Inhibitors of Autoactivation of Plasma Hyaluronan-Binding Protein (Factor VII Activating Protease)

Abstract

Plasma hyaluronan-binding protein (PHBP), a serine protease that can activate coagulation factor VII and prourokinase, circulates in a single-chain form (pro-PHBP) and autoproteolytically converts to an active twochain form with the aid of an effector such as spermidine and heparin. It has been postulated that PHBP plays roles in regulating inflammation, vascular function, fibrosis and atherosclerosis. From the comprehensive screening of natural sources for inhibitors of spermidine-induced pro-PHBP autoactivation, we identified several compounds with a polyphenol feature. Of these inhibitors, tannic acid (IC 50 ‫020.0؍‬ m mM), delphinidin (IC 50 ‫970.0؍‬ m mM), hamamelitannin (IC 50 ‫91.0؍‬ m mM), (؊)-epicatechin gallate (IC 50 ‫42.0؍‬ m mM), and 3,5-di-O-caffeoylquinic acid (IC 50 ‫0.1؍‬ m mM) were potent and selective, and did not inhibit heparin-induced pro-PHBP autoactivation and the active form of PHBP at concentrations 100 times higher than the respective IC 50 values. From evaluation of the activities of related compounds, it has been suggested that a compound with multiple aromatic rings with plural phenolic hydroxyl substituents exhibits potent activity. The inhibitory actions of delphinidin, hamamelitannin, (؊)-epicatechin gallate and 3,5-di-O-caffeoylquinic acid were attenuated by catechol, a minimum polyphenol unit. Thus, it is likely that pro-PHBP binds these potent inhibitors through its site(s) that recognize a catechollike structure. Our results would facilitate understanding of the molecular mechanism of pro-PHBP autoactivation and rational design of a compound for suppressing unregulated pro-PHBP activation.

Elucidation of Crucial Structures for a Catechol-Based Inhibitor of Plasma Hyaluronan-Binding Protein (Factor VII Activating Protease) Autoactivation

“…10,[14][15][16] Most of these inhibitors have a polyphenol feature. In particular, potent inhibitors have plural catechol units, such as galloyl and caffeoyl groups.…”

“…In particular, potent inhibitors have plural catechol units, such as galloyl and caffeoyl groups. 15) Since catechol attenuates the inhibitory action of these inhibitors, the presence of catechol-binding sites in pro-PHBP has been postulated. 15) In this study, we investigated the structureactivity relationships of catechol-based compounds to facilitate the designing of a potent inhibitor.…”

“…1A). Since compounds with plural catechol units have been shown to be more potent than ones with a single catechol unit, 15) we examined the activity of analog 10, which had two catechol units bridged via a conjugated nitrile group. Compound 10 potently inhibited spermidine-induced pro-PHBP autoactivation (IC 50 ¼ 0:060 AE 0:001 mM) (Fig.…”

“…This is compatible with the structures of potent compounds identified in previous investigations. 15) In tannic acid (IC 50 ¼ 0:020 mM), hamamelitannin (IC 50 ¼ 0:19 mM), and 3,5-di-O-caffeoylquinic acid (IC 50 ¼ 1:0 mM), conjugated ester bonds can serve as EWGs. A pyrylium system functions as an EWG in delphinidin (IC 50 ¼ 0:079 mM) and cyanidin (IC 50 ¼ 0:13 mM).…”

“…A pyrylium system functions as an EWG in delphinidin (IC 50 ¼ 0:079 mM) and cyanidin (IC 50 ¼ 0:13 mM). 15) Pro-PHBP activation is a regulated process involving distinct mechanisms. Polyamine-mediated activation can play a role in inflammatory conditions.…”