Inhibition of activity/expression, or genetic deletion, of ERO1 alpha blunts arsenite geno- and cyto-toxicity

Our recent studies suggest that arsenite stimulates the crosstalk between the inositol 1, 4, 5-triphosphate receptor (IP3R) and the ryanodine receptor (RyR) via a mechanism dependent on endoplasmic reticulum (ER) oxidoreductin1 alpha (ERO1 alpha) up-regulation. Under these conditions, the fraction of Ca2+ released by the RyR via an ERO1 alpha-dependent mechanism was promptly cleared by the mitochondria and critically mediated O-2(-center dot) formation, responsible for the triggering of time-dependent events associated with strand scission of genomic DNA and delayed mitochondrial apoptosis. We herein report that, in differentiated C2C12 cells, this sequence of events can be intercepted by genetic deletion of ERO1 alpha as well as by EN460, an inhibitor of ERO1 alpha activity. Similar results were obtained for the early effects mediated by arsenite in proliferating U937 cells, in which however the long-term studies were hampered by the intrinsic toxicity of the inhibitor. It was then interesting to observe that ISRIB, an inhibitor of p-eIF2 alpha, was in both cell types devoid of intrinsic toxicity and able to suppress ERO1 alpha expression and the resulting downstream effects leading to arsenite geno- and cyto-toxicity. We therefore conclude that pharmacological inhibition of ERO1 alpha activity, or expression, effectively counteracts the deleterious effects induced by the metalloid via a mechanism associated with prevention of mitochondrial O-2(-center dot) formation.

Automated summary

Arsenite stimulates crosstalk between IP3R and RyR by up-regulating ERO1α, leading to mitochondrial clearance of Ca2+ and triggering DNA strand scission and mitochondrial apoptosis. Inhibiting ERO1α expression can effectively counteract the geno- and cyto-toxic effects induced by arsenite.