Blood in the joint: effects of hemarthrosis on meniscus health and repair techniques.

Injury to the meniscus is common and frequently leads to the development of post-traumatic osteoarthritis (PTOA). Many times meniscus injuries occur coincident with anterior cruciate ligament (ACL) injuries and lead to a bloody joint effusion. Hemarthrosis, or bleeding into the joint, has been implicated in degeneration of joint tissues. The goal of this review paper is to understand the pathophysiology of blood-induced joint damage, the possible effects of blood on meniscus tissue, and the implications for current meniscus repair techniques that involve the introduction of blood-derived products into the joint. In this review, we illustrate the similarities in the pathophysiology of joint damage due to hemophilic arthropathy (HA) and osteoarthritis (OA). Although numerous studies have revealed the harmful effects of blood on cartilage and synovium, there is currently a gap in knowledge regarding the effects of hemarthrosis on meniscus tissue homeostasis, healing, and the development of PTOA following meniscus injury. Given that many meniscus repair techniques utilize blood-derived and marrow-derived products, it is essential to understand the effects of these factors on meniscus tissue and the whole joint organ to develop improved strategies to promote meniscus tissue repair and prevent PTOA development.

Rhizobium radiobacter bacteremia in a neonate.

Rhizobium radiobacter bacteremia is an infrequent cause of human infection. We report a rare manifestation of R. radiobacter infection in which bacteremia occurred in a newborn infant without other risk factors.

Productive human immunodeficiency virus type 1 (HIV-1) infection of nonproliferating human monocytes.

Human immunodeficiency virus type 1 (HIV-1) infection of T lymphocytes requires cellular proliferation and DNA synthesis. Human monocytes were shown to have low DNA synthesis rates, yet the monocytotropic BaL isolate of HIV-1 was able to infect these cells efficiently. Monocytes that were irradiated to assure no DNA synthesis could also be readily infected with HIV-1BaL. Such infections were associated with the integration of HIV-1BaL DNA into the high molecular weight, chromosomal DNA of monocytes. Thus, normal, nonproliferating monocytes differ from T lymphocytes in that a productive HIV-1 infection can occur independently of cellular DNA synthesis. These results suggest that normal nonproliferating mononuclear phagocytes, which are relatively resistant to the destructive effects of this virus, may serve as persistent and productive reservoirs for HIV-1 in vivo.

Interferon (IFN)-alpha activation of human blood mononuclear cells in vitro and in vivo for nitric oxide synthase (NOS) type 2 mRNA and protein expression: possible relationship of induced NOS2 to the anti-hepatitis C effects of IFN-alpha in vivo.

Although researchers have noted high level activation of rodent mononuclear phagocytes for nitric oxide (NO) synthase type 2 (S2) expression and NO production with a variety of agents such as interferon (IFN) gamma and endotoxin, it has been difficult to demonstrate activation of human mononuclear phagocytes. The purpose of this study was to determine if IFN-alpha serves as an activator in vitro and in vivo in humans. Treatment of normal monocytes or mononuclear cells in vitro with IFN-alpha caused a dose-dependent increase in monocyte NOS2 activity and NO production, and increased expression of NOS2 protein and mRNA expression. To determine if in vivo administration of IFN-alpha also modulated NOS2, we studied blood cells from patients with hepatitis C before and after IFN-alpha therapy. Untreated patients with chronic hepatitis C virus infection had levels of NOS activity and NOS2 antigen in freshly isolated mononuclear cells similar to those of healthy subjects, and they expressed minimal or no NOS2 mRNA. However, IFN-alpha treatment of patients with hepatitis C infection was associated with a significant elevation in mononuclear cell NOS activity, NOS2 antigen content, and NOS2 mRNA content. IFN-alpha-treated patients had significant decreases in levels of serum alanine aminotransferase and plasma hepatitis C mRNA. The degree of IFN-alpha-enhanced mononuclear cell NOS2 antigen content correlated significantly with the degree of reduction in serum alanine aminotransferase levels. Thus, IFN-alpha treatment of cells in vitro or administration of IFN-alpha to hepatitis C patients in vivo increases expression of mononuclear cell NOS2 mRNA expression, NOS activity, NOS2 antigen expression, and NO production. Since NO has been reported to have antiviral activity for a variety of viruses, we speculate that induced NO production may be related to the antiviral action(s) of IFN-alpha in hepatitis C infection.

The role of nitric oxide in the pathogenesis of spontaneous murine autoimmune disease: increased nitric oxide production and nitric oxide synthase expression in MRL-lpr/lpr mice, and reduction of spontaneous glomerulonephritis and arthritis by orally administered NG-monomethyl-L-arginine.

MRL-lpr/lpr mice spontaneously develop various manifestations of autoimmunity including an inflammatory arthropathy and immune complex glomerulonephritis. This study examines the role of nitric oxide, a molecule with proinflammatory actions, in the pathogenesis of MRL-lpr/lpr autoimmune disease. MRL-lpr/lpr mice excreted more urinary nitrite/nitrate (an in vivo marker of nitric oxide production) than did mice of normal strains and MRL-(+/+) and B6-lpr/lpr congenic strains. In addition, MRL-lpr/lpr peritoneal macrophages had an enhanced capacity to produce nitric oxide in vitro as well as increased nitric oxide synthase activity, and certain tissues from MRL-lpr/lpr mice had increased expression of inducible nitric oxide synthase (NOS) mRNA and increased amounts of material immunoreactive for inducible NOS. Oral administration of NG-monomethyl-L-arginine, a nitric oxide synthase inhibitor, prevented the development of glomerulonephritis and reduced the intensity of inflammatory arthritis in MRL-lpr/lpr mice. By using interspecific backcross mice, the gene for inducible NOS (Nosi) was mapped to mouse chromosome 11. This chromosomal localization was different from those loci that we have previously demonstrated to be linked to enhanced susceptibility to renal disease in an MRL-lpr/lpr cross. However, the chromosomal location of the NOS gene was consistent with an insulin-dependent diabetes locus identified in an analysis of nonobese diabetic (NOD) mice. These results suggest that elevated nitric oxide production could be important in the pathogenesis of autoimmunity, and that treatments to block the production of nitric oxide or block its effects might be valuable therapeutically.

Nitric oxide in Tanzanian children with malaria: inverse relationship between malaria severity and nitric oxide production/nitric oxide synthase type 2 expression.

Nitric oxide (NO)-related activity has been shown to be protective against Plasmodium falciparum in vitro. It has been hypothesized, however, that excess NO production contributes to the pathogenesis of cerebral malaria. The purpose of this study was to compare markers of NO production [urinary and plasma nitrate + nitrite (NOx)], leukocyte-inducible nitric oxide synthase type 2 (NOS2), and plasma TNF-alpha and IL-10 levels with disease severity in 191 Tanzanian children with and without malaria. Urine NOx excretion and plasma NOx levels (corrected for renal impairment) were inversely related to disease severity, with levels highest in subclinical infection and lowest in fatal cerebral malaria. Results could not be explained by differences in dietary nitrate ingestion among the groups. Plasma levels of IL-10, a cytokine known to suppress NO synthesis, increased with disease severity. Leukocyte NOS2 antigen was detectable in all control children tested and in all those with subclinical infection, but was undetectable in all but one subject with cerebral malaria. This suppression of NO synthesis in cerebral malaria may contribute to pathogenesis. In contrast, high fasting NOx levels and leukocyte NOS2 in healthy controls and asymptomatic infection suggest that increased NO synthesis might protect against clinical disease. NO appears to have a protective rather than pathological role in African children with malaria.

Increased expression of blood mononuclear cell nitric oxide synthase type 2 in rheumatoid arthritis patients.

Nitric oxide (NO) is an important inflammatory mediator in nonhuman animal models of rheumatoid arthritis (RA). The purpose of the present study was to determine whether blood mononuclear cells from patients with active RA (as compared to control subjects) have higher levels of NO synthase type 2 (NOS2) and produce more NO in vitro. Leukocytes from 25 RA patients and 20 normal subjects were examined. Arthritis activity was assessed by tender and swollen joint counts, duration of morning stiffness, patient assessment of pain, physician and patient global assessment of disease activity, the modified Stanford Health Assessment Questionnaire, and by blood levels of acute phase reactants. Blood mononuclear cell NOS enzyme activity/antigen content and nitrite/nitrate formation in vitro were measured. Blood mononuclear cells from RA patients had increased NOS activity and increased NOS2 antigen content as compared to those from normal subjects, and responded to interferon-gamma with increased NOS expression and nitrite/nitrate production in vitro. NOS activity of freshly isolated blood mononuclear cells correlated significantly with disease activity, as assessed by render and swollen joint counts. Our results demonstrate that patients with RA have systemic activation for NOS2 expression, and that the degree of activation correlates with disease activity. Increased NOS2 expression and NO generation may be important in the pathogenesis of RA.

Clinical and serologic manifestations of autoimmune disease in MRL-lpr/lpr mice lacking nitric oxide synthase type 2.

Nitric oxide (NO) is an important mediator of the inflammatory response. MRL-lpr/lpr mice overexpress inducible nitric oxide synthase (NOS2) and overproduce NO in parallel with the development of an autoimmune syndrome with a variety of inflammatory manifestations. In previous studies, we showed that inhibiting NO production with the nonselective nitric oxide synthase (NOS) inhibitor NG-monomethyl-arginine reduced glomerulonephritis, arthritis, and vasculitis in MRL-lpr/lpr mice. To define further the role of NO and NOS2 in disease in MRL-lpr/lpr mice, mice with targeted disruption of NOS2 were produced by homologous recombination and bred to MRL-lpr/lpr mice to the N4 generation. MRL-lpr/lpr littermates homozygous for disrupted NOS2 (-/-), heterozygous for disrupted NOS2 (+/-), or wildtype (+/+) were derived for this study. Measures of NO production were markedly decreased in the MRL-lpr/lpr (-/-) mice compared with MRL-lpr/lpr (+/+) mice, with intermediate production by the MRL-lpr/lpr (+/-) mice. There was no detectable NOS2 protein by immunoblot analysis of the spleen, liver, kidney, and peritoneal macrophages of the (-/-) animals, whereas that of (+/+) was high and (+/-) intermediate. The (-/-) mice developed glomerular and synovial pathology similar to that of the (+/-) and (+/+) mice. However, (-/-) mice and (+/-) mice had significantly less vasculitis of medium-sized renal vessels than (+/+) mice. IgG rheumatoid factor levels were significantly lower in the (-/-) mice as compared with (+/+) mice, but levels of anti-DNA antibodies were comparable in all groups. Our findings show that NO derived from NOS2 has a variable impact on disease manifestations in MRL-lpr/lpr mice, suggesting heterogeneity in disease mechanisms.

Dynamic loading enhances integrative meniscal repair in the presence of interleukin-1.

OBJECTIVE: Meniscal tears are a common knee injury and increased levels of interleukin-1 (IL-1) have been measured in injured and degenerated joints. Studies have shown that IL-1 decreases the shear strength, cell accumulation, and tissue formation in meniscal repair interfaces. While mechanical stress and IL-1 modulate meniscal biosynthesis and degradation, the effects of dynamic loading on meniscal repair are unknown. The purpose of this study was to determine the effects of mechanical compression on meniscal repair under normal and inflammatory conditions. EXPERIMENTAL DESIGN: Explants were harvested from porcine medial menisci. To simulate a full-thickness defect, a central core was removed and reinserted. Explants were loaded for 4h/day at 1 Hz and 0%-26% strain for 14 days in the presence of 0 or 100 pg/mL of IL-1. Media were assessed for matrix metalloproteinase (MMP) activity, aggrecanase activity, sulfated glycosaminoglycan (S-GAG) release, and nitric oxide (NO) production. After 14 days, biomechanical testing and histological analyses were performed. RESULTS: IL-1 increased MMP activity, S-GAG release, and NO production, while decreasing the shear strength and tissue repair in the interface. Dynamic loading antagonized IL-1-mediated inhibition of repair at all strain amplitudes. Neither IL-1 treatment nor strain altered aggrecanase activity. Additionally, strain alone did not alter meniscal healing, except at the highest strain magnitude (26%), a level that enhanced the strength of repair. CONCLUSIONS: Dynamic loading blocked the catabolic effects of IL-1 on meniscal repair, suggesting that joint loading through physical therapy may be beneficial in promoting healing of meniscal lesions under inflammatory conditions.

Tumor cell killing by phorbol ester--differentiated human leukemia cells.

The tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate causes differentiation of cells of the human leukemia cell line HL60 to nondividing macrophage-like cells. These differentiated cells are cytotoxic for tumor cells (including parent, untreated HL60 cells) in vitro. Agents that induce this desirable differentiation to nondividing, antitumor effector cells may be useful in the experimental treatment of leukemia.

Macrophage tumor killing: influence of the local environment.

Tumor killing by activated macrophages is not a highly determined biologic event, but a relative capability influenced by the local environment. An intrinsic macrophage cytotoxic effector system is modulated by serum and other environmental factors that can either enhance or suppress tumor killing. Activated macrophages kill tumor cells only when a regulating threshold drops to a critically low level.

Receptor-mediated modulation of human monocyte, neutrophil, lymphocyte, and platelet function by phorbol diesters.

The tumor promoting phorbol diesters elicit a variety of responses from normal and leukemic blood cells in vitro by apparently interacting with cellular receptors. The biologically active ligand [20-(3)H] phorbol 12,13-dibutyrate ([(3)H]PDBu) bound specifically to intact human lymphocytes, monocytes, polymorphonuclear leukocytes (PMN), and platelets, but not to erythrocytes. Binding, which was comparable for all four blood cell types, occurred rapidly at 23 degrees and 37 degrees C, reaching a maximum by 20-30 min usually followed by a 30-40% decrease in cell associated radioactivity over the next 30-60 min. The time course for binding was temperature dependent with equilibrium binding occurring after 120-150 min at 4 degrees C, with no subsequent loss of cell-associated radioactivity at this temperature. Bound [(3)H]PDBu could be eluted by addition of unlabeled PDBu. Scatchard analysis of data from 4 degrees C binding studies revealed linear plots with high affinity receptors in these cell types with dissociation constants and receptors per cell of 60 nM and 7.8 x 10(5)/cell for lymphocytes, 51 nM and 15.5 x 10(5)/cell for monocytes, 38 nM and 4.0 x 10(5)/cell for PMN, and 19 nM and 2.9 x 10(4)/cell for platelets. Structure-activity studies using unlabeled phorbol-related compounds demonstrated a close correlation between their abilities to inhibit binding of [(3)H]PDBu to cells and their abilities to induce cellular responses (monocyte and PMN H(2)O(2) secretion, lymphocyte (3)HTdR incorporation, and platelet tritiated serotonin release); phorbol and 4-alpha phorbol were inactive while phorbol 12-myristate 13-acetate (PMA), PDBu, mezerein, and phorbol 12,13-diacetate (in decreasing order of potency) inhibited [(3)H]PDBu binding and elicited the various responses. Thus, these high affinity, specific receptors for the phorbol diesters, present on monocytes, lymphocytes, PMN, and platelets, mediate the pleiotypic effects induced by these ligands.

Monocyte chemotactic peptide receptor. Functional characteristics and ligand-induced regulation.

Monocytes, macrophages, and neutrophils will demonstrate several important cellular functions in response to synthetic formylated oligopeptides. N-formyl-norleucyl-leucyl-phenylalanyl-norleucyl-tyrosyl-lysine (fNLPNTL) was a potent chemoattractant for human blood monocytes; a 1.0-nM concentration induced a maximal chemotactic response. Binding of 125I-labeled fNLPNTL to the monocyte formyl peptide receptor was rapid, specific, and saturable at 4, 24, or 37 degrees C. At 4 degrees C, monocytes from several different donors demonstrated between 10,000 and 18,000 receptors/cell with a dissociation constant (Kd) of 1.7-2.7 nM. The association of the 125I peptide with the cells was irreversible at the elevated temperatures and exceeded the amount of surface receptor by approximately four-fold, suggesting receptor-mediated peptide endocytosis. Processing of rhodamine-labeled fNLPNTL by monocytes was observed directly by video intensification microscopy. At 37 degrees C, diffuse membrane fluorescence was seen initially, followed by rapid aggregation and internalization of the peptide. Monocytes incubated with fNLPNTL displayed a temperature dependent loss of surface binding capacity (receptor down-regulation). This decrease was due to a decrease in surface receptor number rather than to a decrease in receptor affinity. A dose-response curve for peptide-induced receptor down-regulation correlated with a dose-response curve for 125I-labeled fNLPNTL uptake, suggesting that each uptake event led to the loss of one surface receptor. Surface receptor replenishment following down-regulation was rapid and not dependent on new protein synthesis, but was inversely related to both the time and peptide concentration used to induce down-regulation. An exact correlation between receptor down-regulation and functional deactivation of the chemotactic response could not be demonstrated.

Nuclear expression of the 50- and 65-kD Rel-related subunits of nuclear factor-kappa B is differentially regulated in human monocytic cells.

The nuclear factor (NF)-kappa B transcription factor system is composed of at least four inducible nucleoprotein adducts termed p50, p55 (NF-kappa B p50), p75 (NF-kappa B p65), and p85 (c-Rel). These proteins are expressed in the nuclei of activated T cells in a distinctly biphasic fashion, with p55 and p75 induction occurring within minutes whereas the induction of p50 and p85 occurs after several hours. In contrast, p50 and p55 are constitutively expressed in the nuclei of U937 and THP-1 monocytic cells. However, cellular activation is required for the nuclear expression of p75 in these cells. Additionally, activation of monocytic cells does not result in a significant induction of p85. Tumor necrosis factor alpha induces the nuclear expression of p55 and p75 in these monocytic cells within 20 min, presumably reflecting the liberation of these proteins from I kappa B. In contrast, phorbol myristate acetate (PMA) induces the expression of these proteins with delayed kinetics, raising the possibility that PMA is incapable of mediating the efficient release of p55 and p75 from I kappa B in these cells. These findings highlight important differences in the regulation of these proteins in monocytic cells versus T cells and suggest that the induced expression of NF-kappa B p65 in monocytes may play a central role in the activation of HIV-1 gene expression.

Acute myeloblastic leukemia in paroxysmal nocturnal hemoglobinuria. Evidence of evolution from the abnormal paroxysmal nocturnal hemoglobinuria clone.

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hematopoietic stem cell disorder in which the blood cells demonstrate aberrant interactions with serum complement. In part, this is due to the absence of the complement regulatory protein, decay accelerating factor (DAF). A small number of patients with PNH have gone on to develop acute nonlymphocytic leukemia, which is thought to arise from the injured marrow as a second hematopoietic disorder. We have studied a patient with PNH who developed acute myeloblastic leukemia (AML); the blasts from this patient were found to lack DAF as measured by polyclonal antibody binding and fluorescence flow cytometry as well as by immunoblotting. The blasts from 11 other patients with AML bound anti-DAF antibody in amounts similar to normal mononuclear cells from healthy donors. Cells of the human leukemia cell lines HL-60, K562, U937, and HEL also bound anti-DAF antibody. In addition to DAF deficiency, blasts from the PNH patient had undetectable alkaline phosphatase activity, in contrast to human leukemia cell lines. These data suggest that the leukemic cells of the PNH patient arose out of the PNH clone and that AML in the setting of PNH is not a separate disorder.

Oxygen, nitric oxide and articular cartilage.

Molecular oxygen is required for the production of nitric oxide (NO), a pro-inflammatory mediator that is associated with osteoarthritis and rheumatoid arthritis. To date there has been little consideration of the role of oxygen tension in the regulation of nitric oxide production associated with arthritis. Oxygen tension may be particularly relevant to articular cartilage since it is avascular and therefore exists at a reduced oxygen tension. The superficial zone exists at approximately 6% O2, while the deep zone exists at less than 1% O2. Furthermore, oxygen tension can alter matrix synthesis, and the material properties of articular cartilage in vitro. The increase in nitric oxide associated with arthritis can be caused by pro-inflammatory cytokines and mechanical stress. Oxygen tension significantly alters endogenous NO production in articular cartilage, as well as the stimulation of NO in response to both mechanical loading and pro-inflammatory cytokines. Mechanical loading and pro-inflammatory cytokines also increase the production of prostaglandin E2 (PGE2). There is a complex interaction between NO and PGE2, and oxygen tension can alter this interaction. These findings suggest that the relatively low levels of oxygen within the joint may have significant influences on the metabolic activity, and inflammatory response of cartilage as compared to ambient levels. A better understanding of the role of oxygen in the production of inflammatory mediators in response to mechanical loading, or pro-inflammatory cytokines, may aid in the development of strategies for therapeutic intervention in arthritis.

In vivo modulation of macrophage tumoricidal activity: enhanced tumor cell killing by peritoneal macrophages from mice given injections of sodium periodate.

Sodium periodate (NaIO4) administered ip to mice was nontoxic and enhanced the in vitro tumoricidal activity of their peritoneal macrophages. The injection ip of 1 ml of 5 mM NaIO4 caused an influx of polymorphonuclear leukocytes (PMN) at 5-24 hours followed by an accumulation of macrophages and disappearance of the PMN at 48-72 hours. These peritoneal macrophages from mice given injections of NaIO4 were noncytotoxic and nontumoricidal in the absence of lipopolysaccharide (LPS), but in the presence of 5-25 ng/ml or more LPS in vitro, they became markedly cytotoxic and cytocidal for tumor cells. Peritoneal macrophages from mice given injections of phosphate-buffered saline became cytotoxic or cytocidal only with amounts of LPS exceeding 100-500 ng/ml in vitro. Like the peritoneal macrophages from BCG-infected mice that demonstrated selective tumor cytotoxicity, macrophages from mice given injections of NaIO4 had minimal lytic activity for nontransformed normal embryo fibroblasts. Thus when given ip to mice, the simple chemical NaIO4, much like complex and heterogeneous biologic preparations such as BCG, caused differentiation of peritoneal macrophages toward the tumoricidal state.

Spontaneous tumor cell killing by human blood monocytes and human peritoneal macrophages: lack of alteration by endotoxin or quenchers of reactive oxygen species.

Human mononuclear phagocytes (monocytes and macrophages) act as effectors in the destruction of tumor cells. Peritoneal macrophages from normal or infertile women killed a variety of tumor cells in vitro more efficiently than did blood monocytes from the same subjects. Lysis depended on the effector-to-target cell ratio and was neither reproduced by supernatants from nor lysates of the mononuclear phagocytes. Normal fibroblasts were not lysed. Lipopolysaccharide (10(1)-10(4) ng/ml) did not alter the monocyte- or macrophage-mediated tumor cell killing. The monocytes and macrophages had equivalent basal and phorbol 12,13-myristate acetate-stimulated H2O2 and O-2 production, and the reactive oxygen species scavengers or quenchers catalase, superoxide dismutase, mannitol, and L-histidine did not diminish the killing. These observations suggest that the spontaneous tumor cell killing by human mononuclear phagocytes was not mediated by reactive oxygen species.

Enhanced macrophage tumoricidal activity and tumor suppression or regression caused by heat-killed Candida albicans.

The growth of line-10 hepatoma in male Sewall Wright strain 2 guinea pigs was totally suppressed when tumor cells were mixed with heat-killed Candida albicans. In a significant number of animals, injection of C. albicans into established tumors 10-12 mm in diameter caused complete, rapid tumor regression. Guinea pigs whose tumors regressed or were suppressed as a result of injection of C. albicans rejected subsequent challenges at distant sites with the line-10 hepatoma, which indicated the development of systemic immunity to the tumor. Untreated control guinea pigs had positive delayed hypersensitivity reactions to intradermally injected C. albicans, which suggested prior natural exposure of the animals to C. albicans antigens. Peritoneal macrophages from mice that had received ip injections of phosphate-buffered saline (PBS) or C. albicans were not cytocidal for mouse 3T12 tumor cells in vitro. However, macrophages from the mice given injections of C. albicans, unlike those from mice given PBS, were markedly tumoricidal in the presence of 1 ng or more endotoxin/ml in vitro. These results demonstrated that heat-killed C. albicans, when inoculated into the peritoneal cavity, increased the tumoricidal potential of peritoneal macrophages.

Relationship of acivicin-induced monocytoid differentiation of human myeloid leukemia cells to acivicin-induced modulation of growth factor, cytokine, and protooncogene mRNA expression.

We have previously noted that the glutamine antagonist acivicin (alpha S,5S-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid) induces monocytoid differentiation of freshly isolated human myeloid leukemia cells and HL-60 cells. This study was designed to determine the effects of acivicin on the levels of HL-60 cell mRNA transcripts of several cytokines, growth factors, and protooncogenes implicated in the control of hematopoietic cell proliferation and differentiation. Control HL-60 cells did not express mRNA for granulocyte-colony-stimulating factor, granulocyte-macrophage-colony-stimulating factor, interleukin 3, or interleukin 6, and acivicin or phorbol myristate acetate did not induce their expression. Phorbol myristate acetate reduced expression of c-myc, c-myb, and heat shock protein 70 and enhanced those of macrophage-colony-stimulating factor and c-fms. Acivicin caused a decreased expression of c-myc, and an increased expression of mRNA for interleukin 1 beta and tumor necrosis factor alpha (TNF-alpha). The drug also caused an initial increase in c-myb, followed by a subsequent decrease below baseline levels. Supernatants and lysates of acivicin-treated HL-60 cells contained increased levels of interleukin 1 beta. Both TNF-alpha and interleukin 1 beta have been shown previously to influence hematopoietic cell differentiation. In our experiments, exogenous interleukin 1 added to HL-60 cells did not induce differentiation, but the combination of interleukin 1 and TNF synergistically enhanced the process. Pretreatment of the cells with TNF enhanced their responsiveness to subsequent treatment with interleukin 1. Our results demonstrate that the glutamine antagonist acivicin modulates HL-60 cell expression of TNF-alpha, interleukin 1 beta, c-myc, and c-myb and suggest that interleukin 1 beta and TNF-alpha might (in an autocrine manner) cause the differentiation.