Evaluation of the effect of green tea and its constituents on embryo development in a zebrafish model

As one of the most popular beverages, green tea has attracted much interest for its beneficial effects on human health. However, the toxicity of green tea and its underlying mechanism are still poorly understood. Here, we evaluated the effect of green tea and its constituents on development by exposing zebrafish embryos to them. Morphologic results demonstrated that 0.1% and 0.2% green tea increased mortality, delayed epiboly of gastrulation, and shortened body length. Green tea altered the expression pattern of dlx3, cstlb, myod, and papc and decreased the expression levels of wnt5 and wnt11, suggesting that green tea disturbed convergence and extension movement through the downregulation of wnt5 and wnt11. The increased expression of the dorsal gene chordin and reduced expression of wnt8 and its target genes vox and vent in embryos exposed to 0.1% and 0.2% green tea indicated that green tea could affect dorsoventral differentiation by inhibiting the wnt8 signaling pathway. Additionally, green tea could inhibit epiboly progression by disrupting F-actin organization or removing F-actin in vegetal yolks during gastrulation. However, no malformation was caused by exposure to the five catechins and gallic acid individually. The mixture of constituents showed a similar effect to green tea solution on the embryos, such as smaller eyes and head, shorter body length, and slower heart rate, which indicated that the effect of green tea solution on embryo development was mainly due to the comprehensive effect of multiple components in the green tea solution.