Multiple Sclerosis Drug Fingolimod Induces Thrombotic Microangiopathy in Deoxycorticosterone Acetate/Salt Hypertension

We examined whether fingolimod (FTY720), an S1PR (sphingosine-1-phosphate receptor) modulator, has beneficial or harmful effects on mineralocorticoid/salt-induced renal injury. Uninephrectomized rats on 0.9% NaCl/0.3% KCl drinking solution were randomly divided into control, control+FTY720, deoxycorticosterone acetate (DOCA), and DOCA+FTY720 groups and administered vehicle, vehicle+FTY720, DOCA+vehicle, and DOCA+FTY720 for 4 weeks, respectively. Only the DOCA+FTY720 group had reduced survival rates and showed hemolysis because of intravascular mechanical fragmentation of erythrocytes and thrombocytopenia. Both the DOCA+FTY720 and DOCA groups developed malignant hypertension, which was more severe in the DOCA+FTY720 group. In the DOCA+FTY720 group only, thrombotic microangiopathy involving severe renal arteriole endothelial cell injury was observed and was characterized by fibrinoid necrosis and onion-skin lesions in arterioles. There were fewer circulating endothelial progenitor cells in the DOCA+FTY720 group but more in the DOCA group compared with the control group. Expression levels of VEGF (vascular endothelial growth factor), S1PR1, and S1PR3 in renal arteriole endothelial cells were significantly greater in the DOCA+FTY720 and DOCA groups compared with the control group, with levels being similar between the 2 groups. Expression levels of endothelial nitric oxide synthase in renal arteriole endothelial cells were significantly lower in the DOCA+FTY720 group only. The control+FTY720 group showed reduced circulating endothelial progenitor cells but no significant functional or pathological changes in kidneys or changes in blood pressure. Exposure of uninephrectomized rats to DOCA/salt+FTY720 for 4 weeks induced renal arteriolar endothelial cell injury, resulting in the development of thrombotic microangiopathy. Consideration of this possibility is recommended when prescribing FTY720.