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Event: 973

Key Event Title

A descriptive phrase which defines a discrete biological change that can be measured. More help

KE5 : Decrease, AKT/eNOS activity

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. More help
Decrease, AKT/eNOS activity
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Biological Context

Structured terms, selected from a drop-down menu, are used to identify the level of biological organization for each KE. More help
Level of Biological Organization
Cellular

Cell term

The location/biological environment in which the event takes place.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.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help
Cell term
endothelial cell of vascular tree

Organ term

The location/biological environment in which the event takes place.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.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help

Key Event Components

The KE, as defined by a set structured ontology terms consisting of a biological process, object, and action with each term originating from one of 14 biological ontologies (Ives, et al., 2017; https://aopwiki.org/info_pages/2/info_linked_pages/7#List). Biological process describes dynamics of the underlying biological system (e.g., receptor signalling).Biological process describes dynamics of the underlying biological system (e.g., receptor signaling).  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 signaling 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.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help
Process Object Action
catalytic activity nitric oxide synthase, endothelial decreased
catalytic activity AKT kinase 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
Hypertension KeyEvent Frazer Lowe (send email) Not under active development Under Development

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 KE.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
Bos taurus Bos taurus High NCBI
Rattus norvegicus Rattus norvegicus High NCBI
Mus musculus Mus musculus High NCBI

Life Stages

An indication of the the relevant life stage(s) for this KE. More help
Life stage Evidence
All life stages Not Specified

Sex Applicability

An indication of the the relevant sex for this KE. More help
Term Evidence
Unspecific Not Specified

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. More help

Endothelial nitric oxide synthase (eNOS) is responsible for the generation of nitric oxide (NO), which is an important regulator of vascular homeostasis. The activity of eNOS can be regulated through calmodulin-mediated dimerization, tetrahydrobiopterin-mediated conversion of L-arginine to L-citrulline, protein-protein interactions with heat shock protein 90 and caveolin, S-nitrosylation, acetylation and phosphorylation (Atochin et al., 2007; Qian and Fulton, 2013). eNOS has been shown to be phosphorylated at multiple sites including tyrosine (Y), serine (Ser) and threonine (Thr) residues. Serine-threonine protein kinase AKT, a multifunctional regulator of cellular processes like glucose metabolism and proliferation, can directly phosphorylate eNOS at Ser1177/Ser1179, leading to increased eNOS enzymatic activity and subsequent NO production (Dimmeler et al., 1999; Fulton et al., 1999). Inhibition of AKT or a mutation of the AKT phosphorylation site on eNOS attenuates eNOS phosphorylation and its activity, resulting in decreased NO bioavailability and endothelial dysfunction (Dimmler et al. 1999)

How It Is Measured or Detected

A description of the type(s) of measurements that can be employed to evaluate the KE and the relative level of scientific confidence in those measurements.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). Do not provide detailed protocols. More help

Western blot analysis can be performed to determine the expression levels of phosphorylated eNOS, phosphorylated Akt, total Akt and total eNOS proteins using the appropriate anti-phospho-eNOS, anti-phospho-Akt, anti-eNOS, and anti-Akt antibodies. Alternatively, eNOS activity can be measured using the conversion of L-arginine to L-citrulline assay.

ELISA kits for AKT/eNOS and phospho AKT/eNOS expression are commercially available.

Domain of Applicability

A description of the scientific basis for the indicated domains of applicability and the WoE calls (if provided).  More help

Decreased Akt and eNOS activity was observed in humans, cows, mice and rats following exposure to stressors.

Cigarette smoke exposure was shown to inhibit the phosphorylation of AKT and eNOS in VEGF-stimulated human umbilical vein endothelial cells (HUVECs), resulting in decreased NO levels (Michaud et al. 2006).

In rat aortic rings, exposure to methylglyoxal and high concentrations of glucose decreased endothelium-dependent relaxation.  Further experiments in rat endothelial cells and HUVECs demonstrated a reduction in eNOS phosphorylation and activity, and reduced NO levels in response to the same stressors (Dhar et al. 2010).

In bovine aortic endothelial cells, AKT and eNOS phosphorylation were decreased following exposure to the peroxynitrite source; SIN-1, with an associated reduction in NO bioavailability.  These effects were ameliorated by treatment with the ROS scavenger DMPO (Das et al. 2014).

eNOS knockout mice are routinely used as models of hypertension.  Such mice display reduced bioavailability of NO and impaired vasodilation (Huang et al. 1995).

Reduced AKT/eNOS phosphorylation was reported under conditions of hyperglycaemia (in mice) and in HUVECs following treatment with high concentrations of glucose.  Aortic rings from hyperglycaemic mice demonstrated impaired vasodilation.  Resveratrol treatment was shown to improve vasodilation and eNOS phosphorylation in wild-type mice, but not AKT knockout mice.  Transfection of HUVECs with AKT siRNA abolished resveratrol-enhanced eNOS phosphorylation and NO release (Li et al. 2017),

References

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

Atochin, D.N., Wang, A., Liu, V.W.T., Critchlow, J.D., Dantas, A.P.V., Looft-Wilson, R., Murata, T., Salomone, S., Shin, H.K., Ayata, C., et al. (2007). The phosphorylation state of eNOS modulates vascular reactivity and outcome of cerebral ischemia in vivo. J. Clin. Invest. 117, 1961–1967.

Das A, Gopalakrishnan B, Druhan LJ, Wang TY, De Pascali F, Rockenbauer A, Racoma I, Varadharaj S, Zweier JL, Cardounel AJ, Villamena FA.  Reversal of SIN-1-induced eNOS dysfunction by the spin trap, DMPO, in bovine aortic endothelialcells via eNOS phosphorylation.  Br J Pharmacol. 2014, 171(9):2321-34. doi: 10.1111/bph.12572.

Dhar A, Dhar I, Desai KM, Wu L.  Methylglyoxal scavengers attenuate endothelial dysfunction induced by methylglyoxal and high concentrations of glucose.  Br J Pharmacol. 2010, 161(8):1843-56.

Dimmeler, S., Fleming, I., Fisslthaler, B., Hermann, C., Busse, R., and Zeiher, A.M. (1999). Activation of nitric oxide synthase in endothelial cells by Akt-dependent phosphorylation. Nature 399, 601–605.

Fulton, D., Gratton, J.P., McCabe, T.J., Fontana, J., Fujio, Y., Walsh, K., Franke, T.F., Papapetropoulos, A., and Sessa, W.C. (1999). Regulation of endothelium-derived nitric oxide production by the protein kinase AKT. Nature 399, 597–601.

Huang PL, Huang Z, Mashimo H, Bloch KD, Moskowitz MA, Bevan JA, Fishman MC.    Hypertension in mice lacking the gene for endothelial nitric oxide synthase.  Nature. 1995, 377(6546):239-42.

Li JY, Huang WQ, Tu RH, Zhong GQ, Luo BB, He Y.  Resveratrol rescues hyperglycemia-induced endothelial dysfunction via activation of Akt.  Acta Pharmacol Sin. 2017, 38(2):182-191.

Michaud SE, Dussault S, Groleau J, Haddad P, Rivard A.J. Cigarette smoke exposure impairs VEGF-induced endothelial cell migration: role of NO and reactive oxygen species.  Mol Cell Cardiol. 2006 Aug;41(2):275-84.

Qian, J., and Fulton, D. (2013). Post-translational regulation of endothelial nitric oxide synthase in vascular endothelium. Oxid. Physiol. 4, 347.