title: Effect of 710 nm visible light irradiation on neurite outgrowth in primary rat cortical neurons following ischemic insult.
abstract: OBJECTIVE
  We previously reported that 710 nm Light-emitting Diode (LED) has a protective effect through cellular immunity activation in the stroke animal model. However, whether LED directly protects neurons suffering from neurodegeneration was entirely unknown. Therefore, we sought to determine the effects of 710 nm visible light irradiation on neuronal protection and neuronal outgrowth in an in vitro stroke model.
  
  
  METHODS
  Primary cultured rat cortical neurons were exposed to oxygen-glucose deprivation (OGD) and reoxygenation and normal conditions. An LED array with a peak wavelength of 710 nm was placed beneath the covered culture dishes with the room light turned off and were irradiated accordingly. LED treatments (4 min at 4 J/cm(2) and 50 mW/cm(2)) were given once to four times within 8h at 2h intervals for 7 days. Mean neurite density, mean neurite diameter, and total fiber length were also measured after microtubule associated protein 2 (MAP2) immunostaining using the Axio Vision program. Synaptic marker expression and MAPK activation were confirmed by Western blotting.
  
  
  RESULTS
  Images captured after MAP2 immunocytochemistry showed significant (p<0.05) enhancement of post-ischemic neurite outgrowth with LED treatment once and twice a day. MAPK activation was enhanced by LED treatment in both OGD-exposed and normal cells. The levels of synaptic markers such as PSD 95, GAP 43, and synaptophysin significantly increased with LED treatment in both OGD-exposed and normal cells (p<0.05).
  
  
  CONCLUSIONS
  Our data suggest that LED treatment may promote synaptogenesis through MAPK activation and subsequently protect cell death in the in vitro stroke model.
authors.affiliation: Center for Neuroscience Research, SMART Institute of Advanced Biomedical Science, Konkuk University, Seoul, Republic of Korea.
authors.forename: Dong-Hee
authors.initials: DH
authors.lastname: Choi
authors.forename: Kyoung-Hee
authors.initials: KH
authors.lastname: Lee
authors.forename: Ji-Hye
authors.initials: JH
authors.lastname: Kim
authors.forename: Moon Young
authors.initials: MY
authors.lastname: Kim
authors.forename: Jeong Hoon
authors.initials: JH
authors.lastname: Lim
authors.forename: Jongmin
authors.initials: J
authors.lastname: Lee
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000502:physiology / Q000528:radiation effects*; D019610:Cytoprotection; D000076122:Disks Large Homolog 4 Protein; D004789:Enzyme Activation; D019922:GAP-43 Protein / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008027:Light; D008565:Membrane Proteins / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000096:biosynthesis; D016501:Neurites / Q000502:physiology / Q000528:radiation effects*; D009474:Neurons / Q000502:physiology / Q000528:radiation effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020521:Stroke / Q000503:physiopathology*; D013569:Synapses / Q000378:metabolism / Q000502:physiology / Q000528:radiation effects*
chemical_list: D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D019922:GAP-43 Protein; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D020929:Mitogen-Activated Protein Kinase Kinases