Oxidative stress causes nuclear factor-κB activation in acute hypovolemic hemorrhagic shock

Nuclear Factor κB (NFκB) is an ubiquitous rapid response transcription factor involved in inflammatory reactions and exerts its action by expressing cytokines, chemokines, and cell adhesion molecules. We investigated the role of NF-κB in acute hypovolemic hemorrhagic (Hem) shock. Hem shock was induced in male anesthetized rats by intermittently withdrawing blood from an iliac catheter over a period of 20 min (bleeding period) until mean arterial blood pressure (MAP) fell and stabilized within the range of 20-30 mmHg. Hemorrhagic shocked rats died in 26.3 ± 2.1 min following the discontinuance of bleeding, experienced a marked hypotension (mean arterial blood pressure = 20-30 mmHg) and had enhanced plasma levels of Tumor Necrosis Factor-α (200 ± 15 pg/ml, 20 min after the end of bleeding). Furthermore, aortas taken 20 min after bleeding from hemorrhagic shocked rats showed a marked hypo-reactivity to phenylephrine (PE; 1nM to 10 μM) compared with aortas harvested from sham shocked rats. Hem shocked rats also had increased levels of TNF-α mRNA in the liver (15-20 min after the end of bleeding) and enhanced plasma levels of 2,5-dihydroxybenzoic acid (2,5-DHBA; 6 ± 2.2 μm), 2,3-dihydroxybenzoic acid (2,3-DHBA; 13 ± 2.1 μm), both studied to evaluate OH^·production. Electrophoretic mobility shift assay showed that liver NF-κB binding activity increased in the nucleus 10 min after the end of hemorrhage and remained elevated until the death of animals. Western blot analysis suggested that the levels of inhibitory IκBα protein in the cytoplasm became decreased at 5 min after the end of bleeding. IRFI-042, a vitamin E analogue (20 mg/kg intraperitoneally 2 min after the end of bleeding), inhibited the loss of IκBα protein from the cytoplasm and blunted the increase in NF-κB binding activity. Furthermore IRFI-042 increased survival time (117.8 ± 6.51 min; p < .01) and survival rate (vehicle = 0% and IRFI-042 = 80%, at 120 min after the end of bleeding), reverted the marked hypotension, decreased liver mRNA for TNF-α, reduced plasma TNF-α (21 ± 4.3 pg/ml), and restored to control values the hypo-reactivity to PE. Our results suggest that acute blood loss (50% of the estimated total blood volume over a period of 20 min) causes early activation of NF-κB, likely through an increased production of reactive oxygen species. This experiment indicates that NF-κB-triggered inflammatory cascade becomes early activated during acute hemorrhage even in the absence of resuscitation procedures.