Enhanced hippocampal TIAM2S expression alleviates cognitive deficits in Alzheimer's disease model mice.

BACKGROUND: Dendritic spine dysfunction is a key feature of Alzheimer's disease (AD) pathogenesis. Human T-cell lymphoma invasion and metastasis 2 (TIAM2) is expressed in two isoforms, the full length (TIAM2L) and a short transcript (TIAM2S). Compared to TIAM2L protein, which is undetectable, TIAM2S protein is abundant in human brain tissue, especially the hippocampus, and can promote neurite outgrowth in our previous findings. However, whether enhanced hippocampal TIAM2S expression can alleviate cognitive deficits in Alzheimer's disease model mice remains unclear. METHODS: We crossbred 3xTg-AD with TIAM2S mice to generate an AD mouse model that carries the human TIAM2S gene (3xTg-AD/TIAM2S mice). The Morris water maze and object location tests assessed hippocampus-dependent spatial memory. Lentiviral-driven shRNA or cDNA approaches were used to manipulate hippocampal TIAM2S expression. Golgi staining and Sholl analysis were utilized to measure neuronal dendrites and dendritic spines in the mouse hippocampi. RESULTS: Compared to 3xTg-AD mice, 3xTg-AD/TIAM2S mice displayed improved cognitive functions. According to the hippocampus is one of the earliest affected brain regions by AD, we further injected TIAM2S shRNA or TIAM2S cDNA into mouse hippocampi to confirm whether manipulating hippocampal TIAM2S expression could affect AD-related cognitive functions. The results showed that the reduced hippocampal TIAM2S expression in 3xTg-AD/TIAM2S mice abolished the memory improvement effect, whereas increased hippocampal TIAM2S levels alleviated cognitive deficits in 3xTg-AD mice. Furthermore, we found that TIAM2S-mediated memory improvement was achieved by regulating dendritic plasticity. CONCLUSIONS: These results will provide new insights into connecting TIAM2S with AD and support the notion that TIAM2S should be investigated as potential AD therapeutic targets.

TIAM2S-positive microglia enhance inflammation and neurotoxicity through soluble ICAM-1-mediated immune priming.

TIAM Rac1-associated GEF 2 short form (TIAM2S) as an oncoprotein alters the immunity of peripheral immune cells to construct an inflammatory tumor microenvironment. However, its role in the activation of microglia, the primary innate immune cells of the brain, and neuroinflammation remains unknown. This study investigated the mechanism underlying TIAM2S shapes immune properties of microglia to facilitate neuron damage. Human microglial clone 3 cell line (HMC3) and human brain samples were applied to determine the presence of TIAM2S in microglia by western blots and double immunostaining. Furthermore, TIAM2S transgenic mice combined with multiple reconstituted primary neuron-glial culture systems and a cytokine array were performed to explore how TIAM2S shaped immune priming of microglia and participated in lipopolysaccharide (LPS)-induced neuron damage. TIAM2S protein was detectable in HMC3 cells and presented in a small portion (~11.1%) of microglia in human brains referred to as TIAM2S-positive microglia. With the property of secreted soluble factor-mediated immune priming, TIAM2S-positive microglia enhanced LPS-induced neuroinflammation and neural damage in vivo and in vitro. The gain- and loss-of-function experiments showed soluble intercellular adhesion molecule-1 (sICAM-1) participated in neurotoxic immune priming of TIAM2S+ microglia. Together, this study demonstrated a novel TIAM2S-positive microglia subpopulation enhances inflammation and neurotoxicity through sICAM-1-mediated immune priming.

Tolerized Microglia Protect Neurons Against Endotoxin-Induced TNF-α Production via an LBP-Dependent Intracellular p38 MAPK Signaling Pathway.

The development of microglial endotoxin tolerance (ET) is a critical event in protecting neurons against excessive immune responses when microglia are administered two consecutive lipopolysaccharide (LPS) challenges. However, the intrinsic mechanisms of microglia shape ET programs and protect neurons remain unclear. This study aimed to determine whether extracellular autocrine cascades or intracellular signaling pathways are involved in ET microglia-mediated tumor necrosis factor-alpha (TNF-α) reduction and neuroprotection. Neuron-glia cultures composed of astroglia, neurons, and microglia were performed in different conditions: with or without serum or LPS-binding proteins (LBP), along with an induction approach of ET. Enzyme-linked immunosorbent assay results revealed that LPS induced TNF-α tolerance of microglia in an LBP-dependent manner. Furthermore, we determined whether the early pro-inflammatory cytokines induced by LPS might contribute to the development of microglial ET. Our data showed that the neutralization of TNF-α using an anti-TNF-α antibody had no change in the TNF-α tolerance of microglia during the ET challenge. Furthermore, pre-incubation of TNF-α, interleukin-1 beta, and prostaglandin E2 failed to induce any TNF-α tolerance in microglia after LPS treatment. Moreover, using three specific chemical inhibitors that respectively blocked the activities of the mitogen-activated protein kinases (MAPKs) namely p38, c-Jun N-terminal kinase and extracellular signal-related kinases revealed that inhibition of p38 MAPK by SB203580 disrupted the tolerated microglia-mediated TNF-α reduction and neuroprotection. In summary, our findings demonstrated that the LPS pre-treatment immediately programmed the microglial ET to prevent endotoxin-induced TNF-α production and neuronal damage through the intracellular p38 MAPK signaling pathway.

Through Reducing ROS Production, IL-10 Suppresses Caspase-1-Dependent IL-1ß Maturation, thereby Preventing Chronic Neuroinflammation and Neurodegeneration.

Chronic neuroinflammation contributes to the pathogenesis of Parkinson's disease (PD). However, cellular and molecular mechanisms by which chronic neuroinflammation is formed and maintained remain elusive. This study aimed to explore detailed mechanisms by which anti-inflammatory cytokine interleukin-10 (IL-10) prevented chronic neuroinflammation and neurodegeneration. At 24 h after an intranigral injection of lipopolysaccharide (LPS), levels of NLRP3, pro-caspase-1, pro-IL-1ß, active caspase-1, and mature IL-1ß in the midbrain were much higher in IL-10-/- mice than wildtype mice. Mechanistically, IL-10-/- microglia produced more intracellular reactive oxygen species (iROS) and showed more profound activation of NADPH oxidase (NOX2) than wildtype microglia. Meanwhile, suppression of NOX2-derived iROS production blocked LPS-elicited caspase-1 activation and IL-1ß maturation in IL-10-/- microglia in vitro and in vivo. One month after intranigral LPS injection, IL-10-/- mice revealed more profound microglial activation and dopaminergic neurodegeneration in the substantia nigra than wildtype mice. Importantly, such PD-like pathological changes were prevented by IL-1ß neutralization. Collectively, IL-10 inhibited LPS-elicited production of NOX2-derived iROS thereby suppressing synthesis of NLRP3, pro-caspase-1 and pro-IL-1ß and their activation and cleavage. By this mechanism, IL-10 prevented chronic neuroinflammation and neurodegeneration. This study suggested boosting anti-inflammatory effects of IL-10 and suppressing NLRP3 inflammasome activation could be beneficial for PD treatment.

TIAM2S as a novel regulator for serotonin level enhances brain plasticity and locomotion behavior.

TIAM2S, the short form of human T-cell lymphoma invasion and metastasis 2, can have oncogenic effects when aberrantly expressed in the liver or lungs. However, it is also abundant in healthy, non-neoplastic brain tissue, in which its primary function is still unknown. Here, we examined the neurobiological and behavioral significance of human TIAM2S using the human brain protein panels, a human NT2/D1-derived neuronal cell line model (NT2/N), and transgenic mice that overexpress human TIAM2S (TIAM2S-TG). Our data reveal that TIAM2S exists primarily in neurons of the restricted brain areas around the limbic system and in well-differentiated NT2/N cells. Functional studies revealed that TIAM2S has no guanine nucleotide exchange factor (GEF) activity and is mainly located in the nucleus. Furthermore, whole-transcriptome and enrichment analysis with total RNA sequencing revealed that TIAM2S-knockdown (TIAM2S-KD) was strongly associated with the cellular processes of the brain structural development and differentiation, serotonin-related signaling, and the diseases markers representing neurobehavioral developmental disorders. Moreover, TIAM2S-KD cells display decreased neurite outgrowth and reduced serotonin levels. Moreover, TIAM2S overexpressing TG mice show increased number and length of serotonergic fibers at early postnatal stage, results in higher serotonin levels at both the serum and brain regions, and higher neuroplasticity and hyperlocomotion in latter adulthood. Taken together, our results illustrate the non-oncogenic functions of human TIAM2S and demonstrate that TIAM2S is a novel regulator of serotonin level, brain neuroplasticity, and locomotion behavior.

Correlation between interleukin-6 levels and methadone maintenance therapy outcomes.

BACKGROUND: The outcome of methadone maintenance therapy (MMT) varies in each patient with opioid use disorder (OUD). Opioid abuse activates proinflammatory processes by increasing cytokine production and impairing neurotrophic factor expression, and possibly leads to a vicious cycle that hinders recovery. Therefore, we investigated whether markers of inflammation and neurotrophic expression correlate with the MMT outcomes in OUD patients. METHOD: We investigated OUD patients undergoing MMT and followed them up for 12 weeks. We measured plasma tumor necrosis factor (TNF)-α, C-reactive protein (CRP), interleukin (IL)-6, IL-1ß, transforming growth factor (TGF)-ß1, brain-derived neurotrophic factor (BDNF), urinary morphine tests, and plasma morphine levels at baseline and on weeks 1, 4, 8, and 12 during MMT. Multiple linear regressions and generalized estimating equations (GEEs) were used to examine the correlation between the cytokine and BDNF levels and MMT outcomes. RESULTS: We initially enrolled 104 patients, but only 78 patients completed end-of-study assessments. Plasma levels of CRP, TGF-ß1, and BDNF fell during MMT. Plasma IL-6 levels were significantly associated with plasma morphine levels (P = 0.005) and urinary morphine-positive (+) results (P = 0.04), and significantly associated with poor compliance (P = 0.009) and early dropout from MMT (P = 0.001). However, other cytokine and BDNF levels were not consistently associated with MMT outcomes. CONCLUSION: Higher IL-6 levels were associated with poor MMT outcomes. Additional studies on regulating IL-6 expression to improve treatment outcomes in OUD patients might be warranted.

Immunoregulatory effects of very low density lipoprotein from healthy individuals and metabolic syndrome patients on glial cells.

Epidemiological studies have reported that elderly patients with metabolic syndrome (MetS) are significantly more likely to develop neuronal degenerative diseases than those without MetS. Our previous study showed that patients with MetS had significantly higher levels of negatively charged very low density lipoproteins (VLDLs) in the plasma than healthy controls. Highly electronegative VLDL is a key risk factor for endothelial dysfunction and atrial fibrillation. However, the impact of negatively charged VLDL in brain immunity remains unclear. In this study, VLDLs were isolated from normal healthy (nVLDL) individuals or patients with MetS (metVLDL). Primary astroglia and microglia mixed cell cultures as well as microglial-enriched cultures were used to test the effects of VLDLs. Microglia/astroglia activation as evidenced by their morphological changes and production of pro-inflammatory factors, such as tumor necrosis factor-α (TNF-α) and prostaglandin E2 (PGE2), were assessed by immunofluorescence staining and ELISA, respectively. Our results showed that metVLDLs mainly act on the microglia, and not the astroglia, with low concentration (0.05-0.5 µg/mL) inducing cell morphological changes and decreased cellular processes in the microglia. However, nVLDL treatment at these concentrations had no effects on microglia and astroglia. Most importantly, TNF-α and PGE2 levels significantly increased in the microglia treated with metVLDL via a dose-dependent manner. Together, our data indicate that metVLDLs can contribute to MetS-associated brain disorders through microglia activation and neuroinflammation.

Correlation of cytokines, BDNF levels, and memory function in patients with opioid use disorder undergoing methadone maintenance treatment.

BACKGROUND: Patients with opioid use disorder (OUD) show memory deficiencies and impaired treatment outcomes. Emerging evidence suggests that opioid abuse activates proinflammatory processes by increasing cytokine production and impairing neuroprotection, which damages the memory function in OUD patients. Therefore, we investigated whether plasma-based inflammatory and neurotrophic markers correlate with memory function in OUD patients. METHOD: OUD patients undergoing methadone maintenance therapy (MMT) were investigated and followed up for 12 weeks. Plasma tumor necrosis factor (TNF)-α, C-reactive protein (CRP), interleukin (IL)-6, transforming growth factor (TGF)-ß1, brain-derived neurotrophic factor (BDNF) levels, and Wechsler Memory Scale-Revised (WMS-R) scores were assessed at baseline and after 12 weeks of MMT. Multiple linear regressions and generalized estimating equations (GEEs) were used to examine the correlation between cytokines and memory performance. RESULTS: We enrolled 89 patients at baseline; 47 patients completed the end-of-study assessments. Although Pearson correlations showed that CRP and TGF-ß1 levels were significantly, negatively associated with some memory indices, the results were not significant after correction. The GEE results, controlled for several confounding factors and multiple testing, showed that changes in TNF-α levels were negatively correlated with changes in the visual memory index (P = 0.01), and that changes in IL-6 levels were negatively correlated with changes in the verbal memory index (P = 0.009). CONCLUSION: Memory performance, TNF-α, and IL-6 levels in OUD patients were negative correlated. Additional studies on regulating TNF-α and IL-6 expression to improve memory function in OUD patients might be warranted.

WWOX Phosphorylation, Signaling, and Role in Neurodegeneration.

Homozygous null mutation of tumor suppressor WWOX/Wwox gene leads to severe neural diseases, metabolic disorders and early death in the newborns of humans, mice and rats. WWOX is frequently downregulated in the hippocampi of patients with Alzheimer's disease (AD). In vitro analysis revealed that knockdown of WWOX protein in neuroblastoma cells results in aggregation of TRAPPC6AΔ, TIAF1, amyloid ß, and Tau in a sequential manner. Indeed, TRAPPC6AΔ and TIAF1, but not tau and amyloid ß, aggregates are present in the brains of healthy mid-aged individuals. It is reasonable to assume that very slow activation of a protein aggregation cascade starts sequentially with TRAPPC6AΔ and TIAF1 aggregation at mid-ages, then caspase activation and APP de-phosphorylation and degradation, and final accumulation of amyloid ß and Tau aggregates in the brains at greater than 70 years old. WWOX binds Tau-hyperphosphorylating enzymes (e.g., GSK-3ß) and blocks their functions, thereby supporting neuronal survival and differentiation. As a neuronal protective hormone, 17ß-estradiol (E2) binds WWOX at an NSYK motif in the C-terminal SDR (short-chain alcohol dehydrogenase/reductase) domain. In this review, we discuss how WWOX and E2 block protein aggregation during neurodegeneration, and how a 31-amino-acid zinc finger-like Zfra peptide restores memory loss in mice.

More inflammation but less brain-derived neurotrophic factor in antisocial personality disorder.

Antisocial personality disorder (ASPD) is highly comorbid with substance use disorders (SUDs). We hypothesize that chronic neuroinflammation and the loss of neurotrophic factors prompts the pathogenesis of both disorders. We used ELISA to measure plasma levels of proinflammatory (tumor necrosis factor-α [TNF-α], C-reactive protein [CRP]) and anti-inflammatory factors (transforming growth factor-ß1 [TGF-ß1] and interleukin-10 [IL-10]), and brain-derived neurotrophic factor (BDNF) in male patients with ASPD (n=74), SUDs (n=168), ASPD comorbid with SUDs (ASPD+SUDs) (n=438), and Healthy Controls (HCs) (n=81). A multivariate analysis of covariance (MANCOVA) controlled for possible confounders was used to compare cytokines and BDNF levels between groups. The results of MANCOVA adjusted for age showed a significant (p<0.001) main effect of diagnosis on inflammatory factors and BDNF expression in these groups. ASPD, SUDs, and ASPD+SUDs patients had significantly (p<0.001) higher TNF-α levels but lower TGF-ß1 and BDNF levels. SUDs and ASPD+SUDs patients had higher IL-10 levels than did ASPD patients and HCs. There was no difference in IL-10 levels between HCs and ASPD. Moreover, subgrouping SUDs and ASPD±SUDs into opioid use disorder (OUD) and other SUDs groups showed that the IL-10 levels were specifically higher in OUD and ASPD±OUD groups than other SUDs (P≤0.001). We conclude that uncontrolled inflammation and losing neurotrophic factors, with or without comorbid SUDs, underlies ASPD. IL-10 expression might be more specifically associated with OUD.

Comparing clinical responses and the biomarkers of BDNF and cytokines between subthreshold bipolar disorder and bipolar II disorder.

Patients with subthreshold hypomania (SBP; subthreshold bipolar disorder) were indistinguishable from those with bipolar disorder (BP)-II on clinical bipolar validators, but their analyses lacked biological and pharmacological treatment data. Because inflammation and neuroprogression underlies BP, we hypothesized that cytokines and brain-derived neurotrophic factor (BDNF) are biomarkers for BP. We enrolled 41 drug-naïve patients with SBP and 48 with BP-II undergoing 12 weeks of pharmacological treatment (valproic acid, fluoxetine, risperidone, lorazepam). The Hamilton Depression Rating Scale (HDRS) and Young Mania Rating Scale (YMRS) were used to evaluate clinical responses at baseline and at weeks 0, 1, 2, 4, 8, and 12. Inflammatory cytokines (tumour necrosis factor [TNF]-α, transforming growth factor [TGF]-ß1, interleukin [IL]-6, IL-8 and IL-1ß) and BDNF levels were also measured. Mixed models repeated measurement was used to examine the therapeutic effect and changes in BDNF and cytokine levels between the groups. HDRS and YMRS scores significantly (P < 0.001) declined in both groups, the SBP group had significantly lower levels of BDNF (P = 0.005) and TGF-ß1 (P = 0.02). Patients with SBP and BP-II respond similarly to treatment, but SBP patients may have different neuroinflammation marker expression.

Identification of a specific α-synuclein peptide (α-Syn 29-40) capable of eliciting microglial superoxide production to damage dopaminergic neurons.

BACKGROUND: Misfolded α-synuclein (α-Syn) aggregates participate in the pathogenesis of synucleinopathies, such as Parkinson's disease. Whereas much is known about how the various domains within full-length α-Syn (FL-α-Syn) contribute to the formation of α-Syn aggregates and therefore to their neurotoxicity, little is known about whether the individual peptides that can be generated from α-syn, possibly as intermediate metabolites during degradation of misfolded α-Syn aggregates, are neurotoxic themselves. METHODS: A series of synthesized α-Syn peptides, corresponding to the locus in FL-α-Syn containing alanine 30, substitution of which with a proline causes a familial form of Parkinson's disease, were examined for their capacity of inducing release of microglial superoxide. The neurotoxicity of these peptides was measured according to their influence on the ability of neuroglial cultures deficient in gp91 (phox) , the catalytic unit of NADPH oxidase (Nox2), or wild-type cultures to take up (3)H-labeled dopamine and on the number of tyrosine hydroxylase-staining-positive neurons. Western blots and confocal images were utilized to analyze membrane translocation of p47 (phox) and p67 (phox) , phosphorylation of p47 (phox) and Erk1/2 kinase, and binding of α-Syn peptides to gp91 (phox) . Activation of brain microglia in mice injected with α-Syn peptides was demonstrated by immunostaining for major histocompatibility complex (MHC)-II along with qPCR for Iba-1 and MHC-II. RESULTS: We report α-Syn (29-40) as a specific peptide capable of activating microglial Nox2 to produce superoxide and cause dopaminergic neuronal damage. Administered to mice, this peptide also activated brain microglia to increase expression of MHC-II and Iba-1 and stimulated oxidation reaction. Exploring the underlying mechanisms showed that α-Syn (29-40) peptide triggered Nox2 to generate extracellular superoxide and its metabolite H2O2 by binding to the catalytic unit gp91 (phox) of Nox2; diffusing into cytosol, H2O2 activated Erk1/2 kinase to phosphorylate p47 (phox) and p67 (phox) and further activated Nox2, establishing a positive feedback loop to amplify the Nox2-mediated response. CONCLUSIONS: Collectively, our study suggests novel information regarding how α-Syn causes neuronal injury, possibly including mechanisms involving abnormal metabolites of α-Syn aggregates.

Neurons and astroglia govern microglial endotoxin tolerance through macrophage colony-stimulating factor receptor-mediated ERK1/2 signals.

Endotoxin tolerance (ET) is a reduced responsiveness of innate immune cells like macrophages/monocytes to an endotoxin challenge following a previous encounter with the endotoxin. Although ET in peripheral systems has been well studied, little is known about ET in the brain. The present study showed that brain immune cells, microglia, being different from peripheral macrophages, displayed non-cell autonomous mechanisms in ET formation. Specifically, neurons and astroglia were indispensable for microglial ET. Macrophage colony-stimulating factor (M-CSF) secreted from these non-immune cells was essential for governing microglial ET. Neutralization of M-CSF deprived the neuron-glia conditioned medium of its ability to enable microglia to form ET when microglia encountered two lipopolysaccharide (LPS) treatments. Recombinant M-CSF protein rendered enriched microglia refractory to the second LPS challenge leading to microglial ET. Activation of microglial M-CSF receptor (M-CSFR; also known as CSF1R) and the downstream ERK1/2 signals was responsible for M-CSF-mediated microglial ET. Endotoxin-tolerant microglia in neuron-glia cultures displayed M2-like polarized phenotypes, as shown by upregulation of M2 marker Arg-1, elevated production of anti-inflammatory cytokine interleukin 10, and decreased secretion of pro-inflammatory mediators (tumor necrosis factor α, nitric oxide, prostaglandin E2 and interleukin 1ß). Endotoxin-tolerant microglia protected neurons against LPS-elicited inflammatory insults, as shown by reduced neuronal damages in LPS pre-treatment group compared with the group without LPS pre-treatment. Moreover, while neurons and astroglia became injured during chronic neuroinflammation, microglia failed to form ET. Thus, this study identified a distinct non-cell autonomous mechanism of microglial ET. Interactions of M-CSF secreted by neurons and astroglia with microglial M-CSFR programed microglial ET. Loss of microglial ET could be an important pathogenetic mechanism of inflammation-associated neuronal damages.

The Differential Levels of Inflammatory Cytokines and BDNF among Bipolar Spectrum Disorders.

OBJECTIVE: Emerging evidence suggests that inflammation and neurodegeneration underlies bipolar disorder. To investigate biological markers of cytokines and brain-derived neurotrophic factor between bipolar I, bipolar II, and other specified bipolar disorder with short duration hypomania may support the association with inflammatory dysregulation and bipolar disorder and, more specifically, provide evidence for other specified bipolar disorder with short duration hypomania patients were similar to bipolar II disorder patients from a biological marker perspective. METHODS: We enrolled patients with bipolar I disorder (n=234), bipolar II disorder (n=260), other specified bipolar disorder with short duration hypomania (n=243), and healthy controls (n=140). Their clinical symptoms were rated using the Hamilton Depression Rating Scale and Young Mania Rating Scale. Inflammatory cytokine (tumor necrosis factor-α, C-reactive protein, transforming growth factor-ß1, and interleukin-8) and brain-derived neurotrophic factor levels were measured in each group. Multivariate analysis of covariance and linear regression controlled for possible confounders were used to compare cytokine and brain-derived neurotrophic factor levels among the groups. RESULTS: Multivariate analysis of covariance adjusted for age and sex and a main effect of diagnosis was significant (P<.001). Three of the 5 measured biomarkers (tumor necrosis factor-α, transforming growth factor-ß1, and interleukin-8) were significantly (P=.006, .01, and <.001) higher in all bipolar disorder patients than in controls. Moreover, covarying for multiple associated confounders showed that bipolar I disorder patients had significantly higher IL-8 levels than did bipolar II disorder and other specified bipolar disorder with short duration hypomania patients in multivariate analysis of covariance (P=.03) and linear regression (P=.02) analyses. Biomarkers differences between bipolar II disorder and other specified bipolar disorder with short duration hypomania patients were nonsignificant. CONCLUSION: The immunological disturbance along the bipolar spectrum was most severe in bipolar I disorder patients. Other specified bipolar disorder with short duration hypomania patients and bipolar II disorder patients did not differ in these biological markers.

α-Synuclein, a chemoattractant, directs microglial migration via H2O2-dependent Lyn phosphorylation.

Malformed α-Synuclein (α-syn) aggregates in neurons are released into the extracellular space, activating microglia to induce chronic neuroinflammation that further enhances neuronal damage in α-synucleinopathies, such as Parkinson's disease. The mechanisms by which α-syn aggregates activate and recruit microglia remain unclear, however. Here we show that α-syn aggregates act as chemoattractants to direct microglia toward damaged neurons. In addition, we describe a mechanism underlying this directional migration of microglia. Specifically, chemotaxis occurs when α-syn binds to integrin CD11b, leading to H2O2 production by NADPH oxidase. H2O2 directly attracts microglia via a process in which extracellularly generated H2O2 diffuses into the cytoplasm and tyrosine protein kinase Lyn, phosphorylates the F-actin-associated protein cortactin after sensing changes in the microglial intracellular concentration of H2O2. Finally, phosphorylated cortactin mediates actin cytoskeleton rearrangement and facilitates directional cell migration. These findings have significant implications, given that α-syn-mediated microglial migration reaches beyond Parkinson's disease.

A placebo-controlled trial of dextromethorphan as an adjunct in opioid-dependent patients undergoing methadone maintenance treatment.

BACKGROUND: Low-dose dextromethorphan (DM) might have anti-inflammatory and neurotrophic effects mechanistically remote from an NMDA receptor. In a randomized, double-blind, controlled 12 week study, we investigated whether add-on dextromethorphan reduced cytokine levels and benefitted opioid-dependent patients undergoing methadone maintenance therapy (MMT). METHODS: Patients were randomly assigned to a group: DM60 (60mg/day dextromethorphan; n = 65), DM120 (120mg/day dextromethorphan; n = 65), or placebo (n = 66). Primary outcomes were the methadone dose required, plasma morphine level, and retention in treatment. Plasma tumor necrosis factor (TNF)-α, C-reactive protein, interleukin (IL)-6, IL-8, transforming growth factor-ß1, and brain-derived neurotrophic factor (BDNF) levels were examined during weeks 0, 1, 4, 8, and 12. Multiple linear regressions with generalized estimating equation methods were used to examine the therapeutic effect. RESULTS: After 12 weeks, the DM60 group had significantly longer treatment retention and lower plasma morphine levels than did the placebo group. Plasma TNF-α was significantly decreased in the DM60 group compared to the placebo group. However, changes in plasma cytokine levels, BDNF levels, and the methadone dose required in the three groups were not significantly different. CONCLUSIONS: We provide evidence-decreased concomitant heroin use-of low-dose add-on DM's efficacy for treating opioid-dependent patients undergoing MMT.

PGE2 Inhibits IL-10 Production via EP2-Mediated ß-Arrestin Signaling in Neuroinflammatory Condition.

Regulatory mechanisms of the expression of interleukin-10 (IL-10) in brain inflammatory conditions remain elusive. To address this issue, we used multiple primary brain cell cultures to study the expression of IL-10 in lipopolysaccharide (LPS)-elicited inflammatory conditions. In neuron-glia cultures, LPS triggered well-orchestrated expression of various immune factors in the following order: tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2), and lastly IL-10, and these inflammatory mediators were mainly produced from microglia. While exogenous application of individual earlier-released pro-inflammatory factors (e.g., TNF-α, IL-1ß, or PGE2) failed to induce IL-10 expression, removal of LPS from the cultures showed the requirement of continuing presence of LPS for IL-10 expression. Interestingly, genetic disruption of tnf-α, its receptors tnf-r1/r2, and cox-2 and pharmacological inhibition of COX-2 activity enhanced LPS-induced IL-10 production in microglia, which suggests negative regulation of IL-10 induction by the earlier-released TNF-α and PGE2. Further studies showed that negative regulation of IL-10 production by TNF-α is mediated by PGE2. Mechanistic studies indicated that PGE2-elicited suppression of IL-10 induction was eliminated by genetic disruption of the PGE2 receptor EP2 and was mimicked by the specific agonist for the EP2, butaprost, but not agonists for the other three EP receptors. Inhibition of cAMP-dependent signal transduction failed to affect PGE2-mediated inhibition of IL-10 production, suggesting that a G protein-independent pathway was involved. Indeed, deficiency in ß-arrestin-1 or ß-arrestin-2 abolished PGE2-elicited suppression of IL-10 production. In conclusion, we have demonstrated that COX-2-derived PGE2 inhibits IL-10 expression in brain microglia through a novel EP2- and ß-arrestin-dependent signaling pathway.

Microglial regulation of immunological and neuroprotective functions of astroglia.

Microglia and astroglia play critical roles in the development, function, and survival of neurons in the CNS. However, under inflammatory conditions the role of astrogliosis in the inflammatory process and its effects on neurons remains unclear. Here, we used several types of cell cultures treated with the bacterial inflammogen LPS to address these questions. We found that the presence of astroglia reduced inflammation-driven neurotoxicity, suggesting that astrogliosis is principally neuroprotective. Neutralization of supernatant glial cell line-derived neurotrophic factor (GDNF) released from astroglia significantly reduced this neuroprotective effect during inflammation. To determine the immunological role of astroglia, we optimized a highly-enriched astroglial culture protocol and demonstrated that LPS failed to induce the synthesis and release of TNF-α and iNOS/NO. Instead we found significant enhancement of TNF-α and iNOS expression in highly-enriched astroglial cultures required the presence of 0.5-1% microglia, respectively. Thus suggesting that microglial-astroglial interactions are required for LPS to induce the expression of pro-inflammatory factors and GDNF from astroglia. Specifically, we found that microglia-derived TNF-α plays a pivotal role as a paracrine signal to regulate the neuroprotective functions of astrogliosis. Taken together, these findings suggest that astroglia may not possess the ability to directly recognize the innate immune stimuli LPS, but rather depend on crosstalk with microglia to elicit release of neurotrophic factors as a counterbalance to support neuronal survival from the collateral damage generated by activated microglia during neuroinflammation.

The ADH1B and DRD2 gene polymorphism may modify the protective effect of the ALDH2 gene against heroin dependence.

Understanding the influences of genes involved in dopamine and serotonin metabolism, such as the aldehyde dehydrogenase 2 (ALDH2) and alcohol dehydrogenase 1B (ADH1B) genes, is critical for understanding addictive behavior. In addition, dopamine D2 receptor (DRD2) gene may also interact with the dopamine metabolizing genes and link to addiction. Therefore, we investigated the association between the ALDH2, ADH1B and DRD2 polymorphisms and heroin dependence. Heroin-dependent Han Chinese patients (n=304) and healthy controls (n=335) were recruited. Genotypes of ALDH2, ADH1B and DRD2 polymorphisms were analyzed using a polymerase chain reaction with restriction fragment length polymorphism. The frequency of the ALDH2*1/*1 genotype was significantly lower in heroin-dependent patients than in controls, but the frequency of ADH1B and DRD2 genotypes was not significantly different. Further stratification of the ALDH2 gene with the ADH1B gene showed that the protective effect of ALDH2*1/*1 existed only in patients who also carried the ADH1B*1/*1 and ADH1B*1/*2 genotype. Logistic regression analysis showed a significant interaction between ALDH2 and ADH1B (P=0.022) and DRD2, ALDH2 and ADH1B in patients (P=0.037). The ALDH2*1/*1, ADH1B*1/*1, and ADH1B*1/*2 genotypes may interact and protect their carriers against heroin dependence and the protective effect may be varied by the DRD2 gene polymorphism. We conclude that the protective effect of the ALDH2 polymorphism against heroin dependence may be modified by the ADH1B and DRD2 polymorphism.

Dextromethorphan attenuated inflammation and combined opioid use in humans undergoing methadone maintenance treatment.

Recent studies show that proinflammatory cytokines might be related to the development of opioid dependence (physiological, psychological, or both). In a double-blind, randomly stratified clinical trial investigating whether add-on dextromethorphan (60-120 mg/day) attenuated inflammation and the combined use of opioids in heroin-dependent patients undergoing methadone maintenance treatment, we evaluated whether inflammation is related to the progression of opioid dependence. All participants (107 heroin-dependent patients and 84 nondependent healthy controls) were recruited from National Cheng Kung University Hospital. Their plasma cytokine levels were measured to evaluate the effect of add-on dextromethorphan. Plasma TNF-α and IL-8 levels were significantly higher in long-term heroin-dependent patients than in healthy controls (p < 0.001). Chronic heroin-use-induced TNF-α and IL-8 levels were significantly (p < 0.05) attenuated in patients treated for 12 weeks with add-on dextromethorphan. Moreover, both tolerance to methadone and the combined use of opioids were significantly (p < 0.05) attenuated in patients taking dextromethorphan. We conclude that dextromethorphan might be a feasible adjuvant therapeutic for attenuating inflammation and inhibiting methadone tolerance and combined opioid use in heroin-dependent patients.