Molecular ordering of the initial signaling events of CD95

A DNA origami device spatially controls CD95 signalling to induce immune tolerance in rheumatoid arthritis

DNA origami is capable of spatially organizing molecules into sophisticated geometric patterns with nanometric precision. Here we describe a reconfigurable, two-dimensional DNA origami with geometrically patterned CD95 ligands that regulates immune cell signalling to alleviate rheumatoid arthritis. In response to pH changes, the device reversibly transforms from a closed to an open configuration, displaying a hexagonal pattern of CD95 ligands with ~10 nm intermolecular spacing, precisely mirroring the spatial arrangement of CD95 receptor clusters on the surface of immune cells. In a collagen-induced arthritis mouse model, DNA origami elicits robust and selective activation of CD95 death-inducing signalling in activated immune cells located in inflamed synovial tissues. Such localized immune tolerance ameliorates joint damage with no noticeable side effects. This device allows for the precise spatial control of cellular signalling, expanding our understanding of ligand-receptor interactions and is a promising platform for the development of pharmacological interventions targeting these interactions.

CD95/Fas ligand mRNA is toxic to cells through more than one mechanism

CD95/Fas ligand (CD95L) induces apoptosis through protein binding to the CD95 receptor. However, CD95L mRNA also induces toxicity in the absence of CD95 through induction of DISE (Death Induced by Survival Gene Elimination), a form of cell death mediated by RNA interference (RNAi). We now report that CD95L mRNA processing generates a short (s)RNA nearly identical to shL3, a commercial CD95L-targeting shRNA that led to the discovery of DISE. Neither of the miRNA biogenesis proteins Drosha nor Dicer are required for this processing. Interestingly, CD95L toxicity depends on the core component of the RISC, Ago2, in some cell lines, but not in others. In the HCT116 colon cancer cell line, Ago 1-4 appear to function redundantly in RNAi. In fact, Ago 1/2/3 knockout cells retain sensitivity to CD95L mRNA toxicity. Toxicity was only blocked by mutation of all in-frame start codons in the CD95L ORF. Dying cells exhibited an enrichment of RISC bound (R)-sRNAs with toxic 6mer seed sequences, while expression of the non-toxic CD95L mutant enriched for loading of R-sRNAs with nontoxic 6mer seeds. However, CD95L is not the only source of these R-sRNAs. We find that CD95L mRNA may induce DISE directly and indirectly, and that alternate mechanisms may underlie CD95L mRNA processing and toxicity.

Branching out in different directions: Emerging cellular functions for the Arp2/3 complex and WASP-family actin nucleation factors

The actin cytoskeleton impacts practically every function of a eukaryotic cell. Historically, the best-characterized cytoskeletal activities are in cell morphogenesis, motility, and division. The structural and dynamic properties of the actin cytoskeleton are also crucial for establishing, maintaining, and changing the organization of membrane-bound organelles and other intracellular structures. Such activities are important in nearly all animal cells and tissues, although distinct anatomical regions and physiological systems rely on different regulatory factors. Recent work indicates that the Arp2/3 complex, a broadly expressed actin nucleator, drives actin assembly during several intracellular stress response pathways. These newly described Arp2/3-mediated cytoskeletal rearrangements are coordinated by members of the Wiskott-Aldrich Syndrome Protein (WASP) family of actin nucleation-promoting factors. Thus, the Arp2/3 complex and WASP-family proteins are emerging as crucial players in cytoplasmic and nuclear activities including autophagy, apoptosis, chromatin dynamics, and DNA repair. Characterizations of the functions of the actin assembly machinery in such stress response mechanisms are advancing our understanding of both normal and pathogenic processes, and hold great promise for providing insights into organismal development and interventions for disease.

Chinese Cordyceps: Bioactive Components, Antitumor Effects and Underlying Mechanism-A Review

Chinese Cordyceps is a valuable source of natural products with various therapeutic effects. It is rich in various active components, of which adenosine, cordycepin and polysaccharides have been confirmed with significant immunomodulatory and antitumor functions. However, the underlying antitumor mechanism remains poorly understood. In this review, we summarized and analyzed the chemical characteristics of the main components and their pharmacological effects and mechanism on immunomodulatory and antitumor functions. The analysis revealed that Chinese Cordyceps promotes immune cells' antitumor function by via upregulating immune responses and downregulating immunosuppression in the tumor microenvironment and resetting the immune cells' phenotype. Moreover, Chinese Cordyceps can inhibit the growth and metastasis of tumor cells by death (including apoptosis and autophagy) induction, cell-cycle arrest, and angiogenesis inhibition. Recent evidence has revealed that the signal pathways of mitogen-activated protein kinases (MAPKs), nuclear factor kappaB (NF-κB), cysteine-aspartic proteases (caspases) and serine/threonine kinase Akt were involved in the antitumor mechanisms. In conclusion, Chinese Cordyceps, one type of magic mushroom, can be potentially developed as immunomodulator and anticancer therapeutic agents.

B cell-T cell interplay in immune regulation: A focus on follicular regulatory T and regulatory B cell functions

B cells are the core components of humoral immunity. A mature B cell can serve in multiple capacities, including antibody production, antigen presentation, and regulatory functions. Forkhead box P3 (FoxP3)-expressing regulatory T cells (Tregs) are key players in sustaining immune tolerance and keeping inflammation in check. Mounting evidence suggests complex communications between B cells and Tregs. In this review, we summarize the yin-yang regulatory relationships between B cells and Tregs mainly from the perspectives of T follicular regulatory (Tfr) cells and regulatory B cells (Bregs). We discuss the regulatory effects of Tfr cells on B cell proliferation and the germinal center response. Additionally, we review the indispensable role of B cells in ensuring homeostatic Treg survival and describe the function of Bregs in promoting Treg responses. Finally, we introduce a new subset of Tregs, termed Treg-of-B cells, which are induced by B cells, lake the expression of FoxP3 but still own immunomodulatory effects. In this article, we also enumerate a sequence of research from clinical patients and experimental models to clarify the role of Tfr cells in germinal centers and the role of convention B cells and Bregs to Tregs in the context of different diseases. This review offers an updated overview of immunoregulatory networks and unveils potential targets for therapeutic interventions against cancer, autoimmune diseases and allograft rejection.

Pathophysiological Roles of Actin-Binding Scaffold Protein, Ezrin

Ezrin is one of the members of the ezrin/radixin/moesin (ERM) family of proteins. It was originally discovered as an actin-binding protein in the microvilli structure about forty years ago. Since then, it has been revealed as a key protein with functions in a variety of fields including cell migration, survival, and signal transduction, as well as functioning as a structural component. Ezrin acts as a cross-linker of membrane proteins or phospholipids in the plasma membrane and the actin cytoskeleton. It also functions as a platform for signaling molecules at the cell surface. Moreover, ezrin is regarded as an important target protein in cancer diagnosis and therapy because it is a key protein involved in cancer progression and metastasis, and its high expression is linked to poor survival in many cancers. Small molecule inhibitors of ezrin have been developed and investigated as candidate molecules that suppress cancer metastasis. Here, we wish to comprehensively review the roles of ezrin from the pathophysiological points of view.

Phase separation in immune signalling

Immune signalling pathways convert pathogenic stimuli into cytosolic events that lead to the resolution of infection. Upon ligand engagement, immune receptors together with their downstream adaptors and effectors undergo substantial conformational changes and spatial reorganization. During this process, nanometre-to-micrometre-sized signalling clusters have been commonly observed that are believed to be hotspots for signal transduction. Because of their large size and heterogeneous composition, it remains a challenge to fully understand the mechanisms by which these signalling clusters form and their functional consequences. Recently, phase separation has emerged as a new biophysical principle for organizing biomolecules into large clusters with fluidic properties. Although the field is still in its infancy, studies of phase separation in immunology are expected to provide new perspectives for understanding immune responses. Here, we present an up-to-date view of how liquid-liquid phase separation drives the formation of signalling condensates and regulates immune signalling pathways, including those downstream of T cell receptor, B cell receptor and the innate immune receptors cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) and retinoic acid-inducible gene I protein (RIG-I). We conclude with a summary of the current challenges the field is facing and outstanding questions for future studies.

CD95/Fas protects triple negative breast cancer from anti-tumor activity of NK cells

The apoptosis inducing receptor CD95/Fas has multiple tumorigenic activities. In different genetically engineered mouse models tumor-expressed CD95 was shown to be critical for cell growth. Using a combination of immune-deficient and immune-competent mouse models, we now establish that loss of CD95 in metastatic triple negative breast cancer (TNBC) cells prevents tumor growth by modulating the immune landscape. CD95-deficient, but not wild-type, tumors barely grow in an immune-competent environment and show an increase in immune infiltrates into the tumor. This growth reduction is caused by infiltrating NK cells and does not involve T cells or macrophages. In contrast, in immune compromised mice CD95 k.o. cells are not growth inhibited, but they fail to form metastases. In summary, we demonstrate that in addition to its tumor and metastasis promoting activities, CD95 expression by tumor cells can exert immune suppressive activities on NK cells, providing a new target for immune therapy.

Nanoscale FasL Organization on DNA Origami to Decipher Apoptosis Signal Activation in Cells

Cell signaling is initiated by characteristic protein patterns in the plasma membrane, but tools to decipher their molecular organization and activation are hitherto lacking. Among the well-known signaling pattern is the death inducing signaling complex with a predicted hexagonal receptor architecture. To probe this architecture, DNA origami-based nanoagents with nanometer precise arrangements of the death receptor ligand FasL are introduced and presented to cells. Mimicking different receptor geometries, these nanoagents act as signaling platforms inducing fastest time-to-death kinetics for hexagonal FasL arrangements with 10 nm inter-molecular spacing. Compared to naturally occurring soluble FasL, this trigger is faster and 100× more efficient. Nanoagents with different spacing, lower FasL number or higher coupling flexibility impede signaling. The results present DNA origami as versatile signaling scaffolds exhibiting unprecedented control over molecular number and geometry. They define molecular benchmarks in apoptosis signal initiation and constitute a new strategy to drive particular cell responses.

TNF receptor agonists induce distinct receptor clusters to mediate differential agonistic activity

Monoclonal antibodies (mAb) and natural ligands targeting costimulatory tumor necrosis factor receptors (TNFR) exhibit a wide range of agonistic activities and antitumor responses. The mechanisms underlying these differential agonistic activities remain poorly understood. Here, we employ a panel of experimental and clinically-relevant molecules targeting human CD40, 4-1BB and OX40 to examine this issue. Confocal and STORM microscopy reveal that strongly agonistic reagents induce clusters characterized by small area and high receptor density. Using antibody pairs differing only in isotype we show that hIgG2 confers significantly more receptor clustering than hIgG1 across all three receptors, explaining its greater agonistic activity, with receptor clustering shielding the receptor-agonist complex from further molecular access. Nevertheless, discrete receptor clustering patterns are observed with different hIgG2 mAb, with a unique rod-shaped assembly observed with the most agonistic mAb. These findings dispel the notion that larger receptor clusters elicit greater agonism, and instead point to receptor density and subsequent super-structure as key determinants.

Role of Cholesterol and Lipid Rafts in Cancer Signaling: A Promising Therapeutic Opportunity?

Cholesterol is a lipid molecule that plays an essential role in a number of biological processes, both physiological and pathological. It is an essential structural constituent of cell membranes, and it is fundamental for biosynthesis, integrity, and functions of biological membranes, including membrane trafficking and signaling. Moreover, cholesterol is the major lipid component of lipid rafts, a sort of lipid-based structures that regulate the assembly and functioning of numerous cell signaling pathways, including those related to cancer, such as tumor cell growth, adhesion, migration, invasion, and apoptosis. Considering the importance of cholesterol metabolism, its homeostasis is strictly regulated at every stage: import, synthesis, export, metabolism, and storage. The alterations of this homeostatic balance are known to be associated with cardiovascular diseases and atherosclerosis, but mounting evidence also connects these behaviors to increased cancer risks. Although there is conflicting evidence on the role of cholesterol in cancer development, most of the studies consistently suggest that a dysregulation of cholesterol homeostasis could lead to cancer development. This review aims to discuss the current understanding of cholesterol homeostasis in normal and cancerous cells, summarizing key findings from recent preclinical and clinical studies that have investigated the role of major players in cholesterol regulation and the organization of lipid rafts, which could represent promising therapeutic targets.

Anti-proliferation and apoptosis-inducing effects of sodium aescinate on retinoblastoma Y79 cells

AIM

To investigate the anti-proliferation and apoptosis-inducing effects of sodium aescinate (SA) on retinoblastoma Y79 cells and its mechanism.

METHODS

Y79 cells were cultured at different drug concentrations for different periods of time (24, 48, and 72h). The inhibitory effect of SA on proliferation of Y79 cells was detected by the cell counting kit-8 (CCK-8) assay, and the morphology of Y79 cells in each group was observed under an inverted microscope. An IC50 of 48h was selected for subsequent experiments. After pretreatment with SA for 24 and 48h, cellular DNA distribution and apoptosis were detected by flow cytometry. Real-time qunatitative polymerase chain reaction (RT-qPCR) and Western blot were used to assess changes in related genes (CDK1, CyclinB1, Bax, Bcl-2, caspase-9, caspase-8, and caspase-3).

RESULTS

SA inhibited proliferation and induced apoptosis of Y79 cells in a time-dependent and concentration-dependent manner. Following its intervention in the cell cycle pathway, SA can inhibit the expression of CDK1 and CyclinB1 at the mRNA and protein levels, and block cells in the G2/M phase. In caspase-related apoptotic pathways, up-regulation of Bax and down-regulation of Bcl-2 caused caspase-9 to self-cleave and further activate caspase-3. What's more, the caspase-8-mediated extrinsic apoptosis pathway was activated, and the activated caspase-8 was released into the cytoplasm to activate caspase-3, which as a member of the downstream apoptotic effect group, initiates a caspase-cascade reaction that induces cell apoptosis.

CONCLUSION

SA inhibits the proliferation of Y79 cells by arresting the cell cycle at the G2/M phase, and induces apoptosis via the caspase-related apoptosis pathway, indicating that SA may have promising potential as a chemotherapeutic drug.

Cucurbita ficifolia Fruit Extract Induces Tp53/Caspase-Mediated Apoptosis in MCF-7 Breast Cancer Cells

The second most biggest cancer worldwide is breast cancer. There is an increasing need for safer, effective, and affordable drug candidates from natural sources to treat breast cancer. In the present investigation, the anticancer effect of Cucurbita ficifolia Bouché (C. ficifolia) fruit extract was tested on the human breast cancer cells such as MCF-7. The cells were exposed with different doses of C. ficifolia, for the assessment of IC₅₀ concentrations on the MCF-7 cell lines for 24 hs. The effect of C. ficifolia fruit extract on morphological and apoptotic changes were evaluated by specific fluorescence staining techniques and real-time PCR in a time-dependent manner for 24 hs and 48 hs. The IC₅₀ value for C. ficifolia fruit extract was found to be 90 μg/mL. Morphological alteration and apoptotic distinctiveness aspect like chromatin condensation and nuclear fragmentation were noticed in C. ficifolia extract exposed breast cancer cells. Further, we observed that C. ficifolia extract-induced programmed cell death in the MCF-7 cells were mediated with the elevated expression of the tumor suppressor gene such as p53 and apoptotic markers such as caspase-8, caspase-9, caspase-3, fatty acid synthase (FAS), Fas-associated protein with death domain (FADD), Bcl-2 homologous antagonist/killer (BAK), and Bcl-2-associated X protein (BAX). These observations established that C. ficifolia significantly concealed the cell division and provoked p53/caspase-mediated programmed cell death. Further, we noticed that this cell death in MCF-7 cells is concentration and time dependent. As evaluated through the comet assay, C. ficifolia induced DNA damage; further upon increasing the duration of the treatment, the DNA damage was higher than before. Thus, our study concludes that C. ficifolia could serve as an effective anticancer agent through vital gene modulation.

Higher-order assemblies in innate immune and inflammatory signaling: A general principle in cell biology

Higher-order supramolecular complexes-dubbed signalosomes carry out key signaling and effector functions in innate immunity and inflammation. In this review, we present several recently discovered signalosomes that are formed either by stable protein-protein interactions or by dynamic liquid-liquid phase separation. Structural features of these signalosomes are highlighted to elucidate their functions and biological insights.

On the role of sphingolipids in cell survival and death

Sphingolipids, universal components of biological membranes of all eukaryotic organisms, from yeasts to mammals, in addition of playing a structural role, also play an important part of signal transduction pathways. They participate or, also, ignite several fundamental subcellular signaling processes but, more in general, they directly contribute to key biological activities such as cell motility, growth, senescence, differentiation as well as cell fate, i.e., survival or death. The sphingolipid metabolic pathway displays an intricate network of reactions that result in the formation of multiple sphingolipids, including ceramide, and sphingosine-1-phosphate. Different sphingolipids, that have key roles in determining cell fate, can induce opposite effects: as a general rule, sphingosine-1-phosphate promotes cell survival and differentiation, whereas ceramide is known to induce apoptosis. Furthermore, together with cholesterol, sphingolipids also represent the basic lipid component of lipid rafts, cholesterol- and sphingolipid-enriched membrane microdomains directly involved in cell death and survival processes. In this review, we briefly describe the characteristics of sphingolipids and lipid membrane microdomains. In particular, we will consider the involvement of various sphingolipids per se and of lipid rafts in apoptotic pathway, both intrinsic and extrinsic, in nonapoptotic cell death, in autophagy, and in cell differentiation. In addition, their roles in the most common physiological and pathological contexts either as pathogenetic elements or as biomarkers of diseases will be considered. We would also hint how the manipulation of sphingolipid metabolism could represent a potential therapeutic target to be investigated and functionally validated especially for those diseases for which therapeutic options are limited or ineffective.

Long and short isoforms of c-FLIP act as control checkpoints of DED filament assembly

The assembly of the death-inducing signaling complex (DISC) and death effector domain (DED) filaments at CD95/Fas initiates extrinsic apoptosis. Procaspase-8 activation at the DED filaments is controlled by short and long c-FLIP isoforms. Despite apparent progress in understanding the assembly of CD95-activated platforms and DED filaments, the detailed molecular mechanism of c-FLIP action remains elusive. Here, we further addressed the mechanisms of c-FLIP action at the DISC using biochemical assays, quantitative mass spectrometry, and structural modeling. Our data strongly indicate that c-FLIP can bind to both FADD and procaspase-8 at the DED filament. Moreover, the constructed in silico model shows that c-FLIP proteins can lead to the formation of the DISCs comprising short DED filaments as well as serve as bridging motifs for building a cooperative DISC network, in which adjacent CD95 DISCs are connected by DED filaments. This network is based on selective interactions of FADD with both c-FLIP and procaspase-8. Hence, c-FLIP proteins at the DISC control initiation, elongation, and composition of DED filaments, playing the role of control checkpoints. These findings provide new insights into DISC and DED filament regulation and open innovative possibilities for targeting the extrinsic apoptosis pathway.

MicroRNAs in cancer cell death pathways: Apoptosis and necroptosis

To protect tissues and the organism from disease, potentially harmful cells are removed through programmed cell death processes, including apoptosis and necroptosis. These types of cell death are critically controlled by microRNAs (miRNAs). MiRNAs are short RNA molecules that target and inhibit expression of many cellular regulators, including those controlling programmed cell death via the intrinsic (Bcl-2 and Mcl-1), extrinsic (TRAIL and Fas), p53-and endoplasmic reticulum (ER) stress-induced apoptotic pathways, as well as the necroptosis cell death pathway. In this review, we discuss the current knowledge of apoptosis and necroptosis pathways and how these are impaired in cancer cells. We focus on how miRNAs disrupt apoptosis and necroptosis, thereby critically contributing to malignancy. Understanding which and how miRNAs and their targets affect cell death pathways could open up novel therapeutic opportunities for cancer patients. Indeed, restoration of pro-apoptotic tumor suppressor miRNAs (apoptomiRs) or inhibition of oncogenic miRNAs (oncomiRs) represent strategies that are currently being trialed or are already applied as miRNA-based cancer therapies. Therefore, better understanding the cancer type-specific expression of apoptomiRs and oncomiRs and their underlying mechanisms in cell death pathways will not only advance our knowledge, but also continue to provide new opportunities to treat cancer.

CD95/Fas and metastatic disease: What does not kill you makes you stronger

CD95 (also known as Fas) is the prototype of death receptors; however, evidence suggests that this receptor mainly implements non-apoptotic signaling pathways such as NF-κB, MAPK, and PI3K that are involved in cell migration, differentiation, survival, and cytokine secretion. At least two different forms of CD95 L exist. The multi-aggregated transmembrane ligand (m-CD95 L) is cleaved by metalloproteases to release a homotrimeric soluble ligand (s-CD95 L). Unlike m-CD95 L, the interaction between s-CD95 L and its receptor CD95 fails to trigger apoptosis, but instead promotes calcium-dependent cell migration, which contributes to the accumulation of inflammatory Th17 cells in damaged organs of lupus patients and favors cancer cell invasiveness. Novel inhibitors targeting the pro-inflammatory roles of CD95/CD95 L may provide attractive therapeutic options for patients with chronic inflammatory disorders or cancer. This review discusses the roles of the CD95/CD95 L pair in cell migration and metastasis.

Mechanisms of natural killer cell-mediated cellular cytotoxicity

Cellular cytotoxicity, the ability to kill other cells, is an important effector mechanism of the immune system to combat viral infections and cancer. Cytotoxic T cells and natural killer (NK) cells are the major mediators of this activity. Here, we summarize the cytotoxic mechanisms of NK cells. NK cells can kill virally infected of transformed cells via the directed release of lytic granules or by inducing death receptor-mediated apoptosis via the expression of Fas ligand or TRAIL. The biogenesis of perforin and granzymes, the major components of lytic granules, is a highly regulated process to prevent damage during the synthesis of these cytotoxic molecules. Additionally, NK cells have developed several strategies to protect themselves from the cytotoxic activity of granular content upon degranulation. While granule-mediated apoptosis is a fast process, death receptor-mediated cytotoxicity requires more time. Current data suggest that these 2 cytotoxic mechanisms are regulated during the serial killing activity of NK cells. As many modern approaches of cancer immunotherapy rely on cellular cytotoxicity for their effectiveness, unraveling these pathways will be important to further progress these therapeutic strategies.

Impact of p85α Alterations in Cancer

The phosphatidylinositol 3-kinase (PI3K) pathway plays a central role in the regulation of cell signaling, proliferation, survival, migration and vesicle trafficking in normal cells and is frequently deregulated in many cancers. The p85α protein is the most characterized regulatory subunit of the class IA PI3Ks, best known for its regulation of the p110-PI3K catalytic subunit. In this review, we will discuss the impact of p85α mutations or alterations in expression levels on the proteins p85α is known to bind and regulate. We will focus on alterations within the N-terminal half of p85α that primarily regulate Rab5 and some members of the Rho-family of GTPases, as well as those that regulate PTEN (phosphatase and tensin homologue deleted on chromosome 10), the enzyme that directly counteracts PI3K signaling. We highlight recent data, mapping the interaction surfaces of the PTEN⁻p85α breakpoint cluster region homology (BH) domain, which sheds new light on key residues in both proteins. As a multifunctional protein that binds and regulates many different proteins, p85α mutations at different sites have different impacts in cancer and would necessarily require distinct treatment strategies to be effective.

Ketamine-induced hypnosis and neuroplasticity in mice is associated with disrupted p-MEK/p-ERK sequential activation and sustained upregulation of survival p-FADD in brain cortex: Involvement of GABAA receptor

Ketamine (KET) is an antidepressant and hypnotic drug acting as an antagonist at excitatory NMDA glutamate receptors. The working hypothesis postulated that KET-induced sleep in mice results in dysregulation of mitogen-activated protein kinases (MAPK) MEK-ERK sequential phosphorylation and upregulation of survival p-FADD and other neuroplastic markers in brain. Low (5-15 mg/kg) and high (150 mg/kg) doses of KET on target proteins were assessed by Western immunoblot in mouse brain cortex. During the time course of KET (150 mg/kg)-induced sleep (up to 50 min) p-MEK was increased (up to +79%) and p-ERK decreased (up to -46%) indicating disruption of MEK to ERK signal. Subhypnotic KET (5-15 mg/kg) also revealed uncoupling of p-MEK (+13-81%) to p-ERK (unchanged content). KET did not alter contraregulatory MAPK mechanisms such as inactivated p-MEK1 (ERK dampening) and phosphatases MKP1/2/3 (ERK dephosphorylation). As other relevant findings, KET (5, 15 and 150 mg/kg) upregulated p-FADD in a dose-dependent manner, and for the hypnotic dose the effect paralleled the time course of sleep which resulted in increased p-FADD/FADD ratios. KET (150 mg/kg) also increased NF-κΒ and PSD-95 neuroplastic markers. Flumazenil (a neutral allosteric antagonist at GABA_A receptor) prolonged KET sleep and blocked p-MEK upregulation, indicating the involvement of this receptor as a negative modulator. SL-327 (a MEK inhibitor) augmented KET sleep, further indicating the relevance of reduced p-ERK1/2 in KET-induced hypnosis. These findings suggest that hypnotic and subhypnotic doses of KET inducing uncoupling of p-MEK to p-ERK signal and regulation of p-ERK (downregulation) and p-FADD (upregulation) may participate in the expression of some of its adverse effects (e.g. amnesia, dissociative effects).

Hepatitis B Spliced Protein (HBSP) Suppresses Fas-Mediated Hepatocyte Apoptosis via Activation of PI3K/Akt Signaling

Hepatitis B spliced protein (HBSP) is known to associate with viral persistence and pathogenesis; however, its biological and clinical significance remains poorly defined. Acquired resistance to Fas-mediated apoptosis is thought to be one of the major promotors for hepatitis B virus (HBV) chronicity and malignancy. The purpose of this study was to investigate whether HBSP could protect hepatocytes against Fas-initiated apoptosis. We showed here that HBSP mediated resistance of hepatoma cells or primary human hepatocytes (PHH) to agonistic anti-Fas antibody (CH11)- or FasL-induced apoptosis. Under Fas signaling stimulation, expression of HBSP inhibited Fas aggregation and prevented recruitment of the adaptor molecule Fas-associated death domain (FADD) and procaspase-8 (or FADD-like interleukin-1β-converting enzyme [FLICE]) into the death-inducing signaling complex (DISC) while increasing recruitment of cellular FLICE-inhibitory protein L (FLIP_L) into the DISC. Those effects may be mediated through activation of the phosphoinositide 3-kinase (PI3K)/Akt pathway as evidenced by increased cellular phosphatidylinositol (3,4,5)-trisphosphate (PIP3) content and PI3K activity and enhanced phosphorylation of mTORC2 and PDPK1 as well as Akt itself. Confirmedly, inhibition of PI3K by LY294002 reversed the effect of HBSP on Fas aggregation, FLIP_L expression, and cellular apoptosis. These results indicate that HBSP functions to prevent hepatocytes from Fas-induced apoptosis by enhancing PI3K/Akt activity, which may contribute to the survival and persistence of infected hepatocytes during chronic infection.IMPORTANCE Our study revealed a previously unappreciated role of HBSP in Fas-mediated apoptosis. The antiapoptotic activity of HBSP is important for understanding hepatitis B virus pathogenesis. In particular, HBV variants associated with hepatoma carcinoma may downregulate apoptosis of hepatocytes through enhanced HBSP expression. Our study also found that Akt is centrally involved in Fas-induced hepatocyte apoptosis and revealed that interventions directed at inhibiting the activation or functional activity of Akt may be of therapeutic value in this process.

CD95/Fas ligand mRNA is toxic to cells

CD95/Fas ligand binds to the death receptor CD95 to induce apoptosis in sensitive cells. We previously reported that CD95L mRNA is enriched in sequences that, when converted to si/shRNAs, kill all cancer cells by targeting critical survival genes (Putzbach et al., 2017). We now report expression of full-length CD95L mRNA itself is highly toxic to cells and induces a similar form of cell death. We demonstrate that small (s)RNAs derived from CD95L are loaded into the RNA induced silencing complex (RISC) which is required for the toxicity and processing of CD95L mRNA into sRNAs is independent of both Dicer and Drosha. We provide evidence that in addition to the CD95L transgene a number of endogenous protein coding genes involved in regulating protein translation, particularly under low miRNA conditions, can be processed to sRNAs and loaded into the RISC suggesting a new level of cell fate regulation involving RNAi.

Hepatitis B Virus Surface Antigen Enhances the Sensitivity of Hepatocytes to Fas-Mediated Apoptosis via Suppression of AKT Phosphorylation

The Fas receptor/ligand system plays a prominent role in hepatic apoptosis and hepatocyte death. Although hepatitis B virus (HBV) surface Ag (HBsAg) is the most abundant HBV protein in the liver and peripheral blood of patients with chronic HBV infection, its role in Fas-mediated hepatocyte apoptosis has not been disclosed. In this study, we report that HBsAg sensitizes HepG2 cells to agonistic anti-Fas Ab CH11-induced apoptosis through increasing the formation of SDS-stable Fas aggregation and procaspase-8 cleavage but decreasing both the expression of cellular FLIP_L/S and the recruitment of FLIP_L/S at the death-inducing signaling complex (DISC). Notably, HBsAg increased endoplasmic reticulum stress and consequently reduced AKT phosphorylation by deactivation of phosphoinositide-dependent kinase-1 (PDPK1) and mechanistic target of rapamycin complex 2 (mTORC2), leading to enhancement of Fas-mediated apoptosis. In a mouse model, expression of HBsAg in mice injected with recombinant adenovirus-associated virus 8 aggravated Jo2-induced acute liver failure, which could be effectively attenuated by the AKT activator SC79. Based on these results, it is concluded that HBsAg predisposes hepatocytes to Fas-mediated apoptosis and mice to acute liver failure via suppression of AKT prosurviving activity, suggesting that interventions directed at enhancing the activation or functional activity of AKT may be of therapeutic value in Fas-mediated progressive liver cell injury and liver diseases.

The protective effects of HGF against apoptosis in vascular endothelial cells caused by peripheral vascular injury

Closed vascular injuries have danger of developing critical tissue ischemia with a high risk of amputation and limb loss. However, limited effective strategies exist at present. In this study, we investigate the role of hepatocyte growth factor (HGF) on apoptosis of vascular endothelial cells (VECs). First, apoptosis of VECs was induced by hypoxia treatment with or without HGF. Annexin V-7AAD apoptosis assay revealed that HGF overexpression significantly reduced VEC apoptosis. Then a closed peripheral vascular injury animal model was created by balloon catheter in female New Zealand rabbit. The VECs overexpressing HGF were injected into balloon injury rabbit. TUNEL and caspase 3 staining assays revealed that balloon catheter-treated artery showed severe intimal hyperplasia, with a 70% apoptosis rate (P < 0.05, vs. sham group), while HGF-overexpressing group showed a significant reduction of apoptosis. Furthermore, the expressions of Fas/FasL and their downstream apoptosis-related proteins were significantly decreased in HGF-overexpressing group when compared with those in balloon injury group as detected by western blot analysis. All these data indicated that HGF exhibited anti-apoptotic effects during VEC apoptosis, which might be mediated by the inhibition of Fas/FasL pathway. Our study provides a theoretic basis for the application of HGF in the gene therapy of closed peripheral vascular injury.

Aggregation of lipid rafts activates c-met and c-Src in non-small cell lung cancer cells

Background

Activation of c-Met, a receptor tyrosine kinase, induces radiation therapy resistance in non-small cell lung cancer (NSCLC). The activated residual of c-Met is located in lipid rafts (Duhon et al. Mol Carcinog 49:739-49, 2010). Therefore, we hypothesized that disturbing the integrity of lipid rafts would restrain the activation of the c-Met protein and reverse radiation resistance in NSCLC. In this study, a series of experiments was performed to test this hypothesis.

Methods

NSCLC A549 and H1993 cells were incubated with methyl-β-cyclodextrin (MβCD), a lipid raft inhibitor, at different concentrations for 1 h before the cells were X-ray irradiated. The following methods were used: clonogenic (colony-forming) survival assays, flow cytometry (for cell cycle and apoptosis analyses), immunofluorescence microscopy (to show the distribution of proteins in lipid rafts), Western blotting, and biochemical lipid raft isolation (purifying lipid rafts to show the distribution of proteins in lipid rafts).

Results

Our results showed that X-ray irradiation induced the aggregation of lipid rafts in A549 cells, activated c-Met and c-Src, and induced c-Met and c-Src clustering to lipid rafts. More importantly, MβCD suppressed the proliferation of A549 and H1993 cells, and the combination of MβCD and radiation resulted in additive increases in A549 and H1993 cell apoptosis. Destroying the integrity of lipid rafts inhibited the aggregation of c-Met and c-Src to lipid rafts and reduced the expression of phosphorylated c-Met and phosphorylated c-Src in lipid rafts.

Conclusions

X-ray irradiation induced the aggregation of lipid rafts and the clustering of c-Met and c-Src to lipid rafts through both lipid raft-dependent and lipid raft-independent mechanisms. The lipid raft-dependent activation of c-Met and its downstream pathways played an important role in the development of radiation resistance in NSCLC cells mediated by c-Met. Further studies are still required to explore the molecular mechanisms of the activation of c-Met and c-Src in lipid rafts induced by radiation.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4501-8) contains supplementary material, which is available to authorized users.

Early activation of CD95 is limited and localized to the cytotoxic synapse

The cytotoxic synapse formed between cytotoxic T lymphocytes or natural killer cells expressing CD95L and target cells with CD95 on their surface is a key pathway for apoptosis induction by the immune system. Despite similarities with the immune synapse in antigen presenting cells, little is known about the role of the spatiotemporal organization of agonistic proteins/receptor interactions for CD95 signaling. Here, we have developed an artificial cytotoxic synapse to examine how mobility and geometry of an anti-CD95 agonistic antibody affect receptor aggregation and mobility, ie the first step of receptor activation. By measuring the distribution, diffusion coefficient, and fraction of immobile CD95 receptor in living cells, we show that at short times, the initial activation of CD95 occurs locally and is limited to the contact region of the cytotoxic synapse. This anisotropic activation of apoptotic signaling supports a role for confined interactions on the efficiency of signal transduction that may have implications for biomedical applications of extrinsic apoptosis induction.

Changes in membrane lipids drive increased endocytosis following Fas ligation

Once activated, some surface receptors promote membrane movements that open new portals of endocytosis, in part to facilitate the internalization of their activated complexes. The prototypic death receptor Fas (CD95/Apo1) promotes a wave of enhanced endocytosis that induces a transient intermixing of endosomes with mitochondria in cells that require mitochondria to amplify death signaling. This initiates a global alteration in membrane traffic that originates from changes in key membrane lipids occurring in the endoplasmic reticulum (ER). We have focused the current study on specific lipid changes occurring early after Fas ligation. We analyzed the interaction between endosomes and mitochondria in Jurkat T cells by nanospray-Time-of-flight (ToF) Mass Spectrometry. Immediately after Fas ligation, we found a transient wave of lipid changes that drives a subpopulation of early endosomes to merge with mitochondria. The earliest event appears to be a decrease of phosphatidylcholine (PC), linked to a metabolic switch enhancing phosphatidylinositol (PI) and phosphoinositides, which are crucial for the formation of vacuolar membranes and endocytosis. Lipid changes occur independently of caspase activation and appear to be exacerbated by caspase inhibition. Conversely, inhibition or compensation of PC deficiency attenuates endocytosis, endosome-mitochondria mixing and the induction of cell death. Deficiency of receptor interacting protein, RIP, also limits the specific changes in membrane lipids that are induced by Fas activation, with parallel reduction of endocytosis. Thus, Fas activation rapidly changes the interconversion of PC and PI, which then drives enhanced endocytosis, thus likely propagating death signaling from the cell surface to mitochondria and other organelles.

Sevoflurane inhibits the malignant potential of head and neck squamous cell carcinoma via activating the hypoxia‑inducible factor-1α signaling pathway in vitro

Sevoflurane, an inhalational anesthetic, is extensively used during oral cancer surgery. However, the effect of sevoflurane on head and neck squamous cell carcinoma (HNSCC) remains unclear. The objective of the present study was to investigate the effects of sevoflurane on the proliferation, apoptosis and invasion in HNSCC cell lines and the underlying molecular mechanism. The Cell Counting Kit-8 assay was used to evaluate cell proliferation. Apoptosis was analyzed by flow cytometry. Cell invasion was evaluated using the Transwell invasion assay. The expression levels of Akt, p-Akt (Ser473), hypoxia‑inducible factor-1α (HIF-1α), Fas and Bcl-2 were measured by western blotting. Significant inhibition of cell proliferation and induction of apoptosis were observed in FaDu and CAL-27 cells following sevoflurane treatment. The expression of Akt, p-Akt (Ser473) and Bcl-2 was supressed, while that of Fas was significantly increased, which was partly associated with the activation of the HIF-1α pathway. In addition, the results revealed a statistically significant inhibition of cell invasion in the FaDu cell line following exposure to 2 and 4% sevoflurane for 2, 4, 6 and 8 h. Therefore, the present study demonstrated that sevoflurane decreased the malignant behavior of HNSCC cell lines in vitro, which was associated with activation of the HIF-1α pathway.

Knockdown of c‑Myc activates Fas-mediated apoptosis and sensitizes A549 cells to radiation

Several studies have demonstrated that cancer radiosensitivity is associated with the deregulation of c‑Myc, but the relationship between c‑Myc and Fas in radioresistance of lung adenocarcinoma remains unclear. In this study, we established radiation-resistant A549 cell model (A549/R), and investigated the roles of c‑Myc and Fas in radiation-induced cytotoxicity of A549 cells. Apoptosis detection showed that there were fewer apoptotic cells in A549/R cells treated with radiation than in A549 cells. Western blotting results demonstrated the inverse expression pattern of c‑Myc and Fas in A549 and A549/R cells. Suppression of c‑Myc expression by small interfering RNA (siRNA) displayed enhancement of Fas-mediated apoptosis in A549/R cells, accompanying a significant decrease of Bid, Bcl‑2, pro‑caspase‑8, -9 and -3 and increase of Bax. In contrast, Fas-mediated apoptosis was attenuated while Fas expression was suppressed by ectopic expression of c‑Myc in A549 cells. Moreover, decreased cell viability and increased induction of apoptosis were observed in A549/R cells followed by combinational treatment of c‑Myc siRNA and irradiation, whereas, upregulation of c‑Myc reduced the sensitivity of A549 cells to irradiation. These results indicated that c‑Myc and Fas regulated the sensitivity of A549 cells to irradiation by regulating caspase‑8-mediated Bid activation and the subsequent association with the mitochondrial pathway of apoptosis.

Role of caspases in CD95-induced biphasic activation of acid sphingomyelinase

Acid sphingomyelinase (A-SMase) plays an important role in the initiation of CD95 signaling by forming ceramide-enriched membrane domains that enable clustering and activation of the death receptors. In TNF-R1 and TRAIL-R1/R2 signaling, A-SMase also contributes to the lysosomal apoptosis pathway triggered by receptor internalization. Here, we investigated the molecular mechanism of CD95-mediated A-SMase activation, demonstrating that A-SMase is located in internalized CD95-receptosomes and is activated by the CD95/CD95L complex in a biphasic manner.Since several caspases have been described to be involved in the activation of A-SMase, we evaluated expression levels of caspase-8, caspase-7 and caspase-3 in CD95-receptosomes. The occurrence of cleaved caspase-8 correlated with the first peak of A-SMase activity and translocation of the A-SMase to the cell surface which could be blocked by the caspase-8 inhibitor IETD.Inhibition of CD95-internalization selectively reduced the second phase of A-SMase activity, suggesting a fusion between internalized CD95-receptosomes and an intracellular vesicular pool of A-SMase. Further analysis demonstrated that caspase-7 activity correlates with the second phase of the A-SMase activity, whereas active caspase-3 is present at early and late internalization time points. Blocking caspases-7/ -3 by DEVD reduced the second phase of A-SMase activation in CD95-receptosomes suggesting the potential role of caspase-7 or -3 for late A-SMase activation.In summary, we describe a biphasic A-SMase activation in CD95-receptosomes indicating (I.) a caspase-8 dependent translocation of A-SMase to plasma membrane and (II.) a caspase-7 and/or -3 dependent fusion of internalized CD95-receptosomes with intracellular A-SMase-containing vesicles.

Effects of 1alpha, 25-dihydroxyvitamin D3 on programmed cell death of Ishikawa endometrial cancer cells through ezrin phosphorylation

This study investigated the effects of 1α, 25-dihydroxyvitamin D₃-induced cell death and its underlying molecular mechanisms in Ishikawa endometrial carcinoma cells. The effects of 1α, 25-dihydroxyvitamin D₃ on Ishikawa cells were examined by 3-[4,5-dimethylthiazol-2-yl]-2.5-diphenyl-tetrazolium bromide, thiazolyl blue (MTT) assay. 1α, 25-dihydroxyvitamin D₃ was shown to induce programmed cell death in Ishikawa endometrial carcinoma cells by activation of caspase-3 and caspase-9, along with elevation of Bcl-2 and Bcl-xL. Cell viability was reduced by 1α, 25-dihydroxyvitamin D₃ in a concentration-dependent manner up to 2.5 μM. In addition, ezrin phosphorylation increased with the 1α, 25-dihydroxyvitamin D₃ concentration (0-0.5 μM). The protein level of caspase-9 was increased by 1α, 25-dihydroxyvitamin D₃ up to 0.5 μM. This is the first report regarding the efficacy and molecular mechanisms underlying the effects of 1α, 25-dihydroxyvitamin D₃ in endometrial cancer cells. Our findings indicate that 1α, 25-dihydroxyvitamin D₃ induces endometrial cancer cell death in a concentration-dependent manner. Impact statement Up to date, there is no report about the efficacy and molecular underlying mechanisms on the effect of vitamin D₃ in endometrial cancer cells. Our findings indicate that 1α, 25-dihydroxyvitamin D_3. which is an active metabolite of vitamin D₃, induces Ishikawa endometrial cancer cell death in a concentration-dependent manner by activation of caspase-3 and -9, along with elevation of Bcl-2 and Bcl-xL. In addition, the same concentration of 1α, 25-dihydroxyvitamin D₃ that provoked apoptotic signals caused phosphorylation of ezrin at threonine 567 in a VDR-dependent manner. This study suggests that 1α, 25-dihydroxyvitamin D₃ within the optimal range (0.5 uM) would induce apoptosis through Fas-ezrin-caspase-3, -8, -9 signalling axis which may be a critical cell death regulator in Ishikawa endometrial cancer cell. Further study will be more interesting to address molecular connections or prove this critical optimal concentration range of vitamin D.

Interactome disassembly during apoptosis occurs independent of caspase cleavage

Protein-protein interaction networks (interactomes) define the functionality of all biological systems. In apoptosis, proteolysis by caspases is thought to initiate disassembly of protein complexes and cell death. Here we used a quantitative proteomics approach, protein correlation profiling (PCP), to explore changes in cytoplasmic and mitochondrial interactomes in response to apoptosis initiation as a function of caspase activity. We measured the response to initiation of Fas-mediated apoptosis in 17,991 interactions among 2,779 proteins, comprising the largest dynamic interactome to date. The majority of interactions were unaffected early in apoptosis, but multiple complexes containing known caspase targets were disassembled. Nonetheless, proteome-wide analysis of proteolytic processing by terminal amine isotopic labeling of substrates (TAILS) revealed little correlation between proteolytic and interactome changes. Our findings show that, in apoptosis, significant interactome alterations occur before and independently of caspase activity. Thus, apoptosis initiation includes a tight program of interactome rearrangement, leading to disassembly of relatively few, select complexes. These early interactome alterations occur independently of cleavage of these protein by caspases.

Sphingolipid Organization in the Plasma Membrane and the Mechanisms That Influence It

Sphingolipids are structural components in the plasma membranes of eukaryotic cells. Their metabolism produces bioactive signaling molecules that modulate fundamental cellular processes. The segregation of sphingolipids into distinct membrane domains is likely essential for cellular function. This review presents the early studies of sphingolipid distribution in the plasma membranes of mammalian cells that shaped the most popular current model of plasma membrane organization. The results of traditional imaging studies of sphingolipid distribution in stimulated and resting cells are described. These data are compared with recent results obtained with advanced imaging techniques, including super-resolution fluorescence detection and high-resolution secondary ion mass spectrometry (SIMS). Emphasis is placed on the new insight into the sphingolipid organization within the plasma membrane that has resulted from the direct imaging of stable isotope-labeled lipids in actual cell membranes with high-resolution SIMS. Super-resolution fluorescence techniques have recently revealed the biophysical behaviors of sphingolipids and the unhindered diffusion of cholesterol analogs in the membranes of living cells are ultimately in contrast to the prevailing hypothetical model of plasma membrane organization. High-resolution SIMS studies also conflicted with the prevailing hypothesis, showing sphingolipids are concentrated in micrometer-scale membrane domains, but cholesterol is evenly distributed within the plasma membrane. Reductions in cellular cholesterol decreased the number of sphingolipid domains in the plasma membrane, whereas disruption of the cytoskeleton eliminated them. In addition, hemagglutinin, a transmembrane protein that is thought to be a putative raft marker, did not cluster within sphingolipid-enriched regions in the plasma membrane. Thus, sphingolipid distribution in the plasma membrane is dependent on the cytoskeleton, but not on favorable interactions with cholesterol or hemagglutinin. The alternate views of plasma membrane organization suggested by these findings are discussed.

Fas-Fas Ligand: Checkpoint of T Cell Functions in Multiple Sclerosis

Fas and Fas Ligand (FasL) are two molecules involved in the regulation of cell death. Their interaction leads to apoptosis of thymocytes that fail to rearrange correctly their T cell receptor (TCR) genes and of those that recognize self-antigens, a process called negative selection; moreover, Fas–FasL interaction leads to activation-induced cell death, a form of apoptosis induced by repeated TCR stimulation, responsible for the peripheral deletion of activated T cells. Both control mechanisms are particularly relevant in the context of autoimmune diseases, such as multiple sclerosis (MS), where T cells exert an immune response against self-antigens. This concept is well demonstrated by the development of autoimmune diseases in mice and humans with defects in Fas or FasL. In recent years, several new aspects of T cell functions in MS have been elucidated, such as the pathogenic role of T helper (Th) 17 cells and the protective role of T regulatory (Treg) cells. Thus, in this review, we summarize the role of the Fas–FasL pathway, with particular focus on its involvement in MS. We then discuss recent advances concerning the role of Fas–FasL in regulating Th17 and Treg cells’ functions, in the context of MS.

Dietary n-3 PUFAs augment caspase 8 activation in Staphylococcal aureus enterotoxin B stimulated T-cells

Epidemiological studies have linked consumption of n-3 PUFAs with a variety of beneficial health benefits, particularly with respect to putative anti-inflammatory effects. Unfortunately, many of these results remain somewhat controversial because in most instances there has not been a linkage to specific molecular mechanisms. For instance, dietary exposure to low levels of mercury has been shown to be damaging to neural development, but concomitant ingestion of n-3 PUFAs as occurs during consumption of fish, has been shown to counteract the detrimental effects. As the mechanisms mediating the neurotoxicity of environmental mercury are not fully delineated, it is difficult to conceptualize a testable molecular mechanism explaining how n-3 PUFAs negate its neurotoxic effects. However, environmental exposure to mercury also has been linked to increased autoimmunity. By way of a molecular understanding of this immuno-toxic association, disruption of CD95 signaling is well established as a triggering factor for autoimmunity, and we have previously shown that environmentally relevant in vitro and dietary exposures to mercury interfere with CD95 signaling. In particular we have shown that activation of caspase 8, as well as downstream activation of caspase 3, in response to CD95 agonist stimulation is depressed by mercury. More recently we have shown in vitro that the n-3 PUFA docosahexaenoic acid counteracts the negative effect of mercury on CD95 signaling by restoring caspase activity. We hypothesized that concomitant ingestion of n-3 PUFAs with mercury might be protective from the immuno-toxic effects of mercury, as it is with mercury's neuro-toxic effects, and in the case of immuno-toxicity this would be related to restoration of CD95 signal strength. We now show that dietary ingestion of n-3 PUFAs generally promotes CD95 signaling by upregulating caspase 8 activation. Apart from accounting for the ability of n-3 PUFAs to specifically counteract autoimmune sequelae of mercury exposure, this novel finding for the first time suggests a testable molecular mechanism explaining the overall anti-inflammatory properties of n-3 PUFAs.

The Fas Ligand/Fas Death Receptor Pathways Contribute to Propofol-Induced Apoptosis and Neuroinflammation in the Brain of Neonatal Rats

A number of experimental studies have reported that exposure to common, clinically used anesthetics induce extensive neuroapoptosis and cognitive impairment when applied to young rodents, up to 2 weeks old, in phase of rapid synaptogenesis. Propofol is the most used general anesthetic in clinical practice whose mechanisms of neurotoxicity on the developing brain remains to be examined in depth. This study investigated effects of different exposures to propofol anesthesia on Fas receptor and Fas ligand expressions, which mediate proapoptotic and proinflammation signaling in the brain. Propofol (20 mg/kg) was administered to 7-day-old rats in multiple doses sufficient to maintain 2-, 4- and 6-h duration of anesthesia. Animals were sacrificed at 0, 4, 16 and 24 h after termination of anesthesia. It was found that propofol anesthesia induced Fas/FasL and downstream caspase-8 expression more prominently in the thalamus than in the cortex. Opposite, Bcl-2 and caspase-9, markers of intrinsic pathway activation, were shown to be more influenced by propofol treatment in the cortex. Further, we have established upregulation of caspase-1 and IL-1β cytokine transcription as well as subsequent activation of microglia that is potentially associated with brain inflammation. Behavioral analyses revealed that P35 and P60 animals, neonatally exposed to propofol, had significantly higher motor activity during three consecutive days of testing in the open field, though formation of the intersession habituation was not prevented. This data, together with our previous results, contributes to elucidation of complex mechanisms of propofol toxicity in developing brain.

The signaling pathways by which the Fas/FasL system accelerates oocyte aging

In spite of great efforts, the mechanisms for postovulatory oocyte aging are not fully understood. Although our previous work showed that the FasL/Fas signaling facilitated oocyte aging, the intra-oocyte signaling pathways are unknown. Furthermore, the mechanisms by which oxidative stress facilitates oocyte aging and the causal relationship between Ca2+ rises and caspase-3 activation and between the cell cycle and apoptosis during oocyte aging need detailed investigations. Our aim was to address these issues by studying the intra-oocyte signaling pathways for Fas/FasL to accelerate oocyte aging. The results indicated that sFasL released by cumulus cells activated Fas on the oocyte by increasing reactive oxygen species via activating NADPH oxidase. The activated Fas triggered Ca2+ release from the endoplasmic reticulum by activating phospholipase C-γ pathway and cytochrome c pathway. The cytoplasmic Ca2+ rises activated calcium/calmodulin-dependent protein kinase II (CaMKII) and caspase-3. While activated CaMKII increased oocyte susceptibility to activation by inactivating maturation-promoting factor (MPF) through cyclin B degradation, the activated caspase-3 facilitated further Ca2+releasing that activates more caspase-3 leading to oocyte fragmentation. Furthermore, caspase-3 activation and fragmentation were prevented in oocytes with a high MPF activity, suggesting that an oocyte must be in interphase to undergo apoptosis.

The dual role of autophagy under hypoxia-involvement of interaction between autophagy and apoptosis

Hypoxia is one of severe cellular stress and it is well known to be associated with a worse outcome since a lack of oxygen accelerates the induction of apoptosis. Autophagy, an important and evolutionarily conserved mechanism for maintaining cellular homeostasis, is closely related to the apoptosis caused by hypoxia. Generally autophagy blocks the induction of apoptosis and inhibits the activation of apoptosis-associated caspase which could reduce cellular injury. However, in special cases, autophagy or autophagy-relevant proteins may help to induce apoptosis, which could aggravate cell damage under hypoxia condition. In addition, the activation of apoptosis-related proteins-caspase can also degrade autophagy-related proteins, such as Atg3, Atg4, Beclin1 protein, inhibiting autophagy. Although the relationship between autophagy and apoptosis has been known for rather complex for more than a decade, the underlying regulatory mechanisms have not been clearly understood. This short review discusses and summarizes the dual role of autophagy and the interaction and molecular regulatory mechanisms between autophagy and apoptosis under hypoxia.

The emerging role of acid sphingomyelinase in autophagy

Autophagy, the main intracellular process of cytoplasmic material degradation, is involved in cell survival and death. Autophagy is regulated at various levels and novel modulators of its function are being continuously identified. An intriguing recent observation is that among these modulators is the sphingolipid metabolising enzyme, Acid Sphingomyelinase (A-SMase), already known to play a fundamental role in apoptotic cell death participating in several pathophysiological conditions. In this review we analyse and discuss the relationship between autophagy and A-SMase describing how A-SMase may regulate it and defining, for the first time, the existence of an A-SMase-autophagy axis. The imbalance of this axis plays a role in cancer, nervous system, cardiovascular, and hepatic disorders.

Regulation of hippocampal Fas receptor and death-inducing signaling complex after kainic acid treatment in mice

Kainic acid (KA)-induced brain neuronal cell death (especially in the hippocampus) was shown to be mainly mediated by the intrinsic (mitochondrial) apoptotic pathway. This study investigated the regulation of the extrinsic apoptotic pathway mediated by Fas ligand/Fas receptor and components of the indispensable death-inducing signaling complex (DISC) in the hippocampus (marked changes) and cerebral cortex (modest changes) of KA-treated mice. KA (45mg/kg) induced a severe behavioral syndrome with recurrent motor seizures (scores; maximal at 60-90min; minimal at 72h) with activation of hippocampal pro-apoptotic JNK (+2.5 fold) and increased GFAP (+57%) and nuclear PARP-1 fragmentation (+114%) 72h post-treatment (delayed neurotoxicity). In the extrinsic apoptotic pathway (hippocampus), KA (72h) reduced Fas ligand (-92%) and Fas receptor aggregates (-24%). KA (72h) also altered the contents of major DISC components: decreased FADD adaptor (-44%), reduced activation of initiator caspase-8 (-47%) and increased survival FLIP-S (+220%). Notably, KA (72h) upregulated the content of anti-apoptotic p-Ser191 FADD (+41%) and consequently the expression of p-FADD/FADD ratio (+1.9-fold), a neuroplastic index. Moreover, the p-FADD dependent transcription factor NF-κB was also increased (+61%) in the hippocampus after KA (72h). The convergent adaptation of the extrinsic apoptotic machinery 72h after KA in mice (with otherwise normal gross behavior) is a novel finding which suggests the induction of survival mechanisms to partly counteract the delayed neuronal death in the hippocampus.

Targeting cholesterol with β-cyclodextrin sensitizes cancer cells for apoptosis

We found that targeting cholesterol with beta-cyclodextrin (bCD) and its derivatives disrupted signal transduction between PI3K and AKT, attenuating AKT pro-survival signals. In their absence, 2-deoxyglucose (2DG) caused anti-apoptotic protein Mcll to dissociate from pro-apoptotic Bak at mitochondria. Normally Bak is sequestered by its inhibitory associations with Mcll and Bcl-xL, and only when Bak is released from both, is it free to form oligomers through which cytochrome c can escape into the cytosol. Thus an addition of a bcl-2 antagonist dissociates Bak from Bcl-xL, triggering cytochrome c release and inducing apoptosis. 2DG-bCD can also sensitize type II cancer cells for TRAIL-mediated apoptosis.

The neuroplastic index p-FADD/FADD and phosphoprotein PEA-15, interacting at GABAA receptor, are upregulated in brain cortex during midazolam-induced hypnosis in mice

Fas-associated death domain (FADD) adaptor is involved in the signaling of metabotropic G protein-coupled receptors, whose agonists stimulate its phosphoryaltion (p) increasing p-FADD/FADD ratio in brain. Whether FADD might also participate in the activation of dissimilar receptors such as the ligand-gated ion channels is not known. This study investigated the role of FADD and phosphoprotein-enriched in astrocytes of 15 kDa (PEA-15, a FADD partner) in the activation of γ-aminobutyric acid-A (GABAA) receptor, which mediates the hypnotic effect of midazolam. The main findings revealed that during the time course of midazolam (60 mg/kg)-induced hypnosis in mice (about 2 h) p-FADD (and p-FADD/FADD ratio) as well as p-PEA (and its phosphorylating Akt1 kinase) were markedly increased (36-80%) in brain cortex, and these effects were partially (only p-FADD) or fully prevented by flumazenil (a neutral allosteric ligand) and FG 7142 (a partial negative allosteric ligand) acting at GABAA receptors. The upregulation of cortical p-FADD/FADD was exclusively observed in the nucleus (up to 2.8-fold), where the transciption factor NF-κB was also increased (up to 46%), and that of p-PEA/p-Akt1 only in the cytosol (up to 53%), suggesting that p-FADD/p-PEA/p-Akt1 are involved in sleep-induced neuroplasticity. Repeated treatment with midazolam (60 mg/kg, 4 days) induced behavioral (prolonged sleep latency and reduced sleeping time) and neurochemical (reduced p-FADD/p-PEA contents) tolerance. These findings indicated that p-FADD/p-PEA are novel molecules in GABAA receptor signaling and that cortical p-PEA and p-FADD, working in tandem, are involved in the complex molecular processes leading to the hypnotic effect of midazolam in mice.

In vivo Effects in Melanoma of ROCK Inhibition-Induced FasL Overexpression

Ectopic Fas-ligand (FasL) expression in tumor cells is responsible for both tumor escape through tumor counterattack of Fas-positive infiltrating lymphocytes and tumor rejection though inflammatory and immune responses. We have previously shown that RhoA GTPase and its effector ROCK negatively control FasL membrane expression in murine melanoma B16F10 cells. In this study, we found that B16F10 treatment with the ROCK inhibitor H1152 reduced melanoma development in vivo through FasL membrane overexpression. Although H1152 treatment did not reduce tumor growth in vitro, pretreatment of tumor cells with this inhibitor delayed tumor appearance, and slowed tumor growth in C57BL/6 immunocompetent mice. Thanks to the use of mice-bearing mutated Fas receptors (B6/lpr), we found that reduced tumor growth, observed in immunocompetent mice, was linked to FasL overexpression induced by H1152 treatment. Tumor growth analysis in immunosuppressed NUDE and IFN-γ-KO mice highlighted major roles for T lymphocytes and IFN-γ in the H1152-induced tumor growth reduction. Histological analyses of subcutaneous tumors, obtained from untreated versus H1152-treated B16F10 cells, showed that H1152 pretreatment induced a strong intratumoral infiltration of leukocytes. Cytofluorometric analysis showed that among these leukocytes, the number of activated CD8 lymphocytes was increased. Moreover, their antibody-induced depletion highlighted their main responsibility in tumor growth reduction. Subcutaneous tumor growth was also reduced by repeated intravenous injections of a clinical ROCK inhibitor, Fasudil. Finally, H1152-induced ROCK inhibition also reduced pulmonary metastasis implantation independently of T cell-mediated immune response. Altogether, our data suggest that ROCK inhibitors could become interesting pharmacological molecules for melanoma immunotherapy.

Signal Integration during T Lymphocyte Activation and Function: Lessons from the Wiskott-Aldrich Syndrome

Over the last decades, research dedicated to the molecular and cellular mechanisms underlying primary immunodeficiencies (PID) has helped to understand the etiology of many of these diseases and to develop novel therapeutic approaches. Beyond these aspects, PID are also studied because they offer invaluable natural genetic tools to dissect the human immune system. In this review, we highlight the research that has focused over the last 20 years on T lymphocytes from Wiskott–Aldrich syndrome (WAS) patients. WAS T lymphocytes are defective for the WAS protein (WASP), a regulator of actin cytoskeleton remodeling. Therefore, study of WAS T lymphocytes has helped to grasp that many steps of T lymphocyte activation and function depend on the crosstalk between membrane receptors and the actin cytoskeleton. These steps include motility, immunological synapse assembly, and signaling, as well as the implementation of helper, regulatory, or cytotoxic effector functions. The recent concept that WASP also works as a regulator of transcription within the nucleus is an illustration of the complexity of signal integration in T lymphocytes. Finally, this review will discuss how further study of WAS may contribute to solve novel challenges of T lymphocyte biology.

The role of CD95 and CD95 ligand in cancer

CD95 (Fas/APO-1) and its ligand, CD95L, have long been viewed as a death receptor/death ligand system that mediates apoptosis induction to maintain immune homeostasis. In addition, these molecules are important in the immune elimination of virus-infected cells and cancer cells. CD95L was, therefore, considered to be useful for cancer therapy. However, major side effects have precluded its systemic use. During the last 10 years, it has been recognized that CD95 and CD95L have multiple cancer-relevant nonapoptotic and tumor-promoting activities. CD95 and CD95L were discovered to be critical survival factors for cancer cells, and were found to protect and promote cancer stem cells. We now discuss five different ways in which inhibiting or eliminating CD95L, rather than augmenting, may be beneficial for cancer therapy alone or in combination with standard chemotherapy or immune therapy.