Introduction and objectives: Hypertension (HT) is the most common modifiable risk factor for cardiovascular disease, Strategies to control HT have a limited success, so there is an unmet need for identification of more efficient treatments for HT. A better understanding of the mechanisms regulating blood pressure could identify novel pathways that can be potential drug targets, so that we can treat HT with a mechanistic-driven approach. Here we explored the changes in G protein-coupled receptors (GPCR) contractile responses of mesenteric arteries in a mice model of essential hypertension.

Methods: We have used a mice model of essential HT (BPN, blood pressure normal, and BPH, blood pressure high) to explore changes in expression and functional contribution of several GPCR expressed in vascular smooth muscle cells (VSMCs). Mice were anesthetized by isoflurane inhalation (5% O2 at 2.5 Lmin-1) and sacrificed by cervical dislocation, following the EC guiding principles regarding the care and use of animals (Directive 2010/63/UE). Microarrays, qPCR and immunocytochemical techniques in isolated VSMCs were used to explore expression, whereas the contractile responses of endothelial-denuded mesenteric arteries in response to agonists and/or modulators of the receptors using wire and pressure myography provide the functional correlate.  

Results: Microarrays of vascular smooth muscle cells (VSMCs) from BPN and BPH mesenteric arteries provided differential expression of several elements in GPCR signaling pathways. Differential transcriptome profiling identified P2Y6 purinergic receptor mRNA as one of the top upregulated transcripts in BPH, which correlates with augmented UTP-induced contractions in BPH arteries. Angiotensin-II (AgII)-induced contraction was also higher in BPH mice despite having lower AT1R expression and was sensitive to P2Y6R modulators. Proximity Ligation Assay (PLA) and super-resolution microscopy showed closer localization of P2Y6R and AT1R at the membrane of BPH VSMCs suggesting a functional role for P2Y6R/AT1R complexes in the hypertensive phenotype. In spite of this increased response, we found reduced circulating AgII levels and less hypotensive effect in response to chronic treatment with the ATR1 blocker losartan, indicating that overstimulation of the renin-angiotensin aldosterone system does not contribute to HT in BPH. Intriguingly, BPN but not BPH mice were resistant to AgII-induced hypertension and showed reduced P2Y6R expression in VSMCs.

Conclusions: Altogether, we suggest that increased functional coupling between P2Y6 and ATII receptors may contribute to enhanced vascular reactivity during hypertension. In this regard, P2Y6R blockers could represent a novel strategy to treat hypertension.