Aspirin inhibits stem cell proliferation during freshwater Dugesia japonica regeneration by STAT3/SOX2/OCT4 signaling pathway

As a widely used drug in clinical practice, aspirin has a large number of residual drugs and metabolites discharged into the environment during the pharmaceutical process or after taking the drug. Aspirin content and its metabolite, salicylic acid, have been reported and detected in several river water samples and municipal wastewaters. However, little is known about the toxicity mechanisms of this drug in aquatic invertebrates. In this study, we examine the toxic effect and investigate the toxicity mechanism of aspirin in planarian, which own the excellent regeneration and sensitive toxicity detection ability. Planarian is treated with 0.7 mM aspirin for 6 h, 48 h, 3 d and 5 d, and the mRNA and protein expression levels of the stem cells markers, in parallel with the target genes of the signaling pathway are analyzed by RT-qPCR, whole-mount immunofluorescence, and Western blot. The results show that aspirin strongly inhibits stem cell proliferation and causes retarded blastemas growth in planarians. Furthermore, the mRNA and protein expression levels of stem cells markers and the target genes dramatically decrease after the aspirin treatment. Meanwhile, the expression level of apoptotic cells also shows a downward trend. Their significant and coincident downregulations after the aspirin treatment suggest that aspirin regulates planarian regeneration via STAT3/SOX2/OCT4 signaling pathway. Our work reveals the toxicological effect and the mechanism of aspirin to the planarian, and provides basic data for therapeutic applications of aspirin in regeneration and warns about the ecological damage of aspirin abuse.