Cannabidiol ameliorates PTSD-like symptoms by inhibiting neuroinflammation through its action on CB2 receptors in the brain of male mice.

Post-traumatic stress disorder (PTSD) is a debilitating mental health disease related to traumatic experience, and its treatment outcomes are unsatisfactory. Accumulating research has indicated that cannabidiol (CBD) exhibits anti-PTSD effects, however, the underlying mechanism of CBD remains inadequately investigated. Although many studies pertaining to PTSD have primarily focused on aberrations in neuronal functioning, the present study aimed to elucidate the involvement and functionality of microglia/macrophages in PTSD while also investigated the modulatory effects of CBD on neuroinflammation associated with this condition. We constructed a modified single-prolonged stress (SPS) mice PTSD model and verified the PTSD-related behaviors by various behavioral tests (contextual freezing test, elevated plus maze test, tail suspension test and novel object recognition test). We observed a significant upregulation of Iba-1 and alteration of microglial/macrophage morphology within the prefrontal cortex and hippocampus, but not the amygdala, two weeks after the PTSD-related stress, suggesting a persistent neuroinflammatory phenotype in the PTSD-modeled group. CBD (10 mg/kg, i.p.) inhibited all PTSD-related behaviors and reversed the alterations in both microglial/macrophage quantity and morphology when administered prior to behavioral assessments. We further found increased pro-inflammatory factors, decreased PSD95 expression, and impaired synaptic density in the hippocampus of the modeled group, all of which were also restored by CBD treatment. CBD dramatically increased the level of anandamide, one of the endocannabinoids, and cannabinoid type 2 receptors (CB2Rs) transcripts in the hippocampus compared with PTSD-modeled group. Importantly, we discovered the expression of CB2Rs mRNA in Arg-1-positive cells in vivo and found that the behavioral effects of CBD were diminished by CB2Rs antagonist AM630 (1 mg/kg, i.p.) and both the behavioral and molecular effects of CBD were abolished in CB2Rs knockout mice. These findings suggest that CBD would alleviate PTSD-like behaviors in mice by suppressing PTSD-related neuroinflammation and upregulation and activation of CB2Rs may serve as one of the underlying mechanisms for this therapeutic effect. The present study offers innovative experimental evidence supporting the utilization of CBD in PTSD treatment from the perspective of its regulation of neuroinflammation, and paves the way for leveraging the endocannabinoid system to regulate neuroinflammation as a potential therapeutic approach for psychiatric disorders.

Single-Nucleus Transcriptome Profiling from the Hippocampus of a PTSD Mouse Model and CBD-Treated Cohorts.

Post-traumatic stress disorder (PTSD) is the most common psychiatric disorder after a catastrophic event; however, the efficacious treatment options remain insufficient. Increasing evidence suggests that cannabidiol (CBD) exhibits optimal therapeutic effects for treating PTSD. To elucidate the cell-type-specific transcriptomic pathology of PTSD and the mechanisms of CBD against this disease, we conducted single-nucleus RNA sequencing (snRNA-seq) in the hippocampus of PTSD-modeled mice and CBD-treated cohorts. We constructed a mouse model by adding electric foot shocks following exposure to single prolonged stress (SPS+S) and tested the freezing time, anxiety-like behavior, and cognitive behavior. CBD was administrated before every behavioral test. The PTSD-modeled mice displayed behaviors resembling those of PTSD in all behavioral tests, and CBD treatment alleviated all of these PTSD-like behaviors (n = 8/group). Three mice with representative behavioral phenotypes were selected from each group for snRNA-seq 15 days after the SPS+S. We primarily focused on the excitatory neurons (ExNs) and inhibitory neurons (InNs), which accounted for 68.4% of the total cell annotations. A total of 88 differentially upregulated genes and 305 differentially downregulated genes were found in the PTSD mice, which were found to exhibit significant alterations in pathways and biological processes associated with fear response, synaptic communication, protein synthesis, oxidative phosphorylation, and oxidative stress response. A total of 63 overlapping genes in InNs were identified as key genes for CBD in the treatment of PTSD. Subsequent Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that the anti-PTSD effect of CBD was related to the regulation of protein synthesis, oxidative phosphorylation, oxidative stress response, and fear response. Furthermore, gene set enrichment analysis (GSEA) revealed that CBD also enhanced retrograde endocannabinoid signaling in ExNs, which was found to be suppressed in the PTSD group. Our research may provide a potential explanation for the pathogenesis of PTSD and facilitate the discovery of novel therapeutic targets for drug development. Moreover, it may shed light on the therapeutic mechanisms of CBD.

Comparison between cannabidiol and sertraline for the modulation of post-traumatic stress disorder-like behaviors and fear memory in mice.

RATIONALE AND OBJECTIVES: Post-traumatic stress disorder (PTSD) is characterized by poor adaptation to a traumatic experience and disturbances in fear memory regulation, and currently lacks effective medication. Cannabidiol is a main constituent of Cannabis sativa; it has no psychotomimetic effects and has been implicated in modulating fear learning in mammals. Using a mouse PTSD model, we investigated the effects of CBD on PTSD-like behaviors and the modulation of trauma-related fear memory, a crucial process leading to core symptoms of PTSD. METHODS: We applied the modified pre-shock model to evaluated PTSD-like behaviors from days 3 to 26. The measures included the freezing time to the conditioned context, open field test, elevated plus maze test, and social interaction test. CBD and sertraline were administered at different stages of fear memory. RESULTS: CBD (10 mg/kg, i.p.) administration alleviated main PTSD-like symptoms in the mouse pre-shock model by attenuating trauma-related fear memory and anxiety-like behavior, and increasing social interaction behavior. The effects of CBD were apparent irrespective of whether it was administered before, during, or after re-exposure to the aversive context. However, sertraline (15 mg/kg, p.o.) was only effective when administered before the behavioral test. CBD also reduced the consolidation, retrieval, and reconsolidation of trauma-related fear memory, whereas sertraline only reduced fear-memory retrieval. CONCLUSION: CBD produced anti-PTSD-like actions in mice and disrupted trauma-related fear memory by interfering with multiple aspects of fear memory processing. These findings indicate that CBD may be a promising candidate for treating PTSD.

Minocycline protects against lipopolysaccharide-induced cognitive impairment in mice.

RATIONALE: The role of glial cells, especially microglia and astrocytes, in neuroinflammation and cognition has been studied intensively. Lipopolysaccharide (LPS), a commonly used inducer of neuroinflammation, can cause cognitive impairment. Minocycline is known to possess potent neuroprotective activity, but its effect on LPS-induced cognitive impairment is unknown. OBJECTIVES: This study aims to investigate the effects of minocycline on LPS-induced cognitive impairment and glial cell activation in mice. METHODS: Behavioral tests were conducted for cognitive function, immunohistochemistry for microglial and astrocyte response, and quantitative PCR for mRNA expression of proinflammatory cytokines. RESULTS: Minocycline significantly reversed the decreased spontaneous alternation induced by intrahippocampal administration of LPS in the Y-maze task. In the Morris water maze place navigation test, minocycline decreased the escape latency and distance traveled compared to LPS-treated mice. In the probe test, minocycline-treated mice spent more time in the target quadrant and crossed the platform area more frequently than animals in the LPS-treated group. Minocycline produced a significant decrease in the number of Iba-1- and GFAP-positive hippocampal cells compared to the LPS-treated group. Minocycline-treated mice had significantly reduced hippocampal TNF-α and IL-1ß mRNA levels compared with LPS-treated animals. Minocycline caused a significant increase in hippocampal BDNF expression compared to the LPS-treated group. CONCLUSIONS: Minocycline can attenuate LPS-induced cognitive impairments in mice. This effect may be associated with its action to suppress the activation of microglia and astrocytes and to normalize BDNF expression. Since neuroinflammatory processes and cognitive impairments are implicated in neurodegenerative disorders, minocycline may be a promising candidate for treating such diseases.

Pterostilbene attenuates lipopolysaccharide-induced learning and memory impairment possibly via inhibiting microglia activation and protecting neuronal injury in mice.

The present study aims to evaluate the effects of pterostilbene on lipopolysaccharide (LPS)-induced learning and memory impairment as well as the possible changes of microglia and neurons. Firstly, learning and memory function was investigated by behavioral tests. Pterostilbene attenuated LPS-induced learning and memory impairment tested by Y-maze and Morris water maze. Secondly, immunohistochemical method was used to study the changes of microglia and neurons. The results showed that pterostilbene produced a significant decrease in the number of Iba-1 and Doublecortin (DCX) positive cells and a significant increase in neuronal nuclear antigen (NeuN)-stained area of neurons in mouse hippocampal compared to the LPS group. Finally, an in vitro study was performed to further confirm the inhibitory effect on microglia activation and protective effect on neurons exerted by pterostilbene. The results demonstrated that pterostilbene significantly inhibited microglia activation, showing the obvious decrease of LPS-induced production of NO, TNF-α and IL-6 in N9 microglial cells. In addition, the viability of SH-SY5Y cells decreased by conditioned media of LPS-activated N9 microglial cells was remarkably recovered by pterostilbene. In summary, the present study demonstrated for the first time that pterostilbene attenuated LPS-induced learning and memory impairment, which may be associated with its inhibitory effect on microglia activation and protective effect on neuronal injury.

Neuronal injury, but not microglia activation, is associated with ketamine-induced experimental schizophrenic model in mice.

Schizophrenia is a chronic debilitating psychiatric disorder affecting as many as 1% of the population worldwide. Unfortunately, its etiology and pathophysiology are poorly defined. Previous studies have shown that neuronal injury and microglia activation were observed in the schizophrenic patients. The present study aims to evaluate the role of neurons and microglia in ketamine-induced experimental schizophrenic model to further understand its pathophysiology. Firstly, ketamine was used to simulate the behavior abnormalities associated with schizophrenia. The effects of ketamine on mouse locomotor activity, Y-maze task, novel object recognition, and forced swimming test were studied. The results showed that ketamine (25, 50, and 100mg/kg i.p.) administered acutely or repeatedly (for 7 days) can increase the locomotor number significantly. In Y-maze task, ketamine (25, 50, and 100mg/kg) impaired spontaneous alternation after both acute and repeated treatments. In novel object recognition test, acute or chronic ketamine treatment showed no significant effect on mouse exploratory preference behavior. In forced swimming test, repeated treatment of ketamine (100mg/kg) enhanced the immobility duration. Secondly, immunohistochemical method was used to study the changes of neurons and microglia. The results showed that acute treatment of ketamine (100mg/kg) had no effect on neurons in the prefrontal cortex or hippocampus (1, 3, 5, and 7 days after the treatment). In contrast, repeated treatment of ketamine caused neuronal impairment in mouse hippocampus (3rd day, 5th day and 7th day after the final administration). The results of immunohistochemistry demonstrated that microglia in the prefrontal cortex and hippocampus were not affected after acute or repeated administration of ketamine. Finally, the neuronal impairment caused by repeated administration of ketamine was further investigated from the oxidative stress aspects. The results showed that repeated administration of ketamine increased nitric oxide (NO) and nitric oxide synthase (NOS) in prefrontal cortex, hippocampus and serum, while decreased SOD in hippocampus and serum. In summary, chronic ketamine treatment to mice successfully mimics the core behavioral deficits in schizophrenia. It is demonstrated for the first time that neuronal injury was associated with the chronic ketamine-induced experimental schizophrenic model, while microglial cells may play little role in this model. Oxidative stress may contribute to the significant neuronal injury in mouse brain induced by chronic ketamine treatment.