Effect of low-intensity argon laser irradiation on mitochondrial respiration

Evaluation of Photobiomodulation and Boldine as Alternative Treatment Options in Two Diabetic Retinopathy Models

Diabetic retinopathy causes progressive and irreversible damage to the retina through activation of inflammatory processes, overproduction of oxidative species, and glial reactivity, leading to changes in neuronal function and finally ischemia, edema, and hemorrhages. Current treatments are invasive and mostly applied at advanced stages, stressing the need for alternatives. To this end, we tested two unconventional and potentially complementary non-invasive treatment options: Photobiomodulation, the stimulation with near-infrared light, has shown promising results in ameliorating retinal pathologies and insults in several studies but remains controversial. Boldine, on the other hand, is a potent natural antioxidant and potentially useful to prevent free radical-induced oxidative stress. To establish a baseline, we first evaluated the effects of diabetic conditions on the retina with immunofluorescence, histological, and ultrastructural analysis in two diabetes model systems, obese LepR^db/db mice and organotypic retinal explants, and then tested the potential benefits of photobiomodulation and boldine treatment in vitro on retinal explants subjected to high glucose concentrations, mimicking diabetic conditions. Our results suggest that the principal subcellular structures affected by these conditions were mitochondria in the inner segment of photoreceptors, which displayed morphological changes in both model systems. In retinal explants, lactate metabolism, assayed as an indicator of mitochondrial function, was altered, and decreased photoreceptor viability was observed, presumably as a consequence of increased oxidative-nitrosative stress. The latter was reduced by boldine treatment in vitro, while photobiomodulation improved mitochondrial metabolism but was insufficient to prevent retinal structural damage caused by high glucose. These results warrant further research into alternative and complementary treatment options for diabetic retinopathy.

The Rationale for Photobiomodulation Therapy of Vaginal Tissue for Treatment of Genitourinary Syndrome of Menopause: An Analysis of Its Mechanism of Action, and Current Clinical Outcomes

Objective: Light, particularly in the visible to far-infrared spectrum, has been applied to the female genital tract with lasers and other devices for nearly 50 years. These have included procedures on both normal and neoplastic tissues, management of condylomata, endometriosis, and menometrorrhagia, and, more recently, a number of fractional laser devices have been applied for the management of genitourinary syndrome of menopause (GSM) and stress urinary incontinence (SUI), and to achieve so-called vaginal rejuvenation. Photobiomodulation therapy (PBMT) has been proposed as an alternative for use in managing GSM and SUI.

Methods: This article reviews the biological basis, symptoms, and management of GSM, and investigates the current status and rationale for the use of PBMT.

Results and conclusions: Based on the preliminary evidence available, PBMT is safe and appears to be efficacious in treating GSM.

Effects of Light-Emitting Diode Therapy on the Performance of Biceps Brachii Muscle of Young Healthy Males After 8 Weeks of Strength Training: A Randomized Controlled Clinical Trial

Vieira, KVSG, Ciol, MA, Azevedo, PH, Pinfildi, CE, Renno, ACM, Colantonio, E, and Tucci, HT. Effects of light-emitting diode therapy on the performance of biceps brachii muscle of young healthy males after 8 weeks of strength training: a randomized controlled clinical trial. J Strength Cond Res 33(2): 433-442, 2019-We assessed the effect of adding light-emitting diode therapy (LEDT) to an 8-week strength training of biceps brachii in healthy young males. Forty-five participants were randomized into training plus LEDT, training plus sham LEDT, and control groups (n = 15 each). Individuals in the LEDT groups participated in strength training performed in a Scott machine at their maximum number of elbow flexion-extension repetitions. The LEDT was applied to biceps brachii of dominant limb at the end of training sessions (device "on" for LEDT and "off" for sham LEDT). Training loads were re-evaluated every 2 weeks. Controls did not receive training during 8 weeks. All groups were evaluated for 1 repetition maximum (1RM) and fatigue at baseline and 8 weeks. Additionally, the 2 LEDT groups were evaluated every 2 weeks for 1-RM and number of elbow flexion-extension repetitions. The groups were statistically different in mean difference and mean percent change of 1-RM from baseline to week 8 (p < 0.001). Analyzing the 2 LEDT groups, we found an interaction between group and time (p = 0.02), with a slightly faster increase in 1-RM for the LEDT than the sham LEDT. Over time, both groups decreased the number of repetitions of elbow flexion-extension (differences not statistically significant), possibly because of the increase of load over time. We found no difference in change of fatigue index among the 3 groups. Our study showed potential benefits to 1RM when LEDT is applied after a strength training session. Future studies might assess whether different doses of LEDT can reduce fatigue in strength training.

Periodontal and peri-implant wound healing following laser therapy

Laser irradiation has numerous favorable characteristics, such as ablation or vaporization, hemostasis, biostimulation (photobiomodulation) and microbial inhibition and destruction, which induce various beneficial therapeutic effects and biological responses. Therefore, the use of lasers is considered effective and suitable for treating a variety of inflammatory and infectious oral conditions. The CO2 , neodymium-doped yttrium-aluminium-garnet (Nd:YAG) and diode lasers have mainly been used for periodontal soft-tissue management. With development of the erbium-doped yttrium-aluminium-garnet (Er:YAG) and erbium, chromium-doped yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers, which can be applied not only on soft tissues but also on dental hard tissues, the application of lasers dramatically expanded from periodontal soft-tissue management to hard-tissue treatment. Currently, various periodontal tissues (such as gingiva, tooth roots and bone tissue), as well as titanium implant surfaces, can be treated with lasers, and a variety of dental laser systems are being employed for the management of periodontal and peri-implant diseases. In periodontics, mechanical therapy has conventionally been the mainstream of treatment; however, complete bacterial eradication and/or optimal wound healing may not be necessarily achieved with conventional mechanical therapy alone. Consequently, in addition to chemotherapy consisting of antibiotics and anti-inflammatory agents, phototherapy using lasers and light-emitting diodes has been gradually integrated with mechanical therapy to enhance subsequent wound healing by achieving thorough debridement, decontamination and tissue stimulation. With increasing evidence of benefits, therapies with low- and high-level lasers play an important role in wound healing/tissue regeneration in the treatment of periodontal and peri-implant diseases. This article discusses the outcomes of laser therapy in soft-tissue management, periodontal nonsurgical and surgical treatment, osseous surgery and peri-implant treatment, focusing on postoperative wound healing of periodontal and peri-implant tissues, based on scientific evidence from currently available basic and clinical studies, as well as on case reports.

Use of low-level laser therapy (808 nm) to muscle fatigue resistance: a randomized double-blind crossover trial

OBJECTIVE

The purpose of this study was to investigate whether low-level laser (light) therapy (LLLT) can provide fatigue resistance via maximum repetitions (RM) with an isokinetic dynamometer, and decrease electromyography fatigue index (EFI).

BACKGROUND DATA

LLLT has been used to increase muscle performance when applied before or after intense exercises.

MATERIALS AND METHODS

This study was a randomized, double-blind, crossover trial with placebo. Seven young men (21±3 years of age) who were clinically healthy, were allocated into two groups: active laser (LLLT) and placebo laser (Placebo). Both groups were assessed at baseline, at one training session, and at the end of this study. Baseline and final assessments recorded the number of RM of knee flexion-extensions using an isokinetic dynamometer at 60 degrees/sec in conjunction with EFI recorded by median frequency. The training sessions consisted of three sets of 20 RM of knee flexion-extensions using an isokinetic dynamometer at 60 degrees/sec plus LLLT (808 nm, 100 mW, 4 J), or placebo, applied to quadriceps femoris muscles between sets, and after the last series of this exercise. After 1 week (washout period), all volunteers were exchanged among groups and then all assessments were repeated.

RESULTS

LLLT group increased RM (52%; p=0.002) with a small EFI for the vastus medialis (p=0.004) and rectus femoris (p=0.004).

CONCLUSIONS

These results suggest an increased muscle fatigue resistance when LLLT is applied during rest intervals, and after the last series of intense exercises.

Effect of low-level laser therapy on lung injury induced by hindlimb ischemia/reperfusion in rats

To investigate the effect of low-level laser therapy (LLLT 650 nm) on the lung remote organ injury induced by hindlimb ischemia/reperfusion (I/R). The experiments were performed on 50 healthy mature male Wistar rats weighing mean 230 ± 20 g. The rats were randomly allocated into five equal groups as follows: normal group (animals nonmanipulated), sham group (operated with no ischemia), laser group (animals nonmanipulated and irradiated with laser), I/R group, and I/R + LLLT group. Rats were prepared for sterile surgery, and then, right hindlimbs were subjected to I/R induced by the femoral artery occlusion for duration of 120 min, followed by a 60-min reperfusion. The LLLT (K30 handheld probe, AZOR, Technica, Russia, 650 nm, 30 mW, surface area = 1 cm(2), 60 S/cm(2), energy density = 1.8 J/cm(2)) was carried out by irradiating the rats over a unique point on the skin over the right upper bronchus for 5 and 15 min after initiating reperfusion for 3 min. At the end of the trial, rats were euthanized under deep anesthesia and the right lung tissues were removed. Myeloperoxidase (MPO) and superoxide dismutase (SOD) activities and nitric oxide (NO), malondialdehyde (MDA), and glutathione (GSH) levels were measured in the lung tissues. The tissue samples were further examined histopathologically under light microscopy. It was found that I/R elevated MPO activity, MDA, and NO levels accompanied by a reduction in SOD activities and GSH levels (P < 0.05). LLLT restored MDA and NO levels, MPO and SOD activity, GSH levels, and lung injury scores (P < 0.05). In light of these findings, the LLLT has alleviated the lung tissue injuries after skeletal muscle I/R in this experimental model.

Effects of low-level laser therapy on biceps braquialis muscle fatigue in young women

OBJECTIVE

This study aims to investigate the effects of low-level laser therapy (LLLT) on biceps brachi muscular fatigue in 20 young females.

BACKGROUND DATA

Exhausting physical activity leads to muscular fatigue, which could decrease muscular strength, and may cause impairment in motor control and muscle pain. Several biochemical and biophysical resources have been studied in an attempt to accelerate the recovery of muscle fatigue. Among these, LLLT is emphasized.

METHODS

Twenty subjects were randomized in one laser group and one placebo group in two sessions of a crossover design experimental procedure; the second session taking place within 7 days of the first. In the first session, subjects underwent a collection of surface electromyographic (SEMG) data of the biceps brachii muscle, followed by active or placebo LLLT at the same muscle, followed then by another EMG sample of biceps brachii. Blood samples were collected five times during the experimental procedure. Second session procedures were identical to the first, with exception of LLLT, which was the opposite of the first session. The fatigue protocol consisted of 60 sec of elbow flexion-extension movement performed with 75% of one maximum repetition. Blood lactate, EMG fatigue, and the number of elbow flexion-extension repetitions during the fatigue protocol were used to evaluate the effects of laser therapy (808 nm wavelength, 100 mW output power, power density of 35.7 W/cm(2), 70 sec each point and 7 J/point on eight points).

RESULTS

No statistical differences were found for eletromyographic fatigue and blood lactate values between groups. Mean numbers of elbow flexion-extension repetitions were 22.6 ± 7.58 after placebo, and 25.1 ± 9.89 after active LLLT group, but these differences were not statistically significant (p=0.342).

CONCLUSIONS

LLLT had limited effects on delaying muscle fatigue in a young female sample, although a tendency was observed in the active laser group toward showing lower electromyography fatigue of biceps brachii muscle. No intergroup differences were found in the number of muscle contractions and lactate concentration.

Increased cell proliferation and differential protein expression induced by low-level Er:YAG laser irradiation in human gingival fibroblasts: proteomic analysis

Erbium-doped yttrium aluminum garnet (Er:YAG) laser treatment has demonstrated favorable wound healing effect after periodontal therapy. One of the reasons may be the positive biological effect of the low-level laser on the irradiated tissues, although the mechanism remains unclear. The aim of this study was to investigate the effect of low-level Er:YAG laser irradiation on cell proliferation and laser-induced differential expression of proteins in human gingival fibroblasts (HGFs) by proteomic analysis. In the first experiment, HGFs were exposed to low-level Er:YAG laser irradiation and the laser-induced cell proliferation and damage were evaluated on day 3. In the second experiment, proteomic analysis was performed on day 1 after irradiation. The peptides prepared from HGFs were analyzed by a hybrid ion trap-Fourier transform mass spectrometer, Mascot search engine, and UniProtKB database. A significant increase in cell proliferation without cell damage after irradiation was observed. Among the total identified 377 proteins, 59 proteins, including galectin-7, which was associated with the process of wound healing, were upregulated and 15 proteins were downregulated in laser-treated HGFs. In the third experiment, the increase in messenger RNA (mRNA) and protein expression of galectin-7 in the irradiated HGFs was validated by various analytical techniques. In addition, the effect of recombinant human galectin-7 on the modulation of HGFs proliferation was confirmed. The results indicate that low-level Er:YAG laser irradiation can promote HGF proliferation and induce a significant change in protein expression and the upregulation of galectin-7 expression may partly contribute to the increase in cell proliferation.

Absorption of monochromatic and narrow band radiation in the visible and near IR by both mitochondrial and non-mitochondrial photoacceptors results in photobiomodulation

In addition to the major functions performed by in the cell, mitochondria play a major role in cell-light interaction. Accordingly it is generally accepted that mitochondria are crucial in cell photobiomodulation; however a variety of biomolecules themselves proved to be targets of light irradiation. We describe whether and how mitochondria can interact with monochromatic and narrow band radiation in the red and near IR optical regions with dissection of both structural and functional effects likely leading to photobiostimulation. Moreover we also report that a variety of biomolecules localized in mitochondria and/or in other cell compartments including cytochrome c oxidase, some proteins, nucleic acids and adenine nucleotides are light sensitive with major modifications in their biochemistry. All together the reported investigations show that the elucidation of the mechanism of the light interaction with biological targets still remains to be completed, this needing further research, however the light sensitivity of a variety of molecules strongly suggests that photobiomodulation could be used in both in photomedicine and in biotechnology.

Are the mitochondrial respiratory complexes blocked by NO the targets for the laser and LED therapy?

Effects of laser (442 and 532 nm) and light-emitting diode (LED) (650 nm) radiation on mitochondrial respiration and mitochondrial electron transport rate (complexes II-III and IV) in the presence of nitric oxide (NO) were investigated. It was found that nitric oxide (300 nM-10 μM) suppresses mitochondrial respiration. Laser irradiation of mitochondria (442 nm, 3 J cm(-2)) partly restored mitochondrial respiration (approximately by 70 %). Irradiation with green laser (532 nm) or red LED (650 nm) in the same dose had no reliable effect. Evaluation of mitochondrial electron transport rate in complexes II-III and IV and effects of nitric oxide demonstrated almost similar sensitivity of complex II-III and IV to NO, with approximately 50 % inhibition at NO concentration of 3 μM. Subsequent laser or LED irradiation (3 J cm(-2)) showed partial recovery of electron transport only in complex IV and only under irradiation with blue light (442 nm). Our results support the hypothesis of the crucial role of cytochrome c oxidase (complex IV) in photoreactivation of mitochondrial respiration suppressed by NO.

The effect of light-emitting diode and laser on mandibular growth in rats

OBJECTIVE

To evaluate the effect of a light-emitting diode (LED) and/or low-level laser (LLL) with or without the use of anterior bite jumping appliances (also known as functional appliances [FAs]) on mandibular growth in rats.

MATERIALS AND METHODS

Thirty-six 8-week-old male Sprague-Dawley rats weighing 200 g were obtained from Charles River Canada (St. Constant, QC, Canada) and were divided into six groups of six animals each. Groups were as follows: group 1: LLL; group 2: LLL + FA; group 3: LED; group 4: LED + FA; group 5: FA; and group 6: control (no treatment). Mandibular growth was evaluated by histomorphometric and micro computed tomographic (microCT) analyses.

RESULTS

The LED and LED + FA groups showed an increase in all condylar tissue parameters compared with other groups.

CONCLUSION

The LED-treated groups showed more mandibular growth stimulation compared with the laser groups.

Effect and clinical implications of the low-energy diode laser on bone cell proliferation

Laser is a simple, noninvasive technique that has proven useful for treating damaged tissue. However, its effects on bone regeneration and the mechanisms involved are poorly understood. The objective of this study was to evaluate the effects on MG-63 cell proliferation of application of a pulsed diode laser (Ezlase) of 940 nm at low energy levels. After 24 hr of culture, osteoblasts underwent pulsed laser radiation at 0.5, 1, 1.5, and 2 W and fluences of 1-5 J. A control group was not irradiated. After the treatment, cells were incubated for 24 hr, and cell proliferation was analyzed using a spectrophotometric measure of cell respiration (MTT assay). Results were expressed as percentage proliferation versus controls. At 24-hr culture, cell proliferation was increased in laser-treated cells at intensities of 0.5, 1, and 1.5 W/cm(2) versus controls; the energy density was positively correlated with cell growth, which reached a peak at 3 J and decreased at higher fluences. The use of pulsed low-level laser with low-energy density range thus appears to exert a biostimulatory effect on bone tissue. Although the data on cell proliferation are robust, in-depth investigation is required into the effect of these irradiation doses on other cell parameters. The present findings demonstrate that laser therapy could be highly useful in tissue regeneration in different clinical settings, including nursing, physical therapy, dentistry, and traumatology.

Effect of 808 nm low-level laser therapy in exercise-induced skeletal muscle fatigue in elderly women

Aging process involves several structural changes in muscle tissue which lead to decrease in musculoskeletal function. One of the most common physiological modifications is the increase in fatigability in elderly people, which leads to inability to maintain strength and motor control. In this context, low-level laser therapy (LLLT) has demonstrated positive results in reducing fatigue during physical exercise. Thus, this study aimed to investigate the effects of LLLT on skeletal muscle fatigue in elderly women. Twenty-four subjects divided in two groups entered a crossover randomized triple-blinded placebo-controlled trial. Active LLLT (808 nm wavelength, 100 mW, energy 7 J) or an identical placebo LLLT was delivered on the rectus femoris muscle immediately before a fatigue protocol. Subjects performed a fatigue protocol which consisted of voluntary isotonic contractions of knee flexion-extension performed with a load corresponding to 75 % of 1-MR (Maximum Repetition) during 60 s. Surface electromyography (SEMG) signals were recorded from rectus femoris muscle of dominant lower limb to evaluate peripheral fatigability using median frequency analysis of SEMG signal. The number of repetitions of flexion-extension during fatigue protocol was also compared between groups. The values of median frequency were used to calculate the slope coefficient. The results showed no difference in the slope comparing placebo LLLT and active LLLT groups (p = 0.293). However, a significant difference was observed in the number of repetitions between groups, after active LLLT, subjects demonstrated significantly higher number of repetitions (p = 0.047). In this study, LLLT was efficient in increasing the mean number of repetitions during knee flexion-extension exercise, although results have not shown delay electromyographic fatigue.

Low-level diode laser therapy reduces lipopolysaccharide (LPS)-induced bone cell inflammation

In this study, the aim is to investigate the cytologic effects of inflammatory bone cells after in vitro low-level laser therapy (LLLT). A human osteosarcoma cell line (MG63) was cultured, infected with lipopolysaccharide (LPS) and exposed to low-level laser treatment at 5 or 10 J/cm(2) using a 920 nm diode laser. MG63 cell attachment was observed under a microscope, and cell viability was quantified by mitochondrial colorimetric assay (MTT). LPS-treated MG63 cells were irradiated with LLLT, and the inflammatory markers iNOS, TNF-α and IL-1, were analyzed by reverse transcription polymerase chain reaction (RT-PCR) and Western blot. The data were collected and analyzed by one-way analysis of variance (ANOVA); p < 0.05 indicated a statistically significant difference. Low-level laser treatment on MG63 cells increased their ability to attach and survive. After irradiation, the expression levels of iNOS, TNF-α and IL-1 in LPS-infected MG63 cells decreased over time (p < 0.05).

CONCLUSIONS

low-level diode laser treatment increased the MG63 cell proliferative ability and decreased the expression of inflammatory mediators in MG63 cells.

Stability of dental implants after irradiation with an 830-nm low-level laser: a double-blind randomized clinical study

Little is known about the benefits of low-level laser therapy (LLLT) on improvement of stability of dental implants. The aim of this randomized clinical study was to assess the LLLT effect on implants stability by means of resonance frequency analysis (RFA). Thirty implants were distributed bilaterally in the posterior mandible of eight patients. At the experimental side, the implants were submitted to LLLT (830 nm, 86 mW, 92.1 J/cm(2), 0.25 J, 3 s/point, at 20 points), and on the control side, the irradiation was simulated (placebo). The first irradiation was performed in the immediate postoperative period, and it was repeated every 48 h in the first 14 days. The initial implant stability quotient (ISQ) of the implants was measured by means of RFA. New ISQ measurements were made after 10 days, 3, 6, 9, and 12 weeks. The initial ISQ values ranged from 65-84, with a mean of 76, undergoing a significant drop in stability from the 10th day to the 6th week in the irradiated group, and presenting a gradual increase from the 6th to the 12th week. The highest ISQ values were observed on the 10th day in the irradiated group, and the lowest in the 6th week in both groups. Under the conditions of this study, no evidence was found of any effect of LLLT on the stability of the implants when measured by RFA. Since high primary stability and good bone quality are of major relevancy for a rigid bone-implant interface, additional LLLT may have little impact macroscopically.

Prophylactic low-level light therapy for the treatment of hypertrophic scars and keloids: a case series

BACKGROUND AND OBJECTIVES

Hypertrophic and keloid scars result from alterations in the wound healing process. Treating abnormal scars remains an important challenge. The aim of this case series was to investigate the effectiveness of near infrared (NIR) light emitting diode (LED) treatment as a prophylactic method to alter the wound healing process in order to avoid or attenuate the formation of hypertrophic scars or keloids.

STUDY DESIGN/PATIENTS AND METHODS

Three patients (age 27-57) of phototypes I-III with hypertrophic scars or keloids due to acne or surgery participated in this case series. Following scar revision by surgery or CO(2) laser ablation on bilateral areas, one scar was treated daily by the patient at home with non-thermal, non-ablative NIR LED (805 nm at 30 mW/cm(2)) for 30 days. Efficacy assessments, conducted up to a year post-treatment, included the Vancouver Scar scale (VSS), clinical global assessment of digital photographs, and quantitative profilometry analysis using PRIMOS. Safety was documented by adverse effects monitoring.

RESULTS

Significant improvements on the NIR-treated versus the control scar were seen in all efficacy measures. No significant treatment-related adverse effects were reported.

CONCLUSION

Possible mechanisms involved are inhibition of TGF-beta I expression. Further studies in larger group of patients are needed to evaluate this promising technique.

Pulsing influences photoradiation outcomes in cell culture

BACKGROUND AND OBJECTIVES

Skin pigmentation can adversely affect phototherapy outcomes. Delivering pulsed light has been suggested as a means of enhancing efficacy. Suitable pulse frequencies remain indeterminate, often being selected empirically. This study was undertaken to determine whether pulsed light delivery mitigates the filtering effect of melanin pigment on photomodulation in vitro.

STUDY DESIGN AND METHODS

Human HEP-2 cells were cultured in complete DMEM media. Photoradiation was delivered through 0.025% melanin filters at 670 nm (5.0 J/cm(2)/treatment/24 hours) for 72 hours at different pulse rates. Group A received no light treatment. Group B received treatments without pulsing. Groups C, D, E, F, and G received treatments at 6, 18, 36, 100, and 600 Hz. Cell proliferation was assessed by MTT assay and oxidative burst was measured using the 2.7 dichloro-fluorescein-diacetate assay.

RESULTS

Cell proliferation was maximally stimulated at 100 Hz at 48 and 72 hours (n = 4, P< or =0.05). Oxidative burst was maximally stimulated at 600 Hz (n = 4, P< or =0.05). All frequencies were stimulatory at 48 and 72 hours (n = 4, P< or =0.05).

CONCLUSION

This investigation suggests that light pulsing may improve outcomes by mitigating the filtration effects of cutaneous melanin. Further studies to further define these effects are warranted.

Superpulsed laser irradiation increases osteoblast activity via modulation of bone morphogenetic factors

BACKGROUND AND OBJECTIVE

Laser therapy is a new approach applicable in different medical fields when bone loss occurs, including orthopedics and dentistry. It has also been used to induce soft-tissue healing, for pain relief, bone, and nerve regeneration. With regard to bone synthesis, laser exposure has been shown to increase osteoblast activity and decrease osteoclast number, by inducing alkaline phosphatase (ALP), osteopontin, and bone sialoprotein expression. Studies have investigated the effects of continuous or pulsed laser irradiation, but no data are yet available on the properties of superpulsed laser irradiation. This study thus aimed to investigate the effect of superpulsed laser irradiation on osteogenic activity of human osteoblast-like cells, paying particular attention to investigating the molecular mechanisms underlying the effects of this type of laser radiation.

STUDY DESIGN/MATERIALS AND METHODS

Human osteoblast-like MG-63 cells were exposed to 3, 7, or 10 superpulsed laser irradiation (pulse width 200 nanoseconds, minimum peak power 45 W, frequency 30 kHz, total energy 60 J, exposure time 5 minutes). The following parameters were evaluated: cell growth and viability (light microscopy, lactate dehydrogenase release), calcium deposits (Alizarin Red S staining), expression of bone morphogenetic factors (real-time PCR).

RESULTS

Superpulsed laser irradiation decreases cell growth, induces expression of TGF-beta2, BMP-4, and BMP-7, type I collagen, ALP, and osteocalcin, and increases the size and the number of calcium deposits. The stimulatory effect is maximum on day 10, that is, after seven applications.

CONCLUSIONS

Reported results show that superpulsed laser irradiation, like the continuous and pulsed counterparts, possesses osteogenic properties, inducing the expression of molecules known to be important mediators of bone formation and, as a consequence, increasing calcium deposits in human MG-63 cells. Moreover, the data suggest a new potential role for PPARgamma as a regulator of osteoblast proliferation.

Regulation of skin collagen metabolism in vitro using a pulsed 660 nm LED light source: clinical correlation with a single-blinded study

It has been reported that skin aging is associated with a downregulation in collagen synthesis and an elevation in matrix metalloproteinase (MMP) expression. This study investigated the potential of light-emitting diode (LED) treatments with a 660 nm sequentially pulsed illumination formula in the photobiomodulation of these molecules. Histological and biochemical changes were first evaluated in a tissue-engineered Human Reconstructed Skin (HRS) model after 11 sham or LED light treatments. LED effects were then assessed in aged/photoaged individuals in a split-face single-blinded study. Results yielded a mean percent difference between LED-treated and non-LED-treated HRS of 31% in levels of type-1 procollagen and of -18% in MMP-1. No histological changes were observed. Furthermore, profilometry quantification revealed that more than 90% of individuals showed a reduction in rhytid depth and surface roughness, and, via a blinded clinical assessment, that 87% experienced a reduction in the Fitzpatrick wrinkling severity score after 12 LED treatments. No adverse events or downtime were reported. Our study showed that LED therapy reversed collagen downregulation and MMP-1 upregulation. This could explain the improvements in skin appearance observed in LED-treated individuals. These findings suggest that LED at 660 nm is a safe and effective collagen-enhancement strategy.

Effect of visible and infrared polarized light on the healing process of full-thickness skin wounds: an experimental study

OBJECTIVE AND BACKGROUND DATA

Polarized light has already been experimentally and clinically used in an effort to promote wound healing, but the findings have been equivocal. The aim of this study was to evaluate the effect of visible and infrared polarized light of a specific range of wavelength (580-3400 nm) on the secondary healing of full-thickness skin wounds in rats.

MATERIALS AND METHODS

Forty male Wistar rats were used, divided in two groups of 20 animals each. A standardized open full-thickness skin wound was created on the back of each animal. In the first group the rats were exposed to polarized light (40 mW/cm(2) and 2.4 J/cm(2)) for 7 min on a daily basis (total daily dose = 16.8 J/cm(2)), while the second group acted as controls. Clinical and histological evaluation of wound healing were performed on days 5, 10, 15, and 20 post-wound. The size of the wounds was measured with the use of planimetry, whereas epithelialization, inflammatory response, neovascularization, and collagen formation were histologically assessed.

RESULTS

According to our findings, the group exposed to light therapy showed statistically significantly faster epithelialization seen on days 10 and 15 post-wound compared to controls, as well as better quality of the healing process (although not statistically significantly) at all time points.

CONCLUSION

In conclusion, this specific fraction of polarized light seems to have beneficial effects on wound healing, leading to faster epithelialization and qualitatively better wound healing.

Low-intensity light therapy: exploring the role of redox mechanisms

Low-intensity light therapy (LILT) appears to be working through newly recognized photoacceptor systems. The mitochondrial electron transport chain has been shown to be photosensitive to red and near-infrared (NIR) light. Although the underlying mechanisms have not yet been clearly elucidated, mitochondrial photostimulation has been shown to increase ATP production and cause transient increases in reactive oxygen species (ROS). In some cells, this process appears to participate in reduction/oxidation (redox) signaling. Redox mechanisms are known to be involved in cellular homeostasis and proliferative control. In plants, photostimulation of the analogous photosynthetic electron transport chain leads to redox signaling known to be integral to cellular function. In gene therapy research, ultraviolet lasers are being used to photostimulate cells through a process that also appears to involve redox signaling. It seems that visible and near visible low-intensity light can be used to modulate cellular physiology in some nonphotosynthetic cells, acting through existing redox mechanisms of cellular physiology. In this manner, LILT may act to promote proliferation and/or cellular homeostasis. Understanding the role of redox state and signaling in LILT may be useful in guiding future therapies, particularly in conditions associated with pro-oxidant conditions.

Mitochondrial signaling in mammalian cells activated by red and near-IR radiation

Mitochondrial signaling is an information channel between the mitochondrial respiratory chain and the nucleus for the transduction signals regarding the functional state of the mitochondria. The present review examines the question whether radiation of visible and near-IR (IR-A) radiation can activate this retrograde-type cellular signaling pathway. Experimental data about modulation of elements of mitochondrial retrograde signaling by the irradiation (mitochondrial membrane potential DeltaPsi(m), reactive oxygen species ROS, Ca(2+), NO, pH(i), fission-fusion homeostasis of mitochondria) are reviewed. The terminal enzyme of the mitochondrial respiratory chain cytochrome c oxidase is considered as the photoacceptor. Functions of cytochrome c oxidase as a signal generator as well as a signal transducer in irradiated cells are outlined.

The use of light-emitting diodes to stimulate mitochondrial function and liver regeneration of partially hepatectomized rats

The biostimulating effect of laser radiation has been observed in many areas of Medicine. However, there are still several questions to be answered, among them the importance of light coherence in the stimulatory process. In the present study, we used light-emitting diodes (LED) to promote the stimulation of liver regeneration after partial hepatectomy in rats. Fourteen male Wistar rats weighing 200-250 g were submitted to partial hepatectomy (70%) followed by LED light irradiation (630 nm) of the remaining part of the liver at two doses, i.e., 10 (N = 7) and 140 (N = 7) J/cm(2). A group irradiated with laser, 590 nm (N = 7, 15 J/cm(2)) was performed for the study of proliferating cell nuclear antigen-labeling index. Data are reported as mean +/- SEM. Statistical comparisons of the groups were performed by analysis of variance for parametric measurements followed by the Bonferroni post-test, with the level of significance set at P < 0.05. Respiratory mitochondrial activity was increased in the irradiated groups (states 3 and 4; P < 0.05), with better results for the group exposed to the lower LED dose (10 J/cm(2)). The proliferating cell nuclear antigen-labeling index, by immunohistochemical staining, was similar for both LED-exposed groups (P > 0.05) and higher than for the control group (P < 0.05). The cell proliferation index obtained with LED and laser were similar (P > 0.05). In conclusion, the present results suggest that LED irradiation promotes biological stimulatory effects during the early stage of liver regeneration and that LED is as effective as laser light, independent of the coherence, divergence and cromaticity.

Melanin Density Affects Photobiomodulation Outcomes in Cell Culture

OBJECTIVE

This study investigated the influence of melanin on the outcome of photoradiation at 670 nm in a cell culture model.

BACKGROUND DATA

Melanins are naturally occurring cutaneous pigments. Human skin is classified into six skin types based on melanin content.

METHODS

Gelatin photo filters were fabricated with varying melanin contents. Human HEP-2 and murine L929 cell lines were cultured in complete Dulbecco's Modified Eagle's Medium (DMEM) media. Photoradiation at 670 nm delivering 5.0 J/cm(2) per treatment/24 h (50 J/cm(2) total fluence) was carried out with melanin filters placed between the light source and the wells using a light-emitting diode (LED) device. Five groups based on percent melanin were treated: group 1, no filter; group 2, gelatin alone; group 3, 0.0125%; group 4, 0.025%; and group 5, 0.050%. Cell proliferation was measured using CyQuant and 3-(4,5-dimethylthiazol-2-yl)-2,5-disphenyl tetrasodiumbromide (MTT) assays for 240 h post-photoradiation.

RESULTS

The Proliferation Index (PI) as measured by CyQuant assay was not statistically different amongst the groups in either cell line. MTT assay results demonstrated a significant dose response effect (p < or = 0.05) in both cell lines with activity inversely proportional to melanin concentration. The relative PI values by MTT assay at 144 h for groups 1, 2, 3, and 4, respectively, were 1.44 +/- 0.06, 1.28 +/- 0.05, 1.20 +/- 0.07, and 1.06 +/- 0.04 for the L-929 cells, and 1.61 +/- 0.03, 1.47 +/- 0.06, 1.35 +/- 0.03, and 1.19 +/- 0.06 for the HEP-2 cells (n = 4; p < 0.05).

CONCLUSION

These results demonstrate that cutaneous melanin content should be taken into consideration in photobiomodulation paradigms. Further studies to quantify these effects are warranted.

Reciprocity of exposure time and irradiance on energy density during photoradiation on wound healing in a murine pressure ulcer model

BACKGROUND

Energy density and exposure time reciprocity is assumed and routinely used in low-level light therapy (LLLT) regimens. This study examined dose reciprocity effects on wound healing.

METHODS

Pressure ulcers were created on seven groups of C57/BL mice (n = 18). Photoradiation was administered (18 days; 5 J/cm(2)/day @ 670 nm) using a custom LED apparatus and treatment matrix varying both intensity and exposure. Control animals were treated similarly, without photoradiation. Ulcer staging was performed using a standardized scale. Changes in stage, wound area and wound closure rates were measured. Histology was performed.

RESULTS

Photostimulatory effects at day 7 occurred with parameters of 125 seconds @ 40 mW x 1/day; 625 seconds @ 8 mWx1/day; 62.5 seconds @ 40 mWx2/day; and 312.5 seconds @ 8 mWx2/day; and at day 18 using 625 seconds @ 8 mW and 312.5 seconds @ 8 mWx2/day. Statistically significant increases in wound closure rates occurred using 625 seconds @ 8 mW; 62.5 seconds @ 40 mWx2/day; and 312.5 seconds @ 8 mWx2/day treatments. Mean ulcer grade scores were similar to controls.

CONCLUSIONS

Varying irradiance and exposure time to achieve a specified energy density affects phototherapy outcomes in this model. Variation of exposure time and irradiance may account for conflicting results in the literature. Further studies of these effects are warranted.

Increase of bone volume by a nanosecond pulsed laser irradiation is caused by a decreased osteoclast number and an activated osteoblasts

The biostimulatory effects of laser irradiation focus not only in the field of soft tissue but also bone formation. Studies have shown that the light of a nanosecond pulsed laser which has a high peak power can produce stress waves in tissue. We have hypothesized that nanosecond pulsed laser irradiation stimulates bone formation. Our aim was to clarify the mechanism of increased bone volume by nanosecond pulsed laser irradiation. Rat femur was irradiated with a Q-switched Nd:YAG laser, which has a wavelength of 1064 nm. The quantification of trabecular architecture using three-dimensional morphometric analysis and measurement of bone mineral density (BMD) using pQCT was performed on day 1, day 3, day 5, and day 7 after laser irradiation. The laser effects on bone cells were also investigated using histological and immunohistochemical analysis. On day 1 after laser irradiation, bone volume (BV/TV), trabecular thickness (Tb.Th), and other parameters of the irradiated group did not significantly differ from the non-irradiation group (control). However, the mean BV/TV, Tb.Th, mineral apposition rate, and BMD of the laser group on day 7 after laser irradiation were significantly greater than those of the control. On histological analysis, the number of TRAP-positive osteoclasts was lower on day 3 after laser irradiation. Osteoblasts with activated clearance were seen in the laser irradiated group on day 1 and day 3. These data reveal that the increased bone volume by nanosecond pulsed laser irradiation causes an increase in osteoblast activity and a decrease in osteoclast number.

Laser Therapy Improves Healing of Bone Defects Submitted to Autologus Bone Graft

OBJECTIVE

The aim of the present study was to assess histologically the effect of low-level laser thrapy (LLLT) (lambda 830 nm) on the healing of bone defects associated with autologous bone graft.

BACKGROUND DATA

LLLT has been used on the modulation of bone healing because of the photo-physical and photochemical properties of some wavelengths. The use of correct and appropriate parameters has been shown to be effective in the promotion of a positive biomodulative effect on the healing bone.

METHODS

Sixty male Wistar rats were divided into four groups: G1 (control), G2 (LLLT on the surgical bed), G3 (LLLT on the graft), and G4 (LLLT on both the graft and the surgical bed). The dose per session was 10 J/cm(2), and it was applied to the surgical bed (G2/G4) and on the bone graft (G3/G4). LLLT was carried out every other day for 15 days (lambda 830 nm, phi = 0.5 cm(2), 50 Mw, 10 J/cm(2)). The dose was fractioned in four points. The animals were sacrificed 15, 21, and 30 days after surgery; specimens were taken and routinely processed (wax, cut, and stain with H&E and Sirius red stains). Light microscopic analysis was performed by a pathologist.

RESULTS

In the groups in which the LLLT was used trans-operatively on the surgical bed (G2/G4), bone remodeling was both quantitatively and qualitatively more evident when compared to subjects of groups G1 and G3.

CONCLUSION

The present study indicates that the use of LLLT trans-operatively resulted in a positive biomodulative effect on the healing of bone defects associated with autologous bone grafts.

A study of the effects of phototherapy dose interval on photobiomodulation of cell cultures

BACKGROUND AND OBJECTIVES

Dosimetry and treatment frequency are controversial phototherapy issues. Efficacy of dose fractionation on photobiomodulation was evaluated in vitro.

STUDY DESIGN/MATERIALS AND METHODS

Human HEP-2 and murine L-929 cell lines were cultured in complete DMEM media. Photoradiation (670 nm, 5 J/cm2/treatment, 50 J/cm2 total energy delivery), was performed varying treatments per 24 hour period: Group I (Controls)-0, Group II-1/d, Group III-2/d, Group IV-4/d. Cell proliferation was measured using Cyquant (fluorescent DNA content) and MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrasolium bromide) assays for 240 hours post therapy. A proliferation index: PI = (#Cells Experimental(t) / #Cells Control(t)) was computed.

RESULTS

MTT assay results demonstrated maximal response in Group III (P < 0.05, n = 3). Cyquant maxima occurred in HEP-2 Groups II and III (P < 0.045) and L-929 Group III (P < 0.091).

CONCLUSIONS

Cellular response to dose frequency varies. More frequent treatments (2/24 hours) increased metabolism and proliferation in both cell lines. Further investigation of dose fractionation in phototherapy is warranted.

Photobiomodulation partially rescues visual cortical neurons from cyanide-induced apoptosis

Near-infrared light via light-emitting diode treatment has documented therapeutic effects on neurons functionally inactivated by tetrodotoxin or methanol intoxication. Light-emitting diode pretreatment also reduced potassium cyanide-induced cell death, but the mode of death via the apoptotic or necrotic pathway was unclear. The current study tested our hypothesis that light-emitting diode rescues neurons from apoptotic cell death. Primary neuronal cultures from postnatal rat visual cortex were pretreated with light-emitting diode for 10 min at a total energy density of 30 J/cm2 before exposing to potassium cyanide for 28 h. With 100 or 300 microM potassium cyanide, neurons died mainly via the apoptotic pathway, as confirmed by electron microscopy, Hoechst 33258, single-stranded DNA, Bax, and active caspase-3. In the presence of caspase inhibitor I, the percentage of apoptotic cells in 300microM potassium cyanide was significantly decreased. Light-emitting diode pretreatment reduced apoptosis from 36% to 17.9% (100 microM potassium cyanide) and from 58.9% to 39.6% (300 microM potassium cyanide), representing a 50.3% and 32.8% reduction, respectively. Light-emitting diode pretreatment significantly decreased the expression of caspase-3 elicited by potassium cyanide. It also reversed the potassium cyanide-induced increased expression of Bax and decreased expression of Bcl-2 to control levels. Moreover, light-emitting diode decreased the intensity of 5-(and -6) chloromethy-2', 7-dichlorodihydrofluorescein diacetate acetyl ester, a marker of reactive oxygen species, in neurons exposed to 300 microM potassium cyanide. These results indicate that light-emitting diode pretreatment partially protects neurons against cyanide-induced caspase-mediated apoptosis, most likely by decreasing reactive oxygen species production, down-regulating pro-apoptotic proteins and activating anti-apoptotic proteins, as well as increasing energy metabolism in neurons as reported previously.

Proliferative effect of the aqueous extract of Hyptis pectinata on liver regeneration after partial hepatectomy in rats

PURPOSE: This study was carried out to assess the effects of the aqueous extract of Hyptis pectinata leaves on liver regeneration and on serum enzymes (AST, ALT and gamma-GT) after 67% partial hepatectomy in rats. METHODS: AST, ALT and gamma-GT, were determined by conventional procedures using a spectrophotometer (Model E2250-CELM). Liver regeneration was evaluated by immunohistochemical staining for proliferating cell nuclear antigen (PCNA). RESULTS:Oral pretreatment during 4 days at 100 mg/kg increased liver regeneration index. At 200 mg/kg, AST level was statistically decreased in comparison to the group submited to distilled water administration. The other enzymes assessed disclosed no difference when all groups were compared. CONCLUSION: The present study shows that the aqueous extract of Hyptis pectinata leaves contains some biological active principles that stimulate liver regeneration at 100 mg/kg and cause slight hepatic protection at 200 mg/kg.

Low-level laser irradiation promotes proliferation and differentiation of human osteoblasts in vitro

OBJECTIVES

The aim of the present study was to investigate the effect of low-level laser irradiation on proliferation and differentiation of a human osteoblast cell line.

BACKGROUND DATA

It was previously found that low-level laser therapy (LLLT) enhances bone repair in experimental models.

MATERIALS AND METHODS

Cultured osteoblast cells were irradiated using He-Ne laser irradiation (632 nm; 10 mW power output). On the second and third day after seeding the osteoblasts were exposed to laser irradiation. The effect of irradiation on osteoblast proliferation was quantified by cell count and colorimetric MTT (dimethylthiazol tetrazolium bromide) assay 24 and 48 h after second irradiation.

RESULTS

A significant 31-58% increase in cell survival (MTT assay) and higher cell count in the once-irradiated as compared to nonirradiated cells was monitored. Differentiation and maturation of the cells was followed by osteogenic markers: alkaline phosphatase (ALP), osteopontin (OP), and bone sialoprotein (BSP). A two-fold enhancement of ALP activity and expression of OP and BSP was much higher in the irradiated cells as compared to non-irradiated osteoblasts.

CONCLUSION

We conclude that LLLT promotes proliferation and maturation of human osteoblasts in vitro. These results may have clinical implications.

Enhancement of liver regeneration by the association of Hyptis pectinata with laser therapy

Since new molecules that normally would accelerate regeneration can also be potentialized by light, the use of new substances combined with laser therapy seems to be a natural type of experiment. Therefore, the purpose of this study was to assess the effects of Hyptis pectinata leaves on liver regeneration after partial hepatectomy (PH) associated with laser therapy. Twenty-four rats were divided into four groups--PH(control), PHL (laser therapy), PH200 (200 mg/kg of Hyptispectinata), and PHL200 (200 mg/kg of the plant and laser)--which were submitted to 67% hepatectomy. Laser treatment consisted of focusing the light on the remaining liver after hepatectomy. The data analyzed were serum levels of aminotransferases, liver regeneration, and mitochondrial function. Group PH200 showed a statistically significant decrease in AST levels, and PHL200 disclosed an augmentation in ALT levels. The liver regeneration index was significantly increased in group PHL200. Concerning liver mitochondrial respiratory assay, groups PH200 and PHL200 showed lower state 3 levels than groups PH and PHL. Group PHL showed an increase in state 4 levels and a reduction in membrane potential and RCR. The present study shows that the association of the aqueous extract of Hyptis pectinata leaves at 200 mg/kg with intraoperative laser therapy can stimulate liver regeneration and cause a reduction in liver mitochondrial respiratory function without altering its phosphorylative activity.

Propagation of electromagnetic radiation in mitochondria?

Mitochondria are the main source of ultra-weak chemiluminescence generated by reactive oxygen species, which are continuously formed during the mitochondrial oxidative metabolism. Vertebrate cells show typically filamentous mitochondria associated with the microtubules of the cytoskeleton, forming together a continuous network (mitochondrial reticulum). The refractive index of both mitochondria and microtubules is higher than the surrounding cytoplasm, which results that the mitochondrial reticulum can act as an optical waveguide, i.e. electromagnetic radiation can propagate within the network. A detailed analysis of the inner structure of mitochondria shows, that they can be optically modelled as a multi-layer system with alternating indices of refraction. The parameters of this multi-layer system are dependent on the physiologic state of the mitochondria. The effect of the multi-layer system on electromagnetic radiation propagating along the mitochondrial reticulum is analysed by the transfer-matrix method. If induced light emission could take place in mitochondria, the multi-layer system could lead to lasing action like it has been realized in technical distributed feedback laser. Based on former reports about the influence of external illumination on the physiology of mitochondria it is speculated whether there exists some kind of long-range interaction between individual mitochondria mediated by electromagnetic radiation.

Enhancement of bone formation in rat calvarial bone defects using low-level laser therapy

OBJECTIVE

To evaluate the effect of low-level laser therapy (LLLT), using a GaAlAs diode laser device, on bone healing and growth in rat calvarial bone defects.

STUDY DESIGN

An animal trial of 4 weeks' duration was conducted using a randomized blind, placebo-controlled design. Standardized round osseous defects of 2.7 mm diameter were made in each parietal bone of 20 rats (n=40 defects). The animals were randomly divided into an experimental and a control group of 10 animals each. In the experimental group, a GaAlAs diode laser was applied immediately after surgery and then daily for 6 consecutive days. The control group received the same handling and treatment, but with the laser turned off. Five rats from each group were killed on day 14 and the remainder on day 28 postoperatively. From each animal, tissue samples from one defect were prepared for histochemistry and samples from the contralateral defect for histology. Levels of calcium, phosphorus, and protein were determined by using atomic absorption spectrometry, colorimetry, and photometry, respectively. Student t-test and Mann-Whitney were used for statistical analyses.

RESULTS

At both time points the tissue samples from the experimental animals contained significantly more calcium, phosphorus, and protein than the controls. Similarly, histological analyses disclosed more pronounced angiogenesis and connective tissue formation, and more advanced bone formation in the experimental group than in the controls.

CONCLUSION

LLLT may enhance bone formation in rat calvarial bone defects.

Photobiological Basis and Clinical Role of Low-Intensity Lasers in Biology and Medicine

The purpose of this article is to provide a comprehensive review on the clinical role of low intensity laser therapy (laser photostimulation) in biology and medicine. Studies on wound healing and pain relief are highlighted to show the clinical efficacy of laser therapy. Controversies about the use of low intensity laser as a therapeutic modality for wound healing and pain relief are presented and a brief explanation is provided to overcome these controversies. The importance of standard parameters is emphasized for the applications of low intensity lasers in biology and medicine. A justification has been made to warrant further research on the use of low intensity laser as a therapeutic modality. Although the therapeutic applications of low intensity laser are imminent, the heterogeneity in treatment protocols and study design calls for a vigilant interpretation of the findings.

Promotion of angiogenesis by low energy laser irradiation

The effect of low energy laser (He-Ne) irradiation (LELI) on the process of angiogenesis in the infarcted rat heart and in the chick chorioallantoic membrane (CAM), as well as the proliferation of endothelial cells in tissue culture, was investigated. Formation of new blood vessels in the infarcted rat heart was monitored by counting proliferating endothelial cells in blood vessels. In the CAM model, defined areas were laser-irradiated or nonirradiated and blood vessel density was recorded in each site in the CAM at various time intervals. Laser irradiation caused a 3.1-fold significant increase in newly formed blood vessels 6 days post infarction, as compared with nonirradiated rats. In the CAM model, a slight inhibition of angiogenesis up to 2 days post irradiation and a significant enhancement of angiogenesis in the laser-irradiated foci as compared with control nonirradiated spots were evident. The LELI caused a 1.8-fold significant increase in the rate of proliferation in endothelial cells in culture over nonirradiated cells. It is concluded that LELI can promote the proliferation of endothelial cells in culture, which may partially explain the augmentation of angiogenesis in the CAM model and in the infarcted heart. These results may have clinical significance by offering therapeutic options to ameliorate angiogenesis in ischemic conditions.