Small-Molecule G Protein-Coupled Receptor Kinase Inhibitors Attenuate G Protein-Coupled Receptor Kinase 2-Mediated...

Vasoconstrictor-driven G protein-coupled receptor (GPCR)/phospholipase C (PLC) signaling increases intracellular Ca²⁺ concentration to mediate arterial contraction. To counteract vasoconstrictor-induced contraction, GPCR/PLC signaling can be desensitized by G protein-coupled receptor kinases (GRKs), with GRK2 playing a predominant role in isolated arterial smooth muscle cells. In this study, we use an array of GRK2 inhibitors to assess their effects on the desensitization of UTP and angiotensin II (AngII)-mediated arterial contractions. The effects of GRK2 inhibitors on the desensitization of UTP- or AngII-stimulated mesenteric third-order arterial contractions, and PLC activity in isolated mesenteric smooth muscle cells (MSMC), were determined using wire myography and Ca²⁺ imaging, respectively. Applying a stimulation protocol to cause receptor desensitization resulted in reductions in UTP- and AngII-stimulated arterial contractions. Preincubation with the GRK2 inhibitor paroxetine almost completely prevented desensitization of UTP- and attenuated desensitization of AngII-stimulated arterial contractions. In contrast, fluoxetine was ineffective. Preincubation with alternative GRK2 inhibitors (Takeda compound 101 or CCG224063) also attenuated the desensitization of UTP-mediated arterial contractile responses. In isolated MSMC, paroxetine, Takeda compound 101, and CCG224063 also attenuated the desensitization of UTP- and AngII-stimulated increases in Ca²⁺, whereas fluoxetine did not. In human uterine smooth muscle cells, paroxetine reversed GRK2-mediated histamine H₁ receptor desensitization, but not GRK6-mediated oxytocin receptor desensitization. Utilizing various small-molecule GRK2 inhibitors, we confirm that GRK2 plays a central role in regulating vasoconstrictor-mediated arterial tone, highlighting a potentially novel strategy for blood pressure regulation through targeting GRK2 function.