Gαq-Biased AT1R Signaling in Smooth Muscle Cells Cause Hypertension and Vascular Dysfunction

Angiotensin II (ANG) is the main effector peptide of the renin-angiotensin system and exerts its physiological effects through the ANG type 1 receptor (AT1R). The AT1R is a member of G protein-coupled receptors (GPCR) family, which can adopt different conformations that can either bias G-protein coupling or β-arrestin signaling. The G-protein–mediated signaling through Gαq is generally associated with detrimental effects of ANG while β-arrestin pathway is reported to elicit cardioprotective effects. We hypothesize that in the absence of β-arrestin signaling, activation of biased AT1R/Gαq signaling in vascular smooth muscle cells (SMC) results in elevated blood pressure and vascular dysfunction through an AT1R dependent mechanism. To test this hypothesis, we developed a transgenic mouse model inducible expressing a mutant AT1R (AT1RTSTS-AAAA), that prevents β-arrestin binding and would signal predominantly through the Gαq pathway, after Cre-recombinase activation. The mouse models were validated by culturing primary fibroblasts from mice carrying inducible AT1RWildType (AT1RWT) or AT1RTSTS-AAAA, respectively and inducing expression with an adenovirus expressing Cre. Primary fibroblasts from AT1RWT or AT1RTSTS-AAAA exhibited Cre-inducible expression of tdTomato, serving as an indicator for the transgene expression. When compared to AT1RWT, there was in increase in phosphorylated-extracellular signal-regulated kinase (P-ERK) in AT1RTSTS-AAAA in response to ANG. Next, we bred AT1RTSTS-AAAA transgenic mice with mice carrying tamoxifen-inducible SMC-specific CRE (SMCCRE, S-TSTS). Tamoxifen injection successfully activated AT1RTSTS-AAAA transgene, which was confirmed by tdTomato reporter staining and western blot from aortic tissue. Systolic blood pressure (SBP) was significantly elevated in S-TSTS mice 1-week post-tamoxifen injection compared to control mice (SBP 140.01±6.99 vs. 106.97±2.89 mmHg, p< 0.05). Candesartan was administered in drinking water (10 mg/kg/day) once hypertension (HT) was established. One week after candesartan treatment, HT was effectively reversed in S-TSTS mice (SBP 99.93±2.16 vs. 94.19±1.18 mmHg). After removing candesartan for 2-weeks, the SBP once again increased in S-TSTS mice (SBP 140.28±7.13 vs. 111.94±4.05 mmHg, p< 0.05), indicating an AT1R-dependent mechanism. Mesenteric arteries from S-TSTS mice demonstrated a decrease in vasorelaxation in response to acetylcholine (ACh, p< 0.05), which was restored by preincubation with Tempol and ROCK inhibitor (p< 0.05). Furthermore, S-TSTS mice exhibited a robust increase in vasoconstriction in response to ANG (p< 0.05), which was abolished by losartan treatment (p< 0.05). Removal of endothelium in S-TSTS mice resulted in an increased in ANG-induced vasoconstriction (p< 0.05), indicating that vascular smooth muscle cells predominantly mediate this response. Our results indicate that activation of AT1R-mediated G-protein signaling leads to HT and vascular dysfunction via redox and ROCK signaling pathways. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.