Novel Gut Microbiota Modulator, Which Markedly Increases Akkermansia muciniphila Occupancy, Ameliorates Experimental Colitis in Rats.

BACKGROUND: Since gut microbiota is involved in the pathogenesis of inflammatory bowel disease (IBD), antibiotics or probiotics may be attractive options for the treatment of IBD. Akkermansia muciniphila is expected as a next-generation probiotic for IBD, and OPS-2071 is a novel quinolone with potent antibacterial activity against Clostridioides difficile. AIMS: The aim of this study is to assess the potential of OPS-2071 as a gut microbiota modulator for IBD. METHODS: Minimum inhibitory concentrations of several bacteria in the human intestinal microbiota were determined. Microbiota changes in the feces were typed using metagenomic analysis after oral administration of OPS-2071 (100 mg/kg) twice a day to normal rats. The amounts of mucin were determined using the Fecal Mucin Assay Kit. The effects of OPS-2071 (1, 3, 10 mg/kg) twice a day on fecal symptoms and fecal microbiota were evaluated in a colitis rat model induced by free access to drinking water containing 3% dextran sulfate sodium for 10 days. RESULTS: OPS-2071 showed notably low antibacterial activity against only A. muciniphila in spite of higher antimicrobial activity against other strains of intestinal bacteria. OPS-2071 rapidly and dramatically increased the occupancy of A. muciniphila as well as the amount of mucin in the feces of normal rats. OPS-2071 (10 mg/kg) significantly suppressed the exacerbation of stool scores, especially the bloody stool score, with the increase in A. muciniphila occupancy. CONCLUSIONS: OPS-2071 is expected to be a new therapeutic option for IBD as a gut microbiota modulator by significantly increasing A. muciniphila occupancy.

Molecular basis for G2 arrest induced by 2'-C-cyano-2'-deoxy-1-beta-D-arabino-pentofuranosylcytosine and consequences of checkpoint abrogation.

2'-C-cyano-2'-deoxy-1-beta-D-arabino-pentofuranosylcytosine (CNDAC) is a nucleoside analogue with a novel mechanism of action that is currently being evaluated in clinical trials. Incorporation of CNDAC triphosphate into DNA and extension during replication leads to single-strand breaks directly caused by beta-elimination. These breaks, or the lesions that arise from further processing, cause cells to arrest in G2. The purpose of this investigation was to define the molecular basis for G2 checkpoint activation and to delineate the sequelae of its abrogation. Cell lines derived from diverse human tissues underwent G2 arrest after CNDAC treatment, suggesting a common mechanism of response to the damage created. CNDAC-induced G2 arrest was instituted by activation of the Chk1-Cdc25C-Cdk1/cyclin B checkpoint pathway. Neither Chk2, p38, nor p53 was required for checkpoint activation. Inhibition of Chk1 kinase with 7-hydroxystaurosporine (UCN-01) abrogated the checkpoint pathway as indicated by dephosphorylation of checkpoint proteins and progression of cells through mitosis and into G1. Cell death was first evident in hematologic cell lines after G1 entry. As indicated by histone H2AX phosphorylation, DNA damage initiated by CNDAC incorporation was transformed into double-strand breaks when ML-1 cells arrested in G2. Some breaks were manifested as chromosomal aberrations when the G2 checkpoint of CNDAC-arrested cells was abrogated by UCN-01 but also in a minor population of cells that escaped to mitosis during treatment with CNDAC alone. These findings provide a mechanistic rationale for the design of new strategies, combining CNDAC with inhibitors of cell cycle checkpoint regulation in the therapy of hematologic malignancies.

Cellular and biochemical mechanisms of the resistance of human cancer cells to a new anticancer ribo-nucleoside, TAS-106.

We have established variants of DLD-1 human colon carcinoma and HT-1080 human fibrosarcoma cells resistant to the new anticancer ribo-nucleosides, 1-(3-C-ethynyl-beta-D-ribo-pentofuranosyl)-cytosine (ECyd, TAS-106) and 1-(3-C-ethynyl-beta-D-ribo-pentofuranosyl)uracil (EUrd). Both variants were shown to have decreased (3- to 24-fold decrease) uridine-cytidine kinase (UCK) activity, and exhibited cross-resistance to EUrd and TAS-106. Based on the IC(50) values determined by chemosensitivity testing, a 41- to 1102-fold resistance to TAS-106 was observed in the resistant cells. TAS-106 concentration-dependently inhibited RNA synthesis, while its effect on DNA synthesis was negligible. The degree of resistance (14- to 3628-fold resistance) calculated from the inhibition of RNA synthesis tended to be close to the degree of chemoresistance of tested cells to TAS-106. The experiments on the intracellular metabolism of TAS-106 in the parental cells revealed a rapid phosphorylation to its nucleotides, particularly the triphosphate (ECTP), its major active metabolite. The amount of TAS-106 transported into the resistant cells was markedly reduced and the intracellular level of ECTP was decreased from 1/19 to below the limit of detection; however, the unmetabolized TAS-106 as a percentage of the total metabolite level was high as compared with the parental cells. The ratio of the intracellular level of ECTP between parental and resistant cells tended to approximate to the degree of resistance calculated from the inhibitory effect on RNA synthesis. These results indicate that the TAS-106 sensitivity of cells is correlated with the intracellular accumulation of ECTP, which may be affected by both the cellular membrane transport mechanism and UCK activity.