Abstract
Age-related macular degeneration (AMD) represents a major reason for blindness in the elderly population. Oxidative stress is a predominant factor in the pathology of AMD. We previously evaluated the effects of phospholipid complex of quercetin (Q-PC) on oxidative injury in ARPE-19 cells, but the underlying mechanisms are not fully understood. Herein, the solid dispersion of quercetin-PC (Q-SD) was prepared with solubility being 235.54 μg/mL in water and 2.3×104 μg/mL in chloroform, which were significantly higher than that of quercetin (QT) and Q-PC. Q-SD also exhibited a considerably higher dissolution rate than QT and Q-PC. Additionally, Q-SD had Cmax of 4.143 μg/mL and AUC of 12.015 μg·h/mL in rats, suggesting better bioavailability than QT and Q-PC. Then, a mouse model of dry AMD (Nrf2 wild-type (WT) and Nrf2 knockout (KO)) was established for evaluating the effects of Q-SD in vivo. Q-SD more potently reduced retinal pigment epithelium sediments and Bruch's membrane thickness than QT and Q-PC at 200 mg/kg in Nrf2 WT mice and did not work in Nrf2 KO mice at the same dosage. Additionally, Q-SD significantly decreased ROS and MDA contents and restored SOD, GSH-PX, and CAT activities of serum and retinal tissues in Nrf2 WT mice, but not in Nrf2 KO mice. Furthermore, Q-SD more potently increased Nrf2 mRNA expression and stimulated its nuclear translocation in retinal tissues of Nrf2 WT mice. Q-SD significantly increased the expression of Nrf2 target genes HO-1, HQO-1, and GCL of retinal tissues in Nrf2 WT mice, not in Nrf2 KO mice. Altogether, Q-SD had improved physicochemical and pharmacokinetic properties compared to QT and Q-PC and exhibited more potent protective effects on retina oxidative injury in vivo. These effects were associated with activation of Nrf2 signaling and upregulation of antioxidant enzymes.
Highlights
Age-related macular degeneration (AMD) is a leading irreversible blindness in elderly people all over the world. This disease can be generally divided into two categories, namely, dry AMD and wet AMD. The former is characterized by choroidal capillary atrophy, drusen, and retinal pigment epithelium (RPE) atrophy, and geographic atrophy of the macular region commonly occurs in its advanced stage, resulting in decreased visual acuity and even wet AMD
The primary antibodies used in Western blot analyses against nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), NQO-1, glutamate cysteine ligase (GCL), Glyceraldehyde phosphate dehydrogenase (GAPDH), and Lamin B, and the secondary antibody Goat Anti-Rabbit IgG/HRP were all obtained from Abcam (Cambridge, UK)
The results showed that the equilibrium solubility of quercetin phospholipid complex (Q-SD) in both water and chloroform was significantly higher than that of QT and Q-PC (Table 1)
Summary
Age-related macular degeneration (AMD) is a leading irreversible blindness in elderly people all over the world. This disease can be generally divided into two categories, namely, dry AMD and wet AMD. The former is characterized by choroidal capillary atrophy, drusen, and retinal pigment epithelium (RPE) atrophy, and geographic atrophy of the macular region commonly occurs in its advanced stage, resulting in decreased visual acuity and even wet AMD. The wet AMD is primarily featured by choroidal neovascularization (CNV), leading to retinal exudation and hemorrhage and eventually serious impairment of vision [1, 2]. The underlying mechanism of dry AMD pathology remains largely unknown, and there are no effective therapeutic options for dry AMD
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