Elevated CREB activity in embryonic fibroblasts of gene-targeted histamine deficient mice

Objectives: Histamine is a known inducer of cAMP-responsive element binding protein (CREB), which plays a key role in initiation of adipogenesis. Our present goal was to study how histamine deficiency impacts CREB signalling and adipogenesis. Methods: We used a histidine-decarboxylase gene-targeted (HDC KO) mice model lacking endogenous histamine. We measured CREB activity and expression by EMSA, Western blot and real-time RT-PCR, as well as cAMP levels by ELISA in primary embryonic fibroblasts derived from WT and HDC KO mice. The ability of these cells to form adipocytes was also tested in preliminary experiments. Results: We found that in the absence of the histamine, cells show higher constitutive CREB activity and greatly increased intracellular cAMP levels, as well as that in contrast to WT cells, HDC KO fibroblasts are more prone to differentiate into adipocytes. Conclusion: These data suggest a newly recognised inhibitory role for histamine in CREB activity and draws attention to the potential role of histamine in adipocyte differentiation. Received 20 November 2006; returned for revision 30 December 2006; accepted by M. Parnham 18 April 2007     

吗啡长时程作用对培养SK-N-SH细胞表达fosB基因的影响

目的探讨吗啡长时程作用时SK-N-SH细胞fosB基因表达的改变.方法建立慢性吗啡依赖SK-N-SH细胞模型,分别采用放射免疫法 (radioimmunoassay, RIA)、电泳迁移率改变分析(electrophoresis mobility shift assay, EMSA) 和RT-PCR检测cAMP(cyclic adenosine 3′,5′-monophosphate)、 CREB (cyclic AMP-responsive element-binding protein) 的DNA结合活性和fosB mRNA表达.结果吗啡长时程作用SK-N-SH细胞CREB的DNA结合活性及fosB mRNA水平升高.结论吗啡长时程作用诱导SK-N-SH细胞fosB基因表达上调可能通过CREB的DNA结合活性升高而调控.     

G protein‐coupled oestrogen receptor stimulation ameliorates iron‐ and ovariectomy‐induced memory impairments through the cAMP/PKA/CREB signalling pathway

Iron accumulation in the brain has been associated with neurodegenerative disorders, and imaging studies in humans indicate that iron content in brain regions correlates with poor performance in cognitive tasks. In rats, iron overload impairs memory retention in a variety of memory tasks. Although the effects of iron on cognition in rodents are extensively reported, no previous study has been conducted in female rats. The incidence of certain dementias, such as Alzheimer's disease, is higher in women after menopause compared to aged‐matched men. The role of oestrogen depletion in memory deficits in menopausal women is still a matter of debate. The present study aimed to characterise the effects of iron overload on memory in female rats by investigating the effects of ovariectomy (OVX, an experimental model of oestrogen depletion) in rats submitted to iron overload, as well as examining the effects of G protein‐coupled oestrogen receptor (GPER) agonism on memory impairments induced by iron and OVX. Female rats received iron (30 mg kg^‐1, orally) or vehicle at postnatal days 12‐14 and were submitted to OVX in adulthood. Results showed that either iron or OVX impaired memory for object placement and inhibitory avoidance. The selective GPER agonist G1, administered immediately after training, reversed both iron‐ and OVX‐induced memory impairments. G1 effects were abolished by protein kinase A (PKA) inhibition, suggesting the involvement of the cAMP/PKA/CREB signalling pathway. The search for novel oestrogen agonists with positive effects on cognition may be promising for the development of treatments for memory disorders.     

异氟醚抑制老龄小鼠脑记忆提取及相关转录因子CREB的表达

目的:研究异氟醚对脑记忆提取及相关转录因子CREB合成的影响。方法 :老龄C57/BL6小鼠,接受Morris水迷宫定位航行训练,使其形成对隐蔽于水下平台定位的空间参考记忆后随机分为麻醉组、载气对照组和空白对照组,前两组分别接受异氟醚麻醉(4 h,1个最低肺泡有效浓度)、30%O24 h吸入,空白对照组不接受任何处理。于麻醉后1 d、1周和1个月重复位置回想测试,观察麻醉前、后平台象限距离百分比的变化。取已形成记忆的小鼠随机分为位置回想测试组、位置回想测试加麻醉组和空白对照组,分别接受位置回想测试、位置回想测试加异氟醚麻醉和无任何处理。于麻醉后1 d、1周和1个月重复位置回想测试。免疫荧光染色和实时定量RT-PCR分别检测位置回想测试后激活的脑CREB(p-CREB)表达和CREB mRNA水平。结果:麻醉前麻醉组平台象限距离百分与两个对照组相比无统计学差异,而麻醉后1 d和1周麻醉组平台象限距离百分比明显低于两个对照组,麻醉后1个月3组之间无统计学差异。麻醉后1 d,位置回想测试加麻醉组p-CREB的表达低于位置回想测试组(P<0.01)。结论:异氟醚麻醉可抑制老龄小鼠记忆提取及其相关的转录因子CREB的合成和激活。     

Effects of blockade of voltage-sensitive Ca/Na channels by a novel phenylpyrimidine derivative, NS-7, on CREB phosphorylation in focal cerebral ischemia in the rat

NS-7 is a novel blocker of voltage-sensitive Ca²⁺ and Na⁺ channels, and it significantly reduces infarct size after occlusion of the middle cerebral artery. Persistent activation of cyclic AMP response element binding protein (CREB), which can be induced by increase in intracellular Ca²⁺ concentrations or other second messengers, has recently been found to be closely associated with neuronal survival in cerebral ischemia. The present study was therefore undertaken to evaluate the neuroprotective effects of NS-7 by analyzing changes in CREB phosphorylation in a focal cerebral ischemia model. CREB phosphorylation in the brain of rats was investigated immunohistochemically at 3.5–48-h recirculation after 1.5-h occlusion of the middle cerebral artery. NS-7 (1 mg/kg; NS-7 group) or saline (saline group) was intravenously injected 5 min after the start of recirculation. The NS-7 group showed significantly milder activation of CREB phosphorylation in various cortical regions after 3.5 h of recirculation than the saline group. The inner border zone of ischemia in the NS-7 group subsequently exhibited a moderate, but persistent, increase in number of phosphorylated CREB-positive neurons with no apparent histological damage. By contrast, the saline group displayed a marked, but only transient, increase in number of immunopositive neurons in this border zone after 3.5 h of recirculation, and this was followed by clear suppression of CREB phosphorylation and subsequent loss of normal neurons. These findings suggest that: (1) the marked enhancement of CREB phosphorylation in the acute post-ischemic phase may be triggered largely by an influx of calcium ions as a result of activation of the voltage-sensitive Ca²⁺ and Na⁺ channels; and that (2) the neuroprotective effects of NS-7 may be accompanied by persistent activation of CREB phosphorylation in the inner border zone of ischemia.     

Molecular and systems mechanisms of memory consolidation and storage

Until recently, memory consolidation and storage had been traditionally viewed as a permissive process derived from learning-activated molecular signaling cascades which include activations of the NMDA receptors, CaMKII, PKC, PKA and other kinases, new protein synthesis and CREB-mediated gene expression, and subsequent structural modifications at certain synapses. However, the time-scale of such a cascade is incompatible with the timescale of systems-level memory consolidation. Furthermore, increasing evidence suggests that synaptic proteins and structures are not stationary, but rather are highly dynamical and subjected to metabolic turnovers which would cause drift in synaptic efficacy and subsequently unstable neural circuits. Recent experiments using inducible gene- or protein-knockout techniques reveal that post-learning NMDA receptor and CaMKII reactivations are required for the systems-level consolidation of both hippocampal-dependent and hippocampal-independent memories. Furthermore, the reactivations of the NMDA receptors are also necessary for the long-term storage of old memories in the neural circuits. Therefore, the NMDA receptor reactivation-mediated synaptic reentry reinforcement (SRR) process may represent the unifying cellular mechanism in linking the consolidation and storage of long-term memories from the molecular level to the systems-level.