tretinoin and Macular-Degeneration

Delivery of therapeutic proteins, such as antiangiogenic proteins, to the eye is a demonstrated method for the control of age-related macular degeneration (AMD). However, one of the key limitations is the requirement for frequent and repeated intraocular injections. In this article, we demonstrate that repeated protein production in the eye can be stimulated from the cytomegalovirus (CMV) promoter without repeat intraocular injections using a small molecule, all-trans retinoic acid (ATRA). ATRA by systemic delivery can stimulate protein production multiple times in the eye. Administration of ATRA resulted in stimulation of gene expression to relevant levels that block abnormal blood vessel growth in an experimental animal model for AMD. These data support the principles of this technological discovery to therapeutic applications for chronic ocular diseases.

Topics: Adenoviridae; Animals; Choroidal Neovascularization; Cytomegalovirus; Enzyme-Linked Immunosorbent Assay; Eye; Eye Proteins; Female; Gene Expression; Genetic Therapy; Genetic Vectors; Luciferases; Macular Degeneration; Mice; Mice, Inbred BALB C; Nerve Growth Factors; Polymerase Chain Reaction; Promoter Regions, Genetic; Serpins; Time Factors; Tretinoin

In early age-related macular degeneration (AMD), lipid-containing deposits (drusen) accumulate in Bruch's membrane underlying the retinal pigment epithelium (RPE). Recent studies indicate that apolipoprotein E (apoE) may play a role in lipid trafficking in AMD. Compared with the apoE3 allele, the apoE4 and apoE2 alleles are associated with decreased and increased risk for AMD, respectively; drusen contain high levels of apoE, and apoE null mice develop lipid deposits in Bruch's membrane similar to those observed in AMD. Primary cultures of human RPE cells expressing the apoE3 allele were grown on Transwell culture plates. Western blotting, ELISA assay, and mass spectrometry confirmed that apoE3 was secreted into the apical and basal chambers and that secretion was upregulated by thyroid hormone, 9-cis-retinoic acid, and 22(R)-hydroxycholesterol. In addition, basally secreted apoE associated with exogenously added HDL. These results indicate that apoE secretion can be regulated by specific hormones and that apoE associates with HDL. The findings are consistent with a role for apoE in lipid trafficking through Bruch's membrane and may be relevant to AMD.

Topics: Adult; Alleles; Amino Acid Sequence; Apolipoproteins E; Biological Transport; Bruch Membrane; Cells, Cultured; Humans; Hydroxycholesterols; Lipid Metabolism; Lipoproteins, HDL; Macular Degeneration; Male; Molecular Sequence Data; Pigment Epithelium of Eye; Polymorphism, Genetic; Retinal Pigments; Tretinoin

RPE65 is essential in the operation of the visual cycle and functions as a chaperone for all-trans-retinyl esters, the substrates for isomerization in the visual cycle. RPE65 stereospecifically binds all-trans-retinyl esters with a K(D) of 47 nM. It is shown here by using a quantitative fluorescence technique, that Accutane (13-cis-retinoic acid), a drug used in the treatment of acne but that causes night blindness, binds to RPE65 with a K(D) of 195 nM. All-trans-retinoic acid binds with a K(D) of 109 nM. The binding of the retinoic acids to RPE65 is competitive with all-trans-retinyl ester binding, and this competition inhibits visual cycle function. A retinoic acid analog that binds weakly to RPE65 is not inhibitory. These data suggest that RPE65 function is rate-limiting in visual cycle function. They also reveal the target through which the retinoic acids induce night blindness. Finally, certain forms of retinal and macular degeneration are caused by the accumulation of vitamin A-based retinotoxic products, called the retinyl pigment epithelium-lipofuscin. These retinotoxic products accumulate during the normal course of rhodopsin bleaching and regeneration after the operation of the visual cycle. Drugs such as Accutane may represent an important approach to reducing the accumulation of the retinotoxic lipofuscin by inhibiting visual cycle function. The identification of RPE65 as the visual cycle target for the retinoic acids makes it feasible to develop useful drugs to treat retinal and macular degeneration while avoiding the substantial side effects of the retinoic acids.

Topics: Animals; Cattle; Diterpenes; Eye Proteins; Macular Degeneration; Proteins; Retinyl Esters; Tretinoin; Vitamin A