Biomedical Engineering Reference
In-Depth Information
NP
ROS
Activates
cytokine growth
factor cascade
DNA damage/
mutagenicity
Receptor
tyrosine kinase
MAP kinase
Nucleus
TNF-α, IL-1β
TGF-β
1
Fibrosis
FIGURE 19.5
Possible mechanistic pathway for pulmonary toxicity induced by exposure to NPs. Exposure
to NPs may lead to oxidative stress due to increased production of ROS and downstream signaling responses
that promote fibrosis and produce genotoxicity. NP, nanoparticle; ROS, reactive oxygen species. (Reprinted
with permission from Li JJ et al. Nanoparticle-induced pulmonary toxicity.
Experimental Biology and
Medicine
. 2010;235:1025-33.)
protein, and monocyte chemotactic protein in rodent lungs [159]. When receptor tyrosine kinases,
mitogen-activated protein kinases, and transcriptional factors, such as nuclear factor-kB and signal
transducer and activator of transcription 1, are activated, the genes involved in inflammation and
fibrosis are transcribed and expressed [160]. Stimulation of IL-1β and TNF-α heightens the expres-
sion of profibrotic proteins. More specifically, the latter is known to upregulate the production of
transforming growth factor (TGF)-β
1
, which potentiates collagen deposition by fibroblasts [161],
while the former is associated with the expression of platelet-derived growth factor (PDGF)-AA
and its receptor, PDGF receptor-a, which increases proliferation of myofibroblasts, promoting the
formation of immature collagenous tissue within the lung [160].
19.9.2.2 Glutathione Measurement
Glutathione (GSH), an antioxidant, protects the cells from free radicals. GSH level is quantified
using Ellman's reagent [162]. The level of GSH in the cells is used as a stress marker and is expressed
as micromole per milligram of protein.
19.9.2.3 Lipid Peroxidation Assay
Lipid peroxidation level is estimated by extracting lipid hydroperoxide from cell lysate in chloro-
form. A solution containing ferrous ion is then added to the cell extract, which on reaction with lipid
hydroperoxide, yields ferric ions. The resulting ferric ion is the determined colorimetric method
using thiocyanate ion as chromogen and 13-hydroperoxy-octadecadienoic acid as standard [163].
Malondialdehyde (MDA), a product of lipid peroxide decomposition, serves as a reliable indica-
tor of lipid peroxidation [123]. The extent of membrane lipid peroxidation is estimated by measur-
ing the formation of MDA. MDA is one of the end products of membrane lipid peroxidation. MDA
formed is evaluated using the thiobarbituric acid reactive species (TBARS) assay. This method is
based on the quantification of the colored complex formed between thiobarbitutic acid (TBA) and
MDA after acid hydrolysis reaction. This method was applied for the assessment of lipid peroxida-
tion effects of NPs such as silica NPs [121] and CeO
2
N Ps [164].
