ERB-041, a selective ERβ agonist, inhibits iNOS production in LPS-activated peritoneal macrophages of endometriosis via suppression of NF-κB activation

Objective: The aim of the present study was to assess the anti-inflammatory effects of selective ER beta (ER beta) agonist on lipopolysaccharide (LPS)-induced inducible nitric oxide synthase (iNOS) production in peritoneal macrophages (PMs) of endometriosis (EMS). Methods: ER alpha (ER alpha) and ER beta expressions in PMs were analyzed by RT-PCR and immunoblot. The PMs of endometriosis were exposed to increasing concentrations of ER beta agonist ERB-041 over a period from 0.5 to 8 h before stimulation with LPS and the levels of iNOS protein were evaluated by immunoblot. Subsequently, the PMs were pretreated with vehicle, ERB-041 or ER alpha agonist PPT before exposing to LPS. iNOS expression, p65 protein and active extracellular signal-regulated kinases (ERKs) level accumulated in the nuclear were detected by immunoblot. For experiment investigating the role of ERKs in LPS-induced iNOS expression, the PMs were pretreated with U0126, a specific ERK inhibitor, for 60 min before LPS treatment and iNOS expression was detected by immunoblot. Results: The PMs of EMS expressed ER beta to a greater extent compared with normal women. Pretreatment the PMs with ERB-041 resulted in a significant inhibition of LPS-induced iNOS expression and NF-kappa B activation by preventing its nuclear translocation. The ERKs pathway was involved in the LPS-induced iNOS production and was not repressed by the activation of ERs. Conclusion: The inhibitory effect of ER beta agonist on LPS-induced iNOS production in PMs of EMS is likely mediated via repressing of nuclear factor-kappa B (NF-kappa B) but not ERKs signaling pathways. (C) 2009 Elsevier Ltd. All rights reserved.