Structure-Function Relationship of the 20-HETE-GPR75 pairing: Development and characterization of agonist, partial agonists, and receptor blockers.

20-Hydroxyeicosatetraenoic acid (20-HETE) and its receptor (20HR), GPR75 (Gq), exhibit diverse bioactions that promote the activation of pro-hypertensive, -diabetic and -obesity signals. The pharmacological properties associated with analogues that target GPR75 remain unclear. The screening of 20-HETE and synthetic 20-HETE analogues using changes of intracellular calcium (iCa ) in the endothelial cell line, EA.hy926, as a measure of 20HR activation, revealed that the compounds 20-HETE (10 nM), sodium 20-hydroxyeicosa-5Z,14Z-dienoate (20-5,14-HEDE) (10 nM) and sodium 14-((6-hydroxyhexyl)oxy)tetradec-5(Z)-enoate (5Z-HOTE) (10 nM) promote significant and comparable elevations in iCa . In EA.hy926 cells, 20-HETE elicited a half-maximal effective concentrations (EC50) with respect to iCa of 1.228 e-9 M while 20-5,14-HEDE's EC50 was 6.908 e-10 M. The water-soluble derivative of 20-5,14-HEDE, SOLAGO, exhibited a marked and leftward shift in the dose-response with an EC50 of 2.702 e-10 M. Interestingly, sodium 19(R)- and 19(S)-hydroxyeicosa-5(Z),14(Z)-dienoate, analogues of 19(R)-HETE, an endogenous 20HR blocker (20HRB), demonstrated partial agonist activity; elevating iCa to 1.6- and 2-fold over baseline vehicle treatment, respectively. With respect to 20HR blockers, the water-soluble 20HRBs 2,5,8,11,14,17-hexaoxanonadecan-19-yl 20-hydroxyeicosa-6(Z),15(Z)-dienoate (20-SOLA) and N-disodium succinate-20-hydroxyeicosa-6(Z),15(Z)-diencarboxamide (AAA) displayed potent half-maximal inhibitory concentrations (IC50s) of 8.059 e-10 and 5.356 e-10 M, respectively. The 19(R)-HETE analogue sodium (19(R)-hydroxyeicosa-5(Z),14(Z)-dienoyl)glycinate (19(R)-HEDGE) also demonstrated a strong yet less potent IC50 response of 6.715 e-9 M. Further studies are necessary to better understand the structure-function relationships between 20HR agonists, partial agonists, and receptor blockers. These data would allow for the development of novel 20HRBs for the treatment of various pathologies associated with elevations in 20-HETE including hypertension, cancer, diabetes, and obesity.