Aluminium toxicity (with reference to Copper) in the aqueous environment and the mechanisms of its glutathione-mediated detoxification in the brine shrimp (Artemia franciscana)

Abstract

Glutathione (y-glutamylcysteinylglycine) is a vital and ubiquitous component of biological systems that has been demonstrated to have a protective role against the toxicity of a wide array of xenobiotics and their metabolic by-products. It has been shown to detoxify many metals by direct and indirect mechanisms; but this is not the case with Al. Inputs of this metal into the environment have increased substantially since the industrial revolution, due to its use in industrial processes and the advent of acid rain. As such, it is crucial that the full implications of such exposure upon the environment is investigated thoroughly. Levels of Cu have also increased, but, on account of its greater acute toxicity, it has been the focus of a much larger amount of research. These two metals (but principally Al) are the focus of both the ecotoxicological and biochemical research herein.
Work involving aspects of Al and Cu behaviour and toxicity has been carried out at both an ecosystem and organism level. Ecosystem studies, in the form of chemodynamics experiments, have been conducted in an attempt to understand and contrast their transport in the aqueous environment and the speciation that occurs as a result. These concentrations have then been put into the context of what happened to two test species (the brine shrimp Artemiafranciscana and the bacterium Vibrio fischerii), and, in the case of Al, a field study entailing chemical and biological monitoring. In addition, studies were undertaken which showed that Al bioaccumulates in A. franciscana (which is farmed for aquaculture and is increasingly utilised in toxicity studies as a substitute for higher animals). Further toxicity tests, involving the depletion of glutathione in
A. franciscana, showed that the tripeptide has a protective effect against the toxicity of the metal to these creatures.
An analytical method (utilising high performance liquid chromatography with electrochemical detection) was then developed for measuring reduced and oxidized glutathione in A. franciscana.
This was then applied to investigate the relationship between glutathione redox status and Al exposure in aqueous systems. Reduced glutathione was shown to be depleted and subsequently induced by Al exposure, and to have a protective role against Al toxicity. Furthermore, its redox status indicated that free radical production was not the underlying mechanism responsible for the deleterious effects of Al in A. franciscana, as with many other metals studied. NMR studies were
conducted which showed an interaction between Al and glutathione. These studies suggest a possible detoxification and excretion mechanism for Al involving glutathione.