Low level laser irradiation stimulates mitochondrial membrane potential and disperses subnuclear promyelocytic leukemia protein

Lilach Gavish*, Yael Asher, Yechiel Becker, Yosef Kleinman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

93 Scopus citations


Background and Objectives: Low level laser irradiation (LLLI) is used to promote wound healing. Molecularly it is known to stimulate mitochondrial membrane potential (MMP), cytokine secretion, and cell proliferation. This study was designed to determine the influence of LLLI on the kinetics of MMP stimulation and decay, specific cytokine gene expression, and subcellular localization of promyelocytic leukemia (PML) protein on HaCaT human keratinocytes. Study Design/Material and Methods: The cells were irradiated by a 780 nm titanium-sapphire (Ti-Sa) laser with 2 J/cm2 energy density. MMP was monitored with Mitotracker, a mitochondrial voltage-sensitive fluorescent dye. Cytokine gene expression was carried out using semiquantitative-reverse transcription polymerase chain reaction. Subcellular localization of PML protein, a cell-cycle checkpoint protein, was determined using immunofluorescent staining. Results: The fluorescence intensity of MMP was increased immediately after the end of LLLI by 148 ± 6% over control (P<0.001). Subsequently it decayed, reaching 51 ± 14% of the control level (P<0.01) within 200 minutes. This decay was characterized by an exponential curve (R = 0.96) with a lifetime of 79 ± 36 minutes (P<0.05). Following irradiation, the expression of interleukin-loc, interleukin-6, and keratinocyte growth factor (KGF) genes were transiently upregulated; but the expression of the proinflammatory gene interleukin-1β, was suppressed. The subnuclear distribution of PML was altered from discrete domains to its dispersed form within less than 1 hour after LLLI. Conclusions: These changes reflect a biostimulative boost that causes a shift of the cell from a quiescent to an activated stage in the cell cycle heralding proliferation and suppression of inflammation. Further characterization of MMP kinetics may provide a quantitative basis for assessment of the effect of LLLI in the clinical setting.

Original languageAmerican English
Pages (from-to)369-376
Number of pages8
JournalLasers in Surgery and Medicine
Issue number5
StatePublished - 2004


  • Biostimulation
  • Cell cycle
  • Cytokine
  • Keratinocyte
  • Lasers
  • Photobiology


Dive into the research topics of 'Low level laser irradiation stimulates mitochondrial membrane potential and disperses subnuclear promyelocytic leukemia protein'. Together they form a unique fingerprint.

Cite this