Diabetes milieu is a complex metabolic disease that has been known to associate with high risk of various neurological disorders. Hyperglycemia in diabetes could dramatically increase neuronal glucose levels which leads to neuronal damage, a phenomenon referred to as glucose neurotoxicity. On the other hand, the impact of hyperglycemia on astrocytes has been less explored. Astrocytes play important roles in brain energy metabolism through neuron-astrocyte coupling. As the component of blood brain barrier, glucose might be primarily transported into astrocytes, hence, impose direct impact on astrocyte metabolism and function. In the present study, we determined the effect of high glucose on the energy metabolism and function of primary astrocytes. Hyperglycemia level glucose (25 mM) induced cell cycle arrest and inhibited proliferation and migration of primary astrocytes. Consistently, high glucose decreased cyclin D1 and D3 expression. High glucose enhanced glycolytic metabolism, increased ATP and glycogen content in primary astrocytes. In addition, high glucose activated AMP-activated protein kinase (AMPK) signaling pathway in astrocytes. In summary, our in vitro study indicated that hyperglycemia might impact astrocyte energy metabolism and function phenotype. Our study provides a potential mechanism which may underlie the diabetic cerebral neuropathy and warrant further in vivo study to determine the effect of hyperglycemia on astrocyte metabolism and function.

Endothelin-1 (ET-1) is a vasoactive peptide that is elevated in aqueous humor as well as circulation of primary open angle glaucoma (POAG) patients. ET-1 has been shown to promote degeneration of optic nerve axons and apoptosis of retinal ganglion cells (RGCs), however, the precise mechanisms are still largely unknown. In this study, RNA-seq analysis was used to assess changes in ET-1 mediated gene expression in primary RGCs, which revealed that 23 out of 156 differentially expressed genes (DEGs) had known or predicted mitochondrial function, of which oxidative phosphorylation emerged as the topmost enriched pathway. ET-1 treatment significantly decreased protein expression of key mitochondrial genes including cytochrome C oxidase copper chaperone (COX17) and ATP Synthase, H + transporting, Mitochondrial Fo Complex (ATP5H) in primary RGCs and in vivo following intravitreal ET-1 injection in rats. A Seahorse ATP rate assay revealed a significant decrease in the rate of mitochondrial ATP production following ET-1 treatment. IOP elevation in Brown Norway rats showed a trend towards decreased expression of ATP5H. Our results demonstrate that ET-1 produced a decrease in expression of vital components of mitochondrial electron transport chain, which compromise bioenergetics and suggest a mechanism by which ET-1 promotes neurodegeneration of RGCs in glaucoma. Glaucoma is an optic neuropathy with an approximate prevalence of 60.5 million people worldwide and is projected to reach 111 million by 2040 1,2 .The disease is commonly associated with elevated intraocular pressure (IOP), accompanied by optic nerve degeneration and loss of retinal ganglion cells (RGCs) 3,4. RGC death via apoptosis is a culminating event in the pathophysiology of glaucoma, stemming from optic nerve axonal injury, leading to visual field loss. Elevated IOP is a major risk factor in primary open-angle-glaucoma and current therapeutic approaches are aimed at lowering IOP with medications, laser treatment, or surgery 5,6. However in some patients, the progression of the disease continues to occur slowly 7 despite lowering IOP, hence there is a compelling need for neuroprotection of RGCs and optic nerve axons and as an additional therapeutic modality. The molecular changes occurring specifically in the RGCs, during the progression of glaucoma, contributing to neurodegeneration, are still poorly understood; hence identifying new therapeutic targets could provide more efficacious neuroprotective treatments. ET-1 is a 21 amino acid vasoactive peptide that acts through two G-protein coupled receptors namely, ET A and ET B receptors, to produce diverse effects in various ocular tissues 8-11. A growing body of evidence suggests that endothelins and their receptors are major contributors to neuronal damage in glaucoma 11-16. The role of endothelins in glaucomatous neurodegeneration has been the subject of several review articles 12,17,18. However, the detailed cellular and molecular mechanisms that contribute to ET-1 mediated-neurodegeneration are not

Background-Primary astrocyte cultures have been used for decades to study astrocyte functions in health and disease. The current primary astrocyte cultures are mostly maintained in serum-containing medium which produces astrocytes with a reactive phenotype as compared to in vivo quiescent astrocytes. The aim of this study was to establish a serum-free astrocyte culture medium that maintains primary astrocytes in a quiescent state.New Method-Serum free astrocyte base medium (ABM) supplemented with basic fibroblast growth factor 2 (FGF2) and epidermal growth factor (EGF) (ABM-FGF2-EGF) or serum supplemented DMEM (MD-10%FBS) was used to culture primary astrocytes isolated from cerebral cortex of postnatal day 1 C57BL/6 mice.Results-Compared to astrocytes cultured in MD-10%FBS medium, astrocytes in ABM-FGF2-EGF had higher process bearing morphologies similar to in vivo astrocytes. Western blot, immunostaining, quantitative polymerase chain reaction and metabolic assays revealed that astrocytes maintained in ABM-FGF2-EGF had enhanced glycolytic metabolism, higher glycogen content, lower GFAP expression, increased glutamine synthase, and glutamate transporter-1 mRNA levels as compared to astrocytes cultured in MD-10% FBS medium.Comparison to existing methods-These observations suggest that astrocytes cultured in ABM-FGF2-EGF media compared to the usual FBS media promote quiescent and biosynthetic phenotype similar to in vivo astrocytes. Conclusion-This media provides a novel method for studying astrocytes functions in vitro under physiological and pathological conditions.

Introduction Cholesterol sulfate (CS) is one of the most important known sterol sulfates in human plasma and present as a normal constituent in a variety of human tissues. In both the brain and periphery, CS serves as a substrate for the synthesis of sulfonated adrenal steroids such as pregnenolone sulfate and Dehydroepiandrosterone (DHEA) sulfate and as a constituent of many biological membranes including red blood cells where it functions as a stabilizing agent. It also acts as endogenous regulator of cholesterol synthesis. It is known that CS serves as a substrate for synthesizing other sterol sulfates in the brain. However, the role of CS in neurological insult and brain metabolism is unknown. Our goal in this study is to investigate the neuroprotective action of CS as well as its effect on brain energy metabolism. Materials and Methods Primary astrocytes were prepared from the cortex of postnatal day 0–2 C57BL/6 pups and seeded in Dulbecco's modified eagle medium (DMEM) with 10% FBS under normal glucose (5.5 mM). HT‐22 cells were maintained in high glucose (25 mM) DMEM supplemented with charcoal stripped FBS. The neuroprotective effect of CS and its role on cell metabolism were determined in primary astrocyte and HT‐22 cells using Calcien AM cell viability assay, flow cytometry, seahorse extracellular flux analysis, and metabolism assay kits. Results CS protects HT22 cells against glutamate toxicity and impact astrocyte metabolism by increasing ATP, and glycogen contents. Conclusion Our study demonstrated that CS have neuroprotective effect and modulate brain energy metabolism. Further studies are needed to determine the mechanisms underlying the neuroprotective action of CS and its action on brain energy metabolism. Support or Funding Information This work was partly supported by National Institutes of Health grants 1R21NS087209‐01A1 (SY) and R01NS088596 (SY). This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.