Combined activity of nicotine and caffeine in the amphibian model Xenopus laevis

Nicotine and caffeine are widely consumed pharmacologically active substances. Approximately 90% of smokers also consume caffeine regularly and tend to drink more coffee than non-smokers. This co-consumption is particularly relevant, as experimental studies suggest that caffeine may enhance the teratogenic effects of other substances, including nicotine. Once ingested, both compounds are excreted and enter the environment, where they have been detected in wastewater and surface waters at concentrations ranging from ng/L to µg/L. Their presence classifies them as emerging contaminants, with the potential to harm non-target aquatic organisms exposed involuntarily. Previous studies in rodents and chicken embryos have shown that combined exposure to nicotine and caffeine can intensify adverse effects on embryonic development, increasing the risk of congenital anomalies. These observations underline the importance of considering their potential interactions, especially during pregnancy, when teratogenic exposures can severely affect fetal development. In light of these concerns, this study investigated the developmental toxicity of nicotine and caffeine using Xenopus laevis, a well-established freshwater model whose embryonic stages are considered representative of those in higher vertebrates. Embryos were exposed from the 4–8 cell stage, following a modified FETAX protocol. Tested concentrations reflected environmentally relevant levels. The results showed distinct phenotypic abnormalities, such as edema, intestinal and tail deformities, alongside elevated oxidative stress and marked dysregulation of key developmental genes. These findings reinforce the need for further ecotoxicological research and regulatory attention regarding the developmental risks posed by nicotine and caffeine in aquatic environments and their broader implications for public health.