LFA-1-dependent tumoricidal activity of cisplatin-treated macrophages

Naive mouse macrophages become activated following recognition of L5178Y lymphoma cells via concurrent ligation of CD40, NKG2D, and CD18 molecules

Under different circumstances, tumors can inhibit or activate macrophage (Mphi) effector functions. We studied the mechanisms of tumor-Mphi interactions leading to Mphi activation. The results show that L5178Y mouse T cell lymphoma cells can prime naive mouse Mphi to subsequent LPS stimulation, resulting in increased NO production and antilymphoma effects in vitro. L5178Y cells, but not naive splenocytes, primed Mphi to ligation of TLR4 but not TLR9. L5178Y-primed Mphi incubated with LPS showed down-regulation of CD40 and up-regulation of NKG2D expression. Although L5178Y T cell lymphoma cells primed naive mouse Mphi, several other mouse and human cells lines failed to prime mouse Mphi. Neither L5178Y-conditioned supernatants nor coculture of Mphi and L5178Y cells in Transwells resulted in priming, indicating that direct L5178Y cell-Mphi contact was needed. Several receptor-ligand pairs are reciprocally expressed on Mphi and L5178Y cell membranes and can be potentially involved in Mphi priming. Of these, the CD40-CD154 pair played the most important role, as blocking the interaction of these molecules substantially reduced in vitro Mphi priming. Furthermore, simultaneous blocking of interactions between CD40-CD154, NKG2D-H60, and CD18-ICAM-1/2 led to complete abrogation of Mphi-mediated NO secretion and complete inhibition of Mphi-mediated tumor cell cytostasis. The priming of Mphi to LPS with L5178Y cells was also observed in vivo. These results suggest that contact with certain tumor cells via CD40, NKG2D, and CD18 molecules on the Mphi may facilitate Mphi-mediated antitumor immune surveillance.

Interleukin-1β expression in murine J774A.1 macrophages exposed to platinum compounds: The role of p38 and ERK 1/2 mitogen-activated protein kinases

Although skin and respiratory sensitizing properties of platinum compounds have been proved in humans and mice, little is known about signal transduction pathways leading to cytokine production in the induction phase. It is generally assumed that induction of skin sensitization, but not skin irritation, is associated with a rapid increase in the IL-1beta mRNA expression. In this study, IL-1beta expression and a role of mitogen-activated protein kinases (MAPKs) in this process were investigated in murine macrophages J774A.1 exposed to four platinum compounds. Potassium tetrachloroplatinate (K(2)PtCl(4); TCPP), ammonium tetrachloroplatinate ((NH(4))(2)PtCl(4); TCPA), ammonium hexachloroplatinate ((NH(4))(2)PtCl(6); HCPA) showed a very similar range of cytotoxic concentrations (IC(50) values: 238 microM+/-30; 269 microM+/-39 and 245 microM+/-31, respectively) as assessed in the 24-h MTT reduction test. Cytotoxicity of cis-diammineplatinum dichloride (cisplatin) was considerably higher (IC(50) of 23 microM+/-4). While increased expression of IL-1beta mRNA was observed in the macrophages exposed to each test compound, IL-1beta protein production was detected in cell lysates after treatment with TCPP, TCPA and HCPA for 24h (concentration range of 150-350 microM) as well as for 2h (450-650 microM). The treatment with each compound resulted in the phosphorylation of both p38 MAPK and ERK 1/2 (p44/42). Blocking the activation of p38 MAPK as well as ERK 1/2 with specific inhibitors (SB203580 and U0126, respectively) down-regulated the IL-1beta expression. Interestingly, the skin irritant sodium dodecyl sulfate did not trigger phosphorylation of these kinases, nor induced IL-1beta production. These data suggest that p38 MAPK and ERK 1/2 play an important role in induction of IL-1beta expression in J774A.1 macrophages exposed to test platinum compounds.

Interaction between cisplatin treated murine peritoneal macrophages and L929 cells: involvement of adhesion molecules, cytoskeletons, upregulation of Ca2+ and nitric oxide dependent cytotoxicity

Murine peritoneal macrophages on treatment with cisplatin (10 microg/ml) showed increased binding to L929 cells. Cisplatin treated macrophage on co-incubation with L929 cells form a distinct cytoplasmic contact between the two cells. The plasmalemmae of the two cells fuse over a large surface area. The formation of contact between the cisplatin treated macrophage and L929 cell results in the induction of apoptosis in L929 cell. Untreated macrophages did not form a contact with L929 cells and no apoptosis is observed in L929 cells. Immunofluorescence microscopical studies clearly show the participation of cytoskeleton and the adhesion molecules in the formation of contact between the two cells. Further, a significant enhancement of the expression of iNOS and cytosolic Ca2+ was observed in cisplatin treated macrophages co-incubated with L929 cells. Cisplatin treated macrophages produced significant amount of NO when co-incubated with L929 cells, while there was minimal production of NO by untreated macrophages co-incubated with L929 cells. Cisplatin treated macrophage-induced L929 cell death was NO dependent, since L-NMMA (500 microM) significantly inhibited the cytotoxicity of L929 cells. The addition of excess L-arginine (2mM) reversed the L-NMMA induced inhibition of NO production and L929 cell cytotoxicity.

Tumoristatic effects of anti-CD40 mAb-activated macrophages involve nitric oxide and tumour necrosis factor-alpha

Effector cells of the innate immune system have diverse functions that can result in tumour inhibition or tumour progression. Activation of macrophages by CD40 ligation has been shown to induce antitumour effects in vitro and in vivo. Here we investigated the role of nitric oxide (NO) and tumour necrosis factor-alpha (TNF-alpha) as mediators in the tumoristatic effects of murine peritoneal macrophages activated with agonistic anti-CD40 monoclonal antibody (alphaCD40) alone and following further stimulation with bacterial lipopolysaccharide (LPS). We found that macrophages activated in vivo by alphaCD40 exhibited tumoristatic activity in vitro against B16 melanoma cells; the tumoristatic effect correlated with the level of NO production and was enhanced by LPS. Use of the NO inhibitor L-nitro-arginine-methyl esterase (L-NAME) and evaluation of macrophages from inducible NO synthase (iNOS)-knockout (KO) mice following alphaCD40 activation showed reduced tumoristatic activity. CD40 ligation enhanced expression of TNF-alpha. Macrophage tumoristatic activity following alphaCD40 treatment was reduced by TNF-alpha mAb or use of macrophages from TNF-alpha-KO mice. However, further stimulation of alphaCD40-activated macrophages with LPS resulted in strong tumoristatic activity that was much less dependent on NO or TNF-alpha. Taken together, these results suggest that NO and TNF-alpha are involved in, but not solely responsible for, the antitumour effects of macrophages after activation by CD40 ligation.

In vitro activation of murine peritoneal macrophages by monocyte chemoattractant protein-1: upregulation of CD11b, production of proinflammatory cytokines, and the signal transduction pathway

The CC chemokine monocyte chemotactic protein-1 (MCP-1) is a major mediator of monocyte/macrophage infiltration at the inflammatory sides under both physiologic and pathologic conditions. We report the ability of MCP-1 to activate murine peritoneal macrophages in vitro for enhanced expression of CD11b, macrophage-mediated cytotoxicity, and production of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1). The macrophages treated with MCP-1 in vitro displayed significant cytolytic activity toward TNF-alpha-sensitive L929 cells in a dose-dependent manner. The macrophage-mediated L929 cytotoxicity was blocked in the presence of anti-TNF-alpha antibodies, suggesting the involvement of TNF-alpha. Production of TNF-alpha and IL-1 macrophages on MCP-1 treatment was maximum at 24 h of incubation with 100 ng/ml MCP-1. Enhanced TNF-alpha and IL-1beta mRNA expression was also demonstrated by RT-PCR, which revealed transcription of interferon gamma (IFN-gamma), IL-12, and related T cell-specific chemokine genes, KC and IP-10, in the MCP-1-treated macrophages. The pharmacologic inhibitors pertussis toxin (100 ng/ml), wortmannin (200 ng/ml), H-7 (10 microM), PD98059 (25 microM), and genistein (10 microg/ml) significantly inhibited TNF-alpha and IL-1 production in the MCP1-treated macrophages, suggesting the involvement of G-proteins, phosphoinositol-3-kinase (PI3K), protein kinase C, p42/44 MAPK, and tyrosine kinases in this process.

Expression and activation of RAS and mitogen-activated protein kinases in macrophages treated in vitro with cisplatin: regulation by kinases, phosphatases and Ca2+/calmodulin

Cisplatin (cis-dichlorodiammineplatinum II), a potent antitumour compound, stimulates immune responses by activating monocytes/macrophages and other cells of the immune system. However, the exact mechanism by which cisplatin activates these cells is poorly characterized and attempts are being made to understand this mechanism. Previous studies from this laboratory have shown that Lyn, a protein tyrosine kinase of the src family, and nuclear factor (NF)-kappaB are involved in cisplatin-induced macrophage activation. Recent studies suggest that the RAS and mitogen-activated protein (MAP) kinases function as a connecting link between activated lyn and NF-kB, which raises the possibility of their involvement in cisplatin-induced macrophage activation. Therefore, this study was undertaken to investigate the effect of cisplatin treatment on the expression/activation of RAS (a low molecular weight GTP-binding protein) and MAP kinases in murine peritoneal macrophages. The underlying mechanism of expression/activation of RAS and MAP kinases in cisplatin-treated macrophages was also investigated. Immunoblotting and immune-complex kinase assays revealed that cisplatin treatment of macrophages leads to increased expression/activation of RAS and MAP kinases, with optimal expression/activation at 15 min of treatment. Using a battery of specific inhibitor/modulators of different signalling molecules, this study shows that expression and activation of MAP kinases are two unrelated processes. It was also observed that kinase (protein tyrosine and protein kinase C) inhibitor and Ca2+/calmodulin antagonist inhibit expression/activation of RAS/MAP kinases in macrophages, whereas phosphatases (protein tyrosine and serine/threonine) inhibitor up-regulate these kinases.

Antigen presentation by cisplatin-activated macrophages: role of soluble factor(s) and second messengers

Cisplatin [cis-dichlorodiammine platinum (II)], a potent anti-tumour compound, stimulates immune responses by activating macrophages and other cells of the immune system. The mechanism by which cisplatin activates these cells is poorly characterized. Present investigations were undertaken to study the mechanism of antigen presentation by cisplatin-treated macrophages. Cisplatin-treated macrophages showed a biphasic pattern of antigen presentation to keyhole limpet haemocyanin (KLH)-primed T cells. The second phase of antigen presentation was not due to the continuous presence of cisplatin in the culture medium; rather, it was induced by soluble factors released by cisplatin-treated macrophages. Co-incubation of macrophages with cisplatin and inhibitor of serine/threonine or protein tyrosine phosphatase resulted in an augmentation of cisplatin-induced antigen presentation. In contrast, treatment of macrophages with cisplatin and inhibitor of protein kinase C or protein tyrosine kinase inhibited cisplatin-induced antigen presentation. These observations suggest that antigen presentation by cisplatin-treated macrophages is regulated by reversible action of protein phosphatases and kinases. The antigen-presenting ability of cisplatin-treated macrophages was also inhibited by EGTA, nifedipine, TMB-8, W-7 and calmidazolium, suggesting the probable involvement of Ca2+, calmodulin and calmodulin-dependent kinases in this process.