Involvement of Ras and MAP kinase (ERK-1) in cisplatin-induced activation of murine bone marrow-derived macrophages

Cisplatin (cis-diamminedichloroplatinum II), a potent antitumor compound, stimulates immune responses by activating monocytes/macrophages and other cells of the immune system. However, the mechanism by which cisplatin activates these cells is poorly characterised. Our earlier findings indicate that cisplatin treatment stimulates rapid tyrosine phosphorylation in a number of cellular proteins in murine macrophages. This initial tyrosine phosphorylation is an important regulatory mechanism and is followed by activation of several other proteins. In the present study, we report the involvement of other key molecules and the role of tyrosine phosphorylation in their activation in the signaling cascade of cisplatin. We observed the involvement of Ras (a low molecular weight GTP-binding protein) and ERK-1 (a MAP kinase) in this signaling cascade. Cisplatin treatment results in an increase in the expression of both Ras and ERK-1 in a dose-dependent manner, which was dependent upon tyrosine phosphorylation. Genistein a PTK inhibitor inhibited the cisplatin induced expression of Ras and ERK-1. These findings indicate that Ras and ERK-1 are important signaling molecules involved in the tumoricidal activation of macrophages with cisplatin and is dependent on initial tyrosine phosphorylation.

Cisplatin-treated macrophages produce oncostatin M: regulation by serine/threonine and protein tyrosine kinases/phosphatases and Ca2+/calmodulin

In the present study it was investigated whether cisplatin-treated murine peritoneal macrophages produce oncostatin M (OSM) and what is the underlying mechanism. The culture supernatants of cisplatin-treated macrophages significantly inhibited the proliferation of OSM-sensitive cell line A375. Within 15 min of cisplatin treatment significant OSM was synthesized and secreted by macrophages. Inhibitors of serine/threonine and protein tyrosine phosphatases augmented cisplatin-induced OSM production of macrophages. The protein kinase C and protein tyrosine kinase inhibitors significantly inhibited OSM production of cisplatin-treated macrophages. The OSM production of cisplatin-treated macrophages was also inhibited in the presence of Ca2+ chelators, Ca2+ channel blocker and calmodulin/calmodulin-dependent kinase inhibitors. These data suggest that OSM production of cisplatin-treated macrophages is regulated by opposing actions of phosphatases and kinases. It is also suggested that OSM production of cisplatin-treated macrophages is dependent on Ca2+, calmodulin and calmodulin-dependent kinase.

Expression of LFA-1 adhesion molecules on cisplatin-treated macrophages

Appropriately activated mononuclear phagocytes mediate contact-dependent tumoricidal activity. Adhesion structures involved in contact-dependent tumor cytotoxicity have not been defined. The present study was aimed at identifying the adhesion structure involved in the tumoricidal activity of cisplatin-activated murine peritoneal macrophages. Tumor cells of different histological origin were used as targets in a 24-h cytotoxicity assay. Anti-CD18 (LFA-1 beta) substantially inhibited macrophage cytotoxicity whereas anti-LFA-1 alpha marginally inhibited macrophage-mediated cytotoxicity. When combined together, almost complete inhibition of tumoricidal activity was observed. Activated macrophages showed augmented binding to target cells and anti-LFA MAb inhibited the binding of resting and activated macrophages to target cells. Cisplatin augmented the expression of LFA-1 alpha and beta integrins and LPS had no effect as assessed by immunoprecipitation. These results implicate that in cisplatin activated macrophages LFA-1 alpha and beta integrins are important molecules in contact-dependent tumoricidal activity.

Effect of aging on the tumoricidal functions of murine peritoneal macrophages

The present investigation was carried out to study the effect of aging on the activation of murine peritoneal macrophages by lipopolysaccharide (LPS) plus interferon-gamma (IFN-gamma) to tumoricidal state. Age-dependent alteration in macrophage-mediated tumor cell binding, cytotoxicity, cytostasis and production of the tumoricidal effector molecules oncostatin M, tumor necrosis factor and nitric oxide (NO) was studied. Macrophages (1.5 x 10(5)) obtained from mice of different age groups were separated on the basis of the reproductive status of the mice into prereproductive (young), reproductive (adult) and postreproductive (old) for studying their activation. Macrophages obtained from the old mice were found to be least responsive to the activation signal of LPS + IFN-gamma for macrophage-mediated tumoricidal activity and production of effector molecules. The macrophages of the old mice did not express inducible nitric oxide synthase, an enzyme responsible for the production of NO by activated macrophages. Macrophages of the adult and young groups showed better response; however, optimal response was observed in the macrophages of adult mice. The reasons for the observed difference in the response of macrophages are discussed.

Protein kinase C: a potential pathway of macrophage activation with cisplatin

Cisplatin (CP) has been reported to activate murine macrophages to tumoricidal state, however, its mechanism of action is not known. In the present study it is reported that the production of: (a) interleukin-1 (IL-1); (b) tumor necrosis factor (TNF); (c) nitric oxide (NO); and (d) macrophage-mediated cytotoxicity by cisplatin-treated bone marrow-derived macrophages were inhibited by PKC inhibitors H-7 and chelerythrine chloride. Also, it was observed that treatment of macrophages with CP resulted in the translocation of PKC from the cytosol to the membrane fraction. These findings suggest the involvement of PKC in the activation of bone marrow-derived macrophages with cisplatin.

Murine peritoneal macrophages treated with cisplatin and interferon-gamma undergo NO-mediated apoptosis via activation of an endonuclease

We investigated whether murine peritoneal macrophages treated with cisplatin or interferon (IFN)-gamma alone, or in combination, could undergo apoptosis, and whether this results either from the cytotoxic effect of the activating agents or indirectly in an autocrine manner by the cytotoxic molecules released by them upon activation. Our data suggest that cisplatin, which has been shown to induce apoptosis in a number of normal as well as tumor cell types, did not induce apoptosis in murine peritoneal macrophages nor was apoptosis caused by IFN-gamma. However, combined treatment with cisplatin and IFN-gamma induced apoptosis in macrophages as studied by percent DNA fragmentation assay, qualitative analysis of DNA on agarose gel electrophoresis, and morphological and nuclear alterations studied by phase contrast and fluorescence microscopy. The factor responsible for inducing apoptosis in macrophages was found to be a higher concentration of NO produced by them upon activation with cisplatin and IFN-gamma. Macrophages treated with cisplatin or IFN-gamma alone produced a low level of NO and did not undergo apoptosis. The inhibitor of NO synthase, L-NMMA, prevented apoptosis in macrophages treated with cisplatin and IFN-gamma, suggesting the involvement of NO in the induction of apoptosis in macrophages. The role of NO in inducing apoptosis in macrophages was further confirmed by the observation that direct treatment with sodium nitroprusside, a NO donor, resulted in apoptosis in macrophages. We have also shown that NO-induced apoptosis in macrophages activated with cisplatin and IFN-gamma requires activation of an endonuclease, as the endonuclease inhibitor, aurine tricarboxylic acid, prevented apoptosis in them.

Effect of tumor cells on the activation of murine lymphocytes and macrophages by cisplatin and FK565

Murine peritoneal macrophages on in vitro treatment with cisplatin (5 micrograms/ml) or FK565 (10 micrograms/ml) showed an enhanced production of tumor necrosis factor (TNF) and reactive nitrogen intermediates (RNI). Similarly, treatment of splenic lymphocytes with these agents also led to an enhanced production of TNF. Co-incubation of macrophages or splenic lymphocytes with P815 (a murine mastocytoma) cells in vitro in the absence of cisplatin or FK565 also resulted in an augmented TNF production, however, it had no effect on the RNI production by macrophages. TNF production of cisplatin- or FK565-treated macrophages got synergistically enhanced in the presence of P815 cells in the presence of P815 whereas the production of RNI was inhibited. Incubation of splenic lymphocytes with P815 cells in the presence of cisplatin or FK565 resulted in an inhibition of TNF production. Indomethacin-treated P815 cells were observed to be less effective in inhibiting nitrite production of macrophages compared to untreated tumor cells. Pretreatment of P815 cells with cisplatin or FK565 before co-incubation did not alter the TNF production of macrophages whereas it inhibited the same in lymphocytes. This study shows that activation of macrophages and lymphocytes is independently influenced by P815 tumor cells in combination with chemoimmunotherapeutic drugs cisplatin and FK565.

Endotoxin-induced protein phosphorylation in macrophages is modulated by tumor cells

Tumor cells are known to modulate the antitumor functions of endotoxin or cytokine-stimulated macrophages, however, their mechanism of action is not known. We have recently shown that Dalton's lymphoma (DL, a murine spontaneous T cell lymphoma) alter the activation of macrophages by lipopolysaccharide (LPS). In this investigation, the effects of DL cells on protein kinase C (PKC) activity, calcium uptake and protein tyrosine phosphorylation in murine peritoneal macrophages was studied. Treatment of macrophages with LPS resulted in the translocation of PKC from cytosol to the membrane fraction. Incubation of macrophages with DL cells or DL cell lysate (DLL) resulted in a significant decrease in the PKC activity in membrane fraction compared to the LPS-treated macrophages incubated without DL cells or DLL. DL cells were also found to inhibit the accumulation and influx of calcium in the macrophages in response to LPS. On the other hand, DL cells augmented the protein tyrosine phosphorylation in murine macrophages. Only viable DL cells were found to increase the protein tyrosine phosphorylation whereas DLL did not have any effect on protein tyrosine phosphorylation in macrophages. These results thus suggest that tumor cells and/or their products can differentially effect the phosphorylation of different proteins involved in cell signalling.

Cisplatin-induced activation of murine bone marrow-derived macrophages require protein tyrosine phosphorylation

The aim of the present study is to evaluate the involvement of tyrosine phosphorylation in the signal transduction mechanism of cisplatin-induced macrophage activation in vitro. Stimulation of bone marrow-derived macrophages (BMDM) with cisplatin (CP) resulted in a time- and dose-dependent phosphorylation of several proteins having estimated molecular weights of approximately 18, 20, 21, 30, 33, 35, 39, 41, 44, 58 and 123 kD, detected by immunoblot using anti-phosphotyrosine antibody. CP-induced tyrosine phosphorylation was inhibited by the tyrosine kinase inhibitor genistein. Using this inhibitor, we were able to correlate tyrosine phosphorylation with several functional effects of CP on murine bone marrow-derived macrophages (BMDM). Treatment of macrophages with genistein before incubation with CP completely inhibited the CP-induced tumoricidal activation of macrophages as well as production of TNF and NO, whereas pre-treatment of macrophages with phosphatase inhibitor sodium vanadate upregulated macrophage activation in addition to enhanced protein tyrosine phosphorylation. Taken together, these data suggest that tyrosine phosphorylation play a critical regulatory role in the activation of macrophages with CP.

Cisplatin-stimulated murine bone marrow-derived macrophages secrete oncostatin M

Cisplatin (CP), a widely used anticancer drug activates cells of the immune system to a tumoricidal state, and thus functions as a potent biological response modifier. Expression of oncostatin M (OSM), a novel cytokine having a growth regulatory effect, was studied in bone marrow-derived macrophages treated with cisplatin. Supernatants from CP-stimulated macrophages were found to be cytostatic for OSM-sensitive A375 melanoma cells. Immunoblot analysis with anti-OSM antibody revealed that expression of OSM in macrophages upon CP stimulation is a rapid process and within 30 min of CP treatment, a significant amount of OSM is secreted into the culture supernatant. These results therefore indicate that CP can stimulate murine bone marrow-derived macrophages to produce OSM which can be implicated as one of the cytostatic/ cytocidal factors in the antitumour action of cisplatin-stimulated macrophages.

Cisplatin and interferon-gamma treated murine macrophages induce apoptosis in tumor cell lines

Macrophages, treated in vitro with a combination of cisplatin and interferon (IFN)-gamma, have been shown to develop enhanced tumoricidal activity against a number of tumor cell types, through mechanisms which remain largely unknown. In the present study, we have investigated the mechanism involved in the tumor cell cytotoxicity mediated by cisplatin and lFN-gamma treated macrophages, and the effector molecules involved therein. Peritoneal macrophages treated with cisplatin and IFN-gamma, when co-cultured with different tumor cell types, caused tumor cell death by induction of apoptosis. Evidence for this was provided by percent specific DNA fragmentation assay, by specific pattern of internucleosomal DNA fragmentation detected by agarose gel electrophoresis and by microscopic examination of the cells, which revealed nuclear alterations, characteristic of apoptosis. The time kinetics studies of DNA fragmentation, loss in cell viability and apoptotic cell population showed linearity with time; most of the cells that underwent apoptosis were found to be viable even after 24 h co-culture. Macrophages induced apoptosis in tumor targets even in the absence of cell-to-cell contact, i.e. via diffusible effector molecules. In P815 cells, NO produced by cisplatin and IFN-gamma treated macrophages was found to induce apoptosis as addition of N(G)-monomethyl L-arginine (L-NMMA), a specific inhibitor of NO synthase to the co-culture, prevented apoptosis in P815 cells. Further, direct treatment of P815 cells with the NO donor, sodium nitroprusside (SNP), resulted in apoptosis. In L929 cells, the effector molecule was found to be tumor necrosis factor (TNF)-alpha as apoptosis was blocked by the addition of anti-TNF-alpha antibodies to the co-culture but the addition of L-NMMA or SNP had no effect. The study thus shows that cisplatin and IFN-gamma treated macrophages can kill tumor cells by extracellular release of effector molecules which act by inducing apoptosis in a target cell-specific manner.

Clinical correlates of interferon gamma production in patients with tuberculosis

To determine if the capacity to produce interferon (IFN) gamma is related to the clinical manifestations of tuberculosis, we correlated Mycobacterium tuberculosis-induced IFN-gamma production by peripheral blood mononuclear cells (PBMCs) with clinical, radiographic, and laboratory variables for 63 human immunodeficiency virus (HIV)-negative patients and 43 HIV-positive patients with tuberculosis. For HIV-negative patients whose chest radiographs showed moderately advanced disease, the mean IFN-gamma concentration +/- SD was 1,639 +/- 388 pg/mL, whereas that for patients with far-advanced disease was 327 +/- 100 pg/mL (P = .0001). For HIV-infected patients who had only pleuropulmonary disease, the mean IFN-gamma concentration was 1,002 +/- 257 pg/mL, whereas that for patients with disease outside the lungs and pleura was 149 +/- 55 pg/mL (P = .0004). Multivariate analysis confirmed that the radiographic extent of disease and the site of disease were the only independent predictors of IFN-gamma production in HIV-negative and HIV-infected patients (P < or = .001). We conclude that reduced IFN-gamma production by PBMCs is a marker of severe tuberculosis in both HIV-negative and HIV-infected patients with tuberculosis.

Effect of prolactin on nitric oxide and interleukin-1 production of murine peritoneal macrophages: role of Ca2+ and protein kinase C

In vitro treatment of macrophages with prolactin (PRL) was found to increase the production of nitric oxide (NO) and interleukin-1 (IL-1). Production of NO and IL-1 by macrophages got additively enhanced on simultaneous treatment with LPS and PRL. The production of NO was, however, decreased when the macrophages were treated with a combination of PRL and nifedipine, a Ca2+ blocker indicating a role of Ca2+ in the activation of macrophages with PRL. PRL-treated macrophages showed an enhanced translocation of protein kinase C (PKC) from cytosol to the membrane, indicating that PRL activates macrophages via the activation of PKC.

Antitumor activity studies of newly synthesized N-salicyloyl-N'-(p-hydroxybenzthioyl)hydrazine and its copper(II) complex both in vivo and in vitro

A new ligand N-salicyloyl-N'-(p-hydroxybenzthioyl) hydrazine (H2STPH) and its Cu(II) complex [Cu(SPTH)] were prepared and characterized by analytical and physicochemical studies. In vivo antitumor activity of [Cu(STPH)] has been tested against breast tumor in C3H/J strain mice and in vitro on P-815 (murine mastocytoma) and K-562 (human erythroleukemia) cells. LD50 values were estimated at a dose level of 100 mg/kg body weight and a light microscopic study also carried out.

Activation of P388D1 macrophage cell line by chemotherapeutic drugs

It has been found that certain antineoplastic drugs impart their function with a distinct duality. Besides being tumoricidal, they are capable of acting as immunopotentiator. This led us to investigate the effect of cytosine arabinoside (CA), vincristine sulphate (VS), cyclophosphamide (CS), mitomycin C (MMC), hydroxy urea (HU) and lipopolysaccharide (LPS) on a macrophage cell line P388D1. Supernatants collected from P388D1 cells treated with CA, VS, CS, MMC, HU or LPS demonstrated enhanced production of tumor necrosis factor (TNF) confirmed by bioassay on L929 tumor target cells and increased interleukin-1 (IL-1) production by standard thymocyte proliferation bioassay. Also, supernatants showed increased amounts of nitric oxide and lysozyme using Griess reaction and reduction in turbidity of Micrococcus lysodeikticus, respectively. The above findings demonstrate that these drugs may be used not only as chemotherapeutic agents but also as macrophage-activating agents.

Ebola virus disease. Recognizing the face of a rare killer

Because of international travel and immigration, US physicians should be aware of the signs and symptoms of Ebola virus disease. It should be suspected in any recent traveler who presents with manifestations of viral hemorrhagic fever and in laboratory workers exposed to animals from endemic areas who show symptoms. Infected persons should be given supportive care to help them survive the acute phase of infection. Fortunately, adequate preventive measures are already in place in US hospitals and laboratories because of the prevalence of AIDS and hepatitis. However, aid should be provided to the World Health Organization and developing countries such as Zaire to support further research into the epidemiology and natural history of the virus, which may help prevent future deadly epidemics.

Cisplatin stimulates protein tyrosine phosphorylation in macrophages

Cisplatin [cis-dichlorodiamine platinum (II)], a potent anti-tumor compound, stimulates immune responses by activating monocyte-macrophages and other cells of the immune system. The mechanism by which cisplatin activates these cells is poorly characterized. Since protein tyrosine phosphorylation appears to be a major intracellular signalling event that mediates cellular responses, we examined whether cisplatin alters tyrosine phosphorylation in macrophages. We found that cisplatin increased tyrosine phosphorylation of several proteins in peritoneal macrophages and in P388D1 and IC-21 macrophage cell lines. Treatment of macrophages with tyrosine kinase inhibitors, genestein and lavendustin A, inhibited cisplatin-stimulated protein tyrosine phosphorylation in macrophages. Macrophages treated with cisplatin also exhibit increased fluorescence with anti-phosphotyrosine-FITC antibody. These data indicate that protein tyrosine phosphorylation plays a role in cisplatin-induced activation of macrophages.

Induction of protein tyrosine phosphorylation in macrophages incubated with tumor cells

The cellular and molecular interaction between monocyte/macrophage and tumor cells leading to macrophage activation is not clearly understood. Since protein tyrosine phosphorylation appears to be a major intracellular signalling event, we checked whether the tumor cells alter tyrosine phosphorylation of proteins in macrophages. We found that both L929 and Yac-1 tumor cells induced increased tyrosine phosphorylation of several polypeptides in peritoneal as well as P388D-1 and IC-21 macrophages. Macrophages co-cultured with tumor cells also showed increased fluorescence with anti-phosphotyrosine-FITC antibody. These observations suggest that increased tyrosine phosphorylation plays a role in tumor cell-induced activation of macrophages.

Role of calcium and calmodulin in the activation of murine peritoneal macrophages with cisplatin

When fura-2/AM loaded peritoneal macrophages were treated with cisplatin, it resulted in a rapid increase in the intracellular free calcium. Calcium modulating agents, EGTA, nifedipine, and TMB-8, and the calmodulin antagonist W-7 inhibited cisplatin-induced tumoricidal activity of murine peritoneal macrophages. Supernatants collected from macrophages treated with cisplatin and EGTA, nifedipine, TMB-8 or W-7 demonstrated decreased tumor necrosis factor (TNF) and interleukin-1 (IL-1) activity in comparison to supernatants collected from macrophages treated with cisplatin alone. Similarly, TNF and IL-1 activity were significantly inhibited in paraformaldehyde (PFA)-fixed macrophages and freeze-thaw lysates of macrophages treated with cisplatin and different calcium and calmodulin-modulating agents. These results suggest that calcium and calmodulin are important in the cisplatin-mediated activation of murine peritoneal macrophages to tumoricidal state.

Effect of in vivo administration of cisplatin on the colony forming ability of murine bone marrow cells

In vitro colony forming ability of bone marrow cells obtained from cisplatin-treated C3H/He mice was studied. Mice were administered cisplatin in a single intraperitoneal dose of 10 mg/kg body wt, 24 h prior to the harvest of femoral bone marrow cells. Incubation of untreated bone marrow cells without any CSF in vitro showed little colony forming ability which was marginally enhanced in cisplatin-treated bone marrow cells. Presence of M-CSF (250 U/ml) or GM-CSF (250 U/ml) in the culture medium significantly augmented the colony forming ability of both untreated and cisplatin-treated bone marrow cells. In the presence of M-CSF, colony forming units-macrophage (CFU-M) were predominantly high in untreated bone marrow cells, followed with CFU-granulocyte-macrophage (CFU-GM). The number of CFU-M was significantly up-regulated in response to M-CSF in bone marrow cells obtained from cisplatin administered mice, whereas the number of CFU-GM remained unchanged, as compared to untreated mice. Both CFU-M and CFU-GM were enhanced in the presence of GM-CSF in untreated bone marrow cells. Cisplatin-treated bone marrow cells on incubation in the presence of GM-CSF showed a significant enhancement of CFU-M and GM as compared to untreated samples. IL-1 (100 U/ml) in the presence of M-CSF significantly up-regulated colony forming ability of cisplatin-treated bone marrow cells, whereas TNF (100 U/ml) inhibited the colony forming ability.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of interferon-gamma, tumor necrosis factor, interleukin-1 and interleukin-6 on the modulation of anti-tumor responses of bone marrow derived macrophages

Non-adherent bone marrow cells (NABMC) obtained from BALB/c mice were incubated in medium alone or containing granulocyte--macrophage-colony stimulating factor(GM-CSF) or macrophage-colony stimulating factor (M-CSF) for 4 days to obtain bone marrow derived macrophages. Treatment of GM-CSF or M-CSF derived macrophages with interferon-gamma (IFN-gamma) (50 U/ml), tumor necrosis factor (TNF) (500 U/ml), interleukin-1 (IL-1) (200 U/ml) or interleukin-6 (IL-6) (100 U/ml) for 24 h rendered them significantly cytotoxic to different tumor cells. These macrophages also produced enhanced amounts of soluble or membrane associated TNF. Medium derived macrophages showed little cytotoxicity against tumor cells and production of TNF on treatment with TNF, IFN-gamma, IL-1 or IL-6. M-CSF or GM-CSF derived macrophages on treatment with IFN-gamma showed enhanced release of nitrite as compared to medium derived macrophages. TNF, IL-1 or IL-6 did not induce nitrite production in bone marrow derived macrophages. Out of the different combinations tested, only IFN-gamma plus TNF-treated macrophages showed enhancement in nitrite production as compared to that of IFN-gamma alone.

Increased production of interleukin-1 and tumor necrosis factor by human monocytes treated in vitro with cisplatin or other biological response modifiers

Supernatants collected from cisplatin, lipopolysaccharide (LPS), muramyl dipeptide (MDP) or interferon-gamma (IFN-gamma) treated human monocytes enhance the thymocyte proliferation by a submitogenic concentration of concanavalin A. Also supernatants collected from cisplatin or IFN-gamma treated monocytes demonstrated enhanced cytotoxicity against actinomycin-D treated L 929 cells, suggesting that cisplatin or rIFN-gamma treated monocytes release tumor necrosis factor (TNF) into the culture medium. The supernatant collected from untreated monocytes showed only little IL-1 and TNF activity.

Production of reactive nitrogen intermediates by bone marrow-derived macrophages on treatment with cisplatin in vitro

L929 culture medium (a source of macrophage colony stimulating factor (M-CSF) or recombinant granulocyte-macrophage colony stimulating factor (rGM-CSF)-derived bone marrow macrophages treated with cisplatin or lipopolysaccharide (LPS) (10 micrograms/ml) were effective in the production of L-arginine-dependent reactive nitrogen intermediates (RNI) and generation of tumouricidal activity. The abilities of RNI secretion and related tumouricidal activity against P815 mastocytoma cells were compared. These parameters were found to be closely correlated in various experiments. RNI secretion and generation of bone marrow macrophage-mediated tumouricidal activity were significantly inhibited by L-N-monomethyl arginine (L-NMMA), a specific inhibitor of the L-arginine pathway, but L-NMMA did not inhibit macrophage-mediated killing of tumour necrosis factor (TNF)-sensitive Wehi cells, suggesting that activated macrophages exhibit at least two cytolytic mechanisms, one by L-arginine-dependent nitric oxide pathway and another by TNF-mediated killing. The present findings suggest that the mechanism of tumour cell killing by activated macrophages may differ, depending on the tumour cell type, and reactive nitrogen intermediates play a major role in cisplatin-mediated activation of bone marrow-derived macrophages.

Studies on the intracellular Ca2+, protein kinase activity, and ATP contents of cisplatin- and rIFN-Y-treated non-adherent mononuclear cells

The in vitro effect of cisplatin or rIFN-Y on the intracellular free calcium, protein kinase activity and ATP content of non-adherent mononuclear cells (nMNC) from human peripheral blood was assessed. We observed that treatment of nMNC with cisplatin enhanced the [Ca2+]i, ATP level, and protein kinase activity; whereas rIFN-Y-treated nMNC showed significant rises in ATP level and protein kinase activity only. We also observed that cisplatin-treated nMNC showed an instantaneous rise in [Ca2+]i when NK-sensitive K562 cells were added to the effector cells.

Effect of interferon-gamma priming on the activation of murine peritoneal macrophages to tumouricidal state by cisplatin, IL-1, and tumour necrosis factor (TNF): production of IL-1 and TNF

The effect of interferon-gamma (IFN-gamma) priming of murine peritoneal macrophages on the activation to tumouricidal state by cisplatin, lipopolysaccharide (LPS)-IL-1 and TNF was investigated. Cisplatin-, LPS-, IL-1- or TNF-treated IFN-gamma-primed macrophages showed significantly enhanced tumouricidal activity and binding to tumour cells, compared with unprimed treated or untreated macrophages. Macrophages treated with cisplatin, LPS, IL-1 and TNF produced released and membrane-associated IL-1 and TNF activity which was significantly enhanced after priming with IFN-gamma. These observations suggest the use of IFN-gamma along with these biological response modifiers in designing immunotherapeutic protocols for treatment of malignancy.