Isabel Cabas

17α-Ethynylestradiol alters the immune response of the teleost gilthead seabream (Sparus aurata L.) both in vivo and in vitro.

There is increasing public attention concerning the effect of endocrine disruptor chemicals (EDCs) on the immune system. One important group belonging to EDCs are the environmental estrogens. Commonly found in the effluents in wastewater treatment plants, 17α-ethynylestradiol (EE(2)) which is used in contraceptive pills, is an endocrine disruptor with strong estrogenic effects. This study aims to investigate the capacity of EE(2) to modulate in vivo and in vitro the innate immune response of the gilthead seabream (Sparus aurata L.), a teleost species of great commercial value. For this purpose, adult specimens were bath-exposed to EE(2) (0, 5 and 50 ng/L) and then immunized with hemocyanin in the presence of the adjuvant aluminum. The results indicate that, after 15 days of EE(2)-exposure, the disruptor was able to inhibit in a dose-dependent manner the induction of interleukin-1β (IL-1β) gene expression, but did not significantly alter the specific antibody titer. To shed light on the role played by EE(2) into seabream immune response, leukocytes were exposed in vitro to several concentrations of EE(2) (0, 0.5, 5, 50 and 500 ng/ml) for 3, 16 and 48 h and the production of reactive oxygen intermediates, the phagocytic activity and the gene expression profile of these cells were analyzed. EE(2) was seen to inhibit both cellular activities and to alter the immune gene expression profile in primary macrophages. Thus, low concentrations of EE(2) increase the mRNA levels of IL-1 β, IL-6, tumour necrosis factor α and tumour growth factor β in non-activated macrophages. In contrast, EE(2) treatment of activated macrophages resulted in the decreased expression of pro-inflammatory genes and the increased expression of genes encoding anti-inflammatory and tissue remodeling/repair enzymes. Taken together, our results suggest that EE(2) might alter the capacity of fish to appropriately respond to infection although it does not behave as an immunosuppressor.

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

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.

Dietary intake of 17α-ethinylestradiol promotes leukocytes infiltration in the gonad of the hermaphrodite gilthead seabream.

A wide variety of chemicals discharged from industrial and municipal sources have been reported to disrupt the endocrine system of animals, which may be exposed via the food chain and contaminated water. 17α-Ethinylestradiol (EE(2)), a drug used in oral contraceptives and hormone replacement therapy, has a widespread presence in the aquatic environment. Current knowledge on the sensitivity of marine fish to estrogenic environmental chemicals is limited. We report here the effects of dietary intake of EE(2) on gilthead seabream, a marine hermaphrodite teleost, focusing on the immune events that take place in the gonad. When seabream males were fed with 5, 50, 125 and 200μg EE(2)/g food for 7, 14, 21 and 28days an infiltration of acidophilic granulocytes and B lymphocytes occurred in the testis as the same time that spermatogenesis is disrupted. Moreover, the dietary intake of EE(2) promoted a dose-dependent up-regulation of the expression of genes coding for cytokines, chemokines and adhesion molecules correlated with a leukocyte infiltration.

Natural and synthetic estrogens modulate the inflammatory response in the gilthead seabream (Sparus aurata L.) through the activation of endothelial cells.

Sex steroids are known to deeply alter processes other than fish reproduction, including fish growth, intermediary metabolism, osmoregulation and immunity. We have previously reported that 17β-estradiol (E(2)), the main fish estrogen, promotes the mobilization of acidophilic granulocytes from the head kidney, the bone marrow equivalent in fish, to the gonad in the bony fish gilthead seabream (Sparus aurata L.). The aim of this study was to investigate the effects of E(2) and 17α-ethinylestradiol (EE(2)), an endocrine disruptor with strong estrogenic effects commonly found in the aquatic environment, on the ability of gilthead seabream endothelial cells (ECs) to promote leukocyte infiltration. E(2) and EE(2) were seen to affect ECs in different ways. Thus, E(2) was able to increase the production of nitric oxide (NO) and up-regulate the expression of the key activation markers, interleukin-1β, CC chemokine ligand 4, interleukin-8, E-selectin and matrix metalloproteinase 9, when used alone or combined with bacterial DNA. In contrast, EE(2) failed to affect NO release and reduced the up-regulation of the above genes promoted by bacterial DNA. Moreover, we found that leukocyte adhesion to ECs was enhanced by E(2) treatment. Collectively, these results suggest that estrogens modulate fish leukocyte trafficking during an inflammatory process by activating ECs.

Testosterone implants modify the steroid hormone balance and the gonadal physiology of gilthead seabream (Sparus aurata L.) males.

Androgens can induce complete spermatogenesis in immature or prepubertal teleost fish; however, many aspects of the role of androgens in adult teleost spermatogenesis remain elusive. We used the in situ forming microparticle (ISM) system containing 1mg of testosterone (T)/kg body weight (T-ISM) in a homogenous population of gilthead seabream at testicular involution stage to study in vivo the effects of T on the sex steroid hormone balance and on the physiology of the gilthead seabream gonad. The levels of T, 11-ketotestosterone (11KT) and 17β-estradiol (E2) in plasma, gonad and liver were determined in T-ISM implanted specimens after 7, 14, 21 and 28 days. The effect of T-ISM was evaluated on (i) de novo synthesis and metabolism of T in the gonad and liver by measuring the gene expression levels of the main steroidogenic proteins involved, (ii) the progress of spermatogenesis, (iii) the presence of different leukocyte cell types in the gonad, and (iv) the mRNA expression of some genes involved in the leukocyte migratory influx into the gonad and of some immune-relevant molecules. T-ISM implants promote an increase of T up to supra-physiological levels which induce a depletion of E2 levels and maintain the 11KT levels at physiological concentrations. The gene expression profile of some steroidogenic enzymes in gonad and liver ruled out the transformation of T into estrogenic compounds following T-ISM implantation. Moreover, androgens may also be involved in the leukocyte migratory influx, which occurred even when cytokine, chemokine and cell adhesion molecule gene expressions were down-regulated. Moreover, T-ISM implants block germ cell proliferation, although increased dmrt1 gene expression may prevent the complete depletion of germ cells in the gonad. Furthermore, T down-regulated the expression of several tlr genes, which may result in the inhibition of the immune response in the gonad through the impaired ability to recognize and respond to pathogens.

Specific and non-overlapping functions of testosterone and 11-ketotestosterone in the regulation of professional phagocyte responses in the teleost fish gilthead seabream.

Sex hormones, both estrogens and androgens, have a strong impact on immunity in mammals. In fish, the role of androgens in immunity has received little attention and contradictory conclusions have been obtained. However, it is well known that sex steroids are involved in fish growth, osmoregulation and gonad remodelation. In this study, we examine the in vitro effects of testosterone and 11-ketotestosterone, the two main fish androgens, on the professional phagocytes of the teleost fish gilthead seabream (Sparus aurata L.). Although both testosterone and 11-ketotestosterone failed to modulate the respiratory burst of seabream phagocytes, testosterone but not 11-ketotestosterone was able to increase the phagocytic ability of non-activated phagocytes. Curiously, 11-ketotestosterone was more powerful than testosterone at inducing the expression of its own receptor, namely androgen receptor b (ARb), in acidophilic granulocytes (AGs), but none of them affected the basal ARb expression levels in macrophages (MØ). Furthermore, although physiological concentrations of testosterone exerted a pro-inflammatory effect on both AGs and MØs, 11-ketotestosterone showed an anti-inflammatory effect in AGs and a strong pro-inflammatory effect in MØs. Interestingly, both androgens modulated the expression of toll-like receptors in these two immune cell types, suggesting that androgens might regulate the sensitivity of phagocytes to pathogens and damage signals. Testosterone and 11-ketotestosterone have a competitive effect, at least, on the modulation of the expression of some genes. Therefore, our results show for the first time a non-overlapping role for testosterone and 11-ketotestosterone in the regulation of professional phagocyte functions in fish.

Sex Steroids Modulate Fish Immune Response

For some time behavioural and ecological studies have suggested that sex steroid hormones regulate several immune processes in fish. For example, the immunocompetence handicap hypothesis relates the heritability of parasite resistance with secondary sexual ornaments, which are determined and maintained by androgens. Such ornaments are probably a good indicator to potential mates of genetic resistance to infections (Dijkstra et al., 2007; Roberts et al., 2004). Among vertebrates, the prevalence and intensity of parasitic infections is higher in males than females (Klein, 2004). Some fish species show altered sex steroid hormones levels upon parasite infection. The main alterations recorded upon infection are decreases in androgen, estrogen and vitelogenin serum levels (Hecker & Karbe, 2005). For example, during an infective period of vibriosis, silver seabream showed gradually increasing testosterone serum levels, whereas serum estradiol levels significantly decreased at an early stage of infection and remained low until death. This process coincided with increasing macrophages phagocytic activity (Deane et al., 2001). Such field studies prompted immunologists to try to establish how sex steroid hormones are able to alter the functions of the circulating leukocytes. In fish, most existing information on reproductive-immune interactions deals with the modulation of immune responses by circulating hormones, including cortisol, growth hormone, prolactin and reproductive hormones and some proopiomelanocortin-derived peptides (Engelsma et al., 2002; Harris & Bird, 2000). Although the exact effect of these endocrine mediators depends on the species, in general, they are known to modulate immune responses by integrating the activities of all the systems. In this way they help to adapt the organism to its environment (Lutton & Callard, 2006). From a reproductive biology point of view, the leukocytes located in mammalian gonads orchestrate important reproductive physiology processes, including gametogenesis and steroidogenesis. A long time has passed since leukocytes were first described in the gonad of teleosts. Since them, several types of leukocytes have been described in the testis of different teleost species using light and electron microscopy. Moreover, differences in the number and localization of leukocytes within the testis have also been observed during the different stages of the reproductive cycle (Besseau & Faliex, 1994; Billard, 1983; Brusle-Sicard & Fourcault, 1997; Lo Nostro, 2004; Scott & Sumpter, 1989). Thus, in the gametogenic activity and spawning stages some macrophages have been described in the interstitial tissue of the rainbow trout testis (Loir et al., 1995), whereas in the post-spawning stage a

The Effect of 17α-Ethynylestradiol on Steroidogenesis and Gonadal Cytokine Gene Expression Is Related to the Reproductive Stage in Marine Hermaphrodite Fish

Pollutants have been reported to disrupt the endocrine system of marine animals, which may be exposed through contaminated seawater or through the food chain. Although 17α-ethynylestradiol (EE2), a drug used in hormone therapies, is widely present in the aquatic environment, current knowledge on the sensitivity of marine fish to estrogenic pollutants is limited. We report the effect of the dietary intake of 5 µg EE2/g food on different processes of testicular physiology, ranging from steroidogenesis to pathogen recognition, at both pre-spermatogenesis (pre-SG) and spermatogenesis (SG) reproductive stages, of gilthead seabream (Sparus aurata L.), a marine hermaphrodite teleost. A differential effect between pre-SG and SG specimens was detected in the sex steroid serum levels and in the expression profile of some steroidogenic-relevant molecules, vitellogenin, double sex- and mab3-related transcription factor 1 and some hormone receptors. Interestingly, EE2 modified the expression pattern of some immune molecules involved in testicular physiology. These differences probably reflect a developmental adjustment of the sensitivity to EE2 in the gilthead seabream gonad.

Selective estrogen receptor modulators differentially alter the immune response of gilthead seabream juveniles.

17α-ethynylestradiol (EE2), a synthetic estrogen used in oral contraceptives and hormone replacement therapy, tamoxifen (Tmx), a selective estrogen-receptor modulator used in hormone replacement therapy, and G1, a G protein-coupled estrogen receptor (GPER) selective agonist, differentially increased the hepatic vitellogenin (vtg) gene expression and altered the immune response in adult gilthead seabream (Sparus aurata L.) males. However, no information exists on the effects of these compounds on the immune response of juveniles. This study aims, for the first time, to investigate the effects of the dietary intake of EE2, Tmx or G1 on the immune response of gilthead seabream juveniles and the capacity of the immune system of the specimens to recover its functionality after ceasing exposures (recovery period). The specimens were immunized with hemocyanin in the presence of aluminium adjuvant 1 (group A) or 120 (group B) days after the treatments ceased (dpt). The results indicate that EE2 and Tmx, but not G1, differentially promoted a transient alteration in hepatic vtg gene expression. Although all three compounds did not affect the production of reactive oxygen intermediates, they inhibited the induction of interleukin-1β (il1b) gene expression after priming. Interestingly, although Tmx increased the percentage of IgM-positive cells in both head kidney and spleen during the recovery period, the antibody response of vaccinated fish varied depending on the compound used and when the immunization was administered. Taken together, our results suggest that these compounds differentially alter the capacity of fish to respond to infection during ontogeny and, more interestingly, that the adaptive immune response remained altered to an extent that depends on the compound.

Estrogen receptor 2b deficiency impairs the antiviral response of zebrafish.

Although several studies have demonstrated the ability of some endocrine disruptive chemicals (EDCs) to alter the physiology of zebrafish, the immune-reproductive interaction has received little attention in this species. In this study, we used a homozygous line carrying an insertion of 8 amino acids in the ligand-binding domain of the estrogen receptor 2b gene (esr2b) to further understand the role of estrogen signaling on innate immunity. Adult mutant fish showed distorted sexual ratios related with alterations in testicular morphology and supraphysiological testosterone and 17β-estradiol (E2) levels. Immunity-wise, although esr2b mutant fish showed unaltered antibacterial responses, they were unable to mount an effective antiviral response upon viral challenge. RT-qPCR analysis demonstrated that mutant fish were able to induce the genes encoding major antiviral molecules, including Ifnphi1, Ifnphi2, Infphi3, Mxb and Mxc, and the negative feedback regulator of cytokine signaling Socs1. Notably, although esr2b mutant larvae showed a similar resistance to SVCV infection to their wild type siblings, waterborne E2 increased their viral susceptibility. Similarly, the exposure of adult wild type zebrafish to E2 also resulted in increased susceptibility to SVCV infection. Finally, the administration of recombinant Ifnphi1 hardly reversed the higher viral susceptibility of esr2b mutant zebrafish, suggesting that elevated socs1 levels impair Ifn signaling. All together, these results uncover an important role for E2 and Esr signaling in the fine-tuning of sexual hormone balance and the antiviral response of vertebrates.