Low-level light therapy for zymosan induced arthritis in rats

Ana P. Castano, Dai Tianhong, Tatiana N. Demidova-Rice, Elena V. Salomatina, Anna N. Yaroslavsky, Ilya Yaroslavsky, Richard Cohen, William A. Apruzzese, Michael H. Smotrich, Michael R. Hamblin

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


It has been known for many years that low level laser (or light) therapy (LLLT) can ameliorate the pain, swelling and inflammation associated with various forms of arthritis. Light is absorbed by mitochondrial chromophores leading to an increase in ATP, reactive oxygen species and/or cyclic AMP production and consequent gene transcription via activation of transcription factors. However, despite many reports about the positive effects of LLLT in medicine, its use remains controversial. Our laboratory has developed animal models designed to objectively quantify response to LLLT and compare different light delivery regimens. In the arthritis model we inject zymosan into rat knee joints to induce inflammatory arthritis. We have compared illumination regimens consisting of a high and low fluence (3 J/cm2 and 30 J/cm 2), delivered at a high and low irradiance (5 mW/cm2 and 50 mW/cm2) using 810-nm laser light daily for 5 days, with the effect of conventional corticosteroid (dexamethasone) therapy. Results indicated that illumination with 810-nm laser is highly effective (almost as good as dexamethasone) at reducing swelling and that longer illumination time was more important in determining effectiveness than either total fluence delivered or irradiance. Experiments carried out using 810-nm LLLT on excisional wound healing in mice also confirmed the importance of longer illumination times. These data will be of value in designing clinical trials of LLLT.

Original languageEnglish
Title of host publicationMechanisms for Low-Light Therapy II
Publication statusPublished - 2007
Externally publishedYes
EventMechanisms for Low-Light Therapy II - San Jose, CA, United States
Duration: 21 Jan 200721 Jan 2007

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
ISSN (Print)1605-7422


ConferenceMechanisms for Low-Light Therapy II
Country/TerritoryUnited States
CitySan Jose, CA


  • Biomodulation
  • Biostimulation
  • Cold laser
  • Low-level light therapy
  • Wound healing
  • Zymosan-induced arthritis

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Biomaterials
  • Radiology, Nuclear Medicine and Imaging


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