The role of TLR4-mediated PTEN/PI3K/AKT/NF-κB signaling pathway in neuroinflammation in hippocampal neurons

The β2-adrenergic receptor controls inflammation by driving rapid IL-10 secretion

The mammalian nervous system communicates important information about the environment to the immune system, but the underlying mechanisms are largely unknown. Secondary lymphoid organs are highly innervated by sympathetic neurons that secrete norepinephrine (NE) as the primary neurotransmitter. Immune cells express adrenergic receptors, enabling the sympathetic nervous system to directly control immune function. NE is a potent immunosuppressive factor and markedly inhibits TNF-α secretion from innate cells in response to lipopolysaccharide (LPS). In this study, we demonstrate that NE blocks the secretion of a variety of proinflammatory cytokines by rapidly inducing IL-10 secretion from innate cells in response to multiple Toll-like receptor (TLR) signals. NE mediated these effects exclusively through the β2-adrenergic receptor (ADRB2). Consequently, Adrb2^-/- animals were more susceptible to L. monocytogenes infection and to intestinal inflammation in a dextran sodium sulfate (DSS) model of colitis. Further, Adrb2^-/- animals rapidly succumbed to endotoxemia in response to a sub-lethal LPS challenge and exhibited elevated serum levels of TNF-α and reduced IL-10. LPS-mediated lethality in WT animals was rescued by administering a β 2-specific agonist and in Adrb2^-/- animals by exogenous IL-10. These findings reveal a critical role for ADRB2 signaling in controlling inflammation through the rapid induction of IL-10. Our findings provide a fundamental insight into how the sympathetic nervous system controls a critical facet of immune function through ADRB2 signaling.

Cyanidin attenuates Aβ25-35-induced neuroinflammation by suppressing NF-κB activity downstream of TLR4/NOX4 in human neuroblastoma cells

Cyanidin is polyphenolic pigment found in plants. We have previously demonstrated that cyanidin protects nerve cells against Aβ_25-35-induced toxicity by decreasing oxidative stress and attenuating apoptosis mediated by both the mitochondrial apoptotic pathway and the ER stress pathway. To further elucidate the molecular mechanisms underlying the neuroprotective effects of cyanidin, we investigated the effects of cyanidin on neuroinflammation mediated by the TLR4/NOX4 pathway in Aβ_25-35-treated human neuroblastoma cell line (SK-N-SH). SK-N-SH cells were exposed to Aβ_25-35 (10 μmol/L) for 24 h. Pretreatment with cyanidin (20 μmol/L) or NAC (20 μmol/L) strongly inhibited the NF-κB signaling pathway in the cells evidenced by suppressing the degradation of IκBα, translocation of the p65 subunit of NF-κB from the cytoplasm to the nucleus, and thereby reducing the expression of iNOS protein and the production of NO. Furthermore, pretreatment with cyanidin greatly promoted the translocation of the Nrf2 protein from the cytoplasm to the nucleus; upregulating cytoprotective enzymes, including HO-1, NQO-1 and GCLC; and increased the activity of SOD enzymes. Pretreatment with cyanidin also decreased the expression of TLR4, directly improved intracellular ROS levels and regulated the activity of inflammation-related downstream pathways including NO production and SOD activity through TLR4/NOX4 signaling. These results demonstrate that TLR4 is a primary receptor in SK-N-SH cells, by which Aβ_25-35 triggers neuroinflammation, and cyanidin attenuates Aβ-induced inflammation and ROS production mediated by the TLR4/NOX4 pathway, suggesting that inhibition of TLR4 by cyanidin could be beneficial in preventing neuronal cell death in the process of Alzheimer's disease.

Molybdenum bupropion combined neurotoxicity in rats

Heavy metal toxicity is a common foodborne problem in Egypt, especially in combination. Molybdenum toxicity has been studied as a model of the heavy metal toxicity. Molybdenum could promote toxicity via oxidative-inflammatory mechanisms. Bupropion is a well-known antidepressant that has anti-oxidant mechanisms. It exerts a cytoprotective action against molybdenum induced metal toxicity. The aim of the study is to evaluate the effects of combined bupropion and molybdenum in a toxic animal model. The results showed that the combination of bupropion and high doses of molybdenum was extremely toxic with an evident animal fatality. Bupropion showed a clear anti-oxidant/anti-inflammatory profile detected by the ELISA assay of malondialdehyde (MDA), reduced glutathione, and interleukin -6 (IL-6), and real-time gene expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and tumor necrosis factor-α (TNF-α). The immunohistochemistry of nuclear factor Kappa Beta (NF-κB) showed that bupropion reduced the inflammatory response induced by the molybdenum neurotoxicity. Despite the improved laboratory profile, the animals were extremely intoxicated with recorded fatalities raising the question about other pathways and mechanisms explaining the drug metal interaction. Furthermore, Bupropion even in normal doses was toxic to the animals. Choroid plexus hyperplasia was reported in the histological examination of the animal brain loaded with bupropion, and choroid plexus papilloma was recorded in the combined drug metal group. More wide-scale studies are needed to verify the safety of the current antidepressant medications for the long-term therapy. It is important to focus on drug metal interaction as a possible cause of neuropathology.

Up-Regulation of miR-130b-3p Activates the PTEN/PI3K/AKT/NF-κB Pathway to Defense against Mycoplasma gallisepticum (HS Strain) Infection of Chicken

Mycoplasma gallisepticum (MG) is the pathogen of chronic respiratory disease (CRD), hallmarked by vigorous inflammation in chickens, causing the poultry industry enormous losses. miRNAs have emerged as important regulators of animal diseases. Previous miRNA sequencing data has demonstrated that miR-130b-3p is up-regulated in MG-infected chicken embryo lungs. Therefore, we aimed to investigate the function of miR-130b-3p in MG infection of chickens. RT-qPCR results confirmed that miR-130b-3p was up-regulated both in MG-infected chicken embryo lungs and chicken embryonic fibroblast cells (DF-1 cells). Furthermore, functional studies showed that overexpression of miR-130b-3p promoted MG-infected DF-1 cell proliferation and cell cycle, whereas inhibition of miR-130b-3p weakened these cellular processes. Luciferase reporter assay combined with gene expression data supported that phosphatase and tensin homolog deleted on chromosome ten (PTEN) was a direct target of miR-130b-3p. Additionally, overexpression of miR-130b-3p resulted in up-regulations of phosphatidylinositol-3 kinase (PI3K), serine/threonine kinase (AKT), and nuclear factor-κB (NF-κB), whereas inhibition of miR-130b-3p led to the opposite results. Altogether, upon MG infection, up-regulation of miR-130b-3p activates the PI3K/AKT/NF-κB pathway, facilitates cell proliferation and cell cycle via down-regulating PTEN. This study helps to understand the mechanism of host response to MG infection.

Carnosic acid protects mice from high-fat diet-induced NAFLD by regulating MARCKS

Non-alcoholic fatty liver disease (NAFLD) comprises a spectrum of liver damage characterized by abnormal hepatic fat accumulation and inflammatory response. Although the molecular mechanisms responsible for the disease are not yet fully understood, the pathogenesis of NAFLD likely involves multiple signals. The identification of effective therapeutic strategies to target these signals is of utmost importance. Carnosic acid (CA), as a phenolic diterpene with anticancer, anti-bacterial, anti-diabetic and neuroprotective properties, is produced by many species of the Lamiaceae family. Myristoylated alanine-rich C-kinase substrate (MARCKS) is a major protein kinase C (PKC) substrate in many different cell types. In the present study, wild-type C57BL/6 and MARCKS-deficient mice were randomly divided into the normal chow- or high-fat (HF) diet-fed groups. The HF diet increased the fasting glucose and insulin levels, and promoted glucose intolerance in the wild-type mice. MARCKS deficiency further upregulated intolerance, fasting glucose and insulin. The HF diet also promoted hepatic steatosis, serum alanine transaminase (ALT) and aspartate transaminase (AST) activity, inflammation and lipid accumulation in the wild-type mice. These responses were accelerated in the MARCKS-deficient mice. Importantly, increased inflammation and lipid accumulation were associated with phosphoinositide 3-kinase (PI3K)/AKT, NLR family pyrin domain containing 3 (NLRP3)/nuclear factor-κB (NF-κB) and sterol regulatory element binding protein-1c (SREBP-1c) signaling pathway activation. The mice treated with CA exhibited a significantly improved glucose and insulin tolerance. The production of pro-inflammatory cytokines and lipid accumulation were suppressed by CA. Significantly, MARCKS was reduced in mice fed the HF diet. CA treatment upregulated MARCKS expression compared to the HF group. Furthermore, the activation of the PI3K/AKT, NLRP3/NF-κB and SREBP-1c signaling pathways was inhibited by CA. Taken together, our data suggest that CA suppresses inflammation and lipogenesis in mice fed a HF diet through MARCKS regulation. Thus, CA may be prove to be a useful anti-NAFLD agent.

Anti-inflammatory activity of Khayandirobilide A from Khaya senegalensis via NF-κB, AP-1 and p38 MAPK/Nrf2/HO-1 signaling pathways in lipopolysaccharide-stimulated RAW 264.7 and BV-2 cells

BACKGROUND

Immunocytes-involved inflammation is considered to modulate the damage in various diseases. Herein, novel therapeutics suppressing over-activation of immunocytes could prove an effective strategy to prevent inflammation-related diseases.

PURPOSE

The objective of this study is to evaluate the anti-inflammatory activity of Khayandirobilide A (KLA), a new andirobin-type limonoid with modified furan ring isolated from the Khaya senegalensis (Desr.) A. Juss., and to explore its potential underlying mechanisms in LPS-stimulated inflammatory models.

METHODS

The structure of KLA was elucidated on the basis of 1D- and 2D-NMR spectroscopic data as well as HR-ESI-MS. As for its anti-inflammatory effect, the production of pro-inflammatory mediators and cytokines in LPS-stimulated RAW 264.7 and BV-2 cells were measured by Griess reagent, ELISA and qRT-PCR. The relevant proteins including nuclear factor κB (NF-κB), p-AKT, p-p38 and Nrf2/HO-1 were investigated by western blot. Nuclear localisations of NF-κB, activator protein-1 (AP-1) and Nrf2 were also examined by western blot and immunofluorescence.

RESULTS

KLA could inhibit the production of LPS-induced NO with IC₅₀ values of 5.04 ± 0.14 µM and 4.97 ± 0.5 µM in RAW 264.7 and BV-2 cells, respectively. KLA also attenuated interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) at the protein and mRNA levels. Further mechanistic studies demonstrated the activation of NF-κB and AP-1 were reduced by KLA. Moreover, KLA elevated expression of heme oxygenase-1(HO-1) via inducing Keap1 autophagic degradation and promoting Nrf2 nuclear translocation. Despite KLA induced the phosphorylation of mitogen-activated protein kinases (MAPKs) family, inhibiting the phosphorylation of p38 by its specific inhibitor SB203580 attenuated the degradation of KLA-induced Keap1, and then reduced KLA-induced Nrf2 nuclear translocation and HO-1 expression. Furthermore, SB203580, Brusatol (a Nrf2 specific inhibitor) and ZnPP (a HO-1 specific inhibitor) could partly reverse the suppressive effects of KLA on LPS-induced NO production and mRNA levels of pro-inflammatory genes.

CONCLUSION

These data displayed that KLA possessed anti-inflammatory activity, which was attributed to inhibit the release of LPS-stimulated inflammatory mediators via suppressing the activation of NF-κB, AP-1, and upregulating the induction of p38 MAPK/Nrf2-mediated HO-1.

Interactions of Notch1 and TLR4 signaling pathways in DRG neurons of in vivo and in vitro models of diabetic neuropathy

Understanding the interactions between Notch1 and toll-like receptor 4 (TLR4) signaling pathways in the development of diabetic peripheral neuropathy may lead to interpretation of the mechanisms and novel approaches for preventing diabetic neuropathic pain. In the present study, the interactions between Notch1 and TLR4 signaling pathways were investigated by using dorsal root ganglion (DRG) from diabetic neuropathic pain rats and cultured DRG neurons under high glucose challenge. The results showed that high glucose induced not only Notch1 mRNA, HES1 mRNA, and TLR4 mRNA expression, but also Notch1 intracellular domain (NICD1) and TLR4 protein expression in DRG neurons. The proportion of NICD1-immunoreactive (IR) and TLR4-IR neurons in DRG cultures was also increased after high glucose challenge. The above alterations could be partially reversed by inhibition of either Notch1 or TLR4 signaling pathway. Inhibition of either Notch1 or TLR4 signaling pathway could improve mechanical allodynia and thermal hyperalgesia thresholds. Inhibition of Notch1 or TLR4 signaling also decreased tumor necrosis factor-α (TNF-α) levels in DRG from diabetic neuropathic rats. These data imply that the interaction between Notch1 and TLR4 signaling pathways is one of the important mechanisms in the development or progression of diabetic neuropathy.

Role of 3-Acetyl-11-Keto-Beta-Boswellic Acid in Counteracting LPS-Induced Neuroinflammation via Modulation of miRNA-155

Neuroinflammation is one of the most important mechanisms underlying neurodegeneration. Lipopolysaccharide (LPS) is a potent inflammogen which causes cognitive dysfunction. Boswellia serrata is known since many years as a powerful anti-inflammatory herbal drug. Its beneficial effect mainly arises from inhibition of 5-lipoxygenase (5-LO) enzyme. 3-acetyl-11-keto-β-boswellic acid (AKBA) is the most potent 5-LO inhibitor extracted from the oleo-gum-resin of Boswellia serrata. The aim of the present work is to study the molecular mechanisms underlying the anti-inflammatory and neuroprotective effects of AKBA and dexamethasone (DEX) in LPS-induced neuroinflammatory model. A single intraperitoneal (i.p.) dose of LPS (0.8 mg/kg) was injected to induce cognitive dysfunction. The LPS-treated mice were administered for 7 days with either AKBA or DEX at intraperitoneal doses of 5 and 1 mg/kg, respectively. Cognitive, locomotor functions, and anxiety level were first examined. The level of the phosphorylated inhibitory protein for NF-κB, IκB-α (P-IκB-α), was measured, and the expression levels of the inflammatory microRNA-155 (miR-155) and its target gene, suppressor of cytokine signaling-1 (SOCS-1), were determined in the brain. Moreover, the level of carbonyl proteins as a measure of oxidative stress and several cytokines as well as markers for apoptosis and amyloidogenesis was detected. Results showed that AKBA and DEX reversed the behavioral dysfunction induced by LPS. AKBA decreased P-IκB-α, miRNA-155 expression level, and carbonyl protein content. It restored normal cytokine level and increased SOCS-1 expression level. It also showed anti-apoptotic and anti-amyloidogenic effects in LPS-injected mice. These findings suggest AKBA as a therapeutic drug for alleviating the symptoms of neuroinflammatory disorders.

LY294002, a PI3K inhibitor, attenuates Tourette syndrome in rats

The present study was designed to investigate the effects of LY294002 on Tourette syndrome (TS) in rats. TS model was induced in rats by DOI (the selective 5-HT2A/2C agonist 1- (2, 5- dimethoxy -4 - iodophenyl) -2- aminopropane). Behavior was assessed by stereotypic score and autonomic activity. Inflammatory cytokines such as interleukin-6 (IL-6), interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in serum and striatum were detected. The protein levels of PI3K/Akt/NF-B in striatum were detected by Western Blot. LY294002 treatment significantly reduced IL-6, IL-1β and TNF-α in serum and striatum of TS rats, Also, highly expressed P-PI3K, P-Akt, P-NF-κBp65, P-IκBα in TS rats were restored respectively by LY294002 treatment as indicted in western blot analysis and immunohistochemistry analysis. Thus, it was supposed that the protective effect of LY294002 against TS in rat might be associated with the regulation of PI3K/Akt/NF-B pathway.

Overexpression of Circular RNA ciRS-7 Abrogates the Tumor Suppressive Effect of miR-7 on Gastric Cancer via PTEN/PI3K/AKT Signaling Pathway

Gastric cancer (GC) has one of the highest mortality rates of malignancies globally. Currently, ciRS-7, a novel circular RNA, has emerged as a potential sponge for miR-7. However, few studies on ciRS-7 in GC have been performed. In this study, we investigated the clinical significance and function of ciRS-7 in GC. First, the expression levels of ciRS-7 in 102 primary GC tissues and the matched para-carcinoma tissues were evaluated and the clinical relevance was confirmed in an independent validation cohort (n = 154). Second, the effects of ciRS-7 on miR-7, PTEN, and PI3K were evaluated. Finally, the function of ciRS-7 in GC was analyzed with cell lines and nude mice. The expression of ciRS-7 was significantly upregulated in GC tissues compared with the matched para-carcinoma tissues (P = 0.0023), and the upregulation of ciRS-7 was linked to poor survival in the testing (P = 0.0143) and validation cohort (P = 0.0061). Multivariate survival analysis revealed that ciRS-7 was probably an independent risk factor of overall survival (P < 0.05). Furthermore, overexpression of ciRS-7 blocked the miR-7-induced tumor suppression in MGC-803 and HGC-27 cells and led to a more aggressive oncogenic phenotype, via antagonizing miR-7-mediated PTEN/PI3K/AKT pathway. ciRS-7 may act as a prospective prognostic biological marker and a promising therapeutic target for GC. J. Cell. Biochem. 119: 440-446, 2018. © 2017 Wiley Periodicals, Inc.

Anticancer effect of curcumin inhibits cell growth through miR-21/PTEN/Akt pathway in breast cancer cell

Curcumin is a polyphenol extracted from turmeric, which that belongs to the Zingiberaceae family. Curcumin has numerous effects, including anti-inflammatory, antitumor, anti-oxidative and antimicrobial effects. However, the effects of curcumin on human breast cancer cells remain largely unknown. The aim of the present study was to investigate the anticancer effects and the mechanisms by which curcumin affects breast cancer cells. The anticancer effect of curcumin on cell viability and cytotoxicity on human breast cancer MCF-7 cells was analyzed using 3-(4,5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium bromide and lactate dehydrogenase assays, respectively. Cell apoptosis of MCF-7 cells was detected using flow cytometry, 4′,6-diamidino-2-phenylindolestaining assay and caspase-3/9 activity kits. Reverse transcription-quantitative polymerase chain reaction was used to analyze microRNA-21 (miR-21) expression in MCF-7 cells. The protein expression of phosphatase and tensin homolog (PTEN) and phospho-protein kinase B (pAkt) was determined by western blot analysis. miR-21 was transfected into MCF-7 cells and the anticancer effect of curcumin on cell viability and the expression of PTEN and pAkt was analyzed. The present results demonstrated that curcumin inhibited cell viability and induced cytotoxicity of MCF-7 cells in a concentration- and time-dependent manner, by inducing apoptosis and increasing caspase-3/9 activities. In addition, curcumin downregulated miR-21 expression in MCF-7 cells by upregulating the PTEN/Akt signaling pathway. The present study has for the first time, to the best of our knowledge, revealed the anticancer effect of curcumin in suppressing breast cancer cell growth, and has elucidated that the miR-21/PTEN/Akt signaling pathway is a key mechanism for the anticancer effects of curcumin.

Association of adipocyte enhancer-binding protein 1 with Alzheimer's disease pathology in human hippocampi

Adipocyte enhancer binding protein 1 (AEBP1) activates inflammatory responses via the NF-κB pathway in macrophages and regulates adipogenesis in preadipocytes. Up-regulation of AEBP1 in the hippocampi of patients with Alzheimer's disease (AD) has been revealed by microarray analyses of autopsied brains from the Japanese general population (the Hisayama study). In this study, we compared the expression patterns of AEBP1 in normal and AD brains, including in the hippocampus, using immunohistochemistry. The subjects were 24 AD cases and 52 non-AD cases. Brain specimens were immunostained with antibodies against AEBP1, tau protein, amyloid β protein, NF-κB, GFAP and Iba-1. In normal brains, AEBP1 immunoreactivity mainly localized to the perikarya of hippocampal pyramidal neurons, and its expression was elevated in the pyramidal neurons and some astrocytes in AD hippocampi. Although AEBP1 immunoreactivity was almost absent in neurons containing neurofibrillary tangles, AEBP1 was highly expressed in neurons with pretangles and in the tau-immunopositive, dystrophic neurites of senile plaques. Nuclear localization of NF-κB was also observed in certain AEBP1-positive neurons in AD cases. Comparison of AD and non-AD cases suggested a positive correlation between the expression level of AEBP1 and the degree of amyloid β pathology. These findings imply that AEBP1 protein has a role in the progression of AD pathology.

Combination of alpha-synuclein immunotherapy with anti-inflammatory treatment in a transgenic mouse model of multiple system atrophy

Multiple system atrophy (MSA) is a fatal neurodegenerative disorder characterized by the pathological accumulation of alpha-synuclein (α-syn) in oligodendrocytes. Therapeutic efforts to stop or delay the progression of MSA have yielded suboptimal results in clinical trials, and there are no efficient treatments currently available for MSA patients. We hypothesize that combining therapies targeting different aspects of the disease may lead to better clinical outcomes. To test this hypothesis, we combined the use of a single-chain antibody targeting α-syn modified for improved central nervous system penetration (CD5-D5) with an unconventional anti-inflammatory treatment (lenalidomide) in the myelin basic protein (MBP)-α-syn transgenic mouse model of MSA. While the use of either CD5-D5 or lenalidomide alone had positive effects on neuroinflammation and/or α-syn accumulation in this mouse model of MSA, the combination of both approaches yielded better results than each single treatment. The combined treatment reduced astrogliosis, microgliosis, soluble and aggregated α-syn levels, and partially improved behavioral deficits in MBP-α-syn transgenic mice. These effects were associated with an activation of the Akt signaling pathway, which may mediate cytoprotective effects downstream tumor necrosis factor alpha (TNFα). These results suggest that a strategic combination of treatments may improve the therapeutic outcome in trials for MSA and related neurodegenerative disorders.

KV 7/M channels as targets for lipopolysaccharide-induced inflammatory neuronal hyperexcitability

KEY POINTS

Neuroinflammation associated with CNS insults leads to neuronal hyperexcitability, which may culminate in epileptiform discharges. Application of the endotoxin lipopolysaccharide (LPS) to brain tissue initiates a neuroinflammatory cascade, providing an experimental model to study the mechanisms of neuroinflammatory neuronal hyperexcitability. Here we show that LPS application to hippocampal slices markedly enhances the excitability of CA1 pyramidal cells by inhibiting a specific potassium current, the M-current, generated by K_V 7/M channels, which controls the excitability of almost every neuron in the CNS. The LPS-induced M-current inhibition is triggered by sequential activation of microglia, astrocytes and pyramidal cells, mediated by metabotropic purinergic and glutamatergic transmission, leading to blockade of K_V 7/M channels by calcium released from intracellular stores. The identification of the downstream molecular target of neuroinflammation, namely the K_V 7/M channel, potentially has far reaching implications for the understanding and treatment of many acute and chronic brain disorders.

ABSTRACT

Acute brain insults and many chronic brain diseases manifest an innate inflammatory response. The hallmark of this response is glia activation, which promotes repair of damaged tissue, but also induces structural and functional changes that may lead to an increase in neuronal excitability. We have investigated the mechanisms involved in the modulation of neuronal activity by acute inflammation. Initiating inflammatory responses in hippocampal tissue rapidly led to neuronal depolarization and repetitive firing even in the absence of active synaptic transmission. This action was mediated by a complex metabotropic purinergic and glutamatergic glia-to-neuron signalling cascade, leading to the blockade of neuronal K_V 7/M channels by Ca²⁺ released from internal stores. These channels generate the low voltage-activating, non-inactivating M-type K⁺ current (M-current) that controls intrinsic neuronal excitability, and its inhibition was the predominant cause of the inflammation-induced hyperexcitability. Our discovery that the ubiquitous K_V 7/M channels are the downstream target of the inflammation-induced cascade, has far reaching implications for the understanding and treatment of many acute and chronic brain disorders.

A Novel Parkinson's Disease Drug Candidate with Potent Anti-neuroinflammatory Effects through the Src Signaling Pathway

Numerous drug treatments are available for Parkinson's disease (PD), an age-related neurodegenerative disease, but most cause serious side effects. Therefore, novel therapeutic strategies that halt disease progression and allow for long-term administration are urgently needed. Neuroinflammation critically contributes to the pathogenesis of PD. Here, we report the discovery and optimization of phloroglucinol derivatives, a novel class of anti-neuroinflammatory compounds. Structural modifications of the hit compound 3-methyl-1-(2,4,6-trihydroxyphenyl)butan-1-one produced 43 derivatives, including a preclinical candidate (compound 21), that exhibited potent in vitro anti-neuroinflammatory effects, good blood-brain barrier penetration, and desirable safety margins in mice at a median lethal dose (LD₅₀) >5000 mg/kg. Its in vivo efficacy was demonstrated in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)- and MPTP/probenecid (prob)-induced subacute and chronic PD models, respectively, and α-synuclein transgenic mice. Mechanistic studies revealed neuroinflammation inhibition by targeting Src/phosphatase and tensin homologue deleted on chromosome 10 (PTEN)/Akt signaling might be promising. We highlighted the potential usefulness of phloroglucinol derivatives in PD treatment.

Correlations of PTEN genetic polymorphisms with the risk of depression and depressive symptoms in a Chinese population

OBJECTIVE

This study aimed to investigate the correlations of three common single nucleotide polymorphisms (SNPs) in the PTEN gene (rs701848 T>C, rs2735343 G>C and rs112025902 A>T) with the risk of depression and depressive symptoms in a Chinese population.

METHODS

From July 2011 to June 2013, a total of 384 patients with depression and 400 healthy individuals were included in this study. These SNPs in the PTEN gene were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and direct sequencing. The Hamilton Depression Rating Scale (HAMD) was used to evaluate the severity of depression.

RESULTS

The C allele of rs701848, the C allele of rs2735343 and the T allele of rs112025902 were associated with an increased risk of depression (odds ratio [OR]=3.814, 95% CI: 3.093-4.703, P<0.001; OR=2.642, 95% CI: 2.152-3.242, P<0.001; OR=2.882, 95% CI: 2.347-3.539, P<0.001; respectively). Depression patients carrying C allele (TC+CC) of rs701848 and carrying T allele (AT+TT) of rs112025902 had higher HAMD total scores and HAMD anxiety factor scores than those carrying TT genotype of rs701848 and carrying AA genotype of rs112025902 (all P<0.05). Furthermore, depression patients carrying C allele (GC+CC) of rs2735343 had lower HAMD total scores and HAMD factors associated with depression scores than those carrying GG genotype (both P<0.05). Logistic regression analysis revealed that rs701848, rs2735343 and rs112025902 polymorphisms in the PTEN gene may be independent risk factors of depression (relative risk [RR]=1.807, 95% CI=1.023-3.193, P=0.042; RR=1.759, 95% CI=1.033-2.995, P=0.038; RR=1.646, 95% CI=1.018-2.663, P=0.042; respectively).

CONCLUSION

Our findings provide evidence that rs701848, rs2735343 and rs112025902 polymorphisms in the PTEN gene may be correlated with the risk of depression and depressive symptoms in the Chinese population.

Vaccinium bracteatum Thunb. Exerts Anti-Inflammatory Activity by Inhibiting NF-κB Activation in BV-2 Microglial Cells

This study was designed to evaluate the pharmacological effects of Vaccinium bracteatum Thunb. methanol extract (VBME) on microglial activation and to identify the underlying mechanisms of action of these effects. The anti-inflammatory properties of VBME were studied using lipopolysaccharide (LPS)-stimulated BV-2 microglial cells. We measured the production of nitric oxide (NO), inducible NO synthase (iNOS), cyclooxygenase (COX)-2, prostaglandin E₂ (PGE₂), tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6) as inflammatory parameters. We also examined the effect of VBME on intracellular reactive oxygen species (ROS) production and the activity of nuclear factor-kappa B p65 (NF-κB p65). VBME significantly inhibited LPS-induced production of NO and PGE₂ and LPS-mediated upregulation of iNOS and COX-2 expression in a dose-dependent manner; importantly, VBME was not cytotoxic. VBME also significantly reduced the generation of the pro-inflammatory cytokines TNF-α, IL-1β, and IL-6. In addition, VBME significantly dampened intracellular ROS production and suppressed NF-κB p65 translocation by blocking IκB-α phosphorylation and degradation in LPS-stimulated BV2 cells. Our findings indicate that VBME inhibits the production of inflammatory mediators in BV-2 microglial cells by suppressing NF-κB signaling. Thus, VBME may be useful in the treatment of neurodegenerative diseases due to its ability to inhibit inflammatory mediator production in activated BV-2 microglial cells.

Exercise Preconditioning Regulates the Toll-Like Receptor 4/Nuclear Factor-κB Signaling Pathway and Reduces Cerebral Ischemia/Reperfusion Inflammatory Injury: A Study in Rats

OBJECTIVE

To explore the influence of exercise preconditioning (EP) on the activity of the toll-like receptor (TLR)4/nuclear factor (NF)-κB signaling pathway in a rat model of cerebral ischemia/reperfusion (I/R) inflammatory injury.

METHODS

Ischemia was induced in rats using transient middle cerebral artery occlusion (tMCAO) after 3 weeks of EP. Fifty-four rats were divided into sham, MCAO, and EP+MCAO groups. Following the induction of cerebral I/R injury, rats were scored for neurological deficits. Various techniques were used to evaluate ischemic infarct volume and explore pathological changes in tissue morphology after cerebral I/R injury, wherein the levels of TLR4 and NF-κB were analyzed. In addition, enzyme-linked immunosorbent assays were used to detect the levels of tumor necrosis factor (TNF)-α and interleukin (IL)-1β in peripheral serum.

RESULTS

Twenty-four hours after cerebral I/R injury, the neurological deficit scores decreased and ischemic cortical damage alleviated in EP+MCAO group; the number of TLR4- and NF-κB-positive cells, the expression of TLR4 and NF-κB in the ischemic side, and the concentrations of TNF-α and IL-1β in the peripheral serum were lower in EP+MCAO group than those in the MCAO group (P <.05).

CONCLUSIONS

The present study indicates that EP can improve cerebral I/R-induced neurological deficits in rats, reduce infarct volume, mitigate pathological damage in the ischemic cortex, and exert neuroprotective effects. The mechanism underlying these effects might involve the regulation of the TLR4/NF-κB signaling pathway and the inhibition of central and peripheral inflammatory cascades during cerebral I/R injury.

The Immune System and the Role of Inflammation in Perinatal Depression

Major depression during pregnancy is a common psychiatric disorder that arises from a complex and multifactorial etiology. Psychosocial stress, sex, hormones, and genetic vulnerability increase the risk for triggering mood disorders. Microglia and toll-like receptor 4 play a crucial role in triggering wide and varied stress-induced responses mediated through activation of the inflammasome; this leads to the secretion of inflammatory cytokines, increased serotonin metabolism, and reduction of neurotransmitter availability along with hypothalamic-pituitary-adrenal axis hyperactivity. Dysregulation of this intricate neuroimmune communication network during pregnancy modifies the maternal milieu, enhancing the emergence of depressive symptoms and negative obstetric and neuropsychiatric outcomes. Although several studies have clearly demonstrated the role of the innate immune system in major depression, it is still unclear how the placenta, the brain, and the monoaminergic and neuroendocrine systems interact during perinatal depression. Thus, in the present review we describe the cellular and molecular interactions between these systems in major depression during pregnancy, proposing that the same stress-related mechanisms involved in the activation of the NLRP3 inflammasome in microglia and peripheral myeloid cells in depressed patients operate in a similar fashion in the neuroimmune placenta during perinatal depression. Thus, activation of Toll-like receptor 2 and 4 signaling and the NLRP3 inflammasome in placental immune cells may promote a shift of the Th1/Th2 bias towards a predominant Th1/Th17 inflammatory response, associated with increased secretion of pro-inflammatory cytokines, among other secreted autocrine and paracrine mediators, which play a crucial role in triggering and/or exacerbating depressive symptoms during pregnancy.

The E3 Ubiquitin Ligase c-Cbl Inhibits Microglia-Mediated CNS Inflammation by Regulating PI3K/Akt/NF-κB Pathway

BACKGROUND

Microglia-mediated inflammation may play an important role in the pathophysiology progression of neurodegenerative diseases, such as Parkinson's disease (PD), but the molecular mechanisms are poorly understood.

AIMS

This study sought to determine whether E3 ubiquitin ligase c-Cbl plays a role in the brain inflammation and to explore the relevant molecular mechanism.

METHODS

After BV2 microglial cells and c-Cbl-deficient mice were treated with lipopolysaccharide (LPS), neuroinflammation and microglial activation were evaluated by immunohistochemistry, ELISA and Western blot. We further investigated the possible mechanism of c-Cbl in regulating microglial activation.

RESULTS

Here, we showed that the E3 ubiquitin ligase c-Cbl had high expression in brain tissues including substantia nigra pars compacta (SNc), striatum and hippocampus, and it was abundantly expressed in microglia. Systemic LPS administration resulted in more severe microglial activation in CNS and increased expression of brain proinflammatory factors (TNF-α, IL-6, IL-1β and MCP-1) in c-Cbl knockout mice than wild type mice (WT). Downregulation of c-Cbl expression with c-Cbl siRNA in BV-2 microglial cells demonstrated a more robust increase in the proinflammatory factors release and NF-κB p65 nuclear translocation than that in control siRNA. Interestingly, Akt phosphorylation induced by LPS was also significantly augmented after c-Cbl knockdown. Moreover, blockade of PI3K/Akt activation by LY294002 significantly reduced inflammation response and NF-κB p65 nuclear translocation.

CONCLUSION

In sum, c-Cbl inhibits expression of LPS-stimulated proinflammatory cytokines and chemokines in microglia. We demonstrate an unprecedented role for c-Cbl in microglia-mediated neuroinflammation involving PI3K/Akt/NF-κB pathway.

Selected gene profiles of stressed NSC-34 cells and rat spinal cord following peripheral nerve reconstruction and minocycline treatment

The present study was conducted to investigate the effects of minocycline on the expression of selected transcriptional and translational profiles in the rat spinal cord following sciatic nerve (SNR) transection and microsurgical coaptation. The mRNA and protein expression levels of B cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), caspase-3, major histocompatibility complex I (MHC I), tumor necrosis factor-α (TNF-α), activating transcription factor 3 (ATF3), vascular endothelial growth factor (VEGF), matrix metalloproteinase 9 (MMP9), and growth associated protein-43 (GAP-43) were monitored in the rat lumbar spinal cord following microsurgical reconstruction of the sciatic nerves and minocycline treatment. The present study used semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. As a PCR analysis of spinal cord tissue enabled the examination of the expression patterns of all cell types including glia, the motorneuron-like NSC-34 cell line was used to investigate expression level changes in motorneurons. As stressors, oxygen glucose deprivation (OGD) and lipopolysaccharide (LPS) treatment were performed. SNR did not induce significant degeneration of ventral horn motorneurons, whereas microglia activation and synaptic terminal retraction were detectable. All genes were constitutively expressed at the mRNA and protein levels in untreated spinal cord and control cells. SNR significantly increased the mRNA expression levels of all genes, albeit only temporarily. In all genes except MMP9 and GAP-43, the induction was seen ipsilaterally and contralaterally. The effects of minocycline were moderate. The expression levels of MMP9, TNF-α, MHC I, VEGF, and GAP-43 were reduced, whereas those of Bax and Bcl-2 were unaffected. OGD, but not LPS, was toxic for NSC-34 cells. No changes in the expression levels of Bax, caspase-3, MHC I or ATF3 were observed. These results indicated that motorneurons were not preferentially or solely responsible for SNR-mediated upregulation of these genes. MMP9, TNF-α, VEGF and Bcl-2 were stress-activated. These results suggest that a substantial participation of motorneurons in gene expression levels in vivo. Minocycline was also shown to have inhibitory effects. The nuclear factor-κB signalling pathway may be a possible target of minocycline.

Toll-Like Receptor 4 Deficiency Impairs Motor Coordination

The cerebellum plays an essential role in balance and motor coordination. Purkinje cells (PCs) are the sole output neurons of the cerebellar cortex and are critical for the execution of its functions, including motor coordination. Toll-like receptor (TLR) 4 is involved in the innate immune response and is abundantly expressed in the central nervous system; however, little is known about its role in cerebellum-related motor functions. To address this question, we evaluated motor behavior in TLR4 deficient mice. We found that TLR4(-∕-) mice showed impaired motor coordination. Morphological analyses revealed that TLR4 deficiency was associated with a reduction in the thickness of the molecular layer of the cerebellum. TLR4 was highly expressed in PCs but not in Bergmann glia or cerebellar granule cells; however, loss of TLR4 decreased the number of PCs. These findings suggest a novel role for TLR4 in cerebellum-related motor coordination through maintenance of the PC population.

Microarray expression profile analysis of long noncoding RNAs in premature brain injury: A novel point of view

Long noncoding RNAs (lncRNAs) are abundant in the central nervous system and have a key role in brain function as well as many neurological disorders. However, the regulatory function of lncRNAs in the premature brain has not been well studied. This study described the expression profile of lncRNAs in premature mice using microarray technology. 1999 differentially expressed lncRNAs and 955 differentially expressed mRNAs were identified. Gene Ontology (GO) and pathway analysis showed that these lncRNAs were involved in multiple biological processes, including the nervous system development and inflammatory response. Additionally, the lncRNA-mRNA-network and TF-gene-lncRNA-network were constructed to identify core regulatory lncRNAs and transcription factors. The sex-determining region of Y chromosome (SRY) gene may be a key transcription factor that regulates premature brain development and injury. This study for the first time represents an expression profile of differentially expressed lncRNAs in the premature brain and may provide a novel point of view into the mechanisms of premature brain injury.

Alginate-Derived Oligosaccharide Inhibits Neuroinflammation and Promotes Microglial Phagocytosis of β-Amyloid

Alginate from marine brown algae has been widely applied in biotechnology. In this work, the effects of alginate-derived oligosaccharide (AdO) on lipopolysaccharide (LPS)/β-amyloid (Aβ)-induced neuroinflammation and microglial phagocytosis of Aβ were studied. We found that pretreatment of BV2 microglia with AdO prior to LPS/Aβ stimulation led to a significant inhibition of production of nitric oxide (NO) and prostaglandin E₂ (PGE₂), expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) and secretion of proinflammatory cytokines. We further demonstrated that AdO remarkably attenuated the LPS-activated overexpression of toll-like receptor 4 (TLR4) and nuclear factor (NF)-κB in BV2 cells. In addition to the impressive inhibitory effect on neuroinflammation, we also found that AdO promoted the phagocytosis of Aβ through its interaction with TLR4 in microglia. Our results suggested that AdO exerted the inhibitory effect on neuroinflammation and the promotion effect on microglial phagocytosis, indicating its potential as a nutraceutical or therapeutic agent for neurodegenerative diseases, particularly Alzheimer’s disease (AD).

14-3-3γ Regulates Lipopolysaccharide-Induced Inflammatory Responses and Lactation in Dairy Cow Mammary Epithelial Cells by Inhibiting NF-κB and MAPKs and Up-Regulating mTOR Signaling

As a protective factor for lipopolysaccharide (LPS)-induced injury, 14-3-3γ has been the subject of recent research. Nevertheless, whether 14-3-3γ can regulate lactation in dairy cow mammary epithelial cells (DCMECs) induced by LPS remains unknown. Here, the anti-inflammatory effect and lactation regulating ability of 14-3-3γ in LPS-induced DCMECs are investigated for the first time, and the molecular mechanisms responsible for their effects are explored. The results of qRT-PCR showed that 14-3-3γ overexpression significantly inhibited the mRNA expression of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β (IL-1β) and inducible nitric oxide synthase (iNOS). Enzyme-linked immunosorbent assay (ELISA) analysis revealed that 14-3-3γ overexpression also suppressed the production of TNF-α and IL-6 in cell culture supernatants. Meanwhile, CASY-TT Analyser System showed that 14-3-3γ overexpression clearly increased the viability and proliferation of cells. The results of kit methods and western blot analysis showed that 14-3-3γ overexpression promoted the secretion of triglycerides and lactose and the synthesis of β-casein. Furthermore, the expression of genes relevant to nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPKs) and lactation-associated proteins were assessed by western blot, and the results suggested that 14-3-3γ overexpression inactivated the NF-κB and MAPK signaling pathways by down-regulating extracellular signal regulated protein kinase (ERK), p38 mitogen-activated protein kinase (p38MAPK) and inhibitor of NF-κB (IκB) phosphorylation levels, as well as by inhibiting NF-κB translocation. Meanwhile, 14-3-3γ overexpression enhanced the expression levels of β-casein, mammalian target of rapamycin (mTOR), ribosomal protein S6 kinase 1 (S6K1), serine/threonine protein kinase Akt 1 (AKT1), sterol regulatory element binding protein 1 (SREBP1) and peroxisome proliferator-activated receptor gamma (PPARγ). These results suggest that 14-3-3γ was able to attenuate the LPS-induced inflammatory responses and promote proliferation and lactation in LPS-induced DCMECs by inhibiting the activation of the NF-κB and MAPK signaling pathways and up-regulating mTOR signaling pathways to protect against LPS-induced injury.

PI3Kγ deficiency enhances seizures severity and associated outcomes in a mouse model of convulsions induced by intrahippocampal injection of pilocarpine

Phosphatidylinositol 3-kinase (PI3K) is an enzyme involved in different pathophysiological processes, including neurological disorders. However, its role in seizures and postictal outcomes is still not fully understood. We investigated the role of PI3Kγ on seizures, production of neurotrophic and inflammatory mediators, expression of a marker for microglia, neuronal death and hippocampal neurogenesis in mice (WT and PI3Kγ(-/-)) subjected to intrahippocampal microinjection of pilocarpine. PI3Kγ(-/-) mice presented a more severe status epilepticus (SE) than WT mice. In hippocampal synaptosomes, genetic or pharmacological blockade of PI3Kγ enhanced the release of glutamate and the cytosolic calcium concentration induced by KCl. There was an enhanced neuronal death and a decrease in the doublecortin positive cells in the dentate gyrus of PI3Kγ(-/-) animals after the induction of SE. Levels of BDNF were significantly increased in the hippocampus of WT and PI3Kγ(-/-) mice, although in the prefrontal cortex, only PI3Kγ(-/-) animals showed significant increase in the levels of this neurotrophic factor. Pilocarpine increased hippocampal microglial immunolabeling in both groups, albeit in the prelimbic, medial and motor regions of the prefrontal cortex this increase was observed only in PI3Kγ(-/-) mice. Regarding the levels of inflammatory mediators, pilocarpine injection increased interleukin (IL) 6 in the hippocampus of WT and PI3Kγ(-/-) animals and in the prefrontal cortex of PI3Kγ(-/-) animals 24h after the stimulus. Levels of TNFα were enhanced in the hippocampus and prefrontal cortex of only PI3Kγ(-/-) mice at this time point. On the other hand, PI3Kγ deletion impaired the increase in IL-10 in the hippocampus induced by pilocarpine. In conclusion, the lack of PI3Kγ revealed a deleterious effect in an animal model of convulsions induced by pilocarpine, suggesting that this enzyme may play a protective role in seizures and pathological outcomes associated with this condition.

Docosahexaenoic acid (DHA): a modulator of microglia activity and dendritic spine morphology

BACKGROUND

Recent studies have revealed that excessive activation of microglia and inflammation-mediated neurotoxicity are implicated in the progression of several neurological disorders. In particular, chronic inflammation in vivo and exposure of cultured brain cells to lipopolysaccharide (LPS) in vitro can adversely change microglial morphology and function. This can have both direct and indirect effects on synaptic structures and functions. The integrity of dendritic spines, the postsynaptic component of excitatory synapses, dictates synaptic efficacy. Interestingly, dysgenesis of dendritic spines has been found in many neurological diseases associated with ω-3 polyunsaturated fatty acid (PUFA) deficiency and cognitive decline. In contrast, supplemented ω-3 PUFAs, such as docosahexaenoic acid (DHA), can partly correct spine defects. Hence, we hypothesize that DHA directly affects synaptic integrity and indirectly through neuron-glia interaction. Strong activation of microglia by LPS is accompanied by marked release of nitric oxide and formation of lipid bodies (LBs), both dynamic biomarkers of inflammation. Here we investigated direct effects of DHA on synaptic integrity and its indirect effects via microglia in the hippocampal CA1 region.

METHODS

Microglia (N9) and organotypic hippocampal slice cultures were exposed to the proinflammagen LPS (100 ng/ml) for 24 h. Biochemical and morphological markers of inflammation were investigated in microglia and CA1 regions of hippocampal slices. As biomarkers of hyperactive microglia, mitochondrial function, nitric oxide release and LBs (number, size, LB surface-associated proteins) were assessed. Changes in synaptic transmission of CA1 pyramidal cells were determined following LPS and DHA (25-50 μM) treatments by recording spontaneous AMPA-mediated miniature excitatory postsynaptic currents (mEPSCs).

RESULTS

Microglia responded to LPS stimulation with a significant decrease of mitochondrial function, increased nitric oxide production and an increase in the formation of large LBs. LPS treatment led to a significant reduction of dendritic spine densities and an increase in the AMPA-mediated mEPSC inter-event interval (IEI). DHA normalized the LPS-induced abnormalities in both neurons and microglia, as revealed by the restoration of synaptic structures and functions in hippocampal CA1 pyramidal neurons.

CONCLUSION

Our findings indicate that DHA can prevent LPS-induced abnormalities (neuroinflammation) by reducing inflammatory biomarkers, thereby normalizing microglia activity and their effect on synaptic function.

Differential effects of lipopolysaccharide on energy metabolism in murine microglial N9 and cholinergic SN56 neuronal cells

There are significant differences between acetyl-CoA and ATP levels, enzymes of acetyl-CoA metabolism, and toll-like receptor 4 contents in non-activated microglial N9 and non-differentiated cholinergic SN56 neuroblastoma cells. Exposition of N9 cells to lipopolysaccharide caused concentration-dependent several-fold increases of nitrogen oxide synthesis, accompanied by inhibition of pyruvate dehydrogenase complex, aconitase, and α-ketoglutarate dehydrogenase complex activities, and by nearly proportional depletion of acetyl-CoA, but by relatively smaller losses in ATP content and cell viability (about 5%). On the contrary, SN56 cells appeared to be insensitive to direct exposition to high concentration of lipopolysaccharide. However, exogenous nitric oxide resulted in marked inhibition pyruvate dehydrogenase and aconitase activities, depletion of acetyl-CoA, along with respective loss of SN56 cells viability. These data indicate that these two common neurodegenerative signals may differentially affect energy-acetyl-CoA metabolism in microglial and cholinergic neuronal cell compartments in the brain. Moreover, microglial cells appeared to be more resistant than neuronal cells to acetyl-CoA and ATP depletion evoked by these neurodegenerative conditions. Together, these data indicate that differential susceptibility of microglia and cholinergic neuronal cells to neurotoxic signals may result from differences in densities of toll-like receptors and degree of disequilibrium between acetyl-CoA provision in mitochondria and its utilization for energy production and acetylation reactions in each particular group of cells. There are significant differences between acetyl-CoA and ATP levels and enzymes of acetyl-CoA metabolism in non-activated microglial N9 and non-differentiated cholinergic SN56 neuroblastoma cells. Pathological stimulation of microglial toll-like receptors (TLRs) triggered excessive synthesis of microglia-derived nitric oxide (NO)/NOO radicals that endogenously inhibited pyruvate dehydrogenase complex (PDHC), aconitase, and α-ketoglutarate dehydrogenase complex. However, it caused none or small suppressions of acetyl-CoA and microglial viability, respectively. Microglia-derived NO inhibited same enzymes in cholinergic neuronal cells causing marked viability loss because of acetyl-CoA deficits evoked by its competitive consumption by energy producing and acetylcholine/N-acetyl-l-aspartate (NAA) synthesizing pathways.

Early molecular and behavioral response to lipopolysaccharide in the WAG/Rij rat model of absence epilepsy and depressive-like behavior, involves interplay between AMPK, AKT/mTOR pathways and neuroinflammatory cytokine release

The mammalian target of rapamycin (mTOR) pathway has been recently indicated as a suitable drug target for the prevention of epileptogenesis. The mTOR pathway is known for its involvement in the control of the immune system. Since neuroinflammation is recognized as a major contributor to epileptogenesis, we wished to examine whether the neuroprotective effects of mTOR modulation could involve a suppression of the neuroinflammatory process in epileptic brain. We have investigated the early molecular mechanisms involved in the effects of intracerebral administration of the lipopolysaccharide (LPS) in the WAG/Rij rat model of absence epilepsy, in relation to seizure generation and depressive-like behavior; we also tested whether the effects of LPS could be modulated by treatment with rapamycin (RAP), a specific mTOR inhibitor. We determined, in specific rat brain areas, levels of p-mTOR/p-p70S6K and also p-AKT/p-AMPK as downstream or upstream indicators of mTOR activity and tested the effects of LPS and RAP co-administration. Changes in the brain levels of pro-inflammatory cytokines IL-1β and TNF-α and their relative mRNA expression levels were measured, and the involvement of nuclear factor-κB (NF-κB) was also examined in vitro. We confirmed that RAP inhibits the aggravation of absence seizures and depressive-like/sickness behavior induced by LPS in the WAG/Rij rats through the activation of mTOR and show that this effect is correlated with the ability of RAP to dampen and delay LPS increases in neuroinflammatory cytokines IL-1β and TNF-α, most likely through inhibition of the activation of NF-κB. Our results suggest that such a mechanism could contribute to the antiseizure, antiepileptogenic and behavioral effects of RAP and further highlight the potential therapeutic usefulness of mTOR inhibition in the management of human epilepsy and other neurological disorders. Furthermore, we show that LPS-dependent neuroinflammatory effects are also mediated by a complex interplay between AKT, AMPK and mTOR with specificity to selective brain areas. In conclusion, neuroinflammation appears to be a highly coordinated phenomenon, where timing of intervention may be carefully evaluated in order to identify the best suitable target.

Toll-like receptor 4: innate immune regulator of neuroimmune and neuroendocrine interactions in stress and major depressive disorder

Major depressive disorder (MDD) poses one of the highest disease burdens worldwide. Yet, current treatments targeting serotonergic and noradrenaline reuptake systems are insufficient to provide long-term relief from depressive symptoms in most patients, indicating the need for new treatment targets. Having the ability to influence behavior similar to depressive symptoms, as well as communicate with neuronal and neuroendocrine systems, the innate immune system is a strong candidate for MDD treatments. Given the complex nature of immune signaling, the main question becomes: What is the role of the innate immune system in MDD? The current review presents evidence that toll-like receptor 4 (TLR4), via driving both peripheral and central immune responses, can interact with serotonergic neurotransmission and cause neuroendocrine disturbances, thus integrating with widely observed hallmarks of MDD. Additionally, through describing the multi-directional communication between immune, neural and endocrine systems in stress, TLR4—related mechanisms can mediate stress-induced adaptations, which are necessary for the development of MDD. Therefore, apart from exogenous pathogenic mechanisms, TLR4 is involved in immune changes as a result of endogenous stress signals, playing an integral part in the pathophysiology, and could be a potential target for pharmacological treatments to improve current interventions for MDD.