Falcarindiol Isolated from Notopterygium incisum Inhibits the Quorum Sensing of Pseudomonas aeruginosa.

Quorum sensing (QS) is employed by the opportunistic pathogen Pseudomonas aeruginosa to regulate physiological behaviors and virulence. QS inhibitors (QSIs) are potential anti-virulence agents for the therapy of P. aeruginosa infection. During the screening for QSIs from Chinese herbal medicines, falcarindiol (the major constituent of Notopterygium incisum) exhibited QS inhibitory activity. The subinhibitory concentration of falcarindiol exerted significant inhibitory effects on the formation of biofilm and the production of virulence factors such as elastase, pyocyanin, and rhamnolipid. The mRNA expression of QS-related genes (lasB, phzH, rhlA, lasI, rhlI, pqsA, and rhlR) was downregulated by falcarindiol while that of lasR was not affected by falcarindiol. The transcriptional activation of the lasI promoter was inhibited by falcarindiol in the P. aeruginosa QSIS-lasI selector. Further experiments confirmed that falcarindiol inhibited the las system using the reporter strain Escherichia coli MG4/pKDT17. Electrophoretic mobility shift assay (EMSA) showed that falcarindiol inhibited the binding of the transcription factor LasR and the lasI promoter region. Molecular docking showed that falcarindiol interacted with the Tyr47 residue, leading to LasR instability. The decrease of LasR-mediated transcriptional activation was responsible for the reduction of downstream gene expression, which further inhibited virulence production. The inhibition mechanism of falcarindiol to LasR provides a theoretical basis for its medicinal application.

Anti-neoplastic efficacy of Haimiding on gastric carcinoma and its mechanisms.

AIM: To study the anti-neoplastic effect of Haimiding and its mechanisms of action. METHODS: Experiments using MTT and colony formation were carried out to study the in vitro anti-neoplastic action of Haimiding, its in vivo anti-neoplastic action was studied by observing its effect on the weight of tumors in FC mice and S(180), H(22) tumor bearing mice, as well as their life spans. The effect of Haimiding on cell apoptosis and different stages of cell cycles in human gastric carcinoma cells were studied by flow cytometry. Its effect on [Ca(2+)](i) of human gastric carcinoma cells and the source of Ca(2+) during the change of [Ca(2+)](i) were observed by confocal laser scanning technique. RESULTS: Haimiding showed a definite cytotoxicity to 8 human tumor cell lines, which was most prominent against BGC-823, E(ca-109) and HCT-8 tumor cells. It also exhibited an obvious inhibition on colony formation of the above tumor cell lines, which was most prominent in E(ca-109) tumor cells. It showed obvious inhibition on the growth of tumor in FC mice and S(180) bearing mice as well as prolonged the life span of H(22) bearing mice. It was able to induce apoptosis and elevate intracellular [Ca(2+)](i) concentration of tumor cells. The source of Ca(2+) came from both extracellular Ca(2+) influx and intracellular Ca(2+) release. CONCLUSION: Haimiding is composed of a TCM preparation and 5-flurouracil. Its anti-neoplastic potency is highly enhanced by synergism as compared with either one of its components. Its mechanisms of anti-neoplastic action can be attributed to its action to initiate apoptosis of tumor cells by opening the membrane calcium channel and inducing intracellular Ca(2+) release to elevate [Ca(2+)](i) of the tumor cells.