Search PubMed⌕ Search

Biomedical subjects

M Sironi

Publications and source records attributed to M Sironi.

At least 127 records · Page 7Linked to original sources
PubMed1993

Migration of natural killer cells across endothelial cell monolayers.

Under certain conditions, NK cells accumulate rapidly at extrahematic sites. In an effort to define the mechanisms underlying recruitment of NK cells in tissues, we investigated their ability to migrate across endothelial cell (EC) monolayers. A considerable proportion of NK cells adhered to EC and about 30 to 40% of the adherent NK cells migrated across EC. NK cells were two to three times more efficient than resting unseparated T cells but were considerably less efficient than monocytes. Exposure of NK cells to IL-2 or of EC to IL-1, TNF, or IFN-gamma augmented transendothelial migration. mAb directed against CD18 and CD11a inhibited binding and migration of NK cells across resting or IL-1-activated EC, whereas anti-CD11b and c mAb did not. Thus, the LFA-1 pathway is a crucial determinant of the adhesive and migratory interactions of NK cells with vascular endothelium. Using IL-1-activated EC, We found that anti-VLA-4 and anti-VCAM-1 mAb, utilized in concert with anti-CD18, significantly reduced adhesion and transmigration. The CS-1 peptide of fibronectin had no effect on binding and migration but, when used in concert with anti-CD18 and anti-VCAM-1 (but not anti-VLA-4), caused a small, but significant, increase in inhibition. The capacity to bind and migrate across endothelial monolayers underlies the recruitment of NK cells in tissues under certain physiologic and pathologic conditions.

Amino Acid Sequence↗
PubMed1993

Interleukin-1 type II receptor: a decoy target for IL-1 that is regulated by IL-4.

Interleukin-1 (IL-1) interacts with cells through two types of binding molecules, IL-1 type I receptor (IL-1R I) and IL-1R II. The function of IL-1R II is unknown. In studies using monoclonal antibodies, IL-1 prolonged the in vitro survival of polymorphonuclear cells (PMN) through IL-1R I, and IL-4 antagonized the action of IL-1 by inducing expression and release of IL-1R II. Dexamethasone also induced expression and release of the IL-1R II in PMN. These results, together with the effect of antibodies to IL-1R on IL-1-induced production of cytokines in monocytes, indicate that IL-1 acts on myelomonocytic cells through IL-1R I and that IL-1R II inhibits IL-1 activity by acting as a decoy target for IL-1. The existence of multiple pathways of regulation emphasizes the need for tight control of IL-1 action.

Antibodies, Monoclonal↗
PubMed1993

Type II interleukin-1 receptor is not expressed in cultured endothelial cells and is not involved in endothelial cell activation.

Interleukin-1 (IL-1) profoundly affects a number of functions of endothelial cells (EC). It was previously shown that EC express the type I 80-Kd IL-1 receptor (IL-1 RI). In this study we define the expression and functional significance of the type II IL-1R (IL-1 RII) in EC. Human umbilical vein EC did not express appreciable levels of IL-1 RII mRNA as assessed by Northern analysis or reverse transcription and polymerase chain reaction. Exposure to various cytokines (including IL-4, which augments IL-1 RII in neutrophils) failed to induce IL-1 RII mRNA. The binding of radiolabeled IL-1 beta to EC was blocked by antitype I (M4) but not by antitype II (M22) monoclonal antibodies (MoAbs). MoAbs directed against the IL-1 RI (M1 and M4) inhibited the induction of IL-6 and adhesion molecules in EC by IL-1, whereas an anti-IL-1 RII (M22) was inactive. The human IL-1 receptor antagonist (IL-1ra) preferentially interacts with IL-1 RI versus IL-1 RII in the mouse. IL-1 ra inhibited the response of mouse endothelial cells to IL-1. We conclude that EC selectively express the IL-1 RI and that this is involved in the response of this cell type to IL-1.

Animals↗
PubMed1993

Molecular mapping and detoxification of the lipid A binding site by synthetic peptides.

Endotoxin [lipopolysaccharide (LPS)], the major antigen of the outer membrane of Gram-negative bacteria, consists of a variable-size carbohydrate chain that is covalently linked to N,O-acylated beta-1,6-D-glucosamine disaccharide 1,4'-bisphosphate (lipid A). The toxic activity of LPS resides in the lipid A structure. The structural features of synthetic peptides that bind to lipid A with high affinity, detoxify LPS in vitro, and prevent LPS-induced cytokine release and lethality in vivo were defined. The binding thermodynamics were comparable to that of an antigen-antibody reaction. Such synthetic peptides may provide a strategy for prophylaxis and treatment of LPS-mediated diseases.

Amino Acid Sequence↗
PubMed1993

Divergent effects of interleukin-10 on cytokine production by mononuclear phagocytes and endothelial cells.

Interleukin-10 (IL-10), a product of T helper type 2 (TH2) cells and monocytes, inhibits cytokine production in mononuclear phagocytes. Given the similarities and interrelationship between cells of the monocyte-macrophage lineage and endothelial cells, we examined the effects of IL-10 on vascular endothelium. Murine IL-10 induced low levels of IL-6 production and amplified induction of IL-6 by lipopolysaccharide (LPS) or IL-1 in the murine tEND.1 endothelioma line, used for these studies because it retains properties of normal endothelium. The effect was more evident after prolonged (48-72 h) exposure to IL-10. IL-10 had similar activity on other endothelioma lines, whereas it inhibited IL-6 production by peritoneal macrophages. Induction and amplification of cytokine production by IL-10 was associated with higher levels of mRNA, which were maintained longer (up to 48 h) than in controls. In addition to IL-6, murine IL-10 induced or amplified expression of the chemoattractant cytokines monocyte chemotactic protein-1 (MCP-1) and KC. Human IL-10 inhibited IL-6 release by LPS-stimulated human peripheral blood mononuclear cells, whereas it did not interfere with cytokine production by LPS- or IL-1-stimulated human umbilical vein endothelial cells. The selective inhibitory action of IL-10 on mononuclear phagocytes versus endothelial cells may play a role in the pathophysiology of TH2-directed responses.

Animals↗
PubMed1993

Inhibitors of cytochrome P450 suppress tumor necrosis factor production.

We tested the effect of different inhibitors of cytochrome P450 on tumor necrosis factor (TNF) production. Metyrapone and SKF525A (100 and 50 mg/kg, ip, respectively) suppressed serum TNF induced by cotreatment with endotoxin (LPS), (2.5 micrograms/mouse). Inhibition was independent of endogenous corticosteroids since it was also observed in adrenalectomized mice. In vitro production of TNF by endotoxin-stimulated human monocytes was also inhibited by metyrapone and SKF525A. Since lipoxygenase (LO) inhibitors also block TNF production and metyrapone was reported to inhibit LO, we suggest that inhibition by metyrapone and SKF525A might be due to inhibition of either LO or a cytochrome P450 implicated in the oxidation of endogenous substrates involved in the inflammatory response.

Animals↗
PubMed1993

Differential expression of the common beta and specific alpha chains of the receptors for GM-CSF, IL-3, and IL-5 in endothelial cells.

The present study was designed to reexamine the interaction of granulocyte-macrophage colony-stimulating factor (GM-CSF) with endothelial cells (EC) and to investigate the expression of CSF receptor chains in these cells. In agreement with previous data, GM-CSF induced directional migration and, to a lesser degree, proliferation of human umbilical vein EC. When compared to basic fibroblast growth factor, GM-CSF was comparable in terms of chemotactic activity and was substantially less active in terms of proliferation. Binding studies confirmed the presence of receptors for GM-CSF (GM-CSFR) on EC. The expression of the beta chain common to the GM-CSFR, IL-3 receptor, and IL-5 receptor, as well as of the individual alpha chains, was studied by Northern analysis and/or reverse transcription and polymerase chain reaction. EC expressed high levels of the common beta chain transcripts. Expression of the alpha(GM) and alpha(IL-5) chain mRNA was minimal or absent in normal EC, though the transformed ECV304 endothelial cell line had substantial amounts of alpha(GM) chain mRNA. Unexpectedly, EC expressed alpha(IL-3) chain transcripts. IL-3 induced migration of EC across polycarbonate filters, whereas IL-5 was inactive.

Animals↗
PubMed1993

Mast cells do not contribute to the rapid appearance of TNF in the serum of LPS-treated mice: a study with mast cell-deficient mice.

Mast cells have been proposed to be an important source of tumor necrosis factor (TNF). The purpose of this work was to investigate their relevance in the rapid appearance of TNF in the serum of mice after injection of an endotoxin (lipopolysaccharide, LPS). We have therefore measured TNF levels in serum and spleen homogenates of mast cell-deficient mice (WBB6F1-W/Wv) or their normal littermate controls. The results indicated that mast cell-deficient mice are not defective in their LPS-induced TNF production. They also tend to produce more interleukin 6 (IL-6) than normal mice. To test other conditions where mast cells might be stimulated to produce TNF, we measured TNF in mice injected with the mast cell degranulator, compound 48/80 or during anaphylactic shock. Anaphylactic shock induced very low levels of TNF in the serum, while compound 48/80 (4.2 mg/kg) was ineffective. These data suggest that mast cells do not contribute significantly to systemic TNF production in these experimental models.

Anaphylaxis↗
PubMed1993

Tripartite differentiation (squamous, glandular, and melanocytic) of a primary cutaneous neuroendocrine carcinoma. An immunocytochemical and ultrastructural study.

We report a case of primary cutaneous neuroendocrine carcinoma (PCNEC) with squamous, glandular, and melanocytic differentiation and associated Bowen disease. The paranuclear globular positivity of low-molecular-weight cytokeratins agrees with the ultrastructural observations of paranuclear fibrous bodies in the small neuroendocrine cells, while the diffuse cytoplasmic positivity corresponds to the sparse intermediate filaments in large cells with squamous differentiation. "Transitional forms" are characterized by both diffuse and globular cytoplasmic positivity for cytokeratins and by the ultrastructural evidence of neuroendocrine and squamous features. Therefore the ultrastructural demonstration of intracytoplasmic tonofibrils and tonofilaments, intercellular glandular lumina, lined by well-formed microvilli, and immature premelanosomes in the neurosecretory cells supports the proposed tripartite differentiation of neuroendocrine cells of this case of PCNEC.

Aged↗
PubMed1993

An oncocytic carcinoma of the pancreas with pulmonary and subcutaneous metastases.

A 72-year-old man with an oncocytic carcinoma of the pancreas of 3 years' duration was treated by pancreatoduodenectomy; 5 and 16 months later, two pulmonary metastases and one subcutaneous metastasis of the thigh were removed. No sign of local recurrence or metastases was present at 20-month follow-up. It is suggested that oncocytic carcinomas of the pancreas have a favorable prognosis if treated surgically.

Aged↗
PubMed1993

Role of acute-phase proteins in interleukin-1-induced nonspecific resistance to bacterial infections in mice.

Treatment with a single low dose (80 to 800 ng) of interleukin-1 (IL-1) 24 h before a lethal bacterial challenge of granulocytopenic and normal mice enhances nonspecific resistance. Since IL-1 induces secretion of acute-phase proteins, liver proteins which possess several detoxifying effects, we investigated the role of these proteins in the IL-1-induced protection. Inhibition of liver protein synthesis with D-galactosamine (GALN) completely inhibited the IL-1-induced synthesis of acute-phase proteins. GALN pretreatment abolished the protective effect of IL-1 on survival completely (neutropenic mice infected with Pseudomonas aeruginosa) or partially (nonneutropenic mice infected with Klebsiella pneumoniae). Pretreatment with IL-6, a cytokine induced by IL-1, did not reproduce the protection offered after IL-1 pretreatment, nor did it enhance or deteriorate the IL-1-enhanced resistance to infection. A protective effect of IL-1 via effects on glucose homeostasis during the acute-phase response was investigated by comparing plasma glucose levels in IL-1-treated mice and control mice before and during infection. Although glucose levels in IL-1-pretreated mice were somewhat higher in the later stages of infection, no significant differences from levels in control mice were present, and the glucose levels in control-treated animals never fell to hypoglycemic values. We conclude that the IL-1-induced nonspecific resistance is mediated neither by the induction of IL-6 nor by the effects of IL-1 on glucose homeostasis. Acute-phase proteins generated after IL-1 pretreatment, however, seem to play a critical role in the IL-1-induced protection to infection.

Acute-Phase Proteins↗
PubMed1993

Differential regulation of cytokine production in lipopolysaccharide tolerance in mice.

We investigated the pattern of down-regulation of cytokine production in endotoxin (lipopolysaccharide [LPS]) tolerance. A 4-day treatment with LPS (35 micrograms per mouse) was followed by a challenge on day 6 with one more injection of LPS. Circulating tumor necrosis factor (TNF) and interleukin-6 (IL-6) could not be induced (> 99% inhibition) by LPS in LPS-tolerant mice; colony-stimulating factor (CSF) was also down-regulated by more than 95%, whereas interferon (IFN) and IL-1 syntheses were only partially inhibited. To study the mechanism of cytokine down-regulation in tolerance, we attempted to reverse the tolerant state by pretreatment with phorbol 12-myristate 13-acetate (PMA) (4 micrograms per mouse) 10 min before the LPS challenge. PMA completely restored IL-6 production and partially that of CSF. PMA had no effect on IFN production and inhibited the induction of IL-1. TNF production was also not restored by PMA. To investigate the role of endogenously produced cytokines in the development of LPS tolerance, we administered IL-6, TNF, or IL-1 alpha, using the same treatment schedule as that for LPS. Whereas IL-6 had no effect, IL-1 alpha or TNF induced partial tolerance to LPS in terms of inhibition of LPS-stimulated TNF and IL-6 production. However, a full LPS-tolerant state could not be induced by administration of recombinant cytokines, suggesting the existence of additional mechanisms, such as a loss of LPS receptors or changes in release of soluble binding proteins.

Animals↗
PubMed1993

Modulation of systemic interleukin-6 induction by central interleukin-1.

Centrally administered interleukin (IL)-1 [both alpha and beta forms, 200 ng/rat intracerebroventricularly (icv)] results in a larger increase in serum IL-6 than after systemic injection, indicating the brain's role in the acute phase response. This action was prevented by the IL-1-receptor antagonist IL-1Ra (20 micrograms/rat icv). Neither antiserum against corticotropin-releasing factor (CRF) nor the alpha-helical-CRF antagonist (25 micrograms/rat icv) affected IL-6 induction by central IL-1 beta, which, however, was significantly prevented by the synthetic glucocorticoid dexamethasone [3 mg/kg intraperitoneally (ip)]. Naloxone, the opiate antagonist, but not naloxone methiodide, its quaternary salt that does not penetrate the blood-brain barrier (both administered at 10 mg/kg ip), antagonized this action of IL-1 beta. After intracerebroventricular IL-1 beta, IL-6 levels in brain areas (striatum, hippocampus, hypothalamus) were extremely low, suggesting that the brain does not significantly contribute to IL-6 synthesis in this condition. The results show that induction of high serum IL-6 levels by central IL-1 beta is mediated by brain IL-1 receptors and is sensitive to inhibition by corticosteroids. The inhibitory effect of naloxone suggests that central opiates are required for this action of IL-1 beta.

Animals↗
PubMed1993

Early down-regulation of TNF production by LPS tolerance in human monocytes: comparison with IL-1 beta, IL-6, and IL-8.

We studied the effect of a 4-hr preexposure to LPS on the ability of human monocytes to respond to a subsequent stimulation with LPS in terms of cytokine production. LPS-preexposed monocytes did not produce TNF on LPS restimulation, but they retained the ability to produce IL-1 beta, IL-6, and IL-8. LPS-tolerant monocytes were still capable of producing TNF when restimulated with zymosan. Down-regulation of TNF by LPS tolerance was also evident at the mRNA level. To investigate the possible mechanisms underlying this phenomenon, we also studied the effect of LPS preexposure on membrane CD14, which was suggested to be an LPS receptor, and on intracellular cAMP, an inhibitor of TNF production. LPS induced a 50% decrease in CD14 expression. On the other hand, the increase in cAMP levels by LPS was not affected by preexposure to LPS. In conclusion, (a) TNF is more rapidly down-regulated than IL-1 beta, IL-6, and IL-8 during LPS tolerance in vitro; (b) early LPS tolerance is associated with decreased CD14, which might partially explain the decreased LPS response; and (c) a feedback mechanism controlling TNF synthesis, cAMP elevation, is not down-regulated in LPS tolerance.

Antigens, CD↗
PubMed1993

Suppression of interleukin-6 production in endotoxin tolerance in a mouse glioma cell line: reversal by phorbol ester.

Tolerance to endotoxin (lipopolysaccharide, LPS) was shown to be mediated by an inhibition of cytokine production. We have studied the effect of 3-day pretreatment with LPS on production of IL-6 in response to a subsequent challenge with LPS in a mouse glioma. The results indicated that in this model, a complete blockage of IL-6 production is induced by LPS pretreatment. This is associated with a decrease of LPS-induced IL-6 mRNA levels. LPS-induced IL-6 production can be restored by PMA, as it was previously observed in vivo, suggesting that down-regulation of IL-6 response in LPS tolerance occurs at the transcriptional level, probably by down-regulating protein kinase C or some other PMA-activable signaling system. IL-6 production is also down-regulated by 3-day preincubation with IL-6 and, to a lesser extent, with IL-1 or TNF, indicating that IL-6 can down-regulate its own production.

Animals↗
PubMed1992

Expression and involvement of c-fos and c-jun protooncogenes in programmed cell death induced by growth factor deprivation in lymphoid cell lines.

Cell death induced by growth factor withdrawal is a programed event in which gene transcription and translation are required. Thus, it is likely that genes encoding for transcriptional factors can play an important role in this process. We have tested this hypothesis by analyzing c-fos and c-jun protooncogene expression and involvement in lymphoid cells deprived of growth factors. Interleukin (IL)-6- and IL-2-dependent mouse cell lines undergo programmed cell death after growth factor deprivation. Northern blot analysis shows that c-fos and c-jun protooncogenes are rapidly induced (within 60 min) after growth factor deprivation in IL-6- and IL-2-dependent mouse cells. Induction is transient, being undetectable at 120 min after deprivation. Induction of these protooncogenes is at the transcriptional level, as demonstrated by actinomycin D and nuclear run-off experiments. Antisense oligonucleotides directed against c-fos and c-jun mRNAs consistently reduced the expression of these genes in treated cells. This reduction was associated with increased survival of growth factor-deprived lymphoid cells, thus suggesting that the expression of c-fos and c-jun protooncogenes may represent an important early event in the activation of the genetic program of cell death.

Base Sequence↗
PubMed1992

Synthesis of platelet-activating factor by polymorphonuclear neutrophils stimulated with interleukin-8.

Human interleukin-8 (IL-8) was evaluated for its capability to induce the synthesis and release of platelet-activating factor (PAF) from human polymorphonuclear neutrophils (PMN). IL-8 promotes in a dose-dependent fashion (1-100 ng/ml) a rapid synthesis of PAF, which is only partially released. The synthesis of PAF is preceded by the activation of acetyl-CoA: 1-alkyl-2-lyso-sn-glycero-3-phosphocholine acetyl-transferase, suggesting that IL-8 activates the "remodeling pathway" of PAF synthesis. By thin layer chromatography and reverse-phase high pressure liquid chromatography, we demonstrated that PAF synthesized by human PMN stimulated with IL-8 is heterogeneous: the 2-acetylated phospholipids having the biological and physicochemical characteristics of PAF include the 1-O-alkyl form, which is produced in large extent (51%), and the 1-acyl form (20%). The analysis of the individual molecular species of radyl chain indicated nine peaks, 16:0 and 18:0 being the predominant forms. These results identify PAF as a direct product of IL-8 stimulation in PMN.

Acetyltransferases↗