FIGURE 1.

Cytotoxicity analyses and the effects of cisplatin and honokiol (HNK) on protein expression and cellular localization of Occludin and E-Cadherin. (A) To determine cell toxicity of cisplatin and HNK, cell viability assay namely MTT [(3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide)] assay was carried out. Up to 10 μM of cisplatin and 15 μM of HNK, no cytotoxicity was detected. (B) Western-blotting was performed to evaluate the effect of HNK on the protein expression of E-Cadherin and Occludin. (C) Two-dimension polarized cell culture system showed cisplatin treatment induced redistribution of tight junction protein Occludin (in green) from the apical membrane region toward the cytosol as disorganized and multiple layers of signals were observed. Similar to that of Occludin, E-Cadherin (in red) moved from the lateral membrane toward the cytosol as a thicker E-Cadherin signal and increased cytosolic E-Cadherin signal were observed upon cisplatin treatment. This redistribution of junction proteins was partly decreased in the HNK co-incubation group. Cartoon images depicted and summarized the observed phenomenon. (D) Signal dispersion analysis showed in cisplatin-treated group, both Occludin and E-Cadherin are more dispersed into the cytosol than control or HNK-treated cells (1.42- and 1.84-fold more dispersed for Occludin and E-Cadherin, respectively). At least 3–5 independent experiments were performed. N.S. indicated no statistical difference. Asterisk indicated significant difference at p < 0.05. a–d, indicated significant (p < 0.05) difference between groups. Data were expressed as fold change as compared with control condition.