The inhibition of neutrophil-endothelial cell adhesion by hyaluronan independent of CD44.

OBJECTIVE: To study the effect of hyaluronan on cell adhesion and recruitment both in vitro and in vivo, since hyaluronan both inhibits restenosis and is anti-inflammatory. When administered to animals undergoing angioplasty the recruitment of cells into the restenotic plaque is inhibited, as well as into inflammatory lesions. The recent discovery that ICAM-1 binds hyaluronan and exhibits the B(X(7))B HA binding motif, led us also to investigate whether cell adhesion could be modulated by hyaluronan. MATERIALS AND METHODS: Human neutrophils were adhered to human umbilical vein (HUVEC) or Ea.hy.926 HUVEC cells stimulated with phorbol myristate acetate (PMA) or tumour necrosis factor (TNFalpha). Neutrophil binding in vivo utilized FMLP-stimulated hamster cheek pouch post-capillary venules. RESULTS: Hyaluronan inhibited human neutrophil adhesion to both PMA and TNFalpha-stimulated HUVEC. Ea.hy.926 human immortal HUVECs expressed ICAM-1 in response to TNFalpha and PMA. E-selectin was also upregulated by 6 h with TNFalpha but not significantly with PMA. TNFalpha induced CD44 expression within 4 h, but PMA not significantly up to 6 h. However, specific binding of [125I]hyaluronan to Ea.hy.926 cells was increased by PMA-stimulation at 4 h. Neutrophil adhesion to PMA-stimulated Ea.hy.926 HUVECs was inhibited in a concentration dependent fashion by both anti-ICAM-1 and hyaluronan (1 ng/ml-10 microg/ml) at 4 h. At 1 mg/ml adhesion was stimulated by hyaluronan. Hyaluronan had no effect on neutrophil adhesion to resting Ea.hy.926 cells. Hyaluronan (25 mg/kg, i.v.) inhibited cell adhesion to FMLP-stimulated post capillary venules of the hamster cheek pouch, whilst leaving cell rolling unaffected. CONCLUSIONS: These results show that hyaluronan, at concentrations below those where intra-molecular associations occur, binds selectively to stimulated endothelial cells and inhibits neutrophil adhesion in vitro and in vivo via a mechanism which may involve molecules other than CD44, such as ICAM-1.

Heat-shock proteins and their role in chondrocyte protection, an application for autologous transplantation.

Articular cartilage injury presents a unique therapeutic challenge. As cartilage possesses no blood or nerve supply of its own it has a particular susceptibility to early injury and a poor capacity for self-repair. Treatment options are limited and injury can eventually lead to osteoarthritis. Autologous chondrocyte transplantation is an exciting therapeutic development, but despite initial encouraging results, graft failure and formation of fibro- as opposed to hyaline cartilage remain problematic. Bleeding is an inevitable consequence of surgery, and blood-induced cartilage damage is well documented. It is hypothesised here that protecting chondrocytes against blood could significantly improve results. Heat-shock protein induction may confer chondroprotection. The expression of heat-shock proteins in human chondrocytes and rat femoral head cartilage following heat shock was analysed by Western blotting, and red-blood-cell-induced chondrocyte death was assessed by cell viability and apoptosis by flow cytometry. We demonstrate that heat-shock induced expression of heat-shock protein 70 (HSP70) (rat and human) and HSP32 (human). Blood and blood products reduced rat cartilage proteoglycan synthesis and human chondrocyte viability, and induced human chondrocyte apoptosis at concentrations considerably lower than those reported previously. The induction of HSP70 in rat cartilage was ineffective in reducing chondrocyte death in the absence or presence of red blood cells or red cell products. Heat shock to human chondrocytes reduced low levels of apoptosis (<20%) and cell death induced by low levels of blood products, but not higher levels. Induction of HSP32 with diacetylrhein appeared to be more effective and may hold greater promise. Blood has potent adverse effects on chondrocytes and the induction and chondroprotective effects of heat-shock proteins could be applied to increase the initial success of implanted chondrocytes improving the outcome of autologous chondrocyte transplantation.

Possible new role for NF-kappaB in the resolution of inflammation.

Inflammation involves the sequential activation of signaling pathways leading to the production of both pro- and anti-inflammatory mediators. Although much attention has focused on pro-inflammatory pathways that initiate inflammation, relatively little is known about the mechanisms that switch off inflammation and resolve the inflammatory response. The transcription factor NF-kappaB is thought to have a central role in the induction of pro-inflammatory gene expression and has attracted interest as a new target for the treatment of inflammatory disease. We show here that NF-kappaB activation in leukocytes recruited during the onset of inflammation is associated with pro-inflammatory gene expression, whereas such activation during the resolution of inflammation is associated with the expression of anti-inflammatory genes and the induction of apoptosis. Inhibition of NF-kappaB during the resolution of inflammation protracts the inflammatory response and prevents apoptosis. This suggests that NF-kappaB has an anti-inflammatory role in vivo involving the regulation of inflammatory resolution.

Nitric oxide synthase inhibitors have opposite effects on acute inflammation depending on their route of administration.

The bulk of published data has shown that NO is proinflammatory. However, there also exists the conflicting notion that NO may be protective during an inflammatory insult. In an attempt to resolve this issue, we have compared the effects on inflammation of a range of NO synthase (NOS) inhibitors given either directly to the site of the inflammatory lesion or systemically. It was found that in the carrageenin-induced pleurisy, a single intrapleural injection of the selective inducible NO inhibitors S-(2-aminoethyl) isothiourea (AE-ITU; 3 and 10 mg/kg) and N-(3-(aminomethyl)-benzyl) acetamidine (1400W; 10 mg/kg) or the selective endothelial cell NOS inhibitor L-N(5)(1-iminoethyl)-ornithine (10 mg/kg) not only exacerbated inflammation at the very early stages of the lesion (1-6 h), but also prevented inflammatory resolution. By contrast, administering NOS inhibitors systemically ameliorated the severity of inflammation throughout the reaction. To elucidate the mechanisms by which inhibition of NO synthesis locally worsened inflammation, we found an increase in histamine, cytokine-induced neutrophil chemoattractant, superoxide, and leukotriene B(4) levels at the inflammatory site. In conclusion, this work shows that the local production of NO is protective by virtue of its ability to regulate the release of typical proinflammatory mediators and, importantly, that NOS inhibitors have differential anti-inflammatory effects depending on their route of administration.

Heme oxygenase isoform expression in cellular and antibody-mediated models of acute inflammation in the rat.

Heme oxygenase (HO) is the rate-limiting enzyme in the catabolism of heme to biliverdin, carbon monoxide (CO), and free iron. The enzyme exists as a constitutive isoform (HO-2) and an inducible isoform (HO-1), which is also a stress protein (HSP32). HO-1 has previously been shown to be associated with the resolution phase of a non-immune model of acute inflammation. In addition, elevation of the enzyme was markedly anti-inflammatory. In the present study, these observations have been extended to two pleural models of immune-driven inflammation in the rat, an immediate type III hypersensitivity (Arthus) reaction and a delayed type IV hypersensitivity reaction. Whilst these models have differing inflammatory mechanisms and time courses, they both showed HO activity to be maximal during the resolution phase. This activity was associated with increases in exudate bilirubin (a breakdown product of biliverdin) and increased expression of HO-1. Immunocytochemical analysis of inflammatory cell smears from the two models showed that HO-1 and HO-2 expression was restricted to mononuclear cells in the type IV hypersensitivity reaction, but included the polymorphonuclear cell population in the type III hypersensitivity reaction. Thus, irrespective of the pathogenesis of the lesion, evidence is accumulating to suggest that HO-1 has a universal role in the resolution of inflammation.

COX-1, COX-2, and COX-3 and the future treatment of chronic inflammatory disease.

A new generation of non-steroidal anti-inflammatory drugs has been described that selectively targets the inducible isoform of cyclo-oxygenase, cyclo-oxygenase 2 (COX-2). This isoform is expressed at sites of inflammation, which has led to the speculation that its inhibition could provide all the benefits of current nonsteroidal anti-inflammatory drugs, but without their major side-effects on the gastrointestinal system (which are due to inhibition of COX-1). We have shown that COX-2 (identified by use of specific antibodies) is induced during the resolution of an inflammatory response, inhibition of COX-2 resulting in persistence of the inflammation due to the prevention of the synthesis of a range of anti-inflammatory prostanoids. We propose that there is a third isoform of this enzyme family, COX-3, a proposal that will have implication for the prescription of both existing and new generation anti-inflammatory drugs, and might represent a new therapeutic target.

An Alu element from the K18 gene confers position-independent expression in transgenic mice.

We have identified a 323-base pair fragment of the 5'-flanking sequence of the K18 gene, which confers position-independent and copy number-dependent expression on two heterologous transgenes. This fragment is composed primarily of an Alu repetitive element. Its activity in mice is correlated with its RNA polymerase III promoter activity and its orientation-dependent ability to inhibit potential transcriptional interference in a transfection assay. However, the activity of the Alu element is not correlated with its enhancer blocking activity, a characteristic of insulator elements. In addition, this Alu element did not block the suppressive effect of co-injecting mouse alpha satellite DNA with the transgene. This Alu element is likely responsible for at least part of the protective effects of the sequences flanking the K18. These results suggest that transcriptionally active Alu elements may eliminate transcriptional interference of neighboring genes. This Alu element is one component of the locus control region associated with the K18 gene. Other Alu repetitive elements may also function to define regulatory domains.

Resolution of inflammation.

Acute inflammatory reactions, in contrast to chronic inflammatory reactions, are usually self-limiting and resolve. We have investigated the resolving phase of a number of immune and non-immune inflammatory reactions induced in the pleural cavity of rats. COX-2 is expressed during resolution of these models. Using carrageenan pleurisy, we showed that this enzyme has a proinflammatory role as the reaction develops but an antiinflammatory role as the lesion resolves. This antiinflammatory role is associated with production of cyclopentenone prostaglandins and the absence of PGE2. Dual COX-1/COX-2 inhibitors or COX-2 inhibitors when given at the peak of the inflammatory response delay resolution, an effect reversed by replacing CyPGs into the pleural space. PGF2alpha like the CyPGs appears to have a role in resolving this reaction. Stress proteins are also induced in a variety of acute inflammatory models during resolution. Heme oxygenase-1 (HO-1) is one such protein so too are members of the hsp70 family. An inducer of HO-1 promotes resolution whereas an inhibitor is proinflammatory. In most cases it appears to be the macrophage that is the source of proteins necessary for resolution to occur. Understanding how proinflammatory pathways switch to the antiinflammatory pathways necessary for resolution to take place may eventually allow the exploitation of endogenous antiinflammatory pathways in the treatment of chronic inflammation.

Inducible cyclooxygenase may have anti-inflammatory properties.

Cyclooxygenase (COX) has two isoforms. Generally, COX 1 is constitutively expressed in most tissues, where it maintains physiological processes; inducible COX 2 is considered a pro-inflammatory enzyme and a chief target for the treatment of inflammatory diseases. Here we present evidence that COX 2 may have anti-inflammatory properties. In carrageenin-induced pleurisy in rats, the predominant cells at 2 hours are polymorphonuclear leucocytes, whereas mononuclear cells dominate from 24 hours until resolution at 48 hours. In this model, COX 2 protein expression peaked initially at 2 hours, associated with maximal prostaglandin E2 synthesis. However, at 48 hours there was a second increase in COX 2 expression, 350% greater than that at 2 hours. Paradoxically, this coincided with inflammatory resolution and was associated with minimal prostaglandin E2 synthesis. In contrast, levels of prostaglandin D2, and 15deoxy delta(12-14)prostaglandin J2 were high at 2 hours, decreased as inflammation increased, but were increased again at 48 hours. The selective COX 2 inhibitor NS-398 and the dual COX 1/COX 2 inhibitor indomethacin inhibited inflammation at 2 hours but significantly exacerbated inflammation at 48 hours. This exacerbation was associated with reduced exudate prostaglandin D2 and 15deoxy delta(12-14)prostaglandin J2 concentrations, and was reversed by replacement of these prostaglandins. Thus, COX 2 may be pro-inflammatory during the early phase of a carrageenin-induced pleurisy, dominated by polymorphonuclear leucocytes, but may aid resolution at the later, mononuclear cell-dominated phase by generating an alternative set of anti-inflammatory prostaglandins.

Destruction of articular cartilage by alpha 2 macroglobulin elastase complexes: role in rheumatoid arthritis.

OBJECTIVE: Neutrophil elastase accounts for the ability of some fresh rheumatoid synovial fluids to degrade cartilage matrix in vitro. The aim of this study was to determine if enzyme activity could result from depletion of synovial fluid inhibitors or protection of the enzyme from inhibition. METHODS: The ability of synovial fluids to inhibit porcine pancreatic elastase was investigated together with chemical pretreatments capable of inactivating alpha 1 protease inhibitor (alpha 1PI) or preventing formation of alpha 2 macroglobulin (alpha 2M) elastase complexes. Subsequently, complexes of human neutrophil elastase with alpha 2M were prepared and applied to frozen sections of cartilage. Proteoglycan loss was quantified by alcian blue staining and scanning and integrating microdensitometry. Parallel studies were carried out using a low molecular weight chromogenic elastase substrate. The effects of alpha 1PI and SF on these systems were investigated. Finally, synovial fluids were subjected to gel filtration and the fractions assayed for elastase activity. High molecular weight fractions were pooled, concentrated, and tested for their ability to degrade cartilage sections. RESULTS: All synovial fluids reduced the activity of porcine pancreatic elastase, the inhibition mainly being attributable to alpha 1PI, whereas remaining activity resulted from complexes of elastase with alpha 2M. Complexes of human neutrophil elastase with alpha 2M were shown to cause proteoglycan degradation in frozen sections of human articular cartilage. Alpha 1PI prevented alpha 2M elastase complexes from degrading cartilage but not the chromogenic substrate. The data suggested that alpha 1PI does not inhibit elastase bound to alpha 2M but sterically hinders the complex. However, only one of five synovial fluids was able to completely block the actions of alpha 2M elastase complexes against cartilage. Gel filtration of rheumatoid synovial fluids showed elastase and cartilage degrading activity to be associated with fractions that contained alpha 2M, and not with fractions expected to contain free enzyme. CONCLUSIONS: The data suggest that synovial fluid alpha 2M elastase complexes can degrade cartilage matrix in rheumatoid arthritis.

Effects of hyaluronan on models of immediate and delayed hypersensitivity in the rat.

Others have previously shown that superoxide dismutase conjugated with hyaluronan (HA) retains enzymic activity but is non-immunogenic. Whether HA could be widely used to prevent sensitisation to protein/polypeptide therapeutics is not known. In this study we investigated the effects of HA on bovine serum albumin (BSA) and methylated BSA pleural reactions in sensitised rats (active Arthus and delayed hypersensitivity reactions respectively) and on a reverse passive Arthus reaction in which rats received an intravenous injection of rabbit immunoglobulin and intrapleural challenge with goat anti rabbit immunoglobulin. HA suppressed the active Arthus and delayed hypersensitivity models when administered at the time of sensitisation but only the delayed hypersensitivity model at the time of intrapleural challenge. HA did not modulate the reverse passive Arthus reaction. The results show no evidence that simple mixing of HA with antigens masks antigenic determinants. However, HA appeared to have suppressive effects on both antibody and cell-mediated immune reactions. Therefore it may not be necessary to conjugate protein/polypeptide therapeutics to HA in order to prevent immune sensitisation.

The effects of cyclooxygenase 2 inhibitors on cartilage erosion and bone loss in a model of Mycobacterium tuberculosis-induced monoarticular arthritis in the rat.

Selective cyclooxygenase 2 (COX 2) inhibitors NS-398 and nimesulide were investigated for their effects on patellar cartilage and bone content in a model of Mycobacterium tuberculosis (M.tb)-induced monoarticular arthritis in the rat. The protective/destructive properties of these nonsteroidal antiinflammatory drugs (NSAIDs) were compared with piroxicam, known to accelerate cartilage breakdown and reduce bone erosion in this model in comparison to untreated arthritic controls. Male CFHB Wistar rats were injected intraarticularly with heat killed M.tb into the left stifle joint, resulting in loss of patellar cartilage glycosaminoglycans (GAG), bone erosion and inflammation. The right stifle joint received saline. Animals were dosed daily, p.o., with NS-398 (1, 10 mg/kg), nimesulide (0.5, 5 mg/kg) or piroxicam (10 mg/kg). Four days after M.tb injection, patellar GAG content, bone weight and joint swelling were measured in drug-treated animals and untreated arthritic controls. Changes in the left joint were compared to the right. The expression and distribution of COX 2 protein was determined by immunocytochemistry in synovial tissue from arthritic controls over the time course. Focal accumulations of inflammatory cells were positively immunolabelled for COX 2 in the synovium from the left stifle joint of untreated arthritic animals, 6 h after injection of M.tb. Labeling of inflammatory cell infiltrates increased and was widespread in the synovium at 24 h. By day 4 fibroblasts were positively labelled for COX 2 in addition to polymorphonuclear and mononuclear leukocytes. Piroxicam and nimesulide at the higher dose significantly exacerbated M.tb-induced cartilage GAG loss while NS-398 was without effect. Both COX 2 inhibitors did not alter M.tb-induced patellar bone loss. In contrast, piroxicam significantly reduced bone loss. All COX inhibitors significantly reduced joint swelling. In conclusion, the selective inhibition of COX 2 may result in the amelioration of synovitis with a lowered risk of NSAID-induced cartilage damage in rheumatic disease.

Differential effects of inhibitors of cyclooxygenase (cyclooxygenase 1 and cyclooxygenase 2) in acute inflammation.

The anti-inflammatory activity of drugs more selective for cyclooxgenase isoform inhibition (cyclooxygenase 1, cyclooxygenase 2), were compared in rat carrageenin-induced pleurisy. Suppression of inflammation by cyclooxygenase 2-selective inhibitors, NS-398 (N-[-2-cyclohexyloxy]-4-nitrophenyl methanesulphonamide) and nimesulide (4-nitro-2-phenoxy-methanesulfonanilide), and by piroxicam and aspirin, more selective for cyclooxygenase 1, was measured. Piroxicam and aspirin significantly inhibited inflammatory cell influx, exudate and prostaglandin E2 formation, 6 h after carrageenin injection. Cyclooxygenase 2 inhibitors had little effect on these parameters with NS-398 alone reducing prostaglandin E2 levels, but increasing levels of leukotriene B4. In contrast, at 3 h after carrageenin injection, cyclooxygenase 2 inhibitors significantly inhibited all inflammatory parameters however suppression with piroxicam and aspirin was greater, and more pronounced than at 6 h. NS-398 and nimesulide dosing did not reduce thromboxane B2 production from platelets isolated from rats with carrageenin-induced pleurisy, demonstrating that at the doses used, cyclooxygenase 2 inhibitors did not inhibit cyclooxygenase 1, as platelets contain only this isoform. Therefore, in the rat carrageenin-induced pleurisy, drugs more selective for the inhibition of cyclooxygenase 1 attenuate inflammation over a wider time frame than cyclooxygenase 2-selective drugs, suggesting a significant role for cyclooxygenase 1 in this model. Inhibition of cyclooxygenase 2 by NS-398 however, resulted in an increase in the potent chemoattractant leukotriene B4.

Inhibition of inducible nitric oxide synthase by peroxisome proliferator-activated receptor agonists: correlation with induction of heme oxygenase 1.

Genetic knock-out in mice of peroxisome proliferator-activated receptor-alpha (PPAR alpha) can prolong inflammation in response to leukotriene B4. Although cyclooxygenase 2 has been shown to be induced by PPAR activation, the effect of PPAR agonists on the key inflammatory enzyme systems of nitric oxide synthase (NOS) and stress proteins has not been investigated. The effect on these of naturally occurring eicosanoid PPAR agonists (leukotriene B4 and 8(S)-hydroxyeicosatetraenoic acid, which are PPAR alpha selective; PGA2, PGD2, PGJ2, and delta12PGJ2, which are PPAR gamma selective) and the synthetic PPAR alpha agonist Wy14,643 was examined in activated RAW264.7 murine macrophages. Leukotriene B4 and 8(S)-hydroxyeicosatetraenoic acid stimulated nitrite accumulation, indicative of enhanced NOS activity. PGA2, PGD2, PGJ2, delta12PGJ2, and Wy14,643 reduced nitrite accumulation, with delta12PGJ2 being the most effective. The mechanism behind this reduction was examined using Western blotting. Inhibition of nitrite accumulation was associated with a fall in inducible NOS protein and an induction of heme oxygenase 1, correlating both dose dependently and temporally. Other proteins examined (cyclooxygenase 2, heme oxygenase 2, heat shock protein 70, and glucose-regulated protein 78) were unaffected. The data suggest that naturally occurring PPAR agonists can inhibit the inducible NOS enzyme pathway. This inhibition may be mediated by modulation of the stress protein, heme oxygenase 1. Thus, the generation of eicosanoid breakdown products during inflammation may contribute to its eventual resolution by activation of the PPAR system. This system may thus represent a novel target for therapeutic intervention in inflammatory disease.

Effects of diacerhein on granuloma induced cartilage breakdown in the mouse.

OBJECTIVE: Diacerhein, an anti-osteoarthritic agent, was tested for its ability to suppress synthesis of proinflammatory cytokines in a model of granuloma-induced cartilage breakdown. DESIGN: 50 TO mice received a subcutaneous implant of cotton-wrapped rat femoral head cartilage for a period of 2 weeks. Animals (N = 10/group) were dosed daily with either 6 mg/kg p.o. diclofenac or diacetylrhein at 5, 15 or 50 mg/kg p.o. in 0.1.ml 1% gum tragacanth which served as a control. Implanted cartilages were assayed for glycosaminoglycan (GAG) and hydroxyproline content. The surrounding granulomas were assayed for interleukin-1 alpha (IL-1 alpha), tumour necrosis factor-alpha (TNF-alpha) and IL-6. Statistical analysis was by Mann-Whitney U test. RESULTS: Diclofenac had no significant effect on GAG or hydroxyproline content of implanted cartilage or on granuloma cytokine concentrations. Diacerhein protected implanted cartilages against hydroxyproline loss, implanted control cartilages contained 220 micrograms hydroxyproline compared with diacerhein at 5, 15 and 50 mg/kg which produced a 21, 16 and 59% decrease in hydroxyproline loss compared with non-implanted controls (P < 0.05, 0.05 and 0.001) respectively. Diacerhein also protected against GAG loss at 5 mg/kg and 50 mg/kg, control cartilages contained 134 micrograms GAG compared with diacerhein at 5 mg/kg and 50 mg/kg which produced a 24 and 38% decrease in GAG loss respectively (P < 0.05 for both). Diacerhein significantly reduced granuloma interleukin-1 alpha content at 5 mg/kg (control level of 2.4 micrograms/ml reduced by 58%; P < 0.05), reduced TNF-alpha at 5 mg/kg and 15 mg/kg (reduced by 61%: P < 0.01 and 49%: P < 0.05 respectively; control level of 469 pg/ml) and reduced IL-6 at 15 mg/kg and 50 mg/kg (control level of 537 pg/ml reduced by 60 and 51%, respectively; P < 0.01 for both). CONCLUSIONS: The mechanism of the chondroprotective effects of diacerhein is not understood but may be explained by a reduction in the concentrations of proinflammatory cytokines.

Differential effects of inhibition of isoforms of cyclooxygenase (COX-1, COX-2) in chronic inflammation.

OBJECTIVE AND DESIGN: The anti-inflammatory effects of therapeutic dosing of drugs with greater selectivity for the inhibition of the constitutive (COX-1) or inducible isoform (COX-2) of cyclooxygenase were assessed in a model of chronic inflammation. METHODS: The murine chronic granulomatous tissue air pouch model involves the subcutaneous injection of air into the dorsum of mice followed 24 h later by the intrapouch injection of an inflammatory stimulus (0.5 ml of Freund's complete adjuvant containing 0.1% croton oil). Aspirin, more selective in vitro for the inhibition of COX-1 (10,200 (mg/kg) and nimesulide, a selective in vitro inhibitor of COX-2 (0.5, 5 mg/kg) were dosed p.o. daily from 3 days after injection of the inflammatory stimulus. Granuloma dry weight, vascularity and COX activity (measured as PGE2) were assessed at various time points throughout the inflammatory lesion to resolution at day 28. A second COX-2 inhibitor, NS 398 (0.1, 1, 10 mg/kg), was dosed p.o. daily from 3 days after the injection of the inflammatory stimulus and its effects on granuloma dry weight, vascularity and COX activity were measured at 7 days. RESULTS: Aspirin (200 mg/kg) significantly inhibited levels of PGE2 throughout the time course and at the lower dose (10 mg/kg) from day 14. Nimesulide (5 mg/kg) however, significantly increased levels of PGE2 at days 5 and 21, but at 0.5 mg/kg was without effect. Aspirin (200 mg/kg) significantly reduced granuloma dry weight at day 14 but had no effect on granuloma vascularity at day 7. In contrast, nimesulide (5 mg/kg) significantly increased granuloma vascularity at day 7 and granuloma dry weight at day 14. NS-398 at all doses had no effect on granuloma dry weight, vascularity or COX activity 7 days after the injection of the inflammatory stimulus. CONCLUSION: In this model of chronic inflammation, aspirin, more selective for the inhibition of COX-1 is more effective than the selective COX-2 inhibitors nimesulide and NS-398 at inhibiting granuloma dry weight, vascularity and COX activity.

The codependence of angiogenesis and chronic inflammation.

Angiogenesis is the growth of new blood vessels from existing ones. It is an important aspect of new tissue development, growth, and tissue repair. It is also a component of many diseases including cancer, blindness, and chronic inflammation such as rheumatoid arthritis (RA) and psoriasis. There is considerable evidence to suggest that angiogenesis and chronic inflammation are codependent; recent studies have begun to reveal the nature of this link, which involves both augmentation of cellular infiltration and proliferation and overlapping roles of regulatory growth factors and cytokines. Through these studies, we have begun to understand the codependence of chronic inflammation and angiogenesis, the potential benefits of targeting angiogenesis in the treatment of chronic inflammation, and of targeting chronic inflammation to affect angiogenesis.