IL-25 Induces M2 Macrophages and Reduces Renal Injury in Proteinuric Kidney Disease

The kidney contains receptors for the cytokine IL-25, but the effects of IL-25 in CKD are unknown. Here, we induced adriamycin nephropathy in both BALB/c mice and severe combined immunodeficient (SCID) mice, and we injected IL-25 for 7 consecutive days starting at day 5 after adriamycin administration. BALB/c mice treated with IL-25 had less glomerulosclerosis, tubular atrophy, interstitial expansion, and proteinuria than control mice at day 28. IL-25 increased the levels of IL-4 and IL-13 in serum, kidney, renal draining lymph nodes, and CD4+ lymphocytes. IL-25 also directly suppressed effector macrophages in vitro and in vivo and induced alternatively activated (M2) macrophages in vivo. However, in SCID mice and in BALB/c mice treated with IL-4/13-neutralizing antibody, IL-25 failed to protect against renal injury and did not induce M2. In conclusion, IL-25 protects against renal injury in adriamycin nephropathy in mice by, at least in part, inducing Th2 immune responses.