Angiotensin(1-7) and ACE2, “The Hot Spots” of Renin-Angiotensin System, Detected in the Human Aqueous Humor



Mervi Holappa 1, Jarkko Valjakka 1, Anu Vaajanen*, 2, 3
1 BioMediTech, University of Tampere, Tampere, Finland
2 Department of Ophthalmology, Tampere University Hospital, Tampere, Finland
3 SILK, Department of Ophthalmology, School of Medicine, University of Tampere, Tampere, Finland


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© Holappa et al.; Licensee Bentham Open.

open-access license: This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

* Address correspondence to this author at the Department of Ophthalmology, Tampere University Hospital, P.O. Box 2000, 33521 Tampere, Finland; Tel: +358-3-31164852; E-mail: anu.vaajanen@fimnet.fi


Abstract

Background:

The main purpose of the study was to establish whether essential components of the renin-angiotensin system (RAS) exist in the human aqueous humor.

Methods:

Forty-five patients ≥ 60 (74±7) years of age undergoing cataract surgery at Tampere University Hospital were randomly selected for the prospective study. The exclusion criterion was the use of oral antihypertensive medicine acting via renin-angiotensin system. Aqueous humor samples were taken at the beginning of normal cataract extraction. The samples were frozen and stored at -80 °C. The concentrations of intraocular endogenous RAS components Ang(1-7), ACE2, and ACE1 were measured using ELISA.

Results:

Concentration medians of Ang(1-7), ACE2, and ACE1 in the aqueous humor were: Ang(1-7) 4.08 ng/ml, ACE2 2.32 ng/ml and ACE1 0.35 ng/ml. The concentrations were significantly higher in glaucomatous than in non-glaucomatous eyes, ACE1 (p=0.014) and Ang(1-7) (p=0.026) vs non-glaucomatous eyes.

Conclusions:

Ang(1-7), ACE2 and ACE1 are found in the human aqueous humor. The observations are consistent with the conception that local tissue-RAS exists in the human eye and it might have a role in the control of intraocular pressure.

Keywords: Angiotensin (1-7), angiotensin converting enzyme 2, angiotensin II, angiotensin converting enzyme 1, aqueous humor, glaucoma, renin-angiotensin system.