Abstract
Purpose :
Müller glia play a major role in providing metabolic support to the neural retina and as such, they are known to produce anti-oxidant molecules to protect retinal neurons. During retinal degeneration, pro-inflammatory cytokines such as transforming growth factor-β1 (TGF-β1) and heparin-binding epidermal growth factor (HB-EGF) are produced, which may modulate the production of neuroprotective molecules by Müller cells. The aim of this study was therefore to investigate whether these two cytokines may modify the production of antioxidant molecules by Müller cells.
Methods :
Müller glial cells (MIO-M1 cell line) were cultured in the presence of TGF-β1 (50ng/mL) or HB-EGF (50ng/ml) for 3 days and 6 days respectively. Cells and culture supernatants were collected and examined for the presence of the antioxidants heme oxygenase-1 (HO1) and NAD(P)H:quinone acceptor oxidoreductase 1 (NQO1) using RT-PCR and ELISA methods. Cells cultured in medium alone were used as controls. Concentrations of each of these molecules were determined by extrapolation to standard curves.
Results :
The results showed that MIO-M1 cells express mRNA coding for HO1 and NQO1 and that there was a significant upregulation in the production and release of HO1 upon treatment with TGF-β1. However, this effect was not observed when cells were cultured with HB-EGF. In contrast, a significant downregulation of NQO1 enzyme activity was identified when cells were cultured in the presence of TGF-β1 when compared with the controls. No changes in NQ01 activity were observed in cells cultured in the presence of HB-EGF.
Conclusions :
The present findings suggest that the antioxidant molecules HO1 and NQO1 might work in concert to inhibit intracellular reactive oxidative species (ROS) induced by oxidative stress during retinal degeneration. Although both TGF-β1 and HB-EGF have been linked to retinal gliosis, HB-EGF has also been associated with the regenerative response of Müller cells, which may prevent antioxidant dysregulation in these cells. The observation that HO1 is upregulated by TGF-β1 whilst the NQ01 activity is decreased by this cytokine, suggests that Müller glia might possess compensatory mechanisms to regulate antioxidant production in response to inflammatory stimulus, and this merits further investigations.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.