Copper-induced oxidative damage on astrocytes: protective effect exerted by human high density lipoproteins

In the present study, we confirmed that copper ions induce oxidative damage in human astrocytes in culture, as demonstrated by the significant increase in the levels of hydroperoxides and in the fluorescence intensity of the fluorescent probe dichloro-dihydrofluorescein diacetate (H(2)DCFDA). The compositional changes were associated with a significant decrease in cell viability in astrocytes treated with 10 microM Cu(++) with respect to control cells. Astrocytes incubated with copper ions in the presence of high density lipoproteins (HDL) isolated from plasma of normolipemic subjects showed lower levels of hydroperoxides and a higher cell viability with respect to cells oxidized alone. Moreover, a significant decrease in the levels of hydroperoxides was observed in oxidized astrocytes treated with HDL. These results demonstrate that HDL exert a protective role against lipid peroxidation. The protective effect could be related to the ability of HDL to bind metal ions at the lipoprotein surface and/or to a stimulation of the efflux of lipid hydroperoxides from cell membranes as demonstrated in other cell types. Oxidative damage of astrocytes was induced at a copper concentration similar to that observed in cerebrospinal fluid (CSF) of patients affected by neurodegenerative diseases such as Alzheimer's (AD) and Parkinson's diseases (PD). Lipoprotein particles similar for density and chemical composition to plasma HDL were recently isolated in human CSF, therefore, the protective role exerted by HDL against Cu(++)-induced oxidative damage of astrocytes could be of physiological relevance.     

Understanding base-assisted desulfurization using a variety of disulfide-bridged peptides

A recently rediscovered reaction of base-assisted lanthionine formation has been applied to several systems of disulfide-bridged peptides. In addition to previously described nonapeptides consisting of i, i+3 cystine linkages, the reaction has now been extended to systems consisting of shorter (i, i+2) and longer (i, i+4) disulfide bridges. The desulfurization reaction is also compatible with disulfide bridges formed through homocysteines and penicillamines, yielding unusual amino acids such as cystathionine and beta,beta-dimethyl lanthionine (referred to as "penthionine") in a peptide chain, respectively. Systematic study of this transformation has provided several new insights into its mechanism. We have observed formation of dehydroalanine and dehydrovaline residues resulting from i, i+2-bridged cysteines and i, i+3-bridged cysteine/penicillamine peptides, respectively, thereby supporting a beta-elimination/Michael-addition mechanism for this transformation. Amino acid analysis and NMR data from total correlation spectroscopy (TOCSY) and (1)H-(13)C heteronuclear single quantum correlation (HSQC) experiments show three diastereomeric lanthionine-bridged peptides in the product mixture. But in the case of desulfurization of a cysteine/homocysteine containing disulfide-bridged peptide, Michael addition appears to be stereoselective, yielding a single stereoisomer of cystathionine within the peptide. According to molecular modeling and CD spectroscopy, constrained peptides such as those containing penicillamine are less likely to undergo facile desulfurization. Flexibility of the torsional angles (C(alpha)H-C(alpha)-C(beta)-S) corresponding to the cysteine residues and temperature appear to be contributing factors determining the extent of desulfurization.     

Noladin ether, a putative novel endocannabinoid: inactivation mechanisms and a sensitive method for its quantification in rat tissues

The occurrence of the novel proposed endocannabinoid, noladin ether (2-arachidonyl glyceryl ether, 2-AGE) in various rat organs and brain regions, and its inactivation by intact C6 glioma cells, were studied. 2-AGE was measured by isotope dilution liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry, with a detection limit of 100 fmol. A compound with the same mass and chromatographic/chemical properties as 2-AGE was found in whole brain, with the highest amounts in the thalamus and hippocampus. Synthetic [(3)H]2-AGE was inactivated by intact rat C6 glioma cells by a time- and temperature-dependent process consisting of cellular uptake and partial incorporation into phospholipids. Further data suggested that 2-AGE is taken up by cells via the anandamide/2-arachidonoyl glycerol (2-AG) membrane transporter(s), and biosynthesized in a different way as compared to 2-AG.     

Short-term hypergravity influences NGF and BDNF expression, and mast cell distribution in the lungs and heart of adult male mice

In this study we investigate the effects of short-term hypergravity on lung and heart neurotrophins and mast cell distribution. Our results showed that brain derived-neurotrophic factor (BDNF) protein and mRNA expression are increased in the lungs of mice exposed to hypergravity while in the heart hypergravity causes a marked reduction in BDNF mRNA expression, and a decrease in BDNF protein. Compared to controls, nerve growth factor (NGF) protein was expressed more in the heart of rotated mice. These observations demonstrate that altered hypergravity can affect, though differentially, the local expression of NGF and BDNF proteins and their mRNAs in the lung and heart and indicates that short-term exposure to hypergravity causes a marked increase in BDNF, but not in NGF in the lungs of adult mice. Moreover, mast cells, which are NGF-producing cells and implicated in cardiac and respiratory activity, increased in number in proximity to blood vessels in the heart and in lung airway epithelium of rotated mice. This study indicates that hypergravity influences cardiovascular and respiratory tissue and suggests a neurotrophin involvement in the reaction to this environmental exposure.     

Inhibition of nitric-oxide synthase-I (NOS-I)-dependent nitric oxide production by lipopolysaccharide plus interferon-gamma is mediated by arachidonic acid. Effects on NFkappaB activation and late inducible NOS expression

Previous results have indicated that lipopolysaccharide (LPS) plus interferon-gamma (IFNgamma) inhibits nitric-oxide synthase (NOS)-I activity in glial cells. We report here that arachidonic acid (AA) plays a pivotal role in this response, which was consistently reproduced in different glial cell lines and in primary rat astrocytes. This notion was established using pharmacological inhibitors of phospholipase A2 (PLA2), cytosolic PLA2 (cPLA2) antisense oligonucleotides, and AA add-back experiments. This approach not only allowed the demonstration that AA promotes inhibition of NOS-I activity but also produced novel experimental evidence that LPS/IFNgamma itself is a potential stimulus for NOS-I. Indeed, LPS/IFNgamma fails to generate nitric oxide (NO) via NOS-I activation simply because it activates the AA-dependent signal that impedes NOS-I activity. Otherwise, LPS/IFNgamma promotes NO formation, sensitive to exogenous AA, in cells in which cPLA2 is pharmacologically inhibited or genetically depleted. Because NO suppresses the NFkappaB-dependent NOS-II expression, inactivation of NOS-I by the LPS/IFNgamma-induced AA pathway provides optimal conditions for NFkappaB activation and subsequent NOS-II expression. Inhibition of cPLA2 activity, while reducing the availability of AA, consistently inhibited NFkappaB activation and NOS-II mRNA induction and delayed NO formation. These responses were promptly reestablished by addition of exogenous AA. Finally, we have demonstrated that the LPS/IFNgamma-dependent tyrosine phosphorylation of NOS-I and inhibition of its activity are mediated by endogenous AA.     

Lactose-induced cell death of beta-galactosidase mutants in Kluyveromyces lactis

The Kluyveromyces lactis lac4 mutants, lacking the beta-galactosidase gene, cannot assimilate lactose, but grow normally on many other carbon sources. However, when these carbon sources and lactose were simultaneously present in the growth media, the mutants were unable to grow. The effect of lactose was cytotoxic since the addition of lactose to an exponentially-growing culture resulted in 90% loss of viability of the lac4 cells. An osmotic stabilizing agent prevented cells killing, supporting the hypothesis that the lactose toxicity could be mainly due to intracellular osmotic pressure. Deletion of the lactose permease gene, LAC12, abolished the inhibitory effect of lactose and allowed the cell to assimilate other carbon substrates. The lac4 strains gave rise, with unusually high frequency, to spontaneous mutants tolerant to lactose (lar1 mutation: lactose resistant). These mutants were unable to take up lactose. Indeed, lar1 mutation turned out to be allelic to LAC12. The high mutability of the LAC12 locus may be an advantage for survival of K. lactis whose main habitat is lactose-containing niches.     

Effect of homocysteinylation of low density lipoproteins on lipid peroxidation of human endothelial cells

Homocysteine-thiolactone (HcyT) is a toxic product whose synthesis is directly proportional to plasma homocysteine (Hcy) levels. Previous studies demonstrated that the interaction between HcyT and low density lipoproteins (LDL) induces the formation of homocystamide-LDL adducts (Hcy-LDL). Structural and functional alterations of Hcy-LDL have been described and it has been suggested that homocysteinylation could increase atherogenicity of LDL. Oxidative damage of endothelial cells (EC) is considered to be a critical aspect of the atherosclerotic process. To further investigate the molecular mechanisms involved in the atherogenicity of homocysteinylated LDL, we studied the effect of interaction between Hcy-LDL and EC on cell oxidative damage, using human aortic endothelial cells (HAEC) as experimental model. Homocysteinylation of LDL was carried out by incubation of LDL, isolated from plasma of healthy normolipemic subjects, with HcyT (10-100 microM). In our experimental conditions, homocysteinylation treatment was not accompanied by oxidative damage of LDL. No modifications of apoprotein structure and physico-chemical properties were observed in Hcy-LDL with respect to control LDL (c-LDL), as evaluated using the intrinsic fluorescence of tryptophan and the probe Laurdan incorporated in lipoproteins. Our results demonstrated that Hcy-LDL incubated at 37 degrees C for 3 h with HAEC, induced an oxidative damage on human EC with a significant increase of lipid hydroperoxides in cells incubated with Hcy-LDL with respect to cell incubated with c-LDL. The compositional changes were associated with a significant decrease viability in cells treated with Hcy-LDL. The relationship between the levels of -SH groups of LDL and the oxidative damage of HAEC has been demonstrated. These results suggest that Hcy-LDL exert a cytotoxic effect that is likely related to an increase in lipid peroxidation and oxidative damage of EC.