CNTF
Ciliary neurotrophic factor (CNTF)
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Within the supraoptic nucleus (SON) of a 35-day-old rat, we previously demonstrated a collateral sprouting response that reinnervates the partially denervated neural lobe (NL) after unilateral lesion of the hypothalamo-neurohypophysial tract. Others have shown a decreased propensity for axonal sprouting in an aged brain; therefore, to see if the SON exhibits a decreased propensity for axonal sprouting as the animal ages, we performed a unilateral lesion in the 125-day-old rat SON. Ultrastructural analysis of axon profiles in the NL of the 125-day-old rat demonstrated an absence of axonal sprouting following injury. We previously demonstrated that ciliary neurotrophic factor (CNTF) promotes process outgrowth from injured magnocellular neuron axons in vitro. Thus, we hypothesized that the lack of axonal sprouting in the 125-day-old rat SON may be due to a reduction in CNTF or the CNTF receptor components. To this point, we found that as the rat ages there is significantly less CNTF receptor alpha (CNTFRα) protein in the uninjured, 125-day-old rat compared to the uninjured, 35-day-old rat. We also observed that protein levels of CNTF and the CNTF receptor components were increased in the SON and NL following injury in the 35-day-old rat, but there was no difference in the protein levels in the 125-day-old rat. Altogether, the results presented herein demonstrate that the plasticity within the SON is highly dependent on the age of the rat, and that a decrease in CNTFRα protein levels in the 125-day-old rat may contribute to the loss of axonal sprouting following axotomy.
MeSH Terms
- Aging
- Animals
- Axons
- Axotomy
- Ciliary Neurotrophic Factor Receptor alpha Subunit
- Male
- Neural Pathways
- Rats
- Rats, Sprague-Dawley
- Supraoptic Nucleus
Keywords
- CNTF
- CNTFRα
- RRID:AB_2136105
- RRID:AB_2276485
- RRID:AB_397120
- RRID:AB_476697
- RRID:AB_518526
- RRID:AB_518680
- RRID:AB_631590
- aging
- axonal sprouting
- neural lobe
- supraoptic nucleus
Although a major risk factor for Alzheimer's disease (AD), the "aging" parameter is not systematically considered in preclinical validation of anti-AD drugs. To explore how aging affects neuronal reactivity to anti-AD agents, the ciliary neurotrophic factor (CNTF)-associated pathway was chosen as a model. Comparison of the neuroprotective properties of CNTF in 6- and 18-month old mice revealed that CNTF resistance in the older animals is associated with the exclusion of the CNTF-receptor subunits from rafts and their subsequent dispersion to non-raft cortical membrane domains. This age-dependent membrane remodeling prevented both the formation of active CNTF-receptor complexes and the activation of prosurvival STAT3 and ERK1/2 pathways, demonstrating that age-altered membranes impaired the reactivity of potential therapeutic targets. CNTF-receptor distribution and CNTF signaling responses were improved in older mice receiving dietary docosahexaenoic acid, with CNTF-receptor functionality being similar to those of younger mice, pointing toward dietary intervention as a promising adjuvant strategy to maintain functional neuronal membranes, thus allowing the associated receptors to respond appropriately to anti-AD agents.
MeSH Terms
- Aging
- Animals
- Brain
- Cell Membrane
- Ciliary Neurotrophic Factor
- Dietary Fats, Unsaturated
- Docosahexaenoic Acids
- MAP Kinase Signaling System
- Male
- Membrane Microdomains
- Mice, Inbred C57BL
- Neurons
- Nootropic Agents
- Receptor, Ciliary Neurotrophic Factor
- STAT3 Transcription Factor
- Signal Transduction
Keywords
- Brain aging
- Ciliary neurotrophic factor
- Dietary lipids
- Docosahexaenoic acid
- Lipid rafts
- Neuronal membranes
Like other parts of the central nervous system, the adult mammalian optic nerve is difficult to regenerate after injury. Transplantation of the peripheral nerve or a Schwann cell (SC) graft can promote injured axonal regrowth. We tried to develop a new type of tissue-engineered SC graft that consisted of SCs seeded onto a poly(lactic-co-glycolic acid)/chitosan conduit. Meanwhile, SCs were transfected along the ciliary neurotrophic factor (CNTF) gene in vitro by electroporation to increase their neurotrophic effect. Four weeks after transplantation, GAP-43 labelled regenerating axons were found in the SC grafts, and axons in the CNTF-SC graft were longer than those in the SC graft. Tissue-engineered SC grafts can provide a feasible environment for optic nerve regeneration and may become an alternative for bridging damaged nerves and repairing nerve defects in the future.
MeSH Terms
- Aging
- Animals
- Axons
- Cell Line
- Ciliary Neurotrophic Factor
- Fluorescent Antibody Technique
- GAP-43 Protein
- Inflammation
- Lactic Acid
- Male
- Mice
- Microscopy, Fluorescence
- Nerve Regeneration
- Optic Nerve
- Polyglycolic Acid
- Polylactic Acid-Polyglycolic Acid Copolymer
- Rats
- Rats, Sprague-Dawley
- Schwann Cells
- Tissue Engineering
- Tissue Scaffolds
- Transfection
The impact of intraventricular ciliary neurotrophic factor (CNTF) on motor function in aged rats was evaluated. Spontaneous locomotion and motor coordination were quantified in young (5-6 months) and aged (24-25 months) rats. Relative to young animals, aged rats were significantly less active, fell more rapidly from a rotating rod, and were unable to maintain their balance on a wooden beam. Aged animals received bilateral intraventricular implants of polymer-encapsulated fibroblasts that were genetically modified to secrete CNTF. Controls received either no implant or capsules loaded with mock transfected cells. One month after implantation the aged animals that received CNTF implants were significantly more active and were improved on the rotorod and beam balance tests. The improvement in performance on the rotorod and beam balance tests was dependant on the task difficulty and dissipated at higher rotations (rotorod) and smaller beam widths (beam balance). No recovery was seen in aged animals receiving control implants. Postmortem removal of the encapsulated cells confirmed that they continued to secrete CNTF. These data are the first to suggest that intracerebral delivery of CNTF might be useful for slowing or reversing age-related changes in motor function.
MeSH Terms
- Age Factors
- Aging
- Animals
- Behavior, Animal
- Cell Line
- Cerebral Ventricles
- Ciliary Neurotrophic Factor
- Cricetinae
- Enzyme-Linked Immunosorbent Assay
- Fibroblasts
- Male
- Motor Activity
- Postural Balance
- Psychomotor Performance
- Rats
- Rats, Sprague-Dawley
- Recovery of Function
- Time Factors
- Transfection
Genotypic associations between polymorphisms in the ciliary neurotrophic factor (CNTF) and CNTF receptor ([[CNTFR]]) genes and muscular strength phenotypes in 154 middle-aged men (45-49 yr) and 138 women (38-44 yr) and 99 older men (60-78 yr) and 102 older women (60-80 yr) were tested to validate earlier association studies. Allelic interaction effects were hypothesized between alleles of CNTF and [[CNTFR]]. We performed analysis of covariance with age, height, and fat-free mass (FFM) as covariates. FFM was anthropometrically estimated by the equation of Durnin-Womersley. Isometric, concentric, and eccentric torques for the knee flexors (KF) and extensors (KE) were measured using Biodex dynamometry. In the older male group, T-allele carriers of the C-1703T polymorphism in [[CNTFR]] performed significantly better on all noncorrected KF torques, whereas only noncorrected KE isometric torque at 120 degrees and concentric torque at 240 degrees/s were higher than the C/C homozygotes (P < 0.05). When age, height, and FFM were used as covariates, T-allele carriers performed only better on KE and KF isometric torque at 120 degrees (P < 0.05). Concentric KF torque at 180 degrees/s was lower in middle-aged female A-allele carriers compared with the T/T subjects for the T1069A polymorphism in [[CNTFR]]. After correction for age, height, and FFM, middle-aged female A-allele carriers exhibited lower values on all concentric KF strength measures and isometric torque at 120 degrees . There was a lack of association with the CNTF G-6A polymorphism in men, with inconclusive results for a limited number of phenotypes in women. No significant CNTF/[[CNTFR]] allele interaction effects were found. Results indicate that [[CNTFR]] C-1703T and T1069A polymorphisms are significantly associated with muscle strength in humans.
MeSH Terms
- Adult
- Age Factors
- Aged
- Aging
- Ciliary Neurotrophic Factor
- Cohort Studies
- Female
- Gene Frequency
- Genotype
- Humans
- Knee
- Longitudinal Studies
- Male
- Middle Aged
- Muscle Strength
- Muscle, Skeletal
- Phenotype
- Receptor, Ciliary Neurotrophic Factor
- Sex Factors
- Torque
We have previously shown that not only motoneurons and dorsal root ganglion cells but also small neurons, presumably interneurons in the spinal cord, may undergo apoptotic cell death as a result of neonatal peripheral nerve transection in the rat. With the aid of electron microscopy, we have here demonstrated that apoptosis in the spinal cord is confined to neurons and does not involve glial cells at the survival time studied (24 hours). To define the relative importance of the loss of a potential target (motoneuron) and a potential afferent input (dorsal root ganglion cell) for the induction of apoptosis in interneurons in this situation, we have compared the distributions and time courses for TUNEL labeling, which detects apoptotic cell nuclei, in the L5 segment of the spinal cord and the L5 dorsal root ganglion after sciatic nerve transection in the neonatal (P2) rat. In additional experiments, we studied the effects on TUNEL labeling of interneurons after treatment of the cut sciatic nerve with either ciliary neurotrophic factor (CNTF) to rescue motoneurons or nerve growth factor (NGF) to rescue dorsal root ganglion cells. The time courses of the TUNEL labeling in motoneurons and interneurons induced by the lesion show great similarities (peak at 8-48 hours postoperatively), whereas the labeling in dorsal root ganglion cells occurs later (24-72 hours). Both CNTF and NGF decrease the number of TUNEL-labeled interneurons, but there is a regional difference, in that CNTF preferentially saves interneurons in deep dorsal and ventral parts of the spinal cord, whereas the rescuing effects of NGF are seen mainly in the superficial dorsal horn. The results are interpreted as signs of a trophic dependence on both the target and the afferent input for the survival of interneurons neonatally.
MeSH Terms
- Afferent Pathways
- Aging
- Animals
- Animals, Newborn
- Apoptosis
- Axotomy
- Cell Survival
- Ciliary Neurotrophic Factor
- Ganglia, Spinal
- In Situ Nick-End Labeling
- Interneurons
- Motor Neurons
- Nerve Degeneration
- Nerve Growth Factor
- Rats
- Rats, Sprague-Dawley
- Sciatic Nerve
- Spinal Cord
Members of the ciliary neurotrophic factor (CNTF)/leukemia inhibitory factor (LIF)/cardiotrophin gene family are potent survival factors for embryonic and lesioned motoneurons. These factors act via receptor complexes involving gp130 and LIFR-beta and ligand binding leads to activation of various signaling pathways, including phosphorylation of Stat3. The role of Stat3 in neuronal survival was investigated in mice by Cre-mediated gene ablation in motoneurons. Cre is expressed under the neurofilament light chain (NF-L) promoter, starting around E12 when these neurons become dependent on neurotrophic support. Loss of motoneurons during the embryonic period of naturally occurring cell death is not enhanced in NF-L-Cre; Stat3(flox/KO) mice although motoneurons isolated from these mice need higher concentrations of CNTF for maximal survival in culture. In contrast, motoneuron survival is significantly reduced after facial nerve lesion in the adult. These neurons, however, can be rescued by the addition of neurotrophic factors, including CNTF. Stat3 is essential for upregulation of Reg-2 and Bcl-xl expression in lesioned motoneurons. Our data show that Stat3 activation plays an essential role for motoneuron survival after nerve lesion in postnatal life but not during embryonic development, indicating that signaling requirements for motoneuron survival change during maturation.
MeSH Terms
- Aging
- Animals
- Animals, Newborn
- Axotomy
- Calcium-Binding Proteins
- Cell Death
- Cell Survival
- Cells, Cultured
- Ciliary Neurotrophic Factor
- DNA-Binding Proteins
- Facial Nerve Injuries
- Gene Deletion
- Integrases
- Lithostathine
- Mice
- Mice, Knockout
- Motor Neurons
- Nerve Tissue Proteins
- Nervous System
- Neurofilament Proteins
- Organ Specificity
- Promoter Regions, Genetic
- Proto-Oncogene Proteins c-bcl-2
- RNA, Messenger
- STAT3 Transcription Factor
- Signal Transduction
- Trans-Activators
- Viral Proteins
- bcl-X Protein
The capacity of the central nervous system for axonal growth decreases as the age of the animal at the time of injury increases. Changes in the expression of neurotrophic factors within embryonic and early postnatal spinal cord suggest that a lack of trophic support contributes to this restrictive growth environment. We examined neurotrophic factor gene profiles by ribonuclease protection assay in normal neonate and normal adult spinal cord and in neonate and adult spinal cord after injury. Our results show that in the normal developing spinal cord between postnatal days 3 (P3) and P10, compared to the normal adult spinal cord, there are higher levels of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin 3 (NT-3), and glial-derived neurotrophic factor (GDNF) mRNA expression and a lower level of ciliary neurotrophic factor (CNTF) mRNA expression. Between P10 and P17, there is a significant decrease in the expression of NGF, BDNF, NT-3, and GDNF mRNA and a contrasting steady and significant increase in the level of CNTF mRNA expression. These findings show that there is a critical shift in neurotrophic factor expression in normal developing spinal cord between P10 and P17. In neonate spinal cord after injury, there is a significantly higher level of BDNF mRNA expression and a significantly lower level of CNTF mRNA expression compared to those observed in the adult spinal cord after injury. These findings suggest that high levels of BDNF mRNA expression and low levels of CNTF mRNA expression play important roles in axonal regrowth in early postnatal spinal cord after injury.
MeSH Terms
- Aging
- Animals
- Animals, Newborn
- Brain-Derived Neurotrophic Factor
- Ciliary Neurotrophic Factor
- Gene Expression Regulation, Developmental
- Glial Cell Line-Derived Neurotrophic Factor
- Nerve Growth Factor
- Nerve Growth Factors
- Nerve Tissue Proteins
- Neurotrophin 3
- Rats
- Rats, Sprague-Dawley
- Reference Values
- Spinal Cord
- Spinal Cord Injuries
Delivery of neurotrophic factors to the injured spinal cord has been shown to stimulate neuronal survival and regeneration. This indicates that a lack of sufficient trophic support is one factor contributing to the absence of spontaneous regeneration in the mammalian spinal cord. Regulation of the expression of neurotrophic factors and receptors after spinal cord injury has not been studied in detail. We investigated levels of mRNA-encoding neurotrophins, glial cell line-derived neurotrophic factor (GDNF) family members and related receptors, ciliary neurotrophic factor (CNTF), and c-fos in normal and injured spinal cord. Injuries in adult rats included weight-drop, transection, and excitotoxic kainic acid delivery; in newborn rats, partial transection was performed. The regulation of expression patterns in the adult spinal cord was compared with that in the PNS and the neonate spinal cord. After mechanical injury of the adult rat spinal cord, upregulations of NGF and GDNF mRNA occurred in meningeal cells adjacent to the lesion. BDNF and p75 mRNA increased in neurons, GDNF mRNA increased in astrocytes close to the lesion, and GFRalpha-1 and truncated TrkB mRNA increased in astrocytes of degenerating white matter. The relatively limited upregulation of neurotrophic factors in the spinal cord contrasted with the response of affected nerve roots, in which marked increases of NGF and GDNF mRNA levels were observed in Schwann cells. The difference between the ability of the PNS and CNS to provide trophic support correlates with their different abilities to regenerate. Kainic acid delivery led to only weak upregulations of BDNF and CNTF mRNA. Compared with several brain regions, the overall response of the spinal cord tissue to kainic acid was weak. The relative sparseness of upregulations of endogenous neurotrophic factors after injury strengthens the hypothesis that lack of regeneration in the spinal cord is attributable at least partly to lack of trophic support.
MeSH Terms
- Aging
- Animals
- Animals, Newborn
- Astrocytes
- Axotomy
- Disease Models, Animal
- Female
- Gene Expression Regulation
- Kainic Acid
- Meninges
- Nerve Growth Factors
- RNA, Messenger
- Rats
- Rats, Sprague-Dawley
- Receptors, Nerve Growth Factor
- Schwann Cells
- Spinal Cord
- Spinal Cord Injuries
- Wounds, Nonpenetrating
The relationship between ciliary neurotrophic factor (CNTF) genotype and muscle strength was examined in 494 healthy men and women across the entire adult age span (20-90 yr). Concentric (Con) and eccentric (Ecc) peak torque were assessed using a Kin-Com isokinetic dynamometer for the knee extensors (KE) and knee flexors (KF) at slow (0.52 rad/s) and faster (3.14 rad/s) velocities. The results were covaried for age, gender, and body mass or fat-free mass (FFM). Individuals heterozygous for the CNTF null (A allele) mutation (G/A) exhibited significantly higher Con peak torque of the KE and KF at 3.14 rad/s than G/G homozygotes when age, gender, and body mass were covaried (P < 0.05). When the dominant leg FFM (estimated muscle mass) was used in place of body mass as a covariate, Con peak torque of the KE at 3.14 rad/s was also significantly greater in the G/A individuals (P < 0.05). In addition, muscle quality of the KE (peak torque at 3.14 rad x s(-1) x leg muscle mass(-1)) was significantly greater in the G/A heterozygotes (P < 0.05). Similar results were seen in a subanalysis of subjects 60 yr and older, as well as in Caucasian subjects. In contrast, A/A homozygotes demonstrated significantly lower Ecc peak torque at 0.52 rad/s for both KE and KF compared with G/G and G/A groups (P < 0.05). No significant relationships were observed at 0.52 rad/s between genotype and Con peak torque. These data indicate that individuals exhibiting the G/A genotype possess significantly greater muscular strength and muscle quality at relatively fast contraction speeds than do G/G individuals. Because of high positive correlations between fast-velocity peak torque and muscular power, these findings suggest that further investigations should address the relationship between CNTF genotype and muscular power.
MeSH Terms
- Adult
- Aged
- Aged, 80 and over
- Aging
- Alleles
- Body Weight
- Ciliary Neurotrophic Factor
- Female
- Genotype
- Humans
- Isometric Contraction
- Longitudinal Studies
- Male
- Middle Aged
- Muscle, Skeletal
In this study we have examined whether the slower rate of CNS remyelination that occurs with age is associated with a change in growth factor expression patterns, an association that would provide further support for a causal relationship between growth factors and remyelination. Using quantitative in situ hybridization we have shown that there are differences in IGF-I, TGF-beta 1, and PDGF-A mRNA expression during remyelination of lysolecithin-induced demyelination in the spinal cord of young adult and old adult rats. IGF-I and TGF-beta1 mRNA expression in old rats had a delayed and lower peak expression compared to young rats. The initial increase in PDGF-A mRNA expression was delayed in old rats compared to young rats, but after 5 days both age groups had similar patterns of expression, as was the expression pattern of FGF-2 mRNA at all survival times. In neither age group were increases in CNTF, NT-3, or GGF-2 mRNA expression detected. An analysis of the macrophage response using oligonucleotide probes for scavenger receptor-B mRNA indicated that differences in the macrophage response in young and old animals was the likely cause of the age related change in IGF-I and TGF-beta 1 mRNA expression patterns. On the basis of these data we suggest a model of remyelination in which PDGF is involved in the initial phase of oligodendrocyte progenitor recruitment, while IGF-I and TGF-beta 1 trigger the differentiation of the recruited cells into myelinating oligodendrocytes.
MeSH Terms
- Aging
- Animals
- CD36 Antigens
- Female
- Fibroblast Growth Factor 2
- Gene Expression
- Glial Fibrillary Acidic Protein
- Growth Substances
- In Situ Hybridization
- Insulin-Like Growth Factor I
- Lysophosphatidylcholines
- Membrane Proteins
- Molecular Sequence Data
- Myelin Sheath
- Nerve Degeneration
- Nerve Regeneration
- Oligonucleotide Probes
- Platelet-Derived Growth Factor
- RNA, Messenger
- Rats
- Rats, Sprague-Dawley
- Receptors, Immunologic
- Receptors, Lipoprotein
- Receptors, Scavenger
- Scavenger Receptors, Class B
- Spinal Cord
- Transforming Growth Factor beta
- Transforming Growth Factor beta1
After sciatic nerve lesion in the adult rat, motoneurons survive and regenerate, whereas the same lesion in the neonatal animal or an avulsion of ventral roots from the spinal cord in adults induces extensive cell death among lesioned motoneurons with limited or no axon regeneration. A number of substances with neurotrophic effects have been shown to increase survival of motoneurons in vivo and in vitro. Here we have used semiquantitative in situ hybridization histochemistry to detect the regulation in motoneurons of mRNAs for receptors to ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), glial cell line-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) 1-42 days after the described three types of axon injury. After all types of injury, the mRNAs for GDNF receptors (GFRalpha-1 and c-RET) and the LIF receptor [[LIFR]] were distinctly (up to 300%) up-regulated in motoneurons. The CNTF receptor CNTFRalpha mRNA displayed only small changes, whereas the mRNA for membrane glycoprotein 130 (gp130), which is a critical receptor component for LIF and CNTF transduction, was profoundly down-regulated in motoneurons after ventral root avulsion. The BDNF full-length receptor trkB mRNA was up-regulated acutely after adult sciatic nerve lesion, whereas after ventral root avulsion trkB was down-regulated. The NT-3 receptor trkC mRNA was strongly down-regulated after ventral root avulsion. The results demonstrate that removal of peripheral nerve tissue from proximally lesioned motor axons induces profound down-regulations of mRNAs for critical components of receptors for CNTF, LIF, and NT-3 in affected motoneurons, but GDNF receptor mRNAs are up-regulated in the same situation. These results should be considered in relation to the extensive cell death among motoneurons after ventral root avulsion and should also be important for the design of therapeutical approaches in cases of motoneuron death.
MeSH Terms
- Aging
- Animals
- Animals, Newborn
- Axotomy
- Cell Survival
- Denervation
- Motor Neurons
- Nerve Regeneration
- RNA, Messenger
- Rats
- Rats, Sprague-Dawley
- Receptors, Growth Factor
- Reference Values
- Sciatic Nerve
- Spinal Cord
- Spinal Nerve Roots
- Up-Regulation
- Wounds and Injuries
Activation of the Janus kinases (JAK) and signal transducers and activator of transcription (STAT) proteins in response to specific cytokines and growth factors has been investigated primarily in cells of non-neuronal origin. More recently, the JAKs and the STATs have also been found to be active in the developing and mature brain, providing evidence for important roles played by these molecules in the control of neuronal proliferation, survival and differentiation. Nothing, however, is known about their occurrence and role(s) in the aged brain. We, therefore, investigated the presence of Stat3 and Stat1 in aged-rat brain, and have found that the Stat3 protein was markedly down regulated with respect to adult tissue, while Stat1 remained invariant. We also investigated the potential role of some growth factors in the activation of the JAK/STAT in mature neurons, exposing primary neuronal cells to ciliary neurotrophic factor (CNTF), basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF). Besides CNTF, which is known to recruit Stat3, we found that Stat3 was also tyrosine phosphorylated by bFGF. These data are indicative of an important role of Stat3 and Stat1 in regulating the physiological status of mature neurons.
MeSH Terms
- Aging
- Animals
- Antibodies, Monoclonal
- Brain
- Brain Chemistry
- Cells, Cultured
- DNA-Binding Proteins
- Female
- Gene Expression Regulation, Developmental
- Janus Kinase 1
- Male
- Neurons
- Phosphorylation
- Pregnancy
- Protein-Tyrosine Kinases
- Rats
- Rats, Sprague-Dawley
- STAT1 Transcription Factor
- STAT3 Transcription Factor
- Signal Transduction
- Trans-Activators
Cultured and transplanted adrenal medullary cells respond to ciliary neurotrophic factor (CNTF) with neurite formation and improved cell survival although the presence of the CNTF receptor-alpha (CNTFRalpha) has been unclear. This study show that CNTFRalpha mRNA was expressed in the postnatal day 1 as well as in the adult rat adrenal medulla. The highest CNTFRalpha mRNA signal was found in the ganglion cells of the adrenal medulla. After transplantation of adrenal medullary tissue the CNTFRalpha mRNA levels were down-regulated in the chromaffin cells. CNTF treatment of grafts did not normalize the receptor levels, but treatment with nerve growth factor (NGF) did. Thus, we demonstrate that CNTFRalpha mRNA is expressed in adrenal medulla, the levels becomes down-regulated after transplantation, but normalized after treatment with NGF.
MeSH Terms
- Adrenal Medulla
- Aging
- Animals
- Animals, Newborn
- Chromaffin Cells
- Eye
- Female
- In Situ Hybridization
- Nerve Growth Factor
- RNA, Messenger
- Rats
- Rats, Sprague-Dawley
- Receptor, Ciliary Neurotrophic Factor
- Reference Values
- Transplantation, Heterotopic
Ciliary neurotrophic factor (CNTF) participates in the survival of motor neurons and reduces the denervation-induced atrophy of skeletal muscles. Experiments performed in rats show a decrease in peripheral CNTF synthesis during aging, associated with an overexpression of its alpha-binding receptor component by skeletal muscles. Measurement of sciatic nerve CNTF production and of the muscular performance developed by the animals revealed a strong correlation between the two studied parameters (r = 0.8; p < 0.0003). Furthermore, the twitch and tetanic tensions measured in the isolated soleus skeletal muscle in 24-month-old animals increased 2. 5-fold by continuous in vivo administration of CNTF. Analyses of the activation level of leukemia inhibitory factor receptor beta- and signal transducer and activator of transcription 3-signaling molecules in response to exogenous CNTF revealed an increased tyrosine phosphorylation positively correlated with the twitch tension developed by the soleus muscle of the animals.
MeSH Terms
- Aging
- Animals
- Blotting, Northern
- Body Weight
- Ciliary Neurotrophic Factor
- Enzyme-Linked Immunosorbent Assay
- Male
- Muscle Contraction
- Muscle Development
- Muscle Proteins
- Muscle, Skeletal
- Nerve Growth Factors
- Nerve Tissue Proteins
- Rats
- Receptor Protein-Tyrosine Kinases
- Receptor, Ciliary Neurotrophic Factor
- Receptors, Nerve Growth Factor
- Sciatic Nerve
- Signal Transduction
- Swimming
To investigate when the neurotrophic cytokines ciliary neurotrophic factor (CNTF), leukaemia inhibitory factor (LIF), oncostatin-M (OSM), interleukin-6 (IL-6) and cardiotrophin-1 (CT-1) act on developing sensory neurones and whether they co-operate with neurotrophins in regulating neuronal survival, we studied the in vitro trophic effects of these factors on two well-characterized populations of cranial sensory neurones at closely staged intervals throughout embryonic development. The cutaneous sensory neurones of the trigeminal ganglion, which show an early, transient survival response to BDNF and NT3 before becoming NGF-dependent, were supported by CNTF, LIF, OSM and CT-1 during the late fetal period, several days after the neurones become NGF-dependent. At this stage of development, these cytokines promoted the survival of a subset of NGF-responsive neurones. The enteroceptive neurones of the nodose ganglion, which retain dependence on BDNF throughout fetal development, were supported throughout their development by CNTF, LIF, OSM and CT-1, and displayed an additional survival response to IL-6 in the late fetal period. These findings indicate that populations of sensory neurones display different developmental patterns of cytokine responsiveness and show that embryonic trigeminal neurones pass through several phases of differing neurotrophic factor survival requirements.
MeSH Terms
- Aging
- Animals
- Brain
- Cell Survival
- Cytokines
- Electrophysiology
- Mice
- Nerve Growth Factors
- Neurons, Afferent
- Nodose Ganglion
- Trigeminal Ganglion
Cell culture and animal models suggest a significant influence of ciliary neurotrophic factor (CNTF) on cholinergic neurotransmitter systems. We therefore conducted an explorative pilot study to investigate the influence of a null mutation allele of the CNTF gene on ChAT (choline acetyltransferase) and AChE (acetylcholine esterase) activities in various regions of human post mortem brain tissue. Additionally, we determined NT3 (neurotrophin 3) levels, a factor which exhibits neurotrophic properties at cholinergic neurons, and the concentration of which in these brain regions varies with CNTF genotype. Homozygous carriers of the mutation lack CNTF completely, whereas heterozygotes have a CNTF level which is about half that of non-carriers. There was a trend toward lower ChAT and AChE activity levels in the cingulate cortex in individuals homozygous or heterozygous for the mutation when compared with non-mutant individuals. Additionally, higher NT3 concentrations were found in this region, as well as in the frontal cortex and caudate nucleus. ChAT and AChE activities in the frontal cortex and caudate nucleus were not significantly linked to CNTF genotype. These results are, however, preliminary and need to be further explored. The individuals investigated were heterogenous with respect to a range of parameters; nevertheless, the hypothesis that genetic variants for neurotrophic factors play a role in diseases of neural development and plasticity deserves further examination.
MeSH Terms
- Acetylcholinesterase
- Adult
- Aging
- Brain Chemistry
- Choline O-Acetyltransferase
- Ciliary Neurotrophic Factor
- DNA
- Female
- Genotype
- Humans
- Male
- Nerve Growth Factors
- Nerve Tissue Proteins
- Neurotrophin 3
The capacity of CNS neurons for axonal regrowth after injury decreases as the age of the animal at time of injury increases. After spinal cord lesions at birth, there is extensive regenerative growth into and beyond a transplant of fetal spinal cord tissue placed at the injury site. After injury in the adult, however, although host corticospinal and brainstem-spinal axons project into the transplant, their distribution is restricted to within 200 micron of the host/transplant border. The aim of this study was to determine if the administration of neurotrophic factors could increase the capacity of mature CNS neurons for regrowth after injury. Spinal cord hemisection lesions were made at cervical or thoracic levels in adult rats. Transplants of E14 fetal spinal cord tissue were placed into the lesion site. The following neurotrophic factors were administered at the site of injury and transplantation: brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), neurotrophin-4 (NT-4), ciliary-derived neurotrophic factor (CNTF), or vehicle alone. After 1-2 months survival, neuroanatomical tracing and immunocytochemical methods were used to examine the growth of host axons within the transplants. The neurotrophin administration led to increases in the extent of serotonergic, noradrenergic, and corticospinal axonal ingrowth within the transplants. The influence of the administration of the neurotrophins on the growth of injured CNS axons was not a generalized effect of growth factors per se, since the administration of CNTF had no effect on the growth of any of the descending CNS axons tested. These results indicate that in addition to influencing the survival of developing CNS and PNS neurons, neurotrophic factors are able to exert a neurotropic influence on injured mature CNS neurons by increasing their axonal growth within a transplant.
MeSH Terms
- Aging
- Animals
- Animals, Newborn
- Axons
- Biomarkers
- Brain-Derived Neurotrophic Factor
- Ciliary Neurotrophic Factor
- Fetal Tissue Transplantation
- Nerve Growth Factors
- Nerve Regeneration
- Nerve Tissue Proteins
- Neurotrophin 3
- Rats
- Rats, Sprague-Dawley
- Serotonin
- Spinal Cord
- Spinal Cord Injuries
We developed a sensitive enzyme-linked immunosolvent assay for measuring ciliary neurotrophic factor (CNTF) and examined age-related changes in the CNTF contents of a variety of rat tissues during postnatal development. CNTF contents were substantially higher in the sciatic nerve and spinal cord than in the other tissues tested, the kidney coming third. In all the tissues except the sciatic nerve (90 ng/g), the CNTF content was less than 1 ng/g at 1 week of age, then gradually increased. It was highest at 5 weeks of age in the sciatic nerve (3171 ng/g), spinal cord (118 ng/g), and kidney (36.8 ng/g), after which it slowly decreased. In contrast, the maximum in the brain stem (9 ng/g) and cerebellum (3.6 ng/g) was at 8 weeks of age, whereas in skeletal muscle it was at 2 weeks of age (14.6 ng/g). These findings indicate that CNTF functions in the postnatal development of the rat.
MeSH Terms
- Aging
- Animals
- Brain
- Ciliary Neurotrophic Factor
- Enzyme-Linked Immunosorbent Assay
- Nerve Growth Factors
- Nerve Tissue Proteins
- Rats
- Recombinant Proteins
- Sciatic Nerve
- Spinal Cord
- Tissue Distribution
Virtually all cell populations in the vertebrate nervous system undergo massive "naturally-occurring" or "programmed" cell death (PCD) early in development. Initially neurons and glia are overproduced followed by the demise of approximately one-half of the original cell population. In this review we highlight current hypotheses regarding how large-scale PCD contributes to the construction of the developing nervous system. More germane to the theme of this symposium, we emphasize that the survival of cells during PCD depends critically on their ability to access "trophic" molecular signals derived primarily from interactions with other cells. Here we review the cell-cell interactions and molecular mechanisms that control neuronal and glial cell survival during PCD, and how the inability of such signals to suppress PCD may contribute to cell death in some diseases such as spinal muscular atrophy. Finally, by using neurotrophic factors (e.g. CNTF, GDNF) and genes that control the cell death cascade (e.g. Bcl-2) as examples, we underscore the importance of studying the mechanisms that control neuronal and glial cell survival during normal development as a means of identifying molecules that prevent pathology-induced cell death. Ultimately this line of investigation could reveal effective strategies for arresting neuronal and glial cell death induced by injury, disease, and/or aging in humans.
MeSH Terms
- Aging
- Animals
- Apoptosis
- Cell Survival
- Embryonic and Fetal Development
- Humans
- Models, Neurological
- Nervous System
- Nervous System Diseases
- Neuroglia
- Neurons
- Vertebrates
The activities of ciliary neurotrophic factor (CNTF) were initially thought to be restricted to cells in the nervous system. However, the recent identification of its receptor specificity-conferring alpha component ([[CNTFR]] alpha) in skeletal muscle has provided the clue to the unexpected actions of CNTF in the periphery. In the present study, we demonstrated that the mRNA expression of [[CNTFR]] alpha in chick skeletal muscle was decreased by approximately 10-fold after nerve transection; this finding is in sharp contrast to the dramatic up-regulation observed in denervated rat muscle. As a first step toward investigating the differential regulation of [[CNTFR]] alpha in chick and rat, we examined the mRNA expression of [[CNTFR]] alpha in different types of muscle following nerve injury in young and adult animals. Our findings demonstrated that the differential expression of [[CNTFR]] alpha observed in denervated skeletal muscle of the chick and rat was not dependent on age or muscle type. The temporal profile of the changes in [[CNTFR]] alpha expression was, however, dependent on the age of the chick as well as the types of muscles. Furthermore, the low level of [[CNTFR]] alpha expression observed in denervated chick muscle recovered to almost control levels in regenerating skeletal muscle. Taken together, our findings provided the first extensive analysis on the mRNA expression of [[CNTFR]] alpha and the alpha subunit of the acetylcholine receptor in various skeletal muscles of the chick following nerve injury and regeneration.
MeSH Terms
- Aging
- Animals
- Blotting, Northern
- Chickens
- Down-Regulation
- Muscle Denervation
- Muscle Development
- Muscle, Skeletal
- Nerve Crush
- RNA, Messenger
- Rats
- Receptor, Ciliary Neurotrophic Factor
- Receptors, Nerve Growth Factor
- Regeneration
- Sciatic Nerve
- Transcription, Genetic
CNTF is a cytosolic molecule expressed postnatally in myelinating Schwann cells and in a subpopulation of astrocytes. Although CNTF administration prevents lesion-mediated and genetically determined motor neuron degeneration, its physiological function remained elusive. Here it is reported that abolition of CNTF gene expression by homologous recombination results in a progressive atrophy and loss of motor neurons in adult mice, which is functionally reflected by a small but significant reduction in muscle strength.
MeSH Terms
- Aging
- Animals
- Base Sequence
- Cells, Cultured
- Ciliary Neurotrophic Factor
- Cloning, Molecular
- DNA, Single-Stranded
- Gene Expression Regulation
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Mutant Strains
- Molecular Sequence Data
- Motor Neurons
- Muscles
- Nerve Degeneration
- Nerve Tissue Proteins
- Spinal Cord
Ciliary neurotrophic factor (CNTF) has a variety of effects on different neuronal populations in vitro, but little has been reported concerning its effects in vivo. This study examined the effects of CNTF administration on peripheral nerves both in young growing rats and in more mature animals. In both young and fully grown rats, CNTF stimulated levels of substance P and calcitonin gene related peptide in sensory spinal ganglia. In immature rats, CNTF increased compound nerve conduction velocity and motor nerve conduction velocity. By contrast, electrophysiological measurements were not affected in fully grown animals. There was a biphasic dose response to CNTF for the electrophysiologic changes with larger changes noted at a dose of 0.1 micrograms/g body weight than at a dose of 0.25 micrograms/g. There were no behavioral changes noted at either dose of the factor. These observations indicate that CNTF administration in vivo can influence neural physiology, and suggest that the factor may be useful for the treatment of disorders involving either sensory or motor peripheral nerves.
MeSH Terms
- Aging
- Analysis of Variance
- Animals
- Calcitonin Gene-Related Peptide
- Ciliary Neurotrophic Factor
- Female
- Ganglia, Spinal
- Humans
- Motor Neurons
- Nerve Growth Factors
- Nerve Tissue Proteins
- Neural Conduction
- Neurons, Afferent
- Peripheral Nerves
- Rats
- Rats, Sprague-Dawley
- Recombinant Proteins
- Substance P
- Tibial Nerve
The regional and subcellular localization in the central nervous system (CNS) of postnatal day 5, day 15, and adult rats of ciliary neurotrophic factor (CNTF) mRNA was examined by in situ hybridization with biotinylated riboprobes. Probe specificity was determined by Northern blot analysis of poly(A) RNA extracted from adult rat brain using digoxigenin labeled riboprobes and chemiluminescent detection. Both a 4 kb and a 1.2 kb transcript were detected in the cortex and brainstem. In situ hybridization revealed that CNTF mRNA was widely distributed in neurons and glia throughout the CNS at each of the developmental time points. The density of the neuronal hybridization signal was found to be greater in neuronal nuclei than in their cytoplasm. In the nucleus of most neurons, CNTF mRNA distribution was concentrated in a perinucleolar fashion. Alternate sections from the same animals, which were incubated with a specific polyclonal antibody against a CNTF peptide fragment, revealed that both neurons and glia in postnatal day 5, day 15, and adult rat brain were immunoreactive for CNTF.
MeSH Terms
- Aging
- Animals
- Animals, Newborn
- Brain
- Ciliary Neurotrophic Factor
- In Situ Hybridization
- Luminescent Measurements
- Nerve Growth Factors
- Nerve Tissue Proteins
- Neurons
- RNA, Messenger
- Rats
Neurotrophins and neural cytokines are two broad classes of neurotrophic factors. It has been reported that ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF) prevent the degeneration of axotomized neonatal motor neurons. In addition, BDNF is transported retrogradely to alpha-motor neurons following injection into the muscle, and patterns of BDNF expressed in spinal cord and muscle suggest a physiological role for this factor in motor neurons. In the present study, we characterize the effects of BDNF on axotomized neonatal facial motor neurons and extend these observations to adult models of motor neuron injury (axotomy-induced phenotypic injury of lumbar motor neurons). BDNF reduces axotomy-induced degeneration of neonatal neurons by 55% as determined by Nissl staining (percentage of surviving neurons in vehicle-treated cases, 25%; in BDNF-treated cases, 80%). Rescued neurons have an intact organelle structure but appear smaller and slightly chromatolytic on electron microscopic analysis. As demonstrated by intense retrograde labeling with horseradish peroxidase (HRP) applied to the proximal stump of the facial nerve, neurons rescued by BDNF have intact mechanisms of fast axonal transport. CNTF did not appear to have significant effects on neonatal motor neurons, but the lack of efficacy of this factor may be caused by its rapid degradation at the application site. BDNF is not capable of reversing the axotomy-induced reduction in transmitter markers [i.e., the acetylcholine-synthesizing enzyme choline acetyltransferase (ChAT) or the degrading enzyme acetylcholinesterase (AChE) in neonatal or adult animals or the axotomy-induced up-regulation of the low-affinity neurotrophin receptor p75NGFR (nerve growth factor receptor) in adult motor neurons. However, BDNF appears to promote the expression of p75NGFR in injured neonatal motor neurons. In concert, the findings of the present study suggest that BDNF can significantly prevent cell death in injured motor neurons. However, this neurotrophin may not be a retrograde signal associated with the induction and/or maintenance of some mature features of motor neurons, particularly their transmitter phenotype.
MeSH Terms
- Acetylcholinesterase
- Aging
- Animals
- Animals, Newborn
- Axonal Transport
- Axons
- Brain-Derived Neurotrophic Factor
- Choline O-Acetyltransferase
- Ciliary Neurotrophic Factor
- Denervation
- Immunohistochemistry
- Male
- Microscopy, Electron
- Motor Neurons
- Nerve Degeneration
- Nerve Growth Factors
- Nerve Tissue Proteins
- Phenotype
- Rats
- Rats, Sprague-Dawley
- Sciatic Nerve
O-2A progenitor cells are bipotential glial precursors that give rise to both oligodendrocytes and type-2 astrocytes on a precise schedule in the rat CNS. Studies in culture suggest that oligodendrocyte differentiation occurs constitutively, while type-2 astrocyte differentiation requires an exogenous inducer such as fetal calf serum. Here we describe a rat brain cell culture system in which type-2 astrocytes develop on schedule in the absence of exogenous inducers. Coincident with type-2-astrocyte development, the cultures produce an approximately 20 kd type-2-astrocyte-inducing factor(s). Purified cultures of type-1 astrocytes can produce a similar factor(s). Under conditions where they produce type-2-astrocyte-inducing factor(s), both brain and type-1 astrocyte cultures produce a factor(s) with ciliary neurotrophic (CNTF)-like activity. Purified CNTF, like the inducers from brain and type-1 astrocyte cultures, prematurely induces type-2 astrocyte differentiation in brain cultures. These findings suggest that type-2 astrocyte development is initiated by a CNTF-like protein produced by type-1 astrocytes.
MeSH Terms
- Aging
- Animals
- Animals, Newborn
- Astrocytes
- Brain
- Cell Differentiation
- Cells, Cultured
- Ciliary Neurotrophic Factor
- Embryonic and Fetal Development
- Female
- Fluorescent Antibody Technique
- Nerve Growth Factors
- Nerve Tissue Proteins
- Oligodendroglia
- Optic Nerve
- Pregnancy
- Rats
- Rats, Inbred Strains
- Retina