The hidden network of biocrust successional stages in the High Arctic: Revealing abiotic and biotic factors shaping microbial and metazoan communities

Despite the important role that biocrust communities play in maintaining ecosystem structure and functioning in deglaciated barren soil, few studies have been conducted on the dynamics of biotic communities and the impact of physicochemical characteristics in shaping the different successional stages. In this study an integrated approach encompassing physicochemical parameters and molecular taxonomy was used for identifying the indicator taxa and the presence of intra- and inter-kingdom interactions in five different crust/biocrust successional stages: i) physical crust, ii) cyanobacteria-dominated biocrust, iii) cyanobacteria/moss-dominated biocrust, iv) moss-dominated biocrust and v) bryophyte carpet. The phylum Gemmatimonadota was the bacterial indicator taxon in the early stage, promoting both inter- and intra-kingdom interactions, while Cyanobacteria and Nematoda phyla played a pivotal role in formation and dynamics of cyanobacteria-dominated biocrusts. A multitrophic community, characterized by a shift from oligotrophic to copiotrophic bacteria and the presence of saproxylic arthropod and herbivore insects was found in the cyanobacteria/moss-dominated biocrust, while a more complex biota, characterized by an increased fungal abundance (classes Sordariomycetes, Leotiomycetes, and Dothideomycetes, phylum Ascomycota), associated with highly trophic consumer invertebrates (phyla Arthropoda, Rotifera, Tardigrada), was observed in moss-dominated biocrusts. The class Bdelloidea and the family Hypsibiidae (phyla Rotifera and Tardigrada, respectively) were metazoan indicator taxon in bryophyte carpet, suggesting their potential role in shaping structure and function of this late successional stage. Nitrogen and phosphorus were the main physicochemical limiting factors driving the shift among different crust/biocrust successional stages. Identification and characterization of indicator taxa, biological intra- and inter-kingdom interactions and abiotic factors driving the shift among different crust/biocrust successional stages provide a detailed picture on crust/biocrust dynamics, revealing a strong interconnection among micro- and macrobiota systems. These findings enhance our understanding of biocrust ecosystems in High Arctic, providing valuable insights for their conservation and management in response to environmental shifts due to climate change.

Mental Health of Adolescents Exposed to the War in Ukraine

Importance

With exposure to traumatic events and reduced access to mental health care, adolescents of Ukraine during the Russian invasion since February 2022 are at high risk of psychiatric conditions. However, the actual mental health burden of the war has scarcely been documented.

Objective

To investigate the prevalence of a positive screen for psychiatric conditions among adolescents amidst the ongoing war in Ukraine as well as their associations with war exposure.

Design, Setting, and Participants

This cross-sectional study reports the results from the first wave of the Adolescents of Ukraine During the Russian Invasion cohort, the largest cohort study on Ukrainian adolescents' mental health during the Russian invasion since 2022. Using self-reported questionnaires, the national-level prevalence of a positive screen for various psychiatric conditions was estimated among adolescents aged 15 years or older attending secondary school in Ukraine in person or online (including those residing abroad but attending Ukrainian secondary school online) and the prevalence among Ukrainian adolescents living abroad due to the war.

Exposure

Self-reported exposure to war.

Main Outcomes and Measures

A positive screen for psychiatric conditions. The association between self-reported war exposure and a positive screen for each of the psychiatric conditions was also evaluated.

Results

A total of 8096 Ukrainian adolescents (4988 [61.6%] female) living in Ukraine or abroad were included in the analyses. Based on national-level estimates, 49.6% of the adolescents were directly exposed to war, 32.0% screened positive for moderate or severe depression, 17.9% for moderate or severe anxiety, 35.0% for clinically relevant psychological trauma, 29.5% for eating disorders, and 20.5% for medium risk or higher of substance use disorder. The burden of psychiatric symptoms was similarly large among Ukrainian adolescents living abroad. Adolescents exposed to war were more likely to screen positive for depression (prevalence ratio [PR], 1.39; 95% CI, 1.29-1.50), anxiety (PR, 1.62; 95% CI, 1.45-1.81), clinically relevant psychological trauma (PR, 1.41; 95% CI, 1.32-1.50), eating disorders (PR, 1.21; 95% CI, 1.12-1.32), and substance use disorder (PR, 1.11; 95% CI, 0.98-1.25).

Conclusions and Relevance

The findings of this study suggest that the mental health burden of Ukrainian adolescents amidst the Russian invasion of Ukraine is substantial. Mental health care efforts to alleviate the mental health burden of Ukrainian adolescents are needed.

Identification of multivariable Boolean patterns in microbiome and microbial gene composition data

Virtually every biological system is governed by complex relations among its components. Identifying such relations requires a rigorous or heuristics-based search for patterns among variables/features of a system. Various algorithms have been developed to identify two-dimensional (involving two variables) patterns employing correlation, covariation, mutual information, etc. It seems obvious, however, that comprehensive descriptions of complex biological systems need also to include more complicated multivariable relations, which can only be described using patterns that simultaneously embrace 3, 4, and more variables. The goal of this manuscript is to (a) introduce a novel type of associations (multivariable Boolean patterns) that can be manifested between features of complex systems but cannot be identified (described) by traditional pair-vise metrics; (b) propose patterns classification method, and (c) provide a novel definition of the pattern's strength (pattern's score) able to accommodate heterogeneous multi-omics data. To demonstrate the presence of such patterns, we performed a search for all possible 2-, 3-, and 4-dimensional patterns in historical data from the Human Microbiome Project (15 body sites) and collection of H. pylori genomes associated with gastric ulcers, gastritis, and duodenal ulcers. In all datasets under consideration, we were able to identify hundreds of statistically significant multivariable patterns. These results suggest that such patterns can be common in microbial genomics/microbiomics systems.

The battle for mental well-being in Ukraine: mental health crisis and economic aspects of mental health services in wartime

The ongoing war in Ukraine is having profound impacts on both the local and global economy, as well as the infrastructure and overall well-being of the people. The prolonged duration of the conflict, coupled with its many related consequences such as total uncertainty, unfavorable economic conditions, and a distressing media backdrop, have a lasting impact on the mental health of the population. The ongoing war in Ukraine has exposed weaknesses in the national mental health care system and underscored the importance of mental health economics. To prevent further mental health problems, it is crucial to develop a comprehensive set of measures aimed at strengthening the capacity of the mental health care system in Ukraine. Currently, Ukraine's mental health care system suffers from a lack of financial and human resources, which hinders its ability to provide adequate support to those in need. To address this issue, joint efforts between Ukrainian mental health stakeholders and the international governmental and non-governmental organizations are needed to provide support and capacity building for mental health services in Ukraine.

Impact of PVC microplastics on soil chemical and microbiological parameters

Microplastics (MPs) are emerging pollutants whose occurrence is a global problem in natural ecosystems including soil. Among MPs, polyvinyl chloride (PVC) is a well-known polymer with remarkable resistance to degradation, and because its recalcitrant nature serious environmental concerns are created during manufacturing and waste disposal. The effect of PVC (0.021% w/w) on chemical and microbial parameters of an agricultural soil was tested by a microcosm experiment at different incubation times (from 3 to 360 days). Among chemical parameters, soil CO₂ emission, fluorescein diacetate (FDA) activity, total organic C (TOC), total N, water extractable organic C (WEOC), water extractable N (WEN) and SUVA₂₅₄ were considered, while the structure of soil microbial communities was studied at different taxonomic levels (phylum and genus) by sequencing bacterial 16S and fungal ITS2 rDNA (Illumina MiSeq). Although some fluctuations were found, chemical and microbiological parameters exhibited some significant trends. Significant (p < 0.05) variations of soil CO₂ emission, FDA hydrolysis, TOC, WEOC and WEN were found in PVC-treated soils over different incubation times. Considering the structure of soil microbial communities, the presence of PVC significantly (p < 0.05) affected the abundances of specific bacterial and fungal taxa: Candidatus_Saccharibacteria, Proteobacteria, Actinobacteria, Acidobacteria and Bacteroides among bacteria, and Basidiomycota, Mortierellomycota and Ascomycota among fungi. After one year of experiment, a reduction of the number and the dimensions of PVC was detected supposing a possible role of microorganisms on PVC degradation. The abundance of both bacterial and fungal taxa at phylum and genus level was also affected by PVC, suggesting that the impact of this polymer could be taxa-dependent.

Study Protocol: Adolescents of Ukraine During the Russian Invasion (AUDRI) Cohort

BACKGROUND

Since February 14, 2022, Ukraine has once again been under attack by the Russian forces, putting the nation in one of the biggest emergencies in Europe since World War II. This puts Ukrainians at high risk of psychiatric disorders, amidst unseen attacks on infrastructure that have put massive strain on Ukraine's mental health services. Despite this, the prevalence of psychiatric disorders among adolescents and their changes over time have not yet been documented in Ukraine during the invasion. More generally, there is a need to more comprehensively uncover the long-term consequences of war on youth, especially their risks and protective factors.

METHODS

The Adolescents of Ukraine During the Russian Invasion (AUDRI) Cohort is the largest cohort of war-affected Ukrainian adolescents. We will recruit adolescents aged 15 to 18 years attending any school in Ukraine. Data collection will start early 2023, and will be held via online questionnaires every six months during the war as well as after the war has terminated. We will use several well-validated tools to screen for PTSD, depression, anxiety, substance use disorder, and eating disorders. In addition, we will ask participants about possible risks and protective factors of their mental health including resilience and social capital. Using the cohort, we will evaluate the trends in psychiatric disorder prevalence among adolescents in Ukraine over time and evaluate risks and protective factors of adolescents' mental health.

DISCUSSION

The AUDRI Cohort will provide a unique opportunity to learn more about trauma and resilience among youth in conflict settings, in addition to aiding international efforts to save the mental health of youth in Ukraine. At-risk adolescents identified from our study can directly become beneficiaries of targeted intervention themselves. Building evidence on the mental health of adolescents is especially valuable, as protecting the mental health of war-affected adolescents could help rebuild society and have positive consequences for generations to come.

Dynamics of hospitalizations and staffing of Ukraine's mental health services during the Russian invasion

BACKGROUND

Since February 2022, the people of Ukraine have experienced devastating losses due to the Russian invasion, increasing the demand for mental healthcare across the nation. Using longitudinal data on mental health facilities across the nation up to summer 2022, we aimed to provide an updated picture of Ukrainian mental health services during the 2022 Russian invasion.

METHODS

We conducted a nationwide longitudinal study on Ukrainian inpatient mental health facilities during the Russian invasion since February 2022. We obtained responses from the heads of 30 inpatient mental health facilities, which represent 49.2% of all psychiatric hospitals in Ukraine. Information on hospitalizations and the number, displacement, and injuries of staff in April and July-September 2022 was obtained from each facility.

RESULTS

Facilities across Ukraine reported similar staff shortages in both April and August-September 2022, despite an increase in the number of hospitalizations in July 2022 and a similar percentage of hospitalizations related to war trauma (11.6% in July vs. 10.2% in April, Wilcoxon signed-rank test P = 0.10). Hospitalizations related to war trauma became more dispersed across the nation in July 2022, likely reflecting the return of internally and externally displaced persons to their original locations.

CONCLUSIONS

The mental health needs and services changed drastically in the first half-year of the Russian invasion of Ukraine, with those in need more dispersed across the country over time. International aid may need to be scaled up to stably provide mental healthcare, given the displacement of the mental healthcare workforce.

Mental health services in Ukraine during the early phases of the 2022 Russian invasion

BACKGROUND

In February 2022, Russia began its invasion of Ukraine. War increases the demand for mental healthcare among affected populations, but with devastating losses across the nation, it is unclear if Ukrainian mental health services are able to meet the needs of the people.

AIMS

We aimed to evaluate the state of Ukrainian in-patient mental health services, which remains the backbone of the nation's psychiatric services, early in the 2022 Russian invasion.

METHOD

We conducted a nationwide cross-sectional study on Ukrainian in-patient mental health facilities during the 2022 Russian invasion. Using an online questionnaire, we obtained responses from the heads of 32 in-patient mental health facilities across Ukraine, representing 52.5% of all in-patient mental health facilities in the nation. We gathered information on hospital admissions, staff, humanitarian aid received and the additional needs of each facility.

RESULTS

Hospital admissions were reduced by 23.5% during the war (April 2022) compared with before the war (January 2022). Across facilities, 9.6% of hospital admissions in April 2022 were related to war trauma, with facilities reporting percentages as high as 30.0%. Facilities reported reductions in staff, with 9.1% of total medical workers displaced and 0.5% injured across facilities. One facility reported that 45.6% of their total medical workers were injured. Although facilities across Ukraine have received humanitarian aid (such as medical supplies, food, volunteers), they reported additionally needing equipment as well as more staff.

CONCLUSIONS

The mental health service structure in Ukraine has been severely damaged during the 2022 invasion, with staff shortages despite a significant number of hospital admissions related to war trauma.

The global movement towards a public health approach to substance use disorders

Drug misuse is a global problem. Markets that supply illegal drugs often span international borders. However, each country has different primary drugs of use, populations that are using and consequences of use. The policy approach of each country to addressing substance use disorders can be characterized along a continuum between purely public health approaches and purely law enforcement approaches. Historically, a law enforcement approach has been the primary strategy in much of the world. However, there is a growing movement towards use of a public health approach. This article provides four case examples, Ukraine, Philippines, Nigeria and Peru, where there is movement to develop addiction public health infrastructure. The work varies by country, but includes regulatory changes, workforce development and resource allocation all of which are supported by the United Nations Office on Drugs and Crime (UNODC) and multi-national organizations that provide training and technical assistance, funded primarily by the European Union and United States governments. All four countries highlighted have barriers to moving towards a more public health approach which may include popularity of the law enforcement approach, turbulent government environments, and economics of being a drug producing nation. However, whether starting from the top down with changed policies, such as Ukraine or from the bottom up with training community members as in the Philippines, each country provides an example of how donor resources can be applied to make the transition towards a more humane and evidence-based approach to addressing substance use disorders.Key MessagesWhile the primary approach to addressing drug use has focussed resources on law enforcement for over 100 years, many countries are adopting elements of a public health approach including prevention and treatment of the harms of drug use including substance use disorders.There is a growing global movement to make policy towards drugs and drug users more humane and evidence-based.Donor nation resources can be applied in a variety of combinations to improve care and outcomes for people who use drugs in low- and middle-income countries.

Mental health services in Scandinavia and Eurasia: comparison of financing and provision

The aim of this study was to compare financial and human resources for mental health services in selected Scandinavian and Eurasian countries. A cross-sectional descriptive and analytical approach was adopted to analyse questionnaire data provided by members of the Ukraine-Norway-Armenia Partnership Project. We compared Scandinavia (Sweden and Norway) and Eurasia (Armenia, Georgia, Kyrgyzstan and Ukraine). Health expenditure in Eurasia was generally below 4% of gross domestic product, with the exception of Georgia (10.2%), compared with 11% in Scandinavia. Inpatient hospital care commonly exceeded 50% of the mental health budget. The central governments in Eurasia paid for over 50% of the health expenditure, compared to 2% in Scandinavia. The number of mental health personnel per head of population was much smaller in Eurasia than Scandinavia. Financial and human resources were limited in Eurasia and mainly concentrated on institutional services. Health activities were largely managed by central governments. Community-based mental healthcare was poorly implemented, compared to Scandinavia, especially for children and adolescents.

EMOTIONAL IMPACT OF THE COVID-19 PANDEMIC ON HEALTHCARE WORKERS IN UKRAINE

OBJECTIVE

The aim: To study the emotional impact of the COVID-19 pandemic on healthcare workers in Ukraine.

PATIENTS AND METHODS

Materials and methods: 1087 healthcare workers across all regions of Ukraine completed an online questionnaire. Respondents were divided into two groups: A - 863 (79.4%), В - 224 (20.6%), according to whether or not they experienced anxiety/fear related to COVID-19.

RESULTS

Results: Such factors as risk of contracting COVID-19, news of new cases, insufficient staff in healthcare facilities, risk of transmission of COVID-19 to family or friends, risk of death from COVID-19, the threat of the spread of the COVID-19 pandemic were associated with high level of anxiety/fear among healthcare workers. Factors that facilitate coping with stress included absence of Covid-19 cases among staff, recovering patients, availability of gear and protective equipment and absence of COVID-19 infected among loved ones, relieving stress (relaxation, going info sports and so on), communication with family and friends to relieve stress and get support, avoidance of COVID-19 media reports in particular on deaths connected cases, getting information about the spread of Covid-19 only from legitimate sources.

CONCLUSION

Conclusions: The data obtained in this study indicate an urgent need for the development and implementation of preventive and rehabilitation measures aimed at stabilizing the psycho-emotional state of health workers and improving the quality of care in the special conditions of the COVID-19 pandemic. Achieving these goals will be facilitated by taking into account the specifics of the response to COVID-19 and measures to reduce the effects of stress while enhancing the effects of stressors among health care workers.

Prognostic Assessment of Stress-Related Factors in Healthcare Workers During the COVID-19 Pandemic

INTRODUCTION

The COVID-19 pandemic is an extraordinary challenge for all countries and affects the psychological wellbeing of healthcare professionals working with people suffering from COVID-19 and puts them at a high risk of mental health problems. The aim of the study was to identify stress-related factors that affect the mental health of healthcare workers during the COVID-19 pandemic in Ukraine.

SUBJECTS AND METHODS

A total of 1098 Ukrainian healthcare workers were surveyed using an online questionnaire consisting of questions relating to a) socio-demographic characteristics; b) perceptions of the COVID-19 related situation; and c) stress and protective factors. Respondents were divided into two groups, depending on whether they provided care to the patients with COVID-19 or not.

RESULTS

Of the 1087 healthcare workers, 863 (79.4%) were found to have anxiety / fear caused by the COVID-19. No significant difference was detected between professionals who did and did not provide personal assistance to patients with COVID-19 concerning anxiety / fear related to COVID-19 (p=0.0776). Based on logistic regression model (χ²(6)=263.70, p=0.000) the most significant predictive factors for anxiety / fear caused by the COVID-19 were factors related to safety and risk perception (the risk of getting infected, dying, infecting loved ones, perception of the threat of the epidemic spread), information factors (constant news about COVID-19), as well as factors related to the organisation of care (lack of staff in health care facilities).

CONCLUSIONS

Negative risk perception, high consumption of COVID-19 news, and shortage of staff in health care facilities were significant predictors of anxiety / fear caused by the COVID-19.

Transitioning to community-based mental healthcare: reform experiences of five countries

Following the growing global focus on deinstitutionalisation in the past 50 years, accessible community mental health services was a highlighted commitment in the European Mental Health Action Plan 2013–2020 to improve well-being of patients and families. The progress of transition has been uneven in some Eastern European countries. This paper aims to update and reflect on the examples of five countries across the region.

The Implementation of the WHO Mental Health Gap Intervention Guide (mhGAP-IG) in Ukraine, Armenia, Georgia and Kyrgyz Republic

Despite the increasing burden of mental disorders, a lot of people worldwide suffer a gap in receiving necessary care in these countries. To close this gap, the WHO has developed mhGAP training modules aimed at scaling up mental health and substance use disorders services, especially in low- and middle-income countries. This article presents the experience of implementing the Mental Health Gap Action Programme (mhGAP) in Ukraine, Armenia, Georgia, and Kyrgyz Republic. Data were gathered from an electronic questionnaire administered to representatives from higher educational institutions where the Mental Health Gap Action Programme Intervention Guide (mhGAP-IG) was implemented in existing curricula for medical students, interns, and residents in family medicine and neurology, practicing physicians, and master's program in mental health students. More than 700 students went through the programs that provided the feedback. Evaluations of program effectiveness mainly involved standard discipline tests or pre- and post-tests proposed in the mhGAP trainer manual. This finding suggested that mhGAP-IG can be successfully adapted and implemented both on undergraduate and on postgraduate education levels and among medical and nonmedical specialists. Future evaluations need to more definitively assess the clinical effectiveness of mhGAP-IG implementation.

Helicobacter pylori infection downregulates the DNA glycosylase NEIL2, resulting in increased genome damage and inflammation in gastric epithelial cells

Infection with the Gram-negative, microaerophilic bacterium Helicobacter pylori induces an inflammatory response and oxidative DNA damage in gastric epithelial cells that can lead to gastric cancer (GC). However, the underlying pathogenic mechanism is largely unclear. Here, we report that the suppression of Nei-like DNA glycosylase 2 (NEIL2), a mammalian DNA glycosylase that specifically removes oxidized bases, is one mechanism through which H. pylori infection may fuel the accumulation of DNA damage leading to GC. Using cultured cell lines, gastric biopsy specimens, primary cells, and human enteroid-derived monolayers from healthy human stomach, we show that H. pylori infection greatly reduces NEIL2 expression. The H. pylori infection-induced downregulation of NEIL2 was specific, as Campylobacter jejuni had no such effect. Using gastric organoids isolated from the murine stomach in coculture experiments with live bacteria mimicking the infected stomach lining, we found that H. pylori infection is associated with the production of various inflammatory cytokines. This response was more pronounced in Neil2 knockout (KO) mouse cells than in WT cells, suggesting that NEIL2 suppresses inflammation under physiological conditions. Notably, the H. pylori-infected Neil2-KO murine stomach exhibited more DNA damage than the WT. Furthermore, H. pylori-infected Neil2-KO mice had greater inflammation and more epithelial cell damage. Computational analysis of gene expression profiles of DNA glycosylases in gastric specimens linked the reduced Neil2 level to GC progression. Our results suggest that NEIL2 downregulation is a plausible mechanism by which H. pylori infection impairs DNA damage repair, amplifies the inflammatory response, and initiates GC.

Mental Health Conditions and Co-morbidities Among Internally Displaced Populations (IDPs) in Ukraine

Reliable epidemiological data on the burden of mental health conditions and key risk factors is crucial in helping to design appropriate trauma-informed mental health and psychosocial support responses for the estimated 1.4 million IDPs in Ukraine. The aim of the proposed study is to collect evidence on mental health and psychosocial support needs among IDPs in order to help inform mental health policy in Ukraine.

The specific objectives were to:

– measure the prevalence of mental health conditions of post-traumatic stress disorder (PTSD), depression, anxiety, and their co-morbidity;

– examine the characteristics associated with the mental disorders (e.g. gender, age, trauma exposure, socio-economic stressors);

– draft evidence-based recommendations for mental health and psychosocial support to relevant governmental and professional bodies in Ukraine.

The study used a cross-sectional survey conducted throughout Ukraine in 2016 with 2203 IDPs aged 18 years and over. Descriptive and multivariate regression analyses were used. PTSD prevalence was 32% (22% men; 36% women), depression–22% (16% men; 25% women), and anxiety prevalence was 17% (13% men; 20% women). There were also high levels of co-morbidity between PTSD, anxiety and depression. Key factors statistically significantly associated with mental disorders included female gender, older age, cumulative trauma exposure, more recent displacement and a bad household economic situation. The findings provided sufficient evidence to draft the trauma-informed mental health policy recommendations to key policy-makers in Ukraine.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Reforming Undergraduate Psychiatry Training in Ukraine

In Ukraine, mental health problems are common yet the mental health services available are still old fashioned and based on healthcare approaches used in the Soviet Union, providing mainly inpatient services and rudimentary community services. The World Health Organization (WHO) introduced the Mental Health Gap Action Programme (mhGAP) to reduce the mental health treatment gap all over the world and 2 years later introduced the WHO mhGAP-Intervention Guide (mhGAP-IG), version 2.0 (2016) as not only an educational tool, but also an evidence based guideline to scale up services for mental, neurological and substance use (MNS) conditions with an objective to reduce gap between available health systems capacity and resources for mental health. The main aim of this paper is to describe reforms of undergraduate psychiatry training in Ukraine using Kyiv Medical University as a case example. Kyiv Medical University (KMU) is the first university in Ukraine to introduce the mhGAP-IG in Ukraine. The revised psychiatry curricula in KMU aims to strengthens the evidence based teaching practices, to put emphasis on community orientated mental health care, and to use interactive teaching methods that the university hopes will attract more future doctors to psychiatry and ideally contribute towards the reduction of the mental health treatment-gap in Ukraine.

The cardiovascular benefits of indiscriminate supplementation of omega-3 fatty acids; meta-analysis and decision-making approach

AIM

The meta-analysis was conducted to estimate of the cardiovascular benefits of indiscriminate supplementation of omega-3 capsules. The results, expressed in terms of quality adjusted life years (QALY) intuitively understood by the general public, can be the basis for the (personal) decision on whether to take omega-3 supplements.

METHODS

The results of meta-analysis of eight double-blind, placebo-controlled clinical trials are expressed in terms of QALY, using the Markov model and Monte Carlo simulations.

RESULTS

Omega-3 supplementation results in a 8% decrease of the risk of cardiac death, unless the patients are treated by statins. Results indicate that omega-3 supplementation may prolong QALY by about a month. Old people gain less, whereas DM-2 patients and people with history of CV events gain more.

DISCUSSION

Our analysis yielded an algorithm for estimating benefit from omega-3 supplementation, based on the age and the individual risk of CV events of the patient.

Regulation of B7-H1 (PD-L1) expression by gastric epithelial cells and development of Treg cells during Helicobacter pylori infection (HUM8P.328)

Helicobacter pylori (H. pylori) infects &gt;50% of the world’s population and is linked to peptic ulcers and gastric cancer. We have previously shown that H. pylori upregulates B7-H1 expression on GEC, which, in turn, suppress T cell proliferation and induction of Treg cells in vitro, but the mechanism was unknown. Herein, we investigated the underlying mechanisms behind H. pylori-mediated upregulation of B7-H1 expression by GEC and its functional relevance to chronic infection. Using H. pylori wild type and isogenic mutant strains we showed that H. pylori requires its type 4 secretion system (T4SS) component cytotoxin associated gene A (CagA) and peptidoglycan for B7-H1 upregulation in GEC. In vivo confirmation was obtained when infection of C57BL/6 mice with H. pylori PMSS1 strain, containing a functional T4SS, but not with H. pylori SS1 strain lacking this delivery system, led to upregulation of B7-H1 expression, increased bacterial load, induction of Treg cell in the stomach and increased IL-10 in the serum. Interestingly, B7-H1 knock out mice showed less Treg cells and reduced bacterial loads. We also showed that H. pylori uses p38 MAPK pathway to upregulate B7-H1 expression in GEC. Our observations suggest that H. pylori T4SS contributes to the ability to evade immune-mediated clearance by modulating expression of B7-H1 in GEC. These observations may have important implications in vaccine efforts directed at H. pylori.

Evaluation of antioxidants: scope, limitations and relevance of assays

Peroxidation of lipids, particularly polyunsaturated fatty acid residues (PUFA) of phospholipids and cholesterol esters, is a process of marked implications: it shortens the shelf-life of food and drugs, it causes fragmentation of DNA, it damages cellular membranes and it promotes the genesis of many human diseases. Much effort is therefore devoted to a search for "potent antioxidants", both synthetic and from natural sources, mostly plants. This, in turn, requires a reliable, simple, preferably high throughput assay of the activity of alleged antioxidants. The most commonly used assays are based on measurements of the total antioxidant capacity (TAC) of a solution, as evaluated either by determining the rate of oxidation of the antioxidant or by measuring the protection of an easily determined indicator against oxidation by the antioxidants. The commonly used assays utilized for ranking antioxidants share three common problems: (i) They usually evaluate the effects of those antioxidants that quench free radicals, which constitute only a part of the body's antioxidative network, in which enzymes play the central role. (ii) Both the capacity and potency of antioxidants, as obtained by various methods, do not necessarily correlate with each other. (iii) Most estimates are based on methods conducted in solution and are therefore not necessarily relevant to processes that occur at the lipid-water interfaces in both membranes and micro emulsions (e.g. lipoproteins). Given this "state of art", many researchers, including us, try to develop a method based on the formation of hydroperoxides (LOOH) upon peroxidation of PUFA in lipoproteins or in model membranes, such as liposomes. In these systems, as well as in lipoproteins, the most apparent effect of antioxidants is prolongation of the lag time preceding the propagation of a free radical chain reaction. In fact, under certain conditions both water soluble antioxidants (e.g. vitamin C and urate) and the lipid soluble antioxidant tocopherol (vitamin E), promote or even induce peroxidation. Based on the published data, including our results, we conclude that terms such as 'antioxidative capacity' or 'antioxidative potency' are context-dependent. Furthermore, criteria of the efficacy of antioxidants based on oxidation in solution are not necessarily relevant to the effects of antioxidants on peroxidation in biological systems or model lipid assemblies, because the latter processes occur at water/lipid interfaces. We think that evaluation of antioxidants requires kinetic studies of the biomarker used and that the most relevant characteristic of 'oxidative stress' in the biological context is the kinetics of ex vivo peroxidation of lipids. We therefore propose studying the kinetics of lipid-peroxidation in the absence of the studied antioxidant and in its presence at different antioxidant concentrations. These protocols mean that antioxidants are assayed by methods commonly used to evaluate oxidative stress. The advantage of such evaluation is that it enables quantization of the antioxidants' efficacy in a model of relevance to biological systems. In view of the sensitivity of the lag time preceding peroxidation, we propose studying how much antioxidant is required to double the lag observed prior to rapid peroxidation. The latter quantity (C(2lag)) can be used to express the strength of antioxidants in the relevant system (e.g. LDL, serum or liposomes).

Host S-nitrosylation inhibits clostridial small molecule-activated glucosylating toxins

The global prevalence of severe Clostridium difficile infection highlights the profound clinical significance of clostridial glucosylating toxins. Virulence is dependent on the autoactivation of a toxin cysteine protease, which is promoted by the allosteric cofactor inositol hexakisphosphate (InsP(6)). Host mechanisms that protect against such exotoxins are poorly understood. It is increasingly appreciated that the pleiotropic functions attributed to nitric oxide (NO), including host immunity, are in large part mediated by S-nitrosylation of proteins. Here we show that C. difficile toxins are S-nitrosylated by the infected host and that S-nitrosylation attenuates virulence by inhibiting toxin self-cleavage and cell entry. Notably, InsP(6)- and inositol pyrophosphate (InsP(7))-induced conformational changes in the toxin enabled host S-nitrosothiols to transnitrosylate the toxin catalytic cysteine, which forms part of a structurally conserved nitrosylation motif. Moreover, treatment with exogenous InsP(6) enhanced the therapeutic actions of oral S-nitrosothiols in mouse models of C. difficile infection. Allostery in bacterial proteins has thus been successfully exploited in the evolutionary development of nitrosothiol-based innate immunity and may provide an avenue to new therapeutic approaches.

Copper-induced peroxidation of phosphatidylserine-containing liposomes is inhibited by nanomolar concentrations of specific antioxidants

Copper-induced peroxidation of liposomal palmitoyllinoleoyl-phosphatidylcholine (PLPC) is inhibited by alpha-tocopherol at micromolar concentrations. In our previous study we found that when the liposomes contain phosphatidylserine (PS), nanomolar concentrations of Toc were sufficient to inhibit peroxidation. In an attempt to gain understanding of the origin of this extreme antioxidative potency, we tested the antioxidative potency of 36 additional antioxidants and the dependence of their potency on the presence of PS in the liposomes. The results of these studies reveal that only 11 of the tested antioxidants possess similar antioxidative potency to that of Toc. These include trolox, butylated hydroxytoluene (BHT), curcumin, nordihydroguaiaretic acid (NDGA), diethylstilbestrol (DES), 2 of the 13 tested flavonoids (luteolin and 7,3',4'-trihydroxyflavone; T-414), alpha-naphthol, 1,5-, 1,6- and 1,7-dihydroxynaphthalenes (DHNs). Propyl gallate (PG), methyl syringate, rosmarinic acid, resveratrol, other flavonoids, as well as beta-naphthol, 1,2-, 1,3-, 1,4-, 2,3-, 2,6-, and 2,7-DHNs were either moderately antioxidative or pro-oxidative. For liposomes made of PLPC (250 microM) and PS (25 microM) the "lag" preceding copper-induced peroxidation (5 microM copper) was doubled upon addition of 30-130nM of the "super-active" antioxidants. We propose that the mechanism responsible for the extreme antioxidative potency against copper-induced peroxidation in PS-containing liposomes involves replenishment of the antioxidant in a ternary PS-copper-antioxidant complex. Based on structure-activity relationship of the 37 tested antioxidants, the "super-antioxidative potency" is attributed to the recycling of relatively stable semiquinone or semiquinone-like radicals.

Oxidation of liposomal cholesterol and its effect on phospholipid peroxidation

Lipid peroxidation is believed to play an important role in the pathogenesis of many diseases. Much research has therefore been devoted to peroxidation of different lipids in biomembranes and in model systems (liposomes) of different compositions. Yet, in spite of the relative simplicity of the liposomes, the existing literature is insufficient to reach definite conclusions regarding basic questions including the susceptibility of cholesterol to oxidation, its effect on the peroxidation of polyunsaturated phospholipids such as palmitoyllinoleoylphosphatidylcholine (PLPC) and how cholesterol influences the effect of water-soluble antioxidants such as urate on the peroxidation. The aim of the present study was to clarify these issues. Its major findings are that: (i) AAPH-induced peroxidation of cholesterol is slow and independent of the peroxidation of PLPC. In turn, AAPH-induced peroxidation of PLPC is not affected by cholesterol, independent of the presence of urate in the system. (ii) Cholesterol is not susceptible to copper-induced oxidation, but its inclusion in PLPC liposomes affects the peroxidation of PLPC, slowing down the initial stage of oxidation but promoting later stages. (iii) Addition of urate accelerates copper-induced peroxidation of PLPC in the absence of cholesterol, whereas in cholesterol-containing liposomes it inhibits PLPC oxidation. We attribute the complexity of the observed kinetics to the known cholesterol-induced rigidization of liquid crystalline bilayers.

Acute myocardial infarction is associated with increased susceptibility of serum lipids to copper-induced peroxidation in vitro

BACKGROUND

Low-density lipoprotein (LDL) oxidation in the arterial intima plays a pivotal role in atherogenesis. Under physiologic conditions, several mechanisms protect LDL against oxidation, including hydrolysis of oxidation products by high-density lipoprotein (HDL)-associated enzymes. Some of these protective mechanisms are less effective under acute phase conditions.

HYPOTHESIS

Conditions of acute phase response, including acute myocardial infarction (MI), may be expected to result in increased susceptibility of serum lipids to oxidation. The present study was undertaken to test this possibility.

METHODS

Using our previously developed spectroscopic method, we have monitored prospectively the kinetics of copper-induced oxidation of serum lipids obtained from 15 men during and after acute MI. This was tested within 6 h from the onset of chest pain, on Days 1, 3, and 7 of infarction and 1 year after recovery.

RESULTS

The lag phase preceding oxidation of serum lipids was much shorter during the first week after MI when compared with values obtained after recovery (52-59 vs. 107 min, respectively, p <0.001). During the first week after MI, we observed no significant correlations between kinetic parameters and serum lipid composition, in contrast both to the correlations previously reported for hyperlipidemic patients and to the similar correlations observed in the present study after recovery.

CONCLUSIONS

Acute MI is associated with an increased susceptibility of serum lipids to oxidation in vitro. This propensity for oxidation may reflect enhanced in vivo formation of free radicals and/or reduced efficiency of defense mechanisms. Both these possibilities may carry detrimental effects on the course, complications, and prognosis of the patients after acute MI.

Effect of a Short-Term Graded Exhaustive Exercise on the Susceptibility of Serum Lipids to Oxidation

The objective of our study was to evaluate the effect of short-term intensive exercise on the susceptibility of serum lipids to ex-vivo peroxidation. We assessed the association between aerobic capacity, serum composition, and serum lipid oxidizability as well as the association between aerobic capacity and the effect of short-term maximal exercise on the kinetics of ex-vivo copper-induced peroxidation of serum lipids. The study involved 30 healthy male volunteers (age 22-39 years, BMI 19.4-29.8). Following 12-hr fasting, blood was withdrawn for determination of blood lipids, LDL, HDL, and TG, and Vitamin E, and for oxidizability assay of the serum lipids. Subsequently, each volunteer underwent an incremental all-out cardiopulmonary exercise stress test (CPET), performed on a motor-driven treadmill (Quinton Q65, USA). The test protocol was a modified Balke protocol. The results of this test were expressed in terms of mass-dependent maximal oxygen uptake (VO2max, ml.kg(-1).min (-1)) and of ventilatory anaerobic threshold (VAT, ml.kg(-1).min(-1)). Immediately after exercise, blood was re-drawn for the determination of serum Vitamin E and for ex-vivo oxidizibility assay, expressed in terms of maximal absorption of oxidation products (OD(max), absorbance units), maximal rate of their production (V(max), OD min(-1)) and the time at which the rate was maximal (t(max), min). Maximal graded exercise had no significant effect on the susceptibility of serum lipids to peroxidation as measured by OD(max) (p = 0.38 at 245 nm, and 0.27 at 268 nm),V(max) (p = 0.34 at 245 nm, and 0.49 at 268 nm) and t(max) (p = 0.17 at 245 nm, and 0.07 at 268 nm). Also no effect was found on the concentration of serum Vitamin E (p = 0.39). Aerobic capacity was not associated either with the susceptibility of serum lipids to ex-vivo peroxidation or with serum Vitamin E concentration. The present findings indicate that a short graded maximal exercise, lasting 8-12 min, is not sufficient to increase the susceptibility of the serum lipids to peroxidation. Thus it may be assumed that the antioxidant capacity of most healthy subjects provides proper protection from a short exhaustive exercise challenge. Also, aerobic capacity in the range represented by our subjects does not seem to influence the susceptibility of serum lipids to peroxidation.

A CD8+ T cell heptaepitope minigene vaccine induces protective immunity against Chlamydia pneumoniae

An intact T cell compartment and IFN-gamma signaling are required for protective immunity against Chlamydia. In the mouse model of Chlamydia pneumoniae (Cpn) infection, this immunity is critically dependent on CD8(+) T cells. Recently we reported that Cpn-infected mice generate an MHC class I-restricted CD8(+) Tc1 response against various Cpn Ags, and that CD8(+) CTL to multiple epitopes inhibit Cpn growth in vitro. Here, we engineered a DNA minigene encoding seven H-2(b)-restricted Cpn CTL epitopes, the universal pan-DR epitope Th epitope, and an endoplasmic reticulum-translocating signal sequence. Immunization of C57BL/6 mice with this construct primed IFN-gamma-producing CD8(+) CTL against all seven CTL epitopes. CD8(+) T cell lines generated to minigene-encoded CTL epitopes secreted IFN-gamma and TNF-alpha and exhibited CTL activity upon recognition of Cpn-infected macrophages. Following intranasal challenge with Cpn, a 3.6 log reduction in mean lung bacterial numbers compared with control animals was obtained. Using a 20-fold increase in the Cpn challenging dose, minigene-vaccinated mice had a 60-fold reduction in lung bacterial loads, compared with controls. Immunization and challenge studies with beta(2)-microglobulin(-/-) mice indicated that the reduction of lung Cpn burdens was mediated by the MHC class I-dependent CD8(+) T cells to minigene-included Cpn CTL epitopes, rather than by pan-DR epitope-specific CD4(+) T cells. This constitutes the first demonstration of significant protection achieved by immunization with a CD8(+) T cell epitope-based DNA construct in a bacterial system and provides the basis for the optimal design of multicomponent anti-Cpn vaccines for humans.

Lipid peroxidation cannot be used as a universal criterion of oxidative stress

Oxidative stress is a term used to denote the imbalance between the concentrations of reactive oxygen and nitrogen species and the defense mechanisms of the body. Although it is generally accepted that such an imbalance plays a pivotal role in many pathologies, the term "oxidative stress" remains ill defined. In an attempt to evaluate the relationship between various assays of oxidative stress, we have analyzed the correlations between the results reported in those publications in which "oxidative stress" has been assayed by at least two methods. We found good correlations between the concentrations of several peroxidation products, including malondialdehyde, F2-Isoprostanes, lipid hydroperoxides, conjugated dienes, glutathione and protein carbonyls, but not with other criteria of "individual oxidative status" such as the concentration of antioxidants and products of DNA fragmentation (the "comet" assay). In light of these findings, we divide the assays used for evaluation of "oxidative stress" into the following three categories: (i) assays based on measuring the concentrations of oxidation products of lipids, proteins and DNA, as well as the concentrations of antioxidants, (ii) assays used to evaluate the oxidative and reductive capacity of biological fluids and (iii) assays used to evaluate the ex vivo susceptibility of lipids to oxidation upon their exposure to a source of free radicals. Our analyses demonstrate that oxidative stress cannot be defined in universal terms. Two results are of special interest:1.the commonly used criteria based on lipid peroxidation can not be regarded as a general estimate of the individual "oxidative status".2.the levels of antioxidants exhibit a non-monotonic relation with other criteria for oxidative stress. Further research is required to evaluate the significance of the latter finding.

Bacillus clausii probiotic strains: antimicrobial and immunomodulatory activities

The clinical benefits observed with probiotic use are mainly attributed to the antimicrobial substances produced by probiotic strains and to their immunomodulatory effects. Currently, the best-documented probiotic bacteria used in human therapy are lactic acid bacteria. In contrast, studies aiming to characterize the mechanisms responsible for the probiotic beneficial effects of Bacillus are rare. The current work seeks to contribute to such characterization by evaluating the antimicrobial and immunomodulatory activities of probiotic B. clausii strains. B. clausii strains release antimicrobial substances in the medium. Moreover, the release of these antimicrobial substances was observed during stationary growth phase and coincided with sporulation. These substances were active against Gram-positive bacteria, in particular against Staphylococcus aureus, Enterococcus faecium, and Clostridium difficile. The antimicrobial activity was resistant to subtilisin, proteinase K, and chymotrypsin treatment, whereas it was sensitive to pronase treatment. The evaluation of the immunomodulatory properties of probiotic B. clausii strains was performed in vitro on Swiss and C57 Bl/6j murine cells. The authors demonstrate that these strains, in their vegetative forms, are able to induce NOS II synthetase activity, IFN-gamma production, and CD4 T-cell proliferation.

Kinetics of lipid peroxidation in mixtures of HDL and LDL, mutual effects

In view of the proposed central role of LDL oxidation in atherogenesis and the established role of HDL in reducing the risk of atherosclerosis, several studies were undertaken to investigate the possible effect of HDL on LDL peroxidation. Since these investigations yielded contradictory results, we have conducted systematic kinetic studies on the oxidation in mixtures of HDL and LDL induced by different concentrations of copper, 2, 2'-azo bis (2-amidinopropane) hydrochloride (AAPH) and myeloperoxidase (MPO). These studies revealed that oxidation of LDL induced either by AAPH or MPO is inhibited by HDL under all the studied conditions, whereas copper-induced oxidation of LDL is inhibited by HDL at low copper/lipoprotein ratio but accelerated by HDL at high copper/lipoprotein ratio. The antioxidative effects of HDL are only partially due to HDL-associated enzymes, as indicated by the finding that reconstituted HDL, containing no such enzymes, inhibits peroxidation induced by low copper concentration. Reduction of the binding of copper to LDL by competitive binding to the HDL also contributes to the antioxidative effect of HDL. The acceleration of copper-induced oxidation of LDL by HDL may be attributed to the hydroperoxides formed in the "more oxidizable" HDL, which migrate to the "less oxidizable" LDL and enhance the oxidation of the LDL lipids induced by bound copper. This hypothesis is supported by the results of experiments in which native LDL was added to oxidizing lipoprotein at different time points. When the native LDL was added prior to decomposition of the hydroperoxides in the oxidizing lipoprotein, the lag preceding oxidation of the LDL was much shorter than the lag observed when the native LDL was added at latter stages, after the level of hydroperoxides became reduced due to their copper-catalyzed decomposition. The observed dependence of the interrelationship between the oxidation of HDL and LDL on the oxidative stress should be considered in future investigations regarding the oxidation of lipoprotein mixtures.

The dose-dependent effect of copper-chelating agents on the kinetics of peroxidation of low-density lipoprotein (LDL)

Copper-induced peroxidation of lipoproteins involves continuous production of free radicals via a redox cycle of copper. Formation of Cu(I) during Cu(II)-induced peroxidation of LDL was previously demonstrated by accumulation of the colored complexes of Cu(I) in the presence of one of the Cu(I)-specific chelators bathocuproine (BC) or neocuproine (NC). All the studies conducted thus far employed high concentrations of these chelators (chelator/Cu(II) > 10). Under these conditions, at low copper concentrations the chelators prolonged the lag preceding oxidation, whereas at high copper concentrations the chelators shortened the lag. In an attempt to gain understanding of these non-monotonic effects, we have studied systematically the peroxidation of LDL (0.1 microM, 50 microg protein/mL) at varying concentrations of NC or BC over a wide range of concentrations of the chelators and copper. These studies revealed that: (i) At copper concentrations of 5 microM and below, NC prolonged the lag in a monotonic, dose-dependent fashion typical for other complexing agents. However, unlike with other chelators, the maximal rate of oxidation was only slightly reduced (if at all). (ii) At copper concentrations of 15 microM and above, the addition of about 20 microM NC or BC resulted in prolongation of the lag, but this effect became smaller at higher concentrations of the chelators, and at yet higher concentrations the lag became much shorter than that observed in the absence of chelators. Throughout the whole range of NC concentrations, the maximal rate of peroxidation increased monotonically upon increasing the NC concentration. (iii) Unlike in the absence of chelators, the prooxidative effect of copper did not exhibit saturation with respect to copper, up to copper concentrations of 30 microM. Based on these results we conclude that the copper-chelates can partition into the hydrophobic core of LDL particles and induce peroxidation by forming free radicals within the core. This may be significant with respect to the understanding of the possible mechanisms of peroxidation by chelated transition metals in vivo.

Kinetic analysis of copper-induced peroxidation of HDL, autoaccelerated and tocopherol-mediated peroxidation

Comparison of the kinetic profiles of copper-induced peroxidation of HDL and LDL at different copper concentrations reveals that under all the studied experimental conditions HDL is more susceptible to oxidation than LDL. The mechanism responsible for HDL oxidation is a complex function of the copper/HDL ratio and of the tocopherol content of the HDL. At high copper concentrations, the kinetic profiles were similar to those observed for LDL oxidation, namely, relatively rapid accumulation of oxidation products, via an autoaccelerated, noninhibited mechanism, was preceded by an initial "lag phase." Under these conditions, the maximal peroxidation rate (V(max)) of HDL and LDL depended similarly on the molar ratio of bound copper/lipoprotein. Analysis of this dependency in terms of the binding characteristics of copper to lipoprotein, yielded similar dissociation constant (K = 10(-6) M) but different maximal binding capacities for the two lipoproteins (8 Cu(+2)/HDL as compared to 17 Cu(+2)/LDL). Given the size difference between HDL and LDL, these results imply that the maximal surface density of bound copper is at least 2-fold higher for HDL than for LDL. This difference may be responsible for the higher susceptibility of HDL to copper-induced oxidation in the presence of high copper concentrations. At relatively low copper concentrations, the kinetic profile of HDL oxidation was biphasic, similar to but more pronounced than the biphasic kinetics observed for the oxidation of LDL lipids at the same concentration of copper. Our results are consistent with the hypothesis that the first phase of rapid oxidation occurs via a tocopherol-mediated-peroxidation (TMP) mechanism. Accordingly, enrichment of HDL with tocopherol resulted in enhanced accumulation of hydroperoxides during the first phase of copper-induced oxidation. Notably, the maximal accumulation during the first phase decreased upon increasing the ratio of bound copper/HDL. This behavior can be predicted theoretically for peroxidation via a TMP mechanism, in opposition to autoaccelerated peroxidation. The possible pathophysiological significance of these findings is discussed.

Interaction of hyaluronic acid-linked phosphatidylethanolamine (HyPE) with LDL and its effect on the susceptibility of LDL lipids to oxidation

The amphiphilic polysaccharide hyaluronic acid-linked phosphatidylethanolamine (HyPE), synthesized by covalently binding dipalmitoyl-phosphatidylethanolamine (DPPE) to short chain hyaluronic acid (mol. wt. approximately = 30 000), interacts with low-density lipoproteins (LDL), to form a 'sugar-decoration' of the LDL surface. This results in an increase in the apparent size of the LDL particles, as studied by photon correlation spectroscopy, and in broadening of the 1H NMR signals of the LDL's phospholipids. Experiments conducted with fluorescently-labeled HyPE indicate that the interaction of HyPE with LDL involves incorporation of the hydrocarbon chains of this amphiphilic polysaccharide into the outer monolayer of the LDL. This interaction also inhibits the copper-induced oxidation of the LDL polyunsaturated fatty acids, avoiding oxidation altogether when the concentration of HyPE is higher than a tenth of the concentration of the LDL's phospholipids. This can not be attributed to competitive binding of copper by HyPE. We propose that the protection of LDL lipids against copper-induced oxidation is due to formation of a sugar network around the LDL.

Copper-induced LDL peroxidation: interrelated dependencies of the kinetics on the concentrations of copper, hydroperoxides and tocopherol

Excessive uptake of oxidized low density lipoprotein plays a role in the onset of atherosclerosis. Lipid-associated antioxidants, the most abundant of which is tocopherol (vitamin E), are therefore believed to have anti-atherogenic properties. By contrast, hydroperoxides enhance the peroxidation of low density lipoprotein. We demonstrate that none of these compounds markedly affect the maximal rate of oxidation of low density lipoprotein, whereas the lag preceding rapid oxidation is prolonged by tocopherol but shortened by hydroperoxides. The corresponding 'prolongation' and 'shortening' can be compensated by each other in low density lipoprotein preparations enriched with both these compounds. The dependence of the balance between the effects of tocopherol and hydroperoxides on the copper concentration indicates that the antioxidative effect of vitamin E increases with the oxidative stress.

Susceptibility of serum lipids to copper-induced peroxidation correlates with the level of high density lipoprotein cholesterol

As a first step in evaluating the significance of our recently developed method of monitoring the kinetics of copper-induced oxidation in unfractionated serum, we recorded the kinetics of lipid oxidation in the sera of 62 hyperlipidemic patients and analyzed the correlation between oxidation and lipid composition of the sera [high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, and triglycerides]. We used six factors to characterize the kinetics of oxidation, namely, the maximal absorbance of oxidation products (ODmax), the maximal rate of their production (Vmax), and the time at which the rate was maximal (t(max)) at two wavelengths (245 nm, where 7-ketocholesterol and conjugated dienic hydroperoxides absorb intensely, and 268 nm, where the absorbance is mostly due to dienals). The major conclusions of our analyses are that: (i) Both ODmax and Vmax correlate positively with the sum of concentrations of the major oxidizable lipids, cholesterol, and cholesteryl esters. (ii). The value of t(max), which is a measure of the lag preceding oxidation and therefore reflects the resistance of the serum lipids to copper-induced oxidation, exhibits a negative correlation with HDL cholesterol. Although this finding accords with the observation of shorter lags for HDL than for LDL, it is apparently inconsistent with the role of HDL as an antirisk factor in coronary heart diseases.

LDL-associated phospholipase A does not protect LDL against lipid peroxidation in vitro

The irreversible proteinase inhibitor Pefabloc (4-[2-aminoethyl] benzenesulfonyl fluoride) inactivates LDL-catalyzed hydrolysis of the short-chain fluorescent phospholipid C6-NBD-PC (1-acyl-2-(N-4-nitrobenzo-2-oxa-1,3-diazole)-aminocaproyl phosphatidylcholine). The dose-dependence of this inactivation is similar to that obtained previously for the inhibitory effect of Pefabloc on the hydrolysis of platelet activating factor (PAF) by the LDL-associated PAF acetylhydrolase (PAF-AH), in agreement with the notion that the hydrolysis of C6-NBD-PC and PAF is catalyzed by the same enzyme (LDL-associated phospholipase A; LDL-PLA). This conclusion is also supported by the finding that hydrolysis of C6-NBD-PC by LDL becomes inactivated by LDL oxidation only at late stages of the oxidation, similar to the effect of oxidation on the hydrolysis of PAF by the LDL-associated PAF-AH. Under conditions of complete inactivation of this enzyme towards C6-NBD-PC, the kinetics of lipid peroxidation, induced either by copper ions or by the free radical generator AAPH at varying doses of the prooxidant, was similar to that observed when the PLA was active (i.e., in the absence of Pefabloc). Hence, LDL-associated PLA (PAF-AH) does not protect LDL lipids from peroxidation. Similar results were obtained with fractionated LDL in albumin-containing buffer and for non-fractionated serum, in which copper-induced peroxidation was also not influenced by inactivation of the enzyme responsible for hydrolysis of C6-NBD-PC. Phospholipolysis of short chain phospholipids by LDL-PLA may still play a protective role against the toxic effects of oxidized phospholipids by reducing their internalization into cells (Schmitt et al. 1995).

Lipid oxidation in unfractionated serum and plasma

In an attempt to develop an assay for the susceptibility of plasma lipids to oxidation, we have studied the kinetics of copper-induced oxidation in diluted serum and plasma prepared with different anticoagulants (heparin, citrate and EDTA) by monitoring the absorbance of oxidation-products at several wavelengths. These studies revealed the complex and interrelated effects of the water-soluble antioxidant ascorbic acid, citrate and chloride ions on the kinetics of copper-induced oxidation of plasma lipids. Specifically, the onset of oxidation induced by copper-citrate chelates is only slightly affected by chloride ions and is accelerated upon increasing the copper concentration. By contrast, in the absence of citrate, the lag preceding oxidation in diluted serum or plasma (but not the maximal rate of oxidation) depends markedly on the chloride concentration in the diluting medium. In the absence of Cl-, the lag preceding oxidation is a decreasing saturable function of copper concentration, whereas in a normal phosphate-buffered saline solution (PBS), the lag shows a biphasic dependence on copper concentration such that at copper concentrations above 10-30 microM (depending on the extent of plasma dilution), increasing the concentration of copper results in prolongation of the lag. This dependence of copper-induced oxidation on the concentration of copper is not observed for dialyzed serum unless ascorbic acid is added. Our interpretation of these results is that water-soluble reductants and chloride ions act synergistically to stabilize Cu+, on the expense of Cu2+. Quenching of free radicals by Cu+ may be responsible for the prolongation of the lag at high copper concentrations, with no reduction of the maximal rate of oxidation. In spite of the complex dependencies described above, spectrophotometric monitoring of the kinetics of oxidation of plasma lipids, under 'optimized conditions' (50-fold diluted serum, in PBS containing 720 microM sodium citrate and 100 microM copper), agrees with independent measurements of the consumption of polyunsaturated fatty acids. Hence, the spectroscopic method may become useful for evaluation of the susceptibility of plasma lipids to oxidation. This possibility, however, has yet to be elucidated through investigations of the correlation between the susceptibility of serum lipids to copper-induced oxidation in vitro and clinical factors of significance.

Kinetic analysis of copper-induced peroxidation of LDL

We have employed our recently developed spectroscopic method of continuous monitoring of lipid oxidation to study the formation and decomposition of hydroperoxides in the time course of LDL oxidation. The results show satisfactory agreement with simulated time courses based on the following assumptions: (a) Both the rates of formation and decomposition of hydroperoxides depend on the ratio of bound copper to LDL as computed under the assumption that each LDL particle has 17 equivalent copper binding sites characterized by a dissociation constant K = 1 microM. (b) Peroxidation is initiated by copper-catalyzed decomposition of hydroperoxides (LOOH) into peroxy radicals (LOO.) and other products, including dienals. Under these assumptions, the rate of accumulation of LOOH can be computed from the equation (equation in text). The agreement between the simulated and experimentally-observed kinetics supports the assumptions used for simulations. The close agreement between the values of lipid oxidizability (kp/square root 2kt) obtained for LDL (0.035 (Ms)[-1/2]) and previously published data on the oxidizability of linoleates (0.02-0.11 (Ms)[-1/2]) lends further support for these assumptions.

The effect of albumin on copper-induced LDL oxidation

In an attempt to gain deeper understanding of the mechanism or mechanisms responsible for the protective effect of serum albumin against Cu(2+)-induced peroxidation of low density lipoprotein (LDL), we have examined the influence of the concentrations of bovine serum albumin (BSA), Cu2+ and LDL on the kinetics of peroxidation. Since the common method of monitoring the oxidation by continuous recording of the absorbance of conjugated dienes at 234 nm cannot be used at high BSA-concentrations because of the intensive absorption of BSA, we have monitored the time-dependent increase of absorbance at 245 nm. At this wavelength, conjugated dienes absorb intensely, whereas the background absorbance of BSA is low. Using this method, as well as the TBARS assay for determination of malondialdehyde, over a large range of BSA concentrations, we show that in many cases the influence of BSA on the kinetics of oxidation can be compensated for by increasing the concentration of copper. This reconciles the apparent contradiction between previously published data. Detailed studies of the kinetic profiles obtained under different conditions indicate that binding of Cu2+ to albumin plays the major role in its protective effect while other mechanisms contribute much less than copper binding. This conclusion is consistent with the less pronounced effect of BSA on the oxidation induced by the free radical generator AAPH. It is also shown that the copper-albumin complex is capable of inducing LDL oxidation, although the kinetics of the latter process is very different from that of copper-induced oxidation. Nevertheless, when compared to copper induced oxidation at similar concentration of the oxidation-promotor, the kinetics of oxidation induced by copper-albumin complex is very different and is consistent with a tocopherol mediated peroxidation, characteristic under low radical flux. Similar kinetics was observed for copper-induced oxidation only at much lower copper concentrations.

Continuous monitoring of intermediates and final products of oxidation of low density lipoprotein by means of UV-spectroscopy

The most widely used routine technique for determination of LDL 'oxidizability' is the continuous monitoring of the absorption at 234 nm in the UV spectrum of LDL, following the addition of an oxidation promotor such as copper ions. This absorption is commonly attributed to the conjugated dienes formed upon oxidation as the major intermediate, namely the hydroperoxides of polyunsaturated fatty acids, mostly linoleate hydroperoxides. These, however, are not the only products of oxidation that absorb light at 234 nm. Other products, particularly 7-ketocholesterol, also absorb light at the same wavelength. Furthermore, enals and dienals also absorb in the wavelength range of 210-300 nm. The aim of the present work was to develop a simple spectroscopic method for more detailed investigation of the kinetics of lipoprotein oxidation. The method is based on continuous measurement of the UV spectrum in the wavelength range of 210-300 nm and subsequent decomposition of the spectra into four absorption bands due to hydroperoxides, 7-ketocholesterol, dienals and enals. The sixth derivatives of the spectra, recorded during the first seven hours of copper-induced oxidation of LDL were used to monitor the growth and subsequent decay of the hydroperoxides. The resultant time course, in conjunction with difference spectra obtained after the concentration of these intermediates decay to zero, enabled us to determine the spectra of the other oxidation products and, by that, to evaluate their time dependencies. Based on these results, we present a series of four simple equations that can be used to evaluate the concentrations of the individual products of LDL oxidation from UV absorption measurements of the mixtures ar merely four different wavelengths. The resultant time dependencies of the accumulation of four major products of lipid oxidation are consistent with published data obtained through separation and chemical analysis. This simple method can be used for more meaningful routine kinetic measurements of lipids oxidation.

Copper-induced lipid oxidation in unfractionated plasma: the lag preceding oxidation as a measure of oxidation-resistance

In spite of the pathological significance of oxidation of plasma lipids, no method is currently available for the evaluation of the susceptibility of these lipids to oxidation in unfractionated plasma. Here we demonstrate that copper-induced oxidation of diluted plasma, in the presence of citrate can be monitored continuously by recording the absorbance at 245 nm. The kinetics of accumulation of oxidation products in unfractionated plasma is a sum of lipid oxidation products obtained in low and high density lipoproteins isolated from the same plasma. The kinetic profiles are reproducible and can be performed with plasma samples even after prolonged storage at 4 degrees C (up to two months) or after freezing and thawing of the plasma. Being simple and reproducible, yet correlating with the oxidizability of low and high density lipoproteins, this method can be used to evaluate the "oxidation resistance" of plasma lipids and thus serve as a standard index of the susceptibility of the plasma lipids of patients to oxidation-inflicted pathologies, including atherosclerosis.