minocycline and Optic-Nerve-Diseases

The second-generation tetracycline, minocycline, has been shown to exhibit neuroprotective therapeutic benefits in many neurodegenerative diseases including experimental glaucoma and optic nerve transection (ONT). This study investigated the mechanism underlying minocycline neuroprotection in a model of ONT. ONT was applied unilaterally in 36 Wistar rat eyes. The rats were randomly divided into a minocycline (22 mg/kg/d) treatment group and a saline treatment group (control). Treatment (minocycline or saline) was given by intraperitoneal injections initiated 3 d before ONT and continued daily until the end of the experiment. The involvement of pro-apoptotic, pro-survival and inflammatory pathways was analyzed by quantitative Real-Time Polymerase Chain Reaction at 4 h and 3 d after the transection in both treatment groups. The involvement of Bcl-2 protein was evaluated by immunohistochemistry. We found that Minocycline significantly increased the expression of the antiapoptotic gene bcl-2 4 h after transection (n = 8, p = 0.008) and decreased the expression of Bax at the same time point (n = 8, p = 0.03). Tumor Necrosis Factor α (TNFα), Inhibitor of Apoptosis Protein (IAP1) and Gadd45α were significantly upregulated in the retinas of eyes with ONTs compared to control (n = 10 for each gene, p = 0.02, p = 0.03, p = 0.04, respectively) but this effect was unaffected by minocycline. This study further support that the mechanism underlying minocycline neuroprotection involves the Bcl-2 gene family, suggesting that minocycline has antiapoptotic properties that support its value as a promising neuroprotective drug.

Topics: Animals; Baculoviral IAP Repeat-Containing 3 Protein; bcl-2-Associated X Protein; Cell Cycle Proteins; Cytokines; Disease Models, Animal; Gene Expression Regulation; Inhibitor of Apoptosis Proteins; Minocycline; Neuroprotective Agents; Nitric Oxide Synthase Type II; Nuclear Proteins; Optic Nerve Diseases; Proto-Oncogene Proteins c-bcl-2; Rats; Rats, Wistar; Retina; RNA, Messenger; Thy-1 Antigens; Time Factors

Minocycline, a second-generation tetracycline with anti-inflammatory and anti-apoptotic properties, was reported to be neuroprotective in experimental glaucoma and optic nerve transection as well as in other neurodegenerative diseases. The purpose of this study was to investigate the mechanism underlying that neuroprotective effect in murine glaucoma.. Elevated intraocular pressure was induced in 159 rats by the translimbal photocoagulation laser model. Minocycline 22 mg/kg or saline was injected intraperitoneally starting 3 days before the induction of glaucoma, and continued daily until the animals were sacrificed. The effect of minocycline on gene expression was evaluated using a quantitative polymerase chain reaction (PCR) array for apoptosis. The involvement of selected pro-apoptotic, pro-survival, and inflammatory genes was further analyzed by quantitative real-time PCR at multiple time points. Immunohistochemistry was used to study the effect of minocycline on microglial activation and to localize Bcl-2 changes.. Minocycline significantly increased the anti-apoptotic gene Bcl-2 expression at day 8 and day 14 after the induction of glaucoma (p = 0.04 and p = 0.03 respectively), and decreased IL-18 expression in the retina at day 14 and day 30 (p = 0.04 and p < 0.001 respectively). PCR arrays suggested that additional genes were affected by minocycline, including Tp53bp2, TRAF4, osteoprotegerin, caspase 1 and 4, and members of the tumor necrosis factor superfamily. Additionally, minocycline decreased the amount of activated microglia in glaucomatous eyes.. These results suggest that minocycline upregulates pro-survival genes and downregulates apoptotic genes, thus shifting the balance toward the anti-apoptotic side in experimental glaucoma.

Topics: Animals; Anti-Bacterial Agents; Apoptosis Regulatory Proteins; bcl-2-Associated X Protein; bcl-Associated Death Protein; Disease Models, Animal; Gene Expression Regulation; Glaucoma; Injections, Intraperitoneal; Interleukin-18; Microglia; Minocycline; Optic Nerve Diseases; Proto-Oncogene Proteins c-bcl-2; Rats; Rats, Wistar; Real-Time Polymerase Chain Reaction; Retinal Ganglion Cells; Up-Regulation

To investigate the mechanism of secondary degeneration of the optic nerve, and to evaluate the neuroprotective effect of minocycline in this process.. A partial transection model that morphologically separates primary and secondary degeneration was applied unilaterally in 152 Wistar rat eyes. The involvement of pro-apoptotic, pro-survival and inflammatory pathways was analyzed by quantitative real-time PCR and immunohistochemistry at multiple time points. The neuroprotective effect of daily intraperitoneal injections of minocycline 22 mg/kg/day was evaluated at 7, 11 and 21 days post-injury. Retrograde labeling of retinal ganglion cells (RGCs) with fluorogold was via the superior colliculus, and surviving RGCs were counted using retinal whole mounts.. Both primary and secondary degeneration led to a significant up-regulation of the pro-apoptotic genes, GADD45α, ei24 and CDK2, and the pro-survival gene, IAP-1. These processes differed, however, in their reaction to minocycline. Minocycline protected RGC death from secondary degeneration at 11 days (6 ± 8% loss compared to 37 ± 7% in the saline-treated group, n = 15, P = 0.012), and at 21 days (42 ± 7% versus 64 ± 7% respectively, n = 15, P = 0.06) after partial transection. In contrast, its effect on primary degeneration was not significant.. While the genetic profile supported similarities between primary and secondary degeneration of the optic nerve, the specific effect of minocycline on secondary degeneration revealed a potential difference between the two. The mechanism underlying secondary degeneration, and its role in optic neuropathies such as glaucoma, awaits further studies.

Topics: Animals; Apoptosis Regulatory Proteins; Baculoviral IAP Repeat-Containing 3 Protein; Cell Cycle Proteins; Cell Survival; Cyclin-Dependent Kinase 2; Disease Models, Animal; Gene Expression Regulation; Immunohistochemistry; Inhibitor of Apoptosis Proteins; Injections, Intraperitoneal; Minocycline; Nerve Crush; Nerve Degeneration; Neuroprotective Agents; Nuclear Proteins; Optic Nerve Diseases; Rats; Rats, Wistar; Retinal Ganglion Cells; Reverse Transcriptase Polymerase Chain Reaction

In the context of the retinal ganglion cell (RGC) axon degeneration in the optic nerve that occurs in glaucoma, microglia become activated, then phagocytic, and redistribute in the optic nerve head. The authors investigated the potential contribution of retinal microglia activation to glaucoma progression in the DBA/2J chronic mouse glaucoma model.. The authors treated 6-week-old DBA/2J mice for 25 weeks with minocycline, a tetracycline derivative known to reduce microglia activation and to improve neuronal survival in other models of neurodegenerative disease. They quantified RGC numbers and characterized microglia activation, gliosis, and both axonal integrity and retrograde tracer transport by RGCs in mice systemically treated with minocycline or vehicle only.. Minocycline reduced microglial activation and improved RGC axonal transport and integrity, yet it had no effect on the characteristic age-related ocular changes that lead to chronically elevated pressure and did not alter Müller or astrocyte gliosis. Specifically, minocycline increased the fraction of microglia with resting ramified morphology and reduced levels of Iba1 mRNA and protein, a microglia-specific calcium ligand linked to activation. The reduction in microglial activation was coupled to significant improvement in RGC axonal transport, as measured by neuronal retrograde tracing from the superior colliculus. Finally, minocycline treatment significantly decoupled RGC axon loss from increased intraocular pressure.. These observations suggest that in glaucoma, retina and optic nerve head microglia activation may be a factor in the early decline in function of the optic nerve and its subsequent degeneration.

Topics: Animals; Axonal Transport; Calcium-Binding Proteins; Cell Survival; Disease Models, Animal; Glaucoma; Gliosis; Injections, Intraperitoneal; Intraocular Pressure; Mass Spectrometry; Mice; Mice, Inbred DBA; Microfilament Proteins; Microglia; Minocycline; Neuroprotective Agents; Optic Nerve Diseases; Retina; Retinal Ganglion Cells; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger