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Peter Koulen, Andrew J Payne, Krupa R Patel, Yuliya Naumchuk, Simon Kaja; Inositol 1, 4, 5-trisphosphate receptors and ryanodine receptors control intracellular calcium signaling in adult rat optic nerve head astrocytes. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2274.
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© ARVO (1962-2015); The Authors (2016-present)
In glaucomatous retinopathy, pathological changes to optic nerve head astrocytes (ONHAs) include activation, migration, extracellular matrix remodeling and altered gene and protein expression. However, little is known regarding intracellular signaling pathways in ONHAs. We conducted a detailed quantitative analysis of intracellular Ca2+ signaling in ONHAs.
We optimized the culture of primary cultured adult rat ONHAs and performed a detailed immunocytochemical analysis of expression and distribution of intracellular Ca2+ channels. Optical imaging of the intracellular Ca2+ concentration was used to determine the ion channel-specific contributions to stimulus-induced Ca2+ release from intracellular stores.
We identified strong immunoreactivities for type 1 and type 2 inositol 1, 4, 5-trisphosphate receptors (IP3Rs) in the endoplasmic reticulum and the nuclear envelope, respectively. Immunoreactivity for type 3 IP3R was not detected in primary cultured ONHAs. All ryanodine receptor (RyR) subtypes showed strong immunoreactivity in primary cultured ONHAs. Our functional analyses revealed significant responses to pharmacological stimulus-induced intracellular Ca2+ release from both IP3Rs and RyRs. Subcellular quantification of intracellular Ca2+ transients showed differential IP3R-mediated Ca2+ release in nuclear vs. cytosolic compartments indicating a strong correlation with the differential subcellular distribution of IP3R subtypes and type 2 IP3R as the major contributor to intracellular Ca2+ release.
ONHAs utilize differentially distributed intracellular Ca2+ channels to control their intracellular Ca2+ homeostasis. Our data provides a critical foundation for future studies investigating potential changes in Ca2+ signaling in ONHAs as a result of glaucomatous retinopathy. Furthermore, our protocol for primary culture of adult rat ONHAs provides new feasibility data for using ONHAs for drug discovery research for glaucomatous retinopathy and related disorders affecting the optic nerve and optic nerve head.
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