Soluble Guanylyl Cyclase Alpha1 Subunit: A New Marker for Estrogenicity of Endocrine Disruptor Compounds

Endocrine‐disrupting chemicals (EDCs) include widespread naturally occurring and synthetic substances in the environment that adversely affect humans and wildlife. Because of the increasing numbers of EDCs, screening methods and ideal biomarkers to determine EDC potencies at relevant environmental concentrations need to be drastically improved. Soluble guanylyl cyclase α1 subunit (sGCα1) is an abundant cytosolic protein ubiquitously expressed in most tissues. We previously showed that sGCα1 is specifically and highly up‐regulated by estrogen (E2) in vivo and in vitro, even though it lacks estrogen‐responsive elements. The aim of the present study was to evaluate sGCα1 protein expression as a potential marker for xenoestrogenic 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 byproducts, and pesticides at a range of doses including those with proven xenoestrogenic activity. We demonstrated that E2 increased sGCα1 expression in GH3 cells as well as in other E2‐responsive tumor cell lines. Moreover, this effect was fully dependent on estrogen receptor (ER) activation. Importantly, sGCα1 protein levels were strongly up‐regulated by all the EDCs tested, even by those exhibiting low or null ER binding capacity. We provide evidence that the in vitro sGCα1 protein assay may be a very sensitive and powerful tool to identify compounds with estrogenic activity, which could improve current mammalian‐based screening methods. Environ Toxicol Chem 2019;38:2719–2728. © 2019 SETAC