Dichromatic laser radiation effects on DNA ofEscherichia coliand plasmids

Cytochrome c oxidase is discussed as a possible photoacceptor when cells are irradiated with monochromatic red to near-IR radiation. Four primary action mechanisms are reviewed: changes in the redox properties of the respiratory chain components following photoexcitation of their electronic states, generation of singlet oxygen, localized transient heating of absorbing chromophores, and increased superoxide anion production with subsequent increase in concentration of the product of its dismutation, H2O2. A cascade of reactions connected with alteration in cellular homeostasis parameters (pHi, [Cai], cAMP, Eh, [ATP] and some others) is considered as a photosignal transduction and amplification chain in a cell (secondary mechanisms).

This investigation reviewed experimental studies of laser irradiation of wound healing in mice and rats published from 2003 to August 2008, respectively, to assess putative stimulatory effects of this treatment. Animal models, including rodents, attempt to reflect human wound healing and associated problems such as dehiscence, ischemia, ulceration, infection, and scarring. They have played a key role in furthering understanding of underlying mechanisms involved in impaired wound healing, and in testing new therapeutic strategies including laser irradiation. Original research papers investigating effects of laser or monochromatic light therapy on wound healing in mice and rats and published from January 2003 to August 2008 were retrieved from library sources, PubMed and Medline databases, reference lists from retrieved papers, and hand searches of relevant journals. Papers were selected for this review with regard to specific inclusion and exclusion criteria. Studies were critically reviewed in terms of study design, methodology, and appropriateness of laser irradiation parameters. The literature search identified eight studies in mice and 39 in rats. A variety of wound models were investigated, including acute-wound, impaired-healing, and chronic-wound models. Considerable variation was observed in research design, methodology, and irradiation parameters employed, limiting comparison of research findings between studies. Inadequate reporting of key experimental details, or errors in specification and/or calculation of key irradiation parameters was also found. Evidence from the studies reviewed suggested that use of red or infrared wavelength at a range of dosage parameters (median 4.2 J cm(-2)) results in significant benefits in measured parameters of wound healing. Interestingly, coherence does not seem essential to the photobiomodulatory effects of 'laser' phototherapy. Studies reviewed consistently demonstrated the ability of laser or monochromatic light to photobiomodulate wound healing processes in experimental wounds in rats and mice, and strongly support the case for further controlled research in humans.