Sulforaphane Activates Brain-Derived Neurotrophic Factor (BDNF) Transcription by NF-E2-Related factor-2 (Nrf2), Showing Prevention Effects on the Microglial of Stressed Mice

Background: Accumulating evidence suggested that sulforaphane (SFN) showed prevention effects in stressed mice by activating the NF-E2-related factor-2 (Nrf2). However, the mechanism remains poorly understood. The present study aimed to investigate whether the prevention effects of SFN in stressed mice by activating brain-derived neurotrophic factor (BDNF) transcription on the microglial and revising abnormal dendritic spine morphology. Methods: In vitro study, we performed the Luciferase assay, Chromatin immunoprecipitation assay, Immunofluorescence, and Western blot to investigate whether SFN could activate Nrf2, resulting in BDNF transcription on the BV2 cell. In vivo study, we employed the Social defeat stress mice model, Behavior test, Western blots, Immunofluorescence, and Enzyme-linked immunosorbent assay to further explore whether the prevention effects of SFN in stressed mice by activating BDNF transcription on the microglial and revising abnormal dendritic spine morphology.Results: First, we found that SFN could activate Nrf2, resulting in Nrf2 binding to the BDNF exon I promoter, leading to BDNF protein expression on the BV2 cell. Second, SFN attenuated the decreased levels of Nrf2, and increased levels of MeCP2 expression, revising abnormal BDNF expression in the stressed mice. Third, we further found that the SFN could attenuate the decreased levels of Nrf2 and increased levels of MeCP2 expression on the microglial and revising microglial dysfunction in the stressed mice. Fourth, SFN could attenuate the increased levels of pro-inflammatory cytokine and the decreased levels of anti-inflammatory cytokine release in the stressed mice. Finally, SFN showed prevention effects and revised abnormal dendritic spine morphology in the stressed mice. Conclusions: Therefore, the prophylactic effects of SFN in the stressed mice by activating BDNF transcription on the microglial and revising abnormal dendritic spine morphology.

BDNF-TrkB signaling in oxytocin neurons contributes to maternal behavior

Brain-derived neurotrophic factor (Bdnf) transcription is controlled by several promoters, which drive expression of multiple transcripts encoding an identical protein. We previously reported that BDNF derived from promoters I and II is highly expressed in hypothalamus and is critical for regulating aggression in male mice. Here we report that BDNF loss from these promoters causes reduced sexual receptivity and impaired maternal care in female mice, which is concomitant with decreased oxytocin (Oxt) expression during development. We identify a novel link between BDNF signaling, oxytocin, and maternal behavior by demonstrating that ablation of TrkB selectively in OXT neurons partially recapitulates maternal care impairments observed in BDNF-deficient females. Using translating ribosome affinity purification and RNA-sequencing we define a molecular profile for OXT neurons and delineate how BDNF signaling impacts gene pathways critical for structural and functional plasticity. Our findings highlight BDNF as a modulator of sexually-dimorphic hypothalamic circuits that govern female-typical behaviors.

Chronic Mild Stress Modulates Activity-Dependent Transcription of BDNF in Rat Hippocampal Slices

Although activity-dependent transcription represents a crucial mechanism for long-lasting experience-dependent changes in the hippocampus, limited data exist on its contribution to pathological conditions. We aim to investigate the influence of chronic stress on the activity-dependent transcription of brain-derived neurotrophic factor (BDNF). Theex vivomethodology of acute stimulation of hippocampal slices obtained from rats exposed to chronic mild stress (CMS) was used to evaluate whether the adverse experience may alter activity-dependent BDNF gene expression. CMS reduces BDNF expression and that acute depolarization significantly upregulates total BDNF mRNA levels only in control animals, showing that CMS exposure may alter BDNF transcription under basal conditions and during neuronal activation. Moreover, while the basal effect of CMS on total BDNF reflects parallel modulations of all the transcripts examined, isoform-specific changes were found after depolarization. This different effect was also observed in the activation of intracellular signaling pathways related to the neurotrophin. In conclusion, our study discloses a functional alteration of BDNF transcription as a consequence of stress. Being the activity-regulated transcription a critical process in synaptic and neuronal plasticity, the different regulation of individual BDNF promoters may contribute to long-lasting changes, which are fundamental for the vulnerability of the hippocampus to stress-related diseases.

Nicotine induces chromatin remodelling through decreases in the methyltransferases GLP, G9a, Setdb1 and levels of H3K9me2

Studies examining the epigenetic effects of nicotine are limited, but indicate that nicotine can promote a transcriptionally permissive chromatin environment by increasing acetylation of histone H3 and H4. To further explore nicotine-induced histone modifications, we measured histone methyltransferase (HMT) mRNA expression as well as total and promoter-specific H3K9me2 levels. Following administration of nicotine, HMT mRNA and H3K9me2 levels were examined in mouse primary cortical neuronal culture and cortex extracted from mice injected intraperitoneally, as well as in human lymphocyte culture. Furthermore, Bdnf/BDNF mRNA levels were examined as an epigenetically regulated read-out of gene expression. There was a significant decrease of the HMT GLP, G9a and Setdb1 mRNA expression in the nicotine-treated tissue examined, with significant decreases seen in both total and promoter-specific H3K9me2 levels. Increasing doses of nicotine resulted in significant decreases in Bdnf/BDNF promoter specific H3K9me2 binding, leading to enhanced Bdnf/BDNF transcription. Taken together, our data suggest that nicotine reduces markers of a restrictive epigenomic state, thereby leading to a more permissive epigenomic environment.