Chang Ho Ahn

In Vivo and In Vitro Effects of a HIF-1α Inhibitor, RX-0047

HIF‐1α plays a major role in activating gene transcription and is important for maintaining homeostasis under hypoxic conditions. Since tumors are often in a hypoxic state, HIF‐1α is a potential target for the development of novel cancer therapeutics. This study was performed to determine the antitumoral efficacy of an antisense HIF‐1α inhibitor, RX‐0047 on different human cancer cell lines (MDA‐MB 231, HME50‐T, PC‐3, Panc‐1 and A549) in vitro. A549 lung cancer and PC‐3 prostate cancer cells containing a luciferase gene reporter were used for in vivo xenograft animal models. Progressive tumor development was quantified using live animal BLI (bioluminescence imaging) in addition to ex vivo imaging and histology. All cell lines tested were sensitive to inhibition of cell growth with 10 nM and higher ranges of RX‐0047, additionally RX‐0047 sensitizes cells to ionizing radiation treatments. Finally, RX‐0047 (30 mg/kg) inhibited the formation of human lung metastasis in xenograft mouse models and reduced tumor size in flank models. J. Cell. Biochem. 104: 985–994, 2008.

Clavulanic acid stimulates sexual behaviour in male rats

Sexual behaviour in rats can be used to predict putative effects on human sexual behaviour. Anecdotic reports exist, that the beta-lactamase inhibitor, clavulanic acid exerts sexual stimulating activities in monkeys. To characterize these pro-sexual activities, clavulanic acid was tested in three doses and compared to one dose of a sexually inhibitory dose of the selective serotonin reuptake inhibitor, paroxetine, in sexually-experienced male rats, selected for a moderate level of sexual performance in a standard 30-min test with an oestrus female. After acute administration, clavulanic acid had minor sexual stimulating effects at the highest dose in the number of intromissions and in the first ejaculation series. After sub-chronic 7-days treatment, clavulanic acid increased the number of ejaculations at all three doses and reduced the number of intromissions in the 1st series at the highest dose. After chronic 14 days treatment, a similar but stronger pro-sexual profile was observed. The sexual side effects of paroxetine were as expected, including slight sexual inhibitory effects after acute administration, but somewhat stronger overall inhibitory effects after 7 and 14-days pretreatment, particularly notable in the decreasing number of animals contributing to the 2nd ejaculation series, which was even stronger after 14-days treatment. One week after cessation of treatment, the paroxetine group had completely recovered, whereas the highest dose-group of clavulanic acid still showed some pro-sexual effects. This remarkable pro-sexual activity of clavulanic acid cannot readily be explained by its mechanism of action as a beta-lactamase inhibitor but could be due to unexpected central activity of the compound.

Synthesis and Antitumor Activity of Fluorocyclopentenyl-Pyrimidines

Synthesis of fluorocyclopentenyl pyrimidine nucleosides 6–9 was enantiopurely accomplished employing oxidative rearrangement, RCM reaction and electrophilic fluorination starting from d-ribose. Cytosine analog 8 was found to exhibit significant anticancer activity in various human tumor cell lines.

Clavulanic acid increases dopamine release in neuronal cells through a mechanism involving enhanced vesicle trafficking.

Clavulanic acid is a CNS-modulating compound with exceptional blood-brain barrier permeability and safety profile. Clavulanic acid has been proposed to have anti-depressant activity and is currently entering Phase IIb clinical trials for the treatment of Major Depressive Disorder (MDD). Studies have also shown that clavulanic acid suppresses anxiety and enhances sexual functions in rodent and primate models by a mechanism involving central nervous system (CNS) modulation, although its detailed mechanism of action has yet to be elucidated. To further examine its potential as a CNS modulating agent as well as its mechanism of action, we investigated the effects of clavulanic acid in neuronal cells. Our results indicate that clavulanic acid enhances dopamine release in PC12 and SH-SY5Y cells without affecting dopamine synthesis. Furthermore, using affinity chromatography we were able to identify two proteins, Munc18-1 and Rab4 that potentially bind to clavulanic acid and play a critical role in neurosecretion and the vesicle trafficking process. Consistent with this result, an increase in the translocation of Munc18-1 and Rab4 from the cytoplasm to the plasma membrane was observed in clavulanic acid treated cells. Overall, these data suggest that clavulanic acid enhances dopamine release in a mechanism involving Munc18-1 and Rab4 modulation and warrants further investigation of its therapeutic use in CNS disorders, such as depression.

Clavulanic acid inhibits MPP+-induced ROS generation and subsequent loss of dopaminergic cells

Clavulanic acid is a psychoactive compound that has been shown to modulate central nervous system activity. Importantly, in neurotoxin-induced animal models, clavulanic acid has been shown to improve motor function (Huh et al., 2010) suggesting that it can be neuroprotective; however, the mechanism as how clavulanic acid can induce neuroprotection is not known. We demonstrate here that clavulanic acid abrogates the effects of the neurotoxin 1-methyl-4-phenylpyridinium (MPP(+)) which mimics Parkinsons disease (PD) by inducing neurodegeneration. To further establish the mechanism we identified that clavulanic acid inhibits neurotoxin-induced loss of mitochondrial membrane potential and ROS production. Consistent with these results, neurotoxin-induced increase in Bax levels was also decreased in clavulanic acid treated cells. Importantly, neurotoxin-induced release of cytochrome c levels as well as caspase activation was also inhibited in clavulanic acid treated cells. In addition, Bcl-xl levels were also restored and the Bcl-xl/Bax ratio that is critical for inducing apoptosis was increased in clavulanic acid treated cells. Overall, these results suggest that clavulanic acid is intimately involved in inhibiting neurotoxin-induced loss of mitochondrial function and induction of apoptosis that contributes towards neuronal survival.

Clavulanic acid protects neurons in pharmacological models of neurodegenerative diseases

Clavulanic acid is a psychoactive compound with excellent blood‐brain barrier permeability and safety profiles. Previous studies showed that clavulanic acid suppresses anxiety in rodents and in a primate model. In addition, clavulanic acid is thought to enhance sexual function in animal models via central nervous system (CNS) mechanisms. To further examine its potential as a CNS‐modulating agent, we investigated the effects of clavulanic acid in neurotoxin‐induced animal models that emulate neurodegenerative disease symptoms. Clavulanic acid was administered to rodents that were exposed to kainic acid or 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP). Using histochemical staining of brain sections, we demonstrated that clavulanic acid protects hippocampal and dopaminergic neurons from toxin‐induced acute death. We also observed that clavulanic acid improves motor function in MPTP‐treated mice in a behavioral test. These data indicate that clavulanic acid may have neuroprotective effects and warrants further investigation of its therapeutic use in CNS disorders, such as Parkinsons and Alzheimers disease. Drug Dev Res 71:351–357, 2010.

Development of 3-aryl-1-isoquinolinamines as potent antitumor agents based on CoMFA

Various substituted 3-aryl-1-isoquinolinamines were designed and synthesized based on the previously constructed CoMFA model. Most of the synthesized compounds showed excellent potency in eight different human tumor cell lines as expected. In order to find the exact cytotoxic mechanism of these 3-aryl-1-isoquinolinamines, we analyzed the cell cycle dynamics by flow cytometry and found that 3-aryl-1-isoquinolinamine 6k-treated HeLa cells were arrested in G2/M phase, which is related to apoptosis.

QSID Tool: a new three-dimensional QSAR environmental tool

QSID Tool (Quantitative structure–activity relationship tool for Innovative Discovery) was developed to provide an easy-to-use, robust and high quality environmental tool for 3D QSAR. Predictive models developed with QSID Tool can accelerate the discovery of lead compounds by enabling researchers to formulate and test hypotheses for optimizing efficacy and increasing drug safety and bioavailability early in the process of drug discovery. QSID Tool was evaluated by comparison with SYBYL® using two different datasets derived from the inhibitors of Trypsin (Böhm etxa0al., J Med Chem 42:458, 1999) and p38-MAPK (Liverton etxa0al., J Med Chem 42:2180, 1999; Romeiro etxa0al., J Comput Aided Mol Des 19:385, 2005; Romeiro etxa0al., J Mol Model 12:855, 2006). The results suggest that QSID Tool is a useful model for the prediction of new analogue activities.