Investigation of Novel Inhibitor for the Serotonin 5HT2A Receptor

Abstract

The serotonin 5HT2A Receptor (5HT2AR) signaling pathway plays a vital role in platelet function in vivo, and has been implicated in the genesis of several forms of cardiovascular disorders. However, despite its clear involvement in such processes, there are no antagonists that are currently available for managing thrombotic disease which target this pathway. In light of the fact that the ligand binding of 5HT2AR is contained, at least in part, within the second extracellular loop (EL2), we investigated the function‐blocking activity of an antibody (abbreviated EL2Ab) that targets this domain. Our results revealed that 100 nM of EL2Ab significantly inhibited the “limited” human platelet aggregation and shape change induced by 15 μM 5HT. Moreover, 100 nM of EL2Ab also significantly reversed the ability of serotonin to enhance ADP‐induced platelet aggregation. This inhibitory effect was found to be dose dependent. Also, we found that EL2Ab (100 nM) did not have any detectable effects on aggregation by 10 μM of the agonist ADP alone. Similar results were also obtained under in vitro conditions in mouse platelets. In terms of ex vivo platelet aggregation, injections of 150 nM EL2Ab into live C57BL/6 mice before their blood was collected for testing, revealed complete blockade of (15 μM) serotonin‐induced aggregation/shape change, substantial‐ and dose‐dependent reversal‐ of serotonin‐enhanced, ADP‐induced aggregation; but no effect on aggregation by 1 μM U46619 control. As for its in vivo activity, it was found that injections of 150 nM EL2Ab prolonged the time for occlusion in a carotid artery thrombosis model, indicating that EL2Ab protects against thrombogenesis. Collectively, these results clearly demonstrate that EL2Ab exerts 5HT2AR‐specific anti‐platelet effects, thus making it the first function‐blocking antibody against these receptors and a potential therapeutic agent. Moreover, the identification of a functionally active 5HT2AR sequence should significantly aid molecular modeling study predictions for organic derivatives which possess in vivo activity.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.