All nonsteroidal antiinflammatory drugs (NSAIDs) inhibit neutrophil aggregation (homotypic cell-cell adhesion) and do so without affecting expression of CD11b/CD18. Since the first step in acute inflammation is a critical interaction between neutrophils and the vascular endothelium (heterotypic cell-cell adhesion), we determined whether NSAIDs diminish the adherence of neutrophils to the endothelium. At antiinflammatory concentrations (0.5-5 mM) sodium salicylate, an NSAID that does not inhibit prostaglandin synthesis, inhibited stimulated but not unstimulated neutrophil adherence to endothelial cells (IC50 < 1 mM, P < 0.00001). Salicylates have previously been shown to inhibit oxidative phosphorylation and, predictably, sodium salicylate inhibited oxidative phosphorylation, as evidenced by depletion of ATP stores (875 +/- 75 pmol/10(6) PMN, [2.92 +/- 0.25 mM]) in stimulated (FMLP, 0.1 microM) but not resting neutrophils treated with antiinflammatory doses of sodium salicylate (EC50 = 1 mM, P < 0.00001). Indomethacin and piroxicam (10 and 30 microM) only minimally decreased ATP concentrations in stimulated and resting neutrophils. ATP is metabolized to adenosine, and we have previously demonstrated that both endogenously released (180-200 nM) and exogenous adenosine (IC50 = 250 nM) inhibit stimulated neutrophil adherence to endothelial cells. To determine whether the increased metabolism of ATP and the resultant increase in adenosine release were responsible for inhibition of neutrophil adhesion to endothelium, we determined whether addition of adenosine deaminase (ADA, 0.125 IU/ml), an enzyme that converts extracellular adenosine to its inactive metabolite, inosine, affected inhibition of neutrophil adhesion to endothelium by stimulated neutrophils. ADA significantly reversed inhibition of neutrophil adherence to endothelium by sodium salicylate (0.5-5 mM, P < 0.00001). This suggests that sodium salicylate inhibits neutrophil adherence by increasing adenosine release. Whereas indomethacin and piroxicam (10-50 microM) also inhibited stimulated neutrophil adherence to endothelial cells, ADA did not affect their inhibition of adherence. These studies demonstrate a heretofore unexpected antiinflammatory mechanism for salicylates: salicylates increase ATP hydrolysis and thereby enhance release of adenosine. Moreover, these data are consistent with the hypothesis that NSAIDs differ from one another with respect to their mechanisms of action.
No abstract
Corticosteroids are the preeminent antin-flammatory agents altoh the molular menims that impart their efficacy have not been defined. The endo u plays a critical role in infmmation by ding crcaing leukocytes into extravascular tissue by expr g adhesive molecules for leukocytes [e.g., endothelalleukocyte adhesion molecule 1 (ELAM-1) and intercellular ad ocule 1 (ICAM-1)]. We therefore determined whether corticosterolds suppress inflammation by inhibiting elll exp n of adhesion molecules for neutrophils (polymorphonulear leuko-cytes). Preincubation of endothelial cells with endoin [lipo-polysaccharlde (LPS), 1 pg/ml] led to a 4-fold inC in subsequent adherence of polymorphonucer leukocytes (P < 0.0001, n = 10) to endothellal cells, an ire that was markedy attenuated when endothelial cells were treated with dexamethasone (ICso < 1 nM, P < 0.0001, n = 6 or 7) during preincubation with LPS. Moreover, the steroid receptor agonist cortsol (10 pM), but not Its inactive metabolite tetrahydrocorti-sol (10 JpM), diminhed LPS-induced endothelial cell adhesive-ness. Further evidence that the action of dexamethasone was mediated through ligation of corticosteroid eceptrs [human glucocorticoid receptors (hGRs)] was provided by exits utlizing the steroid antagonist RU-486. RU-486 (10 pM), which prevents transiocation of ligted hGR to the nu ses by nhib-iting diction of hGR from heat shock protein 90, m y aborted the effect of dexamethasone on adhesiveness of endo-thelial cells (P < 0.0005, n = 3). Treatment of e e cells with LPS (1 pg/ml) stimulated t io of ELAM-1, as shown by Northern blot analysis, and expressin of membrane-associated ELAM-1 and ICAM-1, as shown by quantitative immunofluorescence (both P < 0.001, n = 9). De s_ markedly inhibited LPS-stimulated accumul of mRNA for ELAM-1 and expression of ELAM-1 and ICAM-1 (IC_% < 10 nM, both P < 0.001, n = 4-9); inhibition of exp by dexamethasone was reversed by RU-486 (both P < 0.005, n = 4-6). As in the adhesion studies, cortsol but not tetahydro cortisol inhibited expression of ELAM-1 and ICAM-1 (bothP < 0.005, n = 3 or 4). In contrast, sodium sallcylate (1 mM) inhibited neither adhesion nor expressin of these adesn molecules. These studies suggest that antan by de h-asone ofendotoxin-induced inflammation is a specifc s of the general biological principle that the glucocortcod receptor is a hormone-dependent regulator of transcription.
The observation that aspirin inhibits the increment in tissue plasminogen activator (t-PA) activity induced by venous occlusion of the forearm became controversial with the publication of several nonconfirmatory studies. The current study was performed to confirm the original observation and determine the mechanism by which aspirin suppresses the incremental t-PA activity induced by venous occlusion. Aspirin (650 mg/d X 2) caused no change in resting levels of t-PA antigen (t-PA:Ag) or activity, plasminogen activator inhibitor 1 antigen (PAI-1:Ag), or activity or t-PA-PAI-1 complexes. In contrast, aspirin reduced the increments induced by venous occlusion as follows: t-PA:Ag by 45% (P = .001); t-PA activity (euglobulin lysis time, ELT) by 43% (P = .006); and t-PA activity (alpha 2-plasmin inhibitor-plasmin complexes, PIPC) by 41% (P = .003). The inhibition of incremental t-PA activity measured as ELT or PIPC was linearly correlated with the inhibition of incremental t-PA:Ag (respectively, r = .75, P less than .02; r = .67, P less than .05). Aspirin had no effect on the increment in PAI-1:Ag induced by venous occlusion, but similar to the effect on t- PA:Ag, aspirin induced a 51% inhibition of the increment in t-PA-PAI-1 complex formation. Aspirin did not alter the ability of alpha 2-plasmin inhibitor to bind plasmin, nor the ability of plasma to support the fibrin-catalyzed generation of plasmin by t-PA, nor the subsequent formation of PIPC. Aspirin inhibits the t-PA activity induced by venous occlusion primarily by inhibiting the release of t-PA antigen.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.