Different behavioral and pathological changes between epilepsy-associated depression and primary depression models

SKF83959 Attenuates Memory Impairment and Depressive-like Behavior during the Latent Period of Epilepsy via Allosteric Activation of the Sigma-1 Receptor

Memory impairment and emotional disorder are two common clinical comorbidities in patients with epilepsy. It is imperative to develop a novel therapeutic agent or a strategy. 6-Chloro-7,8-dihydroxy-3-methyl-1-(3-methylphenyl)-2,3,4,5-tetrahydro-1H-3-benzazepine (SKF83959) is a dopamine-1 receptor agonist and sigma-1 receptor allosteric modulator, which displays the neuron-protective and anti-neuroinflammation activity. We examined the effect of SKF83959 on the memory impairment and emotional disorder in the latent period of epilepsy using the mice post-status epilepticus model. We found that SKF83959 ameliorated memory impairment and depressive-like mood, alleviated the neuron damage and the formation of gliosis in hippocampus, suppressed the rise of pro-inflammatory cytokines, including tumor necrosis factor-α and interleukin-1β, and induced nitric oxide synthase in the latent period of epilepsy. Additionally, SKF83959 significantly inhibited the activity of calcineurin and glycogen synthase kinase-3β. All of these protective actions were reversed by BD1047 (a sigma-1 receptor antagonist). In addition, the intra-hippocampus injection of ketoconazole (a dehydroepiandrosterone synthesis inhibitor) also reversed the protective activity of SKF83959. Thus, we concluded that SKF83959 ameliorated the memory impairment and depressive-like mood in epilepsy via allosterically activating the sigma-1 receptor and subsequently inhibiting the calcineurin/glycogen synthase kinase-3β pathway.

Impact of Stress on Epilepsy: Focus on Neuroinflammation-A Mini Review

Epilepsy, one of the most common neurological disorders worldwide, is characterized by recurrent seizures and subsequent brain damage. Despite strong evidence supporting a deleterious impact on seizure occurrence and outcome severity, stress is an overlooked component in people with epilepsy. With regard to stressor duration and timing, acute stress can be protective in epileptogenesis, while chronic stress often promotes seizure occurrence in epilepsy patients. Preclinical research suggests that chronic stress promotes neuroinflammation and leads to a depressive state. Depression is the most common psychiatric comorbidity in people with epilepsy, resulting in a poor quality of life. Here, we summarize studies investigating acute and chronic stress as a seizure trigger and an important factor that worsens epilepsy outcomes and psychiatric comorbidities. Mechanistic insight into the impact of stress on epilepsy may create a window of opportunity for future interventions targeting neuroinflammation-related disorders.

Comparison of clinical efficacy of oxcarbazepine and lamotrigine combined with escitalopram, and impact on prognostic quality of life in treating patients with epilepsy and depressive disorder

This study aimed to investigate the clinical efficacy of oxcarbazepine and lamotrigine combined with escitalopram in treating patients with epilepsy and depressive disorder, and their influence on the prognostic quality of life. A total of 108 patients with epilepsy and depression were selected as research participants. Among them, 53 patients were treated by oxcarbazepine combined with escitalopram (group A) and 55 patients were treated by lamotrigine combined with escitalopram (group B). Following six-month treatment, efficacy, epilepsy frequency and duration, Hamilton Depression Rating (HAMD) and Montgomery-Asberg Depression Rating (MADRS) scores, adverse reactions, improvement of electroencephalogram (EEG) epileptic discharge, quality of life, 1-year drug retention rate and withdrawal reasons of the two groups were compared. There was no remarkable difference in the total efficacy rate between both groups. The number and duration of epileptic seizures, improvement of EEG epileptic discharge and quality of life in the two groups significantly improved after treatment, with no marked difference. HAMD and MADRS scores of patients from group B were significantly lower after treatment compared with those of patients from group A. The incidence rate of adverse reactions in group B was dramatically lower compared with group A, and the 1-year drug retention rate of group B was dramatically higher compared with that in group A. Both oxcarbazepine and lamotrigine combined with escitalopram exhibited good efficacy in patients with epilepsy and depressive disorder, and they may effectively improve the prognostic quality of life of patients. Lamotrigine combined with escitalopram presented with a better antidepressant effect and safety, with higher patient tolerance.

The P2X7 receptor in activated microglia promotes depression- and anxiety-like behaviors in lithium -pilocarpine induced epileptic rats

Depressive and anxious behaviors are the most common psychiatric symptoms of epilepsy, and may aggravate the epileptic condition and affect the patient's quality of life. Accumulating data obtained from both experimental animal models and patients have convincingly shown a critical role of P2X7 receptor (P2X7R) during depression and anxiety. Our study showed for the first time that the P2X7R is involved in promoting depression- and anxiety-like behaviors in lithium pilocarpine-induced epileptic rats. More importantly, direct anti-depressive and anti-anxiety effects were produced by the P2X7R antagonist Brilliant Blue G (BBG) is in this study, and the effect was similar to that of the classic anti-depressant and anti-anxiety drug fluoxetine. We also found that BBG did not affect the development of spontaneous recurrent seizures (SRS) and had a neuroprotective effect via inhibition of microglial activation after status epilepticus (SE). Thus, our data provide evidence that the P2X7R in activated microglia promotes depression- and anxiety-like behaviors in lithium-pilocarpine induced epileptic rats. Since previous studies have indicated that some anti-depression and anti-anxiety drugs may exacerbate seizures, our data support that the P2X7R is a promising therapeutic target for epilepsy associated with depression and anxiety.

Anti-inflammatory treatment with a soluble epoxide hydrolase inhibitor attenuates seizures and epilepsy-associated depression in the LiCl-pilocarpine post-status epilepticus rat model

PURPOSE

This study aimed to investigate whether 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU), a soluble epoxide hydrolase inhibitor with anti-inflammatory effects, could alleviate spontaneous recurrent seizures (SRS) and epilepsy-associated depressive behaviours in the lithium chloride (LiCl)-pilocarpine-induced post-status epilepticus (SE) rat model.

METHODS

The rats were intraperitoneally (IP) injected with LiCl (127 mg/kg) and pilocarpine (40 mg/kg) to induce SE. A video surveillance system was used to monitor SRS in the post-SE model for 6 weeks (from the onset of the 2nd week to the end of the 7th week after SE induction). TPPU (0.1 mg/kg/d) was intragastrically given for 4 weeks from the 21st day after SE induction in the SRS + 0.1 TPPU group. The SRS + PEG 400 group was given the vehicle (40% polyethylene glycol 400) instead, and the control group was given LiCl and PEG 400 but not pilocarpine. The sucrose preference test (SPT) and forced swim test (FST) were conducted to evaluate the depression-like behaviours of rats. Immunofluorescent staining, enzyme-linked immunosorbent assay, and western blot analysis were performed to measure astrocytic and microglial gliosis, neuronal loss, and levels of soluble epoxide hydrolase (sEH), cytokines [tumour necrosis factor alpha (TNF-α), interleukin (IL)-1β, and IL-6], and cyclic adenosine monophosphate (cAMP)-response element binding protein (CREB).

RESULTS

The frequency of SRS was significantly decreased at 6 weeks and 7 weeks after SE induction in the 0.1TPP U group compared with the SRS + PEG 400 group. The immobility time (IMT) evaluated by FST was significantly decreased, whereas the climbing time (CMT) was increased, and the sucrose preference rate (SPR) evaluated by SPT was in an increasing trend. The levels of sEH, TNF-α, IL-1β, and IL-6 in the hippocampus (Hip) and prefrontal cortex (PFC) were all significantly increased in the SRS + PEG 400 group compared with the control group; neuronal loss, astrogliosis, and microglial activation were also observed. The astrocytic and microglial activation and levels of the pro-inflammatory cytokines in the Hip and PFC were significantly attenuated in the TPPU group compared with the SRS + PEG 400 group; moreover, neuronal loss and the decreased CREB expression were significantly alleviated as well.

CONCLUSION

TPPU treatment after SE attenuates SRS and epilepsy-associated depressive behaviours in the LiCl-pilocarpine induced post-SE rat model, and it also exerts anti-inflammatory effects in the brain. Our findings suggest a new therapeutic approach for epilepsy and its comorbidities, especially depression.

Xiaoyaosan exerts antidepressant-like effects by regulating the functions of astrocytes and EAATs in the prefrontal cortex of mice

Background

Mounting evidence indicates that the cerebral cortex is an important physiological system of emotional activity, and its dysfunction may be the main cause of stress. Glutamate is the primary excitatory neurotransmitter in the central nervous system (CNS), which initiates rapid signal transmission in the synapse before its reuptake into the surrounding glia, specifically astrocytes (ASTs). The astrocytic excitatory amino acid transporters 1 (EAAT1) and 2 (EAAT2) are the major transporters that take up synaptic glutamate to maintain optimal extracellular glutamic levels, thus preventing accumulation in the synaptic cleft and ensuing excitotoxicity. Growing evidence has shown that excitotoxicity is associated with depression. Therefore, we hypothesized that the underlying antidepressant-like mechanism of Xiaoyaosan (XYS), a Chinese herbal formula, may be related to the regulation of astrocytic EAATs. Therefore, we studied the antidepressant mechanism of XYS on the basis of EAAT dysfunction in ASTs.

Methods

Eighty adult C57BL/6 J mice were randomly divided into 4 groups: a control group, a chronic unpredictable mild stress (CUMS) group, a Xiaoyaosan (XYS) treatment group and a fluoxetine hydrochloride (Flu) treatment group. Except for the control group, mice in the other groups all received chronic unpredictable mild stress for 21 days. Mice in the control and CUMS groups received gavage administration with 0.5 mL of normal saline (NS) for 21 days, and mice in the XYS and Flu treatment groups were administered dosages of 0.25 g/kg/d and 2.6 mg/kg/d by gavage. The effects of XYS on the depressive-like behavioral tests, including the open field test (OFT), forced swimming test (FST) and sucrose preference test (SPT), were examined. The glutamate (Glu) concentrations of the prefrontal cortex (PFC) were detected with colorimetry. The morphology of neurons in the PFC was observed by Nissl staining. The expression of glial fibrillary acidic protein (GFAP), NeuN, EAAT1 and EAAT2 proteins in the PFC of mice was detected by using Western blotting and immunohistochemistry. Quantitative real-time PCR (qPCR) was used to detect the expression of the GFAP, NeuN, EAAT1 and EAAT2 genes in the PFC of mice.

Results

The results of behavioral tests showed that CUMS-induced mice exhibited depressive-like behavior, which could be improved in some tests with XYS and Flu treatment. Immunohistochemistry and Western blot analysis showed that the protein levels of GFAP, NeuN, EAAT1 and EAAT2 in the PFC of CUMS mice were significantly lower than those in the control group, and these changes could be reversed by XYS and Flu. The results of qPCR analysis showed that the expression of GFAP, NeuN, EAAT1 and EAAT2 mRNAs in the PFC of CUMS mice was not significantly changed, with the exception of EAAT2, compared with that of the control group, while the expression of the above mRNAs was significantly higher in the XYS and Flu groups than that in the CUMS group.

Conclusion

XYS may exert antidepressant-like effects by improving the functions of AST and EAATs and attenuating glutamate-induced neuronal damage in the frontal cortex.

Antidepressant-like Effects Induced by Chronic Blockade of the Purinergic 2X7 Receptor through Inhibition of Non-like Receptor Protein 1 Inflammasome in Chronic Unpredictable Mild Stress Model of Depression in Rats

Objective

Purinergic 2X7 receptor (P2X7R) activation is known to be involved in pathogenesis of depression. Our aims were to investigate P2X7R-activated inflammasome pathways in parallel with induction of depression and to test the antidepressant-like effects of the selective P2X7R antagonist Brilliant Blue G (BBG) in a rat model of chronic unpredictable mild stress (CUMS).

Methods

Male Wistar albino rats were divided into control, CUMS, CUMS+BBG25 (25 mg/kg/day) and CUMS+BBG50 (50 mg/kg/day) groups (n=10 for each group). Various stressors were applied to rats for 6 weeks to establish the CUMS model and daily BBG treatment was started at the end of 3rd week. Sucrose preference test and forced swim test (FST) were performed to assess antidepressant-like effects. Brain samples were obtained for real-time polymerase chain reaction and immunohistochemistry analysis.

Results

In FST, duration of immobility was reduced in the CUMS+BBG50 group. Also, BBG treatment significantly enhanced sucrose preference. While NLRP3 gene expression levels were unchanged in rats exposed to the CUMS protocol, expression levels of other inflammasome pathway factors NLRP1, caspase-1, ASC, NF-κB, IL-1β, IL-6 and P2X7R were increased. BBG treatment reduced expression levels of these factors. Likewise, Iba-1 and GFAP immunoreactivities were enhanced by the CUMS protocol and this action was reversed by BBG treatment.

Conclusion

Chronic administration of BBG in CUMS model results in antidepressant-like activity in a dose dependent manner. Molecular and histological results show that these effects might be at least partially related to the suppression of inflammasome-related neuroinflammatory responses and suggest involvement of NLRP1 in depression.