Rapid Alterations of BDNF Protein Levels in the Rat Brain after Focal Ischemia: Evidence for Increased Synthesis and Anterograde Axonal Transport (original) (raw)
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Molecular Brain Research, 1996
Levels of BDNF mRNA and protein were measured in the rat brain using in situ hybridization and a two-site enzyme immunoassay. Under basal conditions, the highest BDNF concentration was found in the dentate gyrus (88 ng/g), while the levels in CA3 (50 ng/g), CA1 (18 ng/g) and parietal cortex (8 ng/g) were markedly lower. Following 10 min of forebrain ischemia, BDNF protein increased transiently in the dentate gyrus (to 124% of control at 6 h after the insult) and CA3 region (to 131% of control, at 1 week after the insult). In CA1 and parietal cortex, BDNF protein decreased to 73-75% of control at 24 h. In contrast, BDNF mRNA expression in dentate granule cells and CA3 pyramidal layer was transiently elevated to 287 and 293% of control, respectively, at 2 h, whereas no change was detected in CA1 or neocortex. The regional BDNF protein levels shown here correlate at least partly with regional differences in cellular resistance to ischemic damage, which is consistent with the hypothesis of a neuroprotective role of BDNF.
The Journal of Neuroscience, 1997
A sensitive immunohistochemical technique was used, along with highly specific affinity-purified antibodies to brain-derived neurotrophic factor (BDNF), to generate a detailed mapping of BDNF immunoreactivity (BDNF-ir) throughout the adult rat CNS. A parallel analysis of sites of BDNF synthesis was performed with in situ hybridization techniques using a cRNA probe to the exon encoding mature rat BDNF protein. These combined data revealed (1) groups of cell bodies containing diffuse BDNF-ir throughout the CNS that were strongly correlated with fields of cells containing BDNF mRNA; (2) varying degrees of BDNF-ir outside of cell bodies, in what appeared to be fibers and/or terminals; and (3) many regions containing extremely heavy BDNF-immunoreactive fiber/terminal labeling that lacked BDNF mRNA (e.g., medial habenula, central nucleus of the amygdala, bed nucleus of stria terminalis, lateral septum, and spinal cord). The latter observation suggested that in these regions BDNF was derived from anterograde axonal transport by afferent systems. In the two cases in which this hypothesis was tested by the elimination of select afferents, BDNF immunostaining was completely eliminated. These data, along with the observation that BDNF-ir was rarely found within dendrites or fibers en passage, suggest that BDNF protein produced in adult CNS neurons is polarized primarily along axonal processes and is preferentially stored in terminals within the innervation target.
Journal of Cerebral Blood Flow & Metabolism, 1997
Preischemic hyperglycemia or superimposed hy percapnia exaggerates brain damage caused by transient fore brain ischemia. Because high regional levels of brain-derived neurotrophic factor (BDNF) protein correlate with resistance to ischemic damage, we studied the expression of BDNF mRNA using in situ hybridization in rats subjected to 10 minutes of forebrain ischemia under normoglycemic, hyperglycemic, or hypercapnic conditions. Compared with normoglycemic ani mals, the increase of BDNF mRNA in dentate granule cells was attenuated and thatfin CA3 pyramidal neurons completely pre vented in hyperglycemic rats. No ischemia-induced increases Brain-derived neurotrophic factor (BDNF) is a mem ber of a family of neurotrophic molecules called the neu rotrophins (Lindsay et aI., 1994). It is widely but un evenly distributed in the brain, with the highest mRNA levels in the hippocampal formation, particularly in the dentate gyrus and CA3 region (Ernfors et ai., 1990; Hofer et ai., 1990). Although its role in the mature brain is poorly understood, BDNF may have a neuroprotective effect. This contention is supported by the fact that vari ous brain insults lead to an upregulation of the BDNF gene. These encompass epileptic seizures (Ernfors et aI., 1991; Isackson et ai., 1991), hypoglycemic coma (Lind-Abbreviation used: BDNF, brain-derived neurotrophic factor.
Brain Pathology, 2006
The neurotrophin family of growth factors, which includes Nerve Growth Factor (NGF), Brain-Derived Neurotrophic Factor (BDNF), Neurotrophin-3 (NT3) and Neurotrophin-4/5 (NT4/5) bind and activate specific tyrosine kinase (Trk) receptors to promote cell survival and growth of different cell populations. For these reasons, growing attention has been paid to the use of neurotrophins as therapeutic agents in neurodegeneration, and to the regulation of the expression of their specific receptors by the ligands. BDNF expression, as revealed by immunohistochemistry, is found in the pre-subiculum, CA1, CA3, and dentate gyrus of the hippocampus. Strong TrkB immunoreactivity is present in most CA3 neurons but only in scattered neurons of the CA1 area. Weak TrkB immunoreactivity is found in the granule cell layer of the dentate gyrus. Unilateral grafting of BDNF-transfected fibroblasts into the hippocampus resulted in a marked increase in the intensity of the immunoreaction and in the number of TrkB-immunoreactive neurons in the granule cell layer of the dentate gyrus, pre-subiculum and CA1 area in the vicinity of the graft. No similar effects were produced after the injection of control mock-transfected fibroblasts. Delayed cell death in the CA1 area was produced following 5 min of forebrain ischemia in the gerbil. The majority of living cells in the CA1 area at the fourth day were BDNF/TrkB immunoreactive. Unilateral grafting of control mock-transfected or BDNF fibroblasts two days before ischemia resulted in a moderate non-specific protection of TrkB-negative, but not TrkB-positive cells, in the CA1 area of the grafted side. This finding is in line with a vascular and glial reaction, as revealed, by immunohistochemistry using astroglial and microglial cell markers. This astroglial response was higher in the grafted side than in the contralateral side in ischemic gerbils, but no differences were seen between BDNF-producing and non-BDNF-producing grafts. However, grafting of BDNF-producing fibroblasts two days before ischemia significantly and specifically prevented nerve cells from dying in the CA1 area of the ipsilateral hippocampus. Cell survival was associated with increased TrkB immunoreactivity as the majority of living cells were TrkB immunoreactive. Thus, our results show that BDNF is able to up-regulate the expression of TrkB in control and pathological states, and that BDNF prevention of neuronal death following transient forebrain ischemia is associated with increased expression of its specific receptor.
Time-course of GDNF and its receptor expression after brain injury in the rat
Neuroscience Letters, 2008
The aim of the present work was to perform, by in situ hybridization, a time-course analysis of the glial cell line-derived neurotrophic factor (GDNF) and its receptor mRNA expression in two models of brain injury in the rat: (a) excitotoxic lesion by ibotenic acid injection in the hippocampal formation; (b) mechanical lesion by needle insertion through the cerebral cortex including the white matter of the corpus callosum. The time-course analysis, ranging from 6 h to 8 days, showed that the GDNF and its receptor (RET, GFR␣-1 and GFR␣-2) mRNA expressions were differentially up-regulated in both models of lesion. This in vivo regulation of the GDNF and its receptor mRNA expression indicates their involvement in the process of neuronal protection and regeneration occurring after brain injury.
Molecular Brain Research, 2001
Chronic bilateral common carotid artery occlusion (BCCAO) induces moderate ischemia (oligemia) in the rat forebrain in the absence of overt neuronal damage. In situ hybridization for brain-derived neurotrophic factor (BDNF) mRNA was used to search for a molecular response to moderate ischemia. BDNF mRNA was significantly increased in the hippocampal granule cells at 6 h of occlusion (ANOVA, Tukey test P,0.05). At 1, 7 and 14 days BDNF mRNA levels returned to control levels. The frequency of BDNF gene expression at 6 h was 83%, which was significantly higher than the 7% incidence of histological injury in the hippocampus (Fisher's exact test, P,0.002). Cerebral blood flow was reduced to 75% of control levels in the hippocampus after 1 week of BCCAO when measured with the autoradiographic method. Measurements of tissue flow with a microprobe for laser Doppler flow excluded decreases into the ischemic range during the period when elevated gene expression was observed. Prolonged moderate ischemia (oligemia) is a sufficient stimulus for BDNF gene expression in the hippocampus. These molecular studies provide direct evidence for an involvement of the hippocampus in the BCCAO model.
Expression of NGFI-B mRNA in a rat focal cerebral ischemia-reperfusion model
Molecular Brain Research, 1996
. Cerebral ischemia is known to induce the expression of several immediate early genes IEGs , including c-fos and c-jun, which Ž . subsequently regulate a number of late effector genes. In this study, we examined the expression of NGFI-B or nur 77 mRNA in a rat focal cerebral ischemia-reperfusion model. NGFI-B is a member of the IEGs which encodes for a nuclear receptor and is rapidly induced Ž . by nerve growth factor NGF . Northern blot analysis showed a rapid but transient enhancement of NGFI-B mRNA, a peak level for which was observed at 30 min of reperfusion following 60 min ischemic insult. At the peak level, quantitative analysis of the blot indicated a 12-fold and 4-fold increase of NGFI-B mRNA in the ischemic cortex and ipsilateral hippocampus, respectively, as compared to the sham-operated control. No apparent changes in mRNA levels were observed within contralateral sites of the cortex. Results from in Ž . situ hybridization showed that severe ischemia 60 min resulted in a marked increase of NGFI-B mRNA throughout the entire ischemic cerebral cortex. The increase was particularly notable in the frontal, occipital, perirhinal and piriform cortical regions and in the dentate gyrus and CA1-3 regions of the ipsilateral hippocampus. A marked induction was also noted in the ipsilateral caudate putamen. Unlike the induction profile of NGFI-B mRNA, severe ischemia resulted in bilateral increases of its family gene, NGFI-A mRNA. The spatial induction profile is similar to that of NGFI-B mRNA in both hemispheres, except within the region of the contralateral dentate gyrus which showed low levels of NGFI-A mRNA. The expression pattern of NGF and BDNF mRNA, upstream genes of NGFI-B, were also examined. Interestingly, the temporal and spatial expression patterns of BDNF mRNA were very similar to that of NGFI-A mRNA under the same conditions, whereas increased NGF and NGFI-B mRNA were observed only in the ipsilateral hemisphere. It is likely that multiple andror overlapping pathways are activated subsequent to ischemic challenge which in turn are crucial for cell survival andror functional recovery following focal cerebral ischemia.
Experimental Neurology, 2000
We have performed unilateral transection of the medial forebrain bundle (MFB) and studied BDNF mRNA and trkB mRNA levels at different postlesion times in the nigrostriatal system by means of in situ hybridization. BDNF mRNA levels were transiently induced in the substantia nigra pars compacta at 1 day postaxotomy. The disposition of BDNF mRNA expressing cells at this postlesion time in substantia nigra mimicked that of the dopaminergic neurons expressing the mRNA for the dopamine transporter. TrkB mRNA levels remained unaltered in the ventral mesencephalon at the different postlesion times examined-1 to 14 days. In contrast, trkB mRNA levels were significantly induced in the striatum at the longer postlesion time examined-14 days-when all neurodegenerative events are completed. It is becoming apparent that nigral BDNF mRNA levels are anterogradely transported to its target tissue in striatum. However, following axotomy, the lesion site represents a second potential target for BDNF action. Consequently, we also analyzed the pattern of mRNA expression for BDNF and trkB at the lesion site where dopaminergic axons are disconnected. There, we found notable inductions of both BDNF mRNA and trkB mRNA levels at 4 days postaxotomy. BDNF mRNA expressing cells were confined at the site of axotomy, which coincided precisely to that showing induction of trkB mRNA. Altogether, our results anticipate promising trophic roles of BNDF in the injured nigrostriatal system. 2000 Academic Press
Brain-derived neurotrophic factor blood levels in two models of transient brain ischemia in rats
General physiology and biophysics, 2013
We monitored possible influence of transient focal and global brain ischemia on BDNF blood level. In both models noticeable fluctuation of BDNF concentration mainly in reperfusion was observed. During the first 90 min, BDNF in total blood and in blood cells continuously decreased in both models but plasma BDNF raised at 40 min and peaked at 90 min of reperfusion. Our data confirm the impact of transient brain ischemia on BDNF levels in the circulatory system, suggest blood cells as a possible source of BDNF and demonstrate the interdependence of blood compartments and physiological state of an affected organism.
European Journal of Neuroscience, 1995
Messenger RNA for brain-derived neurotrophic factor (BDNF) is distributed in many brain regions and regulated by excitatory neuronal activity. Despite numerous studies of BDNF mRNA, the distribution and regulation of BDNF protein are poorly understood because of the difficulty of its quantitative measurement. We have established a two-site enzyme immunoassay that detects trace amounts of BDNF protein (> 1 pg/assay) but not other neurotrophins or growth factors. The highest levels of BDNF in adult rat brain were found in the hippocampus, followed by the hypothalamus, neocortex, cerebellum, thalamus and striatum. This pattern is similar, but not identical, to the distribution of BDNF mRNA. A similar disparity between BDNF protein and mRNA levels was observed in their changes after hilus lesion-induced limbic seizures. In limbic structures, BDNF concentrations remained elevated 4 days after seizure onset, whereas BDNF mRNA has been reported previously to return to basal levels within 46 h. The temporal and spatial differences between the dynamics of protein and mRNA levels suggest the importance of post-translational and/or subcellular processes for BDNF production. The persistence of the increases in BDNF content was also reflected in its biological activity, e.g. peptidergic differentiation activity. After limbic seizures, neuropeptide Y content was most markedly and persistently elevated in the entorhinal/amygdaloid region, where the most sustained up-regulation of BDNF protein was observed. These results suggest that the sustained increase of BDNF protein in these limbic structures is involved in prolonged post-seizure phenomena, including peptidergic alterations.