4-o-methylascochlorin and ascochlorin

Chemopreventive or anticancer agents induce cancer cells to apoptosis through the activation of adenosine AMP-activated protein kinase (AMPK), which plays a major role as energy sensors under ATP-deprived condition or ROS generation. In this study, we compared the effects of ascochlorin (ASC), from the fungus Ascochyta viciae, and its derivatives on AMPK activity. We also examined a regulatory mechanism for hypoxia-inducible factor-1α (HIF-1α) stabilization in response to 4-O-methylascochlorin (MAC). We found that AMPK activation was mainly involved with MAC, but not ASC and 4-O-carboxymethylascochlorin (AS-6), indicating that the substitution of 4-O-methyl group from 4-O-hydroxyl group of ASC is important in the activation of AMPK and the expression of HIF-1α. MAC-stabilized HIF-1α via AMPK activation triggered by lowering the intracellular ATP level, not by ROS generation, increases glucose uptake and the expression of vascular endothelial growth factor (VEGF) and glucose transporter 1 (GLUT-1), major target genes of HIF-1α. Moreover, MAC-induced AMPK activity suppressed survival factors, including mTOR and ERK1/2 or translational regulators, including p70S6K and 4E-BP1. Our data suggest that AMPK is a key determinant of MAC-induced HIF-1α expression in response to energy stress, further implying its involvement in MAC-induced apoptosis.

Topics: Adenosine Triphosphate; Alkenes; AMP-Activated Protein Kinases; Apoptosis; Cell Line, Tumor; Gene Knockdown Techniques; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Methylation; Phenols; Promoter Regions, Genetic; Protein Stability; Reactive Oxygen Species; Ribosomal Protein S6 Kinases, 70-kDa; RNA, Small Interfering; Terpenes; TOR Serine-Threonine Kinases

Nuclear receptor family proteins are structurally related transcription factors activated by specific lipophilic compounds. Because they are activated by a variety of hormonal molecules, including retinoic acid, vitamin D, and steroid hormones, they are assumed to be promising targets for clinical drugs. We previously found that one ascochlorin (1) derivative, 4-O-carboxymethyl-ascochlorin (2), is a potent agonist of peroxisome proliferator activated receptor gamma (PPARgamma). Here, we synthesized derivatives of 1, designated as a lead compound, to create new modulators of nuclear hormone receptors. Two derivatives, 4-O-carboxymethyl-2-O-methylascochlorin (9) and 4-O-isonicotinoyl-2-O-methylascochlorin (10), showed improved agonistic activity for PPARgamma and induced differentiation of a progenitor cell line, C3H10T1/2. We also found that 1, dehydroascofuranon (29), and a 2,4-O-diacetyl-1-carboxylic acid derivative of 1 (5) specifically activated estrogen receptors, PPARalpha, and an androgen receptor. All of the derivatives (1-29) activated the pregnane X receptor. These results suggest that the chemical structure of 1 is useful in designing novel modulators of nuclear receptors.

Topics: Alkenes; Animals; Cell Differentiation; Cells, Cultured; Fibroblasts; Furans; Genes, Reporter; Genetic Vectors; Glycolates; Humans; Inhibitory Concentration 50; Ligands; Mice; Models, Molecular; Osteosarcoma; Phenols; Plasmids; Receptors, Cytoplasmic and Nuclear; Recombinant Proteins; Rosiglitazone; Thiazoles; Thiazolidinediones; Transcription Factors; Transfection