Characterization of the apoptotic effects of human tumor necrosis factor: development of highly rapid and specific bioassay for human tumor necrosis factor and lymphotoxin using human target cells

Effects of conidia of various Aspergillus species on apoptosis of human pneumocytes and bronchial epithelial cells

Aspergillus species can cause mycoses in human and animals. Previously, we demonstrated that A. fumigatus conidia from a human isolate inhibited apoptosis in human pneumocytes and bronchial epithelial cells. In the current study, we studied the effects of A. fumigatus conidia non-human origin and A. flavus, A. nidulans, A. niger and A. oryzae conidia on human cells apoptosis. Human pneumocytes or bronchial epithelial cells were simultaneously exposed to apoptotic inductors and aspergilli conidia. The cell cultures were analyzed by flow cytometry, immunoblotting, and examination of nuclear morphology. Similar to A. fumigatus conidia, A. flavus conidia inhibited cellular apoptosis while A. nidulans, A. niger and A. oryzae conidia did not affect apoptosis. We further studied the species specificity of conidia: there were no differences in the inhibition of apoptosis by A. fumigatus conidia from either human or bird isolates. In order to determine whether the inhibition of apoptosis by conidia is limited to certain strains, the effect on human cell apoptosis of different A. fumigatus human clinical isolates and A. fumigatus of environmental origin was evaluated. All A. fumigatus isolates inhibited apoptosis; an anti-apoptotic factor was released by conidia. For TNF-induced apoptosis, the anti-apoptotic effect of conidia of all isolates was found to be associated with a reduction of caspase-3 in human cells. The results suggest that suppression of apoptosis may play a role in reducing the efficacy of host defense mechanisms during infection with Aspergillus species.

Constitutive activation of AKT pathway inhibits TNF-induced apoptosis in mitochondrial DNA-deficient human myelogenous leukemia ML-1a

TNF plus protein synthesis inhibitor cycloheximide-induced apoptosis in human myelogenous leukemia ML-1a but not in C19, respiration minus mitochondrial DNA-deficient C19 cells, derived from ML-1a. To investigate how mitochondrial DNA depletion inhibits apoptosis, we investigated AKT. Both AKT and its phosphorylated form were observed only in C19, indicating that depletion of mtDNA increased protein and the active form of AKT. Treatment of C19 with LY294002, which inhibits PI-3 kinase and inhibits AKT, significantly increased apoptosis induction by TNF plus cycloheximide and eliminated phosphorylation of AKT. These results indicate that AKT activation was induced by the depletion of mtDNA and inhibited TNF-induced apoptosis.

Aspergillus fumigatus conidia inhibit tumour necrosis factor- or staurosporine-induced apoptosis in epithelial cells

A major innate immune response to inhaled conidia of the opportunistic pathogen Aspergillus fumigatus (Af) is the synthesis of pro-inflammatory cytokines, which include tumour necrosis factor (TNF)-alpha, a known inducer of apoptosis. Modulation of host cell apoptosis has been reported to be one of the mechanisms whereby pathogens overcome host cell defences. Our study was designed to investigate whether or not Af conidia could modulate apoptosis induced by TNF-alpha or staurosporine (STS). Exposure of epithelial cells treated by these inducers and exposed to Af conidia decreased the number of apoptotic cells detected by Annexin V staining, analysis of nuclear morphology, terminal deoxynucleotidyl transferase-mediated fluorescein-dUTP nick end-labelling reaction and immunoblotting. Inhibition of apoptosis by Af conidia was seen in cells of the A549 pneumocyte II line, human tracheal epithelial 16HBE and primary human respiratory cells. Inhibition of apoptosis by Af conidia was also observed when apoptosis was induced by co-cultivating A549 cells with activated human alveolar macrophages. Unlike Af conidia, conidia of Cladosporium cladosporioides as well as latex beads or killed Af conidia have no inhibitory effect on TNF-alpha or STS-induced apoptosis. For TNF-induced apoptosis, the observed anti-apoptotic effect of Af conidia was found to be associated with a significant reduction of caspase-3.

Epithelial cells infected with Chlamydophila pneumoniae (Chlamydia pneumoniae) are resistant to apoptosis

The obligate intracellular pathogen Chlamydophila pneumoniae (Chlamydia pneumoniae) initiates infections in humans via the mucosal epithelia of the respiratory tract. Here, we report that epithelial cells infected with C. pneumoniae are resistant to apoptosis induced by treatment with drugs or by death receptor ligation. The induction of protection from apoptosis depended on the infection conditions since only cells containing large inclusions were protected. The underlying mechanism of infection-induced apoptosis resistance probably involves mitochondria, the major integrators of apoptotic signaling. In the infected cells, mitochondria did not respond to apoptotic stimuli by the release of apoptogenic factors required for the activation of caspases. Consequently, active caspase-3 was absent in infected cells. Our data suggest a direct modulation of apoptotic pathways in epithelial cells by C. pneumoniae.

Regulation of apoptosis by respiration: cytochrome c release by respiratory substrates

Cytochrome c release from mitochondria is essential for apoptosis. Using human myelogenous leukemia ML-1a, its respiration-deficient and reconstituted cells, we demonstrated that respiratory function is essential for tumor necrosis factor-induced cytochrome c release. In a cell free system using mitochondrial fraction from ML-1a, initiation of respiration by substrates for complexes I, II, and III but not IV released cytochrome c, suggesting that reduction of coenzyme Q or complex III is essential for cytochrome c release. In the same system, disruption of mitochondrial outer membrane was neither enough nor the cause for cytochrome c release by succinate. These observations define an early pathway in which a change in respiration releases cytochrome c.

Neutral sphingomyelinase: past, present and future

Sphingomyelin and its metabolic products are now known to have second messenger functions in a variety of cellular signaling pathways. At the epicenter of the sphingomyelin--cell signaling pathway is a family of phospholipases called sphingomyelinases. These enzymes cleave sphingomyelin to produce ceramide and phosphocholine. Ceramide in turn serves as a lipid second messenger that induces a variety of cell regulatory phenomenon such as programmed cell death (apoptosis), cell differentiation, cell proliferation, and sterol homeostasis. Neutral sphingomyelinase (N-SMase) is a Mg2+ sensitive enzyme that can be activated by a host of physiologically relevant and structurally diverse molecules like tumor necrosis factor-alpha (TNF-alpha), oxidized human low density lipoproteins (Ox-LDL), and several growth factors. Large amounts of ceramide accumulate in human fatty streaks and plaques along with Ox-LDL, growth factors, and proinflammatory cytokines in human atherosclerosis. A further role of ceramide and N-SMase in atherosclerosis was uncovered by the finding that Ox-LDL and TNF-alpha stimulated N-SMase activity. In turn, ceramide and/or a homolog serves as an important stress signaling molecule in signal transduction, which leads to apoptosis. Interestingly, an antibody against N-SMase can abrogate Ox-LDL and TNF-alpha induced apoptosis, and therefore may be useful for additional studies of apoptosis in experimental animals. Overexpression of recombinant human N-SMase in human aortic smooth muscle cells markedly stimulate apoptosis, presumably via the multioligomerization of the 'death domain'. Since plaque stability is an integral aspect of atherosclerosis management, activation of N-SMase and subsequent apoptosis may be vital events in the onset of plaque rupture, stroke and heart failure. In contrast to these observations in human hepatocytes, TNF-alpha mediated N-SMase activation did not induce apoptosis. Rather it stimulated the maturation of sterol regulatory element (SRE) binding protein (SREBP-1). Moreover, a cell permeable ceramide was found to reconstitute the phenomenon above in a sterol-independent fashion. These findings provide alternate avenues for therapy of patients with hypercholesterolemia and atherosclerosis. The findings reported here suggests that N-SMase plays important cell regulatory roles and provide an exciting opportunity to further these findings to understand the pathophysiology of human disease states.

Tumor necrosis factor in peritoneal fluid from asymptomatic infertile women

BACKGROUND

Tumor necrosis factor-alpha (TNF-alpha) is a cytokine that can be found in the peritoneal fluid (PF) of patients with endometriosis and pelvic inflammatory disease (PID) as a response to inflammatory disorders and infections. The cytotoxic effect of this cytokine could be a factor participating in the pathology of various gynecological diseases, and could also be accountable for the high immunological response and damage to the tubal epithelium. The objective of this study was to establish the presence of TNF-alpha in asymptomatic infertility and its association with various isolated bacteria.

METHODS

Ten milliliters of PF were collected from each of 73 patients by means of laparoscopy and cultured in synthetic medium and McCoy cells for the isolation of aerobic and anaerobic bacteria, as well as for Chlamydia trachomatis. The activity of TNF-alpha was determined by means of a bioassay using L-929 cells.

RESULTS

Forty-three percent of the PFs showed positive TNF-alpha activity, while the laparoscopic evaluation showed that 32 patients had Fallopian tube occlusion (FTO), 7 had endometriosis, 30 had PID, and 4 had myomas and adhesions. TNF-alpha activity was found to be high in FTO patients (p < 0.05). Positive cultures were found in 50.7% of patients; of these, 31.5% had PID (p < 0.05), and only 20.5% of positive cultures were TNF-alpha positive. Chlamydia trachomatis (16%) was the most frequently isolated bacteria in these patients.

CONCLUSIONS

The detection of TNF-alpha could be useful in the diagnosis of active infectious and inflammatory diseases in asymptomatic infertile patients.

The development of a bi-specific anti-CD161A x anti-tumor antibody for rat NK cell targeting

In order to improve the therapeutic efficacy of adoptive immunotherapy of cancer using IL-2-activated NK (A-NK) cells, we developed a bi-specific monoclonal antibody (BimAb) 3.2.3xCC52. One specificity of the BimAb (mAb 3.2.3) was directed against rat CD161A (NKR-P1A) which has been shown to be an activation structure on rat NK cells involved in lysis of target cells and cytokine secretion. The other specificity (mAb CC52) was directed against a tumor associated antigen on the rat colon adenocarcinoma cell line CC531. The hybridomas producing 3.2.3 and CC52 were fused, resulting in a quadroma producing the desired 3.2.3xCC52 BimAb. The hybridomas produced antibodies of different isotypes (IgG2b and IgG1 respectively) which enabled us to pre-select quadromas with a high likelihood for production of BimAb, through testing for the production of bi-isotypic antibodies. Production of functional BimAb by the selected quadromas was demonstrated in an assay showing enhanced conjugate formation between CD161A+ cells and CC531 tumor cells. We also tested the 3.2.3xCC52 BimAb for its capacity to enhance NK cell-mediated lysis of CC531 tumor cells in 4 h and 19 h 51Cr release assays; in a prolonged (2 day) tumor neutralization assay using a tetrazolium salt (MTT)-based assay; and in tests for apoptosis using Annexin V-FITC. Although this BimAb was not demonstrated to cause enhanced lysis of CC531 cells by CD161A+ effector cells in vitro, it might be a useful tool to enhance the number of NK cells at the tumor site and/or prolong contact between tumor cells and NK cells in vivo, thereby probably enhancing the therapeutic efficacy of NK cells.

Expression of tumor necrosis factor-alpha gene during allograft rejection following rat liver transplantation

BACKGROUND/AIMS

Tumor necrosis factor-alpha (TNF-alpha) is believed to play a role in hepatic allograft rejection. However, the specific cellular population responsible for TNF-alpha production during hepatic allograft rejection is not known. Circulating monocyte-macrophage cells are the primary systemic sources of TNF-alpha. In the liver, Kupffer cells are the main producers of TNF-alpha. In this study, we determined which cells are involved in TNF-alpha production during allograft rejection after orthotopic liver transplantation.

METHODS

In situ hybridization was used to identify cells with TNF-alpha mRNA in the liver. Immunohistochemical staining with ED2 and ED3 was used to differentiate between cellular types (Kupffer cells versus infiltrating monocytes). To detect DNA fragmentation in liver cells, TdT-mediated biotin-dUTP nick-end labeling (TUNEL) was done. Studies were performed in the rat liver transplant model using rejecting (ACI to LEW) and non-rejecting (ACI to ACI) donor/recipient combinations.

RESULTS

In the control group, cells with TNF-alpha mRNA were rarely observed. In the rejection group, TNF-alpha mRNA was observed in mononuclear cells that were mainly within the vessels of the portal region and occasionally in the sinusoids. The cells with the signals for TNF-alpha mRNA were ED2-negative and ED3-positive. DNA fragmentation was observed in hepatocytes as well as infiltrating mononuclear cells.

CONCLUSIONS

The main producer of TNF-alpha may be infiltrating mononuclear cells such as monocyte-macrophage cells rather than Kupffer cells during allograft rejection after liver transplantation. Circulating monocyte-macrophages may play a role in the control of allograft rejection.

Activation of CPP32-like protease in tumor necrosis factor-induced apoptosis is dependent on mitochondrial function

Mitochondria have been implicated in apoptosis, however, the precise mechanisms whereby mitochondria exert their effect are not clear. To gain further insights, we generated a panel of cells from ML-1a cells that were rendered respiration deficient by ethidium bromide treatment. Two respiration-deficient clones were subsequently reconstituted by fusion with platelets. Respiration-deficient clones were resistant to TNF-induced apoptosis, whereas ML-1a and reconstituted clones were sensitive. In contrast, inhibition of proliferation and induction of differentiation by TNF were still observed in respiration deficient clones, suggesting a selective requirement of respiration in TNF-induced apoptosis. Furthermore the apoptosis machinery is not completely altered in respiration-deficient cells because they underwent apoptosis after staurosporine treatment. Next, we showed that apoptosis induced by TNF and staurosporine were blocked by z-DEVD-CH2F, an inhibitor of CPP32-like cysteine protease, suggesting the involvement of CPP32-like protease in both apoptosis signaling pathways. Interestingly, TNF activated CPP32-like protease in the parental and reconstituted clones but not in respiration-deficient clones, and staurosporine in all clones. Thus, the apoptosis signaling block in respiration-deficient clones is located at a step before CPP32-like protease activation, which can be bypassed by staurosporine.

Tumor cell cytolysis mediated by valorphin, an opioid-like fragment of hemoglobin beta-chain

Valorphin, an endogenous opioid-like hemoglobin fragment, is cytotoxic for L929 and K562 tumor cells in 10(-7)-10(-13) M concentration range. Because cytolytic effects induced by valorphin in K562 cells are inhibited by naloxone, opioid receptors should be involved in induction of valorphin-mediated tumor cell death. Three distinct cytolytic processes, differing in the onset time and the development time, take place with K562 cells within 10-18 h of incubation with valorphin. All three processes are not associated with apoptotic mechanism of cell death.

Tumor necrosis factor-alpha suppresses hematopoiesis in children with myelodysplasia

The term myelodysplasia (MDS) refers to a group of bone marrow failure syndromes which are relatively rare in childhood. The pathogenesis of MDS is unknown, but a variety of chromosomal, molecular, and cytochemical abnormalities have been reported. We describe a 4-month-old female with MDS who presented with severe neutropenia and refractory anemia with excess blasts (RAEB). Bone marrow progenitor cell assays showed decreased erythroid and myeloid colony formation as compared to normal marrow, and the patient's serum further diminished colony formation of both her own and control marrow. These observations suggested the presence of a soluble factor inhibitory to hematopoiesis. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of total RNA derived from the patient's bone marrow mononuclear cells revealed highly elevated tumor necrosis factor-alpha (TNF-alpha) mRNA levels. Using a similar RT-PCR profile, TNF-alpha mRNA levels were found to be elevated in two other children with myelodysplasia. We conclude that TNF-alpha is produced in large amounts by bone marrow mononuclear cells of children with MDS, and we hypothesize that TNF-alpha plays an important role in the pathophysiology of the ineffective hematopoiesis observed in MDS.