[Show abstract][Hide abstract] ABSTRACT: To discover novel cell division cycle 25 (CDC25) B inhibitors and elucidate the mechanisms of inhibition in cancer cells.
Cell growth inhibition was detected by MTT assay, the cell cycle was analyzed by flow cytometry, and protein expression and phosphorylation was examined by Western blot analysis.
LGH00031 inhibited CDC25B irreversibly in vitro in a dose-dependent manner, and impaired the proliferation of tumor cell lines. In synchronized HeLa cells, LGH00031 delayed the cell cycle progression at the G(2)/M phase. LGH00031 increased cyclin-dependent kinase 1 (CDK1) tyrosine 15 phosphorylation and cyclin B1 protein level. The activity of LGH00031 against CDC25B in vitro relied on the existence of 1,4-dithiothreitol (DTT) or dihydrolipoic acid and oxygen. The oxygen free radical scavenger catalase and superoxide dismutase reduced the inactivation of CDC25 by LGH00031, confirming that reactive oxygen species (ROS) mediate the inactivation process in vitro. LGH00031 accelerated cellular ROS production in a dose-dependent manner, and N-acetyl cysteine (NAC) markedly decreased the ROS production induced by LGH00031. Correspondingly, the LGH00031-induced decrease in cell viability and cell cycle arrest, cyclin B1 protein level, and phosphorylation of CDK1 tyrosine 15 were also rescued by NAC that decreased ROS production.
The activity of LGH00031 at the molecular and cellular level is mediated by ROS.
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to design and synthesize a series of high activity compounds against aspartyl protease beta-secretase (BACE-1) bearing hydroxyethylene (HE) framework.
First, we designed the small library based on our previous work and rational analysis. Subsequently, thirteen compounds were selected and synthesized using skilled solid phase synthetic methods to explore the relationship between structure and activity. We then used molecular modeling to explain the possible binding mode.
Thirteen new compounds (6-18) have been designed, synthesized and bioassayed. Their structures were determined by nuclear magnetic resonance (NMR) spectra, low- and high-resolution mass spectra and optical rotation. Most compounds have shown moderate to excellent activities, and compound 10, which contains fewer amino acids and amide bonds than GRL-7234, was about 5-fold more potent than the control compound 4 discovered by Merck. The molecular modeling results have indicated the possible binding mode and explained the difference between compounds 10 and 16, providing direction for further study.
This study yielded several high activity compounds bearing fewer amino acids and amide bonds than previous compounds, providing insight into the further development of potent BACE-1 inhibitors for the treatment of Alzheimer's disease.
[Show abstract][Hide abstract] ABSTRACT: The mangrove ecosystem is a largely unexplored source for actinomycetes with the potential to produce biologically active secondary metabolites. Consequently, we set out to isolate, characterize and screen actinomycetes from soil and plant material collected from eight mangrove sites in China. Over 2,000 actinomycetes were isolated and of these approximately 20%, 5%, and 10% inhibited the growth of Human Colon Tumor 116 cells, Candida albicans and Staphylococcus aureus, respectively, while 3% inhibited protein tyrosine phosphatase 1B (PTP1B), a protein related to diabetes. In addition, nine isolates inhibited aurora kinase A, an anti-cancer related protein, and three inhibited caspase 3, a protein related to neurodegenerative diseases. Representative bioactive isolates were characterized using genotypic and phenotypic procedures and classified to thirteen genera, notably to the genera Micromonospora and Streptomyces. Actinomycetes showing cytotoxic activity were assigned to seven genera whereas only Micromonospora and Streptomyces strains showed anti-PTP1B activity. We conclude that actinomycetes isolated from mangrove habitats are a potentially rich source for the discovery of anti-infection and anti-tumor compounds, and of agents for treating neurodegenerative diseases and diabetes.
[Show abstract][Hide abstract] ABSTRACT: Cell division cycle 25 (CDC25) phosphatases have recently been considered as potential targets for the development of new cancer therapeutic agents. We aimed to discover novel CDC25B inhibitors in the present study.
A molecular level high-throughput screening (HTS) assay was set up to screen a set of 48000 pure compounds.
HTS, whose average Z' factor is 0.55, was finished and LGH00045, a mixed-type CDC25B inhibitor with a novel structure and relative selectivity for protein tyrosine phosphatases, was identified. Furthermore, LGH00045 impaired the proliferation of tumor cells and increased cyclin-dependent kinase 1 inhibitory tyrosine phosphorylation. In synchronized HeLa cells, LGH00045 delayed cell cycle progression at the G2-M transition.
LGH00045, a novel CDC25B inhibitor identified through HTS, showed good inhibition on the proliferation of tumor cells and affected the cell cycle progression, which makes it a good hit for further structure modification.
[Show abstract][Hide abstract] ABSTRACT: The aim of the present study was to discover novel protein tyrosine phosphatase 1B (PTP1B) inhibitors. We expressed and purified the human PTP1B catalytic domain and set up a molecular level high-throughput screening (HTS) assay to screen a set of 48,000 pure compounds.
HTS was finished with an averaged Zo factor of 0.63, and LGH00081, a competitive inhibitor of PTP1B with novel structure and relatively good selectivity for receptor-type protein tyrosine phosphatases, was identified.
We established a molecular level assay which is useful for the screening of PTP1B inhibitors with therapeutic potential. The novel competitive PTP1B inhibitor LGH00081 offers a good start for structure modification and cellular functional activity study.
[Show abstract][Hide abstract] ABSTRACT: Caspase-1, the most efficient enzyme in processing the proinflammatory cytokines interleukin 1beta and interleukin 18 in humans, is associated with inflammatory diseases such as rheumatoid arthritis, osteoarthritis, and some neuronal diseases. We previously reported that isoquinoline-1,3,4-trione and its derivatives are novel caspase-3 inhibitors that could attenuate apoptosis in vitro and in vivo. Here we report a novel derivative of isoquinoline-1,3,4-trione that is highly potent in inhibiting caspase-1 activity in an irreversible and slow-binding manner, thus inhibiting cellular caspase-1 activity and the maturation of interleukin 1beta in U-937 cells.