Protective effect of minocycline on LPS-induced mitochondrial dysfunction and decreased seizure threshold through nitric oxide pathway

Minocycline Acts as a Neuroprotective Agent Against Tramadol-Induced Neurodegeneration: Behavioral and Molecular Evidence

Background

Previous evidence indicates that tramadol (TRA) can lead to neurodegenerative events and minocycline (MIN) has neuroprotective properties.

Aim of the Study

The current research evaluated the neuroprotective effects of MIN for TRA-promoted neurodegeneration.

Methods

Sixty adult male rats were placed into the following groups: 1 (received 0.7 ml/rat of normal saline, IP), 2 (received 50 mg/kg of TRA, i.p.), 3, 4, 5 (administered TRA as 50 mg/kg simultaneously with MIN at 20, 40, and 60 mg/kg, IP, respectively), and 6 (received MIN alone as 60 mg/kg, IP). The treatment procedure was 21 days. An open field test (OFT) was used to measure motor activity and anxiety-related behavior. Furthermore, oxidative stress; hippocampal inflammation; apoptotic parameters as well as activity of mitochondrial complexes I, II, III, and IV; ATP levels; and mitochondrial membrane potential (MMP) were evaluated. In addition, histomorphological alteration was assessed in two regions of the hippocampus: Cornu Ammonis (CA1) and dentate gyrus (DG).

Results

MIN treatment could inhibit TRA-induced anxiety and motor activity disturbances (P < 0.05). In addition, MIN could attenuate reactive oxygen species (ROS), H2O2, oxidized glutathione (GSSG), and malondialdehyde (MDA) level (P < 0.05), while there was increased reduced glutathione (GSH), total antioxidant capacity (TAC), ATP, MMP, and BCL2 levels (P < 0.05) and also elevation of SOD, GPX, GSR (P < 0.05), and mitochondrial complexes I, II, III, and IV activity (P < 0.05) in TRA-treated rats. In consistence with these findings, MIN could reduce TNF/TNF-α, IL1B/IL1-β, BAX, and CASP3 levels (P < 0.05) in TRA-treated rats. MIN also restored the quantitative (P < 0.05) and qualitative histomorphological sequels of TRA in both CA1 and DG areas of the hippocampus.

Conclusions

MIN probably has repositioning capability for inhibition of TRA-induced neurodegeneration via modulation of inflammation, oxidative stress, apoptosis, and mitochondrial disorders.

Neuroimmune response and oxidative stress in the prefrontal cortex mediate seizure susceptibility in experimental colitis in male mice

Inflammatory bowel disease (IBD) is a chronic gastrointestinal disorder. Oxidative stress and inflammatory responses have a vital role in the pathophysiology of IBD as well as seizure. IBD is associated with extraintestinal manifestations. This study aimed to explore the relationship between colitis and susceptibility to seizures, with a focus on the roles of neuroinflammation and oxidative stress in acetic acid-induced colitis in mice. Forty male Naval Medical Research Institute mice were divided into four groups: control, colitis, pentylenetetrazole (PTZ), and colitis + PTZ. Colitis was induced by intrarectal administration of acetic acid, and seizures were induced by intravenous injection of PTZ 7 days postcolitis induction. Following the measurement of latency to seizure, the mice were killed, and their colons and prefrontal cortex (PFC) were dissected. Gene expression of inflammatory markers including interleukin-1β, tumor necrosis factor-alpha, NOD-like receptor protein 3, and toll-like receptor 4, as well as total antioxidant capacity (TAC), malondialdehyde (MDA), and nitrite levels were measured in the colon and PFC. Histopathological evaluations were performed on the colon samples. Data were analyzed by t-test or one-way variance analysis. Colitis decreased latency to seizure, increased gene expression of inflammatory markers, and altered levels of MDA, nitrite, and TAC in both the colon and PFC. Simultaneous induction of colitis and seizure exacerbated the neuroimmune response and oxidative stress in the PFC and colon. Results concluded that neuroinflammation and oxidative stress in the PFC at least partially mediate the comorbid decrease in seizure latency in mice with colitis.

Gut-brain barrier dysfunction bridge autistic-like behavior in mouse model of maternal separation stress: A behavioral, histopathological, and molecular study

Autism spectrum disorder (ASD) is a fast-growing neurodevelopmental disorder throughout the world. Experiencing early life stresses (ELS) like maternal separation (MS) is associated with autistic-like behaviors. It has been proposed that disturbance in the gut-brain axis-mediated psychiatric disorders following MS. The role of disruption in the integrity of gut-brain barrier in ASD remains unclear. Addressing this knowledge gap, in this study we aimed to investigate role of the gut-brain barrier integrity in mediating autistic-like behaviors in mouse models of MS stress. To do this, mice neonates are separated daily from their mothers from postnatal day (PND) 2 to PND 14 for 3 hours. During PND58-60, behavioral tests related to autistic-like behaviors including three-chamber sociability, shuttle box, and resident-intruder tests were performed. Then, prefrontal cortex (PFC), hippocampus, and colon samples were dissected out for histopathological and molecular evaluations. Results showed that MS is associated with impaired sociability and social preference indexes, aggressive behaviors, and impaired passive avoidance memory. The gene expression of CLDN1 decreased in the colon, and the gene expression of CLDN5, CLDN12, and MMP9 increased in the PFC of the MS mice. MS is associated with decrease in the diameter of CA1 and CA3 areas of the hippocampus. In addition, MS led to histopathological changes in the colon. We concluded that, probably, disturbance in the gut-brain barrier integrities mediated the autistic-like behavior in MS stress in mice.

Minocycline protects against lipopolysaccharide-induced glial cells activation and oxidative stress damage in the medial prefrontal cortex (mPFC) of the rat

PURPOSE/AIM

Neuroinflammation and oxidative stress have been encountered in neurodegenerative diseases such as Alzheimer's disease (AD). However, the neuroprotective effects of minocycline against lipopolysaccharide (LPS)-induced glial cells activation and oxidative stress damage in the medial prefrontal cortex (mPFC) of rats are still elusive. The purpose of this study is to investigate the effects of minocycline and memantine, an N-methyl-D-aspartate (NMDA) receptor antagonist, on the microglia and astrocytes expression, as well as oxidative stress levels in the mPFC of LPS injected rats.

MATERIALS AND METHODS

Fifty adult Male Sprague Dawley rats were divided into five groups: control, LPS (5 mg/kg), LPS treated with minocycline (25 mg/kg), LPS treated with minocycline (50 mg/kg) and LPS treated with memantine (10 mg/kg). The immunohistochemistry and western blotting were used to analyse the expressions and densities of microglia marker (Iba-1) and astrocyte marker, (GFAP) while enzyme-linked immunosorbent assay (ELISA) was used to measure the protein carbonyl (PCO), malondialdehyde (MDA), catalase (CAT), and superoxide dismutase (SOD) levels.

RESULTS

In comparison to the control group, the expression and density of Iba-1 and GFAP were significantly enhanced in the LPS group (p < 0.05). LPS group also exhibited significantly higher levels of PCO and MDA (p < 0.05) and significantly lower levels of CAT and SOD (p < 0.05) when compared to the control group. Both minocycline and memantine-treated LPS rats were able to protect against these effects.

CONCLUSION

Minocycline, like memantine treatment, reduces oxidative stress in the mPFC of LPS rats via inhibition of glial cells activation.

A high seizure burden increases several prostaglandin species in the hippocampus of a Scn1a+/- mouse model of Dravet syndrome

Dravet syndrome is an intractable epilepsy with a high seizure burden that is resistant to current anti-seizure medications. There is evidence that neuroinflammation plays a role in epilepsy and seizures, however few studies have specifically examined neuroinflammation in Dravet syndrome under conditions of a higher seizure burden. Here we used an established genetic mouse model of Dravet syndrome (Scn1a+/- mice), to examine whether a higher seizure burden impacts the number and morphology of microglia in the hippocampus. Moreover, we examined whether a high seizure burden influences classical inflammatory mediators in this brain region. Scn1a+/- mice with a high seizure burden induced by thermal priming displayed a localised reduction in microglial cell density in the granule cell layer and subgranular zone of the dentate gyrus, regions important to postnatal neurogenesis. However, microglial cell number and morphology remained unchanged in other hippocampal subfields. The high seizure burden in Scn1a+/- mice did not affect hippocampal mRNA expression of classical inflammatory mediators such as interleukin 1β and tumour necrosis factor α, but increased cyclooxygenase 2 (COX-2) expression. We then quantified hippocampal levels of prostanoids that arise from COX-2 mediated metabolism of fatty acids and found that Scn1a+/- mice with a high seizure burden displayed increased hippocampal concentrations of numerous prostaglandins, notably PGF2α, PGE2, PGD2, and 6-K-PGF1A, compared to Scn1a+/- mice with a low seizure burden. In conclusion, a high seizure burden increased hippocampal concentrations of various prostaglandin mediators in a mouse model of Dravet syndrome. Future studies could interrogate the prostaglandin pathways to further better understand their role in the pathophysiology of Dravet syndrome.

The neurobiological mechanisms and therapeutic prospect of extracellular ATP in depression

BACKGROUND

Depression is a prevalent psychiatric disorder with high long-term morbidities, recurrences, and mortalities. Despite extensive research efforts spanning decades, the cellular and molecular mechanisms of depression remain largely unknown. What's more, about one third of patients do not have effective anti-depressant therapies, so there is an urgent need to uncover more mechanisms to guide the development of novel therapeutic strategies. Adenosine triphosphate (ATP) plays an important role in maintaining ion gradients essential for neuronal activities, as well as in the transport and release of neurotransmitters. Additionally, ATP could also participate in signaling pathways following the activation of postsynaptic receptors. By searching the website PubMed for articles about "ATP and depression" especially focusing on the role of extracellular ATP (eATP) in depression in the last 5 years, we found that numerous studies have implied that the insufficient ATP release from astrocytes could lead to depression and exogenous supply of eATP or endogenously stimulating the release of ATP from astrocytes could alleviate depression, highlighting the potential therapeutic role of eATP in alleviating depression.

AIM

Currently, there are few reviews discussing the relationship between eATP and depression. Therefore, the aim of our review is to conclude the role of eATP in depression, especially focusing on the evidence and mechanisms of eATP in alleviating depression.

CONCLUSION

We will provide insights into the prospects of leveraging eATP as a novel avenue for the treatment of depression.

Effect of quercetin-loaded poly (lactic-co-glycolic) acid nanoparticles on lipopolysaccharide-induced memory decline, oxidative stress, amyloidogenesis, neurotransmission, and Nrf2/HO-1 expression

Neuroinflammation contributes to the pathogenesis of several neurodegenerative disorders. This study examined the neuroprotective effect of quercetin (QUR)-loaded poly (lactic-co-glycolic) acid (PLGA) nanoparticles (QUR NANO) against the neurotoxicity induced by lipopolysaccharide (LPS) in mice. A QUR NANO formulation was prepared and characterized by differential scanning calorimetry, X-ray diffraction, entrapment efficiency (EE), high-resolution transmission electron microscopy, field emission scanning electron microscopy, and in vitro drug release profile. Levels of glutathione, malondialdehyde, catalase, inducible nitric oxide synthase (iNOS), amyloid beta 42 (Aβ42), β-secretase, gamma-aminobutyric acid (GABA), and acetylcholine esterase (AChE) were measured in the mouse brain tissues. The gene expression of nuclear factor erythroid-related factor 2 (Nrf-2) and heme oxygenase-1 (HO-1) were also determined. The prepared QUR NANO formulation showed 92.07 ± 3.21% EE and drug loading of 4.62 ± 0.55. It exhibited clusters of nano-spherical particles with smooth surface areas, and the loading process was confirmed. In vivo, the QUR NANO preserved the spatial memory of mice and protected the hippocampus from LPS-induced histological lesions. The QUR NANO significantly reduced the levels of malondialdehyde, iNOS, Aβ42, β-secretase, and AChE in brain tissue homogenates. Conversely, QUR NANO increased the glutathione, catalase, and GABA concentrations and upregulated the expression of Nrf-2 and HO-1 genes. Remarkably, the neuroprotective effect of QUR NANO was significantly greater than that of herbal QUR. In summary, the prepared QUR NANO formulation was efficient in mitigating LPS-induced neurotoxicity by reducing memory loss, oxidative stress, and amyloidogenesis while preserving neurotransmission and upregulating the expression of Nrf2 and HO-1 genes. This study addresses several key factors in neuroinflammatory disorders and explores the potential of QUR-loaded nanoparticles as a novel therapeutic approach to alleviate these factors.

Unmasking hidden risks: The surprising link between PDE5 inhibitors and seizure susceptibility

BACKGROUND

Phosphodiesterase 5 inhibitors (PDE5i) are the first line treatment for erectile dysfunction; however, several articles and case reports have shown central nervous system effects, that can cause seizures in susceptible patients. This study aims to describe the changes caused by the use of Sildenafil and Tadalafil through the analysis of abnormalities expressed in the electrocorticogram (ECoG) of rats and evaluate the seizure threshold response and treatment of seizures with anticonvulsants.

MATERIALS AND METHODS

The study used 108 rats (Wistar). Before surgery for electrode placement in dura mater, the animals were randomly separated into 3 experiments for electrocorticogram analysis. Experiment 1: ECoG response to using PD5i (Sildenafil 20mg/kg and Tadalafil 2.6mg/kg p.o.). Experiment 2: ECoG response to the use of PD5i in association with Pentylenetetrazole (PTZ-30 mg/kg i.p.), a convulsive model. Experiment 3: ECoG response to anticonvulsant treatment (Phenytoin, Phenobarbital and Diazepam) of seizures induced by association IPDE5 + PTZ. All recordings were made thirty minutes after administration of the medication and analyzed for ten minutes, only once. We considered statistical significance level of *p<0.05, **p<0.01 and ***p < 0.001.

RESULTS

After administration of Sildenafil and Tadalafil, there were increases in the power of recordings in the frequency bands in oscillations in alpha (p = 0.0920) and beta (p = 0.602) when compared to the control group (p<0.001). After the use of Sildenafil and Tadalafil associated with PTZ, greater potency was observed in the recordings during seizures (p<0.001), however, the Sildenafil group showed greater potency when compared to Tadalafil (p<0.05). Phenobarbital and Diazepam showed a better response in controlling discharges triggered by the association between proconvulsant drugs.

CONCLUSIONS

PDE5i altered the ECoG recordings in the rats' motor cortexes, demonstrating cerebral asynchrony and potentiating the action of PTZ. These findings demonstrate that PDE5i can lower the seizure threshold.

Possible role of NO/NMDA pathway in the autistic-like behaviors induced by maternal separation stress in mice

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder. Maternal separation (MS) stress is an established model of early-life stress associated with autistic-like behaviors. Altered glutamatergic and nitrergic neurotransmissions may contribute to the pathophysiology of ASD. However, the specific mechanisms underlying these alterations and their relationship to MS-induced autistic-like behaviors remain unclear. Addressing this knowledge gap, this study aims to elucidate the involvement of the nitric oxide (NO)/ N-methyl-D-aspartate (NMDA) pathway in MS-induced autistic-like behaviors in mice. This knowledge has the potential to guide future research, potentially leading to the development of targeted interventions or treatments aimed at modulating the NO/NMDA pathway to ameliorate ASD symptoms. Ninety male Naval Medical Research Institute (NMRI) mice were assigned to six groups (n = 15) comprising a control group (treated with saline) and five groups subjected to MS and treated with saline, ketamine, NMDA, L-NAME, and L-arginine. Behavioral tests were conducted, including the three-chamber test, shuttle box, elevated plus-maze, and marble burying test. Gene expression of iNOS, nNOS, and NMDA-R subunits (NR2A and NR2B), along with nitrite levels, was evaluated in the hippocampus. The findings demonstrated that MS induced autistic-like behaviors, accompanied by increased gene expression of iNOS, nNOS, NR2B, NR2A, and elevated nitrite levels in the hippocampus. Modulation of the NO/NMDA pathway with activators and inhibitors altered the effects of MS. These results suggest that the NO/NMDA pathway plays a role in mediating the negative effects of MS and potentially contributes to the development of autistic-like behaviors in maternally separated mice.

Isoamericanin A improves lipopolysaccharide-induced memory impairment in mice through suppression of the nicotinamide adenine dinucleotide phosphateoxidase-dependent nuclear factor kappa B signaling pathway

Alzheimer's disease (AD) is the most frequent cause of dementia in the elderly. Isoamericanin A (ISOA) is a natural lignan possessing great potential for AD treatment. This study investigated the efficacy of ISOA on memory impairments in the mice intrahippocampal injected with lipopolysaccharide (LPS) and the underlying mechanism. Y-maze and Morris Water Maze data suggested that ISOA (5 and 10 mg/kg) ameliorated short- and long-term memory impairments, and attenuated neuronal loss and lactate dehydrogenase activity. ISOA exerted anti-inflammatory effect demonstrating by the reduction of ionized calcium-binding adapter molecule 1 positive cells and suppression of marker protein and pro-inflammation cytokines expressions induced by LPS. ISOA suppressed the nuclear factor kappa B (NF-κB) signaling pathway by inhibiting IκBα phosphorylation and NF-κB p65 phosphorylation and nuclear translocation. ISOA inhibited superoxide and intracellular reactive oxygen species accumulation by reducing nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation, demonstrating by suppressing NADP+ and NADPH contents, gp91phox expression, and p47phox expression and membrane translocation. These effects were enhanced in combination with NADPH oxidase inhibitor apocynin. The neuroprotective effect of ISOA was further proved in the in vitro models. Overall, our data revealed a novel pharmacological activity of ISOA: ameliorating memory impairment in AD via inhibiting neuroinflammation.

Ameliorative effects of Albizia adianthifolia aqueous extract against pentylenetetrazole-induced epilepsy and associated memory loss in mice: Role of GABAergic, antioxidant defense and anti-inflammatory systems

Albizia adianthifolia (Schumach.) (Fabaceae) is a medicinal herb used for the treatment of epilepsy and memory impairment. This study aims to investigate the anticonvulsant effects of Albizia adianthifolia aqueous extract against pentylenetetrazole (PTZ)-induced spontaneous convulsions in mice; and determine whether the extract could mitigate memory impairment, oxidative/nitrergic stress, GABA depletion and neuroinflammation. Ultra-high performance liquid chromatography/mass spectrometry analysis was done to identify active compounds from the extract. Mice were injected with PTZ once every 48 h until kindling was developed. Animals received distilled water for the normal group and negative control groups, doses of extract (40, 80, or 160 mg/kg) for the test groups and sodium valproate (300 mg/kg) for the positive control group. Memory was measured using Y maze, novel object recognition (NOR) and open field paradigms, while the oxidative/nitrosative stresses (MDA, GSH, CAT, SOD and NO), GABAergic transmission (GABA, GABA-T and GAD) and neuro-inflammation (TNF-α, IFN-γ, IL- 1β, and IL-6) were determined. Brain photomicrograph was also studied. Apigenin, murrayanine and safranal were identified in the extract. The extract (80-160 mg/kg) significantly protected mice against seizures and mortality induced by PTZ. The extract significantly increased the spontaneous alternation and the discrimination index in the Y maze and NOR tests, respectively. PTZ kindling induced oxidative/nitrosative stress, GABA depletion, neuroinflammation and neuronal cells death was strongly reversed by the extract. The results suggest that the anticonvulsant activity of Albizia adianthifolia extract is accompanied by its anti-amnesic property, and may be supported by the amelioration of oxidative stress, GABAergic transmission and neuroinflammation.

Protective effects of vanillic acid on autistic-like behaviors in a rat model of maternal separation stress: Behavioral, electrophysiological, molecular and histopathological alterations

Compounds derived from herbs exhibit a range of biological properties, including anti-inflammatory, antioxidant, and neuroprotective properties. However, the exact mechanism of action of these compounds in various neurological disorders is not fully discovered yet. Herein, the present work detected the effect of Vanillic acid (VA), a widely-used flavoring agent derived from vanillin, on autistic-like behaviors to assess the probable underlying mechanisms that mediate behavioral, electrophysiological, molecular, and histopathological alterations in the rat model of maternal separation (MS) stress. Maternal separated rats were treated with VA (25, 50, and 100 mg/kg interperitoneally for 14 days). In addition, anxiety-like, autistic-like behaviors, and learning and memory impairment were evaluated using various behavioral tests. Hippocampus samples were assessed histopathologically by H&E staining. Levels of malondialdehyde (MDA) and antioxidant capacity (by the FRAP method), as well as nitrite levels, were measured in brain tissue. Moreover, gene expression of inflammatory markers (IL-1β, TLR-4, TNF-α, and NLRP3) was evaluated in the hippocampus. Electrophysiological alterations were also estimated in the hippocampus by long-term potentiation (LTP) assessments. Results showed that VA reversed the negative effects of MS on behavior. VA increased the diameter and decreased the percentage of dark neurons in the CA3 area. Accordingly, VA decreased MDA and nitrite levels and increased the antioxidant capacity in brain samples and decreased the expression of all inflammatory genes. VA treated rats showed significant improvements in all LTP parameters. This study provided evidence suggesting a possible role for VA in preventing autism spectrum disorder (ASD) by regulating immune signaling.

Nicorandil Exerts Anticonvulsant Effects in Pentylenetetrazol-Induced Seizures and Maximal-Electroshock-Induced Seizures by Downregulating Excitability in Hippocampal Pyramidal Neurons

N-(2-hydroxyethyl) nicotinamide nitrate (nicorandil), a nitrate that activates adenosine triphosphate (ATP)-sensitive potassium (K_ATP) channels, is generally used in the treatment of angina and offers long-term cardioprotective effects. It has been reported that several K_ATP channel openers can effectively alleviate the symptoms of seizure. The purpose of this study was to investigate the improvement in seizures induced by nicorandil. In this study, seizure tests were used to evaluate the effect of different doses of nicorandil by analysing seizure incidence, including minimal clonic seizure and generalised tonic-clonic seizure. We used a maximal electroshock seizure (MES) model, a metrazol maximal seizure (MMS) model and a chronic pentylenetetrazol (PTZ)-induced seizure model to evaluate the effect of nicorandil in improving seizures. Each mouse in the MES model was given an electric shock, while those in the nicorandil group received 0.5, 1, 2, 3 and 6 mg/kg of nicorandil by intraperitoneal injection, respectively. In the MMS model, the mice in the PTZ group and the nicorandil group were injected subcutaneously with PTZ (90 mg/kg), and the mice in the nicorandil group were injected intraperitoneally with 1, 3 and 5 mg/kg nicorandil, respectively. In the chronic PTZ-induced seizure model, the mice in the PTZ group and the nicorandil group were injected intraperitoneally with PTZ (40 mg/kg), and the mice in the nicorandil group were each given 1 and 3 mg/kg of PTZ at a volume of 200 nL. Brain slices containing the hippocampus were prepared, and cell-attached recording was used to record the spontaneous firing of pyramidal neurons in the hippocampal CA1 region. Nicorandil (i.p.) significantly increased both the maximum electroconvulsive protection rate in the MES model and the seizure latency in the MMS model. Nicorandil infused directly onto the hippocampal CA1 region via an implanted cannula relieved symptoms in chronic PTZ-induced seizures. The excitability of pyramidal neurons in the hippocampal CA1 region of the mice was significantly increased after both the acute and chronic administration of PTZ. To a certain extent, nicorandil reversed the increase in both firing frequency and proportion of burst spikes caused by PTZ (P < 0.05). Our results suggest that nicorandil functions by downregulating the excitability of pyramidal neurons in the hippocampal CA1 region of mice and is a potential candidate for the treatment of seizures.

Ellagic acid through attenuation of neuro-inflammatory response exerted antidepressant-like effects in socially isolated mice

Recent studies have been demonstrated that neuroinflammation plays a crucial role in the pathophysiology of depression. Therefore, anti-inflammatory medications could be regarded as a potentially effective treatments for depression. Ellagic acid (EA) is a natural polyphenol with antioxidant and anti-inflammatory properties. This study aimed to evaluate the antidepressant-like effect of EA in a mouse model of social isolation stress (SIS), considering its potential anti-neuroinflammatory properties. In this study, 48 male mice were divided into six groups (n = 8), including saline-treated control (socially conditioned (SC)) group and SIS (isolation conditioned (IC)) groups treated with saline or EA at doses of 12.5, 25, 50, and 100 mg/kg, respectively. Saline and EA were administrated intraperitoneally for 14 constant days. Immobility time in the forced swimming test (FST) and grooming activity time in the splash test were measured. The gene expression of inflammatory cytokines relevant to neuroinflammation was assessed in the hippocampus by real-time PCR. Results showed that SIS significantly increased immobility time in the FST and reduced grooming activity time in the splash test. In addition, the expression of inflammatory genes, including TNF-α, IL-1β, and TLR4 increased in IC mice's hippocampi. Findings showed that EA decreased immobility time in the FST and increased grooming activity time in the splash test. Moreover, EA attenuated neuroimmune-response in the hippocampus. In conclusion, finding determined that EA, through attenuation of neuroinflammation in the hippocampus, partially at least, exerted an antidepressant-like effect in the mouse model of SIS.

Microglia sustain anterior cingulate cortex neuronal hyperactivity in nicotine-induced pain

BACKGROUND

Long-term smoking is a risk factor for chronic pain, and chronic nicotine exposure induces pain-like effects in rodents. The anterior cingulate cortex (ACC) has been demonstrated to be associated with pain and substance abuse. This study aims to investigate whether ACC microglia are altered in response to chronic nicotine exposure and their interaction with ACC neurons and subsequent nicotine-induced allodynia in mice.

METHODS

We utilized a mouse model that was fed nicotine water for 28 days. Brain slices of the ACC were collected for morphological analysis to evaluate the impacts of chronic nicotine on microglia. In vivo calcium imaging and whole-cell patch clamp were used to record the excitability of ACC glutamatergic neurons.

RESULTS

Compared to the vehicle control, the branch endpoints and the length of ACC microglial processes decreased in nicotine-treated mice, coinciding with the hyperactivity of glutamatergic neurons in the ACC. Inhibition of ACC glutamatergic neurons alleviated nicotine-induced allodynia and reduced microglial activation. On the other hand, reactive microglia sustain ACC neuronal excitability in response to chronic nicotine, and pharmacological inhibition of microglia by minocycline or liposome-clodronate reduces nicotine-induced allodynia. The neuron-microglia interaction in chronic nicotine-induced allodynia is mediated by increased expression of neuronal CX3CL1, which activates microglia by acting on CX3CR1 receptors on microglial cells.

CONCLUSION

Together, these findings underlie a critical role of ACC microglia in the maintenance of ACC neuronal hyperactivity and resulting nociceptive hypersensitivity in chronic nicotine-treated mice.

Implication of nitrergic system in the anticonvulsant effects of ferulic acid in pentylenetetrazole-induced seizures in male mice

OBJECTIVES

Seizures are abnormal discharge of neurons in the brain. Ferulic acid (FA) is a phenolic compound with antioxidant and neuroprotective effects. The present study aimed to investigate the role of the nitrergic system in the anticonvulsant effect of FA in pentylenetetrazol (PTZ)-induced seizures in male mice.

METHODS

64 male Naval Medical Research Institute (NMRI) mice weighing 25-29 g were randomly divided into eight experimental groups (n=8). FA at doses 5, 10, and 40 mg/kg alone and in combination with L-nitro-arginine methyl ester (L-NAME) (nitric oxide synthase inhibitor) or L-arginine (L-arg) (nitric oxide [NO] precursor) was administrated (intraperitoneal). PTZ was injected (i.v. route) 30 min after drugs administration (1 mL/min). Seizure onset time was recorded and the nitrite levels of prefrontal cortex and serum were determined by the Griess method.

RESULTS

FA at doses of 10 and 40 mg/kg significantly increased the seizure threshold as well as reduced the serum and brain NO levels in comparison to the saline-received group. Co-administration of the effective dose of FA (10 mg/kg) plus L-arg significantly decreased the seizure threshold in comparison to the effective dose of FA alone. Co-injection of the sub-effective dose of FA (5 mg/kg) with L-NAME significantly increased the seizure threshold as well as significantly decreased the brain NO level in comparison to the sub-effective dose of FA alone.

CONCLUSIONS

We showed that the nitrergic system, partially at least, mediated the anticonvulsant effect of FA in PTZ-induced seizures in mice. We concluded that L-NAME potentiated while L-arg attenuated the anticonvulsant effect of FA.

Minocycline alleviated scopolamine-induced amnesia by regulating antioxidant and cholinergic function

BACKGROUND AND AIM

Minocycline, a tetracycline derivative, has been found to exert neuroprotective properties. The current project aimed to assess the antioxidant status and cholinergic function in the amnesia induced by scopolamine.

METHODS

We evaluated the passive avoidance performance, acetylcholine esterase (AChE) enzyme activity, and the oxidative stress indicators in the following groups: Normal control, scopolamine, and the treatment groups (the animals were given minocycline (10-30 mg/kg)).

RESULTS

Scopolamine (intraperitoneal) injection was associated with impairment of passive avoidance performance and neurotoxicity. Minocycline pronouncedly ameliorated scopolamine injury as presented by the increased latency time to darkness and stay time in lightness along with the decreased darkness entry. Moreover, minocycline decreased lipid peroxidation, while it elevated the levels of superoxide dismutase, AChE enzymes, and thiol groups in both the cortex and hippocampus.

CONCLUSION

Our data suggested that minocycline modulated the antioxidant status and AChE in the brains, which may contribute to its protective effects against scopolamine-induced amnesia.

Chronic stress but not acute stress decreases the seizure threshold in PTZ-induced seizure in mice: role of inflammatory response and oxidative stress

Seizure is paroxysmal abnormal electrical discharges in the cerebral cortex. Inflammatory pathways and oxidative stress are involved in the pathophysiology of seizures. Stress can induce an oxidative stress state and increase the production of inflammatory mediators in the brain. We investigated the effects of acute and chronic stresses on the seizure threshold in pentylenetetrazol (PTZ)-induced seizures in mice, considering oxidative stress and inflammatory mediators in the prefrontal cortex. In this study, 30 male Naval Medical Research Institute (NMRI) mice were divided into 3 groups, including acute stress, chronic stress, and control groups. PTZ was used for the induction of seizures. The gene expression of inflammatory markers (IL-1β, TNF-α, NLRP3, and iNOS), malondialdehyde (MDA) level, nitrite level, and total antioxidant capacity (TAC) were assessed in the prefrontal cortex and serum. Our results showed that stress could increase the expression of inflammatory cytokines genes and oxidative stress in the prefrontal cortex of the brain and serum following PTZ-induced seizures, which is associated with increased seizure sensitivity and decreased the seizure threshold. The effects of chronic stress were much more significant than acute stress. We concluded that the effects of chronic stress on seizure sensitivity and enhancement of neuroinflammation and oxidative stress are much greater than acute stress.

Pexidartinib (PLX3397) through restoring hippocampal synaptic plasticity ameliorates social isolation-induced mood disorders

Social behavior is essential for the well-being and survival of individuals. However, social isolation is a serious public health issue, especially during the COVID-19 pandemic, affecting a significant number of people worldwide, and can lead to serious psychological crises. Microglia, innate immune cells in the brain, are strongly implicated in the development of psychiatry. Although many microglial inhibitors have been used to treat depression, there is no literature report on pexidartinib (PLX3397) and social isolation. Herein, we adopted PLX3397 to investigate the role of microglia in the modulation of social isolation. Our results found that social isolation during adolescence caused depressive-like, but not anxiety-like behavior in mice in adulthood, with enhanced expression of the microglial marker Iba1 in the hippocampus. In addition, treatment with PLX3397 reduced the expression of the microglial marker Iba1, decreased the mRNA expression of IL-1β, increased the mRNA expression of Arg1, elevated the protein levels of DCX and GluR1 and restored the dendritic spine branches and density, ultimately mitigating depressive-like behavior in mice. These findings suggest that inhibition of microglia in the hippocampus could ameliorate mood disorders in mice, providing a new perspective for the treatment of psychiatric disorders such as depression.

Maternal Acetate Supplementation Reverses Blood Pressure Increase in Male Offspring Induced by Exposure to Minocycline during Pregnancy and Lactation

Emerging evidence supports that hypertension can be programmed or reprogrammed by maternal nutrition. Maternal exposures during pregnancy, such as maternal nutrition or antibiotic use, could alter the offspring’s gut microbiota. Short-chain fatty acids (SCFAs) are the major gut microbiota-derived metabolites. Acetate, the most dominant SCFA, has shown its antihypertensive effect. Limited information exists regarding whether maternal acetate supplementation can prevent maternal minocycline-induced hypertension in adult offspring. We exposed pregnant Sprague Dawley rats to normal diet (ND), minocycline (MI, 50 mg/kg/day), magnesium acetate (AC, 200 mmol/L in drinking water), and MI + AC from gestation to lactation period. At 12 weeks of age, four groups (n = 8/group) of male progeny were sacrificed. Maternal acetate supplementation protected adult offspring against minocycline-induced hypertension. Minocycline administration reduced plasma acetic acid level, which maternal acetate supplementation prevented. Additionally, acetate supplementation increased the protein level of SCFA receptor G protein-coupled receptor 41 in the offspring kidneys. Further, minocycline administration and acetate supplementation significantly altered gut microbiota composition. Maternal acetate supplementation protected minocycline-induced hypertension accompanying by the increases in genera Roseburia, Bifidobacterium, and Coprococcus. In sum, our results cast new light on targeting gut microbial metabolites as early interventions to prevent the development of hypertension, which could help alleviate the global burden of hypertension.

Modulation of astrocyte activity and improvement of oxidative stress through blockage of NO/NMDAR pathway improve posttraumatic stress disorder (PTSD)-like behavior induced by social isolation stress

BACKGROUND

It has been well documented that social isolation stress (SIS) can induce posttraumatic stress disorder (PTSD)-like behavior in rodents, however, the underlying mechanism is remained misunderstood. In the current study, we aimed to elucidate the role of NO/NMDAR pathway in PTSD-like behavior through modulating of astrocyte activity and improvement of oxidative stress.

METHODS

Male NMRI mice were used to evaluate the memory function by using Morris water maze (MWM) and fear memory extinction by using freezing response. We used MK-801 (NMDAR-antagonist), L-NNA (NOS-inhibitor), NMDA (NMDAR-agonist), and L-arginine (NO-agent) to find a proper treatment. Also, immunohistochemistry, RT-PCR, and oxidative stress assays were used to evaluate the levels of astrocytes and oxidative stress. We used five mice in each experimental task.

RESULTS

Our results revealed that SIS could induce learning and memory dysfunction as well as impairment of fear memory extinction in MWM and freezing response tests, respectively. Also, we observed that combined treatment including blockage of NOS (by L-NNA, 0.5 mg/kg) and NMDAR (by MK-801, 0.001 mg/kg) at subeffective doses could result in improvement of both memory and fear memory. In addition, we observed that SIS significantly increases the GFAP expression and astrocyte activity, which results in significant imbalance in oxidative stress. Coadministration of MK-801 and L-NNA at subeffective doses not only decreases the expression of GFAP, but also regulates the oxidative stress imbalance CONCLUSION: Based on these results, it could be hypothesized that blockage of NO/NMDAR pathway might be a novel treatment for PTSD-like behavior in animals by inhibiting the astrocyte and regulating oxidative stress level.

USE OF KETOGENIC DIET THERAPY IN EPILEPSY WITH MITOCHONDRIAL DYSFUNCTION: A SYSTEMATIC AND CRITICAL REVIEW

With the development of molecular techniques over time more than %60 of epilepsy has associated with mitochondrial (mt) dysfunction. Ketogenic diet (KD) has been used in the treatment of epilepsy since the 1920s. Aim. To evaluate the evidence behind KD in mt dysfunction in epilepsy. Methods. Databases PubMed, Google Scholar and MEDLINE were searched in an umbrella approach to 12 March 2021 in English. To identify relevant studies specific search strategies were devised for the following topics: (1) mitochondrial dysfunction (2) epilepsy (3) KD treatment. Results. From 1794 papers, 36 articles were included in analysis: 16 (%44.44) preclinical studies, 11 (%30.55) case reports, 9 (%25) clinical studies. In all the preclinic studies, KD regulated the number of mt profiles, transcripts of metabolic enzymes and encoding mt proteins, protected the mice against to seizures and had an anticonvulsant mechanism. Case reports and clinical trials have reported patients with good results in seizure control and mt functions, although not all of them give good results as well as preclinical. Conclusion. Healthcare institutions, researchers, neurologists, health promotion organizations, and dietitians should consider these results to improve KD programs and disease outcomes for mt dysfunction in epilepsy.

Reconnoitering the transformative journey of minocycline from an antibiotic to an antiepileptic drug

Minocycline, a second-generation tetracycline antibiotic is being widely tested in animals as well as clinical settings for the management of multiple neurological disorders. The drug has shown to exert protective action in a multitude of neurological disorders including spinal-cord injury, stroke, multiple sclerosis, amyotrophic lateral sclerosis, Huntington's disease, and Parkinson's disease. Being highly lipophilic, minocycline easily penetrates the blood brain barrier and is claimed to have excellent oral absorption (~100% bioavailability). Minocycline possesses anti-inflammatory, immunomodulatory, and anti-apoptotic properties, thereby supporting its use in treating neurological disorders. The article henceforth reviews all the recent advances in the transformation of this antibiotic into a potential antiepileptic/antiepileptogenic agent. The article also gives an account of all the clinical trials undertaken till now validating the antiepileptic potential of minocycline. Based on the reported studies, minocycline seems to be an important molecule for treating epilepsy. However, the practical therapeutic implementations of this molecule require extensive mechanism-based in-vitro (cell culture) and in-vivo (animal models) studies followed by its testing in randomized, placebo controlled and double-blind clinical trials in large population as well as in different form of epilepsies.

Effects of Forkhead box O1 on lipopolysaccharide-induced mitochondrial dysfunction in human cervical squamous carcinoma SiHa cells

Persistent infection and chronic inflammation play important roles in the development of cervical squamous cell carcinoma. Forkhead box O1 (FOXO1) is a notable regulator of mitochondrial metabolism, which is involved in the occurrence and development of tumors. The present study explored the effects of FOXO1 in human cervical squamous carcinoma SiHa cells. The expression of FOXO1 was examined using reverse transcription-quantitative PCR, western blotting and immunohistochemical staining. SiHa cell migration and proliferation were detected using Transwell and ³H-TdR assays. Mitochondrial functions were assessed based on reactive oxygen species (ROS) generation and changes in the mitochondrial membrane potential (ΔΨm). The present study revealed that lipopolysaccharide (LPS) stimulation significantly inhibited the expression of FOXO1 in cervical squamous carcinoma SiHa cells; while silencing FOXO1 resulted in the accumulation of mitochondrial ROS, a decrease in the ΔΨm and abnormal morphology of mitochondria. Accordingly, enhancing FOXO1 expression or treatment with metformin, which protects mitochondrial function, reversed LPS-induced mitochondrial dysfunction, cell pyroptosis, migration and proliferation of cervical squamous carcinoma SiHa cells. Overall, the current study indicated that treatment with FOXO1 could potentially be used as therapeutic strategy to prevent LPS-induced cervical squamous cell carcinoma-related dysfunction in a mitochondria-dependent manner.

Role of hypothalamic-pituitary adrenal-axis, toll-like receptors, and macrophage polarization in pre-atherosclerotic changes induced by social isolation stress in mice

It has been well documented that chronic stress can induce atherosclerotic changes, however, the underlying mechanisms is yet to be established. In this regard, this study aimed to elucidate the relation between hypothalamic-pituitary adrenal-axis (HPA-axis), toll-like receptors (TLRs), as well as M1/M2 macrophage ratio and pre-atherosclerotic changes in social isolation stress (SIS) in mice. We used small interfering RNA against the glucocorticoid receptor (GR) to evaluate the relation between HPA-axis and TLRs. C57BL/6J mice were subjected to SIS and RT-PCR, ELISA, flow cytometry, and immunohistochemistry were used to assess the relations between pre-atherosclerotic changes and TLRs, macrophage polarization, pro-inflammatory cytokines, and cell adhesion molecules in aortic tissue. We used TAK-242 (0.3 mg/kg, intraperitoneally), a selective antagonist of TLR4, as a possible prophylactic treatment for atherosclerotic changes induced by SIS. We observed that isolated animals had higher serum concentration of corticosterone and higher body weight in comparison to normal animals. In isolated animals, results of in vitro study showed that knocking-down of the GR in bone marrow-derived monocytes significantly decreased the expression of TLR4. In vivo study suggested higher expression of TLR4 on circulating monocytes and higher M1/M2 ratio in aortic samples. Pathological study showed a mild pre-atherosclerotic change in isolated animals. Finally, we observed that treating animals with TAK-242 could significantly inhibit the pre-atherosclerotic changes. SIS can possibly increase the risk of atherosclerosis through inducing abnormal HPA-axis activity and subsequently lead to TLR4 up-regulation, vascular inflammation, high M1/M2 ratio in intima. Thus, TLR4 inhibitors might be a novel treatment to decrease the risk of atherosclerosis induced by chronic stress.

Nitric oxide modulation in neuroinflammation and the role of mesenchymal stem cells

Nitric oxide is a versatile mediator formed by enzymes called nitric oxide synthases. It has numerous homeostatic functions and important roles in inflammation. Within the inflamed brain, microglia and astrocytes produce large amounts of nitric oxide during inflammation. Excessive nitric oxide causes neuronal toxicity and death and mesenchymal stem cells can be used as an approach to limit the neuronal damage caused by neuroinflammation. Mesenchymal stem cell therapy ameliorates inflammation and neuronal damage in disease models of Alzheimer's disease, Parkinson's disease, and other neuroinflammatory disorders. Interestingly, we have reported that in vitro, mesenchymal stem cells themselves contribute to a rise in nitric oxide levels through microglial cues. This may be an undesirable effect and highlights a possible need to explore acellular approaches for mesenchymal stem cell therapy in the central nervous system.

Bactericidal/Permeability-Increasing Protein Improves Cognitive Impairment in Diabetic Mice via Blockade of the LPS-LBP-TLR4 Signaling Pathway

Emerging evidence suggests that the bactericidal/permeability-increasing protein (BPI) is involved in the process of cognitive impairment in diabetes. However, its underlying mechanism remains elusive. In this study, we found that BPI affects cognitive impairment due to diabetes through the lipopolysaccharide (LPS)-lipopolysacharide-binding protein (LBP)-toll-like receptor 4 (TLR4) signaling pathway. We examined the expression of BPI, LPS, LBP, CD14, and TLR4 in established mouse models of diabetes induced by high-fat diet (HFD) in combination with streptozotocin (STZ). Diabetic mice were then injected with adeno-associated-virus carrying BPI overexpression vectors and LPS. Fasting blood glucose, plasma insulin, and serum levels of inflammatory factors were examined. Then, glucose tolerance and, insulin resistance tests were used to measure systemic insulin sensitivity. Next, hippocampal tissue injury and cell apoptosis were examined by hematoxylin-eosin (HE) and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining. Diabetic mice displayed increased LPS expression and activation of the LPS-CD14-TLR4 signaling pathway. HFD mice following LPS treatment showed significantly increased serum levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6, and expressions of Bcl-2-associated X protein (Bax) and Aβ but decreased expression of Bcl-2 in hippocampal tissues, as well as enhanced fasting blood glucose, plasma insulin, glucose tolerance, insulin tolerance, cell apoptosis, aggravated hippocampal tissue injury and, ultimately, cognitive impairment. However, overexpression of BPI was able to rescue the aforementioned phenotypes driven by LPS treatment. Taken together, BPI could potentially provide relief from cognitive impairment in diabetic mice by disrupting the LPS-LBP-TLR4 signaling pathway, underscoring a possible alternative therapeutic strategy against the cognitive impairment associated with diabetes.

Disrupted eNOS activity and expression account for vasodilator dysfunction in different stage of sepsis

AIMS

Sepsis is a severe endothelial dysfunction syndrome. The role of endothelial nitric oxide synthase (eNOS) in endothelial dysfunction induced by sepsis is controversial. To explore the role of eNOS in vascular dysfunction.

MAIN METHODS

The effect of sepsis on vasodilation and eNOS levels was examined in septic mouse arteries and in cell models.

KEY FINDINGS

In early sepsis mouse arteries, endothelium-dependent relaxation decreased and phosphorylation of the inhibitory Thr495 site in endothelial nitric oxide synthase increased. Mechanically, the phosphorylation of endothelial nitric oxide synthase at Thr497 in bovine aortic endothelial cells occurred in a protein kinase C-α dependent manner. In late sepsis, both nitric oxide-dependent relaxation responses and endothelial nitric oxide synthase levels were decreased in septic mice arteries. Endothelial nitric oxide synthase levels expression levels decreased in tumor necrosis factor-α-treated human umbilical vein endothelial cells and this could be prevented by the ubiquitin proteasome inhibitor (MG-132). MG-132 could reverse the decrease in endothelial nitric oxide synthase expression and improve nitric oxide-dependent vasodilator dysfunction in septic mice arteries.

SIGNIFICANCE

These data indicate that vasodilator dysfunction is induced by the increased phosphorylation of endothelial nitric oxide synthase in early sepsis and its degradation in late sepsis.

Anticonvulsant Effect of Alcea aucheri on Pentylenetetrazole and Maximal Electroshock Seizures in Mice

Introduction:

This study was designed to investigate the possible anticonvulsant effect of acute administration of an aqueous extract of flowers of Alcea aucheri (EFA) in two in vivo seizure models.

Methods:

Seizures were induced in male adult Swiss mice by administration of Pentylenetetrazol (PTZ) or Maximal Electroshock (MES). Mice were randomly subjected to receive saline, EFA (8.75–175 mg.kg⁻¹), or diazepam intraperitoneally (i.p.) 15 or 30 min before PTZ injection. In another experiment, mice were treated (i.p.) with saline, EFA (8.75–350 mg.kg⁻¹), or phenytoin 15 or 30 min before the MES test. Diazepam and phenytoin were used as reference drugs.

Results:

EFA (175 mg.kg⁻¹) significantly increased the PTZ-induced seizure threshold compared with the saline control group 15 min after its administration. In the MES test, the extract (35 mg.kg⁻¹) increased the latency to onset of tonic Hind Limb Extension (HLE) (seizure activity) compared with the saline group 15 min after treatment. Also, 30 min after treatment, EFA (35, 70, and 175 mg.kg⁻¹) increased the latency to onset of the seizure, decreased the duration of the seizure (70 mg.kg⁻¹), and decreased seizure occurrence (350 mg.kg⁻¹) compared with those of the saline group. At both time points, the extract at all doses significantly reduced the mortality rate compared with the saline group.

Conclusion:

These findings provide evidence of a possible anticonvulsant effect of A. aucheri in PTZ and MES seizure models in mice.

The role of nitric oxide in glutaric acid-induced convulsive behavior in pup rats

Glutaric acidaemia type I (GA-I) is a cerebral organic disorder characterized by the accumulation of glutaric acid (GA) and seizures. As seizures are precipitated in children with GA-I and the mechanisms underlying this disorder are not well established, we decided to investigate the role of nitric oxide (NO) in GA-induced convulsive behaviour in pup rats. Pup male Wistar rats (18-day-old) were anesthetized and placed in stereotaxic apparatus for cannula insertion into the striatum for injection of GA. The experiments were performed 3 days after surgery (pup rats 21-day-old). An inhibitor of NO synthesis (N-G-nitro-l-arginine methyl ester-L-NAME, 40 mg/kg) or saline (vehicle) was administered intraperitoneally 30 min before the intrastriatal injection of GA (1 µl, 1.3 µmol/striatum) or saline. Immediately after the intrastriatal injections, the latency and duration of seizures were recorded for 20 min. The administration of L-NAME significantly increased the latency to the first seizure episode and reduced the duration of seizures induced by GA in pup rats. The administration of the NO precursor l-arginine (L-ARG; 80 mg/kg) prevented the effects of L-NAME. Besides, GA significantly increased nitrate and nitrite (NOx) levels in the striatum of pup rats and the preadministration of L-NAME prevented this alteration. L-ARG blocked the reduction of striatal NOx provoked by L-NAME. These results are experimental evidence that NO plays a role in the seizures induced by GA in pup rats, being valuable in understanding the physiopathology of neurological signs observed in children with this organic acidaemia and to develop new therapeutic strategies.

HDAC2 hyperexpression alters hippocampal neuronal transcription and microglial activity in neuroinflammation-induced cognitive dysfunction

Background

Inflammation can induce cognitive dysfunction in patients who undergo surgery. Previous studies have demonstrated that both acute peripheral inflammation and anaesthetic insults, especially isoflurane (ISO), are risk factors for memory impairment. Few studies are currently investigating the role of ISO under acute peri-inflammatory conditions, and it is difficult to predict whether ISO can aggravate inflammation-induced cognitive deficits. HDACs, which are essential for learning, participate in the deacetylation of lysine residues and the regulation of gene transcription. However, the cell-specific mechanism of HDACs in inflammation-induced cognitive impairment remains unknown.

Methods

Three-month-old C57BL/6 mice were treated with single versus combined exposure to LPS injected intraperitoneally (i.p.) to simulate acute abdominal inflammation and isoflurane to investigate the role of anaesthesia and acute peripheral inflammation in cognitive impairment. Behavioural tests, Western blotting, ELISA, immunofluorescence, qRT-PCR, and ChIP assays were performed to detect memory, the expressions of inflammatory cytokines, HDAC2, BDNF, c-Fos, acetyl-H3, microglial activity, Bdnf mRNA, c-fos mRNA, and Bdnf and c-fos transcription in the hippocampus.

Results

LPS, but not isoflurane, induced neuroinflammation-induced memory impairment and reduced histone acetylation by upregulating histone deacetylase 2 (HDAC2) in dorsal hippocampal CaMKII⁺ neurons. The hyperexpression of HDAC2 in neurons was mediated by the activation of microglia. The decreased level of histone acetylation suppressed the transcription of Bdnf and c-fos and the expressions of BDNF and c-Fos, which subsequently impaired memory. The adeno-associated virus ShHdac2, which suppresses Hdac2 after injection into the dorsal hippocampus, reversed microglial activation, hippocampal glutamatergic BDNF and c-Fos expressions, and memory deficits.

Conclusions

Reversing HDAC2 in hippocampal CaMKII⁺ neurons exert a neuroprotective effect against neuroinflammation-induced memory deficits.