PMID- 9098097
OWN - NLM
STAT- MEDLINE
DCOM- 19970729
LR  - 20220321
IS  - 0891-5849 (Print)
IS  - 0891-5849 (Linking)
VI  - 22
IP  - 7
DP  - 1997
TI  - Lipofuscin accumulation in cultured retinal pigment epithelial cells causes 
      enhanced sensitivity to blue light irradiation.
PG  - 1229-34
AB  - Lipofuscin accumulates with age within secondary lysosomes of retinal pigment 
      epithelial (RPE) cells of humans and many animals. The autofluorescent lipofuscin 
      pigment has an excitation maximum within the range of visible blue light, while 
      it is emitting in the yellow-orange area. This physico-chemical property of the 
      pigment indicates that it may have a photo-oxidative capacity and, consequently, 
      then should destabilize lysosomal membranes of blue-light exposed RPE. To test 
      this hypothesis, being of relevance to the understanding of age-related macular 
      degeneration, cultures of heavily lipofuscin-loaded RPE cells were 
      blue-light-irradiated and compared with respect to lysosomal stability and cell 
      viability to relevant controls. To rapidly convert primary cultures of RPE, 
      obtained from neonatal rabbits, into aged, lipofuscin-loaded cells, they were 
      allowed to phagocytize artificial lipofuscin that was prepared from outer 
      segments of bovine rods and cones. Following blue-light irradiation, lysosomal 
      membrane stability was measured by vital staining with the lysosomotropic weak 
      base, and metachromatic fluorochrome, acridine orange (AO). Quantifying red (high 
      AO concentration within intact lysosomes with preserved proton gradient over 
      their membranes) and green fluorescence (low AO concentration in nuclei, damaged 
      lysosomes with decreased or lost proton gradients, and in the cytosol) allowed an 
      estimation of the lysosomal membrane stability after blue-light irradiation. 
      Cellular viability was estimated with the delayed trypan blue dye exclusion test. 
      Lipofuscin-loaded blue-light-exposed RPE cells showed a considerably enhanced 
      loss of both lysosomal stability and viability when compared to control cells. 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.
FAU - Wihlmark, U
AU  - Wihlmark U
AD  - Department of Ophthalmology, University Hospital, Linkoping, Sweden.
FAU - Wrigstad, A
AU  - Wrigstad A
FAU - Roberg, K
AU  - Roberg K
FAU - Nilsson, S E
AU  - Nilsson SE
FAU - Brunk, U T
AU  - Brunk UT
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - United States
TA  - Free Radic Biol Med
JT  - Free radical biology & medicine
JID - 8709159
RN  - 0 (Lipofuscin)
RN  - 0 (Protons)
RN  - F30N4O6XVV (Acridine Orange)
RN  - I2ZWO3LS3M (Trypan Blue)
SB  - IM
MH  - Acridine Orange/metabolism
MH  - Animals
MH  - Cell Membrane/metabolism
MH  - Cell Survival
MH  - Cells, Cultured
MH  - *Light
MH  - Lipofuscin/*metabolism/pharmacology
MH  - Lysosomes/metabolism
MH  - Macular Degeneration/pathology
MH  - Microscopy, Fluorescence
MH  - Pigment Epithelium of Eye/cytology/*metabolism/*radiation effects
MH  - Protons
MH  - Rabbits
MH  - Trypan Blue/metabolism
EDAT- 1997/01/01 00:00
MHDA- 1997/01/01 00:01
CRDT- 1997/01/01 00:00
PHST- 1997/01/01 00:00 [pubmed]
PHST- 1997/01/01 00:01 [medline]
PHST- 1997/01/01 00:00 [entrez]
AID - S0891584996005552 [pii]
AID - 10.1016/s0891-5849(96)00555-2 [doi]
PST - ppublish
SO  - Free Radic Biol Med. 1997;22(7):1229-34. doi: 10.1016/s0891-5849(96)00555-2.