Arsenious Acid

Disrupted-in-schizophrenia-1 (DISC1) is a scaffold protein that plays a pivotal role in orchestrating signaling pathways involved in neurodevelopment, neural migration, and synaptogenesis. Among those, it has recently been reported that the role DISC1 in the Akt/mTOR pathway can shift from a global translational repressor to a translational activator in response to oxidative stress induced by arsenic. In this study we are providing evidence that DISC1 can directly bind arsenic via a C-terminal cysteine motif (C-X-C-X-C). A series of fluorescence-based binding assays were conducted with a truncated C-terminal domain construct of DISC1 and a of series of single, double, and triple cysteine mutants. We found that arsenous acid, a trivalent arsenic derivative, specifically binds to the C-terminal cysteine motif of DISC1 with low micromolar affinity. All three cysteines of the motif are required for high-affinity binding. Electron microscopy experiments combined with in silico structural predictions revealed that that the C-terminal of DISC1 forms an elongated tetrameric complex. The cysteine motif is consistently predicted to be located within a loop, fully exposed to solvent, providing a simple molecular framework to explain the high-affinity of DISC1 toward arsenous acid. This study sheds light on a novel functional facet of DISC1 as an arsenic binding protein and highlights its potential role as both a sensor and translational modulator within the Akt/mTOR pathway.

To investigate the effect of artesunate and arsenous acid and their combination on the proliferation and apoptosis of human multiple myeloma cells and their mechanism.

Human multiple myeloma cell line RPMI 8226 cells were cultured and treated with 0, 1, 2, 4, 8 nmol/L arsenous acid and 0, 40, 80, 160, 320 μmol/L artesunate, respectively. The inhibition of cell growth was detected by CCK-8 assay. The apoptosis rate was detected by flow cytometry. QPCR was used to detect the mRNA expression of cell proliferation and apoptosis-related factors. The expression of cell proliferation, apoptosis-related factors and PI3K/AKT pathway protein were detected by Western blot.

CCK-8 assay showed that the growth of multiple myeloma cells was inhibited by arsenous acid and artesunate. The IC₅₀ of arsenous acid was 1.96 nmol/L, and artesunate was 153.96 μmol/L. Flow cytometry showed that arsenous acid, artesunate, and their combination could significantly increase the apoptosis of multiple myeloma cells. QPCR and Western blot showed that the arsenous acid, artesunate, and their combination treatment could inhibit the expression of mRNA and protein of cell proliferation-related factors interleukin-6 and vascular endothelial growth factor (P<0.05), inhibit apoptosis-related factor BCL-xl and promote the expression of mRNA and protein of Bax (P<0.05), and reduce the protein expression of p-PI3K and p-AKT in PI3K/AKT signaling pathway (P<0.05). Moreover, the combination effect of the two drugs on cell apoptosis and the above mentioned factors was obviously stronger than that of the two drugs alone.

Artesunate combined with arsenous acid inhibits proliferation and promotes apoptosis of tumor cells through PI3K/AKT signaling pathway, and is superior to the effect of two drugs alone.