Tau dephosphorylation and microfilaments disruption are upstream events of the anti-proliferative effects of DADS in SH-SY5Y cells

Introduction Material and methods Material Cell cultures and treatments Microscopy analysis SOD1 enzyme assay Cell fractionation and Western blotting Determination of protein carbonylation Analysis of cell cycle and apoptosis Statistical analysis Results DADS induces cytoskeletal alterations in SH-SY5Y cells Superoxide is implicated in microfilaments and microtubules disruption DADS induces PP1-mediated Tau dephosphorylation DADS-mediated ROS increase is responsible for Tau dephosphorylation Discussion Garlic organosulphur compounds have been successfully used as redox anti-proliferative agents. In this work, we dissect the effects of diallyl disulphide (DADS) focusing on the events upstream of cell cycle arrest and apoptosis induced in neuroblastoma SH-SY5Y cells. We demonstrate that DADS is able to cause early morphological changes, cytoskeleton oxidation, microfilaments reduction and depolymerization of microtubules. These events are attenuated in cells stably overexpressing the antioxidant enzyme SOD1, suggesting that superoxide plays a crucial role in destabilizing cytoskeleton. Moreover, we evidence that the main microtubules-associated protein Tau undergoes PP1-mediated dephosphorylation as demonstrated by treatment with okadaic acid as well as by immunoreaction with anti-Tau-1 antibody, which specifically recognizes its dephosphorylated forms. Tau dephosphorylation is inhibited by the two-electron reductants NAC and GSH ester but not by SOD1. The inability of DADS to induce apoptosis in neuroblastoma-differentiated cells gives emphasis to the anti-proliferative activity of DADS, which can be regarded as a promising potent anti-neuroblastoma drug by virtue of its widespread cytoskeleton disrupting action on proliferating cells.