Article

Ocular neuroprotection by siRNA targeting caspase-2

Neuropharmacology and Neurobiology Section, School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK.
Cell Death & Disease (Impact Factor: 5.01). 06/2011; 2(6):e173. DOI: 10.1038/cddis.2011.54
Source: PubMed

ABSTRACT

Retinal ganglion cell (RGC) loss after optic nerve damage is a hallmark of certain human ophthalmic diseases including ischemic optic neuropathy (ION) and glaucoma. In a rat model of optic nerve transection, in which 80% of RGCs are eliminated within 14 days, caspase-2 was found to be expressed and cleaved (activated) predominantly in RGC. Inhibition of caspase-2 expression by a chemically modified synthetic short interfering ribonucleic acid (siRNA) delivered by intravitreal administration significantly enhanced RGC survival over a period of at least 30 days. This exogenously delivered siRNA could be found in RGC and other types of retinal cells, persisted inside the retina for at least 1 month and mediated sequence-specific RNA interference without inducing an interferon response. Our results indicate that RGC apoptosis induced by optic nerve injury involves activation of caspase-2, and that synthetic siRNAs designed to inhibit expression of caspase-2 represent potential neuroprotective agents for intervention in human diseases involving RGC loss.

Download full-text

Full-text

Available from: Zubair Ahmed
  • Source
    • "The most advanced programs for ocular indications are Quark's QPI-007 designed to silence Caspase 2, currently in Phase II/III for the treatment of Non-arteritic Anterior Ischemic Optic Neuropathy (NAION) and Sylentis' bamosiran (SYL040012), targeting β2-Adrenergic Receptor (ADRB2) for the treatment of glaucoma, in phase IIb. QPI- 1007 is a 19-nt modified siRNA that has shown to be safe when injected intravitreally (IVT) to animal models and humans (Ahmed et al., 2011; Solano et al., 2014). The compound is currently being investigated in a phase II/III trial to analyze whether multiple IVT doses of this compound are able to improve visual acuity in patients suffering NAION. "
    [Show abstract] [Hide abstract]
    ABSTRACT: RNA interference is a cellular mechanism by which small molecules of double stranded RNA modulate gene ex-pression acting on the concentration and/or availability of a given messenger RNA. Almost 10 years after Fire and Mello received the Nobel Prize for the discovery of this mechanism in flat worms, RNA interference is on the edge of becoming a new class of therapeutics. With various phase III studies underway, the following years will determine whether RNAi-therapeutics can rise up to the challenge and become mainstream medicines. The present review gives a thorough overview of the current status of this technology focusing on the path to the clinic of this new class of compounds.
    Full-text · Article · Jun 2015 · EXCLI Journal
  • Source
    • "In further experiments, 5 mM of Pen1 or Pen1-C6DN was injected. Intravitreal injections were repeated every 7 days based on previous experiments with other caspase inhibitors (Ahmed et al., 2011). Twenty micrograms per eye of siCASP2 was injected along with either 5 mM Pen1 or Pen1-C6DN. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We have previously shown that crushing the optic nerve induces death of retinal ganglion cells by apoptosis, but suppression of CASP2, which is predominantly activated in retinal ganglion cells, using a stably modified short interfering RNA CASP2, inhibits retinal ganglion cell apoptosis. Here, we report that combined delivery of short interfering CASP2 and inhibition of CASP6 using a dominant negative CASP6 mutant activates astrocytes and Müller cells, increases CNTF levels in the retina and leads to enhanced retinal ganglion cell axon regeneration. In dissociated adult rat mixed retinal cultures, dominant negative CASP6 mutant + short interfering CASP2 treatment also significantly increases GFAP(+) glial activation, increases the expression of CNTF in culture, and subsequently increases the number of retinal ganglion cells with neurites and the mean retinal ganglion cell neurite length. These effects are abrogated by the addition of MAB228 (a monoclonal antibody targeted to the gp130 component of the CNTF receptor) and AG490 (an inhibitor of the JAK/STAT pathway downstream of CNTF signalling). Similarly, in the optic nerve crush injury model, MAB228 and AG490 neutralizes dominant negative CASP6 mutant + short interfering CASP2-mediated retinal ganglion cell axon regeneration, Müller cell activation and CNTF production in the retina without affecting retinal ganglion cell survival. We therefore conclude that axon regeneration promoted by suppression of CASP2 and CASP6 is CNTF-dependent and mediated through the JAK/STAT signalling pathway. This study offers insights for the development of effective therapeutics for promoting retinal ganglion cell survival and axon regeneration.
    Full-text · Article · Apr 2014 · Brain
  • Source
    • "If an AMPAR lacks a GluA2 subunit, then it will be permeable to Ca2+. The presence of a GluA2 subunit will almost always render the channel impermeable to Ca2+ [8]. This is determined by post- transcriptional modification-RNA editing of the Q/R editing site of the GluA2 mRNA. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Glaucoma is a progressive neurodegenerative disease of retinal ganglion cells (RGCs) associated with characteristic axon degeneration in the optic nerve. Excitotoxic damage due to increased Ca2+ influx, possibly through NMDA-type glutamate receptors, has been proposed to be a cause of RGC dysfunction and death in glaucoma. Recent work has found that expression of another potentially critical receptor, the Ca2+-permeable AMPA receptor (CP-AMPAR), is elevated during various pathological conditions (including ALS and ischemia), resulting in increased neuronal death. Here we test the hypothesis that CP-AMPARs contribute to RGC death due to elevated Ca2+ influx in glaucoma. AMPA receptors are impermeable to Ca2+ if the tetrameric receptor contains a GluA2 subunit that has undergone Q/R RNA editing at a site in the pore region. The activity of ADAR2, the enzyme responsible for this RNA editing, generally ensures that the vast majority of GluA2 proteins are edited. Here, we demonstrate that ADAR2 levels decrease in a mouse model of glaucoma in which IOP is chronically elevated. Furthermore, using an in vitro model of RGCs, we find that knockdown of ADAR2 using siRNA increased the accumulation of Co2+ in response to glutamate, and decreased the rectification index of AMPA currents detected electrophysiologically, indicating an increased Ca2+ permeability through AMPARs. The RGCs in primary culture also exhibited increased excitotoxic cell death following knock down of ADAR2. Furthermore, cell death was reversed by NASPM, a specific blocker for CP-AMPARs. Together, our data suggest that chronically elevated IOP in adult mice reduces expression of the ADAR2 enzyme, and the loss of ADAR2 editing and subsequent disruption of GluA2 RNA editing might potentially play a role in promoting RGC neuronal death as observed in glaucoma.
    Full-text · Article · Mar 2014 · PLoS ONE
Show more