(Note: Emphasis in all quotes are ours)
"The presence of the age pigment lipofuscin is associated with numerous
age-related diseases. In the retina lipofuscin is located within the pigment epithelium
where it is exposed to high oxygen and visible light, a prime environment for the
generation of reactive oxygen species."
"We postulate that lipofuscin may compromise retinal cell function by causing
loss of lysosomal integrity and that this may be a major contributory factor to the
pathology associated with retinal light damage and diseases such as age-related macular
degeneration."
"Acute white-light damage to rods depends on the amount of rhodopsin available for bleaching during light exposure. ..Because photoreversal is faster than metabolic regeneration of rhodopsin by several orders of magnitude, the photon catch capacity of the retina is significantly augmented during blue-light illumination, which may explain the greater susceptibility of the retina to blue light than to green light However, blue light can also affect function of several blue-light-absorbing enzymes that may lead to the induction of retinal damage.
CONCLUSIONS: Short time exposure to blue light has deleterious effects on retinal morphology..... Photoreversal of bleaching, which occurs only in blue but not in green light, increases the photon-catch capacity of the retina and may thus account for the difference in the damage potential between blue and green light."
"It is generally concluded that lipofuscin can contribute to the pathogenesis of age related macular degeneration (AMD). Early on Young has postulated that light exposure may accelerate AMD and some forms of retinitis pigmentosa (RP). Today we know that indeed in several animal models of RP light exposure can significantly enhance the disease progression."
Accumulation of lipofuscin (LF) is a prominent feature of aging in the human retinal pigment epithelium (RPE) cells. This age pigment exhibits substantial photoreactivity, which may increase the risk of retinal photodamage and contribute to age-related maculopathy.(AMRD)."
"These results indicate the potential role of hydrophobic components of lipofuscin in blue light-induced damage to the RPE."
"The action spectrum of singlet oxygen formation indicated that this process was strongly wavelength-dependent and its efficiency decreased with increasing wavelength by a factor of ten, comparing 420 nm and 520 nm."
"Lipofuscin accumulates with age in a variety of highly metabolically active cells, including the retinal pigment epithelium (RPE) of the eye, where its photoreactivity has the potential for cellular damage. The aim of this study was to assess the phototoxic potential of lipofuscin in the retina."
"Exposure of lipofuscin-fed cells to short wavelength visible light (390-550 nm) caused lipid peroxidation (increased levels of malondialdehyde and 4-hydroxy-nonenal), protein oxidation (protein carbonyl formation), loss of lysosomal integrity, cytoplasmic vacuolation, and membrane blebbing culminating in cell death. This effect was wavelength-dependent because light exposure at 550 to 800 nm had no adverse effect on lipofuscin-loaded cells. These results confirm the photoxicity of lipofuscin in a cellular system and implicate it in cell dysfunction such as occurs in ageing and retinal diseases."
"It is concluded that the accumulation of lipofuscin within secondary lysosomes of RPE sensitizes these cells to blue light by inducing photo-oxidative alterations of their lysosomal membranes resulting in a presumed leakage of lysosomal contents to the cytosol with ensuing cellular degeneration of apoptotic type. The suggested mechanism may have bearings on the development of age-related macular degeneration.".
"CONCLUSION: Blue wavelength light without exogenous protoporphyrin IX has a cytotoxic effect on confluent cultures of retinal pigment epithelium, suggesting that endogenous photosensitizers may be present in retinal pigment epithelial cells. Protoporphyrin IX has an additive cytotoxic effect in the presence of blue light, suggesting that this photosensitizer is capable of mediating blue-light-induced retinal pigment epithelial damage. Since protoporphyrin IX is present in blood and tissue fluids, and the retina is chronically exposed to light, protoporphyrin IX-mediated free radical formation may occur in vivo and may play a role in retinal pigment epithelial changes that occur early in the pathogenesis of age-related macular degeneration."
"These findings provide additional support for the role of RPE pigments in "blue light toxicity" as well as indicating that accumulation of lipofuscin may contribute to increased photooxidation in the aging RPE".
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