Tie2 Expressing Monocytes/Macrophages in Human Tumors / 肿瘤防治研究

Tie2 expressing monocytes/macrophages (TEMs) are a subtype of monocytes or macrophages which expressing tyrosine kinase receptor Tie2. They can exist in peripheral blood and tissues of both human and mouse. TEMs can participate in the formation of tumor microenvironment by accelerating tumor angiogenesis, lymphangiogenesis and immunosuppression. At present, TEMs have been found to have potential diagnostic and prognostic guiding significance for a variety of tumors, and they are expected to provide new directions and strategies for tumor therapy. This paper reviews the research progress of TEMs in tumor.

Effect and mechanism of monocytes/macrophages TREM-1 on acute lung injury in rats with severe heatstroke / 解放军医学杂志

Objective: To investigate the effect of the monocytes/macrophages on acute lung injury in rats with severe heatstroke, by modulating the expression of triggering receptor expressed on myeloid cells-1 (TREM-1). Methods: Forty rats were randomized evenly into the control group (Con group), heatstroke group (HS group), the low dose inhibitor group (LD group) and the high dose inhibitor group (HD group). Before heatstroke induction, the rats of LD and HD groups were administrated with a 50 mg/kg and 100 mg/kg bolus of LP-17, respectively. All rats were exposed to an environment with temperature of (40 ± 2) °C and humidity of 65% ± 5% for 60 minutes to induce heatstroke. Enzyme-linked immunosorbent assay (ELISA) was utilized to quantify the concentration of tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-1β in the peripheral blood and pulmonary tissue. The expression of TREM-1 on peripheral monocytes was identified by flow cytometry. Moreover, the histological phenotypes were evaluated after HE stain and the expression of inducible nitric oxide synthase (iNOS) was analyzed by immunohistochemistry in pulmonary tissues. Furthermore, Western blotting was used to detect the protein level of TREM-1 and monocyte chemoattractant protein-1 (MCP-1). Results: Compared to HS rat, in rats pretreated with LP-17, the levels of TNF-α, IL-6 and IL-1β in peripheral blood (P<0.01) and pulmonary tissue (P<0.01) were descended; the upregulation of TREM-1 on peripheral monocytes was alleviated in (P<0.01); the histological injury (P<0.01) were reduced; the protein levels of iNOS, TREM-1 and MCP-1 (P<0.01) were down-regulated. Conclusion: The down-regulation of the TREM-1 activity on the monocytes/macrophages in the peripheral blood and lung tissue by the bolus of LP-17 benefit to ameliorate the lung injury induced by heatstroke via inhibiting inflammation, oxidative stress and chemokine.

Peptidoglycan Up-Regulates CXCL8 Expression via Multiple Pathways in Monocytes/Macrophages

Peptidoglycan (PG), the gram positive bacterial pathogen-associated molecular patterns (PAMP), is detected in a high proportion in macrophage-rich atheromatous regions, and expression of chemokine CXCL8, which triggers monocyte arrest on early atherosclerotic endothelium, is elevated in monocytes/macrophages in human atherosclerotic lesion. The aim of this study was to investigate whether PG induced CXCL8 expression in the cell type and to determine cellular signaling pathways involved in that process. Exposure of THP-1 cell, human monocyte/macrophage cell line, to PG not only enhanced CXCL8 release but also profoundly induced il8 gene transcription. PG-induced release of CXCL8 and induction of il8 gene transcription were blocked by OxPAPC, an inhibitor of TLR-2/4 and TLR4, but not by polymyxin B, an inhibitor of LPS. PG-mediated CXCL8 release was significantly attenuated by inhibitors of PI3K-Akt-mTOR pathways. PKC inhibitors, MAPK inhibitors, and ROS quenchers also significantly attenuated expression of CXCL8. The present study proposes that PG contributes to inflammatory reaction and progression of atherosclerosis by inducing CXCL8 expression in monocytes/macrophages, and that TLR-2, PI3K-Akt-mTOR, PKC, ROS, and MAPK are actively involved in the process.

FSL-1, a Toll-like Receptor 2/6 Agonist, Induces Expression of Interleukin-1alpha in the Presence of 27-hydroxycholesterol

We investigated the question of whether cholesterol catabolite can influence expression of inflammatory cytokines via Toll-like receptors (TLR) in monocytic cells. Treatment of THP-1 monocytic cells with 27-hydroxycholesterol (27OHChol) resulted in induction of gene transcription of TLR6 and elevated level of cell surface TLR6. Addition of FSL-1, a TLR6 agonist, to 27OHChol-treated cells resulted in transcription of the IL-1alpha gene and enhanced secretion of the corresponding gene product. However, cholesterol did not affect TLR6 expression, and addition of FSL-1 to cholesterol-treated cells did not induce expression of IL-1alpha . Using pharmacological inhibitors, we investigated molecular mechanisms underlying the expression of TLR6 and IL-1alpha. Treatment with Akt inhibitor IV or U0126 resulted in significantly attenuated expression of TLR6 and IL-1alpha induced by 27OHChol and 27OHChol plus FSL-1, respectively. In addition, treatment with LY294002, SB202190, or SP600125 resulted in significantly attenuated secretion of IL-1alpha . These results indicate that 27OHChol can induce inflammation by augmentation of TLR6-mediated production of IL-1alpha in monocytic cells via multiple signaling pathways.

Multiple Signaling Molecules are Involved in Expression of CCL2 and IL-1beta in Response to FSL-1, a Toll-Like Receptor 6 Agonist, in Macrophages

TLR6 forms a heterodimer with TLR2 and TLR4. While proinflammatory roles of TLR2 and TLR4 are well documented, the role of TLR6 in inflammation is poorly understood. In order to understand mechanisms of action of TLR6 in inflammatory responses, we investigated the effects of FSL-1, the TLR6 ligand, on expression of chemokine CCL2 and cytokine IL-1beta and determined cellular factors involved in FSL-1-mediated expression of CCL2 and IL-1beta in mononuclear cells. Exposure of human monocytic leukemia THP-1 cells to FSL-1 resulted not only in enhanced secretion of CCL2 and IL-1beta, but also profound induction of their gene transcripts. Expression of CCL2 was abrogated by treatment with OxPAPC, a TLR-2/4 inhibitor, while treatment with OxPAPC resulted in partially inhibited expression of IL-1beta. Treatment with FSL-1 resulted in enhanced phosphorylation of Akt and mitogen-activated protein kinases and activation of protein kinase C. Treatment with pharmacological inhibitors, including SB202190, SP6001250, U0126, Akt inhibitor IV, LY294002, GF109203X, and RO318220 resulted in significantly attenuated FSL-1-mediated upregulation of CCL2 and IL-1beta. Our results indicate that activation of TLR6 will trigger inflammatory responses by upregulating expression of CCL2 and IL-1beta via TLR-2/4, protein kinase C, PI3K-Akt, and mitogen-activated protein kinases.

Interleukin-18 enhances cytokine secretion by monocytes activated through direct contact with T lymphocytes / 第二军医大学学报

Objective: To study whether interleukin (IL)-18 is involved in the activation of monocytes through direct contact with T cells and the related intracellular mechanism. Methods: T cells and monocytes were isolated and purified from the peripheral blood of healthy donors by magnetic beads. Phytohemagglutinin (PHA) pre-stimulated T cells were fixed by 1% paraformaldehyde and were then co-cultured with monocytes at a T cell: monocyte ratio of 4:1. TNF-α and IL-18 levels in the supernatants were assayed by ELISA. Expression of IL-18 receptor α chain (IL-18Rα) on the surface of monocytes was analyzed by flow cytometry. Results: Monocytes activated by PHA-stimulated T cells produced significantly more TNF-α than by unstimulated T cells; non-cultured T cells or monocytes hardly produced any TNF-α. Upon direct cellular contact, PHA prestimulated T cells also up-regulated IL-18Rα expression on the surface of monocytes and induced IL-18 production in monocytes, which could be suppressed by nuclear factor (NF)-κB inhibitor (N-acetyl-L-cysteine, NAC) or phosphatidyl-inositol (PT) 3 kinase inhibitor (LY294002), but not by mitogen activated protein kinase (MAPK) inhibitor (SB203580). Neutralizing anti-IL-18 monoclonal antibody dose-dependently inhibited the production of TNF-α by monocyte-stimulated T cells. IL-18 failed to induce TNF-α production by cultured monocytes alone, while dose-dependently enhanced TNF-α production in monocyte-stimulated T cells, which could be inhibited by NAC or LY294002, but not by SB203580. Conclusion: By direct cellular contact T cells can stimulate monocytes to produce TNF-α and IL-18, up-regulate IL-18 receptor expression in monocytes, and activate intracellular NF-κB and PI3 kinase pathways. IL-18 can enhance T cell ability to stimulate TNF-α production by monocytes, which is dependent on the activation of NF-κB and PI3 kinase pathways.

Nitric Oxide Synthesis is Modulated by 1,25-Dihydroxyvitamin D3 and Interferon-gamma in Human Macrophages after Mycobacterial Infection

BACKGROUND: Little information is available the role of Nitric Oxide (NO) in host defenses during human tuberculosis (TB) infection. We investigated the modulating factor(s) affecting NO synthase (iNOS) induction in human macrophages. METHODS: Both iNOS mRNA and protein that regulate the growth of mycobacteria were determined using reverase transcriptase-polymerase chain reaction and western blot analysis. The upstream signaling pathways were further investigated using iNOS specific inhibitors. RESULTS: Here we show that combined treatment with 1,25-dihydroxyvitamin D3 (1,25-D3) and Interferon (IFN)-gamma synergistically enhanced NO synthesis and iNOS expression induced by Mycobacterium tuberculosis (MTB) or by its purified protein derivatives in human monocyte-derived macrophages. Both the nuclear factor-kappaB and MEK1-ERK1/2 pathways were indispensable in the induction of iNOS expression, as shown in toll like receptor 2 stimulation. Further, the combined treatment with 1,25-D3 and IFN-gamma was more potent than either agent alone in the inhibition of intracellular MTB growth. Notably, this enhanced effect was not explained by increased expression of cathelicidin, a known antimycobacterial effector of 1,25-D3. CONCLUSION: These data support a key role of NO in host defenses against TB and identify novel modulating factors for iNOS induction in human macrophages.

Interleukin-1 beta production by monocytes from leprosy patients

The cause responsible for the lack of an efficient cell-mediated immunity or a delayed type hypersensitivity to M. leprae in lepromatous patients is poorly understood. But the resistance to M. leprae infection in humans is likely mediated by the activated macrophages to present M. leprae antigen to T cells for cell-mediated immunity. Phenolic glycolipid-I (PGL-I) is a M. leprae-specific antigen and is supposed to play a significant role in the long lasting unresponsiveness in lepromatous leprosy. In this study, IL-1 activities were tested among leprosy patients to evaluate monocyte function and the role of IL-1 in the immunosuppression in leprosy. We found that peripheral blood mononuclear cells (PBMCs) from tuberculoid patients were strongly reactive to M. leprae (mean cpm; 28,853 +/- 28,916), but the proliferative responses of PBMCs from lepromatous patients (mean cpm; 6,051 +/- 803) were significantly lower. IL-1 concentration in culture supernatant of monocytes from lepromatous patients was similar to that from tuberculoid patients with stimulation of M. leprae (lepromatous: 1,014 +/- 637 pg/ml, tuberculoid: 1,012 +/- 167 pg/ml) or lipopolysaccharides (IPS) (lepromatous: 3,479 +/- 2,188 pg/ml, tuberculoid: 4,246 +/- 2,432 pg/ml). The IL-1 concentration is sera from lepromatous patients (42 +/- 30 pg/ml) tended to be higher than those from tuberculoid patients (28 +/- 69 pg/ml). And there was no significant difference in IL-1 production between peritoneal macrophages from mice sensitized with PGL-1 and those from nonsensitized mice. In conclusion, this study suggests that the immunosuppression in lepromatous patients may not be due to the decreased production of IL-1. And the increased IL-1 activity in sera may affect the inflammatory response of lepromatous patients.