To date, most in vitro toxicological studies of nanoparticles are based on the assessment of acute cytotoxicity. Few studies have focused on changes in gene expression, in particular at low (non-cytotoxic) doses of nanoparticles. Here we exposed primary human bronchial epithelial cells (PBEC) to generation 4 polyamidoamine (PAMAM) dendrimers with neutral (OH) or positive (NH2) terminating groups and evaluated transcriptomics using next generation sequencing (RNA Seq) technology. First, dose-response studies using the Lactate Dehydrogenase assay (LDH) were conducted in order to elucidate the dose range at which acute cytotoxicity was elicited in PBECs. Non-cytotoxic doses (48 h exposure) were selected for subsequent experiments. Using FITC-labeled PAMAMs, we showed that the majority of the nanoparticles were localized in perinuclear lysosomes. The uptake of PAMAMs appeared to occur through an active mechanism and PAMAM-NH2 were internalized to a greater degree than PAMAM-OH. PAMAM-NH2 but not PAMAM-OH were found to induce changes in gene transcription even at low doses when no overt cell death was observed. Notably, significant down-regulation of cell cycle-related genes was detected by Gene Ontology (GO) enrichment analysis. The latter data were corroborated by experiments showing that PAMAM-NH2 treatment leads to cell cycle arrest in PBECs. Taken together, we have demonstrated that low doses of cationic dendrimers alter gene expression in human lung cells. This study indicates that systems biology and computational approaches can aid in the prediction of nanomaterial toxicity and may uncover the underlying mechanism of cellular responses. Further work is warranted to address biological effects of nanomaterials occurring at low doses of exposure, in order to understand the effects of these materials.

Systems biology approaches reveal low-dose effects of dendrimers

248th National Meeting (2014)

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