Effect and Structure-Activity Relationship Between Isatin and its Dimer Indirubin on Neural Development of Transgenic Zebrafish

Objective Isatin (2,3-indolinedione, ISA), as an indole oxide, is widely distributed in mammalian tissues and fluids, with concentrations varying from less than 0.1 to greater than 10 μM. Indirubin (2-(2-oxo-1h-indol-3-ylidene)-1h-indol-3-one, IND), as a bisindole alkaloid, is a dimer of indigo. Recent research indicated these two medications could regulate neural activity, however the precise effects of these two drugs on neural cells remained undefined This study aims to investigate the effects of ISA and IND on neural cells development and the underlying mechanisms. Methods Zebrafish embryos at 24 hpf were treated with different concentrations of ISA and IND (0.001, 0.01, 0.1, 1, and 10 μM) for 24 h. The number of neural cells and the length of motor neuronal axons, as well as the length of intersegmental vessels at 72 hpf, were observed by confocal microscopy. The body length of zebrafish larvae was measured through bright-field photography using a Nikon stereomicroscope. Movement distance and trajectory of zebrafish were detected by the Zebralab video tracking system. Results The results demonstrate that during the early embryonic development of zebrafish, ISA can inhibit the number of zebrafish neurons, the length of motor neuronal axons, the movement distance of zebrafish, and the development of intersegmental vessels (ISVs) in a dose-dependent manner. Conversely, IND not only promotes the number of zebrafish neurons but also enhances the length of motor neuronal axons, and the movement distance of zebrafish, without the growth of ISVs in zebrafish. Besides, both drugs have no significant impact on the early morphological development of zebrafish. Conclusion ISA played an inhibitory effect on neural development, possible by inhibiting ISVs development in zebrafish. While IND had a promotional effect on neural development of zebrafish, and was expected to be a potential neuroprotective agent. Furthermore, present study suggested that two drugs with a dimeric relationship could exert different effects.