Induction Of Brain-derived Neurotrophic Factor mRNA Research Articles

Selective inhibition of extracellular signal-regulated kinases 1/2 blocks nerve growth factor to brain-derived neurotrophic factor signaling and suppresses the development of and reverses already established pain behavior in rats

Brain-derived neurotrophic factor (BDNF) plays a key role in the development of pathological pain. Although it is known that nerve growth factor (NGF) induces BDNF mRNA through extracellular signal-regulated kinases (ERK), whether ERK1/2 or ERK5, two closely related members of the ERK family, mediate this signal is still unclear because classical MEK inhibitors block both pathways. We studied the involvement of ERK-signaling in NGF induction of BDNF in PC12 cells, cultured dorsal root ganglia neurons, and in rats subjected to neuropathic pain models using ERK1/2- and ERK5-specific tools. Selective activation of ERK1/2 upregulated BDNF mRNA in PC12 cells, whereas selective ERK5 activation did not. AZD6244, a potent selective inhibitor of ERK1/2 activation, blocked NGF induction of BDNF mRNA in vitro suggesting that NGF induction of BDNF is mediated by ERK1/2. siRNA experiments indicated that both ERK1 or ERK2 can signal suggesting that both pathways must be blocked to prevent NGF-induced increase in BDNF mRNA. I.p. injection of AZD6244 prevented the development of pain in rats subjected to the chronic constriction injury and reversed already established pain in the spared nerve injury model. Immunohistochemical studies showed decreased phospho-ERK1/2-immunoreactivity in dorsal root ganglia and BDNF immunoreactivity in ipsilateral spinal dorsal horn in the drug-treated rats. Our results suggest the possible use of AZD6244, already in human clinical trials as an anticancer agent, for the treatment of pathological pain.

BDNF induction with mild exercise in the rat hippocampus

Although chronic voluntary physical activity has been shown to enhance hippocampal brain-derived neurotrophic factor (BDNF) expression in animals, the effects of forced exercise on a treadmill have not been fully investigated. We assessed induction of c- fos and BDNF expression with acute exercise at different running intensities. The mRNA for c- fos, a marker for neuronal activation, was up-regulated even under low-intensity running (15 m/min), although its induction appeared to be intensity dependent. On the other hand, increases in BDNF mRNA and protein were seen only at low-intensity running. At moderate-intensity running (25 m/min) which elevated blood lactate and corticosterone levels, induction of BDNF mRNA, but not its protein, was even depressed. Our study shows the first evidence that with an acute low-intensity exercise that is minimally stressful, hippocampal activation and BDNF expression can be achieved lending support to the idea that mild exercise could yield to greater benefits in hippocampal functions compared to the more strenuous forms.

Modulation of DOI-induced increases in cortical BDNF expression by group II mGlu receptors

Previous studies have shown that 5-hydroxytryptamine 2A (5-HT 2A) receptor activation induces changes in the pattern of brain-derived neurotrophic factor (BDNF) mRNA expression in the neocortex and hippocampus, and that 5-HT 2A receptor blockade interferes with the induction of BDNF mRNA by stress. Recent studies have also shown that activation of metabotropic glutamate group II (mGlu2/3) receptors suppresses 5-HT 2A receptor-stimulated excitatory postsynaptic potentials/currents (EPSP/Cs) in pyramidal neurons in medial prefrontal cortex. Conversely, blockade of mGlu2/3 receptors enhances 5-HT-induced EPSCs. The current study examined the effects of the highly selective mGlu2/3 agonist (1 S,2 S,5 R,6 S)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylate monohydrate (LY354740) and the mGlu2/3 antagonist 2 S-2-amino-2-(1 S,2 S-2-carboxycycloprop-1-yl)-3(xanthy-9-yl)propanoic acid (LY341495) on BDNF mRNA expression in medial prefrontal cortex induced by the hallucinogen and 5-HT 2A/2B/2C agonist 1-(2,5-dimethoxy-4-iodophenethyl)-2-aminopropane (DOI). LY354740 (0.1–10 mg/kg) dose-dependently suppressed DOI-induced BDNF mRNA levels in medial prefrontal cortex. In contrast, the mGlu2/3 antagonist LY341495 (1 mg/kg) enhanced DOI-induced BDNF mRNA levels. BDNF mRNA expression was not altered by administration of the mGlu agonist or the antagonist alone. These results are discussed with respect to a potential role for group II mGlu agonists in the treatment of depression and schizophrenia.

The induction of BDNF and c-fos mRNA in the hippocampal formation after febrile seizures.

In this study we investigated the expression of brain-derived neurotrophic factor (BDNF) and c-fos mRNA in the hippocampal formation after febrile seizures (FSs) with in situ hybridization histochemistry using riboprobes. The induction of BDNF mRNA was firstly observed in the dentate gyrus at 30 min after FSs. The expression in the dentate gyrus peaked at 3 h and returned to basal level at 24 h. It was also observed in the CA3 of hippocampus from 2 to 3 h. The induction of c-fos mRNA was observed in the dentate gyrus at 30 min and 1 h. These observations suggest that BDNF and c-fos are the genes whose expression can be altered by FSs and might be related to pathologic alterations after FSs.

Effects of Age and Gender on the Expression of Brain-Derived Neurotrophic Factor mRNA in Rat Retrosplenial Cortex Following Administration of Dizocilpine

Using in situ hybridization, we studied the effects of age and gender on the expression of brain-derived neurotrophic factor (BDNF) mRNA and heat shock protein hsp-70 mRNA in the rat retrosplenial cortex following administration of the noncompetitive NMDA receptor antagonist (+)-MK-801 (dizocilpine). Male and female Sprague–Dawley rats (5 weeks, 12 weeks, or 10 months old) were given a single intraperitoneal injection of saline (1 ml/kg) or dizocilpine (0.3, 1.0, or 3.0 mg/kg). No expression of BDNF mRNA and hsp-70 mRNA was detected in the rat retrosplenial cortex after administration of saline (1 ml/kg, IP). Administration of dizocilpine (0.3, 1.0, or 3.0 mg/kg, IP) caused a marked induction of BDNF mRNA and hsp-70 mRNA in the retrosplenial cortex of male and female rats, in a dose-dependent manner. Female rats were more sensitive to the induction of BDNF mRNA and hsp-70 mRNA in the retrosplenial cortex by dizocilpine as compared to male rats. It was also found that adult (12 weeks old) and aged (10 months old) rats were more sensitive to the induction of hsp-70 mRNA and BDNF mRNA in the retrosplenial cortex by dizocilpine as compared to young (5 weeks old) rats. These results suggest that the age and gender differences observed in the expression of BDNF mRNA and hsp-70 mRNA in the retrosplenial cortex by dizocilpine may be associated with the differences in dizocilpine-induced neurotoxicity observed with gender and age within the same region.

Expression of neurotrophins BDNF and NT-3, and their receptors in rat brain after administration of antipsychotic and psychotrophic agents.

We have investigated the potential role of neurotrophic factors in antipsychotic drug action by examining the effects of antipsychotic and psychotropic treatments on the mRNA expression of brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and their receptors, trkB and trkC, respectively, in rat brain. Neither acute nor chronic clozapine treatment significantly affected the expression of these mRNAs in any brain area investigated, except for a decrease in trkB expression in the granule cells of the olfactory bulb. We then examined the effects of the psychotropic agent MK-801. MK-801 (5 mg/kg; 4 h) significantly increased BDNF mRNA in the entorhinal cortex, but did not influence NT-3, trkB, or trkC expression in any brain area except for the olfactory bulb. The induction of BDNF mRNA by MK-801 was attenuated by pre-treatment (1 h prior to MK-801 administration) with the antipsychotics, clozapine (25 mg/kg) and haloperidol (2 mg/kg), but not with the antidepressant desipramine (15 mg/kg). Finally, we confirmed that the effects of MK-801 on BDNF mRNA were reflected in the respective changes in BDNF protein levels: MK-801 significantly increased anti-BDNF reactivity in the entorhinal cortex (126 +/- 7% of control) while concomitantly decreasing in the hippocampus (71 +/- 2% of control). These data do not support the hypothesis that neurotrophins play an important role in antipsychotic drug action, but rather suggest that induction of BDNF in the entorhinal cortex may play a significant role in the psychotropic action of MK-801.

Expression of neurotrophin mRNAs in the dorsal root ganglion after spinal nerve injury

Neurotrophins have specificity toward distinct subpopulations of dorsal root ganglion (DRG) neurons with different neurotrophin receptors. It has been suggested that neurotrophins also play important roles in mature DRG neurons after injury. In the present study, we examined the expression of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin 3 (NT-3) mRNAs in the DRG after a peripheral nerve injury. The data showed that following a spinal nerve ligation, the level of NGF mRNA increased 4 times over the normal level and was maintained at a high level for a period of 3 weeks. The induction of BDNF mRNA was brief (lasting less than 3 days) and lesser in quantity (∼1.7 times increase) compared to NGF expression. The expression of NT-3 mRNA was not detected either in normal or nerve injured rats. Results suggest that different neurotrophins play different functional roles in the DRG after spinal nerve injury.

VIP and PACAP potentiate the action of glutamate on BDNF expression in mouse cortical neurones.

In view of the neurotrophic effect of vasoactive intestinal peptide (VIP), the regulation of brain-derived neurotrophic factor (BDNF) expression by VIP and the related peptide pituitary adenylate cyclase-activating polypeptide (PACAP) was analysed by Northern blot in primary cultures of cortical neurones. Results reported in this article demonstrate that VIP and PACAP stimulate the expression of BDNF mRNA in primary cultures of cortical neurones and astrocytes. In primary cultures of cortical neurones, induction of BDNF mRNA by VIP and PACAP is completely inhibited by the N-methyl-D-aspartate (NMDA) receptor antagonists MK-801 and AP5, therefore indicating that VIP and PACAP do not stimulate BDNF expression directly but rather by potentiating the effect of glutamate tonically released by neurones and acting at NMDA receptors. In addition to its neurotrophic effects, BDNF has been shown to be involved in neuronal plasticity and results reported here suggest that by stimulating BDNF expression, VIP and PACAP could modulate synaptic plasticity in the cerebral cortex.

Expression of brain-derived neurotrophic factor (BDNF) mRNA in rat retrosplenial cortex following administration of phencyclidine.

The non-competitive NMDA receptor antagonists such as phencyclidine (PCP) cause neurotoxicity in the retrosplenial cortex of rat brain. However, the precise mechanism(s) underlying the neurotoxicity of NMDA receptor antagonists is currently unclear. Using an in situ hybridization technique, we studied the effects of PCP on expression of brain-derived neurotrophic factor (BDNF) mRNA in the rat brain. No expression of BDNA mRNA was observed in the retrosplenial cortex of rats treated with vehicle, although a high basal level of BDNF mRNA was detected in the hippocampus of control rats. Administration of PCP (12.5, 25 or 50 mg/kg, i.p., 6 hours) caused marked induction of BDNF mRNA in the retrosplenial cortex, in a dosedependent manner. These results suggest that the expression of BDNF mRNA may occur as a trophic response to the neurotoxicity of NMDA receptor antagonists such as PCP.

Early induction of mRNA for calbindin-D 28k and BDNF but not NT-3 in rat hippocampus after kainic acid treatment

The influence of kainic acid (KA), which induces acute seizures, on expression of mRNA for the calcium-binding protein, calbindin-D 28k, brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) and early-response genes [c- fos, zif268 (NGFI-A), nur77 (NGFI-B)] was examined in rat hippocampus by Northern blot analysis. A significant increase (3.2-fold) in BDNF mRNA was observed 1 h after KA injection (12 mg/kg i.p.) and peak expression (9.4-fold) occurred 3 h after KA. The induction of BDNF mRNA was preceded by the induction of c- fos, mRNA (30 min after KA) and was followed by the induction of calbindin-D 28k mRNA (3.5-fold 3 h after KA; a maximal response was at 3–6 h after KA). Region-specific changes, analyzed by immunocytochemistry and in situ hybridization, indicated that the most dramatic increases in calbindin protein and mRNA after KA treatment were in the dentate gyrus. Although calbindin-D 28k and BDNF mRNAs were induced, a 3.4–3.8-fold decrease in NT-3 mRNA was observed by Northern analysis 3–24 h after KA treatment. Calbindin-D 28k gene expression was also examined in rats with a chronic epileptic state characterized by recurrent seizures established with an episode of electrical stimulation-induced status epilepticus (SE). When these animals were examined 30 days post-SE, no changes in hippocampal calbindin-D 28k mRNA were observed. Our findings suggest that the induction of calbindin-D 28k mRNA (which may be interrelated to the induction of BDNF mRNA) is an early response which may not be related to enhanced neuronal activity or seizures per se, but rather to maintaining neuronal viability.