Annals of Clinical & Laboratory Science 34:277-286 (2004)
© 2004 Association of Clinical Scientists
Angiotensin II Regulation of TGF-ß in Murine Mesangial Cells Involves Both PI3 Kinase and MAP Kinase
Alan Perlman1,3,
Loredo M. Lawsin1,
Padmaja Kolachana1,
Motoyasu Saji1,2,
Jack Moore, Jr.1 and
Mathew D. Ringel1,2
1 Department of Internal Medicine, Washington Hospital Center, and Medstar Research Institute, Washington, DC; 2 Divisions of Endocrinology and Oncology, Ohio State University, Columbus, OH; and 3 Division of Nephrology and Hypertension, Weil Medical College of Cornell University, New York, NY.
Address correspondence to Alan Perlman, M.D., The Rogosin Institute, Weil Medical College of Cornell University, 505 East 70th Street, New York, NY 10021, USA; tel 212 746 1580; fax 212 746 8439; e-mail perlmaa{at}mail.rockefeller.edu.
Introduction: Chronic activation of the angiotensin II (AngII) type 1 receptor (AT-1) is a central event in the development of chronic kidney disease (CKD), in part through enhanced expression of TGF-ß, and AT-1 receptor blockade inhibits the progression to CKD in a variety of disease states. The AT-1 receptor is a heptahelical Gaq/11-coupled receptor that initiates phospholipase C activity and release of intracellular calcium; recent data suggest that the AT-1 receptor can also activate the epidermal growth factor receptor (EGFR), although the roles of specific EGF-mediated signaling cascades in AT-1 effects on mesangial cell biology are uncertain. We hypothesized that 2 EGFR-activated pathways, PI3 kinase and MAP kinase, are stimulated by the AT-1 receptor and, in part, regulate the effects of AngII on TGF-ß1 levels in mesangial cells. Methods: We examined the effects of AT-1 receptor activation on EGFR, PI3 kinase, and MAP kinase activation in murine mesangial cells. Upon achieving 60–80% confluence, the medium was changed to low-serum for 48 hr and cells were exposed to either the AT-1 receptor blocker, losartan, the EGFR blocker, AG1478, or control medium, and then stimulated with AngII. Similar experiments were performed using LY294002 and U0126, specific inhibitors of PI3 kinase and MEK, respectively. Total cellular protein lysates and RNA were isolated. Activation of the receptors and pathways was evaluated by immunoblotting and levels of TGF-ß mRNA were measured using real-time quantitative RT-PCR. Results: AngII induced autophosphorylation of EGFR (pY1068) and activated Akt and ERK, downstream targets of PI3 kinase and MAP kinase, respectively. AngII-mediated EGFR autophosphorylation was inhibited by losartan and AG1478. AG1478 also inhibited both basal and AngII-mediated activation of Akt and ERK. Finally, AngII-mediated increase in TGF-ß mRNA was inhibited by losartan, AG1478, LY249002, and U0126. Conclusions: Stimulation of the AT-1 receptor in murine mesangial cells results in activation of the EGF receptor with subsequent signaling through PI3 kinase and MAP kinase, thereby regulating TGF-ß mRNA levels. These data suggest that AT-1 receptor signaling pathways through EGFR may serve as a therapeutic target to inhibit the development of CKD.
Keywords: angiotensin II type 1 receptor, TGF-ß, Akt, ERK, losartan
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ANG II induces c-Jun NH2-terminal kinase activation and proliferation of human mesangial cells via redox-sensitive transactivation of the EGFR
Am J Physiol Renal Physiol,
December 1, 2007;
293(6):
F1889 - F1897.
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Copyright © 2004 by the Association of Clinical Scientists.
