Purchase this article with an account.
Y. He, J. Ge, T.-T. Joyce; Mitochondrial Defects and Dysfunction in Calcium Regulation in Glaucomatous Trabecular Meshwork Cells. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4887.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Disruption in intracellular calcium ion (Ca2+) homeostasis has important consequences for health. Persistent Ca2+ overload induces mitochondrial permeability transition pore (MPTP) opening prompting mitochondrial release of calcium (mCICR) and ROS into the cytosol which, in turn, compromises mitochondrial function. Here, we examined intracellular Ca2+ levels and mitochondrial vulnerability to Ca2+ stress in trabecular meshwork (TM) of individuals with primary open angle glaucoma (POAG).
Primary cultures of TM cells from POAG (GTM) and age-matched, non-diseased (NTM) individuals obtained by standard surgical trabeculectomy, from postmortem donors eyes, were treated with the following calcium regulators: mitochondrial respiratory chain I inhibitor, rotenone (ROT); mitochondrial permeability transition pore (MPTP) inhibitor, cyclosporine A (CsA) and aristolochic acid (ArA); Ca2+ chelators, BAPTA/AM, or EDTA; mitochondrial Ca2+ uniporter inhibitor, ruthenium red (RR); Ca2+/Na+ exchanger inhibitor, trifluoperazine; and the inositol 1,4,5-triphosphate receptor type 3 (IP3R) inhibitors, 2-aminoethoxydiphenyl borane (2-APB) or Xestospongin C (Xe-C). Ca2+ concentrations in the cytoplasm ([Ca2+]c) and mitochondria ([Ca2+]m) were determined by confocal microscopy and flow cytometry using the fluorescent Ca2+ indicators, fluo-3/AM and rhod-2/AM, respectively. Mitochondrial membrane potential (ΔΨm) was examined using the fluorescent probe tetramethylrhodamine ethyl ester (TMRE). We also studied the expression of cyclophilin D, a protein that induces MPTP opening.
There was increased [Ca2+]c, [Ca2+]m, mCICR, MPTP opening and expression of cyclophilin D, and decreased ΔΨm in POAG TM cells compared to controls. ROT artificially exacerbated these conditions in GTM cells. Chelation of [Ca2+]c and inhibition of IP3R and MPTP opening suppressed mitochondrial dysfunction and reduced the additional effects of ROT in GTM cells.
We propose that POAG TM cells have defective mitochondrial function, which causes them to be abnormally vulnerable to Ca2+ stress. The dysfunction in calcium regulation by these cells may contribute to the failure of this tissue to control IOP. Pharmacological inhibitors of IP3R, MPTP opening, and cyclophilin D could have clinical implications for primary open angle glaucoma.
This PDF is available to Subscribers Only