RESUMO
Diabetes mellitus is a chronic disease involving persistent hyperglycemia, which causes an imbalance between reactive oxygen species and antioxidant enzymes and results in damage to various tissues, including the brain. Many societies have traditionally employed medicinal plants to control the hyperglycemia. Pouteria ramiflora, a species occurring in the savanna biome of the Cerrado (Brazil) has been studied because of its possible ability to inhibit carbohydrate digestion. Rats with streptozotocin-induced diabetes treated with an alcoholic extract of Pouteria ramiflora show an improved glycemic level, increased glutathione peroxidase activity, decreased superoxide dismutase activity, and reduced lipid peroxidation and antioxidant status. The extract also restored myosin-Va expression and the nuclear diameters of pyramidal neurons of the CA3 subregion and that of the polymorphic cells of the hilus. We conclude that Pouteria ramiflora extract exerts a neuroprotective effect against oxidative damage and myosin-Va expression and is able to prevent hippocampal neuronal loss in the CA3 and hilus subfields of diabetic rats. However, future studies are needed to understand the mechanism of action of Pouteria ramiflora extract in acute and chronic diabetes.
Assuntos
Encéfalo/patologia , Diabetes Mellitus Experimental/tratamento farmacológico , Diabetes Mellitus Experimental/patologia , Fármacos Neuroprotetores , Pouteria/química , Animais , Antioxidantes/metabolismo , Glicemia/metabolismo , Western Blotting , Peso Corporal/efeitos dos fármacos , Encéfalo/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Imuno-Histoquímica , Peroxidação de Lipídeos/efeitos dos fármacos , Masculino , Miosina Tipo V/biossíntese , Estresse Oxidativo/fisiologia , Extratos Vegetais/farmacologia , Folhas de Planta/química , Células Piramidais/efeitos dos fármacos , Células Piramidais/metabolismo , Ratos , Ratos Wistar , Superóxido Dismutase/metabolismoRESUMO
Thyroid hormones (THs) are essential for brain development, where they regulate gliogenesis, myelination, cell proliferation and protein synthesis. Hypothyroidism severely affects neuronal growth and establishment of synaptic connections. Triiodothyronine (T3), the biologically active form of TH, has a central function in these activities. So, Myosin-Va (Myo-Va), a molecular motor protein involved in vesicle and RNA transport, is a good candidate as a target for T3 regulation. Here, we analyzed Myo-Va expression in euthyroid and hypothyroid adult rat brains and synaptosomes. We observed a reduction of Myo-Va expression in cultured neural cells from newborn hypothyroid rat brain, while immunocytochemical experiments showed a punctate distribution of this protein in the cytoplasm of cells. Particularly, Myo-Va co-localized with microtubules in neurites, especially in their varicosities. Myo-Va immunostaining was stronger in astrocytes and neurons of controls when compared with hypothyroid brains. In addition, supplementation of astrocyte cultures with T3 led to increased expression of Myo-Va in cells from both euthyroid and hypothyroid animals, suggesting that T3 modulates Myo-Va expression in neural cells both in vivo and in vitro. We have further analyzed Myo-Va expression in U373 cells, a human glioblastoma line, and found the same punctate cytoplasmic protein localization. As in normal neural cells, this expression was also increased by T3, suggesting that the modulatory mechanism exerted by T3 over Myo-Va remains active on astrocyte tumor cells. These data, coupled with the observation that Myo-Va is severely affected in hypothyroidism, support the hypothesis that T3 activity regulates neural motor protein expression, taking Myo-Va as a model. As a consequence, reduced T3 activity could supposedly affect axonal transport and synaptic function, and could therefore explain disturbances seen in the hypothyroid brain.
Assuntos
Sistema Nervoso Central/metabolismo , Regulação da Expressão Gênica/fisiologia , Cadeias Pesadas de Miosina/biossíntese , Miosina Tipo V/biossíntese , Tri-Iodotironina/farmacologia , Animais , Animais Recém-Nascidos , Linhagem Celular Tumoral , Células Cultivadas , Sistema Nervoso Central/efeitos dos fármacos , Feminino , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Camundongos , Camundongos Knockout , Gravidez , RatosRESUMO
Myosins are molecular motors associated with the actin cytoskeleton that participate in the mechanisms of cellular motility. During the development of the nervous system, migration of nerve cells to specific sites, extension of growth cones, and axonal transport are dramatic manifestations of cellular motility. We demonstrate, via immunoblots, the expression of myosin Va during early stages of embryonic development in chicks, extending from the blastocyst period to the beginning of the fetal period. The expression of myosin Va in specific regions and cellular structures of the nervous system during these early stages was determined by immunocytochemistry using a polyclonal antibody. Whole mounts of chick embryos at 24-30-h stages showed intense immunoreactivity of the neural tube in formation along its full extent. Cross-sections at these stages of development showed strong labeling in neuroepithelial cells at the basal and apical regions of the neural tube wall. Embryos at more advanced periods of development (48 h and 72 h) showed distinctive immunolabeling of neuroepithelial cells, neuroblasts and their cytoplasmic extensions in the mantle layer of the stratified neural tube wall, and neuroblasts and their cytoplasmic extensions in the internal wall of the optic cup, as well as a striking labeling of cells in the apparent nuclei of cranial nerves and budding fibers. These immunolocalization studies indicate temporal and site-specific expression of myosin Va during chick embryo development, suggesting that myosin Va expression is related to recruitment for specific cellular tasks.
Assuntos
Cadeias Pesadas de Miosina/biossíntese , Miosina Tipo V/biossíntese , Sistema Nervoso/embriologia , Sistema Nervoso/metabolismo , Neurônios/metabolismo , Animais , Especificidade de Anticorpos , Biomarcadores , Diferenciação Celular/fisiologia , Embrião de Galinha , Nervos Cranianos/embriologia , Células Epiteliais/citologia , Células Epiteliais/metabolismo , Olho/embriologia , Regulação da Expressão Gênica no Desenvolvimento , Imuno-Histoquímica , Sistema Nervoso/citologia , Neurônios/citologiaRESUMO
The presence of Myosin Va (an actin-based molecular motor) in the peripheral nervous system was examined and its subcellular distribution within the axons of the sciatic nerve was demonstrated via immunocytochemistry. Myosin Va (M-Va) in the nerve was detected by using SDS-PAGE and Western blot techniques with a polyclonal antibody specifically raised against the M-Va globular tail domain. In addition, purification of M-Va from the rat sciatic nerve prior to immunoblotting yielded a M-Va standard band. Likewise, optical immunocytochemical procedures revealed the presence of M-Va, particularly in the cortical axoplasmic territory, but also in the Schwann cell soma. The above experiments were carried out both on intact as well as on severed sciatic nerves with similar results. The proximal stumps of severed sciatic nerves (from 0 to 72 h after injury) were labelled in vivo with (35)S-methionine. SDS-PAGE autoradiography of the immunoabsorbed M-Va from the radiolabelled homogenized nerve tissue showed a significant increment of the radioactive intensity of M-Va heavy chain band through time. Moreover, a significant increment of transcripts coding for M-Va heavy chain was detected through time using RT-PCR after nerve injury and compared to intact nerves. This data suggest that M-Va is up-regulated in a time-dependent manner. The latter suggests a possible involvement of M-Va in nerve regeneration processes.
Assuntos
Actinas/fisiologia , Miosina Tipo V/fisiologia , Regeneração Nervosa/fisiologia , Nervo Isquiático/lesões , Actinas/biossíntese , Animais , Axônios/metabolismo , Western Blotting , Imuno-Histoquímica , Miosina Tipo V/biossíntese , Ratos , Ratos Wistar , Nervo Isquiático/fisiologiaRESUMO
Myosin-V is involved in organelle and vesicle trafficking in Saccharomyces cerevisiae and in other eukaryotic cells from yeast to human. In the present study, we determined by FACS that the major subpopulations of the peripheral blood mononuclear cells express myosin-V with similar fluorescence intensity. Confocal microscopy showed intense labeling for myosin-V at the centrosomal region and a punctate staining throughout the cytoplasm, frequently associated with the central microtubule arrays and the actin-rich cortex. Some degree of overlap with an endolysosomal marker and dynein light-chain 8 k was found at the cell center. Striking colocalization was observed with the major histocompatibility complex (MHC) class II molecules near the cell surface. Treatment with phytohemagglutinin, which induces T-lymphocyte activation, associated with MHC class II expression, increased the levels of myosin-V protein and mRNA for the three members of class V myosins. These data suggest that class V myosins might be involved in relevant functions in the immune response.