Submitted on December 16, 2008
Revised on April 12, 2009
Accepted on April 27, 2009
Pressure activates epidermal growth factor receptor (EGFR) leading to the induction of iNOS via NF
B and STAT3 in human proximal tubule cells (HKC-8)
Nalini Vidyarthini Broadbelt1, Jie Chen2, Randi B. Silver3, Dix P Poppas4, and Diane Felsen2*
1 Weill Cornell Med. college
2 Weill Medical College of Cornell University
3 Cornell University
4 Weill Cornell Medical College
* To whom correspondence should be addressed. E-mail: dfelsen{at}med.cornell.edu.
Ureteral obstruction (UO) leads to increased pressure and inducible nitric oxide synthase (iNOS) expression. This study examined the involvement of epidermal growth factor receptor (EGFR), nuclear factor kappa B (NF
B) and signal transducers and activators of transcription 3 (STAT3) in iNOS induction in human proximal tubule cells (HKC-8) in response to pressure or epidermal growth factor (EGF.) HKC-8 cells were subjected to 60 mmHg pressure or EGF from (0 - 36 hrs). iNOS was rapidly induced in response to EGF, earlier than that of pressure. The addition of EGFR, NFB and STAT3 inhibitors significantly suppressed pressure or EGF stimulated iNOS mRNA and protein expression. Analysis of the activated states of EGFR, NFB p65 and STAT3 following exposure to both stimuli demonstrated phosphorylation within 2.5 min. Anti-EGF antibody inhibited iNOS induction in pressurized HKC-8 cells, providing evidence that endogenous EGF mediates the response to pressure. In UO, when pressure is elevated, pEGFR was detected in the apical surface of the renal tubules, validating the in vitro findings. These data indicate that EGFR, NFB and STAT3 are required for human iNOS gene induction in response to pressure or EGF, indicating a similar mechanism of activation.
