Radhakrishnan Rakesh, Leung Matthias, Yochim Drew, Roehrich Heidi, McPherson Scott W, Lobo Glenn P
Department of Ophthalmology and Visual Neurosciences University of Minnesota Minneapolis Minnesota USA.
FASEB Bioadv. 2025 Sep 2;7(8):e70044. doi: 10.1096/fba.2025-00173. eCollection 2025 Aug.
Mutations in the gene in Stargardt disease (STGD1) cause enhanced accumulation of cytotoxic lipofuscin, manifesting in RPE atrophy and photoreceptor dysfunction. One component of lipofuscin is the all--retinal derivative, pyridinium bisretinoid A2E. Since ocular A2E biosynthesis relies on all--retinal, which is obtained from circulating all--retinol bound to retinol binding protein 4 (RBP4-ROL), we hypothesized that modulating vitamin A receptors, such as RBPR2, which regulate serum RBP4-ROL homeostasis, should in principle attenuate A2E production. In silico analysis revealed multiple retinoic acid response element (RARE) binding sites on the murine gene promoter, which was confirmed in vitro by EMSA and ChIP assays. In vitro luciferase assays showed that promoter activity was induced by exogenous β-carotene (BC) metabolites. Dietary BC supplementation of mice, a mouse model for STGD1, increased hepatic all--retinoic acid and 9--retinoic acid production, which induced mRNA expression. This mechanism decreased serum RBP4 protein levels, fundus lipofuscin autofluorescence, and ocular A2E accumulation, altogether improving photoreceptor and RPE function. Conversely, such a rescue was not observed in either mice fed a diet devoid of BC or in double knockout ; mice. Thus, there was a significant inverse correlation between dietary BC supplementation and gene presence in mice, to that of lipofuscin accumulation in mice on diets devoid of BC or in ; mice. Our results provide impetus to include dietary obtained BC for STGD1 patients with gene mutations and identify a novel role for the vitamin A receptor RBPR2 in this process.
斯塔加特病(STGD1)中该基因的突变会导致细胞毒性脂褐质的积累增加,表现为视网膜色素上皮(RPE)萎缩和光感受器功能障碍。脂褐质的一个成分是全反式视黄醛衍生物吡啶鎓双视黄醛A2E。由于眼部A2E的生物合成依赖于全反式视黄醛,而全反式视黄醛是从与视黄醇结合蛋白4(RBP4-ROL)结合的循环全反式视黄醇中获得的,我们推测调节维生素A受体,如调节血清RBP4-ROL稳态的RBPR2,原则上应该会减弱A2E的产生。计算机分析揭示了小鼠该基因启动子上多个维甲酸反应元件(RARE)结合位点,这在体外通过电泳迁移率变动分析(EMSA)和染色质免疫沉淀(ChIP)试验得到了证实。体外荧光素酶试验表明,该启动子活性受外源β-胡萝卜素(BC)代谢产物诱导。给STGD1小鼠模型补充膳食BC,可增加肝脏全反式视黄酸和9-顺式视黄酸的产生,从而诱导该基因的mRNA表达。这一机制降低了血清RBP4蛋白水平、眼底脂褐质自发荧光以及眼部A2E的积累,总体上改善了光感受器和RPE功能。相反,在喂食不含BC饮食的该基因敲除小鼠或双敲除该基因的小鼠中均未观察到这种挽救作用。因此,在喂食不含BC饮食的该基因敲除小鼠或双敲除该基因的小鼠中,膳食补充BC与该基因的存在之间存在显著的负相关,与脂褐质积累之间也存在显著的负相关。我们的研究结果为给携带该基因突变的STGD1患者补充膳食来源的BC提供了依据,并确定了维生素A受体RBPR2在此过程中的新作用。