Lack of binding of bacterial lipopolysaccharide to mouse lung macrophages and restoration of binding by gamma interferon.

Although peritoneal resident macrophages (PRM) or peritoneal exudate macrophages (PEM) were activated by lipopolysaccharide (LPS) to kill tumor cells in vitro, lung macrophages (LM) obtained by mincing lung tissues or by harvesting bronchial lavage were not activated by LPS under any experimental conditions, i.e., different LPS concentrations, incubation times and cytotoxicity assay methods. The unresponsiveness of LM to LPS was seen in all of the mouse strains tested. Treatment of LM with indomethacin did not affect the unresponsiveness, although it greatly augmented the cytotoxicity of PRM stimulated with LPS. LM treated in vitro with crude lymphokines (LK) did not show cytotoxicity, but became sensitive to LPS and cytotoxic for tumor cells. LM treated first with crude LK and then with LPS were cytotoxic, but LM treated first with LPS and then with crude LK were not. The ability of crude LK to render LM responsive to LPS was neutralized by rabbit anti-mouse gamma interferon (IFN-gamma) antiserum but not by anti-mouse IFN-(alpha + beta) antiserum. LM treated with recombinant murine IFN-gamma became responsive to LPS and showed cytotoxicity. LM were resistant to direct toxicity of LPS under conditions in which significant populations of PRM and PEM died. However, LM became sensitive to direct toxicity of LPS by treatment with crude LK or recombinant murine IFN-gamma. Fluorescence microscopy showed that almost all PRM and PEM were stained with fluorescein isothiocyanate (FITC)-LPS, while less than 5% of the LM were stained. Instead, approximately 60% of the LM treated with the crude LK or recombinant IFN-gamma for 20 h were stained with FITC-LPS. Fluorescence-activated cell sorter (FACS) analysis confirmed this result. The staining of IFN-gamma treated LM with FITC-LPS was inhibited by polymyxin B or unlabeled LPS. These results suggest that the defective responsiveness of LM to LPS is due to the lack or very low expression of LPS-binding sites on the cell surface and that in vitro treatment with IFN-gamma brings about the expression of them and renders LM responsive to LPS.

Cytochalasin D inhibits lipopolysaccharide-induced tumor necrosis factor production in macrophages.

We reported previously that a reorganization of microfilaments can be observed when macrophages are stimulated with lipopolysaccharide (LPS). This reorganization is not detected with current methods in macrophages of an LPS-nonresponsive C3H/HeJ mouse. These results suggest that the observed microfilament response might be involved in a macrophage-activating process induced by LPS. To investigate this, we studied the effect of cytochalasin D (CD), which inhibits reorganization of microfilaments, on LPS-induced tumor necrosis factor (TNF) production. A concentration of CD incapable of affecting filamentous actin by itself was used in these experiments. When this concentration of CD was added after LPS stimulation, microfilament reorganization and TNF production were inhibited. The suppressive effect of CD on TNF production was confirmed by the observation that TNF-alpha mRNA expression was also inhibited by CD. This inhibitory effect of CD was not specific to TNF, because the production of interleukin-1 and prostaglandin E2 were also inhibited. These effects of CD were observed only when CD was added within the first 20 min after LPS stimulation. These results suggest that the CD-sensitive microfilament response is essential in the signaling pathway for the production of certain monokines in LPS-stimulated macrophages.

Erythromycin promotes monocyte to macrophage differentiation.

Recent reports have suggested that long-term administration of erythromycin (EM) appears to ameliorate some of chronic inflammatory processes where macrophages and lymphocytes play important roles. Our study was initiated to examine the effect of EM on monocyte-macrophage lineage in vitro. EM (1 approximately 100 micrograms/ml) significantly increased the number of adherent monocyte-derived macrophages after 7 days of culture. The combination of EM and macrophage colony stimulating factor (M-CSF) synergistically increased the number of monocyte-derived macrophages, while the combination of EM and granulocyte-macrophage colony stimulating factor exerted an additive effect. Culture with EM induced the expression of a surface antigen CD71, one of the activation markers of macrophages as compared with control cultures. The combination of EM plus M-CSF significantly enhanced H2O2-producing capacity of those cells as compared with M-CSF alone. A differentiation process of monocytoid THP-1 cells was also augmented by EM. These results indicate that EM promotes differentiation of human monocyte-macrophage lineage, altering their functions.

Antilymphocytic activity of erythromycin distinct from that of FK506 or cyclosporin A.

Erythromycin (EM), a macrolide antibiotic has been recently reported to depress the extent of inflammation irrespective of its antimicrobial action. Our study was initiated to examine the effect of EM on T cell proliferation in vitro, since other macrolide antibiotics FK506 and rapamycin (RAP) have been well known to possess strong immunosuppressive or anti-inflammatory potential. EM had a suppressive effect on the proliferative response of human lymphocytes stimulated with mitogens and antigens, while EM had no effect on concanavalin A (Con A)-induced interleukin-2 (IL-2) production or IL-2R alpha (CD25) expression. Delayed addition of EM after the first 48 hours of mitogenic stimulation did suppress IL-2-dependent proliferation of Con A blasts, whereas pretreatment with EM for the first 48 hours of stimulation did not impede the subsequent IL-2-dependent proliferation of obtained blast cells. The results indicate that EM suppresses T cell proliferation at a late stage in the activation process by impairing their response to IL-2. This antilymphocytic action of EM was quite distinct from that of FK506 or cyclosporin A (CsA) but was similar to that of RAP. Unlike RAP, however, EM did not antagonize FK506-induced suppression but potentiated the action of FK506 and CsA. The addition of an enteric hormone motilin, a receptor of which was previously found to be occupied by EM, unaffected the lymphocyte proliferation and the subsequent EM-induced suppression. These data suggest that EM operates through an undefined mechanism probably distinct from that of FK506, CsA, RAP or motilin.

Interferon-gamma or BCG restores the responsiveness of mouse lung macrophages to lipopolysaccharide.

While mouse peritoneal macrophages respond well to lipopolysaccharide, lung macrophages were neither activated for tumor cell cytotoxicity nor killed directly by it. The unresponsiveness of lung macrophages was ascribed to lack of expression of lipopolysaccharide-binding sites on the cell surface. It was found that in vitro treatment of lung macrophages with interferon-gamma or in vivo sensitization of them with viable BCG restored the response by expression of the lipopolysaccharide binding sites. The modes of action of interferon-gamma and BCG in expressing the binding sites on mouse lung macrophages are discussed.

[Activation of macrophages with Hochu-ekkito].

We attempted to analyse the mode of action of Hochu-ekkito on host defense mechanism, especially the effect of the drug on macrophage activation. Peptone-induced murine peritoneal exudate macrophages were incubated with/without Hochu-ekkito and interferon-gamma (IFN-gamma) for 16 hours at 37 degrees C, and then the supernatants harvested were assayed for the activities of TNF, IL-1 and prostaglandin E2. Cytotoxic activity of the macrophages against 51Cr-labeled EL-4 tumor cells was also assayed. It was found that Hochu-ekkito rendered macrophages cytotoxic against EL-4 cells. Hochu-ekkito also augmented the production of TNF, IL-1 or Prostaglandin E2 from macrophages. Synergistic effect of IFN-gamma for augmenting production of TNF or cytotoxic activity was noted. These results suggested that Hochu-ekkito activated macrophages directly in vitro.

Appearance of a cell surface antigen associated with the activation of peritoneal macrophages in mice.

A relatively large population of murine peritoneal exudate macrophages induced with viable BCG or heat-killed Corynebacterium parvum was stained by the antiserum prepared against purified gangliotetraosyl ceramide (asialo GM1), while only a small population of peritoneal resident macrophages or peritoneal exudate macrophages induced with proteose peptone was stained. The cytotoxicity assay of those macrophages with anti-asialo GM1 plus complement supported these results. Peritoneal macrophages induced with BCG or C. parvum showed strong cytotoxicity for EL4 cells in vitro, while resident or peptone-induced peritoneal macrophages showed no cytotoxicity. BCG- or C. parvum-induced peritoneal cells contained both NK cells and cytotoxic macrophages, and either in vivo or in vitro pretreatment of the cells with anti-asialo GM1 and complement abolished the activities of both types of cells. Peptone-induced peritoneal macrophages incubated with lymphokines (LK) or lipopolysaccharide (LPS) were cytotoxic for EL4 cells and contained an increased number of cells stained by anti-asialo GM1. The cytotoxicity of these in vitro activated macrophages was reduced by treatment with anti-asialo GM1 plus complement. When peptone-induced peritoneal macrophages were incubated with LK, the number of cells stained by anti-Ia antiserum increased, but the number did not increase when the macrophages were incubated with LPS. Pretreatment of peptone-induced macrophages with anti-asialo GM1 plus complement did not affect the ability of the macrophages to be activated by LK. These results taken together strongly suggest that the antigen(s) reactive with anti-asialo GM1 is expressed on the cell surface of cytotoxic peritoneal macrophages in mice.

Delayed-type hypersensitivity (DTH) in BCG-sensitized mice I. Lack of suppressor T cell activity on DTH to sheep red blood cells.

Mice pretreated with an intravenous (i.v.) injection of BCG (BCG-sensitized mice) and then immunized intravenously with a high dose (10(8)--10(9)) of sheep red blood cells (SRBC) 2 weeks later developed strong delayed-type hypersensitivity (DTH) to SRBC, as in mice pretreated with cyclophosphamide (CY) (CY-treated mice) and then immunized with SRBC 2 days later; normal mice given the same dose of SRBC did not show such DTH. The mechanism of this strong DTH to SRBC which developed in BCG-sensitized mice was studied, by comparing it with that in CY-treated mice. The transfer of either whole spleen cells or thymus cells, but not serum, obtained from mice immunized with i.v. injections of 10(9) SRBC 4 days previously (hyperimmune mice) did not suppress either the induction or the expression of DTH to SRBC in BCG-sensitized mice, but suppressed those in CY-treated mice. The suppressor cells were SRBC-specific T cells. Adoptive transfer of DTH to SRBC by spleen cells from either BCG-sensitized mice of CY-treated mice to hyperimmune recipients failed. The adoptive transfer of DTH from BCG-sensitized mice to normal recipients also failed if the spleen cells from hyperimmune mice were cotransferred. Whole body irradiation (600 rad) of mice 2 hr before or after the time of immunization with SRBC reduced significantly DTH to SRBC in both BCG-sensitized and CY-treated mice. It was noticed that the total number of spleen cells in BCG-sensitized mice was 3--4 times larger than that in CY-treated mice. From these results, we conclude that the entity of effector T cells of DTH to SRBC induced in BCG-sensitized mice and in CY-treated mice was not different in terms of susceptibility to suppressor T cells and irradiation, but that the total numbers of effector T cells generated in these mice differed remarkably, resulting in the above-described different responsiveness to suppressor T cells transferred passively.

Preexposure of macrophages to low doses of lipopolysaccharide inhibits the expression of tumor necrosis factor-alpha mRNA but not of IL-1 beta mRNA.

LPS is known to be a potent activator of macrophages and induces the production of TNF-alpha and IL-1. However, the signaling events and regulatory mechanisms required for the activation of macrophages by LPS have not been resolved precisely. We show that LPS modulates its own response in macrophages. Proteose peptone-induced murine peritoneal macrophages (P-PEM) produce significant amount of TNF-alpha and IL-1 after stimulation with LPS. However, preexposure of macrophages to low doses (less than 1 ng/ml) of LPS renders them refractory to stimulation by a second round of LPS, as evaluated by production of TNF-alpha. The loss of sensitivity to a second round of LPS was selective for TNF-alpha production as the LPS-primed macrophages retained the ability to produce IL-1. Northern blot analysis was performed with total RNA obtained from control and LPS- (1 ng/ml) primed P-PEM after 3-h stimulation with a second round of LPS. The expression of TNF-alpha mRNA was inhibited in LPS-primed P-PEM, whereas the expression of IL-1 beta mRNA was the same in control and LPS-primed P-PEM, consistent with the data of biologic activities of these two cytokines. Zymosan-induced TNF-alpha production was the same in control and LPS-primed macrophages, indicating that not all of the pathways required for TNF-alpha production were affected by LPS priming. Monokines such as human (h) rIL-1 alpha, hrTNF-alpha, hrIL-6, and murine rIFN-beta could not substitute for the action of low doses of LPS, and addition of indomethacin could not restore TNF-alpha production. These results suggest that exposure of macrophages to low doses of LPS suppresses the production of TNF-alpha, but not of IL-1, by inhibiting the expression of mRNA through a noncyclooxygenase-dependent mechanism. Thus, LPS-induced production of TNF-alpha and IL-1 in macrophages are differently regulated.

LPS induces selective translocation of protein kinase C-beta in LPS-responsive mouse macrophages, but not in LPS-nonresponsive mouse macrophages.

Translocation of protein kinase C (PKC) after PMA or LPS stimulation has been studied in thioglycolate (TGC)-elicited murine peritoneal macrophages. Among the PKC subtypes we examined (alpha, beta, gamma, delta, and epsilon) by indirect immunostaining and immunoblot analysis, conventional PKC-beta, as well as novel PKC-delta and PKC-epsilon were found to exist in TGC-elicited C3H/HeN mouse macrophages. Translocation of PKC-beta to the Triton-stable cytoskeleton could be seen in macrophages after stimulation by both PMA and LPS. On the other hand, novel PKCs redistributed only after PMA stimulation. Macrophages obtained from LPS-nonresponsive C3H/HeJ mice also exhibited PKC-beta, and the m.w., cellular distribution, and cellular content of this enzyme could not be distinguished from those of C3H/HeN macrophages. These macrophages exhibited PKC-delta and PKC-epsilon, as did the C3H/HeN macrophages. In these macrophages, however, LPS did not induce any remarkable change in the intracellular distribution of PKC-delta and PKC-epsilon or PKC-beta, whereas PMA was able to induce the translocation of PKC-beta to the cytoskeleton. These results suggest that LPS stimulation induces selective redistribution of PKC-beta in LPS-responsive macrophages, whereas a defect related to LPS unresponsiveness exists in C3H/HeJ mouse macrophages before the PKC activation. Translocation of PKC-beta can be understood to be an important event in LPS signaling in macrophages.

Suppression of TNF-alpha mRNA expression in LPS-primed macrophages occurs at the level of nuclear factor-kappa B activation, but not at the level of protein kinase C or CD14 expression.

Previously, we reported that preexposure of proteose peptone-elicited murine peritoneal exudate macrophages (P-PEM) to a low dose of LPS suppressed the expression of TNF-alpha mRNA, but not of IL-1 beta mRNA, induced by a second round of LPS exposure. To elucidate the mechanisms underlying this hyporesponsiveness to LPS, we focused on two molecules: nuclear factor (NF)-kappa B and CD14. Activation of NF-kappa B induced by a second round of LPS was suppressed in LPS-primed P-PEM much like the suppression of TNF-alpha mRNA expression. However, protein kinase C (PKC), a candidate as an activator of NF-kappa B, was not desensitized by LPS priming. LPS-induced TNF-alpha production was not affected by depletion of PKC, and LPS could not induce translocation of PKC. CD14 expression showed no significant difference between control and primed P-PEM. In contrast with J774.1 cells and thioglycolate medium-elicited macrophages (T-PEM), P-PEM exhibited serum-independent TNF-alpha production, and a polyclonal Ab to murine CD14 had no inhibitory effect on the LPS-induced TNF-alpha production by P-PEM. These results suggest that priming by LPS causes blockage at an early step, at least before the activation of NF-kappa B, in the LPS signal transduction pathway, but not at the expression of CD14. Our results also suggest that, in P-PEM, in contrast to J774.1 cells and T-PEM, neither PKC nor CD14 is involved in the LPS-induced activation and suppression of TNF-alpha gene expression.

Interleukin-10 contributes development of macrophage suppressor activities by macrophage colony-stimulating factor, but not by granulocyte-macrophage colony-stimulating factor.

Macrophages are known to possess suppressor activities in immune responses. To determine the effects of GM-CSF and M-CSF on the expression of macrophage suppressor activities, monocyte-derived macrophages cultured with GM-CSF (GM-Mphis) were compared with those cultured with M-CSF (M-Mphis) for antigen-specific proliferation and interferon-gamma (IFN-gamma) production by lymphocytes. Both GM-Mphis and M-Mphis equally suppressed lymphocyte proliferation, but only M-Mphis suppressed IFN-gamma production in response to purified protein derivative (PPD). M-Mphis, but not GM-Mphis, released IL-10 not only in the course of macrophage differentiation but also in response to PPD after maturation to macrophages. From the results that (i) exogenous IL-10 suppressed IFN-gamma production, but not proliferation of lymphocytes, and that (ii) neutralizing antibody to IL-10 reversed suppressor activities of M-Mphis on IFN-gamma production, but not lymphocyte proliferation, it appeared that IL-10 was the major factor responsible for suppression of IFN-gamma production. Thus, these results suggest that only M-CSF augments IL-10-dependent suppressor activity of macrophages on IFN-gamma production and that both GM-CSF and M-CSF induce IL-10-independent macrophage suppressor activity on lymphocyte proliferation.

Human alveolar macrophages and granulocyte-macrophage colony-stimulating factor-induced monocyte-derived macrophages are resistant to H2O2 via their high basal and inducible levels of catalase activity.

Human alveolar macrophages (A-MPhi) and macrophages (MPhi) generated from human monocytes under the influence of granulocyte-macrophage colony-stimulating factors (GM-MPhi) express high levels of catalase activity and are highly resistant to H(2)O(2). In contrast, MPhi generated from monocytes by macrophage colony-stimulating factors (M-MPhi) express low catalase activity and are about 50-fold more sensitive to H(2)O(2) than GM-MPhi or A-MPhi. Both A-MPhi and GM-MPhi but not M-MPhi can induce catalase expression in both protein and mRNA levels when stimulated with H(2)O(2) or zymosan. M-MPhi but not GM-MPhi produce a large amount of H(2)O(2) in response to zymosan or heat-killed Staphylococcus aureus. These findings indicate that GM-MPhi and A-MPhi but not M-MPhi are strong scavengers of H(2)O(2) via the high basal level of catalase activity and a marked ability of catalase induction and that catalase activity of MPhi is regulated by colony-stimulating factors during differentiation.

Enhancement of macrophage colony-stimulating factor-induced growth and differentiation of human monocytes by interleukin-10.

Interleukin-10 (IL-10) has been reported to be a negative cytokine for monocytes/macrophages. In the present study, we showed that IL-10 is rather a positive cytokine and augments the growth and differentiation of human monocytes stimulated with macrophage colony-stimulating factor (M-CSF). Highly purified adherent human monocytes were cultured for 7 days with M-CSF in the presence or absence of IL-10. The number of recovered cells increased in the culture of monocytes with M-CSF + IL-10 compared to the culture with M-CSF alone. IL-10 alone was not enough to maintain the survival and differentiation of monocytes into macrophages. Morphological change cultured in M-CSF was also accelerated by addition of IL-10, and macrophages cultured in M-CSF + IL-10 were more elongated compared to macrophages cultured with M-CSF alone. Binding of 125I-M-CSF to monocytes incubated with M-CSF + IL-10 was about 1.7-fold higher than that to monocytes incubated with M-CSF alone. In accordance with the binding study, Northern blot analysis showed that the levels of the expression of c-fms, M-CSF receptor, mRNA in macrophages cultured in M-CSF + IL-10 were higher than that in macrophages cultured in M-CSF alone. Macrophages cultured in M-CSF + IL-10 expressed higher level of Fc gamma RI, II, III, and showed augmented Fc gamma receptor mediated phagocytosis. The former also produced higher level of H2O2 and O2-, when stimulated with zymosan, and of IL-6 when stimulated with lipopolysaccharide compared to the latter. These results taken together suggest that IL-10 augments the growth and differentiation of human monocytes cultured in M-CSF.

Restoration of lipopolysaccharide-mediated cytotoxic macrophage induction in C3H/HeJ mice by interferon-gamma or a calcium ionophore.

Proteose peptone-induced peritoneal exudate macrophages (PEM) from C3H/HeJ mice do not respond to lipopolysaccharide (LPS) in vitro in terms of activation for tumor cytotoxicity. This unresponsiveness of PEM was overcome by addition of culture supernatant of normal mouse spleen cells stimulated with insoluble concanavalin A. The supernatant component responsible for the restoration of PEM sensitivity to LPS was indicated to be interferon (IFN)-gamma, because pretreatment of the supernatant with anti-mouse IFN-gamma antiserum, but not with anti-IFN-(alpha + beta) antiserum, abolished the supernatant activity and because recombinant murine IFN-gamma (rIFN-gamma) could replace the supernatant effect. Not only the LPS activation of tumor cytotoxicity of PEM but also the sensitivity of PEM to the lethal toxicity of LPS was restored by rIFN-gamma. IFN-gamma action in restoring the LPS responsiveness of PEM was mimicked by a calcium ionophore, A23187, but not by phorbol 12-myristate 13-acetate. These results suggest that IFN-gamma can restore LPS responsiveness of PEM from C3H/HeJ mice and that elevation of the intracellular calcium level is involved in the action of IFN-gamma.

Effects of granulocyte-macrophage colony-stimulating factor and colony-stimulating factor-1 on the proliferation and differentiation of murine alveolar macrophages.

Murine alveolar macrophages (AM) were shown to have proliferative ability and to form colonies in vitro. The factors in lung-conditioned medium (CM) and L929-CM which stimulate the proliferation of AM were considered to be granulocyte-macrophage colony-stimulating factor (GM-CSF) and CSF-1, respectively, because recombinant murine (rm)GM-CSF and recombinant human (rh)CSF-1 could replace the activities of lung-CM and L929-CM, respectively. The phenotype of the cells in the colonies formed by AM incubated with rmGM-CSF or lung-CM was AM-like; more than 90% of the cells were stained by anti-asialo GM1 but not by FITC-LPS, and had AM-like morphology. Expression of Mac-1 Ag determined by M1/70HL in these cells as well as original AM was low. However, the phenotype of the cells in the colonies formed by AM incubated with rhCSF-1 or L929-CM was peritoneal macrophage (PM)-like; more than 90% of the cells were stained by FITC-LPS and M1/70HL, but not by anti-asialo GM1, and showed PM-like morphology. The cells in the colonies formed by AM incubated with rmGMCSF changed their phenotype after treatment with rhCSF-1; the percentage of cells stained by anti-asialo GM1 decreased, and that of cells stained by FITC-LPS increased. The cells in the colonies formed by AM incubated with rhCSF-1 never changed their phenotype after incubation with rmGM-CSF. In contrast to AM, more than 90% of the cells in all colonies formed by PM incubated with either rmGM-CSF, rhCSF-1, lung-CM, or L929-CM were stained by FITC-LPS but not by anti-asialo GM1. These results show that although AM and PM can proliferate, AM, in contrast to PM, are bipotential cells that can differentiate into two types of macrophages responding to distinct types of CSF, and that one of the molecular mechanisms controlling macrophage heterogeneity may be based on the type of CSF produced at distinct tissues.