[Weekly variation of sudden cardiac death in northen Tunisia]

BACKGROUND

The sudden cardiac death remains a major public health problem. Several studies have reported weekly variation of this dramatic event.

AIM

The aim of this work is to determine the day-of-week variability in sudden cardiac death in northen Tunisia.

METHODS

We prospectively collected clinical, socio demographic and autopsic data of victims of sudden cardiac death occurring in the northern Tunisia between october 1 st ,2010 and september 30,2012.

RESULTS

The study population included 392 men and 108 women with a mean age of 52.27 + / - 15.8 years. Three quarters of the victims was sedentary, 57.9% were smoker and a family history of sudden death was identified in 9.8% of cases. The vast majority of deaths had occurred either in a public place (41.4%) or at home (36.6%). Ischemic heart disease was the leading cause of death with 267 cases (53.4%); however a negative autopsy was found in 13.9% of victims. The highest sudden death occurrence was on Sundays (17.8%) and the lowest on Mondays (11.4% p: 0.01).The same weekly variation was noted among both men and women , and also in victims > 60 years, a minimum of events occurred on Mondays (11.6%) and a maximum on Sundays (21.9%). In addition, we found the same peak of mortality on Sunday (18.8%) in young adults and the nadir on Monday (10.3%).

CONCLUSIONS

The present study demonstrates marked variation in the occurrence of sudden cardiac death in the northern Tunisia with peak on Sundays and nadir on Mondays. No age or gender- related differences were found in weekly variation of sudden death.

WNT signaling and chondrocytes: from cell fate determination to osteoarthritis physiopathology

CONTEXT

Osteoarthritis (OA) is an articular disorder leading to the degradation of articular cartilage phenotypical chondrocytes modifications, including the acquisition of a fibroblast-like morphology, decreased expression of collagen type II, and increased expression of fetal collagen type I, metalloproteinase 13 and nitric oxide synthase. This promotes matrix degradation and unsuccessful cartilage repair. WNT signaling constitutes one of the most critical biological processes during cell fate assignment and homeostasis.

OBJECTIVES

This review aims to give an insight on results from the studies that were interested in the involvement of WNT in OA.

METHODS

Studies were selected through a pubmed search.

RESULTS

Recent genetic data showed that aberration in WNT signaling may be involved in OA. WNT signals are transduced through at least three cascades: the canonical WNT/β-catenin pathway, the WNT/Ca(2+) pathway and the WNT/planar cell polarity pathway. Most of the studies used in-vitro models to elucidate the involvement of WNT in the physiopathology of OA. These studies analyzed the expression pattern of WNT pathway components during OA such as WNT5, WNT7, co-receptor LRP, β-catenin, WNT target genes (c-jun, cyclins) and/or the interaction of these components with the secretion of OA most important markers such as IL-1, collagens, MMPs. Results from these studies are in favor of a deep involvement of the WNT signaling in the physiopathology of OA either by having a protective or a destructive role.

CONCLUSION

Deeper researches may eventually allow scientists to target WNT pathway in order to help develop efficient therapeutic approaches to treat OA.

Notch signaling is involved in human articular chondrocytes de-differentiation during osteoarthritis

CONTEXT

During osteoarthritis (OA), chondrocytes undergo de-differentiation, resulting in the acquisition of a fibroblast-like morphology, decreased expression of collagen type II (colII) and aggrecan, and increased expression of collagen type I (colI), metalloproteinase 13 (MMP13) and nitric oxide synthase (eNOS). Notch signaling plays a crucial role during embryogenesis. Several studies showed that Notch is expressed in adulthood.

OBJECTIVE

The aim of our study was to confirm the involvement of Notch signaling in human OA at in vitro and ex vivo levels.

MATERIALS AND METHODS

Normal human articular chondrocytes were cultured during four passages either treated or not with a Notch inhibitor: DAPT. Human OA cartilage was cultured with DAPT for five days. Chondrocytes secreted markers and some Notch pathway components were analyzed using Western blotting and qPCR.

RESULTS

Passaging chondrocytes induced a decrease in the cartilage markers: colII and aggrecan. DAPT-treated chondrocytes and OA cartilage showed a significant increase in healthy cartilage markers. De-differentiation markers, colI, MMP13 and eNOS, were significantly reduced in DAPT-treated chondrocytes and OA cartilage. Notch1 expression was proportional to colI, MMP13 and eNOS expression and inversely proportional to colII and aggrecan expression in nontreated cultured chondrocytes. Notch ligand: Jagged1 increased in chondrocytes culture. DAPT treatment resulted in reduced Jagged1 expression. Notch target gene HES1 increased during chondrocyte culture and was reduced when treated with DAPT.

CONCLUSION

Targeting Notch signaling during OA might lead to the restitution of the typical chondrocyte phenotype and even to chondrocyte redifferentiation during the pathology.

Sudden death due to hydatid disease: a six-year study in the northern part of Tunisia

Human ecchinococcosis also known as hydatid disease is a zoonotic infection caused by the tapeworm Ecchinococcus with 2-3 Million cases worldwide. We hereby report a 6 years period study of Sudden death due to hydatidosis aiming to analyze the epidemiological criteria, death circumstances, and autopsy observations attributed to hydatid disease. During the past 6 years, 26 death cases were due to hydatid disease. Our analysis shows that the sex ratio (M/F) was 1.6, the mean age was 31-year old, and 65% of the subjects lived in rural places. In 17 cases, death occurred in the victim's place, five victims died after a heavy exercise, and in two cases, death occurred immediately after trauma. At autopsy, 91% of the cysts were found in the liver. In three cases, death followed a septic state, and in two cases, it followed an acute respiratory failure. Death was attributed to anaphylaxis in 17 cases.

Wnt signaling is involved in human articular chondrocyte de-differentiation in vitro

Osteoarthritis is the most prevalent form of arthritis in the world. Certain signaling pathways, such as the wnt pathway, are involved in cartilage pathology. Osteoarthritic chondrocytes undergo morphological and biochemical changes that lead to chondrocyte de-differentiation. We investigated whether the Wnt pathway is involved in de-differentiation of human articular chondrocytes in vitro. Human articular chondrocytes were cultured for four passages in the presence or absence of IL-1 in monolayer or micromass culture. Changes in cell morphology were monitored by light microscopy. Protein and gene expression of chondrocyte markers and Wnt pathway components were determined by Western blotting and qPCR after culture. After culturing for four passages, chondrocytes exhibited a fibroblast-like morphology. Collagen type II and aggrecan protein and gene expression decreased, while collagen type I, matrix metalloproteinase 13, and nitric oxide synthase expressions increased. Wnt molecule expression profiles changed; Wnt5a protein expression, the Wnt target gene, c-jun, and in Wnt pathway regulator, sFRP4 increased. Treatment with IL-1 caused chondrocyte morphology to become more filament-like. This change in morphology was accompanied by extinction of col II expression and increased col I, MMP13 and eNOS expression. Changes in expression of the Wnt pathway components also were observed. Wnt7a decreased significantly, while Wnt5a, LRP5, β-catenin and c-jun expressions increased. Culture of human articular chondrocytes with or without IL-1 not only induced chondrocyte de-differentiation, but also changed the expression profiles of Wnt components, which suggests that the Wnt pathway is involved in chondrocyte de-differentiation in vitro.

The roles of canonical and non-canonical Wnt signaling in human de-differentiated articular chondrocytes

Osteoarthritis is the most prevalent form of arthritis in the world and it is becoming a major public health problem. Osteoarthritic chondrocytes undergo morphological and biochemical changes that lead to de-differentiation. The involvement of signaling pathways, such as the Wnt pathway, during cartilage pathology has been reported. Wnt signaling regulates critical biological processes. Wnt signals are transduced through at least three intracellular signaling pathways including the canonical Wnt/β-catenin pathway, the Wnt/Ca2 + pathway and the Wnt/planar cell polarity pathway. We investigated the involvement of the Wnt canonical and non-canonical pathways in human articular chondrocyte de-differentiation in vitro. Human articular chondrocytes were cultured through four passages with no treatment, or with sFRP3 treatment, an inhibitor of Wnt pathways, or with DKK1 treatment, an inhibitor of the canonical pathway. Chondrocyte-secreted markers and Wnt pathway components were analyzed using western blotting and qPCR. Inhibition of the Wnt pathway showed that the canonical Wnt signaling probably is responsible for inhibition of collagen II expression, activation of metalloproteinase 13 expression and regulation of Wnt7a and c-jun expression during chondrocyte de-differentiation in vitro. Our results also suggest that expressions of eNOS, Wnt5a and cyclinE1 are regulated by non-canonical Wnt signaling.

[Sudden death during sport activity in Tunisia: autopsy study in 32 cases]

PURPOSE

To develop profile of the victims and to study circumstances, causes of death and autopsy findings.

METHODS

Retrospective study of cases of sudden death in sport activity whose autopsy was performed in forensic department of Tunis, between January 2005 and December 2009.

RESULTS

During study period, 32 cases of SD in sport activity were recorded. These are amateur athletes predominantly male (84% of cases). Victims are aged between 15 and 79 years with an average age of about 33.16 years. Young subjects whose age is less than 35 years representing 68.7% of cases. 9.3% of victims had a family history of SD and 18.7% of cases had a known cardiac history. The sports most involved are running (40.6% of cases), football (31.3% of cases) and dance (12.5% of cases). Sixty-nine percent of victims died during sports activities. Presence of witnesses was noted in all cases; however, none of these witnesses has begun resuscitation. Cause of death was cardiac in 84.4% of cases. In young athletes, hypertrophic cardiomyopathy is the leading cause (nine cases), followed by arrhythmogenic right ventricular dysplasia (three cases). Among other causes, there is the myocardial bridge, congenital anomalies of the coronary arteries, aortic dissection and dilated cardiomyopathy. Beyond 35 years, coronary artery diseases represent the cause of death (nine cases). Only case of death secondary to non-cardiac disease occurred after a severe asthma attack. In four cases (12.5%), no cause of death was identified after a complete autopsy accompanied by further investigations. The cause of the death was imputed to a rhythmic pathology.

CONCLUSION

This is the first study dealing with autopsy in SD in sport have provided a specific profile of victims. Other studies on larger samples and using standardized autopsy protocols are needed.

Expression patterns of Notch receptors and their ligands in human osteoarthritic and healthy articular cartilage

Notch pathway plays a pivotal role in cell fate determination. There is much interest surrounding its therapeutic potential, in osteoarthritis, but the expression profile of Notch-related molecules, as well as their relation with cartilage pathological parameters, remains unclear. The purpose of our study is to analyze the expression pattern of Notch family members, type II and type I collagen, in normal (healthy) and osteoarthritic human knee cartilage. Osteoarthritic cartilages were obtained from 3 patients undergoing a total knee replacement. Macroscopically normal cartilage was dissected from 3 human knees at the time of autopsy or surgery. Immunohistochemical staining was performed using Notch1,2,3 and 4, Delta, Jagged, type II collagen and type I collagen antibodies. In healthy cartilage, type II collagen was abundantly expressed while type I was absent. This latter increased proportionally to the osteoarthritic grade. Type II collagen expression remained intense in osteoarthritic cartilage. In healthy cartilage as well as in cartilage with minor lesions, Notch family member's proteins were not or just weakly expressed at the surface and in the cells. However, Notch molecules were over-expressed in osteoarthritic cartilage compared to healthy one. This expression pattern was different according to the cartilage zone and the severity of OA. Our data suggest that Notch signaling is activated in osteoarthritic cartilage, compared to healthy cartilage, with a much more abundant expression in the most damaged areas.

[Rudimentary horn pregnancy: an unusual cause of spontaneous hemoperitoneum during the second-trimester of pregnancy]

Spontaneous hemoperitoneum during pregnancy is an unusual but serious event. We report a case of profuse spontaneous hemoperitoneum resulting from the rupture of a non-communicating rudimentary uterine horn at 26 weeks of gestation. An emergency laparotomy was performed and a 900 g birth weight safe infant was delivered. We performed a hemi-hysterectomy in the same time. Fetal and maternal outcomes resulted without complication. Causes of spontaneous hemoperitoneum are discussed.

Genetic identification of decomposed cadavers using nails as DNA source

Blood or muscle can be used as a DNA source for the genetic identification of recently deceased persons. If the post mortem interval increases, bones and teeth are used. In this case, collection and DNA isolation will be more difficult and time consuming. The aim of this study was to evaluate the use of nails as an alternative DNA source for the genetic identification of decomposed cadavers. DNA extraction from 5mg of fingernails from 7 volunteers using 1h cell lysis in a standard buffer and a DNA purification on QIAamp DNA mini kit columns allowed to acquire a mean quantity of 100 ng DNA/mg nail. This was unexpected, as blood and muscle contain comparable amounts of DNA. Our protocol allowed to obtain full PowerPlex 16 DNA profiles from 10 cadavers characterized by post mortem intervals ranging from 5 days to more than 6 months. The good quality of these profiles indicated that DNA from nail is well preserved. In conclusion, nails are very easy to collect and contain large amounts of good quality DNA that can be extracted within a few hours. They may therefore represent an attractive DNA source not only for routine, but also for urgent genetic identification of decomposed cadavers.

[Anxiety and depressive disorders in 4,425 long term benzodiazepine users in general practice]

Consumption rates of anxiolytic drugs, and especially of benzodiazepines, remain very high in France compared to other Western countries, whereas clinical guidelines limit their indications to short term treatments and only for some precise anxiety disorders. Recent epidemiologic surveys in the community indicated that more than 15% of people used once or more an anxiolytic drug in the past year. The issue of chronic treatments is particularly crucial because of their poor benefit/risk ratio in most anxiety disorders (limited efficacy, cognitive side effects, withdrawal and dependence problems). To address this important public health issue, and knowing that, in France, benzodiazepines are prescribed mainly by general physicians, our aims were to explore psychiatric diagnoses in GP's patients with chronic use of anxiolytic benzodiazepines. We included 4 425 patients consuming such drugs regularly for six months or more, and assessed their anxiety and depression symptoms through various clinical scales (Hospital Anxiety and Depressive scale - HAD, Clinical Global Impression scale - CGI, Sheehan Disability Scale - SDS, Cognitive Dependence to Benzodiazepines scale - CDB) and with the Mini International Neuropsychiatric Interview for DSM IV criteria. Only 2.2% of the subjects had neither anxious nor depressive symptoms as indicated by low scores on both subscores (less than 8) of the HAD scale, used as a screener. Nearly three quarters of the 4,257 subjects (73.2%), had CGI scores of at least 5 (markedly ill to extremely ill). Social and familial disability was also high in more than 40% of the sample (marked to extreme disruption according to SDS scores). About half of the sample had CDB scores suggesting a benzodiazepine dependence. According to the MINI, 85.1% of the patients had at least one current DSM IV diagnosis of affective disorder. The most frequent diagnoses were major depressive episode (60%), generalized anxiety disorder (61.2%), and panic disorder (22.5%). An anxiety and depressive comorbidity wad found in 41.9% of the subjects. Some methodological limitations must be taken into account in the discussion of our results, and especially the fact that the included patients were not supposed to be totally representative of all patients consuming anxiolytic benzodiazepines in general practice. However, the size of our sample is sufficiently large to limit possible biases in patient selection. The main result of this study is that a great majority of the patients had significant symptomatology, in particular major depressive episodes and generalized anxiety disorder, often with marked severity and disability. These data are in line with the knowledge of a lack of efficacy of benzodiazepines in depressive and most anxiety disorders, despite long term treatment. They also confirm the current guidelines which recommend prescribing serotoninergic antidepressants, and not benzodiazepines, when long term treatments are needed for severe and chronic affective disorders. This epidemiologic study leads to the conclusion that a specific and attentive diagnostic assessment should be done in all patients receiving benzodiazepines for more than three months, in order to purpose in many cases other long term therapeutic strategies.

A crosstalk between the Wnt and the adhesion-dependent signaling pathways governs the chemosensitivity of acute myeloid leukemia

Relapses following chemotherapy are a major hindrance to patients' survival in acute myeloid leukemia (AML). To investigate the role of the hematopoietic niche in the chemoresistance of leukemic cells, we examined two pathways: one mediated by adhesion molecules/integrins, and the other by soluble factors of the morphogen Wnt pathway. In our study, both the adhesion of leukemic blasts to fibronectin and the addition of Wnt antagonists induced, independently, resistance of AML cells to daunorubicin in a cell survival assay. Using pharmacological inhibitors and siRNA, we showed that both resistance pathways required the activity of the glycogen synthase kinase 3beta (GSK3beta). Moreover, the AML cell protection downstream of GSK3beta was mediated by NF-kappaB. A link between the adhesion and the Wnt pathway was found, as adhesion of U937 on human osteoblasts, a component of the hematopoietic niche, triggered the secretion of the Wnt antagonist sFRP-1 and supported resistance to daunorubicin. The osteoblast-conditioned medium could also confer chemoresistance to U937 cells cultured in suspension, and this cell protective effect was abrogated after depletion of sFRP-1. In the context of this potential double in vivo resistance, modulators of the common signal GSK3beta and of its target NF-kappaB could represent important novel therapeutic tools.

Establishment of a novel anaplastic large-cell lymphoma-cell line (COST) from a ‘small-cell variant’ of ALCL

Anaplastic large-cell lymphoma (ALCL) is a distinct biological and cytogenetic entity with a broad spectrum of morphological features (common type, small-cell variant and lymphohistiocytic variant). Few cell lines of ALCL are available and they all originate from primary tumors demonstrating the common type morphology (ie large-sized lymphoma cells). We established a new ALCL cell line (COST) from the peripheral blood of a patient with a small-cell variant of ALCL, at diagnosis. Cells growing in vitro and in SCID mice consisted of two populations, that is, small- and large-sized cells as seen in the patient's tumor. Both large and small malignant cells were positive for CD43/MT1 T-cell associated antigen, perforin, granzyme B and TIA-1, but negative for CD2, CD3, CD5, CD7, CD4 and CD8 antigens. Standard cytogenetic studies as well as multiplex FISH confirmed the presence of the canonical t(2;5)(p23;q35) translocation, but also revealed additional numerical and structural abnormalities. The COST cell line is the first ALCL small-cell variant cell line, and thus provides a potentially useful tool for further functional and molecular studies that should improve our understanding of the small-cell variant of ALCL, which is more frequently complicated by a leukemic phase.

Expression of the oncogenic NPM-ALK chimeric protein in human lymphoid T-cells inhibits drug-induced, but not Fas-induced apoptosis

Anaplastic large cell lymphomas (ALCLs) are frequently associated with the t(2;5)(p23;q35) translocation, leading to the expression of NPM-ALK, a fusion protein linking nucleophosmin and anaplastic lymphoma kinase, a receptor tyrosine kinase. In ALCLs, dimerization of NPM-ALK leads to constitutive autophosphorylation and activation of the kinase, necessary for NPM-ALK oncogenicity. To investigate whether NPM-ALK, like other oncogenic tyrosine kinases, can inhibit drug-induced apoptosis, we permanently transfected NPM-ALK into Jurkat T-cells. As in ALCLs, NPM-ALK was expressed as a constitutively kinase-active 80 kDa protein, and could be detected by immunocytochemistry in nucleoli, nuclei and cytoplasm. Doxorubicin-induced apoptosis (assessed by cell morphology and annexin V-FITC binding) was significantly inhibited in two independent NPM-ALK-expressing clones (5.2+/-1.8 and 7.5+/-0.8% apoptosis), compared to control vector-transduced cells (36+/-6.7%). Similar results were observed with etoposide. In contrast, Fas-induced apoptosis was not inhibited. Cytochrome c release into the cytosol was delayed in doxorubicin-, but not anti-Fas-treated transfectant cells, indicating that apoptosis inhibition occurred upstream of mitochondrial events. Using NPM-ALK mutants, we demonstrated that inhibition of drug-induced apoptosis: (1) requires functional kinase activity, (2) does not involve phospholipase C-gamma, essential for NPM-ALK-mediated mitogenicity and (3) appears to be phosphoinositide 3-kinase independent, despite a strong Akt/PKB activation observed in wild type NPM-ALK-expressing cells. These results suggest that the NPM-ALK antiapoptotic and mitogenic pathways are distinct.

Ligation of the CD44 adhesion molecule inhibits drug-induced apoptosis in human myeloid leukemia cells

Adhesion molecules can improve hematopoietic cell survival; however, their role in leukemic cell resistance to drug-induced apoptosis is poorly documented. The CD44 adhesion molecule is strongly expressed on acute myeloid leukemia (AML) blasts. Using 2 myeloid cell lines, HL60 and NB4, evidence is presented that prior incubation with the CD44-specific monoclonal antibody (mAb) A3D8, reported to induce differentiation of AML blasts, significantly decreases apoptosis induced by 3 drugs used in AML chemotherapy: daunorubicin (DNR), mitoxantrone, and etoposide. In addition, in HL60 cells, CD44 ligation with A3D8 mAb fully abrogates the DNR-triggered generation of ceramide, a lipid second messenger involved in the DNR apoptotic signaling pathway. Moreover, results show that the A3D8 mAb and Bcl-2 additively inhibit DNR-induced apoptosis in HL60 cells overexpressing Bcl-2. These results suggest that, to eradicate AML blasts, the differentiation-inducing anti-CD44 mAb A3D8 should not be administered prior to apoptosis-inducing drugs.

Autocrine IL-2-dependent growth of a newly established CD3+, CD16−, CD56+, CD57+, JH−, TCRβ−, TCRγ− leukemia cell line (NOI-90)

Leukemic cells from a 45-year-old male patient with a CD3+, CD56+, CD57+, CD7+ acute lymphoblastic leukemia were cultured in vitro in the absence of any added growth factor for up to 6 years and a continuous lymphoblastoid cell line (NOI-90) was established. NOI-90 cells have the same phenotype and karyotype as initial leukemic cells. Southern blot of DNA from NOI-90 cells showed that TCRbeta, TCRgamma, and J(H) were in germ line. Two and 25% of NOI-90 cells were positive when stained with the IOT14 and 7G7/B6 moAbs, which recognize the CD25 molecule (IL-2R alpha chain); moreover, 4% and 13% of the cells were positive when stained with the TU-27 and mik beta3 moAbs which recognize the CD122 molecule (IL-2Rbeta chain). Equilibrium binding experiments with radiolabelled IL-2 revealed the presence of a small number of high affinity IL-2R on both fresh and continuously growing cells. Media conditioned by NOI-90 cells could induce proliferation of an IL-2-dependent cell line and this IL-2 activity could be detected by a sensitive immunoenzymatic assay using antibodies recognizing distinct epitopes of IL-2. Moreover, IL-2 activity could be adsorbed by immunoaffinity on anti-IL-2 polyclonal purified IgG and the retained molecule displayed a m.w. of 14.5 kDa in SDS-PAGE. In addition, IL-2 immunoreactive molecules could be revealed in the cytoplasm of the cells. Finally, IL-2 fixed on the cell membrane could be detected by indirect immunofluorescence. Although added IL-2 could not induce cell proliferation, monoclonal antibodies against CD25, CD122 and IL-2 could specifically inhibit spontaneous cell proliferation in a dose-dependent manner. NOI-90 cells failed to demonstrate any cytotoxic activity against the K-562, Raji or Daudi cells. These findings indicate that NOI-90 cells are of non-T, non-B, origin lacking NK activity but proliferate under an autocrine pathway which involves, at least partly, the IL-2/IL-2R system.

Influence of Bcl-2 overexpression on the ceramide pathway in daunorubicin-induced apoptosis of leukemic cells

We have previously demonstrated that daunorubicin (DNR) induces apoptosis in some leukemic myeloid cell lines. We investigated a potential protective role for Bcl-2 in apoptosis induced by DNR in two leukemic cell lines, one myeloid and one lymphoid, overexpressing the anti-apoptotic gene Bcl-2. Parental cells treated with DNR exhibited classical features of apoptosis 6 h after drug exposure, all the cells being dead after 30-48 h. In contrast, overexpression of Bcl-2 significantly delayed, but did not prevent the occurrence of DNR-induced apoptosis, with no surviving cells 96 h after drug exposure. To elucidate the mechanism of the protection mediated by Bcl-2, we explored the signaling pathway which initiates DNR-induced apoptosis. In this report, we show that, in both the myeloid and lymphoid parental cell lines, DNR triggered a sphingomyelin (SM) hydrolysis after 10-15 min with a concomitant ceramide generation. Moreover, exogenous ceramide induced DNA fragmentation in these cells, with levels similar to those observed with DNR treatment. In contrast, Bcl-2 overexpression protected the cells against apoptosis induced by ceramide treatment, without preventing the early SM hydrolysis nor the ceramide generation in these cells. Our results strongly suggest that Bcl-2-mediated protection of DNR-induced apoptosis is effected downstream of the SM-ceramide signaling pathway.

Increased gadd153 messenger RNA level is associated with apoptosis in human leukemic cells treated with etoposide

Treatment of leukemic cells with topoisomerase inhibitors can lead to growth arrest and subsequent apoptotic cell death. The relationships between cell cycle regulation and apoptosis triggering remain poorly understood. The gadd153 gene encodes the nuclear protein CHOP 10 that acts as a negative modulator of CCAAT/enhancer binding protein transcriptional factors and inhibits cell cycle progression. We have investigated the relationships between gadd153 gene expression and apoptosis induction in four human leukemic cell lines with different sensitivities to apoptosis induced by etoposide (VP-16), a topoisomerase II inhibitor. The gadd153 gene was constitutively expressed in the four studied cell lines. In U937 and HL-60 cells that were very sensitive to apoptosis induction by the drug, VP-16 induced a time- and dose-dependent increase of gadd153 gene mRNA expression. Using agarose gel electrophoresis and a quantitative filter elution assay, apoptotic DNA fragmentation was observed to begin when gadd153 gene expression increased. Equitoxic doses of VP-16 (as defined using a 96-h 3-4,5-dimethylthiazol-2,5-diphenyltetrazolium bromide assay) did not increase the gadd153 mRNA level in K562 and KCL22 cell lines that were more resistant to apoptosis induction by the drug. Nuclear run-on and mRNA stability experiments demonstrated that VP-16 treatment increased gadd153 gene transcription in the sensitive U937 cells. Cycloheximide did not prevent gadd153 expression increase. Both gadd153 mRNA level increase and internucleosomal DNA fragmentation were inhibited by N-tosyl-L-phenylalanine chloromethylketone, a serine threonine protease inhibitor, N-acetyl-leucyl-leucyl-norleucinal, an inhibitor of calpain, N-acetylcysteine, an inhibitor of oxidative metabolism, and overexpression of Bcl-2. Z-VAD and Z-DEVD peptides that inhibit interleukin 1beta-converting enzyme-like proteases suppressed DNA fragmentation without preventing gadd153 mRNA increase in VP-16-treated U937 cells. These results indicate that gadd153 gene expression increase occurs downstream of events sensitive to N-tosyl-L-phenylalanine chloromethylketone, calpain inhibitor I, and Bcl-2 and upstream of interleukin 1beta-converting enzyme-related proteases activation in leukemic cells in which treatment with VP-16 induces rapid apoptosis.

Daunorubicin-induced internucleosomal DNA fragmentation in acute myeloid cell lines

The study was designed to evaluate the implication of apoptosis in myeloid leukemic cell death induced by daunorubicin (DNR) and to identify the possible factors which may influence this process. DNR-induced apoptosis was characterized by morphology and DNA fragmentation in six leukemic myeloid cell lines which expressed different differentiation phenotypes. In phenotypically mature HL-60 and U937 cells, DNR induced typical apoptosis with characteristic morphological changes and intense internucleosomal DNA fragmentation within a narrow concentration range (0.5-2 microM). When these cells were treated with higher doses of DNR, large DNA fragments (100 kbp), but not internucleosomal fragments, were identified. DNR-induced DNA fragmentation in HL-60 and U937 was inhibited by antioxidants such as N-acetylcysteine (N-ac) or pyrrolidine-dithiocarbamate (PDTC). In the phenotypically immature KG1a, KG1, HEL and ML1 cell lines DNR induced no characteristic apoptotic morphological features as well as very low levels of internucleosomal DNA fragmentation, whereas large DNA fragments (200 kbp) were observed in KG1a treated with 7 microM DNR. Since the latter expressed P-glycoprotein (P-gp), the role of P-gp in the lack of apoptotic response to DNR was investigated. One P-gp inhibitor (verapamil) slightly improved DNR-induced DNA fragmentation in KG1a cells whereas the combination of verapamil and buthionine-sulfoximine (BSO), which depletes glutathion store, further increased internucleosomal DNA fragmentation. In conclusion, DNR induced internucleosomal DNA fragmentation in some but not all AML cells; the magnitude of this process being influenced by both intracellular drug concentration and oxidative balance.

Basic fibroblast growth factor and hematopoiesis

Basic fibroblast growth factor (bFGF or FGF-2) is an angiogenic and pleiotropic factor involved in the proliferation and differentiation of numerous cell types. It is expressed mostly in tissues of mesoderm and neuroectoderm origin, and plays an important role in the mesoderm induction, together with transforming growth factor-beta (TGF-beta). Although hematopoietic cells derive from the mesoderm, relatively few studies have addressed the role of bFGF in the hematopoietic system until recently. It appears that bFGF is expressed and produced by bone marrow stromal cells, as well as by cells from several mature peripheral blood lineages. It is released and stored in the bone marrow extra-cellular matrix. FGF-receptors (FGF-Rs) are expressed on nearly every cell of hematopoietic origin tested so far. Growing evidence shows that bFGF can positively regulate hematopoiesis, by acting on various cellular targets: stromal cells, early and committed hematopoietic progenitors, and possibly some mature blood cells. It synergizes with hematopoietic cytokines, or antagonizes the negative regulatory effects of another factor, TGF-beta, thus potentially playing a central role in hematopoiesis.

Expression of basic fibroblast growth factor (bFGF) and FGF-receptors in human leukemic cells

Recent reports have suggested that basic fibroblast growth factor (bFGF) could play a permissive role in hematopoiesis, in combination with specific colony-stimulating factors. We investigated the expression of bFGF and FGF-receptors (FGF-Rs) in leukemic cell lines of various hematopoietic lineages. Three protein isoforms of bFGF of approximately 18, 22 and 24 kDa were detected in the myeloid cell line K562, but not in myelomonocytic or lymphoid (T or B) cell lines. In vitro-induced differentiation of K562 cells did not change the pattern of expression of the different bFGF isoforms. Accordingly, the mRNA of bFGF was found expressed in K562, but not in other leukemic lines tested, as assayed by reverse transcript amplification (RT-PCR). Using the same technique, we searched for the presence of high affinity FGF-Rs on these cells: in eight out of ten cell lines tested, mRNA for at least one FGF-R among FGF-R1, FGF-R3 or FGF-R4 was expressed, whereas FGF-R2 was never detected. We found that two cell lines were responsive to bFGF in different biological assays: (i) in K562 myeloid cells induced to differentiate by hemin, preincubation with bFGF and heparin increased cell viability and decreased hemin-induced DNA fragmentation, without affecting erythroid differentiation; and (ii) in U937 monocytic cells, the production of plasminogen activator was increased by bFGF or aFGF in combination with heparin. Binding experiments with 125I-bFGF (up to 200 pM) in the presence of heparin revealed high affinity receptors on the K562 and U937 cell lines (1177 +/- 440 and 392 +/- 184 sites/cell, Kd = 61.7 +/- 8.6 and 43.1 +/- 13.5 pM, respectively). Thus our results strongly suggest that cells of hematopoietic origin could express functional FGF-receptors.

The role of fibroblast growth factor-2 (FGF-2) in hematopoiesis

Basic fibroblast growth factor (bFGF or FGF-2) is an angiogenic and pleiotropic growth factor involved in the proliferation and differentiation of numerous cell types. It is expressed mostly in tissues of mesoderm and neuroectoderm origin, and is thought to play an important role in the mesoderm induction. Although hematopoietic cells derive from the mesoderm, relatively few studies have, until recently, addressed the role of FGF-2 in hematopoiesis. FGF-2 is expressed in cells of the bone marrow including stromal cells, and possibly cells from several hematopoietic cell lineages. It is stored in the bone marrow extra-cellular matrix and released by enzymes such as heparanase, plasmin, or phospholipase C and D. FGF-receptors (FGF-Rs) are expressed in leukemic cell lines and in hematopoietic cells. FGF-2 positively regulates hematopoiesis, by acting on stromal cells, on early and committed hematopoietic progenitors, and possibly on some mature blood cells. The action of FGF-2 is most likely indirect since its action, on megakaryocytopoiesis for example, is abrogated by anti-IL6 antibodies. It synergizes with hematopoietic cytokines, or antagonizes the negative regulatory effects of TGF-beta. Taken together, these results demonstrate that FGF-2 is a potent hematopoietic growth factor that is likely to play an important role in physiological and pathological hematopoiesis.

Interleukin 2 production and interleukin 2 receptor expression by human immature leukemic T cells

In order to determine the role of interleukin 2 (IL2) on the proliferation of leukemic cells from patients with T-cell acute lymphoblastic leukemia (T-ALL) we studied the production of IL2, the function of IL2 receptors (IL2R) expressed on T-ALL cells and their IL-2-dependent in vitro proliferation. Leukemic cells from six out of 17 T-ALL/T-cell non-Hodgkin's lymphoma patients with a prothymocyte (stage I) or a mature thymocyte (stage III), but not with a common thymocyte (stage II) phenotype, could proliferate, in a dose-dependent manner, in response to recombinant IL2 (rIL2) and anti-Tac and TU27 moAbs as well as polyclonal anti-IL2 purified immunoglobulin G could inhibit this IL2-induced cell proliferation. Both crude or/and Amicon-concentrated media conditioned by T-ALL cells from 10 out of 13 tested patients contained IL2 activity as assessed by colorimetric biological and immunoenzymatic assays; this biologic activity was due to a 14.5 kDa molecule adsorbed by anti-IL2 antibodies in an immunoaffinity assay. Although less than 10% of fresh leukemic cells expressed IL2R alpha (Tac) chain, a 24 h cell incubation in the absence of any mitogenic stimulation induced IL2R alpha chain expression in five out of 13 patients (11-83% Tac+ cells). Morever, Tac mRNA transcripts could be detected in fresh cells from all 10 patients tested. Staining of fresh leukemic cells with an IL-2R beta-chain-specific monoclonal antibody and flow cytometry analysis revealed that 4-13% of leukemic cells were positive. Binding experiments with 125I-rIL2 showed a small number of high affinity IL2R on fresh cells from three T-ALL patients (114-200 sites/cell, dissociation constant = 101-181 pm). Finally, antibodies against IL2R alpha, IL2R beta and IL2 could inhibit both IL2 driven and spontaneous cell proliferation of most patients' T-ALL cells, although in some cases an heterogenous pattern of inhibition was observed. Taken together, these findings strongly suggest that an IL2/IL2R-dependent mechanism could be involved in the proliferation of some T-ALL cells.