Dose response effects of 810nm laser light on mouse primary cortical neurons

• Published in: Lasers in surgery and medicine Vol. 43; no. 8; pp. 851 - 859
• Main Authors: Sharma, Sulbha K, Kharkwal, Gitika B, Sajo, Mari, Huang, Ying-Ying, Fsee, Luis De Taboada, McCarthy, Thomas, Hamblin, Michael R
• Format: Journal Article
• Language: English
• Published: 01.09.2011
• Subjects: ATP; Brain; Calcium; calcium oxide; Central nervous system; Cortex; Embryos; Fluorescent indicators; Injuries; Intracellular levels; Lasers; Light effects; Membrane potential; Mitochondria; Neurons; Nitric oxide; Reactive oxygen species; Stroke
• ISSN: 1096-9101
• DOI: 10.1002/lsm.21100

Background and Objectives In the past four decades numerous studies have reported the efficacy of low level light (laser) therapy (LLLT) as a treatment for diverse diseases and injuries. Recent studies have shown that LLLT can biomodulate processes in the central nervous system and has been extensively studied as a stroke treatment. However there is still a lack of knowledge on the effects of LLLT at the cellular level in neurons. The present study aimed to study the effect of 810nm laser on several cellular processes in primary cortical neurons cultured from embryonic mouse brains. Study Design/Materials and Methods Neurons were irradiated with fluences of 0.0,0.3, 3, 10, or 30J/cm2 of 810-nm laser delivered over varying times at 25mW/cm2 and intracellular levels of reactive oxygen species (ROS), nitric oxide and calcium were measured using fluorescent probes within 5minutes of the end of irradiation. The changes in mitochondrial function in response to light were studied in terms of adenosine triphosphate (ATP) and mitochondrial membrane potential (MMP). Results Light induced a significant increase in calcium, ATP and MMP at lower fluences and a decrease at higher fluences. ROS was significantly induced at low fluences, followed by a decrease and a second larger increase at 30J/cm2. Nitric oxide levels showed a similar pattern of a double peak but values were less significant compared to ROS. Conclusions The results suggest that LLLT at lower fluences is capable of inducing mediators of cell signaling processes which in turn may be responsible for the beneficial stimulatory effects of the low level laser. At higher fluences beneficial mediators are reduced and high levels of Janus-type mediators such as ROS and NO (beneficial at low concentrations and harmful at high concentrations) may be responsible for the damaging effects of high-fluence light and the overall biphasic dose response. Lasers Surg. Med. ? 2011 Wiley-Liss, Inc.