Immunomodulation by 17β-estradiol in bivalve hemocytes

Abstract

.-In mammals, estrogens have dose-and cell-type-specific effects on immune cells and may act as pro-and anti-inflammatory stimuli, depending on the setting. In the bivalve mollusc Mytilus, the natural estrogen 17␤-estradiol (E2) has been shown to affect neuroimmune functions. We have investigated the immunomodulatory role of E 2 in Mytilus hemocytes, the cells responsible for the innate immune response. E2 at 5-25 nM rapidly stimulated phagocytosis and oxyradical production in vitro; higher concentrations of E 2 inhibited phagocytosis. E2-induced oxidative burst was prevented by the nitric oxide (NO) synthase inhibitor N G -monomethyl-L-arginine and superoxide dismutase, indicating involvement of NO and O 2 Ϫ ; NO production was confirmed by nitrite accumulation. The effects of E2 were prevented by the antiestrogen tamoxifen and by specific kinase inhibitors, indicating a receptor-mediated mechanism and involvement of p38 MAPK and PKC. E2 induced rapid and transient increases in the phosphorylation state of PKC, as well as of a aCREB-like (cAMP responsive element binding protein) transcription factor, as indicated by Western blot analysis with specific anti-phospho-antibodies. Localization of estrogen receptor-␣-and -␤-like proteins in hemocytes was investigated by immunofluorescence confocal microscopy. The effects of E2 on immune function were also investigated in vivo at 6 and 24 h in hemocytes of E2-injected mussels. E2 significantly affected hemocyte lysosomal membrane stability, phagocytosis, and extracellular release of hydrolytic enzymes: lower concentrations of E2 resulted in immunostimulation, and higher concentrations were inhibitory. Our data indicate that the physiological role of E2 in immunomodulation is conserved from invertebrates to mammals. estrogen; innate immunity; kinase-mediated cell signaling; Mytilus IN MAMMALS, ESTROGENS EXERT a broad spectrum of activities on a wide variety of cells and tissues, including the immune system. Estrogens have dose-and cell-type-specific effects on immune cells and may act as pro-and anti-inflammatory stimuli, depending on the setting (5,22,24,43). 17␤-Estradiol (E 2 ) can modulate the function of neutrophil granulocytes, monocytes, and macrophages; these cell types have been reported to express intracellular and membrane estrogen receptors (ERs), and their response to E 2 can be mediated by nuclear, classical or "genomic" pathways, as well as by rapid, "nongenomic" mechanisms of action (2,3,24,45). These latter mechanisms may be initiated at membrane or cytosolic locations (29,39,49) and can result in direct local effects (e.g., modification or ion fluxes) and regulation of gene transcription secondary to activation of cytosolic kinase cascades (5,22,24,29,43).Among invertebrates, estrogens have been identified in bivalve molluscs (25,34,40,43), in which their role has been mainly investigated in the control of gametogenesis (20,21,30,33,34). However, there is evidence that estrogen can represent an important signaling molecule that is involved in roles ot...

Effect of 17β-estradiol on adhesion of Mytilus galloprovincialis hemocytes to selected substrates. Role of alpha2 integrin subunit

“…The use of GF-109203X and/or Gö6976, in order to inhibit each PKC isoforms in 17b-estradiol treated cells, revealed the important role of PKC in the adhesion of hemocytes, thus verifying previous data concerning a PKC-mediated immunomodulation in hemocytes of mussels [24,57]. Moreover, Ottaviani et al [64] suggested that IL-8 triggers conformational changes, induces chemotaxis and increases phagocytic activity in M. galloprovincialis hemocytes through PKA and PKC pathway.…”

“…Moreover, integrins orchestrate multiple functions including proliferation, differentiation, gene expression, changes in intracellular pH, apoptosis and death [17,18]. Estrogens, such as 17b-estradiol (E 2 ), are among the endocrinedisrupting compounds and exert a broad spectrum of activities on a wide range of cells and tissues [19e22], among these the immune system of marine invertebrates [23,24]. 17b-estradiol is commonly present in mussel gonads and plays a major role in sexual differentiation, gonad development and oocyte growth [25].…”

Bisphenol-A alters gene expression and functional parameters in molluscan hepatopancreas

“…This route of exposure, that allows for direct administration of estrogens into the animal open circulatory system leading to distribution from the blood (hemolymph) to the tissues, including the hepatopancreas, has been largely utilised for evaluating the effects of natural and environmental estrogens in bivalve molluscs (Gagnè et al, 2001;Canesi et al, 2005Canesi et al, , 2006Canesi et al, , 2007Le Curieux-Belfond et al, 2005;Gauthier-Clerc et al, 2006;. In Mytilus sp., exogenous E 2 added to the seawater (200-2000 ng/l) is taken up and progressively metabolised (within 7 days) to an esterified, inactive form that is stored in the tissues, this indicating that mussels can tightly regulate the concentration of free E 2 (Janer et al, 2005).…”

“…In bivalves, direct administration into the blood (hemolymph) by injection into the adductor muscle sinus has been widely utilised for identifying the possible targets of both natural and environmental estrogens (Gagnè et al, 2001;Canesi et al, 2005Canesi et al, , 2006Canesi et al, , 2007Le Curieux-Belfond et al, 2005;GauthierClerc et al, 2006;. The concentrations of BPA (ng/g dry weight/mussel) were in the same range as those previously shown to affect mussel immune parameters in the same experimental conditions (Canesi et al, 2005) and comparable to environmental exposure levels (Pojana et al, 2004 A c c e p t e d M a n u s c r i p t 6…”

“…In bivalve molluscs, injection into the adductor muscle sinus allows for direct administration of estrogens into the animal open circulatory system leading distribution from the blood (hemolymph) to the tissues, including the hepatopancreas (Le Curieux-Belfond et al, 2005). This method has been largely utilised for evaluating the effects of natural and environmental estrogens in bivalves (Gagnè et al, 2001;Canesi et al, 2005Canesi et al, , 2006Canesi et al, , 2007Gauthier-Clerc et al, 2006;.…”