RON kinase inhibition reduces renal endothelial injury in sickle cell disease mice

Sickle cell disease patients are at increased risk of developing a chronic kidney disease. Endothelial dysfunction and inflammation associated with hemolysis lead to vasculopathy and contribute to the development of renal disease. Here we used a Townes sickle cell disease mouse model to examine renal endothelial injury. Renal disease in Townes mice was associated with glomerular hypertrophy, capillary dilation and congestion, and significant endothelial injury. We also detected substantial renal macrophage infiltration, and accumulation of macrophage stimulating protein 1 in glomerular capillary. Treatment of human cultured macrophages with hemin or red blood cell lysates significantly increased expression of macrophage membrane-associated protease that might cleave and activate circulating macrophage stimulating protein 1 precursor. Macrophage stimulating protein 1 binds to and activates RON kinase, a cell surface receptor tyrosine kinase. In cultured human renal glomerular endothelial cells, macrophage stimulating protein 1 induced RON downstream signaling, resulting in increased phosphorylation of ERK and AKT kinases, expression of Von Willebrand factor, increased cell motility, and re-organization of F-actin. Specificity of macrophage stimulating protein 1 function was confirmed by treatment with RON kinase inhibitor BMS-777607 that significantly reduced downstream signaling. Moreover, treatment of sickle cell mice with BMS-777607 significantly reduced glomerular hypertrophy, capillary dilation and congestion, and endothelial injury. Taken together, our findings demonstrated that RON kinase is involved in the induction of renal endothelial injury in sickle cell mice. Inhibition of RON kinase activation may provide a novel approach for prevention of the development of renal disease in sickle cell disease.