Beta-globin gene cluster haplotypes in the Corsican and Sardinian populations

The distribution of beta-globin cluster haplotypes has been studied in the populations of Corsica (France) and Sardinia (Italy). The analysis was carried out using five restriction fragment length polymorphism markers on chromosome 11 inside the beta-globin cluster using the restriction enzymes HincII and HindIII. The results show a remarkable heterogeneity within the two islands. However, the presence of rare haplotypes common to the most conservative areas (Nuoro and Corte) of the two islands is particularly interesting. These data support the hypothesis of a common origin of the populations of Sardinia and Corsica during the middle and upper Paleolithic periods and could be interpreted as a founder effect.     

Cyclic phosphinamides and phosphonamides, novel series of potent matrix metalloproteinase inhibitors with antitumour activity

The design, synthesis, and structure–activity relationship (SAR) of a series of novel nonpeptidic cyclic phosphon- and phosphinamide-based hydroxamic acids as inhibitors of matrix metalloproteinases MMP-1, MMP-3, and MMP-9 are presented. Based on modelling studies and X-ray analysis, a model of the binding mode of these novel compounds in the MMP active site was obtained. This model provided a rational explanation for the observed SAR data, which included a systematic study of different S1′ directed substituents, zinc-complexing groups, chirality, and variation of the cyclic phosphon- and phosphinamide rings. The in vivo effect of four compounds in a human fibrosarcoma mouse model (HT1080) was evaluated and compared to that of a reference compound, Prinomastat. Inhibition of tumour growth was observed for all four compounds.     

In vitro evidence for an antioxidant role of 3-hydroxykynurenine and 3-hydroxyanthranilic acid in the brain

We investigated the in vitro effect of 3-hydroxykynurenine (3HKyn), 3-hydroxyanthranilic acid (3HAA), kynurenine (Kyn) and anthranilic acid (AA) on various parameters of oxidative stress in rat cerebral cortex and in cultured C6 glioma cells. It was demonstrated that 3HKyn and 3HAA significantly reduced the thiobarbituric acid-reactive substances (TBA-RS) and chemiluminescence measurements in rat cerebral cortex, indicating that these metabolites prevent lipid peroxidation in the brain. In addition, GSH spontaneous oxidation was significantly prevented by 3HAA, but not by the other kynurenines in cerebral cortex. We also verified that 3HKyn and 3HAA significantly decreased the peroxyl radicals induced by the thermolysis of 2,2'-azo-bis-(2-amidinopropane)-derived peroxyl radicals, and to a higher degree than the classical peroxyl scavenger trolox. 2-Deoxy-d-ribose degradation was also significantly prevented by 3HKyn, implying that this metabolite was able to scavenge hydroxyl radicals. Furthermore, the total antioxidant reactivity of C6 glioma cells was significantly increased when these cells were exposed from 1 to 48h to 3HKyn, being the effect more prominent at shorter incubation times. TBA-RS values in C6 cells were significantly reduced by 3HKyn when exposed from 1 to 6h with this kynurenine. However, C6 cell morphology was not altered by 3HKyn. Finally, we tested whether 3HKyn could prevent the increased free radical production induced by glutaric acid (GA), the major metabolite accumulating in glutaric acidemia type I, by evaluating the isolated and combined effects of these compounds on TBA-RS levels and 2',7'-dihydrodichlorofluorescein (DCFH) oxidation in rat brain. GA provoked a significant increase of TBA-RS values and of DCFH oxidation, effects that were attenuated and fully prevented, respectively, by 3HKyn. The results strongly indicate that 3HKyn and 3HAA behave as antioxidants in cerebral cortex and C6 glioma cells from rats.     

Kynurenines Impair Energy Metabolism in Rat Cerebral Cortex

Growing evidence indicates that some metabolites derived from the kynurenine pathway, the major route of l-tryptophan catabolism, are involved in the neurotoxicity associated with several brain disorders, such as Huntington’s disease, Parkinson’s disease and Alzheimer’s disease, as well as in glutaryl-CoA dehydrogenase deficiency (GAI). Considering that the pathophysiology of the brain damage in these neurodegenerative disorders is not completely defined, in the present study, we investigated the in vitro effect of l-kynurenine (Kyn), kynurenic acid (KA), 3-hydroxykynurenine (3HK), 3-hydroxyanthranilic acid (3HA) and anthranilic acid (AA) on some parameters of energy metabolism, namely glucose uptake, ¹⁴CO₂ production from [U-¹⁴C] glucose, [1-¹⁴C] acetate and [1,5-¹⁴C] citrate, as well as on the activities of the respiratory chain complexes I–IV and Na⁺,K⁺-ATPase activity in cerebral cortex from 30-day-old rats. We observed that all compounds tested, except l-kynurenine, significantly increased glucose uptake and inhibited ¹⁴CO₂ production from [U-¹⁴C] glucose, [1-¹⁴C] acetate and [1,5-¹⁴C] citrate. In addition, the activities of complexes I, II and IV of the respiratory chain were significantly inhibited by 3HK, while 3HA inhibited complexes I and II activities and AA inhibited complexes I–III activities. Moreover, Na⁺,K⁺-ATPase activity was not modified by these kynurenines. Taken together, our present data provide evidence that various kynurenine intermediates provoke impairment of brain energy metabolism.     

Adenosine in the central nervous system: release mechanisms and extracellular concentrations

Adenosine has several functions within the CNS that involve an inhibitory tone of neurotransmission and neuroprotective actions in pathological conditions. The understanding of adenosine production and release in the brain is therefore of fundamental importance and has been extensively studied. Conflicting results are often obtained regarding the cellular source of adenosine, the stimulus that induces release and the mechanism for release, in relation to different experimental approaches used to study adenosine production and release. A neuronal origin of adenosine has been demonstrated through electrophysiological approaches showing that neurones can release significant quantities of adenosine, sufficient to activate adenosine receptors and to modulate synaptic functions. Specific actions of adenosine are mediated by different receptor subtypes (A(1), A(2A), A(2B) and A(3)), which are activated by various ranges of adenosine concentrations. Another important issue is the measurement of adenosine concentrations in the extracellular fluid under different conditions in order to know the degree of receptor stimulation and understand adenosine central actions. For this purpose, several experimental approaches have been used both in vivo and in vitro, which provide an estimation of basal adenosine levels in the range of 50-200 nM. The purpose of this review is to describe pathways of adenosine production and metabolism, and to summarize characteristics of adenosine release in the brain in response to different stimuli. Finally, studies performed to evaluate adenosine concentrations under physiological and hypoxic/ischemic conditions will be described to evaluate the degree of adenosine receptor activation.     

1,25(OH)2 vitamin D3 signalling on immature rat Sertoli cells: gamma-glutamyl transpeptidase and glucose metabolism

1α,25-Dihydroxyvitamin D₃ (1,25-D₃) is critical for the maintenance of normal male reproduction since reduced fertility is observed in vitamin D-deficient rats. Gamma-glutamyl transpeptidase (GGT) is a membrane-bound enzyme that is localized on Sertoli cells and catalyses the transfer of the gamma-glutamyl residues to an amino acid or peptide acceptor. Sertoli cells are also responsible for providing nutrients, as lactate, to the development of germ cells. The aim of this study was to investigate the effect and the mechanism of action of 1,25-D₃ on GGT on Sertoli cell functions from 30-day-old immature rat testis. Results demonstrated that 1,25-D₃ stimulates GGT activity at Sertoli cells plasma membrane through a PKA-dependent mechanism of action, which was not dependent of active de novo protein synthesis. The hormone increases glucose uptake, as well as lactate production and release by Sertoli cells without altering the reactive oxygen species (ROS) generation. In addition, 1,25-D₃ did not change reduced glutathione (GSH) amount or oxygen consumption, and diminished Sertoli cell death. These findings demonstrate that 1,25-D₃ stimulatory effect on GGT activity, glucose uptake, LDH activity and lactate production seem to be an important contribution of Sertoli cells for germ cells nutrition and for a full and active ongoing spermatogenesis.