Reactive oxidants mediate TNF-alpha-induced leukocyte adhesion to rat mesenteric venular endothelium

Abstract

We investigated the role of reactive oxygen metabolites (ROMs) as potential mediators of tumor necrosis factor-alpha (TNF-alpha)-stimulated neutrophil adhesion to rat mesenteric venules in vivo, using intravital microscopy and fixed whole mount preparations of mesentery. Intraperitoneal injection of TNF-alpha significantly increased leukocyte rolling, adhesion, and emigration in a dose- and time-dependent manner. Leukocyte adhesion and emigration, but not rolling, were significantly attenuated by prior intravenous administration of monoclonal anti-intercellular adhesion molecule-1 (ICAM-1). Rolling leukocyte flux was significantly attenuated by intravenous preadministration of superoxide dismutase (SOD), catalase, or both. Only catalase or SOD plus catalase significantly inhibited leukocyte adhesion. Catalase alone inhibited emigration. Moreover, postadhesive treatment with catalase but not SOD, 4 h after TNF-alpha administration reduced the flux of rolling (but not adherent) leukocytes that had previously increased in response to TNF-alpha. Intragastric allopurinol (50 mg/kg at 3 and 18 h before TNF-alpha administration) or 3 wk of a tungsten-enriched diet substantially inhibited xanthine oxidase activity but had no significant effects on the above parameters of neutrophil dynamics. In parallel experiments using fixed whole mount preparations of the mesoappendix stained specifically for neutrophil esterase, neutrophil adhesion 2 h after TNF-alpha administration was also inhibited by continuous intravenous administration of catalase but not by SOD, intragastric allopurinol, or tungsten diet. These findings suggest that ROMs, apparently not from xanthine oxidase, are important mediators of TNF-alpha-induced upregulation of neutrophil adhesion in rat mesenteric venules.

Suppression of Cytokine-lnduced Neutrophil Accumulation in Rat Mesenteric Venules in vivo by General Anesthesia

“…(In that study the significant increase in neutrophil adhesion was blocked with a murine anti-ICAM antibody.) While one could postulate that anesthe sia-induced hypotension might decrease the shear rate in mesenteric vessels, we observed no such hypotension in our rats [23], and this would be expected to increase (not inhibit) neutrophil accumulation. However, because blood flow and shear stress were not measured in these rats, we cannot definitely state how the anesthetics af fected neutrophil accumulation, only that they did so, and did so strikingly.…”

“…However, based upon the leukocyte counts, the decrease in neutrophil adhesion due to these anesthet ic agents does not seem to reflect a nonspecific suppres sion of circulating leukocytes. Furthermore, we believe that the TNF-a-induced increase in neutrophil adhesion is probably not a consequence of differences in wall shear rate caused by TNF-a, because in other experiments using similar doses and times of TNF-a administration, we found a highly significant TNF-a-induced increase in neu trophil adhesion, after correcting for differences in wall shear rate [23]. In that study we used both intravital microscopy and whole-mount preparations to comple ment each other and to obviate the obscuring effect of general anesthesia.…”

“…We have con firmed that the response to TNF-a is dose dependent and is strikingly increased 2-4 h after intraperitoneal admin istration. While this finding is not novel [23], it repro duces a consistent, conventional agonist response, against which we could evaluate the potentially confounding inhibitory effects of conventionally employed anesthetic regimens.…”

“…2) and because this proved to be a time period relevant to many [23], but certainly not all [37,38], intravital microscopy studies. In fact, we saw the same suppression at 1 h (data not shown).…”

Interaction of Platelet Activating Factor, Reactive Oxygen Species Generated by Xanthine Oxidase, and Leukocytes in the Generation of Hepatic Injury After Shock/Resuscitation

“…Certainly the localization of this inflammation and injury in the distal (pericentral) hepatic sinusoids and central hepatic veins, which corresponds to the mesenteric and intestinal venules, and which also corresponds with the localization of endothelial xanthine oxidase, 38 strongly supports this concept. Reactive oxidants mediate neutrophil accumulation in this injury, as they do in other injury models, by signaling the upregulation of vascular adhesion molecules, [61][62][63] as previously described in the feline small intestine 13,14,54 and in other organs. Unfortunately, due to the limited availability and the extraordinary expense of specific inhibitors to these molecules for the rat, we were unable to explore the specific adhesion molecules that might be involved in this model.…”