Low-Dose Arsenic Trioxide Modulates the Differentiation of Mouse Embryonic Stem Cells

Arsenic (As) is a well-known environmental pollutant, while arsenic trioxide (ATO) has been proven to be an effective treatment for acute promyelocytic leukemia, however, the mechanism underlying its dual effects is not fully understood. Embryonic stem cells (ESCs) exhibit properties of stemness and serve as a popular model to investigate epigenetic modifiers including environmental pollutants. Herein, the effects of low-dose ATO on differentiation were evaluated <i>in vitro</i> using a mouse ESCs (mESCs) cell line, CGR8. Cells treated with 0.2–0.5 μM ATO for 3–4 days had slight inhibition of proliferation with elevation of apoptosis, but obvious alterations of differentiation by morphological checking and alkaline phosphatase (AP) staining. Moreover, ATO exposure significantly decreased the mRNA expression of the stemness maintenance genes including <i>Oct4</i>, <i>Nanog</i>, and <i>Rex-1</i> (<i>P</i> < 0.01), whereas obviously increased some tissue-specific differentiation marker genes such as <i>Gata4</i>, <i>Gata-6</i>, <i>AFP</i>, and <i>IHH</i>. These alterations were consistent with the differentiation phenotype induced by retinoic acid (RA) and the expression patterns of distinct pluripotency markers such as SSEA-1 and Oct4. Furthermore, low-dose ATO led to a quantitative increase in Caspase 3 (CASP3) activation and subsequent cleavage of Nanog around 27 kDa, which corresponded with the mouse Nanog cleaved by CASP3 in a tube cleavage assay. Taken together, we suggest that low-dose ATO exposure will induce differentiation, other than apoptosis, of ESCs, such effects might be tuned partially by ATO-induced CASP3 activation and Nanog cleavage coupling with other differentiation related genes involved. The present findings provide a preliminary action mechanism of arsenic on the cell fate determination