Effects of transforming growth factor-beta on murine astrocyte glutamine synthetase activity. Implications in neuronal injury

AMPA receptor inhibition alleviates inflammatory response and myocardial apoptosis after myocardial infarction by inhibiting TLR4/NF-κB signaling pathway

Myocardial infarction leads to myocardial inflammation and apoptosis, which are crucial factors leading to heart failure and cardiovascular dysfunction, eventually resulting in death. While the inhibition of AMPA receptors mitigates inflammation and tissue apoptosis, the effectiveness of this inhibition in the pathophysiological processes of myocardial infarction remains unclear. This study investigated the role of AMPA receptor inhibition in myocardial infarction and elucidated the underlying mechanisms. This study established a myocardial infarction model by ligating the left anterior descending branch of the coronary artery in Sprague-Dawley rats. The findings suggested that injecting the AMPA receptor antagonist NBQX into myocardial infarction rats effectively alleviated cardiac inflammation, myocardial necrosis, and apoptosis and improved their cardiac contractile function. Conversely, injecting the AMPA receptor agonist CX546 into infarcted rats exacerbated the symptoms and tissue damage, as reflected by histopathology. This agonist also stimulated the TLR4/NF-κB pathway, further deteriorating cardiac function. Furthermore, the investigations revealed that AMPA receptor inhibition hindered the nuclear translocation of P65, blocking its downstream signaling pathway and attenuating tissue inflammation. In summary, this study affirmed the potential of AMPA receptor inhibition in countering inflammation and tissue apoptosis after myocardial infarction, making it a promising therapeutic target for mitigating myocardial infarction.

Transforming growth factor β (TGF-β) pathway in the immunopathogenesis of multiple sclerosis (MS); molecular approaches

INTRODUCTION

Multiple sclerosis (MS) is an acute demyelinating disease with an autoimmune nature, followed by gradual neurodegeneration and enervating scar formation. Dysregulated immune response is a crucial dilemma contributing to the pathogenesis of MS. The role of chemokines and cytokines, such as transforming growth factor-β (TGF-β), have been recently highlighted regarding their altered expressions in MS. TGF-β has three isoforms, TGF-β1, TGF-β2, and TGF-β3, that are structurally similar; however, they can show different functions.

RESULTS

All three isoforms are known to induce immune tolerance by modifying Foxp3⁺ regulatory T cells. Nevertheless, there are controversial reports concerning the role of TGF-β1 and 2 in the progression of scar formation in MS. At the same time, these proteins also improve oligodendrocyte differentiation and have shown neuroprotective behavior, two cellular processes that suppress the pathogenesis of MS. TGF-β3 shares the same properties but is less likely contributes to scar formation, and its direct role in MS remains elusive.

DISCUSSION

To develop novel neuroimmunological treatment strategies for MS, the optimal strategy could be the one that causes immune modulation, induces neurogenesis, stimulates remyelination, and prevents excessive scar formation. Therefore, regarding its immunological properties, TGF-β could be an appropriate candidate; however, contradictory results of previous studies have questioned its role and therapeutic potential in MS. In this review article, we provide an overview of the role of TGF-β in immunopathogenesis of MS, related clinical and animal studies, and the treatment potential of TGF-β in MS, emphasizing the role of different TGF-β isoforms.

Photobiomodulation Promotes Repair Following Spinal Cord Injury by Regulating the Transformation of A1/A2 Reactive Astrocytes

After spinal cord injury (SCI), reactive astrocytes can be classified into two distinctive phenotypes according to their different functions: neurotoxic (A1) astrocytes and neuroprotective (A2) astrocytes. Our previous studies proved that photobiomodulation (PBM) can promote motor function recovery and improve tissue repair after SCI, but little is known about the underlying mechanism. Therefore, we aimed to investigate whether PBM contributes to repair after SCI by regulating the activation of astrocytes. Male rats subjected to clip-compression SCI were treated with PBM for two consecutive weeks, and the results showed that recovery of motor function was improved, the lesion cavity size was reduced, and the number of neurons retained was increased. We determined the time course of A1/A2 astrocyte activation after SCI by RNA sequencing (RNA-Seq) and verified that PBM inhibited A1 astrocyte activation and promoted A2 astrocyte activation at 7 days postinjury (dpi) and 14 dpi. Subsequently, potential signaling pathways related to A1/A2 astrocyte activation were identified by GO function analysis and KEGG pathway analysis and then studied in animal experiments and preliminarily analyzed in cultured astrocytes. Next, we observed that the expression of basic fibroblast growth factor (bFGF) and transforming growth factor-β (TGF-β) was upregulated by PBM and that both factors contributed to the transformation of A1/A2 astrocytes in a dose-dependent manner. Finally, we found that PBM reduced the neurotoxicity of A1 astrocytes to dorsal root ganglion (DRG) neurons. In conclusion, PBM can promote better recovery after SCI, which may be related to the transformation of A1/A2 reactive astrocytes.

Alcohol and IL-6 Alter Expression of Synaptic Proteins in Cerebellum of Transgenic Mice with Increased Astrocyte Expression of IL-6

Recent studies indicate that neuroimmune factors, including the cytokine interleukin-6 (IL-6), play a role in the CNS actions of alcohol. The cerebellum is a sensitive target of alcohol, but few studies have examined a potential role for neuroimmune factors in the actions of alcohol on this brain region. A number of studies have shown that synaptic transmission, and in particular inhibitory synaptic transmission, is an important cerebellar target of alcohol. IL-6 also alters synaptic transmission, although it is unknown if IL-6 targets are also targets of alcohol. This is an important issue because alcohol induces glial production of IL-6, which could then covertly influence the actions of alcohol. The persistent cerebellar effects of both IL-6 and alcohol typically involve chronic exposure and, presumably, altered gene and protein expression. Thus, in the current studies we tested the possibility that proteins involved in inhibitory and excitatory synaptic transmission in the cerebellum are common targets of alcohol and IL-6. We used transgenic mice that express elevated levels of astrocyte produced IL-6 to model persistently elevated expression of IL-6, as would occur in alcohol use disorders, and a chronic intermittent alcohol exposure/withdrawal paradigm (CIE/withdrawal) that is known to produce alcohol dependence. Multiple cerebellar synaptic proteins were assessed by Western blot. Results show that IL-6 and CIE/withdrawal have both unique and common actions that affect synaptic protein expression. These common targets could provide sites for IL-6/alcohol exposure/withdrawal interactions and play an important role in cerebellar symptoms of alcohol use such as ataxia.

Evidence for a dynorphin-mediated inner ear immune/inflammatory response and glutamate-induced neural excitotoxicity: an updated analysis

Acoustic overstimulation (AOS) is defined as the stressful overexposure to high-intensity sounds. AOS is a precipitating factor that leads to a glutamate (GLU)-induced Type I auditory neural excitotoxicity and an activation of an immune/inflammatory/oxidative stress response within the inner ear, often resulting in cochlear hearing loss. The dendrites of the Type I auditory neural neurons that innervate the inner hair cells (IHCs), and respond to the IHC release of the excitatory neurotransmitter GLU, are themselves directly innervated by the dynorphin (DYN)-bearing axon terminals of the descending brain stem lateral olivocochlear (LOC) system. DYNs are known to increase GLU availability, potentiate GLU excitotoxicity, and induce superoxide production. DYNs also increase the production of proinflammatory cytokines by modulating immune/inflammatory signal transduction pathways. Evidence is provided supporting the possibility that the GLU-mediated Type I auditory neural dendritic swelling, inflammation, excitotoxicity, and cochlear hearing loss that follow AOS may be part of a brain stem-activated, DYN-mediated cascade of inflammatory events subsequent to a LOC release of DYNs into the cochlea. In support of a DYN-mediated cascade of events are established investigations linking DYNs to the immune/inflammatory/excitotoxic response in other neural systems.

SILAC-Based Quantification of TGFBR2-Regulated Protein Expression in Extracellular Vesicles of Microsatellite Unstable Colorectal Cancers

Microsatellite unstable (MSI) colorectal cancers (CRCs) are characterized by mutational inactivation of Transforming Growth Factor Beta Receptor Type 2 (TGFBR2). TGFBR2-deficient CRCs present altered target gene and protein expression. Such cellular alterations modulate the content of CRC-derived extracellular vesicles (EVs). EVs function as couriers of proteins, nucleic acids, and lipids in intercellular communication. At a qualitative level, we have previously shown that TGFBR2 deficiency causes overall alterations in the EV protein content. To deepen the basic understanding of altered protein dynamics, this work aimed to determine TGFBR2-dependent EV protein signatures in a quantitative manner. Using a stable isotope labeling with amino acids in cell culture (SILAC) approach for mass spectrometry-based quantification, 48 TGFBR2-regulated proteins were identified in MSI CRC-derived EVs. Overall, TGFBR2 deficiency caused upregulation of several EV proteins related to the extracellular matrix and nucleosome as well as downregulation of proteasome-associated proteins. The present study emphasizes the general overlap of proteins between EVs and their parental CRC cells but also highlights the impact of TGFBR2 deficiency on EV protein composition. From a clinical perspective, TGFBR2-regulated quantitative differences of protein expression in EVs might nominate novel biomarkers for liquid biopsy-based MSI typing in the future.

Changes in Parameters of Oxidative Stress, Immunity, and Behavior in Endurance Athletes During a Preparation Period in Winter

Michalickova, D, Minic, R, Kotur-Stevuljevic, J, Andjelkovic, M, Dikic, N, Kostic-Vucicevic, M, Slanar, O, and Djordjevic, B. Changes in parameters of oxidative stress, immunity, and behavior in endurance athletes during a preparation period in winter. J Strength Cond Res 34(10): 2965-2973, 2020-The current study monitored markers of immunological and oxidative status in 9 male elite endurance athletes: V[Combining Dot Above]O2max: 68 ± 11 ml·kg·min, age: 24 ± 2.5 years, and training loads: 128 ± 21 metabolic equivalents-h·wk during a 3-month preparation period in winter (January-March). Self-rated state of moods evaluation (by Profile of Mood States questionnaire) was performed, and blood samples were collected at the beginning and end of the study. Spectrophotometric methods and enzyme-linked immunosorbent assay were used for parameters' determination. The level of concanavalin A (ConA)-stimulated interferon-γ (IFN-γ) from peripheral blood mononuclear cells (PBMCs) was increased (562 [147-852] vs. 1,097 [451-1842] pg·ml, p = 0.013). Also, the level of transforming growth factor-1 (TGF-β1) in serum was elevated (2.5 [1.4-5.1] vs. 7.2 [4.9-8.2] ng·ml, p = 0.015). There was no change in the level of peptidoglycan (PGN)-stimulated interleukin (IL)-10 from PBMCs. There were no significant changes in PBMCs proliferation/viability on stimulation with ConA and PGN during the study. No changes in superoxide dismutase, prooxidative-antioxidative balance, total oxidant status (TOS), and thiobarbituric acid reactive substances were observed along the study. Total antioxidant status (TAS) was increased (910 ± 174 vs. 1,090 ± 102 μmol·L, p = 0.018), and activity of paraoxonase (PON1) was decreased (523 ± 295 vs. 335 ± 183 U·L, p = 0.003) at the end of the study. Advanced oxidation protein products were increased (25 ± 7.9 vs. 42 ± 7.6 μmol·L, p = 0.011). The self-rated sense of vigor significantly declined (20 ± 2.1 vs. 14 ± 3.4, p = 0.045). In conclusion, 3 months of regular training in winter induced prominent changes in cytokines, biomarkers of oxidative stress, and antioxidative enzyme activity. These changes might increase susceptibility of athletes to disease and muscle damage and consequently lead to performance reduction.

Neuroprotection of a sesamin derivative, 1, 2-bis [(3-methoxyphenyl) methyl] ethane-1, 2-dicaroxylic acid (MMEDA) against ischemic and hypoxic neuronal injury

Objective(s):

Stroke may cause severe neuronal damage. The sesamin have been demonstrated to possess neuroprotection by its antioxidant and anti-inflammatory properties. One sesamin derivative was artificially composited, 1, 2-bis [(3-methoxyphenyl) methyl] ethane-1, 2-dicaroxylic acid (MMEDA) had been developed to study its antioxidative activity and neuroprotection.

Materials and Methods:

The infaction of Sprague Dawley (SD) rats and hypoxia models of BV-2 microglia or PC12 cells were investigated for in vivo and in vitro test respectively. Lipid peroxidation and reactive oxygen species (ROS), prostaglandin E₂ (PGE₂) and related signaling pathways from hypoxic cells were analyzed by ELISA or Western blot assay, respectively.

Results:

MMEDA showed a protective effect when given 90 min after the focal cerebral ischemia. The neuroprotection of MMEDA was further confirmed by attenuating ROS and PGE₂ release from hypoxic BV-2 or PC12 cells. MMEDA significantly reduced hypoxia-induced JNK and caspase-3 (survival and apoptotic pathways) in PC12 cells.

Conclusion:

The neuroprotective effect of MMEDA on ischemia/hypoxia models was involved with its antioxidative activity and anti-inflammatory effects. These results suggest that MMEDA exert effective neuroprotection against ischemia/hypoxia injury.

Andrographolide stimulates p38 mitogen-activated protein kinase-nuclear factor erythroid-2-related factor 2-heme oxygenase 1 signaling in primary cerebral endothelial cells for definite protection against ischemic stroke in rats

Stroke pathogenesis involves complex oxidative stress-related pathways. The nuclear factor erythroid-2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) pathways have been considered molecular targets in pharmacologic intervention for ischemic diseases. Andrographolide, a labdane diterpene, has received increasing attention in recent years because of its various pharmacologic activities. We determined that andrographolide modulates the mitogen-activated protein kinase (MAPK)-Nrf2-HO-1 signaling cascade in primary cerebral endothelial cells (CECs) to provide positive protection against middle cerebral artery occlusion (MCAO)-induced ischemic stroke in rats. In the present study, andrographolide (10 μM) increased HO-1 protein and messenger RNA expressions, Nrf2 phosphorylation, and nuclear translocation in CECs, and these activities were disrupted by a p38 MAPK inhibitor, SB203580, but not by the extracellular signal-regulated kinase inhibitor PD98059 or c-Jun amino-terminal kinase inhibitor SP600125. Similar results were observed in confocal microscopy analysis. Moreover, andrographolide-induced Nrf2 and HO-1 protein expressions were significantly inhibited by Nrf2 small interfering RNA. Moreover, HO-1 knockdown attenuated the protective effect of andrographolide against oxygen-glucose deprivation-induced CEC death. Andrographolide (0.1 mg/kg) significantly suppressed free radical formation, blood-brain barrier disruption, and brain infarction in MCAO-insulted rats, and these effects were reversed by the HO-1 inhibitor zinc protoporphyrin IX. The mechanism is attributable to HO-1 activation, as directly evidenced by andrographolide-induced pronounced HO-1 expression in brain tissues, which was highly localized in the cerebral capillary. In conclusion, andrographolide increased Nrf2-HO-1 expression through p38 MAPK regulation, confirming that it provides protection against MCAO-induced brain injury. These findings provide strong evidence that andrographolide could be a therapeutic agent for treating ischemic stroke or neurodegenerative diseases.

Glutamine Synthetase: Role in Neurological Disorders

Glutamine synthetase (GS) is an ATP-dependent enzyme found in most species that synthesizes glutamine from glutamate and ammonia. In brain, GS is exclusively located in astrocytes where it serves to maintain the glutamate-glutamine cycle, as well as nitrogen metabolism. Changes in the activity of GS, as well as its gene expression, along with excitotoxicity, have been identified in a number of neurological conditions. The literature describing alterations in the activation and gene expression of GS, as well as its involvement in different neurological disorders, however, is incomplete. This review summarizes changes in GS gene expression/activity and its potential contribution to the pathogenesis of several neurological disorders, including hepatic encephalopathy, ischemia, epilepsy, Alzheimer's disease, amyotrophic lateral sclerosis, traumatic brain injury, Parkinson's disease, and astroglial neoplasms. This review also explores the possibility of targeting GS in the therapy of these conditions.

Protective effect of a sesamin derivative, 3-bis (3-methoxybenzyl) butane-1, 4-diol on ischemic and hypoxic neuronal injury

Background

Stroke is one of the leading causes of neuronal death. Sesamin is known for neuroprotection by its antioxidant and anti-inflammatory properties but it lacks blood–brain barrier (BBB) activity. A panel of sesamin derivatives was screened and 3-bis (3-methoxybenzyl) butane-1,4-diol (BBD) was selected for high BBB activity and tested for its neuroprotective effect.

Methods

The focal cerebral ischemia of Sprague–Dawley rats and hypoxia models of murine BV-2 microglia or PC12 cells under oxygen/glucose deprivation were used for in vivo and in vitro test, respectively. Lipid peroxidation and superoxide dismutase (SOD) activity from the ischemic brain were tested and reactive oxygen species (ROS), cytokine production, prostaglandin (PGE₂) and related signaling pathways from hypoxic cells were examined by ELISA or Western blot assay, respectively.

Results

BBD showed a protective effect when given 90 min after the focal cerebral ischemia. It also reduced lipid peroxidation and preserved SOD activity from the ischemic brain. The mechanism of BBD was further confirmed by attenuating ROS, cytokine production, and PGE₂ release from hypoxic BV-2 or PC12 cells. BBD significantly reduced hypoxia-induced c-Jun N-terminal kinases (JNK) and modulated AKT-1 and caspase-3 (survival and apoptotic pathways) in BV-2 cells, and inhibited hypoxia-induced JNK and cyclooxygenase-2 activation in PC12 cells.

Conclusions

The neuroprotective effect of BBD on ischemia/hypoxia models was involved with antioxidant and anti-inflammatory effects. The result would help the development of new CNS drug for protection of ischemia/hypoxia injury.

CB2 receptor agonists protect human dopaminergic neurons against damage from HIV-1 gp120

Despite the therapeutic impact of anti-retroviral therapy, HIV-1-associated neurocognitive disorder (HAND) remains a serious threat to AIDS patients, and there currently remains no specific therapy for the neurological manifestations of HIV-1. Recent work suggests that the nigrostriatal dopaminergic area is a critical brain region for the neuronal dysfunction and death seen in HAND and that human dopaminergic neurons have a particular sensitivity to gp120-induced damage, manifested as reduced function (decreased dopamine uptake), morphological changes, and reduced viability. Synthetic cannabinoids inhibit HIV-1 expression in human microglia, suppress production of inflammatory mediators in human astrocytes, and there is substantial literature demonstrating the neuroprotective properties of cannabinoids in other neuropathogenic processes. Based on these data, experiments were designed to test the hypothesis that synthetic cannabinoids will protect dopaminergic neurons against the toxic effects of the HIV-1 protein gp120. Using a human mesencephalic neuronal/glial culture model, which contains dopaminergic neurons, microglia, and astrocytes, we were able to show that the CB1/CB2 agonist WIN55,212-2 blunts gp120-induced neuronal damage as measured by dopamine transporter function, apoptosis and lipid peroxidation; these actions were mediated principally by the CB2 receptor. Adding supplementary human microglia to our cultures enhances gp120-induced damage; WIN55,212-2 is able to alleviate this enhanced damage. Additionally, WIN55,212-2 inhibits gp120-induced superoxide production by purified human microglial cells, inhibits migration of human microglia towards supernatants generated from gp120-stimulated human mesencephalic neuronal/glial cultures and reduces chemokine and cytokine production from the human mesencephalic neuronal/glial cultures. These data suggest that synthetic cannabinoids are capable of protecting human dopaminergic neurons from gp120 in a variety of ways, acting principally through the CB2 receptors and microglia.

Effects of Lactobacillus gasseri OLL2809 and α-lactalbumin on university-student athletes: a randomized, double-blind, placebo-controlled clinical trial

Strenuous exercise reduces immune cell function and increases the risk of respiratory and gastrointestinal infections. In addition, it affects mood state and causes physical fatigue. Athletes require both mental and physical conditioning to execute good performance. In this study, we conducted a randomized, double-blind, placebo-controlled clinical trial to evaluate the immunopotentiation and fatigue-alleviation effects of Lactobacillus gasseri OLL2809 (LG2809) and α-lactalbumin (αLA) in university-student athletes after strenuous exercise. A total of 44 university students who performed strenuous exercise daily were separated into 3 groups to receive a 4-week course of placebo, 100 mg LG2809, or 100 mg LG2809 in combination with 900 mg αLA, respectively. Before and after each dietary treatment, the subjects performed strenuous cycle ergometer exercise for 1 h. Before and after each exercise session, blood samples and visual analogue scale scores for fatigue were obtained. In addition, the mood of each subject before and after the dietary treatment was evaluated using the Profile of Mood States (POMS) questionnaire. LG2809 ingestion was effective in preventing reduced natural killer cell activity due to strenuous exercise and elevating mood from a depressed state. In addition, LG2809 + αLA was found to alleviate minor resting fatigue, which was supported objectively by the significant reduction in the serum reactive oxygen metabolites and transforming growth factor β1 levels. These effects could be helpful for athletes to maintain mental and physical condition.

Glial cell activity is maintained during prolonged inflammatory challenge in rats

We evaluated the expression of glial fibrillary acidic protein (GFAP), glutamine synthetase (GS), ionized calcium binding adaptor protein-1 (Iba-1), and ferritin in rats after single or repeated lipopolysaccharide (LPS) treatment, which is known to induce endotoxin tolerance and glial activation. Male Wistar rats (200-250 g) received ip injections of LPS (100 µg/kg) or saline for 6 days: 6 saline (N = 5), 5 saline + 1 LPS (N = 6) and 6 LPS (N = 6). After the sixth injection, the rats were perfused and the brains were collected for immunohistochemistry. After a single LPS dose, the number of GFAP-positive cells increased in the hypothalamic arcuate nucleus (ARC; 1 LPS: 35.6 ± 1.4 vs control: 23.1 ± 2.5) and hippocampus (1 LPS: 165.0 ± 3.0 vs control: 137.5 ± 2.5), and interestingly, 6 LPS injections further increased GFAP expression in these regions (ARC = 52.5 ± 4.3; hippocampus = 182.2 ± 4.1). We found a higher GS expression only in the hippocampus of the 6 LPS injections group (56.6 ± 0.8 vs 46.7 ± 1.9). Ferritin-positive cells increased similarly in the hippocampus of rats treated with a single (49.2 ± 1.7 vs 28.1 ± 1.9) or repeated (47.6 ± 1.1 vs 28.1 ± 1.9) LPS dose. Single LPS enhanced Iba-1 in the paraventricular nucleus (PVN: 92.8 ± 4.1 vs 65.2 ± 2.2) and hippocampus (99.4 ± 4.4 vs 73.8 ± 2.1), but had no effect in the retrochiasmatic nucleus (RCA) and ARC. Interestingly, 6 LPS increased the Iba-1 expression in these hypothalamic and hippocampal regions (RCA: 57.8 ± 4.6 vs 36.6 ± 2.2; ARC: 62.4 ± 6.0 vs 37.0 ± 2.2; PVN: 100.7 ± 4.4 vs 65.2 ± 2.2; hippocampus: 123.0 ± 3.8 vs 73.8 ± 2.1). The results suggest that repeated LPS treatment stimulates the expression of glial activation markers, protecting neuronal activity during prolonged inflammatory challenges.

Preferential sensitivity of human dopaminergic neurons to gp120-induced oxidative damage

The dopamine (DA)-rich midbrain is known to be a key target of human immunodeficiency virus (HIV)-1. Studies of simian immunodeficiency virus (SIV)-induced neuropathogenesis recently established that there is a major disruption within the nigrostriatal dopaminergic system characterized by marked depletion of dopaminergic neurons, microglial cell activation, and reactive astrocytes. Using a human mesencephalic neuronal/glial culture model, which contains dopaminergic neurons, microglia, and astrocytes, experiments were performed to characterize the damage to dopaminergic neurons induced by HIV-1 gp120. Functional impairment was assessed by DA uptake, and neurotoxicity was measured by apoptosis and oxidative damage. Through the use of this mesencephalic neuronal/glial culture model, we were able to identify the relative sensitivity of dopaminergic neurons to gp120-induced damage, manifested as reduced function (decreased DA uptake), morphological changes, and reduced viability. We also showed that gp120-induced oxidative damage is involved in this neuropathogenic process.

TGFbeta1 stimulates the over-production of white matter astrocytes from precursors of the "brain marrow" in a rodent model of neonatal encephalopathy

Background

In children born prematurely and those surviving cerebral ischemia there are white matter abnormalities that correlate with neurological dysfunction. Since this injury occurs in the immature brain, when the majority of subventricular zone (SVZ) cells generate white matter oligodendrocytes, we sought to study the effect this injury has on gliogenesis from the SVZ. We hypothesized that there is aberrant glial cell generation from the SVZ after neonatal hypoxia ischemia (H/I) that contributes to an increased astrogliogenesis with concomitant oligodendroglial insufficiency. Mechanistically we hypothesized that an increase in specific locally produced cytokines during recovery from injury were modifying the differentiation of glial progenitors towards astrocytes at the expense of the more developmentally-appropriate oligodendrocytes.

Methodology/Principal Finding

For these studies we used the Vannucci H/I rat model where P6 rats are subjected to unilateral common carotid ligation followed by 75 min of systemic hypoxia. Retroviral lineage tracing studies combined with morphological and immunohistochemical analyses revealed the preferential generation of SVZ-derived white matter astrocytes instead of oligodendrocytes post hypoxia/ischemia. Microarray and QRT-PCR analyses of the damaged SVZ showed increased expression of several cytokines and receptors that are known to promote astrocyte differentiation, such as EGF, LIF and TGFß signaling components. Using gliospheres to model the neonatal SVZ, we evaluated the effects of these cytokines on signal transduction pathways regulating astrocyte generation, proliferation and differentiation. These studies demonstrated that combinations of EGF, LIF and TGFß1 reconstituted the increased astrogliogenesis. TGFß1-induced Smad 2/3 phosphorylation and the combination of EGF, LIF and TGFß1 synergistically increased STAT3 phosphorylation over single or double cytokine combinations. Pharmacologically inhibiting ALK5 signaling in vitro antagonized the TGFß1-induced increase in astrocyte generation and antagonizing ALK5 signaling in vivo similarly inhibited astrogliogenesis within the SVZ during recovery from H/I.

Conclusion/Significance

Altogether, these data indicate that there is aberrant specification of glial precursors within the neonatal SVZ during recovery from neonatal H/I that is a consequence of altered cytokine signaling. Our studies further suggest that antagonizing the ALK5 receptor will restore the normal pattern of cell differentiation after injury to the immature brain.

Down-regulation of the TGF-beta target gene, PTPRK, by the Epstein-Barr virus encoded EBNA1 contributes to the growth and survival of Hodgkin lymphoma cells

The Epstein-Barr virus (EBV) contributes to the growth and survival of Hodgkin lymphoma (HL) cells. Here we report that down-regulation of the transforming growth factor-beta (TGF-beta) target gene, protein tyrosine phosphatase receptor kappa (PTPRK), followed EBV infection of HL cells and was also more frequently observed in the Hodgkin and Reed-Sternberg (HRS) cells of EBV-positive compared with EBV-negative primary HL. The viability and proliferation of EBV-positive HL cells was decreased by overexpression of PTPRK, but increased following the knockdown of PTPRK expression in EBV-negative HL cells, demonstrating that PTPRK is a functional tumor suppressor in HL. EBV suppressed the TGF-beta-mediated activation of PTPRK expression, suggesting disruption of TGF-beta signaling upstream of PTPRK. This was confirmed when we showed that the Epstein-Barr nuclear antigen-1 (EBNA1) decreased Smad2 protein levels and that this was responsible for PTPRK down-regulation. EBNA1 decreased the half-life of Smad2 but did not interact with Smad2. By down-regulating Smad2 protein expression, EBNA1 apparently disables TGF-beta signaling, which subsequently decreases transcription of the PTPRK tumor suppressor. We speculate that loss of the phosphatase function of PTPRK may activate as-yet-unidentified growth-promoting protein tyrosine kinases, which in turn contribute to the pathogenesis of EBV-positive HL.

Illuminating the interrelated immune and endocrine adaptations after multiple exposures to short immobilization stress by in vivo blocking of IL-6

Intermittent psychological stress was induced in adult rats by 2 h/day of immobilization stress for 4 days, with or without blocking the function of IL-6 by using an anti-IL-6 antibody. Basal concentrations of serum corticosterone, IL-1β, IL-6, and TNF-α were assessed 24 h after the last intervention, as were levels of glucocorticoid receptors (GR) and activities of glucocorticoid-inducible enzymes (tyrosine aminotransferase and glutamine synthetase) in muscle and liver. Whole blood cultures were used to assess both spontaneous and LPS-induced reactivity of peripheral blood mononuclear cells. Stress increased corticosterone concentration in a manner partially modulated by IL-6. Serum IL-1β concentration was downregulated during stress when IL-6 was blocked ( P < 0.01). LPS-induced IL-6 secretion by peripheral blood mononuclear cells in vitro correlated positively with serum IL-1β concentration in antibody-treated groups, independently of stress ( R = 0.70 in nonstressed and R = 0.78 in stressed rats; both P < 0.05), whereas serum corticosterone concentration correlated positively with LPS-induced secretion of IL-6 only in control rats ( R = 0.66; P < 0.05). Reductions in liver GR levels indicated independent effects of stress (34.5%) and anti-IL-6 antibody (16.7%) and additive effects for both (62.5%). Similar results are reported for vastus muscle. Conversely, stress increased tyrosine aminotransferase and glutamine synthetase activities in muscle and liver with a significant ( P < 0.05) effect of anti-IL-6 antibody only seen in stressed livers. In conclusion, IL-6 plays a role in maintaining circulating IL-1β concentration after multiple exposures to stress, thus promoting a continued elevation of corticosterone release; in peripheral tissues, IL-6 antagonizes the effects of glucocorticoids, especially at the level of GR concentration.

Macrophages and HIV-1: dangerous liaisons

HIV-1, like the other lentiviruses, has evolved the ability to infect nondividing cells including macrophages. HIV-1 replication in monocytes/macrophages entails peculiar features and differs in many respects from that in CD4 T lymphocytes. HIV-1 exhibits different tropism for CD4 T cells and macrophages. The virus can enter macrophages via several routes. Mitosis is not required for nuclear import of viral DNA or for its integration into the host cell genome. Specific cellular factors are required for HIV-1 transcription in macrophages. The assembly and budding of viral particles in macrophages take place in late endosomal compartments. Viral particles can use the exosome pathway to exit cells. Given their functions in host defence against pathogens and the regulation of the immune response plus their permissivity to HIV-1 infection, monocytes/macrophages exert a dual role in HIV infection. They contribute to the establishment and persistence of HIV-1 infection, and may activate surrounding T cells favouring their infection. Furthermore, monocytes/macrophages act as a Trojan horse to transmit HIV-1 to the central nervous system. They also exhibit antiviral activity and express many molecules that inhibit HIV-1 replication. Activated microglia and macrophages may also exert a neurotrophic and neuroprotective effect on infected brain regulating glutamate metabolism or by secretion of neurotrophins. This review will discuss specific aspects of viral replication in monocytes/macrophages and the role of their interactions with the cellular environment in HIV-1 infection swinging between protection and pathogenesis.

Reduction and expansion of the glutamine synthetase expressing zone in livers from tetracycline controlled TGF-beta1 transgenic mice and multiple starved mice

BACKGROUND/AIMS

To learn more about tissue remodelling in fibrotic livers of tetracycline-controlled TGF-beta1 transgenic mice (TGF-beta1-on-mice) and during regeneration after removal of the fibrotic stimulus (off-mice), we investigated the expression of glutamine synthetase (GS), an exclusive pericentrally expressed enzyme.

METHODS

GS was localised immunohistochemically and quantified by real-time RT-PCR and enzymatic activity measurement. Apoptosis in livers of TGF-beta1-on-mice was demonstrated by in situ apoptosis detection kit (TUNEL reaction).

RESULTS

Livers of TGF-beta1-on-mice harbour a reduced number of GS-positive hepatocytes and expression of GS is downregulated, while multiple starved mice serving as controls for malnutrition during TGF-beta1 exposure surprisingly showed an impressive amplification of GS-positive hepatocytes. Apoptotic events were frequent around central veins in livers of TGF-beta1-on-mice, while in multiple induced mice apoptosis was dominant around all vessels and weak in midzonal areas. During regeneration from fibrosis, control levels were regained within 21 days. Beta-catenin was dislocated from plasma membrane to cytoplasm exclusively in pericentral hepatocytes during a short time slot after a unique expression of TGF-beta1.

CONCLUSIONS

Reduction of GS in TGF-beta1-on-mice results from apoptosis of GS-positive hepatocytes rather than downregulation of GS expression. Beta-catenin seems involved in the recovery of GS-positive hepatocytes.

T-cell and neuronal apoptosis in HIV infection: implications for therapeutic intervention

The pathogenesis of HIV infection involves the selective loss of CD4+ T cells contributing to immune deficiency. Although loss of T cells leading to immune dysfunction in HIV infection is mediated in part by viral infection, there is a much larger effect on noninfected T cells undergoing apoptosis in response to activation stimuli. In the subset of patients with HIV dementia complex, neuronal injury, loss, and apoptosis are observed. Viral proteins, gp120 and Tat, exhibit proapoptotic activities when applied to T cell and neuronal cultures by direct and indirect mechanisms. The pathways leading to cell death involve the activation of one or more death receptor pathways (i.e., TNF-alpha, Fas, and TRAIL receptors), chemokine receptor signaling, cytokine dysregulation, caspase activation, calcium mobilization, and loss of mitochondrial membrane potential. In this review, the mechanisms involved in T-cell and neuronal apoptosis, as well as antiapoptotic pathways potentially amenable to therapeutic application, are discussed.

Up-regulation of glutamate concentration in the putamen and in the prefrontal cortex of asymptomatic SIVmac251-infected macaques without major brain involvement

We quantified putamen and prefrontal cortex metabolites in macaques with simian immunodeficiency virus infection and searched for virological and histological correlates. Fourteen asymptomatic macaques infected since 8-78 months (median: 38) were compared with eight uninfected ones. Absolute concentrations of acetate, alanine, aspartate, choline, creatine, GABA, glutamate, glutamine, lactate, myo-inositol, N-acetylaspartate, taurine and valine were determined by ex vivo proton magnetic resonance spectroscopy. Glutamate concentration in the CSF was determined by HPLC. Gliosis was assessed by glial fibrillary acidic protein and CD68 immunohistochemistry. Glutamate concentration was slightly increased in the prefrontal cortex (19%, p = 0.0152, t-test) and putamen (13%, p = 0.0354, t-test) of the infected macaques, and was unaffected in the CSF. Myo-inositol concentration was increased in the prefrontal cortex only (27%, p = 0.0136). The concentrations of glutamate and myo-inositol in the prefrontal cortex were higher in the animals with marked or intense microgliosis (p = 0.0114). The other studied metabolites, including N-acetylaspartate, were not altered. Glutamate concentration may thus increase in the cerebral parenchyma in asymptomatic animals, but is not accompanied by a detectable decrease in N-acetylaspartate concentration (neuronal dysfunction). Thus, there are probably compensatory mechanisms that may limit glutamate increase and/or counterbalance its effects.

TGF-betas and their roles in the regulation of neuron survival

Transforming growth factor-betas (TGF-betas) are a still growing superfamily of cytokines with widespread distribution and diverse biological functions. They fall into several subfamilies including the TGF-betas 1, 2, and 3, the bone morphogenetic proteins (BMPs), the growth/differentiation factors (GDFs), activins and inhibins, and the members of the glial cell line-derived neurotrophic factor family. Following a brief description of their general roles and signaling in development, maintenance of homeostasis, and disease, we shall focus on their distribution in the CNS and their involvement in regulating neuron survival and death.

Expression of excitatory amino acid transporter-1 in brain macrophages and microglia of HIV-infected patients. A neuroprotective role for activated microglia?

Recent experimental studies showed that activated macrophages/microglia (AMM) express excitatory amino acid transporters (EAATs), suggesting that, in addition to their neurotoxic properties, they also have a neuroprotective role by clearing extracellular glutamate and producing antioxidant glutathione. To test this hypothesis in human, the brain of 12 HIV-positive patients and 3 controls were immunostained for EAAT-1. EAAT-1 was expressed by AMM in all HIV-infected cases but not in HIV-negative controls. Expression varied according to the disease stage. In 5 cases with active HIV-encephalitis (HIVE), AMM strongly expressed EAAT-1 in the white matter and basal ganglia, analogous to HLA-DR and CD68 expression. There was weaker expression in the cortex and perineuronal microglial cells were not involved. In a case with "burnt out" HIVE following highly active antiretroviral therapy (HAART), EAAT-1 expression was mild, identical to that of HLA-DR and CD68 in the white matter and cortex and involved perineuronal microglial cells. In 3 AIDS patients without HIVE and in 3 pre-AIDS cases, EAAT-1 expression in the white matter was weaker than HLA-DR and CD68 expression; there was stronger correlation in the gray matter where perineuronal microglial cells were stained predominantly. Our findings in humans tend to confirm that AMM, particularly perineuronal microglial cells, play a neuroprotective role in the early stages of HIV infection and, possibly, following treatment. This is in keeping with the early microglial activation seen in pre-AIDS cases, and the late occurrence of neuronal loss. It may also explain the reversible cognitive disorders following treatment in some cases.

Expression of excitatory amino acid transporter-2 (EAAT-2) and glutamine synthetase (GS) in brain macrophages and microglia of SIVmac251-infected macaques

Na+-dependent transporters for glutamate (excitatory amino acid transporters, EAATs) clear extracellular glutamate in the brain and prevent excitotoxic neuronal damage. Glutamine synthetase (GS) provides metabolic support for neurones by producing the neurotrophic amino acid glutamine. EAAT and GS expression has recently been demonstrated in macrophages and microglial cells in vitro, and in two models of acute inflammation in vivo. This observation might modify our current understanding of brain inflammation, which considers activated microglia and brain macrophages as the main neurotoxic cells through their production of a variety of neurotoxins, including glutamate. EAAT and GS expression by these cells would entail neuroprotective and neurotrophic properties, counterbalancing the deleterious consequences of microglial activation. Macaque infection by the simian immunodeficiency virus (SIV) is considered the most relevant model for human acquired immunodeficiency syndrome (AIDS), including chronic inflammation of the brain at the early asymptomatic stage of the infection, followed by an AIDS-like disease where neuronal death occurs. We studied the expression of EAAT-2 and GS in the brains of three SIVmac251-infected and two noninfected cynomolgus macaques. We found that both microglia and brain macrophages expressed EAAT-2 and GS in infected primates, suggesting that these cells might, like astrocytes, clear extracellular glutamate and provide glutamine to neurones. Microglia and macrophages could thus have neuroprotective and neurotrophic properties in addition to their production of neurotoxins. This finding might explain the contrast between early intense microglial activation and the late occurrence of neuronal apoptotic cell death, which is mainly observed at the terminal stage of the disease.

Microarray technology and its application on nicotine research

Since its development, microarray technique has revolutionized almost all fields of biomedical research by enabling high-throughput gene expression profiling. Using cDNA microarrays, thousands of genes from various organisms have been examined with respect to differentiation/development, disease diagnosis, and drug discovery Nevertheless, research on nicotine using cDNA microarrays has been rather limited. Therefore, it is our intention in this article to report the findings of our cDNA microarray study on nicotine. We first present an overview of the microarray technology, particularly focusing on the factors related to microarray design and analysis. Second, we provide a detailed description of several newly identified biological pathways in our laboratory, such as phosphatidylinositol signaling and calcium homeostasis, which are involved in response to chronic nicotine administration. Additionally, we illustrate how comparisons between microarray studies help identify candidate genes that potentially may explain the observed inverse association between smoking and schizophrenia. Lastly, given the early stage of microarray research on nicotine, we elaborate on the need for an efficient analysis of genetic networks to further enhance our understanding of the mechanisms involved in nicotine abuse and addiction.

Functional role of TGF beta in Alzheimer's disease microvascular injury: lessons from transgenic mice

Recent studies have implicated pro- and anti-inflammatory cytokines as integral to Alzheimer's disease (AD) pathogenesis. Among them, transforming growth factor-beta (TGF-beta) is emerging as an important factor in regulating inflammatory responses. This multifunctional cytokine might be centrally involved in several aspects of AD pathogenesis by regulating beta-amyloid precursor protein synthesis and processing, plaque formation, astroglial and microglial response and neuronal cell death. Among all of these potential roles, studies in transgenic and infusion animal models have shown that TGF-beta may primarily contribute to AD pathogenesis by influencing A beta production and deposition, which in turn might result in damage to the brain microvasculature. The lessons learned from these models are of great interest not only for understanding of the role of TGF-beta in AD, but also for future treatments where testing of anti-inflammatory agents such as ibuprofen and an amyloid vaccine hold great promise. In this regard, further elucidation of the signal pathways by which TGF-beta exerts its effect in AD might lead to specific targets for further therapeutic intervention.

Inflammation and Alzheimer's disease

Inflammation clearly occurs in pathologically vulnerable regions of the Alzheimer's disease (AD) brain, and it does so with the full complexity of local peripheral inflammatory responses. In the periphery, degenerating tissue and the deposition of highly insoluble abnormal materials are classical stimulants of inflammation. Likewise, in the AD brain damaged neurons and neurites and highly insoluble amyloid beta peptide deposits and neurofibrillary tangles provide obvious stimuli for inflammation. Because these stimuli are discrete, microlocalized, and present from early preclinical to terminal stages of AD, local upregulation of complement, cytokines, acute phase reactants, and other inflammatory mediators is also discrete, microlocalized, and chronic. Cumulated over many years, direct and bystander damage from AD inflammatory mechanisms is likely to significantly exacerbate the very pathogenic processes that gave rise to it. Thus, animal models and clinical studies, although still in their infancy, strongly suggest that AD inflammation significantly contributes to AD pathogenesis. By better understanding AD inflammatory and immunoregulatory processes, it should be possible to develop anti-inflammatory approaches that may not cure AD but will likely help slow the progression or delay the onset of this devastating disorder.

Is glutamine a 'conditionally essential' amino acid in Duchenne muscular dystrophy?

To determine whether whole body protein kinetics are altered in Duchenne muscular dystrophy (DMD), six 9 +/- 1-year-old children with DMD and five weight and height matched controls, received intravenous infusion of L-[1-(13)C]leucine and L-[2-(15)N]glutamine in the post-absorptive state. Glutamine rate of appearance was approximatly 24% lower in DMD boys than in controls (321 +/- 22 vs 425 +/- 37 micromol kg(-1)h(-1), P< 0.05) resulting from a 32% decrease in glutamine de novo synthesis (230 +/- 21 vs 340 +/- 34 micromol kg(-1)h(-1), P< 0.05). Whereas there was no difference between groups in estimates of protein degradation and synthesis, leucine oxidation rate was 44% higher in DMD boys than in controls (23 +/- 2 vs 16 +/- 2 micromol kg(-1)h(-1), P< 0.05). The data suggest that the dramatic mucle mass loss observed in DMD boys is associated with a) significant protein wasting, since increased leucine oxidation reflects a more negative whole body leucine balance, and b) a significant decrease in glutamine availability in the postabsorptive state. Glutamine might therefore be a 'conditionally essential' amino-acid in DMD.

Dependence of neurones on astrocytes in a coculture system renders neurones sensitive to transforming growth factor beta1-induced glutamate toxicity

Transforming growth factor beta1 (TGF-beta1) has been implicated in formation of astrocyte scars, which prevents axonal regeneration. A coculture system of astrocytes and cerebellar cells was used to investigate possible neurotoxic effects of TGF-beta1. Although not directly neurotoxic, TGF-beta1 was toxic to cerebellar cells in the presence of astrocytes. This toxicity is based on an effect of the cytokine on astrocytes, as conditioned medium from astrocyte cultures treated with TGF-beta1 was more toxic by a similar mechanism. This neurotoxicity was mediated by glutamate present in the culture medium as demonstrated by inhibition by MK-801. Astrocytic ability to metabolise glutamate was compromised by TGF-beta1, as this cytokine increased glutamate concentration. The astrocytes in the coculture system responded to the presence of neurones by secreting neuroprotective interleukin-6, which was partly protective against the TGF-beta1-induced toxicity. In the coculture system, neurones responded to the presence of astrocytes by a reduction in resistance to glutamate toxicity. On addition of TGF-beta1, which compromised astrocytic clearance of glutamate, this reduction in resistance to glutamate toxicity led to a reduction in neuronal survival. These results suggest that when neurones are cocultured with astrocytes they become dependent on astrocytes for survival. This dependence makes neurones susceptible to damage when astrocytes are activated by substances such as TGF-beta1.

Effects of transforming growth factor-beta (isoforms 1-3) on amyloid-beta deposition, inflammation, and cell targeting in organotypic hippocampal slice cultures

The transforming growth factor-beta (TGF-beta) family consists of three isoforms and is part of a larger family of cytokines regulating differentiation, development, and tissue repair. Previous work from our laboratory has shown that TGF-beta1 can increase amyloid-beta protein (Abeta) immunoreactive (Abetair) plaque-like deposits in rat brain. The aim of the current study was to evaluate all three isoforms of TGF-beta for their ability to affect the deposition and neurotoxicity of Abeta in an organotypic, hippocampal slice culture model of Abeta deposition. Slice cultures were treated with Abeta either with or without one of the TGF-beta isoforms. All three isoforms can increase Abeta accumulation (over Abeta treatment alone) within the slice culture, as determined by ELISA. However, there are striking differences in the pattern of Abetair among the three isoforms of TGF-beta. Isoforms 1 and 3 produced a cellular pattern of Abeta staining that colocalizes with GS lectin staining (microglia). TGF-beta2 produces dramatic Abeta staining of pyramidal neurons in layers CA1-CA2. In addition to cellular Abeta staining, plaque-like deposits are increased by all of the TGF-betas. Although no gross toxicity was observed, morphological neurodegenerative changes were seen in the CA1 region when the slices were treated with Abeta plus TGF-beta2. Our results demonstrate important functional differences among the TGF-beta isoforms in their ability to alter the cellular distribution and degradation of Abeta. These changes may be relevant to the pathology of Alzheimer's disease (AD).

Effects of transforming growth factor-beta (isoforms 1-3) on amyloid-beta deposition, inflammation, and cell targeting in organotypic hippocampal slice cultures

The transforming growth factor-beta (TGF-beta) family consists of three isoforms and is part of a larger family of cytokines regulating differentiation, development, and tissue repair. Previous work from our laboratory has shown that TGF-beta1 can increase amyloid-beta protein (Abeta) immunoreactive (Abetair) plaque-like deposits in rat brain. The aim of the current study was to evaluate all three isoforms of TGF-beta for their ability to affect the deposition and neurotoxicity of Abeta in an organotypic, hippocampal slice culture model of Abeta deposition. Slice cultures were treated with Abeta either with or without one of the TGF-beta isoforms. All three isoforms can increase Abeta accumulation (over Abeta treatment alone) within the slice culture, as determined by ELISA. However, there are striking differences in the pattern of Abetair among the three isoforms of TGF-beta. Isoforms 1 and 3 produced a cellular pattern of Abeta staining that colocalizes with GS lectin staining (microglia). TGF-beta2 produces dramatic Abeta staining of pyramidal neurons in layers CA1-CA2. In addition to cellular Abeta staining, plaque-like deposits are increased by all of the TGF-betas. Although no gross toxicity was observed, morphological neurodegenerative changes were seen in the CA1 region when the slices were treated with Abeta plus TGF-beta2. Our results demonstrate important functional differences among the TGF-beta isoforms in their ability to alter the cellular distribution and degradation of Abeta. These changes may be relevant to the pathology of Alzheimer's disease (AD).

Microglia and macrophages are major sources of locally produced transforming growth factor-beta1 after transient middle cerebral artery occlusion in rats

The potentially neurotrophic cytokine transforming growth factor-beta1 (TGF-beta1) is locally expressed following human stroke and experimental ischemic lesions, but the cellular source(s) and profile of induction have so far not been established in experimental focal cerebral ischemia. This study presents the time course and a cellular localization of TGF-beta1 mRNA, visualized by in situ hybridization combined with immunohistochemical staining for microglia, macrophages, or astrocytes, on brain sections from adult spontaneously hypertensive rats subjected to transient proximal occlusion of their middle cerebral artery. Six hours after ischemia, an early and transient neuronal and microglial expression of TGF-beta1 mRNA was observed in the extraischemic cingulate and frontal cortices. Both early and protracted expression of TGF-beta1 mRNA in the caudate-putamen and neocortical infarcts and in the caudate-putamen penumbra colocalized with OX42/ED1-immunoreactive microglia and macrophages, whereas TGF-beta1 mRNA in the neocortical penumbra colocalized with OX42/ED1-immunoreactive cells of a microglial morphology. No astrocytes were double-labeled. The number of TGF-beta1 mRNA-expressing microglia and macrophages increased strongly during the first week. Thereafter, TGF-beta1 mRNA became increasingly restricted to the neocortical penumbra (3 weeks), and after 3 months it was confined to activated microglia in the anterior commissure. Our data establish activated microglia and macrophages as the major source of TGF-beta1 mRNA following experimental focal cerebral ischemia. Consequently, TGF-beta1-mediated functions may be exerted by microglia both in the early degenerative phase, and later in combination with blood-borne macrophages, in the remodeling and healing phase after focal cerebral ischemia.

TGF-beta receptors-I and -II immunoexpression in Alzheimer's disease: a comparison with aging and progressive supranuclear palsy

The transforming growth factor-betas (TGF-betas) influence cell survival, and TGF-beta2 shows increased immunoexpression in neurofibrillary tangle-bearing neurons and reactive glia in Alzheimer's disease (AD) and progressive supranuclear palsy (PSP). We compared immunohistochemical expression of TGF-beta type I (RI) and type II (RII) receptors in eight patients with AD, eight controls and three cases of progressive supranuclear palsy. Mild intraneuronal immunoreactivity for the RI receptor was observed in all cases. Intraneuronal TGF-beta RII receptor immunoexpression was more common in all groups, and its frequency did not differ between groups. We observed increased immunoreactivity for both RI and RII subtypes in reactive glia in the AD frontal cortex (RI: U = 0.5, p = 0.002; and RII: U = 9.000, p = 0.006) and parahippocampal gyrus (RI: U = 9.500, p = 0.013; RII: U = 14.5, p = 0.05) compared to control cases. We conclude that TGF-beta RI and II immunoreactivity is increased in reactive glia in AD and progressive supranuclear palsy, and RI immunoreactivity may occasionally be increased in neurons in cases with advanced AD.

Regulation of the spatiotemporal pattern of expression of the glutamine synthetase gene

Glutamine synthetase, the enzyme that catalyzes the ATP-dependent conversion of glutamate and ammonia into glutamine, is expressed in a tissue-specific and developmentally controlled manner. The first part of this review focuses on its spatiotemporal pattern of expression, the factors that regulate its levels under (patho)physiological conditions, and its role in glutamine, glutamate, and ammonia metabolism in mammals. Glutamine synthetase protein stability is more than 10-fold reduced by its product glutamine and by covalent modifications. During late fetal development, translational efficiency increases more than 10-fold. Glutamine synthetase mRNA stability is negatively affected by cAMP, whereas glucocorticoids, growth hormone, insulin (all positive), and cAMP (negative) regulate its rate of transcription. The signal transduction pathways by which these factors may regulate the expression of glutamine synthetase are briefly discussed. The second part of the review focuses on the evolution, structure, and transcriptional regulation of the glutamine synthetase gene in rat and chicken. Two enhancers (at -6.5 and -2.5 kb) were identified in the upstream region and two enhancers (between +156 and +857 bp) in the first intron of the rat glutamine synthetase gene. In addition, sequence analysis suggests a regulatory role for regions in the 3' untranslated region of the gene. The immediate-upstream region of the chicken glutamine synthetase gene is responsible for its cell-specific expression, whereas the glucocorticoid-induced developmental appearance in the neural retina is governed by its far-upstream region.

Chronic fatigue syndrome: an immunological perspective

OBJECTIVE

The aim of this study is to review research examining an immunological basis for chronic fatigue syndrome (CFS) and to discuss how a disturbance in immunity could produce central nervous system (CNS)-mediated symptoms.

METHOD

Data relevant to the hypothesis that abnormal cytokine release plays a role in the pathogenesis of CFS are reviewed as well as recent evidence relating to potential mechanisms by which immune products may enter the brain and produce a disturbance in CNS processes.

RESULTS

Examinations of cytokine levels in patients with CFS have produced inconclusive results. Recent evidence suggests that abnormal release of cytokines within the CNS may cause neural dysfunction by a variety of complex mechanisms.

CONCLUSION

Neuropsychiatric symptoms in patients with CFS may be more closely related to disordered cytokine production by glial cells within the CNS than to circulating cytokines. This possibility is discussed in the context of unresolved issues in the pathogenesis of CFS.

Cytokine Regulation of Human Microglial Cell IL-8 Production

IL-8 involvement in neutrophil activation and chemotaxis may be important in inflammatory responses within the central nervous system, secondary to meningitis, encephalitis, and traumatic injury. The source of IL-8 within the brain during these inflammatory processes, however, is unknown. To explore the role of microglia in the production of IL-8, human fetal microglia, which are the resident macrophages of the brain, were treated with LPS and pro- and anti-inflammatory cytokines to determine their effects on IL-8 production. We found that IL-8 protein levels increased in response to LPS or IL-1β, or to TNF-α, which also corresponded to elevated IL-8 mRNA levels by RT-PCR. Pretreatment with IL-4, IL-10, or TGF-β1 potently inhibited the stimulatory effects of these proinflammatory agents. These findings indicate that human microglia synthesize IL-8 in response to proinflammatory stimuli, and that anti-inflammatory cytokines down-regulate the production of this chemokine. These results may have important therapeutic implications for certain central nervous system insults involving inflammation.

Endothelial cell conditioned media mediated regulation of glutamine synthetase activity in glial cells

The responsiveness of late passage C-6 glial cells to human retinal endothelial cell-conditioned medium (HREC-CM) was examined using glutamine synthetase (GS) activity as test parameter. Treatment with 50% or 100% HREC-CM for 4-5 days slightly affected the morphology but significantly increased GS activity. Increased glial GS activity induced by vascular endothelial cells is of relevance in preventing extracellular glutamate toxicity and regulating the brain/retinal blood barrier.

TGF-beta in the central nervous system: potential roles in ischemic injury and neurodegenerative diseases

The Transforming Growth Factor-betas (TGF-beta) are a group of multifunctional proteins whose cellular sites of production and action are widely distributed throughout the body, including the central nervous system (CNS). Within the CNS, various isoforms of TGF-beta are produced by both glial and neural cells. When evaluated in either cell culture or in vivo models, the various isoforms of TGF-beta have been shown to have potent effects on the proliferation, function, or survival of both neurons and all three glial cell types, astrocytes, microglia and oligodendrocytes. TGF-beta has also been shown to play a role in several forms of acute CNS pathology including ischemia, excitotoxicity and several forms of neurodegenerative diseases including multiple sclerosis, Parkinson's disease, AIDS dementia and Alzheimer's disease.

Gender differences in host defense mechanisms

Extensive studies in both humans and animals have shown that females express enhanced levels of immunoreactivity compared to males. Whereas this provides females with increased resistance to many types of infection, it also makes them more susceptible to autoimmune diseases. This review will focus on gender-related differences in non-specific host defense mechanisms with a particular emphasis on monocyte/macrophage function and a primary product of monocytes: interleukin-1 (IL-1). Immunomodulatory cytokines such as IL-1 are influenced by gender-sensitive hormones, and reciprocally, these cytokines influence gender-specific hormones and tissues. Patients with chronic fatigue syndrome (CFS) are predominantly women, therefore it may be useful to look toward gender-specific differences in immune function to find a key for this poorly understood syndrome.

Stimulation of glutamine synthetase activity by excitatory amino acids in astrocyte cultures derived from aged mouse cerebral hemispheres may be associated with non-N-methyl-D-aspartate receptor activation

We have been using glial cells derived from aged mouse cerebral hemispheres (MACH) at several passages to study the responsiveness of astrocytes to microenvironmental signals in culture. In the present study, we examined the effects of excitatory amino acids on the activity of glutamine synthetase, a marker for astrocytes. MACH glia cell passages 25 to 29 were used. Culture groups were Dulbecco's modified Eagle's medium +10% fetal bovine serum (control); glutamate 100 microM; gamma-amino-3-hydroxy-5-methyl isoxazole-4-propionic acid (AMPA) 50 microM; kainic acid 10 microM; N-methyl-D-aspartate (NMDA) 10 microM. In all treated groups glutamine synthetase activity was significantly higher than in controls. We speculate that this increase represents an enhanced differentiation of immature astrocytes. In a second series, we examined the effects of glutamate receptor antagonists on glutamine synthetase activity as follows. MACH cultures were treated with glutamate 100 microM in combinations with either L(+)-2-amino-3-phosphonopropionic acid (L-AP3; 50 microM); D(-)-2-amino-5-phosphonopentanoic acid (D-AP5; 50 microM) or 6,7-dinitroquinoxaline-2,3-dione (DNQX, 50 microM). The increase in GS activity produced by glutamate was inhibited by the non-selective NMDA receptor antagonist, DNQX, but not by the metabotropic receptor antagonist, L-AP3 or a selective NMDA receptor antagonist, D-AP5. We also found that in cultures treated with glutamate, a number of astrocytes resembled "reactive astrocytes" morphologically. These astrocytes were absent in cultures treated with glutamate+DNQX. The findings provide supportive evidence that astrocytes from aged mouse cerebral hemispheres respond to excitatory amino acids and that this response is mediated by non-NMDA receptor activation.

Opposite effects of TGF-beta 1 on rapidly- and slowly-triggered excitotoxic injury

Transforming growth factor-beta (TGF-beta) has been shown to protect central neurons against diverse metabolic and excitotoxic challenges. We induced different types of excitotoxic injury on cultured rat hippocampal neurons and investigated TGF-beta 1 for its protective activity. TGF-beta 1 (0.3-10 ng/ml) effectively blocked excitotoxic injury of cultured rat hippocampal neurons induced by short-term exposure to the selective agonist N-methyl-D-aspartate (NMDA; 100 microM, 20 min). Excitotoxic injury caused by long-term exposure to the non-NMDA agonists kainate (50 microM, 24 hr) or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA; 10 microM, 24 hr) caused a similar reduction in neuronal viability. However, treatments with TGF-beta 1 (0.1-10 ng/ml) actually potentiated this slowly-triggered excitotoxic injury. Cultures of rat cerebellar neurons enriched for Purkinje cells have been shown to express AMPA/kainate receptors with significant permeability to Ca2+ and to be uniquely sensitive to non-NMDA receptor-mediated neurotoxicity. In this culture system, short-term exposure to kainate (100 microM; 30 min) in Na(+)-free extracellular solution caused a pronounced decrease in neuronal viability, and this toxicity was also significantly reduced in cultures treated with TGF-beta 1 (10 ng/ml). These results suggest that TGF-beta 1 has the capacity to protect neurons against rapidly-triggered, Ca(2+)-mediated excitotoxic injury, but significantly potentiates slowly-triggered types of excitotoxic injury. This complex action of TGF-beta 1 could have important implications for the use of TGF-beta s and related growth factors in the treatment of neurodegenerative diseases.

Cytokine-stimulated astrocytes damage human neurons via a nitric oxide mechanism

Astrocytes have been reported to play a neuropathogenic role within the brain, although little is known about the mechanism underlying astrocyte-mediated neuronal injury. We investigated the hypothesis that cytokine-stimulated astrocytes adversely affect neuronal cell survival via generation of the free radical nitric oxide (NO). Primary human astrocytes produced substantial amounts of NO in response to interleukin (IL)-1 alpha or IL-1 beta, which was blocked by the NO synthase inhibitor NG-mono-methyl-L-arginine (NMMA). IL-1 beta-induced NO production was markedly potentiated by interferon (IFN)-gamma. IL-1 receptor agonist protein (IRAP) totally blocked NO generation by cytokine-stimulated astrocytes. Using reverse transcription-polymerase chain reaction and sequencing analyses of the astrocyte NO synthase gene, we found a single band encoding for a 615 bp product that was identical to the corresponding sequence reported for human hepatocytes. Treatment of human fetal brain cell cultures with IL-1 beta plus IFN-gamma resulted in marked neuronal loss, as assessed by microscopic analysis and measurement of lactate dehydrogenase release. This cytokine-induced neuronal damage was blocked by simultaneous treatment of the brain cell cultures with NMMA or IRAP, suggesting a critical role of IL-1. These findings indicate that cytokine-stimulated astrocytes are neurotoxic via a NO-mediated mechanism and point to potential new therapies for neurodegenerative disorders that involve cytokines and reactive astrocytes.

Transforming growth factor-beta2 increases NMDA receptor-mediated excitotoxicity in rat cerebral cortical neurons independently of glia

The ability of transforming growth factor-beta2 (TGFbeta2) to directly regulate neuronal sensitivity to glutamate and N-methyl-D-aspartate (NMDA) excitotoxicity in rat cerebral cortical neurons was investigated. Mixed neuronal-glial cultures treated with TGFbeta2 (1-10 ng/ml) exhibited a significant 25-50% increase in neuronal death compared to control cultures. TGFbeta2 potentiation of this endogenous glutamate excitotoxicity was blocked by the selective NMDA receptor antagonist, 2-amino-5-phosphonovalerate. In addition, neuronal death induced by brief NMDA exposure in both mixed neuronal-glial and pure neuronal cultures was increased by TGFbeta2 (1-30 ng/ml) with a similar dose-response curve. These findings indicate that TGFbeta2, at physiologically relevant concentrations, potentiates NMDA receptor-mediated excitotoxicity and that this occurs independently of TGFbeta2 effects on glia.

Effects of exogenous transforming growth factor-beta 1 on spinal cord injury in rats

This study was undertaken to examine the effect of transforming growth factor-beta 1 (TGF-beta 1) administered into the subarachnoid space after spinal cord injury (SCI) on the increased production of inducible-nitric oxide synthase (i-NOS) in the injured spinal cord in rats. The expression of i-NOS mRNA after SCI was remarkably down-regulated by TGF-beta 1 in vivo. Rats treated with TGF-beta 1 showed a better outcome regarding hindlimb motor dysfunction in the first 5 days after injury compared to the saline-treated rats. However, the final outcome was not better and fibrous scar formation in the injured spinal cord was more evident, which was demonstrated as increased immunoreactivity of fibronectin in the later stage after SCI. These results provide evidence of both positive and negative contributions of TGF-beta 1 to the pathology associated with SCI.