Abstract
Purpose:
The molecular mechanism of the proper balance between angiogenic activators and inhibitors remains elusive. Previously, our proteomic approach demonstrated that early signaling molecules, including prohibitin, PP2A, vimentin, HIF1 and JAK2, might be involved in AMD. We hypothesize that conjugated double bond containing natural products may regulate the protective mechanisms in retinal and RPE cells through anti-angiogenesis and anti-apoptosis. The current study was designed to investigate how anti-angiogenic molecules, that include anthocyanin and melatonin, modulates angiogenesis and how the proper balance of pro- and anti-angiogenic signaling can be obtained in the vascular microenvironment.
Methods:
Selected natural products containing conjugated double bond were tested in vitro (ARPE-19), in vivo (C3HeB/FeJ mice), or in ovo (chick embryo). Extraction of Hibiscus sabdariffa calyx was performed by soaking 100 g of the powder in 1 L of distilled water for overnight, followed by filtration. Freshly prepared Hibiscus extracts were injected in fertilized eggs of Gallus domesticus at 2, 5, 7, and 10 days and were incubated at 37.5 °C for additional 5, 7, 10, and 19 days. The altered Angiogenesis upon treatment was analyzed by angiogenic index (enumeration of branch points) or blood vessel counts/field. For in vivo experiments, proteomic changes in three groups of mice (12 light/12 dark, constant light, constant light/melatonin) were analyzed by 2D SDS-PAGE, mass spectrometry, and Western blotting.
Results:
The Hibiscus sabdariffa plant possesses a high content of anthocyanins (>100 mg cyaniding rutinoside/100 g plants). The treatment of anthocyanin-rich extracts from Hibiscus sabdariffa at (10 microg/35 g) in ovo resulted in 80-90% of inhibition of blood vessel formation in dose- and time-dependent manner. Supplementation of melatonin to mice under constant light-exposed retina reverses light-induced cytoskeletal reorganization.
Conclusions:
Disruption of angiogenesis was observed by melatonin or anthocyanin-rich extracts from Hibiscus sabdariffa. Our proteomic data suggests that anthocyanin could be involved in VEGFR/Angiotensis II pathway, whereas anti-angiogenic melatonin may control the intermediate filament formation through vimentin/PP2A network.