The combination of a selective nicotinic agonist and modulator protects against cellular damage in 2 models of glaucoma
Purpose: Our goal was to determine the neuroprotective capabilities of an alpha-7 (α7) nicotinic specific agonist (PNU 282987) in the presence of a selective α 7modulator (PNU-120596) in two models of glaucoma using adult pig retinal ganglion cells (RGCs). Also, we sought to determine the practicality of a ‘single variable’ controlled model of glaucoma (optic nerve cut) using adult RGCs through two methodologies (isolated RGC culture & eye-cup preparations).
Methods: Lauren Bader (S^3 – 2005) found that pre-exposure of isolated RGCs to nicotinic agonists significantly reduced the excitotoxic effects of glutamate. Meagan Stewart (S^3 – 2006) observed that the addition of the specific modulator (which will only enhance the activity of the receptor after activation) appeared to raise survival above control levels. Therefore we modified our culture system and did not add glutamate to the cultures. It has been suggested that isolating the RGCs (which involves cutting the optic nerve) and the addition of glutamate (to mimic excitotoxicity) changes two variables. In addition, we added the agonist / modulator to eye-cup preparations which involve cutting the optic nerve, but not isolating the RGCs.
Results: Through the fluorescent labeling of adult pig RGCs, the viability of the combination drug approach in question was measured. After 96 hours in culture, with chronic exposure to agonist and modulator, we observed an average of a 40% higher survival rate of RGCS exposed to the drug combination than in control culture media. Not only were there more live cells in the experimental culture conditions, but also the living cells displayed signs of greater overall viability. Specifically, RGCs exposed to the drug combination displayed more neuronal processes with branches as well as more intense staining; both of which may indicate healthier cells. Retinal slices were prepared from the eyecup preparations and cells in the RGC layer counted. Preliminary results support the concept of enhanced survival of RGCs when exposed to the drug combination.
Discussion: Although our results are preliminary in nature, the data reinforces the idea of using nicotinic compounds as neuroprotectors to prevent apototic cell death in glaucoma. The results also indicate that isolated adult pig RGCs and adult pig RGCs left in a partially intact eye may both act as viable 'single cariable' models of glaucoma.
Faculty Mentor: David Linn, Biomedical Sciences
Page last modified July 30, 2009