scholarly journals Leishmania donovani-Induced Expression of Suppressor of Cytokine Signaling 3 in Human Macrophages: a Novel Mechanism for Intracellular Parasite Suppression of Activation

2003 ◽  
Vol 71 (4) ◽  
pp. 2095-2101 ◽  
Author(s):  
Sylvie Bertholet ◽  
Harold L. Dickensheets ◽  
Faruk Sheikh ◽  
Albert A. Gam ◽  
Raymond P. Donnelly ◽  
...  
Keyword(s):  
Leishmania Donovani ◽  
De Novo ◽  
Polymyxin B ◽  
Cytokine Signaling ◽  
Suppressor Of Cytokine Signaling ◽  
Necrosis Factor Alpha ◽  
Human Macrophages ◽  
Factor Alpha ◽  
Kinetics Of ◽  
Socs3 Mrna

ABSTRACT Leishmania donovani protozoan parasites, the causative agent of visceral leishmaniasis, establish an infection partly by interfering with cytokine signaling in the host macrophages. Therefore, we investigated the expression of the suppressor of cytokine signaling (SOCS) genes in human macrophages infected with L. donovani. The expression of SOCS3 mRNA was induced transiently after exposure to live or heat-killed parasites, but not purified lipophosphoglycan, while that of other SOCS genes remained unchanged. SOCS3 gene expression was not dependent on phagocytosis or on cytokines released by L. donovani-infected macrophages, such as interleukin-1β or tumor necrosis factor alpha. In addition, Leishmania used a different signaling pathway(s) than bacterial lipopolysaccharide to induce SOCS3 mRNA, as indicated by the kinetics of induction and sensitivity to polymyxin B inhibition. Finally, phosphorylation of the STAT1 transcription factor was significantly reduced in L. donovani-infected macrophages and required de novo transcription. The induction of SOCS3 provides a potent inhibitory mechanism by which intracellular microorganisms may suppress macrophage activation and interfere with the host immune response.

scholarly journals Major Outer Membrane Protein Omp25 of Brucella suis Is Involved in Inhibition of Tumor Necrosis Factor Alpha Production during Infection of Human Macrophages

2001 ◽  
Vol 69 (8) ◽  
pp. 4823-4830 ◽  
Author(s):  
Véronique Jubier-Maurin ◽  
Rose-Anne Boigegrain ◽  
Axel Cloeckaert ◽  
Antoine Gross ◽  
Maria-Teresa Alvarez-Martinez ◽  
...  
Keyword(s):  
Tumor Necrosis Factor ◽  
Tumor Necrosis Factor Alpha ◽  
Tumor Necrosis ◽  
Macrophage Infection ◽  
Necrosis Factor Alpha ◽  
Human Macrophages ◽  
Tnf Α ◽  
Brucella Suis ◽  
Factor Alpha ◽  
Necrosis Factor

ABSTRACT Brucella spp. can establish themselves and cause disease in humans and animals. The mechanisms by whichBrucella spp. evade the antibacterial defenses of their host, however, remain largely unknown. We have previously reported that live brucellae failed to induce tumor necrosis factor alpha (TNF-α) production upon human macrophage infection. This inhibition is associated with a nonidentified protein that is released into culture medium. Outer membrane proteins (OMPs) of gram-negative bacteria have been shown to modulate macrophage functions, including cytokine production. Thus, we have analyzed the effects of two major OMPs (Omp25 and Omp31) of Brucella suis 1330 (wild-type [WT] B. suis) on TNF-α production. For this purpose, omp25and omp31 null mutants of B. suis(Δomp25 B. suis and Δomp31 B. suis, respectively) were constructed and analyzed for the ability to activate human macrophages to secrete TNF-α. We showed that, in contrast to WTB. suis or Δomp31 B. suis, Δomp25 B. suis induced TNF-α production when phagocytosed by human macrophages. The complementation of Δomp25 B. suis with WT omp25 (Δomp25-omp25 B. suis mutant) significantly reversed this effect: Δomp25-omp25 B. suis-infected macrophages secreted significantly less TNF-α than did macrophages infected with the Δomp25 B. suismutant. Furthermore, pretreatment of WT B. suis with an anti-Omp25 monoclonal antibody directed against an epitope exposed at the surface of the bacteria resulted in substancial TNF-α production during macrophage infection. These observations demonstrated that Omp25 of B. suis is involved in the negative regulation of TNF-α production upon infection of human macrophages.

Endocytosis and Ca2+ are required for endotoxin-stimulated TNF-alpha release by rat Kupffer cells

1996 ◽  
Vol 271 (5) ◽  
pp. G920-G928 ◽  
Author(s):  
S. N. Lichtman ◽  
J. Wang ◽  
C. Zhang ◽  
J. J. Lemasters
Keyword(s):  
Kupffer Cells ◽  
Cytochalasin B ◽  
De Novo ◽  
Tnf Alpha ◽  
Mrna Levels ◽  
Necrosis Factor Alpha ◽  
Endosomal Acidification ◽  
A Cell ◽  
Factor Alpha ◽  
Free Media

Endotoxin [lipopolysaccharide (LPS)] is a cell wall polymer derived from Gram-negative bacteria that stimulates macrophages to produce a variety of inflammatory mediators. In these studies, we examined LPS-stimulated formation of tumor necrosis factor-alpha (TNF-alpha) by cultured rat Kupffer cells. Cytochalasin B and methylpalmitate, blockers of endocytosis, decreased LPS-stimulated TNF-alpha release by > 92%. Bafilomycin A, monensin, and chloroquine, which prevent endosomal acidification, also blocked LPS-stimulated release of TNF-alpha by > 90%. Cytochalasin B and bafilomycin A decreased TNF-alpha mRNA levels by > 90% after LPS stimulation. Consistent with the requirement for LPS uptake and processing was the observation that Kupffer cells required 30 min of contact with LPS for maximal TNF-alpha release. LPS-stimulated TNF-alpha release was unaltered by incubation in Ca(2+)-free ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid medium, and A-23187, a Ca2+ ionophore, failed to stimulate TNF-alpha release in the absence of LPS. However, nisoldipine, a Ca2+ channel blocker, suppressed LPS-stimulated TNF-alpha release in cells cultured both in Ca(2+)-containing and Ca(2+)-free media. Although thapsigargin did not block TNF-alpha release, this depleter of intracellular Ca2+ stores blocked LPS-stimulated TNF-alpha synthesis in Ca(2+)-free medium and decreased TNF-alpha mRNA levels by 80%. Furthermore, LPS induced a late rise in intracellular free Ca2+ demonstrated by video microscopy of fura 2-loaded Kupffer cells. De novo protein and RNA synthesis were required, since cycloheximide and actinomycin D also inhibited LPS-stimulated TNF-alpha release. We compared free TNF-alpha secreted into culture supernatants with cell-associated TNF-alpha and found that cytochalasin B, bafilomycin A, chloroquine, monensin, and nisoldipine did not increase bound, cell-associated TNF-alpha. We conclude that endocytosis and endocytic processing may be necessary for LPS-stimulated TNF-alpha release from Kupffer cells. Ca2+ release, regulated by dihydropyridine-sensitive Ca2+ channels, also appears to be necessary for LPS-induced signaling and may arise from intracellular stores associated with the endosome/lysosome compartment.

In vivo E-selectin upregulation correlates early with infiltration of PMN, later with PBL entry: MAbs block both

1996 ◽  
Vol 270 (1) ◽  
pp. H183-H193 ◽  
Author(s):  
R. M. Binns ◽  
S. T. Licence ◽  
A. A. Harrison ◽  
E. T. Keelan ◽  
M. K. Robinson ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Interleukin 1 ◽  
Inflammatory Infiltration ◽  
Necrosis Factor Alpha ◽  
Inflammatory Processes ◽  
Factor Alpha ◽  
Kinetics Of ◽  
Necrosis Factor

The endothelial molecule E-selectin binds most leukocyte subsets in vitro. Yet its role in regulating the very different kinetics of inflammatory infiltration of different leukocyte subsets in vivo is unclear. The kinetics of E-selectin upregulation and polymorphonuclear leukocyte (PMN) and blood lymphocyte (PBL) localization in inflammation induced by interleukin-1 alpha (IL-1 alpha), tumor necrosis factor-alpha (TNF-alpha), phytohemagglutinin (PHA), and phorbol myristate acetate (PMA) were investigated in a well-established inbred pig trafficking model. They differed markedly both for these three labeled indicators of inflammation and in each of the four inflammatory processes. In each, E-selectin upregulation correlated with early PMN entry and later with PBL infiltration but was more protracted than both. The importance of E-selectin was confirmed by marked inhibition of PMN and PBL entry (up to > 60%) by F(ab')2 anti-E-selectin. Involvement of other molecules was illustrated by similar or greater inhibition with anti-CD18 F(ab')2. We conclude that, like CD18, E-selectin is necessary for most PMN and PBL infiltration but alone is insufficient, consistent with the involvement of several alternative multistep molecular mechanisms in this entry.

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