The Xylariaceae (Ascomycete) is a large family and currently comprises more than 36 genera. So far, at least one third of these genera have been chemically investigated.
1)One of these specific metabolites repeatedly isolated from this family is azaphilone, with various substitution groups linked to the main skeleton.2,3) Although previous publications showed that azaphilones exhibit broad activities in many biological systems, such as cholesteryl ester transfer protein, 4) monoamine oxidase inhibition, 5) endothelin receptor binding, 6) the inhibition of gp120-CD4 binding, 7) telomerase inhibition, 8) the induction of Epstein-Barr virus, 9) and antimicrobial activities, 3,10,11) there is no report about the inhibition of nitric oxide (NO) production by azaphilones.NO is synthesized from L-arginine by nitric oxide synthase (NOS). Currently, three distinct isoforms of NOS have been identified: Neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS).12) Of these, iNOS is an important enzyme involved in the regulation of inflammation 13) and in the generation of a large amount of NO.14) Overproduction of NO by iNOS has been implicated in various pathological processes including septic shock, tissue damage following inflammation, and rheumatoid arthritis. [15][16][17][18][19] Therefore, suppression of nitric oxide (NO) production in macrophages could be a target for potential anti-inflammatory drugs.In the present study, we screened the inhibitory activity of fifteen azaphilones, which were isolated from mushrooms belonging to the Xylariaceae family, and also elucidated the mechanism of inhibition of NO production stimulated by lipopolysaccharide (LPS) in RAW 264.7 cells.
MATERIALS AND METHODS
Isolation of AzaphilonesFifteen azaphilones, specifically daldinins C, E and F (1-3) from Hypoxylon fuscum, 20,21) multiformin D (4) from H. multiforme, 11) sassafrins A-C (5-7) from Creospharia sassafras, 10) entonaemin A (8) and rubiginosins A-C (9-11) from H. rubiginosin, 22) cohaerins A and B (12, 13) from H. cohaerens, 23) rutilins A and B (14, 15) from H. rutilin, 24) were isolated from xylariaceous fungi and their structures characterized by a combination of NMR spectrometry and X-ray crystallographic analysis.Cell Culture RAW 264.7 cells, a mouse macrophage cell line, were grown in RPMI 1640 supplemented with 10% fetal bovine serum, kanamycin (50 mg/ml), and ampicillin (60 mg/ml) at 37°C in an atmosphere of 5% CO 2 and 95% air.Inhibition of NO Production of Fifteen Azaphilones One hundred microliters of RAW 264.7 cells (8ϫ10 5 cells/ ml) was pipetted into the wells of 96-well culture plates and then cultured. After 24 h incubation, 50 ml of medium containing various concentrations of each azaphilone derivative diluted in DMSO was added to each well. The final DMSO concentration was less than 0.1%. At this concentration, DMSO did not show any NO-induction without stimulation with LPS. Then, 50 ml of vehicle or LPS purified from Pantoea agglomerans (4 mg/ml) was added to each well. The cells were further in...