Effects of helium-neon laser irradiation and local anesthetics on potassium channels in pond snail neurons

Low-Power Red and Infrared Laser Effects on Cells Deficient in DNA Repair

Introduction: Low-level lasers are successfully used to prevent and treat diseases in soft oral and bone tissues, particularly diseases in oral cavity caused by chemotherapy and radiotherapy in oncology. However, controversy exists as to whether these lasers induce molecular side effects, mainly on DNA. The aim of this work was to assess the effects of low-power lasers on mutant Escherichia coli cells in DNA repair. Methods: Escherichia coli wild type cultures as well as those lacking recombination DNA repair (recA ^-) and la SOS responses (lexA ^-) irradiated with lasers at different energy densities, powers, and emission modes for cell viability and morphology assessment were used in this study. Results: Laser irradiation: (i) did not affect cell viability of non-mutant and lexA ^- cells but decreased viability in recA ^- cultures; (ii) altered morphology of wild type and lexA, depending on the energy density, power, emission mode, and wavelength. Conclusion: Results show that low-level lasers have lethal effects on both recombination DNA repair and SOS response bacterial cells but do not induce morphological modifications in these cells.

Neuroprotective Effects Against POCD by Photobiomodulation: Evidence from Assembly/Disassembly of the Cytoskeleton

Postoperative cognitive dysfunction (POCD) is a decline in memory following anaesthesia and surgery in elderly patients. While often reversible, it consumes medical resources, compromises patient well-being, and possibly accelerates progression into Alzheimer's disease. Anesthetics have been implicated in POCD, as has neuroinflammation, as indicated by cytokine inflammatory markers. Photobiomodulation (PBM) is an effective treatment for a number of conditions, including inflammation. PBM also has a direct effect on microtubule disassembly in neurons with the formation of small, reversible varicosities, which cause neural blockade and alleviation of pain symptoms. This mimics endogenously formed varicosities that are neuroprotective against damage, toxins, and the formation of larger, destructive varicosities and focal swellings. It is proposed that PBM may be effective as a preconditioning treatment against POCD; similar to the PBM treatment, protective and abscopal effects that have been demonstrated in experimental models of macular degeneration, neurological, and cardiac conditions.

Low-intensity red and infrared laser effects at high fluences on Escherichia coli cultures

Semiconductor laser devices are readily available and practical radiation sources providing wavelength tenability and high monochromaticity. Low-intensity red and near-infrared lasers are considered safe for use in clinical applications. However, adverse effects can occur via free radical generation, and the biological effects of these lasers from unusually high fluences or high doses have not yet been evaluated. Here, we evaluated the survival, filamentation induction and morphology of Escherichia coli cells deficient in repair of oxidative DNA lesions when exposed to low-intensity red and infrared lasers at unusually high fluences. Cultures of wild-type (AB1157), endonuclease III-deficient (JW1625-1), and endonuclease IV-deficient (JW2146-1) E. coli, in exponential and stationary growth phases, were exposed to red and infrared lasers (0, 250, 500, and 1000 J/cm2) to evaluate their survival rates, filamentation phenotype induction and cell morphologies. The results showed that low-intensity red and infrared lasers at high fluences are lethal, induce a filamentation phenotype, and alter the morphology of the E. coli cells. Low-intensity red and infrared lasers have potential to induce adverse effects on cells, whether used at unusually high fluences, or at high doses. Hence, there is a need to reinforce the importance of accurate dosimetry in therapeutic protocols.

Nucleotide excision repair pathway assessment in DNA exposed to low-intensity red and infrared lasers

Low-intensity lasers are used for prevention and management of oral mucositis induced by anticancer therapy, but the effectiveness of treatment depends on the genetic characteristics of affected cells. This study evaluated the survival and induction of filamentation of Escherichia coli cells deficient in the nucleotide excision repair pathway, and the action of T₄endonuclease V on plasmid DNA exposed to low-intensity red and near-infrared laser light. Cultures of wild-type (strain AB1157) E. coli and strain AB1886 (deficient in uvrA protein) were exposed to red (660 nm) and infrared (808 nm) lasers at various fluences, powers and emission modes to study bacterial survival and filamentation. Also, plasmid DNA was exposed to laser light to study DNA lesions produced in vitro by T₄endonuclease V. Low-intensity lasers:i) had no effect on survival of wild-type E. coli but decreased the survival of uvrA protein-deficient cells,ii) induced bacterial filamentation, iii) did not alter the electrophoretic profile of plasmids in agarose gels, andiv) did not alter the electrophoretic profile of plasmids incubated with T₄ endonuclease V. These results increase our understanding of the effects of laser light on cells with various genetic characteristics, such as xeroderma pigmentosum cells deficient in nucleotide excision pathway activity in patients with mucositis treated by low-intensity lasers.

Protein conformational modulation by photons: a mechanism for laser treatment effects

Responsiveness to low-level laser treatment (LLTT) at a wavelength of 450-910 nm has established it as an effective treatment of medical, veterinary and dental chronic pain, chronic inflammation conditions (arthritis and macular degeneration), wound repair, and lymphoedema, yet the mechanisms underlying the effectiveness of LLLT remain unclear. However, there is now sufficient evidence from recent research to propose an integrated model of LLLT action. The hypothesis presented in this paper is that external applications of photons (through laser at an appropriate dose) modulates the nervous system through an integrated mechanism. This stimulated mechanism involves protein-to-protein interaction, where two or more proteins bind together to facilitate molecular processes, including modification of proteins by members of SUMO (small ubiquitin-related modifier proteins) and also protein phosphorylation and tyrosination. SUMO has been shown to have a role in multiple nuclear and perinuclear targets, including ion channels, and in the maintenance of telomeres and the post-translational modification of genes. The consequence of laser application in treatment, therefore, can be seen as influencing the transmission of neural information via an integrated and rapid modulation of ion channels, achieved through both direct action on photo-acceptors (such as cytochrome c-oxidase) and through indirect modulation via enzymes, including tyrosine hydroxylase (TH), tyrosine kinases and tyrosine kinase receptors. This exogenous action then facilitates an existing photonic biomodulation mechanism within the body, and initiates ion channel modulation both in the periphery and the central nervous system (CNS). Evidence indicates that the ion channel modulation functions predominately through the potassium channels, including two pore leak channels (K2P), which act as signal integrators from the periphery to the cortex. Photonic action also transforms SUMOylation processes at the cell membrane, nucleus and telomeres via signalling processes from the mitochondria (which is the main target of laser absorption) to these targets. Under the hypothesis, these observed biological effects would play a part in the bystander effect, the abscopal effect, and other systemic effects observed with the application of low level laser (LLLT). The implications of the hypothesis are important in that they point to mechanisms that can account for the effectiveness of laser in the treatment and prevention of inflammatory diseases, chronic pain and neurodegenerative disorders.

Low-level laser (light) therapy (LLLT) for treatment of hair loss

OBJECTIVE

Alopecia is a common disorder affecting more than half of the population worldwide. Androgenetic alopecia, the most common type, affects 50% of males over the age of 40 and 75% of females over 65. Only two drugs have been approved so far (minoxidil and finasteride) and hair transplant is the other treatment alternative. This review surveys the evidence for low-level laser therapy (LLLT) applied to the scalp as a treatment for hair loss and discusses possible mechanisms of actions.

METHODS AND MATERIALS

Searches of PubMed and Google Scholar were carried out using keywords alopecia, hair loss, LLLT, photobiomodulation.

RESULTS

Studies have shown that LLLT stimulated hair growth in mice subjected to chemotherapy-induced alopecia and also in alopecia areata. Controlled clinical trials demonstrated that LLLT stimulated hair growth in both men and women. Among various mechanisms, the main mechanism is hypothesized to be stimulation of epidermal stem cells in the hair follicle bulge and shifting the follicles into anagen phase.

CONCLUSION

LLLT for hair growth in both men and women appears to be both safe and effective. The optimum wavelength, coherence and dosimetric parameters remain to be determined.

Does low-level laser therapy have an antianesthetic effect? A review

Because local anesthetics are vasodilators, they tend to be absorbed into the bloodstream from the operative field as a result of the vasodilation of peripheral arterioles. To counteract this vasodilation, vasoconstrictive agents are often included in local anesthetic solutions to provide a longer duration of anesthesia. Low-level laser therapy (LLLT) has the same benefits, such as microcirculation activation and more-efficient tissue metabolism, analgesic effects, and vasodilatation. If LLLT is used to prevent pain postoperatively, improvements in local circulation and increased vasodilatation may increase the absorption of a local anesthetic agent. This may reduce the duration of the anesthesia, thereby allowing postoperative pain management to begin sooner. The maximal intensity of pain occurs during the first hours after surgery, when the local anesthetic has worn off. Theoretically, postoperative pain control can be increased with the use of a local anesthetic with a more-prolonged action. If a treatment method has both analgesic and antianesthetic effects, then the method may block its own effects. We review whether LLLT applied postoperatively to operated-on areas has an antianesthetic effect, that is, whether pain in the first hours after surgery was greater for patients who received LLLT than for control patients. Not too much evidence supports the antianesthetic effects of LLLT. However, additional experimental and clinical studies must be performed to investigate the effects of LLLT on the duration of anesthesia.