TNFα released from LPS-activated microglia can both up- and down-regulate the inducible antioxidant system in astrocytes

CORREA F., SANDBERG M

París - Francia

Congreso; IXth European Meeting on Glial Cell Functions in Health and Disease; 2009

Gluthatione (GSH) is a ubiquitous intracellular peptide with diverse functions that include detoxification, antioxidant defense, maintenance of thiol status and modulation of cell proliferation. Disturbance in the cellular redox balance, due to enhanced ROS production and/or impaired antioxidant defense, eventually leads to oxidative alterations of biological macromolecules, such as proteins, lipids and nucleic acids. These events produce cellular malfunction and eventually cell death. For brain, oxidative stress has been connected with the loss of neurons during the progression of neurological diseases like Parkinson
s disease (PD), Alzheimer
s disease (AD), Huntington
s disease (HS), stroke and other neuroinflammatory diseases. Astrocytes are known to be an important source of neuronal GSH. Astrocytes highly express antioxidant responsive elements (ARE)- driven genes in response to oxidative stress. Our main goal is to understand the effects of microglial activation on astrocytes expression of GSH, g-glutamyl-cystein ligase (GCL) and other enzymes activated by Nrf2. We exposed astrocytes to microglial-conditioned medium (MCM) and analysed the content of GSH and the activity of GCL, the rate-limiting enzyme in GSH synthesis. Briefly, microglial cultures were stimulated with different doses of LPS for 24h. Next, astrocyte cultures were exposed to MCM for 24 or 72 h. A down regulation of GSH was observed when astroglia were cultured in MCM using 10 ng/ml of LPS whereas higher concentrations 100-1000ng/ml elevated the GSH levels in astroglia at 24 h post-exposure. After 72 h no stimulatory effect but a decrease on GSH levels in MCH cultured astroglia was observed even for the higher concentrations of LPS. When a blocking antibody against TNF-a was used, the effects of MCM on GSH levels were prevented, suggesting an involvement of this cytokine both in the up- and down-regulation of the antioxidant system in astrocytes.