IRAP deficiency preserves renal function and attenuates pathology in aged mice.

Senescent cell accumulation and fibrosis play a fundamental role in kidney ageing. Our aim was to determine whether the angiotensin IV/insulin-regulated aminopeptidase (IRAP) axis of the renin-angiotensin system contributes to renal function decline, fibrosis, and senescent cell accumulation in aged mice. We studied the role of IRAP in kidney ageing using IRAP knockout (KO) mice, as well as in wild-type (WT) mice treated with an IRAP inhibitor. Complementary proximal tubule and collecting duct cell models were used to determine the mechanisms by which IRAP inhibition exerts protective effects. Glomerular filtration rate (GFR) declined by 25% in WT mice between 3 and 23 months of age, concomitant with marked increases in albumin excretion, glomerulosclerosis, tubulointerstitial fibrosis, and accumulation of senescent cells in the proximal tubules of the kidney. IRAP KO mice were protected against age-related decline in GFR, renal fibrosis, and senescence burden compared with age-matched WT mice. IRAP inhibition for 4 weeks (HFI-419, 500 ng/kg/min) in 28-month-old WT mice similarly prevented age-related decline in GFR and attenuated expression of cellular senescence markers. Using an in vitro model of cultured proximal tubule cells, IRAP inhibition mitigated the pro-senescent effects of oxidative stress. This was associated with shifts in the metabolic phenotype of proximal tubular cells, indicating the senoprotective effects of IRAP inhibition may be mediated in part via mitochondrial function. These studies provide evidence that IRAP deficiency is protective against chronic renal cellular senescence, fibrosis, and functional decline. Therefore, IRAP inhibition has therapeutic potential to attenuate pathological cardiorenal ageing through senoprotective mechanisms.