Estrogen Reduces 11β‐Hydroxysteroid Dehydrogenase Type 1 in Liver and Visceral,but Not Subcutaneous,Adipose Tissue in Rats

Following menopause, body fat is redistributed from peripheral to central depots. This may be linked to the age related decrease in estrogen levels. We hypothesized that estrogen supplementation could counteract this fat redistribution through tissue‐specific modulation of glucocorticoid exposure. We measured fat depot masses and the expression and activity of the glucocorticoid‐activating enzyme 11β‐hydroxysteroid dehydrogenase type 1 (11βHSD1) in fat and liver of ovariectomized female rats treated with or without 17β‐estradiol. 11βHSD1 converts inert cortisone, or 11‐dehydrocorticosterone in rats into active cortisol and corticosterone. Estradiol‐treated rats gained less weight and had significantly lower visceral adipose tissue weight than nontreated rats (P < 0.01); subcutaneous adipose weight was unaltered. In addition, 11βHSD1 activity/expression was downregulated in liver and visceral, but not subcutaneous, fat of estradiol‐treated rats (P < 0.001 for both). This downregulation altered the balance of 11βHSD1 expression and activity between adipose tissue depots, with higher levels in subcutaneous than visceral adipose tissue of estradiol‐treated animals (P < 0.05 for both), opposite the pattern in ovariectomized rats not treated with estradiol (P < 0.001 for mRNA expression). Thus, estrogen modulates fat distribution, at least in part, through effects on tissue‐specific glucocorticoid metabolism, suggesting that estrogen replacement therapy could influence obesity related morbidity in postmenopausal women.     

Selection and optimization of MCF‐7 cell line for screening selective inhibitors of 11β‐hydroxysteroid dehydrogenase 2

An 11β‐hydroxysteroid dehydrogenase type 1 (11β‐HSD1) produces glucocorticoid (GC) from 11‐keto metabolite, and its modulation has been suggested as a novel approach to treat metabolic diseases. In contrast, type 2 isozyme 11β‐HSD2 is involved in the inactivation of glucocorticoids (GCs), protecting the non‐selective mineralocorticoid receptor (MR) from GCs in kidney. Therefore, when 11β‐HSD1 inhibitors are pursued to treat the metabolic syndrome, preferential selectivity of inhibitors for type 1 over type 2 isozyme is rather important than inhibitory potency. Primarily, to search for cell lines with 11β‐HSD2 activity, we investigated the expression profiles of enzymes or receptors relevant to GC metabolism in breast, colon, and bone‐derived cell lines. We demonstrated that MCF‐7 cells had high expression for 11β‐HSD2, but not for 11β‐HSD1 with its cognate receptor. Next, for the determination of enzyme activity indirectly, we adopted homogeneous time resolved fluorescence (HTRF) cortisol assay. Obviously, the feasibility of HTRF to cellular 11β‐HSD2 was corroborated by constructing inhibitory response to an 11b‐HSD2 inhibitor glycyrrhetinic acid (GA). Taken together, MCF‐7 that overexpresses type 2 but not type 1 enzyme is chosen for cellular 11β‐HSD2 assay, and our results show that a nonradioactive HTRF assay is applicable for type 2 as well as type 1 isozyme. Copyright © 2010 John Wiley & Sons, Ltd.     

Gender-specific links between hepatic 11beta reduction of cortisone and adipokines

Objective: Reduction of cortisone to cortisol is mediated by 11β‐hydroxysteroid dehydrogenase type 1 (11βHSD1), a putative key enzyme in obesity‐related complications. Experimental studies suggest that adipokines, notably leptin and tumor necrosis factor‐α (TNF‐α), are of importance for 11βHSD1 activity. We hypothesized that the regulation of hepatic preceptor glucocorticoid metabolism is gender‐specific and associated with circulating levels of leptin and TNF‐α receptors and/or sex hormones. Research Methods and Procedures: A total of 34 males and 38 women (14 premenopausal and 22 postmenopausal) underwent physical examination and fasting blood sampling. Insulin sensitivity was tested by euglycemic hyperinsulinemic clamps, and hepatic 11βHSD1 enzyme activity was estimated by the conversion of orally‐ingested cortisone to cortisol. Results: Hepatic 11βHSD1 activity was negatively associated with leptin and soluble TNF (sTNF) r1 and sTNFr2 in males. These correlations remained significant after adjustment for age and insulin sensitivity, and for sTNF‐α receptors also after adjustment of BMI and waist circumference. In contrast, 11β reduction of cortisone was positively associated to leptin in females after adjustment for BMI and waist circumference. Discussion: Hepatic 11β reduction shows different links to circulating adipocyte‐derived hormones in males and females. This emphasizes the need for further studies on tissue‐specific regulation of 11βHSD1 in both genders.     

Purification of glutathione S‐transferase enzyme from quail liver tissue and inhibition effects of (3aR,4S,7R,7aS)‐2‐(4‐((E)‐3‐(aryl)acryloyl)phenyl)‐3a,4,7,7a‐tetrahydro‐1H‐4,7‐methanoisoindole‐1,3(2H)‐dione derivatives on the enzyme activity

The use of quail meat and eggs has made this animal important in recent years, with its low cost and high yields. Glutathione S‐transferases (GST, E.C.2.5.1.18) are an important enzyme family, which play a critical role in detoxification system. In our study, GST was purified from quail liver tissue with 47.88‐fold purification and 12.33% recovery by glutathione agarose affinity chromatography. The purity of enzyme was checked by SDS‐PAGE method and showed a single band. In addition, inhibition effects of (3aR,4S,7R,7aS)‐2‐(4‐((E)‐3‐(aryl)acryloyl)phenyl)‐3a,4,7,7a‐tetrahydro‐1H‐4,7methanoisoindole‐1,3(2H)‐dion derivatives ( 1a–g ) were investigated on the enzyme activity. The inhibition parameters (IC₅₀ and K_i values) were calculated for these compounds. IC₅₀ values of these derivatives ( 1a–e ) were found as 23.00, 15.75, 115.50, 10.00, and 28.75 μM, respectively. K_i values of these derivatives ( 1a–e ) were calculated in the range of 3.04 ± 0.50 to 131.50 ± 32.50 μM. However, for f and g compounds, the inhibition effects on the enzyme were not found.     

Anticonvulsant Activity of Enantiomeric N‐trans‐Cinnamoyl Derivatives of 2‐Aminopropan‐1‐ols and 2‐Aminobutan‐1‐ols

Epilepsy, one of the most frequent neurological disorders, is still insufficiently treated in about 30% of patients. As a consequence, identification of novel anticonvulsant agents is an important issue in medicinal chemistry. In the present article we report synthesis, physicochemical, and pharmacological evaluation of N‐trans‐cinnamoyl derivatives of R and S‐2‐aminopropan‐1‐ol, as well as R and S‐2‐aminobutan‐1‐ol. The structures were confirmed by spectroscopy and for derivatives of 2‐aminopropan‐1‐ols the configuration was evaluated by means of crystallography. The investigated compounds were tested in rodent models of seizures: maximal electroshock (MES) and subcutaneous pentetrazol test (scPTZ), and also in a rodent model of epileptogenesis: pilocarpine‐induced status prevention. Additionally, derivatives of 2‐aminopropan‐1‐ols were tested in benzodiazepine‐resistant electrographic status epilepticus rat model as well as in vitro for inhibition of isoenzymes of cytochrome P450. All of the tested compounds showed promising anticonvulsant activity in MES. For R(–)‐(2E)‐N‐(1‐hydroxypropan‐2‐yl)‐3‐phenylprop‐2‐enamide pharmacological parameters were found as follows: ED₅₀ = 76.7 (68.2–81.3) mg/kg (MES, mice i.p., time = 0.5 h), ED₅₀ = 127.2 (102.1–157.9) mg/kg (scPTZ, mice i.p., time = 0.25 h), TD₅₀ = 208.3 (151.4–230.6) mg/kg (rotarod, mice i.p., time = 0.25 h). Evaluation in pilocarpine status prevention proved that all of the reported compounds reduced spontaneous seizure activity and act as antiepileptogenic agents. Both enantiomers of 2‐aminopropan‐1‐ols did not influence cytochrome P450 isoenzymes activity in vitro and are likely not to interact with CYP substrates in vivo. Chirality 28:482–488, 2016. © 2016 Wiley Periodicals, Inc.     

Molecular Screening of the 11β‐HSD1 Gene in Men Characterized by the Metabolic Syndrome

Adipose tissue type 1 11β‐hydroxysteroid dehydrogenase (11β‐HSD1), which generates hormonally active cortisol from inactive cortisone, has been shown to play a central role in adipocyte differentiation and abdominal obesity‐related metabolic complications. The objective was to investigate whether genetic variations in the human 11β‐HSD1 gene are associated with the metabolic syndrome among French‐Canadian men. We sequenced all exons, the exon‐intron splicing boundaries, and 5′ and 3′ regions of the human 11β‐HSD1 gene in 36 men with the metabolic syndrome, as defined by the National Cholesterol Education Program‐Adult Treatment Panel III, and two controls. Three intronic sequence variants were identified: two single‐nucleotide polymorphisms in intron 3 (g.4478T>G) and intron 4 (g.10733G>C) and one insertion in intron 3 (g.4437‐4438insA). The relative allele frequency was 19.6%, 22.1%, and 19.6% for the g.4478G, g.10733C, and g.4438insA alleles, respectively. One single‐nucleotide polymorphism was identified in exon 6 (c.744G>C or G248G). The frequency of the c.744C allele was only 0.46% in a sample of 217 men. Variants were not associated with components of the metabolic syndrome except for plasma apolipoprotein B levels. In conclusion, molecular screening of the 11β‐HSD1 gene did not reveal any sequence variations that can significantly contribute to the etiology of the metabolic syndrome among French‐Canadians.     

Effects of solvent fractions of Allomyrina dichotoma larvae through the inhibition of in vitro BACE1 and β‐amyloid(25–35)‐induced toxicity in rat pheochromocytoma PC12 cells

Amyloid‐β peptide (Aβ) generation initiated by β‐site amyloid precursor protein cleaving enzyme 1 BACE1 is a critical cause of Alzheimer's disease. In the course of our ongoing investigation of natural anti‐dementia resources, the ethyl acetate (EtOAc) fraction exerted strong BACE1‐specific inhibition with the half maximal inhibitory concentration (IC₅₀) value of 9.2 × 10^?5 μg/mL. Furthermore, Aβ(25–35)‐induced cell death was predominantly prevented by the EtOAc fraction of Allomyrina dichotoma larvae through diminishing of cellular oxidative stress and attenuating apoptosis by inhibiting caspase‐3 activity. Taken together, the present study demonstrated that A. dichotoma larvae possess novel neuroprotective properties not only via the selective and specific inhibition of BACE1 activity but also through the alleviation of Aβ(25–35)‐induced toxicity, which may raise the possibility of therapeutic application of A. dichotoma larvae for preventing and/or treating dementia.     

Synthesis,Biological Evaluation,and Molecular Docking Studies of Novel 4‐[4‐Arylpyridin‐1(4H)‐yl]benzoic Acid Derivatives as Anti‐HIV‐1 Agents

The structural similarities between N1 substituted 1,4‐dihydropyridines and the known gp41 inhibitors, NB ‐2 and NB ‐64 , were considered in the current research for the design of some novel anti‐HIV‐1 agents. A series of novel 4‐[4‐arylpyridin‐1(4H)‐yl]benzoic acid derivatives were synthesized and after a comprehensive structural elucidation were screened for in vitro anti‐HIV‐1 activity. Most of the tested compounds displayed moderate to good inhibitory activity against HIV‐1 growth and were evaluated for in vitro cytotoxic activity using XTT assay at the concentration of 100 μm . Among the tested compounds, 1c , 1d and 1e showed potent anti‐HIV‐1 activity against P24 expression at 100 μm with inhibition percentage of 84.00%, 76.42% and 80.50%, respectively. All the studied compounds possessed no significant cytotoxicity on MT‐2 cell line. The binding modes of these compounds to gp41 binding site were determined through molecular docking study. Docking studies proved 1a as the most potent compound and binding maps exhibited that the activities might be attributed to the electrostatic and hydrophobic interactions and additional H‐bonds with the gp41 binding site. The Lipinski's ‘rule of five’ and drug‐likeness criteria were also calculated for the studied compounds. All derivatives obeyed the Lipinski's ‘rule of five’ and had drug‐like features. The findings of this study suggest that novel 4‐[4‐arylpyridin‐1(4H)‐yl]benzoic acid might be a promising scaffold for the discovery and development of novel anti‐HIV‐1 agents.     

11beta-hydroxysteroid dehydrogenase type 1 in adipose tissue and prospective changes in body weight and insulin resistance

Objective: Increased mRNA and activity levels of 11β‐hydroxysteroid dehydrogenase type 1 (11βHSD1) in human adipose tissue (AT) are associated with obesity and insulin resistance. The aim of our study was to investigate whether 11βHSD1 expression or activity in abdominal subcutaneous AT of non‐diabetic subjects are associated with subsequent changes in body weight and insulin resistance [homeostasis model assessment of insulin resistance (HOMA‐IR)]. Research Methods and Procedures: Prospective analyses were performed in 20 subjects (two whites and 18 Pima Indians) who had baseline measurements of 11βHSD1 mRNA and activity in whole AT (follow‐up, 0.3 to 4.9 years) and in 47 Pima Indians who had baseline assessments of 11βHSD1 mRNA in isolated adipocytes (follow‐up, 0.8 to 5.3 years). Results: In whole AT, although 11βHSD1 mRNA levels showed positive associations with changes in weight and HOMA‐IR, 11βHSD1 activity was associated with changes in HOMA‐IR but not in body weight. 11βHSD1 mRNA levels in isolated adipocytes were not associated with follow‐up changes in any of the anthropometric or metabolic variables. Discussion: Our results indicate that increased expression of 11βHSD1 in subcutaneous abdominal AT may contribute to risk of worsening obesity and insulin resistance. This prospective relationship does not seem to be mediated by increased 11βHSD1 expression in adipocytes.     

The role of 11β-hydroxysteroid dehydrogenase type 2 in human hypertension

Cortisol and aldosterone have the same in vitro affinity for the mineralocorticoid receptor (MR), although in vivo only aldosterone acts as a physiologic agonist of the MR, despite circulating levels of cortisol in humans and corticosterone in rodents being three orders of magnitude higher than aldosterone levels. In mineralocorticoid target organs the enzyme 11β-hydroxysteroid dehydrogenase type 2 (11βHSD2) inactivates 11-hydroxy steroids, to their inactive keto-forms, thus protecting the nonselective MR from activation by glucocorticoids. The gene is highly expressed in all sodium-transporting epithelia, particularly in the kidney and colon, but also in human placenta and vascular wall. Mutations in the HSD11B2 gene cause a rare monogenic juvenile hypertensive syndrome called apparent mineralocorticoid excess (AME). In AME, compromised 11βHSD2 enzyme activity results in activation of the MR by cortisol, causing sodium retention, hypokalaemia, and salt-dependent hypertension. Whereas mutations or inhibition of 11βHSD2 by licorice have been clearly shown to produce a congenital or acquired syndrome of mineralocorticoid excess, the questions remaining are the extent to which subtle abnormalities in MR/11βHSD2 mechanisms may contribute to essential hypertension. Studies in patients with essential hypertension showed a prolonged half-life of cortisol and an increased ratio of urinary cortisol to cortisone metabolites, suggesting a deficient 11βHSD2 activity. These abnormalities may be genetically determined, as suggested by the association of a microsatellite flanking the HSD11B2 gene with hypertension in black patients with end-stage kidney disease and with salt sensitivity of blood pressure in healthy subjects. These findings indicate that variants of the HSD11B2 gene may contribute to the enhanced blood pressure response to salt and possibly to hypertension in humans.     

The β‐sheet breakers and π‐stacking

Fibrillation of β‐amyloid is recognized as a key process leading to the development of Alzheimer's disease. Small peptides called β‐sheet breakers were found to inhibit the process of β‐amyloid fibrillation and to dissolve amyloid fibrils in vitro, in vivo, and in cell culture studies [1,2]. The mechanism by which peptide inhibition takes place remains elusive and a detailed model needs to be established. Here, we present new insights into the possible role of consecutive Phe residues, present in the structure of β‐sheet breakers, supported by the results obtained by means of MD simulations. We performed a 30‐ns MD of two β‐sheet breakers: iAβ5 (LPFFD) and iAβ6 (LPFFFD) which have two and three consecutive Phe residues, respectively. We have found that Phe rings in these peptides tend to form stacked conformations. For one of the peptides – iAβ6 – the calculated electrostatic contribution to free energy of one of the conformers with three rings stacked (c2) is significantly lower than that corresponding to the unstacked one (c1), two rings stacked (c0) and second conformer with three rings stacked (c3). This may favor the interaction of the c2 conformer with the target on amyloid fibril. We hypothesize that the mechanism of inhibition of amyloidogenesis by β‐sheet breaker involves competition among π‐stacked Phe residues of the inhibitor and π‐stacking within the β‐amyloid fibril. iAβ6 may be a promising candidate for a lead compound of amyloidogenesis inhibitors. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

Mutations of key hydrophobic surface residues of 11β‐hydroxysteroid dehydrogenase type 1 increase solubility and monodispersity in a bacterial expression system

11β‐Hydroxysteroid dehydrogenase type 1 (11β‐HSD1) is a key enzyme in the conversion of cortisone to the functional glucocorticoid hormone cortisol. This activation has been implicated in several human disorders, notably the metabolic syndrome where 11β‐HSD1 has been identified as a novel target for potential therapeutic drugs. Recent crystal structures have revealed the presence of a pronounced hydrophobic surface patch lying on two helices at the C‐terminus. The physiological significance of this region has been attributed to facilitating substrate access by allowing interactions with the endoplasmic reticulum membrane. Here, we report that single mutations that alter the hydrophobicity of this patch (I275E, L266E, F278E, and L279E in the human enzyme and I275E, Y266E, F278E, and L279E in the guinea pig enzyme) result in greatly increased yields of soluble protein on expression in E. coli. Kinetic analyses of both reductase and dehydrogenase reactions indicate that the F278E mutant has unaltered K_m values for steroids and an unaltered or increased k_cat. Analytical ultracentrifugation shows that this mutation also decreases aggregation of both the human and guinea pig enzymes, resulting in greater monodispersity. One of the mutants (guinea pig F278E) has proven easy to crystallize and has been shown to have a virtually identical structure to that previously reported for the wild‐type enzyme. The human F278E enzyme is shown to be a suitable background for analyzing the effects of naturally occurring mutations (R137C, K187N) on enzyme activity and stability. Hence, the F278E mutants should be useful for many future biochemical and biophysical studies of the enzyme.     

Synthesis,Structure, and Biological Applications of α‐Fluorinated β‐Amino Acids and Derivatives

This review gives a broad overview of the state of play with respect to the synthesis, conformational properties, and biological activity of α‐fluorinated β‐amino acids and derivatives. General methods are described for the preparation of monosubstituted α‐fluoro‐β‐amino acids (Scheme 1). Nucleophilic methods for the introduction of fluorine predominantly involve the reaction of DAST with alcohols derived from α‐amino acids, whereas electrophilic sources of fluorine such as NFSI have been used in conjunction with Arndt? Eistert homologation, conjugate addition or organocatalyzed Mannich reactions. α,α‐Difluoro‐β‐amino acids have also been prepared using DAST; however, this area of synthesis is largely dominated by the use of difluorinated Reformatsky reagents to introduce the difluoro ester functionality (Scheme 9). α‐Fluoro‐β‐amino acids and derivatives analyzed by X‐ray crystal and NMR solution techniques are found to adopt preferred conformations which are thought to result from stereoelectronic effects associated with F located close to amines, amides, and esters (Figs. 2–6). α‐Fluoro amide and β‐fluoro ethylamide/amine effects can influence the secondary structure of α‐fluoro‐β‐amino acid‐containing derivatives including peptides and peptidomimetics (Figs. 7–9). α‐Fluoro‐β‐amino acids are also components of a diverse range of bioactive anticancer (e.g., 5‐fluorouracil), antifungal, and antiinsomnia agents as well as protease inhibitors where such fluorinated analogs have shown increased potency and spectrum of activity.     

Design,Synthesis and Bioevaluation of Two Series of 3‐[(1‐Benzyl‐1H‐1,2,3‐triazol‐4‐yl)methyl]quinazolin‐4(3H)‐ones and N‐(1‐Benzylpiperidin‐4‐yl)quinazolin‐4‐amines

Two series of 3‐[(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)methyl]quinazolin‐4(3H)‐ones and N‐(1‐benzylpiperidin‐4‐yl)quinazolin‐4‐amines were designed initially as potential acetylcholine esterase inhibitors. Biological evaluation demonstrated that N‐(1‐benzylpiperidin‐4‐yl)quinazolin‐4‐amines significantly inhibited AChE activity. Especially, two compounds of them were found to be the most potent with relative AChE inhibition percentages of 87 % in comparison to donepezil. The docking studies with AChE showed similar interactions between donepezil and four derivatives. N‐(1‐Benzylpiperidin‐4‐yl)quinazolin‐4‐amines also exhibited significant DPPH scavenging effects. The two series of compound also exerted moderate to good cytotoxicity against three human cancer cell lines, including SW620 (human colon cancer), PC‐3 (prostate cancer), and NCI?H23 (lung cancer), with 3‐[(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)methyl]quinazolin‐4(3H)‐one being the most cytotoxic agent. 3‐[(1‐Benzyl‐1H‐1,2,3‐triazol‐4‐yl)methyl]quinazolin‐4(3H)‐one significantly induced early apoptosis and arrested the SW620 cells at G2/M phase. From this study, two compounds of N‐(1‐benzylpiperidin‐4‐yl)quinazolin‐4‐amines could serve as new leads for further design and AChE inhibitors, while 3‐[(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)methyl]quinazolin‐4(3H)‐one could serve as a new lead for the design and development of more potent anticancer agents.     

Chiral Piperazine‐2,5‐dione Derivatives as Effective α‐Glucosidase Inhibitors. Part 4

The potential to inhibit α‐ and β‐glucosidases of a series of chiral piperazine‐2,5‐dione derivatives was investigated. Three of the seven compounds tested, viz., 1, 5b , and 5c , showed to be non competitive inhibitors of α‐glucosidase, whereas they exhibited very low inhibitory activity towards β‐glucosidase. The most active compound, 5c (K_I of α‐glucosidase=5 μm), had a 100‐fold α‐glucosidase/β‐glucosidase inhibitor selectivity.     

Antibacterial and membrane‐damaging activities of β‐bungarotoxin B chain

This study investigates whether the B chain of β‐bungarotoxin exerted antibacterial activity against Escherichia coli (Gram‐negative bacteria) and Staphylococcus aureus (Gram‐positive bacteria) via its membrane‐damaging activity. The B chain exhibited a growth inhibition effect on E. coli but did not show a bactericidal effect on S. aureus. The B‐chain bactericidal action on E. coli positively correlated with an increase in membrane permeability in the bacterial cells. Lipopolysaccharide (LPS) layer destabilization and lipoteichoic acid (LTA) biosynthesis inhibition in the cell wall increased the B‐chain bactericidal effect on E. coli and S. aureus. The B chain induced leakage and fusion in E. coli and S. aureus membrane‐mimicking liposomes. Compared with LPS, LTA notably suppressed the membrane‐damaging activity and fusogenicity of the B chain. The B chain showed similar binding affinity with LPS and LTA, whereas LPS and LTA binding differently induced B‐chain conformational change as evidenced by the circular dichroism spectra. Taken together, our data indicate that the antibacterial action of the B chain is related to its ability to induce membrane permeability and suggest that the LPS‐induced and LTA‐induced B‐chain conformational change differently affects the bactericidal action of the B chain. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.     

Improved anticancer potency by head‐to‐tail cyclization of short cationic anticancer peptides containing a lipophilic β2,2‐amino acid

We have recently reported a series of synthetic anticancer heptapeptides (H‐KKWβ^2,2WKK‐NH₂) containing a central achiral and lipophilic β^2,2‐amino acid that display low toxicity against non‐malignant cells and high proteolytic stability. In the present study, we have further investigated the effects of increasing the rigidity and amphipathicity of two of our lead heptapeptides by preparing a series of seven to five residue cyclic peptides containing the two most promising β^2,2‐amino acid derivatives as part of the central lipophilic core. The peptides were tested for anticancer activity against human Burkitt's lymphoma (Ramos cells), haemolytic activity against human red blood cells (RBC) and cytotoxicity against healthy human lung fibroblast cells (MRC‐5). The results demonstrated a considerable increase in anticancer potency following head‐to‐tail peptide cyclization, especially for the shortest derivatives lacking a tryptophan residue. High‐resolution NMR studies and molecular dynamics simulations together with an annexin‐V‐FITC and propidium iodide fluorescent assay showed that the peptides had a membrane disruptive mode of action and that the more potent peptides penetrated deeper into the lipid bilayer. The need for new anticancer drugs with novel modes of action is demanding, and development of short cyclic anticancer peptides with an overall rigidified and amphipathic structure is a promising approach to new anticancer agents. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.     

Dodecyl α‐L‐Rhamnopyranosyl‐(1→2)‐β‐D‐fucopyranoside Derivatives from the Glandular Trichome Exudate of Erodium pelargoniflorum

Chemical investigation of the glandular trichome exudate of Erodium pelargoniflorum (Geraniaceae) led to the isolation of two dodecyl disaccharide derivatives, named pelargoside A1 and pelargoside B1 ( 1 and 2 , resp.). The structures of 1 and 2 were determined as dodecyl 4‐O‐acetyl‐α‐L ‐rhamnopyranosyl‐(1→2)‐4‐O‐acetyl‐β‐D ‐fucopyranoside and dodecyl 3,4‐di‐O‐acetyl‐α‐L ‐rhamnopyranosyl‐(1→2)‐4‐O‐acetyl‐β‐D ‐fucopyranoside, respectively, by spectroscopic studies, including 2D‐NMR, and chemical transformations. In addition, undecyl, tridecyl, and tetradecyl homologs of 1 and 2 , named pelargosides A2–A4 and pelargosides B2–B4, were also characterized as minor constituents of the exudate.     

Mitofusin‐2 knockdown increases ER–mitochondria contact and decreases amyloid β‐peptide production

Mitochondria are physically and biochemically in contact with other organelles including the endoplasmic reticulum (ER). Such contacts are formed between mitochondria‐associated ER membranes (MAM), specialized subregions of ER, and the outer mitochondrial membrane (OMM). We have previously shown increased expression of MAM‐associated proteins and enhanced ER to mitochondria Ca²⁺ transfer from ER to mitochondria in Alzheimer's disease (AD) and amyloid β‐peptide (Aβ)‐related neuronal models. Here, we report that siRNA knockdown of mitofusin‐2 (Mfn2), a protein that is involved in the tethering of ER and mitochondria, leads to increased contact between the two organelles. Cells depleted in Mfn2 showed increased Ca²⁺ transfer from ER to mitchondria and longer stretches of ER forming contacts with OMM. Interestingly, increased contact resulted in decreased concentrations of intra‐ and extracellular Aβ₄₀ and Aβ₄₂. Analysis of γ‐secretase protein expression, maturation and activity revealed that the low Aβ concentrations were a result of impaired γ‐secretase complex function. Amyloid‐β precursor protein (APP), β‐site APP‐cleaving enzyme 1 and neprilysin expression as well as neprilysin activity were not affected by Mfn2 siRNA treatment. In summary, our data shows that modulation of ER–mitochondria contact affects γ‐secretase activity and Aβ generation. Increased ER–mitochondria contact results in lower γ‐secretase activity suggesting a new mechanism by which Aβ generation can be controlled.