Epicatechin isolated from Tripterygium wilfordii extract reduces tau-GFP-induced neurotoxicity in zebrafish embryo through the activation of Nrf2.

Tau plays important roles in the assembly and stabilization of the microtubule structure to facilitate axonal transport in mammalian brain. The intracellular tau aggregates to form paired helical filaments leading to neurodegenerative disorders, collectively called tauopathies. In our previous report, we established a zebrafish model to express tau-GFP to induce neuronal death, which could be directly traced in vivo. Recently, we used this model to screen 400 herbal extracts and found 45 of them to be effective on reducing tau-GFP-induced neuronal death. One of the effective herbal extracts is the Tripterygium wilfordii stem extract. HPLC analysis and functional assay demonstrated that epicatechin (EC) is the major compound of Tripterygium wilfordii stem extract to decrease the neurotoxicity induced by tau-GFP. Using a luciferase reporter assay in the zebrafish, we confirmed that EC could activate Nrf2-dependent antioxidant responses to significantly increase the ARE-controlled expression of luciferase reporter gene. These data suggest that EC from the Tripterygium wilfordii stem extract could diminish tau-GFP-induced neuronal death through the activation of Nrf2.

Characterization of the high molecular weight Cd-binding complex in water hyacinth (Eichhornia crassipes) when exposed to Cd.

Water hyacinth ( Eichhornia crassipes) is a rapid-growing freshwater vascular plant that has been used to remove heavy metals in contaminated water. But the transportation and distribution of the absorbed heavy metal in the plant are not clear. In this study, water hyacinth was exposed to cadmium (Cd, 10 microM, pulse) and then transferred to a Cd-free solution (chase). The Cd content in the tissues was measured, and the Cd-binding complexes were isolated and identified. We found that (1) in two days, up to 80% of the Cd in the solution was absorbed by the plant, and the Cd could not be released back to the growth solution in the chase period; (2) approximately 1 mg of Cd was accumulated in the water hyacinth/g of dry weight in this condition; (3) invading Cd was bound rapidly as the low-molecular-weight (LMW) complex serving as the transient form for further sequestration; (4) the LMW complex in water hyacinth contained no phytochelatins and was different from the LMW complex in fission yeast; (5) the Cd absorbed in the plant was essentially stored in the high-molecular-weight (HMW) form after 1 week; (6) a small fraction of the absorbed Cd was found in the upper part of the plant (stem and leaves) in the form of complexes; (7) the HMW complex was composed of phytochelatins PC 3 and PC 4 primarily, with only a small amount of PC 2; (8) a rare PC-related peptide was found in the HMW complex that might be derived from PC 3. These observations contribute to the further understanding of water hyacinth in serving as an efficient and reliable accumulator for heavy metals.