Structure-activity relationships of the plasminogen modulator SMTP with respect to the inhibition of soluble epoxide hydrolase.

A family of fungal metabolites, SMTP, is a small-molecule plasminogen modulator that enhances plasminogen activation, leading to thrombolysis. We recently demonstrated that SMTP-7 effectively treats ischemic stroke due to its thrombolytic activity as well as anti-inflammatory action, which is attributable to soluble epoxide hydrolase (sEH) inhibition. In this paper, we studied detailed structure-activity relationships of plasminogen modulation and sEH inhibition using 25 SMTP congeners including six newly synthesized ones. The results clearly demonstrate that the structure of the N-linked side chain of SMTP congeners markedly affect their activities toward plasminogen modulation and inhibitions of the two activities of sEH (C-terminal epoxide hydrolase and N-terminal phosphatase). A slight change in the N-linked side chain results in affording selectivity of SMTP congeners. Many congeners, which lacked plasminogen modulation activity, differently inhibited the two sEH activities depending on the structures of the N-linked side chain. Some congeners were active in plasminogen modulation and inhibition of both activities of sEH. These results help comprehensive understanding of ideal design of a drug useful for ischemic diseases that are associated with inflammation, such as stroke.