Evidence for a role of nuclear factor-κB in acute hypovolemic hemorrhagic shock

Abstract

Background. In acute hypovolemic shock, a rapid systemic release of the inflammatory cytokine tumor necrosis factor (TNF-α) contributes to vascular failure. Nuclear factor κB (NF-κB) is an ubiquitous rapid-response transcription factor involved in inflammatory reactions and exerts its effect by expressing cytokines, chemokines, and cell adhesion molecules. The purpose of this study was to evaluate the role of NF-κB in acute hypovolemic hemorrhagic shock. Methods. Hemorrhagic shock was induced in anesthetized male rats by intermittently withdrawing blood from an iliac catheter for 20 minutes (bleeding period) until mean arterial blood pressure (MAP) decreased and stabilized within the range of 20 to 30 mm Hg. Two minutes after bleeding was discontinued the rats received tacrolimus (100 μg/kg), an inhibitor of NFκB activation, or its vehicle. We then evaluated survival rate and survival time, liver NF-κB activation by means of electrophoretic mobility shift assay, liver IκBα protein in the cytoplasm, hepatic TNF-α messenger RNA expression, plasma TNF-α, arterial blood pressure, and the contractile response of aortic rings to phenylephrine. Results. Rats that underwent hemorrhagic shock died 28 ± 2 minutes after bleeding was discontinued, experienced marked hypotension (MAP, 20-30 mm Hg), and had enhanced plasma levels of TNF-α (218 ± 28 pg/mL 20 minutes after bleeding was discontinued). Aortas taken 20 minutes after bleeding was discontinued in rats that underwent hemorrhagic shock showed marked hyporeactivity to phenylephrine (1 nmol/L-10 μmol/L) compared with aortas harvested from sham shocked rats. Rats that underwent hemorrhagic shock also had increased levels of TNF-α messenger RNA in the liver. Furthermore, electrophoretic mobility shift assay showed that liver NF-κB binding activity increased in the nucleus, and Western blot analysis suggested that the levels of inhibitory IκBα protein in the cytoplasm decreased. Tacrolimus (100 μg/kg, administered 2 minutes after bleeding was discontinued) inhibited the loss of IκBα protein from the cytoplasm and prevented NF-κB binding activity in the nucleus. Moreover, tacrolimus increased survival time (118 ± 7 minutes; P