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.
Written by:
Kramarenko II, Morinelli TA, Bunni MA, Raymond JR Sr, Garnovskaya MN. Are you the author?
Department of Medicine (Nephrology Division), Medical University of South Carolina, Charleston, SC, USA.
Reference: Cancer Manag Res. 2012;4:195-205.
doi: 10.2147/CMAR.S31847
PubMed Abstract
PMID: 22904641
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