Background-The inability to inhibit multiple mediators of septic shock represents a major hurdle in the treatment of septic shock. In vivo inhibition of nuclear factor (NF)-kappaB activation, a transcription factor regulating expression of many proinflammatory genes, could provide a useful strategy for the treatment of septic shock. Methods and Results-In rats challenged with lipopolysaccharide (LPS) 8 mg/kg IV, we determined the time course of NF-kappaB activation and expression of multiple inflammatory signals: tumor necrosis factor-alpha (TNF-alpha), cyclooxygenase-2 (COX-2), cytokine-inducible neutrophil chemoattractant (CINC), and intercellular adhesion molecule-1 (ICAM)-1. We studied the effects of in vivo inhibition of NF-kappaB activation using pyrrolidine dithiocarbamate (PDTC) on the expression of these mediators. NF-kappaB activation preceded the induction of TNF-alpha, COX-2, CINC, and ICAM-1 mRNAs. PDTC prevented the LPS-induced NF-kappaB activation but did not inhibit activation of the transcription factors AP-1, Sp-1, and CREB. PDTC inhibited the LPS-induced expression of TNF-alpha, COX-2, CINC, and ICAM-1 mRNA and proteins and reduced the LPS-induced increases in plasma TNF-alpha, 6-keto-prostaglandin F(1alpha), and CINC concentrations. Inhibition of expression of these mediators prevented the increases in myeloperoxidase activity (a measure of neutrophil sequestration) in the heart, lungs, and liver. Conclusions-NF-kappaB activation correlates with LPS-induced expression of TNF-alpha, COX-2, CINC, and ICAM-1 genes in vivo. PDTC inhibits NF-kappaB activation and expression of these proinflammatory genes and their products. Thus, blocking NF-kappaB activation may be an effective strategy in the treatment of septic shock.

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To defi ne the roles of endothelial-intrinsic nuclear factor B (NF-B) activity in host defense and multiple organ injury in response to sepsis, we generated double transgenic (TG) mice (EC-rtTA/I-B ␣ mt) that conditionally overexpress a degradation-resistant form of the NF-B inhibitor I-B ␣ (I-B ␣ mt) selectively on vascular endothelium. The ECrtTA/I-B ␣ mt mice had no basal, but a relatively high level of doxycycline-inducible, I-B ␣ mt expression. I-B ␣ mt expression was detected in endothelial cells, but not in fi broblasts, macrophages, and whole blood cells, confi rming that transgene expression was restricted to the endothelium. When subjected to endotoxemia, EC-rtTA/I-B ␣ mt mice showed endothelial-selective blockade of NF-B activation, repressed expression of multiple endothelial adhesion molecules, reduced neutrophil infi ltration into multiple organs, decreased endothelial permeability, ameliorated multiple organ injury, reduced systemic hypotension, and abrogated intravascular coagulation. When subjected to cecal ligation and puncture -induced sepsis, the TG mice had less severe multiple organ injury and improved survival compared with wild-type (WT) mice. WT and EC-rtTA/I-B ␣ mt mice had comparable capacity to clear three different pathogenic bacteria. Our data demonstrate that endothelial NF-B activity is an essential mediator of septic multiple organ infl ammation and injury but plays little role in the host defense response to eradicate invading pathogenic bacteria.