Targeting c-fms kinase attenuates chronic aristolochic acid nephropathy in mice

Aristolochic acid nephropathy (AAN) is a progressive kidney disease caused by some Chinese herbal medicines, but treatment remains ineffective. Macrophage accumulation is an early feature in human and experimental AAN; however, the role of macrophages in chronic AAN is unknown. We report here that targeting macrophages with fms-I, a selective inhibitor of the tyrosine kinase activity of the macrophage colony-stimulating factor receptor, suppressed disease progression in a mouse model of chronic AAN. Treatment with fms-I (10mg/kg/BID) from day 0 to 28 (prevention study) or from day 14 to 28 (intervention study) substantially inhibited macrophage accumulation and significantly improved renal dysfunction including a reduction in proteinuria and tubular damage. Progressive interstitial fibrosis (myofibroblast accumulation and collagen deposition) and renal inflammation (increased expression of MCP-1, MIF, and TNF-a) were also attenuated by fms-I treatment. These protective effects involved inhibition of TGF-ß/Smad3 and NF-kB signaling. In conclusion, the present study establishes that macrophages are key inflammatory cells that exacerbates progressive tubulointerstitial damage in chronic AAN via mechanisms associated with TGF-ß/Smad3-mediated renal fibrosis and NF- _kB-driven renal inflammation. Targeting macrophages via a c-fms kinase inhibitor may represent a novel therapy for chronic AAN.