Respiratory epithelial cells demonstrate lactoferrin receptors that increase after metal exposure.
Human airway epithelial cells can increase expression of both lactoferrin and ferritin after exposure to catalytically active metal. These proteins transport and store metal, with coordination sites fully complexed, and therefore can diminish the oxidative stress. The intracellular transport of lactoferrin results in a transfer of complexed metal to ferritin, where it is stored in a less reactive form. This effort to control the injurious properties of metals would be facilitated by lactoferrin receptors (LfRs) on airway epithelial cells. We tested the hypotheses that 1) LfRs exist on respiratory epithelial cells and 2) exposure to both an air pollution particle, which has abundant concentrations of metals, and individual metal salts increase the expression of LfRs. Before exposure to either the particle or metals, incubation of BEAS-2B cells with varying concentrations of 125I-labeled lactoferrin demonstrated lactoferrin binding that was saturable. Measurement of 125I-lactoferrin binding after the inclusion of 100 micrograms/ml of oil fly ash in the incubation medium demonstrated increased binding within 5 min of exposure, which reached a maximal value at 45 min. Inclusion of 1.0 mM deferoxamine in the incubation of BEAS-2B cells with 100 micrograms/ml of oil fly ash decreased lactoferrin binding. Comparable to the particle, exposure of BEAS-2B cells to either 1.0 mM vanadyl sulfate or 1.0 mM iron (III) sulfate, but not to nickel sulfate, for 45 min elevated LfR activity. We conclude that LfRs on respiratory epithelial cells increased after exposure to metal. LfRs could participate in decreasing the oxidative stress presented to the lower respiratory tract by complexing catalytically active metals. (+info)
Role of soluble metals in oil fly ash-induced airway epithelial injury and cytokine gene expression.
Particulate matter (PM) metal content and bioavailability have been hypothesized to play a role in the health effects epidemiologically associated with PM exposure, in particular that associated with emission source PM. Using rat tracheal epithelial cells in primary culture, the present study compared and contrasted the acute airway epithelial effects of an emission source particle, residual oil fly ash (ROFA), with that of its principal constitutive transition metals, namely iron, nickel, and vanadium. Over a 24-h period, exposure to ROFA, vanadium, or nickel plus vanadium, but not to iron or nickel, resulted in increased epithelial permeability, decreased cellular glutathione, cell detachment, and lytic cell injury. Treatment of vanadium-exposed cells with buthionine sulfoximine further increased cytotoxicity. Conversely, treatment with the radical scavenger dimethylthiourea inhibited the effects in a dose-dependent manner. RT-PCR analysis of RNA isolated from ROFA-exposed rat tracheal epithelial cells demonstrated significant macrophage inflammatory protein-2 and interleukin-6 gene expression as early as 6 h after exposure, whereas gene expression of inducible nitric oxide synthase was maximally increased 24 h postexposure. Again, vanadium (not nickel) appeared to be mediating the effects of ROFA on gene expression. Treatment with dimethylthiourea inhibited both ROFA- and vanadium-induced gene expression in a dose-dependent manner. Corresponding effects were observed in interleukin-6 and macrophage inflammatory protein-2 synthesis. In summary, generation of an oxidative stress was critical to induction of the ROFA- or vanadium-induced effects on airway epithelial gene expression, cytokine production, and cytotoxicity. (+info)
Residual oil fly ash and charged polymers activate epithelial cells and nociceptive sensory neurons.
Residual oil fly ash (ROFA) is an industrial pollutant that contains metals, acids, and unknown materials complexed to a particulate core. The heterogeneous composition of ROFA hampers finding the mechanism(s) by which it and other particulate pollutants cause airway toxicity. To distinguish culpable factors contributing to the effects of ROFA, synthetic polymer microsphere (SPM) analogs were synthesized that resembled ROFA in particle size (2 and 6 microm in diameter) and zeta potential (-29 mV). BEAS-2B human bronchial epithelial cells and dorsal root ganglion neurons responded to both ROFA and charged SPMs with an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) and the release of the proinflammatory cytokine interleukin-6, whereas neutral SPMs bound with polyethylene glycol (0-mV zeta potential) were relatively ineffective. In dorsal root ganglion neurons, the SPM-induced increases in [Ca(2+)](i) were correlated with the presence of acid- and/or capsaicin-sensitive pathways. We hypothesized that the acidic microenvironment associated with negatively charged colloids like ROFA and SPMs activate irritant receptors in airway target cells. This causes subsequent cytokine release, which mediates the pathophysiology of neurogenic airway inflammation. (+info)
Variable pulmonary responses from exposure to concentrated ambient air particles in a rat model of bronchitis.
Chronic bronchitis may be considered a risk factor in particulate matter (PM)-induced morbidity. We hypothesized that a rat model of human bronchitis would be more susceptible to the pulmonary effects of concentrated ambient particles (CAPs) from Research Triangle Park, NC. Bronchitis was induced in male Sprague-Dawley rats (90-100 days of age) by exposure to 200 ppm sulfur dioxide (SO2), 6 h/day x 5 days/week x 6 weeks. One day following the last SO2 exposure, both healthy (air-exposed) and bronchitic (SO2-exposed) rats were exposed to filtered air (three healthy; four bronchitic) or CAPs (five healthy; four bronchitic) by whole-body inhalation, 6 h/day x 2 or 3 days. Pulmonary injury was determined either immediately (0h) or 18 h following final CAPs exposure. The study protocol involving 0 h time point was repeated four times (study #A, November, 1997; #B, February, 1998; #C and #D, May, 1998), whereas the study protocol involving 18 h time point was done only once (#F). In an additional study (#E), rats were exposed to residual oil fly ash (ROFA), approximately 1 mg/ m(3)x6 h/day x 3 days to mimic the CAPs protocol (February, 1998). The rats allowed 18 h recovery following CAPs exposure (#F) did not depict any CAPs-related differences in bronchoalveolar lavage fluid (BALF) injury markers. Of the four CAPs studies conducted (0 h time point), the first (#A) study (approximately 650 microg/m3 CAPs) revealed significant changes in the lungs of CAPs-exposed bronchitic rats compared to the clean air controls. These rats had increased BALF protein, albumin, N-acetyl glutaminidase (NAG) activity and neutrophils. The second (#B) study (approximately 475 microg/m3 CAPs) did not reveal any significant effects of CAPs on BALF parameters. Study protocols #C (approximately 869 microg/m3 CAPs) and #D (approximately 907 microg/m3 CAPs) revealed only moderate increases in the above mentioned BALF parameters in bronchitic rats exposed to CAPs. Pulmonary histologic evaluation of studies #A, #C, #D, and #F revealed marginally higher congestion and perivascular cellularity in CAPs-exposed bronchitic rats. Healthy and bronchitic rats exposed to ROFA (approximately 1 mg/m3) did not show significant pulmonary injury (#E). Analysis of leachable elemental components of CAPs revealed the presence of sulfur, zinc, manganese, and iron. There was an apparent lack of association between pulmonary injury and CAPs concentration, or its leachable sulfate or elemental content. In summary, real-time atmospheric PM may result in pulmonary injury, particularly in susceptible models. However, the variability observed in pulmonary responses to CAPs emphasizes the need to conduct repeated studies, perhaps in relation to the season, as composition of CAPs may vary. Additionally, potential variability in pathology of induced bronchitis or other lung disease may decrease the ability to distinguish toxic injury due to PM. (+info)
Diminished injury in hypotransferrinemic mice after exposure to a metal-rich particle.
Using the hypotransferrinemic (Hp) mouse model, we studied the effect of altered iron homeostasis on the defense of the lung against a catalytically active metal. The homozygotic (hpx/hpx) Hp mice had greatly diminished concentrations of both serum and lavage fluid transferrin relative to wild-type mice and heterozygotes. Fifty micrograms of a particle containing abundant concentrations of metals (a residual oil fly ash) was instilled into wild-type mice and heterozygotic and homozygotic Hp animals. There was an oxidative stress associated with particle exposure as manifested by decreased lavage fluid concentrations of ascorbate. However, rather than an increase in lung injury, diminished transferrin concentrations in homozygotic Hp mice were associated with decreased indexes of damage, including concentrations of relevant cytokines, inflammatory cell influx, lavage fluid protein, and lavage fluid lactate dehydrogenase. Comparable to other organs in the homozygotic Hp mouse, siderosis of the lung was evident, with elevated concentrations of lavage fluid and tissue iron. Consequent to these increased concentrations of iron, proteins to store and transport iron, ferritin, and lactoferrin, respectively, were increased when assayed by immunoprecipitation and immunohistochemistry. We conclude that the lack of transferrin in Hp mice did not predispose the animals to lung injury after exposure to a particle abundant in metals. Rather, these mice demonstrated a diminished injury that was associated with an increase in the metal storage and transport proteins. (+info)
Oil fly ash-induced elevation of plasma fibrinogen levels in rats.
Particulate matter air pollution (PM) has been associated with morbidity and mortality from ischemic heart disease and stroke in humans. It has been hypothesized that alveolar inflammation, resulting from exposure to PM, may induce a state of blood hypercoagulability, triggering cardiovascular events in susceptible individuals. Previous studies in our laboratory have demonstrated acute lung injury with alveolar inflammation in rats following exposure to residual oil fly ash (ROFA), an emission source particulate. In addition, increased mortality has been documented following exposure to ROFA in rats with preexistent cardiopulmonary disease. ROFA's toxicity derives from its soluble metal content, which appears also to drive the toxicity of ambient PM. The present study was conducted to test the hypothesis that exposure of rats to a toxic PM, like ROFA, would adversely alter hemostatic parameters and cardiovascular risk factors thought to be involved in human epidemiologic findings. Sixty-day-old male Sprague-Dawley rats were exposed by intratracheal instillation (IT) to varying doses (0.3, 1. 7, or 8.3 mg/kg) of ROFA, 8.3 mg/kg Mt. Saint Helen's volcanic ash (MSH, control particle), or 0.3 ml saline (SAL, control). At 24 h post-IT, activated partial thromboplastin time (APTT), prothrombin time (PT), plasma fibrinogen (PF), plasma viscosity (PV), and complete blood count (CBC) were performed on venous blood samples. No differences from control were detected in APTT and PT in ROFA-exposed rats; however, ROFA exposure did result in elevated PF, at 8.3 mg/kg only. In addition, PV values were elevated in both ROFA and MSH-exposed rats relative to SAL-control rats, but not significantly. Although no changes were detected in APTT and PT, alteration of important hematologic parameters (notably fibrinogen) through PM induction of an inflammatory response may serve as biomarkers of cardiovascular risk in susceptible individuals. (+info)
Induction of pulmonary matrilysin expression by combustion and ambient air particles.
The molecular mechanism(s) by which chemically complex air pollution particles mediate their adverse health effects is not known. We have examined the ability of combustion and ambient air particles to induce pulmonary matrilysin expression due to the well-documented role of matrix metalloproteinases in tissue injury and repair responses. Rats were exposed to saline, residual oil fly ash (2.5 mg/rat), or ambient air particles (2.5 mg/rat) via intratracheal instillation and examined 3-72 h after exposure. Saline-exposed animals had low levels of matrilysin mRNA, whereas the animals exposed to either complex particle showed an early induction of pulmonary matrilysin gene expression as well as of the 19-kDa activated form of matrilysin. Immunocytochemistry and in situ hybridization analyses identified the alveolar macrophages and monocytes as primary sources of air pollution particle-induced matrilysin expression. Matrilysin gene induction and protein activation by combustion and ambient air particles correlated with the early histopathological changes produced by these particles. These results demonstrate the ability of combustion and ambient air particles to induce pulmonary matrilysin expression and suggest a role for this matrix metalloproteinase in the initiation of lung injury produced by these particles. (+info)
The Indian Ocean experiment: widespread air pollution from South and Southeast Asia.
The Indian Ocean Experiment (INDOEX) was an international, multiplatform field campaign to measure long-range transport of air pollution from South and Southeast Asia toward the Indian Ocean during the dry monsoon season in January to March 1999. Surprisingly high pollution levels were observed over the entire northern Indian Ocean toward the Intertropical Convergence Zone at about 6 degrees S. We show that agricultural burning and especially biofuel use enhance carbon monoxide concentrations. Fossil fuel combustion and biomass burning cause a high aerosol loading. The growing pollution in this region gives rise to extensive air quality degradation with local, regional, and global implications, including a reduction of the oxidizing power of the atmosphere. (+info)