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Methamphetamine is a widely abused psychostimulant and one of the main targets of dopamine transporter (DAT). Methamphetamine reduces DAT‐mediated dopamine uptake and stimulates dopamine efflux leading to increased synaptic dopamine levels many folds above baseline. Methamphetamine also targets DAT‐expressing peripheral immune cells, reduces wound healing and increases infection susceptibility. Peripheral immune cells such as myeloid cells, B cells and T cells express DAT. DAT activity on monocytes and macrophages exhibits immune suppressive properties via an autocrine paracrine mechanism, where deletion or inhibition of DAT activity increases inflammatory responses. In this study, utilizing a mouse model of daily single dose of methamphetamine administration, we investigated the impact of the drug on DAT expression in peripheral immune cells. We found in methamphetamine‐treated mice that DAT expression was down‐regulated in most of the innate and adaptive immune cells. Methamphetamine did not increase or decrease the total number of innate and adaptive immune cells but changed their immunophenotype to low‐DAT‐expressing phenotype. Moreover, serum cytokine distributions were altered in methamphetamine‐treated mice. Therefore, resembling its effect in the CNS, in the periphery, methamphetamine regulates DAT expression on peripheral immune cell subsets, potentially describing methamphetamine regulation of peripheral immunity. [ABSTRACT FROM AUTHOR]

Age‐related immune dysfunctions, such as decreased T‐cell output, are closely related to pathologies like cancers and lack of vaccine efficacy among the elderly. Engineered fusokine, GIFT‐7, a fusion of interleukin 7 (IL‐7) and GM‐CSF, can reverse aging‐related lymphoid organ atrophy. We generated a GIFT‐7 fusokine tumor vaccine and employed it in aged syngeneic mouse models of glioblastoma and found that peripheral vaccination with GIFT‐7TVax resulted in thymic regeneration and generated durable long‐term antitumor immunity specifically in aged mice. Global cytokine analysis showed increased pro‐inflammatory cytokines including IL‐1β in the vaccinated group that resulted in hyperactivation of dendritic cells. In addition, GIFT‐7 vaccination resulted in increased T‐cell trafficking to the brain and robust Th‐17 long‐term effector memory T‐cell formation. TCR‐seq analysis showed increased productive frequency among detected rearrangements within the vaccinated group. Overall, our data demonstrate that aging immune system can be therapeutically augmented to generate lasting antitumor immunity. [ABSTRACT FROM AUTHOR]

Objectives: The objective of this study was to explore the effect of periodontitis on Th‐cell subsets in local and systemic environments. Methods: A total of 32 male Sprague‒Dawley rats were randomly divided into periodontitis and control groups. Silk ligatures were applied to the mandibular first (M1) molars in the periodontitis group. Inflammation and alveolar bone loss around the M1 molars were analyzed by histological staining and microcomputed tomography. The mRNA expression of interferon‐γ (IFN‐γ), interleukin 4 (IL‐4), IL‐17, and IL‐10 in the gingiva was measured by qRT‐PCR. The proportions of Th1, Th2, Th17, and Treg cells in the submandibular lymph nodes, peripheral blood, and jaw bone marrow were tested using flow cytometry. Results: More inflammatory cells and alveolar bone resorption were found in the periodontitis group, with upregulated mRNA expression of IFN‐γ, IL‐17, and IL‐10. The proportion of Th1 and Th17 cells was significantly elevated in submandibular lymph nodes, and the proportion of Th1, Th2, and Th17 cells was significantly elevated in peripheral blood, while the proportion of Th1, Th17, and Treg cells was significantly elevated in jaw bone marrow in the periodontitis group. Conclusion: This study suggests that periodontitis affects the differentiation of Th‐cell subsets in both local and systemic environments, resulting in an increased proportion of proinflammatory cells. [ABSTRACT FROM AUTHOR]

Microglia represent one effector arm of CNS innate immunity as evident by their role in pathogen recognition. We previously reported that exposure of microglia to Staphylococcus aureus ( S. aureus), a prevalent CNS pathogen, led to elevated Toll-like receptor 2 (TLR2) expression, a pattern recognition receptor capable of recognizing conserved structural motifs associated with gram-positive bacteria such as S. aureus. In this study, we demonstrate that the proinflammatory cytokine tumor necrosis factor-α (TNF-α) enhances TLR2 expression in microglia, whereas interleukin-1β has no significant effect. To determine the downstream signaling events responsible for elevated microglial TLR2 expression in response to TNF-α, a series of signal transduction inhibitors were employed. Treatment with caffeic acid phenethyl ester, an inhibitor of redox-mediated nuclear factor-kappa B activation, significantly attenuated TNF-α-induced TLR2 expression. Similar results were observed with the IKK-2 and IκB-α inhibitors SC-514 and BAY 11-7082, respectively. In contrast, no significant alterations in TLR2 expression were observed with protein kinase C or p38 mitogen-activated protein kinase inhibitors. A definitive role for TNF-α was demonstrated by the inability of S. aureus to augment TLR2 expression in microglia isolated from TNF-α knockout mice. In addition, TLR2 expression was significantly attenuated in brain abscesses of TNF-α knockout mice. Collectively, these results indicate that in response to S. aureus, TNF-α acts in an autocrine/paracrine manner to enhance TLR2 expression in microglia and that this effect is mediated, in part, by activation of the nuclear factor-kappa B pathway. [ABSTRACT FROM AUTHOR]

Nucleic acid sensing is a critical mechanism by which the immune system monitors for pathogen invasion. A set of germline‐encoded innate immune receptors detect microbial DNA in various compartments of the cell, such as endosomes, the cytosol, and the nucleus. Sensing of microbial DNA through these receptors stimulates, in most cases, interferon regulatory factor‐dependent type I IFN synthesis followed by JAK/STAT‐dependent interferon‐stimulated gene expression. In contrast, the detection of DNA in the cytosol by AIM2 assembles a macromolecular complex called the inflammasome, which unleashes the proteolytic activity of a cysteine protease caspase‐1. Caspase‐1 cleaves and activates the pro‐inflammatory cytokines such as IL‐1β and IL‐18 and a pore‐forming protein, gasdermin D, which triggers pyroptosis, an inflammatory form of cell death. Research over the past decade has revealed that AIM2 plays essential roles not only in host defense against pathogens but also in inflammatory diseases, autoimmunity, and cancer in inflammasome‐dependent and inflammasome‐independent manners. This review discusses the latest advancements in our understanding of AIM2 biology and its functions in health and disease. [ABSTRACT FROM AUTHOR]

Bone infections are difficult to diagnose and treat, especially when a prosthetic joint replacement or implant is involved. Bone loss is a major complication of osteomyelitis, but the mechanism behind has mainly been investigated in cell cultures and has not been confirmed in human settings. Inflammation is important in initiating an appropriate immune response to invading pathogens. However, many of the signaling molecules used by the immune system can also modulate bone remodeling and contribute to bone resorption during osteomyelitis. Our current knowledge of the inflammatory response relies heavily on animal models as research based on human samples is scarce. Staphylococcus aureus is one of the most common causes of bone infections and is the pathogen of choice in animal models. The regulation of inflammatory genes during prosthetic joint infections and implant‐associated osteomyelitis has only been studied in rodent models. It is important to consider the validity of an animal model when results are extrapolated to humans, and both bone composition and the immune system of pigs has been shown to be more similar to humans, than to rodents. Here in vivo studies on the inflammatory response to prosthetic joint infections and implant‐associated osteomyelitis are reviewed. [ABSTRACT FROM AUTHOR]

Inflammasomes are the central signaling hubs of the inflammatory response. They process cytosolic evidence of infection, cell damage, or metabolic disturbances, and elicit a pro-inflammatory response mediated by members of the interleukin-1 family of cytokines and pyroptotoic cell death. On the molecular level, this is accomplished by the sensor-nucleated recruitment and oligomerization of the adapter protein ASC. Once a tunable threshold is reached, cooperative assembly of ASC into linear filaments and their condensation into macromolecular ASC specks promotes an all-or-none response. These structures are highly regulated and provide a unique signaling platform or compartment to control the activity of caspase-1 and likely other effectors. Emerging evidence indicates that ASC specks are also released from inflammasome-activated cells and accumulate in inflamed tissues, where they can continue to mature cytokines or be internalized by surrounding cells to further nucleate ASC specks in their cytosol. Little is known about the mechanisms governing ASC speck release, uptake, and endosomal escape, as well as its contribution to inflammation and disease. Here, we describe the different outcomes of inflammasome activation and discuss the potential function of extracellular ASC specks. We highlight gaps in our understanding of this central process of inflammation, which may have direct consequences on the modulation of host responses and chronic inflammation. [ABSTRACT FROM AUTHOR]

Toll-like receptors (TLRs) orchestrate immune responses to a wide variety of danger- and pathogen-associated molecular patterns. Compared to the central nervous system (CNS), expression profile and function of TLRs in the human peripheral nervous system (PNS) are ill-defined. We analyzed TLR expression of satellite glial cells (SGCs) and microglia, glial cells predominantly involved in local immune responses in ganglia of the human PNS and normal-appearing white matter (NAWM) of the CNS, respectively. Ex vivo flow cytometry analysis of cell suspensions obtained from human cadaveric trigeminal ganglia (TG) and NAWM showed that both SGCs and microglia expressed TLR1-5, TLR7, and TLR9, although expression levels varied between these cell types. Immunohistochemistry confirmed expression of TLR1-TLR4 and TLR9 by SGCs in situ. Stimulation of TG- and NAWM-derived cell suspensions with ligands of TLR1-TLR6, but not TLR7 and TLR9, induced interleukin 6 (IL-6) secretion. We identified CD45LOWCD14POS SGCs and microglia, but not CD45HIGH leukocytes and CD45NEG cells as the main source of IL-6 and TNF-α upon stimulation with TLR3 and TLR5 ligands. In conclusion, human TG-resident SGCs express a broad panel of functional TLRs, suggesting their role in initiating and orchestrating inflammation to pathogens in human sensory ganglia. [ABSTRACT FROM AUTHOR]

Naegleria fowleri, a free-living amoeba that is found in diverse environmental habitats, can cause a type of fulminating hemorrhagic meningoencephalitis, primary amoebic meningoencephalitis (PAM), in humans. The pathogenesis of PAM is not fully understood, but it is likely to be primarily caused by disruption of the host's nervous system via a direct phagocytic mechanism by the amoeba. Naegleria fowleri trophozoites are known to secrete diverse proteins that may indirectly contribute to the pathogenic function of the amoeba, but this factor is not clearly understood. In this study, we analyzed the inflammatory responses in BV-2 microglial cells induced by excretory and secretory proteins of N. fowleri (NfESP). Treatment of BV-2 cells with NfESP induced the expression of various cytokines and chemokines, including the proinflammatory cytokines IL-1α and TNF-α. NfESP-induced IL-1α and TNF-α expression in BV-2 cells were regulated by p38, JNK, and ERK MAPKs. NfESP-induced IL-1α and TNF-α production in BV-2 cells were effectively downregulated by inhibition of NF-kB and AP-1. These results collectively suggest that NfESP stimulates BV-2 cells to release IL-1α and TNF-α via NF-kB- and AP-1-dependent MAPK signaling pathways. The released cytokines may contribute to inflammatory responses in microglia and other cell types in the brain during N. fowleri infection. [ABSTRACT FROM AUTHOR]

The innate immune response in the central nervous system ( CNS) participates in both synaptic plasticity and neural damage. Emerging evidence from human and animal studies supports the role of the neuroimmune system response in many actions of ethanol (EtOH) on the CNS. Research studies have shown that alcohol stimulates brain immune cells, microglia, and astrocytes, by activating innate immune receptors Toll-like receptors (TLRs) and NOD-like receptors (inflammasome NLRs) triggering signaling pathways, which culminate in the production of pro-inflammatory cytokines and chemokines that lead to neuroinflammation. This review focuses on evidence that indicates the participation of TLRs and the inflammasome NLRs signaling response in many effects of EtOH on the CNS, such as neuroinflammation associated with brain damage, cognitive and behavioral dysfunction, and adolescent brain development alterations. It also reviews findings that indicate the role of TLR4-dependent signaling immune molecules in alcohol consumption, reward, and addiction. The research data suggest that overactivation of TLR4 or NLRs increases pro-inflammatory cytokines and mediators to cause neural damage in the cerebral cortex and hippocampus, while modest TLR4 activation, along with the generation of certain cytokines and chemokines in specific brain areas (e.g., amygdala, ventral tegmental area), modulate neurotransmission, alcohol drinking, and alcohol rewards. Elimination of TLR4 and NLRP3 abolishes many neuroimmune effects of EtOH. Despite much progress being made in this area, there are some research gaps and unanswered questions that this review discusses. Finally, potential therapies that target neuroimmune pathways to treat neuropathological and behavioral consequences of alcohol abuse are also evaluated. [ABSTRACT FROM AUTHOR]

Obesity contributes to systemic inflammation, which is associated with the varied pathogenesis of neurodegenerative diseases. Growing evidence has demonstrated that endurance exercise ( EE) mitigates obesity-induced brain inflammation. However, exercise-mediated anti-inflammatory mechanisms remain largely unknown. We investigated how treadmill exercise ( TE) reverses obesity-induced brain inflammation, mainly focusing on toll-like receptor-4 ( TLR-4)-dependent neuroinflammation in the obese rat brain after 20 weeks of a high-fat diet ( HFD). TE in HFD-fed rats resulted in a significant lowering in the homeostasis model assessment of insulin resistance index, the area under the curve for glucose and abdominal visceral fat, and also improved working memory ability in a passive avoidance task relative to sedentary behaviour in HFD-fed rats, with the exception of body weight. More importantly, TE revoked the increase in HFD-induced proinflammatory cytokines ( tumour necrosis factor α and interleukin-1β) and cyclooxygenase-2, which is in parallel with a reduction in TLR-4 and its downstream proteins, myeloid differentiation 88 and tumour necrosis factor receptor associated factor 6, and phosphorylation of transforming growth factor β-activated kinase 1, IkBα and nuclear factor-κB. Moreover, TE reduced an indicator of microglia activation, ionised calcium-binding adapter molecule-1, and also decreased glial fibrillary acidic protein, an indicator of gliosis formed by activated astrocytes in the cerebral cortex and the hippocampal dentate gyrus, compared to HFD-fed sedentary rats. Finally, EE up-regulated the expression of anti-apoptotic protein, Bcl-2, and suppressed the expression of pro-apoptotic protein, Bax, in the hippocampus compared to HFD-fed sedentary rats. Taken together, these data suggest that TE may exert neuroprotective effects as a result of mitigating the production of proinflammatory cytokines by inhibiting the TLR4 signalling pathways. The results of the present study suggest that the unique combination of the beneficial effects of TE on the restoration of the blood profile and the anti-inflammatory and anti-apoptotic effects on cognitive function should inspire further investigations into its therapeutic potential for metabolic disorders and neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Cerebral endothelial cells ( CECs) forming the blood-brain barrier are at the interface of the immune and the central nervous systems and thus may play an important role in the functional integration of the two systems. Here, we investigated how CECs recognize and respond to pathogen- and damage-associated molecular patterns to regulate the functions of the neurovascular unit. First we detected the expression of several NOD-like receptors ( NLRs) - including NOD1, NOD2, NLRC4, NLRC5, NLRP1, NLRP3, NLRP5, NLRP9, NLRP10, NLRP12, NLRA, and NLRX - in human brain endothelial cells. Inflammatory cytokines, such as interferon-γ, tumor necrosis factor-α, and IL-1β had stimulatory effects on the transcription of many of these receptors. Expression of key inflammasome components ( NOD2, NLRP3, and caspase 1) along with caspase-cleaved interleukins IL-1β and IL-33 could be induced by priming with lipopolysaccharide and activation with muramyl dipeptide. In addition, combined treatment with lipopolysaccharide and muramyl dipeptide resulted in IL-1β secretion in a caspase- and ERK1/2 kinase-dependent manner. Our findings demonstrate that NLRs and inflammasomes can be activated in cerebral endothelial cells, which may confer a yet unexplored role to the blood-brain barrier in neuroimmune and neuroinflammatory processes. [ABSTRACT FROM AUTHOR]

The foot processes of astrocytes cover over 60% of the surface of brain microvascular endothelial cells, regulating tight junction integrity. Retraction of astrocyte foot processes has been postulated to be a key mechanism in pathology. Therefore, movement of an astrocyte in response to a proinflammatory cytokine or even limited retraction of processes would result in leaky junctions between endothelial cells. Astrocytes lie at the gateway to the CNS and are instrumental in controlling leukocyte entry. Cultured astrocytes typically have a polygonal morphology until stimulated. We hypothesized that cultured astrocytes which were induced to stellate would have an activated phenotype compared with polygonal cells. We investigated the activation of astrocytes derived from adult macaques to the cytokine TNF-α under resting and stellated conditions by four parameters: morphology, intermediate filament expression, adhesion, and cytokine secretion. Astrocytes were stellated following transient acidification; resulting in increased expression of GFAP and vimentin. Stellation was accompanied by decreased adhesion that could be recovered with proinflammatory cytokine treatment. Surprisingly, there was decreased secretion of proinflammatory cytokines by stellated astrocytes compared with polygonal cells. These results suggest that astrocytes are capable of multiple phenotypes depending on the stimulus and the order stimuli are applied. J. Cell. Physiol. 228: 1284-1294, 2013. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Background: Deoxyribonucleic acids (DNA) of periodontal pathogens, Porphyromonas gingivalis ( Pg) and Tannerella forsythia, stimulate cytokine production in human monocytic cells (THP- 1) through Toll-like receptor 9 (TLR-9) and nuclear factor-KB signaling. Fusobacterium nucleatum (Fn) is one of the most frequently isolated bacteria in periodontally diseased tissues and is reported to synergize with Pg, enhancing the pathogenicity. We investigate inflammatory mediator production in THP- 1 cells challenged with Fn and Streptococcus sanguinis (Ss) DNA, a non-pathogenic oral bacteria, and further assess whether cytokines triggered by whole pathogens or Pg lipopolysaccharide (LPS) are affected by TLR-9 signaling inhibitors (chloroquine). Methods: THP-1 cells were stimulated with Pg-DNA (100 ng/µL), Fn-DNA (100 ng/µL), Ss-DNA (100 ng/µL), Pg-LPS (10 ng/µL), and heat-killed whole bacteria (multiplicity of infection, 1:100) for 16 hours with or without chloroquine pretreatment (10 µg/mL). lnterleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor-α levels were determined using enzyme-linked immunosorbent assay. Statistical analyses included analysis of variance with multiple comparisons using Dunnett or Tukey methods and paired t test. A value of P<0.05 was significant. Results: Inflammatory mediator levels were increased in response to all the stimuli with the exception of Ss-DNA (P<0.05). Chloroquine pretreatment significantly decreased cytokine production from THP-1 cells with the exception of IL-6 production triggered by whole Fn and Ss (P<0.05). Conclusions: Differences exist among oral bacterial DNA in inducing immune responses. By altering the conditions in cytosolic compartments, we can interfere with cellular responses triggered by extracellular receptor activation. Thus, alternative treatment approaches targeted to intracellular receptors might be of benefit in controlling periodontal inflammation. [ABSTRACT FROM AUTHOR]

Collagenase-3 (matrix metalloproteinase, MMP-13) plays an important role in the degradation of cartilage in pathologic conditions. MMP-13 is elevated in joint tissues in both rheumatoid arthritis (RA) and osteoarthritis (OA). In addition, inflammation-stimulated synovial fibroblasts are able to release MMP-13 and other cytokines in these diseases. The peroxisome proliferator-activated receptor-γ (PPARγ) ligands are recently considered as new anti-inflammatory compounds and these ligands were reported to ameliorate inflammatory arthritis. The aim of this study is to evaluate the mechanisms how PPARγ ligands inhibit the inflammatory response in synovial fibroblasts. Two PPARγ ligands, cyclopentenone prostaglandin 15-deoxy-Δ12,14-prostaglandin-J2 (15d-PGJ2) and synthetic thiazolidinedione compound ciglitazone were examined in this study. Here we found that 15d-PGJ2 and ciglitazone markedly inhibited TNF-α-induced MMP-13 production in human synovial fibroblasts. In addition, activation of nuclear factor κB (NF-κB) is strongly associated with MMP-13 induction by TNF-α and the activation of NF-κB was determined by Western blot, reporter assay, and immunofluorescence. It was found that 15d-PGJ2 markedly attenuated the translocation of NF-κB by direct inhibition of the activation of IKK via a PPARγ-independent manner. Ciglitazone also inhibits TNF-α-induced MMP-13 expression by suppressing NF-κB activation mainly via the modulation of p38-MAPK. Collectively, our data demonstrate that 15d-PGJ2 and ciglitazone attenuated TNF-α-induced MMP-13 expression in synovial fibroblasts primarily through the modulation of NF-κB signaling pathways. These compounds may have therapeutic application in inflammatory arthritis. J. Cell. Physiol. 226: 3242-3250, 2011. © 2011 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

J. Neurochem. (2011) 119, 736-748. Abstract Microglia are important innate immune effectors against invading CNS pathogens, such as Staphylococcus aureus ( S. aureus), a common etiological agent of brain abscesses typified by widespread inflammation and necrosis. The NLRP3 inflammasome is a protein complex involved in IL-1β and IL-18 processing following exposure to both pathogen- and danger-associated molecular patterns. Although previous studies from our laboratory have established that IL-1β is a major cytokine product of S. aureus-activated microglia and is pivotal for eliciting protective anti-bacterial immunity during brain abscess development, the molecular machinery responsible for cytokine release remains to be determined. Therefore, the functional role of the NLRP3 inflammasome and its adaptor protein apoptosis-associated speck-like protein (ASC) in eliciting IL-1β and IL-18 release was examined in primary microglia. Interestingly, we found that IL-1β, but not IL-18 production, was significantly attenuated in both NLRP3 and ASC knockout microglia following exposure to live S. aureus. NLRP3 inflammasome activation was partially dependent on autocrine/paracrine ATP release and α- and γ-hemolysins produced by live bacteria. A cathepsin B inhibitor attenuated IL-β release from NLRP3 and ASC knockout microglia, demonstrating the existence of alternative inflammasome-independent mechanisms for IL-1β processing. In contrast, microglial IL-18 secretion occurred independently of cathepsin B and inflammasome action. Collectively, these results demonstrate that microglial IL-1β processing is regulated by multiple pathways and diverges from mechanisms utilized for IL-18 cleavage. Understanding the molecular events that regulate IL-1β production is important for modulating this potent proinflammatory cytokine during CNS disease. [ABSTRACT FROM AUTHOR]

Increases of cytokine in the blood play important roles in the pathogenesis of influenza-associated encephalopathy. TNF-α was administered intravenously to wild-type mice, after which blood, CSF and brain tissue were obtained, and changes in BBB permeability, the amounts of MMP-9 and TIMP-1, and the localization of activated MMP were assessed. There was a significant increase in BBB permeability after 6 and 12 hr. MMP-9 was increased after 3 hr in the brain and cerebrospinal fluid, which was earlier than in the serum. TIMP-1 protein in the brain increased significantly after MMP-9 had increased. Activation of MMP-9 was observed in neurons in the cerebral cortex and hippocampus, and in vascular endothelial cells. These findings suggest that an increase in blood TNF-α promotes activation of MMP-9 in the brain, and may also induce an increase in permeability of the BBB. Early activation of MMP-9 in the brain may contribute to an early onset of neurological disorders and brain edema prior to multiple organ failure in those inflammatory diseases associated with highly increased concentrations of TNF-α in the blood, such as sepsis, burns, trauma and influenza-associated encephalopathy. [ABSTRACT FROM AUTHOR]

Background: Postmortem human alcoholic brain has increased expression of proinflammatory cytokines ( He and Crews, 2007 ). Nuclear factor κB (NF-κB) is a transcription factor known to induce proinflammatory cytokine expression. Ethanol exposure increases NF-κB–DNA binding in rat brain ( Crews et al., 2006 ) and in brain slice cultures in vitro ( Zou and Crews, 2006 ). Using hippocampal-entorhinal cortex (HEC) brain slice cultures, we explored the effect of ethanol on NF-κB–DNA binding, proinflammatory gene expression, and sensitivity to glutamate neurotoxicity. Methods: The HEC brain slice cultures are prepared from rats on P7 and used after 2 weeks in culture. NF-κB–DNA binding is determined by EMSA, NF-κB subunit–DNA binding by ELISA and mRNA by RT-PCR. Multiple antibody immunohistochemistry and confocal microscopy are used to characterize cell types expressing ethanol-induced genes. Results: Ethanol treatment results in a progressive increase in NF-κB–DNA binding that includes large increases in NF-κB subunit p50 protein–DNA binding. The expression of NF-κB proinflammatory target genes progressively increased with time of ethanol treatment. Ethanol induces proinflammatory cytokines TNFα, MCP-1, and IL-1β, proinflammatory proteases TACE, and tissue plasminogen activator (tPA) as well as inducible nitric oxide synthase. Blockade of NF-κB by using NF-κB p65 siRNA and BHT reduces ethanol induction of proinflammatory genes. Neutralizing antibody to proinflammatory cytokine TNFα reduces ethanol induction of proinflammatory genes, suggesting cytokine propagation of proinflammatory gene induction. Furthermore, neutralizing antibodies to proinflammatory cytokines and protease tPA inhibitors blunt ethanol sensitization to glutamate neurotoxicity. Conclusions: These findings indicate that ethanol treatment increases NF-κB–DNA binding and proinflammatory gene expression in brain slices. Ethanol-induced innate immune proinflammatory gene induction alters neurotransmission and likely contributes to alcoholic neurodegeneration. [ABSTRACT FROM AUTHOR]

Der p2 is a major allergen from Dermatophagoides pteronyssinus, the main species of house dust mite and a major inducer of asthma, inducing harmful respiratory inflammatory responses by activating cells in the respiratory tract, leading to an unstable status. We hypothesize that Der p2 may induce local inflammatory responses by directly affecting airway smooth muscle (ASM) cells. In this study, we demonstrated that Der p2 raised nuclear factor-kappa B (NF-κB) and extracellular signal-regulated kinase (ERK) 1/2 activation and induced a high level of proinflammatory cytokines expression in primary cultured ASM cells. Der p2 activated the MyD88 signaling pathway through toll-like receptor (TLR) 2, not through TLR4. Notably, Der p2 stimulated ASM cells to increase phosphorylation of ERK1/2 and expression of c-Fos, which were also important in the T helper type 2 (Th2) immune response. These results suggest that Der p2 induces asthma through the MyD88 signaling pathway in respiratory tissue. J. Cell. Physiol. 220: 311–318, 2009. © 2009 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Abstract: Inflammatory responses in the brain are involved in the etiopathogenesis and sequelae of seizures. Ligation of microglial CD40 plays a role in the development of inflammatory responses in the central nervous system (CNS). Our study showed that there was an increased CD40 expression on activated microglia in the brain injury after lithium pilocarpine-induced status epilepticus (SE) in rats. Since peroxisome proliferator-activated receptor gamma (PPARγ) acts as a regulator of CNS inflammation and a powerful pharmacological target for counteracting CNS diseases, we investigated the role of the PPARγ agonist, rosiglitazone, in the modulation of CD40 expression and in the pathological processes of inflammation after SE. We found that rosiglitazone inhibited the expression of CD40, tumor necrosis factor (TNF-α), and microglial activation in different regions of hippocampus. The results were indicated by immunohistochemistry, Western blot, and ELISA, respectively. Rosiglitazone also prevented neuronal loss in the CA1 area after SE observed by Nissl-staining. These protective effects were significantly reversed by the co-treatment with T0070907, a selective antagonist of the PPARγ, which clearly demonstrated a PPARγ-dependent mechanism. Our data provide evidence that rosiglitazone considerably attenuates inflammatory responses after SE by suppressing CD40 expression and microglial activation. Our data also support the idea that rosiglitazone might be a potential neuroprotective agent in epilepsy. [Copyright &y& Elsevier]

Gap junctions facilitate direct cytoplasmic communication between neighboring cells, facilitating the transfer of small molecular weight molecules involved in cell signaling and metabolism. Gap junction channels are formed by the joining of two hemichannels from adjacent cells, each composed of six oligomeric protein subunits called connexins. Of paramount importance to CNS homeostasis are astrocyte networks formed by gap junctions, which play a critical role in maintaining the homeostatic regulation of extracellular pH, K+, and glutamate levels. Inflammation is a hallmark of several diseases afflicting the CNS. Within the past several years, the number of publications reporting effects of cytokines and pathogenic stimuli on glial gap junction communication has increased dramatically. The purpose of this review is to discuss recent observations characterizing the consequences of inflammatory stimuli on homocellular gap junction coupling in astrocytes and microglia as well as changes in connexin expression during various CNS inflammatory conditions. [ABSTRACT FROM AUTHOR]

Toll-like receptor 3 (TLR3) participates in the innate immune response by recognizing viral pathogens. In this study, human brain astrocytes were found to constitutively express TLR3, and this expression was increased by interferon-γ (IFN-γ) or double-stranded RNA (dsRNA). Treatment employing dsRNA in astrocytes induced IFN regulatory factor 3 (IRF3) phosphorylation, dimer formation and nuclear translocation followed by STAT1 activation. This treatment also activated nuclear factor-κB, p38 and c-Jun N-terminal kinase significantly, while activating extracellular signal-regulated kinase to a lesser extent. Treatment with anti-TLR3 antibody inhibited dsRNA-mediated interleukin-6 (IL-6) production. In the presence of mitogen-activated protein kinase inhibitors, astrocytes failed to secrete IL-6 in response to dsRNA treatment. Therefore, dsRNA-induced IL-6 production is dependent on mitogen-activated protein kinases and type I IFN production is dependent on IRF3 in brain astrocytes. These results suggest that brain inflammation, which produces inflammatory cytokines and type I IFNs, may enhance TLR3 expression in astrocytes. Additionally, upregulated TLR3 might modulate inflammatory processes by producing proinflammatory cytokines. [ABSTRACT FROM AUTHOR]

Transforming growth factor β (TGF-β) is a multifunctional cytokine that regulates a number of biological responses including chemotaxis, cell cycle progression, differentiation, and apoptosis of cells. Even though temporal and spatial expression of TGF-β3 suggests its role in chick limb development, it is not well characterized how TGF-β3 regulates chondrogenic differentiation of limb bud mesenchymal cells. In this study, differential display polymerase chain reaction (DD-PCR) screening and reverse transcription PCR analysis revealed that the mRNA expression of the gap junction protein, connexin 43 (Cx43), was significantly decreased during the first treatment of TGF-β3 for 24 h in cultured chick leg bud mesenchymal cells. Treatment of these cells with lindane, a general gap junction blocker, or expression of dominant negative Cx43 increased apoptotic cell death and decreased the level of integrin β4 protein, in a manner similar to that observed when these cells were exposed to TGF-β3. Similarly, exposure of cultured leg chondroblasts to a functional blocking antibody against integrin-β4 induced an increase in apoptosis. Treatment of cells with TGF-β3 decreased the membrane translocation of PKC-α, leading to activation of ERK. The increase in apoptotic cell death triggered by TGF-β3 and dominant negative Cx43 was blocked by inhibition of ERK but increased by inhibition of PKC. Collectively, these data indicate that, in cultured chick leg bud mesenchyme cells, TGF-β3 treatment downregulates Cx43 and induces apoptotic cell death via downregulation of integrin β4, activation of ERK and suppression of PKC-α activation. J. Cell. Physiol. 214: 345–353, 2008. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The interleukin-12 (IL-12) family of cytokines which includes IL-12, IL-23, and IL-27 play critical roles in T cell differentiation and are important modulators of multiple sclerosis and experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. Previously, we demonstrated that peroxisome proliferator-activated receptor (PPAR) -α agonists suppress the development of EAE. The present studies demonstrated that the PPAR-α agonist fenofibrate inhibited the secretion of IL-12p40, IL-12p70 (p35/p40), IL-23 (p19/p40), and IL-27p28 by lipopolysaccharide-stimulated microglia. The cytokines interferon-γ and tumor necrosis factor-α also stimulated IL-12 p40 and IL-27 p28 expression by microglia, which was suppressed by fenofibrate. Furthermore, fenofibrate inhibited microglial expression of CD14 which plays a critical role in TLR signaling, suggesting a mechanism by which this PPAR-α agonist regulates the production of these pro-inflammatory molecules. In addition, fenofibrate suppressed the secretion of IL-12p40, IL-23, and IL-27p28 by lipopolysaccharide-stimulated astrocytes. Importantly, fenofibrate suppression of EAE was associated with decreased expression of IL-12 family cytokine mRNAs as well as mRNAs encoding TLR4, CD14, and MyD88 known to play critical roles in MyD88-dependent TLR signaling. These novel observations suggest that PPAR-α agonists including fenofibrate may modulate the development of EAE, at least in part, by suppressing the production of IL-12 family cytokines and MyD88-dependent signaling. [ABSTRACT FROM AUTHOR]

In contrast to the role of lipopolysaccharide from Gram-negative bacteria, the role of Gram-positive bacterial components in inducing inflammation in the CNS remains controversial. We studied the potency of highly purified lipoteichoic acid and muramyl dipeptide isolated from Staphylococcus aureus to activate primary cultures of rat microglia. Exposure of pure microglial cultures to lipoteichoic acid triggered a significant time- and dose-dependent production of pro-inflammatory cytokines (tumour-necrosis factor-α, interleukin-1β, interleukin-6) and nitric oxide. Muramyl dipeptide strongly and selectively potentiated lipoteichoic acid-induced inducible nitric oxide synthase expression and nitric oxide production. However, it did not have any significant influence on the production of pro-inflammatory cytokines. As bacterial components are recognised by the innate immunity through Toll-like receptors (TLRs) we showed that lipoteichoic acid was recognised in microglia by the TLR2 and lipopolysaccharide by the TLR4, as cells isolated from mice lacking TLR2 or TLR4 did not produce pro-inflammatory cytokines and nitric oxide upon lipoteichoic acid or lipopolysaccharide stimulation, respectively. Lipoteichoic acid-induced glia activation was mediated by p38 and ERK1/2 MAP kinases, as pretreatment with inhibitor of p38 or ERK1/2 decreased lipoteichoic acid-induced cytokine release, iNOS mRNA expression and nitric oxide production. The observed pro-inflammatory response induced by lipoteichoic acid-activated microglia could play a major role in the inflammatory response of CNS induced by Gram-positive bacteria. [ABSTRACT FROM AUTHOR]

The recent discovery of the family of Toll-like receptors has vastly expanded our understanding of the mechanisms by which the innate immune system recognizes and responds to a wide variety of microbial and endogenous pathogens. Toll-like receptors are transmembrane proteins that upon ligation with their cognate ligands trigger the production of cytokines, enzymes and other inflammatory agents. In the CNS Toll-like receptors are expressed predominantly by glial cells. In particular, the vastly abundant astrocytes are likely to be the major contributors to inflammatory responses within the CNS. Studies of the murine brain abscess model revealed that Toll-like receptor 2 plays a pivotal role in the generation of immune responses to Staphylococcus aureus. Although Toll-like receptor signaling is essential in antimicrobial defense, it may also lead to bystander injury of CNS tissue. [ABSTRACT FROM AUTHOR]

Inflammation during the perinatal period has become a recognized risk factor for developmental brain injuries over the past decade or more. To fully understand the relationship between inflammation and brain development, a comprehensive knowledge about the immune system within the brain is essential. Microglia are resident immune cells within the central nervous system and play a critical role in the development of an inflammatory response within the brain. Microglia are critically involved with both the innate and adaptive immune system, regulating inflammation and cell damage within the brain via activation of Toll-like receptors, production of cytokines, and a myriad of other intracellular and intercellular processes. In this article, microglial physiology is reviewed along with the role of microglia in developmental brain injuries in humans and animal models. Last, microglial functions within the innate and adaptive immune system will be summarized. Understanding the processes of inflammation and microglial activation is critical for formulating effective preventative and therapeutic strategies for developmental brain injuries. MRDD Research Reviews 2006;12:105–112. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Staphylococcusis a leading cause of the potentially blinding disease microbial keratitis. Even with the use of antibiotic therapy, the host inflammatory response continues to damage the cornea, which may lead to blindness. Manipulation of the host response may help improve patient outcome from this devastating disease. We aim to understand the contribution of the host response toStaphylococcus aureusinfection. AS. aureuskeratitis mouse model was developed in both C57BL/6 and BALB/c mice using two different strains ofS. aureus(8325-4 and Staph 38). Twenty-four hours postinfection, mice were killed and eyes were harvested for enumeration of bacteria, polymorphonuclear leucocytes, chemokines and cytokines. The laboratory strain 8325-4 was not as virulent as the clinical isolate Staph 38.In vitrodata showed a 250-fold increase in invasion of human corneal epithelial cells by Staph 38 compared to 8325-4. BALB/c mice were susceptible toS. aureusinfection whereas C57BL/6 mice were resistant. The resistant C57BL/6 mice were polarized towards a Th2 response, which may be protective for these mice. IL-4, IL-10 and IL-6 were elevated significantly in C57BL/6 mice infected with Staph 38 (P <0.05). Macrophage inflammatory peptide (MIP)-2 was also significantly elevated in C57BL/6 mice (P < 0.001). The susceptible BALB/c mice had a muted cytokine response, which suggests thatS. aureusmight be‘walled off’ during infection and might avoid host defences. IL-4, IL-10 and IL-6 cytokines may be protective during Gram-positive corneal infection and therefore may be useful for adjunct therapies in the treatment of this disease. [ABSTRACT FROM AUTHOR]

Microglial activation is a hallmark of brain abscess. The continual release of proinflammatory mediators by microglia following bacterial challenge may contribute, in part, to the destruction of surrounding normal tissue characteristic of brain abscess. Therefore, attenuating chronic microglial activation during the course of CNS bacterial infections may have therapeutic benefits. The purpose of this study was to evaluate the ability of the natural peroxisome proliferator-activated receptor (PPAR)-γ agonist 15-deoxy-Δ12,14- prostaglandin J2 (15d-PGJ2) to modulate microglial activation in response to Staphylococcus aureus, one of the main etiologic agents of brain abscess in humans. 15d-PGJ2 was a potent inhibitor of proinflammatory cytokine (IL-1β, TNF-α, IL-12 p40) and CC chemokine (MIP-1β, MCP-1) production in primary microglia, but had no effect upon the expression of select CXC chemokines (MIP-2, KC). 15d-PGJ2 also selectively inhibited the S. aureus-dependent increase in microglial TLR2, CD14, MHC class II, and CD40 expression, whereas it had no effect on the co-stimulatory molecules CD80 and CD86. Microarray analysis revealed additional inflammatory mediators modulated by 15d-PGJ2 in primary microglia following S. aureus exposure, the majority of which were chemokines. These results suggest that suppressing microglial activation through the use of 15d-PGJ2 may lead to the sparing of damage to normal brain parenchyma that often results from brain abscess. [ABSTRACT FROM AUTHOR]

Abstract During bacterial infections of the CNS, activated microglia could support leucocyte recruitment to the brain through the synthesis of cyto- and chemokines. In turn, invading leucocytes may feedback on microglial cells to influence their chemokine release pattern. Here, we analyzed the capacity of interferon-γ (IFNγ) to serve as such a leucocyte-to-microglia signal. Production of cyto- and chemokines was stimulated in mouse microglia cultures by treatments with lipopolysaccharide (LPS) from Gram-negative Escherichia coli or cell walls from Gram-positive Streptococcus pneumoniae (PCW). IFNγ presence during the stimulation (0.1–100 ng/mL) modulated the patterns of LPS- and PCW-induced cyto- and chemokine release in a dose-dependent, potent and complex manner. While amounts of TNFα and IL-6 remained nearly unchanged, IFNγ enhanced the production of IL-12, MCP-1 and RANTES, but attenuated that of KC, MIP-1α and MIP-2. Release modulation was obtained with IFNγ preincubation (treatment of cells before LPS or PCW administration), coincubation and even delayed addition to an ongoing LPS or PCW stimulation. Together the changes observed for the microglial chemokine release under IFNγ would shift the chemoattractive profile from favouring neutrophils to a preferential attraction of monocytes and T lymphocyte populations – as actually seen during the course of bacterial meningitis. The findings support the view of activated microglia as a major intrinsic source for an instant production of a variety of chemokines and suggest that leucocyte-derived IFNγ could potentially regulate the microglial chemokine release pattern. [ABSTRACT FROM AUTHOR]