DNA methylation of the Tacr2 gene in a CUMS model of depression.

Tacr2, the gene encoding the NK2 receptor, belongs to G protein-coupled receptors. Accumulating evidence has indicated that the tachykinin receptors may contribute to the pathophysiology of depression. During the last decade, some studies have shown that Tacr2 activation is involved in the modulation of emotional processes. However, the extent, to which stress impacts Tacr2 expression remains unclear. The molecular mechanisms underlying depression also remain poorly understood. In this study, we subjected adult male Sprague Dawley (SD) rats to chronic unpredictable mild stress (CUMS) to induce a depression-like phenotype. We then measured the body weight and performed the sucrose preference test, forced swimming test (FST) and open field test to detect the effects of stress on anhedonia and activity. Western blotting and real-time PCR were used to study the protein and mRNA expression levels of Tacr2, respectively, in the hypothalamus. To explore DNA methylation of the Tacr2 gene, we used methylated DNA immunoprecipitation sequencing (MeDIP-seq). Additionally, we used the bisulfite sequencing PCR (BSP) to further verify the DNA methylation levels of the Tacr2 receptor gene in rats. We found that the CUMS-sensitive rats exhibited a decrease in body weight and sucrose preference, a decrease in the distance traveled, rearing frequency and velocity in the open field test, and an increase in immobility time in the FST. Compared with the expression in the control rats, Tacr2 protein and mRNA expression in the hypothalamus significantly increased in the CUMS-sensitive rats; however, the DNA methylation levels of the Tacr2 gene were significantly lower than in the control rats. In summary, according to our findings, the stress-induced increase in Tacr2 expression in the hypothalamus correlated with a specific decrease in DNA methylation of the Tacr2 gene. These results may enrich the understanding of the pathological processes of depression and provide insights into therapeutic approaches for its treatment.

WSKY, a traditional Chinese decoction, rescues cognitive impairment associated with NMDA receptor antagonism by enhancing BDNF/ERK/CREB signaling.

Warm­supplementing kidney yang (WSKY) is an herbal prescription that has been used in Traditional Chinese Medicine for the treatment of psychiatric conditions. A previous study by our group found that WSKY significantly improved cognitive function of schizophrenia patients. In the present study, the effects of WSKY on cognitive function and their underlying mechanisms were investigated. WSKY was administered to an MK­801­induced rat model of chronic schizophrenia for 14 days. Memory performance was assessed using the Morris water maze (MWM) test. The expression of brain­derived neurotrophic factor (BDNF), activation of cAMP response element binding protein (pCREB/CREB) and activation of extracellular signal­regulated kinase (pERK/ERK) in the hippocampus was detected using western blot analysis. In the acquisition phase of the MWM test, the escape latency was significantly increased in the MK­801­treated group compared with the normal control group (P<0.01). Treatment with WSKY for 14 days at doses of 100 or 250 mg/kg rescued this cognitive impairment (P<0.05). In the probe test, 250 mg/kg WSKY treatment increased the time spent in the target quadrant (P<0.05) and number of platform crossings (P<0.01). Western blot analysis demonstrated that the levels of BDNF expression in the hippocampus of rats without behavioral tests were elevated following 14 days of WSKY treatment, and the effect of WSKY treatment on hippocampal BDNF expression was presented in an inverted U­shaped dose­response pattern. The pERK1/2 in the hippocampus was significantly enhanced following 100 mg/kg (P<0.01) and 250 mg/kg (P<0.01) WSKY treatment, while only 250 mg/kg WSKY increased the phosphorylation of CREB (P<0.01). The results of the present study indicated that WSKY enhances cognitive performance via the upregulation of BDNF/ERK/CREB signaling, and that WSKY has potential therapeutic implications for cognitive impairment of schizophrenia.

Histone modifications of the Crhr1 gene in a rat model of depression following chronic stress.

Multiple lines of evidence suggest a link between depression and changes in hypothalamic-pituitary-adrenal (HPA)-axis hormone dynamics, including altered regulation of the corticotrophin-releasing hormone (CRH) and its main receptor, corticotrophin-releasing hormone receptor 1 (CRHR1). However, the precise molecular mechanisms underlying depression remain poorly understood. In this study, we employed a model of depression in rats by subjecting animals to 21 days of chronic unpredictable mild stress (CUMS). Real-time PCR and western blotting were used to study the mRNA and protein expression levels of CRHR1 in the hypothalamus. In addition, chromatin immunoprecipitation assays were used to detect histone methylation at the Crhr1 gene promoter; the levels of histone H3 trimethylation at lysines 4 (H3K4) and 9 (H3K9) reflect active transcription and transcriptional repression, respectively. Rats exposed to CUMS exhibited significant reduction in locomotion and sucrose preference. These behavioral alterations were associated with elevated expression levels of CRHR1 mRNA and protein in the hypothalamus of rats in the CUMS group. We also found that the levels of H3K9 trimethylation at the Crhr1 gene promoter in the CUMS group were significantly lower than those in the control group, whereas H3K4 trimethylation levels were the same for both groups. Taken together, our findings suggest that the increase in CRHR1 expression in the hypothalamus of stressed rats correlates with a decrease in the repressive chromatin state caused by reduced H3K9 trimethylation levels. These data are the first in vivo evidence of a role for chromatin modifications in the regulation of Crhr1 gene expression in the hypothalamus, and may provide novel insight into therapeutic approaches to treat depression.

Recombinant human foamy virus, a novel vector for neurological disorders gene therapy, drives production of GAD in cultured astrocytes.

Human foamy virus (HFV), with its nonpathogenic nature and several unique features for gene transfer, is a promising vector system for neurological disorders gene therapy. The question of whether HFV vectors can be developed for the expression of therapeutic genes in primary astrocytes of the brain may be of interest. First, efficient expression for foreign genes, which is critical for the potentials of HFV-derived vector in gene therapy, was successfully demonstrated in rat-cultured astrocytes by the enhanced green fluorescent protein (EGFP) transduction through an HFV vector bearing an EGFP expression cassette. Second, HFV vectors containing human glutamic acid decarboxylase (GAD) complementary DNA, which encodes an inhibitory neurotransmitter gamma-aminobutyric acid (GABA)-producing enzyme, were used to examine the function of GAD on GABA synthesis in cultured astrocytes. We found that the transduction of GAD vector resulted in isoform-specific expression of GAD, synthesis of a significant amount of GABA and tonical GABA release, and behavioral recovery in rat Parkinson's disease (PD) models. These results suggested that HFV vector had the ability to transduce astrocytes and HFV vector-derived GAD expression in astrocytes provided a potential strategy for the treatment of neurological disorders associated with hyperexcitable or diminished inhibitory activity.