title: Absorption measurements of cell monolayers relevant to mechanisms of laser phototherapy: reduction or oxidation of cytochrome c oxidase under laser radiation at 632.8 nm.
abstract: OBJECTIVE
  The objective of this work was a further investigation of redox mechanisms of laser phototherapy on the cellular level.
  
  
  BACKGROUND
  Cytochrome c oxidase, the terminal enzyme of the mitochondrial respiratory chain, is believed to work as the photoacceptor to modulate cellular metabolism in laser phototherapy.
  
  
  METHODS
  The changes in the absorption spectra of HeLa-cell monolayers before and after irradiation at 632.8 nm using fast multi-channel recording were evaluated by the intensity ratio between the peaks at 770 and 670 nm (intensity ratio criterion).
  
  
  RESULTS
  By the intensity ratio criterion, the irradiation effects (reduction or oxidation of the photoacceptor) depended on the initial redox status of cytochrome c oxidase. The irradiation (three times at 632.8 nm, dose = 6.3 x 103 J/m(2), tau(irrad.) = 10 sec, tau(record.) = 600 msec) of cells initially characterized by relatively oxidized cytochrome c oxidase caused first a reduction of the photoacceptor, and then its oxidation (a bell-shaped curve). The irradiation by the same scheme of the cells with initially relatively reduced cytochrome c oxidase caused first oxidation and then a slight reduction of the enzyme (a curve opposite to the bell-shaped curve).
  
  
  CONCLUSIONS
  The experimental results of our work demonstrate that irradiation at 632.8 nm causes either a (transient) relative reduction of the photoacceptor, putatively cytochrome c oxidase, or its (transient) relative oxidation, depending on the initial redox status of the photoacceptor. The maximum in the bell-shaped dose-dependence curve or the minimum of the reverse curve is the turning point between the prevailing of oxidation or reduction processes. Our results are evidence that the bell-shaped dose dependences recorded for various cellular responses are characteristic also for redox changes in the photoacceptor, cytochrome c oxidase.
authors.affiliation: Institute of Laser and Information Technologies of Russian Academy of Sciences, Troitsk, Moscow Region 142190, Russian Federation. tkaru@isan.troitsk.ru
authors.forename: Tiina I
authors.initials: TI
authors.lastname: Karu
authors.forename: Ludmila V
authors.initials: LV
authors.lastname: Pyatibrat
authors.forename: Sergei F
authors.initials: SF
authors.lastname: Kolyakov
authors.forename: Natalya I
authors.initials: NI
authors.lastname: Afanasyeva
mesh_terms: D000042:Absorption; D003576:Electron Transport Complex IV / Q000378:metabolism* / Q000528:radiation effects*; D006367:HeLa Cells; D006801:Humans; D007834:Lasers; D010084:Oxidation-Reduction / Q000528:radiation effects
chemical_list: D003576:Electron Transport Complex IV