Comparing the Impact of NIR, Visible and UV Light on ROS Upregulation via Photoacceptors of Mitochondrial Complexes in Normal, Immune and Cancer Cells.

The effect of UV/visible/NIR light (380/450/530/650/808/1064 nm) on ROS generation, mitochondrial activity and viability is experimentally compared in human neuroblastoma cancer cells. The absorption of photons by mitochondrial photoacceptors in Complexes I, III and IV is in detail investigated by sequential blocking with selective pharmaceutical blockers. Complex I absorbs UV/blue light by heme P450, resulting in a very high rate (14 times) of ROS generation leading to cell death. Complex III absorbs green light, by cytochromes b, c1 and c, and possesses less ability for ROS production (seven times), so that only irradiation lower than 10 mW cm causes an increase in cell viability. Complex IV is well-known as the primary photoacceptor for red/NIR light. Light of 650/808 nm at 10-100 mW cm generates a physiological ROS level about 20% of a basal concentration, which enhance mitochondrial activity and cell survival, while 1064 nm light does not show any distinguished effects. Further, ROS generation induced by low-intensity red/NIR light is compared in neurons, immune and cancer cells. Red light seems to more rapidly stimulate ROS production, mitochondrial activity and cell survival than 808 nm. At the same time, different cell lines demonstrate slightly various rates of ROS generation, peculiar to their cellular physiology.