Soluble guanylyl cyclase alpha1 subunit: a new marker for estrogenicity of endocrine disruptor compounds

Abstract

Endocrine disruptor compounds (EDCs) comprise naturally occurring and synthetic substances widely spread in the environment that adversely affect human and wildlife. Because of the increasing number of EDCs, screening methods and ideal biomarkers to determine EDC potency at relevant environmental concentrations need to be exhaustively improved. Soluble guanylyl cyclase alpha1 subunit (sGC alpha1) is an abundant cytosolic protein ubiquitously expressed in most tissues. We previously showed that sGC alpha1 is specifically and highly up-regulated by estrogen (E2) in vivo and in vitro, although it lacks estrogen responsive elements. The aim of this work was to evaluate sGC alpha1 protein expression as a potential marker for EDC exposure in the E2-responsive lactosomatotroph-derived pituitary cell line GH3. Cells were incubated with a wide variety of EDCs such as heavy metals and a metalloid, synthetic E2 derivatives, plastic by-products, and pesticides at a range of doses including those having proven xenoestrogenic activity. We demonstrated that E2 increased sGC alpha1 expression in GH3 cells as well as in other E2-responsive tumor cell lines. Moreover, this effect was fully dependent on ER activation. Importantly, sGC alpha1 protein levels were strongly up-regulated by all the EDCs tested, even by those exhibiting low or null estrogen receptor (ER) binding capacity. Here we provide evidence that in vitro sGC alpha1 protein assay may be a very sensitive and powerful tool to identify compounds with estrogenic activity, which could improve current mammalian-based screening methods.