A simplified model of hypoxic injury in primary cultured rat hepatocytes

Summary The Anaeropack system for cell culture, which was originally designed for the growth of anaerobic bacteria, was used to produce a hypoxic atmosphere for cultured hepatocytes. We measured changes in the oxygen and carbon dioxide concentrations and the atmospheric temperature in an airtight jar. We also measured changes in the pH of the medium during hypoxia to assess the accuracy of this system. Moreover, we used three durations (2, 3, and 4 h) of hypoxia and 8 h of reoxygenation in cultured rat hepatocytes, and then measured the lactate dehydrogenase (LDH), ketone body concentration (acetoacetate + β-hydroxybutyrate), and the ketone body ratio (KBR: acetoacetate/β-hydroxybutyrate) in the medium in order to assess the suitability of this system as a model for reperfusion following liver ischemia. The oxygen concentration dropped to 1% or less within 1 h. The concentration of carbon dioxide rose to about 5% at 30 min after the induction of the hypoxic conditions, and was maintained at this level for 5 h. No effect of the reaction heat produced by the oxygen absorbent in the jar was recognized. The extent of cell injury produced by changing the hypoxic parameters was satisfactorily reflected by the KBR, the ketone body concentration, and the LDH activity released into the medium. Because this model can duplicate the conditions of the hepatocytes during revascularization following ischemic liver, and the Anaeropack system for cell culture is easy to manipulate, it seems suitable for the experimental study of hypoxic injury and revascularization in vitro.     

Synthesis of aza- and thia-spiroheterocycles and attempted synthesis of spiro sulfonium compounds related to salacinol

The synthesis of aza- and thia-spiroheterocycles and the attempted synthesis of spiro sulfonium compounds related to salacinol are described. The binding of the nanomolar inhibitor swainsonine to Drosophila Golgi alpha-mannosidase II (dGMII) involves a large contribution of interactions between the six-membered ring of the inhibitor and the hydrophobic pocket within the enzyme active site. Salacinol, a naturally occurring sulfonium ion, is one of the active principles in the aqueous extracts of Salacia reticulata that are traditionally used in Sri Lanka and India for the treatment of diabetes. Spiro aza- and thia-heterocycles and a spiro analogue of salacinol were designed with the expectation that the hydrocarbon portions would make hydrophobic contributions to binding. The former sets of compounds were synthesized successfully but the salacinol analogue proved to be elusive. The stereochemistry of the final compounds was determined by means of 1D-NOESY experiments. The aza- and thia-heterocycles were not effective inhibitors of Golgi alpha-mannosidase II or human maltase glucoamylase.     

Effects of food deprivation on 24 h-changes in brain and liver carbohydrate and ketone body metabolism of rainbow trout

Plasma glucose, lactate and acetoacetate, brain glycogen and acetoacetate, and liver acetoacetate, glycogen and lactate in fed rainbow trout exhibited daily changes. However, no daily changes were observed in the activities of the brain enzymes glycogen synthetase, 6-phosphofructo 1-kinase, and lactate dehydrogenase. Depending on the length of the previous fasting period most daily changes observed in the metabolic parameters of fed fish disappeared, except for liver acetoacetate levels, which displayed daily changes in both fed and fasted fish. These results suggest that feeding is an important factor regulating most daily changes in the brain and liver carbohydrate and ketone body metabolism of rainbow trout.     

Design, synthesis and biological activity of novel peptidyl benzyl ketone FVIIa inhibitors

Herein is described the synthesis of a novel class of peptidyl FVIIa inhibitors having a C-terminal benzyl ketone group. This class is designed to be potentially suitable as stabilization agents of liquid formulations of rFVIIa, which is a serine protease used for the treatment of hemophilia A and B inhibitor patients. A library of compounds was synthesized with different tripeptide sequences, N-terminals and d-amino acids in the P3 position. Cbz-d-Phe-Phe-Arg-bk (33) was found to be the best candidate with a potency of K_i = 8 μM and no substantial inhibition of related blood coagulation factors (thrombin and FXa). Computational studies revealed that 33 has a very stable binding conformation due to intramolecular hydrogen bonds, which cannot be formed with l-Phe in the P3 position. Nonpolar amino acids were found to be superior, probably due to a minimization of the cost of desolvation upon binding to FVIIa.     

A polyisoprenylated ketone from Calophyllum enervosum

A polyisoprenylated ketone named enervosanone has been isolated from the stem bark of Calophyllum enervosum together with three known compounds, cambogin, osajaxanthone and epicatechin. Their structures were determined by spectroscopic analysis. The antimicrobial evaluations of the isolated compounds were also reported.     

A novel protease from Entamoeba histolytica homologous to members of the family S28 of serine proteases

Serine proteases are one of the biologically most important and widely distributed enzyme families. A protease capable of degrading the substrate Suc-AAF-AMC was isolated from axenically grown trophozoites of Entamoeba histolytica. The enzyme was purified by ion-exchange chromatography and electroelution, and appeared on 2D-PAGE as a spot of 60 kDa and pI of 4.65. Data obtained from zymogram suggest the active protease is present either as homodimer (130 kDa) or homotetramer (250 kDa). The optimal temperature of the enzyme was 37 degrees C, and it exhibited activity over a broad pH range. The protease was strongly inhibited by TPCK and chelating agents. The enzymatic activity was restored upon addition of calcium. BLAST analysis with the sequence of internal peptides of the protein revealed two open reading frames within the genome of E. histolytica, homologous to members of the family S28, clan SC of serine proteases.     

Mcl-1 fragment induces apoptosis through direct interaction with Bax

Mcl-1 full-length (Mcl-1^1-350), a tightly regulated protein, plays an important role in protecting cells against apoptosis. Cleavage of Mcl-1 at Asp127 by caspase (Mcl-1^C1) contributes to the regulation of Mcl-1 expression, but its pro-apoptotic function remains controversial. Here, we reported that Mcl-1^128-350 expression induced caspase-dependent apoptosis. We demonstrated that Mcl-1^128-350 but not Mcl-1^1-350 interacts with Bax. This interaction required an intact BH3 Mcl-1^128-350 domain and leads to Bax activation and translocation to mitochondria. The silencing of Bax, but not of Bak, prevented Mcl-1^128-350 induced apoptosis. In conclusion, Mcl-1^128-350 exerts a pro-apoptotic function governed by its capacity to interact with Bax.

Structured summary

MINT-7306752: Mcl-1 (uniprotkb:Q07820) physically interacts (MI:0915) with BAK (uniprotkb:Q16611) by anti tag coimmunoprecipitation (MI:0007)MINT-7306728: Mcl-1 (uniprotkb:Q07820) physically interacts (MI:0914) with BAX (uniprotkb:Q07812) and BAK (uniprotkb:Q16611) by anti tag coimmunoprecipitation (MI:0007)MINT-7307171: F1 ATPase (uniprotkb:Q5TC12), Mcl-1 (uniprotkb:Q07820) and BAX (uniprotkb:Q07812) colocalize (MI:0403) by cosedimentation through density gradients (MI:0029)     

Plasmodium falciparum: biochemical characterization of the cysteine protease falcipain-2'

The Plasmodium falciparum cysteine proteases falcipain-2 and falcipain-3 are hemoglobinases and potential antimalarial drug targets. The falcipain-2' gene was identified recently and is nearly identical in sequence to falcipain-2. The product of this gene has not been studied previously. The mature protease domain of falcipain-2' was expressed in Escherichia coli, purified, and refolded to active enzyme. Functional analysis revealed similar biochemical properties to those of falcipain-2, including pH optima (pH 5.5-7.0), reducing requirements, and substrate preference. Studies with cysteine protease inhibitors showed similar inhibition of falcipain-2 and falcipain-2', although specificities were not identical. Considering activity against the presumed biological substrate, both enzymes readily hydrolyzed hemoglobin. Our results confirm that falcipain-2' is an active hemoglobinase and suggest that falcipain-2 and falcipain-2' play similar roles in erythrocytic parasites but that, for promising cysteine protease inhibitors, it will be important to confirm activity against this additional target.     

Candida tenuis Xylose Reductase Catalyzed Reduction of Aryl Ketones for Enantioselective Synthesis of Active Oxetine Derivatives

Candida tenuis xylose reductase shows high catalytic efficiencies in carbonyl reduction of acetophenone and 1‐phenyl‐1‐propanone derivatives. The quite low substrate solubility in aqueous buffer systems is circumvented by addition of methanol or by two‐phase solvent systems. In the latter, methanol improves the substrate phase transfer as solvent mediator and leads to reasonable space/time yields. Resulting enantiomerically pure chiral alcohols are key intermediates for synthesis of active pharmaceutical ingredients. (R)‐Atomoxetine is exemplarily synthesized in four steps, and the further use for generation of other oxetine derivatives and a polo‐like kinase 1 inhibitor are discussed. Chirality 00:000–000, 2012. © 2012 Wiley Periodicals, Inc.     

Synthesis and analytical investigation of C‐terminally modified peptide aldehydes and ketone: application to oxime ligation

C‐terminally modified peptides aldehyde (glycinal and alpha‐oxo aldehyde peptides) and ketone (pyruvic acid‐containing peptide) were synthesised to get new insights into the mechanism of acido‐catalysed oxime ligation. Their tetrahedral hydrated forms were investigated in solution and in the gas phase, using NMR and in‐source collision‐induced dissociation mass spectrometry, respectively, and the kinetics of the oximation reactions followed using analytical HPLC. The results obtained confirmed that the first step of the oximation reaction was the limiting step for the pyruvic acid‐containing peptides because of the steric effect and of the carbon angular strain of the ketone. The second step is the determining step for the aldehyde peptides because the basicity of the oxygen of the hydroxyl function of the tetrahedral form is greater for glycinal than for alpha‐oxo aldehyde. These data strongly suggest that the hydrated form of the aldehyde partner has to be considered when oxime reactions are performed in aqueous buffer. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.