Soluble Epoxide Hydrolase As An Anti-Inflammatory Target Of The Thrombolytic Stroke Drug Candidate Smtp-7

• Published in: Blood 2013-11, Vol.122 (21), p.2336-2336
• Main Authors: Suzuki, Eriko, Matsumoto, Naoki, Shibata, Keita, Hashimoto, Terumasa, Honda, Kazuo, Hasumi, Keiji
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V122.21.2336.2336

During the past decade, the thrombolytic enzyme tissue plasminogen activator (t-PA)-based treatment has been the standard therapy for acute ischemic stroke. However, due to its hemorrhagic risk and narrow therapeutic time window (TTW), only limited patients benefit from t-PA-based therapy, and the development of an alternative therapeutic agent is urgently needed. Reducing inflammation within the infarction area to rescue penumbra is particularly important. SMTP-7 is a small molecule that enhances plasminogen activation by modulating plasminogen conformation. SMTP-7 promotes plasmin formation and clot clearance in vivo and it is effective in treating thrombotic and embolic strokes in experimental models in rodents and a nonhuman primate. Unexpectedly, SMTP-7 reduces hemorrhagic transformation and has extended TTW as compared with t-PA. The distinct effects of SMTP-7 are partly explained by suppression of inflammatory responses following thrombolytic reperfusion, unlike t-PA. Experiments with animal inflammatory disease models (ulcerative colitis, Crohn's disease, and Guillain-Barré syndrome models) suggest that the anti-inflammatory action of SMTP-7 is independent of thrombolytic activity, as a thrombolytically inactive congener, SMTP-44D, exhibits anti-inflammatory action in those models. In this study, we searched for anti-inflammatory target of SMTP and found soluble epoxide hydrolase (sEH) as a possible candidate. We searched for a target protein using an SMTP-conjugated affinity matrix, which was synthesized by coupling SMTP-50, a congener with a primary amino group on the side chain, with gel beads. Mouse liver homogenates were subjected to affinity chromatography on this matrix, and specifically bound proteins were analyzed by peptide mass fingerprint. As a result, 4 major bound proteins were assigned to full length or fragments of soluble epoxide hydrolase (sEH), a hybrid enzyme with epoxide hydrolase activity in the C-terminal domain and lipid phosphatase activity in the N-terminal domain. The sEH hydrolase converts epoxy fatty acids, such as epoxyeicosatrienoic acids (EETs) which are endogenous anti-inflammatory lipid mediators, to less-active diol forms, such as dihydroeicosatrienoic acids (DHETs). The sEH phosphatase is implicated in lipid metabolism and hydrolysis of lysophospatidic acid, whereas its precise biological role is still unclear. SMTP-7 and SMTP-44D inhibited both hydrolase (IC50 20 and 27 µM, respectively) and phosphatase (IC50 6