Triclorosilane-mediated stereoselective synthesis of β-amino esters and their conversion to highly enantiomerically enriched β-lactams

A highly stereoselective trichlorosilane-mediated reduction of N-benzyl enamines was developed; the combination of a low cost, easy to make metal-free catalyst and an inexpensive chiral auxiliary allowed to perform the reaction on substrates with different structural features often with total control of the stereoselectivity. By easy deprotection through hydrogenolysis followed by conversion of β-aminoester to 2-azetidinones, the synthesis of enantiomerically pure β-lactams (>98% e.e.) was successfully accomplished.

Nitric oxide/reactive oxygen species generation and nitroso/redox imbalance in heart failure: from molecular mechanisms to therapeutic implications

Adaptation of the heart to intrinsic and external stress involves complex modifications at the molecular and cellular levels that lead to tissue remodeling, functional and metabolic alterations, and finally to failure depending upon the nature, intensity, and chronicity of the stress. Reactive oxygen species (ROS) have long been considered as merely harmful entities, but their role as second messengers has gradually emerged. At the same time, our comprehension of the multifaceted role of nitric oxide (NO) and the related reactive nitrogen species (RNS) has been upgraded. The tight interlay between ROS and RNS suggests that their imbalance may implicate the impairment in physiological NO/redox-based signaling that contributes to the failing of the cardiovascular system. This review initially provides basic concepts on the role of nitroso/oxidative stress in the pathophysiology of heart failure with a particular focus on sources of ROS/RNS, their downstream targets, and endogenous modulators. Then, the role of NO/redox regulation of cardiomyocyte function, including calcium homeostasis, electrogenesis, and insulin signaling pathways, is described. Finally, an overview of old and emerging therapeutic opportunities in heart failure is presented, focusing on modulation of NO/redox mechanisms and discussing benefits and limitations.

The effect of losartan treatment on the response of diabetic cardiomyocytes to ATP depletion

The present work aimed to investigate the effect of losartan treatment of healthy and diabetic rats on cardiomyocyte response to ATP depletion. Cells were isolated from normoglycemic (N) and streptozotocin-injected (55 mg/kg) rats (D) treated or not treated with losartan (20 mg/kg/day in the drinking water; NL and DL, respectively) for 3 weeks. In each group of cells, enzyme activities such as glucose-6-phosphate (G6PDH) and glycerol-3-phosphate dehydrogenases (G3PDH), lactate/pyruvate, glycogen levels and citrate synthase were measured as an index of glycolytic dysregulation and mitochondrial mass, respectively. Cells were then challenged with NaCN (2 mM) in glucose-free Tyrode solution (metabolic intoxication, MI), a protocol to study ischemia at cell level. Under these conditions, the time to contractile failure up to rigor-type hyper-contracture in field-stimulated cells and K(ATP) current activation by patch-clamp recordings were measured. In comparison with N and NL, D cells presented higher G6PDH and cytoplasmic G3PDH activities, lactate/pyruvate, glycogen content but similar levels of citrate synthase, and decay time of contraction. When subjected to MI, D cells showed delayed activation of the K(ATP) current (25.7±7.1 min; p<0.001 vs. N and NL), increased time to contractile failure and rigor-type hyper-contracture (p<0.001 vs. N and NL). In cells from DL rats both functional (time to rigor and to K(ATP) current activation) and metabolic parameters, approached values similar to those measured in N and NL cells. These results demonstrate that diabetic cardiomyocytes from rats treated with losartan, maintain the capacity to respond promptly to ATP depletion reaching contractile failure, rigor-type hypercontracture and K(ATP) opening with a similar timing of N cells.

Functional coupling of angiotensin II type 1 receptor with insulin resistance of energy substrate uptakes in immortalized cardiomyocytes (HL-1 cells)

BACKGROUND AND PURPOSE

Increased angiotensin II levels and insulin resistance coexist at the early stages of cardiomyopathies. To determine whether angiotensin II increases insulin resistance in cardiomyocytes, we studied the effect of angiotensin II on basal and insulin-stimulated transport rate of energy substrates in immortalized cardiomyocytes (HL-1 cells).

EXPERIMENTAL APPROACH

Glucose and palmitic acid uptakes were measured using [(3)H]2-deoxy-D-glucose and [(14)C]palmitic acid, respectively, in cells exposed or not exposed to angiotensin II (100 nM), angiotensin II plus irbesartan or PD123319, type 1 and 2 receptor antagonists, or PD98059, an inhibitor of ERK1/2 activation. Cell viability, DNA, protein synthesis and surface area were evaluated by the MTT test, [(3)H]thymydine, [(3)H]leucine and morphometric analysis, respectively. Type 1 receptor levels were measured by western blot analysis.

KEY RESULTS

Basal uptakes of glucose and palmitic acid by HL-1 cells (0.37+/-0.07 and 7.31+/-0.22 pmol per 10(4)cells per min, respectively) were both stimulated by 100 nM insulin (+91 and +64%, respectively). Cells exposed to angiotensin II remained viable and did not show signs of hypertrophy. In these conditions, the basal palmitic acid uptake of the cells increased (11.41+/-0.46 pmol per 10(4) cells per min) and insulin failed to stimulate the uptake of glucose and fatty acids. Changes in the rate of uptake of energy substrates were prevented or significantly reduced by irbesartan or PD98059.

CONCLUSIONS AND IMPLICATIONS

Angiotensin II is a candidate for increasing insulin resistance in cardiomyocytes. Our results suggest a further mechanism for the cardiovascular protection offered by the angiotensin II type 1 receptor blockers.

Effect of structural modifications of ganglioside GM2 on intra-molecular carbohydrate-to-carbohydrate interaction and enzymatic susceptibility

The effect of inter-molecular carbohydrate-to-carbohydrate interaction on basic cell biological processes has been well documented and appreciated. In contrast, very little is known about the intra-molecular carbohydrate-to-carbohydrate interaction. The presence of an interaction between the GalNAc and the Neu5Ac in GM2 detected by NMR spectroscopy represents a well-defined intra-molecular carbohydrate-to-carbohydrate interaction. This intriguing interaction is responsible for the GM2-epitope, GalNAcbeta1-->4(Neu5Acalpha2-->3)Gal-, to exhibit a rigid and compact conformation. We hypothesized that this compact conformation may be the cause for both the GalNAc and the Neu5Ac in GM2 to be refractory to enzymatic hydrolysis and the GM2 activator protein is able to interact with the compact trisaccharide GM2-epitope, rendering the GalNAc and the Neu5Ac accessible to beta-hexosaminidase A and sialidase. We have used a series of structurally modified GM2 to study the effect of modifications of sugar chains on the conformation and enzymatic susceptibility of this ganglioside. Our hypothesis was borne out by the fact that when the GalNAcbeta1-->4Gal linkage in GM2 was converted to the GalNAcbeta1-->6Gal, both the GalNAc and the Neu5Ac became susceptible to beta-hexosaminidase A and sialidase, respectively, without GM2 activator protein. We hope our work will engender interest in identifying other intra-molecular carbohydrate-to-carbohydrate interactions in glycoconjugates.

Methylamine-dependent release of nitric oxide and dopamine in the CNS modulates food intake in fasting rats

BACKGROUND AND PURPOSE

Methylamine is an endogenous aliphatic amine exhibiting anorexigenic properties in mice. The aim of this work was to show whether methylamine also modifies feeding behaviour in rats and, if so, to identify the mediator(s) responsible for such effects.

EXPERIMENTAL APPROACH

Microdialysis experiments with the probe inserted in the periventricular hypothalamic nucleus were carried out in 12 h starved, freely moving rats. Collected perfusate samples following methylamine injection (i.c.v.) were analysed for nitric oxide by chemiluminescence and for dopamine and 5-hydroxytryptamine content by HPLC. Kv1.6 potassium channel expression was reduced by antisense strategy and this decrease quantified by semi-quantitative RT-PCR analysis.

KEY RESULTS

Methylamine showed biphasic dose-related effects on rat feeding. At doses of 15-30 microg per rat, it was hyperphagic whereas higher doses (60-80 microg) were hypophagic. Methylamine stimulated central nitric oxide (+115% vs. basal) following hyperphagic and dopamine release (60% over basal values) at hypophagic doses, respectively. Treatment with L-N(G)-nitro-L-arginine-methyl ester (i.c.v. 2 microg 10 microl(-1)) or with alpha-methyl-p-tyrosine (i.p. 100 mg kg(-1)) before methylamine injection, reduced nitric oxide output and hyperphagia, or dopamine release and hypophagia respectively. Moreover, hypophagia and hyperphagia, as well as nitric oxide and dopamine release were significantly reduced by down-regulating brain Kv1.6 potassium channel expression.

CONCLUSIONS AND IMPLICATIONS

The effects of methylamine on feeding depend on the hypothalamic release of nitric oxide and dopamine as a result of interaction at the Kv1.6 channels. The study of methylamine levels in the CNS may provide new perspectives on the physiopathology of alimentary behaviour.

Enantioselective direct aldol reaction "on water" promoted by chiral organic catalysts

[structure: see text]. 1,1'-Binaphthyl-2,2'-diamine-based (S)-prolinamides in the presence of stearic acid were able to promote the direct aldol condensation of cyclohexanone and other ketones with different aldehydes in the presence of a massive amount of water in very good yields, high diastereoselectivity, and up to 99% ee. The behavior of both C2- and C1-symmetric catalysts in combination with different additives was investigated, and a preliminary experiment of recovering and recycling of the catalytic system was also attempted.

4-methyl benzylamine stimulates food consumption and counteracts the hypophagic effects of amphetamine acting on brain Shaker-like Kv1.1 channels

1.--4-methyl benzylamine (4-MBZ; 28 microg, 231 nmol) elicits a hyperphagic response in starved mice in contrast to the hypophagia induced by the parent compound benzylamine (BZ; 33 microg, 231 nmol) or by amphetamine (AMPH, 2 mug). 2.--In mice starved for only 4 h, and therefore with little stimulation to eat, the maximal increase in food consumption induced by intracerebroventricular (i.c.v.)-injected 4-MBZ was 190% over that of the controls (ED(50) 8.3+/-2.7 microg mouse(-1); 68+/-22 nmol mouse(-1)), whereas after i.p. administration, these values were 160% and approximately 129 mg kg(-1), respectively. 3.--The hyperphagic effect of 4-MBZ was reduced by more than 60% in mice pretreated with antisense oligodeoxyribonucleotide (aODN(1)) previously found to selectively inhibit (over 50%) the expression of Shaker-like Kv1.1 channels. 4.--In mice highly stimulated to eat after 12-h fasting, 4-MBZ (28 microg) significantly reduced (to about 70%) the hypophagic response by AMPH (2 microg) or BZ (33 microg). Conversely, these two compounds reduced (respectively, by 69 and 44%) the hyperphagic response of 4-MBZ in 4-h fasting mice. 5.--4-MBZ (28 microg) also reduced the hypermotility and the stimulation of inspection activity elicited by AMPH in mice and the release of DA stimulated by AMPH (2 microg) from the nucleus accumbens of rats. We hypothesize that 4-MBZ elicits hyperphagic effects probably by opening Shaker-like Kv1.1 subtypes in the brain, whereas AMPH and BZ are hypophagic by blocking these channels.

An experimental re-investigation of the role of aromatic–aromatic interactions in a templated synthesis of a macrocyclic pseudopeptide

The experimental re-investigation of a reported synthesis of a macrocyclic pseudopeptide promoted by bis(tetrabutylammonium)terephthalate allowed us to elucidate the nature of the non-bonding interactions between the reagents and the template; while the involvement of aromatic-aromatic interactions could be ruled out, the relevance of the role of the carboxylate ion was confirmed.

Prolonged n-3 polyunsaturated fatty acid supplementation ameliorates hepatic steatosis in patients with non-alcoholic fatty liver disease: a pilot study

BACKGROUND

Recent studies suggest a role of n-3 long-chain polyunsaturated fatty acids (n-3 PUFA) as peroxisome proliferator-activated receptor-alpha ligands in improving non-alcoholic fatty liver disease (NAFLD) in rodents. However, data in humans are still lacking.

AIM

To evaluate the efficacy of prolonged PUFA supplementation in patients with NAFLD.

METHODS

Fifty-six patients with NAFLD were enrolled. Among the overall eligible patients, 42 assumed n-3 PUFA 1-g capsule daily for 12 months, whereas 14 refused the treatment and were analysed as controls. All patients underwent haematochemical and ultrasound follow-up.

RESULTS

Polyunsaturated fatty acid supplementation significantly decreased serum aspartate transaminase (P = 0.003), alanine transaminase (P = 0.002), gamma-glutamyl transpeptidase (P = 0.03), triglycerides (P = 0.02) and fasting glucose (P = 0.02) in comparison with controls. Circulating arachidonate and n-6/n-3 fatty acid ratio was reduced (P = 0.0002, and P = 0.0001 respectively) in treated patients. Moreover, ultrasonography demonstrated improvement of liver echotexture after PUFA (P = 0.0001), and increase of Doppler perfusion index (P = 0.001), whereas no significant changes occurred in controls.

CONCLUSIONS

Supplementation with n-3 PUFA improves biochemical, ultrasonographic and haemodynamic features of liver steatosis. Our study supports the efficacy of n-3 PUFA as a new therapeutic approach in the treatment of NAFLD.

Synthesis of new enantiomerically pure macrocycles containing phenanthroline subunits

New enantiomerically pure macrocycles have been prepared by combining 1,10-phenanthroline 2,9-dicarboxylic acid and two alpha-amino-acids linked through spacers. Different diamine linkers have been employed in order to modify the dimensions and the properties of the macrocycles whose structures have been studied by 1H and 13C NMR spectroscopy. The ability of the (L)-valine containing macrocycles to bind metal ions and phenolic molecules has been investigated by 1H NMR experiments and Molecular Mechanics calculations.

Activity and expression of semicarbazide-sensitive benzylamine oxidase in a rodent model of diabetes: interactive effects with methylamine and alpha-aminoguanidine

Previous data indicate that methylamine injection in fasted healthy mice produced a hypophagic effect dependent of neuronal K(v)1.6 channels expression and increased by alpha-aminoguanidine, an inhibitor of semicarbazide-sensitive benzylamine oxidase enzymes mainly involved in amine degradation. In the present work we have investigated: 1) the level of expression and activity of the semicarbazide-sensitive benzylamine oxidase; 2) the effect of methylamine alone and in the presence of alpha-aminoguanidine on food intake of genetic obese and type II diabetes mice (the db/db mice). Db/db mice showed higher levels of semicarbazide-sensitive benzylamine oxidase activities in adipose tissue and in plasma than their lean counterpart (db/db(+) mice). Methylamine (30-75 microg, i.c.v.) showed similar hypophagic effects in obese and lean mice consistently with the levels of neuronal K(v)1.6 found in both animal strains. Alpha-aminoguandine (50 mg/kg, i.p.) increased methylamine (i.c.v.) hypophagia in both obese and lean mice and only in obese mice when methylamine was given i.p. These results suggest a crucial role of semicarbazide-sensitive benzylamine oxidase activity in controlling methylamine hypophagia in hyperphagic diabetic mice.

Oxidative Stress by Monoamine Oxidase Mediates Receptor-Independent Cardiomyocyte Apoptosis by Serotonin and Postischemic Myocardial Injury

BACKGROUND

Serotonin (5-hydroxytryptamine [5-HT]), released by activated platelets during cardiac ischemia, is metabolized by the mitochondrial enzyme monoamine oxidase A (MAO-A). Because hydrogen peroxide is one of the byproducts of 5-HT degradation by MAO-A, we investigated the potential role of reactive oxygen species generated by MAOs in 5-HT-dependent cardiomyocyte death and post-ischemia-reperfusion cardiac damage.

METHODS AND RESULTS

Treatment of isolated adult rat cardiomyocytes with 5-HT induced intracellular oxidative stress and cell apoptosis. The apoptotic cascade triggered by 5-HT involves release of cytochrome c, upregulation of proapoptotic Bax protein, and downregulation of antiapoptotic Bcl-2 protein. These effects were prevented by inhibition of amine transporter or MAO, antioxidants, or iron chelation. In contrast, cardiomyocyte apoptosis was only slightly affected by the 5-HT(2B) receptor antagonist SB 206553. In vivo, inhibition of MAO-A largely reduced myocardial ultrastructural damage induced by 30 minutes of ischemia followed by 60 minutes of reperfusion in the rat heart. Cardioprotective effects of MAO inhibitors were associated with the prevention of postischemic oxidative stress, neutrophil accumulation, and mitochondrial-dependent cell death and were not reverted by SB 206553. Administration of MAO-A inhibitors during ischemia was still effective in preventing cardiac damage.

CONCLUSIONS

Our results supply the first direct evidence that oxidative stress induced by MAO is responsible for receptor-independent apoptotic effects of 5-HT in cardiomyocytes and postischemic myocardial injury. These findings provide new insight into the mechanisms of 5-HT action in the heart and may constitute the basis for novel therapies.

Methylamine: a new endogenous modulator of neuron firing?

Increasing evidence suggests that not only ammonia, but also its alkyl-derivatives, including methylamine, may modulate neuron firing. Methylamine occurs endogenously from amine catabolism and its tissue levels increase in some pathological conditions, including diabetes. Interestingly, methylamine and ammonia levels are reciprocally controlled by a semicarbazide-sensitive amine oxidase activity that deaminates methylamine to formaldehyde with the production of ammonia and hydrogen peroxide. As already described for ammonia, methylamine also targets the voltage-operated neuronal potassium channels, probably inducing release of neurotransmitter(s). From this interaction it has been observed that methylamine is 1) hypophagic in mice without producing amphetamine-like effects and 2) a stimulator of nitric oxide release from rat hypothalamus. Methylamine hypophagia is also maintained in genetically obese and diabetic mice and is increased when these animals are pre-treated with -amino guanidine, an inhibitor of methylamine oxidative deamination. The effect of -amino guanidine suggests a potential beneficial effect of this drug, and other such inhibitors, in controlling food intake in animals with disturbed eating behavior. Moreover, the activity of methylamine as an inducer of NO release suggests a role for the amine and for the enzymatic activity that degrades it in neurodegenerative diseases.

The reduction of food intake induced in mice by benzylamine and its derivatives

Characterisation of the pharmacological profile of non-physiological amine oxidase substrates could help to identify the endogenous role of this class of enzymes. Previous studies have suggested that benzylamine, a common non-physiological substrate for monoamine and tissue-bound or soluble benzylamine oxidases, could behave as a potassium channel blocking agent. Potassium channel blockers are known to modify several forms of animal behaviour including food consumption. To characterise further the pharmacological profile of benzylamine and the role of amine oxidases, we have studied the effect of benzylamine on mice food intake. Our results confirm that benzylamine produces a reduction in mice feeding in a similar manner to that obtained by amphetamine. The anorectic effect of benzylamine and amphetamine in mice was potentiated by pretreatment with amine oxidase inhibitors. In addition, the introduction of substituents in the aromatic ring of benzylamine did not produce compounds with a higher anorectic potency than the one measured with benzylamine.