Exploring potential biomarker responses to lithium in Daphnia magna from the perspectives of function and signaling networks

Intensive usage of electronic appliances containing lithium batteries causes an accumulation of e-trash. Environmental exposure to lithium batteries contaminates ecosystems. In air and water, the batteries form lithium hydroxide (LiOH) on their surfaces. LiOH enters the aquatic environment and contaminates the aquatic ecosystem by being absorbed into biological organisms. In this study, in order to identify meaningful potential biomarkers that appear in response to lithium, we measured significantly up- and down-regulated genes after LiOH exposure by conducting a microarray. In addition, we explored the functions of differentially expressed daphnia genes, and we conducted a comparative analysis in other species, Daphnia spp. to humans, then analyzed the signaling pathways using the human gene set derived from daphnia sequences that are differentially expressed in response to LiOH using the NCBI-BLAST tool and Pathway studio. As a result, we identified signaling pathways and suggested several potential biomarkers that are up- or down-regulated in response to lithium. This study may contribute to the development of a biomonitoring system which can detect the ecotoxicity of lithium. Furthermore, lithium toxicity in humans can be predicted, so the study may also provide potential biomarkers of lithium exposure in humans.