Abstract
Purpose: :
To identify biochemical mechanisms by which specific small molecules enhance survival of isolated photoreceptor cells in culture. Upon dissociation from the retina photoreceptors undergo morphological changes and degeneration. We investigated the basic metabolic needs of photoreceptors in culture by evaluating the biochemical effects of small molecules that were found to enhance their survival. The overall goal of this study is to identify which biochemical activities of energy metabolism are most tightly linked to photoreceptor cell survival in culture.
Methods: :
Several small molecules were identified that enhance survival of dissociated rod photoreceptor cells in culture. We tested these small molecules for effects on various metabolic activities including activity of respiratory complexes, mitochondrial uncoupling, production of reactive oxygen species, and concentrations of mitochondrial and glycolytic metabolic intermediates; comparing the effects of small molecules that enhance photoreceptor survival with those that do not. We are using this data to establish a database from which we will identify biochemical activities that are most tightly linked to survival of isolated photoreceptors.
Results: :
In our compound screen, we observed pro-survival compounds that uncoupled respiration in isolated photoreceptors and the retina. Other molecules shown to enhance survival demonstrated repression of Complex I mitochondrial respiration. Comparing these effects on metabolism with derivatives of parent compounds suggest that uncoupling of respiration is not linked with enhanced survival. Other results suggest that repression of respiration by multiple mechanisms may be linked to survival. We are investigating the specific sites at which these effects may enhance survival and how these compounds might over-ride otherwise toxic metabolic insults. Additional studies are underway to identify other biochemical activities such as stimulation or suppression of reactive oxygen species that also may link the effects of these compounds to enhanced photoreceptor survival.
Conclusions: :
We find that small molecules that can enhance survival of isolated photoreceptors in culture have multiple types of activities. These findings suggest that it will be necessary to establish a matrix of information about the biochemical activities of the compounds and their effects on cell survival to identify which biochemical activities have the greatest influence on photoreceptor cell survival.
Keywords: photoreceptors • metabolism • drug toxicity/drug effects