Tumor necrosis factor alpha up-regulates in an autocrine manner the synthesis of plasminogen activator inhibitor type-1 during induction of monocytic differentiation of human HL-60 leukemia cells

1,25-Dihydroxyvitamin D3 induces human myeloid cell differentiation via the mTOR signaling pathway

1,25-Dihydroxyvitamin D₃ or 1,25(OH)₂D₃ is known to play an important role in the differentiation of human myeloid cells. However, the molecular mechanism underlying the 1,25(OH)₂D₃-mediated differentiation of human myeloid cells is incompletely understood. Here, we report that 1,25(OH)₂D₃ induces differentiation of human myeloid cell lines such as U937 and THP-1 cells via the mammalian target of rapamycin (mTOR) signaling pathway. Both the expression of the differentiation marker CD14 and activation of the mTOR signaling pathway were induced by 1,25(OH)₂D₃ in phorbol 12-myristate 13-acetate (PMA)-differentiated U937 and THP-1 cells. The 1,25(OH)₂D₃-induced expression of CD14 in PMA-differentiated U937 and THP-1 cells was prevented by mTOR inhibitors, PP242 and Torin1. The 1,25(OH)₂D₃-induced morphological changes as characteristics of differentiated myeloid cells were also reversed after PP242 and Torin1 treatment. Silencing of either regulatory-associated protein of mTOR (Raptor) or rapamycin-insensitive companion of mTOR (Rictor) in PMA-differentiated THP-1 cells with small-interfering RNA resulted in the inhibition of CD14 expression and morphological changes induced by 1,25(OH)₂D₃, indicating that both mTORC1 and mTORC2 were important for the differentiation of myeloid THP-1 cells. Previous studies have shown that phosphatidic acid (PA) maintains the stability of the mTOR complex. Here we found that the attenuation of PA production with 1-butanol or a PLD inhibitor prevented the 1,25(OH)₂D₃-induced upregulation of CD14. Taken together, our results show that 1,25(OH)₂D₃ enhances the differentiation of human myeloid cells through the mTOR signaling pathway.

Maggot secretions suppress pro-inflammatory responses of human monocytes through elevation of cyclic AMP

AIMS/HYPOTHESIS

Maggots of the blowfly Lucilia sericata are used for the treatment of chronic wounds. As monocytes may contribute to the excessive inflammatory responses in such wounds, this study focussed on the effects of maggot secretions on the pro-inflammatory activities of these cells.

METHODS

Freshly isolated monocytes were incubated with a range of secretions for 1 h and then stimulated with lipopolysaccharides (range 0-100 ng/ml) or lipoteichoic acid (range 0-5 microg/ml) for 18 h. The expression of cell surface molecules, cytokine and chemokine levels in culture supernatants, cell viability, chemotaxis, and phagocytosis and killing of Staphylococcus aureus were measured.

RESULTS

Maggot secretions dose-dependently inhibited production of the pro-inflammatory cytokines TNF-alpha, IL-12p40 and macrophage migration inhibitory factor by lipopolysaccharides- and lipoteichoic acid-stimulated monocytes, while enhancing production of the anti-inflammatory cytokine IL-10. Expression of cell surface receptors involved in pathogen recognition remained unaffected by secretions. In addition, maggot secretions altered the chemokine profile of monocytes by downregulating macrophage inflammatory protein-1beta and upregulating monocyte chemoattractant protein-1 and IL-8. Nevertheless, chemotactic responses of monocytes were inhibited by secretions. Furthermore, maggot secretions did not affect phagocytosis and intracellular killing of S. aureus by human monocytes. Finally, secretions induced a transient rise in the intracellular cyclic AMP concentration in monocytes and Rp-cyclic AMPS inhibited the effects of secretions.

CONCLUSIONS/INTERPRETATION

Maggot secretions inhibit the pro-inflammatory responses of human monocytes through a cyclic AMP-dependent mechanism. Regulation of the inflammatory processes by maggots contributes to their beneficial effects on chronic wounds.

Combination of all-trans retinoic acid and paclitaxel-induced differentiation and apoptosis in human glioblastoma U87MG xenografts in nude mice

BACKGROUND

Glioblastoma, which is the most malignant brain tumor, remains incurable and almost always causes death. As a new treatment strategy, the combination of all-trans retinoic acid (ATRA) and paclitaxel was explored for controlling the growth of glioblastoma U87MG xenografts.

METHODS

Human glioblastoma U87MG xenografts were developed in athymic nude mice for treatments with ATRA, paclitaxel, and ATRA plus paclitaxel. The efficacy of treatments in controlling tumor growth was assessed by histologic examination, Western blot analysis, and immunofluorescent labelings.

RESULTS

Astrocytic differentiation in U87MG xenografts was associated with increased GFAP expression and decreased telomerase expression. The combination of ATRA and paclitaxel was found to cause more apoptosis than paclitaxel alone. Apoptosis occurred with down-regulation of MEK-2 and overexpression of p-ERK, p-JNK, and p-p38 MAPK. Down-regulation of both Akt and p-Akt also favored the apoptotic process. Combination therapy activated the receptor-mediated pathway of apoptosis with induction of TNF-alpha, activation of caspase-8, and cleavage of Bid to tBid. Combination therapy also induced the mitochondria-mediated pathway of apoptosis with an increase in the Bax:Bcl-2 ratio and mitochondrial release of cytochrome c and Smac/Diablo into the cytosol. In addition, combination therapy promoted phosphorylation of Bcl-2 for its inactivation and down-regulated NF-kappaB and BIRC proteins, indicating suppression of several cell survival factors. Western blot analysis demonstrated that activation of cysteine proteases such as calpain, caspase-12, caspase-9, and caspase-3 contributed to apoptosis. Immunofluorescent labelings confirmed overexpression of cysteine proteases in apoptosis.

CONCLUSIONS

Treatment of U87MG xenografts with a combination of ATRA and paclitaxel induced differentiation and also multiple molecular mechanisms for apoptosis.

Microparticles of human atherosclerotic plaques enhance the shedding of the tumor necrosis factor-alpha converting enzyme/ADAM17 substrates, tumor necrosis factor and tumor necrosis factor receptor-1

Human atherosclerotic plaques express the metalloprotease tumor necrosis factor (TNF)-alpha converting enzyme (TACE/ADAM-17), which cleaves several transmembrane proteins including TNF and its receptors (TNFR-1 and TNFR-2). Plaques also harbor submicron vesicles (microparticles, MPs) released from plasma membranes after cell activation or apoptosis. We sought to examine whether TACE/ADAM17 is present on human plaque MPs and whether these MPs would affect TNF and TNFR-1 cellular shedding. Flow cytometry analysis detected 12,867 +/- 2007 TACE/ADAM17(+) MPs/mg of plaques isolated from 25 patients undergoing endarterectomy but none in healthy human internal mammary arteries. Plaque MPs harbored mainly mature active TACE/ADAM17 and dose dependently cleaved a pro-TNF mimetic peptide, whereas a preferential TACE/ADAM17 inhibitor (TMI-2) and recombinant TIMP-3 prevented this cleavage. Plaque MPs increased TNF shedding from the human cell line ECV-304 overexpressing TNF (ECV-304(TNF)), as well as TNFR-1 shedding from activated human umbilical vein endothelial cells or ECV-304(TNF) cells, without affecting TNF or TNFR-1 synthesis. MPs also activated the shedding of the endothelial protein C receptor from human umbilical vein endothelial cells. All these effects were inhibited by TMI-2. The present study shows that human plaque MPs carry catalytically active TACE/ADAM17 and significantly enhance the cell surface processing of the TACE/ADAM17 substrates TNF, TNFR-1, and endothelial protein C receptor, suggesting that TACE/ADAM17(+) MPs could regulate the inflammatory balance in the culprit lesion.

Combination of retinoic acid and tumor necrosis factor overcomes the maturation block in a variety of retinoic acid-resistant acute promyelocytic leukemia cells

Retinoic acid (RA) overcomes the maturation block in t(15:17) acute promyelocytic leukemia (APL), leading to granulocytic differentiation. Patients receiving RA alone invariably develop RA resistance. RA-resistant cells can serve as useful models for the development of treatments for both APL and other leukemias. Previously, we showed that RA and tumor necrosis factor (TNF) promote monocytic differentiation of the APL cell line NB4 and U937 monoblastic cells. Here, we report that combining TNF with RA leads to maturation of several RA-resistant APL cells along a monocytic pathway, whereas UF-1, a patient-derived RA-resistant cell line, showed characteristics of granulocytic differentiation. We found distinct differences in gene regulation between UF-1 cells and cells showing monocytic differentiation. Although IRF-7 was up-regulated by TNF and RA in all cells tested, expression of c-jun and PU.1 correlated with monocytic differentiation. Furthermore, synergistic induction of PU.1 DNA binding and macrophage colony-stimulating factor receptor (m-CSF-1R) mRNA was observed only in cells differentiating into monocytes. Using neutralizing antibodies against m-CSF-1R or its ligand, we found that inhibiting this pathway strongly reduced CD14 expression in response to RA and TNF, suggesting that this pathway is essential for their synergy in RA-resistant leukemia cells. (Blood. 2004;104:3335-3342)

Expression of the Angiogenic Factor Thymidine Phosphorylase in THP-1 Monocytes: Induction by Autocrine Tumor Necrosis Factor-α and Inhibition by Aspirin

The angiogenic factor thymidine phosphorylase (TP) is highly expressed in human monocytes and macrophages, and its expression has been linked to the pathology and progression of solid tumors, rheumatoid arthritis, and gastric ulcers. In this study, TP mRNA and enzyme activity were found to be up-regulated upon the induction of differentiation of the human monocyte cell line THP-1 by phorbol 12-myristate 13-acetate (PMA). TP expression in THP-1 cells was similarly increased by tumor necrosis factor-alpha (TNFalpha). Because monocytes and macrophages are a predominant source of TNFalpha, the up-regulation of TP upon THP-1 differentiation could have been caused by the autocrine production of TNFalpha. In support of this hypothesis, PMA increased TNFalpha mRNA levels; furthermore, the increase in TP expression with PMA treatment was partially blocked by a neutralizing antibody to TNFalpha, particularly at the earlier time points. This data also suggested there may be additional mechanisms regulating TP expression upon PMA treatment of the cells. The induction of TP by TNFalpha was mimicked by an antibody to the TNFalpha receptor R2 (TNF-R2; p75), but not by an antibody to TNF-R1 (p55), suggesting that the TNF-R2 plays a role in the regulation of TP expression. The PMA-induced increase in TP expression was blocked by aspirin but not by the related agent indomethacin, suggesting that aspirin's effect was not caused by the inhibition of cellular cyclooxygenases. An alternative mechanism by which aspirin inhibits gene expression is the modulation of the transcription factor NFkappaB, and the TNFalpha-induced increase in TP mRNA was blocked by a cell-permeable NFkappaB inhibitory peptide. Furthermore, TNFalpha increased and aspirin (but not indomethacin) decreased NFkappaB DNA-binding activity in THP-1 cells. In conclusion, the modulation of TP expression in monocytes by pro- and anti-inflammatory agents suggests that its angiogenic-related actions could contribute to the inflammatory response associated with a number of pathophysiological conditions.

Modulation of PAI-1 and proMMP-9 syntheses by soluble TNFalpha and its receptors during differentiation of the human monocytic HL-60 cell line

During phorbol ester-induced differentiation of HL-60 monocytic cells, tumor necrosis factoralpha (TNFalpha) synthesis and secretion are increased, which contributes to the autocrine regulation of TNFalpha-responsive genes. We investigated how, during phorbol ester-induced differentiation of HL-60 cells, the secreted TNFalpha modulated plasminogen activator inhibitor type I (PAI-1) and gelatinase B (MMP-9) syntheses, two proteins involved in pericellular proteolysis. The differentiation-induced release of TNFalpha, was abolished by the hydroxamate-based matrix metalloproteinase (MMP) inhibitor, RU36156. RU36156 or a neutralizing anti-TNFalpha significantly down-regulated PAI-1 synthesis exclusively during the early phases of differentiation (from promyelocyte to monocytic-like cells), which underlined the activating role of autocrine TNFalpha during this time range. As cells progressed to monocyte/macrophage phenotype, they still released TNFalpha, but RU36156 or anti-TNFalpha no longer had an effect on PAI-1 synthesis. This lack of effect was not due to a default of TNFalpha signaling since PAI-1 synthesis was still stimulated in response to exogenous TNFalpha. TNFalpha receptor RI was also actively released and was shown to reduce TNFalpha activity which may account for the inability of soluble TNFalpha to up-regulate PAI-1 synthesis. In later mature stage, cells became susceptible to exogenous TNFalpha-induced apoptosis and rapidly lost their ability to respond to TNFalpha. The MMP-9 synthesis followed similar regulation as PAI-1. Isolated human blood monocytes-derived macrophages behave like HL-60-derived macrophages. In conclusion, these results show that during leukocyte differentiation, time windows exist during which the autocrine TNFalpha is active and then down-regulated by RI, which may temper a continuous up-regulation of the synthesis of proteins involved in pericellular proteolysis.

Synergy between all-trans retinoic acid and tumor necrosis factor pathways in acute leukemia cells

The nuclear receptor ligand all-trans retinoic acid (ATRA) causes dramatic terminal differentiation of acute promyelocytic leukemia (APL) cells in vitro and in patients, but it is less active in other malignancies. However, downstream mediators of the effects of ATRA are not well understood. We used a cDNA microarray to search for ATRA-regulated genes in the APL cell line NB4 and found that ATRA regulated several members of the tumor necrosis factor (TNF) pathway. Here we show that TNF can synergize with ATRA to induce differentiation, showing monocytic characteristics more typical of differentiation mediated by TNF than by ATRA. ATRA and TNF can also induce differentiation of the non-APL cell line U937. Underlying this response was an increase in TNF-induced nuclear factor-kappaB (NF-kappaB) DNA binding within 2 hours in the presence of ATRA and activation of NF-kappaB DNA binding and transcriptional activity in response to ATRA alone within 48 hours of ATRA treatment. Furthermore, we found a synergistic induction of the NF-kappaB target genes BCL-3, Dif-2, and TNF receptor 2 (TNFR2) in response to the combination of TNF and ATRA. These genes have been previously shown to play a role in TNF signaling, and amplification of such genes may represent a mechanism whereby TNF and ATRA can act synergistically. We propose that ATRA can prime cancer cells for differentiation triggered by TNF and suggest that targeting the TNF pathway in combination with ATRA may represent a novel route to treat leukemias.

Tumor necrosis factor-alpha stimulates the epithelial-to-mesenchymal transition of human colonic organoids

An epithelial-mesenchymal transition (EMT) characterizes the progression of many carcinomas and it is linked to the acquisition of an invasive phenotype. Given that the tumor microenvironment is an active participant in tumor progression, an important issue is whether a reactive stroma can modulate this process. Using a novel EMT model of colon carcinoma spheroids, we demonstrate that their transforming-growth factor-beta1 (TGF-beta)-induced EMT is accelerated dramatically by the presence of activated macrophages, and we identify tumor necrosis factor-alpha (TNF-alpha) as the critical factor produced by macrophages that accelerates the EMT. A synergy of TNF-alpha and TGF-beta signaling promotes a rapid morphological conversion of the highly organized colonic epithelium to dispersed cells with a mesenchymal phenotype, and this process is dependent on enhanced p38 MAPK activity. Moreover, exposure to TNF-alpha stimulates a rapid burst of ERK activation that results in the autocrine production of this cytokine by the tumor cells themselves. These results establish a novel role for the stroma in influencing EMT in colon carcinoma, and they identify a selective advantage to the stromal presence of infiltrating leukocytes in regulating malignant tumor progression.

Inhibition of p70(S6) kinase during transforming growth factor-beta 1/vitamin D(3)-induced monocyte differentiation of HL-60 cells allows tumor necrosis factor-alpha to stimulate plasminogen activator inhibitor-1 synthesis

We investigated intracellular mechanisms involved in the up-regulation of plasminogen activator inhibitor I (PAI-1) synthesis by human recombinant tumor necrosis factor-alpha (TNF) during monocyte differentiation of HL-60 cells triggered by the transforming growth factor-beta1/vitamin D(3) (TGF/D3) mixture. TGF/D3-treated cells expressed surface monocytic markers and produced noticeable amounts of PAI-1 but stopped to proliferate. A reduced p70 S6 kinase (p70(S6K)) phosphorylation was also observed and, in this situation, TNF dramatically enhanced PAI-1 synthesis. Similarly, TNF significantly up-regulated PAI-1 synthesis when p70(S6K) phosphorylation was inhibited by rapamycin. This phenomenon was not due to a general decrease in protein synthesis but involved the activation of gene transcription rather than PAI-1 mRNA stabilization. The level of the transcriptional regulator factor E2F1, a repressor of PAI-1 gene expression, was shown to be down-modulated in TGF/D3- as well as in rapamycin-treated cells. Furthermore, the apoptotic effect of TNF in HL-60 cells appeared to be prevented by the addition of either TGF/D3 or rapamycin. In conclusion, these results indicate that inhibition of p70(S6K) phosphorylation during TGF/D3-induced monocyte differentiation of HL-60 cells is a determinant factor that allows TNF to exert its up-regulating effect on PAI-1 synthesis while protecting cells from apoptosis.

Effect of atorvastatin on plasminogen activator inhibitor type-1 synthesis in human monocytes/macrophages

The fibrinolytic inhibitor plasminogen activator inhibitor type 1 (PAI-1) plays a role in the development of atherothrombosis and is produced by macrophages that infiltrate the atherosclerotic vessel wall. Because statins are effective in reducing atherosclerosis, we investigated if they modulate the synthesis of PAI-1 in human monocytes/macrophages. To this end, we studied the effect of atorvastatin in different models of monocyte/macrophage differentiation, such as differentiated human promyelocytic cell line HL-60 and human peripheral blood monocyte-derived macrophages. HL-60 cells were differentiated along monocyte lineage by phorbol myristate acetate (PMA) or a mixture of transforming growth factor-beta type 1 (TGF-beta1)/1alpha,25-dihydroxyvitamin D3 (D3). In these conditions, PAI-1 synthesis was strongly induced and atorvastatin upregulated this synthesis, especially during TGF-beta1/D3-induced differentiation. Recombinant human tumor necrosis factor-alpha (TNF-alpha) strongly upregulated PAI-1 synthesis in PMA- or TGF-beta1/D3-differentiated cells, and the potentiating effect of atorvastatin was of the same order as in the absence of TNF-alpha. Mevalonate reversed the enhancing effect of atorvastatin. In mature human monocyte-derived macrophages, atorvastatin, alone or in combination with TNF-alpha, TGF-beta1, or PMA, did not exert any significant effect on PAI-1 synthesis. Basal production of urokinase (uPA), which was below detection limits in HL-60 cells and very low in human monocyte-derived macrophages, was not altered by atorvastatin. These results show that atorvastatin upregulates PAI-1 synthesis during the early stages of monocyte/macrophage differentiation, but has no effect on PAI-1 and uPA synthesis in mature human monocyte-derived macrophages. Atorvastatin did not significantly interact with the upregulating action of TNF-alpha on PAI-1 synthesis during differentiation.

Daunorubicin attenuates tumor necrosis factor-alpha-induced biosynthesis of plasminogen activator inhibitor-1 in human umbilical vein endothelial cells

The anthracycline antibiotic daunorubicin is reported to induce apoptosis in cells by triggering ceramide generation through de novo synthesis or sphingomyelin hydrolysis. Treatment of human umbilical vein endothelial cells (HUVEC) with daunorubicin markedly decreased the mRNA expression and protein release of plasminogen activator inhibitor-1 (PAI-1). This cellular event was accompanied by a significant increase in the total ceramide content in HUVEC. On the other hand, tumor necrosis factor (TNF)-alpha treatment of HUVEC led to an increase in both PAI-1 mRNA expression and protein release, and an enhancement of total ceramide content was also observed. The stimulating effect of TNF-alpha on PAI-1 synthesis was attenuated by the pretreatment of HUVEC with daunorubicin. Interestingly, the daunorubicin-induced increase in ceramide content was blocked by addition of the potent ceramide synthase inhibitor fumonisin B(1), while the TNF-alpha-induced ceramide increase was not affected by this drug. Fumonisin B(1) treatment restored the daunorubicin-induced decrease in PAI-1 release to approximately 70% of the control, but did not affect the TNF-alpha-induced increase in PAI-1 release. Thus, these data imply the possibility that the subcellular topology of ceramide production determines its lipid mediator function in the regulation of PAI-1 synthesis in HUVEC, because both TNF-alpha and daunorubicin could increase the ceramide levels.