Relaxin Attenuates Organ Fibrosis via an Angiotensin Type 2 Receptor Mechanism in Aged Hypertensive Female Rats

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Abstract

Background The antifibrotic effects of recombinant human relaxin (RLX) in the kidney are dependent on an interaction between its cognate receptor (RXFP1) and the angiotensin type 2 receptor (AT 2 R) in male models of disease. Whether RLX has therapeutic effects, which are also mediated via AT 2 R, in hypertensive adult and aged/reproductively senescent females is unknown. Thus, we determined whether treatment with RLX provides cardiorenal protection via an AT 2 R-dependent mechanism in adult and aged female stroke-prone spontaneously hypertensive rats (SHRSPs). Methods In 6-month-old (6MO) and 15-month-old ([15MO]; reproductively senescent) female SHRSP, systolic BP (SBP), GFR, and proteinuria were measured before and after 4 weeks of treatment with vehicle (Veh), RLX (0.5 mg/kg per day s.c.), or RLX+PD123319 (AT 2 R antagonist; 3 mg/kg per day s.c.). Aortic endothelium-dependent relaxation and fibrosis of the kidney, heart, and aorta were assessed. Results In 6MO SHRSP, RLX significantly enhanced GFR by approximately 25% (P=0.001) and reduced cardiac fibrosis (P=0.01) as compared with vehicle-treated counterparts. These effects were abolished or blunted by PD123319 coadministration. In 15MO females, RLX reduced interstitial renal (P=0.02) and aortic (P=0.003) fibrosis and lowered SBP (13±3 mm Hg; P=0.04) relative to controls. These effects were also blocked by PD123319 cotreatment (all P=0.05 versus RLX treatment alone). RLX also markedly improved vascular function by approximately 40% (P<0.001) in 15MO SHRSP, but this was not modulated by PD123319 cotreatment. Conclusions The antifibrotic and organ-protective effects of RLX, when administered to a severe model of hypertension, conferred cardiorenal protection in adult and reproductively senescent female rats to a great extent via an AT 2 R-mediated mechanism.

Original languageEnglish
Pages (from-to)1781-1792
Number of pages12
JournalKidney360
Volume2
Issue number11
DOIs
Publication statusPublished - Nov 2021

Keywords

  • aging
  • angiotensin type 2 receptor
  • basic science
  • cardiovascular system
  • females
  • fibrosis
  • hypertension
  • rats
  • relaxin

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