ortho-Halogen naphthaleins as specific inhibitors of Lactobacillus casei thymidylate synthase. Conformational properties and biological activity

Thymidylate synthase (TS) (EC 2.1.1.45), an enzyme involved in the DNA synthesis of both prokaryotic and eukaryotic cells, is a potential target for the development of anticancer and antinfective agents. Recently, we described a series of phthalein and naphthalein derivatives as TS inhibitors. These compounds have structures unrelated to the folate (Non-Analogue Antifolate Inhibitors, NAAIs) and were selective for the bacterial versus the human TS (hTS). In particular, halogen-substituted molecules were the most interesting. In the present paper the halogen derivatives of variously substituted 3,3-bis(4-hydroxyphenyl)-1H,3H-naphtho[2,3-c]furan-1-one (1-5) and 3,3-bis(4-hydroxyphenyl)-1H,3H-naphtho[1,8-c,d]pyran-1-one (6-14) were synthesized to investigate the biological effect of halogen substitution on the inhibition and selectivity for the TS enzymes. Conformational properties of the naphthalein series were explored in order to highlight possible differences between molecules that show species-specific biological profile with respect to non species-specific ones. With this aim, the conformational properties of the synthesized compounds were investigated by NMR, in various solvents and at different temperatures, and by computational analysis. The apparent inhibition constants (K(i)) for Lactobacillus casei TS (LcTS) were found to range from 0.7 to 7.0 microM, with the exception of the weakly active iodo-derivatives (4, 10, 13); all] the compounds were poorly active against hTS. The di-halogenated compounds 7, 8, 14 showed the highest specificity towards LcTS, their specificity index (SI) ranging between 40 and >558. The di-halogenated 1,8-naphthalein derivatives (7-10) exhibited different conformational properties with respect to the tetra-haloderivatives. Though a clear explanation for the observed specificity by means of conformational analysis is difficult to find, some interesting conformational effects are discussed in the context of selective recognition of the compounds investigated by the LcTS enzyme.     

Probiotic characteristics and in vitro compatibility of a combination of Bifidobacterium breve M-16 V,Bifidobacterium longum subsp. infantis M-63 and Bifidobacterium longum subsp. longum BB536

The consumption of probiotic-based products has risen greatly in recent decades. Due to their probiotic characteristics, microorganisms such as lactobacilli and bifidobacteria are in daily use in the production of food supplements. In the present study, three bifidobacterial strains (Bifidobacterium breve M-16 V, Bifidobacterium longum subsp. infantis M-63 and Bifidobacterium longum subsp. longum BB536) were tested for growth compatibility, resistance to antimicrobial agents, antibacterial activity against pathogens, resistance to gastric acidity, bile salt hydrolysis and adhesion to the human intestinal epithelial cell line HT29. All of these strains were resistant to gentamycin, but none showed in vitro growth incompatibility or the presence of known resistance determinants. B. breve M-16 V had the best probiotic characteristics and, indeed, was the only strain possessing antibacterial activity against Escherichia coli and Klebsiella pneumoniae. All strains were resistant to simulated gastric juice, while only B. longum subsp. longum BB536 and B. breve M-16 V showed a bile salt hydrolytic activity. Interestingly, a strong adhesion to HT29 cells was observed in all Bifidobacterium strains. In conclusion, B. breve M-16 V, B. longum subsp. longum BB536 and B. longum subsp. infantis M-63 showed several promising characteristics as probiotic strains.     

Rescue of Fructose-Induced Metabolic Syndrome by Antibiotics or Faecal Transplantation in a Rat Model of Obesity

A fructose-rich diet can induce metabolic syndrome, a combination of health disorders that increases the risk of diabetes and cardiovascular diseases. Diet is also known to alter the microbial composition of the gut, although it is not clear whether such alteration contributes to the development of metabolic syndrome. The aim of this work was to assess the possible link between the gut microbiota and the development of diet-induced metabolic syndrome in a rat model of obesity. Rats were fed either a standard or high-fructose diet. Groups of fructose-fed rats were treated with either antibiotics or faecal samples from control rats by oral gavage. Body composition, plasma metabolic parameters and markers of tissue oxidative stress were measured in all groups. A 16S DNA-sequencing approach was used to evaluate the bacterial composition of the gut of animals under different diets. The fructose-rich diet induced markers of metabolic syndrome, inflammation and oxidative stress, that were all significantly reduced when the animals were treated with antibiotic or faecal samples. The number of members of two bacterial genera, Coprococcus and Ruminococcus, was increased by the fructose-rich diet and reduced by both antibiotic and faecal treatments, pointing to a correlation between their abundance and the development of the metabolic syndrome. Our data indicate that in rats fed a fructose-rich diet the development of metabolic syndrome is directly correlated with variations of the gut content of specific bacterial taxa.     

Functional response of the small multidrug resistance protein EmrE to mutations in transmembrane helix 2

Escherichia coli EmrE is a small multidrug resistance protein encompassing four transmembrane (TM) sequences that oligomerizes to confer resistance to antimicrobials. Here we examined the effects on in vivo protein accumulation and ethidium resistance activity of single residue substitutions at conserved and variable positions in EmrE transmembrane segment 2 (TM2). We found that activity was reduced when conserved residues localized to one TM2 surface were replaced. Our findings suggest that conserved TM2 positions tolerate greater residue diversity than conserved sites in other EmrE TM sequences, potentially reflecting a source of substrate polyspecificity.     

Reorganization of prion protein membrane environment during low potassium-induced apoptosis in primary rat cerebellar neurons

We studied the changes occurring in the membrane environment of prion protein (PrP) during apoptosis induced by low potassium in primary rat cerebellar neurons. Ceramide levels increased during apoptosis-inducing treatment, being doubled with respect to time-matched controls after 24 h. Sphingomyelin levels were parallely decreased, while cholesterol and ganglioside contents were not affected. Changes in ceramide and sphingomyelin composition were exclusively restricted to a detergent-resistant membrane fraction. The pro-apoptotic treatment was accompanied by the down-regulation of PrP and of the non-receptor kinase Fyn. The levels of PrP and Fyn were correspondingly reduced in the detergent-resistant membrane fraction. In control cells, the membrane microenvironment separated by immunoprecipitation with anti-PrP antibody contained 80% of the detergent-resistant PrP and 35% and 38% of the sphingolipids and cholesterol respectively. Upon low potassium treatment, 20% of the PrP originally present in the detergent-resistant fraction was immunoprecipitated, together with 19% of sphingolipids and 22% of cholesterol. Thus, PrP in the immunoprecipitate from apoptotic cells was ninefold less than in control ones, while sphingolipids and cholesterol were about 50% with respect to controls cells. The molar ratio between cholesterol, sphingomyelin and ceramide was 15 : 6 : 1 in the PrP-rich environment from control neurons, and 6 : 2 : 1 in that from apoptotic cells.     

Identification of differentially expressed microRNAs by microarray: a possible role for microRNA genes in pituitary adenomas

MicroRNAs (miRNAs) are small non-coding RNAs that control gene expression by targeting mRNA. It has been demonstrated that miRNA expression is altered in many human cancers, suggesting that they may play a role in human neoplasia. To determine whether miRNA expression is altered in pituitary adenomas, we analyzed the entire miRNAome in 32 pituitary adenomas and in 6 normal pituitary samples by microarray and by Real-Time PCR. Here, we show that 30 miRNAs are differentially expressed between normal pituitary and pituitary adenomas. Moreover, 24 miRNAs were identified as a predictive signature of pituitary adenoma and 29 miRNAs were able to predict pituitary adenoma histotype. miRNA expression could differentiate micro- from macro-adenomas and treated from non-treated patient samples. Several of the identified miRNAs are involved in cell proliferation and apoptosis, suggesting that their deregulated expression may be involved in pituitary tumorigenesis. Predictive miRNAs could be potentially useful diagnostic markers, improving the classification of pituitary adenomas.