Estrogen Signaling through the G Protein–Coupled Estrogen Receptor Regulates Granulocyte Activation in Fish

Abstract

Neutrophils are major participants in innate host responses. It is well known that estrogens have an immune-modulatory role, and some evidence exists that neutrophil physiology can be altered by these molecules. Traditionally, estrogens act via classical nuclear estrogen receptors, but the identification of a G protein–coupled estrogen receptor (GPER), a membrane estrogen receptor that binds estradiol and other estrogens, has opened up the possibility of exploring additional estrogen-mediated effects. However, information on the importance of GPER for immunity, especially, in neutrophils is scant. In this study, we report that gilthead seabream (Sparus aurata L.) acidophilic granulocytes, which are the functional equivalent of mammalian neutrophils, express GPER at both mRNA and protein levels. By using a GPER selective agonist, G1, it was found that GPER activation in vitro slightly reduced the respiratory burst of acidophilic granulocytes and drastically altered the expression profile of several genes encoding major pro- and anti-inflammatory mediators. In addition, GPER signaling in vivo modulated adaptive immunity. Finally, a cAMP analog mimicked the effects of G1 in the induction of the gene coding for PG-endoperoxide synthase 2 and in the induction of CREB phosphorylation, whereas pharmacological inhibition of protein kinase A superinduced PG-endoperoxide synthase 2. Taken together, our results demonstrate for the first time, to our knowledge, that estrogens are able to modulate vertebrate granulocyte functions through a GPER/cAMP/protein kinase A/CREB signaling pathway and could establish therapeutic targets for several immune disorders in which estrogens play a prominent role.

G Protein-Coupled Estrogen Receptor 1 Regulates Human Neutrophil Functions

“…We have previously reported that GPER1 signals via an adenylate cyclase/cAMP/PKA/CREB pathway in bony fish granulocytes [22]. It was found here that GPER1 not only uses a similar signaling pathway in human neutrophils, but also signals through p38 MAPK and ERK, as has been demonstrated in cancer cell lines [8,11,12,35].…”

“…However, the activation induced by GPER1 signaling is not identical to the classical activation observed with LPS, since while both G1 and LPS stimulate CXCL8 release, G1 fails to induce the release of IL1RA . These observations contrast with the inability of GPER1 to consistently enhance the respiratory burst of bony fish granulocytes and its anti-inflammatory effect on these cells in which the sustained induction of genes encoding Ptgs2, prostaglandin D2 synthase, and IL-10 was observed upon G1 stimulation [22]. Moreover, G1 promotes a differential effect on neutrophil-respiratory burst compared to estrogens, which have been found to reduce superoxide anion release by human neutrophils [25,26].…”

“…Despite all this evidence pointing to the crucial role of GPER signaling in the regulation of the inflammatory response, the impact of GPER1 signaling in innate immune cells is largely unknown. We have previously shown that estrogens are able to modulate granulocyte functions in teleost fish through a GPER1/cAMP/protein kinase A (PKA)/cAMP response element-binding protein (CREB) signaling pathway [22]. Whether this signaling pathway is evolutionarily conserved is unknown.…”

International Union of Basic and Clinical Pharmacology. XCVII. G Protein–Coupled Estrogen Receptor and Its Pharmacologic Modulators

“…G-1 was also recently shown to modulate the respiratory burst in vertebrate granulocytes (neutrophils) as well as pro-and anti-inflammatory gene expression profiles (Cabas et al, 2013). A direct immunomodulatory function of G-1 in the endothelium was also demonstrated through attenuation of the tumor necrosis factor a-induced upregulation of proinflammatory adhesion molecules intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 (Chakrabarti and Davidge, 2012).…”

Immune-Endocrine Interactions in the Fish Gonad during Infection: An Open Door to Vertical Transmission

“…mda5, melanoma differentiation-associated gene 5; lgp2, laboratory of genetics and physiology 2; mavs, mitochondrial antiviral signaling; traf3, tumor necrosis factor (TNF) receptor-associated factor 3; tank, TRAF3, family member-associated NF-kB activator 3; tbk1, TANK-binding kinase 1; irf, IFN regulatory factor; mx, myxovirus (influenza) resistance protein; pkr, dsRNA-dependent protein kinase receptor; er, estrogen receptor. Interestingly, ER activity has been shown to modulate innate immune signaling pathways in dendritic cells and macrophages in humans and fish [138][139][140][141]. The positive correlation observed between ERs and several molecules of the IFN pathway suggested that the modulation of the expression of ERs, together with the changes observed in the E 2 serum levels influence the ability of the immune system to react upon NNV infection.…”