Fig. 1.

Tea polyphenols (TP) effectively attenuate STS-induced cytotoxicity and morphological collapse in hippocampal neurons. (A) STS inhibited cell viability in a dose-dependent manner. 0.4 μM of STS caused a decline of 40 % in cell viability. The scatter dot plot presented both mean ± s.e.m and individual values. ** p < 0.01 and *** p < 0.001 was examined in relative to the control group (STS = 0.0 μM). (B) TP rescued the cell viability in concentrations of 0.5–10 μM. # p < 0.05, ## p < 0.01, and ### p < 0.001 was calculated in relative to the set of STS = 0.4 μM. (C) LDH cytotoxicity assay confirmed the rescue of neurons from STS-induced toxicity by TP. (D-E) TUNEL assay verified the inhibition of STS-induced (0.4 μM) apoptosis by TP (10 μM), whereas the activity of TP was antagonized through the inhibition of TrkB activity mediated by K252a (0.2 μM). Scale bar = 50 μm. (***) or (###) p < 0.001 was calculated in relative to the control, STS, or STS + TP group, respectively; n.s, no significance. (F-H) TP (10 μM) rescued the neurons from STS-induced morphological collapse. Cells were immunofluorescence stained with β-III tubulin for visualizing the neurite (F), cell morphology (G), and DAPI for nuclei (H), Scale bar = 50 μM. STS treatment heavily destroyed the neurite and caused morphological collapse in neurons, responding to apoptotic nuclei indicated by DAPI staining. TP attenuated STS-induced toxicity and maintained the cell morphology.