Identification and quantitation of apoptotic cells following anti-CD3 activation of murine G0 T cells

Neurotransmitters and Neuropeptides decrease PD-1 in T cells of healthy subjects and patients with hepatocellular carcinoma (HCC), and increase their proliferation and eradication of HCC cells

T cells of aged people, and of patients with either cancer or severe infections (including COVID-19), are often exhausted, senescent and dysfunctional, leading to increased susceptibilities, complications and mortality. Neurotransmitters and Neuropeptides bind their receptors in T cells, and induce multiple beneficial T cell functions. Yet, T cells of different people vary in the expression levels of Neurotransmitter and Neuropeptide receptors, and in the magnitude of the corresponding effects. Therefore, we performed an individual-based study on T cells of 3 healthy subjects, and 3 Hepatocellular Carcinoma (HCC) patients. HCC usually develops due to chronic inflammation. The inflamed liver induces reduction and inhibition of CD4⁺ T cells and Natural Killer (NK) cells. Immune-based therapies for HCC are urgently needed. We tested if selected Neurotransmitters and Neuropeptides decrease the key checkpoint protein PD-1 in human T cells, and increase proliferation and killing of HCC cells. First, we confirmed human T cells express all dopamine receptors (DRs), and glutamate receptors (GluRs): AMPA-GluR3, NMDA-R and mGluR. Second, we discovered that either Dopamine, Glutamate, GnRH-II, Neuropeptide Y and/or CGRP (10nM), as well as DR and GluR agonists, induced the following effects: 1. Decreased significantly both %PD-1⁺ T cells and PD-1 expression level per cell (up to 60% decrease, within 1 h only); 2. Increased significantly the number of T cells that proliferated in the presence of HCC cells (up to 7 fold increase), 3. Increased significantly T cell killing of HCC cells (up to 2 fold increase). 4. Few non-conventional combinations of Neurotransmitters and Neuropeptides had surprising synergistic beneficial effects. We conclude that Dopamine, Glutamate, GnRH-II, Neuropeptide Y and CGRP, alone or in combinations, can decrease % PD-1⁺ T cells and PD-1 expression per cell, in T cells of both healthy subjects and HCC patients, and increase their proliferation in response to HCC cells and killing of HCC cells. Yet, testing T cells of many more cancer patients is absolutely needed. Based on these findings and previous ones, we designed a novel "Personalized Adoptive Neuro-Immunotherapy", calling for validation of safety and efficacy in clinical trials.

PML risk stratification using anti-JCV antibody index and L-selectin

Background:

Natalizumab treatment is associated with progressive multifocal leukoencephalopathy (PML) development. Treatment duration, prior immunosuppressant use, and JCV serostatus are currently used for risk stratification, but PML incidence stays high. Anti-JCV antibody index and L-selectin (CD62L) have been proposed as additional risk stratification parameters.

Objective:

This study aimed at verifying and integrating both parameters into one algorithm for risk stratification.

Methods:

Multicentric, international cohorts of natalizumab-treated MS patients were assessed for JCV index (1921 control patients and nine pre-PML patients) and CD62L (1410 control patients and 17 pre-PML patients).

Results:

CD62L values correlate with JCV serostatus, as well as JCV index values. Low CD62L in natalizumab-treated patients was confirmed and validated as a biomarker for PML risk with the risk factor “CD62L low” increasing a patient’s relative risk 55-fold ( p < 0.0001). Validation efforts established 86% sensitivity/91% specificity for CD62L and 100% sensitivity/59% specificity for JCV index as predictors of PML. Using both parameters identified 1.9% of natalizumab-treated patients in the reference center as the risk group.

Conclusions:

Both JCV index and CD62L have merit for risk stratification and share a potential biological relationship with implications for general PML etiology. A risk algorithm incorporating both biomarkers could strongly reduce PML incidence.

Role of the K(Ca)3.1 K+ channel in auricular lymph node CD4+ T-lymphocyte function of the delayed-type hypersensitivity model

BACKGROUND AND PURPOSE

The intermediate-conductance Ca(2+)-activated K(+) channel (K(Ca)3.1) modulates the Ca(2+) response through the control of the membrane potential in the immune system. We investigated the role of K(Ca)3.1 on the pathogenesis of delayed-type hypersensitivity (DTH) in auricular lymph node (ALN) CD4(+) T-lymphocytes of oxazolone (Ox)-induced DTH model mice.

EXPERIMENTAL APPROACH

The expression patterns of K(Ca)3.1 and its possible transcriptional regulators were compared among ALN T-lymphocytes of three groups [non-sensitized (Ox-/-), Ox-sensitized, but non-challenged (Ox+/-) and Ox-sensitized and -challenged (Ox+/+)] using real-time polymerase chain reaction, Western blotting and flow cytometry. KCa 3.1 activity was measured by whole-cell patch clamp and the voltage-sensitive dye imaging. The effects of K(Ca)3.1 blockade were examined by the administration of selective K(Ca)3.1 blockers.

KEY RESULTS

Significant up-regulation of K(Ca)3.1a was observed in CD4(+) T-lymphocytes of Ox+/- and Ox+/+, without any evident changes in the expression of the dominant-negative form, K(Ca)3.1b. Negatively correlated with this, the repressor element-1 silencing transcription factor (REST) was significantly down-regulated. Pharmacological blockade of K(Ca)3.1 resulted in an accumulation of the CD4(+) T-lymphocytes of Ox+/+ at the G0/G1 phase of the cell cycle, and also significantly recovered not only the pathogenesis of DTH, but also the changes in the K(Ca)3.1 expression and activity in the CD4(+) T-lymphocytes of Ox+/- and Ox+/+.

CONCLUSIONS AND IMPLICATIONS

The up-regulation of K(Ca)3.1a in conjunction with the down-regulation of REST may be involved in CD4(+) T-lymphocyte proliferation in the ALNs of DTH model mice; and K(Ca)3.1 may be an important target for therapeutic intervention in allergy diseases such as DTH.

Upregulation of KCa3.1 K(+) channel in mesenteric lymph node CD4(+) T lymphocytes from a mouse model of dextran sodium sulfate-induced inflammatory bowel disease

The intermediate-conductance Ca(2+)-activated K(+) channel KCa3.1/KCNN4 plays an important role in the modulation of Ca(2+) signaling through the control of the membrane potential in T lymphocytes. Here, we study the involvement of KCa3.1 in the enlargement of the mesenteric lymph nodes (MLNs) in a mouse model of inflammatory bowel disease (IBD). The mouse model of IBD was prepared by exposing male C57BL/6J mice to 5% dextran sulfate sodium for 7 days. Inflammation-induced changes in KCa3.1 activity and the expressions of KCa3.1 and its regulators in MLN CD4(+) T lymphocytes were monitored by real-time PCR, Western blot, voltage-sensitive dye imaging, patch-clamp, and flow cytometric analyses. Concomitant with an upregulation of KCa3.1a and nucleoside diphosphate kinase B (NDPK-B), a positive KCa3.1 regulator, an increase in KCa3.1 activity was observed in MLN CD4(+) T lymphocytes in the IBD model. Pharmacological blockade of KCa3.1 elicited the following results: 1) a significant decrease in IBD disease severity, as assessed by diarrhea, visible fecal blood, inflammation, and crypt damage of the colon and MLN enlargement compared with control mice, and 2) the restoration of the expression levels of KCa3.1a, NDPK-B, and Th1 cytokines in IBD model MLN CD4(+) T lymphocytes. These findings suggest that the increase in KCa3.1 activity induced by the upregulation of KCa3.1a and NDPK-B may be involved in the pathogenesis of IBD by mediating the enhancement of the proliferative response in MLN CD4(+) T lymphocyte and, therefore, that the pharmacological blockade of KCa3.1 may decrease the risk of IBD.

TGF-β1-ROS-ATM-CREB signaling axis in macrophage mediated migration of human breast cancer MCF7 cells

Macrophages in the tumor microenvironment play an important role in tumor cell survival. They influence the tumor cell to proliferate, invade into surrounding normal tissues and metastasize to local and distant sites. In this study, we evaluated the effect of conditioned medium from monocytes and macrophages on growth and migration of breast cancer cells. Macrophage conditioned medium (MϕCM) containing elevated levels of cytokines TNF-α, IL-1β and IL-6 had a differential effect on non-invasive (MCF7) and highly invasive (MDA-MB-231) breast cancer cell lines. MϕCM induced the secretion of TGF-β1 in MCF7 cells. This was associated with apoptosis in a fraction of cells and generation of reactive oxygen and nitrogen species (ROS and RNS) and DNA damage in the remaining cells. This, in turn, increased expression of cAMP response element binding protein (CREB) and vimentin resulting in migration of cells. These effects were inhibited by neutralization of TNF-α, IL-1β and IL-6, inhibition of ROS and RNS, DNA damage and siRNA mediated knockdown of ATM. In contrast, MDA-MB-231 cells which had higher basal levels of pCREB were not affected by MϕCM. In summary, we have found that pro-inflammatory cytokines secreted by macrophages induce TGF-β1 in tumor cells, which activate pCREB signaling, epithelial-mesenchymal-transition (EMT) responses and enhanced migration.

Aberrant CD200/CD200R1 expression and function in systemic lupus erythematosus contributes to abnormal T-cell responsiveness and dendritic cell activity

INTRODUCTION

CD200 is a type I transmembrane glycoprotein that can regulate the activation threshold of inflammatory immune responses, polarize cytokine production, and maintain immune homeostasis. We therefore evaluated the functional status of CD200/CD200 receptor 1 (CD200R1) interactions in subjects with systemic lupus erythematosus (SLE).

METHODS

Serum CD200 level was detected by ELISA. The expression of CD200/CD200R1 by CD4+ T cells and dendritic cells (DCs) was examined by flow cytometry, and then compared between SLE patients and healthy controls. Peripheral blood mononuclear cells were stained with carboxyfluorescein diacetate succinimidyl ester and annexin V/propidium iodide for evaluation of the effect of CD200 on cell proliferation and apoptosis. In addition, the effect of CD200 on DC function was determined by transwell migration assay as well as by measurement of binding and phagocytosis of apoptotic cells.

RESULTS

In SLE patients, the number of CD200+ cells and the level of soluble CD200 were significantly higher than in healthy controls, whereas the expression of CD200R1 by CD4+ T cells and DCs was decreased. Furthermore, the increased CD200 expression by early apoptotic cells contributed to their diminished binding and phagocytosis by DCs in SLE. Importantly, the engagement of CD200 receptor on CD4+ T cells with CD200-Fc fusion protein in vitro reduced the differentiation of T-helper type 17 cells and reversed the defective induction of CD4+CD25highFoxP3+ T cells by transforming growth factor beta in SLE patients. Conversely, blockade of CD200-CD200R1 interaction with anti-CD200R1 antibody promoted CD4+ T-cell proliferation.

CONCLUSION

CD200 and CD200R1 expression and function are abnormal in SLE and may contribute to the immunologic abnormalities in SLE.

Allergen-induced cytokine phenotypes in mice: role of CD4 and CD8 T cell populations

BACKGROUND

CD4+ T cells expressing type 2 cytokines have been implicated in the pathogenesis of asthma to high-molecular-weight allergens. Topical exposure of BALB/c strain mice to low-molecular-weight chemical contact and respiratory allergens stimulates type 1 and type 2 cytokine secretion phenotypes, respectively.

OBJECTIVE

To examine the relative frequencies of cytokine-positive CD4+ and CD8+ T cells and their contributions to these cytokine secretion profiles. Methods Draining auricular lymph nodes were isolated 13 days after initiation of topical exposure of female BALB/c strain mice to chemical allergen, or to vehicle alone. The frequency of intracellular cytokine (IL-4 and IFN-gamma)-positive CD4+ and CD8+ lymphocytes was enumerated by flow cytometry. The relative contribution of CD4+ and CD8+ cells to cytokine secretion profiles was assessed by negative selection.

RESULTS

Exposure to allergen resulted in an increased frequency of both IFN-gamma+ CD4+ and CD8+ lymphocytes, although there were no marked differences between trimellitic anhydride (TMA)- and 2,4-dinitrochlorobenzene (DNCB)-activated lymph node cells. Treatment with TMA induced approximately five times as many IL-4+ CD4+ cells as did exposure to DNCB. This pattern of cytokine staining was also observed for a further pair of contact and respiratory allergens; respectively, formalin and fluorescein isothiocyanate.

CONCLUSION

These data demonstrate that the divergent immune responses induced in mice by different classes of chemical allergen are independent of changes in the frequency of IFN-gamma+ cells, but are associated with differential frequencies of IL-4-expressing CD4+ T cells.

The cell cycle phases of DNA damage and repair initiated by topoisomerase II-targeting chemotherapeutic drugs

Although cytostasis and cytotoxicity induced by cancer chemotherapy drugs targeting topoisomerase II (topoII) arise in specific cell cycle phases, it is unknown whether the drug-initiated DNA damage triggering these responses, or the repair (reversal) of this damage, differs between cell cycle phases or between drug classes. Accordingly, we used a flow cytometric alkaline unwinding assay to measure DNA damage (strand breakage (SB)) and SB repair in each cell cycle compartment of human cancer cell lines treated with clinically relevant concentrations of doxorubicin, daunomycin, etoposide, and mitoxantrone. We found that treated HeLa and A549 cells exhibited the greatest SB in G2/M phase, the least in G1 phase, and generally an intermediate amount in S phase. The cell cycle phase specificity of the DNA damage appeared to be predictive of the cell cycle phase of growth arrest. Furthermore, it appeared to be dependent on topoIIalpha expression as the extent of SB did not differ between cell cycle compartments in topoIIalpha-diminished A549(VP)28 cells. HeLa cells were apparently unable to repair doxorubicin-initiated SB. The rate of repair of etoposide-initiated SB in HeLa cells and of mitoxantrone-initiated SB in HeLa and A549 cells was similar in each cell cycle compartment. In A549 cells, the rate of repair of doxorubicin and etoposide-initiated SB differed between cell cycle phases. Overall, these results indicate that the cell cycle phase specificity of cytostasis and cytotoxicity induced in tumor cells by topoII-targeting drugs may be directly related to the cell cycle phase specificity of the drug-initiated DNA damage. Analysis by cell cycle compartment appears to clarify some of the intercellular heterogeneity in the extent of drug-initiated DNA damage and cytotoxicity previously observed in cancer cells analyzed as a single population; this approach might be useful in resolving inconsistent results reported in investigations of tumor cell topoII content versus response to topoII-targeting drugs.

Interleukin-4 biases differentiation of B cells from Trypanosoma cruzi-infected mice and restrains their fratricide: role of Fas ligand down-regulation and MHC class II-transactivator up-regulation

In the present work, we demonstrate that interleukin (IL)-4 is able to rescue B cells from Trypanosoma cruzi-infected mice, counteracting the strong apoptotic signals that these cells received in vivo. We have observed that IL-4 restrains the apoptosis of immunoglobulin (Ig)M(+) and IgG(+) B cells from infected and normal mice without inducing them to proliferate. In addition, IL-4 does not modify the quantity or quality of the antibodies secreted by B cells from infected mice, as it blocks their terminal differentiation to plasma cells and favors memory pathway. It is interesting that the protective effect of IL-4 over B cells from infected mice is mediated, at least partly, by the down-regulation of Fas ligand (FasL) expression, which leads to interference in the apoptosis executed by these B cells through the Fas/FasL death pathway. Accordingly, a marked up-regulation of the "FasL gene repressor" class II transactivator was observed, suggesting that this would be one mechanism underlying the IL-4-mediated FasL down-regulation.

Antigen-specific dose-dependent system for the study of an inheritable and reversible phenotype in mouse CD4+ T cells

The transgenic T-cell receptor in mouse TEa CD4+ lymphocytes recognizes an endogenous peptide, Ealpha52-68, presented in the context of the major histocompatibility complex class II molecule I-Ab. In response to an optimal peptide concentration TEa cells enter the cell cycle and proliferate. However, a single exposure to high doses of the specific peptide diminished cell expansion upon subsequent restimulation. This hyporesponsive, or anergic, phenotype can still be detected after multiple restimulations indicating that the hyporesponsiveness persists despite cell division and it was inherited by daughter cells. Furthermore, we demonstrated that this hypoproliferative response is associated with high p27Kip1 and cyclin E protein levels, and reduced intracellular interleukin-2 (IL-2) expression. Addition of exogenous IL-2 was required to reset p27Kip1 levels in the progeny derived from hyporesponsive TEa cells. Thus, we have established antigen dose-dependent induction of a reversible, inheritable (i.e. epigenetic) phenotype and we have identified at least three components of the network of interactions: p27Kip1 cyclin E, and IL-2 expression.

Interferon gamma eliminates responding CD4 T cells during mycobacterial infection by inducing apoptosis of activated CD4 T cells

In Mycobacterium bovis Bacille Calmette-Guérin (BCG)-infected wild-type mice, there was a large expansion of an activated (CD44(hi)) splenic CD4 T cell population followed by a rapid contraction of this population to normal numbers. Contraction of the activated CD4 T cell population in wild-type mice was associated with increased apoptosis of activated CD4 T cells. In BCG-infected interferon (IFN)-gamma knockout (KO) mice, the activated CD4 T cell population did not undergo apoptosis. These mice accumulated large numbers of CD4(+)CD44(hi) T cells that were responsive to mycobacterial antigens. Addition of IFN-gamma to cultured splenocytes from BCG-infected IFN-gamma KO mice induced apoptosis of activated CD4 T cells. IFN-gamma-mediated apoptosis was abolished by depleting adherent cells or Mac-1(+) spleen cells or by inhibiting nitric oxide synthase. Thus, IFN-gamma is essential to a regulatory mechanism that eliminates activated CD4 T cells and maintains CD4 T cell homeostasis during an immune response.

Dopamine stimulates redox-tyrosine kinase signaling and p38 MAPK in activation of astrocytic C6-D2L cells

An increase in dopamine (DA) availability in rat brain has been suggested to participate in certain neurodegenerative processes. However, the regulatory effects of DA on glial cells have not been extensively studied. Using a rat C6 glioma cell line stably expressing recombinant D2L receptors, we have found that micromolar levels of DA stimulate mitogenesis and glial fibrillary acidic protein (GFAP) expression, both serving as parameters of reactive gliosis. This mitogenesis occurs about 29 h after exposure to DA and requires D2-receptor-mediated intracellular redox-tyrosine kinase activation. Either DA or quinpirole, a D2 receptor agonist, stimulates protein tyrosine phosphorylation. Application of either DPI, a potent inhibitor of NADPH-dependent oxidase, or NAC, an anti-oxidant, effectively prevented DA-induced tyrosine phosphorylation and DNA synthesis. Preincubation of (+)-butaclamol, a D2 receptor antagonist, inhibits both DA-stimulated tyrosine phosphorylation and mitogenesis. DA at micromolar levels also stimulates GFAP expression. This DA-regulated GFAP expression can be completely inhibited by SB203580, a selective p38 MAPK inhibitor, but not influenced by (+)-butaclamol and genistein, a protein tyrosine kinase inhibitor. Thus, our data suggest that regulation of DNA synthesis and GFAP expression induced by DA is mediated by independent signaling pathways. The mitogenesis requires a D2-receptor-mediated protein tyrosine kinase cascade, while GFAP expression needs a D2-receptor-independent p38 MAPK activation. This observation may help to understand the processes of reactive gliosis in some dopaminergic-related neurodegenerative diseases.

Optimal storage conditions for preserving granulocyte viability as monitored by Annexin V binding in whole blood

It is important in the laboratory to develop techniques to preserve leucocyte viability in blood specimens for subsequent flow cytometric analysis. This article describes a new simple whole blood lysis method using Annexin V FITC staining which can be used to define both early and late apoptosis of granulocytes in heterogeneous cell populations, without the need for additional stains or to purify the cells (which may result in loss of the cells of interest). The differential Annexin V binding assay was in good agreement with the light microscopy reference method and showed excellent correlation with 7-aminoactinomycin D (7-AAD) staining. It was not affected by problems of morphological interpretation and artifactal changes of granulocyte deformability noted using light microscopy, or the technical difficulties encountered due to red cell contamination using the 7-AAD method. Using this new differential Annexin V staining method, we determined the optimum conditions that maintain granulocyte viability for subsequent flow cytometric analysis and are now employed in our laboratory. These conditions were lithium heparin (Hep) anticoagulated whole blood specimens kept at 4 degrees C with the addition of nutrient medium. Specimens that are anticoagulated with acid citrate dextrose (ACD) or ethyl-diacetyl-tetraacetic acid (EDTA) should also be treated similarly to preserve granulocyte viability and to overcome problems associated with identification of cell populations by flow cytometry.

Influence of transforming growth factor beta1 (TGF-beta1) on the behaviour of porcine thyroid epithelial cells in primary culture through thrombospondin-1 synthesis

Transforming growth factor beta1 (TGF-beta1) is a secreted polypeptide that is thought to play a major role in the regulation of folliculogenesis and differentiation of thyroid cells. On porcine thyroid follicular cells cultured on plastic substratum, TGF-beta1, in a concentration-dependent way, promoted the disruption of follicles, cell spreading, migration and confluency by a mechanism that did not involve cell proliferation. TGF-beta1 strongly activated the production of thrombospondin-1 and (alpha)vbeta3 integrin in a concentration-dependent manner whereas the expression of thyroglobulin was unaffected. Anisomycin, an inhibitor of protein synthesis, inhibited the effect of TGF-beta1 on cell organization. Thrombospondin-1 reproduced the effect of TGF-beta1. In the presence of thrombospondin-1 cells did not organize in follicle-like structures but, in contrast, spreaded and reached confluency independently of cell proliferation. This effect is suppressed by an RGD-containing peptide. The adhesive properties of thrombospondin-1 for thyroid cells were shown to be mediated by both the amino-terminal heparin-binding domain and the RGD domain of thrombospondin-1. Adhesion was shown to involve (alpha)vbeta3 integrin. The results show that TGF-beta1 exerted an influence upon function and behaviour of follicle cells partly mediated by the synthesis of thrombospondin-1 and of its receptor (alpha)vbeta3 integrin.

Apoptotic human lymphocytes have diminished CD4 and CD8 receptor expression

We used quantitative multiparameter flow cytometric assays to simultaneously detect viable, apoptotic, and necrotic human peripheral blood mononuclear cells (PBMC) and immunophenotyped lymphocyte subsets within the PBMC. Apoptosis was induced by a spectrum of treatments, including camptothecin, cisplatin, dexamethasone, hyperthermia, staurosporine, and etoposide in anti-CD3 mAb-stimulated cells and by cyclohexamide in both quiescent and stimulated cells; apoptosis in the latter was augmented by anti-fas mAb. We found that CD4(+) and CD8(+) cells were significantly underrepresented in the apoptotic PBMC and that the percentage of CD4(+) and CD8(+) PBMC each markedly decreased as apoptosis increased. This suggested that surface expression of these receptors was lessened on apoptotic CD4(+) and CD8(+) cells. This was directly confirmed by observation of sorted CD4(+) PBMC. This analysis of a wide variety of apoptotic stimuli demonstrates that diminished CD4 and CD8 surface receptor expression is a common feature of human T lymphocyte apoptosis.

A rapid single-laser flow cytometric method for discrimination of early apoptotic cells in a heterogenous cell population

A recently reported cytometric method described the possibility of discriminating apoptotic from necrotic cells using FITC-labelled annexin V and propidium iodide (PI). Nevertheless, the brightness of PI-staining and its extensive spectral emission overlap with phycoerythrin (PE) does not permit the study of a subset of a heterogenous cell population with single laser instrumentation. The surface staining of a subset with PE in a heterogenous cell population therefore requires another exclusion dye to detect necrotic cells. We used 7-amino-actinomycin D (7-AAD) that can be excited by the 488 nm argon laser line. 7-AAD emits in the far red range of the spectrum and 7-AAD spectral emission can be separated from the emissions of FITC and PE. The fluorescence parameters allow characterization of necrotic (7-AAD+ annexin V-FITC+ cells), apoptotic (7-AAD-annexin V-FITC+ cells) and viable cells (7-AAD- annexin V-FITC- cells) in a subset of PE+ cells. The value of this method was demonstrated by measuring apoptosis and necrosis in a model of HL-60 cells exposed to different inducers of cell death. The method was validated by fluorescent cell sorting in combination with morphologic examination of the sorted cells. The technique we present is particularly valuable in a clinical setting because it enables rapid multiparameter analysis of necrosis and early apoptosis in combination with cell surface phenotyping with a single laser. We present the effects of haemopoietic growth factor deprivation on myeloid progenitor CD34+ cells as an example of its application.

Aryl hydrocarbon receptor regulation of ceramide-induced apoptosis in murine hepatoma 1c1c7 cells. A function independent of aryl hydrocarbon receptor nuclear translocator

The relationship between aryl hydrocarbon receptor (AHR) content and susceptibility to apoptosis was examined in the murine hepatoma 1c1c7 cell line and a series of variants having different levels of AHR expression. Exposure of 1c1c7 cultures to N-acetylsphingosine (C2-ceramide) caused a concentration-dependent inhibition of cell proliferation, loss of viability, and induction of apoptosis as monitored by analyses of DNA fragmentation and caspase activation. A variant cell line (Tao) having approximately 10% of the AHR content of 1c1c7 cells also arrested following exposure to C2-ceramide, but did not undergo apoptosis. Modulation of 1c1c7 and Tao AHR contents by transfection of Ahr antisense and sense constructs, respectively, confirmed the relationship between AHR content and susceptibility to C2-ceramide-induced apoptosis. C2-ceramide also induced the apoptosis of an AHR-containing cell line lacking the aryl hydrocarbon receptor nuclear translocator protein. AHR ligands (i.e. 2,3,7,8-tetrachlorodibenzo-p-dioxin and alpha-naphthoflavone) neither induced apoptosis nor modulated the development of apoptosis in C2-ceramide-treated 1c1c7 cultures. AHR content did not affect staurosporine- or doxorubicin-induced apoptosis. These results suggest the AHR modulates aspects of ceramide signaling associated with the induction of apoptosis but not cell cycle arrest, and does so by a mechanism that is independent of its interaction with aryl hydrocarbon receptor nuclear translocator and exogenous AHR ligands.

Comparison of seven quantitative assays to assess lymphocyte cell death during HIV infection: measurement of induced apoptosis in anti-Fas-treated Jurkat cells and spontaneous apoptosis in peripheral blood mononuclear cells from children infected with HIV

The study of apoptosis in relation to various human disease states, particularly HIV infection, has seen a tremendous increase in activity. In this article, values obtained by seven different assays, designed to quantify apoptosis and applicable to the study of HIV infection, are compared in two cell systems: (1) stimulus-induced apoptosis in Jurkat cells treated with anti-Fas antibody and (2) spontaneous apoptosis in PBMCs isolated from HIV-infected children. The methods used included measurement of cells with subdiploid DNA content, labeling of DNA strand breaks by the TUNEL reaction, annexin V surface labeling for the detection of exposed phosphatidylserine, cytoplasmic antigen labeling with the apoptosis-specific antibody Apo 2.7, detection of changes in flow cytometric light-scattering properties, trypan blue dye exclusion by light microscopy, and detection of changes in cellular chromatin by fluorescence microscopy. These methods produced well-correlated values in the Jurkat system, whereas the same set of methods produced more discrepant values in the PBMC analyses, especially in those patients with low CD4 counts. Specifically, our results showed that the trypan blue test was unacceptable for quantification of apoptosis during HIV infection, whereas TUNEL, of all the methods tested, showed excellent overall correlation in both cell systems, was highly specific, and matched microscopic observation of the cells. Although many of the methods were suited to the study of a homogeneous cell line, caution must be exercised when examining cell death in a heterogeneous cell mixture from an HIV-infected individual.

Measurement of apoptosis

The cell dying by apoptosis undergoes a sequence of morphological, biochemical, and molecular changes which are characteristic, and often unique, to this mode of cell death. Specific features of apoptotic cells resulting from these changes, which serve as markers used to reveal the apoptotic mode of cell death and to quantify the extent of apoptosis in cultures or in tissue, are reviewed. Analysis of these features by flow or image cytometry is the most commonly used approach to detect, quantify, and study various aspects of apoptosis. Flow or laser scanning cytometry also offer all the advantages of rapid, accurate and multiparametric measurements to investigate the biological processes associated with cell death. Numerous methods have been developed to identify apoptotic and necrotic cells, which are widely used in various disciplines, particularly in oncology and immunology. The methods based on changes in cell morphology, plasma membrane molecular structure and transport function, function of cell organelles, DNA stability to denaturation and endonucleolytic DNA degradation are reviewed and their applicability in the research laboratory and in the clinical setting is discussed. The most common pitfalls and improper use of the methodology in analysis of cell death and in data interpretation are also discussed.

Reduction of intrafollicular apoptosis in chemotherapy-induced alopecia by topical calcitriol-analogs

Chemotherapy-induced alopecia is thought to result from cytotoxic and apoptosis-related damage to the hair follicle. This study was designed to confirm whether keratinocyte apoptosis is indeed induced in growing (= anagen) hair follicles of C57 BL/6 mice after the injection of cyclophosphamide, using improved methods for histologic detection of apoptotic cells in murine skin. More importantly, we asked whether topical calcitriol-analogs are able to modulate cyclophosphamide-induced apoptosis in vivo, because there are conflicting reports on the effects of calcitriols on apoptosis in vitro. Anagen was induced in telogen mice on day 0 by depilation. Starting on day 5 post-depilation, the back skin of mice was topically treated with either 0.2 microg 1,25-dihydroxyvitamin D3, 2.0 microg calcipotriol, 0.02 microg KH 1060, or vehicle (ethanol) only. On the last day of treatment (i.e., day 9 post-depilation), all mice received 150 mg cyclophosphamide i.p. per kg as a single dose to induce alopecia, or vehicle (aqua dist.). Analysis of the treated skin by in situ-end labeling (using a modified terminal UTP nucleotide end labeling technique suitable for murine skin), by Hoechst 33342 stain, and by DNA electrophoresis on days 10 and 14, revealed the induction of massive apoptosis in cyclophosphamide-treated anagen hair bulbs, which was most prominent on day 10, whereas controls showed no follicular apoptosis. The calcitriol-pretreated groups demonstrated a significant reduction of apoptosis, with a maximal inhibition seen on day 14. This confirms that cyclophosphamide indeed induces massive keratinocyte apoptosis in anagen hair follicles, and provides evidence that topical calcitriol-analogs can suppress epithelial cell apoptosis in vivo. The mouse model employed here offers an excellent tool for dissecting the as yet poorly understood controls of keratinocyte apoptosis in situ and its pharmacologic manipulation.

Age-associated modulation of apoptosis and activation in murine B lymphocytes

We have investigated the influence of age on B-cell responsiveness. The present study showed that the B-cell mitogen, lipopolysaccharide (LPS), similarly stimulated the proliferation of purified B lymphocytes obtained from either young mice (3 months) or old mice (24 months). In contrast, expression of the differentiation marker, alkaline phosphatase (ALP), was about fourfold higher in young mice than in older mice upon stimulation with LPS or with dextran sulfate (DXS) and interleukin-5 (IL-5). The occurrence of apoptosis during aging was then studied: unexpectedly, spontaneous cell death was double in B lymphocytes from young mice compared to older animals. Stimulation with DXS with or without IL-5 rescued B lymphocytes from cell death in young mice but protection decreased with aging, and no longer occurred in 24-month-old mice B cells. Meanwhile, the protective activity conferred by IL-4 was maintained at similar levels throughout aging. However, B cells from old mice were more responsive to apoptosis induction with cycloheximide, dibutyryl cAMP and dexamethasone. Together, the present results indicate an age-associated alteration in apoptosis and activation of B lymphocytes which could contribute to the age-related decline of the immune response.

[Significance of apoptotic processes in radiotherapy. I]

According to a considerable amount of publications apoptosis plays an important role for radio- and chemotherapy. The most important results related to this issue will be described in 2 independent articles, covering the following topics: Part I: I. definition, morphology, biochemical processes, II. clinical relevant detection assays, III. signal transduction. Part II: significance of apoptosis for radio- and chemotherapy.

Apoptosis-suppressor gene bcl-2 expression after traumatic brain injury in rats

Neuronal death after experimental traumatic brain injury (TBI) has features of both apoptosis and necrosis. Neurons in the peritrauma cortex, hippocampus, and dentate gyrus are particularly vulnerable. The apoptosis-suppressor gene bcl-2 is induced in brain after ischemia and epilepsy-induced injury and may serve to regulate neuronal death. We studied expression of bcl-2 mRNA and protein after experimental TBI in rats. To determine whether bcl-2 protein expression occurred in cells with evidence of apoptosis, triple-labeling studies were performed using (1) antibody against bcl-2, (2) bis-benzimide dye to examine gross nuclear morphology, and (3) terminal deoxynucleotidyl transferase-mediated biotin-dUTP nick-end labeling (TUNEL) to assess for DNA fragmentation. At 6 and 24 hr, bcl-2 mRNA was induced in ipsilateral peritrauma cortex, hippocampus, and dentate gyrus. By 72 hr the increase in bcl-2 mRNA was detected only in cortex. bcl-2 protein was induced at 8, 24, 72, and 168 hr in ipsilateral cortex and hippocampus. Cells expressing bcl-2 protein included neurons in the peritrauma cortex, hippocampus, hilus, and dentate gyrus. The gross nuclear morphology of neurons expressing bcl-2 appeared normal. Furthermore, biochemical evidence of DNA fragmentation, in a pattern characteristic of either apoptosis or necrosis, was seldom seen in neurons expressing bcl-2 protein (bcl-2 colocalized with TUNEL in 0-2% of TUNEL-positive cells observed). These data suggest that bcl-2 may play an important role in the regulation of neuronal death after TBI, and they support a role for bcl-2 as an inducible neuroprotective gene.

Interleukin 1 beta-converting enzyme related proteases/caspases are involved in TRAIL-induced apoptosis of myeloma and leukemia cells

The Fas/APO-1/CD95 ligand (CD95L) and the recently cloned TRAIL ligand belong to the TNF-family and share the ability to induce apoptosis in sensitive target cells. Little information is available on the degree of functional redundancy between these two ligands in terms of target selectivity and intracellular signalling pathway(s). To address these issues, we have expressed and characterized recombinant mouse TRAIL. Specific detection with newly developed rabbit anti-TRAIL antibodies showed that the functional TRAIL molecule released into the supernatant of recombinant baculovirus-infected Sf9 cells is very similar to that associated with the membrane fraction of Sf9 cells. CD95L resistant myeloma cells were found to be sensitive to TRAIL, displaying apoptotic features similar to those of the CD95L- and TRAIL-sensitive T leukemia cells Jurkat. To assess if IL-1beta-converting enzyme (ICE) and/or ICE-related proteases (IRPs) (caspases) are involved in TRAIL-induced apoptosis of both cell types, peptide inhibition experiments were performed. The irreversible IRP/caspase-inhibitor Ac-YVAD-cmk and the reversible IRP/caspase-inhibitor Ac-DEVD-CHO blocked the morphological changes, disorganization of plasma membrane phospholipids, DNA fragmentation, and loss of cell viability associated with TRAIL-induced apoptosis. In addition, cells undergoing TRAIL-mediated apoptosis displayed cleavage of poly(ADP)-ribose polymerase (PARP) that was completely blocked by Ac-DEVD-CHO. These results indicate that TRAIL seems to complement the activity of the CD95 system as it allows cells, otherwise resistant, to undergo apoptosis triggered by specific extracellular ligands. Conversely, however, induction of apoptosis in sensitive cells by TRAIL involves IRPs/caspases in a fashion similar to CD95L. Thus, differential sensitivity to CD95L and TRAIL seems to map to the proximal signaling events associated with receptor triggering.

Radiation-induced apoptosis: relevance to radiotherapy

Radiation-induced apoptosis is reviewed in terms of: (a) the identification of apoptotic and necrotic cells, (b) observations in vitro and in vivo of radiation-induced apoptosis, (c) genes controlling apoptosis, (d) evidence that the target may be the plasma membrane or nuclear DNA, (e) quantitative comparisons of apoptotic death and reproductive (clonogenic) death, (f) the importance of radiation-induced apoptosis in radiotherapy, and (g) studies of radiation-induced apoptosis that are needed. High priority should be placed on determining the molecular pathways that are important in the expression and modulation of radiation-induced apoptosis. Specifically, the events that modulate the apoptosis that occurs in interphase before the cell can divide should be distinguished from the events before division that modulate the misrepair of DNA damage, that results in chromosomal aberrations observed in mitotic cells, which in turn cause the progeny of the dividing cell with aberrations to die by either apoptosis or necrosis. Then, molecular events that determine whether a cell that divides with or without a chromosomal aberration will produce progeny that apoptose or necrose need to be identified. These considerations are important for determining how modulation of radiation-induced apoptosis will affect the ultimate clonogenic survival, and possibly genomic instability in the surviving progeny.

A new flow cytometric method for discrimination of apoptotic cells and detection of their cell cycle specificity through staining of F-actin and DNA

Drug-initiated apoptosis of human leukemia HL-60, THP-1, and U-937 cells was studied via multiparameter flow cytometry and cell sorting. A new flow cytometric method that allows both identification and quantitation of apoptotic cells and estimation of their cell cycle specificity is presented. The method is based on paraformaldehyde fixation followed by staining of F-actin and DNA with fluorescein isothiocyanate (FITC)-phalloidin and propidium iodide (PI), respectively. Bivariate green fluorescence (F-actin) vs. side scatterplots of HL-60 cells treated with 10 microM etoposide for 4 h showed two cell populations, one with high green fluorescence and low side scatter and one with low green fluorescence and high side scatter. Sorting revealed cells with intact nuclei in the high green fluorescence/low side scatter population and cells with fragmented nuclei in the low green fluorescence/high side scatter population, demonstrating that the cells in the latter population were apoptotic. Exposure of HL-60 cells to 10 microM etoposide for 4 h resulted in S-phase selective apoptosis, whereas 5 micrograms/ml cycloheximide initiated apoptosis mainly in G0/G1-phase and S-phase cells. The apoptotic response of HL-60 cells to 20 GY gamma-irradiation was selective for S-phase and G2 + M-phase cells. The present method offers the opportunity to estimate the cell cycle distributions of both the apoptotic and the nonapoptotic cell populations, which is especially valuable when apoptosis occurs in association with cell cycle perturbations. A similar shift from one to two cell populations in green fluorescence vs. side scatter-plots, similar to that observed for HL-60 cells, was observed in the THP-1 and U-937 cell lines secondary to etoposide treatment.

Detection and quantification of live, apoptotic, and necrotic human peripheral lymphocytes by single-laser flow cytometry

Regulation of peripheral lymphocyte number involves a poorly understood balance between cell renewal and loss. Disrupting this balance leads to a large number of disease states. Methods which allow qualitative and quantitative measurements of cell viability are increasingly valuable to studies directed at revealing the mechanisms underlying apoptotic and necrotic cell death. Here, we have characterized a method using single-laser flow cytometry that differentiates and quantifies the relative number of live, apoptotic, and late-stage apoptotic and necrotic peripheral lymphocytes. Following in vitro gamma irradiation and staining with acridine orange in combination with ethidium bromide, three distinct populations were seen by bivariate analysis of green versus red fluorescence. The identity of each distinct fluorescent population (whether live, apoptotic, or necrotic) was determined by sorting and examination of cellular morphology by electron microscopy. This flow cytometric method is directly compared with the techniques of trypan blue exclusion and DNA fragmentation to quantify cell death following exposure to various doses of in vitro gamma irradiation and postirradiation incubation times. We extend our findings to illustrate the utility of this method beyond analyzing radiation-induced apoptotic peripheral blood mononuclear cells (PBMC); similar fluorescent patterns are shown for radiation- and corticosteroid-treated murine thymocytes, activated human PBMC, and PBMC from human immunodeficiency virus-infected individuals. Our results demonstrate that dual-parameter flow cytometric analysis of acridine orange-ethidium bromide-stained lymphocytes is overall a superior method with increased sensitivity, greater accuracy, and decreased subjectivity in comparison with the other methods tested. By using standard laser and filter settings commonly available to flow cytometric laboratories, this method allows rapid measurement of a large number of cells from a heterogeneous sample.

Anti-CD3-induced apoptosis in T-cells from young and old mice

Light scatter measurements using flow cytometry indicated that T cells from young and old mice undergo apoptosis following activation with immobilized anti-CD3. The percentage of cells in apoptosis after 20 h activation was significantly greater (p < .001) in cultures containing cells from older animals. The mean percentages of apoptotic T cells from young and old mice after 20 h activation were 19.3% and 33.0%, respectively. The proportion of viable cells after 20 h activation was significantly higher (p < .003) in the young (mean = 78.4%) than in the old animals (mean = 65.8%). Simultaneous measurements of light scatter and fluorescence indicated that apoptotic T cells contained both the CD4+ and the CD8+ T-cell phenotypes. The frequency of apoptotic CD8+ T cells was elevated (p < .007) in older animals, where the mean percentage was 15.1%, compared to 5.3% in the young. The most dramatic difference between young and old (p < .0008) was seen in the percentages of viable CD4+ T cells after 20 h activation. The mean viable CD4+ T-cell percentage was 33.7% in- the young and 21.4% in the old. CD4+ cells expressing high levels of CD45RB (CD45RBhi) after activation for 20 h possessed light scatter and bright fluorescence properties characteristic of viable cells, whereas CD4+/CD45RBlo density cells could be identified as apoptotic based on their decreased CD4 fluorescence and scatter characteristics. CD4+ cells from young animals were predominantly CD45RBhi, whereas CD4+ cells from the old had greater levels of CD454RBlo cells. In addition to light scatter changes, measurement of DNA content after 40 h activation revealed the presence of a sub-G1 DNA apoptotic peak and a viable cell cycle distribution. After 40 h of activation, there was an increase in the percentage of apoptotic cells in both young and old mice, with the greatest increase seen in the cells from older animals. Further evidence supporting the process of apoptosis in 40 h-activated cells was confirmed by the appearance of DNA strand breaks detected by in situ nick translation.