Mechanism of Action of KL-50, a Candidate Imidazotetrazine for the Treatment of Drug-Resistant Brain Cancers.

Aberrant DNA repair is a hallmark of cancer, and many tumors display reduced DNA repair capacities that sensitize them to genotoxins. Here, we demonstrate that the differential DNA repair capacities of healthy and transformed tissue may be exploited to obtain highly selective chemotherapies. We show that the novel N3-(2-fluoroethyl)imidazotetrazine "KL-50" is a selective toxin toward tumors that lack the DNA repair protein O6-methylguanine-DNA-methyltransferase (MGMT), which reverses the formation of O6-alkylguanine lesions. We establish that KL-50 generates DNA interstrand cross-links (ICLs) by a multistep process comprising DNA alkylation to generate an O6-(2-fluoroethyl)guanine (O6FEtG) lesion, slow unimolecular displacement of fluoride to form an N1,O6-ethanoguanine (N1,O6EtG) intermediate, and ring-opening by the adjacent cytidine. The slow rate of N1,O6EtG formation allows healthy cells expressing MGMT to reverse the initial O6FEtG lesion before it evolves to N1,O6EtG, thereby suppressing the formation of toxic DNA-MGMT cross-links and reducing the amount of DNA ICLs generated in healthy cells. In contrast, O6-(2-chloroethyl)guanine lesions produced by agents such as lomustine and the N3-(2-chloroethyl)imidazotetrazine mitozolomide rapidly evolve to N1,O6EtG, resulting in the formation of DNA-MGMT cross-links and DNA ICLs in healthy tissue. These studies suggest that careful consideration of the rates of chemical DNA modification and biochemical DNA repair may lead to the identification of other tumor-specific genotoxic agents.

IL-10 constrains sphingolipid metabolism to limit inflammation.

Interleukin-10 (IL-10) is a key anti-inflammatory cytokine that can limit immune cell activation and cytokine production in innate immune cell types1. Loss of IL-10 signalling results in life-threatening inflammatory bowel disease in humans and mice-however, the exact mechanism by which IL-10 signalling subdues inflammation remains unclear2-5. Here we find that increased saturated very long chain (VLC) ceramides are critical for the heightened inflammatory gene expression that is a hallmark of IL-10 deficiency. Accordingly, genetic deletion of ceramide synthase 2 (encoded by Cers2), the enzyme responsible for VLC ceramide production, limited the exacerbated inflammatory gene expression programme associated with IL-10 deficiency both in vitro and in vivo. The accumulation of saturated VLC ceramides was regulated by a decrease in metabolic flux through the de novo mono-unsaturated fatty acid synthesis pathway. Restoring mono-unsaturated fatty acid availability to cells deficient in IL-10 signalling limited saturated VLC ceramide production and the associated inflammation. Mechanistically, we find that persistent inflammation mediated by VLC ceramides is largely dependent on sustained activity of REL, an immuno-modulatory transcription factor. Together, these data indicate that an IL-10-driven fatty acid desaturation programme rewires VLC ceramide accumulation and aberrant activation of REL. These studies support the idea that fatty acid homeostasis in innate immune cells serves as a key regulatory node to control pathologic inflammation and suggests that 'metabolic correction' of VLC homeostasis could be an important strategy to normalize dysregulated inflammation caused by the absence of IL-10.

Commensal microbiota from patients with inflammatory bowel disease produce genotoxic metabolites.

Microbiota-derived metabolites that elicit DNA damage can contribute to colorectal cancer (CRC). However, the full spectrum of genotoxic chemicals produced by indigenous gut microbes remains to be defined. We established a pipeline to systematically evaluate the genotoxicity of an extensive collection of gut commensals from inflammatory bowel disease patients. We identified isolates from divergent phylogenies whose metabolites caused DNA damage and discovered a distinctive family of genotoxins-termed the indolimines-produced by the CRC-associated species Morganella morganii. A non-indolimine-producing M. morganii mutant lacked genotoxicity and failed to exacerbate colon tumorigenesis in mice. These studies reveal the existence of a previously unexplored universe of genotoxic small molecules from the microbiome that may affect host biology in homeostasis and disease.

LACC1 bridges NOS2 and polyamine metabolism in inflammatory macrophages.

The mammalian immune system uses various pattern recognition receptors to recognize invaders and host damage and transmits this information to downstream immunometabolic signalling outcomes. Laccase domain-containing 1 (LACC1) protein is an enzyme highly expressed in inflammatory macrophages and serves a central regulatory role in multiple inflammatory diseases such as inflammatory bowel diseases, arthritis and clearance of microbial infection1-4. However, the biochemical roles required for LACC1 functions remain largely undefined. Here we elucidated a shared biochemical function of LACC1 in mice and humans, converting L-citrulline to L-ornithine (L-Orn) and isocyanic acid and serving as a bridge between proinflammatory nitric oxide synthase (NOS2) and polyamine immunometabolism. We validated the genetic and mechanistic connections among NOS2, LACC1 and ornithine decarboxylase 1 (ODC1) in mouse models and bone marrow-derived macrophages infected by Salmonella enterica Typhimurium. Strikingly, LACC1 phenotypes required upstream NOS2 and downstream ODC1, and Lacc1-/- chemical complementation with its product L-Orn significantly restored wild-type activities. Our findings illuminate a previously unidentified pathway in inflammatory macrophages, explain why its deficiency may contribute to human inflammatory diseases and suggest that L-Orn could serve as a nutraceutical to ameliorate LACC1-associated immunological dysfunctions such as arthritis or inflammatory bowel disease.

Securinega Alkaloids from the Twigs of Securinega suffruticosa and Their Biological Activities.

Seven new Securinega alkaloids, securingines A-G (1-7), together with seven known analogues (8-14), were isolated from the twigs of Securinega suffruticosa. Their chemical structures were elucidated by a combined approach of spectroscopic analysis, chemical methods, ECD calculations, and DP4+ probability analysis. The full NMR assignments and the absolute configuration of compound 8 are also reported. In addition, all the isolated phytochemicals (1-14) were assessed for their cytotoxic, anti-inflammatory, and potential neuroprotective activities. Compound 4 showed cytotoxic activity (IC50 values of 1.5-6.8 µM) against four human cell lines (A549, SK-OV-3, SK-MEL-2, and HCT15). Compounds 3, 10, 12, and 13 showed potent inhibitory effects on nitric oxide production (IC50 values of 12.6, 12.1, 1.1, and 7.7 µM, respectively) in lipopolysaccharide-stimulated murine microglia BV-2 cells. Compound 5 exhibited a nerve growth factor production effect (172.6 ± 1.2%) in C6 glioma cells at 20 µg/mL.

Structural Characterization of Terpenoids from Abies holophylla Using Computational and Statistical Methods and Their Biological Activities.

Three new diterpenoids (1-3) and three new triterpenoids (4-6) were isolated from the trunk of Abies holophylla together with 19 known terpenoids. The chemical structures of 1-6 were determined through NMR and MS data analyses. Also, the structural assignments of some of these compounds were verified and elucidated utilizing computational methods coupled with a statistical procedure (CP3, DP4, and DP4+). All the isolated compounds were evaluated for their cytotoxicity against four human cancer cell lines (A549, SK-OV-3, SK-MEL-2, and HCT-15). In addition, the compounds were tested for their anti-inflammatory effects in lipopolysaccharide-stimulated murine microglia BV2 cells by measuring nitric oxide levels, and for their neuroprotective activity in C6 cells through induction of nerve growth factor.

Sesterterpenoid and Steroid Metabolites from a Deep-Water Alaska Sponge Inhibit Wnt/ß-Catenin Signaling in Colon Cancer Cells.

The Wnt/ß-catenin signaling pathway is known to play critical roles in a wide range of cellular processes: cell proliferation, differentiation, migration and embryonic development. Importantly, dysregulation of this pathway is tightly associated with pathogenesis in most human cancers. Therefore, the Wnt/ß-catenin pathway has emerged as a promising target in anticancer drug screening programs. In the present study, we have isolated three previously unreported metabolites from an undescribed sponge, a species of Monanchora (Order Poecilosclerida, Family Crambidae), closely related to the northeastern Pacific species Monanchora pulchra, collected from deep waters off the Aleutian Islands of Alaska. Through an assortment of NMR, MS, ECD, computational chemical shifts calculation, and DP4, chemical structures of these metabolites have been characterized as spirocyclic ring-containing sesterterpenoid (1) and cholestane-type steroidal analogues (2 and 3). These compounds exhibited the inhibition of ß-catenin response transcription (CRT) through the promotion of ß-catenin degradation, which was in part implicated in the antiproliferative activity against two CRT-positive colon cancer cell lines.

Cyclopeptides from the Sponge Stylissa flabelliformis.

Three new cyclopeptides, phakellistatins 20-22 (1-3), as well as 10 known cyclopeptides of the same structural class were isolated from the tropical sponge Stylissa flabelliformis. By a combination of chemical and spectroscopic methods, the structures of the new compounds were determined to be an epimeric mixture of cycloheptapeptides (1) and two epimeric cyclodecapeptides (2 and 3) related to the phakellistatins. The cyclopeptides were evaluated for in vitro cytotoxicity against a variety of cancer cell lines, and compounds 2 and 3 exhibited significant activity.

WS9326H, an Antiangiogenic Pyrazolone-Bearing Peptide from an Intertidal Mudflat Actinomycete.

WS9326H (1), a new cyclic peptide, was isolated from a mudflat-derived Streptomyces strain. Based on analysis by 1D/2D NMR, UV spectroscopy, and mass spectrometry, compound 1 was determined to have the gross structure of a cyclic heptapeptide bearing an unprecedented pyrazolone ring connected to a d-arabinitol via an amide bond. The absolute configuration of 1 was established by multistep chemical derivatizations, comprehensive NMR, and LC/MS analyses of the derivatives and quantum mechanics-based computational methods. WS9326H (1) displayed significant antiangiogenesis activity.

Cucurbitane Triterpenoids from the Fruits of Momordica Charantia Improve Insulin Sensitivity and Glucose Homeostasis in Streptozotocin-Induced Diabetic Mice.

SCOPE: Momordica charantia (M. charantia) has antidiabetic effects, and cucurbitane-type triterpenoid is one of the compounds of M. charantia. This study aims to investigate whether the new cucurbitane-type triterpenoids affect insulin sensitivity both in vitro and in vivo, and the underlying mechanisms. METHODS AND RESULTS: Four compounds (C1-C4) isolated from the ethanol extract of M. charantia enhance glucose uptake in C2C12 myotubes via insulin receptor substrate-1 (IRS-1) rather than via adenosine monophosphate-activated protein kinase. The most potent, compound 2 (C2), significantly increases the activation of IRS-1 and downstream signaling pathways, resulting in glucose transporter 4 translocation. Furthermore, these C2-induced in vitro effects are blocked by specific signal inhibitors. We further evaluate the antidiabetic effect of C2 using a streptozotocin (STZ)-induced diabetic mouse model. Consistent with in vitro data, treatment with C2 (1.68 mg kg-1 ) significantly decreases blood glucose level and enhances glycogen storage in STZ-injected mice. These effects appear to be mediated by the IRS-1 signaling pathway in skeletal muscle, not in adipose and liver tissues, suggesting that C2 improves hyperglycemia by increasing glucose uptake into skeletal muscle. CONCLUSION: Our findings demonstrate that the new cucurbitane-type triterpenoids have potential for prevention and management of diabetes by improving insulin sensitivity and glucose homeostasis.

Bioactive Triterpenoids from the Twigs of Chaenomeles sinensis.

Chaenomeles sinensis has been consumed traditionally for the treatment of throat diseases, diarrhea, inflammatory diseases, and dry beriberi. Repeated chromatography of the CHCl3-soluble fraction from the 80% MeOH extract of C. sinensis twigs led to the isolation of three new triterpenoids, sinenic acid A (1), 3ß-O-cis-feruloyl-2α,19α-dihydroxyurs-12-en-28-oic acid (2), and 3ß-O-cis-caffeoylbetulin (3), together with 20 analogues. The chemical structures of 1-3 were determined using diverse NMR techniques and HRMS data analysis, chemical methods, and computational approaches supported by advanced statistics (CP3). All the purified compounds were evaluated not only for their cytotoxicity against four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT-15) but for their potential neuroprotective effects through induction of nerve growth factor in C6 glioma cells. Their anti-inflammatory effects were also assessed by measuring nitric oxide levels in lipopolysaccharide-insulted murine microglia BV2 cells.

Anti-Neurodegenerative Biflavonoid Glycosides from Impatiens balsamina.

Four biflavonoid glycosides, balsamisides A-D (1-4), and nine known compounds (5-13) were obtained from the white petals of Impatiens balsamina. The 2D structures of the purified phytochemicals were established using conventional NMR techniques in addition to the new long-range HSQMBC NMR experiment. Acid hydrolysis followed by experimental and quantum-mechanics-based ECD data analysis permitted full configurational assignment of the purified metabolites. Compounds 1-13 were assessed for their potential to impede the generation of nitric oxide in lipopolysaccharide-stimulated BV2 cells. They were also investigated for potential neuroprotective activity using C6 cells and cytotoxicity against some human tumor cell lines, but were inactive (IC50 > 10 µM) against all the cell lines.

In silico investigation of lavandulyl flavonoids for the development of potent fatty acid synthase-inhibitory prototypes.

BACKGROUND: Inhibition of fatty acid synthase (FAS) is regarded as a sensible therapeutic strategy for the development of optimal anti-cancer agents. Flavonoids exhibit potent anti-neoplastic properties. METHODS: The MeOH extract of Sophora flavescens was subjected to chromatographic analyses such as VLC and HPLC for the purification of active flavonoids. The DP4 chemical-shift analysis protocol was employed to investigate the elusive chirality of the lavandulyl moiety of the purified polyphenols. Induced Fit docking protocols and per-residue analyses were utilized to scrutinize structural prerequisites for hampering FAS activity. The FAS-inhibitory activity of the purified flavonoids was assessed via the incorporation of [3H] acetyl-CoA into palmitate. RESULTS: Six flavonoids, including lavandulyl flavanones, were purified and evaluated for FAS inhibition. The lavandulyl flavanone sophoraflavanone G (2) exhibited the highest potency (IC50 of 6.7±0.2µM), which was more potent than the positive controls. Extensive molecular docking studies revealed the structural requirements for blocking FAS. Per-residue interaction analysis demonstrated that the lavandulyl functional group in the active flavonoids (1-3 and 5) significantly contributed to increasing their binding affinity towards the target enzyme. CONCLUSION: This research suggests a basis for the in silico design of a lavandulyl flavonoid-based architecture showing anti-cancer effects via enhancement of the binding potential to FAS. GENERAL SIGNIFICANCE: FAS inhibition by flavonoids and their derivatives may offer significant potential as an approach to lower the risk of various cancer diseases and related fatalities. In silico technologies with available FAS crystal structures may be of significant use in optimizing preliminary leads.

Stereochemical Studies of the Karlotoxin Class Using NMR Spectroscopy and DP4 Chemical-Shift Analysis: Insights into their Mechanism of Action.

After publication of karlotoxin 2 (KmTx2; 1), the harmful algal bloom dinoflagellate Karlodinium sp. was collected and scrutinized to identify additional biologically active complex polyketides. The structure of 1 was validated and revised at C49 using computational NMR tools including J-based configurational analysis and chemical-shift calculations. The characterization of two new compounds [KmTx8 (2) and KmTx9 (3)] was achieved through overlaid 2D HSQC NMR techniques, while the relative configurations were determined by comparison to 1 and computational chemical-shift calculations. The detailed evaluation of 2 using the NCI-60 cell lines, NMR binding studies, and an assessment of the literature supports a mode of action (MoA) for targeting cancer-cell membranes, especially of cytostatic tumors. This MoA is uniquely different from that of current agents employed in the control of cancers for which 2 shows sensitivity.

Cytotoxic activity of rearranged drimane meroterpenoids against colon cancer cells via down-regulation of ß-catenin expression.

Colorectal cancer has emerged as a major cause of death in Western countries. Down-regulation of ß-catenin expression has been considered a promising approach for cytotoxic drug formulation. Eight 4,9-friedodrimane-type sesquiterpenoids (1-8) were acquired using the oxidative potential of Verongula rigida on bioactive metabolites from two Smenospongia sponges. Compounds 3 and 4 contain a 2,2-dimethylbenzo[d]oxazol-6(2H)-one moiety as their substituted heterocyclic residues, which is unprecedented in such types of meroterpenoids. Gauge-invariant atomic orbital NMR chemical shift calculations were employed to investigate stereochemical details with support of the application of advanced statistics such as CP3 and DP4. Compounds 2 and 8 and the mixture of 3 and 4 suppressed ß-catenin response transcription (CRT) via degrading ß-catenin and exhibited cytotoxic activity on colon cancer cells, implying that their anti-CRT potential is, at least in part, one of their underlying antineoplastic mechanisms.

Palbinone from Paeonia suffruticosa protects hepatic cells via up-regulation of heme oxygenase-1.

Paeonia suffruticosa has been traditionally employed for vitalizing blood circulation and alleviating liver and inflammatory diseases. The pathways by which palbinone (PB) isolated from P. suffruticosa mediates heme oxygenase-1 (HO-1) induction were investigated using the specific inhibitors for PI3K and mitogen activated protein kinases pathways. The effect of PB-treatment on Nrf2 translocalization and HO-1-antioxidant response element (ARE) regulation was examined employing Western blot and luciferase assays. PB induced HO-1 expression via the activation of Nrf2 in the hepatic cells, and ARE-dependent genes were stimulated via the PB-mediated Nrf2 activation. PB-mediated HO-1 expression could be involved with PI3K/Akt and ERK1/2 pathways. Our study suggests the mechanism by which PB induces HO-1 expression in the hepatic cells. This might substantiate the traditional applications of P. suffruticosa for the treatment of oxidative stress-related diseases including oxidant and inflammatory-mediated vascular and liver diseases.

In vitro and in vivo hepatoprotective effect of ganodermanontriol against t-BHP-induced oxidative stress.

ETHNOPHARMACOLOGICAL RELEVANCE: Ganoderma lucidum (Fr.) Karst. (Ganodermataceae) is a mushroom which is used as a traditional remedy in the treatment of human diseases such as hepatitis, liver disorders, hypercholesterolemia, arthritis, bronchitis and tumorigenic diseases. This study targets the evaluation of hepatoprotective activity of ganodermanontriol, a sterol isolated from Ganoderma lucidum, and the investigation of its mechanism of action in Hepa1c1c7 and murine liver cells upon tert-butyl hydroperoxide (t-BHP)-induced inflammation. t-BHP was utilized to stimulate an anti-inflammatory reaction in the hepatic cell lines and murine hepatic tissue examined. Western blot and reverse transcription-quantitative polymerase chain reaction (RT-PCR) were used to estimate the expression of ganodermanontriol (GDT)-induced proteins, including heme oxidase-1 (HO-1) and mitogen-activated protein kinases (MAPKs) as well as the corresponding mRNA. Luciferase assays were conducted to evaluate the interaction between NF-E2-related factor-2 (Nrf-2), the antioxidant response element (ARE), and the promoter region of the HO-1 gene and subsequent gene expression. Biochemical markers for hepatotoxicity were monitored to assess whether GDT protected the cells from the t-BHP-mediated oxidative stimuli. RESULTS: GDT induced HO-1 expression via the activation of Nrf-2 nuclear translocation and the subsequent transcription of the HO-1 gene in vitro and in vivo, which seemed to be regulated by phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) and p38 signaling pathways. GDT exhibited in vitro and in vivo hepatoprotective activity as determined by the lowered levels of hepatic enzymes and malondialdehydes and the elevated glutathione levels. CONCLUSIONS: This study validates the ethnopharmacological application of Ganoderma lucidum as a treatment for hepatic disorders. GDT induced in vitro and in vivo anti-inflammatory activity in t-BHP-damaged hepatic cells through the expression of HO-1, and in which PI3K/Akt and p38 kinases are involved. Our study motivates further research in the exploration of potent hepatoprotective agents from Ganoderma lucidum.

A novel natural phenyl alkene with cytotoxic activity.

A novel phenyl alkene (1) was isolated from a mixture of three Florida sponges, Smenospongia aurea, Smenospongia cerebriformis, and Verongula rigida. Unlike terpenoids or amino acid derivatives, which are commonly known classes of secondary metabolites from these genera, the chemical structure of 1 showed an unprecedented linear phenyl alkene skeleton. Through comprehensive analyses of NMR and MS data, the gross structure of 1 was determined to be (E)-10-benzyl-5,7-dimethylundeca-1,5,10-trien-4-ol. The absolute configuration at C-4 was established as R by a modified Mosher's method. Based on the relative configuration between C-4 and C-7, the absolute configuration at C-7 was assigned as S. Compound 1 showed in vitro cytotoxic activity against HL-60 human leukemia cancer cells with an IC50 value of 8.1 µM. Molecular docking study suggests that the structure of compound 1 matches the pharmacophore of eribulin required to display cytotoxic activity through the inhibition of microtubule activity.

Inhibition of fatty acid synthase by ginkgolic acids from the leaves of Ginkgo biloba and their cytotoxic activity.

Fatty acid synthase (FAS) has been proposed to be a new drug target for the development of anticancer agents because of the significant difference in expression of FAS between normal and tumour cells. Since a n-hexane-soluble extract from Ginkgo biloba was demonstrated to inhibit FAS activity in our preliminary test, we isolated active compounds from the n-hexane-soluble extract and evaluated their cytotoxic activity in human cancer cells. Three ginkgolic acids 1-3 isolated from the n-hexane-soluble extract inhibited the enzyme with IC(50) values 17.1, 9.2 and 10.5 µM, respectively, and they showed cytotoxic activity against MCF-7 (human breast adenocarcinoma), A549 (human lung adenocarcinoma) and HL-60 (human leukaemia) cells. Our findings suggest that alkylphenol derivatives might be a new type of FAS inhibitor with cytotoxic activity.