NADPH diaphorase localization and nitric oxide synthetase activity in the retina and anterior uvea of the rabbit eye

doi:10.1016/0006-8993(93)91400-M

Brain Research

Volume 610, Issue 2, 7 May 1993, Pages 194-198

https://doi.org/10.1016/0006-8993(93)91400-M Get rights and content

Abstract

The distribution of the enzyme nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase was examined histochemically in the retina, iris, ciliary processes, cornea and conjunctiva of the rabbit eye. The epithelial cells of the ciliary process, iris, conjunctiva and, to a lesser extent, the cornea all showed intense staining. In the retina, staining for NADPH diaphorase was intense in the inner segments of the photoreceptors and a sparsely distributed population of amacrine cells. In addition, another population of amacrine cells, some presumed ganglion cells as well as a number of horizontal cells, stained less intensely for the enzyme. The retina, ciliary processes and, as a comparison, the cerebellum of the rabbit all contain nitric oxide synthetase (NOS) activity, as each tissue can metabolize citrulline from arginine. This process is Ca²⁺ dependent and is reduced by the NOS inhibitor, N^G-monomethyl-l-arginine. The presence of NOS activity in the ciliary processes and the localization of NADPH diaphorase in the ciliary epithelial cells are of significance as they suggest that the ciliary epithelial cells may contain NOS which would imply a role for nitric oxide in aqueous humour production.

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The ocular surface immune system can be regulated by NO produced by NOS enzymes expressed in endothelial cells of blood vessels and various of immune cells [142]. Possible NO activity has been identified in epithelial cells of the conjunctiva using NADPH diaphorase staining [133]. Nitrite has been found in ocular surface lavage fluid at a concentration of 10.3 ± 0.9 μM and it has also been hypothesized that this was produced from NO via eNOS in endothelial cells [143].
Nitric oxide (NO) has a wide array of biological functions including the regulation of vascular tone, neurotransmission, immunomodulation, stimulation of proinflammatory cytokine expression and antimicrobial action. These functions may depend on the type of isoform that is responsible for the synthesis of NO. NO is found in various ocular tissues playing a pivotal role in physiological mechanisms, namely regulating vascular tone in the uvea, retinal blood circulation, aqueous humor dynamics, neurotransmission and phototransduction in retinal layers. Unregulated production of NO in ocular tissues may result in production of toxic superoxide free radicals that participate in ocular diseases such as endotoxin-induced uveitis, ischemic proliferative retinopathy and neurotoxicity of optic nerve head in glaucoma. However, the role of NO on the ocular surface in mediating physiology and pathophysiological processes is not fully understood. Moreover, methods used to measure levels of NO in the biological samples of the ocular surface are not well established due to its rapid oxidation. The purpose of this review is to highlight the role of NO in the physiology and pathophysiology of ocular surface and propose suitable techniques to measure NO levels in ocular surface tissues and tears. This will improve the understanding of NO's role in ocular surface biology and the development of new NO-based therapies to treat various ocular surface diseases. Further, this review summarizes the biochemistry underpinning NO's antimicrobial action.
The vital role for nitric oxide in intraocular pressure homeostasis
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Citation Excerpt :
Immuno-affinity studies of intact porcine tissues show that ciliary epithelial cells express nNOS and iNOS (Meyer et al., 1999) and expression is retained by non-pigmented epithelial cells in culture (Shahidullah et al., 2007). These findings were validated using a second method, whereby NADPH diaphorase staining (reflective of NOS activity) localized to ciliary epithelium of rabbit (Osborne et al., 1993). Another study using a biochemical activity assay of dissected ciliary processes showed presence of a constitutive form of NOS (nNOS or eNOS) in bovine eyes (Geyer et al., 1997).
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Mechanical stretch and increases in arteriolar transmural pressure induce the endothelial cells to release contracting factors affecting the tone of arteriolar smooth muscle cells and pericytes. Close interaction between nitric oxide (NO), lactate, arachidonic acid metabolites, released by the neuronal and glial cells during neural activity and energy-generating reactions of the retina strive to optimize blood flow according to the metabolic needs of the tissue. NO, which plays a central role in neurovascular coupling, may exert its effect, by modulating glial cell function involved in such vasomotor responses.
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The purpose of this study was to evaluate the ability of the predominant carotenoids (lutein and zeaxanthin) of the macular pigment of the human retina, to protect SK-N-SH human neuroblastoma cells against DNA damage induced by different RNOS donors. Although astaxanthin has never been isolated from the human eye, it was included in this study because its structure is very close to that of lutein and zeaxanthin and because it affords protection from UV-light. DNA damage was induced by GSNO-MEE, a nitric oxide donor, by Na₂N₂O₃, a nitroxyl anion donor and by SIN-1, a peroxynitrite-generating agent.
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NADPH diaphorase localization and nitric oxide synthetase activity in the retina and anterior uvea of the rabbit eye

Abstract

Neuron

Neurosci. Lett.

Brain Res.

J. Neurosci. Methods

Brain Res.

Nitric oxide mediates glutamate-linked enhancement of cGMP levels in the cerebellum

Nitric oxide synthetase and neuronal NADPH-diaphorase are identical in brain and peripheral tissues

A method for the demonstration of NADPH-diaphorase activity in anuran species using unfixed retinal whole mounts

Arch. Histol. Cytol.

Development of catecholaminergic, indoleamine-accumulating and NADPH-diaphorase amacrine cells in rabbit retinae

J. Comp. Neurol.