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Aop: 314

AOP Title

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Activation of estrogen receptor in immune cells leading to exacerbation of systemic lupus erythematosus

Short name:

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Exacerbation of SLE by activation of estrogen receptor

Graphical Representation

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Click to download graphical representation template

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Authors

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Yasuharu Otsubo (1) Takao Ashikaga (1) Tomoki Fukuyama (1) Ken Goto (1) Shinko Hata (1) Shigeru Hisada (1) Shiho Ito (1) Hiroyuki Komatsu (1) Sumie Konishi (1) Tadashi Kosaka (1) Kiyoshi Kushima (1) Shogo Matsumura (1) Takumi Ohishi (1) Junichiro Sugimoto (1) Yasuhiro Yoshida (1)

(1) AOP Working Group, Testing Methodology Committee, The Japanese Society of Immunotoxicology

Corresponding author: Yasuharu Otsubo (otsubo-yasuharu@snbl.co.jp)

Point of Contact

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Yasuharu Otsubo   (email point of contact)

Contributors

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  • Takumi Ohishi
  • Yasuharu Otsubo

Status

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Author status OECD status OECD project SAAOP status
Under development: Not open for comment. Do not cite Under Development 1.73 Included in OECD Work Plan


This AOP was last modified on January 09, 2020 17:26

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Revision dates for related pages

Page Revision Date/Time
Activation of estrogen receptor in immune cells December 29, 2019 18:35
Induction of GATA3 expression by STAT6:ER fusion protein December 29, 2019 20:56
Overproduction of IL-4 from Th2 cell December 29, 2019 20:59
Increase of anti-single/double-stranded DNA antibody from autoreactive B cell December 29, 2019 21:02
Exacerbation of systemic lupus erythematosus December 29, 2019 21:05
Activation of estrogen receptor leads to Induction of GATA3 expression December 29, 2019 21:07
Induction of GATA3 expression leads to Overproduction of IL-4 December 29, 2019 21:09
Overproduction of IL-4 leads to Increase of autoantibody production December 29, 2019 21:11
Increase of autoantibody production leads to Exacerbation of SLE December 29, 2019 21:13
Estrogen May 08, 2019 11:40
Bisphenol A December 29, 2019 18:38

Abstract

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This AOP describes the linkage between the activation of estrogen receptor (ER)α and the exacerbation of the autoimmune disease systemic lupus erythematosus (SLE).  SLE is an autoimmune disease characterized by overproduction of a variety of anti-cell nuclear and other pathogenic autoantibodies. It is characterized by B-cell hyperactivity, polyclonal hypergammaglobulinemia, and immune complex deposition.

Estrogen Receptors (ERs), ERα and ERβ, are a group of proteins that are activated by the steroid hormone estrogen and are widely expressed in most tissue types, including most immune cells.  ERs can be activated with exogenous and endogenous estrogens.  Also, there are numerous xenoestrogens that exist in the environment and imitate estrogen. Bisphenol A is an example of a xenoestrogen that is considered an endocrine disrupting compound (EDC).

Estrogen Receptors (ERs), ERα and ERβ, are a group of proteins that are activated by the steroid hormone estrogen and are widely expressed in most tissue types, including most immune cells.  ERs can be activated with exogenous and endogenous estrogens.  Also, there are numerous xenoestrogens that exist in the environment and imitate estrogen.  Bisphenol A is an example of a xenoestrogen that is considered an endocrine disrupting compound (EDC).

Binding of ER in immune cells by a xenoestrogen or endogenous ER marks the molecular initiating event (MIE), which results in induction of GATA3 expression (KE1). 

One theory of immune regulation involves homeostasis between T-helper 1 (Th1) and T-helper2 (Th2) activity.  Hyperactivation of ERα skew the immune system from a T helper 1 (Th1) to a Th2 profile and exacerbates autoimmune diseases and allergic diseases.

Complexes formed by the binding of ERα to stressors such as estrogen or EDC transport into cell nuclei, where they activate the transcription of specific genes. Excessive ERα-activation promotes the differentiation of naive CD4+ T cells into mature Th2 cells. This pathway leads to the overproduction of the cytokine interleukin-4 (IL-4) from Th2 cells and anti-single/double-stranded DNA antibody from autoreactive B cell are increased, which results in the adverse outcome of exacerbated SLE.

We have identified a number of key events along this pathway and determined the key event relationships, based on which we have created an AOP for activation of ERα in immune cells leading to exacerbated SLE.


Background (optional)

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It has long been appreciated that most autoimmune disorders are characterized by increased prevalence in females, suggesting a potential role for sex hormones (estrogen) in the etiology of autoimmunity.  ERs are involved in a wide range of physiological function.  Women generally exhibit a stronger response to a variety of antigens including ER ligands than men, which is perhaps one reason that they are more prone to develop autoimmune and allergic diseases such as SLE in greater severity than men.  This AOP could be helpful to assess the type of Th2 dominant autoimmune disorders

Humans and mammals have two ligand-activated transcription factors that bind estrogen, encoded by separate genes, estrogen receptor alpha (ESR1/ERα) and estrogen receptor beta (ESR2/ERβ) (Maria, B. 2015). The estrogen receptors are composed of several domains important for hormone binding, DNA binding, dimer formation, and activation of transcription (Green S. 1986, Kumar V. 1986, Warnmark A. 2003). The ERs’ expression patterns and functions vary in a receptor subtype, cell- and tissue-specific manner. In the adult human, large-scale sequencing approaches show that ERα mRNA is detected in numerous human tissues, with the highest levels in the uterus, liver, ovary, muscle, mammary gland, pituitary gland, adrenal gland, spleen and heart, and at lower levels in the prostate, testis, adipose tissue, thyroid gland, lymph nodes and spleen (Fagerberg L. 2014, Sayers EW. 2012) (www.ncbi.nlm.nih.gov/UniGene). In the same data sets, human ERβ mRNA is primarily detected in the lung and testis. There is increased ERα and decreased ERβ mRNA expression in PBMCs of SLE patients (Inui A. 2007). Although ERs are widely expressed in most tissue types, including most immune cells, this AOP mainly addresses hyperactivation of ERα in immune cells.

The effects of ERα signaling on T cells appear to be estrogen-dose dependent, i.e., low doses of estrogen stimulate a Th1 response, but higher doses promote a Th2 response (Priyanka HP. 2013). This AOP describes events occurring when high levels of estrogen shift the Th1/Th2 balance toward increased Th2 activity.


Summary of the AOP

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Events: Molecular Initiating Events (MIE)

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Key Events (KE)

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Adverse Outcomes (AO)

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Sequence Type Event ID Title Short name
MIE 1710 Activation of estrogen receptor in immune cells Activation of estrogen receptor
KE 1711 Induction of GATA3 expression by STAT6:ER fusion protein Induction of GATA3 expression
KE 1712 Overproduction of IL-4 from Th2 cell Overproduction of IL-4
KE 1713 Increase of anti-single/double-stranded DNA antibody from autoreactive B cell Increase of autoantibody production
AO 1714 Exacerbation of systemic lupus erythematosus Exacerbation of SLE

Relationships Between Two Key Events
(Including MIEs and AOs)

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Title Adjacency Evidence Quantitative Understanding
Activation of estrogen receptor leads to Induction of GATA3 expression adjacent Moderate Moderate
Induction of GATA3 expression leads to Overproduction of IL-4 adjacent Moderate Moderate
Overproduction of IL-4 leads to Increase of autoantibody production adjacent Moderate Moderate
Increase of autoantibody production leads to Exacerbation of SLE adjacent Moderate Moderate

Network View

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Stressors

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Name Evidence Term
Estrogen High
Bisphenol A Moderate

Life Stage Applicability

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Life stage Evidence
All life stages Moderate

Taxonomic Applicability

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Term Scientific Term Evidence Link
Homo sapiens Homo sapiens Moderate NCBI

Sex Applicability

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Sex Evidence
Mixed High

Overall Assessment of the AOP

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The immune system is the most complex and sophisticated in the body's defense mechanisms . Estrogen plays a role in controlling the immune balance. Hyperactivation of ERα can skew the immune system from a Th1 to a Th2 profile. This Th1/Th2 shift is one of the most important immunologic changes during gestation and occurs due to a progressive increase of estrogens, which reach peak level in the third trimester of pregnancy. At these high levels, estrogens suppress Th1-mediated responses and stimulate Th2-mediated responses (Doria A. 2006). Incidence of flare in patients with SLE is increased during pregnancy and within the 3-months postpartum (Amanda E. 2018). Thus, ERα activation can potentially induce immunoactivation-derived adverse outcomes, one effect of which could be exacerbation of SLE. The present AOP focused on ERα activation-induced exacerbation of SLE.

In general, ERα is activated when bound to a stressor, which subsequently binds to estrogen response elements (EREs) to transactivate or to suppress specific target genes. In naive CD4+ T cells, T cell expansion shifts toward a Th2 phenotype that produces Th2 cytokines such as IL-4, IL-5, IL-10, and IL-13, thereby increasing antibody production from autoantibody-producing B cells. We have identified a number of key events (KE) along this pathway and used these key event relationships (KER) to create an AOP that describes the activation of ERα leading to exacerbation of SLE.  

Ordinary estrogen levels in women are 20-30 pg/mL during diestrus, 100-200 pg/mL during estrus, and 5000-10000 pg/mL during pregnancy (Offner H. 2000). While BPA binds in some assays with less than 2000‑fold affinity compared to the binding of estradiol to estrogen receptors, it still has dramatic effects (Krishnan AV. 1993). Since each KE is quantifiable and shows similar dose responses with the stressors in vitro, the activation of ER leading to exacerbation of SLE comprise a suitable AOP. Additionally, each KER is based on sufficient scientific evidence and exhibits no contradiction with dose response of adjacent KE.

Since ERα expresses in the cells of a vast variety of (vertebrate) species (Maria B. 2015) and there is common functionality in the immune systems of at least humans and mice, this AOP might be applicable to many mammal species, including humans and rodents.

Essentiality of KEs – what would be good is to have a table listing references that have demonstrated occurrence of individual KEs and their relationship with the AO.

 

Evidence assessment – here listing knockout or overexpression studies that intervene with a KE to show its essentiality to the AO

 

Quantitative assessment – if you have this informaiton

 [Otsubo2]We will reconsider it and revise later.

 [SH3]It seems like KE1 is not needed as it is not described much.

 

 [Otsubo4]We want to discuss about it in WebEX meeting.

Domain of Applicability

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The proposed AOP describes the activation of ERα leading to exacerbation of SLE is dependent on estrogen level, which means it varies with life stage, sex, and age. SLE frequently develops or progresses when sympathoadrenomedullary and gonadal hormone levels are altered during pregnancy, the postpartum period, or menopause as well as during exposure to estrogen and includes the risk of preeclampsia or premature birth (Wilder RL. 1999, Whitelaw DA. 2008). Women using oral contraceptives that contain estrogen or undergoing hormone replacement therapy are susceptible to major flare ups and exacerbation of the disease (Whitelaw DA. 2007).

Since stressor-induced outcomes in humans are mimicked by similar responses in rodents, Th2 dominant conditions induced by activation of ERα is considered likely to occur in a variety of mammalian species.


Essentiality of the Key Events

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Stressor , MIE and later events: ER knock out (KO) mice

It has been determined in a murine model of SLE that ERα is required for disease progression and that ERα deficiency impedes the course of the disease (Bynote KK. 2008).

The NZB/W F1 mouse is the oldest classical model of lupus generated by the F1 hybrid between the NZB and NZW strains. Both NZB and NZW display limited autoimmunity, while NZB/W F1 hybrids develop severe lupus-like phenotypes comparable to that of lupus patients. SLE in the NZB/W F1 strain is strongly biased toward females, and this is at least in part due to estrogen levels. Indeed, ovariectomy of NZB/W F1 mice not only delayed onset of the disease but also decreased autoantibody titer. Meanwhile, restoration of estradiol in ovariectomized NZB/W F1 mice reestablished high numbers of autoantibody-producing (DNA-specific) B cellsDNA-specific B cells, and thereby suggests a pathogenic role of estrogen in lupus (Daniel P. 2011).

In females of the lupus-prone NZB/NZW F1 strain, disruption of estrogen receptor-α (ERα or Esr1) both attenuated glomerulonephritis and increased survival. ERα deficiency also retarded development of anti-histone/DNA antibodies, suggesting that ERα promotes loss of immunologic tolerance. The presence of many autoantibodies is a hallmark of SLE. In particular, autoantibodies directed to double-stranded DNA (dsDNA) are characteristic (Isenberg DA. 2007). ERα deficiency in NZB/NZW F1 males increased survival and reduced anti-dsDNA antibodies, suggesting that ERα also modulates lupus in males (Bynote KK. 2008).

 

KE1 and later events: Stat6 KO mice

CD4 T cells from Stat6-knockout mice are not able to drive Th2 differentiation and cell expansion under null Th cell (ThN) conditions with added with IL-4 (Zhu J. 2001)

 

KE1 and later events: GATA3 KO mice

Th2 differentiation is completely abolished both in vitro and in vivo when GATA3 is conditionally deleted in peripheral CD4 T cells. Th2 cells from both knockout animals showed reduction in IL-4, IL-5, IL-13, and IL-10 production. Conversely, IFN-γ production was increased even under Th2 conditions (Zhu J. 2004, Pai SY. 2004).


Evidence Assessment

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Quantitative Understanding

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Considerations for Potential Applications of the AOP (optional)

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References

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  1. Maria, B., Ruixin, H., Chin-Yo, L., Cecilia, W., Jan-Ake, G. (2015). Estrogen receptor signaling during vertebrate development. Biochim Biophys Acta 1849: 142-151.
  2. Green S, Walter P, Chambon P, et al. Human oestrogen receptor cDNA: sequence, expression and homology to v-erb-A. Nature. 1986; 320:134-139.
  3. Kumar V, Green S, Chambon P, et al. Localisation of the oestradiol-binding and putative DNA-binding domains of the human oestrogen receptor. The EMBO journal. 1986; 5: 2231-2236.
  4. Warnmark A, Treuter E, Gustafsson JA, et al. Activation functions 1 and 2 of nuclear receptors: molecular strategies for transcriptional activation. Molecular endocrinology (Baltimore, Md). 2003; 17:1901-1909.
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  7. Sayers EW, Barrett T, Federhen S, et al. Database resources of the National Center for Biotechnology Information. Nucleic acids research. 2012; 40: D13-25.
  8. Priyanka HP, Krishnan HC, Singh RV, Hima L, Thyagarajan S. Estrogen modulates in vitro T cell responses in a concentration- and receptor-dependent manner: effects on intracellular molecular targets and antioxidant enzymes. Mol Immunol. 2013;56(4):328-39.
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  17. Daniel, P., Allison, S., Yiming, Y., Ying-Yi, Z. and Laurence, M. (2010). Murine Models of Systemic Lupus erythematosus. Journal of Biomedicine and Biotechnology 2011: ArticleID 271694
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  21. Pai SY, Truitt ML, Ho IC. GATA-3 deficiency abrogates the development and maintenance of T helper type 2 cells. Proc Natl Acad Sci U S A. 2004 Feb 17;101(7):1993-8.