Vascular endothelial cells and pulmonary epithelial cells: uptake and response to metal oxide nanoparticles

Nanomaterials are promoted as a promising technology in highly diverse applications, but concerns about risks of these materials have stimulated extensive research on the adverse effects of manufactured nanoparticles. Our research utilized ex vivo tissues to study quantification of unlabeled nanoparticles in biological media and in vitro cultures of human cells, treated with suspensions of low-solubility metal oxide materials, to study uptake, cell signaling, and gene regulation. The effects of nanoparticles on the cardiovascular system occur because inhaled nanoparticles may enter systemic circulation, or are directly injected into systemic circulation for medical applications, causing adverse health effects. Silicon dioxide (Si02) particles with sizes between 20-100 nm were used in our studies because they have many commercial and medical applications and can be readily modified with surface functional groups. Our hypothesis is two-fold. First, we hypothesize that tissue uptake and deposition of Si02 nanoparticles can be measured by sedimentation field-flow fractionation (SdFFF) after particle isolation using enzyme digestion. We also hypothesize that the adverse effects associated with nanoparticle exposures are greater in vascular cells than pulmonary and colorectal cell lines, due to the formation of reactive oxygen species, which may stimulate apoptosis. The results presented here demonstrate the cellular uptake of nano and submicron-sized Si02 using the traditional methods of microscopy. Additionally, the method of SdFFF, which is typically used to separate macromolecules, colloids, and particles, was used in combination with enzyme digestion to provide a novel, useful method to simultaneously measure both the size and concentration of particles in tissues. The toxic effects of metal oxide particle treatment on vascular, pulmonary and colon cells were evaluated. Significant cytotoxicity and inflammation were observed with vascular endothelial cells, but little to no adverse effects were seen in pulmonary and colon cancer epithelial cells at concentrations of 1-316 pg/cm2. Nano-sized SiC>2 caused apoptosis in vascular endothelial cells that was ameliorated by pretreatment with 5 mM of the antioxidant, N-acetyl-L-cysteine. Our results show that exposures of endothelial cells to high concentrations of nano-sized Si02 may have serious adverse cardiovascular consequences. Furthermore, these results provide insights into treatments, such as the use of antioxidants, for persons exposed to significant levels of metal oxide nanoparticles.