Increase in the nitric oxide release without changes in cell viability of macrophages after laser therapy with 660 and 808 nm lasers

Reprogramming Macrophage Phenotypes With Photobiomodulation for Improved Inflammation Control in ENT Organ Tissues

Photobiomodulation (PBM), a noninvasive phototherapy that utilizes wavelengths between red and near-infrared light, has emerged as a promising approach for controlling inflammation by modulating macrophage polarization. This review investigates the therapeutic potential of PBM in treating ENT-specific inflammatory conditions, such as chronic rhinosinusitis and otitis media, focusing on its effects on macrophage phenotypes and evidence from preclinical studies. By promoting mitochondrial activity, increasing adenosine triphosphate production, and modulating reactive oxygen species, PBM has been shown to shift macrophages from a pro-inflammatory to an anti-inflammatory phenotype. Studies have demonstrated that PBM enhances tissue repair, reduces inflammatory markers, and promotes wound healing. Moreover, PBM facilitates the polarization of M2 macrophages, a crucial factor in resolving mucosal inflammation in the nasal, pharyngeal, and middle ear cavities, as well as restoring tissue homeostasis. The anti-inflammatory effects of PBM are attributed to its ability to influence several molecular mechanisms involved in inflammation regulation, particularly in ENT organ tissues, where recurrent inflammation can lead to chronic conditions such as otitis media or sinusitis. Furthermore, this review compares PBM to competing methods for reprogramming macrophages and treating inflammation, highlighting its advantages of minimal toxicity, simplicity, and precision in controlling ENT immune responses.

Effect of exercise training with laser phototherapy on homeostasis balance resistant to hypercoagulability in seniors with obesity: a randomized trial

The prevalence of obesity has increased the incidence of obesity-related coagulation disorders. The current study assessed the effectiveness of combined aerobic exercise and laser phototherapy on the coagulation profile and body measurements in older adults with obesity compared to aerobic exercise alone, which has not been adequately explored. We included 76 obese people (50% women and 50% men) with a mean age of 67.83 ± 4.84 years and a body mass index of 34.55 ± 2.67 kg/m². The participants were randomly assigned to the experimental group (which received aerobic training with laser phototherapy) and the control group (which received aerobic training alone) for three months. From the baseline to the final analysis, the absolute changes in specific coagulation biomarker levels (fibrinogen, fibrin fragment D, prothrombin time, Kaolin-Cephalin Coagulation Time), and contributing parameters (C-reactive protein and total cholesterol), were assessed. In comparison to the control group, the experimental group showed significant improvements in all evaluated measures (p < 0.001). So, in comparison to aerobic exercise alone, combined aerobic exercise and laser phototherapy had superior positive effects on coagulation biomarkers and decreased the risk of thromboembolism throughout a three-month intervention period in senior obese persons. Therefore, we suggest adopting laser phototherapy for individuals with a greater risk of hypercoagulability.The research was entered into the database of clinical trials under the identification NCT04503317.

Detection of Membrane Potential-Dependent Rhodopsin Fluorescence Using Low-Intensity Light Emitting Diode for Long-Term Imaging

Microbial rhodopsin is a family of photoreceptive membrane proteins that commonly consist of a seven-transmembrane domain and a derivative of vitamin-A, retinal, as a chromophore. In 2011, archaeorhodopsin-3 (AR3) was shown to exhibit voltage-dependent fluorescence changes in mammalian cells. Since then, AR3 and its variants have been used as genetically encoded voltage indicators, in which mostly intense laser stimulation (1-1000 W/cm2) is used for the detection of dim fluorescence of rhodopsin, leading to high spatiotemporal resolution. However, intense laser stimulation potentially causes serious cell damage, particularly during long-term imaging over minutes. In this study, we present the successful detection of voltage-sensitive fluorescence of AR3 and its high fluorescence mutant Archon1 in a variety of mammalian cell lines using low-intensity light emitting diode stimulation (0.15 W/cm2) with long exposure time (500 ms). The detection system enables real-time imaging of drug-induced slow changes in voltage within the cells for minutes harmlessly and without fluorescence bleaching. Therefore, we demonstrate a method to quantitatively understand the dynamics of slow changes in membrane voltage on long time scales.

[Low level laser therapy: molecular mechanisms of anti-inflammatory and regenerative effects]

Laser therapy as a physiotherapeutic method has been successfully used for a long time in the treatment of various pathologies, but the action mechanisms of low level laser therapy (LLLT) remain understudied.

OBJECTIVE

To perform the analysis of published results of LLLT investigations, to describe the physical principles of photobiomodulation, its action mechanisms on various cells and tissues, therapeutic intervention and efficiency of the technique.

MATERIAL AND METHODS

The search of articles was done for the period from 2014 to 2022. The preference was given to the articles for the last 5 years in the PubMed database depending on keywords: low level laser therapy, photobiomodulation, exosomes, monocytes, macrophages.

RESULTS AND DISCUSSION

This article represents the current conceptions about the action mechanisms and reproduced effects of low level laser therapy, the photobiomodulation influence on the inflammation and reparative processes in human body by intervention on cells and their signal pathways. The discussion of research results and probable causes of conflicting data are performed, as well as the efficacy assessment of laser irradiation in different conditions and diseases is made.

CONCLUSION

Laser therapy has certain variety of advantages, among which: non-invasiveness and availability, long-term service of equipment, stable intensity of light radiation and the ability to use in various wavelength ranges. The technique efficacy was proven for a large number of diseases. However, for the successful application of photobiomodulation in clinical practice in current evidence-based medicine, additional investigations are necessary to determine the best dosimetric radiation parameters, as well as further study of action mechanisms on various human cells and tissues.

Improved healing and macrophage polarization in oral ulcers treated with photobiomodulation (PBM)

OBJECTIVES

The effect of photobiomodulation (PBM) treatment on wound healing and macrophage polarization was investigated in vivo. Animal models of oral ulcers were simulated through chemically induced oral ulcers in rats.

MATERIALS AND METHODS

PBM treatment using an infrared pulsed laser was used to treat oral ulcers in the animal models. Twelve Sprague-Dawley rats were randomly divided into four groups depending on set absorbed energy: Group 1 (control), Group 2 (30 J), Group 3 (60 J), and Group 4 (100 J). Laser treatment was performed every other day for 8 days after ulcer confirmation. Parameters used were as follows: wavelength 808 nm, power output 50 mW, spot size 10 mm, frequency 10 Hz, and pulse duration 1 millisecond. Ulcers were measured to determine the effect of the treatments over time. Histology, immunostaining, and real-time polymerase chain reaction analyses were performed to evaluate the effect of PBM treatment on macrophage-related (IL-6/IL-10) and wound-healing-related (TNF-α/TGF-β/MMP-2) cytokine expression.

RESULTS

Histological examinations indicate that the PBM treatment stimulated a higher level of wound recovery after 8 days of treatment at 60 J absorbed energy compared to other treatment groups. Analyses of relative gene expression of proinflammatory, anti-inflammatory, and tissue remodeling cytokines indicate that the macrophages in the tissue samples were predominantly characterized as M2 subtypes (alternatively activated), which possibly accounts for the accelerated tissue repair in the animal model of oral ulcer.

CONCLUSION

This preliminary study stands as a proof of concept regarding the potential use of infrared laser PBM treatment for oral ulcers which have not been previously investigated upon. PBM treatment affects macrophage polarization and enhances wound healing. Further experimentation will be conducted to expand the understanding of how PBM treatment affects the healing mechanism of ulcers.

Photobiomodulation enhances the Th1 immune response of human monocytes

This study aims to evaluate the effects of photobiomodulation (PBM) on human monocytes, assessing the oxidative burst and ultimate fungicidal potential of these cells, as well as the gene expression at the mRNA level of CD68, CD80, CD163, CD204, IL-6, TNF-α and IL-10 in derived macrophages. Primary cultures of human monocytes were irradiated with an InGaAlP (660 nm)/GaAlAs (780 nm) diode laser (parameters: 40 mW, 0.04 cm², 1 W/cm²; doses: 200, 400 and 600 J/cm²). Cells were submitted to the chemiluminescence assay, and a microbicidal activity assay against Candida albicans was performed. Reactive oxygen species (ROS) and nitric oxide (NO) production were measured, and cell viability was assessed by the exclusion method using 0.2% Trypan blue reagent. Irradiated monocytes were cultured for 72 h towards differentiation into macrophages. Total RNA was extracted, submitted to reverse transcription and real-time PCR. The results were analysed by ANOVA and the Tukey test (α = 0.05). Irradiated monocytes revealed a significant increase in their intracellular and extracellular ROS (P < 0.001). The 660 nm wavelength and 400 J/cm² dose were the most relevant parameters (P < 0.001). The fungicidal capacity of the monocytes was shown to be greatly increased after PBM (P < 0.001). PBM increased the expression of TNF-α (P = 0.0302) and the production of NO (P < 0.05) and did not impair monocyte viability. PBM induces a pro-inflammatory Th1-driven response in monocytes and macrophages.

Review on the Cellular Mechanisms of Low-Level Laser Therapy Use in Oncology

Photobiomodulation (PBM) using low-level laser therapy (LLLT) is a treatment that is increasingly used in oncology. Studies reported enhancement of wound healing with reduction in pain, tissue swelling and inflammatory conditions such as radiation dermatitis, oral mucositis, and lymphedema. However, factors such as wavelength, energy density and irradiation frequency influence the cellular mechanisms of LLLT. Moreover, the effects of LLLT vary according to cell types. Thus, controversy arose as a result of poor clinical response reported in some studies that may have used inadequately planned treatment protocols. Since LLLT may enhance tumor cell proliferation, these will also need to be considered before clinical use. This review aims to summarize the current knowledge of the cellular mechanisms of LLLT by considering its effects on cell proliferation, metabolism, angiogenesis, apoptosis and inflammation. With a better understanding of the cellular mechanisms, bridging findings from laboratory studies to clinical application can be improved.

Intraperitoneal Phototherapy Suppresses Inflammatory Reactions in a Surgical Model of Peritonitis

BACKGROUND

Standard treatment for diffuse peritonitis due to colorectal perforation may be insufficient to suppress inflammatory reaction in sepsis. Thus, developing new treatments is important. This study aimed to examine whether intraperitoneal irradiation by artificial sunlight suppresses inflammatory reaction in a lipopolysaccharide (LPS)-induced peritonitis model after surgical treatments.

MATERIALS AND METHODS

Mice were divided into naive, nontreatment (NT), and phototherapy (PT) groups. In the latter two groups, LPS was intraperitoneally administered to induce peritonitis and removed by intraperitoneal lavage after laparotomy. The PT group was irradiated with artificial sunlight intraperitoneally. We evaluated the local and systemic inflammatory reactions. Murine macrophages were irradiated with artificial sunlight after stimulation by LPS, and cell viability and expression of tumor necrotizing factor-α (TNF-α) were evaluated.

RESULTS

As a local inflammatory reaction, the whole cell count, the expression of interleukin-6 and TNF-α in the intra-abdominal fluid, and the peritoneal thickness were significantly lower in the PT group than in the NT group. As a systematic inflammatory reaction, the expression of serum TNF-α, granulocyte macrophage colony-stimulating factor, monocyte chemotactic protein-1, macrophage inflammatory protein (MIP)-1α, and MIP-1β were significantly lower in the PT group than in the NT group. Irradiation by artificial sunlight suppressed the expression of TNF-α in murine macrophages without affecting cell viability.

CONCLUSIONS

Intraperitoneal irradiation by artificial sunlight could suppress local and systemic inflammatory reactions in the LPS-induced peritonitis murine model. These effects may be associated with macrophage immune responses.

Attenuation of the inflammatory response and polarization of macrophages by photobiomodulation

In spinal cord injury (SCI), inflammation is a major mediator of damage and loss of function and is regulated primarily by the bone marrow-derived macrophages (BMDMs). Photobiomodulation (PBM) or low-level light stimulation is known to have anti-inflammatory effects and has previously been used in the treatment of SCI, although its precise cellular mechanisms remain unclear. In the present study, the effect of PBM at 810 nm on classically activated BMDMs was evaluated to investigate the mechanisms underlying its anti-inflammatory effects. BMDMs were cultured and irradiated (810 nm, 2 mW/cm²) following stimulation with lipopolysaccharide and interferon-γ. CCK-8 assay, 2',7'-dichlorofluorescein diacetate assay, and ELISA and western blot analysis were performed to measure cell viability, reactive oxygen species production, and inflammatory marker production, respectively. PBM irradiation of classically activated macrophages significantly increased the cell viability and inhibited reactive oxygen species generation. PBM suppressed the expression of a marker of classically activated macrophages, inducible nitric oxide synthase; decreased the mRNA expression and secretion of pro-inflammatory cytokines, tumor necrosis factor alpha, and interleukin-1 beta; and increased the secretion of monocyte chemotactic protein 1. Exposure to PBM likewise significantly reduced the expression and phosphorylation of NF-κB p65 in classically activated BMDMs. Taken together, these results suggest that PBM can successfully modulate inflammation and polarization in classically activated BMDMs. The present study provides a theoretical basis to support wider clinical application of PBM in the treatment of SCI.

Evaluation of angiogenesis, inflammation, and healing on irradiated skin graft with low-level laser therapy in rats (Rattus norvegicus albinus wistar)

The reconstructive techniques have been widely used in Veterinary Medicine. The post-operative adjuvants therapies like the low-level laser therapy (LLLT) are used to decrease inherent complications to reconstructive surgeries. This article purposed to define the LLLT effects on the healing, inflammation, and vascularization of the skin grafts in applicable time intervals to veterinary surgical routine. Forty rats (Rattus norvegicus albinus wistar) were used and each one was submitted to autogenous cutaneous mesh grafting in the interescapular region. The rats were randomly distributed in five groups (G1, G2, G3, G4, and G5) in accordance with the 6 J/cm² or 10 J/cm² dose every 3 or 5 days. These treatments were applied on the skin graft for 15 days. The histochemical evaluation with Picrosirius showed greater expression of collagen type 1 - red in grafts of G5 (p < 0.05), while in G1 did not; the expression of collagen type III - green was not induced by LLLT. The histochemical evaluation with hematoxylin-eosin showed greater numbers of fibroblasts in grafts of G4 (p < 0.05) and less hemorrhage in grafts of G5 (p < 0.05). There was modulation of the inflammatory response in irradiated skin grafts. It is concluded the exhibition of the skin grafts to 6 J/cm² or 10 J/cm² dose every 5 days improved the healing and the modulation of the local inflammation.

Photobiomodulation and different macrophages phenotypes during muscle tissue repair

Macrophages play a very important role in the conduction of several regenerative processes mainly due to their plasticity and multiple functions. In the muscle repair process, while M1 macrophages regulate the inflammatory and proliferative phases, M2 (anti‐inflammatory) macrophages direct the differentiation and remodelling phases, leading to tissue regeneration. The aim of this study was to evaluate the effect of red and near infrared (NIR) photobiomodulation (PBM) on macrophage phenotypes and correlate these findings with the repair process following acute muscle injury. Wistar rats were divided into 4 groups: control; muscle injury; muscle injury + red PBM; and muscle injury + NIR PBM. After 2, 4 and 7 days, the tibialis anterior muscle was processed for analysis. Macrophages phenotypic profile was evaluated by immunohistochemistry and correlated with the different stages of the skeletal muscle repair by the qualitative and quantitative morphological analysis as well as by the evaluation of IL‐6,TNF‐α and TGF‐β mRNA expression. Photobiomodulation at both wavelengths was able to decrease the number of CD68⁺ (M1) macrophages 2 days after muscle injury and increase the number of CD163⁺ (M2) macrophages 7 days after injury. However, only NIR treatment was able to increase the number of CD206⁺ M2 macrophages (Day 2) and TGF‐β mRNA expression (Day 2, 4 and 7), favouring the repair process more expressivelly. Treatment with PBM was able to modulate the inflammation phase, optimize the transition from the inflammatory to the regeneration phase (mainly with NIR light) and improve the final step of regeneration, enhancing tissue repair.

Mechanisms and applications of the anti-inflammatory effects of photobiomodulation

Photobiomodulation (PBM) also known as low-level level laser therapy is the use of red and near-infrared light to stimulate healing, relieve pain, and reduce inflammation. The primary chromophores have been identified as cytochrome c oxidase in mitochondria, and calcium ion channels (possibly mediated by light absorption by opsins). Secondary effects of photon absorption include increases in ATP, a brief burst of reactive oxygen species, an increase in nitric oxide, and modulation of calcium levels. Tertiary effects include activation of a wide range of transcription factors leading to improved cell survival, increased proliferation and migration, and new protein synthesis. There is a pronounced biphasic dose response whereby low levels of light have stimulating effects, while high levels of light have inhibitory effects. It has been found that PBM can produce ROS in normal cells, but when used in oxidatively stressed cells or in animal models of disease, ROS levels are lowered. PBM is able to up-regulate anti-oxidant defenses and reduce oxidative stress. It was shown that PBM can activate NF-kB in normal quiescent cells, however in activated inflammatory cells, inflammatory markers were decreased. One of the most reproducible effects of PBM is an overall reduction in inflammation, which is particularly important for disorders of the joints, traumatic injuries, lung disorders, and in the brain. PBM has been shown to reduce markers of M1 phenotype in activated macrophages. Many reports have shown reductions in reactive nitrogen species and prostaglandins in various animal models. PBM can reduce inflammation in the brain, abdominal fat, wounds, lungs, spinal cord.