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Savigni DL, O'Hare Doig RL, Szymanski CR, Bartlett CA, Lozić I, Smith NM, Fitzgerald M. Three Ca2+ channel inhibitors in combination limit chronic secondary degeneration following neurotrauma. Neuropharmacology 2013; 75:380-90. [PMID: 23958451 DOI: 10.1016/j.neuropharm.2013.07.034] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 07/24/2013] [Accepted: 07/30/2013] [Indexed: 01/29/2023]
Abstract
Following neurotrauma, cells beyond the initial trauma site undergo secondary degeneration, with excess Ca2+ a likely trigger for loss of neurons, compact myelin and function. Treatment using inhibitors of specific Ca2+ channels has shown promise in preclinical studies, but clinical trials have been disappointing and combinatorial approaches are needed. We assessed efficacy of multiple combinations of three Ca2+ channel inhibitors at reducing secondary degeneration following partial optic nerve transection in rat. We used lomerizine to inhibit voltage gated Ca2+ channels; oxidised adenosine-triphosphate (oxATP) to inhibit purinergic P2X7 receptors and/or 2-[7-(1H-imidazol-1-yl)-6-nitro-2,3-dioxo-1,2,3,4-tetrahydro quinoxalin-1-yl]acetic acid (INQ) to inhibit Ca2+ permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. Only the three Ca2+ channel inhibitors delivered in combination significantly preserved visual function, as assessed using the optokinetic nystagmus visual reflex, at 3 months after injury. Preservation of retinal ganglion cells was partial and is unlikely to have accounted for differential effects on function. A range of the Ca2+ channel inhibitor combinations prevented swelling of optic nerve vulnerable to secondary degeneration. Each of the treatments involving lomerizine significantly increased the proportion of axons with normal compact myelin. Nevertheless, limiting decompaction of myelin was not sufficient for preservation of function in our model. Multiple combinations of Ca2+ channel inhibitors reduced formation of atypical node/paranode complexes; outcomes were not associated with preservation of visual function. However, prevention of lengthening of the paranodal gap that was only achieved by treatment with the three Ca2+ channel inhibitors in combination was an important additional effect that likely contributed to the associated preservation of the optokinetic reflex using this combinatorial treatment strategy.
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Affiliation(s)
- Donna L Savigni
- Experimental and Regenerative Neurosciences, The University of Western Australia, Crawley, WA 6009, Australia; School of Animal Biology, The University of Western Australia, Crawley, WA 6009, Australia
| | - Ryan L O'Hare Doig
- Experimental and Regenerative Neurosciences, The University of Western Australia, Crawley, WA 6009, Australia; School of Animal Biology, The University of Western Australia, Crawley, WA 6009, Australia
| | - Charis R Szymanski
- Experimental and Regenerative Neurosciences, The University of Western Australia, Crawley, WA 6009, Australia; School of Animal Biology, The University of Western Australia, Crawley, WA 6009, Australia
| | - Carole A Bartlett
- Experimental and Regenerative Neurosciences, The University of Western Australia, Crawley, WA 6009, Australia; School of Animal Biology, The University of Western Australia, Crawley, WA 6009, Australia
| | - Ivan Lozić
- Experimental and Regenerative Neurosciences, The University of Western Australia, Crawley, WA 6009, Australia; School of Chemistry and Biochemistry, The University of Western Australia, Crawley, WA 6009, Australia
| | - Nicole M Smith
- Experimental and Regenerative Neurosciences, The University of Western Australia, Crawley, WA 6009, Australia; School of Chemistry and Biochemistry, The University of Western Australia, Crawley, WA 6009, Australia
| | - Melinda Fitzgerald
- Experimental and Regenerative Neurosciences, The University of Western Australia, Crawley, WA 6009, Australia; School of Animal Biology, The University of Western Australia, Crawley, WA 6009, Australia.
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Szymanski CR, Chiha W, Morellini N, Cummins N, Bartlett CA, O'Hare Doig RL, Savigni DL, Payne SC, Harvey AR, Dunlop SA, Fitzgerald M. Paranode Abnormalities and Oxidative Stress in Optic Nerve Vulnerable to Secondary Degeneration: Modulation by 670 nm Light Treatment. PLoS One 2013; 8:e66448. [PMID: 23840470 PMCID: PMC3686728 DOI: 10.1371/journal.pone.0066448] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 05/05/2013] [Indexed: 11/25/2022] Open
Abstract
Secondary degeneration of nerve tissue adjacent to a traumatic injury results in further loss of neurons, glia and function, via mechanisms that may involve oxidative stress. However, changes in indicators of oxidative stress have not yet been demonstrated in oligodendrocytes vulnerable to secondary degeneration in vivo. We show increases in the oxidative stress indicator carboxymethyl lysine at days 1 and 3 after injury in oligodendrocytes vulnerable to secondary degeneration. Dihydroethidium staining for superoxide is reduced, indicating endogenous control of this particular reactive species after injury. Concurrently, node of Ranvier/paranode complexes are altered, with significant lengthening of the paranodal gap and paranode as well as paranode disorganisation. Therapeutic administration of 670 nm light is thought to improve oxidative metabolism via mechanisms that may include increased activity of cytochrome c oxidase. Here, we show that light at 670 nm, delivered for 30 minutes per day, results in in vivo increases in cytochrome c oxidase activity co-localised with oligodendrocytes. Short term (1 day) 670 nm light treatment is associated with reductions in reactive species at the injury site. In optic nerve vulnerable to secondary degeneration superoxide in oligodendrocytes is reduced relative to handling controls, and is associated with reduced paranode abnormalities. Long term (3 month) administration of 670 nm light preserves retinal ganglion cells vulnerable to secondary degeneration and maintains visual function, as assessed by the optokinetic nystagmus visual reflex. Light at a wavelength of 670 nm may serve as a therapeutic intervention for treatment of secondary degeneration following neurotrauma.
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Affiliation(s)
- Charis R. Szymanski
- Experimental and Regenerative Neurosciences, School of Animal Biology, The University of Western Australia, Crawley, Western Australia, Australia
| | - Wissam Chiha
- Experimental and Regenerative Neurosciences, School of Animal Biology, The University of Western Australia, Crawley, Western Australia, Australia
| | - Natalie Morellini
- Experimental and Regenerative Neurosciences, School of Animal Biology, The University of Western Australia, Crawley, Western Australia, Australia
| | - Nadia Cummins
- Experimental and Regenerative Neurosciences, School of Animal Biology, The University of Western Australia, Crawley, Western Australia, Australia
| | - Carole A. Bartlett
- Experimental and Regenerative Neurosciences, School of Animal Biology, The University of Western Australia, Crawley, Western Australia, Australia
| | - Ryan L. O'Hare Doig
- Experimental and Regenerative Neurosciences, School of Animal Biology, The University of Western Australia, Crawley, Western Australia, Australia
| | - Donna L. Savigni
- Experimental and Regenerative Neurosciences, School of Animal Biology, The University of Western Australia, Crawley, Western Australia, Australia
| | - Sophie C. Payne
- Experimental and Regenerative Neurosciences, School of Animal Biology, The University of Western Australia, Crawley, Western Australia, Australia
| | - Alan R. Harvey
- Experimental and Regenerative Neurosciences, School of Anatomy, Physiology and Human Biology, The University of Western Australia, Crawley, Western Australia, Australia
| | - Sarah A. Dunlop
- Experimental and Regenerative Neurosciences, School of Animal Biology, The University of Western Australia, Crawley, Western Australia, Australia
| | - Melinda Fitzgerald
- Experimental and Regenerative Neurosciences, School of Animal Biology, The University of Western Australia, Crawley, Western Australia, Australia
- * E-mail:
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