Inhibition of mitocondrial complex IV in cell death and the influence of light.

Purpose Characterise the mechanism by which the mitochondrial complex IV poison sodium azide kills RGC‐5 cells (cell line with certain ganglion cell properties) in the dark and determine the influence of white and red light. Methods RGC‐5 cell cultures in 96‐ or 12‐well plates were exposed to different concentrations of sodium azide in the dark or under white (400‐700nm, 1000 lux) or red (625‐635nm, 1000lux) light. Cells were analysed 24‐96 hours later for production of reactive oxygen species (ROS), cell viability (MTT procedure) and for apoptosis (staining for phosphatidylserine and DNA breakdown). Also, cultures were subjected to immunocytochemistry for the localisation of certain antigens or their proteins extracted and subjected to electrophoresis and western blotting for various proteins involved in cell death. Results Sodium azide (5mM)‐induced apoptosis of RGC‐5 cells is characterised by positive membrane staining for phosphatidylserine, breakdown of DNA, a generation of ROS production, the activation of p38 MAPK and by inhibition with the caspase inhibitor z‐VAD‐fmk. Sodium azide also caused p38 MAPK to be translocated from the nucleus to the cytoplasm and the stimulation of alpha fordrin and caspase‐3 content. White light exacerbated and red light reduced the effects of sodium azide that occurred in the dark. Conclusion Red light as opposed to white light acting directly on the retina might protect neurones from dying by apoptosis where their mitochondria are affected.