Keratinocyte-Derived Cytokine in the Hippocampus Disrupts Extinction of Conditioned Fear Memory in Tumor-Bearing Mice.

While patients with cancer show a higher prevalence of psychiatric disorders than the general population, the mechanism underlying this interaction remains unclear. The present study examined whether tumor-bearing (TB) mice show psychological changes using the conditioned fear paradigm and the role of cytokines in these changes. TB mice were established by transplantation with mouse osteosarcoma AXT cells. These TB mice were then found to exhibit disruption in extinction of conditioned fear memory. Eighteen cytokines in serum were increased in TB mice, among which i.c.v. injection of interleukin (IL)-1ß and IL-6 strengthened fear memory in normal mice. Contents of IL-17 and keratinocyte-derived cytokine (KC) in the amygdala and KC in the hippocampus were increased in TB mice. KC mRNA in both the amygdala and hippocampus was also increased in TB mice, and i.c.v. injection of KC dose-dependently strengthened fear memory in normal mice. In addition, injection of IL-1ß, but not IL-6, increased KC mRNA in the amygdala and hippocampus. In TB mice KC mRNA was increased in both astrocytes and microglia of the amygdala and hippocampus. The microglia inhibitor minocycline, but not the astrocyte inhibitor fluorocitrate, alleviated disruption in extinction of conditioned fear memory in TB mice. Microinjection of KC into the hippocampus, but not into the amygdala, increased fear memory in normal mice. These findings indicate that TB mice show an increase in serum cytokines, including IL-1ß, that increases KC production in microglia of the hippocampus, which then disrupts extinction of fear memory.

Single cell molecular alterations reveal target cells and pathways of conditioned fear memory.

OBJECTIVES: Recent evidence indicates that hippocampus is important for conditioned fear memory (CFM). Though few studies consider the roles of various cell types' contribution to such a process, as well as the accompanying transcriptome changes during this process. The purpose of this study was to explore the transcriptional regulatory genes and the targeted cells that are altered by CFM reconsolidation. METHODS: A fear conditioning experiment was established on adult male C57 mice, after day 3 tone-cued CFM reconsolidation test, hippocampus cells were dissociated. Using single cell RNA sequencing (scRNA-seq) technique, alterations of transcriptional genes expression were detected and cell cluster analysis were performed and compared with those in sham group. RESULTS: Seven non-neuronal and eight neuronal cell clusters (including four known neurons and four newly identified neuronal subtypes) has been explored. Among them, CA subtype 1 has characteristic gene markers of Ttr and Ptgds, which is speculated to be the outcome of acute stress and promotes the production of CFM. The results of KEGG pathway enrichment indicate the differences in the expression of certain molecular protein functional subunits in long-term potentiation (LTP) pathway between two types of neurons (DG and CA1) and astrocytes, thus providing a new transcriptional perspective for the role of hippocampus in the CFM reconsolidation. More importantly, the correlation between the reconsolidation of CFM and neurodegenerative diseases-linked genes is substantiated by the results from cell-cell interactions and KEGG pathway enrichment. Further analysis shows that the reconsolidation of CFM inhibits the risk-factor genes App and ApoE in Alzheimer's Disease (AD) and activates the protective gene Lrp1. CONCLUSIONS: This study reports the transcriptional genes expression changes of hippocampal cells driven by CFM, which confirm the involvement of LTP pathway and suggest the possibility of CFM-like behavior in preventing AD. However, the current research is limited to normal C57 mice, and further studies on AD model mice are needed to prove this preliminary conclusion.

Neurobiological mechanisms in the regulation of conditioned fear memory by the retrieval-extinction paradigm / 中华行为医学与脑科学杂志

Fear memories are temporarily suppressed after repeated retrieval, a phenomenon known as memory extinction.How to reduce or even eliminate fear memory is the key to the treatment of fear related diseases such as post-traumatic stress disorder(PTSD). A single extinction training based on Pavlov's fear regulation task could only inhibit the expression of conditioned fear memory traces, but it could not eliminate the acquired conditioned fear memory. However, according to the reconsolidation theory based on memory, the retrieval-extinction paradigm has a more lasting effect on the erasure and rewriting of fear memory, and can effectively prevent the return of fear memory. Studies have shown that extraction-regression is closely related to a variety of neurotransmitter receptors such as glutamate receptor(GluR), dopamine receptor(DAR), L-type voltage-gated calcium channels(LVGCs) and cannabinoid. Moreover, its effect is closely related with factors such as retrieval-extinction memory stage. At present, most of the researches on extracted boundary conditions only stay at the level of behavior, with little understanding and exploration on the level of molecular mechanism. From the perspective of molecular neurobiology, with different stages of memory and different types of receptors and molecular mechanisms, this research reviewed the mechanisms of retrieval-extinction in recent years.It provided valuable signaling pathways, molecular targets and research directions for the treatment of fear-related diseases such as PTSD.

Comparative metabolic profiling of posterior parietal cortex, amygdala, and hippocampus in conditioned fear memory.

Fear conditioning and retrieval are suitable models to investigate the biological basis of various mental disorders. Hippocampus and amygdala neurons consolidate conditioned stimulus (CS)-dependent fear memory. Posterior parietal cortex is considered important for the CS-dependent conditioning and retrieval of fear memory. Metabolomic screening among functionally related brain areas provides molecular signatures and biomarkers to improve the treatment of psychopathologies. Herein, we analyzed and compared changes of metabolites in the hippocampus, amygdala, and posterior parietal cortex under the fear retrieval condition. Metabolite profiles of posterior parietal cortex and amygdala were similarly changed after fear memory retrieval. While the retrieval of fear memory perturbed various metabolic pathways, most metabolic pathways that overlapped among the three brain regions had high ranks in the enrichment analysis of posterior parietal cortex. In posterior parietal cortex, the most perturbed pathways were pantothenate and CoA biosynthesis, purine metabolism, glutathione metabolism, and NAD+ dependent signaling. Metabolites of posterior parietal cortex including 4'-phosphopantetheine, xanthine, glutathione, ADP-ribose, ADP-ribose 2'-phosphate, and cyclic ADP-ribose were significantly regulated in these metabolic pathways. These results point to the importance of metabolites of posterior parietal cortex in conditioned fear memory retrieval and may provide potential biomarker candidates for traumatic memory-related mental disorders.

Increase in brain l-lactate enhances fear memory in diabetic mice: Involvement of glutamate neurons.

Previous reports suggest that diabetes mellitus is associated with psychiatric disorders, including depression and anxiety, but the mechanisms involved are unknown. We have reported that streptozotocin (STZ)-induced diabetic mice show enhancement of conditioned fear memory. To clarify the mechanisms through which diabetes affects conditioned fear memory, the present study investigated the role of l-lactate and glutamatergic function in enhancement of conditioned fear memory in diabetes. l-lactate levels in the amygdala and hippocampus, which are known to play important roles in fear memory, were significantly increased in STZ-induced diabetic mice. The glucose transporter (GLUT) 1 was significantly increased both in the amygdala and in the hippocampus. In contrast, GLUT3, the monocarboxylic acid transporter (MCT) 1 and MCT2 in the amygdala and hippocampus were not altered in STZ-induced diabetic mice. I.c.v. injection of l-lactate to non-diabetic mice significantly increased duration of freezing, whereas the MCT inhibitor 4-CIN significantly inhibited duration of freezing in STZ-induced diabetic mice. Injection of l-lactate significantly increased glutamate levels in the amygdala and hippocampus. Duration of freezing induced by l-lactate was significantly inhibited by the AMPA receptor antagonist NBQX. In addition, injection of NBQX into the amygdala and hippocampus significantly inhibited duration of freezing in STZ-induced diabetic mice. These results suggest that l-lactate levels are increased in the amygdala and hippocampus in diabetic mice, which may enhance fear memory though activation of glutamatergic function in the amygdala and hippocampus.

Orengedokuto and san'oshashinto improve memory deficits by inhibiting aging-dependent activation of glycogen synthase kinase-3ß.

BACKGROUND AND AIM: The aging-dependent activation of glycogen synthase kinase-3ß (GSK-3ß) has been suggested to be important in the onset of dementia. To discover novel therapeutic Kampo medicines for dementia, we examined the effects of orengedokuto (OGT; huáng lián jiedú tang) and san'oshashinto (SST; san huáng xiè xin tang) on memory deficits and GSK-3ß activity in senescence-accelerated prone mice (SAMP8). EXPERIMENTAL PROCEDURE: The object recognition test (ORT) and conditioned fear memory test (CFT) were employed to elucidate short-term working memory and long-term fear memory. The activity of GSK-3ß and the phosphorylation of related molecules were measured using a kinase assay and Western blotting. RESULTS AND CONCLUSION: OGT and SST attenuated memory deficits in SAMP8 in ORT, but not in CFT. In ex vivo experiments, cortical GSK-3ß activity was significantly stronger in SAMP8 than in SAMR1. The enhanced cortical GSK-3ß activity in SAMP8 was accompanied by a significant increase in the level of phosphorylated collapsin response mediator protein-2 (CRMP2), an important factor that is involved in the regulation of microtubule stability. OGT and SST attenuated not only increases in cortical GSK-3ß activity, but also the levels of phosphorylated CRMP2 in SAMP8. In vitro experiments, flavonoids contained in these kampo medicines, inhibited GSK-3ß activity in concentration-dependent manners. These results suggest that OGT and SST prevent aging-induced short-term working memory deficits by inhibiting aging-dependent elevations in the cortical GSK-3ß activity and subsequent CRMP2 phosphorylation.

Abolishment of fear memory-disruptive effects REM sleep deprivation by harmane.

Harmane, as a neuromodulator, implicates in the learning and memory processes. However, rapid eye movement (REM) sleep deprivation negatively affects these processes. Here, we investigated the effects of harmane (2.5 mg/kg) on the regulation of fear memory in free moving groups (FMG), large platform groups (LPG) and REM-deprived mice. We employed a flower pot technique for REM sleep deprivation and a Pavlovian fear conditioning paradigm for assessment of fear memories. FMGs received two or three pre-training intraperitoneal administrations of harmane at 12 h intervals, impaired contextual memory retention but those received three harmane administrations showed an auditory memory disruption. LPGs, with or without harmane, did not alter fear memories compared to their respective FMGs, indicating the inability of stress on fear responses of FMGs. Moreover, 12, 24 and 36 h REM sleep deprivation impaired contextual memory retrieval, while 24 and 36 h REM sleep deprivation impaired auditory fear memory retention. Furthermore, harmane only abolished contextual and auditory fear memory deficits induced by 24 h REM sleep deprivation. The data suggests a modulatory role for harmane in REM sleep deprivation response on fear memory.

Role of the amygdala GABA-A receptors in ACPA-induced deficits during conditioned fear learning.

The basolateral amygdala (BLA) is a key structure for the emotional processing and storage of memories associated with emotional events, especially fear. On the other hand, endocannabinoids and CB1 receptors play a key role in learning and memory partly through long-term synaptic depression of GABAergic synapses in the BLA. The aim of this study was to explore the effects of GABA-A receptor agonist and antagonist in the fear-related memory acquisition deficits induced by ACPA (a selective CB1 cannabinoid receptor agonist). This study used context and tone fear conditioning paradigms to assess fear-related memory in male NMRI mice. Our results showed that the pre-training intraperitoneal administration of ACPA (0.5mg/kg) or (0.1 and 0.5mg/kg) decreased the percentage of freezing time in the contextual and tone fear conditioning, respectively. This indicated an impaired context- or tone-dependent fear memory acquisition. Moreover, the pre-training intra-BLA microinjection of GABA-A receptor agonist, muscimol, at 0.05 and 0.5µg/mouse impaired context-dependent fear memory, while the same doses of GABA-A antagonist, bicuculline, impaired tone-dependent fear memory. However, a subthreshold dose of muscimol or bicuculline increased the effect of ACPA at 0.1 and 0.5 or 0.05mg/kg on context- or tone-dependent fear memory, respectively. In addition, bicuculline at the lower dose increased the ACPA response on locomotor activity compared to its respective group. Such findings highlighted an interaction between BLA GABAergic and cannabinoidergic systems during the acquisition phase of conditioned fear memories.

Neurobiological mechanisms of conditioned fear memory reconsolidation / 中国病理生理杂志

Post-traumatic stress disorder (PTSD) is a reactive mental disorder that occurs after an individual was exposed to a traumatic event,and the core of the treatment is the extinction of conditioned fear memory caused by stress.Fear memory is an incentive mechanism based on external stimuli that occupy a central position in the defense system.Traditional memory concept convinced that the original memory traces were in an unstable state when the memory was activated.This process is called memory reconsolidation.The research has proved the existence of the fear memory reconsolidation,but the specific mechanism of reconsolidation has not been clarified.The animal studies show that many brain sites and molecular mechanisms are involved in the process of fear memory reconsolidation.Understanding the underlying mechanisms of fear memory reconsolidation is conducive to the treatment of specific phobias and PTSD.This review summarized the brain structure and molecular mechanism of conditioned fear memory reconsolidation,providing a new direction for the in-depth study of conditioned fear memory reconsolidation and PTSD.

Neurobiological mechanisms of conditioned fear memory reconsolidation / 中国病理生理杂志

Post-traumatic stress disorder (PTSD) is a reactive mental disorder that occurs after an individual was exposed to a traumatic event,and the core of the treatment is the extinction of conditioned fear memory caused by stress.Fear memory is an incentive mechanism based on external stimuli that occupy a central position in the defense system.Traditional memory concept convinced that the original memory traces were in an unstable state when the memory was activated.This process is called memory reconsolidation.The research has proved the existence of the fear memory reconsolidation,but the specific mechanism of reconsolidation has not been clarified.The animal studies show that many brain sites and molecular mechanisms are involved in the process of fear memory reconsolidation.Understanding the underlying mechanisms of fear memory reconsolidation is conducive to the treatment of specific phobias and PTSD.This review summarized the brain structure and molecular mechanism of conditioned fear memory reconsolidation,providing a new direction for the in-depth study of conditioned fear memory reconsolidation and PTSD.