Alterations of human erythrocyte membrane fluidity by oxygen-derived free radicals and calcium

Extracellular vesicles regulate the transmission of insulin resistance and redefine noncommunicable diseases

Noncommunicable diseases (NCDs), such as diabetes and related neurological disorders, are considered to not be directly transmissible from one person to another. However, NCDs may be transmissible in vivo through extracellular vesicles (EVs). A long-term high-fat diet (HFD) can induce a series of health issues like hyperlipidemia, type 2 diabetes mellitus (T2DM), and diabetic peripheral neuropathy (DPN) due to insulin resistance. Multiple molecular signaling changes can stimulate insulin resistance, especially blocking insulin signaling by increased insulin resistance inducer (phosphorylation of negative regulatory sites of insulin receptor substrate (IRS) proteins) and decreased tyrosine phosphorylation of insulin receptor substrate (phosphorylation of positive regulatory sites of IRS), thus leading to reduced phosphorylation of AKT enzymes. Current efforts to treat T2DM and prevent its complications mainly focus on improving insulin sensitivity, enhancing insulin secretion, or supplementing exogenous insulin based on a common assumption that insulin resistance is noncommunicable. However, insulin resistance is transmissible within multiple tissues or organs throughout the body. Exploring the regulatory roles of EVs in developing insulin resistance may provide novel and effective preventive and therapeutic strategies.

Calcium dynamically alters erythrocyte mechanical response to shear

Red blood cells (RBC) are constantly exposed to varying mechanical forces while traversing the cardiovascular system. Upon exposure to mechanical stimuli (e.g., shear stress), calcium enters the cell and prompts potassium-efflux. Efflux of potassium is accompanied by a loss of intracellular fluid; thus, the volume of RBC decreases proportionately (i.e., 'Gárdos effect'). The mechanical properties of the cell are subsequently impacted due to complex interactions between cytosolic viscosity (dependent on cell hydration), the surface-area-to-volume ratio, and other molecular processes. The dynamic effects of calcium on RBC mechanics are yet to be elucidated, although accumulating evidence suggests a vital role. The present study thus examined the effects of calcium on contemporary biomechanical properties of RBC in conjunction with high-precision geometrical analyses with exposure to shear. Mechanical stimulation of RBC was performed using a co-axial Couette shearing system to deform the cell membrane; intracellular signaling events were observed via fluorescent imaging. Calcium was introduced into RBC using ionophore A23187. Increased intracellular calcium significantly impaired RBC deformability; these impairments were mediated by a calcium-induced reduction of cell volume through the Gárdos channel. Extracellular calcium in the absence of the ionophore only had an effect under shear, not at stasis. Under low shear, the presence of extracellular calcium induced progressive lysis of a sub-population of RBC; all remaining RBC exhibited exceptional capacity to deform, implying preferential removal of potentially aged cells. Collectively, we provide evidence of the mechanism by which calcium acutely regulates RBC mechanical properties.

Antihyperglycaemic, haemorheological and antioxidant activities of Lychnis chalcedonica L. extract in a streptozotocin-induced rat model of diabetes mellitus

Background New therapeutic strategies, such as the use of agents to correct rheological disorders, are needed for the prevention and treatment of angiopathy in diabetic patients. The aim of this work was to study the antihyperglycaemic, haemorheologic and antioxidant activities of an extract from the flowering plant Lychnis chalcedonica L. (ELC) and 20-hydroxyecdysone using the streptozotocin-induced model of diabetic rats. Methods The streptozotocin-induced model of diabetes was produced using streptozotocin at a dose of 50 mg/kg (ip). Animals from the experimental groups were treated with ELC (150 mg/kg) or 20-hydroxyecdysone (1.1 mg/kg) intragastrically in 1% aqueous starch mucilage daily, for 14 days; rats of control groups received an equal volume of starch mucilage. The following parameters were measured: glucose concentration (GC) in blood, whole blood viscosity (WBV), conjugated dienes in RBC membranes. Macro- and microrheological indicators (viz. plasma viscosity, haematocrit, RBC aggregation (T1/2) and the RBC elongation index (EI)) were additionally measured in rats that received ELC, and in the control group. Results After treatment with ELC, the GC in rats was 19% lower than that in the control group (14.7 ± 0.9 mM compared to 18.2 ± 1.1 mM). Rats with streptozotocin-induced diabetes have hyperviscosity syndrome, which is characterized by increased WBV, increased RBC aggregation and decreased deformability. ELC treatment reduced WBV at shear rates of 10-90 s-1 by 5-8%, and T1/2 and EI in the experimental group were 31% and 5-10% higher compared to the control group. 20-Hydroxyecdysone decreased WBV at shear rates of 10-90 s-1 by 3-11%. Finally, ELC and 20-hydroxyecdysone lowered the content of conjugated dienes by 27% and by 26% compared to the control groups. Conclusion In the streptozotocin-induced diabetic rat model, ELC showed measurable antihyperglycaemic activity; ELC and 20-hydroxyecdysone demonstrated similar haemorheological, and antioxidant activities.

The Effect of Antioxidants on the Properties of Red Blood Cells From Patients With Sickle Cell Anemia

Oxidative damage to red blood cells (RBCs) may contribute to pathogenesis of sickle cell anemia. Reducing the deleterious effects of oxidants by exposing RBCs to a number of antioxidants has been shown to have protective effects against lipid and protein peroxidation. We hypothesize that antioxidants may also have beneficial effects on the abnormal membrane permeability of sickle cells. Increased cation permeability of these cells encourages HbS polymerization by causing RBC dehydration and also leads to externalization of the prothrombotic aminophospholipid phosphatidylserine (PS). Three antioxidants with different mechanisms of action were investigated - dithiothreitol, N-acetylcysteine, and quercetin. All three were found to inhibit the main cation pathways responsible for dehydration - the deoxygenation-induced cation conductance (or Psickle), the Ca2+-activated K+ channel (or Gardos channel), and the K+-Cl- cotransporter. They also reduced Ca2+-induced PS exposure and hemolysis. Findings provide evidence for additional beneficial actions of antioxidants in maintenance of rheology and reducing vascular adhesion and further inform the rationale for their clinical use.

The effect of xanthine oxidase and hypoxanthine on the permeability of red cells from patients with sickle cell anemia

Red cells from patients with sickle cell anemia (SCA) are under greater oxidative challenge than those from normal individuals. We postulated that oxidants generated by xanthine oxidase (XO) and hypoxanthine (HO) contribute to the pathogenesis of SCA through altering solute permeability. Sickling, activities of the main red cell dehydration pathways (Psickle , Gardos channel, and KCl cotransporter [KCC]), and cell volume were measured at 100, 30, and 0 mmHg O2 , together with deoxygenation-induced nonelectrolyte hemolysis. Unexpectedly, XO/HO mixtures had mainly inhibitory effects on sickling, Psickle , and Gardos channel activities, while KCC activity and nonelectrolyte hemolysis were increased. Gardos channel activity was significantly elevated in red cells pharmacologically loaded with Ca2+ using the ionophore A23187, consistent with an effect on the transport system per se as well as via Ca2+ entry likely via the Psickle pathway. KCC activity is controlled by several pairs of conjugate protein kinases and phosphatases. Its activity, however, was also stimulated by XO/HO mixtures in red cells pretreated with N-ethylmaleimide (NEM), which is thought to prevent regulation via changes in protein phosphorylation, suggesting that the oxidants formed could also have direct effects on this transporter. In the presence of XO/HO, red cell volume was better maintained in deoxygenated red cells. Overall, the most notable effect of XO/HO mixtures was an increase in red cell fragility. These findings increase our understanding of the effects of oxidative challenge in SCA patients and are relevant to the behavior of red cells in vivo.

Hemorheological effects of secoisolariciresinol in ovariectomized rats

BACKGROUND

Postmenopausal women often develop hemorheological disorders which may affect the systemic blood circulation and present a cardiovascular risk factor.

OBJECTIVE

We evaluated effects of secoisolariciresinol (SECO), a phytoestrogen, on hemorheological parameters and lipid peroxidation in a model of the age-related and/or surgical menopause induced by ovariectomy in rats.

METHODS

Arterial blood was sampled from sham-operated female rats, ovariectomized rats (OVX), and OVX treated with SECO (OVXSECO) (20 mg/kg/day intragastrically for two weeks). Plasma estrogen concentration and the following hemorheological parameters were measured: RBC aggregation (half-time of aggregation, T1/2; amplitude of aggregation, AMP; aggregation index, AI), RBC deformability (elongation index, EI), whole blood viscosity at the shear rate of 3-300 s-1, plasma viscosity, hematocrit, plasma fibrinogen. Lipid peroxidation was evaluated by measuring conjugated dienes (CD) and thiobarbituric acid reactive substances (TBARS) in plasma.

RESULTS

Ovariectomy in rats caused a 60% decrease in plasma estrogen level and triggered the development of macro- and microhemorheological abnormalities. Blood viscosity increased by 12-31%, RBC elongation index reduced by 16-28%, and T1/2 and AI increased by 35% and 29% respectively. The increase in blood viscosity correlated predominantly with reduced RBC deformability. Plasma CD and TBARS were elevated by 47% and 104% respectively. SECO therapy for OVX rats reduced blood viscosity by 9-18% and T1/2 by 32%, and increased EI by 4-17%. SECO therapy disrupted the correlation between blood viscosity and RBC deformability. Lipid peroxidation was significantly inhibited, as shown by the reduction in CD and TBARS plasma concentrations by 89% and 70% respectively. SECO did not affect plasma viscosity, estrogen or fibrinogen levels.

CONCLUSIONS

SECO treatment for OVX rats improves blood macro- and microrheological parameters, possibly through antioxidant protection of RBC.

Alterations of hepatocyte function with free radical generators and reparation or prevention with coffee polyphenols

Liver diseases are linked in the majority of cases to oxidative stress that antioxidants could neutralize with reducing liver injury. Chlorogenic acid, a coffee polyphenol, possesses antioxidant prosperities. The aim of this study was to evaluate in vitro preventive and corrective effects of cholorogenic acid in hepatocyte toxicity induced by free radicals. Hepatocytes were isolated from adult male Wistar rats. To determine corrective effects and reparation, cells were first exposed to two free radical generators (hydrogen peroxide/iron sulfate for hydroxyl radical formation, and phenazine methosulfate/nicotinamide adenine dinucleotide for superoxide anion formation) for 12H and thereafter treated by chlorogenic acid (1 and 10 μM final concentration) for another 12H. To show preventive effects, cells were pretreated by chlorogenic acid and thereafter exposed to free radical generators. Hepatocyte proliferation, glucose uptake, ATP contents, membrane fluidity and integrity, and intracellular redox status were investigated after 24H culture. The results showed that chlorogenic acid reversed the decrease in cell proliferation, glucose uptake and ATP levels, the increased LDH release and the reduced membrane fluidity and restored the oxidant/antioxidant status under oxidative stress. When pre-treated with chlorogenic acid, hepatocytes became very resistant to oxidative conditions and cellular homeostasis was maintained. In conclusion, chlorogenic acid displayed not only corrective but also preventive effects in hepatocytes exposed to oxidative stress and could be beneficial in patients with or at risk of liver diseases.

Inhalation of methane preserves the epithelial barrier during ischemia and reperfusion in the rat small intestine

BACKGROUND

Methane is part of the gaseous environment of the intestinal lumen. The purpose of this study was to elucidate the bioactivity of exogenous methane on the intestinal barrier function in an antigen-independent model of acute inflammation.

METHODS

Anesthetized rats underwent sham operation or 45-min occlusion of the superior mesenteric artery. A normoxic methane (2.2%)-air mixture was inhaled for 15 min at the end of ischemia and at the beginning of a 60-min or 180-min reperfusion. The integrity of the epithelial barrier of the ileum was assessed by determining the lumen-to-blood clearance of fluorescent dextran, while microvascular permeability changes were detected by the Evans blue technique. Tissue levels of superoxide, nitrotyrosine, myeloperoxidase, and endothelin-1 were measured, the superficial mucosal damage was visualized and quantified, and the serosal microcirculation and mesenteric flow was recorded. Erythrocyte deformability and aggregation were tested in vitro.

RESULTS

Reperfusion significantly increased epithelial permeability, worsened macro- and microcirculation, increased the production of proinflammatory mediators, and resulted in a rapid loss of the epithelium. Exogenous normoxic methane inhalation maintained the superficial mucosal structure, decreased epithelial permeability, and improved local microcirculation, with a decrease in reactive oxygen and nitrogen species generation. Both the deformability and aggregation of erythrocytes improved with incubation of methane.

CONCLUSION

Normoxic methane decreases the signs of oxidative and nitrosative stress, improves tissue microcirculation, and thus appears to modulate the ischemia-reperfusion-induced epithelial permeability changes. These findings suggest that the administration of exogenous methane may be a useful strategy for maintaining the integrity of the mucosa sustaining an oxido-reductive attack.

Hemorheological parameters and their correlations in OXYS rats: a new model of hyperviscosity syndrome

Rheohaemapheresis aims to normalize major rheological parameters and is used to treat patients with dry age-related macular degeneration (AMD). While effective, this approach is invasive and requires specially trained personnel. Therefore, the search for novel effective compounds with hemorheological properties that can be taken orally to treat AMD is justified. The use of a robust rodent model of AMD with high blood viscosity is crucial to test the efficacy of potential hemorheological drugs to treat this disease. The objective of this study was to investigate whether OXYS rats, generally used as an animal model of AMD, have hyperviscosity syndrome. The results of this study show that blood viscosity in OXYS rats at low (3-10 s -1) and high (45-300 s -1) shear rates were 14-20% and 7-10% higher than in Wistar rats, while hematocrit and plasma viscosity were not different. Red blood cells (RBCs) in OXYS rats were more prone to aggregation as shown by 39% shorter half-time than in Wistar rats. RBCs were also more rigid in OXYS than in Wistar rats as shown by 21-33% lower index of elongation at the shear stress of 1-7 Pa. These data indicate that OXYS rats have hyperviscosity syndrome as the result of abnormal RBC deformability and aggregation. We propose to use OXYS rats as an animal model for preclinical studies to test compounds with hemorheological properties aimed to treat AMD.

Peridynamic Modeling of Ruptures in Biomembranes

We simulate the formation of spontaneous ruptures in supported phospholipid double bilayer membranes, using peridynamic modeling. Experiments performed on spreading double bilayers typically show two distinct kinds of ruptures, floral and fractal, which form spontaneously in the distal (upper) bilayer at late stages of double bilayer formation on high energy substrates. It is, however, currently unresolved which factors govern the occurrence of either rupture type. Variations in the distance between the two bilayers, and the occurrence of interconnections (“pinning sites”) are suspected of contributing to the process. Our new simulations indicate that the pinned regions which form, presumably due to Ca²⁺ ions serving as bridging agent between the distal and the proximal bilayer, act as nucleation sites for the ruptures. Moreover, assuming that the pinning sites cause a non-zero shear modulus, our simulations also show that they change the rupture mode from floral to fractal. At zero shear modulus the pores appear to be circular, subsequently evolving into floral pores. With increasing shear modulus the pore edges start to branch, favoring fractal morphologies. We conclude that the pinning sites may indirectly determine the rupture morphology by contributing to shear stress in the distal membrane.

Pre-training Catechin gavage prevents memory impairment induced by intracerebroventricular streptozotocin in rats

Objective:

To evaluate the effects of Catechin (CAT) on memory acquisition and retrieval in the animal model of sporadic alzheimer’s disease (sAD) induced by intracerebroventricular (icv) injection of streptozotocin (STZ) in passive avoidance memory test.

Methods:

Thirty adult rats were divided into 5 experimental groups (n=6). Animals were treated by icv saline/STZ (3 mg/kg) injection at day one and 3 after cannulation. The STZ+CAT group received 40 mg/kg CAT by daily gavages for 10 days, after icv STZ treatment and before training. The step-through latency (STL) and time spent in the dark compartment (TDC) were evaluated to examine the memory acquisition and retrieval. All tests were performed in Qom University of Medical Sciences, Qom, Iran, from April to December 2013.

Results:

The STZ treatment significantly decreased STL and increased the number of entries to the dark compartment on the training day. It also increased TDC, on day one and 7 after training. Pre-training gavage of CAT reversed the STL significantly (p=0.027). The CAT treatment also decreased the TDC in both early and late retrieval, in respect to STZ group.

Conclusion:

This data suggests that CAT as an antioxidant could improve both memory acquisition and retrieval in the animal model of sAD.

Effects of Different Phases of Cigarette Smoke on Lipid Peroxidation and Membrane Structure in Liposomes

This paper discloses for the first time the effects of the gas phase (GP) and the tar of cigarette smoke on lipid peroxidation (LPO) and on the structure of different lipid regions in liposomes. The LPO development was analysed in terms of the total unsaturation of lipids (double-bond, DB, content) and the formation of dienic conjugates (DC), ketodienes (KD), and malonic dialdehyde (MDA). As expected, the exposure of liposomes to either the GP or the tar led to a significant decrease in the DB content. However, the formation of oxidation products revealed different dynamics: MDA generation was inhibited, while the formation of DC and KD increased during the first few hours of the LPO development followed by its inhibition. The smoke constituents exhibited opposite effects on the structure of the lipid bilayer of liposomes: the GP markedly enhanced the microviscosity of liposomal membranes, whereas the tar caused a drastic lowering of microviscosity.

Mechanisms, treatment and prevention of cellular injury and death from delayed events after aneurysmal subarachnoid hemorrhage

INTRODUCTION

Subarachnoid hemorrhage (SAH) patients often develop brain injury as a result of a number of delayed complications, resulting in significant morbidity and mortality. Many of these complications arise due to delayed cerebral ischemia, which occurs secondary to the hemorrhage.

AREAS COVERED

The mechanisms of the delayed injury are reviewed, including angiographic vasospasm, cortical spreading ischemia, small arteriolar constriction, microthromboemboli, free radical injury and inflammation. Some current and prospective therapies for SAH are discussed, in the context of these complications. Statins have been particularly promising in experimental studies.

EXPERT OPINION

Multiple mechanisms are involved in the pathogenesis of the delayed insult after SAH. New drugs may need to target multiple pathways to injury. Trials aiming to treat complications after SAH could benefit from taking into account the multifactorial pathogenesis of delayed insults.

Epigallocatechin gallate attenuates L-DOPA-induced apoptosis in rat PC12 cells

In this study, the protective effects of EGCG on L-3,4-dihydroxyphenylalanine (L-DOPA)-induced oxidative cell death in catecholaminergic PC12 cells, the in vitro model of Parkinson's disease, were investigated. Treatment with L-DOPA at concentrations higher than 150 µM caused cytotoxicity in PC12 cells, as determined using the 3-(4,5-dimetylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry detection. The apoptotic ratio was similar in cells treated with 100 µM EGCG plus 150 µM L-DOPA (5.02%) and the control (0.96%) (P > 0.05), and was lower than that of cells treated with L-DOPA only (32.24%, P < 0.05). The generation level of ROS (% of control) in cells treated with EGCG plus L-DOPA was lower than that in cells treated with L-DOPA only (123.90% vs 272.32%, P < 0.05). The optical density in production of TBARS in cells treated with L-DOPA only was higher than that in the control (0.27 ± 0.05 vs 0.08 ± 0.04, P < 0.05), and in cells treated with EGCG only (0.14 ± 0.02, P < 0.05), and EGCG plus L-DOPA (0.13 ± 0.02, P < 0.05). The intracellular level of GSH in cells treated with EGCG plus L-DOPA was higher than that in cells treated with L-DOPA only (233.25 ± 16.44 vs 119.23 ± 10.25, P < 0.05). These results suggest that EGCG protects against L-DOPA-induced oxidative apoptosis in PC12 cells, and might be a potent neuroprotective agent.

The role of EPR spectroscopy in studies of the oxidative status of biological systems and the antioxidative properties of various compounds

In this era of intense study of free radicals and antioxidants, electron paramagnetic resonance (EPR) is arguably the best-suited technique for such research, particularly when considering biochemical and biological systems. No attempt was made to cover all the topics of EPR application but instead attention was restricted to two areas that are both novel and received less attention in previous reviews. In the first section, the application of EPR in assessing the oxidative status of various biological systems, using endogenous stabile paramagnetic species, such as the ascorbyl radical, semiquinone, melanin, and oxidized pigments, is addressed. The second section covers the use of EPR in the emerging field of antioxidant development, using EPR spin-trapping and spin-probing techniques. In both sections, in addition to giving an overview of the available literature, examples (mostly from the authors? recent work) are also presented in sufficient detail to illustrate how to explore the full potential of EPR. This review aims at encouraging biologists, chemists and pharmacologists interested in the redox metabolism of living systems, free radical chemistry or antioxidative properties of new drugs and natural products to take advantage of this technique for their investigations.

Cornin ameliorates cerebral infarction in rats by antioxidant action and stabilization of mitochondrial function

This study was conducted to investigate the efficacy of cornin, an iridoid glycoside, in an experimental cerebral ischemia induced by middle cerebral artery occlusion (MCAO) and reperfusion (I/R), and to elucidate the potential mechanism. Adult male Sprague-Dawley rats were subjected to MCAO for 1 h, then reperfusion for 23 h. Behavioral tests were used to evaluate the damage to central nervous system. The cerebral infarct volume and histopathological damage were assessed to evaluate the brain pathophysiological changes. Spectrophotometric assay methods were used to determine the activities of superoxide dismutase (SOD) and glutathione-peroxidase (GPx). Contents of malondialdehyde (MDA), the generation of reactive oxygen species (ROS) as well as respiratory control ratio and respiratory enzymes of the brain mitochondria were also determined. The results showed that cornin significantly decreased neurological deficit scores, and reduced cerebral infarct volume and degenerative neurons. Meanwhile, cornin significantly increased the brain ATP content, improved mitochondrial energy metabolism, inhibited the elevation of MDA content and ROS generation, and attenuated the decrease of SOD and GPx activities in brain mitochondria. These findings indicate that cornin has protective potential against cerebral ischemia injury and its protective effects may be due to amelioration of cerebral mitochondrial function and its antioxidant property.

Basic study on active changes in biological function of mouse liver graft in cold storage after low-dose x-irradiation

We previously reported that low-dose X-irradiation alleviates ischemia-reperfusion injury such as mouse paw edema. In this study, we examined active changes in the biological function of mouse liver grafts in cold storage after low-dose X-irradiation. Mouse livers were sham-irradiated or were irradiated with 0.25, 0.5, 1.0, or 5.0 Gy of X-ray and stored for 4, 8, 24, or 48 h in preservation or saline solution. The results show that storage for 24 h in saline solution after 0.5 Gy irradiation significantly increased the activity of superoxide dismutase (SOD) and catalase. Following storage for 4, 8, or 48 h in preservation solution, lipid peroxide levels of the 0.5 Gy irradiated group were significantly lower than those of the sham irradiated group. Following storage for 24 h in preservation solution, the activity of SOD and catalase of the 1.0 Gy irradiated group were significantly higher than those of the sham irradiated group. Hepatocytes stored in saline solution were vacuolated. However, no vacuole formation was observed in hepatocytes stored in preservation solution. These findings suggest that low-dose irradiation significantly activates antioxidative functions of liver grafts. Moreover, the dose at which enhancement of antioxidative function occurs in livers stored in preservation solution, which contains glutathione, is significantly higher than that in saline solution.

The effects of taurine, hypotaurine, and taurine homologs on erythrocyte morphology, membrane fluidity and cytoskeletal spectrin alterations due to diabetes, alcoholism and diabetes-alcoholism in the rat

Taurine (TAU) and compounds representing a TAU analog (hypotaurine = HYTAU) or homolog (aminomethanesulfonic acid = AMSA, homotaurine = HMTAU) were tested for their counteracting effects against alterations in erythrocyte (RBC) morphology, membrane fluidity and cytoskeletal spectrin distribution due to diabetes, alcoholism and diabetes-alcoholism in male Goto-Kakizaki rats (made diabetic with a high fat diet and alcoholic upon feeding on a flavored alcohol solution) and Wistar-Kyoto rats (serving as controls). Both diabetes and alcoholism changed the RBC discoidal biconcave shape to a spiculated one, lowered membrane fluidity, and caused spectrin to become marginalized. While AMSA and HYTAU returned the RBC shape to normal, HMTAU made it only discoidal, and TAU was without effect. All test compounds, but TAU, maintained the membrane fluidity normal; and HYTAU and AMSA, but not TAU or HMTAU, kept spectrin uniformly distributed. The noted effects were correlated with compound structure and RBC values for malondialdehyde and cholesterol/phospholipid ratio.

In vitro effects of oxygen on physico-chemical properties of horse erythrocyte membrane

Whether direct exposure to different concentrations (0%, 13%, 100%) of oxygen may affect horse erythrocyte membrane fluidity (EMF) and fatty acid (FA) composition was studied during 1 (T60) and 2h (T120) exposure. EMF was investigated at the head group level and hydrophobic core thanks to phosphorus nucleus 31 ((31)P) nuclear magnetic resonance ((31)P NMR) and electronic paramagnetic resonance (EPR) using two spin probes: 5-nitroxydestearic acid and 16-doxylstearic acid. Lipid structure of the membranes was studied by gas liquid chromatography. 4-Hydroxy-2E-nonenal was also analyzed as a marker of lipid peroxidation. It increased at T120 13% and 100% oxygen whereas there were no significant changes in membrane dynamic or structure. Correlation was demonstrated between EMF and partial pressure of oxygen in the blood ( [Formula: see text] ). In vitro high rate of oxygenation was efficient to induce lipid peroxidation but did not change membrane dynamics. This may be due to a low free radical production in vitro or to the high red blood cells antioxidant properties.

Anesthetic-mediated protection/preconditioning during cerebral ischemia

Cerebral ischemia is a multi-faceted neurodegenerative pathology that causes cellular injury to neurons within the central nervous system. In light of the underlying mechanisms being elucidated, clinical trials to find possible neuroprotectants to date have failed, thus highlighting the need for new putative targets to offer protection. Recent evidence has clearly shown that anesthetics can confer significant protection and or induce a preconditioning effect against cerebral ischemia-induced injury. This review will focus on the putative protection/preconditioning that is afforded by anesthetics, their possible interaction with GABA(A) and glutamate receptors and two-pore potassium channels. In addition, the interaction with inflammatory, apoptotic and underlying molecular (particularly immediately early genes and inducible nitric oxide synthase etc) pathways, the activation of K(ATP) channels and the ability to provide lasting protection will also be addressed.

[Long-term effects of iterative diving on visual field, color vision and contrast sensitivity in professional divers]

PURPOSE

To assess long-term functional effects of iterative diving, we studied visual field, color vision, and contrast sensitivity in 21 French Navy professional divers and 21 controls.

PATIENTS AND METHODS

This retrospective study investigated a population of 21 divers and 21 controls. All subjects were male. The inclusion criterion for divers was a total number of dives greater or equal to 1,000. Exclusion criteria for the two groups were glaucoma, ocular hypertension, smoking, and vasospastic risks. Additional exclusion criteria for controls were any history of diving practice and of hyperbaric oxygen therapy. The visual field was examined with a Humphrey Central 30-2 threshold test. Moreover, we explored spatial contrast sensitivity using Metrovision Moniteur Ophtalmologique "STAT" program and color vision with desaturated 15 hue test.

RESULTS

None of the divers had any loss of spatial contrast sensitivity. There was a high frequency of yellow-blue axis color vision defects (45.2%) in the diver group. Regarding visual field, corrected pattern standard deviation was significantly higher in divers (p<0.01).

CONCLUSION

These findings suggest that iterative diving may cause subclinical functional effects on vision. Further studies will be needed to determine the exact setting of this repercussion upon macula and/or the optic nerve.

Effect of maternal manganese blood levels on erythrocyte calcium-pump activity in newborns

Manganese (Mn) is widely distributed in the biosphere but occurs in only trace amounts in animal tissues. Although Mn deficiency and toxicity both have pathological consequences, the underlying biochemical lesions have not been well defined. In vitro studies suggest that transport proteins are affected by Mn, lead (Pb), and selenium (Se). Among these transport proteins, the calmodulin-regulated calcium pump (Ca(2+)Mg(2+)ATPase) could be inhibited by Mn. In order to understand Mn biochemical pathways, we examined the relationships between Mn blood levels and red blood cell Ca-pump activity among 248 mothers and newborns, environmentally exposed to Mn, Pb, and Se.

POPULATION AND METHODS

248 mother-newborn pairs were recruited at Robert Debré University Hospital (Paris). Blood Mn and Pb concentrations were measured by absorption spectrophotometry. Se was measured by fluorometric method. Red blood cell membrane suspensions were obtained for Ca-pump activity measurements. Linear and quadratic regression models and Pearson correlation were performed.

RESULTS

A non-linear parabolic relationship between maternal Mn blood levels and newborn Ca-pump activity was discovered from the analysis of the observed data. The peak level of maternal Mn that corresponded to a maximal activity of the newborn Ca-pump was estimated at 23.9 microg/l with a 95% confidence interval of 17.6 to 32.4 microg/l. An inhibition of this enzyme was observed at low and high levels of maternal Mn. The relationships between the newborn Ca-pump activity and maternal Se and Pb levels became non-significant after adjustment on all the co-factors included in the final model.

CONCLUSION

Maternal environmental exposure to Mn, as reflected by maternal blood levels of this metal, is associated with a reduced activity of newborn erythrocyte Ca-pump in a non-linear pattern. Mn levels between 17.6 and 32.4 microg/l in maternal blood probably correspond to the optimal physiological concentration for the metabolism of this enzyme in newborns.

Mechanisms of action of green tea catechins, with a focus on ischemia-induced neurodegeneration

Catechins are dietary polyphenolic compounds associated with a wide variety of beneficial health effects in vitro, in vivo and clinically. These therapeutic properties have long been attributed to the catechins' antioxidant and free radical scavenging effects. Emerging evidence has shown that catechins and their metabolites have many additional mechanisms of action by affecting numerous sites, potentiating endogenous antioxidants and eliciting dual actions during oxidative stress, ischemia and inflammation. Catechins have proven to modulate apoptosis at various points in the sequence, including altering expression of anti- and proapoptotic genes. Their anti-inflammatory effects are activated through a variety of different mechanisms, including modulation of nitric oxide synthase isoforms. Catechins' actions of attenuating oxidative stress and the inflammatory response may, in part, account for their confirmed neuroprotective capabilities following cerebral ischemia. The versatility of the mechanisms of action of catechins increases their therapeutic potential as interventions for numerous clinical disorders. However, more epidemiological and clinical studies need to be undertaken for their efficacy to be fully elucidated.

Evaluation of single intratesticular injection of calcium chloride for nonsurgical sterilization of male Black Bengal goats (Capra hircus): a dose-dependent study

This study describes the induction of chemosterilization in three groups each of six adult male Black Bengal goats at 30 days after a single bilateral intratesticular injection of a calcium chloride (CaCl(2), 2H(2)O) solution at the doses of 10, 20 or 40 mg/kg body weight/testis, always in a 2 ml volume of normal saline. Another one group of animals received only 2 ml of normal saline per testis as a control. The induction of chemosterilization was measured using relative testicular weight as well as histomorphological parameters including seminiferous tubular architecture and germ cell association in seminiferous tubules along with morphology of the interstitial space. Biochemical markers included activities of testicular Delta(5), 3beta-hydroxysteroid dehydrogenase (Delta(5), 3beta-HSD), 17beta-hydroxysteroid dehydrogenase (17beta-HSD), catalase, glutathione peroxidase (GPx), glutathione S-transferase (GST) and superoxide dismutase (SOD) as well as monitoring the level of testicular thiobarbituric acid reactive substances (TBARS), conjugated dienes and reduced glutathione (GSH) content along with plasma concentrations of testosterone, LH and FSH. Histomorphological measures of testes showed total necrosis of testicular tissue at 30 days after an injection of either 20 or 40 mg CaCl(2) along with fibrosis in seminiferous tubules and interstitial spaces. Infiltration of leucocytes was observed with the 40 mg dose. Disintegration of germ cell arrangement in seminiferous tubules and washing out of germ cells from the tubules were noted with the 10mg dose. Relative organ weights, plasma concentrations of testosterone, testicular activities of Delta(5), 3beta-HSD, 17beta-HSD, catalase, GPx, GST, and SOD and testicular contents of GSH all were declined. Increases occurred in testicular TBARS, conjugated dienes and plasma concentrations of LH and FSH with each of the treatments by comparison with the control group. Plasma concentrations of cortisol and fasting blood sugar level as well as packed cell volume (PCV) and total plasma protein were recorded to monitor the changes of chronic stress in the experimental animals. Changes in these parameters were not significant. An intratesticular injection of calcium chloride at specified doses could be a suitable method of sterilization in preference to surgical castration of goats.

Clomethiazole: mechanisms underlying lasting neuroprotection following hypoxia-ischemia

Damage after hypoxia-ischemia (HI) is observed in both cortical and subcortical regions. In this study, we employed a "Levine" rat model of HI (left carotid ligation + 1 h global hypoxia on PND-26) and used histological and electrophysiological paradigms to assess the long-term neuroprotective properties of clomethiazole (CMZ; a GABA(A) receptor modulator). Key enzymes involved in inflammation, namely nitric oxide synthase (NOS) and arginase, were also examined to assess potential CMZ mechanisms not involving GABA-R activation. Assessments were carried out 3 and 90 days post-HI. Extensive CNS lesions were evident after HI ipsilaterally at both short- and long-term intervals. CMZ significantly decreased the lesion size at 3 and 90 days (P<0.01; P<0.05). Evoked field potential analyses were used to assess hippocampal CA1 neuronal activity ex vivo. Electrophysiological measurements contralateral to the occlusion revealed impaired neuronal function after HI relative to short- and long-term controls (P<0.001, 3 and 14 days; P<0.01, 90 days), with CMZ treatment providing near complete protection (P<0.001 at 3 and 14 days; P<0.01 at 90 days). Both NOS and arginase activities were significantly increased at 3 days (P<0.01), with arginase remaining elevated at 90 days post-HI (P<0.05) ipsilaterally. CMZ suppressed the HI-induced increase in iNOS and arginase activities (P<0.001; P<0.05). These data provide evidence of long-term functional neuroprotection by CMZ in a model of HI. We further conclude that under conditions of HI, functional deficits are not restricted to the ipsilateral hemisphere and are due, at least in part, to changes in the activity of NOS and arginase.

Melatonin strongly interacts with zwitterionic model membranes—evidence from Fourier transform infrared spectroscopy and differential scanning calorimetry

Interactions of melatonin with zwitterionic dipalmitoyl phosphatidylcholine (DPPC) multilamellar liposomes (MLVs) were investigated as a function of temperature and melatonin concentration (1-30 mol%) by using two noninvasive techniques, namely Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). The investigation of the C-H, CO, and PO2- antisymmetric double stretching modes in FTIR spectra and DSC studies reveal that melatonin changes the physical properties of the DPPC bilayers by decreasing the main phase transition temperature, abolishing the pretransition, ordering the system in the gel phase, and increasing the dynamics of the system both in the gel and liquid crystalline phases. It also causes significant decrease in the wavenumber for the CO stretching and PO2- antisymmetric double bond stretching bands, which indicates strong hydrogen bonding The results imply that melatonin locates in the interfacial region of the membrane. Furthermore, in the DSC curve, more than one signal is observed at high melatonin concentrations (24 and 30 mol%), which indicates melatonin-induced phase separation in DPPC membranes.

The role of antioxidants in models of inflammation: Emphasis on l-arginine and arachidonic acid metabolism

Inflammatory processes are made up of a multitude of complex cascades. Under physiological conditions these processes aid in tissue repair. However, under pathophysiological environments, such as wound healing and hypoxia-ischaemia (HI), inflammatory mediators become imbalanced, resulting in tissue destruction. This review addresses the changes in reactive oxygen species (ROS), L-arginine and arachidonic acid metabolism in wound healing and HI and subsequent treatments with promising anti-oxidants. Even though these models may appear divergent, anti-oxidant treatments are nevertheless still having favourable effects. On the basis of recent findings, it is apparent that protection with anti-oxidants is not solely attributed to scavenging of ROS. In addition, the actions of anti-oxidants must be considered in light of the inflammatory process being assessed. To this end, there does not appear to be any universally applicable single mechanism to explain the actions of anti-oxidants.

Antioxidant effects of water- and lipid-soluble nitroxide radicals in liposomes

Liposomes are today useful tools in different fields of science and technology. A lack of stability due to lipid peroxidation is the main problem in the extension of the use of these formulations. Recent investigative works have reported the protective effects of stable nitroxide radicals against oxidative processes in different media and under different stress conditions. Our group has focused its attention on the natural aging of liposomes and the protection provided by the water- and lipid-soluble nitroxide radicals 2,2,6,6-tetramethylpiperdine-1-oxyl (TEMPO) and doxylstearic acids (5-DSA, 12-DSA, and 16-DSA), respectively. Unilamellar liposomes were incubated under air atmosphere at 37 degrees C, both in the absence and in the presence of these radicals. Conjugated dienes, lipid hydroperoxides, TBARS, membrane fluidity, and nitroxide ESR signal intensity were followed as a function of time. Our results demonstrated that doxylstearic acids were more efficient than TEMPO in retarding lipid peroxidation at all the concentrations tested. The inhibition percentages, depending on the total nitroxide concentration, were not proportional to the lipid-water partition coefficient. Furthermore, time-course ESR signals showed a slower decrease for doxylstearic acids than for TEMPO. No significant differences were found among 5-DSA, 12-DSA, and 16-DSA. We concluded that the nitroxide radical efficiency as antioxidant directly depends on both nitroxide concentration and lipophilicity.

Neuroprotective effects of (-)-epigallocatechin gallate following hypoxia-ischemia-induced brain damage: novel mechanisms of action

(-)-Epigallocatechin gallate (EGCG) is a potent antioxidant that is neuroprotective against ischemia-induced brain damage. However, the neuroprotective effects and possible mechanisms of action of EGCG after hypoxia-ischemia (HI) have not been investigated. Therefore, we used a modified "Levine" model of HI to determine the effects of EGCG. Wistar rats were treated with either 0.9% saline or 50 mg/kg EGCG daily for 1 day and 1 h before HI induction and for a further 2 days post-HI. At 26-days-old, both groups underwent permanent left common carotid artery occlusion and exposure to 8% oxygen/92% nitrogen atmosphere for 1 h. Histological assessment showed that EGCG significantly reduced infarct volume (38.0+/-16.4 mm(3)) in comparison to HI + saline (99.6+/-15.6 mm(3)). In addition, EGCG significantly reduced total (622.6+/-85.8 pmol L-[(3)H]citrulline/30 min/mg protein) and inducible nitric oxide synthase (iNOS) activity (143.2+/-77.3 pmol L-[(3)H]citrulline/30 min/mg protein) in comparison to HI+saline controls (996.6+/-113.6 and 329.7+/-59.6 pmol L-[(3)H]citrulline/30 min/mg protein for total NOS and iNOS activity, respectively). Western blot analysis demonstrated that iNOS protein expression was also reduced. In contrast, EGCG significantly increased endothelial and neuronal NOS protein expression compared with HI controls. EGCG also significantly preserved mitochondrial energetics (complex I-V) and citrate synthase activity. This study demonstrates that the neuroprotective effects of EGCG are, in part, due to modulation of NOS isoforms and preservation of mitochondrial complex activity and integrity. We therefore conclude that the in vivo neuroprotective effects of EGCG are not exclusively due to its antioxidant effects but involve more complex signal transduction mechanisms.

Down-regulation of iron regulatory protein 1 activities and expression in superoxide dismutase 1 knock-out mice is not associated with alterations in iron metabolism

Iron and oxygen (O2) are intimately associated in many well characterized patho-physiological processes. These include oxidation of the [4Fe-4S] cluster of mitochondrial aconitase and inactivation of this Krebs cycle enzyme by the superoxide anion (O2*-), a product of the one-electron of reduction O2. In contrast to the apparent toxicity of this reaction, the biological consequences of O2*- -mediated inactivation of the cytosolic counterpart of mitochondrial aconitase, commonly known as iron regulatory protein 1 (IRP1), are not clear. Apart from its ability to convert citrate to iso-citrate, IRP1 in its apo-form binds to iron-responsive elements in the untranslated regions of mRNAs coding for proteins involved in iron metabolism, to regulate their synthesis and thus control the cellular homeostasis of this metal. Here, we show that in superoxide dismutase 1 (SOD1) knock-out mice, lacking Cu,Zn-SOD, an enzyme that acts to reduce the concentration of O2*- mainly in cytosol, not only is aconitase activity of IRP1 inhibited but the level of IRP1 is also strongly decreased. Despite such an evident alteration in IRP1 status, SOD1-deficient mice display a normal iron metabolism phenotype. Our findings clearly show that under conditions of O2*- -mediated oxidative stress, IRP1 is not essential for the maintenance of iron metabolism in mammals.

Oxidatively modified fibrinogen modulates blood rheological parameters

We studied the effect of UV-oxidized fibrinogen with oxidation degrees of 10 and 20% on rheological parameters of the blood. The effect of fibrinogen with 10% oxidation degree was moderate and variable, which attests to its partial compensation with the pool of natural antioxidants. The effect of fibrinogen with 20% oxidation degree was more pronounced. It dramatically decreased deformability of erythrocytes, delayed formation of linear aggregates, accelerated formation of 3D-aggregates, enhanced the total hydrodynamic strength of aggregates, but decreased stability of the largest aggregates. It did not increase plasma viscosity, but enhanced viscosity of the blood at all shear rates. At both degrees of oxidation, suspension stability of the blood decreased, the Caisson viscosity did not change, and the difference between the values of Caisson and asymptotic viscosities markedly increased. On the whole, oxidative fibrinogen produces negative changes in blood rheological parameters, and its effect depends on the degree of oxidation.

Lipid diffusion in sperm plasma membranes exposed to peroxidative injury from oxygen free radicals

Unsaturated lipids in sperm plasma membranes are very susceptible to peroxidation when exposed to reactive oxygen species (ROS). In this investigation we have incubated ram spermatozoa in the presence of two ROS generating systems, ascorbate/FeSO4 and potassium peroxychromate (K3CrO8), and examined their effects on membrane fluidity by measuring fluorescence recovery after photobleaching (FRAP) of a lipid reporter probe 5-(N-octadecanoyl)-aminofluorescein (ODAF). Peroxidation was monitored by malonaldehyde formation and changes in fluorescence emission of 4,4-difluoro-5-(4-phenyl-1,3-butadienyl)-4-bora-3a,4a-diaza-s-indacene-3-undecanoic acid (C11-BODIPY(581/591)). Ascorbate/FeSO4-induced peroxidation was inhibited by Vitamin E, butylated hydroxyanisole (BHA), 1,4-diazobicyclo(2,2,2)octane (DABCO), and to a lesser extent by ethanol. Added superoxide dismutase (SOD), gluthathione peroxidase (GPX), and catalase were ineffective scavengers. K3CrO8 induced very rapid peroxidation that could be delayed, but not prevented, by Vitamin E, BHT, DABCO, ethanol, and mannitol; once again SOD, GPX, and catalase were ineffective scavengers. Neither peroxidation with ascorbate/FeSO4 nor K3CrO8, or added H2O2 or malonaldehyde perturbed ODAF diffusion in any region of the sperm plasma membrane. Vitamin E tended to enhance diffusion rates. Exogenous cumene hydroperoxide, however, reduced ODAF diffusion to low levels on the sperm head. These results suggest that the adverse effects of ROS on spermatozoa are more likely to be caused by direct oxidation of proteins and membrane permeabilisation than disturbance of lipid fluidity.

Role of Ca2+ in radiation-induced damage in murine splenocytes

PURPOSE

To address the links between calcium, peroxidation, cell damage and death and the response of the enzymes involved in free radical metabolism, in splenocytes of mice irradiated with gamma-rays.

MATERIALS AND METHODS

Splenocytes of Swiss albino mice were irradiated with various doses (0-7 Gy) of gamma-rays (60Co) at a dose-rate of 0.0575 Gy s(-1). Membrane peroxidation and fluidity were determined by the thiobarbituric acid-reactive substances (TBARS) method, and fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH), respectively. Apoptosis was analysed by nucleosomal ladder formation and activity of NF-kappaB by electrophoretic mobility shift assay (EMSA). The specific activities of the antioxidant enzymes, lactate dehydrogenase (LDH), levels of nitric oxide (NO*) and glutathione were determined spectrophotometrically. Modulatory effects of Ca2+ were examined at 3 Gy using different concentrations (1, 3 and 5 mM) in the presence or absence of the ionophore A23187.

RESULTS

Irradiation of splenocytes resulted in enhanced peroxidative damage. membrane fluidity, apoptosis and DNA binding activity of NF-kappaB. The specific activities of LDH and antioxidant enzymes superoxide dismutase (SOD), DT-diaphorase (DTD), glutathione S-transferase (GST) and levels of glutathione (GSH) and NO* were increased with radiation dose up to 4Gy. Ca2+ augmented the radiation-induced responses. The presence of ionophore A23187 potentiated the modulatory effects of Ca2+.

CONCLUSIONS

These findings show that Ca2+ augments radiation damage and is more effective intracellularly. Ca2+, peroxidation, cellular damage and apoptosis are possibly interlinked through signals, as is evident from the increased activity of NF-kappaB and generation of NO*. The enhanced antioxidant status suggests an attempt made by the irradiated cells to maintain their normal functions.

Biochemical assessments of oxidative stress, erythrocyte membrane fluidity and antioxidant status in professional soccer players and sedentary controls

BACKGROUND

Physical exercise is characterized by an increase in oxygen consumption by the whole body. This leads to a decrease in antioxidant levels that could promote both an increase in the markers of lipoprotein peroxidation and damage to the erythrocyte membrane with consequent modification of membrane fluidity.

MATERIALS AND METHODS

Different markers of oxidative stress, erythrocyte membrane fluidity and antioxidant status were determined in 20 professional soccer players and 20 sedentary controls. Plasma lipoperoxides and kinetics of Cu-stimulated plasma peroxidation were measured together with hydrosoluble (albumin, uric acid and vitamin C), liposoluble (vitamin E and bilirubin) and enzymatic (superoxide dismutase and glutathione peroxidase) serum antioxidants. Erythrocyte membrane rigidity was determined by measuring fluorescence anisotropy (rs) of the fluorescent probe 1, 3, 5 diphenylexatriene.

RESULTS

The sportsmen showed higher levels of the following plasmatic antioxidants: ascorbic acid (P<0.0001), uric acid (P<0.0001), alpha-tocopherol (P=0.03) and superoxide dismutase activity (P=0.0001). According to this evidence, the lipoperoxide levels (P=0.0158), the duration of the latency phase of plasma peroxidation (P=0.0123) and erythrocytes membrane fluidity (P=0.0152) were found to be significantly higher in the soccer players.

DISCUSSION

Athletes undergoing regular and adequate training show improved antioxidant status together with a more fluid membrane status, which could contribute to improving both peripheral resistance to insulin and all the functional metabolic interchanges in the cellular membrane.