Plasmalogens protect unsaturated lipids against UV-induced oxidation in monolayer

Oxidative stress results from the attack by free radicals of several cellular targets (proteins, DNA and lipids). The cell equilibrium is a direct consequence of the pro-/antioxidant balance. In order to understand the physiological processes involved in oxidative stress, we followed oxidation of unsaturated lipids using a biomimetic system: Langmuir monolayers. The oxidation mode chosen was UV-irradiation and the lipid model was a polyunsaturated phospholipid: 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLPC). The monomolecular film technique was used to measure membrane rheology before and after UV-irradiation. We showed that the UV-irradiation of a DLPC monomolecular film led to a molecular area and surface elasticity modulus decrease that attests to the apparition of new molecular species at the air-water interface. The antioxidant effect of a synthetic plasmalogen (1-O-(1'-(Z)-hexadecenyl)-2-O-oleoyl-sn-glycero-3-phosphocholine or P(PLM)OPE) was tested on the oxidation of DLPC. Indeed, for about 25% mol P(PLM)OPE in mixed DLPC/P(PLM)OPE monolayers, a complete inhibition of the molecular area and the surface elasticity modulus decreases was observed in our experimental conditions. Lower P(PLM)OPE quantities delayed but did not prevent the DLPC oxidation in mixed monolayers.     

Origin and diffusion of mtDNA haplogroup X

A maximum parsimony tree of 21 complete mitochondrial DNA (mtDNA) sequences belonging to haplogroup X and the survey of the haplogroup-associated polymorphisms in 13,589 mtDNAs from Eurasia and Africa revealed that haplogroup X is subdivided into two major branches, here defined as “X1” and “X2.” The first is restricted to the populations of North and East Africa and the Near East, whereas X2 encompasses all X mtDNAs from Europe, western and Central Asia, Siberia, and the great majority of the Near East, as well as some North African samples. Subhaplogroup X1 diversity indicates an early coalescence time, whereas X2 has apparently undergone a more recent population expansion in Eurasia, most likely around or after the last glacial maximum. It is notable that X2 includes the two complete Native American X sequences that constitute the distinctive X2a clade, a clade that lacks close relatives in the entire Old World, including Siberia. The position of X2a in the phylogenetic tree suggests an early split from the other X2 clades, likely at the very beginning of their expansion and spread from the Near East.     

Nitric oxide inhibits spleen cell proliferative response after burn injury by inducing cytostasis,apoptosis, and necrosis of activated T lymphocytes: role of the guanylate cyclase

We previously showed that an overproduction of nitric oxide (NO) by macrophages was responsible for the collapse of lymphoproliferative responses after burn injury in rats. First, we demonstrate here that 10 days post-burn, the inhibition of splenocyte response to concanavalin-A results from cytostatic, apoptotic, and necrotic effects of NO on activated T cells. This was evidenced by various criteria at the levels of DNA, mitochondria, and plasma membrane. Inhibition of NO synthase by S-methylisothiourea (10 microM) normalized all the parameters. Second, we show that two soluble guanylate cyclase (sGC) inhibitors, LY83583 and ODQ, restored the proliferative response in a concentration-dependent manner. LY83583 (0.5 microM) rescued T cells from apoptosis. Similar results were obtained with KT5823 (5 microM) a specific inhibitor of protein kinase G (PKG). In contrast, neither LY83583 nor KT5823 inhibited NO-induced necrosis. These results suggest that NO blocked T cells in the G1 phase and induced apoptosis through a sGC-PKG-dependent pathway and necrosis through an independent one.     

Lipid peroxidation in skeletal muscle of obese as compared to endurance-trained humans: a case of good vs. bad lipids?

Intra-myocellular triglycerides (IMTG) accumulate in the muscle of obese and endurance-trained (ET) humans and are considered a pathogenic factor in the development of insulin resistance, in the former. We postulate that this paradox may be associated with the peroxidation status of the IMTG. IMTG content was the same in the obese and ET subjects. The lipid peroxidation/IMTG ratio was 4.2-fold higher in the obese subjects. Hence, obesity results in an increased level of IMTG peroxidation while ET has a protective effect on IMTG peroxidation. This suggests a link between the lipid peroxidation/IMTG ratio and insulin resistance.     

3H]BHDP as a novel and selective ligand for sigma1 receptors in liver mitochondria and brain synaptosomes of the rat

The binding profile of [(3)H]BHDP ([(3)H]N-benzyl-N'-(2-hydroxy-3,4-dimethoxybenzyl)-piperazine) was evaluated. [(3)H]BHDP labelled a single class of binding sites with high affinity (K(d)=2-3 nM) in rat liver mitochondria and synaptic membranes. The pharmacological characterization of these sites using sigma reference compounds revealed that these sites are sigma receptors and, more particularly, sigma1 receptors. Indeed, BHDP inhibited [(3)H]pentazocine binding, a marker for sigma1 receptors, with high affinity in a competitive manner. BHDP is selective for sigma1 receptors since it did not show any relevant affinity for most of the other receptors, ion channels or transporters tested. Moreover, in an in vitro model of cellular hypoxia, BHDP prevented the fall in adenosine triphosphate (ATP) levels caused by 24 h hypoxia in cultured astrocytes. Taken together, these results demonstrate that [(3)H]BHDP is a potent and selective ligand for sigma1 receptors showing cytoprotective effects in astrocytes.     

ERK 1/2- and JNKs-dependent synthesis of interleukins 6 and 8 by fibroblast-like synoviocytes stimulated with protein I/II,a modulin from oral streptococci,requires focal adhesion kinase

Protein I/II, a pathogen-associated molecular pattern from oral streptococci, is a potent inducer of interleukin-6 (IL-6) and IL-8 synthesis and release from fibroblast-like synoviocytes (FLSs), cells that are critically involved in joint inflammation. This synthesis implicates ERK 1/2 and JNKs as well as AP-1-binding activity and nuclear translocation of NF-kappaB. The mechanisms by which protein I/II activates MAPKs remain, however, elusive. Because focal adhesion kinase (FAK) was proposed to play a role in signaling to MAPKs, we examined its ability to contribute to the MAPKs-dependent synthesis of IL-6 and IL-8 in response to protein I/II. We used FAK-/- fibroblasts as well as FAK+/+ fibroblasts and FLSs transfected with FRNK, a dominant negative form of FAK. The results demonstrate that IL-6 and IL-8 release in response to protein I/II was strongly inhibited in both protein I/II-stimulated FAK-/- and FRNK-transfected cells. Cytochalasin D, which inhibits protein I/II-induced phosphorylation of FAK (Tyr-397), had no effect either on activation of ERK 1/2 and JNKs or on IL-6 and IL-8 release. Taken together, these results indicate that IL-6 and IL-8 release by protein I/II-activated FLSs is regulated by FAK independently of Tyr-397 phosphorylation.     

A recombinant β-O-glucosidase from Caldocellum saccharolyticum to hydrolyse desulfo-glucosinolates

Glucosinolates, natural compounds found in Brassicaceae, can easily be transformed into desulfo-glucosinolates by action of Helix pomatia sulfatase. The recombinant -O-glucosidase from Caldocellum saccharolyticum does not catalyse glucosinolate degradation but can hydrolyse desulfo-glucosinolates (thio-d-glucosidic substrates) to produce the corresponding pure nitriles, including valuable homochiral representatives.     

Characterisation of aphid myrosinase and degradation studies of glucosinolates

Myrosinase from Brevicoryne brassicae was purified by ammonium sulfate fractionation, dialysis, and chromatography on a DEAE column. The chromatography yielded a single peak and a 115.6-fold purification. Further FPLC gel filtration gave a single peak at 120 kDa. Denaturing SDS/PAGE of the protein revealed a single band at 60 kDa, indicating that the native B. brassicae myrosinase is a dimer. Kinetic parameters towards 8 glucosinolates were calculated. Strong differences of V(max) and K(m) were observed depending on the substrate. Degradation products of each glucosinolate were identified and quantified by GC-MS and GLC-FID, respectively. Using both crude aphid homogenates and purified myrosinase, two unique hydroxyglucosinolates, 3-butenyl- and benzyl-isothiocyanates were identified from progoitrin ((2S)-2-hydroxybut-3-enyl-glucosinolate) and sinalbin (4-hydroxybenzyl-glucosinolate) degradation respectively. Addition of ascorbic acid to the reaction mixtures containing sinalbin and progoitrin caused the production of hydroxylated degradation products usually associated with plant myrosinase metabolisation. The occurrence of the myrosinase system in B. brassicae is discussed in terms of similar allelochemical adaptation between the herbivore and its host plant.