Prooxidant and antioxidant mechanisms in aquatic organisms

Abstract

A consequence of all aerobic life is the production of potentially harmful, partially reduced species of molecular oxygen (oxyradicals) that occurs as a result of normal oxygen metabolism. In view of this potential for harm, aerobic organisms have evolved a complex armamentorium of defenses to protect them against the possible ravages of oxyradical production. A recent growing body of evidence indicates a marked penchant for augmented oxyradical production in aquatic organisms resulting largely from anthropogenic pollutant outfalls. Two consequences of environmental contamination might be envisaged; certain compounds which cause increased oxyradical flux could exacerbate the deleterious effects of oxyradicals or the increased fluxes could affect induction of antioxidant enzymes thereby overcoming the stresses imposed by the contaminating compound(s). This review describes the various adaptational mechanisms and responses, including the toxicological consequences, associated with oxyradical production. The broad phylogenetic spectrum of examples discussed herein illustrate that while there are numerous differences among the phyla with respect to both pro- and anti-oxidant mechanisms to establish a vigorous basis of inquiry, enough striking similarities also exist to suggest the use of aquatic organisms as alternative models to mammals in various areas of oxyradical research, e.g. aging and cancer. In addition, the potential use of anti-oxidant responses, e.g. induction of specific anti-oxidant enzymes as biomarkers of environmental contamination is reviewed.