Chemical Investigation of Marine-Derived Fungus Aspergillus flavipes for Potential Anti-Inflammatory Agents

The marine fungus, Aspergillus flavipes (MTCC 5220), was isolated from the pneumatophore of a mangrove plant Acanthus ilicifolius found in Goa, India. The crude extract of A. flavipes was found to show anti-inflammatory activity. It blocked interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) production in lipopolysaccharide (LPS)-activated THP-1 cells with IC₅₀ of 2.69±0.5 μM and 6.64±0.4 μM, respectively. The chemical investigation led to the isolation of optically inactive 4β-[(1E)-propen-1-yl]cyclopentane-1β,2β-diol ( 1 ) along with a new optically active diastereoisomeric compound, 4β-[(1E)-propen-1-yl]cyclopentane-1β,2α-diol ( 2 ). In addition, the fungus also produced known compounds (+)-terrein ( 3 ), butyrolactone I ( 4 ) and butyrolactone II ( 5 ) in high yields. Among these, (+)-terrein ( 3 ) exhibited IL-6 and TNF-α inhibition activity with IC₅₀ of 8.5±0.68 μM and 15.76±0.18 μM, respectively, while butyrolactone I ( 4 ) exhibited IC₅₀ of 12.03±0.85 μM (IL-6) and 43.29±0.76 μM (TNF-α) inhibition activity with low toxicity to host cells in LPS stimulated THP-1 cells. This is the first report of the isolation and characterization of 4β-[(1E)-propen-1-yl]cyclopentane-1β,2α-diol ( 2 ). The structures of all the isolated compounds were elucidated on the basis of extensive detailed NMR spectroscopic data. Anti-inflammatory activity of the fungi A. flavipes is presented here for the first time, which was due to (+)-terrein and butyrolactone I, as the major constituents and they can be further explored in the therapeutic area.     

Synthesis of (R)-norbgugaine and its potential as quorum sensing inhibitor against Pseudomonas aeruginosa

(R)-Bgugaine is a natural pyrrolidine alkaloid from Arisarum vulgare, which shows antifungal and antibacterial activity. In this Letter, we have accomplished the simple synthesis of norbgugaine (demethylated form of natural bgugaine) employing Wittig olefination and cat. hydrogenation as the key steps and its biological studies are reported for the first time. The synthesized norbgugaine was evaluated for inhibition of quorum sensing mediated virulence factors (motility, biofilm formation, pyocyanin pigmentation, rhamnolipid production and LasA protease) in Pseudomonas aeruginosa wherein swarming motility is reduced by 95%, and biofilm formation by 83%.     

Genome Sequencing Unveils a Novel Sea Enterotoxin-Carrying PVL Phage in Staphylococcus aureus ST772 from India

Staphylococcus aureus is a major human pathogen, first recognized as a leading cause of hospital-acquired infections. Community-associated S. aureus (CA-SA) pose a greater threat due to increase in severity of infection and disease among children and healthy adults. CA-SA strains in India are genetically diverse, among which is the sequence type (ST) 772, which has now spread to Australia, Europe and Japan. Towards understanding the genetic characteristics of ST772, we obtained draft genome sequences of five relevant clinical isolates and studied the properties of their PVL-carrying prophages, whose presence is a defining hallmark of CA-SA. We show that this is a novel prophage, which carries the structural genes of the hlb-carrying prophage and includes the sea enterotoxin. This architecture probably emerged early within the ST772 lineage, at least in India. The sea gene, unique to ST772 PVL, despite having promoter sequence characteristics typical of low expression, appears to be highly expressed during early phase of growth in laboratory conditions. We speculate that this might be a consequence of its novel sequence context. The crippled nature of the hlb-converting prophage in ST772 suggests that widespread mobility of the sea enterotoxin might be a selective force behind its ‘transfer’ to the PVL prophage. Wild type ST772 strains induced strong proliferative responses as well as high cytotoxic activity against neutrophils, likely mediated by superantigen SEA and the PVL toxin respectively. Both proliferation and cytotoxicity were markedly reduced in a cured ST772 strain indicating the impact of the phage on virulence. The presence of SEA alongside the genes for the immune system-modulating PVL toxin may contribute to the success and virulence of ST772.     

Bacterial biofilms and quorum sensing: fidelity in bioremediation technology

Increased contamination of the environment with toxic pollutants has paved the way for efficient strategies which can be implemented for environmental restoration. The major problem with conventional methods used for cleaning of pollutants is inefficiency and high economic costs. Bioremediation is a growing technology having advanced potential of cleaning pollutants. Biofilm formed by various micro-organisms potentially provide a suitable microenvironment for efficient bioremediation processes. High cell density and stress resistance properties of the biofilm environment provide opportunities for efficient metabolism of number of hydrophobic and toxic compounds. Bacterial biofilm formation is often regulated by quorum sensing (QS) which is a population density-based cell–cell communication process via signaling molecules. Numerous signaling molecules such as acyl homoserine lactones, peptides, autoinducer-2, diffusion signaling factors, and α-hydroxyketones have been studied in bacteria. Genetic alteration of QS machinery can be useful to modulate vital characters valuable for environmental applications such as biofilm formation, biosurfactant production, exopolysaccharide synthesis, horizontal gene transfer, catabolic gene expression, motility, and chemotaxis. These qualities are imperative for bacteria during degradation or detoxification of any pollutant. QS signals can be used for the fabrication of engineered biofilms with enhanced degradation kinetics. This review discusses the connection between QS and biofilm formation by bacteria in relation to bioremediation technology.     

Nuclear accumulation of multiple protein kinases during prolactin-induced proliferation of Nb2 rat lymphoma cells

Intracellular kinases play important roles in signal transduction and are involved in the surface receptor-mediated regulation of cellular functions, including mitogenesis. In the present study, we examined the possible involvement of various protein kinases in the passage of a mitogenic signal from the cell surface to the nucleus of Nb₂ cells, a rat nodal lymphoma cell line in which prolactin is a mitogen. Following a prolactin challenge, various kinase activities were monitored at short intervals in different cellular fractions over a 60 min period. Protein kinase C (PKC) activity in the cytosolic fraction rapidly declined to 50% of its original activity within the first 30 min, while PKC activity in the nuclear fractions increased sharply, reaching its highest level by 30 min following a prolactin challenge. There were also increases in both casein kinase and protein tyrosine kinase (PTK) activities in the nuclear fractions during the first 30 min following a prolactin challenge that paralleled PKC activity. The activities of all three kinases declined thereafter, reaching levels close to their respective basal values by 60 min following initiation of prolactin treatment. These observations suggest the possibility that multiple protein kinases may be involved in mitogenic signal transduction for prolactin in Nb₂ cells. © 1996 Wiley-Liss, Inc.     

Landscape of mobile genetic elements and their antibiotic resistance cargo in prokaryotic genomes

Prokaryotic Mobile Genetic Elements (MGEs) such as transposons, integrons, phages and plasmids, play important roles in prokaryotic evolution and in the dispersal of cargo functions like antibiotic resistance. However, each of these MGE types is usually annotated and analysed individually, hampering a global understanding of phylogenetic and environmental patterns of MGE dispersal. We thus developed a computational framework that captures diverse MGE types, their cargos and MGE-mediated horizontal transfer events, using recombinases as ubiquitous MGE marker genes and pangenome information for MGE boundary estimation. Applied to ∼84k genomes with habitat annotation, we mapped 2.8 million MGE-specific recombinases to six operational MGE types, which together contain on average 13% of all the genes in a genome. Transposable elements (TEs) dominated across all taxa (∼1.7 million occurrences), outnumbering phages and phage-like elements (<0.4 million). We recorded numerous MGE-mediated horizontal transfer events across diverse phyla and habitats involving all MGE types, disentangled and quantified the extent of hitchhiking of TEs (17%) and integrons (63%) with other MGE categories, and established TEs as dominant carriers of antibiotic resistance genes. We integrated all these findings into a resource (proMGE.embl.de), which should facilitate future studies on the large mobile part of genomes and its horizontal dispersal.     

Stimulation of adhesion molecule expression in human endothelial cells (HUVEC) by adrenomedullin and corticotrophin

Adrenomedullin (AM) and corticotrophin (ACTH) are both vasoactive peptides produced by a variety of cell types, including endothelial cells. Although AM and ACTH are considered to be important in the control of blood pressure and the response to stress, respectively, their role in inflammation and the immune response has not been clarified. This study shows, with the use of a cell-based ELISA, that AM and ACTH induce cell surface expression of the adhesion molecules E-selectin, VCAM-1, and ICAM-1 on human umbilical vein endothelial cells (HUVEC). Furthermore, this effect appears to be mediated in part via elevation of cAMP, given that both peptides elevate cAMP, the cell-permeable cAMP analog dibutyryl cAMP is able to mimic induction of all three cell adhesion molecules and the effect of AM and ACTH is inhibited by the adenylyl cyclase inhibitor SQ-22536. These findings demonstrate a role for AM and ACTH in the regulation of the immune and inflammatory response. E-selectin; intercellular adhesion molecule-1; vascular cell adhesion molecule-1; adrenomedullin; adrenocorticotropic hormone; human umbilical vein endothelial cells     

Proteomics opens doors to the mechanisms of developmentally regulated secretion

The program of multicellular development in Dictyostelium discoideum culminates with the assembly of a rugged, environmentally resistant spore coat around each spore cell. After synthesis, the proteins that will constitute the coat are stored in prespore vesicles (PSVs) until an unknown developmental signal triggers the PSVs to move to the cell surface where they fuse with the plasma membrane and secrete their cargo by exocytosis. These events occur synchronously in 80% of the cells in each developing multicellular aggregate, and thus the system offers a unique opportunity to study the developmental regulation of protein secretion in situ. Proteomic analysis of purified PSVs identified many of the constituent proteins, which in turn has lead to novel hypotheses and new experimental avenues regarding the molecular mechanisms regulating secretion from the PSVs.