Single-prolonged stress activates the transcription factor ATF6α branch of the unfolded protein response in rat neurons of dorsal raphe nucleus

Baicalein exerts anxiolytic and antinociceptive effects in a mouse model of posttraumatic stress disorder: Involvement of the serotonergic system and spinal delta-opioid receptors

Post-traumatic stress disorder (PTSD) is a serious mental disease featured by a stress dysfunction that occurs after an individual has faced intense mental stress, often accompanied by anxiety and chronic pain. Currently, the mainstream drug for PTSD is serotonin reuptake inhibitors (SSRIs), however, their pain management for patients is limited. Baicalein, a Chinese traditional herbal medicine, has shown promising results in treating anxiety, depression, and pain. In this study, we found that baicalein may alleviate single prolonged stress (SPS)-induced PTSD-like behaviors in mice without altering baseline nociceptive sensitivity or activity. Meanwhile, baicalein increased the noradrenaline (NE) and serotonin (5-HT) content and decreased the ratio of 5-hydroxyindoleacetic acid (5-HIAA)/5-HT by inhibiting the activity of monoamine oxidase A (MAO-A) in SPS-induce mice. The anxiolytic and antinociceptive effects induced by baicalein were totally abolished by 5-HT depleting agents. Moreover, the anxiolytic effects of baicalein could be abolished by the 5-HT_1A receptor antagonist WAY-100635, and the analgesic effects could be abolished by delta-opioid receptor antagonists in the spinal. Taken together, our study provides compelling evidence that baicalein reversed anxiety-like behaviors and neuropathic pain in PTSD through serotonergic system and spinal delta-opioid receptors.

Activated cell-cycle CDK4/CyclinD1-pRB-E2F1 signaling pathway is involved in the apoptosis of dorsal raphe nucleus in the rat model of PTSD

Dysregulation of the dorsal raphe nucleus (DRN) has been revealed to contribute to cognitive and arousal impairments associated with post-traumatic stress disorder (PTSD) in an animal model. In our research an acute exposure to single prolonged stress (SPS) was used to establish PTSD rat model and the effects related to cell-cycle signaling pathway in DRN were examined. Apoptosis in DRN was detected by TUNEL staining, showing that DRN apoptosis number was sharply increased after SPS. SPS triggered cell-cycle CDK4/CyclinD1-pRB-E2F1 signal pathway. Treatment with CDK4 inhibitor Abemaciclib successfully attenuated the DRN apoptosis and rescued decreased spatial learning and memory abilities in SPS rats, indicating that activation of CDK4/CyclinD1-pRB-E2F1 pathway was involved in DRN apoptosis, which may be one of the pathogenesis for PTSD.

Downregulation of miR156-Targeted PvSPL6 in Switchgrass Delays Flowering and Increases Biomass Yield

MiR156/SQUAMOSA PROMOTER BINDING-LIKEs (SPLs) module is the key regulatory hub of juvenile-to-adult phase transition as a critical flowering regulator. In this study, a miR156-targeted PvSPL6 was identified and characterized in switchgrass (Panicum virgatum L.), a dual-purpose fodder and biofuel crop. Overexpression of PvSPL6 in switchgrass promoted flowering and reduced internode length, internode number, and plant height, whereas downregulation of PvSPL6 delayed flowering and increased internode length, internode number, and plant height. Protein subcellular localization analysis revealed that PvSPL6 localizes to both the plasma membrane and nucleus. We produced transgenic switchgrass plants that overexpressed a PvSPL6-GFP fusion gene, and callus were induced from inflorescences of selected PvSPL6-GFP_OE transgenic lines. We found that the PvSPL6-GFP fusion protein accumulated mainly in the nucleus in callus and was present in both the plasma membrane and nucleus in regenerating callus. However, during subsequent development, the signal of the PvSPL6-GFP fusion protein was detected only in the nucleus in the roots and leaves of plantlets. In addition, PvSPL6 protein was rapidly transported from the nucleus to the plasma membrane after exogenous GA₃ application, and returned from the plasma membrane to nucleus after treated with the GA₃ inhibitor (paclobutrazol). Taken together, our results demonstrate that PvSPL6 is not only an important target that can be used to develop improved cultivars of forage and biofuel crops that show delayed flowering and high biomass yields, but also has the potential to regulate plant regeneration in response to GA₃.

TLR4/MyD88/NF-κB-Mediated Inflammation Contributes to Cardiac Dysfunction in Rats of PTSD

Post-traumatic stress disorder (PTSD) is related with myocardial injury and cardiac dysfunction, while the molecular mechanism has not been clear. This study investigated whether TLR4/MyD88/NF-κB-mediated inflammation involved in myocardial injury of PTSD. Adult male Wistar rats were exposed to single-prolonged stress (SPS), which was used broadly as a animal model of PTSD. Morris Water Maze (MWM) test and forced swimming test (FST) was carried out for behavioral testing. The protein expression of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) in the left ventricular of heart and TLR4/MyD88/NF-κB-mediated inflammation were examined. Our results showed that there were obvious increased in the protein expression of ANP and BNP in heart after exposure to SPS, SPS also significantly enhanced the serum level of IL-1β and TNF-α, and meanwhile, the TLR4/MyD88/NF-κB pathway were activated. These results demonstrated that the TLR4/MyD88/NF-κB pathway were involved in the myocardial injury of PTSD, which might be one of possible molecular mechanism contributed to the pathogenesis of cardiac dysfunction in PTSD.

Involvement of calcineurin/NFATc4 pathway in a single-prolonged stress-based rat model of post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is a mental disease associated with the exposure of traumatic stress, and results in the structural and functional changes of hippocampus. Calcineurin (CaN), a calcium/calmodulin-regulated protein phosphatase ubiquitously expressed in brain, has a very important role in the fear extinction, neuronal structure and neuronal excitability. With CaN activation, its down target nuclear factor of activated T cells (NFATs) dephosphorylated and then translocated from the cytoplasm to the nucleus to affect neuronal function, resulting in the function changes of brain structure such as hippocampus. Increasing evidence has suggested that CaN/NFATs signaling are involved in the regulation of mental disorders like Alzheimer's disease, depression, while little is known about its effects on the molecular mechanisms on PTSD. This study seek to know the relationship between PTSD and CaN/NFATc4 pathway, and to detect whether CaN/NFATc4 pathway are involved in the hippocampus dysfunctions in a single-prolonged stress (SPS)-based rat model of PTSD. Our results have showed that after 4 days exposed to SPS, the protein expression of CaN up-regulated and the NFATc4 dephosphorylated and imported into the nucleus; while at the 7 and 14 day exposed to SPS, with the down-regulation of CaN, the expression of phosphorylate-NFATc4 increased. Our results show that CaN/NFATc4 pathway were involved in the development of PTSD model, which suggested that the changes of CaN/NFATc4 pathway may be one of the pathological molecular mechanism in the dysfunction of hippocampus in PTSD.

Role of apoptosis in the Post-traumatic stress disorder model-single prolonged stressed rats

Post-traumatic stress disorder (PTSD) is a stress-related mental disorder which occurs following exposure to traumatic events. A number of brain neuroimaging studies have revealed that PTSD patients have reduced volume and abnormal functions in the hippocampus and the amygdala. However, the pathogenesis of abnormalities in certain brain regions, as induced by PTSD, remains unclear. Recent studies, using the single prolonged stress (SPS) model, an animal model of PTSD, have found that abnormal apoptosis in certain brain regions, including the hippocampus, the amygdala, and the medial prefrontal cortex (mPFC); these areas are closely associated with emotion and cognition. In this review, we summarize the mechanism of apoptosis in SPS rats, including the endoplasmic reticulum (ER) and the mitochondria pathways. For the ER pathway, three individual pathways: PERK, IRE1, and ATF6 showed different roles on apoptosis and neuroprotection. Three key factors are thought to be involved in the mitochondrial pathway and PTSD-induced apoptosis: corticosteroid receptors, apoptosis-related factors, and anti-apoptosis factors. We have investigated the role of these factors and have attempted to identify which factors of the pathways are more focused towards neuronal protection, and which are more direct towards apoptosis. We also discussed the role of autophagy and the specific differences between autophagy and apoptosis in SPS rats. Finally, we discussed emerging researches related to anti-apoptosis treatment, including PERK inhibitors, IRE1 inhibitors, and metformin; collectively, these were exciting, but limited, This review provides a summary of the current understanding of apoptosis in SPS rats and the potential anti-apoptosis treatment strategies for PTSD.

The nuclear transportation routes of membrane-bound transcription factors

Membrane-bound transcription factors (MTFs) are transcription factors (TFs) that are anchored in membranes in a dormant state. Activated by external or internal stimuli, MTFs are released from parent membranes and are transported to the nucleus. Existing research indicates that some plasma membrane (PM)-bound proteins and some endoplasmic reticulum (ER) membrane-bound proteins have the ability to enter the nucleus. Upon specific signal recognition cues, some PM-bound TFs undergo proteolytic cleavage to liberate the intracellular fragments that enter the nucleus to control gene transcription. However, lipid-anchored PM-bound proteins enter the nucleus in their full length for depalmitoylation. In addition, some PM-bound TFs exist as full-length proteins in cell nucleus via trafficking to the Golgi and the ER, where membrane-releasing mechanisms rely on endocytosis. In contrast, the ER membrane-bound TFs relocate to the nucleus directly or by trafficking to the Golgi. In both of these pathways, only the fragments of the ER membrane-bound TFs transit to the nucleus. Several different nuclear trafficking modes of MTFs are summarized in this review, providing an effective supplement to the mechanisms of signal transduction and gene regulation. Moreover, targeting intracellular movement pathways of disease-associated MTFs may significantly improve the survival of patients.

Molecular Mechanisms of IRE1α-ASK1 Pathway Reactions to Unfolded Protein Response in DRN Neurons of Post-Traumatic Stress Disorder Rats

The goal of this study was to further elucidate the molecular mechanisms of post-traumatic stress disorder (PTSD) pathogenesis and to provide experimental evidence for new drug targets for effective PTSD treatment. Expression changes of IRE1α, ASK1, and other downstream molecules of the IRE1α-ASK1 endoplasmic reticulum stress (ERS) signaling pathway were investigated. JNK, P38, CHOP, Bcl-2, and Bax were analyzed at both protein and mRNA levels of dorsal raphe nucleus (DRN) neurons of PTSD rats. The rat PTSD model was established via the single-prolonged stress (SPS) method. Animals were randomly divided into five groups: a normal control group, a 1-day SPS group, a 4-days SPS group, a 7-day SPS group, and a 14-day SPS group. Spatial memory and learning ability of rats were evaluated subsequent to SPS using the Morris water maze test. Changes of IRE1α expression in the control and SPS groups were detected via immunohistochemistry (IHC). Protein and mRNA expressions of IRE1α, ASK1, JNK, P38, CHOP, Bcl-2, and Bax in the control and SPS groups were detected via Western blot and RT-PCR, respectively. The Morris water maze test revealed significantly longer average escape latencies in all SPS groups compared to the control group. In the spatial probe test, the percentage of time spent in the target quadrant was significantly lower in the SPS groups compared to control. IHC revealed increased positive expression of IRE1α subsequent to SPS challenge, reaching maximal levels on days four and seven (P < 0.01), while significantly decreasing on day 14 (P < 0.01). Western blot and RT-PCR revealed that protein and mRNA expressions of IRE1α, ASK1, JNK, CHOP, and P38 were significantly increased compared to control, peaking on days one, four, and seven post-SPS before returning to previous levels. Compared to control, expressions of Bcl-2 and Bax presented an initial increasing tendency followed by a decrease. A peak of Bcl-2 expression appeared early on day one following SPS, then decreased to a steady level. Bax expression in the SPS groups remained constant during early stages after SPS (days one to three) compared to control; however, expression significantly increased on day four and maintained a high level. In summary, 1) SPS challenge significantly activated the IRE1α-ASK1-JNK and IRE1α-ASK1-P38 apoptosis-signaling pathways in DRN neurons of PTSD rats. This resulted in a cascade of downstream reactions and ultimately apoptosis of DRN neurons. 2) Increased expression of apoptosis-associated molecules Bcl-2 and Bax in DRN neurons following SPS challenge was revealed as a central mechanism, inducing apoptosis of DRN neurons in PTSD rats.