Integrative approach to elucidate the embryological effects of caffeine in Cyprinus carpio: Bioconcentration and alteration of oxidative stress-related gene expression patterns.

Caffeine (CAF) is an alkaloid, which acts as a central nervous system (CNS) stimulant drug. In recent years, CAF has been recurrently detected in water bodies, generating deleterious effects in aquatic organisms. The information on the toxic effects of CAF in the environment is still limited. Thus, the objective of this work was to determine whether CAF at environmentally relevant concentrations (CAF concentrations were selected based on studies on the worldwide occurrence of this compound and on the toxicity of CAF in aquatic species) is capable of inducing alterations to embryonic development and alteration of oxidative stress-related gene expression patterns in Cyprinus carpio. For this purpose, common carp embryos (2 hpf) were exposed to realistic concentrations of CAF until 96 hpf. Alterations to embryonic development and teratogenic effects were evaluated at 12, 24, 48, 72 and 96 hpf. In addition, oxidative stress in carp embryos at 72 and 96 hpf was evaluated by cellular oxidation biomarkers (lipoperoxidation level, hydroperoxide content and carbonyl protein content) and antioxidant enzymes activities (superoxide dismutase and catalase). Oxidative stress-related gene expression (sod, cat and gpx1) was also evaluated. Our results showed that CAF concentrations above 500 ng/L are capable of producing teratogenic effects. Furthermore, CAF was able to induce alterations such cardiac malformations, somite alterations, pericardial edema and chorda malformations. Concerning oxidative stress, the results demonstrated that CAF induce oxidative damage on the embryos of C. carpio. Our outcomes also showed up-regulations in genes related to antioxidant activity sod, cat and gpx by CAF exposure. In conclusion CAF at environmentally relevant concentrations is able to alter the embryonic development of common carp by the oxidative stress pathway. Based on the above evidence, it can be inferred that acute exposure to CAF can lead to a toxic response that significantly harms fish's health, adversely affecting their essential organs' functioning.