Augmented Endothelial Specific Cationic Amino Acid Transporter‐1 Expression Prevents Renal Fibrosis and Inflammation and Loss of Renal Function in Heart Failure

Abstract

INTRODUCTIONIt is now well established that impaired renal function associated with heart failure (HF) increases morbidity and mortality in HF patients. There are no effective treatments to rescue renal function in HF and the precise mechanisms that drive renal injury in HF remain elusive. Transport of L‐arginine via cationic amino acid transporter‐1 (CAT‐1) influences renal nitric oxide bioavailability. We hypothesised that impaired L‐arginine transport via CAT‐1 is central to the development of renal dysfunction in HF.METHODSAdult male 18–26 week old wild‐type mice (WT), transgenic mice with dilated cardiomyopathy (DCM) and double transgenic mice with DCM and endothelial‐specific overexpression of CAT1 (HFCAT‐1) were used (n=8 per group). Transgenic mice with dilated cardiomyopathy (DCM) have cardiac specific overexpression of Mammalian sterile 20‐like kinase‐1 (Mst1) which leads to apoptosis and DCM. The double transgenic HFCAT‐1 mouse model has endothelial specific overexpression of CAT1 driven by the Tie‐2 promotor and cardiac specific overexpression of Mst1. Cardiac and renal function were assessed via echocardiography and via calculating the albumin to creatinine ratio, respectively. Fibrosis was assessed via Masson's trichrome staining. Renal inflammation was assessed via expression of pro‐ and anti‐inflammatory gene expression. Plasma nitrate and nitrite levels were assessed via ELISA. Isolated renal cells from WT mice (n=3) were incubated with CAT1 antisense (2.5 μM) or its scrambled oligonucleotide for a period of 4‐h and then CAT1, collagen III and collagen IV expression were measured by PCR.RESULTSExpression of renal CAT1 was less in DCM mice (by 21%) compared to WT mice (P=0.04) and this was restored in HFCAT1 mice. Urinary albumin/creatinine ratio was greater in DCM mice (by 72%) compared to WT (P=0.04). Urinary albumin/creatinine ratio was normalized in HFCAT1 mice. Renal mRNA expression of Il6 was less in HFCAT‐1 mice than DCM mice (P=0.03). Renal mRNA expression of Il10 was 57% less in DCM mice than in WT mice and this was restored in HFCAT‐1 mice (P<0.05). Renal mRNA expression of Pai1 was greater in DCM mice (by 42%), but not HFCAT‐1 mice, compared to WT mice (P=0.01). Tubulointerstitial and glomerular fibrosis were 89% and 76% greater respectively in DCM mice than in WT mice (P<0.05). Tubulointerstitial and glomerular fibrosis were normalized in HFCAT‐1 mice. CAT1 antisense reduced the expression of CAT1 mRNA in isolated renal cells by 46% and collagen III expression in these cells was 8 fold greater compared to control. Ejection fraction was 33% less in DCM mice than in WT (P<0.01) and this was not restored in HFCAT1 mice (P=0.24).CONCLUSIONRestoration of endothelial specific CAT1 expression normalizes renal inflammation and fibrosis and prevents the loss of GFR in experimental HF.Support or Funding InformationNHMRC Program grant (DK) and Baker Heart and Diabetes Institute Early Career Grant (NR)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.