Purinergic Receptors in the Eye

A special issue of Vision (ISSN 2411-5150).

Deadline for manuscript submissions: closed (31 May 2018) | Viewed by 20795

Special Issue Editor


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Guest Editor
Department of Ophthalmology, Osaka Medical College, 2-7, Daigaku-machi, Takatsuki, Osaka 569-8686, Japan
Interests: glaucoma; ocular blood flow; ocular pharmacology; P2X7 receptor
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Special Issue Information

Dear Colleagues,

Purinergic receptors, also known as purinoceptors, are a family of plasma membrane molecules found in almost all mammalian tissues. In the field of purinergic signaling, these receptors play a role in many physiological functions such as learning, memory, locomotion, and sleep. More specifically, they are involved in several cellular functions, including proliferation and migration of neural stem cells, vascular reactivity, apoptosis and cytokine secretion. The term “purinergic receptor” was originally introduced to illustrate specific classes of membrane receptors that mediate relaxation of gut smooth muscle as a response to the release of ATP (P2 receptors) or adenosine (P1 receptors). P2 receptors have further been divided into subclasses: P2X, P2Y. P2X receptors are a family of ligand-gated ion channels that allow the passage of ions across cell membranes. P2Y receptors are a family of G protein-coupled receptors that initiate an intracellular chain of reactions.

Some of purinergic receptors have been found to play important roles in the ocular tissues including the lacrimal gland, the cornea, the trabecular meshwork, the lens, and the retina. For example, the P2X7 receptor possesses unique features that are likely to be of both physiological and pathophysiological significance. Expression of the P2X7 receptor has been demonstrated in most types of cells in the retina; these include neurons such as the retinal ganglion cells, as well as glia and vascular cells. For instance, stimulation of P2X7 receptor has been reported to be involved in neuronal and microvascular cell death under pathogenic condition like ischemia, glaucoma, and diabetic retinopathy.

The current Special Issue is open to submissions of unpublished experimental articles and review papers on the following and related topics:

  • Fundamental basis of purinergic receptors

  • Physiological roles of purinergic receptors

  • Pathological roles of purinergic receptors

  • Purinergic receptors as a potential therapeutic target for ocular diseases

Dr. Tetsuya Sugiyama
Guest Editor

Manuscript Submission Information

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Keywords

  • purinergic receptors

  • ATP

  • adenosine

  • lacrimal gland

  • cornea

  • trabecular meshwork

  • lens

  • retina

  • retinal ganglion cells

  • vascular cells

  • glia

  • glaucoma

  • diabetic retinopathy

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Published Papers (5 papers)

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Editorial

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3 pages, 139 KiB  
Editorial
Special Issue for Purinergic Receptors, Particularly P2X7 Receptor, in the Eye
by Tetsuya Sugiyama
Vision 2018, 2(3), 30; https://doi.org/10.3390/vision2030030 - 24 Jul 2018
Viewed by 2705
(This article belongs to the Special Issue Purinergic Receptors in the Eye)

Research

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12 pages, 1033 KiB  
Article
Purinergic Vasotoxicity: Role of the Pore/Oxidant/KATP Channel/Ca2+ Pathway in P2X7-Induced Cell Death in Retinal Capillaries
by Maho Shibata, Eisuke Ishizaki, Ting Zhang, Masanori Fukumoto, Alma Barajas-Espinosa, Tong Li and Donald G. Puro
Vision 2018, 2(3), 25; https://doi.org/10.3390/vision2030025 - 25 Jun 2018
Cited by 15 | Viewed by 3686
Abstract
P2X7 receptor/channels in the retinal microvasculature not only regulate vasomotor activity, but can also trigger cells in the capillaries to die. While it is known that this purinergic vasotoxicity is dependent on the transmembrane pores that form during P2X7 activation, events [...] Read more.
P2X7 receptor/channels in the retinal microvasculature not only regulate vasomotor activity, but can also trigger cells in the capillaries to die. While it is known that this purinergic vasotoxicity is dependent on the transmembrane pores that form during P2X7 activation, events linking pore formation with cell death remain uncertain. To better understand this pathophysiological process, we used YO-PRO-1 uptake, dichlorofluorescein fluorescence, perforated-patch recordings, fura-2 imaging and trypan blue dye exclusion to assess the effects of the P2X7 agonist, benzoylbenzoyl-ATP (BzATP), on pore formation, oxidant production, ion channel activation, [Ca2+]i and cell viability. Experiments demonstrated that exposure of retinal microvessels to BzATP increases capillary cell oxidants via a mechanism dependent on pore formation and the enzyme, NADPH oxidase. Indicative that oxidation plays a key role in purinergic vasotoxicity, an inhibitor of this enzyme completely prevented BzATP-induced death. We further discovered that vasotoxicity was boosted 4-fold by a pathway involving the oxidation-driven activation of hyperpolarizing KATP channels and the resulting increase in calcium influx. Our findings revealed that the previously unappreciated pore/oxidant/KATP channel/Ca2+ pathway accounts for 75% of the capillary cell death triggered by sustained activation of P2X7 receptor/channels. Elucidation of this pathway is of potential therapeutic importance since purinergic vasotoxicity may play a role in sight-threatening disorders such as diabetic retinopathy. Full article
(This article belongs to the Special Issue Purinergic Receptors in the Eye)
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Review

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628 KiB  
Review
CD40, a Novel Inducer of Purinergic Signaling: Implications to the Pathogenesis of Experimental Diabetic Retinopathy
by Carlos S. Subauste
Vision 2017, 1(3), 20; https://doi.org/10.3390/vision1030020 - 12 Aug 2017
Cited by 3 | Viewed by 4012
Abstract
Diabetic retinopathy is a leading complication of diabetes. Death of capillary cells with resulting capillary degeneration is a central feature of this disease. Chronic low-grade inflammation has been linked to the development of retinal capillary degeneration in diabetes. CD40 is an upstream inducer [...] Read more.
Diabetic retinopathy is a leading complication of diabetes. Death of capillary cells with resulting capillary degeneration is a central feature of this disease. Chronic low-grade inflammation has been linked to the development of retinal capillary degeneration in diabetes. CD40 is an upstream inducer of a broad range of inflammatory responses in the diabetic retina and is required for death of retinal capillary cells. Recent studies uncovered CD40 as a novel inducer of purinergic signaling and identified the CD40-ATP-P2X7 pathway as having a key role in the induction of inflammation in the diabetic retina and programmed cell death of retinal endothelial cells. Full article
(This article belongs to the Special Issue Purinergic Receptors in the Eye)
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253 KiB  
Review
The Role of the P2X7 Receptor in Ocular Stresses: A Potential Therapeutic Target
by Mélody Dutot, Elodie Olivier, Anaïs Wakx and Patrice Rat
Vision 2017, 1(2), 14; https://doi.org/10.3390/vision1020014 - 17 May 2017
Cited by 10 | Viewed by 5292
Abstract
The P2X7 receptor is expressed in both anterior and posterior segments of the eyeball. In the ocular surface, the P2X7 receptor is activated in case of external aggressions: preservatives and surfactants induce the activation of P2X7 receptors, leading to either apoptosis, inflammation, or [...] Read more.
The P2X7 receptor is expressed in both anterior and posterior segments of the eyeball. In the ocular surface, the P2X7 receptor is activated in case of external aggressions: preservatives and surfactants induce the activation of P2X7 receptors, leading to either apoptosis, inflammation, or cell proliferation. In the retina, the key endogenous actors of age-related macular degeneration, diabetic retinopathy, and glaucoma act through P2X7 receptors’ activation and/or upregulation of P2X7 receptors’ expression. Different therapeutic strategies aimed at the P2X7 receptor exist. P2X7 receptor antagonists, such as divalent cations and Brilliant Blue G (BBG) could be used to target either the ocular surface or the retina, as long as polyunsaturated fatty acids may exert their effects through the disruption of plasma membrane lipid rafts or saffron that reduces the response evoked by P2X7 receptor stimulation. Treatments against P2X7 receptor activation are proposed by using either eye drops or food supplements. Full article
(This article belongs to the Special Issue Purinergic Receptors in the Eye)
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406 KiB  
Review
Targeting the P2X7 Receptor in Age-Related Macular Degeneration
by Dongli Yang
Vision 2017, 1(2), 11; https://doi.org/10.3390/vision1020011 - 31 Mar 2017
Cited by 13 | Viewed by 4427
Abstract
The P2X7 receptor (P2X7R) is a membrane receptor for the extracellular adenosine triphosphate (ATP). It functions as a ligand-gated non-selective cation channel and can mediate formation of a large non-selective membrane pore. Activation of the P2X7R induces multiple downstream events, including oxidative stress, [...] Read more.
The P2X7 receptor (P2X7R) is a membrane receptor for the extracellular adenosine triphosphate (ATP). It functions as a ligand-gated non-selective cation channel and can mediate formation of a large non-selective membrane pore. Activation of the P2X7R induces multiple downstream events, including oxidative stress, inflammatory responses and cell death. Although the P2X7R has been identified in the retinal pigment epithelium (RPE) and different layers of retina, its biological and pathological functions as well as its downstream signaling pathways in the RPE and retina are not yet fully understood. Better understanding of the function of P2X7R in the RPE and retina under normal and disease states might lead to novel therapeutic targets in retinal diseases, including age-related macular degeneration (AMD). This brief review will mainly focus on recent findings on in vitro and in vivo evidence for the role of the P2X7R in the RPE and AMD. Full article
(This article belongs to the Special Issue Purinergic Receptors in the Eye)
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