Tetramethylpyrazine promotes SH-SY5Y cell differentiation into neurons through epigenetic regulation of Topoisomerase IIβ

Abstract

Tetramethylpyrazine (TMP) is an active compound extracted from the traditional Chinese medicinal herb Chuanxiong. Recently, it has been reported that TMP enhances neurogenesis, and promotes neural stem cell differentiation toward neurons. However, its molecular basis remains unknown. Topoisomerase IIβ (TopoIIβ) is a nuclear enzyme with an essential role in neuronal development. This study aimed to investigate whether TopoIIβ is involved in TMP-induced neuronal differentiation. We examined the effect of TMP on neuronal differentiation of SH-SY5Y cells. It was found that TMP inhibited cell proliferation and induced G0/G1 cell cycle arrest. TMP promoted SH-SY5Y cells to differentiate toward post-mitotic neurons characterized by long, out-branched neurites and up-regulated neuronal markers, microtubule-associated protein 2 (MAP2) and tau. Meanwhile, we demonstrated that TopoIIβ was highly expressed following TMP treatment. To unravel how TMP affects TopoIIβ expression, two chromatin active markers, acetylated histone H3 (Ac-H3) and acetylated histone H4 (Ac-H4) were examined in this study. Our data showed that the levels of Ac-H3 and Ac-H4 were positively correlated with TopoIIβ expression in the processes of neuronal differentiation. We further performed chromatin immunoprecipitation (ChIP) analysis and identified that TMP enhanced the recruitment of Ac-H3 and Ac-H4 to the TopoIIβ gene promoter region. Therefore, we concluded that TMP may stimulate neuronal differentiation of SH-SY5Y cells through epigenetic regulation of TopoIIβ. These results suggest a novel molecular mechanism underlying TMP-promoted neuronal differentiation.