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Biomedical subjects

Bruce N Cronstein

Publications and source records attributed to Bruce N Cronstein.

At least 19 recordsLinked to original sources
PubMed2006

The adenosine system selectively inhibits TLR-mediated TNF-alpha production in the human newborn.

Human newborns are susceptible to microbial infection and mount poor vaccine responses, yet the mechanisms underlying their susceptibility are incompletely defined. We have previously reported that despite normal basal expression of TLRs and associated signaling intermediates, human neonatal cord blood monocytes demonstrate severe impairment in TNF-alpha production in response to triacylated (TLR 2/1) and diacylated (TLR 2/6) bacterial lipopeptides (BLPs). We now demonstrate that in marked contrast, BLP-induced synthesis of IL-6, a cytokine with anti-inflammatory and Th2-polarizing properties, is actually greater in neonates than adults. Remarkably, newborn blood plasma confers substantially reduced BLP-induced monocyte synthesis of TNF-alpha, while preserving IL-6 synthesis, reflecting the presence in neonatal blood plasma of a soluble, low molecular mass inhibitory factor (<10 kDa) that we identify as adenosine, an endogenous purine metabolite with immunomodulatory properties. The neonatal adenosine system also inhibits TNF-alpha production in response to whole microbial particles known to express TLR2 agonist activity, including Listeria monocytogenes, Escherichia coli (that express BLPs), and zymosan particles. Selective inhibition of neonatal TNF-alpha production is due to the distinct neonatal adenosine system, including relatively high adenosine concentrations in neonatal blood plasma and heightened sensitivity of neonatal mononuclear cells to adenosine A3 receptor-mediated accumulation of cAMP, a second messenger that inhibits TLR-mediated TNF-alpha synthesis but preserves IL-6 production. We conclude that the distinct adenosine system of newborns polarizes TLR-mediated cytokine production during the perinatal period and may thereby modulate their innate and adaptive immune responses.

Adenosine↗
PubMed2006

Adenosine A(2A) receptors play a role in the pathogenesis of hepatic cirrhosis.

1. Adenosine is a potent endogenous regulator of inflammation and tissue repair. Adenosine, which is released from injured and hypoxic tissue or in response to toxins and medications, may induce pulmonary fibrosis in mice, presumably via interaction with a specific adenosine receptor. We therefore determined whether adenosine and its receptors contribute to the pathogenesis of hepatic fibrosis. 2. As in other tissues and cell types, adenosine is released in vitro in response to the fibrogenic stimuli ethanol (40 mg dl(-1)) and methotrexate (100 nM). 3. Adenosine A(2A) receptors are expressed on rat and human hepatic stellate cell lines and adenosine A(2A) receptor occupancy promotes collagen production by these cells. Liver sections from mice treated with the hepatotoxins carbon tetrachloride (CCl(4)) (0.05 ml in oil, 50 : 50 v : v, subcutaneously) and thioacetamide (100 mg kg(-1) in PBS, intraperitoneally) released more adenosine than those from untreated mice when cultured ex vivo. 4. Adenosine A(2A) receptor-deficient, but not wild-type or A(3) receptor-deficient, mice are protected from development of hepatic fibrosis following CCl(4) or thioacetamide exposure. 5. Similarly, caffeine (50 mg kg(-1) day(-1), po), a nonselective adenosine receptor antagonist, and ZM241385 (25 mg kg(-1) bid), a more selective antagonist of the adenosine A(2A) receptor, diminished hepatic fibrosis in wild-type mice exposed to either CCl(4) or thioacetamide. 6. These results demonstrate that hepatic adenosine A(2A) receptors play an active role in the pathogenesis of hepatic fibrosis, and suggest a novel therapeutic target in the treatment and prevention of hepatic cirrhosis.

Adenosine↗
PubMed2006

The inflammatory process of gout and its treatment.

Gouty arthritis is a characteristically intense acute inflammatory reaction that erupts in response to articular deposits of monosodium urate (MSU) crystals. Important recent molecular biologic advances in this field have given us a clear picture of the mechanistic basis of gouty inflammation. The innate immune inflammatory response is critically involved in the pathology of gout. Specifically, MSU crystals promote inflammation directly by stimulating cells via Toll-like receptor signaling and by providing a surface for cleavage of C5 and formation of complement membrane attack complex (C5b-9), culminating in secretion of cytokines, chemokines, and other inflammatory mediators with a dramatic influx of neutrophils into the joint. Despite the detailed mechanistic picture for gouty inflammation, there are no placebo-controlled, randomized clinical studies for any of the therapies commonly used, although comparative studies have demonstrated that many nonsteroidal anti-inflammatory drugs are equivalent to indomethacin with respect to controlling acute gouty attacks. In general, the first line of anti-inflammatory therapy for acute gout is nonsteroidal anti-inflammatory drugs, and the selective cyclo-oxygenase-2 inhibitor celecoxib can be used where appropriate. The second line of treatment is glucocorticosteroids, given systemically (oral, intravenous, or intramuscular) or intra-articularly. Alternatively, synthetic adrenocorticotropic hormone is effective, partly via induction of adrenal glucocorticosteroids and partly via rapid peripheral suppression of leukocyte activation by melatonin receptor 3 signaling. The third line of treatment is oral colchicine, which is highly effective when given early in an acute gouty attack, but it is poorly tolerated because of predictable gastrointestinal side effects.

Adrenal Cortex Hormones↗
PubMed2006

Suppression of inflammation by low-dose methotrexate is mediated by adenosine A2A receptor but not A3 receptor activation in thioglycollate-induced peritonitis.

Prior studies demonstrate that adenosine, acting at one or more of its receptors, mediates the anti-inflammatory effects of methotrexate in animal models of both acute and chronic inflammation. Both adenosine A2A and A3 receptors contribute to the anti-inflammatory effects of methotrexate treatment in the air pouch model of inflammation, and the regulation of inflammation by these two receptors differs at the cellular level. Because different factors may regulate inflammation at different sites we examined the effect of low-dose weekly methotrexate treatment (0.75 mg/kg/week) in a model of acute peritoneal inflammation in adenosine A2A receptor knockout mice and A3 receptor knockout mice and their wild-type littermates. Following intraperitoneal injection of thioglycollate there was no significant difference in the number or type of leukocytes, tumor necrosis factor alpha (TNF-alpha) and IL-10 levels that accumulated in the thioglycollate-induced peritoneal exudates in adenosine A2A knockout mice or wild-type control mice. In contrast, there were more leukocytes, TNF-alpha and IL-10 in the exudates of the adenosine A3 receptor-deficient mice. Low-dose, weekly methotrexate treatment increased the adenosine concentration in the peritoneal exudates of all mice studied, and reduced the leukocyte accumulation in the wild-type mice and A3 receptor knockout mice but not in the A2A receptor knockout mice. Methotrexate reduced exudate levels of TNF-alpha in the wild-type mice and A3 receptor knockout mice but not the A2A receptor knockout mice. More strikingly, IL-10, a critical regulator of peritoneal inflammation, was increased in the methotrexate-treated wild-type mice and A3 knockout mice but decreased in the A2A knockout mice. Dexamethasone, an agent that suppresses inflammation by a different mechanism, was similarly effective in wild-type mice, A2A mice and A3 knockout mice. These findings provide further evidence that adenosine is a potent regulator of inflammation that mediates the anti-inflammatory effects of methotrexate. Moreover, these data provide strong evidence that the anti-inflammatory effects of methotrexate and adenosine are mediated by different receptors in different inflammatory loci, an observation that may explain why inflammatory diseases of some organs but not of other organs respond to methotrexate therapy.

Adenosine↗
PubMed2006

Pharmacogenetics in the rheumatic diseases.

Designing a therapeutic plan that involves the least risk of toxicity and the greatest chance of success is the goal of the modern physician. To better achieve this goal an understanding of the genetic basis for drug efficacy and toxicity is essential. Here we review the available information on the pharmacogenetics of drugs commonly used to treat rheumatic diseases in the hope that the application of this information to the patient will contribute to more effective and safer therapies for rheumatoid arthritis, systemic lupus erythematosus, and other inflammatory diseases.

Antirheumatic Agents↗
PubMed2005

Tumor necrosis factor-alpha prevents desensitization of Galphas-coupled receptors by regulating GRK2 association with the plasma membrane.

We have reported previously that interleukin-1 and tumor necrosis factor (TNF)-alpha increase expression and function of adenosine A2A receptors (A2ARs), although the increased function is disproportionate to the increment in expression. We therefore studied the effect of TNF-alpha on A2A R function and desensitization in human monocytoid THP-1 cells. We observed that TNF-alpha regulates activity of A2A Rs and other G protein-coupled receptors (GPCRs) by altering their ligand-mediated desensitization. Pretreatment of resting cells with the A2AR agonist 2-[p-(2-carboxyethyl)phenethylamino]-5'-N-ethylcarboxamidoadenosine (CGS 21680) or the pan-adenosine receptor agonist 5'-N-ethylcarboxamidoadenosine quickly desensitized cAMP responses to CGS 21680 restimulation, but TNF-alpha treatment prevented A2AR desensitization. As expected, A2A R occupancy induced translocation of GPCR kinase-2 (GRK2) to the plasma membrane (PM). We were surprised to find that after TNF-alpha treatment, A2AR occupancy not only failed to induce GRK2 translocation to PM but also decreased GRK2 association with PM. TNF-alpha altered GRK2 translocation in response to the beta-adrenergic receptor agonist isoproterenol in a similar manner. Similar to GRK2, beta-arrestin associated with PM after A2A R stimulation in control cells but not in TNF-alpha-treated cells. C2-ceramide, a downstream mediator in the sphingomyelinase (SMase)-dependent pathway, mimicked the effect of TNF-alpha on GRK2 translocation. Moreover, inhibitors of the SMases and an inhibitor of c-Jun NH2-terminal kinase, also a downstream effector in the SMase pathway, reversed TNF-alpha-mediated effects on GRK2 translocation and A2A R desensitization. These results suggest a novel form of cross-talk between TNF-alpha receptors and GPCRs; TNF-alpha enhances GPCR function by preventing agonist-induced desensitization of GPCRs by diminishing agonist-dependent recruitment of GRK2 and beta-arrestin to PM by a SMase pathway-mediated mechanism.

Arrestins↗
PubMed2005

Adenosine A2A receptor stimulation increases angiogenesis by down-regulating production of the antiangiogenic matrix protein thrombospondin 1.

Topical adenosine A2A receptor agonists promote wound healing by, among other effects, increasing microvessel formation. Results of representational display analysis of human umbilical vein endothelial cells suggested that A2A receptor occupancy modulates expression of the antiangiogenic matrix protein thrombospondin 1 (TSP1). We therefore determined whether A2A receptor occupation stimulates angiogenesis by modulating TSP1 secretion. Human microvascular endothelial cells (HMVEC) were treated with medium alone, 2-p-[2-carboxyethyl] phenethyl-amino-5'-N-ethylcarboxamido-adenosine (CGS-21680), or 2-[2-(4-chlorophenyl)ethoxy]adenosine (MRE0094), selective A2A receptor agonists. TSP1 protein secretion was down-regulated after treatment with the A2A agonists CGS-21680 or MRE0094 in a dose-dependent manner (EC50 = 6.65 nM and 0.23 microM respectively). The selective A2A receptor antagonist 4-[2-[7-amino-2-(2-furyl)[1,2,4]triazolo-[2,3-a][1,3,5]triazin-5-ylamino]ethyl]phenol (ZM241385) but not the A1 and A2B receptor antagonists diphenylcyclopentylxanthine, enprofylline, and N-(4-acetylphenyl)-2-[4-(2,3,6,7-tetrahydro-2,6-dioxo-1,3-dipropyl-1H-purin-8-yl)phenoxy]acetamide (MRS1706) completely abrogated the A2A receptor agonist-mediated effect on TSP1. Vascular tube formation by HMVEC was increased by adenosine A2A receptor agonists in a dose-dependent fashion (EC50 = 0.1 microM for both), and this effect was reversed by the A2A antagonist. Moreover, in the presence of antibodies to TSP1 and CD36, the receptor for TSP1, the adenosine A2A receptor agonists stimulated no increase in vascular tube formation. These results indicate that the angiogenic effects of adenosine A2A receptor activation are, at least in part, caused by the suppression of TSP1 secretion.

Adenosine↗
PubMed2005

Genetically based resistance to the antiinflammatory effects of methotrexate in the air-pouch model of acute inflammation.

OBJECTIVE: Low-dose methotrexate (MTX), a mainstay in the treatment of rheumatoid arthritis, is effective in only 60-70% of patients, a finding mirrored by poor antiinflammatory efficacy in some animal models, most notably collagen-induced arthritis. To determine whether genetic factors or the model itself is responsible for the poor response to MTX, we directly compared the responses of 4 inbred mouse strains to MTX in the air-pouch model of acute inflammation. METHODS: The exudate leukocyte count and adenosine concentration were determined in inbred mice treated with MTX (0.75 mg/kg intraperitoneally every week for 4 weeks) or vehicle 4 hours after injection of carrageenan into the air pouch using previously described methods. Quantitative trait locus mapping was performed using an in silico, or computer-based, method to identify loci potentially associated with each phenotype. RESULTS: MTX significantly reduced the exudate leukocyte count in C57BL/6J and BALB/cJ mice, but not DBA/1J (the strain used in the collagen-induced arthritis model) or DBA/2J mice. In a parallel manner, MTX increased adenosine concentration in inflammatory exudates of C57BL/6J and BALB/cJ mice, but not DBA/1J or DBA/2J mice. Antiinflammatory and adenosine responses to MTX in DBA/1J x C57BL/6J F(1) and F(2) offspring were most consistent with single genetic loci being responsible for each phenotype. In silico mapping identified partially overlapping loci containing candidate genes involved in both responses. CONCLUSION: Genetic factors contribute to the antiinflammatory efficacy of MTX, and a single locus involved in MTX-induced adenosine up-regulation is likely responsible for the observed resistance to MTX in DBA/1J mice.

Acute Disease↗
PubMed2005

An interaction between genetic factors and gender determines the magnitude of the inflammatory response in the mouse air pouch model of acute inflammation.

The widely used mouse air pouch model of acute inflammation is inducible in a variety of inbred strains, but the potential influence of genetic background and gender on inflammation severity has never been examined. We directly compared the degree of inflammation induced in the air pouch model across four commonly utilized inbred strains in both male and female mice. We then applied an in silico mapping method to identify loci potentially associated with determining inflammation severity for each gender. Air pouches were induced by subcutaneous injection 3 (3 cc) and 5 (1.5 cc) days prior to the experiment. 4h after carrageenan injection, exudates were retrieved and leukocyte concentration quantified using a hemocytometer. The in silico mapping method was applied as described below. The strain order for mean leukocyte count/mL in inflamed exudates differed between genders. In males, the order was C57BL/6J > BALB/cByJ > DBA/2J > DBA/1J, while in females the order was BALB/cByJ > DBA/2J > C57BL/6J > DBA/1J. The difference in inflammation severity between genders reached significance only in C57BL/6J mice. Independent in silico analysis based on phenotypic data from male versus female mice identified distinct sets of loci as potentially associated with the exudate count reached. We conclude that the degree of inflammation induced in the mouse air pouch model of inflammation is strain-specific and, therefore, genetically based, and the pattern of interstrain differences is altered in male relative to female mice. The loci identified by in silico mapping likely contain genes with differential roles in determining this phenotype between genders.

Acute Disease↗
PubMed2005

Low-dose methotrexate: a mainstay in the treatment of rheumatoid arthritis.

Methotrexate administered weekly in low doses is a mainstay in the therapy of rheumatoid arthritis. Although originally developed as a folate antagonist for the treatment of cancer, its mechanism of action in the therapy of rheumatoid arthritis remains less clear. Several mechanisms have been proposed including inhibition of T cell proliferation via its effects on purine and pyrimidine metabolism, inhibition of transmethylation reactions required for the prevention of T cell cytotoxicity, interference with glutathione metabolism leading to alterations in recruitment of monocytes and other cells to the inflamed joint, and promotion of the release of the endogenous anti-inflammatory mediator adenosine. These mechanisms of action and the role of methotrexate in the suppression of rheumatoid arthritis are reviewed.

Animals↗
PubMed2004

Interferon-gamma impedes reverse cholesterol transport and promotes foam cell transformation in THP-1 human monocytes/macrophages.

BACKGROUND: Cholesterol 27-hydroxylase, an enzyme expressed at high levels by human monocytes/macrophages, provides a first line of defense against the development of atherosclerosis. Prior studies have suggested that the cytokine interferon-gamma (IFN-gamma) promotes atherosclerosis. We therefore examined the effect of IFN-g on macrophage foam cell formation and on expression of the anti-atherogenic 27-hydroxylase in THP-1 human monocytes/macrophages. MATERIAL/METHODS: THP-1 monocytes and acetylated LDL-treated THP-1 macrophages were incubated in the presence or absence of IFN-gamma (500 U/ml) with or without the addition of IFN- gamma receptor blocking or neutralizing antibody. Foam cell formation was quantified based on percentage of macrophages harboring oil red O-stained globules. Cellular mRNA and protein were isolated. 27-Hydroxylase message was measured by RT-PCR and 27-hydroxylase protein by immunoblot. RESULTS: IFN-gamma -treated THP-1 macrophages exhibit increased foam cell transformation compared to untreated cells under cholesterol loading conditions. IFN-gamma-promoted foam cell formation is abolished by pre-treatment with either IFN-gamma neutralizing or IFN-gamma receptor blocking antibody. IFN-gamma diminishes cholesterol 27-hydroxylase expression in THP-1, and this IFN-gamma -induced downregulation is prevented by pre-treating the cultured cells with either IFN-gamma neutralizing or IFN-gamma receptor blocking antibody. CONCLUSIONS: Imbalances in cellular cholesterol flux within macrophages lead to formation of lipid-laden foam cells, a critical step in the pathogenesis of atherosclerosis. We have demonstrated that IFN-gamma, acting through the IFN-gamma receptor, decreases expression of 27-hydroxylase and increases propensity to foam cell formation in the cell line THP-1. These observations suggest that one mechanism by which IFN-g promotes atherosclerosis may involve affecting expression of cholesterol 27-hydroxylase, a cholesterol homeostatic protein.

Antibodies↗
PubMed2004

Adenosine A2A receptor occupancy stimulates expression of proteins involved in reverse cholesterol transport and inhibits foam cell formation in macrophages.

Transport of cholesterol out of macrophages is critical for prevention of foam cell formation, the first step in the pathogenesis of atherosclerosis. Proteins involved in this process include cholesterol 27-hydroxylase and adenosine 5'-triphosphate-binding cassette transporter A1 (ABCA1). Proinflammatory cytokines and immune complexes (IC) down-regulate cholesterol 27-hydroxylase and impede cholesterol efflux from macrophages, leading to foam cell formation. Prior studies have suggested occupancy of the anti-inflammatory adenosine A2A receptor (A2AR) minimizes early atherosclerotic changes in arteries following injury. We therefore asked whether A2AR occupancy affects macrophage foam cell formation in response to IC and the cytokine interferon-gamma. We found that the selective A2AR agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamido-adenosine (CGS-21680) inhibited foam cell formation in stimulated THP-1 human macrophages, and the effects of CGS-21680 were reversed by the selective A2AR antagonist 4-(2-[7-amino-2-(2-furyl) [1, 2, 4]triazolo[2,3-a] [1, 3, 5]triazin-5-ylamino]ethyl)phenol. In confirmation of the role of A2AR in prevention of foam cell formation, CGS-21680 also inhibited foam cell formation in cultured murine peritoneal macrophages but did not affect foam cell formation in A2AR-deficient mice. Agents that increase foam cell formation also down-regulate cholesterol 27-hydroxylase and ABCA1 expression. Therefore, we determined the effect of A2AR occupancy on expression of these reverse cholesterol transport (RCT) proteins and found that A2AR occupancy stimulates expression of message for both proteins. These results indicate that one mechanism for the antiatherogenic effects of adenosine is stimulation of the expression of proteins involved in RCT. These findings suggest a novel approach to the development of agents that prevent progression of atherosclerosis.

ATP Binding Cassette Transporter 1↗
PubMed2004

Adenosine receptors and wound healing.

Recent studies have demonstrated that application of topical adenosine A2A receptor agonists promotes more rapid wound closure and clinical studies are currently underway to determine the utility of topical A2A adenosine receptor agonists in the therapy of diabetic foot ulcers. The effects of adenosine A2A receptors on the cells and tissues of healing wounds have only recently been explored. We review here the known effects of adenosine A2A receptor occupancy on the cells involved in wound healing.

Adenosine↗