Algae are fundamental organisms in the trophic networks of aquatic ecosystems. Even small changes in their populations can have a great impact on the balance of the entire ecosystem, therefore, it is key to understand how they are affected by the appearance of pollutants.
Triclosan is an antimicrobial compound found in everyday cosmetics such as mouthwashes, toothpastes, deodorants, and soaps. Its increasingly widespread use, together with the inability of wastewater treatment plants to completely eliminate it, has contributed to its appearance in aquatic ecosystems, where it exerts toxic effects on the organisms that inhabit them.
Although the toxicity of triclosan in algae had already been previously described, the mechanisms of said toxicity were unknown. According to scientists, knowing them is a fundamental step in understanding how the cosmetics we use every day affect ecosystems.
A work published inAquatic Toxicology has answered this question. Researchers from the Autonomous University of Madrid (UAM) and the University of A Coruña reveal the cellular responses that are involved in the toxicity that this compound produces on green algaeChlamydomonas reinhardtii.
To study the cellular response, the researchers used different fluorochromes that indicate cellular responses, using the biophysical technique of flow cytometry and analysis of protein profiles, gene expression and photosynthetic measurements.
Large changes in cellular responses
The results showed that triclosan induces significant changes in Ca homeostasis.2+ intracellular free ([Ca2+]i) and an overproduction of reactive oxygen species (superoxide anion and hydrogen peroxide), which produces oxidative stress, loss of cytoplasmic membrane integrity, depolarization of the cytoplasmic membrane, reduction of metabolic activity, acidification of intracellular pH, depolarization of the mitochondrial membrane and, finally, apoptosis or cell death.
The results also showed that photosynthesis, an essential activity in maintaining the biosphere, is greatly affected. In addition, Triclosan produced alterations in the expression of genes involved in Ca signaling.2+ intracellular free, oxidative stress, photosynthesis and apoptosis, as well as changes in the protein profiles of proteins related to oxidative stress and photosynthetic activity
The ca2+ Intracellular free is a second messenger involved in the perception and signaling of a wide variety of biotic and abiotic stresses (including pollutants). In order to investigate the role of [Ca2+]i in cellular response after exposure to triclosan, the researchers used BAPTA-AM, an intracellular Ca chelator2+ that by kidnapping it avoids changes in [Ca2+]i. In this way, it can be studied whether the cellular response to the poison depends totally or partially on [Ca2+]i.
The results showed that the pre-incubation with BAPTA-AM prevented the toxic effects of triclosan on the cellular response parameters studied. Therefore, it was possible to show that the [Ca2+]i plays a key role in the overall cellular response behind the toxicity of triclosan and probably other contaminants.
Diagram of the cellular responses elicited by triclosan in Chlamydomonas reinhardtii. / González-Pleiter et al. (2017)
González-Pleiter M, Rioboo C, Reguera M, Abreu I, Leganés F, Cid Á, Fernández-Piñas F. "Calcium mediates the cellular response of Chlamydomonas reinhardtii to the emerging aquatic pollutant Triclosan".Aquat Toxicol.2017 May; 186: 50-66. DOI: 10.1016 / j.aquatox.2017.02.021