Macrophages, reactive nitrogen species, and lung injury
Evidence has accumulated over the past several years demonstrating that lung injury following inhalation of irritants like ozone is due, not only to direct effects of the chemical, but also indirectly to the actions of inflammatory mediators released by infiltrating macrophages. Among the mediators involved in the cytotoxic process, reactive nitrogen species (RNS) are of particular interest because of their well-documented cytotoxic potential. Findings that macrophage suppression blocks RNS production and ozone-induced toxicity provide strong support for a role of these cells and inflammatory mediators in lung injury. Recent investigations have focused on understanding pathways by which macrophages become activated to release RNS. One protein that has attracted considerable attention is caveolin-1, a membrane scaffolding molecule that functions to negatively regulate cell signaling. The fact that expression of caveolin-1 is down-regulated in macrophages after ozone inhalation suggests a mechanism controlling the release of cytotoxic mediators by these inflammatory cells.
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Available from: Samira Tliba
- "Pro-inflammatory activation of vascular endothelium caused by ischemia, infectious agents, cytokines, reactive oxygen species (ROS) including superoxide and H2O2 and other pathological mediators, is implicated in cardiac, pulmonary, cerebral and peripheral vascular pathology , , , . Such activation, manifested among other signs by expression of cell adhesion molecules including vascular cell adhesion molecule 1 (VCAM), in turn aggravates inflammation via adhesion and trafficking of activated leukocytes, enhanced vascular permeability and thrombosis . "
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ABSTRACT: Pro-inflammatory activation of vascular endothelium is implicated in pathogenesis of severe conditions including stroke, infarction and sepsis. We have recently reported that superoxide dismutase (SOD) conjugated with antibodies (Ab/SOD) that provide targeted delivery into endothelial endosomes mitigates inflammatory endothelial activation by cytokines and agonists of Toll-like receptors (TLR). The goal of this study was to appraise potential utility and define the mechanism of this effect. Ab/SOD, but not non-targeted SOD injected in mice alleviated endotoxin-induced leukocyte adhesion in the cerebral vasculature and protected brain from ischemia-reperfusion injury. Transfection of endothelial cells with SOD, but not catalase inhibited NFκB signaling and expression of Vascular Cell Adhesion Molecule-1 induced by both cytokines and TLR agonists. These results affirmed that Ab/SOD-quenched superoxide anion produced by endothelial cells in response to proinflammatory agents mediates NFκB activation. Furthermore, Ab/SOD potentiates anti-inflammatory effect of NO donors in endothelial cells in vitro, as well as in the endotoxin-challenged mice. These results demonstrate the central role of intracellular superoxide as a mediator of pro-inflammatory activation of endothelium and support the notion of utility of targeted interception of this signaling pathway for management of acute vascular inflammation.
PLoS ONE 10/2013; 8(10):e77002. DOI:10.1371/journal.pone.0077002 · 3.23 Impact Factor
Available from: Romain Solinhac
- "Macrophages play a key role in the immune response being the first cells to be exposed to microorganisms. These cells are considered as sentinel cells against infectious pathogens and involved in phagocytosis, antigen presentation, production of antimicrobial effector molecules and release of cytokines and chemokines that in turn contribute to immune cell recruitment and activation [18-20]. The recognition of microorganisms by macrophages occurs through a major receptor family expressed in distinct cell subsets and tissues called the Toll-Like Receptors (TLR) [21-23]. "
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ABSTRACT: T-2 toxin is known to be one of the most toxic trichothecene mycotoxins. Exposure to T-2 toxin induces many hematologic and immunotoxic disorders and is involved in immuno-modulation of the innate immune response. The objective of this work was to evaluate the effects of T-2 toxin on the activation of macrophages by different agonists of Toll-like receptors (TLR) using an in vitro model of primary porcine alveolar macrophages (PAM). Cytotoxic effects of T-2 toxin on PAM were first evaluated. An IC50 of 19.47 ± 0.9753 nM was determined for the cytotoxicity of T-2 toxin. A working concentration of 3 nM of T-2 toxin was chosen to test the effect of T-2 toxin on TLR activation; this dose was not cytotoxic and did not induce apoptosis as demonstrated by Annexin/PI staining. A pre-exposure of macrophages to 3 nM of T-2 toxin decreased the production of inflammatory mediators (IL-1 beta, TNF-alpha, nitric oxide) in response to LPS and FSL1, TLR4 and TLR2/6 agonists respectively. The decrease of the pro-inflammatory response is associated with a decrease of TLR mRNA expression. By contrast, the activation of TLR7 by ssRNA was not modulated by T-2 toxin pre-treatment. In conclusion, our results suggest that ingestion of low concentrations of T-2 toxin affects the TLR activation by decreasing pattern recognition of pathogens and thus interferes with initiation of inflammatory immune response against bacteria and viruses. Consequently, mycotoxins could increase the susceptibility of humans and animals to infectious diseases.
Veterinary Research 04/2012; 43(1):35. DOI:10.1186/1297-9716-43-35 · 2.82 Impact Factor
Available from: Paul R Reynolds
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ABSTRACT: Receptors for advanced glycation end-products (RAGE) are multiligand cell surface receptors of the immunoglobin family expressed by epithelium and macrophages, and expression increases following exposure to cigarette smoke extract (CSE). The present study sought to characterize the proinflammatory contributions of RAGE expressed by alveolar macrophages (AMs) following CSE exposure. Acute exposure of mice to CSE via nasal instillation revealed diminished bronchoalveolar lavage (BAL) cellularity and fewer AMs in RAGE knockout (KO) mice compared with controls. Primary AMs were obtained from BAL, exposed to CSE in vitro, and analyzed. CSE significantly increased RAGE expression by wild-type AMs. Employing ELISAs, wild-type AMs exposed to CSE had increased levels of active Ras, a small GTPase that perpetuates proinflammatory signaling. Conversely, RAGE KO AMs had less Ras activation compared with wild-type AMs after exposure to CSE. In RAGE KO AMs, assessment of p38 MAPK and NF-κB, important intracellular signaling intermediates induced during an inflammatory response, revealed that CSE-induced inflammation may occur in part via RAGE signaling. Lastly, quantitative RT-PCR revealed that the expression of proinflammatory cytokines including TNF-α and IL-1β were detectably decreased in RAGE KO AMs exposed to CSE compared with CSE-exposed wild-type AMs. These results reveal that primary AMs orchestrate CSE-induced inflammation, at least in part, via RAGE-mediated mechanisms.
AJP Lung Cellular and Molecular Physiology 04/2012; 302(11):L1192-9. DOI:10.1152/ajplung.00099.2012 · 4.08 Impact Factor
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