Spatial coordination of cell-adhesion molecules and redox cycling of iron in the microvascular inflammatory response to pulmonary injury.
ABSTRACT Transmigration of phagocytic leukocytes (PLCs) from the peripheral blood into injured lung requires a conversion of the microvascular endothelial cells (ECs) to the proinflammatory phenotypes and spatiotemporal interplay of different types of cell adhesion molecules (CAMs) on PLC and endothelium. The present report is focused on involvement of iron-dependent redox signaling in spatial coordination of lung CAM due to either a pulmonary trauma or endotracheal iron administration in rats. Redox alterations, deposition of 3-nitrotyrosine, expression of VE-cadherin, ICAM-1, and the PLC integrins, and the status of thioredoxin, Ref-1, NF-kappaB and Nrf2 redox-sensitive elements in the alveolar microvasculature were assessed with EPR spectroscopy, immunobloting, and confocal microscopy. We demonstrated for the first time in vivo that the presence of catalytically active iron, deposition of myeloperoxidase, and induction of the oxidative stress in the lung-injury models were accompanied by (a) downregulation of VE-cadherin, (b) upregulation and polarization of ICAM-1 and the PLC integrins, and (c) nuclear translocation and interaction of thioredoxin, Ref-1, and NF-kappaB and complex structural changes in EC and PLC at the sites of their contacts. The studies suggested that a part of the proinflammatory action of iron in the lung resulted from its stimulation of the redox-sensitive factors.
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ABSTRACT: Although iron is known to be a component of the pathogenesis and/or maintenance of acute lung injury (ALI) in experimental animals and human subjects, the majority of these studies have focused on disturbances in iron homeostasis in the airways resulting from exposure to noxious gases and particles. Considerably less is known about the effect of increased plasma levels of redox-reactive non-transferrin bound iron (NTBI) and its impact on pulmonary endothelium. Plasma levels of NTBI can increase under various pathophysiological conditions, including those associated with ALI, and multiple mechanisms are in place to affect the [Fe(2+)]/[Fe(3+)] redox steady state. It is well accepted, however, that intracellular transport of NTBI occurs after reduction of [Fe(3+)] to [Fe(2+)] (and is mediated by divalent metal transporters). Accordingly, as an experimental model to investigate mechanisms mediating vascular effects of redox reactive iron, rat pulmonary artery endothelial cells (RPAECs) were subjected to pulse treatment (10 min) with [Fe(2+)] nitriloacetate (30 μM) in the presence of pyrithione, an iron ionophore, to acutely increase intracellular labile pool of iron. Cellular iron influx and cell shape profile were monitored with time-lapse imaging techniques. Exposure of RPAECs to [Fe(2+)] resulted in: (i) an increase in intracellular iron as detected by the iron sensitive fluorophore, PhenGreen; (ii) depletion of cell glutathione; and (iii) nuclear translocation of stress-response transcriptional factors Nrf2 and NFkB (p65). The resulting iron-induced cell alterations were characterized by cell polarization and formation of membrane cuplike and microvilli-like projections abundant with ICAM-1, caveolin-1, and F-actin. The iron-induced re-arrangements in cytoskeleton, alterations in focal cell-cell interactions, and cell buckling were accompanied by decrease in electrical resistance of RPAEC monolayer. These effects were partially eliminated in the presence of N,N'-bis (2-hydroxybenzyl) ethylenediamine-N,N'-diacetic acid, an iron chelator, and Y27632, a Rho-kinase inhibitor. Thus acute increases in labile iron in cultured pulmonary endothelium result in structural remodeling (and a proinflammatory phenotype) that occurs via post-transcriptional mechanisms regulated in a redox sensitive fashion.Biology of Metals 11/2011; 25(1):203-17. DOI:10.1007/s10534-011-9498-2 · 2.69 Impact Factor
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ABSTRACT: Macroautophagy (mAG) is a lysosomal mechanism of degradation of cell self-constituents damaged due to variety of stress factors, including ionizing irradiation. Activation of mAG requires expression of mAG protein Atg8 (LC3) and conversion of its form I (LC3-I) to form II (LC3-II), mediated by redox-sensitive Atg4 protease. We have demonstrated upregulation of this pathway in the innate host defense Paneth cells of the small intestine (SI) due to ionizing irradiation and correlation of this effect with induction of pro-oxidant inducible nitric oxide synthase (iNOS). CD2F1 mice were exposed to 9.25 Gy gamma-ionizing irradiation. Small intestinal specimens were collected during 7 days after ionizing irradiation. Assessment of ionizing irradiation-associated alterations in small intestinal crypt and villus cells and activation of the mAG pathway was conducted using microscopical and biochemical techniques. Analysis of iNOS protein and the associated formation of nitrites and lipid peroxidation products was performed using immunoblotting and biochemical analysis, and revealed increases in iNOS protein, nitrate levels and oxidative stress at day 1 following ionizing irradiation. Increase in immunoreactivity of LC3 protein in the crypt cells was observed at day 7 following ionizing irradiation. This effect predominantly occurred in the CD15-positive Paneth cells and was associated with accumulation of LC3-II isoform. The formation of autophagosomes in Paneth cells was confirmed by transmission electron microscopy (TEM). Up-regulation of LC3 pathway in the irradiated SI was accompanied by a decreased protein-protein interaction between LC3 and chaperone heat shock protein 70. A high-level of LC3-immunoreactivity in vacuole-shaped structures was spatially co-localized with immunoreactivity of 3-nitro-tyrosine. The observed effects were diminished in iNOS knockout B6.129P2-NOS2(tm1Lau)/J mice subjected to the same treatments. We postulate that the observed up-regulation of mAG in the irradiated small intestine is at least in part mediated by the iNOS signalling mechanism.The Journal of Pathology 10/2009; 219(2):242-52. DOI:10.1002/path.2591 · 7.33 Impact Factor
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ABSTRACT: Abstract Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are severe syndromes resulting from the diffuse damage of the pulmonary parenchyma. ALI and ARDS are induced by a plethora of local or systemic insults, leading to the activation of multiple pathways responsible for injury, resolution, and repair or scarring of the lungs. Despite the large efforts aimed at exploring the roles of different pathways in humans and animal models and the great strides made in understanding the pathogenesis of ALI/ARDS, the only viable treatment options are still dependent on ventilator and cardiovascular support. Investigation of the pathophysiological mechanisms responsible for initiation and resolution or advancement toward lung scarring in ALI/ARDS animal models led to a better understanding of the disease's complexity and helped in elucidating the links between ALI and systemic multiorgan failure. Although animal models of ALI/ARDS have pointed out a variety of new ideas for study, there are still limited data regarding the initiating factors, the critical steps in the progression of the disease, and the central mechanisms dictating its resolution or progression to lung scarring. Recent studies link deficiency of intersectin-1s (ITSN-1s), a prosurvival protein of lung endothelial cells, to endothelial barrier dysfunction and pulmonary edema as well as to the repair/recovery from ALI. This review discusses the effects of ITSN-1s deficiency on pulmonary endothelium and its significance in the pathology of ALI/ARDS.09/2013; 3(3):478-98. DOI:10.1086/674439