Relationship:980

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Key Event Relationship Overview

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Description of Relationship

Upstream Event Downstream Event/Outcome
Oxidative Stress, Increase GTPCH-1, Decrease

AOPs Referencing Relationship

AOP Name Type of Relationship Weight of Evidence Quantitative Understanding
Oxidative Stress Leading to Hypertension Directly Leads to Moderate Weak

Taxonomic Applicability

Name Scientific Name Evidence Links
Bos taurus Bos taurus Moderate NCBI
Mus musculus Mus musculus Moderate NCBI
Homo sapiens Homo sapiens Moderate NCBI
Rattus norvegicus Rattus norvegicus Moderate NCBI

How Does This Key Event Relationship Work

Exposure to known inducers of oxidative stress such as cigarette smoke extract (Ismail et al., 2015) or peroxynitrite (Zhao et al., 2013) causes the loss of GTPCH-1 activity, resulting in decreased levels of tetrahydrobiopterin (BH4) and subsequent uncoupling of endothelial nitric oxide synthase (eNOS).

Weight of Evidence

Biological Plausibility

It is well-established that BH4 is highly susceptible to oxidation by ROS, leading to dysfunctional eNOS (Lee and Griendling, 2008). Several studies demonstrated that GTPCH-1 is also affected by oxidative stress, which provides evidence for moderate biological plausibility. In vitro exposure to chemically synthesized peroxynitrite inhibited GTPCH-1 activity in a dose-dependent manner (Zhao et al., 2013). This inhibition as well as increased ubiquitination of GTPCH-1 were observed in cultured bovine aortic endothelial cells (BAECs) and streptozotocin-induced diabetes in mice following peroxynitrite treatment. Ubiquitination of GTPCH-1 leads to its degradation, which is equivalent to a decrease in GTPCH-1. In another study, GTPCH-1 levels were reduced by cigarette smoke extract (CSE) exposure in BAECs (Ismail et al., 2015). There is also evidence that CSE promoted GTPCH-1 degradation by increasing proteasomal activity. Further support is observed in humans where cardiac reperfusion patients experienced oxidative stress which was associated with reduced GTPCH-1 activity (Jayaram et al., 2015).

Empirical Support for Linkage

Include consideration of temporal concordance here

In a rat model of aortic coarctation-associated hypertension, increased ROS (1.75 nmol DCF/mg protein/min) and decreased GTPCH-1 protein expression (western blot band intensity of 0.0087±0.005) were observed (Cervantes-Pérez et al., 2012). However, following clofibrate treatment (100 mg/kg/day, 7 days), ROS was reduced by approximately 30% and GTPCH-1 band intensity increased to 0.0087±0.005. This study provides evidence that there is a dependent change between oxidative stress and GTPCH-1, but we found no dose-response relationship, so empirical support for this KER is weak.

Uncertainties or Inconsistencies

No uncertainties or inconsistencies were found for this KER.

Quantitative Understanding of the Linkage

Is it known how much change in the first event is needed to impact the second? Are there known modulators of the response-response relationships? Are there models or extrapolation approaches that help describe those relationships?

As the relationship between oxidative stress and GTPCH-1 is not well-studied, there is limited quantitative understanding of this linkage.

Evidence Supporting Taxonomic Applicability

Several studies showed decreased GTPCH-1 activity and/or protein expression under oxidative stress in cardiac reperfusion patients, bovine endothelial cells, a mouse model of diabetes and a rat model of hypertension (Cervantes-Pérez et al., 2012; Ismail et al., 2015; Jayaram et al., 2015; Zhao et al., 2013).

References

Cervantes-Pérez, L.G., Ibarra-Lara, M. de la L., Escalante, B., Del Valle-Mondragón, L., Vargas-Robles, H., Pérez-Severiano, F., Pastelín, G., and Sánchez-Mendoza, M.A. (2012). Endothelial nitric oxide synthase impairment is restored by clofibrate treatment in an animal model of hypertension. Eur. J. Pharmacol. 685, 108–115.

Ismail, R., Elmahdy, M., AbdelGhany, T., Lowe, F., and Zweier, J. (2015). Cigarette smoke constituents cause endothelial dysfunction due to oxidative depletion of tetrahydrobiopterin and activation of the ubiquitin proteasome system. Free Radic. Biol. Med. Under review.

Jayaram, R., Goodfellow, N., Zhang, M.H., Reilly, S., Crabtree, M., De Silva, R., Sayeed, R., and Casadei, B. (2015). Molecular mechanisms of myocardial nitroso-redox imbalance during on-pump cardiac surgery. Lancet Lond. Engl. 385 Suppl 1, S49

Lee, M.Y., and Griendling, K.K. (2008). Redox signaling, vascular function, and hypertension. Antioxid. Redox Signal. 10, 1045–1059.

Zhao, Y., Wu, J., Zhu, H., Song, P., and Zou, M.-H. (2013). Peroxynitrite-dependent zinc release and inactivation of guanosine 5’-triphosphate cyclohydrolase 1 instigate its ubiquitination in diabetes. Diabetes 62, 4247–4256.