670 nm LED ameliorates inflammation in the CFH(-/-) mouse neural retina

The roles of macrophage migration inhibitory factor in retinal diseases

Macrophage migration inhibitory factor (MIF), a multifunctional cytokine, is secreted by various cells and participates in inflammatory reactions, including innate and adaptive immunity. There are some evidences that MIF is involved in many vitreoretinal diseases. For example, MIF can exacerbate many types of uveitis; measurements of MIF levels can be used to monitor the effectiveness of uveitis treatment. MIF also alleviates trauma-induced and glaucoma-induced optic nerve damage. Furthermore, MIF is critical for retinal/choroidal neovascularization, especially complex neovascularization. MIF exacerbates retinal degeneration; thus, anti-MIF therapy may help to mitigate retinal degeneration. MIF protects uveal melanoma from attacks by natural killer cells. The mechanism underlying the effects of MIF in these diseases has been demonstrated: it binds to cluster of differentiation 74, inhibits the c-Jun N-terminal kinase pathway, and triggers mitogen-activated protein kinases, extracellular signal-regulated kinase-1/2, and the phosphoinositide-3-kinase/Akt pathway. MIF also upregulates Toll-like receptor 4 and activates the nuclear factor kappa-B signaling pathway. This review focuses on the structure and function of MIF and its receptors, including the effects of MIF on uveal inflammation, retinal degeneration, optic neuropathy, retinal/choroidal neovascularization, and uveal melanoma.

Photobiomodulation Therapy for Age-Related Macular Degeneration and Diabetic Retinopathy: A Review

Purpose

Photobiomodulation therapy (PBT) has emerged as a possible treatment for age-related macular degeneration (AMD) and diabetic retinopathy (DR). This review seeks to summarize the application of PBT in AMD and DR.

Methods

The National Clinical Trial (NCT) database and PubMed were queried using a literature search strategy and reviewed by the authors.

Results

Fourteen studies examining the application of PBT for AMD and nine studies examining the application of PBT for diabetic macular edema (DME) were extracted from 60 candidate publications.

Discussion

Despite notable methodological differences between studies, PBT has been reported to treat certain DR and AMD patients. DR patients with center involving DME and VA ≥ 20/25 have demonstrated response to treatment. AMD patients at Age-Related Eye Disease Study Stages 2–4 with VA ≥20/200 have also shown response to treatment. Results of major clinical trials are pending.

Conclusion

PBT remains an emergent therapy with possible applications in DR and AMD. Further, high powered studies monitored by a neutral party with standard devices, treatment delivery and treatment timing are needed.

Photobiomodulation therapy in age-related macular degeneration

PURPOSE OF REVIEW

To review the available data supporting the use of photobiomodulation therapy (PBT) in the treatment of age-related macular degeneration (AMD).

RECENT FINDINGS

PBT might be used in treating nonexudative AMD. Limited evidence suggests that exudative AMD may also benefit from PBT.

SUMMARY

The optimal device would deliver doses of 60 J/cm2 or more with a multiwavelength composition through the pupil over short treatment intervals. Safe upper limits have not been established. More studies are needed to evaluate the efficacy of PBT in treating exudative and nonexudative AMD.

Near Infrared (NIR) Light Therapy of Eye Diseases: A Review

Near infrared (NIR) light therapy, or photobiomodulation therapy (PBMT), has gained persistent worldwide attention in recent years as a new novel scientific approach for therapeutic applications in ophthalmology. This ongoing therapeutic adoption of NIR therapy is largely propelled by significant advances in the fields of photobiology and bioenergetics, such as the discovery of photoneuromodulation by cytochrome c oxidase and the elucidation of therapeutic biochemical processes. Upon transcranial delivery, NIR light has been shown to significantly increase cytochrome oxidase and superoxide dismutase activities which suggests its role in inducing metabolic and antioxidant beneficial effects. Furthermore, NIR light may also boost cerebral blood flow and cognitive functions in humans without adverse effects. In this review, we highlight the value of NIR therapy as a novel paradigm for treatment of visual and neurological conditions, and provide scientific evidence to support the use of NIR therapy with emphasis on molecular and cellular mechanisms in eye diseases.

Photobiomodulation Mediates Neuroprotection against Blue Light Induced Retinal Photoreceptor Degeneration

Potent neuroprotective effects of photobiomodulation with 670 nm red light (RL) have been demonstrated in several models of retinal disease. RL improves mitochondrial metabolism, reduces retinal inflammation and oxidative cell stress, showing its ability to enhance visual function. However, the current knowledge is limited to the main hypothesis that the respiratory chain complex IV, cytochrome c oxidase, serves as the primary target of RL. Here, we demonstrate a comprehensive cellular, molecular, and functional characterization of neuroprotective effects of 670 nm RL and 810 nm near-infrared light (NIRL) on blue light damaged murine primary photoreceptors. We show that respiratory chain complexes I and II are additional PBM targets, besides complex IV, leading to enhanced mitochondrial energy metabolism. Accordingly, our study identified mitochondria related RL- and NIRL-triggered defense mechanisms promoting photoreceptor neuroprotection. The observed improvement of mitochondrial and extramitochondrial respiration in both inner and outer segments is linked with reduced oxidative stress including its cellular consequences and reduced mitochondria-induced apoptosis. Analysis of regulatory mechanisms using gene expression analysis identified upregulation α-crystallins that indicate enhanced production of proteins with protective functions that point to the rescued mitochondrial function. The results support the hypothesis that energy metabolism is a major target for retinal light therapy.

670nm light treatment following retinal injury modulates Müller cell gliosis: Evidence from in vivo and in vitro stress models

Photobiomodulation (PBM) with 670 nm light has been shown to accelerate wound healing in soft tissue injuries, and also to protect neuronal tissues. However, little data exist on its effects on the non-neuronal components of the retina, such as Müller cells (MCs), which are the principal macroglia of the retina that play a role in maintaining retinal homeostasis. The aim of this study was to explore the effects of 670 nm light on activated MCs using in vivo and in vitro stress models. Adult Sprague-Dawley rats were exposed to photo-oxidative damage (PD) for 24 h and treated with 670 nm light at 0, 3 and 14 days after PD. Tissue was collected at 30 days post-PD for analysis. Using the in vitro scratch model with a human MC line (MIO-M1), area coverage and cellular stress were analysed following treatment with 670 nm light. We showed that early treatment with 670 nm light after PD reduced MC activation, lowering the retinal expression of GFAP and FGF-2. 670 nm light treatment mitigated the production of MC-related pro-inflammatory cytokines (including IL-1β), and reduced microglia/macrophage (MG/MΦ) recruitment into the outer retina following PD. This subsequently decreased photoreceptor loss, slowing the progression of retinal degeneration. In vitro, we showed that 670 nm light directly modulated MC activation, reducing rates of area coverage by suppressing cellular proliferation and spreading. This study indicates that 670 nm light treatment post-injury may have therapeutic benefit when administered shortly after retinal damage, and could be useful for retinal degenerations where MC gliosis is a feature of disease progression.

Retinal pigment epithelium in the pathogenesis of age-related macular degeneration and photobiomodulation as a potential therapy?

The retinal pigment epithelium (RPE) comprises a monolayer of cells located between the neuroretina and the choriocapillaries. The RPE serves several important functions in the eye: formation of the blood-retinal barrier, protection of the retina from oxidative stress, nutrient delivery and waste disposal, ionic homeostasis, phagocytosis of photoreceptor outer segments, synthesis and release of growth factors, reisomerization of all-trans-retinal during the visual cycle, and establishment of ocular immune privilege. Age-related macular degeneration (AMD) is the leading cause of blindness in developed countries. Dysfunction of the RPE has been associated with the pathogenesis of AMD in relation to increased oxidative stress, mitochondrial destabilization and complement dysregulation. Photobiomodulation or near infrared light therapy which refers to non-invasive irradiation of tissue with light in the far-red to near-infrared light spectrum (630-1000 nm), is an intervention that specifically targets key mechanisms of RPE dysfunction that are implicated in AMD pathogenesis. The current evidence for the efficacy of photobiomodulation in AMD is poor but its safety profile and proposed mechanisms of action motivate further research as a novel therapy for AMD.

Near infra-red light attenuates corneal endothelial cell dysfunction in situ and in vitro

In the present study mechanical damage to the corneal endothelium was induced by elevation of intraocular pressure (IOP, 140 mmHg, 60 min) to one eye of rats, delivered either in complete darkness or in the presence of red light (16.5 W/m², 3000 lx, 625-635 nm). IOP raised in the dark revealed the endothelium to be damaged as staining for the gap junction protein ZO-1 was irregular in appearance with some cells displaced in position or lost to leave gaps or holes. This damage was clearly attenuated when red light was focused through the pupil during the insult of raised IOP. Moreover, staining of endothelium with JC-1 dye showed mitochondria to be activated by both elevated IOP and red light but the activation of mitochondria persisted longer for red light. We interpret this finding to suggest that raised IOP causes apoptosis of endothelial cells and that their mitochondria are activated in the initial stages of the process. In contrast, red light activates mitochondria to induce a protective mechanism to counteract the negative influence of raised IOP on endothelial cells. Evidence is provided to support this notion by the finding that red light stimulates mitochondrial cytochrome oxidase IV (COX IV). Moreover, mitochondria in corneal endothelial cell cultures are activated by red light, revealed by staining with JC-1, that results in an increased rate of proliferation and are also able to counteract toxic insults (sodium azide or cobalt chloride) to the cultures. The present studies therefore show that a non-toxic level of red light attenuates damage to the corneal endothelium both in situ and in vitro through action on COX IV located in mitochondria that results in an enhancement of a cell's survival mechanisms. The study provides proof of principle for the non-invasive use of red-light therapy to attenuate any dysfunctions associated with the corneal endothelium and so preserve maximum visual acuity.