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Relationship: 3646

Title

A descriptive phrase which clearly defines the two KEs being considered and the sequential relationship between them (i.e., which is upstream, and which is downstream). More help

Activation, ERα leads to Decreased, release of kisspeptin from AVPV neurons

Upstream event

The causing Key Event (KE) in a Key Event Relationship (KER). More help

Activation, ERα

Downstream event

The responding Key Event (KE) in a Key Event Relationship (KER). More help

Decreased, release of kisspeptin from AVPV neurons

Key Event Relationship Overview

The utility of AOPs for regulatory application is defined, to a large extent, by the confidence and precision with which they facilitate extrapolation of data measured at low levels of biological organisation to predicted outcomes at higher levels of organisation and the extent to which they can link biological effect measurements to their specific causes.Within the AOP framework, the predictive relationships that facilitate extrapolation are represented by the KERs. Consequently, the overall WoE for an AOP is a reflection in part, of the level of confidence in the underlying series of KERs it encompasses. Therefore, describing the KERs in an AOP involves assembling and organising the types of information and evidence that defines the scientific basis for inferring the probable change in, or state of, a downstream KE from the known or measured state of an upstream KE. More help

AOPs Referencing Relationship

AOP Name	Adjacency	Weight of Evidence	Quantitative Understanding	Point of Contact	Author Status	OECD Status
Activation, estrogen receptor alpha leads to prolonged estrus cycle via decreased kisspeptin release	adjacent	Moderate		John Frisch (send email)	Under development: Not open for comment. Do not cite

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KER.In general, this will be dictated by the more restrictive of the two KEs being linked together by the KER. More help

Term	Scientific Term	Evidence	Link
mammals	mammals	High	NCBI

Sex Applicability

An indication of the the relevant sex for this KER. More help

Sex	Evidence
Unspecific	High

Life Stage Applicability

An indication of the the relevant life stage(s) for this KER. More help

Term	Evidence
Adult, reproductively mature	Moderate
Juvenile	Moderate

Key Event Relationship Description

Provides a concise overview of the information given below as well as addressing details that aren’t inherent in the description of the KEs themselves. More help

Estrogen receptor Alpha (ERa) is a nuclear transcription factor involved in regulation of many physiological processes in mammals. Binding by estrogen induces the transcription of target genes. Here we focus on the role of ERa in the hypothalamus- pituitary-gonadal (HPG) axis through activation of kisspeptin.

Kisspeptin is a key signalling neuropeptide hormone in mammals. Positive feedback for kisspeptin hormone production is due to increased levels of ligand binding to Estrogen Receptor Alpha (ERa) receptors in neurons from the anteroventral periventricular nucleus (AVPV) region of the hypothalamus, while negative feedback for kisspeptin hormone production is due to ERa receptor activation of the neurons from the arcuate nucleus (ARC) region of the hypothalamus (Uenoyama et al. 2021).

Developmental exposure to estrogenic compounds has been suggested to disrupt signalling in the hypothalamus–pituitary–gonadal (HPG) axis via impaired response by anteroventral periventricular nucleus (AVPV) neurons in releasing kisspeptin (Bateman and Patisaul 2008; Homma et al. 2009; Navarro et al. 2009; Patisaul et al. 2009; Ichimura et al. 2015a; Ichimura et al. 2015b; Ichimura et al. 2016).

Evidence Collection Strategy

Include a description of the approach for identification and assembly of the evidence base for the KER. For evidence identification, include, for example, a description of the sources and dates of information consulted including expert knowledge, databases searched and associated search terms/strings. Include also a description of study screening criteria and methodology, study quality assessment considerations, the data extraction strategy and links to any repositories/databases of relevant references.Tabular summaries and links to relevant supporting documentation are encouraged, wherever possible. More help

This Key Event Relationship was part of an Environmental Protection Agency effort to develop AOPs that establish scientifically supported causal linkages between alternative endpoints measured using new approach methodologies (NAMs) and guideline apical endpoints measured in Tier 1 and Tier 2 test guidelines (U.S. EPA, 2024) employed by the Endocrine Disruptor Screening Program (EDSP). A series of key events that represent significant, measurable, milestones connecting molecular initiation to apical endpoints indicative of adversity were identified based on scientific review articles and empirical studies. Additionally, scientific evidence supporting the causal relationships between each pair of key events was assembled and evaluated. The present effort focused primarily on empirical studies with laboratory rodents and other mammals.

Empirical studies are focused on increased activation of estrogen receptor alpha and resulting decreased release of kisspeptin from anteroventral periventricular nucleus (AVPV) neurons, in support of development of AOP 609.

Authors of KER 3646 did a further evaluation of published peer-reviewed literature to provide additional evidence in support of the key event relationship. The literature used to support this KER began with the test guidelines and followed to primary, secondary, and/or tertiary works concerning the relevant underlying biology. In addition, search engines were used to target journal articles with terms ‘estrogen receptor alpha’ and ‘kisspeptin.’

Evidence Supporting this KER

Addresses the scientific evidence supporting KERs in an AOP setting the stage for overall assessment of the AOP. More help

Biological Plausibility

Addresses the biological rationale for a connection between KEupstream and KEdownstream. This field can also incorporate additional mechanistic details that help inform the relationship between KEs, this is useful when it is not practical/pragmatic to represent these details as separate KEs due to the difficulty or relative infrequency with which it is likely to be measured. More help

Increased activation of estrogen receptor alpha and resulting decreased release of kisspeptin from anteroventral periventricular nucleus (AVPV) neurons have been studied in laboratory mammals by toxicants known to increase estrogen receptor activation (Feng et al. 2015; Cao et al. 2018; Wang et al. 2018). Studies involving dosing of laboratory mammals with various forms of estrogen (e.g. estradiol benzoate, ethylenestradiol, 17beta-estradiol) are supportive of the mechanism of neonatal exposure to estrogen compounds causing a subsequent decrease in release of kisspeptin from anteroventral periventricular nucleus (AVPV) neurons (Bateman and Patisaul 2008; Homma et al. 2009; Navarro et al. 2009; Patisaul et al. 2009; Ichimura et al. 2015a; Ichimura et al. 2015b). Increased activation of estrogen receptor alpha, or estrogenicity, is generally studied in mammalian cell lines in vitro (U.S. EPA, 2024) and rarely confirmed in laboratory mammal studies in vivo. Gene knock-out studies have been useful in essentiality of ERa and kisspeptin genes in the hypothalamus- pituitary-gonadal (HPG) axis, with subsequent hormone addition restoring normal function (d'Anglemont de Tassigny et al. 2007; Clarkson et al. 2008; Dubois et al. 2015).

Empirical Evidence

Provides specific (citable) evidence that supports the idea of a change in the upstream KE (KEupstream) leading to, or being associated with, a subsequent change in the downstream KE (KEdownstream), assuming the perturbation of KEupstream is sufficient. More help

Evidence for activation of estrogen receptor alpha by a toxicant is established in mammalian cell lines in vitro through screening for estrogenicity (Escande et al. 2006; Shanle and Xu 2011; Huang et al. 2014). In vivo laboratory mammal studies measure decreased kisspeptin mRNA and/or immunoreactive kisspeptin neurons, with the observed effect attributed to the inferred mechanism of estrogen receptor activation from a compound determined to be an estrogen receptor alpha agonist from in vitro estrogenicity results (Feng et al. 2015; Cao et al. 2018; Wang et al. 2018). Studies of laboratory mammals exposed to various forms of estrogen show a subsequent decreased release of kisspeptin from anteroventral periventricular nucleus (AVPV) neurons (Bateman and Patisaul 2008; Homma et al. 2009; Navarro et al. 2009; Patisaul et al. 2009; Ichimura et al. 2015a; Ichimura et al. 2015b).

Uncertainties and Inconsistencies

Addresses inconsistencies or uncertainties in the relationship including the identification of experimental details that may explain apparent deviations from the expected patterns of concordance. More help

Known modulating factors

This table captures specific information on the MF, its properties, how it affects the KER and respective references.1.) What is the modulating factor? Name the factor for which solid evidence exists that it influences this KER. Examples: age, sex, genotype, diet 2.) Details of this modulating factor. Specify which features of this MF are relevant for this KER. Examples: a specific age range or a specific biological age (defined by...); a specific gene mutation or variant, a specific nutrient (deficit or surplus); a sex-specific homone; a certain threshold value (e.g. serum levels of a chemical above...) 3.) Description of how this modulating factor affects this KER. Describe the provable modification of the KER (also quantitatively, if known). Examples: increase or decrease of the magnitude of effect (by a factor of...); change of the time-course of the effect (onset delay by...); alteration of the probability of the effect; increase or decrease of the sensitivity of the downstream effect (by a factor of...) 4.) Provision of supporting scientific evidence for an effect of this MF on this KER. Give a list of references. More help

Quantitative Understanding of the Linkage

Captures information that helps to define how much change in the upstream KE, and/or for how long, is needed to elicit a detectable and defined change in the downstream KE. More help

Response-response Relationship

Provides sources of data that define the response-response relationships between the KEs. More help

Time-scale

Information regarding the approximate time-scale of the changes in KEdownstream relative to changes in KEupstream (i.e., do effects on KEdownstream lag those on KEupstream by seconds, minutes, hours, or days?). More help

Known Feedforward/Feedback loops influencing this KER

Define whether there are known positive or negative feedback mechanisms involved and what is understood about their time-course and homeostatic limits. More help

Positive feedback for kisspeptin hormone production is due to increased levels of ligand binding to Estrogen Receptor Alpha (ERa) receptors in neurons from the anteroventral periventricular nucleus (AVPV) region of the hypothalamus, while negative feedback for kisspeptin hormone production is due to ERa receptor activation of the neurons from the arcuate nucleus (ARC) region of the hypothalamus (Uenoyama et al. 2021).

Domain of Applicability

A free-text section of the KER description that the developers can use to explain their rationale for the taxonomic, life stage, or sex applicability structured terms. More help

Life Stage: Applies to adult, reproductively mature and juveniles.

Sex: Applies to both males and females.

Taxonomic: Primarily studied in humans and laboratory rodents. Plausible for most mammals due to conserved role of kisspeptin in hormone pathways involved in the hypothalamus-pituitary-gonadal axis processes. For vertebrates, largely absent from bird species; role in fish uncertain as some evidence suggests a compensatory rather than required role, and perhaps reduced function (Sivalingam et al. 2022).

References

List of the literature that was cited for this KER description. More help

Bateman HL, Patisaul HB. 2008. Disrupted female reproductive physiology following neonatal exposure to phytoestrogens or estrogen specific ligands is associated with decreased GnRH activation and kisspeptin fiber density in the hypothalamus. Neurotoxicology 29(6): 988-997.

Cao XY, Hua X, Xiong JW, Zhu WT, Zhang J, Chen L. 2018. Impact of Triclosan on Female Reproduction through Reducing Thyroid Hormones to Suppress Hypothalamic Kisspeptin Neurons in Mice. Frontiers in Molecular Neuroscience 11(6).

Clarkson J, d'Anglemont de Tassigny X, Moreno AS, Colledge WH, Herbison AE. 20008. Kisspeptin-GPR54 signaling is essential for preovulatory gonadotropin-releasing hormone neuron activation and the luteinizing hormone surge. The Journal of Neuroscience 2008 28(35): 8691-8697.

d'Anglemont de Tassigny X, Fagg LA, Dixon JP, Day K, Leitch HG, Hendrick AG, Zahn D, Franceschini I, Caraty A, Carlton MB, Aparicio SA, Colledge WH. 2007. Hypogonadotropic hypogonadism in mice lacking a functional Kiss1 gene. Proceedings of the National Academy of Science 104(25): 10714-10719.

Dubois SL, Acosta-Martínez M, DeJoseph MR, Wolfe A, Radovick S, Boehm U, Urban JH, Levine JE. 2015. Positive, but not negative feedback actions of estradiol in adult female mice require estrogen receptor α in kisspeptin neurons. Endocrinology 156(3): 1111-1120.

Escande A, Pillon A, Servant N, Cravedi JP, Larrea F, Muhn P, Nicolas JC, Cavailles V, Balaguer P. 2006. Evaluation of ligand selectivity using reporter cell lines stably expressing estrogen receptor alpha or beta. Biochemical Pharmacology 71(10): 1459-1469.

Feng X, Wang X, Cao X, Xia Y, Zhou R, Chen L. 2015. Chronic Exposure of Female Mice to an Environmental Level of Perfluorooctane Sulfonate Suppresses Estrogen Synthesis Through Reduced Histone H3K14 Acetylation of the StAR Promoter Leading to Deficits in Follicular Development and Ovulation. Toxicological Sciences 148(2): 368-379.

Homma T, Sakakibara M, Yamada S, Kinoshita M, Iwata K, Tomikawa J, Kanazawa T, Matsui H, Takatsu Y, Ohtaki T, Matsumoto H, Uenoyama Y, Maeda K, Tsukamura H. 2009. Significance of neonatal testicular sex steroids to defeminize anteroventral periventricular kisspeptin neurons and the GnRH/LH surge system in male rats. Biology of Reproduction 81(6): 1216-25.

Huang R, Sakamuru S, Martin MT, Reif DM, Judson RS, Houck KA, Casey W, Hsieh JH, Shockley KR, Ceger P, Fostel J, Witt KL, Tong W, Rotroff DM, Zhao T, Shinn P, Simeonov A, Dix DJ, Austin CP, Kavlock RJ, Tice RR, Xia M. 2014. Profiling of the Tox21 10K compound library for agonists and antagonists of the estrogen receptor alpha signaling pathway. Scientific Reports 4: 5664.

Ichimura R, Takahashi M, Morikawa T, Inoue K, Maeda J, Usuda K, Yokosuka M, Watanabe G, Yoshida M. 2015a. Prior attenuation of KiSS1/GPR54 signaling in the anteroventral periventricular nucleus is a trigger for the delayed effect induced by neonatal exposure to 17alpha-ethynylestradiol in female rats. Reproductive Toxicology 51: 145-156.

Ichimura R, Takahashi M, Morikawa T, Inoue K, Kuwata K, Usuda K, Yokosuka M, Watanabe G, Yoshida M. 2015b. The Critical Hormone-Sensitive Window for the Development of Delayed Effects Extends to 10 Days after Birth in Female Rats Postnatally Exposed to 17alpha-Ethynylestradiol. Biology of Reproduction 93(2): 32.

Ichimura R, Takahashi M, Morikawa T, Inoue K, Kuwata K, Usuda K, Yokosuka M, Watanabe G, Yoshida M. 2016. Neonatal exposure to SERMs disrupts neuroendocrine development and postnatal reproductive function through alteration of hypothalamic kisspeptin neurons in female rats. Neurotoxicology 56: 64-75.

Navarro VM, Sánchez-Garrido MA, Castellano JM, Roa J, García-Galiano D, Pineda R, Aguilar E, Pinilla L, Tena-Sempere M. 2009. Persistent impairment of hypothalamic KiSS-1 system after exposures to estrogenic compounds at critical periods of brain sex differentiation. Endocrinology. 150(5): 2359-2367.

Patisaul HB, Todd KL, Mickens JA, Adewale HB. 2009. Impact of neonatal exposure to the ERalpha agonist PPT, bisphenol-A or phytoestrogens on hypothalamic kisspeptin fiber density in male and female rats. Neurotoxicology. 30(3): 350-357.

Shanle EK, Xu W. 2011. Endocrine disrupting chemicals targeting estrogen receptor signaling: identification and mechanisms of action. Chemical Results in Toxicology 24(1): 6-19.

Sivalingam M, Ogawa S, Trudeau VL, Parhar IS. 2022. Conserved functions of hypothalamic kisspeptin in vertebrates. General and Comparative Endocrinology 317: 113973.

Uenoyama, Y., Inoue, N., Nakamura, S., and Tsukamura, H. 2021. Kisspeptin Neurons and Estrogen–Estrogen Receptor α Signaling: Unraveling the Mystery of Steroid Feedback System Regulating Mammalian Reproduction. International Journal of Molecular Sciences 22(17): 9229.

U.S. Environmental Protection Agency. 2004. EDSP Test Guidelines and Guidance Document. https://www.epa.gov/test-guidelines-pesticides-and-toxic-substances/edsp-test-guidelines-and-guidance-document (retrieved 25 July 2025).

Wang X, Bai Y, Tang C, Cao X, Chang F, Chen L. 2018. Impact of Perfluorooctane Sulfonate on Reproductive Ability of Female Mice through Suppression of Estrogen Receptor α-Activated Kisspeptin Neurons. Toxicological Sciences 165(2): 475-486.

Italics indicate edits from John Frisch October 2025. A full list of updates can be found in the Change Log on the View History page.