Reliable Screening of Dye Phototoxicity by Using a Caenorhabditis elegans Fast Bioassay

PLoS One. 2015 Jun 3;10(6):e0128898. doi: 10.1371/journal.pone.0128898. eCollection 2015.


Phototoxicity consists in the capability of certain innocuous molecules to become toxic when subjected to suitable illumination. In order to discover new photoactive drugs or characterize phototoxic pollutants, it would be advantageous to use simple biological tests of phototoxicy. In this work, we present a pilot screening of 37 dyes to test for phototoxic effects in the roundworm Caenorhabditis elegans. Populations of this nematode were treated with different dyes, and subsequently exposed to 30 min of white light. Behavioral outcomes were quantified by recording the global motility using an infrared tracking device (WMicrotracker). Of the tested compounds, 17 dyes were classified as photoactive, being phloxine B, primuline, eosin Y, acridine orange and rose Bengal the most phototoxic. To assess photoactivity after uptake, compounds were retested after washing them out of the medium before light irradiation. Dye uptake into the worms was also analyzed by staining or fluorescence. All the positive drugs were incorporated by animals and produced phototoxic effects after washing. We also tested the stress response being triggered by the treatments through reporter strains. Endoplasmic reticulum stress response (hsp-4::GFP strain) was activated by 22% of phototoxic dyes, and mitochondrial stress response (hsp-6::GFP strain) was induced by 16% of phototoxic dyes. These results point to a phototoxic perturbation of the protein functionality and an oxidative stress similar to that reported in cell cultures. Our work shows for the first time the feasibility of C. elegans for running phototoxic screenings and underscores its application on photoactive drugs and environmental pollutants assessment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acridine Orange / chemistry
  • Acridine Orange / pharmacology
  • Animals
  • Biological Assay*
  • Caenorhabditis elegans / drug effects*
  • Caenorhabditis elegans / physiology
  • Caenorhabditis elegans / radiation effects
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism
  • Coloring Agents / chemistry
  • Coloring Agents / pharmacology*
  • Endoplasmic Reticulum Stress / drug effects
  • Endoplasmic Reticulum Stress / genetics
  • Endoplasmic Reticulum Stress / radiation effects
  • Eosine I Bluish / chemistry
  • Eosine I Bluish / pharmacology
  • Eosine Yellowish-(YS) / chemistry
  • Eosine Yellowish-(YS) / pharmacology
  • Gene Expression Regulation
  • Genes, Reporter
  • Heat-Shock Proteins / genetics
  • Heat-Shock Proteins / metabolism
  • High-Throughput Screening Assays*
  • Light
  • Mitochondria / drug effects
  • Mitochondria / metabolism
  • Mitochondria / radiation effects
  • Photosensitizing Agents / chemistry
  • Photosensitizing Agents / pharmacology*
  • Rose Bengal / chemistry
  • Rose Bengal / pharmacology
  • Thiazoles / chemistry
  • Thiazoles / pharmacology


  • Caenorhabditis elegans Proteins
  • Coloring Agents
  • Heat-Shock Proteins
  • Hsp-4 protein, C elegans
  • Photosensitizing Agents
  • Thiazoles
  • Rose Bengal
  • primuline
  • Acridine Orange
  • Eosine I Bluish
  • Eosine Yellowish-(YS)

Grants and funding

This work was supported by grants PICTStartup and PAEBT2009-19 from Ministry of Science and Technology Argentina, and CTQ2013-48767-C3-3R from the Ministerio de Economía y Competitividad, Spain. The strains used in this work were provided by the CGC Center, which is supported by the NIH, and the C. elegans knockout consortium. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.