Long-term in vivo inhibition of CNS neurodegeneration by Bcl-XL gene transfer

Abstract

The inherently low regenerative capacity of the CNS demands effective strategies to inhibit neurodegeneration in acute lesions but also in slowly progressive neurological disorders. Therefore, therapeutic targets that can interact with the degeneration cascade to block, not just postpone, neuronal degeneration need to be defined. Bcl-X(L), a protein protecting the integrity of the mitochondrial membrane potential, was investigated for its neuroprotective properties in a long-term in vivo model of neuronal cell death. An AAV-2-based vector was used to express both Bcl-X(L) and EGFP in retinal ganglion cells (RGCs) of the adult rat retina. Transection of the optic nerve results in degeneration of RGCs in control retinae, while Bcl-X(L)-overexpressing ganglion cells were protected from degeneration. At 2 weeks after axotomy, 94% of the transduced RGCs survived the lesion (15% in controls). For the first time, we investigated RGC survival up to 8 weeks after axotomy and detected that 46% of the Bcl-X(L)-overexpressing RGCs still survived, representing significantly increased neuroprotection compared to neurotrophin-based approaches. We could also show that the axons of AAV-Bcl-X(L)-transduced RGCs remained morphologically intact after the lesion, thus providing the basis for regeneration-inducing attempts.

Kv1.1 and Kv1.3 channels contribute to the degeneration of retinal ganglion cells after optic nerve transection in vivo

“…Transcript expression was monitored for several genes known to have important roles in RGC death after axotomy. 5,[6][7][8]26,27 Quantitative real-time reverse transcriptase-PCR (qRT-PCR) on whole retinas was conducted at 7 days after axotomy, a time when RGC apoptosis is well underway but before these cells are lost. 3,8 First, mRNA expression in naive healthy retinas was compared with axotomized control retinas that had been treated with control siRNA against firefly luciferase.…”

“…Kv1.1 depletion increased mRNA expression of Bcl-X L , a molecule that protects the mitochondrial membrane potential and is neuroprotective for injured RGCs. 27 Note that RGCs comprise only B7% of retinal cells and 25-50% of RGCs degenerate by 7 days; 2,3,24 thus, transcript changes in individual RGCs are likely underrepresented.…”

AAV-mediated gene therapy for retinal disorders: from mouse to man

“…85 This demonstrates that in delivering neurotrophic factors that protect RGCs from death, preservation of retinal function must also be considered. AAV-mediated delivery of the gene encoding an antiapoptotic protein, Bcl-X L , allows survival of more than 40% of RGCs 8 weeks after optic nerve crush (compared with 15% in sham-treated eyes), 86 and combining this with AAV.GDNF delivery potentiates the treatment effect such that 67% of RGCs survive. 87 Damage to the optic nerve and loss of RGCs are also features of multiple sclerosis, which can be modelled in mice by inducing experimental allergic encephalomyelitis, using systemic sensitization with spinal emulsion.…”

Potentiation of in vivo neuroprotection by BclXL and GDNF co-expression depends on post-lesion time in deafferentiated CNS neurons

“…4 Thus, several studies focused at the maintenance of mitochondrial integrity by overexpression of antiapoptotic members of the Bcl-2 family of proteins. [5][6][7] This strategy proved to be significantly more efficient than caspase inhibition, although in long-term studies substantial neuronal cell loss was still observed. 5,8 Neurotrophic factors used in traumatic lesion paradigms only shortly postponed neuronal degeneration.…”

“…[5][6][7] This strategy proved to be significantly more efficient than caspase inhibition, although in long-term studies substantial neuronal cell loss was still observed. 5,8 Neurotrophic factors used in traumatic lesion paradigms only shortly postponed neuronal degeneration. 9,10 Glial cell line-derived neurotrophic factor (GDNF) is a promising candidate in the long-term treatment of Parkinson's disease, although recent clinical trials demonstrated divergent outcomes.…”