Dietary Spirulina Supplementation Protects Visual Function From Photostress by Suppressing Retinal Neurodegeneration in Mice.

PURPOSE: We investigated whether daily consumption of Spirulina, an antioxidant generating cyanobacterial nutritional supplement, would suppress photostress-induced retinal damage and prevent vision loss in mice. METHODS: Six-week-old male BALB/cAJcl mice were allowed constant access to either a standard or Spirulina-supplemented diet (20% Spirulina) that included the antioxidants, ß-carotene and zeaxanthin, and proteins for 4 weeks. Following dark adaptation, mice were exposed to 3000-lux white light for 1 hour and returned to their cages. Visual function was analyzed by electroretinogram, and retinal histology by hematoxylin and eosin staining, terminal deoxynucleotidyl transferase-mediated, deoxyuridine triphosphate nick-end labeling (TUNEL) assay, and immunohistochemistry. Retinal expression of proteins, reactive oxygen species (ROS), and mRNAs were measured using immunoblot analysis, enzyme-linked immunosorbent assay (ELISA), 2',7'-dichlorofluorescein-diacetate, or ROS Brite 700 Dyes, and real-time reverse-transcription polymerase chain reaction, respectively. RESULTS: Light-induced visual function impairment was suppressed by constant Spirulina intake. Thinning of the photoreceptor layer and outer segments, photoreceptor cell death, decreased rhodopsin protein, and induction of glial fibrillary acidic protein were ameliorated in the Spirulina-intake group. Increased retinal ROS levels after light exposure were reduced by Spirulina supplementation. Light-induced superoxide dismutase 2 and heme oxygenase-1 mRNAs in the retina, and Nrf2 activation in the photoreceptor cells, were preserved with Spirulina supplementation, despite reduced ROS levels, suggesting two pathways for suppressing ROS, scavenging and induction of endogenous antioxidative enzymes. Light-induced MCP-1 retinal mRNA and proteins were also suppressed by Spirulina. CONCLUSIONS: Spirulina ingestion protected retinal photoreceptors from photostress in the retina. TRANSLATIONAL RELEVANCE: Spirulina has potential as a nutrient supplement to prevent vision loss related to oxidative damage in the future.

Neuroprotective effect of bilberry extract in a murine model of photo-stressed retina.

Excessive exposure to light promotes degenerative and blinding retinal diseases such as age-related macular degeneration and retinitis pigmentosa. However, the underlying mechanisms of photo-induced retinal degeneration are not fully understood, and a generalizable preventive intervention has not been proposed. Bilberry extract is an antioxidant-rich supplement that ameliorates ocular symptoms. However, its effects on photo-stressed retinas have not been clarified. In this study, we examined the neuroprotective effects of bilberry extract against photo-stress in murine retinas. Light-induced visual function impairment recorded by scotopic and phototopic electroretinograms showing respective rod and cone photoreceptor function was attenuated by oral administration of bilberry extract through a stomach tube in Balb/c mice (750 mg/kg body weight). Bilberry extract also suppressed photo-induced apoptosis in the photoreceptor cell layer and shortening of the outer segments of rod and cone photoreceptors. Levels of photo-induced reactive oxygen species (ROS), oxidative and endoplasmic reticulum (ER) stress markers, as measured by real-time reverse transcriptase polymerase chain reaction, were reduced by bilberry extract treatment. Reduction of ROS by N-acetyl-L-cysteine, a well-known antioxidant also suppressed ER stress. Immunohistochemical analysis of activating transcription factor 4 expression showed the presence of ER stress in the retina, and at least in part, in Müller glial cells. The photo-induced disruption of tight junctions in the retinal pigment epithelium was also attenuated by bilberry extract, repressing an oxidative stress marker, although ER stress markers were not repressed. Our results suggest that bilberry extract attenuates photo-induced apoptosis and visual dysfunction most likely, and at least in part, through ROS reduction, and subsequent ER stress attenuation in the retina. This study can help understand the mechanisms of photo-stress and contribute to developing a new, potentially useful therapeutic approach using bilberry extract for preventing retinal photo-damage.

Blue-violet light emitting diode (LED) irradiation immediately controls socket bleeding following tooth extraction: clinical and electron microscopic observations.

OBJECTIVE: Bleeding control is a major concern during dental surgery. A novel photocoagulation method using an irradiating blue-violet light emitting diode (LED) was investigated. BACKGROUND: Some dental light-curving units can emit blue-violet wavelengths around 380-515 nm with two peaks (410 nm and 470 nm). These wavelengths can cover the maximum absorption spectra of hemoglobin (430 nm). MATERIALS AND METHODS: Blue-violet LED 380-515 nm, 750 mW/cm(2), 10 sec (7.5 J/cm(2)) was used. Irradiation was performed for 10 sec or an additional 10 sec for 10 cases of tooth extraction at a distance of 1 cm from the socket. Bleeding was stopped by conventional roll pressure in another five cases as a control. Bleeding time for both procedures was measured. A Mann-Whitney U test was used for statistical analysis. In vitro transmission electron microscope (TEM) studies were performed to clarify the mechanism of hemostasis by blue-violet LED irradiation. RESULTS: Irradiation with the blue-violet LED yielded immediate hemostasis of the socket. Five cases showed coagulation within the first 10 sec, and another five cases required an additional 10 sec to fully control the bleeding. In contrast, the conventional method required 2-5 min (median 180 sec) to obtain hemostasis. The difference between the time required to stop the bleeding in the two methods was found to be statistically significant (p = 0.0014). A week later, the LED-irradiated sockets were healed uneventfully with epithelial covering. TEM showed the formation of a thin amorphous layer and an adjacent agglutination of platelets and other cellular elements under the layer at the interface of the irradiated blood. CONCLUSION: Blue-violet LED irradiation of bleeding sockets caused immediate clot formation and hemostasis. This procedure was safe and reliable and showed no adverse effects.