Coding and non-coding roles of MOCCI (C15ORF48) coordinate to regulate host inflammation and immunity.

Mito-SEPs are small open reading frame-encoded peptides that localize to the mitochondria to regulate metabolism. Motivated by an intriguing negative association between mito-SEPs and inflammation, here we screen for mito-SEPs that modify inflammatory outcomes and report a mito-SEP named "Modulator of cytochrome C oxidase during Inflammation" (MOCCI) that is upregulated during inflammation and infection to promote host-protective resolution. MOCCI, a paralog of the NDUFA4 subunit of cytochrome C oxidase (Complex IV), replaces NDUFA4 in Complex IV during inflammation to lower mitochondrial membrane potential and reduce ROS production, leading to cyto-protection and dampened immune response. The MOCCI transcript also generates miR-147b, which targets the NDUFA4 mRNA with similar immune dampening effects as MOCCI, but simultaneously enhances RIG-I/MDA-5-mediated viral immunity. Our work uncovers a dual-component pleiotropic regulation of host inflammation and immunity by MOCCI (C15ORF48) for safeguarding the host during infection and inflammation.

Pro-apoptotic properties and mitochondrial functionality in platelet-like-particles generated from low Aspirin-incubated Meg-01 cells.

Long-term therapy with low Aspirin (ASA) dose is basis to prevent thrombotic acute events. However, the anti-platelet mechanisms of ASA remain not completely known. The aim was to analyze if in vitro exposure of human megakaryocytes to low ASA concentration may alter the apoptotic features of the newly formed platelets. Cultured Meg-01 cells, a human megakaryoblastic cell line, were stimulated to form platelets with 10 nmol/L phorbol 12-myristate-13-acetate (PMA) in the presence and absence of ASA (0.33 mmol/L). Results revealed that platelet-like particles (PLPs) derived from ASA-exposed Meg-01 cells, showed higher content of pro-apoptotic proteins Bax and Bak than PLPs from non-ASA incubated Meg-01 cells. It was accompanied of reduced cytochrome C oxidase activity and higher mitochondrial content of PTEN-induced putative kinase-1 in PLPs from ASA-incubated Meg-01 cells. However, only after calcium ionophore A23187 stimulation, caspase-3 activity, the cytosolic cytochrome C content, and reduction of mitochondrial membrane potential were higher in PLPs from ASA-incubated megakaryocytes than in those from Meg-01 without ASA. Nitric oxide synthase 3 content was higher in PLPs from ASA-exposed Meg-01 cells than in PLPs from non-ASA incubated Meg-01 cells. The L-arginine antagonist, NG-Nitro-L-arginine Methyl Ester, reduced caspase-3 activity in A23187-stimulated PLPs generated from ASA-incubated Meg-01 cells. As conclusions exposure of megakaryocyte to ASA promotes that the newly generated PLPs have, under stimulating condition, higher sensitivity to go into apoptosis than those PLPs generated from Meg-01 cells without ASA. It could be associated with differences in mitochondrial functionality and NO formation.

Characteristics and Possible Role of Bovine Sperm Head-to-Head Agglutination.

Although sperm head-to-head agglutination has been reported in many mammalian species, the biological significance of this unique sperm-sperm interaction remains largely unknown. Here, we aimed to examine the functional characteristics of agglutinated bovine sperm to determine the possible role of sperm agglutination in the fertilization process. We initially examined temporal changes to the degree of head-to-head agglutination in culture, and found that bovine sperm agglutinated despite the lack of sperm agglutination inducers in medium. Sperm viability and motility were evaluated by SYBR14/PI and JC-1 staining, respectively, to identify the relationship between sperm agglutination and fertilizing ability. Agglutinated sperm had increased motility, viability, and intact mitochondrial function compared with unagglutinated sperm. Furthermore, we found that heparin significantly increased the percentage of unagglutinated sperm, but did not affect viability of both agglutinated and unagglutinated sperm, suggesting that sperm agglutination dictated the viability. In conclusion, agglutinated bovine sperm maintained viability and motility for a longer time than unagglutinated sperm. Thus, we propose that the head-to-head agglutination is a crucial sperm-sperm interaction to ensure the fertilizing ability of sperm.

Increased lipid metabolism impairs NK cell function and mediates adaptation to the lymphoma environment.

Natural killer (NK) cells play critical roles in protection against hematological malignancies but can acquire a dysfunctional state, which limits antitumor immunity. However, the underlying reasons for this impaired NK cell function remain to be uncovered. We found that NK cells in aggressive B-cell lymphoma underwent substantial transcriptional reprogramming associated with increased lipid metabolism, including elevated expression of the transcriptional regulator peroxisome activator receptor-γ (PPAR-γ). Exposure to fatty acids in the lymphoma environment potently suppressed NK cell effector response and cellular metabolism. NK cells from both diffuse large B-cell lymphoma patients and Eµ-myc B-cell lymphoma-bearing mice displayed reduced interferon-γ (IFN-γ) production. Activation of PPAR-γ partially restored mitochondrial membrane potential and IFN-γ production. Overall, our data indicate that increased lipid metabolism, while impairing their function, is a functional adaptation of NK cells to the fatty-acid rich lymphoma environment.

HLA class II antibodies induce necrotic cell death in human endothelial cells via a lysosomal membrane permeabilization-mediated pathway.

Antibody-mediated rejection (AMR) is the major cause of allograft loss after solid organ transplantation. Circulating donor-specific antibodies against human leukocyte antigen (HLA), in particular HLA class II antibodies are critical for the pathogenesis of AMR via interactions with endothelial cells (ECs). To investigate the effects of HLA class II antibody ligation to the graft endothelium, a model of HLA-DR antibody-dependent stimulation was utilized in primary human ECs. Antibody ligation of HLA class II molecules in interferon-γ-treated ECs caused necrotic cell death without complement via a pathway that was independent of apoptosis and necroptosis. HLA-DR-mediated cell death was blocked by specific neutralization of antibody ligation with recombinant HLA class II protein and by lentiviral knockdown of HLA-DR in ECs. Importantly, HLA class II-mediated cytotoxicity was also induced by relevant native allele-specific antibodies from human allosera. Necrosis of ECs in response to HLA-DR ligation was mediated via hyperactivation of lysosomes, lysosomal membrane permeabilization (LMP), and release of cathepsins. Notably, LMP was caused by reorganization of the actin cytoskeleton. This was indicated by the finding that LMP and actin stress fiber formation by HLA-DR antibodies were both downregulated by the actin polymerization inhibitor cytochalasin D and inhibition of Rho GTPases, respectively. Finally, HLA-DR-dependent actin stress fiber formation and LMP led to mitochondrial stress, which was revealed by decreased mitochondrial membrane potential and generation of reactive oxygen species in ECs. Taken together, ligation of HLA class II antibodies to ECs induces necrotic cell death independent of apoptosis and necroptosis via a LMP-mediated pathway. These findings may enable novel therapeutic approaches for the treatment of AMR in solid organ transplantation.

Pinellia pedatisecta lectin exerts a proinflammatory activity correlated with ROS-MAPKs/NF-κB pathways and the NLRP3 inflammasome in RAW264.7 cells accompanied by cell pyroptosis.

Pinellia pedatisecta, a widely used herb in Chinese medicine, has proinflammatory toxicity related to its Pinellia pedatisecta lectin (PPL), but the mechanism is still unknown. However, for safer use, it is necessary to clarify its proinflammatory mechanism. Herein, we studied the mechanism in RAW264.7 cells. PPL decreased the mitochondrial membrane potential (MMP) and increased the outflow of calcium, accompanied by the overproduction of reactive oxygen species (ROS), which resulted in the activation of the MAPK and NF-κB pathways and the release of IL-1ß. The maturation of IL-1ß relied on caspase-1 p20, the active caspase-1, as demonstrated by adding caspase-1 inhibitor. While caspase-1 was associated with the activation of the NLRP3 inflammasome, we further found that the stimulation of PPL also contributed to the activation. In addition, TXNIP was downregulated, whereas NLRP3/caspase-1 p20/ASC was upregulated, and there was binding of TXNIP with NLRP3. There was also binding of NLRP3 with ASC and caspase-1. Further, we found that N-acetylcysteine (NAC), an ROS scavenger, could inhibit the PPL-stimulated activation of these pathways and the release of IL-1ß. Moreover, PPL led to cell pyroptosis with pyknotic nuclei and plasma membrane rupture, which could be inhibited by NAC. All of these findings demonstrated an important role of ROS in the inflammation caused by PPL. Taken together, our data provide new mechanistic insights into the possible endogenous signaling pathways involved in the inflammation of RAW264.7 cells, stimulated by PPL.

ARID5B regulates metabolic programming in human adaptive NK cells.

Natural killer (NK) cells with adaptive immunological properties expand and persist in response to human cytomegalovirus. Here, we explored the metabolic processes unique to these cells. Adaptive CD3-CD56dimCD57+NKG2C+ NK cells exhibited metabolic hallmarks of lymphocyte memory, including increased oxidative mitochondrial respiration, mitochondrial membrane potential, and spare respiratory capacity. Mechanistically, we found that a short isoform of the chromatin-modifying transcriptional regulator, AT-rich interaction domain 5B (ARID5B), was selectively induced through DNA hypomethylation in adaptive NK cells. Knockdown and overexpression studies demonstrated that ARID5B played a direct role in promoting mitochondrial membrane potential, expression of genes encoding electron transport chain components, oxidative metabolism, survival, and IFN-γ production. Collectively, our data demonstrate that ARID5B is a key regulator of metabolism in human adaptive NK cells, which, if targeted, may be of therapeutic value.

Systematic identification of anti-interferon function on hepatitis C virus genome reveals p7 as an immune evasion protein.

Hepatitis C virus (HCV) encodes mechanisms to evade the multilayered antiviral actions of the host immune system. Great progress has been made in elucidating the strategies HCV employs to down-regulate interferon (IFN) production, impede IFN signaling transduction, and impair IFN-stimulated gene (ISG) expression. However, there is a limited understanding of the mechanisms governing how viral proteins counteract the antiviral functions of downstream IFN effectors due to the lack of an efficient approach to identify such interactions systematically. To study the mechanisms by which HCV antagonizes the IFN responses, we have developed a high-throughput profiling platform that enables mapping of HCV sequences critical for anti-IFN function at high resolution. Genome-wide profiling performed with a 15-nt insertion mutant library of HCV showed that mutations in the p7 region conferred high levels of IFN sensitivity, which could be alleviated by the expression of WT p7 protein. This finding suggests that p7 protein of HCV has an immune evasion function. By screening a liver-specific ISG library, we identified that IFI6-16 significantly inhibits the replication of p7 mutant viruses without affecting WT virus replication. In contrast, knockout of IFI6-16 reversed the IFN hypersensitivity of p7 mutant virus. In addition, p7 was found to be coimmunoprecipitated with IFI6-16 and to counteract the function of IFI6-16 by depolarizing the mitochondria potential. Our data suggest that p7 is a critical immune evasion protein that suppresses the antiviral IFN function by counteracting the function of IFI6-16.

Fuzheng Qingjie Granules Inhibit Growth of Hepatoma Cells via Inducing Mitochondria-Mediated Apoptosis and Enhancing Immune Function.

Fuzheng Qingjie (FZQJ) granules, a compound Chinese medicine, have been used as an adjuvant therapy for alimentary tract cancers. However, the underlying anticancer mechanisms are still not well understood. In the present study, HepG2 cells were treated with FZQJ-containing serum. Cell proliferation was evaluated using MTT assay. Apoptosis was analyzed using a flow cytometer. Cell ultrastructure was observed under a transmission electron microscope. The mitochondrial membrane potential (Δψ) was examined with JC-1 dye. In H22 tumor-bearing mice, CD4+ T cells, CD8+ T cells, CD3+ T cells, and natural killer (NK) cells in peripheral blood were evaluated cytometrically. Interleukin (IL)-2 and tumor necrosis factor (TNF)-α levels were measured using radioimmunoassay.The mRNA levels of Bax and Bcl-2 were examined by reverse transcription-polymerase chain reaction. The protein levels of Bax, Bcl-2, cytochrome C, caspase 3 and 9, PARP, and CD69 were examined by Western blotting. The apoptotic cells in tissues were observed using TUNEL method. Alanine transaminase (ALT), aspartate transaminase (AST), blood urea nitrogen (BUN), and creatinine (CRE) were detected by an automatic biochemical analyzer. The results showed that FZQJ-containing serum remarkably inhibited proliferation of HepG2 cells in dose- and time-dependent manners, induced HepG2 cell apoptosis and caused a decrease of Δψ. Analysis of tumor tissue showed that FZQJ-induced apoptosis was accompanied by downregulation of Bcl-2 and upregulation of Bax, release of cytochrome c, activation of caspase 3 and 9, and cleavage of PARP. In addition, FZQJ increased the percentages of CD4+ T and NK cells, the ratio of CD4+/CD8+ T cells as well as the levels of serum TNF-α. FZQJ also increased CD69 expression in tumor tissue. No hepatorenal toxicity was observed in H22 tumor-bearing mice. These results indicated that FZQJ could inhibit the growth of hepatoma cells via regulating immune function and inducing mitochondria mediated apoptosis.

Human endometrial mesenchymal stem cells exhibit intrinsic anti-tumor properties on human epithelial ovarian cancer cells.

Epithelial ovarian cancer (EOC) is the most lethal tumor of all gynecologic tumors. There is no curative therapy for EOC thus far. The tumor-homing ability of adult mesenchymal stem cells (MSCs) provide the promising potential to use them as vehicles to transport therapeutic agents to the site of tumor. Meanwhile, studies have showed the intrinsic anti-tumor properties of MSCs against various kinds of cancer, including epithelial ovarian cancer. Human endometrial mesenchymal stem cells (EnSCs) derived from menstrual blood are a novel source for adult MSCs and exert restorative function in some diseases. Whether EnSCs endow innate anti-tumor properties on EOC cells has never been reported. By using tumor-bearing animal model and ex vivo experiments, we found that EnSCs attenuated tumor growth by inducing cell cycle arrest, promoting apoptosis, disturbing mitochondria membrane potential and decreasing pro-angiogenic ability in EOC cells in vitro and/or in vivo. Furthermore, EnSCs decreased AKT phosphorylation and promoted nuclear translocation of Forkhead box O-3a (FoxO3a) in EOC cells. Collectively, our findings elucidated the potential intrinsic anti-tumor properties of EnSCs on EOC cells in vivo and in vitro. This research provides a potential strategy for EnSC-based anti-cancer therapy against epithelial ovarian cancer.

Metabolic syndrome is associated with increased seminal inflammatory cytokines and reproductive dysfunction in a case-controlled male cohort.

PROBLEM: The impact of metabolic syndrome (MetS) associated systemic inflammation on the male reproductive tract requires further investigation. METHOD OF STUDY: A cross-sectional case-controlled study design consisting of a control group (n=32) and a MetS (n=42) group was used. Variables include MetS diagnostic criterion, serum C-Reactive Protein (CRP), routine semen analysis, spermatozoa mitochondrial membrane potential (MMP) and DNA fragmentation (DF), as well as TNF-α, IL-1ß, IL6 and IL8 concentrations in serum and semen. RESULTS: Serum and seminal levels of TNF-α, IL-1ß, IL6 and IL8 were all significantly increased in the MetS group. Ejaculation volume, sperm concentration, total sperm count, progressive and total motility and vitality were significantly decreased and sperm with abnormal MMP and DF were increased in the MetS group. CONCLUSION: The results suggest that MetS is associated with decreased fertility parameters in males, as well as local reproductive tract inflammation, in the absence of leukocytospermia.

DNA damage and apoptosis in blood neutrophils of inflammatory bowel disease patients and in Caco-2 cells in vitro exposed to betanin.

Inflammatory bowel diseases (IBD) are chronic, relapsing, inflammatory disorders of the gastrointestinal tract, and continuing colonic inflammation is considered an important risk factor in the development of colorectal cancer. Our previous studies showed that beetroot (Beta vulgaris var. rubra) products and their major component betanin modulate the reactive oxygen species (ROS) production and DNA damage in 12-O-tetradecanoylphorbol 13-acetate (TPA) stimulated human polymorphonuclear neutrophils of healthy volunteers. The aim of the present study was to evaluate the effects of betanin on the oxidative DNA damage and apoptosis in neutrophils isolated from blood of patients with inflammatory bowel disease--ulcerative colitis (UC) and Crohn's disease (CD). The results were compared with those obtained in colon carcinoma-derived Caco-2 cells. Betanin treatment at the concentration of 100 µM for 24 h increased DNA damage assessed by comet assay in IBD patients' neutrophils. A similar effect although less pronounced was observed in Caco-2 cells. Treatment of Caco-2 cells with H2O2 caused a 4-fold increase of DNA strand breaks in comparison to untreated cells, but pre-treatment with betanin reduced DNA damage in these cells. Betanin also induced procaspase-3 cleavage and caspase-3 activity accompanied by the loss of mitochondrial transmembrane potential, indicating its pro-apoptotic activity. These results suggest that betanin may support mechanisms that lead to the release of ROS and apoptotic cell death. In this way betanin may exert anti-inflammatory and potentially cancer preventive activity.

Effective activation of antioxidant system by immune-relevant factors reversely correlates with apoptosis of Eisenia andrei coelomocytes.

Oxidative stress is harmful to the microbes but also to the host, and may result in bystander damage or death. Because of this, respiratory burst triggered in phagocytes by pathogens is counteracted by production of antioxidative factors. The aim of this work was to examine effectiveness of the latter system in earthworms Eisenia andrei by induction of reactive oxygen species, lipofuscin and phenoloxidase by natural (LPS, zymosan, Micrococus luteus) and synthetic (phorbol ester, PMA) stimulants. The compounds impaired numbers, viability (increased apoptosis) and composition of coelomocytes, and triggered the antioxidant activity of catalase and selenium-dependent glutathione peroxidase. The natural pathogenic compounds, unlike PMA, strongly activated antioxidative responses that diminished cell apoptosis. Moreover, repeated exposure to the same or different pathogenic compounds did not induce respiratory burst exhausted phenotype showing that coelomocytes are constantly at bay to withstand numerous infections. The current study reveals importance and efficiency of the oxidative-antioxidative systems in annelids but also confirms its evolutionary conservatism and complexity even in lower taxa of the animal kingdom.

Pre-stimulation of CD81 expression by resting B cells increases proliferation following EBV infection, but the overexpression of CD81 induces the apoptosis of EBV-transformed B cells.

Hepatitis C virus (HCV) E2 protein binds to CD81, which is a component of the B cell co-stimulatory complex. The E2-CD81 interaction leads to B cell proliferation, protein tyrosine phosphorylation and to the hypermutation of immunoglobulin genes. Epidemiological studies have reported a high prevalence of B cell non-Hodgkin lymphoma (NHL) in HCV-positive patients, suggesting a potential association between HCV and Epstein-Barr virus (EBV) in the genesis of B lymphocyte proliferative disorders. In the present study, in order to investigate the association between EBV and HCV in B cells, we created an in vitro EBV-induced B cell transformation model. CD81 was gradually overexpressed during transformation by EBV. B cells isolated from HCV-positive patients grew more rapidly and clumped together earlier than B cells isolated from healthy donors following EBV infection. Pre-stimulation of CD81 expressed by resting B cells with anti-CD81 monoclonal antibody (mAb) or HCV E2 accelerated the generation of lymphoblastoid cell lines (LCLs) by EBV infection. These cells proliferated prominently through the early expression of interleukin-10 and intracellular latent membrane protein (LMP)-l. By contrast, the overexpression of CD81 on EBV-transformed B cells by anti-CD81 mAb or HCV E2 protein induced apoptosis through reactive oxygen species (ROS)-mediated mitochondrial dysfunction. These results suggest that the engagement of CD81 expressed by B cells has differential effects on B cell fate (proliferation or apoptosis) according to EBV infection and the expression level of CD81.

Mitochondrial function provides instructive signals for activation-induced B-cell fates.

During immune reactions, functionally distinct B-cell subsets are generated by stochastic processes, including class-switch recombination (CSR) and plasma cell differentiation (PCD). In this study, we show a strong association between individual B-cell fates and mitochondrial functions. CSR occurs specifically in activated B cells with increased mitochondrial mass and membrane potential, which augment mitochondrial reactive oxygen species (mROS), whereas PCD occurs in cells with decreased mitochondrial mass and potential. These events are consequences of initial slight changes in mROS in mitochondria(high) B-cell populations. In CSR-committed cells, mROS attenuates haeme synthesis by inhibiting ferrous ion addition to protoporphyrin IX, thereby maintaining Bach2 function. Reduced mROS then promotes PCD by increasing haeme synthesis. In PCD-committed cells, Blimp1 reduces mitochondrial mass, thereby reducing mROS levels. Identifying mROS as a haeme synthesis regulator increases the understanding of mechanisms regulating haeme homeostasis and cell fate determination after B-cell activation.

Influenza A virus protein PB1-F2 translocates into mitochondria via Tom40 channels and impairs innate immunity.

Mitochondria contribute to cellular innate immunity against RNA viruses. Mitochondrial-mediated innate immunity is regulated by signalling molecules that are recruited to the mitochondrial membrane, and depends on the mitochondrial inner membrane potential (Δψm). Here we examine the physiological relevance of Δψm and the mitochondrial-associating influenza A viral protein PB1-F2 in innate immunity. When expressed in host cells, PB1-F2 completely translocates into the mitochondrial inner membrane space via Tom40 channels, and its accumulation accelerates mitochondrial fragmentation due to reduced Δψm. By contrast, PB1-F2 variants lacking a C-terminal polypeptide, which is frequently found in low pathogenic subtypes, do not affect mitochondrial function. PB1-F2-mediated attenuation of Δψm suppresses the RIG-I signalling pathway and activation of NLRP3 inflammasomes. PB1-F2 translocation into mitochondria strongly correlates with impaired cellular innate immunity, making this translocation event a potential therapeutic target.

Necroptosis takes place in human immunodeficiency virus type-1 (HIV-1)-infected CD4+ T lymphocytes.

Human immunodeficiency virus type 1 (HIV-1) infection is characterized by progressive depletion of CD4+ T lymphocytes and dysfunction of the immune system. The numbers of CD4+ T lymphocytes in the human body are maintained constantly by homeostatic mechanisms that failed during HIV-1 infection, resulting in progressive loss of CD4+ T cells mainly via apoptosis. Recently, a non-apoptotic form of necrotic programmed cell death, named necroptosis, has been investigated in many biological and pathological processes. We then determine whether HIV-1-infected cells also undergo necroptosis. In this report, we demonstrate that HIV-1 not only induces apoptosis, but also mediates necroptosis in the infected primary CD4+ T lymphocytes and CD4+ T-cell lines. Necroptosis-dependent cytopathic effects are significantly increased in HIV-1-infected Jurkat cells that is lack of Fas-associated protein-containing death domain (FADD), indicating that necroptosis occurs as an alternative cell death mechanism in the absence of apoptosis. Unlike apoptosis, necroptosis mainly occurs in HIV-infected cells and spares bystander damage. Treatment with necrostatin-1(Nec-1), a RIP1 inhibitor that specifically blocks the necroptosis pathway, potently restrains HIV-1-induced cytopathic effect and interestingly, inhibits the formation of HIV-induced syncytia in CD4+ T-cell lines. This suggests that syncytia formation is mediated, at least partially, by necroptosis-related processes. Furthermore, we also found that the HIV-1 infection-augmented tumor necrosis factor-alpha (TNF-α) plays a key role in inducing necroptosis and HIV-1 Envelope and Tat proteins function as its co-factors. Taken together,necroptosis can function as an alternative cell death pathway in lieu of apoptosis during HIV-1 infection, thereby also contributing to HIV-1-induced cytopathic effects. Our results reveal that in addition to apoptosis, necroptosis also plays an important role in HIV-1-induced pathogenesis.

Ganglioside GD2 in reception and transduction of cell death signal in tumor cells.

BACKGROUND: Ganglioside GD2 is expressed on plasma membranes of various types of malignant cells. One of the most promising approaches for cancer immunotherapy is the treatment with monoclonal antibodies recognizing tumor-associated markers such as ganglioside GD2. It is considered that major mechanisms of anticancer activity of anti-GD2 antibodies are complement-dependent cytotoxicity and/or antibody-mediated cellular cytotoxicity. At the same time, several studies suggested that anti-GD2 antibodies are capable of direct induction of cell death of number of tumor cell lines, but it has not been investigated in details. In this study we investigated the functional role of ganglioside GD2 in the induction of cell death of multiple tumor cell lines by using GD2-specific monoclonal antibodies. METHODS: Expression of GD2 on different tumor cell lines was analyzed by flow cytometry using anti-GD2 antibodies. By using HPTLC followed by densitometric analysis we measured the amount of ganglioside GD2 in total ganglioside fractions isolated from tumor cell lines. An MTT assay was performed to assess viability of GD2-positive and -negative tumor cell lines treated with anti-GD2 mAbs. Cross-reactivity of anti-GD2 mAbs with other gangliosides or other surface molecules was investigated by ELISA and flow cytometry. Inhibition of GD2 expression was achieved by using of inhibitor for ganglioside synthesis PDMP and/or siRNA for GM2/GD2 and GD3 synthases. RESULTS: Anti-GD2 mAbs effectively induced non-classical cell death that combined features of both apoptosis and necrosis in GD2-positive tumor cells and did not affect GD2-negative tumors. Anti-GD2 mAbs directly induced cell death, which included alteration of mitochondrial membrane potential, induction of apoptotic volume decrease and cell membrane permeability. This cytotoxic effect was mediated exclusively by specific binding of anti-GD2 antibodies with ganglioside GD2 but not with other molecules. Moreover, the level of GD2 expression correlated with susceptibility of tumor cell lines to cytotoxic effect of anti-GD2 antibodies. CONCLUSIONS: Results of this study demonstrate that anti-GD2 antibodies not only passively bind to the surface of tumor cells but also directly induce rapid cell death after the incubation with GD2-positive tumor cells. These results suggest a new role of GD2 as a receptor that actively transduces death signal in malignant cells.

Increased oxidative stress and the apoptosis of regulatory T cells in obese mice but not resistant mice in response to a high-fat diet.

High fat feeding induces a variety of obese and lean phenotypes in inbred rodents. Obesity is a pro-inflammatory state, and regulatory T cells (Tregs) are essential negative regulators of inflammation. We aimed to determine the involvement of Tregs in the mice susceptible or resistant to high-fat diet (HFD). In the study, diet-induced obese (DIO) mice experienced significant increases in weight gain, energy intake, fat masses, plasma lipid and proinflammatory cytokines in comparison with control and diet-resistant (DR) mice. Also, Tregs production decreased in DIO mice. HFD diminished mitochondrial transmembrane potential (MTP) in the spleen Tregs of DIO mice and reinforced apoptosis compared with that in DR mice. Moreover, HFD significantly decreased antioxidant enzymes expressions and increased reactive oxygen species (ROS) productions in the Tregs of DIO mice, but not in those of DR mice, which should provide valuable evidence for unraveling the pathogenesis of inflammation found in this obese mice model.

CD24-triggered caspase-dependent apoptosis via mitochondrial membrane depolarization and reactive oxygen species production of human neutrophils is impaired in sepsis.

Apoptosis is the most common pathway of neutrophil death under both physiological and inflammatory conditions. In this study, we describe an apoptotic pathway in human neutrophils that is triggered via the surface molecule CD24. In normal neutrophils, CD24 ligation induces death through depolarization of the mitochondrial membrane in a manner dependent on caspase-3 and caspase-9 and reactive oxygen species. Proinflammatory cytokines such as TNF-α, IFN-γ, and GM-CSF upregulated the expression of CD24 in vitro, favoring the emergence of a new CD16(high)/CD24(high) subset of cultured neutrophils. We observed that CD24 expression (at both mRNA and protein levels) was significantly downregulated in neutrophils from sepsis patients but not from patients with systemic inflammatory response syndrome. This downregulation was reproduced by incubation of neutrophils from healthy controls with corticosteroids or with plasma collected from sepsis patients, but not with IL-10 or TGF-ß. Decreased CD24 expression observed on sepsis neutrophils was associated with lack of functionality of the molecule, because cross-ligation of CD24 failed to trigger apoptosis in neutrophils from sepsis patients. Our results suggest a novel aspect of CD24-mediated immunoregulation and represent, to our knowledge, the first report showing the role of CD24 in the delayed/defective cell death in sepsis.