Many Faces of Renin-angiotensin System - Focus on Eye

Abstract

The renin-angiotensin system (RAS), that is known for its role in the regulation of blood pressure as well as in fluid and electrolyte homeostasis, comprises dozens of angiotensin peptides and peptidases and at least six receptors. Six central components constitute the two main axes of the RAS cascade. Angiotensin (1-7), an angiotensin converting enzyme 2 and Mas receptor axis (ACE2-Ang(1-7)-MasR) counterbalances the harmful effects of the angiotensin II, angiotensin converting enzyme 1 and angiotensin II type 1 receptor axis (ACE1-AngII-AT1R) Whereas systemic RAS is an important factor in blood pressure regulation, tissue-specific regulatory system, responsible for long term regional changes, that has been found in various organs. In other words, RAS is not only endocrine but also complicated autocrine system. The human eye has its own intraocular RAS that is present e.g. in the structures involved in aqueous humor dynamics. Local RAS may thus be a target in the development of new anti-glaucomatous drugs. In this review, we first describe the systemic RAS cascade and then the local ocular RAS especially in the anterior part of the eye.

COVID-19: Ophthalmological Aspects of the SARS-CoV 2 Global Pandemic

“…aqueous [20]. Therefore, it is currently unclear if sole ocular contact with SARS-CoV 2 can manifest in an infection [17].…”

“…At the moment, it is unclear whether SARS-CoV 2 can cause more severe eye disease beyond keratoconjunctivitis. Due to the presence of ACE-2 in the retina [19] and aqueous [20], uveitis or involvement of the posterior pole might, however, be possibleand maybe even linked to an increased viral load. As patients with a high viral load are, however, also more likely to develop severe or critical illness, severe eye problems might, at the moment, largely go unnoticed as these patients are often treated in intensive care units for much more severe, life-threatening conditions.…”

Can the Coronavirus Disease 2019 (COVID-19) Affect the Eyes? A Review of Coronaviruses and Ocular Implications in Humans and Animals

“…ACE2 has been found in the aqueous humor. 31 However, the expression of ACE2 in more anterior tissues such as the conjunctiva or cornea has yet to be established. Hence, more research exploring the hypothesis of SARS-CoV-2 ocular infection through ACE2 has to be conducted.…”

The Ocular Surface and the Coronavirus Disease 2019: Does a Dual ‘Ocular Route’ Exist?

“…The presence of ACE2, which normally helps regulate blood pressure, is widespread throughout the body, and the eye is not excluded [12,13]. The human ocular globe has its own intraocular renin-angiotensin system, which is present not only on the surface of the eye (e.g., conjunctiva and cornea), but also inside the eye (trabecular meshwork, aqueous humor, iris, ciliary body, non-pigmented ciliary epithelium, and retina) [14]. TMPRSS2 is also highly expressed in various tissues, including cornea limbal stem cells, substantiating that in the cornea ACE2 and TMPRSS2 are coexpressed in the same cell [15].…”