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

2015 ◽  
Vol 35 (6) ◽  
pp. 2309-2319 ◽  
Author(s):  
Won Seok Yang ◽  
Joon-Seok Kim ◽  
Nam Jeong Han ◽  
Mee Jeong Lee ◽  
Su-Kil Park
Keyword(s):  
Signal Transduction ◽  
Epithelial Cells ◽  
Tyrosine Kinase ◽  
High Glucose ◽  
Toll Like Receptor ◽  
Tubular Epithelial Cells ◽  
Spleen Tyrosine Kinase ◽  
Toll Like Receptor 4 ◽  
Proximal Tubular Epithelial Cells ◽  
Proximal Tubular

Background/Aims: High glucose activates spleen tyrosine kinase (Syk) in human proximal tubular epithelial cells (HK-2 cells), which leads to NF-κB activation and transforming growth factor-ß1 (TGF-ß1) 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-κB p65 nuclear translocation, and TGF-ß1 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.

High glucose‐induced oxidative stress causes apoptosis in proximal tubular epithelial cells and is mediated by multiple caspases

2003 ◽  
Vol 17 (8) ◽  
pp. 1-21 ◽  
Author(s):  
David A. Allen ◽  
Steven M. Harwood ◽  
Mira Varagunam ◽  
Martin J. Raftery ◽  
Muhammad M. Yaqoob
Keyword(s):  
Oxidative Stress ◽  
Epithelial Cells ◽  
High Glucose ◽  
Tubular Epithelial Cells ◽  
Proximal Tubular Epithelial Cells ◽  
Proximal Tubular

High ambient glucose is effect neutral on cell death and proliferation in human proximal tubular epithelial cells

2005 ◽  
Vol 289 (2) ◽  
pp. F401-F409 ◽  
Author(s):  
Christudas Morais ◽  
Justin Westhuyzen ◽  
Betty Pat ◽  
Glenda Gobe ◽  
Helen Healy
Keyword(s):  
Epithelial Cells ◽  
High Glucose ◽  
Culture Media ◽  
Primary Cultures ◽  
Cellular Growth ◽  
Glucose Medium ◽  
Tubular Epithelial Cells ◽  
Proximal Tubular Epithelial Cells ◽  
Proximal Tubular ◽  
Low Glucose

In vitro models of diabetic nephropathy that assess the role of hyperglycemia on proximal tubular cell turnover commonly compare cells in a high-glucose medium (25 or 30 mM) with a low-glucose medium (5 to 6.1 mM). Any cellular growth changes observed are usually attributed to the effect of high glucose. We hypothesize that in such experiments, glucose concentrations in the low-glucose medium may decline during the course of the experiments to levels that inhibit cell growth leading to the comparative conclusion that high glucose induces hyperplasia and/or hypertrophy. In this study, primary cultures of human proximal tubular epithelial cells (PTEC) and immortalized HK-2 cells were exposed to low (5 mM) or high (17, 30, or 47 mM) glucose for up to 6 days (PTEC) and 48 h (HK-2). When culture media were not replenished, low glucose induced a significant increase in necrosis and release of lactate dehydrogenase and a decrease in proliferation, metabolic activity, and protein content without any changes in apoptosis. High-glucose media failed to induce any of these changes. Glucose was undetectable in the low-glucose culture medium after 72 h. No significant differences were observed between any of the treatment groups when culture media were replenished daily. We conclude that regular replenishment of culture media is necessary to prevent the emergence of artifactual and misleading differences between high- and low-glucose groups. The current knowledge of the pathophysiology of high glucose based on cell culture systems may need to be reevaluated.

scholarly journals PDGF receptor-β uses Akt/mTORC1 signaling node to promote high glucose-induced renal proximal tubular cell collagen I (α2) expression

2017 ◽  
Vol 313 (2) ◽  
pp. F291-F307 ◽  
Author(s):  
Falguni Das ◽  
Nandini Ghosh-Choudhury ◽  
Balachandar Venkatesan ◽  
Balakuntalam S. Kasinath ◽  
Goutam Ghosh Choudhury
Keyword(s):  
Epithelial Cells ◽  
High Glucose ◽  
Specific Inhibitor ◽  
Collagen I ◽  
Pdgf Receptor ◽  
Tubular Epithelial Cells ◽  
Mtorc1 Signaling ◽  
Proximal Tubular Epithelial Cells ◽  
Proximal Tubular ◽  
Mtorc1 Activation

Increased expression of PDGF receptor-β (PDGFRβ) has been shown in renal proximal tubules in mice with diabetes. The core molecular network used by high glucose to induce proximal tubular epithelial cell collagen I (α2) expression is poorly understood. We hypothesized that activation of PDGFRβ by high glucose increases collagen I (α2) production via the Akt/mTORC1 signaling pathway in proximal tubular epithelial cells. Using biochemical and molecular biological techniques, we investigated this hypothesis. We show that high glucose increases activating phosphorylation of the PDGFRβ, resulting in phosphorylation of phosphatidylinositol 3-kinase. A specific inhibitor, JNJ-10198409, and small interfering RNAs targeting PDGFRβ blocked this phosphorylation without having any effect on MEK/Erk1/2 activation. We also found that PDGFRβ regulates high glucose-induced Akt activation, its targets tuberin and PRAS40 phosphorylation, and finally, mTORC1 activation. Furthermore, inhibition of PDGFRβ suppressed high glucose-induced expression of collagen I (α2) in proximal tubular cells. Importantly, expression of constitutively active Akt or mTORC1 reversed these processes. As a mechanism, we found that JNJ and PDGFRβ knockdown inhibited high glucose-stimulated Hif1α expression. Furthermore, overexpression of Hif1α restored expression of collagen I (α2) that was inhibited by PDGFRβ knockdown in high glucose-stimulated cells. Finally, we show increased phosphorylation of PDGFRβ and its association with Akt/mTORC1 activation, Hif1α expression, and elevated collagen I (α2) levels in the renal cortex of mice with diabetes. Our results identify PDGFRβ as a driver in activating Akt/mTORC1 nexus for high glucose-mediated expression of collagen I (α2) in proximal tubular epithelial cells, which contributes to tubulointerstitial fibrosis in diabetic nephropathy.

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