Toll-like 4 receptor inhibitor TAK-242 decreases neuroinflammation in rat brain frontal cortex after stress

TLR4 signaling modulation of PGC1-α mediated mitochondrial biogenesis in the LPS-Chronic mild stress model: Effect of fluoxetine and pentoxiyfylline

AIM

The addition of repeated lipopolysaccharide (LPS) to chronic mild stress was recently proposed in our lab as an alternative model of depression, highlighting the possible interaction between stress and immune-inflammatory pathways in predisposing depression. Given that CMS-induced depressive behavior was previously related to impaired hippocampal energy metabolism and mitochondrial dysfunction, our current study aimed to investigate the interplay between toll-like receptor 4 (TLR4) signaling and peroxisome proliferator-activated receptor gamma coactivators-1-alpha (PGC1-α) as a physiological regulator of energy metabolism and mitochondrial biogenesis in the combined LPS/CMS model.

MAIN METHODS

Male Wistar rats were exposed to either LPS (50 μg/kg i.p.) over 2 weeks, CMS protocol for 4 weeks or LPS over 2 weeks followed by 4 weeks of CMS (LPS/CMS). Three additional groups of rats were exposed to LPS/CMS protocol and treated with either pentoxifylline (PTX), fluoxetine (FLX) or a combination of both. Rats were examined for behavioral, neurochemical, gene expression and mitochondrial ultra-structural changes.

KEY FINDINGS

LPS/CMS increased the expression of TLR4 and its downstream players; MyD88, NFκB and TNF-α along with an escalation in hippocampal-energy metabolism and p-AMPK. Simultaneously LPS/CMS attenuated the expression of PGC1-α/NRF1/Tfam and mt-DNA. The antidepressant (AD) 'FLX', the TNF-α inhibitor 'PTX' and their combination ameliorated the LPS/CMS-induced changes. Interestingly, all the aforementioned changes induced by the LPS/CMS combined model were significantly less than those induced by CMS alone.

SIGNIFICANCE

Blocking the TLR4/NFκB signaling enhanced the activation of the PGC1-α/NRF1/Tfam and mt-DNA content independent on the activation of the energy-sensing kinase AMPK.

Assessing the role of toll-like receptor in isolated, standard and enriched housing conditions

Depression is a common psychiatric disorder that has been poorly understood. Consequently, current antidepressant agents have clinical limitations. Until today, most have exhibited the slow onset of therapeutic action and, more importantly, their effect on remission has been minimal. Thus, the need to find new forms of therapeutic intervention is urgent. The inflammation hypothesis of depression is widely acknowledged and is one that theories the relationship between the function of the immune system and its contribution to the neurobiology of depression. In this research, we utilized an environmental isolation (EI) approach as a valid animal model of depression, employing biochemical, molecular, and behavioral studies. The aim was to investigate the anti-inflammatory effect of etanercept, a tumor necrosis factor-α inhibitor on a toll-like receptor 7 (TLR 7) signaling pathway in a depressive rat model, and compare these actions to fluoxetine, a standard antidepressant agent. The behavioral analysis indicates that depression-related symptoms are reduced after acute administration of fluoxetine and, to a lesser extent, etanercept, and are prevented by enriched environment (EE) housing conditions. Experimental studies were conducted by evaluating immobility time in the force swim test and pleasant feeling in the sucrose preference test. The mRNA expression of the TLR 7 pathway in the hippocampus showed that TLR 7, MYD88, and TRAF6 were elevated in isolated rats compared to the standard group, and that acute treatment with an antidepressant and anti-inflammatory drugs reversed these effects. This research indicates that stressful events have an impact on behavioral well-being, TLR7 gene expression, and the TLR7 pathway. We also found that peripheral administration of etanercept reduces depressive-like behaviour in isolated rats: this could be due to the indirect modulation of the TLR7 pathway and other TLRs in the brain. Furthermore, fluoxetine treatment reversed depressive-like behaviour and molecularly modulated the expression of TLR7, suggesting that fluoxetine exerts antidepressant effects partially by modulating the TLR7 signaling pathway.

The selenium-containing compound 3-((4-chlorophenyl)selanyl)-1-methyl-1H-indole reverses depressive-like behavior induced by acute restraint stress in mice: modulation of oxido-nitrosative stress and inflammatory pathway

RATIONALE AND OBJECTIVES

Stress-induced alterations in oxidative and inflammatory parameters have been implicated in the pathophysiology of mood disorders. Based on the antioxidant and anti-inflammatory properties of the selenium-containing compound 3-((4-chlorophenyl)selanyl)-1-methyl-1H-indole (CMI), we assessed its ability to reverse depression-like behavioral alterations, neuroinflammation, and oxidative imbalance induced by acute restraint stress.

METHODS

Mice submitted to restraint for 240 min received CMI (1 or 10 mg/kg, orally) 10 min after the end of the stress induction. Behavioral and biochemical tests were carried out after further 30 min.

RESULTS

Restraint-induced depression-like behavior in the tail suspension test (TST), splash test, and new object exploration test was reversed by CMI. None of the treatments evoked locomotor alteration. In addition, CMI abrogated restraint-induced increases in plasma levels of corticosterone and in markers of oxidative stress and impaired superoxide dismutase and catalase activity in the prefrontal cortex (PFC) and hippocampus (HC). CMI also blocked stress-induced downregulation of mRNA levels of glucocorticoid receptor and brain-derived neurotrophic factor and upregulation of nuclear factor kappa B, inducible nitric oxide synthase, tumor necrosis alpha, indoelamine-2,3-dioxygenase, and glycogen synthase kinase 3 beta in PFC and HC.

CONCLUSIONS

These preclinical results indicate that administration of selenium-containing compounds might help to treat depression associated with inflammation and oxidative stress. Graphical abstract ᅟ.

Maternal deprivation increases microglial activation and neuroinflammatory markers in the prefrontal cortex and hippocampus of infant rats

A relationship between neuroinflammation and the development of psychiatric disorder have been revealed by many studies in the past decade. Although studies have shown that stressors can induce long-term changes that may be related to behavioral responses, these alterations have been poorly studied soon after a stressor, such as maternal deprivation (MD). Thus, this study was designed to investigate the acute effect of experimental induction of MD on inflammatory and microglial activation markers in the brain of infant rats. Early MD was induced from postnatal day (PND) 1-10. On PND 10 the prefrontal cortex (PFC) and hippocampus from MD and control groups were removed to investigate microglial activation and neuroinflammatory markers. In the PFC the expressions of cluster of differentiation molecule 11B (CD11B), toll-like receptor (TLR)-2, and TLR-4 were increased in rats subjected to MD. The arginase expression was elevated in the PFC and hippocampus of maternally deprived rats. The cytokines interleukin-5 (IL-5), -6, -7, -10, tumor necrosis factor (TNF-α), and interferon gamma (INF-γ) were increased in the PFC of MD rats group. In the PFC the macrophage inflammatory proteins (MIP)-1α levels were reduced in MD rats group. In the hippocampus only the levels of TNF-α and INF-γ were elevated in infant rats subjected to MD. In conclusion, our results support the hypothesis that neuroinflammation and microglial activation, mainly in the PFC, could be involved with changes in the brain resident cells following MD, and these alterations could be associated to the development of psychiatric conditions late in life.

Behavioral effects of toll-like receptor-4 antagonist 'eritoran' in an experimental model of depression: role of prefrontal and hippocampal neurogenesis and γ-aminobutyric acid/glutamate balance

Depression is the disease of the modern era. The lack of response to the available antidepressants, which were developed on the basis of the monoaminergic deficit hypothesis of depression, has encouraged scientists to think about new mechanisms explaining the pathogenesis of depression. In this context, the inflammatory theory has emerged to clarify many aspects of depression that the previous theories have failed to explain. Toll-like receptor-4 (TLR-4) has a regulatory role in the brain's immune response to stress, and its activation is suggested to play a pivotal role in the pathophysiology of depression. In this study, we tested eritoran (ERI), a TLR-4 receptor-4 antagonist, as a potential antidepressant. We investigated the effect of long-term administration of ERI in three different doses on behavioral changes, hippocampal and prefrontal cortex (PFC) neurogenesis, and γ-aminobutyric acid (GABA)/glutamate balance in male Wistar rats exposed to chronic restraint stress (CRS). Long-term administration of ERI ameliorated CRS-induced depressive-like symptoms and hypothalamic-pituitary-adrenal axis hyperactivity alongside reducing levels of hippocampal and PFC inflammatory cytokines, restoring GABA and glutamate balance, and enhancing PFC and hippocampal neurogenesis, by increasing BDNF gene and protein expression in a dose-dependent manner. The results demonstrate an antidepressant-like activity of ERI in Wistar rats exposed to CRS, which may be largely mediated by its ability to reduce neuroinflammation, increase BDNF, and restore GABA/glutamate balance in prefrontal cortex and hippocampus. Nonetheless, further studies are needed to characterize the mechanism of the antidepressant effect of ERI.

Stress-induced disturbances along the gut microbiota-immune-brain axis and implications for mental health: Does sex matter?

Women are roughly twice as likely as men to suffer from stress-related disorders, especially major depression and generalized anxiety. Accumulating evidence suggest that microbes inhabiting the gastrointestinal tract (the gut microbiota) interact with the host brain and may play a key role in the pathogenesis of mental illnesses. Here, the possibility that sexually dimorphic alterations along the gut microbiota-immune-brain axis could play a role in promoting this female bias of mood and anxiety disorders will be discussed. This review will also analyze the idea that gut microbes and sex hormones influence each other, and that this reciprocal crosstalk may come to modulate inflammatory players along the gut microbiota-immune-brain axis and influence behavior in a sex-dependent way.

Cystitis-induced bladder pain is Toll-like receptor 4 dependent in a transgenic autoimmune cystitis murine model: a MAPP Research Network animal study

Altered Toll-like receptor (TLR)4 activation has been identified in several chronic pain conditions but has not been well studied in interstitial cystitis/bladder pain syndrome (IC/BPS). Our previously published human studies indicated that patients with IC/BPS present altered systemic TLR4-mediated inflammatory responses, which were significantly correlated with reported pain severity. In the present study, we sought to determine whether altered TLR4 activation plays a role in pelvic/bladder pain seen in patients with IC/BPS using our validated IC/BPS-like transgenic autoimmune cystitis model (URO-OVA). URO-OVA mice developed responses consistent with pelvic and bladder pain after cystitis induction, which was associated with increased splenocyte production of TLR4-mediated proinflammatory cytokines IL-1β, IL-6, and TNF-α. Increased spinal expression of mRNAs for proinflammatory cytokines IL-6 and TNF-α, glial activation markers CD11b and glial fibrillary acidic protein, and endogenous TLR4 ligand high mobility group box 1 was also observed after cystitis induction. Compared with URO-OVA mice, TLR4-deficient URO-OVA mice developed significantly reduced nociceptive responses, although similar bladder inflammation and voiding dysfunction, after cystitis induction. Intravenous administration of TAK-242 (a TLR4-selective antagonist) significantly attenuated nociceptive responses in cystitis-induced URO-OVA mice, which was associated with reduced splenocyte production of TLR4-mediated IL-1β, IL-6, and TNF-α as well as reduced spinal expression of mRNAs for IL-6, TNF-α, CD11b, glial fibrillary acidic protein, and high mobility group box 1. Our results indicate that altered TLR4 activation plays a critical role in bladder nociception independent of inflammation and voiding dysfunction in the URO-OVA model, providing a potential mechanistic insight and therapeutic target for IC/BPS pain.

Baicalin ameliorates neuroinflammation-induced depressive-like behavior through inhibition of toll-like receptor 4 expression via the PI3K/AKT/FoxO1 pathway

Background

Baicalin, which is isolated from Radix Scutellariae, possesses strong biological activities including an anti-inflammation property. Recent studies have shown that the anti-inflammatory effect of baicalin is linked to toll-like receptor 4 (TLR4), which participates in pathological changes of central nervous system diseases such as depression. In this study, we explored whether baicalin could produce antidepressant effects via regulation of TLR4 signaling in mice and attempted to elucidate the underlying mechanisms.

Methods

A chronic unpredictable mild stress (CUMS) mice model was performed to explore whether baicalin could produce antidepressant effects via the inhibition of neuroinflammation. To clarify the role of TLR4 in the anti-neuroinflammatory efficacy of baicalin, a lipopolysaccharide (LPS) was employed in mice to specially activate TLR4 and the behavioral changes were determined. Furthermore, we used LY294002 to examine the molecular mechanisms of baicalin in regulating the expression of TLR4 in vivo and in vitro using western blot, ELISA kits, and immunostaining. In the in vitro tests, the BV2 microglia cell lines and primary microglia cultures were pretreated with baicalin and LY292002 for 1 h and then stimulated 24 h with LPS. The primary microglial cells were transfected with the forkhead transcription factor forkhead box protein O 1 (FoxO1)-specific siRNA for 5 h and then co-stimulated with baicalin and LPS to investigate whether FoxO1 participated in the effect of baicalin on TLR4 expression.

Results

The administration of baicalin (especially 60 mg/kg) dramatically ameliorated CUMS-induced depressive-like symptoms; substantially decreased the levels of interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α) in the hippocampus; and significantly decreased the expression of TLR4. The activation of TLR4 by the LPS triggered neuroinflammation and evoked depressive-like behaviors in mice, which were also alleviated by the treatment with baicalin (60 mg/kg). Furthermore, the application of baicalin significantly increased the phosphorylation of phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT), and FoxO1. The application of baicalin also promoted FoxO1 nuclear exclusion and contributed to the inhibition of the FoxO1 transactivation potential, which led to the downregulation of the expression of TLR4 in CUMS mice or LPS-treated BV2 cells and primary microglia cells. However, prophylactic treatment of LY294002 abolished the above effects of baicalin. In addition, we found that FoxO1 played a vital role in baicalin by regulating the TLR4 and TLR4-mediating neuroinflammation triggered by the LPS via knocking down the expression of FoxO1 in the primary microglia.

Conclusion

Collectively, these results demonstrate that baicalin ameliorated neuroinflammation-induced depressive-like behaviors through the inhibition of TLR4 expression via the PI3K/AKT/FoxO1 pathway.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1474-8) contains supplementary material, which is available to authorized users.

More dampened monocytic Toll-like receptor 4 response to lipopolysaccharide and its association with cognitive function in Chinese Han first-episode patients with schizophrenia

OBJECTIVE

Accumulating evidence suggests alterations of the innate immune system are related to schizophrenia, although the precise mechanism remains to be elucidated. In this study, we aimed to detect the monocytic toll-like receptor 4 (TLR4) expression under basal and lipopolysaccharide (LPS)-stimulated conditions in first-episode (FE) Han Chinese patients with schizophrenia, as well as its association with cognitive function.

METHODS

Whole blood samples were taken in 42 FE schizophrenia patients and 36 healthy controls. Expressions of TLR4 on monocytes under basal and LPS-stimulated conditions were measured with flow cytometry. Psychopathological symptoms of schizophrenia were assessed by the Positive and Negative Syndrome Scale (PANSS) and the MATRICS Consensus Cognitive Battery (MCCB) was administered to all of the participants.

RESULTS

We found no differences in percentage and mean fluorescence intensity (MFI) of TLR4 expression on monocytes between patients and controls at basal status. However, LPS challenge resulted in a lower cell-surface level of TLR4 on monocytes in FE schizophrenia patients as compared to healthy controls (TLR4+%: F = 4.092, p = 0.047; TLR4 + MFI: F = 4.820, p = 0.031). In addition, correlation analysis together with multivariate linear regression analysis identified basal percentage of TLR4 in monocytes as the beneficial factor for visual learning and working memory in FE patients with schizophrenia.

CONCLUSIONS

Our findings suggested that TLR4 may be involved in the pathophysiology of schizophrenia, corroborating the role of innate immunity-related functional deficits in increased risk of schizophrenia.

6-Gingerol attenuates LPS-induced neuroinflammation and cognitive impairment partially via suppressing astrocyte overactivation

6-Gingerol, the major component of gingerols extracted from Zingiber officinale, has been shown to exhibit anti-inflammatory and antioxidant bioactivities. Since neuroinflammation plays an important role in neurodegenerative diseases, such as Alzheimer's disease (AD), and astrocytes have been considered important in the process of neurodegeneration, it was of interest to know whether 6-gingerol reduced astrocytes activation or even attenuated cognitive impairment. Here we examined the neuroprotective effects of 6-gingerol in lipopolysaccharide (LPS)-induced disorder models both in vitro and in vivo. C6 astroglioma cells treated with LPS were found to release excessive pro-inflammatory cytokines, including TNF-α and IL-6, and also increase intercellular ROS, NO, and iNOS (i.e. NOS2). All these were blocked by 6-gingerol in a concentration-dependent manner. The spatial learning and memory of rats challenged with LPS (10 μg, i.c.v.) in the absence or presence of 6-gingerol were evaluated using the Morris water-maze (MWM) test. 6-Gingerol attenuated LPS-induced imapirement of MWM learning and memory in a dose-dependent manner. Besides, 6-gingerol inhibited LPS-induced increases in levels of GFAP and TNF-α in the rat brain. The results suggest that 6-gingerol suppresses astrocyte overactivation, through which it contributes to improvement of cognitive ability.

Hippocampal Mrp8/14 signaling plays a critical role in the manifestation of depressive-like behaviors in mice

Background

Depression is one of the most common mental disorders characterized mainly by low mood and loss of interest or pleasure. About a third of patients with depression do not respond to classic antidepressant treatments. Recent evidence suggests that Mrp8/14 (myeloid-related protein 8/14) plays a crucial role in cognitive dysfunction and neuroinflammatory diseases, yet its role in mood regulation remains largely uninvestigated. In the present work, we explored the potential role of Mrp8/14 in the progression of depression.

Methods

After 4 weeks of chronic unpredictable mild stress (CUMS), depressive-like symptoms and Mrp8/14 were determined. To verify the effects of Mrp8/14 on depressive-like behaviors, the inhibitor TAK-242 and recombinant Mrp8/14 were used. Furthermore, the molecular mechanisms in Mrp8/14-induced behavioral and biological changes were examined in vivo and ex vivo.

Results

Four-week CUMS contributed to the development of depressive symptoms. Mrp8 and Mrp14 were upregulated in the hippocampus and serum after exposure to CUMS. Pharmacological inhibition of Mrp14 attenuated CUMS-induced TLR4/NF-κB signaling activation and depressive-like behaviors. Furthermore, central administration of recombinant Mrp8, Mrp14, and Mrp8/14 resulted in neuroinflammation and depressive-like behaviors. Mrp8/14-provoked proinflammatory effects and depressive-like behaviors were improved by pretreatment with a TLR4 inhibitor. Moreover, pharmacological inhibition of TLR4 reduced the release of nitric oxide and reactive oxygen species in Mrp8/14-activated BV2 microglia.

Conclusions

These data suggest that the hippocampal Mrp8/14-TLR4-mediated neuroinflammation contributes to the development of depressive-like behaviors. Targeting the Mrp8/14 may be a novel promising antidepressant approach.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1296-0) contains supplementary material, which is available to authorized users.

Effect of CD14/TLR4 antagonist on GnRH/LH secretion in ewe during central inflammation induced by intracerebroventricular administration of LPS

BACKGROUND

Immune stress induced by lipopolysaccharide (LPS) influences the gonadotropin-releasing hormone (GnRH)/luteinizing hormone (LH) secretion. Presence of LPS interacting Toll-like receptor (TLR) 4 in the hypothalamus may enable the direct action of LPS on the GnRH/LH secretion. So, the aim of the study was to investigate the influence of intracerebroventricular (icv) injection of TLR4 antagonist on GnRH/LH secretion in anestrous ewes during LPS-induced central inflammation. Animals were divided into three groups icv-treated with: Ringer-Locke solution, LPS and TLR4 antagonist followed by LPS.

RESULTS

It was demonstrated that TLR4 antagonist reduced LPS-dependent suppression of GnRH gene expression in the preoptic area and in the medial basal hypothalamus, and suppression of receptor for GnRH gene expression in the anterior pituitary gland. It was also shown that TLR4 antagonist reduced suppression of LH release caused by icv injection of LPS. Central administration of LPS stimulated TLR4 gene expression in the medial basal hypothalamus.

CONCLUSIONS

It was indicated that blockade of TLR4 prevents the inhibitory effect of centrally acting LPS on the GnRH/LH secretion. This suggests that some negative effects of bacterial infection on the hypothalamic-pituitary-gonadal axis activity at the hypothalamic level may be caused by central action of LPS acting through TLR4.

Controllable and uncontrollable stress differentially impact pathogenicity and survival in a mouse model of viral encephalitis

Intranasal instillation of vesicular stomatitis virus (VSV) into mice given controllable stress (modeled by escapable foot shock, ES) resulted in enhanced pathogenicity and decreased survival relative to infected mice given uncontrollable stress (modeled by inescapable foot shock, IS) and non-shocked control mice. Survival likely reflected differential cytokine gene expression that may have been regulated by miR146a, a predicted stress-responsive upstream regulator. Controllability also enhanced the accumulation of brain T resident memory cells that persisted long after viral clearance. The unexpected facilitatory effect of ES on antiviral neuroimmune responses and pathogenicity may arise from differential immunoactivating and immunosuppressive effects of uncontrollable and controllable stress.

Antiphospholipid antibodies in epilepsy: A systematic review and meta-analysis

BACKGROUND

Autoimmunity is believed to play an important causative role in the pathogenesis of epilepsy. There are evidences for the presence of autoantibodies in patients with epilepsy. To date, many studies have assessed the presence of antiphospholipid antibodies (aPLs) in epilepsy patients, though the relationship has been inconclusive.

AIMS

The aim of this systematic review and meta-analysis was to evaluate the presence of aPLs in epileptic patients as compared to healthy controls.

METHODS

Five electronic databases (PubMed, Web of Science, Embase, Scopus and Google Scholar) were searched systematically. Study-specific odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using random-effects model. Quality assessment was carried out by using the modified 9-star Newcastle-Ottawa Scale (NOS). L'Abbé plots were generated to visually inspect heterogeneity while publication bias was evaluated via visualization of contour- enhanced funnel plots, and Begg's and Egger's tests.

RESULTS

Based on the inclusion criteria, 14 studies were selected involving 1248 epilepsy patients and 800 healthy controls. The majority of epilepsy was categorised as generalised or partial and none had comorbidity with autoimmune diseases. Significant presence of both anticardiolipin (aCL) antibodies (OR: 5.16, 95% CI: 3.21-8.28, p < 0.00001) and anti-β2- glycoprotein I (anti-β2-GPI) antibodies (OR: 2.95, 95% CI: 1.07-8.11, p = 0.04) exhibited comorbid association with epilepsy patients as compared to healthy controls. Subgroup analyses revealed that presence of aCL antibodies was more specifically observed in paediatrics (OR: 4.57, 95% CI: 2.57-8.15, p < 0.00001) than adults (OR: 4.24, 95% CI: 1.80-10.01, p = 0.001). The odds of aCL antibody presence was higher in partial epilepsy patients (OR: 7.88, 95% CI: 3.23-19.24, p < 0.00001) than that of generalised (OR: 3.76, 95% CI: 2.15-6.59, p < 0.00001) and in Asian epileptic patients (OR: 9.56, 95% CI: 2.69-33.95, p = 0.0005) than Europeans (OR: 4.35, 95% CI: 2.74-6.92, p < 0.00001). The presence of anti-β2-GPI antibodies was significant in paediatric (OR: 6.44, 95% CI: 1.39-29.89, p = 0.02) and African population with epilepsies (OR: 10.59, 95% CI: 1.22-92.25, p = 0.03). NOS of the majority of the studies (11/14) indicated a high methodological quality. No substantial heterogeneity was observed either from the quantitative analysis or from the L'Abbé plots while no significant publication bias was detected from funnel plots; Begg's and Egger's tests.

CONCLUSION

Since none of the epilepsy subjects exhibited any comorbid autoimmune disorders, significant presence of aCL and anti-β2-GPI antibodies indicate towards their contribution in immune-mediated general pathogenesis of epilepsy.

Effects of the gut-liver axis on ischaemia-mediated hepatocellular carcinoma recurrence in the mouse liver

BACKGROUND & AIMS

There is growing evidence that liver graft ischemia-reperfusion (I/R) is a risk factor for hepatocellular carcinoma (HCC) recurrence, but the mechanisms involved are unclear. Herein, we tested the hypothesis that mesenteric congestion resulting from portal blood flow interruption induces endotoxin-mediated Toll-like receptor 4 (Tlr4) engagement, resulting in elevated liver cancer burden. We also assessed the role of remote ischemic preconditioning (RIPC) in this context.

METHODS

C57Bl/6j mice were exposed to standardized models of liver I/R injury and RIPC, induced by occluding the hepatic and femoral blood vessels. HCC was induced by injecting RIL-175 cells into the portal vein. We further evaluated the impact of the gut-liver axis (lipopolysaccharide (LPS)-Tlr4 pathway) in this context by studying mice with enhanced (lipopolysaccharide infusion) or defective (Tlr4^-/- mice, gut sterilization, and Tlr4 antagonist) Tlr4 responses.

RESULTS

Portal triad clamping provoked upstream mesenteric venous engorgement and increased bacterial translocation, resulting in aggravated tumor burden. RIPC prevented this mechanism by preserving intestinal integrity and reducing bacterial translocation, thereby mitigating HCC recurrence. These observations were linked to the LPS-Tlr4 pathway, as supported by the high and low tumor burden displayed by mice with enhanced or defective Tlr4 responses, respectively.

CONCLUSIONS

Modulation of the gut-liver axis and the LPS-Tlr4 response by RIPC, gut sterilization, and Tlr4 antagonism represents a potential therapeutic target to prevent I/R lesions, and to alleviate HCC recurrence after liver transplantation and resection.

LAY SUMMARY

Cancer recurrence can occur after liver resection or liver transplantation for hepatocellular carcinoma (HCC). This study suggests that intestinal venous congestion, which often occurs during liver surgery, favors the translocation of gut-derived bacterial products in the portal vein, thereby facilitating cancer recurrence by enhancing the signaling of Toll-like receptor 4 in the liver. Using a mouse model of HCC recurrence, we show that strategies that (i) reduce bacterial translocation (by gut decontamination, or by protecting the intestine from venous ischemia damage) or (ii) inhibit Tlr4 signaling in the liver, could reduce cancer recurrence.

Histone Deacetylase 2 Inhibitor CAY10683 Alleviates Lipopolysaccharide Induced Neuroinflammation Through Attenuating TLR4/NF-κB Signaling Pathway

Neuroinflammation involves in the progression of many central nervous system diseases. Several studies have shown that histone deacetylase (HDAC) inhibitors modulated inflammatory responses in lipopolysaccharide (LPS) stimulated microglia. While, the mechanism is still unclear. The aim of present study was to investigate the effect of HDAC2 inhibitor CAY10683 on inflammatory responses and TLR4/NF-κB signaling pathways in LPS activated BV2 microglial cells and LPS induced mice neuroinflammation. The effect of CAY10683 on cell viability of BV2 microglial cells was detected by CCK-8 assay. The expressions of inflammatory cytokines were analyzed by western blotting and RT-PCR respectively. The TLR4 protein expression was measured by western blotting, immunofluorescence, immunohistochemistry respectively. The protein expressions of MYD88, phospho-NF-κB p65, NF-κB-p65, acetyl-H3 (AH3), H3, and HDAC2 were analyzed by western blotting. We found that CAY10683 could inhibit expression levels of inflammatory cytokine TNF-α and IL-1β in LPS activated BV2 microglial cells and LPS induced mice neuroinflammation. It could induce TLR4, MYD88, phospho-NF-κB p65, and HDAC2 expressions. Moreover, CAY10683 increased the acetylation of histones H3 in LPS activated BV2 microglial cells and LPS induced mice neuroinflammation. Taken together, our findings suggested that HDAC2 inhibitor CAY10683 could suppress neuroinflammatory responses and TLR4/NF-κB signaling pathways by acetylation after LPS stimulation.

Effects of oregano essential oil on brain TLR4 and TLR2 gene expression and depressive-like behavior in a rat model

The aim of the present study was to evaluate the effects of oregano essential oil (OEO) on the hippocampus and prefrontal cortex TLR 2/4 gene expression and depressive like behavior induced by chronic unpredictable stress (CUS). Sucrose preference and forced swim tests were adopted to examine the antidepressant effect. Control (CON), OEO, CUS, and CUS + OEO groups were used. The OEO and CUS + OEO groups received OEO (0.2 mL/kg, i.p.), CON and CUS received saline (0.2 mL/kg, i.p.), and the positive drug groups of CUS rats received fluoxetine (10 mg/kg) and diazepam (3 mg/kg) once daily for 14 days. The expression of TLR 2/4 was determined using real time quantitative polymerase chain reaction with the SYBR green reporter dye. The compositions of the OEO were determined by gas chromatography-mass spectroscopy. The main constituents were thymol (20.72%), gamma-terpinene (8.83%), borneol (8.72%), cymene (6.83%), carvacrol (6.274%), alfa-terpinene (5.26%), and sabinene (4.92%). Administration of OEO significantly alleviated the depressive symptoms of CUS. A higher level of TLR2/4 mRNA was seen in the brain of CUS group (P < 0.05). The CUS-induced increases in the TLR2/4 levels were not reversed by OEO. According to the present study OEO may have the antidepressant-like activity but have no effect on the stress-induced TLR-2/4 upregulation.

Ex-vivo generation of drug-eluting islets improves transplant outcomes by inhibiting TLR4-Mediated NFkB upregulation

The systemic administration of immunosuppressive and anti-inflammatory drugs is routinely employed in organ transplantation to minimize graft rejection and improve graft survival. Localized drug delivery has the potential to improve transplant outcomes by providing sustained exposure to efficacious drug concentrations while avoiding systemic immunosuppression and off-target effects. Here, we describe the synthesis of a novel prodrug and its direct covalent conjugation to pancreatic islets via a cleavable linker. Post-transplant, linker hydrolysis results in the release of a potent anti-inflammatory antagonist of TLR4, localized to the site of implantation. This covalent islet modification significantly reduces the time and the minimal effective dose of islets necessary to achieve normoglycemia in a murine transplantation model. In streptozotocin-induced diabetic C57BL/6 mice a syngeneic transplant of ∼100 modified islets achieved a 100% cure rate by the end of a 4-week monitoring period, compared to a 0% cure rate for untreated control islets. Overall, this direct prodrug conjugation to islets is well tolerated and preserves their functionality while affording significantly superior transplant outcomes. The development of drug-eluting tissues that deliver sustained and localized doses of small-molecule therapeutics represents a novel pathway for enhancing success in transplantation.

Targets for Drug Therapy for Autism Spectrum Disorder: Challenges and Future Directions

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by persistent deficits in social communication and interaction and restricted, repetitive patterns of behavior, interests, and activities. Various factors are involved in the etiopathogenesis of ASD, including genetic factors, environmental toxins and stressors, impaired immune responses, mitochondrial dysfunction, and neuroinflammation. The heterogeneity in the phenotype among ASD patients and the complex etiology of the condition have long impeded the advancement of the development of pharmacological therapies. In the recent years, the integration of findings from mouse models to human genetics resulted in considerable progress toward the understanding of ASD pathophysiology. Currently, strategies to treat core symptoms of ASD are directed to correct synaptic dysfunctions, abnormalities in central oxytocin, vasopressin, and serotonin neurotransmission, and neuroinflammation. Here, we present a survey of the studies that have suggested molecular targets for drug development for ASD and the state-of-the-art of medicinal chemistry efforts in related areas.

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.

TLR4 Signaling Pathway Modulators as Potential Therapeutics in Inflammation and Sepsis

Toll-Like Receptor 4 (TLR4) signal pathway plays an important role in initiating the innate immune response and its activation by bacterial endotoxin is responsible for chronic and acute inflammatory disorders that are becoming more and more frequent in developed countries. Modulation of the TLR4 pathway is a potential strategy to specifically target these pathologies. Among the diseases caused by TLR4 abnormal activation by bacterial endotoxin, sepsis is the most dangerous one because it is a life-threatening acute system inflammatory condition that still lacks specific pharmacological treatment. Here, we review molecules at a preclinical or clinical phase of development, that are active in inhibiting the TLR4-MyD88 and TLR4-TRIF pathways in animal models. These are low-molecular weight compounds of natural and synthetic origin that can be considered leads for drug development. The results of in vivo studies in the sepsis model and the mechanisms of action of drug leads are presented and critically discussed, evidencing the differences in treatment results from rodents to humans.

Therapeutic Effectiveness of Anti-RAGE Antibody Administration in a Rat Model of Crush Injury

Crush injury patients often have systemic inflammatory response syndrome that leads to multiple organ failure. Receptor for advanced glycation endproducts (RAGE) functions as a pattern recognition receptor that regulates inflammation. We evaluated the effects of anti-RAGE antibody in a crush injury model. Pressure was applied to both hindlimbs of rats for 6 h by 3.0-kg blocks and then released. Animals were randomly divided into the sham (RAGE-Sh) group, crush (RAGE-Ctrl) group or anti-RAGE antibody-treated crush (RAGE-Tx) group. Samples were collected at 3, 6 and 24 h after releasing pressure. In the RAGE-Ctrl group, fluorescent immunostaining in the lung showed upregulated RAGE expression at 3 h. The serum soluble RAGE (sRAGE) level, which reflects the amount of RAGE expression in systemic tissue, increased at 6 h. Serum interleukin 6 (IL-6; systemic inflammation marker) increased immediately at 3 h. Histological analysis revealed lung injury at 6 and 24 h. Administration of anti-RAGE antibody before releasing compression inhibited upregulated RAGE expression in the lung alveoli, suppressed RAGE-associated mediators sRAGE and IL6, attenuated the lung damage and improved the 7-day survival rate. Collectively, our results indicated that the use of anti-RAGE antibody before releasing compression is associated with a favourable prognosis following crush injury.

Current and novel anti-inflammatory drug targets for inhibition of cytokines and leucocyte recruitment in rheumatic diseases

Objectives

Many studies of disease state mechanisms reveal that unbridled inflammation is to blame for many of the symptoms associated with autoimmune diseases such as Crohn’s and Rheumatoid Arthritis (RA). While therapies aimed at decreasing levels of pro-inflammatory cytokines exist, some have failed clinically or have extensive adverse effects. The aim of this review is to discuss common drug targets for anti-inflammatory therapies as well as explore potential mechanisms of action for new therapies. Various studies done on novel mechanisms targeting pro-inflammatory cytokine release as well as leukocyte chemotaxis have been researched for discussion here. Both of these contribute to tissue injury and patient symptoms in inflammatory and autoimmune disease states.

Key findings

While many current drug targets suppress inflammation via the receptor, research aimed at identifying new compounds and signaling mechanisms is ongoing to identify new targets within pro-inflammatory signaling pathways, or specific immune cell types.

Conclusions

While glucocorticoids and monoclonal antibodies have shown to be efficacious, some patients have encountered mixed results. Biologic therapies also come with a high price tag Thus, novel compounds with new immune drug targets are ideal for patients whose therapies have not been successful.

Electroacupuncture Improved Hippocampal Neurogenesis following Traumatic Brain Injury in Mice through Inhibition of TLR4 Signaling Pathway

The protective role of electroacupuncture (EA) treatment in diverse neurological diseases such as ischemic stroke is well acknowledged. However, whether and how EA act on hippocampal neurogenesis following traumatic brain injury (TBI) remains poorly understood. This study aims to investigate the effect of EA on hippocampal neurogenesis and neurological functions, as well as its underlying association with toll-like receptor 4 (TLR4) signaling in TBI mice. BrdU/NeuN immunofluorescence was performed to label newborn neurons in the hippocampus after EA treatment. Water maze test and neurological severity score were used to evaluate neurological function posttrauma. The hippocampal level of TLR4 and downstream molecules and inflammatory cytokines were, respectively, detected by Western blot and enzyme-linked immunosorbent assay. EA enhanced hippocampal neurogenesis and inhibited TLR4 expression at 21, 28, and 35 days after TBI, but the beneficial effects of EA on posttraumatic neurogenesis and neurological functions were attenuated by lipopolysaccharide-induced TLR4 activation. In addition, EA exerted an inhibitory effect on both TLR4/Myd88/NF-κB and TLR4/TRIF/NF-κB pathways, as well as the inflammatory cytokine expression in the hippocampus following TBI. In conclusion, EA promoted hippocampal neurogenesis and neurological recovery through inhibition of TLR4 signaling pathway posttrauma, which may be a potential approach to improve the outcome of TBI.

Inflammation-dependent cerebrospinal fluid hypersecretion by the choroid plexus epithelium in posthemorrhagic hydrocephalus

The choroid plexus epithelium (CPE) secretes higher volumes of fluid (cerebrospinal fluid, CSF) than any other epithelium and simultaneously functions as the blood-CSF barrier to gate immune cell entry into the central nervous system. Posthemorrhagic hydrocephalus (PHH), an expansion of the cerebral ventricles due to CSF accumulation following intraventricular hemorrhage (IVH), is a common disease usually treated by suboptimal CSF shunting techniques. PHH is classically attributed to primary impairments in CSF reabsorption, but little experimental evidence supports this concept. In contrast, the potential contribution of CSF secretion to PHH has received little attention. In a rat model of PHH, we demonstrate that IVH causes a Toll-like receptor 4 (TLR4)- and NF-κB-dependent inflammatory response in the CPE that is associated with a ∼3-fold increase in bumetanide-sensitive CSF secretion. IVH-induced hypersecretion of CSF is mediated by TLR4-dependent activation of the Ste20-type stress kinase SPAK, which binds, phosphorylates, and stimulates the NKCC1 co-transporter at the CPE apical membrane. Genetic depletion of TLR4 or SPAK normalizes hyperactive CSF secretion rates and reduces PHH symptoms, as does treatment with drugs that antagonize TLR4-NF-κB signaling or the SPAK-NKCC1 co-transporter complex. These data uncover a previously unrecognized contribution of CSF hypersecretion to the pathogenesis of PHH, demonstrate a new role for TLRs in regulation of the internal brain milieu, and identify a kinase-regulated mechanism of CSF secretion that could be targeted by repurposed US Food and Drug Administration (FDA)-approved drugs to treat hydrocephalus.

Inflammation and Immune Regulation as Potential Drug Targets in Antidepressant Treatment

Growing evidence supports a mutual relationship between inflammation and major depression. A variety of mechanisms are outlined, indicating how inflammation may be involved in the pathogenesis, course and treatment of major depression. In particular, this review addresses 1) inflammatory cytokines as markers of depression and potential predictors of treatment response, 2) findings that cytokines interact with antidepressants and non-pharmacological antidepressive therapies, such as electroconvulsive therapy, deep brain stimulation and physical activity, 3) the influence of cytokines on the cytochrome (CYP) p450-system and drug efflux transporters, and 4) how cascades of inflammation might serve as antidepressant drug targets. A number of clinical trials have focused on agents with immunmodulatory properties in the treatment of depression, of which this review covers nonsteroidal anti-inflammatory drugs (NSAIDs), cytokine inhibitors, ketamine, polyunsaturated fatty acids, statins and curcumin. A perspective is also provided on possible future immune targets for antidepressant therapy, such as toll-like receptor-inhibitors, glycogen synthase kinase-3 inhibitors, oleanolic acid analogs and minocycline. Concluding from the available data, markers of inflammation may become relevant factors for more personalised planning and prediction of response of antidepressant treatment strategies. Agents with anti-inflammatory properties have the potential to serve as clinically relevant antidepressants. Further studies are required to better define and identify subgroups of patients responsive to inflammatory agents as well as to define optimal time points for treatment onset and duration.

Neuroprotective Effects of Resatorvid Against Traumatic Brain Injury in Rat: Involvement of Neuronal Autophagy and TLR4 Signaling Pathway

Accumulating evidence indicates that autophagy and inflammatory responses contributes to secondary brain injury after traumatic brain injury (TBI), and toll-like receptor 4 (TLR4) is considered to involvement of this cascade and plays an important role. The present study was designed to determine the hypothesis that administration of resatorvid (TAK-242), a TLR4 antagonist, might provide a neuroprotective effect by inhibit TLR4-mediated pathway in a TBI rat model. Rat subjected to controlled cortical impact injury were injected with TAK-242 (0.5 mg/kg, i.v. injected) 10 min prior to injury. The results demonstrated that TAK-242 treatment significantly attenuated TBI-induced neurons loss, brain edema, and neurobehavioral impairment in rats. Immunoblotting analysis showed that TAK-242 treatment reduced TBI-induced TLR4, Beclin 1, and LC3-II levels, and maintained p62 levels at 24 h. Double immunolabeling demonstrated that LC3 dots co-localized with the hippocampus pyramidal neurons, and TLR4 was localized with the hippocampus neurons and astrocytes. In addition, the expression of TLR4 downstream signaling molecules, including MyD88, TRIF, NF-κB, TNF-α, and IL-1β, was significantly downregulated in hippocampus tissue by Western blot analysis. In conclusion, our findings indicate that pre-injury treatment with TAK-242 could inhibit neuronal autophagy and neuroinflammation responses in the hippocampus in a rat model of TBI. The neuroprotective effects of TAK-242 may be related to modulation of the TLR4-MyD88/TRIF-NF-κB signaling pathway. Furthermore, the study also suggests that TAK-242, an attractive potential drug, may be a promising drug candidate for TBI.

TNFAIP3, a negative regulator of the TLR signaling pathway, is a potential predictive biomarker of response to antidepressant treatment in major depressive disorder

Inflammation and abnormalities in Toll-like receptor (TLR) expression and activation have been linked to major depressive disorder (MDD). However, negative regulators of TLR pathways have not been previously investigated in this context. Here, we sought to investigate the association of depression severity, measured by the 17-item Hamilton Depression Rating Scale (HAMD-17), with mRNA expression levels of negative regulators of the TLR pathway, including SOCS1, TOLLIP, SIGIRR, MyD88s, NOD2 and TNFAIP3, in peripheral blood mononuclear cells (PBMCs) from 100 patients with MDD and 53 healthy controls, before and after treatment with antidepressants. Positive regulators of the TLR4 pathway, including Pellino 1, TRAF6 and IRAK1, were also investigated. Among all patients, MyD88s, and TNFAIP3 mRNAs were expressed at lower levels in PBMCs from patients with MDD. Multiple linear regression analyses revealed that TNFAIP3 mRNA expression before treatment was inversely correlated with severity of depression and effectively predicted improvement in HAMD-17 scores. Among 79 treatment-completers, only TNFAIP3 mRNA was significantly increased by treatment with antidepressants for 4 weeks. Treatment of human monocytes (THP-1) and mouse microglia (SIM-A9) cell lines with fluoxetine significantly increased TNFAIP3 mRNA expression and suppressed IL-6 levels. The suppressive effect of fluoxetine on IL-6 was attenuated by knockdown of TNFAIP3 expression. These findings suggest that both dysfunction of the negative regulatory system in patients with MDD and antidepressant treatment exert anti-inflammatory effects, at least in part through increased expression of the TNFAIP3 gene. They also indicate that modulating expression of the TNFAIP3 gene to rebalance TLR-mediated inflammatory signaling may be potential therapeutic strategy for treating MDD.

Inhibition of TLR4 Signalling-Induced Inflammation Attenuates Secondary Injury after Diffuse Axonal Injury in Rats

Increasing evidence suggests that secondary injury after diffuse axonal injury (DAI) damages more axons than the initial insult, but the underlying mechanisms of this phenomenon are not fully understood. Recent studies show that toll-like receptor 4 (TLR4) plays a critical role in promoting adaptive immune responses and have been shown to be associated with brain damage. The purpose of this study was to investigate the role of the TLR4 signalling pathway in secondary axonal injury in the cortices of DAI rats. TLR4 was mainly localized in microglial cells and neurons, and the levels of TLR4 downstream signalling molecules, including TLR4, myeloid differentiation primary response gene 88, toll/IR-1-(TIR-) domain-containing adaptor protein inducing interferon-beta, interferon regulatory factor 3, interferon β, nuclear factor κB (NF-κB) p65, and phospho-NF-κB p65, significantly increased and peaked at 1 d after DAI. Inhibition of TLR4 by TAK-242 attenuated apoptosis, neuronal and axonal injury, and glial responses. The neuroprotective effects of TLR4 inhibition were associated with decreases in the levels of TLR4 downstream signalling molecules and inflammatory factors, including interleukin-1β, interleukin-6, and tumour necrosis factor-α. These results suggest that the TLR4 signalling pathway plays an important role in secondary injury and may be an important therapeutic target following DAI.

CLI-095 decreases atherosclerosis by modulating foam cell formation in apolipoprotein E-deficient mice

Toll-like receptor 4 (TLR4) is considered to have a critical role in the occurrence and development of atherosclerosis in atherosclerosis-prone mice; however, it remains uncertain whether treatment with a TLR4 inhibitor may attenuate atherosclerosis. The present study aimed to determine the vascular protective effects of the TLR4 inhibitor CLI-095 on apolipoprotein E‑deficient (ApoE‑/‑) mice. ApoE‑/‑ mice were fed either chow or a high‑fat diet, and were treated with or without CLI‑095 for 10 weeks. The mean atherosclerotic plaque area in the aortic sections of CLI‑095‑treated mice was 54.3% smaller than in the vehicle‑treated mice (P=0.0051). In vitro, murine peritoneal macrophages were treated with or without CLI‑095, and were subsequently stimulated with oxidized low‑density lipoprotein. Treatment with CLI‑095 markedly reduced the expression levels of lectin‑like oxidized low‑density lipoprotein receptor‑1 and acyl-coenzyme A:cholesterol acyltransferase‑1, and significantly upregulated the expression levels of ATP‑binding cassette transporter A1, predominantly via suppressing activation of the TLR4/nuclear factor‑κB signaling pathway. The results of the present study indicated that the TLR4 inhibitor CLI‑095 has the ability to suppress the progression of atherosclerosis in an in vivo model by reducing macrophage foam cell formation.

Gastro-protective and Anti-stress Efficacies of Monomethyl Fumarate and a Fumaria indica Extract in Chronically Stressed Rats

Results of the very first experiments conducted to evaluate therapeutic potentials of a fumarate containing Fumaria indica extract and of fairly low daily oral doses of monomethyl fumarate for prevention of chronic unavoidable foot-shock stress-induced gastric ulcers, and possible involvement of diverse neuro-hormonal and oxidative process in their stress response desensitizing effects are reported and discussed in this article. Preventive effects of 21 daily oral 60, 120, and 240 mg/kg doses of a standardized 50 % methanolic F. indica extract (MFI) and 1.25, 2.50, and 5.00 mg/kg/day of pure monomethyl fumarate (MMF) were compared in rats subjected to one hour daily unavoidable foot-shocks. A pharmaceutically well-standardized Withania somnifera (WS) root extract was used as a reference herbal anti-stress agent in all experiments. Effects of the treatments on stress-induced alterations in body weight, adrenal and spleen weights, gastric ulcer and ulcer index, weight of glandular stomach, protective mucosal glycoprotein content, cellular proliferation, oxidative stress on stomach fundus, and brain tissues of male rats were quantified. Other parameters quantified were plasma corticosterone levels, brain monoamine levels, and expressions of the cytokines TNF-α, IL-10, and IL-1β in blood and brain of stressed and treated rats. Most but not every observed stress-induced anomalies were suppressed or completely prevented by both MFI and pure MMF treatments in dose-dependent manner. Qualitatively, the observed activity profiles of both of them were similar to those of WS dose tested. These results reveal that both MFI and MMF are potent gastro-protective agents against chronic unavoidable stress-induced ulcers and strongly suggest that they act as regulators or modulators of monoamine, corticosterone, and cytokine homeostasis.

Osmotin attenuates LPS-induced neuroinflammation and memory impairments via the TLR4/NFκB signaling pathway

Toll-like receptor 4 (TLR4) signaling in the brain mediates autoimmune responses and induces neuroinflammation that results in neurodegenerative diseases, such as Alzheimer’s disease (AD). The plant hormone osmotin inhibited lipopolysaccharide (LPS)-induced TLR4 downstream signaling, including activation of TLR4, CD14, IKKα/β, and NFκB, and the release of inflammatory mediators, such as COX-2, TNF-α, iNOS, and IL-1β. Immunoprecipitation demonstrated colocalization of TLR4 and AdipoR1 receptors in BV2 microglial cells, which suggests that osmotin binds to AdipoR1 and inhibits downstream TLR4 signaling. Furthermore, osmotin treatment reversed LPS-induced behavioral and memory disturbances and attenuated LPS-induced increases in the expression of AD markers, such as Aβ, APP, BACE-1, and p-Tau. Osmotin improved synaptic functionality via enhancing the activity of pre- and post-synaptic markers, like PSD-95, SNAP-25, and syntaxin-1. Osmotin also prevented LPS-induced apoptotic neurodegeneration via inhibition of PARP-1 and caspase-3. Overall, our studies demonstrated that osmotin prevented neuroinflammation-associated memory impairment and neurodegeneration and suggest AdipoR1 as a therapeutic target for the treatment of neuroinflammation and neurological disorders, such as AD.

Stress-induced neuroinflammation is mediated by GSK3-dependent TLR4 signaling that promotes susceptibility to depression-like behavior

Most psychiatric and neurological diseases are exacerbated by stress. Because this may partially result from stress-induced inflammation, we examined factors involved in this stress response. After a paradigm of inescapable foot shock stress that causes learned helplessness depression-like behavior, eighteen cytokines and chemokines increased in mouse hippocampus, peaking 6-12h after stress. A 24h prior pre-conditioning stress accelerated the rate of stress-induced hippocampal cytokine and chemokine increases, with most reaching peak levels after 1-3h, often without altering the maximal levels. Toll-like receptor 4 (TLR4) was involved in this response because most stress-induced hippocampal cytokines and chemokines were attenuated in TLR4 knockout mice. Stress activated glycogen synthase kinase-3 (GSK3) in wild-type mouse hippocampus, but not in TLR4 knockout mice. Administration of the antidepressant fluoxetine or the GSK3 inhibitor TDZD-8 reduced the stress-induced increases of most hippocampal cytokines and chemokines. Stress increased hippocampal levels of the danger-associated molecular pattern (DAMP) protein high mobility group box 1 (HMGB1), activated the inflammatory transcription factor NF-κB, and the NLRP3 inflammasome. Knockdown of HMGB1 blocked the acceleration of cytokine and chemokine increases in the hippocampus caused by two successive stresses. Fluoxetine treatment blocked stress-induced up-regulation of HMGB1 and subsequent NF-κB activation, whereas TDZD-8 administration attenuated NF-κB activation downstream of HMGB1. To test if stress-induced cytokines and chemokines contribute to depression-like behavior, the learned helplessness model was assessed. Antagonism of TNFα modestly reduced susceptibility to learned helplessness induction, whereas TLR4 knockout mice were resistant to learned helplessness. Thus, stress-induces a broad inflammatory response in mouse hippocampus that involves TLR4, GSK3, and downstream inflammatory signaling, and these stress responses contribute to susceptibility to depression-like behavior in mice.

Innate immune receptor Toll-like receptor 4 signalling in neuropsychiatric diseases

The innate immunity is a stereotyped first line of defense against pathogens and unspecified damage signals. One of main actors of innate immunity are the Toll-like receptors (TLRs), and one of the better characterized members of this family is TLR-4, that it is mainly activated by Gram-negative bacteria lipopolysaccharide. In brain, TLR-4 organizes innate immune responses against infections or cellular damage, but also possesses other physiological functions. In the last years, some evidences suggest a role of TLR-4 in stress and stress-related neuropsychiatric diseases. Peripheral and brain TLR-4 activation triggers sickness behavior, and its expression is a risk factor of depression. Some elements of the TLR-4 signaling pathway are up-regulated in peripheral samples and brain post-mortem tissue from depressed and suicidal patients. The "leaky gut" hypothesis of neuropsychiatric diseases is based on the existence of an increase of the intestinal permeability which results in bacterial translocation able to activate TLR-4. Enhanced peripheral TLR-4 expression/activity has been described in subjects diagnosed with schizophrenia, bipolar disorder and in autistic children. A role for TLR-4 in drugs abuse has been also proposed. The therapeutic potential of pharmacological/genetic modulation of TLRs signaling pathways in neuropsychiatry is promising, but a great preclinical/clinical scientific effort is still needed.

Cocaine-mediated induction of microglial activation involves the ER stress-TLR2 axis

Background

Neuroinflammation associated with advanced human immunodeficiency virus (HIV)-1 infection is often exacerbated by chronic cocaine abuse. Cocaine exposure has been demonstrated to mediate up-regulation of inflammatory mediators in in vitro cultures of microglia. The molecular mechanisms involved in this process, however, remain poorly understood. In this study, we sought to explore the underlying signaling pathways involved in cocaine-mediated activation of microglial cells.

Methods

BV2 microglial cells were exposed to cocaine and assessed for toll-like receptor (TLR2) expression by quantitative polymerase chain reaction (qPCR), western blot, flow cytometry, and immunofluorescence staining. The mRNA and protein levels of cytokines (TNFα, IL-6, MCP-1) were detected by qPCR and ELISA, respectively; level of reactive oxygen species (ROS) production was examined by the Image-iT LIVE Green ROS detection kit; activation of endoplasmic reticulum (ER)-stress pathways were detected by western blot. Chromatin immunoprecipitation (ChIP) assay was employed to discern the binding of activating transcription factor 4 (ATF4) with the TLR2 promoter. Immunoprecipitation followed by western blotting with tyrosine antibody was used to determine phosphorylation of TLR2. Cocaine-mediated up-regulation of TLR2 expression and microglial activation was validated in cocaine-injected mice.

Results

Exposure of microglial cells to cocaine resulted in increased expression of TLR2 with a concomitant induction of microglial activation. Furthermore, this effect was mediated by NADPH oxidase-mediated rapid accumulation of ROS with downstream activation of the ER-stress pathways as evidenced by the fact that cocaine exposure led to up-regulation of pPERK/peIF2α/ATF4 and TLR2. The novel role of ATF4 in the regulation of TLR2 expression was confirmed using genetic and pharmacological approaches.

Conclusions

xThe current study demonstrates that cocaine-mediated activation of microglia involves up-regulation of TLR2 through the ROS-ER stress-ATF4-TLR2 axis. Understanding the mechanism(s) involved in cocaine-mediated up-regulation of ROS-ER stress/TLR2 expression and microglial activation could have implications for the development of potential therapeutic targets aimed at resolving neuroinflammation in cocaine abusers.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0501-2) contains supplementary material, which is available to authorized users.

For whom the endocannabinoid tolls: Modulation of innate immune function and implications for psychiatric disorders

Toll-like receptors (TLRs) mediate the innate immune response to pathogens and are critical in the host defence, homeostasis and response to injury. However, uncontrolled and aberrant TLR activation can elicit potent effects on neurotransmission and neurodegenerative cascades and has been proposed to trigger the onset of certain neurodegenerative disorders and elicit detrimental effects on the progression and outcome of established disease. Over the past decade, there has been increasing evidence demonstrating that the endocannabinoid system can elicit potent modulatory effects on inflammatory processes, with clinical and preclinical evidence demonstrating beneficial effects on disease severity and symptoms in several inflammatory conditions. This review examines the evidence supporting a modulatory effect of endocannabinoids on TLR-mediated immune responses both peripherally and centrally, and the implications for psychiatric disorders such as depression and schizophrenia.

Antidepressants normalize elevated Toll-like receptor profile in major depressive disorder

RATIONALE

Abnormalities in Toll-like receptor (TLR) expression in depression have been inferred in part from observed increases in TLR4 levels in peripheral blood mononuclear cells (PBMCs) and postmortem brains of depressed and suicidal patients. Our previous study found differences in the TLR expression in PBMCs between healthy controls and patients with major depressive disorder. Normalization of increased TLR4 in PBMCs by cognitive behavior psychotherapy has been reported. However, the effects of antidepressants remain unknown.

OBJECTIVES

Changes in TLR1-9 expression levels of PBMCs were examined in 56 patients with MDD. The 17-item Hamilton Depression Rating Scale (HAMD-17) and mRNA expression levels of TLRs were assessed in parallel with a housekeeping gene using qRT-PCR before and after treatment with antidepressants.

RESULTS

TLR3, TLR4, TLR5, TLR7, TLR8, and TLR9 were expressed at elevated levels in patients with MDD and were significantly decreased by treatment with antidepressants for 4 weeks. Antidepressant treatment completely normalized TLR3, TLR5, TLR7, TLR8, and TLR9 levels, whereas TLR1, TLR2, TLR4, and TLR6 were decreased to below normal levels. A subgroup analysis found that only TLR3 was significantly higher at baseline in the nonremission group. In addition, a multiple linear regression analysis revealed that only low TLR3 before treatment predicted improvement in HAMD-17 scores.

CONCLUSIONS

These findings suggest that antidepressant treatment exerts anti-inflammatory effects in patients with MDD and identify TLR profiles as a predictor of response to antidepressant therapy. Further studies investigating the effects of manipulating individual TLRs on depression are needed to fully elucidate the underlying mechanism.

Depressive-like immobility behavior and genotype × stress interactions in male mice of selected strains

In this study, we investigated whether basal immobility time of C57BL/6J mice, which are commonly used in transgenesis, interferes with detection of depressive-like behavior in the tail suspension test (TST) after chronic restraint stress (CRS). We included in the study mice of the C57BL/6N strain, not previously compared with C57BL/6J for behavior in the TST, and contrasted both strains with NMRI mice which exhibit low basal immobility. NMRI, C57BL/6J, and C57BL/6N male mice (n = 20 per strain) were tested under basal conditions and after CRS (2 h daily for 14 d). NMRI and C57BL/6J mice were differentiated in the TST by low and high basal immobility times, respectively, while the C57BL/6N and NMRI mice showed similar levels of basal immobility. CRS extended the immobility time of NMRI mice in the TST, whereas both C57BL/6J and C57BL/6N mice were unaffected regardless of their initial phenotype. We explored whether detailed analysis of activity microstructure revealed effects of CRS in the TST, which are not apparent in the overall comparison of total immobility time. Interestingly, unlike C57BL/6J and/6N strains which showed no sensitivity to CRS, stressed NRMI mice displayed distinct activity microstructure. In contrast to behavioral differences, all stressed mice showed significant retardation in body weight gain, decreased thymus weight and increased adrenal cortex size. However, after CRS, enlargement of the adrenal medulla was observed in both C57BL/6J and C57BL/6N mice, suggesting similar sympatho-medullary activation and stress coping mechanism in these substrains.

TAK-242, a Toll-Like Receptor 4 Antagonist, Protects against Aldosterone-Induced Cardiac and Renal Injury

Cardiovascular and renal inflammation induced by Aldosterone (Aldo) plays an important role in the pathogenesis of hypertension and renal fibrosis. Toll-like receptor 4 (TLR4) signaling contributes to inflammatory cardiovascular and renal diseases, but its role in Aldo-induced hypertension and renal damage is not clear. In the current study, rats were treated with Aldo-salt combined with TAK-242 (a TLR4 signaling antagonist) for 4 weeks. Hemodynamic, cardiac and renal parameters were assayed at the indicated time. We found that Aldo-salt–treated rats present cardiac and renal hypertrophy and dysfunction. Cardiac and renal expression levels of TLR4 as well as levels of molecular markers attesting inflammation and fibrosis are increased by Aldo infusion, whereas the treatment of TAK-242 reverses these alterations. TAK-242 suppresses cardiac and renal inflammatory cytokines levels (TNF-a, IL-1β and MCP-1). Furthermore, TAK-242 inhibits hypertension, cardiac and renal fibrosis, and also attenuates the Aldo-induced Epithelial-Mesenchymal Transition (EMT). In experimental hyperaldosteronism, upregulation of TLR4 is correlated with cardiac and renal fibrosis and dysfunction, and a TLR4 signaling antagonist, TAK-242, can reverse these alterations. TAK-242 may be a therapeutic option for salt-sensitive hypertension and renal fibrosis.

Blockade of high mobility group box-1 signaling via the receptor for advanced glycation end-products ameliorates inflammatory damage after acute intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a devastating disease with no specific treatment. Increasing evidence indicates that inflammatory response plays a critical role in ICH-induced damage. High mobility group box-1 protein (HMGB1) may trigger inflammatory response via three putative receptors: receptor for advanced glycation end-products (RAGE), toll-like receptor-2 (TLR2) and toll-like receptor-4 (TLR4). Which receptor participates in HMGB1-induced inflammation during acute ICH is unknown. Using a rat model to examine the early phase of injury in collagenase-induced ICH, we found that treating animals with HMGB1 antagonist significantly reduced the expression of all three receptors. Treating animals with the HMGB1 antagonist EP or RAGE antagonist FPS-ZM1 significantly reduced inflammatory cell infiltration and expression of IL-1β, matrix metalloproteinase-9 in the perihematoma after ICH. Treatment with EP or FPS-ZM1 also led to greater neurobehavioral function and less brain edema, hemorrhage volume and brain damage after ICH. In contrast, treatment with TLR2/4 antagonists did not significantly affect these post-ICH outcomes. Our results suggest that RAGE may play a specific role in the acute phase of ICH, so targeting the HMGB1-RAGE signaling pathway may be a promising therapeutic strategy.

Effects of exercise on brain and peripheral inflammatory biomarkers induced by total sleep deprivation in rats

Background

Physical exercise induces neuroprotection through anti-inflammatory effects and total sleep deprivation is reported an inflammatory process. We examined whether 7 weeks of exercise training attenuates markers of inflammation during total sleep deprivation (24-h wakefulness) in the rat brain and periphery.

Methods

Four groups of 10 rats were investigated: Sedentary control, Sedentary sleep-deprived, Exercised control, and Exercised sleep-deprived. Sleep deprivation and exercise training were induced using slowly rotating wheels and a motorized treadmill. We examined mRNA expression of pro-inflammatory (IL-1β, TNF-α, and IL-6) cytokine-related genes using real-time PCR, and protein levels in the hippocampus and frontal cortex, as well as circulating concentrations.

Results

Compared to Sedentary control rats, hippocampal and cortical IL-1β mRNA expressions in Sedentary sleep-deprived rats were up-regulated (p < 0.05 and p < 0.01 respectively). At the protein level, hippocampal IL-1β and TNF-α and cortical IL-6 contents were higher in Sedentary sleep-deprived rats (p < 0.001, p < 0.05, p < 0.05, respectively). Peripherally, TNF-α, IL-6 and norepinephrine concentrations were higher in Sedentary sleep-deprived rats compared to Sedentary control (p < 0.01, p < 0.001, p < 0.01, respectively). Exercise training reduced the sleep deprivation-induced hippocampal IL-1β increases (mRNA expression and protein content) (p < 0.05 and p < 0.001), and TNF-α content (p < 0.001). At the periphery, exercise reduced sleep deprivation-induced increase of IL-6 concentration (p < 0.05) without effect on TNF-α and norepinephrine.

Conclusions

We demonstrate that a 7-week exercise training program before acute total sleep deprivation prevents pro-inflammatory responses in the rat hippocampus, particularly the IL-1β cytokine at the gene expression level and protein content.

Analgesic effect of TAK-242 on neuropathic pain in rats

BACKGROUND

The current study investigated the analgesic effect of the Toll-like receptor 4 (TLR4) specific antagonist TAK-242 on neuropathic pain in rats and its underlying mechanism.

METHODS

A total of 132 adult Sprague-Dawley (SD) rats were randomly divided into four groups: the sham operation group, the neuropathic pain model group, the TAK-242 low-dose treatment group, and the TAK-242 high-dose treatment group. The heat pain and mechanic pain thresholds of rats were detected on preoperative day 1 and postoperative days 1, 3, 7, and 10. The expression levels of IκBα, p65, IL-1β, and TNF-α in the spinal cord dorsal horn were detected on postoperative day 7 in one group of rats.

RESULTS

Compared with rats in the sham operation group, the heat pain and mechanic pain thresholds of the rats in the neuropathic pain model group significantly decreased; their expression levels of p65, IL-1β, and TNF-α significantly increased; and their expression level of IkBα significantly decreased. Compared with the neuropathic pain group, high doses of TAK-242 significantly inhibited the expression of p65, IL-1β, and TNF-α; significantly increased the expression level of IkBα; and upregulated the heat pain and mechanic pain thresholds.

CONCLUSION

TAK-242 might improve neuropathic pain through downregulation of the NF-κB pathway.

Information processing in the CNS: a supramolecular chemistry?

How does central nervous system process information? Current theories are based on two tenets: (a) information is transmitted by action potentials, the language by which neurons communicate with each other-and (b) homogeneous neuronal assemblies of cortical circuits operate on these neuronal messages where the operations are characterized by the intrinsic connectivity among neuronal populations. In this view, the size and time course of any spike is stereotypic and the information is restricted to the temporal sequence of the spikes; namely, the "neural code". However, an increasing amount of novel data point towards an alternative hypothesis: (a) the role of neural code in information processing is overemphasized. Instead of simply passing messages, action potentials play a role in dynamic coordination at multiple spatial and temporal scales, establishing network interactions across several levels of a hierarchical modular architecture, modulating and regulating the propagation of neuronal messages. (b) Information is processed at all levels of neuronal infrastructure from macromolecules to population dynamics. For example, intra-neuronal (changes in protein conformation, concentration and synthesis) and extra-neuronal factors (extracellular proteolysis, substrate patterning, myelin plasticity, microbes, metabolic status) can have a profound effect on neuronal computations. This means molecular message passing may have cognitive connotations. This essay introduces the concept of "supramolecular chemistry", involving the storage of information at the molecular level and its retrieval, transfer and processing at the supramolecular level, through transitory non-covalent molecular processes that are self-organized, self-assembled and dynamic. Finally, we note that the cortex comprises extremely heterogeneous cells, with distinct regional variations, macromolecular assembly, receptor repertoire and intrinsic microcircuitry. This suggests that every neuron (or group of neurons) embodies different molecular information that hands an operational effect on neuronal computation.

Association between toll-like receptors expression and major depressive disorder

Accumulating evidences suggest that Toll-like receptors (TLRs) were involved in the pathophysiology of major depressive disorder. TLR4 was thought to be associated with major depressive disorder in animal model, but the others were still unknown. In order to examine TLR1-9 mRNA expression levels in peripheral blood and their relationships with the psychopathology of major depressive disorder, 30 patients with major depressive disorder were compared with 29 healthy controls. The 17-item Hamilton Depression Rating Scale (HAMD-17) was used to assess the severity of major depression. The mRNA expression levels of TLRs were examined in parallel with a housekeeping gene using real-time polymerase chain reaction (RT-PCR). Analysis of covariance with age and body mass index adjustment revealed a significantly higher expression of TLR3, 4, 5 and 7 mRNA but lower expression of TLR1 and 6 in patients with major depressive disorder as compared with healthy controls. Multiple linear regression analysis revealed that TLR4 was an independent risk factor relating to severity of major depression. These findings suggest that TLRs, especially TLR4, may be involved in the psychopathology of major depression.

Inflammation and lithium: clues to mechanisms contributing to suicide-linked traits

Suicide is one of the leading causes of death in the United States, yet it remains difficult to understand the mechanistic provocations and to intervene therapeutically. Stress is recognized as a frequent precursor to suicide. Psychological stress is well established to cause activation of the inflammatory response, including causing neuroinflammation, an increase of inflammatory molecules in the central nervous system (CNS). Neuroinflammation is increasingly recognized as affecting many aspects of CNS functions and behaviors. In particular, much evidence demonstrates that inflammatory markers are elevated in traits that have been linked to suicidal behavior, including aggression, impulsivity and depression. Lithium is recognized as significantly reducing suicidal behavior, is anti-inflammatory and diminishes aggression, impulsivity and depression traits, each of which is associated with elevated inflammation. The anti-inflammatory effects of lithium result from its inhibition of glycogen synthase kinase-3 (GSK3). GSK3 has been demonstrated to strongly promote inflammation, aggressive behavior in rodents and depression-like behaviors in rodents, whereas regulation of impulsivity by GSK3 has not yet been investigated. Altogether, evidence is building supporting the hypothesis that stress activates GSK3, which in turn promotes inflammation, and that inflammation is linked to behaviors associated with suicide, including particularly aggression, impulsivity and depression. Further investigation of these links may provide a clearer understanding of the causes of suicidal behavior and provide leads for the development of effective preventative interventions, which may include inhibitors of GSK3.