Selective production of staplabin and SMTPs in cultures of Stachybotrys microspora fed with precursor amines

Semisynthetic Approach toward Biologically Active Derivatives of Phenylspirodrimanes from S. chartarum

The phenylspirodrimanes (PSDs) from Stachybotrys chartarum represent a structurally diverse group of meroterpenoids, which, on the one hand, exhibit a structural exclusivity since their occurrence is not known for any other species and, on the other hand, offer access to chemically and biologically active compounds. In this study, phenylspirodrimanes 1-3 were isolated from S. chartarum and their water-mediated Cannizzaro-type transformation was investigated using quantum chemical DFT calculations substantiated by LC-MS and NMR experiments. Considering the inhibitory activity of PSDs against proteolytic enzymes and their modulatory effect on plasminogen, PSDs 1-3 were used as a starting material for the synthesis of their corresponding biologically active lactams. To access the library of the PSD derivatives and screen them against physiologically relevant serine proteases, a microscale semisynthetic approach was developed. This allowed us to generate the library of 35 lactams, some of which showed the inhibitory activity against physiologically relevant serine proteases such as thrombin, FXIIa, FXa, and trypsin. Among them, the agmatine-derived lactam 16 showed the highest inhibitory activity against plasma coagulation factors and demonstrated the anticoagulant activity in two plasma coagulation tests. The semisynthetic lactams were significantly less toxic compared to their parental natural PSDs.

Progress in Isoindolone Alkaloid Derivatives from Marine Microorganism: Pharmacology, Preparation, and Mechanism

Compound 1 (SMTP-7, also FGFC1), an isoindolone alkaloid from marine fungi Starchbotrys longispora FG216 and fungi Stachybotrys microspora IFO 30018, possessed diverse bioactivities such as thrombolysis, anti-inflammatory and anti-oxidative properties, and so on. It may be widely used for the treatment of various diseases, including cerebral infarction, stroke, ischemia/reperfusion damage, acute kidney injury, etc. Especially in cerebral infarction, compound 1 could reduce hemorrhagic transformation along with thrombolytic therapy, as the traditional therapies are accompanied with bleeding risks. In the latest studies, compound 1 selectively inhibited the growth of NSCLC cells with EGFR mutation, thus demonstrating its excellent anti-cancer activity. Herein, we summarized pharmacological activities, preparation of staplabin congeners—especially compound 1—and the mechanism of compound 1, with potential therapeutic applications.

Absolute configuration determination of SMTP-7 via microcrystal electron diffraction (MicroED)

The absolute configuration of a clinically important drug candidate, SMTP-7, with only micron-sized powders available, is directly obtained via microcrystal electron diffraction (MicroED) analysis.

Potent efficacy of Stachybotrys microspora triprenyl phenol-7, a small molecule having anti-inflammatory and antioxidant activities, in a mouse model of acute kidney injury

Acute kidney injury (AKI) increases the risk of chronic kidney disease (CKD), complicates existing CKD, and can lead to the end-stage renal disease. However, there are no approved effective therapeutics for AKI. Recent studies have suggested that inflammation and oxidative stress are the primary causes of AKI. We previously reported the potential anti-inflammatory and antioxidant activities of Stachybotrys microspora triprenyl phenol-7 (SMTP-7). The aim of the present study was to evaluate the efficacy of SMTP-7 in AKI model mice. AKI was induced in mice by ischemia of the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after the removal of right kidney. The efficacy of SMTP-7 was determined by measuring the renal function using urine and serum samples and morphological assessment. For deciphering the mechanism of action of SMTP-7, inflammatory cytokines and oxidative stress in kidney were detected. SMTP-7 (0.01, 0.1, 1, 10 mg/kg) dose-dependently improved the renal function. In addition, it improved the damage to renal tubules and exhibited anti-inflammatory and antioxidant activities in the kidney of AKI mice. These results indicate the potential of SMTP-7 as a medicinal compound for the treatment of AKI.

Impact of SMTP Targeting Plasminogen and Soluble Epoxide Hydrolase on Thrombolysis, Inflammation, and Ischemic Stroke

Stachybotrys microspora triprenyl phenol (SMTP) is a large family of small molecules derived from the fungus S. microspora. SMTP acts as a zymogen modulator (specifically, plasminogen modulator) that alters plasminogen conformation to enhance its binding to fibrin and subsequent fibrinolysis. Certain SMTP congeners exert anti-inflammatory effects by targeting soluble epoxide hydrolase. SMTP congeners with both plasminogen modulation activity and anti-inflammatory activity ameliorate various aspects of ischemic stroke in rodents and primates. A remarkable feature of SMTP efficacy is the suppression of hemorrhagic transformation, which is exacerbated by conventional thrombolytic treatments. No drug with such properties has been developed yet, and SMTP would be the first to promote thrombolysis but suppress disease-associated bleeding. On the basis of these findings, one SMTP congener is under clinical study and development. This review summarizes the discovery, mechanism of action, pharmacological activities, and development of SMTP.

Efficacy of SMTP-7, a small-molecule anti-inflammatory thrombolytic, in embolic stroke in monkeys

SMTP-7 (Stachybotrys microspora triprenyl phenol-7) is a small molecule that promotes thrombolysis and suppresses inflammation possibly through plasminogen modulation and soluble epoxide hydrolase (sEH) inhibition, respectively. Here, we demonstrate an efficacy of SMTP-7 in a severe embolic stroke model in monkeys. The middle cerebral artery was embolized by an autologous blood clot. Saline, SMTP-7, or tissue-type plasminogen activator (t-PA) (n = 5 in each group) was given after 3 hours, and neurologic deficit scoring and infarct characterization were performed after 24 hours. Hemorrhagic infarct-accompanied premature death was observed for two animals in t-PA group. SMTP-7 treatment significantly reduced the sizes of infarct by 65%, edema by 37%, and clot by 55% compared to saline treatment. Plasma levels of the products of plasminogen activation (plasmin-α2-antiplasmin complex) and sEH reaction (dihydroxyeicosatrienoic acid) in SMTP-7 group were 794% (P < 0.05) and 60% (P = 0.085) compared to saline group, respectively. No significant changes in the plasma levels of MMP-9, CRP, MCP-1, and S100B were found. There was an inverse correlation between plasmin-α2-antiplasmin complex level and infarct volume (r = 0.93, P < 0.05), suggesting a role of thrombolysis in the SMTP-7 action to limit infarct development. In conclusion, SMTP-7 is effective in treating severe embolic stroke in monkeys under conditions where t-PA treatment tends to cause hemorrhagic infarct-associated premature death.

Confirmation of the absolute configuration of Stachybotrin C using single-crystal X-ray diffraction analysis of its 4-bromobenzyl ether derivative

The absolute configuration of Stachybotrin C was confirmed in this study. After synthesizing the dimethyl ethers of Stachybotrin C, the C-8 epimer was analyzed by 1D NOESY. However, the stereochemistry determination was difficult through the NOE correlations. Instead, the di(4-bromobenzyl) ether of Stachybotrin C was derived and used for X-ray diffraction analysis, because its single crystal was easier to obtain than that of the original Stachybotrin C. The stereochemistry of Stachybotrin C was determined to be (8S, 9R). This derivatization approach may also be used to prepare single crystals of the analogues.

Producing Novel Fibrinolytic Isoindolinone Derivatives in Marine Fungus Stachybotrys longispora FG216 by the Rational Supply of Amino Compounds According to Its Biosynthesis Pathway

Many fungi in the Stachybotrys genus can produce various isoindolinone derivatives. These compounds are formed by a spontaneous reaction between a phthalic aldehyde precursor and an ammonium ion or amino compounds. In this study, we suggested the isoindolinone biosynthetic gene cluster in Stachybotrys by genome mining based on three reported core genes. Remarkably, there is an additional nitrate reductase (NR) gene copy in the proposed cluster. NR is the rate-limiting enzyme of nitrate reduction. Accordingly, this cluster was speculated to play a role in the balance of ammonium ion concentration in Stachybotrys. Ammonium ions can be replaced by different amino compounds to create structural diversity in the biosynthetic process of isoindolinone. We tested a rational supply of amino compounds ((±)-3-amino-2-piperidinone, glycine, and l-threonine) in the culture of an isoindolinone high-producing marine fungus, Stachybotrys longispora FG216. As a result, we obtained four new kinds of isoindolinone derivatives (FGFC4–GFC7) by this method. Furthermore, high yields of FGFC4–FGFC7 confirmed the outstanding production capacity of FG216. Among the four new isoindolinone derivatives, FGFC6 and FGFC7 showed promising fibrinolytic activities. The knowledge of biosynthesis pathways may be an important attribute for the discovery of novel bioactive marine natural products.

Protective Effect of Stachybotrys microspora Triprenyl Phenol-7on the Deposition of IgA to the Glomerular Mesangium in Nivalenol-induced IgA Nephropathy Using BALB/c Mice

Activators of tissue proteolysis including Stachybotrys microspora triprenyl phenol (SMTP)-7 are a new class of agents that are expected to be effective for amelioration of chronic tissue destructive diseases. The present study was performed to examine whether SMTP-7 is effective for the amelioration or protection of early-stage IgA nephropathy (IgAN) induced by nivalenol (NIV) in female BALB/c mice. In Experiment 1, mice were administered NIV at 24 ppm in diet for 8 weeks, and during the NIV treatment, they were intraperitoneally injected with SMTP-7 (10 mg/kg) three times a week. In Experiment 2, mice were injected similarly with SMTP-7 during the last 4 weeks of a 16-week NIV treatment. Immunofluorescence analysis revealed an inhibitory effect of SMTP-7 on the glomerular deposition of IgA in Experiment 1; however, it was ineffective in Experiment 2. On the other hand, SMTP-7 did not affect the serum concentration of IgA in both experiments. These results suggest that SMTP-7 has a potential to decrease the progression of IgAN induced by NIV through inhibition of local accumulation of IgA in the glomerular mesangium, while it was ineffective for suppression of IgA production. On the other hand, SMTP-7 was found to be ineffective for already deposited IgA, suggesting that SMTP-7 may not be effective for ameliorating advanced IgAN.

A new series of the SMTP plasminogen modulators with a phenylamine-based side chain

SMTPs are a family of small-molecule plasminogen modulators that enhance plasminogen activation. SMTP-7, one of the most potent congeners, is effective in treating thrombotic cerebral infarction. The SMTP molecule consists of a tricyclic γ-lactam moiety, a geranylmethyl group, and an N-linked side chain. The presence of both an aromatic group and a negatively ionizable group in the N-linked side chain is crucial for activity. Investigations of the congeners with a phenylglycine-based side chain suggest that a phenolic hydroxy group affects potency. In this study, we isolate and characterize a series of novel SMTP congeners with a phenylamine-based N-linked side chain. Of the 11 congeners isolated, SMTP-19 (with a 4-phenylcarboxylic acid moiety), SMTP-22 (with a 3-hydroxyphenyl-4-carboxylic acid moiety) and SMTP-25 (with a 2-hydroxyphenyl-3-carboxylic acid moiety) are as potent as SMTP-7 in plasminogen-modulating activity. Their isomers with a carboxylic acid group and/or a phenolic hydroxy group at different positions have <40% of the activity of these congeners. Both SMTP-22 and SMTP-25 have >1.7 times more oxygen radical absorbance capacity as compared with SMTP-7.

SMTP (Stachybotrys microspora triprenyl phenol) enhances clot clearance in a pulmonary embolism model in rats

Background

Stachybotrys microspora triprenyl phenols (SMTPs) are a novel family of small molecules that enhance both activation and fibrin-binding of plasminogen. While their effects on fibrinolysis have been characterized in vitro, little is known about their activity in vivo with respect to plasminogen activation and blood clot clearance.

Results

To select a potent SMTP congener for the evaluation of its action in vitro and in vivo, we tested several SMTP congeners with distinct structural properties for their effects on plasminogen activation. As a result, SMTP-7 (orniplabin) was found to have distinguished activity. Several lines of biochemical evidence supported the idea that SMTP-7 acted as a plasminogen modulator. SMTP-7 elevated plasma level of plasmin-α₂-antiplasmin complex, an index of plasmin formation in vivo, 1.5-fold in mice after the intravenous injections at doses of 5 and 10 mg kg^-1. In a rat pulmonary embolism model, SMTP-7 (5 mg kg^-1) enhanced the rate of clot clearance ~3-fold in the absence of exogenous plasminogen activator. Clot clearance was enhanced further by 5 mg kg^-1 of SMTP-7 in combination with single-chain urokinase-type plasminogen activator.

Conclusions

Our results show that SMTP-7 is a superior plasminogen modulator among the SMTP family compounds and suggest that the agent enhances plasmin generation in vivo, leading to clearance of thrombi in a model of pulmonary embolism.

Structure-activity relationships of 11 new congeners of the SMTP plasminogen modulator

The fungal metabolite Stachybotrys microspora triprenyl phenols (SMTPs) are small-molecule plasminogen modulators that enhance plasminogen activation. The SMTP molecule consists of a tricyclic γ-lactam moiety, an isoprene side-chain and an N-linked side-chain. Previous investigations have demonstrated that the N-linked side-chain is crucial for its activity. In this study, we have isolated 11 new SMTP congeners with a variety of N-linked side-chain structures, to investigate structure-activity relationships. Active compounds included congeners with a carboxyl or a sulfonic acid group in the N-linked side-chain, whereas not all the congeners with a carboxyl group were active. Of these congeners, that with methionine or tyrosine as the N-linked side-chain moiety was more active than that with an aliphatic amino acid. Congeners without ionizable group in the N-linked side-chain were essentially inactive.

Small-molecule modulators of zymogen activation in the fibrinolytic and coagulation systems

The coagulation and fibrinolytic systems are central to the hemostatic mechanism, which works promptly on vascular injury and tissue damage. The rapid response is generated by specific molecular interactions between components in these systems. Thus, the regulation mechanism of the systems is programmed in each component, as exemplified by the elegant processes in zymogen activation. This review describes recently identified small molecules that modulate the activation of zymogens in the fibrinolytic and coagulation systems.

Isolation and absolute configuration of SMTP-0, a simplest congener of the SMTP family nonlysine-analog plasminogen modulators

SMTP-0, a new simple congener of the SMTP nonlysine-analog plasminogen modulators, was isolated from a culture of Stachybotrys microspora. Based on the physico-chemical data, SMTP-0 was shown to be an enantiomer of the antimicrobial compound stachybotrin B. The absolute configuration of SMTP-0 was determined by the modified Mosher method. The stereochemistry was further confirmed using an epimer of SMTP-0. Unlike most SMTPs with an amino acid side chain linked to the nitrogen atom of the lactam moiety, SMTP-0, which lacks the N-linked side chain, showed no plasminogen modulator activity.

Total synthesis and structure revision of stachybotrys spirolactams

The spirolactam structure 1 reported in 1996 by Roggo et al. has been enantioselectively synthesized in 20 steps from (+)-Wieland-Miescher ketone. Spectra of this synthetic lactam differed from those of the natural spirolactam from the Roggo group, leading to the hypothesis that the natural lactam may be the regioisomer 27, a structure previously ascribed by Jarvis et al. to the natural product stachybotrylactam. This hypothesis was confirmed by the first total synthesis of (-)-stachybotrylactam (27). Double reductive amination of two molecules of aldehyde 29 with one molecule of l-lysine led by analogous chemistry to the first synthesis of the pseudosymmetric "dimer" 30, whose spectra corresponded to those of the natural "dimer" originally assigned structure 5 by the Roggo group.