Luiz Philippe da Silva Sergio

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-level laser irradiation alters mRNA expression from genes involved in DNA repair and genomic stabilization in myoblasts

Low-level lasers are used for the treatment of diseases in soft and bone tissues, but few data are available regarding their effects on genomic stability. In this study, we investigated mRNA expression from genes involved in DNA repair and genomic stabilization in myoblasts exposed to low-level infrared laser. C2C12 myoblast cultures in different fetal bovine serum concentrations were exposed to low-level infrared laser (10, 35 and 70 J cm−2), and collected for the evaluation of DNA repair gene expression. Laser exposure increased gene expression related to base excision repair (8-oxoguanine DNA glycosylase and apurinic/apyrimidinic endonuclease 1), nucleotide excision repair (excision repair cross-complementation group 1 and xeroderma pigmentosum C protein) and genomic stabilization (ATM serine/threonine kinase and tumor protein p53) in normal and low fetal bovine serum concentrations. Results suggest that genomic stability could be part of a biostimulation effect of low-level laser therapy in injured muscles.

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.

TP53 and ATM mRNA expression in skin and skeletal muscle after low-level laser exposure

ABSTRACT Low-level lasers are widespread in regenerative medicine, but the molecular mechanisms involved in their biological effects are not fully understood, particularly those on DNA stability. Therefore, this study aimed to investigate mRNA expression of genes related to DNA genomic stability in skin and skeletal muscle tissue from Wistar rats exposed to low-level red and infrared lasers. For this, TP53 (Tumor Protein 53) and ATM (Ataxia Telangiectasia Mutated gene) mRNA expressions were evaluated by real-time quantitative PCR (RT-qPCR) technique 24 hours after low-level red and infrared laser exposure. Our data showed that relative TP53 mRNA expression was not significantly altered in both tissues exposed to lasers. For ATM, relative mRNA expression in skin tissue was not significantly altered, but in muscle tissue, laser exposure increased relative ATM mRNA expression. Low-level red and infrared laser radiations alter ATM mRNA expression related to DNA stability in skeletal muscle tissue.

Chronic Obstructive Pulmonary Disease: From Injury to Genomic Stability

ABSTRACT Chronic obstructive pulmonary disease (COPD) is the fourth cause of death in the world and it is currently presenting a major global public health challenge, causing premature death from pathophysiological complications and rising economic and social burdens. COPD develops from a combination of factors following exposure to pollutants and cigarette smoke, presenting a combination of both emphysema and chronic obstructive bronchitis, which causes lung airflow limitations that are not fully reversible by bronchodilators. Oxidative stress plays a key role in the maintenance and amplification of inflammation in tissue injury, and also induces DNA damages. Once the DNA molecule is damaged, enzymatic mechanisms act in order to repair the DNA molecule. These mechanisms are specific to repair of oxidative damages, such as nitrogen base modifications, or larger DNA damages, such as double-strand breaks. In addition, there is an enzymatic mechanism for the control of telomere length. All these mechanisms contribute to cell viability and homeostasis. Thus, therapies based on modulation of DNA repair and genomic stability could be effective in improving repair and recovery of lung tissue in patients with COPD.

Low power lasers on genomic stability

Exposure of cells to genotoxic agents causes modifications in DNA, resulting to alterations in the genome. To reduce genomic instability, cells have DNA damage responses in which DNA repair proteins remove these lesions. Excessive free radicals cause DNA damages, repaired by base excision repair and nucleotide excision repair pathways. When non-oxidative lesions occur, genomic stability is maintained through checkpoints in which the cell cycle stops and DNA repair occurs. Telomere shortening is related to the development of various diseases, such as cancer. Low power lasers are used for treatment of a number of diseases, but they are also suggested to cause DNA damages at sub-lethal levels and alter transcript levels from DNA repair genes. This review focuses on genomic and telomere stabilization modulation as possible targets to improve therapeutic protocols based on low power lasers. Several studies have been carried out to evaluate the laser-induced effects on genome and telomere stabilization suggesting that exposure to these lasers modulates DNA repair mechanisms, telomere maintenance and genomic stabilization. Although the mechanisms are not well understood yet, low power lasers could be effective against DNA harmful agents by induction of DNA repair mechanisms and modulation of telomere maintenance and genomic stability.

Low-level lasers affect uncoupling protein gene expression in skin and skeletal muscle tissues

Wavelength, frequency, power, fluence, and emission mode determine the photophysical, photochemical, and photobiological responses of biological tissues to low-level lasers. Free radicals are involved in these responses acting as second messengers in intracellular signaling processes. Irradiated cells present defenses against these chemical species to avoid unwanted effects, such as uncoupling proteins (UCPs), which are part of protective mechanisms and minimize the effects of free radical generation in mitochondria. In this work UCP2 and UCP3 mRNA gene relative expression in the skin and skeletal muscle tissues of Wistar rats exposed to low-level red and infrared lasers was evaluated. Samples of the skin and skeletal muscle tissue of Wistar rats exposed to low-level red and infrared lasers were withdrawn for total RNA extraction, cDNA synthesis, and the evaluation of gene expression by quantitative polymerase chain reaction. UCP2 and UCP3 mRNA expression was differently altered in skin and skeletal muscle tissues exposed to lasers in a wavelength-dependent effect, with the UCP3 mRNA expression dose-dependent. Alteration on UCP gene expression could be part of the biostimulation effect and is necessary to make cells exposed to red and infrared low-level lasers more resistant or capable of adapting in damaged tissues or diseases.

Emphysema induced by elastase alters the mRNA relative levels from DNA repair genes in acute lung injury in response to sepsis induced by lipopolysaccharide administration in Wistar rats

ABSTRACT Purpose/Aim of the study: Patients suffering from chronic obstructive pulmonary disease (COPD) in association with acute respiratory distress syndrome (ARDS) present oxidative stress in lung cells, with production of free radicals and DNA lesions in pulmonary and adjacent cells. Once the DNA molecule is damaged, a set of enzymatic mechanisms are trigged to preserve genetic code integrity and cellular homeostasis. These enzymatic mechanisms include the base and the nucleotide excision repair pathways, as well as telomere regulation. Thus, the aim of this work was to evaluate the mRNA levels from APEX1, ERCC2, TP53, and TRF2 genes in lung tissue from Wistar rats affected by acute lung injury in response to sepsis and emphysema. Materials and Methods: Adult male Wistar rats were randomized into 4 groups (n = 6, for each group): control, emphysema, sepsis, and emphysema with sepsis. Pulmonary emphysema was induced by intratracheal instillation of elastase (12 IU/animal) and sepsis induced by intraperitoneal Escherichia coli lipopolysaccharide (LPS) injection (10 mg/kg). Lungs were removed, and samples were withdrawn for histological analysis and total RNA extraction, cDNA synthesis, and mRNA level evaluation by real time quantitative polymerase chain reaction. Results: Data show acute lung injury by LPS and emphysema by elastase and that APEX1, ERCC2, TP53, and TRF2 mRNA levels are increased significantly (p < 0.01) in emphysema with sepsis group. Conclusion: Our results suggest that alteration in mRNA levels from DNA repair and genomic stability could be part of cell response to acute lung injury in response to emphysema and sepsis.