# Multiple species toxicity of selected platinum group of elements: focusing on Hydra vulgaris gene expression responses

## TL;DR

This study examines how platinum group elements affect different aquatic species, focusing on gene expression changes in Hydra vulgaris.

## Contribution

The study introduces new insights into the sublethal toxicity and gene expression responses of Hydra vulgaris to platinum group elements.

## Key findings

- Hydra vulgaris showed sublethal morphological effects at low concentrations of iridium, palladium, platinum, and ruthenium.
- All tested platinum group elements significantly altered gene expression in protein turnover and degradation pathways.
- Palladium influenced multiple biological processes at very low concentrations, including DNA repair and oxidative stress.

## Abstract

The aquatic toxicity of the most abundant platinum group of elements (PGE) was investigated using a multispecies test battery, and more specifically in Hydra vulgaris at the morphological and gene expression levels. Bacteria (Aliivibrio fisheri), algae (Raphidocelis subcapitata), Daphnia magna and hydra were exposed to increasing concentrations of the following elements: iridium (Ir), palladium (Pd), platinum (Pt), rhodium (Rh) and ruthenium (Ru). The data revealed that the hydra and algae were more sensitive than the daphnids and the marine bacteria. In hydra, no lethal toxicity based on irreversible morphological changes was observed, however sublethal effects were noticed (tentacle budding, budding) with an EC20 at 10 µg/L for Ir, and Pd, Pt and Ru, EC20s at 20 µg/L. Rh produced no significant sublethal morphological changes. All tested PGE produced significant gene expression changes in pathways involved in protein turnover and degradation (ubiquitin and autophagy). Pd influenced genes at threshold concentrations reaching to <0.3 µg/L for protein turnover and degradation, oxidative stress, DNA repair and regeneration of 8-oxoguanosine, as well as for stem factor pathways. Rh, which was not (sub)lethally toxic based on morphology, influenced DNA repair of oxidized DNA and protein turnover pathways. In conclusion, PGE has the potential to alter protein turnover and induce oxidative DNA damage at environmentally relevant concentrations for receiving waters near wastewater discharges in urban area.