The effects of red to near-infrared light on mitochondrial function

Abstract

Red to near-infrared (NIR) light therapy is a non-invasive, drug-free therapy comprising a broad spectrum of wavelengths between 630nm and 1000nm, which allows the light photon to penetrate from 0.5mm to 50mm through the skin to reach the target tissue and mediate cellular response. Therapeutic benefits of red-to-NIR light therapy have been reported in neurodegenerative diseases such as Parkinson’s disease (PD) and Alzheimer’s disease (AD). Neuronal mitochondria have been identified as the primary target for red and NIR light. At the cellular level, preclinical studies in animal models have shown promising effects in increasing adenosine triphosphate (ATP) production in response to light treatment, but how red-to-NIR light affects mitochondrial complexes and function has yet to be identified. This project aims to: (1) Investigate the effects of both continuous and pulsed red-to-NIR light on neuron metabolism; (2) explore the influence of continuous red-to-NIR light on mitochondrial complex respiration; (3) determine if red-to-NIR light aids neuron cell resistance to external stress. In order to conduct this project, SH-SY5Y neuroblastoma cells were exposed to both continuous and pulsed light treatment protocols. During the pulsed light treatment experiment, KCl stress was applied to explore the resistance of light-irradiated SH-SY5Y to external stress. Our results revealed that 850nm continuous light irradiation led to the greatest increments in intact cell respiration. At mitochondrial complex-level, 850nm and 940nm light wavelengths were the most effective in stimulating electron transport system capacity and cytochrome c oxidase activity. This suggests that 850nm and 940nm continuous light-irradiated SH-SY5Y cells possess higher cell viability and have the potential to cope with an increased ATP demand. Furthermore, exposure to 830nm and 940nm pulsed light demonstrated an improvement in the resistance of SH-SY5Y cells to KCl-induced stress. Overall, this thesis provides insights into neuronal metabolism in response to red-to-NIR light therapy at both intact cell and mitochondrial complex-specific levels, and demonstrates the potential of red-to-NIR light therapy in ameliorating neurodegenerative diseases.