Activity of Bradykinin B(2) Receptor Is Regulated by Long-Chain Polyunsaturated Fatty Acids

The molecular and cellular mechanisms by which long-chain polyunsaturated fatty acids (LCPUFA) exert their beneficial effects on cardiovascular health remain obscure. While both LCPUFA and bradykinin (BK) signaling pathway play a role in the cardiovascular system, any direct link between the two is yet to be established. Using picosecond time-resolved fluorescence microscopy and a genetically engineered bradykinin B(2) receptor (B(2)R) sensor (B2K-CC), we detected LCPUFA-induced conformational responses in the B(2)R similar to those caused by its cognate ligand, BK. The selective B(2)R antagonist (HOE-140) blocked the eicosapentaenoic acid (EPA, C20∶5, n-3) induced conformational response of the B2K-CC. Further analysis suggests that LCPUFA are capable of direct, B(2)R-dependent activation of extracellular ligand-regulated kinases (ERK). From a wide range of fatty acids studied, varying in chain length, saturation, and position of double bonds, EPA, docosahexaenoic (DHA, C22∶6, n-3), docosadienoic (DDA, C22∶2, n-6), and dihomo-gamma linoleic (DGLA, C20∶3, n-6) fatty acids caused the highest ERK phosphorylation. EPA or DHA dependent ERK phosphorylation was inhibited by the selective B(2)R antagonist. We show that LCPUFA stimulates downstream signaling by B(2)R such as B(2)R-dependent phosphorylation and expression regulation of endothelial nitric-oxide synthase (eNOS). Further analysis indicated that LCPUFA also alters levels of the eNOS transcription factor, kruppel-like factor 2 (KLF2). Moreover we show that EPA increases membrane fluidity on the same time scale as B(2)R conformational response, suggesting that partitioning of LCPUFA into bilayer is a primary step required for receptor activation. In summary our data show that LCPUFA activate B(2)R receptor at nanomolar concentrations suggesting a novel molecular mechanism by which fatty acids may affect the cardiovascular system.