Upregulation Of Growth-associated Protein-43 Research Articles

Hypoxic preconditioned MSCs-derived small extracellular vesicles for photoreceptor protection in retinal degeneration

Photoreceptor apoptosis is an important pathogenesis of retinal degeneration and a primary cause of vision loss with limited treatment methods. Mesenchymal stem/stromal cells-derived small extracellular vesicles (MSC-sEVs) have shown therapeutic value in various ocular disorders. Recent studies have revealed that hypoxic preconditioning can improve the effectiveness of MSC-sEVs in tissue regeneration. However, whether hypoxic preconditioned MSC-sEVs (Hyp-sEVs) exert superior effects on photoreceptor protection relative to normoxic conditioned MSC-sEVs (Nor-sEVs) remains unclear. Here, we reported that Hyp-sEVs further improved retinal structure, recovered retinal function, and suppressed photoreceptor apoptosis in N-methyl-N-nitrosourea (MNU)-induced mouse model compared with Nor-sEVs. Hyp-sEVs also exhibited enhanced anti-apoptotic roles in MNU-provoked 661 W cell injury in vitro. We then analyzed the protein profiles of Nor-sEVs and Hyp-sEVs by LC-MS/MS and found that growth-associated protein 43 (GAP43) was enriched in Hyp-sEVs. The knockdown of GAP43 abolished the retinal therapeutic effects of Hyp-sEVs. Mechanistically, hypoxic stimulation-induced hypoxia-inducible factor-1α (HIF-1α) activation was responsible for preventing tripartite motif-containing protein 25 (TRIM25)-mediated GAP43 ubiquitination and degradation, leading to the upregulation of GAP43 in Hyp-sEVs. Together, our findings uncover the efficacy and mechanism of Hyp-sEVs-based photoreceptor protection and highlight the potential of Hyp-sEVs as optimized therapeutics for retinal degeneration.Graphical abstract

Inhibition of miR-221-3p promotes axonal regeneration and repair of primary sensory neurons via regulating p27 expression.

This study aimed to explore the key microRNA (miRNA) playing a vital role in axonal regeneration with a hostile microenvironment after spinal cord injury. Based on the theory that sciatic nerve conditioning injury (SNCI) could promote the repair of the injured dorsal column. Differentially expressed miRNAs were screened according to the microarray, revealing that 47 known miRNAs were differentially expressed after injury and perhaps involved in nerve regeneration. Among the 47 miRNAs, the expression of miR-221-3p decreased sharply in the SNCI group compared with the simple dorsal column lesion (SDCL) group. Subsequently, it was confirmed that p27 was the target gene of miR-221-3p from luciferase reporter assay. Further, we found that inhibition of miR-221-3p expression could specifically target p27 to upregulate the expression of growth-associated protein 43 (GAP-43), α-tubulin acetyltransferase (α-TAT1) together with α-tubulin, and advance the regeneration of dorsal root ganglion (DRG) neuronal axons. Chondroitin sulfate proteoglycans (CSPGs) are the main components of glial scar, which can hinder the extension and growth of damaged neuronal axons. After CSPGs were used in this study, the results demonstrated that restrained miR-221-3p expression also via p27 promoted the upregulation of GAP-43, α-TAT1, and α-tubulin and enhanced the axonal growth of DRG neurons. Hence, miR-221-3p could contribute significantly to the regeneration of DRG neurons by specifically regulating p27 in the p27/CDK2/GAP-43 and p27/α-TAT1/α-tubulin pathways even in the inhibitory environment with CSPGs.

Research on Polycaprolactone-Gelatin Composite Scaffolds Carrying Nerve Growth Factor for the Repair of Spinal Cord Injury.

Objective This study was to investigate the mechanism of action of polycaprolactone/gelatin (PCL/GE) composite fiber scaffold with nerve growth factor (NGF) in the recovery of spinal cord injury (SCI). Methods Sixty female Sprague-Dawley (SD) rats were randomly assigned to the negative control group, the positive control group, the PCL/GE scaffold group, and the collagen-binding structural domain nerve growth factor (CBD-NGF)/PCL/GE scaffold group, with 15 rats in each group. Spinal cord transection was used to establish SCI models in rats. The negative control group received sham surgery, while the other three groups were given spinal cord transection at the tenth thoracic vertebra (T10) segment. The rats in the PCL/GE scaffold group were implanted with a 4 mm PCL/GE composite fiber scaffold, and those in the CBD-NGF/PCL/GE scaffold group were implanted with a CBD-NGF/PCL/GE composite fiber scaffold. The Basso–Beattie–Bresnahan (BBB) locomotor rating scale was used to evaluate the locomotor ability of the hind limbs of the rats, and the amplitude and latency of motor evoked potentials (MEP) were recorded by neurophysiological testing at 12 w postoperatively. The levels of growth-associated protein 43 (GAP43) and neurofilament protein 200 (NF200) in the spinal cord tissue of the injury site were determined using Western Blot at 12 w after surgery. Spinal cord tissues of 2 cm within the injury site, the thoracic segment above the injury site, and the lumbar segment below the injury site were collected from the measurement of axonal transport using fluorescent retrograde tracer fluorogold, and the integrated absorbance (IA) values of FC-positive cells were calculated. Results After treatment, the negative control rats showed normal locomotion function of the hind limb with the highest BBB scores, while the positive control rats had the lowest BBB scores and showed paraplegia. The scaffold groups exhibited better locomotion function of the hind limb and higher BBB scores than the positive controls, with greater improvement observed in the CBD-NGF/PCL/GE scaffold group (P < 0.05). Compared with the positive controls, the PCL/GE scaffold group and CBD-NGF/PCL/GE scaffold group exhibited significantly shorter latency and increased amplitude of MEP, with more significant changes observed in the CBD-NGF/PCL/GE scaffold group (P < 0.05). Compared with the positive control group, the GAP43 and NF200 levels of spinal cord tissue were significantly elevated in both the PCL/GE scaffold group and the CBD-NGF/PCL/GE scaffold group, and the changes were more pronounced in the CBD-NGF/PCL/GE scaffold group (P < 0.05). The differences in the IA values of FC-positive cells in the spinal cord tissue of the lumbar segment below the injury site among the four groups did not come up to the statistical standard (P > 0.05). Compared with the positive control group, the FC-positive cell IA values of spinal cord tissue in the thoracic segment above the injury area were markedly increased in the PCL/GE scaffold group and the CBD-NGF/PCL/GE scaffold group, and the alterations were more significant in the CBD-NGF/PCL/GE scaffold group (P < 0.05). Conclusion PCL/GE composite fiber scaffold with NGF significantly improves motor and neurological functions in the hind limbs of SCI rats and promotes the recovery of axonal transport, and the mechanism may be associated with the upregulation of GAP43 and NF200 levels in spinal cord injury site tissues.

The isoform-specific functions of the c-Jun N-terminal kinase (JNK) in a mouse model of antiretroviral-induced painful peripheral neuropathy

Nucleoside reverse transcriptase inhibitors (NRTIs) are associated with the development of painful neuropathies and may further aggravate sensory neuropathy produced by HIV-1 infection, leading to discontinuation of NRTI therapy by HIV patients. Following antiretroviral-induced peripheral neuropathy, c-Jun N-terminal kinase (JNK) is activated in the dorsal root ganglia (DRG) and spinal cord. However, the contribution of individual JNK genes remains unknown. Here, we have tested the behavioural mechanical sensitivity of JNK1, JNK2 and JNK3 knockout (KO) mice in the von Frey test after treatment with 2’,3’-dideoxycytidine (ddC). Protein expression was investigated in the spinal cord of wild type (wt) and KO mice by western blotting. The onset of neuropathic pain was prevented by the deletion of JNK3, leading us to hypothesize that JNK3 protein plays a major role in the regulation of pain threshold in antiretroviral neuropathy. The growth-associated protein 43 (GAP-43) and the transcription factor c-Jun are involved in regeneration processes. This study revealed an up-regulation of GAP-43 and c-Jun protein, 14 days after ddC administration. JNK1 deletion induced a significant reduction in c-Jun phosphorylation and GAP-43 protein contents. In contrast, there was no difference in ddC-induced reduction of hind paw intraepidermal nerve fibre density in all JNK KO mice. Overall, these findings indicate that JNK3 plays a critical role in regulating ddC neurotoxicity-induced mechanical pain hypersensitivity, while JNK1 is important for activation of c-Jun and GAP-43 as a critical pathway of a regeneration program. These data highlight the impact of individual JNK isoforms on antiretroviral neurotoxicity and neuro-regeneration processes.

Ligusticum chuanxiong exerts neuroprotection by promoting adult neurogenesis and inhibiting inflammation in the hippocampus of ME cerebral ischemia rats.

Cerebral ischemia, also known as stroke, can stimulate the proliferation and migration of endogenous neural stem cells (NSCS) in subventricular zone of the lateral ventricle and subgranularzone of the dentate gyrus in the adult hippocampus as a defense response to damage. However, the proliferation of endogenous NSCS is insufficient for central nervous system repair. Neurogenesis and anti-neuroinflammation are two important aspects for neuroprotection. Rhizome Ligusticum chuanxiong (LC), the dried rhizomes of Ligusticum striatum DC., has been widely used to treat stroke for over hundreds of years in Traditional Chinese Medicine. of the study: Previous reports on pharmacological mechanism of LC mainly focus on the cerebral blood flow and thrombolysis. We aim to explore whether LC provides neuroprotective effect by increasing neurogenesis and inhibiting the IL-1β, TNF-α and expressions of glial fibrillary acidic protein. LC extract was delivered to microsphere-embolized (ME) cerebral ischemia Wister rats to examine its neuroprotection. Body weight, neurological scores, hematoxylin-eosin staining (HE), TUNEL assay were conducted for neurological damage. Neurogenesis was evaluated by assessing the expression of Doublecortin (DCX) and neurogenic differentiation1 (NeuroD1) through immunofluorescence staining. Western blot performed to measure the protein levels of growth associated protein-43(GAP-43), glial fibrillary acidic protein (GFAP). IL-1β and TNF-α was detected by Elisa. LC alleviated pathomorphological change and apoptosis of neurons in the hippocampus caused by ME surgery. Furthermore, LC significantly increased the DCX in the DG of adult rat hippocampus at 14 days after surgery. A significant upregulation of GAP-43 compared to the ME after LC was administered. Besides, LC decreased pro-inflammatory cytokine (IL-1β, TNF-α) and protein level of GFAP. The finding suggested that LC had the ability to protect neurons by promoting the endogenous proliferation of neuroblast and production of neural differentiation factor in rats after ischemia injury. Meanwhile, LC can anti-neuroinflammation, which is important for the treatment of neuron injury. Accordingly, LC perhaps a promising medicine for neuron damage therapy after cerebral ischemia.

Rosa canina L. methanolic extract prevents heat stress-induced memory dysfunction in rats.

What is the central question of this study? Heat stress has harmful effects on the brain structure and synaptic density via induction of oxidative stress and neuroinflammation, which result in neuronal damage in the hippocampus and thereby cognitive impairments. In this study, we investigate the effect of Rosa canina treatment on cognitive function in heat stress-exposed rats and its underlying mechanisms. What is the main finding and its importance? We show that R.canina improves cognitive deficits induced by heat stress by attenuation of oxidative stress and neuroinflammation and by upregulation of synaptic proteins in the hippocampus. The aim of the study was to evaluate the effects of aqueous methanolic extract of Rosa canina (RC) dried fruits on oxidative stress, inflammation, synaptic degeneration and memory dysfunction induced by heat stress (HS) in rats. Sixty adult male Wistar rats were randomly divided into five groups as follows: the control group received normal saline (NS); the HS group was exposed to heat stress (43°C) for 15min once a day for 2weeks; and HS+R groups were exposed to heat stress and received one of three doses (250, 500 or 1000mgkg-1 ) of RC methanolic extract for 2weeks. A passive avoidance test and a Y-maze test were performed to assess learning and memory. The levels of reactive oxygen species were assessed. The serum cortisol concentration and hippocampal total antioxidant capacity, superoxide dismutase and glutathione peroxidase were also detected using spectrophotometry. The protein expressions of c-Fos, heat-shock protein-70, tumour necrosis factor-α, growth-associated protein43, post-synaptic density-95 and synaptophysin were evaluated in the hippocampal tissue. The results showed that RC significantly improved cognitive dysfunction induced by HS, which was accompanied by downregulation of tumour necrosis factor-α and upregulation of growth-associated protein43 and synaptophysin proteins in the hippocampus of HS-exposed rats. Furthermore, RC significantly attenuated serum cortisol concentrations and upregulated heat shock protein-70 and c-Fos in the hippocampus. In addition, the administration of RC attenuated reactive oxygen species levels and enhanced antioxidant defense in the hippocampus. These findings indicate that RC attenuated the deleterious effect of HS on cognition through its antioxidant properties and by enhancing synaptic function and plasticity.

Enriched environment elevates expression of growth associated protein-43 in the substantia nigra of SAMP8 mice.

An enriched environment protects dopaminergic neurons from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neuronal injury, but the underlying mechanism for this is not clear. Growth associated protein-43 (GAP-43) is closely associated with neurite outgrowth and axon regeneration during neural development. We speculate that an enriched environment can reduce damage to dopaminergic neurons by affecting the expression of GAP-43. This study is designed to test this hypothesis. Three-month-old female senescence-accelerated mouse prone 8 (SAMP8) mice were housed for 3 months in an enriched environment or a standard environment. These mice were then subcutaneously injected in the abdomen with 14 mg/kg MPTP four times at 2-hour intervals. Morris water maze testing demonstrated that learning and memory abilities were better in the enriched environment group than in the standard environment group. Reverse-transcription polymerase chain reaction, immunohistochemistry and western blot assays showed that mRNA and protein levels of GAP-43 in the substantia nigra were higher after MPTP application in the enriched environment group compared with the standard environment group. These findings indicate that an enriched environment can increase GAP-43 expression in SAMP8 mice. The upregulation of GAP-43 may be a mechanism by which an enriched environment protects against MPTP-induced neuronal damage.

Transcription Factor Brn-3b Overexpression Enhances Neurite Outgrowth in PC12 Cells Under Condition of Hypoxia.

Transcription factor Brn-3b plays a key role in retinal ganglion cell differentiation, survival, and axon outgrowth during development. However, the precise role of Brn-3b in the normal adult retina as well as during neurodegeneration is unclear. In the current study, the effect of overexpression of Brn-3b was assessed in vitro, in PC12 cells under conditions of normoxia and hypoxia. Immunoblot analysis showed that overexpression of Brn-3b in PC12 cells as well as 661W cells produced significant increase in the growth cone marker, growth-associated protein-43 (GAP-43), and acetylated-tubulin (ac-TUBA). In addition, an increased immunostaining for GAP-43 and ac-TUBA was observed in PC12 cells overexpressing Brn-3b, which was accompanied by a marked increase in neurite outgrowth, compared to PC12 cells overexpressing theempty vector. In separate experiments, one set of PC12 cells transfected either with a Brn-3b expression vector or an empty vector was subjected to conditions of hypoxia for 2h, while another set of similarly transfected PC12 cells was maintained in normoxic conditions. It was found that the upregulation of GAP-43 and ac-TUBA in PC12 cells overexpressing Brn-3b under conditions of normoxia was sustained under conditions of hypoxia. Immunocytochemical analysis revealed not only an upregulation of GAP-43 and ac-TUBA, but also increased neurite outgrowth in PC12 cells transfected with Brn-3b as compared to PC12 cells transfected with empty vector in both normoxia and hypoxia. The findings have implications for a potential role of Brn-3b in neurodegenerative diseases in which hypoxia/ischemia contribute to pathophysiology of the disease.

Effects of transplanted neural stem cells on synaptogenesis in APP/PS1 mice

To explore the effects of transplanted neural stem cells (NSCs) on synaptogenesis in an Alzheimer' disease (AD) murine model and related mechanism. Twenty 9-month-old APP/PS1 double transgenic mice were randomly divided into 2 groups. One group received NSCs transplantation (NSC group) in bilateral hippocampi while another group received an equal volume of 0.01 mol/L phosphate buffer saline (PBS group) as a negative control group. Ten wild-type mice were selected as the positive control group (WT group) without any treatment. After 8-week transplantation, the expressions of synaptophysin (SYN) and growth associated protein-43 (GAP-43) proteins in hippocampal areas were analyzed by immunofluorescence and Western blot. The number and structure of synapses in transplanted regions were observed by electron microscopy. (1) Immunofluorescence staining showed that NSC-induced neurons highly expressed SYN and GAP-43 at the protein levels; (2) the expression of SYN and GAP-43 significantly increased in the NSC group versus the PBS group (F = 58.367, P < 0.01; F = 75.296, P < 0.01). No difference existed in the SYN level between NSC and WT groups (P > 0.05). However, the GAP-43 expression was significantly higher than that of the WT group (P < 0.01); (3) ultrastructure showed that the number of synapses in the NSC group with normal morphology (12.1 ± 2.1) increased than that in the PBS group (6.5 ± 2.2) (F = 15.981, P < 0.01). No difference existed between NSC and WT groups (11.0 ± 1.4) (P > 0.05). NSC-induced neurons increase the number of synapses by an up-regulation of synaptic proteins, SYN and GAP-43. Thus synaptogenesis may be a key factor in improving the symptom of AD mice.

The neurogenic response of cardiac resident nestin(+) cells was associated with GAP43 upregulation and abrogated in a setting of type I diabetes

BackgroundCardiac nestin(+) cells exhibit properties of a neural progenitor/stem cell population characterized by the de novo synthesis of neurofilament-M in response to ischemic injury and 6-hydroxydopamine administration. The induction of growth associated protein 43 (GAP43) was identified as an early event of neurogenesis. The present study tested the hypothesis that the de novo synthesis of neurofilament-M by nestin(+) cells was preceded by the transient upregulation of GAP43 during the acute phase of reparative fibrosis in the infarcted male rat heart. Secondly, a seminal feature of diabetes is impaired wound healing secondary to an inadequate neurogenic response. In this regard, an additional series of experiments tested the hypothesis that the neurogenic response of cardiac nestin(+) cells was attenuated in a setting of type I diabetes.MethodsThe neurogenic response of cardiac nestin(+) cells was examined during the early phase of reparative fibrosis following permanent ligation of the left anterior descending coronary artery in the adult male rat heart. The experimental model of type I diabetes was created following a single injection of streptozotocin in adult male rats. The impact of a type I diabetic environment on the neurogenic response of cardiac nestin(+) cells was examined during myocardial infarction and following the administration of 6-hydroxydopamine.ResultsDuring the early phase of scar formation/healing, the density of GAP43/nestin(+) fibres innervating the peri-infarct/infarct region was significantly increased, whereas neurofilament-M/nestin(+) fibres were absent. With ongoing scar formation/healing, a temporal decrease of GAP43/nestin(+) fibre density and a concomitant increase in the density of innervating neurofilament-M/nestin(+) fibres were observed. The neurogenic response of cardiac nestin(+) cells during scar formation/healing was inhibited following the superimposition of type I diabetes. The de novo synthesis of neurofilament-M by nestin(+) cells after 6-hydroxydopamine administration was likewise attenuated in the heart of type I diabetic rats whereas the density of GAP43/nestin(+) fibres remained elevated.ConclusionThe transient upregulation of GAP43 apparently represents a transition event during the acquisition of a neuronal-like phenotype and a type I diabetic environment attenuated the neurogenic response of cardiac nestin(+) cells to ischemia and 6-hydroxydopamine.

Up-regulation of GAP-43 in the chinchilla ventral cochlear nucleus after carboplatin-induced hearing loss: Correlations with inner hair cell loss and outer hair cell loss

Inner ear damage leads to nerve fiber growth and synaptogenesis in the ventral cochlear nucleus (VCN). In this study, we documented the relationship between hair cell loss patterns and synaptic plasticity in the chinchilla VCN using immunolabeling of the growth associated protein-43 (GAP-43), a protein associated with axon outgrowth and modification of presynaptic endings. Unilateral round window application of carboplatin caused hair cell degeneration in which inner hair cells (IHC) were more vulnerable than outer hair cells (OHC). One month after carboplatin treatment (0.5–5 mg/ml), we observed varying patterns of cochlear hair cell loss and GAP-43 expression in VCN. Both IHC loss and OHC loss were strongly correlated with increased GAP-43 immunolabeling in the ipsilateral VCN. We speculate that two factors might promote the expression of GAP-43 in the VCN; one is the loss of afferent input through IHC or the associated type I auditory nerve fibers. The other occurs when the medial olivocochlear efferent neurons lose their cochlear targets, the OHC, and may as compensation increase their synapse numbers in the VCN.

Magnetic stimulation modulates structural synaptic plasticity and regulates BDNF–TrkB signal pathway in cultured hippocampal neurons

Repetitive transcranial magnetic stimulation (rTMS) is a neuropsychiatric tool that can be used to investigate the neurobiology of learning and cognitive function. Few studies have examined the effects of low frequency (⩽1Hz) magnetic stimulation (MS) on structural synaptic plasticity of neurons in vitro, thus, the current study examined its effects on hippocampal neuron and synapse morphology, as well as synaptic protein markers and signaling pathways. Similarly, both intensities of low frequency magnetic stimulation (1Hz) activated brain-derived neurotrophic factor (BDNF) and tropomyosin-related kinase B (TrkB) pathways, including the pathways for mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) and for phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt). Specifically, low intensity magnetic stimulation (LIMS, 1.14Tesla, 1Hz) promoted more extensive dendritic and axonal arborization, as well as increasing synapses density, thickening PSD (post synaptic density) and upregulation of synaptophysin (SYN), growth associated protein 43 (GAP43) and post synaptic density 95 (PSD95). Conversely, high intensity magnetic stimulation (HIMS, 1.55Tesla, 1Hz) appeared to be detrimental, reducing dendritic and axonal arborization and causing apparent structural damage, including thinning of PSD, less synapses and disordered synaptic structure, as well as upregulation of GAP43 and PSD95, possibly for their ability to mitigate dysfunction. In conclusion, we infers that low frequency magnetic stimulation participates in regulating structural synaptic plasticity of hippocampal neurons via the activation of BDNF–TrkB signaling pathways.

Reduced hippocampus volume in the mouse model of Posttraumatic Stress Disorder

Some, but not all studies in patients with posttraumatic stress disorder (PTSD), report reduced hippocampus (HPC) volume. In particular it is unclear, whether smaller hippocampal volume represents a susceptibility factor for PTSD rather than a consequence of the trauma. To gain insight into the relationship of brain morphology and trauma exposure, we investigated volumetric and molecular changes of the HPC in a mouse model of PTSD by means of in vivo Manganese Enhanced Magnetic Resonance Imaging (MEMRI) and ex vivo ultramicroscopic measurements. Exposure to a brief inescapable foot shock led to a volume reduction in both left HPC and right central amygdala two months later. This volume loss was mirrored by a down-regulation of growth-associated protein-43 (GAP43) in the HPC. Enriched housing decreased the intensity of trauma-associated contextual fear, independently of whether it was provided before or after the shock. Beyond that, enriched housing led to an increase in intracranial volume, including the lateral ventricles and the hippocampus, and to an up-regulation of GAP43 as revealed by MEMRI and Western blot analysis, thus partially compensating for trauma-related HPC volume loss and down-regulation of GAP43 expression. Together these data demonstrate that traumatic experience in mice causes a reduction in HPC and central amygdala volume possibly due to a shrinkage of axonal protrusions. Enriched housing might induce trophic changes, which may contribute to the amelioration of trauma-associated PTSD-like symptoms at behavioural, morphological and molecular levels.

ENHANCED EXPRESSION OF CARDIAC NERVE GROWTH FACTOR AND NERVE SPROUTING MARKERS IN RATS FOLLOWING GASTRIC PERFORATION

Endotoxemia and/or systemic inflammation may lead to disturbances in the cardiac autonomic nervous system and consequent arrhythmia. The underlying mechanism remains unclear. Therefore, we investigated the expression of nerve growth factor (NGF) and its association with cardiac sympathovagal balance in a rodent model of self-limited peritonitis. Male Wistar rats were randomized into the following groups: normal control, sham, gastric perforation (GP), and GP treated with methylprednisolone. Cardiac expression of NGF, growth-associated protein 43 (GAP43), along with other nerve markers were evaluated at several time points (6 h to 2 weeks) after GP. An autoregressive process was performed on each detrended electrocardiogram to calculate the heart rate power spectrum. Compared with the normal control and sham groups, expression of NGF was significantly elevated for 1 week after GP. We also found the up-regulated GAP43 and tyrosine hydroxylase protein levels in the GP group, which persisted after recovery from peritonitis. Gastric perforation caused a biphasic change in the ratio of low-frequency to high-frequency power (an index of sympathovagal balance), with an initial decrease followed by recovery at 24 h. Increased NGF and cardiac sympathetic marker expression were temporally associated with the restoration of the cardiac sympathovagal balance. Methylprednisolone abrogated the NGF up-regulation induced by GP and delayed the resumption of sympathovagal balance. We conclude that GP resulted in up-regulation of cardiac NGF, GAP43, and tyrosine hydroxylase expression that coincided with recovery of cardiac sympathovagal balance. Moreover, methylprednisolone can effectively block GP-induced NGF up-regulation.

Repeated restraint stress and corticosterone injections during late pregnancy alter GAP-43 expression in the hippocampus and prefrontal cortex of rat pups

In the offspring of prenatal stress animals, overactivity and impaired negative feedback regulation of the hypothalamic–pituitary–adrenal axis are consistent finding. However, little was known about how prenatal stress can permanently alter developmental trajectories of pup's brain. Growth-associated protein-43 (GAP-43) is a presynaptic membrane phosphoprotein whose expression increases during developmental events such as axonal outgrowth or remodeling and synaptogenesis. Phosphorylation of GAP-43 by protein kinase C was correlated with enhanced axonal growth and transmitter release. In adult animals, increase of GAP-43 correlated with monoaminergic deficit in neuropsychiatric disorders. The present study examines the effects of repeated maternal restraint stress on the level of GAP-43 in the brain of rat pups. The results showed that prenatal stress significantly increased GAP-43 level in the PFC of rat pup during PND 7–14 as compared to control but not significant difference when observed at PND 21. Increased GAP-43 expression was also observed in the pup's hippocampus during the same postnatal periods. However, when observed at PND 60, pups born from stressed mother showed a significant lower (p<0.001) GAP-43 expression as compare with control group. These changes indicate the direct effect of corticosteroid hormone, since repeated maternal injection with corticosterone (CORT, 40mg/kg) during GD 14–21 also gave the same results. PND 7–14 is the peak period of synaptogenesis in these brain areas and abnormal axon sprouting and reorganization may lead to a defect in synaptic pruning at later stage of life. The results suggested that maternal stress is harmful to the developing brain and upregulation of GAP-43 indicated a protective mechanism against the toxicity of maternal stress hormone. Prenatal stress alter the normal developmental trajectories in the pup's brain may underlies the mechanism link between early life stress and neuropsychopathology in later life.

GAP-43 is essential for the neurotrophic effects of BDNF and positive AMPA receptor modulator S18986

Positive alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor modulators include benzamide compounds that allosterically modulate AMPA glutamate receptors. These small molecules that cross the blood-brain barrier have been shown to act as a neuroprotectant by increasing the levels of endogenous brain-derived neurotrophic factor (BDNF). Positive AMPA receptor modulators have also been shown to increase the levels of growth-associated protein-43 (GAP-43). GAP-43 plays a major role in many aspects of neuronal function in vertebrates. The goal of this study was to determine whether GAP-43 was important in mediating the actions of positive AMPA receptor modulator (S18986) and BDNF. Using cortical cultures from GAP-43 knockout and control mice, we show that (1) GAP-43 is upregulated in response to S18986 and BDNF in control cultures; (2) this upregulation of GAP-43 is essential for mediating the neuroprotective effects of S18986 and BDNF; (3) administration of S18986 and BDNF leads to an increase in the expression of the glutamate transporters GLT-1 and GLAST that are key to limiting excitotoxic cell death and this increase in GLT-1 and GLAST expression is completely blocked in the absence of GAP-43. Taken together this study concludes that GAP-43 is an important mediator of the neurotrophic effects of S18986 and BDNF on neuronal survival and plasticity, and is essential for the success of positive AMPA receptor modulator-BDNF-based neurotrophin therapy.

Xylazine promotes axonal regeneration in the crushed optic nerve of adult rats

Xylazine, an alpha-2 adrenergic agonist, activates the endogenous trophic factors and neuronal survival signaling. Here, we tested the regenerative effect of xylazine on damaged optic nerve axons in adult rats. After optic nerve crush, xylazine was intraperitoneally injected into three groups of rats: a single administration immediately after the crush, intermittent administration, and daily administration. On day 14, the regenerated axons were quantitatively evaluated by anterograde labeling. Everyday administration but neither single nor intermittent administration markedly increased the number of labeled axons beyond the crush site, with upregulation of growth-associated protein-43 in the ganglion cell layer and the regenerated axons. It was concluded that xylazine promotes axonal regeneration in damaged optic nerves of adult rats.

TRANSIENT MAINTENANCE IN BIOREACTOR IMPROVES HEALTH OF NEURONAL CELLS

To examine whether a neuronal cell suspension can be held in vitro for a relatively short period without compromising survival rates and functionality, we have set up an experimental protocol planning 24 h of suspension culture in a rotary wall vessel (RWV) bioreactor before plating in a conventional adherent system. Apoptosis measurement and activated caspase-8, -9, and -3 detection have demonstrated that survey of the cells was not affected. The activity of major antioxidant enzymes (AOE), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT), was significantly decreased in RWV-maintained cells. A significant decrease of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) is coupled with a level of activated nuclear factor-kappaB (NF-kappaB) protein significantly lower in RVW cells than in the control. On the contrary, the level of IL-6 expression did not change between the test and the control. A significant up-regulation of growth-associated protein-43 (GAP-43), peroxisome proliferator-activated receptor-beta/delta (PPARbeta/delta), and acyl-CoA synthetase 2 (ACS2) in RWV cells has been detected. We provide the evidence that primary neuronal cells, at an early stage of development, can be maintained in a suspension condition before adherent plating. This experimental environment does not induce detrimental effects but may have an activator role, leading cells to development and maturation in a tridimensional state.

Cell death or survival: Molecular and connectional conditions for olivocochlear neurons after axotomy

We aimed to determine whether rat olivocochlear neurons survive axotomy inflicted through cochlear ablation, or if they degenerate. To estimate their intrinsic potential for axonal regeneration, we investigated the expression of the transcription factor c-Jun and the growth-associated protein-43 (GAP43). Axonal tracing studies based on application of Fast Blue into the cochlea and calcitonin gene-related peptide immunostaining revealed that many, but not all, lateral olivocochlear neurons in the ipsilateral lateral superior olive degenerated upon cochleotomy. A decrease of their number was noticed 2 weeks after the lesion, and 2 months postoperative the population was reduced to approximately one quarter (27–29%) of its original size. No further reduction took place at longer survival times up to 1 year. Most or all shell neurons and medial olivocochlear neurons survived axotomy. Following cochleotomy, 56–60% of the lateral olivocochlear neurons in the ipsilateral lateral superior olive were found to co-express c-Jun and GAP43. Only a small number of shell and medial olivocochlear neurons up-regulated c-Jun expression, and only a small number of shell neurons expressed GAP43. Up-regulation of c-Jun and GAP43 in lateral olivocochlear neurons upon axotomy suggests that they have an intrinsic potential to regenerate after axotomy, but cell counts based on the markers Fast Blue and calcitonin gene-related peptide indicate that this potential cannot be exploited and degeneration is induced instead. The survival of one quarter of the axotomized lateral olivocochlear neurons and of all, or almost all, shell and medial olivocochlear neurons appeared to depend on connections of these cells to other regions than the cochlea by means of axon collaterals, which remained intact after cochleotomy.

Neutralization of CD95 ligand promotes regeneration and functional recovery after spinal cord injury.

The clinical outcome of spinal cord injury (SCI) depends in part on the extent of secondary damage, to which apoptosis contributes. The CD95 and tumor necrosis factor (TNF) ligand/receptor systems play an essential role in various apoptotic mechanisms. To determine the involvement of these ligands in SCI-induced damage, we neutralized the activity of CD95 ligand (CD95L) and/or TNF in spinal cord-injured mice. Therapeutic neutralization of CD95L, but not of TNF, significantly decreased apoptotic cell death after SCI. Mice treated with CD95L-specific antibodies were capable of initiating active hind-limb movements several weeks after injury. The improvement in locomotor performance was mirrored by an increase in regenerating fibers and upregulation of growth-associated protein-43 (GAP-43). Thus, neutralization of CD95L promoted axonal regeneration and functional improvement in injured adult animals. This therapeutic strategy may constitute a potent future treatment for human spinal injury.