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Ting Zhang, Ling Zhu, Weiyong Shen, Mark C Gillies; The effect of Serine/Glycine metabolism on Müller cells mitochondrial function, redox homeostasis and cells’ survival under oxidative stress. Invest. Ophthalmol. Vis. Sci. 2017;58(8):803.
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© ARVO (1962-2015); The Authors (2016-present)
There has been a recent surge of interest in the role of serine/glycine metabolism in cancer, but its role in the pathogenesis of retinal diseases remains unclear. Serine/glycine metabolism plays an important role in cellular anti-oxidative capacity through regulating Glutathione (GSH) synthesis, a key factor that maintains cell redox homeostasis. We aim to explore the effects of serine/glycine pathway on the function of Müller cell mitochondria and the redox environment that maintains cell survival during oxidative stress.
We induced oxidative stress in MIO-M1 and hPMCs (human primary Müller cells) by exposing them to low concentrations of hydrogen peroxide (H2O2). We used CBR-5884, a specific inhibitor of phosphoglycerate dehydrogenase (PHGDH), a rate limiting enzyme in serine/glycine metabolism, to inhibit serine/glycine metabolism. Alamarblue assay and LDH assay were performed to evaluate cells survival. Seahorse experiments were conducted to determine the mitochondrial function of MIO-M1 and hPMCs treated with CBR-5884 and/or supplementation with exogenous serine and glycine. Reactive oxygen species (ROS), GSH levels and apoptosis (Annexin V/Propidium Iodide assay) were detected by flow cytometry on MIO and hPMCs. Hoechst, PI and Calcium AM immune-fluorescence staining were used to identify viable, apoptotic and dead cells.
There was a significant reduction of MIO and hPMCs cell viability as well as an increased cytotoxicity after the serine/glycine synthesis pathway was inhibited under conditions of oxidative stress. Cell viability was improved by exogenous application of serine/glycine. MIO and hPMCs exhibited decreased mitochondrial ATP production in response to serine/glycine pathway inhibition. GSH levels were reduced, and ROS levels were significantly increased after inhibiting serine/glycine metabolism under oxidative stress compared with untreated and controls that were rescued with exogenous application of serine/glycine. Meanwhile, rates of apoptosis and cell death significantly increased in the MIO and hPMCs when they were exposed to H2O2 and the Serine/Glycine pathway was inhibited.
Serine/glycine metabolism appears to be important for Müller cells survival under oxidative stress, probably through maintaining mitochondrial function and generating GSH to counteract ROS.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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