Histone deacetylase-2 is involved in stress-induced cognitive impairment via histone deacetylation and PI3K/AKT signaling pathway modification.

Exposure to chronic stress upregulates blood glucocorticoid levels and impairs cognition via diverse epigenetic mechanisms, such as histone deacetylation. Histone deacetylation can lead to transcriptional silencing of many proteins involved in cognition and may also cause learning and memory dysfunction. Histone deacetylase­2 (HDAC2) has been demonstrated to epigenetically block cognition via a reduction in the histone acetylation level; however, it is unknown whether HDAC2 is involved in the cognitive decline induced by chronic stress. To the best of authors' knowledge, this is the first study to demonstrate that the stress hormone corticosteroid upregulate HDAC2 protein levels in neuro­2a cells and cause cell injuries. HDAC2 knockdown resulted in a significant amelioration of the pathological changes in N2a cells via the upregulation of histone acetylation and modifications in the phosphoinositide 3­kinase/protein kinase B signaling pathway. In addition, the HDAC2 protein levels were upregulated in 12­month­old female C57BL/6J mice under chronic stress in vivo. Taken together, these findings suggested that HDAC2 may be an important negative regulator involved in chronic stress­induced cognitive impairment.

[Change of Ankyrin G Promoter Activity Following Treatment with Sodium Valproate at Different Concentrations].

OBJECTIVE: To investigate whether sodium valproate (VPA) directly regulates the activity of Ankyrin G(AnkG) promoter in vitro. METHODS: The mouse AnkG promoter sequence was identified by comparing both human and mouse AnkG promoter sequences. The promoter was amplified from C57BL/6 mouse genome DNA and cloned into pGL3 Luciferase reporter vector. The Luciferase activity was detected in N2a and 293T cells and then treated with 0,0.5, and 1 mmol/L VPA for 12 h. The transcription activity of AnkG promoter in cells and the activity of VPA-treated Luciferase reporter vector in cells were detected using dual Luciferase reporter assay. RESULTS: The AnkG promoter clone and its expression vector were successfully established, as confirmed by enzyme digestion and sequencing. The AnkG promoter showed high transcription activity in both N2a and 293T cells. The Luciferase activity was significantly induced following 0.5 mmol/L VPA treatment in both N2a and 293T cells. CONCLUSIONS VPA can up-regulate the AnkG expression via directly increasing its transcription activity. Thus, the in vivo AnkG expression may be directly regulated by the VPA at transcriptional level.

Tubastatin A/ACY-1215 improves cognition in Alzheimer's disease transgenic mice.

Histone deacetylase 6 (HDAC6) is currently being discussed as a promising therapeutic target for the treatment of Alzheimer's disease (AD). Mounting evidence indicates that increased HDAC6 expression may contribute to AD-associated neurodegeneration, although beneficial effects have also been identified. In the present study, we tested the potential of two selective HDAC6 inhibitors, tubastatin A and ACY-1215, to rescue cognitive deficits in a mouse model of AD. We found that both tubastatin A and ACY-1215 alleviated behavioral deficits, altered amyloid-ß (Aß) load, and reduced tau hyperphosphorylation in AD mice without obvious adverse effects. Our data suggested that tubastatin A and ACY-1215 not only promoted tubulin acetylation, but also reduced production and facilitated autophagic clearance of Aß and hyperphosphorylated tau. Further, the decreased hyperphosphorylated tau and increased tubulin acetylation may account for the improved microtubule stability in AD mice after tubastatin A/ACY-1215 treatment. These preclinical results support the detrimental role of HDAC6 in AD, and offer prospective approaches for using tubastatin A/ACY-1215 as potential therapeutic strategy for AD.