Flavia de Paoli

Effect of laser therapy on DNA damage

Whereas the biostimulative effect on tissues using low intensity laser therapy for treating many diseases has been described, the photobiological basis and adverse effects are not well understood. The aim of this study, using experimental models, is to observe the combined effect of physical damage (laser) and a chemical agent (hydrogen peroxide) on Escherichia coli cultures and bacterial plasmids.

Low-level infrared laser effect on plasmid DNA

Low-level laser therapy is used in the treatment of many diseases based on its biostimulative effect. However, the photobiological basis for its mechanism of action and adverse effects are not well understood. The aim of this study, using experimental models, was to evaluate the effects of laser on bacterial plasmids in alkaline agarose gel electrophoresis and Escherichia coli cultures. The electrophoretic profile of bacterial plasmids in alkaline agarose gels were used for studying lesions in DNA exposed to infrared laser. Transformation efficiency and survival of Escherichia coli AB1157 (wild-type), BH20 (fpg/mutM-), BW9091 (xth-), and DH5αF’Iq (recA-) cells harboring pBSK plasmids were used as experimental models to assess the effect of laser on plasmid DNA outside and inside of cells. Data indicate low-level laser: (1) altered the electrophoretic profile of plasmids in alkaline gels at 2,500-Hz pulsed-emission mode but did not alter at continuous wave, 2.5- and 250-Hz pulsed-emission mode; (2) altered the transformation efficiency of plasmids in wild-type and fpg/mutM-E. coli cells; (3) altered the survival fpg/mutM-, xthA- and recA-E. coli cultures harboring pBSK plasmids. Low-level infrared laser with therapeutic fluencies at high frequency in pulsed-emission modes have effects on bacterial plasmids. Infrared laser action can differently affect the survival of plasmids in E. coli cells proficient and deficient in DNA repair mechanisms, therefore, laser therapy protocol should take into account fluencies, frequencies and wavelength of laser, as well as tissue conditions and genetic characteristics of cells before beginning treatment.

Low-intensity infrared laser increases plasma proteins and induces oxidative stress in vitro.

Low-intensity laser therapy is based on the excitation of endogenous chromophores in biotissues and free-radical generation could be involved in its biological effects. In this work, the effects of the low-intensity infrared laser on plasma protein content and oxidative stress in blood from Wistar rats were studied. Blood samples from Wistar rats were exposed to low-intensity infrared laser in continuous wave and pulsed-emission modes at different fluencies. Plasma protein content and two oxidative stress markers (thiobarbituric acid-reactive species formation and myeloperoxidase activity) were carried out to assess the effects of laser irradiation on blood samples. Low-intensity infrared laser exposure increases plasma protein content, induces lipid peroxidation, and increases myeloperoxidase activity in a dose- and frequency-dependent way in blood samples. The low-intensity infrared laser increases plasma protein content and oxidative stress in blood samples, suggesting that laser therapy protocols should take into account fluencies, frequencies, and wavelengths of the laser before beginning treatment.

Low intensity infrared laser induces filamentation in Escherichia coli cells

Low intensity continuous wave and pulsed emission modes laser is used in treating many diseases and the resulting biostimulative effect on tissues has been described, yet the photobiological basis is not well understood. The aim of this wok was to evaluate, using bacterial filamentation assay, effects of laser on Escherichia coli cultures in exponential and stationary growth phase. E. coli cultures, proficient and deficient on DNA repair, in exponential and stationary growth phase, were exposed to low intensity infrared laser, aliquots were spread onto microscopic slides, stained by Gram method, visualized by optical microscopy, photographed and percentage of bacterial filamentation were determined. Low intensity infrared laser with therapeutic fluencies and different emission modes can induce bacterial filamentation in cultures of E. coli wild type, fpg/mutM, endonuclease III and exonuclease III mutants in exponential and stationary growth phase. This study showed induction of bacterial, filamentation in E. coli cultures expose to low intensity infrared laser and attention to laser therapy protocols, which should take into account fluencies, wavelengths, tissue conditions, and genetic characteristics of cells before beginning treatment.

Laser for treatment of aphthous ulcers on bacteria cultures and DNA

Low-intensity red lasers are proposed for treatment of oral aphthous ulcers based on biostimulative effects. However, effects of low-intensity lasers at fluences used in clinical protocols on DNA are controversial. The aim of this work was to evaluate the effects of low-intensity red laser on survival and induction of filamentation of Escherichia coli cells, and induction of DNA lesions in bacterial plasmids. Escherichia coli cultures were exposed to laser (660 nm, 100 mW, 25 and 45 J cm(-2)) to study bacterial survival and filamentation. Also, bacterial plasmids were exposed to laser to study DNA lesions by electrophoretic profile and action of DNA repair enzymes. Data indicate that low-intensity red laser: (i) had no effect on survival of E. coli wild type, exonuclease III and formamidopyrimidine DNA glycosylase/MutM protein but decreased the survival of endonuclease III deficient cultures; (ii) induced bacterial filamentation, (iii) there was no alteration in the electrophoretic profile of plasmids in agarose gels, (iv) there was no alteration in the electrophoretic profile of plasmids incubated with formamidopyrimidine DNA glycosylase/MutM protein and endonuclease III enzymes, but it altered the electrophoretic profile of plasmids incubated with exonuclease III. Low-intensity red laser at therapeutic fluences has an effect on the survival of E. coli endonuclease III deficient cells, induces bacterial filamentation in E. coli cultures and DNA lesions targeted by exonuclease III.

Low intensity infrared laser effects on Escherichia coli cultures and plasmid DNA

Biostimulative effect of low intensity laser in tissues has been described on a photobiological basis and clinical protocols are recommended for treatment of various diseases. The aim of this work was to evaluate effects of laser exposure on the survival of Escherichia coli cultures and plasmid topological forms. Escherichia coli cultures and plasmids were exposed to infrared laser to study bacterial survival and electrophoretic profile, respectively. Data indicate low intensity infrared laser: (i) had no effect on E. coli wild type, endonuclease IV, exonuclease III, formamidopyrimidine DNA glycosylase/MutM protein and endonuclease III deficient cultures, but decreased the survival of E. coli UvrA protein deficient cultures; (ii) there was no alteration in the electrophoretic profile of plasmids. Exposure to low intensity infrared laser decreases survival of Escherichia coli cultures deficient in nucleotide excision repair of DNA and this effect could depend on fluences, wavelength and tissues conditions.

Low-intensity red and infrared lasers on XPA and XPC gene expression

Laser devices emit monochromatic, coherent, and highly collimated intense beams of light that are useful for a number of biomedical applications. However, for low-intensity lasers, possible adverse effects of laser light on DNA are still controversial. In this work, the expression of XPA and XPC genes in skin and muscle tissue exposed to low-intensity red and infrared lasers was evaluated. Skin and muscle tissue of Wistar rats were exposed to low-intensity red and infrared lasers at different fluences in continuous mode emission. Skin and muscle tissue samples were withdrawn for total RNA extraction, cDNA synthesis, and evaluation of actin gene expression by quantitative polymerase chain reaction. Data obtained show that laser radiation alters the expression of XPA and XPC mRNA differently in skin and muscle tissue of Wistar rats, depending on physical (fluence and wavelength) and biological (tissue) parameters. Laser light could modify expression of genes related to the nucleotide excision repair pathway at fluences and wavelengths used in clinical protocols.

Evaluation of DNA Damage Induced by Therapeutic Low-Level Red Laser

Biological effects of monochromatic lights on cells have aroused interest regarding an active and non-innocuous effect on human skin. The aim of this work was to evaluate DNA damage induced by low-level red laser at doses and frequencies used in therapeutic protocols. For this purpose, E. coli cultures and bacterial plasmids were used to assess bacterial survival, filamentation, DNA lesions and in vitro DNA repair induced by low-level red laser exposure at low doses in continuous wave and pulsed emission mode. Data indicate that low-level red laser does not affect the survival of E. coli cultures, topological forms of DNA, and does not induce DNA lesions targeted by endonuclease IV, formamidopyrimidine DNA glycosylase and endonuclease III, but rather that it induces bacterial filamentation in wild type and DNA repair-deficient E. coli cultures and DNA lesions targeted by exonuclease III. Monochromatic red light could activate survival and/or adaptive mechanisms against harmful radiations.

DNA damage in blood cells exposed to low-level lasers

In regenerative medicine, there are increasing applications of low‐level lasers in therapeutic protocols for treatment of diseases in soft and in bone tissues. However, there are doubts about effects on DNA, and an adequate dosimetry could improve the safety of clinical applications of these lasers. This work aimed to evaluate DNA damage in peripheral blood cells of Wistar rats induced by low‐level red and infrared lasers at different fluences, powers, and emission modes according to therapeutic protocols.

Low intensity infrared laser affects expression of oxidative DNA repair genes in mitochondria and nucleus

Practical properties and physical characteristics of low intensity lasers have made possible their application to treat soft tissue diseases. Excitation of intracellular chromophores by red and infrared radiation at low energy fluences with increase of mitochondrial metabolism is the basis of the biostimulation effect but free radicals can be produced. DNA lesions induced by free radicals are repaired by the base excision repair pathway. In this work, we evaluate the expression of POLγ and APEX2 genes related to repair of mitochondrial and nuclear DNA, respectively. Skin and muscle tissue of Wistar rats were exposed to low intensity infrared laser at different fluences. One hour and 24 hours after laser exposure, tissue samples were withdrawn for total RNA extraction, cDNA synthesis, and evaluation of POLγ and APEX2 mRNA expression by real time quantitative polymerase chain reaction. Skin and muscle tissue of Wistar rats exposed to laser radiation show different expression of POLγ and APEX2 mRNA depending of the fluence and time after exposure. Our study suggests that a low intensity infrared laser affects expression of genes involved in repair of oxidative lesions in mitochondrial and nuclear DNA.