9-cis-retinal and Blindness

The retinoid (visual) cycle consists of a series of biochemical reactions needed to regenerate the visual chromophore 11-

Topics: Acyltransferases; Administration, Oral; Animals; Blindness; Chitosan; Cone Opsins; Disease Models, Animal; Diterpenes; Dogs; Dose-Response Relationship, Drug; Electroretinography; Female; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Opsins; Photoreceptor Cells, Vertebrate; Retinal Pigment Epithelium; Retinaldehyde; Rod Opsins; Tomography, Optical Coherence

To design and develop a drug-delivery system containing a combination of poly(D,L-lactide-co-glycolide) (PLGA) microparticles and alginate hydrogel for sustained release of retinoids to treat retinal blinding diseases that result from an inadequate supply of retinol and generation of 11-cis-retinal.. To study drug release in vivo, either the drug-loaded microparticle-hydrogel combination was injected subcutaneously or drug-loaded microparticles were injected intravitreally into Lrat(-/-) mice. Orally administered 9-cis-retinoids were used for comparison and drug concentrations in plasma were determined by HPLC. Electroretinography (ERG) and both chemical and histologic analyses were used to evaluate drug effects on visual function and morphology.. Lrat(-/-) mice demonstrated sustained drug release from the microparticle/hydrogel combination that lasted 4 weeks after subcutaneous injection. Drug concentrations in plasma of the control group treated with the same oral dose rose to higher levels for 6-7 hours but then dropped markedly by 24 hours. Significantly increased ERG responses and a markedly improved retinal pigmented epithelium (RPE)-rod outer segment (ROS) interface were observed after subcutaneous injection of the drug-loaded delivery combination. Intravitreal injection of just 2% of the systemic dose of drug-loaded microparticles provided comparable therapeutic efficacy.. Sustained release of therapeutic levels of 9-cis-retinoids was achieved in Lrat(-/-) mice by subcutaneous injection in a microparticle/hydrogel drug-delivery system. Both subcutaneous and intravitreal injections of drug-loaded microparticles into Lrat(-/-) mice improved visual function and retinal structure.

Topics: Acyltransferases; Administration, Oral; Alginates; Animals; Blindness; Delayed-Action Preparations; Disease Models, Animal; Diterpenes; Drug Delivery Systems; Drug Therapy, Combination; Electroretinography; Female; Glucuronic Acid; Hexuronic Acids; Humans; Hydrogel, Polyethylene Glycol Dimethacrylate; Injections, Subcutaneous; Intravitreal Injections; Lactic Acid; Male; Mice; Mice, Mutant Strains; Microspheres; Polyglycolic Acid; Polylactic Acid-Polyglycolic Acid Copolymer; Retinaldehyde; Retinoids

To determine the impairment of the transient pupillary light reflex (TPLR) due to severe retinal dysfunction and degeneration in a murine model of Leber congenital amaurosis (LCA) and in patients with the disease.. Direct TPLR was elicited in anesthetized, dark-adapted Rpe65(-/-) and control mice with full-field light stimuli (0.1 second duration) of increasing intensities (-6.6 to +2.3 log scot-cd. m(-2)). 9-cis-Retinal was administered orally to a subset of Rpe65(-/-) mice, and TPLR was recorded 48 hours after the treatment. TPLR was also measured in a group of patients with LCA.. Baseline pupillary diameters in Rpe65(-/-) and control mice were similar. TPLR thresholds of Rpe65(-/-) mice were elevated by 5 log units compared with those of control animals. The waveform of the TPLR in Rpe65(-/-) mice was similar to that evoked by 4.8-log-unit dimmer stimuli in control mice. Treatment of Rpe65(-/-) mice with 9-cis-retinal lowered the TPLR threshold by 2.1 log units. Patients with LCA had baseline pupillary diameters similar to normal, but the TPLR was abnormal, with thresholds elevated by 3 to more than 6 log units. When adjusted to the elevation of TPLR threshold, pupillary constriction kinetics in most patients were similar to those in normal subjects.. Pupillometry was used to quantify visual impairment and to probe transmission of retinal signals to higher nervous centers in a murine model of LCA and in patients with LCA. Mouse results were consistent with a dominant role of image-forming photoreceptors driving the early phase of the TPLR when elicited by short-duration stimuli. The objective and noninvasive nature of the TPLR measurement, and the observed post-treatment change toward normal in the animal model supports the notion that this may be a useful outcome measure in future therapeutic trials of LCA.

Topics: Adolescent; Adult; Animals; Blindness; Carrier Proteins; Child; Child, Preschool; cis-trans-Isomerases; Dark Adaptation; Diterpenes; Electrophysiology; Eye Proteins; Female; Humans; Infant; Light; Male; Mice; Mice, Knockout; Middle Aged; Proteins; Pupil Disorders; Reflex, Pupillary; Retinal Degeneration; Retinaldehyde

The visual process is initiated by the photoisomerization of 11-cis-retinal to all-trans-retinal. For sustained vision the 11-cis-chromophore must be regenerated from all-trans-retinal. This requires RPE65, a dominant retinal pigment epithelium protein. Disruption of the RPE65 gene results in massive accumulation of all-trans-retinyl esters in the retinal pigment epithelium, lack of 11-cis-retinal and therefore rhodopsin, and ultimately blindness. We reported previously (Van Hooser, J. P., Aleman, T. S., He, Y. G., Cideciyan, A. V., Kuksa, V., Pittler, S. J., Stone, E. M., Jacobson, S. G., and Palczewski, K. (2000) Proc. Natl. Acad. Sci. U. S. A. 97, 8623-8628) that in Rpe65-/- mice, oral administration of 9-cis-retinal generated isorhodopsin, a rod photopigment, and restored light sensitivity to the electroretinogram. Here, we provide evidence that early intervention by 9-cis-retinal administration significantly attenuated retinal ester accumulation and supported rod retinal function for more than 6 months post-treatment. In single cell recordings rod light sensitivity was shown to be a function of the amount of regenerated isorhodopsin; high doses restored rod responses with normal sensitivity and kinetics. Highly attenuated residual rod function was observed in untreated Rpe65-/- mice. This rod function is likely a consequence of low efficiency production of 11-cis-retinal by photo-conversion of all-trans-retinal in the retina as demonstrated by retinoid analysis. These studies show that pharmacological intervention produces long lasting preservation of visual function in dark-reared Rpe65-/- mice and may be a useful therapeutic strategy in recovering vision in humans diagnosed with Leber congenital amaurosis caused by mutations in the RPE65 gene, an inherited group of early onset blinding and retinal degenerations.

Topics: Animals; Blindness; Carrier Proteins; cis-trans-Isomerases; Disease Models, Animal; Diterpenes; Electroretinography; Eye Proteins; Mice; Microscopy, Electron; Optic Atrophy, Hereditary, Leber; Pigment Epithelium of Eye; Proteins; Retinaldehyde

Mutations in the retinal pigment epithelium gene encoding RPE65 are a cause of the incurable early-onset recessive human retinal degenerations known as Leber congenital amaurosis. Rpe65-deficient mice, a model of Leber congenital amaurosis, have no rod photopigment and severely impaired rod physiology. We analyzed retinoid flow in this model and then intervened by using oral 9-cis-retinal, attempting to bypass the biochemical block caused by the genetic abnormality. Within 48 h, there was formation of rod photopigment and dramatic improvement in rod physiology, thus demonstrating that mechanism-based pharmacological intervention has the potential to restore vision in otherwise incurable genetic retinal degenerations.

Topics: Administration, Oral; Animals; Blindness; Carrier Proteins; Child; cis-trans-Isomerases; Disease Models, Animal; Diterpenes; Eye Proteins; Female; Humans; Male; Mice; Mice, Knockout; Pigment Epithelium of Eye; Proteins; Retinal Degeneration; Retinal Rod Photoreceptor Cells; Retinaldehyde; Retinoids; Time Factors