The most unkindest cut of all: on the multiple roles of mammalian caspases

Vitamin C Supplementation in the Treatment of Autoimmune and Onco-Hematological Diseases: From Prophylaxis to Adjuvant Therapy

Vitamin C is a water-soluble vitamin introduced through the diet with anti-inflammatory, immunoregulatory, and antioxidant activities. Today, this vitamin is integrated into the treatment of many inflammatory pathologies. However, there is increasing evidence of possible use in treating autoimmune and neoplastic diseases. We reviewed the literature to delve deeper into the rationale for using vitamin C in treating this type of pathology. There is much evidence in the literature regarding the beneficial effects of vitamin C supplementation for treating autoimmune diseases such as Systemic Lupus Erythematosus (SLE) and Rheumatoid Arthritis (RA) and neoplasms, particularly hematological neoplastic diseases. Vitamin C integration regulates the cytokines microenvironment, modulates immune response to autoantigens and cancer cells, and regulates oxidative stress. Moreover, integration therapy has an enhanced effect on chemotherapies, ionizing radiation, and target therapy used in treating hematological neoplasm. In the future, integrative therapy will have an increasingly important role in preventing pathologies and as an adjuvant to standard treatments.

Chemical modification of melphalan as a key to improving treatment of haematological malignancies

Chemical modification of known, effective drugs is one method to improve chemotherapy. Thus, the object of this study was to generate melphalan derivatives with improved cytotoxic activity in human cancer cells (RPMI8226, HL60 and THP1). Several melphalan derivatives were synthesised, modified in their two important functional groups. Nine analogues were tested, including melphalan compounds modified: only at the amino group, by replacing the amine with an amidine group containing a morpholine ring (MOR-MEL) or with an amidino group and dipropyl chain (DIPR-MEL); only at the carboxyl group to form methyl and ethyl esters of melphalan (EM-MEL, EE-MEL); and in a similar manner at both functional groups (EM-MOR-MEL, EE-MOR-MEL, EM-DIPR-MEL, EE-DIPR-MEL). Melphalan derivatives were evaluated for cytotoxicity (resazurin viability assay), genotoxicity (comet assay) and the ability to induce apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labelling, TUNEL, phosphatidylserine externalisation, chromatin condensation, activity of caspases 3/7, 8 and 9 and intracellular concentration of calcium ions) in comparison with the parent drug. Almost all derivatives, with the exception of MOR-MEL and DIPR-MEL, were found to be more toxic than melphalan in all cell lines evaluated. Treatment of cultures with the derivatives generated a significant higher level of DNA breaks compared to those treated with melphalan, especially after longer incubation times. In addition, all the melphalan derivatives demonstrated a high apoptosis-inducing ability in acute monocytic and promyelocytic leukemia cells. This study showed that the mechanism of action of the tested compounds differed depending on the cell line, and allowed the selection of the most active compounds for further, more detailed investigations.

Caspase-3 cleavage of dishevelled induces elimination of postsynaptic structures

During the development of vertebrate neuromuscular junction (NMJ), agrin stabilizes, whereas acetylcholine (ACh) destabilizes AChR clusters, leading to the refinement of synaptic connections. The intracellular mechanism underlying this counteractive interaction remains elusive. Here, we show that caspase-3, the effector protease involved in apoptosis, mediates elimination of AChR clusters. We found that caspase-3 was activated by cholinergic stimulation of cultured muscle cells without inducing cell apoptosis and that this activation was prevented by agrin. Interestingly, inhibition of caspase-3 attenuated ACh agonist-induced dispersion of AChR clusters. Furthermore, we identified Dishevelled1 (Dvl1), a Wnt signaling protein involved in AChR clustering, as the substrate of caspase-3. Blocking Dvl1 cleavage prevented induced dispersion of AChR clusters. Finally, inhibition or genetic ablation of caspase-3 or expression of a caspase-3-resistant form of Dvl1 caused stabilization of aneural AChR clusters. Thus, caspase-3 plays an important role in the elimination of postsynaptic structures during the development of NMJs.

Caspase 3 activity in isolated fetal rat lung fibroblasts and rat periodontal ligament fibroblasts: cigarette smoke induced alterations

Background

Cigarette smoking is the leading cause of preventable death and has been implicated in pathogenesis of pulmonary, oral and systemic diseases. Smoking during pregnancy is a risk factor for the developing fetus and may be a major cause of infant mortality. Moreover, the oral cavity, and all cells within are the first to be exposed to cigarette smoke and may be a possible source for the spread of toxins to other organs of the body. Fibroblasts in general are morphologically heterogeneous connective tissue cells with diverse functions. Apoptosis or programmed cell death is a crucial process during embryogenesis and for the maintenance of homeostasis throughout life. Deregulation of apoptosis has been implicated in abnormal lung development in the fetus and disease progression in adults. Caspases are proteases which belong to the family of cysteine aspartic acid proteases and are key components for downstream amplification of intracellular apoptotic signals. Of 14 known caspases, caspase-3 is the key executioner of apoptosis. In the present study we explored the hypothesis that cigarette smoke (CS) extract activates caspase-3 in two types of fibroblasts, both of which would be exposed directly to cigarette smoke, isolated fetal rat lung fibroblasts and adult rat periodontal ligament (PDL) fibroblasts.

Methods

Isolated fetal rat lung fibroblasts and adult PDLs were used. Cells were exposed to different concentrations of CS for 60 min. Caspase-3 activity and its inhibition by Z-VAD-fmk were measured by caspase-3 fluorometric assay. The effect of CSE on cellular viability was measured using the MTT formazan assay. Caspase-3 expression was detected by western blot analysis and cellular localization of caspase-3 was determined by immunofluorescence using fluorescence microscopy.

Results

It was observed in fetal rat lung fibroblast cells that CSE extract significantly (p<0.05) increased caspase-3 activity and decrease cell proliferation. However, no significant changes in activity or viability were observed in PDLs.

Conclusions

This indicates CS activates caspase-3 the key regulatory point in apoptosis in fetal rat lung fibroblast cells suggesting that smoking during pregnancy may alter the developmental program of fetal lung, jeopardizing the establishment of critical cellular mechanisms necessary to expedite pulmonary maturation at birth.of critical cellular mechanisms necessary to expedite pulmonary maturation at birth.

The physiological response of protease inhibition in dystrophic muscle

Duchenne muscular dystrophy (DMD) is caused by the production of a non-functional dystrophin gene product and a failure to accumulate functional dystrophin protein in muscle cells. This leads to membrane instability, loss of Ca(2+) homoeostasis and widespread cellular injury. Associated with these changes are increased protease activities in a variety of proteolytic systems. As such, there have been numerous investigations directed towards determining the therapeutic potential of protease inhibition. In this review, evidence from genetic and/or pharmacological inhibition of proteases as a treatment strategy for DMD is systematically evaluated. Specifically, we review the potential roles of calpain, proteasome, caspase, matrix metalloproteinase and serine protease inhibition as therapeutic approaches for DMD. We conclude that despite early results to the contrary, inhibition of calpain proteases is unlikely to be successful. Conversely, evidence suggests that inhibition of proteasome, matrix metalloproteinases and serine proteases does appear to decrease disease severity. An important caveat to these conclusions, however, is that the fundamental cause of DMD, dystrophin deficiency, is not corrected by this strategy. Hence, this should not be viewed as a cure, but rather, protease inhibitors should be considered for inclusion in a therapeutic cocktail. Physiological Relevance. Selective modulation of protease activity has the potential to profoundly change intracellular physiology resulting in a possible treatment for DMD. However, alteration of protease activities could also lead to worsening of disease progression by promoting the accumulation of substrates in the cell. The balance of benefit and potential damage caused by protease inhibition in human DMD patients is largely unexplored.

Non-apoptotic function of caspases in a cellular model of hydrogen peroxide-associated colitis

Oxidative stress, caused by reactive oxygen species (ROS), is a major contributor to inflammatory bowel disease (IBD)-associated neoplasia. We mimicked ROS exposure of the epithelium in IBD using non-tumour human colonic epithelial cells (HCEC) and hydrogen peroxide (H2 O2 ). A population of HCEC survived H2 O2 -induced oxidative stress via JNK-dependent cell cycle arrests. Caspases, p21(WAF1) and γ-H2AX were identified as JNK-regulated proteins. Up-regulation of caspases was linked to cell survival and not, as expected, to apoptosis. Inhibition using the pan-caspase inhibitor Z-VAD-FMK caused up-regulation of γ-H2AX, a DNA-damage sensor, indicating its negative regulation via caspases. Cell cycle analysis revealed an accumulation of HCEC in the G1 -phase as first response to oxidative stress and increased S-phase population and then apoptosis as second response following caspase inhibition. Thus, caspases execute a non-apoptotic function by promoting cells through G1 - and S-phase by overriding the G1 /S- and intra-S checkpoints despite DNA-damage. This led to the accumulation of cells in the G2 /M-phase and decreased apoptosis. Caspases mediate survival of oxidatively damaged HCEC via γ-H2AX suppression, although its direct proteolytic inactivation was excluded. Conversely, we found that oxidative stress led to caspase-dependent proteolytic degradation of the DNA-damage checkpoint protein ATM that is upstream of γ-H2AX. As a consequence, undetected DNA-damage and increased proliferation were found in repeatedly H2 O2 -exposed HCEC. Such features have been associated with neoplastic transformation and appear here to be mediated by a non-apoptotic function of caspases. Overexpression of upstream p-JNK in active ulcerative colitis also suggests a potential importance of this pathway in vivo.

Interconnections between apoptotic, autophagic and necrotic pathways: implications for cancer therapy development

The rapid accumulation of knowledge on apoptosis regulation in the 1990s was followed by the development of several experimental anticancer- and anti-ischaemia (stroke or myocardial infarction) drugs. Activation of apoptotic pathways or the removal of cellular apoptotic inhibitors has been suggested to aid cancer therapy and the inhibition of apoptosis was thought to limit ischaemia-induced damage. However, initial clinical studies on apoptosis-modulating drugs led to unexpected results in different clinical conditions and this may have been due to co-effects on non-apoptotic interconnected cell death mechanisms and the ‘yin-yang’ role of autophagy in survival versus cell death. In this review, we extend the analysis of cell death beyond apoptosis. Upon introduction of molecular pathways governing autophagy and necrosis (also called necroptosis or programmed necrosis), we focus on the interconnected character of cell death signals and on the shared cell death processes involving mitochondria (e.g. mitophagy and mitoptosis) and molecular signals playing prominent roles in multiple pathways (e.g. Bcl2-family members and p53). We also briefly highlight stress-induced cell senescence that plays a role not only in organismal ageing but also offers the development of novel anticancer strategies. Finally, we briefly illustrate the interconnected character of cell death forms in clinical settings while discussing irradiation-induced mitotic catastrophe. The signalling pathways are discussed in their relation to cancer biology and treatment approaches.

Colonic neoplasia in acromegaly: increased proliferation or deceased apoptosis?

Patients with acromegaly have higher prevalence of colorectal neoplasms. The pathogenetic mechanism is still unclear and may be related to sustained increase in serum GH-IGF1. We aimed to evaluate the proliferative and apoptotic markers in samples of colonic mucosa obtained during screening colonoscopic biopsy from patients with acromegaly and study their relationship to serum IGF-1 and GH levels. The study subjects included 32 patients with acromegaly (4 female), 10 healthy controls (irritable bowel syndrome) and 10 positive controls (non-acromegalic colonic adenocarcinoma). Patients with acromegaly were divided into two groups, active disease (AD) and disease in remission (AR). Two biopsies each were obtained during colonoscopy from the right colon, transverse colon and rectosigmoid region. All the polyps were biopsied and subjected to histopathological examination. Immunohistochemistry for proliferation marker (Ki-67) and apoptotic markers (caspase-3 and TdT-Mediated dUTP Nick-End Labeling (TUNEL) was carried out in the histopathological samples. Indices of proliferation were significantly different in patients with acromegaly as compared to healthy controls. The mean Ki-67 positivity was 45.1 ± 17.7% in AD and 45.6 ± 23.1% in AR, as compared to 10 ± 5% in healthy controls. While none of the healthy controls had Ki-67 positivity beyond the lower third of crypts, among patients with acromegaly 12/32 (37.5%) had mid-third positivity (P = 0.000) and 15/32 (46.8%) had full length of crypt positively (P = 0.00). Immunostaining for caspase-3 was negative in patients with acromegaly and healthy controls. TUNEL was strongly positive in patients with colonic adenocarcinoma but not in healthy controls and patients with acromegaly. IGF-1 levels were higher in those with Ki-67 positivity in the superficial mucosa. Patients with acromegaly have increased proliferation of colonic epithelial cells. Elevated levels of serum IGF1 are associated with increase proliferation in the superficial crypt cells.

Mechanisms of carbon nanotube-induced toxicity: focus on oxidative stress

Nanotechnologies are emerging as highly promising technologies in many sectors in the society. However, the increasing use of engineered nanomaterials also raises concerns about inadvertent exposure to these materials and the potential for adverse effects on human health and the environment. Despite several years of intensive investigations, a common paradigm for the understanding of nanoparticle-induced toxicity remains to be firmly established. Here, the so-called oxidative stress paradigm is scrutinized. Does oxidative stress represent a secondary event resulting inevitably from disruption of biochemical processes and the demise of the cell, or a specific, non-random event that plays a role in the induction of cellular damage e.g. apoptosis? The answer to this question will have important ramifications for the development of strategies for mitigation of adverse effects of nanoparticles. Recent examples of global lipidomics studies of nanoparticle-induced tissue damage are discussed along with proteomics and transcriptomics approaches to achieve a comprehensive understanding of the complex and interrelated molecular changes in cells and tissues exposed to nanoparticles. We also discuss instances of non-oxidative stress-mediated cellular damage resulting from direct physical interference of nanomaterials with cellular structures.

Myelodysplastic syndromes: an update on molecular pathology

The myelodysplastic syndromes (MDS) are a heterogeneous group of myeloid disorders characterised by impaired peripheral blood cell production due to bone marrow dysplasia affecting one or more of the major myeloid cell lines. MDS are one of five major categories of myeloid neoplasms according to the World Health Organization (WHO) classification system for haematological cancers. Given their cytological and cytogenetic heterogeneity, these diseases probably constitute a group of molecularly distinct entities with variable degrees of ineffective haematopoiesis and susceptibility to leukaemic transformation. Recent studies provide some insights into the physiopathology of MDS. In the early stages, one mechanism contributing to hypercellular marrow and peripheral blood cytopenia is a significant increase in programmed cell death (apoptosis) in haematopoietic cells. Furthermore, altered responses in relation to cytokines, the immune system and bone marrow stroma also contribute to the disease phenotype. Deletions of chromosome 5q31-q32 are the most common recurring cytogenetic abnormalities detected in MDS. The 5q- syndrome is a new entity recognised in the WHO classification since 2001 and is associated with a good prognosis. Haploinsufficiency of multiple genes mapping to the common deleted region at 5q31-32 may contribute to the pathogenesis of 5q- syndrome and other MDS with 5q- deletion. Many studies have demonstrated that altered DNA methylation and histone acetylation can alter gene transcription. Abnormal methylation of transcription promoter sites is universal in patients with MDS, and the number of involved loci is increased in high-risk disease and secondary leukaemias. A better understanding of the pathogenesis of MDS can contribute to the development of new treatments such as hypomethylating drugs, immunomodulatory agents such as lenalidomide, and immunosuppressive drugs aimed at reversing the specific alteration that results in improvement in patients with MDS.

Electrochemical sensing for caspase 3 activity and inhibition using quantum dot functionalized carbon nanotube labels

A novel electrochemical sensing platform for sensitive determination of caspase 3 activity and inhibition was developed by combining the site-specific recognition and cleavage of the DEVD-peptide with quantum dots as signal amplification.

[Detection of apoptosis in vivo: comparison of different methods in histological sections of subcutaneous xenografts of HT29 human colon adenocarcinoma]

Apoptosis detection in histological section is very important, but usual methods (TUNEL and morphologic changes) are controversial. Immunohistochemical stains of activated proteins during apoptosis improve detection of cell death in tissue sections. Activated caspase-3 and cleaved cytokeratin-18 are more and more used.

OBJECTIVE

This study compared immunohistochemical markers (activated caspase-3, cleaved cytokeratin-18 and two antibodies not yet evaluated: activated caspase-7 and cleaved PARP-1), cellular morphology and TUNEL.

MATERIAL AND METHODS

Tumour xenografts of the human colon cancer cell line HT29 were used, treated by photodynamic therapy, to obtain large numbers of cells undergoing apoptosis. Apoptotic cells were quantified and apoptotic indices were determined for each marker.

RESULTS

Comparison of apoptosis index indicated statistically best sensibility with activated-caspase-3 and cleaved-cytokeratin-19.

CONCLUSION

Immunohistochemistry for activated caspase-3 and cleaved cytkeratin-18 appear to be an easy, sensitive, and reliable method for detecting and quantifying apoptosis in this model. There are therefore recommended for the detection and quantification of apoptosis in tissue sections. Other markers as cleaved PARP-1 and activated caspase-7 can be an interessant solution: advantages and inconvenience for each methods are exposed.

Cell death by SecTRAPs: thioredoxin reductase as a prooxidant killer of cells

BACKGROUND

SecTRAPs (selenium compromised thioredoxin reductase-derived apoptotic proteins) can be formed from the selenoprotein thioredoxin reductase (TrxR) by targeting of its selenocysteine (Sec) residue with electrophiles, or by its removal through C-terminal truncation. SecTRAPs are devoid of thioredoxin reductase activity but can induce rapid cell death in cultured cancer cell lines by a gain of function.

PRINCIPAL FINDINGS

Both human and rat SecTRAPs killed human A549 and HeLa cells. The cell death displayed both apoptotic and necrotic features. It did not require novel protein synthesis nor did it show extensive nuclear fragmentation, but it was attenuated by use of caspase inhibitors. The redox active disulfide/dithiol motif in the N-terminal domain of TrxR had to be maintained for manifestation of SecTRAP cytotoxicity. Stopped-flow kinetics showed that NADPH can reduce the FAD moiety in SecTRAPs at similar rates as in native TrxR and purified SecTRAPs could maintain NADPH oxidase activity, which was accelerated by low molecular weight substrates such as juglone. In a cellular context, SecTRAPs triggered extensive formation of reactive oxygen species (ROS) and consequently antioxidants could protect against the cell killing by SecTRAPs.

CONCLUSIONS

We conclude that formation of SecTRAPs could contribute to the cytotoxicity seen upon exposure of cells to electrophilic agents targeting TrxR. SecTRAPs are prooxidant killers of cells, triggering mechanisms beyond those of a mere loss of thioredoxin reductase activity.

Cell death in health and disease

Cell death is clearly an important factor in development, homeostasis, pathology and in aging, but medical efforts based on controlling cell death have not become major aspects of medicine. There are several reasons why hopes have been slow to be fulfilled, and they present indications for new directions in research. Most effort has focused on the machinery of cell death, or the proximate effectors of apoptosis and their closely associated and interacting proteins. But cells have many options other than apoptosis. These include autophagy, necrosis, atrophy and stepwise or other alternate means of self-disassembly. The response of a cell to a noxious or otherwise intimidating signal will depend heavily on the history, lineage and current status of the cell. Many metabolic and other processes adjust the sensitivity of cells to signals, and viruses aggressively attempt to regulate the death of their host cells. Another complicating factor is that many deathassociated proteins may have functions totally unrelated to their role in cell death, generating the possibility of undesirable side effects if one interferes with them. In the future, the challenge will be more to understand the challenge to the cell from a more global standpoint, including many more aspects of metabolism, and work toward alleviating or provoking the challenge in a targeted fashion.

Cytotoxic activity of the third-generation bisphosphonate zoledronic acid in acute myeloid leukemia

The third-generation bisphosphonate zoledronic acid (ZOL) has recently been shown to be active against human tumour and leukemic cell lines. The purpose of this study was to evaluate the antileukemic potential of ZOL in acute myeloid leukemia (AML). We determined the lethal concentration 50% (LC 50) using the WST-1 assay of ZOL as being 287.9 microg/ml after 24 h and 108.3 microg/ml after 96 h in HL 60 cells and to be 382.4 and 43.2 microg/ml, respectively, in nine samples from patients with AML. The ZOL induced inhibition of proliferative activity of HL 60 cells could not be abrogated by the hematopetic growth factors G-CSF and GM-CSF. ZOL was found to by cytotoxic in HL 60 cells without activation of caspase 3. ZOL was not cross resistant with cytarabine as shown by the linear correlation of LC 50s. Both agents, however, exerted an additive cytotoxicity as revealed by isobologram-analysis and combination index. These data warrant further investigation of ZOL in the treatment of AML.

The effects of benzene exposure on apoptosis in epithelial lung cells: localization by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) and the immunocytochemical localization of apoptosis-related gene products

Although benzene, a well-known human carcinogen, has been shown to induce apoptosis in vitro, no studies have been carried out to confirm and characterize its role in activating apoptosis in vivo. The present study investigated the effects of benzene inhalation on the epithelial cells lining the respiratory tract including bronchioles, terminal bronchioles, respiratory bronchioles and alveoli of male Sprague-Dawley rats. Inhalation of benzene 300 ppm for 7 days induced apoptotic changes in the parenchymal components in the lung that significantly exceeded the events of programmed cell death in normal control tissues. Apoptosis was confirmed by the electrophoretic analysis of internucleosomal DNA fragmentation of benzene-exposed lung tissues, which exhibited 180-200 bp laddering subunits indicative of genomic DNA degradation. Furthermore, semi-quantitative analysis of intracellular localization of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling TUNEL) showed a significant (p < 0.001) increase in the apoptotic index calculated for bronchiolar 73.5%, terminal bronchiolar (65%), and respiratory bronchiolar 60.8% segmental epithelial components as well as alveolar (55%) epithelia. Analysis of immunohistochemical expression of apoptosis-related gene products also supported the hypothesis that benzene can induce apoptosis in chemosensitive target cells in the lung parenchyma. Quantitative immunhistochemistry showed a statistically significant increase p < 0.001 in the immunoreactive staining index for cytochrome c, Apaf-1 (apoptosis activating factor-1), DNA fragmentation factor, and representative cysteine proteases including caspase-1, caspase-2L, caspase-8 and caspase-9. Thus this is the first study of the respiratory system that demonstrates that benzene inhalation induces lung cell apoptosis as confirmed by DNA electrophoresis, in situ nick end labeling, and the upregulation of apoptosis-related gene products that facilitate caspase-cleaved enzymes which lead to cell degradation via programmed cell death. These responses may represent an important defense mechanism within the parenchymal cells of the respiratory system that reduce mutational hazard and the potential carcinogenic effects of benzene-initiated pathogenesis.

The effect of intracellular ascorbate on the susceptibility of HL60 and Jurkat cells to chemotherapy agents

Chemotherapy agents initiate tumour cell apoptosis and this is thought to involve oxidative stress. In this study we have investigated the effect of the important antioxidant Vitamin C (ascorbate) on the response of HL60 and Jurkat cells to three chemotherapy drugs, namely etoposide, melphalan and arsenic trioxide (As(2)O(3)). Cells grown in routine culture media are deficient in ascorbate and to determine its effect on chemotherapy drug-induced apoptosis we supplemented the cells prior to drug exposure. We found that ascorbate had a varied effect on apoptosis and cell cycle progression. Etoposide-induced apoptosis in HL60 cells was significantly increased in ascorbate-loaded cells as measured by caspase-3 activation and DNA degradation, and this appeared to reflect a decrease in the number of necrotic cells rather than increased cytotoxicity. In contrast, ascorbate had no effect on etoposide-induced apoptosis in Jurkat cells. In both cell types melphalan-induced apoptosis was unaffected by intracellular ascorbate, whereas both apoptosis and growth arrest with low concentrations of As(2)O(3) were diminished. These results indicate that intracellular ascorbate can affect cell responses to chemotherapy drugs in a complex and somewhat unpredictable manner and that it may play an important role in the responsiveness of tumour cells to chemotherapy regimes.

Old yellow enzyme interferes with Bax-induced NADPH loss and lipid peroxidation in yeast

The yeast transcriptional response to murine Bax expression was compared with the changes induced by H(2)O(2) treatment via microarray technology. Although most of the Bax-responsive genes were also triggered by H(2)O(2) treatment, OYE3, ICY2, MLS1 and BTN2 were validated to have a Bax-specific transcriptional response not shared with the oxidative stress trigger. In knockout experiments, only deletion of OYE3, coding for yeast Old yellow enzyme, attenuated the rate of Bax-induced growth arrest, cell death and NADPH decrease. Lipid peroxidation was completely absent in DeltaOYE3 expressing Bax. However, the absence of OYE3 sensitized yeast cells to H(2)O(2)-induced cell death, and increased the rate of NADPH decrease and lipid peroxidation. Our results clearly indicate that OYE3 interferes with Bax- and H(2)O(2)-induced lipid peroxidation and cell death in Saccharomyces cerevisiae.

Host cell killing by the West Nile Virus NS2B-NS3 proteolytic complex: NS3 alone is sufficient to recruit caspase-8-based apoptotic pathway

The West Nile Virus (WNV) non-structural proteins 2B and 3 (NS2B-NS3) constitute the proteolytic complex that mediates the cleavage and processing of the viral polyprotein. NS3 recruits NS2B and NS5 proteins to direct protease and replication activities. In an effort to investigate the biology of the viral protease, we cloned cDNA encoding the NS2B-NS3 proteolytic complex from brain tissue of a WNV-infected dead crow, collected from the Lower Merion area (Merion strain). Expression of the NS2B-NS3 gene cassette induced apoptosis within 48 h of transfection. Electron microscopic analysis of NS2B-NS3-transfected cells revealed ultra-structural changes that are typical of apoptotic cells including membrane blebbing, nuclear disintegration and cytoplasmic vacuolations. The role of NS3 or NS2B in contributing to host cell apoptosis was examined. NS3 alone triggers the apoptotic pathways involving caspases-8 and -3. Experimental results from the use of caspase-specific inhibitors and caspase-8 siRNA demonstrated that the activation of caspase-8 was essential to initiate apoptotic signaling in NS3-expressing cells. Downstream of caspase-3 activation, we observed nuclear membrane ruptures and cleavage of the DNA-repair enzyme, PARP in NS3-expressing cells. Nuclear herniations due to NS3 expression were absent in the cells treated with a caspase-3 inhibitor. Expression of protease and helicase domains themselves was sufficient to trigger apoptosis generating insight into the apoptotic pathways triggered by NS3 from WNV.

Electroconvulsive Shock Induces Neuron Death in the Mouse Hippocampus: Correlation of Neurodegeneration with Convulsive Activity

The relationship between convulsive activity evoked by repeated electric shocks and structural changes in the hippocampus of Balb/C mice was studied. Brains were fixed two and seven days after the completion of electric shocks, and sections were stained by the Nissl method and immunohistochemically for apoptotic nuclei (the TUNEL method). In addition, the activity of caspase-3, the key enzyme of apoptosis, was measured in brain areas immediately after completion of electric shocks. The number of neurons decreased significantly in field CA1 and the dentate fascia, but not in hippocampal field CA3. The numbers of cells in CA1 and CA3 were inversely correlated with the intensity of convulsions. Signs of apoptotic neuron death were not seen, while caspase-3 activity was significantly decreased in the hippocampus after electric shocks. These data support the notion that functional changes affect neurons after electric shock and deepen our understanding of this view, providing direct evidence that there are moderate (up to 10%) but significant levels of neuron death in defined areas of the hippocampus. Inverse correlations of the numbers of cells with the extent of convulsive activity suggest that the main cause of neuron death is convulsions evoked by electric shocks.

Nuclear substructure reorganization during late-stage erythropoiesis is selective and does not involve caspase cleavage of major nuclear substructural proteins

Enucleation, a rare feature of mammalian differentiation, occurs in 3 cell types: erythroblasts, lens epithelium, and keratinocytes. Previous investigations suggest that caspase activation functions in lens epithelial and keratinocyte enucleation, as well as in early erythropoiesis encompassing erythroid burst-forming unit (BFU-E) differentiation to proerythroblast. To determine whether caspase activation contributes to later erythropoiesis and whether nuclear substructures other than chromatin reorganize, we analyzed distributions of nuclear subcompartment proteins and assayed for caspase-induced cleavage of subcompartmental target proteins in mouse erythroblasts. We found that patterns of lamin B in the filamentous network interacting with both the nuclear envelope and DNA, nuclear matrix protein NuMA (Nuclear mitotic apparatus), and splicing factors Sm and SC35 persisted during nuclear condensation, consistent with effective transcription of genes expressed late in differentiation. Thus, nuclear reorganization prior to enucleation is selective, allowing maintenance of critical transcriptional processes independent of extensive chromosomal reorganization. Consistent with these data, we found no evidence for caspase-induced cleavage of major nuclear subcompartment proteins during late erythropoiesis, in contrast to what has been observed in early erythropoiesis and in lens epithelial and keratinocyte differentiation. These findings imply that nuclear condensation and extrusion during terminal erythroid differentiation involve novel mechanisms that do not entail major activation of apoptotic machinery.

Chlorimipramine: A novel anticancer agent with a mitochondrial target

Mitochondria have been suggested to be a potential intracellular target for cancer chemotherapy. In this report, we demonstrate the ability of the tricyclic antidepressant chlorimipramine to kill human glioma cells in vitro by a molecular mechanism resulting in an increase in caspase 3 activity following inhibition of glioma oxygen consumption. Studies with isolated rat mitochondria showed that chlorimipramine specifically inhibited mitochondrial complex III activity, which causes decreased mitochondrial membrane potential as well as mitochondrial swelling and vacuolation. The use of chlorimipramine in human as an effective, non-toxic cancer therapeutic having a strong selectivity between cancer cells and normal cells on the basis of their mitochondrial function is discussed.

Caspase inhibitors as neuroprotective agents

Apoptotic neuronal cell death has been demonstrated to occur in the central nervous system (CNS), following both acute injury and during chronic neurodegenerative conditions. Currently, the majority of experimental evidence for a role of caspases in CNS damage has been established following acute neuronal insults, including ischaemic stroke, traumatic brain injury and spinal cord injury. In vitro and in vivo models have been used to demonstrate caspase activation, and treatment with available caspase inhibitors can provide significant protection. Overall, acute neuronal injury represents a major unmet medical need and caspase inhibitors may be an attractive approach to preserve neuronal function by extending the therapeutic window and providing long-term neuroprotection. Currently, several inhibitors are in preclinical drug development and this review summarises recent advances in the development of novel caspase inhibitors for the treatment of acute neuronal injury.

Full-length expanded ataxin-3 enhances mitochondrial-mediated cell death and decreases Bcl-2 expression in human neuroblastoma cells

Machado-Joseph disease (MJD) is an autosomal dominant spinocerebellar degeneration characterized by a wide range of clinical manifestations. An unstable CAG trinucleotide repeat expansion in MJD gene on long arm of chromosome 14 has been identified as the pathologic mutation of MJD and apoptosis was previously shown to be responsible for the neuronal cell death of the disease. In this study, we utilized human neuronal SK-N-SH cells stably transfected with HA-tagged full-length MJD with 78 polyglutamine repeats to examine the effects of polyglutamine expansion on neuronal cell survival in the early stage of disease. Various pro-apoptotic agents were used to assess the tolerance of the mutant cells and to compare the differences between cells with and without mutant ataxin-3. Concentration- and time-dependent experiments showed that the increase in staurosporine-induced cell death was more pronounced and accelerated in cells containing expanded ataxin-3 via MTS assays. Interestingly, under basal conditions, Western blot and immunocytochemical analyses showed a significant decrease of Bcl-2 protein expression and an increase of cytochrome c in cells containing expanded ataxin-3 when compared with those of the parental cells. The same reduction of Bcl-2 was further confirmed in fibroblast cells with mutant ataxin-3. In addition, exogenous expression of Bcl-2 desensitized SK-N-SH-MJD78 cells to poly-Q toxicity. These results indicated that mitochondrial-mediated cell death plays a role in the pathogenesis of MJD. In our cellular model, full-length expanded ataxin-3 that leads to neurodegenerative disorders significantly impaired the expression of Bcl-2 protein, which may be, at least in part, responsible for the weak tolerance to polyglutamine toxicity at the early stage of disease and ultimately resulted in an increase of stress-induced cell death upon apoptotic stress.

Epstein-Barr virus-encoded latent membrane protein 1 promotes stress-induced apoptosis upstream of caspase-2-dependent mitochondrial perturbation

Previous studies have shown that Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP1) enhances etoposide-induced apoptosis in epithelial cells. Our study was undertaken to further dissect the modulation of tumor cell apoptosis by this viral protein. Using an inducible system of LMP1 expression in HeLa cells, we show herein that etoposide-triggered apoptosis, as evidenced by nuclear condensation and caspase-3 activation, is enhanced by LMP1. LMP1 also potentiates etoposide-induced processing and activation of caspase-2 in this model and enhances the dissipation of mitochondrial transmembrane potential and the release of cytochrome c in response to etoposide. Moreover, cisplatin-triggered activation of caspases 2 and 3 is potentiated upon expression of LMP1. A similar LMP1-mediated enhancement of cisplatin-induced caspase activation was seen upon stable transfection of wild-type LMP1 into the nasopharyngeal carcinoma cell line, TW03. Finally, using deletion mutants of LMP1 to determine the region of LMP1 required for apoptosis potentiation, we found that amino acids 350-386 (located within the CTAR2 domain) were responsible for sensitizing cells to cisplatin. We conclude that LMP1-dependent potentiation of stress-induced apoptosis occurs at an early step in the apoptosis cascade, upstream of the activation of caspase-2, and involves the C-terminal signaling domain of LMP1. These findings could have important ramifications for the treatment of EBV-associated malignancies of epithelial origin, including nasopharyngeal carcinoma.

Clinical utility of cytokeratins as tumor markers

Cytokeratins, belonging to the intermediate filament (IF) protein family, are particularly useful tools in oncology diagnostics. At present, more than 20 different cytokeratins have been identified, of which cytokeratins 8, 18, and 19 are the most abundant in simple epithelial cells. Upon release from proliferating or apoptotic cells, cytokeratins provide useful markers for epithelial malignancies, distinctly reflecting ongoing cell activity. It appears that motifs in certain cytokeratins make them likely substrates for caspase degradation, and their subsequent release occurs during the intermediate events in apoptosis. The clinical value of determining soluble cytokeratin protein fragments in body fluids lies in the early detection of recurrence and the fast assessment of the efficacy of therapy response in epithelial cell carcinomas. The three most applied cytokeratin markers used in the clinic are tissue polypeptide antigen (TPA), tissue polypeptide specific antigen (TPS), and CYFRA 21-1. TPA is a broad spectrum test that measures cytokeratins 8, 18, and 19. TPS and CYFRA 21-1 assays are more specific and measure cytokeratin 18 and cytokeratin 19, respectively. By following patients with repeated testing during management, the oncologist may obtain critical information regarding the growth activity in symptomatic patients. Although their main use is to monitor treatment and evaluate response to therapy, early prognostic information particularly on tumor progression and metastasis formation is also provided for several types of cancers. Cytokeratin tumor markers can accurately predict disease status before conventional methods and offer a simple, noninvasive, cheap, and reliable tool for more efficient management.

Central administration of a caspase inhibitor impairs shuttle-box performance in rats

Recent studies suggest that caspase-3-mediated mechanisms are essential for neuronal plasticity. N-benzyloxycarbonyl-Asp(OMe)-Glu(OMe)-Val- Asp(OMe)-fluoromethyl ketone (z-DEVD-fmk), a caspase inhibitor with predominant specificity toward caspase-3, has been shown to block long-term potentiation in hippocampal slices. Intrahippocampal infusion of a caspase-3 inhibitor to rats has been shown to significantly impair spatial memory in the water maze. The present work was designed to study whether i.c.v. administration of a caspase-3 inhibitor z-DEVD-fmk impairs learning in other tasks related to specific forms of memory in rats. The rats received bilateral injections of z-DEVD-fmk or N-benzyloxycarbonyl-Phe-Ala-fluoromethyl ketone (z-FA-fmk) ("control" peptide) at a dose of 3 nmol. Administration of z-DEVD-fmk significantly decreased the number of avoidance reactions in some blocks of trials in the active avoidance (shuttle box) learning, while z-FA-fmk had no effect as compared with intact rats. However, only a slight effect of the caspase inhibitor across the session was found. z-DEVD-fmk impaired development of some essential components of the two-way active avoidance performance, such as escape reaction, conditioned fear reaction, and inter-trial crossings. Measurement of caspase-3 activity in rat brain regions involved in active avoidance learning revealed most expressed z-DEVD-fmk-related inhibition of the enzyme activity (about 30%) in the fronto-parietal cortex. A similar effect was close to significant in the hippocampus, but not in the other cerebral structures studied. In primary cultures of cerebellar neurons z-DEVD-fmk (2-50 microM) inhibited caspase-3 activity by 60-87%. We suggest that moderate inhibition of caspase-3 resulting from the central administration of z-DEVD-fmk to rats may impair active avoidance learning. Taking into account previous data on the involvement of neuronal caspase-3 in neuroplasticity phenomena we assume that the enzyme may be important for selected forms of learning.

Distinguishing modes of cell death using the ImageStream® multispectral imaging flow cytometer

BACKGROUND

Here we demonstrate the ability of the ImageStream 100 Multispectral Imaging Cytometer to discriminate between live, necrotic, and early and late apoptotic cells, using unique combinations of photometric and morphometric features.

METHODS

Live, necrotic, and early and late apoptotic cells were prepared and analyzed by immunofluorescence microscopy, conventional flow cytometry, and imaging flow cytometry, both as single populations and as a heterogeneous mixture of cells.

RESULTS

Live (annexin V(-), 7-AAD(-)) and early apoptotic (annexin V(+), 7-AAD(-)) cells were readily identifiable using either conventional or ImageStream based flow cytometric methods. However, inspection of multispectral images of cells demonstrated that the annexin V(+), 7-AAD(+) population contained both necrotic and late-stage apoptotic cells. Although these cells could not be distinguished using conventional flow cytometric techniques, they were separable using unique combinations of photometric and morphometric measures available using ImageStream technologies.

CONCLUSIONS

Using multispectral imagery, morphologically distinct cell populations can be distinguished using features not available with conventional flow cytometers. In particular, the ability to couple morphometric with photometric measures makes it possible to distinguish live cells from cells in the early phases of apoptosis, as well as late apoptotic cells from necrotic cells.

Kostmann syndrome: severe congenital neutropenia associated with defective expression of Bcl-2, constitutive mitochondrial release of cytochrome c, and excessive apoptosis of myeloid progenitor cells

Kostmann syndrome, or severe congenital neutropenia (SCN), is an autosomal recessive disorder of neutrophil production. To investigate the potential role of apoptosis in SCN, bone marrow aspirates and biopsies were obtained from 4 patients belonging to the kindred originally described by Kostmann and 1 patient with SCN of unknown inheritance. An elevated degree of apoptosis was observed in the bone marrow of these patients, and a selective decrease in B-cell lymphoma-2 (Bcl-2) expression was seen in myeloid progenitor cells. Furthermore, in vitro apoptosis of bone marrow-derived Kostmann progenitor cells was increased, and mitochondrial release of cytochrome c was detected in CD34+ and CD33+ progenitors from patients, but not in controls. Administration of granulocyte colony-stimulating factor (G-CSF) restored Bcl-2 expression and improved survival of myeloid progenitor cells. In addition, cytochrome c release was partially reversed upon incubation of progenitor cells with G-CSF. In sum, these studies establish a role for mitochondria-dependent apoptosis in the pathogenesis of Kostmann syndrome and yield a tentative explanation for the beneficial effect of growth factor administration in these patients. (Blood. 2004;103:3355-3361)

Apoptosis and macrophage clearance of neutrophils: regulation by reactive oxygen species

Inflammation is a beneficial host response to foreign challenge involving numerous soluble factors and cell types, including polymorphonuclear granulocytes or neutrophils. Programmed cell death (apoptosis) of neutrophils has been documented in vitro as well as in vivo, and is thought to be important for the resolution of inflammation, as this process allows for engulfment and removal of senescent cells prior to their necrotic disintegration. Studies in recent years have begun to unravel the mechanism of macrophage clearance of apoptotic cells, and evidence has accrued for a critical role of externalization and oxidation of plasma membrane phosphatidylserine, and its subsequent recognition by macrophage receptors, in this process. Activated neutrophils generate vast amounts of reactive oxygen species for the purpose of killing ingested micro-organisms, and these reactive metabolites may also modulate the life-span, as well as the clearance, of the neutrophil itself. This review aims to address the latter topic, as well as to summarize current knowledge on the molecular mechanisms of neutrophil apoptosis and macrophage clearance of these cells at the site of inflammation.

Induction of apoptosis and stress response in ovarian carcinoma cell lines treated with ST1926, an atypical retinoid

To understand the molecular mechanisms mediating apoptosis induction by a novel atypical retinoid, ST1926, the cellular response to drug treatment was investigated in IGROV-1 ovarian carcinoma cells carrying wild-type p53 and a cisplatin-resistant p53 mutant subline (IGROV-1/Pt1). Despite a similar extent of drug-induced DNA strand breaks, the level of apoptosis was substantially higher in p53 wild-type cells. p53 activation and early upregulation of p53-target genes were consistent with p53-dependent apoptosis in IGROV-1 cells. Stress-activated protein kinases were activated in both cell lines in response to ST1926. This event and activation of AP-1 were more pronounced in IGROV-1/Pt1 cells, in which the modulation of DNA repair-associated genes suggests an increased ability to repair DNA damage. Inhibition of JNK or p38 stimulated ST1926-induced apoptosis only in IGROV-1 cells, whereas inhibition of ERKs enhanced apoptosis in both the cell lines. Such a pattern of cellular response and modulation of genes implicated in DNA damage response supports that the genotoxic stress is a critical event mediating drug-induced apoptosis. The results are consistent with apoptosis induction through p53-dependent and -independent pathways, regulated by MAP kinases, which likely play a protective role.

Caspase activity is essential for long-term potentiation

Slices from rat hippocampus were incubated with the caspase-3 inhibitor N-benzyloxycarbonyl-Asp-Glu-Val-Asp fluoromethylketone (Z-DEVD-FMK) or with the inactive peptide N-benzyloxycarbonyl-Phe-Ala fluoromethylketone (Z-Phe-Ala-FMK) for 30 min. The peptides changed neither input-output curves nor paired-pulse effects at 70-msec interpulse intervals, nor amplitudes of pop spikes in the CA1 region 1.0-6.9 hr after the incubation. Slices taken 1.0-1.4 hr after Z-DEVD-FMK or inactive peptide treatment demonstrated similar long-term potentiation (LTP) curves; however, LTP was suppressed significantly (P<0.001) 1.5-3.4 hr after Z-DEVD-FMK treatment when compared to the corresponding inactive peptide group. LTP magnitude correlated with time after Z-DEVD-FMK (r= -0.74; P<0.02) but did not depend on time after the inactive peptide treatment. After 3.5 hr, LTP was blocked completely. Z-DEVD-FMK did not have a significant effect on presynaptic function. The results are the first evidence that inhibition of caspase-3 significantly decreases or fully blocks LTP in the CA1 region and suggest that caspase-3 is essential for LTP. Candidate caspase-3 substrates that may be cleaved for LTP induction and maintenance are discussed.

Loss of drug-induced activation of the CD95 apoptotic pathway in a cisplatin-resistant testicular germ cell tumor cell line

Testicular germ cell tumors (TGCTs) are unusually sensitive to cisplatin. In the present study the role of the CD95 death pathway in cisplatin sensitivity of TGCT cells was studied in Tera and its in vitro acquired cisplatin-resistant subclone Tera-CP. Cisplatin induced an increase in CD95 membrane expression, which preceded the onset of apoptosis. Cisplatin-induced apoptosis was efficiently blocked by caspase-8 inhibitor zIETD-fmk in Tera cells, but only partially in Tera-CP cells. In addition, cisplatin induced FADD and caspase-8 recruitment to the CD95 receptor in Tera cells, which was not noticed in Tera-CP cells. Moreover, overexpression of vFLIP reduced apoptosis induction by cisplatin in Tera cells. CD95L-blocking experiments revealed the involvement of CD95/CD95L interactions in cisplatin-induced apoptosis of Tera cells as well as cisplatin-sensitive 833KE TGCT cells. Tera and 833KE cells, treated with low doses of cisplatin, were sensitive for an apoptosis-inducing anti-CD95 antibody. In contrast, CD95L blocking had no effect on cisplatin-induced apoptosis in Tera-CP or Scha, an intrinsic resistant TGCT cell line, nor did anti-CD95 antibody induce additional apoptosis in cisplatin-treated Tera-CP or Scha cells. Taken together, these results show that (1) cisplatin sensitivity of TGCT cells is dependent on the activation of the CD95 death pathway and (2) loss of cisplatin-induced activation of this CD95 signaling pathway may result in resistance to cisplatin.

Structural pathways and prevention of heart failure and sudden death

We review the macroscopic and microscopic anatomy of myocardial disease associated with heart failure (HF) and sudden cardiac death (SCD) and focus on the prevention of SCD in light of its structural pathways. Compared to patients without SCD, patients with SCD exhibit 5- to 6-fold increases in the risks of ventricular arrhythmias and SCD. Epidemiologically, left ventricular hypertrophy by ECG or echocardiography acts as a potent dose-dependent SCD predictor. Dyslipidemia, a coronary disease risk factor, independently predicts echocardiographic hypertrophy. In adult SCD autopsy studies, increases in heart weight and severe coronary disease are constant findings, whereas rates of acute coronary thrombi vary remarkably. The microscopic myocardial anatomy of SCD is incompletely defined but may include prevalent changes of advanced myocardial disease, including cardiomyocyte hypertrophy, cardiomyocyte apoptosis, fibroblast hyperplasia, diffuse and focal matrix protein accumulation, and recruitment of inflammatory cells. Hypertrophied cardiomyocytes express "fetospecific" genetic programs that can account for acquired long QT physiology with risk for polymorphic ventricular arrhythmias. Structural heart disease associated with HF and high SCD risk is causally related to an up-regulation of the adrenergic renin-angiotensin-aldosterone pathway. In outcome trials, suppression of this pathway with combinations of beta-blockers, angiotensin-converting enzyme inhibitors, angiotensin-II receptor blockers, and mineralocorticoid receptor blockers have achieved substantial total mortality and SCD reductions. Contrarily, trials with ion channel-active agents that are not known to reduce structural heart disease have failed to reduce these risks. Device therapy effectively prevents SCD, but whether biventricular pacing-induced remodeling decreases left ventricular mass remains uncertain.

Cold-induced apoptosis of rat liver endothelial cells: involvement of the proteasome

BACKGROUND

We have previously shown that in cultured liver endothelial cells the mere sequence of hypothermia and rewarming induces a pronounced, iron-dependent apoptosis that is likely to contribute to hepatic preservation injury. Here we study the involvement of proteases in this cold-induced apoptosis.

METHODS

Cultured liver endothelial cells were incubated in preservation solutions at 4 degrees C in the absence or presence of protease inhibitors. Cell injury and different protease activities were assessed.

RESULTS

Cold incubation of liver endothelial cells in University of Wisconsin or histidine-tryptophan-ketoglutarate (HTK) solution led to marked cell injury, which was strongly inhibited by the protease inhibitor 3,4-dichloroisocoumarin (DCI) (lactate dehydrogenase release: 86.0+/-2.6% in HTK and 4.0+/-0.4% in HTK + DCI after 24 hr of cold incubation). Determination of protease activity showed a doubling in the activity of a Suc-Leu-Leu-Val-Tyr-AMC-cleaving protease and some increase in a relatively low Suc-Ala-Ala-Ala-AMC-cleaving activity after 8 hr of cold incubation in HTK solution or 16 hr in University of Wisconsin solution. Further characterization of the protease activities showed that they belonged to two different proteases, with the major activity being calcium independent, inhibited by DCI, MG-132, and lactacystin, and strongly decreased by immunoprecipitation with an antiproteasome antibody. Preincubation of the cells with the iron chelator deferoxamine prevented the cold-induced increase of both activities.

CONCLUSION

These results show that (i) the proteasome and possibly, in addition, a serine protease are involved in cold-induced apoptosis of liver endothelial cells and (ii) the protease activation is downstream from the increase in intracellular chelatable iron.

Extract from the leaves of Toona sinensis roemor exerts potent antiproliferative effect on human lung cancer cells

Recent study indicated that the components of Toona sinensis Roemor have potent anti-inflammatory and analgesic effects. These components have also been reported to inhibit the growth of boils in vivo. In this study, we investigated the effect of crude extract from the leaves of Toona sinensis Roemor on the proliferation of A549 lung cancer cells. We found that the extract effectively blocked cell cycle progression by inhibiting the expression of cyclin D1 and E in A549 cells. Additionally, incubation of the extract led to activation of caspase-3-like proteases and apoptotic cell death. Conversely, the extract did not show any significant cytotoxic effect on primarily cultured human foreskin fibroblasts or MRC-5 human lung fibroblasts. Therefore, antiproliferative action of the extract is specific for tumor cells. Our results suggest that the components of Toona sinensis Roemor have potent anticancer effects in vitro and identification of the useful components in the extract may lead to the development of a novel class of anticancer drugs.

S29 ribosomal protein induces apoptosis in H520 cells and sensitizes them to chemotherapy

Non-small cell lung cancer (NSCLC) is the most prevalent type of lung cancer especially in India and displays resistance to anticancer treatment. In our earlier study we had isolated a cDNA clone from rat thymocytes induced to undergo apoptosis, which was found to encode S29 ribosomal protein [Biochem. Biophys. Res. Commun. 277 (2000) 476]. In the present study an attempt has been made to find out whether enhanced expression of S29 cDNA can kill NSCLC H520 cells. We found that S29 induced apoptosis and augmented the effect of anticancer drugs. Expressions of several molecular determinants of apoptosis were analyzed in order to understand the mechanism of apoptosis induced by S29. We observed downregulation of the expression of inhibitors of apoptosis proteins (IAPs) Bcl-2, Bcl-X(L), and survivin and upregulation of pro-apoptotic p53 and Bax as assessed by Western blotting. Mitochondrial release of cytochrome c and activation of initiator caspase-8 and -9 and effector caspase-3, followed by cleavage of nuclear substrate poly(ADP-ribose) polymerase, were also observed. Permeability transition as determined by changes in DeltaPsi(m) was not a requirement for cytochrome c release. There was a marginal increase in the release of apoptosis inducing factor (AIF) and reduction of NF-kappaB dependent transcriptional activity. There was non-involvement of calcium and the telomerase activity, a proliferation marker.

Paclitaxel-induced apoptosis in BJAB cells proceeds via a death receptor-independent, caspases-3/-8-driven mitochondrial amplification loop

Caspase-8 is a key effector of death-receptor-triggered apoptosis. In a previous study, we demonstrated, however, that caspase-8 can also be activated in a death receptor-independent manner via the mitochondrial apoptosis pathway, downstream of caspase-3. Here, we show that caspases-3 and -8 mediate a mitochondrial amplification loop that is required for the optimal release of cytochrome c, mitochondrial permeability shift transition, and cell death during apoptosis induced by treatment with the microtubule-damaging agent paclitaxel (Taxol). In contrast, Smac release from mitochondria followed a different pattern, and therefore seems to be regulated independently from cytochrome c release. Taxol-induced cell death was inhibited by the use of synthetic, cell-permeable caspase-3- (zDEVD-fmk) or caspase-8-specific (zIETD-fmk) inhibitors. Apoptosis signaling was not affected by a dominant-negative FADD mutant (FADD-DN), thereby excluding a role of death receptor signaling in the amplification loop and drug-induced apoptosis. The inhibitor experiments were corroborated by the use of BJAB cells overexpressing the natural serpin protease inhibitor, cytokine response modifier A. These data demonstrate that the complete activation of mitochondria, release of cytochrome c, and execution of drug-induced apoptosis require a mitochondrial amplification loop that depends on caspases-3 and -8 activation. In addition, this is the first report to demonstrate death receptor-independent caspase-8 autoprocessing in vivo.

Granulocyte colony-stimulating factor inhibits spontaneous cytochrome c release and mitochondria-dependent apoptosis of myelodysplastic syndrome hematopoietic progenitors

Low-risk myelodysplastic syndromes (MDS), including refractory anemia and sideroblastic anemia, are characterized by increased apoptotic death of erythroid progenitors. The signaling pathways that elicit this pathologic cell death in MDS have, however, remained unclear. Treatment with erythropoietin in combination with granulocyte colony-stimulating factor (G-CSF) may synergistically improve the anemia in patients with MDS, with a concomitant decrease in the number of apoptotic bone marrow precursors. Moreover, we have previously reported that G-CSF inhibits Fas-induced caspase activation in sideroblastic anemia (RARS). The present data demonstrate that almost 50% of erythroid progenitor cells derived from patients with MDS exhibit spontaneous release of cytochrome c from mitochondria with ensuing activation of caspase-9, whereas normal erythroid progenitors display neither of these features. G-CSF significantly inhibited cytochrome c release and suppressed apoptosis, most noticeably in cells from patients with sideroblastic anemia. Furthermore, inhibition of caspase-9 suppressed both spontaneous and Fas-mediated apoptosis of erythroid progenitors in all low-risk MDS cases studied. We propose that the increased sensitivity of MDS progenitor cells to death receptor stimulation is due to a constitutive activation of the mitochondrial axis of the apoptotic signaling pathway in these cells. These studies yield a mechanistic explanation for the beneficial clinical effects of growth factor administration in patients with MDS, and provide a model for the study of growth factor-mediated suppression of apoptosis in other bone marrow disorders.

Influence of p53 and p21(WAF1) expression on sensitivity of cancer cells to cladribine

The present study was performed to gain insight into the role of p53 and p21(WAF1) on the cytotoxicity of the purine analogue cladribine (2-CdA) on cancer cells. Drug sensitivity, cell cycle distribution and drug-induced cell death were compared in three lines derived from the colorectal carcinoma HCT116: the p53+/+ cell line containing wild-type p53 and the p53-/- and p21(WAF1)-/- lines, in which both alleles of p53 or p21(WAF1) were deleted by homologous recombination, respectively. p53-/- and p21(WAF1)-/- cells were significantly more resistant to the cytotoxic effects of 2-CdA than the p53+/+ cells. p53+/+ cells and p21(WAF1)-/-, but not p53-/- cells, displayed wt-p53 protein accumulation and arrested in S-phase after exposure to 2-CdA. mRNA analysis of the transporter hENT1 and of enzymes involved in drug metabolism did not show alterations which might explain a drug-resistant phenotype in the p53-/- or p21(WAF1)-/- cells. Exposure of p53+/+ cells to 2-CdA resulted in expression of p21(WAF1) mRNA and protein, enhanced expression of uncleaved PARP-1, and a higher degree both of apoptosis and necrosis than in p53-/- and p21(WAF1)-/- cells exposed to 2-CdA. Addition of the specific PARP-1 inhibitor 3-AB to 2-CdA-treated cells rendered p53+/+ cells resistant to this drug. Bax levels were reduced in the p53-/- while they increased in the p53+/+ line and remained stable in the p21(WAF1)-/- cells. We conclude that p53 and p21(WAF1) status of cancer cells influences their sensitivity to 2-CdA cytotoxicity. This may involve alterations in the apoptotic cascade as well as in PARP-1-dependent cell death.

The sensitizer 2,4-dinitrofluorobenzene activates caspase-3 and induces cell death in a skin dendritic cell line

In this work, a dendritic cell line derived from mouse skin (FSDC) was used, as an in vitro experimental model, to evaluate the cytotoxic effect of two chemical sensitizers, a strong sensitizer (2,4-dinitrofluorobenzene, DNFB) and a weak sensitizer (2,4-dichloronitrobenzene, DCNB). The results indicated that DNFB reduces the cellular metabolism of FSDC, as evaluated by the reduction of the tetrazolium salt, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT). All the DNFB concentrations tested, ranging from 5.2 micro M to 26 micro M, significantly inhibited the MTT reduction after 1 hour of cell exposure to the sensitizer. In contrast, incubation of FSDC with the weak sensitizer DCNB had no significant effect on the MTT reduction assay. When the cells were incubated with DNFB (13 micro M), for 3 and 6 hours, morphological changes characteristics of cell death by apoptosis were observed, as assessed by propidium iodide (PI) DNA staining and annexin-V externalization analysis. These results correlate well with an increase of caspase-3-like activity after FSDC exposure to DNFB (13 micro M) for 6 hours. Together, these results indicate that apoptotic death of skin dendritic cells occurs after exposure to the sensitizer DNFB, although necrotic cell death was also observed when the cells were incubated with high concentrations of DNFB (26 micro M), or after long periods of cell exposure to the chemical DNFB (13 micro M, for 6 hours).

Molluscum contagiosum: recent advances in pathogenic mechanisms, and new therapies

Two poxviruses, Molluscum contagiosum virus (MCV) and Variola virus are specific to humans. MCV is present worldwide and is directly passed by direct skin to skin contact to produce cutaneous and, rarely, mucosal lesions. It occurs predominantly in preadolescent children, sexually active adults, participants in sports with skin to skin contact, and in individuals with impaired cellular immunity. MCV characteristically proliferates within the follicular epithelium, and with routine fixation produces an area of retraction artifact separating layers 1 to 3 of CD34+ stromal cells that immediately surround the follicle from the surrounding dermis. This feature may be obscured when the lesions are inflamed, usually after rupture into the surrounding dermis. MCV is a cytoplasmically replicating virus. MCV-infected cells grow in size, while internal organelles are dislocated and eventually obliterated by a large intracytoplasmic inclusion. Rupture and discharge of the virus-packed cells occurs in a process similar to membrane debris and MCV accumulate in the crater-like ostium; MCV infection is spread by contact with infectious debris. In HIV-1-positive patients the histologic features, as well as the clinical features, may be atypical in patients with MCV infections. Not only are the lesions often large, but they may be verrucous and markedly hyperkeratotic. Recent sequencing of the MCV genome has increased our understanding and investigations into its mechanisms for avoiding host defense mechanisms. These include regions which encode for homologues of cellular chemokines and chemokine-binding proteins, a homolog of MHC1 and a viral FLICE-like inhibitory protein. Treatment, until recently, has depended upon tissue destruction including curettage, cryotherapy, CO(2) laser, electrodesiccation, trichloracetic acid and cantharadin. Recently, topical immune modulators have been used with some success. Understanding of the MCV genome is providing the basis for the development of drugs for therapy and prevention of MCV infections.

Identification of a novel gelsolin truncate in the vertical and metastatic phase malignant melanomas

Examination of 38 human melanoma samples by Western blotting analysis with anti-gelsolin antibodies showed that a new 85 kDa truncated gelsolin (GSNp85), co-expressed with wild-type gelsolin, was frequently expressed in vertical growth phase melanomas (Clark level II-IV) and metastatic growth phase melanomas. The GSNp85 truncate was not expressed in radial growth phase melanomas (Clark level I), acquired naevi, other skin cancers or normal skin tissues. Peptide-sequencing analysis revealed that GSNp85 lacks the C-terminal domain of wild-type gelsolin at the region containing the caspase-8 recognition site IETD. Caspase-8 processing was detected in GSNp85-positive but not GSNp85-negative melanomas. These data suggest that GSNp85 is a cleavage product of caspase-8 and may be useful as a new marker for the vertical or metastatic growth phase of malignant melanoma.

In vitro evaluation of bendamustine induced apoptosis in B-chronic lymphocytic leukemia

Bendamustine is a novel cytostatic agent, with activity in non-Hodgkin's lymphomas including B-chronic lymphocytic leukemia (B-CLL). The knowledge about its mode of action, however, is still limited. Here, we investigated the in vitro ability of bendamustine to induce apoptosis on freshly isolated peripheral lymphocytes in B-CLL and analyze the potential underlying mechanisms of action for inducing apoptosis. In CLL cells taken from 37 previously treated and untreated CLL patients, we investigated the influence of bendamustine alone, and in combination with fludarabine, on the induction of apoptosis and changes of Bcl-2 and Bax expression on mRNA and protein level using the RNase protection assay or flow cytometry, respectively. Apoptotic cells were determined with flow cytometry using the fluorescent DNA-binding agent 7-ADD. Using bendamustine alone in concentrations from 1 microg/ml to 50 microg/ml, a dose- and time-dependent manner of cytotoxicity from 30.4% to 94.8% after 48 h could be observed. The LD50 for untreated and pretreated CLL cells was 7.3 or 4.4 microg/ml, respectively. The median apoptotic rate was similar in both groups. The combination of bendamustine with fludarabine led to a highly synergistic effect in inducing apoptosis, which was 150% higher than expected for bendamustine plus fludarabine. The level of the initial Bcl-2 and Bax protein and the m-RNA expression remained unchanged during the incubation with bendamustine. In conclusion, this study demonstrates for the first time the in vitro efficacy of bendamustine in inducing apoptosis in B-CLL cells alone and in combination with fludarabine.