Phosphatidylserine, a death knell

The ability of human TIM1 to bind phosphatidylethanolamine enhances viral uptake and efferocytosis compared to rhesus and mouse orthologs

T-cell Immunoglobulin and Mucin (TIM)-family proteins facilitate the clearance of apoptotic cells, are involved in immune regulation, and promote infection of enveloped viruses. These processes are frequently studied in experimental animals such as mice or rhesus macaques, but functional differences among the TIM orthologs from these species have not been described. Previously, we reported that while all three human TIM proteins bind phosphatidylserine (PS), only human TIM1 (hTIM1) binds phosphatidylethanolamine (PE), and that this PE-binding ability contributes to both phagocytic clearance of apoptotic cells and virus infection. Here we show that rhesus macaque TIM1 (rhTIM1) and mouse TIM1 (mTIM1) bind PS but not PE and that their inability to bind PE makes them less efficient than hTIM1. We also show that alteration of only two residues of mTIM1 or rhTIM1 enables them to bind both PE and PS, and that these PE-binding variants are more efficient at phagocytosis and mediating viral entry. Further, we demonstrate that the mucin domain also contributes to the binding of the virions and apoptotic cells, although it does not directly bind phospholipid. Interestingly, contribution of the hTIM1 mucin domain is more pronounced in the presence of a PE-binding head domain. These results demonstrate that rhTIM1 and mTIM1 are inherently less functional than hTIM1, owing to their inability to bind PE and their less functional mucin domains. They also imply that mouse and macaque models underestimate the activity of hTIM1.

OxLDL enhances procoagulant activity of endothelial cells by TMEM16F-mediated phosphatidylserine exposure

Oxidized low-density lipoprotein (oxLDL), a key component in atherosclerosis and hyperlipidemia, is a risk factor for atherothrombosis in dyslipidemia, yet its mechanism is poorly understood. In this study, we used oxLDL-induced human aortic endothelial cells (HAECs) and high-fat diet (HFD)-fed mice as a hyperlipidemia model. Phosphatidylserine (PS) exposure, cytosolic Ca2+, reactive oxygen species (ROS), and lipid peroxidation were measured by flow cytometer. TMEM16F expression was detected by immunofluorescence, western blot, and reverse transcription polymerase chain reaction. Procoagulant activity (PCA) was measured by coagulation time, intrinsic/extrinsic factor Xase, and thrombin generation. We found that oxLDL-induced PS exposure and the corresponding PCA of HAECs were increased significantly compared with control, which could be inhibited over 90% by lactadherin. Importantly, TMEM16F expression in oxLDL-induced HAECs was upregulated by enhanced intracellular Ca2+ concentration, ROS, and lipid peroxidation, which led to PS exposure. Meanwhile, the knockdown of TMEM16F by short hairpin RNA significantly inhibited PS exposure in oxLDL-induced HAECs. Moreover, we observed that HFD-fed mice dramatically increased the progress of thrombus formation and accompanied upregulated TMEM16F expression by thromboelastography analysis, FeCl3-induced carotid artery thrombosis model, and western blot. Collectively, these results demonstrate that TMEM16F-mediated PS exposure may contribute to prothrombotic status under hyperlipidemic conditions, which may serve as a novel therapeutic target for the prevention of thrombosis in hyperlipidemia.

Antineoplastic effect of compounds C14 and P8 on TNBC and radioresistant TNBC cells by stabilizing the K-Ras4BG13D/PDE6δ complex

Introduction

Breast cancer (BC) is the leading cause of cancer-related deaths among women, with triple-negative breast cancer (TNBC) representing one of the most aggressive and treatment-resistant subtypes. In this study, we aimed to evaluate the antitumor potential of C14 and P8 molecules in both TNBC and radioresistant TNBC cells. These compounds were chosen for their ability to stabilize the complex formed by the overactivated form of K-Ras4BG13D and its membrane transporter (PDE6δ).

Methods

The antitumor potential of C14 and P8 was assessed using TNBC cell lines, MDA-MB-231, and the radioresistant derivative MDA-MB-231RR, both carrying the K-Ras4B> G13D mutation. We investigated the compounds' effects on K-Ras signaling pathways, cell viability, and tumor growth in vivo.

Results

Western blotting analysis determined the negative impact of C14 and P8 on the activation of mutant K-Ras signaling pathways in MDA-MB-231 and MDA-MB-231RR cells. Proliferation assays demonstrated their efficacy as cytotoxic agents against K-RasG13D mutant cancer cells and in inducing apoptosis. Clonogenic assays proven their ability to inhibit TNBC and radioresistant TNBC cell clonogenicity. In In vivo studies, C14 and P8 inhibited tumor growth and reduced proliferation, angiogenesis, and cell cycle progression markers.

Discussion

These findings suggest that C14 and P8 could serve as promising adjuvant treatments for TNBC, particularly for non-responders to standard therapies. By targeting overactivated K-Ras and its membrane transporter, these compounds offer potential therapeutic benefits against TNBC, including its radioresistant form. Further research and clinical trials are warranted to validate their efficacy and safety as novel TNBC treatments.

Biomimetic Nanomaterials for the Immunomodulation of the Cardiosplenic Axis Postmyocardial Infarction

The spleen is an important mediator of both adaptive and innate immunity. As such, attempts to modulate the immune response provided by the spleen may be conducive to improved outcomes for numerous diseases throughout the body. Here, biomimicry is used to rationally design nanomaterials capable of splenic retention and immunomodulation for the treatment of disease in a distant organ, the postinfarct heart. Engineered senescent erythrocyte-derived nanotheranostic (eSENTs) are generated, demonstrating significant uptake by the immune cells of the spleen including T and B cells, as well as monocytes and macrophages. When loaded with suberoylanilide hydroxamic acid (SAHA), the nanoagents exhibit a potent therapeutic effect, reducing infarct size by 14% at 72 h postmyocardial infarction when given as a single intravenous dose 2 h after injury. These results are supportive of the hypothesis that RBC-derived biomimicry may provide new approaches for the targeted modulation of the pathological processes involved in myocardial infarction, thus further experiments to decisively confirm the mechanisms of action are currently underway. This novel concept may have far-reaching applicability for the treatment of a number of both acute and chronic conditions where the immune responses are either stimulated or suppressed by the splenic (auto)immune milieu.

Biological age as estimated by baseline circulating metabolites is associated with incident diabetes and mortality

OBJECTIVES

It is unclear how metabolomic assessment of biological aging performs in non-White populations and whether such an approach can predict future mortality. We aimed to evaluate the application of serum metabolomics combined with machine learning methodologies to predict incident diabetes and mortality in a Thai population.

DESIGN, SETTING AND PARTICIPANTS

We analyzed serum samples and mortality data over 11 years from among 454 participants with no previous history of diabetes and with a fasting plasma glucose ≥85th percentile (5.4 mmol/L) but <7 mmol/L.

MEASUREMENTS

Untargeted serum metabolomics were assessed using liquid chromatography/mass spectrometry. A deep artificial neural network was used to predict biological age based on serum metabolite profiles and chronological age.

RESULTS

The mean age of participants was 40.5 ± 6.4 years, and 70.8% were men. We found a significant positive correlation between metabolomic age and chronological age (r = 0.71, P < 0.001). After 5 years, 61 of 404 participants with available glycated hemoglobin status (15.1%) progressed to diabetes. Chronological age was associated with incident diabetes but was not significant (P = 0.08), after adjusting for BMI and sex. Metabolomic age was significantly related to incident diabetes after controlling for BMI and sex (P < 0.05). Over the 11-year follow-up, 10 participants died owing to non-accidental causes. When metabolomic age and chronological age were included together in the model, metabolomic age (but not chronological age) was associated with mortality, independent of age, sex, and BMI. Among all identifiable metabolites, beta-D-mannosylphosphodecaprenyl and phosphatidylserines were the five leading metabolites associated with mortality.

CONCLUSION

We concluded that serum metabolomic profile was associated with incident diabetes as well as mortality over our 11-year study period, which may render it potentially useful in assessing biological aging in humans.

Cancer Immunotherapy Based on Cell Membrane-Coated Nanocomposites Augmenting cGAS/STING Activation by Efferocytosis Blockade

Innate immunity triggered by the cGAS/STING pathway has the potential to improve cancer immunotherapy. Previously, the authors reported that double-stranded DNA (dsDNA) released by dying tumor cells can trigger the cGAS/STING pathway. However, owing to efferocytosis, dying tumor cells are engulfed and cleared before the damaged dsDNA is released; hence, immunologic tolerance and immune escape occur. Herein, a cancer-cell-membrane biomimetic nanocomposites that exhibit tumor-immunotherapeutic effects are synthesized by augmenting the cGAS/STING pathway and suppressing efferocytosis. Once internalized by cancer cells, a combined chemo/chemodynamic therapy would be triggered, which damages their nuclear and mitochondrial DNA. Furthermore, the releasing Annexin A5 protein could inhibit efferocytosis effect and promote immunostimulatory secondary necrosis by preventing phosphatidylserine exposure, resulting in the burst release of dsDNA. These dsDNA fragments, as molecular patterns to immunogenic damage, escape from the cancer cells, activate the cGAS/STING pathway, enhance cross-presentation inside dendritic cells, and promote M1-polarization of tumor-associated macrophages. In vivo experiments suggest that the proposed nanocomposite could recruit cytotoxic T-cells and facilitate long-term immunological memory. Moreover, when combined with immune-checkpoint blockades, it could augment the immune response. Therefore, this novel biomimetic nanocomposite is a promising strategy for generating adaptive antitumor immune responses.

Effects of Nitro-Oxidative Stress on Biomolecules: Part 1-Non-Reactive Molecular Dynamics Simulations

Plasma medicine, or the biomedical application of cold atmospheric plasma (CAP), is an expanding field within plasma research. CAP has demonstrated remarkable versatility in diverse biological applications, including cancer treatment, wound healing, microorganism inactivation, and skin disease therapy. However, the precise mechanisms underlying the effects of CAP remain incompletely understood. The therapeutic effects of CAP are largely attributed to the generation of reactive oxygen and nitrogen species (RONS), which play a crucial role in the biological responses induced by CAP. Specifically, RONS produced during CAP treatment have the ability to chemically modify cell membranes and membrane proteins, causing nitro-oxidative stress, thereby leading to changes in membrane permeability and disruption of cellular processes. To gain atomic-level insights into these interactions, non-reactive molecular dynamics (MD) simulations have emerged as a valuable tool. These simulations facilitate the examination of larger-scale system dynamics, including protein-protein and protein-membrane interactions. In this comprehensive review, we focus on the applications of non-reactive MD simulations in studying the effects of CAP on cellular components and interactions at the atomic level, providing a detailed overview of the potential of CAP in medicine. We also review the results of other MD studies that are not related to plasma medicine but explore the effects of nitro-oxidative stress on cellular components and are therefore important for a broader understanding of the underlying processes.

Molecular regulation and therapeutic implications of cell death in pulmonary hypertension

Pulmonary hypertension (PH) is a clinical and pathophysiological syndrome caused by changes in pulmonary vascular structure or function that results in increased pulmonary vascular resistance and pulmonary arterial pressure, and it is characterized by pulmonary endothelial dysfunction, pulmonary artery media thickening, pulmonary vascular remodeling, and right ventricular hypertrophy, all of which are driven by an imbalance between the growth and death of pulmonary vascular cells. Programmed cell death (PCD), different from cell necrosis, is an active cellular death mechanism that is activated in response to both internal and external factors and is precisely regulated by cells. More than a dozen PCD modes have been identified, among which apoptosis, autophagy, pyroptosis, ferroptosis, necroptosis, and cuproptosis have been proven to be involved in the pathophysiology of PH to varying degrees. This article provides a summary of the regulatory patterns of different PCD modes and their potential effects on PH. Additionally, it describes the current understanding of this complex and interconnected process and analyzes the therapeutic potential of targeting specific PCD modes as molecular targets.

P34L Mutation of swine TIM-1 enhances its ability to mediate Japanese encephalitis virus infection

Japanese encephalitis virus (JEV) is a major causative agent of neurological infection affecting humans and pigs. Human T Cell Immunoglobulin and Mucin Domain 1 (hTIM-1) enhances the infection of JEV through virion-associated phosphatidylserine (PS) binding. Here, five swine TIM-1 (sTIM-1) gene variants were cloned from pig lung tissues by reverse-transcriptase polymerase chain reaction (RT-PCR). Sequence alignment analysis revealed that the gene homology between the sTIM-1 and hTIM-1 was 42.3-43.8%. Furthermore, ectopic expression of all five sTIM-1 variants in 293 T cells can promote JEV entry and infection. However, sTIM-1 V3 exhibited significantly less potent at promoting virus entry compared to the other four variants. Further studies revealed that the 34th amino acid of sTIM-1is critical for the entry of JEV, which is Pro34 in sTIM-1V3 while Leu34 in other four sTIM-1 variants. Mechanically, leucine at locus 34 was associated with the membrane distribution of sTIM-1, thereby affecting viral entry and infection. In total, our findings provide evidence that the PS receptor sTIM-1 promotes the infection of JEV and that the 34th amino acid position is critical for sTIM-1 to mediate viral infection.

Externalized phosphatidylinositides on apoptotic cells are eat-me signals recognized by CD14

Apoptotic cells are rapidly engulfed and removed by phagocytes after displaying cell surface eat-me signals. Among many phospholipids, only phosphatidylserine (PS) is known to act as an eat-me signal on apoptotic cells. Using unbiased proteomics, we identified externalized phosphatidylinositides (PIPs) as apoptotic eat-me signals recognized by CD14⁺ phagocytes. Exofacial PIPs on the surfaces of early and late-apoptotic cells were observed in patches and blebs using anti-PI(3,4,5)P₃ antibody, AKT- and PLCδ PH-domains, and CD14 protein. Phagocytosis of apoptotic cells was blocked either by masking exofacial PIPs or by CD14 knockout in phagocytes. We further confirmed that exofacial PIP⁺ thymocytes increased dramatically after in vivo irradiation and that exofacial PIP⁺ cells represented more significant populations in tissues of Cd14^−/− than WT mice, especially after induction of apoptosis. Our findings reveal exofacial PIPs to be previously unknown cell death signals recognized by CD14⁺ phagocytes.

Myocardial ischemia/reperfusion injury: Mechanisms of injury and implications for management (Review)

Myocardial infarction is one of the primary causes of mortality in patients with coronary heart disease worldwide. Early treatment of acute myocardial infarction restores blood supply of ischemic myocardium and decreases the mortality risk. However, when the interrupted myocardial blood supply is recovered within a certain period of time, it causes more serious damage to the original ischemic myocardium; this is known as myocardial ischemia/reperfusion injury (MIRI). The pathophysiological mechanisms leading to MIRI are associated with oxidative stress, intracellular calcium overload, energy metabolism disorder, apoptosis, endoplasmic reticulum stress, autophagy, pyroptosis, necroptosis and ferroptosis. These interplay with one another and directly or indirectly lead to aggravation of the effect. In the past, apoptosis and autophagy have attracted more attention but necroptosis and ferroptosis also serve key roles. However, the mechanism of MIRI has not been fully elucidated. The present study reviews the mechanisms underlying MIRI. Based on current understanding of the pathophysiological mechanisms of MIRI, the association between cell death-associated signaling pathways were elaborated, providing direction for investigation of novel targets in clinical treatment.

Structural effects of zinc on phosphatidylserine-containing lipid membranes: kinetic analysis of membrane reorganization

Zinc induces reorganization of phosphatidylserine-containing lipid membranes.

Crystal structures of phosphatidyl serine synthase PSS reveal the catalytic mechanism of CDP-DAG alcohol O-phosphatidyl transferases

Phospholipids are the major components of the membrane in all type of cells and organelles. They also are critical for cell metabolism, signal transduction, the immune system and other critical cell functions. The biosynthesis of phospholipids is a complex multi-step process with high-energy intermediates. Several enzymes in different metabolic pathways are involved in the initial phospholipid synthesis and its subsequent conversion. While the "Kennedy pathway" is the main pathway in mammalian cells, in bacteria and lower eukaryotes the precursor CDP-DAG is used in the de novo pathway by CDP-DAG alcohol O-phosphatidyl transferases to synthetize the basic lipids. Here we present the high-resolution structures of phosphatidyl serine synthase from Methanocaldococcus jannaschii crystallized in four different states. Detailed structural and functional analysis of the different structures allowed us to identify the substrate binding site and show how CDP-DAG, serine and two essential metal ions are bound and oriented relative to each other. In close proximity to the substrate binding site, two anions were identified that appear to be highly important for the reaction. The structural findings were confirmed by functional activity assays and suggest a model for the catalytic mechanism of CDP-DAG alcohol O-phosphatidyl transferases, which synthetize the phospholipids essential for the cells.

A metal-free salalen ligand with anti-tumor and synergistic activity in resistant leukemia and solid tumor cells via mitochondrial pathway

PURPOSE

Since the discovery of the well-known cis-platin, transition metal complexes are highly recognized as cytostatic agents. However, toxic side effects of the metal ions present in the complexes may pose significant problems for their future development. Therefore, we investigated the metal-free salalen ligand WQF 044.

METHODS

DNA fragmentations in leukemia (Nalm6) and solid tumor cells (BJAB, MelHO, MCF-7, RM82) proved the apoptotic effects of WQF 044, its overcoming of resistances and the cellular pathways that are affected by the substance. The apoptotic mechanisms finding were supported by western blot analysis, measurement of the mitochondrial membrane potential and polymerase chain reactions.

RESULTS

A complex intervention in the mitochondrial pathway of apoptosis with a Bcl-2 and caspase dependence was observed. Additionally, a wide range of tumors were affected by the ligand in a low micromolar range in-vitro. The compound overcame multidrug resistances in P-gp over-expressed acute lymphoblastic leukemia and CD95-downregulated Ewing's sarcoma cells. Quite remarkable synergistic effects with vincristine were observed in Burkitt-like lymphoma cells.

CONCLUSION

The investigation of a metal-free salalen ligand as a potential anti-cancer drug revealed in promising results for a future clinical use.

Phosphatidylserine externalized on the colonic capillaries as a novel pharmacological target for IBD therapy

Inflammatory bowel disease (IBD) is a chronic and relapsing disorder for many people associated with poor health. Although there are some clinical drugs for IBD treatment, the development of effective therapeutics on IBD patients has always been necessary. Here, we show that externalized phosphatidylserine (PS) is observed on the surface of colonic capillaries. Annexin A5 (ANXA5) with high affinity for PS has a good targeting to the colon and effectively alleviates experimental colitis. In contrast, ANXA5 mutant (A5m) lacking the PS-binding ability, has no accumulation in the colon and no therapeutic effects on colitis. Mechanistic investigations indicate that ANXA5 reduces the inflammatory cell infiltration by inhibiting endothelial cell activation dependent on PS-binding ability. With the increasing of PS exposure on activated HUVECs (human umbilical vein endothelial cells), ANXA5 binding induces the internalization of TLR4 via PS-dependent endocytosis. We provide new insights on the molecular mechanism of ANXA5 for its anti-inflammatory effect. Our data suggest that PS-externalization is a potential target of ANXA5 aiming at targeted drug delivery (TDD) for IBD treatment.

Phosphatidylserine Supplementation as a Novel Strategy for Reducing Myocardial Infarct Size and Preventing Adverse Left Ventricular Remodeling

Phosphatidylserines are known to sustain skeletal muscle activity during intense activity or hypoxic conditions, as well as preserve neurocognitive function in older patients. Our previous studies pointed out a potential cardioprotective role of phosphatidylserine in heart ischemia. Therefore, we investigated the effects of phosphatidylserine oral supplementation in a mouse model of acute myocardial infarction (AMI). We found out that phosphatidylserine increases, significantly, the cardiomyocyte survival by 50% in an acute model of myocardial ischemia-reperfusion. Similar, phosphatidylserine reduced significantly the infarcted size by 30% and improved heart function by 25% in a chronic model of AMI. The main responsible mechanism seems to be up-regulation of protein kinase C epsilon (PKC-ε), the main player of cardio-protection during pre-conditioning. Interestingly, if the phosphatidylserine supplementation is started before induction of AMI, but not after, it selectively inhibits neutrophil's activation, such as Interleukin 1 beta (IL-1β) expression, without affecting the healing and fibrosis. Thus, phosphatidylserine supplementation may represent a simple way to activate a pre-conditioning mechanism and may be a promising novel strategy to reduce infarct size following AMI and to prevent myocardial injury during myocardial infarction or cardiac surgery. Due to the minimal adverse effects, further investigation in large animals or in human are soon possible to establish the exact role of phosphatidylserine in cardiac diseases.

Oxygenated phosphatidylethanolamine navigates phagocytosis of ferroptotic cells by interacting with TLR2

During cancer therapy, phagocytic clearance of dead cells plays a vital role in immune homeostasis. The nonapoptotic form of cell death, ferroptosis, exhibits extraordinary potential in tumor treatment. However, the phagocytosis mechanism that regulates the engulfment of ferroptotic cells remains unclear. Here, we establish a novel pathway for phagocytic clearance of ferroptotic cells that is different from canonical mechanisms by using diverse ferroptosis models evoked by GPX4 dysfunction/deficiency. We identified the oxidized phospholipid, 1-steaoryl-2-15-HpETE-sn-glycero-3-phosphatidylethanolamine (SAPE-OOH), as a key eat-me signal on the ferroptotic cell surface. Enriching the plasma membrane with SAPE-OOH increased the efficiency of phagocytosis of ferroptotic cells by macrophage, a process that was suppressed by lipoprotein-associated phospholipase A₂. Ligand fishing, lipid blotting, and cellular thermal shift assay screened and identified TLR2 as a membrane receptor that directly recognized SAPE-OOH, which was further confirmed by TLR2 inhibitors and gene silencing studies. A mouse mammary tumor model of ferroptosis verified SAPE-OOH and TLR2 as critical players in the clearance of ferroptotic cells in vivo. Taken together, this work demonstrates that SAPE-OOH on ferroptotic cell surface acts as an eat-me signal and navigates phagocytosis by targeting TLR2 on macrophages.

Quantitative analysis of red blood cell membrane phospholipids and modulation of cell-macrophage interactions using cyclodextrins

The plasma membrane of eukaryotic cells is asymmetric with respect to its phospholipid composition. Analysis of the lipid composition of the outer leaflet is important for understanding cell membrane biology in health and disease. Here, a method based on cyclodextrin-mediated lipid exchange to characterize the phospholipids in the outer leaflet of red blood cells (RBCs) is reported. Methyl-α-cyclodextrin, loaded with exogenous lipids, was used to extract phospholipids from the membrane outer leaflet, while delivering lipids to the cell to maintain cell membrane integrity. Thin layer chromatography and lipidomics demonstrated that the extracted lipids were from the membrane outer leaflet. Phosphatidylcholines (PC) and sphingomyelins (SM) were the most abundant phospholipids in the RBCs outer leaflet with PC 34:1 and SM 34:1 being the most abundant species. Fluorescence quenching confirmed the delivery of exogenous lipids to the cell outer leaflet. The developed lipid exchange method was then used to remove phosphatidylserine, a phagocyte recognition marker, from the outer leaflet of senescent RBCs. Senescent RBCs with reconstituted membranes were phagocytosed in significantly lower amounts compared to control cells, demonstrating the efficiency of the lipid exchange process and its application in modifying cell–cell interactions.

Burst release of encapsulated annexin A5 in tumours boosts cytotoxic T-cell responses by blocking the phagocytosis of apoptotic cells

Cancer immunotherapies, particularly therapeutic vaccination, do not typically generate robust anti-tumour immune responses. Here, we show that the intratumoral burst release of the protein annexin A5 from intravenously injected hollow mesoporous nanoparticles made of diselenide-bridged organosilica generates robust anti-tumour immunity by exploiting the capacity of primary tumours to act as antigen depots. Annexin A5 blocks immunosuppressive apoptosis and promotes immunostimulatory secondary necrosis by binding to the phagocytic marker phosphatidylserine on dying tumour cells. In mice bearing large established tumours, the burst release of annexin A5 owing to diselenide-bond cleavage under the oxidizing conditions of the tumour microenvironment and the reducing intracellular conditions of tumour cells induced systemic cytotoxic T-cell responses and immunological memory associated with tumour regression and the prevention of relapse, and led to complete tumour eradication in about 50% of mice with orthotopic breast tumours. Reducing apoptosis signalling via in situ vaccination could be a versatile strategy for the generation of adaptive anti-tumour immune responses.

Biosynthetic Enzymes of Membrane Glycerophospholipid Diversity as Therapeutic Targets for Drug Development

Biophysical properties of membranes are dependent on their glycerophospholipid compositions. Lysophospholipid acyltransferases (LPLATs) selectively incorporate fatty chains into lysophospholipids to affect the fatty acid composition of membrane glycerophospholipids. Lysophosphatidic acid acyltransferases (LPAATs) of the 1-acylglycerol-3-phosphate O-acyltransferase (AGPAT) family incorporate fatty chains into phosphatidic acid during the de novo glycerophospholipid synthesis in the Kennedy pathway. Other LPLATs of both the AGPAT and the membrane bound O-acyltransferase (MBOAT) families further modify the fatty chain compositions of membrane glycerophospholipids in the remodeling pathway known as the Lands' cycle. The LPLATs functioning in these pathways possess unique characteristics in terms of their biochemical activities, regulation of expressions, and functions in various biological contexts. Essential physiological functions for LPLATs have been revealed in studies using gene-deficient mice, and important roles for several enzymes are also indicated in human diseases where their mutation or dysregulation causes or contributes to the pathological condition. Now several LPLATs are emerging as attractive therapeutic targets, and further understanding of the mechanisms underlying their physiological and pathological roles will aid in the development of novel therapies to treat several diseases that involve altered glycerophospholipid metabolism.

Disruption of Phosphatidylserine Synthesis or Trafficking Reduces Infectivity of Ebola Virus

The outer leaflet of the viral membrane of Ebola virus (EBOV) virions is enriched with phosphatidylserine (PtdSer), which is thought to play a central role in viral tropism, entry, and virus-associated immune evasion. We investigated the effects of inhibiting synthesis and/or export of PtdSer to the cell surface of infected cells on viral infectivity. Knockdown of both PtdSer synthase enzymes, PTDSS1 and PTDSS2, effectively decreased viral production. Decreased PtdSer expression resulted in an accumulation of virions at the plasma membrane and adjacent of intracellular organelles, suggesting that virion budding is impaired. The addition of inhibitors that block normal cellular trafficking of PtdSer to the plasma membrane resulted in a similar accumulation of virions and reduced viral replication. These findings demonstrate that plasma membrane-associated PtdSer is required for efficient EBOV budding, increasing EBOV infectivity, and could constitute a potential therapeutic target for the development of future countermeasures against EBOV.

TIM-1 As a Signal Receptor Triggers Dengue Virus-Induced Autophagy

Dengue virus (DENV) infection triggers the activation of autophagy to facilitate the viral replication cycle from various aspects. Although a number of stimulators are proposed to activate autophagy, none of them appears prior to the uncoating process. Given that T-cell immunoglobulin and mucin domain 1 (TIM-1) receptor is a putative DENV receptor and promotes apoptotic body clearance by autophagy induction, it raises the possibility that TIM-1 may participate in the activation of DENV-induced autophagy. In this study, confocal images first revealed the co-localization of TIM-1 with autophagosomes in DENV-induced autophagy rather than rapamycin-induced autophagy, suggesting the co-transportation of TIM-1 with DENV during infection. The treatment of siRNA to knockdown TIM-1 expression in DENV-infected GFP-microtubule-associated protein light chain 3 (LC3)-Huh7.5 cells revealed that TIM-1 is required not only for DENV cellular internalization but also for autophagy activation. Furthermore, knockdown p85, a subunit of phosphoinositide 3-kinases (PI3Ks), which is co-localized with TIM-1 at rab5-positive endosomes caused the reduction of autophagy, indicating that TIM-1-mediated DENV-induced autophagy requires p85. Taken together, the current study uncovered TIM-1 as a novel factor for triggering autophagy in DENV infection through TIM-1-p85 axis, in addition to serving as a DENV receptor.

Immunization With Mycobacterium tuberculosis Antigens Encapsulated in Phosphatidylserine Liposomes Improves Protection Afforded by BCG

Liposomes have been long considered as a vaccine delivery system but this technology remains to be fully utilized. Here, we describe a novel liposome-based subunit vaccine formulation for tuberculosis (TB) based on phosphatidylserine encapsulating two prominent TB antigens, Ag85B, and ESAT-6. We show that the resulting liposomes (Lipo-AE) are stable upon storage and can be readily taken up by antigen presenting cells and that their antigenic cargo is delivered and processed within endosomal cell compartments. The Lipo-AE vaccine formulation combined with the PolyIC adjuvant induced a mixed Th1/Th17-Th2 immune response to Ag85B but only a weak response to ESAT-6. An immunization regimen based on systemic delivery followed by mucosal boost with Lipo-AE resulted in the accumulation of resident memory T cells in the lungs. Most importantly though, when Lipo-AE vaccine candidate was administered to BCG-immunized mice subsequently challenged with low dose aerosol Mycobacterium tuberculosis, we observed a significant reduction of the bacterial load in the lungs and spleen compared to BCG alone. We therefore conclude that the immunization with mycobacterial antigens delivered by phosphatidylserine based liposomes in combination with Poly:IC adjuvant may represent a novel BCG boosting vaccination strategy.

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.

Inflammation Resolution and the Induction of Granulocyte Apoptosis by Cyclin-Dependent Kinase Inhibitor Drugs

Inflammation is a necessary dynamic tissue response to injury or infection and it's resolution is essential to return tissue homeostasis and function. Defective or dysregulated inflammation resolution contributes significantly to the pathogenesis of many, often common and challenging to treat human conditions. The transition of inflammation to resolution is an active process, involving the clearance of inflammatory cells (granulocytes), a change of mediators and their receptors, and prevention of further inflammatory cell infiltration. This review focuses on the use of cyclin dependent kinase inhibitor drugs to pharmacologically target this inflammatory resolution switch, specifically through inducing granulocyte apoptosis and phagocytic clearance of apoptotic cells (efferocytosis). The key processes and pathways required for granulocyte apoptosis, recruitment of phagocytes and mechanisms of engulfment are discussed along with the cumulating evidence for cyclin dependent kinase inhibitor drugs as pro-resolution therapeutics.

Proteins Regulating Microvesicle Biogenesis and Multidrug Resistance in Cancer

Microvesicles (MV) are emerging as important mediators of intercellular communication. While MVs are important signaling vectors for many physiological processes, they are also implicated in cancer pathology and progression. Cellular activation is perhaps the most widely reported initiator of MV biogenesis, however, the precise mechanism remains undefined. Uncovering the proteins involved in regulating MV biogenesis is of interest given their role in the dissemination of deleterious cancer traits. MVs shed from drug-resistant cancer cells transfer multidrug resistance (MDR) proteins to drug-sensitive cells and confer the MDR phenotype in a matter of hours. MDR is attributed to the overexpression of ABC transporters, primarily P-glycoprotein and MRP1. Their expression and functionality is dependent on a number of proteins. In particular, FERM domain proteins have been implicated in supporting the functionality of efflux transporters in drug-resistant cells and in recipient cells during intercellular transfer by vesicles. Herein, the most recent research on the proteins involved in MV biogenesis and in the dissemination of MV-mediated MDR are discussed. Attention is drawn to unanswered questions in the literature that may prove to be of benefit in ongoing efforts to improve clinical response to chemotherapy and circumventing MDR.

Heat Shock Proteins as Immunomodulants

Heat shock proteins (Hsps) are conserved molecules whose main role is to facilitate folding of other proteins. Most Hsps are generally stress-inducible as they play a particularly important cytoprotective role in cells exposed to stressful conditions. Initially, Hsps were generally thought to occur intracellulary. However, recent work has shown that some Hsps are secreted to the cell exterior particularly in response to stress. For this reason, they are generally regarded as danger signaling biomarkers. In this way, they prompt the immune system to react to prevailing adverse cellular conditions. For example, their enhanced secretion by cancer cells facilitate targeting of these cells by natural killer cells. Notably, Hsps are implicated in both pro-inflammatory and anti-inflammatory responses. Their effects on immune cells depends on a number of aspects such as concentration of the respective Hsp species. In addition, various Hsp species exert unique effects on immune cells. Because of their conservation, Hsps are implicated in auto-immune diseases. Here we discuss the various metabolic pathways in which various Hsps manifest immune modulation. In addition, we discuss possible experimental variations that may account for contradictory reports on the immunomodulatory function of some Hsps.

Magnetic-activated cell sorting is not completely effective at reducing sperm DNA fragmentation

PURPOSE

To determine whether there is a homogeneous reduction of sperm DNA fragmentation (SDF) in sperm samples recovered from the MACS procedure, compared to spermatozoa in the initial ejaculate (NEAT) and those retained in the column.

METHODS

This study investigated the relative change in sperm DNA quality (SDF) of neat ejaculates (10 idiopathic infertile and 10 normozoospermic patients) to subpopulations of spermatozoa that had passed through the column (MACS-) and those retained (MACS+) by the annexin-V conjugated microbeads.

RESULTS

While the MACS protocol was capable of reducing the mean proportion of SDF (59.2%; P = 0.000) and sperm with highly degraded DNA (SDD; 65.7%, P = 0.000) in all patients, the reduction was not homogeneous across the patient cohort. A significant positive correlation (r = 0.772, P = 0.000) was apparent between the level of SDF in the NEAT ejaculate and the efficacy of SDF reduction observed in the MACS- fraction.

CONCLUSION

MACS is capable of reducing the proportion of SDF, especially spermatozoa with a highly degraded DNA molecule. However, this reduction did not preclude the presence of a small subpopulation of spermatozoa with damaged DNA in the MACS- fraction. The MACS protocol was two- to threefold more efficient when the SDF in NEAT ejaculate was equal to or greater than 30%. In 4 of 20 individuals, the level of SDF after MACS resulted in semen for ICSI with a higher or non-significant reduction when compared to SDF observed in the NEAT ejaculate.

Application of molecular imaging technology in neurotoxicology research

Molecular imaging has been widely applied in preclinical research. Among these new molecular imaging modalities, microPET imaging can be utilized as a very powerful tool that can obtain the measurements of multiple biological processes in various organs repeatedly in a same subject. This review discusses how this new approach provides noninvasive biomarker for neurotoxicology research and summarizes microPET findings with multiple radiotracers on the variety of neurotoxicity induced by toxic agents in both the rodent and the nonhuman primate brain.

Cell type-resolved human lung lipidome reveals cellular cooperation in lung function

Cell type-resolved proteome analyses of the brain, heart and liver have been reported, however a similar effort on the lipidome is currently lacking. Here we applied liquid chromatography-tandem mass spectrometry to characterize the lipidome of major lung cell types isolated from human donors, representing the first lipidome map of any organ. We coupled this with cell type-resolved proteomics of the same samples (available at Lungmap.net). Complementary proteomics analyses substantiated the functional identity of the isolated cells. Lipidomics analyses showed significant variations in the lipidome across major human lung cell types, with differences most evident at the subclass and intra-subclass (i.e. total carbon length of the fatty acid chains) level. Further, lipidomic signatures revealed an overarching posture of high cellular cooperation within the human lung to support critical functions. Our complementary cell type-resolved lipid and protein datasets serve as a rich resource for analyses of human lung function.

Membrane heat shock protein 70: a theranostic target for cancer therapy

Members of the 70 kDa stress protein family are found in nearly all subcellular compartments of nucleated cells where they fulfil a number of chaperoning functions. Heat shock protein 70 (HSP70), also termed HSPA1A, the major stress-inducible member of this family is overexpressed in a large variety of different tumour types. Apart from its intracellular localization, a tumour-selective HSP70 membrane expression has been determined. A membrane HSP70–positive tumour phenotype is associated with aggressiveness and therapy resistance, but also serves as a recognition structure for targeted therapies. Furthermore, membrane-bound and extracellularly residing HSP70 derived from tumour cells play pivotal roles in eliciting anti-tumour immune responses. Herein, we want to shed light on the multiplicity of different activities of HSP70, depending on its intracellular, membrane and extracellular localization with the goal to use membrane HSP70 as a target for novel therapies including nanoparticle-based approaches for the treatment of cancer.

This article is part of the theme issue ‘Heat shock proteins as modulators and therapeutic targets of chronic disease: an integrated perspective’.

Real-Time Imaging of Retinal Ganglion Cell Apoptosis

Monitoring real-time apoptosis in-vivo is an unmet need of neurodegeneration science, both in clinical and research settings. For patients, earlier diagnosis before the onset of symptoms provides a window of time in which to instigate treatment. For researchers, being able to objectively monitor the rates of underlying degenerative processes at a cellular level provides a biomarker with which to test novel therapeutics. The DARC (Detection of Apoptosing Retinal Cells) project has developed a minimally invasive method using fluorescent annexin A5 to detect rates of apoptosis in retinal ganglion cells, the key pathological process in glaucoma. Numerous animal studies have used DARC to show efficacy of novel, pressure-independent treatment strategies in models of glaucoma and other conditions where retinal apoptosis is reported, including Alzheimer’s disease. This may forge exciting new links in the clinical science of treating both cognitive and visual decline. Human trials are now underway, successfully demonstrating the safety and efficacy of the technique to differentiate patients with progressive neurodegeneration from healthy individuals. We review the current perspectives on retinal ganglion cell apoptosis, the way in which this can be imaged, and the exciting advantages that these future methods hold in store.

Preparation and Properties of Asymmetric Synthetic Membranes Based on Lipid and Polymer Self-Assembly

Cell membrane asymmetry is a common structural feature of all biological cells. Researchers have tried for decades to better study its formation and its function in membrane-regulated phenomena. In particular, there has been increasing interest in developing synthetic asymmetric membrane models in the laboratory, with the aim of studying basic physical chemistry properties that may be correlated to a relevant biological function. The present article aims to summarize the main presented approaches to prepare asymmetric membranes, which are most often made from lipids, polymers, or a combination of both.

Review of the Association between Splenectomy and Chronic Thromboembolic Pulmonary Hypertension

Recent evidence suggests that there may be a link between splenectomy and the later development of pulmonary hypertension, in particular World Health Organization group IV pulmonary hypertension (chronic thromboembolic pulmonary hypertension). Epidemiological studies have demonstrated an odds ratio as high as 18 for the development of chronic thromboembolic pulmonary hypertension after splenectomy in comparison with matched control subjects who have not undergone splenectomy. The mechanisms governing the association between removal of the spleen and the subsequent development of chronic thromboembolic pulmonary hypertension remain incompletely understood; however, recent advances in understanding of coagulation homeostasis have shed some light on this association. Splenectomy increases the risk of venous thromboembolic disease, a necessary precursor of chronic thromboembolic pulmonary hypertension, by generating a prothrombotic state. This prothrombotic state likely results from a reduction in the removal of circulating procoagulant factors from the bloodstream after splenectomy. Although much is to be learned, circulating microparticles have emerged as the most likely mediator for the development of thrombosis after splenectomy. Apparently because of a reduction in reticuloendothelial cell clearance, microparticle levels are elevated in patients after splenectomy. Elevated circulating microparticle levels have been linked to thromboembolism and pulmonary hypertension in a dose-dependent fashion. It is important for health care providers to be aware of the link between splenectomy and chronic thromboembolic pulmonary hypertension. We are optimistic that clarification of the exact mechanisms that govern this association will yield clinical guidelines and potential treatments.

Apoptotic Cell Clearance in Drosophila melanogaster

The swift clearance of apoptotic cells (ACs) (efferocytosis) by phagocytes is a critical event during development of all multicellular organisms. It is achieved through phagocytosis by professional or amateur phagocytes. Failure in this process can lead to the development of inflammatory autoimmune or neurodegenerative diseases. AC clearance has been conserved throughout evolution, although many details in its mechanisms remain to be explored. It has been studied in the context of mammalian macrophages, and in the nematode Caenorhabditis elegans, which lacks “professional” phagocytes such as macrophages, but in which other cell types can engulf apoptotic corpses. In Drosophila melanogaster, ACs are engulfed by macrophages, glial, and epithelial cells. Drosophila macrophages perform similar functions to those of mammalian macrophages. They are professional phagocytes that participate in phagocytosis of ACs and pathogens. Study of AC clearance in Drosophila has identified some key elements, like the receptors Croquemort and Draper, promoting Drosophila as a suitable model to genetically dissect this process. In this review, we survey recent works of AC clearance pathways in Drosophila, and discuss the physiological outcomes and consequences of this process.

Microparticles in Hematological Malignancies: Role in Coagulopathy and Tumor Pathogenesis

Microparticles (MP) are submicron vesicles released from various cells in response to activation, injury or apoptosis. They contain different structural and functional proteins and RNAs, which contribute to physiological intercellular "crosstalk" and to the pathogenesis of various diseases including cancer. In hematological malignancies, these MPs participate in the initiation and propagation of thrombosis through different pathways. They have a role in the angiogenesis, malignant cell survival and metastasis. MPs act as a mediator of resistance of leukemic cells to chemotherapy. The number of MPs is one of the prognostic factors following stem cell transplant, and studies have also found they contribute to the pathogenesis of graft versus host disease. MPs are being tested as therapeutic options in leukemias and graft versus host disease. Future studies should help us understand the interactions between MPs and cancer cells better, thereby opening new approaches for treatment of hematological malignancies.

A Novel Therapeutic Strategy for Cancer Using Phosphatidylserine Targeting Stearylamine-Bearing Cationic Liposomes

There is a pressing need for a ubiquitously expressed antigen or receptor on the tumor surface for successful mitigation of the deleterious side effects of chemotherapy. Phosphatidylserine (PS), normally constrained to the intracellular surface, is exposed on the external surface of tumors and most tumorigenic cell lines. Here we report that a novel PS-targeting liposome, phosphatidylcholine-stearylamine (PC-SA), induced apoptosis and showed potent anticancer effects as a single agent against a majority of cancer cell lines. We experimentally proved that this was due to a strong affinity for and direct interaction of these liposomes with PS. Complexation of the chemotherapeutic drugs doxorubicin and camptothecin in these vesicles demonstrated a manyfold enhancement in the efficacies of the drugs both in vitro and across three advanced tumor models without any signs of toxicity. Both free and drug-loaded liposomes were maximally confined to the tumor site with low tissue concentration. These data indicate that PC-SA is a unique and promising liposome that, alone and as a combination therapy, has anticancer potential across a wide range of cancer types.

Fluorescent Sensors Based on Aggregation-Induced Emission: Recent Advances and Perspectives

Fluorescent sensors with advantages of excellent sensitivity, rapid response, and easy operation are emerging as powerful tools in environmental monitoring, biological research, and disease diagnosis. However, conventional fluorophores featured with π-planar structures usually suffer from serious self-quenching in the aggregated state, poor photostability, and small Stokes' shift. In contrast to conventional aggregation-caused quenching (ACQ) fluorophores, the newly emerged aggregation-induced emission fluorogens (AIEgens) are featured with high emission efficiency in the aggregated state, which provide unique opportunities for various sensing applications with advantages of high signal-to-noise ratio, strong photostability, and large Stokes' shift. In this review, we will first briefly give an introduction of the AIE concept and the turn-on sensing principles. Then, we will discuss the recent examples of AIE sensors according to types of analytes. Finally, we will give a perspective on the future developments of AIE sensors. We hope this review will inspire more endeavors to devote to this emerging world.