Discovery of Carbono(di)thioates as Indoleamine 2,3-Dioxygenase 1 Inhibitors.

A structure-activity relationship study unexpectedly showed that carbonothioates 4a and 4b, obtained by a unique alkaline hydrolysis of 2-alkylthio-oxazolines 3a and 3b, respectively, are a novel scaffold for indoleamine 2,3-dioxygenase 1 (IDO1) inhibitors. Derivatization of the carbonothioates enhanced inhibitory activity against IDO1 and cellular kynurenine production without cytotoxicity and led to the discovery of the related scaffolds carbonodithioates 5 and cyanocarbonimidodithioates 6 as IDO1 inhibitors. Incorporation of an OH group provided the most potent analogue 5i. UV-visible absorption spectroscopy of the Soret band, as well as docking and peptide mapping studies, suggested that these molecules bind to the heme in the active site of IDO1. Our unique IDO1 inhibitors are potential leads for future development.

Cyclic analogue of S-benzylisothiourea that suppresses kynurenine production without inhibiting indoleamine 2,3-dioxygenase activity.

Kynurenine is biosynthesised from tryptophan catalysed by indoleamine 2,3-dioxygenase (IDO). The abrogation of kynurenine production is considered a promising therapeutic target for immunological cancer treatment. In the course of our IDO inhibitor programme, formal cyclisation of the isothiourea moiety of the IDO inhibitor 1 afforded the 5-Cl-benzimidazole derivative 2b-6, which inhibited both recombinant human IDO (rhIDO) activity and cellular kynurenine production. Further derivatisation of 2b-6 provided the potent inhibitor of cellular kynurenine production 2i (IC50 = 0.34 µM), which unexpectedly exerted little effect on the enzymatic activity of rhIDO. Elucidation of the mechanism of action revealed that compound 2i suppresses IDO expression at the protein level by inhibiting STAT1 expression in IFN-γ-treated A431 cells. The kynurenine-production inhibitor 2i is expected to be a promising starting point for a novel approach to immunological cancer treatment.

Synthesis and inhibitory activity on hepatitis C virus RNA replication of 4-(1,1,1,3,3,3-hexafluoro-2-hydroxy-2-propyl)aniline analogs.

Using our recently developed assay system for full-genome-length hepatitis C virus (HCV) RNA replication in human hepatoma-derived Li23 cells (ORL8), we identified 4-(1,1,1,3,3,3-hexafluoro-2-hydroxy-2-propyl)aniline analog 1a as a novel HCV inhibitor. Structural modifications of 1a provided a series of sulfonamides 7 with much more potent HCV RNA replication-inhibitory activity than ribavirin. Compound 7a showed an additive anti-HCV effect in combination with standard anti-HCV therapy (IFN-α plus ribavirin). Since 7a generated reactive oxygen species (ROS) in the ORL8 system and its anti-HCV activity was blocked by vitamin E, its anti-HCV activity may be mediated at least in part by ROS.

Assessing primary and bacterial production rates in biofilms on pebbles in Ishite stream, Japan.

Various measurements of microbial productivity in streambed pebble biofilms were analyzed almost monthly for 1 year to quantify the importance of primary production as an autochthonous source of organic matter utilized to support heterotrophic bacterial production in the dynamic food web within this natural microbial habitat. Bacterial density varied from 0.3x10(8) to 1.4x10(8) cells cm-2, and chlorophyll a concentration ranged from 0.7 to 25.9 microg cm-2, with no coupled oscillation between seasonal changes in these two parameters. In bottle incubation experiments, the instantaneous bacterial growth rate of bacteria was significantly correlated with their production rate [measured by frequency of dividing cells (FDC)] as follows: ln mu=0.138FDC-3.003 (n=15, r2=0.445, p<0.001). FDC values in the pebble biofilms increased with fluctuations during the study period, ranging from 3.6% to 9.2%. Bacterial production rates largely fluctuated between 0.15 to 0.92 microg C cm-2 h-1, and its seasonal pattern was similar to that of bacterial density. Net primary production measured between May 2002 to November 2002 attained minimum level (0.5 microg C cm-2 h-1) in June and maximum level (1.9 microg C cm-2 h-1) in August. Percentages of bacterial production to net primary production ranged between 21% and 120%. Because this ratio extends both below and above 100% for these parameters, it is likely that both autochthonous and allochthonous supplies of organic matter are important for production of bacteria in the pebble biofilms that develop in rapidly flowing fresh water streams.