RGS4 inhibits angiotensin II signaling and macrophage localization during renal reperfusion injury independent of vasospasm

Kidney Int. 2015 Apr;87(4):771-83. doi: 10.1038/ki.2014.364. Epub 2014 Dec 3.

Abstract

Vascular inflammation is a major contributor to the severity of acute kidney injury. In the context of vasospasm-independent reperfusion injury we studied the potential anti-inflammatory role of the Gα-related RGS protein, RGS4. Transgenic RGS4 mice were resistant to 25 min injury, although post-ischemic renal arteriolar diameter was equal to the wild type early after injury. A 10 min unilateral injury was performed to study reperfusion without vasospasm. Eighteen hours after injury, blood flow was decreased in the inner cortex of wild-type mice with preservation of tubular architecture. Angiotensin II levels in the kidneys of wild-type and transgenic mice were elevated in a sub-vasoconstrictive range 12 and 18 h after injury. Angiotensin II stimulated pre-glomerular vascular smooth muscle cells (VSMCs) to secrete the macrophage chemoattractant RANTES, a process decreased by angiotensin II R2 (AT2) inhibition. However, RANTES increased when RGS4 expression was suppressed implicating Gα protein activation in an AT2-RGS4-dependent pathway. RGS4 function, specific to VSMC, was tested in a conditional VSMC-specific RGS4 knockout showing high macrophage density by T2 MRI compared with transgenic and non-transgenic mice after the 10 min injury. Arteriolar diameter of this knockout was unchanged at successive time points after injury. Thus, RGS4 expression, specific to renal VSMC, inhibits angiotensin II-mediated cytokine signaling and macrophage recruitment during reperfusion, distinct from vasomotor regulation.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Angiotensin II / metabolism*
  • Angiotensin II / pharmacology
  • Angiotensin II Type 2 Receptor Blockers / pharmacology
  • Animals
  • Aorta / cytology
  • Arterioles / physiopathology
  • Cells, Cultured
  • Chemokine CCL5 / metabolism
  • Humans
  • Kidney Cortex / blood supply*
  • Kidney Cortex / metabolism
  • Macrophages
  • Mice
  • Mice, Knockout
  • Muscle, Smooth, Vascular / cytology
  • Myocytes, Smooth Muscle / drug effects
  • Myocytes, Smooth Muscle / metabolism*
  • RGS Proteins / genetics
  • RGS Proteins / metabolism*
  • Receptor, Angiotensin, Type 2 / metabolism
  • Renal Circulation
  • Reperfusion Injury / metabolism*
  • Reperfusion Injury / pathology
  • Reperfusion Injury / physiopathology
  • Signal Transduction
  • Vasoconstriction*

Substances

  • Angiotensin II Type 2 Receptor Blockers
  • Chemokine CCL5
  • RGS Proteins
  • Receptor, Angiotensin, Type 2
  • Angiotensin II
  • RGS4 protein