cytochrome-c-t and Glaucoma

Glaucoma is a neurodegenerative disease of visual system characterized by gradual loss of retinal ganglion cells (RGC). Since mitochondrial dysfunction of RGC is significantly involved in the pathological mechanisms of glaucoma, and hydrogen sulfide (H

Topics: Animals; Cytochromes c; Disease Models, Animal; Glaucoma; Hydrogen Sulfide; Mitochondria; Neurodegenerative Diseases; Rats; Reactive Oxygen Species; Retinal Ganglion Cells

To determine whether intraocular pressure (IOP) elevation alters OPA1 expression and triggers OPA1 release, as well as whether the uncompetitive N-methyl-d-aspartate (NMDA) glutamate receptor antagonist memantine blocks OPA1 release and subsequent apoptotic cell death in glaucomatous DBA/2J mouse retina.. Preglaucomatous DBA/2J mice received memantine (5 mg/kg, intraperitoneal injection, twice daily for 3 months) and IOP in the eyes was measured monthly. RGC loss was counted after FluoroGold labeling. OPA1, Dnm1, Bcl-2, and Bax mRNA were measured by qPCR. OPA1 protein was assessed by immunohistochemistry and Western blot. Apoptotic cell death was assessed by TUNEL staining.. Memantine treatment significantly increased RGC survival in glaucomatous DBA/2J mice and increased the 75-kDa OPA1 isoform, but did not alter the 80- and 90-kDa isoforms. The isoforms of OPA1 were significantly increased in the cytosol of the vehicle-treated glaucomatous retinas but were significantly decreased in memantine-treated glaucomatous retinas. OPA1 immunoreactivity was decreased in the photoreceptors of both vehicle- and memantine-treated glaucomatous retinas, but was increased in the outer plexiform layer of only the memantine-treated glaucomatous retinas. Memantine blocked apoptotic cell death in the GCL, increased Bcl-2 gene expression, and decreased Bax gene expression.. OPA1 release from mitochondria in glaucomatous mouse retina is inhibited by blockade of glutamate receptor activation. Because this OPA1 effect was accompanied by increased Bcl-2 expression, decreased Bax expression, and apoptosis blockade, glutamate receptor activation in the glaucomatous retina may involve a distinct mitochondria-mediated cell death pathway.

Topics: Animals; Apoptosis; bcl-2-Associated X Protein; Blotting, Western; Cell Survival; Cytochromes c; Dynamin I; Excitatory Amino Acid Antagonists; Female; Gene Expression; Glaucoma; GTP Phosphohydrolases; Immunohistochemistry; In Situ Nick-End Labeling; Injections, Intraperitoneal; Intraocular Pressure; Memantine; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Mitochondria; Polymerase Chain Reaction; Proto-Oncogene Proteins c-bcl-2; Receptors, N-Methyl-D-Aspartate; Retinal Diseases; Retinal Ganglion Cells; RNA, Messenger

Increased intraocular pressure (IOP) leads, by an unknown mechanism, to apoptotic retinal ganglion cell (RGC) death in glaucoma. We now report cleavage of the autoinhibitory domain of the protein phosphatase calcineurin (CaN) in two rodent models of increased IOP. Cleaved CaN was not detected in rat or mouse eyes with normal IOP. In in vitro systems, this constitutively active cleaved form of CaN has been reported to lead to apoptosis via dephosphorylation of the proapoptotic Bcl-2 family member, Bad. In a rat model of glaucoma, we similarly detect increased Bad dephosphorylation, increased cytoplasmic cytochrome c (cyt c), and RGC death. Oral treatment of rats with increased IOP with the CaN inhibitor FK506 led to a reduction in Bad dephosphorylation and cyt c release. In accord with these biochemical results, we observed a marked increase in both RGC survival and optic nerve preservation. These data are consistent with a CaN-mediated mechanism of increased IOP toxicity. CaN cleavage was not observed at any time after optic nerve crush, suggesting that axon damage alone is insufficient to trigger cleavage. These findings implicate this mechanism of CaN activation in a chronic neurodegenerative disease. These data demonstrate that increased IOP leads to the initiation of a CaN-mediated mitochondrial apoptotic pathway in glaucoma and support neuroprotective strategies for this blinding disease.

Topics: Analysis of Variance; Animals; Apoptosis; bcl-Associated Death Protein; Blotting, Western; Calcineurin; Calcineurin Inhibitors; Cytochromes c; Female; Glaucoma; Intraocular Pressure; Male; Mice; Mice, Inbred DBA; Mitochondria; Optic Nerve; Phosphorylation; Rats; Rats, Inbred BN; Retinal Ganglion Cells; Tacrolimus