Toll-Like Receptor 4/Spleen Tyrosine Kinase Complex in High Glucose Signal Transduction of Proximal Tubular Epithelial Cells

作者：Yang Won Seok; Kim Joon Seok; Han Nam Jeong; Lee Mee Jeong; Park Su Kil^*

来源：Cellular Physiology and Biochemistry, 2015, 35(6): 2309-2319.

DOI：10.1159/000374034

• High glucose
• High-mobility group box-1
• MyD88
• Spleen tyrosine kinase
• Toll-like receptor 4
• Transforming growth factor-beta 1

Background/Aims: High glucose activates spleen tyrosine kinase (Syk) in human proximal tubular epithelial cells (HK-2 cells), which leads to NF-kappa B activation and transforming growth factor-beta 1 (TGF-beta 1) production. We explored the signal transduction pathway from high glucose to Syk activation. Methods: The pathway was evaluated by siRNA transfection, immunoprecipitation and Western blot. Results: High glucose stimulated Syk activation within 10 min. Depletion of toll-like receptor 4 (TLR4) attenuated high glucose-induced Syk activation, NF-kappa B p65 nuclear translocation, and TGF-beta 1 production. In addition, TLR4 inhibitor (CLI-095), TLR4-neutralizing antibody, and depletion of myeloid differentiation factor 88 (MyD88) all attenuated high glucose-induced Syk activation. As an evidence of TLR4 activation, interleukin-1 receptor-associated kinase 1 was recruited to MyD88 and TLR4 upon exposure to high glucose. Syk was co-immunoprecipitated with TLR4, and Syk bound to TLR4 was activated by high glucose. High-mobility group box-1 (HMGB-1), an endogenous activator of TLR4, rapidly increased in TLR4 immunoprecipitates upon high glucose stimulation, and this association was reduced by N-acetylcysteine, an antioxidant. An HMGB-1 inhibitor glycyrrhizin suppressed high glucose-induced Syk activation. Conclusion: Syk is constitutively associated with TLR4. High glucose induces an immediate, reactive oxygen species-dependent, extracellular release of HMGB-1 which binds to TLR4 and activates it, leading to Syk activation.

• 出版日期2015