Quercetin impairs learning and memory in normal mice via suppression of hippocampal phosphorylated cyclic AMP response element-binding protein expression

Quercetin is a naturally occurring dietary flavonol and several reports have shown that quercetin substantially affects cognitive function in disease models, which suggests that quercetin might be a useful agent for treatment of memory dysfunction. However, only one report has examined the effects of quercetin on normal cognitive function. In the present study, we investigated the potential deleterious effects of quercetin on normal cognitive function using Western blot assays and the following behavioral tasks: passive avoidance, Y-maze, and Morris water maze. In the passive avoidance task, pre-acquisition administration of quercetin (10, 20, or 40 mg/kg, p.o.) caused significant cognitive impairments in mice (P < 0.05 or P < 0.01). Quercetin-treated groups (10, 20, or 40 mg/kg, p.o.) also showed significant memory impairments compared with the control group in the Y-maze task (P < 0.05). In the Morris water maze task, there were no significant differences among the groups during training trial sessions, but at the probe trial session, the quercetin-treated group (40 mg/kg, p.o.) spent significantly less time in the target quadrant than did the control group (P < 0.05). In Western blot assays of hippocampal tissue, we found that quercetin-treated groups showed decreased expression of phosphorylated Akt (pAkt), phosphorylated calcium-calmodulin kinase II (pCaMKII), and phosphorylated cyclic AMP response element-binding protein (pCREB). These results suggest that acute administration of quercetin impairs cognitive function by suppression of pAkt and pCaMKII, which, in turn, decreases pCREB expression in the hippocampus.     

Tianeptine increases brain-derived neurotrophic factor expression in the rat amygdala

Chronic restraint stress affects hippocampal and amygdalar synaptic plasticity as determined by electrophysiological, morphological and behavioral measures, changes that are inhibited by some but not all antidepressants. The efficacy of some classes of antidepressants is proposed to involve increased phosphorylation of cAMP response element binding protein (CREB), leading to increased expression of neurotrophic factors, such as brain-derived neurotrophic factor (BDNF). Conversely, some studies suggest that acute and chronic stress downregulate BDNF expression and activity. Accordingly, the aim of the current study was to examine total and phosphorylated CREB (pCREB), as well as BDNF mRNA and protein levels in the hippocampus and amygdala of rats subjected to chronic restraint stress in the presence and absence of the antidepressant tianeptine. In the hippocampus, chronic restraint stress increased pCREB levels without affecting BDNF mRNA or protein expression. Tianeptine administration had no effect upon these measures in the hippocampus. In the amygdala, BDNF mRNA expression was not modulated in chronic restraint stress rats given saline in spite of increased pCREB levels. Conversely, BDNF mRNA levels were increased in the amygdala of chronic restraint stress/tianeptine rats in the absence of changes in pCREB levels when compared to non-stressed controls. Amygdalar BDNF protein increased while pCREB levels decreased in tianeptine-treated rats irrespective of stress conditions. Collectively, these results demonstrate that tianeptine concomitantly decreases pCREB while increasing BDNF expression in the rat amygdala, increases in neurotrophic factor expression that may participate in the enhancement of amygdalar synaptic plasticity mediated by tianeptine.     

Chronic lithium treatment increases the expression of brain-derived neurotrophic factor in the rat brain

RATIONALE: Oxazepam has been demonstrated to slow reaction times and increase the rate of omission errors in attentional experiments. This suggests that action monitoring might also be impaired. OBJECTIVES: The present study used the event-related brain potential (ERP) technique to investigate this hypothesis. The P3b component to targets was taken as an indicator of the target evaluation process, and the response-locked error-related negativity (ERN) served as an indicator of action monitoring. We hypothesized that the amplitudes of ERN and P3b would be reduced as an effect of oxazepam. METHODS: A simple "oddball" reaction time experiment was conducted in a double-blind crossover study of 30 mg oxazepam versus placebo. In order to investigate variations in attentional allocation, separate experimental runs were undertaken with target frequencies of 50% and 80%. RESULTS: ERN and P3b amplitudes were lower in the 80% target condition than in the 50% condition. Oxazepam did not affect behavioral parameters but was associated with an ERN of lower amplitude than the placebo condition. ERN amplitude variations between target conditions remained unchanged. CONCLUSIONS: Although the intake of 30 mg oxazepam did not impair behavioral performance, measures of the electrophysiological recordings show that action monitoring processes were altered. We argue that this may be related to the anxiolytic properties of the drug and may constitute an important causal factor for behavioral impairments after the intake of oxazepam.     

Effect of chronic olanzapine treatment on nerve growth factor and brain-derived neurotrophic factor in the rat brain.

Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are proteins involved in neuronal survival, neurite outgrowth and synapse formation. Recent observations suggest that treatment with typical and atypical antipsychotic drugs affect NGF and BDNF levels in the rat brain. The atypical antipsychotic olanzapine has a low incidence of side effects, such as extrapyramidal and anticholinergic symptoms. Since NGF and BDNF are involved in the regulation of cholinergic, dopaminergic and serotonergic neurons in the central nervous system (CNS) we hypothesized that chronic olanzapine treatment will influence the distribution of NGF and BDNF in the rat brain. To test this hypothesis we administered olanzapine for 29 days in the drinking water at the doses of 3 and 15 mg/kg body weight and measured the levels of NGF and BDNF in the brain of Wistar rats. Olanzapine increased NGF in the hippocampus, occipital cortex and hypothalamus. In contrast, olanzapine decreased BDNF in the hippocampus and frontal cortex. Although the significance of these findings is not clear, a heuristic hypothesis is that olanzapine's clinical effects and a favorable side effect profile are in part mediated by neurotrophins.     

Combined treatment with imipramine and metyrapone induces hippocampal and cortical brain-derived neurotrophic factor gene expression in rats

The problem of drug-resistant depression indicates a strong need for alternative antidepressant therapies. Recently it was shown that joint administration of imipramine (IMI) and metyrapone (MET), an inhibitor of glucocorticoid synthesis, produced a more potent "antidepressant" effect in the forced swimming test than did treatment with either drug alone. Our studies also showed that co-administration of IMI and MET to drug-resistant, unipolar depressed patients effected a clinical improvement. In addition, recent studies indicated a role of the brain-derived neurotrophic factor (BDNF) in the mechanism of action of antidepressant drugs (ADs). Since the most potent effect of ADs on BDNF gene expression was found after prolonged treatment, in the present research we investigated the influence of repeated treatment with IMI (5 or 10 mg/kg) and MET (50 mg/kg), given separately or jointly (twice daily for 14 day), on the BDNF mRNA level (the Northern blot) in the hippocampus and cerebral cortex. The experiment was carried out on male Wistar rats. The tissue for biochemical assays was collected 24 h after the last dose of IMI and MET. The obtained results showed that in the hippocampus IMI (10 mg/kg) and cerebral cortex IMI (5 mg/kg) and MET (50 mg/kg) significantly elevated the BDNF mRNA level. Joint administration of IMI (10 mg/kg) and MET (50 mg/kg) induced a more potent increase BDNF gene expression in both the examined brain regions (compared to the treatment with either drug alone). Moreover, the obtained results suggested that BDNF may be involved in the mechanism of the synergistic antidepressant effect of IMI and MET in drug-resistant depressed patients.     

Nitric oxide regulates c-fos expression in nucleus tractus solitarii induced by baroreceptor activation via cGMP-dependent protein kinase and cAMP response element-binding protein phosphorylation

Activation of the arterial baroreceptors induces expression of the proto-oncogene c-fos in the nucleus tractus solitarii (NTS), the terminal site of baroreceptor afferents in the medulla oblongata. This induced expression is an intracellular event that is crucial to long-term maintenance of stable blood pressure. Using Sprague-Dawley rats maintained under propofol anesthesia, we evaluated the role and delineated the underlying molecular mechanisms of nitric oxide (NO) in this process. Baroreceptor activation induced by 30 min of sustained hypertension significantly and sequentially increased the level of cyclic GMP-dependent protein kinase I (PKG-I), phosphorylated cyclic AMP response element-binding protein (pCREB), c-fos mRNA, and Fos protein in the NTS. All of these up-regulated expressions were significantly attenuated in animals that were pretreated immediately before baroreceptor activation with bilateral microinjection into the NTS of a selective neuronal nitric-oxide synthase (nNOS) inhibitor, 7-nitroindazole (2.5 pmol), or a soluble guanylyl cyclase (sGC) inhibitor, 1-H-[1,2,4]oxadiaolo[4,3-a]quinoxalin-1-one (1 nmol). Bilateral NTS microinjection of a cell-permeable cGMP analog, 8-bromoguanosine-3',5'-cyclic monophosphate (10 nmol) significantly elevated the level of pCREB or c-fos mRNA in the NTS. On the other hand, the up-regulated CREB phosphorylation or c-fos induction evoked in the dorsomedial medulla by baroreceptor activation was significantly antagonized by NTS application of a cell-permeable cGMP antagonist, (R)p-8-bromoguanosine-3',5'-cyclic monophosphorothioate (5 nmol), or a PKG inhibitor, (8R,9S,11S)-(-)-9-methoxy-carbamyl-8-methyl-2,3,9,10-tetrahydro-8,11-epoxy-1H,8H,11H,-2,7b,11a-trizadizo-benzo(a,g)cycloocta(c,d,e)-trinden-1-one (1 nmol). We conclude that NO derived from nNOS in the NTS on baroreceptor activation may participate in c-fos expression via phosphorylation of CREB in a process that engages the sGC/cGMP/PKG-I signaling cascade.     

Bidirectional changes in water-maze learning following recombinant adenovirus-associated viral vector (rAAV)-mediated brain-derived neurotrophic factor expression in the rat hippocampus

Alterations in hippocampal brain-derived neurotrophic factor (BDNF) expression have been implicated in the pathogenesis of emotional and cognitive dysfunction. Here, we induced BDNF overexpression in the rat hippocampus using recombinant adenovirus-associated viral (rAAV) vectors, and studied its long-term (2 months postinduction) effects on anxiety-related behaviour, exploration in the open field, and spatial learning in the water maze. Although the treatment successfully led to substantial elevation of hippocampal BDNF levels, its effect on spatial learning was bidirectional: a subset of rAAV-induced BDNF-overexpressing rats performed well above control level, whereas the rest were clearly impaired. This behavioural distinction corresponded to two markedly different levels of BDNF overexpression. The increase in dorsal hippocampal BDNF content achieved in the 'water-maze-impaired' subgroup was twice that attained in the 'water-maze-improved' rats. Although neither subgroup of rAAV-induced BDNF-overexpressing rats differed from controls in the open field, the 'water-maze-impaired' subgroup also showed a significant anxiolytic effect. Our results suggest that hippocampal BDNF elevation significantly affects cognitive and emotional behaviours, but the direction and magnitude of the effects critically depend on the precise levels of overexpression. This factor must be taken into account in future studies examining the functional consequences of hippocampal BDNF overexpression.     

骨骼肌中脑源性神经营养因子的表达与中枢性肥胖的相关性研究

目的研究小鼠骨骼肌中脑源性神经营养因子(BDNF)与中枢性肥胖的相关性。方法将50只新生健康小鼠随机分为对照组20只和实验组30只。实验组自小鼠出生当天起,按3 mg·g^-1·d^-1的剂量颈部皮下注射10%谷氨酸钠,连续5 d;对照组同法注射等剂量0.9%NaCl。根据实验要求对小鼠进行剔除,最终对照组和实验组各12只小鼠。每2周测定小鼠体重并计算Lee’s指数,每周测定体温。8周末取血,检测血清中血脂含量,分离肾周白色脂肪(WAT)和肩胛间棕色脂肪(BAT)并称重。用Western blotting法检测骨骼肌中BDNF的表达水平。结果6周末,实验组和对照组的体重分别为(39.71±2.55)和(32.83±2.30)g,Lee’s指数分别为(365.02±3.83)和(337.54±4.10)g^1/3·cm^-1,8周末,实验组和对照组的体重分别为(48.12±3.61)和(39.51±3.52)g,Lee’s指数分别为(361.93±7.12)和(325.17±6.87)g^1/3·cm^-1,差异均有统计学意义(P<0.05,P<0.01或P<0.001)。实验组和对照组的6周末体温分别为(36.30±0.07)和(36.67±0.07)℃,7周末体温分别为(36.40±0.08)和(36.79±0.10)℃,8周末体温分别为(36.31±0.09)和(36.80±0.10)℃,差异均有统计学意义(均P<0.05)。8周末,实验组和对照组的总胆固醇分别为(2.91±0.25)和(1.86±0.51)mmol·L^-1,三酰甘油分别为(1.48±0.62)和(0.81±0.23)mmol·L^-1,低密度脂蛋白分别为(0.37±0.06)和(0.29±0.05)mmol·L^-1,WAT分别为(0.75±0.08)和(0.24±0.05)g,BAT分别为(0.31±0.07)和(0.17±0.01)g,BAT/WAT分别为(0.41±0.08)和(0.71±0.12),BDNF相对表达量分别为(0.63±0.07)和(0.98±0.06),差异均有统计学意义(P<0.05,P<0.01或P<0.001)。结论骨骼肌中BDNF表达下调,可能通过影响能量代谢,导致小鼠中枢性肥胖。     

Influences of chronic venlafaxine,olanzapine and nicotine on the hippocampal and cortical concentrations of brain-derived neurotrophic factor (BDNF)

Brain-derived neurotrophic factor (BDNF) is a key neurotrophic factor in the brain. It plays an important role in the etiopathogenesis and pharmacotherapy of mental disorders, such as depression or schizophrenia. In recent years, studies have shown that cognitive processes, which are impaired in the course of mental disorders, significantly change BDNF levels in the brain.Administered to rats at a dose of 20 mg/kg (b.d. for 5 weeks), venlafaxine (VEN) increases BDNF levels in the hippocampus and cortex, compared to controls. Administered at a dose of 0.5 mg/kg (b.d. for 5 weeks), olanzapine (OLA) significantly increases BDNF levels in both the cortex and the hippocampus. Similarly, nicotine (NIC) administered at a dose of 0.2 mg/kg (b.d. for 5 weeks) increases BDNF concentrations in both the hippocampus and the cortex. Combined administration of NIC with VEN or OLA does not increase BDNF levels in the hippocampus or the cortex.Based on our study, it can be claimed that BDNF mediates behavioral responses only to drugs used individually and participates in the antidepressant and procognitive effects of the study compounds. BDNF also initiates plastic changes and modulation of synaptic activity in rat brains.     

Minocycline up-regulates the expression of brain-derived neurotrophic factor and nerve growth factor in experimental autoimmune encephalomyelitis

Previous evidence demonstrated that minocycline could ameliorate clinical severity of experimental autoimmune encephalomyelitis and exhibit several anti-inflammatory and neuroprotective activities. However, few studies have been carried out to assess its effects on the expression of neurotrophins in experimental autoimmune encephalomyelitis or multiple sclerosis. Here we investigated the alteration of brain-derived neurotrophic factor and nerve growth factor in the sera, cerebral cortex, and lumbar spinal cord of experimental autoimmune encephalomyelitis C57 BL/6 mice in vivo as well as the splenocytes culture supernatants in vitro after minocycline administration. Our results demonstrated that minocycline could up-regulate the expression of brain-derived neurotrophic factor and nerve growth factor both in peripheral (sera and splenocytes culture supernatants) and target organs (cerebral cortex and lumber spinal cord) of mice with experimental autoimmune encephalomyelitis. These data suggest that up-regulation of neurotrophins in experimental autoimmune encephalomyelitis may be a novel neuroprotective mechanism of minocycline.     

Chronic unpredictable stress-induced reduction in the hippocampal brain-derived neurotrophic factor (BDNF) gene expression is antagonized by zinc treatment

Preclinical data indicate the antidepressant activity of zinc and the involvement of the brain-derived neurotrophic factor (BDNF) in this mechanism. The present study investigates the effect of chronic (16 days) combined treatment with zinc (15 mg/kg zinc hydroaspartate) and imipramine (5 mg/kg) in chronic unpredictable stress (CUS) on the BDNF mRNA level in the rat brain. Moreover, serum zinc concentrations were also assessed. CUS induced a significant reduction in the BDNF mRNA level in the hippocampus by 21% but had no effect in the frontal cortex. Repeated treatment with zinc induced a significant increase in the BDNF mRNA level in the hippocampus in the unstressed animals by 12% and as in the chronically stressed animals by 14%, compared to the appropriate controls. Imipramine treatment did not affect this factor. However, combined treatment of zinc and imipramine induced a 12% elevation of the BDNF mRNA level in the stressed but not in the unstressed rats. CUS induced a 19% reduction in the serum zinc concentration, whereas combined treatment of zinc and imipramine reduced this concentration by 24% in the unstressed and increased it (by 20%) in the stressed animals. These results indicate that: 1) CUS induces a reduction in the BDNF gene expression with a concomitant diminution of serum zinc concentration and 2) the CUS-induced reduction in the BDNF gene expression is antagonized by chronic treatment with zinc.     

骨髓基质细胞对脑创伤大鼠神经营养因子表达水平的影响

目的:研究骨髓基质细胞(BMSCs)治疗脑创伤大鼠后内源性的神经生长因子(NGF)和脑源性神经营养因子(BDNF)的影响。方法:采用大鼠骨髓中提取出来的骨髓基质细胞,进行体外扩增后,静脉移植于大鼠脑创伤模型中,在治疗后1、3、5、7、14d,ELISA法检测损伤半球NGF和BDNF的浓度,并与对照组对比,进行统计学分析。免疫组化法检测骨髓基质细胞在损伤脑组织中的表达。结果:骨髓基质细胞经股静脉移植后可在损伤的脑组织中表达。治疗组NGF和BDNF的表达于伤后1d至7d逐渐增加,于第7天达到高峰,至第14天降至较低水平。结论:骨髓基质细胞经股静脉移植后可在损伤的脑组织中表达。移植后的骨髓基质细胞可增加损伤脑组织中的NGF和BDNF的表达,与时间有相关性。体外扩增的骨髓基质细胞对于创伤性脑损伤具有治疗作用。     

Transcriptional regulation of basal cyclooxygenase-2 expression in murine lung tumor-derived cell lines by CCAAT/enhancer-binding protein and activating transcription factor/cAMP response element-binding protein

Activation of N-methyl-D-aspartate-selective ionotropic glutamate receptors (NMDA receptors) requires two agonists, glutamate and glycine. These ligands are thought to bind to the NR2 and NR1 subunits, respectively, apparently ruling out the formation of functional homomeric receptors. However, NMDA-mediated currents are observed when the mammalian NR1 subunit is expressed alone in Xenopus laevis oocytes. These currents have been generally ascribed to a functional association between NR1 and the endogenous glutamate receptor subunit XenU1. To determine whether such a functional association does in fact occur, we have isolated cDNAs for both XenU1 and XenU1a, a presumed nonallelic counterpart. We investigated whether the coexpression of either XenU1 or XenU1a with NR1 in either X. laevis oocytes and human embryonic kidney (HEK) 293 cells had any effect on the observed NMDA receptor responses. In oocytes, coinjection of XenU1 with NR1 did not increase the observed currents compared with injection of NR1 alone; similarly, in HEK 293 cells, coexpression of XenU1 and NR1 did not result in the formation of functional channels. We also found no pharmacological or biochemical evidence for interaction between the two subunits. We conclude, therefore, that XenU1 does not associate with the NR1 subunit and that an alternative explanation must be sought for the channels observed when NR1 is expressed alone in oocytes.     

Effects of chronic manganese exposure on the learning and memory of rats by observing the changes in the hippocampal cAMP signaling pathway

Chronic manganese exposure can produce cognitive deficits; however, the underlying mechanism remains unclear; reliable peripheral biomarker of Mn neurotoxicity have not yet been fully developed. Hence, this study aimed to investigate the mechanism of Mn-induced cognitive deficits and the potential biomarker of Mn neurotoxicity in rats. Thirty-two male Sprague Dawley rats were divided into four groups; these groups received intraperitoneal injections of 0, 5, 10 and 20 mg Mn/kg once daily, five days/week for 18 weeks. Learning and memory were assessed via Morris water maze test. Hippocampal and plasma Mn concentrations were measured through graphite furnace atomic absorption spectrometry. The levels of plasma BDNF, hippocampal BDNF, cAMP, protein kinase A, and pCREB were assessed through ELISA or Western blot. Results showed that the Mn concentrations in the hippocampus and plasma of the Mn-treated rats were higher than those of the control rats. Mn exposure impaired the learning and memory of rats. Plasma BDNF levels and hippocampal BDNF, cAMP, protein kinase A, and pCREB levels were significantly lower in the Mn-treated rats than in the control rats. Plasma BDNF levels were negatively correlated with the escape latency and the hippocampal and plasma Mn concentrations. By contrast, plasma BDNF levels were positively correlated with the number of platform crossings and the hippocampal cAMP and BDNF levels. Therefore, Mn impaired learning and memory probably by inhibiting the hippocampal cAMP signaling pathway in rats. Plasma BDNF levels may also be a potential effect biomarker of Mn neurotoxicity.