Abstract
Purpose :
Neurodegenerative diseases, such as age-related macular degeneration or retinitis pigmentosa, are relevant diseases in ophthalmology. Currently available therapies are not yet able to sufficiently stop the gradual neurodegeneration. An important role in neuroprotection is the BDNF / tropomyosin receptor kinase B (TrκB)-pathway. Receptor activation leads to cell growth and neuroprotection. However, previous studies showed that BDNF is not suitable as an exogenously administered therapeutic agent. Therefore, this research project investigates an alternative ligand, a TrκB-aptamer. The used aptamer is a high-affinity agonist to TrκB and potentially more suitable as a therapeutic agent than BDNF, as it is only a partial agonist of TrκB. This project focused on finding the appropriate concentration of the aptamer that would effectively activate TrκB without inducing side effects. In addition, we investigated the time course of receptor activation and the neuroprotective effect of the aptamer in a blue-light stress model.
Methods :
All experiments were performed ex vivo on retinal explants from porcine eyes. Tested aptamer concentrations were 10nM, 100nM, 200nM and 500nM. The expression of various markers (including BDNF, p-Akt, TNFα, HSP70) was examined both by qRT-PCR and Western blot. Retinal neurodegeneration was induced by blue-light irradiation thereby inducing oxidative stress. The effects were analyzed by caspase 3/7 assay and TUNEL-staining.
Results :
The most effective TrκB-Aptamer concentration was 100nM with a treatment time of 24h. The aptamer was able to effectively activate the TrκB receptor at 100nM. With a longer treatment time of 48h, already a concentration of 10nM led to effective receptor activation proven by the phosphorylation state of p-Akt. Furthermore, these two concentrations did not induce an increase in the expression of cell stress markers, such as TNFα and HSP70. Exposure to blue- light was used to investigate the aptamers neuroprotective effect. Treatment with 100nM aptamer prevented apoptosis in stressed cells and decreased the induced oxidative stress by half.
Conclusions :
The aptamer was well tolerated in the retina and effectively activated TrκB. Neuroprotective effects were induced with a concentration of 100nM, and cells were rescued from apoptosis in a blue light stress model.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.