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Direct and indirect effects of single walled carbon nanotubes on RAW 264.7 macrophages: role of iron.

Authors
Kagan-VE; Tyurina-YY; Tyurin-VA; Konduru-NV; Potapovich-AI; Osipov-AN; Kisin-ER; Schwegler-Berry-D; Mercer-R; Castranova-V; Shvedova-AA
Source
Toxicol Lett 2006 Aug; 165(1):88-100
NIOSHTIC No.
20030624
Abstract
Single-walled carbon nanotubes (SWCNT), nano-cylinders with an extremely small diameter (1-2 nm) and high aspect ratio, have unique physico-chemical, electronic and mechanical properties and may exhibit unusual interactions with cells and tissues, thus necessitating studies of their toxicity and health effects. Manufactured SWCNT usually contain significant amounts of iron that may act as a catalyst of oxidative stress. Because macrophages are the primary responders to different particles that initiate and propagate inflammatory reactions and oxidative stress, we utilized two types of SWCNT: (1) iron-rich (non-purified) SWCNT (26 wt.% of iron) and (2) iron-stripped (purified) SWCNT (0.23 wt.% of iron) to study their interactions with RAW 264.7 macrophages. Ultrasonication resulted in predominantly well-dispersed and separated SWCNT strands as evidenced by scanning electron microscopy. Neither purified nor non-purified SWCNT were able to generate intracellular production of superoxide radicals or nitric oxide in RAW 264.7 macrophages as documented by flow-cytometry and fluorescence microscopy. SWCNT with different iron content displayed different redox activity in a cell-free model system as revealed by EPR-detectable formation of ascorbate radicals resulting from ascorbate oxidation. In the presence of zymosan-stimulated RAW 264.7 macrophages, non-purified iron-rich SWCNT were more effective in generating hydroxyl radicals (documented by EPR spin-trapping with 5,5-dimethyl-1-pyrroline-N-oxide, DMPO) than purified SWCNT. Similarly, EPR spin-trapping experiments in the presence of zymosan-stimulated RAW 264.7 macrophages showed that non-purified SWCNT more effectively converted superoxide radicals generated by xanthine oxidase/xanthine into hydroxyl radicals as compared to purified SWCNT. Iron-rich SWCNT caused significant loss of intracellular low molecular weight thiols (GSH) and accumulation of lipid hydroperoxides in both zymosan-and PMA-stimulated RAW 264.7 macrophages. Catalase was able to partially protect macrophages against SWCNT induced elevation of biomarkers of oxidative stress (enhancement of lipid peroxidation and GSH depletion). Thus, the presence of iron in SWCNT may be important in determining redox-dependent responses of macrophages.
Keywords
Iron-compounds; Microscopy; Oxidation; Oxidative-processes; Oxides; Nanotechnology
Contact
Center for Free Radical and Antioxidant Health, Department of EOH, Bridgeside Point, 100 Technology Drive, Suite 350, Pittsburgh, PA 15219, United States
CODEN
TOLED5
CAS No.
7439-89-6
Publication Date
20060801
Document Type
Journal Article
Email Address
vkagan@eoh.pitt.edu
Funding Type
Grant
Fiscal Year
2006
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-008282
Issue of Publication
1
ISSN
0378-4274
NIOSH Division
HELD
Priority Area
Disease and Injury: Asthma and Chronic Obstructive Pulmonary Disease
Source Name
Toxicology Letters
State
WV; PA
Performing Organization
University of Pittsburgh at Pittsburgh
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