Janet R. Sparrow
Anthony Donn Professor of Ophthalmic Sciences (in
Columbia University?Medical Center
United States of America
Vitamin A aldehyde-conjugates accumulate as lipofuscin in retinal pigment epithelial (RPE) cells and have been linked to disease processes in some inherited forms of macular degeneration as well as age-related macular degeneration. These bisretinoid constituents of lipofuscin are unique to RPE and in addition to A2E include all-trans-retinal dimer and its conjugates, phosphatidyl-dihydropyridine bisretinoid (A2-DHP-PE) and a conjugate of all-trans-retinal and glycerophosphoethanolamine (A2-GPE). The excitation and emission spectra of these compounds can also account for the inherent autofluorescence of the retina (fundus autofluorescence). Dr. Sparrow’s laboratory has shown that the adverse effects of RPE lipofuscin pigments are attributable, at least in part, to their detergent-like structure and their photo-sensitive properties. In the latter case, bisretinoids can generate reactive forms of oxygen; they also undergo photooxidation and photodegradation. The photo-cleavage products of A2E consists of a complex mixture of aldehyde-bearing fragments that includes the small dicarbonyls methylglyoxal and glyoxal that are responsible for damaging modifications of proteins – advanced glycation end-products (AGEs). AGE-modified proteins are present in drusen. We are applying our understanding of RPE bisretinoids to clinical interpretations and measurements of fundus autofluorescence. Taken together work in the laboratory contributes to the elucidation of pathology in several retinal disorders including recessive Stargardt disease, retinitis pigmentosa, pattern dystrophies and age-related macular degeneration. Therapeutic strategies her laboratory investigates to target bisretinoids include antioxidants, inhibitors of complement activation, small molecules that inhibit their formation and gene-based therapy.
Understanding the composition of RPE bisretinoid lipofuscin and conditions modulating its formation Investigating links between RPE lipofuscin and drusen formation in age-related macular degeneration Development of therapies to limit RPE lipofuscin formation Interpretation of patterns of fundus autofluorescence in retinal disorders Quantitation of fundus autofluorescence intensities