Deletion of the 20‐HETE receptor (GPR75) impairs myogenic tone of renal preglomerular arteries

Abstract

20‐Hydroxyeicosatetraenoic acid (20‐HETE), one of the principal cytochrome P450 (CYP)‐derived eicosanoids, is a potent vasoactive lipid whose vascular effects include stimulation of smooth muscle contractility, migration and proliferation, as well as endothelial cell dysfunction and inflammation. Increased levels of 20‐HETE in experimental animals and in humans are associated with hypertension, stroke, myocardial infarction and vascular diseases. We recently identified GPR75, an orphan G‐protein (Gaq/11) coupled receptor (GPCR), as a specific cellular target to which 20‐HETE binds and through which it activates a signaling cascade that culminates in many of the functional outcomes attributed to 20‐HETE in vitro and in vivo (Garcia et al, Circ. Res., 2017). To further establish the role of GPR75 as a 20‐HETE target for its bioactions, global GPR75 knockout (Gpr75−/−) mice were generated. A breeding colony of Gpr75+/−XGpr75+/− has been established and experiments were conducted to assert the genotype and assess whether a basic phenotype exists. Levels GPR75 mRNA were undetectable in brain, liver, heart, aorta and kidney from Gpr75−/− mice. Levels of Gpr75 mRNA in liver, heart and aorta tissues from Gpr75+/− (HET) was lower compared to littermate Gpr75+/+ (WT) mice. The initial phenotypic characterization showed no differences between WT and transgenic mice in body weight or systolic blood pressure (93±4, 89±5 and 88±6 mmHg in male and female WT, Gpr75+/− and Gpr75−/− mice, respectively). There were no significant gender differences in body weight or blood pressure. Since 20‐HETE has been shown to promote vasoconstriction, increase vascular reactivity and contribute to the myogenic response in renal and cerebral microvessels, we assessed whether deficiencies in GPR75 affects myogenic response in preglomerular arterioles (~50–80 μm). The myogenic response was markedly impaired in arteries from Gpr75−/− mice as internal diameter increased in response to increasing pressure and in response to 100 mmHg, internal diameter of arteries from Gpr75−/− and Gpr75+/− mice was 119.5±1.22 and 101.7±3.1 μm, respectively, as compared to 80.3±3.4 μm in arteries from WT (p<0.05). These results, together with our finding that in vascular smooth muscle cells 20‐HETE‐GPR75 pairing leads to inhibition of the BKca channels and increases in intracellular calcium concentration which contribute to vasoconstriction, suggest that deficiency in the expression of GPR75 mediates the impaired myogenic response because 20‐HETE is lacking its cellular target.Support or Funding InformationSupported by NIH grant HL139793 and Regeneron Pharmaceuticals Inc.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.