Abstract WMP35: Low Level Laser Therapy (LLLT) Protects Against Oxygen-Glucose Deprivation-Induced Neuron Death by Modulating Nitric Oxide and ROS Production In Vitro

Abstract

Background: LLLT has been shown to be neurorprotective against cerebral ischemia in animals. Initial human clinical trials demonstrated safety and potential beneficial profiles. A pivotal clinical trial with TLT is ongoing for ischemic stroke. However, the underlying neuroprotective mechanisms require further definition. We previously showed LLLT protected primary neurons against OGD. In the current study, we tested the hypothesis that LLLT may attenuate OGD-induced nitric oxide (NO) and ROS production and associated cell survival signaling, causing reduced cell death in primary mouse cortical neurons. Method: At day 8 of culture, neurons were subjected to 4 hr OGD. LLLT was applied at 2 hr reoxygenation. NO level, nNOS expression, ROS level, and cell survival signaling were measured post-LLLT. Cell death was measured at 20 hr after OGD. Results were expressed as fold of normal control, mean ± SEM, n = 3-5 per group, P <0.05 was considered statistically significant. Results: OGD significantly increased NO level in primary neurons (2.12 ± 0.47, 2.67 ± 1.07, and 2 ± 0.77 at 5 min, 30 min and 1 hr post-treatment, respectively), but the increase was significantly reduced by LLLT (1.08 ± 0.44 at 5 min and 1.45 ± 0.73 at 30 min post-LLLT). OGD also significantly increased nNOS mRNA level (2.17 ± 0.42, 3.99 ± 1.7, and 2.60 ± 0.7 at 5 min, 30 min and 1 hr post-treatment, respectively), while the increase was significantly ameliorated by LLLT (0.50 ± 0.08 at 30 min and 0.34 ± 0.45 at 1 hr post-LLLT). Additionally, 50 uM NO donor SNAP exposure for 48 hr induced 23.6 ± 2.5% cell death, which was significantly ameliorated by LLLT (12.3 ± 4.2% cell death), indicating LLLT may directly protect NO-mediated neurotoxicity. Furthermore, LLLT significantly reduced OGD-induced ROS production at 5 min, 30 min and 1 hr post-LLLT. Finally, OGD suppressed neuron survival signaling p-Akt and Bcl-2 protein expressions, but they were significantly rescued by LLLT. Conclusion: These results suggest LLLT protection against OGD may be partially through reducing OGD-induced NO and ROS production, and restoring OGD-suppressed cell survival signaling.