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H Thoenen

Publications and source records attributed to H Thoenen.

At least 91 records · Page 5Linked to original sources
PubMed1991

Regional distribution, developmental changes, and cellular localization of CNTF-mRNA and protein in the rat brain.

Ciliary neurotrophic factor (CNTF) is a potent survival molecule for a variety of embryonic neurons in culture. The developmental expression of CNTF occurs clearly after the time period of the physiological cell death of CNTF-responsive neurons. This, together with the sites of expression, excludes CNTF as a target-derived neuronal survival factor, at least in rodents. However, CNTF also participates in the induction of type 2 astrocyte differentiation in vitro. Here we demonstrate that the time course of the expression of CNTF-mRNA and protein in the rat optic nerve (as evaluated by quantitative Northern blot analysis and biological activity, respectively) is compatible with such a glial differentiation function of CNTF in vivo. We also show that the type 2 astrocyte-inducing activity previously demonstrated in optic nerve extract can be precipitated by an antiserum against CNTF. Immunohistochemical analysis of astrocytes in vitro and in vivo demonstrates that the expression of CNTF is confined to a subpopulation of type 1 astrocytes. The olfactory bulb of adult rats has comparably high levels of CNTF to the optic nerve, and here again, CNTF-immunoreactivity is localized in a subpopulation of astrocytes. However, the postnatal expression of CNTF in the olfactory bulb occurs later than in the optic nerve. In other brain regions both CNTF-mRNA and protein levels are much lower.

Amino Acid Sequence↗
PubMed1991

The synthesis of nerve growth factor and brain-derived neurotrophic factor in hippocampal and cortical neurons is regulated by specific transmitter systems.

Both nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) exert neurotrophic actions on the cholinergic neurons of the basal forebrain nuclei. These neurotrophic factors are synthesized by hippocampal and cortical neurons that are located in the projection field of the basal forebrain cholinergic neurons. Both in vivo and in vitro the levels of NGF- and BDNF-mRNAs are increased up to 20-fold by kainic acid via non-NMDA glutamate receptors. Enhancement of the effectiveness of the GABAergic system by benzodiazepam or direct GABA agonists blocks the effect of kainic acid and reduces the basic levels of NGF- and BDNF-mRNAs. Whereas the increases in both NGF- and BDNF-mRNAs above normal levels are mediated by non-NMDA receptors, maintenance of the normal levels of NGF- and BDNF-mRNAs seems to be mediated predominantly by NMDA receptors. The regulation of NGF and BDNF synthesis via specific transmitter systems is discussed in the context of the refined tuning of synaptic functions, the potential implications for memory functions, and the possible therapeutic consequences for the treatment of Alzheimer's disease.

Alzheimer Disease↗
PubMed1991

Effect of ciliary neurotrophic factor (CNTF) on motoneuron survival.

We have demonstrated that the extensive degeneration of motoneurons in the rat facial nucleus after transection of the facial nerve in newborn rats can be prevented by local ciliary neurotrophic factor (CNTF) administration. CNTF differs distinctly from known neurotrophic molecules such as NGF, BDNF and NT-3 in both its molecular characteristics (CNTF is a cytosolic rather than a secretory molecule) and its broad spectrum of biological activities. CNTF is expressed selectively by Schwann cells and astrocytes of the peripheral and central nervous system, respectively, but not by target tissues of the great variety of CNTF-responsive neurons. CNTF mRNA is not detectable by Northern blot or PCR analysis during embryonic development and immediately after birth. However, during the second post-natal week, a more than 30-fold increase in CNTF mRNA and protein occurs in the sciatic nerve. Since the period of low CNTF levels in peripheral nerves coincides with that of high vulnerability of motoneurons (i.e. axonal lesion results in degeneration of motoneuron cell bodies), insufficient availability of CNTF may be the reason for the rate of lesion-induced cell death of early post-natal motoneurons. Highly enriched embryonic chick motoneurons in culture are supported at survival rates higher than 60% by CNTF, even in single cell cultures, indicating that CNTF acts directly on motoneurons. In contrast to CNTF, the members of the neurotrophin gene family (NGF, BDNF and NT-3) do not support the survival of motoneurons in culture. However, aFGF and bFGF show distinct survival activities which are additive to those of CNTF, resulting in the survival of virtually all motoneurons cultured in the presence of CNTF and bFGF.

Animals↗
PubMed1991

Cell-type-specific regulation of nerve growth factor (NGF) synthesis in non-neuronal cells: comparison of Schwann cells with other cell types.

We have previously shown that after peripheral nerve lesion the synthesis of NGF is induced in cells of the nerve sheath (Heumann et al., 1987a). Further analysis led to the identification of growth factors and intracellular mechanisms responsible for this induction in sciatic fibroblasts (Lindholm et al., 1988; Hengerer et al., 1990). The present work aimed at the elucidation of the regulation of NGF synthesis in Schwann cells. A variety of cytokines and peptide growth factors, including interleukin-1 (IL-1) and platelet-derived growth factor (PDGF), which are known to increase NGF-mRNA in fibroblasts and astrocytes, failed to do so in Schwann cell cultures. Forskolin (FK), an activator of adenylate cyclase, increased the level of NGF-mRNA eightfold within 3 hr of incubation. The effect of FK on NGF-mRNA was mimicked by analogs of cAMP but not by dideoxyforskolin, an FK derivative not activating adenylate cyclase. Application of norepinephrine and isoproterenol also augmented the NGF-mRNA content. Pretreatment of Schwann cells with N-[2-(methylamino)ethyl]-5-isoquinoline sulfonamide dihydrochloride (H-8), an inhibitor of cyclic-nucleotide-dependent protein kinases, decreased both basal and elevated levels of NGF-mRNA. Ionomycin, a Ca2+ ionophore, and phorbol 12-myristate 13-acetate (TPA), an activator of protein kinase C, potentiated the effect of FK in an H-8-sensitive manner. We show that the action of FK is independent of changes in mRNA stability and of protein synthesis. Thus, in cultured Schwann cells upregulation of NGF-mRNA expression seems to be mainly achieved by a cAMP-triggered transcriptional activation of the NGF gene. Another striking difference between various glial cell types was revealed by application of transforming growth factor beta-1 (TGF-beta 1), which is the strongest inducer of NGF-mRNA in cultured astrocytes (Lindholm et al., 1990). Schwann cells responded to TGF-beta 1 by decreasing basal as well as FK-induced NGF-mRNA levels. Together with previously published work, our results show that cell-type-specific mechanisms not only account for the different control of NGF expression in neurons as compared to glial cells, but also reveal a surprising specificity of regulatory mechanisms in different non-neuronal cell types, even those derived from the same tissue such as fibroblasts and Schwann cells of peripheral nerves.

Animals↗
PubMed1990

Nerve growth factor levels and choline acetyltransferase activity in the brain of aged rats with spatial memory impairments.

Nerve growth factor (NGF) and choline acetyltransferase (ChAT) activity levels were measured in 7 different brain regions in young (3-month-old) and aged (2-years-old) female Sprague-Dawley rats. Prior to analysis the spatial learning ability of the aged rats was assessed in the Morris' water maze test. In the aged rats a significant, 15-30%, increase in NGF levels was observed in 4 regions (septum, cortex, olfactory bulb and cerebellum), whereas the levels in hippocampus, striatum and the brainstem were similar to those of the young rats. The NGF changes did not correlate with the behavioral performance within the aged group. Minor 15-30%, changes in ChAT activity were observed in striatum, brainstem and cerebellum, but these changes did not correlate with the changes in NGF levels in any region. The results indicate that brain NGF levels are maintained at normal or supranormal levels in rats with severe learning and memory impairments. The results, therefore, do not support the view that the marked atrophy and cell loss in the forebrain cholinergic system that is known to occur in the behaviorally impaired aged rats is caused by a reduced availability of NGF in the cholinergic target areas. The results also indicate that the slightly increased levels of NGF are not sufficient to prevent the age-dependent atrophy of cholinergic neurons, although they might be important for the stimulation of compensatory functional changes in a situation where the system is undergoing progressive degeneration.

Aging↗
PubMed1990

Ciliary neurotrophic factor prevents the degeneration of motor neurons after axotomy.

The period of natural cell death in the development of rodent motor neurons is followed by a period of sensitivity to axonal injury. In the rat this early postnatal period of vulnerability coincides with that of very low ciliary neurotrophic factor (CNTF) levels in the sciatic nerve before CNTF increases to the high, adult levels. The developmental time course of CNTF expression, its regional tissue distribution and its cytosolic localization (as suggested by its primary structure) favour a role for CNTF as a lesion factor rather than a target-derived neurotrophic molecule like nerve growth factor. Nevertheless CNTF exhibits neurotrophic activity in vitro on different populations of embryonic neurons. To determine whether the vulnerability of motor neurons to axotomy in the early postnatal phase is due to insufficient availability of CNTF, we transected the axons of newborn rat motor neurons and demonstrated that local application of CNTF prevents the degeneration of the corresponding cell bodies.

Animals↗
PubMed1990

Activity dependent regulation of BDNF and NGF mRNAs in the rat hippocampus is mediated by non-NMDA glutamate receptors.

The mRNAs of nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF) exhibit a similar, though not identical, regional and cellular distribution in the rodent brain. In situ hybridization experiments have shown that BDNF, like NGF, is predominantly expressed by neurons. The neuronal localization of the mRNAs of these two neurotrophic molecules raised the question as to whether neuronal activity might be involved in the regulation of their synthesis. After we had demonstrated that depolarization with high potassium (50 mM) resulted in an increase in the levels of both BDNF and NGF mRNAs in cultures of hippocampal neurons, we investigated the effect of a large number of transmitter substances. Kainic acid, a glutamate receptor agonist, was by far the most effective in increasing BDNF and NGF mRNA levels in the neurons, but neither N-methyl-D-aspartic acid (NMDA) nor inhibitors of the NMDA glutamate receptors had any effect. However, the kainic acid mediated increase was blocked by antagonists of non-NMDA receptors. Kainic acid also elevated levels of BDNF and NGF mRNAs in rat hippocampus and cortex in vivo. These results suggest that the synthesis of these two neurotrophic factors in the brain is regulated by neuronal activity via non-NMDA glutamate receptors.

Animals↗
PubMed1990

Immunoelectron microscopic localization of laminin in normal and regenerating mouse sciatic nerve.

Laminin, the major non-collagenous protein of basement membranes, has been shown to be a potent stimulator of neurite outgrowth, to potentiate neuronal survival and to stimulate Schwann cell division in vitro. The aim of the present study was to determine the ultrastructural localization of laminin in the mouse sciatic nerve during development and regeneration in order to elucidate whether laminin might also evoke similar effects in vivo. For this purpose polyclonal antibodies against laminin were used for pre-embedding electron microscopic immunocytochemistry of tissue sections from mouse sciatic nerves. In the adult, although laminin immunoreactivity was found to be predominantly associated with basement membranes as expected, the surface membranes of Schwann cells also displayed weak labelling. This distribution pattern was similar in developing sciatic nerves with the exception that laminin immunoreactivity was generally higher and also found to be present on interstitial collagen fibres. One week following sciatic nerve transection, strong laminin immunoreactivity was seen on regenerating axons growing along laminin-positive basement membrane tubes in the distal stump of the transected nerve. Our results demonstrate that laminin immunoreactivity is not restricted to basement membranes of the mouse sciatic nerve, but is also found in direct contact with adult, developing and regenerating axons as well as on the surface of Schwann cells. The finding of laminin immunoreactivity on extracellular matrix components, axons and Schwann cell membranes under conditions of growth and regeneration makes it more likely that axons are able to interact with laminin not only in vitro but also in vivo.

Aging↗
PubMed1990

Lesion-induced increase in nerve growth factor mRNA is mediated by c-fos.

Lesion of the sciatic nerve caused a rapid increase in c-fos and c-jun mRNA that was followed about 2 hr later by an increase in nerve growth factor (NGF) mRNA. To evaluate whether the initial increase in c-fos mRNA is causally related to the subsequent increase in NGF mRNA, we performed experiments with fibroblasts of transgenic mice carrying an exogenous c-fos gene under the control of a metallothionein promoter. In primary cultures of these fibroblasts, CdCl2 evoked a rapid increase in exogenous c-fos mRNA, followed immediately by an increase in endogenous c-jun mRNA and with a slight delay by an increase in NGF mRNA. In fibroblasts of C3H control mice, CdCl2 had no effect on the mRNA levels of the protooncogenes c-fos and c-jun or of NGF. Additional evidence for a causal relationship between c-fos induction and the subsequent increase in NGF mRNA was obtained in cotransfection experiments. Fibroblasts of C3H control mice were cotransfected with a metallothionein-promoter-driven c-fos expression vector and a NGF promoter-chloramphenicol acetyltransferase reporter gene construct. Induction of the exogenous c-fos by CdCl2 resulted in increased activity of the NGF promoter. DNase I footprint experiments demonstrated that a binding site for transcription factor AP-1 (Fos/Jun heterodimer) in the first intron of the NGF gene was protected following c-fos induction. That this protected AP-1 site indeed was functional in the regulation of NGF expression was verified by deletion experiments and by a point mutation in the corresponding AP-1 binding region in the NGF promoter-chloramphenicol acetyltransferase reporter construct.

Animals↗
PubMed1990

Regional and cellular codistribution of interleukin 1 beta and nerve growth factor mRNA in the adult rat brain: possible relationship to the regulation of nerve growth factor synthesis.

We have found a regional distribution of IL 1 beta mRNA and IL 1 activity in the normal adult rat brain, which reveals at least partially a colocalization with nerve growth factor (NGF). The predominantly neuronal signal patterns were found over the granule cells of the dentate gyrus, the pyramidal cells of the hippocampus, the granule cells of the cerebellum, the granule and periglomerular cells of the olfactory bulb, and over dispersed cells of the ventromedial hypothalamus and of the frontal cortex. In these areas also the highest levels of IL 1 activity were observed. In the striatum and septum much lower levels of IL 1 beta mRNA and IL 1 activity (shown for the striatum), most likely synthesized by glial cells, could be determined. IL 1 beta-expressing cells were mainly found in brain regions that also synthesize NGF mRNA as shown by in situ hybridization. NGF mRNA could be demonstrated over pyramidal cells of the hippocampus, granule cells of the dentate gyrus, periglomerular cells of the olfactory bulb and over prefrontal cortex neurons. These data indicate that IL 1 beta, among other factors, might also play a regulatory role in the synthesis of NGF in the CNS, as has been demonstrated in the peripheral nervous system (Lindholm, D., R. Heumann, M. Meyer, and H. Thoenen. 1987. Nature (Lond.). 330:658-659).

Animals↗
PubMed1990

Transforming growth factor-beta 1 stimulates expression of nerve growth factor in the rat CNS.

Transforming growth factor-beta 1 (TGF-beta 1) markedly increased the mRNA encoding nerve growth factor (NGF) in cultured rat astrocytes in a time- and concentration-dependent manner. The maximal effect of TGF-beta 1 (a 50-fold increase in NGF-mRNA) was reached after 24 h incubation. The TGF-beta-mediated increase in NGF-mRNA results from enhanced transcription as shown in nuclear run-on studies and in transfection assays using the NGF promoter linked to a chloramphenicol acetyltransferase (CAT) reporter gene. TGF-beta 1 also increased its own expression in astrocytes as well as that of the proto-oncogene c-fos. Intraventricular injection of TGF-beta 1 resulted in an increase of NGF-mRNA levels in the rat hippocampus (3-4 fold) showing that TGF-beta 1 is also effective in increasing NGF expression in vivo.

Animals↗
PubMed1990

Developmental loss of laminin from the interstitial extracellular matrix correlates with decreased laminin gene expression.

The expression of the polypeptide subunits of the glycoprotein laminin in developing mouse tissues was analysed by immunoblots and Northern blots, and by immunohistochemistry at the ultrastructural level. In the neonate, almost all the laminin of the sciatic nerve was freely extractable and was located mainly in the mesenchymal interstitial extracellular matrix, rather than in basement membranes. During the first two postnatal weeks, the distribution of laminin shifted to assume the adult pattern, most being located in basement membranes and insoluble under physiological conditions. Analysis of laminin subunit expression showed that both the mRNA for the laminin B chains and the corresponding polypeptides are widely expressed in nerve and other tissues, the mRNA levels decreasing during the first two postnatal weeks as the amount of laminin in the tissue increased. In contrast, the A chain mRNA and polypeptide were undetectable in nerve at any age studied, although they were present in perinatal kidney and placenta. It is proposed that the large amount of soluble laminin present in the developing interstitial extracellular matrix is a consequence of the high levels of expression of laminin mRNA, the subsequent decrease in expression resulting in the adult distribution where most laminin is insoluble within the basement membrane.

Animals↗
PubMed1990

Survival effect of ciliary neurotrophic factor (CNTF) on chick embryonic motoneurons in culture: comparison with other neurotrophic factors and cytokines.

In previous studies, it has been demonstrated that ciliary neurotrophic factor (CNTF) has a potent survival effect on various populations of neurons in culture, in particular, neurons isolated from chick ciliary, dorsal root sensory, and sympathetic ganglia (Barbin et al., 1984). After recent investigations demonstrated that CNTF prevents the degeneration of motoneurons in newborn rats after axonal lesion (Sendtner et al., 1990), the question arose as to whether CNTF also has a survival effect on embryonic chick motoneurons at the developmental stage where physiological cell death occurs. To study this, it was essential to develop an isolation and culture procedure for the survival of chick E6 spinal motoneurons in which non-neuronal cells were eliminated and the motoneurons were highly enriched. In these cultures, virtually all of the initially plated motoneurons survived for at least 3 d in the presence of muscle extract, which was chosen as a positive control. Retrograde labeling of the motoneurons prior to their isolation showed that there is more than an 80% enrichment for motoneurons by the method used. The retrogradely labeled neurons also fulfilled the morphological criteria (diameter of neurons, appearance of processes) to identify motoneurons independent of retrograde labeling. Under these conditions, CNTF at a concentration of 1.5 ng/ml (EC50, 0.023 ng/ml) supported maximally 64% of the initially plated spinal motoneurons after 3 d and 53% after 6 d (the longest time period investigated). Other neurotrophic factors, such as NGF, brain-derived neurotrophic factor (BDNF), and neurotrophin-3, had no survival effect at all, even at concentrations up to 10 micrograms/ml for NGF and BDNF.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Molecular cloning and expression of brain-derived neurotrophic factor.

During the development of the vertebrate nervous system, many neurons depend for survival on interactions with their target cells. Specific proteins are thought to be released by the target cells and to play an essential role in these interactions. So far, only one such protein, nerve growth factor, has been fully characterized. This has been possible because of the extraordinarily (and unexplained) large quantities of this protein in some adult tissues that are of no relevance to the developing nervous system. Whereas the dependency of many neurons on their target cells for normal development, and the restricted neuronal specificity of nerve growth factor have long suggested the existence of other such proteins, their low abundance has rendered their characterization difficult. Here we report the full primary structure of brain-derived neurotrophic factor. This very rare protein is known to promote the survival of neuronal populations that are all located either in the central nervous system or directly connected with it. The messenger RNA for brain-derived neurotrophic factor was found predominantly in the central nervous system, and the sequence of the protein indicates that it is structurally related to nerve growth factor. These results establish that these two neurotrophic factors are related both functionally and structurally.

Amino Acid Sequence↗
PubMed1989

Inhibition of exocytosis by intracellularly applied antibodies against a chromaffin granule-binding protein.

Exocytotic secretion requires the interaction and fusion of secretory vesicles with the plasma membrane. This process could be mediated by specific recognition molecules acting as intracellular, membrane-bound receptors and ligands. One possible component of such a recognition site on the plasma membrane is a protein of relative molecular mass (Mr) 51,000 (51K) that has been isolated from bovine adrenal chromaffin cells. This protein binds strongly to chromaffin granules, the secretory vesicles of these cells. To determine the function of this membrane-anchored chromaffin granule-binding protein in exocytosis, we tested the effect of intracellularly injected antibodies on secretion. Here we show, by two independent techniques in two different cell types, that antibodies against this protein inhibit exocytosis. In rat pheochromocytoma cell cultures, monospecific antibodies, applied by erythrocyte ghost fusion, impair the release of 3H-noradrenaline. The same antibodies, introduced into individual chromaffin cells through a patch pipette, block exocytosis, as revealed by the measurement of membrane capacitance. These results demonstrate the functional involvement in exocytosis of a plasma membrane protein with high affinity for secretory vesicles.

Adrenal Medulla↗
PubMed1989

The survival of chick retinal ganglion cells in response to brain-derived neurotrophic factor depends on their embryonic age.

The survival effects of brain-derived neurotrophic factor (BDNF) on the ganglion cells of the chick retina were studied in vitro at different embryonic ages. We found these effects to be strongly age-dependent: at E5, when the first ganglion cell axons have crossed the optic chiasm, but not yet reached the tectum, ganglion cells survived on a laminin substrate irrespective of the presence or absence of BDNF. At E6, when the axons of the first-generated ganglion cells reached the rostral pole of the tectum, the ganglion cells began to show a dependency on BDNF for survival, but the majority of them were alive after 2 days in vitro in the absence of BDNF. With increasing age, the BDNF dependency for survival increased, and at E11, the majority of the ganglion cells plated were dependent on BDNF for survival. It is at this age that the maximal number of axons can be found in vivo in the optic nerve, the subsequent elimination of ganglion cells and their axons resulting in the loss of hundreds of thousands of them over the next few days. Taken together, these data indicate that retinal ganglion cells depend on BDNF for survival only when their axons have reached their target in vivo. This situation is reminiscent of that described in the peripheral nervous system for the nerve growth factor responsiveness of mouse trigeminal sensory neurons during the period of innervation of their target.

Age Factors↗
PubMed1988

Interleukin 1 increases stability and transcription of mRNA encoding nerve growth factor in cultured rat fibroblasts.

The lymphokine interleukin 1 (IL-1) rapidly increases the levels of mRNA encoding nerve growth factor (NGF) in primary cultures of fibroblasts isolated from adult rat sciatic nerves. The effect of IL-1 on NGF-mRNA was not inhibited by cycloheximide, which itself increased the NGF-mRNA. From the blocking ability of actinomycin D, it was deduced that the IL-1 action depends on continuous RNA synthesis and that the half-life of NGF-mRNA is about 90 min. Nuclear run-on studies showed that, although IL-1 enhances the low basic NGF-mRNA transcription, the main effect of IL-1 results from stabilization of the NGF-mRNA. In addition, indirect evidence is presented indicating that the IL-1 effect of NGF-mRNA levels involves activation of phospholipase A2.

Animals↗