CK2 negatively regulates the extinction of remote fear memory

Cognitive behavioral therapy, rooted in exposure therapy, is currently the primary approach employed in the treatment of anxiety-related conditions, including post-traumatic stress disorder (PTSD). In laboratory settings, fear extinction in animals is a commonly employed technique to investigate exposure therapy; however, the precise mechanisms underlying fear extinction remain elusive. Casein kinase 2 (CK2), which regulates neuroplasticity via phosphorylation of its substrates, has a significant influence in various neurological disorders, such as Alzheimer's disease and Parkinson's disease, as well as in the process of learning and memory. In this study, we adopted a classical Pavlovian fear conditioning model to investigate the involvement of CK2 in remote fear memory extinction and its underlying mechanisms. The results indicated that the activity of CK2 in the medial prefrontal cortex (mPFC) of mice was significantly upregulated after extinction training of remote cued fear memory. Notably, administration of the CK2 inhibitor CX-4945 prior to extinction training facilitated the extinction of remote fear memory. In addition, CX-4945 significantly upregulated the expression of p-ERK1/2 and p-CREB in the mPFC. Our results suggest that CK2 negatively regulates remote fear memory extinction, at least in part, by inhibiting the ERK-CREB pathway. These findings contribute to our understanding of the underlying mechanisms of remote cued fear extinction, thereby offering a theoretical foundation and identifying potential targets for the intervention and treatment of PTSD.

Infralimbic YTHDF1 is necessary for the beneficial effects of acute mild exercise on auditory fear extinction retention

Exposure therapy is the most effective approach of behavioral therapy for anxiety and post-traumatic stress disorder (PTSD). But fear is easy to reappear even after successful extinction. So, identifying novel strategies for augmenting exposure therapy is rather important. It was reported that exercise had beneficial effects on cognitive and memory deficits. However, whether exercise could affect fear memory, especially for fear extinction remained elusive. Here, our results showed that exposure to acute mild exercise 1 or 2 h before extinction training can augment recent fear extinction retention and 2 h for the remote fear extinction retention. These beneficial effects could be attributed to increased YTHDF1 expression in medial prefrontal cortex (mPFC). Furthermore, by using an AAV-shRNA-based approach to silence YTHDF1 expression via stereotactic injection in prelimbic cortex (PL) or infralimbic cortex (IL), respectively, we demonstrated that silence YTHDF1 in IL, but not in PL, blunted augmentation of exposure therapy induced by acute mild exercise and accompanied with decreased NR2B and GluR1 expression. Moreover, YTHDF1 modulated dendritic spines remodeling of pyramidal neuron in IL. Collectively, our findings suggested that acute mild exercise acted as an effective strategy in augmenting exposure therapy with possible implications for understanding new treatment underlying PTSD.

The Retrotransposition of L1 is Involved in the Reconsolidation of Contextual Fear Memory in Mice

BACKGROUND

The long interspersed element-1 (L1) participates in memory formation, and DNA methylation patterns of L1 may suggest resilience or vulnerability factors for Post-Traumatic Stress Disorder (PTSD), of which the principal manifestation is a pathological exacerbation of fear memory. However, the unique roles of L1 in the reconsolidation of fear memory remain poorly understood.

OBJECTIVE

The study aimed to investigate the role of L1 in the reconsolidation of context-dependent fear memory.

METHODS

Mice underwent fear conditioning and fear recall in the observation chambers. Fear memory was assessed by calculating the percentage of time spent freezing in 5 min. The medial prefrontal cortex (mPFC) and hippocampus were removed for further analysis. Open Reading Frame 1 (ORF1) mRNA and ORF2 mRNA of L1 were analyzed by real-time quantitative polymerase chain reaction. After reactivation of fear memory, lamivudine was administered and its effects on fear memory reconsolidation were observed.

RESULTS

ORF1 and ORF2 mRNA expressions in the mPFC and hippocampus after recent (24 h) and remote (14 days) fear memory recall exhibited augmentation via different temporal and spatial patterns. Reconsolidation of fear memory was markedly inhibited in mice treated with lamivudine, which could block L1. DNA methyltransferase mRNA expression declined following lamivudine treatment in remote fear memory recall.

CONCLUSION

The retrotransposition of L1 participated in the reconsolidation of fear memory after reactivation of fear memory, and with lamivudine treatment, spontaneous recovery decreased with time after recent and remote fear memory recall, providing clues for understanding the roles of L1 in fear memory.

Corticosterone Induced the Increase of proBDNF in Primary Hippocampal Neurons Via Endoplasmic Reticulum Stress

Major depression disorder is one of the most common psychiatric disorders that greatly threaten the mental health of a large population worldwide. Previous studies have shown that endoplasmic reticulum (ER) stress plays an important role in the pathophysiology of depression, and current research suggests that brain-derived neurotrophic factor precursor (proBDNF) is involved in the development of depression. However, the relationship between ER and proBDNF in the pathophysiology of depression is not well elucidated. Here, we treated primary hippocampal neurons of mice with corticosterone (CORT) and evaluated the relationship between proBDNF and ERS. Our results showed that CORT induced ERS and upregulated the expression of proBDNF and its receptor, Follistatin-like protein 4 (FSTL4), which contributed to significantly decreased neuronal viability and expression of synaptic-related proteins including NR2A, PSD95, and SYN. Anti-proBDNF neutralization and ISRIB (an inhibitor of the ERS) treatment, respective ly, protected neuronal viabilities and increased the expression of synaptic-related proteins in corticosterone-exposed neurons. ISRIB treatment reduced the expression of proBDNF and FSTL4, whereas anti-proBDNF treatment did not affect ERS markers (Grp78, p-PERK, ATF4) expression. Our study presented evidence that CORT-induced ERS negatively regulated the neuronal viability and the level of synaptic-related protein of primary neurons via the proBDNF/FSTL4 pathway.

The Role of miR-150 in Stress-Induced Anxiety-Like Behavior in Mice

Stress plays a crucial role in several psychiatric disorders, including anxiety. However, the underlying mechanisms remain poorly understood. Here, we used acute stress (AS) and chronic restraint stress (CRS) models to develop anxiety-like behavior and investigate the role of miR-150 in the hippocampi of mice. Corticosterone levels as well as glutamate receptors in the hippocampus were evaluated. We found that anxiety-like behavior was induced after either AS or CRS, as determined by the open-field test (OFT) and elevated plus-maze test (EPM). Increased corticosterone levels were observed in the blood of AS and CRS groups, while the expression of miR-150 mRNA in the hippocampus was significantly decreased. The expressions of GluN2A, GluR1, GluR2, and V-Glut2 in the hippocampus were decreased after either AS or CRS. Hippocampal GAD67 expression was increased by AS but not CRS, and GluN2B expression was decreased by CRS but not AS. Adult miR-150 knockout mice showed anxiety-like behavior, as assessed by the OFT and EPM. The expressions of GluN2A, GluN2B, GluR1, and GluR2 were also downregulated, but the expression of V-Glut2 was upregulated in the hippocampi of miR-150 knockout mice compared with wild-type mice. Interestingly, we found that the miR-150 knockout mice showed decreased dendrite lengths, dendrite branchings, and numbers of dendrite spines in the hippocampus compared with wild-type mice. These results suggest that miR-150 may influence the synaptic plasticity of the hippocampus and play a significant role in stress-induced anxiety-like behavior in adult mice.