Carbon nanotubes degraded by neutrophil myeloperoxidase induce less pulmonary inflammation.
We have shown previously that single-walled carbon nanotubes can be catalytically biodegraded over several weeks by the plant-derived enzyme, horseradish peroxidase. However, whether peroxidase intermediates generated inside human cells or biofluids are involved in the biodegradation of carbon nanotubes has not been explored. Here, we show that hypochlorite and reactive radical intermediates of the human neutrophil enzyme myeloperoxidase catalyse the biodegradation of single-walled carbon nanotubes in vitro, in neutrophils and to a lesser degree in macrophages. Molecular modelling suggests that interactions of basic amino acids of the enzyme with the carboxyls on the carbon nanotubes position the nanotubes near the catalytic site. Importantly, the biodegraded nanotubes do not generate an inflammatory response when aspirated into the lungs of mice. Our findings suggest that the extent to which carbon nanotubes are biodegraded may be a major determinant of the scale and severity of the associated inflammatory responses in exposed individuals.
Kagan
Valerian E
VE
Department of Environmental and Occupational Health, Center for Free Radical and Antioxidant Health, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA. kagan@pitt.edu
Konduru
Nagarjun V
NV
Feng
Weihong
W
Allen
Brett L
BL
Conroy
Jennifer
J
Volkov
Yuri
Y
Vlasova
Irina I
II
Belikova
Natalia A
NA
Yanamala
Naveena
N
Kapralov
Alexander
A
Tyurina
Yulia Y
YY
Shi
Jingwen
J
Kisin
Elena R
ER
Murray
Ashley R
AR
Franks
Jonathan
J
Stolz
Donna
D
Gou
Pingping
P
Klein-Seetharaman
Judith
J
Fadeel
Bengt
B
Star
Alexander
A
Shvedova
Anna A
AA
D000818:Animals; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D008958:Models, Molecular; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000633:toxicity* / Q000648:ultrastructure; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology*; D009195:Peroxidase / Q000378:metabolism*; D011014:Pneumonia / Q000139:chemically induced* / Q000473:pathology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman
D007074:Immunoglobulin G; D037742:Nanotubes, Carbon; D017382:Reactive Oxygen Species; D009195:Peroxidase