Biomedical subjects

Andrew J Ghio

Publications and source records attributed to Andrew J Ghio.

At least 55 records · Page 3Linked to original sources

PubMed2003

DMT1 expression is increased in the lungs of hypotransferrinemic mice.

Despite a lack of transferrin, hypotransferrinemic (Hp) mice demonstrate an accumulation of iron in peripheral organs including the lungs. One potential candidate for such transferrin-independent uptake of iron is divalent metal transporter-1 (DMT1), an established iron transporter. We tested the hypothesis that increased concentrations of iron in the lungs of Hp mice are associated with elevations in DMT1 expression. With the use of inductively coupled plasma emission spectroscopy, measurements of nonheme iron confirmed significantly elevated concentrations in the lung tissue of Hp mice relative to the wild-type mice. Western blot analyses for the expression of two isoforms of DMT1 in the Hp mice relative to the wild-type animals demonstrated an elevation for the isoform that lacks an iron-responsive element (IRE) with significant decrements in the expression of +IRE DMT1. With the use of immunohistochemistry, -IRE DMT1 was localized to both airway epithelial cells and alveolar macrophages in wild-type mice. Staining appeared increased in both types of cells in the Hp mice. Elevated concentrations of both tissue nonheme iron and expression of -IRE DMT1 in the Hp mice were associated with increased quantities of -IRE mRNA. There was no difference between wild-type and homozygotic Hp mice in the amount of mRNA for DMT1 +IRE. We conclude that differences between Hp and wild-type mice in nonheme iron concentrations were accompanied by increases in the expression of -IRE DMT1. Increased expression of -IRE DMT1 in the lungs of the Hp mice could be responsible for elevated concentrations of the metal in these tissues.

Animals↗

PubMed2003

Oxalate deposition on asbestos bodies.

We report on a deposition of oxalate crystals on ferruginous bodies after occupational exposure to asbestos demonstrated in 3 patients. We investigated the mechanism and possible significance of this deposition by testing the hypothesis that oxalate generated through nonenzymatic oxidation of ascorbate by asbestos-associated iron accounts for the deposition of the crystal on a ferruginous body. Crocidolite asbestos (1000 microg/mL) was incubated with 500 micromol H(2)O(2) and 500 micromol ascorbate for 24 hours at 22 degrees C. The dependence of oxalate generation on iron-catalyzed oxidant production was tested with the both the metal chelator deferoxamine and the radical scavenger dimethylthiourea. Incubation of crocidolite, H(2)O(2), and ascorbate in vitro generated approximately 42 nmol of oxalate in 24 hours. Oxalate generation was diminished significantly by the inclusion of either deferoxamine or dimethylthiourea in the reaction mixture. Incubation of asbestos bodies and uncoated fibers isolated from human lung with 500 micromol H(2)O(2) and 500 micromol ascorbate for 24 hours at 22 degrees C resulted in the generation of numerous oxalate crystals. We conclude that iron-catalyzed production of oxalate from ascorbate can account for the deposition of this crystal on ferruginous bodies.

Asbestos, Crocidolite↗

PubMed2003

DMT1: a mammalian transporter for multiple metals.

DMT1 has four names, transports as many as eight metals, may have four or more isoforms and carries out its transport for multiple purposes. This review is a start at sorting out these multiplicities. A G185R mutation results in diminished gastrointestinal iron uptake and decreased endosomal iron exit in microcytic mice and Belgrade rats. Comparison of mutant to normal rodents is one analytical tool. Ectopic expression is another. Antibodies that distinguish the isoforms are also useful. Two mRNA isoforms differ in the 3' UTR: +IRE DMT1 has an IRE (Iron Responsive Element) but -IRE DMT1 lacks this feature. The +/-IRE proteins differ in the distal 18 or 25 amino acid residues after shared identity for the proximal 543 residues. A major function is serving as the apical iron transporter in the lumen of the gut. The +IRE isoform appears to have that role. Another role is endosomal exit of iron. Some evidence indicts the -IRE isoform for this function. In our ectopic expression assay for metal uptake, four metals--Fe2+, Mn2+, Ni2+ and Co2+--respond to the normal DMT1 cDNA but not the G185R mutant. Two metals did not--Cd2+ and Zn2+--and two--Cu2+ and Pb2+--remain to be tested. In competition experiments in the same assay, Cd2+, Cu2+ and Pb2+ inhibit Mn2+ uptake but Zn2+ did not. In rodent mutants, Fe and Mn appear more dependent on DMT1 than Cu and Zn. Experiments based on ectopic expression, specific antibodies that inhibit metal uptake and labeling data indicate that Fe3+ uptake depends on a different pathway in multiple cells. Two isoforms localize differently in a number of cell types. Unexpectedly, the -IRE isoform is in the nuclei of cells with neuronal properties. While the function of -IRE DMT1 in the nucleus is speculative, one may safely infer that this localization identifies new role(s) for this multifunctional transporter. Management of toxic challenges is another function related to metal homeostasis. Airways represent a gateway tissue for metal entry. Preliminary evidence using specific PCR primers and antibodies specific to the two isoforms indicates that -IRE mRNA and protein increase in response to exposure to metal in lungs and in a cell culture model; the +IRE form is unresponsive. Thus the -IRE form could be part of a detoxification system in which +IRE DMT1 does not participate. How does iron status affect other metals' toxicity? In the case of Mn, iron deficiency may enhance cellular responses.

Amino Acid Sequence↗

PubMed2003

Exposure to concentrated ambient air particles alters hematologic indices in humans.

Descriptions of changes in hematological indices have contested the premise that the biological effects of suspended particulate matter (PM) are restricted to the lung. Employing approximately 40 hematologic parameters reflecting blood cells, chemistries, mediators, and coagulation factors, we tested the hypothesis that exposure to concentrated ambient air particles (CAPs) can be associated with changes in hematologic indices in normal humans. Twenty healthy young volunteers were exposed to either filtered air (n = 5) or CAPs (n = 15) with a mean PM mass of 120.5 +/- 14.0 microg/m3 and a range from 15.0-357.6 microg/m3. Hematologic indices were measured. Changes in all parameters are expressed as the absolute value either immediately after or 24 h after exposure. Differences between responses of those individuals exposed to filtered air and CAPs were tested using the T-test of independent means. If significant differences between the two groups were suggested by the T-test (p < .10), the relationship was further evaluated employing linear regression techniques. Regression analysis verified significant linear relationships between particle mass the individual was exposed to and (1) decrements in WBC count 24 h later, (2) decreases in lactate dehydrogenase (LDH) concentration 24 h later, and (3) elevations in fibrinogen levels 24 h later. There were no changes in either inflammatory mediators in the blood or indices of coagulation/fibrinolysis other than fibrinogen. We conclude that exposure of healthy volunteers to CAPs can be associated with decreases of both white blood cell (WBC) count and LDH and increased concentrations of fibrinogen in the blood.

Adult↗

PubMed2003

Iron and iron-related proteins in the lower respiratory tract of patients with acute respiratory distress syndrome.

OBJECTIVE: An increased oxidative stress in the lower respiratory tract of individuals with acute respiratory distress syndrome is considered to be one mechanism of lung injury in these patients. Cell and tissue damage resulting from an oxidative stress can ultimately be the consequence of a disruption of normal iron metabolism and an increased availability of catalytically active metal. Using bronchoalveolar lavage fluid, we quantified concentrations of iron and iron-related proteins in the lower respiratory tract in patients with acute respiratory distress syndrome and healthy volunteers. DESIGN: A clinical study to quantify iron and iron-related proteins in the lower respiratory tract in patients with acute respiratory distress syndrome and healthy volunteers. PATIENTS: We studied 14 patients with acute respiratory distress syndrome and 28 healthy volunteers. MAIN RESULTS: Comparable to previous investigation, protein, albumin, and cytokine concentrations in the bronchoalveolar lavage fluid were significantly increased in acute respiratory distress syndrome patients. The concentrations of total and nonheme iron were also increased in the lavage fluid of patients. Concentrations of hemoglobin, haptoglobin, transferrin, transferrin receptor, lactoferrin, and ferritin in the bronchoalveolar lavage fluid were all significantly increased in acute respiratory distress syndrome patients. CONCLUSIONS: We conclude that bronchoalveolar lavage fluid indices reflect a disruption of normal iron metabolism in the lungs of acute respiratory distress syndrome patients. Increased concentrations of available iron in acute respiratory distress syndrome may participate in catalyzing oxidant generation destructive to the tissues of the lower respiratory tract. However, increased metal availability is also likely to elicit an increased expression of transferrin receptor, lactoferrin, and ferritin in the lower respiratory tract which will function to diminish this oxidative stress.

Adult↗

PubMed2002

Haptoglobin reduces lung injury associated with exposure to blood.

The biological functions of the acute- phase protein haptoglobin (Hp) may be related to its ability to bind hemoglobin (Hb) or to modulate immune response. Hp is expressed at a high level in lung cells, yet its protective role(s) in the lung is not known. With the use of transgenic mice overexpressing Hp in alveolar macrophages, we demonstrated that Hp diminished Hb-induced lung injury when the lung was exposed to whole blood. In transgenic mouse lungs, Hb was more efficiently removed, and the induction of stress- responsive heme oxygenase-1 gene was significantly lower when compared with wild-type mice. At 24 h after blood treatment, the ferritin level that serves as an index for intracellular iron content was also lower in alveolar macrophages in transgenic mice than in wild-type mice. We propose that an Hp-mediated Hb catabolism process exists in alveolar macrophages. This process is likely coupled to an iron mobilization pathway and may be an efficient mechanism to reduce oxidative damage associated with hemolysis.

Animals↗

PubMed2002

Rapid mtDNA deletion by oxidants in rat liver mitochondria after hemin exposure.

The amounts of superoxide and hydrogen peroxide generated by mitochondria under physiological conditions can be enhanced by cellular stress. This study tested the hypothesis that the response to hemin-induced stress, which includes heme oxygenase-1 (HO-1) induction, predisposes to oxidative damage of mitochondrial DNA (mtDNA). Hepatic mitochondria from control, hemin-, and CO-exposed rats were incubated with tert-butyl hydroperoxide (tert-BH) or the NO donor 1,2,3,4-oxatriazolium, 5-amino-3- (3,4-dichlorophenyl)-chloride (GEA 3162). Mitochondrial total and oxidized glutathione (GSH and GSSG), total and free iron, and 8-oxo-7, 8-dihydro-2' deoxyguanosine (8-OHdG) were determined with and without oxidants. As expected, oxidation by tert-BH induced significant GSH depletion and increased amounts of free iron and 8-OhdG. Oxidant exposure rapidly produced a large mtDNA deletion involving the coding regions for cytochrome c oxidase (COX 1) and NADH dehydrogenase (ND1 and ND2). Hemin and CO greatly exacerbated susceptibility to the deletion of mtDNA by tert-BH, and this was attenuated by preincubation with GSH methyl ester. Analysis of mitochondria-associated proteins Bax and Bcl-xl in hemin- and CO-exposed rats showed significant responses, revealing interactions with apoptotic pathways. Thus, hemin-induced mitochondrial events sensitize a specific region of the mitochondrial genome to deletion, which is related to depletion of GSH and is not explained by effects of CO. This mtDNA damage is associated with altered expression of mitochondrial cell death proteins, thereby suggesting a novel mechanism for systemic or environmental pro-oxidants to influence apoptosis.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2002

Iron-binding and storage proteins in sputum.

Induced sputum (IS) and bronchoalveolar lavage (BAL) sample different lung compartments, with IS obtaining secretions from the surfaces of the bronchial airways and BAL sampling secretions from the alveolar airspaces. Deposition of iron-containing particulate matter occurs preferentially in the bronchial airways compared to the distal airspaces. Iron-binding and storage proteins have been measured in BAL in healthy humans, where they act to sequester and detoxify available iron; however, their comparative levels in the airways are not well defined. Seventeen (n = 17) healthy, nonsmoking volunteers underwent sputum induction and fiber-optic bronchoscopy with lavage in order to measure and compare the levels of iron and iron-binding and storage proteins in BAL, bronchial lavage (BL), and IS. Relative to BAL and BL specimens, concentrations of total iron, ferritin, lactoferrin, and total iron binding capacity (TIBC) were significantly increased and transferrin decreased in IS. Immunohistochemical staining showed increased ferritin, lactoferrin, and TIBC in IS. Constitutive levels of iron and iron-binding and storage proteins (except for transferrin) are in greatest concentration in the bronchial airways relative to the alveolar airspaces in healthy humans. We speculate that these proteins reflect activated antioxidant defense mechanisms resulting from the preferential deposition of iron-containing particulate matter in the airways. The finding of decreased transferrin with increased ferritin suggests a local cellular response via iron-response elements (IRE) associated with the mRNAs for these two iron-binding proteins.

Adolescent↗

PubMed2002

Effect of metal removal on the toxicity of airborne particulate matter from the Utah Valley.

Epidemiological studies have linked the inhalation of airborne particulate matter (PM) to increased morbidity and mortality in humans. However, the mechanisms of toxicity of these particles remain unclear. Some hypotheses state that the toxicity might stem from PM transition metal content, adhered organic compounds, the biological component, or ultrafine particle content. In order to analyze metal involvement in PM toxicity, human airway epithelial cell line (BEAS-2B) cultures were exposed for 24 h to an aqueous extract of PM collected in the Utah Valley. A portion of the extract was treated with Chelex, an agent that removes cations (including transition metals) from solution. Removal of the majority of the metal mass was confirmed by inductively coupled plasma (ICP) analyses. Cells that were incubated with the untreated extract (62-1000 microg dry extract equivalent) showed a significant concentration-dependent increase in the inflammatory mediator interleukin-8 (IL-8) when compared to the control cells. However, cells incubated with Chelex-treated extract produced no change (relative to control) in IL-8. We exposed rats in vivo for 24 h to the same treatments as the cells and found significant increases in lactate dehydrogenase (LDH) and total protein in the rats exposed to the untreated extract and to the Chelex-treated extract with metals added back to achieve original concentrations. There was an attenuation of the observed LDH and total protein increases in the rats instilled with the Chelex-treated extract. Taken together, our results suggest that removal of metal cations attenuates cellular responses to the aqueous extract and support a role for transition metal involvement in PM-associated increases in morbidity and mortality.

Air Pollutants↗

PubMed2002

In vivo lipid-derived free radical formation by NADPH oxidase in acute lung injury induced by lipopolysaccharide: a model for ARDS.

Intratracheal instillation of lipopolysaccharide (LPS) activates alveolar macrophages and infiltration of neutrophils, causing lung injury/acute respiratory distress syndrome. Free radicals are a special focus as the final causative molecules in the pathogenesis of lung injury caused by LPS. Although in vitro investigation has demonstrated radical generation after exposure of cells to LPS, in vivo evidence is lacking. Using electron spin resonance (ESR) and the spin trap alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN), we investigated in vivo free radical production by rats treated with intratracheal instillation of LPS. ESR spectroscopy of lipid extract from lungs exposed to LPS for 6 h gave a spectrum consistent with that of a POBN/carbon-centered radical adduct (aN=14.94+/-0.07 G and abetaH=2.42+/-0.06 G) tentatively assigned as a product of lipid peroxidation. To further investigate the mechanism of LPS-initiated free radical generation, rats were pretreated with the phagocytic toxicant GdCl3, which significantly decreased the production of radical adducts with a corresponding decrease in neutrophil infiltration. NADPH oxidase knockout mice completely blocked phagocyte-mediated, ESR-detectable radical production in this model of acute lung injury. Rats treated intratracheally with LPS generate lipid-derived free radicals via activation of NADPH oxidase.

Animals↗

PubMed2002

Iron increases expression of iron-export protein MTP1 in lung cells.

Accumulation of reactive iron in acute and chronic lung disease suggests that iron-driven free radical formation could contribute to tissue injury. Safe transport and sequestration of this metal is likely to be of importance in lung defense. We provide evidence for the expression and iron-induced upregulation of the metal transporter protein-1 (MTP1) genes in human and rodent lung cells at both the protein and mRNA levels. In human bronchial epithelial cells, a 3.8-fold increase in mRNA level and a 2.4-fold increase in protein level of MTP1 were observed after iron exposure. In freshly isolated human macrophages, as much as an 18-fold increase in the MTP1 protein level was detected after incubation with an iron compound. The elevation in expression of MTP1 gene was also demonstrated in iron-instilled rat lungs and in hypotransferrinemic mouse lungs. This is similar to our previous findings with divalent metal transporter-1 (DMT1), an iron transporter that is required for iron uptake and intracellular iron trafficking. These studies suggest the presence of iron mobilization and/or detoxification pathways in the lung that are crucial for iron homeostasis and lung defense.

Animals↗

PubMed2002

Carbon monoxide promotes hypoxic pulmonary vascular remodeling.

CO is a biologically active gas that produces cellular effects by multiple mechanisms. Because cellular binding of CO by heme proteins is increased in hypoxia, we tested the hypothesis that CO interferes with hypoxic pulmonary vascular remodeling in vivo. Rats were exposed to inspired CO (50 parts/million) at sea level or 18,000 ft of altitude [hypobaric hypoxia (HH)], and changes in vessel morphometry and pulmonary pressure-flow relationships were compared with controls. Vascular cell single strand DNA (ssDNA) and proliferating cell nuclear antigen (PCNA) were assessed, and changes in gene and protein expression of smooth muscle alpha-actin (sm-alpha-actin), beta-actin, and heme oxygenase-1 (HO-1) were evaluated by Western analysis, RT-PCR, and immunohistochemistry. After 21 days of HH, vascular pressure at constant flow and vessel wall thickness increased and lumen diameter of small arteries decreased significantly. The presence of CO, however, further increased both pulmonary vascular resistance (PVR) and the number of small muscular vessels compared with HH alone. CO + HH also increased vascular PCNA and nuclear ssDNA expression compared with hypoxia, suggesting accelerated cell turnover. CO in hypoxia downregulated sm-alpha-actin and strongly upregulated beta-actin. CO also increased lung HO activity and HO-1 mRNA and protein expression in small pulmonary arteries during hypoxia. These data indicate an overall propensity of CO in HH to promote vascular remodeling and increase PVR in vivo.

Actins↗

PubMed2002

Iron uptake and Nramp2/DMT1/DCT1 in human bronchial epithelial cells.

The capacity of natural resistance-associated macrophage protein-2 [Nramp2; also called divalent metal transporter-1 (DMT1) and divalent cation transporter-1 (DCT1)] to transport iron and its ubiquitous expression make it a likely candidate for transferrin-independent uptake of iron in peripheral tissues. We tested the hypothesis that non-transferrin-bound iron uptake by airway epithelial cells is associated with Nramp2/DMT1/DCT1 and that exposure to iron can increase Nramp2/DMT1/DCT1 mRNA and protein expression and transport of this metal. Exposure of BEAS-2B cells to ferric ammonium citrate (FAC) resulted in a decrease in Fe(3+) concentration in the supernatant that was dependent on time and initial iron concentration. In the presence of internalized calcein, FAC quenched the fluorescent signal, indicating intracellular transport of the metal. The Nramp2/DMT1/DCT1 mRNA isoform without an iron-response element (IRE) increased with exposure of BEAS-2B cells to FAC. RT-PCR demonstrated no change in the mRNA for the isoform with an IRE. Similarly, Western blot analysis for the isoform without an IRE confirmed an increased expression of this protein after FAC exposure, whereas the isoform with an IRE exhibited no change. Finally, immunohistochemistry revealed an increase in the isoform without an IRE in the rat lung epithelium after instillation of FAC. Comparable to mRNA and protein increases, iron transport was elevated after pretreatment of BEAS-2B cells with iron-containing compounds. We conclude that airway epithelial cells increase mRNA and expression of the Nramp2/DMT1/DCT1 without an IRE after exposure to iron. The increase results in an elevated transport of iron and its probable detoxification by these cells.

Bronchi↗

PubMed2002

Oxidative stress activates anion exchange protein 2 and AP-1 in airway epithelial cells.

Anion exchange protein 2 (AE2) is a membrane-bound protein that mediates chloride-bicarbonate exchange. In addition to regulating intracellular pH and cell volume, AE2 exports superoxide (O.) to the extracellular matrix in an HCO-dependent process. Given this ability to export O., we hypothesized that expression of AE2 in the lung is regulated by oxidative stress. AE2 mRNA and protein expression was measured by RT-PCR and Western blot analysis, respectively, in differentiated human bronchial epithelial cells exposed to H(2)O(2) (100 microM). Alterations in in vivo AE2 protein expression were evaluated in lung tissue of rats exposed to 70% O(2). The role of transcription factor activator protein (AP)-1 in oxidant regulation of AE2 was evaluated by EMSA and by immunoblotting of nuclear phospho-c-jun. Results show increased AE2 mRNA and protein expression after oxidant exposure. This was preceded by transient increases in DNA binding of AE2-specific AP-1 and phosphorylation of c-jun. This study demonstrates that AE2 expression is regulated by oxidative stress in airway epithelial cells and that this regulation correlates with activation of AP-1.

Anion Transport Proteins↗

PubMed2002

Overexpression of extracellular superoxide dismutase decreases lung injury after exposure to oil fly ash.

The mechanism of tissue injury after exposure to air pollution particles is not known. The biological effect has been postulated to be mediated via an oxidative stress catalyzed by metals present in particulate matter (PM). We utilized a transgenic (Tg) mouse model that overexpresses extracellular superoxide dismutase (EC-SOD) to test the hypothesis that lung injury after exposure to PM results from an oxidative stress in the lower respiratory tract. Wild-type (Wt) and Tg mice were intratracheally instilled with either saline or 50 microg of residual oil fly ash (ROFA). Twenty-four hours later, specimens were obtained and included bronchoalveolar lavage (BAL) and lung for both homogenization and light histopathology. After ROFA exposure, EC-SOD Tg mice showed a significant reduction in BAL total cell counts (composed primarily of neutrophils) and BAL total protein compared with Wt. EC-SOD animals also demonstrated diminished concentrations of inflammatory mediators in BAL. There was no statistically significant difference in BAL lipid peroxidation; however, EC-SOD mice had lower concentrations of oxidized glutathione in the BAL. We conclude that enhanced EC-SOD expression decreased both lung inflammation and damage after exposure to ROFA. This supports a participation of oxidative stress in the inflammatory injury after PM exposure rather than reflecting a response to metals alone.

Air Pollutants↗

PubMed2002

Iron regulates xanthine oxidase activity in the lung.

The iron chelator deferoxamine has been reported to inhibit both xanthine oxidase (XO) and xanthine dehydrogenase activity, but the relationship of this effect to the availability of iron in the cellular and tissue environment remains unexplored. XO and total xanthine oxidoreductase activity in cultured V79 cells was increased with exposure to ferric ammonium sulfate and inhibited by deferoxamine. Lung XO and total xanthine oxidoreductase activities were reduced in rats fed an iron-depleted diet and increased in rats supplemented with iron, without change in the ratio of XO to total oxidoreductase. Intratracheal injection of an iron salt or silica-iron, but not aluminum salts or silica-zinc, significantly increased rat lung XO and total xanthine oxidoreductase activities, immunoreactive xanthine oxidoreductase, and the concentration of urate in bronchoalveolar fluid. These results suggest the possibility that the production of uric acid, a major chelator of iron in extracellular fluid, is directly influenced by iron-mediated regulation of the expression and/or activity of its enzymatic source, xanthine oxidase.

Animals↗

PubMed2002

Biologic effects of oil fly ash.

Epidemiologic studies have demonstrated increased human morbidity and mortality with elevations in the concentration of ambient air particulate matter (PM). Fugitive fly ash from the combustion of oil and residual fuel oil significantly contributes to the ambient air particle burden. Residual oil fly ash (ROFA) is remarkable in the capacity to provoke injury in experimental systems. The unique composition of this emission source particle makes it particularly useful as a surrogate for ambient air PM in studies of biologic effects testing the hypothesis that metals mediate the biologic effects of air pollution particles. A majority of the in vitro and animal model investigations support the postulate that transition metals present in ROFA (especially vanadium) participate in Fenton-like chemical reactions to produce reactive oxygen species. This is associated with tyrosine phosphorylation, nuclear factor kappa B and other transcription factor activation, induction of inflammatory mediator expression, and inflammatory lung injury. It is also evident that vanadium accounts for a significant portion of the biologic activity of ROFA. The extrapolation of this body of investigation on ROFA to the field of ambient air PM is difficult, as particles in numerous environments have such small amounts of vanadium.

Air Pollutants↗

PubMedDate not supplied

Activation of EGF receptors mediates pulmonary vasoconstriction induced by residual oil fly ash.

Residual oil fly ash (ROFA) is a constituent of pollutant particles that can produce lung injury and activate protein tyrosine phosphorylation cascade. In this study, we determined whether or not protein tyrosine phosphorylation caused lung injury, and if so, identified critical tyrosinephosphorylated proteins that mediated the injury. ROFA was instilled intratracheally into perfused rabbit lungs and injury responses, including increase in pulmonary artery pressure (Ppa), lung weight gain, as well as release of interleukin (IL)-1beta, IL-6, IL-8, and nitrite/nitrate were measured. ROFA increased Ppa and IL-1beta, but inhibited nitrite/nitrate accumulation. Vanadyl sulfate at concentration equivalent to the amount of vanadium detected in the perfusate of ROFA-treated lungs induced similar changes. ROFA enhanced tyrosine phosphorylation of lung proteins, including a 170-kDa protein, likely the epidermal growth factor (EGF) receptor as shown by immunoprecipitation. Pretreatment with genistein, a tyrosine kinase inhibitor, blocked the increase in Ppa and tyrosine phosphorylation of the 170-kDa protein. Intravascular administration of human EGF increased Ppa, and pretreatment with PD153035, an EGF receptor-specific tyrosine kinase inhibitor, attenuated ROFA-induced pulmonary vasoconstriction. These results indicate that tyrosine phosphorylation of EGF receptors in the lung, possibly as a result of inhibition of protein tyrosine phosphatases, mediates constriction of pulmonary vessels induced by ROFA.

Air Pollutants↗