Characterization of functionally relevant G protein-coupled receptors in endometriotic epithelial cells

Abstract

Endometriosis is a chronic inflammatory disease characterized by the invasion of endometrial cells outside the uterine cavity. Current treatments for the disease, whose typical symptoms are pain and infertility, are unsatisfactory, relying on the surgical removal of the lesions and hormonal therapies with high symptom relapse and collateral effects, respectively. The aim of the present study was to exploit the rationale for G protein-coupled receptors (GPCRs) as non-hormonal therapeutic targets for this disease. To this end, human endometriotic epithelial cells 12Z were employed to characterize GPCR-mediated increases in intracellular Ca²⁺ concentrations ([Ca²⁺]_i) using fluo-4, and cell invasion was measured using Boyden chamber assays. The results showed that the GPCR ligands oxytocin, bradykinin, histamine, lysophosphatidic acid, and sphingosine 1-phosphate (S1P) efficiently increased [Ca²⁺]_i and induced cell invasion in endometriotic cells. In contrast, neuropeptide S, previously identified as a pro-invasive mediator, did not increase [Ca²⁺]_i in 12Z cells. Notably, pretreatment with pertussis toxin significantly reduced S1P-dependent [Ca²⁺]_i increase and cell invasion, highlighting the involvement of G_i-mediated signaling. Employing specific agonists and/or antagonists of S1P receptor isoforms, we demonstrated that S1P₁/S1P₃/S1P₅, but not S1P₂/S1P₄ mediated the [Ca²⁺]_i increases in this cellular model. Moreover, activation of S1P₁/S1P₄/S1P₅, but not S1P₂/S1P₃, efficiently stimulated cell invasion. Taken together, we identified several GPCRs that are functionally relevant in human endometriotic epithelial cells and may potentially serve as targets for non-hormonal therapy of endometriosis.

Keywords: Cell invasion; Endometriosis; G-protein coupled receptor ligands; Intracellular calcium levels; Non-hormonal targets; Sphingosine 1-phosphate receptors.