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Event: 202

Key Event Title

The KE title should describe a discrete biological change that can be measured. It should generally define the biological object or process being measured and whether it is increased, decreased, or otherwise definably altered relative to a control state. For example “enzyme activity, decreased”, “hormone concentration, increased”, or “growth rate, decreased”, where the specific enzyme or hormone being measured is defined. More help

Inhibition, Nuclear factor kappa B (NF-kB)

Short name
The KE short name should be a reasonable abbreviation of the KE title and is used in labelling this object throughout the AOP-Wiki. The short name should be less than 80 characters in length. More help
Inhibition, Nuclear factor kappa B (NF-kB)

Biological Context

Structured terms, selected from a drop-down menu, are used to identify the level of biological organization for each KE. Note, KEs should be defined within a particular level of biological organization. Only KERs should be used to transition from one level of organization to another. Selection of the level of biological organization defines which structured terms will be available to select when defining the Event Components (below). More help
Level of Biological Organization

Cell term

Further information on Event Components and Biological Context may be viewed on the attached pdf.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable. More help
Cell term

Organ term

Further information on Event Components and Biological Context may be viewed on the attached pdf.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable. More help
Organ term
immune system

Key Event Components

Further information on Event Components and Biological Context may be viewed on the attached pdf.Because one of the aims of the AOP-KB is to facilitate de facto construction of AOP networks through the use of shared KE and KER elements, authors are also asked to define their KEs using a set of structured ontology terms (Event Components). In the absence of structured terms, the same KE can readily be defined using a number of synonymous titles (read by a computer as character strings). In order to make these synonymous KEs more machine-readable, KEs should also be defined by one or more “event components” consisting of a biological process, object, and action with each term originating from one of 22 biological ontologies (Ives, et al., 2017; See List). Biological process describes dynamics of the underlying biological system (e.g., receptor signalling). The biological object is the subject of the perturbation (e.g., a specific biological receptor that is activated or inhibited). Action represents the direction of perturbation of this system (generally increased or decreased; e.g., ‘decreased’ in the case of a receptor that is inhibited to indicate a decrease in the signalling by that receptor).Note that when editing Event Components, clicking an existing Event Component from the Suggestions menu will autopopulate these fields, along with their source ID and description. To clear any fields before submitting the event component, use the 'Clear process,' 'Clear object,' or 'Clear action' buttons. If a desired term does not exist, a new term request may be made via Term Requests. Event components may not be edited; to edit an event component, remove the existing event component and create a new one using the terms that you wish to add. More help
Process Object Action
I-kappaB kinase/NF-kappaB signaling transcription factor NF-kappa-B subunit decreased

Key Event Overview

AOPs Including This Key Event

All of the AOPs that are linked to this KE will automatically be listed in this subsection. This table can be particularly useful for derivation of AOP networks including the KE. Clicking on the name of the AOP will bring you to the individual page for that AOP. More help
AOP Name Role of event in AOP Point of Contact Author Status OECD Status
Glucocorticoid Receptor, Activation KeyEvent Carlie LaLone (send email) Open for comment. Do not cite
IKK complex inhibition leading to liver injury KeyEvent Nanette Vrijenhoek (send email) Under development: Not open for comment. Do not cite
IL-1 inhibition KeyEvent Yutaka Kimura (send email) Open for citation & comment EAGMST Under Review


This is a structured field used to identify specific agents (generally chemicals) that can trigger the KE. Stressors identified in this field will be linked to the KE in a machine-readable manner, such that, for example, a stressor search would identify this as an event the stressor can trigger. NOTE: intermediate or downstream KEs in one AOP may function as MIEs in other AOPs, meaning that stressor information may be added to the KE description, even if it is a downstream KE in the pathway currently under development.Information concerning the stressors that may trigger an MIE can be defined using a combination of structured and unstructured (free-text) fields. For example, structured fields may be used to indicate specific chemicals for which there is evidence of an interaction relevant to this MIE. By linking the KE description to a structured chemical name, it will be increasingly possible to link the MIE to other sources of chemical data and information, enhancing searchability and inter-operability among different data-sources and knowledgebases. The free-text section “Evidence for perturbation of this MIE by stressor” can be used both to identify the supporting evidence for specific stressors triggering the MIE as well as to define broad chemical categories or other properties that classify the stressors able to trigger the MIE for which specific structured terms may not exist. More help

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) can be selected from an ontology. In many cases, individual species identified in these structured fields will be those for which the strongest evidence used in constructing the AOP was available in relation to this KE. More help
Term Scientific Term Evidence Link
Homo sapiens Homo sapiens High NCBI
Mus musculus Mus musculus High NCBI
Rattus norvegicus Rattus norvegicus High NCBI

Life Stages

The structured ontology terms for life-stage are more comprehensive than those for taxa, but may still require further description/development and explanation in the free text section. More help
Life stage Evidence
All life stages High

Sex Applicability

The authors must select from one of the following: Male, female, mixed, asexual, third gender, hermaphrodite, or unspecific. More help
Term Evidence
Unspecific High

Key Event Description

A description of the biological state being observed or measured, the biological compartment in which it is measured, and its general role in the biology should be provided. For example, the biological state being measured could be the activity of an enzyme, the expression of a gene or abundance of an mRNA transcript, the concentration of a hormone or protein, neuronal activity, heart rate, etc. The biological compartment may be a particular cell type, tissue, organ, fluid (e.g., plasma, cerebrospinal fluid), etc. The role in the biology could describe the reaction that an enzyme catalyses and the role of that reaction within a given metabolic pathway; the protein that a gene or mRNA transcript codes for and the function of that protein; the function of a hormone in a given target tissue, physiological function of an organ, etc. Careful attention should be taken to avoid reference to other KEs, KERs or AOPs. Only describe this KE as a single isolated measurable event/state. This will ensure that the KE is modular and can be used by other AOPs, thereby facilitating construction of AOP networks. More help

The NF-κB pathway consists of a series of events where the transcription factors of the NF-κB family play the key role. The canonical NF-κB pathway can be activated by a range of stimuli, including TNF receptor activation by TNF-a. Upon pathway activation, the IKK complex will be phosphorylated, which in turn phosphorylates IkBa. This NF-κB inhibitor will be K48-linked ubiquitinated and degradated, allowing NF-κB to translocate to the nucleus. There, this transcription factor can express pro-inflammatory and anti-apoptotic genes. Furthermore, negative feedback genes are also transcribed and include IkBa and A20. When the NF-κB pathway is inhibited, its translocation will be delayed (or absent), resulting in less or no regulation of NF-κB target genes. This can be achieved by IKK inhibitors, proteasome inhibitors, nuclear translocation inhibitors or DNA-binding inhibitors (Gupta et al., 2010; Liu et al., 2017). Therefore, inhibition of IL-1R activation suppresses NF-κB.

How It Is Measured or Detected

One of the primary considerations in evaluating AOPs is the relevance and reliability of the methods with which the KEs can be measured. The aim of this section of the KE description is not to provide detailed protocols, but rather to capture, in a sentence or two, per method, the type(s) of measurements that can be employed to evaluate the KE and the relative level of scientific confidence in those measurements. Methods that can be used to detect or measure the biological state represented in the KE should be briefly described and/or cited. These can range from citation of specific validated test guidelines, citation of specific methods published in the peer reviewed literature, or outlines of a general protocol or approach (e.g., a protein may be measured by ELISA).Key considerations regarding scientific confidence in the measurement approach include whether the assay is fit for purpose, whether it provides a direct or indirect measure of the biological state in question, whether it is repeatable and reproducible, and the extent to which it is accepted in the scientific and/or regulatory community. Information can be obtained from the OECD Test Guidelines website and the EURL ECVAM Database Service on Alternative Methods to Animal Experimentation (DB-ALM). ?

NF-κB transcriptional activity: Beta lactamase reporter gene assay (Miller et al. 2010)

NF-κB transcription: Lentiviral NF-κBGFP reporter with flow cytometry (Moujalled et al. 2012)

IκBα phosphorylation: Western blotting (Miller et al. 2010)

NF-κB p65 (Total/Phospho) ELISA

ELISA for IL-6, IL-8, and Cox

Domain of Applicability

This free text section should be used to elaborate on the scientific basis for the indicated domains of applicability and the WoE calls (if provided). While structured terms may be selected to define the taxonomic, life stage and sex applicability (see structured applicability terms, above) of the KE, the structured terms may not adequately reflect or capture the overall biological applicability domain (particularly with regard to taxa). Likewise, the structured terms do not provide an explanation or rationale for the selection. The free-text section on evidence for taxonomic, life stage, and sex applicability can be used to elaborate on why the specific structured terms were selected, and provide supporting references and background information.  More help

The binding of sex steroids to their respective steroid receptors directly influences NF-κB signaling, resulting in differential production of cytokines and chemokines (McKay and Cidlowski, 1999; Pernis, 2007). 17b-estradiol regulates pro-inflammatory responses that are transcriptionally mediated by NF‑κB through a negative feedback and/or transrepressive interaction with NF-κB (Straub, 2007). Progesterone suppresses innate immune responses and NF-κB signal transduction reviewed by Klein et al. (Klein and Flanagan, 2016). Androgen-receptor signaling antagonises transcriptional factors NF-κB(McKay and Cidlowski, 1999).

Evidence for perturbation of this molecular initiating event by stressor

Dex inhibits IL-1β gene expression in LPS-stimulated RAW 264.7 cells by blocking NF-κB/Rel and AP-1 activation (Jeon et al., 2000).

Various inhibitors for NF‐κB, such as dimethyl fumarate, curcumin, iguratimod, epigalocathechin gallate (EGCG), and DHMEQ inhibits lLPS-induced NF-κB activation and LPS-induced secretion of IL-1β (McGuire et al., 2016; Mucke, 2012; Peng et al., 2012; Suzuki and Umezawa, 2006; Wang et al., 2020; Wang et al., 2018; Wheeler et al., 2004).

TAK-242 (Matsunaga et al., 2011) inhibit TLR4 itself. There are several IRAK4 inhibitors (Lee et al., 2017). These molecules block the upstream signal to NF‐κB activation. IRAK4 has recently attracted attention as a therapeutic target for inflammation and tumor diseases (Chaudhary et al., 2015).

LPS treatment induced a significant upregulation of the mRNA and release of IL-1β from retinal microglia. Minocycline inhibited its releases. Thus, minocycline might exert its antiinflammatory effect on microglia by inhibiting the expression and release of IL-1β (Wang et al., 2005).

Caspase-1 inhibition reduced the release of IL-1β in organotypic slices exposed to LPS+ATP. Administration of pralnacasan (intracerebroventricular, 50 μg) or belnacasan (intraperitoneal, 25–200 mg/kg) to rats blocked seizure-induced production of IL-1β in the hippocampus, and resulted in a twofold delay in seizure onset and 50% reduction in seizure duration (Ravizza et al., 2006).

Belnacasan, an orally active IL-1β converting enzyme/caspase-1 inhibitor, blocked IL-1β secretion with equal potency in LPS-stimulated cells from familial cold urticarial associated symdrome and control subjects (Stack et al., 2005).

In LPS-induced acute lung injury (ALI) mice model, LPS induced inflammatory cytokines such as TNF-α, IL-6, IL-13 and IL-1β were significantly decreased by cinnamaldehyde (CA) (Huang and Wang, 2017).

The suppressing capacities of six cinnamaldehyde-related compounds were evaluated and compared by using the LPS-primed and ATP-activated macrophages. At concentrations of 25~100 mM, cinnamaldehyde and 2-methoxy cinnamaldehyde dose-dependently inhibited IL-1β secretion (Ho et al., 2018).

In vitro, CA decreased the levels of pro-IL-1β and IL-1β in cell culture supernatants, as well as the expression of NLRP3 and IL-1β mRNA in cells. In vivo, CA decreased IL-1β production in serum. Furthermore, CA suppressed LPS-induced NLRP3, p20, Pro-IL-1β, P2X7 receptor (P2X7R) and cathepsin B protein expression in lung, as well as the expression of NLRP3 and IL-1β mRNA (Xu et al., 2017).

IL-1Ra binds IL-1R but does not initiate IL-1 signal transduction (Dripps et al., 1991). Recombinant IL-1Ra (anakinra) is fully active in blocking the IL-1R1, and therefore, the biological activities of IL-1α and IL-1β. The binding of IL-1α and IL-1β to IL-1R1 can be suppressed by soluble IL-1R like rilonacept (Kapur and Bonk, 2009). The binding of IL-1β to IL-1R1 can be inhibited by anti-IL-1β antibody (canakinumab and gevokizumab) (Church and McDermott, 2009) (Roell et al., 2010).

IL-1 is known to mediates autoinflammatory syndrome, such as cryopyrin-associated periodic syndrome, neonatal-onset multisystem inflammatory disease and familial Mediterranean fever. Blocking of binding of IL-1 to IL-1R1 by anakinra, canakinumab, and rilonacept have been already used to treat these autoinflammatory syndrome associated with overactivation of IL-1 signaling (Quartier, 2011).

Dex inhibits IL-1β gene expression in LPS-stimulated RAW 264.7 cells by blocking NF‐κB/Rel and AP-1 activation (Jeon et al., 2000).

Inhibition of IL-1 binding to IL-1R or the decreased production of IL-1b leads to the suppression of IL-1R signaling leading to NF‐κB activation.

Evidence for Perturbation by Stressor


List of the literature that was cited for this KE description. Ideally, the list of references, should conform, to the extent possible, with the OECD Style Guide ( (OECD, 2015). More help

Chaudhary, D., Robinson, S., Romero, D.L. (2015), Recent advances in the discovery of small molecule inhibitors of interleukin-1 receptor-associated kinase 4 (IRAK4) as a therapeutic target for inflammation and oncology disorders. J Med Chem 58: 96-110, 10.1021/jm5016044

Church, L.D., McDermott, M.F. (2009), Canakinumab, a fully-human mAb against IL-1beta for the potential treatment of inflammatory disorders. Curr Opin Mol Ther 11: 81-89,

Dripps, D.J., Brandhuber, B.J., Thompson, R.C., et al. (1991), Interleukin-1 (IL-1) receptor antagonist binds to the 80-kDa IL-1 receptor but does not initiate IL-1 signal transduction. J Biol Chem 266: 10331-10336,

Gupta, S.C., Sundaram, C., Reuter, S., et al. (2010), Inhibiting NF-kappaB activation by small molecules as a therapeutic strategy. Biochim Biophys Acta 1799: 775-787, 10.1016/j.bbagrm.2010.05.004

Ho, S.C., Chang, Y.H., Chang, K.S. (2018), Structural Moieties Required for Cinnamaldehyde-Related Compounds to Inhibit Canonical IL-1beta Secretion. Molecules 23, 10.3390/molecules23123241

Huang, H., Wang, Y. (2017), The protective effect of cinnamaldehyde on lipopolysaccharide induced acute lung injury in mice. Cell Mol Biol (Noisy-le-grand) 63: 58-63, 10.14715/cmb/2017.63.8.13

Jeon, Y.J., Han, S.H., Lee, Y.W., et al. (2000), Dexamethasone inhibits IL-1 beta gene expression in LPS-stimulated RAW 264.7 cells by blocking NF-kappa B/Rel and AP-1 activation. Immunopharmacology 48: 173-183,

Kapur, S., Bonk, M.E. (2009), Rilonacept (arcalyst), an interleukin-1 trap for the treatment of cryopyrin-associated periodic syndromes. P t 34: 138-141,

Klein, S.L., Flanagan, K.L. (2016), Sex differences in immune responses. Nat Rev Immunol 16: 626-638, 10.1038/nri.2016.90

Lee, K.L., Ambler, C.M., Anderson, D.R., et al. (2017), Discovery of Clinical Candidate 1-{[(2S,3S,4S)-3-Ethyl-4-fluoro-5-oxopyrrolidin-2-yl]methoxy}-7-methoxyisoquinoli ne-6-carboxamide (PF-06650833), a Potent, Selective Inhibitor of Interleukin-1 Receptor Associated Kinase 4 (IRAK4), by Fragment-Based Drug Design. J Med Chem 60: 5521-5542, 10.1021/acs.jmedchem.7b00231

Liu, T., Zhang, L., Joo, D., et al. (2017), NF-kappaB signaling in inflammation. Signal Transduct Target Ther 2, 10.1038/sigtrans.2017.23

Matsunaga, N., Tsuchimori, N., Matsumoto, T., et al. (2011), TAK-242 (resatorvid), a small-molecule inhibitor of Toll-like receptor (TLR) 4 signaling, binds selectively to TLR4 and interferes with interactions between TLR4 and its adaptor molecules. Mol Pharmacol 79: 34-41, 10.1124/mol.110.068064

McGuire, V.A., Ruiz-Zorrilla Diez, T., Emmerich, C.H., et al. (2016), Dimethyl fumarate blocks pro-inflammatory cytokine production via inhibition of TLR induced M1 and K63 ubiquitin chain formation. Sci Rep 6: 31159, 10.1038/srep31159

McKay, L.I., Cidlowski, J.A. (1999), Molecular control of immune/inflammatory responses: interactions between nuclear factor-kappa B and steroid receptor-signaling pathways. Endocr Rev 20: 435-459, 10.1210/edrv.20.4.0375

Mucke, H.A. (2012), Iguratimod: a new disease-modifying antirheumatic drug. Drugs Today (Barc) 48: 577-586, 10.1358/dot.2012.48.9.1855758

Peng, H., Guerau-de-Arellano, M., Mehta, V.B., et al. (2012), Dimethyl fumarate inhibits dendritic cell maturation via nuclear factor kappaB (NF-kappaB) and extracellular signal-regulated kinase 1 and 2 (ERK1/2) and mitogen stress-activated kinase 1 (MSK1) signaling. J Biol Chem 287: 28017-28026, 10.1074/jbc.M112.383380

Pernis, A.B. (2007), Estrogen and CD4+ T cells. Curr Opin Rheumatol 19: 414-420, 10.1097/BOR.0b013e328277ef2a

Quartier, P. (2011), Interleukin-1 antagonists in the treatment of autoinflammatory syndromes, including cryopyrin-associated periodic syndrome. Open Access Rheumatol 3: 9-18, 10.2147/oarrr.S6696

Ravizza, T., Lucas, S.M., Balosso, S., et al. (2006), Inactivation of caspase-1 in rodent brain: a novel anticonvulsive strategy. Epilepsia 47: 1160-1168, 10.1111/j.1528-1167.2006.00590.x

Roell, M.K., Issafras, H., Bauer, R.J., et al. (2010), Kinetic approach to pathway attenuation using XOMA 052, a regulatory therapeutic antibody that modulates interleukin-1beta activity. J Biol Chem 285: 20607-20614, 10.1074/jbc.M110.115790

Stack, J.H., Beaumont, K., Larsen, P.D., et al. (2005), IL-converting enzyme/caspase-1 inhibitor VX-765 blocks the hypersensitive response to an inflammatory stimulus in monocytes from familial cold autoinflammatory syndrome patients. J Immunol 175: 2630-2634,

Straub, R.H. (2007), The complex role of estrogens in inflammation. Endocr Rev 28: 521-574, 10.1210/er.2007-0001

Suzuki, E., Umezawa, K. (2006), Inhibition of macrophage activation and phagocytosis by a novel NF-kappaB inhibitor, dehydroxymethylepoxyquinomicin. Biomed Pharmacother 60: 578-586, 10.1016/j.biopha.2006.07.089

Wang, A.L., Yu, A.C., Lau, L.T., et al. (2005), Minocycline inhibits LPS-induced retinal microglia activation. Neurochem Int 47: 152-158, 10.1016/j.neuint.2005.04.018

Wang, F., Han, Y., Xi, S., et al. (2020), Catechins reduce inflammation in lipopolysaccharide-stimulated dental pulp cells by inhibiting activation of the NF-kappaB pathway. Oral Dis 26: 815-821, 10.1111/odi.13290

Wang, Y., Tang, Q., Duan, P., et al. (2018), Curcumin as a therapeutic agent for blocking NF-kappaB activation in ulcerative colitis. Immunopharmacol Immunotoxicol 40: 476-482, 10.1080/08923973.2018.1469145

Wheeler, D.S., Catravas, J.D., Odoms, K., et al. (2004), Epigallocatechin-3-gallate, a green tea-derived polyphenol, inhibits IL-1 beta-dependent proinflammatory signal transduction in cultured respiratory epithelial cells. J Nutr 134: 1039-1044, 10.1093/jn/134.5.1039

Xu, F., Wang, F., Wen, T., et al. (2017), Inhibition of NLRP3 inflammasome: a new protective mechanism of cinnamaldehyde in endotoxin poisoning of mice. Immunopharmacol Immunotoxicol 39: 296-304, 10.1080/08923973.2017.1355377