of the paramagnetic ion in terms of toxicity and relaxivity for this precise treelike structure and the potential of 1 to be a favorable candidate for brain-targeting MRI. Complexes 1 and 2 displayed high hydrosolubility (0.1 M) and revealed no in vitro neuronal toxicity at concentrations as high as 1 mM. Considering manganese(II) complex 1, the in vivo nontoxicity at 20 mM (100% rats survival) is very likely due to a slow diffusion of the compound, meaning a controlled release of the paramagnetic ions. Finally, T(1) relaxivity of 4.2 mM(-1).s(-1) for 2 and T(2) relaxivity of 17.4 mM(-1).s(-1) for 1 at 4.7 T were measured and are higher than that of the commercial MRI contrast agents GdDTPA and MnDPDP, respectively.
Asunto(s)
Medios de Contraste/química , Dendrímeros/química , Manganeso/química , Animales , Medios de Contraste/farmacocinética , Medios de Contraste/toxicidad , Dendrímeros/farmacocinética , Dendrímeros/toxicidad , Interacciones Hidrofóbicas e Hidrofílicas , Imagen por Resonancia Magnética , Magnetismo , Peso Molecular , Ácido Pentético/química , Ratas , Sensibilidad y Especificidad , Solubilidad , Distribución TisularRESUMEN
The failure of the remyelination processes in multiple sclerosis contributes to the formation of chronic demyelinated plaques that lead to severe neurological deficits. Long-term cuprizone treatment of C57BL/6 mice resulted in pronounced white matter pathology characterized by oligodendrocyte depletion, irreversible demyelination and persistent functional deficits after cuprizone withdrawal. The use of a combination of in vivo diffusion tensor magnetic resonance imaging (DT-MRI) and histological analyses allowed for an accurate longitudinal assessment of demyelination. Injection of triiodothyronine (T(3)) hormone over a 3 week interval after cuprizone withdrawal progressively restored the normal DT-MRI phenotype accompanied by an improvement of clinical signs and remyelination. The effects of T(3) were not restricted to the later stages of remyelination but increased the expression of sonic hedgehog and the numbers of Olig2(+) and PSA-NCAM(+) precursors and proliferative cells. Our findings establish a role for T(3) as an inducer of oligodendrocyte progenitor cells in adult mouse brain following chronic demyelination.
Asunto(s)
Enfermedades Desmielinizantes/diagnóstico , Enfermedades Desmielinizantes/tratamiento farmacológico , Imagen de Difusión por Resonancia Magnética , Recuperación de la Función/efectos de los fármacos , Hormonas Tiroideas/uso terapéutico , Triyodotironina/uso terapéutico , Animales , Mapeo Encefálico , Anhidrasa Carbónica II/metabolismo , Enfermedad Crónica , Cuprizona , Enfermedades Desmielinizantes/inducido químicamente , Modelos Animales de Enfermedad , Femenino , Proteínas Hedgehog/metabolismo , Antígenos Comunes de Leucocito/metabolismo , Ratones , Ratones Endogámicos C57BL , Microscopía Electrónica de Transmisión , Vaina de Mielina/metabolismo , Vaina de Mielina/ultraestructura , Proteínas del Tejido Nervioso/metabolismo , Molécula L1 de Adhesión de Célula Nerviosa/metabolismo , Antígeno Nuclear de Célula en Proliferación/metabolismo , Ácidos Siálicos/metabolismo , Factores de Tiempo , Triyodotironina/sangreRESUMEN
We sequentially analyzed the serum IgG response against normal mouse brain during experimental autoimmune encephalomyelitis in SJL/J mice injected with CFA, Bordetella pertussis toxin (BPT) and proteolipid protein 139-151 peptide, compared with mice that received CFA and BPT or were uninjected. Dynamic changes were observed from day 0 to day 28 in the 3 groups. Six highly discriminant antigenic bands (kappa=0.974) were identified. Three non-myelin proteins were characterized (mitochondrial aconitase hydratase 2, phosphoglycerate mutase 1, brain specific pyruvate deshydrogenase). The IgG response against two of them was less frequent in EAE whereas it was associated with multiple sclerosis in our previous work.
Asunto(s)
Autoantígenos/inmunología , Encéfalo/inmunología , Encefalomielitis Autoinmune Experimental/sangre , Encefalomielitis Autoinmune Experimental/inmunología , Inmunoglobulina G/sangre , Aconitato Hidratasa/inmunología , Animales , Autoanticuerpos/sangre , Western Blotting , Femenino , Ratones , Proteína Proteolipídica de la Mielina/inmunología , Fragmentos de Péptidos/inmunología , Fosfoglicerato Mutasa/inmunología , Complejo Piruvato Deshidrogenasa/inmunología , Espectrometría de Masa por Láser de Matriz Asistida de Ionización DesorciónRESUMEN
Diffusion tensor magnetic resonance imaging (DT-MRI) was applied for in vivo quantification of myelin loss and regeneration. A transgenic mouse line (Oligo-TTK) expressing a truncated form of the herpes simplex virus 1 thymidine kinase gene (hsv1-tk) in oligodendrocytes was studied along with two induced phenotypes of myelin pathology. Myelin loss and axonal abnormalities differentially affect values of DT-MRI parameters in the brain of transgenic mice. Changes in the anisotropy of the white matter were assessed by calculating and mapping the radial (D perpendicular) and axial (D parallel) water diffusion to axonal tracts and fractional anisotropy (FA). A significant increase in D perpendicular attributed to the lack of myelin was observed in all selected brain white matter tracts in dysmyelinated mice. Lower D parallel values were consistent with the histological observation of axonal modifications, including reduced axonal caliber and overexpression of neurofilaments and III beta-tubulin. We show clearly that myelination and axonal changes play a role in the degree of diffusion anisotropy, because FA was significantly decreased in dysmyelinated brain. Importantly, myelin reparation during brain postnatal development induced a decrease in the magnitude of D( perpendicular) and an increase in FA compared with the same brain before recovery. The progressive increase in D parallel values was attributed to the gain in normal axonal morphology. This regeneration was confirmed by the detection of enlarged oligodendrocyte population, newly formed myelin sheaths around additional axons, and a gradual increase in axonal caliber.
Asunto(s)
Encefalopatías/patología , Enfermedades Desmielinizantes/patología , Imagen de Difusión por Resonancia Magnética , Recuperación de la Función/fisiología , Animales , Animales Recién Nacidos , Anisotropía , Antivirales/administración & dosificación , Encéfalo/citología , Encéfalo/efectos de los fármacos , Encéfalo/metabolismo , Encéfalo/patología , Encéfalo/virología , Encefalopatías/tratamiento farmacológico , Encefalopatías/metabolismo , Encefalopatías/virología , Mapeo Encefálico , Enfermedades Desmielinizantes/tratamiento farmacológico , Enfermedades Desmielinizantes/metabolismo , Enfermedades Desmielinizantes/virología , Ganciclovir/administración & dosificación , Procesamiento de Imagen Asistido por Computador/métodos , Inmunohistoquímica/métodos , Ratones , Ratones Transgénicos , Microscopía Electrónica de Transmisión/métodos , Proteína Básica de Mielina/metabolismo , Fibras Nerviosas Mielínicas/metabolismo , Fibras Nerviosas Mielínicas/patología , Fibras Nerviosas Mielínicas/ultraestructura , Oligodendroglía/metabolismo , Oligodendroglía/patología , Oligodendroglía/ultraestructura , Proteínas Serina-Treonina Quinasas/genética , Proteínas Tirosina Quinasas/genética , Recuperación de la Función/efectos de los fármacos , Factores de TiempoRESUMEN
The purpose of this study was to perform serial texture analysis of brain MRI of cuprizone-treated mice for the assessment of regional demyelination and remyelination. Cuprizone-fed mice undergo a brain demyelination process. This process was followed over 56 days by MRI in the olfactory bulbs, cerebellum, putamen and brain stem. The texture of T2-weighted images has been analyzed at two levels: (1) with the average intensity as first order parameter and (2) with several higher order parameters for the best differentiation between myelinated (controls) and demyelinated brains. The most pertinent of these parameters, called horizontal gray level nonuniformity (HGLNU), has been selected by stepwise discriminant analysis. The time evolution of the average value of HGLNU not only confirmed the overall demyelination tendency followed by the average intensity, but also more precisely characterized a transitory remyelination on day 41 in the olfactory bulbs and cerebellum, in agreement with already published immunohistochemical destructive studies.