Monocyte-astrocyte networks and the regulation of chemokine secretion in neurocysticercosis

Neuroimmune interaction in seizures and epilepsy: focusing on monocyte infiltration

Epilepsy is a major neurological condition that affects millions of people globally. While a number of interventions have been developed to mitigate this condition, a significant number of patients are refractory to these treatments. Consequently, other avenues of research are needed. One such avenue is modulation of the immune system response to this condition, which has mostly focused on microglia, the resident immune cells of the central nervous system (CNS). However, other immune cells can impact neurological conditions, principally blood-borne monocytes that can infiltrate into brain parenchyma after seizures. As such, this review will first discuss how monocytes can be recruited to the CNS and how they can be distinguished from there immunological cousins, microglia. Then, we will explore what is known about the role monocytes have within seizure pathogenesis and epilepsy. Considering how little is known about monocyte function in seizure- and epilepsy-related pathologies, further studies are warranted that investigate infiltrated blood-borne monocytes as a potential therapeutic target for epilepsy treatment.

Model systems for investigating disease processes in neurocysticercosis

Neurocysticercosis (NCC) occurs following brain infection by larvae of the cestode Taenia solium. It is the leading cause of preventable epilepsy worldwide and therefore constitutes a critical health challenge with significant global relevance. Despite this, much is still unknown about many key pathogenic aspects of the disease, including how cerebral infection with T. solium results in the development of seizures. Over the past century, valuable mechanistic insights have been generated using both clinical studies and animal models. In this review, we critically assess model systems for investigating disease processes in NCC. We explore the respective strengths and weaknesses of each model and summarize how they have contributed to current knowledge of the disease. We call for the continued development of animal models of NCC, with a focus on novel strategies for understanding this debilitating but often neglected disorder.

TNF-α blockade suppresses pericystic inflammation following anthelmintic treatment in porcine neurocysticercosis

Background

Neurocysticercosis (NCC) is an infection of the brain with the larval cyst of the tapeworm, Taenia solium. Cysticidal treatment induces parasite killing resulting in a post inflammatory response and seizures, which generally requires corticosteroid treatment to control inflammation. The nature of this response and how to best control it is unclear. We investigated the anti-inflammatory effects of pretreatment with etanercept (ETN), an anti-tumor necrosis factor agent, or dexamethasone (DEX), a high potency corticosteroid, on the post treatment inflammatory response in naturally infected pigs with neurocysticercosis after a single dose of the cysticidal drug praziquantel (PZQ).

Methodology/Principal findings

We followed the methods from a previously developed treatment model of NCC in naturally infected swine. The four study groups of infected pigs included 3 groups treated with PZQ on day 0: PZQ-treated alone (100 mg/kg PO; n = 9), pretreated with dexamethasone (DEX, 0.2 mg/kg IM administered on days -1, +1 and +3; n = 6), and pretreated with etanercept (ETN, 25 mg IM per animal on days -7 and 0; n = 6). The fourth group remained untreated (n = 3). As measured by quantitative RT-PCR, ETN pretreatment depressed transcription of a wide range of proinflammatory, regulatory and matrix protease encoding genes at 120 hr post PZQ treatment in capsules of cysts that demonstrated extravasated Evans Blue (EB) (a measure of blood brain barrier dysfunction) compared to animals not receiving ETN. Transcription was significantly depressed for the proinflammatory genes tumor necrosis factor (TNF)-α, and interferon (IFN)-γ; the inflammation regulating genes cytotoxic T-lymphocyte-associated protein (CTLA)4, interleukin (IL)-13 and transforming growth factor (TGF)-β; the tissue remodeling genes matrix metalloprotease (MMP)1 and 9, tissue inhibitors of metalloproteases (TIMP)1 and 2, and the genes regulating endothelial function vascular endothelial growth factor (VEGF)1, angiopoietin (Ang)1, Ang 2, and platelet endothelial cell adhesion molecule (PECAM)-1. In contrast, transcription was only modestly decreased in the DEX pretreated pigs compared to PZQ alone, and only for TNF-α, IL-6, IFN-γ, TGF-β and Ang1. IL-10 was not affected by either ETN or DEX pretreatments. The degree of inflammation, assessed by semi-quantitative inflammatory scores, was modestly decreased in both ETN and DEX pretreated animals compared to PZQ treated pigs whereas cyst damage scores were moderately decreased only in cysts from DEX pretreated pigs. However, the proportion of cysts with EB extravasation was not significantly changed in ETN and DEX pretreated groups.

Conclusions/Significance

Overall, TNF-α blockade using ETN treatment modulated expression of a large variety of genes that play a role in induction and control of inflammation and structural changes. In contrast the number of inflammatory cells was only moderately decreased suggesting weaker effects on cell migration into the inflammatory capsules surrounding cysts than on release of modulatory molecules. Taken together, these data suggest that TNF-α blockade may provide a viable strategy to manage post-treatment pericystic inflammation that follows antiparasitic therapy for neurocysticercosis.

Infection of the brain with larvae of the tapeworm Taenia solium is called neurocysticercosis (NCC), a disease with varied and serious neurological symptoms. Therapy requires antiparasitic drugs and corticosteroids to prevent seizures caused by treatment due to inflammation around dying parasites. The gene expression of the proinflammatory molecule tumor necrosis factor alpha (TNF-α) is increased in NCC. We treated three groups of naturally infected pigs with an antiparasitic drug: one group was also pretreated with an anti-TNF-α inhibitor, the second one with a corticosteroid, and the third was not pretreated. All pigs were infused with Evans blue dye (EB), which leaks where the blood brain barrier is damaged by inflammation around cysts. We compared the expression of several genes involved in inflammation, healing and fibrosis and regulation of vascular function in tissues surrounding cysts. In inflamed samples showing leaked EB, the inhibition of TNF-α suppressed nearly all the genes assessed, and this suppression was significantly stronger than the moderate decrease caused by corticosteroid pretreatment on most of the genes. On microscopic examination, the inflammation observed was slightly decreased with both pretreatments in relation to the group that was not pretreated. We believe that the inflammatory route that includes TNF-α should be further explored in the search for better management of inflammation directed to degenerating cysts.

Comparison of monocyte gene expression among patients with neurocysticercosis-associated epilepsy, Idiopathic Epilepsy and idiopathic headaches in India

Background

Neurocysticercosis (NCC), a neglected tropical disease, inflicts substantial health and economic costs on people living in endemic areas such as India. Nevertheless, accurate diagnosis using brain imaging remains poorly accessible and too costly in endemic countries. The goal of this study was to test if blood monocyte gene expression could distinguish patients with NCC-associated epilepsy, from NCC-negative imaging lesion-free patients presenting with idiopathic epilepsy or idiopathic headaches.

Methods/Principal findings

Patients aged 18 to 51 were recruited from the Department of Neurological Sciences, Christian Medical College and Hospital, Vellore, India, between January 2013 and October 2014. mRNA from CD14+ blood monocytes was isolated from 76 patients with NCC, 10 Recovered NCC (RNCC), 29 idiopathic epilepsy and 17 idiopathic headaches patients. A preliminary microarray analysis was performed on six NCC, six idiopathic epilepsy and four idiopathic headaches patients to identify genes differentially expressed in NCC-associated epilepsy compared with other groups. This analysis identified 1411 upregulated and 733 downregulated genes in patients with NCC compared to Idiopathic Epilepsy. Fifteen genes up-regulated in NCC patients compared with other groups were selected based on possible relevance to NCC, and analyzed by qPCR in all patients’ samples. Differential gene expression among patients was assessed using linear regression models. qPCR analysis of 15 selected genes showed generally higher gene expression among NCC patients, followed by RNCC, idiopathic headaches and Idiopathic Epilepsy. Gene expression was also generally higher among NCC patients with single cyst granulomas, followed by mixed lesions and single calcifications.

Conclusions/Significance

Expression of certain genes in blood monocytes can distinguish patients with NCC-related epilepsy from patients with active Idiopathic Epilepsy and idiopathic headaches. These findings are significant because they may lead to the development of new tools to screen for and monitor NCC patients without brain imaging.

Taenia solium is a parasite normally transmitted between humans and pigs in areas with poor sanitation. Neurocysticercosis (NCC) occurs when humans are infected with larvae of T. solium that are shed with human feces and the larvae establish in the brain. NCC is often accompanied by neurological symptoms such as epilepsy. In fact, NCC causes approximately one-third of epilepsy cases in areas where T. solium is common. Unfortunately, diagnosis of NCC requires brain computerized tomography or magnetic resonance imaging, tools rarely accessible to people living where NCC is prevalent. This study tested whether genes expressed in blood monocytes, a type of white blood cell, could distinguish between people with epilepsy caused by NCC from those with epilepsy of unknown cause (idiopathic). We compared gene expression in people with NCC and epilepsy, people with idiopathic epilepsy, people cured of NCC and people without NCC or epilepsy but with headaches. We identified 15 genes which were expressed differently in the four different groups indicating that monocyte gene expression patterns in people with NCC and epilepsy are different than people with idiopathic epilepsy. These findings could lead to better understanding how humans respond to NCC and to diagnostic tests which would not require brain imaging.

The effect of tobacco smoke exposure on the generation of reactive oxygen species and cellular membrane damage using co-culture model of blood brain barrier with astrocytes

Brain tissue is known to be vulnerable to the exposure by tobacco smoke. Tobacco smoke can induce generation of reactive oxygen species (ROS), causing inflammatory activity and blood-brain barrier (BBB) impairment. The aim of the present study was to investigate the effect of tobacco smoke on cell cytotoxicity, generation of ROS, and cellular membrane damage in astrocytes and BBB using a co-culture system. Cell viability of U373MG cells was reduced in a dose-dependent manner, ranging from 96.7% to 40.3% by tobacco smoke condensate (TSC). Cell viability of U373MG co-cultured with human brain microvascular endothelial cells (HBMECs) was 104.9% at the IC50 value of TSC. Trans-epithelial electric resistance values drastically decreased 80% following 12-h incubation. The value was maintained until 48 h and then increased at 72-h incubation (85%). It then decreased to 75% at 120 h. Generation of ROS increased in a dose-dependent manner, ranging from 102.7% to 107.9%, when various concentrations of TSC (4-16 mg/mL) were administered to the U373MG monoculture. When TSC was added into U373MG co-cultured with HBMECs, production of ROS ranged from 101.7% to 102.6%, slightly increasing over 12 h. Maximum exposure-generated ROS of 104.8% was reached at 24 h. Cell cytotoxicity and oxidative stress levels in the U373MG co-culture model system with HBMECs were lower than U373MG monoculture. HBMECs effectively acted as a barrier to protect the astrocytes (U373MG) from toxicity of TSC.

Control of autoimmune CNS inflammation by astrocytes

Multiple sclerosis is a neurologic disease caused by immune cell infiltration into the central nervous system, resulting in gray and white matter inflammation, progressive demyelination, and neuronal loss. Astrocytes, the most abundant cell population in the central nervous system (CNS), have been considered inert scaffold or housekeeping cells for many years. However, recently, it has become clear that this cell population actively modulates the immune response in the CNS at multiple levels. While being exposed to a plethora of cytokines during ongoing autoimmune inflammation, astrocytes modulate local CNS inflammation by secreting cytokines and chemokines, among other factors. This review article gives an overview of the most recent understanding about cytokine networks operational in astrocytes during autoimmune neuroinflammation and highlights potential targets for immunomodulatory therapies for multiple sclerosis.

Immunology of Taenia solium taeniasis and human cysticercosis

The life cycle of Taenia solium, the pork tapeworm, is continuously closed in many rural settings in developing countries when free roaming pigs ingest human stools containing T. solium eggs and develop cysticercosis, and humans ingest pork infected with cystic larvae and develop intestinal taeniasis, or may also accidentally acquire cysticercosis by faecal-oral contamination. Cysticercosis of the human nervous system, neurocysticercosis, is a major cause of seizures and other neurological morbidity in most of the world. The dynamics of exposure, infection and disease as well as the location of parasites result in a complex interaction which involves immune evasion mechanisms and involutive or progressive disease along time. Moreover, existing data are limited by the relative lack of animal models. This manuscript revises the available information on the immunology of human taeniasis and cysticercosis.

Adult human glia, pericytes and meningeal fibroblasts respond similarly to IFNy but not to TGFβ1 or M-CSF

The chemokine Interferon gamma-induced protein 10 (IP-10) and human leukocyte antigen (HLA) are widely used indicators of glial activation and neuroinflammation and are up-regulated in many brain disorders. These inflammatory mediators have been widely studied in rodent models of brain disorders, but less work has been undertaken using human brain cells. In this study we investigate the regulation of HLA and IP-10, as well as other cytokines and chemokines, in microglia, astrocytes, pericytes, and meningeal fibroblasts derived from biopsy and autopsy adult human brain, using immunocytochemistry and a Cytometric Bead Array. Interferonγ (IFNγ) increased microglial HLA expression, but contrary to data in rodents, the anti-inflammatory cytokine transforming growth factor β1 (TGFβ1) did not inhibit this increase in HLA, nor did TGFβ1 affect basal microglial HLA expression or IFNγ-induced astrocytic HLA expression. In contrast, IFNγ-induced and basal microglial HLA expression, but not IFNγ-induced astrocytic HLA expression, were strongly inhibited by macrophage colony stimulating factor (M-CSF). IFNγ also strongly induced HLA expression in pericytes and meningeal fibroblasts, which do not basally express HLA, and this induction was completely blocked by TGFβ1, but not affected by M-CSF. In contrast, TGFβ1 did not block the IFNγ-induced increase in IP-10 in pericytes and meningeal fibroblasts. These results show that IFNγ, TGFβ1 and M-CSF have species- and cell type-specific effects on human brain cells that may have implications for their roles in adult human brain inflammation.

Endoscopic scoring system for extraparenchymal neurocysticercosis

OBJECTIVE

To propose a scoring system using endoscopy for assessment of the inflammatory alterations caused by neurocysticercosis (NCC) inside the ventricular cavities and the basal subarachnoid space.

METHODS

Video recordings of the endoscopic procedures in patients with hydrocephalus secondary to NCC were assessed in a two-phase study. In the first phase (n = 10), the assigned score of each patient was correlated with the cerebrospinal fluid values obtained by lumbar and ventricular puncture. Reproducibility was determined using an intraclass correlation coefficient. In the second phase (n = 30), the prognostic value of the score was tested by comparing it with the patient's Karnofsky performance score (KPS) 3 months after endoscopy.

RESULTS

The score included four main components: ependymal findings, number of involved sites, abnormalities in the subarachnoid space, and other alterations. These values were summed to produce a total score, which correlated strongly with both protein and cell counts from ventricular cerebrospinal fluid. The intraclass correlation coefficient of the global score was 0.85. In the second phase, the scores were divided into mild, moderate, and severe categories (6, 15, and 9 patients). The initial KPS was similar between the groups (P = 0.56); however, when measured 3 months later, there were significant differences (P = 0.02). The logistic regression analysis of patients with a score in the severe range (odds ratio = 0.09; 95% confidence interval, 0.06-0.64) showed a reduced chance for achieving a good outcome (KPS ≥90) after 3 months.

CONCLUSIONS

Our scoring system enables endoscopic classification of the damage caused by NCC in the ventricular and basal subarachnoid space. The score has a biologic basis and a good internal reproducibility. The score seems to be useful for determining the short-term prognosis, and patients with high scores require additional therapeutic measures to improve their outcomes.

Mechanisms regulating monocyte CXCL8 secretion in neurocysticercosis and the effect of antiparasitic therapy

Neurocysticercosis (NCC) due to infection with Taenia solium is a major cause of epilepsy worldwide. Larval degeneration, which may follow antiparasitic treatment, results in clinical symptoms due to inflammatory cell influx. Mechanisms regulating this are not well understood, but chemokines have a key role. Stimulation of human monocytes by cyst Ags from NCC-infected pigs showed that scolex and membrane Ags drive CXCL8 and CCL2 secretion. Antiparasitic treatment of pigs increased CXCL8 in response to brain, but not muscle, cyst Ags. Cyst-fluid Ags did not elicit monocyte chemokine secretion, inhibited LPS-induced CXCL8 by up to 89%, but did not alter CCL2 secretion. This effect was inhibited by anti-IL-10 Abs. Plasma CXCL8, TNF-α, IL-10, eotaxin, IL-1, IL-1ra, soluble IL-1R-II, and soluble TNFR-I and -II levels were evaluated in 167 NCC patients. Patients had lower plasma CXCL8 and TNF-α concentrations than control subjects. In summary, larval Ags from brain and muscle cysts differentially regulate chemokine secretion. Cyst-fluid inhibits CXCL8, and this is blocked by anti-IL-10 Abs. CXCL8 concentrations are decreased in patient plasma. Following anti-parasitic therapy, scolex and membrane Ags are exposed, and cyst fluid is decreased, leading to inflammatory cell influx. Taken together, the cellular, porcine, and human data may explain, in part, why NCC is usually asymptomatic but may cause proinflammatory symptoms, particularly following treatment.

Severe cysticercal meningitis: clinical and imaging characteristics

In disease-endemic areas, severe cysticercal meningitis (SCM) is characterized by intense inflammatory cerebrospinal fluid (CSF) and negative bacterial and fungal cultures. There have been no systematic studies of SCM. We characterized patients with SCM and compare them with neurocysticercosis (NC) patients with mild CSF abnormalities by conducting a nine-year retrospective review at a neurological referral center. Two groups of patients were compared: group A, those with severe CSF pleocytosis > 1,000 cells/mm(3) (n = 12), and group B, those with CSF pleocytosis <or= 1,000 cells/mm(3) (n = 126). All patients had positive CSF results in an enzyme-linked immunosorbent assay for cysticercal antigens and negative CSF cultures for bacteria, fungi, and mycobacteria. Intracranial hypertension, meningeal signs, CSF hypoglycorrachia, and a longer clinical course of NC were more frequently seen in group A. It is likely that SCM often goes unrecognized. Its correct identification may reduce morbidity and risks of unnecessary surgery in patients with chronic NC and CSF shunts.

Do helminths cause epilepsy?

Both helminthiases and epilepsy occur globally, and are particularly prevalent in developing regions of the world. Studies have suggested an association between epilepsy and helminth infection, but a causal relationship is not established in many helminths, except perhaps with neurocysticercosis. We review the available literature on the global burden of helminths, and the epidemiological evidence linking helminths to epilepsy. We discuss possible routes that helminths affect the central nervous system (CNS) of humans and the immunological response to helminth infection in the CNS, looking at possible mechanisms of epileptogenesis. Finally, we discuss the current gaps in knowledge about the interaction between helminths and epilepsy.

Human astrocytic bradykinin B(2) receptor modulates zymosan-induced cytokine expression in 1321N1 cells

Bradykinin is an important modulator of the neurons and glial cells of the nervous system. Bradykinin secreted from neurons affects astrocytic functions such as neurovascular coupling and astrocytic cytokine production. In human astrocytes, however, the detailed mechanism of bradykinin-mediated modulation of astrocytic functions has not yet been fully elucidated. Here, we report the functional expression of the bradykinin B(2) receptor and its modulation of zymosan-induced cytokine expression in human astrocytoma 1321N1 cells. Bradykinin increased cytosolic [Ca(2+)] in a concentration-dependent manner, whereas [des-Arg(10)] kallidin (an agonist of the B(1) receptor) did not have this effect. Bradykinin also triggered intracellular InsP(3) production. Pretreating the cells with HOE140 (icatibant acetate, a B(2) receptor antagonist) inhibited the bradykinin-induced increase in cytosolic [Ca(2+)] and InsP(3) production. In contrast, [des-Arg(10)]HOE140 (a B(1) receptor antagonist) did not show any inhibitory effect. Bradykinin increased the zymosan-induced expression of TNF-alpha, and interleukin 1beta (IL-1beta) but did not affect the expression of interleukin 6 (IL-6) or interleukin 10 (IL-10). Interestingly, a cyclooxygenase-2 specific inhibitor blocked the bradykinin-induced effect. In contrast to the result in human glioma cells, bradykinin inhibits the zymosan-induced expression of TNF-alpha and IL-1beta in rat astrocytes, which shows a species-dependent manner. These data suggest that bradykinin B(2) receptors are expressed in human astrocytoma cells and that they modulate the expression pattern of inflammatory cytokines.

Inflammatory cytokines stimulate the chemokines CCL2/MCP-1 and CCL7/MCP-3 through NFkB and MAPK dependent pathways in rat astrocytes [corrected]

The chemokines CCL2 and CCL7 are upregulated in the brain during several neurodegenerative and acute diseases associated with infiltration of peripheral leukocytes. Astrocytes can respond to inflammatory cytokines like IL-1beta and TNF-alpha by producing chemokines. This study aims to test the ability of IL-1beta and TNF-alpha to stimulate CCL2 and CCL7 protein production in rat astrocyte cultures, and to elucidate signaling pathways involved in the cytokine-stimulated chemokine upregulation. Astrocytes were stimulated with IL-1beta or TNF-alpha, and CCL2 and CCL7 levels determined by ELISA. Our results show that IL-1beta and TNF-alpha each stimulate production of the chemokines CCL2 and CCL7 in astrocytes in a concentration- and time-dependent manner, with CCL2 showing a more rapid and robust response to the cytokine treatment than CCL7. As a first step to determine the signaling pathways involved in CCL2 and CCL7 upregulation, we stimulated astrocytes with IL-1beta or TNF-alpha in the presence of selective inhibitors of MAPK pathways (SB203580 and SB202190 for p38, SP600125 for JNK, and U0126 for ERK) or NFkappaB pathways (MG-132 and SC-514). We found that NFkappaB pathways are important for the cytokine-stimulated CCL2 and CCL7 production, whereas MAPK pathways involving p38 and JNK, but not ERK, may also contribute but to a lesser extent. These data document for the first time that CCL7 protein production can be stimulated in astrocytes by cytokines, and that the upregulation may involve NFkappaB- and p38/JNK-regulated pathways. In addition, our results suggest that CCL2 and CCL7 share similarities in the signaling pathways necessary for their upregulation.

Comparison of cerebrospinal fluid obtained by ventricular endoscopy and by lumbar puncture in patients with hydrocephalus secondary to neurocysticercosis

BACKGROUND

Compare the differences between proteins, glucose, and morphological cellular counts from ventricular cerebrospinal fluid obtained by neuroendoscopy and lumbar puncture.

METHODS

This was a retrospective, transversal study. From January 2003 until June 2006, 30 neuroendoscopies were performed on patients with hydrocephalus secondary to NCC. Samples of CSF were extracted by lumbar puncture and ventricular neuroendoscopy, and their levels of glucose, proteins, number of leukocytes, and morphological differences (PMN including eosinophiles, monocytes, and lymphocytes) were subsequently measured and studied. Traumatic CSF results were excluded. Twenty-five patients with histopathologic confirmation of the NCC diagnosis were analyzed. The average age of the patients was 42 years (SD, 19.8 years) and female-male ratio was 10:15.

RESULTS

The differences in glucose values, between lumbar and ventricular CSF, were not statistically significant-lumbar, 45.28 mg/dL and ventricular, 53.92 mg/dL (P = .129). The differences in the protein values and leukocyte counts were statistically significant (P < .05) with the highest values found in lumbar CSF. The presence of monocytes was higher than that of PMNs in both fluids (P < .05). We did not find eosinophiles in any CSF.

CONCLUSIONS

We did not find differences in the glucose values as described by previous studies, but our findings showed differences in the values of proteins, PMN leukocytes, and monocytes. The presence of more monocytes could be explained by their incremented activation by the parasite antigen and chronicity of the disease. Translational trials with uniform criteria are needed to determinate the immune process in the several presentations of the disease in humans.

Both TLR2 and TLR4 are required for the effective immune response in Staphylococcus aureus-induced experimental murine brain abscess

Toll-like receptors (TLRs) play central roles in the innate reaction to bacterial products and transmit specific immune responses against these pathogens. TLRs are expressed on numerous cell types, including innate immune cells, and on astrocytes, neurons, and microglial cells of the central nervous system (CNS). Lipoproteins and lipopolysaccharides are specifically recognized by TLR2 and TLR4, respectively. We examined the in vivo role of TLR2 and TLR4 in Staphylococcus aureus-induced brain abscess. Phenotypically, 87% of TLR2(-/-) mice and 43% of TLR4(-/-) mice died whereas all wild-type (WT) mice recovered. Clearance of bacteria from the CNS was significantly delayed in TLR2(-/-) mice compared with TLR4(-/-) and WT animals. Recruitment of granulocytes and macrophages to the CNS, as well as microglial activation and expansion, was up-regulated in TLR2(-/-) mice. Although inflammation persisted especially in the CNS of TLR2(-/-) mice, but also of TLR4(-/-) mice, WT mice terminated the infection more effectively. Collectively, these data show that the immune response to experimental S. aureus-induced brain abscess depends crucially on the recognition of S. aureus by TLR2 but that TLR4 is also required for an optimal intracerebral immune response in this disorder.

Monocytes infected with Mycobacterium tuberculosis regulate MAP kinase-dependent astrocyte MMP-9 secretion

Tuberculosis (TB) of the CNS (CNS-TB) carries a high mortality. Disease pathology is characterized by widespread destruction of CNS tissues. Matrix metalloproteinase-9 (MMP-9) is able to catabolyze specific components of the CNS tissue matrix and blood-brain barrier. Increased cerebrospinal fluid MMP-9 concentrations are associated with tissue damage, leukocyte infiltration, and death in CNS-TB. Using zymography, Western analysis, and transcription factor assays, we investigated mechanisms regulating MMP-9 activity in CNS-TB. We demonstrate that conditioned media from monocytes infected with Mycobacterium tuberculosis (CoMTB) induce MMP-9 secretion from astrocytes (U373-MG). IL-1beta and TNF-alpha are necessary but not sufficient for such induction of astrocyte MMP-9 secretion. CoMTB up-regulates AP-1 DNA-binding activity, and the c-Jun, FosB, and JunB subunits are particularly increased. MMP-9 secretion from CoMTB-stimulated astrocytes is dependent on the activity of p38, Erk, and Jnk MAPKs. Phosphorylation of p38, Erk, and Jnk is activated rapidly, peaking 30 min poststimulation with CoMTB. Inhibition of IL-1beta but not TNF-alpha in CoMTB decreases p38, Erk, and Jnk activity in astrocytes. Consistently, IL-1beta signals through the MAPK cascade at physiological levels, whereas TNF-alpha, IL-6, IL-10, CCL-2, CCL-5, and CXCL-8 (all present in CoMTB) do not. In summary, the data suggest that monocyte-dependent cytokine networks may play a key role in the development of a matrix-degrading environment during CNS-TB.

Neurocysticercal antigens stimulate chemokine secretion from human monocytes via an NF-kappaB-dependent pathway

Neurocysticercosis, infection with larval Taenia solium, is a common, serious neuroparasitic infection. Larval degeneration results in inflammatory cell influx and granuloma formation which leads to clinical symptomatology. The role of chemokines in such cell influx is unknown. We demonstrate that monocyte stimulation by T. solium larval antigen (TsAg) results in a differential profile of CXCL8/IL-8 (146.5+/-8.5ng/ml after 24h), CCL2/MCP-1 (267+/-4 ng/ml after 48 h) and CCL3/MIP-1alpha (1.72+/-0.43 ng/ml after 8 h) secretion. There was coordinate mRNA accumulation reaching maximum at 1h for CCL3 and 2 h for CXCL8 and CCL2. TsAg induced maximal nuclear binding of p65, p50 and c-rel subunits of the transcriptional regulator NF-kappaB by 2 h. IkappaBalpha but not IkappaBbeta was degraded within 10 min before resynthesis by 2 h. Pre-treatment with the broad-spectrum NF-kappaB inhibitor pyrrolidine dithiocarbamate caused complete abrogation of TsAg-induced CCL2 secretion (p=0.005) and 91% reduction of CXCL8 secretion (p=0.0003). TsAg was unable to induce CXCL8 promoter activity in Toll-like receptor (TLR)-2 or TLR-4/MD-2 transfected HeLa cells in the absence of lectins or other adaptor molecules. In summary, our data demonstrate that TsAg induces chemokine secretion via specific pathways dependent on NF-kappaB but not TLR-4/TLR-2, and indicate a potential mechanism whereby larval degeneration results in brain inflammation.