Phospholipase A2-Induced Remodeling Processes on Liquid-Ordered/Liquid-Disordered Membranes Containing Docosahexaenoic or Oleic Acid: A Comparison Study.

Vesicle cycling, which is an important biological event, involves the interplay between membrane lipids and proteins, among which the enzyme phospholipase A2 (PLA2) plays a critical role. The capacity of PLA2 to trigger the budding and fission of liquid-ordered (L(o)) domains has been examined in palmitoyl-docosahexaenoylphosphatidylcholine (PDPC) and palmitoyl-oleoylphosphatidylcholine (POPC)/sphingomyelin/cholesterol membranes. They both exhibited a L(o)/liquid-disordered (L(d)) phase separation. We demonstrated that PLA2 was able to trigger budding in PDPC-containing vesicles but not POPC ones. The enzymatic activity, line tension, and elasticity of the membrane surrounding the L(o) domains are critical for budding. The higher line tension of Lo domains in PDPC mixtures was assigned to the greater difference in order parameters of the coexisting phases. The higher amount of lysophosphatidylcholine generated by PLA2 in the PDPC-containing mixtures led to a less-rigid membrane, compared to POPC. The more elastic L(d) membranes in PDPC mixtures exert a lower counteracting force against the L(o) domain bending.

Higher stress response and altered quality of life in schizophrenia patients with low membrane levels of docosahexaenoic acid.

Schizophrenia is a severe, chronic, and heterogeneous mental disorder that affects approximately 1% of the world population. Ongoing research aims at clustering schizophrenia heterogeneity into various "biotypes" to identify subgroups of individuals displaying homogeneous symptoms, etiopathogenesis, prognosis, and treatment response. The present study is in line with this approach and focuses on a biotype partly characterized by a specific membrane lipid composition. We have examined clinical and biological data of patients with stabilized schizophrenia, including the fatty acid content of their erythrocyte membranes, in particular the omega-3 docosahexaenoic acid (DHA). Two groups of patients of similar size were identified: the DHA- group (N = 19) with a lower proportion of membrane DHA as compared to the norm in the general population, and the DHAn group (N = 18) with a normal proportion of DHA. Compared to DHAn, DHA- patients had a higher number of hospitalizations and a lower quality of life in terms of perceived health and physical health. They also exhibited significant higher interleukin-6 and cortisol blood levels. These results emphasize the importance of measuring membrane lipid and immunoinflammatory biomarkers in stabilized patients to identify a specific subgroup and optimize non-pharmacological interventions. It could also guide future research aimed at proposing specific pharmacological treatments.

Structural Changes Induced by Resveratrol in Monounsaturated and Polyunsaturated Phosphatidylcholine-Enriched Model Membranes.

Resveratrol (Resv) is considered to exert a beneficial impact due to its radical scavenger, anti-microbial and anti-inflammatory properties through several mechanisms that could include its interaction with the cell plasma membrane. To address this issue, we investigated the influence of Resv on membrane lipid order and organization in large unilamellar vesicles composed of different lipids and ratios. The studied lipid membrane models were composed of phosphatidylcholine (PC) species (either palmitoyl-docosahexaenoyl phosphatidylcholine (PDPC) or palmitoyl-oleoyl phosphatidylcholine (POPC)), sphingomyelin (SM) and cholesterol (Chol). This study found that the addition of Resv resulted in complex membrane reorganization depending on the degree of fatty acid unsaturation at the sn-2 position, and the Lipid/Resv and SM/Chol ratios. Resv rigidified POPC-containing membranes and increased liquid-ordered (Lo) domain formation in 40/40/20 POPC/SM/Chol mixtures as this increase was lower at a 33/33/34 ratio. In contrast, Resv interacted with PDPC/SM/Chol mixtures in a bimodal manner by fluidizing/rigidifying the membranes in a dose-dependent way. Lo domain formation upon Resv addition occurred via the following bimodal mode of action: Lo domain size increased at low Resv concentrations; then, Lo domain size decreased at higher ones. To account for the variable effect of Resv, we suggest that it may act as a "spacer" at low doses, with a transition to a more "filler" position in the lipid bulk. We hypothesize that one of the roles of Resv is to tune the lipid order and organization of cell plasma membranes, which is closely linked to important cell functions such as membrane sorting and trafficking.

The interaction of antipsychotic drugs with lipids and subsequent lipid reorganization investigated using biophysical methods.

The interaction of antipsychotic drugs (AP) with lipids and the subsequent lipid reorganization on model membranes was assessed using a combination of several complementary biophysical approaches (calorimetry, plasmon resonance, fluorescence microscopy, X-ray diffraction and molecular modeling). The effect of haloperidol (HAL), risperidone (RIS), and 9-OH-risperidone (9-OH-RIS) was examined on single lipid and mixtures comprising lipids of biological origin. All APs interact with lipids and induced membrane reorganization. APs showed higher affinity for sphingomyelin than for phosphatidylcholine. Cholesterol increased AP affinity for the lipid bilayer and led to the following AP ranking regarding affinity and structural changes: RIS >9-OH-RIS >HAL. Liquid-ordered domain formation and bilayer thickness were differentially altered by AP addition. Docking calculations helped understanding the observed differences between the APs and offer a representation of their conformation in the lipid bilayer. Present results indicate that AP drugs may change membrane compartmentalization which could differentially modulate the signaling cascade of the dopamine D2 receptor for which APs are ligands.

Nature and determinants of social actions during a mass shooting.

Reactions to danger have been depicted as antisocial but research has shown that supportive behaviors (e.g., helping injured others, giving information or reassuring others) prevail in life-threatening circumstances. Why is it so? Previous accounts have put the emphasis on the role of psychosocial factors, such as the maintenance of social norms or the degree of identification between hostages. Other determinants, such as the possibility to escape and distance to danger may also greatly contribute to shaping people's reactions to deadly danger. To examine the role of those specific physical constraints, we interviewed 32 survivors of the attacks at 'Le Bataclan' (on the evening of 13-11-2015 in Paris, France). Consistent with previous findings, supportive behaviors were frequently reported. We also found that impossibility to egress, minimal protection from danger and interpersonal closeness with other crowd members were associated with higher report of supportive behaviors. As we delved into the motives behind reported supportive behaviors, we found that they were mostly described as manifesting cooperative (benefits for both interactants) or altruistic (benefits for other(s) at cost for oneself) tendencies, rather than individualistic (benefits for oneself at cost for other(s)) ones. Our results show that supportive behaviors occur during mass shootings, particularly if people cannot escape, are under minimal protection from the danger, and feel interpersonal closeness with others. Crucially, supportive behaviors underpin a diversity of motives. This last finding calls for a clear-cut distinction between the social strategies people use when exposed to deadly danger, and the psychological motivations underlying them.

Factors Associated With a Higher Score of Burnout in a Population of 860 French Psychiatrists.

Burnout rates are estimated to be twice as high among healthcare professionals as in the general working population, and studies indicate rising incidence. The present study aimed to identify the contextual factors associated with self-reported burnout rates among French psychiatrists. A total of 860 French or French-speaking psychiatrists completed an online questionnaire when they registered for a major psychiatric conference. The Copenhagen Burnout Inventory, a validated scale that independently appraises personal, work- and patient-related dimensions, was used to assess the degree of perceived burnout. Respondents were divided into lower risk and higher risk groups. The latter contained the 25% of individuals who scored the highest on each of the three dimensions of the CBI scale. Univariate analysis showed that private practice was associated with lower levels of risk on the personal and work-related dimensions. Working for the public sector and long hours were both associated with a higher score on the work-related dimension. Interestingly, none of the variables we investigated, except from poor atmosphere at work, correlated with the patient-related dimension. Among public-sector psychiatrists, female gender, longer hours, and more consultations per week were associated with a higher score on the work-related dimension. Working four or more night shifts per month was significantly associated with a higher score of burnout risk on all three dimensions. Private- and public-sector practitioners who mainly treated patients with schizophrenia had a higher score of burnout risk. Multivariate analysis showed that a poor atmosphere at work, longer hours, and working four or more night shifts were significantly associated with higher score of burnout risk. A nonreassuring working environment and more stressors while treating patients each had a possibly negative impact. Although this study only examined the factors that distinguish between clinicians with the lowest versus highest CBI burnout risk scores, it opens up important avenues for research and development of programs to reduce burnout risk within the French healthcare system.

Abnormal transbilayer distribution of phospholipids in red blood cell membranes in schizophrenia.

Abnormalities in membrane lipids have been repeatedly reported in patients with schizophrenia. These abnormalities include decreased phosphatidylethanolamine (PE) and n-3 and n-6 polyunsaturated fatty acids in peripheral and brain cell membranes. The present study investigates the hypothesis of an overrepresentation of PE in the external leaflet of the red blood cell (RBC) membrane in patients with schizophrenia. The assumption was that this modification of PE asymmetrical distribution could explain the reported lipid membrane abnormalities. Phosphatidylethanolamine located in the external leaflet was specifically labeled in RBC membranes from 65 medicated patients with schizophrenia and 38 healthy controls. Labeled (external) and non-labeled (internal) PE and their respective fatty acid composition were analyzed by mass spectrometry. A significant increase in the percentage of external leaflet PE was found in RBC membranes in 63.1% of the patients. In this subgroup, a significant depletion of n-3 and n-6 polyunsaturated fatty acids from internally located PE was also observed. Age, sex and antipsychotic treatment were not associated with the transbilayer membrane distribution of PE. Potential mechanisms underlying these abnormalities may involve membrane phospholipid transporters or degradative enzymes involved in phospholipid metabolism. The anomaly described could characterize a subgroup among patients with schizophrenia.

Modification of membrane heterogeneity by antipsychotic drugs: an X-ray diffraction comparative study.

Lipid mixtures are used to mimic biological membranes as they allow characterization of lipid lateral domains defined by their specific lipid molecular organization. Therapeutic agents such as antipsychotic drugs (AP) that may interact with lipids arrangement are likely to modify membrane biological properties. The present study describes the effect of 2 typical and 5 atypical antipsychotic drugs on an aqueous co-dispersion of a lipid mixture made of egg phosphatidylcholine (PC)/brain sphingomyelin (SM)/cholesterol (1/1/1 mol/mol/mol). Lamellar liquid-ordered (Lo) and liquid-disordered (Ld) phase coexistence was identified in the control and antipsychotic-added mixtures at 37 degrees C using synchrotron small-angle X-ray scattering methods (XRD). Intensity of the Bragg peaks was used to generate electron density profiles (EDP) allowing bilayer thickness calculation. All antipsychotic except from amisulpride induced a Lo phase bilayer thickness (d(pp)) decrease. Chlorpromazine, haloperidol, amisulpride and 9-0H-risperidone induced a Ld d(pp) increase while ziprazidone, risperidone and clozapine induced a Ld d(pp) decrease, indicating that antipsychotic atypicality is not associated with a specific d(pp) modification on our lipid model mixture. Results are discussed in terms of competition of antipsychotic compounds with cholesterol and mode of reorganization of lateral domains. A pharmacological relevance of these changes is also discussed.

Structure and thermotropic phase behaviour of detergent-resistant membrane raft fractions isolated from human and ruminant erythrocytes.

Detergent-resistant membrane raft fractions have been prepared from human, goat, and sheep erythrocyte ghosts using Triton X-100. The structure and thermotropic phase behaviour of the fractions have been examined by freeze-fracture electron microscopy and synchrotron X-ray diffraction methods. The raft fractions are found to consist of vesicles and multilamellar structures indicating considerable rearrangement of the original ghost membrane. Few membrane-associated particles typical of freeze-fracture replicas of intact erythrocyte membranes are observed in the fracture planes. Synchrotron X-ray diffraction studies during heating and cooling scans showed that multilamellar structures formed by stacks of raft membranes from all three species have d-spacings of about 6.5 nm. These structures can be distinguished from peaks corresponding to d-spacings of about 5.5 nm, which were assigned to scattering from single bilayer vesicles on the basis of the temperature dependence of their d-spacings compared with the multilamellar arrangements. The spacings obtained from multilamellar stacks and vesicular suspensions of raft membranes were, on average, more than 0.5 nm greater than corresponding arrangements of erythrocyte ghost membranes from which they were derived. The trypsinization of human erythrocyte ghosts results in a small decrease in lamellar d-spacing, but rafts prepared from trypsinized ghosts exhibit an additional lamellar repeat 0.4 nm less than a lamellar repeat coinciding with rafts prepared from untreated ghosts. The trypsinization of sheep erythrocyte ghosts results in the phase separation of two lamellar repeat structures (d=6.00; 5.77 nm), but rafts from trypsinized ghosts produce a diffraction band almost identical to rafts from untreated ghosts. An examination of the structure and thermotropic phase behaviour of the dispersions of total polar lipid extracts of sheep detergent-resistant membrane preparations showed that a reversible phase separation of an inverted hexagonal structure from coexisting lamellar phase takes place upon heating above about 30 degrees C. Non-lamellar phases are not observed in erythrocytes or detergent-resistant membrane preparations heated up to 55 degrees C, suggesting that the lamellar arrangement is imposed on these membrane lipids by interaction with non-lipid components of rafts and/or that the topology of lipids in the erythrocyte membrane survives detergent treatment.

Antipsychotic medication, functional outcome and quality of life in schizophrenia: focus on amisulpride.

BACKGROUND: Restoration of quality of life is considered as the ultimate treatment goal in the management of schizophrenia and is important for destigmatising the disease. However, few studies, including the most recent, have collected quality of life data prospectively or evaluated the relationship of treatment with quality of life. SCOPE: Amisulpride is an atypical antipsychotic drug which has been described to have potency in improving negative symptoms of chronic schizophrenia and whose use is associated with a relatively low rate of emergence of extrapyramidal side-effects. These properties may contribute to a beneficial effect on quality of life. A systematic literature review of functional outcome in clinical trials with amisulpride was performed in order to assess the effect of this drug on quality of life and social functioning in patients. The Medline database was searched for all studies of amisulpride in schizophrenia which reported functional and quality of life outcomes up until 30 September 2009. FINDINGS: Only one dedicated study assessing functional outcome or quality of life as a primary outcome criterion was identified. This demonstrated significant improvement in subjective well-being in patients with schizophrenia initiating treatment with amisulpride, and a correlation between this improvement and amelioration of psychopathology. In addition, functional outcome rating scales were used as secondary outcome measures in eight randomised clinical trials, and two naturalistic observational studies. Amisulpride treatment was associated with improvement in functional outcome, with effect sizes that were comparable between studies. Improvements in functional outcome are consistently greater than those observed in patients treated with haloperidol and similar in magnitude to those seen with three other atypical antipsychotics, namely olanzapine, ziprasidone and risperidone. A patient-reported outcome measure was used in only one comparative study, and demonstrated perception of a superior benefit with amisulpride compared to haloperidol. These findings could to some extent be replicated in several large naturalistic studies under standard conditions of care. CONCLUSIONS: The data from studies on functional outcome and subjective well-being provide consistent information supporting the use of amisulpride for the treatment of schizophrenia in order to improve social functioning, integration into the community and autonomy, which are critical for the overall quality of life of patients with schizophrenia.

Effect of sphingosine on domain morphology in giant vesicles.

Sphingosine is a bioactive molecule which is known to participate in the regulation of a number of cellular processes such as apoptosis, cell differentiation, growth, etc. Sphingosine was observed to exhibit different domain morphology depending on the surrounding lipid matrix in biomimetic systems such as giant vesicles. Our current results showed that in a glycerophospholipid matrix sphingosine segregated in gel leaf-like domains whereas cholesterol presence increased its miscibility by melting gel domains in a concentration-dependent manner. Sphingosine and cholesterol did not form merging liquid domains on the micron scale as observed for sphingomyelin and cholesterol. However, we were able to visualize that sphingosine appears as a stabilizer and amplifier of domains in liquid-ordered phase by increasing the temperature of their formation and fraction. These results imply that sphingosine acts as a modulator of the lipid domain formation and thus it could exert its biological role, not only through direct binding to proteins, but also indirectly by influencing their sorting in membranes and modulating the processes of signal transduction.

Liquid-liquid immiscibility under non-equilibrium conditions in a model membrane: an X-ray synchrotron study.

Several non-random lipid mixtures have been proposed as models of lipid plasma membrane, as they mimic the ability of biomembranes to form lateral domains. Biological membranes are characterised by a succession of localised transient steady-state lipid organisations rather than stable equilibria. This suggests that several quasi at-equilibrium lipid organisations may exist at different times in the same local patch of membranes. Identification of the conditions which can mimic heterogeneous dynamic membrane states in a lipid membrane model is a challenge. This is of particular importance as the lateral organisation of lipids mixtures in fully equilibrated samples may differ from the arrangement found in quasi at-equilibrium conditions. To address this issue, we have performed a real-time synchrotron X-ray diffraction study in ternary mixtures of egg-phosphatidylcholine/egg-sphingomyelin and cholesterol using a 0.5 degrees C/15 s step within a 20-50-20 degrees C thermal cycle. In the present study, all ternary mixtures displayed lamellar phase separation. A d-spacing value was observed reversibly during the heating and cooling scan for each of the two coexisting phases. In mixtures with a cholesterol concentration from 20 to 50 mol%, a liquid-ordered (Lo) and liquid-disordered (Ld) phase separation was observed in the 20-50 degrees C thermal range. These results are discussed in terms of a specific interaction between lipid molecular aggregates.

The use of amisulpride in the treatment of acute psychosis.

The management of acute episodes in schizophrenia is frequently initiated in the psychiatric emergency department and requires rapid intervention to relieve distress and psychiatric symptoms. Both non-pharmacological and pharmacological interventions are needed to calm the patient and prevent potential harm to the patient or others. Treatment is a step-by-step process including management of behavioral symptomatology, diagnosis of potential organic causes, and evaluation of potential substance abuse. Better care is delivered if predefined standard operating procedures are adopted systematically. The ultimate goal of treatment is to establish a therapeutic alliance with the patient. Atypical antipsychotics given orally are recommended as a first-line treatment. As the treatment endpoint is calmness rather than sleep, a non-sedative antipsychotic agent is usually preferred. Drug tolerance is a major issue for the patient. Amisulpride is an effective atypical antipsychotic agent in this context. The optimal dose is 800 mg/day, which is effective on positive and negative symptoms and can be given from the first day with a low risk of extrapyramidal symptoms. Since drug-drug interactions are limited, agitation and anxiety may be controlled by short-term adjunctive therapy with benzodiazepines. In conclusion, amisulpride is an appropriate first-line treatment for the management of acute psychosis.

Comparative lipid analysis and structure of detergent-resistant membrane raft fractions isolated from human and ruminant erythrocytes.

The lipid composition and structure of detergent-resistant membrane rafts from human, goat, and sheep erythrocytes is investigated. While the sphingomyelin:cholesterol ratio varied from about 1:5 in human to 1:1 in sheep erythrocytes a ratio of 1:1 was found in all raft preparations insoluble in Triton X-100 at 4 degrees C. Excess cholesterol is excluded from rafts and saturated molecular species of sphingomyelin assayed by gas chromatography-mass spectrometry determines the solubility of cholesterol in the detergent. Freeze-fracture electron microscopy shows that vesicles and multilamellar structures formed by membrane rafts have undergone considerable rearrangement from the original membrane. No membrane-associated particles are observed. Synchrotron X-ray diffraction studies showed that d spacings of vesicle preparations of rafts cannot be distinguished from ghost membranes from which they are derived. Dispersions of total polar lipid extracts of sheep rafts show phase separation of inverted hexagonal structure upon heating and this phase coexists with multilamellar structures at 37 degrees C.

Modulation of the phase heterogeneity of aminoglycerophospholipid mixtures by sphingomyelin and monovalent cations: maintenance of the lamellar arrangement in the biological membranes.

The phase behaviour of mixed molecular species of phosphatidylethanolamine, phosphatidylserine and sphingomyelin of biological origin were examined in aqueous co-dispersions using synchrotron X-ray diffraction. The co-dispersions of phospholipids studied were aimed to model the mixing of lipids populating the cytoplasmic and outer leaflets in the resting or "scrambled" activated cell membrane. Mixtures enriched with phosphatidylethanolamine and phosphatidylserine were characterized by a phase separation of non-lamellar phases (cubic and inverted hexagonal) with a lamellar gel phase comprising the most saturated molecular species. Inclusion of sphingomyelin in the mixture resulted in a suppression of the hexagonal-II phase in favour of lamellar phases at temperatures where a proportion of the phospholipid was fluid. The effect was also dependent on the total amount of sphingomyelin in ternary mixtures, and the lamellar phase dominated in mixtures containing more than 30 mol%, irrespective of the relative proportions of phosphatidylserine/sphingomyelin. A transition from gel to liquid-crystal phase was detected by wide-angle scattering during heating scans of ternary mixtures enriched in sphingomyelin and was shown by thermal cycling experiments to be coupled with a hexagonal-II phase to lamellar transition. In such samples there was evidence of a coexistence of non-lamellar phases with a lamellar gel phase. A transition of the gel phase to the fluid state on heating from 35 to 41 degrees C was evidenced by a progressive increase in the lamellar d-spacing. The presence of calcium enhanced the phase separation of a lamellar gel phase from a hexagonal-II phase in mixtures enriched in phosphatidylserine. This effect was counteracted by charge screening with 150 mM NaCl. The effect of sphingomyelin on stabilizing the lamellar phase is discussed in the context of an altered composition in the cytoplasmic/outer leaflets of the plasma membrane resulting from scrambling of the phospholipid distribution. The results suggest that a lamellar structure can be retained by the inward translocation of sphingomyelin in biological membranes. The presence of monovalent cations serves also to stabilize the bilayer in activated cells where a translocation of aminoglycerophospholipids and an influx of calcium occur simultaneously.

Rafts promote assembly and atypical targeting of a nonenveloped virus, rotavirus, in Caco-2 cells.

Rotavirus follows an atypical pathway to the apical membrane of intestinal cells that bypasses the Golgi. The involvement of rafts in this process was explored here. VP4 is the most peripheral protein of the triple-layered structure of this nonenveloped virus. High proportions of VP4 associated with rafts within the cell as early as 3 h postinfection. In the meantime a significant part of VP4 was targeted to the Triton X-100-resistant microdomains of the apical membrane, suggesting that this protein possesses an autonomous signal for its targeting. At a later stage the other structural rotavirus proteins were also found in rafts within the cells together with NSP4, a nonstructural protein required for the final stage of virus assembly. Rafts purified from infected cells were shown to contain infectious particles. Finally purified VP4 and mature virus were shown to interact with cholesterol- and sphingolipid-enriched model lipid membranes that changed their phase preference from inverted hexagonal to lamellar structures. Together these results indicate that a direct interaction of VP4 with rafts promotes assembly and atypical targeting of rotavirus in intestinal cells.