Intracellular trafficking pathways in silver nanoparticle uptake and toxicity in Caenorhabditis elegans

Abstract

We used the nematode Caenorhabditis elegans to study the roles of endocytosis and lysosomal function in uptake and subsequent toxicity of silver nanoparticles (AgNP) in vivo. To focus on AgNP uptake and effects rather than silver ion (AgNO₃) effects, we used a minimally dissolvable AgNP, citrate-coated AgNPs (CIT-AgNPs). We found that the clathrin-mediated endocytosis inhibitor chlorpromazine reduced the toxicity of CIT-AgNPs but not AgNO₃. We also tested the sensitivity of three endocytosis-deficient mutants (rme-1, rme-6 and rme-8) and two lysosomal function deficient mutants (cup-5 and glo-1) as compared to wild-type (N2 strain). One of the endocytosis-deficient mutants (rme-6) took up less silver and was resistant to the acute toxicity of CIT-AgNPs compared to N2s. None of those mutants showed altered sensitivity to AgNO₃. Lysosome and lysosome-related organelle mutants were more sensitive to the growth-inhibiting effects of both CIT-AgNPs and AgNO₃. Our study provides mechanistic evidence suggesting that early endosome formation is necessary for AgNP-induced toxicity in vivo, as rme-6 mutants were less sensitive to the toxic effects of AgNPs than C. elegans with mutations involved in later steps in the endocytic process.

• In vivo endocytosis
• lysosome
• nanoparticle uptake
• nanotoxicology

Acknowledgements

The authors are grateful for the support of Dr Stella M. Marinakos in the preparation and characterization of the nanoparticles used in this study, and all the researchers and administrators in the leadership of the Center for the Environmental Implications of NanoTechnology (CEINT). We also thank Drew Day for manuscript review.

Declaration of interest

The authors report no conflicts of interest in this work.

The authors acknowledge funding provided through the National Science Foundation (NSF) and the Environmental Protection Agency (EPA) under the NSF Cooperative Agreement EF-0830093, Center for the Environmental Implications of NanoTechnology (CEINT). Any opinions, findings, conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF or the EPA. This work has not been subjected to EPA review and no official endorsement should be inferred. The N2 strain was provided by the C. elegans Reverse Genetics Core Facility at UBC, which is part of the International C. elegans Gene Knockout Consortium and is supported by the National Institute of Health - Office of Research Infrastructure Programs (P40 OD010440). Strain RB950 was provided by the C. elegans Gene Knockout Project at OMRF, which is part of the International C. elegans Gene Knockout Consortium.

Supplementary material available online

Supplementary Figures S1–S3