The angiotensin II receptor type 1b is the primary sensor of intraluminal pressure in cerebral artery smooth muscle cells

Paulo W. Pires, Eun A. Ko, Harry A.T. Pritchard, Michael Rudokas, Evan Yamasaki, Scott Earley

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

Key points: The angiotensin II receptor type 1b (AT1Rb) is the primary sensor of intraluminal pressure in cerebral arteries. Pressure or membrane-stretch induced stimulation of AT1Rb activates the TRPM4 channel and results in inward transient cation currents that depolarize smooth muscle cells, leading to vasoconstriction. Activation of either AT1Ra or AT1Rb with angiotensin II stimulates TRPM4 currents in cerebral artery myocytes and vasoconstriction of cerebral arteries. The expression of AT1Rb mRNA is ∼30-fold higher than AT1Ra in whole cerebral arteries and ∼45-fold higher in isolated cerebral artery smooth muscle cells. Higher levels of expression are likely to account for the obligatory role of AT1Rb for pressure-induced vasoconstriction. Abstract: Myogenic vasoconstriction, which reflects the intrinsic ability of smooth muscle cells to contract in response to increases in intraluminal pressure, is critically important for the autoregulation of blood flow. In smooth muscle cells from cerebral arteries, increasing intraluminal pressure engages a signalling cascade that stimulates cation influx through transient receptor potential (TRP) melastatin 4 (TRPM4) channels to cause membrane depolarization and vasoconstriction. Substantial evidence indicates that the angiotensin II receptor type 1 (AT1R) is inherently mechanosensitive and initiates this signalling pathway. Rodents express two types of AT1R – AT1Ra and AT1Rb – and conflicting studies provide support for either isoform as the primary sensor of intraluminal pressure in peripheral arteries. We hypothesized that mechanical activation of AT1Ra increases TRPM4 currents to induce myogenic constriction of cerebral arteries. However, we found that development of myogenic tone was greater in arteries from AT1Ra knockout animals compared with controls. In patch-clamp experiments using native cerebral arterial myocytes, membrane stretch-induced cation currents were blocked by the TRPM4 inhibitor 9-phenanthrol in both groups. Further, the AT1R blocker losartan (1 μm) diminished myogenic tone and blocked stretch-induced cation currents in cerebral arteries from both groups. Activation of AT1R with angiotensin II (30 nm) also increased TRPM4 currents in smooth muscle cells and constricted cerebral arteries from both groups. Expression of AT1Rb mRNA was ∼30-fold greater than AT1Ra in cerebral arteries, and knockdown of AT1Rb selectively diminished myogenic constriction. We conclude that AT1Rb, acting upstream of TRPM4 channels, is the primary sensor of intraluminal pressure in cerebral artery smooth muscle cells.

Original languageEnglish (US)
Pages (from-to)4735-4753
Number of pages19
JournalJournal of Physiology
Volume595
Issue number14
DOIs
StatePublished - Jul 15 2017
Externally publishedYes

Keywords

  • cation channel
  • GPCR
  • mechanosensitivity
  • myogenic response
  • vasoconstriction

ASJC Scopus subject areas

  • Physiology

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