Roles of ROS in TGF-β1 signaling

다국어 초록 (Multilingual Abstract)

To investigate the possible roles of reactive oxygen species(ROS) in transforming growth factor-β1(TGF-β1) signal transduction, quiescent human lung fibroblast(HLF) cells were stimulated with TGF-β1. TGF-β1 stimulation resulted in rapid and transient burst of ROS with maximal increase at 5-10 min after treatment. This ROS increase was inhibited by antioxidants, glutathione(GSH) and N-acetylcysteine(NAC). TGF-β1 induced protein tyrosine phosphorylation at 10 min after treatment, which was abolished by NAC, indicating that ROS mediates TGF-β1-induced tyrosine phosphorylation. Direct addition of H₂O₂ resulted in tyrosine phosphorylation of the same size protein. TGF-β1 treatment stimulated IL-6 gene expression and protein synthesis. Antioxidants including NAC, GSH, and catalase abolished TGF-β1-induced IL-6 gene expression, and direct H₂O₂ treatment induced IL-6 expression in a dose-dependent manner. Furthermore, NAC released the suppressive effects of TGF-β1 on HLF cell proliferation. These results suggest that TGF-β1 induces transient increase of intracellular H₂O₂ production, which turns on protein tyrosine kinase activation regulating downstream events of IL-6 gene expression or cell growth. In addition, there are growing evidences that antioxidant genes are involved in cytokine signaling and immune response. As a result to identify the regulatory proteins of thioredoxin(TRX), a murine homologue for human vitamin D3 up-regulated protein 1(hVDUP1) was identified from a yeast two-hybrid screen. Co-transfection into 293 cells and precipitation assays confirmed that mouse VDUP1(mVDUP1) bound to TRX, but it failed to bind to a Cys-32. and Cys-35 mutant TRX, suggesting the redox-active site is critical for binding. in VDUP1 was ubiquitously expressed in various tissues and located in the cytoplasm. Biochemical analysis showed that in VDUP1 inhibited the insulin reducing activity of TRX. When cells were treated with various stress stimuli such as H₂O₂ and heat shock, in VDUP1 was significantly induced.