Role of mitogen-activated protein kinases in activation-induced apoptosis of T cells

Monovalent Anti-CD3 Antibodies Effectively Eliminate the TCR-Positive Fraction of TCR-Deleted Allogeneic CAR-T Cells to Prevent GVHD

Chimeric antigen receptor-transduced T (CAR-T) cell therapy is an effective cell therapy against advanced hematological tumors. However, the use of autologous T cells limits its timely and universal generation. Allogeneic CAR-T cell therapy may be a good alternative as a ready-to-use therapeutic. Graft-versus-host disease (GVHD) is an obstacle for allogeneic CAR-T cells, but can be prevented by TCR deletion through genome editing. However, the remaining TCR-positive cells must be eliminated by costly, large-scale magnetic cell separation. Therefore, an alternative method for removing TCR-positive cells is needed. In this study, we found that monovalent anti-CD3 Abs such as Fab and single-chain variable fragment (scFv), but not whole IgG, induce apoptosis of in vitro expanded T cells, thereby effectively depleting residual TCR-positive T cells during TCR-deleted CAR-T cell generation and ultimately preventing xenogeneic GVHD in vivo. Thus, monovalent anti-CD3 treatment during allogeneic CAR-T cell manufacturing would be an efficient method to prevent GVHD.

Mitochondrial control of lymphocyte homeostasis

Mitochondria play a multitude of essential roles within mammalian cells, and understanding how they control immunity is an emerging area of study. Lymphocytes, as integral cellular components of the adaptive immune system, rely on mitochondria for their function, and mitochondria can dynamically instruct their differentiation and activation by undergoing rapid and profound remodelling. Energy homeostasis and ATP production are often considered the primary functions of mitochondria in immune cells; however, their importance extends across a spectrum of other molecular processes, including regulation of redox balance, signalling pathways, and biosynthesis. In this review, we explore the dynamic landscape of mitochondrial homeostasis in T and B cells, and discuss how mitochondrial disorders compromise adaptive immunity.

A novel trivalent non-Fc anti-CD3 Collabody preferentially induces Th1 cell apoptosis in vitro and long-lasting remission in recent-onset diabetic NOD mice

Specific anti-CD3 treatment is deemed to be a promising therapy for allograft rejection and type 1 diabetes (T1D). Fc receptor (FcR) reduced-binding antibodies, by avoiding adverse effects of Fc and FcR interaction, have good therapeutic potential. We generated a trivalent anti-mouse-CD3 Collabody, h145CSA, by using a triplex-forming collagen-like peptide (Gly-Pro-Pro)10 to drive the trimerization of the Fab fragments. Exposure to h145CSA, but not its bivalent counterparts 145-2C11 and h145chIgGAA (FcR reduced-binding format), upregulates FasL expression on Th1 cells and causes Th1 cell apoptosis. Administration of h145CSA invokes minimal mitogenic effects in mice. The ability of multiple dosing of h145CSA to induce splenic CD4+ T-cell depletion is comparable to bivalent antibodies but is characterized by more rapid CD4+ T-cell recovery kinetics. h145CSA is more potent than h145chIgGAA in inducing long-lasting remission in recent-onset diabetic NOD mice. Its therapeutic effect is accompanied by a significantly lower percentage of CD4+IFNγ+ T cells and a higher Treg/Th1 ratio in pancreatic and mesenteric lymph nodes. The results of our study demonstrate that trivalent non-Fc anti-CD3 Collabody has the potential to be used in the treatment of T1D.

Proteomic Analysis of Two Weight Classes of Mule Duck "foie gras" at the End of an Overfeeding Period

The weight of the liver is one of the important selection criteria in the quality of “foie gras”. This factor is highly variable despite the fact that individuals are reared, overfed and slaughtered in the same way. In this study, we performed an analysis of the proteome profile of two weight classes of light (between 550 and 599 g) and heavy (more than 700 g) livers. For the analysis of the proteic extracts, a liquid chromatographic analysis coupled with mass spectrometry was carried out. In low-weight livers, aerobic energy metabolism, protein metabolism and lipid metabolism oriented toward export and beta-oxidation were overexpressed. On the contrary, high weight livers were characterized by anaerobic energy metabolism and a more active protein catabolism associated with cell apoptosis and reorganization of the cell structure.

Immune-Inflammation in Atherosclerosis: A New Twist in an Old Tale

Background and Objective:

Atherosclerosis, a chronic and progressive inflammatory disease, is triggered by the activation of endothelial cells followed by infiltration of innate and adaptive immune cells including monocytes and T cells in arterial walls. Major populations of T cells found in human atherosclerotic lesions are antigen-specific activated CD4+ effectors and/or memory T cells from Th1, Th17, Th2 and Treg subsets. In this review, we will discuss the significance of T cell orchestrated immune inflammation in the development and progression of atherosclerosis.

Discussion:

Pathogen/oxidative stress/lipid induced primary endothelial wound cannot develop to a full-blown atherosclerotic lesion in the absence of chronically induced inflammation. While the primary inflammatory response might be viewed as a lone innate response, the persistence of such a profound response over time must be (and is) associated with diverse local and systemic T cell responses. The interplay between T cells and innate cells contributes to a phenomenon called immuneinflammation and has an impact on the progression and outcome of the lesion. In recent years immuneinflammation, an old term, has had a comeback in connecting the puzzle pieces of chronic inflammatory diseases.

Conclusion:

Taking one-step back and looking from afar at the players of immune-inflammation may help us provide a broader perspective of these complicated interactions. This may lead to the identification of new drug targets and the development of new therapies as well as preventative measures.

JNK1 and ERK1/2 modulate lymphocyte homeostasis via BIM and DRP1 upon AICD induction

The Activation-Induced Cell Death (AICD) is a stimulation-dependent form of apoptosis used by the organism to shutdown T-cell response once the source of inflammation has been eliminated, while allowing the generation of immune memory. AICD is thought to progress through the activation of the extrinsic Fas/FasL pathway of cell death, leading to cytochrome-C release through caspase-8 and Bid activation. We recently described that, early upon AICD induction, mitochondria undergo structural alterations, which are required to promote cytochrome-C release and execute cell death. Here, we found that such alterations do not depend on the Fas/FasL pathway, which is instead only lately activated to amplify the cell death cascade. Instead, such alterations are primarily dependent on the MAPK proteins JNK1 and ERK1/2, which, in turn, regulate the activity of the pro-fission protein Drp1 and the pro-apoptotic factor Bim. The latter regulates cristae disassembly and cooperate with Drp1 to mediate the Mitochondrial Outer Membrane Permeabilization (MOMP), leading to cytochrome-C release. Interestingly, we found that Bim is also downregulated in T-cell Acute Lymphoblastic Leukemia (T-ALL) cells, this alteration favouring their escape from AICD-mediated control.

The Role of Reactive Oxygen Species in Regulating T Cell-mediated Immunity and Disease

T lymphocytes rely on several metabolic processes to produce the high amounts of energy and metabolites needed to drive clonal expansion and the development of effector functions. However, many of these pathways result in the production of reactive oxygen species (ROS), which have canonically been thought of as cytotoxic agents due to their ability to damage DNA and other subcellular structures. Interestingly, ROS has recently emerged as a critical second messenger for T cell receptor signaling and T cell activation, but the sensitivity of different T cell subsets to ROS varies. Therefore, the tight regulation of ROS production by cellular antioxidant pathways is critical to maintaining proper signal transduction without compromising the integrity of the cell. This review intends to detail the common metabolic sources of intracellular ROS and the mechanisms by which ROS contributes to the development of T cell-mediated immunity. The regulation of ROS levels by the glutathione pathway and the Nrf2-Keap1-Cul3 trimeric complex will be discussed. Finally, T cell-mediated autoimmune diseases exacerbated by defects in ROS regulation will be further examined in order to identify potential therapeutic interventions for these disorders.

Suppression of colitis-associated carcinogenesis through modulation of IL-6/STAT3 pathway by balsalazide and VSL#3

BACKGROUND AND AIM

Recent studies suggest that the anti-inflammatory agent balsalazide (BSZ) and probiotic agent VSL#3 have potential therapeutic benefits for the treatment of patients with inflammatory bowel disease. However, their effectiveness in preventing colitis-associated carcinogenesis (CAC) remains uncertain. The aim of the present study was to determine the chemopreventive effects of BSZ and VSL#3 in the murine azoxymethane (AOM)/dextran sodium sulfate (DSS) model.

METHODS

C57B/L6J mice were randomly divided into four groups: CAC group, BSZ group, VSL#3 group, and BSZ + VSL#3 group. After 2 weeks, the AOM/DSS model was induced by AOM injection followed by two cycles of 2% DSS.

RESULTS

During first and second cycles of DSS, the number of F4/80-positive macrophages was significantly lower in the drug-treated groups compared with the CAC group (P < 0.05). At the endpoint, the total numbers of tumors in the drug-treated groups were significantly low compared with the CAC group (P < 0.05), and the drug-treated groups had significantly lower F4/80-positive macrophages in the tumor stroma (P < 0.01). The protein production of macrophage inflammatory protein 1 beta, monocyte chemoattractant protein-1, interleukin (IL)-6, and IL-10 in the colon tissues decreased in concordance with the plasma concentrations of the cytokines (P < 0.05). The drug-treated groups revealed lower expression of p-STAT3 compared with the CAC group. In addition, BCL2 decreased, and BAX increased markedly in the BSZ + VSL#3 group.

CONCLUSIONS

These results revealed that BSZ and VSL#3 have chemopreventive effects against CAC through IL-6/STAT3 suppression. BSZ and VSL#3 could be suitable options for chemoprevention of colorectal cancer.

Vitamin K1 exerts antiproliferative effects and induces apoptosis in three differently graded human colon cancer cell lines

Vitamin K1 has been demonstrated as having anticancer potentiality mainly in liver cancer cells. Beyond the reported mechanisms of cancer inhibition (cell cycle arrest and induction of apoptosis), a possible control by vitamin K1 on molecules affecting cell growth could be hypothesized. In the literature, few (if any) data are available on its antitumor effects on colon cancer cells. Therefore, the aims of the study were to investigate in three differently graded human colon cancer cell lines (Caco-2, HT-29, and SW480) the effects of increasing concentrations of vitamin K1 (from 10 μM to 200 μM) administered up to 72 h on (1) cell proliferation, (2) apoptosis with the possible involvement of the MAPK pathway, and (3) polyamine biosynthesis. Vitamin K1 treatment caused a significant antiproliferative effect and induced apoptosis in all the cell lines, with the involvement of the MAPK pathway. A concomitant and significant decrease in the polyamine biosynthesis occurred. This is the first study demonstrating a significant polyamine decrease in addition to the antiproliferative and proapoptotic effects following vitamin K1 administration to colon cancer cell lines. Therapeutically, combinations of vitamin K1 with polyamine inhibitors and/or analogues may represent a suitable option for chemoprevention and/or treatment in future strategies for colorectal cancer management.

Temperature fluctuations during deep temperature cryopreservation reduce PBMC recovery, viability and T-cell function

The ability to analyze cryopreserved peripheral blood mononuclear cell (PBMC) from biobanks for antigen-specific immunity is necessary to evaluate response to immune-based therapies. To ensure comparable assay results, collaborative research in multicenter trials needs reliable and reproducible cryopreservation that maintains cell viability and functionality. A standardized cryopreservation procedure is comprised of not only sample collection, preparation and freezing but also low temperature storage in liquid nitrogen without any temperature fluctuations, to avoid cell damage. Therefore, we have developed a storage approach to minimize suboptimal storage conditions in order to maximize cell viability, recovery and T-cell functionality. We compared the influence of repeated temperature fluctuations on cell health from sample storage, sample sorting and removal in comparison to sample storage without temperature rises. We found that cyclical temperature shifts during low temperature storage reduce cell viability, recovery and immune response against specific-antigens. We showed that samples handled under a protective hood system, to avoid or minimize such repeated temperature rises, have comparable cell viability and cell recovery rates to samples stored without any temperature fluctuations. Also T-cell functionality could be considerably increased with the use of the protective hood system compared to sample handling without such a protection system. This data suggests that the impact of temperature fluctuation on cell integrity should be carefully considered in future clinical vaccine trials and consideration should be given to optimal sample storage conditions.

Effects of heavy metals on mitogen-activated protein kinase pathways

The signaling pathways leading to cellular protection or cell death following exposure to heavy metals have not been fully clarified. Mitogen-activated protein kinases (MAPKs), i.e., extracellular signal-regulated protein kinase (ERK), c-Jun NH(2)-terminal kinase (JNK) and p38 MAPK transmit extracellular signals into the nucleus, and have been shown to participate in a diverse array of cellular functions such as cell growth, differentiation and apoptosis. Treatment with cadmium, inorganic mercury or tributyltin can activate ERK, JNK and p38 MAPK, and induces the expression of c-fos and c-jun genes prior to the development of apoptosis. However, the members of the MAPK family appear to be differentially activated depending on the heavy metal and the cell type exposed. Consequently, various cellular responses may be caused by the distinct pattern of MAPKs activation. MAPKs may be one of the important cellular signal transduction pathways affected by various environmental pollutants, including heavy metals.

The role of Raf-1 kinase in diabetic retinopathy

Many metabolic pathways, including oxidative stress, PKC and the polyol pathway have been implicated in the development of diabetic retinopathy, but despite extensive research, its pathogenesis remains unclear. Recent studies have shown the role of a low-molecular-weight GTP-binding protein (H-Ras)-mediated signaling pathway in its development. The key effector protein of Ras function is a threonine/serine kinase-Raf kinase, and this kinase is involved in a variety of functions, including the cell cycle and proliferation and apoptosis. In animal models of diabetic retinopathy, Raf kinase is activated in the retina and its microvasculature. Activated Raf kinase is associated with increased apoptosis of retinal capillary cells, the process that precedes the development of retinal histopathology, and inhibition of Raf kinase ameliorates apoptosis. In clinical settings, inhibitors of Raf kinase have shown promising results in cancer treatment, and Raf kinase antisense oligonucleotides, iCo 007, is now in Phase II trial for macular edema, a chronic ocular disease associated with retinal neovascularization. Further elucidating the role of Raf kinase in diabetic retinopathy, and advances in the generation of antisense therapy for chronic diseases, should help test Raf antisense oligonucleotides for the treatment of this blinding complication that diabetic patients fear the most.

Deletion of alloreactive T cells by veto cytotoxic T lymphocytes is mediated through extracellular signal-regulated kinase phosphorylation

BACKGROUND

Anti third-party cytotoxic T lymphocytes (CTLs) were shown to exhibit marked veto activity, thereby inducing transplantation tolerance across major histocompatibility antigens. Elimination of effector cells requires co-expression of CD8 and FasL on the veto cells and is mediated through CD8-major histocompatibility complex (MHC) class I interaction and Fas-Fas ligand signaling.

METHODS

To further interrogate the signaling events induced in the effector cells on their interaction with veto cell populations, effector cells from 2C transgenic mice were preincubated with different signaling inhibitors and were subject to fluorescence-activated cell sorting and western blot analysis.

RESULTS

Screening with inhibitors revealed specific inhibition only with the map kinase (MEK)/extracellular signal regulated kinase (ERK) inhibitor, U0126. Accordingly, fluorescence-activated cell sorting and western blot analysis showed that ERK phosphorylation is induced in the effector cells within 1 hr of incubation with the veto cells. ERK phosphorylation had no effect on the Fas expression level, nor was it reduced when using effector cells from Fas KO mice. Examination of ERK phosphorylation in high and low MHC-I expressing effectors revealed marked differences, suggesting that the interaction between CD8 on the veto CTL, and MHC-I on the effector cells is likely responsible for ERK phosphorylation. Furthermore, XIAP in 2C cells is specifically reduced on binding to the cognate veto cells during the mixed lymphocyte reaction but before the appearance of Annexin V reactivity.

CONCLUSIONS

These results suggest that the interaction between CD8 on veto CTL and the MHC class I alpha3 domain on the effector cell, leads to phosphorylation of MEK/ERK in the latter cell, associated with a significant reduction of XIAP levels which, in turn, enables potent triggering of Fas-FasL mediated apoptosis on cognate binding of the veto CTLs.

KiSS1 metastasis suppressor gene product induces suppression of tyrosine kinase receptor signaling to Akt, tumor necrosis factor family ligand expression, and apoptosis

The powerful metastasis suppressor function of KiSS1 gene products has been demonstrated in both clinical studies and experimental models, but its mechanism is still incompletely understood. Studies on the antimetastatic function of KiSS1 and GPR54 largely focused on the autocrine inhibition of cell motility, despite experimental evidence of an alternative post-migratory effect. We showed previously that the activation of its cognate receptor GPR54 by kisspeptin-10 suppressed the capacity of the prometastatic chemokine receptor CXCR4 to induce chemotaxis in response to stromal cell derived factor 1 and abolished the activation of Akt by CXCR4. We demonstrate here that activation of GPR54 can also abolish the activation of Akt by the tyrosine kinase receptors for epidermal growth factor and insulin. The signaling of GPR54 was sufficient to trigger apoptosis in epithelial and lymphoid cell lines. Surprisingly, this phenomenon depended largely on the activation of extracellular signal-regulated kinase (ERK) rather than the inhibition of Akt. Activation of GPR54 resulted in the ERK-dependent expression of tumor necrosis factor-alpha and FasL in a lymphoid cell line, the latter being the main trigger of apoptosis. These data provide novel mechanisms relevant to a potential autocrine metastasis suppression effect of KiSS1 on GPR54-positive tumor cells. More importantly, they also establish an experimental basis for a paracrine mode of action by which kisspeptins suppress the metastatic potential of tumor cells lacking expression of the receptor, as observed in several animal models of metastasis. The action on stromal cells significantly broadens the clinical relevance of this metastasis suppressor.

Galectin-8 induces apoptosis in Jurkat T cells by phosphatidic acid-mediated ERK1/2 activation supported by protein kinase A down-regulation

Galectins have been implicated in T cell homeostasis playing complementary pro-apoptotic roles. Here we show that galectin-8 (Gal-8) is a potent pro-apoptotic agent in Jurkat T cells inducing a complex phospholipase D/phosphatidic acid signaling pathway that has not been reported for any galectin before. Gal-8 increases phosphatidic signaling, which enhances the activity of both ERK1/2 and type 4 phosphodiesterases (PDE4), with a subsequent decrease in basal protein kinase A activity. Strikingly, rolipram inhibition of PDE4 decreases ERK1/2 activity. Thus Gal-8-induced PDE4 activation releases a negative influence of cAMP/protein kinase A on ERK1/2. The resulting strong ERK1/2 activation leads to expression of the death factor Fas ligand and caspase-mediated apoptosis. Several conditions that decrease ERK1/2 activity also decrease apoptosis, such as anti-Fas ligand blocking antibodies. In addition, experiments with freshly isolated human peripheral blood mononuclear cells, previously stimulated with anti-CD3 and anti-CD28, show that Gal-8 is pro-apoptotic on activated T cells, most likely on a subpopulation of them. Anti-Gal-8 autoantibodies from patients with systemic lupus erythematosus block the apoptotic effect of Gal-8. These results implicate Gal-8 as a novel T cell suppressive factor, which can be counterbalanced by function-blocking autoantibodies in autoimmunity.

Zinc induces ERK-dependent cell death through a specific Ras isoform

The effect of Zn on p53-independent cell death was examined in IIC9 embryonic fibroblasts. Despite the fact that these cells are p53-minus, Zn-mediated death occurs via an apoptotic mechanism. Death is facilitated by the presence of the Zn ionophore, pyrithione, indicating that intracellular Zn initiates the death response. Our investigations of the mechanism of Zn action demonstrate that Zn induces the death of IIC9 cells in a manner that is ERK-dependent. Expression of dn-(dominant negative)Ras attenuates ERK1/2 activation by Zn, and correspondingly reduces its cytotoxic effects. Raf-RBD pull-down experiments confirm that Zn treatment activates Ras and identified H-Ras as the specific isoform activated. This contrasts the activation of N-Ras that occurs when IIC9 cells are stimulated with thrombin. Thus, although the prolonged activation of the Ras/ERK pathway by Zn is similar to that seen when induced by mitogen, the distinguishing feature appears to be the isoform specificity of Ras activation.

The TCL1 oncoprotein inhibits activation-induced cell death by impairing PKCtheta and ERK pathways

The TCL1/MTCP1 oncogenes were identified on the basis of their involvement in T-cell prolymphocytic leukemia (T-PLL). TCL1 and MTCP1 proteins directly interact with AKT and modulate the AKT signal-transduction pathway, but the relevance of this mechanism in leukemogenesis remains unclear. We investigate the biologic functions of TCL1 in the T-cell lineage using various cell lines, and primary malignant and normal lymphocytes. In the Jurkat cell line, expression of TCL1 had no effect in unstimulated cells, whereas it abrogated activation-induced cell death (AICD). These cellular effects were concomitant with a major inhibition by TCL1 of PKCtheta and ERK pathways. Secondly, the TCL1-driven T-cell leukemia cell line SUP-T11 was shown to have impaired PKCtheta and ERK phosphorylation upon stimulation, which were restored by TCL1 inhibition using RNA interference. Finally, defects in these pathways were also observed in primary malignant (T-PLL) and transduced normal T lymphocytes expressing TCL1. Altogether, our data demonstrated that TCL1 inhibits AICD in T cells by blocking PKCtheta and ERK activation, upon cellular activation.

Antithymocyte globulins suppress dendritic cell function by multiple mechanisms

BACKGROUND

The polyclonal rabbit antithymocyte and anti-T-cell immunoglobulins (ATGs) Thymoglobulin (TG) and ATG-Fresenius S (ATG-F) have been widely used for the prevention and therapy of allograft rejection and graft versus host disease in transplantation. Although immunosuppressive mechanisms of ATGs on T cells are well studied, less is known about their impact on dendritic cells (DCs).

METHODS

Effects of TG and ATG-F on immune functions and signaling pathways of human monocyte-derived DCs were determined by flow cytometry, enzyme-linked immunosorbent assay, Western blot, apoptosis assays, endocytosis assays, and T cell stimulation assays.

RESULTS

TG and ATG-F bind rapidly and with high affinity to CD11c, CD80, CD86, CD40, CD36, CD38, CD206, and human leukocyte antigen-DR on DCs. TG and, to a lesser extent, ATG-F induce apoptosis in immature and mature DCs. Macropinocytotic and receptor-mediated endocytotic antigen uptake in immature DCs is inhibited by TG and ATG-F due to their binding of the C-type lectins CD206 and CD209. TG and ATG-F induce activation of the mitogen-activated protein kinases ERK1/2 and p38 that contributes to the induction of apoptosis. TG and ATG-F also induce cytoplasmic-nuclear translocation of the NF-kappaB/Rel transcription factors RelB, RelA, p50, and p52. Production of interleukin-12p70 in mature DCs is suppressed by TG and ATG-F. TG and ATG-F reduce the capacity of mature DCs to stimulate allogeneic and autologous T cells.

CONCLUSIONS

ATGs interfere with basic DC functions, suggesting that DCs are relevant targets for the immunosuppressive action of ATGs in transplantation.

Cryopreservation of intact human ovary with its vascular pedicle

BACKGROUND

The aim of this study was to assess the immediate post-thawing injury to the human ovary that was cryopreserved either as a whole with its vascular pedicle or as ovarian cortical strips.

MATERIALS AND METHODS

Bilateral oophorectomy was performed in two women (46 and 44 years old) undergoing vaginal hysterectomy and laparoscopic hysterectomy, respectively. Both women agreed to donate their ovaries for experimental research. In both patients, one of the harvested ovaries was sectioned and cryopreserved (by slow freezing) as ovarian cortical strips of 1.0 x 1.0 x 5.0 mm(3) each. The other ovary was cryopreserved intact with its vascular pedicle. After thawing 7 days later, follicular viability, histology, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick-end labelling (TUNEL) assay (to detect apoptosis) and immunoperoxidase staining (to define Bcl-2 and p53 protein expression profiles) of the ovarian tissue were performed. Tissues from non-cryopreserved ovaries served as control specimens (two cases).

RESULTS

The overall viability of the primordial follicles was 75 and 78% in intact cryopreserved-thawed (C-T) ovaries and 81 and 83% in ovarian cortical strips in the 46- and 44-year-old patients, respectively. Comparable primordial follicle counts, absence of features of necrosis, mean values of apoptosis and weak Bcl-2 and p53 protein expressions were observed both in the intact C-T ovary and in the C-T ovarian cortical strips.

CONCLUSIONS

Cryoperfusion and cryopreservation of entire human ovary can be achieved with the maintenance of excellent viability of the superficial and the deeper tissues using a slow-freezing protocol. Cryopreservation injury is associated neither with significant alteration in the expression pattern of Bcl-2 and p53 proteins in the ovarian tissues nor with significant follicular damage.

Regulated expression of galectin-1 during T-cell activation involves Lck and Fyn kinases and signaling through MEK1/ERK, p38 MAP kinase and p70S6 kinase

Recent evidence has implicated galectins and their carbohydrate ligands as novel regulators of T-cell homeostasis. Galectin-1 (Gal-1), a member of this family, inhibits clonal expansion, induces apoptosis of antigen-primed T lymphocytes and suppresses the development of T-cell-mediated autoimmune diseases in vivo. Because the beta-galactoside-binding protein is expressed in activated but not resting T cells, it has been hypothesized that Gal-1-induced apoptosis may constitute an autocrine suicide mechanism to eliminate activated T cells contributing to the termination of an effector immune response. We undertook this study to investigate the signals and intracellular pathways leading to Gal-1 expression during T-cell activation. When T cells were stimulated either with anti-CD3 or anti-CD28 monoclonal antibody plus PMA in the presence of accessory cells, a sustained up-regulation of Gal-1 was observed, reaching a plateau between days 3 and 5 following CD3 engagement or costimulation through CD28. Investigation of the signal transduction events involved in this process revealed a role for Lck and Fyn kinases, since the Src kinase inhibitor PP1 inhibited the up-regulated expression of Gal-1 following T-cell activation. Downstream signaling routes involve mitogen-activated protein kinase (MAPK) kinase (MEK)1/extracellular signal-regulated kinase (ERK) and p38 MAPK, as Gal-1 expression was prevented by U0126 and SB202190. In addition, expression of Gal-1 involves interleukin (IL)-2-dependent signaling routes triggered by p70S6 kinase, as it could be inhibited by rapamycin. This is the first demonstration of the intracellular pathways that control activation-induced expression of Gal-1, which may reveal potential targets for immune intervention to modulate expression of this beta-galactoside-binding protein in pathological disorders.

Pepsin-Digested Bovine Lactoferrin Induces Apoptotic Cell Death With JNK/SAPK Activation in Oral Cancer Cells

Lactoferrin, a member of the transferrin family, is iron-binding and a strongly cationic 76 kDa glycoprotein. In breast milk it is secreted in high concentrations from glandular epithelia and is also present in other exocrine fluids including saliva. In the present study, we examined the biological mechanisms of apoptosis induced by pepsin-digested-lactoferrin peptide (Lfn-p) in the human oral squamous cell carcinoma cell line SAS. We found that treatment with Lfn-p induced cell death with apoptotic nuclear changes, preceded by the cleavage of caspase-3 and poly (ADP-ribose) polymerase (PARP) in the apoptotic cells. Treatment with Lfn-p induced phosphorylation of extracellular signal-regulated kinase (ERK1/2), a member of the MAP kinase family, at early stages of apoptosis. Another MAP kinase, c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK), was also phosphorylated by treatment with Lfn-p. Pretreatment of SAS cells with SP600125, a JNK/SAPK inhibitor, diminished Lfn-induced apoptosis, as assessed by determining released lactate dehydrogenase activity. On the other hand, the MEK1 inhibitors PD98059 or U0126 showed no effect on repression of cell death, but rather an increase. These results suggest that JNK/SAPK activation may play an important role in Lfn-p-induced apoptotic cell death of human oral squamous cell carcinoma cells.

Rescuing melanoma epitope-specific cytolytic T lymphocytes from activation-induced cell death, by SP600125, an inhibitor of JNK: implications in cancer immunotherapy

Activation-induced cell death (AICD) as well as programmed cell death (PCD) serve to control the expansion of activated T cells to limit untoward side effects of continued effector responses by T cells and to maintain homeostasis. AICD of T cells in tumor immunotherapy can be counterproductive particularly if the activated T cells undergo apoptotic death after the very first secondary encounter of the specific epitope. We examined the extent to which tumor epitope-specific CTLs that are activated and expanded in an in vitro-matured dendritic cell-based primary stimulation protocol undergo AICD following their first secondary encounter of the cognate epitope. Using the MART-1(27-35) epitope as a prototype vaccine epitope, we also examined whether these CTLs could be rescued from AICD. Our results demonstrate that a substantial fraction of MART-1(27-35) epitope-specific primary CTLs undergo AICD upon the very first secondary encounter of the cognate epitope. The AICD in these CTLs is neither caspase dependent nor is it triggered by the extrinsic death signaling pathways (Fas, TNFR, etc.). These CTLs, interestingly, could be rescued from AICD by the JNK inhibitor, SP600125. We also found that SP600125 interferes with their IFN-gamma response but does not block their cytolytic function. The rescued CTLs, however, regain their capacity to synthesize IFN-gamma if continued in culture without the inhibitor. These observations have implications in tumor immunotherapy and in further studies for regulation of AICD in CTLs.

Phosphorylation of PML by mitogen-activated protein kinases plays a key role in arsenic trioxide-mediated apoptosis

The promyelocytic leukemia (PML) protein is a potent growth suppressor and proapototic factor, whereas aberrant fusions of PML and retinoic acid receptor (RAR)-alpha are causal agents in human acute promyelocytic leukemia. Arsenic trioxide (As(2)O(3)) treatment induces apoptosis in acute promyelocytic leukemia cells through an incompletely understood mechanism. We report here that As(2)O(3) treatment induces phosphorylation of the PML protein through a mitogen-activated protein (MAP) kinase pathway. Increased PML phosphorylation is associated with increased sumoylation of PML and increased PML-mediated apoptosis. Conversely, MAP kinase cascade inhibitors, or the introduction of phosphorylation or sumoylation-defective mutations of PML, impair As(2)O(3)-mediated apoptosis by PML. We conclude that phosphorylation by MAP kinase cascades potentiates the antiproliferative functions of PML and helps mediate the proapoptotic effects of As(2)O(3).

Lck Is Required for Activation-Induced T Cell Death after TCR Ligation with Partial Agonists

TCR engagement can induce either T cell proliferation and differentiation or activation-induced T cell death (AICD) through apoptosis. The intracellular signaling pathways that dictate such a disparate fate after TCR engagement have only been partially elucidated. Non-FcR-binding anti-CD3 mAbs induce a partial agonist TCR signaling pattern and cause AICD on Ag-activated, cycling T cells. In this study, we examined TCR signaling during the induction of AICD by anti-CD3 fos, a non-FcR-binding anti-CD3 mAb. This mAb activates Fyn, Lck, and extracellular signal-regulated kinase, and induces phosphorylation of Src-like adapter protein, despite the inability to cause calcium mobilization or TCR polarization. Anti-CD3 fos also fails to effectively activate zeta-associated protein of 70 kDa or NF-kappaB. Using Ag-specific T cells deficient for Fyn or Lck, we provide compelling evidence that activation of Lck is required for the induction of AICD. Our data indicate that a selective and distinct TCR signaling pattern is required for AICD by TCR partial agonist ligands.

Activation of mitogen-activated protein kinases in experimental autoimmune encephalomyelitis

The expression of mitogen-activated protein (MAP) kinases, including extracellular signal-regulated kinase (ERK), c-Jun NH(2)-terminal protein kinase (JNK), and p38, was analyzed in experimental autoimmune encephalomyelitis (EAE) in rats. Western blot analysis showed that the three MAP kinases (phosphorylated ERK (p-ERK), p-JNK, and p-p38) were increased significantly in the spinal cords of rats with EAE at the peak stage as compared with the levels in controls (p<0.05), and both p-ERK and p-JNK declined slightly in the recovery stage of EAE. Immunohistochemistry showed that p-ERK was constitutively expressed in brain cells, including astroglial cells, and showed enhanced immunoreactivity in those cells in EAE, while some T cells and macrophages were weakly immunopositive for p-ERK in EAE lesions. Both p-JNK and p-p38 were intensely immunostained in T cells in EAE lesions, while a few glial cells and astrocytes were weakly positive for both. Taking all these facts into consideration, we postulate that increased expression of the phosphorylated form of each MAP kinase plays an important role in the initiation of acute monophasic EAE. Differential expression of three MAP kinases was discerned in an animal model of human autoimmune central nervous system diseases, including multiple sclerosis.

Caspases and T lymphocytes: a flip of the coin?

In this review, we consider the role caspases play in cell death downstream of death receptors and cell intrinsic death mechanisms. In particular, we focus on these mechanisms in antigen-induced cell death, a mechanism which regulates the number of surviving T cells at the end of an immune response. The relative role of the apoptosome as an amplifier rather than an initiator of apoptosis is considered. Several factors that regulate the susceptibility to activation-induced cell death are considered. These factors emanate from the stimulation of the T-cell receptors and include multiple pathways. Recent work has shown that death receptor signaling can play an interesting role in cell proliferation in both humans and animals. These recent findings are discussed in the light of models of death receptor signaling.

Up-regulated expression of MICA on activated T lymphocytes involves Lck and Fyn kinases and signaling through MEK1/ERK, p38 MAP kinase, and calcineurin

Major histocompatibility complex class I-related chain (MICA) is a cell stress-regulated molecule recognized by cytotoxic cells expressing the NKG2D molecule. MICA can be induced on T cells after CD3 or CD28 engagement. Here, we investigated the intracellular pathways leading to activation-induced expression of MICA. The Src kinase inhibitor PP1 inhibited up-regulated expression of MICA on anti-CD3-stimulated T cells. Downstream signaling routes involved mitogen-activated protein kinase (MAPK) kinase (MEK)1/extracellular signal-regulated kinase (ERK), p38 MAPK, and calcineurin, as MICA expression was prevented by U0126, SB202190, cyclosporin A, and FK506. Also, Lck and Fyn as well as MEK1/ERK and p38 MAPK were found to regulate MICA expression in anti-CD28/phorbol 12-myristate 13-acetate-stimulated T cells. Expression of MICA on activated T cells involved interleukin-2-dependent signaling routes triggered by Janus tyrosine kinases/signal transducer and activators of transcription and p70(S)(6) kinase, as it could be inhibited by AG490 and rapamycin. This is the first demonstration of the intracellular pathways involved in activation-induced expression of MICA, which may reveal potential targets for immune intervention to modulate MICA expression in pathological disorders.

Rapid induction of apoptosis in CD8+ HIV-1 envelope-specific murine CTLs by short exposure to antigenic peptide

During primary viral infection, in vivo exposure to high doses of virus causes a loss of Ag-specific CD8(+) T cells. This phenomenon, termed clonal exhaustion, and other mechanisms by which CTLs are deleted are poorly understood. Here we show evidence for a novel form of cell death in which recently stimulated CD8(+) HIV-1 envelope gp160-specific murine CTLs become apoptotic in vitro after brief exposure to free antigenic peptide (P18-I10). Peak apoptosis occurred within 3 h of treatment with peptide, and the level of apoptosis was dependent on both the time after initial stimulation with target cells and the number of targets. Using T cell-specific H-2D(d)/P18-I10 tetramers, we observed that the apoptosis was induced by such complexes. Induction of apoptosis was blocked by cyclosporin A, a caspase 3 inhibitor, and a mitogen-activated protein kinase inhibitor, but not by Abs to either Fas ligand or to TNF-alpha. Thus, these observations suggest the existence of a Fas- or TNF-alpha-independent pathway initiated by TCR signaling that is involved in the rapid induction of CTL apoptosis. Such a pathway may prove important in the mechanism by which virus-specific CTLs are deleted in the presence of high viral burdens.

CCR5 mediates Fas- and caspase-8 dependent apoptosis of both uninfected and HIV infected primary human CD4 T cells

DESIGN

HIV Env interaction with the corresponding chemokine receptor dictates the molecular mechanism of death of both HIV-infected and uninfected primary CD4 T cells. CXCR4/T tropic HIV virus (X4) triggers CD4 T cell death through a caspase independent mechanism, whereas CCR5/M tropic HIV virus (R5) HIV triggers a caspase dependent death. In the present study, we have investigated the pathway whereby R5 Env-CR5 interactions lead to a caspase dependent cell death.

METHODS

CD4 T cells were infected with X4 or R5 HIV strains, or were mock infected. After infection, cells were treated with caspase inhibitors or decoys of death receptor signaling pathways and cell viability was analyzed. The role of R5 HIV Env in induction of cell death of uninfected T cells was analyzed by co-culturing uninfected CD4 T cells with R5 Env expressing cells in the absence or presence of various inhibitors of death receptor signaling.

RESULTS

Infection of CD4 T cells with R5, but not with X4 HIV strains results in the activation of caspase-8 and cell death that is reversed by a decoy of the Fas receptor. Isolated activation of CCR5 by membrane-bound, or soluble R5 Env causes a Fas- and caspase-8 dependent death also of uninfected CD4 T cells. Additional studies demonstrate that isolated CCR5 activation by R5 Env leads to both de novo expression of FasL and induction of susceptibility to Fas-mediated apoptosis in resting primary CD4 T cells.

CONCLUSIONS

These results ascribe to CCR5 a novel role in activating the Fas pathway and caspase-8 as well as triggering FasL production when activated by R5 Env, ultimately causing CD4 T cell death.

Aberrant T-cell antigen receptor-mediated responses in autoimmune lymphoproliferative syndrome

Autoimmune Lymphoproliferative Syndrome (ALPS) is a disorder of defective lymphocyte apoptosis due to mutations of the Fas receptor and other molecules in the Fas signaling pathway. In addition to accumulation of CD4(-) CD8(-) double-negative (DN) T cells, many patients display a dysregulated cytokine pattern with dysfunctional T cells, suggesting Fas defects may impact pathways of T-cell activation/differentiation. Here, we report two novel mutations in the Fas receptor resulting in an ALPS phenotype. Utilizing flow cytometry, we found anti-CD3 activated CD4(+) T cells from these patients were incapable of fully upregulating activation markers (CD25, CD69, and CD40L) or producing interferon-gamma and IL-2. Additionally, DN T cells were unable to transduce proximal T-cell antigen receptor signals or produce cytokines. Furthermore, DN T cells overexpressed CD57 and phenotypically resembled end-stage effector cells. As DN T cells were essentially anergic, the clinical manifestations of autoimmunity are more likely to be a consequence of aberrant cytokine secretion within the CD4(+) T-cell subpopulation.

Differential roles for extracellularly regulated kinase-mitogen-activated protein kinase in B cell antigen receptor-induced apoptosis and CD40-mediated rescue of WEHI-231 immature B cells

One of the major unresolved questions in B cell biology is how the B cell Ag receptor (BCR) differentially signals to transduce anergy, apoptosis, proliferation, or differentiation during B cell maturation. We now report that extracellularly regulated kinase-mitogen-activated protein kinase (Erk-MAP kinase) can play dual roles in the regulation of the cell fate of the immature B cell lymphoma, WEHI-231, depending on the kinetics and context of Erk-MAP kinase activation. First, we show that the BCR couples to an early (< or =2 h) Erk-MAP kinase signal which activates a phospholipase A(2) pathway that we have previously shown to mediate collapse of mitochondrial membrane potential, resulting in depletion of cellular ATP and cathepsin B execution of apoptosis. Rescue of BCR-driven apoptosis by CD40 signaling desensitizes such early extracellularly regulated kinase (Erk) signaling and hence uncouples the BCR from the apoptotic mitochondrial phospholipase A(2) pathway. A second role for Erk-MAP kinase in promoting the growth and proliferation of WEHI-231 immature B cells is evidenced by data showing that proliferating and CD40-stimulated WEHI-231 B cells exhibit a sustained cycling pattern (8-48 h) of Erk activation that correlates with cell growth and proliferation. This growth-promoting role for Erk signaling is supported by three key pieces of evidence: 1) signaling via the BCR, under conditions that induce growth arrest, completely abrogates sustained Erk activation; 2) CD40-mediated rescue from growth arrest correlates with restoration of cycling Erk activation; and 3) sustained inhibition of Erk prevents CD40-mediated rescue of BCR-driven growth arrest of WEHI-231 immature B cells. Erk-MAP kinase can therefore induce diverse biological responses in WEHI-231 cells depending on the context and kinetics of activation.

Increase of the resistance of human cervical carcinoma cells to cisplatin by inhibition of the MEK to ERK signaling pathway partly via enhancement of anticancer drug-induced NF kappa B activation

In this study, we showed that suppression of the MEK-ERK transduction pathway by a selective inhibitor, 2'-amino-3'-methoxyflavone (PD98059), increased drug resistance of SiHa cells to cisplatin, but not to another common anticancer drug, doxorubicin. The downstream mechanism of this discrepant cellular response was investigated. Both cisplatin and doxorubicin activated nuclear ERK2 and nuclear transcription factor kappa B (NF kappa B) of SiHa cells. However, suppression of the MEK-ERK2 pathway by PD98059 resulted in a further enhancement of cisplatin-induced NF kappa B activation, while no further regulation of NF kappa B was noted in doxorubicin-treated cells. The activation of NF kappa B by cisplatin or doxorubicin was not due to the degradation of cytoplasmic I kappa B alpha, as demonstrated by western blotting. Transfection of a dominant negative I kappa B alpha resulted in a markedly diminished PD98059-induced cisplatin resistance in SiHa cells. Our results suggest that the MEK-ERK signaling pathway plays a role in the chemosensitivity of SiHa cells, and suppression of this pathway increases cisplatin resistance partly via an increase of NF kappa B activation. The mechanism responsible for the discrepant effect of PD98059 on NF kappa B activation and hence the chemosensitivity of SiHa cells towards cisplatin and doxorubicin remains to be investigated.

Defective Fas ligand expression and activation-induced cell death in the absence of IL-2-inducible T cell kinase

The Tec family tyrosine kinase, IL-2-inducible T cell kinase (Itk), plays an important role in TCR signaling. Studies of T cells from Itk-deficient mice have demonstrated that Itk is critical for the activation of phospholipase-Cgamma1, leading to calcium mobilization in response to TCR stimulation. This biochemical defect results in reduced IL-2 production by Itk-deficient T cells. To further characterize the downstream effects of the Itk deficiency, we crossed Itk-/- mice to a TCR-transgenic line and examined T cell responses to stimulation by peptide plus APC. These studies show that Itk is required for maximal activation of early growth responses 2 and 3 and Fas ligand transcription after TCR stimulation. These transcriptional defects lead to reduced activation-induced cell death of stimulated Itk-/- T cells, both in vitro and in vivo. Together these studies define an important role for Itk in TCR signaling, leading to cytokine gene expression and activation-induced cell death.

A role for MAP kinase in the antitumor activity of a nucleoside analog

Nucleoside analogs (NAs) have been used extensively in both antitumor and antiviral therapies. Their general mechanism of action has been postulated to result from incorporation into DNA, leading to disruption of DNA synthesis and DNA polymerase inhibition. To further explore the antitumor mechanisms of NAs we have evaluated ganciclovir (GCV), an NA antiviral agent, in herpes simplex virus thymidine kinase (HSV-TK) gene-modified tumor cells. This system allows specific evaluation of the antitumor effects of NAs because the antitumor effect is directly related to the phosphorylation of the prodrug GCV by the HSV-TK enzyme in the gene-modified tumor cells. We demonstrated that GCV incorporates into DNA and inhibits DNA polymerase, as has been observed in HSV-infected cells and with other antitumor NAs in tumor cells. A novel observation is that GCV activates MAP kinase within 1 hour of GCV exposure. This activation directly correlates with cytotoxicity, because inhibition of the MAP kinase extracellular regulated kinase (Erk) by PD98059, reversed GCV-mediated cytotoxicity. This effect appears to be specific to the Erk pathway, because inhibition of the p38 kinase with SB203580 had no effect on cytotoxicity. Further, GCV does not act as a DNA-damaging agent or activate general DNA-repair mechanisms, but does produce a number of metabolic disruptions, including a reversible decrease in NAD levels. These effects appear to be downstream of the earlier activation of Erk in this system, which may be a novel mechanism of action for GCV cytotoxicity in HSV-TK gene-modified tumor cells, and thus, needs to be further evaluated as the mechanism of tumor cell killing by other antitumor NAs.

Tumor cell growth inhibition and extracellular signal-regulated kinase (ERK) phosphorylation by novel K vitamins

2-(2-hydroxy-ethylsulfanyl)-3-methyl-1,4-naphthoquinone or CPD-5, a K vitamin analog, was previously indicated to be a potent growth inhibitor for Hep 3B hepatoma cells in vitro. Here, we show that CPD-5 and two newly synthesized analogs, 2-(2-hydroxy-ethylsulfanyl)-3-methyl-5- nitro-1,4-naphthoquinone (PD-37) and 2-(2-hydroxy-ethylsulfanyl)-3- methyl-5-acetylamino-1,4-naphthoquinone (PD-42), are potent growth inhibitors of 13 different human cancer cell lines, with IC50 values in the range of 3-54 microM. Phospho-ERK was induced by each of three K vitamin analogs in every cell line in a dose-dependent manner, at growth inhibitory doses. ERK phosphorylation and growth inhibitory effects were strongly correlated, with p=0.0080 for CPD-5, p=0.0076 for PD-37 and p=0.0251 for PD-42. The induction of phospho-ERK and growth inhibition were antagonized by thiol-containing anti-oxidants, but not by catalase, consistent with a possible arylating mechanism. The data show a novel class of growth inhibitors with a wide spectrum of action that induces ERK hyper-phosphorylation, as a possible new growth inhibitory feature.

Nuclear extracellular signal-regulated kinase 2 phosphorylates p53 at Thr55 in response to doxorubicin

In this study, we showed that nuclear ERK2 phosphorylates p53 at Thr55 in response to doxorubicin. p53 was found to physically interact with ERK2 as evidenced by Western blotting of ERK2 coimmunoprecipitated complex. The gene fragment encoded for N-terminal 68 amino acids was subcloned and fused with 6-His. Each serine or threonine site in this fragment, the possible phosphorylation site, was mutated to alanine. The recombinant proteins were used as substrates in ERK2 kinase assay. The results show that ERK2 phosphorylated p53 at Thr55. Further, electromobility shift assay showed that the phosphorylation of p53 by nuclear ERK2 was closely related to the transactivating activity of p53. These findings suggest that ERK2 may play a role in response to DNA damage via interaction with p53.

Mechanism of novel vitamin K analog induced growth inhibition in human hepatoma cell line

BACKGROUND/AIMS

To understand the mechanisms of liver regeneration or hepatoma apoptosis, it is important to estimate the turning point of the signal transduction by growth factor receptor. Since 2-(2-hydroxyethylsulfaryl) 3-methyl-1,4-naphthoquinone or CPD 5 has been shown to mediate the phosphorylation of epidermal growth factor (EGF) receptor in Hep3B hepatoma cells, the differences between EGF and CPD 5-mediated signal transduction were studied.

METHODS

DNA content was measured by Hoechst fluorescent assay. Phosphorylated proteins were described with Western blots or two-dimensional electrophoresis.

RESULTS

CPD 5-induced EGFR phosphorylation was functional to stimulate Ras pathway. However, CPD 5-mediated extracellular signal-regulated kinase (ERK) phosphorylation was not antagonized by inhibition of upstream activation with PD153035. CPD 5 inhibited ERK dephosphorylation in cell lysate, suggesting that ERK phosphorylation by CPD 5 was depending on kinase activity and phosphatase inhibition. Two-dimensional electrophoresis showed extra phospho ERK spot, which was indicated to have close association with CPD 5-induced growth inhibition, since U0126 antagonized growth inhibition and appearance of this spot.

CONCLUSIONS

The turning point of EGFR pathway was proved to have close association with the expressed level of phosphorylated ERK. ERK phosphorylation was suggested to play a critical role in growth factor-induced signal transduction.

Involvement of the extracellular signal-regulated protein kinase (ERK) pathway in the induction of apoptosis by cadmium chloride in CCRF-CEM cells

When CCRF-CEM cells were incubated with 5-40 microM CdCl(2,) apoptosis was observed most clearly at 10 microM. Prior to the development of apoptosis, mitogen-activated protein kinases (MAPKs), i.e. extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 MAPK, were activated with different sensitivity to CdCl(2) exposure. ERK and p38 MAPK were phosphorylated with incubation of 1 microM CdCl(2,) but higher than 20 microM CdCl(2) was required for the clear phosphorylation of JNK. In the time-course study, ERK and p38 MAPK were phosphorylated earlier than JNK after CdCl(2) exposure. The in vitro activities of MAPKs also increased in response to CdCl(2) exposure. Pretreatment with an intracellular Ca(2+) chelator, 1, 2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl) ester (BAPTA/AM), suppressed almost completely CdCl(2)-induced phosphorylation of JNK and p38 MAPK, but not ERK phosphorylation, indicating that the activation of JNK and p38 MAPK depends on the intracellular Ca(2+) but that of ERK does not. On the other hand, treatment with a MAPK/ERK kinase (MEK) inhibitor, U0126 (1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio]butadiene ), suppressed CdCl(2)-induced ERK activation and the apoptosis as well. The inhibition of p38 MAPK activity with SB203580 (4-[4-fluorophenyl]-2-[4-methylsulfinylphenyl]-5-[4-pyridyl]1H- imidaz ole) did not protect cells from apoptosis. The present results showed that the activation of ERK, JNK, and p38 MAPK is differently regulated in CCRF-CEM cells exposed to CdCl(2,) and that the ERK pathway seems to be responsible for the induction of apoptosis by CdCl(2) exposure in this human T cell line.

Non-Fc receptor-binding humanized anti-CD3 antibodies induce apoptosis of activated human T cells

Human trials in organ allografts have demonstrated that murine anti-CD3 mAbs are immunosuppressive. By mimicking Ag, anti-CD3 can produce T cell activation, anergy, or death. Activation of resting T cells in vivo results in dose-limiting cytokine release and is caused by Ab-mediated cross-linking of T cells and Fcgamma receptor (FcR)-bearing cells. With the goal of minimizing cytokine-induced toxicity, anti-CD3 have been engineered to lower Fc binding avidity. Preclinical murine studies have indicated that non-FcR-binding anti-CD3 can induce apoptosis of Ag-activated T cells. Since induction of T cell apoptosis may be an important mechanism of immunosuppression by anti-CD3, we tested whether Fc mutations affect the ability of anti-human CD3 to induce apoptosis of activated T cells. We compared wild-type murine anti-CD3, M291, and OKT3 and their humanized, FcR- and non-FcR-binding structural variants in quantitative assays of T cell apoptosis. Non-FcR-binding variants produced more sustainable phosphorylation of extracellular signal-regulated kinase-2, greater release of IFN-gamma, and more effectively caused activation-dependent T cell apoptosis. Non-FcR-binding variants dissociated more quickly from the T cell surface and caused less internalization of the TCR, which then remained available in greater abundance on the cell surface for signaling. Cross-linking of non-FcR-binding variants by antiglobulin enhanced TCR internalization and minimized induction of T cell apoptosis. We conclude that non-FcR-binding, humanized anti-CD3 have improved ability to induce apoptosis of activated T cells, presumably by allowing durable expression of the TCR and sustained signaling.

Critical role of extracellular signal-regulated kinase (ERK) phosphorylation in novel vitamin K analog-induced cell death

In the present study, we show that 2-(2-hydroxyethylsulfaryl)-3-methyl-1,4-naphthoquinone, or CPD 5, is a potent growth inhibitor for pancreas cancer cell lines (ID(50): 21.4 +/- 3.8, 31.8 +/- 2.7 and 55.2 +/- 4.5 microM for MiaPaCa, Panc-1 and BxPc3, respectively). It induced protein tyrosine phosphor-ylation of hepatocyte growth factor (HGF) receptor (c-Met) or epidermal growth factor receptor (EGFR), which increased progressively to a maximum level at 30 min in Panc-1 cells. The receptor phosphorylation by CPD 5 was indicated to be functional, since these receptors were found to bind with Grb2 or SOS1 protein. CPD 5 was also suggested to induce phosphorylation of external signal-regulated kinase (ERK). EGF induced cell proliferation through ERK phosphorylation, since U0126, which is an inhibitor of ERK phosphorylation, abrogated the increase of cyclin D1 by EGF. HGF increased the amount of p27 protein, suggesting that it is associated with cell differentiation. By contrast, U0126 reduced CPD 5-induced cell death. On two-dimensional electrophoresis, we found an extra type of phospho-ERK, and this was completely and selectively abolished by U0126. These results suggest that ERK phosphorylation, especially the extra spot on two-dimensional gel, is critically associated with CPD 5-mediated cell death.

Apoptosis: a method for evaluating the cryopreservation of whole blood and peripheral blood mononuclear cells

We sought to compare the effect of cryopreservation and storage at -30 degrees C, -70 degrees C and -150 degrees C of human whole blood versus matched peripheral blood mononuclear cell (PBMC) samples using apoptosis as an indicator of cell fitness. Following 10 weeks of storage the samples were thawed and assessed for viability (trypan blue exclusion), levels of apoptosis (using the nuclear stain bis-benzimide) and cell function (ability to be transformed by Epstein-Barr virus, EBV). When comparing storage temperatures, the levels of apoptosis in whole blood and PBMC samples stored at -30 degrees C were significantly higher than the values for samples stored at -70 degrees C or -150 degrees C (P<0.004). Whole blood samples stored at -150 degrees C had significantly less apoptosis than those stored at -70 degrees C (P<0.03). A comparison of the cell preparations showed that at all three storage temperatures there was significant sample deterioration (viability, apoptosis, and function) in whole blood relative to PBMC samples. This study indicates that careful consideration should be given to storage conditions and that apoptosis can be used as a sensitive measure of cell fitness following cryopreservation.

Sphingosylphosphorylcholine is a ligand for ovarian cancer G-protein-coupled receptor 1

Sphingosylphosphorylcholine (SPC) is a bioactive lipid that acts as an intracellular and extracellular signalling molecule in numerous biological processes. Many of the cellular actions of SPC are believed to be mediated by the activation of unidentified G-protein-coupled receptors. Here we show that SPC is a high-affinity ligand for an orphan receptor, ovarian cancer G-protein-coupled receptor 1 (OGR1). In OGR1-transfected cells, SPC binds to OGR1 with high affinity (Kd = 33.3 nM) and high specificity and transiently increases intracellular calcium. The specific binding of SPC to OGR1 also activates p42/44 mitogen-activated protein kinases (MAP kinases) and inhibits cell proliferation. In addition, SPC causes internalization of OGR1 in a structurally specific manner.