Submitted on August 10, 2007
Accepted on March 12, 2008
High glucose-induced NF-
B activation occurs via tyrosine phosphorylation of IB
in human glomerular endothelial cells: Involvement of Syk tyrosine kinase
WON SEOK YANG1, JANG WON SEO2, NAM JEONG HAN1, JUNG CHOI1, KI-UP LEE1, HANJONG AHN3, SANG KOO LEE1, and SU-KIL PARK4*
1 INTERNAL MEDICINE, ASAN MEDICAL CENTER, UNIVERSITY OF ULSAN, SEOUL, Korea, Republic of
2 Internal medicine, Hallym University, Seoul, Korea, Republic of
3 UROLOGY, ASAN MEDICAL CENTER, UNIVERSITY OF ULSAN, Seoul, Korea, Republic of
4 Internal Medicine, ASAN MEDICAL CENTER, UNIVERSITY OF ULSAN, SEOUL, Korea, Republic of; , Korea, Republic of
* To whom correspondence should be addressed. E-mail: skpark{at}amc.seoul.kr.
Activation of nuclear factor-
B (NF-B) occurs by dissociation from IB
after serine or tyrosine phosphorylation of IB, but the way of NF-B activation by high glucose has not been defined. High glucose is known to activate NF-B via protein kinase C and reactive oxygen species (ROS). In this study, we investigated how high glucose activates NF-B for CCL2 production in cultured human glomerular endothelial cells. High glucose increased nuclear translocation of p65 and also increased NF-B DNA binding activity. High glucose-induced NF-B activation occurred without degradation of IB. In agreement with this, there was no increase in serine phosphorylation of IB, while tyrosine phosphorylation of IB was increased by high glucose. High glucose increased the generation of ROS, whereas both -lipoic acid and N-acetylcysteine scavenged the ROS and decreased high glucose-induced tyrosine phosphorylation of IB, nuclear translocation of p65 and NF-B DNA binding activity. Protein kinase C pseudosubstrate inhibited high glucose-induced ROS production, tyrosine phosphorylation of IB and nuclear translocation of p65. Both BAY 61-3606, a specific inhibitor of Syk protein-tyrosine kinase, and siRNA directed against Syk inhibited high glucose-induced tyrosine phosphorylation of IB as well as p65 nuclear translocation. High glucose increased tyrosine phosphorylation of Syk, while it was inhibited by -lipoic acid and protein kinase C pseudosubstrate. In summary, high glucose-induced NF-B activation occurred not by serine phosphorylation of IB. Our data suggest that ROS-mediated tyrosine phosphorylation of IB is the mechanism for high glucose-induced NF-B activation and Syk may play a role for tyrosine phosphorylation of IB.
