New polycyclic tetramate macrolactams with antimycobacterial activity produced by marine-derived Streptomyces sp. KKMA-0239

During our screening for anti-mycobacterial agents against Mycobacterium avium complex (MAC), two new polycyclic tetramate macrolactams (PTMs), named hydroxycapsimycin (1) and brokamycin (2), were isolated along with the known PTM, ikarugamycin (3), from the culture broth of marine-derived Streptomyces sp. KKMA-0239. The relative structures of 1 and 2 were elucidated by spectroscopic data analyses, including 1D and 2D NMR. Furthermore, the absolute configuration of 1 was confirmed by a single-crystal X-ray diffraction analysis. Compounds 2 and 3 exhibited moderate antimycobacterial activities against MAC, including clinically isolated drug-resistant M. avium.

Synthesis and biological evaluation of nectriatide derivatives, potentiators of amphotericin B activity

Nectriatide 1a, a naturally occurring cyclic tetrapeptide, has been reported to a potentiator of amphotericin B (AmB) activity. In order to elucidate its structure-activity relationships, we synthesized nectriatide derivatives with different amino acids in solution-phase synthesis and evaluated AmB-potentiating activity against Candida albicans. Among them, C-and N-terminal protected linear peptides were found to show the most potent AmB-potentiating activity.

Mavintramycin A is a promising antibiotic for treating Mycobacterium avium complex infectious disease

Mycobacterium avium complex (MAC) is a serious disease that is mainly caused by infection with the non-tuberculous mycobacteria (NTM), Mycobacterium avium and Mycobacterium intracellulare. Seven new compounds, designated mavintramycins A-G (1-7), were isolated along with structurally related compounds, including amicetin (9) and plicacetin (10), from the culture broth of Streptomyces sp. OPMA40551 as anti-MAC compounds that were active against M. avium and M. intracellulare. Among them, mavintramycin A showed the most potent and selective inhibition of M. avium and M. intracellulare. Furthermore, mavintramycin A was active against more than 40 clinically isolated M. avium, including multidrug-resistant strains, and inhibited the growth of M. avium in a persistent infection cell model using THP-1 macrophages. Mavintramycin A also exhibited in vivo efficacy in silkworm and mouse infection assays with NTM. An experiment to elucidate its mechanism of action revealed that mavintramycin A inhibits protein synthesis by binding to 23S ribosomal RNA in NTM. Mavintramycin A, with a different chemical structure from those of clinically used agents, is a promising drug candidate for the treatment of MAC infectious disease.

Haneummycin, a new 22-membered macrolide lactam antibiotic, produced by marine-derived Streptomyces sp. KM77-8

A new antibiotic named haneummycin (1) was isolated from a culture broth of marine-derived Streptomyces sp. KM77-8 by solvent extraction and HPLC using a C4 column. The structure of 1 was elucidated including relative stereochemistry as a new 22-membered macrolide lactam associated with a cyclopentanone and three sugars by various spectroscopic analyses, such as MS and NMR. Compound 1 displayed significant antibacterial activities against Gram-positive bacteria including vancomycin-resistant Enterococcus faecium (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) with both MIC values of 8.0 µg ml-1.

New potentiators of amphotericin B activity, shodoamides A to C produced by Pseudophialophora sp. BF-0158

During our screening program for new potentiators of amphotericin B activity against Candida albicans, shodoamides A to C (1-3) were isolated from a culture broth of the fungus Pseudophialophora sp. BF-0158 fermented under shaking conditions. A known congener named shodoamide D (4) in this paper was obtained from a culture broth of the BF-0158 strain fermented under static conditions. The structures of 1-4 were assigned based on spectroscopic analyses, including NMR and MS, and were found to have a common N-(2´,3´,4´-trihydroxybutyl)-6-methyl-2,4-tetradecadienamide structure. Compounds 1-3 exhibited no antifungal activity, but they induced up to 32-fold increases in amphotericin B activity against C. albicans by a microdilution method.

Marine Compounds from the Far Eastern Organisms

The term "Far East" implies a huge geographical region that consists of Eastern and Southeastern Asia, Eastern Russia and includes the waters of two oceans-the Pacific and Indian [...].

Screening for microbial potentiators of neutral lipid degradation in CHO-K1 cells

A cell-based assay was conducted to screen microbial culture broths for potentiators of neutral lipid degradation in Chinese Hamster Ovary K1 cells. A total of 5,363 microbial cultures from fungi and actinomycetes were screened in this assay. Brefeldin A (1) from fungal cultures was found to promote the degradation of triacylglycerol (TG) with an EC₅₀ of 2.6 µM. Beauveriolides I (2), III (3), beauverolides A (4), B (5), and K (6) from fungal cultures showed potentiating effect on cholesteryl ester (CE) degradation with EC₅₀s ranging from 0.02 to 0.13 µM. Among these compounds, 2 and 6 exhibited the strongest activities (EC₅₀, 0.02 µM). From actinomycete cultures, oxohygrolidin (7) (EC₅₀ for TG and CE, > 1.7 and 0.8 µM, respectively) and hygrolidin (8) (EC₅₀ for TG and CE, 0.08 and 0.004 µM, respectively) promoted degradation of CE more preferably than TG.

Binding of phenochalasin A, an inhibitor of lipid droplet formation in mouse macrophages, on G-actin

Phenochalasin A, a unique phenol-containing cytochalasin produced by the marine-derived fungus Phomopsis sp. FT-0211, was originally discovered in a cell morphological assay of observing the inhibition of lipid droplet formation in mouse peritoneal macrophages. To investigate the mode of action and binding proteins, phenochalasin A was radio-labeled by ¹²⁵I. Iodinated phenochalasin A exhibited the same biological activity as phenochalasin A. [¹²⁵I]Phenochalasin A was found to be associated with an approximately 40 kDa protein, which was identified as G-actin. Furthermore, detail analyses of F-actin formation in Chinese hamster ovary cells (CHO-K1 cells) indicated that phenochalasin A (2 µM) caused elimination of F-actin formation on the apical site of the cells, suggesting that actin-oriented specific function(s) in cytoskeletal processes are affected by phenochalasin A.

Kimidinomycin, a new antibiotic against Mycobacterium avium complex, produced by Streptomyces sp. KKTA-0263

During our screening for antibiotics against Mycobacterium avium complex (MAC) with a mass spectrometry network-based indexing approach, a new compound named kimidinomycin was isolated from the culture broth of Streptomyces sp. KKTA-0263 by solvent extraction, HP20 column chromatography, and preparative HPLC. From the structural elucidation, the compound possesses a 38-membered macrolide structure with an N-methylguanidyl group at the terminal side chain. The compound exhibited antimycobacterial activity against M. avium, M. intracellulare, M. smegmatis, and M. bovis BCG with respective MIC values of 12.5, 0.78, 12.5, and 25.0 µg ml-1.

Novel angular naphthopyrone formation by Arp1p dehydratase involved in Aspergillus fumigatus melanin biosynthesis

Conidial pigment is an important virulence factor in Aspergillus fumigatus, a human fungal pathogen. The biosynthetic gene cluster for 1,8-dihydroxynaphthalene (DHN)-melanin in A. fumigatus consists of six genes, alb1, ayg1, arp1, arp2, abr1 and abr2. In contrast to black DHN-melanin fungi such as Magnaporthe grisea, the polyketide synthase Alb1p in A. fumigatus produces naphthopyrone YWA1 instead of 1,3,6,8-THN (T4HN) and YWA1 is converted to T4HN by Ayg1p. The yeast transformant expressing Alb1p and Arp1p dehydratase produced an unknown compound which was identified to be a novel angular naphthopyrone named YWA3 formed from YWA1. In addition, the amount of YWA3 produced was much more than that of YWA2 formed by non-enzymatic dehydration from YWA1. To further analyse the reaction in vitro, Arp1p was overexpressed in E. coli and purified. Kinetic analysis revealed Km value of Arp1p for YWA1 to be 41 μM which is comparable with that of Ayg1p for YWA1 in conversion to T4HN. The complex structure modelling well explained the mechanism of YWA3 generation by the dehydration of angular YWA1 by Arp1p. These results indicated the possibility that polymerization of angular naphthopyrone YWA3 but not YWA2 could be involved in the characteristic bluish-green conidial pigmentation of A. fumigatus.

Inhibitory effects of sesquiterpene lactones from the Indonesian marine sponge Lamellodysidea cf. herbacea on bone morphogenetic protein-induced osteoblastic differentiation

A new unique sesquiterpene lactone, bicyclolamellolactone A (1), was isolated together with two known monocyclofarnesol-type sesquiterpenes, lamellolactones A (2) and B (3), from the Indonesian marine sponge Lamellodysidea sp. (cf. L. herbacea). The planar structure of 1 was assigned based on its spectroscopic data (1D and 2D NMR, HRESIMS, UV, and IR spectra). The relative and absolute configuration of 1 was determined by comparison of its calculated and experimental electronic circular dichroism spectra in combination with NOESY correlations. Compounds 1-3 inhibited bone morphogenic protein (BMP)-induced alkaline phosphatase activity in mutant BMP receptor-carrying C2C12 cells with IC₅₀ values of 51, 4.6, and 20 μM, respectively.

Novel bicyclic pyrazoles as potent ALK2 (R206H) inhibitors for the treatment of fibrodysplasia ossificans progressiva

Mutant activin receptor-like kinase-2 (ALK2) is associated with the pathogenesis of fibrodysplasia ossificans progressiva, making it an attractive target for therapeutic intervention. We synthesized a new series of bicyclic pyrazoles and evaluated their mutant ALK2 enzyme inhibitory activities, leading to the identification of 8 as the most potent inhibitor. This compound showed moderate microsomal metabolic stability and human ether-a-go-go related gene (hERG) safety. In C2C12 cells carrying mutant ALK2 (R206H), 8 efficiently inhibited the bone morphogenetic protein (BMP)-induced alkaline phosphatase activity.

Development of an in vivo-mimic silkworm infection model with Mycobacterium avium complex

In vivo-mimic silkworm infection models with Mycobacterium avium and Mycobacterium intracellulare were newly established to evaluate the therapeutic effects of anti-M. avium complex (MAC) antibiotics. Silkworms raised at 37°C died within 72 hours of an injection of M. avium or M.intracellulare (2.5 × 10⁷ colony-forming unit (CFU)/larva·g) into the hemolymph. Clinical anti-mycobacterial (tuberculosis) antibiotics were evaluated under these conditions. Clarithromycin, kanamycin, streptomycin, amikacin, and ciprofloxacin exerted therapeutic effects in a dose-dependent manner, which was consistent with those in the mouse model. Furthermore, three effective actinomycete culture broths were selected in the screening program of our microbial broth library using the silkworm model, and four active metabolites, ohmyungsamycins A and B (1 and 2), chartreusin (3), and griseoviridin (4), were identified. Among these compounds, 1 showed the lowest 50% effective dose (ED₅₀) value (8.5 µg/larva·g), while 3 had the best ED₅₀/minimum inhibitory concentration (MIC) ratio (7.4). These results indicate that silkworm models are a useful tool for identifying anti-MAC antibiotics candidates with veritable therapeutic effects.

Screening for Small Molecule Inhibitors of BMP-Induced Osteoblastic Differentiation from Indonesian Marine Invertebrates

Fibrodysplasia ossificans progressiva (FOP) is a rare congenital disorder with heterotopic ossification (HO) in soft tissues. The abnormal activation of bone morphogenetic protein (BMP) signaling by a mutant activin receptor-like kinase-2 (ALK2) leads to the development of HO in FOP patients, and, thus, BMP signaling inhibitors are promising therapeutic applications for FOP. In the present study, we screened extracts of 188 Indonesian marine invertebrates for small molecular inhibitors of BMP-induced alkaline phosphatase (ALP) activity, a marker of osteoblastic differentiation in a C2C12 cell line stably expressing ALK2(R206H) (C2C12(R206H) cells), and identified five marine sponges with potent ALP inhibitory activities. The activity-guided purification of an EtOH extract of marine sponge Dysidea sp. (No. 256) resulted in the isolation of dysidenin (1), herbasterol (2), and stellettasterol (3) as active components. Compounds 1–3 inhibited ALP activity in C2C12(R206H) cells with IC₅₀ values of 2.3, 4.3, and 4.2 µM, respectively, without any cytotoxicity, even at 18.4–21.4 µM. The direct effects of BMP signaling examined using the Id1WT4F-luciferase reporter assay showed that compounds 1–3 did not decrease the reporter activity, suggesting that they inhibit the downstream of the Smad transcriptional step in BMP signaling.

Evaluation of Anti-Mycobacterial Compounds in a Silkworm Infection Model with Mycobacteroides abscessus

Among four mycobacteria, Mycobacterium avium, M. intracellulare, M. bovis BCG and Mycobacteroides (My.) abscessus, we established a silkworm infection assay with My. abscessus. When silkworms (fifth-instar larvae, n = 5) were infected through the hemolymph with My. abscessus (7.5 × 10⁷ CFU/larva) and bred at 37 °C, they all died around 40 h after injection. Under the conditions, clarithromycin and amikacin, clinically used antimicrobial agents, exhibited therapeutic effects in a dose-dependent manner. Furthermore, five kinds of microbial compounds, lariatin A, nosiheptide, ohmyungsamycins A and B, quinomycin and steffimycin, screened in an in vitro assay to observe anti-My. abscessus activity from 400 microbial products were evaluated in this silkworm infection assay. Lariatin A and nosiheptide exhibited therapeutic efficacy. The silkworm infection model with My. abscessus is useful to screen for therapeutically effective anti-My. abscessus antibiotics.

Penicillic Acid Congener, a New Inhibitor of BMP-Induced Alkaline Phosphatase Activity in Myoblasts, Produced by the Fungus Penicillium sp. BF-0343

During our screening for microbial regulators of bone metabolism, a new compound, 6-ethoxy-5,6-dihydropenillic acid (1), was isolated together with a known and structurally related penicillic acid (2) from the culture broth of the soil-derived fungus Penicillium sp. BF-0343. The structure of 1 was elucidated by various spectroscopic data including nuclear magnetic resonance experiments. Compounds 1 and 2 dose-dependently inhibited bone morphogenetic protein–induced alkaline phosphatase activity in myoblasts with half-maximal inhibitory concentration values of 19.8 and 2.1 μM, respectively.

New Terpendole Congeners, Inhibitors of Sterol O-Acyltransferase, Produced by Volutella citrinella BF-0440

New terpendoles N-P (1–3) were isolated along with 8 structurally related known compounds including terpendoles and voluhemins from a culture broth of the fungus Volutella citrinella BF-0440. The structures of 1–3 were elucidated using various spectroscopic experiments including 1D- and 2D-NMR. All compounds 1–3 contained a common indole–diterpene backbone. Compounds 2 and 3 had 7 and 6 consecutive ring systems with an indole ring, respectively, whereas 1 had a unique indolinone plus 4 consecutive ring system. Compounds 2 and 3 inhibited both sterol O-acyltransferase 1 and 2 isozymes, but 1 lost the inhibitory activity. Structure–activity relationships of fungal indole–diterpene compounds are discussed.

Voluhemins, new inhibitors of sterol O-acyltransferase, produced by Volutella citrinella BF-0440

New compounds, designated voluhemins A (1) and B (2), are isolated from the culture broth of the fungal strain Volutella citrinella BF-0440 along with structurally related known NK12838 (3). Spectroscopic data, including 1D and 2D NMR, elucidated their structures. Compounds 1-3 have a common indoline-diterpene core and two additional isoprenyl moieties. Compounds 1 and 3 contain a hemiaminal unit, while 2 is O-methylated 1. Their inhibitory activities toward sterol O-acyltransferase (SOAT) 1 and 2 isozymes in SOAT1- and SOAT2-expressing Chinese hamster ovary (CHO) cells show that 2 selectively inhibits the SOAT2 isozyme.

2-Epi-anthracimycin, a new cytotoxic agent from the marine-derived actinomycete Streptomyces sp. OPMA00631

A new cytotoxic agent designated as 2-epi-anthracimycin (1) was isolated along with anthracimycin and anthracimycin B (2-demethylanthracimycin) from the culture broth of the marine-derived actinomycete Streptomyces sp. OPMA00631. The structure of 1 was elucidated based on spectroscopic analyses (1D and 2D NMR data and ROESY correlations). Compound 1 exhibited cytotoxicity against Jurkat cells with an IC₅₀ value of 50.5 μM in 20 h. The effect of 1 on the cell cycle distribution of Jurkat cells was investigated. Compound 1 (7.80 μM) increased G1 phase cells from 51.1 to 62.0% and conversely, decreased G2 and M phase cells from 30.7 to 19.3 % in 20 h. At a higher concentration, 1 (250 μM) markedly increased subG1 phase cells (1.9% at 0 h to 16.5% at 20 h), while the proportion of G1 phase cells was maintained (62.3%). These results suggest that 1 exhibits cytotoxicity against Jurkat cells by arresting the cell cycle at the G1 phase.

Steffimycin E, a new anti-mycobacterial agent against Mycobacterium avium complex, produced by Streptomyces sp. OPMA02852

The marine actinomycete strain OPMA02852, identified as the genus Streptomyces, was found to produce anti-mycobacterial compounds against Mycobacterium avium complex (MAC). One new compound, designated as steffimycin E (1), was isolated together with three known steffimycins (steffimycin (2), 10-dihydrosteffimycin (3), and 8-demethoxysteffimycin (4)) from the culture broth of this producing microorganism by solvent extraction, ODS column chromatography, and preparative HPLC. Compound 1 has a tetracyclic quinone structure with a sugar moiety. Compound 1 exhibited anti-mycobacterial activity against M. intracellulare, M. bovis BCG, and M. smegmatis.

Inhibition of cholesteryl ester synthesis by polyacetylenes from Atractylodes rhizome

Using activity guided purification, four known compounds, sesquiterpene atractylenolide III (1), and the polyacetylenes 14-acetoxy-12-senecioyloxytetradeca-2E,8E,10E-trien-4,6-diyn-1-ol (2), 14-acetoxy-12-α-methylbutyl-2E,8E,10E-trien-4,6-diyn-1-ol (3), and 14-acetoxy-12-β -methylbutyl-2E,8E,10E-trien-4,6-diyn-1-ol (4), were isolated from a traditional herbal medicine, Atractylodes rhizome. Structurally similar 3 and 4 (3/4 mixture) were obtained as a mixture. In intact Chinese hamster ovary (CHO) K1 cell assays, 1, 2, and a 3/4 mixture selectively inhibited cholesterol [¹⁴C]oleate synthesis from [¹⁴C]oleate with IC₅₀ values of 73.5 µM, 35.4 µM, and 10.2 µM, respectively, without any effects on cytotoxicity. As a potential target of these inhibitors involved in cholesteryl ester (CE) synthesis, effects on sterol O-acyltransferase (SOAT) activity were investigated using microsomes prepared from CHO-K1 cells as an enzyme source. Hence, these compounds inhibit SOAT activity with IC₅₀ values (211 µM for 1, 29.0 µM for 2, and 11.8 µM for 3/4 mixture) that correlate well with those measured from intact cell assays. Our results strongly suggest that these compounds inhibit CE synthesis by blocking SOAT activity in CHO-K1 cells.

The Anti-atherogenic Activity of Beauveriolide Derivative BVD327, a Sterol O-Acyltransferase 2-Selective Inhibitor, in Apolipoprotein E Knockout Mice

The fungal 13-membered cyclodepsipeptides, beauveriolides I and III, were previously reported to be atheroprotective activity in mouse models via inhibiting sterol O-acyltransferase (SOAT) activity. A total of 149 beauveriolide derivatives (BVDs) synthesized combinatorially were evaluated in in silico absorption, distribution, metabolism and excretion (ADME) analysis and inhibitory activity toward the two SOAT isozymes, SOAT1 and SOAT2. Hence, only 11 BVDs exhibited SOAT2-selective inhibition. Among these, we chose BVD327, which had the highest ADME score, for further evaluation. BVD327 administration (50 mg/kg/d, per os (p.o.)) significantly decreased atherosclerotic lesions in the aorta and heart (25.4 ± 6.9 and 20.6 ± 2.9%, respectively) in apolipoprotein E knockout (Apoe-/-) mice fed a cholesterol-enriched diet (0.2% cholesterol and 21% fat) for 12 weeks. These findings indicate that beauveriolide derivatives can be used as anti-atherosclerotic agents.

An Unusual Extender Unit Is Incorporated into the Modular Polyketide Synthase of Scopranones Biosynthesis

Scopranones, produced by Streptomyces sp. BYK-11038, are the novel bone morphogenetic protein inhibitors characterized by atypical two scoop-like moieties and a 3-furanone moiety. Two scoop-like moieties connected to a 3-furanone have not previously been reported in natural products, and their biosynthesis must occur via a unique pathway. Feeding experiments using ¹³C-labeled precursors indicated that scopranones were synthesized from three acetates and three butyrates in polyketide-type biosynthesis. Genome mining of Streptomyces sp. BYK-11038 revealed that the candidate biosynthetic gene cluster contains 21 open reading frames (ORFs), including three modular polyketide synthases (PKSs; SprA, SprB, and SprC), which were composed of 4 modules with one loading module and 18 additional ORFs (SprD to SprU) spanning a distance of 55 kbp. The characterization of in-frame deletion mutants and feeding experiments with the predicted extender units indicated that two genes, sprP and sprR, encoding discrete 3-oxoacyl-ACP synthases, and a gene, sprO, encoding crotonyl-CoA reductase, were involved in assembling an unusual C₈ branched extender unit, 2-(2-ethylbutyl)malonyl-CoA. Additionally, three ORFs, sprM, sprN, and sprT, encoding cytochrome P450s and a monooxygenase, are important tailoring enzymes in post-PKS modification. SprT is an essential enzyme for decarboxylative ring contraction via oxidation, which converts the 2-pyranone to a 3-furanone.

Nectriatide, a Potentiator of Amphotericin B Activity from Nectriaceae sp. BF-0114

A new compound, designated nectriatide (1), was isolated as a potentiator of amphotericin B (AmB) activity against Candida albicans from the culture broth of Nectriaceae sp. BF-0114. This structure was elucidated based on spectroscopic analyses (1D and 2D NMR data), chemical methods, and total synthesis. Compound 1 was a unique cyclotetrapeptide consisting of l-N-methyltyrosine, anthranilic acid, l-alanine, and l-valine. Compound 1 and several synthetic derivatives, including linear peptides, potentiated AmB activity against C. albicans by up to 16-fold (the MIC value of AmB decreased from 0.5 μg/mL to 0.031 μg/mL in combination with test compound).

Inhibition of neutral lipid synthesis by avarols from a marine sponge

The effects of 14 sesquiterpene hydroquinones, including 8 marine sponge-derived avarols (1-8) and 6 semisynthetic derivatives (9-14), on lipid droplet accumulation and neutral lipid synthesis in Chinese hamster ovary (CHO) K1 cells were investigated. In intact CHO-K1 cell assays, avarol (1) markedly decreased the number and size of lipid droplets in CHO-K1 cells and exhibited the most potent inhibitory activity on the synthesis of cholesteryl ester (CE) and triglyceride (TG) with IC₅₀ values of 5.74 and 6.80 µM, respectively. In enzyme assays, sterol O-acyltransferase (SOAT), the final enzyme involved in CE biosynthesis, and diacylglycerol acyltransferase (DGAT), the final enzyme involved in TG biosynthesis, were inhibited by 1 with IC₅₀ values of 7.31 and 20.0 µM, respectively, which correlated well with those obtained in the intact cell assay. These results strongly suggest that 1 inhibited SOAT and DGAT activities in CHO-K1 cells, leading to a reduction in the accumulation of CE and TG in lipid droplets.

Total Synthesis and Absolute Configuration of Simpotentin, a Potentiator of Amphotericin B Activity

The total synthesis of simpotentin (1), a new potentiator of amphotericin B activity against Candida albicans, was achieved. Our research results enabled the access of all stereoisomers of 1 and the elucidation of the unknown absolute configuration of 1. Furthermore, one of the stereoisomers is a better amphotericin B potentiator than 1 and is an excellent lead compound for the development of a novel amphotericin B potentiator.

Stereoisomer-Specific Induction of G2/M Phase Arrest and Apoptosis by 9-(E,Z)-Hydroxyoctadecadienoic Acid in Mouse Lymphoma Cells

Hydroxyoctadecadienoic acids (HODEs) are generated by oxidation of linoleic acid in vivo and thought to mediate various pathophysiological responses. In this study, we examined the effects of HODEs on EL4 mouse lymphoma cell growth and found that 9-(E,Z)-HODE inhibited EL4 cell growth in a dose-dependent manner, whereas no such growth inhibition was observed with other isomers (9-(E,E)-, 13-(Z,E)-, or 13-(E,E)-HODE), suggesting that the growth-inhibitory effect of HODEs was stereospecific. Analysis by flow cytometry (FACS) with annexin V and propidium iodide (PI) staining showed that 9-(E,Z)-HODE induced apoptosis with G2/M phase arrest. We next examined the growth inhibition profile of 9-(E,Z)-HODE against a panel of 39 human cancer cell lines (JFCR39). The fingerprint of growth inhibition by 9-(E,Z)-HODE exhibited a high degree of similarity to that by MLN4924, an inhibitor of NEDD8-activating enzyme. The intracellular NEDD8 (ubiquitin-like protein) expression in EL4 cells was decreased by the treatment with 9-(E,Z)-HODE as assessed by immunoblotting and flow cytometry. In conclusion, 9-(E,Z)-HODE specifically induced G2/M phase arrest and apoptosis, and the decrease of NEDD8 expression might be involved in this effect.

Discovery of Nosiheptide, Griseoviridin, and Etamycin as Potent Anti-Mycobacterial Agents against Mycobacterium avium Complex

Mycobacterium avium complex (MAC) is a serious disease mainly caused by M. avium and M. intracellulare. Although the incidence of MAC infection is increasing worldwide, only a few agents are clinically used, and their therapeutic effects are limited. Therefore, new anti-MAC agents are needed. Approximately 6600 microbial samples were screened for new anti-mycobacterial agents that inhibit the growth of both M. avium and M. intracellulare, and two culture broths derived from marine actinomycete strains OPMA1245 and OPMA1730 had strong activity. Nosiheptide (1) was isolated from the culture broth of OPMA1245, and griseoviridin (2) and etamycin (viridogrisein) (3) were isolated from the culture broth of OPMA1730. They had potent anti-mycobacterial activity against M. avium and M. intracellulare with minimum inhibitory concentrations (MICs) between 0.024 and 1.56 μg/mL. In addition, a combination of 2 and 3 markedly enhanced the anti-mycobacterial activity against both M. avium and M. intracellulare. Furthermore, a combination 2 and 3 had a therapeutic effect comparable to that of ethambutol in a silkworm infection assay with M. smegmatis.

Simpotentin, a new potentiator of amphotericin B activity against Candida albicans, produced by Simplicillium minatense FKI-4981

Simpotentin, a new potentiator of amphotericin B activity against Candida albicans and Cryptococcus neoformans, was isolated from the culture broth of Simplicillium minatense FKI-4981 by Diaion HP-20 column chromatography, centrifugal partition chromatography, and preparative HPLC. The structure of simpotentin was elucidated by spectroscopic analyses including NMR and MS. The compound has a mannose core to which two medium-chain fatty acids are linked. Simpotentin was found to potentiate amphotericin B activity against C. albicans by the microdilution method.

Celludinones, new inhibitors of sterol O-acyltransferase, produced by Talaromyces cellulolyticus BF-0307

New indanones, designated celludinones A ((±)-1) and B (2), were isolated from the culture broth of the fungal strain Talaromyces cellulolyticus BF-0307. The structures of celludinones were elucidated by spectroscopic data, including 1D and 2D NMR. Celludinone A was found to be a mixture of racemic isomers ((±)-1), which were isolated by a chiral column. Compounds (+)-1 and (-)-1 inhibited the sterol O-acyltransferase (SOAT) 1 and 2 isozymes in a cell-based assay using SOAT1- and SOAT2-expressing Chinese hamster ovary (CHO) cells, while 2 selectively inhibited the SOAT2 isozyme.

A Mixture of Atropisomers Enhances Neutral Lipid Degradation in Mammalian Cells with Autophagy Induction

Atropisomers with a biaryl dihydronaphthopyranone structure, dinapinones A1 (DPA1) (M position) and A2 (DPA2) (P position), were isolated from the fungus culture broth of Talaromyces pinophilus FKI-3864 as inhibitors of [14C]neutral lipid ([14C]triacylglycerol (TG) and [14C]cholesteryl ester (CE)) synthesis from [14C]oleic acid in Chinese hamster ovary-K1 (CHO-K1) cells. DPA2 inhibited [14C]TG and [14C]CE synthesis (IC50s, 0.65 and 5.6 μM, respectively), but DPA1 had no inhibitory activity on [14C]TG and [14C]CE synthesis even at 12 μM. However, a 1:1 mixture of DPA1 and DPA2 (DPAmix) had the most potent inhibitory activity on [14C]TG and [14C]CE synthesis (IC50s, 0.054 and 0.18 μM, respectively). The mechanism of action of DPAmix was investigated. DPAmix had no effects on the enzymes involved in neutral lipid synthesis, while DPAmix enhanced the degradation of [14C]neutral lipids with concomitant decrease in cytosolic lipid droplets accumulated in CHO-K1 cells. From analysis of autophagy marker proteins, DPAmix caused dose-dependent induction of microtubule-associated protein light chain 3-II (LC3-II) and degradation of p62. In the autophagic flux assay using bafilomycin A1, DPAmix upregulated autophagosome turnover. These results reveal that DPAmix enhances neutral lipid degradation together with induction of autophagy.

Scopranones with Two Atypical Scooplike Moieties Produced by Streptomyces sp. BYK-11038

Three new compounds, designated scopranones A-C, were isolated from the culture broth of a soil isolate, Streptomyces sp. BYK-11038, and shown to be inhibitors of bone morphogenetic protein (BMP) induced alkaline phosphatase activity in a BMP receptor mutant cell line. The structures were elucidated using NMR and other spectral data. The scopranones have an unusual structure with two atypical scooplike moieties linked at the tails to form part of a unique 3-furanone ring.

Anti-Rhizopus activity of tanzawaic acids produced by the hot spring-derived fungus Penicillium sp. BF-0005

A silkworm infection assay with the pathogenic fungus Rhizopus oryzae was established. Microbial culture broths were screened for anti-Rhizopus antibiotics using this assay. A new compound, tanzawaic acid R was isolated along with known and structurally related tanzawaic acids and arohynapene A from the culture broth of the hot spring-derived fungus Penicillium sp. BF-0005. The structure of tanzawaic acid R was elucidated by various spectroscopic data including 1D and 2D nuclear magnetic resonance spectroscopy. Tanzawaic acids A, B, C, and R and arohynapene A exhibited antifungal activity against R. oryzae. Tanzawaic acids A and B dose-dependently exerted therapeutic effects in the silkworm infection assay with R. oryzae.

Design and Synthesis of A-Ring Simplified Pyripyropene A Analogues as Potent and Selective Synthetic SOAT2 Inhibitors

Currently, pyripyropene A, which is isolated from the culture broth of Aspergillus fumigatus FO-1289, is the only compound known to strongly and selectively inhibit the isozyme sterol O-acyltransferase 2 (SOAT2). To aid in the development of new cholesterol-lowering or anti-atherosclerotic agents, new A-ring simplified pyripyropene A analogues have been designed and synthesized based on total synthesis, and the results of structure-activity relationship studies of pyripyropene A. Among the analogues, two A-ring simplified pyripyropene A analogues exhibited equally efficient SOAT2 inhibitory activity to that of natural pyripyropene A. These new analogues are the most potent and selective SOAT2 inhibitors to be used as synthetic compounds and attractive seed compounds for the development of drug for dyslipidemia, including atherosclerotic disease and steatosis.

Saturated Fatty Acids Undergo Intracellular Crystallization and Activate the NLRP3 Inflammasome in Macrophages

OBJECTIVE

Inflammation provoked by the imbalance of fatty acid composition, such as excess saturated fatty acids (SFAs), is implicated in the development of metabolic diseases. Recent investigations suggest the possible role of the NLRP3 (nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain containing 3) inflammasome, which regulates IL-1β (interleukin 1β) release and leads to inflammation, in this process. Therefore, we investigated the underlying mechanism by which SFAs trigger NLRP3 inflammasome activation.

APPROACH AND RESULTS

The treatment with SFAs, such as palmitic acid and stearic acid, promoted IL-1β release in murine primary macrophages while treatment with oleic acid inhibited SFA-induced IL-1β release in a dose-dependent manner. Analyses using polarized light microscopy revealed that intracellular crystallization was provoked in SFA-treated macrophages. As well as IL-1β release, the intracellular crystallization and lysosomal dysfunction were inhibited in the presence of oleic acid. These results suggest that SFAs activate NLRP3 inflammasome through intracellular crystallization. Indeed, SFA-derived crystals activated NLRP3 inflammasome and subsequent IL-1β release via lysosomal dysfunction. Excess SFAs also induced crystallization and IL-1β release in vivo. Furthermore, SFA-derived crystals provoked acute inflammation, which was impaired in IL-1β-deficient mice.

CONCLUSIONS

These findings demonstrate that excess SFAs cause intracellular crystallization and subsequent lysosomal dysfunction, leading to the activation of the NLRP3 inflammasome, and provide novel insights into the pathogenesis of metabolic diseases.

Biseokeaniamides A, B, and C, Sterol O-Acyltransferase Inhibitors from an Okeania sp. Marine Cyanobacterium

Biseokeaniamides A, B, and C (1-3), structurally novel sterol O-acyltransferase (SOAT) inhibitors, were isolated from an Okeania sp. marine cyanobacterium. Their structures were elucidated by spectroscopic analyses and degradation reactions. Biseokeaniamide B (2) exhibited moderate cytotoxicity against human HeLa cancer cells, and compounds 1-3 inhibited both SOAT1 and SOAT2, not only at an enzyme level but also at a cellular level. Biseokeaniamides (1-3) are the first linear lipopeptides that have been shown to exhibit SOAT-inhibitory activity.

Isomethoxyneihumicin, a new cytotoxic agent produced by marine Nocardiopsis alba KM6-1

A new cytotoxic agent designated isomethoxyneihumicin (1 and 2), a mixture of lactam-lactim tautomers, was isolated along with methoxyneihumicin (3) from the culture broth of the marine Nocardiopsis alba KM6-1. The structures of 1 and 2 were elucidated in spectroscopic analyses (1D and 2D NMR data, and ROESY correlations). Isomethoxyneihumicin (15.0 μM) and 3 (15.0 μM) arrested the cell cycle of Jurkat cells at the G2/M phase (66 and 67%) in 12 h. Isomethoxyneihumicin and 3 exhibited cytotoxicity against Jurkat cells with IC₅₀ values of 6.98 and 30.5 μM in 20 h, respectively. These results strongly suggest that isomethoxyneihumicin and 3 exhibit cytotoxicity against Jurkat cells by inhibiting the cell cycle at the G2/M phase.

Discovery of SOAT2 inhibitors from synthetic small molecules

Synthesis of new functionalized molecules and identification of biofunctional molecules can lead to the development of therapeutic leads and molecular tools for biomedical research. We have recently reported oxa-hetero-Diels-Alder reactions of enones with isatins to provide functionalized spirooxindole tetrahydropyran derivatives. Twenty-one compounds from the spirooxindole tetrahydropyran derivatives and related molecules were screened for inhibition of sterol O-acyltransferase (SOAT) isozymes SOAT1 and SOAT2. Three racemic derivatives inhibited the SOAT2 isozyme with three-fold or better selectivity for SOAT2 than for SOAT1. The enantiomerically enriched forms of the most efficient racemic inhibitor of SOAT2 were further evaluated; one enantiomer inhibited SOAT2 with an IC50 of 1.5μM and was 10-fold more selective for SOAT2 than SOAT1.

Beauvericin counteracted multi-drug resistant Candida albicans by blocking ABC transporters

Multi-drug resistance of pathogenic microorganisms is becoming a serious threat, particularly to immunocompromised populations. The high mortality of systematic fungal infections necessitates novel antifungal drugs and therapies. Unfortunately, with traditional drug discovery approaches, only echinocandins was approved by FDA as a new class of antifungals in the past two decades. Drug efflux is one of the major contributors to multi-drug resistance, the modulator of drug efflux pumps is considered as one of the keys to conquer multi-drug resistance. In this study, we combined structure-based virtual screening and whole-cell based mechanism study, identified a natural product, beauvericin (BEA) as a drug efflux pump modulator, which can reverse the multi-drug resistant phenotype of Candida albicans by specifically blocking the ATP-binding cassette (ABC) transporters; meantime, BEA alone has fungicidal activity in vitro by elevating intracellular calcium and reactive oxygen species (ROS). It was further demonstrated by histopathological study that BEA synergizes with a sub-therapeutic dose of ketoconazole (KTC) and could cure the murine model of disseminated candidiasis. Toxicity evaluation of BEA, including acute toxicity test, Ames test, and hERG (human ether-à-go-go-related gene) test promised that BEA can be harnessed for treatment of candidiasis, especially the candidiasis caused by ABC overexpressed multi-drug resistant C. albicans.

Simplifungin and Valsafungins, Antifungal Antibiotics of Fungal Origin

The targets of antifungal antibiotics in clinical use are more limited than those of antibacterial antibiotics. Therefore, new antifungal antibiotics with different mechanisms of action are desired. In the course of our screening for antifungal antibiotics of microbial origins, new antifungal antibiotics, simplifungin (1) and valsafungins A (2) and B (3), were isolated from cultures of the fungal strains Simplicillium minatense FKI-4981 and Valsaceae sp. FKH-53, respectively. The structures of 1 to 3 including their absolute stereochemistries were elucidated using various spectral analyses including NMR and collision-induced dissociation (CID)-MS/MS as well as chemical approaches including modifications to the Mosher's method. They were structurally related to myriocin. They inhibited the growth of yeast-like and zygomycetous fungi with MICs ranging between 0.125 and 8.0 μg/mL. An examination of their mechanisms of action by the newly established assay using LC-MS revealed that 1 and 2 inhibited serine palmitoyltransferase activity, which is involved in sphingolipid biosynthesis, with IC50 values of 224 and 24 nM, respectively.

Pyranonigrin L, a New Antioxidant, Produced by the Hot Spring-derived Fungus Penicillium adametzii BF-0003

A new antioxidant, designated pyranonigrin L, was isolated from the culture materials of the hot spring-derived fungus Penicillium adametzii BF-0003 by solvent extraction, ODS column chromatography, and HPLC. Its planar structure was elucidated using various analytical techniques including UV, IR, and NMR spectroscopy and MS. Its absolute configuration was determined by a comparison of its circular dichroism (CD) spectrum with those of structurally related compounds. Pyranonigrin L was found to exhibit anti-oxidative activity with an EC50 value of 553 μM.