Timing, hosts and locations of (grouped) events of NanoImpactNet

NanoSafetyCluster - Compendium 2012
nanomaterials. Risk assessment will be performed in close
collaboration between all consortium members. Members of our
consortium possess considerable expertise in Physiologically-
Based-Pharmaco-Kinetics (PBPK) modelling. These models can be
extended to incorporate the variability seen in animal data and the
uncertainty due to lack of knowledge, an important feature of risk
assessment. PBPK models have been used in describing the
distribution of the internal dose across different target organs. The
target organ dose is better correlated with the biological
responses than the external exposure. As acknowledged by
SCENIHR (2007), there is currently no established PBPK model for
the distribution of nanoparticles in the body. In this project, we
plan to extend this model, based on the inhalation mode of
exposure, to other exposure routes such as intravenous injection
and dermal exposure, thus taking it beyond the current state-ofthe-art.
(Q)SAR [(Quantitative) Structure-Activity Relationship)] is
the quantitative correlation of the biological (ecological,
toxicological or pharmacological) activity to the structure of
chemical compounds, which allows the prediction of the so-called
"drug efficacy" of a structurally related compound. (Q)SAR is
highly desirable as an approach which could replace extensive
animal testing. To date, few attempts at (Q)SAR modeling were
made for ENs. However, a (Q)SAR-like model, linking the particle
physico-chemical characteristics with the immune response to
nanoparticles is highly desirable because it helps to better
understand the dose-response relationship, and to mitigate hazard
with better designs for manufactured nanoparticles, by supplying
important information on particle characteristics. Our approach
will thus combine the immune hazard data (in vitro and in vivo) and
modelling generated in this project with further information on
exposure obtained in the public domain and other ongoing
research projects, to develop a strategy for risk assessment of
nanomaterials.
In synopsis, our multidisciplinary approach will contribute to the
elucidation of the hazardous effects of ENs on the immune system,
and will allow us to perform reliable and sound assessment of the
risks to human health posed by these materials. Our studies will
benefit a) citizens, because we address issues related to human
health; b) researchers, because we will generate new knowledge in
material production, and on mechanisms of interaction of
nanomaterials with biological systems; and c) industry (including
SMEs), because we plan to incorporate our characterization
protocols and risk assessment guidelines into a Quality Handbook
(QHB), which can provide support to interested parties. Moreover,
our consortium provides a template for collaborations between
European and US institutes as demonstrated by several joint
publciations.
2.4 Important achievements
In the following sections, some important research results are
highlighted (and see list below of selected publications from our
consortium).
2.4.1 Interaction of carbon nanotubes with immunecompetent
cells
Biopersistence, tissue distribution, immune and inflammatory
responses to SWCNT are largely dependent on their recognition
and uptake by phagocytozing cells. Previous studies on
macrophage recognition of apoptotic cells have revealed that the
exposition of the phospholipid, phosphatidylserine (PS) on the
surface of apoptotic cells serves as an important recognition signal
for phagocytic cells (Fadeel and Xue, Crit. Rev. Biochem. Mol. Biol.,
2009). Several partners of the NANOMMUNE consortium have
now shown that SWCNT coating with the “eat-me” signal, PS
makes nanotubes recognizable by macrophages, including primary
human monocyte-derived macrophages and dendritic cells
(Konduru et al., PLoS-ONE, 2009). Aspiration of PS-coated SWCNT
in mice stimulated their uptake by alveolar macrophages in vivo.
These studies also demonstrated that PS-coated SWCNT triggered
less pro-inflammatory cytokine secretion than non-coated
nanotubes.
Enzymatic biodegradation of SWCNT by the plant enzyme,
horseradish peroxidase has been reported by US partners
belonging to the NANOMMUNE consortium (Allen et al., J. Am.
Chem. Soc., 2009). In addition, several members of our consortium
have recently demonstrated a novel route of biodegradation of
SWCNT through enzymatic catalysis by human neutrophil-derived
myeloperoxidase (hMPO) (Kagan et al., Nat. Nanotech., 2010).
Biodegradation occurred in primary human neutrophils and to a
lesser extent in macrophages. Biodegradation of SWCNT was
enhanced when nanotubes were pre-coated with immunoglobulin
(IgG) to promote neutrophil internalization of SWCNT through Fc
receptors. Furthermore, using an established mouse model of
pharyngeal aspiration of SWCNT, it was shown that biodegradation
attenuated the characteristic inflammatory responses to carbon
nanotubes. These findings strongly indicate that novel biomedical
applications of carbon nanotubes may be achievable under
conditions of carefully controlled biodegradation. More recently,
our consortium has reported enhanced pulmonary inflammatory
and fibrotic responses to SWCNT in myeloperoxidase-deficient
mice (in press). These studies were co-funded by US funding
agencies.
2.4.2 Gene expression profiling of nanoparticle-exposed
cells and tissues
Monitoring nanomaterial-induced immune responses by changes
at the transcription level may be a valuable approach in terms of
providing information on signalling pathways involved. One may
assume that alterations in nanomaterial-induced gene expression
can be rather subtle and, hence, focusing on discovery of biological
pathways rather than individual genes is likely to provide a more
informative view of the underlying processes. In the
NANOMMUNE consortium, both in vitro (WP3) and in vivo (WP4)
models are included for the characterization of immune responses
using transcriptomics. The results will be used to generate novel
hypotheses for further experimental testing and to describe
nanomaterial and cell-specific changes in gene expression, i.e. to
define novel “nanotoxicogenomic signatures”. In the first study
(unpublished), cytotoxicity testing of two commonly used
nanoparticles, ZnO and TiO 2 was performed using primary human
macrophages and dendritic cells as well as the leukemic Jurkat cell
line. Exposure to ZnO nanoparticles triggered a dose-dependent
loss of cell viability. Transcriptomics analysis using Illumina
Sentrix® HumanHT-12 Expression BeadChips disclosed that the
expression of different metallothionein genes was significantly
upregulated in all three cell types after exposure to ZnO. These
findings are in accordance with the observation that ZnO
nanoparticles undergo rapid dissolution in cell culture. Further
154 Compendium of Projects in the European NanoSafety Cluster