Abstract
Purpose: :
To show that blue light in particular influences mitochondrial functions in vitro to potentially elicit retinal cell death in situ.
Methods: :
Semi-confluent cultures of RGC-5 (a cell line with certain ganglion cell properties) cells were exposed to blue (465-470nm, 400 lux), white (400-800nm, 1000 lux) or red (625-635nm, 1000 lux) light over 24 or 48 hours. Thereafter cells in 96-well plates were analysed for viability (MTT procedure) and their inner membrane potential (JC-1). Proteins from cells in culture were also extracted and individual oxidative phosphorylation (OXPHOS) complexes quantified by electrophoresis/western blotting. RGC-5 cells on coverslips were also processed for the localisation of mitochondria (mitotracker) or the presence of cytochrome-c. In addition immunocytochemistry was used to localise individual OXPHOS complexes.
Results: :
Blue and white light caused a loss of cell viability with blue light being much more effective. Red light had a negligible influence on cell viability. Double staining of cells with DAPI and either JC-1, mitotracker or cytochrome-c showed that blue light caused a change in the inner membrane electrochemical potential, mitochondrial morphology and the release of mitochondrial located cytochrome-c into the cytoplasm. Analysis of individual OXPHOS complexes by immunocytochemistry and western blotting showed differential effects. Complex II is down-regulated and complex I unaffected, while complex III, IV and V are up-regulated.
Conclusions: :
Of the light that impinges on the retina, the blue light component in particular affects mitochondrial functions negatively as might occur with the many mitochondria located to ganglion cells in situ. The present studies also suggest that blue light has a direct influence on fluorophores associated with complex II, III, IV and V of mitochondrial OXPHOS.
Keywords: ganglion cells • mitochondria • radiation damage: light/UV