The Atypical Chemokine Receptor 2 Limits Progressive Fibrosis after Acute Ischemic Kidney Injury

Following renal ischemia-reperfusion injury (IRI), resolution of inflammation allows tubular regeneration, whereas ongoing inflammatory injury mediated by infiltrating leukocytes leads to nephron loss and renal fibrosis, typical hallmarks of chronic kidney disease. Atypical chemokine receptor 2 (ACKR2) is a chemokine decoy receptor that binds and scavenges inflammatory CC chemokines and reduces local leukocyte accumulation. We hypothesized that ACKR2 limits leukocyte infiltration, inflammation, and fibrotic tissue remodeling after renal IRI, thus preventing progression to chronic kidney disease. Compared with wild type, Ackr2 deficiency increases CC chemokine ligand 2 levels in tumor necrosis factor stimulated tubulointerstitial tissue in vitro. In Ackr2-deficient mice with early IRI 1 or 5 days after transient renal pedicle clamping, tubular injury was similar to wild type, although accumulation of mononuclear phagocytes increased in postischemic Ackr2(-/-) kidneys. Regarding long-term outcomes, Ackr2(-/-) kidneys displayed more tubular injury 5 weeks after IRI, which was associated with persistently increased renal infiltrates of mononuclear phagocytes, T cells, Ly6Chi9h inflammatory macrophages, and inflammation. Moreover, Ackr2 deficiency caused substantially aggravated renal fibrosis in Ackr2(-/-) kidneys 5 weeks after IRI, shown by increased expression of matrix molecules, renal accumulation of a-smooth muscle actin positive myofibroblasts, and bone marrow derived fibrocytes. ACKR2 is important in limiting persistent inflammation, tubular loss, and renal fibrosis after ischemic acute kidney injury and, thus, can prevent progression to chronic renal disease.