3'UTR AU-Rich Elements (AREs) and the RNA-Binding Protein Tristetraprolin (TTP) Are Not Required for the LPS-Mediated Destabilization of Phospholipase-Cß-2 mRNA in Murine Macrophages.

We have shown previously that bacterial lipopolysaccharide (LPS)-mediated suppression of phospholipase-Cß-2 (PLCß-2) expression is involved in M1 (inflammatory) to M2-like (wound healing) phenotypic switching of macrophages triggered by adenosine. This suppression is mediated post-transcriptionally by destabilization of PLCß-2 mRNA (messenger ribonucleic acid). To investigate the mechanism of this LPS-mediated destabilization, we examined the roles of RNA-binding agents including microRNAs and RNA-binding proteins that are involved in regulating stability of mRNAs encoding growth factors, inflammatory mediators, and proto-oncogenes. Adenylate and uridylate (AU)-rich elements (AREs) in 3'UTRs are specific recognition sites for RNA-binding proteins including tristetraprolin (TTP), HuR, and AUF1 and for microRNAs that are involved in regulating mRNA stability. In this study, we investigated the role of TTP and AREs in regulating PLCß-2 mRNA stability. The 3'UTR of the PLCß-2 gene was inserted into the pLightswitch luciferase reporter plasmid and transfected into RAW264.7 cells. LPS suppressed luciferase expression from this reporter. Luciferase expression from mutant 3'UTR constructs lacking AREs was similarly downregulated, suggesting that these regions are not required for LPS-mediated suppression of PLCß-2. TTP was rapidly upregulated in both primary murine macrophages and RAW264.7 cells in response to LPS. Suppression of PLCß-2 by LPS was examined using macrophages from mice lacking TTP (TTP-/-). LPS suppressed PLCß-2 expression to the same extent in wild type (WT) and TTP-/- macrophages. Also, the rate of decay of PLCß-2 mRNA in LPS-treated macrophages following transcriptional blockade was similar in WT and TTP-/- macrophages, clearly indicating that TTP is not involved in LPS-mediated destabilization of PLCß-2 mRNA in macrophages.

Adenosine augments IL-10-induced STAT3 signaling in M2c macrophages.

The alternatively activated macrophage phenotype induced by IL-10 is called M2c. Adenosine is an endogenous purine nucleoside that accumulates in the extracellular space in response to metabolic disturbances, hypoxia, inflammation, physical damage, or apoptosis. As adenosine is known to regulate classically activated M1 and IL4- and IL-13-activated M2a macrophages, the goal of the present study was to explore its effects on M2c macrophages. We found that adenosine augmented the IL-10-induced expression of TIMP-1 and arginase-1 by the mouse macrophage cell line RAW 264.7 and by mouse BMDMs. The effects of AR stimulation on IL-10-induced TIMP-1 or arginase-1 expression were lacking in A2BAR KO macrophages. The role of A2BAR on TIMP-1 production of RAW 264.7 cells was confirmed with specific agonist BAY606583 and antagonist PSB0788. AR stimulation augmented IL-10-induced STAT3 phosphorylation in macrophages, and pharmacological inhibition or silencing of STAT3 using siRNA reduced the stimulatory effect of AR stimulation on TIMP-1 production. In contrast to its stimulatory effect on IL-10-induced STAT3 activation, adenosine inhibited IL-6-induced STAT3 phosphorylation and SAA3 expression. In conclusion, adenosine enhances IL-10-induced STAT3 signaling and M2c macrophage activation.

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.

Adenosine promotes alternative macrophage activation via A2A and A2B receptors.

Adenosine has been implicated in suppressing the proinflammatory responses of classically activated macrophages induced by Th1 cytokines. Alternative macrophage activation is induced by the Th2 cytokines interleukin (IL)-4 and IL-13; however, the role of adenosine in governing alternative macrophage activation is unknown. We show here that adenosine treatment of IL-4- or IL-13-activated macrophages augments the expression of alternative macrophage markers arginase-1, tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), and macrophage galactose-type C-type lectin-1. The stimulatory effect of adenosine required primarily A(2B) receptors because the nonselective adenosine receptor agonist 5'-N-ethylcarboxamidoadenosine (NECA) increased both arginase activity (EC(50)=261.8 nM) and TIMP-1 production (EC(50)=80.67 nM), and both pharmacologic and genetic blockade of A(2B) receptors prevented the effect of NECA. A(2A) receptors also contributed to the adenosine augmentation of IL-4-induced TIMP-1 release, as both adenosine and NECA were less efficacious in augmenting TIMP-1 release by A(2A) receptor-deficient than control macrophages. Of the transcription factors known to drive alternative macrophage activation, CCAAT-enhancer-binding protein ß was required, while cAMP response element-binding protein and signal transducer and activator of transcription 6 were dispensable in mediating the effect of adenosine. We propose that adenosine receptor activation suppresses inflammation and promotes tissue restitution, in part, by promoting alternative macrophage activation.

A2A adenosine receptors and C/EBPbeta are crucially required for IL-10 production by macrophages exposed to Escherichia coli.

We recently showed that A(2A) adenosine receptor activation by endogenous adenosine contributes to interleukin-10 (IL-10) production in polymicrobial sepsis. Here we investigated the molecular mechanisms underpinning this interaction between adenosine receptor signaling and infection by exposing macrophages to Escherichia coli. We demonstrated using receptor knockout mice that A(2A) receptor activation is critically required for the stimulatory effect of adenosine on IL-10 production by E coli-challenged macrophages, whereas A(2B) receptors have a minor role. The stimulatory effect of adenosine on E coli-induced IL-10 production did not require toll-like receptor 4 (TLR4) or MyD88, but was blocked by p38 inhibition. Using shRNA we demonstrated that TRAF6 impairs the potentiating effect of adenosine. Measuring IL-10 mRNA abundance and transfection with an IL-10 promoter-luciferase construct indicated that E coli and adenosine synergistically activate IL-10 transcription. Sequential deletion analysis and site-directed mutagenesis of the IL-10 promoter revealed that a region harboring C/EBP binding elements was responsible for the stimulatory effect of adenosine on E coli-induced IL-10 promoter activity. Adenosine augmented E coli-induced nuclear accumulation and DNA binding of C/EBPbeta. C/EBPbeta-deficient macrophages failed to produce IL-10 in response to adenosine and E coli. Our results suggest that the A(2A) receptor-C/EBPbeta axis is critical for IL-10 production after bacterial infection.

Adenosine augments IL-10 production by macrophages through an A2B receptor-mediated posttranscriptional mechanism.

Adenosine receptor ligands have anti-inflammatory effects and modulate immune responses by up-regulating IL-10 production by immunostimulated macrophages. The adenosine receptor family comprises G protein-coupled heptahelical transmembrane receptors classified into four types: A1, A2A, A2B, and A3. Our understanding of the signaling mechanisms leading to enhanced IL-10 production following adenosine receptor occupancy on macrophages is limited. In this study, we demonstrate that adenosine receptor occupancy increases IL-10 production by LPS-stimulated macrophages without affecting IL-10 promoter activity and IL-10 mRNA levels, indicating a posttranscriptional mechanism. Transfection experiments with reporter constructs containing sequences corresponding to the AU-rich 3'-untranslated region (UTR) of IL-10 mRNA confirmed that adenosine receptor activation acts by relieving the translational repressive effect of the IL-10 3'-UTR. By contrast, adenosine receptor activation failed to liberate the translational arrest conferred by the 3'-UTR of TNF-alpha mRNA. The IL-10 3'-UTR formed specific complexes with proteins present in cytoplasmic extracts of RAW 264.7 cells. Adenosine enhanced binding of proteins to a region of the IL-10 3'-UTR containing the GUAUUUAUU nonamer. The stimulatory effect of adenosine on IL-10 production was mediated through the A(2B) receptor, because the order of potency of selective agonists was 5'-N-ethylcarboxamidoadenosine (NECA) > N6-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (IB-MECA) > 2-chloro-N6-cyclopentyladenosine (CCPA) = 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethyl-carboxamidoadenosine (CGS-21680). Also, the selective A2B antagonist, alloxazine, prevented the effect of adenosine. Collectively, these studies identify a novel pathway in which activation of a G protein-coupled receptor augments translation of an anti-inflammatory gene.

Inflammatory cells during wound repair: the good, the bad and the ugly.

Damage to any tissue triggers a cascade of events that leads to rapid repair of the wound - if the tissue is skin, then repair involves re-epithelialization, formation of granulation tissue and contraction of underlying wound connective tissues. This concerted effort by the wounded cell layers is accompanied by, and might also be partially regulated by, a robust inflammatory response, in which first neutrophils and then macrophages and mast cells emigrate from nearby tissues and from the circulation. Clearly, this inflammatory response is crucial for fighting infection and must have been selected for during the course of evolution so that tissue damage did not inevitably lead to death through septicemia. But, aside from this role, exactly what are the functions of the various leukocyte lineages that are recruited with overlapping time courses to the wound site, and might they do more harm than good? Recent knockout and knockdown studies suggest that depletion of one or more of the inflammatory cell lineages can even enhance healing, and we discuss new views on how regulation of the migration of inflammatory cells to sites of tissue damage might guide therapeutic strategies for modulating the inflammatory response.

Adenosine stimulates CREB activation in macrophages via a p38 MAPK-mediated mechanism.

Adenosine is an endogenously released autocoid that has potent receptor-mediated modulatory effects on macrophage function. The intracellular pathways mediating these effects are incompletely understood. Since adenosine receptor occupancy has been associated with activation of the cAMP-PKA system as well as of p38 MAPK and p42/44 MAPK, all of which can activate the CREB transcription factor system, we hypothesized that adenosine would activate CREB in macrophages. Using RAW 264.7 macrophages, we found that extracellular adenosine enhanced CREB transcriptional activity and increased phosphorylation of nuclear CREB. On the other hand, adenosine failed to alter CREB DNA binding. Adenosine stimulated both p38 and p42/44 MAPK activation. The p38 MAPK pathway inhibitor SB203580 but not the p42/44 MAPK pathway blocker PD98059 decreased adenosine-induced CREB activation, indicating that p38 MAPK but not p42/44 MAPK is an upstream mediator of CREB activation. Thus, some of the immunomodulatory effects of adenosine in macrophages may be explained by its augmenting effect on CREB activation.

An angiogenic switch in macrophages involving synergy between Toll-like receptors 2, 4, 7, and 9 and adenosine A(2A) receptors.

Adenosine A(2A) receptor (A(2A)R) agonists synergize with Escherichia coli (E. coli) LPS [toll-like receptor (TLR)4 agonist] to up-regulate vascular endothelial growth factor (VEGF) expression in murine macrophages. Here, we demonstrate that TLR2, TLR7, and TLR9, but not TLR3 and TLR5 agonists, also synergize with A(2A)R agonists and adenosine to up-regulate VEGF, while simultaneously strongly down-regulating TNFalpha expression. In the absence of adenosine or A(2A)R agonists, Porphyromonas gingivalis (P. gingivalis) LPS and PAM(3)CAG (TLR2 agonists), resiquimod (R848) (TLR7 agonist), and non-methylated CpG DNA (TLR9 agonist) strongly up-regulate TNFalpha expression, with no effect on VEGF. In the presence of adenosine or A(2A)R agonists, but not A(1)R agonists, TLR2, 4, 7, and 9 agonists strongly up-regulate VEGF expression, while simultaneously down-regulating TNFalpha. C57BL/10ScN (TLR4 deletion mutant) macrophages produce TNFalpha in response to TLR2, 3, 7, and 9 agonists, but not the TLR4 agonist E. coli LPS. With adenosine or A(2A)R agonists, TLR2, 7, and 9, but not TLR4 agonists, also synergistically up-regulate VEGF, while down-regulating TNFalpha expression. Polyinosinic-polycytidilic acid (poly(I:C)) (TLR3 agonist) stimulates TNFalpha expression in macrophages from both C57BL/10ScSn and C57BL/10ScN mice, but has little effect on VEGF expression in the presence of adenosine or A(2A)R agonists. R-flagellins from Serratia marcescens (S. marcescens) and Salmonella muenchen (S. muenchen) do not stimulate TNFalpha expression in either C57BL/10ScSn or C57BL10/ScN mice, and have no effect on VEGF production in the presence of adenosine or A(2A)R agonists. While adenosine and A(2A)R agonists strongly down-regulate TNFalpha protein expression induced by TLR2, 3, 4, 7, and 9 agonists, TNFalpha mRNA and NF-kappaB activation are not reduced. We propose a novel signaling pathway in murine macrophages involving synergy between TLRs 2, 4, 7, and 9 and A(2A)Rs, that up-regulates VEGF and down-regulates TNFalpha expression, thus acting as an angiogenic switch. This angiogenic switch may play an important role in ischemia when TLR agonists are present, providing an interface between innate immunity and wound healing.

cDNA microarray analysis reveals a nuclear factor-kappaB-independent regulation of macrophage function by adenosine.

Adenosine is released into the extracellular space from nerve terminals and cells subjected to ischemic stress. This nucleoside modulates a plethora of cellular functions via occupancy of specific receptors. Adenosine is also an important endogenous regulator of macrophage function, because it suppresses the production of a number of proinflammatory cytokines by these cells. However, the mechanisms of this anti-inflammatory effect have not been well characterized. We hypothesized that adenosine may exert some of its anti-inflammatory effects by decreasing activation of the transcription factor nuclear factor-kappaB (NF-kappaB), because gene expression of most of the proinflammatory cytokines inhibited by adenosine is dependent on NF-kappaB activation. Using bacterial lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages, we found that adenosine as well as adenosine receptor agonists decreased the production of tumor necrosis factor (TNF)-alpha, a typical NF-kappaB-regulated cytokine. This effect of adenosine was not due to an action on the process of TNF-alpha release, because adenosine suppressed also the intracellular levels of TNF-alpha. However, cDNA microarray analysis revealed that mRNA levels of neither TNF-alpha nor other cytokines were altered by adenosine in either LPS-activated or quiescent macrophages. In addition, although LPS induced expression of a number of other, noncytokine genes, including the adenosine A2b receptor, adenosine did not affect the expression of these genes. Furthermore, adenosine as well as adenosine receptor agonists failed to decrease LPS-induced NF-kappaB DNA binding, NF-kappaB promoter activity, p65 nuclear translocation, and inhibitory kappaB degradation. Together, our results suggest that the anti-inflammatory effects of adenosine are independent of NF-kappaB.

Regulation of vascular endothelial growth factor gene expression in murine macrophages by nitric oxide and hypoxia.

Vascular endothelial growth factor (VEGF) expression in murine peritoneal macrophages is strongly upregulated by hypoxia via transcriptional and posttranscriptional mechanisms. Interferon-gamma (IFN-gamma) with Escherichia coli lipopolysaccharide (LPS) also upregulates expression of VEGF, as well as of the inducible nitric oxide synthase (iNOS). Hypoxia (1% O(2)) upregulates VEGF expression in macrophages from both wild-type and iNOS knockout mice, indicating that hypoxic upregulation of VEGF is independent of iNOS. However, the iNOS inhibitor aminoguanidine (AG) decreases the VEGF expression induced by LPS/IFN-gamma, indicating an important role for NO. NO-dependent induction of VEGF is strongly dependent on cell density. LPS/IFN-gamma treatment induces minimal VEGF protein expression in macrophages cultured at low cell densities (<0.25 x 10(6) cells/cm(2)); at higher cell densities (>0.25 x 10(6) cells/cm(2)) that lead to conditions of pericellular hypoxia, however, induction of VEGF expression was strong. Transient transfection of RAW 264.7 cells with luciferase reporter constructs of the murine VEGF promoter indicates that both hypoxia and LPS/IFN-gamma independently induce VEGF promoter activity, irrespective of cell density. Although LPS/IFN-gamma treatment induces transcriptional activation of the VEGF promoter, significant levels of VEGF protein are only expressed by cells at high density under conditions of pericellular hypoxia. This suggests an important regulatory role for hypoxia at the posttranscriptional level. Deletion analysis of the VEGF promoter shows that the hypoxia response element region and its immediate flanking sequences are essential for both hypoxia and LPS/IFN-gamma-induced VEGF promoter activation.

Effects of nitric oxide releasing poly(vinyl alcohol) hydrogel dressings on dermal wound healing in diabetic mice.

Healing of chronic wounds such as diabetic foot ulcers is a significant clinical problem. Methods of accelerating healing in these difficult lower extremity sites include use of growth factor-loaded gels, hyperbaric oxygen, grafts, and artificial skin replacements. Nitric oxide (NO) has been proposed as a possible active agent for enhancing wound healing. This study examines the in vitro and in vivo responses to a novel hydrogel that produces therapeutic levels of NO. A hydrogel wound dressing was fabricated using ultraviolet light-initiated polymerization from poly(vinyl alcohol) with a NO donor covalently coupled to the polymer backbone. NO release from the NO-modified hydrogel was shown to occur over a time period of up to 48 hours, and there was no associated decrease in fibroblast growth or viability in vitro associated with NO hydrogels. Fibroblasts in culture with NO hydrogels had an increased production of extracellular matrix compared with cells cultured without the NO hydrogels. Preliminary animal studies in a diabetic mouse, impaired wound healing model were conducted comparing low (0.5 mM) and high (5 mM) doses of NO. Time to complete closure was similar in control wounds and NO-treated wounds; however, at 8 days control wounds were significantly smaller than NO-treated wounds. By days 10 to 13 this delay was no longer apparent. Granulation tissue thickness within the wounds at days 8 and 15 and scar tissue thickness after wound closure were increased in animals exposed to higher dose NO hydrogels. The results of this study suggest that exogenous NO released from a hydrogel wound dressing has potential to modulate wound healing.

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.