Adenosine 5′-triphosphate stimulates the increase of TGF-β1 in rat mesangial cells under high-glucose conditions via reactive oxygen species and ERK1/2

Aim: To investigate the role of adenosine 5'-triphosphate (ATP)-induced generation of reactive oxygen species (ROS) and phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) in the production of transforming growth factor-beta 1 (TGF-beta 1) in cultured rat glomerular mesangial cells under high-glucose conditions. Methods: Subconfluent glomerular mesangial cells were serum-starved for 24 h and pretreated with suramin, diphenylenechloride iodonium (DPI) or PD98059 followed by stimulation with a high concentration of glucose (30 mmol/L D-glucose) or ATP (300 mu mol/L). Extracellular and total ATP and ROS production were detected using commercially available kits. Phosphorylation of ERK1/2 was evaluated by Western blot. TGF-beta 1 mRNA expression was examined by real-time PCR. Results: Suramin had a dose-dependent inhibitory effect on the generation of ROS induced by high glucose. Extracellular ATP production by mesangial cells increased markedly after a 2-h incubation with high glucose. ROS production was upregulated in mesangial cells after 5 min incubation with 300 mu mol/L ATP and was sustained for 120 min. ERK1/2 was significantly activated after 5 min incubation of mesangial cells with ATP, this activation was partially inhibited by DPI. The effects of high glucose on TGF-beta 1 mRNA were markedly inhibited by suramin, DPI or PD98059. Conclusion: Our results suggest that a high concentration of glucose increases the extracellular levels of ATP in mesangial cells within a short time-frame. ATP, in turn, activates ERK1/2, an effect which is at least partially dependent on ROS, which results in the upregulation of TGF-beta 1.