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Subunits of the epithelial sodium channel family are differentially expressed in the retina of mice with ocular hypertension
Author(s) -
Dyka Frank M.,
May Christian A.,
Enz Ralf
Publication year - 2005
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2005.03177.x
Subject(s) - epithelial sodium channel , retina , retinal pigment epithelium , ganglion cell layer , biology , intraocular pressure , optic nerve , ganglion , microbiology and biotechnology , endocrinology , anatomy , medicine , sodium , ophthalmology , chemistry , neuroscience , organic chemistry
Glaucoma is a prevalent cause of blindness, resulting in the apoptotic death of retinal ganglion cells and optic nerve degeneration. The disease is often associated with elevated intraocular pressure, however, molecular mechanisms involved in ganglion cell death are poorly understood. To identify proteins contributing to this pathological process, we analysed the retinal gene expression of DBA/2J mice that develop an elevated intraocular pressure by the age of 6 months with subsequent ganglion cell loss. In this study, we identified subunits of the epithelial sodium channel (ENaC) family that are specifically expressed under elevated intraocular pressure. Using reverse transcriptase polymerase chain reaction we observed a significant increase of α‐ENaC in the neuronal retina of DBA/2J mice when compared with control animals, while β‐ENaC and γ‐ENaC were not detectable in this tissue. Specific immune sera to ENaC subunits showed up‐regulation of α‐ENaC in synaptic and nuclear layers of the retina, and in the retinal pigment epithelium. Consistent with our polymerase chain reaction data, β‐ENaC was not detected by specific antibodies in the retina, while γ‐ENaC was only present in the retinal pigment epithelium under ocular hypertension. Finally, the increase of α‐ENaC gene expression in the neuronal retina and the retinal pigment epithelium was not observed in other tissues of DBA/2J mice. Since the intraocular pressure is regulated by the transport of aqueous humour across epithelial structures of the eye that in turn is associated with ion flux, the specific up‐regulation of ENaC proteins could serve as a protecting mechanism against elevated intraocular pressure.