Programmed cell clearance: molecular regulation of the elimination of apoptotic cell corpses and its role in the resolution of inflammation

Exogenous Oxidative Stress in Human Spermatozoa Induces Opening of the Mitochondrial Permeability Transition Pore: Effect on Mitochondrial Function, Sperm Motility and Induction of Cell Death

Oxidative stress (OS) and disrupted antioxidant defense mechanisms play a pivotal role in the etiology of male infertility. The alterations in reactive oxygen species (ROS) production and calcium (Ca2+) homeostasis are the main activators for the mitochondrial permeability transition pore (mPTP) opening. The mPTP opening is one of the main mechanisms involved in mitochondrial dysfunction in spermatozoa. This alteration in mitochondrial function adversely affects energy supply, sperm motility, and fertilizing capacity and contributes to the development of male infertility. In human spermatozoa, the mPTP opening has been associated with ionomycin-induced endogenous oxidative stress and peroxynitrite-induced nitrosative stress; however, the effect of exogenous oxidative stress on mPTP opening in sperm has not been evaluated. The aim of this study was to determine the effect of exogenous oxidative stress induced by hydrogen peroxide (H2O2) on mPTP opening, mitochondrial function, motility, and cell death markers in human spermatozoa. Human spermatozoa were incubated with 3 mmol/L of H2O2 for 60 min, and intracellular Ca2+ concentration, mPTP opening, mitochondrial membrane potential (ΔΨm), ATP levels, mitochondrial reactive oxygen species (mROS) production, phosphatidylserine (PS) externalization, DNA fragmentation, viability, and sperm motility were evaluated. H2O2-induced exogenous oxidative stress caused increased intracellular Ca2+, leading to subsequent mPTP opening and alteration of mitochondrial function, characterized by ΔΨm dissipation, decreased ATP levels, increased mROS production, and the subsequent alteration of sperm motility. Furthermore, H2O2-induced opening of mPTP was associated with the expression of apoptotic cell death markers including PS externalization and DNA fragmentation. These results highlight the role of exogenous oxidative stress in causing mitochondrial dysfunction, deterioration of sperm motility, and an increase in apoptotic cell death markers, including PS externalization and DNA fragmentation, through the mPTP opening. This study yielded new knowledge regarding the effects of this type of stress on mitochondrial function and specifically on mPTP opening, factors that can contribute to the development of male infertility, considering that the role of mPTP in mitochondrial dysfunction in human sperm is not completely elucidated. Therefore, these findings are relevant to understanding male infertility and may provide an in vitro model for further research aimed at improving human sperm quality.

Immunomodulatory Effects of Bacterial Toll-like Receptor Ligands on the Phenotype and Function of Milk Immune Cells in Dromedary Camel

(1) Toll-like receptors (TLR) are a family of pattern recognition receptors that sense distinct molecular patterns of microbial origin. Although the immune cell composition of camel milk has been recently described, host-pathogen interaction studies in the camel mammary gland are still scarce. The present study aimed to use a whole milk stimulation assay for investigating the modulatory effect of selected Toll-like receptor (TLR) ligands on the phenotype and function of milk immune cells. (2) Methods-camel milk samples (n = 7) were stimulated in vitro with the TLR4 ligand LPS or the TLR2/1 ligand Pam3CSK4, and separated milk cells were evaluated for stimulation-induced shape change, the expression of cell surface markers, phagocytosis, apoptosis, ROS production, and NETosis. Stimulation with PMA was used as a control stimulation. (3) Results-all stimulants induced shape change in milk cells, change in the expression of several cell markers, and increased cell apoptosis and NETosis. In addition, stimulation with Pam3CSK4 and PMA was associated with enhanced ROS production, while only PMA stimulation resulted in enhanced bacterial phagocytosis by milk immune cells. (4) Conclusions-our data indicates selective modulating effects of the TLR ligands LPS and Pam3CSK4 on camel milk phagocytes. These results may have implications for the use of synthetic TLR agonists as immunomodulatory adjuvants of the immune response to intra-mammary vaccines against mastitis pathogens.

Accumulation of Deleterious Effects in Gastric Epithelial Cells and Vascular Endothelial Cells In Vitro in the Milieu of Helicobacter pylori Components, 7-Ketocholesterol and Acetylsalicylic Acid

The Gastric pathogen Helicobacter pylori (HP) may influence the development of coronary heart disease (CHD). H. pylori induce reactive oxygen species (ROS), which transform cholesterol to 7-ketocholesterol (7-kCh), a CHD risk factor. Acetylsalicylic acid (ASA)—an Anti-aggregation drug used in CHD patients—may increase gastric bleeding and inflammation. We examined whether H. pylori driven ROS effects in the cell cultures of gastric epithelial cells (AGS) and vascular endothelial cells (HUVEC) progress in the milieu of 7-kCh and ASA. Cell cultures, exposed to 7-kCh or ASA alone or pulsed with the H. pylori antigenic complex—Glycine acid extract (GE), urease (UreA), cytotoxin associated gene A (CagA) protein or lipopolysaccharide (LPS), alone or with 7-kCh and ASA—were examined for ROS, apoptosis, cell integrity, interleukin (IL)-8, the activation of signal transducer, the activator of transcription 3 (STAT3), and wound healing. ASA and 7-kCh alone, and particularly in conjunction with H. pylori components, increased the ROS level and the rate of apoptosis, which was followed by cell disintegration, the activation of STAT3, and IL-8 elevation. AGS cells were unable to undergo wound healing. The cell ROS response to H. pylori components may be elevated by 7-kCh and ASA.

Adipose tissue-derived mesenchymal stem cells' acellular product extracellular vesicles as a potential therapy for Crohn's disease

The breakdown of gastrointestinal tract immune homeostasis leads to Crohn's disease (CD). Mesenchymal stem cells (MSCs) have demonstrated clinical efficacy in treating CD in clinical trials, but there is little known about the mechanism of healing. Considering the critical roles of macrophage polarization in CD and immunomodulatory properties of MSCs, we sought to decipher the interaction between adipose‐derived MSCs and macrophages, including their cytokine production, regulation of differentiation, and pro‐/anti‐inflammatory function. RNA extraction and next generation sequencing was performed in adipose tissue from healthy control patients' mesentery (n = 3) and CD mesentery (n = 3). Infiltrated macrophage activation in the CD mesentery was tested, MSCs and extracellular vesicles (EVs) were isolated to compare the regulation of macrophage differentiation, cytokines production, and self‐renewal capacities in vitro. CD patients' mesentery has increased M1 macrophage polarization and elevated activation. MSCs and their derived EVs, isolated from inflamed Crohn's mesentery, leads to a rapid differentiation of monocytes to a M1‐like polarized phenotype. Conversely, MSCs and their derived EVs from healthy, non‐Crohn's patients results in monocyte polarization into a M2 phenotype; this is seen regardless of the adipose source of MSCs (subcutaneous fat, omentum, normal mesentery). EVs derived from MSCs have the ability to regulate macrophage differentiation. Healthy MSCs and their associated EVs have the ability to drive monocytes to a M2 subset, effectively reversing an inflammatory phenotype. This mechanism supports why MSCs may be an effective therapeutic in CD and highlights EVs as a novel therapeutic for further exploration.

Defective apoptotic cell clearance activates innate immune response to protect Caenorhabditis elegans against pathogenic bacteria

Appropriate clearance of dead cells generated by apoptosis is critical to the development of multicellular organisms and tissue homeostasis. In mammals, the removal of apoptotic cell is mediated by polarized monocyte/macrophage populations of the innate immune system. The innate immune system is essential for anti-viral and anti-microbial defense. However, our current understanding of the relationship between apoptotic cell clearance and the innate immune response has remained rather limited. Here, we study how apoptotic cell clearance programs contribute to the innate immune response in C. elegans. We find apoptotic cell clearance mutant worms are more resistant to pathogenic bacteria of Pseudomonas aeruginosa PA14 and Salmonella typhimurium SL1344 due to significant upregulation of innate immune-dependent pathogen response genes. In addition, genetic epistasis analysis indicates that defects in apoptotic cell clearance can activate the innate immune response through PMK-1 p38 MAPK and MPK-1/ERK MAPK pathways in C. elegans. Taken together, our results provide evidence that insufficient clearance of apoptotic cell can protect Caenorhabditis elegans from bacterial infection through innate immune response activation.

Study on Anti-Inflammatory Effect and Major Anti-Inflammatory Components of PSORI-CM02 by Zebrafish Model

PSORI-CM02 is an optimization formula of PSORI-CM01, which is a clinical herbal formula for the treatment for psoriasis in the Guangdong Provincial Hospital of Chinese Medicine. Previous research indicates that it plays a critical role in anti-inflammation and immunoregulation. Rhizoma smilacis glabrae (RSG) is one herbal medicine of PSORI-CM02, whose effective anti-inflammatory component is astilbin. This study aims to test the anti-inflammatory and immunoregulation effects of astilbin as well as RSG in PSORI-CM02, and we, respectively, used the CuSO₄-induced neutrophil-specific transgenic zebrafish model Tg(mpx: EGFP) and the melanin allele mutated Albino strain zebrafish model to visualize the effects of neutrophil recruitment and macrophage phagocytosis. Our data indicated that both PSORI-CM02 and astilbin had anti-inflammatory effects, leading to a reduction in the recruitment of neutrophils and promotion in macrophage phagocytosis. Nevertheless, the negative liquor of Rhizoma smilacis glabrae (PSORI-CM02 without RSG) also had anti-inflammatory and promoting macrophage phagocytosis effects. The results revealed the formula excluding RSG also had anti-inflammatory and immunoregulation effects, which demonstrated that RSG was not the major anti-inflammatory herbal medicine in PSORI-CM02. Similarly, astilbin was not the major anti-inflammatory active ingredient in the formula. The anti-inflammatory and the promotion of macrophage phagocytosis effect of PSORI-CM02 in vivo zebrafish were the results of multiple component interaction, which was the common characteristic of the Chinese medicine compound.

Insights Into Mechanisms of Tumor and Immune System Interaction: Association With Wound Healing

A large number of studies have presented a great deal of information about tumor and immune system interaction. Nevertheless, the problem of tumor evasion from the immune reaction is still difficult to resolve. Understanding the ways in which immunosuppressive tumor microenvironment develops and maintains its potential is of utmost importance to ensure the best use of the suppressed immune functions. The study presents a review covering the data on tumor-associated antigens, mechanisms of tumor evasion from the immune reactions, and search for common immunosuppressive processes of tumor growth and normal wound healing. The study discusses the important role of monocytes/macrophages in the regulation of immune system reactions. We suggest that the simultaneous actions of growth factors and pro-inflammatory cytokines may result in the suppression of the immune system. The study describes intracellular signaling molecules that take part in the regulation of the myeloid cell functions. If the hypothesis is proved correct, the indicated interaction of cytokines could be regarded as a prospective target for antitumor therapy.

Systemic Lupus Erythematosus and DNA Degradation and Elimination Defects

Introduction: Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that is characterized by the production of autoantibodies specific for components of the cell nucleus and that causes damage to body tissues and organs. The pathogenesis of SLE remains unclear, with numerous studies pointing to a combination of genetic and environmental factors. A critical stage in SLE development is cell necrosis, in which undegraded chromatin and nucleoproteins are released into the blood, resulting in circulating cell-free DNA and serum nucleoproteins that trigger anti-dsDNA autoantibody production. This systematic literature review aimed to examine whether SLE stems from a DNA degradation and elimination defect. Materials and Methods: An advanced literature search was conducted in PubMed using the following keywords: [("SLE" OR "Systemic Lupus Erythematosus" OR "Lupus")] AND [("DNA" OR "DNA Degradation")] AND [("Defect Elimination")]. More articles were obtained from the references of the identified articles and basic Google searches. Twenty-five peer-reviewed articles published within the past 10 years (2007-2018) were included for review. Results: The findings of each study are summarized in Tables 1, 2. Discussion and Conclusion: The etiopathogenesis of SLE remains controversial, which limits therapeutic inventions for this disease. However, SLE is a DNA degradation and elimination disorder caused by uncleared histones and nuclear material that leak into the extracellular space and form cell-free DNA, triggering an immune response that destroys tissues and organs. Under normal conditions, apoptosis allows DNA and other nuclear material to be efficiently cleared through degradation and additional complex mechanisms such that this material does not trigger the immune system to produce nuclear autoantibodies.

Human Embryonic Stem Cell-Derived Retinal Pigment Epithelium-Role in Dead Cell Clearance and Inflammation

Inefficient removal of dying retinal pigment epithelial (RPE) cells by professional phagocytes can result in debris formation and development of age-related macular degeneration (AMD). Chronic oxidative stress and inflammation play an important role in AMD pathogenesis. Only a few well-established in vitro phagocytosis assay models exist. We propose human embryonic stem cell-derived-RPE cells as a new model for studying RPE cell removal by professional phagocytes. The characteristics of human embryonic stem cells-derived RPE (hESC-RPE) are similar to native RPEs based on their gene and protein expression profile, integrity, and barrier properties or regarding drug transport. However, no data exist about RPE death modalities and how efficiently dying hESC-RPEs are taken upby macrophages, and whether this process triggers an inflammatory responses. This study demonstrates hESC-RPEs can be induced to undergo anoikis or autophagy-associated cell death due to extracellular matrix detachment or serum deprivation and hydrogen-peroxide co-treatment, respectively, similar to primary human RPEs. Dying hESC-RPEs are efficiently engulfed by macrophages which results in high amounts of IL-6 and IL-8 cytokine release. These findings suggest that the clearance of anoikic and autophagy-associated dying hESC-RPEs can be used as a new model for investigating AMD pathogenesis or for testing the in vivo potential of these cells in stem cell therapy.

The Impact of Protein Acetylation/Deacetylation on Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease in which the body’s immune system mistakenly attacks healthy cells. Although the exact cause of SLE has not been identified, it is clear that both genetics and environmental factors trigger the disease. Identical twins have a 24% chance of getting lupus disease if the other one is affected. Internal factors such as female gender and sex hormones, the major histocompatibility complex (MHC) locus and other genetic polymorphisms have been shown to affect SLE, as well as external, environmental influences such as sunlight exposure, smoking, vitamin D deficiency, and certain infections. Several studies have reported and proposed multiple associations between the alteration of the epigenome and the pathogenesis of autoimmune disease. Epigenetic factors contributing to SLE include microRNAs, DNA methylation status, and the acetylation/deacetylation of histone proteins. Additionally, the acetylation of non-histone proteins can also influence cellular function. A better understanding of non-genomic factors that regulate SLE will provide insight into the mechanisms that initiate and facilitate disease and also contribute to the development of novel therapeutics that can specifically target pathogenic molecular pathways.

Time after seawater transfer influences immune cell abundance and responses to SAV3 infection in Atlantic salmon

Pancreas disease (PD) caused by salmonid alphavirus (SAV) severely affects salmonid aquaculture during the seawater phase. To characterize immune cells in target tissues for SAV infection, heart, pancreas and pyloric caeca were analysed from two groups of fish adapted to seawater for 2 and 9 weeks. The sections were scored for the relative abundance of cells expressing MHC class II, IgM, CD3, CD8 or neutrophil/granulocyte markers using immuno-histochemical techniques. In general, necrosis of tissue was more severe in fish infected at 2 weeks post-seawater transfer (wpt) compared with those infected at 9 wpt. At 9 wpt, there were higher numbers of MHC II+ cells in heart, pancreas and pyloric caeca, IgM+ cells in heart and pancreas, and CD3+ cells in pancreas compared to those infected at 2 wpt. The majority of the immune cells infiltrating PD-affected tissues were MHC II+ and CD3+ cells suggesting that antigen-presenting cells and T lymphocytes are the main types of immune cells responding to SAV infection. All the investigated cell types were also observed in pyloric caeca of infected fish, suggesting that this tissue may play a role in the immune response to SAV.

Anti-inflammatory and proresolution activities of bergapten isolated from the roots of Ficus hirta in an in vivo zebrafish model

Bergapten (5-methoxypsoralen), a coumarin-derivate compound isolated from Ficus hirta roots, was evaluated for its anti-inflammatory and proresolution activities in a tail-cutting-induced zebrafish larvae model. Bergapten was evaluated using a caudal fin-wounded transgenic zebrafish line "Tg(corola: eGFP)" to visualize the effects of the recruitment and clearance of neutrophils and macrophages at the injury site. We found that bergapten significantly suppressed the recruitment of neutrophils and macrophages toward the injury site, as well as promoted the clearance of neutrophils and macrophages from the wound site. We also investigated the reactive oxygen species (ROS) and nitric oxide (NO) level of bergapten in a tail-cutting-induced inflammation zebrafish model. The Results revealed that bergapten effectively inhibited the tail-cutting-induced production of ROS and NO in zebrafish larvae. This study reported for the first time the potential anti-inflammatory and proresolution activities of bergapten in an in vivo zebrafish model, suggesting that bergapten may be a potential candidate for inflammation therapy.

Single-walled carbon nanotubes modulate pulmonary immune responses and increase pandemic influenza a virus titers in mice

Background

Numerous toxicological studies have focused on injury caused by exposure to single types of nanoparticles, but few have investigated how such exposures impact a host’s immune response to pathogen challenge. Few studies have shown that nanoparticles can alter a host’s response to pathogens (chiefly bacteria) but there is even less knowledge of the impact of such particles on viral infections. In this study, we performed experiments to investigate if exposure of mice to single-walled carbon nanotubes (SWCNT) alters immune mechanisms and viral titers following subsequent influenza A virus (IAV) infection.

Methods

Male C57BL/6 mice were exposed to 20 μg of SWCNT or control vehicle by intratracheal instillation followed by intranasal exposure to 3.2 × 10⁴ TCID₅₀ IAV or PBS after 3 days. On day 7 mice were euthanized and near-infrared fluorescence (NIRF) imaging was used to track SWCNT in lung tissues. Viral titers, histopathology, and mRNA expression of antiviral and inflammatory genes were measured in lung tissue. Differential cell counts and cytokine levels were quantified in bronchoalveolar lavage fluid (BALF).

Results

Viral titers showed a 63-fold increase in IAV in SWCNT + IAV exposed lungs compared to the IAV only exposure. Quantitation of immune cells in BALF indicated an increase of neutrophils in the IAV group and a mixed profile of lymphocytes and neutrophils in SWCNT + IAV treated mice. NIRF indicated SWCNT remained in the lung throughout the experiment and localized in the junctions of terminal bronchioles, alveolar ducts, and surrounding alveoli. The dual exposure exacerbated pulmonary inflammation and tissue lesions compared to SWCNT or IAV single exposures. IAV exposure increased several cytokine and chemokine levels in BALF, but greater levels of IL-4, IL-12 (P70), IP-10, MIP-1, MIP-1α, MIP-1β, and RANTES were evident in the SWCNT + IAV group. The expression of tlr3, ifnβ1, rantes, ifit2, ifit3, and il8 was induced by IAV alone but several anti-viral targets showed a repressed trend (ifits) with pre-exposure to SWCNT.

Conclusions

These findings reveal a pronounced effect of SWCNT on IAV infection in vivo as evidenced by exacerbated lung injury, increased viral titers and several cytokines/chemokines levels, and reduction of anti-viral gene expression. These results imply that SWCNT can increase susceptibility to respiratory viral infections as a novel mechanism of toxicity.

Electronic supplementary material

The online version of this article (10.1186/s12985-017-0909-z) contains supplementary material, which is available to authorized users.

Intestinal macrophages in Peyer's patches, sacculus rotundus and appendix of Angora rabbit

The largest pool of macrophages in the body is harboured by the intestinal mucosa. As the principal phagocytic component of the immune system, macrophages are essential for maintaining mucosal homeostasis as they prevent commensal bacteria from adhering to mucosal epithelial cells. This study provides a RAM11 immunohistochemical and electron microscopic investigation of the existence, localization and distribution of intestinal macrophages in organized gut-associated lymphoid tissue (GALT), including Peyer's patches (PPs), the sacculus rotundus (SR) and the appendix, in the Angora rabbit. Although rabbit intestinal macrophages did not express the tissue macrophage marker macrosialin (CD68), they expressed RAM11. RAM11-positive intestinal macrophages were mostly localized to the subepithelial dome region, interfollicular area and germinal centres (GCs) of the GALT and the lamina propria or submucosa of the ileum and jejunum devoid of PPs and were also observed in the follicle-associated epithelium of PPs, but not in that of the SR and appendix. RAM11-positive macrophages containing engulfed apoptotic bodies were present in the GCs of the lymphoid follicles in the GALT. Electron microscopy further revealed multiple macrophages containing apoptotic bodies within the GCs of the follicles in the GALT. Some macrophage aggregations were observed in the GC and between the GC and the corona region of the follicles in the SR and appendix. Rabbit intestinal macrophages thus undertake both potent phagocytic activity and the efficient scavenging of apoptotic cells. Immunohistochemical data suggest that RAM11 can be reliably used for the determination of intestinal macrophages in the GALT of rabbits.

Programmed cell clearance: From nematodes to humans

Programmed cell clearance is a highly regulated physiological process of elimination of dying cells that occurs rapidly and efficiently in healthy organisms. It thus ensures proper development as well as homeostasis. Recent studies have disclosed a considerable degree of conservation of cell clearance pathways between nematodes and higher organisms. The externalization of the anionic phospholipid phosphatidylserine (PS) has emerged as an important "eat-me" signal for phagocytes and its exposition on apoptotic cells is controlled by phospholipid translocases and scramblases. However, there is mounting evidence that PS exposure occurs not only in apoptosis, but may also be actively expressed on the surface of cells undergoing other forms of cell death including necrosis; PS is also expressed on the surface of engulfing cells. Additionally, PS may act as a "save-me" signal during axonal regeneration. Here we discuss mechanisms of PS exposure and its recognition by phagocytes as well as the consequences of PS signaling in nematodes and in mammals.

Selected metabolic aspects of elastin and collagen fiber proteolysis in diseases of the respiratory system - the significance of α1 antitrypsin deficiency

The process of elastin and collagen fiber destruction was presented based on the example of the changes taking place in the course of chronic obstructive pulmonary disease and primary spontaneous pneumothorax. In 1963, when analyzing patients with α1 antitrypsin deficiency, Dr Laurell and Dr Eriksson hypothesized that elastolysis plays a role in the pathogenesis of emphysema, which marked the beginning of studies aimed at analyzing this process. The present work concerns new scientific reports regarding the hypothesis. The most important risk factors include protease-antiprotease imbalance and α1 antitrypsin protein deficiency.

Innate sensing of oxidation-specific epitopes in health and disease

Ageing, infections and inflammation result in oxidative stress that can irreversibly damage cellular structures. The oxidative damage of lipids in membranes or lipoproteins is one of these deleterious consequences that not only alters lipid function but also leads to the formation of neo-self epitopes - oxidation-specific epitopes (OSEs) - which are present on dying cells and damaged proteins. OSEs represent endogenous damage-associated molecular patterns that are recognized by pattern recognition receptors and the proteins of the innate immune system, and thereby enable the host to sense and remove dangerous biological waste and to maintain homeostasis. If this system is dysfunctional or overwhelmed, the accumulation of OSEs can trigger chronic inflammation and the development of diseases, such as atherosclerosis and age-related macular degeneration. Understanding the molecular components and mechanisms that are involved in this process will help to identify individuals with an increased risk of developing chronic inflammation, and will also help to indicate novel modes of therapeutic intervention.

Therapies targeting lipid peroxidation in traumatic brain injury

Lipid peroxidation can be broadly defined as the process of inserting a hydroperoxy group into a lipid. Polyunsaturated fatty acids present in the phospholipids are often the targets for peroxidation. Phospholipids are indispensable for normal structure of membranes. The other important function of phospholipids stems from their role as a source of lipid mediators - oxygenated free fatty acids that are derived from lipid peroxidation. In the CNS, excessive accumulation of either oxidized phospholipids or oxygenated free fatty acids may be associated with damage occurring during acute brain injury and subsequent inflammatory responses. There is a growing body of evidence that lipid peroxidation occurs after severe traumatic brain injury in humans and correlates with the injury severity and mortality. Identification of the products and sources of lipid peroxidation and its enzymatic or non-enzymatic nature is essential for the design of mechanism-based therapies. Recent progress in mass spectrometry-based lipidomics/oxidative lipidomics offers remarkable opportunities for quantitative characterization of lipid peroxidation products, providing guidance for targeted development of specific therapeutic modalities. In this review, we critically evaluate previous attempts to use non-specific antioxidants as neuroprotectors and emphasize new approaches based on recent breakthroughs in understanding of enzymatic mechanisms of lipid peroxidation associated with specific death pathways, particularly apoptosis. We also emphasize the role of different phospholipases (calcium-dependent and -independent) in hydrolysis of peroxidized phospholipids and generation of pro- and anti-inflammatory lipid mediators. This article is part of a Special Issue entitled SI:Brain injury and recovery.

Characteristics of Mitochondrial Transformation into Human Cells

Mitochondria can be incorporated into mammalian cells by simple co-incubation of isolated mitochondria with cells, without the need of transfection reagents or any other type of intervention. This phenomenon was termed mitochondrial transformation, and although it was discovered in 1982, currently little is known regarding its mechanism(s). Here we demonstrate that mitochondria can be transformed into recipient cells very quickly, and co-localize with endogenous mitochondria. The isolated mitochondria interact directly with cells, which engulf the mitochondria with cellular extensions in a way, which may suggest the involvement of macropinocytosis or macropinocytosis-like mechanisms in mitochondrial transformation. Indeed, macropinocytosis inhibitors but not clathrin-mediated endocytosis inhibition-treatments, blocks mitochondria transformation. The integrity of the mitochondrial outer membrane and its proteins is essential for the transformation of the mitochondria into cells; cells can distinguish mitochondria from similar particles and transform only intact mitochondria. Mitochondrial transformation is blocked in the presence of the heparan sulfate molecules pentosan polysulfate and heparin, which indicate crucial involvement of cellular heparan sulfate proteoglycans in the mitochondrial transformation process.

Milk fat globule E-8 and interleukin 17 in systemic lupus erythematosus: partners in crime?

Objectives

Systemic lupus erythematosus (SLE) is a multi-factorial, autoimmune disease with a wide array of manifestations. The pro-inflammatory cytokine interleukin (IL)-17 has been implicated in the inflammatory response and tissue damage in SLE; however, its correlation with disease activity is still questionable. Meanwhile, efficient clearance of apoptotic cells is required for immune tolerance. An abnormally low or high level of milk fat globule (MFG-E8) can result in impaired apoptotic cell clearance and the subsequent autoimmune response. In this study, we endeavoured to compare the levels of MFG-E8 and IL-17 in SLE patients and healthy controls and to reveal the alleged association of these levels with SLE disease activity.

Material and methods

Serum samples from 57 SLE patients and 30 healthy control subjects were examined for quantitation of MFG-E8 and IL-17 levels using ELISA. Systemic lupus erythematosus disease activity was calculated using the SLE Disease Activity Index (SLEDAI). Clinical manifestations and laboratory findings of the patients were also recorded.

Results

We report that serum MFG-E8 levels were significantly elevated in the sera of SLE patients compared to healthy controls (p-value = 0.019). Likewise, IL-17 levels were higher in SLE patients (p-value < 0.001). A positive correlation was revealed between MFG-E8 level and proteinuria. Surprisingly, there was a poor correlation between disease activity and the levels of either IL-17 or MFG-E8.

Conclusions

Although serum MFG-E8 and IL-17 levels were higher in SLE patients than in normal controls, our results indicate that they cannot accurately reflect the disease activity. Meanwhile, further studies are needed to assess MFG-E8 and IL-17 as potential therapeutic targets in SLE patients.

Identifying the role of cytochrome c in post-resuscitation pathophysiology

Cytochrome c, an electron carrier that normally resides in the mitochondrial intermembrane space, may translocate to the cytosol under ischemic and hypoxic conditions and contribute to mitochondrial permeability transition pore opening. In addition, reperfusion of brain tissue following ischemia initiates a cell death cascade that includes cytochrome c-mediated induction of apoptosis. Further studies are needed to determine the contribution of cytochrome c in the regulation of cell death, as well as its value as an in vivo prognostic marker after cardiac arrest and resuscitation.

Phospholipid scramblase 1 is required for β2-glycoprotein I binding in hypoxia and reoxygenation-induced endothelial inflammation

Multiple pathologic conditions, including hemorrhage, tumor angiogenesis, and ischemia-reperfusion events, will result in hypoxia and subsequent reperfusion. Previous studies have analyzed the lipid changes within whole tissues and indicated that ischemia-reperfusion altered tissue and cellular phospholipids. Using an in vitro cell culture model of hypoxia and reoxygenation, we examined the endothelial lipid changes. We hypothesized that phospholipid scramblase 1, a protein that regulates bilayer asymmetry, is involved in altering the phospholipids of endothelial cells during hypoxia, a component of ischemia, leading to β2-glycoprotein I and IgM binding and subsequent lipid-mediated, inflammatory responses. We have completed the first comprehensive study of steady-state phospholipid scramblase 1 mRNA levels, protein expression, and activity under conditions of hypoxia and reoxygenation. Phospholipid scramblase 1 regulates phosphatidylserine exposure in response to oxygen stress, leading to β2-glycoprotein I and IgM binding and lipid-mediated, inflammatory responses.

Loading of nuclear autoantigens prototypically recognized by systemic lupus erythematosus sera into late apoptotic vesicles requires intact microtubules and myosin light chain kinase activity

Most cases of systemic lupus erythematosus (SLE) are characterized by an impaired clearance of apoptotic cells in various tissues. Non-cleared apoptotic waste is considered an immunogen driving the autoimmune response in patients with SLE. During the execution of apoptosis, membrane blebs are formed and filled with cellular components. Here, we evaluate the cytoskeletal pathway(s) responsible for the loading of SLE prototypic nuclear autoantigens into the apoptotic cell-derived membranous vesicles (ACMV) generated during late phases of apoptosis. HeLa cells expressing a fusion protein of histone H2B with green fluorescent protein (GFP) were irradiated with ultraviolet (UV)-B to induce apoptosis. The appearance and trafficking of chromatin-derived material was monitored by fluorescence microscopy. Specific inhibitors of cytoskeletal pathways were employed to identify the motile elements involved in translocation and trafficking of the nuclear components. We observed that immediately after their appearance the ACMV did not contain histone H2B(GFP) ; in this phase the fluorescence was contained in the nuclear remnants and the cytoplasm. Within consecutive minutes the ACMV were loaded with chromatin-derived material, whereas the loading of simultaneously created ACMV with histone H2B(GFP) was not uniform. Some ACMV were preferentially filled and, consequently, showed a remarkably higher histone H2B(GFP) accumulation. Inhibitors of the cytoskeleton revealed that functional microtubules and myosin light chain kinase are required for nuclear shrinkage and loading of nuclear material into the ACMV, respectively.

Antibodies against native and oxidized cardiolipin and phosphatidylserine and phosphorylcholine in atherosclerosis development

Background

Antibodies against cardiolipin and phosphatidylserine (anti-CL and anti-PS) are associated with thrombosis. In contrast, we determined that IgM antibodies against oxidized CL and PS (OxCL and OxPS) and phosphorylcholine (anti-PC) could be protection markers for cardiovascular disease (CVD).

Methods

226 individuals with established hypertension (diastolic pressure>95 mmHg) from the European Lacidipine Study on Atherosclerosis. Antibodies were tested by ELISA. As a surrogate measure of atherosclerosis, the mean of the maximum intima-media thicknesses (IMT) in the far walls of common carotids and bifurcations was determined by ultrasonography at the time of inclusion and 4 years following inclusion.

Results

Increases in IMT measures at follow-up were significantly less common in subjects which at baseline had high IgM anti-OxPS and anti-PC at above 75^th percentile: OR 0,45, CI (0,23–0,86) and OR 0.37, CI (0,19–0,71), p = 0.0137 respectively and above 90^th percentile: OR 0.32, CI (0,12–0,84) and OR 0.39, CI (0,15–1.00), p = 0.050 and OR 0,22, CI (0,08–0,59) p = 0,0029. IgM anti-OxCL was negatively associated with IMT increases (OR, 0.32, CI (0,12–0,84), p = 0231). There were no associations for IgM anti-PS or anti-CL. Anti-PC, as determined herein by a commercial ELISA, was strongly associated with data from our previously published in house ELISA (R = 0,87; p<0,0001).) Anti-PC was also a risk marker at low levels (below 25^th percentile; OR = 2,37 (1,16–4,82), p = 0,0177).

Conclusions

High levels of IgM anti-OxPS and anti-OxCL, but not traditional anti-phospholipid antibodies (anti-PS and anti-CL), are associated with protection against atherosclerosis development. In addition, low IgM anti-PC was a risk marker but high a protection marker.

Oxidized phosphatidylserine: production and bioactivities

Recent development of analytical methods for lipid hydroperoxides and preparation of highly pure lipid hydroperoxides have revealed the important new pathophysiological roles of oxidized phospholipids. Generation of reactive oxygen species and subsequent oxidative stress leads to random oxidation of membrane phospholipids. However, recent studies have reported that anionic phospholipid molecules such as phosphatidylserine (PS) and cardiolipin are preferentially oxidized during apoptosis, resulting in efficient apoptosis execution and apoptotic cell clearance by phagocytes. This review is exclusively focused on selective production of oxidized PS (oxPS) during apoptosis as well as the novel roles of oxPS under pathophysiological conditions.

Low Levels of Antibodies Against Oxidized but not Nonoxidized Cardiolipin and Phosphatidylserine Are Associated with Atherosclerotic Plaques in Systemic Lupus Erythematosus

Objective.

We have reported that the prevalence of atherosclerotic plaques and their echolucency was increased in systemic lupus erythematosus (SLE). We here study antibodies against oxidized cardiolipin (anti-OxCL) and phosphatidylserine (anti-OxPS) in SLE and in relation to atherosclerosis measures.

Methods.

Patients with SLE (n = 114) were compared with age- and sex-matched population-based controls (n = 122). Common carotid intima-media thickness and plaque occurrence were determined by B-mode ultrasonography. Plaques were graded according to echogenicity as 1–4, with 1 being echolucent. Antibodies were determined by ELISA.

Results.

In the SLE group, the prevalence of low IgM anti-OxPS and low total IgM levels (below 33rd percentile) was increased compared to controls (p = 0.045 and p = 0.0079, respectively). Among SLE patients with atherosclerotic plaques, the prevalence of low IgM anti-OxPS (p = 0.0019) and anti-OxCL (p = 0.031) was increased. Only IgM anti-OxPS remained significant (p = 0.019) after adjusting for other significant factors. Echolucent plaques (total, or left side) were more prevalent among SLE patients with low IgM anti-OxCL and anti-OxPS when controlled for other significant factors (p < 0.05). Low total IgM was independently associated with echolucent plaque on left side (p < 0.05), but not other atherosclerosis measures. IgM anticardiolipin antibodies (aCL) and antiphosphatidylserine antibodies (anti-PS) were higher among SLE patients with cardiopulmonary disease, including arterial, valvular, and venous disease (p < 0.05). There were no associations between antibodies and other disease manifestations or activity. Both anti-OxCL and anti-OxPS, in contrast to aCL, and anti-PS, were cofactor−β2-glycoprotein I (β2-GPI)-independent.

Conclusion.

The prevalence of low levels of IgM anti-OxCL and anti-OxPS (both cofactor-β2-GPI-independent) is associated with the presence of plaques and echolucent plaques in SLE.

Macrophage clearance of neutrophil extracellular traps is a silent process

Neutrophil extracellular traps (NETs) facilitate the extracellular killing of pathogens. However, in recent years, excessive NET formation has been implicated in several pathological conditions. Indeed, NETs that are not removed from tissues or from the circulation might serve to trigger autoimmune responses. We observed that physiological amounts of DNase I do not suffice to completely degrade NETs in vitro, suggesting that additional mechanisms are required for the removal of these extracellular structures. We show in this article that human monocyte-derived macrophages are able to engulf NETs in a cytochalasin D-dependent manner, indicating that this is an active, endocytic process. Furthermore, preprocessing of NETs by DNase I facilitated their clearance by macrophages. In addition, both recombinant C1q and endogenous C1q derived from human serum were found to opsonize NETs, and this facilitated NET clearance. Upon internalization, NETs were apparently degraded in lysosomes, as treatment with chloroquine led to accumulation of extranuclear DNA in human monocyte-derived macrophages. Finally, uptake of NETs alone did not induce proinflammatory cytokine secretion, whereas LPS-induced production of IL-1β, IL-6, and TNF-α was promoted by the uptake of NETs. In summary, we show that macrophages are capable of clearance of NETs and that this occurs in an immunologically silent manner.

Another look at the life of a neutrophil

Neutrophils are considered as the privates of the innate immune system. They are born in the bone marrow, migrate to the tissues where they kill putative intruders. After their job they are quickly removed from the battlefield by macrophages. This view of a predetermined pathway fitted nicely in their short lifespan of 5 h. However, recent studies indicated that their lifespan was in the order of several days. Recently, it became clear that neutrophils have functions beyond killing of pathogens. The reported half-life of 5 h is hardly compatible with those functions. Moreover, the organism actively invests in rescuing primed neutrophils from clearance by the body. It appears that their half-life is highly dependent on the method used to measure their life span. Here, we discuss the literature and show that neutrophils compartmentalize which could explain partially the differences reported for their lifespan. Moreover, the methodology to label neutrophils ex-vivo could have similar deteriorating effects on their lifespan as found for transfused red blood cells.

Eosinophil apoptosis and clearance in asthma

Asthma is an increasingly common respiratory condition characterized by reversible airway obstruction, bronchial hyper-responsiveness and airway inflammation with a clear unmet need for more effective therapy. Eosinophilic asthma is a phenotype of the condition that features increased blood or sputum eosinophils whose numbers correlate with disease severity. Several lines of evidence are now emerging, which implicate increased persistence of eosinophils in the lungs of patients with asthma as a consequence of inhibition of and defects in the apoptotic process, together with impaired apoptotic cell removal mechanisms. This article will update our knowledge of the mechanisms controlling eosinophil apoptosis and clearance, together with evidence implicating defects in apoptosis and pro-inflammatory cell removal in asthma. Recent developments in novel therapies for asthma that target eosinophil apoptotic and/or clearance pathways will also be discussed.

Specificity of lipoprotein-associated phospholipase A(2) toward oxidized phosphatidylserines: liquid chromatography-electrospray ionization mass spectrometry characterization of products and computer modeling of interactions

Ca(2+)-independent lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is a member of the phospholipase A(2) superfamily with a distinguishing characteristic of high specificity for oxidatively modified sn-2 fatty acid residues in phospholipids that has been especially well characterized for peroxidized species of phosphatidylcholines (PC). The ability of Lp-PLA(2) to hydrolyze peroxidized species of phosphatidylserine (PS), acting as a recognition signal for clearance of apoptotic cells by professional phagocytes, as well as the products of the reaction has not been investigated. We performed liquid chromatography-electrospray ionization mass spectrometry-based structural characterization of oxygenated, hydrolyzed molecular species of PS-containing linoleic acid in either the sn-2 position (C(18:0)/C(18:2)) or in both sn-1 and sn-2 positions (C(18:2)/C(18:2)), formed in the cytochrome c- and H(2)O(2)-driven enzymatic oxidation reaction. Cytochrome c has been chosen as a catalyst of peroxidation reactions because of its likely involvement in PS oxidation in apoptotic cells. We found that Lp-PLA(2) catalyzed the hydrolysis of both nontruncated and truncated (oxidatively fragmented) species of oxidized PS species, albeit with different efficiencies, and performed detailed characterization of the major reaction products: oxygenated derivatives of linoleic acid as well as nonoxygenated and oxygenated species of lyso-PS. Among linoleic acid products, derivatives oxygenated at the C(9) position, including 9-hydroxyoctadecadienoic acid (9-HODE), a potent ligand of G protein-coupled receptor G2A, were the most abundant. Computer modeling of interactions of Lp-PLA(2) with different PS-oxidized species indicated that they are able to bind in the proximity (<5 Å) of Ser273 and His351 of the catalytic triad. For 9-hydroxy and 9-hydroperoxy derivatives of oxidized PS, the sn-2 ester bond was positioned very close (<3 Å) to the Ser273 residue, a nucleophile directly attacking the sn-2 bond, thus favoring the hydrolysis reaction. We suggest that oxidatively modified free fatty acids and lyso-PS species generated by Lp-PLA(2) may represent important signals facilitating and regulating the execution of apoptotic and phagocytosis programs essential for the control of inflammation.

Phagocyte dynamics in a highly regenerative urochordate: insights into development and host defense

Phagocytosis is a cellular process by which particles and foreign bodies are engulfed and degraded by specialized cells. It is functionally involved in nutrient acquisition and represents a fundamental mechanism used to remove pathogens and cellular debris. In the marine invertebrate chordate Botryllus schlosseri, cell corpse engulfment by phagocytic cells is the recurrent mechanism of programmed cell clearance and a critical process for the successful execution of asexual regeneration and colony homeostasis. In the present study, we have utilized a naturally occurring process of vascular parabiosis coupled with intravascular microinjection of fluorescent bioparticles and liposomes as tools to investigate the dynamics of phagocyte behavior in real-time during cyclical body regeneration. Our findings indicate that B. schlosseri harbors two major populations of post-mitotic phagocytes, which display distinct phagocytic specificity and homing patterns: a static population that lines the circulatory system epithelia, and a mobile population that continuously recirculates throughout the colony and exhibits a characteristic homing pattern within mesenchymal niches called ventral islands (VI). We observed that a significant proportion of ventral island phagocytes (VIP) die and are engulfed by other VIP following takeover. Selective impairment of VIP activity curtailed zooid resorption and asexual development. Together, these findings strongly suggest that ventral islands are sites of phagocyte homing and turnover. As botryllid ascidians represent invertebrate chordates capable of whole body regeneration in a non-embryonic scenario, we discuss the pivotal role that phagocytosis plays in homeostasis, tissue renewal and host defense.

Fish and mammalian phagocytes differentially regulate pro-inflammatory and homeostatic responses in vivo

Phagocytosis is a cellular mechanism that is important to the early induction of antimicrobial responses and the regulation of adaptive immunity. At an inflammatory site, phagocytes serve as central regulators for both pro-inflammatory and homeostatic anti-inflammatory processes. However, it remains unclear if this is a recent evolutionary development or whether the capacity to balance between these two seemingly contradictory processes is a feature already displayed in lower vertebrates. In this study, we used murine (C57BL/6) and teleost fish (C. auratus) in vitro and in vivo models to assess the evolutionary conservation of this dichotomy at a site of inflammation. At the level of the macrophage, we found that teleost fish already displayed divergent pro-inflammatory and homeostatic responses following internalization of zymosan or apoptotic bodies, respectively, and that these were consistent with those of mice. However, fish and mice displayed significant differences in vivo with regards to the level of responsiveness to zymosan and apoptotic bodies, the identity of infiltrating leukocytes, their rate of infiltration, and the kinetics and strength of resulting antimicrobial responses. Unlike macrophages, significant differences were identified between teleost and murine neutrophilic responses. We report for the first time that activated murine, but not teleost neutrophils, possess the capacity to internalize apoptotic bodies. This internalization translates into reduction of neutrophil ROS production. This may play an important part in the recently identified anti-inflammatory activity that mammalian neutrophils display during the resolution phase of inflammation. Our observations are consistent with continued honing of inflammatory control mechanisms from fish to mammals, and provide added insights into the evolutionary path that has resulted in the integrated, multilayered responses that are characteristic of higher vertebrates.

Cytochrome c produces pores in cardiolipin-containing planar bilayer lipid membranes in the presence of hydrogen peroxide

Interaction of cytochrome c with cardiolipin in the presence of hydrogen peroxide induces peroxidase activity in cytochrome c and the ability to oxidize membrane lipids. These cytochrome c properties play a substantial role in the cytochrome c-mediated apoptotic reactions. In the present study the electric properties (specific capacitance and integral conductance) of the cardiolipin-containing asolectin planar bilayer lipid membranes (pBLM) in the presence of cytochrome c and hydrogen peroxide were studied. Cytochrome c interaction with cardiolipin-containing pBLM in the presence of hydrogen peroxide resulted in the dramatic increase of the conductance, pore production, their growth up to 3.5 nm diameter and subsequent membrane destruction. In the absence of hydrogen peroxide cytochrome c demonstrated almost no effect on the membrane capacitance and conductance. The data obtained prove the pivotal role of cytochrome c and membrane lipids in the permeabilization of pBLM. Correlation of apoptotic reactions and cytochrome c-mediated membrane permeability is discussed.

Evaluation of the capacity of oxidized phosphatidylserines to induce the expression of cytokines in monocytes and dendritic cells

Oxidized phospholipids are known to be key signaling molecules in the onset of several diseases involving inflammation. The aim of this study was to evaluate the effect of oxidized phosphatidylserines (oxPS) in modulating the immune system, through cytokine production. Flow cytometry analysis was used to evaluate the oxPS capacity to induce the expression of different cytokines by monocytes, myeloid dendritic cells (mDCs) and DCs CD14(-/low)CD16(+). oxPS were formed during oxidation induced by the hydroxyl radical. Among the four families of oxPS studied, only oxPS modified in the polar head with formation of a terminal hydroperoxyacetaldehyde upregulated the production of cytokines IL-8 and TNF-α by monocytes and DCs subsets (mDCs and CD14(-/low)CD16(+) DCs). This family of oxPS showed the capacity to upregulate the production of IL-1β, IL-6, and MIP-1β from the same type of cells. A significant raise in the percentage of monocytes and dendritic cells producing the studied cytokines was observed, when compared with basal control. Oxidation products modified in the fatty acyl chain did not upregulate TNF and IL-8. oxPS with terminal hydroperoxyacetaldehyde has pro-inflammatory properties. This outcome may help to understand the biological role of phosphatidylserine oxidation products in inflammatory processes and in dysfunctions of immune system.

Cross talk between engulfment receptors stabilin-2 and integrin αvβ5 orchestrates engulfment of phosphatidylserine-exposed erythrocytes

Efficient cell corpse clearance is critical for health in organisms. Apoptotic cells displaying phosphatidylserine (PS) are recognized by engulfment receptors and ingested through two conserved pathways. In one pathway, engulfment receptor brain-specific angiogenesis inhibitor 1 (BAI-1) or integrin functions upstream of ELMO/DOCK180 and activate the small GTPase Rac1. In the other pathway, engulfment receptor CED-1 or stabilin-2 acts in concert with the adaptor protein GULP to activate Rac1. Stabilin-2, a PS receptor, facilitates phagocytosis of apoptotic cells and mediates the production of anti-inflammatory cytokines. Here, we propose that the stabilin-2 extracellular domain consisting of integrin-binding fasciclin 1 (FAS1) domains coordinates the activities of the two phagocytic pathways via direct interactions with integrin. Interactions between stabilin-2 and integrin were determined using biochemical assays, including coimmunoprecipitation and fluorescence resonance energy transfer (FRET). These interactions appear to have functional relevance, since knockdown of endogenous αvβ5 expression or treatment with a function-blocking αvβ5 antibody significantly decreased stabilin-2-mediated phagocytosis in the absence of soluble factors. Our data collectively suggest that the engulfment receptors of the two phagocytic pathways communicate with each other to orchestrate engulfment of damaged erythrocytes. Coordinated phagocytic signaling would be advantageous for physiological and pathological circumstances that require rapid clearance of abnormal (apoptotic or aged) cells.

Saposin C coupled lipid nanovesicles specifically target arthritic mouse joints for optical imaging of disease severity

Rheumatoid arthritis is a chronic inflammatory disease affecting approximately 1% of the population and is characterized by cartilage and bone destruction ultimately leading to loss of joint function. Early detection and intervention of disease provides the best hope for successful treatment and preservation of joint mobility and function. Reliable and non-invasive techniques that accurately measure arthritic disease onset and progression are lacking. We recently developed a novel agent, SapC-DOPS, which is composed of the membrane-associated lysosomal protein saposin C (SapC) incorporated into 1,2-dioleoyl-sn-glycero-3-phospho-L-serine (DOPS) lipid nanovesicles. SapC-DOPS has a high fusogenic affinity for phosphatidylserine-enriched microdomains on surfaces of target cell membranes. Incorporation of a far-red fluorophore, CellVue Maroon (CVM), into the nanovesicles allows for in vivo non-invasive visualization of the agent in targeted tissue. Given that phosphatidylserine is present only on the inner leaflet of healthy plasma membranes but is “flipped” to the outer leaflet upon cell damage, we hypothesized that SapC-DOPS would target tissue damage associated with inflammatory arthritis due to local surface-exposure of phosphatidylserine. Optical imaging with SapC-DOPS-CVM in two distinct models of arthritis, serum-transfer arthritis (e.g., K/BxN) and collagen-induced arthritis (CIA) revealed robust SapC-DOPS-CVM specific localization to arthritic paws and joints in live animals. Importantly, intensity of localized fluorescent signal correlated with macroscopic arthritic disease severity and increased with disease progression. Flow cytometry of cells extracted from arthritic joints demonstrated that SapC-DOPS-CVM localized to an average of 7–8% of total joint cells and primarily to CD11b+Gr-1+ cells. Results from the current studies strongly support the application of SapC-DOPS-CVM for advanced clinical and research applications including: detecting early arthritis onset, assessing disease progression real-time in live subjects, and providing novel information regarding cell types that may mediate arthritis progression within joints.

Common genetic variations in the NALP3 inflammasome are associated with delayed apoptosis of human neutrophils

Background

Neutrophils are key-players in the innate host defense and their programmed cell death and removal are essential for efficient resolution of inflammation. These cells recognize a variety of pathogens, and the NOD-like receptors (NLRs) have been suggested as intracellular sensors of microbial components and cell injury/stress. Some NLR will upon activation form multi-protein complexes termed inflammasomes that result in IL-1β production. NLR mutations are associated with auto-inflammatory syndromes, and our previous data propose NLRP3 (Q705K)/CARD-8 (C10X) polymorphisms to contribute to increased risk and severity of inflammatory disease by acting as genetic susceptibility factors. These gene products are components of the NALP3 inflammasome, and approximately 6.5% of the Swedish population are heterozygote carriers of these combined gene variants. Since patients carrying the Q705K/C10X polymorphisms display leukocytosis, the aim of the present study was to find out whether the inflammatory phenotype was related to dysfunctional apoptosis and impaired clearance of neutrophils by macrophages.

Methods and Findings

Patients carrying the Q705K/C10X polymorphisms displayed significantly delayed spontaneous as well as microbe-induced apoptosis compared to matched controls. Western blotting revealed increased levels and phosphorylation of Akt and Mcl-1 in the patients' neutrophils. In contrast to macrophages from healthy controls, macrophages from the patients produced lower amounts of TNF; suggesting impaired macrophage clearance response.

Conclusions

The Q705K/C10X polymorphisms are associated with delayed apoptosis of neutrophils. These findings are explained by altered involvement of different regulators of apoptosis, resulting in an anti-apoptotic profile. Moreover, the macrophage response to ingestion of microbe-induced apoptotic neutrophils is altered in the patients. Taken together, the patients display impaired turnover and clearance of apoptotic neutrophils, pointing towards a dysregulated innate immune response that influences the resolution of inflammation. The future challenge is to understand how microbes affect the activation of inflammasomes, and why this interaction will develop into severe inflammatory disease in certain individuals.

Modulation of macrophage activity by aflatoxins B1 and B2 and their metabolites aflatoxins M1 and M2

Aflatoxins are natural contaminants frequently found both in food and feed. Many of them exert immunomodulatory properties in mammals; therefore, the aim of the current study was to investigate immune-effects of AFB1, AFB2, AFM1 and AFM2, alone and differently combined, in J774A.1 murine macrophages. MTT assay showed that AFB1, alone and combined with AFB2, possess antiproliferative activity only at the highest concentration; such effect was not shown by their hydroxylated metabolites, AFM1 and AFM2, respectively. However, the immunotoxic effects of the aflatoxins evaluated in the current study may be due to the inhibition of production of active oxygen metabolites such as NO. Cytofluorimetric assay in macrophages exposed to aflatoxins (10-100 μM) revealed that their cytoxicity is not related to apoptotic pathways. Nevertheless, a significant increase of the S phase cell population accompanied by a decrease in G0/G1 phase cell population was observed after AFB1 treatment. In conclusion, the results of the current study suggest that aflatoxins could compromise the macrophages functions; in particular, co-exposure to AFB1, AFB2, AFM1 and AFM2 may exert interactions which can significantly affect immunoreactivity.

Mechanisms underlying production and externalization of oxidized phosphatidylserine in apoptosis: involvement of mitochondria

The present study was performed by using selective inhibitors of caspase-8 and caspase-3 functioning upstream and downstream from mitochondria, respectively to determine whether mitochondria are involved in the mechanisms underlying production and externalization of oxidized phosphatidylserine (PSox) during Fas-mediated apoptosis. Treatment with anti-Fas antibody induced caspase-3 activation, chromatin condensation, release of cytochrome c (cyt c) from mitochondria into the cytosol as well as production of PSox and its exposure to the cell surface in Jurkat cells. Inhibition of caspase-8 by pretreatment with Z-IETD-FMK, a membrane permeable selective caspase-8 inhibitor reduced mitochondrial cyt c release, the amount of PSox not only within but also on the surface of Jurkat cells, caspase-3 activation, and apoptotic cell number after treatment with anti-Fas antibody. In contrast, Z-DEVD-FMK, a membrane permeable selective caspase-3 inhibitor was unable to inhibit cyt c release, and the amount of PSox both within and on the surface of the cells after anti-Fas antibody, although it suppressed caspase-3 activation and apoptosis. Thus, these results strongly suggest that mitochondria play an important role in production of PSox and subsequent its externalization during apoptosis.

Cryopreserved mesenchymal stromal cells display impaired immunosuppressive properties as a result of heat-shock response and impaired interferon-γ licensing

Human mesenchymal stromal cells (MSC) can suppress T-cell activation in vitro in an indoleamine 2,3-dioxygenase (IDO)-dependent manner. However, their clinical effects on immune ailments have been inconsistent, with a recent phase III study showing no benefit in acute graft-versus-host disease (GvHD). We here tested the hypothesis that the banked, cryopreserved MSC often used in clinical trials display biologic properties distinct from that of MSC in the log phase of growth typically examined in pre-clinical studies. In freshly thawed cryopreserved MSC derived from normal human volunteers, we observed that MSC up-regulate heat-shock proteins, are refractory to interferon (IFN)-γ-induced up-regulation of IDO, and are compromised in suppressing CD3/CD28-driven T cell proliferation. Immune suppressor activity, IFN-γ responsiveness and induction of IDO were fully restored following 24 h of MSC tissue culture post-thaw. These results highlight a possible cause for the inefficacy of MSC-based immunotherapy reported in clinical trials using cryopreserved MSC thawed immediately prior to infusion.

Structural characterization of oxidized glycerophosphatidylserine: evidence of polar head oxidation

Non-oxidized phosphatidylserine (PS) is known to play a key role in apoptosis but there is considerable research evidence suggesting that oxidized PS also plays a role in this event, leading to the increasing interest in studying PS oxidative modifications. In this work, different PS (1-palmitoyl-2-linoleoyl-sn-glycero-3-phospho-L-serine (PLPS), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS), and 1,2-dipalmitoyl-sn-glycero-3-phospho-L-serine (DPPS) were oxidized in vitro by hydroxyl radical, generated under Fenton reaction conditions, and the reactions were monitored by ESI-MS in negative mode. Oxidation products were then fractionated by thin layer chromatography (TLC) and characterized by tandem mass spectrometry (MS/MS). This approach allowed the identification of hydroxyl, peroxy, and keto derivatives due to oxidation of unsaturated fatty acyl chains. Oxidation products due to oxidation of serine polar head were also identified. These products, with lower molecular weight than the non-modified PS, were identified as [M - 29 - H](-) (terminal acetic acid), [M - 30 - H](-) (terminal acetamide), [M - 13 - H](-) (terminal hydroperoxyacetaldehyde), and [M - 13 - H](-) (terminal hydroxyacetaldehyde plus hydroxy fatty acyl chain). Phosphatidic acid was also formed in these conditions. These findings confirm the oxidation of the serine polar head induced by the hydroxyl radical. The identification of these modifications may be a valuable tool to evaluate phosphatidylserine alteration under physiopathologic conditions and also to help understand the biological role of phosphatidylserine oxidation in the apoptotic process and other biological functions.

Global phospholipidomics analysis reveals selective pulmonary peroxidation profiles upon inhalation of single-walled carbon nanotubes

It is commonly believed that nanomaterials cause nonspecific oxidative damage. Our mass spectrometry-based oxidative lipidomics analysis of all major phospholipid classes revealed highly selective patterns of pulmonary peroxidation after inhalation exposure of mice to single-walled carbon nanotubes. No oxidized molecular species were found in the two most abundant phospholipid classes: phosphatidylcholine and phosphatidylethanolamine. Peroxidation products were identified in three relatively minor classes of anionic phospholipids, cardiolipin, phosphatidylserine, and phosphatidylinositol, whereby oxygenation of polyunsaturated fatty acid residues also showed unusual substrate specificity. This nonrandom peroxidation coincided with the accumulation of apoptotic cells in the lung. A similar selective phospholipid peroxidation profile was detected upon incubation of a mixture of total lung lipids with H(2)O(2)/cytochrome c known to catalyze cardiolipin and phosphatidylserine peroxidation in apoptotic cells. The characterized specific phospholipid peroxidation signaling pathways indicate new approaches to the development of mitochondria-targeted regulators of cardiolipin peroxidation to protect against deleterious effects of pro-apoptotic effects of single-walled carbon nanotubes in the lung.

Gene-dependent cell death in yeast

Caspase-dependent apoptotic cell death has been extensively studied in cultured cells and during embryonic development, but the existence of analogous molecular pathways in single-cell species is uncertain. This has reduced enthusiasm for applying the advanced genetic tools available for yeast to study cell death regulation. However, partial characterization in mammals of additional genetically encoded cell death mechanisms, which lead to a range of dying cell morphologies and necrosis, suggests potential applications for yeast genetics. In this light, we revisited the topic of gene-dependent cell death in yeast to determine the prevalence of yeast genes with the capacity to contribute to cell-autonomous death. We developed a rigorous strategy by allowing sufficient time for gene-dependent events to occur, but insufficient time to evolve new populations, and applied this strategy to the Saccharomyces cerevisiae gene knockout collection. Unlike sudden heat shock, a ramped heat stimulus delivered over several minutes with a thermocycler, coupled with assessment of viability by automated counting of microscopic colonies revealed highly reproducible gene-specific survival phenotypes, which typically persist under alternative conditions. Unexpectedly, we identified over 800 yeast knockout strains that exhibit significantly increased survival following insult, implying that these genes can contribute to cell death. Although these death mechanisms are yet uncharacterized, this study facilitates further exploration.

Apoptotic cell clearance in chronic inflammation of lateral neck cysts

The mechanism driving accumulation of large numbers of apoptotic and necrotic neutrophils in inflamed lateral neck cysts (LNC), in the absence of infection, remains obscure. The cellular content of cysts obtained from 17 patients was co-cultured with human macrophages. Phagocytosis levels of cyst-derived neutrophils were determined and compared to the uptake of spontaneously apoptotic neutrophils. Simultaneously, the expression of cytokines in macrophages exposed to cyst contents was measured. In comparison to spontaneously apoptotic neutrophils, the phagocytosis of LNC-derived neutrophils by macrophages was inefficient. An inverse correlation between neutrophil content in LNC and their uptake was observed. Macrophages co-cultured with cyst contents responded with variable expression of IL-6, TNF-α and IL-10. The hindered clearance of apoptotic neutrophils in LNC may lead to secondary necrosis of these cells and stimulation of the inflammatory reaction. Together with local production of anti-inflammatory cytokines, this may fuel chronic inflammation in the cysts.