Homeostatic control of lymphocyte survival: potential origins and implications

Therapeutic Efficacy of Interferon-Gamma and Hypoxia-Primed Mesenchymal Stromal Cells and Their Extracellular Vesicles: Underlying Mechanisms and Potentials in Clinical Translation

Multipotent mesenchymal stromal cells (MSCs) hold promises for cell therapy and tissue engineering due to their self-renewal and differentiation abilities, along with immunomodulatory properties and trophic factor secretion. Extracellular vesicles (EVs) from MSCs offer similar therapeutic effects. However, MSCs are heterogeneous and lead to variable outcomes. In vitro priming enhances MSC performance, improving immunomodulation, angiogenesis, proliferation, and tissue regeneration. Various stimuli, such as cytokines, growth factors, and oxygen tension, can prime MSCs. Two classical priming methods, interferon-gamma (IFN-γ) and hypoxia, enhance MSC immunomodulation, although standardized protocols are lacking. This review discusses priming protocols, highlighting the most commonly used concentrations and durations, along with mechanisms and in vivo therapeutics effects of primed MSCs and their EVs. The feasibility of up-scaling their production was also discussed. The review concluded that priming with IFN-γ or hypoxia (alone or in combination with other factors) boosted the immunomodulation capability of MSCs and their EVs, primarily via the JAK/STAT and PI3K/AKT and Leptin/JAK/STAT and TGF-β/Smad signalling pathways, respectively. Incorporating priming in MSC and EV production enables translation into cell-based or cell-free therapies for various disorders.

TNFα and IFNγ rapidly activate PI3K-AKT signaling to drive glycolysis that confers mesenchymal stem cells enhanced anti-inflammatory property

Background

Mesenchymal stem/stromal cells (MSCs) acquire immunosuppressive capacity only in an inflammatory microenvironment. This can be recapitulated in vitro by treating MSCs with inflammatory cytokines TNFα and IFNγ, which induce indoleamine 2,3-dioxygenase (IDO) and TNF-stimulated gene-6 (TSG-6). However, the signaling pathways downstream of the cytokines remain to be elucidated.

Methods

Inflammatory bowel disease (IBD) mouse model was established by subjecting mice to dextran sulfate sodium (DSS) in drinking water for 7 days. Human UC-MSCs were pretreated with TNF-α and IFN-γ for 24 h and were then infused intravenously at day 2 of DSS administration. Colon tissues were collected for length measurement and histopathological examination. The serum level of IL-6 in mice was measured by enzyme-linked immunosorbent assay. Real-time PCR and Western blot were used to examine the mRNA level and protein expression. MSCs overexpressing constitutive active AKT or dominant negative AKT were generated and were analyzed. The glycolysis level of the MSCs was measured using Extracellular Flux Analyzer. 2-NBDG was used to monitor the uptake of glucose by MSCs.

Results

TNFα and IFNγ treatment led to rapid consumption of glucose and metabolic skewing toward glycolysis in MSCs, which was required for the therapeutic efficacy of MSCs on IBD. Blockade of glycolysis in MSCs inhibited the expression of immunomodulatory molecules, IDO and TSG-6, as well as the therapeutic effect on IBD. Moreover, PI3K-AKT signaling axis was rapidly activated and was required for the skewing toward glycolysis induced by TNFα and IFNγ. MSCs expressing dominant negative AKT were compromised in their therapeutic efficacy on IBD.

Conclusion

The glycolysis-dependent anti-inflammatory property of MSCs conferred by inflammatory cytokines is mediated by PI3K-AKT signaling pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03178-3.

Immune-metabolic interactions in homeostasis and the progression to NASH

The incidence of non-alcoholic fatty liver disease (NAFLD) has increased significantly over the past two decades. NAFLD ranges from simple steatosis (NAFL) to nonalcoholic steatohepatitis (NASH) and predisposes to fibrosis and hepatocellular carcinoma (HCC). The importance of the immune system in hepatic physiology and in the progression of NAFLD is increasingly recognized. At homeostasis, the liver participates in immune defense against pathogens and in tolerance of gut-derived microbial compounds. Hepatic immune cells also respond to metabolic stimuli and have a role in NAFLD progression to NASH. In this review, we discuss how metabolic perturbations affect immune cell phenotype and function in NAFL and NASH, and then focus on the role of immune cells in liver homeostasis and in the development of NASH.

Characterization of immune cell subtypes in three commonly used mouse strains reveals gender and strain-specific variations

The lack of consensus on bone marrow (BM) and splenic immune cell profiles in preclinical mouse strains complicates comparative analysis across different studies. Although studies have documented relative distribution of immune cells from peripheral blood in mice, similar studies for BM and spleen from naïve mice are lacking. In an effort to establish strain- and gender-specific benchmarks for distribution of various immune cell subtypes in these organs, we performed immunophenotypic analysis of BM cells and splenocytes from both genders of three commonly used murine strains (C57BL/6NCr, 129/SvHsd, and BALB/cAnNCr). Total neutrophils and splenic macrophages were significantly higher in C57BL/6NCr, whereas total B cells were lower. Within C57BL/6NCr female mice, BM B cells were elevated with respect to the males whereas splenic mDCs and splenic neutrophils were reduced. Within BALB/cAnNCr male mice, BM CD4⁺ Tregs were elevated with respect to the other strains. Furthermore, in male BALB/cAnNCr mice, NK cells were elevated with respect to the other strains in both BM and spleen. Splenic CD4⁺ Tregs and splenic CD8⁺ T cells were reduced in male BALB/c mice in comparison to female mice. Bone marrow CD4⁺ T cells and mDCs were significantly increased in 129/SvHsd whereas splenic CD8⁺ T cells were reduced. In general, males exhibited higher immature myeloid cells, macrophages, and NK cells. To our knowledge, this study provides a first attempt to systematically establish organ-specific benchmarks on immune cells in studies involving these mouse strains.

Metabolic Stress in the Immune Function of T Cells, Macrophages and Dendritic Cells

Innate and adaptive immune cells from myeloid and lymphoid lineages resolve host infection or cell stress by mounting an appropriate and durable immune response. Upon sensing of cellular insults, immune cells become activated and undergo rapid and efficient functional changes to unleash biosynthesis of macromolecules, proliferation, survival, and trafficking; unprecedented events among other mammalian cells within the host. These changes must become operational within restricted timing to rapidly control the insult and to avoid tissue damage and pathogen spread. Such changes occur at high energy cost. Recent advances have established that plasticity of immune functions occurs in distinct metabolic stress features. Evidence has accumulated to indicate that specific metabolic signatures dictate appropriate immune functions in both innate and adaptive immunity. Importantly, recent studies have shed light on whether successfully manipulating particular metabolic targets is sufficient to modulate immune function and polarization, thereby offering strong therapeutic potential for various common immune-mediated diseases, including inflammation and autoimmune-associated diseases and cancer. In this review, we detail how cellular metabolism controls immune function and phenotype within T cells and macrophages particularly, and the distinct molecular metabolic programming and targets instrumental to engage this regulation.

Long-term antigen exposure irreversibly modifies metabolic requirements for T cell function

Energy metabolism is essential for T cell function. However, how persistent antigenic stimulation affects T cell metabolism is unknown. Here, we report that long-term in vivo antigenic exposure induced a specific deficit in numerous metabolic enzymes. Accordingly, T cells exhibited low basal glycolytic flux and limited respiratory capacity. Strikingly, blockade of inhibitory receptor PD-1 stimulated the production of IFNγ in chronic T cells, but failed to shift their metabolism towards aerobic glycolysis, as observed in effector T cells. Instead, chronic T cells appeared to rely on oxidative phosphorylation (OXPHOS) and fatty acid oxidation (FAO) to produce ATP for IFNγ synthesis. Check-point blockade, however, increased mitochondrial production of superoxide and reduced viability and effector function. Thus, in the absence of a glycolytic switch, PD-1-mediated inhibition appears essential for limiting oxidative metabolism linked to effector function in chronic T cells, thereby promoting survival and functional fitness.

Hypoxia and Mucosal Inflammation

Sites of inflammation are defined by significant changes in metabolic activity. Recent studies have suggested that O2 metabolism and hypoxia play a prominent role in inflammation so-called "inflammatory hypoxia," which results from a combination of recruited inflammatory cells (e.g., neutrophils and monocytes), the local proliferation of multiple cell types, and the activation of multiple O2-consuming enzymes during inflammation. These shifts in energy supply and demand result in localized regions of hypoxia and have revealed the important function off the transcription factor HIF (hypoxia-inducible factor) in the regulation of key target genes that promote inflammatory resolution. Analysis of these pathways has provided multiple opportunities for understanding basic mechanisms of inflammation and has defined new targets for intervention. Here, we review recent work addressing tissue hypoxia and metabolic control of inflammation and immunity.

Metabolic Cooperation and Competition in the Tumor Microenvironment: Implications for Therapy

The tumor microenvironment (TME) is an ensemble of non-tumor cells comprising fibroblasts, cells of the immune system, and endothelial cells, besides various soluble secretory factors from all cellular components (including tumor cells). The TME forms a pro-tumorigenic cocoon around the tumor cells where reprogramming of the metabolism occurs in tumor and non-tumor cells that underlies the nature of interactions as well as competitions ensuring steady supply of nutrients and anapleoretic molecules for the tumor cells that fuels its growth even under hypoxic conditions. This metabolic reprogramming also plays a significant role in suppressing the immune attack on the tumor cells and in resistance to therapies. Thus, the metabolic cooperation and competition among the different TME components besides the inherent alterations in the tumor cells arising out of genetic as well as epigenetic changes supports growth, metastasis, and therapeutic resistance. This review focuses on the metabolic remodeling achieved through an active cooperation and competition among the three principal components of the TME—the tumor cells, the T cells, and the cancer-associated fibroblasts while discussing about the current strategies that target metabolism of TME components. Further, we will also consider the probable therapeutic opportunities targeting the various metabolic pathways as well as the signaling molecules/transcription factors regulating them for the development of novel treatment strategies for cancer.

The multidrug-resistance transporter Abcc3 protects NK cells from chemotherapy in a murine model of malignant glioma

Abcc3, a member of the ATP-binding cassette transporter superfamily, plays a role in multidrug resistance. Here, we found that Abcc3 is highly expressed in blood-derived NK cells but not in CD8(+) T cells. In GL261 glioma-bearing mice treated with the alkylating agent temozolomide (TMZ) for 5 d, an early increased frequency of NK cells was observed. We also found that Abcc3 is strongly upregulated and functionally active in NK cells from mice treated with TMZ compared to controls. We demonstrate that Abcc3 is critical for NK cell survival during TMZ administration; more importantly, Akt, involved in lymphocyte survival, is phosphorylated only in NK cells expressing Abcc3. The resistance of NK cells to chemotherapy was accompanied by increased migration and homing in the brain at early time points. Cytotoxicity, evaluated by IFNγ production and specific lytic activity against GL261 cells, increased peripherally in the later phases, after conclusion of TMZ treatment. Intra-tumor increase of the NK effector subset as well as in IFNγ, granzymes and perforin-1 expression, were found early and persisted over time, correlating with a profound modulation on glioma microenvironment induced by TMZ. Our findings reveal an important involvement of Abcc3 in NK cell resistance to chemotherapy and have important clinical implications for patients treated with chemo-immunotherapy.

Transient delay of radiation-induced apoptosis by phorbol acetate

The mechanisms of interference of a model tumour promoter 12-O-tetra-decanoylphorbol-13-acetate (TPA) with radiation-induced apoptosis in human peripheral lymphocytes have been investigated. The cells were treated with TPA under various conditions and thereafter exposed to a single lethal dose of gamma radiation. Morphological and biochemical changes characteristic of apoptosis were followed up to 72 h of post-irradiation time. Acute exposure to low concentration of TPA resulted in delay in the onset of radiation-induced apoptosis (determined as morphological changes and rate of mitochondrial demise) by 24-48 h as compared to the irradiated, sham TPA-treated cells. The time course of this delay correlated well with confinement of the p53 protein to the cytoplasm and increase in bcl-2 levels at the nuclear periphery of irradiated cells. Our results indicate that confinement of p53 in the cytoplasm is one of the potential mechanisms by which TPA interferes with the process of radiation-induced apoptosis in human lymphocytes.

Metabolism and oxidative stress response pathways in kidney cancer: a tale of chance and necessity

Over 270,000 patients are affected with kidney cancer worldwide and 120,000 died from this disease in 2014. Over the last few decades, important progress has been made in our understanding of the genetic and molecular mechanisms underlying the growth of these tumors, which has led to improvement in patient care. Some of the most significant recent advances came from the increasing number of large datasets generated by bioinformatics (genomics, proteomics, etc.) and their integration to characterize the genetic and molecular factors responsible for kidney tumor development and survival. Interestingly, deregulated metabolism and oxidative stress pathways are commonly found in advanced-stage kidney tumors and are important factors to consider and potentially target when developing therapeutic approaches.

BH3-only protein Bim is associated with the degree of Helicobacter pylori-induced gastritis and is localized to the mitochondria of inflammatory cells in the gastric mucosa

BH3-only protein, Bim, is a pro-apoptotic protein that mediates mitochondria-dependent cell death. However, the role of Bim in Helicobacter pylori-associated gastritis remains unclear. This study aimed to assess the cellular localization of Bim and its possible role in H. pylori-induced gastritis. The study was conducted on biopsy specimens obtained from 80 patients who underwent upper gastrointestinal endoscopy (H. pylori-negative: n=30, positive: n=50). Association between Bim mRNA expression and severity of gastritis was evaluated and the localization of Bim was examined by immunofluorescence. Bim mRNA expression was positively correlated with the degree of gastritis, as defined by the Sydney system. Immunohistochemical analysis confirmed increased Bim expression in H. pylori-infected gastric mucosa compared with uninfected mucosa in both humans and mice. Bim localized in myeloperoxidase- and CD138-positive cells of H. pylori-infected lamina propria and submucosa of the gastric tract, indicating that this protein is predominantly expressed in neutrophils and plasma cells. In contrast, Bim did not localize in CD20-, CD3-, or CD68-positive cells. Bim was expressed in the mitochondria, where it was partially co-localized with activated Bax and cleaved-PARP. In conclusion, Bim is expressed in neutrophils and plasma cells in H. pylori-associated gastritis, where it may participate in the termination of inflammatory response by causing mitochondria-mediated apoptosis in specific leucocytes.

Overexpression of ATP-activated P2X7 receptors in the intestinal mucosa is implicated in the pathogenesis of Crohn's disease

BACKGROUND

Extracellular nucleotides released in conditions of cell stress alert the immune system from tissue injury or inflammation. We hypothesized that the P2X7 receptor (P2X7-R) could regulate key elements in inflammatory bowel disease pathogenesis.

METHODS

Colonoscopy samples obtained from patients with Crohn's disease (CD), ulcerative colitis, and controls were used to analyze P2X7-R expression by RT and real-time PCR, immunohistochemistry, and confocal microscopy. Inflammatory response was determined by the levels of cytokines by enzyme-linked immunosorbent assay in cultures of intestinal explants. Apoptosis was determined by the TUNEL assay. P2X7-R C57BL/6 mice were treated with trinitrobenzene sulfonic acid or dextran sulfate sodium (DSS) for inducing colitis.

RESULTS

P2X7-R was expressed in higher levels in inflamed CD epithelium and lamina propria, where it colocalizes more with dendritic cells and macrophages. Basal levels of P2X7-R mRNA were higher in CD inflamed mucosa compared with noninflamed CD and controls and were upregulated after interferon-γ in controls. Apoptotic rates were higher in CD epithelium and lamina propria compared with ulcerative colitis and controls. Levels of tumor necrosis factor-α, interleukin (IL)-1β, and IL-17 were higher, whereas IL-10 was lower in CD compared with controls. Levels of tumor necrosis factor-α-α and interleukin-1β increased after adenosine-triphosphate and decreased after KN62 treatment in CD. P2X7-R animals did not develop trinitrobenzene sulfonic acid or DSS colitis.

CONCLUSIONS

The upregulation of P2X7-R in CD inflamed mucosa is consistent with the involvement of purinoceptors in inflammation and apoptosis. These observations may implicate purinergic signaling in the pathogenesis of intestinal inflammation, and the P2X7-R may represent a novel therapeutic target in CD.

A mathematical model for a T cell fate decision algorithm during immune response

We formulate and analyze an algorithm of cell fate decision that describes the way in which division vs. apoptosis choices are made by individual T cells during an infection. Such model involves a minimal number of known biochemical mechanisms: it basically relies on the interplay between cell division and cell death inhibitors on one hand, and membrane receptors on the other. In spite of its simplicity, the proposed decision algorithm is able to account for some significant facts in immune response. At the individual level, the existence of T cells that continue to replicate in the absence of antigen and the possible occurrence of T cell apoptosis in the presence of antigen are predicted by the model. Moreover, the latter is shown to yield an emergent collective behavior, the observed delay in clonal contraction with respect to the end of antigen stimulation, which is shown to arise just from individual T cell decisions made according to the proposed mechanism.

Breed-specific hematological phenotypes in the dog: a natural resource for the genetic dissection of hematological parameters in a mammalian species

Remarkably little has been published on hematological phenotypes of the domestic dog, the most polymorphic species on the planet. Information on the signalment and complete blood cell count of all dogs with normal red and white blood cell parameters judged by existing reference intervals was extracted from a veterinary database. Normal hematological profiles were available for 6046 dogs, 5447 of which also had machine platelet concentrations within the reference interval. Seventy-five pure breeds plus a mixed breed control group were represented by 10 or more dogs. All measured parameters except mean corpuscular hemoglobin concentration (MCHC) varied with age. Concentrations of white blood cells (WBCs), neutrophils, monocytes, lymphocytes, eosinophils and platelets, but not red blood cell parameters, all varied with sex. Neutering status had an impact on hemoglobin concentration, mean corpuscular hemoglobin (MCH), MCHC, and concentrations of WBCs, neutrophils, monocytes, lymphocytes and platelets. Principal component analysis of hematological data revealed 37 pure breeds with distinctive phenotypes. Furthermore, all hematological parameters except MCHC showed significant differences between specific individual breeds and the mixed breed group. Twenty-nine breeds had distinctive phenotypes when assessed in this way, of which 19 had already been identified by principal component analysis. Tentative breed-specific reference intervals were generated for breeds with a distinctive phenotype identified by comparative analysis. This study represents the first large-scale analysis of hematological phenotypes in the dog and underlines the important potential of this species in the elucidation of genetic determinants of hematological traits, triangulating phenotype, breed and genetic predisposition.

Rapid effector function of memory CD8+ T cells requires an immediate-early glycolytic switch

Antigen-experienced memory T cells acquire effector function with innate-like kinetics; however, the metabolic requirements of these cells are unknown. Here we show that rapid interferon-γ (IFN-γ) production of effector memory (EM) CD8(+) T cells, activated through stimulation mediated by the T cell antigen receptor (TCR) and the costimulatory receptor CD28 or through cognate interactions, was linked to increased glycolytic flux. EM CD8(+) T cells exhibited more glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity at early time points, before proliferation commenced, than did naive cells activated under similar conditions. CD28 signaling via the serine-threonine kinase Akt and the metabolic-checkpoint kinase mTORC2 was needed to sustain TCR-mediated immediate-early glycolysis. Unlike glycolysis in proliferating cells, immediate-early glycolysis in memory CD8(+) T cells was rapamycin insensitive. Thus, CD8(+) memory T cells have an Akt-dependent 'imprinted' glycolytic potential that is required for efficient immediate-early IFN-γ recall responses.

Activated lymphocytes as a metabolic model for carcinogenesis

Metabolic reprogramming is a key event in tumorigenesis to support cell growth, and cancer cells frequently become both highly glycolytic and glutamine dependent. Similarly, T lymphocytes (T cells) modify their metabolism after activation by foreign antigens to shift from an energetically efficient oxidative metabolism to a highly glycolytic and glutamine-dependent metabolic program. This metabolic transition enables T cell growth, proliferation, and differentiation. In both activated T cells and cancer cells metabolic reprogramming is achieved by similar mechanisms and offers similar survival and cell growth advantages. Activated T cells thus present a useful model with which to study the development of tumor metabolism. Here, we review the metabolic similarities and distinctions between activated T cells and cancer cells, and discuss both the common signaling pathways and master metabolic regulators that lead to metabolic rewiring. Ultimately, understanding how and why T cells adopt a cancer cell-like metabolic profile may identify new therapeutic strategies to selectively target tumor metabolism or inflammatory immune responses.

Effect of glucose availability on glucose transport in bovine mammary epithelial cells

Primary bovine mammary epithelial cells (BMEC) were cultured in media containing varying concentrations of glucose, to determine the effects of glucose availability on glucose transport and its mechanism in bovine mammary gland. The BMEC incubated with 10 and 20 mM glucose had twofold greater glucose uptake than that with 2.5 mM glucose (P < 0.05). Increased glucose availability enhanced the cell proliferation (P < 0.05). As the glucose uptake is mediated by facilitative glucose transporters (GLUTs), the expression of GLUT mRNA was investigated. Compared with the control (2.5 mM), 5 and 10 mM glucose did not influence the abundance of GLUT1 mRNA (P < 0.05), whereas 20 mM glucose decreased the GLUT1 mRNA expression in the BMEC (P < 0.05). The expression of GLUT8 mRNA was not affected by any concentration of glucose (P > 0.05). As GLUTs are coupled with hexokinases (HKs) in regulating glucose uptake, the expression of HKs and their activities were also studied. The HK activity was greater in 5, 10 and 20 mM glucose than that in 2.5 mM glucose (P < 0.05). The expression of HK2 mRNA rather than HK1 mRNA was detected in the BMEC; however, the abundance of HK2 mRNA was not elevated by any concentrations of glucose compared with control (P > 0.05). Furthermore, addition of 3-bromopyruvate (30, 50 or 70 μM), an inhibitor of HK2, resulted in the decrease of glucose uptake and cell proliferation at both 2.5 and 10 mM glucose (P < 0.05). Therefore, the glucose concentrations may affect glucose uptake partly by altering the activity of HKs, and HK2 may play an important role in the regulation of glucose uptake in the BMEC.

Regulation of immune responses by mTOR

mTOR is an evolutionarily conserved serine/threonine kinase that plays a central role in integrating environmental cues in the form of growth factors, amino acids, and energy. In the study of the immune system, mTOR is emerging as a critical regulator of immune function because of its role in sensing and integrating cues from the immune microenvironment. With the greater appreciation of cellular metabolism as an important regulator of immune cell function, mTOR is proving to be a vital link between immune function and metabolism. In this review, we discuss the ability of mTOR to direct the adaptive immune response. Specifically, we focus on the role of mTOR in promoting differentiation, activation, and function in T cells, B cells, and antigen-presenting cells.

Adenosine and hypoxia-inducible factor signaling in intestinal injury and recovery

The gastrointestinal mucosa has proven to be an interesting tissue in which to investigate disease-related metabolism. In this review, we outline some of the evidence that implicates hypoxia-mediated adenosine signaling as an important signature within both healthy and diseased mucosa. Studies derived from cultured cell systems, animal models, and human patients have revealed that hypoxia is a significant component of the inflammatory microenvironment. These studies have revealed a prominent role for hypoxia-induced factor (HIF) and hypoxia signaling at several steps along the adenine nucleotide metabolism and adenosine receptor signaling pathways. Likewise, studies to date in animal models of intestinal inflammation have demonstrated an almost uniformly beneficial influence of HIF stabilization on disease outcomes. Ongoing studies to define potential similarities with and differences between innate and adaptive immune responses will continue to teach us important lessons about the complexity of the gastrointestinal tract. Such information has provided new insights into disease pathogenesis and, importantly, will provide insights into new therapeutic targets.

Identification of the couple GSK3α/c-Myc as a new regulator of hexokinase II in benzo[a]pyrene-induced apoptosis

The early apoptotic events induced by environmental pollutants with carcinogenic properties are poorly understood. Here, we focus on the early cytotoxic effects of benzo[a]pyrene (B[a]P). In F258 rat hepatic epithelial cells, B[a]P induces intrinsic apoptosis via a mitochondrial dysfunction characterized by the release of hexokinase II (HKII) from the mitochondria. Cancer cells often have an anomalous cell energy metabolism; since HKII dysfunction regulates B[a]P-induced apoptosis in F258 cells, but may also alter cell energy metabolism, HKII release from the mitochondria may represent an important B[a]P-related carcinogenic issue. Thus in the present study, we aimed at deciphering the mechanisms underlying HKII dysfunction upon B[a]P exposure. We show that while glycogen synthase kinase 3 beta (GSK3β) regulated the expression of HKII at the transcriptional level, glycogen synthase kinase 3 alpha (GSK3α) was involved in B[a]P-induced apoptosis via a decrease in c-Myc expression. The reduced level of c-Myc caused the relocation of HKII from the mitochondria to the cytosol, thereby being involved in the formation of reactive oxygen species and apoptosis. In conclusion, we show that the couple GSK3α/c-Myc plays a key role in B[a]P-induced early apoptotic cell signaling via HKII dysfunction.

The class III kinase Vps34 promotes T lymphocyte survival through regulating IL-7Rα surface expression

IL-7Rα-mediated signals are essential for naive T lymphocyte survival. Recent studies show that IL-7Rα is internalized and either recycled to cell surface or degraded. However, how the intracellular process of IL-7Rα trafficking is regulated is unclear. In this paper, we show that Vps34, the class III PI3K, plays a critical role in proper IL-7Rα intracellular trafficking. Mice lacking Vps34 in T lymphocytes had a severely reduced T lymphocyte compartment. Vps34-deficient T lymphocytes exhibit increased death and reduced IL-7Rα surface expression, although three major forms of autophagy remain intact. Intracellular IL-7Rα in normal T lymphocytes at steady state is trafficked through either early endosome/multivesicular bodies to the late endosome-Golgi for surface expression or to the lysosome for degradation. However, Vps34-deficient T cells have mislocalized intracellular Eea1, HGF-regulated tyrosine kinase substrate, and Vps36 protein levels, the combined consequence of which is the inability to mobilize internalized IL-7Rα into the retromer pathway for surface display. Our studies reveal that Vps34, though dispensable for autophagy induction, is a critical regulator of naive T cell homeostasis, modulating IL-7Rα trafficking, signaling, and recycling.

Apoptosis and autophagy in the regulation of T lymphocyte function

During the development and normal function of T lymphocytes, the cells are subject to several checkpoints at which they must "decide" to live or die. At these critical times and during homeostasis, the molecules that regulate the classical apoptotic pathways and survival pathways such as autophagy have critical roles in controlling this decision. Our laboratory has focused on the roles of apoptotic and autophagic proteins in T lymphocyte development and function. Using genetic models in mice and in vitro analyses of T cell functions, we have outlined critical roles for the Bcl-2 family (regulators of the intrinsic pathway of apoptosis), c-FLIP (an anti-apoptotic protein in the extrinsic pathway of apoptosis), and autophagy in T lymphocytes.

Glycolytic rate and lymphomagenesis depend on PARP14, an ADP ribosyltransferase of the B aggressive lymphoma (BAL) family

Poly(ADP-ribose)polymerase (PARP)14--a member of the B aggressive lymphoma (BAL) family of macrodomain-containing PARPs--is an ADP ribosyltransferase that interacts with Stat6, enhances induction of certain genes by IL-4, and is expressed in B lymphocytes. We now show that IL-4 enhancement of glycolysis in B cells requires PARP14 and that this process is central to a role of PARP14 in IL-4-induced survival. Thus, enhancements of AMP-activated protein kinase activity restored both IL-4-induced glycolytic activity in Parp14(-/-) B cells and prosurvival signaling by this cytokine. Suppression of apoptosis is central to B-lymphoid oncogenesis, and elevated macro-PARP expression has been correlated with lymphoma aggressiveness. Strikingly, PARP14 deficiency delayed B lymphomagenesis and reversed the block to B-cell maturation driven by the Myc oncogene. Collectively, these findings reveal links between a mammalian ADP ribosyltransferase, cytokine-regulated metabolic activity, and apoptosis; show that PARP14 influences Myc-induced oncogenesis; and suggest that the PARP14-dependent capacity to increase cellular metabolic rates may be an important determinant of lymphoma pathobiology.

Characterization of the metabolic phenotype of rapamycin-treated CD8+ T cells with augmented ability to generate long-lasting memory cells

Background

Cellular metabolism plays a critical role in regulating T cell responses and the development of memory T cells with long-term protections. However, the metabolic phenotype of antigen-activated T cells that are responsible for the generation of long-lived memory cells has not been characterized.

Design and Methods

Using lymphocytic choriomeningitis virus (LCMV) peptide gp33-specific CD8⁺ T cells derived from T cell receptor transgenic mice, we characterized the metabolic phenotype of proliferating T cells that were activated and expanded in vitro in the presence or absence of rapamycin, and determined the capability of these rapamycin-treated T cells to generate long-lived memory cells in vivo.

Results

Antigen-activated CD8⁺ T cells treated with rapamycin gave rise to 5-fold more long-lived memory T cells in vivo than untreated control T cells. In contrast to that control T cells only increased glycolysis, rapamycin-treated T cells upregulated both glycolysis and oxidative phosphorylation (OXPHOS). These rapamycin-treated T cells had greater ability than control T cells to survive withdrawal of either glucose or growth factors. Inhibition of OXPHOS by oligomycin significantly reduced the ability of rapamycin-treated T cells to survive growth factor withdrawal. This effect of OXPHOS inhibition was accompanied with mitochondrial hyperpolarization and elevation of reactive oxygen species that are known to be toxic to cells.

Conclusions

Our findings indicate that these rapamycin-treated T cells may represent a unique cell model for identifying nutrients and signals critical to regulating metabolism in both effector and memory T cells, and for the development of new methods to improve the efficacy of adoptive T cell cancer therapy.

G-CSF downregulates natural killer cell-mediated cytotoxicity in donors for hematopoietic SCT

In G-CSF-mobilized hematopoietic SCT (HSCT), natural killer (NK) cells have a critical role in GVHD and GVL effects. However, regulation of NK cell response to G-CSF remains unclear. This study assayed G-CSF effects in both HSCT donors and NK-92MI cells. The donors who received G-CSF had significantly decreased NK cell cytotoxicity. Levels of phosphatidylinositol 3-kinase (PI3K) and phosphorylated (p)-Akt, but not mammalian target of rapamycin (mTOR), were downregulated in NK cells from G-CSF-injected donors. G-CSF also decreased cytotoxicity without affecting viability and NF-κB of NK-92MI cells. PI3K and p-ERK expression were also decreased in G-CSF-treated NK-92MI cells, and their inhibitors, wortmannin and PD98059, respectively, both enhanced the downregulation of cytotoxicity. These effects were accompanied by decreased expression of a cytotoxicity-related gene, triosephosphate isomerase (TPI). Wortmannin, but not PD98059, enhanced the downregulation of TPI in G-CSF-treated NK-92MI cells, indicating a correlation between PI3K and TPI. We conclude that G-CSF-impaired NK cell cytotoxicity may accompany PI3K/Akt signaling. The effect is transient and NK cells may recover after G-CSF clearance, suggesting that G-CSF-mobilized HSCT may benefit both acute GVHD prevention and late-phase GVL promotion in HSCT recipients.

Akt requires glucose metabolism to suppress puma expression and prevent apoptosis of leukemic T cells

The PI3K/Akt pathway is activated in stimulated cells and in many cancers to promote glucose metabolism and prevent cell death. Although inhibition of Akt-mediated cell survival may provide a means to eliminate cancer cells, this survival pathway remains incompletely understood. In particular, unlike anti-apoptotic Bcl-2 family proteins that prevent apoptosis independent of glucose, Akt requires glucose metabolism to inhibit cell death. This glucose dependence may occur in part through metabolic regulation of pro-apoptotic Bcl-2 family proteins. Here, we show that activated Akt relies on glycolysis to inhibit induction of Puma, which was uniquely sensitive to metabolic status among pro-apoptotic Bcl-2 family members and was rapidly up-regulated in glucose-deficient conditions. Importantly, preventing Puma expression was critical for Akt-mediated cell survival, as Puma deficiency protected cells from glucose deprivation and Akt could not readily block Puma-mediated apoptosis. In contrast, the pro-apoptotic Bcl-2 family protein Bim was induced normally even when constitutively active Akt was expressed, yet Akt could provide protection from Bim cytotoxicity. Up-regulation of Puma appeared mediated by decreased availability of mitochondrial metabolites rather than glycolysis itself, as alternative mitochondrial fuels could suppress Puma induction and apoptosis upon glucose deprivation. Metabolic regulation of Puma was mediated through combined p53-dependent transcriptional induction and control of Puma protein stability, with Puma degraded in nutrient-replete conditions and long lived in nutrient deficiency. Together, these data identify a key role for Bcl-2 family proteins in Akt-mediated cell survival that may be critical in normal immunity and in cancer through Akt-dependent stimulation of glycolysis to suppress Puma expression.

Expression, regulation and function of phosphofructo-kinase/fructose-biphosphatases (PFKFBs) in glucocorticoid-induced apoptosis of acute lymphoblastic leukemia cells

BACKGROUND

Glucocorticoids (GCs) cause apoptosis and cell cycle arrest in lymphoid cells and constitute a central component in the therapy of lymphoid malignancies, most notably childhood acute lymphoblastic leukemia (ALL). PFKFB2 (6-phosphofructo-2-kinase/fructose-2,6-biphosphatase-2), a kinase controlling glucose metabolism, was identified by us previously as a GC response gene in expression profiling analyses performed in children with ALL during initial systemic GC mono-therapy. Since deregulation of glucose metabolism has been implicated in apoptosis induction, this gene and its relatives, PFKFB1, 3, and 4, were further analyzed.

METHODS

Gene expression analyses of isolated lymphoblasts were performed on Affymetrix HGU133 Plus 2.0 microarrays. GCRMA normalized microarray data were analyzed using R-Bioconductor packages version 2.5. Functional gene analyses of PFKFB2-15A and -15B isoforms were performed by conditional gene over-expression experiments in the GC-sensitive T-ALL model CCRF-CEM.

RESULTS

Expression analyses in additional ALL children, non-leukemic individuals and leukemic cell lines confirmed frequent PFKFB2 induction by GC in most systems sensitive to GC-induced apoptosis, particularly T-ALL cells. The 3 other family members, in contrast, were either absent or only weakly expressed (PFKFB1 and 4) or not induced by GC (PFKFB3). Conditional PFKFB2 over-expression in the CCRF-CEM T-ALL in vitro model revealed that its 2 splice variants (PFKFB2-15A and PFKFB2-15B) had no detectable effect on cell survival. Moreover, neither PFKFB2 splice variant significantly affected sensitivity to, or kinetics of, GC-induced apoptosis.

CONCLUSIONS

Our data suggest that, at least in the model system investigated, PFKFB2 is not an essential upstream regulator of the anti-leukemic effects of GC.

Insulin effect on glucose transport in thymocytes and splenocytes from rats with metabolic syndrome

Metabolic syndrome (MS) may comprise several clinical conditions such as obesity, diabetes and inflammatory disorders, which are characterized by metabolic imbalances. The study of glucose transport and regulation by insulin in lymphocytes is important, since the way they increase inflammation and susceptibility to infections are common in MS. We studied glucose internalization in isolated thymocytes and splenocytes, its regulation by insulin, and the role of three glucose transporters (Gluts) in control and in MS rats. Control glucose internalization and insulin responses were lower in splenocytes than in thymocytes. Control and insulin-induced glucose internalization in thymocytes declined with age, while transport by splenocyte continued to respond to insulin. Control thymocyte glucose internalization was blocked by antibodies against Glut 1 and 4, while the insulin response also was blocked by an anti-Glut 3 antibody. On four month old control and insulin-induced response, splenocyte transport was only blocked by Glut 1 and 4 antibodies. At six months splenocyte glucose internalization depended on Glut 1 and was less sensitive to the effects of an anti-Glut 4 antibody. In MS splenocytes the capacity of anti-Glut 1 antibodies to inhibit control and insulin-dependent glucose transport was less significant, and we found that in MS rats, glucose internalization was dependent on Glut 3 and Glut 4. In summary, the altered metabolic state present in MS rats shows signs of modulation of glucose internalization by the Glut1, Glut 3 and Glut 4 transporters, compared with its own age control.

Intertwined pathways of programmed cell death in immunity

Programmed cell death (PCD) occurs widely in species from every kingdom of life. It has been shown to be an integral aspect of development in multicellular organisms, and it is an essential component of the immune response to infectious agents. An analysis of the phylogenetic origin of PCD now shows that it evolved independently several times, and it is fundamental to basic cellular physiology. Undoubtedly, PCD pervades all life at every scale of analysis. These considerations provide a backdrop for understanding the complexity of intertwined, but independent, cell death programs that operate within the immune system. In particular, the contributions of apoptosis, autophagy, and necrosis in the resolution of an immune response are considered.

Triple expression of B7-1, B7-2 and 4-1BBL enhanced antitumor immune response against mouse H22 hepatocellular carcinoma

OBJECTIVES

Costimulatory signals are essential for T-cell activation and hence play a very important role in antitumor immunity. B7 and 4-1BBL which belongs to tumor necrosis factor (TNF) family provide costimulatory interaction for T-cell activation and function. This study investigated the role of B7 and 4-1BBL in the amplification of tumor immunity by transduction of the B7-1, B7-2 and 4-1BBL into mouse hepatocellular carcinoma cell line H22.

METHODS

The tumorigenicity of H22 variants expressing either B7-1, B7-2 (H22/B7-1/B7-2) or 4-1BBL was compared with an H22 variant expressing B7-1, B7-2 and 4-1BBL (H22/B7-1/B7-2/4-1BBL). The study next investigated whether the combination of B7-1/B7-2 and 4-1BBL cell injection induced cytotoxic T lymphocyte (CTL) response and IL-2/IFN-γ secretion. The immune mechanisms underlying this combination treatment were then analyzed.

RESULTS

Syngeneic BALB/c mice injected with H22/B7-1/B7-2/4-1BBL cells that expressed elevated levels of B7-1, B7-2 and 4-1BBL showed a tumor development frequency of 50% compared with 100% in mice injected with the H22 parental line, H22/neo, H22/B7-1/B7-2 and H22/4-1BBL. Mice inoculated with H22 tumor cells expressing B7-1, B7-2 and 4-1BBL developed a strong cytotoxic T lymphocyte response and long-term immunity against wild-type tumor, suggesting a synergistic effect between the B7 and 4-1BBL costimulatory pathways. Results showed that H22/B7-1/B7-2/4-1BBL tumor vaccines probably protect the infiltrating lymphocytes from apoptosis and induce NF-κB activation to improve T-cell-mediated antitumor response.

CONCLUSIONS

In this study, the antitumor consequences of using B7-1, B7-2 and 4-1BBL gene transfer have demonstrated the therapeutic potential of gene therapy approach for hepatocellular carcinoma.

Metabolic shifts in immunity and inflammation

Sites of ongoing inflammation and triggered immune responses are characterized by significant changes in metabolic activity. Recent studies have indicated that such shifts in tissue metabolism result from a combination of profound recruitment of inflammatory cells (neutrophils and monocytes) and high proliferation rates among lymphocyte populations. The resultant shifts in energy supply and demand can result in metabolic acidosis and diminished delivery and/or availability of oxygen, leading to hypoxia extensive enough to trigger transcriptional and translation changes in tissue phenotype. Such phenotypic shifts can imprint fundamental changes to tissue metabolism. In this study, we review recent work addressing metabolic changes and metabolic control of inflammation and immunity.

Intrinsic and extrinsic control of effector T cell survival and memory T cell development

Following infection or vaccination T cells expand exponentially and differentiate into effector T cells in order to control infection and coordinate the multiple effector arms of the immune system. Soon after this expansion, the majority of antigen-specific T cells die to reattain homeostasis and a small pool of memory T cells forms to provide long-term immunity to subsequent re-infection. Our understanding of how this process is controlled has improved considerably over the recent years, but many questions remain outstanding. This review focuses on the recent advancements in this area with an emphasis on how the contraction of activated T cells is coordinately regulated by a combination of factors extrinsic and intrinsic to the activated T cells.

Estrogen augments the T cell-dependent but not the T-independent immune response

Estrogen plays a critical regulatory role in the development and maintenance of immunity. Its role in the regulation of antibody synthesis in vivo is still not completely clear. Here, we have compared the effect of estrogen on T cell-dependent (TD) and T cell-independent type 2 (TI-2) antibody responses. The results provide the first evidence that estrogen enhances the TD but not the TI-2 response. Ovariectomy significantly decreased, while estrogen re-administration increased the number of hapten-specific IgM- and IgG-producing cells in response to TD antigen. In vitro experiments also show that estrogen may have a direct impact on B and T cells by inducing rapid signaling events, such as Erk and AKT phosphorylation, cell-specific Ca(2+) signal, and NFkappaB activation. These non-transcriptional effects are mediated by classical estrogen receptors and partly by an as yet unidentified plasma membrane estrogen receptor. Such receptor- mediated rapid signals may modulate the in vivo T cell-dependent immune response.

IL-7 is essential for homeostatic control of T cell metabolism in vivo

It has become apparent that T cells require growth signals to maintain function and viability necessary to maintain proper immune homeostasis. One means by which cell extrinsic signals may mediate these effects is by sustaining sufficient basal cell metabolism to prevent cell atrophy. The role of metabolism and the specific growth factors essential to maintain metabolism of mature T cells in vivo, however, are poorly defined. As IL-7 is a nonredundant cytokine required for T cell development and survival and can regulate T cell metabolism in vitro, we hypothesized it may be essential to sustain metabolism of resting T cells in vivo. Thus, we generated a model for conditional expression of IL-7R in mature T cells. After IL-7R deletion in a generally normal lymphoid environment, T cells had reduced responses to IL-7, including abrogated signaling and maintenance of antiapoptotic Bcl-2 family expression that corresponded to decreased survival in vitro. T cell survival in vivo was also reduced after loss of the IL-7R in a T cell-intrinsic manner. Additionally, IL-7R deletion resulted in delayed growth and proliferation following stimulation. Importantly, in vivo excision of IL-7R led to T cell atrophy that was characterized by delayed mitogenesis and reduced glycolytic flux. These data are the first to identify an in vivo requirement for a specific cell extrinsic signal to sustain lymphocyte metabolism and suggest that control of glycolysis by IL-7R may contribute to the well-described roles of IL-7 in T cell development, homeostatic proliferation, and survival.

IL-7 enhances thymic human T cell development in "human immune system" Rag2-/-IL-2Rgammac-/- mice without affecting peripheral T cell homeostasis

IL-7 is a central cytokine in the development of hematopoietic cells, although interspecies discrepancies have been reported. By coculturing human postnatal thymus hematopoietic progenitors and OP9-huDL1 stromal cells, we found that murine IL-7 is approximately 100-fold less potent than human IL-7 for supporting human T cell development in vitro. We investigated the role of human IL-7 in newborn BALB/c Rag2(-/-)gamma(c)(-/-) mice transplanted with human hematopoietic stem cells (HSC) as an in vivo model of human hematopoiesis using three approaches to improve IL-7 signaling: administration of human IL-7, ectopic expression of human IL-7 by the transplanted human HSC, or enforced expression of a murine/human chimeric IL-7 receptor binding murine IL-7. We show that premature IL-7 signaling at the HSC stage, before entrance in the thymus, impeded T cell development, whereas increased intrathymic IL-7 signaling significantly enhanced the maintenance of immature thymocytes. Increased thymopoiesis was also observed when we transplanted BCL-2- or BCL-x(L)-transduced human HSC. Homeostasis of peripheral mature T cells in this humanized mouse model was not improved by any of these strategies. Overall, our results provide evidence for an important role of IL-7 in human T cell development in vivo and highlight the notion that IL-7 availability is but one of many signals that condition peripheral T cell homeostasis.

The serine/threonine kinase LKB1 controls thymocyte survival through regulation of AMPK activation and Bcl-XL expression

LKB1 is a serine/threonine kinase that directly activates the energy sensor AMP-activated protein kinase (AMPK) in response to bioenergetic stress, and mainly acts as a tumor suppressor that controls cell polarity and proliferation. Although LKB1 is expressed in multiple tissues including the thymus and the spleen, its roles in T-cell development and function remain unknown. Here, we show that T-cell-specific deletion of LKB1 resulted in reduced survival of double-positive (DP) thymocytes and impaired generation of both CD4 and CD8 single-positive thymocytes. Disruption of LKB1 not only prevented the activation of AMPK but also impaired the expression of anti-apoptotic protein Bcl-XL. Importantly, ectopic expression of either Bcl-XL or the constitutively active AMPK mutant significantly rescued DP thymocytes from LKB1 deficiency-induced cell death. Moreover, ectopic expression of the constitutively active AMPK mutant was found to restore the expression of Bcl-XL in LKB1-deficient DP thymocytes. These findings identify LKB1 as a critical factor for the survival of DP thymocytes through regulation of AMPK activation and Bcl-XL expression.

CD4+ T cell-derived IL-2 signals during early priming advances primary CD8+ T cell responses

Stimulating naïve CD8⁺ T cells with specific antigens and costimulatory signals is insufficient to induce optimal clonal expansion and effector functions. In this study, we show that the activation and differentiation of CD8⁺ T cells require IL-2 provided by activated CD4⁺ T cells at the initial priming stage within 0–2.5 hours after stimulation. This critical IL-2 signal from CD4⁺ cells is mediated through the IL-2Rβγ of CD8⁺ cells, which is independent of IL-2Rα. The activation of IL-2 signaling advances the restriction point of the cell cycle, and thereby expedites the entry of antigen-stimulated CD8⁺ T-cell into the S phase. Besides promoting cell proliferation, IL-2 stimulation increases the amount of IFNγ and granzyme B produced by CD8⁺ T cells. Furthermore, IL-2 at priming enhances the ability of P14 effector cells generated by antigen activation to eradicate B16.gp33 tumors in vivo. Therefore, our studies demonstrate that a full CD8⁺ T-cell response is elicited by a critical temporal function of IL-2 released from CD4⁺ T cells, providing mechanistic insights into the regulation of CD8⁺ T cell activation and differentiation.

Mitochondrial metabolism and cancer

Historically, it has been assumed that glycolytic metabolism, not mitochondrial metabolism, is essential for tumor cell proliferation. However, most tumor cells have functional mitochondria, and recent studies suggest that the citric acid cycle (TCA) cycle intermediates are precursors for synthesis of nucleotides, lipids, and amino acids. Here we review the accumulating evidence that mitochondrial metabolism plays an essential role in tumor cell proliferation.

Phosphoinositide (3,4,5)-triphosphate binding to phosphoinositide-dependent kinase 1 regulates a protein kinase B/Akt signaling threshold that dictates T-cell migration, not proliferation

The present study explored the consequences of phosphoinositide (3,4,5)-triphosphate [PI(3,4,5)P(3)] binding to the pleckstrin homology (PH) domain of the serine/threonine kinase 3-phosphoinositide-dependent kinase 1 (PDK1). The salient finding is that PDK1 directly transduces the PI(3,4,5)P(3) signaling that determines T-cell trafficking programs but not T-cell growth and proliferation. The integrity of the PDK1 PH domain thus is not required for PDK1 catalytic activity or to support cell survival and the proliferation of thymic and peripheral T cells. However, a PDK1 mutant that cannot bind PI(3,4,5)P(3) cannot trigger the signals that terminate the expression of the transcription factor KLF2 in activated T cells and cannot switch the chemokine and adhesion receptor profile of naive T cells to the profile of effector T cells. The PDK1 PH domain also is required for the maximal activation of Akt/protein kinase B (PKB) and for the maximal phosphorylation and inactivation of Foxo family transcription factors in T cells. PI(3,4,5)P(3) binding to PDK1 and the strength of PKB activity thus can dictate the nature of the T-cell response. Low levels of PKB activity can be sufficient for T-cell proliferation but insufficient to initiate the migratory program of effector T cells.

Cytokine-dependent regulation of NADPH oxidase activity and the consequences for activated T cell homeostasis

Cellular dependence on growth factors for survival is developmentally programmed and continues in adult metazoans. Antigen-activated T cell apoptosis in the waning phase of the immune response is thought to be triggered by depletion of cytokines from the microenvironment. T cell apoptosis resulting from cytokine deprivation is mediated by reactive oxygen species (ROS), but their source and position in the apoptotic cascade is poorly understood. RNA interference approaches implicated the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in neglect-induced apoptosis in T cells. Using mice deficient for the catalytic subunit gp91^phox to characterize the molecular link to activated T cell apoptosis, we show that gp91^phox-deficient T (T^−/−) cells generated mitochondrial superoxide but had diminished hydrogen peroxide production in response to neglect, which, in turn, regulated Jun N-terminal kinase–dependent Bax activation and apoptosis. Activated T^−/− cells were distinguished by improved survival after activation by superantigens in vivo, adoptive transfers into congenic hosts, and higher recall responses after immunization. Thus, the NADPH oxidase may regulate adaptive immunity in addition to its previously well-characterized role in the innate response.

A 57-gene expression signature in B-cell chronic lymphocytic leukemia

B-CLL is the most frequent type of leukemia in the Western countries. The disease, common among the elderly, follows a variable course in terms of survival time and symptoms. There is evidence that the accumulation of lymphocytes in peripheral blood and bone marrow is due to a cell resistance to apoptosis rather than to highly proliferative cells. Genetic mechanisms that lead to the development and progression of disease are mainly unknown, although a number of prognostically and diagnostically important genetic markers have been identified. The aim of this study is to investigate the gene expression profile, by a specific chip for microarray analysis, in B-CLL lymphocytes with regard to factors involved in apoptosis cascade, signal transduction, purine metabolism enzymes, interleukin expression, enzymes involved in the responses to oxidative stress. We found relevant results in a set of 19 of the 57 genes considered. IMP dehydrogenase, adenine phosphoribosyltransferase, adenylosuccinate lyase, adenylate kinase, ADORA1, G-protein-coupled receptor kinase 6, Bcl-2-like 1 isoform 2, caspase 6, and 8 were found underexpressed; while ADORA3, Gars-Airs-Gart, adenylate kinase 3, adenylate deaminase, NMN adenylyltransferase, CD26, CD38, interleukins 18 and 4 were found overexpressed. The microarray technique is a powerful method for identification of potential important diagnostic and prognostic markers, besides giving prominence to genes candidate for further studies.

The peptidyl-prolyl isomerase Pin1 facilitates cytokine-induced survival of eosinophils by suppressing Bax activation

The mechanisms through which cytokine signals prevent the activation and mitochondrial targeting of the pro-apoptotic Bcl-2-associated X protein (Bax) are unclear. Here we showed, using primary human eosinophils, that in the absence of the pro-survival cytokines granulocyte macrophage-colony stimulating factor (GM-CSF) or interleukin 5, Bax spontaneously undergoes activation and initiates mitochondrial disruption. Bax inhibition reduced eosinophil apoptosis, even in the absence of cytokines. GM-CSF induced activation of Erk1/2, which phosphorylated Thr167 of Bax, which facilitated de novo interaction of Bax with the prolyl isomerase Pin1. Pin1 blockade led to Bax cleavage, mitochondrial translocation and caspase activation, irrespective of the presence of cytokines. Our findings indicate that Pin1 is a key mediator of pro-survival signaling and a regulator of Bax function.

Autophagy and lymphocyte homeostasis

Lymphocyte homeostasis is tightly regulated in vivo by various factors including cytokines, antigens, and costimulatory signals. Central to this regulation is the intricate balance between survival and apoptosis determined by pro- and antiapoptotic factors, including Bcl-2/Bcl-xL of the Bcl-2 family in the intrinsic death pathway and Fas/FADD of the TNF death receptor superfamily in the extrinsic death pathway. Recent studies have identified a critical role for autophagy, a well-conserved catabolic process in eukaryotic cells, in T and B lymphocyte homeostasis. Autophagy is essential for mature T lymphocyte survival and proliferation. In addition, autophagy can promote T cell death in defined physiologic or pathologic conditions. Autophagy also contributes to the survival of subsets of B lymphocytes, including developing pre-B cells as well as B1 B cells in vivo. Thus, autophagy represents a novel pathway regulating both developing and mature lymphocytes. Future studies are required to investigate the role of autophagy in regulating T and B cell homeostasis during immune responses to pathogens, as well as to define the mechanisms by which autophagy regulates lymphocyte death and survival.

AKT inhibitor, GSK690693, induces growth inhibition and apoptosis in acute lymphoblastic leukemia cell lines

The PI3K/AKT signaling is activated in various hematologic malignancies. We evaluated the effect of a novel, pan-AKT kinase inhibitor, GSK690693, on the proliferation of 112 cell lines representing different hematologic neoplasia. Fifty-five percent of all cell lines tested were sensitive to AKT inhibitor (EC(50)<1 microM), with acute lymphoblastic leukemia (ALL), non-Hodgkin lymphoma, and Burkitt lymphoma showing 89%, 73%, and 67% sensitivity to GSK690693, respectively. The antiproliferative effect was selective for the malignant cells, as GSK690693 did not inhibit the proliferation of normal human CD4(+) peripheral T lymphocytes as well as mouse thymocytes. Phosphorylation of downstream substrates of AKT was reduced in both sensitive and insensitive cell lines on treatment with GSK690693, suggesting that the cause of resistance was not related to the lack of AKT kinase inhibition. Consistent with the role of AKT in cell survival, GSK690693 also induced apoptosis in sensitive ALL cell lines. Overall, our data provide direct evidence for the role of AKT signaling in various hematologic malignancies, especially ALL and some lymphomas.