The bradykinin B2 receptor induces multiple cellular responses leading to the proliferation of human renal carcinoma cell lines

Abstract

Background: The vasoactive peptide bradykinin (BK) acts as a potent growth factor for normal kidney cells, but there have been few studies on the role of BK in renal cell carcinomas. Purpose: In this study, we tested the hypothesis that BK also acts as a mitogen in kidney carcinomas, and explored the effects of BK in human renal carcinoma A498 cells. Methods: The presence of mRNAs for BK B1 and BK B2 receptors in A498 cells was demonstrated by reverse transcription-polymerase chain reaction. To study BK signaling pathways, we employed fluorescent measurements of intracellular Ca2+, measured changes in extracellular pH as a reflection of Na+/H+ exchange (NHE) with a Cytosensor microphysiometer, and assessed extracellular signal-regulated kinase (ERK) activation by Western blotting. Results: Exposure to 100 nM of BK resulted in the rapid elevation of intracellular Ca2+, caused a $30% increase in NHE activity, and a $300% increase in ERK phosphorylation. All BK signals were blocked by HOE140, a BK B2 receptor antagonist, but not by a B1 receptor antagonist. Inhibitor studies suggest that BK-induced ERK activation requires phospholipase C and protein kinase C activities, and is Ca2+/calmodulin-dependent. The amiloride analog 5-(N-methyl-N-isobutyl)-amiloride (MIA) blocked short-term NHE activation and inhibited ERK phosphorylation, suggesting that NHE is critical for ERK activation by BK. BK induced an approximately 40% increase in the proliferation of A498 cells as assessed by bromodeoxyuridine uptake. This effect was blocked by the ERK inhibitor PD98059, and was dependent on NHE activity. Conclusion: We conclude that BK exerts mitogenic effects in A498 cells via the BK B2 receptor activation of growth-associated NHE and ERK. © 2012 Tuca et al, publisher and licensee Dove Medical Press Ltd.