Introduction and Objective: Mechanism of fingolimod in multiple sclerosis (MS) is mainly thought to prevent lymphocyte egress from lymphoid tissues, thereby reducing autoaggressive lymphocyte infiltration into the central nervous system. However, S1P receptors are also expressed by endothelial cells which compose blood-brain barrier (BBB). Hence, fingolimod may also act on endothelial cells forming the BBB and modify the entrance of pathogenic lymphocytes. In this study, we examined how fingolimod affects brain microvascular endothelial cells (BMECs). Recently, we reported that sera from multiple sclerosis (MS) patients down-regulated claudin-5 and up-regulated VCAM-1 in BMECs. Hence, we also evaluated how fingolimod-phosphate affects endothelial cell function against MS sera exposure.
Methods: The protein levels of tight junction (TJ) proteins (claudin-5, occludin), adhesion molecules (ICAM-1, MelCAM), and transendothelial electrical resistance (TEER) of BMECs, which was cultured in the media with or without fingolimod/fingolimod-phosphate, were compared. The effects of sera from MS patients on barrier function and amount of adhesion molecules of BMECs are examined in the presence of fingolimod-phosphate.
Result: Although fingolimod-phosphate did not affect the amount of occludin, ICAM-1, and MelCAM proteins, it increased the claudin-5 protein levels and TEER value in BMECs. On the other hand, fingolimod did not alter the amount of TJ and adhesion proteins as well as TEER in BMECs. Pretreatment with fingolimod-phosphate restored the protein levels of claudin-5 and TEER values in BMECs reduced by MS sera. It also decreased VCAM-1 protein in BMECs, which had been up-regulated by MS sera.
Conclusion: Pretreatment with fingolimod-phosphate prevent BBB disruption caused by MS sera by up-regulating claudin-5, and down-regulating VCAM-1 in BMECs. These results indicate that fingolimod-phosphate may directly act on endothelial cells of BBB and play a part in the reduction of relapse rate in MS patients.