Yaojian Huang

Cytosporone B is an agonist for nuclear orphan receptor Nur77

Nuclear orphan receptor Nur77 has important roles in many biological processes. However, a physiological ligand for Nur77 has not been identified. Here, we report that the octaketide cytosporone B (Csn-B) is a naturally occurring agonist for Nur77. Csn-B specifically binds to the ligand-binding domain of Nur77 and stimulates Nur77-dependent transactivational activity towards target genes including Nr4a1 (Nur77) itself, which contains multiple consensus response elements allowing positive autoregulation in a Csn-B-dependent manner. Csn-B also elevates blood glucose levels in fasting C57 mice, an effect that is accompanied by induction of multiple genes involved in gluconeogenesis. These biological effects were not observed in Nur77-null (Nr4a1-/-) mice, which indicates that Csn-B regulates gluconeogenesis through Nur77. Moreover, Csn-B induced apoptosis and retarded xenograft tumor growth by inducing Nur77 expression, translocating Nur77 to mitochondria to cause cytochrome c release. Thus, Csn-B may represent a promising therapeutic drug for cancers and hypoglycemia, and it may also be useful as a reagent to increase understanding of Nur77 biological function.

Mycoepoxydiene, a fungal polyketide, induces cell cycle arrest at the G2/M phase and apoptosis in HeLa cells

Mycoepoxydiene (MED) is a polyketide isolated from a marine fungus associated with mangrove forests. It contains an oxygen-bridged cyclooctadiene core and an α,β-unsaturated δ-lactone moiety. MED induced the reorganization of cytoskeleton in actively growing HeLa cells by promoting formation of actin stress fiber and inhibiting polymerization of tubulin. MED could induce cell cycle arrest at G2/M in HeLa cells. MED-associated apoptosis was characterized by the formation of fragmented nuclei, PARP cleavage, cytochrome c release, activation of caspase-3, and an increased proportion of sub-G1 cells. Additionally, MED activated MAPK pathways. Interestingly, the time of JNK, p38, and Bcl-2 activation did not correlate with the release of cytochrome c. This study is the first report demonstrating the action mechanism of MED against tumor cell growth. These results provide the potential of MED as a novel low toxic antitumor agent.

Diversities Within Genotypes, Bioactivity and Biosynthetic Genes of Endophytic Actinomycetes Isolated from Three Pharmaceutical Plants

One hundred and fifty endophytic actinomycetes were isolated from three pharmaceutical plants, Annonaceae squamosal, Camptotheca acuminate and Taxus chinensis. Bioactivity test showed that 72.4% of the endophytic actinomycetes displayed inhibition against more than one indicator microorganism. In total, 9.3 and 10.7% showed the cytotoxicity and antioxidant activity, respectively. 3-Amino-5-hydroxybenzoic acid synthase (AHBA), ketosynthase (KS), cytochrome P450 hydroxylases (CYPs) and epoxidase (ES) encoding genes were found in 8.8, 23.8, 2.8 and 11.7% isolates, respectively, by genes screening. The identification based on traditional and molecular methods indicated that diverse genotypes of Streptomyces were distributed in the three pharmaceutical plants, and a few strains of Amycolatopsis were also found in the root of T. chinensis. These results indicated that endophytic actinomycetes associated with pharmaceutical plants could be a promising source of drug leads.

Species Diversity, Distribution, and Genetic Structure of Endophytic and Epiphytic Trichoderma Associated with Banana Roots

Selective isolation, molecular identification and AFLP were used to investigate the distribution of the various species of endophytic and epiphytic Trichoderma associated with banana roots and to compare and contrast their genetic structure. Three specific groups of Trichoderma were observed in the roots of banana. Group one, which made up the largest population, comprised T. asperellum, T. virens, and Hypocrea lixii, which were isolated from both inside and on the surface of the banana roots, while group two, made up of T. atroviride and T. koningiopsis, existed on the surface only. Group three, comprising only T. brevicompactum was isolated from the inside of the roots. The AFLP analysis revealed Nei’s diversity indices of 0.15 and 0.26 for epiphytic T. asperellum and T. virens, respectively. The index values of 0.11 and 0.11 were obtained for endophytic T. asperellum and T. virens, respectively. The genetic diversity within endophytic T. asperellum and T. virens was lower than that within the epiphytes. This suggests that endophytic Trichoderma has a higher genetic conservation and is compatible with the relatively stable microenvironments inside roots.

Phomopsidone A, a novel depsidone metabolite from the mangrove endophytic fungus Phomopsis sp. A123.

One novel pentacyclic depsidone containing an oxetane unit, phomopsidone A (1), together with the reported excelsione (also named as phomopsidone) (2), and four known isobenzofuranones (3-6) were isolated from the mangrove endophytic fungus Phomopsis sp. A123. Their structures were elucidated by 1D and 2D NMR spectroscopic analysis and high resolution mass spectrometry. The bioactivity assays showed that these compounds possess cytotoxic, antioxidant, and antifungal activities.

Mycoepoxydiene Inhibits Lipopolysaccharide-Induced Inflammatory Responses through the of TRAF6 Polyubiquitination

Mycoepoxydiene (MED) is a polyketide isolated from a marine fungus associated with mangrove forests. MED has been shown to be able to induce cell cycle arrest and cancer cell apoptosis. However, its effects on inflammatory response are unclear. Herein we showed that MED exhibited inhibitory effect on inflammatory response induced by lipopolysaccharide (LPS). MED significantly inhibited LPS-induced expression of pro-inflammatory mediators such as tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, and nitric oxide (NO) in macrophages. MED inhibited LPS-induced nuclear translocation of nuclear factor (NF)-κB (NF-κB) p65, IκB degradation, IκB kinase (IKK) phosphorylation, and the activation of extracellular signal-regulated kinase (ERK), c-jun N-terminal kinase (JNK), and p38, suggesting that MED blocks the activation of both NF-κB and mitogen-activated protein kinase (MAPK) pathways. Furthermore, the effects of MED on LPS-induced activation of upstream signaling molecules such as transforming growth factor-β–activated kinase 1 (TAK1), tumor necrosis factor receptor-associated factor 6 (TRAF6) and IL-1 receptor associated kinases1 (IRAK1) were investigated. MED significantly inhibited TAK1 phosphorylation and TRAF6 polyubiquitination, but not IRAK1 phosphorylation and TRAF6 dimerization, indicating that MED inhibits LPS-induced inflammatory responses at least in part through suppression of TRAF6 polyubiquitination. Moreover, MED protected mice from LPS-induced endotoxin shock by reducing serum inflammatory cytokines. These results suggest that MED is a potential lead compound for the development of a novel nonsteroidal anti-inflammatory drug.

Role of tumor metastasis suppressor gene KAI1 in digestive tract carcinomas and cancer cells

The KAI1 gene is identified as a tumor metastasis suppressor gene in many types of cancer. We examined KAI1 gene and its protein KAI1/CD82 expression by in situ hybridization and immunohistochemical analysis, and found that KAI1 mRNA and protein expression were inversely correlated with lymph node and distant metastasis in digestive tract carcinomas, but not with age and gender of the patient, or with tumor differentiation. Moreover, KAI1/CD82 protein expression positively reflected the survival outcome of patients. Western blot analysis showed that VP-16 increased KAI1/CD82 protein expression obviously in various cancer cell lines, especially in those that were highly metastatic. This increased KAI1/CD82 expression was associated with its translocation from the cytomembrane to the nucleus, in which it interacted with nuclear p53 protein, forming a strong complex, observed by confocal microscopy and co-immunoprecipitation, respectively. In nude mice, after feeding with VP-16, the number of tumors metastasized from spleen to liver was obviously reduced, and KAI1/CD82 protein expression became stronger in those metastatic tumors. Accordingly, this demonstrated that KAI1 might be used as an indicator for predicting the clinical outcome, and VP-16 may be clinically considered as a promising candidate for anti-metastasis with regard to its potential to upregulate KAI1 expression.

Kribbella amoyensis sp nov., isolated from rhizosphere soil of a pharmaceutical plant, Typhonium giganteum Engl.

An actinomycete, designated XMU 198(T), was isolated from the rhizosphere soil of a pharmaceutical plant, Typhonium giganteum Engl., collected in Xiamen City, China. 16S rRNA gene sequence analysis showed that the isolate exhibited highest sequence similarities with Kribbella flavida KACC 20148(T), K. karoonensis Q41(T) and K. alba YIM 31975(T) (98.7, 98.4 and 98.2 %, respectively). The chemotaxonomic characteristics further supported the assignment of strain XMU 198(T) to the genus Kribbella: ll-diaminopimelic acid in the cell-wall peptidoglycan; glucose and galactose with minor amounts of ribose as the whole-cell sugars; polar lipids comprising phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine, phosphatidylinositol and unidentified phospholipids; a fatty acid profile characterized by the predominance of iso-C(16 : 0), iso-C(14 : 0) and anteiso-C(15 : 0); and MK-9(H(4)) as the main menaquinone. Gyrase subunit B gene (gyrB) sequence analysis showed that the genetic distances between strain XMU 198(T) and all other members of the genus Kribbella were greater than 0.014, the value used as the threshold for species delineation within this genus. A wide range of genotypic and phenotypic characteristics, as well as DNA-DNA relatedness between strain XMU 198(T) and K. flavida DSM 17836(T) (41.18 %), K. karoonensis Q41(T) (38.02 %) and K. alba DSM 15500(T) (50.58 %), distinguished the isolate from its closest phylogenetic neighbours. On the basis of the above data, a novel species of the genus Kribbella, Kribbella amoyensis sp. nov., is proposed. The type strain is XMU 198(T) ( = DSM 24683(T) = NBRC 107914(T)).

New and highly efficient methodology for screening high-yield strains of cytotoxic deacetylmycoepoxydiene (DAM).

Aims:  To establish a highly efficient methodology for screening high yield strains of cytotoxic deacetylmycoepoxydiene (DAM), to meet the need of research on its mechanism of anti‐tumor properties and in vivo toxicity studies.

Nonomuraea ceibae sp. nov., an actinobacterium isolated from Ceiba speciosa rhizosphere

Strain XMU 110T, isolated from the rhizosphere soil of a flowering tree, Ceiba speciosa, was characterized by polyphasic taxonomy. Phylogenetic analysis based on 16S rRNA gene comparisons revealed that strain XMU 110T showed the highest similarity of 97.9 % to Nonomuraea jabiensis DSM 45507T, and indicated the closest relatives were Nonomuraearoseoviolaceasubsp.roseoviolacea ATCC 27297T (97.8 % 16S rRNA gene sequence similarity) and Nonomuraea salmonea DSM 43678T (97.4 %) after a neighbour-joining analysis. The phenotypic characteristics, as well as the DNA-DNA relatedness values between strain XMU 110T and N. roseoviolaceasubsp. roseoviolacea ATCC 27297T (48.07±1.99 %) and N. salmonea DSM 43678T (40.55±8.30 %), distinguished the novel strain from its closest phylogenetic neighbours. The morphological, physiological and chemotaxonomic characteristics such as phospholipid type, diagnostic diamino acid of the peptidoglycan, whole-cell sugars, major menaquinones and major fatty acids further supported the assignment of strain XMU 110T to the genus Nonomuraea. The G+C content of the genomic DNA was 66.2 mol%. Based on the taxonomic data, strain XMU 110Trepresents a novel species of the genus Nonomuraea, for which the name Nonomuraea ceibae sp. nov. is proposed. The type strain is XMU 110T (=MCCC 1K03213T= KCTC 39826T).