Biphasic dose response in low level light therapy - an update

Michael R. Hamblin, Ying Ying Huang, Sulbha K. Sharma, James Carroll

Research output: Contribution to journalArticlepeer-review

615 Citations (Scopus)

Abstract

Low-level laser (light) therapy (LLLT) has been known since 1967 but still remains controversial due to incomplete understanding of the basic mechanisms and the selection of inappropriate dosimetric parameters that led to negative studies. The biphasic dose-response or Arndt-Schulz curve in LLLT has been shown both in vitro studies and in animal experiments. This review will provide an update to our previous (Huang et al. 2009) coverage of this topic. In vitro mediators of LLLT such as adenosine triphosphate (ATP) and mitochondrial membrane potential show biphasic patterns, while others such as mitochondrial reactive oxygen species show a triphasic dose-response with two distinct peaks. The Janus nature of reactive oxygen species (ROS) that may act as a beneficial signaling molecule at low concentrations and a harmful cytotoxic agent at high concentrations, may partly explain the observed responses in vivo. Transcranial LLLT for traumatic brain injury (TBI) in mice shows a distinct biphasic pattern with peaks in beneficial neurological effects observed when the number of treatments is varied, and when the energy density of an individual treatment is varied. Further understanding of the extent to which biphasic dose responses apply in LLLT will be necessary to optimize clinical treatments.

Original languageEnglish
Pages (from-to)602-618
Number of pages17
JournalDose-Response
Volume9
Issue number4
DOIs
Publication statusPublished - 2011
Externally publishedYes

Keywords

  • Biphasic dose response
  • Low level laser therapy
  • Nitric oxide
  • Photobiomodulation
  • Reactive oxygen species
  • Traumatic brain injury

ASJC Scopus subject areas

  • Toxicology
  • Public Health, Environmental and Occupational Health
  • Health, Toxicology and Mutagenesis
  • Chemical Health and Safety

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