Interleukin-1 receptor antagonist attenuates leukocyte-endothelial interactions in the liver after hemorrhagic shock in the rat

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Abstract
Objective To evaluate the influence of interleukin-1 on leukocyte-endothelial cell interactions and the microcirculation in the liver after hemorrhagic shock by means of intravital microscopy using an interleukin-1 receptor antagonist (IL-1ra). Design Prospective, randomized, blinded, controlled study. Setting University research laboratory. Subjects Anesthetized female Sprague Dawley rats weighing 200 to 230 g. Interventions Hypovolemic shock was induced and maintained for 1 hr (mean arterial pressure 40 mm Hg; cardiac output 50% of baseline). After adequate resuscitation and 5 hrs of reperfusion (mean arterial pressure >100 mm Hg; cardiac output >120% of baseline), the microcirculation in liver sinusoids was examined by intravital fluorescence microscopy. Continuous administration of IL-1ra (5 mg/kg/hr) was started at different times in a prospective, randomized, blinded fashion, either as pretreatment 5 mins before shock induction (n = 6), or as therapy at the time of resuscitation (n = 6). An additional bolus injection of 5 mg/kg of IL-1ra was given to the latter group. Measurements and Main Results Mean arterial pressure, cardiac output, heart rate, and blood gases were comparable in all shock groups during the experiments. The percentage of permanently adherent leukocytes (adhesion time of >20 secs) in the pretreated group was significantly decreased in comparison with the control group (pretreatment group 16.9 +/- 1.9% vs. control group 42.1 +/- 5.4%; p < .001 by analysis of variance; sham group 9.1 +/- 1.1%). Administration of IL-1ra at the time of resuscitation also reduced firm adhesion of leukocytes to sinusoidal endothelium (treated group 28.8 +/- 3.6%, p < .01). Temporary adhesion rates of leukocytes (adhesion time of <20 secs) were unaffected by pretreatment or treatment with IL-1ra with respect to control values. Liver microcirculation was impaired after hemorrhagic shock but not improved by IL-1ra. Conclusions The results show that adhesion of leukocytes to hepatic sinusoidal endothelium is at least partly regulated by interleukin-1. Adherence was attenuated by the application of IL-1ra, which might be due to diminished expression of adhesion receptors by endothelial cells or leukocytes. Even administration of IL-1ra at the time of resuscitation reduces the early inflammatory response in the liver after shock, thus offering a potentially important therapeutic approach. (Crit Care Med 1995; 23:1099-1105)