NSAIDs upregulate beta 2-integrin expression on human neutrophils through a calcium-dependent pathway

Role of NRF2 in protection of the gastrointestinal tract against oxidative stress

The gastrointestinal tract is exposed to a variety of noxious factors, such as Helicobacter pylori, nonsteroidal anti-inflammatory drugs, gastric acid, ischemia-reperfusion, and mental stresses. Theses stressors generate free radicals within gastrointestinal tissues, causing organ injury and functional disturbance. Although the gastrointestinal tract can withstand such oxidative stresses to some extent by enhancing its antioxidant system via nuclear factor erythroid 2-related factor 2-Kelch-like erythroid cell-derived protein with CNC homology-associated protein 1-mediated pathways, acute or chronic exposure to oxidative stress can cause several gastrointestinal tract disorders, such as inflammation, ulcers, cancers, and various functional disturbances. Recent studies have demonstrated that some natural compounds and drugs can upregulate the nuclear factor erythroid 2-related factor 2-mediated antioxidant system, ameliorating or preventing these disorders. Although these compounds may be useful as chemopreventive agents, sufficient evidence for their clinical efficacy has not yet been provided. In addition, it is important to note that excessive nuclear factor erythroid 2-related factor 2 stimulation can be harmful to human health, especially from the standpoint of tumor biology.

Dose-dependent inhibition of gastric injury by hydrogen in alkaline electrolyzed drinking water

Background

Hydrogen has been reported to relieve damage in many disease models, and is a potential additive in drinking water to provide protective effects for patients as several clinical studies revealed. However, the absence of a dose–response relationship in the application of hydrogen is puzzling. We attempted to identify the dose–response relationship of hydrogen in alkaline electrolyzed drinking water through the aspirin induced gastric injury model.

Methods

In this study, hydrogen-rich alkaline water was obtained by adding H₂ to electrolyzed water at one atmosphere pressure. After 2 weeks of drinking, we detected the gastric mucosal damage together with MPO, MDA and 8-OHdG in rat aspirin induced gastric injury model.

Results

Hydrogen-dose dependent inhibition was observed in stomach mucosal. Under pH 8.5, 0.07, 0.22 and 0.84 ppm hydrogen exhibited a high correlation with inhibitory effects showed by erosion area, MPO activity and MDA content in the stomach. Gastric histology also demonstrated the inhibition of damage by hydrogen-rich alkaline water. However, 8-OHdG level in serum did not have significant hydrogen-dose dependent effect. pH 9.5 showed higher but not significant inhibitory response compared with pH 8.5.

Conclusions

Hydrogen is effective in relieving the gastric injury induced by aspirin-HCl, and the inhibitory effect is dose-dependent. The reason behind this may be that hydrogen-rich water directly interacted with the target tissue, while the hydrogen concentration in blood was buffered by liver glycogen, evoking a suppressed dose–response effect. Drinking hydrogen-rich water may protect healthy individuals from gastric damage caused by oxidative stress.

Oxidative stress involvement and gene expression in indomethacin-induced gastropathy

It has been proposed that neutrophil- and oxygen radical-dependent microvascular injuries are important prime events that lead to gastric mucosal injury induced by indomethacin. Reactive oxygen species (ROS) produced by activated neutrophils after indomethacin treatment cause gastric mucosal injury via ROS-mediated oxidation of important biomolecules such as lipid, protein, and DNA. In addition, it has been revealed that indomethacin-induced gastric mucosal injury occurs via gastric epithelial cell apoptosis. However, there is little known about the mechanism of indomethacin-triggered cellular response and apoptotic signaling in gastric mucosal cells. In the present study, we summarize the evidence that supports the involvement of oxidative stress and apoptosis in indomethacin-induced gastropathy, and review the gene expression profiles of gastric epithelial cells after indomethacin treatment determined by DNA microarray analysis.

ICAM-1-mediated leukocyte adhesion is critical for the activation of endothelial LSP1

Leukocyte-endothelial interaction triggers signaling events in endothelial cells prior to transendothelial migration of leukocytes. Leukocyte-specific protein 1 (LSP1), expressed in endothelial cells, plays a pivotal role in regulating subsequent recruitment steps following leukocyte adhesion. In neutrophils, LSP1 is activated by phosphorylation of its serine residues by molecules downstream of p38 MAPK and PKC. Whether leukocyte adhesion to endothelial cells is required for endothelial LSP1 activation remains elusive. In addition, discrepancies in the functions of endothelial and leukocyte LSP1 in leukocyte adhesion prevail. We demonstrate that adhesion of wild-type (Lsp1(+/+)) neutrophils to LSP1-deficient (Lsp1(-/-)) endothelial cells was significantly reduced compared with adhesion to Lsp1(+/+) endothelial cells. Immunoblotting revealed increased phosphorylated endothelial LSP1 in the presence of adherent Lsp1(-/-) neutrophils [stimulated by macrophage inflammatory protein-2 (CXCL2), TNF-α, or thapsigargin], but not cytokine or chemokine alone. Pharmacological inhibition of p38 MAPK by SB-203580 (10 μM) significantly blunted the phosphorylation of endothelial LSP1. Functionally blocking endothelial ICAM-1 or neutrophil β2-integrins diminished neutrophil adhesion and phosphorylation of endothelial LSP1. The engagement of endothelial ICAM-1 cross-linking, which mimics leukocyte adhesion, resulted in phosphorylation of endothelial LSP1. In neutrophil-depleted Lsp1(+/+) mice, administration of ICAM-1 cross-linking antibody resulted in increased phosphorylation of LSP1 and p38 MAPK in TNF-α-stimulated cremaster muscle. In conclusion, endothelial LSP1 participates in leukocyte adhesion in vitro, and leukocyte adhesion through ICAM-1 fosters the activation of endothelial LSP1, an effect at least partially mediated by the activation of p38 MAPK. Endothelial LSP1, in contrast to neutrophil LSP1, is not phosphorylated by cytokine or chemokine stimulation alone.

Direct effects of osteoprotegerin on human bone cell metabolism

PURPOSE

Osteoprotegerin (OPG) affects bone metabolism by intercepting the RANK-RANKL interaction which prevents osteoclastic differentiation and consequently reduces bone resorption. Different bone phenotypes of mice overexpressing OPG and of mice with knockdown of receptor activator of NF-kappaB (RANK) or RANK-ligand (RANKL) suggest that the mechanism of action of the OPG-RANKL-RANK system in regulating bone remodeling is not completely understood. Furthermore, OPG increases bone mass and density independently from reduced osteoclastogenesis which is consistent with the possibility that OPG may directly affect bone metabolism beyond its known role as decoy receptor for RANKL.

METHODS

We treated primary human osteoblastic cells with OPG and inhibitory anti-RANKL antibodies and measured cellular ALP activity, in vitro mineralization, vitronectin receptor protein expression and ERK phosphorylation. We also analyzed the mRNA co-expression of ALP and OPG ex vivo in bone biopsies from acute and old stable vertebral fractures.

RESULTS

OPG directly increased ALP activity and in vitro mineralization of HOC, enhanced expression of the vitronectin receptor thereby increasing adherence of HOC to vitronectin and stimulated ERK phosphorylation. All OPG-mediated effects could be prevented by RANKL antibodies or RANKL-siRNA transfection and MAPK inhibitor PD98059 reduced the stimulatory effect of OPG on integrin alphav expression. In acutely fractured vertebrae OPG and ALP mRNA expression was significantly increased compared to stable vertebral fractures. In conclusion, OPG exerts direct osteoanabolic effects on HOC metabolism via RANKL in addition to its well described role as decoy receptor for RANKL.

High-throughput screening for small-molecule activators of neutrophils: identification of novel N-formyl peptide receptor agonists

We screened a chemolibrary of drug-like molecules for their ability to activate reactive oxygen species (ROS) production in murine phagocytes, and we identified 26 novel compounds with potent neutrophil activating properties. We used substructure screening, fragment-focusing, and structure-activity relationship analyses to further probe the parent library and defined at least two groups of activators of ROS production in murine neutrophils: t-butyl benzene and thiophene-2-amide-3-carboxylic ester derivatives. Further studies of the active compounds revealed 11 compounds that activated ROS production in human neutrophils, and six of these compounds also activated intercellular Ca(2+) mobilization and chemotaxis in human neutrophils. Of the latter compounds, compound 14 (1,3-benzodioxolane-5-carboxylic acid 4'-benzyloxy-3'-methoxybenzylidene-hydrazide) activated neutrophils at nanomolar concentrations, and Ca(2+) mobilization was inhibited by pertussis toxin and N-t-butoxycarbonyl-Phe-Leu-Phe-Leu-Phe (Boc-2), an antagonist of formyl peptide receptors (FPR/FPRL1). Likewise, activation by compound 14 was desensitized after N-formyl-Met-Leu-Phe pretreatment. Similar biological activities were found for compound 104 (1,3-benzodioxolane-5-carboxylic acid 3'-bromo-5'-ethoxy-4'-hydroxybenzylidene-hydrazide), an analog of compound 14. Furthermore, conformational analysis of the activators of chemotaxis and Ca(2+) mobilization showed a high degree of similarity in distances between pharmacophore points of compounds 14 and 104 with a model of FPR published by Edwards et al. (Mol Pharmacol 68:1301-1310, 2005), indicating that conformational features of the agonists identified here are structurally compatible with steric constraints of the ligand-binding pocket of the receptor. Based on these results, we conclude that compounds 14 and 104 represent novel small-molecule agonists of FPR. These studies enhance our understanding of FPR ligand/receptor interactions and structure/activity relationships of phagocyte agonists.

Effects of anti-inflammatory [1, 2, 4]triazolo[4, 3-a] [1, 8]naphthyridine derivatives on human stimulated PMN and endothelial cells: an in vitro study

Background

[1,2,4] triazolo [4, 3-a][1,8]naphthyridine derivatives (including NF161 and NF177) were tested for anti-inflammatory, analgesic and antipyretic properties and for their effects on spontaneous locomotor activity in mice and acute gastrolesivity in rats. Both NF161 and NF177 appeared to be anti-inflammatory and analgesic agents without toxic effects or acute gastrolesivity, but NF161 showed stronger anti-inflammatory activity, whereas NF177 was more active as analgesic.

Methods

An EIA kit was used to investigate the ability of NF161 and NF177 to affect prostaglandin E₂ (PGE₂) and prostacyclin (PGI₂) production by human umbilical vascular endothelial cells (HUVEC).

The compounds' effects on the production of reactive oxygen species (ROS) by human polymorphonuclear cells (PMNs) were studied in an in vitro cell model, evaluating inhibition of superoxide anion (O₂^-.) production induced by N-formylmethionyl-leucyl-phenylalanine (FMLP). Their effects on PMN adhesion to HUVEC were also investigated; they were incubated with PMNs and endothelial cells (EC) and challenged by stimuli including Platelet Activating Factor (PAF), FMLP, Phorbol Myristate Acetate (PMA), Tumor Necrosis Factor-α (TNF-α) and Interleukin-1β (IL-1β). Adhesion was quantitated by computerized micro-imaging fluorescence analysis.

Results

Neither compounds modified PGE₂ or PGI₂ production induced by IL-1α.

O₂^-. production and myeloperoxidase release from PMNs stimulated by FMLP was inhibited in a dose- but not time-dependent manner by both [1,8]naphthyridine derivatives, NF161 being statistically more active than NF177 (P < 0.01).

The compounds inhibited adhesion evoked by the pro-inflammatory stimuli PAF, FMLP, TNF-α and IL-1β in a concentration-dependent manner in the 10^-6–10^-4M range, being more active when PAF was used as stimulus and inactive when cells were challenged by PMA. Both compounds acted both on PMN and HUVEC.

Conclusion

Considering the interesting anti-inflammatory effects of these compounds in in vivo models and the absence of acute gastrolesivity, the study improved knowledge of anti-inflammatory properties of NF161 and NF177, also demonstrating their potential in vitro, through inhibition of O₂^-. production, myeloperoxidase release and PMN adhesion to HUVEC. Negative results on PG production suggest a cyclooxygenase (COX)-independent mechanism.

Indomethacin causes prostaglandin D(2)-like and eotaxin-like selective responses in eosinophils and basophils

We investigated the actions of a panel of nonsteroidal anti-inflammatory drugs on eosinophils, basophils, neutrophils, and monocytes. Indomethacin alone was a potent and selective inducer of eosinophil and basophil shape change. In eosinophils, indomethacin induced chemotaxis, CD11b up-regulation, respiratory burst, and L-selectin shedding but did not cause up-regulation of CD63 expression. Pretreatment of eosinophils with indomethacin also enhanced subsequent eosinophil shape change induced by eotaxin, although treatment with higher concentrations of indomethacin resulted in a decrease in the expression of the major eosinophil chemokine receptor, CCR3. Indomethacin activities and cell selectivity closely resembled those of prostaglandin D(2) (PGD(2)). Eosinophil shape change in response to eotaxin was inhibited by pertussis toxin, but indomethacin- and PGD(2)-induced shape change responses were not. Treatment of eosinophils with specific inhibitors of phospholipase C (U-73122), phosphatidylinositol 3-kinase (LY-294002), and p38 mitogen-activated protein kinase (SB-202190) revealed roles for these pathways in indomethacin signaling. Indomethacin and its analogues may therefore provide a structural basis from which selective PGD(2) receptor small molecule antagonists may be designed and which may have utility in the treatment of allergic inflammatory disease.

Dual function of nonsteroidal anti-inflammatory drugs (NSAIDs): inhibition of cyclooxygenase and induction of NSAID-activated gene

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used drugs for the treatment of inflammatory disease and have a chemopreventive effect on colorectal cancer. NSAIDs inhibit cyclooxygenase (COX)-1 and/or COX-2 activity, but the chemopreventive effect may be, in part, independent of prostaglandin inhibition. NSAID-activated gene (NAG-1) was previously identified as a gene induced by some NSAIDs in cells devoid of COX activity. NAG-1 has proapoptotic and antitumorigenic activity in vitro and in vivo. To determine whether the induction of NAG-1 by NSAIDs is influenced by COX expression, we developed COX-1- and COX-2-overexpressing HCT-116 cells. COX expression did not affect NSAID-induced NAG-1 expression as assessed by transient and stable transfection. Also, NAG-1 expression was not affected by PGE(2) and arachidonic acid, suggesting that NAG-1 induction by NSAIDs occurs by a prostanoid-independent manner. We also report that indomethacin increased NAG-1 expression in a number of cells from tissues other than colorectal. In conclusion, NSAIDs have dual function, induction of NAG-1 expression and inhibition of COX activity that occurs in a variety of cell lines.

Mechanism of non-steroidal anti-inflammatory drug-gastropathy

Non-steroidal anti-inflammatory drugs are recognized to cause gastrointestinal damage impairing the defense ability of gastric mucosal barrier. A variety of mechanisms due to non-steroidal anti-inflammatory drugs direct irritant (topical) action and to their main pharmacological (systemic) effect, is involved in the pathogenesis of non-steroidal anti-inflammatory drugs induced gastropathy. The systemic activity comprises the inhibition of cyclo-oxygenase, but an increasing body of evidence suggests that cyclo-oxygenase-independent mechanisms are involved in the development of gastric injury. In line with this concept, neither cyclo-oxygenase-1 nor cyclo-oxygenase-2 deficient mice develop spontaneous gastrointestinal ulcers and pharmacological inhibition of cyclo-oxygenase-1 or cyclo-oxygenase-2 with selective inhibitors doesn't elicit gastrointestinal damage; suggesting that both isoforms of cyclo-oxygenase enzymes have to be inhibited to induce ulcers. Moreover non-steroidal anti-inflammatory drugs administration in rats, induces the systemic release of tumor necrosis factor-alpha and drives gastric epithelial cells to apoptosis activating the pro-apoptotic cascade of caspases. In response to non-steroidal anti-inflammatory drugs, neutrophils are recruited into the gastric microcirculation through a process that requires activation of adhesion molecules. Although there is virtually no information regarding the regulation of expression of gastric endothelial cell adhesion molecules in response to non steroidal anti-inflammatory drugs, the nuclear factor-kB may represent a potential modulator. Supporting this view, selective proteasome inhibitors inhibit nuclear translocation of nuclear factor-kB induced by tumor necrosis factor-alpha in human endothelial cells in vitro and reduce indomethacin-induced gastric mucosal injury in vivo.

Pioglitazone, a specific PPAR-gamma ligand, inhibits aspirin-induced gastric mucosal injury in rats

BACKGROUND

Neutrophils activation and tumour necrosis factor-alpha (TNF-alpha) induction play a critical role in aspirin-induced gastric mucosal injury. Peroxisome proliferator-activated receptor-gamma (PPAR-gamma), a member of the nuclear hormone receptor superfamily, has recently been implicated as a regulator of inflammatory responses. The aim of the present study was to determine whether pioglitazone, a specific PPAR-gamma ligand, can ameliorate aspirin-induced gastric mucosal injury in rats, and whether the agent can inhibit the increase in neutrophil accumulation associated with TNF-alpha expression.

METHODS

Aspirin-induced injury was produced by the intragastric administration of aspirin (200 mg/kg) and HCl (0.15 N, 8.0 mL/kg). Pioglitazone was given to the rats by gastric intubation 1 h before the aspirin administration. Thiobarbituric acid-reactive substances and tissue-associated myeloperoxidase activity were measured in gastric mucosa as indices of lipid peroxidation and neutrophil infiltration. The gastric concentration of TNF-alpha and the expression of TNF-alpha mRNA was determined by ELISA and reverse transcriptase-polymerase chain reaction.

RESULTS

The intragastric administration of acidified aspirin induced hyperemia and haemorrhagic erosions in rat stomachs. The increase in the total gastric erosive area after aspirin administration was significantly inhibited by treatment with pioglitazone in a dose-dependent manner. The increases in thiobarbituric acid-reactive substances and myeloperoxidase activity after aspirin administration were both significantly inhibited by pre-treatment with pioglitazone (10 mg/kg). The gastric content of TNF-alpha increased and the expression of TNF-alpha mRNA was up-regulated after aspirin treatment. However, the peak TNF-alpha mRNA expression 1 h after aspirin administration was inhibited by pioglitazone.

CONCLUSION

Based on these data, the beneficial effects of pioglitazone on aspirin-induced gastric mucosal injury may be attributed to its anti-inflammatory properties.

The role of neutrophils and inflammation in gastric mucosal injury

Gastric inflammation is a highly complex biochemical protective response to cellular/tissue injury. When this process occurs in an uncontrolled manner, the result is excessive cellular/tissue damage that results chronic inflammation and destruction of normal tissue. Current evidence suggests that Helicobacter pylori (H. pylori) infection and nonsteroidal anti-inflammatory drug (NSAID) ingestion are major causative factors in the pathogenesis of gastric mucosal injury in humans. In response to H. pylori infection or NSAID, neutrophils are recruited to the site of inflammation and generate reactive oxygen and nitrogen species and proteases. However, neutrophils are not able to kill the bacteria that live in the gastric mucus, and compounds produced by activated neutrophils themselves may be potentially harmful for normal tissue. It has been shown that leukocyte-vascular endothelial cell interaction is regulated by various cell adhesion molecules, and that this interaction is directly or indirectly modified by many factors, the origin of which is H. pylori and NSAIDs. This review describes the potential role of neutrophils and neutrophil-associated inflammation for gastric oxidative stress and injury induced by H. pylori and/or NSAID.

Nitric oxide-releasing NSAIDs inhibit interleukin-1beta converting enzyme-like cysteine proteases and protect endothelial cells from apoptosis induced by TNFalpha

BACKGROUND

Nitric oxide (NO)-releasing NSAIDs are a new class of NSAID derivatives with markedly reduced gastrointestinal toxicity. Although it has been demonstrated that NO-NSAIDs spare gastric mucosal blood flow, molecular determinants involved in this effect are unknown.

AIM

To investigate the effect of aspirin, naproxen and flurbiprofen, and their NO-derivatives, on gastric apoptosis and endothelial cell damage induced by tumour necrosis factor-alpha (TNFalpha). In other systems, TNFalpha-induced apoptosis is mediated by caspases, a growing family of cysteine proteases similar to the IL-1beta converting enzyme (ICE), and so we have investigated whether NO-NSAIDs modulate ICE-like endopeptidases.

METHODS

Rats were treated orally with aspirin, naproxen and flurbiprofen, or their NO-releasing derivatives in equimolar doses, and were killed 3 h later to assess mucosal damage and caspase activity. Endothelial cells (HUVECs) were obtained from human umbilical cord by enzymatic digestion. Caspase 1 and 3 activities were measured by a fluorimetric assay using selective peptides as substrates and inhibitors. Apoptosis was quantified by ELISA specific for histone-associated DNA fragments and by the terminal transferase nick-end translation method (TUNEL).

RESULTS

In vivo NSAID administration caused a time-dependent increase in gastric mucosal damage and caspase activity. NCX-4016, NO-naproxen and NO-flurbiprofen did not cause any mucosal damage and prevented cysteine protease activation. NSAIDs and NO-NSAIDs stimulated TNFalpha release. Exposure to TNFalpha resulted in a time- and concentration-dependent HUVEC apoptosis, an effect that was prevented by pretreating the cells with NCX-4016, NO-naproxen, NO-flurbiprofen, SNP or Z-VAD.FMK, a pan-caspase inhibitor. The activation of ICE-like cysteine proteases was required to mediate TNFalpha-induced apoptosis of HUVECs. Exogenous NO donors inhibited TNFalpha-induced cysteine protease activation. Inhibition of caspase activity was due to S-nitrosylation of ICE/CPP32-like proteases. NO-NSAIDs prevented IL-1beta release from endotoxin-stimulated macrophages.

CONCLUSIONS

NO-releasing NSAIDs are a new class of non-peptide caspase inhibitors. Inhibition of ICE-like cysteine proteases prevents endothelial cell damage induced by pro-inflammatory agents and might contribute to the gastro-protective effects of NO-NSAIDs.

Salicylates Inhibit Adhesion and Transmigration of T Lymphocytes by Preventing Integrin Activation Induced by Contact With Endothelial Cells

The inhibition of cyclooxygenase does not fully account for the spectrum of activities of nonsteroidal antiinflammatory drugs. It is evident, indeed, that regulation of inflammatory cell function may contribute in explaining some of the effects of these drugs. Tissue recruitment of T cells plays a key role in the development of chronic inflammation. Therefore, the effects of salicylates on T-cell adhesion to and migration through endothelial cell monolayers on collagen were analyzed in an in vitro static system. Aspirin and sodium salicylate reduced the ability of unstimulated T cells to adhere to and transmigrate through cytokine-activated endothelium. Although salicylates did not modify the expression of integrins on T cells, they blunted the increased adherence induced by the anti-β2monoclonal antibody (MoAb) KIM127 and prevented the appearance of an activation-dependent epitope of the CD11/CD18 complex, recognized by the MoAb 24, induced by contact with endothelial cells. Salicylates also induced an increase of intracellular calcium ([Ca2+]i) and activation of protein kinase C (PKC) in T cells, but not cell proliferation and interleukin (IL)-2 synthesis. The reduction of T-cell adhesiveness appears to be dependent on the increase in[Ca2+]i levels, as it could be reversed by blocking Ca2+ influx, but not by inhibiting PKC. Moreover, ionomycin at concentrations giving an increase in [Ca2+]i similar to that triggered by aspirin, strictly reproduced the T-cell phenotypic and functional changes induced by salicylates. Aspirin reduced T-cell adhesion and migration also ex vivo after infusion to healthy volunteers. These data suggest that the antiinflammatory activity of salicylates may be due, at least in part, to an interference with the integrin-mediated binding of resting T lymphocytes to activated endothelium with consequent reduction of a specific T-cell recruitment into inflammatory sites.

Salicylates Inhibit Adhesion and Transmigration of T Lymphocytes by Preventing Integrin Activation Induced by Contact With Endothelial Cells

The inhibition of cyclooxygenase does not fully account for the spectrum of activities of nonsteroidal antiinflammatory drugs. It is evident, indeed, that regulation of inflammatory cell function may contribute in explaining some of the effects of these drugs. Tissue recruitment of T cells plays a key role in the development of chronic inflammation. Therefore, the effects of salicylates on T-cell adhesion to and migration through endothelial cell monolayers on collagen were analyzed in an in vitro static system. Aspirin and sodium salicylate reduced the ability of unstimulated T cells to adhere to and transmigrate through cytokine-activated endothelium. Although salicylates did not modify the expression of integrins on T cells, they blunted the increased adherence induced by the anti-β2monoclonal antibody (MoAb) KIM127 and prevented the appearance of an activation-dependent epitope of the CD11/CD18 complex, recognized by the MoAb 24, induced by contact with endothelial cells. Salicylates also induced an increase of intracellular calcium ([Ca2+]i) and activation of protein kinase C (PKC) in T cells, but not cell proliferation and interleukin (IL)-2 synthesis. The reduction of T-cell adhesiveness appears to be dependent on the increase in[Ca2+]i levels, as it could be reversed by blocking Ca2+ influx, but not by inhibiting PKC. Moreover, ionomycin at concentrations giving an increase in [Ca2+]i similar to that triggered by aspirin, strictly reproduced the T-cell phenotypic and functional changes induced by salicylates. Aspirin reduced T-cell adhesion and migration also ex vivo after infusion to healthy volunteers. These data suggest that the antiinflammatory activity of salicylates may be due, at least in part, to an interference with the integrin-mediated binding of resting T lymphocytes to activated endothelium with consequent reduction of a specific T-cell recruitment into inflammatory sites.

Inhibition of leukocyte adhesion: an alternative mechanism of action for anti-inflammatory drugs

It has been widely accepted that the mechanism of action of nonsteroidal anti-inflammatory drugs (NSAIDs) is the inhibition of prostaglandin synthesis. However, a significant body of evidence suggests that NSAIDs have additional anti-inflammatory mechanisms of action. Here, Federico Díaz-González and Francisco Sánchez-Madrid discuss novel effects of NSAIDs on leukocyte adhesion pathways that may help in the development of new anti-inflammatory agents that selectively block cell adhesion molecules.