Photobiomodulation partially rescues visual cortical neurons from cyanide-induced apoptosis

• Published in: Neuroscience 2006-01, Vol.139 (2), p.639-649
• Main Authors: Liang, H.L., Whelan, H.T., Eells, J.T., Meng, H., Buchmann, E., Lerch-Gaggl, A., Wong-Riley, M.
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis - drug effects; Apoptosis - radiation effects; bcl-2-Associated X Protein - metabolism; Biological and medical sciences; Blotting, Western - methods; Caspase 3; Caspases - metabolism; Cell Count - methods; Cell Nucleus - drug effects; Cell Nucleus - radiation effects; Cell Nucleus - ultrastructure; Cells, Cultured; Cyanides - pharmacology; Densitometry - methods; DNA, Single-Stranded - metabolism; Dose-Response Relationship, Drug; electronic microcopy; Enzyme Inhibitors - pharmacology; Fundamental and applied biological sciences. Psychology; Immunohistochemistry - methods; Light; Microscopy, Electron, Transmission - methods; near-infrared light; Neurons - drug effects; Neurons - radiation effects; Neurons - ultrastructure; Phototherapy - methods; Proto-Oncogene Proteins c-bcl-2 - metabolism; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species - metabolism; ROS; ssDNA; Vertebrates: nervous system and sense organs; Visual Cortex - cytology
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2005.12.047

Near-infrared light via light-emitting diode treatment has documented therapeutic effects on neurons functionally inactivated by tetrodotoxin or methanol intoxication. Light-emitting diode pretreatment also reduced potassium cyanide-induced cell death, but the mode of death via the apoptotic or necrotic pathway was unclear. The current study tested our hypothesis that light-emitting diode rescues neurons from apoptotic cell death. Primary neuronal cultures from postnatal rat visual cortex were pretreated with light-emitting diode for 10 min at a total energy density of 30 J/cm 2 before exposing to potassium cyanide for 28 h. With 100 or 300μM potassium cyanide, neurons died mainly via the apoptotic pathway, as confirmed by electron microscopy, Hoechst 33258, single-stranded DNA, Bax, and active caspase-3. In the presence of caspase inhibitor I, the percentage of apoptotic cells in 300μM potassium cyanide was significantly decreased. Light-emitting diode pretreatment reduced apoptosis from 36% to 17.9% (100μM potassium cyanide) and from 58.9% to 39.6% (300μM potassium cyanide), representing a 50.3% and 32.8% reduction, respectively. Light-emitting diode pretreatment significantly decreased the expression of caspase-3 elicited by potassium cyanide. It also reversed the potassium cyanide-induced increased expression of Bax and decreased expression of Bcl-2 to control levels. Moreover, light-emitting diode decreased the intensity of 5-(and -6) chloromethy-2′, 7-dichlorodihydrofluorescein diacetate acetyl ester, a marker of reactive oxygen species, in neurons exposed to 300μM potassium cyanide. These results indicate that light-emitting diode pretreatment partially protects neurons against cyanide-induced caspase-mediated apoptosis, most likely by decreasing reactive oxygen species production, down-regulating pro-apoptotic proteins and activating anti-apoptotic proteins, as well as increasing energy metabolism in neurons as reported previously.