Induction of murine adenosine A(2A) receptor expression by LPS: analysis of the 5' upstream promoter.

Non-activated macrophages express low levels of A(2A)Rs and lipopolysaccharides (LPS) upregulates A(2A)R expression in an NF-κB-dependent manner. The murine A(2A)R gene is encoded by three exons, m1, m2 and m3. Exons m2 and m3 are conserved, while m1 encodes the 5' untranslated UTR. Three m1 variants have been defined, m1A, m1B and m1C, with m1C being farthest from the transcriptional start site. LPS upregulates A(2A)Rs in primary murine peritoneal and bone-marrow-derived macrophages and RAW264.7 cells by selectively splicing m1C to m2, through a promoter located upstream of m1C. We have cloned ∼1.6 kb upstream of m1C into pGL4.16(luc2CP/Hygro) promoterless vector. This construct in RAW 264.7 cells responds to LPS, and adenosine receptor agonists augmented LPS responsiveness. The NF-κB inhibitors BAY-11 and triptolide inhibited LPS-dependent induction. Deletion of a key proximal NF-κB site (402-417) abrogated LPS responsiveness, while deletion of distal NF-κB and C/EBPß sites did not. Site-directed mutagenesis of CREB (309-320), STAT1 (526-531) and AP2 (566-569) sites had little effect on LPS and adenosine receptor agonist responsiveness; however, mutation of a second STAT1 site (582-588) abrogated this responsiveness. Further analysis of this promoter should provide valuable insights into regulation of A(2A)R expression in macrophages in response to inflammatory stimuli.

Production of vascular endothelial growth factor by murine macrophages: regulation by hypoxia, lactate, and the inducible nitric oxide synthase pathway.

Murine thioglycolate-induced peritoneal macrophages (MPMs) and the murine RAW264.7 macrophage-like cell line (RAW cells) constitutively produce vascular endothelial growth factor (VEGF). VEGF production is increased under hypoxic conditions or after cell activation with interferon-gamma (IFNgamma) and endotoxin (lipopolysaccharide, LPS). In contrast, tumor necrosis factor-alpha is produced only by IFNgamma/LPS-activated cells. Lactate (25 mmol/L) does not increase VEGF production by these cells. However, hypoxia, lactate, and IFNgamma/LPS-activated MPMs express angiogenic activity, whereas normoxic, nonactivated MPMs do not. Lack of angiogenic activity is not due to an antiangiogenic factor(s) in the medium of these cells. Angiogenic activity produced by hypoxia and lactate-treated MPMs is neutralized by anti-VEGF antibody, which also neutralizes most of the angiogenic activity produced by IFNgamma/LPS-activated MPMs. The inducible nitric oxide synthase inhibitors Ng-nitro-L-arginine-methyl ester (1.5 mmol/L) and aminoguanidine (1 mmol/L) block production of angiogenic activity by MPMs and RAW cells. In RAW cells, Ng-nitro-L-arginine-methyl ester and AG block IFNgamma/LPS-activated, but not constitutive, VEGF production, whereas in MPMs, neither constitutive nor IFNgamma/LPS-activated VEGF synthesis is affected. Synthesis of tumor necrosis factor-alpha is also unaffected. In contrast to normoxic, nonactivated MPMs, inducible nitric oxide synthase-inhibited, IFNgamma/LPS-activated MPMs produce an antiangiogenic factor(s). We conclude that VEGF is a major contributor to macrophage-derived angiogenic activity, and that activation by hypoxia, lactate, or IFNgamma/LPS switches macrophage-derived VEGF from a nonangiogenic to an angiogenic state. This switch may involve a posttranslational modification of VEGF, possibly by the process of ADP-ribosylation. ADP-ribosylation by MPM cytosolic extracts or by cholera toxin switches rVEGF165 from an angiogenic to a nonangiogenic state. In IFNgamma/LPS-activated MPMs, the inducible nitric oxide synthase-dependent pathway also regulates the expression of an antiangiogenic factor(s) that antagonizes the bioactivity of VEGF and provides an additional regulatory pathway controlling the angiogenic phenotype of macrophages.

Production of angiogenic activity by human monocytes requires an L-arginine/nitric oxide-synthase-dependent effector mechanism.

Human monocytes (M phi) require stimulation with substances such as bacterial endotoxin [LPS (lipopolysaccharide)] to produce angiogenic activity. In this study, we report that stimulation of M phi with LPS (5 micrograms/ml) in the absence of L-arginine greatly reduced their production of angiogenic activity, as assessed in vivo in rat corneas and in vitro by chemotaxis of human umbilical vein endothelial cells (HU-VECs). D-Arginine did not substitute for L-arginine in the production of angiogenic activity. The nitric oxide synthase (NO synthase, EC 1.14-13.39) inhibitors NG-monomethyl-L-arginine (L-NMMA) and NG-nitro-L-arginine methyl ester (L-NAME) both inhibited the production of angiogenic activity by LPS-stimulated M phi in the presence of L-arginine, suggesting the involvement of this enzyme in the pathway that generates angiogenic activity. Neither of these substances directly inhibited the M phi-derived angiogenic activity. LPS-induced production of the cytokines tumor necrosis factor alpha (TNF-alpha) and interleukin 8 (IL-8) was not significantly reduced when M phi were incubated in the absence of L-arginine. Similarly, L-NMMA and L-NAME did not significantly reduce the LPS-induced production of these cytokines by M phi in the presence of L-arginine. These results suggest that the LPS-stimulation-dependent generation of angiogenic activity by M phi requires an L-arginine-dependent NO-synthase effector mechanism that may be independent of the generation of TNF-alpha and IL-8.

4A11, a monoclonal antibody recognizing a novel antigen expressed on aberrant vascular endothelium. Upregulation in an in vivo model of contact dermatitis.

We describe the production and characterization of a novel monoclonal antibody (MAb) that recognizes a human endothelial cell antigen expressed mainly in inflamed and malignant disease states. We have used immunohistochemistry to determine the spectrum of reactivity of this MAb compared with that of a MAb to factor VIII-related antigen (MAb FVIII). MAb 4A11 does not react with several myeloid or lymphoid cell lines or with peripheral blood cells. Unlike MAb FVIII, MAb 4A11 does not react with platelets. MAb 4A11 reacts with most vascular endothelial cells in lymphoid tissue but with few (< 10%) endothelial cells in thymus, spleen, liver, lung, adrenal gland, placenta, testes, and skin. MAb 4A11 detects endothelial cells in diseased tissues such as rheumatoid and osteoarthritic synovium and psoriatic skin. Vascular endothelial cells in both adrenal tumors and cutaneous Kaposi's sarcomas lesions are MAb 4A11 reactive. In vitro the 4A11 antigen is not detectable on cultured human umbilical vein endothelial cells and its expression is not induced on these cells by treatment with lipopolysaccharide, interferon-gamma, interleukin-1 and -6, or tumor necrosis factor-alpha. However, in an in vivo model of allergic contact dermatitis the 4A11 antigen is upregulated differentially from other endothelial markers such as E-selectin, vascular cell adhesion molecule-1, and intercellular adhesion molecule-1. In this dermal model of inflammation, poison ivy extract is applied to the skin and biopsies taken at 0, 6, and 24 hours. In addition to focal keratinocyte expression, 4A11 antigen is found on 11% of dermal endothelial cells at time 0 and antigen expression increases with time until 24 hours, when 4A11 antigen is present on 63% of the endothelial cells. Using thin layer chromatography, MAb 4A11 reacts with the H-5-2 [Fuc alpha 2Gal beta 4GlcNAc beta 3Gal beta 4Glc beta 1Cer] and Lewis(y)-6 [Fuc alpha 2Gal beta 4(Fuc alpha 3)GlcNAc beta 3Gal beta 4-Glc beta 1Cer] blood group glycolipids. The presence of the novel 4A11 antigen in inflamed and malignant tissues containing many blood vessels and its differential upregulation in allergic contact dermatitis may signify an important function for this antigen in the inflammatory process.

Inhibition of production of monocyte/macrophage-derived angiogenic activity by oxygen free-radical scavengers.

We showed previously that thiol-containing compounds inhibited the production of macrophage-mediated angiogenic activity. Since thiol-containing compounds may act on macrophages by affecting activation and inhibiting the production of oxygen free-radicals, we studied the effects of oxygen free-radical scavengers on production of angiogenic activity by elicited mouse peritoneal macrophages and lipopolysaccharide stimulated normal human monocytes. Monocyte/macrophage conditioned media were potently angiogenic when assayed in rat corneas, while conditioned media, from oxygen free-radical scavenger-treated cells were not. The inhibitory effect of oxygen free-radical scavengers was due to a direct effect on monocyte/macrophage production of angiogenic activity but was not due solely to a decrease in the production of the macrophage-derived angiogenic cytokine tumor necrosis factor-alpha. We conclude that oxygen free-radical scavengers are potent inhibitors of the production of macrophage-mediated angiogenic activity.

Monoclonal antibodies defining shared human macrophage-endothelial antigens.

We have selected several monoclonal antibodies (mAbs) producing using human rheumatoid arthritis (RA) synovial macrophages (m phi s) as immunogen. Of these, mAbs 8H2, 10G7 and 10G9 showed cross reactivity with endothelium, suggesting common antigens between these cell types. We have determined the spectrum of reactivity of these mAbs on hematopoietic cell lines, peripheral blood cells, and inflammatory and non-inflammatory tissues by immunohistochemistry. MAb 8H2 does not react with the myeloid cell lines HL60 (myelocytic), U937 (histiocytic lymphoma), and K562 (erythroleukemia), or with peripheral blood cells. In normal and inflamed tissue sections, mAb 8H2 reacts with m phi s and endothelial cells. In contrast, mAb 10G7 does not react with peripheral blood cells, but reacts with HL60, U937, and K562 cell lines, as well as with m phi s and endothelial cells in inflamed and noninflamed tissues. MAb 10G9 does not react with myeloid cell lines, but reacts with monocytes and platelets in peripheral blood. In both normal and inflamed tissues, mAb 10G9 reacts with m phi s and endothelial cells. The antigens identified by these three mAbs were characterized biochemically, by enzymatic digestion of RA synovial tissue m phi s followed by a cellular ELISA, as well as by reactivity of the mAbs with NIH-3T3 cells genetically engineered to express known myeloid antigens. These mAbs reacted with protein or glycoprotein antigens distinct from the known myeloid antigens CD13, CD14, CD33, CD34, CD36, and c-fms. These mAbs should prove to be a valuable tool for studying m phi s and endothelial cells and their shared antigenic determinants.

Thiol-containing compounds inhibit the production of monocyte/macrophage-derived angiogenic activity.

Macrophage (M phi)-mediated angiogenesis is believed to play an important role in the pathogenesis of rheumatoid arthritis. Gold sodium thiomalate, which is used in the treatment of rheumatoid arthritis, is a potent inhibitor of the production of m phi-derived angiogenic activity. To determine the mechanism of this inhibition, we studied the effects of thiol containing compounds (TCCs) on elicited mouse peritoneal m phi and lipopolysaccharide stimulated normal human monocytes. Monocyte/m phi conditioned media were potently angiogenic when assayed in rat corneas, while conditioned media from viable monocyte/m phi s treated with TCCs (at concentrations of 8.3-16.6 x 10(-5) M) were not. TCCs inhibited production of angiogenic activity by the m phi s rather than affecting other components of the angiogenic response such as the angiogenic factors or the target microvasculature of the rat cornea. Levels of the angiogenic mediator tumor necrosis factor-alpha (TNF-alpha) were not decreased in conditioned media of monocyte/m phi s treated with TCCs. We conclude that TCCs are potent inhibitors of the production of m phi-mediated angiogenic activity. This action of TCCs on m phi s may be in part responsible for the mechanism of action of therapeutic gold compounds in rheumatoid arthritis.

Immunolocalization of endothelial and leukocyte adhesion molecules in human rheumatoid and osteoarthritic synovial tissues.

Leukocyte adhesion to endothelium plays an important role in the development and perpetuation of chronic inflammatory diseases such as rheumatoid arthritis (RA). In order to help define the role of adhesion molecules in arthritic disorders, we have studied the expression of CD11c, endothelial leukocyte adhesion molecule-1 (ELAM-1), vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 in synovial tissues from patients with RA and osteoarthritis (OA) by immunohistochemistry. CD11c is expressed predominantly on macrophages deep within RA and OA synovial tissues, as well as on some synovial tissue lining cells. ELAM-1 has endothelial reactivity, being present mainly on venules and capillaries and staining more blood vessels in RA than OA. VCAM-1 is present predominantly on synovial tissue macrophages and, to a lesser degree, on synovial tissue endothelial cells of venules, capillaries, and arterioles in both RA and OA. Like ELAM-1, VCAM-1 appears to be present more often on endothelial cells in RA than in OA tissues. VCAM-1 is present on macrophages isolated from RA synovium as well as macrophages in situ. Intercellular adhesion molecule-1 is more broadly distributed than the other adhesion molecules, being found on endothelium, macrophages, some fibroblasts, and some lymphocytes in both RA and OA tissues. This study shows that ELAM-1, a molecule that was previously thought to be important mainly in acute inflammatory reactions, is also found in RA, a chronic inflammatory disease, as well as in OA. Thus, ELAM-1 as well as VCAM-1 and intercellular adhesion molecule-1 may be involved in mediating the leukocyte traffic into RA and OA synovium.

Monoclonal antibodies detect monocyte/macrophage activation and differentiation antigens and identify functionally distinct subpopulations of human rheumatoid synovial tissue macrophages.

Monoclonal antibodies (MAbs) to functionally heterogeneous populations of human rheumatoid arthritis (RA) synovial tissue macrophages and lipopolysaccharide (LPS)-activated U937 cells were generated. These MAbs were used to characterize macrophages in situ in the synovial pannus and to study relative antigen expression on the surface of cells isolated from the synovium and from normal peripheral blood. Monoclonal antibody 3D8, an anti-CD13 MAb, reacts with an antigen expressed on the surface of blood monocytes and is a monocyte activation-related antigen that is upregulated by exposure of monocytes to interferon-gamma (IFN-gamma) and LPS. The expression of the 3D8 antigen increases in parallel with MHC class II antigen expression and also is upregulated in culture as monocytes mature to macrophages. 3D8 antigen is expressed strongly on RA synovial tissue lining cells, which are thought to be composed of macrophages. 8D7 antigen expression, detected by MAb 8D7, increases on blood monocytes on cellular activation with LPS and interferon-gamma, but in contrast to the 3D8 antigen, does not increase with monocyte maturation in vitro. The 8D7 antigen is expressed differentially on density-defined macrophage subpopulations isolated from RA synovial tissue and is expressed more strongly on macrophages that are nonangiogenic than those that are angiogenic.

Angiogenic activity is defective in monocytes from patients with alopecia universalis.

Monocyte/macrophages are important components of cell-mediated immune responses in presentation of antigen, as regulators of lymphocyte function, and as sources of cytokines that modulate functions of cells other than those of the immune system. Their role in the pathogenesis of alopecia areata (AA) and universalis (AU) has not been explored. This study is an investigation of the function of peripheral blood monocytes from normal subjects and patients with AA, AU, and alopecia totalis (AT), with respect to the principal macrophage-derived angiogenic factor, tumor necrosis factor alpha (TNF alpha). Because neovascularization is a necessary component in the anagen phase of hair growth and may play a role in the pathology of these disorders, we asked whether monocyte/macrophage angiogenic activity was compromised in these alopecias. Purified preparations of monocytes were activated in culture. Conditioned media were assessed for angiogenic activity on the chick chorioallantoic membrane and for concentration of TNF alpha by enzyme-linked immunosorbent assay (ELISA). Both angiogenic and the TNF concentration were significantly diminished in conditioned media from AU monocytes when compared to those from normal subjects and patients with AA. These results show that the function of AU monocytes may be abnormal and that the abnormality may distinguish AU from AA. Defective monocyte/macrophage function could also play a pathogenic role via effects on neovascularization and/or modulation of the immune response.

Reactivity of human tissues with monoclonal antibodies to myeloid activation and differentiation antigens. An immunohistochemical study.

We have characterized antimyeloid monoclonal antibodies (mAbs) produced to human rheumatoid arthritis (RA) synovial tissue macrophages (MPs) (8D7) and to lipopolysaccharide (LPS)-treated U937 cells (3D8). The 3D8 antigen is upregulated with LPS stimulation of monocytes/MPs and during monocyte maturation. The 8D7 antigen is upregulated on functionally distinct subpopulations of RA synovial tissue MPs. We used immunohistochemistry to determine the spectrum of reactivity of these unique mAbs on myeloid cell suspensions, monocytes, and mature tissue inflammatory and noninflammatory MPs. The antigens identified by the mAbs were characterized biochemically, by immunoprecipitation of solubilized 125I-labelled antigens from cell surfaces, and immunohistochemically by enzymatic digestion of myeloid cells followed by a cellular ELISA. MAb 3D8, characterized as an anti-CD13 antibody, recognizes a 150-170 kd antigen, has almost exclusive myeloid reactivity, but reacts with Langerhans' cells of the skin and thymus, pointing to shared antigens between these cells and MPs. Unlike 3D8 antigen, 8D7 antigen is strongly expressed in inflammatory states, being present on MPs in granulomata as well as in sarcoid lymph nodes. Both mAbs react with frozen and methanol-Carnoy's fixed, paraffin-embedded tissues and detect antigenic differences among human mononuclear phagocytes present in different anatomical sites and in varying stages of differentiation and activation. These mAbs should prove to be a valuable tool for studying heterogenous populations of myeloid cells.

Transforming growth factor-beta (TGF beta) is chemotactic for human monocytes and induces their expression of angiogenic activity.

TGF beta stimulates human blood monocyte migration, with peak migratory response occurring consistently at a concentration of 16-100 fg/ml. Checkerboard analysis revealed both chemotactic and chemokinetic components to this response. At higher concentrations (10-100 pg/ml), TGF beta stimulated expression of angiogenic activity by monocytes. While mRNA for TNF alpha was undetectable in resting monocytes, high steady state levels of TNF alpha mRNA were rapidly induced in TGF beta-treated monocytes. TGF beta is secreted by a number of neoplastic cells as well as normal cells such as platelets and lymphocytes. TGF beta may recruit monocytes from the circulation, and subsequently activate them to express angiogenic activities such as TNF alpha, thus playing an important role in wound repair, inflammation and tumor growth.

Functional heterogeneity of human rheumatoid synovial tissue macrophages.

Neovascularization plays an important role in the formation of the rheumatoid (RA) synovial pannus. A subpopulation of RA macrophages (F3) (density 1.042-1.062 g/ml) has been shown to induce neovascularization in an in vivo rat corneal model of angiogenesis. We have found that conditioned medium from F3 macrophages induced significantly more endothelial migration (p less than 0.001) and mononuclear cell factor activity (p less than 0.001) than did conditioned medium from F2 macrophages (density 0.998-1.042 g/ml). Exposure of these macrophages to lipopolysaccharide did not increase production of these activities. RA synovial tissue macrophages appear to be heterogeneous in their production, and maximally activated for expression of these activities in vivo. F3 macrophages may be important in mediating both the fibroproliferative and destructive phases of RA.

Inhibition of production of macrophage-derived angiogenic activity by the anti-rheumatic agents gold sodium thiomalate and auranofin.

We have investigated the effect of gold sodium thiomalate and auranofin, gold compounds employed in the treatment of rheumatoid arthritis, on production of macrophage-derived angiogenic activity. Elicited mouse peritoneal macrophages were cultured in the presence or absence of gold compounds or thiomalic acid, and the macrophages or their conditioned media were then assayed for their angiogenic activity in rat corneas. Control macrophage conditioned medium was potently angiogenic. In contrast, conditioned medium from gold or thiomalic acid treated macrophages was not. Addition of gold compounds or thiomalic acid to control macrophage conditioned medium did not inhibit its angiogenic activity. Drug treatments did not significantly affect macrophage lactate dehydrogenase release, lysozyme release, or protein synthesis. We conclude that gold sodium thiomalate and auranofin potently reduce the detectable angiogenic activity produced by macrophages.

Effect of macrophage depletion on growth and neovascularization of hamster buccal pouch carcinomas.

The effect of macrophage depletion on growth and neovascularization of 7,12-dimethylbenz(a)anthracene (DMBA)-induced hamster buccal pouch carcinomas (HBPC) was evaluated by quantitating tritiated thymidine (3[H]TdR) incorporation by tumor cells and microvascular endothelium in light microscopic autoradiographs. Tumors that were depleted of macrophages with systemic hydrocortisone acetate (HA) and intratumor injections of antimacrophage serum (AMS) were examined 7 days after treatment. In control animals 30% of infiltrating host cells were esterase-positive tumor-associated macrophages (TAM) and 28.14% of tumor cells and 14.45% of endothelial cells were 3[H]TdR labelled. Hamsters treated with HA or HA and control serum showed no significant reduction in either the number of TAM or proportion of [3H]TdR labelled tumor of endothelial cells. AMS administered alone had no effect on either the content of TAM or 3[H]TdR labelling. In contrast hamsters treated with HA and AMS showed a 54% decrease in TAM and a 50% and 63% reduction in tumor and endothelial cell labelling respectively. These results suggest that growth and neovascularization of these tumors is mediated in part by macrophages.

Macrophage-induced angiogenesis is mediated by tumour necrosis factor-alpha.

Macrophages are important in the induction of new blood vessel growth during wound repair, inflammation and tumour growth. We show here that tumour necrosis factor-alpha (TNF-alpha), a secretory product of activated macrophages that is believed to mediate tumour cytotoxicity, is a potent inducer of new blood vessel growth (angiogenesis). In vivo, TNF-alpha induces capillary blood vessel formation in the rat cornea and the developing chick chorioallantoic membrane at very low doses. In vitro, TNF-alpha stimulates chemotaxis of bovine adrenal capillary endothelial cells and induces cultures of these cells grown on type-1 collagen gels to form capillary-tube-like structures. The angiogenic activity produced by activated murine peritoneal macrophages is completely neutralized by a polyclonal antibody to TNF-alpha, suggesting immunological features are common to TNF-alpha and the protein responsible for macrophage-derived angiogenic activity. In inflammation and wound repair, TNF-alpha could augment repair by stimulating new blood vessel growth; in tumours, TNF-alpha might both stimulate tumour development by promoting vessel growth and participate in tumour destruction by direct cytotoxicity.

Wound healing in porcine skin following low-output carbon dioxide laser irradiation of the incision.

Wound healing of scalpel incisions to the depth of adipose tissue closed with conventional methods was compared with closure by low-output carbon dioxide laser irradiation. In 3 Pitman-Moore minipigs wound healing was evaluated at intervals from 1 to 90 days by the following methods: clinical variables of wound healing; formation of the basement membrane components bullous pemphigoid antigen, laminin, and fibronectin; and histological evaluation of the regeneration of the epidermis, neovascularization, and elastin and collagen formation. There was no significant difference in healing between wounds closed by the various conventional methods and by the low-output carbon dioxide laser.

Stimulation of neovascularization by human rheumatoid synovial tissue macrophages.

Synovial tissue from patients with rheumatoid arthritis was enzymatically dissociated, and single cell suspensions were fractionated into subpopulations by centrifugation on continuous Percoll gradients. Five fractions (F1-F5) with densities of 0.991-0.998 gm/ml, 0.998-1.042 gm/ml, 1.042-1.062 gm/ml, 1.062-1.082 gm/ml, and 1.082-1.180 gm/ml, respectively, were prepared. F3 consistently contained the highest number of macrophages, while F2 and F4 contained substantially fewer macrophages. Macrophages present in F2, F3, and F4 were enriched by differential adherence to fibronectin-coated collagen gels. These macrophage-enriched cell preparations were found to be Fc and C3 positive, esterase positive, and peroxidase negative, to stain positively with anti-HLA-DR, anti-Leu-M3, OKM1, and OKM5 monoclonal antibodies, and to show characteristic features of macrophages by electron microscopy. Macrophages from F3 consistently induced neovascularization in rat corneas, while equal numbers of macrophages from F2 and F4 did not. Fibroblastic synovial cells and cells that did not adhere to fibronectin-coated collagen gels did not induce neovascularization. Within the rheumatoid synovium, there appears to be a major subpopulation of macrophages capable of inducing neovascularization, a process vital to the development of the rheumatoid synovial pannus.