The retinoid (visual) cycle consists of a series of biochemical reactions needed to regenerate the visual chromophore 11- cis -retinal and sustain vision. Genetic or environmental factors affecting chromophore production can lead to blindness. Using animal models that mimic human retinal diseases, we previously demonstrated that mechanism-based pharmacological interventions can maintain vision in otherwise incurable genetic diseases of the retina. Here, we report that after 9- cis -retinal administration to lecithin:retinol acyltransferase - deficient ( Lrat−/− ) mice, the drug was rapidly absorbed and then cleared within 1 to 2 hours. However, when conjugated to form chitosan-9- cis -retinal, this prodrug was slowly absorbed from the gastrointestinal tract, resulting in sustainable plasma levels of 9- cis -retinol and recovery of visual function without causing elevated levels, as occurs with unconjugated drug treatment. Administration of chitosan-9- cis -retinal conjugate intravitreally in retinal pigment epithelium-specific 65 retinoid isomerase (RPE65)-deficient dogs improved photoreceptor function as assessed by electroretinography. Functional rescue was dose dependent and maintained for several weeks. Dosing via the gastrointestinal tract in canines was found ineffective, most likely due to peculiarities of vitamin A blood transport in canines. Use of the chitosan conjugate in combination with 11- cis- 6-ring-retinal, a locked ring analog of 11- cis -retinal that selectively blocks rod opsin consumption of chromophore while largely sparing cone opsins, was found to prolong cone vision in Lrat−/− mice. Development of such combination low-dose regimens to selectively prolong useful cone vision could not only expand retinal disease treatments to include Leber congenital amaurosis but also the age-related decline in human dark adaptation from progressive retinoid cycle deficiency.
视黄醇(视觉)循环由一系列生化反应组成,这些反应是再生视觉发色团 11-顺式
视黄醇和维持视力所必需的。影响发色团生成的遗传或环境因素可导致失明。我们曾利用模拟人类视网膜疾病的动物模型证明,基于机制的药物干预可以维持视网膜遗传疾病的视力,否则这些疾病将无法治愈。在这里,我们报告了卵
磷脂:
视黄醇酰基转移酶缺乏症(Lrat-/-)小鼠服用
9-顺式视黄醛后,药物被迅速吸收,然后在 1 到 2 小时内被清除。然而,当共轭形成
壳聚糖-
9-顺式视黄醇时,这种原药会缓慢地被胃肠道吸收,从而使血浆中的
9-顺式视黄醇水平保持稳定,视觉功能得到恢复,而不会像未共轭药物治疗那样导致
视黄醇水平升高。在视网膜色素上皮细胞特异性 65
视黄醇异构酶(RPE65)缺乏的狗体内静脉注射
壳聚糖-
9-顺式视黄醇共轭物,可改善视网膜电图评估的感光器功能。功能恢复与剂量有关,并可维持数周。通过犬的胃肠道给药效果不佳,这很可能是由于犬体内
维生素 A 血液运输的特殊性。
壳聚糖共轭物与 11-顺式-6-环
视黄醛(11-顺式-
视黄醛的锁环类似物,可选择性地阻断杆状视蛋白对发色团的消耗,同时在很大程度上保护锥状视蛋白)联合使用,可延长 Lrat-/- 小鼠的锥状视力。开发这种选择性延长有用视锥视力的低剂量组合疗法,不仅可以扩大视网膜疾病的治疗范围,将先天性盲症包括在内,而且还可以解决人类因进行性
视黄醇循环缺乏而导致的与年龄相关的暗适应能力下降问题。