ABSTRACT
Polycyclic tetramate macrolactams (PoTeMs) are a group of hybrid PK-NRP natural products having a variable set of carbocyclic rings, a conserved assembly pathway, and diverse bioactivities. We report here the identification of seven new PoTeMs, clifednamides D-J (3-9), along with the known clifednamides A (1) and B (2) through rational pathway refactoring and heterologous expression. Remarkably, clifednamides D (3), G (6), and H (7) feature an unprecedented 27,28-seco skeleton. The cytotoxic activities of compounds 1-9 indicated that the hydroxy group of C-25, the methyl group of C-30, the inner five-membered ring, and the intact macrocycle are all critical for the activities. Meanwhile, the cytochrome P450 enzyme CftS023A and the hydroxylase CftS023E involved in oxidative tailoring of clifednamides were found to decorate the fused 5-6 bicyclic intermediates. Accordingly, the biosynthetic pathway for clifednamides was proposed.
Subject(s)
Anti-Bacterial Agents/biosynthesis , Anti-Bacterial Agents/chemistry , Streptomyces/chemistry , Anti-Bacterial Agents/pharmacology , Bacteria/drug effects , Biosynthetic Pathways , Cell Line, Tumor , Cytochrome P-450 Enzyme System/metabolism , Drug Screening Assays, Antitumor , Humans , Magnetic Resonance Spectroscopy , Microbial Sensitivity Tests , Mixed Function Oxygenases/metabolism , Molecular Structure , Oxidation-Reduction , Soil Microbiology , Streptomyces/metabolismABSTRACT
Psychological stress has been recognized as a well-documented risk factor associated with ß2-adrenergic receptor (ß2-AR) in the development of pancreatic cancer. Aldo-keto reductase 1 member B1 (AKR1B1) is a potential interacting partner of ß2-AR, but the effect of their interaction on pancreatic cancer cells is not known at present. We found a positive correlation between AKR1B1 and ß2-AR expression in pancreatic cancer tissue samples, and co-localization of these proteins in the human pancreatic cancer BXPC-3 cell line. Compared to the controls, the CFPAC-1 and PANC-1 pancreatic cancer cells overexpressing ß2-AR and AKR1B1 respectively showed significantly higher proliferation rates, which is attributed to higher proportion of cells in the S phase and decreased percentage of early apoptotic cells. Furthermore, overexpression of ß2-AR led to a significant increase in the expression of AKR1B1 and phosphorylated extracellular signal-regulated kinase (p-ERK1/2). Overexpression of AKR1B1 significantly decreased ß2-AR levels and increased that of p-ERK1/2. Taken together, ß2-AR directly interacted with and up-regulated AKR1B1 in pancreatic cancer cells, and promoted their proliferation and inhibited apoptosis via the ERK1/2 pathway. Our findings also highlight the ß2-AR-AKR1B1 axis as a potential therapeutic target for pancreatic cancer.
Subject(s)
Aldehyde Reductase/genetics , Pancreatic Neoplasms/genetics , Receptors, Adrenergic, beta-2/metabolism , Adult , Aged , Aged, 80 and over , Aldehyde Reductase/metabolism , Aldo-Keto Reductases , Apoptosis/drug effects , Cell Line, Tumor , Cell Proliferation/drug effects , Female , Gene Expression Regulation, Neoplastic/genetics , Humans , MAP Kinase Signaling System/drug effects , MAP Kinase Signaling System/genetics , Male , Middle Aged , Mitogen-Activated Protein Kinase 3/metabolism , Pancreas/metabolism , Pancreatic Neoplasms/metabolism , Phosphorylation , Proto-Oncogene Proteins c-akt/metabolism , Receptors, Adrenergic, beta-2/genetics , Signal Transduction/drug effects , Up-RegulationABSTRACT
The tuberous roots of Aconitum carmichaeli are largely used in traditional Chinese medicine and widely grown in Jiangyou, Sichuan, China. During the growth process, this medicinal plant releases a large amount of allelochemicals into soil, which retard the growth and development of near and late crops. Therefore, a pure culture experiment was thus carried out by seed soaking to study the allelopathic effects of extracts from tuberous roots of A. carmichaeli (ETR) on the seed germination and young seedling growth of Lolium perenne, Trifolium repens, and Medicago sativa, the late pasture grasses after cultivation of A. carmichaeli. The results showed that three pasture grasses varied significantly in seed germination and young seedling growth in response to ETR concentrations. Seed germination of M. sativa was stimulated by low ERT concentration (0.01 x g(-1)), while all of pasture grass seeds germinated poorly in solution with 1.00 g x L(-1). Seed soaking with 1.00 g x L(-1) also inhibited significantly the growth of pasture young seedlings, with M. sativa showing the highest seedling height reduction of 42.05% in seeding height, followed by T. repens (40.21%) and L. perenne with about 11%. Cultivation of L. perenne could thus be beneficial to increase whole land productivity in A. carmichaeli-pasture grass cropping systems. In addition, hydrolysis of protein, starch, and inositol phosphates was blocked and free amino acids, soluble sugars and phosphorus were decreased in seeds by seed soaking with ETR, which could be one of the reason for the inhibition of seed germination. There was a significant reduction in root vigor, nitrate reductase, and chlorophyll after the seed treatment with ETR, indicating the suppression of nutrient uptake, nitrate assimilation, and photosynthesis by allelopathic chemicals in ETR, which could lead to the slow growth rate of pasture grass seedlings.
