Light-induced vasodilation of coronary arteries and its possible clinical implication

Photobiomodulation for Blood Pressure and Heart Rate Reduction in Mastectomized Women on Hormone Blockers: A Randomized Controlled Trial

Objective: To assess the impact of intravascular laser irradiation of blood (ILIB) on the primitive carotid artery (PCA) hemodynamic variables, specifically blood pressure (BP) and heart rate (HR), in mastectomized patients undergoing hormone blocker treatments. Materials and methods: This study is a controlled, experimental, and randomized clinical trial. Patients were allocated into two groups: the experimental group (G1)-patients who received ILIB therapy using a 660 nm laser targeted at the PCA, and the control group (G2)-patients who did not receive ILIB therapy. Clinical research was conducted weekly, with measurements of systolic blood pressure (SBP), diastolic blood pressure (DBP), and HR. The Mann-Whitney U test for independent samples was used, with a significance level of α = 0.05. Results: Systemic photobiomodulation on the PCA did not demonstrate a statistically significant difference in relation to SBP and DBP. However, for HR, the p-value was <0.05, indicating a significant difference between G1 and G2. The initial mean p > decreased from 142.3 to 116.4 mmHg in G1, and from 130.4 to 119.8 mmHg in G2. The DBP varied from 78.8 to 72.8 mmHg in G1, and from 79.1 to 74.2 mmHg in G2. A statistically significant difference was observed in HR, decreasing from 81.3 to 62.06 bpm in G1, and changing minimally from 74.1 to 75.1 bpm in G2. A considerable reduction was present in the timing of application. Conclusions: ILIB therapy applied to the PCA induces a reduction in BP and, more notably, HR in mastectomized women using the tamoxifen or aromatase inhibitors.

Effects of photobiomodulation therapy (PBMT) over endothelial function in healthy individuals: a preliminary crossover clinical trial

Photobiomodulation therapy (PBMT) causes stimulatory effects that raise cell metabolism. The study aimed to evaluate the effects of PBMT on the endothelial function of healthy individuals. It was a controlled, randomized, crossover, triple-blind trial with 22 healthy volunteers (female: 77.3%), aged 25.45 years which were randomly divided into three groups. PBMT with gallium-aluminum-arsenide (GaAlAs) diode laser (810 nm, continuous-wave mode, 1000 mW, 0.28 cm²) was applied over the radial and ulnar artery regions in two parallel spots: group 1-30 J (n = 22, 107 J/cm²) per spot; group 2-60 J (n = 22, 214 J/cm²) per spot; and group 3-placebo (n = 22, sham). The endothelial function was measured before and immediately after PBMT by the flow-mediated dilation technique (%FMD) with high-resolution ultrasound. Statistical analysis was made with ANOVA for repeated measures, the effect size was measured by Cohen's d, and results are presented as mean and standard error (or 95% confidence intervals). A p-value < 0.05 was considered statistically significant. The %FMD increases 10.4% with 60 J (mean difference = 0.496 mm, 95% CI = 0.42 to 0.57, p < 0.001), 7.3% with 30 J (mean difference = 0.518 mm, 95% CI = 0.44 to 0.59, p < 0.001), and 4.7% with placebo (mean difference = 0.560 mm, 95% CI = 0.48 to 0.63, p < 0.001). We found a small effect size (p = 0.702; d de Cohen = 0.24) without statistical difference between interventions. PBMT with the energy density of 60 J and 30 J did not improve endothelial function.Trial registration number: NCT03252184 (01/09/2017).

Photobiomodulation for the treatment of neuroinflammation: A systematic review of controlled laboratory animal studies

Background

Neuroinflammation is a response that involves different cell lineages of the central nervous system, such as neurons and glial cells. Among the non-pharmacological interventions for neuroinflammation, photobiomodulation (PBM) is gaining prominence because of its beneficial effects found in experimental brain research. We systematically reviewed the effects of PBM on laboratory animal models, specially to investigate potential benefits of PBM as an efficient anti-inflammatory therapy.

Methods

We conducted a systematic search on the bibliographic databases (PubMed and ScienceDirect) with the keywords based on MeSH terms: photobiomodulation, low-level laser therapy, brain, neuroinflammation, inflammation, cytokine, and microglia. Data search was limited from 2009 to June 2022. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. The initial systematic search identified 140 articles. Among them, 54 articles were removed for duplication and 59 articles by screening. Therefore, 27 studies met the inclusion criteria.

Results

The studies showed that PBM has anti-inflammatory properties in several conditions, such as traumatic brain injury, edema formation and hyperalgesia, ischemia, neurodegenerative conditions, aging, epilepsy, depression, and spinal cord injury.

Conclusion

Taken together, these results indicate that transcranial PBM therapy is a promising strategy to treat brain pathological conditions induced by neuroinflammation.

In Vivo Characterization of a Red Light-Activated Vasodilation: A Photobiomodulation Study

Nitric oxide dependent vasodilation is an effective mechanism for restoring blood flow to ischemic tissues. Previously, we established an ex vivo murine model whereby red light (670 nm) facilitates vasodilation via an endothelium derived vasoactive species which contains a functional group that can be reduced to nitric oxide. In the present study we investigated this vasodilator in vivo by measuring blood flow with Laser Doppler Perfusion imaging in mice. The vasodilatory nitric oxide precursor was analyzed in plasma and muscle with triiodide-dependent chemiluminescence. First, a 5–10 min irradiation of a 3 cm² area in the hind limb at 670 nm (50 mW/cm²) produced optimal vasodilation. The nitric oxide precursor in the irradiated quadriceps tissue decreased significantly from 123 ± 18 pmol/g tissue by both intensity and duration of light treatment to an average of 90 ± 17 pmol/g tissue, while stayed steady (137 ± 21 pmol/g tissue) in unexposed control hindlimb. Second, the blood flow remained elevated 30 min after termination of the light exposure. The nitric oxide precursor content significantly increased by 50% by irradiation then depleted in plasma, while remained stable in the hindlimb muscle. Third, to mimic human peripheral artery disease, an ameroid constrictor was inserted on the proximal femoral artery of mice and caused a significant reduction of flow. Repeated light treatment for 14 days achieved steady and significant increase of perfusion in the constricted limb. Our results strongly support 670 nm light can regulate dilation of conduit vessel by releasing a vasoactive nitric oxide precursor species and may offer a simple home-based therapy in the future to individuals with impaired blood flow in the leg.

Nitric oxide storage levels modulate vasodilation and the hypotensive effect induced by photobiomodulation using an aluminum gallium arsenide (AlGaAs) diode laser (660 nm)

The aim of this study was to evaluate the participation of nitric oxide (NO) in the hypotensive and vasorelaxation effect induced by PBM using an aluminum gallium arsenide (AlGaAs) diode laser (660 nm). Male Wistar rats were treated with the inhibitor of nitric oxide synthase (L-NAME). A red laser (660 nm; 63 J/cm²; 56 s/point) was applied to the abdominal region at six different points. Thoracic aorta was dissected for vascular reactivity study, and a laser (660 nm; 96 J/cm²; 56 s) was applied after incubation with the NO donor DETA-NO, PBS, or hydroxicobalamin. Endothelial cells (HUVEC) were treated with DETA-NO or CuSO₄, and then, PBM (63 J/cm²) was applied, and the nitric oxide was detected. Hypertensive L-NAME rats did not exhibit a decrease in blood pressure after PBM. PBM promoted vasodilation in the aorta isolated from normotensive rats, and less effect in the aorta of L-NAME rats and the addition of the NO donor, DETA-NO, promoted greater vasodilation by PBM in the aorta of L-NAME rats. In endothelial cells, an increase in NO, after PBM, was detected; however, with the addition of CuSO₄, which catalyzes the decomposition of NO storage, there was no detection of NO after PBM. The results of this study demonstrate that the hypotensive and vasodilatory effect of PBM with a red laser at 660 nm is modulated by the release of nitric oxide from the storage.

Comparative evaluation of low-level light therapy and ethinyl estradiol and desogestrel combined oral contraceptive for clinical efficacy and regulation of serum biochemical parameters in primary dysmenorrhoea: a prospective randomised multicentre trial

We aimed to compare low-level light therapy with oral contraceptive pills for pain relief and serum levels of nitric oxide and prostaglandin E₂ in patients with primary dysmenorrhoea. This was a randomised, active comparator-controlled, multicentre study. In total, 156 patients were randomised to receive either low-level light therapy with light-emitting diodes (LED) applying on two acupoints, namely, conception vessel 4 (CV4) and CV6 or conventional treatment with oral Marvelon, 30 µg of ethinyl estradiol and 150 µg of desogestrel (DSG/EE), for three consecutive menstrual cycles. The main outcome was the proportion of patients who achieved 33% or more decrease in pain scores measured using the visual analogue scale, which was deemed as efficient rate. Absolute changes in visual analogue scale scores, serum levels of nitric oxide (assessed by nitrites and nitrates reflecting nitric oxide metabolism) and prostaglandin E₂ (measured by enzyme-linked immunosorbent assay) were the secondary outcomes. A total of 135 patients completed the study (73 in the light therapy group and 62 in the DSG/EE group). The efficient rate at the end of treatment was comparable between the groups (73.6% vs. 85.7%, χ² = 2.994, p = 0.084). A more significant reduction in pain scores was observed in the DSG/EE group (39.25% vs. 59.52%, p < 0.001). Serum levels of prostaglandin E₂ significantly decreased from baseline but did not differ between groups (- 109.57 ± 3.99 pg/mL vs. - 118.11 ± 12.93 pg/mL, p = 0.51). Nitric oxide concentration remained stable in both groups. Low-level light therapy with LED-based device applied on acupuncture points CV4 and CV6 demonstrated a similar level of dysmenorrhoea pain reduction to DSG/EE combined contraceptive. Both treatment modalities achieved clinically meaningful levels of pain reduction. Registration on ClinicalTrials.gov: TRN: NCT03953716, Date: April 04, 2019.

Electromagnetic energy (670 nm) stimulates vasodilation through activation of the large conductance potassium channel (BKCa)

INTRODUCTION

Peripheral artery disease (PAD) is a highly morbid condition in which impaired blood flow to the limbs leads to pain and tissue loss. Previously we identified 670 nm electromagnetic energy (R/NIR) to increase nitric oxide levels in cells and tissue. NO elicits relaxation of smooth muscle (SMC) by stimulating potassium efflux and membrane hyperpolarization. The actions of energy on ion channel activity have yet to be explored. Here we hypothesized R/NIR stimulates vasodilation through activation of potassium channels in SMC.

METHODS

Femoral arteries or facial arteries from C57Bl/6 and Slo1-/- mice were isolated, pressurized to 60 mmHg, pre-constricted with U46619, and irradiated twice with energy R/NIR (10 mW/cm2 for 5 min) with a 10 min dark period between irradiations. Single-channel K+ currents were recorded at room temperature from cell-attached and excised inside-out membrane patches of freshly isolated mouse femoral arterial muscle cells using the patch-clamp technique.

RESULTS

R/NIR stimulated vasodilation requires functional activation of the large conductance potassium channels. There is a voltage dependent outward current in SMC with light stimulation, which is due to increases in the open state probability of channel opening. R/NIR modulation of channel opening is eliminated pharmacologically (paxilline) and genetically (BKca α subunit knockout). There is no direct action of light to modulate channel activity as excised patches did not increase the open state probability of channel opening.

CONCLUSION

R/NIR vasodilation requires indirect activation of the BKca channel.

Multidrug-resistant protein inhibitor and phosphodiesterase inhibitor potentiate the vasodilator effect induced by photobiomodulation in isolated aortic rings

A previous work indicates that the red LASER (660 nm) induces vascular relaxation by nitric oxide (NO)-dependent mechanism. NO activates soluble guanylate cyclase (sGC) which produces cGMP, the main effector in the vasodilation pathway. An interesting pharmacological strategy is to control the levels of intracellular cGMP, preventing its efflux (with multidrug-resistant protein blockers, such as MK-571), or preventing its degradation (such as sildenafil, which inhibits the enzyme responsible for cGMP degradation, the phosphodiesterase-5 PDE5). This study aimed to look for pharmacological strategies to improve vasodilation LASER effect in normotensive and hypertensive rats (L-NAME model). The vascular reactivity study was performed in isolated aortic rings from normotensive and hypertensive rats, with a single LASER application and sodium nitroprusside (SNP) treatment. In aortic rings from normotensive rats, MK-571 and sildenafil potentiated the relaxation induced by LASER, compared to control. The vasodilation induced by SNP was potentiated by MK-571 and sildenafil, compared to control. In aortic rings from hypertensive rats, vasodilation effect induced by LASER and by SNP was potentiated just by MK-571, compared to control, with no potentiation by sildenafil. In addition, it was seen that the withdrawal of nitric oxide stocks carried out by L-cysteine is capable of being reversed with the use of the SNP. The results support the evidence that the vasodilation induced by red LASER is potentiated by MK-571 and sildenafil in aortic rings from normotensive rats. However, in aortic rings from L-NAME hypertensive rats, the potentiation in vasodilation was induced just by MK-571.

Experimental and Clinical Applications of Red and Near-Infrared Photobiomodulation on Endothelial Dysfunction: A Review

BACKGROUND

Under physiological conditions, endothelial cells are the main regulator of arterial tone homeostasis and vascular growth, sensing and transducing signals between tissue and blood. Disease risk factors can lead to their unbalanced homeostasis, known as endothelial dysfunction. Red and near-infrared light can interact with animal cells and modulate their metabolism upon interaction with mitochondria's cytochromes, which leads to increased oxygen consumption, ATP production and ROS, as well as to regulate NO release and intracellular Ca²⁺ concentration. This medical subject is known as photobiomodulation (PBM). We present a review of the literature on the in vitro and in vivo effects of PBM on endothelial dysfunction.

METHODS

A search strategy was developed consistent with the PRISMA statement. The PubMed, Scopus, Cochrane, and Scholar electronic databases were consulted to search for in vitro and in vivo studies.

RESULTS

Fifty out of >12,000 articles were selected.

CONCLUSIONS

The PBM can modulate endothelial dysfunction, improving inflammation, angiogenesis, and vasodilatation. Among the studies, 808 nm and 18 J (0.2 W, 2.05 cm²) intracoronary irradiation can prevent restenosis as well as 645 nm and 20 J (0.25 W, 2 cm²) can stimulate angiogenesis. PBM can also support hypertension cure. However, more extensive randomised controlled trials are necessary.

Development of a Red-Light-Controllable Nitric Oxide Releaser to Control Smooth Muscle Relaxation in Vivo

We designed and synthesized a novel Si-rhodamine derivative, NORD-1, as a red-light-controllable nitric oxide (NO) releaser, on the basis of photoredox parameter analysis. Red-light-responsive NO release from NORD-1 was confirmed by ESR spin trapping and quantified with an NO electrode and by means of Griess assay. The NO release cross section (ε_656 nm·Φ_NO) of NORD-1 was calculated to be 3.65 × 10², which is larger than that of a previously reported yellowish-green-light-controllable NO releaser, NO-Rosa5. The photoresponsiveness of NO release from NORD-1 was precise and efficient enough to induce vasodilation ex vivo under Magnus test conditions. Finally, we showed that intracavernous pressure (ICP) could be controlled in rats in vivo with the combination of NORD-1 and a red-light source without increasing systemic blood pressure, which is a serious side effect of usual NO releasers, such as nitroglycerin and isopentyl nitrite. NORD-1 is expected to be a useful chemical tool for NO research, as well as a candidate agent to control the circulatory system.

Energy-dependent effect trial of photobiomodulation on blood pressure in hypertensive rats

The main purpose of this work was to construct an energy-dependent response curve of photobiomodulation on arterial pressure in hypertension animal model. To reach this objective, we have used a two-kidney one clip (2K-1C) rat model. Animals received acute laser light irradiation (660 nm) on abdominal region using different energy (0.6, 1.8, 3.6, 7.2, 13.8, 28.2, 55.8, and 111.6 J), the direct arterial pressure was measured by femoral cannulation, and systolic arterial pressure (SAP), diastolic arterial pressure (DAP), heart rate (HR), and time of effect were obtained. Our results indicated that 660 nm laser light presents an energy-dependent hypotensive effect, and 28.2 J energy irradiation reached the maximum hypotensive effect, inducing a decreased SAP, DAP, and HR (decrease in SAP: - 19.23 ± 1.82 mmHg, n = 11; DAP: - 9.57 ± 2.23 mmHg, n = 11; HR: - 39.15 ± 5.10 bpm, n = 11; and time of hypotensive effect: 3068.00 ± 719.00 s, n = 11). The higher energy irradiation evaluated (111.6 J) did not induce a hypotensive effect and induced an increase in HR (21.69 ± 7.89 bpm, n = 7). Taken together, our results indicate that red laser energy irradiation from 7.2 to 55.8 J is the effective therapeutic window to reduce SAP, DAP, MAP, and HR and induce a long-lasting hypotensive effect in rats, with effect loss at higher energy irradiation (111.6 J).

Photobiomodulation induces hypotensive effect in spontaneously hypertensive rats

To evaluate whether acute photobiomodulation can elicit a hypotensive effect in spontaneously hypertensive rats (SHR). Male SHR were submitted to the implantation of a polyethylene cannula into the femoral artery. After 24 h, baseline measurements of the hemodynamic parameters: systolic, diastolic, and mean arterial pressure, and heart rate were accomplished for 1 h. Afterwards, laser application was simulated, and the hemodynamic parameters were recorded for 1 h. In the same animal, the laser was applied at six different positions of the rat's abdomen, and the hemodynamic parameters were also recorded until the end of the hypotensive effect. The irradiation parameters were red wavelength (660 nm); average optical power of 100 mW; 56 s per point (six points); spot area of 0.0586 cm²; and irradiance of 1.71 W/cm² yielding to a fluency of 96 J/cm² per point. For measuring plasma NO levels, blood was collected before the recording, as well as immediately after the end of the mediated hypotensive effect. Photobiomodulation therapy was able to reduce the systolic arterial pressure in 69% of the SHR submitted to the application, displaying a decrease in systolic, diastolic, and mean arterial pressure. No change in heart rate was observed. Nevertheless, there was an increase in serum nitric oxide levels in the SHR responsive to photobiomodulation. Our results suggest that acute irradiation with a red laser at 660 nm can elicit a hypotensive effect in SHR, probably by a mechanism involving the release of NO, without changing the heart rate.

Erythrocytic bioactivation of nitrite and its potentiation by far-red light

BACKGROUND

Nitrite is reduced by heme-proteins and molybdenum-containing enzymes to form the important signaling molecule nitric oxide (NO), mediating NO signaling. Substantial evidence suggests that deoxygenated hemoglobin within red blood cells (RBCs) is the main erythrocytic protein responsible for mediating nitrite-dependent NO signaling. In other work, infrared and far red light have been shown to have therapeutic potential that some attribute to production of NO. Here we explore whether a combination of nitrite and far red light treatment has an additive effect in NO-dependent processes, and whether this effect is mediated by RBCs.

METHODS AND RESULTS

Using photoacoustic imaging in a rat model as a function of varying inspired oxygen, we found that far red light (660 nm, five min. exposure) and nitrite feeding (three weeks in drinking water at 100 mg/L) each separately increased tissue oxygenation and vessel diameter, and the combined treatment was additive. We also employed inhibition of human platelet activation measured by flow cytometry to assess RBC-dependent nitrite bioactivation and found that far red light dramatically potentiates platelet inhibition by nitrite. Blocking RBC-surface thiols abrogated these effects of nitrite and far-red light. RBC-dependent production of NO was also shown to be enhanced by far red light using a chemiluminescence-based nitric oxide analyzer. In addition, RBC-dependent bioactivation of nitrite led to prolonged lag times for clotting in platelet poor plasma that was enhanced by exposure to far red light.

CONCLUSIONS

Our results suggest that nitrite leads to the formation of a photolabile RBC surface thiol-bound species such as an S-nitrosothiol or heme-nitrosyl (NO-bound heme) for which far red light enhances NO signaling. These findings expand our understanding of RBC-mediated NO production from nitrite. This pathway of NO production may have therapeutic potential in several applications including thrombosis, and, thus, warrants further study.

Airway smooth muscle photorelaxation via opsin receptor activation

Nonvisual opsin (OPN) receptors have recently been implicated in blue light-mediated photorelaxation of smooth muscle in various organs. Since photorelaxation has not yet been demonstrated in airway smooth muscle (ASM) or in human tissues, we questioned whether functional OPN receptors are expressed in mouse and human ASM. mRNA, encoding the OPN 3 receptor, was detected in both human and mouse ASM. To demonstrate the functionality of the OPN receptors, we performed wire myography of ex vivo ASM from mouse and human upper airways. Blue light-mediated relaxation of ACh-preconstricted airways was intensity and wavelength dependent (maximum relaxation at 430-nm blue light) and was inhibited by blockade of the large-conductance calcium-activated potassium channels with iberiotoxin. We further implicated OPN receptors as key mediators in functional photorelaxation by demonstrating increased relaxation in the presence of a G protein receptor kinase 2 inhibitor or an OPN chromophore (9- cis retinal). We corroborated these responses in peripheral airways of murine precision-cut lung slices. This is the first demonstration of photorelaxation in ASM via an OPN receptor-mediated pathway.

Cardio-light: nitric oxide uncaged

Photobiomodulation (PB) is a utilization of low-level laser therapy (LLLT) in the far red (R) to near infrared (NIR) spectrum (600-1000 nm) to wield its therapeutic effects. To explore the therapeutic potential of biomodulation of different tissues, LLLT has been extensively researched, especially in the light of its very low side effect profile. We believe there is an opportunity to unearth its dynamic effects on the coronaries which can be promising for the patients with chronic stable angina. NIR treatment of the heart may be protective on patients after acute myocardial infarction or on ischemic heart conditions that are not accessible to current revascularization procedures.

Effects of light-emitting diodes irradiation on human vascular endothelial cells

Endothelial cell proliferation is a hallmark of angiogenesis and plays a key role in the process of tissue repair. Low-intensity (670 nm) laser irradiation influences endothelial cell proliferation in vitro. Light in the near infrared spectrum may have clinical applications in erectile dysfunction. The purpose of this study was to investigate the effects of irradiation with light-emitting diodes (LEDs) at different wavelengths on human vascular endothelial cells in vitro. Human umbilical vein endothelial cells (HUVECs) were irradiated with LEDs at 410, 480, 595, and 630 nm in doses of 1, 2.5, 5, and 10 J/cm². After 24 h of LED irradiation, effects on cell viability, nitric oxide (NO) secretion, and eNOS expression were assessed by using cell viability assays, Western blot, and real time-polymerase chain reaction, respectively. The cell viability assay demonstrated that irradiation with LEDs at 630 nm significantly increased the proliferation of HUVECs. In addition, irradiation with LEDs at 630 nm was more effective in stimulating NO secretion and eNOS expression from HUVECs than irradiation with LEDs at 410, 480, and 595 nm. Irradiation with LEDs at 630 nm was effective for inducing cell proliferation, NO secretion, and eNOS expression in HUVECs. These results suggest that irradiation with LEDs at 630 nm may be a therapeutic strategy for vasculogenic erectile dysfunction.

Red/near infrared light stimulates release of an endothelium dependent vasodilator and rescues vascular dysfunction in a diabetes model

Peripheral artery disease (PAD) is a morbid condition whereby ischemic peripheral muscle causes pain and tissue breakdown. Interestingly, PAD risk factors, e.g. diabetes mellitus, cause endothelial dysfunction secondary to decreased nitric oxide (NO) levels, which could explain treatment failures. Previously, we demonstrated 670nm light (R/NIR) increased NO from nitrosyl-heme stores, therefore we hypothesized R/NIR can stimulate vasodilation in healthy and diabetic blood vessels. Vasodilation was tested by ex vivo pressure myography in wild type C57Bl/6, endothelial nitric oxide synthase (eNOS) knockout, and db/db mice (10mW/cm² for 5min with 10min dark period). NOS inhibition with N-Nitroarginine methyl ester (L-NAME) or the NO scavenger Carboxy-PTIO (c-PTIO) tested the specificity of NO production. 4,5-Diaminofluorescein diacetate (DAF-2) measured NO in human dermal microvascular endothelial cells (HMVEC-d). R/NIR significantly increased vasodilation in wild type and NOS inhibited groups, however R/NIR dilation was totally abolished with c-PTIO and blood vessel denudation. Interestingly, the bath solution from intact R/NIR stimulated vessels could dilate light naïve vessels in a NO dependent manner. Characterization of the bath identified a NO generating substance suggestive of S-nitrosothiols or non heme iron nitrosyl complexes. Consistent with the finding of an endothelial source of NO, intracellular NO increased with R/NIR in HMVEC-d treated with and without L-NAME (1mM), yet c-PTIO (100µm) reduced NO production. R/NIR significantly dilated db/db blood vessels. In conclusion, R/NIR stimulates vasodilation by release of NO bound substances from the endothelium. In a diabetes model of endothelial dysfunction, R/NIR restores vasodilation, which lends the potential for new treatments for diabetic vascular disease.

The impact of wavelengths of LED light-therapy on endothelial cells

Low level light therapy receives increasing interest in the fields of tissue regeneration and wound healing. Several in vivo studies demonstrated the positive effects of LLLT on angiogenesis. This study aimed to investigate the underlying properties in vitro by comparing the effects of light therapy by light emitting diodes of different wavelengths on endothelial cells in vitro. Human umbilical vein endothelial cells were treated with either 475 nm, 516 nm or 635 nm light. Control cells were not illuminated. 2D proliferation was quantified by manual counting. HUVEC migration was analyzed by performing a 2D wound scratch assay and a 3D bead assay. The influence of LLLT on early vasculogenic events was determined in a 3D fibrin co-culture model with adipose-derived stem cells. Stimulation with both red and green pulsed LED light significantly increased HUVEC proliferation and 3D migration. Moreover, HUVEC showed increased 2D migration potential with green light stimulation. The treatment with blue light was ineffective. Several parameters showed that green light was even more potent to stimulate proliferation and migration of endothelial cells than clinically well-established red light therapy. Further studies have to focus on intracellular mechanisms induced by different wavelengths in order to optimize this promising therapy in tissue regeneration.

Photostimulation of mitochondria as a treatment for retinal neurodegeneration

Absorption of photon energy by neuronal mitochondria leads to numerous downstream neuroprotective effects. Red and near infrared (NIR) light are associated with significantly less safety concerns than light of shorter wavelengths and they are therefore, the optimal choice for irradiating the retina. Potent neuroprotective effects have been demonstrated in various models of retinal damage, by red/NIR light, with limited data from human studies showing its ability to improve visual function. Improved neuronal mitochondrial function, increased blood flow to neural tissue, upregulation of cell survival mediators and restoration of normal microglial function have all been proposed as potential underlying mechanisms of red/NIR light.

Melatonin attenuates thiocyanate-induced vasoconstriction in aortic rings

Cigarette smoking not only has a carcinogenic effect but also leads to an increase in arterial blood pressure. Besides its main components, i.e. nicotine, tar, and carbon monoxide, cigarette smoke also contains thiocyanate. Thiocyanate anions (SCN^-) arise from the detoxification of hydrogen cyanide and its plasma concentrations were found to correlate significantly with cigarette consumption. There is also evidence that atherosclerotic disease progression is much more rapid when serum SCN^- levels are increased. Melatonin, a non-toxic indolamine with various physiologic functions, is believed to protect against inflammatory processes and oxidative stress. It has been demonstrated that melatonin serves as free radical scavenger and represents a potent antioxidant. Therefore, it is believed that melatonin with its atheroprotective effects may be useful either as a sole therapy or in conjunction with others. The aim of this study was to quantify the thiocyanate-induced vasomotor response in aortic tissue and further to examine the potential of melatonin in affecting the generated vasoreactivity. Aortic rings of adult male normotensive Wistar rats were cut into 4-mm rings. Following the administration of thiocyanate in various concentrations, vasomotor response of aortic vessel segments was measured. To assess the effect of melatonin on vasomotor activity, organ bath concentrations were modulated from 60 to 360 pM, which corresponds to physiologic plasma up to the levels of patients with regular oral intake of 3 mg of melatonin as a supplement. Thirty-six rat aortic rings were studied. When exposed to thiocyanate, vessel segments revealed vasoconstriction in a concentration-dependent manner. In rings which were preincubated with melatonin at a concentration of 360 pM, a 56.5% reduction of effect size could be achieved (4.09 ± 1.22 mN versus 9.41 ± 1.74 mN, P < 0.0001). Additionally, administration of 360 pM melatonin at a norepinephrine concentration of 80 mM resulted in a relaxation of 10.9 ± 2.2%. The vasodilatatory effect of melatonin was significantly reduced to 1.3 ± 0.5% when concentration of norepinephrine was doubled (P < 0.002). This study indicates that vessel segments that were exposed to thiocyanate responded with a dose-dependent vasoconstriction. The effect could be markedly attenuated in segments preincubated in melatonin.

Low-level laser therapy for beta amyloid toxicity in rat hippocampus

Beta amyloid (Aβ) is well accepted to play a central role in the pathogenesis of Alzheimer's disease (AD). The present work evaluated the therapeutic effects of low-level laser irradiation (LLI) on Aβ-induced neurotoxicity in rat hippocampus. Aβ 1-42 was injected bilaterally to the hippocampus CA1 region of adult male rats, and 2-minute daily LLI treatment was applied transcranially after Aβ injection for 5 consecutive days. LLI treatment suppressed Aβ-induced hippocampal neurodegeneration and long-term spatial and recognition memory impairments. Molecular studies revealed that LLI treatment: (1) restored mitochondrial dynamics, by altering fission and fusion protein levels thereby suppressing Aβ-induced extensive fragmentation; (2) suppressed Aβ-induced collapse of mitochondrial membrane potential; (3) reduced oxidized mitochondrial DNA and excessive mitophagy; (4) facilitated mitochondrial homeostasis via modulation of the Bcl-2-associated X protein/B-cell lymphoma 2 ratio and of mitochondrial antioxidant expression; (5) promoted cytochrome c oxidase activity and adenosine triphosphate synthesis; (6) suppressed Aβ-induced glucose-6-phosphate dehydrogenase and nicotinamide adenine dinucleotide phosphate oxidase activity; (7) enhanced the total antioxidant capacity of hippocampal CA1 neurons, whereas reduced the oxidative damage; and (8) suppressed Aβ-induced reactive gliosis, inflammation, and tau hyperphosphorylation. Although development of AD treatments has focused on reducing cerebral Aβ levels, by the time the clinical diagnosis of AD or mild cognitive impairment is made, the brain is likely to have already been exposed to years of elevated Aβ levels with dire consequences for multiple cellular pathways. By alleviating a broad spectrum of Aβ-induced pathology that includes mitochondrial dysfunction, oxidative stress, neuroinflammation, neuronal apoptosis, and tau pathology, LLI could represent a new promising therapeutic strategy for AD.

Observation of vasculature alternation by intense pulsed light combined with physicochemical methods

Intense pulsed light (IPL) with low energy insufficient to completely destroy a vasculature was applied to rabbit ears to investigate vasculature alteration. Glycerol was combined with IPL to enhance the transfer efficacy of IPL energy. Both trans-illumination and laser speckle contrast images were obtained and analyzed after treatment. The application of IPL and glycerol combination induced vasodilation and improvement in blood flow. Moreover, such phenomenon was maintained over time. IPL may be applied to treat blood circulatory diseases by inducing vasodilation and to improve blood flow.

Biophysical Approaches for Oral Wound Healing: Emphasis on Photobiomodulation

Significance: Oral wounds can lead to significant pain and discomfort as well as affect overall general health due to poor diet and inadequate nutrition. Besides many biological and pharmaceutical methods being investigated, there is growing interest in exploring various biophysical devices that utilize electric, magnetic, ultrasound, pressure, and light energy. Recent Advances: Significant insight into mechanisms of these biophysical devices could provide a clear rationale for their clinical use. Preclinical studies are essential precursors in determining physiological mechanisms and elucidation of causal pathways. This will lead to development of safe and effective therapeutic protocols for clinical wound management. Critical Issues: Identification of precise events initiated by biophysical devices, specifically photobiomodulation-the major focus of this review, offers promising avenues in improving oral wound management. The primary phase responses initiated by the interventions that distinctly contribute to the therapeutic response must be clearly delineated from secondary phase responses. The latter events are a consequence of the wound healing process and must not be confused with causal mechanisms. Future Direction: Clinical adoption of these biophysical devices needs robust and efficacious protocols that can be developed by well-designed preclinical and clinical studies. Elucidation of the precise molecular mechanisms of these biophysical approaches could determine optimization of their applications for predictive oral wound care.

Low level light therapy by LED of different wavelength induces angiogenesis and improves ischemic wound healing

BACKGROUND AND OBJECTIVE

Low-level light therapy (LLLT) has been revealed as a potential means to improve wound healing. So far, most studies are being performed with irradiation in the red to near-infrared spectra. Recently, we showed that blue light (470 nm) can significantly influence biological systems such as nitric oxide (NO) metabolism and is able to release NO from nitrosyl-hemoglobin or mitochondrial protein complexes. Therefore, the aim of this study was to evaluate and compare the therapeutic value of blue or red light emitting diodes (LEDs) on wound healing in an ischemia disturbed rodent flap model.

STUDY DESIGN/MATERIALS AND METHODS

An abdominal flap was rendered ischemic by ligation of one epigastric bundle and subjected to LED illumination with a wavelength of 470 nm (blue, n = 8) or 629 nm (red, n = 8) each at 50 mW/cm(2) and compared to a non-treated control group (n = 8). Illumination was performed for 10 minutes on five consecutive days.

RESULTS

LED therapy with both wavelengths significantly increased angiogenesis in the sub-epidermal layer and intramuscularly (panniculus carnosus muscle) which was associated with significantly improved tissue perfusion 7 days after the ischemic insult. Accordingly, tissue necrosis was significantly reduced and shrinkage significantly less pronounced in the LED-treated groups of both wavelengths.

CONCLUSIONS

LED treatment of ischemia challenged tissue improved early wound healing by enhancing angiogenesis irrespective of the wavelength thus delineating this noninvasive means as a potential, cost effective tool in complicated wounds.

Low-level-laser irradiation induces photorelaxation in coronary arteries and overcomes vasospasm of internal thoracic arteries

BACKGROUND AND OBJECTIVE

As low-level laser irradiation (LLLI) seems to induce vasodilation besides many other known biological effects, LLLI has been increasingly used in therapy of medical conditions with various irradiation parameters. The aim of this study was to investigate the effect of LLLI on photorelaxation of human coronary and internal thoracic arteries (ITA).

MATERIALS AND METHODS

Thirty vessel segments of ITA used for routine coronary artery bypass grafting as well as left anterior descending coronary arteries (LAD) of patients undergoing cardiac transplantation were cut into 4-mm rings stored in a modified Krebs-Henseleit solution and evaluated in a myograph. Both types of vessel segments were irradiated by a semiconductor non-thermal GaAs diode laser operating at a wavelength of 680 nm. After precontraction with thromboxane agonist U44619, respective relaxation responses were evaluated and compared to pharmacological dilatation induced by substance P.

RESULTS

Mean pharmacological vasodilation by substance P was 22.6 ± 3.3%, 12.8 ± 1.4%, and 20.4 ± 3.2% in macroscopic healthy LAD, LAD with atheromatous plaque, and ITA, respectively. Average photorelaxation induced by LLLI was 16.5 ± 2.0%, 1.9 ± 1.7%, and 6.8 ± 4.7%, accordingly. Vasodilatatory responses induced either by substance P or administration of LLLI were significantly decreased in LAD with atheromatous plaque (P < 0.0001). Vasospasms of ITA segments occurring during experiments could be abandoned when LLLI was administered.

CONCLUSION

Macroscopic healthy LAD exposed to LLLI revealed significant photorelaxation. With the administration of LLLI, 73% of the maximal obtainable effect by an endothelium-dependent vasodilator could be reached. Furthermore, LLLI has the potential to overcome vasospasms of ITA.