Effect of retinoids on the release and gene expression of tumor necrosis factor-alpha in human peripheral blood monocytes

The effect of retinoic acid (RA) and retinol (ROH) on the release of tumor necrosis factor (TNF) by human peripheral blood monocytes (HPBM) was determined. HPBM were cultured for various periods of time in either 5% complete (cAB) or delipidized (DLS) AB serum. TNF release (L929 cytolytic assay) in the presence of cAB occurred during the first 3 days of in vitro culture. Delipidization of AB serum completely inhibited the lipopolysaccharide (LPS)-induced release of TNF by HPBM. Addition of RA (0.5 microM) to DLS restored LPS-induced TNF release by HPBM, and supplementation with ROH (1.0 microM) resulted in release of TNF-like activity, but only after 3 days of in vitro culture. The maintenance of TNF release by the addition of exogenous RA after 3 days of in vitro culture suggested that depletion of endogenous RA was partially responsible for loss of TNF-like activity. The levels of endogenous TNF protein and mRNA were not influenced by delipidization of serum and were found to be similar to those of HPBM cultured in the presence of AB serum. TNF protein and mRNA were undetectable in HPBM ROH-treated cell lysates, although cytolytic activity was observed in culture supernatants. These results suggest that retinoids are required for the release of cytolytic factors from HPBM and that non-TNF cytolytic factors may be released by these cells at different stages of maturation.

Regulation of HIV replication in infected monocytes by IFN-alpha. Mechanisms for viral restriction

In a survey of 15 different virus isolates, no IFN-alpha or IFN-beta activity was detected in culture fluids of HIV-infected T cells or monocytes. Exogenous rIFN-alpha added to T lymphoblast or monocyte cultures induced restriction in replication of the amphotropic HIV that infect both cell types. With IFN-treated HIV-infected T cells, levels of reverse transcriptase (RT) activity in culture fluids were half those in control cultures, but the frequency of infected cells or the levels of p24 Ag released in culture fluids were unchanged. In contrast to the modest effect of IFN on HIV-infected T cells, IFN-induced antiviral activity in monocytes was quite dramatic. Monocytes treated with IFN at the time of virus challenge showed no evidence of HIV infection: no p24 Ag or RT activity, no viral mRNA, and no proviral DNA. In this system, IFN interrupts one or more early event(s) in the virus replication cycle before formation of proviral DNA. Monocyte cultures infected with HIV 7 days before IFN treatment showed a gradual decrease in levels of p24 Ag and RT activity to baseline by 3 wk. HIV-induced cytopathic changes were markedly reduced, and the frequency of productively infected cells was less than or equal to 1% of total cells. Virus particles released 24 h after IFN treatment were 100- to 1000-fold less infectious than equal numbers of control virions. But, monocytes treated with IFN 7 days after HIV infection were not free of the retroviral pathogen: levels of proviral DNA in the IFN-treated and control HIV-infected cells were indistinguishable. The presence of large quantities of proviral DNA in cells with little or no evidence for active transcription documents a situation approaching true microbiological latency.

Regulation of HIV replication in infected monocytes by IFN-alpha. Mechanisms for viral restriction

In a survey of 15 different virus isolates, no IFN-alpha or IFN-beta activity was detected in culture fluids of HIV-infected T cells or monocytes. Exogenous rIFN-alpha added to T lymphoblast or monocyte cultures induced restriction in replication of the amphotropic HIV that infect both cell types. With IFN-treated HIV-infected T cells, levels of reverse transcriptase (RT) activity in culture fluids were half those in control cultures, but the frequency of infected cells or the levels of p24 Ag released in culture fluids were unchanged. In contrast to the modest effect of IFN on HIV-infected T cells, IFN-induced antiviral activity in monocytes was quite dramatic. Monocytes treated with IFN at the time of virus challenge showed no evidence of HIV infection: no p24 Ag or RT activity, no viral mRNA, and no proviral DNA. In this system, IFN interrupts one or more early event(s) in the virus replication cycle before formation of proviral DNA. Monocyte cultures infected with HIV 7 days before IFN treatment showed a gradual decrease in levels of p24 Ag and RT activity to baseline by 3 wk. HIV-induced cytopathic changes were markedly reduced, and the frequency of productively infected cells was less than or equal to 1% of total cells. Virus particles released 24 h after IFN treatment were 100- to 1000-fold less infectious than equal numbers of control virions. But, monocytes treated with IFN 7 days after HIV infection were not free of the retroviral pathogen: levels of proviral DNA in the IFN-treated and control HIV-infected cells were indistinguishable. The presence of large quantities of proviral DNA in cells with little or no evidence for active transcription documents a situation approaching true microbiological latency.

Interferon affects nuclear proteins in cells of clinically sensitive chronic myelogenous leukemia patients

Cytoplasmic protein extracts from chronic myelogenous leukemia (CML) cells contained an activity that altered the electrophoretic mobility of complexes formed between nuclear proteins and the transcriptional enhancers of interferon (IFN)-inducible genes. Exposure of CML cells to IFN-alpha diminished the effect of the CML cytoplasmic proteins on these nuclear protein-DNA complexes. The presence of clinical responsiveness to IFN-alpha correlated with the sensitivity to the IFN-induced change in the electrophoretic mobility of nuclear protein-DNA complexes. These data suggest that the action of IFN-alpha in CML may be linked to a pathway that can result in posttranslational modification of nuclear proteins.

Analysis of peripheral blood granulocyte-macrophage colony growth by limiting dilution assay

Analysis of myeloid progenitor cells in the peripheral blood (peripheral blood colony-forming unit granulocyte-macrophage; PBCFU-GM) is limited by their low frequency and by the presence of inhibitory cell populations. These factors limit the study of cytokines and cellular influences on PBCFU-GM in semisolid media assays and complicate the interpretation of data. We have developed a limiting dilution assay (LDA) in liquid culture for PBCFU-GM that allows evaluation of inhibitory or accessory effects of other cell populations and estimation of progenitor cell frequency. Using this system we have examined the inhibitory effect of autologous monocytes on in vitro colony growth. After monocyte depletion by counterflow centrifugal elutriation and adherence, colony growth with recombinant human granulocyte-macrophage colony-stimulating factor was linear over a wide range of cell densities, indicating a direct proliferative effect on circulating myeloid progenitor cells. Simultaneous PBCFU-GM assays in agar demonstrated monocyte inhibition but did not afford reliable interpretation of either progenitor frequency or linear growth kinetics in a statistically verifiable fashion. LDA in liquid culture may be a useful tool to study the effects of various cytokines and cell populations on PBCFU-GM in vitro and in vivo.

Cellular pharmacology of liposomal cis-bis-neodecanoato-trans-R,R-1,2-diaminocyclohexaneplatinum (II) in mouse resident peritoneal macrophages, Kupffer cells, and hepatocytes

The in vitro and in vivo interaction of liposomal cis-bis-neodecanoato-trans-R,R-1,2-diaminocyclohexaneplatinum++ + (II) (L-NDDP) with mouse resident peritoneal macrophages (RPM), Kupffer cells (KC), and hepatocytes was studied. The peak in vitro uptake of L-NDDP by RPM was 12.5 ng elemental platinum/100 micrograms cell protein and constituted 0.2% of the platinum available for phagocytosis. The subsequent release of platinum by RPM was rapid initially, with a 20-fold increase over the first 4 h, followed by a plateau; ultrafilterable (free) platinum constituted 50% of the total platinum released at 24 h. The retained intracellular platinum in RPM at 24 h was close to 50% of that initially present. The peak in vitro uptake of L-NDDP by KC was 11.3 ng platinum/100 micrograms cell protein and amounted to 0.2% of the platinum available for phagocytosis. The release of platinum by KC was detectable only after 4 h of incubation and increased 3-fold over the next 14 h. The ultrafilterable platinum released by KC at 18 h was 40% of the total platinum released. The retained intracellular platinum in KC at 18 h was 33% of that initially present. The peak in vitro uptake of L-NDDP by hepatocytes was almost 50 ng platinum/100 micrograms cell protein and constituted 0.8% of the platinum available for intake. Following the i.v. injection of L-NDDP, hepatocytes contained up to 6-fold higher platinum concentrations than KC. This observation was supported by transmission electron microscopy showing a higher concentration of multilamellar vesicles within hepatocytes than in KC, 5 min after i.v. injection of L-NDDP. These findings suggest that L-NDDP becomes available to the liver following i.v. injection, that both macrophages and hepatocytes play a role in the metabolism of L-NDDP, and that Kupffer cells could mediate a sustained release of platinum in the liver following the interaction with L-NDDP, indicating the potential of L-NDDP for the treatment of tumors in the liver.

Induction of tissue transglutaminase in human peripheral blood monocytes by intracellular delivery of retinoids

Human peripheral blood monocytes (HPBM) from normal donors, isolated by counter-current centrifugal elutriation into two subpopulations, showed no significant difference in their ability to differentiate in vitro into macrophages as determined by induction of a protein cross-linking enzyme tissue transglutaminase (TGase). The two subpopulations were equally responsive to the augmenting effect of recombinant interferon-gamma (rIFN-gamma) on expression of tissue TGase. In vitro maturation and treatment with rIFN-gamma of HPBM were associated with increased binding of tritiated retinol. Intracellular delivery of retinol rendered this hormone active in inducing the differentiation of HPBM. The retinoid-induced expression of tissue TGase was the result of increased accumulation of the enzyme peptide and not activation of preexisting enzyme. We propose, therefore, that maturation of HPBM, induced by in vitro culture or treatment with rIFN-gamma, is associated with acquisition of cell surface receptors for serum retinol-binding protein.

Effector mechanisms of human monocyte-mediated tumor cytotoxicity in vitro: biochemical, functional, and serological characterization of cytotoxins produced by peripheral blood monocytes isolated by counterflow elutriation

Human peripheral blood monocytes, isolated in high purity by centrifugal counterflow elutriation from normal donors, release cell toxins, herein termed human monocyte toxins (HMTs) upon further stimulation in vitro. The principal form of HMTs produced by these human peripheral blood monocytes has been subjected to biochemical, functional, and serological characterization. By molecular sieving on Sephacryl S-200, HMTs can be resolved into two molecular weight classes. The larger, termed alpha, has a molecular weight of about 120,000, and the smaller, termed beta, has a molecular weight of about 65,000. The beta class is by far the most predominant species and has been further characterized. Chromatofocusing of beta-HMT indicates a slightly acidic nature, since this species is eluted at pH 5.8. Functional characterization of beta-HMT suggests that it is not a trypsin-like protease, since neither alpha,N-tosyl-L-lysylchloromethylketone nor alpha,N-tosyl-L-arginyl methyl ester are capable of causing significant inhibition of the cell-lytic activity of the molecule. Furthermore, cell lysis induced by beta-HMT appears to be independent of oxygen-dependent mechanisms, since catalase is incapable of blocking lysis, and since hydrogen peroxide and superoxide anion are not produced in detectable amounts during lysis. Finally, beta-HMT does not appear to be an arginase, since it is active in arginine-containing medium and further addition of arginine to the assay medium does not inhibit lysis significantly. beta-HMT is serologically related to recombinant human tumor necrosis factor (rHuTNF), since its cell lytic activity can be blocked by a rabbit antiserum against rHuTNF. However, much higher levels of this antiserum are required to achieve neutralization than are required to neutralize a comparable number of cell lytic units of rHuTNF. Furthermore, the results of preliminary immunoprecipitation experiments using the rabbit anti-rHuTNF antiserum suggest that a peptide in the Mr 60,000-70,000 range is recognized by this serum, whereas no signal at Mr 17,000 corresponding to rHuTNF is detectable. Thus, human peripheral blood monocytes can be triggered to release cell toxins, the principal form of which, beta-HMT, appears to be functionally distinct from the cytotoxic proteases reported in the murine system and appears to be molecularly distinct from, but serologically related to rHuTNF.

Characterization of small and large human peripheral blood monocytes: effects of in vitro maturation on hydrogen peroxide release and on the response to macrophage activators

Human peripheral blood monocytes (HPBM) isolated from normal donors by centrifugal elutriation were divided into two populations according to volume. (Median volumes of small monocytes (SM) and large monocytes (LM) were 255 micron and 280 micron, respectively.) H2O2 production was determined during in vitro culture and in response to bacterial lipopolysaccharide (LPS), and to recombinant human interferon-gamma (rIFN-gamma). On day 1, H2O2 production by LM was significantly greater than that by SM. In vitro culture of SM resulted in an augmented ability to produce H2O2. By day 3, SM were the major H2O2 producers. Freshly isolated SM and LM, exposed for 24 hr to LPS and rIFN-gamma, showed different patterns of activation. Both SM and LM responded to LPS, with LM responding maximally at lower doses than SM. Only SM showed a significant augmentation of H2O2 production with rIFN-gamma treatment. We also assessed the effect of in vitro culture with activation. SM but not LM showed an increased H2O2 to LPS and rIFN-gamma after 7 days in culture. Continuous exposure of SM to rIFN-gamma resulted in maximal H2O2 production at day 3 of culture; this pattern was not seen for LPS. The production of H2O2 by HPBM is related to in vitro maturation. The enhanced H2O2 production by HPBM upon exposure to rIFN-gamma may be related to the induction of in vitro maturation.

Characterization of small and large human peripheral blood monocytes: effects of in vitro maturation on hydrogen peroxide release and on the response to macrophage activators

Human peripheral blood monocytes (HPBM) isolated from normal donors by centrifugal elutriation were divided into two populations according to volume. (Median volumes of small monocytes (SM) and large monocytes (LM) were 255 micron and 280 micron, respectively.) H2O2 production was determined during in vitro culture and in response to bacterial lipopolysaccharide (LPS), and to recombinant human interferon-gamma (rIFN-gamma). On day 1, H2O2 production by LM was significantly greater than that by SM. In vitro culture of SM resulted in an augmented ability to produce H2O2. By day 3, SM were the major H2O2 producers. Freshly isolated SM and LM, exposed for 24 hr to LPS and rIFN-gamma, showed different patterns of activation. Both SM and LM responded to LPS, with LM responding maximally at lower doses than SM. Only SM showed a significant augmentation of H2O2 production with rIFN-gamma treatment. We also assessed the effect of in vitro culture with activation. SM but not LM showed an increased H2O2 to LPS and rIFN-gamma after 7 days in culture. Continuous exposure of SM to rIFN-gamma resulted in maximal H2O2 production at day 3 of culture; this pattern was not seen for LPS. The production of H2O2 by HPBM is related to in vitro maturation. The enhanced H2O2 production by HPBM upon exposure to rIFN-gamma may be related to the induction of in vitro maturation.

Effector mechanisms of human monocyte-mediated tumor cytotoxicity in vitro: parameters of induction of cytotoxins from peripheral blood monocytes isolated by counterflow elutriation

Human peripheral blood monocytes, isolated in high purity by centrifugal counterflow elutriation from normal donors, were stimulated in vitro to release cell toxins, herein termed human monocyte toxin(s) (HMT). Bacterial lipopolysaccharide, the lipophilic 6-O-stearoyl derivative of muramyl dipeptide, and 4 beta-phorbol-12 beta-myristate-13 alpha-acetate served as effective induction signals. Induction involved a sequence of transcription, translation, and secretion, all necessary for HMT synthesis and release into the supernatant as determined by blocking of these functions with the drugs actinomycin D, cycloheximide, and monensin, respectively; HMT levels reached a peak within 4-6 h and thereafter declined. The levels of HMT produced varied considerably from donor to donor; one parameter causing this variability appeared to be the plateletapheresis history of the donor. Monocytes from donors subjected to pheresis for the first time were responsive to induction signals immediately after adherence and could not be brought to a higher state of priming for HMT production by further in vitro culture for up to 9 days, with or without recombinant human gamma-interferon. In contrast, monocytes from donors who had recently undergone pheresis (up to 1 wk earlier) were poorly responsive initially to triggering with lipopolysaccharide; however, these cells could be brought to a highly primed state for HMT production by a combination of culture in vitro for several days and a subsequent 24-h exposure to recombinant gamma-interferon (0.1-1.0 units/ml). These primed cells could then be effectively triggered by lipopolysaccharide to release HMT. HMT was found to be cytotoxic (cytostatic/cytolytic) for human and murine tumor cells in vitro.

Centrifugal elutriation as a method for isolation of large numbers of functionally intact human peripheral blood monocytes

Centrifugal elutriation was used further to isolate human peripheral blood monocytes (HPBM) from mononuclear-enriched cells harvested as a secondary component following platelet concentration collection samples. HPBM were recovered in either one or two populations consisting of either total HPBM or small (SM) and large monocytes (LM). The elutriation was carried out at 3,500 +/- 5 rpm for the separation of lymphocytes and HPBM in Ca++- and Mg++-free PBS without EDTA. An average of 5.05 +/- 1.50 X 10(8) HPBM were recovered in the total HPBM with a purity of 95% +/- 3%. The SM and LM were obtained by splitting the total HPBM into two equal populations with an HPBM purity of 92% +/- 3% and 93% +/- 3, respectively, by nonspecific esterase staining. The elutriation media were shown to have no effect on viability by trypan blue exclusion. All three HPBM populations were shown to be histochemically (lack of reactivity to leu-1 and leu-7) and functionally (depletion of NK cell activity) purified from the lymphocyte population. The HPBM populations were enriched in HLA-Dr, OKM-1, OKM-5, MY-8, and leu M-3 monoclonal antibody marker staining. There were no differences in percent positive cells between SM and LM populations for any of the monocyte-specific monoclonal antibodies. All three monocyte populations mediated antibody-dependent cell-mediated cytotoxicity to human red blood cells, with LM mediating more lysis (27.0% +/- 5%) than SM (7% +/- 3%).(ABSTRACT TRUNCATED AT 250 WORDS)