The Photoreactivity of the Retinal Age Pigment Lipofuscin.
Journal of Biological Chemistry 1999;274(34):23828-32
Wassell J, Davies S, Bardsley W, Boulton M
"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." Abstract
Rhodopsin-Mediated Blue-Light Damage to the rat Retina: Effect of Photoreversal
of Bleaching. Invest Ophthalmol Vis Sci 2001 Feb;42(2):497-505
Grimm C, Wenzel A, Williams T, Rol P, Hafezi F, Reme C.
"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." Abstract
Photoreceptor Renewal and the Pigment Epithelium of the Retina-
Congratulations to a Pioneer in Retinal Research: Richard W. Young.
Klin Monatsbl Augenheilkd 2000; 216(3):129-32
"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." Abstract
Blue Light-Induced Singlet Oxygen Generation by Retinal Lipofuscin in Non-Polar Media.
Free Radic Biol Med 1998 May;24(7-8):1107-12
Rozanowska M, Wessels J, Boulton M, Burke JM, Rodgers MA, Truscott TG, Sarna T
"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"
"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." Abstract
Photocytotoxicity of Lipofuscin in Human Retinal Pigment Epithelial Cells.
Free Radic Biol Med 2001 Jul 15;31(2):256-65.
Davies S, Elliott MH, Floor E, Truscott TG, Zareba M, Sarna T, Shamsi FA, Boulton ME.
"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." Abstract
Lipofuscin Accumulation in Cultured Retinal Pigment Epithelial Cells Reduces
Their Phagocytic Capacity. Current Eye Research 1998; 17(8):851-7
Sundelin S, Wihlmark U, Nilsson SE, Brunk UT
"In old age, lipofuscin accumulation may become quite substantial. It has been suggested that pronounced accumulation of lipofuscin is related to decreased RPE function and, possibly, to age-related macular degeneration."
"CONCLUSIONS: Severe lipofuscin accumulation of RPE cells appears to result in a greatly decreased phagocytic capacity. The resulting reduction in ability to cope with the needs of the overlying photoreceptor cells, in order to eliminate the obsolete tips of their POS, may well be of significance in the development of age-related macular degeneration." Abstract
Photosensitization of Retinal Pigment Epithelium by Protoporphyrin IX.
Graefes Archives for Clinical and Experimental Ophthalmology 1998; 236(3):230-3
Bynoe LA, Del Priore LV, Hornbeck R
"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." Abstract
Retinal Pigment Epithelium (RPE) Pigment Granules Stimulate the Photo-oxidation of
Unsaturated Fatty Acids
Free Radicals in Biology and Medicine 1999; 26(11-12):1436-46
Dontsov AE, Glickman RD, Ostrovsky MA.
"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." Abstract
Note: more recent references on the risk of eye damage from light therapy can be found in the section marked - For Therapists