Transcriptional regulation of cytokine expression by diethyldithiocarbamate in human HL-60 promyelocytic leukemia cells

Diethyldithiocarbamate (DDTC) is an investigational agent used to ameliorate chemotherapy- or radiotherapy-induced myelosuppression. We studied the effects of DDTC on the regulation of hematopoietic cytokine production in human myeloid cells. The results demonstrated that DDTC decreases proliferation of human HL-60 promyelocytic leukemia cells in a concentration-dependent manner. DDTC treatment also increased interleukin-alpha (IL-1 alpha), IL-1 beta, and tumor necrosis factor (TNF) expression in these cells. Similar findings were obtained in normal human peripheral blood monocytes. Peak induction of these cytokines occurred 6-12 hr after exposure to DDTC; levels returned to those in control cells by 24-48 hr in HL-60 cells. This effect was specific for IL-1 and TNF in that there was no detectable increase in IL-3, macrophage colony-stimulating factor or granulocyte/macrophage colony-stimulating factor RNA expression. Transcriptional run-on analysis demonstrated that exposure to DDTC increased the rate of TNF gene transcription in HL-60 cells. These data suggest that the myeloprotective effects of DDTC may be mediated, at least in part, by the induction of TNF, IL-1 alpha, and IL-1 beta.

High- versus low-dose oxytocin for labor stimulation

The number of cesarean births for dystocia has increased dramatically in the United States. Central to the management of dystocia is correction of ineffective labor by oxytocin administration, and contemporary obstetric practice is to stimulate labor with a low-dose oxytocin regimen. We prospectively compared a low-dose oxytocin regimen (1-mU/minute dosage increments) with a high-dose regimen (6-mU/minute dosage increments) in 2788 consecutive singleton cephalic pregnancies. The low-dose regimen was used first for 5 months in 1251 pregnancies, and the high-dose regimen in 1537 pregnancies during the subsequent 5 months. Indications for oxytocin stimulation were divided into augmentation (N = 1676) and induction (N = 1112). Labor stimulation was more than 3 hours shorter (P less than .0001) with the high-dose oxytocin regimen and associated with a reduction in neonatal sepsis (0.2 versus 1.3%; P less than .01). Uterine hyperstimulation was more common (55 versus 42%; P less than .0001) with the high-dose regimen, but no adverse fetal effects were observed. High-dose augmentation resulted in significantly fewer forceps deliveries (12 versus 16%; P = .03) and fewer cesareans for dystocia (9 versus 12%; P = .04). Similarly, failed induction was less frequent with high-dose compared with low-dose oxytocin (14 versus 19%; P = .05). Although the high-dose induction regimen was associated with a significantly increased cesarean incidence for fetal distress (6 versus 3%; P = .05), the incidence of umbilical artery cord blood acidemia was not increased in this subset. Induction of labor with high-dose oxytocin is problematic because of risk-benefit considerations. Although induction failed less frequently with the high-dose regimen, cesarean for fetal distress was performed more frequently. In contrast, high-dose oxytocin to augment ineffective spontaneous labor minimized the number of cesareans done for dystocia.

Chorioamnionitis: a harbinger of dystocia

The impact of chorioamnionitis on the course of labor is controversial. Some clinicians believe the infection has stimulatory effects, whereas others suspect inhibitory influences. Two hundred sixty-six pregnancies with chorioamnionitis requiring labor stimulation with oxytocin were matched to uninfected women for maternal age, race, parity, gestational age, oxytocin dosage regimen, indication for labor stimulation, type of labor stimulation, cervical dilatation at initiation of oxytocin, and time for rupture of membranes to initiation of labor stimulation. Chorioamnionitis diagnosed before oxytocin infusion was associated with shorter oxytocin initiation-to-delivery intervals (4.3 versus 5.6 hours; P = .04) and had no significant impact on the cesarean rate compared with matched controls. In contrast, pregnancies complicated by chorioamnionitis detected late in labor were associated with markedly longer oxytocin initiation-to-delivery intervals (12.6 versus 7.9 hours; P less than .0001) and a fourfold increase in cesarean for dystocia compared with matched controls (40 versus 10%; P less than .0001). Thus, the impact of chorioamnionitis on the course of labor can be divided into two clinical presentations. That diagnosed before labor stimulation does not increase the use of cesarean, whereas that diagnosed after oxytocin stimulation may be a sign of abnormal labor, as it was associated with a marked increase in abdominal delivery for dystocia.

Factors affecting the dose response to oxytocin for labor stimulation

For nearly 40 years synthetic oxytocin has been used for labor stimulation by titrating dosage rate to uterine contractions. We used a computerized data base to determine variables affecting the dose response to oxytocin in 1773 pregnancies. Statistically important predictors of required oxytocin dosage included cervical dilatation, parity, and gestational age. Maternal body surface area was found to be associated with a higher oxytocin dosage in women undergoing induction of labor. However, the broad range of the statistical confidence intervals precluded prediction of a given pregnancy's oxytocin requirement.

Functional expression of the macrophage colony-stimulating factor receptor in human THP-1 monocytic leukemia cells

Macrophage colony-stimulating factor (M-CSF) is required for the proliferation, differentiation, and activation of monocytes. High-affinity receptors for M-CSF are encoded by the c-fms proto-oncogene. In the present study, we show that c-fms transcripts are detectable in human THP-1 myeloid leukemia cells. Furthermore, radiolabeled 125I-M-CSF is rapidly internalized into THP-1 cells and then degraded intracellularly. The results also show that treatment of THP-1 cells with M-CSF is associated with the activation of protein kinase C (PKC) and the induction of tumor necrosis factor (TNF) gene expression. TNF transcript levels were low to undetectable in uninduced THP-1 cells, reached maximal levels by 1 hour of exposure to M-CSF, and returned to those of control cells by 24 hours. Transcriptional run-on analysis showed that a low level of TNF transcription is detectable in untreated THP-1 cells, and M-CSF treatment increased the rate of TNF transcription. Pretreatment of THP-1 cells with pertussis toxin inhibited the increase in PKC activity but not the induction of TNF transcripts by M-CSF. Moreover, exposure of THP-1 cells to inhibitors of protein kinase activity blocked the increase in TNF messenger RNA. These findings suggest that at least two M-CSF-mediated signaling pathways exist in THP-1 cells and that the induction of TNF may be regulated by a protein kinase-dependent mechanism distinct from PKC.

Macrophage colony-stimulating factor gene expression in vascular cells and in experimental and human atherosclerosis

The infiltration of monocytes into the vascular wall and their transformation into lipid-laden foam cells characterizes early atherogenesis. Macrophages are also present in more advanced human atherosclerotic plaques and can produce many mediators that may contribute to lesion formation and progression. Macrophage colony-stimulating factor (MCSF) enhances the proliferation and differentiation of monocyte progenitors and is required for the survival and activation of mature monocytes and macrophages. The authors therefore examined the expression of the MCSF gene in cultured human vascular endothelial (EC) and smooth muscle cells (SMC) as well as in atheromatous lesions from rabbits and humans. Growth arrested EC and SMC contain a low level of MCSF mRNA. Bacterial lipopolysaccharide (LPS), recombinant human interleukin-1 alpha (IL-1 alpha) or tumor necrosis factor alpha (TNF alpha) induced MCSF mRNA accumulation in a concentration-dependent manner in both EC and SMC. These stimuli induced large increases in MCSF mRNA with peak induction between 4-8 hours after treatment. LPS, IL-1 alpha, and TNF alpha stimulated EC and SMC also showed increased fluorescent antibody staining for MCSF protein and released immunoreactive MCSF in a time-dependent manner. In contrast, phorbol 12-myristate 13-acetate (PMA) was a less potent inducer of MCSF gene expression and iron-oxidized low-density lipoproteins (ox-LDL) did not increase consistently MCSF mRNA or the synthesis and secretion of immunoreactive protein. Northern analysis of mRNA isolated from the atheromatous aorta of rabbits fed a 1% cholesterol diet for 10 weeks showed elevated MCSF mRNA compared with controls. Immunostaining of atheromatous arterial lesions of rabbits demonstrated MCSF protein in association with intimal SMC as well as macrophages. Furthermore, polymerase chain reaction (PCR) analysis of MCSF mRNA in human atheromata showed higher levels than found in nonatherosclerotic arteries and veins. Since the authors found no mRNA for the MCSF receptor, c-fms, in cultured EC or SMC macrophages are likely the primary target for MCSF within atheromatous vessels. The authors therefore investigated the effects of MCSF on monocyte functions related to foam cell development. Treatment of cultured human monocytes with recombinant human MCSF (10(3) U/ml, 72 hr) led to the accumulation of mRNA for the acetyl-LDL (scavenger) receptor and apolipoprotein E (apo E). These studies establish that vascular EC and SMC produce substantial MCSF in response to a variety of stimuli. The local production of MCSF during atherogenesis may contribute to macrophage survival and proliferation or activate specific macrophage functions such as expression of the scavenger receptor and secretion of apo E.

Maternal and perinatal effects of hypertension at term

This study sought to determine if selected maternal and fetal outcomes in term singleton pregnancies complicated by hypertension during labor differed from those without this complication. All pregnancies delivered at Parkland Memorial Hospital, Dallas, Texas, during 1986 were ascertained using a computerized database. A total of 11,812 term singleton pregnancies ended in delivery during the study period; 1,392 (12%) were complicated by hypertension. Women with a total of 1,383 of these hypertensive pregnancies presented to the hospital with a live fetus. Hypertension was diagnosed in 984 (19%) of the 5,060 primiparous and 399 (6%) of the 6,752 parous women. Hypertension during labor in term singleton pregnancies is associated with increased maternal risks because of the potential complications associated with interventions necessary for successful management. Moreover, hypertension in such pregnancies also increases the perinatal mortality rate. However, this increased rate results from a higher likelihood that fetal death will occur prior to the patient's presentation to the hospital. The risk of fetal morbidity and mortality appears to be low in the hypertensive woman with a term pregnancy admitted to the hospital with a live fetus.

Inhibition of protein kinase C is associated with a decrease in c-myc expression in human myeloid leukemia cells

Treatment of human myeloid leukemic cells with phorbol esters such as 12-O-tetradecanoylphorbol-13-acetate (TPA) is associated with activation and then partial down-regulation of protein kinase C activity. Previous work has suggested that the activation of protein kinase C by TPA contributes to the decrease in c-myc expression during differentiation of these cells. The present studies demonstrate that the decline in c-myc mRNA levels following exposure of HL-60 cells to TPA is preceded by an increase in expression of this gene. In contrast, exposure of HL-60 cells to inhibitors of protein kinase C activity is associated with down-modulation of c-myc expression. Similar findings have been obtained in U-937 myeloid leukemia cells. Taken together, these findings suggest that phorbol esters have a biphasic effect on c-myc expression. Whereas the activation of protein kinase C by phorbol esters may be associated with an increase in c-myc gene expression, the subsequent partial down-regulation of kinase activity may initiate a cascade of events resulting in the down-modulation of c-myc expression.

Mechanisms of X-ray-mediated protooncogene c-jun expression in radiation-induced human sarcoma cell lines

c-jun is a protooncogene associated with neoplastic transformation and is transcriptionally induced by ionizing radiation. To examine the possible mechanisms of radiation-induced c-jun transcription, we analyzed RNA from human tumor cell lines RIT-3 and STSAR-5 following x-irradiation in the presence of protein kinase inhibitors, or the absence of serum and calcium. Protooncogene c-jun expression increased several fold following irradiation of these radiation-induced human sarcoma cell lines. The expression of c-jun was not altered following irradiation in conditioned medium containing serum as compared to that of cells in serum free medium. Depletion of PKC by prolonged TPA treatment resulted in inhibition of c-jun expression. In addition, nonspecific protein kinase inhibitors, staurosporin and H7 attenuated c-jun expression, whereas the analogue of ATP (sangivamycin) did not. Furthermore, the selective inhibitor of cAMP dependent protein kinase HA 1004 did not alter radiation-mediated c-jun induction. These data indicate that ionizing radiation exposure results in c-jun induction which is dependent upon the activation of PKC. Protein kinase C activation and the subsequent expression of the protooncogene c-jun by ionizing radiation may further define the molecular mechanisms of radiation-induced neoplastic transformation.

Tumor necrosis factor gene expression is mediated by protein kinase C following activation by ionizing radiation

Tumor necrosis factor (TNF) production following X-irradiation has been implicated in the biological response to ionizing radiation. Protein kinase C (PKC) is suggested to participate in TNF transcriptional induction and X-ray-mediated gene expression. We therefore studied radiation-mediated TNF expression in HL-60 cells with diminished PKC activity produced by either pretreatment with protein kinase inhibitors or prolonged 12-O-tetradecanoylphorbol-13-acetate treatment. Both treatments resulted in attenuation of radiation-mediated TNF induction. Consistent with these results, we found no detectable induction of TNF expression following X-irradiation in the HL-60 variant deficient in PKC-mediated signal transduction. The rapid activation of PKC following gamma-irradiation was established using an in vitro assay measuring phosphorylation of a PKC specific substrate. A 4.5-fold increase in PKC activity occurred 15 to 30 s following irradiation, which declined to baseline at 60 s. Two-dimensional gel electrophoresis of phosphoproteins extracted from irradiated cells demonstrated in vivo phosphorylation of the PKC specific substrate Mr 80,000 protein at 45 s following X-irradiation. These findings indicate that signal transduction via the PKC pathway is required for the induction of TNF gene expression by ionizing radiation.

Ionizing radiation induces expression and binding activity of the nuclear factor kappa B

Recent studies have demonstrated that treatment of mammalian cells with ionizing radiation is associated with activation of gene expression. Although the signal transduction pathways stimulated by ionizing radiation remain unclear, our previous findings indicate that radiation induces specific genes at the transcriptional level. The present work has examined the effects of ionizing radiation on the transcription factor NF-kappa B. The results demonstrate that ionizing radiation activates DNA binding of nuclear factor (NF)kappa B. This effect was detectable at 2 grays (Gy) and reached a maximum at 5-20 Gy. At a dose of 20 Gy, the increase in NF-kappa B binding activity was maximal at 2-4 h and then declined to pretreatment levels. The results also demonstrate that ionizing radiation transiently increases NF-kappa B mRNA levels. However, the finding that induction of NF-kappa B binding to DNA occurs in the presence of cycloheximide indicates that ionizing radiation activates preexisting NF-kappa B protein. NF-kappa B exists as a cytoplasmic protein before activation. Thus, our results suggest that ionizing radiation induces transduction pathways which include cytoplasmic signaling events.

Effects of hexamethylene bisacetamide on induction of monocytic differentiation of human U-937 myeloid leukemia cells

The present studies have examined the effects of hexamethylene bisacetamide (HMBA) on the human U-937 monocytic cell line. HMBA treatment was associated with: (1) decreases in U-937 cell proliferation, (2) increases in nonspecific esterase activity and cell surface antigen expression consistent with monocytic differentiation, (3) decreases in c-myc gene expression, and (4) induction of tumor necrosis factor (TNF) transcripts. Treatment of U-937 cells with HMBA was also associated with increases in phospholipase A2 activity and increases in the release of arachidonic acid and its metabolites. Dexamethasone, an agent previously shown to inhibit monocytic differentiation, had no detectable effect on the down-regulation of c-myc, but blocked the induction of TNF expression. Taken together, the results demonstrate that HMBA induces monocytic differentiation of U-937 cells and that this effect is sensitive, in part, to dexamethasone.

Regulation of jun-B expression by a cyclic AMP (cAMP)-dependent mechanism in human myeloid cells

The present studies have examined the regulation of the jun-B early response gene by cyclic AMP (cAMP)-dependent signaling pathways. The 2.0-kb jun-B transcript was at low but detectable levels in uninduced human HL-60 myeloid leukemia cells. In contrast, treatment with 1 mmol/L8-bromo-adenosine 3',5'-cyclic monophosphate (8-Br-cAMP) in the presence of isobutylmethylxanthine, an inhibitor of cAMP-dependent phosphodiesterase, was associated with increases in jun-B transcripts that were maximal by 1 hour and then decreased to near pretreatment levels by 6 hours. Similar findings were obtained with 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate (8-CPT-cAMP) and N6,2'-0-dibutyryladenosine 3',5'-cyclic monophosphate (dBt-cAMP). jun-B transcripts were also increased with other agents that increase intracellular cAMP levels, such as prostaglandin E2 (PGE2) and forskolin. Moreover, inhibition of cAMP-dependent protein kinase by the isoquinolinesulfonamide H-8 blocked 8-Br-cAMP-induced increases in jun-B expression. The results of nuclear run-on assays demonstrate that treatment of HL-60 cells with PGE2, forskolin, 8-Br-cAMP, and dBt-cAMP is associated with increases in the rate of jun-B transcription. The present findings also demonstrate that the related jun-D gene is similarly regulated by a cAMP-dependent pathway. Taken together, these findings suggest that stimulation of cAMP-dependent protein kinase is involved in the induction of jun gene expression in myeloid leukemia cells.

Posttranscriptional regulation of the zinc finger-encoding EGR-1 gene by granulocyte-macrophage colony-stimulating factor in human U-937 monocytic leukemia cells: involvement of a pertussis toxin-sensitive G protein

The EGR-1 gene is an immediate early response gene encoding a zinc finger DNA-binding protein. The present studies have examined the regulation of EGR-1 gene expression in human U-937 monocytic leukemia cells treated with granulocyte-macrophage colony-stimulating factor (GM-CSF). The results demonstrate that GM-CSF rapidly and transiently increases EGR-1 gene expression in U-937 cells. Similar findings were obtained in GM-CSF-treated human monocytes. We also show that the regulation of EGR-1 expression by GM-CSF is a pertussis toxin-sensitive event. The results of nuclear run-on assays further demonstrate that the EGR-1 gene is constitutively transcribed in untreated U-937 cells and that GM-CSF has little effect on this rate of transcription. Inhibition of protein synthesis with cycloheximide also had no detectable effect on EGR-1 gene transcription but was associated with superinduction of EGR-1 mRNA levels in GM-CSF-treated cells. Moreover, the half-life of GM-CSF-induced EGR-1 transcripts was prolonged from 33 to 70 min following inhibition of protein synthesis. Taken together, the results indicate that GM-CSF activates signaling pathways which regulate EGR-1 gene expression through a pertussis toxin-sensitive G protein and that these events increase EGR-1 mRNA levels by a posttranscriptional mechanism. This GM-CSF-dependent regulation of EGR-1 expression may provide a mechanism for transducing signals to the nucleus that are involved in the control of gene transcription.

Elective hospitalization in the management of twin pregnancies

We sought to evaluate the effectiveness of a policy of early elective hospitalization on the outcomes of 522 consecutive twin gestations delivered at our institution between 1983-1987. During the first 2 years (1983-1985), 237 twin pregnancies were delivered with a policy of elective hospitalization when twin pregnancy was diagnosed between 24-32 weeks' gestation. When possible, elective hospitalization started at 24 weeks' gestation. Electively admitted women remained hospitalized until 34 weeks' gestation, at which time they were discharged unless complications developed requiring continued hospitalization. During 1985-1987, 285 women with twin gestations were intentionally managed as outpatients unless intercurrent complications required hospitalization. A total of 211 twin pregnancies was excluded from analysis because the women did not present for prenatal care (19%) or were undiagnosed until delivery (22%). Of the remaining 311 pregnancies available for study, 134 were managed when the elective admission policy prevailed and 177 when this policy was not in effect. Although the elective admission policy did result in a small reduction in the incidence of low birth weight among the 58 pregnancies hospitalized electively (mean [+/- SEM] gestational age at elective hospitalization 27.7 +/- 0.3 weeks) compared with outpatient management, this policy did not result in an improvement in prematurity (32 versus 36%; P greater than .05) or perinatal morbidity as reflected by requirement for neonatal intensive care (12 versus 11%; P greater than .05) and mechanical ventilation (8 versus 9%; P greater than .05). Moreover, perinatal mortality was actually higher in the electively hospitalized pregnancies (8 versus 2%; P = .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of tumor necrosis factor gene expression by ionizing radiation in human myeloid leukemia cells and peripheral blood monocytes

Previous studies have demonstrated that ionizing radiation induces the expression of certain cytokines, such as TNF alpha/cachectin. However, there is presently no available information regarding the molecular mechanisms responsible for the regulation of cytokine gene expression by ionizing radiation. In this report, we describe the regulation of the TNF gene by ionizing radiation in human myeloid leukemia cells. The increase in TNF transcripts by x rays was both time- and dose-dependent as determined by Northern blot analysis. Similar findings were obtained in human peripheral blood monocytes. Transcriptional run-on analyses have demonstrated that ionizing radiation stimulates the rate of TNF gene transcription. Furthermore, induction of TNF mRNA was increased in the absence of protein synthesis. In contrast, ionizing radiation had little effect on the half-life of TNF transcripts. These findings indicate that the increase in TNF mRNA observed after irradiation is regulated by transcriptional mechanisms and suggest that production of this cytokine by myeloid cells may play a role in the pathophysiologic effects of ionizing radiation.

Biological consequences of gene regulation after ionizing radiation exposure

Ionizing radiation is a ubiquitous environmental mutagen and carcinogen widely used in cancer therapy. However, little is known about the induction of cellular signaling events and specific gene expression after radiation exposure. We review the accumulating evidence that ionizing radiation induces signal transduction pathways involving activation of protein kinase C and a program of genetic events that may contribute to the biological effects of x rays.

Protein kinase C mediates x-ray inducibility of nuclear signal transducers EGR1 and JUN

The cellular response to ionizing radiation includes growth arrest and DNA repair followed by proliferation. Induction of immediate early response genes may participate in signal transduction preceding these phenotypic responses. We analyzed mRNA expression for different classes of immediate early genes (JUN, EGR1, and FOS) after cellular x-irradiation. Increased expression of the EGR1 and JUN genes was observed within 0.5-3 hr following x-ray exposure. Preincubation with cycloheximide was associated with superinduction of JUN and EGR1 in x-irradiated cells. Inhibition of protein kinase C activity by prolonged stimulation with phorbol 12-myristate 13-acetate or the protein kinase inhibitor H7 prior to irradiation attenuated the increase in EGR1 and JUN transcripts. FOS expression was not coregulated with that of EGR1 following x-irradiation, suggesting a distinct regulatory pathway of this gene as compared with its regulation following serum and phorbol ester. These data implicate the EGR1 and JUN proteins as signal transducers during the cellular response to radiation injury and suggest that this effect is mediated in part by a protein kinase C-dependent pathway.

Expression of the jun-B gene during induction of monocytic differentiation

The AP-1 protein complex binds to specific DNA sequences that regulate transcription of genes responsive to certain growth factors and phorbol esters. This complex is composed of products of the jun and fos gene families. The present studies have examined the effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) on the regulation of jun-B gene expression during induction of monocytic differentiation. Low levels of jun-B transcripts were present in uninduced HL-60 promyelocytic leukemia cells. In contrast, treatment with TPA was associated with rapid increases in jun-B mRNA levels that were maximal at 3 h and remained elevated at 48 h. The induction of jun-B expression by TPA in these cells preceded that of the c-jun and c-fos genes. Similar increases in jun-B transcripts were detectable in TPA-treated THP-1 and U-937 myeloid leukemia cells, although expression of this gene was transient in the more differentiated THP-1 cells. Run-on assays demonstrated low levels of jun-B gene activation in untreated HL-60 cells, whereas TPA treatment was associated with a 6-fold increase in the transcription rate of this gene. This induction of jun-B expression occurred in the absence of de novo protein synthesis. In contrast, inhibition of protein synthesis was associated with superinduction of TPA-induced jun-B mRNA levels and an increase in stability of this transcript. These findings suggest that jun-B gene expression is regulated at both the transcriptional and posttranscriptional levels during induction of monocytic differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of c-jun gene expression by cAMP in HL-60 myeloid leukemia cells

Previous studies have demonstrated that expression of the c-jun proto-oncogene is induced by phorbol esters and other agents that activate protein kinase C. The present work has examined the involvement of cAMP-dependent signaling mechanisms in the regulation of c-jun gene expression. Low levels of c-jun transcripts were detectable in untreated HL-60 myeloid leukemia cells. In contrast, treatment of these cells with 8-bromoadenosine 3',5'-cyclic monophosphate was associated with increases in c-jun expression that were maximal at 3 h and then declined to pretreatment levels. Similar findings were obtained with N6,2'-O-dibutyryladenosine 3',5'-cyclic monophosphate and 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate, but not with 8-bromoguanosine 3',5'-cyclic monophosphate. c-jun transcripts were also increased with agents, such as prostaglandin E2 and forskolin, that increase intracellular cAMP levels. The effects of these agents on c-jun expression were associated with activation of cAMP-dependent protein kinase. Moreover, inhibition of this kinase activity with the isoquinolinesulfonamide derivative H8 was associated with a block in the induction of c-jun expression by cAMP. Nuclear run-on analysis further demonstrated that while c-jun transcription is a low levels in untreated HL-60 cells, treatment with cAMP analogs is associated with an increase in the transcriptional rate of this gene. Taken together, these findings suggested that, in addition to activation of protein kinase C, stimulation of cAMP-dependent protein kinase activity is also involved in the transcriptional induction of c-jun gene expression. The present results similarly demonstrate that c-fos gene transcription is induced in HL-60 cells through a mechanism involving cAMP-dependent protein kinase activity. Since heterodimers of the Jun and Fos proteins have been shown to bind to the phorbol ester-responsive element (AP-1-binding site), the present findings indicate that cAMP-induced signaling events may also regulate gene transcription through formation of Fos/Jun heterodimers and that interaction between phorbol ester- and cAMP-dependent pathways could occur through induction of the c-jun gene in these cells.

Progress of fibrinolysis during tumor necrosis factor infusions in humans. Concomitant increase in tissue-type plasminogen activator, plasminogen activator inhibitor type-1, and fibrin(ogen) degradation products

Several investigators have reported that tumor necrosis factor (TNF) can alter the production of plasminogen activator type-1 (PAI-1) and plasminogen activators (PAs) by endothelial cells in vitro. We have examined the in vivo effects of recombinant human TNF administration on fibrinolysis as assessed by parameters in plasma during a 24-hour period of continuous TNF infusion to 17 cancer patients with active disease. The plasma levels of PAI activity increased sevenfold after 3 and 24 hours of TNF infusion. This was the result of an increase of PAI-1 antigen; PAI-2 antigen was not detectable. Plasma concentrations of tissue-type PA (t-PA) antigen increased twofold to fivefold after 3 and 24 hours of TNF infusion, whereas urokinase-type PA antigen levels in plasma remained unaltered. After 3 hours of TNF infusion the plasma levels of alpha 2-antiplasmin were slightly decreased, 5% on average, suggesting that fibrinolysis continued. After 24 hours of TNF infusion a highly significant increase in fibrin- plus fibrinogen-degradation products, and separately of fibrin degradation products and fibrinogen degradation products, was found. This indicates that fibrinolysis persisted, at least partly, in the presence of high levels of PAI activity. Whereas PAI-1 production increased, t-PA production by human endothelial cells in vitro remains unaltered or even decreases on TNF addition. It has been shown previously that TNF infusion in our patients results in thrombin and fibrin generation. Therefore, it is possible that thrombin, not TNF, is the actual stimulus for t-PA production in our patients. We speculate that fibrin is formed during TNF infusions and that plasmin is generated by t-PA action immediately on the initial formation of (soluble) fibrin molecules. Such a process may explain the generation of degradation products of both fibrin and fibrinogen during infusion of TNF in patients.

Phospholipase A2 activation and autoinduction of tumor necrosis factor gene expression by tumor necrosis factor

Tumor necrosis factor (TNF) acts via a cell surface receptor to induce a variety of cellular events including cytolysis, differentiation, and mitogenesis. The mechanisms underlying the cell specific actions of TNF are not known. In the present study, postreceptor events associated with the autoinduction of TNF expression were examined in HL-60 cells. There was no detectable alteration in phospholipase C activity as measured by inositol phosphate generation or release of choline metabolites following TNF stimulation. However, TNF increased the release of arachidonic acid metabolites from HL-60 cells. This increase in arachidonic acid metabolism was associated with a 40% increase in phospholipase A2 activity. Furthermore, the release of arachidonic acid metabolites was blocked by inhibitors of phospholipase A2. Taken together, these findings indicated that TNF stimulates phospholipase A2 and arachidonic acid metabolism in HL-60 cells. The results also demonstrate that TNF expression is induced 15-30 min after stimulation with TNF and that this effect is associated with an increase in the rate of TNF transcription. This autoinduction of TNF mRNA was blocked by inhibitors of phospholipase A2. While the cyclooxygenase inhibitor indomethacin had no detectable effect, ketoconazole and nordihydroguaiaretic acid, inhibitors of lipoxygenase, also blocked the induction of TNF expression by TNF. These findings suggest that phospholipase A2 and lipoxygenase activity are required for the transcriptional activation of TNF gene expression associated with TNF stimulation of HL-60 cells.

Transcriptional regulation of c-jun gene expression by arabinofuranosylcytosine in human myeloid leukemia cells

Previous studies have demonstrated that 1-beta-D-arabinofuranosylcytosine (ara-C) induces terminal differentiation of human myeloid leukemia cells. Other studies have shown that the c-jun protooncogene is expressed during phorbol ester-induced myeloid differentiation. This work examines the effects of ara-C on c-jun gene expression in human KG-1 myeloid leukemia cells. The results demonstrate that c-jun transcripts are undetectable in uninduced KG-1 cells and that ara-C induces expression of this gene in a concentration- and time-dependent manner. Ara-C treatment was also associated with increases in c-jun transcripts in U-937, THP-1, and HL-60 myeloid leukemia cells. Furthermore, transcriptional run-on analysis has demonstrated that exposure to ara-C increases the rate of c-jun gene transcription. The results also demonstrate that while inhibition of protein synthesis superinduces c-jun mRNA levels in phorbol ester-treated KG-1 cells, cycloheximide had no effect on the induction of c-jun transcripts during ara-C treatment. Moreover, the half-life of c-jun transcripts in ara-C-treated KG-1 cells was 42 min. These findings suggest that the increase in c-jun mRNA observed during ara-C treatment is regulated by a transcriptional mechanism, and that c-jun may be involved in the induction of differentiation and regulation of gene expression by ara-C.

Induction of monocytic differentiation by tumor necrosis factor in phorbol ester-resistant KG-1a cells

Tumor necrosis factor (TNF) is a regulatory cytokine that has pleiotropic effects on hematopoietic cell growth and differentiation. The present studies have examined the effects of TNF on the differentiation of phorbol-ester resistant human KG-la leukemia cells. Treatment with 100 U/mL of TNF or 33 nM 12-O-tetradecanoylphorbol-13-acetate (TPA) had no detectable effect on the growth of KG-1a cells. In contrast, TNF, but not TPA, induced cellular aggregation and expression of the ICAM-1 adhesion molecule in KG-1a cells. Furthermore, KG-1a cells responded to TNF, but not to TPA, with a partial down-regulation of c-myc mRNA levels and induction of M-CSF gene transcription. Previous work suggested that TNF induces M-CSF gene expression through activation of phospholipase A2 and eicosanoid production. The present studies also demonstrate that TNF stimulated phospholipase A2 activity. In contrast, there was no detectable increase in phospholipase A2 activity following TPA treatment. These results indicate that: 1) certain characteristics of the differentiated monocytic phenotype were induced by TNF in the phorbol ester-resistant KG-1a line, and 2) treatment with TNF and not TPA was associated with activation of phospholipase A2 during induction of monocytic differentiation in these cells.

Inhibition of phorbol ester-induced monocytic differentiation and c-fms gene expression by dexamethasone: potential involvement of arachidonic acid metabolites

The treatment of human U-937 leukemia cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) is associated with induction of monocytic differentiation. However, the signaling pathways responsible for induction of the differentiated monocytic phenotype remain unclear. The present studies demonstrate that dexamethasone blocks TPA-induced U-937 cell growth inhibition, adherence, and alpha-naphthyl acetate esterase staining. The results also demonstrate that dexamethasone inhibits the appearance of c-fms transcripts associated with TPA treatment. Run-on transcription assays demonstrated that the c-fms gene is transcriptionally active in uninduced U-937 cells and that the rate of transcription is unchanged after dexamethasone and/or TPA treatment. These findings indicated that TPA increases c-fms expression by a dexamethasone-sensitive posttranscriptional mechanism. Treatment of U-937 cells with TPA was also associated with stimulation of arachidonic acid metabolism. Furthermore, dexamethasone, an inhibitor of phospholipase A2 activity, blocked TPA-induced increases in arachidonic acid release. These findings suggested that TPA may regulate certain features of monocytic differentiation, such as c-fms gene expression, through the formation of arachidonic acid metabolites. Indomethacin, an inhibitor of cyclooxygenase, had no detectable effect on c-fms gene expression. However, the cyclooxygenase metabolite, prostaglandin E2, inhibited the TPA-induced increases in c-fms mRNA levels. Taken together, the results indicate that TPA regulates c-fms gene expression by a dexamethasone-sensitive mechanism and that c-fms mRNA levels are controlled by metabolites of the arachidonic acid pathway.