Nuclear factor-kappa B as a target of cyclosporin in acute hypovolemic hemorrhagic shock

Background: Cyclosporin is an immunosuppressive drug that blocks Nuclear Fa ctor KB (NF-KB) activation. We investigated the role of NF-KB in acute hypo volemic hemorrhagic (Hem) shock and the effects of cyclosporin in this mode l of experimental shock. Methods: Hem shock was induced in male anesthetize d rats by intermittently withdrawing blood from an iliac catheter over a pe riod of 20 min (bleeding period) until mean arterial blood pressure (MAP) f ell and stabilized within the range of 20-30 mmHg. Two minutes after bleedi ng cessation, animals received intravenously cyclosporin (1 mg kg(-1)) or i ts vehicle. Survival rate and survival time were evaluated for 120 min afte r bleeding was discontinued. Plasma TNF-alpha levels were investigated at d ifferent time points after bleeding cessation. Moreover we investigated lev els of TNF-alpha mRNA in the liver, vascular reactivity, liver NF-KB bindin g activity and levels of the inhibitory protein I kappaB alpha in the cytop lasm. Results: Hemorrhagic shocked rats died in 27 +/-6 min following the c essation of bleeding, experienced a marked hypotension (mean arterial blood pressure=20-30 mmHg) and had enhanced plasma levels of Tumor Necrosis Fact or-alpha (208 +/- 22 pg ml(-1), 20 min after the end of bleeding). Furtherm ore, aortas taken 20 min after bleeding from hemorrhagic shocked rats showe d a marked hypo-reactivity to phenylephrine (PE: 1 nM-10 muM) compared with aortas harvested from sham shocked rats. Hem shocked rats also had increas ed levels of TNF-ot mRNA in the liver (15-20 min after the end of bleeding) . Electrophoretic mobility shift assay showed that liver NF-KB binding acti vity increased in the nucleus 10 min after the end of hemorrhage and remain ed elevated until the death of animals. Western blot analysis suggested tha t the levels of inhibitory protein IKB alpha in the cytoplasm decreased at 5 min after the end of bleeding. Cyclosporin inhibited the loss Of IKB alph a protein from the cytoplasm and prevented NF-kappaB binding activity in th e nucleus. Furthermore, cyclosporin increased survival time (118 +/-7 min; P <0.01) and survival rate (vehicle=0% and cyclospofin=80%, at 120 min afte r the end of bleeding), reverted the marked hypotension, decreased liver mR NA for TNF-alpha, reduced plasma TNF-alpha (28 +/-7 pg ml(-1)), and restore d to control values the hypo-reactivity to PE. Conclusions: Our results sug gest that acute blood loss (50% of the estimated total blood volume over a period of 20 min) causes early activation of NF-KB which triggers an inflam matory cascade leading to a fatal outcome. Cyclosporin blocks NF-KB activat ion and protects against hypovolemic hemorrhagic shock. (C) 2001 Elsevier S cience B.V. All rights reserved.