Analysis of cytokine receptor messenger RNA expression in human glioblastoma cells and normal astrocytes by reverse-transcription polymerase chain reaction

Insights into the glioblastoma tumor microenvironment: current and emerging therapeutic approaches

Glioblastoma (GB) is an intrusive and recurrent primary brain tumor with low survivability. The heterogeneity of the tumor microenvironment plays a crucial role in the stemness and proliferation of GB. The tumor microenvironment induces tumor heterogeneity of cancer cells by facilitating clonal evolution and promoting multidrug resistance, leading to cancer cell progression and metastasis. It also plays an important role in angiogenesis to nourish the hypoxic tumor environment. There is a strong interaction of neoplastic cells with their surrounding microenvironment that comprise several immune and non-immune cellular components. The tumor microenvironment is a complex network of immune components like microglia, macrophages, T cells, B cells, natural killer (NK) cells, dendritic cells and myeloid-derived suppressor cells, and non-immune components such as extracellular matrix, endothelial cells, astrocytes and neurons. The prognosis of GB is thus challenging, making it a difficult target for therapeutic interventions. The current therapeutic approaches target these regulators of tumor micro-environment through both generalized and personalized approaches. The review provides a summary of important milestones in GB research, factors regulating tumor microenvironment and promoting angiogenesis and potential therapeutic agents widely used for the treatment of GB patients.

Blood-Brain Barrier Breakdown: An Emerging Biomarker of Cognitive Impairment in Normal Aging and Dementia

The blood–brain barrier (BBB) plays a vital role in maintaining the specialized microenvironment of the neural tissue. It separates the peripheral circulatory system from the brain parenchyma while facilitating communication. Alterations in the distinct physiological properties of the BBB lead to BBB breakdown associated with normal aging and various neurodegenerative diseases. In this review, we first briefly discuss the aging process, then review the phenotypes and mechanisms of BBB breakdown associated with normal aging that further cause neurodegeneration and cognitive impairments. We also summarize dementia such as Alzheimer's disease (AD) and vascular dementia (VaD) and subsequently discuss the phenotypes and mechanisms of BBB disruption in dementia correlated with cognition decline. Overlaps between AD and VaD are also discussed. Techniques that could identify biomarkers associated with BBB breakdown are briefly summarized. Finally, we concluded that BBB breakdown could be used as an emerging biomarker to assist to diagnose cognitive impairment associated with normal aging and dementia.

The Role of Astrocytes in the Modulation ofK+-Cl--Cotransporter-2 Function

Neuropathic pain is characterized by spontaneous pain, pain sensations, and tactile allodynia. The pain sensory system normally functions under a fine balance between excitation and inhibition. Neuropathic pain arises when this balance is lost for some reason. In past reports, various mechanisms of neuropathic pain development have been reported, one of which is the downregulation of K+-Cl--cotransporter-2 (KCC2) expression. In fact, various neuropathic pain models indicate a decrease in KCC2 expression. This decrease in KCC2 expression is often due to a brain-derived neurotrophic factor that is released from microglia. However, a similar reaction has been reported in astrocytes, and it is unclear whether astrocytes or microglia are more important. This review discusses the hypothesis that astrocytes have a crucial influence on the alteration of KCC2 expression.

An atlas of genetic correlations between psychiatric disorders and human blood plasma proteome

BACKGROUND

Psychiatric disorders are a group of complex psychological syndromes with high prevalence. Recent studies observed associations between altered plasma proteins and psychiatric disorders. This study aims to systematically explore the potential genetic relationships between five major psychiatric disorders and more than 3,000 plasma proteins.

METHODS

The genome-wide association study (GWAS) datasets of attention deficiency/hyperactive disorder (ADHD), autism spectrum disorder (ASD), bipolar disorder (BD), schizophrenia (SCZ) and major depressive disorder (MDD) were driven from the Psychiatric GWAS Consortium. The GWAS datasets of 3,283 human plasma proteins were derived from recently published study, including 3,301 study subjects. Linkage disequilibrium score (LDSC) regression analysis were conducted to evaluate the genetic correlations between psychiatric disorders and each of the 3,283 plasma proteins.

RESULTS

LDSC observed several genetic correlations between plasma proteins and psychiatric disorders, such as ADHD and lysosomal Pro-X carboxypeptidase (p value = 0.015), ASD and extracellular superoxide dismutase (Cu-Zn; p value = 0.023), BD and alpha-N-acetylgalactosaminide alpha-2,6-sialyltransferase 6 (p value = 0.007), MDD and trefoil factor 1 (p value = 0.011), and SCZ and insulin-like growth factor-binding protein 6 (p value = 0.011). Additionally, we detected four common plasma proteins showing correlation evidence with both BD and SCZ, such as tumor necrosis factor receptor superfamily member 1B (p value = 0.012 for BD, p value = 0.011 for SCZ).

CONCLUSIONS

This study provided an atlas of genetic correlations between psychiatric disorders and plasma proteome, providing novel clues for pathogenetic and biomarkers, therapeutic studies of psychiatric disorders.

Delineating Astrocytic Cytokine Responses in a Human Stem Cell Model of Neural Trauma

Neuroinflammation has been shown to mediate the pathophysiological response following traumatic brain injury (TBI). Accumulating evidence implicates astrocytes as key immune cells within the central nervous system (CNS), displaying both pro- and anti-inflammatory properties. The aim of this study was to investigate how in vitro human astrocyte cultures respond to cytokines across a concentration range that approximates the aftermath of human TBI. To this end, enriched cultures of human induced pluripotent stem cell (iPSC)-derived astrocytes were exposed to interleukin-1β (IL-1β) (1–10,000 pg/mL), IL-4 (1–10,000 pg/mL), IL-6 (100–1,000,000 pg/mL), IL-10 (1–10,000 pg/mL) and tumor necrosis factor (TNF)-α (1–10,000 pg/mL). After 1, 24, 48 and 72 h, cultures were fixed and immunolabeled, and the secretome/supernatant was analyzed at 24, 48, and 72 h using a human cytokine/chemokine 39-plex Luminex assay. Data were compared to previous in vitro studies of neuronal cultures and clinical TBI studies. The secretome revealed concentration-, time- and/or both concentration- and time-dependent production of downstream cytokines (29, 21, and 17 cytokines, respectively, p<0.05). IL-1β exposure generated the most profound downstream response (27 cytokines), IL-6 and TNF had intermediate responses (13 and 11 cytokines, respectively), whereas IL-4 and IL-10 only led to weak responses over time or in escalating concentration (8 and 8 cytokines, respectively). Notably, expression of IL-1β, IL-6, and TNF cytokine receptor mRNA was higher in astrocyte cultures than in neuronal cultures. Several secreted cytokines had temporal trajectories, which corresponded to those seen in the aftermath of human TBI. In summary, iPSC-derived astrocyte cultures exposed to cytokine concentrations reflecting those in TBI generated an increased downstream cytokine production, particularly IL-1β. Although more work is needed to better understand how different cells in the CNS respond to the neuroinflammatory milieu after TBI, our data shows that iPSC-derived astrocytes represent a tractable model to study cytokine stimulation in a cell type-specific manner.

Tumor necrosis factor reduces the amplitude of rat cortical spreading depression in vivo

OBJECTIVE

Brain damage and ischemia often trigger cortical spreading depression (CSD), which aggravates brain damage. The proinflammatory cytokine tumor necrosis factor (TNF) is significantly upregulated during brain damage, but it is unknown whether TNF influences spreading depression in cerebral cortex in vivo. This question is important because TNF not only furthers inflammatory reactions but might also be neuroprotective. Here we tested the hypothesis that TNF affects CSD, and we explored the direction in which CSD is modified by TNF.

METHODS

CSD, elicited by pressure microinjection of KCl, was recorded in anesthetized rats and mice. TNF was administered locally into a trough, providing local TNF treatment of a cortical area. For further analysis, antibodies to TNF receptor (TNFR) 1 or 2 were applied, or CSD was monitored in TNFR1 and TNFR2 knockout mice. γ-Aminobutyric acid (GABA)A receptors were blocked by bicuculline. Immunohistochemistry localized the cortical expression of TNFR1 and TNFR2.

RESULTS

Local application of TNF to the cortex reduced dose-dependently the amplitude of CSD. This effect was prevented by blockade or knockout of TNFR2 but not by blockade or knockout of TNFR1. TNFR2 was localized at cortical neurons including parvalbumin-positive inhibitory interneurons, and blockade of GABAA receptors by bicuculline prevented the reduction of CSD amplitudes by TNF.

INTERPRETATION

We identified a functional link between TNF and CSD. TNF activates TNFR2 in cortical inhibitory interneurons. The resulting release of GABA reduces CSD amplitudes. In this manner, TNF might be neuroprotective in pathological conditions.

Reciprocal Supportive Interplay between Glioblastoma and Tumor-Associated Macrophages

Glioblastoma multiforme (GBM) is the most lethal and aggressive type of primary brain malignancy. Failures of the traditional therapies in treating GBMs raise the urgent requirement to develop new approaches with more responsive targets. The phenomenon of the high infiltration of tumor-associated macrophages (TAMs) into GBMs has been observed for a long time. Regardless of the limited knowledge about TAMs, the high percentage of supportive TAM in GBM tumor mass makes it possible to be a good target for GBM treatment. In this review, we discussed the unique features of TAMs in GBMs, including their origin, the tumor-supportive properties, the secreted cytokines, and the relevant mechanisms. In addition, we tried to interpret the current understandings about the interplay between GBM cancer cells and TAMs. Finally, the translational studies of targeting TAMs were also described.

Blood-brain barrier dysfunction as a cause and consequence of Alzheimer's disease

The blood-brain barrier (BBB) plays critical roles in the maintenance of central nervous system (CNS) homeostasis. Dysfunction of the BBB occurs in a number of CNS diseases, including Alzheimer's disease (AD). A prevailing hypothesis in the AD field is the amyloid cascade hypothesis that states that amyloid-β (Aβ) deposition in the CNS initiates a cascade of molecular events that cause neurodegeneration, leading to AD onset and progression. In this review, the participation of the BBB in the amyloid cascade and in other mechanisms of AD neurodegeneration will be discussed. We will specifically focus on three aspects of BBB dysfunction: disruption, perturbation of transporters, and secretion of neurotoxic substances by the BBB. We will also discuss the interaction of the BBB with components of the neurovascular unit in relation to AD and the potential contribution of AD risk factors to aspects of BBB dysfunction. From the results discussed herein, we conclude that BBB dysfunction contributes to AD through a number of mechanisms that could be initiated in the presence or absence of Aβ pathology.

Immunobiology of malignant gliomas

The immune system of patients with malignant gliomas is profoundly suppressed. The suppression involves both the cellular and humoral immunity and it is mainly attributable to selective depletion and malfunction of helper T cells. Malignant glioma cells express potent immunosuppressive factors such as transforming growth factor-beta(2), inteleukin-10 and prostaglandin E(2). Malignant glioma cells also produce chemoattractants and immunostimulatory cytokines which may activate the immune cells. However, the production of these stimulatory cytokines is not self-destructive to glioma cells because of the immunosuppression. Rather, the tumour cells use them to gain a growth advantage. Indeed the cytokines may act as a growth stimulator of the tumour cells themselves (autocrine mechanism), they may act as angiogenic factors to endothelial cells (paracrine mechanism) or induce the attracted immune cells to secrete angiogenic factors. Some cytokines produced by malignant glioma cells are known to be growth inhibitory to normal astrocytes. Recent studies on tumour suppressor genes suggest a close link between the aberrant genes and the immunobiologic features of malignant glioma cells.

Reactive astrogliosis after spinal cord injury-beneficial and detrimental effects

Reactive astrogliosis is a pathologic hallmark of spinal cord injury (SCI). It is characterised by profound morphological, molecular, and functional changes in astrocytes that occur within hours of SCI and evolves as time elapses after injury. Astrogliosis is a defense mechanism to minimize and repair the initial damage but eventually leads to some detrimental effects. Reactive astrocytes secrete a plethora of both growth promoting and inhibitory factors after SCI. However, the production of inhibitory components surpasses the growth stimulating factors, thus, causing inhibitory effects. In severe cases of injury, astrogliosis results in the formation of irreversible glial scarring that acts as regeneration barrier due to the expression of inhibitory components such as chondroitin sulfate proteoglycans. Scar formation was therefore recognized from a negative perspective for many years. Accumulating evidence from pharmacological and genetic studies now signifies the importance of astrogliosis and its timing for spinal cord repair. These studies have advanced our knowledge regarding signaling pathways and molecular mediators, which trigger and modulate reactive astrocytes and scar formation. In this review, we discuss the recent advances in this field. We also review therapeutic strategies that have been developed to target astrocytes reactivity and glial scaring in the environment of SCI. Astrocytes play pivotal roles in governing SCI mechanisms, and it is therefore crucial to understand how their activities can be targeted efficiently to harness their potential for repair and regeneration after SCI.

Granulocyte-macrophage colony-stimulating factor as an autocrine survival-growth factor in human gliomas

We studied the expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) and its receptors (GM-CSF.R) in 20 human brain gliomas with different tumor gradings and demonstrated constitutive high levels of both mRNA gene expression and protein production exclusively in the highest-grade tumors (WHO, III-IV grade). Five astrocytic cell lines were isolated in vitro from glioma cells, which had selectively adhered to plates pre-coated with rhGM-CSF. These cells were tumorigenic when xenografted to athymic mice, and produced GM-CSF constitutively in culture. Two lines, particularly lines AS1 and PG1, each from a patient with glioblastoma multiforme, constitutively over-expressed both GM-CSF and GM-CSF.R genes and secreted into their culture media biologically active GM-CSF. Different clones of the AS1 line, isolated after subsequent passages in vitro and then transplanted to athymic mice, demonstrated higher tumorigenic capacity with increasing passages in vivo. Cell proliferation was stimulated by rhGM-CSF in late-stage malignant clones, whereas apoptosis occurred at high frequency in the presence of blocking anti-GM-CSF antibodies. In contrast, rhGM-CSF did not induce any apparent effect in early-stage clones expressing neither GM-CSF nor GM-CSF.R. The addition of rhGM-CSF or rhIL-1β, to cultures induced the overproduction of both GM-CSF and its receptors and increased gene activation for several functional proteins (e.g. NGF, VEGF, VEGF.R1, G-CSF, MHC-II), indicating that these cells may undergo dynamic changes in response to environmental stimuli. These findings thus revealed: (1) that the co-expression of both autocrine GM-CSF and GM-CSF.R correlates with the advanced tumor stage; (2) that an important contribution of GM-CSF in malignant glioma cells is the prevention of apoptosis. These results imply that GM-CSF has an effective role in the evolution and pathogenesis of gliomas.

c-Jun and c-Fos regulate the complement factor H promoter in murine astrocytes

The complement system is a critical component of innate immunity that requires regulation to avoid inappropriate activation. This regulation is provided by many proteins, including complement factor H (CFH), a critical regulator of the alternative pathway of complement activation. Given its regulatory function, mutations in CFH have been implicated in diseases such as age-related macular degeneration and membranoproliferative glomerulonephritis, and central nervous system diseases such as Alzheimer's disease, Parkinson's disease, and a demyelinating murine model, experimental autoimmune encephalomyelitis (EAE). There have been few investigations on the transcriptional regulation of CFH in the brain and CNS. Our studies show that CFH mRNA is present in several CNS cell types. The murine CFH (mCFH) promoter was cloned and examined through truncation constructs and we show that specific regions throughout the promoter contain enhancers and repressors that are positively regulated by inflammatory cytokines in astrocytes. Database mining of these regions indicated transcription factor binding sites conserved between different species, which led to the investigation of specific transcription factor binding interactions in a 241 base pair (bp) region at -416 bp to -175 bp that showed the strongest activity. Through supershift analysis, it was determined that c-Jun and c-Fos interact with the CFH promoter in astrocytes in this region. These results suggest a relationship between cell cycle and complement regulation, and how these transcription factors and CFH affect disease will be a valuable area of investigation.

Detailed analysis of inflammatory and neuromodulatory cytokine secretion from human NT2 astrocytes using multiplex bead array

Astrocytes are a very important cell type in the brain fulfilling roles in both neuroimmunology and neurotransmission. We have conducted the most comprehensive analysis of secreted cytokines conducted to date (astrocytes of any source) to determine whether astrocytes derived from the human Ntera2 (NT2) cell-line are a good model of human primary astrocytes. We have compared the secretion of cytokines from NT2 astrocytes with those produced in astrocyte enriched human brain cultures and additional cytokines implicated in brain injury or known to be expressed in the human brain. The concentration of cytokines was measured in astrocyte conditioned media using multiplex bead array (MBA), where 18 cytokines were measured simultaneously. Resting NT2 astrocytes produced low levels (∼1-30 pg/ml) of MIP1α, IL-6 and GM-CSF and higher levels of MCP-1, IP-10 and IL-8 (1-11 ng/ml) under non-inflammatory conditions. All of these in addition to IL-1β, TNFα, and IL-13, were increased by pro-inflammatory activation (TNFα or IL-1β stimulation). In contrast, IL-2, IL-4, IL-5, IL-7, IL-10, IL-12, LTα, and IFNγ were not detected in astrocyte conditioned media under any of the culture conditions tested. NT2 astrocytes were unresponsive to IL-2 and the adenyl cyclase agonist, forskolin. Interestingly, IFNγ stimulation selectively increased IP-10 secretion only. As astrocytes stimulated with IL-1β or TNFα produced several chemokines in the ng/ml range, we next assessed the chemoattractant properties of these cells. Conditioned media from TNFα-stimulated astrocytes significantly chemoattracted leukocytes from human blood. This study provides the most comprehensive analysis of cytokine production by human astrocytes thus far, and shows that NT2 astrocytes are highly responsive to pro-inflammatory mediators including TNFα and IL-1β, producing cytokines and chemokines capable of attracting leukocytes from human blood. We conclude that in the absence of adult human primary astrocytes that NT2-astrocytes may provide a valuable alternative to study the immunological behaviour of human astrocytes.

Sleeping beauty-mediated somatic mutagenesis implicates CSF1 in the formation of high-grade astrocytomas

The Sleeping Beauty (SB) transposon system has been used as an insertional mutagenesis tool to identify novel cancer genes. To identify glioma-associated genes, we evaluated tumor formation in the brain tissue from 117 transgenic mice that had undergone constitutive SB-mediated transposition. Upon analysis, 21 samples (18%) contained neoplastic tissue with features of high-grade astrocytomas. These tumors expressed glial markers and were histologically similar to human glioma. Genomic DNA from SB-induced astrocytoma tissue was extracted and transposon insertion sites were identified. Insertions in the growth factor gene Csf1 were found in 13 of the 21 tumors (62%), clustered in introns 5 and 8. Using reverse transcription-PCR, we documented increased Csf1 RNAs in tumor versus adjacent normal tissue, with the identification of transposon-terminated Csf1 mRNAs in astrocytomas with SB insertions in intron 8. Analysis of human glioblastomas revealed increased levels of Csf1 RNA and protein. Together, these results indicate that SB-insertional mutagenesis can identify high-grade astrocytoma-associated genes and they imply an important role for CSF1 in the development of these tumors.

Analysis of interleukin (IL)-8 expression in human astrocytomas: associations with IL-6, cyclooxygenase-2, vascular endothelial growth factor, and microvessel morphometry

Malignant astrocytomas are highly vascular neoplasms with potent angiogenic activity. The present study aimed to investigate peripheral and local expression of interleukin (IL)-8 in astrocytomas with possible associations to IL-6, cyclooxygenase-2 (COX-2), vascular endothelial growth factor (VEGF) expression, and microvessel morphometry. IL-6- and IL-8-secreting peripheral blood monocytes (PBMCs) were evaluated in 17 glioblastoma (WHO grade IV), 5 anaplastic astrocytoma (WHO grade III), and 6 diffuse astrocytoma patients (WHO grade II), in parallel with 23 healthy controls using enzyme-linked immunosorbent spot (ELISPOT) assay. The IL-8 expression was assessed immunohistochemically in patients' tumor tissue sections and correlated with the expression of COX-2, VEGF, IL-6, and microvessel morphometry (assessed using CD34 antibody). Eighteen cases were also stained for CD31 and used as an additional vessel marker to validate our results regarding microvessel morphometry. IL-6 and IL-8 were highly secreted in the PBMCs of glioma patients compared with controls (p = 0.0001, p < 0.0001, respectively), with a positive correlation between IL-8 expression and secretion levels (p = 0.001). IL-8 immunoreactivity was detected in malignant cells or macrophages in perivascular areas and in pseudopalisading cells around necrosis and was positively correlated with histological grade (p = 0.0175) and tumor necrosis (p = 0.0793). IL-6 and IL-8 expression levels were positively correlated (p = 0.0036) and associated with COX-2 and VEGF expression (IL-6: p = 0.0133, p = 0.065; IL-8: p = 0.0139, p = 0.0101), but not with microvessel morphometry, by either CD31 or CD34. The coordinate expression and topographical relationship of IL-6, IL-8, COX-2, and VEGF in the same tumor areas (e.g., perinecrotic areas) attest to their intimate liaison in terms of cancer-induced angiogenesis, which is probably secondary to the induction of multiple interdependent molecular pathways. Moreover, our study seems to be the first attempt to link IL-8 expression by tumor cells with histological grade, implicating its potent role in gliomagenesis.

Molecular mechanisms of the combination of retinoid and interferon-gamma for inducing differentiation and increasing apoptosis in human glioblastoma T98G and U87MG cells

Glioblastoma is the deadliest brain tumor that remains incurable. We examined efficacy of combination of retinoid and interferon-gamma (IFN-gamma) in human glioblastoma T98G and U87MG cells. We conjectured that retinoid could induce differentiation with down regulation of telomerase activity to increase sensitivity to IFN-gamma for apoptosis in glioblastoma cells. Indeed, treatment of cells with 1 muM all-trans retinoic acid (ATRA) or 1 muM 13-cis retinoic acid (13-CRA) for 7 days induced astrocytic differentiation with upregulation of glial fibrillary acidic protein (GFAP) and down regulation of telomerase activity. Wright staining and ApopTag assay showed, respectively, morphological and biochemical features of apoptosis in glioblastoma cells following exposure to 200 units/ml IFN-gamma for 48 h. Induction of differentiation was associated with decreases in levels of nuclear factor kappa B (NFkappaB), inducible nitric oxide synthase (iNOS), and production of nitric oxide (NO) so as to increase sensitivity to IFN-gamma for apoptosis. Notably, IFN-gamma induced signal transducer and activator of transcription-1 (STAT-1) to bind to gamma-activated sequence (GAS) of the target gene. Also, IFN-gamma activated caspase-8 and cleaved Bid to truncated Bid (tBid) for translocation to mitochondria. Fura-2 assay showed increases in intracellular free [Ca2+] and activation of calpain in apoptotic cells. Besides, increases in Bax:Bcl-2 ratio and mitochondrial release of cytochrome c and Smac into the cytosol activated caspase-9 and caspase-3 for apoptosis. Taken together, our results showed that retinoid induced astrocytic differentiation with down regulation of telomerase activity and enhanced sensitivity to IFN-gamma for increasing apoptosis in human glioblastoma cells.

Comparative analysis of peripheral and localised cytokine secretion in glioblastoma patients

BACKGROUND

Malignant gliomas are the most common primary brain tumours of both children and adults. The unique aspects of their biology and anatomic site render them refractory to conventional therapeutic strategies such as surgery and chemotherapy. Significant attention has been given, recently, to immunotherapy which, although promising in preclinical studies, has not yet enhanced the survival of patients with glioblastomas.

METHODS

To further understand the immunobiology of glioblastomas in clinical settings, we examined the secretion of four main cytokines in the peripheral blood and in primary cell cultures of 33 human glioblastoma patients. An ELISPOT methodology was used for the first time to examine Th1, and Th2 cytokine secretion from both peripheral lymphocytes and glioma tumour cells.

RESULTS

Th1 cytokines (tumour necrosis factor (TNF-alpha), interferon (IFN-gamma) were markedly reduced compared to control levels (P=0.01 and P<0.001, respectively), whereas in contrast, Th2 (interleukin (IL)-4 and IL-10) were strongly expressed in both peripheral lymphocytes and glioma cell cultures (P=0.05 and P<0.001, respectively).

CONCLUSION

This pattern indicates an 'immunosuppressive status' in glioblastomas which is related to their origination and the evasion of glioma cells from immune surveillance and could account for the failure of immunotherapy in such tumours. Furthermore, ELISPOT methodology can be used for monitoring of cytokine secretion from tumour cells, in addition to the well-established peripheral cytokine secretion.

Differentiation decreased telomerase activity in rat glioblastoma C6 cells and increased sensitivity to IFN-gamma and taxol for apoptosis

Glioblastoma is the deadliest and most prevalent brain tumor, which is not yet amenable to any treatments. Therefore, new and innovative therapeutic strategies need to be developed for treating this deadly disease. We found that all-trans retinoic acid (ATRA) or 13-cis retinoic acid (13-CRA) induced astrocytic differentiation with down regulation of telomerase activity in rat glioblastoma C6 cells and enhanced sensitivity of the cells to interferon-gamma (IFN-gamma) or taxol (TXL) for apoptosis. Sensitivity of differentiated cells to IFN-gamma or TXL was greatly increased for apoptosis with increases in calcineurin expression, Bax:Bcl-2 ratio, mitochondrial release of cytochrome c, and expression and activity of calpain and caspases. Treatment with IFN-gamma activated caspase-8 indicating induction of apoptosis via the receptor-mediated pathway. Notably, IFN-gamma activated the signal transducer and activator of transcription-1 (STAT-1) for signaling via binding to gamma activator sequence (GAS), whereas TXL activated Raf-1 kinase for inactivation of Bcl-2 by its phosphorylation. We confirmed involvement of different proteolytic mechanisms in cell death by pretreating the cells with caspase-8 inhibitor II, calpeptin (calpain inhibitor), and caspase-9 inhibitor I, and caspase-3 inhibitor IV. Results demonstrated that retinoids induced astrocytic differentiation with down regulation of telomerase activity and worked synergistically to enhance sensitivity of cells to the cytotoxic agent IFN-gamma and the cytostatic agent TXL for apoptosis. This combination therapy for differentiation and apoptosis could be highly effective for controlling the malignant growth of glioblastoma.

Human mesenchymal stem cells constitutively express chemokines and chemokine receptors that can be upregulated by cytokines, IFN-beta, and Copaxone

The factors associated with the migration of marrow-derived mesenchymal stem cells (MSCs) when transplanted into the diseased central nervous system (CNS) are unclear. Chemokines are key mediators of selective cell migration in neurodegenerative diseases and related inflammatory processes. We hypothesized that chemokines are likely to be the chief determinants of MSC migration. We, therefore, systematically assessed the expression and modulating factors for chemokines and chemokine receptors in human MSCs (HuMSCs). The present study demonstrates that unstimulated HuMSCs express a broad range of mRNAs encoding cytokines, chemokines, and their receptors. Using chemotaxis assays, we also assessed the functionality of the receptor expression in HuMSC and we show that CXCL12/stromal cell-derived factor-lalpha (SDF-lalpha), CX3CL1/fractalkine, and CXCL10/interferon-gamma (IFN-gamma)-inducible protein (IP-10) lead to significant HuMSC migration. Moreover, we provide evidence that tumor necrosis factor-alpha (TNF-alpha) and IFN-gamma act as major regulators of the expression of chemokines and their receptors in HuMSCs. Correspondingly, we demonstrate for the first time that current multiple sclerosis (MS) therapies, namely, IFN-beta and Copaxone, influence the expression of chemokines and their receptors in HuMSCs at both mRNA and protein levels. Administration of cytokines, including IFN-beta and Copaxone, may be important in stem cell transplantation therapies and perhaps important in the efficacy of existing MS therapies.

Maintenance treatment with interferon-gamma and low-dose cyclophosphamide for pediatric high-grade glioma

BACKGROUND

The prognosis of high-grade glioma in children is poor.

PURPOSE

Interferon-gamma may increase the immune surveillance of glioma cells. Earlier clinical evidence had shown that low dose cyclophosphamide (CPM) increased immune response.

METHODS

After induction treatment with simultaneous radiation and chemotherapy, patients were treated with individually increasing interferon-gamma (IFN-gamma) doses starting from 25 microg/m2/d s.c. increasing up to a maximum of 175 microg/m2/d within 7 weeks. Cyclophosphamide was given at 300 mg/m2 i.v. every 21 days. Forty pediatric glioma patients were enrolled (median age: 8.5 year, male: n = 22). Tumor locations included cerebral cortex (n = 8), basal ganglia (n = 4), brainstem (n = 24), cerebellum (n = 3), spinal cord (n = 1). Histologies were GBM (n = 14), AA (n = 14), LGG (n = 2, diffuse intrinsic pontine glioma). There was grade IV toxicity for thrombocytopenia (10%) and leucopenia (2.5%), grade III toxicity for central nervous (2.5%) and hepatic (5%) side effects, no toxic death. The observation time of the six surviving patients was: 1.2, 1.9, 4.2, 4.4, 4.6 and 4.7 years respectively. The median overall survival (1 year) was not significantly different from a historical control group (0.8 years). The survival of pontine gliomas appeared even inferior when compared to the previous protocol (n.s.).

CONCLUSION

Maintenance treatment with IFN-gamma and low dose CPM has no sufficient beneficial effect for the treatment of high-grade glioma.

Immunohistochemical analysis of platelet-derived growth factor receptor-alpha, -beta, c-kit, c-abl, and arg proteins in glioblastoma: possible implications for patient selection for imatinib mesylate therapy

Inhibition of tyrosine kinase (TK) receptors by synthetic small molecules has become a promising new therapy option in oncology. The TK inhibitor imatinib mesylate selectively targets PDGFR-alpha, -beta, c-kit, c-abl and arg and has proven successful in the treatment of chronic myeloid leukaemia. In recurrent glioblastoma, phase II therapy trials using imatinib mesylate have been initiated. As only a fraction of patients seems to benefit from imatinib mesylate therapy and due to potential side effects and high costs of imatinib mesylate therapy, selection of the right patients is important. The goal of our study was to assess systematically immunohistochemical expression of the major TKs targeted by imatinib mesylate in glioblastoma, as expression of these factors could be used to select patients for imatinib mesylate therapy. In a cohort of 101 glioblastoma patients, anti-PDGFR-alpha, -beta, c-kit, c-abl and arg protein immunohistochemistry was performed. Expression of these proteins was assessed semi-quantitatively and correlated with patient survival.PDGFR-alpha and arg expression in tumor cells was widespread in 1/101 cases, respectively. Focal PDGFR-alpha, -beta, c-kit, c-abl and arg immunolabeling was detected in 25/101, 19/101, 4/101, 7/101 and 31/101 cases, respectively. Statistical analysis did not reveal any correlation between expression of the TKs and patient survival. We show here for the first time in a large series of glioblastomas that PDGFR-alpha, -beta, c-kit, c-abl and arg expression is immunohistochemically detectable in a fraction of cases. The value of anti-tyrosine kinase immunolabeling as predictive factor for patient selection remains to be clarified by comparative analysis of tumor tissue of therapy-responders versus non-responders.

Neuronal and glioma-derived stem cell factor induces angiogenesis within the brain

Stem cell factor (SCF) is overexpressed by neurons following brain injury as well as by glioma cells; however, its role in gliomagenesis remains unclear. Here, we demonstrate that SCF directly activates brain microvascular endothelial cells (ECs) in vitro and induces a potent angiogenic response in vivo. Primary human gliomas express SCF in a grade-dependent manner and induce normal neurons to express SCF in brain regions infiltrated by glioma cells, areas that colocalize with prominent angiogenesis. Downregulation of SCF inhibits tumor-mediated angiogenesis and glioma growth in vivo, whereas overexpression of SCF is associated with shorter survival in patients with malignant gliomas. Thus, the SCF/c-Kit pathway plays an important role in tumor- and normal host cell-induced angiogenesis within the brain.

CD117 expression in glial tumors

C-kit is a proto-oncogene involved in normal growth and development and neoplastic processes, and its product, CD117, is a highly specific immunohistochemical diagnostic marker for gastrointestinal stromal tumors (GISTs). Because GISTs that express immunohistochemically-detectable CD117 respond dramatically to treatment with tyrosine kinase inhibitors, identification of central nervous system tumors that express CD117 might open new therapeutic approaches for treatment of brain tumors. Specimens from 52 glial tumors of various histologic types and grades were assayed for CD117 immunoreactivity, and about 75% of the tumors were positive for CD117 expression; all except a few exhibited strong cytoplasmic and membranous staining. The proportion of high grade tumors of all tumor types with detectable CD117 immunoreactivity was statistically significantly greater than low grade tumors, and glioblastoma and anaplastic oligodendroglioma showed the highest staining grade. These findings support further investigation into the possibility that CD117 has an important role in growth of glial tumors and that patients with brain tumors expressing CD117 might benefit from treatment with receptor tyrosine kinase inhibitors.

Differential expression, shedding, cytokine regulation and function of TNFR1 and TNFR2 in human fetal astrocytes

Tumor necrosis factor (TNF)-alpha induces pleiotropic cellular effects through a 55kDa, type 1 receptor (TNFR1) and a 75kDa type 2 receptor (TNFR2). Moreover, it participates in the pathogenesis of several CNS diseases, including demyelinating diseases. TNF-alpha receptors are differentially expressed and are regulated in many cell types. However, data regarding the TNF-alpha receptor expression and regulation in human astrocytes is limited to date. We investigated TNF- receptor expression, its regulation by cytokines, and its functional role in primary cultured human fetal astrocytes, which are the most abundant cellular population in the central nervous system and are known to be immunologically active. In this study, astrocytes were found to constitutively and predominantly transcribe, translate and shed TNFR1 rather than TNFR2, but TNFR2 expression was increased by adding TNF-alpha, IL-1, and IFN-gamma, but not by adding LPS. To determine the functional roles of TNFR1 and TNFR2 on TNF induction, we investigated NF-kappaB activation and TNF-alpha induction after neutralizing TNFR1 and TNFR2 by an antibody treatment. We found that NF-kappaB activation and TNF-alpha induction are blocked by TNFR1 neutralizing antibody treatments.

Microglia function in brain tumors

Microglia play an important role in inflammatory diseases of the central nervous system (CNS). These cells have also been identified in brain neoplasms; however, as of yet their function largely remains unclear. More recent studies designed to characterize further tumor-associated microglia suggest that the immune effector function of these cells may be suppressed in CNS tumors. Furthermore, microglia and macrophages can secrete various cytokines and growth factors that may contribute to the successful immune evasion, growth, and invasion of brain neoplasms. A better understanding of microglia and macrophage function is essential for the development of immune-based treatment strategies against malignant brain tumors.

Immune modulation of the hypothalamic-pituitary-adrenal (HPA) axis during viral infection

Compelling data has been amassed indicating that soluble factors, or cytokines, emanating from the immune system can have profound effects on the neuroendocrine system, in particular the hypothalamic- pituitary-adrenal (HPA) axis. HPA activation by cytokines (via the release of glucocorticoids), in turn, has been found to play a critical role in restraining and shaping immune responses. Thus, cytokine-HPA interactions represent a fundamental consideration regarding the maintenance of homeostasis and the development of disease during viral infection. Although reviews exist that focus on the bi-directional communication between the immune system and the HPA axis during viral infection (188,235), others have focused on the immunomodulatory effects of glucocorticoids during viral infection (14,225). This review, however, concentrates on the other side of the bi-directional loop of neuroendocrine-immune interactions, namely, the characterization of HPA axis activity during viral infection and the mechanisms employed by cytokines to stimulate glucocorticoid release.

RNA interference targeting transforming growth factor-beta enhances NKG2D-mediated antiglioma immune response, inhibits glioma cell migration and invasiveness, and abrogates tumorigenicity in vivo

Transforming growth factor (TGF)-beta is the key molecule implicated in impaired immune function in human patients with malignant gliomas. Here we report that patients with glioblastoma, the most common and lethal type of human glioma, show decreased expression of the activating immunoreceptor NKG2D in CD8(+) T and natural killer (NK) cells. TGF-beta is responsible for the down-regulation of NKG2D expression in CD8(+) T and NK cells mediated by serum and cerebrospinal fluid of glioma patients in vitro. Moreover, TGF-beta inhibits the transcription of the NKG2D ligand MICA. Interference with the synthesis of TGF-beta1 and TGF-beta2 by small interfering RNA technology prevents the down-regulation of NKG2D on immune cells mediated by LNT-229 glioma cell supernatant and strongly enhances MICA expression in the glioma cells and promotes their recognition and lysis by CD8(+) T and NK cells. Furthermore, TGF-beta silencing results in a less migratory and invasive glioma cell phenotype in vitro. LNT-229 glioma cells deficient in TGF-beta exhibit a loss of subcutaneous and orthotopic tumorigenicity in nude mice, and NK cells isolated from these mice show an activated phenotype. RNA interference targeting TGF-beta1,2 results in a glioma cell phenotype that is more sensitive to immune cell lysis and less motile in vitro and nontumorigenic in nude mice, strongly confirming TGF-beta antagonism as a major therapeutic strategy for the future treatment of malignant gliomas.

CYP2C and IL-6 expression in breast cancer

Besides hepatic P450 (cytochrome P450) metabolism, there is increasing interest in the possibility of intratumoral activation of oxazaphosphorines by P450. Therefore, we investigated the expression of P450 (CYP2C8, CYP2C9, CYP2C18, and CYP2C19) by RT (reverse transcriptase)-polymerase chain reaction (PCR) and of CYP2C9 by Western blotting in 10 different breast tumor samples. Since P450 may be down regulated by interleukin (IL) IL-6, the receptor (R) for IL-6 was analyzed by RT-PCR and IL-6 in supernatants was calculated from ELISA data. None of the breast tumors was positive for CYP2C18 and CYP2C19 mRNA, whereas CYP2C8 and CYP2C9 were detected in all 10 breast tumors. Correspondingly, all breast tumors tested (9 of 10) revealed low, but nevertheless positive, staining of the CYP2C9 protein. All 10 samples were positive for the IL-6 receptor mRNA. ELISA measurement of IL-6 cytokine in supernatants revealed that all measured samples (8 of 10) were producing IL-6, the amounts ranging from 0.004 to 3.1 ng/g(tumor tissue). In summary, we have demonstrated that tumors of the breast express two out of four members of the CYP2C family, indicating that activation of such prodrugs as oxazaphosphorines may take place intratumorally. The presence of the IL-6 receptor and of IL-6 cytokine, which is produced in an autocrine manner, opens up the possibility that the well-known down regulating effect of IL-6 also takes place in breast tumors and might explain the weak or even absent expression of different CYP2C members.

TNF? increases activity of ?-glutamyl transpeptidase in cultured rat astroglial cells

To investigate the presence of gamma-glutamyl transpeptidase (gammaGT) in brain cells, cultures enriched for astroglial cells, neurons, oligodendroglial cells, and microglial cells were studied. Astroglial cultures contained a specific gammaGT activity of 2.3 +/- 0.9 nmol/min/mg protein. A similar specific gammaGT activity was measured for oligodendroglial cultures, whereas microglial cells and neurons contained less than 30% of the specific gammaGT activity of astroglial cultures. The activity of gammaGT in astroglial cultures was elevated strongly by the presence of tumor necrosis factor-alpha (TNFalpha) in a time- and concentration-dependent manner. Maximal activity of gammaGT was observed after incubation of astroglial cultures for 3 days with 30 ng/mL TNFalpha. Under these conditions the specific gammaGT activity was increased by threefold compared to controls. Presence of the gammaGT-inhibitor acivicin completely inhibited gammaGT activity both in TNFalpha-treated and in control cells. In addition, the increase in astroglial gammaGT activity after application of TNFalpha was prevented completely by the presence of the protein synthesis inhibitor cycloheximide. gammaGT is involved in extracellular processing of glutathione (GSH) that is exported by astroglial cells. After TNFalpha-treatment the concentration of GSH in the medium of astroglial cells was reduced significantly compared to control cells. In conclusion, the data presented demonstrate that TNFalpha stimulates gammaGT synthesis in astroglial cells and thereby improves the capacity to process GSH exported by these cells.

Cytokine, chemokine and growth factor gene profiling of cultured human astrocytes after exposure to proinflammatory stimuli

Astrocytes play key roles in CNS development, inflammation, and repair by producing a wide variety of cytokines, chemokines, and growth factors. Understanding the regulation of this network is important for a full understanding of astrocyte functioning. In this study, expression levels of 268 genes encoding cytokines, chemokines, growth factors, and their receptors were established in cultured human adult astrocytes using cDNA arrays. Also, changes in this gene profile were determined following stimulation with TNFalpha, IL-1beta, and IFNgamma. The data obtained reveal a highly reproducible pattern of gene expression not only between different astrocyte cultures from a single source, but also between astrocytes from different donors. They also identify several gene products not previously described for human astrocytes, including a.o. IL-17, CD70, CD147, and BIGH3. When stimulated with TNFalpha astrocytes respond with increased expression of several genes, notably including those encoding the chemokines CCL2 (MCP-1), CCL5 (RANTES), and CXCL8 (IL-8), growth factors including BMP-2A, BMP-3, neuromodulin (GAP43), BDNF, and G-CSF, and receptors such as the CRF receptor, the calcitonin receptor (CTR), and TKT. The response to IL-1beta involves largely the same range of genes, but responses were blunted in comparison to the TNFalpha response. Treatment with IFNgamma had no or only marginal effects on expression of any of the 268 genes analyzed. Astrocytes treated with a mixture of all three stimuli together displayed responses that are largely similar to those found in response to TNFalpha or IL-1beta alone, with only few additional synergistic effects.

Tumour-endothelium interactions in co-culture: coordinated changes of gene expression profiles and phenotypic properties of endothelial cells

Tumour angiogenesis is a complex process based upon a sequence of interactions between tumour cells and endothelial cells. To model tumour/endothelial-cell interactions, we co-cultured U87 human glioma cells with human umbilical vein endothelial cells (HUVECs). U87 cells induced an 'activated' phenotype in HUVECs, including an increase in proliferation, migration and net-like formation. Activation was observed in co-cultures where cells were in direct contact and physically separated, suggesting an important role for soluble factor(s) in the phenotypic and genotypic changes observed. Expressional profiling of tumour-activated endothelial cells was evaluated using cDNA arrays and confirmed by quantitative PCR. Matching pairs of receptors/ligands were found to be coordinately expressed, including TGFbetaRII with TGFbeta3, FGFRII and cysteine-rich fibroblast growth factor receptor (CRF-1) with FGF7 and FGF12, CCR1, CCR3, CCR5 with RANTES and calcitronin receptor-like gene (CALCRL) with adrenomedullin. Consistent with cDNA array data, immunohistochemical staining of expressed proteins revealed the upregulation of Tie-2 receptor in vitro and in vivo. Our data suggest that tumour-induced activation of quiescent endothelial cells involves the expression of angiogenesis-related receptors and the induction of autocrine growth loops. We suggest that tumour cells release growth factors that induce endothelial cells to express specific ligands and their cognate receptors coordinately.

Expression of chemokines and their receptors in human and simian astrocytes: evidence for a central role of TNF alpha and IFN gamma in CXCR4 and CCR5 modulation

Chemokines are key mediators of the selective migration of leukocytes that occurs in neurodegenerative diseases and related inflammatory processes. Astrocytes, the most abundant cell type in the CNS, have an active role in brain inflammation. To ascertain the role of astrocytes during neuropathological processes, we have investigated in two models of primary cells (human fetal and simian adult astrocytes) the repertoire of chemokines and their receptors expressed in response to inflammatory stimuli. We demonstrated that, in the absence of any stimulation, human fetal and simian adult astrocytes express mRNA for receptors APJ, BOB/GPR15, Bonzo/CXCR6, CCR2, CCR3, CCR5, CCR8, ChemR23, CXCR3/GPR9, CXCR4, GPR1, and V28/CX3CR1. Moreover, TNFalpha and IL-1beta significantly increase BOB/GPR15, CCR2, and V28/CX3CR1 mRNA levels in both models. Furthermore, TNFalpha and IFNgamma act synergistically to induce expression of the major coreceptors for HIV infection, CXCR4 and CCR5, at both the mRNA and protein levels in human and simian astrocytes, whereas CCR3 expression was not affected by cytokine treatment. Finally, TNFalpha/IFNgamma was the most significant cytokine combination in leading to a pronounced upregulation in a comparable, time-dependent manner of the production of chemokines IP-10/CXCL10, RANTES/CCL5, MIG/CXCL9, MCP-1/CCL2, and IL-8/CXCL8. In summary, these data suggest that astrocytes serve as an important source of chemokines under the dependence of a complex cytokine regulation, and TNFalpha and IFNgamma are important modulators of chemokines and chemokine receptor expression in human as well as simian astrocytes. Finally, with the conditions we used, there was no difference between species or age of tissue.

Cytokine activity contributes to induction of inflammatory cytokine mRNAs in spinal cord following contusion

Injury of the spinal cord leads to an inflammatory tissue response, probably mediated in part by cytokines. Because a common therapy for acute spinal cord injury is the use of an antiinflammatory synthetic glucocorticoid (methylprednisolone), we sought to determine mechanisms contributing to inflammation shortly after acute injury. Cytokine mRNAs [interleukin (IL)-1alpha, IL-1beta, tumor necrosis factor (TNF)-alpha, and IL-6] were increased during the first 2 hr following weight-drop compression injury by RNase protection assay, prior to the reported appearance of circulating lymphocytes. This immediate pattern of cytokine mRNA induction could be replicated in cultured, explanted spinal cord slices but not in whole blood of injured animals, which is consistent with a tissue source of cytokine mRNAs. Western blotting detected IL-1beta-like immunoreactivity released into culture medium following explantation and pro-IL-1beta-like immunoreactivity in freshly dissected spinal cord tissue. Pharmacologically blocking IL-1 and TNF-alpha receptors significantly reduced expression of IL-1alpha, IL-1beta, and TNF-alpha mRNAs. Finally, mice lacking both IL-1 and TNF-alpha receptors exhibited diminished induction of TNF-alpha, IL-6, and IL-1ra mRNAs following injury. Therefore, we conclude that contusion injury induces an immediate release of cytokines, which then contributes to the induction of cytokine mRNAs.

Analysis of interleukin-6 gene expression in primary human gliomas, glioblastoma xenografts, and glioblastoma cell lines

Our previous study showed that high-grade astrocytomas often expressed high interleukin (IL)-1beta production. Coexpression of IL-1beta and IL-6 has been found in a number of glioma samples and glioma cell lines. To characterize the expression of IL-6 in the human glioma microenvironment, we investigated surgically excised human gliomas, human glioblastoma xenografts, and human glioblastoma cell lines using the reverse transcriptase-polymerase chain reaction (RT-PCR), immunohistochemistry (IHC), and enzyme-linked immunosorbent assay (ELISA). In the 29 primary gliomas, transcripts of IL-6 were less frequently detectable (55.6%) than those of IL-1beta (72.4%) or those of IL-10, IL-8, or IL-1alpha (>80% each). As for IL-6 gene expression, little or no transcription was observed in low-grade astrocytomas, oligodendroglial tumors, and 1 ependymoma. Strong IL-6 gene expression was found in only 5 of 9 glioblastomas. Immunohistochemically, IL-6 antigen was localized in the tumor cells and macrophages in 4 of 7 glioblastomas. In 3 glioblastomas transplanted into nude mice, both IL-1beta and IL-6 were detected only in 1, but othercytokines (IL-8, IL-10, and IL-1alpha) were detected in all 3 xenografts by RT-PCR. Two cell lines both showed IL-6 expression at the mRNA level, and in a cell line with a high level of IL-6 and IL-1beta transcripts, significant production of IL-6 was observed by IHC and ELISA. We concluded that IL-6 produced in tumor tissue may be involved in tumor progression in some glioblastomas, but not in low-grade astrocytomas and oligodendroglial tumors, and that IL-6 gene expression is closely correlated with IL-1beta expression in biopsy tissue, xenografts, and cultures of human gliomas.

IL-1 receptor type I expression in breast cancer

The cytokine interleukin (IL)-1 is known to be involved in angiogenesis and metastasis. A prerequisite for IL-1 signalling is the presence of its receptor. Previously we have shown that glioblastoma cells express the IL-1 receptor type I (IL-1RI). In this study we analysed 11 breast tumour specimens for IL-1RI expression using the reverse transcriptase (RT) polymerase chain reaction (PCR). We found all the 11 breast tumours were positive for IL-1RI. This suggests that paracrine or autocrine produced IL-1 mediated signalling via IL-IRI might take place in breast tumours to control the production of pro-tumourigenic factors such as angiogenic factors and support further progression of tumour growth and metastasis.

Human breast adipocytes express interleukin-6 (IL-6) and its receptor system: increased IL-6 production by beta-adrenergic activation and effects of IL-6 on adipocyte function

Adipocytes produce the inflammatory cytokine interleukin-6 (IL-6); however, it is not known whether these cells express the IL-6 receptor system, how the secretion of this cytokine is regulated, and whether it has a function within adipose tissue. Using cultured human breast adipocytes, we investigated the expression of IL-6 and its receptor system, the effects of IL-6 on main adipocyte functions, and the regulation of IL-6 secretion by catecholamines and glucocorticoids. In the culture system, immunohistochemistry demonstrated expression of IL-6 and its receptor system, consisting of the ligand-binding IL-6 receptor and the signal-transducing protein gp130, in mature adipocytes, but not in undifferentiated adipocyte precursor cells. In freshly isolated adipocytes, RT-PCR detected messenger ribonucleic acids encoding the above proteins. Chronic incubation of adipocytes with 1 nmol/L IL-6 during adipose differentiation reduced glycero-3-phosphate dehydrogenase (GPDH) activity, a marker of adipocyte differentiation, and triglyceride synthesis to 67 +/- 9% of the basal level (mean +/- SEM; P < 0.05) only on day 21. Incubation of differentiated adipocytes with 10 nmol/L IL-6 for 24 h also resulted in a reduction of GPDH activity to 81 +/- 5% (P < 0.05). On the other hand, 24-h exposure to 10 nmol/L IL-6 increased basal glycerol release by 42 +/- 12% (P < 0.01) and isoproterenol-induced glycerol release by 21 +/- 6% (P < 0.05). The same concentration of IL-6, however, did not alter basal or insulin-stimulated glucose transport. IL-6 secretion was acutely and chronically stimulated by 1 micromol/L isoproterenol (peak of 6.2-fold after 3 h; P < 0.001) and only moderately suppressed by 100 nmol/L cortisol (-36 +/- 10%; P < 0.001). In conclusion, human breast adipocytes release substantial amounts of IL-6 and express IL-6 receptor and gp130. The secretion of IL-6 by adipocytes is strongly stimulated by beta-adrenergic activation and is modestly suppressed by glucocorticoids. IL-6 reduces GPDH activity and stimulates lipolysis, suggesting an autocrine/paracrine role of this cytokine in human adipose breast tissue.

Interferons: potential roles in affect

A review of the literature on interferons was conducted and possible roles in neuropsychiatric disorders with affective disturbances are assessed. Interferons and interferon receptors are present in the limbic system where they appear to exert physiological effects pertinent to affect, most potently when levels rise during CNS infections. Interferons interact closely with cytokines and nitric oxide, signaling molecules implicated in depression. Results from knock-out mice suggest a role for interferon-gamma in moderating fear and anxiety, while other lines of evidence point to a role in arousal and circadian rhythms. The interferon-alpha receptor deploys an arginine methyltransferase affecting RNA editing and splicing, which seem to be disrupted in schizophrenia and bipolar disorder. S-Adenosylmethionine (SAMe), an effective antidepressant, may owe its effects in the latter disorders in part to variations in the strength of interferon-alpha signaling impacting RNA processing. Antiviral effects of interferons are of interest in lieu of viral theories of affective disorders. Finally, the relative levels of interferons gamma and alpha might play important roles in neural, and glial, development, as well as the dialog between the CNS and the immune system.

Central nervous system in cerebral malaria: 'Innocent bystander' or active participant in the induction of immunopathology?

Cerebral malaria (CM) is a major life-threatening complication of Plasmodium falciparum infection in humans, responsible for up to 2 million deaths annually. The mechanisms underlying the fatal cerebral complications are still not fully understood. Many theories exist on the aetiology of human CM. The sequestration hypo-thesis suggests that adherence of parasitized erythrocytes to the cerebral vasculature leads to obstruction of the microcirculation, anoxia or metabolic disturbances affecting brain function, resulting in coma. This mechanism alone seems insufficient to explain all the known features of CM. In this review we focus on another major school of thought, that CM is the result of an over-vigorous immune response originally evolved for the protection of the host. Evidence in support of this second hypothesis comes from studies in murine malaria models in which T cells, monocytes, adhesion molecules and cytokines, have been implicated in the development of the cerebral complications. Recent studies of human CM also indicate a role for the immune system in the neurological complications. However, it is likely that multiple mechanisms are involved in the induction of cerebral complications and both the presence of parasitized erythrocytes in the central nervous system (CNS) and immunopathological processes contribute to the pathogenesis of CM. Most studies examining immunopathological responses in CM have focused on reactions occurring primarily in the systemic circulation. However, these also do not fully account for the development of cerebral complications in CM. In this review we summarize results from human and mouse studies that demonstrate morphological and functional changes in the resident glial cells of the CNS. The degree of immune activation and degeneration of glial cells was shown to reflect the extent of neurological complications in murine cerebral malaria. From these results we highlight the need to consider the potentially important contribution within the CNS of glia and their secreted products, such as cytokines, in the development of human CM.

Mitogenic signaling and the relationship to cell cycle regulation in astrocytomas

The activity and regulation of a number of mitogenic signaling pathways is aberrant in astrocytomas, and this is thought to play a crucial role in the development of these tumors. The cascade of events leading to the formation and the progression from low-grade to high-grade astrocytomas is well characterized. These events include activating mutations, amplification, and overexpression of various growth factor receptors (e.g. epidermal growth factor receptor (EGFR), platelet derived growth factor receptor (PDGFR), c-Met), signaling intermediates (e.g. Ras and Protein kinase C (PKC)), and cell cycle regulatory molecules (e.g. mouse double minute-2 (Mdm2), cyclin-dependent kinase-4 (CDK4), and CDK6), that positively regulate proliferation and cell cycle progression. Inactivating mutations and deletions of signaling and cell cycle regulatory molecules that negatively regulate proliferation and cell cycle progression (e.g. p53, p16/INK4a, p14/ARF, p15/INK4b, retinoblastoma protein (Rb), and Phosphatase and tensin homologue deleted from chromosome 10 (PTEN)) also participate actively in the development of the transformed phenotype. Several mitogenic pathways are also stimulated via an autocrine loop, with astrocytoma cells expressing both the receptors and the respective cognate ligand. Due to the multitude of factors involved in astrocytoma pathogenesis, attempts to target a single pathway have not given satisfactory results. The simultaneous targeting of several pathways or the targeting of signaling intermediates, such as Ras or PKC, situated downstream of many growth factor receptor signaling pathways may show more efficacy in astrocytoma therapy. We will give an overview of how the combination of these aberrations drive astrocytoma cells into a relentless proliferation and how these signaling molecules may constitute relevant therapeutic targets.

Peptides as regulators of the immune system: emphasis on somatostatin

Study of the communication between nervous and immune systems culminated in the understanding that cytokines, formerly considered exclusively as immune system-derived peptides, are endogenous to the brain and display central actions. More recently, immune cells have been recognized as a peripheral source of "brain-specific" peptides with immunomodulatory actions. This article reviews studies concerning reciprocal effects of selected cytokines and neuropeptides in the nervous and immune systems, respectively. The functional equivalence of these two categories of communicators is discussed with reference to the example of the actions of neuropeptide somatostatin in the immune system.