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G S Firestein

Publications and source records attributed to G S Firestein.

At least 73 records · Page 4Linked to original sources
PubMed1995

Anti-inflammatory effects of an adenosine kinase inhibitor. Decreased neutrophil accumulation and vascular leakage.

Adenosine inhibits neutrophil function, but also causes cardiovascular side effects when administered systemically. To regulate local adenosine concentrations and minimize toxicity, a novel adenosine kinase inhibitor, GP-1-515, was tested in several acute inflammation models in rats. GP-1-515 inhibited carrageenan-induced rat paw swelling in a dose-dependent manner (maximum inhibition, 47 +/- 3%). In a rat skin lesion model, GP-1-515 significantly reduced cutaneous neutrophil infiltration following an intradermal injection of carrageenan or zymosan-activated plasma, or induction of a reverse passive Arthus reaction. This action appeared to be mediated by endogenous adenosine, inasmuch as a specific A2 adenosine receptor antagonist reversed the effect. GP-1-515 also decreased vascular leakage induced by carrageenan (which is partly neutrophil dependent) and by the neutrophil-independent mediators histamine and bradykinin. Inhibition of leakage was reversed by co-administration of adenosine receptor antagonist. Treatment with anti-inflammatory doses of GP-1-515 had no effect on heart rate or blood pressure. In conclusion, GP-1-515 significantly reduced both neutrophil infiltration and vascular leakage through the release of endogenous adenosine without evidence of cardiovascular side effects.

Adenosine Kinase↗
PubMed1995

Inhibition of neutrophil adhesion by adenosine and an adenosine kinase inhibitor. The role of selectins.

Adenosine and adenosine analogues exhibit anti-inflammatory effects in vitro and in vivo, but their usefulness is limited by profound cardiovascular side effects. Therefore, we synthesized inhibitors of an enzyme involved in adenosine metabolism, adenosine kinase (AK) (EC 2.7.1.20), to enhance endogenous adenosine concentrations at sites of inflammation. GP-1-515 (4-amino-1-(5-amino-5-deoxy-1-beta-D- ribofuranosyl)-3-bromo-pyrazolo[3,4-d]pyrimidine), a novel AK inhibitor, decreased adhesion of activated human neutrophils to cultured endothelial cell monolayers by increasing local adenosine levels. The mechanism of inhibition in this assay seemed to involve selectin blockade and was independent of the beta 2 integrins. GP-1-515 and 2-chloroadenosine (a nonmetabolizable adenosine analogue) had no effect on the surface expression or shedding of adhesion molecules. An agent that disrupts the cytoskeleton, cytochalasin B, mimicked the effect of adenosine on cell adhesion. Interactions between L-selectin and the neutrophil cytoskeleton might be altered by adenosine and could contribute to adenosine-mediated adhesion inhibition.

2-Chloroadenosine↗
PubMed1995

Apoptosis in rheumatoid arthritis synovium.

RA synovial tissue (ST) was studied to determine if and where apoptosis occurs in situ. Genomic DNA was extracted from 5 RA and 1 osteoarthritis ST samples. Agarose gel electrophoresis demonstrated DNA ladders characteristic for apoptosis from each tissue. In situ and labeling (ISEL) was used to identify DNA strand breaks consistent with apoptosis in frozen sections. 12 RA and 4 osteoarthritis ST were studied by ISEL and all were positive, but only 2 of 4 normal tissues were positive. The primary location of apopotic cells was the synovial lining. Some sublining cells were also positive, but lymphoid aggregate staining was conspicuously absent. Immunohistochemistry and ISEL were combined and showed that the lining cells with DNA strand breaks were mainly macrophages, although some fibroblastlike cells were also labeled. Sublining cells with fragmented DNA included macrophages and fibroblasts, but T cells in lymphoid aggregates, which expressed large amounts of bcl-2, were spared. DNA strand breaks in cultured fibroblastlike synoviocytes was assessed using ISEL. Apoptosis could be induced by actinomycin D, anti-fas antibody, IL-1, and TNF-alpha but not by IFN-gamma. Fas expression was also detected on fibroblast-like synoviocytes using flow cytometry. Therefore, DNA strand breaks occur in synovium of patients with arthritis. Cytokines regulate this process, and the cytokine profile in RA (high IL-1/TNF; low IFN-gamma) along with local oxidant injury might favor induction of apoptosis.

Apoptosis↗
PubMed1994

Protection of mice from endotoxic death by 2-methylthio-ATP.

The lethal effects of endotoxin, a bacterial product shed into the blood during bacteremia, are thought to be due to macrophage release of mediators such as tumor necrosis factor alpha and interleukin 1. Although much is known about the pathophysiology of endotoxemia, relatively little is known about the cellular signaling mechanisms that are involved. The data in this study suggest that extracellular adenine nucleotides can influence the development of endotoxin shock. An adenine nucleotide analog, 2-methylthio-ATP, inhibited the endotoxin-stimulated release of toxic mediators (i.e., tumor necrosis factor alpha and interleukin 1), and it protected mice from endotoxin-induced death. These studies suggest a fundamental and unusual role for adenine nucleotides on endotoxin action, and they provide a potentially new therapeutic approach for the control of the pathophysiology of Gram-negative septicemia.

Adenosine Diphosphate↗
PubMed1994

Protective effect of an adenosine kinase inhibitor in septic shock.

Adenosine exhibits potent anti-inflammatory activities but its therapeutic use is limited by cardiovascular side effects. Inhibitors of an enzyme involved in adenosine metabolism, adenosine kinase (EC 2.7.1.20), were evaluated for their ability to enhance endogenous adenosine production. One novel adenosine kinase inhibitor, GP-1-515, was studied in two models of septic shock to assess its protective effects. GP-1-515 significantly decreased mortality in mice that received a lethal i.v. injection of endotoxin. The beneficial effect was accompanied by decreased neutrophil accumulation in the lungs and was reversed by an adenosine receptor antagonist, implying that the effects were mediated by endogenous adenosine. Plasma levels of TNF-alpha, but not IL-1 alpha or IL-6, were lower in the GP-1-515-treated animals. In a second model of sepsis, GP-1-515 increased survival in bacterial peritonitis in rats. The mechanism of action in both models was likely multifactorial, including adenosine-mediated inhibition of neutrophil adhesion, cytokine production, and oxygen radical generation. Adenosine kinase inhibitors have potent anti-inflammatory effects in vitro and in vivo and represent a novel therapeutic approach to the treatment of inflammatory diseases.

Adenosine↗
PubMed1994

Mechanisms of methotrexate action in rheumatoid arthritis. Selective decrease in synovial collagenase gene expression.

OBJECTIVE: To measure the effect of methotrexate (MTX) treatment in rheumatoid arthritis (RA) on the expression of synovial collagenase, stromelysin, and tissue inhibitor of metalloproteinase 1 (TIMP-1) gene expression in a prospective study. METHODS: Serial percutaneous synovial biopsies (pretreatment and after 3-4 months) were performed on the knees of 8 patients (7 with RA, 1 with seronegative arthritis) who were beginning oral MTX therapy. Synovial gene expression was determined by quantitative in situ hybridization using computer-assisted image analysis. RESULTS: After therapy, patients had decreased joint counts, morning stiffness, and erythrocyte sedimentation rates. Synovial inflammation in the biopsy tissues was slightly decreased after therapy. In situ hybridization on pretreatment and posttreatment frozen sections was performed to quantify synovial messenger RNA (mRNA) levels. Collagenase gene expression significantly decreased after MTX therapy (P = 0.006) even though cell density in the region was unchanged. TIMP-1 and stromelysin mRNA levels were not changed by MTX therapy. To study the mechanism of MTX action in vitro, MTX-treated and control fibroblast-like synoviocytes were stimulated with interleukin-1 beta (IL-1 beta). MTX did not alter collagenase or TIMP-1 mRNA levels after IL-1 exposure. CONCLUSION: MTX therapy decreases collagenase gene expression but not TIMP-1 or stromelysin gene expression in the synovium. This action is probably an indirect effect due to an alteration in the synovial cytokine milieu, rather than a direct effect on gene expression.

Adult↗
PubMed1994

Synovial interleukin-1 receptor antagonist and interleukin-1 balance in rheumatoid arthritis.

OBJECTIVE: To quantify interleukin-1 receptor antagonist (IL-1ra) and IL-1 production and gene expression by rheumatoid arthritis (RA) synovial tissue (ST) cells. METHODS: IL-1 alpha, IL-1 beta, and IL-1ra protein levels were measured by enzyme-linked immunosorbent assay in fresh and cultured ST cells, purified synovial macrophages, and fibroblast-like synoviocytes (FLS). The relative expression of the secreted form of IL-1ra (sIL-1ra) and the alternatively spliced intracellular form (icIL-1ra) was determined by reverse transcription polymerase chain reaction (RT-PCR) techniques. RESULTS: IL-1 alpha, IL-1 beta, and IL-1ra were present in fresh and cultured ST cell samples of synovium from RA and osteoarthritis patients. IL-1ra:IL-1 ratios ranged from 1.2 to 3.6, which is below the 10-100-fold excess of IL-1ra needed to inhibit IL-1 bioactivity. Isolated CD14+ synovial macrophages secreted IL-1ra, but the amount was much less than that of alveolar or in vitro-derived macrophages. Cultured FLS contained intracellular IL-1ra but secreted little IL-1ra into the culture supernatants. RT-PCR showed that icIL-1ra mRNA was more abundant than sIL-1ra mRNA in FLS and unfractionated ST cells. CONCLUSION: IL-1ra production by RA ST cells is deficient relative to total production of IL-1.

Arthritis, Rheumatoid↗
PubMed1994

Early synovitis--synoviocytes and mononuclear cells.

Immunohistological observations of synovial tissues obtained at the onset of rheumatoid arthritis (RA) are limited and often reflect the diagnostic confusion inherent in any study of early synovitis. However, a critical analysis of published information and the authors' experience allow certain preliminary conclusions. Synovial lining cell hyperplasia and mononuclear cell infiltration are conspicuous in the earliest examples of synovitis. The changes in RA, however, are indistinguishable from those of other inflammatory joint disease. Conventional T-cell phenotyping does not distinguish early from late synovitis. Mature CD4+ lymphocytes are the predominant cells in both situations, but the presence of B lymphocytes or plasma cells may have diagnostic or prognostic value. The relationship of lining cell hyperplasia to subintimal cell infiltration is not defined; whether they develop simultaneously or one precedes the other remains an important unanswered question. However, it is clear that production of enzymes (metalloproteinases) believed to be important in extracellular matrix destruction is an early event.

Arthritis, Rheumatoid↗
PubMed1994

Expression and functional significance of alternatively spliced CS1 fibronectin in rheumatoid arthritis microvasculature.

Expression of fibronectin (FN) isoforms containing CS1, a 25-amino acid sequence present within the alternatively spliced IIICS region of FN, has been analyzed in rheumatoid arthritis (RA) synovium. Unexpectedly, CS1-containing FN variants were exclusively found on endothelium but not extracellular matrix (ECM) of RA synovium. Lumenal expression of CS1 on RA endothelial cells, as observed by electron microscopy, correlated with inflammation in RA, since normal synovium expressed little CS1 without appreciable decrease in ECM FN. CS1 expression on human endothelial cells was further shown by FN mRNA analyses. In adhesion assays on frozen RA synovial sections, T lymphoblastoid cells expressing functionally activated alpha 4 beta 1 integrin specifically attached to the intravascular surface of RA endothelium. Binding was abrogated by both anti-alpha 4 integrin and CS1 peptides. Our observations suggest direct involvement of CS1-containing FN in recruitment of alpha 4 beta 1-expressing mononuclear leukocytes in synovitis, and provide basis for therapeutic intervention in RA.

Alternative Splicing↗
PubMed1994

Regulation of granulocyte macrophage colony stimulating factor production by human articular chondrocytes. Induction by both tumor necrosis factor-alpha and interleukin 1, downregulation by transforming growth factor beta and upregulation by fibroblast growth factor.

OBJECTIVE: To study the regulation of granulocyte macrophage colony stimulating factor (GM-CSF) production by human articular chondrocytes which may contribute to the local GM-CSF production encountered in rheumatoid joints. This growth factor induces human macrophages to migrate and proliferate, improves their accessory function and increases the expression of HLA-DR antigens on macrophages and macrophage-like synoviocytes. METHODS: GM-CSF was assayed by ELISA and a bioassay in cell and organ culture supernatants from human articular chondrocytes, by in situ hybridization, Northern blot analysis and affinity chromatography. RESULTS: Both interleukin 1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) synergistically or additively stimulated chondrocytes to produce significant amounts of immunoreactive and bioactive GM-CSF with maximum values of 2928 pg/ml (p < 0.0001 both for IL-1 and/or TNF-alpha vs baseline). Affinity chromatography using specific monoclonal antibodies for human GM-CSF resulted in the purification of a chondrocyte derived 22-23 kDa protein. In situ hybridization demonstrated that the number of chondrocytes that expressed GM-CSF mRNA correlated well to the amount of GM-CSF secreted into the cultures. Transforming growth factor beta (TGF-beta) and to a lesser extent interferon-gamma (IFN-gamma) were able to decrease GM-CSF production induced by IL-1 and/or TNF-alpha. In contrast, basic fibroblast growth factor (FGF) in combination with IL-1 strongly increased GM-CSF secretion up to 8.5-fold. IFN-gamma, IL-6, TGF-beta, bFGF and IL-8 given alone failed to induce chondrocytes to produce GM-CSF. Steroids and low concentrations of cyclooxygenase inhibitors in general suppressed cytokine induced GM-CSF production. CONCLUSION: Our data demonstrate that both proinflammatory cytokines IL-1 and TNF-alpha induce an immunoreactive and biologically active GM-CSF by human articular chondrocytes that appears to be downregulated by TGF-beta and upregulated by FGF. GM-CSF produced locally by cartilage cells may be an important cytokine involved in the activation and proliferation of pannus cells, that can be modulated by interactions with cytokines present in the inflamed joints, thus possibly contributing to the chronic infiltration and destruction of cartilage in inflammatory joint diseases.

Cartilage, Articular↗
PubMed1993

cDNA cloning and sequence analysis of the human A3 adenosine receptor.

We report the cloning of the cDNA encoding the homolog of the A3 adenosine receptor (A3AR) from a human heart library. The receptor shares a surprisingly low degree of sequence homology to the rat A3AR. Northern analysis of various human tissues showed the human A3AR gene to be expressed primarily in lung, liver, kidney and heart, with very little expression in the brain or in skeletal muscle.

Amino Acid Sequence↗
PubMed1993

Mutual antagonism between interferon-gamma and tumor necrosis factor-alpha on fibroblast-like synoviocytes: paradoxical induction of IFN-gamma and TNF-alpha receptor expression.

We recently described mutual antagonism between IFN-gamma and TNF-alpha on human fibroblast-like synoviocytes (FLS). TNF-alpha inhibits IFN-gamma-induced HLA-DR expression and IFN-gamma blocks TNF-alpha-dependent synoviocyte proliferation, collagenase production, and GM-CSF secretion. To study the mechanism of antagonism we have analyzed the effect these factors on the expression of cytokine surface receptors. 125I-Labeled cytokine binding was measured on cultured FLS and the results were analyzed by Scatchard plots. Unstimulated synoviocytes expressed 9300 +/- 1560 IFN-gamma binding sites per cell. A single class of high-affinity receptor was observed (Kd = 4.5 +/- 2.5 x 10(-10) M). TNF-alpha did not competitively inhibit 125I-IFN-gamma binding. When FLS were incubated with TNF-alpha (100 ng/ml), there was a paradoxical 49.5 +/- 5.6% increase in the number of binding sites for IFN-gamma (P = 0.001), with no change in the Kd. Unstimulated FLS also expressed 2850 +/- 700 TNF-alpha receptors per cells, with a single Kd consistent with the lower-affinity TNF-alpha receptor (7.4 +/- 0.2 x 10(-10) M). IFN-gamma did not directly interfere with TNF-alpha binding. Preincubation of FLS with 100 U/ml of IFN-gamma resulted in a 28.9 +/- 9.0% increase in TNF-alpha receptor expression (P < 0.008), with no change in the Kd. Low levels of the soluble 55-kD TNF receptor were detected in FLS supernatants. IFN-gamma did not effect soluble TNF receptor production.(ABSTRACT TRUNCATED AT 250 WORDS)

Arthritis, Rheumatoid↗
PubMed1992

Cytokine-induced differentiation of cultured nonadherent macrophages.

Monocytes were isolated from peripheral blood and cultured in vitro for more than 3 weeks in glass chamber slides. Phenotypically and ultrastructurally these nonadherent macrophages (NAM) appear similar to connective tissue resident macrophages. They constitutively secrete a high amount of IL-1ra and little or no IL-1 alpha or IL-1 beta. When exposed to GM-CSF, IL-2, or IFN-gamma for 24 hr, NAM become adherent and undergo dramatic morphological changes. Cytokines treatment primes NAM for increased LPS-mediated TNF production and these GM-CSF- and LPS-treated NAM are cytotoxic to WEHI 164, a TNF-sensitive target. Morphological changes and TNF production are both inhibited by antimetabolites and a variety of antineoplastic drugs. Although morphology inhibition is reversible under certain circumstances, inhibition of TNF synthesis is irreversible. These findings suggest that cytokines might play a role in differentiation and maturation of long-term cultured monocytes. Furthermore, the effects of antimetabolites and antineoplastic drugs on arresting the differentiation processes may significantly impair antitumor functions of macrophages.

Adult↗
PubMed1992

Alpha 4/beta 1 integrin (VLA-4) ligands in arthritis. Vascular cell adhesion molecule-1 expression in synovium and on fibroblast-like synoviocytes.

Expression of vascular cell adhesion molecule-1 (VCAM-1) in synovial tissue was determined using the immunoperoxidase technique. Normal, rheumatoid arthritis (RA), and osteoarthritis (OA) synovia bound VCAM-1 antibodies in the intimal lining as well as blood vessels. The amount of VCAM-1 was significantly greater in the synovial lining of RA and OA tissues compared with normal synovium (p less than 0.002). There was also a trend toward greater levels of VCAM-1 staining in blood vessels of arthritic tissue (RA greater than OA greater than normal). Because VCAM-1 staining was especially intense in the synovial lining, VCAM-1 expression and regulation was studied on cultured fibroblast-like synoviocytes (FLS) derived from this region. Both VCAM-1 and intercellular adhesion molecule 1 were constitutively expressed on FLS. VCAM-1 expression was further increased by exposure to IL-1 beta, TNF-alpha, IL-4, and IFN-gamma. These cytokines (except for IL-4) also induced intercellular adhesion molecule 1 expression on FLS. ELAM was not detected on resting or cytokine-stimulated FLS. The specificity of VCAM-1 for FLS was demonstrated by the fact that only trace amounts were detected on normal and RA dermal fibroblasts. Cytokines induced intercellular adhesion molecule 1 display on dermal fibroblasts but had minimal effect on VCAM-1 expression. Finally, in adherence assays, Jurkat cell binding to resting FLS monolayers was inhibited by antibody to alpha 4/beta 1 integrin (VLA-4), CS-1 peptide from alternatively spliced fibronectin (which is another VLA-4 ligand), and, to a lesser extent, anti-VCAM-1 antibody. After cytokine stimulation of FLS, Jurkat-binding significantly increased, and this increase was blocked by anti-VCAM-1 antibody. Therefore, both CS-1 and VCAM-1 participate in VLA-4-mediated adherence to resting FLS in vitro, and VCAM-1 is responsible for the increase in Jurkat binding mediated by cytokines.

Arthritis, Rheumatoid↗