​​​Inhibition of neuroinflammation and neuronal damage by the selective non-steroidal ERβ agonist AC-186​​ 

Abstract AC-186 (4-[4-4-Difluoro-1-(2-fluorophenyl) cyclohexyl]phenol) is a neuroprotective nonsteroidal selective oestrogen receptor modulator. This study therefore investigated whether inhibition of neuroinflammation contributed to neuroprotective activity of this compound. BV-2 microglia were treated with AC-186 (0.65-5 µM) prior to stimulation with LPS. Levels of pro-inflammatory mediators and proteins were then evaluated. Treatment of LPS-activated BV-2 microglia with AC-186 resulted in significant (p < 0.05) reduction in TNFα, IL-6, NO, PGE2, iNOS and COX-2. Further investigations showed that AC-186 decreased LPS-induced elevated levels of phospho-p65, phospho-IkBα and acetylp65 proteins, while blocking DNA binding and luciferase activity of NF-kB. AC-186 induced significant (p < 0.05) increase in protein expression of ERβ, while enhancing ERE luciferase activity in BV-2 cells. Effects of the compound on microglia oestrogen signalling was confirmed in knockdown experiments which revealed a loss of anti-inflammatory activity of AC-186 following transfection with ERβ siRNA. In vitro neuroprotective activity of AC-186 was demonstrated by inhibition of activated microglia-mediated damage to HT-22 neurons. This study established that AC-186 produces NF-kB-mediated anti-inflammatory activity, which is proposed as a contributory mechanism involved in its neuroprotective actions. It is suggested that the anti-inflammatory activity of this compound is linked to its agonist effect on ERβ.