Arsenic inhibits stem cell differentiation by altering the interplay between the Wnt3a and Notch signaling pathways

Abstract

Millions of people are exposed to arsenic through their drinking water and food, but the mechanisms by which it impacts embryonic development are not well understood. Arsenic exposure during embryogenesis is associated with neurodevelopmental effects, reduced weight gain, and altered locomotor activity, and in vitro data indicates that arsenic exposure inhibits stem cell differentiation. This study investigated whether arsenic disrupted the Wnt3a signaling pathway, critical in the formation of myotubes and neurons, during the differentiation in P19 mouse embryonic stem cells. Cells were exposed to 0, 0.1, or 0.5 μM arsenite, with or without exogenous Wnt3a, for up to 9 days of differentiation. Arsenic exposure alone inhibits the differentiation of stem cells into neurons and skeletal myotubes, and reduces the expression of both β-catenin and GSK3β mRNA to ∼55% of control levels. Co-culture of the arsenic-exposed cells with exogenous Wnt3a rescues the morphological phenotype, but does not alter transcript, protein, or phosphorylation status of GSK3β or β-catenin. However, arsenic exposure maintains high levels of Hes5 and decreases the expression of MASH1 by 2.2-fold, which are anti- and pro-myogenic and neurogenic genes, respectively, in the Notch signaling pathway. While rescue with exogenous Wnt3a reduced Hes5 levels, MASH1 levels stay repressed. Thus, while Wnt3a can partially rescue the inhibition of differentiation from arsenic, it does so by also modulating Notch target genes rather than only working through the canonical Wnt signaling pathway. These results indicate that arsenic alters the interplay between multiple signaling pathways, leading to reduced stem cell differentiation.

Effects of Inorganic Arsenic on Human Prostate Stem-Progenitor Cell Transformation, Autophagic Flux Blockade, and NRF2 Pathway Activation

“…In the human prostate, PrSPCs give rise to basal cells, luminal PrECs, and rare neuroendocrine cells (Strand and Goldstein 2015). Because iAs alters differentiation in a variety of stemprogenitor cells (Bain et al 2016;McCoy et al 2015;Rebuzzini et al 2015;Yen et al 2010), we tested whether iAs influences this process in PrSPCs. Primary PrSPCs cultured for 7 d from diseasefree PrECs were isolated and mixed with embryonic rat urogenital sinus mesenchyme (UGM) and grafted under renal capsules of nude mice.…”

Arsenic Induces Members of the mmu-miR-466-669 Cluster Which Reduces NeuroD1 Expression

“…Previous studies have shown that arsenic at concentrations between 0.1 and 0.5 lM inhibit P19 embryonic stem cell differentiation into skeletal muscle and sensory neurons (Bain et al, 2016;Hong and Bain, 2012;Liu and Bain, 2014;McCoy et al, 2015). One potential mechanism for this inhibition is through changes in miRNA expression in arsenic-exposed cells, as miRNAs have been shown to play a role in arsenic toxicity and carcinogenesis (reviewed in Bustaffa et al, 2014;Paul and Giri, 2015;Ren et al, 2011).…”

Expression of the Major Vault Protein (MVP) and Cellular Vault Particles in Fish

“…RA is derived from vitamin‐A, is a ligand for the transcription factor RA receptor, and has a critical role in development in many models, from fish to amphibians, to birds and mammals (Breitman et al, ; Baier‐Anderson et al, ; Rhinn and Dollé, ). Likewise, arsenate (As) affects cell differentiation and tissue development (McCoy et al, ; Bain et al, ), but neither RA or As affected MVP mRNA expression. The use of phorbol ester and calcium ionophore (P + A) mimics the activation of PKC and elevated intracellular calcium following cell activation and signaling (Rice and Weeks, ), and as with RA and As, this signaling has no impact on MVP mRNA expression in CCO cells under present experimental conditions.…”