Molecular mechanisms of cell proliferation induced by low power laser irradiation

Immunomodulatory effects of photobiomodulation: a comprehensive review

Photobiomodulation, also known as low-level light therapy (LLLT), has emerged as a promising non-invasive treatment modality with significant immunomodulatory effects. This comprehensive review examines the mechanisms underlying photobiomodulation-induced immunomodulation, its effects on specific immune cells, and its clinical applications in immune-related conditions. We explore the cellular and molecular pathways affected by photobiomodulation, including mitochondrial function, reactive oxygen species production, and key signaling cascades. The impact of photobiomodulation on macrophages, T cells, and dendritic cells is discussed, along with its potential in managing autoimmune diseases, inflammatory conditions, and wound healing. Safety considerations, optimal treatment parameters, and future directions in the field are also addressed. This review highlights the growing body of evidence supporting photobiomodulation as a valuable tool in immunomodulation and its potential to revolutionize the treatment of various immune-mediated disorders.

Review on the molecular mechanisms of low-level laser therapy: gene expression and signaling pathways

Low-level laser therapy (LLLT) has been shown to influence cellular and molecular processes in irradiated tissues and cells. By altering gene expression and activating specific laser-induced signaling pathways, LLLT can impact key cellular activities such as proliferation, differentiation, migration, and metabolism. This review focuses on exploring the molecular-level effects of LLLT, examining how different wavelengths interact with various cell lines, including stem cells, to induce these changes in gene expression and signaling pathways. A comprehensive review was performed by analyzing relevant literature published between 2003 and 2024. The search utilized databases such as PubMed, Scopus, MEDLINE, EMBASE, and Google Scholar. Selection criteria were based on the presence of keywords including "gene expression," "signaling pathways," "molecular mechanisms," "photobiomodulation," and "LLLT." Among the 150 recent studies on low-level laser therapy and its molecular and cellular effects on irradiated cells, articles related to changes in gene expression and laser-induced signaling pathways were reviewed. Low-level laser therapy exhibits varying effects based on the parameters and wavelengths used. Red and infrared lasers are particularly effective for promoting cell proliferation, differentiation, reducing inflammation, and enhancing wound healing. Blue lasers tend to inhibit cell proliferation, while green lasers are effective in reducing inflammation and aiding in conditions such as intervertebral disc (IVD) degeneration. These effects are linked to changes in gene expression and laser-induced signaling pathways, highlighting the importance of selecting the appropriate laser type for specific therapeutic goals.

The Use of a Proprietary Near-Infrared Laser to Enhance Wound Healing: A Preliminary Preclinical and Clinical Study

Background

Nonthermal light energy has been used to enhance wound healing. This is known as photobiomodulation. Although preclinical evidence is largely based on laser light, light-emitting diodes (LEDs) form the mainstay of clinical studies owing to the lack of available lasers for nonclinical use. However, it is speculated the 2 technologies exhibit dissimilar biological responses.

Objectives

The influence of a new, commercially available near-infrared laser device on the gene expression profile of human skin relative to an equivalent, near-infrared LED device was evaluated. Additionally, the wound healing potential of the device was examined in practice.

Methods

Defatted human skin was exposed to the laser (3), LED (3), or negative control (3) for 5 days. On Day 6, skin samples were biopsied for ribonucleic acid extraction and gene expression assays run for 107 genes of interest. Twenty patients with chronic wounds were randomized to receive standard wound care ± laser therapy 3 times weekly for 4 weeks, and wounds were analyzed for healing.

Results

The laser altered expression of 45 genes. Highly up-regulated genes (>5-fold change) included those implicated in wound healing and antiaging, whereas highly down-regulated genes included those implicated in inflammation and extracellular matrix integrity. The LED device altered expression of only 1 gene relative to negative controls. The laser reduced mean wound area by 78% and healed 4 of 10 wounds completely. In contrast, 8 of 10 of those receiving standard care exhibited no change.

Conclusions

A proprietary near-infrared laser exhibited superior ability to influence gene expression in healthy skin than an equivalent LED device and induced the healing of chronic wounds.

Level of Evidence 2 Therapeutic

Photobiomodulation of gut microbiota with low-level laser therapy: a light for treating neuroinflammation

The gut microbiota is known to interact with various organs in the body, including the central nervous system, through the gut-brain axis. Intestinal dysbiosis can lead to increased peripheral inflammation and, consequently, affect the brain, resulting in neuroinflammation. Photobiomodulation (PBM) has demonstrated positive regulatory effects on the imbalance of certain body functions, including pain, inflammation, immunity, wound healing, and gut microbiota dysbiosis. Therefore, PBM at the intestinal level could help improve intestinal dysbiosis and reestablish cerebral homeostasis. In this context, this study aimed to conduct a narrative review of the literature on the effects of PBM at the intestinal level on intestinal dysbiosis and neuroinflammation. Overall, the findings highlight that PBM modulates the gut microbiota, suggesting it could serve as a therapy for neurological conditions affecting the gut-brain axis. Future research should focus on further elucidating the molecular mechanisms underlying this therapy.

Effects of low-level laser irradiation on canine fibroblasts

Low-level laser (LLL) therapy is a well-known noninvasive treatment that stimulates fibroblasts to improve wound healing. LLL can improve fibroblast proliferation and migration without causing toxicity. The present study aimed to evaluate the effects of two laser wavelengths at different irradiation times on canine fibroblasts. Fibroblasts were isolated from canine oral mucosa. After seeding for 24 hr, the fibroblasts were irradiated using the Erchonia® EVL dual-diode laser at wavelengths of 405 nm (5 mW) and 640 nm (7.5 mW) with irradiation times of 120, 360, and 1,800 sec. The proliferating and viability cells were evaluated 24 hr after laser irradiation. Wound closure rates were calculated at 0, 24, and 48 hr after laser irradiation. Parameters, including proliferation cell, cell viability, and cell migration, tended to be higher in the 360-sec group (405 nm) and 120-sec group (640 nm) than in other groups. Our findings suggest that LLL therapy at wavelengths of 405 and 640 nm with an irradiation time of 120-360 sec (0.26-0.51 J/cm2) can stimulate the proliferation and migration of canine fibroblasts. This finding may contribute to a better understanding of the beneficial role of LLL stimulation in canine wound healing.

Effect of nutritional stress and photobiomodulation protocol on in vitro viability and proliferation of murine preosteoblast cells

This study aimed to assess the impact of nutritional conditions and irradiation parameters on the viability and proliferation of murine preosteoblasts. MC3T3-E1 cells were maintained under standard culture conditions (αMEM supplemented with 10% fetal bovine serum) or nutritional deficit conditions (αMEM without serum) and irradiated or not (control) with an InGaAlP diode laser at wavelengths of 660 nm (red) or 790 nm (infrared), with doses of 1, 4, or 6 J/cm², in a single dose in continuous mode. Cell viability and proliferation were assessed 24, 48, and 72 h after irradiation using the Alamar blue reduction assay. The cell cycle and events related to cell death were evaluated via propidium iodide (PI) staining and Annexin V/PI assays, respectively, through flow cytometry. The data revealed that in cells cultured with normal nutrition (10% FBS), there was no significant difference (p > 0.05) in cell viability or proliferation among the different irradiation protocols. In contrast, in the experiments conducted under nutritional deficiency, the infrared laser at a dose of 6 J/cm² significantly increased (p < 0.05) cell viability and proliferation compared with those of the control group at 72 h. The data were confirmed by cell cycle and cell death events (Annexin V/PI) assays. These results suggest that in vitro PBM yields more consistent biostimulatory effects on pre-osteoblasts subjected to nutritional deficiency, highlighting the need for attention to simulate these conditions in studies with laser therapy in in vitro bone disease models and in in vitro experiments using PBM for bone tissue engineering.

Progressive Thickening of Retinal Nerve Fiber and Ganglion Cell Complex Layers Following SDM Laser Vision Protection Therapy in Open-Angle Glaucoma

INTRODUCTION

This work aims to determine the effect on nerve fiber layer (NFL) and ganglion cell complex (GCC) thickness trends in eyes with open-angle glaucoma (OAG) treated with Vision Protection Therapy™ (VPT).

METHODS

A retrospective analysis of spectral-domain optical coherence tomography (OCT) measured NFL and GCC thickness trends was performed, excluding eyes with poor-quality scans and principal diagnoses other than OAG. This study compares eyes with OAG managed conventionally with IOP control alone (controls) to eyes managed with the addition of VPT (VPT eyes). The direction (+ or -) and magnitude (microns/year) of the OCT trends were the study endpoints.

RESULTS

Seventy-eight control eyes of 40 patients and 61 VPT-treated eyes of 39 patients were included in the study. Positive NFL trends were noted in 5% of control eyes vs. 71% of VPT eyes (p < 0.0001). Positive GCC trends were noted in 8% of control eyes vs. 43% of VPT eyes (p < 0.0001). Mean NFL trends (µm/year) were - 0.692 for controls vs. 0.347 for VPT (p < 0.0001). Mean GCC trends (µm/year) were - 0.554 for controls vs. - 0.148 for VPT (p = 0.0175).

CONCLUSIONS

The addition of VPT to the conventional management of OAG resulted in highly significant improvements in NFL and GCC trends, indicating a reversal of key indicators of glaucoma severity and progression.

Effectiveness of the Association of Fibrin Scaffolds, Nanohydroxyapatite, and Photobiomodulation with Simultaneous Low-Level Red and Infrared Lasers in Bone Repair

Biomaterials and biopharmaceuticals for correcting large bone defects are a potential area of translational science. A new bioproduct, purified from snake venom and fibrinogen from buffalo blood, aroused interest in the repair of venous ulcers. Expanding potential uses, it has also been used to form biocomplexes in combination with bone grafts, associated with physical therapies or used alone. The aim of this preclinical study was to evaluate low-level laser photobiomodulation (PBM) in critical defects in the calvaria of rats filled with nanohydroxyapatite (NH) associated with the heterologous fibrin biopolymer (HFB). Sixty animals were used, divided into six groups (n = 10 each): G1 (NH); G2 (HFB); G3 (NH + HFB); G4 (NH + PBM); G5 (HFB + PBM); G6 (NH + HFB + PBM). PBM simultaneously used red (R) and infrared (IR) light emission, applied intraoperatively and twice a week, until the end of the experiment at 42 days. Microtomography, bone formation can be seen initially at the margins of the defect, more evident in G5. Microscopically, bone formation demonstrated immature and disorganized trabeculation at 14 days, with remnants of grafting materials. At 42 days, the percentage of new bone formed was higher in all groups, especially in G5 (HFB, 45.4 ± 3.82), with collagen fibers at a higher degree of maturation and yellowish-green color in the birefringence analysis with Picrosirius-red. Therefore, it is concluded that the HFB + PBM combination showed greater effectiveness in the repair process and presents potential for future clinical studies.

Laser Acupuncture Versus Electroacupuncture for Nonsevere Carpal Tunnel Syndrome: A Randomized Controlled Trial

Background

Electroacupuncture (EA) is commonly employed for carpal tunnel syndrome (CTS), whereas laser acupuncture (LA) seems to offer a safer and more convenient alternative. Nevertheless, transitioning from EA to LA requires evidence. This study aims to compare their clinical efficacy and safety.

Methods

A randomized single-blind controlled trial was conducted on 76 CTS patients, with 38 patients assigned to receive EA (EA group) and 38 assigned to receive LA (LA group). Acupoints selected for both groups included PC4, PC6, PC7, PC8, LI4, LI10, LI11, HT3, HT7, and LU10. The intervention consisted of 20 sessions over 4 weeks. Symptom Severity Scale (SSS) and Functional Status Scale (FSS) scores, patients' satisfaction, and adverse events (AEs) were recorded.

Results

The LA group demonstrated significantly greater reductions in SSS and FSS scores than the EA group, with mean differences (MDs) and 95% confidence interval (95% CI) of -4.29 (-5.40 to -3.18) and -0.73 (-1.24 to -0.24), respectively, after 4 weeks of treatment. Complete symptom, functional recovery, and both were also significantly better in the LA group (relative risks [RR] [95% CI]: 14.00 [1.94 to 101.22], 1.58 [1.24 to 2.02], and 14.00 [1.94 to 101.22], respectively). Overall treatment effectiveness and satisfaction levels were notably higher in the LA group. Six patients experienced AEs in the EA group, whereas no AEs were reported in the LA group.

Conclusions

In this study, the findings indicate that LA may offer a safer and more effective alternative to EA. Further studies with longer follow-up periods and assessment of electrodiagnostic changes after intervention are needed.

Burning Mouth Syndrome Treated with Low-Level Laser and Clonazepam: A Randomized, Single-Blind Clinical Trial

OBJECTIVE

Burning mouth syndrome (BMS) is a chronic pain disorder characterized by intraoral burning or dysaesthetic sensation, with the absence of any identifiable lesions. Numerous treatments for BMS have been investigated, though without conclusive results. An analysis was conducted of the efficacy of treatment with a low-level diode laser and clonazepam in patients with BMS, and a study was carried out on the levels of different salivary biomarkers before and after treatment.

MATERIAL AND METHODS

A randomized, single-blind clinical trial was carried out involving 89 patients divided into the following groups: group 1 (laser, The Helbo® Theralite Laser 3D Pocket Probe + clonazepam) (n = 20), group 2 (sham laser placebo) (n = 19), group 3 (laser) (n = 21) and group 4 (clonazepam) (n = 18). Symptom intensity was scored based on a visual analogue scale (VAS). Sialometry was performed before and after treatment, and the Xerostomia Inventory, Oral Health Impact Profile-14 (OHIP-14) and Mini-Nutritional Assessment (MNA) questionnaires were administered. The following markers were measured in saliva samples: interleukins (IL2, IL4, IL5, IL6, IL7, IL8, IL1β, IL10, IL12, IL13, IL17, IL21 and IL23), proteins (MIP-3α, MIP-1α and MIP-1β), GM-CSF, interferon gamma (IFNγ), interferon-inducible T-cell alpha chemoattractant (ITAC), fractalkine and tumor necrosis factor α (TNFα).

RESULTS

A significant decrease in the VAS scores was observed after treatment in group 1 (laser + clonazepam) (p = 0.029) and group 3 (laser) (p = 0.005). In turn, group 3 (laser) showed a decrease in the salivary concentration of fractalkine (p = 0.025); interleukins IL12 (p = 0.048), IL17 (p = 0.020), IL21 (p = 0.008), IL7 (p = 0.001) and IL8 (p = 0.007); proteins MIP1α (p = 0.048) and MIP1β (p = 0.047); and TNFα (p = 0.047) versus baseline. Following treatment, group 1 (laser + clonazepam) showed significant differences in IL21 (p = 0.045) and IL7 (p = 0.009) versus baseline, while group 4 (clonazepam) showed significant differences in IL13 (p = 0.036), IL2 (p = 0.020) and IL4 (p = 0.001). No significant differences were recorded in group 2 (sham laser placebo).

CONCLUSIONS

The low-level diode laser is a good treatment option in BMS, resulting in a decrease in patient symptoms and in salivary biomarkers. However, standardization of the intervention protocols and laser intensity parameters is needed in order to draw more firm conclusions.

Low-Level Laser Therapy for Allergic Rhinitis: A Systematic Review and Meta-Analysis

INTRODUCTION

Allergic rhinitis (AR) is a common allergic disorder that impairs social and physical functioning as well as quality of life. It is characterized by sneezing, rhinorrhea, congestion, and itching which respond suboptimally to drug therapy. Low-level laser therapy (LLLT) has anti-inflammatory and immunosuppressive properties that have shown promise in some studies. We aimed to systematically review LLLT's effectiveness in treating AR and meta-analyze our findings.

METHODS

A systematic search of PubMed, Scopus, and Web of Science was conducted on November 24, 2023. All studies investigating LLLT on AR were included, and a pre-post meta-analysis of nasal symptoms (rhinorrhea, nasal congestion, nasal itching, and sneezing) in the LLLT-treated arm was conducted. Rhinoconjunctivitis quality of life questionnaire (RQLQ) scores before and after LLLT were also meta-analyzed alongside a pairwise meta-analysis of LLLT with placebo, acupuncture, steroids/antihistamines, and ultraviolet lasers. A random-effects model was used with a conservative pre-post correlation of 0.4 and standardized mean difference (SMD) as the effect size.

RESULTS

Sixteen studies were included in this review, and we found that nasal symptoms are alleviated post-LLLT in people with AR (SMD: -1.4, 95 CI: [-2.07 to -1.13], p value <0.001). RQLQ scores were also reduced after LLLT (SMD = -0.72, 95 CI: [-0.94 to -0.50], p value <0.001), and very few adverse events were reported. This meta-analysis, however, had significant publication bias and heterogeneity. When compared to a placebo, LLLT did not significantly improve nasal symptoms (SMD: -0.69, p value = 0.167), which might mean the post-LLLT nasal symptom alleviation is due to a placebo effect. Comparisons to other treatment modalities were too few to deduce anything meaningful, although it does appear that LLLT is less effective than UV lasers.

CONCLUSION

LLLT is most likely effective at alleviating nasal symptomology and has a low likelihood of adverse event incidence, yet more high-quality studies with larger sample sizes are needed to compare LLLT to a placebo to ensure its superiority to the placebo effect, as well as non-inferiority clinical trials to compare it to standard treatments.

Combined Light and Thermal Stimulation of Bone Marrow Stem Cells

Introduction: The purpose of this study is to achieve a significant increase in the proliferative activity of mesenchymal stem cells (MSCs) of the bone marrow (BM) at early passages after laser exposure to a suspension of these cells and to estimate the effect of light and heat components of laser radiation on the proliferation of BM MSCs. Methods: The studies were performed on rats BM MSCs. MSC suspension was placed into the wells and heated by using laser radiation (980 nm wavelength) or a water bath at 70 °C providing similar temperature dynamics. The studies were carried out in 3 comparison groups: (1) control suspension of MSCs, which was not subjected to heating in a water bath or laser exposure; (2) MSC suspension, which was heated for in a water bath; and (3) suspension of MSCs, which was subjected to laser exposure. The exposure times for the 2nd and 3rd experimental groups were 10- 50 seconds. Results: Under optimal parameters of laser action on the suspension of BM MSCs, a six-fold increase in the number of BM MSCs colonies was registered compared to the control. The role of the light and heat components of laser exposure to MSCs was determined by comparable heating of a suspension of BM MSCs in a water bath, at which only a twofold increase in the number of colonies was maximally obtained. Conclusion: The increase in the MSC proliferation activity occurs due to their Thermo-Photobiomodulation. The result obtained is important for practical use in cell transplantation in the treatment of traumatic injuries of bone, cartilage, and tendon tissues when a rapid and multiple increase in the initial number of autologous BM MSCs is required.

The effects of low-level laser therapy on severe acute respiratory syndrome coronavirus 2 infection in HEK293/ACE2 cells

SARS-CoV-2 is a threat to public health due to its ability to undergo crucial mutations, increasing its infectivity and decreasing the vaccine's effectiveness. There is a need to find and introduce alternative and effective methods of controlling SARS-CoV-2. LLLT treats diseases by exposing cells or tissues to low levels of red and near-infrared light. The study aims to investigate for the first time the impact of LLLT on SARS-CoV-2 infected HEK293/ACE2 cells and compare them to uninfected ones. Cells were irradiated at 640 nm, at different fluences. Subsequently, the effects of laser irradiation on the virus and cells were assessed using biological assays. Irradiated uninfected cells showed no changes in cell viability and cytotoxicity, while there were changes in irradiated infected cells. Furthermore, uninfected irradiated cells showed no luciferase activity while laser irradiation reduced luciferase activity in infected cells. Under SEM, there was a clear difference between the infected and uninfected cells.

Brain photobiomodulation therapy on neurological and psychological diseases

Photobiomodulation (PBM) therapy is an innovative treatment for neurological and psychological conditions. Complex IV of the mitochondrial respiratory chain can be stimulated by red light, which increases ATP synthesis. In addition, the ion channels' light absorption causes the release of Ca2+, which activates transcription factors and changes gene expression. Neuronal metabolism is improved by brain PBM therapy, which also promotes synaptogenesis and neurogenesis as well as anti-inflammatory. Its depression-treating potential is attracting attention for other conditions, including Parkinson's disease and dementia. Giving enough dosage for optimum stimulation using the transcranial PBM technique is challenging because of the rapidly increasing attenuation of light transmission in tissue. Different strategies like intranasal and intracranial light delivery systems have been proposed to overcome this restriction. The most recent preclinical and clinical data on the effectiveness of brain PBM therapy are studied in this review article.

Modulation of mitochondrial function with near-infrared light reduces brain injury in a translational model of cardiac arrest

BACKGROUND

Brain injury is a leading cause of morbidity and mortality in patients resuscitated from cardiac arrest. Mitochondrial dysfunction contributes to brain injury following cardiac arrest; therefore, therapies that limit mitochondrial dysfunction have the potential to improve neurological outcomes. Generation of reactive oxygen species (ROS) during ischemia-reperfusion injury in the brain is a critical component of mitochondrial injury and is dependent on hyperactivation of mitochondria following resuscitation. Our previous studies have provided evidence that modulating mitochondrial function with specific near-infrared light (NIR) wavelengths can reduce post-ischemic mitochondrial hyperactivity, thereby reducing brain injury during reperfusion in multiple small animal models.

METHODS

Isolated porcine brain cytochrome c oxidase (COX) was used to investigate the mechanism of NIR-induced mitochondrial modulation. Cultured primary neurons from mice expressing mitoQC were utilized to explore the mitochondrial mechanisms related to protection with NIR following ischemia-reperfusion. Anesthetized pigs were used to optimize the delivery of NIR to the brain by measuring the penetration depth of NIR to deep brain structures and tissue heating. Finally, a model of out-of-hospital cardiac arrest with CPR in adult pigs was used to evaluate the translational potential of NIR as a noninvasive therapeutic approach to protect the brain after resuscitation.

RESULTS

Molecular evaluation of enzyme activity during NIR irradiation demonstrated COX function was reduced in an intensity-dependent manner with a threshold of enzyme inhibition leading to a moderate reduction in activity without complete inhibition. Mechanistic interrogation in neurons demonstrated that mitochondrial swelling and upregulation of mitophagy were reduced with NIR treatment. NIR therapy in large animals is feasible, as NIR penetrates deep into the brain without substantial tissue heating. In a translational porcine model of CA/CPR, transcranial NIR treatment for two hours at the onset of return of spontaneous circulation (ROSC) demonstrated significantly improved neurological deficit scores and reduced histologic evidence of brain injury after resuscitation from cardiac arrest.

CONCLUSIONS

NIR modulates mitochondrial function which improves mitochondrial dynamics and quality control following ischemia/reperfusion. Noninvasive modulation of mitochondria, achieved by transcranial treatment of the brain with NIR, mitigates post-cardiac arrest brain injury and improves neurologic functional outcomes.

Shedding Light on Photobiomodulation Therapy for Age-Related Macular Degeneration: A Narrative Review

BACKGROUND

Photobiomodulation (PBM) relies on the pathophysiological mechanism whereby red to near-infrared light can target mitochondrial activity and promote ATP synthesis. Preclinical and clinical studies have shown promising results in treating intermediate age-related macular degeneration (AMD), since PBM can produce photochemical reactions in endogenous retinal chromophores. Currently, PBM is approved by the Food and Drug Administration and by the European Medicines Agency for the treatment of intermediate AMD. This narrative review aimed to evaluate the available evidence on the effectiveness and safety of PBM in treating intermediate AMD.

METHODS

A comprehensive search was conducted using the PubMed database, employing the keywords "photobiomodulation" and "age-related macular degeneration." All English-language studies published up to June 2023 were reviewed, and the search was expanded to include relevant references from selected articles. The included publications were analyzed for this review.

RESULTS

The available studies on PBM in AMD demonstrated promising but inconsistent results. PBM showed potential in improving best-corrected visual acuity (BCVA) and contrast sensitivity (CS) in patients with AMD. Some studies also suggested a reduction in AMD lesions, such as drusen volume. However, the long-term efficacy and optimal treatment parameters of PBM in AMD remained to be fully determined due to the limitations of the available studies. These included variations in irradiation techniques, wavelengths, exposure times, and treatment sessions, making it challenging to generalize the effectiveness of PBM. Furthermore, the lack of accurate classification of AMD phenotypes in the available studies hindered the understanding of which phenotypes could truly benefit from this treatment. Finally, the strength of evidence varied among studies, with limited sample sizes, unpublished results, and only three randomized sham-controlled trials.

CONCLUSIONS

Currently, the effectiveness of PBM in promoting drusen resorption or preventing progression to advanced forms of AMD, as observed in the cited studies, remains uncertain.

Mitochondrial dysfunction and neurological disorders: A narrative review and treatment overview

Mitochondria play a vital role in the nervous system, as they are responsible for generating energy in the form of ATP and regulating cellular processes such as calcium (Ca2+) signaling and apoptosis. However, mitochondrial dysfunction can lead to oxidative stress (OS), inflammation, and cell death, which have been implicated in the pathogenesis of various neurological disorders. In this article, we review the main functions of mitochondria in the nervous system and explore the mechanisms related to mitochondrial dysfunction. We discuss the role of mitochondrial dysfunction in the development and progression of some neurological disorders including Parkinson's disease (PD), multiple sclerosis (MS), Alzheimer's disease (AD), depression, and epilepsy. Finally, we provide an overview of various current treatment strategies that target mitochondrial dysfunction, including pharmacological treatments, phototherapy, gene therapy, and mitotherapy. This review emphasizes the importance of understanding the role of mitochondria in the nervous system and highlights the potential for mitochondrial-targeted therapies in the treatment of neurological disorders. Furthermore, it highlights some limitations and challenges encountered by the current therapeutic strategies and puts them in future perspective.

Acceleration of gonadal maturity of female striped catfish, Pangasianodon hypophthalmus (Pisces, Pangasiidae) by irradiation to low-power soft-laser

This study was aimed to investigate the effects of red photodiode soft-laser irradiation on gonadal maturity and egg quality of female striped catfish, Pangasianodon hypophthalmus. Four female striped catfish (weighing 700-800 g) at stage I of gonadal maturation (for all treatments) were exposed four times (once a week) to different doses (0.2, 0.4, 0.6, and 0.8 J/cm2) of red photodiode soft-laser in the reproductive acupoint. Doses of 500 IU and 0.5 mL per kg body weight of human chorionic gonadotropin (hCG) and Ovaprim™, respectively were injected intramuscularly at week 4 (positive control), and no treatment (negative control). Finally, gonadal maturation stage (GMS), gonadosomatic index (GSI), hepatosomatic index (HSI), fecundity, and egg diameter were measured at week 5. The results showed that red photodiode soft-laser irradiation of 0.4 J/cm2 dose accelerated GMS IV at early week 3 (100 %) and increases GSI (3.42 %), HSI (1.26 %), fecundity (67,665 eggs/body weight), and egg diameter (1.01 mm) compared to the other treatments. Treatments of 0.2, 0.6, and 0.8 J/cm2 doses, and positive and negative controls only reached GMS III (75 %), III (25 %), I (100 %), II (25 %), and I (100 %), respectively. GSI values were 2.20 %, 1.47 %, 0.93 %, 0.44 %, and 0.42 %, respectively and HSI values were 1.07 %, 0.85 %, 0.7 7%, 0.66 %, and 0.53 %, respectively. Females irradiated with doses of 0.2 and 0.6 J/cm2 had fecundities of 38,822 and 29,530 eggs/body weight, respectively, and egg diameters of 0.88 and 0.29 mm, respectively. These results suggest that a red photodiode soft-laser irradiation accelerates gonadal maturity and improves egg quality in female striped catfish.

Effect of photobiomodulation on the behaviour of mesenchymal stem cells in three-dimensional cultures

Photobiomodulation (PBM) has been proposed as a strategy to improve the regenerative capacity of human adipose-derived stem cells (hASCs). Yet, this effect has been proved in 2D culture conditions. To analyze the effect of different doses of laser irradiation (660 nm) with different levels of energy (1 J, 2 J and 6 J) on hASCs cultured at 2D and 3D conditions. We used gellan gum spongy-like hydrogels as a biomaterial to 3D culture hASCs. Different doses (1-7 daily irradiations) and energy levels (1-6 J) of PBM were applied, and the metabolic activity, viability, proliferation, and release of ROS and IL-8 was evaluated up to 7 days. In 3D, cell proliferation increased at high energy (6 J) and after a single dose of irradiation, while in 2D, metabolic activity and proliferation was enhanced only after 3 doses and independently of the energy. More than 1 dose was needed to promote ROS secretion both in 2D and 3D culture conditions. Interestingly, a decrease of IL-8 secretion was detected only in 3D after 3-7 daily irradiations. Overall, hASCs response to PBM was not only dependent on the energy level and the number of applied stimuli, but also on the in vitro culture conditions.

Recent Mechanisms of Neurodegeneration and Photobiomodulation in the Context of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease and the world's primary cause of dementia, a condition characterized by significant progressive declines in memory and intellectual capacities. While dementia is the main symptom of Alzheimer's, the disease presents with many other debilitating symptoms, and currently, there is no known treatment exists to stop its irreversible progression or cure the disease. Photobiomodulation has emerged as a very promising treatment for improving brain function, using light in the range from red to the near-infrared spectrum depending on the application, tissue penetration, and density of the target area. The goal of this comprehensive review is to discuss the most recent achievements in and mechanisms of AD pathogenesis with respect to neurodegeneration. It also provides an overview of the mechanisms of photobiomodulation associated with AD pathology and the benefits of transcranial near-infrared light treatment as a potential therapeutic solution. This review also discusses the older reports and hypotheses associated with the development of AD, as well as some other approved AD drugs.

625 nm Light Irradiation Prevented MC3T3-E1 Cells from Accumulation of Misfolded Proteins via ROS and ATP Production

Osteoblasts must acquire a considerable capacity for folding unfolded and misfolded proteins (MPs) to produce large amounts of extracellular matrix proteins and maintain bone homeostasis. MP accumulation contributes to cellular apoptosis and bone disorders. Photobiomodulation therapy has been used to treat bone diseases, but the effects of decreasing MPs with photobiomodulation remain unclear. In this study, we explored the efficacy of 625 nm light-emitting diode irradiation (LEDI) to reduce MPs in tunicamycin (TM) induced-MC3T3-E1 cells. Binding immunoglobulin protein (BiP), an adenosine triphosphate (ATP)-dependent chaperone, is used to evaluate the capacity of folding MPs. The results revealed that pretreatment with 625 nm LEDI (Pre-IR) induced reactive oxygen species (ROS) production, leading to the increased chaperone BiP through the inositol-requiring enzyme 1 (IRE1)/X-box binding protein 1s (XBP-1s) pathway, and then restoration of collagen type I (COL-I) and osteopontin (OPN) expression relieving cell apoptosis. Furthermore, the translocation of BiP into the endoplasmic reticulum (ER) lumen might be followed by a high level of ATP production. Taken together, these results suggest that Pre-IR could be beneficial to prevent MP accumulation through ROS and ATP in TM-induced MC3T3-E1cells.

Effect of low-level laser physiotherapy on left ventricular function among patients with chronic systolic heart failure

BACKGROUND

Low-level laser therapy (LLLT) is a promising noninvasive physiotherapeutic approach that has been demonstrated to improve cardiac performance. This study aimed to assess the impact of low-level laser therapy on cardiac functions and clinical status in patients with chronic left ventricular systolic heart failure who were not candidates for cardiac revascularization or resynchronization. A case series of 27 patients received a course of low-level laser physiotherapy, the clinical outcomes, echocardiographic parameters, and serum nitric oxide levels were evaluated before and after LLLT.

RESULTS

Of the total patients enrolled in the study, 21 (or 77.8%) were male, with a mean age of 57.7 ± 6.89 years. NYHA classification significantly improved after low-level laser therapy, 15 patients were in class III,12 were in class IV, and no one was in class II before laser therapy while after laser therapy; 25 patients shifted to class II, two patients were in class III with P < 0.001, Six-minute walk distance test was performed, and the results showed that the mean of 6MWT was less than 200 m (148.556 ± 39.092) before the study but increased to more than 300 after laser therapy (385.074 ± 61.740), left ventricular ejection fraction before laser therapy was 26 ± 7.5 while after laser therapy it became 30 ± 8.6 but diastolic function did not change after low-level laser therapy, the mean peak TR pressure was 40.0 ± 9.0 mmHg and 33.0 ± 7.0 before and after laser therapy respectively P < 0.001. A significant change was observed in NO level from 4.1 ± 1.4 IU/ml before laser therapy to 5.2 ± 1.7 IU/ml after laser therapy P < 0.001.

CONCLUSIONS

Low-level laser therapy may add benefits to improve symptoms, clinical condition, and quality of life in patients with left ventricular systolic dysfunction, further studies are necessary to evaluate the changes in cardiac functions at a longer follow-up duration.

Combined Photobiomodulation and Static Magnetic Fields to Reduce Side Effects from Laser and Radiofrequency Treatments for Dermatological Conditions

Background

Photobiomodulation therapy (PBMT) can significantly reduce inflammation and relieve pain, including postoperative pain and edema. The study aimed to evaluate the performance of a photobiomodulation-based device that includes a static magnetic field (SMF) to treat laser- or intensive and fractional radiofrequency-related side effects, such as pain, redness, and edema in patients treated for different dermatological conditions.

Methods

The study had a prospective, non-randomized, single-center design. Male and female patients aged 18 years or older underwent one or two PBMT-SMF (anti-inflammatory or anti-edematous) sessions on the same day, once or twice a week, after laser or radiofrequency facial treatments due to various dermatological disorders. Variables and efficacy assessments were pain, redness, edema, and their reduction from baseline to the last visit.

Results

Twenty-seven patients were included, seven (25.9%) men and 20 (74.1%) women, with a mean (SD) age of 43.7 (14.1) years. Seven (25.9%) patients were treated with radiofrequency, and 20 (74.1%) patients with a vascular laser (three [15%] for angioma, two [10%] for scars, three [15%] for erythrosis, and 12 [60%] for rosacea). After the PBMT-SMF protocol, overall mean pain reduction was 40 percent, and redness and edema reduction were shown by the pictures taken before and after the PBMT-SMF procedure.

Limitations

The primary limitations were the small number of patients and no quantitative variables for redness and edema.

Conclusion

PBMT-SMF reduced edema and inflammation after treatment with lasers or intensive or fractional radiofrequency for facial conditions, and probably, analgesic and anti-inflammatory drugs.

Combination of Dental-Capping Agents with Low Level Laser Therapy Promotes Proliferation of Stem Cells from Apical Papilla

Background: Direct pulp capping is a vital pulp therapy, which stimulates differentiation of stem cells from apical papilla (SCAPs). SCAPs have multipotential capacity to differentiate into types of cells, contributing to the regeneration of tissues. Objective: Considering the promising effects of dental-capping materials, we aim to investigate the effect of dental dressing materials combined with laser therapy on the percentage of SCAP viability and the consequent dental regeneration capacity. Methods: We collected two immature third molar teeth and isolated SCAPs through collagenase type I enzymatic activity. Isolated SCAPs were then cultured with Dulbecco's modified Eagle's medium and α-minimum essential medium enriched with 15% and 10% fetal bovine serum, respectively. After reaching 70-80% confluency, cells were seeded in a 96-well plate and then treated with mineral trioxide aggregate (MTA), enamel matrix derivative (EMD), biodentine, and low level laser therapy (LLLT) alone and in combination for 24, 48, and 168 h. After that, cell survival rate was assessed using (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assay. Results: We found that combination of MTA, EMD, and LLLT as well as that of biodentine, EMD, and LLLT could lead to significant increase of SCAP viability as compared with other treatment groups. Combination of MTA and biodentine with EMD could also show increased level of SCAP proliferation and viability. However, MTA and biodentine alone reduced SCAP survival rate in all time points. Conclusions: Our conclusion is that LLLT can serve as an enhancer of SCAP proliferation and differentiation rate when added to dental-capping agents such as MTA, EMD, and biodentine. Thus, LLLT combination with effective capping materials will serve as a promising option for dental tissue repair.

[Non-drug technologies in restoring endometrial receptivity as a cause of impaired fertility in women of reproductive age. (Literature review)]

Globally, 13% of the population has difficulty conceiving. In Russia, the proportion of infertile marriages ranges from 8 to 17.5%, with half of all forms of female infertility being the uterine form. The main etiological factors for impaired endometrial receptivity are infectious diseases leading to the development of chronic endometritis (most often found in tuboperitoneal infertility), dishormonal background associated with the development of hyperplastic processes in endocrine infertility, uterine fibroids, chronic endometritis and endometriosis. The frequency of detection of uterine cavity diseases in patients with repeated unsuccessful IVF programs ranges from 18 to 50%. The review examines the etiological factors and other causes of endometrial pathology leading to the development of chronic endometritis, possible mechanisms for the development of impaired growth and receptivity of the endometrium, and, as a consequence, the impossibility of pregnancy. Therapeutic strategies for restoring endometrial thickness and receptivity using pharmacological and non-pharmacological methods are described. Based on the analysis of literature data, it is shown that the use of physiotherapeutic factors in treatment programs that have pronounced anti-inflammatory, immuno- and hormone-modulating, reparative-regenerative, metabolic, vasocorrective and defibrosing effects allows for a relatively short period of time to improve endometrial receptivity, normalize hormonal levels and restore fertility in women of reproductive age, which ensures the possibility of successful embryo implantation, fetal development and childbirth.

Efficacy of Low-Level Laser Therapy in a Rabbit Model of Rhinosinusitis

Little is known about alternative treatment options for rhinosinusitis (RS). We aimed to evaluate the efficacy of low-level laser therapy (LLLT) for RS in experimentally induced rabbit models of RS. A total of 18 rabbits were divided into four groups: a negative control group (n = 3), an RS group without treatment (n = 5, positive control group), an RS group with natural recovery (n = 5, natural recovery group), and an RS group with laser irradiation (n = 5, laser-treated group). Computed tomography and histopathological staining were performed for each group. mRNA and protein expression levels of local cytokines (IFN-γ, IL-17, and IL-5) were also measured. Tissue inflammation revealed a significant improvement in the laser-treated group compared with the RS and natural recovery groups (p < 0.01). In addition, sinus opacification in the CT scans and cytokine expression was reduced in the laser-treated group, though without statistical significance. LLLT could be an effective option for the management of RS concerning radiological, histological, and molecular parameters.

Application of photobiomodulation for chronic pain-related TMD on pain points versus pre-established points: Randomized clinical trial

Photobiomodulation therapy (PTB) is a therapeutic possibility for temporomandibular disorders (TMD), but its effectiveness and protocols for use remain controversial. This study is a RCT that compared the effectiveness of PTB on pain points of the masticatory muscles and TMJs, located through palpation versus application of pre-established points in women with painful TMD, diagnosis by DC/TMD (Diagnostic Criteria for Temporomandibular Disorders - Brazilian Portuguese version). Therefore, a total sample of 54 women, aged between 18 and 60 years, was investigated. Volunteers were randomly randomized and PTB was applied in four different groups with a dose of 4 J and 6 J divided into pre-established application points (PE - G1) and pain points (PD - G2) - Groups 4PE, 4PD, 6PE and 6PD. Four laser applications were performed with a wavelength of 780 nm, one session per week, totaling one month of therapy. The following assessments were performed: DC/TMD, Brief Pain Inventory (BPI), McGill Questionnaire - Short Version (SF-MPQ) and Pain Intensity, Visual Analogue Scale (VAS). Friedman's test was used for within-group comparisons, while the Mann-Whitney test was used for between-group comparisons (p < 0.05). According to the results, laser application on pain points (G2) was more effective. McGill's results showed that regardless of dose, the pain point application group had better outcomes (p = 0.004). Pain intensity evaluation (last days) also showed that application at the pain points was more effective regardless of dose (p = 0.0002). Medians and interquartile deviations showed overall that PTB was more effective at pain points, with a trend towards better outcomes at the 6 J dose. Therefore, it can be concluded that in women with chronic painful TMD, the application of PTB at pain points is more effective than the application at pre-established points. Therefore, individualized PTB protocols are proposed, based on examination palpation of the masticatory structures.

Comparing the Impact of NIR, Visible and UV Light on ROS Upregulation via Photoacceptors of Mitochondrial Complexes in Normal, Immune and Cancer Cells

The effect of UV/visible/NIR light (380/450/530/650/808/1064 nm) on ROS generation, mitochondrial activity and viability is experimentally compared in human neuroblastoma cancer cells. The absorption of photons by mitochondrial photoacceptors in Complexes I, III and IV is in detail investigated by sequential blocking with selective pharmaceutical blockers. Complex I absorbs UV/blue light by heme P450, resulting in a very high rate (14 times) of ROS generation leading to cell death. Complex III absorbs green light, by cytochromes b, c1 and c, and possesses less ability for ROS production (seven times), so that only irradiation lower than 10 mW cm^-2 causes an increase in cell viability. Complex IV is well-known as the primary photoacceptor for red/NIR light. Light of 650/808 nm at 10-100 mW cm^-2 generates a physiological ROS level about 20% of a basal concentration, which enhance mitochondrial activity and cell survival, while 1064 nm light does not show any distinguished effects. Further, ROS generation induced by low-intensity red/NIR light is compared in neurons, immune and cancer cells. Red light seems to more rapidly stimulate ROS production, mitochondrial activity and cell survival than 808 nm. At the same time, different cell lines demonstrate slightly various rates of ROS generation, peculiar to their cellular physiology.

Differential effects of 808-nm light on electron transport chain enzymes in isolated mitochondria: Implications for photobiomodulation initiation

Photobiomodulation is a term for using low-power red to near-infrared light to stimulate a variety of positive biological effects. Though the scientific and clinical acceptance of PBM as a therapeutic intervention has increased dramatically in recent years, the molecular underpinnings of the effect remain poorly understood. The putative chromophore for PBM effects is cytochrome c oxidase. It is postulated that light absorption at cytochrome c oxidase initiates a signaling cascade involving ATP and generation of reactive oxygen species (ROS), which subsequently results in improved cellular robustness. However, this hypothesis is largely based on inference and indirect evidence, and the precise molecular mechanisms that govern how photon absorption leads to these downstream effects remain poorly understood. We conducted low-power PBM-type light exposures of isolated mitochondria to 808 nm NIR light, at a number of irradiances. NIR exposure was found to enhance the activity of complex IV, depress the activity of complex III, and had no effect on the activity of complex II. Further, examining the dose-response of complex IV we found NIR enhancement did not exhibit irradiance reciprocity, indicating the effect on complex IV may not have direct photochemical basis. In summary, this research presents a novel method to interrogate the earliest stages of PBM in the mitochondria, and a unique window into the corresponding molecular mechanism(s) of induction.

Preclinical and Clinical Applications of Photobiomodulation Therapy in Sperm Motility: A Narrative Review

About 50% of infertility problems are related to male factors and reduced sperm motility. The important factor that affects the structure and function of sperm is reactive oxygen species (ROS), and over-concentration of ROS reduces the quality and motility of sperm. Photobiomodulation therapy (PBMT) using red to near-infrared (NIR) light is useful in oxidative stress restoration. It plays a therapeutic role in disorders such as asthenospermia, oligospermia cases, and cryopreserved sperm. It also enhances the metabolic capacity of sperm and increases the low-level and non-harmful intracellular content of Ca2+, nitric oxide (NO), and ROS in the stressed cells. Likewise, it modulates survival intracellular pathways and maintains the motility, viability, DNA, and acrosome integrity of sperm. This article reviews the state-of-the-art preclinical and clinical evidence regarding the efficacy of semen PBMT.

Promoted CD4+ T cell-derived IFN-γ/IL-10 by photobiomodulation therapy modulates neurogenesis to ameliorate cognitive deficits in APP/PS1 and 3xTg-AD mice

Background

The immune system has been implicated in synaptic plasticity, inflammation, and the progression of Alzheimer's disease (AD). However, there were few studies on improving the niche microenvironment of neural stem cells (NSCs) in the brain of AD to promote adult hippocampal neurogenesis (AHN) by regulating the function of non-parenchymal immune cells.

Methods

The lymph nodes of amyloid precursor protein/presenilin 1 (APP/PS1) and 3xTg (APP/PS1/tau) mouse models of AD were treated with photobiomodulation therapy (PBMT) for 10 J/cm² per day for 1 month (10 min for each day), T lymphocytes isolated from these two AD models were treated with PBMT for 2 J/cm² (5 min for each time). The NSCs isolated from hippocampus of these two AD models at E14, and the cells were co-cultivated with PBMT-treated T lymphocyte conditioned medium for NSCs differentiation.

Results

Our results showed that PBMT treatment could promote AHN and reverse cognitive deficits in AD mouse model. The expression of interferon-γ (IFN-γ) and interleukin-10 (IL-10) was upregulated in the brain of these two AD models after PBMT treated, which was induced by the activation of Janus kinase 2 (JAK2)-mediated signal transducer and activator of transcription 4 (STAT4)/STAT5 signaling pathway in CD4⁺ T cells. In addition, elevated CD4⁺ T cell levels and upregulated transforming growth factor-β1 (TGFβ1)/insulin-like growth factors-1 (IGF-1)/brain-derived neurotrophic factor (BDNF) protein expression levels were also detected in the brain. More importantly, co-cultivated the PBMT-treated T lymphocyte conditioned medium with NSCs derived from these two AD models was shown to promote NSCs differentiation, which was reflected in the upregulation of both neuronal class-III β-tubulin (Tuj1) and postsynaptic density protein 95 (PSD95), but the effects of PBMT was blocked by reactive oxygen species (ROS) scavenger or JAK2 inhibitor.

Conclusion

Our research suggests that PBMT exerts a beneficial neurogenesis modulatory effect through activating the JAK2/STAT4/STAT5 signaling pathway to promote the expression of IFN-γ/IL-10 in non-parenchymal CD4⁺ T cells, induction of improvement of brain microenvironmental conditions and alleviation of cognitive deficits in APP/PS1 and 3xTg-AD mouse models.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02617-5.

Novel Therapies for Centralized Pain: a Brief Review

PURPOSE OF REVIEW

Centralized pain presents a complex pathology that many classic pharmacological agents for pain have not been able to sufficiently treat. To date, there are no clear guidelines for preferred treatment methods or comprehensive protocol that addresses confounding factors in this population. We sought to summarize the current field of knowledge around centrally mediated pain and to understand promising novel therapies.

RECENT FINDINGS

Many treatments currently used address not only the centralized pain phenotypem but the impact of central sensitization and the common comorbidities that reside within this population. Some novel therapies with promising evidence include the following: low-dose naltrexone, IV ketamine, acupuncture, aerobic activity, and laser therapy. Non-interventional treatment options include aerobic exercise, cognitive-behavioral therapy, mind-body therapies, virtual reality, and patient education on disease expectations. Much of the literature further emphasizes the importance of patient-level predictors, including factors like pain catastrophizing and social history, on treatment compliance and reported pain relief. We found that there are many potential treatment options for patients with centralized pain, particularly those that can be used as adjunct or combination therapies. The introduction of new approaches should occur in a carefully controlled, titrated manner to avoid exacerbation of pain symptoms. This is successfully conducted through patient-physician communication as this is a highly complex and personalized pain category. Our examination shows that while physicians have many options with proven success, there is a need for studies with longitudinal and larger patient populations to better articulate treatment guidelines.

Photobiomodulation effects in metalloproteinases expression in zymosan-induced arthritis

Matrix metalloproteinases (MMPs) play a crucial role in the degenerative course of rheumatic disorders. They are responsible for cartilage and other joint-associated tissues breakdown. Amid arthritis treatments, photobiostimulation (PBM), a non-thermal and non-invasive low-power laser application, appears to be an outstanding therapy alternative once it has succeeded in MMPs modulation. Thus, this study aimed to evaluate the PBM effects of low infrared laser (830 nm), testing two different energy densities (3 and 30 Jcm^-2) in MMP-2, MMP-9, MMP-13, and MMP-14 as well as the inhibitor TIMP-2 expressions using zymosan-induced arthritis model. C57BL/6 mice were distributed into four groups (n = 8): zymosan-induced arthritis without treatment; zymosan-induced arthritis and dexamethasone-treated; zymosan-induced arthritis and PBM at energy density of 3 Jcm^-2 treated; and zymosan-induced arthritis and PBM at energy density of 30 Jcm^-2 treated. MMPs and TIMP-2 mRNA relative levels by qRT-PCR and proteins expression by immunohistochemical and Western blotting techniques were performed after PBM treatment in the inflamed joint. Our results demonstrated PBM could modulate both mRNA relative levels and proteins expression of the MMP-2, -9, -13, -14, and TIMP-2 in joint tissues, decreasing MMP-9 protein expression and increasing TIMP-2 protein expression. PBM promotes a better arthritis prognostic, modulating metalloproteinase and its inhibitor, especially MMP-9 and TIMP-2 protein expression that is important inflammatory markers. These findings may also corroborate that PBM may regulate MMPs expression using different pathways.

Photobiomodulation therapy for osteoarthritis: Mechanisms of action

Photobiomodulation (PBM) is a non-invasive therapeutic modality with demonstrated effects in many fields related to regenerative medicine. In the field of orthopedics, in particular, PBM at various wavelengths has demonstrated the capacity to trigger multiple biological effects associated with protective mechanisms in musculoskeletal tissues. The articles cited in this review show that devices operating close to or within the near infrared range at low intensities can provoke responses which favor the shift in the predominant catabolic microenvironment typically seen in degenerative joint diseases, especially osteoarthritis (OA). These responses include proliferation, differentiation and expression of proteins associated with stable cell cycles. Additionally, PBM can also modulate oxidative stress, inflammation and pain by exerting regulatory effects on immune cells and blocking the transmission of pain through sensory neuron fibers, without adverse events. Collectively, these effects are essential in order to control the progression of OA, which is in part attributed to exacerbated inflammation and degradative enzymatic reactions which gradually contribute to the destruction of joint tissues. PBM may offer medical experts ease of application, financial viability, efficacy and lack of serious adverse events. Therefore, it may prove to be a suitable ally in the management of mild to moderate degrees of OA. This review explores and discusses the principal biological mechanisms of PBM and how the produced effects may contribute to the amelioration of osteoarthritic progression. Literature was reviewed using PubMed and Google Scholar in order to find studies describing the mechanisms of PBM. The investigation included a combination of nomenclature such as: “photobiomodulation”, “phototherapy”, “laser therapy”, “PBM”, “osteoarthritis”, low level light therapy”, “inflammation” and “cartilage”. We considered only articles written in English, with access to the full text.

Laser oromaxillofacial photobiomodulation therapy: molecular mechanisms, outcomes and considerations

Tweetable abstract Photobiomodulation therapy is largely characterized as a safe therapeutic model that can modulate the activity of inflammatory and immune biomarkers while facilitating a metabolic response that can regenerate damaged tissue.

Near-infrared light reduces β-amyloid-stimulated microglial toxicity and enhances survival of neurons: mechanisms of light therapy for Alzheimer's disease

BACKGROUND

Low-intensity light can decelerate neurodegenerative disease progression and reduce amyloid β (Aβ) levels in the cortex, though the cellular and molecular mechanisms by which photobiomodulation (PBM) protects against neurodegeneration are still in the early stages. Microglia cells play a key role in the pathology of Alzheimer's disease by causing chronic inflammation. We present new results concerning the PBM of both oxidative stress and microglia metabolism associated with the activation of metabolic processes by 808 nm near-infrared light.

METHODS

The studies were carried out using healthy male mice to obtain the microglial cell suspension from the hippocampus. Oligomeric β-amyloid (1-42) was prepared and used to treat microglia cells. Light irradiation of cells was performed using diode lasers emitting at 808 nm (30 mW/cm² for 5 min, resulting in a dose of 10 J/cm²). Mitochondrial membrane potential, ROS level studies, cell viability, apoptosis, and necrosis assays were performed using epifluorescence microscopy. Phagocytosis, nitric oxide and H₂O₂ production, arginase, and glucose 6-phosphate dehydrogenase activities were measured using standard assays. Cytokines, glucose, lactate, and ATP were measurements with ELISA. As our data were normally distributed, two-way ANOVA test was used.

RESULTS

The light induces a metabolic shift from glycolysis to mitochondrial activity in pro-inflammatory microglia affected by oligomeric Aβ. Thereby, the level of anti-inflammatory microglia increases. This process is accompanied by a decrease in pro-inflammatory cytokines and an activation of phagocytosis. Light exposure decreases the Aβ-induced activity of glucose-6-phosphate dehydrogenase, an enzyme that regulates the rate of the pentose phosphate pathway, which activates nicotinamide adenine dinucleotide phosphate oxidases to further produce ROS. During co-cultivation of neurons with microglia, light prevents the death of neurons, which is caused by ROS produced by Aβ-altered microglia.

CONCLUSIONS

These original data clarify reasons for how PBM protects against neurodegeneration and support the use of light for therapeutic research in the treatment of Alzheimer's disease.

Optimization of photo-biomodulation therapy for wound healing of diabetic foot ulcers in vitro and in vivo

Unclear optical parameters make photo-biomodulation (PBM) difficult to implement in diabetic foot ulcer (DFU) clinically. Here, 12 wavelengths (400-900 nm) were used to conduct PBM to heal DFU wounds in vitro and in vivo. PBM at 10 mW/cm² and 0.5-4 J/cm² with all 12 wavelengths promoted proliferation of diabetic wound cells. In a mimic DFU (mDFU) rat model, PBM (425, 630, 730, and 850 nm, and a combination light strategy) promoted mDFU healing. The positive cell proliferation, re-epithelialization, angiogenesis, collagen synthesis, and inflammation were possible mechanisms. The combination strategy had the best effect, which can be applied clinically.

Modulating the Antioxidant Response for Better Oxidative Stress-Inducing Therapies: How to Take Advantage of Two Sides of the Same Medal?

Oxidative stress-inducing therapies are characterized as a specific treatment that involves the production of reactive oxygen and nitrogen species (RONS) by external or internal sources. To protect cells against oxidative stress, cells have evolved a strong antioxidant defense system to either prevent RONS formation or scavenge them. The maintenance of the redox balance ensures signal transduction, development, cell proliferation, regulation of the mechanisms of cell death, among others. Oxidative stress can beneficially be used to treat several diseases such as neurodegenerative disorders, heart disease, cancer, and other diseases by regulating the antioxidant system. Understanding the mechanisms of various endogenous antioxidant systems can increase the therapeutic efficacy of oxidative stress-based therapies, leading to clinical success in medical treatment. This review deals with the recent novel findings of various cellular endogenous antioxidant responses behind oxidative stress, highlighting their implication in various human diseases, such as ulcers, skin pathologies, oncology, and viral infections such as SARS-CoV-2.

Blue Laser Irradiation Decreases the ATP Level in Mouse Skin and Increases the Production of Superoxide Anion and Hypochlorous Acid in Mouse Fibroblasts

Simple Summary

Photobiomodulation studies have reported that blue light irradiation induces the production of reactive oxygen species. We examined the effect of blue laser (405 nm) irradiation on ATP level in the skin and measured the types of reactive oxygen species and reactive nitrogen species. The decrease in the skin ATP level due to blue light irradiation may be caused by oxidative stress due to the generation of reactive oxygen species. These findings highlight the need to consider the effects on the skin when performing photobiomodulation treatment using blue light.

Abstract

Photobiomodulation studies have reported that blue light irradiation induces the production of reactive oxygen species. We investigated the effect of blue laser (405 nm) irradiation on the ATP levels in mouse skin and determined the types of reactive oxygen species and reactive nitrogen species using cultured mouse fibroblasts. Blue laser irradiation caused a decrease in the ATP level in the mouse skin and triggered the generation of superoxide anion and hypochlorous acid, whereas nitric oxide and peroxynitrite were not detected. Moreover, blue laser irradiation resulted in reduced cell viability. It is believed that the decrease in the skin ATP level due to blue light irradiation results from the increased levels of oxidative stress due to the generation of reactive oxygen species. This method of systematically measuring the levels of reactive oxygen species and reactive nitrogen species may be useful for understanding the effects of irradiation conditions.

Feasibility and therapeutic efficacy of a two-week low-level laser acupuncture therapy for shoulder and neck pain in office workers: Protocol for a pilot, single-blind, double-armed, randomised controlled trial

BACKGROUND

Shoulder and neck pain (SNP) is common in office workers and represents a serious public health problem given its detrimental impact on quality of life, physical functioning, personal finances, employers, and the health care system. Management with painkillers has adverse implications such as tolerance, addiction, and opioid abuse. Safe, sustainable, cost-effective, and evidence-based solutions are urgently needed. The non-invasive, painless, non-infectious, and safe modality of low-level laser acupuncture (LLLA) has shown promise for SNP management.

OBJECTIVE

The overarching aim of this study is to provide evidence of the feasibility and therapeutic efficacy of LLLA for office workers with SNP.

METHODS

This is a pilot, single-blind, double-armed, randomised controlled trial on the feasibility and therapeutic efficacy of a two-week LLLA therapy for office workers with SNP, aged 18 to 65 years. Each of the two study groups will contain 35 participants: the intervention group will receive LLLA from a licensed acupuncturist at the researchers' university clinic (10-20 min/session, 3 sessions/week) for two weeks; the control group will receive usual care without painkillers. Outcomes will be measured at baseline, throughout the two-week intervention, and at trial end. Surveys including open-ended questions will be completed. The primary outcome of this study is to evaluate the feasibility of a two-week LLLA therapy for office workers with SNP, as measured by recruitment and completion rates, patient safety, and treatment adherence and compliance. Participants' attitudes, motivation, and challenges to participation, intervention non-compliance, and experience of participating in the trial will be investigated via qualitative data. The secondary outcome is to evaluate the therapeutic efficacy of LLLA on SNP using the visual analogue scale (VAS) and the Short-Form McGill Pain Questionnaire (SF-MPQ); the work productivity and activity assessment (WPAI:SHP); 12-Item Short Form Survey (SF-12) for quality of life assessment; and the past 3-month out-of-pocket (OOP) cost for prescription and non-prescription SNP therapy, which is an indicative of the economic burden of SNP on patients and health care systems. This study was approved by Edith Cowan University's Human Research Ethics Committee (No. 2021-02225-WANG).

RESULTS

Data collection will commence in December 2021 with anticipated completion by December 2022.

CONCLUSIONS

Safe, sustainable, cost-effective, evidence-based interventions are needed to minimise the negative implications of SNP in office workers. LLLA is a promising modality in managing SNP. However, more consolidated evidence is required to provide insight regarding the effectiveness of LLLA. This study is expected to contribute to the challenging work of reducing the burden of SNP in office workers.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry (ANZCTR): ACTRN12621000426886p; https://www.anzctr.org.au/ACTRN12621000426886p.aspx.

The Role of Low-Level Laser Therapy in the Treatment of Multiple Sclerosis: A Review Study

Introduction: Multiple sclerosis (MS) is an autoimmune disease. Inflammatory cells, cytokines and chemokines play a major role in the pathogenesis of the disease. Low-level laser therapy (LLLT) as a photobiostimulation approach could affect a wide range of cellular responses. LLLT inhibits the inflammatory signaling pathway, improves cell viability, inhibits apoptosis, modulates immune responses and induces the production of growth factors. Methods: In this review, we discuss the effect of LLLT on cellular responses and its application in the treatment of MS. Such keywords as "low-level laser therapy", "photobiomodulation" and "multiple sclerosis" were used to find studies related to laser therapy in MS in Google scholar, PubMed and Medline databases. Results: LLLT reduced the inflammatory immune cells and mediators. It also enhanced the regeneration of neurons. Conclusion: Investigations showed that besides current treatment strategies, LLLT could be a promising therapeutic approach for the treatment of MS.

Comparison between the Effect of 810 nm and 940 nm Diode Laser Irradiation on Histopathological Changes in Iatrogenic Oral Ulcers: an Animal Study

STATEMENT OF THE PROBLEM

Considering the relatively high prevalence of oral mucosal ulcers, their fast healing is of significance.

PURPOSE

This study aimed to histopathologically compare the effects of 810 nm and 940 nm diode laser on the healing of iatrogenic oral ulcers in rabbits.

MATERIALS AND METHOD

In this single-blind experimental study, mucosal ulcers measuring 3mm in diameter and 1mm in depth were bilaterally created in the buccal mucosa of 18 rabbits using a biopsy punch. The defects were irradiated with 810 nm diode laser on the right side and 940 nm diode laser on the left side. Biopsy samples of the same depth were obtained from the ulcers on days 3 and 7 followed by histopathological analysis. The intensity of inflammation was determined on hematoxylin-eosin-stained sections using a four-point scale. Data were analyzed employing the Wilcoxon signed rank test.

RESULTS

The degree of inflammation was not significantly different between the 810nm and 940nm diode laser groups on day 3; but on day 7, animals receiving 810 nm experienced a significantly lower degree of inflammation compared to those treated with 940 nm laser (p= 0.028).

CONCLUSION

When comparing 810- and 940-nm diode lasers, 810 nm irradiation significantly decreased the severity of inflammation in oral wounds created on the buccal mucosa of rabbits in a time-dependent manner.

Evaluation of Biological Activity of Different Wavelengths of Low-Level Laser Therapy on the Cancer Prostate Cell Line Compared With Cisplatin

Introduction: Cancer is one of the most important problems in the world. Low-level laser therapy (LLLT) has been emerged as a new approach, having both stimulation and inhibition effects on cellular function. The goal of this study was to analyze and compare the different concentrations of cisplatin and wavelengths of laser therapy on the LnCap cell lines. Methods: LnCap cells were cultured and treated with different concentrations of cisplatin (0.1, 0.4, 0.8, 1.2 and 2 µg/mL for 24 hours) and wavelengths of laser therapy (610, 630 and 810 nm) (0.45 J/cm²) separately. The viability of cells was examined by MTT assay and IC50 was also calculated. Furthermore, a combination of cisplatin IC50 (24 hours) and different wavelengths of the laser was examined. Results: The results of this study showed that 2 µg/mL of cisplatin has the most significant reduction effect on the cell viability of the LnCap cell line. Cisplatin decreased the viability of cells in a dose-dependent manner. Moreover, IC50 of cisplatin was 1.24 µg/mL. On the other hand, LLLT with wavelengths of 610, 630 and 810 nm did not show notable biological effects on cell viability. Conclusion: As known, cisplatin has the capability to reduce the viability of LnCap cell lines. However, LLLT cannot be a remarkable option for the treatment of prostate cancer. Therefore, although laser therapy showed praiseful therapeutic activity against some cancer cell lines, in this study the results indicated that defined laser wavelengths had no inhibitory effects against the prostate cancer cell line.

Effect of Light-Emitting Diode Phototherapy on Allograft Bone After Open Sinus Lift Surgery: A Randomized Clinical Trial (Concurrent Parallel)

Introduction: Phototherapy with a light-emitting diode (LED) is used in medicine due to its potential bio-stimulatory effects on the human body. However, controversy still exists regarding the efficacy of low-level laser therapy (LLLT) and phototherapy with LED. This in vivo study aimed to quantitatively and qualitatively assess the newly formed bone following LED phototherapy of the human maxillary sinuses. Methods: This randomized clinical trial (concurrent parallel) was conducted on 44 patients in two groups (n=22) at the Implant Department of Tehran University of Medical Sciences. Randomization was done by a random sequence generator program. The inclusion criteria were absence of chronic sinusitis and chronic bone marrow conditions, no history of surgery at the site, absence of diabetes mellitus, no history of chemotherapy or radiotherapy, maxillary premolar edentulism, and signing informed consent forms. Group A underwent LED phototherapy with 620 ± 2 nm wavelength for 20 minutes daily for a total of 21 days after sinus lift surgery. Group B served as the control group and did not receive phototherapy. After 6 months, the grafted sites were re-opened for implant placement, and bone biopsy samples were obtained using a trephine bur. The samples were stained with hematoxylin and eosin and inspected under a light microscope. The results were statistically analyzed using the Mann-Whitney U test. Both the surgeon and pathologist were blinded to the group allocation of patients. Results: Forty tissue specimens were analyzed. Insignificant differences existed between the two groups in terms of the degree of inflammation, bone quality, and maturity of collagen. Histological analyses revealed no significant difference in the mineralized areas of bone between the two groups (P >0.05). Conclusion: The results indicated that LED phototherapy cannot significantly enhance osteogenesis after sinus lift surgery. No side effects were observed in the experimental group.

The Effects of Photobiomodulation on Bone Defect Repairing in a Diabetic Rat Model

The purpose of this study is to examine the prospective therapeutic effects of photobiomodulation on the healing of bone defects in diabetic mellitus (DM) using rat models to provide basic knowledge of photobiomodulation therapy (PBMT) during bone defect repair. For in vitro study, an Alizzarin red stain assay was used to evaluate the effect of PBMT on osteogenic differentiation. For in vivo study, micro-computed tomography (microCT) scan, H&E and IHC stain analysis were used to investigate the effect of PBMT on the healing of the experimental calvarial defect (3 mm in diameter) of a diabetic rat model. For in vitro study, the high glucose groups showed lower osteogenic differentiation in both irradiated and non-irradiated with PBMT when compared to the control groups. With the PBMT, all groups (control, osmotic control and high glucose) showed higher osteogenic differentiation when compared to the non-irradiated groups. For in vivo study, the hyperglycemic group showed significantly lower bone regeneration when compared to the control group. With the PBMT, the volume of bone regeneration was increasing and back to the similar level of the control group. The treatment of PBMT in 660 nm could improve the bone defect healing on a diabetic rat calvarial defect model.

Effects of photobiomodulation on glucose homeostasis and morphometric parameters in pancreatic islets of diabetic mice

High-fat diets lead to accumulation of body fat that is associated with the onset of insulin resistance and type II diabetes mellitus. On the other hand, photobiomodulation (PBM) is an electrophysical resource that interacts with cells, stimulating mitochondrial respiration, increasing ATP production, reducing key inflammatory mediators, inhibiting apoptosis, and stimulating angiogenesis. However, little is known about its therapeutic effectiveness on the development of diabetes in diet-induced obese mice. Thus, our aim was to evaluate the effect of PBM applied single point over the pancreas area on glucose homeostasis, insulin expression, and pancreatic morphometric parameters of mice submitted to high-fat diet for 12 weeks. Male mice C57BL6/J were divided into three groups: control group (C), diabetic group (D), and diabetic + PBM (D + PBM). The treatment with PBM started at 9th week and ended in the 12th week, applied 3 × /week. Body mass, fast blood glucose, and glucose and insulin tolerance were evaluated. Immunohistochemistry to detect insulin expression and pancreatic morphometry were also performed. At the end of 12th week, both groups submitted to high-fat diet showed an increase in body mass, adiposity, disturbances on glucose homeostasis, and high insulin expression when compared to the control group. However, mice treated with PBM had more discrete impairments on glucose homeostasis during the glucose tolerance test when compared to untreated D animals. Despite modest, the results were positive and encourage future investigations to explore different doses and duration of PBM to better elucidate its role in obesity-associated type 2 diabetes development.

Efficacy of low-level laser therapy in nerve injury repair-a new era in therapeutic agents and regenerative treatments

BACKGROUND

Traumatic nerve injuries may result in severe motor dysfunctions. Although the microenvironment of peripheral axons favors their regeneration, regenerative process is not always successful.

PURPOSE

We reviewed and discussed the main findings obtained with low-level laser therapy (LLLT), a therapeutic intervention that has been employed in order to achieve an optimized regeneration process in peripheral axons.

SCOPE

Disseminating the best available evidence for the effectiveness of this therapeutic strategy can potentially improve the statistics of success in the clinical treatment of nerve injuries. We found evidence that LLLT optimizes the regeneration of peripheral axons, improving motor function, especially in animal models. Nonetheless, further clinical evidence is still needed before LLLT can be strongly recommended. Although the results are promising, the elucidation of the mechanisms of action and safety assessment are necessary to support highquality clinical studies.

CONCLUSION

The present careful compilation of findings with consistent pro-regenerative evidence and published in respected scientific journals can be valuable for health professionals and researchers in the field, possibly contributing to achieve more promising results in future randomized controlled trials and interventions, providing better prognosis for clinical practice.

Photobiomodulation for the aging brain

Longevity is one of the great triumphs of humanity. Worldwide, the elderly is the fastest growing segment of the population. As a consequence, the number of cases of age-related cognitive decline and neurological diseases associated with aging, such as Alzheimer's and Parkinson's, has been increasing. Among the non-pharmacological interventions studied for the treatment or prevention of age-related neurocognitive impairment, photobiomodulation (PBM) has gained prominence for its beneficial effects on brain functions relevant to aging brains. In animal models, the neuroprotective and neuromodulatory capacity of PBM has been observed. Studies using both animals and humans have shown promising metabolic and hemodynamic effects of PBM on the brain, such as improved mitochondrial and vascular functions. Studies in humans have shown that PBM can improve electrophysiological activity and cognitive functions such as attention, learning, memory and mood in older people. In this paper we will review the main brain effects of PBM during aging, discuss its mechanisms of action relevant to the aging brain, and call for more controlled studies in older populations.