Constitutive Expression and Localization of COX-1 and COX-2 in Rabbit Iris and Ciliary Body

doi:10.1006/exer.2001.0977

Experimental Eye Research

Volume 72, Issue 6, June 2001, Pages 611-621

https://doi.org/10.1006/exer.2001.0977 Get rights and content

Abstract

Prostaglandins are involved in the regulation of intraocular pressure and the blood-aqueous barrier of the eye, and are used for the treatment of glaucoma. The decrease of the constitutively expressed PG-synthesizing enzyme cyclooxygenase-2 (COX-2) has been demonstrated in the ciliary non-pigmented epithelial layer of patients with primary open angle glaucoma. Little is known about the distribution of COX-1 and COX-2 in animals. We investigated this in the iris and ciliary body of the normal rabbit eye. The presence of COX-1 and COX-2 in freshly excised iris and ciliary body tissue from adult New Zealand White albino rabbits was demonstrated by real-time RT-PCR, and Western blot analysis. The localization of both isoforms and of the neuron-specific protein gene product 9.5 was determined by indirect immunofluorescence. Both enzymes are expressed in the iris and the ciliary body. Immunofluorescence studies including double staining techniques localized COX-1 and COX-2 to about 50% of cells in the stromal tissue of iris and ciliary body, mainly on the corneal side. They were co-localized in about 75% of these cells. Whereas all stained cells were positive for COX-1, COX-2 showed a gradient-like distribution in the stroma, with some restriction of expression near the epithelial layers, which we clearly showed to be completely negative for both COX-1 and COX-2. Also, neuronal elements did not show COX-1 or COX-2 immunoreactivity. These results establish the presence of COX-1 and COX-2 on the RNA and protein levels in normal, unstimulated rabbit iris and ciliary body. The pattern of distribution suggests a role for both enzymes in maintaining the physiology of the eye. In contrast to our results in man, non-pigmented epithelial cells of the ciliary body did not express immunoreactivity. This could account for differences in the regulation of intraocular pressure and/or blood-aqueous barrier between human and rabbit eyes.

References (35)

A.A. Abdel-Latif
Release and effects of prostaglandins in ocular tissues
Prostaglandins Leukot Essent. Fatty Acids
(1991)
N.G. Bazan et al.
Signal transduction and gene expression in the eye: a contemporary view of the pro-inflammatory, anti-inflammatory and modulatory roles of prostaglandins and other bioactive lipids
Surv. Ophthalmol.
(1997)
F. Beiche et al.
Up-regulation of cyclooxygenase-2 mRNA in the rat spinal cord following peripheral inflammation
FEBS Lett.
(1996)
L.Z. Bito
Species differences in the responses of the eye to irritation and trauma: a hypothesis of divergence in ocular defense mechanisms, and the choice of experimental animals for eye research
Exp. Eye Res.
(1984)
L.Z. Bito
Prostaglandins: a new approach to glaucoma management with a new, intriguing side effect
Surv. Ophthalmol.
(1997)
T. Brzozowski et al.
Role of prostaglandins generated by cyclooxygenase-1 and cyclooxygenase-2 in healing of ischemia-reperfusion-induced gastric lesions
Eur. J. Pharmacol.
(1999)
K.L. King et al.
Metabolism of arachidonic acid by isolated rabbit ciliary epithelium
Exp. Eye Res.
(1992)
A. Ocklind
Effect of latanoprost on the extracellular matrix of the ciliary muscle. A study on cultured cells and tissue sections
Exp. Eye Res.
(1998)
J.F. Poyer et al.
The effect of topical PGF2 alpha on uveoscleral outflow and outflow facility in the rabbit eye
Exp. Eye Res.
(1992)
B. Resul et al.
Structure-activity relationships and receptor profiles of some ocular hypotensive prostanoids
Surv. Ophthalmol.
(1997)

V.L. Schuster et al.

The prostaglandin transporter is widely expressed in ocular tissues

Surv. Ophthalmol.

(1997)

C.B. Toris et al.

Effects of exogenous prostaglandins on aqueous humor dynamics and blood-aqueous barrier function

Surv. Ophthalmol.

(1997)

D.F. Woodward et al.

The molecular biology and ocular distribution of prostanoid receptors

Surv. Ophthalmol.

(1997)

K. Yamagata et al.

Expression of a mitogen-inducible cyclooxygenase in brain neurons: regulation by synaptic activity and glucocorticoids

Neuron

(1993)

C.B. Camras et al.

The role of endogenous prostaglandins in clinically-used and investigational glaucoma therapy

Prog. Clin. Biol. Res.

(1989)

L.L. DeSantis et al.

Comparison of the effects of prostaglandins and their esters on blood-aqueous barrier integrity and intraocular pressure in rabbits

Prog. Clin. Biol. Res.

(1989)

C.E. Dieterich et al.

[Iris and circulation of aqueous humor]

Albrecht Von Graefes Arch. Klein Exp. Ophthtalmol.

(1971)

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In the past few years, several efflux transporters and metabolizing enzymes have been recognized to restrict ocular drug absorption. In this chapter, we have made an attempt to provide an overview of healthy and disease state impact on the expression of metabolizing enzymes. Moreover, we have also discussed the potential interplay between membrane transporters and metabolizing enzymes within ocular tissues and strategies to circumvent these processes.
Genetic deletion of COX-2 diminishes VEGF production in mouse retinal Müller cells
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Specifically, prostanoids can induce the expression of pro-angiogenic factors such as VEGF and bFGF in a wide variety of cell types (Cheng et al., 1998; Pai et al., 2001), often in a PKA-dependent manner (Cheng et al., 1998; Höper et al., 1997; Amano et al., 2002). COX-2 has been localized to various ocular tissues, and its expression has been found, or can be induced, in the following structures: cornea, iris, ciliary body, various cell types within the neurosensory retina, and the retinal pigment epithelium (RPE) (Yamada et al., 1999; Damm et al., 2001; Maihofner et al., 2001; Ju and Neufeld, 2002; Ershov and Bazan, 1999). The expression of the COX-2 enzyme in these ocular tissues suggests a functional role for its prostanoid products.
Non-steroidal anti-inflammatory drugs (NSAIDs), which inhibit COX activity, reduce the production of retinal VEGF and neovascularization in relevant models of ocular disease. We hypothesized that COX-2 mediates VEGF production in retinal Müller cells, one of its primary sources in retinal neovascular disease. The purpose of this study was to determine the role of COX-2 and its products in VEGF expression and secretion. These studies have more clearly defined the role of COX-2 and COX-2-derived prostanoids in retinal angiogenesis. Müller cells derived from wild-type and COX-2 null mice were exposed to hypoxia for 0–24 h. COX-2 protein and activity were assessed by western blot analysis and GC–MS, respectively. VEGF production was assessed by ELISA. Wild-type mouse Müller cells were treated with vehicle (0.1% DMSO), 10 μM PGE₂, or PGE₂ + 5 μM H-89 (a PKA inhibitor), for 12 h. VEGF production was assessed by ELISA. Hypoxia significantly increased COX-2 protein (p < 0.05) and activity (p < 0.05), and VEGF production (p < 0.0003). COX-2 null Müller cells produced significantly less VEGF in response to hypoxia (p < 0.05). Of the prostanoids, PGE₂ was significantly increased by hypoxia (p < 0.02). Exogenous PGE₂ significantly increased VEGF production by Müller cells (p < 0.0039), and this effect was inhibited by H-89 (p < 0.055). These data demonstrate that hypoxia induces COX-2, prostanoid production, and VEGF synthesis in Müller cells, and that VEGF production is at least partially COX-2-dependent. Our study suggests that PGE₂, signaling through the EP₂ and/or EP₄ receptor and PKA, mediates the VEGF response of Müller cells.
Ocular prostaglandin production and morphology in mice lacking a single isoform of cyclooxygenase
2009, Prostaglandins Leukotrienes and Essential Fatty Acids
Prostaglandins have many important roles in ocular physiology and are used clinically for the treatment of glaucoma. The aim of this study was to analyse the contribution of each cyclooxygenase isoform to ocular prostaglandin production using isoform-specific knockout mice. Ex vivo PGE₂, 6-keto-PGF_1α, and TXB₂ production was measured from whole eyes, corneal tissue, uveoscleral tissue, lens, retina and optic nerve using enzyme-linked immunosorbant assays. Ocular immunohistochemical and histological analysis was also conducted for each genotype. Levels of each of the prostaglandins measured were significantly decreased in the corneal tissue, uveoscleral tissue, lens, retina and optic nerve of COX-1^−/− mice in comparison with wild-type mice. In contrast, COX-2^−/− mice had similar levels of ocular prostaglandin production to wild-type mice. These results suggest that COX-1 is the principal isoform responsible for prostaglandin production in the mouse eye. The absence of COX-1 or COX-2 did not appear to effect ocular development in these mice.
Association of COX2 functional polymorphisms and the risk of vitiligo in Chinese populations
2009, Journal of Dermatological Science
Citation Excerpt :
However, the COX2 gene, rather than the COX1 gene, was constitutively expressed in iridial melanocytes [10]. Similar results were reported by Damm et al. [11]. Most importantly, it has been shown that UV-induced COX2 expression plays a major role in UV-induced PGE2 production [12,13].
Cyclooxygenase-2 (COX2) plays an important role in the production of prostaglandin E2 (PGE2), which is made by epidermal keratinocytes in response to ultraviolet radiation (UVR). PGE2 is important for the proliferation and melanogenesis of epidermal melanocytes, the loss of which leads to vitiligo. COX2-1195A > G, -765G > C, and -8473T > C polymorphisms may influence the mRNA levels of COX2 and affect the production of PGE2 subsequently. Therefore, we supposed that these polymorphisms may be associated with vitiligo.
The aim of the study was to elucidate the association between three functional COX2 polymorphisms and the risk of vitiligo.
This was a hospital-based, case–control study of 755 vitiligo patients and 774 vitiligo-free controls who were frequency matched by age and sex. We genotyped COX2-1195A > G, -765G > C, and -8473T > C polymorphisms by using PCR-restriction fragment length polymorphism (RFLP) method and assessed their respective associations with the risk of vitiligo in Han Chinese populations.
We found a statistically significant increased risk of vitiligo to be associated with the COX2-1195 G variant allele (p = 0.004). Significantly higher vitiligo risks were found among subgroups with these characteristics: age >20 years, male, active, nonsegmental vitiligo, and onset age >20 years. In addition, the interaction between COX2-1195 and COX2-8473 was statistically significant (p = 0.004).
For the first time, we provide evidence that functional polymorphisms in the COX2 gene may influence the risk of vitiligo in Han Chinese populations, suggesting new clues that help to clarify the pathogenesis of vitiligo. Larger studies are needed to verify these findings.
COX-2 expression in the guinea pig cochlea is partly altered by moderate sound exposure
2006, Neuroscience Letters
The cyclooxygenase-2 isoform (COX-2) was found recently to be constitutively expressed in the guinea pig inner ear. To gain knowledge about its role in sound perception, alterations in the COX-2 level of moderate noise-stimulated cochleae were determined. Staining intensities were quantified in different regions using an immunohistochemical staining procedure and computer-assisted system. After 70 dB and 90 dB noise exposure for 1 h at 8000 Hz, COX-2 downregulation was observed in the organ of Corti, which was most prominent in Deiters’ cells near Hensen cells and outer hair cells. In pillar cells, COX-2 levels were only slightly reduced after 70 dB but strongly diminished after 90 dB exposure. In Hensen cells, COX-2 was downregulated after 70 dB stimulation, revealing a decreasing COX-2 content from the third to the first turn of the cochlea and a homogeneously reduced enzyme expression in all three turns after 90 dB. The COX-2 content in inner hair cells was nearly identical to unexposed cochleae after 70 dB exposure but significantly reduced after 90 dB stimulation. In spiral ganglion cells, stria vascularis, spiral ligament and limbus, COX-2 expression was unchanged after 70 dB and 90 dB. We suggest that alterations in COX-2 expression might contribute to diminished sensitivity at the cochlea after noise exposure to reduce subsequent noise distress, termed sound conditioning.
Localization of prostanoid receptors and cyclo-oxygenase enzymes in Guinea pig and human cochlea
2004, Hearing Research
Endogenous production of prostaglandins has been demonstrated in the cochlea, but no information is available on the distribution of the cyclo-oxygenase (COX) enzymes, or prostanoid receptors in the cochlea. The purpose of the present study was to investigate the localization of the FP, EP₁ and EP₃ prostanoid receptors as well as the COX-1 and COX-2 enzymes in the cochlea of guinea pig and man. Cochleas were processed for immunohistochemistry using routine techniques. Appropriate controls comprised incubation with specific blocking peptides, or incubation without primary antibodies. Both in guinea pig and man the FP prostanoid receptor was abundantly distributed in the cochlea, e.g., in stria vascularis, the spiral ligament, spiral ganglion, and organ of Corti. The immunohistochemical staining of the EP₁ and EP₃ receptors in the same structures was significantly weaker and sometimes lacking altogether (e.g., EP₃ receptor in human cochlea). Weak, but mostly consistent immunostaining of the COX-1 enzyme was found in the cochlear structures. The COX-2 enzyme appeared to be lacking. The abundant distribution of the FP receptor in several important cochlear structures both in guinea pig and man suggests a physiological function for PGF_2α in the cochlea. The COX-1 enzyme seems to be constitutively expressed in the cochlea in contrast to COX-2.

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^f2: Address correspondence to: Kay Brune, Institute for Experimental and Clinical Pharmacology and Toxicology, Fahrstr. 17, 91054 Erlangen, Germany.

^f1: Both authors contributed equally to the present manuscript.

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Regular ArticleConstitutive Expression and Localization of COX-1 and COX-2 in Rabbit Iris and Ciliary Body

Abstract

Prostaglandins Leukot Essent. Fatty Acids

Surv. Ophthalmol.

FEBS Lett.

Exp. Eye Res.

Surv. Ophthalmol.

Eur. J. Pharmacol.

Exp. Eye Res.

Exp. Eye Res.

Exp. Eye Res.

Surv. Ophthalmol.

Surv. Ophthalmol.

Surv. Ophthalmol.

Surv. Ophthalmol.

Neuron

The role of endogenous prostaglandins in clinically-used and investigational glaucoma therapy

Prog. Clin. Biol. Res.

Comparison of the effects of prostaglandins and their esters on blood-aqueous barrier integrity and intraocular pressure in rabbits

Prog. Clin. Biol. Res.

[Iris and circulation of aqueous humor]

Albrecht Von Graefes Arch. Klein Exp. Ophthtalmol.

Regular Article
Constitutive Expression and Localization of COX-1 and COX-2 in Rabbit Iris and Ciliary Body