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Relationship: 2968

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

Increase, intracellular calcium leads to Apoptosis

Upstream event

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

Increase, intracellular calcium

Downstream event

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

Apoptosis

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 of MEK-ERK1/2 leads to deficits in learning and cognition via ROS and apoptosis	non-adjacent	High		Travis Karschnik (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 Do not cite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
Homo sapiens	Homo sapiens	Moderate	NCBI
Mus musculus	Mus musculus	Moderate	NCBI
Rattus norvegicus	Rattus norvegicus	Moderate	NCBI

Sex Applicability

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

Sex	Evidence
Unspecific	Moderate

Life Stage Applicability

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

Term	Evidence
All life stages	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

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 KER was identified as part of an Environmental Protection Agency effort to represent putative AOPs from peer-reviewed literature which were heretofore unrepresented in the AOP-Wiki. The KER is referenced in publications which were cited in the originating work for the putative AOP "Activation of MEK-ERK1/2 leads to deficits in learning and cognition via ROS and apoptosis", Katherine von Stackelberg & Elizabeth Guzy & Tian Chu & Birgit Claus Henn, 2015. Exposure to Mixtures of Metals and Neurodevelopmental Outcomes: A Multidisciplinary Review Using an Adverse Outcome Pathway Framework, Risk Analysis, John Wiley & Sons, vol. 35(6), pages 971-1016, June.

This evidence was assembled from a literature search relying on standard search engines such as PubMed, Web of Science, Google Scholar, Environmental Index, Scopus, Toxline, and Toxnet and the search strategy included terms related to metal mixtures, individual metals (e.g., arsenic, lead, manganese, and cadmium), neurodevelopmental health outcomes, and associated Medical Subject Headings (MeSH) terms.

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

It is well established that variations in cytosolic calcium concentration [Ca²⁺]_c trigger key cellular functions, for example, contraction of myofilaments, secretion of hormones and neurotransmitters and modulation of metabolism (Berridge et al., 2003; Rizzuto and Pozzan 2006; Clapham 2007). Moreover, Ca²⁺ also has a major function in triggering mitotic division in numerous cell types (e.g., T lymphocytes and of oocytes) and, conversely, in the regulation of cell death (Giorgi et al., 2008). The notion that the cellular Ca²⁺ overload is highly toxic, causing massive activation of proteases and phospholipases was known to cell biologists since the late 1960s (Pinton et al., 2008).

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

Calcium is a ubiquitous intracellular signal responsible for controlling numerous cellular processes including cell proliferation, differentiation, and survival/death (Clapham 2007). Studies have shown that Cd disrupts intracellular free calcium ([Ca²⁺]_i) homeostasis, leading to apoptosis in a variety of cells, such as skin epidermal cells (Son et al., 2010), hepatic cells (Lemarie et al., 2004; Xie et al., 2010), lymphoblastoid cells (Lemarie et al., 2004), mesangial cells (Wang et al., 2008; Liu and Templeton 2008; Yang et al., 2009), renal tubular cells (Yeh et al., 2009^;Wang et al., 2009), astrocytes (Yang et al., 2008), NIH 3T3 cells (Biagioli et al., 2008), thyroid cancer cells (Liu et al., 2007), and thymocytes (Shen et al., 2001).

Baoshan et al. (2011) determined the role of calcium signaling in Cd-induced neuronal apoptosis. PC12 and SH-SY5Y cells, respectively, were treated with 0–20 µM Cd for 24 h, or with 10 and 20 µM Cd for 0–24 h. Subsequently, [Ca²⁺]_i was measured with a calcium indicator dye, Fluo-3/AM or Fluo-4/AM. We found that treatment with Cd (0–20 µM) resulted in a concentration-dependent increase of [Ca²⁺]_i in PC12 cells. Cd also induced a time-dependent elevation of [Ca²⁺]_i in the cells during the period of 24 h. Similarly, Cd markedly elicited high [Ca²⁺]_i fluorescence intensity in a concentration- and time-dependent manner in SH-SY5Y cells by fluorescence microscopy. Furthermore, Cd-elevated [Ca²⁺]_i level was consistent with decreased cell viability or increased apoptosis of PC12 and SH-SY5Y cells (Chen et al., 2008), suggesting that Cd-induced neuronal apoptosis might be associated with its induction of [Ca²⁺]_i elevation (Baoshan et al., 2011).

Yuan, Yan, et al. (2013) found that treatment with Cd (5, 10, 20 µM) resulted in a concentration-dependent increase of [Ca²⁺]_i in cerebral cortical neurons. To verify the role of [Ca²⁺]_i as a key second messenger, cells were pre-loaded with 10 µM BAPTA-AM for 30 min. Chelating intracellular Ca²⁺ with BAPTA-AM prevented the elevation of [Ca²⁺]_i, demonstrating that the release of intracellular Ca²⁺ is essential for Cd-induced [Ca²⁺]_i overloading. To explore other factors contributing to the calcium overload, we studied the effect of Cd on the activities of ATPases (Yuan et al., 2013). Treatment of cerebral cortical neurons with Cd resulted in a significant loss in the activities of ATPases (P<0.05 or P<0.01), which occurred in a dose-dependent manner. When exposed to 5, 10 and 20 µM of Cd for 12 h, the Na⁺/K⁺-ATPase activity decreased to 70.1%, 52.5% and 27.2% of the control value while the Ca²⁺/Mg⁺-ATPase activity decreased to 62.6%, 49.0% and 25.5% of the control value, respectively. To examine the role of the ER in Cd-induced elevation of [Ca²⁺]_i, we incubated neurons with 2-APB, a blocker of the ER calcium channel (inositol-1, 4, 5-trisphosphate receptor, IP₃R). We observed that the elevation of [Ca²⁺]_i induced by Cd was suppressed by 2-APB after treatment with Cd for 12 h. Taken together, these results demonstrated that [Ca²⁺]_i elevation induced by Cd in cerebral cortical neurons is linked to the release of calcium from the ER (Yuan et al., 2013). Next, to further determine the role of calcium in the regulation of Cd-induced apoptosis, cerebral cortical neurons were incubated with/without Cd (10 µM) in the absence or presence of BAPTA-AM (10 µM). Cd alone (10 µM) induced cell rounding and shrinkage, and BAPTA-AM itself did not alter cell shape. However, BAPTA-AM obviously blocked Cd-induced morphological changes. Furthermore, MTT assay results further demonstrated that BAPTA-AM in part can suppress Cd-induced loss of cell viability in Cd-exposed cerebral cortical neurons. These results suggest that Cd-induced neuronal apoptosis might be associated with its induction of [Ca²⁺]_i elevation (Yuan et al., 2013).

Independent evidence for the involvement of Ca²⁺ influx in the triggering of apoptosis has come from studies with specific Ca²⁺ channel blockers, which abrogate apoptosis in the regressing prostate following testosterone withdrawal (Martikainen and Isaacs 1990) and in pancreatic b-cells treated with serum from patients with type I diabetes (Juntti-Berggren et al., 1993). Other support for the involvement of Ca²⁺ in apoptosis comes from the observation that agents which directly mobilize Ca²⁺can trigger apoptosis in diverse cell types (McConkey and Orrenius 1997).

Wyllie et al., (1984) demonstrated that Ca²⁺ ionophores cause endonuclease activation as well as many of the morphological changes that are typical of apoptosis in thymocytes. Calcium ionophores also trigger apoptosis in prostate tumor cells (Martikainen and Isaacs 1990). Other support for this echanism has come from studies with the endoplasmic reticular Ca²⁺-ATPase inhibitor thapsigargin, the product of the plant, Thapsa garganica, which can also trigger all of the morphological and biochemical events of apoptosis in thymocytes (Jiang et al., 1994) and some other cell types (Levick et al., 1995; Kaneko and Tsukamoto 1994; Choi et al., 1995).

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

The duration and extent of Ca²⁺ influx may determine whether cells survive, die by apoptosis, or undergo necrotic lysis (Choi 1995). According to this paradigm, continuous, but moderate increases in [Ca²⁺]_i such as those produced by a sustained slow influx may cause apoptosis, whereas an exceedingly high influx rate would cause rapid cell lysis (Nicotera et al., 1998). For instance, collaborative work with Dr Stuart A. Lipton’s laboratory has shown that stimulation of cortical neurons with high concentrations of NMDA results in necrosis, whereas exposure to lower concentrations causes apoptosis (Bonfoco et al., 1995). Correspondingly, neuronal death in experimental stroke models is necrotic in the ischemic core, but delayed and apoptotic in the less severely compromised penumbra or border regions (Li et al., 1995; Charriaut-Marlangue et al., 1995). Further studies in our laboratories have shown that intracellular energy levels are rapidly dissipated in necrosis, but not in apoptosis (Cox et al., 1990; Matson et al., 1989). These results suggest that while initial events may be common to both types of cell death, certain metabolic conditions would be required to activate downstream controllers, which direct cells towards the organized execution of apoptosis (Leist and Nicotera 1997).

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

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

References

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

Berridge MJ, Bootman MD, Roderick HL . (2003). Calcium signalling: dynamics, homeostasis and remodelling. Nat Rev Mol Cell Biol 4: 517–529.

Biagioli M, Pifferi S, Ragghianti M, Bucci S, Rizzuto R, et al. (2008) Endoplasmic reticulum stress and alteration in calcium homeostasis are involved in cadmium-induced apoptosis. Cell Calcium 43: 184–195.

Bonfoco E., Krainc D., Ankarcrona M., Nicotera P., Lipton S.A. Apoptosis and necrosis: two distinct events induced respectively by mild and intense insults with NMDA or nitric oxide/superoxide in cortical cell cultures. Proc Natl Acad Sci USA 1995; 92: 72162-72166.

Charriaut-Marlangue C., Margaill I., Walsh R.J., Plotkine M., Ben-An Y. NG-nitro L-arginine methylester (L-NAME) reduces cortical infarct and necrotic damage but not apoptotic cell loss. Sot Neurosci Abstr 1995; 21: 998.

Chen L, Liu L, Huang S (2008) Cadmium activates the mitogen-activated protein kinase (MAPK) pathway via induction of reactive oxygen species and inhibition of protein phosphatases 2A and 5. Free Radic Biol Med 45: 1035–1044

Choi D.W. Calcium: still center-stage in hypoxic-ischemic neuronal death. Trends Neurosci 1995; 18: 58-60.

Choi, M. S., Boise, L. H., Gottschalk, A. R., Quintans, J., and Thompson, C. B. (1995) The role of BCL-XL in CD40-mediated rescue from anti-mu-induced apoptosis in WEHI-231 B lymphoma cells. Eur. J. Immunol. 25, 1352–1357.

Clapham DE (2007) Calcium signaling. Cell 131: 1047–1058.

Clapham DE . (2007). Calcium signaling. Cell 131: 1047–1058.

Cox J.A., Felder CC., Henneberry R.C. Differential expression of excitatory amino acid receptor subtypes in cultured cerebellar neurons. Neuron 1990; 4: 941-947.

Giorgi C, Romagnoli A, Pinton P, Rizzuto R . (2008). Ca2+ signaling, mitochondria and cell death. Curr Mol Med 8: 119–130.

Jiang, S., Chow, S. C., Nicotera, P., and Orrenius, S. (1994) Intracellular Ca2/ signals activate apoptosis in thymocytes: Studies using the Ca2+ ATPase inhibitor thapsigargin. Exp. Cell Res. 212, 84–92.

Juntti-Berggren, L., Larsson, O., Rorsman, P., Ammala, C., Bokvist, K., Wahlander, K., Nicotera, P., Dybukt, J. M., Orrenius, S., Hallberg, A., and Berggren, P. (1993) Increased activity of L-type Ca2+ channels exposed to serum from patients with type I diabetes. Science 261, 86–90.

Kaneko, Y. and Tsukamoto, A. (1994) Thapsigargin-induced persistent intracellular calcium pool depletion and apoptosis in human hepatoma cells. Cancer Lett. 79, 147–155.

Leist M., Nicotera P. The shape of cell death. Biochem Biophys Res Commun 1997; 236: 1-9.

Lemarie A, Lagadic-Gossmann D, Morzadec C, Allain N, Fardel O, et al. (2004) Cadmium induces caspase-independent apoptosis in liver Hep3B cells: role for calcium in signaling oxidative stress-related impairment of mitochondria and relocation of endonuclease G and apoptosis-inducing factor. Free Radic Biol Med 36: 1517–1531.

Levick, V., Coffey, H., and D’Mello, S. R. (1995) Opposing effects of thapsigargin on the survival of developing cerebellar granule neurons in culture. Brain Res. 676, 325–335.

Li Y., Sharov V.G., Jiang N., Zaloga C., Sabbah H.N., Chopp M. Ultrastructural and light microscopic evidence of apoptosis after middle cerebral artery occlusion in the rat. Am J Pathol 1995; 146: 1045-1051.

Liu Y, Templeton DM (2008) Initiation of caspase-independent death in mouse mesangial cells by Cd2+: involvement of p38 kinase and CaMK-II. J Cell Physiol 217: 307–318.

Liu ZM, Chen GG, Vlantis AC, Tse GM, Shum CK, et al. (2007) Calcium-mediated activation of PI3K and p53 leads to apoptosis in thyroid carcinoma cells. Cell Mol Life Sci 6: 1428–1436.

Martikainen, P., and Isaacs, J. (1990) Role of calcium in the programmed cell death of rat ventral prostatic glandular cells. Prostate 17, 175–187

Matson M.P., Guthrie P.B., Hayes B.C., Kater S.B. Roles for mitotic history in the generation and degeneration of hippocampal neuroarchitecture. J Neurosci 1989; 9: 1223-1232.

McConkey, David J., and Sten Orrenius. "The role of calcium in the regulation of apoptosis." Biochemical and biophysical research communications 239.2 (1997): 357-366.

Nicotera, Pierluigi, and Sten Orrenius. "The role of calcium in apoptosis." Cell calcium 23.2-3 (1998): 173-180.

Pinton, Paolo, et al. "Calcium and apoptosis: ER-mitochondria Ca2+ transfer in the control of apoptosis." Oncogene 27.50 (2008): 6407-6418.

Rizzuto R, Pozzan T . (2006). Microdomains of intracellular Ca2+: molecular determinants and functional consequences. Physiol Rev 86: 369–408.

Shen HM, Dong SY, Ong CN (2001) Critical role of calcium overloading in cadmium-induced apoptosis in mouse thymocytes. Toxicol Appl Pharmacol 171: 12–19.

Son YO, Lee JC, Hitron JA, Pan J, Zhang Z, et al. (2010) Cadmium induces intracellular Ca2+- and H2O2-dependent apoptosis through JNK- and p53-mediated pathways in skin epidermal cell line. Toxicol Sci 113: 127–137.

Wang L, Cao J, Chen D, Liu X, Lu H, et al. (2009) Role of oxidative stress, apoptosis, and intracellular homeostasis in primary cultures of rat proximal tubular cells exposed to cadmium. Biol Trace Elem Res 127: 53–68.

Wang SH, Shih YL, Ko WC, Wei YH, Shih CM (2008) Cadmium-induced autophagy and apoptosis are mediated by a calcium signaling pathway. Cell Mol Life Sci 65: 3640–3652.

Wyllie, A. H., Morris, R. G., Smith, A. L., and Dunlop, D. (1984) Chromatin cleavage in apoptosis: Association with condensed chromatin morphology and dependence on macromolecular synthesis. J. Pathol. 142, 67–77.

Xie Z, Zhang Y, Li A, Li P, Ji W, et al. (2010) Cd-induced apoptosis was mediated by the release of Ca2+ from intracellular Ca storage. Toxicol Lett 192: 115–118.

Xu, Baoshan, et al. "Calcium signaling is involved in cadmium-induced neuronal apoptosis via induction of reactive oxygen species and activation of MAPK/mTOR network." PloS one 6.4 (2011): e19052.

Yang CS, Tzou BC, Liu YP, Tsai MJ, Shyue SK, et al. (2008) Inhibition of cadmium-induced oxidative injury in rat primary astrocytes by the addition of antioxidants and the reduction of intracellular calcium. J Cell Biochem 103: 825–834.

Yang LY, Wu KH, Chiu WT, Wang SH, Shih CM (2009) The cadmium-induced death of mesangial cells results in nephrotoxicity. Autophagy 5: 571–572.

Yeh JH, Huang CC, Yeh MY, Wang JS, Lee JK, et al. (2009) Cadmium-induced cytosolic Ca2+ elevation and subsequent apoptosis in renal tubular cells. Basic Clin Pharmacol Toxicol 104: 345–351.

Yuan, Yan, et al. "Cadmium-induced apoptosis in primary rat cerebral cortical neurons culture is mediated by a calcium signaling pathway." PloS one 8.5 (2013): e64330.