Tumor signaling to the bone marrow changes the phenotype of monocytes and pulmonary macrophages during urethane-induced primary lung tumorigenesis in A/J mice

Survival of monocytes and macrophages and their role in health and disease

Macrophages are versatile cells involved in health and disease. These cells act as scavengers to rid the body of apoptotic and senescent cells and debris through their phagocytic function. Although this is a primary function of these cells, macrophages play vital roles in inflammation and repair of damaged tissue. Macrophages secrete a large number of cytokines, chemokines and growth factors that recruit and activate a variety of cell types to inflamed tissue compartments. These cells are also critical in cell-mediated immunity and in the resolution of inflammation. Since macrophages, and their precursors, blood monocytes, are important in regulating and resolving inflammation, prolonged cellular survival in tissue compartments could be detrimental. Thus, factors that regulate the fate of monocyte and macrophage survival are important in cellular homeostasis. In this article, we will explore stimuli and the intracellular pathways important in regulating macrophage survival and implication in human disease.

Growth inhibition and regression of lung tumors by silibinin: modulation of angiogenesis by macrophage-associated cytokines and nuclear factor-kappaB and signal transducers and activators of transcription 3

The latency period for lung tumor progression offers a window of opportunity for therapeutic intervention. Herein, we studied the effect of oral silibinin (742 mg/kg body weight, 5 d/wk for 10 weeks) on the growth and progression of established lung adenocarcinomas in A/J mice. Silibinin strongly decreased both tumor number and tumor size, an antitumor effect that correlates with reduced antiangiogenic activity. Silibinin reduced microvessel size (50%, P < 0.01) with no change in the number of tumor microvessels and reduced (by 30%, P < 0.05) the formation of nestin-positive microvessels in tumors. Analysis of several proteins involved in new blood vessel formation showed that silibinin decreased the tumor expression of interleukin-13 (47%) and tumor necrosis factor-alpha (47%), and increased tissue inhibitor of metalloproteinase-1 (2-fold) and tissue inhibitor of metalloproteinase-2 (7-fold) expression, without significant changes in vascular endothelial growth factor levels. Hypoxia- inducible factor-1 alpha expression and nuclear localization were also decreased by silibinin treatment. Cytokines secreted by tumor cells and tumor-associated macrophages regulate angiogenesis by activating nuclear factor-kappaB (NF-kappaB) and signal transducers and activators of transcription (STAT). Silibinin decreased the phosphorylation of p65NF-kappaB (ser276, 38%; P < 0.01) and STAT-3 (ser727, 16%; P < 0.01) in tumor cells and decreased the lung macrophage population. Angiopoietin-2 (Ang-2) and Ang-receptor tyrosine kinase (Tie-2) expression were increased by silibinin. Therapeutic efficacy of silibinin in lung tumor growth inhibition and regression by antiangiogenic mechanisms seem to be mediated by decreased tumor-associated macrophages and cytokines, inhibition of hypoxia-inducible factor-1 alpha, NF-kappaB, and STAT-3 activation, and up-regulation of the angiogenic inhibitors, Ang-2 and Tie-2.

Transcriptome analysis reveals human cytomegalovirus reprograms monocyte differentiation toward an M1 macrophage

Monocytes are primary targets for human CMV (HCMV) infection and are proposed to be responsible for hematogenous dissemination of the virus. Monocytes acquire different functional traits during polarization to the classical proinflammatory M1 macrophage or the alternative antiinflammatory M2 macrophage. We hypothesized that HCMV induced a proinflammatory M1 macrophage following infection to promote viral dissemination because, biologically, a proinflammatory state provides the tools to drive infected monocytes from the blood into the tissue. To test this hypothesis of monocyte conversion from a normal quiescent phenotype to an inflammatory phenotype, we used Affymetrix Microarray to acquire a transcriptional profile of infected monocytes at a time point our data emphasized is a key temporal regulatory point following infection. We found that HCMV significantly up-regulated 583 (5.2%) of the total genes and down-regulated 621 (5.5%) of the total genes>or=1.5-fold at 4 h postinfection. Further ontology analysis revealed that genes implicated in classical M1 macrophage activation were stimulated by HCMV infection. We found that 65% of genes strictly associated with M1 polarization were up-regulated, while only 4% of genes solely associated with M2 polarization were up-regulated. Analysis of the monocyte chemokinome at the transcriptional level showed that 44% of M1 and 33% of M2 macrophage chemokines were up-regulated. Proteomic analysis using chemokine Ab arrays confirmed the secretion of these chemotactic proteins from HCMV-infected monocytes. Overall, the results identify that the HCMV-infected monocyte transcriptome displayed a unique M1/M2 polarization signature that was skewed toward the classical M1 activation phenotype.

Recombinant human granulocyte colony-stimulating factor enhanced the resolution of venous thrombi

BACKGROUND

Bone marrow-derived cells are recruited into the thrombus during resolution. This study explored whether mobilization of bone marrow cells with recombinant human granulocyte colony-stimulating factor (rhG-CSF) could enhance the resolution of venous thrombi and the accumulation of macrophages in thrombi and explored the effect of rhG-CSF on cysteine-cysteine chemokine receptor 2 (CCR2) expression.

METHODS

The Sprague-Dawley adult rats were randomly divided into four groups: control, sham-operated, thrombus, and treatment groups. Thrombi were induced in the thrombus and treatment group, which received a subcutaneous injection of rhG-CSF once daily for 6 days postoperatively. The thrombus, sham-operated, and control groups received equal volumes of 0.9% saline. The mononuclear cells in peripheral blood were analyzed by an automated hematology analyzer and counted under microscope. The cell marker CD68 was used to determine the number of macrophages in thrombi tissue sections. Levels of monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1alpha (MIP1alpha) in the peripheral blood were detected by enzyme-linked immunosorbent assay. Real-time reverse transcriptase-polymerase chain reaction and Western blot were used to analyze, respectively, the expression of CCR2 messenger RNA in the peripheral blood and CCR2 protein of THP-1 monocyte.

RESULTS

At postoperative days 3 (P < .05) and 7 (P < .01), mononuclear cells significantly increased in treatment group (2.1 +/- 0.3, 4.4 +/- 0.3 x 10(6)/L) vs the thrombus group (1.7 +/- 0.2, 1.3 +/- 0.4 x 10(6)/L). The organization and recanalization of thrombi in treatment group progressed more quickly compared with the thrombus group (P < .01). The macrophage number of the thrombus in the treatment group (338 +/- 26 cells/15 high-power fields) increased significantly vs the thrombus group (125 +/- 11 cells/15 high-power fields, P < .01). No statistical difference was observed between the thrombus and treatment group in the MCP-1 and MIP-1alpha level in peripheral blood. Expressions of the CCR2 gene in the peripheral blood of the treatment group significantly increased compared with the thrombus group (P < .05). Recombinant human G-CSF induced higher expression of CCR2 protein of human monocytic cell line THP-1.

CONCLUSIONS

Bone marrow mobilization enhanced the resolution and recanalization of venous thrombi. This process was associated with increased macrophage accumulation in thrombi, which might be the result of higher CCR2 expression of monocytes.

CLINICAL RELEVANCE

The classic treatment of venous thrombi is anticoagulation. Anticoagulant therapy and thrombolysis both have limited effects on existing thrombi and have a small but significant risk of severe hemorrhage. In clinical practice, we lack specific treatment for patients with venous thrombosis combined with brain hemorrhage or a gastrointestinal activated ulcer, which are contraindicated for anticoagulation and thrombolytic therapy. Enhancing the resolution of venous thrombi would contribute to its therapy. Bone marrow-derived cells are recruited into the thrombus during resolution. Many of these cells express a macrophage phenotype and may represent a population of plastic stem cells that orchestrate thrombus recanalization. Recombinant human granulocyte colony stimulating factor (rhG-CSF) can mobilize monocytic lineage cells into peripheral blood and may contribute to this cell in the thrombi. If rhG-CSF enhances the resolution of venous thrombi and recanalization, it might be used to treat patients with venous thrombi, especially those who have contraindication for anticoagulation and thrombolytic therapy.

A systemic granulomatous response to Schistosoma mansoni eggs alters responsiveness of bone-marrow-derived macrophages to Toll-like receptor agonists

Macrophages play a pivotal role in innate and acquired immune responses to Schistosoma mansoni. Classical (M1) or alternative (M2) activation states of these cells further delineate their roles in tissue damage through innate immunity or fibrotic remodeling, respectively. In the present study, we addressed the following question: Does systemic Th2-type cytokine polarization evoked by S. mansoni affect macrophage differentiation and activation? To this end, we analyzed bone marrow-derived macrophages from mice with S. mansoni egg-induced pulmonary granulomas and unchallenged (or naïve) mice to determine their activation state and their response to specific TLR agonists, including S. mansoni egg antigens. Unlike naïve macrophages, macrophages from Th2-polarized mice constitutively expressed significantly higher "found in inflammatory zone-1" (FIZZ1) and ST2 (M2 markers) and significantly lower NO synthase 2, CCL3, MIP-2, TNF-alpha, and IL-12 (M1 markers). Also, compared with naïve macrophages, Th2-polarized macrophages exhibited enhanced responses to the presence of specific TLR agonists, which consistently induced significantly higher levels of gene and protein levels for M2 and M1 markers in these cells. Together, these data show that signals received by bone marrow precursors during S. mansoni egg-induced granuloma responses dynamically alter the development of macrophages and enhance the TLR responsiveness of these cells, which may ultimately have a significant effect on the pulmonary granulomatous response.

Inflammation and lung carcinogenesis: applying findings in prevention and treatment

Lung carcinogenesis is a complex process requiring the acquisition of genetic mutations that confer the malignant phenotype as well as epigenetic alterations that may be manipulated in the course of therapy. Inflammatory signals in the lung cancer microenvironment can promote apoptosis resistance, proliferation, invasion, metastasis, and secretion of proangiogenic and immunosuppressive factors. Here, we discuss several prototypical inflammatory mediators controlling the malignant phenotype in lung cancer. Investigation into the detailed molecular mechanisms underlying the tumor-promoting effects of inflammation in lung cancer has revealed novel potential drug targets. Cytokines, growth factors and small-molecule inflammatory mediators released in the developing tumor microenvironment pave the way for epithelial-mesenchymal transition, the shift from a polarized, epithelial phenotype to a highly motile mesenchymal phenotype that becomes dysregulated during tumor invasion. Inflammatory mediators within the tumor microenvironment are derived from neoplastic cells as well as stromal and inflammatory cells; thus, lung cancer develops in a host environment in which the deregulated inflammatory response promotes tumor progression. Inflammation-related metabolic and catabolic enzymes (prostaglandin E(2) synthase, prostaglandin I(2) synthase and 15-hydroxyprostaglandin dehydrogenase), cell-surface receptors (E-type prostaglandin receptors) and transcription factors (ZEB1, SNAIL, PPARs, STATs and NF-kappaB) are differentially expressed in lung cancer cells compared with normal lung epithelial cells and, thus, may contribute to tumor initiation and progression. These newly discovered molecular mechanisms in the pathogenesis of lung cancer provide novel opportunities for targeted therapy and prevention in lung cancer.