The extracts of Fructus Akebiae, a preparation containing 90% of the active ingredient hederagenin: serotonin, norepinephrine and dopamine reuptake inhibitor.

Fructus Akebiae is a traditional Chinese herbal extract that has been used for the treatment of depressive disorders in China. Previous studies demonstrated that Fructus Akebiae extracts (FAE) displayed a potent antidepressant-like activity in animal behavior tests and found that the specific active ingredient from the extracts of Fructus Akebiae is hederagenin. However, the underlying mechanism is unknown. Here we provide evidences that FAE enhances the signaling of central monoamines via inhibition of the reuptake of the extracellular monoamines including serotonin (5-HT), norepinephrine (NE) and dopamine (DA). In rat brain membrane preparations and HEK293 cells transfected with human serotonin transporter (SERT), NE transporter (NET) and DA transporter (DAT), we found that FAE displayed marked affinity to rat and cloned human monoamine transporters in ex vivo and in vitro experiments, using competitive radio ligand binding assay. In uptake assays using rat synaptosomes and transfected cells, FAE was found to significantly inhibit all three monoamine transporters in a dose- and time-dependent manner, with a comparable or better potency to their corresponding specific inhibitors. In contrast, FAE (10 µM), showed no significant affinity to a variety array of receptors tested from CNS. In support of our uptake data, in vivo microdialysis studies showed that administration of FAE (12.6, 25, 50 mg/kg) significantly increased extracellular concentrations of 5-HT, NE and DA in frontal cortex of freely moving rats. Taken together, our current study showed for the first time that FAE is a novel triple inhibitor of monoamine transporters, which may be one the mechanisms of its antidepressant activity.

Inhibition of endothelin-1 and hypoxia-induced pulmonary pressor responses in the rat by a novel selective endothelin-A receptor antagonist, di-n-butylaminocarbamyl-L-leucyl-D-tryptophanyl-D-4-chloro-Phe.

Pulmonary hypertension is a kind of disease associated with a very high rate of mortality, and there are not many effective drugs for the treatment. Today, endothelin (ET)-1 receptor antagonists were proved to be effective in the treatment of pulmonary hypertension. Aiming at developing new endothelin-A receptor (ETA) antagonist for treatment of pulmonary hypertension, di-n-butylaminocarbamyl-L-leucyl-D-tryptophanyl-D-4-chloro-Phe, named GF063, was synthesized at base of selective ETA receptor antagonist BQ485 and selected for the further pharmacological characterization. The preliminary pharmacodynamics of GF063 was evaluated by radioligand receptor binding assay and test of antivasoconstriction effects in vitro and in vivo. The integrative pharmacodynamics was evaluated in hypoxia-induced rat pulmonary hypertension. In vitro, GF063 bound to ETA receptor with 100,000-fold higher affinity than to ETB receptor. GF063 concentration dependently inhibited contraction of isolated rat aortic ring induced by ET-1 and shifted the cumulative concentration-contraction response curve to right with no change in the maximal response. In vivo, GF063 inhibited the increase of mean systemic arterial pressure induced by ET-1 in anesthetized rat. In hypoxia-induced rat pulmonary hypertension model, pretreatment with GF063 (40 mg/kg, s.c.) significantly decreased pulmonary artery pressure and right ventricular hypertrophy, also significantly inhibited the increase of ET-1 level in lung, improved hemodynamics, and alleviated the wall thickness of pulmonary vessels. This study indicated that GF063, as a selective ETA receptor antagonist, could inhibit vasoconstriction effects in vivo and in vitro, could prevent pulmonary hypertension induced by hypoxia, and may have great potential to be developed as a new drug of antipulmonary hypertension.

Involvement of tissue transglutaminase in endothelin 1-induced hypertrophy in cultured neonatal rat cardiomyocytes.

A potential link between tissue-type transglutaminase (tTG) and cardiac hypertrophy was suggested recently. However, whether tTG is implicated in hypertrophic agonist-induced cardiac hypertrophy is not yet known. The purpose of this study was to investigate the effects of tTG on cardiomyocyte hypertrophy induced by endothelin (ET) 1. Real-time quantitative RT-PCR and Western blot analysis demonstrated that ET-1 increased the expression of tTG mRNA and protein in cardiomyocytes by activating ET(A) receptors. ET-1 failed to cause increases in cell size and [(3)H]leucine uptake, sarcomere reorganization, and gene induction of the atrial natriuretic factor when cardiomyocytes were treated with monodansylcadaverine, a competitive inhibitor of tTG. Furthermore, the effects of ET-1 on multifunctional activities of tTG were determined by evaluating the incorporation of [(3)H]putrescine into N,N'-dimethylated casein and charcoal absorption, respectively. The results showed that ET-1 did not influence the basal transglutaminase activity of cardiomyocytes but significantly inhibited the 0.1-mmol/L Ca(2+)-stimulated transglutaminase activity. Otherwise, ET-1 elevated the activity of GTPase in a concentration- and time-dependent manner. In vivo, right ventricular hypertrophy induced by 2 weeks of chronic hypoxia was depressed by the tTG inhibitor cystamine (10 to 30 mg/kg, 2 times per day, IP) in a dose-dependent manner. Taken together, our data strongly supported the notion that tTG may act as a positive regulator of the hypertrophic program in response to ET-1. This is probably attributable to the signaling activity of tTG rather than transglutaminase activity.

Pharmacological characterization of 3-azabicyclo[3,2,1] octane-1-yl-l-leucyl-d-tryptophanyl-d-4-Cl-phenylalanine: A novel ET(A) receptor-selective antagonist.

BACKGROUND AND OBJECTIVES: Pulmonary hypertension is a kind of disease associated with a very high rate of mortality. There are not many effective drugs for the treatment of pulmonary hypertension. Treatment with ET-1 receptor antagonists was proved to be effective in the treatment of pulmonary hypertension. Aiming at developing new endothelin A receptor (ET(A)) antagonist for treatment of pulmonary hypertension, 242 peptide compounds were synthesized by structural optimization of a selective ET(A) receptor antagonist BQ-123. Among these, -azabicyclo[3,2,1]octane-1-yl-l-Leucyl-d-tryptophanyl-d-4-Cl-phenylalanine, named ETP-508, was selected for further harmacological characterization. METHODS: Radioligand binding assay was performed to study the binding affinity of ETP-508 for ET(A) and ET(B) receptors. The biological activity of ETP-508 was evaluated in isolated rat aortic ring experiment and in systemic arterial pressure experiment. In addition, hypotensive effect of ETP-508 was investigated on hypoxia-induced pulmonary hypertension. RESULTS: ETP-508 binds to endothelin ET(A) receptor with >10,000-fold higher affinity than to endothelin B receptor in rat lung tissue preparation. ETP-508 inhibited endothelin-1 (ET-1)-induced contraction of isolated rat aortic ring and shifted the cumulative concentration-contraction response curve to ET-1 to right with no change in the maximal response. In vivo, ETP-508 inhibited the increased effect of ET-1 on mean systemic arterial pressure. Pre-treatment with ETP-508 by intravenous infusion significantly inhibited chronic hypoxia-induced pulmonary hypertension and right ventricular hypertrophy. ETP-508 also significantly inhibited the increase in lung ET-1 expression level, hemoglobin, red-cell count and red-cell hematocrit as induced by hypoxia. Furthermore, ETP-508 partially reversed pre-established pulmonary hypertension and right ventricle hypertrophy by chronic hypoxia. CONCLUSION: These results indicated that ETP-508 is a novel highly selective ET(A) receptor antagonist and may have a great potential to be developed as a drug of anti-pulmonary hypertension.

Production of human liver prolidase by Saccharomyces cerevisiae as host cells.

AIM: To clone and express the recombinant human liver prolidase in yeast and explore the activities of both dipeptidase and organophosphoric acid anhydrolase (OPAA). METHODS: The cDNA encoding human liver prolidase derived from healthy adult liver was cloned into the pYES2, an expression vector of S cerevisiae, and then transformed into S cerevisiae INVSc1 by electroporation. The transformant with the highest enzymatic activity was induced by galactose for expression. The optimal induction conditions (temperature, induction time, and the initial amount of inoculation cells) were estimated by orthogonal experimental design. The recombinant prolidase and OPAA activities were assayed by spectrocolorimetric methods. RESULTS: The recombinant enzyme catalyzed the hydrolysis of organophosphorous compound soman as well as the hydrolysis of dipeptide Gly-Pro. Under the optimal induction conditions (20 h, 25 degree, initial OD(600)=0.4), the maximum activities of prolidase and OPAA came to 226.5 and 578 micromol.min(-1).g(-1) protein in cell lysate supernatants, respectively. SDS-PAGE of the recombinant enzyme in disrupted cell supernatants showed a molecular weight of 56 kDa. Intensity scanning of the SDS-PAGE gel revealed that the enzyme accounted for 3.16 % of the total protein in the supernatant. One liter incubation medium produced 7 g of wet yeast cell containing 4.56 mg of the recombination protein. CONCLUSION: The recombinant human liver prolidase produced by yeast cell (S cerevisiae) exhibited both dipeptidase and OPAA activities.

Screening of RNA molecules inhibiting human acetylcholinesterase by virtue of systematic evolution of ligands by exponential enrichment.

AIM: To acquire the specific RNA aptamers inhibiting human red blood cell (RBC) acetylcholinesterase (AChE). METHODS: Systematic evolution of ligands by exponential enrichment (SELEX) aptamer against human red blood cell membrane AChE was selected by microtiter plate method in vitro. The specifity binding to AChE was determined by gel mobility shift analysis. Microcolorispectrophotometric method was used to measure the activity of AChE. RESULTS: The aptamers to human RBC AChE were identified by 9 reiterative rounds. At the same concentration (2.25 micromol/L), the aptamers did not bind to the recombinant human butyrylcholinesterase (rhBChE) but specifically bound to human RBC AChE and inhibited the enzyme activity. CONCLUSION: It is an effective way to isolate the specific AChE inhibitor from the vast oligonucleotide combinatorial library by virtue of SELEX.