1 Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, West Virginia; 2 Division of Applied Research and Technology, National Institute for ...Occupational Safety and Health, Cincinnati, Ohio; 3 Nanotube Team, GBTech, Incorporated, National Aeronautics and Space Administration-Johnson Space Center, Houston, Texas; and 4 Center for Free Radical & Antioxidant Health and 5 Department of Environmental Health, University of Pittsburgh, Pittsburgh, Pennsylvania
Submitted 22 February 2005
; accepted in final form 7 June 2005
Single-walled carbon nanotubes (SWCNT) are new materials of emerging technological importance. As SWCNT are introduced into the life cycle of commercial products, their effects on human health and environment should be addressed. We demonstrated that pharyngeal aspiration of SWCNT elicited unusual pulmonary effects in C57BL/6 mice that combined a robust but acute inflammation with early onset yet progressive fibrosis and granulomas. A dose-dependent increase in the protein, LDH, and -glutamyl transferase activities in bronchoalveolar lavage were found along with accumulation of 4-hydroxynonenal (oxidative biomarker) and depletion of glutathione in lungs. An early neutrophils accumulation ( day 1 ), followed by lymphocyte ( day 3 ) and macrophage ( day 7 ) influx, was accompanied by early elevation of proinflammatory cytokines (TNF- , IL-1 ; day 1 ) followed by fibrogenic transforming growth factor (TGF)- 1 (peaked on day 7 ). A rapid progressive fibrosis found in mice exhibited two distinct morphologies: 1 ) SWCNT-induced granulomas mainly associated with hypertrophied epithelial cells surrounding SWCNT aggregates and 2 ) diffuse interstitial fibrosis and alveolar wall thickening likely associated with dispersed SWCNT. In vitro exposure of murine RAW 264.7 macrophages to SWCNT triggered TGF- 1 production similarly to zymosan but generated less TNF- and IL-1 . SWCNT did not cause superoxide or NO·production, active SWCNT engulfment, or apoptosis in RAW 264.7 macrophages. Functional respiratory deficiencies and decreased bacterial clearance ( Listeria monocytogenes ) were found in mice treated with SWCNT. Equal doses of ultrafine carbon black particles or fine crystalline silica (SiO 2 ) did not induce granulomas or alveolar wall thickening and caused a significantly weaker pulmonary inflammation and damage.
nanoparticles; inflammation; cytokines; microbial infection
Address for reprint requests and other correspondence: A. A. Shvedova, Health Effects Laboratory Div., NIOSH, Morgantown, WV (e-mail: AShvedova{at}cdc.gov )
1 Health Effects Laboratory Division, National
Institute for Occupational Safety and Health, Morgantown, West Virginia
26505; and 2 Division of Applied Research and
Technology, National Institute ...for Occupational Safety and Health,
Cincinnati, Ohio 45226
In previous reports from this study,
measurements of pulmonary inflammation, bronchoalveolar lavage cell
cytokine production and nuclear factor- B activation, cytotoxic
damage, and fibrosis were detailed. In this study, we investigated the
temporal relationship between silica inhalation, nitric oxide (NO), and
reactive oxygen species (ROS) production, and damage mediated by these
radicals in the rat. Rats were exposed to a silica aerosol (15 mg/m 3 silica, 6 h/day, 5 days/wk) for 116 days. We report
time-dependent changes in 1 ) activation of alveolar
macrophages and concomitant production of NO and ROS, 2 )
immunohistochemical localization of inducible NO synthase and the
NO-induced damage product nitrotyrosine, 3 ) bronchoalveolar
lavage fluid NO x and superoxide dismutase concentrations, and 4 ) lung lipid peroxidation levels. The
major observations made in this study are as follows: 1 ) NO
and ROS production and resultant damage increased during silica
exposure, and 2 ) the sites of inducible NO synthase
activation and NO-mediated damage are associated anatomically with
pathological lesions in the lungs.
silicosis; fibrosis; oxidant injury; nitrotyrosine
In vitro studies suggest that silica-induced lung disease may be linked to processes regulated by nuclear factor- κ B (NF- κ B) activation, but this has not been examined in vivo. Rats were exposed ...to a silica aerosol of 15 mg/m 3 (6 h/day, 5 days/wk) for 116 days, and bronchoalveolar lavage (BAL) was conducted at various times during the exposure. Silica-induced pulmonary inflammation and damage were determined by measuring BAL cell differentials and first BAL fluid lactate dehydrogenase (LDH) activity and serum albumin concentrations, respectively. NF- κ B activation and production of tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1) by BAL cells were also measured. The results demonstrate that NF- κ B activation occurred after 5 days exposure, and continued to increase thereafter. BAL cell production of IL-1 and TNF-α had increased incrementally by 10 and 30 days of exposure, respectively. This elevation continued through 79 days of exposure before further increasing at 116 days of exposure. Pulmonary inflammation and damage in silica-exposed rats were also significantly elevated at 5 days of exposure, further increased at a slow rate through 41 days of exposure, and dramatically increased thereafter. Taken together, the results indicate that the initial molecular response of NF- κ B activation in BAL cells occurs in response to low levels of silica deposition in the lung and increases more rapidly versus exposure duration than silica-induced pulmonary inflammation, cellular damage, and cytokine production by BAL cells. This suggests that NF- κ B activation in BAL cells may play an important role in the initiation and progression of silica-induced pulmonary inflammation, cellular damage, and fibrosis.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Previous studies have determined that alpha-quartz (crystalline silica) can cause pulmonary inflammation, damage, and fibrosis. However, the temporal relationship between silica inhalation and ...pulmonary inflammation, damage, and fibrosis has not been fully examined. To address this gap in our knowledge of silica-induced pulmonary fibrosis, a chronic inhalation study using rats was designed. Specifically, rats were exposed to a silica aerosol (15 mg/m3 silica, 6 h/d, 5 d/wk, 116 d), and measurements of pulmonary inflammation, damage, and fibrosis were monitored throughout the study. We report (1) data demonstrating that the silica aerosol generation and exposure system produced a consistent silica aerosol of respirable size particles; (2) the time course of silica deposition in the lung; (3) calculations that demonstrate that the rats were not in pulmonary overload; (4) histopathological data demonstrating time-dependent enhancement of silica-induced alveolitis, epithelial hypertrophy and hyperplasia, alveolar lipoproteinosis, and pulmonary fibrosis in the absence of overload; and (5) biochemical data documenting the development of lipidosis, lung damage, and fibrosis.
Rotary-type percussion dowel drilling machines, which drill horizontal holes in concrete pavement, have been documented to produce respirable crystalline silica concentrations above recommended ...exposure criteria. This places operators at potential risk for developing health effects from exposure. United States manufacturers of these machines offer optional dust control systems. The effectiveness of the dust control systems to reduce respirable dust concentrations on two types of drilling machines was evaluated under controlled conditions with the machines operating inside large tent structures in an effort to eliminate secondary exposure sources not related to the dowel-drilling operation. Area air samples were collected at breathing zone height at three locations around each machine. Through equal numbers of sampling rounds with the control systems randomly selected to be on or off, the control systems were found to significantly reduce respirable dust concentrations from a geometric mean of 54 mg per cubic meter to 3.0 mg per cubic meter on one machine and 57 mg per cubic meter to 5.3 mg per cubic meter on the other machine. This research shows that the dust control systems can dramatically reduce respirable dust concentrations by over 90% under controlled conditions. However, these systems need to be evaluated under actual work conditions to determine their effectiveness in reducing worker exposures to crystalline silica below hazardous levels.
Human epidemiologic studies have found that silicosis may develop or progress even after occupational exposure has ended, suggesting that there is a threshold lung burden above which silica-induced ...pulmonary disease progresses without further exposure. We previously described the time course of rat pulmonary responses to silica inhalation as biphasic, the initial phase characterized by increased but controlled pulmonary inflammation and damage. However, after a threshold lung burden was exceeded, rapid progression of silica-induced pulmonary disease occurred. To test the hypothesis that there is a threshold lung burden above which silica-induced pulmonary disease progresses without further exposure we initiated a study to investigate the relationship between silica exposure, the initiation and progression of silica-induced pulmonary disease, and recovery. Rats were exposed to silica (15 mg/m3, 6 h/day) for either 20, 40, or 60 days. A portion of the rats from each exposure were maintained without further exposure for 36 days to examine recovery. The major findings of this study are: (1) silica-exposed rats were not in pulmonary overload, and lung silica burden decreased with recovery; (2) pulmonary inflammation, damage and lipidosis increased with recovery for rats exposed to silica for 40 and 60 days, but not 20 days; (3) histopathology revealed changes in silica-induced alveolitis, epithelial hypertrophy and hyperplasia, and alveolar lipoproteinosis consistent with bronchoalveolar lavage (BAL) endpoints; and (4) pulmonary fibrosis developed even when exposure was stopped prior to its initial development.
Our laboratory has previously reported results from a rat silica inhalation study which determined that, even after silica exposure ended, pulmonary inflammation and damage progressed with subsequent ...fibrosis development. In the present study, the relationship between silica exposure, nitric oxide (NO) and reactive oxygen species (ROS) production, and the resultant pulmonary damage is investigated in this model. Rats were exposed to silica (15 mg/m3, 6 h/day) for either 20, 40, or 60 days. A portion of the rats from each exposure were sacrificed at 0 days postexposure, while another portion was maintained without further exposure for 36 days to examine recovery or progression. The major findings of this study are: (1) silica-exposed rat lungs were in a state of oxidative stress, the severity of which increased during the postexposure period, (2) silica-exposed rats had significant increase in lung NO production which increased in magnitude during the postexposure period, and (3) the presence of silica particle(s) in an alveolar macrophage (AM) was highly associated with inducible nitric oxide synthase (iNOS) protein. These data indicate that, even after silica exposure has ended, and despite declining silica lung burden, silica-induced pulmonary NO and ROS production increases, thus producing a more severe oxidative stress. A quantitative association between silica and expression of iNOS protein in AMs was also determined, which adds to our previous observation that iNOS and NO-mediated damage are associated anatomically with silica-induced pathological lesions. Future studies will be needed to determine whether the progressive oxidative stress, and iNOS activation and NO production, is a direct result of silica lung burden or a consequence of silica-induced biochemical mediators.
Fracturing quartz produces silica-based radicals on the fracture planes and generates hydroxyl radicals (·OH) in aqueous media.·OH production has been shown to be directly associated with ...quartz-induced cell damage and phagocyte activation in vitro. This·OH production in vitro is inhibited by desferrioxamine mesylate, an Fe chelator, indicating involvement of a Fenton-like reaction. Our objective was to determine if Fe contamination increased the ability of inhaled quartz to cause inflammation and lung injury. Male Fischer 344 rats were exposed 5 hr/day for 10 days to filtered air, 20 mg/ m3freshly milled quartz (57 ppm Fe), or 20 mg/ m3freshly milled quartz contaminated with Fe (430 ppm Fe). High Fe contamination of quartz produced approximately 57% more reactive species in water than quartz with low Fe contamination. Compared to inhalation of quartz with low Fe contamination, high Fe contamination of quartz resulted in increases in the following responses: leukocyte recruitment (537%), lavageable red blood cells (157%), macrophage production of oxygen radicals measured by electron spin resonance or chemiluminescence (32 or 90%, respectively), nitric oxide production by macrophages (71%), and lipid peroxidation of lung tissue (38%). These results suggest that inhalation of freshly fractured quartz contaminated with trace levels of Fe may be more pathogenic than inhalation of quartz alone.
This study examined the possibility of freshly fractured α-quartz being more toxic and inflammatory in vivo than aged quartz of the same composition and particle size. Fresh quartz was generated by a ...jet mill, and used immediately, while aged dust was stored for two months before use. Both the production of hydrogen peroxide and hydroxyl radicals and the analysis of surface radicals verified the enhanced surface activity of fresh quartz. Male Fischer 344 rats were exposed to fresh or aged á-quartz by inhalation (20 mg · m⁻³, 5 h per day, 5 d per week, for 2 weeks) and their pulmonary responses were determined 1—3 d postexposure. Exposure to aged quartz resulted in an increase in cytotoxic and inflammatory parameters. In comparison, the inhalation of freshly cleaved quartz resulted in dramatically greater increases in all of the pulmonary responses. This finding suggests that exposure to freshly machined quartz may result in a greater risk of pulmonary disease.
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