Modulation by tumor necrosis factor-alpha of human astroglial cell production of granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF)

Beneficial actions of melatonin in the management of viral infections: a new use for this "molecular handyman"?

Melatonin (N‐acetyl‐5‐methoxytryptamine) is a multifunctional signaling molecule that has a variety of important functions. Numerous clinical trials have examined the therapeutic usefulness of melatonin in different fields of medicine. Clinical trials have shown that melatonin is efficient in preventing cell damage under acute (sepsis, asphyxia in newborns) and chronic states (metabolic and neurodegenerative diseases, cancer, inflammation, aging). The beneficial effects of melatonin can be explained by its properties as a potent antioxidant and antioxidant enzyme inducer, a regulator of apoptosis and a stimulator of immune functions. These effects support the use of melatonin in viral infections, which are often associated with inflammatory injury and increases in oxidative stress. In fact, melatonin has been used recently to treat several viral infections, which are summarized in this review. The role of melatonin in infections is also discussed herein. Copyright © 2012 John Wiley & Sons, Ltd.

Preoperative thrombocytosis predicts poor survival in patients with glioblastoma

Thrombocytosis, which is defined as a platelet count greater than 400 platelets/nl, has been found to be an independent predictor of shorter survival in various tumors. Release of growth factors from tumors has been proposed to increase platelet counts. Preoperative platelet counts and other clinical and hematological parameters were reviewed from the records of 153 patients diagnosed between 1999 and 2004 with histologically confirmed glioblastoma in order to evaluate the prognostic significance of preoperative thrombocytosis in these patients. The relationship between thrombocytosis and survival was initially analyzed in all patients regardless of further therapy. Univariate log-rank tests showed that the median survival time of 29 patients with preoperative thrombocytosis (19%) was significantly shorter (4 months; 95% confidence interval [95% CI], 3-6 months) compared to 124 patients with normal platelet counts (11 months; 95% CI, 8-13 months; p = 0.0006). Multivariate analysis (Cox proportional hazards model) confirmed preoperative platelet count, age, prothrombin time, and activated partial thromboplastin time to be prognostic factors of survival (all p < 0.05). In a subset of patients (only operated patients with radiation therapy with or without additional chemotherapy), survival was likewise significantly shorter when preoperative thrombocytosis was diagnosed (6 months; 95% CI, 4-12 months) compared to patients with normal platelet count (13 months; 95% CI, 11-15 months; p = 0.0359). In multivariate analysis, age, platelet count, preoperative prothrombin time, and degree of tumor resection retained significance as prognostic factors of survival (all p < 0.05). The results of our study demonstrate preoperative thrombocytosis to be a prognostic factor associated with shorter survival time in patients with glioblastoma.

Interleukin-6 Infusion Blunts Proinflammatory Cytokine Production Without Causing Systematic Toxicity in a Swine Model of Uncontrolled Hemorrhagic Shock

BACKGROUND

Serum elevations of interleukin-6 (IL-6) correlate with multiple organ dysfunction syndrome and mortality in critically injured trauma patients. Data from rodent models of controlled hemorrhage suggest that recombinant IL-6 (rIL-6) infusion protects tissue at risk for ischemia-reperfusion injury. Exogenous rIL-6 administered during shock appears to abrogate inflammation, providing a protective rather than a deleterious influence. In an examination of this paradox, the current study aimed to determine whether rIL-6 decreases inflammation in a clinically relevant large animal model of uncontrolled hemorrhagic shock, (UHS), and to investigate the mechanism of protection.

METHODS

Swine were randomized to four groups (8 animals in each): (1) sacrifice, (2) sham (splenectomy followed by hemodilution and cooling to 33 degrees C), (3) rIL-6 infusion (sham plus UHS using grade 5 liver injury with packing and resuscitation plus blinded infusion of rIL-6 [10 mcg/kg]), and (4) placebo (UHS plus blinded vehicle). After 4 hours, blood was sampled, estimated blood loss determined, animals sacrificed, and lung harvested for RNA isolation. Quantitative reverse transcriptase-polymerase chain reaction was used to assess granulocyte colony-stimulating factor (G-CSF), IL-6, and tumor necrosis factor-alpha (TNFalpha) messenger ribonucleic acid (mRNA) levels. Serum levels of IL-6 and TNFalpha were measured by enzyme-linked immunoassay (ELISA).

RESULTS

As compared with placebo, IL-6 infusion in UHS did not increase estimated blood loss or white blood cell counts, nor decrease hematocrit or platelet levels. As compared with the sham condition, lung G-CSF mRNA production in UHS plus placebo increased eightfold (*p < 0.05). In contrast, rIL-6 infusion plus UHS blunted G-CSF mRNA levels, which were not significantly higher than sham levels (p = 0.1). Infusion of rIL-6 did not significantly affect endogenous production of either lung IL-6 or mRNA. As determined by ELISA, rIL-6 infusion did not increase final serum levels of IL-6 or TNFalpha over those of sham and placebo conditions.

CONCLUSIONS

Exogenous rIL-6 blunts lung mRNA levels of the proinflammatory cytokine G-CSF. The administration of rIL-6 does not increase the local expression of IL-6 nor TNFalpha mRNA in the lung. Additionally, rIL-6 infusion does not appear to cause systemic toxicity.

Melatonin and viral infections

The therapeutic effects of melatonin against viral infections, with emphasis on the Venezuelan equine encephalomyelitis (VEE), are reviewed. Melatonin has been shown to prevent paralysis and death in mice infected with the encephalomyocarditis virus and to decrease viremia. Melatonin also postpones the onset of the disease produced by Semliki Forest virus inoculation and reduces the mortality of West Nile virus-infected mice stressed by either isolation or dexamethasone injection. An increase in the host resistance to the virus via a peripheral immunostimulatory activity is considered responsible for these effects. It has also been demonstrated that melatonin protects some strains of mink against Aleutian disease, and prevents the reduction of B- and T-cells as well as Th1 cytokine secretion in mice infected with leukemia retrovirus. In VEE-infected mice, melatonin postpones the onset of the disease and death for several days and reduces the mortality rate. This protective effect seems to be due to the increase in the production of interleukin-1beta (IL-1beta), as 100% of the infected mice treated with melatonin die when IL-1beta is blocked with antimurine IL-1beta antibodies. Although melatonin administration raises serum levels of tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma), the mortality observed in neutralization experiments with the corresponding anticytokine antibodies, suggests that neither TNF-alpha nor IFN-gamma are essential for the protective effect of melatonin on murine VEE virus infection. Melatonin treatment also enhances the efficiency of immunization against the VEE virus. Reactive oxygen species have been implicated in the dissemination of this virus, and their deleterious effects may be diminished by melatonin. This indole inhibits nitric oxide synthetase activity and it is a potent scavenger of nitric oxide, which also plays an important role in the spread of the VEE virus. In conclusion, the immunomodulatory, antioxidant, and neuroprotective effects of melatonin suggest that this indole must be considered as an additional therapeutic alternative to fight viral diseases.

Melatonin increases interleukin-1beta and decreases tumor necrosis factor alpha in the brain of mice infected with the Venezuelan equine encephalomyelitis virus

The effect of melatonin (MLT) on the brain levels of tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta) in Venezuelan equine encephalomyelitis (VEE) virus infection was determined. Brain homogenates from mice inoculated with 10 LD50 of VEE virus, untreated or treated with 500 microg MLT/kg body weight were assayed by ELISA to measure the levels of TNF-alpha and IL-1beta. MLT was injected daily starting 3 days before and continuing to 7 days after virus inoculation. Infected mice treated with MLT showed decreased levels of TNF-alpha when compared to the untreated infected mice on days 1, 3, 4, and 5 postinoculation (P < 0.001). In contrast, IL-1beta levels increased from days 1 to 5 in the infected mice treated with MLT when compared with the untreated infected animals (P < 0.01). The results suggest that the protective effect of MLT on the VEE virus infection could be due, among other factors, to a decrease in TNF-alpha synthesis along with an increase in the production of IL-1beta.

Expression of granulocyte colony-stimulating factor in recurrent glial tumors is inversely correlated with tumor progression

We have previously reported that in vivo-expression of granulocyte colony-stimulating factor (G-CSF) is a characteristic feature of reactive and neoplastic astrocytes. The aim of the present study was to analyze the expression of G-CSF protein in primary and recurrent astroglial, oligodendroglial and mixed glial-differentiated tumors. G-CSF expression was present in all GFAP-positive tumors excepting glioblastomas. G-CSF expression was significantly reduced in recurrent tumors more dedifferentiated than their primary counterparts. G-CSF expression was absent in all GFAP-negative tumors such as oligodendrogliomas. Our results demonstrate that G-CSF is a highly sensitive differentiation marker of neoplastic astrocytes, which is lost during tumor progression.

The role of tumour necrosis factor, interleukin 6, interferon-gamma and inducible nitric oxide synthase in the development and pathology of the nervous system

Proinflammatory cytokines, tumour necrosis factor (TNF)-alpha, interferon (IFN)-gamma and interleukin (IL)-6, have multiple effects in the central nervous system (CNS) not strictly cytotoxic being involved in controlling neuronal and glial activation, proliferation, differentiation and survival, thus influencing neuronal and glial plasticity, degeneration as well as development and regeneration of the nervous system. Moreover, they can contribute to CNS disorders, including multiple sclerosis. Alzheimer's disease and human immunodeficiency virus-associated dementia complex. Recent results with deficient mice in the expression of those cytokines indicate that they are in general more sensible to insults resulting in neural damage. Some of the actions induced by TNF-alpha, and IFN-gamma, including both beneficial and detrimental, are mediated by inducible nitric oxide synthase (iNOS)-derived nitric oxide (NO) production. NO produced by iNOS may be beneficial by promoting the differentiation and survival of neurons. IL-6 does not induce iNOS, explaining why this cytokine is less often involved in this dual role protection pathology. Some of the proinflammatory as well as the neurotrophic effects of those cytokines also involve upregulation of cell adhesion molecules (CAM). Those apparently conflicting results may be reconciled considering that proinflammatory cytokines are involved in promoting the disease, mostly by inducing expression of CAM leading to alteration of the blood-brain barrier integrity, whereas they have a protective role once disease is established due to its immunosuppressive or neurotrophic role. Understanding the dichotomy pathogenesis/neuroprotection of those cytokines may provide a rationale for better therapeutic strategies.

Hypothesis on the pathogenesis of vacuolar myelopathy, dementia, and peripheral neuropathy in AIDS

Certain aspects of the clinical syndrome of dementia, cerebral atrophy, predominantly sensory neuropathy, and vacuolar myelopathy in AIDS resemble those seen in vitamin B12 deficiency. Pathologically, there are similarities not only in the changes in the spinal cord, but also in the brain and peripheral nerves. The pathogenesis of vacuolar myelopathy may be secondary to a combination of immune mediated myelin and oligodendrocyte injury, and simultaneous impairment of repair mechanisms due to a deficiency of S-adenosylmethionine (SAM). Products derived from macrophages may interfere directly with the methyl transfer cycle through the generation of reactive oxygen intermediates and reactions involving nitric oxide and peroxynitrite which may limit the supply of methionine for conversion to SAM, both by direct interaction as well as through inhibition of methionine synthase. Macrophage activation with secretion of cytokines and other biologically reactive substances within the nervous system is sustained in the late stages of HIV infection by the general effects of immune depletion, including loss of T cells (with concomitant reduction of macrophage regulatory molecules) and recurrent opportunistic infections, and may be further augmented by the local presence of the virus itself (or its surface glycoprotein gp120). This would account for the common, but not exclusive, occurrence of vacuolar myelopathy in AIDS. The ability of the virus and its products to stimulate macrophage and microglial activation may also explain the association between severity of vacuolar myelopathy and the presence of HIV encephalitis. A similar mechanism may underlie the pathogenesis of dementia, cerebral atrophy, and peripheral neuropathy. Local factors or differential susceptibility between the central and peripheral nervous system may determine whether myelinotoxic or neurotoxic processes predominate; the prominence of myelin involvement in the spinal cord, and axonal involvement peripherally may reflect both ends of this range, with the brain manifesting a more equal balance of both processes.

Substance P induces secretion of immunomodulatory cytokines by human astrocytoma cells

In human astrocytoma cell lines, substance P (SP) stimulated interleukin (IL)-8, IL-6, granulocyte macrophage colony-stimulating factor and leukemia inhibitory factor protein secretion. These SP effects were blocked by a specific NK1 tachykinin receptor antagonist. Further, SP stimulation increased the half-life of IL-6 and IL-8 messenger RNAs, suggesting that the synthesis of these cytokines is also regulated post-transcriptionally. SP-induced cytokine release was inhibited by staurosporine and phorbol 12-myristate 13-acetate desensitization suggesting protein kinase C involvement. The demonstration that SP affects cytokine production in glioma cells might be of relevance for the biology of such tumors.

Granulocyte macrophage colony stimulating factor stimulates in vitro proliferation of astrocytes derived from simian mature brains

In the brain, granulocyte-macrophage colony stimulating factor (GM-CSF) may be released by infiltrated cells of the immune system including T and B lymphocytes and mononuclear phagocytes, but also by nervous system resident cells such as microglia and astrocytes. Astrocyte-secreted GM-CSF may play an important role in enhancing the local inflammatory response to central nervous system (CNS) injury and in recruting microglia and activated macrophages. In this study, we demonstrated that GM-CSF, as TNF alpha and IL 6, stimulates in vitro proliferation of simian astrocytes in primary cultures. Results were confirmed by blocking experiments performed with a specific neutralizing mAb directed against GM-CSF. Furthermore, we demonstrated that GM-CSF mediates its effect on these cells through the alpha subunit of the GM-CSF receptor which is constitutively expressed at the membrane of the cultured simian astrocytes as assessed by immunofluorescence. GM-CSF effects on astrocytes could be involved in astrocytosis, a hallmark of various neurological injuries and in inflammatory processes in an autocrine manner.

Cytokines and tumors of the central nervous system

Cytokines are a group of molecules with an extremely broad range of activities on a variety of target cells. This review summarizes the known cytokine and cytokine receptor expression in primary brain tumors and derived cell lines. These expression patterns are compared with those occurring in other CNS diseases, such as virus or bacterial infections, experimental allergic encephalitis, multiple sclerosis, and trauma. A variety of cytokines are expressed during CNS neoplasia; their potential involvement in tumor growth through a variety of mechanisms, such as autocrine or paracrine growth stimulation, angiogenesis, and immune surveillance evasion, are discussed. Finally, results of preliminary therapeutic approaches with cytokines are critically evaluated.

Platelet-activating factor production by human fetal microglia. Effect of lipopolysaccharides and tumor necrosis factor-alpha

Since platelet-activating factor (PAF) exerts neurotoxic effects on brain cells, we explored the possibility of PAF production by human fetal microglial cells in vitro. PAF content in pure cultures was assayed and characterized in basic conditions, and after stimulation with growth factors and cytokines. Results showed that microglia cells synthesized PAF when challenged with tumor necrosis factor-alpha and lipopolysaccharides, whereas other molecules, such as gamma-interferon or basic fibroblast growth factor, were ineffective. The induced PAF production was concentration- and time-dependent. These results are in line with the hypothesis that microglia can start a cascade of events leading to tissue damage, thus playing a central role in the pathogenesis of several central nervous system diseases.

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

To elucidate which cytokine receptors may be expressed by human glioblastoma and normal astrocytic cells, the presence of messenger ribonucleic acid (RNA) for a number of cytokine receptors was examined in 16 glioblastoma cell lines and adult and fetal astrocytes. A complementary deoxyribonucleic acid copy of total RNA was synthesized and amplified with specific primers using the polymerase chain reaction method. The receptors studied were interleukin (IL)-1 receptor type I (IL-1RI) and type II (IL-1RII), p75 and p55 tumor necrosis factor (TNF) receptors (p75TNFR and p55TNFR), interferon (IFN)-alpha/beta and -gamma receptors (IFN-alpha/beta R and IFN-gamma R), granulocyte-macrophage (GM) colony-stimulating factors receptor alpha subunit (GM-CSFR), G-CSF receptor (G-CSFR), M-CSF receptor (c-fms, M-CSFR), stem cell factor receptor (c-kit, SCFR), IL-6 receptor (IL-6R), and IL-8 receptor (IL-8R). Transcripts for IL-1RI, p55TNFR, IFN-alpha/beta R, and IFN-gamma R were present in all cell lines. The presence of IL-1RII, p75TNFR, GM-CSFR, M-CSFR, SCFR, IL-6R, and IL-8R was identified in 13, eight, seven, eight, 14, three, and one cell lines, respectively. Normal astrocytes were positive for IL-1RI, p75TNFR, p55TNFR, IFN-alpha/beta R, IFN-gamma R, M-CSFR, and SCFR, showing a similarity to glioblastoma cells. Expression of IL-1RII was observed in adult astrocytes but not in fetal astrocytes. Furthermore, gene expression was assessed in normal brain tissue and 11 glioblastoma tissue specimens. The normal brain tissue expressed IL-1RI, IL-1RII, IFN-alpha/beta R, M-CSFR, and SCFR. Of the 11 glioblastoma tissue specimens, IL-1RI was positive in 11, IL-1RII in 10, p75TNFR in nine, p55TNFR in nine, IFN-alpha/beta R in 10, IFN-gamma R in 10, GM-CSFR in two, G-CSFR in three, IL-8R in eight, and M-CSFR and SCFR in 11. These expressions were consistent with those in the cell lines, except for IL-8R. It is concluded that glioblastoma cells and normal astrocytes express a similar set of cytokine receptor genes in vitro and in vivo. Possible autocrine loops are suggested for IL-1 alpha/IL-1RI, TNF-alpha/p55TNFR, IFN-beta/IFN-alpha/beta R, M-CSF/M-CSFR, and SCF/SCFR in glioblastomas.

Immunolocalization of granulocyte-colony-stimulating factor in human glial and primitive neuroectodermal tumors

Granulocyte-colony-stimulating factor (G-CSF) is a hematopoietic cytokine that regulates the differentiation of myeloid progenitors and the function of mature neutrophils. It is produced in vitro by monocytes/macrophages, mesothelial cells, fibroblasts and endothelial cells after appropriate induction by inflammatory mediators like IL-1 and TNF. Normal as well as tumorous glial cells can also be induced to produce CSFs in vitro. However, little is yet known about the in vivo expression of G-CSF as a mediator in inflammation and malignancy within the human central nervous system. The aim of the present study was to investigate by immunostaining the expression of the G-CSF protein within non-tumorous and tumorous glial tissues, and primitive neuroectodermal tumors. Using the murine monoclonal anti-G-CSF TM 82/60 antibody, we found high G-CSF expression in astrocytoma WHO grades I and II and reactive brain tissue, low expression in astrocytoma WHO grade III, and none in glioblastoma, oligodendroglioma WHO grades II and III, and medulloblastoma. In consecutive sections of the tissue samples, G-CSF protein was localized in GFAP-positive glial cells, but not in macrophages/microglial cells, which expressed HLA-DR, detected by the antibody CR3/43. Computer-assisted microdensitometric evaluation of the intensity of immunostaining for G-CSF and statistic analysis of the data revealed significant differences between the diagnostic entities studied (p < 0.0001). We conclude that in vivo expression of G-CSF is a characteristic of reactive as well as tumorous astrocytes, with the latter losing this feature at higher degrees of dedifferentiation.

Interleukin-1 and tumor necrosis factor-mediated regulation of C3 gene expression in human astroglioma cells

In this report, we show that in the human astroglioma cell line D54-MG, both interleukin-1 (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) enhance C3 gene expression in a time- and dose-dependent manner. Kinetic analysis demonstrates that after 96 h, C3 mRNA levels increase approximately 30-fold and 20-fold in response to IL-1 beta or TNF-alpha, respectively. C3 protein production increases proportionally, reaching levels 36-fold and 18-fold higher than untreated controls upon exposure to IL-1 beta or TNF-alpha, respectively. D54-MG cells require a minimal 1 h exposure to IL-1 beta in order to enhance C3 gene expression significantly, while 4 to 8 h are required for TNF-alpha. Simultaneous treatment of D54-MG cells with IL-1 beta and interferon-gamma (IFN-gamma) resulted in an additive increase in both C3 mRNA and protein expression, a finding not seen with the combination of TNF-alpha and IFN-gamma. Primary rat astrocytes also express increased C3 mRNA levels after 48 h in response to IL-1 beta (5.3-fold increase) and TNF-alpha (7-fold increase), while an additive effect was observed upon simultaneous treatment with both IL-1 beta and IFN-gamma. In the central nervous system (CNS), endogenous complement and cytokine production by astrocytes, and enhancement by IFN-gamma, a product of activated T cells often seen in the CNS in neural autoimmune disease, may contribute to the pathogenesis of inflammatory demyelinating diseases such as multiple sclerosis.

Influence of interleukin-1 and tumor necrosis factor alpha on the growth of microglial cells in primary cultures of mouse cerebral cortex: involvement of colony-stimulating factor 1

The influence of monokines and CNS-derived colony-stimulating factors (CSF) on the growth of microglia has been studied in mixed glial primary cultures stemming from mouse embryos. We observed that spontaneous growth of microglial cells in the presence of astrocytes is blocked by adding anti-colony-stimulating factor 1 (CSF-1) antibodies to the cultures. Both interleukin-1 (IL-1) and tumor necrosis factor-alpha(TNF alpha) strongly increased the number of microglial cells in mixed glial cultures and this effect was prevented by anti-CSF-1 antibodies. In contrast, anti-interleukin-3 (IL-3) or anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) antibodies did not significantly affect the in vitro growth of microglia. These results provide functional significance to astrocytic productions of CSF-1 and their modulations by IL-1 or TNF alpha.

Human immunodeficiency virus coat protein gp120 inhibits the beta-adrenergic regulation of astroglial and microglial functions

The goal of our study was to assess whether the human immunodeficiency virus (HIV) coat protein gp120 induces functional alterations in astrocytes and microglia, known for their reactivity and involvement in most types of brain pathology. We hypothesized that gp120-induced anomalies in glial functions, if present, might be mediated by changes in the levels of intracellular messengers important for signal transduction, such as cAMP. Acute (10 min) exposure of cultured rat cortical astrocytes or microglia to 100 pM gp120 caused only a modest (50-60%), though statistically significant, elevation in cAMP levels, which was antagonized by the beta-adrenergic receptor antagonist propranolol. More importantly, the protein substantially depressed [by 30% (astrocytes) and 50% (microglia)] the large increase in cAMP induced by the beta-adrenergic agonist isoproterenol (10 nM), without affecting that induced by direct adenylate cyclase stimulation by forskolin. Qualitatively similar results were obtained using a glial fibrillary acidic protein (GFAP)-positive human glioma cell line. The depression of the beta-adrenergic response had functional consequences in both astrocytes and microglia. In astrocytes we studied the phosphorylation of the two major cytoskeletal proteins, vimentin and GFAP, which is normally stimulated by isoproterenol, and found that gp120 partially (40-50%) prevented such stimulation. In microglial cells, which are the major producers of inflammatory cytokines within the brain, gp120 partially antagonized the negative beta-adrenergic modulation of lipopolysaccharide (10 ng/ml)-induced production of tumor necrosis factor alpha. Our results suggest that, by interfering with the beta-adrenergic regulation of astrocytes and microglia, gp120 may alter astroglial "reactivity" and upset the delicate cytokine network responsible for the defense against viral and opportunistic infections.