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AchE Inhibition leads to ACh Synaptic Accumulation
Key Event Relationship Overview
AOPs Referencing Relationship
|AOP Name||Adjacency||Weight of Evidence||Quantitative Understanding||Point of Contact||Author Status||OECD Status|
|Acetylcholinesterase inhibition leading to acute mortality||adjacent||High||Moderate||Cataia Ives (send email)||Under Development: Contributions and Comments Welcome||Under Development|
|Acetylcholinesterase Inhibition Leading to Neurodegeneration||adjacent||High||Moderate||Allie Always (send email)||Under development: Not open for comment. Do not cite|
|Acetylcholinesterase Inhibition leading to Acute Mortality via Impaired Coordination & Movement||adjacent||Allie Always (send email)||Under development: Not open for comment. Do not cite|
Life Stage Applicability
Key Event Relationship Description
AChE is an enzyme responsible for controlling the level of acetylcholine available at neural synapses and neuromuscular junctions. AChE negatively regulates acetylcholine via hydrolysis to acetic acid and choline (Wilson 2010). Inhibition of AChE prevents degradation of acetylcholine which leads to acetylcholine accumulation at neural synapses and neuromuscular junctions in the central and peripheral nervous systems. (Soreq and Seidman, 2001; Lushington 2006, Prado, 2017).
- See KEGG Reaction R01026
Evidence Supporting this KER
- Acetylcholine is a critical neurotransmitter localized to neuronal synapses. Biological plausibility to support the relationship between AChE inhibition and accumulation of acetylcholine is rooted in evidence demonstrating that AChE catalyzes degradation of acetylcholine into choline and acetate. Therefore inhibition of the AChE leads to acetylcholine accumulation.
Uncertainties and Inconsistencies
- No known qualitative inconsistencies or uncertainties associated with this relationship.
Striatal AChE activity and extracellular ACh levels were measured in rats intracerebrally perfused with paraoxon (0, 0.03, 0.1, 1, 10 or 100 μM, 1.5 μl/min for 45 min). Acetylcholine was below the limit of detection at the low dose of paraoxon (0.1 uM), but was transiently elevated (0.5–1.5 hr) with 10 μM paraoxon. Concentration-dependent AchE inhibition was noted but reached a plateau of about 70% at 1 μM and higher concentrations (Ray, 2009).
The relationship between AChE inhibition and ACh accumulation at the synapse can be observed within 30 minutes after application of a AChE inhibitor (Ray, 2009).
Known modulating factors
Known Feedforward/Feedback loops influencing this KER
Domain of Applicability
The literature includes many studies linking increases in acetylcholine in brain tissues after exposure to an OP or carbamate pesticide with increased AChE inhibition in various taxa. Examples include studies with crustacea (Reddy et al., 1990); tadpoles (Nayeemunnisa and Yasmeen, 1986); fish (Rao and Rao 1984; Verma et al., 1981); birds (Kobayashi et al., 1983); and rodents (Kobayashi et al., 1988)
- Wilson, B.W. 2010. Cholinesterases. IN: Kreiger, R. (Ed.). Hayes’ Handbook of Pesticide Toxicology. Third Edition, Volume 2. Elsevier, Amsterdam, The Netherlands. pp. 1457-1478.
- Soreq, H. and S. Seidman. 2001. Acetylcholinesterase – new roles for an old actor. Nat. Rev. Neurosci. 2: 294-302.
- Lushington, G.H., J-X. Guo, and M.M. Hurley. 2006. Acetylcholinesterase: Molecular modeling with the whole toolkit. Curr. Topics Medic. Chem. 6: 57-73.
- Reddy, M. S., Jayaprada, P., and Rao, K. V. R. 1990. Impact of Methylparathion and Malathion on Cholinergic and Non-Cholinergic Enzyme Systems of Penaeid Prawn, Metapenaeus monoceros. Biochem.Int. 22, 769-780.
- Nayeemunnisa and Yasmeen, N. 1986. On the Presence of Calmodulin in the Brain of Control and Methyl Parathion-Exposed Developing Tadpoles of Frog, Rana cyanophlictis. Curr.Sci.(Bangalore) 55, 546-548.
- Rao, K. S. P. and Rao, K. V. R. 1984. Impact of Methyl Parathion Toxicity and Eserine Inhibition on Acetylcholinesterase Activity in Tissues of the Teleost (Tilapia mossambica) - a Correlative Study. Toxicol.Lett. 22, 351-356.
- Verma, S. R., Tonk, I. P., Gupta, A. K., and Dalela, R. C. 1981. In Vivo Enzymatic Alterations in Certain Tissues of Saccobranchus fossilis Following Exposure to Four Toxic Substances. Environ.Pollut.A. 26, 121-127.
- Kobayashi, H., Yuyama, A., Ohkawa, T., and Kajita, T. 1988. Effect of Single or Chronic Injection with a Carbamate, Propoxur, on the Brain Cholinergic System and Behavior of Mice. Jpn.J.Pharmacol. 47, 21-27.
- Kobayashi, H., Yuyama, A., Kudo, M., and Matsusaka, N. 1983. Effects of Organophosphorus Compounds, O,O-Dimethyl O-(2,2-Dichlorovinyl)Phosphate (DDVP) and O,O-Dimethyl O-(3-Methyl 4-Nitrophenyl)Phosphorothioate (Fenitrothion), on Brain Acetylcholine Content and Acetylcholinesterase Activity in Japanese Quail. Toxicology 28, 219-227.
- Kobayashi,H., A. Yuyama, T. Kajita, K. Shimura, T. Ohkawa, and K. Satoh. 1985. Effects of Insecticidal Carbamates on Brain Acetylcholine Content, Acetylcholinesterase Activity and Behavior in Mice. Toxicol. Lett.29(2-3): 153-159.
- Oyama, Y., N. Hori, M.L. Evans, C.N. Allen, and D.O. Carpenter. 1989. Electrophysiological estimation of the actions of acetylcholinesterase inhibitors on acetylcholine receptor and cholinesterase in physically isolated Aplysia neurons. Br. J. Pharmacol. 96:573-582.
- Kobayashi, H., Sato, I., Akatsu, Y., Fujii, S. I., Suzuki, T., Matsusaka, N., and Yuyama, A. 1994. Effects of Single or Repeated Administration of a Carbamate, Propoxur, and an Organophosphate, DDVP, on Jejunal Cholinergic Activities and Contractile Responses in Rats. J.Appl.Toxicol. 14, 185-190.
- Stavinoha, W. B., Ryan, L. C., and Smith, P. W. 1969. Biochemical Effects of an Organophosphorus Cholinesterase Inhibitor on the Rat Brain. Ann.N.Y.Acad.Sci. 160, 378-382.
- Karanth, S., Liu, J., Mirajkar, N., and Pope, C. 2006. Effects of Acute Chlorpyrifos Exposure on In Vivo Acetylcholine Accumulation in Rat Striatum. Toxicol.Appl.Pharmacol. 216, 150-156.
- Pant, Radha, and S. K. Katiyar. 1983. “Effect of Malathion and Acetylcholine on the Developing Larvae Of Philosamia Ricini (Lepidoptera: Saturniidae).” Journal of Biosciences 5 (1): 89–95. https://doi.org/10.1007/BF02702598.
- Ray, A., J. Liu, S. Karanth, Y. Gao, S. Brimijoin, and C. Pope. 2009. “CHOLINESTERASE INHIBITION AND ACETYLCHOLINE ACCUMULATION FOLLOWING INTRACEREBRAL ADMINISTRATION OF PARAOXON IN RATS.” Toxicology and Applied Pharmacology 236 (3): 341–47. https://doi.org/10.1016/j.taap.2009.02.022.
- Siva Prasada Rao, K., and K. V. Ramana Rao. 1984. “Impact of Methyl Parathion Toxicity and Eserine Inhibition on Acetylcholinesterase Activity in Tissues of the Teleost (Tilapia Mossambica)--a Correlative Study.” Toxicology Letters 22 (3): 351–56. https://doi.org/10.1016/0378-4274(84)90113-9.
- Prado, MAM, Marchot, P, Silman, I. Preface: Cholinergic Mechanisms. J Neurochem. 2017 Aug;142 Suppl 2:3-6. doi: 10.1111/jnc.14027.