Cinnamic acid induces neurodevelopmental defects via PPARγ signaling in zebrafish

Cinnamomum cassia Presl is traditional used to warm the body, dispel cold and relieve pain in China. It is a commonly used traditional Chinese medicine and spice in daily heath care. Cinnamic acid (CA) is one of the main active compounds isolated from cinnamon bark. In the present study, we found that CA (4 mg/L and 8 mg/L) caused neurodevelopment defects in zebrafish as evidenced by shortened body length, trunk curvature, behavioral abnormalities and increased mortality. And we explored the potential targets and biological mechanisms of neurotoxicity caused by cinnamic acid using network toxicology and zebrafish experiments. 154 CA related target genes were shared with neurotoxicity-related genes. Using different algorithms in Cytoscape software, 4 key target genes were finally identified as TNF, CASP3, IL6 and PPARG, which were further confirmed with molecular docking. For the next, we confirmed these targets in zebrafish. CA up-regulated tnf-α, il-6 and caspase3 gene expressions, and down-regulated pparg gene expression. Moreover, it can inhibit the activity of AChE, ATPases, CAT and SOD, decreased neuronal fluorescence, and increased macrophages and neutrophile granulocytes, ROS and MDA. In addition, it could induce apoptosis and abnormal neurodevelopmental-related gene expression in zebrafish larvae. Oxidative stress inhibitor astaxanthin could ameliorate the behavioral impairment and the expression of neurodevelopment-related genes. Moreover, when PPAR-γ expression was increased, the behavioral impairment, inflammatory response, oxidative stress, and apoptosis levels were alleviated. All these data demonstrated that the developmental neurotoxicity of CA in zebrafish might be attributed to PPAR-γ mediated oxidative stress, inflammatory response and apoptosis.