G-1 exerts neuroprotective effects through G protein-coupled estrogen receptor 1 following spinal cord injury in mice

Spinal cord injury (SCI) always occurs accidently and leads to motor dysfunction because of biochemical and pathological events. Estrogen has been shown to be neuroprotective against SCI through estrogen receptors (ERs), but the underlying mechanisms have not been fully elucidated. In the present study, we investigated the role of a newly found membrane ER, G protein-coupled Estrogen Receptor 1 (GPR30 or GPER1), and discussed the feasibility of a GPR30 agonist as an estrogen replacement. Forty adult female C57BL/6J mice (10-12 weeks old) were divided randomly into vehicle, G-1, E2, G-1 + G-15 and E2 + G-15 groups. All mice were subjected to SCI using a crushing injury approach. The specific GPR30 agonist, G-1, mimicked the effects of E2 treatment by preventing SCI-induced apoptotic cell death and enhancing motor functional recovery after injury. GPR30 activation regulated phosphatidylinositol 3-kinase (PI3K)/Akt and MAPK/extracellular signal-regulated kinase (ERK) signalling pathways, increased GPR30 and anti-apoptosis proteins Bcl-2 and brain derived neurotrophic factor (BDNF), but decreased the pro-apoptosis factor Bax and cleaved Caspase-3. However, the neuroprotective effects of G-1 and E2 were blocked by the specific GPR30 antagonist, G-15. Thus, GPR30 rather than classic ERs is required to induce estrogenic neuroprotective effects. Given that estrogen replacement therapy may cause unexpected side effects, especially on the reproductive system, GPR30 agonists may represent a potential therapeutic approach for treating SCI.