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Caspase inhibitors block the retinal ganglion cell death following optic nerve transection
P Chaudhary1, F Ahmed, P Quebada
1Department of Ophthalmology/Cell Biology and Anatomy, New York Medical College, Valhalla, NY 10595, USA.
Abstract:
Retinal ganglion cells die by apoptosis following axotomy. The molecular mechanisms of the retinal ganglion cell death are not well understood. In the present study using RT-PCR and in situ hybridization techniques we demonstrated that levels of mRNA for Bcl-2 and Bcl-x decreased after axotomy. Bax levels remained high until 4 days after axotomy, decreased by day 7 and remained low up to day 10. CPP32 levels increased at day 7 and remained high after optic nerve cut. We studied whether inhibitors of CPP32/caspase would save the axotomy induced ganglion cell death. DEVD-CHO (Ac-Asp-Glu-Val-aspartic acid aldehyde) and DEVD-FMK (Z-Asp-Glu-Val-Asp-FMK), caspase inhibitors, when administered intraocularly at the time of optic nerve cut, at days 3 and 7 protect about 30-35% the ganglion cells from death. We further demonstrated that the number of reactive microglia decrease in the retina when the inhibitors were given as compared with retina where no inhibitors were given. The present data offers new avenues for studying the complex interactions between the retinal ganglion cell death and the activation of resident microglia/macrophages.
Insights
Retinal ganglion cell death after optic nerve injury involves apoptosis. Caspase inhibitors like DEVD-CHO and DEVD-FMK protect these cells and reduce microglial activation, offering new therapeutic targets.
Area of Science:
- Neuroscience
- Cell Biology
- Ophthalmology
Background:
- Retinal ganglion cells (RGCs) undergo apoptosis after optic nerve axotomy.
- The precise molecular mechanisms driving RGC death remain unclear.
- Understanding these mechanisms is crucial for developing neuroprotective strategies.
Purpose of the Study:
- To investigate the molecular changes in RGCs following axotomy.
- To determine the role of caspases in RGC apoptosis.
- To evaluate the efficacy of caspase inhibitors in protecting RGCs from death.
Main Methods:
- Reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization to analyze mRNA levels.
- Intraocular administration of caspase inhibitors (DEVD-CHO and DEVD-FMK).
- Assessment of RGC survival and microglial activation post-axotomy.
Main Results:
- Axotomy led to decreased Bcl-2 and Bcl-x mRNA levels, while Bax remained elevated initially.
- CPP32 (caspase) levels increased significantly post-axotomy.
- Intraocular administration of caspase inhibitors protected 30-35% of RGCs and reduced reactive microglia.
Conclusions:
- Caspase activation plays a critical role in RGC apoptosis following axotomy.
- Caspase inhibition represents a potential therapeutic approach for RGC neuroprotection.
- These findings highlight the interplay between RGC death and microglial activation.