title: Combined suppression of CASP2 and CASP6 protects retinal ganglion cells from apoptosis and promotes axon regeneration through CNTF-mediated JAK/STAT signalling.
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.
authors.affiliation: 1 Neurotrauma and Neurodegeneration Section, School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, B15 2TT, UK z.ahmed.1@bham.ac.uk.
authors.forename: Vasanthy
authors.initials: V
authors.lastname: Vigneswara
authors.affiliation: 2 Department of Pathology and Cell Biology, Neurology, Taub Institute for Research on Alzheimer's Disease and the Ageing Brain, Columbia University Medical Centre, New York, USA.
authors.forename: Nsikan
authors.initials: N
authors.lastname: Akpan
authors.affiliation: 1 Neurotrauma and Neurodegeneration Section, School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, B15 2TT, UK.
authors.forename: Martin
authors.initials: M
authors.lastname: Berry
authors.affiliation: 1 Neurotrauma and Neurodegeneration Section, School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, B15 2TT, UK.
authors.forename: Ann
authors.initials: A
authors.lastname: Logan
authors.affiliation: 2 Department of Pathology and Cell Biology, Neurology, Taub Institute for Research on Alzheimer's Disease and the Ageing Brain, Columbia University Medical Centre, New York, USA.
authors.forename: Carol M
authors.initials: CM
authors.lastname: Troy
authors.affiliation: 1 Neurotrauma and Neurodegeneration Section, School of Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Birmingham, B15 2TT, UK.
authors.forename: Zubair
authors.initials: Z
authors.lastname: Ahmed
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D001369:Axons / Q000378:metabolism*; D053143:Caspase 2 / Q000378:metabolism*; D053178:Caspase 6 / Q000378:metabolism*; D020934:Ciliary Neurotrophic Factor / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D009416:Nerve Regeneration / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D009900:Optic Nerve / Q000378:metabolism; D020221:Optic Nerve Injuries / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000502:physiology
chemical_list: D020934:Ciliary Neurotrophic Factor; D050796:STAT3 Transcription Factor; C490360:CASP2 protein, human; C505514:CASP6 protein, human; D053143:Caspase 2; D053178:Caspase 6; D003546:Cysteine Endopeptidases
keywords: CASP2; CASP6; apoptosis; axon regeneration; optic nerve; retinal ganglion cells
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