Human and monkey corneal endothelium expression of low-density lipoprotein receptors.
Receptors for low-density lipoprotein are necessary for high-affinity uptake of lipid and protein essential to cell structure and function. Distinct receptors for acetoacetylated low-density lipoprotein internalize oxidized or enzymatically modified low-density lipoprotein and extracellular matrix components. We identified low-density lipoprotein receptors on cultured human and monkey corneal endothelial cells by the avid incorporation of fluorescently labeled low-density lipoprotein that was competitively inhibited by excess unlabeled low-density lipoprotein but not by unlabeled acetoacetylated low-density lipoprotein. Specific uptake of labeled low-density lipoprotein was greatest in nonconfluent, growing cells and increased after low-density lipoprotein deprivation. Intact endothelial monolayers of whole human cornea also incorporated low-density lipoprotein but not acetoacetylated low-density lipoprotein. After scratch injury of human corneas, spreading endothelium adjacent to areas of cell loss internalized more fluorescent low-density lipoprotein than cells distant from the injury. Blood-aqueous barrier breakdown occurring in ocular diseases and after surgical and nonsurgical trauma may allow leakage of circulating low-density lipoprotein, which provides a rich supply of lipid and protein for endothelial use. Efficient, receptor-mediated, low-density lipoprotein uptake may facilitate repair of damaged corneal endothelial membranes and regeneration of intact, functional cell monolayers.
Elner
S G
SG
Department of Ophthalmology, Kellogg Eye Center, University of Michigan, Ann Arbor 48105.
Elner
V M
VM
Pavilack
M A
MA
Davis
H R
HR
Cornicelli
J A
JA
Yue
B Y
BY
D000090:Acetoacetates / Q000378:metabolism; D000818:Animals; D002232:Carbocyanines; D002455:Cell Division; D002470:Cell Survival; D002478:Cells, Cultured; D002675:Child, Preschool; D003315:Cornea / Q000378:metabolism; D065306:Corneal Injuries; D004728:Endothelium, Corneal / Q000293:injuries / Q000378:metabolism*; D005456:Fluorescent Dyes; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism; D008253:Macaca mulatta; D011817:Rabbits; D011973:Receptors, LDL / Q000096:biosynthesis*; D014945:Wound Healing
D000090:Acetoacetates; D002232:Carbocyanines; D005456:Fluorescent Dyes; D008077:Lipoproteins, LDL; D011973:Receptors, LDL; C024286:3,3'-dioctadecylindocarbocyanine