Reactive Oxygen Species-Mediated Damage of Retinal Neurons: Drug Development Targets for Therapies of Chronic Neurodegeneration of the Retina

Monotropein attenuates oxidative stress via Akt/mTOR-mediated autophagy in osteoblast cells

Oxidative stress is a crucial pathogenic factor in osteoporosis. Autophagy is a cellular self-digestion process that can selectively remove damaged organelles under oxidative stress, and thus presents a potential therapeutic target against osteoporosis. Monotropein is an iridoid glycoside which can increase osteoblastic bone formation and be applied for medicinal purpose in China. The aim of this work is to investigate whether autophagy participates the protection effects of monotropein in osteoblasts under oxidative stress and the possible mechanism of such involvement. Here, monotropein was capable of inhibiting the H₂O₂-induced reactive oxygen species generation in osteoblasts. Monotropein induced autophagy and protected osteoblasts from cytotoxic effects of H₂O₂, as assessed by viability assays, apoptosis and western blotting. Moreover, it significantly attenuated H₂O₂-evoked oxidative stress as measured by malondialdehyde, catalase, and superoxide dismutase levels. Importantly, monotropein reduced the phosphorylation of protein kinase B (Akt), mammalian target of rapamycin (mTOR) and its two downstream proteins (p70S6K and 4EBP1). The autophagy level increased in osteoblasts treated with monotropein as represented by an increased in both Beclin1 expression and the LC3-II/LC3-I ratio. However, the Akt activator (SC79) and mTOR activator (MHY1485) suppressed the autophagy level induced by monotropein in H₂O₂-treated cells. Consequently, the antioxidant effects of monotropein were mediated, at least in part, by enhancing autophagy through the Akt/mTOR pathway. These results suggested that monotropein might be a promising candidate for osteoporosis treatment.

Analysis of vertebrate vision in a 384-well imaging system

Visual impairment affects 253 million people worldwide and new approaches for prevention and treatment are urgently needed. While small molecules with potential beneficial effects can be examined in various model systems, the in vivo evaluation of visual function remains a challenge. The current study introduces a novel imaging system for measuring visually-guided behaviors in larval zebrafish. The imaging system is the first to image four 96-well plates with a single camera for automated measurements of activity in a 384-well format. In addition, it is the first system to project moving visual stimuli and analyze the optomotor response in the wells of a 96-well plate. We found that activity is affected by tricaine, diazepam and flumazenil. Surprisingly, diazepam treatments induce a loss of visual responses, at concentrations that do not affect activity or induce hyperactivity. Overall, our studies show that the developed imaging system is suitable for automated measurements of vertebrate vision in a high-throughput format.

Saffron: A Multitask Neuroprotective Agent for Retinal Degenerative Diseases

Both age related macular degeneration (AMD) and light induced retinal damage share the common major role played by oxidative stress in the induction/progression of degenerative events. Light damaged (LD) rats have been widely used as a convenient model to gain insight into the mechanisms of degenerative disease, to enucleate relevant steps and to test neuroprotectants. Among them, saffron has been shown to ameliorate degenerative processes and to regulate many genes and protective pathways. Saffron has been also tested in AMD patients. We extended our analysis to a possible additional effect regulated by saffron and compared in AMD patients a pure antioxidant treatment (Lutein/zeaxanthin) with saffron treatment. Methods: Animal model. Sprague-Dawley (SD) adult rats, raised at 5 lux, were exposed to 1000 lux for 24 h and then either immediately sacrificed or placed back at 5 lux for 7 days recovery period. A group of animals was treated with saffron. We performed in the animal model: (1) SDS-PAGE analysis; (2) Western Blotting (3) Enzyme activity assay (4) Immunolabelling; in AMD patients: a longitudinal open-label study 29 (±5) months in two groups of patients: lutein/zeaxanthin (19) and saffron (23) treated. Visual function was tested every 8 months by ERG recordings in addition to clinical examination. Results: Enzymatic activity of MMP-3 is reduced in LD saffron treated retinas and is comparable to control as it is MMP-3 expression. LD treated retinas do not present "rosettes" and microglia activation and migration is highly reduced. Visual function remains stable in saffron treated AMD patients while deteriorates in the lutein/zeaxanthin group. Conclusion: Our results provide evidence of an additional way of action of saffron treatment confirming the complex nature of neuroprotective activities of its chemical components. Accordingly, long term follow-up in AMD patients reveals an added value of saffron supplementation treatment compared to classical antioxidant protocol.