Isolation, Synthesis, and Biological Activity of Chlorinated Alkylresorcinols from Dictyostelium Cellular Slime Molds

Eight chlorinated alkylresorcinols, monochasiol A-H (1-8), were isolated from the fruiting bodies of Dictyostelium monochasioides. Compounds 1-8 were synthesized to confirm their structures and to obtain sufficient material for performing biological tests. Monochasiol A (1) selectively inhibited the concanavalin A-induced interleukin-2 production in Jurkat cells, a human T lymphocyte cell line. Monochasiols were biogenetically synthesized by the combination of biosynthetic enzymes relating to the principal polyketides, MPBD and DIF-1, produced by Dictyostelium discoideum.

Evidence that differentiation-inducing factor-1 controls chemotaxis and cell differentiation, at least in part, via mitochondria in D. discoideum

Differentiation-inducing factor-1 [1-(3,5-dichloro-2,6-dihydroxy-4-methoxyphenyl)hexan-1-one (DIF-1)] is an important regulator of cell differentiation and chemotaxis in the development of the cellular slime mold Dictyostelium discoideum However, the entire signaling pathways downstream of DIF-1 remain to be elucidated. To characterize DIF-1 and its potential receptor(s), we synthesized two fluorescent derivatives of DIF-1, boron-dipyrromethene (BODIPY)-conjugated DIF-1 (DIF-1-BODIPY) and nitrobenzoxadiazole (NBD)-conjugated DIF-1 (DIF-1-NBD), and investigated their biological activities and cellular localization. DIF-1-BODIPY (5 µM) and DIF-1 (2 nM) induced stalk cell differentiation in the DIF-deficient strain HM44 in the presence of cyclic adenosine monosphosphate (cAMP), whereas DIF-1-NBD (5 µM) hardly induced stalk cell differentiation under the same conditions. Microscopic analyses revealed that the biologically active derivative, DIF-1-BODIPY, was incorporated by stalk cells at late stages of differentiation and was localized to mitochondria. The mitochondrial uncouplers carbonyl cyanide m-chlorophenylhydrazone (CCCP), at 25-50 nM, and dinitrophenol (DNP), at 2.5-5 µM, induced partial stalk cell differentiation in HM44 in the presence of cAMP. DIF-1-BODIPY (1-2 µM) and DIF-1 (10 nM), as well as CCCP and DNP, suppressed chemotaxis in the wild-type strain Ax2 in shallow cAMP gradients. These results suggest that DIF-1-BODIPY and DIF-1 induce stalk cell differentiation and modulate chemotaxis, at least in part, by disturbing mitochondrial activity.

Induction of Osteopontin by Dengue Virus-3 Infection in THP-1 Cells: Inhibition of the Synthesis by Brefelamide and Its Derivative

Osteopontin (OPN) is a multifunctional matricellular protein produced by a broad range of cells including osteoclasts, macrophages, T cells, endothelial cells, and vascular smooth muscle cells. OPN modulates various physiological and pathological events such as inflammation, wound healing, and bone formation and remodeling. Dengue virus (DENV) infection causes an increase in plasma OPN levels, which is correlated with the severity of symptoms and coagulation abnormalities. DENV infection also induces OPN gene expression in human macrophages. This study investigated the inhibitory effects of brefelamide and its methyl ether derivative on DENV-3 by measuring changes in OPN levels in human THP-1 and 293T cell lines infected at different multiplicities of infection and post-infection time points. OPN mRNA expression and viral RNA were detected by reverse transcriptase quantitative real-time PCR, whereas protein level was determined by enzyme-linked immunosorbent assay. We found that viral copy number was higher in 293T than in THP-1 cells. However, THP-1 constitutively expressed higher levels of OPN mRNA and protein, which were enhanced by DENV-3 infection. Brefelamide and its derivative suppressed OPN production in DENV-3 infected THP-1 cells; the effective doses of these compounds had no effect on uninfected cells, indicating low cytotoxicity. These results suggest that brefelamide and its methyl ether derivative have therapeutic effects in preventing inflammation, coagulopathy, and fibrinolysis caused by OPN upregulation induced by DENV-3 infection.

Halofuginone enhances the chemo-sensitivity of cancer cells by suppressing NRF2 accumulation

The KEAP1-NRF2 system regulates the cellular defence against oxidative and xenobiotic stresses. NRF2 is a transcription factor that activates the expression of cytoprotective genes encoding antioxidative, detoxifying and metabolic enzymes as well as transporters. Under normal conditions, KEAP1 represses NRF2 activity by degrading the NRF2 protein. When cells are exposed to stresses, KEAP1 stops promoting NRF2 degradation, and NRF2 rapidly accumulates and activates the transcription of target genes. Constitutive accumulation of NRF2 via a variety of mechanisms that disrupt KEAP1-mediated NRF2 degradation has been observed in various cancer types. Constitutive NRF2 accumulation confers cancer cells with a proliferative advantage as well as resistance to anti-cancer drugs and radiotherapies. To suppress the chemo- and radio-resistance of cancer cells caused by NRF2 accumulation, we conducted high-throughput chemical library screening for NRF2 inhibitors and identified febrifugine derivatives. We found that application of the less-toxic derivative halofuginone in a low dose range rapidly reduced NRF2 protein levels. Halofuginone induced a cellular amino acid starvation response that repressed global protein synthesis and rapidly depleted NRF2. Halofuginone treatment ameliorated the resistance of NRF2-addicted cancer cells to anti-cancer drugs both in vitro and in vivo. These results provide preclinical proof-of-concept evidence for halofuginone as an NRF2 inhibitor applicable to treatment of chemo- and radio-resistant forms of cancer.

Monoterpene Indole Alkaloid-Like Compounds Based on Diversity-Enhanced Extracts of Iridoid-Containing Plants and Their Immune Checkpoint Inhibitory Activity

A library of iridoid-conjugated indole alkaloid-like compounds was constructed from diversity-enhanced extracts, which constitutes an approach for increasing the chemical diversity of natural-product-like compounds by combining natural product chemistry and diversity-oriented synthesis. Pharmacological screening of the library revealed a seed compound that can be used for the development of small molecular immune checkpoint inhibitors.

Hypofibrinolytic Activity after Total Joint Replacement

Tissue-type plasminogen activator (t-PA), tissue-type plasminogen activator inhibitor (t-PAI), and other factors (platelets, fibrinogen, fibrinogen degrada tion products, antithrombin-III, plasminogen, and α2-plasmin inhibitor [α2-PI]) related to the fibrinolytic system were studied in 21 patients undergoing total joint replacement.

Seventeen of the 21 patients revealed an impaired fibrinolytic activity from the first to seventh postoperative day and a subsequent return to the preopera tive level by the fourteenth postoperative day. There were accompanying increases in the level of α2-PI and in the t-PAI/t-PA ratio, and there was decrease in plas minogen level. Such hypofibrinolytic states may be related to a higher incidence of postoperative thrombosis in total joint replacement patients.

Tension-Type Headache and Physical Activity: An Actigraphic Study

There have been some studies on the relationship between tension-type headache (TTH) and physical activity. However, most previous studies were not prospective and assessed physical activity by questionnaire. Therefore, this study was aimed to investigate the relationship between TTH intensity and physical activity prospectively utilizing computerized ecological momentary assessment and actigraphy Thirty-one TTH patients wore watch-type computers equipped with actigraphy inside for 1 week to record momentary headache intensity and physical activity. Multilevel modelling was used to investigate the effect of headache intensity on the simultaneous and subsequent activity level. There were significant negative associations between headache intensity and the simultaneous and subsequent activity level, and activity level was significantly reduced at headache exacerbations. These results provide objective and quantitative evidence suggesting that TTH negatively affects physical activity.

Design and Synthesis of Structure-Simplified Derivatives of Gonytolide for the Promotion of Innate Immune Responses

Gonytolide A (1), a dimeric chromanone substituted with the γ-lactone, shows promoting activity of innate immune responses. However, biological studies on this compound have been limited by the low amounts of 1 available from natural resources and the difficulty of its synthesis. In this study, we designed and synthesized structure-simplified gonytolide derivatives. Bischromone 10 and biflavone 13 both promoted the mammalian TNF-α signaling pathway and Drosophila innate immunity. They did not contain a chiral center and were easy to synthesize. Hence, they can be used as lead compounds for a new type of immunostimulating drugs and as research reagents.

Oral administration of Dictyostelium differentiation-inducing factor 1 lowers blood glucose levels in streptozotocin-induced diabetic rats

AIMS

Differentiation-inducing factor 1 (DIF-1), originally discovered in the cellular slime mold Dictyostelium discoideum, and its derivatives possess pharmacological activities, such as the promotion of glucose uptake in non-transformed mammalian cells in vitro. Accordingly, DIFs are considered promising lead candidates for novel anti-diabetic drugs. The aim of this study was to assess the anti-diabetic and toxic effects of DIF-1 in mouse 3T3-L1 fibroblast cells in vitro and in diabetic rats in vivo. Main methods We investigated the in vitro effects of DIF-1 and DIF-1(3M), a derivative of DIF-1, on glucose metabolism in 3T3-L1 cells by using capillary electrophoresis time-of-flight mass spectrometry (CE-TOF-MS). We also examined the effects of DIF-1 on blood glucose levels in streptozotocin (STZ)-induced rats.

KEY FINDINGS

CE-TOF-MS revealed that 20μM DIF-1 and 20μM DIF-1(3M) promoted glucose uptake and metabolism in 3T3-L1 cells. Oral administration of DIF-1 (30mg/kg) significantly lowered basal blood glucose levels in STZ-treated rats and promoted a decrease in blood glucose levels after oral glucose loading (2.5g/kg) in the rats. In addition, daily oral administration of DIF-1 (30mg/kg/day) for 1wk significantly lowered the blood glucose levels in STZ-treated rats but did not affect their body weight and caused only minor alterations in the levels of other blood analytes.

SIGNIFICANCE

These results indicate that DIF-1 may be a good lead compound for the development of anti-diabetic drugs.

Agarol, an ergosterol derivative from Agaricus blazei, induces caspase-independent apoptosis in human cancer cells

Agaricus blazei (A. blazei) is a mushroom with many biological effects and active ingredients. We purified a tumoricidal substance from A. blazei, an ergosterol derivative, and named it 'Agarol'. Cytotoxic effects of Agarol were determined by the MTT assay using A549, MKN45, HSC-3, and HSC-4 human carcinoma cell lines treated with Agarol. Apoptosis was detected by flow cytometry analysis. Reactive oxygen species (ROS) levels and mitochondria membrane potential (∆ψm) were also determined by flow cytometry. Western blot analysis was used to quantify the expression of apoptosis-related proteins. Agarol predominantly induced apoptosis in two p53-wild cell lines (A549 and MKN45) compared to the other p53-mutant cell lines (HSC-3 and HSC-4). Further mechanistic studies revealed that induction of apoptosis is associated with increased generation of ROS, reduced ∆ψm, release of apoptosis-inducing factor (AIF) from the mitochondria to the cytosol, upregulation of Bax, and downregulation of Bcl-2. Caspase-3 activities did not increase, and z-VAD-fmk, a caspase inhibitor, did not inhibit the Agarol-induced apoptosis. These findings indicate that Agarol induces caspase-independent apoptosis in human carcinoma cells through a mitochondrial pathway. The in vivo anticancer activity of Agarol was confirmed in a xenograft murine model. This study suggests a molecular mechanism by which Agarol induces apoptosis in human carcinoma cells and indicates the potential use of Agarol as an anticancer agent.

A Derivative of Differentiation-Inducing Factor-3 Inhibits PAK1 Activity and Breast Cancer Cell Proliferation

Differentiation-inducing factors 1-3 (DIFs 1-3), chlorinated alkylphenones identified in the cellular slime mold Dictyostelium discoideum, are considered anti-tumor agents because they inhibit proliferation of a variety of mammalian tumor cells in vitro. Although the anti-proliferative effects of DIF-1 and DIF-3 are well-documented, the precise molecular mechanisms underlying the actions of DIFs have not been fully elucidated. In this study, we examined the effects of DIFs and their derivatives on PAK1, a key serine-threonine kinase, which is activated by multiple ligands and regulates cell proliferation. We examined the effect of DIF derivatives on PAK1 kinase activity in cells. We also examined the effect of DIF-3(+1) derivative on PAK1 kinase activity in vitro, cyclin D1 promoter activity and breast cancer cell proliferation. It was found that some derivatives strongly inhibited PAK1 kinase activity in human breast cancer MCF-7 cells stably over expressing PAK1. Among the derivatives, DIF-3(+1) was most potent, which directly inhibited kinase activity of recombinant purified PAK1 in an in vitro kinase assay. Furthermore, DIF-3(+1) strongly inhibited both cyclin D1 promoter activity and proliferation of MCF-7 and T47D breast cancer cells stably over expressing PAK1 in response to prolactin, estrogen, epidermal growth factor and heregulin. In the present study we propose PAK1 as DIF-3(+1) target mediating its anti-proliferative effect.

Isolation of a Cyclic Depsipetide, Aspergillicin F, and Synthesis of Aspergillicins with Innate Immune-Modulating Activity

Innate immunity is the front line of self-defense against microbial infection. After searching for natural compounds that regulate innate immunity using an ex vivo Drosophila culture system, we identified a new cyclic depsipeptide, aspergillicin F, from the fungus Aspergillus sp., as an innate immune suppressor. The total synthesis and biological evaluation of the aspergillicin family, including aspergillicin F, were performed, revealing that slight structural differences in the side chains of amino acid residues alter innate immunity-regulating activity.

A giant polymer lattice in a polymer-stabilized blue phase liquid crystal

Ultrasmall-angle synchrotron X-ray scattering measurements showed that a three-dimensional polymer lattice of a few 100 nm order with body-centered cubic O(8-) symmetry was formed in a polymer-stabilized blue phase liquid crystal. We obtained clear experimental evidence that the polymer chains condensed selectively in the disclinations within the blue phase during photo-polymerization of monomers in the blue phase.

Derivatives of Dictyostelium differentiation-inducing factors inhibit lysophosphatidic acid-stimulated migration of murine osteosarcoma LM8 cells

Osteosarcoma is a common metastatic bone cancer that predominantly develops in children and adolescents. Metastatic osteosarcoma remains associated with a poor prognosis; therefore, more effective anti-metastatic drugs are needed. Differentiation-inducing factor-1 (DIF-1), -2, and -3 are novel lead anti-tumor agents that were originally isolated from the cellular slime mold Dictyostelium discoideum. Here we investigated the effects of a panel of DIF derivatives on lysophosphatidic acid (LPA)-induced migration of mouse osteosarcoma LM8 cells by using a Boyden chamber assay. Some DIF derivatives such as Br-DIF-1, DIF-3(+2), and Bu-DIF-3 (5-20 μM) dose-dependently suppressed LPA-induced cell migration with associated IC50 values of 5.5, 4.6, and 4.2 μM, respectively. On the other hand, the IC50 values of Br-DIF-1, DIF-3(+2), and Bu-DIF-3 versus cell proliferation were 18.5, 7.2, and 2.0 μM, respectively, in LM8 cells, and >20, 14.8, and 4.3 μM, respectively, in mouse 3T3-L1 fibroblasts (non-transformed). Together, our results demonstrate that Br-DIF-1 in particular may be a valuable tool for the analysis of cancer cell migration, and that DIF derivatives such as DIF-3(+2) and Bu-DIF-3 are promising lead anti-tumor agents for the development of therapies that suppress osteosarcoma cell proliferation, migration, and metastasis.

Structure of Prolyl-tRNA Synthetase-Halofuginone Complex Provides Basis for Development of Drugs against Malaria and Toxoplasmosis

The Chinese herb Dichroa febrifuga has traditionally treated malaria-associated fever. Its active component febrifugine (FF) and derivatives such as halofuginone (HF) are potent anti-malarials. Here, we show that FF-based derivatives arrest parasite growth by direct interaction with and inhibition of the protein translation enzyme prolyl-tRNA synthetase (PRS). Dual administration of inhibitors that target different tRNA synthetases suggests high utility of these drug targets. We reveal the ternary complex structure of PRS-HF and adenosine 5'-(β,γ-imido)triphosphate where the latter facilitates HF integration into the PRS active site. Structural analyses also highlight spaces within the PRS architecture for HF derivatization of its quinazolinone, but not piperidine, moiety. We also show a remarkable ability of HF to kill the related human parasite Toxoplasma gondii, suggesting wider HF efficacy against parasitic PRSs. Hence, our cell-, enzyme-, and structure-based data on FF-based inhibitors strengthen the case for their inclusion in anti-malarial and anti-toxoplasmosis drug development efforts.

Weight loss by Ppc-1, a novel small molecule mitochondrial uncoupler derived from slime mold

Mitochondria play a key role in diverse processes including ATP synthesis and apoptosis. Mitochondrial function can be studied using inhibitors of respiration, and new agents are valuable for discovering novel mechanisms involved in mitochondrial regulation. Here, we screened small molecules derived from slime molds and other microorganisms for their effects on mitochondrial oxygen consumption. We identified Ppc-1 as a novel molecule which stimulates oxygen consumption without adverse effects on ATP production. The kinetic behavior of Ppc-1 suggests its function as a mitochondrial uncoupler. Serial administration of Ppc-1 into mice suppressed weight gain with no abnormal effects on liver or kidney tissues, and no evidence of tumor formation. Serum fatty acid levels were significantly elevated in mice treated with Ppc-1, while body fat content remained low. After a single administration, Ppc-1 distributes into various tissues of individual animals at low levels. Ppc-1 stimulates adipocytes in culture to release fatty acids, which might explain the elevated serum fatty acids in Ppc-1-treated mice. The results suggest that Ppc-1 is a unique mitochondrial regulator which will be a valuable tool for mitochondrial research as well as the development of new drugs to treat obesity.

MR imaging of subcallosal artery infarct causing amnesia after surgery for anterior communicating artery aneurysm

BACKGROUND AND PURPOSE

During surgery to treat an aneurysm in the anterior communicating artery, injury to the subcallosal artery, a perforator of the anterior communicating artery, may lead to infarction that produces basal forebrain amnesia after surgery. Our purpose was to examine whether 3D MR imaging can detect subcallosal artery infarction in patients with amnesia after surgery for an anterior communicating artery aneurysm.

MATERIALS AND METHODS

We evaluated 3D-T2-weighted MR images obtained a median of 4 months after treatment of anterior communicating artery aneurysm for the presence of infarcted foci in 10 consecutive patients with postoperative amnesia. Because the subcallosal artery and its neighboring perforator, the recurrent artery of Heubner, were considered the most easily affected vessels during that surgery, we focused mainly on 8 regions of the subcallosal artery territory per hemisphere and 5 regions of the recurrent artery of Heubner territory per hemisphere.

RESULTS

All 10 patients had infarcts in the territory of the subcallosal artery (median, 9 regions per patient), and most were bilateral (9 of 10 patients). Five patients had additional infarcted foci in the territory of the recurrent artery of Heubner (median, 1 region per patient), all unilateral. Among the regions perfused by the subcallosal artery, the column of the fornix was involved in all patients; the anterior commissure, in 9; and the paraterminal gyrus, in 8 patients.

CONCLUSIONS

3D MR imaging revealed subcallosal artery infarction, the distribution of which was mostly bilateral, presumably owing to the unpairedness of that artery, in patients with postoperative amnesia after anterior communicating artery aneurysm repair.

Structural and functional analysis of the anti-malarial drug target prolyl-tRNA synthetase

Aminoacyl-tRNA synthetases (aaRSs) drive protein translation in cells and hence these are essential enzymes across life. Inhibition of these enzymes can halt growth of an organism by stalling protein translation. Therefore, small molecule targeting of aaRS active sites is an attractive avenue from the perspective of developing anti-infectives. Febrifugine and its derivatives like halofuginone (HF) are known to inhibit prolyl-tRNA synthetase of malaria parasite Plasmodium falciparum. Here, we present functional and crystallographic data on P. falciparum prolyl-tRNA synthetase (PfPRS). Using immunofluorescence data, we show that PfPRS is exclusively resident in the parasite cytoplasm within asexual blood stage parasites. The inhibitor HF interacts strongly with PfPRS in a non-competitive binding mode in presence or absence of ATP analog. Intriguingly, the two monomers that constitute dimeric PfPRS display significantly different conformations in their active site regions. The structural analyses presented here provide a framework for development of febrifugine derivatives that can seed development of new anti-malarials.

Defects in the synthetic pathway prevent DIF-1 mediated stalk lineage specification cascade in the non-differentiating social amoeba, Acytostelium subglobosum

Separation of somatic cells from germ-line cells is a crucial event for multicellular organisms, but how this step was achieved during evolution remains elusive. In Dictyostelium discoideum and many other dictyostelid species, solitary amoebae gather and form a multicellular fruiting body in which germ-line spores and somatic stalk cells differentiate, whereas in Acytostelium subglobosum, acellular stalks form and all aggregated amoebae become spores. In this study, because most D. discoideum genes known to be required for stalk cell differentiation have homologs in A. subglobosum, we inferred functional variations in these genes and examined conservation of the stalk cell specification cascade of D. discoideum mediated by the polyketide differentiation-inducing factor-1 (DIF-1) in A. subglobosum. Through heterologous expression of A. subglobosum orthologs of DIF-1 biosynthesis genes in D. discoideum, we confirmed that two of the three genes were functional equivalents, while DIF-methyltransferase (As-dmtA) involved at the final step of DIF-1 synthesis was not. In fact, DIF-1 activity was undetectable in A. subglobosum lysates and amoebae of this species were not responsive to DIF-1, suggesting a lack of DIF-1 production in this species. On the other hand, the molecular function of an A. subglobosum ortholog of DIF-1 responsive transcription factor was equivalent with that of D. discoideum and inhibition of polyketide synthesis caused developmental arrest in A. subglobosum, which could not be rescued by DIF-1 addition. These results suggest that non-DIF-1 polyketide cascades involving downstream transcription factors are required for fruiting body development of A. subglobosum.