Proceedings of The Physiological Society
University of Manchester (2010) Proc Physiol Soc 19, PC185
Attenuation of vasodilator responses, induced by nanoparticle uptake, in rat aortic rings.
T. Mohamed1, M. Azzawi1, D. Whitehead1, C. Jones2, N. Akbar1, M. Azhar1
1. School of Biology, Chemistry and Health Science, Manchester Metropolitan University, Manchester, United Kingdom. 2. Maternal and Fetal Health Research Group, University of Manchester, Manchester, United Kingdom.
Nanoparticles (NPs) are utilised as tools for medical therapeutics, including imaging diagnostics and drug delivery. However, their nanotoxicological influence on isolated cells and blood vessels remains poorly understood. The aim of the present investigation was to determine the direct influence of nanoparticle (NP) uptake on aortic vessel function, using well characterised nanoparticles of defined size and charge. Monodispersed gold NPs (12 ±3 nm) were synthesised using citrate reaction of gold chloride and characterised by electron microscopy, while monodispersed silica (SiO2) NPs of defined diameter (100 ± 5 nm) and charge (positive, unmodified) were synthesised and characterised using the Malvern zetasizer. Male Wistar rats (150-250 g) were humanely killed by stunning followed by cervical dislocation and 3-4 mm aortic rings dissected away. These were cleared from fat tissue and mounted on fine steel wires in an organ bath setup and bathed in gassed physiological salt solution (PSS, 95% air- 5% CO2 ). Dilator responses to cumulative doses of endothelial dependent (acetylcholine (Ach), 0.01-100 μM) and independent (sodium nitroprusside (SNP), 0.01-10 μM) agonists were determined before and after thirty minute incubation in NPs. Data are given as mean ± SEM. Incubation in gold NPs attenuated both endothelial dependent (Ach) and independent (SNP) responses, being significant for the latter (92.34±1.41% and 59.73± 6.20% relaxation @ 0.3 μM SNP before and after incubation, respectively; P<0.01, n=7, paired student t-test). In contrast, uptake of both positively charged and unmodified silica NPs into endothelial cells led to a reduction in the magnitude of the vasodilator responses to endothelial dependent but not independent agonists. This effect was more pronounced for the positively charged particles (42.08 ± 6.54% and 18.31 ± 4.32% relaxation @ 20μM Ach before and after nanoparticle incubation, respectively, p<0.01; 92± 4.75% and 90 ± 3.20% relaxation @ 0.3 μM SNP, P=ns, n=6, paired student t test). When vessels were co-incubated in superoxide dismutase (300 u/ml), dilator responses to Ach were partially restored, for silica NPs. Our results suggest that the mechanism leading to attenuated dilator responses induced by silica NPs is different to that induced by gold NPs and is influenced by NP surface charge.
Where applicable, experiments conform with Society ethical requirements