Transcriptional Regulation of Brain-Derived Neurotrophic Factor in the Amygdala during Consolidation of Fear Memory

ABSTRACT We have demonstrated previously that brain-derived neurotrophic factor (BDNF) signaling in the amygdala is required for the consolidation of fear memory. This study is designed to characterize the signal cascades by which fear conditioning modulates transcriptional and translational expression of BDNF. Real-time reverse transcription-coupled polymerase chain reaction showed a significant increase in BDNF exon I-and III-containing mRNA in the amygdala of fear-conditioned rats, indicating that fear conditioning was capable of up-regulating BDNF mRNA. Bilateral administration of actinomycin D or anisomycin to the amygdala attenuated conditioning-induced increase in BDNF protein. Inhibitors for N-methyl-D-aspartate (NMDA) receptor, L-type voltage-dependent calcium channel (L-VDCC), adenylyl cyclase, cAMP-dependent protein kinase (PKA), and calcium/calmodulin-dependent kinase IV (CaMKIV) significantly reduced the increase. Moreover, DNA affinity precipitation and chromatin immunoprecipitation assays showed that phosphorylated cAMP response element-binding protein (p-CREB) binding activity in the proximal region of BDNF promoter I and III was significantly increased after fear conditioning. Intra-amygdala administration of cAMP response element decoy DNA before training impaired fear learning. Taken together, these results suggest that calcium influx through NMDA receptors and L-VDCCs during fear conditioning activates PKA and CaMKIV resulting in CREB phosphorylation. The phosphorylated CREB binds to BDNF promoter and up-regulates the expression of BDNF in the amygdala, which helps the consolidation of fear memory

MJ-66 induces malignant glioma cells G2/M phase arrest and mitotic catastrophe through regulation of cyclin B1/Cdk1 complex

Malignant gliomas are among the most devastating cancers as they are resistant to many kinds of treatment. Despite recent advances in the diagnosis and treatment, the prognosis of patients remains very poor and the development of new drug is urgently needed. Here, we report that a synthetic quinazolinone analog 2-(naphthalene-1-yl)-6-pyrrolidinyl-4-quinazolinone (MJ-66) induced glioma cell death. Immunofluorescence staining showed that MJ-66-induced cell death was associated with multinucleated phenotype and multipolar spindles that were typical characteristics of mitotic catastrophe. Flow cytometry analysis revealed that MJ-66 caused glioma cell cycle arrest at G2/M phase and increased the proportion of polyploidy cells. Western blotting indicated that the expression of cyclin B1, Cdk1 pY15 and Cdk1 increased after treatment with MJ-66. MJ-66 effectively inhibited tumor growth and induced apoptosis in the xenograft animal model of U87 human glioma cells. Together, these results suggest that MJ-66 inhibited malignant gliomas growth through inducing mitotic catastrophe by interference with G2/M cell cycle checkpoint which may open a new avenue for the treatment of malignant gliomas

Translational and transcriptional control of Sp1 against ischaemia through a hydrogen peroxide-activated internal ribosomal entry site pathway

The exact mechanism underlying increases in Sp1 and the physiological consequences thereafter remains unknown. In rat primary cortical neurons, oxygen-glucose deprivation (OGD) causes an increase in H2O2 as well as Sp1 in early ischaemia but apparently does not change mRNA level or Sp1 stability. We hereby identified a longer 5′-UTR in Sp1 mRNA that contains an internal ribosome entry site (IRES) that regulates rapid and efficient translation of existing mRNAs. By using polysomal fragmentation and bicistronic luciferase assays, we found that H2O2 activates IRES-dependent translation. Thus, H2O2 or tempol, a superoxide dismutase-mimetic, increases Sp1 levels in OGD-treated neurons. Further, early-expressed Sp1 binds to Sp1 promoter to cause a late rise in Sp1 in a feed-forward manner. Short hairpin RNA against Sp1 exacerbates OGD-induced apoptosis in primary neurons. While Sp1 levels increase in the cortex in a rat model of stroke, inhibition of Sp1 binding leads to enhanced apoptosis and cortical injury. These results demonstrate that neurons can use H2O2 as a signalling molecule to quickly induce Sp1 translation through an IRES-dependent translation pathway that, in cooperation with a late rise in Sp1 via feed-forward transcriptional activation, protects neurons against ischaemic damage

Impact of social relationships on Alzheimer’s memory impairment: mechanistic studies

Abstract Alzheimer’s disease (AD) is characterized by progressive memory and neuronal loss culminating in cognitive impairment that not only affects a person’s living ability but also becomes a society’s as well as a family’s economic burden. AD is the most common form of dementia in older persons. It is expected that the number of people with AD dementia will increase dramatically in the next 30 years, projecting to 75 million in 2030 and 131.5 million in 2050 worldwide. So far, no sufficient evidence is available to support that any medicine is able to prevent or reverse the progression of the disease. Early studies have shown that social environment, particularly social relationships, can affect one’s behavior and mental health. A study analyzing the correlation between loneliness and risk of developing AD revealed that lonely persons had higher risk of AD compared with persons who were not lonely. On the other hand, it has been reported that we can prevent cognitive decline and delay the onset of AD if we keep mentally active and frequently participate in social activities. In this review, we focus on the impact of social behaviors on the progression of cognitive deficit in animal models of AD with a particular emphasis on a mechanistic scheme that explains how social isolation exacerbates cognitive impairment and how social interaction with conspecifics rescues AD patients’ memory deficit