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L Meda

Publications and source records attributed to L Meda.

At least 19 recordsLinked to original sources
PubMed2001

Production of IL-6 by human myoblasts stimulated with Abeta: relevance in the pathogenesis of IBM.

OBJECTIVE: To determine whether amyloid-beta protein (Abeta) can induce the production of proinflammatory cytokines by cultured normal muscle cells. BACKGROUND: Sporadic inclusion body myositis (IBM) is characterized by the presence of rimmed vacuoles and fibrillary inclusions of Abeta in muscle fibers, and often inflammatory cells. Endomysial expression of proinflammatory molecules has suggested an ongoing immune process, but the site of sensitization and the mechanisms that trigger an inflammatory reaction is unknown. METHOD: The authors used Northern blot analysis and specific immunoassays to study the expression and secretion in cell-free supernatants of tumor necrosis factor-alpha (TNFalpha), interleukin-1beta (IL-1beta), and interleukin-6 (IL-6) by purified human myoblasts and C2C12 mouse skeletal muscle cells incubated with Abeta[1-42] or Abeta[25-35] peptides. RESULTS: Nonstimulated muscle cells produced detectable IL-6, whereas secretion of IL-1beta and TNFalpha was absent. Incubation with Abeta peptides increased IL-6 production, whereas TNFalpha and IL-1beta levels remained undetectable. Northern blot analysis of Abeta-stimulated human myoblasts revealed an increase in IL-6 mRNA expression. CONCLUSIONS: Cultured muscle cells increase the constitutive production of IL-6 in response to local deposition of Abeta in sporadic IBM. IL-6 could be a CD8(+) proliferation and differentiation agent, an autocrine proteolysis-inducing factor of damaged myotubes, and a proliferation-stimulating agent for satellite cells to replace the destroyed myofibers in IBM.

Adult↗
PubMed2000

The human astrocytoma cell line U373MG produces monocyte chemotactic protein (MCP)-1 upon stimulation with beta-amyloid protein.

Astrocytes associated with beta-amyloid (Abeta) accumulate in senile plaques of Alzheimer's disease (AD). To investigate the biological effects of Abeta/astrocyte interaction, we examined chemokine production by the human astrocytoma cell line U373MG stimulated with Abeta peptides. Northern blot analysis and specific immunoassays demonstrate that Abeta [1-42] and Abeta [25-35] induce mRNA expression and release of monocyte chemotactic protein (MCP)-1 but not of gamma-interferon inducible protein (IP)-10 by U373MG cells. The observation that Abeta induces astrocyte production of the potent microglia chemoattractant MCP-1 contributes to understanding mechanism of damage exerted by Abeta in AD senile plaques.

Amyloid beta-Peptides↗
PubMed2000

Synergistic effect of beta-amyloid protein and interferon gamma on nitric oxide production by C2C12 muscle cells.

Nitric oxide (NO) is an important mediator of diverse physiological and pathological responses. NO-induced oxidative stress has been proposed in the pathogenesis of muscle tissue damage in inclusion-body myositis (IBM), which is characterized by deposition of beta-amyloid protein (Abeta) in vacuolated muscle fibres. To determine whether Abeta can induce NO production in skeletal muscle, we stimulated C2C12 mouse skeletal muscle cells in vitro with Abeta[1-42] or Abeta[25-35] peptides in the presence or absence of interferon gamma (IFN-gamma). Neither Abeta peptides nor IFN-gamma were able to stimulate nitrite (NO(2)(-)) production by C2C12 cells when given alone. However, combination of IFN-gamma with either Abeta[1-42] or Abeta[25-35] resulted in significant NO(2)(-) release into cell-free supernatants. Northern blot analysis of RNA obtained from Abeta/IFN-gamma-stimulated C2C12 cells revealed increased mRNA accumulation of inducible nitric oxide synthase (iNOS). Moreover, approximately 4% of muscle cells incubated with Abeta peptides and IFN-gamma showed ultrastructural features of DNA fragmentation. These findings, taken together, indicate that the association of Abeta with IFN-gamma stimulates NO(2)(-) production via induction of iNOS gene expression in skeletal muscle cells, with occasional evidence for nuclear changes suggesting apoptotic morphology. These data further support a role for Abeta deposition in the pathogenesis of postulated oxidative damage in IBM.

Amyloid beta-Peptides↗
PubMed1999

Alpha-MSH peptides inhibit production of nitric oxide and tumor necrosis factor-alpha by microglial cells activated with beta-amyloid and interferon gamma.

Alpha-melanocyte stimulating hormone (alpha-MSH) is an ancient tridecapeptide with potent inhibitory activity in all major forms of inflammation. The anti-inflammatory message sequence of alpha-MSH resides in the COOH-terminal tripeptide alpha-MSH[11-13]. We tested the influence of alpha-MSH[1-13] and of alpha-MSH[11-13] in a cultured murine microglia cell line known to produce nitric oxide (NO(-)(2)) and tumor necrosis factor (TNFalpha) when stimulated with beta-amyloid protein (Abeta). Melanocortin peptides significantly inhibited release of both NO(-)(2) and TNFalpha into cell-free supernatants from microglia stimulated with Abeta[1-42] or Abeta[25-35] peptides and interferon gamma (IFNgamma). Northern blot analysis demonstrated that alpha-MSH[1-13] and alpha-MSH[11-13] inhibited accumulation of inducible nitric oxide synthase (iNOS) and TNFalpha mRNA was triggered by Abeta stimulation. Abeta/microglial interaction is believed to promote the progression of inflammatory and neurodegenerative changes in senile plaques in Alzheimer's disease. Our data indicate that alpha-MSH peptides might be used to modulate the local response of the brain to Abeta deposition in this neurodegenerative disease.

Amyloid beta-Peptides↗
PubMed1999

Proinflammatory profile of cytokine production by human monocytes and murine microglia stimulated with beta-amyloid[25-35].

Growing evidence indicates that amyloid (A beta) deposition and phagocyte activation participate in inflammatory reactions in the brain during the course of Alzheimer's disease. To further investigate the effects of A beta-phagocyte interaction, we examined the production of proinflammatory (IL-1beta, IL-6), chemotactic (MIP-1alpha, IP-10) and inhibitory (IL-1Ra, IL-10 and TGFbeta1) cytokines by cultured human monocytes and mouse microglial cells upon stimulation with A beta[25-35]. Northern blot analysis and specific immunoassays demonstrated that A beta[25-35] triggers mRNA expression and release of IL-1beta, IL-1Ra and MIP-1alpha but not of IL-6, IL-10, TGFbeta1 and IP-10 from human monocytes. Similar results were obtained by examining the production of IL-1beta, IL-6 and IL-10 from mouse microglial cells in the same experimental conditions. Taken together, these data indicate that A beta-phagocyte interaction can drive a different response towards cytokine production by monocytes and microglia, with a particular proinflammatory trend, and further support a role for A beta deposition as a triggering factor of inflammatory events in Alzheimer's disease.

Alzheimer Disease↗
PubMed1998

Cultured human monocytes release proinflammatory cytokines in response to myelin basic protein.

In human cultured monocytes we examined the ability of myelin basic protein (MBP) to induce the production of proinflammatory cytokines potentially involved in inflammatory demyelination. Northern blots and specific immunoassays demonstrated that monocytes incubated with optimal doses of MBP showed increased mRNA expression and release of tumor necrosis factor (TNF-alpha), interleukin-1beta (IL-1beta), interleukin-6 (IL-6), interleukin-8 (IL-8) but not of interleukin-12/p40 (IL-12/p40). We also showed that cytokine production by MBP-stimulated monocytes was abrogated by incubation with Dexamethasone. These data suggest that interaction of mononuclear phagocytes with MBP may participate in the regulatory process of cytokine production during inflammatory demyelination and support the beneficial role of corticosteroids therapy in aberrant immune responses to the myelin sheath.

Animals↗
PubMed1998

Melanocortin peptides inhibit production of proinflammatory cytokines and nitric oxide by activated microglia.

Inflammatory processes contribute to neurodegenerative disease, stroke, encephalitis, and other central nervous system (CNS) disorders. Activated microglia are a source of cytokines and other inflammatory agents within the CNS and it is therefore important to control glial function in order to preserve neural cells. Melanocortin peptides are pro-opiomelanocortin-derived amino acid sequences that include alpha-melanocyte-stimulating hormone (alpha-MSH) and adrenocorticotropic hormone (ACTH). These peptides have potent and broad anti-inflammatory effects. We tested effects of alpha-MSH (1-13), alpha-MSH (11-13), and ACTH (1-24) on production of tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), and nitric oxide (NO) in a cultured murine microglial cell line (N9) stimulated with lipopolysaccharide (LPS) plus interferon gamma (IFN-gamma). Melanocortin peptides inhibited production of these cytokines and NO in a concentration-related fashion, probably by increasing intracellular cAMP. When stimulated with LPS + IFN-gamma, microglia increased release of alpha-MSH. Production of TNF-alpha, IL-6, and NO was greater in activated microglia after innmunoneutralization of endogenous alpha-MSH. The results suggest that alpha-MSH is an autocrine factor in microglia. Because melanocortin peptides inhibit production of pro-inflammatory mediators by activated microglia they might be useful in treatment of inflammatory/degenerative brain disorders.

Adrenocorticotropic Hormone↗
PubMed1996

Priming of monocyte respiratory burst by beta-amyloid fragment (25-35).

In the present study we have examined the ability of the beta-amyloid peptide (A beta(25-35)) to modulate the respiratory burst activity of human monocytes in vitro. Incubation of the cells for 24 h with A beta(25-35) as well as with A beta(1-42) resulted in an enhanced production of reactive oxygen radicals (ROI) in response to phorbol 12-myristate 13-acetate (PMA). Such effect was additively increased by coincubation with interferon-gamma (IFN gamma), and was paralleled by modulation of gene and protein expression of some components of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase system. Since the effects of A beta(25-35) were also reproduced in primary rat microglia, our findings indicate that A beta(25-35) can potentiate the ability of mononuclear phagocytes to produce ROI, and add further insights into its biological effects.

Amyloid beta-Peptides↗
PubMed1996

Beta-amyloid (25-35) peptide and IFN-gamma synergistically induce the production of the chemotactic cytokine MCP-1/JE in monocytes and microglial cells.

The molecular mechanisms involved in the development of senile plaques characteristic of aging and Alzheimer's disease are poorly understood. In this study, we examined whether human monocytes and murine microglial cells stimulated with the active fragment of amyloid beta-protein (Abeta(25-35)) express the monocyte chemotactic protein-1 (MCP-1)/JE. We show that upon incubation with Abeta(25-35), human monocytes accumulate MCP-1 mRNA and produce significant amounts of MCP-1. The effect of Abeta(25-35) on MCP-1 secretion was neither mimicked by a scrambled analogue nor affected by polymyxin B sulfate, even though the latter almost completely abolished the effect of LPS on MCP-1 expression. Murine microglial cells stimulated with Abeta(25-35) also expressed high levels of JE mRNA (the murine counterpart of MCP-1) and released bioactive chemotactic factors. In addition, we report that IFN-gamma significantly synergizes with Abeta(25-35) either in human monocytes or in murine microglial cells, and that Abeta(25-35) plus/minus IFN-gamma-mediated early induction of MCP-1 mRNA does not require new protein synthesis. Finally, we provide evidence that the Abeta(25-35)- and Abeta plus IFN-gamma-induced production of MCP-1 is, in large part, mediated in an autocrine fashion by endogenous TNF-alpha. Taken together, our findings uncover another novel biologic action of Abeta(25-35) and might help in better understanding the mechanisms underlying mononuclear phagocyte recruitment and activation into amyloid deposits.

Amyloid beta-Peptides↗
PubMed1995

Activation of microglial cells by beta-amyloid protein and interferon-gamma.

Alzheimer's disease is the most common cause of progressive intellectual failure. The lesions that develop, called senile plaques, are extracellular deposits principally composed of insoluble aggregates of beta-amyloid protein (A beta), infiltrated by reactive microglia and astrocytes. Although A beta, and a portion of it, the fragment 25-35 (A beta (25-35)), have been shown to exert a direct toxic effect on neurons, the role of microglia in such neuronal injury remains unclear. Here we report a synergistic effect between A beta and interferon-gamma (IFN-gamma) in triggering the production of reactive nitrogen intermediates and tumour-necrosis factor-alpha (TNF-alpha) from microglia. Furthermore, using co-culture experiments, we show that activation of microglia with IFN-gamma and A beta leads to neuronal cell injury in vitro. These findings suggest that A beta and IFN-gamma activate microglia to produce reactive nitrogen intermediates and TNF-alpha, and this may have a role in the pathogenesis of neuronal degeneration observed in ageing and Alzheimer's disease.

Aging↗
PubMed1995

Interleukin-12 production by human polymorphonuclear leukocytes.

Human polymorphonuclear leukocytes (PMN) stimulated by lipopolysaccharide (LPS) produce interleukin-12 (IL-12). Both the free IL-12 p40 chain and minute amounts of the biologically active IL-12 p70 heterodimers are produced by PMN. Interferon-gamma (IFN-gamma) enhanced the LPS-induced secretion of both the free IL-12 p40 chain and the p70 heterodimer by approximately fivefold. As observed for other IL-12-producing cell types, the ratio of free p40 chain to p70 heterodimer secreted by LPS-stimulated PMN was approximately 20:1. LPS induced a 100-fold increase of IL-12 p40 mRNA, but had minimal effect on p35 mRNA accumulation. IFN-gamma enhanced the LPS-induced accumulation of p40 mRNA and directly induced a several-fold increase in the accumulation of p35 mRNA. Therefore, the combined effect of LPS and IFN-gamma induced sufficient expression of both p40 and p35 to attain production of the biologically active p70 heterodimer at physiologically relevant concentrations. The ratio between p40 and p35 mRNA abundance in PMN stimulated with both LPS and IFN-gamma was approximately 200:1, explaining the secretion of the free p40 chain in much higher concentrations than the p70 heterodimer. IL-10, an inhibitor of the production of various cytokines in PMN, also suppressed IL-12 mRNA accumulation and secretion by PMN. Because of the important immunoregulatory function of IL-12, in particular induction of IFN-gamma production and facilitation of T helper cell type 1 response, the ability of PMN to produce IL-12 suggests that neutrophils may play an active role in the regulatory interaction between innate resistance and adaptive immunity.

Blotting, Northern↗
PubMed1995

beta-Amyloid(25-35) induces the production of interleukin-8 from human monocytes.

In an effort to unravel some of the cellular actions of beta-amyloid protein (A beta), we investigated its effects on interleukin-8 (IL-8) production from human monocytes. Supernatants harvested from cultured monocytes stimulated with the neurotoxic fragment 25-35 of beta-amyloid [A beta(25-35)] contained significant amounts of IL-8. Northern blot analysis demonstrated that A beta(25-35) also induced IL-8 mRNA accumulation. The effect of A beta(25-35) on IL-8 mRNA accumulation and secretion was not mimicked by a scrambled A beta(25-35) peptide, and was not affected by polymyxin B sulphate, which, on the other hand, almost completely abolished the effect of lipopolysaccharide. Our results uncover a new biological action of beta-amyloid: that of stimulating the production of a chemokine from monocytes.

Amino Acid Sequence↗
PubMed1994

Interleukin 10 (IL-10) upregulates IL-1 receptor antagonist production from lipopolysaccharide-stimulated human polymorphonuclear leukocytes by delaying mRNA degradation.

Polymorphonuclear leukocytes (PMN) have been identified as cells capable of producing a number of pro- and antiinflammatory cytokines in response to specific agonists. Previously, we showed that tumor necrosis factor (TNF), interleukin-1 beta (IL-1 beta), and IL-8, are produced by PMN after stimulation with agonists, such as lipopolysaccharide (LPS). In this study, we demonstrate that LPS is also a potent stimulus for the mRNA expression and release of the IL-1 receptor antagonist (IL-1ra). In addition, we show that the release of IL-1ra from LPS-stimulated PMN is markedly potentiated in the presence of IL-10 (from two to threefold after 18 h of stimulation). Moreover, we observed that this upregulation of IL-1ra production by IL-10 in LPS-stimulated PMN took place through IL-1ra mRNA stabilization. Indeed, the half-life of IL-1ra mRNA was prolonged in PMN stimulated in the presence of IL-10 and LPS, as compared with cells stimulated with LPS alone. That IL-10 selectively upregulates IL-1ra production in LPS-activated PMN, while it inhibits the production of IL-1 beta, TNF, and IL-8 under the same conditions, suggests that IL-10 may be an important physiologic regulator of cytokine production from PMN, and emphasizes the potential role of IL-10 in inflammatory responses.

Cells, Cultured↗
PubMed1994

Modulation of proinflammatory cytokine release from human polymorphonuclear leukocytes by gamma interferon.

Polymorphonuclear leukocytes (PMN) have been identified as important sources of various proinflammatory cytokines. Since Interferon-gamma (IFN-gamma) is one of the activating factors of PMN, we have examined its effect on PMN-derived cytokine production. Recently, we demonstrated that IFN-gamma inhibits the release of IL-8 by PMN stimulated for 2 with different agonists. In this report, we show that the IFN-gamma-dependent inhibition of IL-8 release by PMN stimulated with lipopolysaccharide (LPS), tumor necrosis factor (TNF), and/or interleukin-1 beta (IL-1 beta), but not with Y-IgG, is a transient phenomenon. Indeed, PMN stimulated in the presence of IFN-gamma for 18 hr demonstrated an enhanced expression of IL-8 antigen in cell-free supernatants compared with stimuli alone. This enhanced accumulation of IL-8 partially reflected changes at the level of cell-associated versus cell-secreted IL-8 as PMN incubated with IFN-gamma secreted significantly more IL-8, relative to untreated cells. Unlike IL-8, the LPS-stimulated production of TNF and IL-1 beta, as well as the TNF-stimulated production of IL-1 beta, was markedly enhanced by IFN-gamma over the entire incubation period (up to 18 hr). Addition of anti-TNF and anti-IL-1 beta antibodies to IFN-gamma plus LPS-treated PMN indicated that the LPS-induced production of endogenous TNF and IL-1 beta, which was further potentiated by IFN-gamma pretreatment, mediated in autocrine fashion the enhanced LPS-induced IL-8 accumulation observed at 18 hr. Furthermore, as shown by Northern blot analysis, all the effects of IFN-gamma on LPS-stimulated PMN were paralleled by changes at the level of TNF, IL-1 beta, and IL-8 mRNA expression. Taken together, these findings identify novel biological actions of IFN-gamma as a modulator of the acute inflammatory response.

Cytokines↗
PubMed1993

Interleukin 10 (IL-10) inhibits the release of proinflammatory cytokines from human polymorphonuclear leukocytes. Evidence for an autocrine role of tumor necrosis factor and IL-1 beta in mediating the production of IL-8 triggered by lipopolysaccharide.

In this study we have examined the effects of interleukin 10 (IL-10) on polymorphonuclear leukocytes (PMN), and found that it is a potent inhibitor of tumor necrosis factor (TNF), IL-1 beta, and IL-8 secretion triggered by lipopolysaccharide (LPS). Cytokine production by phagocytosing PMN was also inhibited by IL-10, but to a lesser extent than the LPS-induced production. As shown by Northern blot analysis, IL-10 diminished the levels of TNF, IL-1 beta, and IL-8 mRNAs late after the onset of stimulation of PMN with LPS. In addition, we provide evidence that the kinetics of LPS-induced IL-8 production by PMN is composed of two distinct phases. Specifically, our experiments demonstrated that in the first phase, the production of IL-8 is a process directly induced by LPS that lasts for some hours. After this early wave, a second phase begins that is sustained and leads to an elevated production of IL-8 that appears to be due to the endogenous release of TNF and IL-1 beta. This second wave can in fact be blocked by anti-TNF and anti-IL-1 beta neutralizing antibodies, and by IL-10 as the consequence of its downregulatory effects on TNF and IL-1 beta release. Taken together, these findings identify novel biological actions of IL-10 as a suppressor of the inflammatory response.

Cells, Cultured↗