Mechanisms Of Low-level Laser Therapy Research Articles

Low-level laser therapy alleviates periodontal age-related inflammation in diabetic mice via the GLUT1/mTOR pathway.

Diabetes mellitus (DM) is a chronic age-related disease that was recently found as a secondary aging pattern regulated by the senescence associated secretory phenotype (SASP). The purpose of this study is to detect the potential efficacy and the specific mechanisms of low-level laser therapy (LLLT) healing of age-related inflammation (known as inflammaging) in diabetic periodontitis. Diabetic periodontitis (DP) mice were established by intraperitoneal streptozotocin (STZ) injection and oral P. gingivalis inoculation. Low-level laser irradiation (810nm, 0.1W, 398mW/cm2, 4J/cm2, 10s) was applied locally around the periodontal lesions every 3days for 2 consecutive weeks. Micro-CT and hematoxylin-eosin (HE) stain was analyzed for periodontal soft tissue and alveolar bone. Western blots, immunohistochemistry, and immunofluorescence staining were used to evaluate the protein expression changes on SASP and GLUT1/mTOR pathway. The expression of aging-related factors and SASP including tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 were reduced in periodontal tissue of diabetic mice. The inhibitory effect of LLLT on GLUT1/mTOR pathway was observed by detecting the related factors mTOR, p-mTOR, GLUT1, and PKM2. COX, an intracytoplasmic photoreceptor, is a key component of the anti-inflammatory effects of LLLT. After LLLT treatment a significant increase in COX was observed in macrophages in the periodontal lesion. Our findings suggest that LLLT may regulate chronic low-grade inflammation by modulating the GLUT1/mTOR senescence-related pathway, thereby offering a potential treatment for diabetic periodontal diseases.

The Functions and Mechanisms of Low-Level Laser Therapy in Tendon Repair (Review).

Tendon injury is a common disease of the musculoskeletal system, accounting for roughly 30%–40% of sports system disorder injuries. In recent years, its incidence is increasing. Many studies have shown that low-level laser therapy (LLLT) has a significant effect on tendon repair by firstly activating cytochrome C oxidase and thus carrying out the photon absorption process, secondly acting in all the three phases of tendon repair, and finally improving tendon recovery. The repair mechanisms of LLLT are different in the three phases of tendon repair. In the inflammatory phase, LLLT mainly activates a large number of VEGF and promotes angiogenesis under hypoxia. During the proliferation phase, LLLT increases the amount of collagen type III by promoting the proliferation of fibroblasts. Throughout the remodeling phase, LLLT mainly activates M2 macrophages and downregulates inflammatory factors, thus reducing inflammatory responses. However, it should also be noted that in the final phase of tendon repair, the use of LLLT causes excessive upregulation of some growth factors, which will lead to tendon fibrosis. In summary, we need to further investigate the functions and mechanisms of LLLT in the treatment of tendon injury and to clarify the nature of LLLT for the treatment of diverse tendon injury diseases.

Raman spectroscopic investigation on the biomedical evolution of spinal cord injury and the therapeutic outcomes of its low-level laser therapy

The mechanism of low-level laser therapy (LLLT) of spinal cord injury (SCI) is currently unclear, and clinical application of LLLT treatments lack standardized protocols, since the treatment outcomes depends on various light parameters such as wavelength, fluence intensity, polarization and irradiation duration. In this work, Raman spectroscopy, was adopted to investigate the pathological process of SCI and monitor SCI-LLLT treatment so that accurate guidance on the appropriate selection of irradiation parameters may be achieved by an nonlabelled and nondesctructive intraoperative molecular diagnosis method. In vitro Raman spectroscopy combined with multivariate analysis technology was adopted to investigate the biochemical variations in spinal cord tissue during the progression of SCI and LLLT treatment. Besides, a discriminant model based on the principal component analysis-linear discriminant analysis algorithm (PCA-LDA) was established to distinguish the spectra of spinal tissue at pathological stages. The results of spectral analysis indicated that a series of biochemical events had occurred following SCI, such as chondroitin sulfate proteoglycan (CSPG) aggregation, vascular rupture, demyelination, and cell necrosis. It also demonstrated that LLLT could promote tissue recovery after injury by inhibition of CSPG expression and an increase in the concentration of myelin in tissues. In addition, the discriminant model achieved an accuracy of 96.25 % and 98.13 % for the SCI and SCI-LLLT groups, respectively, which could be used for predicting LLLT treatment outcomes during clinical applications. The study provides support for the development of intraoperative real-time in vivo Raman diagnostic methods to monitor the course of SCI-LLLT, allowing the selection of appropriate laser parameters and therapeutic strategies for clinical treatments.

Low-Level Laser Irradiation Stimulates RANKL-Induced Osteoclastogenesis via the MAPK Pathway in RAW 264.7 Cells

Low-level laser therapy (LLLT) is recognized as an effective medical tool for the treatment of various conditions requiring tissue repair, pain relief, inflammation treatment, and restoration of tissue dysfunction, and its development and research are growing rapidly. However, studies that analyze molecular biology by applying LLLT to osteoclasts are still insufficient to understand the mechanism. In order for LLLT to be suggested as an appropriate treatment method for the treatment of various bone diseases, it is necessary to elucidate the effect and mechanism of LLLT on osteoclast differentiation. In this study, we investigated the effect of LLLT on osteoclast differentiation using murine macrophage (RAW 264.7) cells by means of a Ga-As-Al laser (λ = 810, 80 mW). Our results indicate that LLLT did not induce cytotoxicity in RAW 264.7 cells. When LLLT was applied for 15 s to osteoclasts exposed to RANKL, the expression of NF-κB, ERK, p38, and c-Fos, which are associated with expression of NFATc1, was increased. The RT-PCR results also demonstrated significantly increased expression of osteoclast-specific genes, including NFATc1, TRAP, the calcitonin receptor, and cathepsin K, compared with the control. Taken together, we concluded that low-level laser irradiation induces osteoclastogenesis by enhancing the expression of NF-κB, MAPKs (ERK, p38), c-Fos, and NFATc1 in RAW 264.7 cells. These findings indicate that low-level laser irradiation could be considered a potential treatment option in various metabolic bone diseases that require osteoclastic activity and bone formation.

Besides Photothermal Effects, Low-Level CO2 Laser Irradiation Can Potentiate Skin Microcirculation Through Photobiomodulation Mechanisms.

Background: Improvement of microcirculation is one of the important mechanisms of low-level laser therapy (LLLT) to treat some diseases such as wound healing. Most previous studies have been carried out with multiple lasers other than the 10,600-nm CO2 laser. Recently, the CO2 laser has been used not only as a tool for excision of soft tissues but also for therapeutic applications. Objective: To study whether low-level CO2 laser irradiation can influence microcirculation and further explore the underlying mechanisms. Methods: Seventy-milliwatt (70-mW) CO2 lasers irradiated the forearms of 12 participants and skin blood perfusion (SkBP) was measured with a laser speckle imager. The thermal effect of irradiation was evaluated by measuring the irradiated skin in vivo and the exposed cell suspensions in vitro. Extracellular adenosine triphosphate (eATP) of the human mast cell line (HMC-1) is assessed by luciferin-luciferase assay to explore the potential mechanisms. Results: Irradiation caused dose-dependent increase in SkBP. At a medium dose of 262 J/cm2, SkBP reached its maximum value at 195.8% ± 18.6% of the baseline (n = 12, p < 0.01). Such laser irradiation had a mild thermal effect, heating local skin temperature (SkT) by 6.1°C ± 0.3°C (n = 10) and warming cell suspensions by 4.5°C ± 0.8°C (n = 6). Irradiation dose-dependently lowered eATP levels of HMC-1 cells in vitro. At a medium dose of 262 J/cm2, eATP levels declined to the minimum at 74.8% ± 5.5% of the baseline (n = 12, p < 0.01). This downregulation effect could be significantly inhibited by 100-μM ARL67156, a nonspecific ecto-ATPase inhibitor. On the contrary, heating itself slightly raised the level of eATP. Conclusions: Low-level CO2 laser irradiation can improve microcirculation. Besides the thermal effect, regulation of extravascular eATP by the photobiomodulation mechanism may be involved. This implies that CO2 lasers might be used in LLLT.

Low-level laser therapy in rehabilitation of patients with ischemic heart disease: review of evidence-based studies

Cardiac rehabilitation is one of the main achievements of cardiology and physical rehabilitation medicine in the second half of the 20th century. Based on the methodology of evidence-based medicine, cardiac rehabilitation in a short time evolved from a “fictional” “alternative” unproven treatment direction to completely uncontested and proven multidisciplinary programs. This article presents contemporary findings on cardiorehabilitation and analysis of evidence-based experimental and clinical studies of low-level laser therapy efficiency in patients with ischemic heart disease. Aim. To search for evidence-based investigations on application of low-level laser therapy for rehabilitation of patients with ischemic heart disease and to analyze their major propositions and recommendations.Materials and methods. PEDro, EMBASE, PubMed and Cochrane library electronic databases were searched for randomized clinical trials, systematic reviews, meta-analyses and clinical protocols using the key words within 2000–2019 years. Results and discussion: experimental and clinical investigations were carefully considered and the following findings were analyzed: action mechanisms of low-level laser therapy, its positive influence on myocardial remodeling, infarction area reduction, restenosis prevention and presented cardioprotective effect. More attention was focused at clinical evidence-based studies on application of photobiomodulation in order to increase the efficacy of surgical and percutaneous myocardial revascularization, and in non-invasive cardiology and physical rehabilitation medicine. Conclusion: regular analysis of performed studies and realization of new evidence-based investigation should be conducted to evaluate the efficiency of low-level laser therapy in rehabilitation of patients with ischemic heart disease.

Label-Free Spectral Imaging Unveils Biochemical Mechanisms of Low-Level Laser Therapy on Spinal Cord Injury

Background/Aims: Low-level laser therapy (LLLT) leads to complex photochemical responses during the healing process of spinal cord injury (SCI). Confocal Raman Microspectral Imaging (in combination with multivariate analysis) was adopted to illustrate the underlying biochemical mechanisms of LLLT treatment on a SCI rat model. Methods: Using transversal tissue sections, the Raman spectra can identify areas neighboring the injury site, glial scar, cavity, and unharmed white matter, as well as their correlated cellular alterations, such as demyelination and up-regulation of chondroitin sulfate proteoglycans (CSPGs). Multivariate data analysis methods are used to depict the underlying therapeutic effects by highlighting the detailed content and distribution variations of the biochemical constituents. Results: It is confirmed that photon-tissue interactions might lead to a decay of the inhibitory response to remyelination by suppressing CSPG expression, as also morphologically demonstrated by reduced glial scar and cavity areas. An inter-group comparison semi-quantitatively confirms changes in lipids, phosphatidic acid, CSPGs, and cholesterol during SCI and its LLLT treatment, paving the way for in vitro and in vivo understanding of the biochemical changes accompanying pathobiological SCI events. Conclusion: The achieved results in this work not only have once again proved the well-known cellular mechanisms of SCI, but further illustrate the underlying biochemical variability during LLLT treatment, which provide a sound basis for developing real-time Raman methodologies to monitor the efficacy of the SCI LLLT treatment.

Anti-inflammatory and lymphangiogenetic effects of low-level laser therapy on lymphedema in an experimental mouse tail model.

The aim of the present study was to investigate the therapeutic mechanism of low-level laser therapy (LLLT) in the mouse tail lymphedema model. Six-week-old female mice were classified into the laser treatment group, sham treatment group, and surgical control group (10 mice per group). LLLT was administered daily for 10 min from the surgical day to 11 days (12 times). Macrophage activation and lymphatic vessel regeneration were evaluated through immunohistochemical staining with anti-F4/80 and anti-LYVE-1 antibodies, respectively, at 12 days post-procedure. Quantitative real-time polymerase chain reaction (qPCR) was performed to measure messenger RNA (mRNA) expression of vascular endothelial growth factor A, B, C, R1, R2, and R3 (VEGF-A, VEGF-B, VEGF-C, VEGFR1, VEGFR2, and VEGFR3) at 12 days post-procedure. Student's t and one-way ANOVA tests were performed for statistical analyses. Significance was defined as p < 0.05. The thickness of the tail rapidly increased until 6 days in the laser and sham groups. The mice in the laser group showed a significantly decreased thickness compared with the sham group at 10 and 12 days. Immunohistochemistry assay revealed that LLLT reduced inflammation and induced new lymphatic vessel growth. qPCR showed that expressions of VEGFR3 were (p = 0.002) increased in the laser group. These results suggest that LLLT has anti-inflammatory and lymphangiogenetic effects for the management of lymphedema.

Low-level laser therapy ameliorates disease progression in a mouse model of multiple sclerosis

Multiple sclerosis (MS) is an autoimmune demyelinating inflammatory disease characterized by recurrent episodes of T cell-mediated immune attack on central nervous system (CNS) myelin, leading to axon damage and progressive disability. The existing therapies for MS are only partially effective and are associated with undesirable side effects. Low-level laser therapy (LLLT) has been clinically used to treat inflammation, and to induce tissue healing and repair processes. However, there are no reports about the effects and mechanisms of LLLT in experimental autoimmune encephalomyelitis (EAE), an established model of MS. Here, we report the effects and underlying mechanisms of action of LLLT (AlGaInP, 660 nm and GaAs, 904 nm) irradiated on the spinal cord during EAE development. EAE was induced in female C57BL/6 mice by immunization with MOG35–55 peptide emulsified in complete Freund’s adjuvant. Our results showed that LLLT consistently reduced the clinical score of EAE and delayed the disease onset, and also prevented weight loss induced by immunization. Furthermore, these beneficial effects of LLLT seem to be associated with the down-regulation of NO levels in the CNS, although the treatment with LLLT failed to inhibit lipid peroxidation and restore antioxidant defense during EAE. Finally, histological analysis showed that LLLT blocked neuroinflammation through a reduction of inflammatory cells in the CNS, especially lymphocytes, as well as preventing demyelination in the spinal cord after EAE induction. Together, our results suggest the use of LLLT as a therapeutic application during autoimmune neuroinflammatory responses, such as MS.

Low Level Laser Therapy Reduces the Development of Lung Inflammation Induced by Formaldehyde Exposure.

Lung diseases constitute an important public health problem and its growing level of concern has led to efforts for the development of new therapies, particularly for the control of lung inflammation. Low Level Laser Therapy (LLLT) has been highlighted as a non-invasive therapy with few side effects, but its mechanisms need to be better understood and explored. Considering that pollution causes several harmful effects on human health, including lung inflammation, in this study, we have used formaldehyde (FA), an environmental and occupational pollutant, for the induction of neutrophilic lung inflammation. Our objective was to investigate the local and systemic effects of LLLT after FA exposure. Male Wistar rats were exposed to FA (1%) or vehicle (distillated water) during 3 consecutive days and treated or not with LLLT (1 and 5 hours after each FA exposure). Non-manipulated rats were used as control. 24 h after the last FA exposure, we analyzed the local and systemic effects of LLLT. The treatment with LLLT reduced the development of neutrophilic lung inflammation induced by FA, as observed by the reduced number of leukocytes, mast cells degranulated, and a decreased myeloperoxidase activity in the lung. Moreover, LLLT also reduced the microvascular lung permeability in the parenchyma and the intrapulmonary bronchi. Alterations on the profile of inflammatory cytokines were evidenced by the reduced levels of IL-6 and TNF-α and the elevated levels of IL-10 in the lung. Together, our results showed that LLLT abolishes FA-induced neutrophilic lung inflammation by a reduction of the inflammatory cytokines and mast cell degranulation. This study may provide important information about the mechanisms of LLLT in lung inflammation induced by a pollutant.

Effect of Equal Daily Doses Achieved by Different Power Densities of Low-Level Laser Therapy at 635 nm on Open Skin Wound Healing in Normal and Diabetic Rats

Background and Objective. Despite the fact that the molecular mechanism of low-level laser therapy (LLLT) is not yet known, the exploitation of phototherapy in clinical medicine and surgery is of great interest. The present study investigates the effects of LLLT on open skin wound healing in normal and diabetic rats. Materials and Methods. Four round full-thickness skin wounds on dorsum were performed in male adult nondiabetic (n = 24) and diabetic (n = 24) Sprague–Dawley rats. AlGaInP (635 nm, wavelength; 5 J/cm2, daily dose) was used to deliver power densities of 1, 5, and 15 mW/cm2 three times daily until euthanasia. Results. PMNL infiltration was lower in the irradiated groups (15 mW/cm2). The synthesis and organisation of collagen fibres were consecutively enhanced in the 5 mW/cm2 and 15 mW/cm2 groups compared to the others in nondiabetic rats. In the diabetic group the only significant difference was recorded in the ratio PMNL/Ma at 15 mW/cm2. A significant difference in the number of newly formed capillaries in the irradiated group (5, 15 mW/cm2) was recorded on day six after injury compared to the control group. Conclusion. LLLT confers a protective effect against excessive inflammatory tissue response; it stimulates neovascularization and the early formation of collagen fibres.

English

UNDERSTANDING THE MECHANISMS OF LOW LEVEL LASER THERAPY (LLLT): Low Level Laser Therapy (LLLT) is a rapidly growing modality used in rehabilitation and physical therapy. A number of safe and beneficial therapeutic effects of LLLT have been reported in numerous clinical conditions; however, despite many reports of positive findings from experiments conducted in-vitro, in animal models and in randomized controlled clinical trials worldwide, the use of this scientifically grounded, non-invasive, anti-inflammatory and regulatory modality has yet to find mainstream adoption by medical doctors. The aim of this review is six fold: 1) Introduce the unfamiliar reader, with some medical background, to the contemporary concept of LLLT and its pathophysiological significance, 2) Review the role of the mitochondrial pathway in the mechanisms of LLLT, 3) Provide necessary practical guidance based on personal scientific and clinical experience, 4) Assist manufacturers in their research and development, 5) Help health care practitioners choose and use an adequate light therapy device 6) Outline the prospects of LLLT as an avenue to treat chronic inflammation and pain and to aid in an effective clinical practice.

An inexpensive, automated instrument for laser irradiation of cultured cells.

Laser irradiation of cultured cells is a valuable technique for elucidating the mechanisms of low-level laser therapy, but is often tedious because of the need to manually change the position of the laser beam. Consequently, we developed a computer-based system that automatically moves a cell culture plate over a laser beam and times the exposure. There are presently no commercial devices available for automated laser irradiation of cultured cells. Many investigators thus manually aim and time laser exposure, a time-consuming task that is prone to errors. We used outdated, surplus computer components to construct a system for automated laser exposure of cultured cells. This design strategy makes the system quite inexpensive. Construction and operation of the system is described and an example of its use is presented. Alternate means of accomplishing automated laser irradiation are also presented. Inexpensive and relatively simple devices can be constructed for automated laser irradiation of cultured cells. These devices can eliminate the tedium and errors of manual laser exposure.