RESUMEN
ADAM 17, also known as TACE, is an important sheddase for a number of proteins, including tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-alpha (TGF-alpha), L-selectin, p75, and p55 TNF receptors, and interleukin-1 receptor II (IL-1RII). The presence of ADAM 17 mRNA in adult mouse and rat CNS was recently reported (Karkkainen et al. Mol Cell Neurosci 15:547-560, 2000). However, the cellular origin of ADAM 17 remains unknown. In this study, we have used an anti-ADAM 17 antibody in an immunohistochemical study of its distribution in human adult CNS tissue. Cells with astrocytic and endothelial morphology were ADAM 17-positive. This finding was further confirmed using double immunofluorescence with antibodies against GFAP and von Willebrand factor, which label astrocytes and endothelial cells, respectively. This study demonstrates that ADAM 17 is expressed by astrocytes and endothelial cells in normal brain tissue and may have a role in normal brain function.
Asunto(s)
Astrocitos/enzimología , Encéfalo/enzimología , Circulación Cerebrovascular , Endotelio Vascular/enzimología , Metaloendopeptidasas/metabolismo , Proteínas ADAM , Proteína ADAM17 , Anciano , Anciano de 80 o más Años , Encéfalo/citología , Endotelio Vascular/citología , Humanos , Inmunohistoquímica , Persona de Mediana Edad , Distribución TisularRESUMEN
Fibroblast growth factor-2 (FGF-2) controls in part the timely differentiation of oligodendrocytes into the myelin-producing cells of the CNS. However, although differentiated oligodendrocytes express FGF receptors (R), the effect of FGF-2 on myelin-producing oligodendrocytes in vivo was unknown. In the present study, we show that delivery of FGF-2 into the cerebrospinal fluid of anaesthetized rat pups, aged postnatal day (P) 6 to 9, induced a severe loss of myelin in the caudal anterior medullary velum (AMV). Furthermore, we show that the caudal AMV was myelinated at the time of treatment, so the effects of FGF-2 represent a loss of myelin and not delayed differentiation. This was confirmed by injection of platelet-derived growth factor-AA (PDGF-AA), a factor known to affect the differentiation of PDGF-alphaR expressing oligodendrocyte progenitors, but which did not induce myelin loss in the caudal AMV and did not affect differentiated oligodendrocytes, which do not express PDGF-alphaR. Compared to controls treated with saline or PDGF-AA, FGF-2 induced an accumulation of PLP protein and MBP mRNA within the somata of myelin-producing oligodendrocytes. The results indicate that FGF receptor signalling disrupts myelin production in differentiated oligodendrocytes in vivo and interrupted the transport of myelin-related gene products from the oligodendrocyte cell body to their myelin sheaths.
Asunto(s)
Encéfalo/crecimiento & desarrollo , Diferenciación Celular/fisiología , Factor 2 de Crecimiento de Fibroblastos/metabolismo , Inhibidores de Crecimiento/metabolismo , Vaina de Mielina/metabolismo , Oligodendroglía/metabolismo , Receptores de Factores de Crecimiento de Fibroblastos/metabolismo , Animales , Encéfalo/efectos de los fármacos , Encéfalo/metabolismo , Muerte Celular/efectos de los fármacos , Muerte Celular/fisiología , Diferenciación Celular/efectos de los fármacos , Enfermedades Desmielinizantes/metabolismo , Enfermedades Desmielinizantes/patología , Enfermedades Desmielinizantes/fisiopatología , Femenino , Factor 2 de Crecimiento de Fibroblastos/farmacología , Inhibidores de Crecimiento/farmacología , Masculino , Proteínas de la Mielina/biosíntesis , Proteínas de la Mielina/efectos de los fármacos , Proteínas de la Mielina/genética , Fibras Nerviosas Mielínicas/efectos de los fármacos , Fibras Nerviosas Mielínicas/metabolismo , Fibras Nerviosas Mielínicas/ultraestructura , Oligodendroglía/efectos de los fármacos , Oligodendroglía/patología , Factor de Crecimiento Derivado de Plaquetas/metabolismo , Factor de Crecimiento Derivado de Plaquetas/farmacología , ARN Mensajero/efectos de los fármacos , ARN Mensajero/metabolismo , Ratas , Ratas Wistar , Receptores de Factores de Crecimiento de Fibroblastos/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Transducción de Señal/fisiología , Degeneración Walleriana/inducido químicamente , Degeneración Walleriana/patologíaRESUMEN
The in vivo effects of fibroblast growth factor-2 (FGF-2) and insulin-like growth factor-I (IGF-I) on oligodendrocytes and CNS myelination were determined in the postnatal rat anterior medullary velum (AMV) following injection of both cytokines into the cerebrospinal fluid. Either FGF-2, IGF-I, or saline were administered via the lateral ventricle, twice daily commencing at postnatal day (P) 6. At P9, AMV were immunohistochemically labeled with the Rip antibody, to enable analysis of the numbers of myelin sheaths and of promyelinating and myelinating oligodendrocytes; promyelinating oligodendrocytes are a recognisable immature phenotype which express myelin-related proteins prior to forming myelin sheaths. In parallel experiments, AMV were treated for Western blot analysis to determine relative changes in expression of the myelin proteins 2', 3'-cyclic nucleotide 3'-phosphohydrolase (CNP) and myelin oligodendrocyte glycoprotein (MOG), which, respectively, characterise early and late stages of myelin maturation. In FGF-2-treated AMV, the number of promyelinating oligodendrocytes increased by 87% compared to saline-injected controls. The numbers of myelinating oligodendrocytes and myelin sheaths were not decreased, but conspicuous unmyelinated gaps within fibre tracts were indications of retarded myelination following FGF-2 treatment. Western blot analysis demonstrated decreased expression of CNP and a near-total loss of MOG, confirming that FGF-2 decreased myelin maturation. In contrast, IGF-I had no effect on the number of promyelinating oligodendrocytes, but increased the numbers of myelinating oligodendrocytes and myelin sheaths by 100% and 93%, respectively. Western blot analysis showed that the amount of CNP was increased following IGF-I treatment, correlating with the greater number of oligodendrocytes, but that MOG expression was lower than in controls, suggesting that the increased number of myelin sheaths in IGF-I was not matched by increased myelin maturation. The results provide in vivo evidence that FGF-2 and IGF-I control the numbers of oligodendrocytes in the brain and, respectively, retard and promote myelination.
Asunto(s)
Factor 2 de Crecimiento de Fibroblastos/fisiología , Factor I del Crecimiento Similar a la Insulina/fisiología , Vaina de Mielina/fisiología , Oligodendroglía/fisiología , Puente/crecimiento & desarrollo , Animales , Animales Recién Nacidos , Western Blotting , Inmunohistoquímica , Proteína Básica de Mielina/biosíntesis , Puente/citología , Ratas , Ratas WistarRESUMEN
Differentiation of Trypanosoma brucei in the mammal limits the degree of parasitemia and prepares the trypanosome for passage back into the tsetse fly. In an attempt to define the signals that control differentiation, we found that theophylline, in contrast to indomethacin, blocked differentiation, prolonged parasitemia, elevated prostaglandin and cyclic AMP concentrations of rat plasma, and depressed intratrypanosomal cyclic AMP. Relatively nontoxic drugs that alter differentiation are powerful tools for elucidating the events that control this important process.