Figure 5: HG induces and IGF-1 blocks TXNIP expression in retinal endothelial cells in culture. (A) A rat retinal endothelial cell line (TR-iBRB2) was maintained under low glucose (LG, 5.5 mM) or high glucose (HG, 25 mM) for 24 in low serum (0.2%) in DMEM media [45,59]. Then, the HG medium was changed to LG and further maintained for different time periods (30 min to 24 h). TXNIP mRNA was measured by quantitative real time PCR. HG significantly increases TXNIP mRNA expression when compared to LG. However, when the HG medium was changed to LG, TXNIP mRNA is reduced to the level of LG (without HG exposure) within 30 min and continues to repress up to 24 h. (B). Alternatively, we added IGF-1 (100 ng/ml) in HG medium and determined TXNIP mRNA expression at different times (30 min to 24 h). We found that IGF-1 decreases HG-induced TXNIP expression up to 4 h, then increases at 24 h. In fact, TXNIP mRNA rises at 6 h onwards after IGF-1 addition (not shown). These results suggest that TXNIP mRNA is relatively unstable and decay soon after withdrawal of its inducer, HG. Similarly, IGF-1 inhibition of HG-induced TXNIP mRNA expression also sustains, apparently, when IGF-1/ IGF-1R signal persists (~up to 4-6h) [180]. The molecular mechanisms and signaling pathways involved in insulin/IGF-1 suppression of TXNIP under HG are yet to be determined. (C) HG also increases TXNIP in human retinal endothelial cells (HREC) and mouse microglia (BV2). The role of TXNIP in microglia oxidative stress and inflammation is yet to be determined.