Fingolimod Treatment Is Associated with a Down-Modulation of S1P1 Receptor Protein in the CNS (P02.107)

Abstract

Objective: To determine the effects of fingolimod treatment on the expression of S1P1 receptor protein in the CNS. Background Fingolimod (FTY720, Gilenya) has recently been approved as the first oral therapy for relapsing Multiple Sclerosis. Fingolimod causes internalization and proteasomal degradation of sphingosine 1-phosphate receptor-1 (S1P1) on T cells, thereby favoring their retention in lymph nodes. It remains to be determined whether fingolimod also down-modulates S1P1 receptors in other tissues, including the CNS. Design/Methods: Normal rats and S1P1 transgenic mice were treated with vehicle or fingolimod (0.3mg/kg, the minimal effective dose in Experimental Autoimmune Encephalomyelitis, EAE). Tissues were isolated at various time points after drug treatment and S1P1 protein expression determined in homogenized tissues using western blots, or in cell membrane preparations using competitive 33 P-S1P-S1P receptor binding assays. S1P1-specific binding of 33 P-S1P was detected by competing off binding with (cold) S1P1-selective AUY954. Results: In normal rats, S1P1 protein was detectable in brain and lung (by 33 P-S1P-S1P binding assays), and in S1P1 transgenic mice also in the cardiovascular system (by western blot). In fingolimod-treated rats and mice, the levels of S1P1 were down-modulated by approximately 80% in all tissues, including brain. S1P1 was more rapidly down-modulated in peripheral organs compared to brain tissue, but reductions were comparable after 7 days. Conclusions: It has been reported earlier that MS is associated with increased expression of S1P1 in astrocytes and of S1P in the CNS. Here we show that EAE-therapeutic dosing of fingolimod down-modulates S1P1 receptor protein levels in the brain, presumably in neural cells/glia which make up >90% of the brain cells, thereby antagonizing the pro-inflammatory S1P-S1P1 axis that is intimately involved in astrogliosis and may perturb neural cell function. Disclosure: Dr. Brinkmann has received personal compensation for activities with Novartis as an employee. Dr. Brinkmann has received research support from Novartis. Dr. Streiff has received personal compensation for activities with Novartis as an employee. Dr. Streiff has received research support from Novartis. Dr. Bigaud has received personal compensation from Novartis for activities as an employee. Dr. Bigaud has received research support from Novartis. Dr. Kinzel has received personal compensation for activities with Novartis as an employee. Dr. Kinzel has received research support from Novartis.