G protein‐coupled estrogen receptor activates cell type‐specific signaling pathways in cortical cultures: relevance to the selective loss of astrocytes

Abstract

Selective activation of the G protein‐coupled estrogen receptor has been proposed to avoid some of the side effects elicited by the activation of classical estrogen receptors α and β. Although its contribution to neuroprotection triggered by estradiol in brain disorders has been explored, the results regarding ischemic stroke are contradictory, and currently, there is no consensus on the role that this receptor may play. The present study aimed to investigate the role of GPER in the ischemic insult. For that, primary cortical cultures exposed to oxygen and glucose deprivation (OGD) were used as a model. Our results demonstrate that neuronal survival was strongly affected by the ischemic insult and concurrent GPER activation with G1 had no further impact. In contrast, OGD had a smaller impact on astrocytes survival but G1, alone or combined with OGD, promoted their apoptosis. This effect was prevented by the GPER antagonist G15. The results also show that ischemia did not change the expression levels of GPER in neurons and astrocytes. In this study, we also demonstrate that selective activation of GPER induced astrocyte apoptosis via the phospholipase C pathway and subsequent intracellular calcium rise, whereas in neurons, this effect was not observed. Taken together, this evidence supports a direct impact of GPER activity on the viability of astrocytes, which seems to be associated with the regulation of different signaling pathways in astrocytes and neurons.

G Protein-Coupled Estrogen Receptor Immunoreactivity Fluctuates During the Estrous Cycle and Show Sex Differences in the Amygdala and Dorsal Hippocampus

“…Previous studies have shown that GPER is widely distributed in the brain (50,53,55,56,60,73). Indeed, GPER has been shown to be expressed by neurons, astrocytes and oligodendrocytes (56,57,59,(74)(75)(76)(77) and GPER immunoreactivity has been detected by electron microscopy in both neuronal and glial profiles in the hippocampus (59), which is consistent with the detection of GPER immunoreactivity in cells with either neuronal or glial morphology in our study. Furthermore, we have detected a punctiform pattern of immunoreactivity that is absent in the cell nucleus, in agreement with the reported subcellular localization of GPER, either in the plasma membrane or in the endoplasmic reticulum and Golgi apparatus (52,54,57,(78)(79)(80).…”

Does GPER Really Function as a G Protein-Coupled Estrogen Receptor in vivo?

“…Acute administration of E2 or GPER selective agonists STX or G-1, improved neuron survival rate by 40-45% compared to control in ovariectomized female rats (145). In contrast, G-1 promoted apoptosis of rat embryo cortical astrocytes exposed to oxygen and glucose deprivation, whereas the addition of the GPER antagonist G-15 suppressed this effect, suggesting a direct impact of GPER on the viability of cortical astrocytes (146). Interestingly, administration of G-1 counteracted iron-and ovariectomyinduced memory impairments in female rats (147).…”

Astrocytes contribute to the neuronal recovery promoted by high‐frequency repetitive magnetic stimulation in in vitro models of ischemia

“…The experimental paradigm used in this study was based on previous reports from our group (Roque & Baltazar, 2017;Roque et al, 2018).…”

“…The cells used in the immunocytochemistry assays were cultured on dishes containing coverslips previously coated with polyd-lysine and were fixed immediately after the reperfusion period. All protocols were developed as previously described (Roque & Baltazar, 2017;Roque et al, 2018). Millipore; Cat# MAB3420, RRID:AB_94855) and rabbit anti-Synapsin I (1:4,000; Merck Millipore; Cat# AB1543P, RRID:AB_90757) were incubated for 48 hr at 4°C.…”

“…To fully explore the potential of HF‐rMS after ischemia, it is essential to identify the cellular mechanisms targeted by this approach and how they are modulated. Therefore, two types of primary cortical cultures (neuron‐enriched and neuron‐glia), previously established by our group (Roque & Baltazar, 2017; Roque et al., 2018), exposed to 6 hr of oxygen and glucose deprivation (OGD) followed by reperfusion (OGD/R), were used as an in vitro model of ischemia. After OGD/R, a HF‐rMS protocol was applied to both types of cultures and the effects induced by this approach were assessed through the evaluation of survival markers, as well as neuronal morphometric and synaptic modifications.…”