Upregulation of <i>N</i>-Methyl-D-aspartate Receptor Subunits and c-Fos Expressing Genes in PC12D Cells by Nobiletin

Abstract

The N-methyl-D-aspartate (NMDA) receptor plays a key role in learning and memory. Our recent studies have shown that nobiletin from citrus peels activates the cAMP response element-binding protein (CREB) signaling pathway and ameliorates NMDA receptor antagonist-induced learning impairment by activating extracellular signal-regulated kinase. For the first time, we have shown that nobiletin significantly upregulated mRNA expression of the NMDA receptor subunits NR1, NR2A, and NR2B in PC12D cells. Furthermore, c-Fos mRNA expression also increased due to the action of nobiletin. Our results indicate that nobiletin modulates the expression of essential genes for learning and memory by activating the CREB signaling pathway, and suggest that this action mechanism of nobiletin plays a crucial role in improving NMDA receptor antagonist-induced learning impairment in model animals with dementia.Key words nobiletin; N-methyl-D-aspartate receptor; c-Fos; gene expression; memory impairment; dementia Alzheimer's disease (AD) is an age-related neurodegenerative disorder with progressive learning and memory impairment. The rise in the number of patients with AD is a severe social problem worldwide. It is now widely recognized that the synaptic dysfunction and neurodegeneration in AD is caused by amyloid β (Aβ). 1,2)It is well-known that the N-methyl-D-aspartate (NMDA) receptor, a glutamate receptor, plays a very important role in learning and memory functions and is widely distributed in the brain, notably in the CA1 region of the hippocampus. 3)This receptor is constructed from NR1 and distinct NR2 (A, B, C, or D) subunits. In particular, binding of glutamate requires both NR1 and NR2 subunits; functional NR1/NR2A and NR1/NR2B receptors have a particularly close relationship with long-term potentiation (LTP) that is a form of synaptic plasticity. 4) Cognitive impairment is caused by hypofunction of the NMDA receptor.5) The NR1 subunit is prerequisite for acquisition of spatial memory, object recognition, olfactory discrimination, and contextual fear memory in the hippocampal CA1, 6,7) whereas the NR2A subunit is required for LTP at the hippocampal CA1 synapses, 8) and NR2B contributes to the maintenance of spatial performance. 9) Furthermore, NR1 and NR2B subunit mRNA and protein levels decrease significantly in patients with AD, and the degree of decrease is associated with progression of the neuropathology. 10)Recent studies have demonstrated that learning and memory requires expression of large number of genes that are associated with the cAMP response element (CRE)-binding protein (CREB).11-13) Elevated Ca 2+ level then triggers multiple protein kinase signal pathways that activate LTP by activating protein kinase A (PKA)/mitogen-activated protein kinase (MAPK) kinase (MEK)/MAPK/CREB. As a consequence of CREB activation, transcriptional regulators such as c-Fos, c-jun, and fra1 are activated that cause secondary expression of numerous molecules related to learning and memory.11) In particular, c-Fos constructs activator p...

Nobiletin Reduces Intracellular and Extracellular β-Amyloid in iPS Cell-Derived Alzheimer’s Disease Model Neurons

“…These earlier studies demonstrated that nobiletin induces the activation of the protein A (PKA)/extracellular signal-regulated kinase (ERK)/ cAMP response element (CRE)-binding protein (CREB) intracellular signaling pathway, and subsequently up-regulates CRE-dependent transcription. 16,23) These findings were observed in subclone PC12D of the rat pheochromocytoma cell line PC12. Furthermore, nobiletin elevates the expression of memory-and transcription-related genes in PC12 and PC12D cells.…”

“…In this study, whether nobiletin directly up-regulates neprilysin gene expression remains unclear. Previously, we showed that nobiletin evokes PKA/ERK/CREB signaling 23) and CRE-dependent transcription, 16) thus increasing the gene expression of the CREB-binding protein (CBP), 25) c-Fos, 24) c-jun, and Fra1 (data not shown) in PC12 and PC12D cells. In recent years, a number of studies have implicated epigenetic modifications in the expression of neprilysin.…”

Effects of a Flavonoid-Rich Fraction on the Acquisition and Extinction of Fear Memory: Pharmacological and Molecular Approaches

“…In addition, studies addressing the effects of specific flavonoid subgroups, including flavanols, anthocyanins, flavanones, and flavones, have shown that these constituents display potential to act as cognition-enhancing and neuroprotective agents (Vauzour et al, 2008 ; Kehr et al, 2012 ; Rendeiro et al, 2013 , 2014 ; Vauzour, 2014 ), to prevent many forms of cerebrovascular disease, or to function as anti-anxiety drugs (Hasenöhrl et al, 1998 ; Spencer, 2008 ; Zhang et al, 2012 ). Although studies ex vivo, in vivo , and in vitro have provided evidence supporting the effects of flavonoids on the central nervous system, the cellular, and molecular pathways through which these compounds modulate memory formation are not completely elucidated (Youdim et al, 2004 ; Nakajima et al, 2007 ; Spencer, 2007 ; Williams et al, 2008 ; Ballesteros et al, 2014 ; Kimura et al, 2014 ; Rendeiro et al, 2014 ). However, several studies have established that the hippocampus, which plays a central role as a substrate of fear memory and anxiety (Fendt and Fanselow, 1999 ; Sanders et al, 2003 ) and which is a component of the Behavioral Inhibition System (McNaughton and Gray, 2000 ), appears to be a target for the mnemonic effects of flavonoid metabolites (Bannerman et al, 2004 ; Wang et al, 2006 , 2009 ; Williams et al, 2008 ; Rendeiro et al, 2012 , 2014 ; Oliveira et al, 2013 ; Vauzour, 2014 ).…”

Nobiletin: a citrus flavonoid displaying potent physiological activity

“…Based on its potent physiological activities, nobiletin has become an attractive candidate for use as a therapeutic agent. The physiological activities of nobiletin have been attributed to its ability to modulate cell-signaling pathways, including cAMP response elements (Nagase et al, 2005) and NF-B (Cui et al, 2010), as well as its ability to alter the expression of specific genes (Nemoto et al, 2013;Kimura et al, 2014). However, the molecular mechanisms of nobiletin are not clear because the target receptor molecules to which this compound might bind have not yet been definitively identified.…”