ABSTRACT
The discovery of Streptomyces-produced streptomycin founded the age of tuberculosis therapy. Despite the subsequent development of a curative regimen for this disease, tuberculosis remains a worldwide problem, and the emergence of multidrug-resistant Mycobacterium tuberculosis has prioritized the need for new drugs. Here we show that new optimized derivatives from Streptomyces-derived griselimycin are highly active against M. tuberculosis, both in vitro and in vivo, by inhibiting the DNA polymerase sliding clamp DnaN. We discovered that resistance to griselimycins, occurring at very low frequency, is associated with amplification of a chromosomal segment containing dnaN, as well as the ori site. Our results demonstrate that griselimycins have high translational potential for tuberculosis treatment, validate DnaN as an antimicrobial target, and capture the process of antibiotic pressure-induced gene amplification.
Subject(s)
Antitubercular Agents/pharmacology , Bacterial Proteins/antagonists & inhibitors , Molecular Targeted Therapy , Mycobacterium tuberculosis/drug effects , Peptides, Cyclic/pharmacology , Tuberculosis, Multidrug-Resistant/drug therapy , Animals , Antitubercular Agents/chemistry , Antitubercular Agents/therapeutic use , Cell Line, Tumor , Crystallography, X-Ray , DNA-Directed DNA Polymerase , Disease Models, Animal , Drug Design , Humans , Mice , Microbial Sensitivity Tests , Molecular Sequence Data , Mycobacterium smegmatis/drug effects , Mycobacterium smegmatis/enzymology , Mycobacterium tuberculosis/enzymology , Peptides, Cyclic/chemistry , Peptides, Cyclic/therapeutic use , Protein Structure, Secondary , Streptomyces/chemistry , Streptomyces/drug effects , Streptomyces/metabolism , Tuberculosis, Multidrug-Resistant/microbiologyABSTRACT
Pau d'arco is a plant-derived traditional medicine that acts by poorly understood molecular mechanisms. Here, we studied the effect of pau d'arco on the cytoprotective transcription factor Nrf2. An aqueous extract of pau d'arco stimulated Nrf2-dependent gene expression and led to nuclear localization of Nrf2 in vitro. Chromatographic separation and mass spectrometry of the extract identified benzene trioles or benzene tetraoles within the active fractions. The extract stimulated the mitogen-activated protein kinase/extracellular-signal-regulated kinase kinase (MEK)/extracellular-signal-regulated kinase (ERK1/2) pathway. The pharmacological inhibition of MEK, but not of p38 mitogen-activated protein kinase, glycogen synthase kinase-3 or phosphoinositide 3-kinase was required for the activation of Nrf2-dependent gene expression by pau d'arco, but not for the nuclear translocation of Nrf2. In vivo pau d'arco increased the expression of Nrf2-target genes in the intestine. The results suggest that the activation of Nrf2 could mediate beneficial effects of pau d'arco, in particular in the intestine.
Subject(s)
Gene Expression/drug effects , MAP Kinase Signaling System/drug effects , Medicine, Traditional , Molecular Targeted Therapy , NF-E2-Related Factor 2/metabolism , NF-E2-Related Factor 2/physiology , Phytotherapy , Plant Extracts/pharmacology , Tabebuia , Active Transport, Cell Nucleus , Animals , Female , Heme Oxygenase-1/metabolism , Hep G2 Cells , Humans , Intestines , Intracellular Signaling Peptides and Proteins/physiology , Kelch-Like ECH-Associated Protein 1 , MAP Kinase Signaling System/genetics , MAP Kinase Signaling System/physiology , Mice , Mice, Inbred C57BL , NAD(P)H Dehydrogenase (Quinone)/metabolism , NF-E2-Related Factor 2/genetics , Stimulation, Chemical , WaterABSTRACT
In an antibiotic lead discovery program, the known strain Streptomyces armeniacus DSM19369 has been found to produce three new natural products when cultivated on a malt-containing medium. The challenging structural elucidation of the isolated compounds was achieved by using three independent methods, that is, chemical degradation followed by NMR spectroscopy, a computer-assisted structure prediction algorithm, and X-ray crystallography. The compounds, named armeniaspirolâ A-C (2-4), exhibit a compact, hitherto unprecedented chlorinated spiro[4.4]non-8-ene scaffold. Labeling experiments with [1-(13)C] acetate, [1,2-(13)C2] acetate, and [U-(13)C] proline suggest a biosynthesis through a rare two-chain mechanism. Armeniaspirols displayed moderate to high in vitro activities against gram-positive pathogens such as methicillin-resistant S. aureus (MRSA) or vancomycin resistant E. faecium (VRE). As analogue 2 was active in vivo in an MRSA sepsis model, and showed no development of resistance in a serial passaging experiment, it represents a new antibiotic lead structure.
Subject(s)
Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/therapeutic use , Biological Products/chemistry , Biological Products/pharmacology , Gram-Positive Bacteria/chemistry , Gram-Positive Bacteria/drug effects , Pyrroles/chemistry , Pyrroles/pharmacology , Spiro Compounds/chemistry , Spiro Compounds/pharmacology , Staphylococcal Infections/drug therapy , Staphylococcus aureus/chemistry , Staphylococcus aureus/drug effects , Bacterial Structures , Crystallography, X-Ray , Drug DiscoveryABSTRACT
During a screening campaign for new antimicrobial and antifungal secondary metabolites from several thousand actinomycetes, a novel compound, isolated by activity guided fractionation, was oxachelin (1) from the new Streptomyces sp. GW9/1258. Oxachelin shows strong antibiotic activities against several fungi and Gram(+) bacteria. Additionally, oxachelin is a strong complexing ligand for Fe3+ (siderophore), possibly making it useful e.g. for iron excess diseases.
