Pathway analysis in characterising the toxicological properties of nanomaterials

We are trying to identify what properties of nanoparticles are responsible for their toxicological effects in cell types most likely to be involved in the toxicity of inhaled materials. To do this, we will investigate how nanoparticles interact with cells to produce changes leading to toxicity such as the death of the cells. This will involve identifying which genes and proteins in human lung-derived cell lines in culture (i.e. grown in tissue culture dishes) are affeted when exposed to a range of engineered nanoparticles. Nanoparticles will be engineered to vary in a number of key characteristics, such as chemical composition, size and shape. It is likely that the effects of the nanoparticles on the celluls will depend upon the characteristics of the nanoparticles and the cell type. Hence, the information obtained will be of value in helping predict the likely effects of nanoparticles in humans, in the design of potentially less harmful material and in the future evaluation of novel nanomaterials

The development of novel pharmaceutical and industrial materials based on nanotechnologies requires that they are evaluated for a range of toxicities before they can be administered or released into the environment. There is as yet no agreement as to which characteristics and which endpoints are most appropriate to evaluate for this purpose. Considerable resources would be required to resolve these issues using conventional toxicity testing. We proposed to address such concerns using a novel in vitro approach based on functional genomics and proteomics, using as targets appropriate human cell lines. In addition, we will focus on pathways leading to cell death as an indicator of cellular toxicity as we have extensive expertise in this area.
The overall aim is to identify the key pathways involved in the toxic effects of nanoparticles in different cell types. We will use this information to determine which pysical and chemical characteristics of nanoparticles are responsible for which of their toxic effects. Comparison of the outputs of these studies will help identify robust signals for routine screening of nanoparticles in the future, against which to compare results of in vivo studies and should be of value in product design.
An important route of exposure to nanoparticles is the lung, as is the digestive tract. Here, we will focus initially on lung as the target tissue of interest and will investigate two potential target cell types. We will use cells derived from human pulmonary epithelium, one of the first cellular targets of inhaled particles, and pulmonary fibroblasts which may encounter interstialised particles. We will investigate a range of well characterised nanoparticles, varying in chemical composition (silver, silica, carbon), size, adsorbed content, shape and crystalline state. We will use a broad-based, combined strategy involving functional genomics and proteomics to determine which signalling pathways leading to toxicity, particulalry cell death, are perturbed following interaction of nanoparticles with those target cells. A genetic screen for cell death-inducing and -inhibiting genes will be perfomed by transfection of comprehensive cDNAs and RNAi libraries. Key proteins in signalling pathways will be identified using protein profiling and multidimensional LC-MS. Pathways involved will be identified by combining the genetics and proteomics approach and using bioinformatics approaches to pathway analysis.