Abstract 3115: Low-Level Laser Therapy Protects Against OGD-induced Neurotoxicity Of Primary Cultured Mouse Cortical Neurons

Background: Low level light (or laser) therapy (LLLT) has been studied and practiced for promoting wound healing, reducing pain, inflammation, and ischemic tissue damage. Recently, a series of experimental and clinical investigations have suggested that LLLT may be a novel therapy against hypoxic/ischemic brain damage. A clinical trial of LLLT therapy for ischemic stroke is now on going. However, the molecular mechanism of LLLT-conferred neuroprotection remains poorly defined. In this study, we tested our hypothesis that LLLT may attenuate impairments of mitochondrial function induced by hypoxic/ischemic insults in primary cultured mouse cortical neurons. Method: At day 9 of culture, primary neurons were subjected to 4 hr OGD followed by reoxygenation. One 810-nm LLLT treatment was applied for 2 minutes at 2 hr after reoxygenation. Neurotoxicity was measured after 20 hr after reoxygenation by LDH release assay. We also measured MTT reduction and mitochondria membrane potential (MMP) at 2 hr after LLLT treatment as markers of mitochondrial function. Results: The neurotoxicity study showed that 4 hr OGD plus 20 hr reoxygenation caused 33.8± 3.4% neuronal cell death, while LLLT treatment significantly reduced the neuronal death rate to 23.6± 2.9% (30.2% reduction, n=6, p smaller than 0.05). Mitochondrial functional assays showed OGD decreased MTT reduction to 75.9± 2.68%, but LLLT treatment significantly rescued MTT reduction to 87.6±4.55% (15.4% improvement, n=6, p smaller than 0.05). Furthermore, after OGD, MMP was reduced to 48.9±4.39%, while LLLT treatment significantly ameliorated this reduction to 89.6± 13.9% (83% improvement, n=4, p smaller than 0.05) compared to normoxic controls. Conclusion: The present study suggests that LLLT treatment is protective against OGD-induced neurotoxicity of primary neurons and that this protection may be conferred through preservation or rescue of mitochondrial function.