Increased activity of caspase 3 and caspase 8 in anti-Fas-induced apoptosis in lymphocytes from ageing humans

Proteodynamics in aging human T cells - The need for its comprehensive study to understand the fine regulation of T lymphocyte functions

Cellular life depends mostly on the creation, modification, interactions and destruction of proteins. This is true for every cell, including human T lymphocytes. One way these cells can ascertain the fidelity and at least partial functionality of their proteomes under constant attack of irreversible modulations (e.g., ROS- or glycation-dependent) is proteostasis. However, with cellular aging proteostasis progressively fails and proteostenosis (decreased amounts and functionalities of remaining proteins) occurs. There are several mechanisms involved in the modulation and protection of the proteome in the T cells which include mainly multiple layers of vesicle-bound and cytoplasmic proteases (e.g., lysosomal and proteasomal ones) acting mostly by degradation of obsolete and age-modified proteins. Recently it was shown that another not yet so widely known system consisting of obligatorily calcium-dependent cysteine proteases, the calpains and their inhibitor, the calpastatin serves in T cells as a dual switch, either activating or inactivating different proteins depending on intracellular conditions. Thus the proteolytic elimination of altered proteins as well as modulation of activity of those remaining leads to dynamic change of proteome composition and function (proteodynamics) in aging lymphocytes, so far in an almost unknown way. Aging T cell proteodynamics requires further comprehensive analysis of the resulting lysoproteomic patterns and their changes.

Moderate and intense exercise lifestyles attenuate the effects of aging on telomere length and the survival and composition of T cell subpopulations

Studies indicate that exercise might delay human biological aging, but the effects of long-term exercise on T cell function are not well known. We tested the hypothesis that moderate or intense exercise lifestyle may attenuate the effects of aging on the telomere length and the survival and composition of T cell subpopulations. Elderly (65-85 years) with intense training lifestyle (IT, n = 15), moderate training lifestyle (MT, n = 16), and who never trained (NT, n = 15) were studied. Although the three groups presented the age-associated contraction of the TCD4(+)/TCD8(+) naïve compartments and expansion of the memory compartments, both training modalities were associated with lower proportion of terminally differentiated (CD45RA(+)CCR7(neg)) TCD4(+) and TCD8(+) cells, although among the latter cells, the reduction reached statistical significance only with IT. MT was associated with higher proportion of central memory TCD4(+) cells, while IT was associated with higher proportion of effector memory TCD8(+) cells. However, both training lifestyles were unable to modify the proportion of senescent (CD28(neg)) TCD8(+) cells. Telomeres were longer in T cells in both training groups; with IT, telomere length increased mainly in TCD8(+) cells, whereas with MT, a modest increase in telomere length was observed in both TCD8(+) and TCD4(+) cells. Reduced commitment to apoptosis of resting T cells, as assessed by caspase-3 and Bcl-2 expression, was seen predominantly with IT. Measurement of pro-inflammatory cytokines in serum and peripheral blood mononuclear cell (PBMC)'s supernatants did not show chronic low-grade inflammation in any of the groups. In conclusion, MT and IT lifestyles attenuated some of the effects of aging on the immune system.

Human-gyrovirus-Apoptin triggers mitochondrial death pathway--Nur77 is required for apoptosis triggering

The human gyrovirus derived protein Apoptin (HGV-Apoptin) a homologue of the chicken anemia virus Apoptin (CAV-Apoptin), a protein with high cancer cells selective toxicity, triggers apoptosis selectively in cancer cells. In this paper, we show that HGV-Apoptin acts independently from the death receptor pathway as it induces apoptosis in similar rates in Jurkat cells deficient in either FADD (fas-associated death domain) function or caspase-8 (key players of the extrinsic pathway) and their parental clones. HGV-Apoptin induces apoptosis via the activation of the mitochondrial intrinsic pathway. It induces both mitochondrial inner and outer membrane permebilization, characterized by the loss of the mitochondrial potential and the release into cytoplasm of the pro-apoptotic molecules including apoptosis inducing factor and cytochrome c. HGV-Apoptin acts via the apoptosome, as lack of expression of apoptotic protease-activating factor 1 in murine embryonic fibroblast strongly protected the cells from HGV-Apoptin–induced apoptosis. Moreover, QVD-oph a broad-spectrum caspase inhibitor delayed HGV-Apoptin–induced death. On the other hand, overexpression of the anti-apoptotic BCL-XL confers resistance to HGV-Apoptin–induced cell death. In contrast, cells that lack the expression of the pro-apoptotic BAX and BAK are protected from HGV-Apoptin induced apoptosis. Furthermore, HGV-Apoptin acts independently from p53 signal but triggers the cytoplasmic translocation of Nur77. Taking together these data indicate that HGV-Apoptin acts through the mitochondrial pathway, in a caspase-dependent manner but independently from the death receptor pathway.

Caspase-2 mediates a Brucella abortus RB51-induced hybrid cell death having features of apoptosis and pyroptosis

Programmed cell death (PCD) can play a crucial role in tuning the immune response to microbial infection. Although PCD can occur in different forms, all are mediated by a family of proteases called caspases. Caspase-2 is the most conserved caspase, however, its function in cell death is ill-defined. Previously we demonstrated that live attenuated cattle vaccine strain Brucella abortus RB51 induces caspase-2-mediated and caspase-1-independent PCD of infected macrophages. We also discovered that rough attenuated B. suis strain VTRS1 induces a caspase-2-mediated and caspase-1-independent proinflammatory cell death in infected macrophages, which was tentatively coined "caspase-2-mediated pyroptosis". However, the mechanism of caspase-2-mediated cell death pathway remained unclear. In this study, we found that caspase-2 mediated proinflammatory cell death of RB51-infected macrophages and regulated many genes in different PCD pathways. We show that the activation of proapoptotic caspases-3 and -8 was dependent upon caspase-2. Caspase-2 regulated mitochondrial cytochrome c release and TNFα production, both of which are known to activate caspase-3 and caspase-8, respectively. In addition to TNFα, RB51-induced caspase-1 and IL-1β production was also driven by caspase-2-mediated mitochondrial dysfunction. Interestingly, pore formation, a phenomenon commonly associated with caspase-1-mediated pyroptosis, occurred; however, unlike its role in S. typhimurium-induced pyroptosis, pore formation did not contribute to RB51-induced proinflammatory cell death. Our data suggest that caspase-2 acts as an initiator caspase that mediates a novel RB51-induced hybrid cell death that simulates but differs from typical non-proinflammatory apoptosis and caspase-1-mediated proinflammatory pyroptosis. The initiator role of the caspase-2-mediated cell death was also conserved in cellular stress-induced cell death of macrophages treated with etoposide, naphthalene, or anti-Fas. Caspase-2 also regulated caspase-3 and -8 activation, as well as cell death in macrophages treated with each of the three reagents. Taken together, our data has demonstrated that caspase-2 can play an important role in mediating a proinflammatory response and a hybrid cell death that demonstrates features of both apoptosis and pyroptosis.

Enhanced apoptosis in retinal pigment epithelium under inflammatory stimuli and oxidative stress

Age-related macular degeneration (AMD) is a neurodegenerative disease that causes irreversible central vision loss in the elderly. Retinal pigment epithelium (RPE) has been found to be a key component in AMD pathogenesis. The Ccl2(-/-)/Cx3cr1(-/-) (DKO) mouse on Crb1(rd8) background is created as an AMD model, developing AMD-like retinal lesions. Our study aimed to examine RPE apoptosis in DKO mouse and human ARPE-19 cell line. DKO RPE expressed higher apoptotic proteins when compared with age-matched wild type (WT) RPE in physiological conditions. Apoptosis of primary cultured mouse RPE was evaluated under stimulation with lipopolysaccharide for inflammatory stimulation and 2,3,7,8-tetrachlorodibenzo-p-dioxin or H(2)O(2) for oxidative stress. Compared with WT RPE, DKO RPE was more susceptible to Fas ligand (FasL)-mediated apoptosis under both inflammatory and oxidative stress, with less cell viability and higher expression of apoptotic transcripts and proteins. Decreased cell viability was also observed in ARPE-19 cells under each stimulus. Furthermore, we also investigated the anti-apoptotic effects of decoy receptor 3 (DcR3), a decoy receptor for FasL, on ARPE-19 cells under inflammatory and oxidative stress. DcR3 pre-incubated ARPE-19 cells showed decreased apoptosis, with increased cell viability and decreased expression of apoptotic transcripts and proteins under the stimuli. On the contrary, knockdown of DcR3 in ARPE-19 cells showed totally opposite results. Our study demonstrates that FasL-mediated RPE apoptosis may play a pivotal role in AMD pathogenesis.

Improving immunogenicity and effectiveness of influenza vaccine in older adults

Aging is associated with a decline in immune function (immunosenescence) that leads to progressive deterioration in both innate and adaptive immune functions. These changes contribute to the subsequent increased risk for infectious diseases and their sequelae. Vaccination is the most effective and inexpensive public health strategy for prevention of infection, despite the decreased efficacy of vaccines in older adults due to immunosenescence. The rapid rise in the older adult population globally represents a great challenge for vaccination programs. This article first addresses the status of innate and adaptive immune functions in aging and then focuses on influenza vaccine. The development history of influenza vaccines, current status, and potential strategies to improve the immunogenicity and vaccine effectiveness in older adults are discussed.

Immunosenescence and Challenges of Vaccination against Influenza in the Aging Population

Influenza is an important contributor to morbidity and mortality worldwide. Accumulation of genetic mutations termed antigenic drift, allows influenza viruses to inflict yearly epidemics that may result in 250,000 to 500,000 deaths annually. Over 90% of influenza-related deaths occur in the older adult population. This is at least in part a result of increasing dysregulation of the immune system with age, termed immunosenescence. This dysregulation results in reduced capacity to cope with infections and decreased responsiveness to vaccination. The older adult population is in dire need of improved vaccines capable of eliciting protective responses in the face of a waning immune system. This review focuses on the status of immunity, responses to influenza vaccination, and strategies that are currently being explored to elicit enhanced immune responses in this high risk population.

Fas/FasL-mediated apoptosis and inflammation are key features of acute human spinal cord injury: implications for translational, clinical application

The Fas/FasL system plays an important role in apoptosis, the inflammatory response and gliosis in a variety of neurologic disorders. A better understanding of these mechanisms could lead to effective therapeutic strategies following spinal cord injury (SCI). We explored these mechanisms by examining molecular changes in postmortem human spinal cord tissue from cases with acute and chronic SCI. Complementary studies were conducted using the in vivo Fejota™ clip compression model of SCI in Fas-deficient B6.MRL-Fas-lpr (lpr) and wild-type (Wt) mice to test Fas-mediated apoptosis, inflammation, gliosis and axonal degeneration by immunohistochemistry, Western blotting, gelatin zymography and ELISA with Mouse 32-plex cytokine/chemokine panel bead immunoassay. We report novel evidence that shows that Fas-mediated apoptosis of neurons and oligodendrocytes occurred in the injury epicenter in all cases of acute and subacute SCI and not in chronic SCI or in control cases. We also found significantly reduced apoptosis, expression of GFAP, NF-κB, p-IKappaB and iba1, increased number of CD4 positive T cells and MMP2 expression and reduced neurological dysfunction in lpr mice when compared with Wt mice after SCI. We found dramatically reduced inflammation and cytokines and chemokine expression in B6.MRL-Fas-lpr mice compared to Wt mice after SCI. In conclusion, we report multiple lines of evidence that Fas/FasL activation plays a pivotal role in mediating apoptosis, the inflammatory response and neurodegeneration after SCI, providing a compelling rationale for therapeutically targeting Fas in human SCI.

Age-dependent increases in apoptosis/necrosis ratios in human lymphocytes exposed to oxidative stress

Unlike apoptosis, mechanisms leading to necrosis are less well understood. Moreover, changes in necrosis as a function of age have not been studied in human lymphocytes. H(2)O(2)-induced death of peripheral lymphocytes (56 healthy donors, 24-95 years) was evaluated by flow cytometry and propidium iodide staining, caspase activation, DNA laddering, and electron microscopy. H(2)O(2)-induced stress was associated with high levels of necrosis in young individuals (≤30 years), whereas progressively enhanced apoptotic death was observed in older donors, without changes in overall lymphocyte survival. Thus, apoptosis/necrosis ratios were inverted in young versus elderly (≥65 years) donors. Death was not accompanied by increased caspase activity and, accordingly, unaffected by caspase inhibition; however, it was almost completely prevented by poly ADP ribose polymerase inhibition. In summary, aging was associated with changes in the apoptosis/necrosis ratios, rather than susceptibility per se to H(2)O(2)-induced death, which was caspase independent but poly ADP ribose polymerase dependent. Understanding this switch in death modes may aid in understanding age-related disorders.

Modulation of the apoptotic pathway in skeletal muscle models: the role of growth hormone

Despite numerous studies on the role of growth hormone (GH), its function in skeletal muscle apoptosis secondary to various stimuli is poorly understood. In this study, we used rodent muscle cell lines to analyse cell growth and survival as well as the morphological and molecular markers of cell death in C2C12 and L6C5 myoblasts. These cells were treated either in the presence or absence of GH under serum starvation conditions or in the pro-apoptotic concentrations of hydrogen peroxide (H2O2). Although the cells were responsive to the presence of GH, we did not observe GH modulation of cell growth and survival. The presence of GH did not affect the cell death programme or the expression of apoptotic markers in basal conditions or under oxidative stress. In conclusion, this study indicated that GH "by itself" is not effective in modulating the intracellular pathways leading to cell survival or cell death induced by apoptotic stimuli.

Apoptotic processes in megakaryocytes and platelets

It is becoming increasingly clear that most mammalian cells are capable of undergoing apoptosis and that, within particular lineages, specific apoptotic pathways have evolved to regulate survival and turnover. The role of apoptosis in the megakaryocyte lineage is an intriguing one. Various insults, such as chemotherapeutics, autoantibodies, and human immunodeficiency virus (HIV), have been suggested to induce the apoptotic death of megakaryocytes and/or their progenitors. Conversely, apoptotic processes have been implicated in megakaryocyte development and platelet production. Platelets also contain functional apoptotic pathways, which circumscribe their survival. It has even been suggested that platelet activation responses involve components of the apoptotic machinery, highlighting a potential role for apoptotic processes in hemostasis and thrombosis. This review discusses the current state of knowledge about how apoptosis and apoptotic proteins contribute to the generation and function of megakaryocytes and platelets.

Olprinone attenuates the acute inflammatory response and apoptosis after spinal cord trauma in mice

Background

Olprinone hydrochloride is a newly developed compound that selectively inhibits PDE type III and is characterized by several properties, including positive inotropic effects, peripheral vasodilatory effects, and a bronchodilator effect. In clinical settings, olprinone is commonly used to treat congestive cardiac failure, due to its inotropic and vasodilating effects. The mechanism of these cardiac effects is attributed to increased cellular concentrations of cAMP. The aim of the present study was to evaluate the pharmacological action of olprinone on the secondary damage in experimental spinal cord injury (SCI) in mice.

Methodology/Principal Findings

Traumatic SCI is characterized by an immediate, irreversible loss of tissue at the lesion site, as well as a secondary expansion of tissue damage over time. Although secondary injury should be preventable, no effective treatment options currently exist for patients with SCI. Spinal cord trauma was induced in mice by the application of vascular clips (force of 24 g) to the dura via a four-level T5–T8 laminectomy. SCI in mice resulted in severe trauma characterized by edema, neutrophil infiltration, and production of inflammatory mediators, tissue damage, apoptosis, and locomotor disturbance. Olprinone treatment (0.2 mg/kg, i.p.) 1 and 6 h after the SCI significantly reduced: (1) the degree of spinal cord inflammation and tissue injury (histological score), (2) neutrophil infiltration (myeloperoxidase activity), (3) nitrotyrosine formation, (4) pro-inflammatory cytokines, (5) NF-κB expression, (6) p-ERK1/2 and p38 expression and (7) apoptosis (TUNEL staining, FAS ligand, Bax and Bcl-2 expression). Moreover, olprinone significantly ameliorated the recovery of hind-limb function (evaluated by motor recovery score).

Conclusions/Significance

Taken together, our results clearly demonstrate that olprinone treatment reduces the development of inflammation and tissue injury associated with spinal cord trauma.

Naive CD4 T cells from aged mice show enhanced death upon primary activation

Poor T cell immunity is one of the many defects seen in elderly humans and aged (Ad) mice. We report that naive CD4 T cells from aged mice (ANCD4 cells) showed greater apoptosis upon primary activation than those from young (Yg) mice, with loss of mitochondrial membrane potential, poor activation of Rel family transcription factors and increased DNA damage. Their ability to enhance glycolysis, produce lactate and induce autophagy following activation was also compromised. ANCD4 cells remained susceptible to death beyond first cell division. Activated ANCD4 cells also showed poor transition to a 'central memory' (CM) CD44(high), CD62L(high) phenotype in vitro. This correlated with low proportions of CM cells in Ad mice in vivo. Functionally, too, IFN-gamma responses recalled from T cells of immunized Ad mice, poor to begin with, worsened with time as compared with Yg mice. Thus, ANCD4 cells handle activation-associated stress very poorly due to multiple defects, possibly contributing to poor formation of long-lasting memory.

CD95-mediated apoptosis in naïve, central and effector memory subsets of CD4+ and CD8+ T cells in aged humans

Aging is associated with a decrease in naïve (T(N)) and central memory (T(CM)), and an accumulation of effector memory (T(EM) and T(EMRA)) T cell subsets. Previously, we have demonstrated an increased sensitivity of T(N) and T(CM) CD4+ and CD8+ T cells in aging to TNF-alpha-induced apoptosis. In this investigation, we examined whether similar differential sensitivity is applicable to CD95-mediated apoptosis. We show that T(N) and T(CM) CD4+ and CD8+ T cells from aged subjects are significantly more sensitive to CD95-mediated apoptosis. Increased apoptosis is associated with increased activation of caspase-8 and caspase-3. Both caspase-8 and caspase-3 inhibitors blocked CD95-mediated apoptosis and activation of caspase-8 and caspase-3 in T(N) and T(CM) CD4+ and CD8+ T cells. No significant difference was observed in apoptosis or in activation of caspase-8 and caspase-3 in T(EM) and T(EMRA) CD4+ and CD8+ T cells between young and aged subjects; both populations were relatively and comparably resistant to CD95-mediated apoptosis and caspase activation. No correlation was observed between the sensitivity/resistance of any of the subsets of CD4+ or CD8+T cells to CD95-mediated apoptosis and the expression of CD95. Our data suggest that increased CD95-mediated apoptosis of T(N) and T(CM) CD8+ and CD4+ T cells may play a role in their decline in human aging.

An integrated view of oxidative stress in aging: basic mechanisms, functional effects, and pathological considerations

Aging is an inherently complex process that is manifested within an organism at genetic, molecular, cellular, organ, and system levels. Although the fundamental mechanisms are still poorly understood, a growing body of evidence points toward reactive oxygen species (ROS) as one of the primary determinants of aging. The "oxidative stress theory" holds that a progressive and irreversible accumulation of oxidative damage caused by ROS impacts on critical aspects of the aging process and contributes to impaired physiological function, increased incidence of disease, and a reduction in life span. While compelling correlative data have been generated to support the oxidative stress theory, a direct cause-and-effect relationship between the accumulation of oxidatively mediated damage and aging has not been strongly established. The goal of this minireview is to broadly describe mechanisms of in vivo ROS generation, examine the potential impact of ROS and oxidative damage on cellular function, and evaluate how these responses change with aging in physiologically relevant situations. In addition, the mounting genetic evidence that links oxidative stress to aging is discussed, as well as the potential challenges and benefits associated with the development of anti-aging interventions and therapies.

A paradox of immunodeficiency and inflammation in human aging: lessons learned from apoptosis

Aging is associated with a paradox of immunodeficiency and inflammation (an evidence of hyperactive immune system). Apoptosis is associated with cellular depletion and suppression of inflammatory response. In this brief review, we will present evidence for the role of increased apoptosis in immunodeficiency and paradoxical increased inflammation associated with human aging. In particular, a role of apoptotic cells in failure to generate anti-inflammatory responses and directly activating inflammatory responses will be discussed.

Molecular mechanisms of TNF-α-induced apoptosis in naïve and memory T cell subsets

Aging in humans is associated with progressive decline in T cell function, hyperimmunoglobulinemia, increased prevalence of autoantibodies and decline in naïve CD8(+) T cells and accumulation of memory T cells, which appears to be oligoclonal and display feature of senescence, that is, decreased replication, short telomere length and resistance to apoptosis. Recently memory T cells have been further subdivided into central and effector memory T cells, based upon their migratory and homing properties. They are identified by a number of cell surface makers. In this brief review we will discuss molecular mechanisms of apoptosis in naïve and various types of memory T cells to possibly explain the changes observed in aging, which are very similar to certain autoimmune diseases.

Life and death of lymphocytes: a role in immunesenescence

Human aging is associated with progressive decline in immune functions, increased frequency of infections. Among immune functions, a decline in T cell functions during aging predominates. In this review, we will discuss the molecular signaling in two major pathways of apoptosis, namely death receptor pathway and mitochondrial pathway, and their alterations in both T and B lymphocytes in human aging with a special emphasis on naïve and different memory subsets of CD8+ T cells. We will also discuss a possible role of lymphocyte apoptosis in immune senescence.

Molecular mechanisms of apoptosis in the cells of the immune system in human aging

Aging is associated with progressive decline in immune functions and increased frequency of infections, autoimmunity, and cancer. Among immune functions, a decline in T-cell functions during aging predominates. In this review, I discuss the molecular signaling of three distinct pathways of apoptosis, namely the death receptor pathway, the mitochondrial pathway, and the most recently described endoplasmic reticulum stress pathway, and the relative sensitivity of naive, central memory, and effector memory CD8(+) T-cell subsets to apoptosis. In addition, I review apoptosis, especially via death receptor pathway, in naive and various memory subsets of CD4(+) and CD8(+) T cells (with primary emphasis on CD8(+) naive and memory subsets) in human aging and discuss the role of apoptosis in immune senescence.

Caspase-independent retinal ganglion cell death after target ablation in the neonatal rat

In neonatal rats, superior colliculus (SC) ablation results in a massive and rapid increase in retinal ganglion cell (RGC) death that peaks about 24 h post-lesion (PL). Naturally occurring cell death during normal development, and RGC death after axonal injury in neonatal and adult rats, has primarily been ascribed to apoptosis. Given that normal developmental cell death is reported to involve caspase 3 activation, and blocking caspase activity in adults reduces axotomy-induced death, we examined whether blocking caspases in vivo reduces RGC death after neonatal SC lesions. Neither general nor specific caspase inhibitors increased neonatal RGC survival 6 and 24 h PL. These inhibitors were, however, effective in blocking caspases in another well-defined in vitro apoptosis model, the corpus luteum. Caspase 3 protein and mRNA levels in retinas from normal and SC-lesioned neonatal rats were assessed 3, 6 and 24 h after SC removal using immunohistochemistry, western and northern blots and quantitative real-time polymerase chain reaction. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) was used to independently monitor retinal cell death. The polymerase chain reaction data showed a small but insignificant increase in caspase 3 mRNA in retinas 24 h PL. Western blot analysis did not reveal a significant shift to cleaved (activated) caspase 3 protein. There was a small increase in the number of cleaved caspase 3 immunolabelled cells in the ganglion cell layer 24 h PL but this represented only a fraction of the death revealed by TUNEL. Together, these data indicate that, unlike the situation in adults, most lesion-induced RGC death in neonatal rats occurs independently of caspase activation.

Interferon-gamma acts proapoptotic on hepatic stellate cells (HSC) and abrogates the antiapoptotic effect of interferon-alpha by an HSP70-dependant pathway

The activated hepatic stellate cell (HSC) is an important fibrogenic cell type of the liver. Interferon-alpha (IFN-alpha) has recently been shown to elicit an antiapoptotic effect on activated HSC by a JAK-2-dependent inhibition of caspase-8 activation. As JAK-2 has so far been shown to be a member of the IFN-gamma signal transduction pathway we studied the effect of IFN-gamma on apoptosis as well as on its signaling in primary cultured rat HSC. IFN-gamma elicited a proapoptotic effect in activated HSC. The combination of both, IFN-gamma and IFN-alpha, however, completely cancelled each other's effect. No effect of the two cytokines on major members of apoptosis-regulating systems (CD95, CD95L, bcl-2, bax, bcl-xL, p53, p21WAF1, p27, NFkappaB) could be observed. Western Blot analysis revealed that gene expression of the chaperone HSP70 was found to be downregulated by IFN-gamma but upregulated by IFN-alpha. The effect could be abrogated by administration of both. After transfection of activated HSC with a pCMV-HSP70 M expression vector the proapoptotic effect of IFN-gamma was cancelled. Using HSP70 antisense, the antiapoptotic effect of IFN-alpha was cancelled as well. However IFN-gamma had no effect on upregulation of JAK-2 and pJAK-2 by IFN-alpha. Taken together IFN-gamma and IFN-alpha exert opposite effects on apoptosis in HSC. This effect is mediated by their counteracting effect on HSP70 expression which acts antiapoptotic at the level of caspase-8.

Impairment of gamma/delta T lymphocytes in elderly: implications for immunosenescence

Gamma/delta T lymphocytes cells recognize the antigen in a non-classical way and are considered the third branch of the immune system devoted to defend the integrity of the body. Ageing is characterized by an impairment of the main way of protection (the adaptive branch) but, successfully aged people show compensatory mechanisms of defense such as proneness to inflammation. Moreover, very old subjects show an increased number of NK cells. We have previously demonstrated that gamma delta T lymphocytes are reduced in elderly. In the present paper we have studied some characteristics of these cells to evaluate the possibility that these cells might balance the decreased action of the adaptive branch in successfully aged people. Cytofluorimetric analysis of cells collected from young, old and centenarian subjects has been used to evaluate the ability of these cells to expand in vitro. Here we demonstrate that gamma delta T cells are impaired in the ability to proliferate to different stimuli such as isopentenyl pyrophoshate, that select gamma delta T lymphocytes bearing delta 2 chain, other than to phytohemagglutinin and anti-CD3 that are polyclonal activators. Moreover, we demonstrate that gamma delta T cells in aged and centenarians show an enhanced sensitivity to undergo apoptosis induced both by alpha-Fas and TNF-alpha. All together these data suggest that gamma delta T lymphocytes are impaired in elderly and suggest that the reduced ability to proliferate and the reduced number of circulating gamma delta T lymphocytes is due to the proneness to apoptosis. Finally on the basis of these data, we conclude that gamma delta T lymphocytes, do not participate in the remodeling of the immune system due to the reduction of classical T cell response and replacement by NK cells in elderly.

Role of NF-κB signaling pathway in increased tumor necrosis factor-α-induced apoptosis of lymphocytes in aged humans

In human aging, lymphocytes display increased sensitivity to tumor necrosis factor-alpha (TNF-alpha)-induced apoptosis. TNF-alpha induces both survival and apoptotic signals. The survival signal is mediated by the activation of NF-kappaB. Although a role of certain proapoptotic molecules in aging has been reported, a role of altered NF-kappaB signaling pathway has not been explored in detail. In this study, we have compared TNF-alpha-induced activation of NF-kappaB, phosphorylation of IkappaBalpha, and the expression of IKKbeta between lymphocytes from young and aged humans. Furthermore, we have explored a role of IKKbeta in increased susceptibility of lymphocytes from aged humans to TNF-alpha-induced apoptosis. Lymphocytes from aged humans displayed decreased activation of NF-kappaB, reduced phosphorylation of IkappaBalpha, and decreased expression of IKKbeta. In addition, overexpression of IKKbeta in lymphocytes from aged humans normalized TNF-alpha-induced apoptosis to the level of young subjects. These data suggest a deficiency of NF-kappaB signaling pathway and a role of IKKbeta, at least in part, for increased sensitivity of lymphocytes from aged humans to TNF-alpha-induced apoptosis.

Apoptosis in stress-induced and spontaneously senescent human fibroblasts

Although apoptosis has been shown in vivo to be involved in the aging process, in vitro studies of age-dependent apoptosis are limited. In this study, apoptosis was examined in normal human fibroblasts exposed to H(2)O(2) to induce premature senescence and in spontaneously senescent human fibroblasts. Although apoptosis was not observed for several days after exposure to H(2)O(2), morphological changes indicating apoptosis were evident in about 5% of cells 7 days after exposure to 80microM H(2)O(2), concomitantly with expression of senescent phenotype. The apoptotic changes were preceded by caspase activation in majority of the exposed cells. As well as H(2)O(2)-induced senescent cells, spontaneously senescent human fibroblasts showed apoptotic changes in about 2% of cells and majority of the senescent cells also showed activation of caspases. The results indicate that the apoptosis pathway is activated in H(2)O(2)-induced and spontaneously senescent human fibroblasts in vitro.

A role of fas-associated death domain (FADD) in increased apoptosis in aged humans

Fas-associated death domain (FADD) is an adapter protein that is recruited to the death-inducing signaling complex (DISC) during signaling via death receptors. FADD is a common conduit in both CD95-mediated and TNF-R-mediated apoptosis. In aging, T cells show increased susceptibility to death receptor-induced apoptosis. Therefore, in this investigation, we have examined the role of FADD in increased TNF-alpha-induced apoptosis of lymphocytes from aged humans. Our study shows that FADD expression is increased in lymphocytes from aged humans as compared to those from young subjects. Furthermore, transfection of aged lymphocytes with FADD dominant negative (FADD dn) plasmid resulted in the reduction of TNF-induced apoptosis in aged lymphocytes to a level comparable to that of young subjects. In addition, overexpression of FADD by transfection of lymphocytes from young subjects with wild-type FADD (FADD wt) resulted in increased apoptosis of young lymphocytes to a level comparable to that of young subjects. These data suggest that FADD plays an important role in increased apoptosis in aged lymphocytes signaled via TNF-R.

Hematopoietic stem cells mobilization and immune response in tumor-bearing mice

INTRODUCTION

Malignant diseases are known to modulate the number and function of myeloid, erythroid, and lymphoid cells. Since these cells are derived from hematopoietic stem cells (HSC), it is not clear if the observed effects of cancer on such cells are direct or indirect via stem cells. The purpose of this study was to evaluate the effect of breast cancer upon the levels and activity of peripheral blood hematopoietic stem cells.

MATERIALS AND METHODS

Four weeks following the establishment of 4T1 breast cancers in BALB/c mice, the animals were killed, blood and spleen harvested, and processed for light density mononuclear cells. Colony forming unit in culture assay was used to determine the activity of HSCs. Flow cytometry was used to determine the levels of lineage negative HSCs expressing c-kit and Sca-1 antigen (Lin c-kitSca-1). Mitogenic, cytotoxic and ELISPOT assays were used to evaluate functional properties of cells. Plasma cytokine levels were determined with ELISA assay.

RESULTS

In tumor-bearing mice, there was a 2- and 4-fold increase in the levels and proliferative capacity of HSCs, respectively, compared with controls. Contemporaneously, there was a 13-fold increase in plasma G-CSF in tumor-bearing animals compared with controls (0.225 ng/ml versus 3.0 ng/ml). Furthermore, the number of interferon gamma-secreting cells was significantly increased in tumor-bearing animals. Concurrently, cytotoxic activity of NK cells was significantly increased in tumor-bearing animals as compared with controls (22.4 +/- 10.6 versus 10.3 +/- 2.95; P < 0.05).

SUMMARY

These results suggest that (1) breast cancer mobilizes hematopoietic stem cells in mice presumably through G-CSF production, and (2) that such cancer-mobilized stem cells give rise to immune cell lineages which are functionally hyperactive in their cytotoxic activities. Such cells could be expected to have appreciable therapeutic benefit in terms of cancer cell cytotoxic activity when used as part of stem cell transplantation therapy in cancer patients.

Increased intensities of fas expression on peripheral T-cell subsets in severe autoimmune thyroid disease

Fas (CD95)-Fas ligand (FasL; CD178)-induced apoptosis is necessary for the maintenance of self-tolerance. To clarify whether or not any abnormalities in the Fas-FasL system exist in patients with autoimmune thyroid disease (AITD), we examined the expression of Fas and FasL on peripheral T lymphocytes by three-color flow cytometry in 113 patients with AITD and 49 healthy controls. The intensities of Fas expression in both CD4(+) and CD8(+) T cells decreased in thyrotoxic patients with Graves' disease (GD), but increased in both patients with severe Hashimoto's disease (HD) undergoing treatment and seriously intractable patients with GD continuously positive for thyrotropin (TSH) receptor antibody despite treatment with antithyroid drugs for more than 5 years. The proportion of Fas expression was increased in CD4(+) T cells from patients with untreated GD, and in CD8(+) T cells from patients with severe HD. The proportion of CD8(+) T cells decreased in patients with severe HD. FasL were not expressed on T cells in controls and patients with AITD. These results indicate that (1). the intensities of Fas expression on peripheral T cells increase in severe autoimmune thyroid diseases and (2). both the intensity and the proportion of Fas expression may be important for the induction of apoptosis.

Activation marker expression and apoptotic susceptibility of T-cell clones derived from CD34(+), young and SENIEUR donors

T-cell clones (TCC) derived from human peripheral blood lymphocytes of a young control, a healthy elderly (SENIEUR) donor, or from CD34(+) hematopoietic progenitor cells were utilised in this study to examine how in vivo and in vitro ageing affects T-cell apoptotic capability. The role of CD25, CD28 and the intracellular proteins, FLICE-inhibitory protein (FLIP), receptor-interacting protein (RIP) and caspase 3 were investigated. We observed an age-related decline in the expression of the IL-2 receptor alpha chain CD25, and absence of the co-stimulatory receptor CD28 on three of the four TCC studied. In young donor- and CD34 cell-derived TCC, but not in SENIEUR donor-derived TCC, we observed an age-related increase in susceptibility of the cells to mFas-L-induced apoptosis, which correlated with the age-related decrease of CD25 expression. Expression levels of full-length RIP and FLIP did not show any correlation to apoptotic susceptibility. However, expression levels of the cleaved form of RIP were greatly reduced in the SENIEUR donor-derived TCC, which together with a trend towards increased caspase 3 activity, could indicate an age-related alteration in utilisation of different apoptotic signalling pathways.

A role of inhibitor of apoptosis (IAP) proteins in increased lymphocyte apoptosis in aged humans

Lymphocytes from aged humans show increased death-receptor-mediated apoptosis, which is associated with an increased and early activation of caspases. Inhibitor of apoptosis (IAP) proteins inhibit apoptosis by inhibiting activation and activity of caspases. Therefore, we examine the expression of two of the IAPs, the cIAP-2 and XIAP in lymphocytes from young and aged subjects by Western blotting. Lymphocytes from aged expressed significantly less cIAP2 whereas no difference was observed in XIAP expression between young and aged subjects. These data may suggest that decreased cIAP2 may play a role in increased apoptosis in aged humans. Possible mechanisms for the regulation of IAPs in aging are discussed.

Caspases, apoptosis and aging

Caspases are a group of cysteine dependent aspartate-specific proteases. Originally found as the homolog of Ced-3 in C. elegans, 14 caspases have now been identified in mammals to date. Caspases play important roles in both the intrinsic and extrinsic apoptotic pathways and interact with the non-caspase apoptotic pathways. A number of recent published observations have suggested a strong association between apoptosis, age-related diseases and aging. Findings from our group and others reveal a strong correlation between alterations in caspase activity and aging. In this view point, we summarize current knowledge of the connection between caspases and aging observed in a variety of model systems from cultured cells in vitro to the in vivo models of rodents and humans.

Ethanol promotes T cell apoptosis through the mitochondrial pathway

Clinical reports suggest that acute ethanol intoxication is often associated with lymphopenia. Previously, ethanol was reported to invoke thymocyte apoptosis. We studied the effect of ethanol on T cell apoptosis. In addition, we evaluated the molecular mechanism of ethanol-induced T cell apoptosis. Human T cells harvested from healthy subjects after an alcohol drinking binge showed enhanced T cell apoptosis (before, 0.4 +/- 0.2% versus after, 19.6 +/- 2.5% apoptotic lymphocytes/field; P < 0.001). In in vitro studies, ethanol in a concentration of 50 mm and higher enhanced the apoptosis of Jurkat cells. DNA isolated from ethanol-treated Jurkat cells displayed integer multiples of 180 base pairs. Ethanol decreased Jurkat cell expression of Bcl-2, whereas ethanol increased Jurkat cell expression of Bax. Jurkat cells treated with ethanol also showed translocation of cytochrome C into cytosol. Moreover, a caspase-9 inhibitor partially inhibited ethanol-induced Jurkat cell apoptosis. In in vivo studies, after binge drinking, T cell expression of Bcl-2 also decreased. In addition, binge drinking induced the cleavage of caspase-3, suggesting activation of caspase-3 in T cells. These results suggest that ethanol promotes T cell apoptosis through the activation of intrinsic or mitochondrial pathway.

Antiapoptotic effect of interferon-alpha on hepatic stellate cells (HSC): a novel pathway of IFN-alpha signal transduction via Janus kinase 2 (JAK2) and caspase-8

The hepatic stellate cell (HSC), the pericyte of the liver sinusoids belongs to the mesenchymal cells of the liver. Damaging noxae induce a transformation from the quiescent (vitamin A-storing cell) to the activated (connective tissue-producing cell) state. The balance between proapoptotic and surviving factors decides about the fate of the activated HSC. Interferon-alpha (IFN-alpha) has been shown to elicit antiproliferative and/or antifibrogenic effects in various cell types of mesenchymal origin. We therefore investigated the effect of IFN-alpha on primary cultured rat HSC in their quiescent (day 2) and activated state (day 7). IFN-alpha significantly inhibited spontaneous apoptosis in activated HSC in vitro and simultaneously inhibited cell cycle progression by inducing a G1 arrest. The effect of IFN-a is not accompanied by a modulation of CD95, CD95L, p53, p21(WAF1), p27, bcl-2, bcl-xL, bax, NFkappaB, or IkappaB gene expression. Surprisingly, the IFN-alpha effect could be abolished completely by blocking JAK2 activity or JAK2 translation. The downregulating effect of IFN-alpha on the activity of caspase-8 and caspase-3 could also be neutralized using tyrphostin AG490 or JAK-2 antisense. Taken together IFN-alpha inhibits apoptosis of activated HSC by activation of JAK2 which inhibits the caspase-8 apoptosis pathway.

Apoptosis and reduced influenza A virus specific CD8+ T cells in aging mice

Some studies have reported increased apoptosis in CD8(+) T cells from aged mice. We previously demonstrated diminished virus-specific CD8(+) cytotoxic T lymphocyte (CTL) activity in aged mice in comparison to young mice. The present study investigated the role of apoptosis in age-related influenza virus-specific CD8(+) CTL deficiency. Splenocytes from influenza-primed aged and young mice were stimulated in vitro with virus. The CD8(+) T cell/total lymphocyte ratios correlated with CTL activity and were significantly decreased and increased in aged and young mice, respectively. Fas, FasL, TNF-alpha and TNFR-p55 expression, measured by flow cytometry, ELISA and/or RT-PCR, were significantly elevated in aged mice. Apoptotic CD8(+) T cells (Annexin V binding) were also elevated in aged mice. IL-12 treatment increased CD8(+) CTL activity and IFN-gamma production but did not affect apoptosis. Thus, apoptosis may contribute to reduced influenza virus-specific CD8(+) T cell frequency, CTL deficiency and increased influenza disease in aging.

Tumor necrosis factor-alpha-induced apoptosis in T cells from aged humans: a role of TNFR-I and downstream signaling molecules

Tumor necrosis factor-alpha (TNF-alpha) induces apoptosis predominantly via TNF-receptor I (TNF-RI). We have examined the molecular and biochemical pathways of TNF-alpha-induced apoptosis in T cells from aged and young subjects. Aged subjects show absolute lymphopenia and decreased numbers of both CD4+ and CD8+ T cells. T cells from aged subjects show increased sensitivity to TNF-alpha-induced apoptosis that is associated with increased expression of TNF-RI and decreased expression of TNF-RII in both CD4+ and CD8+ T cells. Agonistic TNF-RI also induced greater apoptosis in T cells from aged subjects as compared to young subjects, suggesting that increased TNF-alpha-induced apoptosis in aging is predominantly mediated via TNF-RI. There was an increased expression of FADD and increased activation of caspase 8 and caspase 3 in lymphocytes from aged humans as compared to young subjects. A role of impaired TNF-RII-mediated signaling in increased apoptosis in aged subjects is also discussed.

The unexpected contribution of immunosenescence to the leveling off of cancer incidence and mortality in the oldest old

In this paper the hypothesis that some features of immunosenescence might impact on the levelling off of cancer incidence and mortality in the oldest old will be considered. In fact, the term immunosenescence suggests that a progressive loss of immune system (IS) function occurs with aging. However, the age-related modifications of the IS can be more properly acknowledged as a 'remodeling' characterized by profound structural changes, which modify the functional properties of IS. We suggest that the expansion with age of natural killer cells (NK) and of T cells which progressively acquire phenotypes intermediate between T lymphocytes and NK cells, together with the age-related changes in the production of inflammatory/anti-inflammatory cytokines, such as INFgamma and IL-4, might create an environment unfavorable for neoplastic growth in the oldest old. In this perspective, studies on immunosenescence likely provide insights on mechanisms responsible for the individual capacity to escape from the life-threatening consequences of cancer outgrowth.

Role of DNA-dependent protein kinase in recognition of radiation-induced DNA damage in human peripheral blood mononuclear cells

The DNA-dependent protein kinase (DNA-PK) complex plays a crucial role in radiation-induced DNA damage recognition. The complex includes the ku heterodimer, which comprises ku 70 and ku 80 subunits, that binds DNA termini of breaks without sequence specificity, and the catalytic subunit DNA-PKCS: The activation of the DNA-PK complex was studied in X-irradiated peripheral blood mononuclear cells (PBMC) from subjects of different ages. Radiation-induced changes in the DNA-binding activity of the ku heterodimer, and in the concentrations of ku 70, ku 80, DNA-PKcs and phosphorylated ku 80 were determined in nuclear and cytoplasmic extracts. DNA-binding activity was increased by irradiation only in the nuclear extract of PBMC from young, but not from elderly subjects, whereas it was found unchanged in cytoplasmic extracts regardless of age. The radiation-induced activation of the DNA-PK complex may result from the increased concentrations of ku 80 and DNA-PKcs in the cytoplasm of PBMC from young, but not from elderly subjects, leading to a higher concentration of phosphorylated ku 80 which readily migrates to the nucleus where, after dimerization with ku 70, binds to DNA breaks. These findings suggest major steps involved in DNA-PK activation, and the intracellular and molecular changes that may account for the age-dependent impairment of DNA repair capacity in irradiated mammalian cells.

Genetic dissection of age-related changes of immune function in mice

Understanding of the genetic basis of normal and abnormal development of the immune response is an enormous undertaking. The immune response, at the most minimal level, involves interactions of antigen presenting cells (APCs), T and B cells. Each of these cells produce cell surface and soluble factors (cytokines) that affect both autocrine and paracrine functions. A second level of complexity needs to consider the development of the macrophage/monocyte lineage as well as the production of the common lymphoid precursor which undergoes distinct maturation steps in the thymus and periphery to form mature T cells as well as in BM (BM) and lymphoid organs to form mature B cells. A third level of complexity involves the immune response to infectious agents including viruses and also the response to tumour antigens. In addition, there are imbalances that predispose to decreased responses (immunodeficiencies) or increased responses (autoimmunity). A fourth level of complexity involves attempts to understand the differences in the immune response that occurs at a very young age, in adults, and at a very old age. This review will focus on the use of C57BL/6 J X DBA/2 J (BXD) recombinant inbred (RI) strains of mice to map genetic loci associated with the production of lymphoid precursors in the BM, development of T cells in the thymus, and T-cell responses to stimulation in the peripheral lymphoid organs in adult and in aged mice. Strategies to improve the power and precision in which complex traits such as the age-related immune response can be mapped is limited with the current set of 35 strains of BXD mice. Strategies to increase these strains by generating recombinant intercross (RIX) strains of mice are being developed to enable this large set of lines to detect quantitative trait loci (QTLs) with a much higher consistency and statistical power. More importantly, the resolution with which these QTLs can be mapped would be greatly improved and, in many cases, adequate to carry out direct identification of candidate genes. It is likely that, given the complexity of the immune system development, the number of cells involved in an immune response, and especially the changes in the immune system with ageing, mapping hundreds of genes will be required to fully understand age-related changes in the immune response. This review outlines ongoing and future strategies that will enable the mapping and identification of these genes.

Apoptotic capability in ageing T cells

The ageing immune system shows a gradual decline in responsiveness to antigens and tumours due to the emergence of immunosenescence. The main functions of T cells are activation, anergy and apoptosis and these are all affected during ageing. Apoptosis is vital in controlling cell numbers, deleting self-reactive T cells and maintaining immune surveillance. One of the principle instigators of death involves the CD95:CD95-ligand interaction and as T cells age both receptor and ligand levels increase. This view will describe the current knowledge of the apoptotic susceptibility of ageing T cells and evaluate the factors that may affect the apoptotic capability of immunosenescent T cells.

Molecular steps of cell suicide: an insight into immune senescence

The cellular and molecular basis of immune senescence is unclear. A number of mechanisms have been proposed. In this issue of the Journal of Clinical Immunology, some of the mechanisms for various immunologic abnormalities in aging are presented. In this article, various molecular steps of both death receptor and mitochondrial pathways of apoptosis in general are reviewed. In particular, the role of apoptosis in T-cell immune senescence is discussed.

Molecular and biochemical pathways of apoptosis in lymphocytes from aged humans

In this study, we investigated a role of apoptosis in lymphopenia and progressive cell-mediated immunodeficiency associated with aging. We examined two major signaling pathways of apoptosis in lymphocytes from aged humans and compared them with lymphocytes from young subjects. Both CD4+ and CD8+ T cell subsets from aged subjects demonstrated increased sensitivity to TNFR-mediated and Fas-mediated apoptosis that was associated with overexpression of death receptors and adapter molecules associated with death signaling. An increased expression and activity of both initiator (caspase 8) and effector (caspase 3) caspases was observed in lymphocytes from aged subjects as compared to young individuals. Furthermore, an increased expression of Bax and decreased expression of Bcl-2 (both at the protein and mRNA level) was found in lymphocytes from aged subjects. These data suggest that increased sensitivity of lymphocytes from aged subjects to death signals may play an important role in the pathogenesis of lymphopenia and T cell deficiency associated with the aging process.